Reducer-integrated motor using simultaneous engagement of gear pairs with small and no differences in teeth number

Abstract

The motors for industrial robots and transporting robots require high-precision positioning, large torque output, and downsizing. However, conventional motors have difficulties in downsizing or supporting large torque. In this research, we propose a novel reducer-integrated motor to solve the problems of existing motors. The proposed reducer-integrated motor has a differential gear mechanism using the simultaneous engagement of two kinds of external and internal gear pairs: one with a small difference in teeth number and the other with no difference in teeth number. Inside the reducer, linear actuators are installed. Two gear pairs with no difference in teeth number are fixed on the base and the gear pair with a small difference in teeth number is set between them. When the linear actuators revolve the external gear, the two kinds of the gear pairs engage simultaneously and the internal gear of the gear pair with a small difference in teeth number outputs the rotation. It is thought that the structure of the proposed motor can realize downsizing of the entire motor system, high load-supporting capacity, and high stiffness. In this paper, the structure and movement of the proposed motor are explained. The geometrical conditions for simultaneous engagement of the two gear pairs with small and no differences in teeth number are clarified. Through the discussion on the solution satisfying the conditions and the relation with the bending strength, a design method for the reducer of this motor is proposed. An experiment conducted on a prototype verifies that the proposed motor works as expected.