Brake pad assembly for a disk brake system and disk brake system

Abstract

The application relates to a brake pad assembly (2) for a disk brake system and to a disk brake system. The disk brake system has a brake piston (11) and a caliper finger (20) movably coupled to the brake piston (11). The brake pad assembly (2) comprises a back plate (4) having a front side for facing a brake disk (1) of the disk brake system and a back side (6), a friction layer (3) arranged at the front side of the back plate (4) for contacting a friction surface of the brake disk (1), and a shim (5) arranged on the back side (6) of the back plate (4). The shim (5) comprises a back surface (12) having a top edge (14) and first and second side edges (16, 17). Further, the back surface (12) of the shim (5) contains a pressure region (13) that is configured to be pushed on by the brake piston (11) or by the caliper finger (20) upon brake application. The shim (5) further comprises a plurality of cutouts (19, 19′, 19″) for noise reduction. The plurality of cutouts (19, 19′, 19″) is arranged at least partly between the pressure region (13) of the back surface (12) of the shim (5) and the top edge (14) of the back surface (12) of the shim (5). Additionally or alternatively, the plurality of cutouts (19, 19′, 19″) is arranged at least partly between the pressure region (13) of the back surface (12) of the shim (5) and at least one of the first side edge (16) and the second side edge (17) of the back surface (12) of the shim (5).

Claims

1. A brake pad assembly (2) for a disk brake system having a brake piston (11) and a caliper finger (20) movably coupled to the brake piston (11), the brake pad assembly (2) comprising a back plate (4) having a front side for facing a brake disk (1) of the disk brake system and a back side (6), a friction layer (3) arranged at the front side of the back plate (4) for contacting a friction surface of the brake disk (1), and a shim (5) arranged on the back side (6) of the back plate (4), wherein the shim (5) comprises a back surface (12) having a top edge (14) and first and second side edges (16, 17), wherein the back surface (12) of the shim (5) contains a pressure region (13) that is configured to be pushed on by the brake piston (11) or by the caliper finger (20) upon brake application, characterized in that the shim (5) comprises a plurality of cutouts (19, 19′, 19″) for noise reduction, wherein the plurality of cutouts (19, 19′, 19″) is arranged at least partly between the pressure region (13) of the back surface (12) of the shim (5) and the top edge (14) of the back surface (12) of the shim (5) and/or wherein the plurality of cutouts (19, 19′, 19″) is arranged at least partly between the pressure region (13) of the back surface (12) of the shim (5) and at least one of the first side edge (16) and the second side edge (17) of the back surface (12) of the shim (5).

2. The brake pad assembly (2) of claim 1, characterized in that the plurality of cutouts (19, 19′, 19″) is arranged at least partly in a region of force transmission between the pressure region (13) of the back surface (12) of the shim (5) and an edge surface of the back surface (12) of the shim (5) upon brake application.

3. The brake pad assembly (2) of claim 1, characterized in that the plurality of cutouts (19, 19′, 19″) is at least partly arranged in a radial direction (15) of the pressure region (13) toward the top edge (14) of the back surface (12) of the shim (5).

4. The brake pad assembly (2) of claim 1, characterized in that the plurality of cutouts (19, 19′, 19″) is partly arranged between the pressure region (13) of the back surface (12) of the shim (5) and the first side edge (16) of the back surface (12) of the shim (5) as well as partly between the pressure region (13) of the back surface (12) of the shim (5) and the second side edge (17) of the back surface (12) of the shim (5).

5. The brake pad assembly (2) of claim 1, characterized in that the pressure region (13) of the back surface (12) of the shim (5) is configured to be pushed on by the brake piston (11) upon brake application, wherein the pressure region (13) has a circular upper edge.

6. The brake pad assembly (2) of claim 5, wherein at least a portion of the plurality of cutouts (19, 19′, 19″) forms a pattern corresponding to a circular segment.

7. The brake pad assembly (2) of claim 1, characterized in that the pressure region (13) of the back surface (12) of the shim (5) is configured to be pushed on by the caliper finger (20) upon brake application, wherein a part of the plurality of cutouts (19, 19′, 19″) is arranged on an essentially straight line between the pressure region (13) and the top edge (14) of the back surface (12) of the shim (5) and wherein another part of the plurality of cutouts (19, 19′, 19″) is arranged on another essentially straight line between the pressure region (13) and at least one of the first side edge (16) and the second side edge (17) of the back surface (12) of the shim (5).

8. The brake pad assembly (2) of claim 7, characterized in that the shim (5) comprises a metal sheet (9), wherein the plurality of cutouts (19, 19′, 19″) is formed in the metal sheet (9).

9. The brake pad assembly (2) of claim 8, characterized in that the shim (5) comprises a rubber layer (10) arranged on a back side of the shim (5), wherein the plurality of cutouts (19, 19′, 19″) is also formed in the rubber layer (10).

