CN101099033A

CN101099033A - Exhaust gas purifying device for internal combustion engine

Info

Publication number: CN101099033A
Application number: CN200680001688.9A
Authority: CN
Inventors: 加藤健治; 广岡重正
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2005-05-19
Filing date: 2006-05-01
Publication date: 2008-01-02
Also published as: JP2006322397A; JP4462107B2; US20080184701A1; EP1882093A1; WO2006123564A1

Abstract

An NOX occluding and reducing catalyst 7 is arranged in an exhaust gas passage 2 of an engine 1 so as to occlude, reduce and purify NOX contained in an exhaust gas. An H2 sensor 33 is arranged in the exhaust gas passage on a downstream side of the NOX occluding and reducing catalyst 7 and a hydrogen component concentration of the exhaust gas is detected. When an amount of NOX occluded in the NOX occluding and reducing catalyst is increased to a predetermined value, an electronic control unit (ECU) 30 of the engine operates the engine at a rich air-fuel ratio, and a regenerating operation, by which a rich air-fuel ratio exhaust gas is supplied to the NOX occluding and reducing catalyst, is executed so as to reduce and purify NOX which is occluded in the NOX occluding and reducing catalyst. At the time of executing the regenerating operation, when the H2 sensor 33 detects hydrogen components in the exhaust gas, ECU 30 finishes the regenerating operation. Due to the foregoing, it is possible to accurately judge the time for terminating the regenerating operation of the NOX occluding and reducing catalyst.

Description

The Exhaust gas purifying device of internal-combustion engine

Technical field

The present invention relates to a kind of Exhaust gas purifying device of internal-combustion engine.More specifically, the present invention relates to a kind of NO that wherein uses _xThe Exhaust gas purifying device of the internal-combustion engine of occlusion reducing catalyst.

Background technique

Comprise NO _xThe Exhaust gas purifying device of the internal-combustion engine of occlusion reducing catalyst is being known in the art.When the air-fuel ratio of the exhaust of inflow catalyst, NO _xNO in the occlusion reducing catalyst occlusion exhaust _xComponent, and, when the air fuel ratio of the exhaust of inflow catalyst during dense or chemically correct fuel, NO _xThe occlusion reducing catalyst is by utilizing the NO of occlusion in the reduction composition reducing catalyst in the exhaust _xIn this regard, the term that uses in this specification " occlusion " comprises the absorption and the meaning that absorbs.

When air-fuel ratio, NO _xThe NO that comprises in the occlusion reducing catalyst occlusion exhaust _xComponent, it is present in the occlusion material such as BaO with the nitrate ion form.Therefore, work as NO _xThe NO of occlusion in the occlusion reducing catalyst _xWhen amount increased, occlusion material had been full of NO _x, catalyzer is difficult to occlusion and is included in the interior NO of exhaust _x

Therefore, using NO _xIn the Exhaust gas purifying device of occlusion reducing catalyst, whenever NO _xThe NO of occlusion in the occlusion reducing catalyst _xWhen amount increases, carry out dense-reinforcement (rich spikeoperation) operation, wherein, the exhaust of dense air fuel ratio is fed to NO _xThe occlusion reducing catalyst reaches a bit of time, thereby can make the NO of catalyzer occlusion _xReduction and purification.For example in Japanese patent application publication No. 2600492, described this dense-reinforcement technique.

When the air fuel ratio of exhaust becomes chemically correct fuel or dense air fuel ratio, be included in significantly increasing in the exhaust such as the amount of the reduction composition of CO and the amount of HC composition.From NO _xThe NO of desorb in the occlusion material of occlusion reducing catalyst _xReact with CO, HC etc., and be reduced into N ₂, and therefore, at NO _xThe NO of occlusion in the occlusion reducing catalyst _xAmount reduce.Therefore, can make NO _xOcclusion reducing catalyst occlusion NO once more under the condition of rare air fuel ratio _x

As mentioned above, dense-intensified operation is attended by the dense air fuel ratio operation of motor, and is attended by adds fuel or reducing agent in exhaust, carries out dense-intensified operation and reduces and purify occlusion at NO _xNO in the occlusion reducing catalyst _x(hereinafter, occlusion is at NO _xNO in the occlusion reducing catalyst _xThis reduction and purification be called as " NO _xThe regeneration of occlusion reducing catalyst ").Therefore, if NO _xAfter the regenerative operation of occlusion reducing catalyst was finished, regenerative operation still continued, and can increase the fuel consumption of motor, perhaps because the discharge of reducing agent makes the discharging variation.

Therefore, need to judge NO _xThe regeneration of occlusion reducing catalyst is finished, and that is to say, needs to judge the NO of all occlusions _xBe reduced and purify, and when regeneration is finished, also need to finish regenerative operation.

For this purpose, Japanese patent application publication No. 2692380 has disclosed a kind of Exhaust gas purifying device, wherein, and at NO _xThe downstream side of the exhaust passage of occlusion reducing catalyst is provided with O ₂Sensor.O ₂The output of sensor is dense or rare the variation according to the air fuel ratio of exhaust.According to this O ₂NO is judged in the output of sensor _xFinishing of occlusion reducing catalyst regeneration.

As mentioned above, dense-during intensified operation, when the exhaust of dense air fuel ratio flows into NO _xDuring the occlusion reducing catalyst, what comprise in exhaust is consumed such as compositions such as HC, CO, so that reduction is at NO _xThe NO of occlusion in the occlusion reducing catalyst _xIn other words, HC, CO etc. are comprised in NO _xInterior oxygen oxidation.Therefore, flow into NO even work as the exhaust of dense air fuel ratio _xOcclusion reducing catalyst, while NO _xBy NO _xIn occlusion reducing catalyst when reduction,, HC, CO etc. are also by from NO _xThe occlusion reducing catalyst is separated the oxygen oxidation of sucking-off.Therefore, at NO _xThe air fuel ratio of the exhaust in the downstream side of occlusion reducing catalyst remains on chemically correct fuel.Then, work as NO _xThe regeneration of occlusion reducing catalyst is finished and all NO _xWhen all being reduced, be included in the interior compositions such as HC, CO of exhaust not by NO _xThe oxidation of occlusion reducing catalyst.This makes NO _xThe air fuel ratio of the exhaust in the downstream side of occlusion reducing catalyst becomes the dense air fuel ratio identical with upstream side.

That is to say, after dense intensified operation begins, NO _xThe air fuel ratio of the exhaust in the downstream side of occlusion reducing catalyst does not become dense air fuel ratio at once, but remains on the value approaching with chemically correct fuel, and works as NO _xAll NO of occlusion reducing catalyst occlusion _xWhen all being reduced, that is to say, only work as NO _xWhen the regeneration of occlusion reducing catalyst is finished, at NO _xThe air fuel ratio of the exhaust in occlusion reducing catalyst downstream side becomes dense air fuel ratio.

According to the device that Japanese patent application publication No. 2692380 discloses, NO _xIt is as follows that the finishing of the regeneration of occlusion reducing catalyst judged.Supervision is arranged on NO _xThe O in the downstream side of occlusion reducing catalyst ₂The output of sensor.When dense intensified operation, when detecting O ₂The output of sensor is then judged NO when chemically correct fuel is transformed into dense air fuel ratio _xThe regeneration of occlusion reducing catalyst is finished.

In this regard, compare with CO, hydrogen has high reducing capacity.Therefore, reducing and purifying occlusion at NO _xNO in the occlusion reducing catalyst _xThe time, when an amount of hydrogen is fed to NO _xDuring the occlusion reducing catalyst, increased NO _xThe NO of occlusion in the occlusion reducing catalyst _xReduction rate, and can reduce and purify NO effectively at short notice _x

Be well known that when air fuel ratio is dense the burning of engine internal fuel produces hydrogen.In addition, following method is known: except the hydrogen that common engine produces in dense air fuel ratio running, the hydrogen in other source is added in the exhaust.

For example, open (Kokai) number 2002-47919 of Japanese uncensored model utility has disclosed a kind of method, wherein, by utilizing the reducing capacity as the hydrogen of strong reductant, judges NO _xThe NO of occlusion reducing catalyst _xOcclusion capacity.

Because hydrogen has high reducing capacity, if NO _xOcclusion flows into NO in catalyzer _xHydrogen composition in the exhaust in the occlusion reducing catalyst by with catalyzer in the NO of occlusion _xThe reaction and consume, and as long as occlusion at NO _xNO in the occlusion reducing catalyst _xExist, the hydrogen composition does not just flow to NO _xThe downstream side of occlusion reducing catalyst.

Therefore, the exhaust in the dense air fuel ratio that comprises hydrogen is fed to NO _xUnder the situation of occlusion reducing catalyst, hydrogen begins to flow into NO _xTime point in the exhaust in the downstream side of occlusion reducing catalyst can be regarded as NO _xAll NO of occlusion in the occlusion reducing catalyst _xThe time point that all is reduced and purifies.Therefore, from beginning time period and the NO of dense intensified operation to the hydrogen composition that detects the downstream side _xThe NO of occlusion in the occlusion reducing catalyst _xAmount corresponding.Therefore, can judge that this time period is long more, NO _xThe NO of occlusion in the occlusion reducing catalyst _xAmount big more.

The technology that the uncensored model utility of Japan open (Kokai) discloses for 2002-47919 number is utilized above-mentioned phenomenon, judges NO _xFinishing of occlusion reducing catalyst regeneration.

In the uncensored model utility of Japan open (Kokai) 2002-47919 number, be used to detect the H of the hydrogen in the exhaust ₂Sensor is arranged on NO _xThe upstream side of occlusion reducing catalyst and downstream side.NO in reduction and purification occlusion _xThe time, according to from upstream H ₂Sensor hydrogen is to downstream H ₂The time difference of sensor hydrogen, judge NO _xThe NO of occlusion in the occlusion reducing catalyst _xAmount whether reduce, that is to say and judge NO _xWhether the occlusion reducing catalyst variation.

Japan uncensored patent disclosure (Kokai) number 2003-120383 has disclosed a kind of method, is used for the concentration control air fuel ratio based on the hydrogen composition in the I. C. engine exhaust.In this is open, in order to prevent when the dense air fuel ratio of theoretical air fuel ratio is moved, the hydrogen that is produced by three-way catalyst causes that the situation of the output error of the lambda sensor that is arranged at the three-way catalyst downstream side occurs, and in order to prevent that carrying out air fuel ratio control according to the output of lambda sensor occurred by the situation of this erroneous effects, downstream side at three-way catalyst is provided with hydrogen sensor, and, proofread and correct air fuel ratio control based on the concentration of hydrogen composition in the exhaust of measuring by hydrogen sensor.

As mentioned above, passing through dense intensified operation to NO _xUnder the situation that the occlusion reducing catalyst is regenerated,, need accurately judge NO in order to prevent to increase the fuel consumption of motor _xThe regeneration of occlusion reducing catalyst is finished.

Yet, described as Japanese patent application publication No. 2692380, when based on being arranged on NO _xNO is judged in the output of the lambda sensor in the downstream side of occlusion reducing catalyst _xWhen the regeneration of occlusion reducing catalyst is finished, in some cases, be difficult to the time of judging that accurately regeneration is finished.

As described below, for when the dense intensified operation, by reductive NOs such as the HC in the exhaust, CO _x, be included in NO _xThe catalyst component such as platinum (Pt) in the occlusion reducing catalyst need be used as reducing catalyst.Yet, in exhaust, comprising under the situation of a large amount of HC compositions, the HC composition is adsorbed on the surface of catalyzer.Therefore, the surface coverage HC composition of catalyzer, catalyst component are difficult to that is to say as reducing catalyst, have caused the problem that catalyst component is capped.

Therefore, when dense intensified operation, be fed to NO _xComprise in the exhaust of the dense air fuel ratio of occlusion reducing catalyst under the situation of a large amount of HC compositions, occlusion is at NO _xNO in the occlusion reducing catalyst _xA part and a part that is included in the HC composition in the exhaust do not flow to NO each other corresponsively _xThe downstream side of occlusion reducing catalyst.

The HC composition that in the exhaust of dense air fuel ratio, comprises not with NO _xPass through NO corresponsively _xThe occlusion reducing catalyst, and when flowing to the downstream side of above-mentioned catalyzer, the lambda sensor that is provided with in the downstream side of catalyzer is judged the air-fuel ratio of exhaust.Therefore, described as Japanese patent application publication No. 2692380, when judging NO according to the output that is arranged on the lambda sensor in catalyzer downstream side _xWhen the regeneration of occlusion reducing catalyst is finished, may go wrong.That is, though unactual the finishing of regeneration, the air fuel ratio of the exhaust that is detected by lambda sensor becomes dense air fuel ratio, and judges mistakenly to regenerate and finish, and has stopped dense intensified operation.The NO when stopping regenerative operation _xWhen the regeneration of occlusion reducing catalyst is not still fully carried out, NO _xThe occlusion reducing catalyst is had at its NO _xOcclusion capacity is by the occlusion NO again that fully regenerates before _xThis causes exhaust gas purification to get insufficient and the discharging variation.

