Mechanical device having worm gear mechanism

A mechanical device having a worm gear mechanism including:

• a worm wheel attached to a rotary shaft;
• and a worm shaft including a worm in mesh with the worm wheel and provided in an accommodation hole of a frame, the worm gear mechanism configured to adjust backlash between the worm and the worm wheel by movement of the worm shaft in an axis line direction, the mechanical device including a position adjusting mechanism,
• the position adjusting mechanism comprising:
• a holder screwed into the accommodation hole on one end-side of the accommodation hole, the holder configured to rotatably support the worm shaft, the holder configured to cause the movement of the worm shaft by rotation;
• an axial force generation part including a screw part, the axial force generation part configured to exert an axial force on the holder by a screwing action resulting from rotation of the screw part, the axial force is a force in the axis line direction;
• and
• a base part provided to the frame, the base part configured to receive a reactive force acting on the axial force generation part as a result of exerting the axial force to the holder.