Reduction motor for drum brakes

Abstract

A reduction motor for a parking brake mechanical actuator (7) for a drum brake, the reduction motor comprising an electric motor (21) and a reduction box (32), wherein the electric motor (21) comprises an output shaft (24) extending along a first axis, the reduction box (32) comprises an output axis extending along a second axis, and wherein the reduction motor further comprises at least one angle device (44) between the electric motor (21) and the reduction box (32) or at the output end of the reduction box (32), the angle device (44) comprising a flat wheel gear pair, the flat wheel gear pair comprising a pinion (25) and a flat gear (34a), the pinion (25) being engaged with the output shaft (24) of the electric motor (21) and meshing with the flat gear (34a) which is part of the reduction box (32).

Description

Technical Field

[0001] The present invention relates to the field of automotive vehicle brakes, and more particularly to a geared motor assembly for operating a shoe of a drum brake to provide reduced overall size. Background Art

[0002] In the automotive industry, the function of an electromechanical parking brake is to stop a stationary vehicle in order to prevent the vehicle from moving unexpectedly. In addition, the invention meets the legal requirements for a second brake system in a vehicle that is independent of the usual hydraulic service brake system and implements further comfort and safety functions, in particular through its self-diagnostic capability.

[0003] It is known from document FR3016015 that, in addition to the hydraulic actuator initially provided, a mechanical actuator can also be installed in a drum brake. Figure 1 The drum brake, marked with 1, comprises a back plate 2 rotating around an axis AX, which is provided with a first arcuate shoe 3 and a second arcuate shoe 4 which are radially movable so that the arcuate shoe can be pressed against a cylindrical inner surface (not shown) of a drum member.

[0004] The shoes 3 and 4 each have a connecting plate 3a, 4a made of a flat metal plate in the form of a circle section, which carries the brake linings 3b, 4b and is mounted radially opposite to each other, with the ends of the shoes bearing on a hydraulic wheel cylinder 6 and a mechanical actuator 7 carried by the back plate 2. These shoes 3 and 4 are further biased toward each other by two return springs 8 and 9 and are pressed against the back plate 2 by springs 10, 11 respectively.

[0005] The wear winding rod 12 extends along the wheel cylinder 6 , a first end of the wear winding rod is supported on the connecting plate 3 a of the first shoe 3 , and a second end of the wear winding rod is supported on the connecting plate 4 a of the second shoe 4 .

[0006] When using the drum brake 1, the wheel cylinder 6 is actuated according to a first operating mode, called "single", which provides progressive braking particularly suitable for braking a vehicle in motion. The wheel cylinder comprises a hydraulic chamber closed at its ends by two pistons which move apart and push the relative ends of the shoes 3 and 4 when the hydraulic pressure increases.

[0007] The mechanical actuator 7 in turn provides parking and emergency braking by moving the relevant ends of the shoe apart, in particular when the wheel cylinder 6 is inoperative, according to the so-called "double servo" operating mode to provide a fast and powerful locking of the wheels of the vehicle. The actuator is driven by an electric motor 21 having an axis AY.

[0008] Indeed, one of the difficulties associated with the use of mechanical actuators is the need to convert the high rotation speeds associated with the low torque of the electric motor into a low displacement with sufficient load. To this end, document FR3016015 teaches the provision of a reduction module that transmits the rotation of the motor 21 to the mechanical actuator 7, more precisely the rotation of the axis AY motor pinion driven directly by the motor. The reduction module is centered on the axis AY and comprises a plurality of steps of an axis AY planetary gear train so as to provide an effective reduction between the output measured at the axis AY output gear coupled to the mechanical actuator 7 and the input measured at the motor pinion. Furthermore, the motor 21 and the reduction module are housed together in a cylindrical housing.

[0009] This architecture of the geared motor, i.e. the combination of the motor 21 and the reduction module requires that the axis of the motor be arranged parallel to the axis of the planetary gear train and the axis of the reduction module be arranged parallel to the axis of the toothed wheel of the mechanical actuator 7. Therefore, the arrangement of the motor relative to the reduction module is set, and the orientation of the geared motor relative to the drum brake plate is also set.

[0010] However, it is desirable to be able to produce a geared motor whose architecture can be adapted to different configurations of available space at the wheel. Furthermore, prior art geared motors are geared motors of large overall size. Summary of the invention

[0011] It is therefore an object of the present invention to provide a geared motor, for example for actuating a parking brake of a drum brake, which geared motor can be easily adapted to different configurations at the wheel.

