WO2001060649A1

WO2001060649A1 - Motor vehicle transmission

Info

Publication number: WO2001060649A1
Application number: PCT/FR2000/000379
Authority: WO
Inventors: Jean-Claude Favarel
Original assignee: Favarel Jean Claude
Priority date: 2000-02-15
Filing date: 2000-02-15
Publication date: 2001-08-23
Also published as: AU2000226779A1

Abstract

The invention concerns a vehicle transmission having at least a device distributing power between two assemblies comprising one or several wheels (2) between which mechanical power is to be distributed. A power distributing device at least comprises a distributor shaft (6) arranged between the two corresponding assemblies and a differential device with limited slip (8) mounted on the distributor shaft (6) between the two assemblies and providing different rotating speeds at the two ends of the distributor shaft. A motor (4) is associated with each assembly comprising one or several wheels. The coupling is produced between each motor (4) output and the distributor shaft (6).

Description

TRANSMISSION FOR MOTOR VEHICLE

The present invention relates to a transmission for a vehicle, in particular a motor vehicle or a truck. The field of application of this invention is all vehicles and is particularly suitable for so-called all-terrain vehicles. It can be passenger cars, cars also called 4 x 4, agricultural machinery, construction machinery, competition cars, trucks, etc. These vehicles always have at least two driving wheels. Most of the time, for so-called all-terrain vehicles, all of their wheels are driven. In the vast majority of cases, the vehicle has an even number of wheels and these are mounted two by two or four by four on axles. A motor, generally a heat engine, drives these wheels. The engine transmits its power to the wheels of an axle and part of this power is transmitted by a shaft to the other, or to the other axles. The transmission between two axles is done for example by a rigid shaft or even by a shaft provided with a limited slip device. Of course, each axle is provided with a differential. It is also known for certain vehicles, in particular site vehicles, to provide a hydraulic motor at each wheel. A heat engine then powers a hydraulic pump which supplies oil to each hydraulic motor.

A disadvantage of the shaft connecting two axles is that it is necessary to size this shaft to make it pass all the power supplied by the heat engine. This tree must therefore be dimensioned accordingly, and its cost price is relatively high.

In the hydraulic solution, it is necessary to provide sensors allowing a good distribution of the power to the drive wheels. The distribution is then carried out by regulating the flow rate of hydraulic fluid. This distribution is managed electronically in many cases, which makes this solution very expensive to obtain good results. The object of the present invention is to provide a new vehicle transmission, suitable for so-called all-terrain vehicles which is as simple as possible while being both very reliable and efficient. Preferably, this transmission will be able to function without sensor and will implement relatively light mechanical parts.

To this end, the transmission that it offers is a transmission for a vehicle having at least one power distribution device between two assemblies comprising one or more wheels between which a mechanical power must be distributed.

According to the invention, at least one power distribution device comprises a distribution shaft arranged between the two corresponding assemblies and a limited slip differential device mounted on the distribution shaft between the two assemblies and allowing different rotation speeds at two ends of the distribution shaft, a motor is associated with each assembly comprising one or more wheels, and a coupling is produced between each motor output and the distribution shaft.

This produces a mechanical coupling between the two sets of the vehicle. This coupling is carried out by means of the distribution shaft which does not transmit all the power of the corresponding motors but only a part of it. The output speed of each motor is transmitted, with or without gear reduction, to the distribution shaft. The limited slip differential device allows small differences in speed between two motor outputs to be tolerated. However, if the difference in speed at the output of two neighboring motors becomes too great, the distribution shaft becomes rigid and the part of this fastest shaft drives the slowest part. Thus, a transfer of power takes place from the engine running faster to the assembly whose engine runs slower. Only a power differential is therefore transmitted by the distribution shaft.

This new transmission uses only mechanical elements that are both very simple and reliable.

