Disc brake comprising two pistons and vehicle comprising at least two such brakes

Abstract

The invention relates to a disc brake (1) comprising a caliper (5) provided with two pistons (17, 19) capable of applying, on command, a pad (23) against a face (13.2) of a disc (13), characterized in that it comprises means for increasing the force required for the advancement of one of the pistons (17, 19) towards the disc (13) relative to the force required for the advancement of the other piston (19, 17) towards the disc (13).

Description

DESCRIPTION TITLE: DISC BRAKE WITH TWO PISTONS AND VEHICLE WITH AT LEAST TWO SUCH BRAKES TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates to a disc brake typically with a floating caliper comprising at least two pistons and to a vehicle comprising at least two such brakes. PREVIOUS STATE OF THE ART

[0002] The plaintiff discovered that two-piston floating caliper disc brakes exhibit operational instability because, depending on the individual brake unit, when hydraulic pressure is applied, one of the two pistons (the torque input piston or the torque output piston) moves toward the brake disc faster than the other piston (the torque output piston or the torque input piston). Thus, the behavior of these two-piston brakes is unpredictable, with no predictable pattern until the brake pads are fully engaged with the disc. This unpredictable behavior prevents optimal noise and vibration reduction.

[0003] It is therefore an object of the present invention to provide a disc brake, preferably with a floating caliper, comprising at least two pistons whose behavior during the application of braking pressure is predetermined or at least pre-terminal. It is also an object of the present invention to provide such a brake optimized to reduce or eliminate noise and vibration. It is also an object of the present invention to provide a vehicle comprising at least two brakes according to the invention. These objects are achieved by a brake comprising means for forcing one of the pistons to approach the disc more quickly than the other piston. The vehicle according to the invention advantageously comprises brakes according to the invention arranged symmetrically with respect to a longitudinal plane of symmetry of the vehicle. DESCRIPTION OF THE INVENTION

[0004] The invention aims to remedy all or part of the drawbacks of the prior art.

[0005] In this regard, the invention relates to a disc brake comprising a caliper equipped with two pistons capable of applying, on command, a pad to one face of a disc characterized in that it comprises means increasing the force required to advance one of the pistons towards the disc compared to the force required to advance the other piston towards the disc, in that it comprises seals and in that one of the seals ensures the increase of the force required to advance one of the pistons towards the disc, in that the increase of the force required to advance one of the pistons towards the disc is achieved by friction, and in that the increase of the force required to advance one of the pistons towards the disc is achieved by a modification of the surface condition of a seal.

[0006] The invention also relates to such a disc brake according to the invention characterized in that said brake is a floating caliper brake.

[0007] The invention also relates to such a disc brake according to the invention characterized in that said brake is a hydraulic brake.

[0008] The invention also relates to such a disc brake according to the invention characterized in that it comprises seals and in that one of the seals ensures the increase of the force necessary for the advancement of one of the pistons towards the disc.

[0009] The invention also relates to such a disc brake according to the invention characterized in that the increase in the force required to advance one of the pistons towards the disc is achieved by the constriction of the seal around said piston.

[0010] The invention also relates to such a disc brake according to the invention characterized in that it comprises receiving and axially guiding cylinders for the pistons, each provided with a groove for receiving a seal, and in that the receiving groove for a first seal of a first piston is deeper than the receiving groove for a second seal of a second piston.

[0011] The invention also relates to such a disc brake according to the invention characterized in that increasing the force required to advance one of the pistons towards the disc is achieved by friction.

[0012] The invention also relates to such a disc brake according to the invention characterized in that increasing the force required to advance one of the pistons towards the disc is achieved by a modification of the surface condition of a seal.

[0013] The invention also relates to such a disc brake characterized in that the difference in force required to advance one of the pistons towards the disc compared to the force required to advance the other piston towards the disc is between 20N and 100N.

[0014] The invention also relates to a motor vehicle characterized in that it comprises at least one disc brake according to the invention.

[0015] The invention also relates to such a motor vehicle according to the invention characterized in that it comprises two brakes according to the invention arranged on a front axle of the vehicle.

[0016] The invention also relates to such a motor vehicle according to the invention characterized in that it comprises two brakes according to the invention arranged on an axle of the vehicle, the brakes being symmetrical with respect to a longitudinal plane of symmetry of the vehicle.

[0017] The invention also relates to such a motor vehicle according to the invention characterized in that it comprises two identical brakes according to the invention arranged on one axle of the vehicle. BRIEF DESCRIPTION OF THE FIGURES

[0018] The present invention will be better understood upon reading the description of non-limiting examples of embodiments, with reference to the attached figures, which illustrate: - [Fig. 1]: a radially external schematic view of a brake according to the invention in the rest position; - [Fig. 2]: a radially external schematic view of a brake according to the invention in braking position; - [Fig. 3]: a radially external schematic view of a first embodiment of a brake according to the invention during the approach of the brake pad towards the disc; [Fig. 4]: a radially external schematic view of a second preferred embodiment of a brake according to the invention during the approach of the brake pad towards the disc. DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT

[0019] For clarity, identical elements are identified by identical reference symbols from one figure to another.

