WO2010130937A1

WO2010130937A1 - Estimating the nitrogen oxide concentration in an internal combustion engine

Info

Publication number: WO2010130937A1
Application number: PCT/FR2010/050901
Authority: WO
Inventors: Antoine Saint-Marcoux; Pascal Emery
Original assignee: Renault Sas
Priority date: 2009-05-11
Filing date: 2010-05-10
Publication date: 2010-11-18
Also published as: EP2430298A1; FR2945320B1; EP2430298B1; FR2945320A1

Abstract

System for estimating at least one output parameter (PSe) of an internal combustion engine (1) comprising at least one cylinder (2), one moving piston (3) driven by a crankshaft (5), means (20, 21) for measuring the temporal variations of the crank angle and of the internal pressure of said cylinder, a calculating means (23) for calculating a plurality of combustion parameters (Xi), such as internal cylinder pressures characteristic of the combustion, variations in the pressure inside the cylinder and engine strokes, from said crank angle measurements and internal cylinder pressures, and an estimating means (24) for estimating at least one engine output parameter (PSe) from said combustion parameters (Xi), the estimating means (24) estimating at least one engine output parameter (PSe) from a weighted sum of said combustion parameters (Xi).

Description

ESTIMATING THE NITROGEN OXIDE CONCENTRATION OF AN INTERNAL COMBUSTION ENGINE

The invention relates to the estimation and regulation of at least one output parameter of an internal combustion engine comprising a plurality of cylinders.

In particular, the invention relates to the estimation of an output parameter of the internal combustion engine made from a measurement of the internal pressure of a cylinder of the engine, as well as the regulation of this output parameter from of this estimate.

Anti-pollution standards and declining fuel consumption are becoming increasingly important issues for car manufacturers. It is therefore necessary to control the combustion phase of vehicle engines to limit pollutant emissions such as nitrogen oxides NO _x , carbon dioxide

CO ₂ , carbon monoxide CO, unburned HC fuels and PM particles, especially for diesel engines.

This requires a perfect control of combustion without neglecting fuel consumption and engine performance.

In addition, when tuning engines out of assembly lines, a single adjustment of the engine is performed according to anti-pollution standards. This unique adjustment must take into account the worst cases for all engines to meet these standards, forcing manufacturers to take safety margins large enough not to exceed these standards.

As is known, many sensors are generally embedded in vehicles for measuring a plurality of magnitudes and state variables, which leads to a significant cost in the manufacture of vehicles.

For example, reference can be made to Japanese Patent Application JP2002371893, in which an estimation of the emission of nitrogen oxides NO _x is made from a measurement of the internal pressure of a cylinder and of 'a quantity of fresh air admitted into the engine. However, the estimation model used is based on a chemical kinetic approach to the development of combustion which is complex and expensive.

One of the aims of the invention is therefore to provide a system and a method for estimating an output parameter of the motor using a minimum of direct measurements of engine states and with a minimum of variable calculations.

Another object of the invention is to provide a system and method for regulating an engine output parameter from its estimate.

According to one aspect of the invention, there is provided a system for estimating at least one output parameter of an internal combustion engine comprising at least one cylinder, a movable piston driven via a crankshaft, means for measuring the temporal variations of the crankshaft angle and the internal pressure of said cylinder.

The system comprises calculating means for calculating a plurality of combustion parameters, such as internal cylinder pressures characteristic of the combustion, internal cylinder pressure variations and engine cycle times, from said measurements of the combustion engine. crankshaft angle and internal cylinder pressure and estimating means for estimating at least one engine output parameter from said combustion parameters.

Thus, it is possible to provide a means for estimating an engine output parameter which takes into account only characteristic values of the internal pressure of a cylinder. Furthermore, it limits the number of sensors used, and the complex calculations of many intermediate variables of the engine state.

Advantageously, the measurement of the internal pressure of the cylinder can be carried out by means of a pressure sensor. It should be noted that each cylinder may be equipped with such a pressure sensor or, more simply, only one of the engine cylinders.

The characteristic output parameters of the engine can be selected from pollutant emissions, combustion noise, fuel consumption, the engine torque and in general all the parameters which represent a state emitted directly or indirectly by combustion in the engine.

Advantageously, the estimating means estimates at least one output parameter of the motor from a weighted sum of said combustion parameters.

In addition, an estimation means is provided that is simple and requires little calculation.

