Disc brake, especially for motor vehicles

Abstract

The invention relates to a disc brake (F) comprising a caliper (E) having opposite each other a fixed brake pad (P1) and a movable brake pad (P2), and an actuation mechanism for the movable brake pad (P2) comprising a screw / nut system and means for transmitting a rotational movement from a drive shaft (4) to the screw / nut system to actuate the movable brake pad (P2), said actuation mechanism being housed in a through housing (L) formed in the caliper (E).The invention consists in that the screw (1) of the screw-nut mechanism is mounted fixed in translation within said housing (L) and can be driven in rotation by the transmission means, while the nut (2), also mounted fixed in rotation within said housing (L), can be driven in translation along the screw (1) when the latter is rotated. The nut (2) carries at least two pistons (9) mounted to bear against the movable brake pad (P2). The translational drive of the nut (2) in a first direction allows the pistons (9) to be driven in translation, thus moving the movable brake pad (P2) towards the fixed brake pad (P1). The translational drive of the nut (2) and the pistons (9) in the opposite direction allows the movable brake pad (P2) to be moved away from the fixed brake pad (P1). Figure 2.

Description

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

[0001] The invention relates to a disc brake, particularly for a motor vehicle, comprising a caliper capable of spanning a sector of a disc attached to a wheel of said vehicle, so as to position a brake pad on each side of the disc, with means for controlling the clamping of the brake pads on the disc. Such a disc brake comprises a caliper having, opposite each other, a fixed brake pad and a movable brake pad, as well as an actuation mechanism for 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 actuation mechanism being housed in a through-hole formed 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 wheel hub. The caliper generally comprises two arms connected by a crossbar and spans a sector of a disc that is fixed to the wheel, with one arm on each side of the disc. The caliper clamps the disc between its arms by means of a pair of friction linings, or brake pads, one on each side of the disc. For braking, these pads are pressed 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 creates friction between the brake pads and the disc, which dissipates the kinetic energy of the wheel as heat and achieves braking.

[0004] The service brake function consists of slowing the vehicle down while it is moving, if necessary to a complete stop. In addition to the service brake, such a disc brake can also be used as an emergency brake and / or parking brake, also called a parking brake.

[0005] Where the disc brake includes electromechanical means for actuation of said brake, said electromechanical means comprise, on the one hand, a screw / nut assembly and, on the other hand, an electric geared motor assembly for rotating the nut of the screw / nut assembly in both directions. A disc brake of this type is, for example, described in FR-A-3 116 576.

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

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

[0008] Thus, the rotation of the nut in a first direction causes the translation of the protruding screw of the caliper arm and therefore the translation of the moving brake pad towards the fixed brake pad, to control the tightening of the disc while the rotation of the nut in the opposite direction causes the translation of the screw in the opposite direction and therefore the spreading of the moving brake pad to control the loosening.

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

[0010] Furthermore, problems also arise related to the axial forces acting on the screw and its interface with the brake pad. Indeed, the drive of the moving brake pad by the screw poses a particular problem when the brake pad is large, as the thrust force is applied axially but only at a specific point on the end of the rod. Consequently, this axial thrust, not distributed over the entire brake pad, can lead to a tightening failure.

[0011] The invention therefore aims to provide 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 invention relates to a disc brake comprising a caliper having, opposite each other, a fixed brake pad and a movable brake pad, as well as an actuation mechanism for the movable brake pad comprising a screw / nut system and means for transmitting a rotational movement from a drive pinion to the screw / nut system to actuate the movable brake pad, said actuation mechanism being housed in a through-hole formed in the caliper characterized in that: The screw of the screw-nut mechanism is fixed in translation within said housing and can be driven in rotation by the transmission means. while the nut, fixed in rotation within said housing, can be driven in translation along the screw when the latter is rotated, said nut having at least two pistons mounted to bear against the movable brake pad, the translational drive of the nut in a first direction allowing the pistons to be driven in translation to move the movable brake pad towards the fixed brake pad and the translational drive in the opposite direction of the nut and the pistons allowing the movable brake pad to be moved away from the fixed brake pad.

[0013] Thus, advantageously, the rotational drive of the screw, which is fixed in translation, by the action of the drive pinion causes the translational movement of the nut, which is itself fixed in rotation. Since the screw is the element of the screw-nut mechanism driven by the drive pinion, the means for transmitting the rotation from the drive pinion to the screw require fewer and less bulky parts than those needed to transmit the rotation from the drive pinion to a nut.

[0014] The means for transmitting a rotational motion from a drive pinion to the screw / nut system are also housed within said housing. These transmission means consist successively, from the drive shaft, of a drive pinion, a planet carrier, a fixed ring gear, and a rotating ring gear. The rotating ring gear is fixed to both the planet carrier and the screw of the screw / nut system. Thus, advantageously, the nut, which is locked against rotation in the housing, is driven in translation by the rotational drive of the screw by the drive shaft.

