FR2970440A1 - MOTOR PROPELLER SYSTEM FOR VEHICLE - Google Patents

Abstract

Motor-driven propulsion system for a vehicle, in particular an automobile, comprising a heat engine (11), a hydraulic motor (13), a hydraulic pressure generating device (12) and a mechanical power output device (15, 23) for driving at minus one shaft (16) of drive wheel (18). A first gear transmission device (20) is between the hydraulic motor and the output device (15, 23), with coupling or decoupling of the hydraulic motor and the output device. A mechanical power distribution device (35) is arranged at the output of the heat engine for power distribution between the pressure generating device and the output device via a second transmission device (50). geared. This second device is between the distribution device (35) and the output device, with coupling or decoupling of the distribution device and the output device.

Description

"MOTOR PROPELLER SYSTEM FOR VEHICLE"

The present invention relates to a motor vehicle propulsion system.

More particularly, the invention relates to a motor-driven propulsion system for a vehicle, in particular an automobile, comprising a heat engine, a hydraulic motor, a device for producing hydraulic pressure for supplying hydraulic power to the hydraulic motor and a power output device. mechanical assembly which can receive mechanical energy from the hydraulic motor and intended to be connected to at least one drive wheel drive shaft of the vehicle.

This type of system is known from EP1898131 in which only the hydraulic motor propels the vehicle by supplying mechanical energy to the mechanical power output device. The heat engine is dedicated to the production of hydraulic pressure by supplying mechanical energy to the hydraulic pressure generating device. The present invention is intended to overcome the disadvantages of the prior art. For this purpose, the subject of the invention is a motor-driven propulsion system for a vehicle, in particular an automobile, comprising a heat engine, a hydraulic motor, a device for producing hydraulic pressure for supplying hydraulic power to the hydraulic motor and a device for mechanical power output able to receive mechanical energy from the hydraulic motor and to be connected to at least one driving wheel drive shaft of the vehicle. The system includes a first geared power transmission device between the hydraulic motor and the power output device, which first device permits coupling or decoupling of the hydraulic motor and the power output device. This system further comprises a mechanical power distribution device disposed at the output of the heat engine to provide mechanical power on the one hand to the hydraulic pressure generating device and on the other hand to the power output device by the intermediate of a second gear power transmission device. This second device being placed between the distribution device and the power output device and allowing a coupling or decoupling of the distribution device and the power output device. In various embodiments of the system according to the invention, one or more of the following provisions may also be used: the mechanical power distribution device comprises an epicyclic gear train with planetary elements and element satellite which are interposed between the engine on the one hand and the hydraulic pressure generating device and the second gear transmission device on the other hand; the epicyclic mechanical power distribution device comprises a double satellite mounted rotating on a satellite door integral with the heat engine, a planetary element connected to the hydraulic pressure generating device being meshing with a series of toothed wheels of the double satellite and a planetary member connected to the second gear power transmission device meshing with another series of double satellite gear wheels; a planetary element brake of the epicyclic gear train is connected to the second gear power transmission device, the brake being interposed between said planetary element and a fixed part of the system; the first power transmission device between the hydraulic motor and the power output device comprises two gear ratios having an idle gear and a fixed gear which allow coupling or decoupling according to the position of a coupling device from crazy gear to a tree supporting it; the second power transmission device placed between the distribution device and the power output device comprises two gear ratios having an idle gear and a fixed gear which allow coupling or decoupling according to the position of a gear device. coupling the idler gear to a shaft supporting it; - The hydraulic pressure generating device comprises a pump connected to a supply tank for supplying hydraulic power to the hydraulic motor. Furthermore, the subject of the invention is also a vehicle, in particular an automobile, comprising at least one driving wheel drive shaft of the vehicle that can be driven by a motor-propulsion system according to the invention, in which the power output device mechanical can be driven by the power delivered by the hydraulic motor, the power delivered by the engine or the power delivered by the hydraulic motor and the following engine on the one hand the operating state of said engines and other the operating state of the first power transmission device allowing coupling or decoupling of the hydraulic motor and the power output device and the second power transmission device allowing a coupling or decoupling of the distribution device and the device power output. Other objects, features and advantages of the invention will become apparent from the following description of one of its embodiments, given by way of non-limiting example, with reference to the accompanying drawings. In the drawings: FIG. 1 is a schematic view of a motor-propulsion system according to the invention, said system being at rest and represented associated with a drive-wheel drive train, as mounted in a vehicle; Figure 2 is a view according to Figure 1 to a vehicle starting state by hydraulic propulsion, without producing hydraulic pressure; Figure 3 is a view according to Figure 1 to a vehicle starting state by hydraulic propulsion, with production of hydraulic pressure using a heat engine; Figure 4 is a view according to Figure 1 to a vehicle starting state by hydraulic and thermal propulsion, with production of hydraulic pressure using the engine; - Figure 5 is a view according to Figure 1 to a state of hydraulic propulsion in second gear ratio of hydraulic power transmission, with production of hydraulic pressure using the engine; FIG. 6 is a view according to FIG. 1 in a state of hydraulic and thermal propulsion, in second gear ratio of hydraulic power transmission device and in first gear ratio of thermal power transmission device, with production of hydraulic pressure using the thermal motor ; Figure 7 is a view according to Figure 1 to a vehicle starting state by thermal propulsion, without producing hydraulic pressure; - Figure 8 is a view according to Figure 1 to a state of thermal propulsion, in second report of thermal power transmission device without producing hydraulic pressure; FIG. 9 is a view according to FIG. 1 of a state of restitution of braking energy, in the first report of a hydraulic power transmission device, with production of hydraulic energy by the hydraulic motor. In the different figures, the same references designate identical or similar elements.

