WO2006095113A1

WO2006095113A1 - System for controlling switchover of a motor vehicle operating conditions between lean and rich modes

Info

Publication number: WO2006095113A1
Application number: PCT/FR2006/050201
Authority: WO
Inventors: Piet Ameloot; Pascal Folliot
Original assignee: Peugeot Citroen Automobiles
Priority date: 2005-03-11
Filing date: 2006-03-08
Publication date: 2006-09-14
Also published as: FR2883041A1; EP1856395A1; FR2883041B1

Abstract

The invention concerns a system wherein the engine (1) is associated with means controlling (6, 7) the air loop thereof, with means controlling (6, 8) the fuel pressure in a common ramp (4) supplying fuel into the cylinders thereof, with means controlling (6, 9) fuel injections (5) into said cylinders and with means switching (6) parameters controlling said means between parameters controlling the operating conditions of the engine (1) in lean mixture and in rich mixture. The invention is characterized in that the switchover means (6) comprise gradual switchover means of control parameters of the air loop controlling means (7) and of the fuel pressure in the common feeding ramp (4) and instantaneous switchover means of parameters of the injection controlling means (5), but delayed towards the end of the gradual switching of the parameters of the other control means, between the lean mode and rich mode values.

Description

Control system for tilting the operation of a motor vehicle engine between pauyre and rich modes.

The present invention relates to a system for controlling the tilting of the operation of a motor vehicle engine between lean and rich modes, to assist the regeneration of a NOx trap integrated in an exhaust line of the engine.

A NOx trap is a pollutant reduction system that processes NOx through sequential operation of the engine in storage and retrieval modes corresponding to operations of the latter in lean mode with λ> 1 and in rich mode with λ <1. When the trap is saturated with NOx, it is regenerated by a tilting of the engine in rich mode with production of reducers, as among others, CO and HC.

This switchover is characterized by parameters, such as the richness, duration and frequency of fuel injections. An operating mode transition of the engine must be made as quickly as possible in complete transparency for the driver of the vehicle, that is to say smoothly and without operating noise change and limiting the penalty associated with the engine. emission of pollutants or overconsumption of fuel. In general, it is known that such a motor is associated with controls for the air loop thereof, with means for controlling the fuel pressure in a common fuel supply system for the cylinders. thereof and means for controlling fuel injections into these cylinders.

In rich operating mode, the injection parameters, ie the amount of fuel injected, the phasing and fuel pressure in the common rail, etc., as well as the parameters of the air loop , ie the air flow, exhaust gas recirculation, also called EGR, and the position of the turbocharger, etc., associated with such a motor, are modified compared to those of the lean mixture Operating. The global adjustment of these various parameters makes it possible to achieve the performance objectives in terms of torque, pollutant emissions, noise, etc. Each state of the engine (poor or rich) is therefore characterized by maps and specific control modules that describe the injection parameters, for example the phasing and the amount of each injection, the fuel pressure in the ramp, etc. , and the parameters of the air loop, such as the air flow, boost pressure, the position of an EGR valve, the position of the turbocharger, etc., which lead to a control of the different actuators the engine, such as the EGR valve, the turbocharger, a throttle valve, injectors or a high pressure pump, etc. This is achieved by means of tilting control parameters of these different means between control parameters of the operation of the engine in lean mixture and control parameters of the operation of the engine in rich mixture.

When switching from the engine from lean mode operation to rich mode operation, the injection and air loop parameters thus switch from one series of mappings and controllers for the lean mode to another series of maps and regulators for the rich mode.

The way in which this changeover is achieved is very important and has a significant impact on the engine performance in terms of noise, torque and pollutant emissions during the changeover phase.

The object of the invention is to propose a system for controlling this changeover.

