Worm reducer

A worm reducer, comprising:

• a housing having a wheel accommodating portion and a worm accommodating portion having a central axis that is at a skewed position relative to a central axis of the wheel accommodating portion and an intermediate portion in an axial direction that opens into the wheel accommodating portion;
• a worm wheel having wheel teeth on an outer circumferential surface thereof and rotatably supported inside the wheel accommodating portion;
• a worm having worm teeth on an outer circumferential surface thereof that engage with the wheel teeth and is rotatably supported inside the worm accommodating portion;
• a support bearing externally fitted onto a tip-end portion of the worm;
• and
• a biasing plate spring configured to bias an inner diameter side member, that is the support bearing or an outer fitting member externally fitted onto the support bearing, toward the worm wheel;
• the biasing plate spring arranged on a far side from the worm wheel in a first direction, that is a biasing direction of the biasing plate spring, in a portion between an outer circumferential surface of the inner diameter side member and an inner circumferential surface of an outer diameter side member that is the worm accommodating portion or an inner fitting member internally fitted into the worm accommodating portion;
• having a load point that is a contact portion with the outer circumferential surface of the inner diameter side member, and a fulcrum that is a portion of contact portions in contact with the inner circumferential surface of the outer diameter side member that is located at a position closest to the load point;
• and
• exhibiting a non-linear spring characteristic in which a spring constant increases as a position of the fulcrum changes to approach the load point as an amount of deflection in the first direction increases.