FR2777232A1 - TRACTION DEVICE FOR HYBRID ELECTRIC VEHICLE - Google Patents

Abstract

It comprises a) a mechanical traction chain comprising a heat engine (1), a transmission system (2) of at least part of the output power of the engine (1) to at least one wheel (3) of the vehicle and a coupling means (4) of said motor (1) to said transmission system (2), b) an electric traction chain comprising an electric energy generator (14) driven by the heat engine (1), a motor electric (9) powered by the generator (14) and mechanically coupled to said transmission system (2) and electrical energy storage means (11) powered by the generator (14). This device further comprises a member (21) for measuring the torque demand of the driver of the vehicle, and means (12) sensitive to this measurement for torque control the motors (1, 9) and the generator (14), so as to establish the requested torque.

Description

The present invention relates to a traction device for

  hybrid electric vehicle and, more particularly, to such a device comprising a) a mechanical traction chain comprising a heat engine, a system for transmitting at least part of the output power of the motor to at least one wheel of the vehicle and means for coupling said motor to said transmission system, and b) an electric traction chain comprising an electric power generator driven by said motor, an electric motor powered by said generator and mechanically coupled to said transmission system and means for storage of electrical energy supplied by said generator. Such a traction device is known from document EP-A-0 648 635, the device described in this document being able to operate selectively according to the mode

  "serial hybrid" or "parallel hybrid" mode.

  It is known that in the series hybrid mode the power necessary for the traction of the vehicle is supplied by the electric motor, the latter being supplied by the alternator and / or the energy storage means (batteries for example), these means being themselves supplied by the generator, an alternator for example,

  which is powered by the heat engine.

  In the parallel hybrid mode, the mechanical energies developed by the two motors can be combined, or used separately, to ensure the

vehicle traction.

  In the device described in the aforementioned document, the heat engine and the electric motor are connected to the transmission of the vehicle via first and second input shafts, respectively, of a planetary gear, the output shaft of said train being connected to the transmission. Control means enable operation of the series hybrid type at low speeds and at low powers and operation of the hybrid type parallel to the speeds

medium and high.

  This device nevertheless has several drawbacks. On the one hand, its structure is complex in the sense that it comprises, in addition to the planetary gear train, a flywheel to impose a direction of rotation on the output shaft of this epicicloidal train, and two brakes for

  ability to block either of the two input shafts.

  On the other hand, the control of this device is also complex. To pass from the "series hybrid" operation to the "parallel hybrid" operation, it is necessary both to apply a brake and to couple the heat engine by acting on a clutch associated with this engine. The braking torque control must be very precise to avoid stalling of the engine or other reactions that negatively affect driving comfort or the level of noise emitted by the engine. The object of the present invention is to provide a traction device for a hybrid electric vehicle

  which does not have the disadvantages mentioned above

  above and which, in particular, is of simple structure, and of simple and flexible control, in particular during transitions between a series hybrid operation and a

  parallel hybrid operation for example.

  These objects of the invention are achieved, as well as

  others which will appear on reading the description

  which follows, with a traction device for a hybrid electric vehicle comprising the mechanical and electric traction chains described in the preamble to

  the present description, this device being remarkable

  in that it comprises, in combination, a member for measuring the torque demand of the vehicle driver, and means sensitive to said measurement for torque control of the heat engine, the electric motor and the generator of electric energy, so as to establish the requested torque. As will be seen below in detail, these control means make it possible to simply switch from one operating mode of the device to another, so as to optimize this operation, in particular from the triple point of view of the motive power supplied, of the energy consumption and reducing air pollution by

the exhaust gas.

  According to one embodiment of the invention, to do this, the device control means also act on the coupling means to selectively activate an operation of the device of the series hybrid type or of the parallel hybrid type. Said coupling means is preferably constituted by a clutch mounted between the output shaft of the engine

  and the input shaft of the transmission system.

  According to the invention also, the transmission system of the device can be a gear

  reducer, a manual or robotic gearbox.

  Other features and advantages of this

  invention will appear on reading the description which

  will follow and upon examination of the appended drawing in which: - Figure 1 is a diagram of a first embodiment of the device according to the invention, and - Figures 2 to 4 schematically illustrate and

  partially variants of the device of FIG. 1.

  Referring to Figure 1 of the accompanying drawing o it appears that the embodiment shown of the device according to the invention comprises a mechanical traction chain comprising a heat engine 1 such as an internal combustion engine for example, and a system transmission 2 of at least part of the output power of the motor 1 to at least one wheel 3

  of a vehicle powered by this device.

  A coupling means 4 provides the connection between the output shaft 5 of the motor 1 and an input shaft 7, or primary shaft, of the transmission system. In the embodiment shown, the means 4 consists

by a controlled clutch.

