GB2579776A

GB2579776A - Disc brake assembly

Info

Publication number: GB2579776A
Application number: GB1820179.8A
Authority: GB
Inventors: Patrick Stephen; Pike Russel
Original assignee: TRW Ltd
Current assignee: TRW Ltd
Priority date: 2018-12-11
Filing date: 2018-12-11
Publication date: 2020-07-08
Also published as: GB201820179D0

Abstract

A disc brake assembly, for a vehicle, comprises a bracket 102 locating a caliper (104, fig 3) and a pair of brake pads 110 located in opposing positions by the caliper (104). The brake pads 110 each comprising a back plate 112 and a friction material 114 mounted on the back plate 112. The caliper (104) applies a braking force to a shim 116 attached to each back plate 112 during a braking operation, thereby forcing the brake pads 110 towards each other. The bracket 102 includes a guide 120 configured to guide motion of the brake pads 110 during the braking operation. A guidance clip (120, fig 4) is interposed between the guide 120 and each brake pad 110. Each shim 116 includes at least one tag (124, fig 4) that extends over the back plate 112 and defines a corresponding friction interface with the guidance clip (120, fig 4).

Description

DISC BRAKE ASSEMBLY

The present invention relates to a disc brake assembly, particularly but not necessarily exclusively for use in vehicles such as road vehicles.

Disc brake assemblies are well-known. They typically comprise a brake rotor configured to rotate with a rotating part of a vehicle and a bracket that is secured to a fixed part of the vehicle. The bracket holds a caliper that locates a pair of brake pads, one brake pad on either side of the rotor. The brake pads comprise a back plate and a friction material mounted on the back plate on a surface facing the brake rotor. The caliper delivers a braking force to a shim attached to a rear of the brake pads, pressing the friction material of the brake pads into frictional contact with the brake rotor. Thus, a frictional force is caused between the brake pads and brake rotor, which acts to slow the rotation of the brake rotor. The bracket also includes a guide that guides movement of the brake pad towards the brake rotor.

During application of a braking force, it is known that disc brake assemblies can show a tendency to vibrate, which can result in unwanted noise output from the assembly. One way in which to combat such unwanted noise is disclosed in US 9 568 055 B2.

US 9 568 055 B2 discloses a pair of guidance clips that arc fitted between the bracket and the brake pad. More particularly, the guidance clips fit within the guide of the bracket and the back plate of the brake pad, preventing direct contact of the two parts and providing a vibration-damping effect. In addition, the guidance clips include an extending arm that applies a pre-load to the brake pad, further preventing unwanted noise. Where the guidance clip contact the brake pad defines friction interfaces, along which the brake pad slides, during application of the braking force.

Poor and/or inconsistent friction interfaces can be detrimental to the operation of the assembly, acting to generate unwanted noise. Such problems can be caused by, for example, oxide growth on the guidance clips, damage to the surface of the brake pad back plate such as paint damage, damage to the interface itself from, for example, manufacturing artefacts such as sharp edges formed on the back plate or a non-square friction interface.

It is an objective of the present invention to ameliorate one or more of the above problems.

According to the invention, there is provided a disc brake assembly for a vehicle, comprising: a bracket locating a caliper; a pair of brake pads, located in opposing positions by the caliper, the brake pads each comprising a back plate and a friction material mounted on the back plate on a surface facing the other of the brake pads; wherein the caliper is configured to apply a braking force to a shim attached to each back plate during a braking operation of the disc brake assembly, forcing the brake pads towards each other; wherein the bracket includes a guide configured to guide motion of the brake pads during the braking operation; further comprising a guidance clip interposed between the guide and each brake pad; characterised in that each shim includes at least one tag that extends over the back plate and defines a friction interface with the guidance clip.

The shim therefore provides a protective surface over the back plate of the brake pad, the shim providing an improved friction interface with the guidance clip. The friction interface may reduce noise and wear resulting from the action of the guidance clip during operation of the disc brake assembly.

A guide and guidance clip may be provided at two opposing ends of the bracket, guiding two opposing ends of the brake pad. The brake pad may therefore he each end by the bracket.

The at least one tag may prevent the guidance clip directly contacting the brake pad.

Any wear or noise caused by direct contact of the guidance clip with the brake pad may therefore he prevented or limited.

The back plate may include a lateral protrusion around which the guidance clip extends.

The lateral protrusion may be seated within the guide.

The guide may form a runner within which the lateral protrusion can slide.

