Structure of joint of robot including drive motor and reduction gear

1. A structure of a joint of a robot in which a first member and a second member are jointed through intermediation of a joint and in which the first member and the second member turn relatively to each other, the structure of the joint comprising:

a drive motor configured to drive the second member with respect to the first member;

a reduction gear including an input shaft configured to receive rotational force of the drive motor, a gear configured to transmit rotational force of the input shaft, a gear support member configured to support the gear, and a reduction gear case to which rotational force of the gear is transmitted; and

an interposition member interposed between the drive motor and the first member, wherein

the drive motor is fixed to the interposition member with a plurality of motor fixing bolts arranged in a circumferential direction,

the interposition member is fixed to the first member,

the gear support member is fixed to the first member with a plurality of support member fixing bolts arranged in the circumferential direction,

the reduction gear case is fixed to the second member,

the motor fixing bolts and the support member fixing bolts are arranged at positions such that a diameter of the positions where the motor fixing bolts are arranged and a diameter of the positions where the support member fixing bolts are arranged are smaller than an outer diameter of the reduction gear case, wherein the outer diameter of the reduction gear case excludes any flange portion, and

the interposition member has a shape for fixing the motor fixing bolts at positions away from the support member fixing bolts.

2. The structure of the joint according to claim 1 , wherein

the robot includes a base fixed on an installation surface, a pivot base configured to rotate with respect to the base, and an arm configured to turn with respect to the pivot base,

the first member is the pivot base, and the second member is the arm.

3. The structure of the joint according to claim 1 , wherein

the interposition member includes a main body formed in an annular shape and a flange portion through which interposition member fixing bolts configured to fix the interposition member to the first member are inserted,

the first member includes a recess for fixing the interposition member,

the drive motor includes a fitting portion configured to be fit into an inner surface of the interposition member,

the interposition member includes a fitting portion configured to be fit into the recess portion of the first member, and

the fitting portion of the drive motor is fit into the interposition member, and the fitting portion of the interposition member is fit into the recess of the first member such that a rotary axis of the input shaft of the reduction gear and a rotary axis of an output shaft of the drive motor are coaxially arranged.

4. The structure of the joint according to claim 3 , wherein

the interposition member includes screw holes configured to fix the motor fixing bolts,

the screw holes are formed in a cylindrical region having a diameter equal to an outer diameter of the fitting portion of the interposition member and extending along a rotary axis of the drive motor.

5. The structure of the joint according to claim 1 , wherein

the reduction gear case is fixed to the second member with a member fixing bolt, and

the member fixing bolt is fixed in a direction from the first member toward the second member.