WO2000061401A1

WO2000061401A1 - Method and device controlling speed reduction ratio in a gearbox associated with an electric engine powering a hybrid motor vehicle

Info

Publication number: WO2000061401A1
Application number: PCT/FR1999/000826
Authority: WO
Inventors: Eric Chauvelier; Stéphane HEMEDINGER
Original assignee: Renault
Priority date: 1998-04-07
Filing date: 1999-04-09
Publication date: 2000-10-19
Also published as: FR2776969B1; FR2776969A1

Abstract

The invention concerns a method which consists in controlling a temporary reduction of the torque delivered to the drive wheels (7) of a motor vehicle, with respect to the torque requested by the vehicle driver, such that the driver spontaneously engages a higher speed reduction ratio (R), in the event it is detected that a predetermined speed threshold has been exceeded by the engine (1) and the ratio (R) engaged when such an occurrence is detected is different from the gearbox highest speed reduction ratio. The invention is applicable to a motor vehicle of the parallel hybrid type.

Description

METHOD AND DEVICE FOR CONTROLLING A CHANGE IN REDUCTION RATIO IN A GEARBOX DRIVING A HYBRID VEHICLE

The present invention relates to a method and a device for controlling a change in reduction ratio in a manually controlled gearbox associated with an electric motor propelling a motor vehicle. More particularly, the invention relates to such a proceαe and to such a device suitable for a vehicle of the so-called "parallel hybrid" type fitted with an electric motor and an internal combustion engine controlled so as to ensure, separately or in combination, the propulsion of the vehicle.

When the propulsion energy of a motor vehicle is supplied, in whole or in part, by an electric motor such as a three-phase asynchronous motor for example, this motor should be prevented from rotating at a speed greater than a predetermined nominal speed, that is to say to run in "overspeed".

In the case of a so-called "parallel hybrid" motor vehicle mentioned above, in which an electric motor and an internal combustion engine are connected upstream of a gearbox, such an over-speed of the electric motor can result from overtraining of its output shaft by that of the heat engine, for example.

An overspeed of the electric motor with respect to an optimal speed does not manifest itself, contrary to what happens with a heat engine, by a reinforcement of its sound emission or by a loss of power.

The driver is not alerted by the perception of this reinforcement or this loss, therefore does not modify the reduction ratio of the 30-speed gearbox accordingly, as would be the case if he were operating a vehicle. classic powered by an internal combustion engine.

The driver of a hybrid vehicle, when the latter is powered only by the electric motor, can therefore

35 ignore that it runs at high speed. If then driver's demand in motive power increases, the internal combustion engine may have to start to also supply power to the input shaft of the gearbox, this starting being carried out in poor conditions, the engine thermal being driven, cold, too quickly by the electric motor. The driver is then surprised by a sudden increase in the noise emitted by the vehicle.

To prevent an electric motor of a hybrid vehicle from running in overdrive, we know from German patent application DE-19528629 a control method which ensures a limitation of the speed of this motor when it is used alone to propel the vehicle .

This process consists, when the speed of rotation of the motor passes above a certain threshold, either to reduce the supply current of the motor, or to switch the operation of the engine towards an operation in electric generator or in engine brake. , or to activate the vehicle brakes, automatically or by sending a signal to this effect to the driver.

This process has several drawbacks. On the one hand it causes a limitation of the top speed of the vehicle, when the latter is traveling at high speed, which can harm driving comfort and the safety of vehicle passengers. On the other hand, if the overspeed of the electric motor comes from its drive by the heat engine, it may happen that an action on the electric motor alone is insufficient to bring the speed of this motor below the overspeed threshold.

The object of the present invention is to provide a method, and to produce a device, for controlling a change in reduction ratio in a manually controlled gearbox associated with an electric motor propelling a motor vehicle, suitable for prevent over-revving of the engine, and this without this process and this device being affected by faults in the engine speed control process mentioned above. These objects of the invention are achieved, as well as others which will appear on reading the description which follows, with a method of controlling a change of reduction ratio in a manual gearbox associated with a electric motor propelling a motor vehicle, this process being remarkable in that a temporary reduction in the torque delivered to the driving wheels of the vehicle is compared with the torque requested by the driver of this vehicle, so that the driver spontaneously engages a gear ratio. higher reduction, if it is detected that the engine is about to exceed a predetermined speed and if the gear engaged during this detection is different from the gear reduction of greater value.

As will be seen below, thanks to the present invention, the use of the electric motor at high speed is not limited while alerting, if necessary, the driver to the urgency of a change in the reduction ratio of the gearbox. of speeds.

This gear change ensures improved engine operation which, after the gear change, operates in an area of better efficiency, at the power required before the shift.