Referring to the figures, reference numeral 10 denotes a motor vehicle propulsion system comprising a heat engine 11, a hydraulic pump 12 for producing hydraulic pressure and a hydraulic motor 13 for supplying mechanical power to a differential 14 connected to transmission shafts 16 driving driving wheels 18 belonging to a vehicle running gear. The differential 14 constitutes a part of a mechanical power output device 15.

The motor-propulsion system 10 according to the invention is dedicated to driving the two drive wheels 18 by using either the energy of the engine 11 or the energy of the hydraulic motor 13. In the power train system 10, the hydraulic pump 12 is part of a hydraulic pressure generating device which comprises a feed tank 19 of known type. The supply reservoir 19 is connected on the one hand to the hydraulic pump 12 by lines 19A and on the other hand to the hydraulic motor 13 by lines 19B. The feed tank 19 may comprise in known manner a low pressure accumulator and a high pressure accumulator which are connected to known type of control means for delivering hydraulic power to the hydraulic motor 13 by managing the pressure reserves. The motor-propulsion system 10 comprises a first power transmission device 20 interposed between the hydraulic motor 13 and the differential 14. This first transmission device 20 is intended to allow a coupling or decoupling of the hydraulic motor 13 and the differential 14.

The first power transmission device 20 comprises a gear 21 of first gear ratio and a gear 22 of the second gear ratio ratio. The gear 21 of the first hydraulic ratio comprises a fixed gear 21A relative to the shaft 13A of the hydraulic motor 13 and an idle gear 21B. The gear 22 of the second hydraulic ratio comprises a fixed gear 22A with respect to the shaft 13A of the hydraulic motor 13 and an idle gear 22B. The idle gears 21B, 22B are rotatably mounted relative to an output shaft 23 which belongs to the power output device 15, an output gear 23A of which is engaged with the differential 14 for driving the transmission shafts 16. coupling device constituted by a friction synchronizer, referenced 26 in the figures, makes it possible to couple or decouple the idle gears 21B, 22B with respect to the output shaft 23. The synchronizer 26 is of known type and is controlled by a control means of known type. The motor-propulsion system 10 comprises a mechanical power distribution device disposed at the output of the heat engine 11. The distribution device is dedicated to providing mechanical power on the one hand to the hydraulic pump 12 and on the other hand to the output shaft 23 which belongs to the mechanical power output device 15. The distribution device comprises an epicyclic gear train 35 provided with a satellite carrier 35A rotatably connected to the output shaft 11A of the heat engine 11. The satellite carrier 35A supports free rotation dual satellites 36, for example two in number. The epicyclic gear 35 comprises a sun gear 37 rotating between the double satellites 36, in the center of the satellite door 35A. The sun gear 37 is integral with an axis 37A driving a gear 38 rotating the axis 12A of the hydraulic pump 12. The epicyclic gear 35 comprises a planetary ring 39 rotating around the satellite gate 35A and double satellites 36. The crown planetary gear 39 is integral with a sleeve 39A of rotation guide. The sleeve 39A rotates about the axis 37A of the sun gear 37. Such a guide sleeve may be called sock shaft.

