The present invention relates to disc brakes and, more particularly, to a disc brake capable of suppressing generation of brake noise,
A known disc brake uses a caliper which has a cylinder portion, a disc-pass portion extending from the cylinder portion across a disc, and a claw portion extending radially inward of the disc from the outer end of the disc-pass portion, A piston is accommodated in the cylinder portion of the caliper, The piston causes one pad to press against one side of the disc, and by the counterforce that is produced at this time, the other pad is pressed against the other side of the disc through the claw portion, thereby obtaining braking force,
The piston used in such a known disc brake is a cylindrical piston, one end of which is open and the other end of which is closed, The wall of the piston has a minimum thickness within the range in which the required mechanical strength can be obtained from the viewpoint of minimizing the weight, Accordingly, the open end surface of the piston, which contacts one pad, has the shape of a ring with a narrow width.
Further, shims, which are each formed by coating rubber on the obverse and reverse surfaces of an iron plate, have heretofore been used to prevent the generation of brake noise. That is, for the outer pad, a shim is interposed between the pad and the claw portion Of the caliper, and for the inner pad, another shim is interposed between the pad and the piston, thereby buffering vibration which creates noise. It should be noted that, for the inner pad, since the open end surface of the piston, which has the shape of a ring with a narrow width, is likely to damage the rubber coating of the shim, a thin stainless steel plate is additionally interposed between the shim and the piston to protect the rubber coating of the shim.
The conventional disc brake, which is provided with shims and a thin plate to buffer vibration as described above, suffers from the problem that the number of constituent elements disadvantageously increases.
In addition, it has been revealed that, since the natural frequency of the above-described thin-walled piston is about 7.2 kHz, which falls within the audible frequency range, if the frequency of vibration occurring between the disc and the pads coincides with the natural frequency, brake noise is generated.
In view of the above-described circumstances, it is an object of the present invention to provide a disc brake capable of preventing the generation of brake noise which would otherwise occur when the frequency of vibration occurring between the disc and the pads coincides with the natural frequency for the piston, without the need of providing a shim and a thin plate.