ELECTROMECHANICAL DISC BRAKE WITH INCREASED COMPACTNESS

Abstract

An electromechanical disc brake comprising a caliper (102), brake pads (P1, P2), a piston (111) mounted for translational movement within the caliper (102) along a longitudinal axis (X), and an electromechanical actuator (108) configured to move the piston (111) against the brake pad (P1) and apply it against a brake disc, said electromechanical actuator (108) comprising an electric motor (M), a reduction system (R), a screw-nut system for translational movement of the piston (111), wherein the reduction system (R) comprises a planet carrier (2) carrying planet gears (4), a planet gear (1) rotated by the electric motor, a fixed ring gear (6) having internal teeth (16), and wherein said planet gears (4) are double planet gears comprising a first pinion (4.1) meshing with the planet gear (1) and a second pinion (4.2) engaging the inner teeth (16) of the crown (6), the said first (4.1) and second (4.2) pinions being fixed together in rotation. [Fig. 2].

Description

Title of the invention: INCREASED COMPACT ELECTROMECHANICAL DISC BRAKE TECHNICAL FIELD AND PREVIOUS ART

[0001] The present invention relates to an electromechanical disc brake with increased compactness.

[0002] A motor vehicle is equipped with a brake on at least one of its wheels. This may be a disc brake or a drum brake.

[0003] In the case of a floating caliper disc brake, this generally includes a caliper mounted to slide on a bracket fixed to a spindle carrier, a piston mounted in the caliper and two brake pads on either side of a disc fixed to the wheel.

[0004] Traditionally, the piston is moved towards the disc, for example by a hydraulic fluid under pressure.

[0005] The aim is to replace hydraulic actuation with electromechanical actuation to avoid having to recover and recycle used brake fluid. Furthermore, an electromechanical brake is not subject to leaks.

[0006] An electromechanical brake, designated EMB (Electromechanical Brake in Anglo-Saxon terminology), comprises, for example, an electric motor, a gearbox, a screw-nut system that converts the motor's rotational force into a translational force at the gearbox output, a piston, and brake pads. When the electric motor is energized, it moves the piston toward the disc via the gearbox and the screw-nut system, applying the brake pad against the disc. When the current is reversed, the electric motor rotates in the opposite direction, the piston retracts, allowing the brake pad to move away from the brake disc. The screw-nut system generally includes a ball screw. This type of brake offers high responsiveness.

[0007] In the automotive field, there are space constraints, so the aim is to reduce the dimensions of the brakes and consequently the dimensions of the electric motor, but the size of the motor is linked to the reduction ratio provided by the gearbox. There is also a need to reduce the number of components in order to increase the reliability of the brake.

[0008] When using a reducer comprising a type I epicyclic gear train with four planet gears, the reduction ratio should ideally not exceed 6:1 due to the constraint of the minimum number of teeth required. Such a ratio is insufficient. One possibility for increasing the reduction ratio is to combine reducers. However, such a combination of reducers has a significant size, which limits the reduction. of the brake's bulk. Description of the invention

[0009] It is therefore one of the aims of the present application to provide a compact electromechanical disc brake.

[0010] The stated objective is achieved by an electromechanical disc brake comprising a caliper, at least one brake pad, a piston, an electric motor, a gearbox, and a device for converting rotational motion into translational motion at the gearbox output. The gearbox comprises a two-stage epicyclic gear train including a planet gear configured to be driven by the electric motor, at least three planet gears, a planet carrier, and a fixed ring gear. The planet gears are double planet gears, with a first axial portion meshing with the planet gear and a second axial portion meshing with the fixed ring gear. The planet carrier is configured to cooperate with the conversion device.

[0011] By using double satellites, the reducer offers both a high reduction ratio and a high compactness. This results in a brake with a reduced footprint.

[0012] In addition, the number of parts of the reducer is reduced, resulting in a decrease in the mass of the reducer and therefore of the brake.