In the distribution device, the planetary ring gear 39 is associated with a brake 41 provided with a fixed guide 41A integral with a frame of the propulsion system 10 and a packing 41B movably mounted on the fixed guide 41A in the axial direction of the sleeve. 39A in order to be able to brake the planet ring gear 39 by securing it to the fixed guide 41A, or to be free with respect to the sun gear ring 39. Each double satellite 36 comprises a toothed wheel 36A driving the sun gear 37 connected to the hydraulic pump 12 and a toothed gear wheel 36B for driving the ring gear 39. The ring gear 39 is connected to the output shaft 23 by means of a second power transmission device 50 which includes a gear gear 51 of the first gear ratio ratio. thermal traction chain and gear 52 of second gear ratio of thermal traction chain. The gear 51 of first thermal ratio comprises firstly a fixed gear 51A relative to the sleeve 39A integral with the ring 39 and on the other hand a pinion 51B. The gear 52 of the second thermal ratio comprises firstly a fixed gear 52A relative sleeve 39A integral with the ring 39 and secondly a pinion 52B. The idle gears 51B, 52B are rotatably mounted relative to the output shaft 23 which belongs to the power output device 15. A friction synchronizer, referenced 56, is used to couple or uncouple the idle gears 51B, 52B relative to said output shaft 23. The synchronizer 56 is, like the synchronizer 26, of known type and is controlled by a known type of control means. Next, on the one hand, the operating state of the heat engine 11, the hydraulic pump 12, the hydraulic motor 13 and the brake 41 and, on the other hand, the hydraulic pressure in the reservoir 19, the drive wheels 18 can be driven by thermal energy, hydraulic energy or a combination of these two energies. The operation of the motor-propulsion system 10 according to the invention is already apparent in part from the foregoing description and will now be detailed. In Figure 1, the propulsion system 10 is shown at rest. In this operating state, the heat engine 11 is stopped, as is the hydraulic motor 13. The hydraulic pump 12 is also stopped and it does not provide hydraulic pressure to the supply tank 19. In FIG. 2, the motorcycle system propellant 10 is shown in a situation corresponding to the starting of a vehicle by the two driving wheels 18, while the pressure in the supply tank 19 is sufficient for driving said driving wheels 18 by means of the hydraulic motor 13. In this state of operation of the propulsion system 10, the heat engine 11 does not intervene because it is stopped, as the hydraulic pump 12. The various parts of the power train by which there is power transmission , between the hydraulic motor 13 and the driving wheels 18 are shown filled with hatching in FIG. 2. The first transmission device 20 has its first ra a gearbox which is engaged because the synchronizer 26 couples the first hydraulic ratio idler gear 21B with the output shaft 23 of the power output device 15. The hydraulic motor 13 converts hydraulic pressure stored in the fuel tank. 19 in torque transmitted to the output shaft 23 through the gear 21 of first hydraulic ratio. The output shaft 23 transmits power to the differential 14 via the output gear 23A. This power reaches the driving wheels 18 by means of the transmission shafts 16. In FIG. 3, the power-train system 10 is represented in a situation corresponding to the starting of a vehicle by the drive wheels 18 while the pressure in the supply reservoir 19 is insufficient for driving the drive wheels 18 by means of the hydraulic motor 13. In this operating situation, the hydraulic pump 12 is driven by the heat engine 11 to charge the supply reservoir 19 so that the latter can supply enough energy to the hydraulic motor 13. Here too, torque is transmitted by the hydraulic motor 13 to the drive wheels 18 because the first hydraulic ratio remains engaged, as in the operating situation described in connection with However, here, the heat engine 11 operates by driving the hydraulic pump 12 which supplies hydraulic energy the feed tank 19. The various parts of the drive train which are driven by hydraulic power between the hydraulic motor 13 and the drive wheels 18 are shown filled with hatching in FIG. 3, to which the different Parts which are driven by thermal energy, between the heat engine 11 and the hydraulic pump 12 are shown filled with a scatter plot.

