EP2438283A2

EP2438283A2 - Engine torque control during an acceleration phase following a deceleration phase

Info

Publication number: EP2438283A2
Application number: EP10728800A
Authority: EP
Inventors: Nicolas Hoffmann; Jacques Portalier
Original assignee: Peugeot Citroen Automobiles SA
Current assignee: PSA Automobiles SA
Priority date: 2009-06-04
Filing date: 2010-05-21
Publication date: 2012-04-11
Also published as: WO2010139880A3; FR2946392B1; FR2946392A1; WO2010139880A2

Abstract

The invention relates to a method for controlling an engine after a phase (82) of deceleration during which fresh air is recirculated into the cylinders, the method being characterized in that during a torque resumption phase (84) immediately following this deceleration phase, the amount of fuel injected into the cylinders is increased as a function of the amount of fresh air recirculated during the deceleration phase.

Description

MOTOR CONTROL METHOD AND DEVICE, VEHICLE EQUIPPED WITH SAID DEVICE, RECORDING MEDIUM

The present invention claims the priority of the French application 0953709 filed June 4, 2009 whose content (text, drawings and claims) is here incorporated by reference.

The invention relates to a method and an engine control device and a vehicle equipped with this engine control device. The invention also relates to an information recording medium for the implementation of the method.

During a deceleration phase, conventionally, the injection of fuel into the engine cylinders is stopped.

During this deceleration phase, it has been proposed to recirculate fresh air to, for example, avoid engine cooling (see for example the patent application FR 0 853 395). This fresh air that is admitted through the intake manifold is not consumed since no fuel is injected and is therefore found in the exhaust manifold of the engine.

[oooδ] By "recirculating" means here the operation of injecting into the intake manifold of the engine gases taken from the exhaust manifold. For this purpose, the engine is equipped with an exhaust gas recirculation circuit. This circuit is known as the Exhaust Gas Recirculation (EGR) circuit.

This deceleration phase is immediately followed by a torque recovery phase when the driver accelerates again.

During the torque recovery phase, the amount of fuel injected is determined as a function of the newly admitted fresh air flow into the intake manifold. For this purpose, the engine intake line is for example equipped with a flowmeter. The newly admitted fresh air is fresh air admitted for the first time times in the intake manifold. This newly admitted fresh air is therefore distinct from recirculated fresh air.

The amount of fuel injected into the cylinders is also determined according to a map that defines for each newly admitted fresh air flow a maximum fuel threshold to be injected beyond which appears a smoke, directly visible by a to be human, at the exit of the muffler.

In this context, the invention aims to improve the torque recovery after the deceleration phase during which fresh air is recirculated.

[ooio] It therefore relates to an engine control method in which, during the torque recovery phase immediately following this deceleration phase, the amount of fuel injected into the cylinders is increased as a function of the amount of air recirculated charges during the deceleration phase.

Measurements of the flow meter can estimate the amount of fresh air newly admitted into the cylinder. On the other hand, from these measurements it is not possible to estimate the amount of recirculated fresh air. Thus, after a deceleration phase during which fresh air is recirculated in the cylinders, the amount of fresh air estimated from the measurements of the flow meter is less than the actual amount of fresh air that the cylinders pass. Indeed, this actual quantity of fresh air results from the sum of the quantity of newly admitted fresh air and the amount of fresh air recirculated. Therefore, by increasing the amount of fuel injected to account for the presence of a larger amount of fresh air in the cylinders than that predicted from the flow meter measurements, the torque recovery is improved after the deceleration phase. .

Embodiments of this method may include one or more of the features of the variants summarized below.

In a variant, during the torque recovery phase, the determination of the quantity of fuel injected is a function of a first mapping associating, with measured quantities of fresh air newly admitted to the cylinders, maximum thresholds of fuel to be injected beyond which smoke appears at the outlet of a muffler. Use the first map to limit the appearance of smoke output of the exhaust during the torque recovery phase while improving torque recovery.

In addition, during an acceleration phase not immediately following the deceleration phase, the method may further comprise determining the quantity of fuel to be injected into the cylinders as a function of a measured quantity of fresh air. newly admitted in these cylinders and a second prerecorded cartography associating, with measured quantities of newly admitted fresh air, maximum fuel thresholds to be injected beyond which smoke appears at the outlet of the exhaust pipe, and the first cartography, used during the torque recovery phase, associates for each measured quantity of fresh air newly admitted to the cylinders a maximum threshold of fuel to be injected at least greater than or equal to the maximum threshold of fuel to be injected associated with the second mapping a newly admitted quantity of fresh air equal to the amount of fresh air recirculated during the deceleration phase . Defining the fuel threshold to be injected from the first mapping ensures a smooth transition between the torque recovery phase and this acceleration phase.