The limited slip differential device used may for example be a visco-coupler. We can also consider other limited slip devices such as for example an electromagnetic clutch or a "classic" self-locking differential. In a preferred embodiment, the motors used are hydraulic motors. In this case, these are by example supplied with oil by a hydraulic pump, itself driven by a heat engine. It can also be a double pump or a set of two (or more) pumps. An advantageous embodiment, for example for making a competition vehicle or saving energy, provides that a distribution box is mounted between the heat engine and the hydraulic pump and that a flywheel is coupled to this distribution box. The flywheel can thus accumulate energy during deceleration and return this energy during acceleration. The motors and the pump (s) are preferably in a closed hydraulic circuit.

In an alternative embodiment, provision can be made to replace the hydraulic motors with electric motors.

According to a first embodiment of the invention, each assembly comprising one or more wheels comprises only one wheel. We then have a motor for each wheel. For reasons of space, this motor is advantageously a hydraulic motor and the differential device provided between two wheels is for example a visco-coupler.

Such a vehicle transmission can be equipped with an energy recovery device and then comprise for example a distribution box connected on the one hand to a heat engine and to a hydraulic pump with variable flow and on the other hand to a flywheel. In this case, the distribution box advantageously comprises a double conical torque to which two flywheels rotating in opposite directions are connected. In this way, gyroscopic effects are avoided.

An alternative embodiment provides that each wheel is mounted at the outlet of a planetary gear train, that a hydraulic motor is mounted at the entry of each planetary gear train and that the planetary gear trains are connected by the distribution shaft at one of their satellites. Such a vehicle transmission can serve as a basis for producing a transmission comprising more than two driving wheels. Such a transmission then comprises several two-wheel transmissions according to the first embodiment; the differential device is a mechanical differential comprising planets and satellites; a connecting shaft connects two neighboring transmissions and a limited slip device is mounted on the connecting shaft between the two corresponding transmissions. It is thus possible to produce transmissions for vehicles with four, six, eight - or even more drive wheels. A transmission for such a vehicle is advantageously such that each differential is fitted with a bevel gear and that the connecting shaft (s) is connected to each two-wheel drive at the level of the bevel gear.

According to a second embodiment of a vehicle transmission according to the invention, each assembly comprising one or more wheels comprises two wheels connected together by a differential, forming an axle. We then have one motor per axle.

Each axle is then for example arranged transversely relative to the vehicle; the distribution shaft is arranged longitudinally relative to the vehicle and each engine is connected to the axle corresponding to the level of the axle differential. The differential device is advantageously a visco-coupler. The coupling between the motor output and the distribution shaft is for example achieved by a toothed belt. This solution is clean and avoids the use of a gear train.

The distribution shaft, at at least one of its ends, advantageously comprises means allowing its coupling with a similar shaft. In this way, it is possible by simple coupling of two shafts, to make from a four-wheel drive vehicle a vehicle with six, eight, etc. drive wheels.

In any case, the invention will be clearly understood with the aid of the description which follows, with reference to the appended schematic drawing, representing by way of nonlimiting examples of embodiments of a transmission according to the invention.

FIG. 1 is a schematic view from above showing the wheels of a vehicle driven using a transmission according to the invention, FIG. 2 is a schematic elevation view of a variant of the transmission shown in FIG. 1,

FIG. 3 is a top view corresponding to FIG. 1 showing two axles according to the invention connected together,

FIG. 4 is an elevation view of a four-wheel drive transmission,

Figure 5 is a top view of the transmission of Figure 4

FIG. 6 is a top view of an eight-wheel drive transmission,

FIG. 7 is an elevation view of an energy recovery transmission according to the invention,

Figure 8 shows an example of a complete transmission for an eight-wheel drive vehicle,

Figure 9 shows the integration of a transmission according to the invention in a channel chassis, Figure 10 is a sectional view along the section line X-X of Figure 9,

Figure 1 1 is a top view corresponding to Figure 1 for an alternative embodiment of a two-wheel drive transmission, Figure 1 2 is an elevational view of the transmission shown in Figure 1 1, and

Figure 1 3 schematically shows in elevation a compact four-wheel powertrain.