[0013] In addition, thanks to obtaining a high reduction ratio, it is possible to reduce the required input torque of the reducer to be applied by the electric motor, which allows the use of a smaller electric motor.

[0014] Advantageously, the profile and / or module of the teeth of the two axial portions of the double satellites can be different, which makes it possible to adapt to different types of environment and to provide an internal space to integrate a screw-nut system, advantageously a ball screw-nut.

[0015] The present invention relates to an electromechanical disc brake comprising a caliper, at least one brake pad, a piston mounted for translational movement within the caliper along a longitudinal axis, and an electromechanical actuator configured to move the piston against the brake pad and apply it to a brake disc. This electromechanical actuator comprises an electric motor, a reduction system, and a device for converting a rotational force into a translational force, configured to apply said translational force to the piston. The reduction system comprises a planet carrier carrying at least three planet gears, a planet gear configured to be rotated by the electric motor, and a ring gear fixed relative to the caliper. This ring gear is provided with internal teeth, and the planet carrier is connected to the conversion device to apply the rotational force to it.These satellites are dual satellites comprising . a first pinion engaging the planetary gear and a second pinion engaging the internal teeth of the crown gear, said first and second pinions being fixed in rotation to each other.

[0016] Preferably, the conversion device comprises a screw, advantageously a ball screw, and a nut, said nut being aligned with the axis of the brake and having a longitudinal end received in the planet carrier. The screw is prevented from rotating by cooperation with the piston.

[0017] In one embodiment, the second pinion has teeth whose profile and / or module is and / or are different from the profile and / or module of the teeth of the first pinion.

[0018] In an advantageous example, the axis of the electric motor is parallel to the axis of the brake and the reduction system includes a first reduction module driving the planetary gear in rotation.

[0019] Very advantageously, the satellite carrier comprises three double satellites.

[0020] Preferably, the first pinion and the second pinion of each satellite are in one piece.

[0021] In one embodiment, the planet carrier has axes parallel to the longitudinal axis of the second reduction module on each of which a double planet is mounted, and a bearing is provided between the axis and the double planet.

[0022] Preferably, the reduction system has a reduction ratio of the order of 80:1, and the reduction ratio between the planetary gear and the output of the planet carrier is at least of the order of 12:1.

[0023] The disc brake is for example a disc brake with a floating caliper. BRIEF DESCRIPTION OF THE FIGURES

[0024] The following description will be better understood with the aid of the attached drawings, in which: [Fig. 1] is a perspective view of an example of an electromechanical brake according to the invention, [Fig.2] is a longitudinal cross-sectional view of the brake of [Fig.1], [Fig.3] is a rear view of the brake from [Fig.1] from which the electric motor and part of the reduction system have been removed, [Fig.4] is a perspective view of an example of an embodiment of a reducer implemented in the single-disc brake according to the invention, [Fig. 5] is a perspective view of the reducer of [Fig. 4] from another viewpoint, [Fig.6] is a perspective view of the reducer of [Fig.4] from which the fixed toothed ring has been omitted. DETAILED DESCRIPTION OF PRODUCTION METHODS

[0025] The front and rear are to be considered in the direction of piston movement when a braking force is applied.

[0026] Figures 1 to 3 show an example of an electromechanical disc brake according to the invention.

[0027] The disc brake F comprises a sliding caliper 102 equipped with guide pins 104 for sliding in bores in a bracket (not shown), which is intended to be fixed to a wheel carrier. The caliper 102 comprises a body 105 and an arch 106 fixed to the body 105 at one end and intended to straddle a brake disc 109 (shown as a dashed line in [Fig. 2]) which is rotationally fixed to the wheel. In the example shown, the body 105 and the arch 106 are two separate parts connected by screws 107.

[0028] The caliper includes a brake actuator 108 and two brake pads PI and P2 ( [Fig.2]).

