JPH0743580A - Lens drive - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a lens driving device which prevents tooth jumping with a lead screw when an impact is applied to a lens barrel. According to the present invention, in a lens driving device in which a lens is moved in the optical axis direction of a lens barrel by a lead screw, a lens holding frame that holds the lens and is movable in the optical axis direction, A rack having a tooth-shaped portion having a lead that is fixed to the lens holding frame and meshes with the lead screw, the rack does not always completely mesh with the lead screw, and impacts the lens barrel. Has a lead extension portion that meshes with the lead screw and prevents tooth jumping with the lead screw.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens driving device in optical equipment such as a camera.

[0002]

2. Description of the Related Art Generally, in a lens driving device, a lead screw is provided as a member for converting a rotational force of a step motor into a movement of a lens in an optical axis direction. This lead screw may cause tooth skipping of the lead screw when an impact is applied to the lens barrel.

In order to prevent the lead screw from jumping, a conventional lens driving device is provided with a tooth profile in which the lead screw is sandwiched between the teeth which are in constant contact with the lead screw and which has no lead in the facing direction. It is designed to prevent the lead screw from jumping.

Further, in such a conventional lens driving device, the step motor for driving the lead screw is screwed to the lens barrel by two positioning pins, and the yoke of the step motor is also screwed when attached to the holding member. It was a thing.

However, in the above-mentioned conventional example, as a measure to prevent tooth jumping of the lead screw, a tooth profile having no lead in the facing direction with the lead screw sandwiched is provided for the tooth which is always in contact with the lead screw. Therefore, there is a problem of noise and malfunction of driving the lead screw.

In order to solve this problem, it is conceivable to provide a tooth profile in which the lead screw is sandwiched between the teeth that are in constant contact with the lead screw, and the leads face each other. Since it is not possible to remove the mold in the opposite direction, it is not possible to provide such a tooth profile for slip prevention, it is difficult to obtain parallelism between the lead screw and the optical axis, and the yoke of the step motor is held by a holding plate. There was a problem that it took a long time to assemble because the screws were also used when attaching to.

An object of the present invention is to solve the above-mentioned drawbacks, and to provide a lens driving device which stabilizes the movement of the motor when driving the motor and drives the step motor with high precision. It is a thing.

[0008]

In order to achieve the above object, the present invention is a lens driving device for moving a lens by a lead screw in the optical axis direction of a lens barrel, while holding the lens and A lens holding frame that is movable in the optical axis direction, and a rack that is fixed to the lens holding frame and has a tooth-shaped portion that has a lead that meshes with the lead screw. It does not mesh with the lead screw, but meshes when an impact is applied to the lens barrel, and has a lead extension that prevents tooth jumping with the lead screw, and the lead screw is Two V-shaped portions are provided on the lens barrel for positioning the bearings when the lens barrel is mounted.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is an exploded view of a lens driving device. In FIG. 1, 1 is a lens, 2 is a lens holding frame, and 3 is a lens holding frame.
Is a sleeve fixed to the lens holding frame 2, 3a is a bar inserted through the sleeve 3, and the bar 3a guides the lens holding frame 2 in the optical axis direction. Reference numeral 4 is a bar for preventing the lens holding frame 2 from rotating around the bar 3a. Reference numeral 5 is a lens barrel.
One end of is held. Reference numeral 6 denotes a fixed plate incorporated in the end portion of the lens barrel 5, and the fixed plate 6 holds the other ends of the bars 3a and 4. Reference numeral 7 is a holding plate of the step motor M for moving the lens holding frame 2 in the optical axis direction.

As shown in FIG. 2, the step motor M comprises a rotor 8 having a lead screw portion 8a and a magnet 8b, and a yoke 9 having a coil and a conductive terminal. Further, as shown in FIG. 2, the holding plate 7 has a bayonet portion 7 into which an elastic claw portion 7a engaging with the lens barrel 5 and a yoke 9 are fitted.
b, contact portion 7c with lens barrel 5, hole 7d for bearing 10
have. To assemble the step motor M, the shaft 10a of the bearing 10 is inserted into the hole 7d of the holding plate 7, and the tip of the lead screw portion 8a of the rotor 8 is attached to the bayonet portion 7b.
Insert the lead screw 8a into the bearing 1
0 is contacted via a bearing, the yoke 9 is fitted to the bayonet portion 7b, and the step motor M is fixed to the holding plate 7. As shown in FIG. 1, the lens barrel 5 is provided with a mounting portion 20 of the holding plate 7 to which the step motor M is fixed. The mounting portion 20 has a first V-shaped portion 20a for receiving the shaft 10a of the bearing 10. The second V-shaped portion 20b for receiving the contact portion 7 and the engaging portion 20c with which the elastic claw portion 7a is engaged.
The holding plate 7 having the step motor M fixed thereto is mounted on the mounting portion 20, and the claw portion 7a is engaged with the engaging portion 20c.
The step motor M is fixed to the lens barrel 5. In FIG. 1, 11 is a rack attached to the sleeve 3 and transmitting the driving force from the rotor 8, and 12 is a rack 11 on the sleeve 3.
It is a rack spring that removes the thrust play that occurs when the is attached.

