FR2950302A1 - METHOD FOR MANAGING THE COUPLING OF THE HEAT ENGINE ON A HYBRID MOTOR VEHICLE - Google Patents

Abstract

A method of managing the coupling of the heat engine (2) on a hybrid motor vehicle (1) comprising a heat engine, an automatic coupling means (6) for this heat engine to driving wheels (8) of the vehicle, and at least one electric vehicle traction machine (20) connected to electric energy accumulators (26), this management method automatically producing, when the accelerator pedal is released, and for low driving speeds, uncoupling of the heat engine (2) when the electric accumulators (26) are not saturated, and a coupling when these accumulators are saturated, characterized in that the electric accumulators (26) being saturated, for small close variations (42) of the accelerator pedal, close to a demand of zero torque to the wheels, the coupling of the engine (2) is maintained.

Description

METHOD FOR MANAGING THE COUPLING OF THE HEAT ENGINE ON A HYBRID MOTOR VEHICLE

The present invention relates to a method of managing the coupling of the heat engine on a hybrid motor vehicle comprising an electric motor, and a vehicle implementing such a method. The parallel hybrid type vehicles using electrical energy, generally have two independent engines, a heat engine driving the drive wheels of the vehicle by a mechanical transmission, and an electric machine also connected to driving wheels, which is powered by accumulators of electrical energy. The mechanical transmission of the heat engine may comprise an automatic control for uncoupling the motor from the driving wheels, for using only the electric machine for pulling the vehicle, or for recovering the kinetic energy of the vehicle by generating an electric current which recharges the vehicles. Accumulators. This automatic control mechanical transmission can be in particular a robotic manual gearbox, a double clutch gearbox, an automatic transmission planetary gear, or a continuously variable transmission. The heat engine may include a controlled start system, connected to a supervision computer. This supervisory computer controls the main traction components to manage the stopping and restarting of the engine as well as its coupling to the driving wheels, in order to reduce the fuel consumption and the emissions of polluting gases, and to optimize driving pleasure. . Especially when the driver releases the accelerator pedal to slow down the vehicle, or during a light braking with the brake pedal, the engine is disconnected from the driving wheels so that it does not brake the vehicle. The electric machine then performs only the braking of the vehicle, which optimizes the recovery of the kinetic energy of the vehicle. When an extended accelerator pedal release, for example in the mountains during a long descent, the electric accumulators can become fully charged, and the electric machine must no longer produce electricity that can not be stored. To ensure driving comfort, as well as safety by avoiding overheating the vehicle's brakes by friction, the engine that delivers an engine brake is then coupled again.

A problem that arises is that one can then have for small variations of the accelerator pedal close to its relaxed position, corresponding to a very low wheel torque demand in absolute value, a succession of couplings and uncoupling which is uncomfortable.

A known system presented in particular in document FR-A1-2722738, comprises an electric machine connected to the driving wheels of the vehicle. When the electric accumulators are saturated, the electric current produced during the slowdowns of the vehicle, is transformed by an inverter to power an electric motor which in turn drives the engine. In this way, a permanent braking capability is maintained by dissipating the kinetic energy of the vehicle by driving the heat engine, the electrical connection between the wheels and this engine making it possible to manage driving pleasure. However, this installation is complex, cumbersome and expensive. The present invention is intended to avoid these disadvantages of the prior art, and provide a simple and effective solution for management of the engine coupling during the deceleration phases, which ensures driving pleasure.

It proposes for this purpose a method of managing the coupling of the heat engine on a hybrid motor vehicle comprising a heat engine, a means of automatic coupling of this engine to the driving wheels of the vehicle, and at least one electric machine of traction of the vehicle connected to accumulators of electrical energy, this management method realizing automatically in case of release of the accelerator pedal and for low speeds of rolling, a disengagement of the engine when the electric accumulators are not saturated, and a coupling when these accumulators are saturated, characterized in that the electric accumulators being saturated, for small close variations of the accelerator pedal, close to a demand of zero torque to the wheels, the coupling of the engine is maintained . An advantage of this management method is that while maintaining the coupling of the engine during small close changes of the accelerator pedal, avoid a succession of close couplings and uncoupling that would be unpleasant. The heat engine drive management method according to the invention may further comprise one or more of the following features, which may be combined with each other. Advantageously, the small close-up variations of the accelerator pedal are substantially between 0 and a small part which can be about 15% of the maximum value of depression of this pedal. Advantageously, the management method waits for the driver's demand to stabilize without small close-up variations for a certain time, to determine whether the heat engine can be uncoupled. Advantageously, the low running speeds for which the engine is coupled or uncoupled when the accelerator pedal is released, are less than a speed of about 60km / h.