The lateral protrusion and guide may be complementarily-shaped.

The lateral protrusion may have a rectangular cross-section that is receivable within a corresponding rectangular cross-section of the guide.

The shape of the lateral protrusion and guide may help to ensure the predictable movement of the brake pad, during operation. Seating the lateral protrusion within the guide may restrict movement of the brake pad in directions which would be detrimental to the assembly, whilst allowing the movement that enables it to clamp against a brake rotor, in use.

The at least one tag may define a friction interface adjacent to a lateral face of the lateral protrusion.

The guidance clip may he a snug fit within the guide.

The guidance clip may include a biasing mechanism for applying a pre-load to the brake pad.

The pre-load may bias the brake pad in a direction towards the friction interface adjacent to the lateral protrusion.

The pre-load may bias the brake pad such that it floats within the bracket This means that it may be biased away from any contact with the bracket except at the friction interfaces defined by the at least one tag.

The biasing mechanism may comprise an extending arm.

The at least one tag may define a friction interface with the extending arm.

The at least one tag may bend at a 90° angle over the hack plate.

The at least one tag may form a square friction interface with the guidance clip.

By "square'', we mean that the surfaces of the guidance clip and tag that form the friction interface arc coincident. This can assist with even spreading of loading and frictional forces.

The square surface may encourage the brake pad to sit square within the bracket and/or may ensure a consistent, evenly distributed, force on the brake pad, which may prevent or limit damage and wear. A chirp noise associated with the guidance clip may also he reduced. The square surface can mitigate for any tapering of the brake pad that may commonly be produced during the manufacturing process.

During manufacture, a sharp edge may be produced on the back plate of the brake pad.

By providing a tag, and preferably a tag with a 900 angle over the back plate, the sharp edge can he prevented from contacting the spring, which can prevent damage to the spring and thus prolong the life of the assembly.

The at least one tag may include a locating tag for locating the shim on the back plate.

The locating tag can therefore both locate the shim and define a friction interface, minimising the requirements for additional components in the assembly.

The locating tag may form a hook around the back plate.

The hook can therefore loop over the brake pad during assembly which helps to locate any other tags.

The at least one tag may include a low-friction coating. The low-frict on coating may comprise a PTFE layer.

The low-friction coating may be provided on the entire shim, for example where the shim is a damping shim.

Alternatively, the tag may be formed of stainless steel, for example where the shim is a stainless steel cover shim.

By having a tag that has the same finish -i.e. surface material -as the shim of which it forms a part, the modification required to form the tag may require no new components to be added to the assembly over an assembly without a tag. In contrast, coating the guidance clip with PTFE would he an additional, complex, and expensive manufacturing step.

The present invention will now he described with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a disc brake assembly in accordance with the invention; Figure 2 is a view from the below of the disc brake assembly of Figure I; Figure 3 is a view from the front of the disc brake assembly of Figure 1; Figure 4 is an enlarged view of Figure 3, highlighting a guidance clip interposed between the bracket and brake pad; Figure 5 is a perspective view of the disc brake assembly of Figure 1 with the caliper and associated components removed; and Figure 6 is a perspective view of a brake pad and shim of the disc brake assembly of Figure 1.

Referring firstly to Figures 1 to 3, there is shown an embodiment of a disc brake assembly 100 for a vehicle. The disc brake assembly 100 comprises a bracket 102 and a caliper 104, the bracket 102 locating the caliper 104. The bracket 102 is configured with mounting points 106 for attachment to a fixed -i.e. non-rotating -part of a vehicle (not shown), which holds the bracket 102 in position. The caliper 104 is secured to the bracket 102 by two pin assemblies 108 located toward either side of the bracket 102. The pin assembly 108 allows the caliper 104 to move within predefined bounds during actuation of the disc brake assembly 100.

The caliper 104 includes a number of pistons (not shown) that apply a force to brake pads 110 that are located within the caliper 104 and supported by the bracket 102. A hydraulic input forces the pistons to act on the brake pads 110 to close the brake pads 110 against a brake rotor (not shown) during the initiation of a braking operation. The pistons act directly on only one of the brake pads 110 due to the floating caliper arrangement of the disc brake assembly 100. The other brake pad 110 is pulled into engagement with the brake rotor by the movement of the caliper 104 itself, as the pistons move the first brake pad 110. Although the present embodiment has a floating caliper arrangement, the present invention is equally applicable to other types of caliper arrangement, such as a fixed caliper arrangement where pistons apply force to both brake pads 110.