Figure 1 shows a top view of two wheels 2 of a vehicle axle. Between these wheels 2, there is shown the transmission enabling them to be driven. This transmission comprises two hydraulic motors 4, a distribution shaft 6, and a visco-coupler 8. Each motor 4 drives an output pinion 10 which itself is engaged with a pinion 1 2 mounted on the distribution shaft 6 The pinions 1 2 are located on either side of the visco-coupler 8. The assembly formed by the output pinions 10, the shaft pinions 1 2 and the visco-coupler 8 are arranged in a casing 1 4 The distribution shaft 6 passes through this casing 14 and has at each of its ends a constant velocity joint 1 6 to which the corresponding wheel 2 is connected by an arm 1 8.

The distribution shaft is formed by two half shafts which are connected at the level of the visco-coupler 8. The latter allows a difference in rotation between the two half shafts of the distribution shaft 6 of the order of a few percent. When the difference in rotational speed increases, the two parts of the distribution shaft 6 become integral by means of the visco-coupler 8. Such a device is known to those skilled in the art. It has a casing inside which are arranged integral disks for some of a half shaft and for others of the other half tree. This casing is filled with a viscous fluid which freezes when it is subjected to excessive shearing.

Figure 2 shows in elevation the transmission described above further equipped with engine means and an energy recovery system. This figure shows the casing 14 and the arms 18 symbolized here by a cross. This figure also shows a heat engine 20, a distribution box 22, a variable flow hydraulic pump 24 and a flywheel 26. The heat engine 20 and the variable flow hydraulic pump 24 are each connected to a pinion 28 placed inside the distribution box 22. Between these two pinions 28 is a pinion 30 engaged with the two pinions 28. This pinion 30 is connected by a shaft 32 to the flywheel 26. The shaft 32 is placed in a housing formed in the casing 14. While the distribution shaft 6 is arranged horizontally, the shaft 32 of the flywheel 26 is for example arranged vertically. As shown in Figure 2, the distribution box 22 is located above the transmission while the flywheel is located below it. The shaft 32 is guided by bearings not shown in the drawing. The flywheel 26 acts as an energy accumulator which stores energy during decelerations and supplies energy during accelerations.

The operation of this transmission is described below. When the vehicle equipped with this transmission drives, the hydraulic pump 24 supplies each hydraulic motor 4. If the grip conditions are identical at the level of each wheel 2, each hydraulic motor 4 rotates at substantially the same speed and the wheels of the vehicle are trained in the same way. The two parts of the distribution shaft 6 then rotate at the same speed of rotation. The visco-coupler 8 sees no power. When a wheel 2 is on slippery ground, the resistive torque opposite to the corresponding motor 4 is reduced and this motor therefore tends to rotate faster. The corresponding pinion 1 2 and the corresponding distribution half-shaft then see their speed of rotation increase. This increase in speed of rotation is transmitted directly to the visco-coupler 12. When the difference in speed of rotation of the two half shafts of the distribution shaft 6 exceeds a predetermined limit, the visco-coupler 16 stiffens the shaft of distribution so as to have on either side of the visco-coupler for close shaft rotation speeds. There is then a transfer of power through the visco-coupler 8 from a half shaft to the other half shaft. There is thus an automatic adjustment, entirely mechanically, of the speed of rotation at each wheel 2. The power delivered at the hydraulic pump 24 is ideally distributed at the level of the wheels 2 without requiring the presence of distribution sensors power. The visco-coupler 8 is in no way used to transmit all the power of the hydraulic pump 24. It is only used to transmit a power differential from one wheel to the other. Figure 3 shows a top view of a four-wheel drive transmission. This transmission is obtained by coupling two two-wheel drive transmissions corresponding to an alternative embodiment of the two-wheel drive transmission in FIG. 1. There are therefore here two axles, each comprising two driving wheels coupled by a connecting shaft 34. Each axle has the same elements as the axle shown in FIG. 1. The only difference is that the limited slip device of FIG. 1 is a visco-coupler 8 whereas in FIG. 3 it is, for the two axles, a conventional differential 36 equipped with a bevel gear 38 and whose sliding is limited. Figure 3, like all the other figures, is a schematic view and in order not to overload it, the means for limiting the slip of the differential 36 have not been shown. These means are known to those skilled in the art.

