FR3043046A1 - METHOD OF CONTROLLING THE TORQUE OF AN ENGINE IN A MOTOR VEHICLE - Google Patents

Abstract

In this method of controlling the torque supplied by an engine of a motor vehicle, a step (100) consists in determining a compensation torque (CcompMot) of the inertia of this motor by multiplying the angular acceleration (dW / dt) of the engine by a predetermined parameter.

Description

METHOD OF CONTROLLING THE TORQUE OF AN ENGINE IN A MOTOR VEHICLE

The present invention relates to a method for controlling the torque of an engine in a motor vehicle. The invention belongs to the field of motor torque control methods in motor vehicles.

A motor vehicle generally comprises a power train comprising a motor coupled to a gearbox.

The gearbox transmits the torque provided by the engine to the vehicle wheels in different gear ratios. The torque that can transmit the gearbox is limited by a predefined torque threshold, depending on the gear ratio, depending on the mechanical dimensioning of the gearbox.

The torque threshold of the gearbox must not be exceeded, as this may damage the gearbox. It is therefore necessary to limit the torque that is provided by the traction motor according to this threshold.

For example, document EP-A2-1,865,175 discloses a method for controlling the torque of the engine of a vehicle, in which the torque of the engine is controlled as a function of a torque threshold transmissible by the gearbox. of the vehicle.

Such a method has the disadvantage that during dynamic phases, such as angular acceleration phases of the engine, a portion of the engine torque serves to accelerate inertia of the drive train. This part of the engine torque, called inertial torque and not transmitted by the gearbox, is not taken into account to control the engine torque, which reduces the dynamic performance of the vehicle. The invention aims to overcome the disadvantages of the prior art by taking into account the inertial torque to control the engine torque.

For this purpose, the present invention proposes a method for controlling the torque supplied by an engine of a motor vehicle, which is remarkable in that it comprises a step of determining a compensation torque for the inertia of this motor by multiplying the angular acceleration of the motor by a predetermined parameter.

Thus, the invention makes it possible to increase the value of the torque of the engine during the angular acceleration phases of the latter and thus to transmit a greater torque to the gearbox.

According to a particular characteristic, this predetermined parameter is proportional to the inertia of the motor.

According to a particular embodiment, the method further comprises a step of determining the angular acceleration of the engine from a measurement of the acceleration of the vehicle.

According to another particular embodiment, the method further comprises a step of determining this angular acceleration from an estimate of the acceleration of the vehicle.

According to a particular characteristic, the vehicle further comprises a gearbox and the method further comprises a step of determining the maximum torque that can be provided by the engine by adding a torque threshold transmissible by this gearbox and the torque compensation.

According to a particular characteristic, the transmissible torque threshold of the gearbox depends on the gear ratio of this gearbox.

According to one particular characteristic, the method furthermore comprises a step of determining a final target torque of the motor taking the minimum between the maximum torque that can be supplied by the motor and the sum of an initial reference torque of the motor and compensation torque. The invention also relates to a motor vehicle comprising a motor and a gearbox and further comprising control means adapted to implement such a torque control method provided by the engine.

According to a particular characteristic, the gearbox is an automatic gearbox. The invention will be better understood and other aspects and advantages will appear more clearly on reading the following description of a particular embodiment, given by way of non-limiting example and with reference to the accompanying drawings. in which: - Figure 1 schematically shows a traction chain of a motor vehicle according to the invention, in a particular embodiment; FIG. 2 is a logic diagram illustrating steps of a control method according to the invention; and FIG. 3 is a graph illustrating the temporal evolution of torque and speed values of the power train of FIG. 1, during the implementation of the control method of FIG. 2.

In the following, we consider, by way of non-limiting example, a motor vehicle comprising a traction chain 1 as shown in Figure 1.

Figure 1 shows the traction chain 1 comprising a motor 2 associated with a gearbox 4 for driving in rotation a wheel train 6 of the vehicle.

The engine 2 is for example a heat engine, electric or hydraulic. The engine 2 may also consist of an assembly of several engines of different types. The angular velocity of the motor shaft 2 is denoted W and is expressed for example in radians per second (rad / s).

A management computer 10 exchanges information with the engine 2 to control its operation.

Note that the gearbox 4 can be automated or not. Therefore, it may be an automatic transmission, a manual gearbox controlled or not, or a dual-clutch gearbox (or DCT), or a continuously variable transmission ( or CVT).

The gearbox 4 can transmit at most a transmissible torque threshold CseuilBV. If this transmissible torque threshold is exceeded, the gearbox 4 may be damaged.

FIG. 2 is a logic diagram showing steps of a control method according to the invention.

