Patent attributes
An electric disk brake is capable of determining an abnormality of a parking brake mechanism while the parking brake mechanism is in operation. A brake force is generated in the following manner. A rotation of an electric motor is slowed down by a differential speed reducing mechanism, and is converted into a linear motion by a ball ramp mechanism so as to advance a piston, which then presses a brake pad against a disk rotor to generate a brake force. A parking brake mechanism can lock a rotation of a rotor of the electric motor and maintain a braked state by rotating an engagement pawl through a plunger of a solenoid and causing the engagement pawl to be engaged with a ratchet wheel coupled to the rotor of the electric motor. A play is provided at a coupling portion of the engagement pawl and the plunger. The play enables the plunger to move within the range of the play while the engagement pawl is engaged with the ratchet wheel, thereby enabling the determination of whether the parking brake mechanism operates normally or abnormally based on whether the plunger moves or not upon application of an electric current to the solenoid while the parking brake mechanism is in an actuated state.
