PITCH ADJUSTING MECHANISM AND PITCH ADJUSTING METHOD FOR ROTARY GEAR

PROBLEM TO BE SOLVED: To adjust pitch of a rotary gear easily by a reproducible method without decreasing base material strength of the rotary gear or causing mechanical vibration.SOLUTION: A pitch adjusting mechanism includes: a boss part 71; a circular plate part 72 which extends radially outward from the boss part 71 and is fixed; and a gear part 73 which is installed around an outer end of the plate part 72, and has a helical gear 73a at its outer periphery. The pitch adjusting mechanism includes: an annular or partially annular groove 74 formed axially in a base of the plate part 72 of the boss part 71 while opened at one axial end of the boss part 71; wedge-like members 82, 83 which are installed axially movably in the groove 74, in slide contact with an inner peripheral surface and outer peripheral surface of the groove 74 or with surface members 84, 85 installed on the inner periphery and outer periphery of the groove, and variably apply contact pressure between an inner periphery and an outer periphery of the groove 74 at a position eccentric from an axial position of the plate part 72 according to axial movement; and a screw member 81 which drives the wedge-like members 82, 83 to move forward and backward in an axial direction.