FR2955893A1 - METHOD AND COMBINATION OF CONTROL INSTALLATIONS FOR DETERMINING THE EXHAUST GAS TEMPERATURE OF A THERMAL ENGINE - Google Patents

Abstract

Method for determining the temperature (T) of the exhaust gases of a heat engine (15) with a combination of control systems (17, 45) of a motor vehicle, these installations being connected by a bus system (47). A first control system (17) determines the operating parameter values of the motor (15) and / or the motor vehicle from signals provided by different sensors and provides the operating parameters by the bus system (47) to the other control installations. A second control system (45) determines the exhaust gas temperature (T) from the values of the operating parameters transmitted by the bus system (47).

Description

FIELD OF THE INVENTION The present invention relates to a method for determining the temperature of the exhaust gases of a heat engine in a combination of control installations of a motor vehicle, these installations being connected by a control system. bus, a method according to which, from signals supplied by different sensors, a first control system provides operating parameter values of the engine and / or the motor vehicle and transmits them to other control facilities via the bus system. The invention also relates to a combination of control installations equipping a motor vehicle for the implementation of such a method, as well as a computer program and a computer program product for the implementation of the invention. process. State of the art For the operation of exhaust gas aftertreatment systems, it is necessary, among other things, to know the temperature of the exhaust gases at different points in the exhaust gas pipe. The temperature of the exhaust gas is for example necessary to manage the operation of catalysts and to determine the need for the regeneration of an oxidation catalyst or a particulate filter.

Different methods are known according to the state of the art for determining the temperature of the exhaust gases in an exhaust aftertreatment installation. The temperature of the exhaust gases is obtained in known manner using temperature sensors by exploiting the signal supplied by the temperature sensors in a control installation; exhaust gas profile models can also be used by calculating a temperature in the broadest sense of the term, from known operating parameters and taking into account thermodynamic and physical relationships.

2 Also, by way of example, the operation of an active noise suppression system (ANC system, also called SAB system) to actively reduce the noise in the exhaust pipe, depends on the temperature of the gases and in particular the temperature of the exhaust gas in the final pipe of the exhaust pipe. In the case of the SAB system, exhaust noise is analyzed in the zone of the end tube in the case of a control installation, this noise is detected electronically by means of a microphone placed in the end pipe. Then, using a control system and a loudspeaker installed upstream or downstream of the end tube zone, a counter-signal corresponding to the noise of the exhaust gas to be analyzed is emitted; this countersignal is generated with substantially the same amplitude but in phase opposition with respect to the exhaust gas signal. This results in a significant reduction of noise. The SAB system is preferably controlled by a separate control facility which, for reasons of cost and space saving, is usually equipped with relatively small resources. In such a control installation, for example, it is not intended to exploit the signals provided by the temperature sensors. In addition, the connection between the sensors would be expensive and fragile. The control system, however, has only a limited supply of operating parameters. For example, only operating parameters such as the engine rotation speed, the engine torque, the traffic speed, etc. are available. These basic parameters or the general data of the motor vehicle are provided, for example, by a system bus, standardized (for example the CAN network controller) according to ISO 11898. The temperature of the exhaust gases as well as other operating parameters of the engine are generally not part of these parameters and it is why, these elements are not first recognized by the control installation, separate.

DISCLOSURE AND ADVANTAGES OF THE INVENTION The object of the present invention is to remedy the disadvantages of the known solutions and relates to a method for determining the temperature of the exhaust gases of a heat engine according to the preamble defined above, characterized in that a second control system determines the temperature of the exhaust gas from the values of the operating parameters transmitted by the bus system. The first control installation may be the engine control unit or the transmission control unit; the second control installation (separate installation) is for example intended to control the SAB system to reduce the noise in the exhaust pipe. All control systems of the vehicle are thus connected by a bus system.

