Electromechanical-type disc brake caliper comprising two mechanical actuators to compensate for an uneven wearing of the one same brake pad

A brake caliper comprising: a set of brake pads positioned on each side of a brake disc; a first actuator including a first drive gearwheel driving a first mobile piston pressing against a first portion of brake pad in order to move same; a second actuator including a second drive gearwheel driving a second mobile piston pressing against a second portion of the pad in order to move same, with a mode of operation that is the opposite of that of the first actuator; a first and a second worm screws which are secured to one another and of opposite hand to one another, rotationally driven and capable of translational movement in their longitudinal direction and in mesh with the first and second gearwheels respectively in order to turn these in opposite directions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a National Stage of PCT international application PCT/FR2018/052920, filed on Nov. 20, 2018, which claims the priority of French Patent Application No. 1761163, filed Nov. 24, 2017, both of which are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The invention relates to an electromechanical-type disc brake caliper for an automotive vehicle, that is equipped with an electric motor driving mechanical actuators.

STATE OF PRIOR ART

In a hydraulic-type disc brake caliper, as well as in an electromechanical-type brake caliper, several actuators can be provided to press together a same pad against the disc when the brake is activated.

The invention more particularly relates to a disc brake caliper including an electromechanical actuator including a first and a second mechanical actuators extending side by side facing a pad. The first actuator pushes a first pad portion which is close to a first end of this pad and the second actuator pushes a second pad portion which is close to a second end of this pad.

A pad includes a support to which a friction lining for coming alone into friction with a face of the disc in order to brake it.

In practice, it appears that such pads wear out unevenly, resulting in a lining thickness which is reduced from one end to the other end of the pad.

In the case of a hydraulic caliper, the uneven thickness of the pad is compensated for by the fact that the actuators which push it are connected to a same hydraulic circuit. With such a circuit, the operation corresponds to that of force feedback control, which thereby enables the actuators to have movements of different lengths.

Concretely, upon braking, the pressurisation of the hydraulic circuit, and thereby of the hydraulic actuators, moves the pistons of these actuators to the disc according to movements that can be different. These movements are carried out until the pistons press the entire pad against the disc, the pressure remaining the same in the circuit and in the actuators at any time.

As a result, with a hydraulic caliper, adjusting an uneven wear of the pad is naturally made.

With an electromechanical-type caliper, it is a same motor which drives the mechanical actuators pushing a pad, through a transmission mechanism such that they move the disc pistons closer to each other in order to press the pad.

If the mechanism ensures a direct type transmission between the motor rotation and the rotation of the members moving the pistons, an uneven thickness of a pad cannot be compensated for because the movements and home positions of the pistons are not necessarily the same.

Concretely, upon braking with such a direct type transmission, as an actuator presses the pad portion it pushes against the disc, the pressing force exerted onto the disc counteracts the motor torque: the motor rotation is locked and the mechanism comes to a halt by stopping the stroke of the other piston.

One object of the invention is to overcome this drawback by providing a transmission mechanism which enables an uneven wear of a pad to be adjusted, in an electromechanical-type brake caliper with mechanical actuators driven by a same electric motor.

DISCLOSURE OF THE INVENTION

To that end, one object of the invention is a brake caliper for overlapping a brake disc, which comprises a set of pads and an electromechanical actuator for pressing a pad against a face of the disc, characterised in that the electromechanical actuator comprises:

an electric motor driving a first mechanical actuator and a second mechanical actuator;

the first mechanical actuator including a first drive gear and a first piston for pressing a first portion of the pad;

the second mechanical actuator including a second drive gear and a second movable piston for pressing a second portion of the pad;

each actuator converting a rotation of its drive gear into a translation of its piston, the first and second actuator having reverse conversion senses;

a transmission module comprising:

a first worm and a second worm having a same longitudinal direction and having reverse winding senses while being rigidly integral with each other, these first and second worms being meshed with the first and second drive gears respectively to simultaneously rotate them in reverse senses;

means for rotatably driving the first and second worms by the electric motor, these means forming a slide connection enabling the first and the second worms to translationally move along the longitudinal direction.

With this solution, when a pad portion comes in contact with the disc, the drive gear of the corresponding actuator comes to a halt, but the worms continue to rotate by being translated to move the piston of the actuator associated with the other part of the pad. The mechanism thus compensates for an uneven wear of the pad by ensuring that this pad is fully pressed against the disc upon braking.

