Gear mechanism and robot having the same

A gear mechanism comprising:

• a base body member;
• a first gear supported on the base body member so as to rotate about a first axis of rotation;
• a second gear capable of being meshed with the first gear;
• a support member supporting the second gear so as to rotate about a second axis of rotation and placed on the base body member so as to be movable in approaching and leaving directions respectively toward and away from the first axis of rotation;
• a support member fastening member configured to fasten the support member to the base body member, the support member fastening member in an unfastened state allowing the support member to move in the approaching and leaving directions relative to the base body member and in a fastened state restraining the support member from moving relative to the base body member by way of a frictional resistance,
• a contact member configured to be able to move in the approaching and leaving directions and be brought into contact with less than an entire circumference of the support member;
• a retaining member engaged in a threaded hole formed in the base body member so as to be capable of being turned to move forward and backward in the approaching and leaving directions, the contact member being moved in the approaching and leaving directions by turning the retaining member to move forward or backward relative to the base body member so that the retaining member supports the support member via the contact member to restrain the support member from moving in the leaving direction away from the first axis of rotation;
• and
• a contact member fastening member for mounting the contact member on the base body member, the contact member fastening member in an unfastened state allowing the contact member to move in the approaching and leaving directions relative to the base body member and in a fastened state restraining the contact member from moving relative to the base body member by way of a frictional resistance.