Disk brake apparatus

A disk brake comprising:

• a caliper main body including a cylinder in which a piston is movably disposed, the piston being configured to press one of a pair of pads against a disk rotor, the pair of pads being disposed on opposite sides of the disk rotor;
• an electric motor disposed at the caliper main body and arranged in alignment with the cylinder in a circumferential direction of the disk rotor;
• a speed reduction mechanism capable of transmitting a rotational force from the electric motor while increasing the rotational force by a plurality of rotational members;
• and
• a piston thrust mechanism disposed coaxially with the cylinder and configured to move forward the piston when the rotational force is transmitted from the speed reduction mechanism, wherein
• the plurality of rotational members includes a first rotational member,
• the first rotational member is disposed in such a manner that the rotational force is transmitted from the electric motor to the first rotational member and comprises a stepped reduction gear, and
• a central axis of the first rotational member is disposed at a position farther away from the cylinder than a rotational axis of the motor.

A disk brake comprising:

• a bracket including a fixation portion fixed to a non-rotatable portion of a vehicle, the bracket being configured to slidably support a pair of pads disposed on opposite sides of a disk rotor;
• a piston configured to press one of the pair of pads against the disk rotor;
• a caliper main body including a cylinder in which the piston is slidably disposed, the caliper main body being slidably disposed at the bracket via a slide pin;
• an electric motor disposed at the caliper main body, and arranged in alignment with the cylinder in a circumferential direction of the disk rotor;
• a speed reduction mechanism capable of transmitting a rotational force from the electric motor while increasing the rotational force by a plurality of rotational members;
• and
• a piston thrust mechanism configured to move forward the piston when the rotational force is transmitted from the speed reduction mechanism, wherein
• the plurality of rotational members includes a first rotational member and a second rotational member,
• the first rotational member is disposed in such a manner that the rotational force is transmitted from the electric motor to the first rotational member and includes a large-diameter rotational portion connected to the electric motor, and a small-diameter rotational portion formed coaxially with the large-diameter rotational portion and connected to a transmission member configured to transmit the rotational force to the second rotational member, and
• the first rotational member is disposed between the fixation portion and the slide pin in a radial direction of the disk rotor.