Electric powertrain equipped with a torque vectoring control device.

Abstract

An electric powertrain characterized in that the rotor hub is a two-part housing 21, 22 enclosing an epicyclic gear train 20 with planetary gears 23 and conical satellite gears 25, similar to that of an automobile gearbox differential; the electric machine, with axial magnetic flux 10a or radial magnetic flux 10r, is framed by two epicyclic gear reducers 30a, 30b, each equipped with a brake 40 associated with the planet carrier 32. Electrohydraulic control is used in group 3, providing the following benefits: increased traction in case of poor grip; torque vectoring control in corners; and electromechanical control is used in groups 4 and 5, providing the following benefits: increased traction in case of poor grip; torque vectoring control in corners; and locking of the geared motor unit, and therefore of the vehicle's wheels, when parked. Figure for the abbreviation: Fig. 5

Description

Title of the invention: Electric powertrain equipped with a torque vectoring control device. TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a powertrain comprising an axial or radial magnetic flux electric machine in a central position, the rotor of which is carried by a housing containing a spherical epicyclic gear train, similar to that of the differential of an automobile gearbox, distributing the torque of the electric machine to two lateral epicyclic gear reducers and each equipped with a planet carrier braking device. STATE OF THE ART

[0002] Publications on electrical machines, epicyclic gear reducers, electro-hydraulic or electro-mechanically controlled braking devices are countless.

[0003] Regarding a rotor whose hub consists of a so-called differential housing, we can cite publication WO2014089613. This is an electric powertrain consisting solely of the electric machine and a differential integrated into the rotor. This differential drives the transmission shafts to the wheels. PRESENTATION OF THE INVENTION

[0004] The object of this invention is an electric powertrain, intended for a sports vehicle, equipped with means improving traction on surfaces with reduced grip and torque vectoring control in corners.

[0005] According to a first characteristic, the rotor hub is a housing containing an epicyclic train with planetary and conical satellites, similar to that of a car gearbox differential.

[0006] According to a second characteristic, the electric machine is of the axial or radial magnetic flux type.

[0007] According to a third feature, the machine is framed on each side by an epicyclic gear reducer.

[0008] According to a fourth feature, the planetary gears of the mechanism in the housing carrying the rotor drive the planetary gears of the lateral epicyclic gear trains. The ring gears are fixed, and the motion and torque outputs are provided by the planet carriers.

[0009] According to other features, Each reducer is equipped with a brake associated with the planet carrier.

[0010] The brake is electro-hydraulically controlled and provides traction gain in case of poor grip, and torque vectoring control in turns.

[0011] The brake is electromechanically controlled with a worm gear and wheel, provides traction gain, torque vector control and locking of the motor-reducer unit, and therefore of the vehicle's wheels, when parking. DETAILED DESCRIPTION OF THE INVENTION

[0012] These features, objectives and advantages of the present invention will become apparent from the detailed description that follows and from the accompanying drawings given by way of non-limiting examples and on which:

[0013] [Fig-1] is a cross-sectional view of the powertrain in the version of an axial magnetic flux electric machine and the reducers without a braking device for the satellite carrier.

[0014] [Fig.2] is a cross-sectional view of the powertrain in radial magnetic flux electric machine version and the reducers without braking device of the satellite carrier.

[0015] [Fig.3] is a cross-sectional view of the powertrain in the version of an axial magnetic flux electric machine and the reducers equipped with an electro-hydraulically controlled satellite carrier braking device.

[0016] [Fig.4] is a cross-sectional view of the right reducer for description of the hydraulic braking device.

[0017] [Fig.5] is a cross-sectional view of the powertrain in the version of an axial magnetic flux electric machine and the reducers equipped with a braking device for the electromechanically controlled satellite carrier.

[0018] [Fig.6] is a cross-sectional view of the right reducer for description of the electromechanical control device.

[0019] [Fig.7] is a cross-sectional view of the powertrain in radial magnetic flux electric machine version and the reducers equipped with an electromechanically controlled satellite carrier braking device.

[0020] The powertrain group 1, shown in cross-section in [Fig.1], comprises an electric machine 10a in a central position and two identical reducers 30a and 30b, arranged on its sides, each receiving from the motor an equal torque distributed by the central mechanism 20 of spherical type with planetary gears 23 and conical satellites 25 similar to a differential of automobile gearbox.

[0021] This mechanism is contained in a 2-part housing, the inner part 21 supports the axis of the satellites 24 and the outer part 22 carries the rotor disc 11 of the axial magnetic flux machine 10a.

