DRUM BRAKE REDUCE MOTOR

Description

TECHNICAL FIELD AND STATE OF THE PRIOR ART

[0001] The present invention relates to the field of motor vehicle brakes, and more specifically to a geared motor assembly for actuating the segments of a drum brake.

[0002] In the automotive industry, the electromechanical parking brake serves to immobilize the vehicle when stationary to prevent it from moving unexpectedly. It also meets the legal requirement for a second braking system independent of the service braking system, usually hydraulic, in the vehicle and fulfills other comfort and safety functions, particularly through its self-diagnostic capability.

[0003] It is known from document FR3016015 to install within a drum brake, a mechanical actuator in addition to the hydraulic actuator initially provided. Such a drum brake, marked by 1 on the figure 1, comprises a plate 2 of revolution with axis AX equipped with first and second segments in an arc of circles 3 and 4 movable radially to be able to be pressed against the cylindrical internal face of a drum not shown.

[0004] The segments 3 and 4 each comprise a core 3a, 4a made of flat sheet metal in the form of a portion of a circular crown which carries a brake lining 3b, 4b, and are mounted diametrically opposite with their ends bearing both on a hydraulic wheel cylinder 6 and on a mechanical actuator 7 carried by the plate 2. These segments 3 and 4 are further returned towards each other by two return springs 8 and 9, and pressed against the plate 2 each by a spring 10, 11.

[0005] A wear adjustment rod 12 extends along the wheel cylinder 6, having a first end bearing on the web 3a of the first segment 3 and a second end bearing on the web 4a of the second segment 4.

[0006] The wheel cylinder 6 is intended to be actuated when using the drum brake 1 according to a first operating mode called "simplex", which ensures progressive braking particularly suitable for braking the vehicle in service. It comprises a hydraulic chamber closed at its ends by two pistons which move apart from each other when the hydraulic pressure increases and pushes the associated ends of the segments 3 and 4.

[0007] The mechanical actuator 7 provides parking and emergency braking by moving the associated ends of the segments apart to ensure rapid and powerful locking of the vehicle wheels in a so-called "duo-servo" operating mode, particularly when the wheel cylinder 6 is inactive. This actuator is driven by an electric motor 21 with axis AY.

[0008] In practice, one of the difficulties associated with the use of a mechanical actuator lies in the need to convert a high rotational speed associated with a low torque of the electric motor, into a low displacement with sufficient effort. For this purpose, the document FR3016015 teaches providing a reduction module which transmits a rotation of the motor 21, more precisely a rotation of a motor pinion of axis AY driven directly by this motor, to the mechanical actuator 7. This reduction module is centered on the axis AY and comprises several stages of epicyclic gear trains of axis AY in order to ensure an effective speed reduction between its output measured at an output pinion of axis AY coupling to the mechanical actuator 7 and its input measured at the motor pinion. In addition, the motor 21 and the reduction module are housed together in a cylindrical housing.

[0009] Such a geared motor architecture, called the association of the motor 21 and the reduction module, requires the axis of the motor to be arranged parallel to the axes of the epicyclic gear trains, and the axis of the reduction module to be arranged parallel to the axes of the toothed wheels of the mechanical actuator 7. The arrangement of the motor relative to the reduction module is therefore fixed, as is the orientation of the geared motor relative to the drum brake plate.

[0010] However, it is desirable to be able to produce a geared motor whose architecture allows it to adapt to different configurations of space available at the wheel level. In addition, the geared motor of the state of the art is bulky.

[0011] WO2018148245 discloses a geared motor for a parking brake comprising an angle transmission between the electric motor and the reducer, the angle transmission comprising a bevel gear. In the document, an electric actuator assembly comprises an electric motor having an output shaft, a reduction gear driven by the output shaft, a linear translation assembly having a gear nut driven by the reduction gear, and a connecting portion of the linear translation assembly. The output shaft drives the reduction gear via a suitable type of gear that can convert a rotational torque of the output shaft into a reduction gear at a right angle. STATEMENT OF THE INVENTION

[0012] 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 can be easily adapted to different configurations at the wheel level.

[0013] The aim stated above is achieved by a geared motor comprising at least one angle transmission formed by a flat wheel gear.

[0014] On the one hand, the implementation of an angle transmission offers greater freedom in the configuration of the geared motor and / or in its orientation in relation to the mechanical actuator of the drum brake. On the other hand, the implementation of an angle transmission with a flat wheel gear offers great latitude in the choice of the orientation of the motor output axis in relation to the reducer.