[0029] The PI pad is located between the actuator 108 and the disc 109, which is fixed to the rotation of the wheel (shown in dashed line), and is designated as the "inner pad". The P2 pad is located between the caliper nose 110, situated at the free end of the arch, and the disc, and is designated as the "outer pad".

[0030] The brake actuator 108 is an electromechanical actuator comprising a electric motor M, a reduction system R, a conversion device V of a rotational displacement into a translational displacement and a piston 111 movable in translation along an axis X. The piston 111 is in contact with the rear face of the brake pad PL The motor M and part of the reduction system R are received in a housing C fixed on the rear of the caliper body.

[0031] In the example shown, the conversion device V from a rotational displacement to a translational displacement is a screw-nut device, advantageously comprising a ball screw 112 and a nut 114. The nut 114 is connected to the output of the reduction system R so as to be driven in rotation by it. The ball screw 112, for its part, is fixed against rotation about the X-axis and moves in translation along this same axis, thus enabling the transmission of the braking force. In this example, a pin 116 between the piston 111 and the nut 114 ensures, by means of a stop, the end of the stroke of the ball screw 112 during the return phase of the piston 111. Alternatively, means comprising a stop, such as a radial stop, are used. The pin can be fixed to either the nut 114 or the piston 111.

[0032] The nut 114 comprises a body 114.1 having a threaded passage cooperating with the ball screw 112 and a flange 114.2 extending radially outwards.

[0033] Bearings 118 are provided between the nut and the caliper body. In this example, the bearings 118 are roller bearings, with rollers 120 interposed. between the rear face of the collar 114.2 and the body 105 of the caliper 102, and rollers 120 are interposed between the outer side face of the body 114.1 of the nut and the body 105 of the caliper 102.

[0034] When the electric motor M is activated in a direction generating braking, the nut 114 is set in rotation around the axis X causing the ball screw 112 to move in translation along the axis X, thus applying the brake pad PI against one face of the brake disc 109, and by reaction the brake pad P2 against the other face of the brake disc 109.

[0035] In the example shown, the reduction system R comprises a first reduction module RI and a second reduction module R2.

[0036] In this example, the electric motor M is arranged on the side of the bracket 102 and the axis XI of its output shaft is parallel to the axis X.

[0037] The first reduction module RI is interposed between the motor M and the second reduction module R2 and ensures the transmission of the rotational force from the axis XI to the axis X. The first reduction module RI is housed in the casing C and comprises a three-wheel train, including a drive pinion meshing with the motor shaft, an idler wheel, and a pinion. The intermediate idler wheel ensures the center distance between the axes XI and X and does not change the ratio between the input pinion of the motor M and the input pinion of the reducer R.

[0038] The second reduction module R2 has an X2 axis ([Fig.3]) coinciding with the X axis.

[0039] Figures 4 to 6 show an example of the realization of the second reduction module R2.

[0040] The second reduction module R2 is a planetary or epi-cycloidal gear reducer comprising two stages.

[0041] The second reduction module R2 comprises a planetary gear 1 driven by the electric motor M via the first reduction module RI, a planet carrier 2 forming a cage, planetary gears 4 and a ring gear 6 which is immobilized against rotation in the yoke body 105. The immobilization against rotation is ensured for example by means of ribs the number of which is determined according to the torque experienced by the part.

[0042] The cage of the satellite carrier 2 comprises a first ring-shaped base 7 and a second ring-shaped base 8 connected by uprights 10, four in the example shown. The rings are centered on the axis XL

[0043] Each satellite 4 is mounted for rotation about an axis 12 fixed at one end to the first base 7 of the cage and at the other end to the second base 8. The ends of the axes are, for example, crimped into the rings. Preferably, bearings (not visible) are provided between each axis 12 and each satellite 4.

[0044] According to the invention, each satellite 4 is a double satellite comprising a first pinion 4.1 forming a first longitudinal portion of the satellite 4 and a second pinion 4.2 forming a second longitudinal portion of the satellite 4. The first pinion 4.1 and the second pinion 4.2 are joined together and preferably as a single unit.