As mentioned above, for NO _xThe regeneration of occlusion reducing catalyst, supply hydrogen composition is effective.Yet, when by the hydrogen composition is fed to NO _xThe occlusion reducing catalyst NO that regenerates _xDuring the occlusion reducing catalyst, unless an amount of hydrogen composition is provided, otherwise be difficult to regenerate fully NO _xOcclusion reducing catalyst, and abundant purifying exhaust gas.

According to the technology of open (Kokai) number 2002-47919 of the uncensored model utility of Japan and 2003-120383 announcement, by H ₂Hydrogen composition in the sensor exhaust.Yet, do not consider NO _xDuring the regeneration of occlusion reducing catalyst, control is fed to the H that comprises in the exhaust of catalyzer ₂The amount of composition.

Summary of the invention

In view of the above problems, the purpose of this invention is to provide a kind of Exhaust gas purifying device of internal-combustion engine, wherein, even comprise in exhaust under the situation of quite a large amount of HC, NO also can suitably regenerate _xOcclusion reducing catalyst, thereby abundant purifying exhaust gas.

In order to achieve the above object,, provide a kind of Exhaust gas purifying device of internal-combustion engine, having comprised: be arranged on the NO in the exhaust passage of internal-combustion engine according to the present invention that claim 1 is described _xThe occlusion reducing catalyst, when the air-fuel ratio of the exhaust of inflow catalyst, this NO _xThe occlusion reducing catalyst passes through one of them of absorption and absorption, and perhaps by absorbing and adsorbing, occlusion is included in the interior NO of exhaust _x, and, when the air fuel ratio of exhaust is chemically correct fuel or dense air fuel ratio, this NO _xThe utilization of occlusion reducing catalyst is included in the NO that being reduced in the exhaust assigned to reduce and purified occlusion _xWith at NO _xThe H of one of them setting at least of the inlet side of occlusion reducing catalyst and the exhaust passage of outlet side ₂Sensor is used to detect the hydrogen constituent concentration of exhaust, and wherein: this Exhaust gas purifying device is carried out regenerative operation, wherein, works as NO _xThe occlusion reducing catalyst will reduce and purify occlusion at NO _xNO in the occlusion reducing catalyst _xThe time, the exhaust of dense air fuel ratio or chemically correct fuel is fed to NO _xThe occlusion reducing catalyst reaches predetermined amount of time, and during regenerative operation, and this Exhaust gas purifying device is based on by H ₂The hydrogen constituent concentration is controlled and is flowed into NO in the exhaust of sensor _xThe air fuel ratio of the exhaust of occlusion reducing catalyst.

That is, according to the invention of claim 1 description, according to being arranged on NO _xAt least the H of one of them in the upstream side of occlusion reducing catalyst and downstream side ₂The hydrogen constituent concentration of sensor is controlled the air fuel ratio of exhaust.

For example, as described below, when utilization is arranged on NO _xThe H in occlusion reducing catalyst downstream side ₂During the hydrogen constituent concentration of sensor, can judge NO _xThe deadline of the regenerative operation of occlusion reducing catalyst.Therefore, regenerative operation can be at NO _xStop when the regenerative operation of occlusion reducing catalyst is finished, and the air fuel ratio of exhaust can turn back to rare air fuel ratio.Therefore, the NO that can suitably regenerate _xThe occlusion reducing catalyst.

Hydrogen constituent concentration in the exhaust changes according to the air fuel ratio of exhaust.Therefore, when based on being arranged on NO _xThe H of the upstream side of occlusion reducing catalyst ₂When the hydrogen constituent concentration in the exhaust of sensor is controlled the air fuel ratio of exhaust, for example, can NO will be flowed into _xHydrogen constituent concentration in the exhaust of occlusion reducing catalyst is controlled to be suitable value, and an amount of hydrogen composition can be fed to NO _xThe occlusion reducing catalyst.Therefore, the NO that can suitably regenerate _xThe occlusion reducing catalyst.

According to the invention that claim 2 is described, a kind of Exhaust gas purifying device of the internal-combustion engine according to claim 1 is provided, wherein, H ₂Sensor is arranged on this NO _xIn the exhaust passage of the outlet side of occlusion reducing catalyst, and when carrying out regenerative operation, according to by outlet side H ₂Sensor to exhaust in the hydrogen constituent concentration judge the time that regenerative operation stops.

According to the invention that claim 2 is described, this H ₂Sensor is arranged on NO at least _xThe outlet side of occlusion reducing catalyst (downstream side).When being used to carry out NO _xWhen the dense intensified operation of the regeneration of occlusion reducing catalyst begins, owing to flow into NO _xThe air fuel ratio of the exhaust of occlusion reducing catalyst becomes dense air fuel ratio, so the hydrogen constituent concentration in the exhaust increases.

Yet, because the reducing capacity of hydrogen is very strong, when hydrogen flows into NO _xDuring the occlusion reducing catalyst, it is reductive NO directly _xComponent, and do not need auxiliary reducing catalyst.Therefore, even when comprising quite a large amount of HC compositions in the exhaust and catalyzer that catalyst surface is coated with HC occurs when covering, the function variation of reducing catalyst, the hydrogen composition that comprises in exhaust also can be well and NO _xReact and consume.

Therefore, though the HC composition in exhaust cause under the situation of covering of catalyzer, as long as NO _xThe regeneration of occlusion reducing catalyst is not finished, the H in the downstream side of catalyzer ₂Sensor just can not detect hydrogen.

In the present invention, in the process of carrying out dense intensified operation, by being arranged on NO _xThe H in the downstream side of occlusion reducing catalyst ₂Sensor is then judged NO under the situation of hydrogen composition _xThe regeneration of occlusion reducing catalyst is finished, and stops regenerative operation.

In view of the above description, in the present invention,, also can accurately judge NO even in exhaust, comprise under the situation of quite a large amount of HC compositions _xThe regeneration of occlusion reducing catalyst is finished, and stops regenerative operation.Therefore, can prevent occurrence of a problem: at NO _xWhen stopping regenerative operation before the regeneration of occlusion reducing catalyst is finished, exhaust gas purification ability variation.In addition, regenerative operation still continues even can prevent regeneration to finish afterwards, and the problem of fuel consumption increase.Therefore, according to the present invention, NO can suitably regenerate _xThe occlusion reducing catalyst.

According to the invention that claim 3 is described, a kind of Exhaust gas purifying device of the internal-combustion engine according to claim 1 is provided, wherein, H ₂Sensor is arranged on NO at least _xIn the exhaust passage of the outlet side of occlusion reducing catalyst, this regenerative operation comprises following operation: at first the exhaust with dense air fuel ratio is fed to NO _xThe occlusion reducing catalyst then, is fed to NO with the exhaust of chemically correct fuel _xThe occlusion reducing catalyst, and, according to the H of outlet side ₂Sensor to the hydrogen constituent concentration determine that the air fuel ratio of exhaust is transformed into the time of chemically correct fuel from dense air fuel ratio.

That is to say that the invention of describing according to claim 3 is by switching to air fuel ratio dense air fuel ratio and chemically correct fuel two steps are carried out regenerative operation.For example, in some cases, adopt NO _xThe high occlusion type NO that occlusion capacity strengthens _xThe occlusion reducing catalyst.High occlusion type NO _xThe occlusion reducing catalyst is that a kind of utilization has and NO _xThe occlusion material of high-affinity significantly increases the NO of per unit volume occlusion _xThe NO of amount _xThe occlusion reducing catalyst.At high occlusion type NO _xIn the occlusion reducing catalyst, because occlusion material and NO _xThe affinity height, therefore separate a large amount of NO of sucking-off at the initial stage of regeneration _xAfterwards, NO _xThe speed of desorb reduces.Therefore, for holomorphosis NO _xThe occlusion reducing catalyst need carry out regenerative operation for a long time.

Therefore, at high occlusion type NO _xIn the regenerative operation of occlusion reducing catalyst,,, the exhaust of dense air fuel ratio is fed to NO at the initial stage of regenerative operation in order to suppress the increase of fuel consumption _xIn the occlusion reducing catalyst, so that the quite a large amount of NO of desorb _xAnd reduction and cleaning catalyst.Afterwards, the air fuel ratio of exhaust converts chemically correct fuel to, and NO _xThe occlusion reducing catalyst is through considerable time holomorphosis.

In this case, at the initial stage of dense intensified operation, quite a large amount of NO _xFrom NO _xThe desorb of occlusion reducing catalyst, be included in the dense air fuel ratio exhaust all hydrogen compositions by with NO _xThe reaction and consume, yet, when the desorb of initial stage is finished and NO _xWhen desorption rate reduced, a part that is included in the hydrogen composition in the exhaust flow to NO _xThe downstream side of occlusion reducing catalyst, and not with NO _xReaction.

In the present invention, as the H in downstream side ₂When sensor arrived the hydrogen composition, the air fuel ratio of exhaust was transformed into chemically correct fuel from dense air fuel ratio.Therefore, even when adopting high occlusion type NO _xDuring the occlusion reducing catalyst, NO _xThe occlusion reducing catalyst also can suitably be regenerated, and can unnecessarily not proceed dense air-fuel ratio operation for a long time when regenerative operation.

In this regard, when the air fuel ratio of exhaust becomes chemically correct fuel, seldom produce hydrogen.Therefore, the H in downstream side ₂Sensor is less than hydrogen.

According to the invention that claim 4 is described, a kind of Exhaust gas purifying device of the internal-combustion engine according to claim 1 is provided, wherein, H ₂Sensor is arranged on NO _xIn the exhaust passage of the inlet side of occlusion reducing catalyst, and when carrying out regenerative operation, control flows into NO _xThe air fuel ratio of the exhaust of occlusion reducing catalyst, feasible H by inlet side ₂The hydrogen constituent concentration of the exhaust of sensor can be a predetermined target value.

That is to say, in the invention that claim 4 is described, NO _xThe H of the inlet side of occlusion reducing catalyst (upstream side) ₂Sensor flows into NO _xThe concentration of the hydrogen composition of occlusion reducing catalyst, and so that the detectable concentration of hydrogen composition becomes the mode of desired value, by the air fuel ratio of feedback control exhaust.

Therefore, when carrying out regenerative operation, can always an amount of hydrogen be fed to NO _xOcclusion reducing catalyst, and the NO that can suitably regenerate _xThe occlusion reducing catalyst.

According to the present invention that claim 5 is described, provide a kind of Exhaust gas purifying device of the internal-combustion engine according to claim 4, wherein, when the beginning regenerative operation, the desired value height of hydrogen constituent concentration, then, As time goes on, the desired value of this hydrogen constituent concentration reduces gradually.

That is to say, in the invention that claim 5 is described, when regenerative operation, flow into NO _xThe concentration of the hydrogen composition of occlusion reducing catalyst is according to NO _xDesorption rate is provided with, wherein, and at this NO _xUnder the desorption rate, from NO _xDesorb NO in the occlusion reducing catalyst _x

When regenerative operation, when flowing into NO _xThe air fuel ratio of the exhaust of occlusion reducing catalyst is during from rare thickening, after air fuel ratio just has been transformed into dense air fuel ratio, from NO _xThe NO of occlusion reducing catalyst desorb _xAmount big.Then, NO _xAmount reduce as time passes.

Therefore, when regenerative operation, flowing into NO _xThe hydrogen constituent concentration of the exhaust of occlusion reducing catalyst is set to height when the beginning regenerative operation, reduce gradually then.In view of the above description, can be according to from NO _xThe NO of occlusion reducing catalyst desorb _xAmount supply the hydrogen composition, and the NO that can suitably regenerate _xThe occlusion reducing catalyst.

According to the invention that claim 6 is described, a kind of Exhaust gas purifying device of the internal-combustion engine according to claim 2 is provided, wherein, according to the H in downstream side ₂Sensor to the concentration of hydrogen composition judge from regenerative operation and begin the time history that finishes to regenerative operation, judge NO _xThe degree of deterioration of occlusion reducing catalyst.

That is to say, in the invention that claim 6 is described, based on the H in downstream side ₂The hydrogen constituent concentration that sensor arrives is judged NO _xThe regeneration of occlusion reducing catalyst is finished.At this moment, according to from NO _xNO is judged in the time history that the beginning of occlusion reducing catalyst regenerative operation finished to regenerative operation _xThe degree of deterioration of occlusion reducing catalyst.

Begin to finishing required time and NO from regenerative operation _xThe NO of occlusion reducing catalyst occlusion _xAmount corresponding.Work as NO _xOcclusion reducing catalyst variation and can be by the NO of occlusion _xAmount when therefore reducing, finishing the required time of regeneration shortens.

Therefore, shorten in the required time under the situation of preset judgment value, can judge NO _xThe occlusion reducing catalyst is variation.

In view of the above description, according to the present invention, NO suitably regenerates _xThe occlusion reducing catalyst can accurately be judged NO _xThe degree of deterioration of occlusion reducing catalyst.

