FR3079191A1 - APPARATUS FOR FIXING TWO OPPOSITE SENSE FORCES AND PARKING BRAKE SYSTEM COMPRISING SUCH A DEVICE - Google Patents

Abstract

Device for applying two opposing forces along a longitudinal axis (X) for a parking brake system, comprising: - a housing (6), - an electric motor (M), - a first part (12) movable in rotation and in translation, said first piece (12) being rotated by the electric motor (M), - two second pieces (10.1, 10.2) movable in translation, each having an end applying the first force and one end connected to the first piece by a screw-nut connection, the second pieces (10.1, 10.2) being displaced in opposite directions, - a spring (30) between the casing (6) and the first piece (12) so as to pressing the first piece against the casing, the spring (30) generating a second force opposing the displacement in translation of the first piece (12) of intensity equal to the maximum intensity of each of the first forces

Description

DEVICE FOR APPLYING TWO OPPOSITE SENSE FORCES AND PARKING BRAKE SYSTEM COMPRISING SUCH A DEVICE

DESCRIPTION

TECHNICAL AREA AND PRIOR ART

The present invention relates to a device for applying to an external environment two forces of the same direction and opposite directions, for example traction forces, the device being able to be implemented in a parking brake system for a motor vehicle.

The braking system of a motor vehicle has a brake at each wheel. The brakes can be disc brakes or drum brakes.

The braking system comprises a service brake system used to slow the vehicle down or to stop it in normal operation, and a parking brake system used to immobilize the vehicles, for example over a long period. This system can also be used in an emergency to immobilize the vehicle.

The parking brake system generally equips the rear brakes and sometimes the four brakes.

The parking brake can be applied by pulling on a brake lever located in the passenger compartment and connected to the brakes by a cable.

More and more often, the lever is replaced by an activation button in the passenger compartment and electric motors located at the brakes. Pressing the button activates the motors, which apply the linings to the drum in the case of a drum brake or the brake pads in the case of disc brakes.

There are brakes that combine a disc brake and a drum brake, the disc brake used for service braking, and the drum brake used for parking braking, the latter having the advantage of confirming braking during brake cooling. These brakes are designated "drum-in-hat". The brake disc in the shape of a cap, the outer part of which forms a conventional brake disc intended to cooperate with the brake pads of a disc brake, and the central part of which forms the drum of the drum brake used for parking braking.

However, for such brakes, the integration of an actuation by electric motor is complex due to the limited space available. One can then use an actuation system called “cable puller” in English terminology disposed between the two rear wheels and which is configured to exert a traction force on cables connected to the parking brake mechanism of each of the wheels. The cable puller replaces the action exerted by the parking brake lever. An example of such a system is described in document FR 2 864 598. The system comprises an electric motor, a toothed wheel driven by the motor, two screws, one fixed on one face of the toothed wheel and the other fixed. on the other face of the toothed wheel and arranged coaxially with the wheel, and cooperating with nuts which are connected to the cables of the parking brake mechanisms. When an order to activate the parking brake is given, the motor is activated, causing the gear wheel and the screws to rotate and the nuts to move towards each other along the axis of rotation and the application of a tensile force on the cables.

It is desirable to balance the tensile forces exerted on the two cables.

In addition, it is desirable that in the event of a break in one of the cables between the cable puller and one of the brakes, a tensile force is applied to the cable connected to the other brake, in order to apply the brake parking on this wheel.

STATEMENT OF THE INVENTION

It is therefore an object of the present invention to provide a device intended to apply two forces of the same direction and of opposite directions, having substantially the same intensity.

It is also an object of the present invention to provide a device intended to apply two forces of the same direction and of opposite directions offering safe operation, in particular in an application to a braking system.

The above-mentioned object is achieved by a force application device comprising an electric motor, a first part driven in rotation about a longitudinal axis by said motor, said first part also being movable in translation along the longitudinal axis, and two second parts intended to exert forces on the external environment. Each of the second pieces is connected to the first piece by a screw-nut connection, so that a rotation of the first piece causes the two second pieces to approach or move away simultaneously from each other along the 'longitudinal axis. The device also comprises elastic means capable of exerting a force against the translation of the first along the longitudinal axis in a direction, of an intensity substantially equal to that of the maximum intensity of each. of the forces that one wishes to apply.

The floating mounting of the first part ensures a balance of the forces exerted by the second parts. In addition, the use of elastic means makes it possible to make up for the clearances and to compensate for any friction at the level of the cables.