The heat engine 11 provides by its output shaft 11A a torque to the satellite gate 35A which rotates the double satellites 36. The brake 41 blocks the rotation of the ring 39, so that the double satellites 36 rotate in said ring 39 which is fixed.

Thus, the corresponding toothed wheels 36A of the satellites 36 rotate the sun gear 37 which rotates the shaft 37A driving the gear 38 and the hydraulic pump 12. In FIG. 4, the propulsion system 10 is represented in a corresponding situation. at the coast start of a vehicle by the driving wheels 18, by hydraulic and thermal propulsion. In this operating situation, the hydraulic pump 12 is driven by the heat engine 11 to charge the supply tank 19 so that the latter can supply enough energy to the hydraulic motor 13 which transmits torque to the drive wheels 18 because the first hydraulic report is engaged. Here, the heat engine 11 is on the other hand in operation to also drive the power output device 15 in addition to the drive performed by the hydraulic motor 13. The various parts of the power train that are driven by energy hydraulic, between the hydraulic motor 13 and the drive wheels 18 are shown filled with hatching in Figure 4, to which the various parts driven by thermal energy are shown filled with a scatter plot. Some parts are represented with the two superimposed filling patterns, such as the output shaft 23.

The first report of the hydraulic power train is still engaged. Thus, with respect to the hydraulic power train between the hydraulic motor 13 and the power output device 15, the operation is unchanged with respect to the operation as described with reference to FIG. 2 and FIG. of power transmission 50 has its first gear ratio which is engaged because the synchronizer 56 couples the idler gear 51B of first thermal ratio with the output shaft 23 of the power output device 15. At startup, there is a certain mechanical resistance transmitted from the drive wheels 18 to the sleeve 39A via the output shaft 23 and the gear 51. The heat engine 11 provides by its output shaft 11A a torque to the satellite gate 35A which rotates the satellites 36. Part of the torque supplied by the heat engine 11 passes from the satellite door 35A to the sun gear 37 via the wheels 36A is another part of the torque provides p ar the heat engine 11 passes the satellite door 35A to the ring 39 via the wheels 36B. In fact, according to the resistance applied to the epicyclic gear train 35 by the hydraulic pump 12 or the power output device 15, the planetary gear train 35 serves as a torque distributor between the heat engine 11 and the said pump 12 or the said output device 15. This torque distribution is induced by the brake effect caused by said pump 12 or by said output device 15 respectively facing the sun gear 37 or the ring 39. In the operating situation corresponding to that of the drive of driving wheels 18 during a hill start, the motor-propulsion system 10 according to the invention makes it possible to benefit from both the power of the hydraulic motor 13 and the power of the heat engine 11. Simultaneously, the hydraulic pump 12 continues to recharge the hydraulic supply reservoir 19 to compensate hydraulic consumption of the hydraulic motor 13. In Figure 5, the power train system is presented in a situation corresponding to the running of a vehicle with the second hydraulic gear engaged. This operating situation is similar to that described with reference to FIG.

