BRAKE PAD AND MANUFACTURE THEREOF

Abstract

A brake pad having a layer of friction material integrally moulded with a backing plate, wherein the backing plate having an electroconductive member moulded within a plate of a fibre-reinforced polymer resin, the electroconductive member extending along a plate direction, the backing plate having a front surface forming an interface with a rear surface of the layer of friction material, wherein the electroconductive member is profiled in a thickness direction of the backing plate to provide at least one projection extending towards the interface or into the layer of friction material and arranged to function as a wear indicator for the brake pad. Also disclosed are methods for manufacturing the brake pad.

Claims

1. A brake pad comprising a layer of friction material integrally moulded with a backing plate, wherein the backing plate comprises an electroconductive member moulded at least partly within a resin plate of a fibre-reinforced polymer resin, wherein the electroconductive member comprises a plate extending along a plate direction of the backing plate, the backing plate having a front surface forming an interface with a rear surface of the layer of friction material, wherein the electroconductive member is profiled in a thickness direction of the backing plate to provide at least one projection extending towards the interface or into the layer of friction material and arranged to function as a wear indicator for the brake pad.

2. (canceled)

3. (canceled)

4. (canceled)

5. A brake pad according to claim 1 wherein the electroconductive member comprises a planar plate having an array of integral extending portions extending from the planar plate into the plate of fibre-reinforced polymer resin to affix together the electroconductive member and the plate of fibre-reinforced polymer resin, the extending portions being formed by punching respective holes in the planar plate.

6. A brake pad according to claim 1 wherein the at least one projection comprises at least one deformed portion extending from the plate towards the interface or into the layer of friction material, wherein the deformed portion functions to enhance a bond between the electroconductive member and the plate of fibre-reinforced polymer resin.

7. A brake pad according to claim 6 wherein the deformed portion is formed by punching a hole in the plate to form a punched extension extending from the plate towards the interface or into the layer of friction material.

8. A brake pad according to claim 1 wherein a free end of at least one projection is within the layer of friction material and spaced forwardly from the interface by a distance of from 1 to 8 mm, or about 3 mm.

9. A brake pad according to claim 1 wherein a free end of at least one projection is located at the interface.

10. A brake pad according to claim 1 wherein a plurality of the projections is provided and respective free ends of at least two of the projections are located at different distances relative to the interface, wherein respective free ends of the plurality of projections are located at a range of from 0 to 5 mm, or from 1 to 5 mm, from the interface.

11. A brake pad according to claim 1 wherein the electroconductive member is composed of a metal, or a steel, or a steel treated with an adhesion enhancing layer to enhance adhesion to the fibre-reinforced polymer resin.

12. A brake pad according to claim 11 wherein the metal electroconductive member is a plate having a wall thickness of from 0.5 to 3 mm.

13. A brake pad according to claim 1 wherein the electroconductive member has a front surface, defined by the front surface of a plurality of the projections, which is located against the front surface of the backing plate.

14. A brake pad according to claim 1 wherein the electroconductive member has a rear surface which defines a rear surface of the backing plate or is located a distance of from 0.1 to 3 mm, or from 0.5 to 2 mm, from a rear surface of the backing plate.

15. A brake pad according to claim 1 wherein the fibre-reinforced polymer resin comprises a thermoset resin comprising reinforcing fibres, or a cross-linked phenolic resin comprising reinforcing fibres.

16. A brake pad according to claim 1 wherein the friction material comprises a cross-linked phenolic resin and friction particles dispersed therein.

17. A brake pad according to claim 1 further comprising an electrical contact member connected to the electroconductive member for electrical connection to an electrical brake wear sensor system.

18. A brake pad according to claim 1 wherein the backing plate has a thickness of from 1 to 10 mm, or optionally about 5 mm.

19. A brake pad according to claim 1 wherein the layer of friction material has a thickness of from 5 to 20 mm, or optionally about 10 mm.

20. A brake pad according to claim 1 wherein the electroconductive member has an area extending along the plate direction which is from 50 to 100% of the area of the layer of friction material.

