Patent ID: 7392959

Claim:
A seat belt retractor for winding a seat belt, comprising: a spool for winding the seat belt, a motor connected to the spool for generating driving torque to rotate the spool, a driving torque transmission mechanism disposed between the motor and the spool and formed of at least one gear for transmitting the driving torque of the motor to the spool, and a torque limiter mechanism disposed in the driving torque transmission mechanism for preventing an excessive load greater than a predetermined level from being transmitted from the spool to the motor, wherein said torque limiter mechanism is formed of a clutch comprising first ratchet teeth with inclined surfaces disposed at a motor side connected to the motor for receiving the driving torque from the motor, second ratchet teeth with inclined surfaces disposed at a spool side connected to the spool for transmitting the driving torque to the spool, and a spring for urging the first and second ratchet teeth to engage together, said inclined surfaces of the first and second ratchet teeth engaging together by the spring to transmit the driving torque from the motor to the spool in a normal state and slipping by compressing the spring to disengage the second ratchet teeth from the first ratchet teeth for preventing the excessive load from being applied from the spool to the motor when the excessive load for rotating the spool in a seat belt withdrawing direction is generated.