According to the invention that claim 7 is described, a kind of Exhaust gas purifying device of internal-combustion engine is provided, comprise the NO in the exhaust passage that is arranged on internal-combustion engine _xThe occlusion reducing catalyst, when the air-fuel ratio of the exhaust of inflow catalyst, this NO _xThe occlusion reducing catalyst is by absorbing and adsorbing one of them, perhaps by absorbing and absorption comes occlusion to be included in NO in the exhaust _x, and when the air fuel ratio of exhaust is chemically correct fuel or dense air fuel ratio, this NO _xThe utilization of occlusion reducing catalyst is included in the reduction composition reduction in the exhaust and purifies the NO of occlusion _x, the Exhaust gas purifying device of this internal-combustion engine also comprises: NO _xThe occlusion reducing catalyst, the upstream side and the downstream side of its exhaust passage of being arranged on internal-combustion engine of being one another in series; And H2 sensor, it is arranged in the exhaust passage between the NOx occlusion reducing catalyst in the NOx occlusion reducing catalyst of the upstream side that is one another in series and downstream side, be used to detect the hydrogen constituent concentration in the exhaust, wherein: when NOx occlusion reducing catalyst will reduce and purify the NOx of occlusion in rare air-fuel ratio operation process at motor, when the exhaust of carrying out wherein dense air fuel ratio or chemically correct fuel is fed to NOx occlusion reducing catalyst and reaches the regenerative operation of predetermined amount of time, according to H ₂Sensor to exhaust in the hydrogen constituent concentration, control flows into NO _xThe air fuel ratio of the exhaust of the upstream side of occlusion reducing catalyst.

That is to say, in the invention that claim 7 is described, two NO _xThe series connection of occlusion reducing catalyst is arranged in the exhaust passage, and H ₂Sensor is arranged on upstream side NO _xOcclusion reducing catalyst and downstream side NO _xBetween the occlusion reducing catalyst.

In so-called serial type catalyzer, wherein, two NO _xThe series connection of occlusion reducing catalyst is provided with NO _xThe upstream side of occlusion reducing catalyst (prime) is at the NO of rare air-fuel ratio operation occlusion _xAmount and NO _xThe downstream side of occlusion reducing catalyst (back level) is at the NO of rare air-fuel ratio operation occlusion _xThe amount difference.In addition, at NO _xDuring the regenerative operation of the upstream side of occlusion reducing catalyst (prime), the state that regeneration is carried out with at NO _xThe difference in the downstream side of occlusion reducing catalyst (back level).Therefore, work as H ₂Sensor is arranged on back level NO _xDuring the downstream side of occlusion reducing catalyst, if based on the H of setting like this ₂The hydrogen constituent concentration control regenerative operation that sensor arrives may go wrong.

In the present invention, because H ₂Sensor is arranged on prime NO _xOcclusion reducing catalyst and back level NO _xBetween the occlusion reducing catalyst, and owing to the H based on setting like this ₂Sensor to exhaust in the hydrogen constituent concentration control regenerative operation that comprises, NO therefore can suitably regenerate _xThe occlusion reducing catalyst.

The invention of Miao Shuing according to Claim 8 provides a kind of Exhaust gas purifying device of the internal-combustion engine according to claim 7, wherein, and the NO of upstream side _xThe NO of occlusion reducing catalyst _xOcclusion capacity is greater than the NO in downstream side _xThe NO of occlusion reducing catalyst _xOcclusion capacity, the NO of upstream side _xThe O of occlusion reducing catalyst ₂Storage capacity is less than the NO in downstream side _xThe O of occlusion reducing catalyst ₂Storage capacity, and, be carried on the NO of upstream side _xThe amount of the platinum composition of occlusion reducing catalyst is greater than the NO that is carried on the downstream side _xThe amount of the platinum composition of occlusion reducing catalyst.

That is to say the invention of Miao Shuing according to Claim 8, the NO of upstream side _xThe NO of occlusion reducing catalyst _xOcclusion capacity is greater than the NO in downstream side _xThe NO of occlusion reducing catalyst _xOcclusion capacity, and the NO of upstream side _xThe O of occlusion reducing catalyst ₂Storage capacity is less than the NO in downstream side _xThe O of occlusion reducing catalyst ₂Storage capacity.In addition, be carried on the NO of upstream side _xThe amount of the platinum composition of occlusion reducing catalyst is greater than the NO that is carried on the downstream side _xThe amount of the platinum composition of occlusion reducing catalyst.

In addition, as the NO of upstream side _xWhen the amount of the carrying Pt of occlusion reducing catalyst increases, be included in the interior most of NO of exhaust in the oxidation of catalyzer place, and become NO ₂Therefore, except the NO of the per unit volume occlusion that makes upstream side _xOutside amount is arranged to greatly, upstream side NO _xThe occlusion effectively of occlusion reducing catalyst, reduction and purification NO _x

At two NO _xThe occlusion reducing catalyst is one another in series under the situation about being provided with, and nearly all occlusion and reduction purify all by upstream side NO _xThe occlusion reducing catalyst is carried out.Therefore, by with upstream side NO _xThe NO of occlusion reducing catalyst _xOcclusion capacity (can be at NO _xThe NO of occlusion in the occlusion reducing catalyst _xMaximum flow) be set to big value, can increase can be by upstream side NO _xThe NO that the occlusion reducing catalyst is handled _xAmount.In addition, by making upstream side NO _xThe storage O of occlusion reducing catalyst ₂Storage capacity reduce, in the regenerative operation process, be included in hydrogen composition in the exhaust and HC and CO composition not with upstream side NO _xThe oxygen of occlusion reaction in the catalyzer of occlusion reducing catalyst, and the most of HC in exhaust and CO composition are used for reductive NO _x

According to the invention that claim 9 is described, a kind of Exhaust gas purifying device of the internal-combustion engine according to claim 7 or 8 is provided, wherein, when carrying out regenerative operation, according to H ₂Sensor to exhaust in the hydrogen constituent concentration, judge to stop time of regenerative operation.

According to the invention of claim 9 description, according to being arranged on prime and back level NO _xH between the occlusion reducing catalyst ₂Hydrogen constituent concentration in the exhaust that sensor arrives is judged the moment that regenerative operation stops.

At serial type NO _xIn the occlusion reducing catalyst, when rare air-fuel ratio operation, be included in the most of NO in the exhaust _xAt prime NO _xOcclusion in the occlusion reducing catalyst.Therefore, prime NO _xThe NO of occlusion in the occlusion reducing catalyst _xAmount is significantly greater than back level NO _xThe NO of occlusion in the occlusion reducing catalyst _xAmount.In view of the foregoing, at serial type NO _xIn the occlusion reducing catalyst, prime NO fully importantly regenerates _xThe occlusion reducing catalyst.

At serial type NO _xIn the occlusion reducing catalyst, give back level NO usually _xThe occlusion reducing catalyst is set relatively large O ₂Storage capacity, level NO after making _xThe occlusion reducing catalyst can have the function of three-way catalyst.O ₂Storage capacity is following ability: NO when the air-fuel ratio of exhaust _xOcclusion reducing catalyst occlusion oxygen, and when the air-fuel ratio of exhaust NO _xThe oxygen of occlusion reducing catalyst desorb occlusion.Therefore, even at prime NO _xAfter the regeneration of occlusion reducing catalyst is finished, quite a large amount of H ₂Composition flows into back level NO _xDuring the occlusion reducing catalyst, the hydrogen composition is by from back level NO _xThe oxygen oxidation of occlusion reducing catalyst desorb.Therefore, at back level NO _xThe outlet side of occlusion reducing catalyst detects less than the hydrogen composition in exhaust.

Therefore, level NO after hydrogen sensor is arranged on _xDuring the outlet side of occlusion reducing catalyst, be difficult to the time of judging that accurately regenerative operation stops.That is to say, although as prime NO _xWhen the occlusion reducing catalyst was finished regeneration, serial type NO had generally regenerated _xThe NO of occlusion reducing catalyst _xOcclusion capacity, but in the exhaust in level downstream side, back, detect less than the hydrogen composition.Therefore, can not accurately judge the time that stops regenerative operation.

According to the present invention, because H ₂Sensor is arranged on serial type NO _xBetween the front stage catalyst of occlusion reducing catalyst and the back level catalyzer, and based on H ₂The time that regenerative operation stops is judged in the output of sensor, and serial type NO can suitably regenerate _xThe occlusion reducing catalyst.

According to the invention that claim 10 is described, a kind of Exhaust gas purifying device of the internal-combustion engine according to claim 7 or 8 is provided, wherein, flow into NO by making _xThe air fuel ratio of the exhaust of occlusion reducing catalyst is dense air fuel ratio and improves its temperature simultaneously, and this device is also carried out and poisoned Regeneration Treatment, so as with from NO _xThe NO of occlusion reducing catalyst _xTogether, the desorb occlusion is at NO _xSulfur oxide in the occlusion reducing catalyst, and, poison in the process of Regeneration Treatment, in execution according to H ₂Sensor to exhaust in the hydrogen constituent concentration, control flows into the NO of upstream side _xThe air fuel ratio of the exhaust of occlusion reducing catalyst.

That is to say, according to the invention of claim 10 description, according to being arranged on prime and back level NO _xH between the occlusion reducing catalyst ₂The output of sensor is carried out and is poisoned Regeneration Treatment control.

When air-fuel ratio, NO _xThe occlusion reducing catalyst with occlusion NO _xSO in the identical mode occlusion exhaust _xYet, because SO _xStrong with the affinity of occlusion material, in case SO _xBe occluded in NO _xIn the occlusion reducing catalyst, then be difficult to only be used for NO by execution _xThe dense intensified operation of occlusion reducing catalyst regeneration makes SO _xFrom NO _xDesorb in the occlusion reducing catalyst.Therefore, in case SO _xBe occluded in NO _xIn the occlusion reducing catalyst, SO then _xGradually in the catalyzer inner accumulated.

Therefore, work as NO _xThe SO of occlusion in the occlusion reducing catalyst _xWhen amount increases, can occlusion at NO _xNO in the occlusion reducing catalyst _xAmount reduce, that is to say NO _xOcclusion capacity reduces.That is to say, caused so-called SO _xPoison.

In order to solve SO _xPoison problem, need poison Regeneration Treatment, wherein, when flowing into NO _xWhen the air fuel ratio of the exhaust of occlusion reducing catalyst remains on dense air fuel ratio, NO _xThe temperature of occlusion reducing catalyst raises.Even in poisoning Regeneration Treatment, when the hydrogen composition is fed to NO _xDuring the occlusion reducing catalyst, also can increase SO _xFrom NO _xThe SO of occlusion reducing catalyst desorb _xDesorption rate, and can finish at short notice and poison Regeneration Treatment.

In this case, in order suitably to poison Regeneration Treatment, for example, need with NO _xThe mode that the regenerative operation of occlusion reducing catalyst is identical is suitably judged the moment that is used to stop poisoning Regeneration Treatment.Yet, at serial type NO _xIn the occlusion reducing catalyst, there are some special circumstances, for example, at prime NO _xThe SO of occlusion in the occlusion reducing catalyst _xAmount with at back level NO _xThe SO of occlusion in the occlusion reducing catalyst _xThe amount difference.Therefore, if according to being arranged on NO _xThe H in occlusion reducing catalyst downstream side ₂The output of sensor poisons Regeneration Treatment, then is difficult to suitably poison Regeneration Treatment.

According to the present invention, according to being arranged on prime and back level NO _xH between the occlusion reducing catalyst ₂The output of sensor poisons Regeneration Treatment.Therefore, except NO _xThe regeneration of occlusion reducing catalyst can also suitably poison Regeneration Treatment.

According to the invention that claim 11 is described, a kind of Exhaust gas purifying device of the internal-combustion engine according to claim 10 is provided, wherein, when execution poisons Regeneration Treatment, according to H ₂Sensor to exhaust in the hydrogen constituent concentration, judge to stop the time of poisoning Regeneration Treatment.

Because hydrogen has very strong reducing capacity, when poisoning Regeneration Treatment, when flowing into NO _xWhen the exhaust in the occlusion reducing catalyst comprises the hydrogen composition, this hydrogen composition immediately with from NO _xThe SO of occlusion reducing catalyst desorb _xReaction.Therefore, in the mode identical, even poisoning Regeneration Treatment, SO with dense intensified operation _xDuring by desorb, the hydrogen composition that is included in the exhaust also can be used to reduce SO _xAnd be consumed.Therefore, there is not hydrogen to flow into NO _xIn the exhaust in the downstream side of occlusion reducing catalyst.

Therefore, with judge NO _xIdentical mode is finished in the regeneration of occlusion reducing catalyst, even in poisoning Regeneration Treatment, and also can be according to being arranged on NO _xThe H in the downstream side of occlusion reducing catalyst ₂SO is judged in the output of sensor _xThe finishing of desorb.

Yet, in this case, at serial type NO _xIn the occlusion reducing catalyst, be included in the most of SO in the exhaust _xBe occluded in prime NO _xIn the occlusion reducing catalyst.Therefore, prime NO importantly _xThe occlusion reducing catalyst is from SO _xFully regeneration in poisoning.

At serial type NO _xIn the occlusion reducing catalyst, back level NO _xCerium dioxide (Ce) composition that the carrying of occlusion reducing catalyst is quite a large amount of is so that strengthen its O ₂Storage capacity.Therefore, be included in the interior SO of exhaust _xWith at back level NO _xThe cerium dioxide combination of occlusion reducing catalyst, and form sulphate.In this case, cerium dioxide and SO _xCombination force be not very strong, SO _xCan be at an easy rate from back level NO _xSeparate sucking-off in the occlusion reducing catalyst.

