Disc brake, especially for motor vehicles

Abstract

The invention relates to a disc brake (F) comprising a caliper (E) comprising, opposite each other, a fixed brake pad (P1) and a movable brake pad (P2), as well as a mechanism for actuating the movable brake pad (P2) comprising a screw / nut system and means for transmitting a rotational movement of a motor shaft (4) to the screw / nut system to actuate the movable brake pad (P2), said actuating mechanism being housed in a housing (L) in the caliper (E). The invention consists in that the screw (1) is mounted fixed in translation in said housing (L) and can be driven in rotation by the transmission means, the nut (2) mounted fixed in rotation in said housing (L) being able to be driven in translation along the screw (1) during rotation of the latter, said nut (2) carrying two pistons (9) bearing against the movable brake pad (P2). Figure 2

Description

Title of the invention: Disc brake, in particular for a motor vehicle.

[0001] The invention relates to a disc brake, in particular for a motor vehicle, comprising a caliper, capable of spanning a sector of a disc secured to a wheel of said vehicle, so as to position a brake pad on each side of the disc, with means for controlling the tightening of the brake pads on the disc. Such a disc brake comprises a caliper comprising, facing one another, a fixed brake pad and a movable brake pad, as well as a mechanism for actuating the movable brake pad comprising a screw / nut system and means for transmitting a rotational movement from a drive shaft to the screw / nut system to actuate the movable brake pad, said actuating mechanism being housed in a through housing provided in the caliper.

[0002] State of the art.

[0003] In a disc brake, a caliper is rotationally fixed to the vehicle, for example to the steering knuckle forming the wheel hub. The caliper generally comprises two branches connected to each other by an arch, and spans a sector of a disc which is fixed to the wheel, with one branch on each side of the disc. The caliper grips the disc between its branches by means of a pair of friction linings, or brake pads, one on each side of the disc. For braking, these pads are clamped against the disc by the action of one or more brake pistons, actuated either by hydraulic pressure when used as a service brake or by electromechanical means when used as a parking brake. This clamping thus creates friction between the brake pads and the disc, which dissipates the kinetic energy of the wheel in the form of heat and achieves braking.

[0004] The service brake function consists of slowing down the vehicle when it is in motion, if necessary until it comes to a complete stop. In addition to the service brake, such a disc brake can be implemented to also perform an emergency brake function and / or a parking brake, also called a parking brake.

[0005] In the case where the disc brake comprises electromechanical means for actuating said brake, said electromechanical means comprise on the one hand a screw / nut group and on the other hand an electric motor-reducer assembly for rotating in both directions the nut of the screw-nut group. A disc brake of this type is, for example, described in FR-A-3 116 576.

[0006] The caliper in this document has two branches, one carrying a brake pad fixed relative to the caliper and the other a brake pad movable relative to the caliper arranged opposite each other, the movable brake pad being driven in movement towards the fixed part using an electromechanical actuator comprising a ball screw-nut system and a rotation control interface from a motor.

[0007] The nut is mounted fixed in translation in a housing of the branch of the caliper and its rotational drive by the rotational control interface of the motor generates the translational movement of the screw, one end of which is connected to the movable brake pad.

[0008] Thus, the rotational drive of the nut in a first direction causes the translation of the screw projecting from the branch of the caliper and therefore the translational drive of the movable brake pad in the direction of the fixed brake pad, to control the tightening of the disc while the rotational drive of the nut in the opposite direction causes the translational movement of the screw in the opposite direction and therefore the separation of the movable brake pad to control the loosening.

[0009] A brake such as described above, however, has a complex structure and, moreover, is relatively bulky, linked in particular to the interface between the motor shaft and the nut.

[0010] Furthermore, problems also arise related to the axial forces exerted on the screw and its interface with the brake pad. Indeed, the driving of the movable brake pad by the screw poses a problem in particular when the brake pad is large, the thrust force being applied axially but only punctually at the end of the rod. As a result, this axial thrust not distributed over the brake pad assembly can lead to a tightening defect.

[0011] The object of the invention is therefore to propose a disc brake of this type in which the structure is simpler and therefore has a reduced size and in which the application of the thrust on the brake pad is better distributed.

