Brakes – Wheel – Axially movable brake element or housing therefor
Reexamination Certificate
1998-10-08
2001-02-20
Oberleitner, Robert J. (Department: 3613)
Brakes
Wheel
Axially movable brake element or housing therefor
C188S073310, C188S073370
Reexamination Certificate
active
06189659
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a disk brake suitably used to apply braking force to a vehicle, for example.
A generally known disk brake includes a caliper having a bridge portion extending over the outer periphery of a disk. A cylinder bore is formed at one side of the bridge portion. An outer leg portion is formed at the other side of the bridge portion. The outer leg portion has at least a pair of claw portions. The disk brake further includes inner and outer friction pads extending in the circumferential direction of the disk at respective positions on both sides of the disk. The friction pads are adapted to be pressed against both sides of the disk by the caliper.
In this type of disk brake, when the brake is activated, a piston provided in the cylinder bore of the caliper is caused to slide toward the disk by a fluid pressure supplied externally so as to press the friction pads against both sides of the disk in cooperation with the claw portions of the outer leg portion, thereby applying braking force to the disk.
When the vehicle is braked by the disk brake, braking torque from the disk that is transmitted through the friction pads undesirably acts as a bending moment on the caliper. Accordingly, the inner friction pad has such a tendency that the surface pressure applied to the disk is relatively high at the entrance side in the rotational direction of the disk and relatively low at the exit side. Consequently, the inner friction pad is likely to wear non-uniformly at the entrance side.
Therefore, according to the conventional technique, the cylinder bore is decentered (i.e., the center axis is shifted) toward the exit side in the rotational direction of the disk with respect to the friction pads. Consequently, the surface pressure of the inner friction pad applied to the disk is reduced at the entrance side, and thus non-uniform wear of the friction pad is suppressed.
Incidentally, the disk brake according to the above-described conventional technique is arranged such that, among the cylinder bore, the bridge portion and the outer leg portion that constitute the caliper, the cylinder bore is decentered toward the exit side in the rotational direction of the disk with respect to the longitudinal center position of the friction pads.
However, the claw portions of the outer leg portion are formed such that the space therebetween is defined as a recess for machining the cylinder bore. Therefore, the recess is usually decentered toward the exit side in the rotational direction of the disk with respect to the friction pads in accordance with the amount that the cylinder bore has been decentered (i.e., decentration of the cylinder bore). As a result of decentering the recess of the outer leg portion toward the exit side in the rotational direction of the disk, the entrance-side claw portion as viewed in the rotational direction of the disk has a large wall thickness in the circumferential direction of the disk in comparison to the exit-side claw portion.
Consequently, when the brake is activated, there is a difference in rigidity between the claw portions. The rigidity difference may cause the claw portions pressing the outer friction pad in particular to differ in the surface pressure from each other. In such a case, the friction pad is worn non-uniformly, and it becomes likely that brake noise, judder and so forth will occur owing to the non-uniform wear of the friction pad.
SUMMARY OF THE INVENTION
In view of the above-described problems associated with the conventional technique, an object of the present invention is to provide a disk brake designed so that even when the cylinder bore is decentered toward the exit side in the rotational direction of the disk with respect to the friction pads, the outer leg portion, which is integral with the bridge portion, has substantially the same rigidity at the entrance and exit sides in the rotational direction of the disk. Thus, it is possible to suppress non-uniform wear of the friction pad when the brakes are applied and to effectively prevent the generation of brake noise or the like.
To solve the above-described problem, the present invention is applied to a disk brake including a caliper having a bridge portion extending over the outer periphery of a disk. A cylinder bore is formed at one side of the bridge portion. An outer leg portion is formed at the other side of the bridge portion. The outer leg portion has at least a pair of claw portions. The disk brake further includes inner and outer friction pads extending in the circumferential direction of the disk at respective positions on both sides of the disk. The friction pads are adapted to be pressed against both sides of the disk by the caliper. The cylinder bore is decentered toward the exit side in the rotational direction of the disk with respect to the friction pads.
According to the present invention, the outer leg portion of the caliper is decentered toward the exit side in the rotational direction of the disk with respect to the friction pads. An entrance-side and exit-side claw portion of the outer leg portion (as viewed in the rotational direction of the disk) have approximately the same wall thickness in the circumferential direction of the disk.
By virtue of the above-described arrangement, each claw portion can be decentered toward the exit side in the rotational direction of the disk with respect to the friction pads by an amount corresponding to the amount of decentration of the cylinder bore. Thus, when the brake is activated, the outer friction pad can be pressed by the claw portions at positions corresponding to the cylinder bore. Furthermore, because the wall thicknesses of the claw portions in the circumferential direction of the disk are approximately equal to each other, the rigidities of the claw portions can be made substantially equal to each other, and the surface pressures of the claw portions pressing the outer friction pad can be made equal to each other.
According to one embodiment of the present invention, the bridge portion of the caliper is decentered toward the exit side in the rotational direction of the disk with respect to the friction pads.
Consequently, the bridge portion can be decentered toward the exit side in the rotational direction of the disk by an amount corresponding to the amount of decentration of the cylinder bore. Accordingly, when the brake is activated, the rigidities of the bridge portion at the entrance and exit sides in the rotational direction of the disk can be made substantially equal to each other.
According to another embodiment of the present invention, at least one of the friction pads has a first and second shim plate provided between the caliper and the back of the friction pad. The first shim plate is placed in contact with the back of the friction pad in such a manner that displacement of the first shim plate relative to the friction pad is limited. The second shim plate is placed in contact with the caliper at one side thereof and in contact with the first shim plate at the other side thereof. The contact surface of the second shim plate that is in contact with the first shim plate has a smaller coefficient of friction than that of the contact surface of the second shim plate that is in contact with the caliper so that the second shim plate is slidable relative to the first shim plate in the circumferential direction of the disk.
Consequently, the second shim plate is more readily slidable relative to the first shim plate than to the caliper. Therefore, when the first shim plate is displaced in the circumferential direction of the disk, together with the friction pad as one unit, during a braking operation, the first shim plate slides relative to the second shim plate in a state where the second shim plate maintains a predetermined contact position with respect to the caliper. The mutual sliding motion of the two shim plates makes it possible to reduce rotational force transmitted from the disk to the caliper.
REFERENCES:
patent: 4341289 (1982-07-01), Smith
patent: 4533025
Doi Kazuhiro
Suzuki Shinji
Tamasho Tadashi
Oberleitner Robert J.
Tokico Ltd.
Wenderoth , Lind & Ponack, L.L.P.
Williams Thomas A.
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