WO2018162815A1

WO2018162815A1 - Method for managing the engine torque in a fuel injection recovery phase

Info

Publication number: WO2018162815A1
Application number: PCT/FR2018/050365
Authority: WO
Inventors: Romain SOUQUET; Sebastien GRALL; Felix GALLIENNE
Original assignee: Psa Automobiles Sa
Priority date: 2017-03-06
Filing date: 2018-02-15
Publication date: 2018-09-13
Also published as: MA47725A; FR3063520B1; EP3592960A1; FR3063520A1

Abstract

The invention relates to a method for managing the torque of a combustion engine in a fuel injection recovery phase (4a) after an injection shut-off (5b) in the combustion engine. A minimum static torque (1) is predetermined to be used as a minimum torque (2) for the combustion engine and to ensure combustion stability in the engine. During an injection recovery phase (4a), following the injection shut-off (5b), the minimum static torque (1), to be used as a minimum torque (2), is replaced by a minimum dynamic torque (3) lower than the minimum static torque (1) for a holding time (6) corresponding to a predetermined number of actual passes through top dead centre positions in one or more of the combustion engine cylinders and to a rise in the minimum torque (2) towards the minimum static torque (1) when said predetermined number is exceeded.

Description

METHOD OF MANAGING MOTOR TORQUE IN A FUEL INJECTION RECOVERY PHASE

The present invention relates to a method of managing an engine torque during a fuel injection recovery phase in a motor vehicle engine. The present invention is in the technical field of torque control of a heat engine, preferably fuel gasoline, ethanol, gas or a mixture of these elements.

It is known to provide a heat engine of a motor control unit. The engine control unit has control means and control, among others, the injection device and the engine torque This engine control unit ensures in particular a good operation of the engine by issuing engine torque instructions. These setpoints of motor torque have repercussions on an air loop setpoint allowed in the engine and on an ignition advance setpoint. In a motor, ignition is the mechanism triggering the initiation of combustion of the fuel-air mixture present in one or more cylinders of the engine. A piston in each cylinder follows a movement back and forth between a High Dead Point, for which the piston reaches the high point of its stroke in the cylinder and a Low Dead Point, for which the piston reaches the low point of its stroke. It is known to advance the ignition and this ignition advance is defined by a flying rotation angle that separates the spark time of the Top Dead Point, a correction away from and in advance of the Dead Point High representing an ignition advance.

It is thus known that a time advance of an ignition point of a mixture of air and fuel injected into at least one cylinder with respect to a passage of the piston by a combustion upper dead point is usually implemented on most engines when tuning.

The engine control unit estimates the minimum torque achievable by the engine. The minimum torque is built on a criterion of combustion stability. This strategy reaches its limits, especially during a torque recovery phase, this phase being also called re-assembly. Thus, the combustion stability criteria are not relevant in the torque recovery phase because the torque tracking is not respected, resulting in rebounds of the engine and a jump of speed during this phase.

The document FR-A-3 000 767 describes a method of managing a torque of a spark ignition engine by a torque structure. The heat engine operates on an optimum ignition advance when a setpoint torque is monitored in an operating mode unbuckled from the torque structure. On the other hand, it has passed into an operating mode terminated following detection of a deceleration with an injection cutoff of the heat engine so that ignition advances calculated during an injection cut-off period are between Advances at minimum and maximum ignition so that the target torque can be monitored during a subsequent acceleration.

However, this does not allow to follow the low torque requests in the resumption of injection phase and the problem of creating bounces and jumps is not resolved by the method disclosed by this document.

Therefore, the problem underlying the present invention is, during a torque recovery phase succeeding a fuel injection cut in a heat engine, to allow a control of the engine torque resulting in not the appearance of rebounds or jumps of engine speed during this phase. [001 1] To achieve this objective, it is provided according to the invention a method of managing a thermal engine torque in a fuel injection recovery phase after an injection cut in the engine, characterized in that it is predetermined a minimum static torque to serve as a minimum torque for the engine and ensure a stability of a combustion in the engine and that, during a phase of resumption of injection following the break of injection, the minimal static torque is replaced by a minimum dynamic torque lower than the minimum static torque during a holding period corresponding to a predetermined number of effective passes of High Dead Points in one or more engine cylinders. and a rise in the minimum torque to the minimum static torque when said predetermined number is exceeded.