Advantageously, the maximum threshold of fuel to be injected from the first mapping is constant and equal to the maximum threshold of fuel to be injected associated by the second mapping to a newly admitted quantity of fresh air equal to the amount of fresh air recirculated. during the deceleration phase, for all measured quantities of newly admitted fresh air less than or equal to the amount of fresh air recirculated during the deceleration phase. Use a first mapping that is identical to the second mapping except values for the measured fresh fresh air quantities less than the recirculated fresh air quantity ensure a smooth transition between the torque recovery phase and the acceleration phase

In a variant, the estimate of the newly admitted amount of fresh air is carried out using a flow meter placed on a fresh air intake line in the engine cylinders. [Ooiδ] In a variant, the amount of fresh air recirculated during the deceleration phase is estimated from the mass flow rate of fresh air at the atmospheric pressure admitted into the cylinders.

The invention also relates to an information recording medium comprising instructions for the execution of the above control method, when these instructions are executed by an electronic computer.

The invention also relates to a suitable engine control device, during a torque recovery phase immediately following a deceleration phase in which fresh air is recirculated in the cylinders, to increase the quantity of fuel injected into the cylinders according to a quantity of fresh air recirculated during this deceleration phase.

Finally, the invention also relates to a vehicle equipped with the engine control device above.

The invention will be better understood on reading the description which follows, given solely by way of nonlimiting example and with reference to the drawings in which:

FIG. 1 is a schematic illustration of the architecture of a motor vehicle equipped with an engine control device,

FIGS. 2 and 3 are illustrations, respectively, of cartographies implemented by the motor control device of FIG.

FIG. 4 is a flow diagram of an engine control method implemented in the vehicle of FIG. 1, and

• Figure 5 is a timing diagram illustrating the evolution of the engine torque of the vehicle of Figure 1 in two different cases.

Figure 1 shows a motor vehicle 2 equipped with a combustion engine 4. The vehicle 2 is for example a car and the engine 4 is for example a diesel engine. The engine 4 comprises cylinders 6 inside which are mounted in translation pistons. In steady state, the temperature rise of the engine 4 is limited by a cooling circuit 8.

The circuit 8 comprises a coolant circulating between, on one side, a radiator 10 and on the other side the engine 4.

The circuit 8 also comprises a regulator 12 adapted to regulate the various members of the circuit 8 so as to maintain the coolant temperature equal to a target value. Typically, the target value of the coolant temperature is reached after the vehicle 2 has traveled more than ten kilometers. For example, this target value may be chosen close to 90 ° C.

The fresh air intake circuit comprises conventionally, an air filter 16 adapted to filter the air from outside the vehicle, a compressor 18 clean to compress the fresh air before the injecting into the cylinders, a booster gas radiator 20, this radiator 20 for cooling the compressed air by the compressor 18, and a housing or butterfly valve 22, adapted to allow and, alternately, to stop the intake of fresh air in an intake manifold 24 distributing the fresh air in each of the cylinders 6.

The vehicle 2 also comprises a circuit 26, provided with a valve 28, to possibly allow a short circuit of fresh air without passing through the radiator 20.

The fresh air admitted into the cylinders 6 serves as oxidant. More specifically, the fresh air admitted into the cylinders 6 is mixed with a fuel to form an explosive mixture. The exhaust gas is collected by an exhaust manifold before being sent to an expander 32. The expander 32 returns the exhaust gas to atmospheric pressure.

The exhaust gas then pass, successively a catalyst 34 and a particulate filter 36 before being discharged outside the vehicle through an outlet 38 of a muffler.

The vehicle 2 is also equipped with a system 40 for recirculating exhaust gas known by the acronym EGR (Exhaust Gas Recirculation). The system 40 is fluidly connected to the outlet of the manifold 30 and to the inlet of the manifold 24 so as to be able to return at least a portion of the exhaust gas collected in the manifold 30 to the manifold 24.

For example, the system 40 includes for this purpose a radiator 42 adapted to cool the exhaust gas collected at the collector 30 and a controllable valve 44 to allow and, alternately, to stop the admission of gases In the manifold 24. The valve 44 is known as the "EGR valve".

