An Adaptive Loading Mechanism Based on Logarithmic Spiral Profile Connection for Planetary Traction Drives

A cylindrical roller planetary traction drive was developed. It comprises a sun roller, three planetary rollers, an outer ring, a stationary carrier and an input shaft. The sun roller is hollow, and is connected through three logarithmic spiral profiles to the input shaft. As the input shaft rotates relative to the sun roller, a wedging action takes place between the input shaft and the sun roller; this makes the sun roller generate a certain amount of elastic deformation, so an appreciable amount of contact load is generated between the sun roller and the planetary roller. The greater the input torque is, the stronger the strength of the wedging action and the greater the contact load, and vice versa; so this configuration is self-actuating. Here, as cylindrical rollers are used in the planetary traction-drive configuration, the spin motion as would present in the case that the tapered rollers were used will not occur. Meanwhile, as a logarithmic spiral is used in the profile connection, the distribution of contact stress between the two connected surfaces will be uniform. This reduces the concentration of contact stress of the connected surfaces, and prolongs the life of the contact fatigue of the contacting surfaces.