FR2945319A1 - SYSTEM AND METHOD FOR CONTROLLING COMBUSTION IN AN INTERNAL COMBUSTION ENGINE. - Google Patents

Abstract

A combustion control system in an internal combustion engine (2) of a motor vehicle, comprising a first actuator (6) capable of controlling a nitrogen oxide level emitted by the engine (2), a second actuator (7) ) capable of controlling a combustion noise of the engine (2), a first regulating means (30) capable of driving the first actuator (6) to regulate in a closed loop the rate of nitrogen oxides emitted by the engine (2). ) and a second regulating means (31) adapted to drive the second actuator (7) for closed-loop control of the combustion noise of the motor (2).

Description

B08-3455 - AxC / CRA

Simplified joint-stock company known as: RENAULT s.a.s. System and method for controlling combustion in an internal combustion engine Invention of: EMERY Pascal RECOVERY Philippe TIGRINE Olivier System and method for controlling combustion in an internal combustion engine

The invention relates to the control of combustion in an internal combustion engine and in particular in a motor vehicle engine. Current pollution standards require motor vehicle manufacturers to improve their engines. In order to pass the pollution control at a lower cost, the manufacturers are obliged to control as precisely as possible the combustion of their engines. A control of the combustion is preponderant on the polluting emissions of the engines. The increased complexity of combustion control systems is also a consequence of these new pollution standards. For example, French patent application FR0609337, filed in the name of the applicant, in which a closed-loop architecture based on the measurement of the pressure in the combustion chamber is used to control the combustion noise. But this system is not precise enough to control the combustion in the engine. International application WO2005 / 028833 discloses a method for adjusting the amount of oxygen, the boost pressure and the fuel injection from a measurement of the boost pressure in the intake manifold and a measurement by oxygen sensor the amount of oxygen admitted upstream of a compressor. But this method does not take into account the dispersion of the various actuators used, such as fuel injectors and the compressor.

One of the aims of the invention is to provide a simple and more accurate means for controlling combustion in an internal combustion engine.

In one embodiment, a combustion control system is proposed in an internal combustion engine of a motor vehicle. This system comprises a first actuator capable of controlling a level of nitrogen oxides emitted by the engine, a second actuator capable of controlling a combustion noise of the engine, a first regulation means able to drive the first actuator to regulate in a loop closed the rate of nitrogen oxides emitted by the engine and a second control means adapted to drive the second actuator for closed-loop control of the combustion noise of the engine. This provides a means for controlling the combustion in an internal combustion engine which takes into account the rate of oxides of nitrogen and the combustion noise emitted during combustion. In addition this means improves the accuracy of the current control systems of combustion. According to one embodiment, the engine comprises at least one cylinder, a movable piston driven by means of a crankshaft, and the system comprises means for measuring the temporal variations of the crankshaft angle and the internal pressure of said crankshaft. cylinder and estimation means able to estimate respectively a level of nitrogen oxides emitted by the engine and a combustion noise of the engine from said measurements, the first regulation means being able to drive the first actuator from a difference between a first setpoint and said estimate of the nitrogen oxide content, and the second regulating means being able to drive the second actuator from a difference between a second setpoint and said estimation of the combustion noise. Thus, an estimation means is provided which avoids the multiple maps used during the engine development phases. According to another embodiment, the second regulating means comprises multiplying means for multiplying said difference, between the second setpoint and the estimation of the combustion noise, with the first difference produced by the first regulating means. The regulating means may also be coupled to each other when they have different control speeds. Indeed, it is possible to connect the regulating means so that the slowest means can stop the fastest means. This saves computing time and allows a stable equilibrium to be achieved to effectively control combustion. In another aspect, there is provided a method of controlling combustion in a motor vehicle internal combustion engine. This method comprises a first closed loop regulation of a nitrogen oxide level emitted by the engine and a second closed loop regulation of a combustion noise of the engine.

According to one embodiment, the engine comprises at least one cylinder and a movable piston driven by means of a crankshaft, and the method comprises a measurement of the temporal variations of the crankshaft angle and the internal pressure of the crankshaft. a first and second estimate respectively of a nitrogen oxide level emitted by the engine and a combustion noise of the engine, and during the first regulation, the rate of nitrogen oxides emitted is regulated. by the motor from a difference between a first setpoint and said first estimate of the nitrogen oxide content, and during the second regulation, the combustion noise of the engine is regulated from a difference between a second setpoint and said second estimation of the combustion noise. According to another embodiment, the combustion noise of the engine is adjusted from said difference between the first setpoint and the first estimate of the nitrogen oxide content.