[0015] Furthermore, within the flat wheel gear, the meshing position of the pinion teeth relative to the flat wheel teeth can vary without changing the operation of the bevel gear, providing additional freedom in the configuration of the geared motor.

[0016] The geared motor can advantageously have a reduced footprint.

[0017] A flat wheel bevel gear connects the motor and the gearbox in a very advantageous manner. For example, a pinion is fixed to the output shaft of the electric motor and meshes with a flat wheel that is part of the gearbox. For example, a pinion is arranged coaxially with the flat wheel and is integral in rotation with it, and drives a toothed wheel of the gearbox.

[0018] Advantageously, a right angle drive connects the reducer output and the parking brake actuator and has a flat wheel gear.

[0019] Preferably, the reducer comprises a train of stepped gears with external contact, each comprising a pinion and a juxtaposed toothed wheel, in each stepped gear the pinion and the toothed wheel are coaxial, superimposed and integral in rotation, the pinion of a gear meshing with the toothed wheel of an adjacent stepped gear.

[0020] The construction of such a reducer offers additional freedom in the configuration of the geared motor.

[0021] The present invention then relates to a geared motor for a mechanical parking brake actuator of a drum brake comprising an electric motor and a reducer, the electric motor comprising an output shaft extending along a first axis and the reducer comprising an output axis extending along a second axis. The geared motor also comprises at least one angle transmission between the electric motor and the reducer or at the output of the reducer, said angle transmission comprising a flat wheel gear.

[0022] Advantageously, the bevel gear comprises a pinion and a flat gear wheel, the pinion being engaged with the output shaft of the electric motor and meshing with the flat gear wheel which is part of the reducer.

[0023] The flat gear wheel can be rotationally fixed to a pinion and forms a stepped gear with it.

[0024] The angle transmission may comprise a pinion intended to mesh with a toothed wheel of the mechanical actuator of the drum brake, the pinion forming a toothed crown carried by one face of a toothed wheel, the toothed crown and the toothed wheel forming a stepped gear.

[0025] Advantageously, the geared motor comprises a first angle transmission and a second angle transmission, the first angle transmission comprising a pinion and a flat toothed wheel, the pinion being engaged with the output shaft of the electric motor and meshing with the flat toothed wheel which is a part of the reducer, and the second angle transmission comprising a pinion intended to mesh with a toothed wheel of the mechanical actuator of the drum brake, the pinion forming a toothed crown carried by one face of a toothed wheel, the toothed crown and the toothed wheel forming a stepped gear.

[0026] For example, the reducer comprises one or more stepped gears each comprising a toothed wheel and a pinion, the toothed wheel and the pinion being coaxial, for example between four and six stepped gears.

[0027] Advantageously, the axes of the stepped gears are orthogonal to the first axis of the electric motor.

[0028] The first axis and the second axis are advantageously intersecting.

[0029] The present invention also relates to a drum brake comprising a drum, a plate, two segments, and a mechanical actuator fixed to the plate for parking braking and a geared motor according to the invention.

[0030] Preferably, the axes of the stepped gears are parallel to the axis of the drum.

[0031] The reducer may comprise a housing having two parallel flat faces extending parallel to the brake plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention will be better understood with the aid of the description which follows and the attached drawings in which: There figure 1 is a perspective view of a drum brake with an electric parking brake actuator according to the state of the art. The figure 2 is a perspective view of a drum brake provided with a geared motor according to an exemplary embodiment of the present invention, the drum and the cover of the geared motor housing not being shown. figure 3 is a detail view of the figure 2 at the level of the angle transmission at the motor output. The figure 4 is a side view of the angle gear of the figure 3 . There Figure 5 is a view is a perspective view of a drum brake provided with a geared motor according to another exemplary embodiment of the present invention, the drum and the cover of the geared motor housing not being shown. DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0033] On the figure 2 , we can see a perspective view of an advantageous example of a geared motor MR1 according to the invention associated with a drum brake 1 comprising an electric parking brake actuator 7.

[0034] The MR1 geared motor comprises an electric motor 21 and a transmission module or reducer 32.

[0035] In the example shown, the electric motor 21 and its output shaft 24 extend along the axis AY and the output axis of the transmission module extends along an axis AZ orthogonal to the axes AY and AZ.

[0036] In this example, the transmission module is intended to extend parallel to plate 2.