Therefore, at serial type NO _xPoisoning in the Regeneration Treatment of occlusion reducing catalyst is at prime NO _xThe time point that poisons the Regeneration Treatment termination of occlusion reducing catalyst, all SO _xAll from back level NO _xSeparate sucking-off in the occlusion reducing catalyst.Therefore, by based on from prime NO _xThe SO of occlusion reducing catalyst _xDesorption state judge to stop moment of poisoning Regeneration Treatment, can more effectively carry out and poison Regeneration Treatment.

According to the present invention, when poisoning Regeneration Treatment, when being arranged on prime and back grade NO _xH between the occlusion reducing catalyst ₂During the hydrogen of sensor in the exhaust, poison Regeneration Treatment and be terminated.Therefore, not only can suitably carry out NO _xThe regeneration of occlusion reducing catalyst but also can suitably carry out SO _xRegeneration.

According to the invention that claim 12 is described, a kind of Exhaust gas purifying device of internal-combustion engine according to Claim 8 is provided, wherein, according to H ₂The concentration of the hydrogen composition in the exhaust that sensor arrives is judged from regenerative operation to begin to the time period of regenerative operation end, and judges the NO of upstream side according to this time period _xThe degree of deterioration of occlusion reducing catalyst.

That is to say, according to the invention of claim 12 description, by being arranged on the H between prime and the back level ₂Serial type NO is judged in the output of sensor _xThe prime NO of occlusion reducing catalyst _xThe degree of deterioration of occlusion reducing catalyst.

At serial type NO _xIn the occlusion reducing catalyst, prime NO _xThe NO of occlusion reducing catalyst _xOcclusion capacity is than back level NO _xThe NO of occlusion reducing catalyst _xOcclusion capacity is more important.On the other hand, serial type NO _xThe degree of deterioration of occlusion reducing catalyst is from prime NO _xThe occlusion reducing catalyst strengthens.Therefore, in order accurately to judge serial type NO _xThe degree of deterioration of occlusion reducing catalyst, hydrogen sensor must be arranged on prime and back level NO _xBetween the occlusion reducing catalyst, rather than be arranged on back level NO _xThe downstream side of occlusion reducing catalyst.In the present invention, H ₂Sensor is arranged on prime and back level NO _xPosition between the occlusion reducing catalyst.Therefore, according to the present invention, serial type NO can suitably regenerate _xThe occlusion reducing catalyst.At this moment, can accurately judge prime NO _xThe degree of deterioration of occlusion reducing catalyst.

From above-mentioned explanation, scrutablely be, according to the invention of in each claim, describing, by based on H ₂Sensor to be included in hydrogen constituent concentration in the exhaust, control NO _xThe regenerative operation of occlusion reducing catalyst, NO can suitably regenerate _xThe occlusion reducing catalyst.

Description of drawings

Fig. 1 illustrates the allocation plan of profile that the present invention is applied to the embodiment of motor vehicle internal combustion engine;

Fig. 2 is the view of the relation between the air fuel ratio that schematically shows hydrogen constituent concentration and exhaust in the exhaust;

Fig. 3 is for describing the NO in the first embodiment of the present invention _xThe flow chart of the regenerative operation of occlusion reducing catalyst;

Fig. 4 is for describing the NO in the second embodiment of the present invention _xThe flow chart of the regenerative operation of occlusion reducing catalyst;

Fig. 5 is for describing the NO in the third embodiment of the present invention _xThe flow chart of the regenerative operation of occlusion reducing catalyst;

Fig. 6 is the NO that is described in the fourth embodiment of the present invention _xDuring the regenerative operation of occlusion reducing catalyst, set the view of hydrogen concentration desired value;

Fig. 7 is for describing the NO in the fifth embodiment of the present invention _xThe flow chart of the deterioration judgment operation of occlusion reducing catalyst;

Fig. 8 is the view that is similar to Fig. 1, is used to describe the structure of the sixth embodiment of the present invention; And

Fig. 9 is the NO that describes in the seventh embodiment of the present invention _xThe flow chart that poisons Regeneration Treatment of occlusion reducing catalyst.

Embodiment

Below with reference to accompanying drawing embodiments of the invention are described.

Fig. 1 illustrates the allocation plan of profile that the present invention is applied to the embodiment of motor vehicle internal combustion engine.

Among Fig. 1, reference character 1 is the internal-combustion engine of Motor Vehicle.In the present embodiment, motor 1 is 4 cylinder gasoline engines, has four cylinder #1 to #4.In cylinder #1 to #4, the Fuelinjection nozzle 111 to 114 that is used for burner oil is arranged on the entry end of cylinder separately.Motor 1 is a lean-combustion engine, and it can move in the wide air fuel ratio scope from dense air fuel ratio to rare air fuel ratio, and in the present embodiment, the major part in the operation area is in rare air fuel ratio operation.

In this enforcement, cylinder #1 to #4 is divided into two cylinder group.In this case, each cylinder group comprises two cylinders, and its ignition timing is not adjacent to each other.For example, in the embodiment shown in fig. 1, the ignition order of lighting cylinder is 1-3-4-2.Therefore, cylinder #1 and #4 form a cylinder group, and cylinder #2 and #3 form a cylinder group.The exhaust end of each cylinder is connected to the gas exhaust manifold of each cylinder.The gas exhaust manifold of each cylinder is connected to the exhaust passage of each cylinder group.

In Fig. 1, reference character 21a is a gas exhaust manifold, the exhaust end that is used for the cylinder group that will be made up of cylinder #1 and #4 is connected to independent exhaust passage 2a, and reference character 21b is gas exhaust manifold, and the exhaust end that is used for the cylinder group that will be made up of cylinder #2 and #3 is connected to independent exhaust passage 2b.In the present embodiment, in

independent exhaust passage

2a, 2b, start catalysts 5a, the 5b that comprises three-way catalyst is set respectively.

Independent exhaust passage

2a, 2b are connected to common exhaust passage 2 in the downstream side of start catalysts.

In common exhaust passage 2, transducer 70 is set, wherein, below with the NO that describes _xThe occlusion reducing catalyst is contained in the housing.

In Fig. 1, reference character the 31, the 33rd, upstream side H ₂Sensor and downstream side H ₂Sensor, it is separately positioned on the inlet side and the outlet side of transducer 70, and this transducer is arranged on the exhaust passage 2.These H ₂Sensor is included in the hydrogen (H in the exhaust ₂) concentration of composition.

In Fig. 1, reference character 30 is electronic control modules (ECU) of motor 1.In the present embodiment, ECU30 is the microcomputer of known type, comprises RAM, ROM and CPU.ECU30 carries out the basic controlling of motor, for example ignition timing control, fuel injection control or the like.

Except above-mentioned basic controlling, the ECU30 of present embodiment carries out regenerative operation, wherein, and whenever NO _xThe NO of occlusion in the occlusion reducing catalyst 7 _xAmount be increased to predetermined value, the amount that the fuel of injection valve 111 to 114 sprays increases, so that make motor move a bit of time under dense air fuel ratio or chemically correct fuel.Like this, NO _xThe NO of occlusion reducing catalyst 7 desorb occlusions _xThereby, can reduce and purifying exhaust gas.

In addition, in the present embodiment, when carrying out above-mentioned regenerative operation, according to H ₂The NO that

sensor

31,33 detects _xThe concentration of the hydrogen composition in the inlet of occlusion reducing catalyst 7 or the exhaust of outlet, the air fuel ratio of exhaust during ECU30 control regenerative operation.

In order to carry out above-mentioned control, column signal under the input end input of ECU30, described signal is the parameter of expression engine operation state.The signal of input is: with the corresponding signal of the inlet pressure of motor, this signal sends from the inlet pressure transducer 41 that is arranged on motor inlet manifold (not shown); With the corresponding signal of the speed of motor, this signal sends from the engine rotation speed sensor 43 that the bent axle (not shown) near motor is provided with; And the signal of the depression amount (opening degree of accelerator pedal) of expression braking pedal, this signal sends from the acceleration opening degree sensor 45 that the accelerator pedal (not shown) near motor 1 is provided with.In addition, input is from H ₂That

sensor

31,33 sends, be included in NO _xH in the exhaust of the entrance and exit of occlusion reducing catalyst 7 ₂Concentration.

The outlet end of ECU30 is connected to the Fuelinjection nozzle 111 to 114 of cylinder by fuel spray circuit (not shown), so that control fuel injection amount and the fuel injection timing that is ejected into each cylinder.

Next, the NO of present embodiment is described _xOcclusion reducing catalyst 7.

The NO of present embodiment _xOcclusion reducing catalyst 7 composed as follows.For example, employing is made catalyst carrier by forming honey comb like steinheilite.Surface in this catalyst carrier is provided with aluminium paint.On this aluminium lamination, be loaded with from alkali metal such as potassium K, sodium Na, lithium Li and caesium Cs, such as the alkaline-earth metal of barium Ba and calcium Ca, and a kind of composition of selecting in the group of forming such as the rare earth metal of lanthanum La, cerium Ce and yttrium Y, and a kind of composition from selecting such as the precious metal of platinum Pt.Flowing into NO _xUnder the situation of the air-fuel ratio of the exhaust of occlusion reducing catalyst, NO _xThe occlusion reducing catalyst absorbs nitrate ion NO in the exhaust ₃ ^-The NO of form _x(NO ₂, NO).When the oxygen concentration of exhaust is lowered, NO _xThe occlusion reducing catalyst is discharged the NO of occlusion _x, in other words, NO _xThe occlusion reducing catalyst according to the air fuel ratio of exhaust to NO _xCarry out occlusion and desorb.

That is to say that motor 1 moves and flow into NO under rare air fuel ratio _xThe exhaust of occlusion reducing catalyst is under the situation of rare air fuel ratio, is included in the NO in the exhaust _x(NO) oxidized, for example on platinum Pt, and become NO ₂, further oxidation forms nitrate ion again.In this case, for example adopt BaO as occlusion material, these nitrate ions are absorbed in the occlusion material, and combine with barium oxide BaO, and with nitrate ion NO ₃ ^-Form be diffused in the occlusion material.Therefore, in lean atmosphere, be included in the NO in the exhaust _xWith the form occlusion of nitrate at NO _xIn the occlusion reducing catalyst.

Flowing into NO _xUnder the situation that oxygen concentration in the exhaust of occlusion reducing catalyst reduces, that is, become under the situation of chemically correct fuel or dense air fuel ratio in the air fuel ratio of exhaust, the nitrogen ion production on the platinum Pt reduces.Therefore, the nitrate ion NO in the occlusion material is carried out in reaction along reverse ₃ ^-With NO ₂Form from the occlusion material desorb.In this case, when such as CO or H ₂Be present in the exhaust or be present under the situation of exhaust NO at the HC composition as the composition of reducing agent ₂On platinum Pt, reduce by these compositions.

In the atmosphere of rare air fuel ratio, NO _xOcclusion reducing catalyst 7 according to above-mentioned mechanism by in occlusion material, being included in NO in the exhaust with the form occlusion of nitrate ion _xTherefore, because the concentration of nitrate ion in occlusion material increases, new nitrate ion is difficult to be absorbed in the occlusion material, and the NO in exhaust _xPurification ratio reduces.Work as NO _xThe NO of occlusion reducing catalyst occlusion _xAmount reaches in limited time, that is to say the nitrate ion concentration increase in the occlusion material and when reaching capacity concentration, NO _xThe occlusion reducing catalyst is difficult to occlusion and is contained in the interior NO of exhaust _x

In the present embodiment, utilize the relation of setting up by experiment in advance based on the parameter of representing engine operational conditions, ECU30 estimates the NO that time per unit produces from motor 1 _xAmount, wherein, described parameter for example is the opening degree of motor inlet pressure, engine speed and accelerator pedal.The motor time per unit produces NO _xThe predetermined percentage and the time per unit NO of amount _xThe NO of occlusion in the occlusion reducing catalyst _xAmount corresponding.Therefore, can be by the NO of combination by the generation of motor time per unit _xThe predetermined percentage of amount calculate NO _xThe NO of occlusion reducing catalyst 7 occlusions _xAmount.Therefore, be called as NO _xThe associated value of counter and NO _xThe NO of occlusion in the occlusion reducing catalyst 7 _xAmount corresponding.

In addition, ECU30 is by carrying out the dense intensified operation NO that regenerates _xThe occlusion reducing catalyst, wherein, whenever this NO _xCounter reaches predetermined value, then by move motor 1 under dense air fuel ratio in the short time exhaust of dense air fuel ratio is fed to NO _xThe occlusion reducing catalyst.In view of the above description, NO _xOcclusion reducing catalyst 7 is always at the NO of occlusion _xMeasure occlusion NO under the very low condition _xTherefore, can make NO _xThe occlusion reducing catalyst keeps high NO _xPurification ratio.

In this regard, replace the above-mentioned NO that uses _xCounter is estimated NO _xNO in the occlusion reducing catalyst 7 _xHold-up, by NO is set _xSensor detects NO _xThe NO of the exhaust in the downstream side of occlusion reducing catalyst 7 _xConcentration, and then judge dense-reinforcement execution moment.

