1. Field of the Invention
The present invention relates to a disk brake apparatus comprising a piston for hydraulically compressing a friction pad, an adjuster for automatically adjusting a gap between the friction pad and a disk rotor, and a parking brake for compressing the piston through the adjuster by a ball-ramp type thrust conversion mechanism.
2. Description of the Background Art
As a disk brake apparatus for a four-wheeled vehicle, there has been provided a disk brake apparatus with a parking brake. The disk brake apparatus with a parking brake comprises a hydraulic actuating mechanism operated through a brake pedal, and a mechanical actuating mechanism pulled and operated through a hand lever or a foot pedal. In general, in this disk brake apparatus with the parking brake, a piston constituting the hydraulic actuating mechanism is positioned at a front opening side of a cylinder bore in a caliper body, an adjuster having an adjusting nut and an adjusting bolt is positioned at the rear (bottom) side of this piston, and a thrust conversion mechanism constituting the mechanical actuating mechanism is positioned at the bottom side of the cylinder.
As the thrust conversion mechanism, a ball-ramp type has been well known in the related art. This ball-ramp type thrust conversion mechanism is arranged in a following manner. A fixed-side cam plate and a driving side cam plate, each of which is formed with a ramp recess for receiving a cam bearing, are positioned to be faced one another. As the driving-side cam plate is rotated by operating a parking brake, thrust for moving the piston toward a disk rotor is produced by a cam action of the ramp recess and the cam bearing. Then, the piston is compressively moved toward the disk rotor through an adjuster by this thrust, and a friction pad is compressed against the disk rotor, whereby a braking force is obtained. In addition, the fixed-side cam plate, the driving-side cam plate, the thrust transfer plate, and a cam spring for biasing the thrust transfer plate toward the driving-side cam plate are received in a substantially cylindrical housing, thereby forming a unit so as to enhance the assemblability (for example, Japanese Patent Examined Publication JP-B-2739879).
In the above-mentioned ball-ramp type thrust conversion mechanism, it was required to restrain a rotation in a circumferential direction of the cylinder as well as a movement a the cylinder axis of the housing, because the fixed-side cam plate, the driving-side cam plate, the thrust transfer plate and the cam spring are accommodated in the substantially cylindrical housing, and they form a unit in total. For this reason, the fixed-side cam plate is engaged with the bottom part of the cylinder bore by projection-recession engagement or through a pin-engagement, thereby being restrained from rotating. In addition, the housing has a mounting piece, which is provided on and projected from the circumferential wall thereof, so that the housing is fitted in the cylinder bore by fastening the mounting piece to a stop ring fitted in the cylinder bore. As a result, a lot of time is required for mounting and machining the fixed-side cam plate as well as for mounting the housing, and the number of components is increased.
USPTO Backgrounds
USPTO Backgrounds