[0012] The subject of the invention is a disc brake comprising a caliper comprising, opposite one another, a fixed brake pad and a movable brake pad, as well as an actuating mechanism for the movable brake pad comprising a screw / nut system and means for transmitting a rotational movement of a motor pinion to the screw / nut system to actuate the movable brake pad, said actuating mechanism being housed in a through housing provided in the caliper, characterized in that: the screw of the screw-nut mechanism is mounted fixed in translation in said housing and can be driven in rotation by the transmission means, while the nut mounted fixed in rotation in said housing can be driven in translation along the screw when the latter is driven in rotation, said nut carrying at least two pistons mounted to bear against the movable brake pad, the translational drive of the nut in a first direction making it possible to drive the pistons in translation to drive the movable brake pad towards the fixed brake pad and the translational drive in the opposite direction of the nut and the pistons making it possible to separate the movable brake pad from the fixed brake pad.

[0013] Thus advantageously, the rotational drive of the screw, fixed in translation, under the effect of the actuation of the motor pinion causes the translational movement of the nut which is itself fixed in rotation. The screw being the element of the screw-nut mechanism which is driven by the motor pinion, the means for transmitting the rotation of the motor pinion to the screw requires a smaller number of parts and less bulky than those necessary to transmit the rotation of the motor pinion to a nut.

[0014] The means for transmitting a rotational movement from a motor pinion to the screw / nut system are thus also housed in said housing. These transmission means are successively constituted, from the motor shaft, by a motor pinion, a planet carrier, a so-called fixed crown and a movable crown. The movable crown is integral with both the planet carrier and the screw of the screw / nut system. Thus, advantageously, the nut locked in rotation in the housing is driven in translation under the effect of the rotational drive of the screw by the motor shaft.

[0015] This crown is advantageously made in one piece with the screw, for example constituting the end of the screw whose other end is engaged in the nut. Preferably, the screw / nut system consists of a ball screw / nut system. A cover covers the electric motor and includes the means for controlling said motor.

[0016] In addition, the nut which carries two pistons driven in translation against the movable brake pad exerts on the latter an axial thrust at two distinct support points allowing a better distribution of this thrust, in particular when the brake pad is of larger dimensions.

[0017] The brake generally comprises a caliper having two branches defining a space between them, so that the brake is thus mounted overlapping on a disc secured to a wheel, a sector of the disc being thus housed between the branches of the caliper each carrying a brake pad. One of the brake pads called mobile is drivable in displacement relative to the other pad called fixed guided in translation along an axis XX- perpendicular to the disc interposed between the brake pads, in a tightening or loosening action. The through housing is provided in one of the branches of the caliper.

[0018] The brake according to the invention therefore has a simplified, more compact structure, and therefore less expensive while providing axial thrust better distributed over the movable brake pad.

[0019] One of the branches of the caliper therefore comprises the housing in which the screw-nut system of the mechanism for actuating the movable brake pad is mounted, this cylindrical housing is open at one end in the space between said branches and accommodates at its other end the means for transmitting the rotation of the motor pinion to the screw.

[0020] According to a preferred embodiment, the nut is in the form of a cylindrical sleeve surrounding the screw, and carrying two projecting, diametrically opposed ears.

[0021] The housing is thus of complementary shape and dimensions to the nut, with two grooves to accommodate the ears of the nut, so that the nut is fixed in translation in the housing of the stirrup and can only be driven in translation in said housing under the effect of the rotation of the screw.

[0022] The two pistons respectively comprise a rod, one end of which is fixed to an ear of the nut and the other end carries the head of the piston intended to project into the space between the branches of the caliper, and to bear against the movable brake pad which is thus also moved and driven in translation towards the fixed brake pad in one direction of rotation of the screw and in withdrawal in the opposite direction of rotation.

[0023] A sealing bellows is sealingly mounted at the end of the housing with the two piston heads.

[0024] According to a first variant, the sealing bellows has a flat part, preferably reinforced by a metal insert, comprising two orifices in which the piston rods are engaged. The sealing bellows is furthermore fixed in a sealed manner to the periphery of the housing, closing said housing, with the piston heads resting against the outer face of said sealing bellows, projecting into the space between the branches of the caliper, the periphery of the holes being fixed in a sealed manner on said piston heads.

[0025] According to a second variant, a housing closure element is provided. This closure element is mounted by form cooperation in said end of the housing and carries the sealing bellows, said closure element comprising two orifices in correspondence with the orifices of the sealing bellows for the passage of the piston rods.

[0026] The brake according to the invention makes it possible to limit the size linked to the interface between the motor pinion and the screw / nut system, which also makes it possible to reduce the number of parts required and, in addition, no radial force is supported by the screw and the interface, the nut behaving like a hydraulic type piston.

[0027] In addition, since two pistons are provided, this provides better flexibility for the dimensions of the brake pads.

