Transmission for off-road vehicle with electrified inter-axle differential

Abstract

On slippery terrain, the wheel of a conventional 4 X 4 vehicle that slips limits the torque of the other three wheels. A classic improvement consists of decoupling the two axles and loading the operational axle using clutches and dog clutches. Here, it is proposed to replace the inter-axle differential with two CVTs (Variable Speed Transmission), therefore, with two epicyclic gear trains T1 and T2 regulated in torque by two actuators MG1 and MG2. A particular arrangement makes the two actuators operate in generator-motor opposition to limit the electrical balance. This design makes the transmission configurable according to the context, without clutch, dog clutch, or gearbox and gives it the flexibility of electric. This invention is rather intended for public works or military machinery, but not only.

Description

Title of the invention: Transmission for all-terrain vehicle with electrified inter-axle differential

[0001] As you know, internal combustion engines do not work well at low speeds. It is up to the transmission to extend their range of use to low speeds, even zero and reverse. This function is very important for four-wheel drive vehicles, particularly for civil engineering or military vehicles. They need a powerful, robust and, above all, agile transmission from the start. You only have to observe the back and forth movements of a loader or a stuck vehicle to be convinced of this. State of the art

[0002] Depending on the circumstances, road conditions, vehicle speed, it may be advantageous to have four-wheel drive or to activate or deactivate partially or totally one of the two axles. Many systems exist for this function, but they all use mechanisms that are often complex, fragile, not very agile or consume energy such as clutches or dog clutches. The use of geared CVTs (Continuously Variable Speed Transmissions) has already been considered, for example in patent FR3114955. However, a CVT, built around an epicyclic gear train controlled by a motor-generator actuator, has a significant electrical consumption in the form of derived power, the reduction of which is the issue of the patent. A solution with two CVTs in motor-generator opposition and with zero electrical balance is proposed below. A second issue is the improvement of the vehicle's grip on the ground.Indeed, in conventional four-wheel drive vehicles, the law of differentials implies that the torque on all wheels is limited by the torque on the slipping wheel, therefore by a relatively low torque. We will see how to improve this situation in the proposed solution. Certainly the system adds a few gears but it replaces the gearbox. Description of the invention

[0003] In the proposed invention, the transmission for a four-wheel drive off-road vehicle mainly comprises: • Two axles, each with their own pair of wheels, their own differential and their own drive shaft, known as the axle shaft. The kinematics of their differential are such that the two axle shafts rotate in opposite directions relative to each other when the four wheels rotate in the same direction. • Two simple epicyclic gear trains, with a ratio of r and -r (ratio of the gears) each with their identical sun gear and crown wheel in pairs, such that each sun gear is connected to one of the two motor-generator actuators MG1 or MG2 torque regulator, each crown wheel drives one of the two axle shafts, that each planet carrier is driven by the main motor MM in a speed ratio of -(lr) / (l+r), that between the crown wheel and the sun gear mesh single planet wheels for the gear train -r and double planet wheels for the gear train r, • Two actuators, motor-generator MG1 and MG2, each of which regulates the torque on its connected planetary gear and thereby regulates the torques on all shafts connected to the transmission according to the law of proportionality of torques in epicyclic gear trains, • A battery, reversible power electronics and an on-board computer to manage everything.

[0004] In a basic application, the powers on the two actuators are equal and opposite, therefore with a zero electrical balance, while the main motor MM provides all the mechanical power necessary for the vehicle through the epicyclic gear trains. Only part of the energy is converted into electricity by the generator actuator and then returned to the motor actuator to contribute to the thrust of the vehicle.

[0005] In a more sophisticated use, each axle reacts according to the torque instruction received on its corresponding actuator. When a wheel slips, detectable by a rapid drop in its torque, only the torque of the opposite wheel on the axle is mechanically limited. The new instruction can then be to neutralize the axle losing grip and to load the remaining operational axle. This is a significant improvement compared to conventional vehicles with differentials which lose their four-wheel drive simultaneously in this case. Certainly the zero electrical balance is lost but the battery can temporarily compensate.

[0006] Patent Fr3114955 concerned the drive of the wheel shafts and not the axle shafts. It required a great similarity of behavior between the right wheel and the left wheel for obvious reasons of vehicle safety. This necessity is also encountered for wheel motors or wheels with individual drive. For the present invention, equality of torques on the axle shafts is not required. On the contrary, the modification of the instructions on the actuators makes it possible to adjust the electrical balance punctually according to the needs of the moment, for example according to: • The battery charge status, • A one-off need for power on an axle, • The location of the center of gravity of the dynamic vehicle or not, • The slipping of one of the wheels. In summary, the ratio of the torque setpoints of the MG1 and MG2 actuators is adjusted in real time in relation to the current electrical balance requirements. Of course, we temporarily lose the equality of torques on both axles and on all wheels, but this makes it possible to limit the size of the battery, already reduced by the objective of zero electrical balance. The torques on the wheels of the same axle, however, always remain equal.