[0015] This crown is advantageously made in one piece with the screw, for example, forming the end of the screw, the other end of which is engaged in the nut. Preferably, the screw / nut system consists of a ball screw / nut system. A cover encloses the electric motor and houses the motor control means.

[0016] In addition, the nut which carries two pistons driven in translation against the movable brake pad exerts an axial thrust on the latter 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 with two arms defining a space between them, such that the brake is mounted overlapping a disc attached to a wheel. A sector of the disc is thus housed between the arms of the caliper, each carrying a brake pad. One of the brake pads, called the moving pad, is steerable relative to the other, called the fixed pad, which is guided in translation along an axis XX- perpendicular to the disc interposed between the brake pads, in a clamping or releasing action. The through-hole is provided in one of the arms of the caliper.

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

[0019] One of the arms of the caliper therefore includes the housing in which the screw-nut system of the actuation mechanism of the movable brake pad is mounted; this cylindrical housing is open at one end in the space between said arms 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 protruding, diametrically opposed lugs.

[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 caliper 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 on an ear of the nut and the other end carries the head of the piston intended to protrude into the space between the arms 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 retreat in the opposite direction of rotation.

[0023] A sealing bellows is mounted in a hermetic manner at the end of the housing with the two piston heads.

[0024] According to a first embodiment, the sealing bellows has a flat portion, preferably reinforced by a metal insert, having two orifices into which the piston rods are engaged. The sealing bellows is further fixed in a hermetic manner to the periphery of the housing, closing said housing, with the piston heads resting against the outer face of said sealing bellows, protruding into the space between the arms of the caliper, the periphery of the holes being fixed in a hermetic manner to said piston heads.

[0025] According to a second embodiment, 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 having two orifices corresponding to 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 bulk associated with the interface between the motor pinion and the screw / nut system, which also makes it possible to reduce the number of parts required and, moreover, no radial force is supported by the screw and interface, the nut behaving like a hydraulic type piston.

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

[0028] Advantageously, the actuation system for the movable pad, comprising the screw / nut system, the two pistons, and the sealing bellows, constitutes a pre-assembled module that can be integrated into the caliper housing. Such a module is thus assembled as a unit which is then integrated into the housing provided for this purpose in the caliper. The periphery of the bellows allows this assembly to be secured by attaching to a groove provided around the opening of the housing.

[0029] Alternatively, this module also includes the closing plate to which the sealing bellows is attached

[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 arms of the caliper to form a housing opening into the space between the arms, the screw / nut system carrying the two pistons and the sealing bellows is mounted in said housing, one end of the screw is connected with the means for transmitting the rotational movement of a drive 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. 1] A perspective view of a disc brake according to the invention

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

[0035] [Fig.3] a lateral 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 the 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 the invention;

[0039] [Fig.7] a lateral perspective view of a screw / nut system according to the invention under module shape;

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

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

[0042] As can be seen in [Fig. 1], the invention relates to a disc brake F comprising a caliper E intended to straddle a sector of a disc D which is fixed to a vehicle wheel, for example on the hub MO.

[0043] This caliper E comprises two arms Bl, B2 defining between them a space El in which brake pads PI, P2 extend opposite each other, intended to be on either side of the sector of the disc.

[0044] One arm of the caliper Bl, also called the nose of the caliper E, carries the brake pad said to be fixed PI relative to the caliper E, while the second arm B2 carries the brake pad said to be mobile P2 relative to the caliper E and the actuation mechanism of the mobile brake pad.

[0045] The arm B2 thus comprises a through bore defining a housing L in which a screw / nut system, actuated by a geared motor, is housed as an actuation mechanism. This screw / nut system preferably consists 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 in 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 drive in rotation of the screw 1.

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

[0048] The satellite gears 8 located radially between the planet carrier 61 and the ring 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 the motor pinion 5 as well as the ring gear 7 by means of planet gears 8. The screw 1 is fixed to the ring gear 7.

[0050] Consequently, when the ring 7 is rotated by the drive pinion 5, the screw 1 is rotated. The nut 2 is held fixed in rotation within 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 protruding lugs 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 of so that the nut 2 is fixed in translation in the housing L of the caliper E, due to the lugs 22 engaged in the grooves R of complementary shapes and dimensions and only driveable in translation in said housing L under the effect of the rotation of the screw 1. The arm B2 also has fixing holes FI for the arm Bl.

[0053] The nut 2 carries two pistons 9 which respectively comprise a rod 91, one end of which is fixed on an lug 22 of the nut 1 and the other end carries the head of the piston 92. This latter end of the rod 91 is also engaged through an orifice O formed 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 protruding into the space El between the arms Bl, B2 of the caliper E as can be seen in [Fig.9].

