REDUCTION MOTOR FOR DRUM BRAKE

Abstract

A reduction motor for a parking brake mechanical actuator of a drum brake comprising an electric motor and a reduction gearbox, in which the electric motor comprises an output shaft extending along a first axis, the reduction gearbox comprises an output shaft extending along a second axis, and in which the reduction motor also comprises at least one angle gear between the electric motor and the reduction gearbox or at the output of the reduction gearbox, the angle gear comprising a crown gear-pair comprising a pinion and a crown gear, the pinion being engaged with the output shaft of the electric motor and meshing with the crown gear which is a part of the reduction gearbox.

Claims

1.-14. (canceled)

15. A geared motor for a mechanical parking brake actuator of a drum brake including an electric motor and a reduction gearbox, wherein the electric motor has an output shaft extending along a first axis, the reduction gearbox includes an output axis extending along a second axis, and wherein the geared motor also includes at least one angle transmission between the electric motor and the reduction gearbox or at the output of the reduction gearbox, said angle transmission comprising a crown gear.

16. The geared motor according to claim 15, wherein the angle transmission comprises a pinion and the crown gear, the pinion being engaged with the output shaft of the electric motor and meshing with the crown gear which is part of the reduction gearbox.

17. The geared motor according to claim 16, wherein the crown gear is rotatably integral with a pinion and forms a stepped gear therewith.

18. The geared motor according to claim 15, wherein the angle transmission includes a pinion for meshing with a toothed wheel of the mechanical actuator of the drum brake, the pinion forming a ring gear carried by a face of a toothed wheel, the ring gear and the toothed wheel forming a stepped gear.

19. The geared motor according to claim 15, including a first angle transmission and a second angle transmission, wherein the first angle transmission includes a pinion and the crown gear, the pinion being engaged with the output shaft of the electric motor and meshing with the crown gear which is part of the reduction gearbox, and wherein the second angle transmission includes a pinion for meshing with a toothed wheel of the mechanical actuator of the drum brake, the pinion forming a ring gear carried by a face of a toothed wheel, the ring gear and the toothed wheel forming a stepped gear.

20. The geared motor according to claim 15, wherein the reduction gearbox includes one or more stepped gears each including a toothed wheel and a pinion, the toothed wheel and the pinion being coaxial.

21. The geared motor according to claim 20, wherein the axes of the stepped gears are orthogonal to the first axis of the electric motor.

22. The geared motor according to claim 20, including four to six stepped gears.

23. A drum brake including a drum, a backing plate, two shoes, and a mechanical actuator attached to the backing plate for parking braking, and a geared motor according to claim 15.

24. A geared motor for a mechanical parking brake actuator of a drum brake including an electric motor and a reduction gear, wherein the electric motor includes an output shaft extending along a first axis, the reduction gear includes an output axis extending along a second axis, and wherein the geared motor also includes at least one angle transmission between the electric motor and the reduction gear, said angle transmission comprising a crown gear.

25. The geared motor according to claim 24, wherein the angle transmission comprises a pinion and the crown gear, the pinion being engaged with the output shaft of the electric motor and meshing with the crown gear which is part of the reduction gearbox.

26. The geared motor according to claim 25, wherein the crown gear is rotatably integral with a pinion and forms a stepped gear therewith.

27. The geared motor according to claim 24, wherein the reduction gearbox includes one or more stepped gears each including a toothed wheel and a pinion, the toothed wheel and the pinion being coaxial.

28. The geared motor according to claim 27, wherein the axes of the stepped gears are orthogonal to the first axis of the electric motor.

29. The geared motor according to claim 24, wherein the first axis and the second axis are intersecting.

30. The geared motor according to claim 24, wherein the first axis and the second axis are intersecting.

31. A drum brake including a drum, a backing plate, two shoes, and a mechanical actuator attached to the backing plate for parking braking, and a geared motor according to claim 24.

32. A geared motor for a mechanical parking brake actuator of a drum brake including an electric motor and a reduction gearbox, wherein the electric motor includes an output shaft extending along a first axis, the reduction gearbox includes an output axis extending along a second axis, and wherein the geared motor also includes at least one angle transmission at the output of the reduction gearbox, said angle transmission comprising a crown gear, a pinion for meshing with a toothed wheel of the mechanical actuator of the drum brake, the pinion forming a ring gear carried by a face of a toothed wheel, the ring gear and the toothed wheel forming a stepped gear.

