GB1589118A

GB1589118A - Disc brakes

Info

Publication number: GB1589118A
Application number: GB3286077A
Authority: GB
Original assignee: Girling Ltd
Current assignee: Girling Ltd
Priority date: 1977-08-05
Filing date: 1977-08-05
Publication date: 1981-05-07
Also published as: JPS5440973A; DE2834100C2; JPS6049778B2; DE2834100A1

Description

(54) IMPROVEMENTS IN DISC BRAKES (71) We, GIRLING LIMITED, a British company of Kings Road, Tyseley, Birmingham 11, West Midlands, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to disc brakes and is particularly concerned with sliding caliper type disc brakes.

Sliding caliper type disc brakes are known and generally comprise a fixed torque member, a directly operated and an indirectly operated brake pad assembly, an actuator and a caliper which straddles the rotatable disc and is slidably mounted relative to the fixed torque member; the arrangement being such that upon application of the directly operated pad assembly to one side of the disc by means of the actuator, which may be a piston and cylinder device, the resulting reaction forces so displace the caliper as to apply the indirectly operated pad assembly to the other side of the disc.

The sliding connection between the caliper and the torque member in such brakes is conventionally achieved by means of guides which constrain the caliper in all but the axial direction and which may comprise two or more sets of pin/hole combinations, the pins being carried in the caliper and being slidable in the holes in the torque member. Alternatively, the pins may be carried by the torque member and be slidable in holes in the caliper.

In such known constructions, each pin is usually of circular section and may be arranged to transmit part of the drag forces experienced by the indirectly operated pad assembly from the caliper to the fixed torque member. In certain other constructions, only one pin carries the drag forces, the other pin or pins being provided only for preventing rotation of the caliper about the drag pin during operation and sometimes for assisting location of the pad assemblies. In another construction, the pins may be provided merely to guide the caliper, and the drag of the pads being taken by means other than the pins, for example, by the torque plate.

A considerable problem which is incurred with all of the latter known constructions arises from the requirement that the spacings between the holes or pins on the caliper must be precisely aligned with the pins or holes, respectively, in the torque member. If this condition is not met then cross-binding occurs when the caliper is caused to slide relative to the torque member.

Binding between the pins and the holes in which they slide is also caused by the pins and holes being mounted in or on different members which undergo different degrees of distortion or deflection during operation, causing the pin/hole spacings to change under different load conditions.

This is an especially important problem with arrangements comprising two pin/hole combinations.

One manner of overcoming the problem of pin/hole positional tolerances has been to make the holes wider than the pins to bias the pins into predetermined positions within the holes by means of springs. The problem with this type of arrangement is that, should the latter springs fail, or be wrongly assembled, the large clearances, might lead to violent shock loadings on the guides. Furthermore because the spring must be made heavy enough to resist vibration forces, friction at the points of reaction to the spring may impede the free sliding of the pins in the holes.

In a further construction described in our copending Application No. 53793/76, the drag forces are transmitted to the torque plate through a single pin of noncircular section which is received in an identically shaped hole formed in the torque plate.

There is provided by the present invention a disc brake comprising a pair of friction pad assemblies, a fixed torque member and a caliper member mounted for axial sliding on the torque member, the caliper containing a hydraulic actuator to effect axial sliding of the caliper on the torque member so that the actuator acts directly on one of the friction pad assemblies applied to one side of the disc, and causes the caliper to act on the other of the friction pad assemblies to apply it by reactive sliding of the caliper to the other side of the disc, wherein between the caliper and the torque member, there is provided a piston of non-circular section, one end of which is slidably received in an identically sectioned piston chamber defined in a limb of the caliper, the piston, or a member non-rotatably connected to the piston, also having a sliding non-rotatable engagement with the torque member, or with a member non-rotatably connected to the torque member.

Thus, the piston acts as an intermediate member which is non-rotatably connected both to the caliper member and to the torque member, and thus the caliper member is effectively non-rotatably connected to the torque member. The engagement between the piston and the torque member can be direct, or can be indirect, for example, the piston may be attached to one of the pads which is then itself nonrotatably mounted in the torque member; and the torque member or said member non-rotatably connected thereto may provide a non-circular sectioned aperture to receive the piston or the member nonrotatably attached thereto. The piston of non-circular section and the identically sectioned piston chamber may, and preferably do, constitute the actuator of the caliper.

The invention is applicable to the two variations of brake design, where in the first, the torque member itself straddles the disc to receive directly the drag forces of the indirect pad, and in the second, the torque member stops short of the disc and the indirect pad transmits its drag forces to the caliper, and thus to the piston of non-circular section.

