TRANSMISSION SYSTEM FOR A MOTOR VEHICLE WHEEL EQUIPPED WITH A BRAKE

Abstract

A transmission system for a motor vehicle wheel, comprising a wheel brake and a drum (14) disposed along the wheel axle (12) and rotating with this wheel (10), containing the wheel brake in a lubricating fluid, an internally toothed ring gear (24) connected to the drum (14), and a pinion (22) engaged with this ring gear (24), achieving a reduction of the motion received from a motor (18). Figure 1

Description

Title of the invention: TRANSMISSION SYSTEM FOR A MOTOR VEHICLE WHEEL EQUIPPED WITH A BRAKE

[0001] The present invention relates to a motor vehicle wheel transmission system equipped with a brake, as well as a motor vehicle comprising such a transmission system.

[0002] A type of electric motor system for an automotive wheel, presented in particular by document US-A1-20140159468, comprises a wheel rim having a central cylindrical part surrounded by the tire, which forms the rotor of an electric machine receiving the stator arranged inside this cylindrical part.

[0003] A transverse plate fixed to the vehicle's suspension, supporting the stator around its perimeter, has on its face facing outwards the central hub which receives the wheel rim. The outer face of the plate receives around the hub two brake shoes separated by a hydraulic piston, which are arranged in a drum formed as a single piece with the rim to constitute a dry-operating drum brake.

[0004] Integration of both the electric machine and the drum brake is obtained in the wheel rim, which limits the number of components.

[0005] However, the integration of a dry-working brake and the electric machine into the wheel poses problems, in particular wear of the brake linings which releases dust that soils the environment, and which can disrupt the operation of nearby components such as the electric machine or the bearings.

[0006] Other problems arise for this type of dry-working brake, such as wear of the drum brake linings altering the operating geometry which changes the braking characteristics, dissipation of wear particles into the atmosphere which is becoming regulated to limit these emissions, or under certain operating conditions noises from squeaking.

[0007] Furthermore, this motorization system, which provides a rotor speed of the electric machine equal to that of the wheel without any intermediate gearing, requires a machine that directly delivers the required torque to the wheel. This does not allow for optimization of the wheel's speed and torque level, leading to problems with the machine's mass, compactness, and cost. The resulting electric machine is centered on the wheel's axle and is relatively heavy, creating a significant unsprung mass that hinders suspension performance, compromising comfort and road handling.

[0008] Another known motorization system comprises a suspension arm pivoting at one end, receiving at the other end the wheel including its drum brake working dry disposed on its axle, this arm forming a casing receiving the electric machine offset from the axle of the wheel and its reducer which are integrated inside.

[0009] Two distinct sub-assemblies are also obtained, formed by the reducer of the electric machine containing a lubricating fluid and the drum brake working dry, each comprising their housings which add unsprung masses and volumes to the suspension.

[0010] The present invention is specifically designed to avoid these problems of the prior art.

[0011] To this end, it proposes a transmission system for a vehicle wheel automobile, comprising a wheel brake, this system being remarkable in that it includes a drum arranged along the wheel axis and rotating with the wheel, containing the wheel brake in a lubricating fluid, a ring with internal teeth linked to the drum, and a pinion engaged with this ring, achieving a multiplication of the movement received from a motor.

[0012] An advantage of this transmission system is that in the same casing the crown with the pinion lubricated by the fluid performing the multiplication of the motorization movement can be arranged, making it possible to make for the motorization a compact machine of reduced mass, and the brake linings working in this fluid which provides low wear, no dissipation of particles into the atmosphere, and greater stability of braking operation, with in particular cooling provided by a circulation of the fluid.

[0013] Moreover, in the case of a motor fixed to a suspension arm in the axis of the pinion, this motor can be offset towards the pivot of this arm, which reduces the unsprung masses.

[0014] The transmission system according to the invention may further comprise one or more of the following features, which may be combined with each other.

[0015] Advantageously, the drum contains a cylindrical braking track which is arranged axially next to the internally toothed ring.

[0016] In this case, the braking track can be formed directly by the cylindrical internal surface of the drum.

[0017] Advantageously, the drum has towards the inner side of the vehicle an opening closed by a fixed circular plate with a dynamic sealing joint between them.

[0018] Advantageously, the transmission system includes a filter disposed in a fluid circulation circuit.

[0019] According to one embodiment, the transmission system includes a suspension arm comprising on its outer side a hub receiving the drum carrying the wheel.

[0020] In this case, the transmission system may include an electric machine disposed on the inner side of the suspension arm, receiving the pinion on its shaft.

[0021] According to one embodiment, the suspension arm includes a pivot for fixing to the vehicle body which is formed parallel to the wheel axis, at the end opposite the wheel hub.

[0022] In this case, advantageously the pinion is arranged between the wheel axle and the suspension pivot.

[0023] The invention also relates to an electric or hybrid motor vehicle, remarkable in that it comprises a transmission system including any of the preceding characteristics, which is fixed on a suspension arm.

[0024] The invention will be better understood and other features and advantages will become more apparent upon reading the following description given by way of example, with reference to the accompanying drawings in which:

[0025] [Fig-1] is a perspective diagram of a transmission system according to the invention fixed on a rear suspension arm of the vehicle;

[0026] [Fig.2] is a cross-sectional diagram of this transmission system passing through the wheel axle; and

[0027] [Fig.3] is a side view diagram of the suspension arm.

[0028] Throughout the document the external direction is on a transverse axis of the vehicle turned towards its external side.