The system may comprise means for measuring a quantity of oxygen admitted into the engine and the calculation means is capable of calculating said combustion parameters from, in addition, the quantity of oxygen admitted into the engine.

The system may also include means for measuring a fuel flow admitted into the engine and the calculating means is adapted to calculate said combustion parameters from, in addition, the fuel flow admitted into the engine.

The system may further comprise means for measuring a flow of fresh air admitted into the engine and the calculating means is able to calculate said combustion parameters from, in addition, the fresh air flow admitted into the engine.

With the help of additional measuring means, the estimation of the output parameters of the motor is specified.

According to another aspect, there is provided a device for regulating an output parameter of an internal combustion engine, comprising means for developing an instruction of the output parameter of the engine, an actuator able to control the output parameter of the engine. engine, an estimation system for estimating the output parameter of the engine, the control device being able to develop a command for said actuator from a difference between said setpoint and said estimate of the output parameter of the engine in order to regulate the output parameter of the motor.

Thus, there is provided a means for closed-loop control of an output parameter of the engine via a measurement of the internal cylinder pressure. This closed-loop regulation makes it possible to adapt the settings concerning the emission standards according to each engine, and thus to reduce dispersions from one engine to another during their manufacture. This reduction of the dispersion of the engines makes it possible to reduce the margins of safety of the manufacturers and in particular to size as much as possible the systems of after-treatment of the pollutant emissions, and advantageously to reduce their volume.

In addition, the devices for post-treatment of pollutant emissions generally include precious metals, such a reduction in their volume allows a saving on the cost of a vehicle.

According to one embodiment, the device comprises means for developing a control setpoint of said actuator and means for calculating a control difference, between said command setpoint and said elaborate control, intended for said actuator.

It will thus be possible to take into account constraints on one of the combustion parameters in order to regulate the output parameter of the motor. One can, for example, take into account a constraint on the flow of air admitted into the engine.

According to another aspect, there is provided a method for estimating at least one output parameter emitted by an internal combustion engine comprising at least one cylinder, a mobile piston driven via a crankshaft, comprising a step measuring the temporal variations of the crankshaft angle and the internal cylinder pressure.

This method comprises a step of calculating a plurality of combustion parameters, such as internal cylinder pressures characteristic of the combustion, internal cylinder pressure variations and engine cycle times, from said measurements of the combustion engine. angle of the crankshaft and the internal pressure of said cylinder and a step of estimating the engine output parameter from said combustion parameters. Advantageously, it is estimated at least one output parameter of the engine from a calculation of a weighted sum of said combustion parameters.

The method may comprise a step of measuring an oxygen quantity admitted into the engine, and during the calculation step, said combustion parameters are calculated from, in addition, the quantity of oxygen allowed in the engine. engine.

The method may also include a step of measuring a fuel flow admitted into the engine, and during the calculation step, said combustion parameters are calculated from, in addition, the fuel flow admitted into the engine.

The method may further comprise a step of measuring a flow rate of fresh air admitted into the engine, and during the calculation step, the combustion parameters are calculated from, in addition, the admitted fresh air flow rate. in the engine.

According to another aspect, there is provided a method for regulating an output parameter of an internal combustion engine, comprising developing an engine output parameter setpoint, estimating the output parameter of the engine, and a regulation of the engine output parameter from a difference between said setpoint and said estimate of the output parameter of the engine.

Advantageously, during the regulation step, a command is developed for an actuator controlling the output parameter of the motor, and a command setpoint of the actuator is furthermore developed and a control difference is calculated between said setpoint of the actuator. command and said elaborate command for said actuator.

Other objects, features and advantages of the invention will become apparent on reading the following description, given solely by way of nonlimiting example, and with reference to the appended drawings, in which: FIG. 1 illustrates an embodiment of a system for estimating at least one output parameter of an internal combustion engine;

FIG. 2 illustrates an embodiment of a device for regulating an output parameter of an internal combustion engine; and

FIG. 3 illustrates another embodiment of a device for regulating an output parameter of an internal combustion engine. FIG. 1 diagrammatically shows a system for estimating at least one output parameter of an internal combustion engine 1.

The characteristic output parameters of the engine 1 can be chosen from pollutant emissions, combustion noise, fuel consumption, engine torque and, in a general manner, all the parameters that represent a state emitted directly or indirectly by the combustion. in the engine 1.

