WO2021260281A1

WO2021260281A1 - Method for controlling the advancement of injection timing of a diesel combustion engine

Info

Publication number: WO2021260281A1
Application number: PCT/FR2021/050757
Authority: WO
Inventors: Serge Laurent
Original assignee: Psa Automobiles Sa
Priority date: 2020-06-23
Filing date: 2021-05-03
Publication date: 2021-12-30
Also published as: EP4168662A1; FR3111672B1; FR3111672A1

Abstract

The invention relates to a method for controlling a diesel combustion engine with a turbocharger and controlled injection, comprising the following steps: monitoring a difference E_F between a set intake air flow and an actual intake air flow; correcting the injection timing C_A in accordance with the difference E_F; monitoring a difference E_P between a set intake air pressure and an actual intake air pressure; and wherein the correction C_A is in accordance with the difference E_F and the difference E_P.

Description

DESCRIPTION

TITLE: INJECTION ADVANCE CONTROL ON A DIESEL COMBUSTION ENGINE

The present invention claims the priority of French application No. 2006533 filed on 06.23.2020, the content of which (text, drawings and claims) is incorporated here by reference.

Technical area

The invention relates to the field of motor vehicles, more particularly to the control of diesel combustion engines of motor vehicles. Prior art

In diesel fuel combustion engines with turbochargers, variations in engine load lead to transient regimes requiring special management in order to maintain pollution control and driveability services. These transient conditions are mainly due to the reaction time of the turbocharger. During an increase in engine load by the driver, manifested by a depression of the accelerator, the corresponding increase in richness of the mixture results, during the transitional phase until the desired air flow is achieved, an increase in the richness of the air-fuel mixture. This transient increase in richness can cause the production of black smoke. This undesirable effect is currently controlled or at least limited by limiting the increase in richness of the mixture, thus leading to a sensation of brio or reduced recovery. Another way to control or limit the production of black smoke is to increase the injection advance. This measure, however, is likely to degrade combustion noise, in other words making the engine noisier and potentially damaging it.

The published patent document CN 105089833 A relates to the control of a fuel combustion engine of the diesel type for railway application, more particularly to the management of the fuel injection at each engine cycle. operation, depending on different parameters. The transient regime issue is not addressed and the engine does not seem to be equipped with a turbocharger.

Published patent document CN 203098068 A relates to a diesel-type fuel combustion engine equipped with a fuel injection system with an electromechanical injection advance adjustment device. However, the issue of a transitional regime is not addressed.

Disclosure of the invention

The object of the invention is to overcome at least one of the drawbacks of the aforementioned state of the art. More particularly, the object of the invention is to provide a control for a diesel engine with a turbocharger which makes it possible to better manage transient speeds, in particular with regard to the speed at which the power is delivered during an increase in engine load. .

The subject of the invention is a method for controlling a diesel combustion engine with a turbocharger and controlled injection, comprising the following actions: monitoring a deviation EF between a set intake air flow rate and a flow rate of real intake air; injection advance CA correction as a function of the EF deviation; remarkable for the following additional action: monitoring a deviation Ep between a set inlet air pressure and an actual inlet air pressure; and in that the CA correction is a function of the EF deviation and the Ep deviation.

According to an advantageous mode of the invention, the correction CA is greater as the difference EF is large and the difference Ep is large.

According to an advantageous embodiment of the invention, the correction CA is determined by a mapping as a function of the deviation EF and the deviation Ep.

According to an advantageous embodiment of the invention, the mapping determines a weighting factor for the correction CA as a function of the deviation EF and the deviation Ep.

According to an advantageous embodiment of the invention, the weighting factor is between 0 and 1. According to an advantageous embodiment of the invention, the correction factor increases monotonically with the difference EF for a difference Ep greater than a minimum non-zero value.

According to an advantageous embodiment of the invention, the correction factor increases monotonically with the deviation Ep for a deviation EF greater than a non-zero minimum value.

According to an advantageous embodiment of the invention, the AC correction is also a function of engine speed n and engine torque T.