[0028] Advantageously, the system for actuating the movable pad comprising the screw / nut system, the two pistons and the sealing bellows constitutes a pre-assembled module which can be integrated into the housing of the caliper. Such a module is therefore assembled in the form of an assembly which is then integrated into the housing provided for this purpose in the caliper. The periphery of the bellows allows this assembly to be fixed by being fixed to a groove provided around the opening of the housing.

[0029] Alternatively, this module also comprises the closing plate on which the sealing bellows is fixed.

[0030] The present invention also relates to a motor vehicle equipped with disc brakes according to the invention.

[0031] The invention also relates to a method of manufacturing a brake according to the invention, in which a through bore is made in one of the branches of the caliper to form a housing opening into the space between the branches, the screw / nut system carrying the two pistons and the sealing bellows is mounted in said housing, one end of the screw is connected to the means for transmitting the rotational movement of a motor pinion connected to an electric motor while the sealing bellows is connected to the periphery of the housing.

[0032] The invention will now be described in more detail with reference to the drawing in which the figures represent:

[0033] [Fig.l] a perspective view of a disc brake according to the invention

[0034] [Fig.2] a cross-sectional view of a caliper of a brake according to the invention;

[0035] [Fig.3] a side perspective view of a nut of the screw / nut system according to the invention;

[0036] [Fig.4] a side perspective view of a nut and pistons of the screw / nut system according to the invention;

[0037] [Fig.5] a perspective view of the stirrup;

[0038] [Fig.6] a rear perspective view of a sealing bellows for a brake according to the invention;

[0039] [Fig.7] a side perspective view of a screw / nut system according to the invention in module form;

[0040] [Fig.8] a cross-sectional view of the system of [Fig.7];

[0041] [Fig.9] a perspective view of a brake according to the invention.

[0042] As can be seen in [Fig.l], the invention relates to a disc brake F comprising a caliper E intended to span a sector of a disc D which is secured to a vehicle wheel, for example on the hub MO.

[0043] This caliper E comprises two branches B1, B2 defining between them a space E1 in which brake pads P1, P2 extend opposite each other. intended to be located on either side of the disk sector.

[0044] A branch of the caliper B1, also called the nose of the caliper E, carries the so-called fixed brake pad PI relative to the caliper E while the second branch B2 carries the so-called mobile brake pad P2 relative to the caliper E and the mechanism for actuating the mobile brake pad.

[0045] The branch B2 thus comprises a through bore defining a housing L in which is housed as an actuating mechanism a screw / nut system actuated by a geared motor. This screw / nut system is preferably made up of a ball screw / nut assembly, comprising a screw 1, a nut 2 and balls 3 engaged in threads of the screw 1 and the nut 2.

[0046] Thus, the screw 1 and the nut 2 extend into the housing L. The screw 1 is mounted to be driven in rotation under the effect of the geared motor and fixed in translation while the nut 2 is mounted fixed in rotation in said housing L and movable in translation in said housing L under the effect of the rotational drive of the screw 1.

[0047] Means for transmitting the rotational movement of a motor pinion 5 allow the rotational drive of the screw 1 and are for example successively constituted, from the motor shaft 4, by a motor pinion 5, a planet carrier 61, a fixed crown 6 and a movable crown 7. The crown 7 is integral with both the planet carrier 6 and the screw 1. Thus, this crown 7 is made in one piece with the screw 1, for example by constituting the end of the screw 1.

[0048] The satellite pinions 8 located radially between the planet carrier 61 and the crown 7 ensure the irreversibility of the movements transmitted inside the brake F.

[0049] The motor pinion 5 is fixed to the motor shaft 4, and the planet carrier 61 meshes with the motor pinion 5 as well as the crown 7 by planet pinions 8. The screw 1 is fixed to the crown 7.

[0050] As a result, when the crown 7 is rotated under the effect of the motor pinion 5, the screw 1 is rotated. The nut 2 is itself held fixed in rotation in the housing L and is then driven in translation along the screw 1.

[0051] The nut 2 is in the form of a cylindrical sleeve 21 surrounding the screw 1, and carrying two projecting ears 22, for example diametrically opposed or placed on either side of the sleeve 21 in mirror symmetry.

[0052] The housing L is thus of complementary shape and dimensions to the nut 2 mounted on the screw 1, having a bore and two grooves R at the periphery of the bore so that the nut 2 is fixed in translation in the housing L of the stirrup E, due to the ears 22 engaged in the grooves R of complementary shapes and dimensions and only drivable in translation in said housing L under the effect of the rotation of the screw 1. The branch B2 further comprises fixing orifices FI for the branch BL

[0053] The nut 2 carries two pistons 9 which respectively comprise a rod 91, one end of which is fixed to an ear 22 of the nut 1 and the other end of which carries the head of the piston 92. This latter end of the rod 91 is also engaged through an orifice O provided at the end of each groove R.