The two axles of this four-wheel drive transmission are substantially identical. The connecting shaft connects these two axles at the level of the conical couples 38. A visco-coupler 40 is arranged on the shaft 34 between the two axles. The connecting shaft 34 is intended to transmit only a power differential which could exist between the two axles of this four-wheel drive transmission. As explained above, the two wheels 2 of the same axle rotate at substantially the same speed. The connecting shaft 34 is also rotated. When the rotational speeds of the wheels at the two axles are identical, the connecting shaft 34 rotates but without transmitting power. If the wheels of one axle start to spin faster than the wheels of the other axle, the visco-coupler 40 stiffens the connecting shaft 34 and power is then transmitted from the axle with the fastest wheels turning towards the axle with the slowest wheels. Here we have a similar operation between the two axles in the operation described above with reference to Figure 1 for the two wheels 2. This transmission is modular. As suggested on the right in FIG. 3, it is possible to couple another axle, identical to the first two, by a connecting shaft, one end of which is shown in dotted lines. This shaft is of course preferably also equipped with a limited slip differential device, such as for example a visco-coupler.

Figures 4 and 5 show an alternative embodiment for a four-wheel drive vehicle. In this example, instead of having one hydraulic motor per wheel, there is one hydraulic motor 4 per axle. We then have a power distribution between the two axles. Each axle has a differential 42, preferably with limited slip, placed each time between two wheels 2. FIG. 5 is a schematic view from above and means have not been shown thereon for example for turning two wheels of an axle.

In known manner, each differential comprises an input shaft 44 and two output shafts 46. The input shaft 44 is a motor shaft while the output shafts 46 make it possible to transmit, via the differential 42, the movement received by the input shaft 44 at the wheels 2. Each input shaft 44 is driven directly by a hydraulic motor 4. The output shafts 46 connecting the wheels 2 to the corresponding differential 42 extend transversely relative to the vehicle . A distribution shaft 48 is formed by two half shafts 50 connected to each other by a limited-slip device 52. Each half shaft 50 is mounted on bearings not shown. It is rotated by the input shaft 44 of the corresponding differential 42. To this end, a pulley 54 is mounted on the input shaft 44, and another pulley 54 is mounted on the corresponding half-shaft 46, facing the other pulley. A belt 56 connects these two pulleys 54.

The limited slip device 52 is for example a visco-coupler. It allows a difference in rotational speed between the two half shafts 50 which it connects on the order of a few percent. This visco- coupler is of the same type as the visco-couplers 8 and 40 described above.

Figure 4 shows in elevation the system described above and also schematically represents the drive means. This figure shows the hydraulic motors 4. They are each connected by a line 58 to a hydraulic pump 24 'with variable flow. The latter is a double pump and is coupled to a flywheel 26 'and to a heat engine 20' via a distribution box 22 '.

The operation is substantially identical to what has been described above. When a hydraulic motor 4 rotates faster than another, the visco-coupler 52 makes the two half shafts 50 integral with one another and thus the distribution shaft 48 transmits part of the power of the hydraulic motor 4 which turns faster towards the other axle. There is thus a distribution of power between the two axles. Compared to the embodiment shown in Figure 3, there are some differences. Here there are only two hydraulic motors while in the embodiment of Figure 3 there are four. In the variant of FIG. 5, it is therefore necessary to provide, for the same overall power of the vehicle, larger hydraulic motors. In addition, the differentials 42 pass all the power of the corresponding hydraulic motor. The differentials 36 in FIG. 3 only see part of the power of the corresponding hydraulic motors 4 pass. For the embodiment of Figure 5, it is therefore necessary to size the differentials 42 and the hydraulic motors 4 for a relatively large power while in the embodiment of Figure 3 smaller hydraulic motors and smaller differentials are used .