The invention also relates to a control unit for a diesel combustion engine with turbocharger and controlled injection, remarkable in that said control unit is configured to carry out the method according to the invention.

The invention also relates to a motor vehicle comprising a diesel combustion engine with turbocharger and controlled injection and a control unit for said combustion engine, remarkable in that said control unit is configured to perform the method according to the invention.

The measures of the invention are advantageous in that they allow the engine to deliver more torque in transient speeds, in particular at altitude, while respecting pollution control constraints. The injection advance CA correction is thus controlled in a more refined and also more efficient manner.

Brief description of the drawings

[Fig 1] is a schematic representation of a diesel combustion engine with turbocharger and controlled injection, equipped with a control unit according to the invention;

[Fig 2] is a flowchart illustrating the principle of transient state control according to the state of the art;

[Fig 3] is a flowchart illustrating the principle of transient regime control according to the invention;

[Fig 4] illustrates a mapping of an injection advance weighting factor according to the invention.

detailed description Figure 1 schematically illustrates a diesel combustion engine 2.

The diesel combustion engine 2 conventionally comprises an engine block 4 forming cylinders receiving pistons 6 for compressing the intake air and injecting diesel fuel therein to cause combustion. The fuel is injected into the combustion chambers by injectors 8. These injectors are supplied with pressurized fuel via a common rail (not shown) and controlled electrically during each engine operating cycle. Still conventionally, the engine 2 comprises an air intake manifold 10, an exhaust manifold 12 and a turbocharger 14, the turbine of which is supplied by the exhaust from the exhaust manifold 12 of the engine and the compressor compresses it. intake air to the intake air manifold 10 of the engine. An exhaust gas recirculation valve 16, commonly designated by the acronym EGR (corresponding to “Exhaust Gas Recycling”) is fluidly disposed between the exhaust line, between the exhaust manifold and the turbocharger 14, and an intake air line connecting the compressor of the turbocharger 14 to the intake air manifold 10. This exhaust gas recirculation valve 16 is essentially intended to reduce the emissions of nitrogen oxides NOx, without increasing the amount of particles produced too much. The production of nitrogen oxides NOx results mainly from high combustion temperatures, typically above 1300 ° C, particularly present in high efficiency direct injection engines. The exhaust gas recirculation valve 16 makes it possible to reduce the rate of NOx at the exhaust outlet, essentially by lowering the combustion temperature via in particular the reduction in the proportion of oxygen, to the detriment of efficiency and consumption. of fuel while increasing the amount of particulate matter released.

The metering of the flue gas is controlled according to the load and the speed to sufficiently reduce the combustion temperature without significantly increasing the production of soot.

The engine comprises a control unit 18 configured in particular to control the fuel injectors 8, as a function of numerous parameters, such as in particular a demand for power on the part of the driver and the engine speed.

The control unit 18 is configured to, upon a demand for an increase in power from the driver, control the fuel injectors 8 so as to increase the torque of the engine while applying an advance correction to the engine. 'injection during the transient regime, that is to say the regime where the turbocharger is in the acceleration phase following the increase in engine load and has not yet reached a new pressure and flow rate of the engine. intake air corresponding to the new engine load.

FIG. 2 illustrates, by means of a flowchart, a principle for determining the injection advance correction CA as a function of the engine speed n, of the engine torque T and of a difference EF between an intake air flow rate of setpoint and an actual intake air flow rate, according to the state of the art. When the engine load increases, a setpoint for the amount of fuel to be injected and an associated air flow setpoint are determined. These two setpoints correspond to increases, meaning that the exhaust flow will increase and the turbocharger rpm will also increase. The set amount of fuel to be injected can be reached immediately, for example from one operating cycle to the next. On the other hand, the intake air flow setpoint cannot be reached immediately given the inertia of the turbocharger. According to FIG. 2, it is known to monitor the difference EF between the setpoint intake air flow rate and the actual intake air flow rate and to provide an injection advance correction CA as a function of the EF deviation. At the 20 ’action, a weighting curve as a function of the EF deviation can be used. Similarly, at the 22 ’action, the injection advance AC correction can be a function of engine speed n and torque T. A weighting map following n and T can also be used. The two weighting factors obtained at actions 20 ’and 22’ are combined with action 24 to determine the injection advance AC correction.