[0054] The rod 91 of the pistons 9 is also engaged in a through orifice 11 provided in a sealing bellows 10.

[0055] This sealing bellows 10 is intended to be placed at the end of the housing L of the caliper 2 to seal said housing L, with the piston heads 92 projecting into the space El between the branches Bl, B2 of the caliper E as can be seen in [Fig.9].

[0056] This sealing bellows 10 has a flat central part 12 made rigid using a metal insert, and in which through orifices 11 are provided, this central part 12 being surrounded by a skirt 13, in particular folded in the shape of an accordion, in a closing element 15 in the form of a metal plate comprising passage orifices for the rods 91 of the pistons 9, the plate 15 having dimensions and a shape allowing forcible engagement in the end of the housing L (as can be seen [Fig.8]).

[0057] Alternatively, the skirt 13 of the sealing bellows 10 is fixed, also folded in an accordion shape, in a fixing groove at the periphery of the end of the housing L, as can be seen in [Fig.2].

[0058] The sealing bellows 10 also has flexible accordion-shaped parts, fixed between the periphery of the through hole 11 of the sealing bellows 10 and the head 92 of a piston 9, making it possible to guarantee the sealing of the housing L during the movement of the pistons 9.

[0059] The sealing bellows 10 is thus mounted in a sealed manner at the end of the housing L with the two piston heads 92 intended to project into the space El between the branches Bl, B2 of the stirrup E, the deployment of the accordion-folded parts maintaining the fixing and the sealing.

[0060] The piston heads 92 bear against the movable brake pad P2. Thus, in a first direction of rotation of the screw 1, the nut 2 is driven in translation so that the pistons 9 are driven in projection into the space E1 and, in abutment against the movable brake pad P2, to drive the latter in translation towards the fixed brake pad P1 to tighten the disc.

[0061] In the opposite direction to the rotation of the screw 1, the nut 2 is driven in translation backwards in the housing L, causing the pistons 9 to withdraw, which separates the movable plate P2 from the fixed plate PI in the direction of loosening.

[0062] At the other end of the housing L, the bore has a larger diameter in which the means for transmitting the rotational movement of the pinion are housed. motor 5 to screw 1 such as a planet carrier 6 and a crown 7. This crown 7 is therefore integral with both the planet carrier 6 and the screw 1. As can be seen in [Fig.3], this crown 7 constitutes the end of the screw 1.

[0063] The through bore is made in the branch B2 of the caliper E to form the housing L opening into the space El between said branch B2 and the branch Bl. The screw / nut system is mounted in said housing, with a piston 9 connected to the nut 2, extending between each ear 22 of the nut 2 and the sealing bellows 10, mounted at the end of the housing L.

[0064] The means for transmitting the rotational movement are mounted at the end of the bore, the end of the screw 1 in the form of a crown 7 being connected to the planet carrier 6 which is engaged with the motor pinion 5, the latter then being connected to the motor shaft 4 of an electric motor M, mounted in a housing B fixed to the bracket E at the outlet of the housing L and closed using a protective cover C.

[0065] The end of each rod 91 of piston 9 being fixed in an orifice of an ear 22 of nut 2, it is possible to adjust the position of this fixing to offset one of the piston heads relative to the other, which makes it possible to adjust the axial thrust stroke of each piston head 92 relative to the movable brake pad. As a result, it is possible to compensate for a difference in axial thrust and therefore a risk of wear of the lining of the brake pad.

[0066] Preferably, the brake pad linings have a material removal on a part of said lining, thus allowing attenuation of the noise of the pad on the disc.

[0067] Of course, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without departing from the scope of the invention.

[0068] NOMENCLATURE F disc brake E stirrup MO hub D disk Bl, B2 branch of the stapes The space between the branches of the stirrup PI fixed brake pad P2 movable brake pad The accommodation R groove O orifice FI fixing hole 1 screw 2 nuts 21 sleeve 22 ear 3 marbles 4 shaft motor 5 motor pinion 61 satellite carrier 6 fixed crown 7 mobile crown 8 satellite pinion 9 piston 91 stem 92 piston head 10 sealing bellows 11 through hole 12 central part 13 skirt 15 closing element M electric motor B electric motor housing C protective cover

