FR3148064A1 - ELECTROMECHANICAL DISC BRAKE WITH INCREASED COMPACTNESS - Google Patents

Abstract

Electromechanical disc brake comprising a caliper (102), brake pads (P1, P2), a piston (111) mounted so as to be movable 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 (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 moving the piston (111) in translation, in which the reduction system (R) comprises a planet carrier (2) carrying planets (4), a sun gear (1) rotated by the electric motor, a fixed crown (6) provided with internal teeth (16), 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 teeth (16) of the crown (6), said first (4.1) and second (4.2) pinions being integral in rotation with each other. [Fig. 2]

Description

ELECTROMECHANICAL DISC BRAKE WITH INCREASED COMPACTNESS TECHNICAL FIELD AND PRIOR ART

The present invention relates to an electromechanical disc brake having increased compactness.

A motor vehicle is equipped with a brake on at least one of the wheels. This can be a disc brake or a drum brake.

In the case of a floating caliper disc brake, it generally comprises a caliper mounted sliding on a yoke fixed to a steering knuckle, a piston mounted in the caliper and two brake pads on either side of a disc fixed to the wheel.

Traditionally, the piston is moved towards the disc, for example by pressurized hydraulic fluid.

The aim is to replace the hydraulic actuation with an electromechanical actuation so as not to have to recover and recycle the used brake fluid. In addition, an electromechanical brake is not subject to leaks.

An electromechanical brake called EMB ("Electromechanical Brake" in English terminology) comprises, for example, an electric motor, a reducer, a screw-nut system converting the rotational force of the motor into translational force at the output of the reducer, the piston and brake pads. When the electric motor is powered, it moves the piston towards the disc via the reducer and the screw-nut system and applies the brake pad against the disc. When the direction of the current is reversed, the electric motor turns in the opposite direction, the piston is moved back, allowing the brake pad to move away from the brake disc. The screw-nut system generally comprises a ball screw. This type of brake offers high responsiveness.

In the automotive field, there are space constraints, so we are trying 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 reducer. We are also trying to reduce the number of components in order to increase the reliability of the brake.

When using a reducer comprising a type I epicyclic gear train with four satellites, the reduction ratio should ideally not exceed 6:1 given the constraint of the minimum number of teeth required. Such a ratio is insufficient. One possibility for increasing the reduction ratio is to combine the reducers. However, such a combination of reducers has a large footprint, which limits the reduction in the brake's footprint.

It is therefore an aim of the present application to offer a compact electromechanical disc brake.

The aim stated above is achieved by an electromechanical disc brake comprising a caliper, at least one brake pad, a piston, an electric motor, a reducer, a device for converting a rotational movement into a translational movement at the output of the reducer, in which the reducer comprises a two-stage epicyclic gear train comprising a sun gear configured to be driven by the electric motor, at least three satellites, a planet carrier, a fixed crown. The satellites are double satellites, a first axial portion of which meshes with the sun gear and a second axial portion meshes with the fixed crown. The planet carrier is configured to cooperate with the conversion device.

By using double satellites, the reducer has both a large reduction ratio and great compactness. The result is a brake with a reduced footprint.

In addition, the number of parts in the reducer is reduced, resulting in a reduction in the mass of the reducer and therefore of the brake.

Furthermore, by obtaining a high reduction ratio, it is possible to reduce the torque required at the input of the reducer to be applied by the electric motor, which allows the use of a reduced-size electric motor.

Advantageously, the profile and/or the 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 system.

The present invention then relates to an electromechanical disc brake comprising a caliper, at least one brake pad, a piston mounted so as to be movable in translation in the caliper along a longitudinal axis, and an electromechanical actuator configured to move the piston against the brake pad and apply it against a brake disc, said electromechanical actuator comprising an electric motor, a reduction system, 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 planets, a sun gear configured to be rotated by the electric motor, a ring gear fixed relative to the caliper, said ring gear being provided with internal teeth, and said planet carrier being connected to the conversion device to apply the rotational force thereto. Said satellites are double satellites comprising a first pinion meshing with the sun gear and a second pinion meshing with the internal teeth of the crown, said first and second pinions being integral in rotation with each other.

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 comprising a longitudinal end received in the planet carrier. The screw is immobilized in rotation by cooperation with the piston.

