FR2921122A3 - Intake gas temperature regulating system, has detecting unit detecting parameters representing operating state of gas treating device, and electronic control unit controlling increasing unit based on detected parameters at level of device - Google Patents

Abstract

The system has a temperature increasing unit increasing temperature of intake gas of an internal combustion engine (10) e.g. oil engine, of a motor vehicle and including a recirculation pipe (42) extended between outlet and inlet zones of respective exhaust and intake manifolds (16, 14) of the engine. A detecting unit with a hydrocarbon content detecting sensor detects parameters representing an operating state of an exhaust gas treating device i.e. oxidation catalyst. An electronic control unit (38) controls the increasing unit based on the detected parameters at the level of the device. An independent claim is also included for a method for regulating an intake gas temperature of an internal combustion engine of a motor vehicle.

Description

B07-2884 - JT / PG PJ 7416 / IA

Simplified joint-stock company known as: RENAULT s.a.s. Intake gas temperature control system of an internal combustion engine, and associated method. Invention of: Philippe ARRIBARD

2 Intake gas temperature control system of an internal combustion engine, and method thereof.

The present invention relates to the automotive field and more particularly to the operation of an internal combustion engine whether of the spark-ignition type or of the Diesel type. More particularly, the invention relates to a system for regulating the temperature of the intake gases of an internal combustion engine of a motor vehicle capable of limiting the emission of polluting particles. Restrictions on the emission of exhaust pollutants from internal combustion engines of motor vehicles require the development of more and more effective abatement strategies. One of these strategies is to recirculate a portion of the exhaust gas from combustion by means of a partial exhaust gas recirculation (EGR) line which is stitched onto the exhaust line of the engine. This is called low pressure recirculation. The reintroduction of the exhaust gas at the intake of the engine makes it possible to reduce the combustion temperature inside the cylinders and thus reduce the emission of particularly harmful NOX nitrogen oxide particles. However, such a partial recirculation of exhaust gas generates in return emissions of HC hydrocarbons and carbon monoxide CO during a cold start and low engine loads, since the mixture of fresh air and of recycled exhaust gas admitted has a relatively low temperature.

Under these conditions, in order to increase the temperature of the incoming gases at the intake of the engine, it is possible, for example, to bypass the charge air cooler of the engine. In the current state of the art, this bypass of the charge air cooler is controlled according to the temperature of the engine coolant and its charge. This solution has the major disadvantage of not allowing a satisfactory compromise to be obtained between, on the one hand, the emission of hydrocarbons and carbon monoxide, and, on the other hand, of nitrogen oxide with small loads. engine or during a cold start. The present invention therefore aims to remedy this drawback. The invention more particularly to provide a system adapted to ensure a particularly precise control of the temperature of the gases to be admitted to the interior of the engine. To this end, the subject of the invention is a system for regulating the temperature of the intake gases of an internal combustion engine of a motor vehicle comprising an exhaust line equipped with a device for treating the exhaust gases of the vehicle. motor and a partial exhaust gas recirculation device in the engine combustion chamber of the type comprising a recirculation pipe stitched on the exhaust line and opening upstream of a turbocharger. The system comprises means for increasing the temperature of the engine intake gases, means for detecting parameters representative of the operating state of the treatment device, and a control unit able to control the means for increasing the temperature of the engines. intake gas as a function of the parameters detected at the level of the treatment device.

In one embodiment, the means for increasing the temperature of the intake gases comprises a recirculation line extending between an exhaust zone of an engine exhaust manifold and an inlet zone of a manifold. intake, and a recirculation valve. Preferably, the system comprises a heat exchanger mounted on the recirculation pipe and traversed by a heat transfer fluid. In one embodiment, the means for increasing the temperature of the intake gases comprise a bypass line for bypassing a heat exchanger through which a mixture of fresh air and recycled exhaust gas and a heat transfer fluid , and an adjusting valve mounted on said pipe. The heat exchanger can be the charge air cooler of the engine. In one embodiment, the detection means comprise a sensor for measuring the hydrocarbon content disposed downstream of the treatment device. Alternatively, the detection means may comprise a sensor for measuring the carbon monoxide content disposed downstream of the treatment device, or temperature sensors arranged upstream and downstream of the treatment device. Advantageously, the treatment device is an oxidation catalyst.