The arrangement of the brake pads 110 can be seen clearly in Figure 5, where the caliper 104 has been removed. The brake pads 110 each include a back plate 112 and a layer of friction material 114 bonded to the back plate 112 and arranged to face the brake rotor, in use. The friction material 114 of each brake pad 110 therefore faces the other, in an opposed relationship, such that the brake rotor will be clamped by the movement of the brake pads 110 towards each other when the brake is applied.

On the rear of each brake pad 110, on the opposite side to the friction material 114, a shim 116 is mounted. The shim 116 acts to provide damping and vibration suppression to the brake pad 110, as well as spreading the force provided by the pistons and caliper 104 over the whole or a larger proportion of the brake pad 110. The shim 116 may, in this embodiment, be formed of a stainless steel material with or without a PTFE coating, although a full choice of materials and coatings will be known to the skilled person and easily implemented in the present assembly.

The back plate 112 of the brake pad 110 is shaped to include a lateral protrusion 1 1 8 on either side, each lateral protrusion 118 being received within a guide 120 formed on the bracket 102. The guide 120 forms a runner that allows the brake pads 110 to slide towards and away from each other during operation of the disc brake assembly 100. The lateral protrusion 1 1 8 fits within the guide 120 and has a rectangular cross-section that corresponds to a complementary rectangular cross-section of the guide 120. Within the guide 120 is seated a guidance clip 122, shown in position in Figure 4. The guidance clip 122 fits between the guide 120 and the lateral protrusion 118, and prevents direct contact of the bracket 102 on the brake pad 110. Each guidance clip 122 fits snugly within each guide 120. This may help to prevent movement of the guidance clip 122 within the guide 120. In addition, the guidance clips 122 are slightly sprung to bias them into engagement with the guide 120.

The guides 120 on either side of the bracket 102 extend all the way through the bracket 102, such that two guides 120 provide guidance for both sides of both brake pads 110. Four guidance clips 122 are provided in total, as the guidance clips 122 are provided separately for each side of each brake pad 110.

The shim 116 is shaped so that is largely corresponds to the shape of the back plate 112, including the lateral protrusion 118. However, each shim 116 also includes a total of four tags 124 which extend over the back plate 112 in a direction towards the friction material 114 of the brake pad 110. The tags 124 are positioned such that they are interposed between the guidance clip 122 and back plate 112 at any point where the guidance clip 122 and back plate 112 make sliding contact, in use. Thus, the tags 124 define friction interfaces 126 with the guidance clips 122. During operation of the disc brake assembly 100, the brake pads 110 will therefore slide through the guides 120 whilst in contact with the guidance clip 122 on the friction interfaces 126.

One of the tags 124 associated with each guidance clip 122 is located on an upper surface 128 of the lateral protrusion 118, forming an upper friction interface 126. As well as providing a friction interface 126, these tags 124 include a portion that extends down a front face 130 of the back plate 112, forming a hook 132 over the back plate 112. During assembly, these hooks 132 will allow the shim 116 to be located on the back plate 112, the remaining tags 124 then being fitted around the brake pad 110. The hooks 132 may be omitted, to form a simpler assembly, whilst still providing the friction interfaces 126.

The other tag 124 associated with each guidance clip 122 is located on a lower, inclined surface 134 of the back plate 112. This surface 134 is angled at approximately 30° to the horizontal and provides a friction interface 126 with a lower portion of the guidance clip 122. The lower portion of the guidance clip 122 comprises an extending arm 136, which forms a biasing mechanism that imparts a pre-load force on the back plate 112 and hence the brake pad 110. In this scenario, the guidance clip 122 may also be termed a guidance spring, due to the biasing force imparted on the brake pad 110. The brake pad 110 is therefore biased to float within the guides 120, making contact only with the guidance clips 122, and being pressed upwards towards an upper surface 138 of the guide 120.

The provision of the tags 124 ensures that there is no rubbing of the brake pad 110 itself -e.g. the back plate 112 -on the guidance clip 122 during sliding motion of the brake pad 110, or at least there is no weight-bearing motion. For example, whilst it may be possible for the back plate 110 to contact the guidance clips 122 in certain circumstances, temporarily, the action of the guidance clip 122 will ensure that the brake pad 110 will naturally centre so as not to contact the guidance clip 122 directly.