In an exemplary embodiment, the second pinion 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.

In an advantageous example, the axis of the electric motor is parallel to the axis of the brake and the reduction system comprises a first reduction module rotating the planetary gear.

Very advantageously, the satellite carrier has three double satellites.

Preferably, the first pinion and the second pinion of each satellite are of a single piece.

In an exemplary embodiment, the planet carrier comprises axes parallel to the longitudinal axis of the second reduction module on each of which a double satellite is mounted, and a bearing is provided between the axis and the double satellite.

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

The disc brake is for example a floating caliper disc brake.

BRIEF DESCRIPTION OF THE FIGURES

The following description will be better understood with the help of the attached drawings, in which:
is a perspective view of an example of an electromechanical brake according to the invention,
is a longitudinal sectional view of the brake of the ,
is a rear view of the brake of the from which the electric motor and part of the reduction system were removed,
is a perspective view of an exemplary embodiment of a reducer implemented in the disc brake according to the invention,
is a perspective view of the reducer of the from another point of view,
is a perspective view of the reducer of the from which the fixed crown gear has been omitted.

DETAILED DESCRIPTION OF EMBODIMENTS

The front and rear are to be considered in the direction of piston movement when applying a braking force.

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

The disc brake F comprises a sliding caliper 102 provided with columns 104 intended to slide in bores made in a yoke (not shown), which is intended to be fixed to a steering knuckle. The caliper 102 comprises a body 105 and an arch 106 fixed to the body 105 by one end and intended to straddle a brake disc 109 (shown in a broken line on the ) integral in rotation with the wheel. In the example shown, the body 105 and the arch 106 are two different parts connected by screws 107.

The caliper has a brake actuator 108 and two brake pads P1 and P2 ( ).

The pad P1 is arranged between the actuator 108 and the disk 109 rotationally fixed to the wheel (shown in a broken line) and is designated the “inner pad”. The pad P2 is arranged between the caliper nose 110 located at the free end of the arch and the disk, and is designated the “outer pad”.

The brake actuator 108 is an electromechanical actuator comprising an electric motor M, a reduction system R, a device V for converting a rotational movement into a translational movement 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 P1. The motor M and a part of the reduction system R are received in a casing C fixed on the rear of the caliper body.

In the example shown, the conversion device V of a rotational movement into a translational movement is a screw-nut device, very advantageously comprising a ball screw 112 and a nut 114. The nut 114 is connected to the output of the reduction system R in order to be driven in rotation by the latter. The ball screw 112 is, for its part, immobilized in rotation about the axis X and moves in translation along this same axis, thus allowing the transmission of the braking force. In this example, a pin 116 between the piston 111 and the nut 114 ensures, by a stop effect, the end of travel of the ball screw 112 in the return phase of the piston 111. Alternatively, means comprising a stop, such as a radial stop, are used. The pin can be indifferently integral with the nut 114 or the piston 111.

The nut 114 comprises a body 114.1 provided with a threaded passage cooperating with the ball screw 112 and a collar 114.2 extending radially outwards.

Bearings 118 are provided between the nut and the body of the caliper. In this example, the bearings 118 are roller bearings, rollers 120 being 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 lateral face of the body 114.1 of the nut and the body 105 of the caliper 102.

When the electric motor M is activated in a braking generation direction, the nut 114 is rotated about the axis X causing the ball screw 112 to move in translation along the axis X, thus applying the brake pad P1 against one face of the brake disc 109, and by reaction the brake pad P2 against the other face of the brake disc 109.

In the example shown, the reduction system R comprises a first reduction module R1 and a second reduction module R2.

In this example, the electric motor M is arranged on the side of the caliper 102 and the axis X1 of its output shaft is parallel to the X axis.

The first reduction module R1 is interposed between the motor M and the second reduction module R2 and ensures the transmission of the rotational force from the axis X1 to the axis X. The first reduction module R1 is housed in the housing C and comprises a three-wheel train, comprising a motor pinion meshing with the motor shaft, an idler wheel and a pinion. The intermediate idler wheel ensures the center distance between the axes X1 and X and does not change the ratio between the input pinion of the motor M and the input pinion of the reducer R.

The second reduction module R2 has an axis X2 ( ) coincides with the X axis.

Figures 4 to 6 show an example of the implementation of the second reduction module R2.

