Disk brake

A disk brake comprising:

• a caliper body including a cylinder capable of containing a piston such that the piston is movable in the cylinder, the piston adapted to press at least one of a pair of pads against a disk, the pair of pads disposed on the respective sides of the disk;
• and
• a parking brake mechanism operable to maintain, at a parking brake applying position, the piston advanced based on a rotation of an electric motor disposed at the caliper body,
• the parking brake mechanism comprising a planetary gear speed reducing mechanism for increasing a rotational force from the electric motor, a rotation/linear motion converting mechanism for converting a rotation of the planetary gear speed reducing mechanism into a linear motion to advance the piston, and a rotation preventing mechanism for preventing a rotation of the planetary gear speed reducing mechanism in a direction causing the piston to return,
• the planetary gear speed reducing mechanism comprising an input gear adapted to rotate in response to an input from the electric motor, a planetary gear adapted to revolve around the input gear according to the rotation of the input gear by being meshed with the input gear, an output member adapted to rotate by the revolution of the planetary gear, and a guide member adapted to allow the planetary gear to revolve around the input gear by reducing the rotation of the planetary gear around its own axis by being meshed with the planetary gear, and rotate by a rotational force from the planetary gear,
• one member of the output member and the guide member adapted to transmit a rotation to the rotation linear motion converting mechanism, the other member of the output member and the guide member adapted to rotate by a predetermined range to act on the rotation preventing mechanism,
• the rotation preventing mechanism comprising an engagement portion formed at the one member, and a lever member supported by the caliper body and adapted to be engaged with and disengaged from the engagement portion by a rotational force from the other member.

A disk brake comprising:

• a parking brake mechanism disposed at a caliper body including a piston adapted to press a pad against a disk, the parking brake mechanism operable to maintain, at a parking brake applying position, a piston advanced based on a rotation of an electric motor;
• a parking brake instruction unit for issuing an instruction to maintain the piston at the parking brake applying position by the parking brake mechanism or an instruction to release maintenance of the piston at the parking brake applying position;
• and
• a controller for driving the electric motor based on a maintaining signal or a releasing signal from the parking brake instruction unit,
• the parking brake mechanism comprising a speed reducing mechanism for increasing a rotational force from the electric motor, a rotation/linear motion converting mechanism for converting a rotation of the speed reducing mechanism into a linear motion, and a rotation preventing mechanism for preventing a rotation of the speed reducing mechanism in a direction causing the piston to return,
• the speed reducing mechanism comprising an input member adapted to rotate in response to an input from the motor, and a pair of output members adapted to rotate in opposing directions so as to increase a rotational input from the input member to provide a rotational output, the speed reducing mechanism constituted by an input-output coaxial type speed reducer in which the pair of output members and the input member are coaxially disposed;
• wherein one output member of the pair of output members transmits a rotation to the rotation/linear motion converting mechanism;
• the rotation preventing mechanism prevents a rotation of the one output member in the direction causing the piston to return;
• the other output member of the pair of output members rotates by a predetermined range to act on the rotation preventing mechanism;
• when the motor causes the input member to rotate so that the piston moves in a return direction, a rotation of the other output member according to the rotation of the input member releases rotation prevention of the rotation preventing mechanism to the one output member;
• and
• the controller starts to drive the electric motor based on the maintaining signal from the parking brake instruction unit, and stops the electric motor after an electric current value causing the piston to be situated at the parking brake applying position by the electric motor is obtained, whereby the rotation preventing mechanism prevents a rotation of the one output member.