In addition, in the case of an application to a parking brake system, each second part is connected to a cable connected to a device for applying the parking brake. The implementation of these elastic means makes it possible, in the event of a break in one of the cables, to apply the tensile force to the other cable and therefore to apply the parking brake partially. In fact, the elastic means make it possible to simulate the traction which would be exerted by the other cable.

The elastic means comprise for example a helical spring mounted in compression and capable of offering a sufficient load.

Advantageously, in an application to a parking brake system, the elastic means have a load of at least 3000 N.

The subject of the present invention is therefore a device intended to apply two first forces of opposite directions along a longitudinal axis, comprising:

- a housing,

- an electric motor,

a first movable part in rotation about the longitudinal axis and movable in translation along said longitudinal axis, said first part being intended to be rotated by the electric motor,

- two second parts able to move in translation only along the longitudinal axis, each comprising a first longitudinal end intended to apply the first force and a second longitudinal end connected to the first part by a screw-nut connection, so that a rotation of the first part causes a translation of the two second parts in opposite directions,

- elastic means between the casing and the first part so as to press the first part against an axial stop, said elastic means being capable of generating a second force, opposing the translational movement of the first part, of substantially greater intensity equal to the maximum intensity of each of the first forces.

Preferably, the second parts are screws and the first part comprises two threads, in which the screws are mounted, the screws being locked in rotation by cooperation with the casing.

For example, the first part comprises a body extending along the longitudinal axis, a radial projection on the external face of the body, said radial projection comprising a first face forming a support for a longitudinal end of the elastic means and a second face in abutment against the axial stop at least in a rest state.

In one advantageous example, the radial projection forms a toothed wheel driven by the electric motor.

According to an additional characteristic, the device comprises a reducer between the electric motor and the toothed wheel and meshing with the toothed wheel, and the teeth of the toothed wheel are capable of sliding relative to the reducer along the longitudinal axis.

Preferably, the elastic means comprise a helical spring mounted in compression.

The present invention also relates to a parking brake system comprising at least two brakes and a force application device according to the present invention, each of the second parts being connected to a brake so as to apply a force thereto when activation of the parking brake system.

In one example, the brakes are drum brakes, each second part being connected to a lever articulated on a plate of a drum brake by a cable.

In another example, the brakes are disc brakes, each second part being connected to a mechanism acting on a piston by a cable.

In another example, the brakes are drum-in-hat brakes, each second part being connected to a lever carried by a drum-in-hat plate by a cable.

The second force is preferably at least 3000 N, and advantageously of the order of 3500 N.

The present invention also relates to a motor vehicle comprising four wheels, a central unit, at least one parking brake system according to the invention, and a means for activating the parking brake system located in the passenger compartment of the vehicle. .

The parking brake system is fitted, for example, at least to the rear wheels.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood on the basis of the description which follows and of the appended drawings in which:

FIG. 1 is a schematic representation of a force application device according to an embodiment in an idle state,

FIG. 2 is a schematic representation of the device of FIG. 1, in a normal activated state,

FIG. 3 is a schematic representation of the device of FIG. 1, in a degraded activated state, the left cable being broken,

- Figure 4 is a schematic representation of the device of Figure

1, in a degraded activated state, the straight cable being broken.

- Figure 5 is a schematic representation of a motor vehicle comprises a parking braking system according to the invention implementing drum brakes.

- Figure 6 is a schematic representation of a motor vehicle comprises a parking braking system according to the invention implementing disc brakes.

- Figure 7 is a schematic representation of a motor vehicle comprises a parking braking system according to the invention implementing drum-in-hat type brakes.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

In the following description, the force application device will be described mainly in an application to a braking system, but it could be applied to other systems.

In FIG. 5, one can see a motor vehicle represented diagrammatically comprising four wheels, two front wheels RF and two rear wheels RR, and a braking system.

The braking system includes a service brake system (not shown) and an FP parking brake system. In the example shown, the parking brake system FP is mounted on the rear wheels RR.

The rear wheels are fitted with drum brakes 2, each provided with a mechanism, which can be activated by pulling on a cable 4 to apply the linings against the drum and ensure parking braking. For example, the mechanism is a lever articulated in rotation on the drum brake plate and separating the two linings from one another, so that they come into contact with the drum.