[0020] Radial orientation refers to the distance from the axis of rotation of a brake disc. Axial orientation refers to a distance or displacement parallel to the axis of rotation of a brake disc. Tangential orientation refers to a distance concentric to the tangent of the brake disc. Internal orientation refers to the direction inward from the vehicle. External orientation refers to the direction outward from the vehicle. Radially external orientation refers to an increase in the distance from the axis of rotation of a brake disc.

[0021] Figure 1 shows the preferred example of a brake 1 according to the present intervention, comprising a yoke (not shown) and a floating caliper 5. The yoke is equipped with means for fixing it to a motor vehicle chassis. The caliper 5 is mounted to slide relative to the yoke on guide pins 7. The caliper 5 has a caliper nose 9 and an arch 11 that overlaps a brake disc 13 which is rotationally fixed to a wheel of a vehicle, typically a front wheel. The clevis also overlaps the brake disc 13. An outer pad 15 with a friction lining is carried by the caliper nose 9. The friction lining of the outer pad 15 is arranged opposite an outer main face 13.1 of the disc 13. The caliper 5 has a first piston 17 at the torque input when the vehicle is moving forward and a second piston 19 at the torque output when the vehicle is moving forward.Forward movement is symbolized in the figures by arrow 21 indicating the direction of rotation of disc 13. Pistons 17 and 19 exert a force, as controlled, on an inner pad 23, in the direction of an internal principal face 13.2 of disc 13, parallel and opposite to the external principal face 13.1. In the advantageous, but not limiting, example shown, the brake 1 is a hydraulic brake; pistons 17 and 19 are housed in parallel cylinders 25, with sealing ensured by seals 27, typically square seals surrounding the pistons. Advantageously, each seal 27 is partially housed in a cylindrical groove formed in the wall of the corresponding cylinder 25. The cylinders 25 are connected to each other and to a hydraulic pressure source P (Figs. 2 to 4). Thus, pistons 17 and 19 are subjected to the same pressure.

[0022] Pistons 17 and 19 advantageously have the same diameter, for example, 36, 43, or 67 mm. Two-piston floating caliper disc brakes are intended for heavy vehicles with a mass exceeding two tonnes, for example, commercial vehicles, and / or high-performance vehicles.

[0023] When pressure P is applied in the cylinders 25, the pistons 17 and 19 advance axially and push the inner pad 23 against the inner face 13.2 of the disc 13. By reaction, the caliper 5 moves back relative to the yoke and the caliper nose 9 applies the outer pad 15 to the outer face 13.1 of the disc 13 as illustrated in Figure 2.

[0024] Unfortunately, the variations in the mass production of the brakes do not allow the simultaneous application of the pistons 17 and 19, the brake pad K 553 23 is positioned at an angle relative to the disc before reaching the equilibrium position illustrated in Figure 2.

[0025] Furthermore, depending on the brake unit in question, piston 17, as illustrated in Figure 3, or piston 19, as illustrated in Figure 4, moves more rapidly towards the disc 13. The braking balance, and in particular the attenuation of noise and vibration, cannot therefore be optimized without knowing in advance, during the design of the brake or at least its adaptation to a vehicle model, which piston moves more rapidly towards the disc 13.

[0026] According to the invention, the force required to advance one of the pistons 17, 19 towards the disc 13 is modified in relation to the force required to advance the other piston 19, 17 towards the disc 13.

[0027] Advantageously, the force required to advance one of the pistons 17, 19 towards the disc 13 is increased relative to the force required to advance the other piston 19, 17 towards the disc 13. Preferably, the increase in the force required to retract the pistons is avoided or minimized in order to avoid or minimize the residual braking torque in the absence of a braking command.

[0028] The increase in the force required to advance one of the pistons 17, 19 towards the disc 13, compared to the force required to advance the other piston 19, 17 towards the disc 13, is sufficient to overcome variations in the force required to advance one of the pistons 17, 19 resulting from manufacturing variations and tolerances within a batch or model of brake. For example, the difference in force required to advance between pistons 17 and 19 is between 5 N and 1000 N, preferably between 1000 N and 200 N, and even more preferably between 20 N and 1000 N, for example, equal to 30 N, 5000 N, or 90 N.

[0029] The increase in the force required to advance one of the pistons 17, 19 towards the disc 13, compared to the force required to advance the other piston 19, 17 towards the disc 13, is advantageously achieved by varying the constricting force of the seal 27 of one of the pistons. For example, the internal diameter of this seal 27 is reduced. Advantageously, the depth of the groove machined in the cylinder receiving this seal 27 is also reduced.

[0030] Alternatively, the increase in the force required to advance one of the pistons 17, 19 towards the disk 13, compared to the force required to advance the other piston 19, 17 towards the disk 13, is achieved by varying the friction force advantageously between the seal 27 and the piston 17 or the piston 19. For example, one of the seals 27 has rheological characteristics different from those of the other seal 27. One of the seals 27 has a different hardness, surface finish (in particular roughness), or coating than the other seal. For example, one of the seals 27 has grooves or, advantageously, a fir-tree or similar pattern, increasing the force required to advance a piston towards the disk 13 without significantly increasing the piston's recoil force.