21. A brake pad according to claim 1 which is an automotive brake pad for an automobile, motor cycle or truck.

22. A brake pad according to claim 1 which is a railway brake pad for a railway locomotive, carriage or truck.

23-71. (canceled)

72. A brake pad comprising a layer of friction material integrally moulded with a backing plate, wherein the backing plate comprises an electroconductive member moulded at least partly within a resin plate of a fibre-reinforced polymer resin, the electroconductive member extending along a plate direction of the backing plate, the backing plate having a front surface forming an interface with a rear surface of the layer of friction material, wherein the electroconductive member is profiled in a thickness direction of the backing plate to provide at least one projection extending towards the interface or into the layer of friction material and arranged to function as a wear indicator for the brake pad, wherein the electroconductive member comprises an electroconductive plate and the at least one projection comprises at least one deformed portion extending from the electroconductive plate towards the interface or into the layer of friction material, the deformed portion functions to enhance a bond between the electroconductive member and the resin plate of fibre-reinforced polymer resin, and the deformed portion is formed by punching a hole in the electroconductive plate to form a punched extension extending from the electroconductive plate towards the interface or into the layer of friction material.

73. A brake pad according to claim 72 wherein the electroconductive plate of the electroconductive member is a planar electroconductive plate having an array of integral extending portions extending from the planar plate into the plate of fibre-reinforced polymer resin to affix together the electroconductive member and the resin plate of fibre-reinforced polymer resin, the extending portions being formed by punching respective holes in the planar electroconductive plate.

74. A brake pad according to claim 72 wherein a plurality of the projections is provided and respective free ends of at least two of the projections are located at different distances relative to the interface.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0039] FIG. 1 is a schematic side cross-section through a brake pad according to a first embodiment of the present invention;

[0040] FIG. 2 is a schematic side cross-section through a brake pad according to a second embodiment of the present invention;

[0041] FIG. 3 is a schematic process flow of a method for manufacturing the brake pad of FIG. 1 or FIG. 2 according to an embodiment of the method of the present invention;

[0042] FIG. 4 is a schematic process flow of a method for manufacturing the brake pad of FIG. 1 or FIG. 2 according to another embodiment of the method of the present invention;

[0043] FIG. 5 is a side view, partly in phantom, of a brake pad according to a further embodiment of the present invention; and

[0044] FIG. 6 is a schematic perspective view, partly in phantom, of the brake pad of FIG. 5.

DETAILED DESCRIPTION

[0045] Referring to FIG. 1, there is shown a brake pad 2 according to an embodiment of the present invention. The brake pad 2 is an automotive brake pad for an automobile, motor cycle or truck or alternatively a railway brake pad for a railway locomotive, carriage or truck.

[0046] The brake pad 2 comprises a layer of friction material 4 integrally moulded with a backing plate 6. The friction material 4 comprises a cross-linked phenolic resin and friction particles dispersed therein. The layer of friction material 4 has a thickness of from 5 to 15 mm, optionally about 10 mm.

[0047] The backing plate 6 has a front surface 8 forming an interface 10 with a rear surface 12 of the layer of friction material 4. The backing plate 6 has a thickness of from 1 to 10 mm, optionally about 5 mm.

[0048] The backing plate 6 comprises an electroconductive member 14 moulded within a plate 16 of a fibre-reinforced polymer resin 18. The electroconductive member 14 extends along the plate direction. The electroconductive member 14 typically has an area extending along the plate direction which is from 50 to 100% of the area of the layer of friction material 4.

[0049] The fibre-reinforced polymer resin 18 comprises a thermoset resin comprising reinforcing fibres. Typically, the resin is a cross-linked phenolic resin comprising reinforcing fibres, optionally further comprising at least one filler material. The reinforcing fibres may comprise a layer of non-woven fibres.

[0050] Suitable phenolic resins for the backing plate 6 and the friction material 4, and suitable moulding conditions to achieve the bonding together of the backing plate 6 and the friction material 4, are disclosed in EP-A-2913552 and EP-A-2921736 which disclose the manufacture of a backing plate of a fibre-reinforced phenolic resin bonded to a layer of friction material.

[0051] The electroconductive member 14 is composed of a metal, typically a steel. The steel surface may have been treated with an adhesion enhancing layer to enhance adhesion to the fibre-reinforced polymer resin 18.

[0052] The metal electroconductive member 14 is a plate having a wall thickness of from 0.5 to 3 mm. The electroconductive member 14 in this embodiment comprises a corrugated plate 20. The corrugated plate 20 has a pitch between the corrugations 22 of from 1 to 4 mm. The corrugated plate 20 has a bulk thickness extending between opposite corrugated outer surfaces 24, 26 of from 3 to 10 mm.