[0012] The above objects are achieved by a geared motor comprising at least one angular transmission formed by a crown gear.

[0013] On the one hand, the implementation of the angular transmission provides greater freedom in the construction of the geared motor and / or in the orientation of the geared motor relative to the mechanical actuator of the drum brake. On the other hand, the implementation of the angular transmission with a crown gear provides great freedom in choosing the orientation of the output shaft of the motor relative to the reduction gearbox.

[0014] Furthermore, within the crown wheel, the meshing position of the pinion teeth relative to the crown wheel teeth can be varied without changing the operation of the angular transmission, thereby providing an additional degree of freedom in the construction of the geared motor.

[0015] Advantageously, the geared motor may have reduced overall dimensions.

[0016] Very advantageously, an angular transmission with a crown gear connects the motor and the reduction gearbox. For example, a pinion is attached to the output shaft of the electric motor and meshes with a crown gear forming part of the reduction gearbox. For example, the pinion is arranged coaxially with the crown gear and is rotatably integral with the crown gear and drives a toothed wheel of the reduction gearbox.

[0017] Advantageously, an angular transmission connects the output of the reduction gearbox and the parking brake actuator, and the angular transmission comprises a crown gear.

[0018] Preferably, the reduction gear box includes an externally contacted stepped gear system, each gear system includes a juxtaposed pinion and a toothed wheel, in each stepped gear, the pinion and the toothed wheel are coaxial and rotatably stacked on each other into a whole, and the pinion of one gear meshes with the toothed wheel of an adjacent stepped gear.

[0019] Producing such a reduction gearbox provides additional degrees of freedom in the construction of the geared motor.

[0020] One subject of the invention is therefore to provide a geared motor for a mechanical parking brake actuator of a drum brake, the geared motor comprising an electric motor and a reduction gearbox, the electric motor comprising an output shaft extending along a first axis, and the reduction gearbox comprising an output axis extending along a second axis. The geared motor also comprises at least one angular transmission between the electric motor and the reduction gearbox or at the output end of the reduction gearbox, the angular transmission comprising a crown gear.

[0021] Advantageously, the angular transmission comprises a pinion and a crown gear, the pinion being engaged with the output shaft of the electric motor and meshing with the crown gear being part of the reduction gearbox.

[0022] The crown gear may be rotatably integral with the pinion gear and form a stepped gear with the pinion gear.

[0023] The angular transmission may comprise a pinion for meshing with a toothed wheel of a mechanical actuator of the drum brake, the pinion forming a toothed ring carried by a surface of the toothed wheel, the toothed ring and the toothed wheel forming a stepped gear.

[0024] Advantageously, the geared motor comprises a first angular transmission 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 being part of the reduction gearbox, and a second angular transmission comprising a pinion for meshing with a toothed wheel of a mechanical actuator of the drum brake, the pinion forming a toothed ring carried by the surface of the toothed wheel, the toothed ring and the toothed wheel forming a stepped gear.

[0025] For example, the reduction gearbox includes one or more stepped gears, each stepped gear includes a toothed wheel and a pinion, and the toothed wheel and the pinion are coaxial, for example, the number of the stepped gears is between four and six.

[0026] Advantageously, the axis of the stepped gear is orthogonal to the first axis of the electric motor.

[0027] Advantageously, the first axis and the second axis intersect.

[0028] Another subject of the invention is a drum brake comprising a drum, a back plate, two shoes, a mechanical actuator attached to the back plate for parking braking and a geared motor according to the invention.

[0029] Preferably, the axis of the stepped gear is parallel to the axis of the drum.

[0030] The reduction housing may include a housing having two parallel flat surfaces extending parallel to the brake back plate. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0033] Figure 2 is a perspective view of a drum brake equipped with a geared motor according to an exemplary embodiment of the present invention, without showing a drum and a cover of a geared motor accommodation portion.

[0034] Figure 3 yes Figure 2 Detailed view of the angle gear at the motor output.

[0035] Figure 4 yes Figure 3 Side view of the angular transmission.

[0036] Figure 5 is a perspective view of a drum brake having a geared motor and installation of the drum brake on a vehicle chassis according to an exemplary embodiment of the present invention, with a drum and a cover of an accommodation portion omitted. DETAILED DESCRIPTION

[0037] exist Figure 2 In it can be seen a perspective view of an advantageous example of a geared motor MR1 according to the invention in connection with a drum brake 1 comprising an electric parking brake actuator 7 .

