GB1573305A

GB1573305A - Vehicle brakes

Info

Publication number: GB1573305A
Application number: GB551976A
Authority: GB
Original assignee: Girling Ltd
Current assignee: Girling Ltd
Priority date: 1976-02-12
Filing date: 1976-02-12
Publication date: 1980-08-20
Also published as: AU2207077A; JPS52110378A; AU507440B2; JPS589853B2

Description

(54) IMPROVEMENTS IN VEHICLE BRAKES (71) We, GIRLING LIMITED, a British Company, of Kings Road, Tyseley, Birmingham B26 L11, 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 vehicle brakes.

The invention is particularly concerned with vehicle brakes of the type comprising a carrier member for fixing to a vehicle frame or like portion, a caliper member, and an actuator for urging a first friction pad onto a braking surface to cause the caliper member to move relative to the carrier member and apply a second friction pad to a second braking surface.

It has been proposed to mount the caliper member on the carrier member by means of a pair of pins which are slidable in respecitve openings in one of the members and are secured to the other of the members. In such constructions the pins are made so as to be snug sliding fit in the openings, to properly locate the caliper against tipping so that, it is usually necessary to centre the pins very accurately in their openings to avoid binding in operation which can results in differential braking at different vehicle wheels arising from different proportions of the available hydraulic line pressure needed to overcome initial resistance to sliding.

Furthermore, under heavy braking the carrier member may distort such that the spacing between the pins or openings carried thereby changes causing the possibility of binding of the pins in their openings.

Our British Patent Specification No.

1,506,709 claims a vehicle disc brake comprising a carrier member for fixing to a vehicle, a caliper member slidably connected to the carrier member and an actuator for urging a first friction pad onto one side of a rotatable disc to cause the caliper member to slide relative to the carrier member and apply a second friction pad to the other side of the disc, the sliding connection between the caliper member and carrier member comprising a pair of pins slidable in one of the members and secured to the other of the members, at least one of the pins being received in an oversized opening in said one of said members, and a resilient sleeve interposed between said oversized opening and said at least one pin so as to surround that pin, the fit of said at least one pin and the sleeve within the oversized opening being such that said at last one pin can at all times effect displacement relative to its associated opening without deformation of the resilient sleeve and means resiliently biassing said at least one pin into an eccentric position within the oversized opening. The provision of the oversized opening minimises any tendency for cross-binding to occur. In particular, it is aimed at reducing the cross-binding caused by the above-mentioned distortion, which still occurs even if the pins are initially perfectly positioned in the openings.

It is an object of the present invention to provide a modification of the arrangement of our prior specification No. 1506709 which is of simpler construction but yet which retains the advantage wherein the pins do not cross-bind, both for the initial mismatch reason, and for the distortion reason.

According to the present invention, there is provided a vehicle disc brake comprising a carrier member for fixing to a vehicle, a caliper member slidably connected to the carrier members, and an actuator for urging a first friction pad onto one side of a rotatable disc to cause the caliper member to slide relative to the carrier member and apply a second friction pad to the other side of the disc, the sliding connection between the caliper member and carrier member comprising a pair of parallel pins slidable in one of the members and secured to the other of the members, at least one of the pins being received in an opening which is oversized (as hereinbefore defined), relative to the lateral dimensions of that pin, in at least the plane containing the pins, and the brake being devoid of resilient biassing means for the pin or pins so that said at least one pin is freely movable in that plane between eccentric positions in which it contacts the wall of its opening.

One embodiment of vehicle disc brake in accordance with the invention comprises a carrier member for fixing to a vehicle, a caliper member slidably connected to the carrier member, and an actuator for urging a first friction pad onto one side of a rotatable disc to cause the caliper member to slide relative to the carrier member and apply a second friction pad to the other side of the disc, the sliding connection between the caliper member and carrier member comprising a pair of parallel pins slidable in one of the members and secured to the other of the members, at least one of the pins being received in an opening which is oversized (as hereinbefore defined), relative to the lateral dimensions of that pin, in at least the plane containing the pins, said at least one pin including a resilient sleeve whose external periphery is of non-circular section, being dimensioned to engage both sides of the opening in a plane normal to said plane containing the pins but to be spaced from both sides of the opening in said plane containing the pins, and the brake being devoid of resilient biassing means for the pin or pins so that said at least one pin is freely movable in that plane between eccentric positions in which it contacts the wall of its opening.