The invention also has the basic characteristic of implementing in the second control installation an exhaust gas temperature module produced in the second control installation and based on a few basic parameters mainly intended for engine management. of the vehicle and taking into account the physical and in particular thermodynamic imperatives and secondly, selected influence parameters, to obtain the temperature of the exhaust gases in particular in the outlet pipe of the exhaust gas pipe . The basic parameters can be, for example, the rotational speed of the motor and the torque supplied. Influence parameters that could affect the temperature of the exhaust gases are for example the engine temperature, the stopping time of the engine, the ambient temperature and / or the speed of movement of the motor vehicle. Other influencing parameters are conceivable. The basic parameters mentioned above and the influencing parameters, for example, are available in the combination of the first control installations of the motor vehicle on the CAN bus and can be interrogated from there, advantageously by the control installation. , definitely and available at any time. Influence parameters are used for operation

4 of the exhaust gas temperature module because the temperature provided by the temperature model may have a deviation as small as possible from the actual temperature (measured temperature) and can thus be adjusted in a complementary manner.

The method according to the invention makes it possible to avoid expensive and fragile temperature sensors. The CAN bus can without additional means, expensive, be connected to the control installation; standardized program routines in the control system allow you to simply read the operating parameters. The temperature of the exhaust gases supplied from the temperature model as well as the partial results of the temperature model are advantageously available even for other internal calculations in the control device. According to another advantageous characteristic, the calculated exhaust gas temperature is determined from the engine temperature and / or the engine stopping time and / or a room temperature and / or ambient temperature. and / or the speed of movement of the motor vehicle. According to another development, the temperature of a room is determined from the temperature of the exhaust gas duct to obtain the temperature of the exhaust gas. According to another development, the exhaust gas temperature prevailing in the end tube of an exhaust gas installation is determined by the second control installation. According to another development, the invention also relates to a combination of control installations and this combination is characterized by a second control installation which determines the temperature of the exhaust gases from the values of the operating parameters transmitted by the control system. bus. In this combination, advantageously, a second control system determines the temperature of the exhaust gas from the values of the operating parameters transmitted by the bus system. According to another advantageous characteristic, the bus system is a network controller bus (CAN bus). According to another characteristic, the second installation controls the active CAN noise suppression system as a function of the temperature of the exhaust gases. According to another characteristic, the second installation controls the flow of the process. The invention also relates to a computer program and a computer program product applying the method described above. Drawings The present invention will be described hereinafter in more detail with the aid of the accompanying drawings in which: - Figure 1 shows the environment of the invention; - Figure 2 shows a diagram giving the temperature of the gases of exhaust as a function of the effective mean pressure delivered by the cylinder and the first rotational speed; - Fig. 3 is a block diagram with the flow of the process according to the invention; - Fig. 4 shows a measurement diagram for exposing the the difference in the temperature of the exhaust gas obtained by the process according to the invention in the end tube relative to the actual values. DESCRIPTION OF EMBODIMENTS OF THE INVENTION FIG. 1 shows a heat engine (internal combustion engine) 15 in the form of a gasoline engine or a diesel engine equipped with an exhaust gas system 13 in which a motor vehicle. The engine 15 is equipped with fuel injectors 16 (a single injector 16 is shown in Figure 1) connected to the control unit 17 of the engine. An intake pipe 19 provides air (arrow 21) to the combustion chambers not shown of the heat engine 15. The intake pipe 19 can be equipped alternatively or in addition to sensors to capture the various state parameters air 21 such as the air temperature and / or its pressure and / or a mass flow of air (not shown). The intake pipe 19 can also be

6 equipped with a throttling device constituting an air flow control member for influencing the mass flow of air. Alternatively or additionally, the engine comprises an exhaust gas recirculation valve, a supply pressure valve or a regulating member for modifying the geometry of the exhaust gas turbocharger as a flow control member. air. The intake pipe 19 is equipped with an air system compressor for compressing the air 21 supplied to the heat engine 15, the compressor itself being part of an exhaust gas turbocharger.

The gas system 13 comprises an exhaust gas duct 23 which receives the exhaust gases 24 emitted by the heat engine 15 and discharges them. A precatalyst 29 (gasoline engine) or an oxidation catalyst 29 (diesel engine) is installed between a first segment 25 and a second segment 27 of the exhaust gas line 23. The exit of the precatalyst / catalyst from The oxidation 29 is connected by the second segment 27 of the exhaust pipe 23 to the inlet of a main catalyst 33 (gasoline engine) or a particulate filter 33 (diesel engine). Depending on the direction of flow, upstream and / or downstream of the catalysts 29 and 33, there are exhaust gas sensors (not shown). In the case of diesel engines, downstream of the particulate filter 33 depending on the direction of passage of the gases, there may be a catalyst for the selective catalytic reaction (SCR); this catalyst is not shown. Behind the catalyst 33, the exhaust gas arrives in a third segment 37 of the exhaust pipe 23. The segment 37 is equipped with damping means 39. Usually, the exhaust gas first arrives in an exhaust muffler and then in an exhaust muffler (these mufflers are not shown separately). The outlet of the muffler 39 opens into a fourth segment, namely the end tube 41 of the exhaust pipe 23. The exhaust gases in the end pipe 41 are referenced 42. end pipe 41 is equipped with an active noise suppression system SAB 43. The SAB system 43 is controlled