For example, such an estimation system could be used to estimate a rate of nitrogen oxides emitted during combustion in the engine 1.

The internal combustion engine 1 comprises a cylinder 2 in which a piston 3 moves by means of a connecting rod 4 connecting the piston 3 to a crankshaft 5 driving the rod 4. A combustion chamber 6 is delimited by said cylinder 2, said piston 3 and a cylinder head 7. The cylinder head 7 is provided with at least two valves 8 and 9 which make it possible to connect the combustion chamber 6 with respectively an intake manifold 10, for possibly air The engine 1 also includes a fuel injector 12 arranged to inject fuel into the combustion chamber 6.

The estimation system comprises two measurement sensors 20, 21 and an electronic control unit 22 (ECU) which comprises a calculation means 23 and an estimation means 24. These means 23, 24 may be included in a software form or in the form of logic circuits embedded in the ECU 22.

The sensor 21 makes it possible to measure at any moment the angle of the crankshaft θ. The sensor 20 makes it possible to measure at any instant the internal pressure P _cy ι of the cylinder 2 which corresponds to the pressure inside the combustion chamber 6. These sensors 20 and 21 each emit a temporal measurement signal, transmitted respectively by connections 25 and 26, towards the calculation means 23. In addition, the estimation system may comprise other measuring means 27 to 29 of engine state variables to specify the estimate of the output parameter of the engine PSe.

The estimation system may comprise, the measuring means 27 for measuring a quantity of oxygen admitted into the engine 1, the measuring means 28 for measuring a fuel flow admitted into the engine 1 and the measuring means 29 for measuring a flow rate of fresh air admitted into the engine 1. The measuring means 27 of the quantity of oxygen admitted into the engine 1 may be an oxygen sensor located in intake manifold 10 or in the exhaust gas manifold 1. The measurement of the fuel flow admitted into the engine 1 may be a fuel setpoint sent to the injector 12. The measuring means 29 of the fresh air flow admitted into the engine 2 may be an air flowmeter located on the intake manifold 10, preferably upstream of the recovery of a portion of the exhaust gas. These measuring means 27 to 29 each emit a temporal measurement signal, transmitted respectively by connections 30 to 32, towards the calculation means 23.

The calculation means 23 makes it possible to calculate a certain number of combustion parameters Xi from the input time signals θ, Pcyi. Moreover, this calculation means 23 can also calculate the combustion parameters Xi from the additional time signals. from the measuring means 27 to 29.

The combustion parameters Xi may be chosen from the moment of start of combustion, the duration of the combustion, the internal pressure of the maximum cylinder, the angle of the crankshaft for which the maximum pressure in the cylinder, the angle of the crankshaft for which a given fraction of the fuel has been burned, the temperature of the exhaust gases, the pressure of the gases to the exhaust. 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 as being only values characteristic of the internal pressure of the cylinder such as internal cylinder pressures characteristic of the combustion P _cy ii, internal pressure variations of the cylinder VP _cy ii and times engine _cycle t _cycle i.

The internal cylinder pressures characteristic of the combustion P _cy ii may be, for example, the internal pressure of the maximum cylinder P _cy imax, the internal pressure of the cylinder at the instant of start of combustion, the internal pressure of the cylinder for an angle of the crankshaft characteristic of the combustion (ie an angle for which a given fraction of the fuel has been burned), the internal pressure of the cylinder when the angle of the crankshaft is equal to 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 VP _cy ii may be, for example, the maximum gradient of the cylinder internal pressure, the minimum gradient of the cylinder internal pressure (VP _cy i) _min , the maximum gradient of the internal pressure of the cylinder. cylinder between the first piloted injection and the injection at the beginning of combustion.

The engine cycle of time t _cyc i _e i can be, for example, the time between CA05 and CA50, or the time between CA05 and CA90, or the time between CA05 and the time when the internal pressure of 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

P maximum value of the ratio - - with VP _cv i representing the gradient

the internal pressure of the cylinder and P _cy i 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 able to sample the measurements of the internal pressure of the cylinder P _cy ι as a function of the measurements of the crankshaft angle θ. Preferably, the sampling pitch of the internal pressure of the cylinder P _cy ι is greater than or equal to 0.5 degrees of the angle of the crankshaft θ. 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 _cy ι. From these sampled values, the calculation means 23 calculates the combustion parameters Xi, described above, and transmits them, via connections 40, towards the estimation means 24.