[0007] In all geared CVTs, the thrust of the actuators replaces the thrust of the main engine at low vehicle speed, especially when the main engine MM is thermal. To benefit from the maximum power at this critical moment, in the case of a stuck vehicle, loading a bucket, etc., the basic speed of the actuators will preferably be set to zero vehicle speed. The constant power phase of the actuators is in principle sufficient for reversing the machine. The reverse gear is also achieved by simply reversing the torques of the two actuators, without using clutches or dog clutches, which provides great agility in maneuvers. In fact, as we will see in the figures, the maximum thrust is available from the start of the machine.

[0008] Pure electric operation can be requested in an enclosed space or for discrete operation. Switching to pure electric mode, i.e. after neutralization of the main motor MM, is done while driving by simply reversing the torque of the actuator operating as a generator. Systematic blocking of the main motor MM subjected to counter torque is not necessarily required as on conventional vehicles, always for the sake of agility and flexibility. Indeed, when the two actuators are both motors, the counter torques on the shaft of the main motor are then opposed. The instructions of the actuators MG1 and MG2 can then be chosen so that they generate equal and opposite forces on the shaft of the main motor MM. As for reverse gear, everything happens smoothly at the level of the electronic control of the actuators.However, for long-term use in electric mode, it is always possible to have a temporary mechanical blocking of the MM main motor shaft using conventional and known techniques.

[0009] As we will see in the figures, the graphic characteristics of the speeds of the two actuators MG1 and MG2 in the diagram, actuator speed / vehicle speed, are perfectly symmetrical with respect to the vertical axis while intersecting the horizontal axis at A and A'. At A and A' the speed of the actuators is low, as is their power. The concern to limit the power requires gradually increasing the speed of the main engine MM while maintaining the vehicle speed close to A. Indeed the speed of the vehicle is not directly linked to the speed of the main engine but to the history of the thrust-resistance balances.

[0010] In fact, the speed variation range of the main motor MM is relatively narrow because CVTs already cover a good part of the vehicle's operating range. A reduced speed range is very favorable for high-performance, high-efficiency combustion engines and for alternative fuels. The vehicle's speed range is then covered in two zones, a so-called low-speed zone where the speed of the combustion engine is constant, except when it starts, until the vehicle speed reaches point A and a so-called high-speed zone where the speed of the combustion engine is gradually increased to maintain the vehicle speed in the point A zone.

[0011] Starting a thermal MM main engine can be envisaged with the vehicle stationary, foot on the brake, as on certain hybrid vehicles, or while moving, the actuators then serving as launchers.

[0012] To have axle shafts rotating in the same direction relative to each other without additional hardware, it is sufficient that at the axle differentials, the meshing teeth of the pairs of bevel or spiral gears are on either side of the axis joining the input pinions.

[0013] The main motor MM drives the two epicyclic gear trains in a speed ratio of -(l+r) / (lr) or -(1 -r) / (1+r) with a preference for reducing the drive speed of the gear train by ratio -r which leads to slower speeds for the auxiliaries.

[0014] The vehicle has a battery of reduced size already due to a minimal electrical balance but also thanks to a possibility of self-recharging. It can be done, while driving and unbalancing the instructions in favor of the generator actuator or while stopped in an isolated environment, the thermal engine driving the two actuators as generators. In addition, the power electronics of the actuators is reversible in order to recover the kinetic energies of the vehicle and the main engine MM.

[0015] The vehicle has, among other things, in its on-board computer, software for managing and controlling the transmission.

[0016] Given the possible brevity of the rebalancing of the electrical balance, the battery can be advantageously replaced by a super capacitor or a combination of the two.

