A planetary power transmission device includes a ring member; a sun member; a first shaft disposed concentrically with the sun member and fixed to the sun member; a plurality of planetary members provided between the ring member and the sun member; support shafts configured to respectively support the planetary members such that the planetary members are rotatable; a carrier member to which the support shafts are fixed, the carrier member being configured to rotate in accordance with revolution of the planetary members along an inner peripheral surface of the ring member; a second shaft fixed to the carrier member so as to be concentric with the first shaft; and a housing configured to accommodate the ring member, the sun member, the planetary members, and the carrier member. An outer peripheral surface of the carrier member is rotatably supported by the housing via a bearing.

A planetary power transmission device includes a ring member; a sun member; a first shaft disposed concentrically with the sun member and fixed to the sun member; a plurality of planetary members provided between the ring member and the sun member; support shafts configured to respectively support the planetary members such that the planetary members are rotatable; a carrier member to which the support shafts are fixed, the carrier member being configured to rotate in accordance with revolution of the planetary members along an inner peripheral surface of the ring member; a second shaft fixed to the carrier member so as to be concentric with the first shaft; and a housing configured to accommodate the ring member, the sun member, the planetary members, and the carrier member. An outer peripheral surface of the carrier member is rotatably supported by the housing via a bearing.

An apparatus includes a first ring having an open annular space and a variable-width groove disposed on an interior peripheral surface of the first ring; a second ring rotatable within the open annular space of the first ring, where the second ring has a respective variable-width groove disposed on an exterior peripheral surface of the second ring; and a plurality of rollers disposed between, and configured to roll on, the interior peripheral surface of the first ring and the exterior peripheral surface of the second ring and rotatable therebetween.

An apparatus includes a first ring having an open annular space and a variable-width groove disposed on an interior peripheral surface of the first ring; a second ring rotatable within the open annular space of the first ring, where the second ring has a respective variable-width groove disposed on an exterior peripheral surface of the second ring; and a plurality of rollers disposed between, and configured to roll on, the interior peripheral surface of the first ring and the exterior peripheral surface of the second ring and rotatable therebetween.

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 apparatus includes a first ring having an open annular space and a variable-width groove disposed on an interior peripheral surface of the first ring; a second ring rotatable within the open annular space of the first ring, where the second ring has a respective variable-width groove disposed on an exterior peripheral surface of the second ring; and a plurality of rollers disposed between, and configured to roll on, the interior peripheral surface of the first ring and the exterior peripheral surface of the second ring and rotatable therebetween.

An apparatus includes a first ring having an open annular space and a variable-width groove disposed on an interior peripheral surface of the first ring; a second ring rotatable within the open annular space of the first ring, where the second ring has a respective variable-width groove disposed on an exterior peripheral surface of the second ring; and a plurality of rollers disposed between, and configured to roll on, the interior peripheral surface of the first ring and the exterior peripheral surface of the second ring and rotatable therebetween.

A drive assembly for use in a piece of home equipment is provided including a center shaft having a central axis. A first drive component has a cavity formed therein and is configured to rotate about the central axis. A second drive component is at least partially nested within the cavity. The second drive component is configured to rotate about the central axis. The first drive component is operably coupled to a first rotary coupling and the second drive component is operably coupled to a second rotary coupling.

A drive assembly for use in a piece of home equipment is provided including a center shaft having a central axis. A first drive component has a cavity formed therein and is configured to rotate about the central axis. A second drive component is at least partially nested within the cavity. The second drive component is configured to rotate about the central axis. The first drive component is operably coupled to a first rotary coupling and the second drive component is operably coupled to a second rotary coupling.

Disclosed is an air pump for a fuel cell that utilizes a speed-reduction traction drive so that a low speed electric motor can be used to drive a high-speed rotodynamic compressor. The rotodynamic compressor is an efficient air pump, but operates at high speeds that would require a specialized high-speed electric motor. The speed-reduction traction drive couples to the compressor and provides a low-speed output that is connected to a lower speed electric motor.