An epicyclic traction drive transmission, including a carrier 7 having a central axis, a sun shaft 9 rotationally mounted within carrier 7 and positioned in the central axis, a plurality of planet rollers 4 mounted on carrier 7 and arranged to rotate on respective angularly equidistant axles 5, and rotationally engage the sun shaft 9, and an outer ring 1. A wedge roller 2,3 associated with each planet roller 4 is free to translate relative to carrier 7; and engages outer ring 1 and respective planetary roller 4 with a frictional or traction coefficient , and the wedge roller 2,3 defining a wedging angle , such that tan /2 is less than . In one form there are two wedge rollers 2,3 for each planet roller, allowing for a wedging action in either direction of rotation.

A multi-stage planetary roller power transmission device includes a high-speed power transmission mechanism including a first sun shaft, a first fixed ring, first planetary rollers disposed between the first sun shaft and the first fixed ring with a first negative clearance, first support shafts, and an annular first carrier into which the first support shafts are press-fitted; and a low-speed power transmission mechanism including a second sun shaft, a second fixed ring, second planetary rollers disposed between the second sun shaft and the second fixed ring with a second negative clearance, second support shafts, and an annular second carrier into which the second support shafts are press-fitted. A clearance amount of the first negative clearance and a clearance amount of the second negative clearance are equal to each other, and the number of the first planetary rollers is smaller than the number of the second planetary rollers.

An electric drive includes a motor and a transmission for transferring torque from the motor to a tool. The transmission includes a plurality of planetary rollers which are driven by a rotary shaft of the motor, and an output ring which is connectable to the tool, and which is driven by the planetary rollers. The transmission further includes a roller casing which is secured to a housing of the motor, and which supports parallel planetary shafts upon which the planetary rollers are mounted for rotation relative to the roller casing, and a bearing having an inner race which engages the roller casing, and an outer race which engages the inner periphery of the output ring.

An electric drive includes a motor and a transmission for transferring torque from the motor to a tool. The transmission includes a plurality of planetary rollers which are driven by a rotary shaft of the motor, and an output ring which is connectable to the tool, and which is driven by the planetary rollers. The transmission further includes a roller casing which is secured to a housing of the motor, and which supports parallel planetary shafts upon which the planetary rollers are mounted for rotation relative to the roller casing, and a bearing having an inner race which engages the roller casing, and an outer race which engages the inner periphery of the output ring.

A variator comprises first and second races disposed for rotation about a variator axis and at least one rolling element disposed in a cavity between the races. In a drive configuration, drive is transmitted between the races and the at least one rolling element; and in a neutral configuration, the at least one rolling element and races are configured whereby the races can move independently of one another. In a method of operating the variator, the neutral configuration is obtained by moving the at least one rolling element to a position in which it ceases to make contact with at least one of the races. The drive configuration is obtained by moving the at least one rolling element to a position in which it makes contact with both of the races.

A planetary traction drive for a driven turbocharger 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. A variation is shown where only a single angular contact ball ramp is used between the ring gear and a clamping traction ring, and the other traction ring is rigidly fixed to the ring gear to reduce part count and complexity.

A planetary traction drive for a driven turbocharger 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. A variation is shown where only a single angular contact ball ramp is used between the ring gear and a clamping traction ring, and the other traction ring is rigidly fixed to the ring gear to reduce part count and complexity.

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.

A frictional roller reducer having a sun roller; a ring roller; a plurality of intermediate rollers having rolling surfaces coming in rolling contact with the sun roller and the ring roller; the sun roller or the ring roller having a pair of roller elements including inclined surface portions on a circumferential surface coming in rolling with rolling surfaces, the inclined surface portions inclined in directions going toward the intermediate rollers in a radial direction as going away from each other in the axial direction; a pressing device pressing the pair of roller elements in directions going closer to each other, and an elastic member arranged between the pair of roller elements, the elastic member urging the pair of roller elements in directions going away from the rolling surface of the intermediate rollers.

A frictional roller reducer having a sun roller; a ring roller; a plurality of intermediate rollers having rolling surfaces coming in rolling contact with the sun roller and the ring roller; the sun roller or the ring roller having a pair of roller elements including inclined surface portions on a circumferential surface coming in rolling with rolling surfaces, the inclined surface portions inclined in directions going toward the intermediate rollers in a radial direction as going away from each other in the axial direction; a pressing device pressing the pair of roller elements in directions going closer to each other, and an elastic member arranged between the pair of roller elements, the elastic member urging the pair of roller elements in directions going away from the rolling surface of the intermediate rollers.