[0017] The main thermal MM engine can be replaced by an electric motor while retaining certain advantages of the hybrid assembly, namely: • Reduced regulation power thanks to the reduction of the torques to be regulated in the epicyclic gear trains, • Improved vehicle grip with adjustable axle load distribution, • A reduced range of motor speed variation favours its better efficiency and the simplicity of its design and construction. • Cooling by a simple fan at the end of the shaft is possible thanks to low speed variation and minimal speed even when the vehicle is stationary, • Increased agility thanks to low inertia actuators relative to the main engine. Figures

[0018] [Fig.l], [Fig.l] shows schematically the transmission for a four-wheel drive all-terrain vehicle according to the invention with: • Two axles (1) and (2) each with their pair of wheels, their differential and their axle drive shaft el and e2. The meshing teeth of the bevel or spiral drive gears of the two differentials on the same side of the axis joining the input pinions (axis ele2) cause the two axle shafts el and e2 to rotate in the opposite direction to each other when the 4 wheels rotate in the same direction. • Two simple epicyclic gear trains T 1(3) and T2(4), of ratio r and -r respectively, each with their identical sun gear and crown two by two, such that each sun gear is connected to one of the two motor-generator actuators MG1 (7) or MG2 (8) torque regulators, each crown drives one of the two axle shafts el or e2, each planet carrier is driven by the main motor MM (6) in a speed ratio of -(lr) / ( 1+r), that between the crown and the sun gear mesh single planet gears for the train T2(4) and double planet gears for the train T 1(3). The double planet gears are formed by two idler gears on the planet carrier which mesh with each other and one of which meshes the crown gear and the other the sun gear. • A main thermal engine MM (6) drives the planet carriers of T2(4) and T1(3) in a rotation speed ratio of -(lr) / (l+r). The aim is to make the characteristics of the trains symmetrical with respect to the axis of the actuator speeds. It is possible either to increase the speed of T1(3), or to decrease the speed of T2(4) with a preference for the second solution. • A gearbox (5) splits the output of the main motor MM into two outputs si and s2 in the drive speed ratio of -(lr) / (l+r) and also ensures speed compatibility with those of the main motor MM (6). The sign - implies that the two outputs si and s2 rotate in opposite directions. • A battery not shown to absorb excess or deficits of the electrical balance of the two actuators (7) and (8) with its reversible power electronics for the recovery of kinetic energies, • An on-board computer (not shown) to manage and control the transmission, among other things. [Fig.2] ], [Fig.2] gives the characteristics of the two epicyclic gear trains for a drive speed of the planet carrier of T2 (3) of 1894 rpm which is also a possible limit of the starting phase of a thermal engine in the low speed configuration of the vehicle. In this zone, called low speed up to point A, A point of intersection of the characteristic with the axis of the speeds of the vehicle, the speed of the main engine MM is constant except during its start. The variation of speed of the vehicle is only ensured by the variations of speed of the actuators. Point I is the point of intersection of the two characteristics and A' is the symmetrical of A.

[0019] [Fig.3] ], [Fig.3] gives the characteristics of the epicyclic gear trains for a planet carrier drive speed of T2(3) at 3789 rpm. In this zone, called high speed, the speed of the thermal engine evolves to maintain the speed of the vehicle close to the intersection of the characteristic of the actuator of the train T2 with the axis of the speeds of the vehicle, that is to say close to the point A. Thus the speed and the power of the actuators are minimal. The points A, A' and I are the points reported from [Fig.2] at 1894 rpm for comparison. In fact the pilot fixes the torques on the wheels according to the acceleration or deceleration needs of the vehicle, torques which are proportional to the torques of the actuators. To meet the above conditions, a moderating software on the on-board computer maintains an optimal speed of the main engine MM such that it is close to the kV / (lr) law, k being a constant characteristic of the vehicle and V its speed.Depending on the circumstances, road conditions, vehicle speed, it may be interesting to partially or completely deactivate an axle and have a variable load distribution on the axles. This amounts to adjusting the actuator instructions without using a clutch or dog clutch. These choices can be initiated by the driver or managed by the on-board computer or both.

[0020] [Fig.4] ], [Fig.4] gives a schematic example of an arrangement of the invention in its compact and concentric version. For the sake of compactness and efficiency, the epicyclic gear trains and their actuators are mounted concentrically on the same axis with all the gears grouped in the same housing linked to the chassis (shown in dot-and-dash lines). Fan blades can be mounted at the free end of the actuator shafts for efficient cooling even at low speed, or even when the vehicle is stationary. Below is the nomenclature of the main elements:

[0021] 11 planetary gear of train 1

[0022] 12 axle shaft el

[0023] 13 planet carriers of train 1

[0024] 14 double satellites of train 1

[0025] 15 crown of train 1

[0026] 16 crown drive pinion of train 1

[0027] 17 MG1 actuator of the planetary gear of train 1

[0028] 18 tachometer

[0029] 19 main engine shaft

[0030] 20 MM main engine

[0031] 21 planetary gear of train 2

[0032] 22 axle shaft e2

[0033] 23 crown of train 2

[0034] 24 satellite door of train 2

[0035] 25 simple satellites of train 2

[0036] 26 casing linked to the chassis

[0037] 27 MG2 actuator of the planetary gear of train 2

[0038] 28 drive pinion of the planet carrier of train 2

[0039] 29 system for temporarily locking the shaft of the main motor MM relative to the crankcase

