2019 年 85 巻 879 号 p. 19-00257
This paper describes a newly invented loading cam that provides a contact force for a planetary roller. A high-speed electric motor with a small reducer and high-power transmission efficiency realizes a powertrain system with a high power density because electric motors can be miniaturized to increase the rotational speed. Planetary traction drive roller reducers are suitable for high-speed driving to avoid meshing vibration as in gears; however, it is difficult to provide a sufficient loading force on the rollers to transmit power. A previously proposed planetary reducer with conical rollers could generate a contact force; however, it lost spin power at the point of contact. The pinion of a planetary roller contacts both a sun roller and a ring so that the pinion must exert a force in opposite directions, inside and outside, at the same time. The new loading mechanism has a pair of cams acting in opposing directions to generate a moment force during contact. This paper presents analytic equations for force and displacement on a pinion that was constructed to agree well with simulations and experimental results. The paper also describes how the analytical equations were used to design the cam and rollers. The cam causes skewing on a pinion because of its asymmetrical profile, which reduces the transmission efficiency. This skewing can be reduced to adjust the rigidity balance of contact points and components. The proposed cam achieves a loading system that provides a contact force to planetary rollers, which is the most important requirement for achieving a planetary roller reducer.
