Drum brake segment comprising a surface or linear drive interface

Abstract

Braking segment (4A) comprising a drive interface (30A) configured to cooperate with a bearing-type connecting element to move the segment (4A) to a braking position and / or to a rest position. Braking assembly, drum brake, and related braking method. Figure for the abstract: Fig. 2

Description

Title of the invention: Drum brake segment comprising a surface or linear drive interface technical field

[0001] The invention relates to the field of drum brakes for motor vehicles. Prior art

[0002] Drum brakes known in the prior art include brake segments which are moved between a rest position and a braking position under the action of a linear actuator.

[0003] Typically, to move a brake segment from its rest position to the braking position, a moving element of the actuator is translated so as to exert a braking force on a first end of the segment's web, causing the segment to rotate around an axis located at a second end of the segment. The segment is returned to its rest position by means such as springs.

[0004] Among other disadvantages of conventional drum brakes, the braking force applied to the segments tends to damage them, by flattening their core. Description of the invention

[0005] The invention aims in particular to reduce the risks of brake segment wear and more generally to improve the efficiency of a drum brake.

[0006] Another objective of the invention is to simplify the mechanism of a drum brake.

[0007] For this purpose, the invention relates to a drum brake segment, comprising a core and a drive element integral with the core, the drive element having at least one drive surface or edge configured to allow a drive member to exert on it a force capable of moving the segment in rotation around a pivot axis of the segment.

[0008] According to the invention, at least one drive surface or edge has, in a direction parallel to the pivot axis, a dimension called width which is greater than a thickness of the core.

[0009] The segment's drive element thus forms a surface or linear drive interface which reduces the risks of deformation or flattening of the segment, particularly during braking.

[0010] In one embodiment, the width of at least one drive surface or edge is greater than or equal to 120%, preferably greater than or equal to 150%, more preferably greater than or equal to 400%, for example equal to 500% of the core thickness.

[0011] In one embodiment, at least one drive surface or edge includes a braking surface or edge configured to allow the drive member to exert on it a force capable of moving the rotating segment in a first direction around said pivot axis.

[0012] In one embodiment, the braking surface or edge is oblique or perpendicular to a plane orthogonal to a direction of actuation of said drive member.

[0013] An oblique orientation of the braking surface or edge makes it possible to compensate for wear clearances. This eliminates the need for a wear clearance compensation mechanism such as those used in prior art brakes.

[0014] More generally, the geometry of the surface(s) or edge(s) of the drive can be adapted according to the kinematics of the segment during its use.

[0015] In one embodiment, at least one drive surface or edge includes a return surface or edge configured to allow the drive member to exert on it a force capable of moving the rotating segment in a second direction around said pivot axis.

[0016] When the segment includes a return surface or edge, the return of the segment does not require return means such as springs which are used in prior art brakes.

[0017] In one embodiment, the braking surface or edge and the return surface or edge define between them a space suitable for receiving a connecting element of said drive member.

[0018] In one embodiment, the drive element includes at least one groove forming said space, the groove having a width defined by a distance between the braking surface or edge and the return surface or edge.

[0019] Preferably, the groove may have at least one end formed by a part of the drive element connecting the braking surface or edge and the return surface or edge to each other.

[0020] The invention also relates to a braking assembly for a drum brake, comprising at least one segment as defined above and at least one drive member configured to cooperate with at least one drive surface or edge of at least one segment so as to be able to move the at least segment in rotation around its pivot axis.

[0021] In one embodiment, at least one drive element is electrically and / or hydraulically controlled.

[0022] In one embodiment, at least one drive element comprises a screw-nut system, for example with balls.

[0023] In one embodiment, at least one drive member comprises at least one connecting element cooperating with at least one drive surface or edge of at least one segment.

[0024] In one embodiment, at least one connecting element comprises one or more bearings, for example roller or ball bearings.

[0025] In one embodiment, said connecting element cooperates with at least one segment according to a pivot joint within a slide formed by the braking and return surfaces or edge.

[0026] The invention also relates to a drum brake comprising a braking assembly as defined above.

[0027] The invention also relates to a braking method for such a drum brake.

[0028] The method preferably comprises applying a force to at least a surface or driving edge of a segment as defined above so as to move the segment in rotation around its pivot axis.

[0029] Among other advantages, the invention makes it possible to increase the braking efficiency of a drum brake by reducing or eliminating the risk of brake shoe wear and / or by reducing or eliminating lateral stresses on the drive mechanism during braking. The inventors have estimated that the invention makes it possible to increase braking torque by approximately 5% compared to a conventional drum brake when the brake is worn.