10. The brake pad assembly (2) of claim 9, characterized in that the plurality of cutouts (19, 19′, 19″) contains at least three cutouts (19, 19′, 19″).

11. The brake pad assembly (2) of claim 1, characterized in that the plurality of cutouts (19, 19′, 19″) contains at least one through hole.

12. The brake pad assembly (2) of claim 11, characterized in that the plurality of cutouts (19, 19′, 19″) contains at least one blind hole.

13. The brake pad assembly (2) of claim 10, characterized in that the plurality of cutouts (19, 19′, 19″) has rounded corners.

14. A disk brake system comprising a brake pad assembly (2) of claim 1 and further comprising the brake piston (11) and the caliper finger (20) movably coupled to the brake piston (11).

Description

[0018] Exemplary embodiments will be described in conjunction with the following figures.

[0019] FIG. 1 shows a schematic cross sectional illustration of a brake pad assembly and a brake disk,

[0020] FIG. 2 shows a more detailed view of the brake pad assembly,

[0021] FIGS. 3(a) and (b) show schematic views of the brake pad assembly and a brake piston,

[0022] FIGS. 4(a) to (d) show different embodiments of the brake pad assembly,

[0023] FIGS. 5(a) and (b) show schematic views of a brake pad assembly according to another embodiment and a caliper finger, and

[0024] FIGS. 6(a) to (d) show further embodiments of the brake pad assembly.

[0025] FIG. 1 shows a brake disk 1 of a of a disk brake system for a vehicle. The disk brake system may comprise a caliper housing, a caliper finger and a brake piston. The disk brake system further comprises a brake pad assembly 2, which may be attached to the caliper finger and/or to the piston. The brake pad assembly 2 has a friction layer 3, which is pushed against a friction surface of the brake disk 1 upon hydraulic or electric actuation of the disk brake system. The friction layer 3 contains a material that shows a good stopping performance and heat transfer when engaging with the brake disk 1. The friction layer 3 is attached to a front side of a back plate 4, which provides structural stability to the brake pad assembly 2. The back plate 4 is typically held by the piston or the caliper finger such that the brake pad assembly 2 is mounted to the piston or caliper finger via the back plate 4. In most embodiments, the back plate 4 is made of a metal, in particular steel. A thickness of the back plate 4 may be at least 3 mm and/or at most 8 mm. The friction layer 3 can have a thickness of at least 8 mm and/or at most 15 mm, for example. The material of the friction layer 3 can for instance comprise at least one of copper, iron sulphide, graphite, zinc powder, basalt, calcium carbonate, tin sulphide, zinc aluminium, phenolic resin, rubber dust and mineral fiber. These materials show good stopping performance and heat transfer when engaging with the brake disk.

[0026] A shim 5 is mounted to a back side 6 of the back plate 4. The shim 5 is glued to the back side 6 of the back plate 4 using an adhesive layer, but may also be formed as a clip-on shim having resilient clips that are configured to contact and engage with an edge surface 7 of the back plate 4 to attach the shim 5 to the back plate 4. The resilient clips may be formed by folded protrusions in an edge portion of the shim 5.

[0027] FIG. 2 shows the back plate 4 and the shim 5 in more detail. Corresponding and reoccurring features shown in the different figures are denoted using the same reference numerals. The shim 5 comprises a layered structure having an adhesive layer 8 for fixing the shim 5 to the back side 6 of the back plate 4, a metal sheet 9, and a rubber layer 10. The metal sheet 9 may be formed by a steel, copper, aluminium or plastic layer. The rubber layer 10 covers a back side of the metal sheet 9. A total thickness of the shim 5 may, e.g., amount to at least 0.2 mm and/or at most 2 mm.

[0028] FIG. 3(a) shows the brake pad assembly 2 and the brake piston 11 of the disk brake system as viewed from the back, i.e., toward the brake disk 1. The brake piston 11 is configured to push against a back surface 12 of the shim 5. The brake piston 11 has a ring-shaped front surface, which leads to a ring-shaped pressure region 13, i.e., a ring-shaped region of the back surface 12 of the shim 5 that is exposed to an axial pressure exerted by the brake piston 11, as shown in FIG. 3(b). FIG. 3(b) does not show the brake piston 11. The back surface 12 of the shim 5 has a top edge 14, which delimits the shim 5 in the upward direction. The upward direction is a radial direction 15. According to the depiction of the figures, the axis of rotation (not shown) of the brake disk 1 would be arranged below the brake pad assembly 2, i.e., toward the bottom in the figures (in a direction opposite the radial direction 15). The back surface 12 of the shim 5 further has a first side edge 16, which is a leading edge on the left in the figures, and a second side edge 17, which is a trailing edge on the right.