Preferably, the brake is of the type in which both of the friction pads are directly received in the carrier, which straddles the disc for this purpose, so that the guide pins are relieved of all pad drag forces. The invention is still applicable to those brakes in which the guide pins do take drag forces, but it is only then of use in reducing cross-binding dur to initial mismatch, and due to spurious twisting movements of the pins under heavy braking, since of course on these brakes, the pins are designed to cope with cross-binding under braking.

The invention is further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a plan view, partly in section, of a vehicle disc brake incorporating the invention; and Figure 2 is a sectional view of an enlarged scale of a detail of the embodiment of Figure 1 taken at a position corresponding to a section on line II-II of Figure 1.

The disc brake shown in Figure 1 is of the general type described in our prior U.K.

patent specification No. 1506709 to which reference is made for further details. The brake is formed of a carrier member generally designated 10 and a caliper member generally designated 12. The carrier member 10 has a downwardly extending portion (not shown) by which the carrier member is adapted to be fixed to a vehicle frame, and a pair of arms 14 which extend across a rotatable brake disc (not shown). The caliper member 12 has a centrally apertured crown portion 16 which interconnects a front limb 18 and a rear limb 20 which extend downwardly on opposite sides of the disc. The rear limb 20 of the caliper member is formed with a pair of hydraulic cylinders containing respective pistons (not shown) which abut against the backing plate 21 of a directly actuated friction pad 22. The backing plate 23 of a second, indirectly actuated friction pad 24 is engaged by the front limb 18 of the caliper member. The carrier member arms 14 are formed with sliding surfaces 25, 27 for engagement with the sides of the backing plates 21, 23 of the friction pads. The pads are therefore slidably mounted in the carrier member so that drag forces experienced by the friction pads when they clamped against the rotating disc are transmitted directly to the carrier member. Lugs (not shown) extending from the pad backing plates 21, 23 slidably seat on shoulders formed on the carrier member arms 14 to control radially inward and preferably also radially outward pad displacement.

Alternatively, only one of the friction pads, preferably the directly actuated friction pad 22 is mounted in the carrier member, the other pad being secured to the caliper limb 18 by way of its backing plate 23. In the latter case, the carrier member does not require arms 14 extending over the disc periphery provided that the sliding connection to be described hereinafter is accommodated wholly on one side of the disc as shown in Figure 1 of our aforementioned specification No. 1506709.

It will be noted that the pad backing plates 21, 23 are dimensioned such that they have a sliding fit between the opposing surfaces 25, 27 on the lugs 14 whereby a clearance "x" can exist between each side of the backing plates and the associated sliding surface on the lugs, this pad abutment clearance being considerably exaggerated in the drawing.

The caliper member is slidably mounted on the carrier member whereby the introduction of hydraulic fluid under pressure into the cylinders to cause the directly actuated pad 22 to be urged against one side of the disc results in the caliper member sliding relative to the carrier member 10 in a direction to move the caliper limb 20 away from the disc and applying the indirectly actuated pad 24 to the other side of the disc.

The sliding connection between the caliper member and carrier member comprises a pair of metallic pins 26 and 28. In the embodiment of Figure 1, each pin includes a resilient sleeve or sheath 38. Whilst one or both of the pins could be slidable in the caliper member, in the illustrated arrangement both pins 26 and 28 are secured to the caliper member and are slidable in openings 30 and 32 in the carrier member. Each pin is secured to the caliper member by a clamping screw 34 which passes through an opening in the caliper member. Sealing boots 36 extending between the pins and the carrier member protect the sliding surfaces of the pins and carrier member and retain the pins in their openings even when the caliper member is removed from the carrier member for servicing.

In the embodiment illustrated, each of the openings 30 and 32 is oversized (as hereinbefore defined) so that a clearance "y" exists, at least in the circumferented direction of the disc, between the pins and the walls of their respective openings. The pin 28 which is the trailing pin in the direction of rotation of the disc may have a smaller clearance than the other pin, since when the distortion takes place under heavy braking, it is the trailing arm of the arms 14 which distorts.

The caliper follows the movement of the deflected arm, so that the position of the trailing pin in its opening hardly varies. The leading pin is thus the one which moves in its opening due to this distortion. The "trailing" side of the brake is that side from which the rotating disc leaves the brake, in the direction of forward motion. The resilient sleeves 38 serve to protect the metallic parts of the pins and reduce impact loading and noise as the pins move between eccentric positions in sliding contact with the walls of their respective bores.

