Seat belt retractor with switching means

#The present invention relates to a seat belt retractor, and particularly, to a motorized seat belt retractor, which can change its operating condition to correspond to the state of an occupant wearing a seat belt or to external signals.

#In a seat belt retractor provided in an automobile, it is preferable to retract an excess amount of a seat belt after the seat belt is pulled and a tongue is engaged with a buckle device, without applying too much stress to the chest or other portions of an occupant normally wearing the seat belt.

#Normally used for winding up a seat belt in a seat belt retractor is a biasing force of a single return spring. When a spring providing a small biasing force is employed in order to reduce stress applied to the chest of an occupant, the force for winding or retracting the seat belt becomes weak, thus lowering its operation and its accommodation to the retracted state.

#FIG. 1 is an exploded perspective view showing components of a seat belt retractor according to an embodiment of the present invention;

#FIG. 2 is an exploded perspective view showing components of a speed-reduction mechanism of the seat belt retractor of the present invention;

#FIG. 3 is a cross-sectional view showing end faces of transmission elements inside the speed-reduction mechanism;

#Hereinafter, an embodiment of the seat belt retractor and the control method for carrying out the present invention will be described with reference to the accompanying drawings.

#FIG. 1 is an exploded perspective view illustrating a schematic structure of an assembly of the seat belt retractor 1 of the present invention including a webbing winding reel 2A; a reel locking mechanism 4; a speed-reduction mechanism casing 11 for accommodating a motor 5 as a driving mechanism and a speed-reduction gear mechanism; a planetary gear unit 30 composing a part of the speed-reduction gear 10 (FIG. 2); and detecting units 40 and 50 for controlling the motor. FIG. 2 is an exploded perspective view showing an internal structure of the speed-reduction mechanism 10 among the components shown in FIG. 1.

#In FIG. 1, the webbing winding reel 2A and the reel locking mechanism 4 as the known mechanisms are illustrated in the assembled state. The webbing winding reel 2A comprises a spool 2 on which a webbing W is wound and a base frame 3 rotatably supporting a spool shaft 15 of the spool 2, and the reel locking mechanism 4 (only its outer profile is shown) for preventing the 10 rotation of the spool 2 is integrally attached to the base frame 3. In this embodiment, a single variable speed DC motor 5 is employed as its driving mechanism. A control unit 9 (see FIG. 7) is provided with a circuit device (not shown) in order to control the rotational speed of the DC motor 5. As a driving mechanism to which a rotational torque is transmitted from the DC motor 5, the speed-reduction mechanism 10 is arranged in the speed-reduction mechanism casing 11.