[0030] The invention also makes it possible to simplify the architecture of drum brakes and to reduce their mass, in particular by eliminating the return springs and the wear adjustment mechanism.

[0031] Other advantages and features of the invention will become apparent from the following detailed, non-limiting description. Brief description of the drawings

[0032] The following detailed description refers to the attached drawings on which: - [Fig. 1] is a schematic front view of a drum brake according to the invention, in a rest configuration; - [Fig.2] is a schematic perspective view of a braking segment in accordance with the invention; - [Fig.3] is a schematic front view of one end of the segment of the [Fig.2]; - [Fig. 4] is a schematic perspective view of part of an organ brake drive of the [Fig.l]; - [Fig. 5] is a schematic perspective view of a subset of the brake of the [Fig.1], comprising one end of a braking segment cooperating with the drive element; - [Fig.6] is a schematic view of the brake of [Fig.1], in a braking configuration. Detailed description of implementation methods

[0033] Figures 1 to 6 include a reference frame indicating orthogonal directions D1, D2 and D3.

[0034] Fig. 1 represents a drum brake 1 intended to be connected to a wheel (not shown) of a motor vehicle (not shown) having an axis of rotation Al parallel to the direction D3.

[0035] In a manner known per se, the brake 1 of [Fig.1] comprises a plate 2, a drum 3, two braking segments 4A and 4B, an anchoring element 5 and a drive member 6.

[0036] The platform 2 is attached to a chassis (not shown) of the vehicle and extends globally in a plane perpendicular to the axis Al of rotation of the wheel.

[0037] The drum 3 has a skirt for carrying the wheel and is mounted for rotation by relative to plate 2, allowing rotation of the drum 3 and therefore of the wheel around the AL axis

[0038] The skirt of the drum 3 has a radially internal surface 8 forming an annular friction track that extends around the axis AL

[0039] In a manner known per se, each of the braking segments 4A and 4B comprises a core 10A / 10B, a sole 11A / 11B and a friction lining 12A / 12B.

[0040] With reference to [Fig.2] which shows in isolation the segment 4A of the brake 1 of [Fig.1], the segment 4A is presented overall in the form of a half-moon shaped piece having a lower end 14A and an upper end 15A.

[0041] In particular, the core 10A of the segment 4A thus has a curvature forming an external edge which carries the sole 11 A, on which the lining 12A is fixed, for example by gluing or riveting.

[0042] With reference to [Fig.1], the curvature of the core 10A and more generally of the segment 4A is centered on the axis Al and corresponds substantially to the curvature of the friction track 8 of the drum 3.

[0043] Segment 4A is arranged so that the lining 12A is opposite the friction track 8 of the drum 3.

[0044] Since segments 4A and 4B are substantially symmetrical with respect to each other in this example, the description of segment 4A applies by analogy to segment 4B.

[0045] In the example of [Fig.1], segments 4A and 4B are mounted floating by their lower end 14A / 14B on the anchoring element 5 which is integral with the plate 2.

[0046] More specifically, segment 4A is arranged on the anchoring element 5 so as to define an axis A2A of rotation of segment 4A with respect to the plate 2. Symmetrically, segment 4B is arranged on anchoring element 5 so as to define an axis A2B of pivoting of segment 4B with respect to plate 2.

[0047] In a manner known per se, the axes A2A and A2B can move during wear, globally along the direction D2.

[0048] In the example of [Fig.1], the axes A2A and A2B are parallel to the direction D3, pass through a plane parallel to the directions DI and D3 and are located at an equidistance from a plane which passes through the axis Al and which is parallel to the directions D2 and D3.

[0049] Regarding the upper ends 15A and 15B of segments 4A and 4B, these cooperate with the drive member 6 which is configured to rotate segments 4A and 4B around axes A2A and A2B (see further below).

[0050] The embodiment described herein corresponds to an operating mode of the brake 1 known as a "simplex" floating type, that is to say, in which, during a braking operation, the drive member 6 simultaneously separates the upper ends 15A and 15B of segments 4A and 4B from each other along an actuation direction A3 parallel to the direction D1. Such separation of the ends 15A and 15B simultaneously causes a rotation of segments 4A and 4B around axes A2A and A2B, respectively, in a first direction S1. Given the symmetry of the assembly, the direction S1 is trigonometric for segment 4A and antitrigonometric for segment 4B (see [Fig. 1]).

[0051] Such a displacement of segments 4A and 4B allows the linings 12A and 12B to be applied against the friction track 8 of the drum 3, so as to brake the wheel.