In this operating situation, the hydraulic pump 12 is driven by the heat engine 11 to charge the supply tank 19 so that the latter can supply enough energy to the hydraulic motor 13. The brake 41 prevents the rotation of the ring 39 The different parts of the power train which are driven by hydraulic power between the hydraulic motor 13 and the driving wheels 18 are shown filled with hatching in FIG. 5, at which the different parts driven. by thermal energy, between the heat engine 11 and the hydraulic pump 12 are shown filled with a scatter plot. The first transmission device 20 has its second gear ratio which is engaged because the synchronizer 26 couples the idle gear 22B of the second hydraulic ratio with the output shaft 23 of the power output device 15. The hydraulic motor 13 converts hydraulic pressure stored in the torque reservoir 19 transmitted to the output shaft 23 through the gear 22 of the second hydraulic ratio. The output shaft 23 transmits power to the driving wheels 18 via the output gear 23A, the differential 14 and then the transmission shafts 16. In FIG. 6, the propulsion system is presented in a situation corresponding to the rolling of a vehicle with the second hydraulic gear engaged and the first gear engaged. This operating situation is similar to that described with reference to FIG. 4, with the second hydraulic gear engaged as shown in FIG. 5. In this operating situation, the hydraulic motor 13 transmits torque towards the drive wheels 18 via the gearing. 22 of the second hydraulic ratio while the hydraulic pump 12 is driven by the heat engine 11 to firstly charge the supply tank 19 and secondly drive the power output device 15 via the gear 51 of the first thermal ratio in addition to the drive performed by the hydraulic motor 13.

The various parts of the drive train which are driven by hydraulic power between the hydraulic motor 13 and the drive wheels 18 are shown filled with hatching in FIG. 6, to which the various parts driven by energy thermal, are represented filled with a cloud of points. Some pieces are represented with the two superimposed fills. The heat engine 11 provides by its output shaft 11A a torque to the satellite gate 35A which rotates the double satellites 36. Part of the torque supplied by the heat engine 11 passes from the satellite gate 35A to the sun gear 37 via the wheels 36A is another part of the torque supplied by the heat engine 11 passes from the satellite door 35A to the ring 39 via the wheels 36B. The epicyclic gear 35 also serves here as a torque distributor between the heat engine 11 and said pump 12 or said output device 15, as a function of the resistance applied to the epicyclic gear train 35 by the hydraulic pump 12 or the power output device 15 .

Here too, the motor-propulsion system 10 according to the invention makes it possible to benefit as much from the power of the hydraulic motor 13 as from the power of the heat engine 11. Simultaneously, the hydraulic pump 12 continues to recharge the hydraulic supply reservoir 19 to compensate the hydraulic consumption of the hydraulic motor 13. The gear ratio selected firstly in the first power transmission device 20, namely the second hydraulic ratio, and secondly in the second power transmission device 50, namely the first thermal report, optimizes the consumption according to the speed of rotation of the drive wheels 18 and the need for acceleration. In Figure 7, the propulsion system is presented in a situation corresponding to the rolling of a vehicle with only the first thermal report engaged. Only the heat engine 11 provides power to the drive wheels 18.