[0037] In the example shown and 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 stepped gears with external contact, preferably four to six in number. In the example of the figure 2 , there are five stepped gears 34, 35, 36, 37 and 38.

[0038] The gears 34, 35, 36 and 37 respectively comprise a first stage in the form of a toothed wheel 34a, 35a, 36a, 37a and a second stage in the form of a pinion 34b, 35b, 36b, 37b rigidly connected to the corresponding toothed wheel with a diameter smaller than the latter. The gear 38 comprises a toothed wheel 38a and a toothed crown 38b.

[0039] The stepped gears 34, 35, 36, 37 and 38 are each designed to be mounted for rotation about a separate fixed axis AX34, AX35, AX36, AX37 and AX38, each of these axes being parallel to each other and arranged in this order following the direction of the reduction, i.e. from the motor pinion to the mechanical actuator 7. They are in particular dimensioned so that the pinion forming the output of a gear meshes with the toothed wheel of the following 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.

[0040] Alternatively, the transmission module has single pinions and gears or single pinions and gears and stepped pinions. Their number and the number of teeth in each are determined by the desired reduction.

[0041] Furthermore, the geared motor MR1 comprises 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.

[0042] The first bevel gear 44 is advantageously of the flat wheel gear type and comprises a pinion 25 and a flat toothed wheel 34a, the pinion 25 meshing with the flat toothed wheel 34a. The pinion 25 is engaged with the output shaft 24 of the electric motor 21.

[0043] The flat gear wheel 34a comprises a wheel whose teeth are formed into a crown on one face of the wheel. On the figure 3 , we can see only the flat wheel gear represented.

[0044] The flat wheel bevel gear offers the advantage of providing freedom in the orientation of the axis of the pinion 25 relative to the axis of the toothed wheel 34a, i.e. great freedom in the choice of the angle of the bevel gear. Indeed, the angle α between the axis AX34 and the axis AY can vary, for example, from 30° to 135°. Thus, there is a large choice of orientations between the motor and the transmission module, to adapt the shape of the geared motor to that of the available space. In addition, the constraints on assembly precision are reduced.

[0045] In addition, the position of the teeth of the pinion 25 relative to the teeth of the toothed wheel 34a may vary. On the figure 4, the meshing length Le corresponds to the length of the engagement zone of the teeth of the pinion with the teeth of the toothed wheel 34a. The pinion 25 can be arranged relative to the toothed wheel with a clearance j. The clearance j is for example 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

[0046] This assembly clearance allowed by the flat wheel gear helps to provide greater freedom in the arrangement of the various elements of the geared motor. The constraints of assembly precision are also further relaxed.

[0047] In addition, a bevel gear with a flat wheel gear offers an efficiency of around 97% to 99%. By comparison, the efficiency of a bevel gear is approximately 30% lower than that of a flat wheel bevel gear.

[0048] In the example shown and advantageously, the second bevel gear is also a flat wheel. The toothed wheel 38a which is driven by the pinion 37b, bears on one of its faces, the upper face in the representation of the figure 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 comprises wheels 48, 50 with parallel axes.

[0049] Pinion 38b has a crown gear. Pinion 38b and toothed wheel 48 form the flat wheel gear of the second right angle drive of the actuator.

[0050] In the example shown, the transmission gear 55 comprises the toothed wheel 48 and a toothed wheel 52, which causes the pistons resting on the ends of the brake segments to move apart and moves them apart in the direction of the drum.

[0051] In a different variant of the invention according to claim 1, the geared motor comprises a flat wheel angle transmission and a conical angle transmission.

[0052] On the Figure 5 , we can see another example of MR2 geared motors according to the invention comprising an angle transmission 46 only at the output. In this example, the output shaft of the electric motor directly drives the toothed wheel 34a. The reduction of each meshed toothed wheel / pinion pair is adapted so that the total reduction is as expected. Indeed, in this example, a reduction stage is removed compared to the example of the figure 2 .

[0053] In another example not shown, the output gear directly meshes with the actuator gear teeth. In this case, the axes of the stepped gears are orthogonal to the axes of the stepped gears of the figure 2 .

[0054] Furthermore, the implementation of a reducer in the form of a stepped gear train also offers great freedom in the shape that the reducer can take. Indeed, the relative arrangement of the axes of the stepped gears is free, only the distances between the axes ensuring tangential meshing of a pinion and a toothed wheel being fixed. Consequently, the gear train can have a more or less deployed shape and thus adapt as best as possible to the environment available around the wheel. For example, the gear train can have a curved shape or an S shape.