Other objects, features and advantages of the invention will appear on reading the following description, given solely by way of nonlimiting example, and with reference to the appended drawings, in which: FIG. performing a combustion control system in an internal combustion engine; FIG. 2 is a schematic view of an embodiment of a combustion control system in an internal combustion engine; and FIG. 3 illustrates an embodiment of a means for estimating an output parameter of the engine. FIG. 1 illustrates, very schematically, a combustion control system 1 in an internal combustion engine 2. The combustion control system 1 comprises an electronic control unit 3 (ECU), sensors 4, 5 for respectively measuring the time variations of the crankshaft angle and the internal cylinder pressure and two actuators 6.7 driven by the ECU 3. The internal combustion engine 2 comprises a cylinder 8 in which a piston 9 moves by means of a connecting rod 10 connecting the piston 9 to a crankshaft 11. A combustion chamber 12 is delimited by said cylinder 8, said piston 9 and a cylinder head 13. The cylinder head 13 is provided with at least two valves 14 , Which make it possible to connect the combustion chamber 12 with respectively an intake manifold 16, for air possibly mixed with a part of the exhaust gases, and a gas exhaust manifold 17. The engine 2 comprises equal a partial recirculation circuit of exhaust gas 18 stitched between the gas exhaust manifold 17 and the intake manifold 16. The sensor 4 can measure at any time the crank angle 0, the sensor 5 allows to measure the internal pressure of the cylinder P, yi which corresponds to the pressure inside the combustion chamber 12. These sensors 4,5 each emit a temporal measurement signal, transmitted respectively by the connections 19 and 20, in the direction of the UCE 3.

The ECU 3 comprises regulation means, detailed hereinafter in FIG. 2, which are each able to produce a command Cmdel, Cmde2, respectively for controlling the actuators 6, 7. Furthermore, the control means may be included in a software form or in the form of logic circuits embedded in the ECU 3. This ECU 3 transmits these commands Cmdel, Cmde2, transmitted respectively by the connections 21 and 22, in the direction of actuators 6.7.

The actuator 6 makes it possible to control the rate of nitrogen oxides emitted by the engine 2. This actuator 6 can be an EGR valve (Exhaust Gas Recirculation in English) mounted in the partial recirculation circuit of the exhaust gases. In a variant, the actuator 6 may be an air flap mounted on the intake manifold 16, or any other means for controlling the flow of gases admitted into the engine 2. In fact, a control of the flow of the admitted gases in the engine 2 directly modifies the rate of nitrogen oxides emitted by the engine 2 after combustion. The actuator 7 makes it possible to control a fuel injection into the engine 2. This actuator 7 can be a fuel injector partially located in the combustion chamber 12 for a diesel type engine. For a gasoline type engine, this fuel injector may be located outside and upstream of the combustion chamber 12. In fact, a control of the injection of fuel into the engine directly modifies the combustion noise of the engine during combustion. combustion. The combustion noise is a sound emission generated by the flame that burns the gas-fuel mixture in the combustion chamber 12. This combustion noise causes a noise nuisance and is considered as a polluting emission of the engine 2. FIG. schematically an embodiment of a combustion control system 1 of the internal combustion engine 2. It is also shown in this figure 2 some elements described in Figure 1.

The combustion control system 1 comprises at least two regulating means 30, 31 for respectively regulating a level of nitrogen oxides emitted during combustion and a combustion noise of the engine.

