Patent ID: 6354528
Filing Date: 2002-03-12
Classification: B60R

Abstract:
A webbing retractor for use with a webbing belt having opposite ends, the webbing retractor comprising:a cylindrical take-up shaft at which one end of a webbing belt is retained; a lock device for restricting rotation of said take-up shaft in a direction for pulling out the webbing belt, during abrupt deceleration of a vehicle; and a pretensioner for forcibly rotating said take-up shaft in the take-up direction opposite to the pulling-out direction during abrupt deceleration of the vehicle; wherein said lock device includes: a frame having a pair of leg plates opposite to each other along an axial direction of the take-up shaft, one of the pair of leg plates being formed with a ratchet hole whose inner peripheral portion serves as internal ratchet teeth, the leg plates having sides; a lock base provided coaxially and relatively rotatable with respect to said take-up shaft, in a vicinity of said one of the pair of leg plates; a lock plate having external teeth meshable with said ratchet teeth, which is substantially integrally held by the lock base, and which restricts rotation of said lock base in said pulling-out direction by meshing of the external teeth with said ratchet teeth; a torsion shaft having opposite ends, provided in said take-up shaft coaxially with said take-up shaft, one end of the torsion shaft being coupled to said take-up shaft, the other end being coupled to said lock base, for integrally rotating said take-up shaft and said lock base, and allowing rotation of said take-up shaft relative to said lock base due to torsion deformation of the torsion shaft; and a lock cover formed with a push nut portion with which a distal end portion of said torsion shaft is engaged, a hook portion with which said lock base is engaged, and an outer peripheral flange portion overlapping said frame, for pinching said one leg plate between one end portion of the take-up shaft and said lock cover and covering said lock base and said lock plate, and wherein the pretensioner includes: a pinion provided coaxially with respect to said take-up shaft at the side of the other leg plate of said pair of leg plates and coupled directly or indirectly to said take-up shaft; a piston having an end portion, on which a rack bar meshable with said pinion is formed in an axial direction; a cylinder having a bottom portion and an end opening in an axial direction of said piston serves, for housing said piston and driving said piston with increase in internal pressure; a gas generator for supplying gas between the bottom portion of said cylinder and said piston during abrupt deceleration of the vehicle; a bearing portion facing an outer peripheral portion of a shaft portion provided coaxially with said pinion on said take-up shaft side of said pinion in a radial direction of the pinion, and having an inner peripheral portion such that a predetermined gap exists between the outer peripheral portion of said shaft portion and the inner peripheral portion; and a plurality of protrusions which are formed to protrude from one having a lower rigidity towards the other having a higher rigidity, of the inner peripheral portion of said bearing portion and the outer peripheral portion of said shaft portion, to thereby be brought into contact with the one having the higher rigidity, said webbing retractor further including: an acceleration sensor for detecting a change in acceleration during abrupt deceleration of the vehicle, and for causing the external teeth of said lock plate to mesh with said internal ratchet teeth, upon detection of said change in acceleration; and urging means provided at the side of the other leg plate of said frame, for urging said take-up shaft in the rotational direction for taking up said webbing belt.