Abstract: A piston seal includes an annular base portion, an inner circumferential lip portion protruding from an inner circumferential side of the base portion to come in sliding contact with an outer circumferential surface of the piston, an outer circumferential lip portion protruding from an outer circumferential side of the base portion to come in contact with the circumferential groove of the cylinder main body, and an intermediate protrusion portion protruding from between the inner circumferential lip portion and the outer circumferential lip portion of the base portion further than the outer circumferential lip portion. A connecting portion is formed to extend in an axial direction of the piston seal and is configured to connect the inner circumferential lip portion and the intermediate protrusion portion is formed between the inner circumferential lip portion and the intermediate protrusion portion.

Abstract: An urging spring (15) urges a friction pad toward the exit side of the rotational direction of a disk when a vehicle equipped with the disk brake runs forward. The urging spring is disposed between a lug portion (11A) of the friction pad and a torque receiving surface (5) of a carrier (2). The distal end of the urging spring is configured to abut against the disk to perform wear detection. The urging spring includes a mounting portion (15A), a first extending portion (15B), a boundary region (15E), a bent portion (15C), and a second extending portion (15D). The boundary region is reduced in width to lower stiffness. The bent portion is increased in width and provided with reinforcing portions, thereby enhancing the stiffness. Thus, the natural frequencies of the second extending portion in the rotational direction K and the vertical direction J come close to each other.

Abstract: A circumferential wall of a circumferential groove near a bottom section of a cylinder main body has an outer wall section extending from a bottom section of the circumferential groove in a radial direction of the cylinder main body, a stepped surface section extending from the outer wall section in a bottom direction of the cylinder main body, and an inner wall section having a flat surface section parallel to the radial direction of the cylinder main body and formed further inside in the radial direction of the cylinder main body than the stepped surface section. The inner wall section is formed at a position at which the center lip section first abuts the inner wall section prior to the outer wall section when the seal member moves toward the bottom section of the cylinder main body.

Abstract: An urging spring (15) urges a friction pad toward the exit side of the rotational direction of a disk when a vehicle equipped with the disk brake runs forward. The urging spring is disposed between a lug portion (11A) of the friction pad and a torque receiving surface (5) of a carrier (2). The distal end of the urging spring is configured to abut against the disk to perform wear detection. The urging spring includes a mounting portion (15A), a first extending portion (15B), a boundary region (15E), a bent portion (15C), and a second extending portion (15D). The boundary region is reduced in width to lower stiffness. The bent portion is increased in width and provided with reinforcing portions, thereby enhancing the stiffness. Thus, the natural frequencies of the second extending portion in the rotational direction K and the vertical direction J come close to each other.

Abstract: A piston seal includes an annular base portion, an inner circumferential lip portion protruding from an inner circumferential side of the base portion to come in sliding contact with an outer circumferential surface of the piston, an outer circumferential lip portion protruding from an outer circumferential side of the base portion to come in contact with the circumferential groove of the cylinder main body, and an intermediate protrusion portion protruding from between the inner circumferential lip portion and the outer circumferential lip portion of the base portion further than the outer circumferential lip portion. A connecting portion is formed to extend in an axial direction of the piston seal and is configured to connect the inner circumferential lip portion and the intermediate protrusion portion is formed between the inner circumferential lip portion and the intermediate protrusion portion.

Abstract: A pressing part is provided at a disk-circumferentially central portion of a base plate member of a shim plate. The pressing part presses a friction pad at the center in the disk circumferential direction of the friction pad when a piston starts to press the friction pad. The pressing part is formed by slitting and raising the disk-circumferentially central portion of the shim plate along the disk radial direction. When the pressing force of the piston is in a low pressure range, the pressing force is transmitted to the friction pad through the pressing part. After the pressing force of the piston has exceeded the low pressure range, the pressing force is transmitted to the friction pad through the whole region in the disk circumferential direction of the piston.

Abstract: A circumferential wall of a circumferential groove near a bottom section of a cylinder main body has an outer wall section extending from a bottom section of the circumferential groove in a radial direction of the cylinder main body, a stepped surface section extending from the outer wall section in a bottom direction of the cylinder main body, and an inner wall section having a flat surface section parallel to the radial direction of the cylinder main body and formed further inside in the radial direction of the cylinder main body than the stepped surface section. The inner wall section is formed at a position at which the center lip section first abuts the inner wall section prior to the outer wall section when the seal member moves toward the bottom section of the cylinder main body.

Abstract: A pressing part is provided at a disk-circumferentially central portion of a base plate member of a shim plate. The pressing part presses a friction pad at the center in the disk circumferential direction of the friction pad when a piston starts to press the friction pad. The pressing part is formed by slitting and raising the disk-circumferentially central portion of the shim plate along the disk radial direction. When the pressing force of the piston is in a low pressure range, the pressing force is transmitted to the friction pad through the pressing part. After the pressing force of the piston has exceeded the low pressure range, the pressing force is transmitted to the friction pad through the whole region in the disk circumferential direction of the piston.