Projections protruding towards a cam plate and a disc are provided on both axial side surfaces of the retainer at a plurality of positions at which phases of the projections in the circumferential direction are offset from pockets. One axial direction surface of the cam plate and the disc are formed with concave portions at portions facing the respective projections. The concave portions have an axial depth deepest at a center portion thereof in the circumferential direction and becoming shallower towards both end portions thereof.

A pivot holder of a friction-roller-type reduction gear has a pair of bearing parts configured to support a rotational shaft of an intermediate roller and having a pivot axis at an eccentric position from a center of the rotational shaft, and a bridging part configured to integrally couple the pair of bearing parts. A carrier has a holder support part configured to rotatably support the bearing parts. An interaxial distance between a center of the pivot axis and the center of the rotational shaft is equal to or smaller than a maximum radius of an outer diameter of the intermediate roller, and the center of the pivot axis is located on an applying line of a torque reaction force of transmission torque to be applied to the pivot holder.

A pivot holder of a friction-roller-type reduction gear has a pair of bearing parts configured to support a rotational shaft of an intermediate roller and having a pivot axis at an eccentric position from a center of the rotational shaft, and a bridging part configured to integrally couple the pair of bearing parts. A carrier has a holder support part configured to rotatably support the bearing parts. An interaxial distance between a center of the pivot axis and the center of the rotational shaft is equal to or smaller than a maximum radius of an outer diameter of the intermediate roller, and the center of the pivot axis is located on an applying line of a torque reaction force of transmission torque to be applied to the pivot holder.

A friction roller-type reduction gear includes a sun roller arranged concentrically with an input shaft, a ring roller having a stationary ring roller element and a moveable ring roller element, a plurality of intermediate rollers configured to be in rolling contact with an outer peripheral surface of the sun roller and an inner peripheral surface of the ring roller, a coupling part configured to couple the ring roller and the output shaft, and a loading cam mechanism having a cam ring and configured to change a contact surface pressure of each rolling contact surface. The outer peripheral surface of the sun roller is a concave curved surface of which a shape of an outer edge in an axial cross-section is a single circular arc-shaped concave curve, and an outer peripheral surface of the intermediate roller is a convex curved surface of which a shape of an outer edge in an axial cross-section is a single circular arc-shaped convex curve.

A friction roller-type reduction gear includes a sun roller arranged concentrically with an input shaft, a ring roller having a stationary ring roller element and a moveable ring roller element, a plurality of intermediate rollers configured to be in rolling contact with an outer peripheral surface of the sun roller and an inner peripheral surface of the ring roller, a coupling part configured to couple the ring roller and the output shaft, and a loading cam mechanism having a cam ring and configured to change a contact surface pressure of each rolling contact surface. The outer peripheral surface of the sun roller is a concave curved surface of which a shape of an outer edge in an axial cross-section is a single circular arc-shaped concave curve, and an outer peripheral surface of the intermediate roller is a convex curved surface of which a shape of an outer edge in an axial cross-section is a single circular arc-shaped convex curve.

A pivot holder of a friction-roller-type reduction gear has a pair of bearing parts configured to support a rotational shaft of an intermediate roller and having a pivot axis at an eccentric position from a center of the rotational shaft, and a bridging part configured to integrally couple the pair of bearing parts. A carrier has a holder support part configured to rotatably support the bearing parts. An interaxial distance between a center of the pivot axis and the center of the rotational shaft is equal to or smaller than a maximum radius of an outer diameter of the intermediate roller, and the center of the pivot axis is located on an applying line of a torque reaction force of transmission torque to be applied to the pivot holder.

A pivot holder of a friction-roller-type reduction gear has a pair of bearing parts configured to support a rotational shaft of an intermediate roller and having a pivot axis at an eccentric position from a center of the rotational shaft, and a bridging part configured to integrally couple the pair of bearing parts. A carrier has a holder support part configured to rotatably support the bearing parts. An interaxial distance between a center of the pivot axis and the center of the rotational shaft is equal to or smaller than a maximum radius of an outer diameter of the intermediate roller, and the center of the pivot axis is located on an applying line of a torque reaction force of transmission torque to be applied to the pivot holder.

A suspension friction drive system and an auto-balancing personal transportation device having same. The suspension friction drive system may include two wheels (at least one of which is a drive wheel) that contact the rim of a wheel to be driven. The wheels preferably contact the rim at a contact angle that increases friction such that wheel driving performance is enhanced. The wheels are also preferably positioned such that some degree of shock absorption is provided and additional absorption may be supported. Various embodiments and features are disclosed including, but not limited to, a suspension frame coupled between the two wheels, the use of at least two drive wheels, a suspension bias mechanism, and a drive wheel substantially centered on the rim.

A suspension friction drive system and an auto-balancing personal transportation device having same. The suspension friction drive system may include two wheels (at least one of which is a drive wheel) that contact the rim of a wheel to be driven. The wheels preferably contact the rim at a contact angle that increases friction such that wheel driving performance is enhanced. The wheels are also preferably positioned such that some degree of shock absorption is provided and additional absorption may be supported. Various embodiments and features are disclosed including, but not limited to, a suspension frame coupled between the two wheels, the use of at least two drive wheels, a suspension bias mechanism, and a drive wheel substantially centered on the rim.

Disclosed is a planetary traction drive for a driven turbocharger that utilizes angular contact ball ramps to provide variable clamping depending on torque throughput. The ball ramps are located between ring rollers and a ring gear, and function to locate the ring gear concentrically to the ring rollers. The angled contact axes of the ball ramps allows use of a low conformity contact between the balls and ball races in the ball ramps to provide efficient movement, while simultaneously locating ring gear concentrically to the traction rings.