As shown in FIGS. 3 and 4, the rack 11 is a tooth-shaped portion 1 having leads that mesh with the lead screw portion 8a.
1a, and the rack 11 has a lead extension portion 11b which is not completely meshed with the lead screw portion 8a at all times and is separated by α shown in FIG. The lead extension portion 11b meshes with the lead screw portion 8a when an impact is applied to the lens barrel 5, and the lead screw portion 8a
This is to prevent tooth skipping with a. Also, the rack 11
Has a pressing piece 11c facing the toothed portion 11a. The pressing piece 11c is pressed by the rack spring 12 shown in FIG. The portion of the rack 11 that comes into contact with the lead screw portion 8a is a tooth-shaped portion 11a and a pressing piece 11c that is pressed by the rack spring 12, and when the rotor 8 rotates, the lead screw portion 8a and the tooth-shaped portion are formed. The rack 11 is driven in the optical axis direction without rattling by meshing with the portion 11a.

When the lead screw portion 8a is fitted between the tooth-shaped portion 11a of the rack 11 and the pressing piece 11c, the claw portion 7a of the holding plate 7 is engaged with the engaging portion 20 of the mounting portion 20.
This is performed when the step motor M is engaged with c and the step motor M is fixed to the lens barrel 5.

As a result, the rack 11, the sleeve 3 and the lens holding frame 2 are driven by the step motor M as shown in FIG.
As shown in FIG. 5, it is configured to be driven in the optical axis direction without play.

That is, when the step motor M is driven, the rotor 8 is rotated to rotate the lead screw portion 8a, and the rack 11 engaged with the lead screw portion 8a and the tooth profile 11a is driven. Is
The lens holding frame 2 is moved in the optical axis direction together with the lens 1 via the sleeve 3. At this time, the rack 11 uses the rack spring 12 to move the tooth-shaped portion 11a to the lead screw portion 8a.
The lens holding frame 2 is engaged so that the lens holding frame 2
Is driven without play in the optical axis direction.

Even when some impact is applied to the lens barrel 5 and tooth jumping between the tooth-shaped portion 11a and the lead screw portion 8a is likely to occur, the rack spring 12 pushes the pressing piece 11c, and the lead screw 11c is pressed. It is possible to prevent tooth jumping between the tooth-shaped portion 11a and the lead screw portion 8a due to the meshing of the lead extension portion 11b with the portion 8a with the space α.

[0017]

As described in detail above, according to the present invention, in a lens driving device for moving a lens in the optical axis direction of a lens barrel by a lead screw, the lens is held and the lens is moved along the optical axis. A lens holding frame that is movable in any direction, and a rack that has a toothed portion that is fixed to the lens holding frame and that has leads that mesh with the lead screw, and that the rack is always completely the lead screw. Does not mesh, but meshes when an impact is applied to the lens barrel, preventing tooth jumping with the lead screw, and as a positioning of the bearing when attaching the lead screw to the lens barrel, 2 By equipping the lens barrel with a V-shaped portion, the parallelism between the lead screw and the lens barrel can be maintained, and the step can be maintained. Since the holding plate with the motor is provided with the claw that elastically engages the lens barrel, the step motor can be assembled to the lens barrel without the need for screws. It is possible.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a lens driving device showing an embodiment of the present invention.

FIG. 2 is an exploded perspective view of a step motor and a holding plate 7 shown in FIG.

3 is an enlarged front view showing the rack shown in FIG. 1. FIG.

FIG. 4 is a perspective view of the rack shown in FIG.

5 is a vertical cross section of the lens driving device shown in FIG. 1. FIG.

6 is a cross-sectional view of the lens driving device shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 lens 2 lens holding frame 3 sleeve 5 lens barrel 7 holding plate 7a claw portion 8a lead screw portion 10 bearing 11 rack 11a toothed portion 12 rack spring 20 mounting portion 20a, 20b V-shaped portion

Claims (4)

[Claims] 1. A lens driving device for moving a lens by a lead screw in an optical axis direction of a lens barrel, and a lens holding frame which holds the lens and is movable in the optical axis direction, and the lens. A rack having a tooth-shaped portion having a lead that is fixed to a holding frame and meshes with the lead screw, and the rack is not always completely meshed with the lead screw, and an impact is applied to the lens barrel. A lens driving device comprising: a lead extension portion that meshes with each other when being twisted to prevent tooth jumping with the lead screw. 2. The lens according to claim 1, wherein the lens barrel has two V-shaped portions for positioning a bearing when the lead screw is attached to the lens barrel. Drive. 3. The lens driving device according to claim 1, further comprising an urging member that presses the toothed portion having the lead of the rack against the lead screw. 4. The lead screw is attached to a shaft of a rotor that constitutes a step motor, and includes a holding plate portion that holds the rotor portion, a tip bearing portion of the lead screw, and a yoke portion. The lens driving device according to claim 1, further comprising a claw portion that elastically engages with the lens barrel.