To this end, the object of the invention is a system for controlling the tilting of the operation of a motor vehicle engine between lean and rich modes, to help the regeneration of a NOx trap integrated in an exhaust line. of the engine and wherein the engine is associated with control means of the air loop thereof, to control means of the fuel pressure in a common fuel supply line of the cylinders thereof , means for controlling the injection of fuel into these cylinders and means for tilting the control parameters of these means between control parameters of the operation of the lean-burn engine and the parameters for controlling the operation of the engine in rich mixture, characterized in that the means for tilting the parameters comprise means of progressive tilting of the parameters control of the control means of the air loop and the fuel pressure in the common supply rail and means for instantaneous switching of the parameters of the injection control means, but deferred towards the end of the progressive changeover of the parameters other control means, between their values of poor mode and rich mode. According to other features of the invention:

in lean mode, the air flow at the inlet of the engine is controlled in a closed loop by an exhaust gas recirculation valve at its inlet; in lean mode, the gas inlet pressure in the engine is controlled in a closed loop by a turbocharger associated with this engine;

- In lean mode, the gas inlet pressure in the engine is controlled in a closed loop by a throttle valve;

- In lean mode, a gas throttle valve in the engine is controlled open loop;

in rich mode, the air flow at the engine inlet is controlled in a closed loop by a throttle valve;

in rich mode, the intake pressure of the gases in the engine is controlled by an exhaust gas recirculation valve at its inlet;

in rich mode, a turbocharger associated with the engine is driven in an open loop;

- In rich mode, a gas throttle valve in the engine is positioned instantaneously, when tilting, to a predetermined position, and is regulated around this position to regulate the air flow to the engine inlet;

the values of the lean mode and rich mode parameters are derived from predetermined mappings;

the progressive tilting means are tilting means according to at least one ramp portion; and

- The ramp is determined from a predetermined map based on engine speed and load. The invention will be better understood on reading the description which follows, given solely by way of example and with reference to the appended drawings, in which:

- Fig.1 is a block diagram illustrating the structure of a system according to the invention;

FIG. 2 illustrates the characterization of the modes of operation of an engine and the transition between these modes;

FIG. 3 illustrates an example of control of so-called slow parameters in lean and rich operating modes of the engine; and FIGS. 4, 5, 6 and 7 illustrate the management of the various parameters for controlling the operation of the engine during a transition from an operation thereof to a lean mixture to a rich mixture operation.

In fact, FIG. 1 shows a motor, for example a motor vehicle diesel, which is designated by the general reference 1 and whose exhaust line 2 is associated with depollution means designated by the general reference 3.

These include for example a NOx trap or others. In a conventional manner, such a motor is associated, for example, with fuel supply means comprising, for example, common fuel supply means, indicated schematically by the general reference 4 in this figure, the operation of which is controlled by injection control means designated by the general reference 5, including any appropriate engine computer.

In addition, this engine is also associated with means 6, constituted for example by any appropriate computer, for controlling the air loop thereof, designated by the general reference 7, means for controlling the fuel pressure. in the common fuel supply line 4 of the cylinders thereof, designated by the general reference 8 and control means of the fuel injections in these cylinders, designated by the general reference 9.

These control means 6 then comprise means for tilting the control parameters of these various means between control parameters of the operation of the engine in lean mixture and in rich mixture. As indicated above and as illustrated in FIG. 2, each mode of operation of the engine, i.e., the lean mode and the rich mode, is characterized by specific maps and control modules which describe the various parameters, for example injection, such as the phasing and the quantity of fuel injected, the pressure in the common rail, etc., and the parameters of the air loop such as the air flow, the pressure the position of the EGR recycling valve, the position of the turbocharger, etc., which lead to a control of the various actuators of the engine. During a transition from a lean mode operation to a rich mode operation, we therefore switch mappings.

In the failover control system according to the invention and in order to manage the mode transitions, the control parameters of the motor operation can be divided into three groups, namely the slow parameters, the fast parameters and the semi-fast parameters. .

The slow parameters are for example the parameters of the air loop. The physical quantities such as the intake air flow in the engine, the boost pressure or the rate of EGR, etc., can not change instantly, that is to say that their time of response is clearly superior to a motor cycle. The associated actuators are the turbocharger, the throttle valve, the EGR valve and the variable swirl valves.

