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. State of the prior art

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

[0003] Typically, to move a braking segment from its rest position to the braking position, a movable element of the actuator is translated so as to exert on a first end of the core of the segment a braking force causing the segment to pivot about an axis located at a second end of the segment. The segment is returned to the rest position by return means such as springs.

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

[0005] The invention aims in particular to reduce the risks of brake segments becoming damaged 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] To this end, the invention relates to a drum brake segment, comprising a core and a drive element secured to the core, the drive element having at least one drive surface or edge configured to allow a drive member to exert thereon a force capable of moving the segment in rotation around a pivot axis of the segment.

[0008] According to the invention, the at least one driving 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 drive element thus forms a surface or linear drive interface which makes it possible to reduce the risks of deformation or damage to the segment, in particular during braking.

[0010] In one embodiment, the width of the at least one driving 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 thickness of the core.

[0011] In one embodiment, the at least one driving surface or edge comprises a braking surface or edge configured to allow the driving member to exert thereon a force capable of moving the segment in rotation 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. It is thus possible to do without a wear clearance compensation mechanism such as implemented in the brakes of the prior art.

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

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

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

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

[0018] In one embodiment, the drive element comprises 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 portion 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 the at least one drive surface or edge of the at least one segment so as to be able to move the at least one segment in rotation around its pivot axis.

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

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

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

[0024] In one embodiment, the 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 the at least one segment according to a pivot connection within a slide formed by the braking and return surfaces or edges.

[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 the at least a driving surface or edge of a segment as defined above so as to move the segment in rotation about 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 the segments being hammered and / or by reducing or eliminating the transverse stresses on the drive member during braking. The inventors have estimated that the invention makes it possible to increase the 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 mechanism for taking up wear clearances.

[0031] Other advantages and characteristics of the invention will appear on reading the detailed, non-limiting description which follows. Brief description of the drawings

[0032] The following detailed description refers to the accompanying drawings in 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 brake 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 [Fig.l]; - [Fig.5] is a schematic perspective view of a subassembly of the brake of [Fig.l], comprising one end of a braking segment cooperating with the drive member; - [Fig.6] is a schematic view of the brake of [Fig.l], in a braking configuration. Detailed description of embodiments

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

[0034] [Fig.l] 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 A1 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 plate 2 is integral with a chassis (not shown) of the vehicle and extends generally in a plane perpendicular to the axis Al of rotation of the wheel.

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

[0038] The skirt of the drum 3 has a radially internal surface 8 forming an annular friction track which 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 base 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.l], the segment 4A is generally in the form of a half-moon 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 11A, on which the lining 12A is fixed, for example by gluing or riveting.

[0042] With reference to [Fig.l], the curvature of the core 10A and more generally of the segment 4A is centered on the axis A1 and corresponds substantially to the curvature of the friction track 8 of the drum 3.

[0043] The segment 4A is arranged so that the lining 12A faces the friction track 8 of the drum 3.

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

[0045] In the example of [Fig.l], the 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 precisely, the segment 4A is arranged on the anchoring element 5 so as to define an axis A2A of rotation of the segment 4A relative to the plate 2. Symmetrically, the segment 4B is arranged on the anchoring element 5 so as to define an axis A2B for pivoting the segment 4B relative to the plate 2.

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

[0048] In the example of [Fig.l], 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 equidistant from a plane which passes through the axis Al and which is parallel to the directions D2 and D3.

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

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

[0051] Such a movement of the segments 4A and 4B makes it possible to apply the linings 12A and 12B 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 a drive element 30A / 30B, also called “drive interface”, integral with the core 10A / 10B of the segment 4A / 4B.

[0053] The following description relates to the drive element 30A of the segment 4A and of course applies by analogy to the drive element 30B of the 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 E1 which extends along the direction D3.

[0055] With reference to [Fig. 3], the part 30A comprises wall elements 31A, 32A and 33A, the wall elements 31A and 33A being spaced from each other in the direction D1 and being connected to each other by the wall element 33A.

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

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

[0058] The surfaces 41A and 42A are driving surfaces of the segment 4A which are respectively called “braking surface” and “return surface”.

[0059] The surfaces 41A and 42A are spaced from each other by a distance XI which defines in this example 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 E1, in this case a bottom of the groove E1.

[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 31A, 32A and 33A have a dimension X2 along the direction D3 which corresponds to a width of the surfaces 41A, 42A and 43A.

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

[0064] In this example, the 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 comprises an opening 50A intended to receive a connecting element of the drive member 6 (see further below).

[0067] In this non-limiting example, the 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 the segment 4A.

[0068] With reference to [Fig.3], the segment 4A comprises in this example ribs 55 making it possible to reinforce the connection between the part 30A and the core 10A.

[0069] Referring now 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 according to a helical connection, by means of threads between which balls are interposed. This connection makes it possible to transform a rotation of the body 60 into 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 the segment 4A.