[0029] A line 18 in the shape of a circular segment, as shown in FIG. 3(b), illustrates a region for arrangement of a plurality of cutouts of the shim. This region is intended to yield a preferred noise cancellation effect of the plurality of cut-outs. The region is arranged between the pressure region 13 and the top edge 14 as well as between the pressure region and the first and second side edges 16, 17. The plurality of cutouts is arranged in this region, i.e., in the radial direction (upward in the figure) from the pressure region 13 and in the tangential direction (to the left and right in the figure) from the pressure region 13.

[0030] Thereby, a damping ratio of shim 5 is efficiently improved by improvement of a structural damping besides material damping. The cutouts 19, 19′, 19″ are not homogeneously distributed across the shim 5, but in the described systematic way so that an optimal decrease of a maximal pressure amplitude is achieved and such that the force flow in realistic braking scenarios is evenly transmitted and distributed over a surface are of the shim. Also the described distribution of the cutouts is suitable for minimizing a friction between contacting faces of the brake pad assembly 2 and supports a conversion of hard contact to soft contact properties. A position, shape and number of holes is chosen to support decoupling of vibration between contacting components, to reduce structure noises, and to support dissipation of airborne noises generated by vibrating parts.

[0031] FIG. 4(a) illustrates the position of the plurality of cutouts, which corresponds to the region indicated by the line 18 in FIG. 3(b). The plurality of cut-outs comprises a number of individual cutouts (each depicted as a circle in FIG. 4(a)). As an example, three of the individual cutouts are denoted using reference numerals 19, 19′, and 19″. The individual cutouts can be formed by round holes as shown in FIG. 4(a) or by elongated holes as shown in FIG. 4(b) (depicted as rectangular lines). The cutouts may be blind holes (e.g., blind bores or grooves) or through holes (e.g., through bores or slots). The plurality of cutouts may as well be formed by a combination of round holes and elongated holes, as shown in FIGS. 4(c) and (d), arranged in the region illustrated by the line 18 in FIG. 3(b). The plurality of cutouts is formed in the metal sheet 9 of the shim 5 and is typically hollow and not filled by a solid material. The plurality of cutouts may also be formed in all layers of the shim 5, i.e. also in the adhesive layer 8 and in the rubber layer 10.

[0032] In another embodiment, the brake pad assembly 2 may be intended to be arranged on a caliper finger side of the brake system. As shown in FIG. 5(a), the brake system may comprise the caliper finger 20 (as viewed from the back, i.e., toward the brake disk 1, in the figure). The caliper finger 20 is configured to push against a back surface 12 of the shim 5 when the brake is applied. The caliper finger 20 is shown to exert axial pressure on the brake pad assembly 2 in the pressure region 13, which in this case comprises a left pressure region 21 and a right pressure region 22, as shown in FIG. 5(b). Lines denoted by reference signs 23 and 24 indicate the positions of the plurality of cutouts 19, 19′, 19″ for preferred noise reduction. In this case a part of the plurality of cutouts 19, 19′, 19″ is arranged on an essentially straight line between the left pressure region 21 and the top edge 14 of the back surface 12 of the shim 5, and another part of the plurality of cutouts 19, 19′, 19″ is arranged on another essentially straight line between the left pressure region 21 and the first side edge 16 of the back surface 12 of the shim 5. Another plurality of cutouts 25, 25′, 25″ is arranged in corresponding positions between the right pressure region 22 and the top and second side edge 14, 17. As it was the case for the embodiment of the brake pad assembly 2 intended for use on the piston side, the preferred position of the plurality of cutouts is between the pressure regions 21, 22 and the top edge 14, i.e. above the pressure regions, as well as between the pressure regions 21, 22 and the first and second side edges 16, 17, i.e. respectively to the left and right of the pressure regions. As further shown in FIGS. 6(a) to (d), the plurality of cutouts 19, 19′, 19″ can be formed by a combination of round holes and elongated holes as explained above.

[0033] Features of the different embodiments which are merely disclosed in the exemplary embodiments may be combined with one another and may also be claimed individually.

LIST OF REFERENCE NUMERALS

[0034] 1 Brake disk

[0035] 2 Brake pad assembly

[0036] 3 Friction layer

[0037] 4 Back plate

[0038] 5 Shim

[0039] 6 Back side of back plate

[0040] 7 Edge surface of back plate

[0041] 8 Adhesive layer

[0042] 9 Metal sheet

[0043] 10 Rubber layer

[0044] 11 Brake piston

[0045] 12 Back surface of shim

[0046] 13 Pressure region

[0047] 14 Top edge of back surface of shim

[0048] 15 Radial direction

[0049] 16 First side edge of back surface of shim

[0050] 17 Second side edge of back surface of shim

[0051] 18 Line illustrating region for arrangement of plurality of cutouts

[0052] 19, 19′, 19″ Plurality of cutouts

[0053] 20 Caliper finger

[0054] 21 Left pressure region

[0055] 22 Right pressure region

[0056] 23, 24 Lines indicating positions of plurality of cutouts

[0057] 25, 25′, 25″ Plurality of cutouts