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

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

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

[0041] In the example shown, the kinematic chain of the transmission module is advantageously 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, the number of which is preferably four to six. Figure 2 In the example of FIG. 3 , 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 toothed wheels 34a, 35a, 36a, 37a and a second step in the form of third pinions 34b, 35b, 36b, 37b, which are rigidly connected to the corresponding toothed wheels and have a smaller diameter than the corresponding toothed wheels. The gear 38 comprises a first pinion 38b and a second toothed wheel 38a.

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

[0044] Alternatively, the transmission module comprises a pinion and a single toothed wheel, or a single pinion and a toothed wheel and a stepped pinion. The number of these gears and the number of teeth of each of these gears is set by the required speed reduction.

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

[0046] Advantageously, the first angular transmission 44 is of the crown gear type and comprises a second pinion 25 and a crown gear 34a with which the second pinion 25 meshes. The second pinion 25 engages with the output shaft 24 of the electric motor 21 .

[0047] The crown gear 34a has a wheel with teeth forming a ring on one side of the wheel. Figure 3 , the crown gear is shown separately.

[0048] The angular transmission with crown gear offers the advantage of providing a degree of freedom in the orientation of the axis of the second pinion 25 relative to the axis of the toothed wheel 34a, i.e. a large degree of freedom in the choice of the angle of the angular transmission. In practice, the angle α between the axis AX34 and the axis AY can vary from 30° to 135°. This offers a wide range of options for the orientation between the motor and the transmission module, in order to adapt the shape of the geared motor to the shape of the available space. In addition, the requirements for mounting precision are reduced.

[0049] In addition, the position of the teeth of the second pinion 25 relative to the teeth of the toothed wheel 34a can be varied. Figure 4 , the meshing length Le corresponds to the length of the area where the teeth of the pinion engage with the teeth of the toothed wheel 34a. The second pinion 25 can be arranged with a clearance j relative to the toothed wheel. 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, even more preferably between + / -2 mm.

[0050] This assembly clearance made possible by the crown gear helps to provide greater freedom in the arrangement of the various elements of the geared motor. The requirements on mounting accuracy are also more relaxed.

[0051] In addition, the angular transmission with crown gear provides 97% to 99% efficiency. In contrast, the efficiency of the angular transmission with bevel gear is about 30% lower than that of the angular transmission with crown gear.

[0052] Advantageously, in the example shown, the second angular transmission also has a crown gear. The second toothed wheel 38a driven by the pinion 37b has a crown gear on one of its surfaces, namely on Figure 2 The upper surface shown carries a first pinion 38b which meshes with a first toothed wheel 48 of a transmission 52 which transmits the rotation of the geared motor to the actuator 7. The transmission comprises a first toothed wheel 48, a wheel 50 having parallel axes.

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

[0054] In the example shown, the transmission 55 comprises a first toothed wheel 48 and a toothed wheel 52 which causes the pistons supported on the ends of the brake shoes to move away and towards the drum.

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

[0056] exist Figure 5 In FIG. 1 , another example of a geared motor MR2 according to the invention can be seen, which includes an angular transmission 46 only at the output end. In this example, the output shaft of the electric motor directly drives the toothed wheel 34a. The reduction in speed of each meshing toothed wheel / pinion pair is adapted so that the total reduction is as desired. In fact, in this example, relative to Figure 2 The example in removes one deceleration step.

[0057] In another example not shown, the toothed wheel at the output directly meshes with the teeth of the toothed wheel of the actuator. In this case, the axis of the stepped gear is orthogonal to Figure 2 The axis of the stepped gear in.

[0058] Furthermore, the implementation of the reduction gearbox in the form of a stepped gear train also provides a large number of degrees of freedom in the form that the reduction gearbox can adopt. The relative arrangement of the axes of the stepped gears is free, only the distance between the axes is set to ensure the tangential meshing of the pinion and the 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 curvilinear form or an S-shaped form.

[0059] Advantageously, the shaft is integral with a plate 53 mounted in the bottom of a housing 54 housing the gear train. For example, the shaft is made in one piece with the plate 53 by molding, or the shaft is made of metal material and overmolded in a plate of plastic material.

[0060] Advantageously, the housing 54 is configured to follow as closely as possible the contour of the gear wheel, in order to further reduce the overall size of the geared motor.

[0061] In the example shown, the housing comprises two parts, a first part 54 . 2 comprising a bottom against which rests a plate 53 carrying the axis of the stepped gear, and a second part (not shown) forming a cover.

