Abstract: An actuator for an electric parking brake system includes a motor, an output member, and a speed reduction device. The speed reduction device includes a transmission mechanism and a self-locking mechanism. The self-locking mechanism includes a fixed member, first and second rotating bodies, and a spring. The second rotating body transmits torque to the output member via a planetary gear mechanism. The spring prevents the brake from driving the motor.

Abstract: An actuator of an electric parking brake system includes a motor, an output member, and a transmission device. The transmission device includes a housing, a self-locking unit and a transmission unit. The self-locking unit includes a fixed sleeve, and a driving member, a driven member and a lock holder that are rotatable with respect to the sleeve. The lock holder supports lock elements arranged to prevent the driven member from turning unless it is driven by the driving member. A planetary gear unit may be provided as part of the transmission device.

Abstract: A self-locking mechanism has a driving member, a driven member, a stationary member, a lock holder and a number of lock elements. The lock holder encircles the driving member and the driven member. The lock holder has a support base and ribs extending from the support base. A lock element is coupled to the axial end portion of each rib. The lock elements are radially positioned between a radially outer surface of the driven member and the inner wall of the stationary member. The distance between the radially outer surface and the inner wall gradually decreases from a center to opposite circumferential sides. The maximum distance between the radially outer surface and the inner wall is greater than the diameter of the lock element, and the minimum distance is less than the diameter of the lock element.

Abstract: An actuator for an electric parking brake system includes a motor, an output member, and a speed reduction device. The speed reduction device includes a transmission mechanism and a self-locking mechanism. The self-locking mechanism includes a fixed member, first and second rotating bodies, and a spring. The second rotating body transmits torque to the output member via a planetary gear mechanism. The spring prevents the brake from driving the motor.

Abstract: An actuator of an electric parking brake system includes a motor, an output member, and a transmission device. The transmission device includes a housing, a self-locking unit and a transmission unit. The self-locking unit includes a fixed sleeve, and a driving member, a driven member and a lock holder that are rotatable with respect to the sleeve. The lock holder supports lock elements arranged to prevent the driven member from turning unless it is driven by the driving member. A planetary gear unit may be provided as part of the transmission device.

Abstract: A self-locking mechanism has a driving member, a driven member, a stationary member, a lock holder and a number of lock elements. The lock holder encircles the driving member and the driven member. The lock holder has a support base and ribs extending from the support base. A lock element is coupled to the axial end portion of each rib. The lock elements are radially positioned between a radially outer surface of the driven member and the inner wall of the stationary member. The distance between the radially outer surface and the inner wall gradually decreases from a center to opposite circumferential sides. The maximum distance between the radially outer surface and the inner wall is greater than the diameter of the lock element, and the minimum distance is less than the diameter of the lock element.