For the implementation of this method, the invention provides a device comprising: a) means for measuring the speed of rotation of the electric motor and the torque required by the driver for the propulsion of the vehicle, b) detection means the reduction ratio engaged in the gearbox, and c) means for controlling the torque delivered to the wheels of the vehicle, sensitive to said measurements and to said report to control a reduction in the torque delivered to said wheels compared to the torque requested by the driver of the vehicle, when said means for measuring the speed of rotation of the motor indicates the imminence of exceeding a speed predetermined by that of the electric motor and that said detection means detect a reduction ratio different from the ratio of greatest value of said gearbox.

Other characteristics and advantages of the present invention will appear on reading the description which follows and on examining the appended drawing in which:

FIG. 1 schematically represents part of a motor vehicle of the parallel hybrid type, improved by the present invention, and

- Figure 2 is a graph useful for explaining the operation of the vehicle of Figure 1.

To remove any ambiguity, it should be recalled that the expression "reduction ratio" of a gearbox designates the ratio of the speed of the output shaft to the speed of the input shaft of this gearbox . In a four-speed gearbox, for example, the first, second, third and fourth gear correspond to ratios varying from approximately 1/12 to 1/1. As a result, the reduction ratio increases with the order of the speed.

Figure 1 shows schematically the organization of a motor vehicle of the parallel hybrid type, powered by an electric motor 1 and a heat engine 2. The electric motor can be a three-phase asynchronous motor for example, while the heat engine can be a motor internal combustion. The output shaft 3 of the electric motor 1 is mechanically coupled to the input shaft (or primary shaft) of a gearbox 4 while the output shaft 5 of the internal combustion engine 2 is selectively couplable to this input shaft, by means of a clutch 6. The output shaft (or secondary shaft) of the gearbox 4 is mechanically coupled to at least one wheel 7 of the vehicle, to drive the latter in rotation and thus ensure the propulsion of the vehicle on a rolling surface of the wheel 7.

The three-phase electric motor 1 is conventionally supplied by an inverter or chopper 8, itself supplied with electrical energy by a battery 9.

Still conventionally, the management of the mechanical energy transmitted to the driving wheels of the vehicle, in particular to the wheel 7, is ensured by electronic control means 10, called "supervisor", which control the operation of the motors 1,2 according to a certain number of parameters such as the torque request formulated by the driver of the vehicle measured by depressing α of an accelerator pedal 11, the state of charge V of the battery 9, etc.

According to the control method according to the invention, the supervisor 10 takes into account the speed N of the electric motor 1 and the reduction ratio R engaged in the gearbox 4. The quantities α, V, N, R are delivered to the supervisor 10 by conventional measurement and detection means well known to those skilled in the art.

To control the mechanical energy applied to the wheel 7 by the motors, the supervisor 10 can act on the inverter 8 by a "torque" command, the latter translating this information into a control of the intensity I and / or of the frequency F of the current supplied to the electric motor 1, for example. The supervisor 10 acts on the internal combustion engine 2 via a motorized throttle valve 12. The supervisor also controls clutch 6, to couple or decouple the output shaft of motor 2, possibly with the desired progressivity.

We now refer to the graph in FIG. 2 to explain the strategy developed by the control method according to the invention. This graph illustrates the evolution of a correction coefficient K varying between 0 and 1, as a function of the speed of rotation of the output shaft 3 of the electric motor 1, that is to say of the primary shaft of the gearbox 4. This multiplying coefficient is intended to correct the set value assigned by the supervisor 10 to the torque applied to the primary shaft of the gearbox.

The graph in FIG. 2 relates to an electric motor for which the entry into overspeed takes place at 6,000 rpm, this value being given by way of illustration and not limitation only.

In a wide range of speeds (0-5500 rpm for example) the coefficient K remains at the value 1 and therefore does not influence the torque in question, which we know is linked to the mechanical power P by the relationship :

P = C • ω where ω is the angular speed of the shaft 3.

According to the present invention, the driver is informed of the imminence of an overshoot by the electric motor 1 of its speed limit (6000 rpm), by a temporary controlled reduction of the engine torque applied to the wheel 7, relative to the torque requested by the driver, as it results from depressing α of the accelerator pedal 11. The driver is sensitive to the loss of motive power which results from this reduction and then tends, instinctively, to restore the level of engine power required by changing the reduction ratio of the gearbox to make it evolve towards a higher ratio. This recovery thus takes place without overshoot of the electric motor, in accordance with one of the aims of the present invention.

Thus, for example, the driver feeling a loss of motive power while the reduction ratio engaged in the gearbox 4 is that commonly called "third speed", will instinctively go from this speed to the fourth speed.

Contrary to what happens in a vehicle powered only by an internal combustion engine, the driver of an electric or hybrid vehicle cannot follow the increase in the speed of the electric motor, at a certain reduction ratio of the gearbox , following that of the noise emitted by this engine. An electric motor operating at constant power at high speed, the driver of a vehicle powered by such an engine is not alerted by a loss of power in this speed range. The present invention remedies the absence, in a vehicle powered by an electric motor, of these conventional signals, by an imposed reduction in the torque supplied by the motor, at high speed, reduction perceived by the driver and causing him to have a reflex gear change.