[0052] In this example, each of the segments 4A and 4B cooperates with the drive member 6 by means of a drive element 30A / 30B, also called a "drive interface", integral with the core 10A / 10B of the segment 4A / 4B.

[0053] The following description relates to the drive element 30A of segment 4A and applies by analogy to the drive element 30B of segment 4B.

[0054] With reference to figures 2 and 3, the drive element 30A is presented in this non-limiting example in the form of a part having a "U" shaped section defining a groove El which extends along the direction D3.

[0055] With reference to [Fig.3], part 30A comprises wall elements 31 A, 32A and 33A, the wall elements 31A and 33A being spaced apart from each other in the direction Dl and being connected to each other by the wall element 33A.

[0056] The wall elements 31 A, 32 A and 33 A have surfaces that delimit the groove EL

[0057] In particular, the wall elements 31A and 32A have surfaces 41A and 42A, respectively, which are opposite each other.

[0058] Surfaces 41A and 42A are drive surfaces of segment 4A which are respectively called "braking surface" and "returning surface".

[0059] The surfaces 41A and 42A are spaced apart from each other by a distance XI which in this example defines a width of the groove El. In this example, the width XI is equal to 13 mm.

[0060] The wall element 33A has a surface 43A which delimits one end of the groove El, in this case a bottom of the groove EL

[0061] In this example, the wall elements 31A, 32A and 33A are connected to each other so that the surfaces 41A, 42A and 43A together form a continuous surface.

[0062] In the example of [Fig.2], the wall elements 31 A, 32A and 33A have a dimension X2 along the direction D3 which corresponds to a width of the surfaces 41A, 42A and 43A.

[0063] In this example, dimension X2 corresponds to a width of part 30A, as well as a length of groove EL

[0064] In this example, dimension X2 is equal to 36 mm.

[0065] The dimension X2 is therefore greater than the thickness X3 of the core 10A which, in this example, is equal to 4.4 mm.

[0066] Still with reference to [Fig.2], the wall element 32A includes an opening 50A intended to receive a connecting element of the drive member 6 (see further below).

[0067] In this non-limiting example, part 30A is fixed to the core 10A, for example by welding, so as to constitute a terminal part of the upper end 15A of segment 4A.

[0068] With reference to [Fig.3], segment 4A in this example includes ribs 55 to reinforce the connection between part 30A and web 10A.

[0069] Now with reference to figures 1 and 4, the drive member 6 is in this example an electrically controlled member provided with a body 60 and actuating screws 61A and 61B forming a ball screw-nut type system.

[0070] In a manner known per se, the screws 61A and 61B comprise a proximal portion which cooperates with the body 60 by means of a helical connection, via threads between which balls are interposed. This connection makes it possible to transform a rotation of the body 60 into a translation of the screws 61A and 61B along the actuation direction A3, in particular between a first position in which a distal end of the screws 61A and 61B is located at a first distance from the body 60 and a second position in which the distal end of the screws 61A and 61B is located at a second distance from the body greater than the first distance.

[0071] Each of the screws 61A and 61B is equipped, at its distal end, with a connecting element 62A / 62B.

[0072] Fig. 4 shows the screw 61A and the corresponding connecting element 62A, the latter being intended to cooperate with the drive surface of segment 4A.

[0073] In this example, the connecting element 62A comprises a shaft 65A having an axis A4 and being integral with the piston 61 A, as well as two bearings 66A movable in rotation relative to the shaft 65A around the axis A4.

[0074] In this example, the bearings 66A are arranged on either side of the piston 61A in the direction D3.

[0075] With reference to [Fig.5] which shows an assembly of the drive member 6 with the segment 4A, the distal end of the screw 61A passes through the opening 50A made in the wall element 32A of the part 30A, so that the connecting element 62A is housed in the groove El of the part 30A.

[0076] The bearings 66A are dimensioned to be able to slide in the groove El along the drive surfaces formed by the part 30A, defining for example a clearance of 0.15 mm and / or an H7 g6 fit. With reference to Figures 3 and 5, the connecting element 62A thus cooperates with the segment 4A via a pivot joint, within a slide formed by the braking surfaces 41A and the return surfaces 42A.

[0077] The preceding description applies of course by analogy to the screw 61B, the connecting element 62B and the segment 4B.

[0078] With reference to [Fig.1], when the drive member 6 is actuated so as to move the screws 61A and 61B from the first to the second position, the connecting elements 62A and 62B exert on the braking surface 41A of the segments 4A and 4B a braking force causing the latter to pivot around their pivot axis A2A and A2B in the direction SI, so as to apply the linings 12A and 12B against the friction track 8 of the drum 3.