Work as NO _xThe NO of occlusion reducing catalyst 7 _xWhen hold-up increases, NO _xThe NO of occlusion reducing catalyst 7 _xPurifying ability reduces, and the NO in the exhaust _xA part through NO _xOcclusion reducing catalyst 7 but not by occlusion in it.Therefore, at NO _xNO is placed in the downstream side of occlusion reducing catalyst 7 _xSensor is worked as NO _xNO in the exhaust of sensor _xConcentration increase and when reaching predetermined value (, work as NO _xThe NO of occlusion in the occlusion reducing catalyst 7 _xWhen amount increases), can carry out dense-intensified operation.

(1) first embodiment

Below with reference to Fig. 2 and Fig. 3, the first embodiment of the present invention is described.

As mentioned above, in the present embodiment, whenever NO _xThe NO of occlusion reducing catalyst 7 _xWhen hold-up reaches prearranging quatity, carry out dense intensified operation, so that NO _x7 regeneration of occlusion reducing catalyst.

For the NO that suitably regenerates _xThe occlusion reducing catalyst need be at NO _xBefore the regeneration of occlusion reducing catalyst is finished, carry out dense intensified operation, and after regeneration was finished, the air fuel ratio of motor operation turned back to rare air fuel ratio.

Usually, described as Japanese patent application publication No. 2692380, by based on being arranged on NO _xThe O in the downstream side of occlusion reducing catalyst ₂NO is judged in the output of sensor _xFinishing of occlusion reducing catalyst regeneration, and in dense intensified operation process, work as O ₂The air fuel ratio in the catalyzer downstream side of sensor is then judged NO when chemically correct fuel is transformed into rare air fuel ratio _xThe regeneration of occlusion reducing catalyst is finished.Work as NO _xWhen the regeneration of occlusion reducing catalyst was finished, the air fuel ratio of exhaust turned back to rare air fuel ratio.

Yet as mentioned above, when the amount of the HC composition in being included in exhaust was big, the HC composition was attached to NO _xThe surface of the catalyst component of occlusion reducing catalyst, and cause the covering that makes the catalysis variation.When causing covering, flow into NO _xThe part of the HC composition that comprises in the exhaust in the occlusion reducing catalyst through catalyzer and not with NO _xReact.Therefore, at NO _xEven occlusion reducing catalyst downstream side is NO _xThe regeneration of occlusion reducing catalyst is not finished as yet, air-fuel ratio.

Therefore, when according to being arranged on NO _xThe O in occlusion reducing catalyst downstream side ₂NO is judged in the output of sensor _xWhen the regeneration of occlusion reducing catalyst was finished, even the regeneration of catalyzer is not finished as yet, dense intensified operation also was terminated in some cases.Therefore, can not fully carry out NO _xThe regeneration of occlusion reducing catalyst.

Therefore, in the present embodiment, be arranged on NO by utilization _xThe H in occlusion reducing catalyst downstream side ₂The output of sensor is when judging NO _xThe regeneration of occlusion reducing catalyst stops dense intensified operation when finishing, solve the problems referred to above.

For example, when the air-fuel ratio of the exhaust of motor, HC, the CO and the H that when burning, produce ₂O causes water-gas shift reaction (CO+H ₂O → CO ₂+ H ₂) or steam reformation (HC+H ₂O → CO ₂+ H ₂), and produce hydrogen.Under the situation of common internal-combustion engine,, produce H by above-mentioned reaction at dense air fuel ratio run duration ₂Yet,, these reactions can further be quickened by three-way catalyst.Therefore, in having the internal-combustion engine of three-way catalyst, be used for NO _xIn the dense-intensified operation process of occlusion reducing catalyst regeneration, comprise quite a large amount of hydrogen in the exhaust, wherein, three-way catalyst for example is at NO _xStart catalysts 5a in the exhaust passage of the upstream side of occlusion reducing catalyst, 5b.

Except three-way catalyst, be arranged on the exhaust passage if can produce the catalyst for preparing hydrogen of water-gas shift reaction or steam reformation effectively, also can in the process of motor, produce hydrogen with dense air fuel ratio operation.

Fig. 2 is air fuel ratio and the H that exhaust is shown ₂The plotted curve that concerns between the production.Fig. 2 shows H in

start catalysts

5a, 5b ₂Relation between the air fuel ratio of production and exhaust.As shown in Figure 2, when air-fuel ratio, the H at the three-way catalyst place ₂Production is zero.Yet, when air fuel ratio exceeds chemically correct fuel and thickens, that is to say, when air fuel ratio reduces, the H at the three-way catalyst place ₂The production substantial linear increases.Though H ₂Actual production differ from one another, but when air fuel ratio reduces, the H that engine combustion is indoor ₂Production and using system H ₂H under the situation of catalyst replaced three-way catalyst ₂Production is linear increasing basically.

The hydrogen composition that produces when carrying out dense intensified operation as mentioned above has very strong reducing capacity.Therefore, the hydrogen composition that so produces can be directly and NO _xComponent reaction, and do not use catalyst component such as Pt.Therefore, even comprise quite a large amount of HC compositions and caused covering in the exhaust, and during the specificity of catalyst variation, the hydrogen composition in exhaust also can be well and NO _xThe NO of desorb in the occlusion reducing catalyst _xReact.

Therefore, as long as NO _xFrom NO _xThe desorb of occlusion reducing catalyst, the hydrogen composition that in exhaust, comprises just by with NO _xNO on the occlusion reducing catalyst _xThe reaction and consume.Therefore, the hydrogen composition that comprises in the exhaust does not flow to NO _xThe downstream side of occlusion reducing catalyst.

Therefore, when carrying out dense intensified operation, by being arranged on NO _xThe H in the downstream side of occlusion reducing catalyst ₂Sensor 33 detects under the situation of the hydrogen composition that comprises in the exhaust, can judge NO _xThe NO of occlusion reducing catalyst _xDesorb (regeneration) is finished.

In this regard, for the H of present embodiment ₂Sensor 33 (31) for example can use the Pd/Ni alloy sensor responsive especially to hydrogen.

The H of this type ₂Sensor is made by KK Toyoda Micro System, and puts goods on the market with trade mark " H2 scan ".Yet the sensor of Shi Yonging not only is confined to above-mentioned particular sensor in the present embodiment.Any sensor can use in the present embodiment, as long as this sensor can monitor the H in the exhaust rapidly, continuously ₂Concentration.

The NO of present embodiment is described below _xThe regenerative operation of occlusion reducing catalyst.

Fig. 3 is for clearly describing the NO of present embodiment _xThe flow chart of the regenerative operation of occlusion reducing catalyst.This operation is processed as a kind of routine, carries out with fixed intervals by ECU30.

In the operation shown in fig. 3, in step 301, judge whether the value of regenerative operation execute flag X is set at 1., when opening in the operation (not shown) of execution NO with the ECU30 branch _xThe NO of occlusion reducing catalyst 7 _xWhen hold-up was increased to predetermined value, the value of this sign X was set at 1.As mentioned above, in the present embodiment, by the NO of independent execution _xHold-up is estimated the operation (not shown), and ECU30 calculates above-mentioned NO _xCounter Value, this value is represented NO with fixed intervals _xThe NO of occlusion reducing catalyst _xHold-up.As this NO _xWhen Counter Value reached predetermined value, the value of regenerative operation execute flag X was set at 1.

In step 301, under the situation of X ≠ 1, NO _xNO in the occlusion reducing catalyst 7 _xHold-up does not reach predetermined value, therefore, does not need the NO that regenerates _xOcclusion reducing catalyst 7.Therefore, this operation stops immediately.In this case, do not carry out dense intensified operation, and motor 1 continues to carry out rare air-fuel ratio operation.

In step 301, under the situation of X=1, program proceeds to step 303, and carries out dense intensified operation (RS).In dense intensified operation, motor 1 moves under predetermined rich air-fuel ratio.Thereby in motor 1 and start

catalysts

5a, 5b, produce hydrogen.Therefore, the exhaust inflow NO that comprises the dense air fuel ratio of hydrogen composition _xIn the occlusion reducing catalyst 7.

Next, in step 305, from NO _xThe H in occlusion reducing catalyst 7 downstream sides ₂Sensor reads in NO _xHydrogen constituent concentration HRR in the exhaust in occlusion reducing catalyst downstream side.In step 307, judge whether hydrogen constituent concentration HRR is not less than predetermined value.In this case, α is the judgment value that is used to prevent false judgment, and be set near zero on the occasion of.

As mentioned above, when carrying out the RS operation, from NO _xOcclusion reducing catalyst 7 desorb NO _x, the hydrogen composition and the NO that in exhaust, comprise _xReaction also consumes.Therefore, by the H in downstream side ₂The hydrogen constituent concentration HRR vanishing that sensor 33 detects.Work as NO _xDesorb when finishing, that is, work as NO _xWhen the regeneration of occlusion reducing catalyst is finished, the H in downstream side ₂Sensor 33 detects hydrogen.

In the present embodiment, in step 307, when the concentration of hydrogen composition exceeds judgment value α, then judge NO _xThe regeneration of occlusion reducing catalyst 7 is finished, and program proceeds to step 309, and the value of regenerative operation execute flag is set at zero.When the value of regenerative operation execute flag is set at zero, at above-mentioned NO _xIn the counter calculating operation, NO _xThe value of counter turns back to zero.

In the next one of this operation was carried out, after step 301, operation stopped immediately, and the termination of dense intensified operation, and the air fuel ratio of exhaust turns back to rare air fuel ratio.

On the other hand, in step 307, under the situation of HRR＜α, judge that the hydrogen composition does not flow to NO _xThe downstream side of occlusion reducing catalyst 7, and NO _xThe regeneration of occlusion reducing catalyst 7 is not finished.Therefore, the executive termination of this operation, and the value of sign X remains on 1.In view of the above description, in the next one operation of this operation, still continue the dense intensified operation of step 303.

In the present embodiment, according to being arranged on NO _xThe H in the downstream side of occlusion reducing catalyst 7 ₂NO is accurately judged in the output of sensor _xThe regeneration of occlusion reducing catalyst 7 is finished, and the termination of dense intensified operation, that is to say that the air fuel ratio of exhaust turns back to rare air fuel ratio.Therefore, the NO that can accurately regenerate _xOcclusion reducing catalyst 7.

In this regard, in configuration shown in Figure 1, H ₂Sensor 31,33 is separately positioned on NO _xThe upstream side of occlusion reducing catalyst 7 and downstream side.Yet, H ₂Sensor 33 can certainly only be arranged on NO _xThe downstream side of occlusion reducing catalyst 7.

(2) second embodiments

The second embodiment of the present invention is described below.

In above-mentioned first embodiment, in the process of carrying out dense intensified operation, when being arranged on NO _xThe H in occlusion reducing catalyst 7 downstream sides ₂When sensor 33 detected hydrogen composition in the exhaust, dense intensified operation stopped, and the air fuel ratio of exhaust is transformed into rare air fuel ratio immediately.Yet some is different with first embodiment for present embodiment following.In the present embodiment, after dense intensified operation stopped, the air fuel ratio of exhaust remained on chemically correct fuel and reaches predetermined amount of time, and this air fuel ratio turns back to rare air fuel ratio then.

As mentioned above, adopt NO recently _xThe high occlusion type NO that occlusion capacity strengthens _xThe occlusion reducing catalyst.At high occlusion type NO _xIn the occlusion reducing catalyst, occlusion material and NO _xThe affinity height.Therefore, at the initial stage of dense intensified operation, at a large amount of NO _xAfter desorb, NO _xDesorption rate descend.Therefore, for holomorphosis NO _xThe occlusion reducing catalyst need be proceeded regenerative operation for a long time.Yet, when motor moves for a long time, can cause the problem of the fuel consumption increase of motor under dense air fuel ratio.When at NO _xWhen proceeding dense air fuel ratio operation under the low condition of desorption rate, HC that comprises in the exhaust and CO not with NO _xReaction, but flow to NO _xThe downstream side of occlusion reducing catalyst.Therefore, make the discharging variation.Therefore, in the present embodiment, at initial stage, from NO _xThe quite a large amount of NO of occlusion reducing catalyst desorb _xAfterwards, dense intensified operation is finished, and motor operates under the chemically correct fuel, and NO _xThe occlusion reducing catalyst is through after considerable time, and regeneration is finished.

In the present embodiment, according to being arranged on NO _xThe H in occlusion reducing catalyst 7 downstream sides ₂The time (air fuel ratio converts the time of chemically correct fuel to) that dense intensified operation stops is judged in the output of sensor 33.

That is to say that when dense intensified operation was carried out, the exhaust that comprises the dense air fuel ratio of hydrogen composition flowed into NO _xThe occlusion reducing catalyst.When from NO _xOcclusion reducing catalyst 7 desorb NO _xThe time, be included in hydrogen composition and NO in the exhaust _xReaction also consumes.Therefore, be arranged on the H in downstream side ₂Sensor 33 does not detect the hydrogen composition.

Yet, at high occlusion type NO _xUnder the situation of occlusion reducing catalyst, in the process of carrying out dense intensified operation, NO _xStarting solution suck and NO _xDesorption rate when sharply descending, NO _xMeasure low.Therefore, a part that is included in the hydrogen composition in the exhaust not with NO _xReaction just flows to the downstream side of catalyzer.