The second reduction module R2 is a planetary or epicyclic gear reducer with two stages.

The second reduction module R2 comprises a sun gear 1 driven by the electric motor M via the first reduction module R1, a planet carrier 2 forming a cage, planet gears 4 and a crown 6 which is immobilized in rotation in the caliper body 105. The immobilization in rotation is ensured for example by means of ribs, the number of which is determined according to the torque absorbed by the part.

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 X1.

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

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 integral with each other and preferably in one piece.

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

The first pinions 4.1 are configured to mesh with the sun gear engaged with an output shaft of the first reduction module R1.

The second pinion 4.2 meshes with an internal toothing 16 of the crown 6.

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 rotation force thereto. The choice of the mechanical connection between the planet carrier and the nut depends on the manufacturing method of the planet carrier and the nut. For example, the connection comprises circular involute splines or dodecagon splines, i.e. with 12 flat sides.

The operation of the reduction module is as follows.

The satellites 4 are driven in rotation by the cooperation between the first pinions 4.1 and the sun gear 1 meshing with the first reduction module driven by the electric motor M.

Due to the meshing of the second pinions 4.2 with the internal teeth of the crown which is fixed, the second pinions 4.2 rotate about the axis X1 in the crown driving the planet carrier. The nut 114 is then driven in rotation.

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

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

For example, a reduction ratio of around 17:1 can be achieved with a second three-satellite reduction module, while a three-satellite epicyclic gear train offers a maximum reduction ratio of around 10:1.

A reduction ratio of around 12:1 can be achieved with a second reduction module with four satellites, while a four-satellite epicyclic gear train offers a maximum reduction ratio of around 6:1. The greater the number of satellites, the more the force is shared between the satellites. It is then possible to reduce the axial size for the same material composing the satellites. The second reduction module has at least 3 satellites, for example 3, 4 or 5 satellites.

Thus, the implementation of such a second reduction module makes it possible to produce a reduction system offering a reduction ratio of around 80:1 with a smaller first reduction module. As a result, the input torque to be applied by the electric motor is lower. A smaller motor is then sufficient, which contributes to an overall reduction in size. For example, an input torque of 1.5 Nm may be sufficient.

The reducer according to the invention is compatible with a parallel configuration, i.e. an architecture in which the axis of rotation X1 of the motor and the axis X of the reducer are parallel and are connected by an intermediate wheel. The reducer according to the invention is also compatible with a series configuration, i.e. an architecture in which the axis of the motor X1 and the axis X of the reducer are coaxial, the connection between the motor M and the reducer R being made for example via an additional epicyclic gear train.

Very advantageously, the second reduction module R2 comprises a central space E which makes it possible to house at least part of the conversion device. In the example shown, a longitudinal end of the ball screw is housed in the planet carrier, which makes it possible to reduce the axial dimension of the electromechanical actuator.

Furthermore, 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.

The second reduction module also has the advantage of having few parts, making it very compact and easy to produce, compared to the series connection of two reduction units.

Since it implements double satellites, the number of shafts is limited, which reduces the number of bearings possibly implemented between the satellite and the shaft.

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

In another exemplary embodiment, the actuator is such that the axis of the electric motor is aligned with the axis of the brake X. In an exemplary embodiment, the reduction system comprises only the reduction module R2, and the electric motor is in direct engagement with the satellites of the reduction module R2.

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

Alternatively, it allows the brake to be kept the same length as a state-of-the-art electromechanical disc brake, while implementing a longer ball screw, the additional length being housed in the planet carrier.

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

Claims (9)

Electromechanical disc brake comprising a caliper (102), at least one brake pad (P1), a piston (111) mounted so as to be movable 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 (P1) 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 planets (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 teeth (16) of the crown (6), said first (4.1) and second (4.2) pinions being integral in rotation with each other. 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). 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). Electromechanical disc brake according to one of claims 1 to 3, in which the axis (X1) 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 (R1) rotating the sun gear (1). Electromechanical disc brake according to one of claims 1 to 4, in which the planet carrier (2) comprises three double planet gears (4). 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 in one piece. 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 planet (4) is mounted, and in which a bearing is provided between the axis (12) and the double planet (4). 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. Electromechanical disc brake according to any one of the preceding claims, characterized in that the disc brake is a floating caliper disc brake.