Patent ID: 7881849

Claim:
An electric parking brake system, comprising: a drum brake that includes: a drum which rotates together with a wheel of a vehicle and of which an inner peripheral face is used as a friction face; a shoe which is fitted to a backing plate that is a non-rotating body so as to be movable relative to the backing plate, and which has a friction member on an outer peripheral face; and a pushing mechanism that pushes the shoe against the friction face to suppress a rotation of the drum; an electric motor; a motion conversion mechanism that converts a rotation of a rotating shaft of the electric motor into a linear motion of an output member of the motion conversion mechanism; a cable that is connected at one end to the output member of the motion conversion mechanism, and that is connected at the other end to the pushing mechanism; a maintaining mechanism that maintains a friction member pushing force that is a force with which the friction member is pushed against the friction face in the drum brake, when electric current is not supplied to the electric motor; and a tension control unit that controls a tension of the cable by controlling the electric motor such that the friction member pushing force in the drum brake is controlled, wherein the tension control unit includes a tension control portion that controls the tension of the cable to a slack-based target tension that is a sum of at least a moving force-based target tension, which is a target value determined based on a moving force applied to the vehicle, and a slack compensation amount, which is used to compensate for a decrease in the friction member pushing force due to a slack in the cable, the slack being caused in accordance with an amount of change in a torque applied to the wheel when the drum brake is on; and a slack compensation amount determination portion that includes at least one of a device that sets the slack compensation amount to a larger value when the vehicle is at a standstill on a downhill slope than when the vehicle is at a standstill on an uphill slope, and a device that sets the slack compensation amount to a larger value when an absolute value of an inclination angle of the road is large than when an absolute value of an inclination angle of the road is small.