7 by a separate control facility 45. The control unit 45 is connected by a CAN network controller bus 47 to the motor control unit 17. According to a preferred development, the installation of the control system 45 is carried out by a computer program with the characteristics of the process or by a computer program product having the characteristics of the process. The term "computer program product" refers to any file or collection of data containing the computer program in memorized form as well as any medium containing such a file or such a collection of data. The SAB system 43 not only serves to reduce the noise in the muffler 39, but also to achieve a further active reduction of the noise in the end pipe 41 of the exhaust pipe 13. For this, in the control installation 45, it captures the noise of the exhaust gas with a microphone not shown installed in the end pipe 41 by an electronic capture and noise analysis. Then, the control installation 45 emits a countersignal via a not shown loudspeaker installed upstream or downstream of the end pipe 41, this counter-signal is generated substantially with the same amplitude but in opposition to phase. The noise reduction function of the SAB system 43 is influenced by the temperature of the exhaust gas 42 in the end line 43, the exhaust gas temperature is not applied separately to the control unit 45 and supplied to the connected CAN bus 47. FIG. 2 shows a diagram showing the temperature of the exhaust gas T as a function of the mean effective pressure P in a cylinder as well as the rotational speed (speed D) of the heat engine 15. The average effective pressure P is correlated with the torque of the engine. The temperature T of the exhaust gas 24, that is to say directly behind the output of the combustion engine 15, is practically a function of the speed of rotation D and the effective average pressure P in the cylinder of the heat engine 15 according to Figure 2.

FIG. 2 shows that, on the one hand, for an exemplary rotation speed of D = 3000 (1 / min), depending on the magnitude of the effective mean pressure P, the temperature of the exhaust gases T can vary between 500 ° C and 750 ° C. On the other hand, in this example, the effective mean pressure P = 6 bars, corresponds to an exhaust gas temperature T between 400 ° C and 850 ° C. Since the information concerning the current effective average pressure P is not available in the CAN bus 47, the temperature of the exhaust gas T is determined, instead of the resulting physical torque M of the heat engine 15. size is available on the CAN bus 47. FIG. 3 is a block diagram of the functions of the control installation 45 as an embodiment of the method for determining the temperature of the exhaust gas T in the end tube 41 of FIG. the suction pipe 13 using an exhaust gas temperature model. As an input parameter of the exhaust gas temperature model, in the example presented, the basic speed parameter D is used for the motor and the internal torque M for the motor can be cyclically requested by the motor. intermediate of the CAN bus 47. As influence parameter which acts on the exhaust gas temperature obtained from the engine rotation speed D and the internal engine torque M, the CAN bus 47 has the engine temperature Tmot, and the speed V of the vehicle. According to another variant, the appropriate influencing parameters can also be the stopping time of the engine and / or the ambient temperature of the vehicle; these parameters are generally available on the CAN bus 47. The processing block 100 reads the engine rotation speed D and the engine torque M in the CAN bus 47 and processes this information using characteristic curves or control fields. characteristics, to determine a modeled temperature Troh exhaust gas bearing the reference 24 in Figure 1. Characteristic curves or characteristic fields thus constitute physical rules and in particular thermodynamic. For example, account is taken of the engine load which dampens the quantities

9 input M giving Mdmpf and D giving Ddampf. The damped influence quantities Mdmpf and Ddmpf as well as the temperature of the raw exhaust gas Troh are available in the control system 45 for possible subsequent treatment and also outside the exhaust gas temperature model. In the other processing blocks 110-140, the temperature of the Troh exhaust gas, modeled as a function of the situation at the end line 41 of the exhaust gas pipe 13, is adapted as closely as possible.

