JP2009169102A5 - - Google Patents

Description

Lens frame moving device using lead screw

The present invention relates to a mechanism for preventing vibration of a lead screw from being transmitted to a lens frame in a lens frame moving device using a lead screw.

In recent years, interchangeable lenses for video cameras, compact digital cameras, and digital cameras have been improved in performance and space saving. In particular, many compact digital cameras have a collapsible mechanism that houses a lens barrel in the camera body except during shooting. A lead screw is used as a means for operating this mechanism.

Also, in order to perform zoom adjustment and focal length adjustment at the time of shooting, a lens frame moving mechanism is adopted that moves the lens frame in the lens barrel in the optical axis direction using a lead screw and performs these adjustments with high accuracy. Yes.

The lead screw is rotated by the rotation of the motor output shaft, and the lens frame screwed to the lead screw is moved in parallel to the optical axis direction. When this lead screw is rotated, the lead screw may vibrate. Due to this vibration, the lens frame screwed to the lead screw vibrates or rattles, and the center of the lens frame is displaced or tilted with respect to the optical axis, which may cause image blurring. Also, abnormal noise may occur when the lens frame moves due to these vibrations and rattling. In order to prevent the vibration of the lead screw during rotation from being transmitted to the lens frame, a mechanism for absorbing vibration between the lead screw and the lens frame has been proposed. Specifically, it is disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 7-325242).
JP 7-325242 A

Patent Document 1 discloses that a lead screw and a lens frame are engaged with each other by a connecting nut. The connecting nut is composed of a nut portion, a loose fitting hole and a connecting claw portion, the nut portion is screwed into the lead screw, the guide shaft is loosely fitted into the loose fitting hole, and the connecting claw portion is a mirror. The frame is elastically engaged. By adopting these structures, vibration generated when the lead screw rotates is absorbed by the connecting nut so that it is not transmitted to the lens frame.

However, providing the coupling claw portion in the nut portion and providing the loose fitting hole in the lens frame increases the number of components, resulting in poor assemblability and increased component costs. Furthermore, there are many parts, so it does not lead to space saving.

The present invention has been made to solve the above problems, and the first invention has a motor, a lead screw disposed in the motor, a guide shaft, and an elastic member, and includes a plurality of lens groups. In the lens barrel moving device disposed in the lens barrel having the first lens frame, the first lens frame that holds the first lens group and the second mirror that holds the second lens group among the plurality of lens groups. A frame, an elastic member disposed between the first lens frame and the second lens frame, a motor disposed on the first lens frame, and the second lens frame. While the nut screwed into the lead screw and one or more of the first lens frame or the second lens frame enabling the second lens frame to slide parallel to the optical axis. The second lens frame has a nut holding portion for holding the nut. The lead screw is loosely fitted to the second lens frame, the second lens frame is urged in the optical axis direction by the elastic member, and the nut holds the nut holding portion when the lead screw vibrates. The lens frame moving device is characterized in that it is slidably held on a plane substantially orthogonal to the optical axis, and the nut holding portion is disposed substantially perpendicular to the optical axis.

Further, the second invention is characterized in that the shape of the nut is such that when the nut slides, at least two corner portions of the nut can slide substantially in contact with the inner wall of the nut holding portion. The lens barrel moving device according to claim 1.

If the lens frame moving device of the present invention is used, the nut held by the lens frame slides on the contact surface between the nut and the lens frame when the lead screw rotates. It is possible to suppress the looseness that occurs during the rotation and reversal. It is also possible to move the lens frame quietly by suppressing vibration and backlash. In addition, it is possible to suppress the positional deviation of the optical axis caused by the installation error of the lead screw. Furthermore, since the number of parts is small, the lens barrel is easy to assemble, leading to space saving. Since the structure of the lens barrel is also simplified, there are few failures and can be easily repaired in the event of a failure.

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a lens barrel moving device according to the first embodiment. FIG. 2 is a view of the lens barrel moving device according to the first embodiment when viewed from the M direction toward the second lens barrel. FIG. 3 is a cross-sectional view of the periphery of the motor of the lens barrel moving device according to the first embodiment. FIG. 4 is an enlarged view of the second lens frame holding the nut in the first embodiment. FIG. 5 is a diagram when the lead screw vibrates in the first embodiment. FIG. 6 is a diagram when the lead screw vibrates in the second embodiment.

Example 1
As shown in FIG. 1, the first lens frame 1 is provided with a lead screw 1c, a guide shaft A5, a spring 2, a spring receiving portion 1a, and a motor 1b.

As shown in FIGS. 1 and 2, the second lens frame 3 is provided with a nut 3a, a nut holding portion 3b, a guide shaft A5, a guide shaft B6, and a lens 3c of the second lens frame.

As shown in FIG. 3, a motor 1 b is attached to the N direction side of the first lens frame 1, and a lead screw 1 c extending from the motor 1 b is substantially parallel to the optical axis L and the lead screw of the second lens frame 3 . The loose fitting hole 3d is loosely fitted and protrudes to the M direction side of the second lens frame 3.

As shown in FIGS. 1 and 2, the guide shaft A5 and the guide shaft B6 are fixed to the first lens frame 1 so as to be substantially parallel to the optical axis L.

Since the spring 2 is provided on the guide shaft A5 and the spring 2 is biased in the M direction and the N direction, when the second lens frame 3 is attached, the second lens frame 3 is moved to the nut 3a. Is pressed. Further, since the first lens frame 1 is biased in the N direction and the second lens frame 3 is biased in the M direction by the biasing force of the spring 2 in both the M and N directions, rattling of both lens frames is prevented. ing.