[0053] The electroconductive member 14 has a rear surface 28 which is located a distance of from 0.1 to 3 mm, optionally from 0.5 to 2 mm, from a rear surface 30 of the backing plate 6. The corrugated plate 20 stiffens or rigidifies the backing plate 6, in particular along the longitudinal direction of the grooves of the corrugated plate 20.

[0054] The electroconductive member 14 is arranged to function as a wear indicator for the brake pad 2. An electrical contact member 30 is connected to the electroconductive member 14 for electrical connection to an electrical brake wear sensor system 32.

[0055] The electroconductive member 14 is profiled in a thickness direction of the backing plate 6 to provide at least one projection 34 extending towards the interface 10. In this embodiment, the at least one projection 34 comprises at least one corrugation 22 of the corrugated plate 20.

[0056] Preferably, and in the illustrated embodiment, the at least one projection 34 extends into the layer of friction material 4. Alternatively, at least one projection 34 terminates at the interface 10.

[0057] A free end 36 of at least one projection 34 is within the layer of friction material 4 and spaced forwardly from the interface 10 by a distance of from 1 to 8 mm, optionally about 3 mm.

[0058] In an alternative construction, additionally a free end 36 of at least one projection 34 is located at the interface 10.

[0059] In another alternative construction, a plurality of the projections 34 is provided and respective free ends 36 of at least two of the projections 34 are located at different distances relative to the interface 34. Typically, respective free ends 36 of the plurality of projections 34 are located at a range of from 0 to 5 mm, optionally from 1 to 5 mm, from the interface 10.

[0060] In use, as the brake pad 2 progressively wears due to cumulative braking use, the friction material surface is worn away and the working front surface of the layer of friction material 4 moves rearwardly towards the electroconductive member 14. Eventually, the disc brake, or other metallic braking member against which the brake pad 2 acts, contacts one of the projections 34, to form an electrical connection between the electroconductive member 14 and the disc brake. This action closes an electrical circuit which is detected by the electrical brake wear sensor system 32. This provides a warning to the driver that the brake pad has been worn down and requires replacement. When the projections 34 are located in front of the interface 34 between the layer of friction material 4 and the backing plate 6, the brake wear indicator system ensures that a signal of brake wear is sent before the layer of friction material 4 has fully worn away and before the brake disc could contact the backing plate 6 during a braking operation. When at least two of the projections 34 are located at different distances relative to the interface 34, this can provide a sequential indication of progressive brake wear and can provide a fail-safe system in the event that a first projection fails to continue to provide a reliable electrical contact with the brake disc.

[0061] Referring to FIG. 2, there is shown a brake pad 202 according to an alternative embodiment of the present invention. This embodiment is the same as for FIG. 1, except that in addition to providing corrugations 22 of the corrugated plate 20, the at least one projection comprises at least one deformed portion 204 extending from the plate 20 towards the interface or into the layer of friction material 4. The deformed portion 204 is formed by punching a hole in the plate 20 to form a punched extension extending from the plate 20 towards the interface 10 or into the layer of friction material 4.

[0062] The deformed portion 204 functions to enhance a bond between the electroconductive member 14 and the plate 16 of fibre-reinforced polymer resin 18.

[0063] In another embodiment, the electroconductive member 14 has a front surface, defined by the front surface of a plurality of the projections 22 or 204, optionally the front surface of a plurality of corrugations 22, which is located against the front surface 8 of the backing plate 6.

[0064] A first method of manufacturing the brake pad 2 will now be described with reference to FIG. 3. This method employs injection moulding to form the backing plate having a wear indicator.

[0065] The method has a first step A of providing in a mould cavity an assembly comprising a first portion comprising an electroconductive member within a fibre-containing polymer resin. A second portion comprising a friction material is adjacent to the first portion. In the first step A, the fibre-reinforced polymer resin is introduced into the mould cavity by injection of the fibre-reinforced polymer resin around the electroconductive member which is located in the cavity.

[0066] In a second step B, the assembly 54 is moulded to form a brake pad 66. The brake pad 66 comprises a layer of the friction material 64, formed from the second portion 62, integrally moulded with a backing plate 68, formed from the first portion 56. The backing plate 68 comprises the electroconductive member 58 moulded within a plate 70 of fibre-reinforced polymer resin.

