Seatbelt retractor

A seatbelt retractor comprising:

• a retractor frame attached to a seat back of a reclining seat and tiltable with the seat back when adjusting a reclining angle of the seat back;
• a spindle rotatably supported by the retractor frame and configured to wind a seatbelt;
• an acceleration sensor attached to the retractor frame and configured to detect acceleration in a longitudinal direction of a vehicle;
• a lock mechanism configured to lock pull-out operation of the seatbelt according to the acceleration in the longitudinal direction of the vehicle detected by the acceleration sensor;
• and
• a posture control mechanism configured to maintain a sensor reference surface of the acceleration sensor horizontally oriented, wherein
• the acceleration sensor includes:
• a sensor cover attached to the retractor frame;
• an inertial body that is moveable in the longitudinal direction of the vehicle when acceleration of a predetermined value or more is applied in the longitudinal direction of the vehicle;
• a sensor housing having a swing shaft along a right/left direction of the vehicle, the sensor housing being supported by the sensor cover and having an inertial body support surface, on which the inertial body is supported, as the sensor reference surface, and the sensor housing being rotatable about the swing shaft by the posture control mechanism according to a tilt angle of the seat back so as to keep the inertial body support surface horizontally oriented;
• and
• a first lever arranged on an upper side of the inertial body and that is displaced together with movement of the inertial body in the longitudinal direction of the vehicle, displacement of the first lever operating to move the lock mechanism toward a locking side, and
• the lock mechanism includes:
• a steering wheel that rotates integrally with the spindle, and that includes a plurality of locking teeth on its outer peripheral surface;
• a second lever having a claw part configured to engage with the locking teeth of the steering wheel so as to lock the steering wheel, the second lever being rotatably supported by a support shaft provided on the retractor frame or a steering wheel cover that tilts integrally with the retractor frame, the second lever having a lower abutment wall biased into contact with an upper surface of the first lever by a force from its self weight of the second lever;
• and
• a counterweight provided separately from the second lever and configured to selectively engage the second lever depending on the tilt angle of the back seat so as to bias the second lever towards an unlocking side.