Under certain operating conditions, especially at altitude (for example from an altitude of 1500m), the difference EF between the setpoint intake air flow rate and the actual intake air flow rate may be permanent then that the exhaust gas recirculation valve is closed, and then lead to prolonged operation of the engine with an AC injection advance correction. Such operating conditions can lead to a significant production of fumes, most often then limited by a reduction in the quantity of fuel injected and thus a reduction in the torque produced.

The invention provides, according to FIG. 3 illustrating a flowchart for determining the injection advance correction CA, to also take into account a difference Ep between a setpoint intake air pressure and an air pressure. actual admission.

To this end, in step 20, a mapping of a weighting factor as a function of the difference EF and the difference Ep can be used, this factor then being combined with action 24 with a weighting factor function of the speed n and of the torque T of the engine determined in action 22, similarly to FIG. 2. Such an approach is advantageous in that at altitude the difference Ep between a setpoint intake air pressure and an actual intake air pressure is low, or even cancels out, then making it possible to limit the injection advance correction CA and to deliver a satisfactory torque.

FIG. 4 illustrates an example of a mapping of the weighting factor as a function of the differences EF and Ep. The vertical axis expresses the weighting factor between 0 and 1. The horizontal axis generally parallel to the plane of the drawing corresponds to the difference EF expressed in mg / cycle and the horizontal axis generally perpendicular to the plane of the drawing according to the perspective corresponds to the deviation Ep expressed in mbar. It can be observed that the weighting factor only becomes large when the deviation EF and the deviation Ep are large. In other words, such an approach makes it possible to limit the effect of the EF deviation on the injection advance CA correction when the Ep deviation is small, and vice versa. The injection advance correction CA will therefore be significant under the influence of the difference EF between a setpoint intake air flow rate and a real intake air flow rate only if the difference Ep between A set intake air pressure and an actual intake air pressure are also significant.

Claims

[Claim 1.] A method of controlling a diesel combustion engine (2) with a turbocharger (14) and controlled injection, comprising the following actions:

- monitoring of an EF difference between a setpoint intake air flow rate and an actual intake air flow rate;

- CA injection advance correction as a function of the EF deviation; characterized by the following additional action:

- monitoring of a deviation Ep between a set inlet air pressure and an actual inlet air pressure; and in that

- the AC correction is a function of the EF deviation and the Ep deviation.

[Claim 2.] A method according to claim 1, characterized in that the correction CA is greater as the deviation EF is large and the deviation Ep is large.

[Claim 3.] Method according to one of claims 1 and 2, characterized in that the AC correction is determined by a mapping as a function of the EF deviation and the Ep deviation.

[Claim 4.] The method of claim 3, characterized in that the mapping determines a weighting factor for the AC correction as a function of the EF deviation and the Ep deviation.

[Claim 5.] A method according to claim 4, characterized in that the weighting factor is between 0 and 1.

[Claim 6.] Method according to one of claims 4 and 5, characterized in that the weighting factor increases monotonically with the difference EF for a difference Ep greater than a minimum non-zero value. [Claim 7.] Method according to one of claims 4 to 6, characterized in that the weighting factor increases monotonically with the deviation Ep for a deviation EF greater than a non-zero minimum value. [Claim 8.] Method according to one of claims 1 to 7, characterized in that the correction CA is also a function of the engine speed n and of the engine torque T. [Claim 9.] Control unit (18) of a diesel combustion engine (2) with turbocharger (14) and controlled injection, characterized in that said control unit (18) is configured to carry out the method according to the one of claims 1 to 8. [Claim 10.] Motor vehicle comprising a diesel combustion engine (2) with turbocharger (14) and controlled injection and a control unit (18) of said combustion engine, characterized in that said unit control (18) is configured to carry out the method according to one of claims 1 to 8.