In the processing block 110, the temperature of the motor Tmot is taken into account as the first parameter in influence. In particular, when the engine is heated from a cold start, the engine 15 and the exhaust pipe 13 are still at ambient temperature and thus cool the exhaust gases passing through them so that that firstly there will be cooled exhaust gas at the end tube 41. The exhaust gases heat up by convection and thermal conduction during the heating of the engine and this has a progressive effect on the driving of the engine. In addition, in the case of a cold start of a relatively rich fuel / air mixture, this also leads to a decrease in the temperature of the exhaust gas. These influences are taken into account by the characteristic curve or the characteristic field so that a correction coefficient Tkorr is determined for the temperature of the exhaust gases in the end pipe 41, this correction coefficient is multiplied by the modeled temperature of Troh exhaust gases. The correction coefficient Tkorr is provided for possible subsequent treatment also beyond the exhaust gas temperature model to be available in the control installation 45. As a second influence parameter, the processing block 120 takes into account the speed V of the vehicle. The motor rotation speed D (V = 0) when the vehicle is stopped and when accelerating, the speed is relatively higher than in the driving mode. Increasing the speed of rotation D of the motor

10 is, however, interpreted in the process block 100 as a large increase in the temperature of the exhaust gas. However, since the heat engine 15 is not loaded when it is stationary, it is necessary in this case that the modeled temperature of the output gases Troh be corrected in the direction of a decrease. The higher the rotation speed D, the lower the correction coefficient Vkorr, which multiplies the modeled temperature Troh. The value Vkorr is determined according to the damped speed Ddmpf obtained in the processing block 100 for a vehicle speed V = 0 beyond a characteristic. The correction coefficient Vkorr is provided for a possible treatment also outside the exhaust gas temperature model in the control installation 45. According to another development of the method, it is also possible to take account of the variable cooling achieved by the wind. of circulation on the intake pipe 13 when the vehicle is traveling at different speeds. The processing block 130 takes into account the temperature TBendrohr of the exhaust pipe 41 in the exhaust temperature model. The muffler 39, in particular the exhaust muffler, can be taken into account. Since neither the temperature of the exhaust pipe 13 nor that of the end pipe 41 is available on the CAN bus 47, they must be modeled. The modeling of the TBendrohr temperature of the component during the temperature rise is done by a strong damping of the exhaust gas temperature Troh, because the components are heated by the exhaust gases and the thermal inertia of the components dampens temperature peaks of the exhaust gases. During cooling, for example, when the vehicle is traveling in an inertial thrust mode, the temperature of the pipe Troh exhaust being lower than the temperature of TBendrohr components, this situation is taken into account so that the cooling takes place only with a long delay, because the exhaust gases are first heated by the hot components. For this, the raw temperature of the Troh exhaust gases is entered using the processing block 100 and it is

11 operates with respect to a characteristic field or a characteristic curve to obtain a value of the temperature of the exhaust gas or correct them by a correction coefficient TBkorr. The temperature Troh of the exhaust gas line, thus reflects the operating state of the engine 15. By exploiting the operating state, it is taken into account that, depending on the operating state of the engine 15, the components accumulate different amounts of heat. The output parameters of the process block 130 are the room temperature TBendrohr of the end line 41 as well as the correction coefficient TBkorr of the temperature of the exhaust pipe Troh. The correction coefficient TBkorr is multiplied by the temperature Troh of the exhaust pipe. The TBkorr correction coefficient and the temperature of the TBendrohr parts are provided for possible subsequent treatment (outside the exhaust temperature model) in the control unit 45. The exhaust temperature model also determines all the characteristic correction coefficients, in particular the three correction coefficients Troh, Vkorr and TBkorr. Of these, the coefficient Troh is determined at the processing point 110, the correction coefficient Vkorr is obtained in the processing block 120 and the correction coefficient TBkorr is obtained in the processing block 130 These correction coefficients are all multiplied by the temperature Troh of the exhaust gas line obtained in the processing block 100. Other correction coefficients such as, for example, the stopping time of the engine 15 or the ambient temperature of the vehicle, may be taken into account. in other developments of the invention.

