EP1630374A1 - Rheological control of the cooling of an engine - Google Patents

Abstract

The engine is cooled by a rheological fluid which in its passive state has a lower thermal conductivity value than in its activated state. The rheological fluid in its passive state has a thermal conductivity value of about a third with regard to the thermal conductivity value of water, and in its active state has a value of somewhat more than three times the thermal conductivity value of water. The rheological fluid has a base substance of silicone oil and a thermal conductivity value range of 0.2 to 1.88 watts per metre kelvin.

Description

The invention relates to an engine with a coolant for cooling the engine.

Such engines can, for example, internal combustion engines, especially internal combustion engines such. B. diesel engines or gasoline engines for motor vehicles, in which the coolant is introduced into cooling channels, so that the internal combustion engine has a coolant jacket.

In a combustion engine, fuel consumption during a cold NEDC test (starting temperature about 24 ° C) is about 10 to 15% higher than in the same test with an engine oil temperature starting at about 90 ° C, the so-called NEDC -Heißtest. This is partly because the lubricating oil at lower temperatures has a higher toughness, and the fuel is condensed on the cylinder walls and registered in the engine oil. In addition, measures are taken to heat the catalyst faster, these are z. As a retardation of the ignition, raising the idle speed and enrichment with Sekundärlufteinblasung. In addition, the majority of the emitted exhaust emissions during the cold start phase of the internal combustion engine, if the catalyst has not yet reached the required operating temperature. At the same time, a large part of the energy supplied is discharged unused as exhaust gas enthalpy. This is a total of about 30 to 40% of the energy of the fuel supplied.

It is known to improve the warm-up phase of the engine by using exhaust gas heat exchangers which heat the engine oil in a complicated manner. On the other hand, it is a problem to protect the engine, in particular the engine oil in this heating from overheating. Therefore, additional high performance oil coolers are used.

DE 27 53 716 relates to a hot air-emitting heater for powered by an internal combustion engine motor vehicles, acted upon by an atmospheric air heat exchanger for heat dissipation of a flowing in a power circuit heat carrier and also in the Switched line circuit, exhaust heat of the engine receiving and to the heat carrier emitting heat exchanger. The line circuit for the heat carrier of the heater is at least with the lubricating oil circuit of the internal combustion engine in heat-conducting connection. Here, a heat transfer to the lubricating oil in a dry sump tank is achieved in that heat is discharged through a flowing in a flow line heat transfer medium to the located in the dry sump tank lubricating oil.

GB 2 381 576 A discloses an exhaust heat recovery device having a heat exchange conduit and a bypass conduit. In the region of the heat exchanger line, a heat exchanger is arranged. At least one valve device is provided in the heat exchanger line and / or the bypass line in order to influence an exhaust gas flow rate in the heat exchanger line. At least the heat exchanger line has a gradient in an exhaust gas flow direction in the installed position.

EP 0 885 758 B1 relates to a method for operating a heat exchanger in the exhaust gas stream of an internal combustion engine for motor vehicles, in which the exhaust gas stream can be divided into a main line and into a bypass line. The heat exchanger is arranged in the bypass line. In a warm-up operation, a backflow can be generated in the main line, which causes a back pressure at the exhaust gas outlet of the internal combustion engine. The warm-up operation is divided into two phases, wherein in the first phase, a higher back pressure than in the second phase is generated. A first valve is disposed in the main conduit between the bypass conduit ports, with a second valve disposed in the bypass conduit downstream of the heat exchanger. In the first phase, both valves are closed, wherein in the second phase, the first valve is closed, but the second valve is open.

DE 199 08 088 A1 relates to an internal combustion engine, in particular a diesel internal combustion engine, for a vehicle, with a passenger compartment heater, an exhaust pipe, a coolant line forming a cooling circuit with a first pump to which the internal combustion engine is connected, and an exhaust gas heat exchanger for Transfer of exhaust heat to one Heating heat exchanger. The exhaust gas heat exchanger is effective between the exhaust pipe and a circulation medium line forming a circulation circuit to which the heating heat exchanger is connected directly or indirectly.

However, DE 199 08 088 A1 also relates to an internal combustion engine, in particular a diesel internal combustion engine, wherein the internal combustion engine is connected to a branching off from the coolant line first bypass, in which a first thermostatic valve is arranged, which largely bypasses the first bypass until reaching an average coolant temperature locks and opens above this coolant temperature. In a parallel to the first bypass extending second bypass, a second thermostatic valve is arranged, which largely blocks the second bypass above the average cooling temperature.

DE 100 47 810 A1 enters a heating circuit with a Zusatzheizvorrichtung for motor vehicles with internal combustion engine, which is part of a separate short-circuit, which is switchable by means of a switching device in the heating circuit. As auxiliary heater, an exhaust system of the engine of the motor vehicle is used, from which the exhaust heat is transferred into the heating circuit. The exhaust heat supply can be raised by engine measures when the exhaust heat requirement falls below the heat requirement of the interior heating system. However, DE 100 47 810 A1 also relates to a method for operating a heating circuit with an auxiliary heating device for motor vehicles with an internal combustion engine, designed as exhaust gas heat exchanger through which the engine exhaust gas and coolant flow. To increase the heating power of the additional heater, the engine operating parameters can be influenced.