Advantageously, the management method requires an independent starting system, a restart of the engine before performing the coupling of the engine. The subject of the invention is also a hybrid vehicle comprising a heat engine, means for automatically coupling this heat engine to the driving wheels of the vehicle, at least one electric vehicle traction machine connected to accumulators of electrical energy, and a method of managing the coupling of this engine to the drive wheels, said management method further comprising any of the preceding features. The automatic coupling means of the heat engine may comprise a clutch. Advantageously, between the clutch and the drive wheels is a transmission automatically achieving changes in the gear ratio. According to a particular arrangement of the hybrid vehicle, the heat engine drives the front wheels of this vehicle, and the electric traction machine drives the rear wheels. The invention will be better understood and other features and advantages will appear more clearly on reading the following description given by way of example, with reference to the appended drawings in which: FIG. 1 is a diagram of FIG. a parallel hybrid vehicle; FIG. 2 is a graph showing, as a function of the speed of the vehicle and of the torque at the drive wheels, a method of managing the coupling of the heat engine according to the prior art; and FIG. 3 is a graph showing, as a function of the speed of the vehicle and of the torque at the driving wheels, a method of managing the coupling of the heat engine according to the invention. Figure 1 schematically shows a hybrid vehicle 1 30 comprising a heat engine 2 which can drive the front wheels 8 of the vehicle by a clutch 6, then a transmission 4 automatically achieving changes in the gear ratio. The engine 2 is started by an independent starting system, comprising in this example an electric starting machine 10 connected to the engine by a transmission belt 12. Advantageously, this starting system has a function of the "Stop and Start" type, which stops the engine 2 when the vehicle 1 immobile for a short time, and automatically restarts when the driver presses the accelerator pedal.

An electric traction machine 20 is connected to the rear axle comprising the rear wheels 24, by a mechanical transmission 22. This electric machine 20 comprises a connection to electric accumulators 26, to deliver a traction torque using the electrical energy stored in these accumulators, or on the contrary brake the vehicle 1 by recharging the accumulators. A supervision computer, not shown, is connected to close-up control computers of the main components such as the heat engine 2, the transmission 4 with its clutch 6, and the electric machine 20, depending on the driver's request and the driving conditions. rolling, send orders to these close computers that realize the various configurations of motorization of the vehicle. In particular, the supervision computer decides the thermal or electrical traction mode, to optimize the consumption of the vehicle and the driving comfort.

It is thus possible to obtain a rolling only in electric mode with a traction by the electric machine 20, or a braking energy recovery, the heat engine 2 being uncoupled from the front driving wheels 8. In this case, when the supervision computer decides to return to traction or braking by the engine 2, the independent starting system 10 restarts the engine to then be coupled to the drive wheels 8 by limiting jolts.

FIG. 2 shows in a graph showing the speed V of the vehicle on the abscissa axis, and the torque C delivered to the drive wheels on the ordinate axis, a brake demand curve of the vehicle 30 when the driver releases the pedal. accelerator, and a maximum braking torque curve 32 that the electric machine 20 can provide when the electric accumulators 26 are not saturated. Below the speed V1 of the vehicle which can correspond to about 60 km / h, the necessary traction power is low enough so that the vehicle can roll only in electric traction. In this case the clutch 6 of the transmission 4 is open, and the electric machine 20 alone ensures the traction of the vehicle 1. In this speed zone during a release of the accelerator pedal, the electric accumulators 26 being not saturated, the braking torque 32 that can ensure the electric machine 20 is larger in absolute value than the braking demand torque 30. In this case, the braking is provided without problem only by the electric machine 20, which recharges The electric accumulators 26. When the charge of the electric accumulators approaches saturation, these accumulators can receive only a reduced electrical power. The braking torque 32 that can be delivered by the electric machine 20 is reduced in absolute value, the maximum braking torque curve rises along the arrow 36, to give a new braking torque curve 34. When the braking torque curve decreased 34 goes up above the braking demand curve 30, as shown in the graph between the speeds V2 and V1, the electric machine 20 delivers insufficient braking torque to meet the driver's demand. In this case, the starting system 10 is operated to restart the engine 2, and automatically couple it by the clutch 6 to the drive wheels 8, to add a braking torque from the engine.

This ensures the safety of the vehicle 1, the engine 2 can deliver for long periods of the necessary braking torque. If the driver positively presses on the accelerator pedal, for example for values greater than 15% of the maximum depression of this pedal, the requested traction torque is high enough to require the systematic coupling of the engine 2, which is performed automatically. A problem that arises is that when the driver slightly presses on the accelerator pedal for a torque demand to the wheels close to a zero value, for example with values between 1 and 15% of the maximum depression of this pedal, the braking torque or the driving torque required by the driver is sufficiently low to allow a stop of the engine 2.

