JPH0996755A - Lens driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens driving device capable of smoothly moving the moving lens frame of a lens barrel by an incorporated driving source without causing vibration and noise, capable of making the cost low with a simple constitution, and capable of making the lens barrel small in size. SOLUTION: As to this lens driving device provided with the moving lens frame 11 holding a lens, a guide 31 guiding the frame 11 in an optical axis direction, a lead screw 10 rotated by the driving source 21 in order to drive the frame 11 in the optical axis direction, and a converting mechanism converting the rotary motion of the screw 10 to rectilinear propagation motion in parallel with the guide 31; when a position where the converting mechanism is brought into press-contact with the screw 10 is projected on a planar surface crossing at a right angle with the shaft of the screw 10, the projected image of the position where the converting mechanism is brought into press-contact with the screw 10 is at least three places.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens barrel having a lens optical system, and more particularly to a lens driving device for the lens barrel.

[0002]

2. Description of the Related Art An autofocus mechanism in a general domestic video camera takes out the contrast of light passing through a photographing optical system from a CCD which is an image pickup device, and moves a focus lens of the optical system so that the contrast value becomes a peak. The method is the most general, but the inner focus optical system, which is advantageous for compactness, is used as the optical system used there. Various methods for driving the focus lens in this optical system have been disclosed, but among them, the method using a lead screw (screw shaft) is the most general.

One example thereof is shown in FIG. 7 (a): central sectional view and (b): front view disclosed in Japanese Patent Laid-Open No. 2-266311. In FIG. 7, a nut 17 is screwed into the lead screw 10 formed on the output shaft of the stepping motor 21 as a conversion mechanism for converting the rotational movement of the lead screw 10 into a linear movement parallel to the optical axis direction. And the bush 12 provided on the movable lens frame 11,
The U groove 121 is engaged with two guide bars 31 and 32 fixed to the lens barrel main body in parallel with the optical axis.

Then, the connecting portion 22 formed on the movable lens frame 11 movable in the optical axis direction is attached to the nut 17
When the lead screw 10 is rotated by the stepping motor 21, the movable lens frame 11 is moved in the optical axis direction by being constantly pressed by the urging force of the spring 19. This spring 19 is a nut 1
7 has a role of eliminating backlash with the lead screw 10.

[0005] As another example, actual Kaihei 2-711.
FIG. 8 (a) disclosed in Japanese Patent Publication No. 55: perspective view, (b):
The front view is shown. In FIG. 8, the guide bar 31, the U-groove 121, and the bush 12 provided on the movable lens frame 11
It is possible to move the movable lens frame 11 in the optical axis direction by rotating the lead screw 10 formed on the output shaft of the stepping motor 21 by combining 32 in the optical axis direction. Is the same as the conventional example.

Then, what is screwed into the lead screw 10 is not a nut but a meshing member 18 as shown in the figure.
In addition, a clamper made of a spring 19 for constantly engaging the lead screw 10 with each other is provided with rigidity in a direction parallel to a plane including the optical axis and the axis of the lead screw 10 at the same time. It is known that the screw 10 is connected to the movable lens frame 11 with a soft connecting member 20 (for example, a leaf spring) in a direction orthogonal to a plane including the axis of the screw 10 at the same time.

[0007]

In the first prior art example described above, when the nut 17 is screwed onto the lead screw 10, the lead screw 10 must be screwed from the tip of the lead screw 10 to a predetermined position. It takes time to assemble. Further, at the time of completion, the tip end of the lead screw 10 is supported by the pivot bearing 23 as shown in the figure, so that the nut 17 cannot be removed from the completed product unless it is disassembled. Further, due to the action of the spring 19, there is a problem that the driving torque required for the stepping motor 21 changes depending on the lens position.

Further, in the second conventional example, the clamper is free in the direction perpendicular to the axis of the lead screw 10. Therefore, the lead screw 10 can be freely attached and detached at any position. Although there is no such inconvenience, the lead screw 10 is placed on the optical axis (guide bar 31
(2) If they are not strictly parallel, a torsional force will act on the leaf spring 20 that is a connecting member and the drive resistance will increase rapidly. It is necessary to select a certain stepping motor 21, which causes a problem of an increase in size of the camera and vibration and noise due to the stepping motor 21.

The present invention has been made to solve the above problems. In other words, the drive source that incorporates the moving lens frame of the lens barrel enables the lens barrel to be moved smoothly without generating vibration or noise, has a simple structure, is low in cost, and can be downsized. It is an object of the present invention to provide a lens driving device.

[0010]

The object of the present invention is achieved by adopting the following constitution.

That is, in the lens driving device, a moving lens frame holding the lens, a guide member for guiding the moving lens frame in the optical axis direction, and a lead screw for moving the moving lens frame in the optical axis direction. And a drive unit for rotating the lead screw, and a carriage unit for converting rotational movement of the lead screw by the drive source into linear movement in a direction parallel to the guide member. A lens driving device characterized in that, when the pressure contact point between the carriage portion and the lead screw is projected onto a plane orthogonal to the rotation axis of the lead screw, the projected images of the pressure contact point are at least three points.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described with reference to the accompanying drawings, FIGS. 1 to 6 and 9. However, the present invention is not limited to the embodiment described below.

First, an embodiment of the present invention will be described in detail with reference to FIGS. 1, 2 and 3.