The final product is the temperature of the exhaust gas Tendrohr in the end line 41 of the exhaust pipe 13, which however has excursions due to the fact that the load varies very rapidly from the heat engine 15. The temperature of the gases Tendrohr exhaust is provided by the installation

12 control 45 for possible use (even outside the exhaust gas temperature model). In the treatment block 140, the overshootings of the temperature of the Tendrohr exhaust gas hitherto obtained in the end tube 41 are eliminated and thus a smooth curve is obtained. This results in further attenuation of the exhaust temperature of Tendronr. The result is the temperature of the exhaust gas T, modeled, final, in the exhaust pipe 41, this temperature is available to be used in particular for the control of the SAB system 43 in the control installation 45. if any other treatment outside the temperature model of the exhaust gas, the final temperature of the exhaust gas T is provided in the end pipe 41 available in the control installation 45.

FIG. 4 shows a measurement diagram representing the difference in the temperature of the exhaust gas T obtained by the exhaust gas temperature model according to the invention in the end pipe 41 with respect to the values actually measured in FIG. the end pipe 41. In the curve 200 of the diagram, there is the measured plot of the temperature T of the exhaust gases in the end pipe 41 for different operating states (urban traffic, traffic on departmental road, displacement on motorway and cold start) as a function of time t. Curve 210 shows the respective deviation from the measured values T of the exhaust gases with respect to the modeled values T of the temperature of the exhaust gases. Using the temperature scale, the diagram shows that the T value of the exhaust gas temperature, modeled, deviates by about 50 ° from the actual values. A permanently oscillating gap or an alternating gap for the different operating states can not be seen. This means that the deviations are similar throughout the test phase.35 NOMENCLATURE

13 exhaust system 15 heat engine 16 fuel injector 17 engine control unit 19 intake line 21 air 23 exhaust gas line 24 exhaust gas line 25 first segment 27 second segment 29, 33 upstream catalyst / oxidation catalyst 37 segment 39 muffler 41 end line 42 exhaust gas 43 system SAB 45 separate control system 47 CAN bus 110-130 treatment blocks25

Claims (1)

CLAIMS 1 °) Method for determining the temperature (T) of the exhaust gas of a heat engine (15) in a combination of control systems (17, 45) of a motor vehicle, these installations being connected by a system bus (47), a method according to which, from signals supplied by different sensors, a first control device (17) provides operating parameter values of the heat engine (15) and / or the motor vehicle Io and transmits them to other control installations via the bus system (47), characterized in that a second control device (45) determines the exhaust gas temperature (T) from the values of the parameters of the 15 transmitted by the bus system (47). 2) A method according to claim 1, characterized in that the temperature of the exhaust gas (T) is determined as a function of the rotational speed (D) of the engine and the torque (M) of the engine. Method according to Claim 2, characterized in that the calculated exhaust gas temperature (T) is determined from the engine temperature (Tmot) and / or the engine stopping time and / or a room temperature (TBendrohr) and / or the ambient temperature and / or the traveling speed (V) of the motor vehicle. 4 °) A method according to claim 1, characterized in that the temperature of a room (TBendrohr) is determined from the temperature (Troh) of the exhaust pipe to obtain the temperature (T) of the exhaust gas. 35'15 5 °) A method according to claim 1, characterized in that one determines the temperature of the exhaust gas (T) in the end tube (41) of an exhaust gas installation (13). ) by the second control installation. 6 °) A combination of control systems (17, 45) of a motor vehicle connected by a bus system (47), - at least a first control device (17) determining the values of the operating parameters of the engine (15) and / or the motor vehicle from the signals supplied by different sensors and these operating parameters are transmitted by the bus system (47) to the other control systems, a combination characterized by a second control installation ( 45) which determines the temperature of the exhaust gas (T) from the values of the operating parameters transmitted by the bus system (47). Combination according to claim 6, characterized in that a first control unit (17) comprises a motor control unit and / or a transmission control unit, and a second control unit (45), controls an active noise canceling system (43). 8 °) Combination according to claim 6, characterized in that the bus system (47) is a network zone controller bus (CAN bus). 9 °) Combination according to claim 6, characterized in thata second control installation (45) controls the active CAN noise canceling system (43) as a function of the temperature (T) of the exhaust gas. 10 °) Combination according to claim 6, characterized in that the second control installation (45), controls the course of the process according to any one of claims 2 to 4. 11 °) Computer program product comprising instructions of program code recorded on a usable medium in a computer, characterized in that it comprises computer readable programming means for carrying out the steps of the method according to any one of claims 2 to 5.