Patent ID: 6655507
Filing Date: 2003-12-02
Classification: B60T

Abstract:
A parking brake apparatus, comprising:an electric motor; a screw mechanism including a screw-threaded shaft adapted to be rotationally driven by said electric motor, and a nut member meshing with said screw-threaded shaft, said nut member being movable along said screw-threaded shaft by the rotation of said screw-threaded shaft; a transmission member connected to said nut member for transmitting a brake operating force to a wheel brake; and a rotation preventing unit for confining said screw-threaded shaft to a stationary portion of a vehicle body thereby preventing rotation of said screw-threaded shaft so as to hold said brake operating force by fixing a position of said nut member relative to said screw-threaded shaft, wherein the rotation preventing unit is an electromagnetic brake comprising: a core fixed to a stationary portion side of said vehicle body; a coil accommodated in said core to surround said screw-threaded shaft; a rotor fixed to an outer periphery of said screw-threaded shaft; a plate opposing to a back side of said rotor, said plate being movable in a longitudinal direction of said screw-threaded shaft; an armature disposed between said stationary portion side of said vehicle body and a front side of said rotor to be movable in the longitudinal direction of said screw-threaded shaft; a first coil spring disposed between said stationary portion side of said vehicle body and said armature; and a second coil spring disposed between said armature and said plate, a biasing force of said first coil spring being set to be stronger than a biasing force of said second coil spring.