The technical effect is to allow to follow the low demands of torque in resumption of injection and to avoid bouncing of the engine. When the injection is resumed, the torque required to comply with the approval of the engine is less than the minimum stabilized torque. This dynamic life situation requires a specific stability criterion. To ensure torque tracking, the method according to the invention therefore allows to have a minimum dynamic torque lower than the minimum static torque.

The method according to the invention consists in detecting the cases of resumption of the injection. In these cases, the minimum static torque, advantageously determined on the engine bed stabilized, does not allow to follow the torque request respecting the approval of the engine. It is then estimated a minimal dynamic torque that can track the torque while avoiding misfires.

The interest of the present invention is mainly technical. The life situation in fuel injection is improved and it is possible to offer several calibration levers, including the minimum dynamic torque, the number of effective passes of High Dead Points during which the minimum dynamic torque is applicable and the rise of torque minimum estimated or minimum torque from the minimum dynamic torque to the minimum static torque. Advantageously, the rise of the minimum torque to the minimum static torque is performed according to a linear slope.

Advantageously, said predetermined number of effective passes of High Dead Points is calibrated, preferably between 1 and 20 PMH.

Advantageously, the calibration of said predetermined number of effective passes of High Dead Points is performed as a function of one or more of the following parameters taken individually or in combination: a gear ratio of a gearbox associated with the engine, a engine speed and a filling of the engine cylinder or cylinders consisting of an instantaneous air ratio admitted to an air admitted at normal atmospheric temperature and pressure in the cylinder or cylinders. Advantageously, the dynamic minimum torque is calculated from a minimum calibratable advance and the filling of the engine cylinder or cylinders. This minimal dynamic torque is provided to control and torque control means to define the moment when reinjection must take place.

Advantageously, the replacement of the static minimum torque by the dynamic minimum torque is done during the injection cutoff after a calibrated time delay starting from a start of the injection cutoff. This ensures consistency of the torque control with anticipation of torque recovery. Otherwise, he torque jumps could occur if the replacement of the minimum static torque with the minimal dynamic torque was done just when the injection was resumed.

Advantageously, the minimum static torque is predetermined by calibration on a test bench at a constant engine speed and engine load. The invention also relates to a power unit of a motor vehicle, the group comprising a heat engine, a device for injecting a fuel into the engine and an engine control unit having control and control means on the one hand, the injection device and, on the other hand, the engine torque, characterized in that, during an injection recovery phase following an injection cutoff detected by the control means of the injection device, the engine torque control means manages the torque in accordance with such a method.

Such a powertrain can guarantee an engine amenity benefit by avoiding rebounds and oscillations engine speed felt by the driver. It is thus ensured a resumption of injection on a minimal dynamic torque which is representative of what the engine is capable of providing for the resumption of injection. Static stability limits are thus pushed back while avoiding misfires.

The solution proposed by the present invention is inexpensive because purely software requiring only software transformations in the engine control unit already present in the powertrain. Finally, the invention relates to a motor vehicle, characterized in that it comprises such a powertrain. The invention is compatible with the new regulations for petrol-fueled engines.

Other features, objects and advantages of the present invention will appear on reading the detailed description which follows and with reference to the accompanying drawings given by way of non-limiting examples and in which:

FIGS. 1 and 2 show, over time, the evolution of static, estimated and dynamic minimum torque curves for injection return and stop events, the minimum estimated torque or minimum torque being lowered to the minimum torque dynamic at the beginning of the resumption of injection phase in Figure 1 and before the start of the resumption of injection phase in Figure 2, so during the injection stop in the latter case. It is to be borne in mind that the figures are given by way of examples and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily at the scale of practical applications. In what follows, reference is made to all the figures taken in combination. When reference is made to a specific figure, this figure is to be taken in combination with the other figure for the recognition of the designated reference numerals. In what follows:

the minimum static torque corresponds to the engine torque obtained by setting in advance the minimum ignition on a stabilized point which makes it possible never to have any misfire.