Such a method can be implemented by the engine management computer 10, but this is not mandatory. As a variant, this method could in fact be implemented by another piece of equipment, directly or indirectly, coupled to this computer 10. This method can be implemented by software modules (or computer software or "software"), or by a combination of electronic circuits (or "hardware") and software modules.

According to the invention, a first step 100 consists in determining a compensation torque CcompMot. The compensation torque CcompMot corresponds to a torque value making it possible to compensate the effect of the inertia torque of the motor 2 during the acceleration phases of the latter.

The inertial torque of the motor 2 is equal to the product of its inertia J by its angular acceleration. The angular acceleration of the motor 2 is noted dW / dt.

The compensation torque is determined by performing the product of a predetermined parameter a and the angular acceleration dW / dt of the motor 2:

CcompMot = a. dW / dt

The parameter a is proportional to the inertia J of the motor 2:

a = sf. J

The coefficient sf is between 0 and 1 and makes it possible to adjust the compensation of the inertial torque of the motor 2.

The first step 100 may include an activation counter for deactivating the first step 100 after a preset number of activations N of this step. The deactivation of the first step 100 after a certain number of activations makes it possible in particular to protect the gearbox from strong repeated requests.

The value of the coefficient sf may, for example, depend on: the engaged ratio of the gearbox (for example the coefficient sf is zero if the engaged ratio is different from the ratios 1, 2 or 3); - the speed of the vehicle (for example the coefficient sf is zero if this speed is greater than 100 km / h); - The position of the vehicle gear lever (for example, in the case of an automatic gearbox, the sf coefficient is zero if the lever is in the position of "Neutral" N or "Parking" P); information provided by an ESP Electronic Stability Program (Electronic Stability Program) calculator; for example the coefficient sf is zero in case of slippage of a wheel of the vehicle. The angular acceleration dW / dt of the engine 2 is for example obtained by a direct measurement by means of a vehicle acceleration sensor. Conventionally, the angular acceleration dW / dt can indeed be determined by effecting the product of the acceleration Acc of the vehicle by a factor k depending on the diameter of the wheels of the vehicle and the reduction of the ratio engaged at the level of the box. speeds: dW / dt = k. Acc

Alternatively, the angular acceleration dW / dt can be provided by an estimate of acc acc acceleration of the vehicle. The acceleration acc estimate of the vehicle can for example be made by subtracting the resistant forces Fresist applied to the vehicle to the traction force traction, then dividing the result of this subtraction by the mass M of the vehicle:

Acc = (Ftraction - Fresist) / M

The tensile force traction is for example the set pulling force to be applied to the wheels of the vehicle.

The resistant forces can for example be estimated by the following equation:

Fresist = (Mg, sin (atan (slope)) + FO + F1, V + F2, V2

With: - g the gravitational constant (equal to 9.81 m / s2); - slope: the slope of the road on which the vehicle is traveling (estimated or measured by a vehicle sensor) expressed in%; - F1, F1 and F2 predefined vehicle coefficients, respectively corresponding to dry friction, viscous and aerodynamic; - V the speed of the vehicle, expressed in m / s.

A second step 200 of the method consists in determining the maximum torque CmaxMot that the motor 2 can apply as a function of the transmittable torque threshold CseuilBV. The maximum torque CmaxMot is determined by adding the transmittable torque threshold CseuilBV of the gearbox 4 and the compensation torque CcompMot determined in the first step 100:

CmaxMot = CseuilBV + CcompMot

The transmissible torque threshold may depend on the gear engaged. For example, the transmittable torque CseuilBV is between 200 and 300 Newton-meter (N.m) and is generally lower for the lower ratios of the gearbox.

A third step 300 of the method consists in determining a final target torque CfinalMot of the motor 2. The final setpoint torque

CfinalMot is determined by taking the minimum between the maximum torque CmaxMot and the sum of an initial motor setpoint torque CinitMot and the compensation torque CcompMot:

CfinalMot = Min (CmaxMot; CinitMot + CcompMot)

The calculation of the initial setpoint torque CinitMot, known per se, is for example made from the torque setpoint to be applied to the wheel train 6 of the vehicle.

FIG. 3 graphically illustrates an example of time evolution of torque values and engine speed 2 during the implementation of the method according to the invention.

The bottom curve illustrates the temporal evolution of the angular velocity W of the motor 2 between times t0 and t8.

The upper curves illustrate the time evolution of the compensation torque CcompMot, the maximum torque CmaxMot and the setpoint torque CinitMot and CfinalMot of the motor 2 between the times t0 and t8.

It is considered to facilitate understanding that the ratio of the gearbox 4 is not changed and the transmittable torque threshold CseuilBV is constant between times t0 and t8.

Between times t0 and t1, the angular velocity W of the motor 2 is constant. The angular acceleration dW / dt is therefore zero and the compensation torque CcompMot is also equal to 0.