The invention also relates to a brake caliper thus defined, wherein the means forming a slide connection and for rotatably driving the worms of the transmission module include:

a rotary shaft rigidly carrying the first and second worms, this shaft being translationally movable along the longitudinal direction;

a translationally fixed gear rotated by the electric motor, this gear comprising a splined through hole in which a splined end of the shaft is engaged.

The invention also relates to a brake caliper thus defined, wherein the means forming a slide connection and for rotatably driving the worms of the transmission module include:

a sleeve rigidly carrying the first and second worms, this sleeve being translationally movable along the longitudinal direction;

a translationally fixed gear rotated by the electric motor;

a rotary shaft which is rigidly integral with and project from the gear by including external splines, this rotary shaft extending along the longitudinal direction by being surrounded by the sleeve;

internal splines carried by the sleeve with which the external splines mesh by form fitting.

The invention also relates to a brake caliper thus defined, wherein the internal splines project from a hub rigidly connected to the sleeve.

The invention also relates to a brake caliper thus defined, wherein the first and second drive gears have oblique teeth and rotate about axes parallel to each other and perpendicular to the longitudinal direction.

The invention also relates to a brake caliper thus defined, comprising a reduction module which transmits rotation of the motor to the means for rotatably driving the first and second worms.

The invention also relates to a disc brake comprising a brake caliper thus defined.

DETAILED DISCLOSURE OF PARTICULAR EMBODIMENTS

As is visible inFIG.1, a floating mounted caliper1comprises a caliper body2which carries a set of pads3and4on either side of a brake disc6, and which is equipped with an electromechanical actuator7to press these pads3and4against the disc6in a braking situation.

The pad3comprises a support3ato which a lining3bis attached. In the same way, the pad4comprises a support4ato which a lining4bis attached.

This electromechanical actuator7represented inFIG.2comprises an electric motor13which drives, through a driving mechanism14, two mechanical actuators8and9arranged facing the pad3.

This pad3extends sidewise, in other words extends in a direction tangential to the disc6. Both mechanical actuators8and9are side by side along the pad3by extending perpendicular to the same. The first actuator8is facing a first portion of the pad3close to a first end of this pad3and the second mechanical actuator9is facing a second portion of the pad3close to a second end of this pad3. The first actuator8is mounted in a first cavity11of the caliper body2along an axis AX1in an axial direction, that is in a direction normal to the brake disc6, whereas the second actuator9is mounted in a second cavity of the caliper body2along an axis AX2parallel to AX1.

The first actuator8comprises a part included in the caliper body2with a first piston8awhich surrounds a first nut8bscrewed about a first axial drive screw8c, and a part outside the caliper body2with a first drive gear8dwith helical teeth, in other words oblique teeth, which is rigidly integral with this first drive screw8c.

The first piston8aand the first nut8bare rotatably locked about the axis AX1but translationally movable along this axis AX1whereas the first drive screw8cand the first drive gear8dare rotatably movable about the axis AX1but translationally locked along this same axis AX1.

This arrangement converts a rotation of the first drive gear8dinto an axial translation of the first piston8aalong axis AX1, in one sense or the other as a function of the sense of rotation of this first drive gear8d.

Analogously, the second actuator9includes a second drive gear9dto move a second piston9aaxially along AX2through a second nut and a second drive screw not represented.

The first and second drive gears8dand9dhave reverse thread senses. The second actuator9thus ensures a conversion of the rotation of its drive gear9dinto a translation of its piston9awhich is reverse to the conversion ensured by the first actuator8. In other words, it is when both drive gears8dand9drotate in reverse senses that the first and second piston8aand9amove in the same axial sense.

The driving mechanism14comprises a transmission module15and a reduction module16which transmits a rotation of the motor13, more precisely a rotation of a motor pinion gear17with oblique teeth directly driven by the motor, to the transmission module15with a speed lower than that of this motor pinion gear17.

The reduction module16comprises as an input an oblique-tooth idler gear18followed by an epicyclic gear train19, with the idler gear18meshed in the motor pinion gear17having the axis AX3, parallel to the axes AX1and AX2, to transmit its rotation to the epicyclic gear train19.