[0031] It is understood that modifications to one of the seals 27 do not compromise the brake's sealing.

[0032] Alternatively, one of the pistons 17, 19 has return means (elastic, magnetic, electrostatic or other) to the position when braking is not applied. K 553

[0033] Figure 3 shows an example of an embodiment of a brake according to the invention, in an intermediate position between the positions of Figure 1 and the position of Figure 2, in which the piston at the torque input 17, i.e., which first receives the movement 21 of the disc 13, presents a force F17 opposing the advancement of the piston 17 towards the inner face 13.2 of the disc 13 that is less than a force F19 opposing the advancement of the piston at the torque output 19 towards the inner face 13.2 of the disc 13. Thus, the side of the inner pad 23 driven by the piston 17 at the torque input comes into contact with the inner face 13.2 of the disc 13 before the side of the inner pad 23 driven by the piston 19 which is at the torque output. This solution has the advantage of self-energising of the pad, meaning that it tends to increase the pressure of the pad due to the movement of the disc.

[0034] Figure 4 shows a preferred embodiment of a brake according to the invention, in a position intermediate between the positions of Figure 1 and Figure 2. In this embodiment, the piston 19, which is the last to receive the movement 21 from the disc 13, exerts a force F19 opposing the advancement of the piston 19 towards the inner face 13.2 of the disc 13. This force is less than the force F17 opposing the advancement of the piston 17 towards the inner face 13.2 of the disc 13. Thus, the side of the inner pad 23 driven by the piston 19 at the output of the torque comes into contact with the inner face 13.2 of the disc 13 before the side of the inner pad 23 driven by the piston 17 at the input of the torque. This embodiment provides better stability of the inner pad 23 during braking engagement.

[0035] Figures 3 and 4 illustrate a non-limiting example of the brake according to the invention in which the caliper 5 slides, establishing contact between the outer pad 15 and the outer face 13.1 of the disc 13 at the moment when the inner pad 23 comes into contact with the inner face 13.2 of the disc 13.

[0036] In a first embodiment, a vehicle according to the invention has two identical brakes according to the invention on the front axle, allowing the standardization of brake production.

[0037] In a second embodiment, a vehicle according to the invention has on the front axle two brakes according to the invention symmetrical with respect to a longitudinal plane of symmetry of the vehicle.

[0038] It is understood that the implementation of brakes with more than two pistons, fixed brakes and / or electric brakes does not fall outside the scope of the present invention. LIST OF DIGITAL REFERENCES

[0039] 1 K 553

Claims

K 553 DEMANDS 1. Disc brake (1) comprising a caliper (5) equipped with two pistons (17, 19) capable of applying, on command, a brake pad (23) to a face (13.2) of a disc (13) characterized in that it comprises means increasing the force required to advance one of the pistons (17, 19) towards the disc (13) relative to the force required to advance the other piston (19, 17) towards the disc (13), in that it comprises seals (27) and in that one of the seals (27) ensures the increase in the force required to advance one of the pistons (17, 19) towards the disc (13), in that the increase in the force required to advance one of the pistons (17, 19) towards the disc (13) is achieved by friction, and in that the increase in the force required to advance one of the pistons (17, 19) towards the disc (13) is achieved by a modification of the surface condition of a seal (27).

2. Disc brake (1) according to claim 1 characterized in that said brake is a floating caliper brake.

3. Disc brake (1) according to claim 1 or 2 characterized in that said brake is a hydraulic brake.

4. Disc brake (1) according to claim 3 characterized in that the increase in the force required to advance one of the pistons (17, 19) towards the disc (13) is achieved by the constriction of the seal (27) around said piston (17,19).

5. Disc brake (1) according to claim 4 characterized in that it comprises receiving and axially guiding cylinders (25) for the pistons (17,19) each provided with a receiving groove for a seal (27) and in that the receiving groove for a first seal (27) of a first piston (17,19) is deeper than the receiving groove for a second seal (27) of a second piston (19,17).

6. Disc brake (1) according to any one of the preceding claims characterized in that the increase in the force required to advance one of the pistons (17, 19) towards the disc (13) is achieved by friction.

7. Disc brake (1) according to any one of the preceding claims characterized in that the difference in force required to advance one of the pistons (17, 19) towards the disc (13) compared to the force required to advance the other piston (19, 17) towards the disc (13) is between 20N and 100N.

8. Motor vehicle characterized in that it comprises at least one brake (1) according to any one of the preceding claims.

9. Motor vehicle according to the preceding claim characterized in that it comprises two brakes (1) according to any one of the claims there 7 arranged on a front axle of the vehicle.

10. Motor vehicle according to claim 8 or 9 characterized in that it comprises two brakes (1) according to any one of claims 11 7 arranged on an axle of the vehicle, the brakes (1) being symmetrical with respect to a longitudinal plane of symmetry of the vehicle.

11. Motor vehicle according to claim 8 or 9 characterized in that it comprises two identical brakes (1) according to any one of claims 1 to 7 arranged on an axle of the vehicle.

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