The FP parking braking system includes a force application device D. The device D is for example mounted on the vehicle chassis between the two rear wheels RR. The braking system also comprises a control means by the driver, arranged in the passenger compartment, for example a button B. A control unit UC is connected to the button B and to the device D.

In Figure 1, we can see a schematic representation of an exemplary embodiment of the device D of force application.

The device D comprises a casing 6 in which are mounted the various elements ensuring the application of forces: an electric motor M electrically connected for example to the vehicle battery, and mechanical means converting the rotation of the motor M into two traction forces F1 and F2 along a longitudinal axis X and opposite directions (Figure 2).

The casing 6 has two openings 8.1, 8.2 aligned along the axis X from which the parts 10.1, 12.2 open, each connected to the parking brake mechanism of a drum brake 2 by a cable 4. The parts 10.1, 10.2 are screws or threaded rods as will be described later.

The mechanical means comprise a first part 12 mounted movable in rotation about the X axis and in translation along the X axis. The first part 12 is intended to be driven in rotation by the motor M. In the example shown , the mechanical means comprise a reduction gear 14 interposed between the motor M and the first part 12, so as to apply a desired reduction ratio. Depending on the engine, it can be envisaged that such a reduction gear is not required.

Furthermore, in the example shown, the motor shaft M is parallel to the axis X. In another example, the motor shaft is intersecting with the axis X and a bevel gear is used.

In the example shown, the first part 12 comprises a body 16 of cylindrical shape with circular section, comprising a first end face 12.1 on the side of one of the openings 8.1, and a second end face 12.2 on the side of the other of the openings 8.2, and an axial passage 18 opening into the first 12.1 and second 12.2 end faces.

The passage 18 comprises a first screw pitch 19.1 with which the screw 10.1 cooperates and a second screw pitch 19.2 inverted with respect to the first screw pitch cooperating with the screw 10.2. One of the screw threads is a step on the right and the other screw thread is a step on the left.

In addition, the screws 10.1, 10.2 are locked in rotation so as to ensure that the rotation of the first part causes the translation of the screws along the X axis.

In the example shown, the casing comprises two sleeves 20.1, 20.2 aligned along the axis X, opening outwards through the orifices 8.1, 8.2 respectively. Advantageously, the internal shape of the sleeves 20.1, 20.2 ensure the locking in rotation of the screws 10.1, 10.2 and the guiding of the screws in translation along the X axis. For example, the screws 10.1, 10.2 include heads 10.11, 10.21 of square shape cooperating with sleeves having an inner section of corresponding square shape. Any other means of locking the screws in rotation about the X axis is conceivable.

In the example shown, the first part has a radial projection 22 on the outer surface of the body. The radial projection 22 forms a toothed wheel meshing with the reducer. The toothed wheel participates in the reduction ratio, it is therefore taken into account in the calculation of the reduction ratio. The teeth of the gear are configured to slide relative to the teeth of the reducer.

The radial projection 22 delimits two axial portions 24.1, 24.2 of the body located on either side of the radial projection 22.

The portion 24.1 cooperates with the casing and provides axial and rotational guidance of the body. Advantageously, a first bearing 26 is provided between the axial portion 24.1 and the casing. Also advantageously, a second bearing 28 cooperates with the axial portion 24 and ensures its axial guidance and in rotation about the axis X. The axial dimensions of the axial portions 24.1, 24.2 and of the first and second bearings 26, 28 are such that the first part is always guided in translation and in rotation whatever the axial position of the first part 12 along the axis X. Advantageously, the bearings 26 and 28 provide prestressing of the spring.

The device also comprises elastic means 30 mounted in compression between a face 22.2 of the radial projection and the casing around the axial portion 24.2, so as to press the first part 12 against the casing.

The casing comprises, on its internal surface, an area forming an axial stop 29 for the first part 12, which has a stop face intended to cooperate with the axial stop 29 of the casing, at least in the rest state. In the representation of FIGS. 1 to 4, the axial stop face 29 is to the left of the first part 12. In the example shown, the axial stop 29 is formed by a face of the first bearing 26 and it is the face 22.1 of the radial projection 22 which bears against the axial abutment face 29 at least at rest.

In another example, the axial stop is formed directly by the casing.

The elastic means 30 comprise for example a helical spring prestressed preferably in compression by length limiting means.

The elastic means are such that they are capable of exerting a load corresponding substantially to the maximum force exerted by each screw.

In the case of an application to a parking brake, the load is at least 3000 N, advantageously of the order of 3500 N.

The operation of the force application device used as cable pul 1 of a parking brake system will now be described.