Claims

Claims

1. Disc brake (F) comprising a caliper (E) comprising, opposite each other, a fixed brake pad (PI) and a movable brake pad (P2), as well as a mechanism for actuating the movable brake pad (P2) comprising a screw / nut system and means for transmitting a rotational movement of a drive shaft (4) to the screw / nut system to actuate the movable brake pad (P2), said actuating mechanism being housed in a through housing (L) provided in the caliper (E), characterized in that the screw (1) of the screw-nut mechanism is mounted fixed in translation in said housing (L) and drivable in rotation by the transmission means, while the nut (2) mounted fixed in rotation in said housing (L) is drivable in translation along the screw (1) when the latter is driven in rotation, said nut (2) carrying at least two pistons (9) mounted in support against the movable brake pad (P2),the translational drive of the nut (2) in a first direction allowing the pistons (9) to be driven in translation to drive the movable brake pad (P2) towards the fixed brake pad (PI) and the translational drive in the opposite direction of the nut (2) and the pistons (9) allowing the movable brake pad (P2) to be moved away from the fixed brake pad (PI).,

2. Disc brake (F) according to claim 1, characterized in that one (B2) of the branches (Bl, B2) of the caliper (E) comprises the housing (L) in which the screw-nut system is mounted, this cylindrical housing (L) with circular section, is open at one end in the space (El) between said branches (Bl, B2) and accommodates at its other end at least in part, the means for transmitting the rotation of the motor pinion (5) to the screw (1).

3. Disc brake (F) according to claim 1 or 2, characterized in that the nut (2) is in the form of a cylindrical sleeve (21) surrounding the screw (2), and carrying two ears (22) projecting from the sleeve (21), diametrically opposed.

4. Disc brake (F) according to claim 3, characterized in that the housing (L) is thus of shape and dimensions complementary to the nut on the screw, with two grooves (R) to accommodate the ears (22) of the nut (2).

5. Disc brake (F) according to one of claims 3 or 4, characterized in that the two pistons (9) respectively comprise a rod (91) one end of which is fixed on an ear (22) of the nut (2) and the other end carries the head (92) of the piston (9) intended to project into the space (El) between the branches (Bl, B2) of the caliper (E), and bearing against the movable brake pad (P2).

6. Disc brake (F) according to claim 5, characterized in that a sealing bellows (10) is mounted in a sealed manner between the end of the housing (L) and the two heads (92) of the piston (9).

7. Disc brake (F) according to claim 6, characterized in that the sealing bellows (10) has a flat part, preferably reinforced by a metal insert, comprising two orifices in which the rods (91) of the pistons (9) are engaged.

8. Disc brake (F) according to one of claims 6 or 7, characterized in that the screw / nut system, the two pistons (9) and the sealing bellows (10) constitute a pre-assembled module which can be integrated into the housing (L) of the caliper (E).

9. Disc brake (F) according to claim 8, characterized in that a closing element (15) of the housing (L) is mounted by form cooperation in the end of the housing (L) and carries the sealing bellows (10), said closing element (15) comprising two orifices in correspondence with the through orifices (11) of the sealing bellows (10) for the passage of the rods (91) of the piston (9).

10. Disc brake (F) according to claim 9, characterized in that the screw / nut system, the two pistons (9), the sealing bellows (10) and the closing plate (15) constitute a pre-assembled module which can be integrated into the housing (L) of the caliper (E).

11. Disc brake (F) according to one of claims 1 to 10, characterized in that the means for transmitting a rotational movement of a motor pinion to the screw / nut system are also housed in said housing (L) and constituted, from the motor shaft (4), of a motor pinion (5), a planet carrier (6) and a movable crown (7), integral with both the planet carrier (6) and the screw (1) of the screw / nut system.

12. Disc brake (F) according to claim 11, characterized in that the crown (7) is made in one piece with the screw (1), such as to constitute the end of the screw (1), the other end of which is engaged in the nut (2).

13. Motor vehicle equipped with disc brakes according to one of claims 1 to 12.

14. Method for manufacturing a disc brake (F) comprising a caliper (E) comprising, opposite each other, a fixed brake pad (PI) and a movable brake pad (P2), as well as a mechanism for actuating the movable brake pad (P2) comprising a screw / nut system and means for transmitting a rotational movement of a motor pinion (5) to the screw / nut system to actuate the movable brake pad (P2), according to one of the claims, characterized in that a through bore is made in one of the branches of the caliper (E) to form a housing (L) opening into the space (El) between the branches (Bl, B2), the screw / nut system is mounted in said housing (L), one end of the screw (1) is connected to the means for transmitting the rotational movement of a motor pinion (5) connected to an electric motor (M) while the end of the nut (2) is fixed to the movable brake pad (P2).

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