The fast parameters are constituted by the quantities and the phasing of the injections. These parameters can be changed from one motor cycle to another. Their response time is very low. The associated actuators are for example the fuel injectors.

The semi-rapid parameters include for their part, for example, the fuel supply pressure in the common engine cylinder feed ramp. The response time of these parameters is between the fast parameters and the slow parameters. The associated actuator is for example a high pressure fuel supply pump.

As indicated above, the control system according to the invention proposes a strategy of switching the motor of the mode of poor operation to a rich operating mode, which allows fast transitions, transparent and clean.

For this purpose, in the system according to the invention, it is proposed to use, for example, predefined ramps to switch the slow and semi-fast parameters from their initial value from lean mode to their final value of rich mode, or any other changeover. progressive and use a direct or instant failover for fast parameters, but deferred towards the end of this gradual switchover of other parameters.

FIG. 3 illustrates a control of slow parameters during a transition between a lean mode operation and a rich mode operation.

In lean mode, the slow physical variables of the motor such as, for example, the air flow, the inlet pressure, etc., and the associated actuators, such as for example the throttle valve, the EGR valve, the turbocharger and the check valves. Variable "swirl", etc. can be controlled in closed loop (BF) or open loop (BO).

For example, the air flow is controlled in a closed loop by the EGR valve, the engine intake pressure is controlled in a closed loop by the turbocharger and the throttle valve is operated in an open loop. But other control structures can be envisaged, such as for example a control of the intake pressure by the butterfly.

It should also be noted that the inlet pressure can be measured in several places, for example at the outlet of the compressor, at the outlet of an air cooler, in the inlet distributor, etc. In rich mode, the slow physical motor variables, such as the air flow or the intake pressure and their associated actuators, such as the throttle valve, the EGR valve, the turbocharger and the variable "swirl" valves , can also be controlled in closed loop or open loop. For example, the air flow can be controlled in a closed loop by the throttle valve, while the engine intake pressure is controlled by the EGR valve and the turbocharger can be operated in open loop.

Of course, different embodiments can be envisaged. FIGS. 4 to 7 illustrate the switchover between a lean mode operation and a rich mode operation of the motor.

This switching can comprise two transition phases.

During the first phase of the transition, the slow physical quantity setpoints, such as, for example, the air flow, the inlet pressure, etc., are gradually changed, that is to say by example by following a ramp, their values mapped in lean mixture to their values mapped in rich mixture, for the same point of operation of the engine, that is to say in regime and load, as is illustrated in FIG. 4.

The actuator position commands related to slow physical quantities, such as for example the EGR valve, the turbocharger and the variable "swirl" valves, with the exception of the throttle valve, are also gradually switched, for example by following a "ramp" ramp, from their last values in lean mixture to their values mapped in rich mixture, as illustrated in FIG.

On the other hand, the throttle butterfly is prepositioned instantaneously on a "prepol" value and is then actuated in a closed loop or an open loop around this prepositioning value, for example to regulate the air flow.

This is illustrated for example in FIG.

A progressive switchover, for example a ramp, is characterized by a transition time between an initial value and a final value. The ramp times used during this phase are the same, for example for all the slow parameters and this value, for example called "rampel", is mapped among others according to the speed and the load of the engine.

It may also be noted that the set point, for example of intake pressure, may follow a path other than a ramp, such as, for example, a dynamically determined set point, taking into account the actual air flow rate.

The second transition phase is activated under the following conditions.

Indeed, this second phase can be activated if the slow parameters arrive at the end of the ramp, if a slow physical quantity such as the air flow reaches a predetermined threshold, called "threshold", resulting for example from a map, or if the difference between the actual value and the set point of a slow physical quantity such as for example the air flow rate reaches a predetermined threshold, called "threshold2". These two thresholds, that is to say the thresholds 1 and 2 threshold are mapped and depend inter alia on the speed and the load of the engine.