The two guide shafts are slidably inserted through holes provided in the second lens frame 3, and the lead screw 1c is rotated by the rotation of the motor 1b and held in the nut holding portion 3b. Screwed onto the nut 3a. Accordingly, the second lens frame 3 can be moved in the M direction and the N direction according to the rotation direction of the motor 1b.

As shown in FIG. 4, when the lead screw 1c is not rotating, the nut 3a is stationary. The shape of the nut 3a is substantially quadrangular, and the central part of each side is substantially concave, and the corners A7 and B8 are substantially arcuate and project. The bottom surface of the nut holding portion 3b is provided substantially perpendicular to the optical axis. The nut 3a is held while the corners A7 and B8 of the nut are substantially in contact with the inner wall of the nut holding part 3b.

FIG. 5 shows the state of the nut 3a when the lead screw 1c vibrates. The axis of the lead screw 1c is represented by a triangular mark, and the locus of the axis when the lead screw 1c vibrates is indicated by a broken line. The shape of the broken line is substantially circular.

The lead screw 1 c is loosely fitted to the second lens frame 3. Since the diameter of the lead screw loose fitting hole 3d of the second lens frame 3 is larger than the range in which the lead screw 1c vibrates, the second lens frame 3 and the lead screw 1c do not contact each other. Thereby, vibration is not transmitted to the second lens frame 3.

When the lead screw 1c rotates, the corner A7 and the corner B8 of the nut 3a are held on the inner wall of the nut holding portion 3b, so that the nut 3a is idled in the rotation direction of the lead screw 1c in the nut holding portion 3b. The lead screw 1c is screwed into the nut 3a.

The bottom surface of the nut 3a slides within the nut holding portion 3b. When the lead screw 1c vibrates when rotating in the R direction, the corner portion A7 of the nut 3a slides in the P direction along the inner wall of the nut holding portion 3b and the corner portion B8 moves in the Q direction as the bottom surface of the nut 3a slides. To slide. Vibration is absorbed by the movement of the nut 3 a and is not transmitted to the second lens frame 3. When the lead screw 1c rotates and vibrates in the S direction, the corner A7 slides in the Q direction, and the corner B8 slides in the P direction to obtain the same effect. Since the vibration is absorbed by the nut 3a, the center of the second lens frame 3 is not displaced from the optical axis L, and the accuracy of the optical axis L is maintained.

(Example 2)
As shown in FIG. 6, the shape of the nut 11 is a triangular shape having a substantially Reuleaux. The corner portion C9 and the corner portion D10 are slidably held on the inner wall of the nut holding portion 3b. Also in this case, as in the first embodiment, when the lead screw 1c vibrates when rotating in the R direction, the corner portion C9 of the nut 11 slides in the P direction along the inner wall of the nut holding portion 3b as the bottom surface of the nut 11 slides. The corner D10 slides in the Q direction. When the lead screw 1c rotates in the S direction, the corner C9 slides in the Q direction and the corner D10 slides in the P direction. As in the first embodiment, the movement of the nut 11 absorbs the vibration of the lead screw 1c by the nut 11, preventing the vibration from being transmitted to the second lens frame, and maintaining the accuracy of the optical axis L.

The shape of the nut and nut holding part in the present invention is not limited to the embodiment. The bottom of the nut is slidably held without rattling when the lead screw 1c rotates. When the lead screw 1c vibrates, the corner of the nut becomes slidable within the nut holding portion, so that the nut absorbs vibration. Any shape that can move is possible. Further, the shape and arrangement of the elastic member are not limited as long as the elastic members bias the lens frames in the optical axis direction.

Further, the arrangement positions of the nut holding portion, the motor and the guide shaft are not limited to the present embodiment. The lens frame in which the motor and the guide shaft are arranged may be either the first lens frame or the second lens frame. The motor and the guide shaft are not necessarily arranged in the same lens frame. The nut holding part may be absent from the lens frame in which the motor is disposed.

FIG. 1 is a perspective view of a lens barrel moving device according to the first embodiment. FIG. 2 is a view of the lens barrel moving device according to the first embodiment when viewed from the M direction toward the second lens barrel. FIG. 3 is a cross-sectional view of the periphery of the motor of the lens barrel moving device according to the first embodiment. FIG. 4 is an enlarged view of the second lens frame holding the nut in the first embodiment. FIG. 5 is a diagram when the lead screw vibrates in the first embodiment. FIG. 6 is a diagram when the lead screw vibrates in the second embodiment.

DESCRIPTION OF SYMBOLS 1 1st lens frame 1a Spring receiving part 1b Motor 1c Lead screw 2 Spring 3 2nd lens frame 3a Nut 3b Nut holding | maintenance part 3c Lens of 2nd lens frame
3d Free screw hole 4 Optical axis 5 Guide shaft A
6 Guide shaft B
7 Corner A
8 Corner B
9 Corner C
10 Corner D
11 Nut

Claims (1)

Motor, wherein the motor is disposed a lead screw, a nut screwed to the lead screw, the guide shaft, elastic member, and, a disposed a lens frame moving device to the lens barrel having a plurality of lens groups ,
Of the plurality of lens groups, a first lens group is held by a first lens frame, a second lens group is held by a second lens frame,
The elastic member is disposed between the first lens frame and the second lens frame;
The elastic member biases the second lens frame in the optical axis direction ,
The motor is disposed in the first lens frame;
The nut is screwed into the lead screw while being in close contact with the second lens frame,
One or more guide shafts that allow the second lens frame to slide parallel to the optical axis are fixed to either the first lens frame or the second lens frame,
The lead screw is loosely fitted into the second lens frame;
The second lens frame is provided with a nut holding portion for holding the nut substantially perpendicular to the optical axis,
When the lead screw rotates with the rotation of the motor and the lead screw vibrates,
The lens frame moving device, wherein the nut is held by the nut holding portion so as to be freely slidable on a plane substantially perpendicular to the optical axis .