Takahisa Kawaguchi

Micro-displacement characteristics under tangential force

In this paper, firstly the obtained analytical results are briefly summarised. Next some experimental results are shown developed using finished ceramic surfaces of ZrO{2} and Al{2}O{3} together with SiC. And comparison of obtained experimental results with theoretical analyses and approximate equations introduced in the preceding works was made. The main conclusions are as follows. (1) Little difference can be seen in appearance between the experimental and calculated displacement behaviours, although frictional force of SiC is higher compared with those of other two ceramics and the slope of the curve after macro-slip of SiC is greater than those of the others. (2) Experimental values of tangential stiffness r{g} at the start of increasing the tangential force lie between calculated values by the two contact models. (3) Experimental values of tangential displacement δ{cmax} at the start of macro-slip are larger than those calculated by the two contact models and this is more evident for ZrO{2}.

Influences of bearing pitch diameter, roller length and roller diameter on the frictional torque of a needle roller thrust bearing

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: o (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.

Frictional torque of cylindrical roller thrust bearing in grease lubrication

In general, greases are widely used as the lubricants of the majority of rolling bearings, but their fluidity or lubrication characteristics are complicated. Therefore, it is not clear how the lubricant flow in bearings is or what the lubrication mechanism is. Also, the effects of grease lubrication on the operating performance of rolling bearings are not clear. In this study, the frictional torque of grease-lubricated cylindrical roller thrust bearings was investigated over a wider range of thrust loads and rotational speeds. For comparison, the same tests were also performed with three types of cylindrical roller thrust bearings, single-row, double-row and triple-row. The frictional torque obtained can be summarized as follows. o (1) The frictional torque is proportional to the square root of the thrust load in a lower load range. (2) The torque is proportional to the thrust load in the higher load range. (3) The torque is very similar in the lower load range regardless of the type of bearing; single-row, double-row or triple-row. However, in the higher load range, the value is nearly inversely proportional to the number of rows.