Therefore, in the present embodiment, when carrying out dense intensified operation, as the H that is arranged on the downstream side ₂Sensor 33 detects the NO in the exhaust _xThe time, then judge from NO _xThe NO of occlusion reducing catalyst 7 _xStarting solution sucks, and the air fuel ratio of exhaust becomes chemically correct fuel.

Fig. 4 is for describing the NO of above-described present embodiment _xThe flow chart of the regenerative operation of occlusion reducing catalyst.This operation is processed as a kind of routine, carries out with fixed intervals by ECU30.

In the present embodiment, except by utilizing the dense intensified operation execute flag X, also by utilizing chemically correct fuel to keep sign Y, regeneration NO _xThe occlusion reducing catalyst.When at above-mentioned NO _xHold-up is estimated in the operation, NO _xWhen Counter Value reached predetermined value, the value of sign Y was set at 1 with the value of sign X.

In Fig. 4, when the operation beginning, judge in step 401 chemically correct fuel keeps the value of sign Y whether to be set at 1.As described below, after dense intensified operation was finished, after the value of sign X was set at 0 (step 411) process predetermined amount of time (step 413 is to step 415), the value of sign Y was set at 0 (step 419).Therefore, in step 401, under the situation of Y ≠ 1, guarantee to finish dense intensified operation and the chemically correct fuel maintenance operation afterwards of dense intensified operation.

Therefore, in step 401, under the situation of Y ≠ 1, not execution in step 403 and later operation, this operation stops immediately.

In step 401, under the situation of Y=1, because regeneration NO _xThe occlusion reducing catalyst, program proceeds to step 403, and according to the value that indicates X, judges whether the dense intensified operation of the initial stage of regenerative operation is finished.Under the situation of X=1 (not finishing), be arranged at NO _xThe downstream side H of occlusion reducing catalyst ₂Sensor 33 detects before the hydrogen composition in the exhaust, continues to carry out dense air-fuel ratio operation.The operation that step 403 is described in 411 is identical to the operation described in 309 with step 301 shown in Figure 3.

On the other hand, in step 403, under the situation of X=1, though this shows that dense intensified operation finishes, chemically correct fuel keeps operation to stop as yet.Therefore, program proceeds to step 413, and the value of counter CT adds 1, and program proceeds to step 415, and judges whether the value that counter CT increases reaches predetermined value beta.In this case, β is the count value corresponding to a time period, wherein, after dense intensified operation is finished, NO _xThe occlusion reducing catalyst should remain on chemically correct fuel.That is to say that β is at initial stage NO _xAfter the desorb, under theoretical air fuel ratio, finish NO _xThe time period that the regeneration of occlusion reducing catalyst is required.The β value is according to NO _xThe ability of occlusion reducing catalyst and type and change.Therefore, preferably the β value is determined by experiment, and wherein, adopts actual NO _xThe occlusion reducing catalyst.

In step 415, under the situation of CT＜β, NO _xThe regeneration of occlusion reducing catalyst is not finished as yet.Therefore, program proceeds to step 417, and motor moves in theoretical air fuel ratio.In view of the above description, the exhaust of chemically correct fuel flows into NO _xOcclusion reducing catalyst 7, and NO _xThe regeneration of occlusion reducing catalyst 7 continues, and increases the fuel consumption of motor 1 not significantly.

In step 415, under the situation of CT 〉=β, because NO _xThe regeneration of occlusion reducing catalyst 7 is finished, and program proceeds to step 419, and the value of sign Y sum counter CT resets to 0.In view of the above description, in next one operation, after the operation of step 401, terminating operation immediately.Like this, do not carry out NO _xThe regenerative operation of occlusion reducing catalyst, and carry out common rare air fuel ratio operation.

According to embodiment shown in Figure 4, in the regenerative operation process, when being arranged on NO _xThe H in occlusion reducing catalyst 7 downstream sides ₂When sensor 33 detected the hydrogen composition that is included in the exhaust, dense intensified operation stopped, and exhaust afterwards remains on predetermined chemically correct fuel.In view of the above description, even when adopting high occlusion type NO _xDuring the occlusion reducing catalyst, NO also can suitably regenerate _xOcclusion reducing catalyst 7.

(3) the 3rd embodiments

The 3rd embodiment is described below.

In above-mentioned first and second embodiments, by being arranged on NO _xThe downstream side H in occlusion reducing catalyst 7 downstream sides ₂Sensor 33 detected hydrogen concentrations are judged termination NO _xThe time of the time of the regenerative operation of occlusion reducing catalyst and the dense intensified operation of termination.

On the other hand, in the present embodiment, the air fuel ratio of control exhaust, thereby at NO _xIn the regenerative operation of occlusion reducing catalyst 7, be arranged on NO _xThe upstream side H of occlusion reducing catalyst upstream side ₂Sensor 31 detected hydrogen constituent concentrations become predetermined value.

As shown in Figure 2, the hydrogen constituent concentration in the exhaust changes according to the air fuel ratio of exhaust.Therefore, if the air fuel ratio of exhaust at NO _xChange during occlusion reducing catalyst regenerative operation, then the concentration of the hydrogen composition in the exhaust also changes, and in some cases, is fed to NO _xThe quantitative change of the hydrogen of occlusion reducing catalyst gets not enough.This may cause NO _xInsufficient regeneration of occlusion reducing catalyst.

In the present embodiment, based on upstream side H ₂The output of sensor 31 is carried out feedback control to the air fuel ratio of exhaust, thereby flows into NO _xThe hydrogen constituent concentration of the exhaust of occlusion reducing catalyst is at NO _xBecome predetermined value during the regenerative operation of occlusion reducing catalyst 7.Because above-mentioned feedback control is at NO _xIn the regenerative process of occlusion reducing catalyst 7, always can give NO _xAn amount of hydrogen composition of occlusion reducing catalyst 7 supplies.

Fig. 5 is for describing the NO of above-described present embodiment _xThe flow chart of the regenerative operation of occlusion reducing catalyst 7.This operation is processed as a kind of routine, carries out with fixed intervals by ECU30.

The operation of Fig. 5 is carried out as follows.At first, in step 501, judge whether the value of regeneration execution flag X is set at 1.In the mode identical, in the present embodiment, work as NO with first and second embodiments _xThe NO of occlusion reducing catalyst 7 _xWhen hold-up is increased to predetermined value, by unshowned, divide the operation open execution with ECU30, the value of sign X is set at 1.

In this regard, the value of the regenerative operation execute flag X of present embodiment can be provided with as follows: for example, after value was set at X=1, through after the predetermined amount of time, this value reset to 0.Perhaps, the value of sign X can reset to 0 according to Fig. 3 and operation shown in Figure 4.

In step 501, under the situation of X=1 (execution regenerative operation), carry out dense intensified operation in step 503, the amount that the fuel of motor 1 sprays increases, and motor 1 moves under dense air fuel ratio.In view of the above description, the exhaust inflow NO that comprises the dense air fuel ratio of hydrogen composition _xOcclusion reducing catalyst 7, and regeneration NO _xOcclusion reducing catalyst 7.

Next, in step 505, from being arranged on NO _xThe H of occlusion reducing catalyst 7 upstream sides ₂Sensor 31 reads in and flows into NO _xHydrogen constituent concentration HRF in the exhaust of occlusion reducing catalyst 7.Step 507 to 509 in, in dense intensified operation, the amount that the fuel of motor 1 sprays reduces (step 509) or increases (step 511), thus the hydrogen constituent concentration value HRP that is accurately measured can be predetermined target value γ.

The NO when target value gamma of hydrogen constituent concentration is passed through the beginning regenerative operation _xThe amount of occlusion and pass through NO _xThe type change of occlusion reducing catalyst.Therefore, preferably the target value gamma of hydrogen constituent concentration based on adopting actual NO _xThe experiment of occlusion reducing catalyst is determined.

In view of the above description, in the present embodiment, work as NO _xDuring occlusion reducing catalyst 7 actual reproduction, always an amount of hydrogen can be fed to NO _xIn the occlusion reducing catalyst 7.Therefore, the NO that can suitably regenerate _xOcclusion reducing catalyst 7.

In this regard, can carry out the NO of present embodiment independently _xThe regenerative operation of occlusion reducing catalyst wherein adopts upstream side H ₂Sensor 31 (as shown in Figure 1).Yet, as mentioned above, can adopt the downstream side H among first or second embodiment ₂Sensor 33 (as shown in Figure 1) carries out regenerative operation.

(4) the 4th embodiments

The fourth embodiment of the present invention is described below.In the present embodiment, with the identical mode of above-mentioned the 3rd embodiment, the air fuel ratio of exhaust is carried out feedback control, thus the H of upstream side ₂Sensor to exhaust in the hydrogen constituent concentration become target value gamma.

The flow chart of the regenerative operation of present embodiment and the 3rd embodiment's identical (as shown in Figure 5).

In above-mentioned the 3rd embodiment, flow at NO _xThe target value gamma of hydrogen constituent concentration HRF in the exhaust of occlusion reducing catalyst 7 is set at fixed value.On the other hand, in the present embodiment, target setting value γ makes passing that it can be in time and changing.Therefore, when beginning (dense intensified operation) at regenerative operation, target value gamma is set at height, and then target setting value γ makes it As time goes on reduce.Present embodiment is only different with the 3rd embodiment on this aspect.

Fig. 6 is the hydrogen composition target value gamma that schematically shows present embodiment with over time plotted curve.As shown in Figure 6, at NO _xWhen the regenerative operation of occlusion reducing catalyst 7 began, the γ value was high.As time goes on, γ reduces gradually.

Work as NO _xThe regenerative operation of occlusion reducing catalyst begins and the exhaust of dense air fuel ratio flows into NO _xDuring the occlusion reducing catalyst, at first, attached to NO _xThe Pt on the occlusion reducing catalyst and the NO of alumina surface _x, and the NO that exists with ionic species at the occlusion material near surface _xSimultaneously by desorb, afterwards, the NO of occlusion in occlusion material _xMove on the surface and from occlusion material inside by desorb.

Therefore, at NO _xThe beginning of the regenerative operation of occlusion reducing catalyst, quite a large amount of NO _xIn short time period by desorb.Afterwards, NO _xThe speed of desorb reduce gradually.Therefore, when regenerative operation begins, be used to reduce NO by desorb _xThe amount of required hydrogen composition is big.Afterwards, reduction is by the NO of desorb like this _xThe amount of required hydrogen composition reduces.

In the present embodiment, as shown in Figure 6, in the regenerative operation process, according to from NO _xThe NO of occlusion reducing catalyst desorb _xDesorption rate, set the hydrogen constituent concentration in the exhaust.Therefore, can be suitably to NO _xThe occlusion reducing catalyst is regenerated.

(5) the 5th embodiments

The fifth embodiment of the present invention is described below.

In the present embodiment, NO _xThe degree of deterioration of occlusion reducing catalyst was judged according to the required time of regenerative operation.The time that regenerative operation is required, that is, as (as shown in Figure 3) as described in first embodiment, the moment that stops regenerative operation is according to downstream side H ₂The output of sensor 33 is determined.

As mentioned above, in first embodiment (as shown in Figure 3), NO _xThe time point that the regeneration of occlusion reducing catalyst 7 is finished is by hydrogen sensor 33 detections in downstream side.In this regard, the needed time section that begins to finish to regeneration from regeneration is according to NO _xThe NO of occlusion in the occlusion reducing catalyst 7 _xAmount increase and reduce.

In above-mentioned each embodiment, according to NO _xCounter Value and at NO _xThe NO that occlusion reducing catalyst downstream side is provided with _xNO is estimated in the output of sensor _xThe NO of occlusion in the occlusion reducing catalyst _xAmount, and whenever this NO _xWhen hold-up reaches predetermined value, carry out regenerative operation.Therefore, think when the beginning regenerative operation NO _xThe NO of occlusion reducing catalyst 7 _xHold-up this as fixed value, and begin to should be basic fixed to time period of finishing from regenerative operation.

Yet, because NO _xTherefore occlusion reducing catalyst 7 variation have reduced NO _xOcclusion capacity.Therefore, for example, using NO _xCounter is estimated NO _xUnder the situation of hold-up, even the NO in the exhaust _xConcentration of component is fixed, because NO _xOcclusion reducing catalyst variation, time per unit NO _xThe NO of occlusion in the occlusion reducing catalyst _xAmount reduce and NO _xThe actual NO of occlusion in the occlusion reducing catalyst _xAmount reduce, less than NO _xThe value of counter.

At NO _xSensor is arranged on NO _xThe downstream side of occlusion reducing catalyst and estimation NO _xUnder the situation of hold-up, work as NO _xDuring the occlusion capacity variation of occlusion reducing catalyst, flow to the NO of occlusion _xThe NO in downstream side _xAmount less than the catalyzer NO of occlusion during variation not _xDischarge.

Therefore, under the situation of catalyst deteriorates, according to NO _xCounter begins under the situation of regenerative operation, and according to NO _xThe output of sensor begins under the situation of regenerative operation, NO _xThe NO of occlusion reducing catalyst _xHold-up reduces when regenerative operation begins.

