GB1567103A

GB1567103A - Disc brake assembly

Info

Publication number: GB1567103A
Application number: GB83778A
Authority: GB
Original assignee: Aisin Seiki Co Ltd; Toyota Motor Corp
Current assignee: Toyota Motor Corp; Aisin Corp
Priority date: 1977-01-10
Filing date: 1978-01-10
Publication date: 1980-05-08
Also published as: JPS5386970A; DE2800501A1

Description

(54) DISC BRAKE ASSEMBLY (71) We, AISIN SEIKI KABUSHIKI KAISHA, of 2-1, Asahimachi, Kariyashi, Aichiken, Japan, and TOYOTA JIDOSHA KOGYO KABUSHIKI KAISHA of No. 1, Toyotacho, Toyotashi, Aichiken, Japan, both corporations organised and existing under the laws of Japan, 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 invention relates to disc brake assemblies for vehicle wheels e.g. of motor vehicles, and particularly, but not exclusively to hydraulically actuable disc brakes. assemblies in which friction pad assemblies are adapted to be urged by hydraulic fluid acting means into engagement with opposite faces of a rotary disc, with at least one of the pad assemblies being mounted on a torque-taking member secured in use to a non-rotary part of the vehicle wheel.

In this type of brake, the friction linings of the pad assemblies are gradually worn as the use of the vehicle brakes is repeated. The linings need to be replaced before they are worn to such an extent that backing plates to which they are bonded directly to engage the rotary disc.

The invention seeks to provide a disc brake assembly intended to provide an audible warning to the driver when the pads are in need of replacement. The disc brake assembly of the invention comprises a torque-taking member that in use is secured to a non-rotary part of the wheel, a friction pad assembly slidably mounted rn the torque-taking member between opposed reaction faces thereof, with a clearance between one of the friction faces and an associated end bearing face of the friction pad assembly, and a spring member secured to the friction pad assembly for biasing the friction pad assembly against the other of the reaction faces, wherein a portion of the spring member extends through the clearance alongside a friction lining of the friction pad assembly, and projects towards a brake disc of the wheel across part of the thickness of the friction lining, for contacting the brake disc and producing an audible warning when the friction lining is worn.

The invention is hereinafter particularly described, by way of example only, with reference to the drawings of which: Figure 1 is a fragmentary side elevation of a disc brake assembly according to the invention; Figure 2 is a section taken along the line Il-Il in Figure 1; Figure 3 is a side view of the anti-rattle spring and part of the friction pad assembly as viewed along the arrow III in Figure 2; and Figure 4 is a perspective view, on an enlarged scale, of the anti-rattle spring of Figures 2 and 3.

Figure 1 shows only the left-hand side of the disc brake assembly according to the invention, the right-hand side being of similar construction.

The brake assembly comprises a torquetaking member 10 which is secured in use to a non-rotary part of a vehicle (not shown) and which includes a pair of spaced arms (only one is shown at 11) which define a recess therebetween and also has a hydraulic brake-actuating cylinder slidably mounted thereon. Each of the arms presents a reaction face, as shown at 19 in Figures 1 and 2, for one or more friction pad assemblies as described below. The brake assembly is used in conjunction with a friction disc 13 (Figure 2) of the wheel, having opposed friction faces 13a and 13b.

The brake assembly 16 disposed adjacent the friction face 13a and a second friction pad assembly (not shown) disposed adjacent the friction face 13b. Each of the arms 11 has a guide recess 14 having a bearing face 14a on which is free to slide the first friction pad assembly in the axial direction of the disc 13. For such sliding movement, the friction pad assembly 16 is provided with lugs or bearing faces at its opposite ends.

The lugs do not appear in Figure i, since their location is behind a caliper 12 which is also free to slide on the common bearing faces 14a as seen in Figure 1. Two bearing faces 1 2a are formed at the opposite edges of the caliper 12 for slidably engaging the bearing faces 14a, as described below.

The brake assembly is provided at its both arms 11 with conventional rattle-preventing spring members 15 for preventing rattling of the caliper 12.

The pad assembly 16 includes a friction lining 18 bonded to a backing plate 17, the friction lining being slightly smaller than the backing plate to provide a peripheral marginal exposed portion of the backing plate 17. The pad assembly 16 is received within the recess between the arms 11. One end bearing face 17a of the backing plate 17 is spaced from the reaction face 19 to form a clearance therebetween when the pad assembly 16 is spring biased against the other reaction face by an antirattle spring 20 formed from resilient sheet metal. A part of the antirattle spring 20 is disposed within the clearance as shown in Figure 2.