The tags 124 protect the brake pad 110, and particularly, the back plate 112, from any damage that could occur from repeated rubbing of the surface of the brake pad 110 with the guidance clip 122. Such damage or wear can be detrimental to the operation of the disc brake assembly 100 as wear of the back plate 112 can result in variable friction during operation, altering the feel or force application of the disc brake assembly 100. Damage can also contribute to chirping or other unwanted noise production of the brake pad 110 or guidance clip 122. Damage may be particularly noticeable where the back plate 112 has a painted coating, as is common. Conversely, the shim 116, which forms the tags 124, is commonly stainless or coated in a low-friction coating such as PIPE, and therefore does not suffer from the same proclivity to damage as the brake pad 110.

The tags 124 can also be advantageous in that they may provide an improved surface for sliding of the brake pad 110 and application of the biasing force from the guidance clip 122. The bending of the tags 124, which can be ensured to be square with the guide 120 and guidance clip 122, provides the improved surface. This can overcome or mitigate for artefacts from the manufacturing process, which may include tapering faces of the back plate 112 or sharp edges that can cause damage to the guidance clip 122. Providing the friction interface 126 between the tag 124 and the guidance clip 122 may overcome both of these issues. The tags 124 of the shim 116 can protect other components from damage from these artefacts or may even act as a more sacrificial component that can be cheaply replaced if damage or unwanted noise were to he produced.

A greater or lesser number of tags 124 may be provided by each of the shims 116.

Moreover, the shims 116 may have differing numbers of tags 124, depending on their specific requirements. For example, tags 124 may he provided on every surface that may come into contact with the guidance clip 122 or may be restricted to use only on those surfaces where sliding contact is usually provided, in use, such as described above.

Claims

CLAIMS1. A disc brake assembly for a vehicle, comprising: a bracket locating a caliper; a pair of brake pads, located in opposing positions by the caliper, the brake pads each comprising a back plate and a friction material mounted on the back plate on a surface facing the other of the brake pads; wherein the caliper is configured to apply a braking force to a shim attached to each back plate during a braking operation of the disc brake assembly, forcing the brake pads towards each other; wherein the bracket includes a guide configured to guide motion of the brake pads during the braking operation; further comprising a guidance clip interposed between the guide and each brake pad; characterised in that each shim includes at least one tag that extends over the back plate and defines a corresponding friction interface with the guidance clip.
2. A disc brake assembly according to claim 1, wherein a guide and guidance clip are provided at two opposing ends of the bracket, guiding two opposing ends of the brake pad.
3. A disc brake assembly according to claim 1 or claim 2, wherein the at least one tag prevents the guidance clip directly contacting the brake pad.
4. A disc brake assembly according to any preceding claim, wherein the back plate includes a lateral protrusion around which the guidance clip extends.
5. A disc brake assembly according to claim 4, wherein the lateral protrusion is seated within the guide.
6. A disc brake assembly according to claim 4 or claim 5, wherein the guide forms a runner within which the lateral protrusion can slide.
7. A disc brake assembly according to any of claims 4 to 6, wherein the lateral protrusion and guide are complementarily-shaped.
8. A disc brake assembly according to any of claims 4 to 7, wherein the lateral protrusion has a rectangular cross-section that is receivable within a corresponding rectangular cross-section of the guide.
9. A disc brake assembly according to any of claims 4 to 8, wherein the at least one tag defines a friction interface adjacent to a lateral face of the lateral protrusion.
10. A disc brake assembly according to any preceding claim, wherein the guidance clip is a snug fit within the guide.
11. A disc brake assembly according to any preceding claim, wherein the guidance clip includes a biasing mechanism for applying a pre-load to the brake pad.
12. A disc brake assembly according to claim 11, wherein the biasing mechanism comprises an extending arm.
13. A disc brake assembly according to claim 11 or claim 12, wherein the at least one tag defines a friction interface with the biasing mechanism.
14. A disc brake assembly according to any preceding claim, wherein the at least one tag bends at a 90° angle over the back plate.
15. A disc brake assembly according to any preceding claim, wherein the at least one tag forms a square friction interface with the guidance clip.
16. A disc brake assembly according to any preceding claim, wherein the at least one tag includes a locating tag for locating the shim on the back plate.
17. A disc brake assembly according to claim 16, wherein the locating tag forms a hook around the hack plate.
18. A disc brake assembly according to any preceding claim, wherein the at least one tag includes a low-friction coating.
19. A disc brake assembly according to any preceding claim. wherein the low-friction coating comprises a PTFE layer.