Regenerative operation begins to finishing the needed time according to NO _xThe NO of the occlusion of occlusion reducing catalyst 7 _xAmount increases and reduces.Therefore, when regenerative operation begins, work as NO _xThe NO of occlusion reducing catalyst 7 occlusions _xWhen amount reduced, regenerative operation began to shorten to finishing the needed time.That is to say that because catalyst deteriorates, the needed time of regenerative operation shortens.

Utilized the above-mentioned fact in the present embodiment.When regenerative operation begin judge NO to finishing the needed time when being shorter than predetermined amount of time _xOcclusion reducing catalyst 7 is variation.

Fig. 7 is the flow chart of the deterioration judgment operation of description present embodiment.This operation is processed as a kind of routine, carries out with fixed intervals by ECU30.

In the present embodiment, the value of measuring the regenerative operation execute flag X that uses among first embodiment (as shown in Figure 3) from 0 become 1 time point to the value of regenerative operation execute flag X from 1 time period that becomes 0 time point, and when this is worth less than predetermined value, judge NO _xOcclusion reducing catalyst 7 variation.

That is to say, in operation as shown in Figure 7, at first, in step 701, judge whether the value of present sign X is set at 1.As mentioned above, by the operation of being carried out by ECU30 separately, when regenerative operation began, sign X was set at 1.

In step 701, under the situation of X=1, next execution in step 703, judge that the value of execute flag XS is set at 1, and the value of regeneration timer CN increases Δ t in step 705.

In this case, judge that execute flag XS is used for only once the sign of decision operation of after finishing regenerative operation execution in step 711 to 715.

The counter of the regeneration timer CN time history that to be expression begin from regenerative operation.In this case, the counter-increments Δ t in step 705 is the interval (time) of cycling shown in Figure 7.Do not carrying out under the situation of regenerative operation, the value of counter CN is always removed in step 717.Therefore, the value of the counter CN that calculates in step 705 equals from the time history of the X=1 of step 701 foundation.

In step 701, under the situation of X ≠ 1, that is to say, do not carrying out NO _xUnder the situation of occlusion reducing catalyst 7 regeneration, program proceeds to step 707, and judges that according to the value of sign XS whether execution of operation this time is the execution first after regenerative operation is finished (from the time of X ≠ 0).

Under the situation of X=1, sign XS always is set at XS=1 in step 703, and during the execution first of the operation behind X ≠ 1, in step 709, sign XS is set at XS=0.

Therefore, in step 707, under the situation of XS=1, this is the execution first of the operation finished from regenerative operation.Therefore, in this case, the value of counter CN equals from NO _xThe regeneration of occlusion reducing catalyst 7 begins to finishing the required time.

Therefore, in step 707, under the situation of X=1, judge in step 711 whether regenerative operation needed time CN is shorter than preset judgment value δ.

Under the situation of CN＜δ, can judge NO _xOcclusion capacity is owing to the variation of catalyzer reduces, and the required time shortening of regenerative operation.Therefore, in step 713, the value of deterioration flag XF is set at 1 (variation).

In step 711, under the situation of CN 〉=δ, the value of sign XF is set at 0 (normally) in step 715.

In this case, at NO _xOcclusion capacity is because under the situation of catalyst deteriorates and variation, δ is the required time of regenerative operation, thereby may cause problem in practice.Therefore, preferably the δ value is determined by the experiment of adopting actual catalyst.

After 715 carried out judgement, the value of counter CN was eliminated and operation this time stops in step 71.In this regard, because the value of XS is set at 0 in step 709, at NO _xAfter the regenerative operation of occlusion reducing catalyst 7 was finished, the decision operation of execution in step 711 to 715 once immediately.Afterwards, after step 707, directly carry out step 717.

As mentioned above, according to present embodiment, suitably carry out NO _xThe regenerative operation of occlusion reducing catalyst 7 can accurately be judged NO _xWhether occlusion reducing catalyst 7 variation.

The deterioration judgment operation of present embodiment is carried out with the regenerative operation of first embodiment (as shown in Figure 3).In addition, carry out above-mentioned the 3rd embodiment (as shown in Figure 5) when simultaneously, and in the regenerative operation process, controlling packet is contained in and flows into NO _xWhen the hydrogen constituent concentration is predetermined value in the exhaust of occlusion reducing catalyst 7, can further strengthen the deterioration judgment precision.

(6) the 6th embodiments

The sixth embodiment of the present invention is described below.

Fig. 8 is the diagrammatic sketch that is similar to Fig. 1, shows the configuration of present embodiment.

Fig. 8 configuration following different with the configuration of Fig. 1 on some.In the configuration of Fig. 8, adopt so-called serial type NO _xThe occlusion reducing catalyst wherein in the exhaust passage, is provided with two NO that are one another in series _xOcclusion reducing catalyst 71,73, the NO of replacement Fig. 1 _xOcclusion reducing catalyst 7.

The serial type NO of present embodiment _xThe occlusion reducing catalyst is formed as follows: prime NO _xOcclusion reducing catalyst 71 and back level NO _xOcclusion reducing catalyst 73 is arranged in the housing 70, reserves proper spacing simultaneously between the two.In the space that between prime and back level, forms, the H among setting and Fig. 2 ₂The H that

sensor

31,33 is identical ₂Sensor 35.

At serial type NO _xIn the occlusion reducing catalyst, as prime NO _xThe characteristic of occlusion reducing catalyst and back level NO _xThe characteristic of occlusion reducing catalyst not simultaneously, serial type NO _xThe exhaust purification performance of occlusion reducing catalyst is from single-stage NO _xThe performance of occlusion reducing catalyst strengthens.

For example, at the serial type NO of present embodiment _xIn the occlusion reducing catalyst, prime NO _xThe NO of occlusion reducing catalyst 71 _xOcclusion capacity is greater than back level NO _xThe NO of occlusion reducing catalyst 73 _xOcclusion capacity, and prime NO _xThe O of occlusion reducing catalyst 71 ₂Storage capacity is less than back level NO _xThe O of occlusion reducing catalyst 73 ₂Storage capacity.In addition, prime NO _xThe Pt catalyst carrier amount of occlusion reducing catalyst 71 is greater than back level NO _xThe Pt catalyst carrier amount of occlusion reducing catalyst 73.

At two NO _xThe occlusion reducing catalyst is one another in series under the situation about being provided with, NO _xAt first at prime NO _xOcclusion in the occlusion reducing catalyst.Because the O of prime ₂Storage capacity is set at a little value, even when carrying out regenerative operation, the hydrogen composition and HC, the CO composition that are included in the exhaust do not react with the oxygen that is included in catalyzer yet, and the major part of hydrogen composition and HC, CO composition is used to reduce NO _x

Because the Pt amount of front stage catalyst carrying increases, the most of NO that comprises in exhaust is oxidized in front stage catalyst, and becomes NO ₂Therefore, the NO of the per unit volume of prime _xHold-up increases.Therefore, except prime NO _xThe occlusion capacity of occlusion reducing catalyst increases be provided with outside, prime NO _xOcclusion reducing catalyst 71 can be realized NO effectively _xOcclusion and reduction.

On the other hand, at back level NO _xIn the occlusion reducing catalyst 73, O ₂Storage capacity is set at higher relatively.Therefore, for example, even when carrying out regenerative operation, through prime NO _xDuring the air-fuel ratio of the exhaust of occlusion reducing catalyst, back level NO _xOcclusion reducing catalyst 73 can remain in the atmosphere near chemically correct fuel.Because NO _xThe occlusion reducing catalyst has the function at the three-way catalyst adjacent with chemically correct fuel, at serial type NO _xIn the occlusion reducing catalyst, when regeneration, back level NO _xOcclusion reducing catalyst 73 is as utilizing from O ₂The three-way catalyst of the oxygen that storage is discharged.Therefore, even at the NO of prime desorb _xBecause same cause is not reduced and flows into back level NO _xDuring occlusion reducing catalyst 73, NO _xAlso can be at back level NO _xOcclusion reducing catalyst 73 places are reduced and purify.

As mentioned above, at serial type NO _xIn the occlusion reducing catalyst, the NO that characteristic differs from one another _xThe occlusion reducing catalyst is separately positioned on prime and back level, thereby strengthens exhaust gas purification efficient.But, as the result who adopts said structure, under the situation of carrying out the control identical, if H with above-mentioned each embodiment ₂Sensor is arranged on back level NO _xThe downstream side of occlusion reducing catalyst 73 may cause problem.

For example, by the mode identical, according to H with first embodiment ₂The output of sensor is judged under the situation of the time that stops regenerative operation, if H ₂Sensor is arranged on back level NO _xThe downstream side of occlusion reducing catalyst 73 is difficult to judge the time that stops regenerative operation.

Reason is described below.At above-mentioned serial type NO _xIn the occlusion reducing catalyst, back level NO _xOcclusion reducing catalyst 73 has relatively large O ₂Storage capacity.Therefore, though when carrying out regenerative operation prime NO _xOcclusion reducing catalyst 71 finishes regenerative operation and the hydrogen composition is included in prime NO _xIn the exhaust of the outlet of occlusion reducing catalyst 71, when these hydrogen compositions warps level NO later _xDuring occlusion reducing catalyst 73, these hydrogen compositions with from back level NO _xThe oxygen that occlusion reducing catalyst 73 is discharged reacts.Therefore, these hydrogen compositions do not flow to back level NO _xThe downstream side of occlusion reducing catalyst 73.

Therefore, work as H ₂Sensor is arranged on back level NO _xThe downstream side of occlusion reducing catalyst 73, and based on H ₂When the time that stops regenerative operation is judged in the output of sensor, unless back level NO _xInstitute's aerobic of occlusion all is discharged from the occlusion reducing catalyst 73, otherwise is difficult to accurately judge the time that stops regenerative operation.

Yet, in fact, at series connection NO _xIn the occlusion reducing catalyst, nearly all NO _xOcclusion and reduction purify all at prime NO _xCarry out back level NO in the occlusion reducing catalyst 71 _xOcclusion reducing catalyst 73 only helps out.Therefore, the NO of occlusion _xAmount much smaller than prime.Therefore, finish prime NO _xAfter the regeneration of occlusion reducing catalyst 71, do not need to proceed regenerative operation.When after the level NO _xDetect in the exhaust in the downstream side of occlusion reducing catalyst before the hydrogen composition, when continuing to carry out regenerative operation, can increase the fuel consumption of motor.

Therefore, in the present embodiment, according to being arranged on prime NO _xOcclusion reducing catalyst 71 and back level NO _xH in the space that forms between the occlusion reducing catalyst 73 ₂Prime NO is judged in the output of sensor _xThe time that the regeneration of occlusion reducing catalyst 71 is finished is so that finish regenerative operation.

Because the regenerative operation of present embodiment is identical with first embodiment (as shown in Figure 3) basically, omits its detailed description at this.

In this regard, described as present embodiment, as prime NO _xWhen the regenerative operation of occlusion reducing catalyst 71 is finished, serial type NO _xThe regenerative operation of occlusion reducing catalyst stops, at back level NO _xThe NO of occlusion in the occlusion reducing catalyst 73 _xAmount increase, and be not reproduced.Yet, as mentioned above, at back level NO _xThe NO of occlusion in the occlusion reducing catalyst 73 _xAmount very little, to such an extent as to the unnecessary back level NO that often carries out _xThe regenerative operation of occlusion reducing catalyst 73.In fact, when carrying out regenerative operation as follows, can not go wrong: motor 1 moves under theoretical air fuel ratio continuously and reaches the certain hour section, and carries out back level NO during this period naturally _xThe regenerative operation of occlusion reducing catalyst 73.

(7) the 7th embodiments

As mentioned above, at NO _xIn the occlusion reducing catalyst, when flowing into NO _xThe exhaust of occlusion reducing catalyst comprises SO _xThe time, under the condition of rare air fuel ratio, SO _xWith NO _xOcclusion is at NO together _xIn the occlusion reducing catalyst.

In this case, NO _xThe NO of occlusion in the occlusion reducing catalyst _xCan be by carrying out regenerative operation relatively simply from NO _x7 desorbs of occlusion reducing catalyst, yet, because SO _xNO with occlusion _xAffinity is strong and produce stable compound, in case so SO _xOcclusion is at NO _xIn the time of in the occlusion reducing catalyst, can not only pass through NO _xThe simple regeneration operation of occlusion reducing catalyst is from NO _xThe occlusion reducing catalyst is separated sucking-off SO _xTherefore, SO _xBe gradually accumulated in the catalyzer, and NO _xThe occlusion reducing catalyst is subjected to SO _xInfluence, that is to say, cause SO _xPoison.

Therefore, usually, when adopting NO _xDuring the occlusion reducing catalyst, whenever the SO of occlusion in catalyzer _xAmount when being increased to certain value, just poison Regeneration Treatment, so that from NO _xDesorb SO in the occlusion reducing catalyst _x

In poisoning Regeneration Treatment, under the operational condition of dense air fuel ratio high exhaust temperature, move motor, make NO _xThe occlusion reducing catalyst keeps high temperature in dense air fuel ratio atmosphere.Even in this case, when comprising the hydrogen composition in the exhaust, also can significantly shorten and poison the Regeneration Treatment time.