The maximum torque CmaxMot is therefore equal to the torque threshold CseuilBV transmitted by the gearbox 4.

The initial setpoint torque CinitMot is also constant and is less than the maximum torque CmaxMot. The final setpoint torque CfinalMot is therefore equal to the CinitMot pair.

Between instants t1 and t2, the initial setpoint torque CinitMot remains constant, but the angular velocity W begins to increase with an angular velocity dW / dt which increases linearly. The compensation torque CcompMot therefore also increases linearly.

The maximum torque CmaxMot and the final target torque CfinalMot therefore also increase linearly between the instants t1 and t2.

Between instants t2 and t3, the initial setpoint torque CinitMot remains constant and the angular velocity W increases linearly, the angular velocity dW / dt is then constant (not zero). The compensation torque CcompMot is therefore also constant (not zero).

The maximum torque CmaxMot and the final target torque CfinalMot are therefore also constant between times t2 and t3.

Between instants t3 and t5, the angular velocity W continues to increase linearly and the initial target torque CinitMot also increases linearly.

The angular velocity dW / dt, the compensation torque CcompMot and the maximum torque CmaxMot therefore remain constant, but the final setpoint torque CfinalMot increases until reaching the value of the maximum torque CmaxMot at time t4.

Between times t4 and t5, the sum of the initial torque CinitMot and the compensation torque CcompMot becomes greater than the maximum torque CmaxMot, the final target torque CfinalMot therefore ceases to increase and is equal to the maximum torque CmaxMot.

Between instants t5 and t6, the angular velocity W continues to increase linearly with the same angular acceleration as between instants t2 and t5, but the initial setpoint torque CinitMot remains constant.

The angular velocity dW / dt, the compensation torque CcompMot and the maximum torque CmaxMot and the final target torque CfinalMot therefore remain constant.

Between instants t6 and t7, the angular velocity W increases with an angular acceleration dW / dt which decreases linearly until time t7 when it becomes zero. The initial setpoint torque CinitMot remains constant.

The compensation torque CcompMot and the maximum torque CmaxMot therefore decrease linearly between the instants t6 and t7, as well as the final target torque CfinalMot which remains equal to the maximum torque CmaxMot (the sum of the initial torque CinitMot and the compensation torque CcompMot is greater than the maximum torque CmaxMot).

Between instants t7 and t8, the angular velocity W of the motor 2 is constant. The angular acceleration dW / dt is therefore zero and the compensation torque CcompMot is also equal to 0. The maximum torque CmaxMot is therefore equal to the torque threshold CseuilBV transmitted by the gearbox 4.

The initial setpoint torque CinitMot is also constant, but is greater than the maximum torque CmaxMot. The final setpoint torque CfinalMot is therefore equal to the maximum torque CmaxMot.

Thus, the implementation of such a control method increases the value of the engine torque during the phases of angular acceleration of the latter and therefore to transmit a larger torque to the gearbox during these phases.

Claims (9)

1. A method of controlling the torque provided by a motor (2) of a motor vehicle, characterized in that it comprises a step (100) of determining a compensation torque (CcompMot) of the inertia of said motor by multiplying the angular acceleration (dW / dt) of the motor (2) by a predetermined parameter. 2. Control method according to claim 1, characterized in that said parameter is proportional to the inertia of the motor (2). 3. A control method according to claim 1 or 2, characterized in that it further comprises a step of determining said angular acceleration (dW / dt) from a measurement of the acceleration of the vehicle. 4. Control method according to claim 1 or 2, characterized in that it further comprises a step of determining said angular acceleration (dW / dt) from an estimate of the acceleration of the vehicle. 5. Control method according to any one of the preceding claims, said vehicle further comprising a gearbox (4), characterized in that it further comprises a step (200) of determining the maximum torque (CmaxMot) which can be provided by said motor (2) by adding a transmissible torque threshold (CseuilBV) by said gearbox (4) and said compensation torque (CcompMot). 6. Control method according to claim 5, characterized in that said transmissible torque threshold (CseuilBV) depends on the gear ratio of said gearbox (4). 7. Control method according to one of claims 5 or 6, characterized in that it further comprises a step (300) of determining a final target torque (CfinalMot) of said motor (2) taking the minimum between said maximum torque (CmaxMot) and the sum of an initial target torque (CinitMot) of said motor (2) and said compensation torque (CcompMot). 8. Motor vehicle comprising a motor (2) and a gearbox (4), characterized in that it further comprises means (10) for controlling adapted to implement steps of a torque control method provided by said motor (2) according to any one of the preceding claims. 9. Motor vehicle according to claim 8, characterized in that said gearbox (4) is an automatic gearbox.