A driver who wishes to immobilize his vehicle, presses the button B for applying the parking brake. The central unit UC sends an order to activate the force application device D so as to cause the brakes to be applied, ie to exert traction on the cables. The shaft of the electric motor M, by turning in a given direction, causes the rotation of the first part 12 via the reduction gear, so that the screws 10.1, 10.2 approach each other and exert traction on the cables 4. Due to the floating mounting of the first part 12 along the longitudinal axis X, the forces applied Fl and F2 on the two cables 4 are naturally balanced (Figure 2), the two forces are equal. A balance game j _equ may appear between the stop face

22.1 and the axial stop 29.

To release the wheels, the motor M turns in the opposite direction to the given direction, causes the spacing of the screws 10.1, 10.2 and the relaxation of the traction forces on the cables 4. The brakes are released.

In the event of the cable 4 breaking to the left in the representation of the figures, the rotation of the first part 12 causes the screw 10.2 to move to the left relative to the first part 12, while in the absence of reaction exerted by the left cable, the screw 10.1 remains stationary relative to the first part 12. Due to the load applied by the spring, the first part 12 is maintained in an axial position allowing the application of a tensile force on the cable 4 right and tightening the right drum brake. A clearance j _c appears between the axial stop 29 and the stop face 22.1 of the first part 12 which corresponds to the compression of the elastic means 30, for the appearance of a reaction force in the elastic means 30 s' opposing the tensile force applied by the right cable 4. The load of the elastic means 30 compensates for the absence of reaction on the other screw 10.2 (FIG. 3). The immobilization of the vehicle obtained by the parking brake is degraded, since braking is only ensured on one brake instead of two, but nevertheless exists. Advantageously, an alert message is sent to the driver, for example in the form of a display on the dashboard and / or an audible signal. Detection is carried out, for example, by measuring the current delivered by the motor when the brake is next activated. In another example, the spring is sufficiently compressed during assembly so that there is no appearance of play between the casing and the first part.

In the event of a cable break on the right, it works similar to that in the event of a break in the left cable, the first part abuts by the face 22.1 against the stop 29 of the casing under the action of the reaction exerted on the cable in good condition. The left drum brake is applied (Figure 4). As with the break in the left cable, an alert message is advantageously sent to the driver.

Advantageously, the motor has an input enabling the parking brake to be unlocked in the event of an engine failure, for example by using a crank.

In the example shown, the first part is in one piece. According to another example, it comprises several parts assembled together.

Alternatively, the elastic means are located to the left of the first part in the representation of the drawings. Alternatively, two elastic means are provided between which the second part is kept in balance.

In FIG. 6, an example of a motor vehicle can be seen comprising a parking brake system implementing disc brakes FD1 and FD2 and a force application device according to the invention.

A disc brake comprises, for example, a yoke fixed on a wallet and overlapping a brake disc fixed to a wheel, a caliper mounted sliding with respect to the yoke and along the axis of the disc, two brake pads arranged on one side and other side of the disc and intended to come into contact with the faces of that, a piston mounted sliding in the caliper and intended to push one of the brake pads in the direction of the disc, which has the effect by reaction d '' apply the other pad on the other side of the disc. During service braking, the piston can be moved by means of a pressurized fluid.

In the parking brake, traction applied to a cable causes the piston to slide by means of a movement conversion mechanism. The movement conversion mechanism comprises for example an eccentric cam driven by a lever whose rotation is ensured by the cable, called a toggle.

The force application device according to the invention via the cables causes the disc brakes FD1 and FD2 to be applied.

In FIG. 7, a motor vehicle can be seen comprising a parking brake system implementing drum-in-hat type brakes DH1, DH2 and a force application device according to the invention.

A drum-in-hat brake combines a disc brake and a drum brake. The disc has the shape of a cap, the central part of which forms a drum, in which is placed a brake plate carrying brake shoes. A disc brake of known type cooperates with the edge of the cap. The disc brake acts as a service brake and the drum brake acts as a parking brake.

The force application device according to the invention via the cables causes the brakes DH1 and DH2 to be applied by applying the linings against the drum.

In the examples shown, only the rear wheels are equipped with a parking brake system. In another example, the four wheels are equipped with a parking brake system. In this case, a force application device is used for the front wheel brakes and a force application device is used for the rear wheel brakes. According to another example, only the front wheels are equipped with a parking brake system comprising a force application device according to the invention.