The synchronizer 26 of the first power transmission device 20 is at rest and leaves free to rotate with respect to the output shaft 23, the idle gears 21B and 22B of the gears 21 and 22 of the hydraulic ratios. The hydraulic motor 13 is at a standstill. The various parts of the traction system driven by thermal energy are shown filled with a cloud of points in Figure 7. The brake 41 is at rest and leaves the ring 39 free to rotate relative to the frame of the propulsion system 10. On the other hand, the hydraulic pump 12 is locked so that the sun gear 37 of the epicyclic gear 35 is locked at a standstill. The heat engine 11 provides by its output shaft 11A a torque to the satellite gate 35 which rotates the dual satellites 36. The wheels 36A of the double satellites 36 roll around the sun gear 37. The gearwheels 36B of the double satellites 36 rotate. the ring gear 39 which supplies mechanical energy to the gear 51 of first thermal ratio in order to drive the driving wheels 18 by rotation via the power output device 15. In FIG. 8, the motor-propulsion system 10 is presented in a situation corresponding to the running of a vehicle with only the second thermal report engaged. Only the heat engine 11 provides power to the drive wheels 18, as in the case of the operation of the propulsion system 10 described in connection with Figure 7. The synchronizer 26 of the first power transmission device 20 is still at rest. The idle gears 21B and 22B of the gears 21 and 22 of the hydraulic ratios are still free to rotate while the hydraulic motor 13 is at a standstill. The various parts of the traction chain which are driven by thermal energy are represented filled with a cloud of points in FIG. 8, as in FIG. 7. The brake 41 is still at rest and leaves the crown 39 free to rotate relative to the frame of the propulsion system 10. The hydraulic pump 12 is still blocked to block the planetary gear 37 of the epicyclic gear train 35 stopped. The heat engine 11 provides a torque to the satellite gate 35 which rotates the double satellites. 36. These rotate the ring gear 39 which supplies mechanical energy to the gear 52 of the second heat transfer ratio belonging to the second power transmission device 50. This mechanical energy drives the drive wheels 18 via the output device of FIG. 15. In FIG. 9, the power-train system 10 is presented in a situation corresponding to the rolling of a vehicle under braking, with a restitution the kinetic energy of the vehicle. This restitution of energy makes it possible to recharge the hydraulic supply reservoir 19. The various parts of the drive train that are driven by the kinetic energy of the vehicle are shown filled with a grid in FIG. 9. In this operating state of the propulsion motor system 10, the kinetic energy torque flows from the driving wheels 18 to the hydraulic motor 13, via the power output device 15 and the first gear ratio gear 21 or the second gear ratio gearing 22. The hydraulic motor 13 functions here as a pump and restores the kinetic energy of the vehicle under braking by converting the kinetic energy torque into hydraulic pressure which is stored in the reservoir 19. In the operating situation of the power train system 10 corresponding to the starting of a vehicle in reverse, the operating principle of the 10 e motor-propulsion system st in accordance with that described in connection with Figure 2 or Figure 3, by reversing the direction of rotation of the hydraulic motor 13. The heat engine 11 does not provide power to the power output device 15, the synchronizer 56 being at rest and not transmitting torque.

Advantageously, the motor-propulsion system 10 makes it possible, in a hybrid hydraulic and thermal motor vehicle, to improve overall energy consumption, especially when the vehicle has to drive at a high speed.

Advantageously, the motor-propulsion system 10 has an architecture that comprises two hydraulic ratios and two thermal ratios combined with the mechanical power distributor constituted by the epicyclic gear, which allows a great combination of gear ratios and hydraulic and / or thermal operation mode.

Thus, the motor-propulsion system 10 proposes six forward gears, namely a first hydraulic ratio, a first hydraulic ratio combined with a first thermal ratio, a second hydraulic ratio, a second hydraulic ratio combined with a first thermal ratio, a first and a second ratio. second heat report. The motor-propulsion system 10 also offers a reverse hydraulic ratio, without complex development. Alternatively, the power train system 10 may also operate with a gear ratio using the first hydraulic ratio combined with the second heat ratio and the second hydraulic ratio combined with the second heat ratio. With this great diversity of gear ratios, it is possible to optimize the overall efficiency of the powertrain system of the hybrid hydraulic and thermal vehicle. Thus it is possible to optimize the carbon dioxide emissions, especially for operation corresponding to a high speed of the vehicle. Advantageously, the release of kinetic energy during braking also increases the overall efficiency of the motor-propulsion system. As a variant of the motor-propulsion system, this variant not being shown in the figures, the output shaft is constituted by two half-shafts, one associated with the thermal gearing gears and the other associated with the hydraulic gear gears. This variant allows a greater compactness of the motor-propulsion system in width and greater ease of implementation of this system in a motor vehicle engine compartment.