[0022] Since the torque must be transmitted from the outer part 22 to the inner part 21, they must be joined together. This connection can be made, for example, by laser welding without the addition of filler metal.

[0023] The housings 21, 22 form the rotor hub. Since this housing is located at the input of the drivetrain, it receives only the engine torque, which is moderate compared to that of the gearboxes, which is located at the output after a reduction stage. Therefore, it is small in size and made of aluminum.

[0024] It is supported by two ball bearings 15.

[0025] In this axial flux electric machine 10a, the rotor disc 11 must be positioned precisely in the space between the two stators 12a and 12b.

[0026] Typically, the rotor is axially positioned using a first shim between the outer ring of one of the bearings and its support in the housing, and a second shim is installed for preload, between the outer ring of the opposite bearing and its support in the housing.

[0027] The purpose of this preload spacer is to prevent the rotor from moving axially relative to the stators under any circumstances. However, since the rotor hub is generally made of steel and the housings of aluminum, a loosening occurs with temperature increase due to differential expansion. Choosing an aluminum housing will drastically reduce differential expansion and consequently the preload level of the bearings, and their load capacity.

[0028] The adjustments for the positioning of the rotor disc 11 and the preload of the bearings 15 are made here by the nuts 16a and 16b, screwed into the housings and bearing against the outer races. One is used for positioning and the other for preload. This method was formerly used in so-called longitudinal gearboxes to adjust the bevel gear of the axle transversely relative to the pinion and to apply the appropriate preload to the bearings supporting the differential housing.

[0029] The electric machine is equipped with separate and independent stator and rotor cooling systems. Each stator has a closed chamber 13 in which a liquid fluid circulates in contact with the coils. The rotor is cooled by air circulation within the closed space of the housings and by forced air circulation through the air gaps via the turbines 14.

[0030] Each planetary gear 23 of the torque distribution train 20 is splined at its end to carry the planetary gear 31 of the reduction gear train 30a,30b.

[0031] This reduction train consists of a ring 34, centered in the housing of the electric machine, blocked in rotation by the screws common to the fixing of the housing 35. The satellites 33 drive a planet carrier 32 which transmits the movement and the torque to a transmission shaft via the splines 32a.

[0032] The planetary gears 31, by driving three or four satellites, have their resultant tangential and radial forces zero. The axial forces can also be canceled out by using reversed helix angles. The bearings 15 supporting the motor rotor are then not affected by the gear teeth forces of the reduction gears.

[0033] The powertrain 2 shown in cross-section in this [Fig.2] differs from the group 1 by the electric machine. The axial magnetic flux electric machine is replaced by a conventional radial flux machine.

[0034] The housing 21,22 and the lateral reducers 30a and 30b are unchanged.

[0035] This powertrain is simpler since the rotor does not need to be precisely axially positioned.

[0036] The bearings 15, unchanged, do not need to be preloaded. The nut-based positioning and preload adjustment system is no longer required.

[0037] The stator is oil-cooled, common with the reducers, the seals between the motor and the reducers are eliminated.

[0038] In addition to simplicity, there is a gain in efficiency through the elimination of seals and preload.

[0039] The powertrain group 3 shown in this [Fig.3] differs from that of group 1 by the addition in each reducer 30a,30b of a brake 40 of the satellite carrier 32.

[0040] Fig. 4 is a cross-sectional view of the reducer 30a equipped with a brake 40 of the planet carrier 32.

[0041] The brake includes a pack of 41 discs, namely: • discs 41a grooved externally and engaged on a sleeve 32a, grooved internally, attached to the satellite carrier 32; • discs 41b internally grooved and engaged on a grooved arrangement 35a belonging to the housing 35.

[0042] The discs 41a, 41b are framed, on the one hand, by a clamping pressure plate 42, and on the other hand by a clamping force application element 43.

[0043] These elements 42,43 for pressurizing the discs 4la,41b, are engaged in the grooves 35a, blocked in rotation.

[0044] Pressure is applied to the organ 43 by a hydraulic piston 50, controlled by an electro-hydraulic pump not shown, pressurizing the chamber 51 through the supply conduit 52.