The first means of regulating the nitrogen oxide content 30 is able to control the actuator 6 to modify the quantity of gas admitted into the engine 2 in order to limit the emission of nitrogen oxide emissions from the engine 2. second regulating means 31 for regulating the combustion noise controls the actuator 7 to modify the quantity of fuel injected into the engine in order to limit the combustion noise of the engine 2. This second regulation means 31 makes it possible to obtain a control of the combustion more accurate than with the only means of regulating the rate of nitrogen oxides 30. In addition, this second regulating means 31 makes it possible to further limit the pollutant emissions of the engine 2. Preferably, these control means regulate the pollutant emissions of engine 2, the oxides of nitrogen and the combustion noise, in a closed loop. By closed-loop control means means regulating means that regulates a variable of a system by controlling a control actuator of said variable from a regulation setpoint and a measured, or estimated, information in real time, the state of the variable to regulate. The combustion control system 1 also comprises an estimating means 32 for estimating the amount of nitrogen oxides emitted by the engine 2 and a means 33 for producing at least one regulation setpoint. The means for regulating the nitrogen oxide content 30 comprises a summing means 34 and a corrector 35. The regulation regulation generating means 33 can supply said instructions from mappings previously established during the phases of setting. point of the engine 2, by physical models or by a computer embedded in the ECU 3. In addition, this means 33 for developing instructions is able to develop maximum instructions not to exceed. The production means 33 emits a nitrogen oxide content setpoint ConsNOx, transmitted via a connection 33a towards the summing means 34 of the means for regulating the nitrogen oxide content 30. The summing means 34 is capable of calculating a difference d1 between the nitrogen oxide rate setpoint ConsNOx and an estimate NOxe supplied by the estimation means 32 and transmitted by a connection 36. Then, this difference d1 is transmitted, by a connection 37 to the corrector 35, which may be, for example, an integral proportional corrector PI known to those skilled in the art. The corrector 35 then develops the Cmdel command to the actuator 6 resulting from the difference d1 received. The estimating means 32 estimates the nitrogen oxides NOxe from the measurements of the internal pressure of the cylinder P and the measurement of the crankshaft angle θ and will be described in FIG.

The combustion control system 1 also comprises a second estimation means 40 for estimating the combustion noise Bre emitted by the engine 2. The second combustion noise control means 31 comprises a summation means 41 and a corrector 42 .

The means 33 for generating control setpoints can also provide a combustion noise setpoint Cons_Br, transmitted by a connection 43 towards the summing means 41 of the second combustion noise control means 31. The summing means 41 is capable of calculating a difference d2 between the combustion noise setpoint Cons_Br and the estimate Bre provided by the second estimation means 40 and transmitted by a connection 44. Then, this difference d2 is transmitted, via a connection 45, to the corrector 42, which may also be, for example, an integral proportional corrector PI known to those skilled in the art. The corrector 42 then develops the command Cmde2 to the actuator 7 resulting from the difference d2 received. The second estimation means 40 estimates the combustion noise Bre from the measurements of the internal pressure of the cylinder P, yi and the measurement of the crank angle O and will be described in FIG. 3. These two control means 30, 31 enable the combustion to be modulated by progressively increasing, in a controlled manner, the pollutant emissions of nitrogen oxides and combustion noise in order to control the combustion in the engine 2. If the estimation of the oxidation rate of oxides of NOxe nitrogen is below the setpoint Cons NOx, the first regulation means 30 increases the flow of air admitted into the engine, either by closing the EGR valve to reduce the partial exhaust gas admitted, or by opening the shutter air located on the intake manifold 16 to increase the flow of fresh air admitted. In the opposite case, if the estimate of the NOxe nitrogen oxide level is greater than the ConsNOx setpoint, the first regulating means 30 decreases the air flow admitted into the engine, ie by opening the EGR valve to increase the partial exhaust gases admitted, or by closing the air flap located on the intake manifold 16 to reduce the flow of fresh air admitted. If the combustion noise estimate Bre is lower than the setpoint Cons_Br, the second regulation means 31 advances the quantity of fuel injected into the engine. In the opposite case, if the combustion noise estimate Bre is greater than the setpoint Cons_Br, the second regulation means 31 delays the amount of fuel injected into the engine. It should be noted that the regulation of the combustion noise is faster than that of the nitrogen oxide level. Indeed, the second regulation means 31 corrects the fuel injection while the first regulating means 30 corrects the flow of the admitted gases, the latter has an additional inertia due to the flow of gas between the control actuator of the rate of nitrogen oxides and the combustion chamber 12 of the engine 2. Furthermore, the fuel injection corrections are performed between two thermodynamic combustion cycles more rapidly than a gas flow correction. In general, the combustion noise setpoint Cons_Br is reached before that of the nitrogen oxide level. In this case, the second regulating means 31 regulates the combustion noise, on the setpoint Cons_Br, while the first regulating means 30 regulates gradually, in a controlled manner, the rate of nitrogen oxides so that the latter reaches the Cons NOx setpoint.

