Fixed position preload is used for a wheel hub, a differential gear box, etc. because it is more compact and rigid than the constant pressure preload. However, as a disadvantage, it is very susceptible to dimensional change, and the preload amount greatly changes due to heat generation and wear. Especially, since tapered roller bearings have larger heat generation and wear than ball bearings, it is necessary to pay sufficient attention when using them at position preload. In this paper, we performed a test simulating the actual use environment of bearings using an apparatus that measures the axial load change with a cylindrical housing, and observed the change in axial load during operation. As a result, it was found that there are two kinds of change in preload, one by dynamic factor and one by static factor. Furthermore, it was revealed that the change of the preload of the dynamic factor is greatly influenced by the formation of the oil film.

An elevator is indispensable vertical transport, especially for high-rise buildings. With regard to elevator control, it is important to quickly suppress the vertical vibration occurring in the car in order to improve the performance and quality. The authors proposed the Damping Support Control (DSC) that uses a method for reducing residual vibration which has been researched for the low rigidity machineries, and presented an optimal parameter design method for the control system. However, it was recently found that a vibration phase and frequency synchronized between the car and the counterweight, a motor-torque difference of a driving sheave would have been minute. Thus the DSC applying the motor control of traction machine was unable to work enough to extinguish the residual vibration. This paper presents that it is possible to effectively reduce the residual vibration by installing a damping support mechanism in the counterweight, and using this in combination with the DSC as a measure to solve this problem.

Strong radiative cooling in orchards at dawn in early spring can cause extensive frost damage to plum trees in Wakayama Prefecture. Although blast fans or fuel-based heaters are typically used in plum orchards, they are not effective under very cold conditions. Here we describe a new heating system that combines blast fans and fuel-based heaters, and describe the feasibility of the method for preventing frost damage. First, the relationships between air temperature, wind speed and precipitation were examined using Japanese Meteorological Agency AMEDAS data. The results showed that strong radiative cooling is an important factor underlying the low early spring temperatures in the study area. Second, the heating effect was roughly estimated for the combined new system. Third, field observations were conducted in a plum orchard in southern Wakayama Prefecture in early spring. The results showed that the temperature lapse rate 5m above the ground ranged from -0.30 to -0.21°C/m. Finally, the heating effect of the fan heater under different combinations of heater power and fan flow rate was predicted by CFD analysis. The results showed some of the advantages of the developed system over blast fans or fuel based-heaters.