The term "oversized" as used herein and in the appended claims is to be defined as meaning the circumferential clearance dimension "y" is greater than the dimension "x" The clearance dimension "y" is arranged to be greater than the dimension "x" for the following reason. During heavy braking, the pads 22, 24 are effectively clamped to both the disc and to the caliper member 12 whereby the caliper tries to move with the disc in a circumferential direction. In order to ensure that the drag forces experienced by the brake pads 22, 24 during such braking are transferred directly to the fixed carrier member 10 by engagement of the backing plates 21, 23 with one of the surfaces 25 or 27 (depending upon the direction of rotation of the disc) and not to any appreciable extent via the sliding connection of either of the pins 26, 28 in their respective openings 30, 32, it is essential that the pad backing plates 21, 23 should engage the surface 25 or 27 before either of the pins 26 or 28 can engage the wall of its associated opening 30 or 32. Provided that the clearance "y" is greater than the clearance "x", this condition will in practice be satisfied.

When the brake is of the type in which the pins are intended and designed to take the drag forces of one of the pads, then the clearance "y" is only of course provided at the other of the pads.

It will also be noted that it is only in the circumferential direction (considered relative to the disc) that the clearance between the pins and the walls of their associated openings is important. As shown in Figure 2, this situation is exploited in that the sleeve 38 is not of constant thickness, having a circular sectioned inner periphery but a non-circular sectioned outer periphery. As shown in Figure 2, in directions substantially perpendicular to the plane containing the pins 26, 28, the sleeve 38 is dimensioned to completely occupy the volume between the metallic part of the pin 28 and the opening 32 but in directions substantially parallel to the plane containing the pins 26, 28, the thickness of the sleeve 38 is reduced to leave oppositely positioned regions having a maximum clearance "y" between the periphery of the sleeve 38 and the wall of the opening 32. By virtue of this arrangement, tilting of the caliper relative to the carrier member in at least one plane is prevented whilst a small degree of relative displacement of the axes of the pins and their associated openings is permitted for the purpose explained above.

In a modified brake (not shown), the pin 28 which may or may not include a resilient sleeve, is a close sliding fit in its opening.

WHAT WE CLAIM IS: 1. A vehicle disc brake comprising a carrier member for fixing to a vehicle, a caliper member slidably connected to the carrier member, and an actuator for urging a first friction pad onto one side of a rotatable disc to cause the caliper member to slide relative to the carrier member and apply a second friction pad to the other side of the disc, the sliding connection between the caliper member and carrier member comprising a pair of parallel pins slidable in one of the members and secured to the other of the members, at least one of the pins being received in an opening which is oversized (as hereinbefore defined), relative to the laterial dimensions of that pin, in at least the plane containing the pins, and the brake being devoid of resilient biassing means for the pin or pins so that said at least one pin is freely movable in that plane

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. sliding relative to the carrier member 10 in a direction to move the caliper limb 20 away from the disc and applying the indirectly actuated pad 24 to the other side of the disc. The sliding connection between the caliper member and carrier member comprises a pair of metallic pins 26 and 28. In the embodiment of Figure 1, each pin includes a resilient sleeve or sheath 38. Whilst one or both of the pins could be slidable in the caliper member, in the illustrated arrangement both pins 26 and 28 are secured to the caliper member and are slidable in openings 30 and 32 in the carrier member. Each pin is secured to the caliper member by a clamping screw 34 which passes through an opening in the caliper member. Sealing boots 36 extending between the pins and the carrier member protect the sliding surfaces of the pins and carrier member and retain the pins in their openings even when the caliper member is removed from the carrier member for servicing. In the embodiment illustrated, each of the openings 30 and 32 is oversized (as hereinbefore defined) so that a clearance "y" exists, at least in the circumferented direction of the disc, between the pins and the walls of their respective openings. The pin 28 which is the trailing pin in the direction of rotation of the disc may have a smaller clearance than the other pin, since when the distortion takes place under heavy braking, it is the trailing arm of the arms 14 which distorts. The caliper follows the movement of the deflected arm, so that the position of the trailing pin in its opening hardly varies. The leading pin is thus the one which moves in its opening due to this distortion. The "trailing" side of the brake is that side from which the rotating disc leaves the brake, in the direction of forward motion. The resilient sleeves 38 serve to protect the metallic parts of the pins and reduce impact loading and noise as the pins move between eccentric positions in sliding contact with the walls of their respective bores. The term "oversized" as used herein and in the appended claims is to be defined as meaning the circumferential clearance dimension "y" is greater than the dimension "x" The clearance dimension "y" is arranged to be greater than the dimension "x" for the following reason. During heavy braking, the pads 22, 24 are effectively clamped to both the disc and to the caliper member 12 whereby the caliper tries to move with the disc in a circumferential direction. In order to ensure that the drag forces experienced by the brake pads 22, 24 during such braking are transferred directly to the fixed carrier member 10 by engagement of the backing plates 21, 23 with one of the surfaces 25 or 27 (depending upon the direction of rotation of the disc) and not to any appreciable extent via the sliding connection of either of the pins 26, 28 in their respective openings 30, 32, it is essential that the pad backing plates 21, 23 should engage the surface 25 or 27 before either of the pins 26 or 28 can engage the wall of its associated opening 30 or 32. Provided that the clearance "y" is greater than the clearance "x", this condition will in practice be satisfied. When the brake is of the type in which the pins are intended and designed to take the drag forces of one of the pads, then the clearance "y" is only of course provided at the other of the pads. It will also be noted that it is only in the circumferential direction (considered relative to the disc) that the clearance between the pins and the walls of their associated openings is important. As shown in Figure 2, this situation is exploited in that the sleeve 38 is not of constant thickness, having a circular sectioned inner periphery but a non-circular sectioned outer periphery. As shown in Figure 2, in directions substantially perpendicular to the plane containing the pins 26, 28, the sleeve 38 is dimensioned to completely occupy the volume between the metallic part of the pin 28 and the opening 32 but in directions substantially parallel to the plane containing the pins 26, 28, the thickness of the sleeve 38 is reduced to leave oppositely positioned regions having a maximum clearance "y" between the periphery of the sleeve 38 and the wall of the opening 32. By virtue of this arrangement, tilting of the caliper relative to the carrier member in at least one plane is prevented whilst a small degree of relative displacement of the axes of the pins and their associated openings is permitted for the purpose explained above. In a modified brake (not shown), the pin 28 which may or may not include a resilient sleeve, is a close sliding fit in its opening. WHAT WE CLAIM IS:

1. A vehicle disc brake comprising a carrier member for fixing to a vehicle, a caliper member slidably connected to the carrier member, and an actuator for urging a first friction pad onto one side of a rotatable disc to cause the caliper member to slide relative to the carrier member and apply a second friction pad to the other side of the disc, the sliding connection between the caliper member and carrier member comprising a pair of parallel pins slidable in one of the members and secured to the other of the members, at least one of the pins being received in an opening which is oversized (as hereinbefore defined), relative to the laterial dimensions of that pin, in at least the plane containing the pins, and the brake being devoid of resilient biassing means for the pin or pins so that said at least one pin is freely movable in that plane

between eccentric positions in which it contacts the wall of its opening.

2. A disc brake as claimed in claim 1, in which the opening is oversized (as hereinbefore defined), relative to the lateral dimensions of said at least one pin, in all planes normal to the longitudinal axis of that pin.

3. A disc brake as claimed in claim 2, in which said at least one pin includes a cylindrical resilient sleeve whose external periphery defines said lateral dimensions of that pin.

4. A disc brake as claimed in claim 1, in which said at least one pin includes a resilient sleeve whose external periphery is of non-circular section.

5. A disc brake as claimed in any of claims 1 to 4, in which only the leading one of said pins, considered in the direction of forward rotation of the disc, is received in an opening which is oversized (as hereinbefore defined).

6. A disc brake as claimed in any of claims 1 to 5, in which both of the friction pads are directly received in the carrier member whereby said pins are relieved of all pad drag forces which occur during brake operation.

7. A vehicle disc brake comprising a carrier member for fixing to a vehicle, a caliper member slidably connected to the carrier member, and an actuator for urging a first friction pad onto one side of a rotatable disc to cause the caliper member to slide relative to the carrier member and apply a second friction pad to the other side of the disc, the sliding connection between the caliper member and carrier member comprising a pair of parallel pins slidable in one of the members and secured to the other of the members, at least one of the pins being received in an opening which is oversized (as hereinbefore defined), relative to the lateral dimensions of that pin, in at least the plane containing the pins, said at least one pin including a resilient sleeve whose external periphery is of non-circular section, being dimensioned to engage both sides of the opening in a plane normal to said plane containing the pins but to be spaced from both sides of the opening in said plane containing the pins, and the brake being devoid of resilient biassing means for the pin or pins so that said at least one pin is freely movable in that plane between eccentric positions in which contacts the wall of its opening.

8. A vehicle disc brake constructed substantially as hereinbefore particularly described with reference to and as illustrated in Figure 1 of the accompanying drawings.

9. A vehicle disc brake constructed substantially as hereinbefore particularly described with reference to Figure 1 as modified by Figure 2 of the accompanying drawings.