Claims (8)

REVENDICATIONS1. Motor-driven propulsion system for a vehicle, in particular an automobile, comprising a heat engine (11), a hydraulic motor (13), a hydraulic pressure generating device (12) for supplying hydraulic power to the hydraulic motor and an output device of mechanical power (15, 23) capable of receiving mechanical energy from the hydraulic motor and intended to be connected to at least one drive wheel drive shaft (18) of the vehicle, characterized in that comprises: a first geared power transmission device (20) between the hydraulic motor (13) and the power output device (15, 23), said first device (20) allowing a coupling or decoupling of the hydraulic motor and the power output device; a mechanical power distribution device (35) disposed at the output of the heat engine (11) for supplying mechanical power on the one hand to the hydraulic pressure generating device (12) and on the other hand to the output device of power (15, 23) through a second gear power transmission device (50), said second device (50) being located between the distribution device (35) and the power output device (15). , 23) and allowing a coupling or decoupling of the distribution device and the power output device. 2. System according to the preceding claim, characterized in that the mechanical power distribution device (35) comprises an epicyclic gear planetary elements (37, 39) and satellite element (36) which are interposed between the motor on the one hand thermal device (11) and secondly the production device hydraulic depression (12) and second power transmission device (50) gear. 3. System according to the preceding claim, characterized in that the mechanical power distribution device (35) epicyclic train comprises a double satellite (36) rotatably mounted on a satellite carrier (35A) integral with the engine (11), a planetary member (37) connected to the hydraulic pressure generating device meshing with a series of double satellite gears (36A) and a sun gear (39) connected to the second gears power transmission device (50). being meshing with another series of gear wheels (36B) of the dual satellite. 4. System according to any one of claims 2 to 3, characterized in that it comprises a brake (41) of planetary element (39) of the epicyclic gear (35) connected to the second power transmission device (50). gear, the brake (41) being interposed between said planetary member (39) and a fixed part of the system. 5. System according to any one of the preceding claims, characterized in that the first power transmission device (20) between the hydraulic motor (13) and the power output device (15, 23) comprises two gear ratios. gears (21, 22) having an idler gear (21B, 22B) and a fixed gear (21A, 22A) which permit coupling or decoupling according to the position of a coupling device (26) of the idler gear to a shaft (23) supporting it. 6. System according to any one of the preceding claims, characterized in that the second power transmission device (50) placed between the distribution device (35) and the power output device (15, 23) has two ratios. gear reduction gear (51, 52) having an idler gear (51B, 52B) and a fixed gear (51A, 52A) which permit coupling or decoupling according to the position of a coupling device (56) of the idler gear to a shaft (23) supporting it. 7. System according to any one of the preceding claims, characterized in that the device for producing hydraulic pressure comprises a pump (12) connected to a supply tank (19) for supplying hydraulic power to the hydraulic motor ( 13). Vehicle, in particular an automobile, comprising at least one drive wheel drive shaft (18) of the vehicle drivable by a propulsion system (10) according to any one of the preceding claims, wherein the device mechanical power output (15, 23) can be driven by the power delivered by the hydraulic motor (13), by the power delivered by the heat engine (11) or the power delivered by the hydraulic motor and by the following heat engine on the one hand the operating state of said motors and on the other hand the operating state of the first power transmission device (20) allowing a coupling or decoupling of the hydraulic motor (13) and the power output device (15, 23) and the second power transmission device (50) allowing a coupling or decoupling of the distribution device (35) and the power output device (15, 23).