JPH04146404A - Lens driving device - Google Patents

Abstract

PURPOSE:To produce a lens driving device which smoothly transmits the movement of a focus motor to a four group moving frame by setting the sandwiching force of an elastic member elastically sandwiching a screw shaft together with a half nut part, stronger than that of a moving frame elastically sandwiching an arm. CONSTITUTION:The sandwiching force of the elastic member 33 sandwiching the screw shaft 28a together with the nut part 32 is set stronger than the sandwiching force of the sandwiching part 30 which is erected on the four group moving frame 23 and sandwiches the arm 31, so that the half nut part 32 is screwed on the screw shaft 28a without having aggravation. On the other hand, the arm 31 and the sandwiching part 30 are coupled so as to be freely oscillated, and the sandwiching force is weak, so that the uncoincidence of the screw shaft 28b and the optical axis of the four group moving frame can be absorbed on this part. Thus, the rotation of the focus motor 28 is transmitted to the four group moving frame 23 via a nut body 29, and the four group moving frame 23 is smoothly and accurately moved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a lens driving device for a photographing lens for a video camera.

BACKGROUND OF THE INVENTION In recent years, with the spread of video cameras, the demand for photographic lenses has increased rapidly, and the demand for smaller lenses has become stronger.

Accordingly, attempts have been made to reduce the size of the lens barrel that holds the photographic lens and improve its performance, such as stabilizing its operation.

Hereinafter, a conventional lens driving device will be explained with reference to FIGS. 7 and 8.

As shown in the figure, 1 is a lens, which is the main body of a lens barrel, and lenses 2, 3, 4 forming an objective lens group 5 are fixed at predetermined positions on this main body 1. 6 is a spacer between the lenses 3 and 4, and 7 is a holding nut for the objective lens group 6. Reference numeral 8 denotes a third group frame coupled to the main body 1, and a lens 9 is fixed to this third group frame 8. 1o is a guide ball installed between the main body 1 and the third group frame 8;
The lens 12.1314 that constitutes the variable magnification lens group 15 is
A second group moving frame 11 holding a is slidably disposed. A screw shaft 16 is rotatably installed between the main body 1 and the third group frame 8, and is screwed into the second group moving frame 11. When the screw shaft 16 rotates, the 92nd group moving frame 11 is moved to the optical axis. 1
It is possible to move in the direction of 7. 18 is a gear fixed to the screw shaft 16; 19 is a motor to which a gear 19a is fixed; the motor 19 is fixed to the main body 1 so that the gear 19a meshes with the gear portion 18 of the screw shaft 16;
It rotates in response to a control signal, rotates the screw shaft 16, and moves the second group moving frame 11.

Reference numeral 2o denotes an iris section, a portion of which is shown, which performs an aperture operation in response to a control signal. A master flange 21 is fixed to the third group moving frame 8, and a plurality of guide poles 22 are installed between the master flange portion 21 and the fourth group frame 8. Reference numeral 23 denotes a 4-group moving frame that is slidably supported by the guide pole 22. Lenses 24, 25, and 26 constituting the focus lens group 27 are fixed to this 4-group moving frame 23. 2B is a focus motor, which is fixed to the master flange 21. Focus motor 28
A nut body 29 that is slidably guided by a support shaft (not shown) is screwed onto the threaded shaft 28a. The lower end of the nut body 29 is engaged with a retaining portion 23a at the upper end of the fourth group moving frame 23. With this configuration, when the focus motor 28 rotates, the fourth group moving frame 2a moves in the direction of its optical axis via the nut body 29.

Above mentioned main body 1, 3 resolution frame 8. The master flange 21 constitutes the outer frame of the lens barrel.

In the above configuration, the lens barrel detects the displacement of the variable magnification lens group 15 using a position detection means (not shown), and moves the focus lens group 27 to a predetermined position based on the detection signal. It is designed to double the movement and focus.

Problems to be Solved by the Invention In a lens drive device having such a conventional configuration, when the focus motor 28 is attached to the master flange 21, the axis of the screw shaft 28a and the optical axis of the fourth group moving frame 23 do not match. Sometimes. In such a state, the engagement between the nut body 29 and the engaging portion 23a of the fourth group moving frame 23 becomes strained, and as shown in FIG. A force is added.

As a result, the movement of the nut 29 in the direction of arrow A due to the rotation of the shaft 28a of the focus motor 28 causes the movement of the fourth group moving frame 2
3 does not follow smoothly, there is a problem in that the operation of the focus motor 28 is not accurately transmitted to the fourth group moving frame 23, resulting in out-of-focus at startup.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a lens driving device that can smoothly and accurately transmit the movement of a focus motor to the fourth group moving frame 23.

Means for Solving the Problems In order to achieve the above object, the present invention provides a master flange that constitutes a part of the outer frame of a lens barrel for a video camera having a plurality of lenses, and a master flange that forms a part of the outer frame of a lens barrel for a video camera having a plurality of lenses. a guide ball installed in the optical axis direction; a moving frame that is slidably supported by the guide ball and to which a focus lens group is fixed; a focus motor that is fixed to an outer frame of the lens barrel and has a threaded shaft; a nut body that is screwed onto the screw shaft and transmits the rotation of the screw shaft to the sliding motion of the moving frame, and the nut body elastically clamps the screw shaft between a half-split nut portion and an elastic member. and an arm that is elastically clamped by the clamping part of the movable frame, and is slidably supported by a support shaft parallel to the screw shaft. The clamping force of the half-split shaft part is made stronger than the clamping force of the clamping part of the movable body.

Further, a convex surface is formed on either the arm or the clamping part, and the arm is configured to be clamped by the clamping part so as to be swingable.