As illustrated by the graph in FIG. 2, the controlled reduction in torque can be obtained, for example, by a linear decrease in the coefficient K, from the value 1, at 5,500 rpm, to the value 0 to 6,000 rpm. Other changes in the value of K can obviously be envisaged, provided that they provide the desired reduction.

The reduction in torque involved can be obtained either by controlling the torque developed by the electric motor 1 alone, or by controlling the torque developed by the internal combustion engine 2 if the latter is coupled to the primary shaft 3 of the gearbox through the clutch 6, or again by a simultaneous control of the torques developed by the two motors, which are added at the level of the shaft 3.

These commands are provided by the supervisor 10, by means of the motorized throttle valve 12 of the internal combustion engine 2 and by means of an appropriate command of the intensity I and / or the frequency F of the electric current delivered by the inverter 8 to the electric motor 1. The supervisor is duly programmed to control the torque applied to the primary shaft, from representative information, in particular:

- of the ratio R engaged in the gearbox 4

- of the torque requested by the driver (depressing α of the pedal 11)

- the speed N of the primary shaft 3.

In the case of a vehicle fitted with a four-speed gearbox, for example, the control strategy is as follows: if the gear engaged in the gearbox corresponds to one of the first, second and third gears and qu 'a positive torque is requested by the driver, the setpoint torque is that requested by the driver, affected by the multiplier coefficient K given by the graph in Figure 2 as a function of the speed N of the electric motor. Thus when approaching the limit speed, the commanded torque will be gradually reduced, according to the invention, to encourage the driver to change speed.

If, on the other hand, the gear engaged in the gearbox corresponds to the fourth gear, the torque commanded by the supervisor and equal to that requested, no correction being applied to the latter. This avoids, in accordance with one of the aims of the invention, reducing the power of the vehicle at high speed, while a incrementing the reduction ratio is not possible anyway.

Of course, the invention is not limited to the embodiment described and shown which has been given only by way of example.

Thus, if the gearshift control method according to the invention has been described above essentially for a vehicle of the parallel hybrid type, it is obviously applicable to a series hybrid vehicle or even to a purely propelled vehicle. electric, for example, so that the driving of this vehicle is close to that of a vehicle conventionally powered by an internal combustion engine.

Claims

1. A method for controlling a change in reduction ratio in a gearbox (4) with manual control associated with an electric motor (1) propelling a motor vehicle, characterized in that a temporary reduction in the torque delivered is controlled to the driving wheels of the vehicle, in relation to the torque requested by the driver of this vehicle, so that the driver spontaneously engages a higher reduction ratio (R), if it is detected that a predetermined speed is exceeded by the engine (1) and if the ratio (R) engaged during this detection is different from the highest reduction ratio of the gearbox.

2. Method according to claim 1, characterized in that said temporary reduction of the torque delivered to the driving wheels of the vehicle is obtained by a torque control of the electric motor (1).

3. Method according to claim 1, suitable for a hybrid type motor vehicle further comprising an internal combustion engine (2) selectively couplable to the output shaft (3) of the electric motor (1), characterized in that said temporary reduction of the torque delivered to the driving wheels (7) is obtained by the torque control of the electric motor (1) and / or of the internal combustion engine (2).

4. Device for implementing the method according to any one of claims 1 to 3, characterized in that it comprises: a) means for measuring the speed of rotation (N) of the electric motor and of the torque requested by the driver for the propulsion of the vehicle, b) means for detecting the reduction ratio (R) engaged in the gearbox (4), and c) means for controlling (10) the torque delivered to the wheels (7 ) of the vehicle, sensitive to said measures and to said audit ratio (R) for controlling a temporary reduction in the torque delivered to said wheels (7) compared to the torque requested by the driver of the vehicle, when said means for measuring the speed (N) of rotation of the engine indicates the impending of a exceeding a predetermined speed by that of the electric motor (1), and that said detection means detect a reduction ratio (R) different from the ratio of greatest value of said gearbox.

5. Device according to claim 4, characterized in that said electric motor (1) is a three-phase asynchronous motor supplied by an inverter (8), and in that said control means (10) act on said inverter (8) to ensure torque control of said motor (1).

6. Device according to any one of claims 4 and 5, suitable for a hybrid type motor vehicle further comprising an internal combustion engine (2) selectively couplable to the output shaft (3) of the electric motor ( 1), characterized in that said control means (10) act on said electric motor (1) and / or on said internal combustion engine (2).

7. Device according to claim 6, characterized in that said control means (10) manage the distribution of the energy delivered by the motors (1, 2) to the wheels (7) of the vehicle.

8. Device according to claim 7, characterized in that said control means (10) act on said internal combustion engine (8) via a motorized throttle body (12).

9. Motor vehicle equipped with a device according to any one of claims 4 to 8.