EP 1 094 214 A2 relates to a heat recovery system having a circulation passage in which a heat transfer medium circulates through an engine cooling unit, and an exhaust heat exchanger for utilizing the exhaust gases of an engine and a passage connecting an outlet side of the circulation passage to an exit of the heat exchanger. The exhaust gas heat exchanger is disposed across the circulation passage at a side upstream of the engine cooling unit. The heat transfer medium, introduced into the exhaust gas heat exchanger is controlled to a lower temperature sufficient to lower a temperature of the water vapor contained in the exhaust gas stream from which heat is transferred to the heat transfer medium to lower its dew point.

But it is also known to achieve intelligent cooling of internal combustion engines by means of additional valves or electric water pumps, water being used as the coolant. Although this has proven successful in practice, the high thermal conductivity and heat capacity of water has not been taken into account in these measures. This is necessary for a full load operation, but reduces the efficiency during the warm-up phase. Another night part of water as a coolant is to be seen in the fact that the maximum operating temperature is limited by the range of about 100 ° C in order to avoid boiling of the water or a local overheating.

JP 2002 323071 (= EP 1 223 362 A2) relates to a fan drive arrangement with an electronically controlled magnetorheological fluid. The assembly is connected to a fan to cool a radiator. The magnetorheological fluid has a semi-solid consistency in an activated state, so that a drive means is entrained by the fluid.

The invention has the object to improve an engine of the type mentioned by simple means to the extent that the engine oil is performed faster in the cold start phase or in the warm-up phase to operating temperature, so that both a reduced fuel consumption and reduced emissions are achieved wherein overheating of the engine oil is to be avoided.

According to the invention the object is achieved in that the coolant is a rheological fluid.

A rheological fluid in the context of the invention is a z. For example, silicone oil-based fluid that includes electrically and / or magnetically-responsive ingredients. By means of a suitable activation device, which For example, generates an electric current and / or a magnetic field, the rheological fluid is placed in an active or passive state. In the passive state, rheological fluid is fluid. In contrast, in the active state, the rheological fluid changes its viscosity and is essentially semi-solid.

The invention is based on the finding that the rheological fluid in its passive state has a lower thermal conductivity than in its active state. The thermal conductivity increases continuously.

Favorable for the purposes of the invention is when the coolant has a rheological fluid with a thermal conductivity of about one third, based on the Wärmeleitwert of water in its passive state and a thermal conductivity of slightly more than three times the thermal conductivity of water when the rheological fluid is activated. Preferably, the rheological fluid has a Wärmeleitwertbereich of about 0.2 to 1.88 W / mK, wherein the Wärmeleitwert of water is at an amount of 0.6 W / mK.

The low thermal conductivity is particularly favorable in a warm-up phase of an internal combustion engine, since the resulting heat is advantageously dissipated not so fast, which in particular the engine oil is quickly led to operating temperature. In its passive state, the rheological fluid acts as a kind of heat insulator.

By contrast, after the warm-up phase, in particular when the internal combustion engine is operated in its full load range, it is expedient if the resulting heat is dissipated quickly. This is achieved due to the high thermal conductivity of the rheological fluid in its activated state. To activate the rheological fluid, the activation device is located at a suitable location. A suitable place can z. Example, be a cylinder wall of the engine and / or cylinder head, the coolant is of course included in coolant channels, which is known per se. The rheological fluid reacts very quickly to the continuous activation by means of the activation device, whereby a continuous increase in the Thermal conductivity is achieved. The rheological fluid transports the heat from the place of origin, for example, the cylinder inner wall to the cylinder outer wall. In order to control this heat transfer, operating parameters of the internal combustion engine or the engine such as engine speed, load and / or temperature can be used, with control signals for the activation device can be provided by means of suitable control algorithms.

Advantageously, by means of the rheological fluid according to the invention, the fuel consumption of the internal combustion engine is significantly reduced, whereby friction losses are reduced, since the engine oil is accelerated to operating temperature, whereby the engine oil provides the required lubricating property more quickly. In addition, measures to heat the catalyst faster, resulting in increased fuel consumption can be reduced, the catalyst is guided by the invention faster to operating temperature. This in turn causes an improved conversion of pollutants, eg. B. NOx. Further, fuel condensation on the cylinder walls is reduced.

Of course, the invention is not limited to the preferred embodiment of an internal combustion engine. The rheological fluid can generally be used as a coolant if the heat is to be transported away from its point of origin. Next, the rheological fluid also other basic materials such. B. have water.

Claims (4)

Engine with a coolant for cooling the engine,
characterized in that
the coolant is a rheological fluid. Engine according to claim 1,
characterized in that
the rheological fluid in its passive state has a lower thermal conductivity than in its activated state. Engine according to claim 1 or 2,
characterized in that
the rheological fluid in its passive state has a Wärmeleitwertbetrag of about one third, based on the Wärmeleitwertbetrag of water, and in its active state, a Wärmeleitwertbetrag of slightly more than three times the thermal conductivity of water. Engine according to one of claims 1 to 3,
characterized in that
the rheological fluid as a base material silicone oil and a calorific value range of 0.2 to 1.88 W / mK.