US3814589A

US3814589A - Converter for catalytic exhaust gas cleaning

Info

Publication number: US3814589A
Application number: US00262004A
Authority: US
Inventors: H Heitland
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 1971-06-11
Filing date: 1972-06-12
Publication date: 1974-06-04
Anticipated expiration: 1991-06-04
Also published as: DE2128990A1

Abstract

A HOUSING HAVING AB INPUT FOR EXHAUST GAS AND AN AUTPUT FOR EMITTING THE CLEAN EXHAUST GAS, THE HOUSING IS MADE FROM A MATERIAL HAVING A HIGH POSITIVE COEFFICIENT OF EXPANSION UNDER HEAT, A CATALYZATOR BODY PLACED IN THE HOUSING AND BEING SECURED IN IT AT ONE END THEREOF DOWNSTREAM OF THE GAS FLOW AND BEING MADE FROM A MATERIAL HAVING A LOW COEFFICIENT OF EXPANSION UNDER HEAT, THE CATALYZATOR BODY AND THE HOUSING BEING ARRANGED FOR RELATIVE MOVEMENT WITH RESPECT TO EACH OTHER UNDER HEAT EXPANSION OF THE HOUSING EXCEPT FOR THE SECURED PORTION OF THE CATALYZATOR BODY, A BYPASS CONDUIT HAVING AN INPUT OPENING TO HOUSING AT A REGION UPSTREAM OF THE EXHAUST GASFLOWAND ADAPTED TO CONNECT THE INPUT TO THE HOUSING WITH THE OUTPUT THEREOF WHEN THE INPUT OPENINGS OF SUCH PIPE CONDUIT IS OPENED, THE CATALYZATOR BODY IS MOUNTED IN THE HOUSING FOR COVERING THE INPUT OPENING OF THE BYPASS CONDUIT AT A PREDETERMINED RANGE OF TEMPERATURES OF THE EXHAUST GAS AND THEREBY FORCING THE EXHAUST GAS TO PASS THROUGH THE CATALYZATOR TO THE INPUT OF THE HOUSING THE CATALYZATOR UNCOVERING THE INPUT OF THE HOUSING AT LEAST PARTLY AND THEREAFTER INCREASINGLY UNCOVERING IT ABOVE A PREDETERMINED TEMPERATURE RANGE OF THE GASES WHEN THE HOUSING MOVES UNDER HEAT EXPANSION RELATIVE TO THE CATALYZATOR.

Description

June 4, 1974 H. HEITLAND 3,814,589

CONVERTER FOR CATALYTIC EXHAUST GAS CLEANING Filed June 12, 1972 United States Patent US. Cl. 23288 F 5 Claims ABSTRACT OF THE DISCLOSURE A housing having an input for exhaust gas and an output for emitting the cleaned exhaust gas, the housing is made from a material having a high positive coefficient of expansion under heat, a catalyzator body placed in the housing and being secured in it at one end thereof downstream of the gas flow and being made from a material having a low coefiicient of expansion under heat, the catalyzator body and the housing being arranged for relative movement with respect to each other under heat expansion of the housing except for the secured portion of the catalyzator body, a bypass conduit having an input opening to housing at a region upstream of the exhaust gas flow and adapted to connect the input to the housing with the output thereof when the input opening of such pipe conduit is opened, the catalyzator body is mounted in the housing for covering the input opening of the bypass conduit at a predetermined range of temperatures of the exhaust gas and thereby forcing the exhaust gas to pass through the catalyzator to the output of the housing, the catalyzator uncovering the input opening at least partly and thereafter increasingly uncovering it above a predetermined temperature range of the gases when the housing moves under heat expansion relative to the catalyzator.

CROSS-REFERENCE TO OTHER APPLICATIONS Reference should be had to the now copending epplication of Peter Manderscheid entitled Combustion FIELD OF THE INVENTION The present invention relates to an exhaust gas cleaning arrangement in general and, more particularly it relates to a converter for catalytically cleaning exhaust gas in motor vehicles by means of a housing containing a catalyzator having a bypass controlled by a valve means which opens such bypass only above a certain temperature value of the exhaust gas.

BACKGROUND OF THE INVENTION It is well known that the catalyzators used for such purpose have only a limited thermal resistivity but for the purpose of cleaning the exhaust gas in a motor vehicle they are subjected to rather high thermal loads. Such thermal loading is due not only to the sensible heat of the exhaust gases passing through the catalyzator but also due to the generation of the heat by the components undergoing diiferent reactions within the exhaust gas.