[0062] Advantageously, the first and second parts comprise a flat bottom.Alternatively, the cover follows the contour of the gear.

[0063] The first portion and the second portion may be symmetrical about a plane passing through a connection region between the first portion and the second portion.

[0064] Advantageously, the housing is made by moulding a plastic material.

[0065] Advantageously, the housing 54 comprises means 56 for attaching the geared motor to the drum brake, more specifically to the back plate, in order to limit movements of the geared motor that could damage the geared motor and / or generate undesirable noises. For example, the means 56 for attaching the geared motor to the plate comprise screw holes 58 that pass through the housing 54 outside the gear along the X direction and in which screws are to be mounted, which screw holes cooperate with corresponding openings provided in the plate.

[0066] Reference numerals 1: Drum brake

[0067] 2: Back panel

[0068] 3: First hoof

[0069] 4: Second hoof

[0070] 3a, 4a: Brake connecting plate

[0071] 3b, 4b: Brake linings

[0072] 6: Hydraulic wheel cylinder

[0073] 7: Mechanical actuator

[0074] 8, 9: Return spring

[0075] 10, 11: Lateral spring

[0076] 12: Worn winding rod

[0077] 21: Electric Motor

[0078] 24: Output shaft

[0079] 25: Second small gear

[0080] 32: Gearbox

[0081] 34, 35, 36, 37, 38: Stepped gears

[0082] 34a, 35a, 36a, 37a: Toothed wheels

[0083] 38a: Second toothed wheel

[0084] 35b, 36b, 37b: small gear

[0085] 38b: First pinion

[0086] 34b: Third pinion

[0087] 44: First angle transmission device

[0088] 46: Second angle transmission device

[0089] 48: First toothed wheel

[0090] 50, 52: Toothed wheel of transmission device

[0091] 53: Board

[0092] 54: Accommodation

[0093] 54.1: The first part of the receiving portion

[0094] 56: Means for attaching a geared motor to a plate

[0095] 58: Screw hole

[0096] AX, AY: axis

[0097] AX34, AX35, AX36, AX37, AX38: Axis of gears 34, 35, 36, 37, 38

[0098] Le: engagement length

[0099] MR1, MR2: geared motors.

Claims

1. A geared motor for a mechanical parking brake actuator (7) of a drum brake, the geared motor comprising an electric motor (21) and a reduction gearbox (32), wherein: The electric motor (21) includes an output shaft (24) extending along a first axis, the reduction gearbox (32) includes an output axis extending along a second axis, and wherein the geared motor also includes at least one angular transmission device (46) at the output end of the reduction gearbox (32), the angular transmission device (46) including a first crown gear, a first pinion (38b) for meshing with a first toothed wheel (48) of the mechanical parking brake actuator (7) of the drum brake, the first pinion (38b) forming a ring gear carried by the surface of a second toothed wheel (38a), the ring gear and the second toothed wheel (38a) forming a first stepped gear.

2. A geared motor according to claim 1, comprising another angular transmission device (44) arranged between the electric motor (21) and the reduction box (32), the other angular transmission device comprising a second pinion (25) and a second crown gear (34a), the second pinion (25) being engaged with the output shaft (24) of the electric motor (21) and meshing with the second crown gear (34a) which is part of the reduction box (32).

3. The geared motor according to claim 2, wherein: The second crown gear (34a) is rotatably integrated with the third pinion gear (34b) and forms a second stepped gear (34) with the third pinion gear.

4. The geared motor according to claim 1, wherein: The reduction gearbox comprises one or more stepped gears (34, 35, 36, 37, 38), each stepped gear comprising a coaxial toothed wheel and a pinion.

5. The geared motor according to claim 4, wherein: The axis of the stepped gear (34, 35, 36, 37, 38) is orthogonal to the first axis of the electric motor (21).

6. The geared motor of claim 4, comprising four to six stepped gears.

7. The geared motor according to claim 1, wherein: The first axis and the second axis intersect.

8. A drum brake comprising a drum, a back plate (2), two shoes (3, 4), a mechanical parking brake actuator (7) attached to the back plate (2) for parking braking and a geared motor according to any one of claims 1 to 7.

9. The drum brake according to claim 8, wherein: The axis of the stepped gear is parallel to the axis of the drum.

10. The drum brake according to claim 8 or 9, wherein: The reduction box includes a receiving portion (54) having two parallel flat surfaces extending parallel to the brake back plate.

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