[0029] Figures 1, 2 and 3 show a rear wheel suspension arm 2 of a vehicle 10, fixed to the vehicle body by a front transverse pivot 4 arranged along a suspension axis 6, which receives at the rear on the outside side a fixed wheel hub 8 arranged along a wheel axis 12.

[0030] A drum 14 has a transverse face turned towards the outside of the vehicle EXT, fixed to the wheel hub 8 by bearings, which supports a rim 30 of the wheel 10 receiving a tire, and has a cylindrical part turned towards the suspension arm 2.

[0031] A circular plate 16 fixed on the outer face of the suspension arm 2, centered on the wheel axle 12, has on its contour a dynamic sealing joint 34 in contact with the inner edge of the cylindrical part of the drum 14 in order to ensure a seal in the closed inner volume of the drum.

[0032] An electric machine 18, arranged along a transverse axis of machine 20, is fixed to the inner face of the suspension arm 2 at a distance D forward of the wheel axle 12. The shaft of the electric machine 18 enters the drum 14 by a drilling of the fixed plate 16 with a seal, carries a motor pinion 22 engaged in the teeth of an internally toothed ring 24, which is centered and fixed in this drum near the plate to form a transmission including a speed reduction.

[0033] A braking device formed in the drum 14 on the inner side of the toothed ring 24, comprises two circular-arc linings 36 held on the outer face of the plate 16, which are pressed on a cylindrical track 32 formed directly on the inner surface of the drum by a hydraulic piston disposed between these two linings.

[0034] The braking device used as a service brake can also be used as a parking brake by providing a control for this brake which remains locked.

[0035] By placing a volume of lubricating fluid in the closed drum 14 with a sealing gasket 34, we obtain both for the transmission including the gear of the pinion 22 and the toothed ring 24, and for the braking device lubrication, and cooling thanks to the fluid circulating inside, and distributing the heat generated by friction over all the external surfaces which facilitates their evacuation.

[0036] Optionally, external cooling fins can be provided, in particular on the drum 14 and on the fixed plate 16, to promote exchanges with the outside air, particularly during prolonged braking.

[0037] The transmission system includes a filter inserted in the fluid circulation, which retains brake lining wear particles carried in the fluid in order to recover them for purification. The transmission system also includes a fluid drain option, allowing the fluid laden with particles to be renewed during maintenance operations. The circuit may additionally include a fluid circulation pump and an external cooling circuit comprising a heat exchanger radiator.

[0038] It should be noted that the wet brake, in the closed and sealed volume of the drum, no longer emits dust into the ambient air, which complies with the new regulations relating to this problem.

[0039] Thanks to the speed reducer, the electric machine 18 rotates at a significantly higher speed than that of the wheel 10, which makes it possible to provide a reduced machine torque in the same proportion as the torque required on the drive wheel, giving a machine with a reduced mass and a small volume.

[0040] The electric machine 18, having a low mass, is brought closer to the axis 6 of the suspension arm 2 by a distance D relative to the wheel axle 12, resulting in a significantly reduced unsprung mass at the wheel 10. compared to a machine located on this wheel axle. Vehicle comfort and road handling are improved.

[0041] Alternatively, the wheel brake can be a disc brake working in the fluid, comprising several superimposed discs connected alternately to the rotating drum 14 and the fixed wheel hub 8, with axial clamping by a hydraulic piston following a technology commonly used in machines.

[0042] It should be noted that brakes working in the fluid show very little wear, which may allow for a braking system to last the entire life of the vehicle without maintenance.

[0043] A wheel transmission system for an electric or hybrid vehicle is obtained which has a high compactness, a low mass, and good efficiency in particular thanks to a single gear between the motor 18 and the wheel 10.

[0044] In general, other types of motorization can be used on the transmission system according to the invention, such as an electric machine detached from the suspension arm and connected to the pinion 22 by a shaft.

Claims

Demands

1. Transmission system for a motor vehicle wheel, comprising a wheel brake, characterized in that it comprises a drum (14) disposed along the wheel axle (12) and rotating with this wheel (10), containing the wheel brake in a lubricating fluid, an internally toothed ring (24) linked to the drum (14), and a pinion (22) engaged with this ring (24), achieving a reduction of the motion received from a motor (18).

2. Transmission system according to claim 1, characterized in that the drum (14) contains a cylindrical braking track (32) which is arranged axially next to the internal toothed ring (24).

3. Transmission system according to claim 2, characterized in that the braking track (32) is formed directly by the cylindrical internal surface of the drum (14).

4. Transmission system according to any one of the preceding claims, characterized in that the drum (14) has towards the inner side of the vehicle an opening closed by a fixed circular plate (16) with a dynamic sealing joint (34) between them.

5. Transmission system according to any one of the preceding claims, characterized in that it comprises a filter disposed in a fluid circulation circuit.

6. Transmission system according to any one of the preceding claims, characterized in that it comprises a suspension arm (2) including on its outer side a hub (8) receiving the drum (14) carrying the wheel (10).

7. Transmission system according to claim 6, characterized in that it comprises an electric machine (18) disposed on the inner side of the suspension arm (2), receiving the pinion (22) on its shaft.

8. Transmission system according to claim 6 or 7, characterized in that the suspension arm (2) has a pivot (4) for attachment to the vehicle body which is formed parallel to the wheel axle (12), at the end opposite the wheel hub (8).

9. Transmission system according to claim 8, characterized in that the pinion (22) is disposed between the wheel axle (12) and the suspension pivot (4).

10. Electric or hybrid motor vehicle, characterized in that it comprises a transmission system according to any one of the preceding claims, which is fixed on a suspension arm (2).