Abstract: An electric actuator includes an electric motor, a nut (a first screw member), and a screw shaft (a second screw member) threadedly inserted through the nut to be able to advance and retreat. Each of threads of the screw shaft includes two flanks and a crest portion connecting the flanks to each other. Grease is used as a lubricant. A groove portion, which is cut out from the crest portion toward a root portion side, is formed on each of the threads of the screw shaft. Further, a taper surface, which flares becoming circumferentially farther away from the groove portion, is formed on at least a part of each of peripheral edges of each groove portion on flank sides. The electric actuator can promote lubrication of a threadedly engaged portion between the first and second screw members, thereby improving motion conversion efficiency and reducing wear on the threadedly engaged portion.

Abstract: The present invention discloses an electric parking brake control device capable of accurately determining operation of an electric actuator. The electric parking brake control device is capable of performing an application process for controlling the electric actuator to move in the direction in which a friction member is pressed against a rotation body that rotates integrally with a wheel and a release process for controlling the electric actuator to move in the direction in which the friction member is moved away from the rotation body. Even upon receiving (time t12) a new operation request for operating the electric actuator during a period (time t1 to t5) from the start of the application process or the release process to the completion of the process, the electric parking brake control device does not change the operation of the electric actuator on the basis of the operation request.

Abstract: Provided is an electric parking brake device which enables a service brake that generates a brake force in accordance with an operation input of a vehicle user and a parking brake that generates a brake force with the function of an electric actuator having operation controlled by a control unit to be obtained. The control unit (C) starts to count in response to an end of detection of the service brake by service brake detection means (66) and stops operation of the control unit (C) after an elapse of a first predetermined time from the start of the count. With this configuration, the load on a battery can be reduced by preventing the control unit from being kept activated for a period of time that is longer than necessary.