[0067] As described with reference to FIGS. 1 and 2, the electroconductive member 58 extends along a plate direction. The backing plate 68 has a front surface forming an interface 72 with a rear surface of the layer of friction material 64. The electroconductive member 58 is profiled in a thickness direction of the backing plate 68 to provide at least one projection 74 extending towards the interface 72 or into the layer of friction material 64 and arranged to function as a wear indicator for the brake pad 66.

[0068] In the second step B, the layer of friction material 64 is located adjacent to the assembly 54 and adjacent contacting surfaces of the layer of friction material 64 and the assembly 54 are bonded together during the moulding step in the second step B. The layer of friction material 64 is a rigid preform 76. Typically, the preform 76 has been pre-shaped to the final shape and configuration of the layer of friction material 64 of the brake pad 66.

[0069] A second method of manufacturing the brake pad 2 will now be described with reference to FIG. 4. This method employs powder impregnation to form the backing plate having a wear indicator.

[0070] The method has a first step A of providing a layer of fibrous material 80.

[0071] In a second step B, a polymer resin powder 82 is impregnated into the layer of fibrous material 80 to form a preform layer 84.

[0072] The second step B comprises the following substeps: (i) the polymer resin powder is scattered onto the layer of fibrous material 80; (ii) an alternating electrical field is applied across the layer of fibrous material 80 to impregnate the polymer resin powder through the thickness of the layer of fibrous material 80; (iii) the impregnated layer is compressed to consolidate the resin-impregnated fibrous layer; (iv) the consolidated layer is heated so as at least partly to cure the resin; and (v) the at least partly cured layer is cut to form a plurality of the portions of the preform layer 84.

[0073] In a third step C, an assembly 86 is formed in a mould cavity 88. The assembly 86 comprises a sandwich 90 of an electroconductive member 92 between two portions of the preform layer 84 and, adjacent to the sandwich 90, a friction material 94. The friction material 94 is a rigid preform layer. Typically, the rigid preform layer has been pre-shaped to the final shape and configuration of the layer of friction material 94 of the resultant brake pad.

[0074] In a fourth step D, the assembly 86 is moulded to form a brake pad 96. The layer of friction material 94 is located adjacent to the assembly 86 and adjacent contacting surfaces of the layer of friction material 94 and the assembly 86 are bonded together during the moulding step.

[0075] The resultant brake pad 96 comprises a layer of friction material 94 integrally moulded with a backing plate 98 formed from the sandwich 90. The backing plate 98 comprises the electroconductive member 92 moulded within a body 100 of a fibre-reinforced polymer resin. The body 100 and the electroconductive member 92 forming first and second aligned plates extending along a plate direction. The body 100 has a front surface 102 forming an interface 104 with a rear surface 106 of the layer of friction material 94. The electroconductive member 92 is profiled in a thickness direction of the body 100 to provide at least one projection 106 extending towards the interface 104 or into the layer of friction material 94 and arranged to function as a wear indicator for the brake pad 96.

[0076] Referring to FIGS. 5 and 6, there is shown a brake pad 302 according to a further embodiment of the present invention. The brake pad 302 is an automotive brake pad for an automobile, motor cycle or truck or alternatively a railway brake pad for a railway locomotive, carriage or truck.

[0077] The brake pad 302 comprises a layer of friction material 304 integrally moulded with a backing plate 306. The friction material 304 comprises a cross-linked phenolic resin and friction particles dispersed therein. The layer of friction material 304 has a thickness of from 5 to 15 mm, optionally about 10 mm.

[0078] The backing plate 306 has a front surface 308 forming an interface 310 with a rear surface 312 of the layer of friction material 304. The backing plate 306 has a thickness of from 3 to 10 mm, optionally about 5 mm.

[0079] The backing plate 306 comprises an electroconductive member 314 moulded at least partly within a plate 316 of a fibre-reinforced polymer resin 318. The electroconductive member 314 extends along the plate direction. The electroconductive member 314 typically has an area extending along the plate direction which is from 50 to 100% of the area of the layer of friction material 304. The electroconductive member 314 stiffens or rigidifies the backing plate 306.

[0080] The fibre-reinforced polymer resin 318 and the friction material 304 may have the same compositions as described above for the first embodiment, and suitable moulding conditions are employed to achieve the bonding together of the backing plate 306 and the friction material 304, as described above.

