EP2534355A1

EP2534355A1 - Method for adjusting an operating parameter of an engine and control system implementing said method

Info

Publication number: EP2534355A1
Application number: EP11708058A
Authority: EP
Inventors: Frédéric Gourves
Original assignee: Peugeot Citroen Automobiles SA
Current assignee: PSA Automobiles SA
Priority date: 2010-02-09
Filing date: 2011-02-02
Publication date: 2012-12-19
Anticipated expiration: 2031-02-02
Also published as: FR2956161A1; WO2011098708A1; EP2534355B1; CN102782296B; CN102782296A; FR2956161B1

Abstract

The invention relates to a method for adjusting an operating parameter of an internal combustion engine (2), including the following steps: creating a stability set value (Cs), calculating an engine stability index (Is), calculating the stability deviation (Es) which is equal to the difference between the stability setting (Cs) and the stability index (Is), and processing of the stability deviation (Es) by a controller (6) that provides an engine control set value (OA, FE) to be applied to the operating parameter of the engine (2). The invention is characterised in that the stability index (Is) is a function of the difference between the measured time derivative of the engine speed at the time of calculation, and the estimated time derivative of the engine speed according to the engine torque and the inertias that inhibit the fluctuation of the rotation speed of the engine.

Description

METHOD FOR CONTROLLING A PARAMETER OF

OPERATION OF AN ENGINE AND CONTROL SYSTEM

IMPLEMENTING SUCH A METHOD

The present invention claims the priority of the French application 1 050874 filed February 9, 201 0 whose content (text, drawings and claims) is here incorporated by reference.

The invention relates to the field of controlling the stability in operation of combustion engines.

[0003] Spark ignition engines have, especially during their operation in partial load, a lower intake pressure at atmospheric pressure. This pressure below atmospheric pressure creates so-called pumping losses which lead to overconsumption of fuel, due to additional work imposed on the engine pistons during the intake phases.

It is known, in spark ignition engines, to use the "crossing" of the valves, that is to say, periods during which the intake and exhaust valves are simultaneously open, to decrease overconsumption related to pumping losses at low load and partial load.

More specifically, to limit the losses by pumping, it is possible to use camshaft phase shifters to adapt the crossing of the intake and exhaust valves. The valve crossing is the particular result of an exhaust delay and an advance on admission. It has the effect of facilitating the aspiration of fresh gases with the flue gases which facilitates the filling of the cylinder.

However, the crossing has an effect on the stability of the engine. It is important in the context of the control of the operation of spark ignition combustion engines to be able to characterize their operating stability. In particular, imposing a too large crossover valves can greatly degrade the engine stability, which is detrimental to both the comfort of the motorist, the proper operation of the engine, and its lifetime. For optimum engine performance, the stability of the engine must be taken into account. Currently in the calculators of engines generally used in series, the crossing levels are calibrated so as to have a compromise between engine robustness and fuel consumption level. These settings are fixed in maps, which do not take into account the actual operation of the engine, and are therefore can precise, and do not achieve an optimal level of consumption, that is to say the weaker possible. It is also known through the French patent application FR2909722 a method of controlling the operating parameters of an internal combustion engine injection, comprising the calculation of an index representative of the stability of an engine and its comparison to a setpoint, in order to optimize the regulated parameters by approaching the stability setpoint. The proposed solutions are satisfactory for adjusting the parameters in steady state, but, the stability index as built in this application is unreliable during operation of the engine in transient.

In the invention, there is provided a control method in which the stability of a combustion engine is more precisely characterized, in particular during the transient operating phases (phases of variation of the rotational speed of the engine ). This method makes it possible to adapt the operating parameters of the engine having an influence on its stability such as the ignition advance or the richness, but is particularly advantageous for adapting the crossover valves and thus optimize fuel consumption. transient engine. More specifically, the invention relates to a method of regulating an operating parameter of an internal combustion engine, comprising the following steps:

- development of a stability directive,

calculation of an index of engine stability,

calculating the stability difference equal to the difference between the stability setpoint and the stability index.