[0056] This sealing bellows 10 has a central flat part 12 made rigid by means of 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 having passage orifices for the rods 91 of the pistons 9, the plate 15 having dimensions and a shape allowing the force 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 ensure 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 protrude into the space El between the arms Bl, B2 of the caliper E, the deployment of the accordion-folded parts maintaining the fixing and the sealing.

[0060] The piston heads 92 are in contact with 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 protruding into the space El and, in contact with the movable brake pad P2, to drive the latter in translation towards the fixed brake pad PI to clamp the disc.

[0061] In the opposite direction of rotation of the screw 1, the nut 2 is driven in translation and retracted in the housing L, causing the pistons 9 to retract, 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 drive pinion 5 to the screw 1 are housed, such as a planet carrier 6 and a ring gear 7. This ring gear 7 is therefore integral with both the planet carrier 6 and the screw 1. As can be seen in [Fig. 3], this ring gear 7 constitutes the end of the screw 1.

[0063] The through bore is made in the arm B2 of the caliper E to form the housing L opening into the space El between said arm B2 and the arm Bl. The screw / nut system is mounted in said housing, with a piston 9 connected to the nut 2, extending between each lug 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 crown-shaped screw 1 7 being connected with the planet carrier 6 which is in contact with the motor pinion 5, the latter being then connected to the motor shaft 4 of an electric motor M, mounted in a housing B fixed on the bracket E at the exit of the housing L and closed with a protective cover C.

[0065] The end of each piston rod 91 of the piston 9 is fixed in an opening in a lug 22 of the nut 2. It is possible to adjust the position of this fixing to offset one of the piston heads relative to the other, thereby adjusting the axial thrust stroke of each piston head 92 relative to the moving brake pad. This makes it possible to compensate for a difference in axial thrust and thus a risk of wear on the brake pad lining.

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

[0067] Of course, the invention is not limited to the examples just described and many modifications can be made to these examples without departing from the scope of the invention.

[0068] NOMENCLATURE F disc brake E caliper MO hub D disk Bl, B2 stapes branch The space between the arms 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 drive shafts 5 motor pinion 61 satellite carrier 6 fixed crown 7 movable crown 8 satellite gear 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

Demands

1. Disc brake (F) comprising a caliper (E) having opposite each other a fixed brake pad (PI) and a movable brake pad (P2), and an actuation mechanism for the movable brake pad (P2) comprising a screw / nut system and means for transmitting a rotational movement from a drive shaft (4) to the screw / nut system to actuate the movable brake pad (P2), said actuation mechanism being housed in a through-hole (L) formed in the caliper (E), characterized in that the screw (1) of the screw-nut mechanism is mounted fixed in translation in said hole (L) and driveable in rotation by the transmission means, while the nut (2) mounted fixed in rotation in said hole (L) is driveable in translation along the screw (1) when the latter is driven in rotation, the nut (2) surrounding the screw (1),the screw / nut system comprising balls (3) engaged in threads of the screw (1) and the nut (2), said nut (2) carrying at least two pistons (9) mounted to bear against the movable brake pad (P2), the translational drive of the nut (2) in a first direction enabling the pistons (9) to be translated in order to move 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) enabling 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 arms (Bl, B2) of the caliper (E) includes the housing (L) in which the screw-nut system is mounted, this cylindrical housing (L) with a circular cross-section, is open at one end in the space (El) between said arms (Bl, B2) and accommodates at its other end at least in part, the means for transmitting the rotation of the drive 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 having two lugs (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 complementary shape and dimensions 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 any 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 protrude into the space (El) between the arms (Bl, B2) of the caliper (E), and bear 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 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, having two orifices in which the rods (91) of the pistons (9) are engaged.

8. Disc brake (F) according to any 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 integrable 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) having two orifices in correspondence with the through orifices (11) of the sealing bellows (10) for the passage of the piston rods (91).

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 integrable into the housing (L) of the caliper (E).

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

13.

14. constituting the end of the screw (1), the other end of which is engaged in the nut (2). Motor vehicle equipped with disc brakes according to any one of claims 1 to 12. A method for manufacturing a disc brake (F) comprising a caliper (E) having, opposite each other, a fixed brake pad (P1) and a movable brake pad (P2), and an actuation mechanism for the movable brake pad (P2) comprising a screw / nut system and means for transmitting a rotational movement from a drive pinion (5) to the screw / nut system to actuate the movable brake pad (P2), according to any one of the claims, characterized in that a through bore is made in one of the arms of the caliper (E) to form a housing (L) opening into the space (E1) between the arms (B1, 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 drive 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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