Patent ID: 7347115

Claim:
A linear actuator for driving a driven member, comprising: housing; an electric motor attached to said housing; and a power transmission mechanism for transmitting motive power of said electric motor to said driven member, said power transmission mechanism including: a fixing portion; a rotation driving portion so connected to said electric motor as to be capable of transmitting the motive power; a rotation driven portion receiving a rotational force from said rotation drive portion and getting rotationally displaced; a converting mechanism for converting a rotational motion of said rotation driven portion into an axis-line directional motion of a movable member so connected to said driven member as to be capable of transmitting the motive power; and a lock member disposed between said fixing portion and said rotation driven member, wherein when a rotational force is inputted to said rotation driving portion to rotate said rotation driven portion, said lock member is guided to a first position in which there decreases a frictional force with said fixing portion and said rotation driven portion, the transmission of the rotational force to said rotation driven portion from said rotation driving portion is thereby permitted, when the rotational force is inputted to said rotation driven portion to rotate said rotation driving portion relatively in one direction, said lock member is guided to a second position in which there increases the frictional force with said fixing portion and said rotation driven portion, the rotation to said rotation driving portion from said rotation driven portion is thereby fixed, and said rotation driven portion receives a force from said driven member so as to rotate in one direction at least in a state where said driven member is driven.