This transmission also has the advantage of being able to produce a modular all-terrain vehicle. One can indeed, for example, go from the four-wheel drive configuration shown in solid lines in FIG. 5 to an eight-wheel drive configuration which then comprises the four wheels shown in solid lines and the four wheels shown in dotted lines. One can for example have a four-wheel chassis on which is mounted the heat engine 20 'and the hydraulic pump 24', as well as a tool or a trailer mounted on an axle and equipped with a hydraulic motor. The trailer or the like, likewise that the chassis, at the level of an axle, comprises two wheels 2, a differential 42, an input shaft 44 driven by a motor 4 as well as two output shafts 46 connecting the differential 42 to the wheels 2. The trailer also comprises a distribution shaft 48 of suitable length, this shaft being provided with a limited-slip device 52 and a drive having two pulleys 54 and a belt 56. To allow coupling of the trailer to the chassis, means are provided for each end of the distribution shaft 48 of the chassis and at one end of the distribution shaft of the trailer. These coupling means are for example constituted by a PTO 57.

Thus, to hang the trailer and connect it to the chassis, it suffices to couple it at the PTO 57, to supply the hydraulic motor 4 with pressurized oil from the hydraulic pump mounted on the chassis and possibly, to make an electrical connection. These operations can be quickly carried out. Of course, if the same hydraulic pump 24 ′ supplies three hydraulic motors instead of two, the speed of rotation of the hydraulic motors will be reduced. In return, the payload of the vehicle is very significantly increased and / or its ground pressure is reduced. Figure 6 shows a transmission for a two-axle tandem vehicle. This transmission is extrapolated from the embodiment shown in FIG. 3. This FIG. 6 shows two four-wheel drive transmissions such as those in FIG. 3. The same references are kept. The only difference here is the length of the connecting shaft 34. As already suggested in dotted lines in FIG. 3, a connecting shaft 60 shown in dotted lines and on which a visco-coupler 62 is mounted connects the two sets of four wheels drive. Of course, the length of the connecting shaft 60 is determined as a function of the length of the vehicle which it is desired to produce. Here, thanks to the connecting shafts 34 and 60 and to the limited-slip differentials 36 and 62, an eight-wheel drive assembly is produced. We have not shown in Figure 6 the means for making the wheels 2 steer. This ensures fully mechanical, without electronic management, excellent power distribution between eight wheels of a vehicle. With the exception of a few percent, necessary in particular when cornering, the speeds of rotation of the eight wheels are substantially identical. The shaft 60 and the differential 62 can also be deleted. In this case, it will be possible to obtain hydraulic regulation for a semi-trailer for example. The flow of differential oil from the lack of adhesion of one group of axles relative to the other group of axles will be limited by a system ranging from a simple nozzle to a servo-control according to the desired performance.

Figures 7 and 8 show an example of drive means which can be associated with the transmission shown in Figure 6. Figure 7 is a block diagram showing how the drive means can act on an axle of the transmission shown in Figure 6 while that FIG. 8 schematically represents the four axles and the corresponding drive means.

In FIG. 7, a heat engine 64 associated with a gearbox 66 is represented. The gearbox output shaft, shown in phantom, is connected to a selection box 68. The latter makes it possible to select the place where the power of the heat engine 64 will be transmitted. This power can be sent either directly to an axle bearing the general reference 70, or to a variable-flow hydraulic pump 72 associated with an energy recovery device. The axle 70 is identical to an axle in FIG. 3 or in FIG. 6. However, the hydraulic motors used must be disengageable here. When the power of the heat engine is transmitted by the selection box 68 directly to this axle 70, the movement leaving the selection box 68 passes to the bevel torque 38 associated with the differential 36. This axle 70 then functions as an axle shown in Figures 4 and 5 since a motor shaft transmits its power to two wheels by means of a differential.