The invention is described further hereinafter, by way of example, with reference to the drawings accompanying the provisional specification in which: Fig. 1 is a sectional side elevation of one embodiment of a disc brake assembly in accordance with the present invention; Fig. 2 shows the torque plate of Fig. 1 viewed from the outboard side; Fig. 3 is the disc brake assembly of Fig.

1 viewed from the inboard side; Fig. 4 is a section along line IV-IV of Figure 1; Fig. 5 is a sectional side elevation of another embodiment of a disc brake assembly in accordance with the present invention; Fig. 6 is a sectional side elevation of yet another embodiment of a disc brake according to the present invention; Fig. 7 is a section along line VII-VII of Figure 6; Fig. 8 is a section along line VIII-VIII of Figure 6; Fig. 9 is a section along line IX-IX of Figure 6; Fig. 10 is a sectional side elevation of a further embodiment of a disc brake assembly in accordance with the present invention; Fig. 11 is a section along line XI-XI of Figure 10; and Fig. 12 is a section along line XII-XII of Figure 10 with the outboard friction pad assembly omitted.

The embodiment illustrated in Fig. 1 comprises a generally U-sectioned caliper member 10 which straddles the brake disc 12 (indicated by dotted lines), the caliper member including a bridge portion 14 located radially outwardly of the disc 12 and a pair of generally radially inwardly extending limbs 16,18 located on each side of the disc. The caliper member 10 is mounted for sliding movement on a torque plate 40 which is rigidly clamped to the frame of a vehicle by bolts passing through holes 34 shown in Figs. 2, 3 and 4.

A piston chamber 22 of non-circular section, defined in the inboard limbs 18 of the caliper 10, slidably receives an identically sectioned piston 24, the end wall of the chamber containing a hydraulic port 125 (Fig. 3) for connecting the chamber to a source of hydraulic fluid. The chamber 22, at its remote end carries a scaper ring 25 bearing on the piston to prevent ingress of dirt. The piston 24 is non-rotatably connected to the inboard pad backing plate 28 to which is attached, for example, by moulding, the inboard friction pad 26, the backing plate 28 and pad 26 also being of non-circular section and passing slidably through an aperture 29 of corresponding non-circular section in the inboard limb 41 of the torque plate 40. As shown in Fig. 4, the non-circular section of the components 26 and 28 is of the same configuration as the non-circular sectioned piston and cylinder bore 24,22 but it is of greater dimensions as is evident from Fig. 1.

To the outboard limb 16 of the caliper is clamped an abutment plate 30' by means of a bolt 31 and a clamp plate 31', the plate 31' abutting and acting on the rear face of the outboard pad backing plate 30 which holds an outboard friction pad 27 which is again of non-circular section. The pad backing plate 30 and pad 27 pass slidably through a correspondingly non-circular sectioned aperture 21 in an outboard portion 42 of the torque plate 40.

On pressurization of hydraulic fluid into the piston chamber 22, the piston 24 is advanced towards the disc 12 so as to apply the inboard friction pad 26 to the disc, the reactive forces generated being such as to displace the caliper 10 in the opposite direction, and in so doing apply the outboard friction pad to the brake disc 12.

Drag forces exerted on the friction pads 26,27 by the disc 12, are directly resisted by the torque plate 40 and, because the friction pads 26,27 and the torque plate apertures 21,29 are non-circular, any tendency for the disc 12 to rotate the friction pads is overcome. Likewise the co-operating non-circular parts prevent rotation of the caliper as a whole relative to the torque plate about the axis of the piston and cylinder.

Fig. 5 shows a second embodiment in which the inboard pad backing plate 28 is secured to the piston 24 by means of a bolt 32, and the outboard pad backing plate is bolted by bolt 31 to the outboard limb of the caliper.

Another embodiment of the invention is illustrated- in Figs. 6 to 9 and differs from the previous embodiments in two distinct ways.

Firstly, whereas in Figs. 1 and 5 the piston 24 was slidably received in the piston chamber 22 alone, in Fig. 6 it is also similarly received in the non-circular aperture 29 of the torque plate 40. Nonrotatably attached to the face of the piston 24,- are the backing plate 28 and the inboard friction pad 26, both being of circular section and being received in a corresponding circular aperture 29' of the torque plate 40.

Secondly, the torque plate 40 does not, in the embodiment shown in Figs. 6 to 9, straddle the brake disc 12 but lies wholly on the inboard side of the brake disc 12.

Consequently, drag forces experienced by the outboard pad are transmitted via the caliper member 10 and the piston 24 to the torque plate 40.