[0081] The electroconductive member 314 is composed of a metal plate, or sheet, typically a steel. As described above, the steel surface may have been treated with an adhesion enhancing layer, for example by an adhesion coating, plasma treatment or chemical treatment, to enhance adhesion to the fibre-reinforced polymer resin 318.

[0082] The metal plate has a wall thickness of from 0.5 to 3 mm, typically 1 mm. The electroconductive member 314 in this embodiment comprises a planar plate 320 which has been punched, to form holes in the planar plate 320 to press out an array of integral extending portions 322 which extend forwardly from the planar plate 320 into the body of the plate 316 of fibre-reinforced polymer resin 318. The array of extending portions 322 extends into, and is moulded within, the plate 316 so that the electroconductive member 314 is securely affixed to the plate 316, and thereby provide that the backing plate 306 has a unitary structure. The extending portions 322 are oriented in different directions, typically opposite directions, within the plate 316 to enhance the bonding between the electroconductive member 314 and the plate 316.

[0083] In the illustrated embodiment, the extending portions 322 comprise substantially semi-circular pressed elements which are inclined at an acute angle, for example from 30 to 60 degrees, such as about 45 degrees, to the planar plate 320. The extending portions 322 form a regular array 324, for example a rectangular array 324. The extending portions 322 include a first sub-array 326a of a plurality of first extending portions 322 being oriented in a first direction and a second sub-array 326b of a plurality of second extending portions 322 being oriented in an opposite second direction. Each sub-array 326a, 326b comprises a plurality of lines of the respective extending portions 322. The sub-arrays 326a, 326b overlap, so that the regular array 324 of extending portions 322 comprises alternating lines of first extending portions 322 and second extending portions 322. However, other arrangements of the extending portions 322 can be employed in accordance with the present invention.

[0084] The extending portions 322 extend into the plate 316 by a distance of from 2 to 5 mm. The spacing between the extending portions 322 is from 2 to 15 mm. The electroconductive member 314 has a rear surface 328 which defines the rear surface 330 of the backing plate 306, and the planar plate 320 is located adjacent to the rear surface of the plate 316 of fibre-reinforced polymer resin 318. Alternatively, the electroconductive member 314 may be moulded within the plate 316 of fibre-reinforced polymer resin 318 and the rear surface 328 is located a distance of from 0.1 to 3 mm, optionally from 0.5 to 2 mm, from the rear surface of the backing plate 306.

[0085] The electroconductive member 314 is arranged to function as a wear indicator for the brake pad 302. An electrical contact member 332 is connected to the electroconductive member 314 for electrical connection of the electroconductive member 314 to an electrical brake wear sensor system (as shown in FIGS. 1 and 2).

[0086] The electroconductive member 314 is profiled in a thickness direction of the backing plate 306 to provide at least one projection 334 extending towards the interface 310. In this embodiment, the at least one projection 334 comprises at least one pressed element 336 extending into the layer of friction material 304. Alternatively, at least one projection 334 terminates at the interface 310. In the illustrated embodiment, there are four pressed elements 336, each located in the vicinity of a respective corner of the brake pad 302. Each pressed element 336 has been formed by punching the planar plate 320 to press out the pressed element 336 so as to be orthogonal to, and extend forwardly from, the planar plate 320 so as to extend into the body of the plate 316 of fibre-reinforced polymer resin 318. A body part 338 of the pressed element 336 is located within the plate 316 of fibre-reinforced polymer resin 318 and a tip part 340 of the pressed element 336 extends into the layer of friction material 304. A free end 342 of at least one projection 334 is within the layer of friction material 304 and spaced forwardly from the interface 310 by a distance of from 1 to 8 mm, typically from 1 to 3 mm.

[0087] The brake pad 302 of the embodiment of FIGS. 5 and 6 may be manufactured as described hereinabove with reference to FIGS. 3 and 4.

[0088] In use, the brake pad 302 is incorporated into a brake system of a vehicle. As the layer of friction material 304 becomes progressively worn away through use, eventually the free end 342 becomes exposed at the surface of the layer of friction material 304. When the free end 342 contacts a metallic part of the brake system, for example a disc against which the brake pad 302 is urged in a braking operation, an electrical circuit is completed by the electroconductive member 314, sending an electrical signal from the electroconductive member 314 to the electrical brake wear sensor system. Accordingly, the brake pad 302 incorporates an integral wear indicator for the brake pad 302.

[0089] Various other modifications to the present invention will be readily apparent to those skilled in the art.