The system of the invention can be advantageously used in a diesel engine. The subject of the invention is also a method for regulating the temperature of the intake gases of an internal combustion engine of a motor vehicle comprising an exhaust line equipped with an engine exhaust gas treatment device and a combustion engine. a device for partial recirculation of exhaust gases in the combustion chamber of the engine of the type comprising a recirculation pipe stitched on the exhaust line and opening upstream of a compressor, in which the temperature of the gases is regulated. intake according to parameters representative of the operating state of the treatment device detected in the exhaust line. Advantageously, the temperature of the inlet gases is increased by a partial recirculation of the exhaust gas reinjected directly upstream of the intake manifold of the engine. It is also possible to increase the temperature of the intake gases by bypassing the charge air cooler of the engine.

The present invention will be better understood from the study of embodiments taken by way of nonlimiting example and illustrated by the accompanying drawings, in which Figures 1 to 4 show schematically an internal combustion engine equipped with a control system. according to a first, second, third and fourth embodiment of the invention, respectively. FIG. 1 schematically shows the general structure of an internal combustion engine 10 for a motor vehicle, which here comprises four cylinders 12 in line. Each cylinder 12 comprises two intake and exhaust ports (not referenced) which can be closed respectively by intake and exhaust valves. The engine 10 also comprises an intake manifold 14 for supplying gas to the intake ports of the cylinders 12 and an exhaust manifold 16 in communication with the orifices

6 exhaust, which is itself connected to an exhaust line 18. The exhaust line 18 comprises a turbine 20 mounted on a shaft 22 common to a compressor 24 disposed in a supply line 26 connected to the collector 14. The exhaust gas conveyed inside the line 18 passes through the turbine 20 which drives the compressor 24 so as to increase the pressure of the air admitted into the cylinders 12. The engine 10 also comprises a partial exhaust gas recirculation or recirculation device (EGR).

For this purpose, a recirculation pipe 28 is stitched on the exhaust line 18 downstream of the turbine 20. A recirculation valve 30, called EGR valve, controls the amount of exhaust gas which is then reinjected by the pipe in the intake manifold 14. The recirculation pipe 28 comprises a heat exchanger 32 through which the exhaust gas and a heat transfer fluid pass so as to obtain a slight cooling of the recycled exhaust gases before they are exhausted. introduction inside the pipe 26. Advantageously, the coolant passing through the heat exchanger 32 is the one used for cooling the engine 10. In the exhaust line 18, is mounted a catalyst 34 of oxidation directly downstream of the turbine 20 and upstream of the recirculation pipe 28. The oxidation catalyst 34 forms an exhaust gas treatment device. Of course, it would also be possible to further provide a particulate filter downstream of the catalyst. The engine 10 further comprises a heat exchanger 36 mounted on the intake pipe 26 between the intake manifold 14 and the compressor 24. The heat exchanger 36 is traversed by the

7 heat transfer fluid passing through the heat exchanger 32 and the gas mixture consisting of recirculated exhaust gas and fresh air conveyed by the pipe 26. The heat exchanger 36 allows to cool the inlet gas before their inlet to the intake manifold 14. The heat exchanger 36 is the charge air cooler of the engine. An electronic control unit 38 ensures the operation of the engine 10 and receives for this purpose a certain amount of information. Different sensors (not shown) are placed in this respect in the pipes and their signals are fed to the control unit 38. Pressure and temperature sensors are for example mounted on the pipes 26 and 28, in the collector Exhaust 16, and on the exhaust line 18. The control unit 38 can in particular control the position of the EGR valve 30 via an electrical connection 40. The control unit 38 also controls the injectors of fuel (not shown) of the engine 10. In operation, the oxidation catalyst 34 is intended to reduce the HC hydrocarbons contained in the exhaust gas conveyed in the line 18. The oxidation catalyst 34 has a temperature called thermal priming below which oxidation of unburned HC hydrocarbons and carbon monoxide CO can not be carried out autonomously. This temperature is of the order of 150 ° C.