As is visible inFIG.4, the epicyclic gear train19comprises an input sun gear20, which is an oblique tooth gear, in which the idler gear18is meshed to rotate this input sun gear20about an axis AX4parallel to the axis AX3. The input sun gear20is extended along its axis of rotation AX4to a straight-tooth sun gear21, this sun gear21meshing with three planet gears22. The planet gears22are pivotably mounted about their axis of revolution to a planet carrier23rotatably movable about the axis AX4. These planet gears22are meshed in a fixed circular ring gear which surrounds them, this ring gear being not represented in the figures.

With this arrangement, the rotation of the input sun gear20enables the planet gears22to rotate not only about their own axis but also with their respective axis about the axis AX4, rotating the planet carrier23at an output speed much lower than the input speed.

The planet carrier23is extended at the output of the epicyclic gear train19to a straight-tooth output pinion gear24, visible inFIG.4, which projects from the centre of the face of the planet carrier23opposite to the planet gears22.

The transmission module15includes an angle transmission gear26rotated about an axis with a longitudinal direction AY perpendicular to the axis AX4, this angle transmission gear26being meshed in the output pinion gear24.

This arrangement converts the rotation of the pinion gear24about the axis AX4into a rotation of the angle transmission gear26about the axis AY which is perpendicular thereto, also called a right angle transmission.

The angle transmission gear26has a central through hole along the axis AY which is splined to form a slide connection of a rotary shaft27one end of which, which is splined accordingly, is slidably engaged in this hole. This slide connection enables the angle transmission gear26to rotatably drive the shaft27while enabling this shaft27to slide along AY.

The shaft27extends along the axis AY in a plane parallel to the plane defined by the axes AX1and AX2and includes a first and a second worm screws28and29which fixedly project from the same, with both worm screws28and29aligned along the axis AY. The first worm screw28is meshed in the first drive gear8dand the second worm screw29is meshed in the second drive gear9d.

This arrangement converts the rotation of the shaft27about the axis AY into a rotation of the first and second drive gears8dand9dabout their respective axes AX1and AX2, with the worm screws28and29integral with the shaft27. These rotations are in turn converted by the first and second mechanical actuators8and9into an axial translation of their respective piston8aand9a.

Both worm screws28and29have reverse winding senses such that a rotation of the shaft27in a sense marked with R inFIG.5causes the output both pistons8aand9a, the mechanical actuators8and9having opposite operating modes. A rotation of the shaft27in a sense reverse to the sense R on the contrary causes both pistons8aand9ato be retracted.

In a braking situation with a pad3having a constant thickness as in the example ofFIG.5, both pad portions3pressed by the pistons come simultaneously in abutment against the disc6when the motor13is actuated.

In a braking situation with a pad3having an uneven wear as inFIG.6, the pad portion3here pressed by the first actuator8comes in abutment on the brake disc6with the portion pressed by the second actuator9. At this stage, the first piston8aas well as the first drive gear8dcome to a halt, the brake disc6being a force opposed to the movement of the pad portion3pressed by the first actuator8.

Since the motor13continues to rotatably drive the shaft27, with the worm screws28and29, thereby it causes this shaft27to be longitudinally translated along AY in a sense marked with T. Under these conditions, the second piston9acarrying the pad portion which is not yet in contact with the disc6continues to progress under the combined effect of the rotation of the shaft27and its translation, since the first and second worm screws28and29are meshed in the first and second drive gears8dand9drespectively, whereas the first drive gear8dis halted.

As soon as the pad portion associated with the second actuator9comes in abutment against the disc6, the shaft27stops translationally moving but continues to rotate about its axis AY thus allowing a simultaneous load rise of the pads against the disc6. The shaft27comes to a halt once a desired torque of the drive gears is reached.

A return to the initial state of the pad3, i.e. in the state before braking, is allowed by rotating the shaft27but in a sense reverse to the sense R, with the same number of revolutions than those made during braking in the sense R, and a translation of the shaft in the sense opposite to T according to the same initial movement amplitude of T. The reverse rotation first causes both pistons8aand9ato be retracted until the piston8ais fully retracted, and then the shaft27translationally moves in the sense opposite to T, while keeping its rotation, until the piston9areturns to the initial position.

Generally, the caliper1according to the invention enables an uneven wear of the pad to be adjusted by associating a rotation of the worm screws with a slide connection, ensuring that when a first pad portion3comes into abutment on the disc6, the other pad portion can continue to move until it arrives in turn in abutment against the disc6with the desired force.

The invention is not restricted to the described embodiment of the transmission module15and allows the use of various architectures as long as worm screws are integral with each other in rotation with the gear, and translationally movable with respect to the same, in other words connected to the gear through a slide connection.

