Patent ID: 7584678
Filing Date: 2009-09-08
Classification: B30B,F16H,Y10S,Y10T

Abstract:
1. A power transmission method for converting a rotational motion of an electric motor into a linear motion, the method comprising the steps of; disposing a feed screw that rotates by an output of the electric motor; disposing a moving case through which the feed screw penetrates in the axis direction, the feed screw being rotatable relatively to the moving case so as to transmit a thrust along the axis direction of the feed screw to a load; disposing a female screw in the moving case, the female screw having an effective diameter that is larger than an effective diameter of the feed screw so as to generate the thrust by engaging with the feed screw in an eccentric manner; disposing a bearing in the moving case for supporting the female screw in a rotatable manner relatively to the moving case, the bearing itself being capable of moving in the axis direction with respect to the moving case; disposing a spring element in the moving case for pressing the female screw via the bearing in the axis direction and for pressing one end surface of the female screw onto the inner surface of the moving case in a no load state; and rotating the feed screw by the electric motor so that the rotation of the feed screw generates the thrust on the female screw and the moving case, and that when a thrust generated on the female screw due to a counterforce received by the moving case from a load becomes larger than a restoring force of the spring element, the female screw moves in the axis direction with respect to the moving case so that one end surface of the female screw separates from the inner surface of the moving case, and that the restraint of relative rotation of the female screw with respect to the moving case is released, and that the feed screw and the female screw rotate in a differential manner to generate the thrust.