Thus, the oxidation catalyst 34 can not function properly at low temperatures, especially during the start of the vehicle and the time required for the thermal activation of the catalyst. This duration is generally of the order of a few hundred seconds during a cold start. At the end of this

In the course of time, the oxidation catalyst 34 sees its temperature cross the threshold of 150 ° C. However, it is also possible that the oxidation catalyst 34 is de-primed, that is to say that the temperature becomes below the threshold of 150 ° C during the operation of the vehicle, for example during a traffic jam. In order to allow the oxidation catalyst 34 to function properly at low temperatures, a recirculation line 42 is provided on the exhaust manifold 16 and opening at the intake pipe 26 immediately upstream of the exhaust manifold. 14, ie downstream of the heat exchanger 36. The recirculation line 42 comprises a recirculation valve 44 so as to control the amount of exhaust gas reinjected inside the intake pipe 26.

On the recirculation pipe 42, there is also provided a heat exchanger 46 traversed by the heat transfer fluid passing through the heat exchangers 32 and 36, and by the recirculated exhaust gas. In order to carry out the functional control of the efficiency of the oxidation catalyst 34, a sensor 48 of the hydrocarbon content HC is disposed directly downstream of the oxidation catalyst 34. The content signal measured by the sensor 48 is brought by an electrical connection 50 to one of the inputs of the electronic control unit 38.

Depending on the content detected by the sensor 48, the control unit 38 determines whether it is necessary to increase the temperature of the gases at the inlet. Indeed, when the HC hydrocarbon content is high, the effectiveness of the oxidation catalyst 34 is relatively low.

9 Therefore, the control unit 38 controls the opening of the recirculation valve 44, via an electrical connection 52, so as to allow injection of hot recirculated exhaust gas directly upstream of the collector 14. Simultaneously, the control unit 38 controls the closing of the recirculation valve 30 to obtain a recirculation of exhaust gas only upstream of the intake manifold 14. Thus, from the hydrocarbon content HC detected, the control unit 38 controls the recirculation of exhaust gas so as to increase the temperature of the exhaust gas and quickly increase the temperature of the oxidation catalyst 34. Thus reduces the time required for activation or reactivation of the oxidation catalyst. Once the hydrocarbon content HC detected by the sensor 38 reaches a level corresponding to the thermal initiation temperature of the oxidation catalyst 34, the control unit 38 controls the closure of the recirculation valve 44 and the reopening of In an alternative embodiment, it may be possible to replace the sensor 48 for measuring the HC hydrocarbon content by a carbon monoxide content measurement sensor CO also disposed downstream of the oxidation catalyst 34. in order to detect the operating efficiency of the latter. The embodiment variant illustrated in FIG. 2 in which the identical elements bear the same references differs only in that the sensor for measuring the HC hydrocarbon content has been replaced by temperature sensors 60, 62 arranged immediately upstream and downstream. downstream of the oxidation catalyst 34 so as to detect whether the temperature thereof is

Above the threshold of 150 ° C. The temperature signals measured by the sensors 60, 62 are respectively fed by electrical connections 64, 66 to inputs of the electronic control unit 38.

