To improve lubricating performance with certainty by feeding a fresh lubricant solution to a bearing at all times through a simple structure.

A recess 14 is installed in a central part in the toothwidth direction of a gear 2 or the like of a spectacle hole 13 installed in a body 1, and this recess 14 is connected to a reflux hole 1a constituting the terminal of a bearing lubricating circulation channel 12, whereby a lubricant solution returned from this reflux hole 1a is made so as to be discharged out of a discharge part 9 through a central part ranging from the recess 14 to the gear 2 to the like. With this constitution, any possible re-inflow of the lubricant solution into a bearing 4 is obviated and thereby a fresh lubricant solution is always suppliable.