In poisoning Regeneration Treatment, work as NO _xWhen occlusion reducing catalyst temperature raises, the sulphate decomposition of generation so that from catalyzer desorb SO _xWork as NO _xWhen the occlusion reducing catalyst remains on dense air fuel ratio, prevent to be separated the SO of sucking-off _xBe occluded in NO once more _xIn the occlusion reducing catalyst.Yet, in fact, as mentioned above because SO _xNO with occlusion _xAffinity is strong, even therefore keep dense air fuel ratio, from NO _xThe SO of the upstream portion desorb of occlusion reducing catalyst _xIn the occlusion once more of downstream part quilt.Therefore, when desorb and occlusion repeatedly, from NO _xThe SO of the upstream portion desorb of occlusion reducing catalyst _xMove to the downstream side gradually.Therefore, make SO _xNeed considerable time from the catalyzer desorb fully.

Therefore, poisoning Regeneration Treatment needs considerable time, and makes the deterioration in fuel consumption of motor.In addition, NO _xThe occlusion reducing catalyst is exposed to for a long time and makes catalyst deteriorates under the high temperature.

Yet because the reducing capacity of hydrogen is very strong, it is convenient to make SO _xFrom NO _xOcclusion reducing catalyst desorb, and in addition, hydrogen with once by the SO of desorb _xReaction, and prevent once by the SO of desorb _xArrived NO by occlusion once more _xIn the occlusion reducing catalyst.Therefore, in poisoning Regeneration Treatment, with H ₂Be fed to NO _xIn the occlusion reducing catalyst, so as in short time period with SO _xFrom NO _xThe occlusion reducing catalyst is separated sucking-off fully.

In this case, with NO _xThe mode that the regenerative operation of occlusion reducing catalyst is identical is worked as SO _xFrom NO _xWhen the occlusion reducing catalyst is separated sucking-off, be included in the exhaust the hydrogen composition by with SO _xThe reaction and consume.Therefore, the hydrogen composition does not flow to NO _xThe downstream side of occlusion reducing catalyst.At all SO _xBy after the desorb, that is to say that all poisoning after Regeneration Treatment finishes, the hydrogen composition flows to NO for the first time _xThe downstream side of occlusion reducing catalyst.

Therefore, by with the identical method of time that judge to stop regenerative operation, also can accurately judge the time of poisoning Regeneration Treatment of stopping.

Yet, adopting serial type NO _xUnder the situation of occlusion reducing catalyst, work as H ₂Sensor is arranged on back level NO _xDuring the downstream side of occlusion reducing catalyst, may occur and the identical problem of problem that is produced during the time that stops regenerative operation is judged.Therefore, be difficult to accurately to judge the time of poisoning Regeneration Treatment of stopping.Therefore, may cause this problem: regenerative operation is unactual to be finished although poison, and the exhaust of high temperature is fed to NO for a long time under dense air fuel ratio _xThe occlusion reducing catalyst.Therefore, work as H ₂Sensor is arranged on back level NO _xThe downstream side of occlusion reducing catalyst stops serial type NO to judge _xThe occlusion reducing catalyst poison Regeneration Treatment during the time, the fuel consumption of motor is owing to the unnecessary dense air fuel ratio operation of motor increases.In addition, be exposed to high temperature following time, NO for a long time when catalyzer _xOcclusion reducing catalyst variation.

In order to increase O ₂Storage capacity, back level NO _xThe cerium dioxide (Ce) that the carrying of occlusion reducing catalyst is quite a large amount of.Though cerium dioxide is easy to combine and be easy to form sulphate with SOx,, in poisoning regeneration process, cerium dioxide and SO _xCombination force is very little, to such an extent as to desorb in a short time easily.

Therefore, in the present embodiment, be arranged on H in the space between prime and the back level by utilization ₂Sensor 35 (as shown in Figure 8) is judged the time that termination poisons regeneration.

Fig. 9 is the flow chart that poisons Regeneration Treatment of describing present embodiment.Operation shown in Figure 9 is identical with the operation of the flow chart of first embodiment's (as shown in Figure 3) regenerative operation basically.The operation of Fig. 9 is only different with the operation of Fig. 3 on following 3.The first, replace mark X, adopt and poison Regeneration Treatment execution mark S.The second, in step 903, replace the dense intensified operation of the step 303 of Fig. 3, carry out and poison regenerative operation, wherein, motor is carried out dense air fuel ratio operation under the condition of high exhaust temperature.The 3rd, in step 905,907, adopt the H that is arranged between prime and the back level ₂The output HRM of sensor 35.Therefore, omitted the detailed description of Fig. 9 herein.

As mentioned above, according to being arranged on prime NO _xOcclusion reducing catalyst and back level NO _xH between the occlusion reducing catalyst ₂The hydrogen constituent concentration that sensor arrives is judged the time that termination poisons Regeneration Treatment.In view of the above description, can prevent the increase of fuel consumption, and NO _xThe variation of occlusion reducing catalyst.

(8) the 8th embodiments

The eighth embodiment of the present invention is described below.

In the present embodiment, when according to being arranged on as shown in Figure 8 serial type NO _xH between occlusion reducing catalyst prime and the back level ₂NO is judged in the output of sensor _xDuring termination time of the regenerative operation of occlusion reducing catalyst, prime NO _xThe degree of deterioration of occlusion reducing catalyst 71 is according to beginning to finishing required time judgement from regenerative operation.

In this regard, the ad hoc approach of judging degree of deterioration is identical with the 5th embodiment's shown in Figure 7 method.Therefore, omitted its detailed description herein.

As mentioned above, at serial type NO _xIn the occlusion reducing catalyst, NO _xOcclusion and reduction purify main by prime NO _xOcclusion reducing catalyst 71 carries out.Therefore, need accurately judge prime NO _xThe degree of deterioration of occlusion reducing catalyst 71.

In the present embodiment, prime NO _xThe degree of deterioration of occlusion reducing catalyst 71 is according to being arranged on serial type NO _xH between the prime of occlusion reducing catalyst and the back level ₂Sensor 35 is judged.In view of the above description, the serial type NO that suitably regenerates _xThe occlusion reducing catalyst can be judged prime NO _xThe degree of deterioration of occlusion reducing catalyst 71.

Claims

1, a kind of Exhaust gas purifying device of internal-combustion engine comprises:

Be arranged on the NO in the exhaust passage of internal-combustion engine _xThe occlusion reducing catalyst, when the air-fuel ratio of the exhaust of inflow catalyst, this NO _xThe occlusion reducing catalyst is by absorbing and adsorbing one of them, perhaps by absorbing and absorption comes occlusion to be included in NO in the exhaust _x, and when the air fuel ratio of exhaust is chemically correct fuel or dense air fuel ratio, this NO _xThe utilization of occlusion reducing catalyst is included in the reduction composition reduction in the exhaust and purifies the NO of occlusion _xWith

Be arranged on NO _xOne of them interior H at least of the inlet side of occlusion reducing catalyst and the exhaust passage of outlet side ₂Sensor, it is used to detect the hydrogen constituent concentration of exhaust, wherein:

This Exhaust gas purifying device is carried out regenerative operation, in this regenerative operation, works as NO _xThe occlusion reducing catalyst will reduce and purify occlusion at NO _xNO in the occlusion reducing catalyst _xThe time, the exhaust of dense air fuel ratio or chemically correct fuel is fed to NO _xThe occlusion reducing catalyst reaches predetermined amount of time, and during regenerative operation, and this Exhaust gas purifying device is based on by H ₂Sensor to exhaust in the hydrogen constituent concentration control and flow into NO _xThe air fuel ratio of the exhaust of occlusion reducing catalyst.

2, the Exhaust gas purifying device of internal-combustion engine as claimed in claim 1, wherein, described H ₂Sensor is arranged on NO _xIn the exhaust passage of the outlet side of occlusion reducing catalyst, and when carrying out described regenerative operation, according to by outlet side H ₂Sensor to exhaust in the hydrogen constituent concentration judge the time that stops regenerative operation.

3, the Exhaust gas purifying device of internal-combustion engine as claimed in claim 1, wherein, described H ₂Sensor is arranged on NO at least _xIn the exhaust passage of the outlet side of occlusion reducing catalyst, described regenerative operation comprises following operation: at first the exhaust with dense air fuel ratio is fed to NO _xThe occlusion reducing catalyst, the exhaust with chemically correct fuel is fed to NO then _xThe occlusion reducing catalyst, and according to the H by outlet side ₂Sensor to the hydrogen constituent concentration determine that the air fuel ratio of exhaust is transformed into the time of chemically correct fuel from dense air fuel ratio.

4, the Exhaust gas purifying device of internal-combustion engine as claimed in claim 1, wherein, H ₂Sensor is arranged on NO _xIn the exhaust passage of the inlet side of occlusion reducing catalyst, and when carrying out regenerative operation, flow into NO _xThe controlled feasible H of the air fuel ratio of the exhaust of occlusion reducing catalyst by inlet side ₂Sensor to exhaust in the hydrogen constituent concentration can be predetermined target value.

5, the Exhaust gas purifying device of internal-combustion engine as claimed in claim 4, wherein, when the beginning regenerative operation, the desired value height of hydrogen constituent concentration, then As time goes on, the desired value of this hydrogen constituent concentration reduces gradually.

6, the Exhaust gas purifying device of internal-combustion engine as claimed in claim 2, wherein, according to H according to the downstream side ₂Sensor to exhaust in the hydrogen constituent concentration judge draw begin the time history that finishes to regenerative operation from regenerative operation, judge NO _xThe degree of deterioration of occlusion reducing catalyst.

7, a kind of Exhaust gas purifying device of internal-combustion engine comprises the NO in the exhaust passage that is arranged on internal-combustion engine _xThe occlusion reducing catalyst, when the air-fuel ratio of the exhaust that flows into this catalyzer, this NO _xThe occlusion reducing catalyst is by absorbing and adsorbing one of them, perhaps by absorbing and absorption comes occlusion to be included in NO in the exhaust _x, and when the air fuel ratio of exhaust is chemically correct fuel or dense air fuel ratio, this NO _xThe utilization of occlusion reducing catalyst is included in the reduction composition reduction in the exhaust and purifies the NO of occlusion _x,

The Exhaust gas purifying device of this internal-combustion engine also comprises:

NO _xThe occlusion reducing catalyst, the upstream side and the downstream side of its exhaust passage of being arranged on internal-combustion engine of being one another in series; And H ₂Sensor, it is arranged on the NO of the upstream side that is one another in series _xThe NO in occlusion reducing catalyst and downstream side _xIn the exhaust passage between the occlusion reducing catalyst, be used to detect the hydrogen constituent concentration in the exhaust, wherein:

Work as NO _xThe occlusion reducing catalyst will reduce and purify the NO of occlusion in rare air-fuel ratio operation process of motor _xThe time, be fed to NO in the exhaust of carrying out wherein dense air fuel ratio or chemically correct fuel _xWhen the occlusion reducing catalyst reaches the regenerative operation of predetermined amount of time, according to H ₂Sensor to exhaust in the hydrogen constituent concentration, control flows into the NO that the upstream is surveyed _xThe air fuel ratio of the exhaust of occlusion reducing catalyst.

8, the Exhaust gas purifying device of internal-combustion engine as claimed in claim 7, wherein, the NO of upstream side _xThe NO of occlusion reducing catalyst _xOcclusion capacity is greater than the NO in downstream side _xThe NO of occlusion reducing catalyst _xOcclusion capacity, the NO of upstream side _xThe O of occlusion reducing catalyst ₂Storage capacity is less than the NO in downstream side _xThe O of occlusion reducing catalyst ₂Storage capacity, and be carried on the NO of upstream side _xThe amount of the platinum composition of occlusion reducing catalyst is greater than the NO that is carried on the downstream side _xThe amount of the platinum composition of occlusion reducing catalyst.

9, as the Exhaust gas purifying device of claim 7 or 8 described internal-combustion engines, wherein, when carrying out described regenerative operation, according to H ₂Sensor to exhaust in the hydrogen constituent concentration, judge to stop time of regenerative operation.

10, as the Exhaust gas purifying device of claim 7 or 8 described internal-combustion engines, wherein, flow into NO by making _xThe air fuel ratio of the exhaust of occlusion reducing catalyst is dense air fuel ratio, and improves its temperature simultaneously, and this device is also carried out and poisoned Regeneration Treatment, so that from NO _xIn the occlusion reducing catalyst, the desorb occlusion is at NO _xSulfur oxide and NO in the occlusion reducing catalyst _x, and

Wherein, poison in the process of Regeneration Treatment, in execution according to H ₂Sensor to exhaust in the hydrogen constituent concentration, control flows into the NO of upstream side _xThe air fuel ratio of the exhaust of occlusion reducing catalyst.

11, the Exhaust gas purifying device of internal-combustion engine as claimed in claim 10, wherein, when execution poisons Regeneration Treatment, according to H ₂Sensor to exhaust in the hydrogen constituent concentration, judge to stop the time of poisoning Regeneration Treatment.

12, the Exhaust gas purifying device of internal-combustion engine as claimed in claim 8, wherein, according to H ₂Hydrogen constituent concentration in the exhaust that sensor arrives is judged from regenerative operation to begin to judge the NO of upstream side according to this time period to the time period of regenerative operation end _xThe degree of deterioration of occlusion reducing catalyst.