Disk brake

Details Disk brake Disk brake

1999-07-20

2001-07-10

Oberleitner, Robert J. (Department: 3613)

Brakes

Wheel

Axially movable brake element or housing therefor

C188S072300, C188S073350, C188S25000B

Reexamination Certificate

active

06257379

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to an open-topped disk brake having means for retracting the pads together with the piston to prevent the pads from dragging the disk when the fluid pressure is released.
An open-topped disk brake has a caliper having a window across which pad pins extend. The pad pins are inserted loosely through pin holes formed in back plates of the friction pads to axially slidably hang the pads. Since tangential torque is borne by the caliper, no torque is applied to the pad pins. By removing the pad pins, the friction pads can be pulled out through the window without the need to dismount the caliper from the vehicle knuckle. Worn pads can thus be replaced easily.
Ordinary disk brakes have pistons slidably received in fluid pressure cylinders formed in the caliper. To brake the disk, the pads are pressed against the disk. In a disk brake with opposed pistons, fluid pressure is applied to the opposed pistons to press both pads against the disk with the respective pistons. In a floating type disk brake, fluid pressure is applied to a piston or pistons on one side to press one of the pads with the pistons and press the other pad with a known reaction mechanism against the disk. When the pressure is released, the pistons are forcibly retracted by piston seals having retractor function as well as sealing function.
When the pressure is released, if only the pistons retract with the pads kept in frictional contact with the disk, the pads will apply dragging force to the disk, causing brake squeaks, uneven wear of the pads and the disk or judder resulting from change in the thickness of the disk. Dragging also incurs waste of energy and abnormal wear of the pads. Conventional disk brakes have therefore means for forcibly retracting the pads together with the pistons when the brake pressure is released, to reliably separate the pads from the disk.
FIG. 9
shows one such means which is disclosed in Japanese patent publication 9-53668 filed by the applicant of this invention. In this arrangement, a thin plate or shim
111
is disposed between the friction pad and the pistons on each side. The friction pads
106
hang from pad pins extending across the window of the caliper. Each shim
111
has first claws
114
resiliently gripping the back plate
106
a
of each pad
106
by engaging its inner side, and third claws
112
resiliently engaged in grooves formed in the pistons near their openings. In order to prevent the shims
111
and back plates
106
a
from moving radially outwardly of the disk, each shim
111
is secured to the back plate
106
a
by clips
116
mounted on the pad pins.
FIG. 10
shows a different conventional arrangement in which the clips
116
are not used. In this arrangement, each shim
111
has second claws
113
resiliently gripping the portions of the back plates
106
a
extending beyond the torque bearing portions of the friction pad
106
so that the friction pad
106
can slide radially of the disk.
In order that the pads can retract together with the pistons, no unnecessary play is permissible in the axial direction of the pistons, while the pads have to be mounted so that they can be slid out through the window when the pad pins are removed. To meet both these requirements, clips
116
are used in the first-mentioned prior art. But this arrangement is economically undesirable because the clips add to the number of brake parts. In the latter conventional arrangement, in which the second claws
113
grip the portions of the back plates
106
a
extending beyond the torque bearing portions of the friction pad
106
, the claws
113
will collide against the torque bearing portions of the caliper every time the brake is applied. The claws will thus be quickly worn and/or deformed to such an extent as to lose their function of holding the back plates
106
a.
The shims disposed between the friction pads and the pistons also help suppress disk brake squeaks. To suppress brake squeaks, it is important not to conduct the movement of the pads during braking directly to the pistons. But in the above prior art, the first and second claws and the clips join the shims directly to the pads in such a manner that the pads and shims can scarcely move in a direction parallel to the sliding surfaces of the pads relative to each other. In such an arrangement, the shims can scarcely suppress brake squeaks.
SUMMARY OF THE INVENTION
The disk brake according to the present invention has first and second shims. Each first shim has first claws gripping the friction pad to eliminate any unnecessary play in the axial direction of the pistons, and second claws coupling the first and second shims together and mounted so as not to interfere with the torque bearing portions. Each second shim has third claws engaging the pistons. The shims and their claws are arranged such that the friction pads and the pistons can move relative to each other in the direction parallel to the sliding surfaces of the pads.
With this arrangement, it is possible to eliminate any unnecessary play in the axial direction of the piston and thus to retract the friction pads together with the pads. The second claws have an outer width greater than the torque bearing width of the friction pads, so that the second claws will never collide against the torque bearing portions of the caliper when the brake is applied. Thus, they maintain their function of resiliently holding the first or second shim.
In order to minimize conduction of micro-vibrations of the pads during braking to the pistons, the first shims are preferably made of a thin rolled steel plate with a resilient material coated on one or both sides thereof.
Each second shim has a single or a plurality of second claws corresponding to the number of pistons on each side. If each second shim has a single second claw, the single claw is preferably formed by cutting the second shim and raising the thus cut portion. If each second shim has a plurality of second claws, they are preferably separate members fixed to the shim by e.g. caulking or welding.
Other features and objects of the present invention will become apparent from the following description made with reference to the accompanying drawings, in which:


REFERENCES:
patent: 4155430 (1979-05-01), Kawamura
patent: 4241812 (1980-12-01), Burgdorf et al.
patent: 4809825 (1989-03-01), Oltmanns, Jr. et al.
patent: 5289903 (1994-03-01), Nagai et al.
patent: 5320200 (1994-06-01), Hashimoto
patent: 5706917 (1998-01-01), Matsuzaki
patent: 6116384 (2000-09-01), Matsumoto et al.
patent: 4020077 (1992-01-01), None
patent: 0138081 (1985-04-01), None
patent: 0747608 (1996-12-01), None
patent: 9-53668 (1997-02-01), None

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