Tomoya Masuyama

Development of a low backlash Crown Reducer

In this paper, we describe a novel low backlash reducer using precessing crown gears. we call this mechanism Crown Reducer. The features of this reducer are low backlash, high reduction ratio, advantage in miniaturizing. These features greatly contribute to design various small mechanisms such as a finger joint of a robot hand. The crown gear pair is meshing in face to face, one acts as a rotor and the other as a stator. The rotor gear has N teeth and the hub is connected to the output shaft. The spokes of rotor gear are elastically deformed according to gears rolling. The stator gear fixed on a housing has N − 1 teeth (or N + 1). The meshing of crown gear pair with several shapes of rack tooth are simulated, and proper parameters of rack to improve high rigidity of teeth are calculated. Finally, backlash and minimum input torque to rotate are evaluated using a prototype reducer.

Observation of Fatigue Damage to Gear Tooth Using Image Processing

The detection of damage in early stage of fatigue is important for a reliable evaluation of gear life and strength. From this point of view, the variation of strain distribution in a tooth due to cyclic load contains useful information because the fatigue crack will initiate as a result of the accumulation of plastic strain. Meanwhile, digital image equipments are widely used in our life and the performance is in progress. We took digital pictures of cyclic loaded tooth by the digital camera and compared with the picture of no load to find displacement. The strain distribution of tooth is calculated by the correlation method using those pictures. The initiation of a micro crack is observed by the method. It is also confirmed by the detection of acoustic emission wave with higher energy. The variation of stress-strain diagram in fatigue process is presented, and this illustrates the increase of strain in the final stage of fatigue.© 2007 ASME