The embodiment illustrated in FIG. 3, in which the identical elements bear the same references differs from the embodiment of FIG. 1 in that instead of the exhaust gas recirculation duct, a pipe is provided. 70 of the heat exchanger 36 stitched immediately upstream thereof and opening upstream of the intake manifold 14. The bypass line 70 comprises a control valve 72 which can be controlled by the control unit 38 via an electrical connection 74. When the control unit 38 detects that it is necessary to increase the temperature of the gases at the intake of the engine via the hydrocarbon content HC detected by the sensor 48, the control unit controls the opening of the control valve 72 so as to by-pass the heat exchanger 36. Thus, the bypass line 70 and the control valve 72 form m means for obtaining an increase in the temperature of the gases provided at the intake of the engine. The embodiment variant illustrated in FIG. 4, in which the identical elements bear the same references, differs from the embodiment of FIG. 3 only in that the sensor for measuring the hydrocarbon content is replaced by measurement sensors 80, 82. the temperature signals respectively arranged upstream and downstream of the oxidation catalyst 34. The temperature signals measured by the sensors 80 and 82 are respectively brought by electrical connections 84 and 86 to the electronic control unit 38.

Although in the embodiments previously described, the means for allowing an increase in the temperature of the gases at the intake of the engine comprise either a recirculation line stitched onto the exhaust manifold and opening directly upstream of the intake manifold. , or a bypass line to by-pass the heat exchanger constituted by the charge air cooler, it is easily understood that it is also possible, without departing from the scope of the invention, to provide to use these two means in combination.

Thanks to the invention, it becomes possible to obtain a particularly effective and economical increase in the temperature of the inlet gas when the oxidation catalyst has a temperature below its thermal initiation temperature. The system according to the invention thus forms a means of assisting the operation of the oxidation catalyst at low temperatures.

Claims (12)

1-System for regulating the temperature of the intake gases of an internal combustion engine of a motor vehicle comprising an exhaust line (18) equipped with a device (34) for treating the exhaust gases of the engine and a device for partial recirculation of the exhaust gases in the engine combustion chamber of the type comprising a recirculation line (28) stitched on the exhaust line and opening upstream of a turbocharger (20, 24), characterized in that it comprises means (42, 44, 70, 72) for increasing the temperature of the engine intake gases, detection means (48; 60, 62; 80, 82) of parameters representative of the operating state of the treatment device, and a control unit (38) adapted to control the means for increasing the temperature of the intake gases according to the parameters detected at the processing device (34). The system of claim 1, wherein the means for increasing the temperature of the intake gases comprises a recirculation line (42) extending between an exhaust zone of an exhaust manifold (16) of the engine and an inlet zone of an intake manifold (14), and a recirculation valve (44). 3-System according to claim 2, comprising a heat exchanger (46) mounted on the recirculation pipe (42) and traversed by a heat transfer fluid. 4-System according to any one of the preceding claims, wherein the means for increasing the temperature of the inlet gases comprise a bypass line (70) for bypassing a heat exchanger (36) through which a mixture of fresh air passes through 13 and recycled exhaust gas and a heat transfer fluid, and a control valve (72) mounted on said pipe. The system of claim 4, wherein the heat exchanger (36) is the charge air cooler of the engine. A system according to any one of the preceding claims, wherein the detection means comprises a sensor (48) for measuring the hydrocarbon content downstream of the treatment device. 7-System according to any one of claims 1 to 5, wherein the detection means comprise a sensor for measuring the carbon monoxide content disposed downstream of the treatment device. 8-System according to any one of claims 1 to 5, wherein the detection means comprise temperature sensors (60, 62; 80, 82) disposed upstream and downstream of the treatment device. 9-System according to any one of the preceding claims, wherein the treatment device is an oxidation catalyst (34). 10-Process for regulating the temperature of the intake gases of a motor vehicle internal combustion engine comprising an exhaust line equipped with an engine exhaust gas treatment device and a partial recirculation device exhaust gases in the combustion chamber of the engine of the type comprising a recirculation pipe stitched on the exhaust line and opening upstream of a turbocharger, characterized in that the temperature of the inlet gases is regulated by function of parameters representative of the operating state of the processing device detected in the exhaust line. 14 11-Process according to claim 10, wherein the temperature of the inlet gas is increased by a partial recirculation of exhaust gas reinjected directly upstream of the intake manifold of the engine. 12-A method according to claim 10 or 11, wherein the temperature of the intake gas is increased by bypassing the charge air cooler of the engine.