Mechanical arm joint

The utility model discloses a mechanical arm joint and relates to a joint for a mechanical arm structure. The utility model aims to provide the mechanical arm joint which is small in size, light in weight and convenient to construct a safe and light mechanical arm. The mechanical arm joint comprises a harmonic speed reducer and a motor, the motor comprises a motor shaft, a wiring sleeve is arranged in the motor shaft, a connecting plate is arranged on the outer wall of the wiring sleeve, the output end of the harmonic speed reducer is fixedly connected with the connecting plate and the inner side of a torque sensor, and annular sealing grooves are distributed in the connecting plate. The torque sensor is connected with the bearing outer side pressing plate through fine threads; a steel wheel of the harmonic speed reducer is fixedly connected with the motor shell and the bearing seat, and an external connector of the motor shell is a threaded hole distributed in the radial direction. A flexible gear of the har