Figs. 7, 8 and 9 show sections through the disc brake in the region where the piston passes through the torque plate 12, in the region of the pad backing plate 28, and in the region of the outboard friction pad 27 respectively.

There is shown in Figs. 10 to 12 yet another embodiment of the invention in which the torque plate has no outboard portion for receiving the outboard friction pad.

However, the inboard pad backing plate 43 is slidably received in the non-circular aperture 29 of the torque plate 40. Owing to the gradual wear of the inboard friction pad 26, the piston 24, which is made of metal, gradually reaches further from the piston chamber 22. This is also the case in the embodiment shown in Fig. 6 this tendency being accompanied by the gradual shift of the surface of the piston 24 into the aperture 29 in the torque member 40.

In the Fig. 6 embodiment, to prevent abrasive grit and dirt being conducted into the interface between the surface of the piston and the aperture, on movement of the piston, there extends between the inboard portion of the torque plate 40 and the caliper member a flexible sealing boot 45.

In the embodiment shown in Fig. 10 the inboard pad backing plate 43, which is made of plastics material, has a greater cross section than the piston chamber 22 and is slidably received in the inboard portion of the torque plate 40. The use of a plastics material for the backing plate is an advantage, in that, the plastics material makes the backing plate less susceptible to interference in operation by ingress of dirt between the backing plate and the surface it slides on, and thus no seating boot, such as boot 45, is needed.

WHAT WE CLAIM IS: - 1. A disc brake comprising a pair of friction pad assemblies, a fixed torque member and a caliper member mounted for axial sliding on the torque member, the caliper containing a hydraulic actuator to effect axial sliding of the caliper on the torque member so that the actuator acts directly on one of the friction pad assemblies applied to one side of the disc, and causes the caliper to act on the other of the friction pad assemblies to apply it by reactive sliding of the caliper to the other side of the disc, wherein, to permit the axial sliding between the caliper and the torque member to be effected, there is provided a piston of non-circular section, one end of which is slidably received in an identically sectioned piston chamber defined in a limb of the caliper, the piston, or a member non-rotatably connected to the piston, also having a sliding non-rotatable engagement with the torque member, or with a member non-rotatably connected to the torque member.

2. A disc brake according to claim wherein the fixed torque member or said member non-rotatably connected to the torque member, is provided with an aperture of non-circular section, and the piston or said member non-rotatably connected thereto, slidably but non-rotatably engages in said aperture of non-circular section.

3. A disc brake according to claim 1 or 2, wherein said member non-rotatably connected to the piston is a friction pad assembly.

4. A disc brake according to claims 2 and 3, wherein said friction pad assembly is slidably received in said non-circular sectioned aperture.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the piston chamber 22, the piston 24 is advanced towards the disc 12 so as to apply the inboard friction pad 26 to the disc, the reactive forces generated being such as to displace the caliper 10 in the opposite direction, and in so doing apply the outboard friction pad to the brake disc 12. Drag forces exerted on the friction pads 26,27 by the disc 12, are directly resisted by the torque plate 40 and, because the friction pads 26,27 and the torque plate apertures 21,29 are non-circular, any tendency for the disc 12 to rotate the friction pads is overcome. Likewise the co-operating non-circular parts prevent rotation of the caliper as a whole relative to the torque plate about the axis of the piston and cylinder. Fig. 5 shows a second embodiment in which the inboard pad backing plate 28 is secured to the piston 24 by means of a bolt 32, and the outboard pad backing plate is bolted by bolt 31 to the outboard limb of the caliper. Another embodiment of the invention is illustrated- in Figs. 6 to 9 and differs from the previous embodiments in two distinct ways. Firstly, whereas in Figs. 1 and 5 the piston 24 was slidably received in the piston chamber 22 alone, in Fig. 6 it is also similarly received in the non-circular aperture 29 of the torque plate 40. Nonrotatably attached to the face of the piston 24,- are the backing plate 28 and the inboard friction pad 26, both being of circular section and being received in a corresponding circular aperture 29' of the torque plate 40. Secondly, the torque plate 40 does not, in the embodiment shown in Figs. 6 to 9, straddle the brake disc 12 but lies wholly on the inboard side of the brake disc 12. Consequently, drag forces experienced by the outboard pad are transmitted via the caliper member 10 and the piston 24 to the torque plate 40. Figs. 7, 8 and 9 show sections through the disc brake in the region where the piston passes through the torque plate 12, in the region of the pad backing plate 28, and in the region of the outboard friction pad 27 respectively. There is shown in Figs. 10 to 12 yet another embodiment of the invention in which the torque plate has no outboard portion for receiving the outboard friction pad. However, the inboard pad backing plate 43 is slidably received in the non-circular aperture 29 of the torque plate 40. Owing to the gradual wear of the inboard friction pad 26, the piston 24, which is made of metal, gradually reaches further from the piston chamber 22. This is also the case in the embodiment shown in Fig. 6 this tendency being accompanied by the gradual shift of the surface of the piston 24 into the aperture 29 in the torque member 40. In the Fig. 6 embodiment, to prevent abrasive grit and dirt being conducted into the interface between the surface of the piston and the aperture, on movement of the piston, there extends between the inboard portion of the torque plate 40 and the caliper member a flexible sealing boot 45. In the embodiment shown in Fig. 10 the inboard pad backing plate 43, which is made of plastics material, has a greater cross section than the piston chamber 22 and is slidably received in the inboard portion of the torque plate 40. The use of a plastics material for the backing plate is an advantage, in that, the plastics material makes the backing plate less susceptible to interference in operation by ingress of dirt between the backing plate and the surface it slides on, and thus no seating boot, such as boot 45, is needed. WHAT WE CLAIM IS: -