[0045] The release of the discs is ensured by the return spring 60, a conical elastic washer, which moves the component 43 away from the disc pack 4L

[0046] Equipping each reduction gear with an electro-hydraulic controlled brake 40 provides very important additional performance for a sporty vehicle: • In the event of low traction on one wheel, the other wheel with traction cannot receive more torque than the one with little or no traction. This is the law of The weaker wheel prevails. By applying the brake corresponding to the wheel with low grip, the equivalent resisting torque in the brake can be applied to the other wheel capable of accepting it within the limits of its own grip; • When traveling at high speed in a curve, the brake corresponding to the wheel on the inside of the curve is partially engaged. The torque received by the inside wheel is reduced by the torque absorbed by the brake. The outside wheel therefore receives a greater torque than the inside wheel. As a result, the vehicle is subjected to a pivoting torque in the direction of the curve.

[0047] The powertrain group 4 shown in cross-section on this [Fig.5] differs from that of group 3 by the control of the brake 40 which becomes electromechanical instead of electrohydraulic.

[0048] This electromechanical control is described in [Fig.6]. The pack of discs 40, the pressure recovery plate 42, the grooved sleeve 32a attached to the planet carrier 32, and the opening spring 60 are unchanged.

[0049] The pressure plate 43 changes in its extension 43a. Recessed ramps 43b each receive a ball 71. Symmetrically to these ramps 43b, with respect to the balls, we have ramps 70a on the disc 70. On the periphery, on only a portion, the disc 70 carries a thread 70b which cooperates with the orthogonally arranged screw 80.

[0050] As it rotates, the screw 80 imparts a rotational movement to the disc 70. As the space for the balls decreases, the disc 70 and the extension 43a of the pressure plate 43 move apart. The plate 43 brings the discs 41 closer together and then applies clamping pressure.

[0051] To facilitate its rotation, the disc 70 rests on a needle bearing 72.

[0052] This electromechanical system, equipped with a worm gear / wheel type motion transmission, is irreversible and stable in all positions

[0053] It allows for the same functions as the electro-hydraulic control system: • increased traction on poor road surfaces; • Torque vectoring control in corners.

[0054] To this we can add an additional feature related to parking. Indeed, since the two brakes are controlled independently, it is possible to close them simultaneously. We then have a parking brake based on adhesion, comparable to that applied to the wheel brakes.

[0055] The powertrain group 5 shown in cross-section in this [Fig. 7] differs from group 4 in the electric machine. The axial magnetic flux electric machine is replaced by a conventional radial flux electric machine. The differences listed between groups 2 and 1 are applicable.

Claims

Demands

1. Electric powertrain comprising either an axial magnetic flux type electric machine (10a) or a radial magnetic flux type electric machine (1 Or), laterally flanked by two identical right-hand epicyclic gear reducers (30a), (30b), each comprising: • a fixed ring gear (34); • a sun gear (31) driven by the tail of a bevel sun gear (23) of the gear train (20); • a power output planet carrier (32) to which a multi-disc brake (40) is associated, characterized in that the rotor of the electric machine: • is carried by a two-part differential housing (21,22) enclosing an epicyclic gear train with bevel sun gears (25) and planet gears (23); • is centered and fixed on the outer casing (22), and the satellite axis (24) is carried by the inner casing (21), the latter being centered in the outer casing (22) and secured to it by welding.

2. Electric powertrain according to claim 1 equipped with an electro-hydraulic brake (40) of the satellite carrier (32) preventing wheel runaway in case of loss of grip (grip control effect) or taking, in cornering, part of the torque intended for the inner wheel (torque vectoring effect) characterized in that it comprises a chamber (51) containing a liquid applying pressure on the piston (50) transmitted to the pressure plate (43) of the pack of discs (41) which then exerts a controlled braking torque on the satellite carrier (32).

3. Electric powertrain according to claim 1 equipped with an electromechanical brake (40) on the satellite carrier (32) preventing wheel spin in case of loss of traction (grip control effect) or diverting, when cornering, a portion of the torque intended for the inside wheel (torque vectoring effect), or locking the wheels when the vehicle is in a parked position, characterized in that it includes: • a worm screw (80); • a disc (70), supported on a needle bearing (72), which has on a peripheral portion a thread (70b) which cooperates with the screw (80) arranged orthogonally, this disc having ramps (70a) for receiving balls (71); • a fixed platform (43) whose extension (43a) includes ramps (43b), facing the ramps (70a) and identical to them, for receiving marbles (71), and that by turning, the screw (80) rotates the disc (70), causing the space for the balls (71) to be reduced, and causing the disc (70) to move away from the extension (43a) of the pressure plate (43), which then moves closer to the pack of discs (41) and exerts a clamping pressure on it, and a controlled braking torque on the satellite carrier (32).

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