- Stability deviation processing by a regulator that provides a motor control setpoint, to be applied to the operating parameter of the engine, wherein the stability index is a function of the difference between the measured time derivative of the engine speed to the moment of calculation, and the estimated time derivative of the engine speed as a function of the engine torque and the inertia opposing the variation of its rotational speed. It is thus possible to regulate the parameters of the engine control having an influence on its stability, including the wealth, the ignition timing, and the crossing of the valves. Depending on the regulated parameter, the setpoint supplied may be used to increase the exhaust temperature, reduce the engine's pollutant emissions or reduce fuel consumption. In the invention, the determination of an index representative of the combustion stability of the engine as a function of the difference between the time derivative of the engine speed measured and the time derivative of the estimated engine speed, that is to say such that it is expected that it is based in particular on the engine torque evaluated by the engine control system and the inertia opposing the variation of the rotational speed of the engine, offers the advantage of allowing the obtaining a reliable index including in the transient engine operating phases.

[001 1] In a preferred embodiment of the invention, the engine control set tends to optimize the crossing of the valves to reduce the fuel consumption of the engine while respecting the stability guideline. Indeed, the method according to the invention is particularly advantageous for regulating the crossing of the valves to reduce the engine consumption, especially in the operating phases of the engine at low and medium load. In practice, the optimization of the valve crossover consists in applying the opening instructions of the intake and exhaust valve closing valves to minimize the fuel consumption, by maximizing the crossing period during which the intake and exhaust valves are simultaneously open, and positioning these openings and closures in the engine cycle as well as possible. The method is applicable to the regulation of other parameters influencing the engine operating stability (ignition advance and richness), but this is not its preferential application, because there are other reliable and simpler methods for regulate: by construction of a stability index as known in the prior art for the stabilized phases, especially immediately after starting the engine, or by using specific probes during the transient phases.

Preferably, a backup strategy is implemented in case of stability deviation greater than a predetermined threshold. High engine instability can lead to engine failure. A backup strategy helps to ensure the reliability of the engine. Such a strategy consists in rapidly returning the engine to an operating point on which its stability is ensured, for example by applying a zero valve crossover, and conservative instructions for ignition advance and richness. Preferably, the process steps are repeated with each combustion in the engine. Thus, a rapid regulation of the parameter in question is obtained, which makes it possible in particular to optimize this parameter by having at all times of the operation of the engine a stability index very close to the stability setpoint. Preferably, the method is implemented during phases of transient operation of the engine. It can also be used during stabilized operation phases. It is indeed in the transient operating phases that the process developed in the invention is of great interest. Indeed, taking into account a function of the derivative of the engine speed, reflecting the evolution of the engine speed, allows the creation of an index representative of the engine operating stability, including while its engine speed is changing, that is to say during its operation in transient phase.

Preferably, the stability index is calculated by the formula

where Is is the stability index, ^< ^ ^<¾Mewee is the measured time derivative of the dt

engine speed at the instant of calculation, which corresponds to a moment when a combustion occurs in a cylinder of the engine, ^ ^{ωτΗεοηζ1ίίε} _es t | _has estimated time derivative of dt regime

of the engine as a function of its estimated torque at the moment of computation and of the inertia opposing the variation of its speed of rotation, ^ω ™™ ^ is the engine speed measured at the instant of the computation, and T _PMH is the time elapsed at the time of calculation since previous combustion.

This calculation method makes it possible to obtain a dimensionless index representative of the operating stability of the engine, including in its phases of transient operation.

Preferably, the estimated time derivative of the engine speed is calculated by the formula: ^{dco Estimée} _ Couple _ Estime

^ ^ equivalent in which Couple_Estime is the estimate of the torque of the motor at, T _PMH is the time elapsed since previous combustion, and J _eq uivait is the translation in the form of a moment of inertia equivalent of the inertia opposing the variation of the motor rotation speed. It is therefore the inertia of the engine or the vehicle brought back to the motor shaft according to the engaged gear ratio. Taking into account the inertia of the vehicle brought back to the motor shaft makes it possible to use the stability indicator in transient and moving vehicle

Preferably, the measured time derivative of the engine speed is determined by the formula: ^had) _r ^{^ω ΡΜΗ ω ΡΜΗ}

dt T _PMH in which ω _{ΡΜΗ η} is the engine speed at the instant of calculation, ( _{ΡΜΗ η} _ _γ the regime at the instant of the preceding combustion.) The approximation of the time derivative of the regime by the study of its variation between two combustions offers a good precision, because of a weak time step and a study between two combustions, which are the events generating the engine speed variations.

The invention also relates to a control system of an internal combustion engine, implementing the method according to one of the preceding claims.

The invention is described in more detail below and with reference to the figures schematically showing the invention in its preferred embodiment for the adjustment of the crossover valves as a parameter influencing the stability.