The implementation of the elastic means also makes it possible to compensate for a release of the brake, for example a release between the sheath and the brake cable.

The elastic means also make it possible to compensate for a relaxation of the brakes, in particular the disc brakes during their cooling, also called roll-away. Cooling the parking brake, after applying it, causes the disc and pads to contract. Without compensation, this contraction would decrease the forces applied elastically by the caliper / piston on the pads. Thanks to the invention, the expanding spring "absorbs" this contraction insofar as it exerts a sufficient force on the cables.

In the example described below, the activated state of the force application device corresponds to the application of tensile force via the screws which pass from a distant state to a close state. In another example, the activated state corresponds to the application of compressive force via the screws which pass from a close state to a distant state.

-NOMENCLATURE2 drum brakes cables casing

8.1, 8.2 openings,

10.1, 10.2 first gearbox body screw

19.1, 19.2 internal threads

20.1, 20.2 radial protruding sleeve

22.1, 22.2 faces of the radial projection

24.1 first portion of the body

24.2 second portion of the body first bearing second bearing axial stop elastic means

B activation button

D force application device

DH1, DH2 drum-in-hat brakes

Fl, F2 tensile forces

FD1, FD2 disc brakes

FP parking brake system

M electric motor

RF front wheels

RR rear wheels

CPU central unit

X longitudinal axis

Claims (13)

1. Device intended to apply two first forces (F1, F2) in opposite directions along a longitudinal axis (X), comprising: - a housing (6), - an electric motor (M), a first part (12) movable in rotation about the longitudinal axis (X) and movable in translation along said longitudinal axis (X), said first part (12) being intended to be rotated by the electric motor ( M) - two second parts (10.1, 10.2) able to move in translation only along the longitudinal axis (X), each having a first longitudinal end intended to apply the first force and a second longitudinal end connected to the first part by a screw-nut connection, so that a rotation of the first part (12) causes the two second parts (10.1,10.2) to translate in opposite directions, - elastic means (30) between the casing (6) and the first part (12) so as to press the first part against an axial stop (29), said elastic means (30) being capable of generating a second force, s opposing the translational movement of the first part (12), of intensity substantially equal to the maximum intensity of each of the first forces (F1, F2). 2. Device according to claim 1, in which the second parts (10.1, 10.2) are screws and the first part comprises two internal threads (19.1, 19.2), in which the screws are mounted, the screws (10.1, 10.2) being blocked in rotation by cooperation with the casing. 3. Device according to claim 1 or 2, wherein the first part (12) comprises a body (16) extending along the longitudinal axis (X), a radial projection (22) on the outer face of the body (16), said radial projection comprising a first face (22.2) forming a support for a longitudinal end of the elastic means (30) and a second face (22.2) bearing against the axial stop (29) at least in a rest state. 4. Device according to claim 3, in which the radial projection (22) forms a toothed wheel driven by the electric motor (M) 5. Device according to claim 4, comprising a reduction gear (14) between the electric motor (M) and the toothed wheel (22) and meshing the toothed wheel (22), and in which the teeth of the toothed wheel (22) are able to slide relative to the reducer (14) along the longitudinal axis (X). 6. Device according to one of claims 1 to 5, wherein the elastic means (30) comprise a helical spring mounted in compression. 7. Parking brake system comprising at least two brakes and a force application device according to one of claims 1 to 6, each of the second parts (10.1,10.2) being connected to a brake so as to apply a force when activating the parking brake system. 8. Parking brake system according to claim 7, wherein the brakes are drum brakes (2), each second part (10.1,10.2) being connected to a lever articulated on a plate of a drum brake (2 ) by a cable (4). 9. Parking brake system according to claim 7, in which the brakes are disc brakes (FD1, FD2), each second part (10.1, 10.2) being connected to a mechanism acting on a piston by a cable (4) . 10. The parking brake system according to claim 7, wherein the brakes are drum-in-hat brakes (DH1, DH2), each second part (10.1, 10.2) being connected to a lever carried by a drum plate. in-hat by a cable (4). 5 11. Parking brake system according to one of claims 7 to 10, wherein the second force is at least 3000 N, and advantageously of the order of 3500 N. 12. Motor vehicle comprising four wheels, a central unit, at least one parking brake system (FP) according to one of claims 7 to 11, and means for activating the parking brake system located in the vehicle interior. 13. Motor vehicle according to claim 12, wherein the parking brake system equips at least the rear wheels.