The vehicle 2 may also comprise different sensors such as, for example, a sensor 48 of the torque Cm produced by the engine 4 on its shaft, a sensor 50 of the engine speed Rm, a sensor 52 of the fresh air temperature. admitted at the collector 24, a sensor 54 of the coolant temperature, a sensor 56 of the position of an accelerator pedal 58, a sensor 60 of the position of a clutch pedal 62 and a flow meter 64 .

The flow meter 64 measures the mass flow rate of newly admitted fresh air output of the filter 16 before admission into the compressor 18.

A controllable injector 65 of fuel is also provided. The injector 65 makes it possible to regulate the quantity of fuel injected into the cylinders 6. More precisely, this injector 65 makes it possible to regulate the injected fuel flow rate.

All of these sensors and controllable elements is connected to an electronic computer 66. To simplify Figure 1, the connections between the computer 66 and these different organs have not been shown.

For example, the computer 66 is a programmable electronic computer capable of executing instructions recorded on an information recording medium. For this purpose, the computer 66 is connected to a memory 68. The memory 68 contains the instructions and the data necessary for the execution of the method of FIG.

In particular, the memory 68 contains two maps 70 and 72 used when determining the amount of fuel to be injected into the cylinders. FIG. 2 illustrates on a graph the content of the map 70. In this graph, the abscissa represents the newly admitted flow rate D _m of fresh air measured by the flowmeter 64. The ordinate axis represents the value of a maximum threshold S _c of fuel to be injected into the cylinders 6. If the quantity of fuel injected into the cylinders 6 is greater than this threshold S _c , then the smoke visible to a human being may appear at the exit 38 of the muffler.

The flow D _m is the mass flow measured. This flow therefore depends on the pressure.

The value D _atm represents the value of the mass flow rate that would be measured if the air admitted into the manifold 24 was at atmospheric pressure. It is considered that the air admitted into the manifold 24 is at atmospheric pressure when it is equal to ± 5% near the atmospheric pressure outside the vehicle 2.

[0042] This value of rate D _atm corresponds to a maximum threshold S _atm fuel to be injected.

FIG. 3 represents in the form of a graph the map 72. This map 72 is identical to the map 70, except that for measured flow values D _m lower than the value D _atm , the threshold S _c is constant and equal to the value S _atm -

The meeting of the sensors 48, 50, 52, 54, 56 and 64, the valves 22 and 44, the injector 65, the computer 66 and its memory 68 form a motor control device.

When the coolant temperature is equal to the target value, or at least greater than a threshold temperature which can be chosen lower than the target temperature (to fix the ideas, a threshold temperature of for example 60 ° C for a motor whose target temperature is 90 ° C), the computer 66 executes, during a phase 80 (Figure 4), a conventional strategy of motor control.

In particular, during phase 80, the injected fuel flow rate is determined as a function of the flow rate D _m of air measured by the flow meter 65 and the mapping 70. More specifically, the mapping 70 is used to limit the amount of fuel injected into the cylinders 6 so that no visible smoke out of the muffler can appear.

As soon as a deceleration request is recognized, the computer controls, during a phase 82, the deceleration of the vehicle. For example, the deceleration phase 82 is triggered when the driver gets off the foot of the accelerator pedal or during a shift gear ratio.

During this deceleration phase 82, the computer implements a strategy in which the EGR valve 44 is open and the throttle body 22 is closed. Under these conditions, fresh air is recirculated in the cylinders 6 on several engine cycles, that is to say on several round-trip piston. This makes it possible, for example, not to excessively cool the motor 4.

While the fresh air is recirculated and the throttle body is closed, the pressure of the recirculated fresh air is close to atmospheric pressure. The recirculated air flow rate can be estimated as being equal to the newly admitted air flow that would be measured by the flow meter 64 at atmospheric pressure. Thus, here, this flow recirculated air is taken equal to the value D _atm .