[0017] FIG. 1 is a general block diagram of the method according to the invention,

FIG. 2 represents an exemplary control strategy implemented by the method according to the invention. [0019] FIG. 3 represents a calculation module of the regulator of FIG. 1.

Figure 1 describes, using block diagrams, the implementation of the method according to the invention. A supervisor 1 determines, for example according to the operating conditions of a motor 2, whether or not the method according to the invention is implemented. In the method according to the invention, the stability of the engine 2 is determined by a calculation function of a stability indicator 3, which gives as a result a stability indicator Is. A calculator 4 supplies a stability setpoint Cs, for example by means of a map specific to the engine 2. A comparator 5, calculates the difference between the two values Cs and Is, to output a signal Es, called deviation or stability error.

The stability deviation Es is then supplied to a regulator 6, in the example a P.I.D type regulator. (derivative integral proportional), but this can be of any other type (LQ, Hinfini, etc.).

The regulator then takes into account the stability deviation Es to calculate a valve crossing setpoint, that is to say in practice an OA inlet opening setpoint and a valve closing setpoint. exhaust FE. This setpoint is transmitted to the engine control member to be applied to the intake and exhaust phase shifters.

The stability indicator must allow to quickly and reliably detect the combustion quality even in transient regime.

For this, the combustion stability indicator uses in the invention 3 main input data:

Measurement of the engine speed

The estimation of the engine torque

- The box report engaged

Stability is characterized in the invention by an index, a function of the difference between the derivative of the engine speed as measured (or more precisely, as calculated using engine speed measurements) with the estimated derivative. that the engine should have because of the engine torque at the time of calculation. This makes it possible to obtain a representative stability index even in the transient motor operating phases.

The measured time derivative of the regime is calculated by the following formula dt T _PMH in which - ω _{ΡΜΗ η} (rad / s) is the engine speed at the moment of calculation, instant corresponding to the instant of a combustion;

- ω _{ΡΜΗ η} _γ (rad / s) the regime at the moment of the previous combustion;

- T _PMH (s) the time elapsed since the previous combustion (ie the time between combustion occurring at the time of calculation and the previous combustion).

This calculation is preferably performed at each combustion of the engine. The regime is measured also with each combustion.

The estimated time derivative of the regime is calculated by the following formula:

= Couple _ Estime

in which :

Torque_Estimate (Nm) is the estimate of the motor torque, given by the motor control system, and Jequivait (kg.m ² ) is the translation in the form of a moment of inertia equivalent of the inertia opposing the variation the speed of rotation of the engine. This is the inertia of the engine or the vehicle brought back to the motor shaft according to the engaged gear ratio.

The estimation of the engine torque, given by the engine control, can be performed according to various more or less complex and precise models. For example, the motor control can use a model based on the following formula:

- CMF

With:

- ηθνθΐ β: ignition advance efficiency

- r | indicated: output indicates function of inlet pressure and speed

- Pci lower calorific value Filling estimation: estimation based on the engine speed, the intake pressure, the opening angles of the intake valves and the closing of the exhaust valves.

Pco: comburivore power

CMF: engine friction mapping

[0030] The equivalent moment of inertia J _equivalent vehicle back on the input shaft box (and hence engine) can in turn be calculated by the formula:

Mass _ Vehicle x R _Wheel χ (1 + ε)

^ equivalent ^ engine

With:

I motor: motor inertia

- Rroue: wheel radius

- Rbv: gear ratio (gear function engaged) and bridge

- r | bv: box yield (function of the engaged ratio)

- Inertia of the rotating parts of the transmission (primary shaft, secondary shaft, transmission shaft, pinion). This is a function of the gear engaged.

The stability index Is is calculated as follows:

This calculation can be averaged over several points in order to perform a low-pass filtering.

Figure 2 shows an example of the course of the engine control strategy implemented by the method according to the invention. We put ourselves in the case where the engine is stable immediately after startup. The engine control device involving a method according to the invention will calculate a crossover instruction of the distribution, according to a first index of stability calculated. The regulation thus achieved will increase the crossing of the valves as long as the engine remains stable (relative to the stability set), and this, according to a variant of the invention, to a certain predetermined limit.

