Patent ID: 7458649

Claim:
An electric parking brake for vehicles having an operating load measuring device, comprising: an actuating device, comprising a motor provided in a housing having a predetermined shape and reversibly rotating in response to a control signal, a pair of gear units engaging with each other through gears formed on circumferential outer surfaces thereof, and rotated through engagement with an output shaft of the motor, and a screw rod coupled to the gear units by a screw coupling so that the screw rod is linearly moved by rotation of the gear unit, thus providing force to lock and unlock the parking brake; an equalizer coupled at a first end thereof to the actuating device and coupled at a second end thereof to a parking cable to pull or loosen the parking cable, which operates a braking device of a wheel, in response to operation of the actuating device; an operating load measuring unit changing an intensity of current (voltage) depending on an intensity of tensioning force of the actuating device, which pulls the equalizer; and an ECU determining an intensity of the operating load, generated by operating the actuating device, using a signal transmitted from the operating load measuring unit, the ECU controlling the actuating device through a feedback control methods wherein the operating load measuring unit comprises: a casing having a space therein such that a cable connection end of the screw rod is inserted into and fastened to a first end of the casing and an equalizer connection shaft extends outside a second end of the casing; a movable compressing member fastened to the equalizer connection shaft in the casing at a position spaced apart from an inner surface of the casing by a predetermined distance; and a piezoelectric sensor provided between the inner surface of the casing and the movable compressing member, and wherein the movable compressing member comprises: a connection shaft having a predetermined diameter and fastened to the equalizer connection shaft while maintaining a position spaced apart from the inner surface of the casing by a predetermined distance; and a compressing flange having a diameter larger than the diameter of the connection shaft and provided on an end of the connection shaft.