This estimation means 24 makes it possible to estimate an output parameter PSe of the engine, for example a level of nitrogen oxides NOx _e , from said combustion parameters Xi calculated. In addition, it outputs the estimated result PSe by a connection 41.

The estimation means 24 can use several models to estimate the output parameter of the engine. Preferably, the models are able to estimate the engine output parameter from a weighted sum of said combustion parameters Xi.

According to a first embodiment, the estimation means 24 comprises a first model capable of calculating the output parameter PSe according to the following equation (1): PSe - Xi equation (1)

N: number of combustion parameters Xi calculated by the calculation means 23; - (X ₁ : weighting constant which varies according to the combustion parameter Xi, and

- i: index of identification of the combustion parameter. According to a second embodiment, the estimation means 24 comprises a second model capable of calculating the output parameter PSe according to the following equation (2):

PSe = exp (^ ^N a, • Xi Λ equation (2)

- exp: exponential mathematical function.

According to a third embodiment, the estimation means 24 comprises a third model capable of calculating the output parameter PSe according to the following equation (3):

PSe = G) - exp (Σ ^N a, - Xi Λ equation (3)

- ω: angular velocity of the engine 1 obtained from measurements of the crankshaft angle θ. Moreover, this estimation means 24 uses models whose weighting constants Ci ₁ have been determined by prior tests.

FIG. 2 schematically shows an embodiment of a regulating device 50 of an output parameter of an internal combustion engine 1. FIG. 1 also shows in this FIG. 2 certain elements described in FIG. .

The regulating device 50 comprises a means 51 for developing a setpoint of the output parameter of the motor PS PS, a regulating means 52 and an estimation module 53. These means 51, 52 and this module 53 can be included in a form software or in the form of onboard logic circuits in the ECU 22.

The estimation module 53 comprises the calculation means 23 and the estimation means 24 as described in FIG. 1, in addition, it estimates an output parameter PSe, which it then transmits via the connection 41 to a means of estimation. calculation 59 of the regulating means 52.

The calculation means 59 also receives, via a connection 54, the setpoint of the output parameter of the motor PS PS produced by the means 51. This calculating means 59 calculates a difference d between said setpoint PS and said PSe estimate of the output parameter of the engine and transmits this difference d by a connection 55 towards a correction means 56 of the regulating means 52 The correction means 56 may be an integral proportional type equalizer PI, or integral proportional derivative type PID, or any other type of corrector known to those skilled in the art. This correction means 56 generates a command Cmde from the difference d received, and transmits this command Cmde by a connection 57 to an actuator 58.

The actuator 58 makes it possible to control the real value of the output parameter of the motor that it is desired to regulate. This actuator 58 may be any means for modifying the values of the engine output parameters, such as for example a fuel injector, an air flap mounted on the intake manifold 10, a recirculation valve for a part of the engines. exhaust gas.

This regulating device 50 makes it possible to regulate the output parameter of the motor via the actuator 58 as a function of a comparison between the setpoint Cons PS and the estimate PSe of the output parameter of the motor.

FIG. 3 diagrammatically shows another embodiment of a regulating device 50 of an output parameter of an internal combustion engine 1. FIG. 3 also shows certain elements described in the previous figures. 1 and 2. In this other embodiment, the regulating device

50 comprises a means 60 for developing a command setpoint Cons Cmde and a second calculating means 61.

This second calculation means 61 receives, on the one hand, the command Cmde produced by the regulation means 5 and which is transmitted by the connection 57, and on the other hand the command setpoint Cons Cmde which is transmitted by a connection 62 from the means 60. The second calculation means 61 calculates a control difference DiffCmde between the command Cmde and the instruction of control Command Cmde and transmits the result via a connection 63 towards the actuator 58.

For example, the output parameter of the engine may be the rate of nitrogen oxides to be regulated, the actuator 58 may be an air flap mounted on the intake manifold 10, Cons Cmde and Cmde respectively represent a setpoint of air flow and a correction of this air flow, the control device 50 thus ensuring the reduction of dispersion of the nitrogen oxides emitted by the engine.

It is thus possible to estimate a rate of oxides of nitrogen in real time using a minimum of calculations and sensors.

The taking into account of the measurement of the internal pressure of the cylinder allows a better estimate of the engine output parameters in comparison with the use of a mapping of the output parameter according to the engine speed and the fuel injected into the chamber of combustion.