Effect of the Invention With the above-described configuration, the present invention makes the clamping force of the elastic member that elastically clamps the screw shaft with the half-split nut part stronger than the clamping force of the clamping part of the movable frame that elastically clamps the arm. Additionally, by forming a convex surface on either the arm or the clamping part and holding the arm in the clamping part so that it can swing freely, the axis of the screw shaft and the optical axis of the moving frame can be aligned. Even when the nut is not engaged, the engagement between the nut body and the holding part of the moving frame does not become strained, and the threaded shaft and nut part are securely screwed together by the elastic member, so that the focus motor can be easily operated. can be transmitted smoothly and accurately.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 6. Note that parts that are the same as those shown in the conventional example are given the same reference numerals and their explanations will be omitted.

As shown in FIGS. 1 to 3, the nut body 29 has a half-split nut portion 32 screwed onto the screw shaft 28a at one end thereof, and a half-split nut portion 32 that is brought into elastic contact with the screw shaft 28a. It has an elastic member 33 to clamp it. Also,
An arm 31 is formed at the other end to be elastically held by a holding part 3o provided upright on the fourth group moving frame 23. A convex surface 31a is formed on the clamped surface of the arm 31 so that the arm 31 can swing freely between the clamping parts 3o and the clamping part 3o. Note that this convex surface 31a may be formed on the clamping surface of the clamping part 3o. Nut body 2 formed in this way
9 is slidably supported by a support shaft 28b installed parallel to the screw shaft 28a.

Here, the clamping force of the elastic member 33 which clamps the threaded shaft 28a together with the nut part 32 is greater than the clamping force of the clamping part 30 which clamps the arm 31, which is provided upright on the fourth group moving frame 23.

In the above configuration, when the focus motor 28 rotates, the screw nut body 29 slides on the support shirt l-28b due to the threaded engagement between the screw shaft 28a and the student discount nut part 32, and the arm 31 and the clamping part of the fourth group moving frame 23 3o, the fourth group moving frame 23 is moved in the optical axis direction.

Here, as explained in the conventional example, the focus motor 2
8 when attaching to the master flange 21 (screw shirt)
The axis of 28a and the optical axis of the fourth group moving frame 23 may not coincide with each other.

In this embodiment, in this embodiment, the clamping force of the elastic member 33 which clamps the screw shirt 28a together with the nut part 32 is applied to the clamping force of the clamping part 3o, which is erected on the fourth group moving frame 23 and clamps the arm 31. Since the force is also strong, the half-split υ nut portion 32 is securely screwed onto the threaded shaft 28a without causing twisting as shown in FIGS. On the other hand, the arm 31 and the clamping part 30 are connected to each other so that they can swing freely, and the clamping force is weak. can.

As a result, the rotation i of the focus motor 28 is
9 to the fourth group moving frame 23, and the fourth group moving frame 23 can be moved smoothly and accurately.

Effects of the Invention As is clear from the description of the embodiments above, according to the present invention, the clamping force of the elastic member that elastically clamps the screw shaft with the half-split screw nut part is applied to the movable frame that elastically clamps the arm. In addition, by forming a convex surface on either the arm or the clamping part, and by holding the arm in the clamping part so that it can swing freely, Even when the optical axis of the moving frame does not coincide with the optical axis of the moving frame, the engagement between the Nand body and the holding part of the moving frame will not be distorted, and the threaded shaft can be securely screwed into the nut part by an elastic member. Therefore, it is possible to provide a lens driving device that can smoothly and accurately transmit the operation of the focus motor.

[Brief explanation of the drawing]

1 is a side sectional view of a lens driving device according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1, and FIG. 3 is a side view taken in the direction of arrow A in FIG. Figure 4 is an exploded perspective view of Figure 3;
Figures 5 and 6 are diagrams showing a defective state of threading between the screw shaft and the nut part, Figure 5 is a front view, Figure 6 is a side view, and Figure 7 is a side cross section of a conventional lens drive device. 8 are enlarged side views of the same essential parts. 1... Main body of lens barrel, 5... Objective lens group, 9... Lens, 15... Variable magnification lens group, 1A... ...Optical axis, 21...
Manutar flange, 22...Guide pole, 2
3...4 group moving frame (moving frame), 27...
・Four force lens J28...Forcane motor, 28a...Screw shaft, 28b...
・-Support shaft, 29...nut body, 3o・
...Holding portion, 31...Arm, 31a.
... Convex surface, 32 ... Nut part, 33 ...
...Elastic member. Name of agent: Patent attorney Akira Okaji and two others Focus motor screw shaft support shaft nut body arm 6ii+ But self 1 Wei f! F) 11th part arm convex surface elastic hammering diagram

Claims (1)

[Claims] (1) A master flange that constitutes a part of the outer frame of a lens barrel for a video camera having a plurality of lenses, a guide pole installed in the master flange in the optical axis direction, and a slider on the guide pole. a movable frame that is movably supported and to which a focus lens group is fixed; a focus motor that is fixed to the outer frame of the lens barrel and has a screw shaft; and a focus motor that is screwed to the screw shaft and controls the rotation of the screw shaft. a nut body that transmits the sliding motion of the moving frame, the nut body elastically clamping the screw shaft with a half-split nut part and an elastic member, and a nut part that is screwed to the screw shaft; and an arm that is elastically clamped by the clamping part, and is slidably supported by a support shaft parallel to the screw shaft, and the clamping force of the half-split nut part is applied to the clamping force of the clamping part of the movable body. A lens drive device that is stronger than force. (2) The lens driving device according to claim 1, wherein a convex surface is formed on either the arm or the clamping part, and the arm is clamped by the clamping part so as to be swingable.