33. The geared motor according to claim 32, wherein the reduction gearbox includes one or more stepped gears each including a toothed wheel and a pinion, the toothed wheel and the pinion being coaxial.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention will be better understood using the following description and the appended drawings in which:

[0032] FIG. 1 is a perspective view of a drum brake with electric parking brake actuator according to the state of the art.

[0033] FIG. 2 is a perspective view of a drum brake fitted with a geared motor according to one exemplary embodiment of the present invention, the drum and the cover of the geared motor housing not being represented.

[0034] FIG. 3 is a detail view of FIG. 2 at the angle transmission at the motor output.

[0035] FIG. 4 is a side view of the angle transmission of FIG. 3.

[0036] FIG. 5 is a perspective view of the mounting of a drum brake with a geared motor according to an exemplary embodiment of the present invention and drum brake on a vehicle chassis, with the drum and the cover of the housing omitted.

DETAILED DISCLOSURE OF PARTICULAR EMBODIMENTS

[0037] In FIG. 2, a perspective view of one advantageous example of a geared motor MR1 according to the invention associated with a drum brake 1 comprising an electric parking brake actuator 7 can be seen.

[0038] The geared motor MR1 includes an electric motor 21 and a transmission module or reduction gearbox 32.

[0039] In the example represented, the electric motor 21 and its output shaft 24 extend along axis AY and the output axis of the transmission module extends along an axis AZ orthogonal to axes AY and AZ.

[0040] In this example, the transmission module is intended to extend in parallel to the backing plate 2.

[0041] In the example represented, advantageously, the kinematic chain of the transmission module is in the form of a so-called compound reduction in which the gear elements are in the form of a linear train of externally contacting stepped gears, preferably four to six in number. In the example of FIG. 2, there are five stepped gears 34, 35, 36, 37 and 38.

[0042] The stepped gears 34, 35, 36 and 37 respectively comprise a first step in the form of a toothed wheel 34a, 35a, 36a, 37a and a second step in the form of a pinion 34b, 35b, 36b, 37b rigidly connected to the corresponding toothed wheel with a smaller diameter than the latter. The gear 38 comprises a toothed wheel 38a and a ring gear 38b.

[0043] The stepped gears 34, 35, 36, 37 and 38 are each arranged to be rotatably mounted about a distinct fixed axis AX34, AX35, AX36, AX37 and AX38, each of these axes being parallel to each other and arranged in that order along the direction of reduction, i.e. from the motor pinion to the mechanical actuator 7. They are especially dimensioned so that the pinion forming the output of one gear meshes with the toothed wheel of the next gear, with the toothed wheel 34a forming the input element of the kinematic chain, while the pinion 38b forms the output element of this chain.

[0044] Alternatively, the transmission module includes pinions and single toothed wheels or single pinions and toothed wheels and stepped pinions. Their number and the number of teeth of each of them are set by the desired reduction.

[0045] Furthermore, the geared motor MR1 has a first angle transmission 44 connecting the motor 21 and the transmission module 32 and a second angle transmission 46 connecting the output of the transmission module and the actuator 7.

[0046] The first angle transmission 44 is advantageously of the crown gear type and comprises a pinion 25 and a crown gear 34a, the pinion 25 meshing with the crown gear 34a. The pinion 25 is engaged with the output shaft 24 of the electric motor 21.

[0047] The crown gear 34a has a wheel with teeth formed in a ring on one side of the wheel. In FIG. 3, the crown gear is represented alone.

[0048] The angle transmission with a crown gear offers the advantage of offering freedom in orienting the axis of the pinion 25 with respect to the axis of the toothed wheel 34a, i.e. a great freedom in selecting the angle of the angle transmission. Indeed, the angle α between the AX34-axis and the axis AY can vary from 30° to 135°. This gives a wide choice of orientations between the motor and the transmission module, to adapt the shape of the geared motor to that of the available space. Further, requirements on mounting accuracy are reduced.

[0049] In addition, the position of the teeth of the pinion 25 relative to the teeth of the toothed wheel 34a can vary. In FIG. 4, the length of meshing Le corresponds to the length of the zone where the teeth of the pinion engage the teeth of the toothed wheel 34a. The pinion 25 can be arranged with respect to the toothed wheel with a clearance j. The clearance j is between +/−1/100 mm and +/−10 mm, advantageously between +/−1/10 mm and +/−5 mm, preferably between +/−1 mm and +/−3 mm and even more preferably between +/−2 mm.

[0050] This assembly clearance allowed by the crown gear contributes to offering greater freedom in the arrangement of the various elements of the geared motor. The requirements of mounting accuracy are also more relaxed.