This second phase of the transition is characterized for slow parameters by a complete changeover of the setpoint values of the physical quantities and the positions of the associated actuators towards the final values in rich mode, such as, for example, the air flow rate, the position of the turbocharger , etc., and for the fast parameters by instantaneous switching as shown in FIG. 7.

The ramp or progressive tilting is then completed. But this second phase is also characterized by the activation of closed-loop control of some slow physical quantities by an associated actuator, such as for example a closed-loop control of the air intake pressure by the EGR valve.

At the end of this second phase which has a very short duration, the transition or the changeover, is considered as finished for the slow parameters. The only parameter considered as semi-rapid in the example described is the fuel pressure in the common fuel feed ramp of the engine cylinders. This ramp pressure is always regulated in a closed loop on a setpoint and this setpoint is usually mapped according to the speed and the load of the engine and mappings exist for the lean mode and for the rich mode.

During the first phase of the transition, the fuel pressure setpoint in the ramp also follows a gradual tilting such as for example a ramp with the same characteristic time "rampel" between the lean value and the rich value on the same operating point of the ramp. engine. After this first transition phase, a second transition phase is implemented on the basis of the same conditions and in the same way as for the slow parameters.

Fast parameters, such as phasing and injection rate, are mapped for each mode. In the first phase transition values, the mapping values associated with the lean mode are still used. When the transition is triggered, according to the conditions indicated above, the setpoints of the fast parameters are instantly changed from their lean value to their rich value (FIG. But this switchover is delayed until the end of the progressive switchover of the other parameters.

It goes without saying of course that other embodiments can be envisaged.

Claims

1. Control system for tilting the operation of a motor vehicle engine (1) between lean and rich modes, to help the regeneration of a NOx trap (3) integrated in an exhaust line (2) of the motor (1) and wherein the motor (1) is associated with control means (6, 7) of the air loop thereof, control means (6, 8) of the pressure of fuel in a common fuel supply ramp (4) of the cylinders thereof, control means (6, 9) injections (5) of fuel in these cylinders and means (6) of tilting Parameter control of these means between control parameters of the operation of the engine (1) in lean mixture and control parameters of the engine operation in rich mixture, characterized in that the switching means (6) parameters include means for gradually switching control parameters of the control means of the air loop (7) and the fuel pressure (8) in the common feed ramp (4) and instantaneous tilting means of the parameters of the control means (9) of the injections (5), but deferred towards the end of the progressive switching of the parameters of the other control means, between their values of poor mode and rich mode.

2. System according to claim 1, characterized in that in lean mode, the air flow at the engine inlet (1) is controlled in a closed loop by an exhaust gas recirculation valve at its inlet. .

3. System according to claim 1 or 2, characterized in that in lean mode, the gas inlet pressure in the engine (1) is controlled in a closed loop by a turbocharger associated with this engine.

4. System according to any one of claims 1 or 2, characterized in that in lean mode, the gas inlet pressure in the engine (1) is controlled in a closed loop by a throttle valve.

5. System according to any one of the preceding claims, characterized in that in lean mode, a throttle valve in the engine (1) is controlled open loop.

6. System according to any one of the preceding claims, characterized in that in rich mode, the air flow at the engine inlet (1) is controlled in a closed loop by a throttle valve.

7. System according to any one of the preceding claims, characterized in that in rich mode, the gas inlet pressure in the engine (1) is controlled by an exhaust gas recirculation valve at the input of that -this.

8. System according to any one of the preceding claims, characterized in that in rich mode, a turbocharger associated with the engine (1) is controlled in an open loop.

9. System according to any one of the preceding claims, characterized in that in rich mode, a throttle valve in the engine (1) is positioned instantaneously, when tilting, on a predetermined position (prepol ), then is regulated around this position to regulate the air flow at the engine inlet.

10. System according to any one of the preceding claims, characterized in that the values of the lean mode and rich mode parameters are derived from predetermined mappings.

11. System according to any one of the preceding claims, characterized in that the progressive tilting means are tilting means according to at least one ramp portion (rampel).

12. System according to claim 11, characterized in that the ramp is determined from a predetermined map according to the speed and the load of the engine (1).