In order that the life of the catalyzators in exhaust gas cleaning arrangements could be extended with respect to the temperature loading which they undergo, there has been previously a bypass proposed which upon exceeding a predetermined value of temperature in the exhaust gas as sensed by a temperature sensitive valve means becomes open and then the exhaust gas will bypass the temperature sensitive catalyzator and being led to the atmosphere. Such arrangement is known from German Utility Model 1,917,133, where in the bed of the catalyzator a temperature sensor is provided which, as the temperature of the exhaust gas exceeds a predetermined value, will operate a valve opening the bypass.

This known arrangement has its disadvantage in that both the temperature as well as the valve are physically exposed to the very aggressive exhaust gas and, therefore, the valve as well as the positioning members thereof must be so solidly constructed so that despite their exposure to heavy corrosion in time they still should be able to provide a reliable functioning of the bypass. It is not sufiicient that the bypass should be opened at high temperatures, but it is also necessary that the bypass must be reliably closed at the proper temperature range of the exhaust gas otherwise a reliable functioning of the converter as an exhaust gas cleaning arrangement cannot be had.

SUMMARY OF 'THE INVENTION It is, therefore, an object of the present invention to provide a converter for use in the cleaning of exhaust gas in motor vehicles which have a construction which eliminates the above-described disadvantages associated with known converters for this purpose.

According to the present invention the catalyzator as well as the housing are manufactured from material having different heat expansion characteristics and the catalyzator is fixedly secured only at a region of the housing which is downstream with respect to the flow direction of the exhaust gas while in a region of the housing which is upstream with respect to the flow direction of the exhaust gas a bypass opening is provided which is open and becomes covered only at temperatures of the exhaust gas lying below a certain temperature value.

Notwithstanding the fact that also in the above-mentioned known arrangement an additional temperature sensor and an additional valve means are provided, the present invention provides that a covering or opening of the input of the bypass is accomplished solely by the special properties of the housing and of the catalyzator as a function of the temperature in the exhaust gas and without any additional mechanical means. The valve means for the operation of the bypass are formed according to the present invention solely by the housing and the catalyzator.

In the event the housing is made from steel which, as well known, possesses a special positive expansion under temperature effects, then if the material of the catalyzator does not have an excessively negative expansion under temperature, which is usually the case, then there is a considerable relative movement between the free or unsecured end of the catalyzator, on one hand, and between the end region of the housing adjacent to such free end of the catalyzator, on the other hand, so that a relatively large portion of the bypass in the housing under a predetermined temperature value of the exhaust gas can be covered, while at higher temperature values it can be uncovered and thereby the bypass opened. According to the present invention and to its preferred aspect when the exhaust gas temperature increases, the cross section of the opening of the bypass will gradually increase as being uncovered by the moving catalyzator which provides an appropriate adjustment in the charging of the catalyzator with exhaust gas at each temperature value.

It is within the scope of the present invention to provide the opening of the bypass in the housing with a special cross-sectional shape which would provide for the charging of the catalyzer with exhaust gas in a predetermined functional relationship with the temperature of the exhaust gas.

The German OLS (laid-open application) 1,921,024 discloses also a device for use in the oxidation of the exhaust gas, and which comprises various thermal expansion characteristics of the materials of diiferent parts in order that a bypass could be released or closed. Such components are, however, parts of a very complicated additional valve mechanism while the present invention proposes the various expansion characteristics under temperature only for the housing and the catalyzator which by having such different thermal properties can effect the controlling of the bypass.

BRIEF DESCRIPTION OF THE DRAWING The invention will become more readily apparent from the following description of a preferred embodiment thereof shown, by way of example, in the accompanying drawing, in which:

The single figure is a side view of an exhaust gas cleaning arrangement including a catalyzator and a bypass, partly in section, according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT With respect to the single figure it is noted that the solid lines illustrate the condition of the state of the catalyzator under permissible temperature values, while the dashed lines illustrate the position of the edges of the catalyzator and of the housing of the cleaning arrangement as they behave under high temperatures of the exhaust gas. It is noted that only the illustrated edges will change their relative position under the high temperature values.