- The dynamic minimum torque corresponds to the engine torque obtained by setting a still lower ignition advance but which is acceptable for a limited time determined, for example the time to spend a few PMH). It is an operating point on which one can only stay a few moments, because misfires of combustion can appear more frequently.

In the remainder of this document The ignition advance is defined by the crank angle of rotation which separates the instant of ignition from the TDC (top dead center) of the engine.

Ignition at TDC means zero ignition advance. An ignition point shift after the TDC is a negative ignition timing. For example an advance of -10 DV (Crankshaft Degree) means a 10 DV ignition after the PMH.

Referring to Figures 1 and 2 which show the evolution of the engine torque and different types of injection as a function of time, the present invention relates to a method for managing a thermal engine torque in a phase of 4a fuel injection recovery after an injection cutoff 5b in the engine.

An injection recovery event curve 4 shows a slot forming a beginning beginning on the left and ending on the right being limited by dotted lines, this slot indicating the resumption of injection 4a. The injection cut-off 5b is shown on an injection recovery event curve 5 by a slot 5b ending just before the injection resumption 4a shown in the injection recovery event curve 4.

According to the present invention, it is predetermined a minimum static torque 1 to serve as a minimum torque 2 for the engine and provide stability of a combustion in the engine. This minimum static torque 1 is implemented by a motor control unit except when a resumption of injection phase 4a takes place.

Indeed, during a resumption of injection phase 4a following the injection cutoff 5b, it is proceeded to replace, as minimum torque 2, the minimum static torque 1 by a minimum dynamic torque 3 less than the torque. minimal static 1. An estimated minimum torque or minimum torque 2 is then controlled to be equal to the dynamic minimum torque 3.

This is done for a duration 6 corresponding to a predetermined number of effective passes of High Dead Points in one or more cylinders of the engine. Then, the minimum estimated torque or minimum torque 2 is controlled to present a rise to the minimum static torque 1 when said predetermined number is exceeded, that is to say when the holding time 6 corresponding to a predetermined number of effective passages Dead Points are exceeded. It is the fact of staying at the point of operation at the minimum dynamic torque during a short period of time which allows a progression of the torque with a felt effect less than if the pair 2 followed the minimal static torque 1 as soon as the injection was resumed. . If this time is not too long, there is no impact for the driver in terms of pleasure, feeling. If we stay too long on the dynamic minimum advance, the driver will feel the misfires and we lose the advantage of the invention. In order not to go beyond a time for which the driver would feel the effects of misfires, this predetermined number of effective High Dead Points passages is preferably between 1 and 20 PMH.

As shown in the figures, the rise of the engine torque, that is to say the minimum estimated torque or minimum torque 2, to the minimum static torque 1 is gradually and continuously, for example according to a slope 7 linear. At the end of this increasing linear slope 7, the minimum estimated torque or minimum torque 2 becomes equal to the minimum static torque 1.

The predetermined number of effective passes of High Dead Points and consequently the holding time 6 of the minimum estimated torque or minimum torque 2 being equal to the dynamic minimum torque 3 can be calibrated. A non-limiting example will be given later.

The calibration of said predetermined number of effective passes of High Dead Points and therefore of the holding time 6 can be performed according to one or more of the following parameters taken individually or in combination: a gear ratio of a box of associated with the engine, engine speed and filling of the engine (s) cylinders of the engine. Such a filling consists of an instantaneous air ratio allowed on an air admitted at normal atmospheric temperature and pressure in the cylinder or cylinders (T = 273K and P = 1013hPa).

The minimum dynamic torque 3 can be calculated from the engine speed and the filling of the cylinder or cylinders of the engine. This dynamic minimum torque 3 can be provided to torque control and control means forming part of the engine control unit to define the moment when the fuel injection must take place.