[0055] 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 molding or they are made of metallic material and are overmolded in a plate made of plastic material.

[0056] The housing 54 is advantageously configured to follow the contours of the gears as closely as possible in order to further reduce the size of the geared motor.

[0057] In the example shown, the housing comprises two parts, a first part 54.2 comprising the base on which rests the plate 53 carrying the axes of the stepped gears and a second part (not shown) forming a cover.

[0058] Advantageously, the first and second parts have a flat bottom. Alternatively, the cover follows the contours of the gears.

[0059] The first and second parts may be symmetrical about a plane passing through the junction area between the first and second parts.

[0060] The housing is advantageously made by molding plastic material.

[0061] Advantageously, the housing 54 comprises means 56 for fixing the geared motor to the drum brake, more particularly to the plate in order to limit the movements of the geared motor which could damage it and / or generate undesirable noise. For example, the means 56 for fixing the geared motor to the plate comprise screw passages 58 passing through the housing 54 in the X direction outside the gears and in which screws are intended to be mounted cooperating with corresponding openings provided in the plate. REFERENCES

[0062] 1: drum brake 2: backing plate 3: first segment 4: second segment 3a, 4a: webs 3b, 4b: brake linings 6: hydraulic wheel cylinder 7: mechanical actuator 8, 9: return springs 10, 11: lateral springs 12: wear adjustment rod 21: electric motor 24: output shaft 25: pinion 32: reduction gear 34; 35, 36, 37, 38: stepped gears 34a, 35a, 36a, 37a, 38a: toothed wheels 34b, 35b, 3.6b, 37b, 38b: pinions 44: first bevel gear 46: second bevel gear 48: transmission gear 50, 52: toothed wheels of the transmission gear 53: plate 54: housing 54.1: first part of the housing 56: means for fixing the geared motor on the plate 58: screw passages AX, AY: axes AX34, AX35, AX36, AX37, AX38: axes of the gears 34; 35, 36, 37, 38 Le: meshing length MR1, MR2: geared motor

Claims

1. A geared motor for a mechanical parking brake actuator (7) of a drum brake including an electric motor (21) and a reduction gearbox (32), wherein the electric motor (21) has an output shaft (24) extending along a first axis, the reduction gearbox (32) includes an output axis extending along a second axis, wherein the geared motor also includes at least one angle transmission (44) between the electric motor (21) and the reduction gearbox (32) and is characterized in that said angle transmission (44) comprises a crown gear.

2. The geared motor according to claim 1, wherein the angle transmission (44) comprises a pinion (25) and a crown gear (34a), the pinion (25) being engaged with the output shaft (24) of the electric motor (21) and meshing with the crown gear (34a) which is part of the reduction gearbox (32).

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

4. The geared motor according to any one of the preceding claims, wherein the geared motor also comprises at least one angle transmission (46) at an output of the reduction gearbox (32), said angle transmission (46) comprising a crown gear.

5. The geared motor according to claim 4, wherein the angle transmission (46) includes a pinion (38b) for meshing with a toothed wheel (48) of the mechanical actuator (7) of the drum brake, the pinion (38b) forming a ring gear carried by a face of a toothed wheel, the ring gear (38b) and the toothed wheel (38a) forming a stepped gear.

6. The geared motor according to any one of claims 1 to 5, wherein the reduction gearbox includes one or more stepped gears (34, 35, 36, 38, 38) each including a toothed wheel and a pinion, the toothed wheel and the pinion being coaxial.

7. The geared motor according to claim 6, wherein the axes of the stepped gears (34, 35, 36, 38, 38) are orthogonal to the first axis of the electric motor (21).

8. The geared motor according to claim 6 or 7, including four to six stepped gears.

9. The geared motor according to one of claims 1 to 8, wherein the first axis and the second axis are intersecting.

10. A drum brake including a drum, a backing plate (2), two shoes (3, 4), and a mechanical actuator (7) attached to the backing plate (2) for parking braking, and a geared motor according to one of claims 1 to 9.

11. The drum brake according to claim 10, wherein the axes of the stepped gears are parallel to the axis of the drum.

12. The drum brake according to claim 10 or 11, wherein the reduction gearbox includes a housing (54) having two parallel planar faces extending in parallel to the brake backing plate.