Lens drive system
AssigneePENTAX Corporation
InventorYoshihiro Yamazaki
Life of this patent
Estimating the term…
Abstract
A lens drive system includes a lens frame having a lens element; a nut member secured to the lens frame; a feed screw shaft having a male thread portion and a non-threaded portion, the male thread portion engaged with a screw hole of the nut member; an engagement portion formed on the nut member and having a deformable screw-engaging portion engaged with the male thread portion; and a motor for rotating the feed screw shaft. The screw-engaging portion is disengaged from the male thread portion when a large force is applied to the engagement portion in an axial direction. When the linear movement of the lens frame and the nut member is restricted during rotation of the feed screw shaft, the engagement portion remains on the male thread portion of the feed screw shaft while the female thread portion is moved onto the non-thread portion.
Claims14
A lens drive system comprising:
- a lens frame having at least one lens element;
- a nut member which is secured to said lens frame, said lens frame and said nut member being movable in an optical axis direction without rotating relative to a base of said lens drive system, the direction of a screw hole of said nut member being parallel with the optical axis;
- a feed screw shaft having a male thread portion and a non-threaded portion, said male thread portion being engaged with said screw hole of said nut member so that said male thread portion is engaged with a female thread portion formed on an inner peripheral surface of said screw hole, a diameter of said non-threaded portion being smaller than an inner diameter of said screw hole;
- an engagement portion formed on said nut member, said engagement portion having at least one deformable screw-engaging portion which is engaged with said male thread portion;
- and
- a motor for rotating said feed screw shaft;
- wherein said engagement portion is forced by rotation of said feed screw shaft to move in an axial direction of said feed screw shaft;
- wherein said screw-engaging portion is disengaged from said male thread portion so that said male thread portion idles with respect to said engagement portion when a force greater than a predetermined value is applied to said engagement portion via said rotation of said feed screw shaft in said axial direction thereof;
- and
- wherein, when the linear movement of said lens frame and said nut member is restricted during the rotation of said feed screw shaft to move said nut member and said lens frame in a direction from said male thread portion toward said non-thread portion, said engagement portion of said nut member remains on said male thread portion of said feed screw shaft while said female thread portion of said nut member is disengaged from said male thread portion of said feed screw shaft to move onto said non-thread portion of said feed screw shaft.
Dependencies are inferred from the claim text.