The exhaust gas passes through the cleaning arrangement in the direction of the arrow from the input conduit 1 through the housing 2 and reaches an output pipe, or tail pipe 3. The housing 2 in the illustrated embodiment is symmetrically formed and comprises an outside shell 4 and a pair of end walls 5 and 6. In the region of the front wall 5 which is the face wall of the apparatus with respect to the flow of the exhaust gas, the shell 4 of the housing 2 has an opening 7 for a bypass conduit 8 which at low temperatures in the exhaust gas is closed since it is covered by the catalyzator 9 and, thereby the bypass conduit 8 is ineffective. The catalyzator body 9 in its back region lying downstream with respect to the flow of the exhaust gas is securely connected with the housing 2 as identified at 10. Such securing is effected not only to provide a simple mechanical securing but also it should be gas tight so that all the gases coming from the input conduit 1 must pass through the catalyzator 9. As mentioned above the catalyzator body 9 is fixedly secured to the housing 10, however, over the rest of its length the catalyzator 9 is only freely surrounded by the housing 2 with a certain clearance so that when the temperature of the exhaust gas changes, due to the different expansion coefiicients of the material of the housing 2 and of the catalyzator 9 under temperature variations, there will be a relative movement taking place in the region of the left hand end of the catalyzator 9 as can be seen in the figure and as can be more clearly seen by the dashed line illustration of the figure. More particularly as can be seen in the illustrated embodiment, a monolithic catalyzator 9 is being used which has a negative coeflicient of expansion under heat, that is, it undergoes a shrinking with increasing temperatures. Accordingly, the left front wall surface 11 of the catalyzator 9, as seen in the figure, will shift itself at high temperatures into the position identified by 11 while the front wall 5 of the housing 2 due to the positive coefficient of expansion underheat of the steel material of which the housing 2 is made, will move into the position identified by 5. Inasmuch as the front wall 5 of the housing will move physically with it the opening 7 of the bypass 8, the catalyzator body 9 will uncover the opening 7 more or less depending on the excessiveness of the temperature and, now, the bypass 8 becomes operative. In order that the bypass 8 could follow the expansion under the heat effect, it is made at 12 in the form of a bellows so that it could resiliently behave under the expansion of the housing 2.

I wish it to be understood that I do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

Having thus described the invention, what I claim as new and desire to be secured by Letters Patent, is as follows: 7

1. A converter for cleaning the exhaust gas of a combustion engine comprising a housing having an input for said exhaust gas and output for emitting the cleaned exhaust gas, said housing being made from a material having a coetficient of expansion under heat, a catalyzator body placed in said housing and being secured in said housing at one end thereof at a point remote from said input and adjacent said output, said catalyzator body being made from a material having another coefficient of expansion under heat, said catalyzator body and said housing being arranged for relative movement with respect to each other under heat expansion of said housing except for the secured portion of said catalyzator body, a bypass conduit means having an input opening to said housing at a point adjacent said input for said exhaust gas and adapted to connect said input to said housing with the output thereof when said input opening of said pipe conduit is opened, said catalyzator body being mounted in said housing for covering said input opening of said bypass conduit at a predetermined range of temperatures of said exhaust gas and thereby forcing said exhaust gas to pass through said catalyzator body to said output of said housing, said catalyzator body uncovering said input opening at least partly and thereafter increasingly uncovering said input opening of said conduit above a predetermined temperature range of said gases when said housing moves under heat expansion relative to said catalyzator body.

2. The converter as claimed in claim 1, wherein said input opening of said bypass conduit is circular in form.

3. The converter as claimed in claim 1, wherein said input opening of said bypass is other than circular in cross section.

4. The converter as claimed in claim 1, wherein said bypass conduit comprises a resilient means for allowing expansion or contraction of said bypass conduit upon heat expansion of said housing and thereby to follow the expansion or contraction of said housing.

5. The converter as claimed in claim 1, wherein said converter body acts as a piston of a valve means by covering and uncovering said input opening of said bypass conduit.

References Cited UNITED STATES PATENTS 1,875,024 8/1932 Kryzanowsky 23288 F 3,201,206 8/1965 Wawrziniok 23--288 F 3,499,269 3/1970 Bois 23-288 F UX 3,712,030 1/1973 Priest 60-28'8 UX JAMES H. TAYMAN, 111., Primary Examiner US. Cl. X.R.