  The device further comprises an electric traction chain comprising an electric energy generator such as an alternator 8, and an electric motor 9 supplied by said alternator 8 through an inverter or chopper 10. Energy storage means 11 , such as storage batteries, are installed so as to constitute a "buffer" electrical energy reservoir, between the alternator 8 and the inverter 10. In the embodiment shown, the electric motor 9 is mounted on the output shaft 17,

  or secondary shaft, of the transmission system 2.

  According to the present invention, the device comprises means 12 for controlling the operation of the engines 1 and 9, as well as the alternator 8. These means are practically constituted by a digital electronic computer duly programmed for this purpose, hereinafter called " supervisor". The control strategy executed by the supervisor is based on knowledge of the value of various parameters, in particular the request for engine torque formulated by the driver of the vehicle, as this request is translated by depressing a of a pedal d accelerator 21, the state of charge of the batteries 11, known by the intensity I which they

  deliver and their capacity, etc ...

  The supervisor acts on the engines 1 and 9, on the alternator 8 and on the state of the clutch 4 by developing appropriate control signals, respectively, of the opening angle 0 of a motorized throttle valve, of the intensity I or of the frequency F of the supply current of the engine 9, of a control unit 14 of the output current of the alternator 8 and of the state E of the clutch 4. In the mode embodiment of the device shown in FIG. 1, the transmission system 2 is constituted by a simple reduction gear with two pinions 15, 16, mounted on the input shaft 7 and on the output shaft 17

of the system, respectively.

  The operation of the device shown is then established as follows. Generally, the torque request C made by the driver of the vehicle being known to the supervisor 12 by depressing a of the accelerator pedal 21, the supervisor acts on the opening angle 3 of the throttle valve of the internal combustion engine 1, on the characteristics I, F of the electric energy supplied to the electric motor 9 by the inverter, on the resistant torque developed by the alternator 8 and on the clutch 4 so that, at losses mechanical in the transmission, we have:

C _ C1 + C2 - C3

  C1 and C2 being the driving torques delivered by the

  engines 1 and 9, C3 the resistant torque of the alternator.

  The supervisor 12 is duly programmed to calculate the torques C1, C2, C3 from the conventional operating parameters of the motors 1 and 9 and from

  the alternator 8, and the characteristics of these machines.

  Advantageously, the speed of the internal combustion engine 1 is adjusted by the supervisor to a value corresponding to a maximum efficiency so as to minimize consumption and therefore air pollution.

  by engine exhaust.

  The supervisor can thus, depending on the information received, control various operating modes of the traction device, in particular in "all electric", in "series hybrid" or in "parallel hybrid". Operation in "all electric" At low vehicle speeds, when the state of charge of the batteries 11 is deemed satisfactory by the supervisor 12, the latter keeps the internal combustion engine 1 stopped and the clutch 4 disengaged. It is then the electric motor 9, powered by the batteries 11 alone, which provides all the power necessary for propelling the vehicle, power applied directly to

gearbox output shaft 2.

  When the vehicle is stopped, this is how the engine

  electric 9 allows the vehicle to be started.

  The device according to the invention may include a mode selector 18 allowing the driver to "force" this operating mode in certain circumstances, to minimize emissions and noise (traffic in

city, for example).

  Incidentally, it will be noted that the selector 18 can be used to force other operating modes, for example "sport" or "economic" variants of the

  hybrid type, or "all thermal" operation.

  Hybrid series operation If the batteries 11 do not have the energy necessary to propel the vehicle under given conditions, due to a previous discharge or a malfunction, the supervisor controls the starting of the heat engine 1 and of the torque which it delivers so that the driving of the alternator 8 which results therefrom provides the electric motor with sufficient energy for the latter to deliver to the wheel 3 the torque requested by the driver. The clutch 4 then being disengaged, no mechanical energy is supplied directly to the wheel 3 by the heat engine 1. The latter can however provide additional power for recharging the batteries 11,

through the alternator 14.

  The supervisor controls the combustion engine 1 and the alternator 8 "in torque" so as to comply with a speed setpoint and to limit fuel consumption and therefore harmful emissions, while limiting the charges and discharges of the batteries 11. The speed of the motor

  thermal, in this operation, can be quite low.

  Hybrid "parallel" operation From a certain vehicle speed, the supervisor 12 increases the speed of the heat engine 1 in order to synchronize it with the speed of rotation of the input shaft of the reduction gear 2, so at

  then be able to activate clutch 4 and ensure, without

  strokes, the transmission of mechanical power

  important coming from the engine 1, to the wheel 3 of the vehicle.

  The electric motor 9 can then be switched off and it is the heat engine 1 which provides all the mechanical power necessary for the propulsion of the vehicle. The operation of the device then ceases

  to be of the "parallel hybrid" type.

  This type of operation can however be restored by the supervisor 12 if the latter perceives a high torque demand from the driver, so that the additional torque requested can be

supplied by the electric motor 9.

  Obviously, if the batteries 11 are discharged, the heat engine can provide additional power

  to recharge these batteries, through the alternator 8.