In case of high instability of the engine (criterion defined for example by a threshold level of the stability error Es), is applied in the variant of the invention here represented a backup strategy, which may for example consist of adoption of a preset crossover of the predefined distribution and ensuring stability in a certain way, for example a zero crossing (request for rapid "uncrossing" of the engine), possibly accompanied by the adoption of advance control instructions at ignition and wealth When the implementation of the backup strategy has found an acceptable level of stability, the system applies again the method according to the invention.

FIG. 3 shows the regulating function of the crossing of the valves implemented in the regulator 6. This regulator 6 integrates a summing function F1 able to take into consideration the output signal of three other functions:

A function of determining the basic setpoint F2 of the crossing of the valves;

A function of correction of the set point F3, a function of the stability deviation Es;

A function for implementing a backup strategy F4. One or more of these functions are active according to the operating strategy determined by the supervisor 1.

According to the orders sent by the supervisor 1, a set of crossover valves (in the form of instructions for controlling the opening of the intake valves and closing of the exhaust valves), at the output of the summation function F1, can be determined:

by a simple open loop (mapping according to the water temperature for example). In this case, the summing function F1 takes into account only the output signal of the function for determining the basic setpoint F2

by an open loop and a PID type regulation for example, which determines a correction as a function of the stability error. In this case the F1 summation function it takes into account the output signal of the basic setpoint determination function F2 the signal of the setpoint correction function F3.

by a backup strategy, which may for example consist of a significant increment or decrement on the open loop. In this case, the summation function F1 takes into consideration the signals of the three functions for determining the basic setpoint F2, the setpoint correction F3, and the implementation of a backup strategy F4.

The invention thus proposes a method for changing the crossing level of the distribution of an engine according to its stability, to adopt a setting allowing the maximum consumption gains obtained by crossing. In other words, it is possible to enslave the crossing at a desired level of stability so as to limit the maximum consumption of the engine.

The invention can also be applied to the regulation of other parameters affecting the stability of the engine, such as the wealth or the ignition advance, aiming at obtaining a greater amount of power. available exhaust energy and / or reduction of polluting emissions.

Claims

claims

1. A method of controlling an operating parameter of an internal combustion engine (2), comprising the steps of:

- development of a stability setpoint (Cs), - calculation of a motor stability index (Is),

calculating the stability difference (Es) equal to the difference between the stability setpoint (Cs) and the stability index (Is).

- Processing of the stability gap (Es) by a regulator (6) which provides a motor control setpoint (OA, FE), to be applied to the operating parameter of the motor (2), characterized in that the index of stability (Is) is a function of the difference between the measured time derivative of the engine speed at the instant of calculation, and the estimated time derivative of the engine speed as a function of the engine torque and the inertia opposing the variation of the engine speed. its speed of rotation.

2. Method according to claim 1, characterized in that the engine control set tends to optimize the crossing of the valves to reduce the fuel consumption of the engine while respecting the stability guideline (Cs).

3. Method according to any one of the preceding claims, characterized in that implements a backup strategy in the event of stability deviation (Es) greater than a predetermined threshold.

4. Method according to any one of the preceding claims, characterized in that the process steps are repeated with each combustion in the engine (2).

5. Method according to any one of the preceding claims, characterized in that it is implemented during phases of transient operation of the motor (2).

6. Method according to any one of the preceding claims, characterized in that the stability index (Is) is calculated by the formula: where ls is the stability index, - ^Memree is the measured time derivative of the dt

engine speed at the moment of calculation, which corresponds to a moment when a combustion occurs) _F. ,

produced in a cylinder of the engine, - _is t | _has estimated time derivative of dt regime

of the engine as a function of its estimated torque at the instant of calculation and the inertia opposing the variation of its rotational speed, ^ω ™™ ^ is the engine speed measured at the instant of calculation, and T _PMH is the time elapsed at the instant of calculation since previous combustion.

7. Method according to claim 6, characterized in that the estimated time derivative of the engine speed is calculated by the formula: ^d0) Estimated _ Couple _ Estime

in which Couple_Estime is the estimate of the engine torque, and J _eq uivait is the translation in the form of an equivalent moment of inertia of the inertia opposing the variation of the rotational speed of the engine.

8. Method according to claim 6 or claim 7, characterized in that the measured time derivative of the engine speed is obtained by the formula:

dt in which) _{PMH n} is the engine speed at the time of calculation, ω _ΡΜΗ _ _n _ the speed at the instant of the previous combustion, and T _PMH is the time elapsed since previous combustion.

9. Control system of an internal combustion engine, implementing the method according to one of the preceding claims.