[0040] 30 reversing pinion of the drive speed of train 2

[0041] [Fig.5], The purpose of [Fig.5] is to confirm that the actuators are in operation motor-generator position in the most useful area of the speed diagram, i.e. between point I of intersection of the characteristics and the vehicle speed axis. The notations used are: - W, C, P are respectively the speeds, the torques, the powers of the organs of the two epicyclic trains of ratio r and -r. - p, c, ps, e are the indices corresponding respectively to the planetary gears, the crown gears, the planet carriers and the axles. - 1 and 2 are respectively relative to the reason trains r and -r. - The + sign for speeds and torques corresponds to the retrograde direction and the sign - in the opposite sense. - The + sign for powers corresponds to a positive power (Motor) and the - sign to a negative power (Generator). The balance of torques on the trains, the speed diagrams, P = CW, determine the matrix [Fig.5]. In results Ppl and Pp2 are indeed powers of opposite signs, which confirms the motor-generator opposition of the actuators in the quadrants considered. Note: the table is established at point I, i.e. crown and vehicle stopped.

[0042] [Fig.6], [Fig.6] for short Applications

[0043] The characteristics in Figures 2 and 3 are given for r = 0.3 and for 100 mN, 30 KW actuators.

[0044] Note: the reason for the train r is here by convention equal to the ratio: primitive diameter of the planetary / primitive diameter of the crown.

[0045] The thrust obtained on the vehicle of the order of 10 kN is essentially determined by the torque of the actuators.

Claims

Claims

1. transmission for a four-wheel drive off-road vehicle based on two CVTs (Continuously Variable Speed Transmission) characterized in that it comprises: • Two axles each with their pair of wheels, their differential and their axle drive shaft rotating in the opposite direction relative to each other when the wheels rotate in the same direction, • Two simple epicyclic gear trains, of ratio r (Tl) and -r (T2) each with their identical sun gear and crown two by two, such that each sun gear is connected to a torque regulator motor-generator actuator, each crown drives one of the two axle shafts, that each planet carrier is driven by the main engine in a speed ratio of -(lr) / (l+r), that between the crown and the sun gear mesh single planet gears for the train of ratio -r (T2) and double planet gears for the train of ratio r (Tl),• A battery to absorb the excess or deficits in the electrical balance of the two actuators with its reversible power electronics, • An on-board computer to control and manage this transmission, among other things.

2. transmission for a four-wheel drive all-terrain vehicle according to claim 1 characterized in that the ratio of the torque setpoints of the two actuators is adjusted in real time in relation to the electrical balance of the moment and the state of charge of the battery.

3. transmission for a four-wheel drive all-terrain vehicle according to claim 1 characterized in that the ratio of the torque setpoints of the actuators is adjusted in real time relative to the limit of slippage of one of the wheels.

4. Transmission for a four-wheel drive all-terrain vehicle according to claim 1 characterized in that the speed range of the vehicle is covered in two zones: a so-called low-speed zone where the speed of the main engine is constant when not starting and a so-called high-speed zone where the speed of the main engine is constant when starting. high speed where the speed of the main engine evolves according to a law close to kV / (lr), k being a constant characteristic of the vehicle and V its speed.

5. Transmission for a four-wheel drive all-terrain vehicle according to claim 1 characterized in that the distribution of torque between the axles is variable at the initiative of the driver or managed by the on-board computer or both.

6. transmission for four-wheel drive all-terrain vehicle according to claim 1 characterized in that the vehicle has a battery which can be recharged while driving or stationary with the possibility of recovering kinetic energy by adjusting the ratio of the actuator settings.

7. Transmission for a four-wheel drive all-terrain vehicle according to claim 1 characterized in that in pure electric mode, the ratio of the torque setpoints of the actuators is chosen so that the counter torques on the shaft of the main motor are equal and opposite.

8. transmission for a four-wheel drive all-terrain vehicle according to claim 1 characterized in that the epicyclic gear trains (T1) and (T2) and their actuators can be mounted concentrically on the same axis and that the gear trains are grouped in the same casing linked to the chassis.

9. Transmission for a four-wheel drive all-terrain vehicle according to claim 1 characterized in that the main engine can be thermal or electric.

10. Transmission for a four-wheel drive off-road vehicle according to claim 1 characterized in that the battery is replaced by a super capacitor or by a combination of the two.

Images