Abstract: Among six follower balls (5) aligned on the input shaft (7), the two balls (5) situated on one end side (A) always engage tightly with one engagement surface (10a), while the other two balls (5) situated on the other end side (B) always engage tightly with the other engagement surface (10b). This regulates the movement of the balls (5) against the engagement surface (10a, 10b) of the cammed streak portions (10) so as to eliminate a backlash played between the balls (5) and the cammed streak portions (10). This makes it possible to prevent the meshing noise from being induced so as to implement a low noise operation. With the point-to-point contact maintained between the cammed streak portions (10) and the balls (5), it is possible to reduce a friction therebetween, thereby improving a torque transmissibility against the follower wheel (4) to insure a smooth rotational movement with a higher precision.

Abstract: Among six follower balls (5) aligned on the input shaft (7), the two balls (5) situated on one end side (A) always engage tightly with one engagement surface (10a), while the other two balls (5) situated on the other end side (B) always engage tightly with the other engagement surface (10b). This regulates the movement of the balls (5) against the engagement surface (10a, 10b) of the cammed streak portions (10) so as to eliminate a backlash played between the balls (5) and the cammed streak portions (10). This makes it possible to prevent the meshing noise from being induced so as to implement a low noise operation. With the point-to-point contact maintained between the cammed streak portions (10) and the balls (5), it is possible to reduce a friction therebetween, thereby improving a torque transmissibility against the follower wheel (4) to insure a smooth rotational movement with a higher precision.