Patent ID: 8292050

Claim:
An electronic mechanical drum brake comprising a drum rotated together with a wheel, a pair of brake shoes respectively including rims provided with linings, which rub against the inner circumferential surface of the drum and generate braking power, attached thereto and webs provided on the inner circumferential surfaces of the rims to reinforce rigidity of the rims, and an actuator provided between the webs of the pair of brake shoes, wherein: the actuator includes a screw shaft provided with a driven gear formed integrally therewith and a left-handed thread at one side thereof and a right-handed thread at the other side thereof, a driving motor to rotate the screw shaft in a regular direction and its reverse direction, a booster unit to increase rotary force of the driving motor and then to transmit the increased rotary force to the driven gear, and nuts screw-connected to both ends of the screw shaft and fixed to the webs; the nuts rectilinearly move along the screw shaft in opposite directions according to rotation of the driving motor, and thus cause the webs connected with the nuts to apply pressure to the pair of brake shoes or release the pressure from the pair of brake shoes so as to perform braking; and the booster unit is a planetary gear device to increase the rotary force of the driving motor and then to transmit the increased rotary force to the driven gear.