In this study, the frictional toque of a needle roller thrust bearing was investigated theoretically and experimentally. In order to evaluate the torque, the roller motion of the bearing was clarified under the condition that the energy loss generated at the contact between the rollers and raceways become minimum. Secondly, by using these results, the relative sliding between the rollers and raceways and the frictional torque of needle roller thrust bearing were obtained. Following the theoretical studies, experimental investigations were carried out with a wide range of thrust loads and rotational speeds. Various types of bearings having different numbers of rollers, different pitch diameters, different roller length and different roller diameters were prepared. The results obtained in this work are summarized as follows: (1)The frictional torque of a needle roller thrust bearing is nearly proportional to the thrust load and roller length. (2)The torque is almost independent of the rotational speed, number of rollers, bearing pitch diameter and roller diameter. (3)Experimental results agree with the theory.
