Internal supporting type expansion shaft

The utility model relates to the technical field of expansion shafts, and discloses an inner supporting type expansion shaft which comprises a mandrel sleeve, a lead screw is rotationally connected to the center position between the inner walls of the mandrel sleeve, a ball screw sleeve is arranged in the middle position of the outer wall of the circumference of the lead screw, and a lead screw female seat is arranged on the outer side of the circumference of the ball screw sleeve. A light source installation base is fixedly installed at the bottom of the mandrel sleeve, three grooves are distributed in the bottom between the inner wall and the outer wall of the mandrel sleeve in a circumferential array mode, and clamping jaws are fixedly installed on the inner walls of the grooves. And the low-voltage direct-current servo motor is matched with the speed reducer, the requirement for clamping workpieces in a 5-150 kg scene is met, meanwhile, the requirement for clamping workpieces does not depend on alternatin