The replacement of the minimum static torque 1 by a minimum dynamic torque 3 can be done during the injection cutoff 5b, so before the injection 4a resumption takes place. This can be done after a calibrated time delay 5a starting from a start of the injection cutoff 5b. This makes it possible to anticipate the recovery of torque and to avoid jumps in torque during this recovery.

For example, without this being limiting, for an engine speed of 1500 revolutions per minute, the dynamic engine torque 3 can be calculated from a cylinder filling of 0.15 and a minimum dynamic advance of -26 ° taken in crankshaft angle with as reference the passage through a Top Dead Center which gives the point 0 °. The stabilized minimum advance can be -21 °.

This can cause instability of the combustion that can last for the duration of holding 6 corresponding to a predetermined number of effective passes of High Dead Points. This instability is tolerable, since it occurs over a short hold period 6 with, for example, a predetermined number of effective High Dead Point passes equal to 4.

The minimum static torque 1 can be predetermined by a calibration on a motor bench at a constant engine speed and engine load.

The invention also relates to a power unit of a motor vehicle, the group comprising a heat engine, a device for injecting a fuel into the engine and an engine control unit having control and control means on the one hand, the injection device and, on the other hand, the engine torque.

During a resumption of injection phase 4a following an injection cutoff 5b detected by the control means of the injection device, the engine torque control means manages the torque in accordance with such a method.

When the torque demand is greater than the minimum engine torque, means for controlling and controlling the injection of the engine control unit. request a discount of the fuel injection. In the case of life of a torque recovery, the engine control unit makes the decision to put the fuel injection on the information on the dynamic minimum torque 3.

The invention finally relates to a motor vehicle equipped with such a powertrain.

The invention is not limited to the described and illustrated embodiments which have been given as examples.

Claims

1. A method for managing a thermal engine torque in a fuel injection recovery phase (4a) after an injection cutoff (5b) in the engine, characterized in that a minimum torque is predetermined statically (1) to serve as the minimum torque (2) for the engine and to ensure a stability of a combustion in the engine and that, during a phase of resumption of injection (4a) following the break of injection (5b), the minimum static torque (1) is replaced by a minimum dynamic torque (3) lower than the minimum static torque (1) for a corresponding holding time (6), as minimum torque (2). a predetermined number of effective high dead point passes in one or more cylinders of the heat engine and a rise in the minimum torque (2) to the minimum static torque (1) when said predetermined number is exceeded.

2. Method according to claim 1, wherein the rise of the minimum torque (2) to the minimum static torque (1) is performed according to a slope (7) linear.

3. Method according to claim 1 or 2, wherein said predetermined number of effective passes of High Dead Points is calibrated, preferably between 1 and 20 PMH.

4. The method of claim 3, wherein the calibration of said predetermined number of effective passes High Dead Points is effected according to one or more parameters taken individually or in combination: a gear ratio of an associated gearbox to the engine, an engine speed and a filling of the engine cylinder or cylinders consisting of an instantaneous air ratio admitted to an air admitted at normal atmospheric temperature and pressure in the cylinder or cylinders.

5. The method of claim 4, wherein the dynamic minimum torque (3) is calculated from a minimum calibratable advance and the filling of the cylinder or cylinders of the engine.

6. Method according to any one of the preceding claims, wherein the replacement of the minimum static torque (1) by a minimum dynamic torque (3) is done during the injection cut-off (5b) after a calibrated delay time (5a) starting from a start of the injection cut-off (5b).

A method as claimed in any one of the preceding claims, wherein the static minimum torque (1) is predetermined by calibration on a test bench at constant engine speed and engine load.

Power train of a motor vehicle, the group comprising a heat engine, a device for injecting a fuel into the engine and an engine control unit having means for controlling and controlling, on the one hand, the device for injection and, secondly, the minimum torque (2), characterized in that, during a resumption of injection phase (4a) following an injection cutoff (5b) detected by the control means of the injection device, the engine torque control means manages the torque according to a method according to any one of the preceding claims.

Motor vehicle, characterized in that it comprises a powertrain according to the preceding claim.