It is thus possible to obtain, during frequent variations of the accelerator pedal in this zone, for example when driving in a traffic jam, successive and close couplings and uncoupling of the engine 2 which cause noise and vibrations, as well as accelerations. longitudinal dimensions of the vehicle. This situation can be uncomfortable. FIG. 3 is a graph comprising the braking demand curve of the vehicle 30 when the driver releases the accelerator pedal, and a minimum positive torque curve C corresponding to the torque from which the engine 2 is systematically started. for a depression of the upper accelerator pedal in this example to 15%. The minimum positive torque curve C 40 stops at the speed V 1, which is advantageously around 60 km / h, from which the heat engine 2 is systematically coupled. For this FIG. 3, the electric accumulators 26 are saturated and the the maximum braking torque curve 34 that can be delivered by the electric machine 20 passes from the speed V3 above the braking demand curve of the vehicle 30 with the accelerator pedal released. It is therefore necessary between the speed V3 and the speed V1, the driver having released the accelerator pedal, coupling the heat engine 2 to ensure the requested braking. In the case where the driver slightly presses on the accelerator pedal to achieve a value greater than 15%, and then releases the pedal, the torque demand to the driver's wheels becomes slightly positive then negative as shown by the curve 42, in oscillating around a couple with no wheels. The torque demand to the wheels 42 passes through two transition zones 44 between the curves 34 and 40, where this positive or negative torque demand C is sufficiently low in absolute value to be able to uncouple the heat engine 2 from the front wheels 8. The method of management of the coupling of the heat engine 2 according to the invention, maintains in the transition zones 44 comprising small close torque demand variations, the coupling of this heat engine to avoid frequent variations in the state of the transmission, which could cause jolts.

Advantageously, the management method then waits for the driver's demand to stabilize for a short time in the transition zone 44, for example several seconds, to uncouple the heat engine 2. Otherwise, the management method keeps the engine thermal 2 coupled.

It is thus possible in a simple and economical manner, with only modifications of the software of the management method, to improve the acoustic and vibrational amenity of the vehicle when the electric accumulators are saturated. The safety of the vehicle is ensured by providing a comfortable and permanent braking torque to the wheels, which allows descending long slopes. In addition, the dynamic response of the vehicle can be improved. If the driver makes a strong demand for torque, for example by pressing hard the accelerator pedal, the engine can respond faster to this request. Advantageously, according to the particular configuration presented in this example of a hybrid vehicle, the heat engine drives the front wheels of the vehicle, which makes it possible to keep a standard powertrain generally used for vehicles with front-wheel-drive wheels, and the electric machine drives the rear wheels. .

Claims (9)

CLAIMS1 - A method for managing the coupling of the heat engine (2) on a hybrid motor vehicle (1) comprising a heat engine, an automatic coupling means (6) of this engine to the driving wheels (8) of the vehicle , and at least one electric traction machine (20) of the vehicle connected to electric energy accumulators (26), this management method realizing automatically in case of release of the accelerator pedal and for low speeds of rolling, a disengagement of the heat engine (2) when the electric accumulators (26) are not saturated, and a coupling when these accumulators are saturated, characterized in that the electric accumulators (26) being saturated, for small close variations (42) of the accelerator pedal, close to a demand of zero torque to the wheels, the coupling of the engine (2) is maintained. 2 - Management method according to claim 1, characterized in that the small close-up variations (42) of the accelerator pedal, are substantially between 0 and a small share that can be about 15% of the maximum value d depression of this pedal. 3 - A management method according to claim 1 or 2, characterized in that it waits for the driver demand stabilizes without small close changes for a time, to determine whether the engine (2) can be uncoupled. 4 - A management method according to any one of the preceding claims, characterized in that the low running speeds for which is made a coupling or uncoupling of the engine (2) when the accelerator pedal is released, are less than a speed (V1) of about 60km / h. 5 - Management method according to any one of the preceding claims, characterized in that it requires an independent starter system (10) a restart of the engine (2) before performing the coupling of the engine. 6 - Hybrid vehicle comprising a heat engine (2), an automatic coupling means (6) of this engine to the driving wheels (8) of the vehicle, at least one electric machine (20) of traction of the vehicle connected to electric energy accumulators (26), and a method of managing the coupling of this heat engine (2) to the driving wheels (8), characterized in that this management method is carried out according to any one of the preceding claims . 7 - hybrid vehicle according to claim 6, characterized in that the automatic coupling means comprises a clutch (6). 8 - hybrid vehicle according to claim 7, characterized in that between the clutch (6) and the driving wheels (8) is a transmission (4) automatically achieving changes in the gear ratio. 9 - hybrid vehicle according to claim 8, characterized in that the engine (2) drives the front wheels (8) of the vehicle, and the electric traction machine (20) drives the rear wheels (24).