Furthermore, in the alternative ofFIG.7, of the transmission module marked with15′, the rotary shaft27′ is translationally fixed by being rigidly integral with the angle transmission gear26′, and the worm screws28′ and29′ are aligned and formed on a distinct sleeve31′. The shaft27′ and the sleeve31extend longitudinally along the axis AY, with the shaft27′ including external splines32along its extent, and the sleeve31surrounding this shaft27′ and the external splines32. The transmission module15′ further comprises a hub33extending between the shaft27′ and the sleeve31by being rigidly connected to the sleeve31in its central region, that is between the worm screws28′ and29′.

The hub33is provided with internal splines34meshed in the external splines32. The shaft27′ and the sleeve31, through the hub33, are thus rotatably coupled while leaving to the sleeve31which carries the worms28′ and29′, a translation degree of freedom along the axis AY with respect to the shaft27′.

With this arrangement, in a braking situation illustrated inFIG.8with a caliper1provided with the transmission module15′ and a pad3having a wear pattern identical to that represented inFIG.6, it is the sleeve31which moves in the sense marked with T, with the hub33sliding on the shaft27′ during their rotation marked with R when the first drive gear8dcomes to a halt.

A return to the initial state of the pad3is allowed by a rotation of the assembly formed by the shaft27′, hub33and sleeve31but in a sense reverse to the sense marked with R, with the same number of revolutions than those made during braking in the sense R. The reverse rotation first causes both pistons8aand9ato be retracted until the piston8ais fully retracted, and then the sleeve31translationally moves in the sense opposite to T, while keeping its rotation, until the piston9areturns to the initial position.

In the example ofFIGS.6and8, the pad portion pressed by the first actuator8has a lining thickness lower than that of the pad portion pressed by the second actuator9, but it is to be noted that the invention not only brings a solution to compensate for this particular wear pattern.

Indeed on the contrary, in the case where the pad portion pressed by the first actuator8has a lining thickness this time higher than that of the pad portion pressed by the second actuator9, the worms28and29or28′ and29′ move in the sense opposite to T during a braking command.

It is also to be noted that the invention could consider dispensing with the hub33, with the internal splines34directly projecting from the sleeve31to mesh in the external splines32of the shaft27′, thus limiting the number of components of the transmission module15′ and simplifying the assembly thereof.

Further, the internal splines34are not necessarily formed in the central region of the sleeve31, as long as they always respect the functional condition of being meshed in the external splines32whatever the wear state of the lining3b. The invention could in particular provide that the external splines32do not extend throughout the extent of the shaft27′, since the maximum movement of the sleeve31with respect to the shaft27′ is restrained by both cases for which one of the lining portions3bis in good condition whereas the other portion is fully spent.

Throughout the figures, the shafts27and27′ are located “above” the first and second drive gears8dand9d, with the axis AX1located between the axes AX3and AX4. But it is to be noted that the invention could provide the shaft27or27′ located “below” the drive gears8dand9d, in other words with the axis AX4closer to the axis of rotation of the brake disc6than AX1is, to respect a different overall size.

In the description below, the operation of the brake according to the invention has been explained in terms of movement of its components in order to facilitate understanding thereof. In practice, in the case of a braking with such an actuator, the movements are minute and this mechanism converts a torque exerted by the motor13into a pressing force exerted by each of the pistons8aand9aon the pad3.

Nomenclature

1 caliper2 caliper body3 pad3a pad support3b pad lining4 pad4a pad support4b pad lining6 brake disc7 electromechanical actuator8 first mechanical actuator8a first piston8b first nut8c first drive screw8d first drive gear9 second mechanical actuator9a second piston9d second drive gear11 first cavity13 electric motor14 driving mechanism15/15′ transmission module16 reduction module17 motor pinion gear18 idler gear19 epicyclic gear train20 input sun gear21 sun gear22 planet gears23 planet carrier24 output pinion gear26 angle transmission gear27; 27′ rotary shaft28; 28′ first worm screw29; 29′ second worm swrew31 sleeve32 external splines33 hub34 internal splinesAX1 axis of translation of the first piston 8a and ofrotation of the first drive gear 8dAX2 axis of translation of the second piston 9a andof rotation of the second drive gear 9dAX3 axis of rotation of the motor pinion gear 17AX4 axis of rotation of the input sun gear 20AY longitudinal axis of rotation of the worm screws