In another variant, the difference d1, between the nitrogen oxide concentration setpoint Cons NOx and the estimate of the nitrogen oxides NOxe, can be emitted, via a connection 50, in the direction of a multiplication means 51 included in the second combustion noise control means 31. This multiplication means 51 also receives the difference d2 between the combustion noise setpoint Br and the estimation of the combustion noise Bre. The multiplication means 51 is able to multiply the two differences d1, d2 between them and transmit the result, via the connection 45, in the direction of the corrector 42 of the second regulation means 31. This variant makes it possible to obtain controlled control of the combustion even in the case where the setpoint Cons NOx is reached before the setpoint Cons_Br. When the setpoint Cons NOx is reached, the difference d1 is zero, and the result of the multiplication of the two differences d1, d2 is also zero. In this case, a zero command transmitted to the corrector 42 of the second regulation means 31 has the effect of stopping the regulation of the combustion noise, the combustion noise is then stabilized close to the setpoint Cons_Br. FIG. 3 illustrates an embodiment of an estimating means 60 of an output parameter PSe of the engine 2. It is also shown in this FIG. 3 some elements described in FIGS. 1 and 2. The control system of FIG. combustion 1 may furthermore comprise other measurement means 27 to 29 of state variables of the engine 2 in order to specify the estimate of the output parameter of the engine PSe. The engine output parameters can be selected from polluting emissions such as nitrogen oxides or carbon dioxide, combustion noise, fuel consumption, engine torque and in general all the parameters which represent a state emitted directly or indirectly by combustion in the engine 2. The combustion control system 1 may comprise, the measuring means 27 for measuring an amount of oxygen admitted into the engine 2, the measuring means 28 for measuring a fuel flow admitted into the engine 2 and the measuring means 29 for measuring a fresh air flow admitted into the engine 2. The measuring means 27 of the quantity of oxygen admitted into the engine 2 may be a probe to oxygen located in intake manifold 16 or in the exhaust gas manifold 17. The measurement of the fuel flow admitted into the engine 2 can be a fuel setpoint sent to the injector 7. The means of The flow rate 29 of the fresh air flow admitted into the engine 2 may be an air flowmeter located on the intake manifold 16, preferably upstream of the recovery of a part of the exhaust gas. These measurement means 27 to 29 each emit a temporal measurement signal, transmitted respectively by connections 61 to 63, in the direction of a calculation means 23. The estimation system 60 comprises the calculation means 23 and a module 24. The calculation means 23 and the estimation module 24 may be included in a software form or in the form of logic circuits embedded in the ECU 3. The calculation means 23 makes it possible to calculate a certain number of parameters. of combustion Xi from input time signals 0, P, yi. In addition, this calculation means 23 can also calculate said combustion parameters Xi from the additional time signals from the measuring means 27 to 29. The combustion parameters Xi can be chosen from the start of combustion time, the duration the maximum internal cylinder pressure, the crankshaft angle for which the maximum pressure in the cylinder, the crankshaft angle for which a given fraction of the fuel has been burned, the temperature of the exhaust gases , the exhaust gas pressure. Other parameters may be envisaged insofar as they are in direct or indirect relation with the combustion phase in the cylinder. Preferably, the combustion parameters Xi are chosen to be only values that are characteristic of the internal pressure of the cylinder, such as internal cylinder pressures characteristic of the Peyli combustion, variations in the internal pressure of the V Peyli cylinder, and cycle times. tcyclei engine. The internal cylinder pressures characteristic of combustion Peyli may be, for example, the internal pressure of the maximum cylinder Peyimax, the internal pressure of the cylinder at the start of combustion, the internal pressure of the cylinder for a crankshaft angle characteristic of combustion (ie an angle for which a given fraction of the fuel has been burned), the internal pressure of the cylinder when the crankshaft angle is 80 ° after the top dead center of the piston. It is noted that the crankshaft angles characteristic of the combustion are well known to those skilled in the art and are generally calculated as a function of the apparent energy release in the cylinder.

The internal pressure variations of the cylinder VPeyli can be, for example, the maximum gradient of the cylinder internal pressure (V Pcyl) max, the minimum gradient of the cylinder internal pressure (V Pcyl) min, the maximum gradient of the pressure cylinder between the first piloted injection and the injection at the start of combustion. The cycle times of the motor tcyclei can be, for example, the time elapsed between CA05 and CA50, or the time elapsed between CA05 and CA90, or the time elapsed between CA05 and the time when the internal pressure of the maximum cylinder is reached, or the time during which the internal pressure of the cylinder is greater than a threshold, or the time during which the internal pressure of the cylinder is equal to the maximum value of the ratio ~ P with V Peyl representing the gradient cyl of the internal pressure of the cylinder; cylinder and Peyl representing the internal pressure of the cylinder. It is noted that the CAx references correspond to the corners of the crankshaft where x% of the fuel has been burned.