The power of the heat engine 64 can also be sent to the variable-flow hydraulic pump and to the energy recovery system. The rotational movement at the outlet of the gearbox 66 is then transmitted via the selection box 68 to a coupler 74. The variable flow hydraulic pump 72 is driven by this coupler via a double bevel torque 76. The rotational movement of the heat engine 64 is transmitted via the coupler 74 and the double bevel gear 76 to the pump 72. Two satellites 78 opposite this double bevel gear are each associated with a flywheel 80. The two satellites 78 rotate in opposite directions so that the two flywheels 80 also rotate in opposite directions. This eliminates the gyroscopic effect that exists when a single flywheel is used. In FIG. 8, there is the heat engine 64, two couplers 74 and four axles 70. Each axle is connected to a neighboring axle by a connecting shaft 34 or 60 and a visco-coupler 40 or 62. As in FIGS. 2 , 4 and 7, a cross indicates the location of an arm 1 8 and / or a wheel axle 2. Here, each coupler 74 is associated with two axles 70.

The complete transmission, including the engine means of FIG. 8, can be housed in a channel chassis as shown in FIG. 9. This FIG. 9 is a section along the section line IX-IX in FIG. 10. To lower the center of gravity, a gear is added between the wheel and the output of the corresponding motor. The two gears (motor output plus additional gear) are shown in dashed lines in FIG. 10. In this figure, the differential 36 and its bevel gear 38 for each axle are also shown in strong lines. In the sections of FIGS. 9 and 10, the contours of a channel chassis 82 are shown in dotted lines. FIG. 9 also shows schematically the shock absorbers 84 and suspension arms 86 of the vehicle. Figures 9 and 10 do not show the drive means but only the transmission.

This design is suitable for transporting / loading heavy vehicles on terrain with low lift. One can also consider placing two vehicles side by side with a channel chassis 82 and then having a large vehicle mounted on the two vehicles placed side by side.

Figures 1 1 and 1 2 show respectively in top view and in elevation an alternative embodiment of the axle shown in Figure 1. Here we find two wheels 2 each driven by a hydraulic motor 4 and connected to each other by a distribution shaft 6 on which is mounted a visco-coupler 8. Each hydraulic motor 4 has an output pinion 10 in engagement with a pinion 12 mounted on the distribution shaft 6. The output pinion 10 and the pinion 12 of the distribution shaft 6 form, for each wheel, part of a planetary gear 88. The axle shown incorporates an energy recovery device. The latter has a double bevel gear 76 'similar to the double bevel gear 76 of Figures 7 and 8. The heat engine 20 is used here to drive a hydraulic pump with variable flow 72' through the double bevel gear 760 II then drives , in the same way as the double bevel gear 76, flywheels 80 'which rotate in opposite directions.

Figure 13 shows another embodiment of a compact powertrain incorporating an energy recovery device. This compact powertrain here has four wheels. So we have two axles in tandem. This embodiment is extrapolated from the embodiment of Figure 3. The entire transmission is housed in the same housing. The conical couples 38 are replaced by a series of pinions including a limited slip device not shown. The center of the housing is thus freed for the installation of a flywheel 26 "and two hydraulic pumps 24". This assembly is driven by a heat engine 20 "via a distribution box 22".

This produces compact autonomous powertrains. These powertrains have two or four drive wheels. To produce a vehicle having more drive wheels, it is then possible to use several powertrains of this type. It is thus possible to produce with a base group many vehicle variants.

It goes without saying that the invention is not limited to the embodiment described above by way of nonlimiting example; on the contrary, it embraces all variants thereof within the scope of the claims below.

The vehicles described above are vehicles with hydrostatic transmission. However, it is quite possible to use electric motors instead of hydraulic motors. The operation of the transmission would not be changed.

The limited slip devices described are visco-couplers or limited slip differentials. Any other limited slip device may also be suitable. One can for example consider using an electromagnetic clutch. The use of a flywheel and a distribution box between the heat engine and the hydraulic pump increases the recovery of the vehicle and energy savings. This can be interesting for a competition vehicle. In other applications, it may be entirely possible to have a direct drive of the hydraulic pump by the heat engine.