  Also, it is understood that during a braking phase, the braking energy can be recovered and transformed into electrical energy by the alternator 8 and the engine.

  electric 9, in order to recharge the batteries 11.

  Of course, the invention is not limited to the embodiment of Figure 1. This is how the electric motor 9 could as well be mounted on the primary shaft 7 of the reduction gear 2 and that the latter could be replaced by a manual or robotic gearbox, as illustrated by the variants of block B of FIG. 1 shown in FIGS. 2 to 4. On the latter, unless otherwise indicated, the means not shown of the device according to the invention are those shown in FIG. 1. In these figures, also, identical reference numbers, possibly assigned a "prime" or a "second", to references used in FIG. 1 identify elements or bodies similar to

those spotted on the latter.

  In Figure 2, there is shown a manual gearbox 2 'controlled by a linkage 19 and a lever, the electric motor 9 being mounted on the primary shaft of the box 2'. Means (not shown) transmit to the supervisor 12 the report R engaged in the box 2 '. This box could be replaced by

  a reducer such as that of FIG. 1.

  In FIGS. 3 and 4, the gearbox 2 "is robotized and the engaged gear R is controlled by the supervisor 12. The use of a robotized gearbox allows the supervisor 12 to synchronize the rotations of the axes as best as possible. gearbox during changes to the R ratio, which is very favorable to driving comfort of the vehicle, reduction of consumption and pollution. The electric motor 9 is mounted on the primary shaft in the device of FIG. 3 and on the secondary tree in that of the

figure 4.

  It now appears that the invention makes it possible to achieve the objectives sought, namely to provide a traction device for a hybrid vehicle which is of simple structure, with a reduced number of components, and of flexible operation by change without jerks of operating modes. In this respect, the "series" hybrid operation makes it possible to benefit from the flexibility of use of the heat engine, in particular to limit harmful emissions during cold starts, to limit the charges and discharges of the batteries, and to use a transmission. with a reduced number of gears, or even a single gear if the electric motor is fitted

  on the drive shaft of the transmission.

  The "parallel" hybrid operation allows to benefit from a good efficiency of the transmission chain and good performances and, except when the driver demands a strong power, to do without

of the electric motor.

  When the mechanical propulsion energy is supplied by the electric motor alone, the clutch is released, or the gearbox is put in neutral. When all the mechanical propulsion energy comes from the heat engine, there is no need to block the shaft of the electric motor. In both cases, it is advantageous to avoid having to block a shaft with a brake, while such brakes are necessary in the

  device of EP-A-0 648 635 cited above.

  The alternator also plays the role of starter and flywheel, which eliminates the need for a specific flywheel. The use of a robotic gearbox makes it possible to dispense with the clutch 4, if the operation of the heat engine is possible from the

low vehicle speeds.

Claims (10)

  1. Traction device for a hybrid electric vehicle comprising: a) a mechanical traction chain comprising a heat engine (1), a transmission system (2; 2 '; 2 ") of at least part of the output power from the engine (1) to at least one wheel (3) of the vehicle and a means of coupling said engine (1) to said transmission system (2; 2 '; 2 "), b) an electric traction chain comprising a generator of electric energy (14) driven by said heat engine (1), an electric motor (9) powered by said generator (14) and mechanically coupled to said transmission system (2; 2 '; 2 ") and storage means of electrical energy (11) supplied by said generator (14), this device being characterized in that it comprises, in combination, c) a member (21) for measuring the torque demand (C) of the driver of the vehicle , and d) means (12) sensitive to said measurement (C) for torque control of said motors (1,9) and said   generator (14) so as to establish the requested torque.   2. Device according to claim 1, characterized in that said control means (12) also act on said coupling means (4) to selectively activate an operation of the device of the   series hybrid or parallel hybrid type.   3. Device according to claim 2, characterized in that said coupling means (4) is a clutch mounted between the output shaft of the heat engine (1) and an input shaft (7) of the system transmission (2; 2 '; 2 ").   4. Device according to any one of   claims 1 to 3, characterized in that said system   transmission is a reduction gear (2).   he 5. Device according to any one of   claims 1 to 3, characterized in that said system   transmission is a manual gearbox (2 '). 6. Device according to any one of   claims 1 to 3, characterized in that said system   transmission is a robotized gearbox (2 ").   7. Device according to claim 5, characterized in that it comprises means for transmitting to the control means (4) the report (R)   engaged in the gearbox (2 ').   8. Device according to claim 6, characterized in that said means (4) control the   gear (R) engaged in the gearbox (2 ").   9. Device according to any one of   claims 4 to 8, characterized in that said motor   electric (9) is mounted on the secondary shaft (17) of the transmission system (2; 2 '; 2 ").   10. Device according to any one of   claims 4 to 8, characterized in that said motor   electric (9) is mounted on the primary shaft (7) of the transmission system (2; 2 ', 2 ").