Patent ID: 8616346

Claim:
An electric disc brake comprising: frictional pads to press a disc; a first carrier supporting the frictional pads; a caliper housing supported to the carrier such that the caliper housing is movable back and forth to press the frictional pads; and a pressing unit pressing the frictional pads, wherein the pressing unit comprises: a piston installed in the caliper housing such that the piston is movable back and forth to press one of the frictional pads; a spindle unit including a nut spindle member allowing the piston to move back and forth and a spindle member screwed with the nut spindle member; and a reduction unit coaxially coupled with the spindle unit, and a motor rotating the reduction unit forward and backward, and wherein the reduction unit comprises: a sun gear coupled with a shaft of the motor; a planet gear engaged with the sun gear; a second carrier coupled with the planet gear to rotate the spindle member; and an internal gear engaged with the planet gear, wherein the internal gear and planet gear are arranged such that in a first position the internal gear and planet gear are engaged to amplify a rotational force of the motor and in a second position the internal gear and planet gear are engaged to transfer the rotational force of the motor to the spindle member without a reduction gear ratio, and wherein the internal gear and planet gear shift from the second position to the first position after the spindle unit presses the piston.