Worm gear reducer

A worm gear reducer comprising:

• a housing including a wheel accommodating portion and a worm accommodating portion that has a central axis at a skew position with respect to a central axis of the wheel accommodating portion and whose intermediate portion in an axial direction is open to the wheel accommodating portion;
• a worm wheel having wheel teeth on an outer circumferential surface thereof and configured to be rotatably supported inside the wheel accommodating portion;
• a worm having worm teeth that mesh with the wheel teeth on an outer circumferential surface thereof and configured to be rotatably supported inside the worm accommodating portion;
• a support bearing fitted around a tip end portion of the worm;
• an elastic urging portion configured to urge a radially inner side member that is the support bearing or an outer fitting member fitted around the support bearing toward a worm wheel side;
• and
• an elastic clamping portion having a pair of clamping plate springs that are disposed on both sides of the radially inner side member in a third direction orthogonal to both a first direction, which is an urging direction by the elastic urging portion and a second direction, which is an axial direction of the worm accommodating portion, in a portion between an outer circumferential surface of the radially inner side member and an inner circumferential surface of a radially outer side member that is the worm accommodating portion or an inner fitting member fitted inside the worm accommodating portion, wherein
• each of the clamping plate springs constituting the pair of clamping plate springs exhibits a non-linear spring characteristic in which a spring constant increases as a deflection amount in a direction including a third-direction component increases
• the clamping plate springs associated with the elastic clamping portion are separate components from the elastic urging portion.