[0079] During such braking in a real situation, the kinematics of segments 4A and 4B is relatively complex and tends to exert on pistons 61A and 61B forces having transverse components perpendicular to the direction A3.

[0080] With reference to [Fig.6], the connection described above between the drive member 6 and the segments 4A and 4B allows a sliding of the connecting elements 62A and 62B on the drive surfaces of the segments 4A and 4B which makes it possible to reduce or cancel the stresses applied on the drive member 6, transverse to the direction A3.

[0081] Furthermore, the orientation of the braking surface of segments 4A and 4B is, in this example, designed to compensate for wear clearances in the linings 12A and 12B. Referring to Figures 1 and 3, the braking surface 41A of segment 4A is indeed oriented obliquely to direction D2, i.e., obliquely to a plane orthogonal to the direction of actuation. A3, so as to compensate for wear clearances. The same applies to segment 4B, symmetrically.

[0082] Conversely, when the drive member 6 is actuated so as to move the screws 61A and 61B towards the first position, the connecting elements 62A and 62B exert on the return surface 42A of the segments 4A and 4B a return force causing the latter to rotate around their pivot axis A2A and A2B in a second direction S2, opposite to the first direction (see [Fig.1]).

[0083] The preceding description is by no means exhaustive, and numerous variations can be implemented without departing from the scope of the invention. In particular, the principles described above relating to the driving of segments 4A and 4B by drive surfaces wider than the thickness of the web of these segments 4A and 4B can be applied in many ways.

[0084] Thus, in an alternative embodiment, not shown, segments 4A and 4B may comprise only a braking surface, similar to surface 41A of segment 4A in [Fig. 3], the function of returning segments 4A and 4B to the rest position being achieved in this case by conventional return means such as springs. In this alternative embodiment, and without limitation, the braking surface may be formed by a flat wall element welded to the segment or by a part corresponding to a portion of part 30A in [Fig. 3] cut at the wall element 33A.

[0085] In another embodiment, not shown, segments 4A and 4B may include both a braking surface and a return surface formed by wall elements similar to wall elements 31A and 32A of part 30A of [Fig.3] which, unlike the embodiment of [Fig.3], may be connected to each other by wall elements spaced apart along the direction D3 so as to form lateral ends of the groove El, in addition to or instead of the wall element 33A of [Fig.3].

[0086] In another embodiment, not shown, segments 4A and 4B can comprise both a braking surface and a return surface formed by a part which differs from part 30A of [Fig.3] in that it comprises an additional wall element extending opposite wall element 33A, so as to present not a “U” but an “O” cross-section.

[0087] Of course, the dimensions of the braking surface and / or the possible return surface of segments 4A and 4B may differ from those illustrated in the figures. For illustrative purposes only, the width of the drive surface(s) may be between 120% and 500% of the thickness of the segment web, and / or a width between the X3 thickness of the segment web and the thickness of a brake rim.

[0088] Furthermore, the braking segments may be asymmetrical and / or include one or more different drive surfaces from one segment to another.

[0089] More generally, the brake can be configured to operate in the simplex mode described above and / or in other operating modes, for example in the operating mode known as "duplex".

[0090] Thus, in an alternative embodiment, not shown, the anchoring element 5 of the brake 1 of [Fig.1] is replaced by a second drive member similar to the member 6, the lower end 14A / 14B of each of the segments 4A and 4B being able to be fitted with a drive part similar to the part 30A of [Fig.3] to be driven by this second drive member.

[0091] For another example, the drive interface of a segment can be made in one piece with the core of that segment.

[0092] Furthermore, the drive element(s) may be different from element 6 described above. By way of exception, the drive may be achieved by a hydraulically actuated cylinder.

[0093] By way of further example, the connecting elements of the drive member, which include the bearings 66A in the example of [Fig. 4], may include other types of rolling and / or sliding elements, in particular one or more roller or ball bearings. For example, the bearings 66A may be replaced by elements of any other geometric shape, configured to slide without rolling on the corresponding surfaces 41A and 42A.