1. A disc brake comprising a pair of friction pad assemblies, a fixed torque member and a caliper member mounted for axial sliding on the torque member, the caliper containing a hydraulic actuator to effect axial sliding of the caliper on the torque member so that the actuator acts directly on one of the friction pad assemblies applied to one side of the disc, and causes the caliper to act on the other of the friction pad assemblies to apply it by reactive sliding of the caliper to the other side of the disc, wherein, to permit the axial sliding between the caliper and the torque member to be effected, there is provided a piston of non-circular section, one end of which is slidably received in an identically sectioned piston chamber defined in a limb of the caliper, the piston, or a member non-rotatably connected to the piston, also having a sliding non-rotatable engagement with the torque member, or with a member non-rotatably connected to the torque member.

5. A disc brake according to any of the

preceding claims, wherein said piston of non-circular section and the identically sectioned piston chamber constitute the actuator of the caliper.

6. A disc brake according to claim 5 wherein said limb of the caliper in which the identically sectioned piston chamber is defined is located on the inboard side of the disc, and the piston of non-circular section acts directly on the friction pad assembly at the inboard side of the disc and indirectly, by reactive sliding of the caliper, on the friction pad assembly at the outboard side of the disc; the torque member providing a non-circular sectioned aperture at the inboard side of the disc to receive therein the friction pad assembly at the inboard side of the disc, that friction pad assembly being non-rotatably connected to the piston of non-circular section.

7. A disc brake according to any of the preceding claims, wherein the friction pad assembly at the outboard side of the disc is supported by an outboard limb of the caliper.

8. A disc brake according to any of the preceding claims 1 to 6, wherein the torque member provides an outboard limb, and the friction pad assembly at the outboard side of the disc is carried by the outboard limb of the torque member.

9. A disc brake according to any of the preceding claims, wherein the friction pad assembly at the outboard side of the disc is pinned to the caliper.

10. A disc brake according to any of the preceding claims, wherein at least the friction pad assembly at the inboard side of the disc consists of a plastics material.

11. A disc brake according to claim 6 or any of the preceding claims 7 to 10 as dependent on claim 6, wherein the friction pad assembly at the inboard side of the disc and said piston of non-circular section are of the same configuration.

12. A disc brake according to any of the preceding claims, wherein the two friction pad assemblies are of the same configuration.

13. A disc brake according to claim 2 or any of preceding claims 3 to 12 as dependent on claim 2, wherein the piston of non-circular section and said non-circular sectioned aperture in the torque member are of the same cross-sectional dimension and the piston is received in the aperture.

14. A disc brake according to claim 13, wherein a flexible sealing means is provided around the piston of non-circular section between the piston chamber thereof and the non-circular sectioned aperture in the fixed torque member.

15. A disc brake according to claim 4 or any of the preceding claims 5 to 12 as dependent on claim 4, wherein said noncircular sectioned aperture is of larger cross sectional dimensions than the piston of non-circular section.

16. A disc brake substantially as hereinbefore described with reference to Figures 1 to 4 of the drawings accompanying the Provisional Specification.

17. A disc brake substantially as hereinbefore described with reference to Figure 5 of the drawings accompanying the Provisional Specificaion.

18. A disc brake substantially as hereinbefore described with reference to Figures 6 to 9 of the drawings accompanying the Provisional Specificaiion.

19. A disc brake substantially as hereinbefore described with reference to Figures 10 to 12 of the drawings accompanying the Provisional Specification.