[0051] In addition, an angle transmission with a crown gear offers an efficiency of 97% to 99%. In comparison, the efficiency of an angle transmission with a bevel gear is about 30% lower than that of an angle transmission with a crown gear.

[0052] Advantageously, in the example represented, the second angle transmission also has a crown gear. The toothed wheel 38a, which is driven by the pinion 37b, carries on one of its faces, the upper face in the representation of FIG. 2, the pinion 38b which meshes with a toothed wheel 48 of a transmission gear 52 which transmits the rotation of the geared motor to the actuator 7. The transmission gear 52 includes wheels 48, 50 with parallel axes.

[0053] The pinion 38b includes a ring gear. The pinion 38b and the toothed wheel 48 form the crown gear of the second angle transmission of the actuator.

[0054] In the example represented, the transmission gear 55 includes the toothed wheel 48 and a toothed wheel 52, which causes pistons bearing on the ends of the brake shoes to be moved apart and moves them apart towards the drum.

[0055] Alternatively, the geared motor includes an angle transmission with a crown gear and a conical angle transmission.

[0056] In FIG. 5, another example of geared motors MR2 according to the invention including an angle transmission 46 at the output only can be seen. In this example, the output shaft of the electric motor drives the toothed wheel 34a directly. The reduction of each meshed toothed wheel/pinion pair is adapted so that the total reduction is as expected. Indeed, in this example one reduction step is removed relative to the example in FIG. 2.

[0057] In another example not represented, the toothed wheel at the output directly meshes with the toothed wheel teeth of the actuator. In this case, the axes of the stepped gears are orthogonal to the axes of the stepped gears in FIG. 2.

[0058] Furthermore, the implementation of a reduction gearbox in the form of a stepped gear train also offers a great deal of freedom in the form that the reduction gearbox can take. The relative arrangement of the axes of the stepped gears is free, with only the distances between the axes being set to ensure tangential meshing of a pinion and a toothed wheel. As a result, the gear train can have a more or less extended shape and thus be adapted to the available environment around the wheel. For example, the gear train can have a curved form or S-shaped form.

[0059] Advantageously, the shafts are integral with a plate 53 which is mounted in the bottom of a housing 54 housing the gear train. For example, they are made in one piece with the plate 53 by moulding, or they are made of a metal material and are overmoulded in a plate of plastic material.

[0060] The housing 54 is advantageously configured to follow the contours of the gears as closely as possible in order to further reduce the overall size of the geared motor.

[0061] In the example represented, the housing includes two parts, a first part 54.2 including the bottom on which the plate 53 carrying the axes of the stepped gears rests and a second part (not shown) forming a cover.

[0062] Advantageously, the first and second parts include a flat bottom. Alternatively, the cover follows the contours of the gears.

[0063] The first and second parts may be symmetrical with respect to a plane passing through the junction zone between the first and second parts.

[0064] The housing is advantageously made by moulding plastic material.

[0065] Advantageously, the housing 54 includes means 56 for attaching the geared motor to the drum brake, more particularly to the backing plate in order to limit movements of the geared motor which could damage it and/or generate undesirable noise. For example, the means 56 for attaching the geared motor to the plate include screw holes 58 passing through the housing 54 in the X direction outside the gears and in which screws are to be mounted, which cooperate with corresponding openings provided in the plate.

REFERENCES

[0066] 1: drum brake [0067] 2: backing plate [0068] 3: first shoe [0069] 4: second shoe [0070] 3a, 4a: brake webs [0071] 3b, 4b: brake linings [0072] 6: hydraulic wheel cylinder [0073] 7: mechanical actuator [0074] 8, 9: return springs [0075] 10, 11: lateral springs [0076] 12: wear take-up rod [0077] 21: electric motor [0078] 24: output shaft [0079] 25: pinion [0080] 32: reduction gearbox [0081] 34; 35, 36, 37, 38: stepped gears [0082] 34a, 35a, 36a, 37a, 38a: toothed wheels [0083] 34b, 35b, 3.6b, 37b, 38b: pinions [0084] 44: first angle transmission [0085] 46: second angle transmission [0086] 48: transmission gear [0087] 50, 52: toothed wheels of the transmission gear [0088] 53: plate [0089] 54: housing [0090] 54.1: first part of the housing [0091] 56: means for attaching the geared motor to the plate [0092] 58: screw holes [0093] AX, AY: axes [0094] AX34, AX35, AX36, AX37, AX38: axes of gears 34; 35, 36, 37, 38 [0095] Le: meshing length [0096] MR1, MR2: geared motor