[0094] The preceding description applies by analogy to a simplex type brake with a fixed pivot, in which the segments are connected by their lower end to an anchoring element defining fixed pivot axes, as well as to a duplex or duo-servo type brake. References

[0095] 1 Brake

[0096] 2 Plateau

[0097] 3 Drum

[0098] 4A, 4B Braking segment

[0099] 5 Anchoring element

[0100] 6 Drive unit

[0101] 8 Friction surface / track

[0102] 10A, 10B Core

[0103] 11 A, 11B Sole

[0104] 12A, 12B Friction lining

[0105] 14A, 14B Lower end of segment

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[0128] 15A, 15B Upper end of segment 30A, 30B Drive element / Drive interface / Drive part 31A, 32A, 33A Wall element 41A Drive surface / Braking surface 42A Drive surface / Return surface 43A Surface 50A Opening 55 Rib 60 Drive body 61 A, 61B Actuating element 62A, 62B Connecting element 65A Shaft 66A Bearing Al Wheel rotation axis A2A, A2B Segment pivot axis A3 Actuation direction A4 Axis D1, D2, D3 Directions El Gap / Groove SI, S2 Segment rotation direction XI Drive interface dimension / Width X2 Groove dimension / Width X3 Segment web thickness

Claims

Demands

1. Drum brake segment (4A, 4B) (1), comprising a web (10A, 10B) and a drive element (30A, 30B) integral with the web (10A, 10B), the drive element (30A, 30B) having at least one drive surface or edge (41A, 42A) configured to allow a drive member (6) to exert on it a force capable of moving the segment in rotation about an axis (A2A, A2B) of pivot of the segment (4A, 4B), characterized in that the at least one drive surface or edge (41A, 42A) has, along a direction (D3) parallel to the axis of pivot (A2A, A2B), a dimension (X2) called width which is greater than or equal to 120% of a thickness (X3) of the soul (10A, 10B).

2. Segment (4A, 4B) according to claim 1, wherein the width (X2) of at least one drive surface or edge (42A, 42A) is greater than or equal to 150%, more preferably greater than or equal to 400%, for example equal to 500% of the thickness (X3) of the core (10A, 10B).

3. Segment (4A, 4B) according to claim 1 or 2, wherein at least one drive surface or edge (41A, 42A) comprises a braking surface or edge (41A) configured to allow the drive member (6) to exert on it a force capable of moving the segment (4A, 4B) in rotation in a first direction (SI) around said pivot axis (A2A, A2B).

4. Segment (4A, 4B) according to claim 3, wherein the braking surface or edge (41 A) is oblique or perpendicular to a plane orthogonal to an actuation direction (A3) of said drive member (6).

5. Segment (4A, 4B) according to any one of claims 1 to 4, wherein at least one drive surface or edge (41A, 42A) comprises a return surface or edge (42A) configured to enable the drive member (6) to exert on it a force capable of moving the segment (4A, 4B) in rotation in a second direction about said pivot axis (A2A, A2B).

6. Segment (4A, 4B) according to claim 5, incorporating the features of claim 3 or 4, wherein the braking surface or edge (41 A) and the return surface or edge (42A) define between them a space (El) suitable for receiving a connecting element (62A, 62B) of said drive unit (6).

7. Segment (4A, 4B) according to claim 6, wherein the drive element (30A, 30B) comprises at least one groove forming said space (El), the groove (El) having a width (XI) defined by a distance between the braking surface or edge (41A) and the return surface or edge (42A), the groove (El) preferably having at least one end formed by a part (33A) of the drive element (30A, 30B) connecting the braking surface or edge (41A) and the return surface or edge (42A) to each other.

8. Drum brake assembly (1), comprising at least one segment (4A, 4B) according to any one of claims 1 to 7 and at least one drive member (6) configured to cooperate with at least one drive surface or edge (41A, 42A) of at least one segment (4A, 4B) so as to be able to move the at least segment (4A, 4B) in rotation about its pivot axis (A2A, A2B).

9. Braking assembly according to claim 8, wherein at least one drive member (6) is electrically and / or hydraulically controlled, at least one drive member (6) preferably comprising a screw-nut system, for example with balls.

10. Braking assembly according to claim 8 or 9, wherein at least one drive member (6) comprises at least one connecting element (62A, 62B) cooperating with at least one drive surface or edge (41A, 41B) of at least one segment (4A, 4B), at least one connecting element (62A, 62B) comprising one or more bearings (66A), for example roller or ball bearings.

11. Braking assembly according to any one of claims 8 to 10, wherein at least one segment (4A, 4B) comprises the features of claim 6 or 7, said connecting element (62A, 62B) cooperating with at least one segment (4A, 4B) according to a pivot connection within a slide formed by the braking surfaces or edge (41A) and return surface (42A).

12. Drum brake (1) comprising a braking assembly according to any one of claims 8 to 11.

13. Braking method for a drum brake (1) according to claim 12, comprising applying a force to at least one drive surface or edge (41A, 42A) of a segment (4A, 4B) according to any one of claims 1 to 7 so as to move the segment (4A, 4B) in rotation about its pivot axis (A2A, A2B).

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