The calculation means 23 is capable of sampling the measurements of the internal pressure of the cylinder P, as a function of the measurements of the crank angle O. Preferably, the sampling pitch of the internal pressure of the cylinder P is greater or equal to 0.5 degrees of the crank angle O. Then, for each cycle of the combustion, the calculation means 23 stores in memory the sampled values of the internal pressure of the cylinder P, yi. From these sampled values, the calculating means 23 calculates the combustion parameters Xi, described above, and transmits them, via connections 64, towards the estimation module 24. This estimation module 24 makes it possible to estimating an output parameter PSe of the engine, for example a NOxe nitrogen oxides content, from said calculated combustion parameters Xi. In addition, it outputs the estimated result PSe via a connection 65.

The estimation module 24 can use several models to estimate the output parameter PSe of the engine. Preferably, the models are able to estimate the output parameter PSe of the motor from a weighted sum of said combustion parameters Xi. According to a first embodiment, the estimation module 24 comprises a first model capable of calculating the output parameter PSe according to the following equation (1): N PSe = Lai • Xi equation (1) Z = i - N: number of combustion parameters Xi calculated by the calculation means 23; - at; : weighting constant that varies according to the combustion parameter Xi; and - i: identification index of the combustion parameter.

According to a second embodiment, the estimation module 24 comprises a second model capable of calculating the output parameter PSe according to the following equation (2): N PSe = exp Lai. Xi equation (2) = 1 i - exp: exponential mathematical function. According to a third embodiment, the estimation module 24 comprises a third model capable of calculating the output parameter PSe according to the following equation (3): ## EQU1 ## - w: angular velocity of the engine 2 obtained from measurements of the crank angle O. Furthermore, this estimation module 24 uses models whose weighting constants a; have been determined by prior tests.

In another variant, the estimation module 24 can provide a pollutant emission estimate from a pollution emission map established as a function of the internal pressure of the cylinder Pcyi and the angle of the crankshaft O. estimate 60 as described in Figure 3 can therefore be used to estimate the NOxe nitrogen oxides in place of the first estimating means 32. Moreover, this estimating means 60 as described in FIG. Figure 3 can also be used to estimate the combustion noise Bre instead of the second estimation means 40.25

Claims (6)

REVENDICATIONS1. Combustion control system in an internal combustion engine (2) of a motor vehicle, characterized in that it comprises a first actuator (6) capable of controlling a rate of nitrogen oxides emitted by the engine (2) a second actuator (7) adapted to control a combustion noise of the engine (2), a first regulating means (30) capable of driving the first actuator (6) to regulate in a closed loop the rate of nitrogen oxides emitted by the motor (2) and a second regulating means (31) capable of driving the second actuator (7) to regulate in a closed loop the combustion noise of the motor (2). 2. System according to claim 1, wherein the motor (2) comprises at least one cylinder (8), a movable piston (9) driven by means of a crankshaft (11), means (4,5) for measuring the temporal variations of the crankshaft angle and the internal pressure of said cylinder and estimating means (32,40) able to respectively estimate a rate of nitrogen oxides emitted by the engine and a combustion noise the engine from said measurements, the first regulating means (30) being able to drive the first actuator (6) from a difference (dl) between a first setpoint and said estimate of the nitrogen oxide content, and the second regulating means (31) being able to drive the second actuator (7) from a difference (d2) between a second setpoint and said estimation of the combustion noise. 3. System according to one of claims 1 and 2, wherein the second regulating means (31) comprises multiplying means for multiplying said difference (d2) between the second setpoint and the estimation of the combustion noise, with the first difference (d1) produced by the first regulating means (30). 4. A method for controlling combustion in an internal combustion engine (2) of a motor vehicle, characterized in that it comprises a first closed-loop regulation of a rate of nitrogen oxides emitted by the engine (2). and a second closed-loop control of a combustion noise of the engine (2). 5. Method according to claim 4, wherein the motor (2) comprises at least one cylinder (8) and a movable piston (9) driven via a crankshaft (11), comprising a measurement of the temporal variations of the angle of the crankshaft and the internal pressure of the cylinder, first and second estimates respectively of a rate of nitrogen oxides emitted by the engine (2) and a combustion noise of the engine (2), and during the first regulation, the rate of oxides of nitrogen emitted by the engine (2) is regulated from a difference between a first setpoint and said first estimate of the nitrogen oxide content, and during the second regulation, it controls the combustion noise of the engine (2) from a difference between a second setpoint and said second estimation of the combustion noise. 6. Method according to one of claims 4 and 5, wherein the combustion noise of the engine (2) is adjusted from said difference between the first setpoint and the first estimate of the rate of nitrogen oxides.