Claims

1. Transmission for a motor vehicle having at least one power distribution device between two assemblies comprising one or more wheels (2) between which a mechanical power is to be distributed, characterized in that at least one power distribution device comprises a drive shaft distribution (6; 48) arranged between the two corresponding sets and a limited slip differential device (8; 36) mounted on the distribution shaft (6; 48) between the two sets and allowing different rotational speeds at the two ends of the distribution shaft, in that a motor (4) is associated with each assembly comprising one or more wheels, and in that a coupling is produced between each motor outlet (4) and the distribution shaft (6; 48).

2. Transmission for vehicle according to claim 1, characterized in that the motors used are hydraulic motors (4).

3. Transmission for vehicle according to claim 2, characterized in that the hydraulic motors (4) are supplied with oil by at least one hydraulic pump (24; 24 '; 24 "; 72; 72'), it (s) - even driven by a heat engine (20,20 ', 20 "; 64).

4. Transmission for vehicle according to claim 3, characterized in that a distribution box (22; 22 '; 22 "; 76) is mounted between the heat engine (20,20', 20"; 64) and the pump hydraulic (24; 24 '; 24 "; 72; 72') and in that a flywheel (26; 26 '; 26"; 80; 80') is coupled to this distribution box (22; 22 '; 22 "; 76).

5. Transmission for vehicle according to one of claims 3 or 4, characterized in that the motors (4) and the pump (24; 24 '; 24 "; 72; 72') are in closed hydraulic circuit.

6. Transmission for vehicle according to one of claims 1 to 5, characterized in that each assembly comprising one or more wheels comprises only one wheel (2).

7. Transmission for vehicle according to claim 6, characterized in that the differential device provided between two wheels is a visco-coupler (8).

8. Transmission for vehicle according to one of claims 6 or 7, characterized in that it comprises a distribution box (2) connected on the one hand to a heat engine (2) and to a hydraulic pump (2) to variable flow and on the other hand to a flywheel (2).

9. Transmission for vehicle according to claim 8, characterized in that the distribution box comprises a double bevel torque (76; 76 ') to which are connected two flywheels (80,80') rotating in opposite directions.

10. Transmission for vehicle according to one of claims 6 to 9, characterized in that each wheel (2) is mounted at the outlet of a planetary gear train (88), in that a hydraulic motor (4) is mounted at the input of each planetary gear (88) and in that the planetary gear (88) are connected by the distribution shaft (6) at one of their satellites.

1 1. Transmission for vehicle, characterized in that it comprises several two-wheel transmissions according to claim 6, in that the differential device is a mechanical differential (36) comprising planets and satellites, in that a shaft link (34) connects two neighboring transmissions and in that a limited slip device (40) is mounted on the connecting shaft (34) between the two corresponding transmissions.

12. Transmission for vehicle according to claim 1 1, characterized in that each differential (36) is equipped with a bevel gear (38) and in that (or the) shaft (s) of connection (34) is connected at each transmission with two wheels (2) at the level of the bevel torque (38).

13. Transmission for vehicle according to one of claims 1 to 5, characterized in that each assembly comprising one or more wheels comprises two wheels (2) connected together by a differential (42), forming an axle.

14. Transmission for vehicle according to claim 1 3, characterized in that each axle is arranged transversely with respect to the vehicle, in that the distribution shaft (48) is disposed longitudinally with respect to the vehicle and in that each engine ( 4) is connected to the axle corresponding to the level of the differential (42) of the axle.

15. Transmission for vehicle according to one of claims

13 or 1 4, characterized in that the differential device is a visco-coupler (52).

16. Transmission for vehicle according to one of claims 1 3 to 1 5, characterized in that the coupling between the engine outlet (4) and the distribution shaft (48.50) is achieved by a toothed belt (56 ).

17. Transmission for vehicle according to one of claims 13 to 16, characterized in that the distribution shaft (48), at at least one of its ends, comprises means allowing its coupling with a similar shaft.