US Patent 7484436 Wave gear device

A wave gear device, wherein, when a wave generator is in a low speed rotating state, a rolling bearing state is formed by a wave bearing and the wave generator and a flexible external gear are held in a relatively rotatable state and when the wave generator is in a high speed rotating state, partition pieces and split side plate pieces forming the retainer of the web bearing are displaced to the outside to stop the rotation of balls in their axes and the revolution thereof. Accordingly, a sliding bearing state is formed by lubricating oil film formed between the wave generator and the flexible external gear and the wave generator and the flexible external gear are held in a relatively rotatable state.