[0073] In this example, the connecting element 62A comprises a shaft 65A having an axis A4 and being integral with the piston 61A, 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 E1 along the drive surfaces formed by the part 30A, defining for example a clearance of 0.15 mm and / or an adjustment H7 g6. With reference to Figures 3 and 5, the connecting element 62A thus cooperates with the segment 4A according to a pivot connection, within a slide formed by the braking surfaces 41A and return surfaces 42A.

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

[0078] With reference to [Fig.l], 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 about 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 the segments 4A and 4B are relatively complex and tend to exert on the 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 sliding of the connection 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 to the drive member 6, transversely to the direction A3.

[0081] Furthermore, the orientation of the braking surface of the segments 4A and 4B is in this example intended to provide a function of taking up wear clearances of the linings 12A and 12B. With reference to FIGS. 1 and 3, the braking surface 41A of the segment 4A is in fact oriented in a direction oblique to the direction D2, that is to say oblique to a plane orthogonal to the actuation direction. 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 pivot around their pivot axis A2A and A2B in a second direction S2, opposite to the first direction (see [Fig.l]).

[0083] The preceding description is of course not limiting and numerous variants can be implemented without departing from the scope of the invention. In particular, the principles described above relating to the driving of the segments 4A and 4B by driving surfaces wider than the thickness of the core of these segments 4A and 4B can be implemented in numerous ways.

[0084] Thus, in an alternative embodiment, not shown, the segments 4A and 4B may comprise only a braking surface, similar to the surface 41A of the segment 4A of [Fig. 3], the function of returning the segments 4A and 4B to the rest position being able in this case to be carried out by conventional return means such as springs. In the context of this alternative and in a non-limiting manner, the braking surface may be formed by a flat wall element welded to the segment or by a part which would correspond to a part of the part 30A of [Fig. 3] cut at the level of the wall element 33A.

[0085] In another alternative embodiment, not shown, the segments 4A and 4B may comprise both a braking surface and a return surface formed by wall elements similar to the wall elements 31A and 32A of the part 30A of [Fig. 3] which, unlike the embodiment of [Fig. 3], may be connected to each other by wall elements spaced apart from each other in the direction D3 so as to constitute lateral ends of the groove E1, in addition to or instead of the wall element 33A of [Fig. 3].

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

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

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

[0089] More generally, the brake may 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 equipped 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 manufactured in a single piece with the core of this segment.

[0092] Furthermore, the drive member(s) may be different from the member 6 described above. In a non-limiting manner, the drive may be carried out by a hydraulically controlled cylinder.

[0093] For another example, the connecting elements of the drive member, which comprise the bearings 66A in the example of [Fig. 4], may comprise other types of rolling and / or sliding members, 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 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 Tray

[0097] 3 Drum

[0098] 4A, 4B Braking segment

[0099] 5 Anchoring element

[0100] 6 Drive member

[0101] 8 Friction surface / track

[0102] 10A, 10B Soul

[0103] 11 A, 11B Sole

[0104] 12A, 12B Friction lining

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

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[0110] [YES]

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[0127]

[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 Body of the member Drive element 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 Dl, 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

Claims

1. Drum brake segment (4A, 4B) comprising a core (10A, 10B) and a drive element (30A, 30B) integral with the core (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 thereon a force capable of moving the segment in rotation about a pivot axis (A2A, A2B) of the segment (4A, 4B), characterized in that the at least one drive surface or edge (41A, 42A) has, in a direction (D3) parallel to the pivot axis (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, in which the width (X2) of the at least one driving 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 the at least one driving surface or edge (41A, 42A) comprises a braking surface or edge (41A) configured to allow the driving member (6) to exert thereon 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 the at least one driving surface or edge (41A, 42A) comprises a return surface or edge (42A) configured to allow the driving member (6) to exert thereon a force capable of moving the segment (4A, 4B) in rotation in a second direction around said pivot axis (A2A, A2B).

6. Segment (4A, 4B) according to claim 5, incorporating the features of claim 3 or 4, in which the braking surface or edge (41 A) and the return surface or edge (42A) define between them a space (El) capable of receiving a connecting element (62A, 62B) of said drive member (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 portion (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. Braking assembly for drum brake (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 the at least one drive surface or edge (41A, 42A) of the 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, in which the at least one drive member (6) is electrically and / or hydraulically controlled, the 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 the at least one drive member (6) comprises at least one connecting element (62A, 62B) cooperating with the at least one driving surface or edge (41A, 41B) of the at least one segment (4A, 4B), the 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, in which the at least one segment (4A, 4B) comprises the characteristics of claim 6 or 7, said connecting element (62A, 62B) cooperating with the at least one segment (4A, 4B) according to a pivot connection within a slide formed by the braking (41 A) and return (42A) surfaces or edges.

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

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

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