[0045] The satellites 4 are distributed angularly in a regular manner around the X2 axis.

[0046] The first 4.1 pinions are configured to mesh with the planetary gear in contact with an output shaft of the first RL reduction module

[0047] The second pinion 4.2 meshes an internal tooth 16 of the crown 6.

[0048] The second base 8 of the cage is configured to transmit the output force to the conversion device V. In the example shown, the planet carrier 2 is mechanically connected to the nut 114 so as to transmit the rotational force to it. The choice of the mechanical connection between the planet carrier and the nut depends on the manufacturing process of the planet carrier and the nut. For example, the connection may have involute splines or dodecagonal splines, i.e., 12 flat sides.

[0049] The operation of the reduction module is as follows.

[0050] The satellites 4 are driven in rotation by the cooperation between the first pinions 4.1 and the planetary 1 in contact with the first reduction module driven by the electric motor M.

[0051] Due to the meshing of the second pinions 4.2 with the internal teeth of the ring gear, which is fixed, the second pinions 4.2 rotate around the axis XI in the ring gear, driving the planet carrier. The nut 114 is then driven in rotation.

[0052] The number of satellites is not limited. Alternatively, the reducer has three satellites; the cage is then adapted and has three uprights.

[0053] The implementation of such a second reduction module makes it possible to obtain a significantly higher reduction ratio than a standard epicycloidal reducer, while having a limited footprint.

[0054] For example, a reduction ratio of around 17:1 can be achieved with a second reduction module with three satellites, whereas an epicyclic train with three satellites offers a maximum reduction ratio of around 10:1.

[0055] A reduction ratio of approximately 12:1 can be achieved with a second four-satellite reduction module, whereas a four-satellite epicyclic gear train offers a maximum reduction ratio of approximately 6:1. The greater the number of satellites, the more the load is distributed among them. It is then possible to reduce the axial dimensions for the same satellite material. The second reduction module comprises at least three satellites, for example, three, four, or five.

[0056] Thus, the implementation of such a second reduction module makes it possible to achieve a The reduction system offers a reduction ratio of approximately 80:1 with a smaller first reduction module. As a result, the input torque required from the electric motor is lower. A smaller motor is then sufficient, contributing to an overall reduction in size. For example, an input torque of 1.5 Nm may be sufficient.

[0057] The gearbox according to the invention is compatible with a parallel configuration, that is to say, an architecture in which the rotation axis XI of the motor and the axis X of the gearbox are parallel and are connected by an intermediate gear. The gearbox according to the invention is also compatible with a series configuration, that is to say, an architecture in which the axis of the motor XI and the axis X of the gearbox are coaxial, the connection between the motor M and the gearbox R being made, for example, via an additional epicyclic gear train.

[0058] Advantageously, the second reduction module R2 includes a central space E which allows at least part of the conversion device to be housed. In the example shown, one longitudinal end of the ball screw is housed in the planet carrier, which reduces the axial dimension of the electromechanical actuator.

[0059] Moreover, and very advantageously, it is possible to choose tooth profiles and / or having different modules between the first pinion 4.1 and the second pinion 4.2 of each satellite, which offers great freedom in particular in the configuration of the internal shape of the reducer, allowing for example to be able to arrange the space in the center of the reducer with greater freedom.

[0060] The second reducing module also has the advantage of having few parts, thus offering great compactness and simplicity of manufacture, compared to the series association of two reducing units.

[0061] Since it uses double satellites, the number of shafts is limited, which reduces the number of bearings possibly used between the satellite and the shaft.

[0062] The second reduction module R2 is preferably made entirely of steel.

[0063] In another embodiment, the actuator is such that the axis of the electric motor is aligned with the axis of the brake X. In one embodiment, the reduction system comprises only the reduction module R2, and the electric motor is directly connected to the satellites of the reduction module R2.