Closed-loop control reduces engine dispersion and reduces engine manufacturing costs, including reducing the volume of pollutant aftertreatment systems.

Claims

A system for estimating at least one output parameter (PSe) of an internal combustion engine (1) comprising at least one cylinder (2), a movable piston (3) driven via a crankshaft (5), means (20, 21) for measuring the time variations of the crankshaft angle and the internal pressure of said cylinder, calculating means (23) for calculating a plurality of combustion parameters (Xi), such as internal combustion cylinder pressures, internal cylinder pressure variations and engine cycle times, from said crankshaft angle and internal cylinder pressure measurements and estimation means. (24) for estimating at least one engine output parameter (PSe) from said combustion parameters (Xi), characterized in that the estimating means (24) estimates at least one engine output parameter (PSe) from a weighted sum of said combus parameters tion (Xi).

2. System according to claim 1, comprising means (27) for measuring an amount of oxygen admitted into the engine and wherein the calculating means (23) is able to calculate said combustion parameters (Xi) from, in In addition, the amount of oxygen allowed in the engine.

3. System according to any one of claims 1 or 2, comprising means (28) for measuring a fuel flow admitted into the engine and wherein the calculation means (23) is able to calculate said combustion parameters (Xi). ) from, in addition, the fuel flow admitted into the engine.

4. System according to any one of claims 1 to 3, comprising means (29) for measuring a fresh air flow rate admitted into the engine and wherein the calculating means (23) is capable of calculating said combustion parameters. (Xi) from, in addition, the flow of fresh air admitted into the engine.

5. A device for regulating an output parameter of an internal combustion engine (1), comprising means (51) for developing a setpoint of the motor output parameter (PS Cons), an actuator (58) capable of controlling the output parameter of the motor, an estimation system (53) according to one of claims 1 to 4 for estimating the parameter motor output (PSe), the control device being able to develop a command (Cmde) for said actuator (58) from a difference (d) between said setpoint (PS Cons) and said estimate of the output parameter the motor (PSe) to regulate the motor output parameter.

6. Device according to claim 5, comprising a means (60) for developing a command setpoint (Cmde Cons) of said actuator (58) and means (61) for calculating a control difference (DiffCmde) between said command setpoint (Cons Cmde) and said elaborate control (Cmde), intended for said actuator (58).

7. Method for estimating at least one output parameter

(PSe) emitted by an internal combustion engine (1) comprising at least one cylinder (2), a movable piston (3) driven via a crankshaft (5), comprising a step of measuring the temporal variations of the angle of the crankshaft and the internal pressure of the cylinder, a step of calculating a plurality of combustion parameters (Xi), such as internal cylinder pressures characteristic of the combustion, internal pressure variations of the cylinder and engine cycle time, from said measurements of the crankshaft angle and the internal pressure of said cylinder and a step of estimating the engine output parameter (PSe) from said combustion parameters (Xi) characterized in that at least one engine output parameter (PSe) is estimated from a calculation of a weighted sum of said combustion parameters (Xi).

8. Process according to claim 7, comprising a step of measuring an amount of oxygen admitted into the engine, and during the calculation step, calculating said combustion parameters (Xi) from in addition, the amount of oxygen allowed in the engine.

9. Method according to any one of claims 7 or 8, comprising a step of measuring a fuel flow rate admitted into the engine, and during the calculation step, said combustion parameters (Xi) are calculated from in addition, the fuel flow admitted into the engine.

10. Method according to any one of claims 7 to 9, comprising a step of measuring a fresh air flow admitted into the engine, and during the calculation step, said combustion parameters (Xi) are calculated. from, in addition, the flow of fresh air admitted into the engine.

1 1. Method for regulating an output parameter of an internal combustion engine (1), comprising a development of a setpoint of the engine output parameter (Cons PS), an estimate according to one of claims 7 to 10 of the motor output parameter (PSe), and a regulation of the motor output parameter from a difference (d) between said setpoint (PS Cons) and said estimate of the motor output parameter (PSe).

12. The method of claim 1 1, wherein, during the control step, a command (Cmde) is developed for an actuator (58) controlling the output parameter of the engine, and which comprises a development of a setpoint control (Command Cmde) of the actuator (58) and a calculation of a control difference (DiffCmde) between said command setpoint (Cmde Cons) and said elaborate command (Cmde) for said actuator (58).