The antirattle spring 20 is shown in greater detail in Figure 4. The spring 20 includes a loop-shaped central portion 22, from one end of which extends a first leg portion 23 for abutting the reaction face 19, and from the other end of which extends a second leg portion 21 for abutting the end bearing face 17a. The looped form.

of the central portion 22 is such that when the spring 20 is unstressed as in Figure 4 an acute angle is formed between the leg portions 21 and 23, but during installation this angle is closed by stressing the central portion 22 so as to bias the friction pad assembly 16 against the opposite reaction face. The second leg portion 21 is formed as a pair of limbs interconnected at their extremities by a connecting portion 25 which extends as a flange normally to the plane of the limbs. The space 26 between the limbs forming the second leg portion 21 is sufficiently wide to receive the leg portion 23 as will be seen in Figure 2. Between the connecting portion 25 and a shoulder 27 defining the junction of the looped central portion 22 and the leg portion, and between the limbs of the leg portion 21, there diagonally protrudes a gripping spur 24. When the brake is assembled, the marginal exposed portion of the backing plate 17 adjacent the end bearing face 17a is gripped between the connecting portion 25 and the gripping spur 24 to prevent accidental displacement of the antirattle spring 20 from the friction pad assembly 16 when the pad assembly is beingmounted within the recess defined by arms 11.

As seen in Figures 2 and 3, the first leg portion 23 projects beyond the second leg portion 21, in a direction towards the disc 13, preferably about 2 to 3 mm length when installed. Some such small projection of the first leg portion 23 is very important to obtain the audible warning of brake wear, as described below. The distance between the frictional face 13a of the disc and the extremity of the first leg portion 23, shown as "l" in Figure 2, is determined by the intended maximum permitted wear of the lining 18 as braking is repeated.

When the brake is assembled, the antirattle spring 20 is first fitted over the end bearing face 17a of the backing plate 17 which it grips as described so that the spring and the pad assembly form a unit that can be handled as one piece. When the resultant assembly is being inserted into the recess between the arms 11, the first leg portion 23 and the second leg portion 21 are urged together by stressing the central portion 22, so that the leg portions are inserted into the clearance defined by the anchoring face 19 and the end bearing face 17a. Having been inserted into the recess, the pad assembly 16 is then permitted to receive the force of the central portion 22. The stress in the central portion 22 urges the leg portions 23 and 21 apart from each other. A biasing force is thus exerted on the pad assembly 16 to resist movement of the pad assembly relative to the torque-taking member 10 when the brake is not applied, thereby preventing generation of annoying noises. The antirattle spring 20, however, permits movement of the pad assembly 16 to close the gap when the vehicle is braked while travelling in the reverse direction. This is desirable, as it provides means for preventing jamming of the friction pad assembly 16 when the associated surfaces of the pad assembly and arms 11 become corroded or dirty. Sensitive and prompt response to the braking fluid pressure is thus ensured.

The central aperture 26 is large enough to accommodate the first leg portion 23, (e.g.

when the clearance is closed as in reverse braking) so that the leg portions and 21 23 do not overlap when the friction pad assembly 16 moves towards the reaction face 19 and transmission of the braking torque is through the leg portions from the end bearing face 17a to the reaction face 19 of the arm 11.

When the friction lining 18 is worn, the projecting end of the first leg portion 23 engages the face 13a of the rotor 13 and produces an irregular sound which is sufficient to alarm the driver that the friction lining is badly worn. The spring 20 thus performs a dual function of anti-rattle spring and warning means, and the audible warning is produced in a very inexpensive, simple and reliable manner.

Claims

WHAT WE CLAIM IS:

1. A disc brake assembly for a vehicle wheel, comprising a torque-taking member that in use is secured to a non-rotary part of the wheel, a friction pad assembly slidably mounted on the torque-taking member between opposed reaction faces thereof, with a clearance between one of the reaction faces and an associated end bearing face of the friction pad assembly, and a spring member secured to the friction pad assembly for biasing the friction pad assembly against the other of the reaction faces, wherein a portion of the spring member extends through the clearance alongside a friction lining of the friction pad assembly, and projects towards a brake disc of the wheel across part of the thickness of the friction lining for contacting the brake disc and producing an audible warning when the friction lining is worn.

2. A disc brake assembly according to claim 1, wherein the spring member is formed from resilient sheet metal and comprises first and second leg portions for insertion in the clearance for abutting, respectively, the one of the reaction faces and the associated end bearing face of the friction pad assembly, resiliently to bias the friction pad assembly against the other of the reaction faces.

3. A disc brake assembly according to claim 2, wherein the spring member comprises a central portion formed as a loop for resiliently biasing apart the leg portions.

4. A disc brake assembly according to claim 2 or claim 3, wherein the first leg portion, which abuts the reaction face of the torque-taking member, is the portion of the spring member which extends through the clearance alongside the friction lining and the second leg portion has associated therewith a flange and a gripping spur which frictionally engage opposite faces of a backing plate of the friction pad assembly to secured the spring member to the friction pad assembly.

5. A disc brake assembly according to claim 4, wherein the second leg portion comprises a central aperture to receive the first leg portion when the clearance is closed as in reverse braking.

6. A disc brake assembly according to any preceding claim, further comprising, a hydraulic brake actuating cylinder slidably mounted on the torque-taking member.

7. A disc brake assembly for braking a vehicle wheel, substantially as particularly described herein with reference to the drawings.