When an acceleration request is recognized, the phase 82 is completed and begins immediately after a phase 84 of torque recovery. This phase 84 is for example identical to phase 80 with the exception that the computer uses the map 72 instead of the map 70. Indeed, immediately after the phase 82, the flow D _m measured by the flow meter is lower than the fresh air flow that actually passes through the cylinders 6 of the engine 4. This mapping 72 takes this situation into account by increasing, for measured flow rates lower than the value D _atm , the value of the threshold S _c . Therefore, during phase 84, the quantity of fuel injected into the cylinders can be increased relative to the quantity of fuel that would have been injected had the mapping 70 been used. This significantly improves the torque recovery at the end of phase 82. Phase 84 lasts, for example, as long as the measured flow rate has not exceeded the value D _atm . As soon as this event occurs, phase 84 ends and returns, for example, to phase 80. FIG. 5 is a graph illustrating the measured evolution of the torque of the motor 4 as a function of time. More precisely, this graph represents the transition at an instant ti between the phase 82 and the phase 84. A curve 90 represents the evolution of the engine torque in the case where, during the phase 84, the cartography 70 is used. In contrast, a curve 92 represents the evolution of the torque of the engine 4 when the mapping 72 is used during the phase 84. As illustrated, the engine torque progresses much more rapidly at the end of the phase 82 when the Mapping 72 is used instead of mapping 70.

Many other embodiments are possible. For example, during phase 82, the throttle body 22 is not necessarily completely closed but may be positioned to greatly reduce the newly admitted fresh air flow rate. By "greatly reduced" is meant a position of the throttle body 22 in which the newly admitted fresh air flow is at most equal to

20% and preferably not more than 10% or 5% of the fresh air flow that would be obtained under the same operating conditions if the throttle body 22 was fully open.

One or more of the sensors described herein may be replaced by estimators suitable for estimating the value of a physical quantity from measurements of other physical quantities and implementing a mathematical model of the behavior of the engine.

Preferably, the deceleration phase 82 is implemented only on certain operating-load ranges.

What has been described to improve the torque recovery can be applied at the end of any phase in which the fuel injection is cut and fresh air recirculated. It is therefore not necessary for this phase to be, for example, intended to prevent engine cooling 4.

Claims

1. Motor control method after a deceleration phase (82) during which fresh air is recirculated in the cylinders, characterized in that, during a phase (84) torque recovery immediately following this phase deceleration, the amount of fuel injected into the cylinders is increased depending on the amount of fresh air recirculated during the deceleration phase.

2. Method according to claim 1, wherein, during the torque recovery phase (84), the determination of the quantity of fuel injected is a function of a measured quantity of newly admitted fresh air in these cylinders and a first mapping associating, to measured quantities of fresh air newly admitted to the cylinders, maximum fuel thresholds to be injected beyond which smoke appears at the outlet of a muffler.

The method of claim 2, wherein:

during an accelerating phase (80) not immediately following the deceleration phase, the method comprises determining the quantity of fuel to be injected into the cylinders as a function of a measured quantity of newly admitted fresh air in these cylinders; cylinders and a second prerecorded cartography associating, with measured quantities of newly admitted fresh air, maximum fuel thresholds to be injected, beyond which smoke appears at the outlet of the exhaust pipe, and

the first mapping, used during the torque recovery phase (84), associates for each measured quantity of fresh air newly admitted to the cylinders a maximum threshold of fuel to be injected at least greater than or equal to the maximum threshold of fuel to be injected associated by the second mapping to a newly admitted quantity of fresh air equal to the amount of fresh air recirculated during the deceleration phase.

4. The method of claim 3, wherein the maximum fuel threshold to be injected from the first mapping is constant and equal to the maximum threshold of injection fuel associated by the second mapping to a freshly admitted quantity of fresh air equal to the amount of fresh air recirculated during the deceleration phase for all measured fresh fresh air quantities less than or equal to the amount of fresh air recirculated during the deceleration phase.

5. Method according to any one of the preceding claims, wherein the estimate of the fresh air quantity newly admitted is carried out using a flow meter placed on a fresh air intake line in the cylinders. of the motor.

6. A method according to any one of the preceding claims, wherein the amount of fresh air recirculated during the deceleration phase is estimated from the mass flow rate of fresh air admitted into the cylinders that would be measured if the air admitted was at atmospheric pressure.

7. Information recording medium, characterized in that it comprises instructions for the execution of a method according to any one of the preceding claims, when these instructions are executed by an electronic computer.

8. Motor control device, characterized in that this device is suitable, during a torque recovery phase immediately following a deceleration phase during which fresh air is recirculated in the cylinders, to increase the amount of fuel injected into the cylinders according to a quantity of fresh air recirculated during this deceleration phase.

Vehicle (2), characterized in that it is equipped with an engine control device according to claim 8.