[0064] The disc brake according to the invention is such that it allows to present a smaller dimension in the X direction compared to electromechanical disc brakes of the prior art having a ball screw of the same length, in particular by using a part of the space available within the planet carrier to house at least a part of the ball screw.

[0065] Alternatively, it allows a brake of the same length as a prior art electromechanical disc brake, while using a longer ball screw, the additional length being housed in the planet carrier.

[0066] The reducer according to the invention makes it possible to maintain an efficiency similar to that of type I epicyclic trains, greater than 95% under normal loading and temperature conditions. REFERENCES

[0067] 1: planetary I: epicyclic gear train of the type 2: Satellite mount F: Disc brake 4: Dual satellite 6: crown 7: First base 8: second base 10: amounts 12: axis 4.1: First pinion 4.2: Second sprocket 16: internal dentition 102: stirrup 104: small columns 105: Stirrup body 106: vault 109: brake disc 107: screw 108: brake actuator 108: electromechanical actuator 110: Stirrup nose 111: piston 112: ball screw 114: nut 116: pawn 114.1: body 114.2: collar 118: bearings

Claims

Claims

1. Electromechanical disc brake comprising a caliper (102), at least one brake pad (PI), a piston (111) mounted to move in translation in the caliper (102) along a longitudinal axis (X), and an electromechanical actuator (108) configured to move the piston (111) against the brake pad (PI) and apply it against a brake disc, said electromechanical actuator (108) comprising an electric motor (M), a reduction system (R), a device (V) for converting a rotational force into a translational force configured to apply said translational force to the piston (111), in which the reduction system (R) comprises a planet carrier (2) carrying at least three satellites (4), a sun gear (1) configured to be rotated by the electric motor, a crown (6) fixed relative to the caliper (102), said crown (6) being provided with internal teeth (16),and said planet carrier (2) being connected to the conversion device to apply the rotational force thereto and in which said planets (4) are double planets comprising a first pinion (4.1) meshing with the sun gear (1) and a second pinion (4.2) meshing with the internal toothing (16) of the crown (6), said first (4.1) and second (4.2) pinions being integral in rotation with each other.,

2. Electromechanical disc brake according to claim 1, in which the conversion device (V) comprises a screw (112), advantageously a ball screw, and a nut (114), said nut (114) being aligned with the axis (X) of the brake and comprising a longitudinal end received in the planet carrier (2), and in which the screw (112) is immobilized in rotation by cooperation with the piston (111).

3. Electromechanical disc brake according to claim 1 or 2, wherein the second pinion (4.2) comprises teeth whose profile and / or module is and / or are different from the profile and / or module of the teeth of the first pinion (4.1).

4. Electromechanical disc brake according to one of claims 1 to 3, in which the axis (XI) of the electric motor (M) is parallel to the axis of the brake and in which the reduction system (R) comprises a first reduction module (RI) driving the sun gear (1) in rotation.

5. Electromechanical disc brake according to one of claims 1 to 4, in which the planet carrier (2) comprises three double satellites (4).

6. Electromechanical disc brake according to one of claims 1 to 5, in which the first pinion (4.1) and the second pinion (4.2) of each satellite (4) are of a single piece.

7. Electromechanical disc brake according to one of claims 1 to 6, in which the planet carrier (2) comprises axes (12) parallel to the longitudinal axis (X2) of the second reduction module on each of which a double satellite (4) is mounted, and in which a bearing is provided between the axis (12) and the double satellite (4).

8. Electromechanical disc brake according to one of claims 1 to 7, in which the reduction system (R) has a reduction ratio of the order of 80:1, and in which the reduction ratio between the sun gear and the output of the planet carrier is at least of the order of 12:

1.

9. An electromechanical disc brake according to any preceding claim, characterized in that the disc brake is a floating caliper disc brake.

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