FIG. 1 is a schematic perspective view of the whole. 2A and 2B are views showing a carriage portion that engages with the lead screw of the main portion of the present invention, where FIG. 2A is a front view and FIG. 2B is a right side view.
(C) is a sectional view taken along the line EE of (b), and (d) is a sectional view taken along the line EE of (b) when the lead screw is included. 3A and 3B are views of a connecting portion that connects the carriage portion to the movable lens frame of the main portion of the present invention, FIG. 3A is a right side view when the carriage portion is reversed, and FIG. 3B is a rear view of the same carriage portion. , (C) is a left side view of the connecting portion of the movable lens frame, (d)
[Fig. 3] is a front view of the connecting portion.

In FIGS. 1 and 2, the movable lens frame 11
Are held movably in the optical axis direction by guide bars 31 and 32 which are guide members for guiding the movable lens frame 11 in the optical axis direction. The carriage unit 40 is connected to the lead screw 10 that is integrated with the output shaft of the stepping motor 21 that is the drive source.
By coupling 0 to the moving lens frame 11, the rotational movement of the lead screw 10 is converted into a rectilinear movement, and the moving lens frame 11 moves on the optical axis.

The lead L of the lead screw 10 means the carriage portion 4 when the lead screw 10 makes one revolution.
Says the distance that 0 moves. In the embodiment, the carriage portion 40 moves by 0.6 mm per one rotation of the lead screw 10. A stepping motor 21 is adopted as a drive source, and in the embodiment, it can be controlled so that δ = 9 ° is rotated per pulse.

As shown in FIG. 2, the carriage portion 40 of the present invention is a connecting member for connecting the carriage screw portions 1a and 1b, the lead screw abutting portions 7a and 7b, the lead screw pressing portion 4 and the movable lens frame 11. Carriage unit connecting legs 5a and 5b, carriage unit rotation stop unit 6 and carriage unit fall-off prevention units 2a, 3a, 2b and 3b are provided. In the present example, the carriage portion 40 is an integrally formed part, but may be a set of individual parts.

The lead screw 1 is attached to the carriage portion 40.
In order to engage 0, the lead screw 10 is pushed in the coupling direction shown in FIG. 2 (d), the carriage drop-out prevention portions 2a, 3a and 2b, 3b are spread, and the lead screw 10 is moved as shown in the figure. 10 is set. At this time, due to the spring property of the lead screw pressing portion 4, the lead screw 10 causes the carriage screw portions 1a and 1b and the lead screw abutting portion 7 to move.
It is pressed down by a and 7b. This means that the carriage unit 40 is pressed against the lead screw 10 at five points of the carriage screw units 1a and 1b, the lead screw abutting units 7a and 7b, and the lead screw pressing unit 4, and the rotational movement of the lead screw 10 is performed by the lens. This constitutes a conversion mechanism for converting into a rectilinear motion parallel to the optical axis.

Then, the positions of the above-mentioned five pressure contact points of the carriage section 40, which are in pressure contact with the outer surface of the lead screw 10, are
When projected on a plane orthogonal to the axis of the lead screw 10, there are at least three projected images P1, P2, P3. As shown in FIG. 6, the angle (α, β, γ) formed by two adjacent portions of the three portions is less than 180 °. For this reason, the carriage portion 40 forms the lead screw 10 as a rotation support centering on the shaft, smoothes the rotation of the lead screw 10, and has the same effect as a conventional nut. Further, since the carriage screw portions 1a and 1b are pressed against the lead screw 10 by the lead screw pressing portion 4, the carriage portion 40 is in a state in which the backlash with the lead screw 10 is also erased.

The advantages of the case where there are three projected images of the pressure contact point will be described. When there are two projected images of the pressure contact portion, the carriage portion 40 cannot be held by only that, so it is necessary to install a holding function of the carriage portion 40. When the holding function is installed on the side of the lens frame (moving lens frame), for example, when considering the configuration of the conventional example shown in FIG. 9 (Japanese Patent Publication No. 7-27099), the guide bar 3 of the carriage unit 40 is considered.
Although the sliding portion 121 is provided as a holding function for No. 1, if the clearance with the guide bar 31 is large, the backlash due to the inclination of the carriage portion 40 becomes large, so that component accuracy is required. Further, it is necessary to have the same axial accuracy as the through holes of both sliding parts 121. If this same axial accuracy is not obtained, the sliding resistance when the carriage part 40 moves the guide bar 31 becomes a load of the motor 211, which is not good. .

Further, the carriage portion drop-off preventing portions 2a, 3a and 2b, 3b are provided to prevent the carriage portion 40 from falling off from the lead screw 10 due to vibration impact or the like.
When the carriage is properly set, the carriage stoppers 2a, 3a, 2b and 3b have a slight clearance with respect to the lead screw 10.

As described above, in the carriage section 40, the lead screw 10 is moved by the lead screw pressing section 4.
Although it is held down by points, the pressure should be kept to the minimum necessary, and the pressure higher than necessary is the lead screw 10.
Driving torque is increased, which is not desirable. That is, the lead screw pressing portion 4 is not tasked with preventing the carriage portion 40 from coming off from the lead screw 10 due to vibration impact or the like. Therefore, if the present invention is used only in an extremely static state, the carriage drop-out prevention portions 2a, 3a, 2b, 3b may be omitted.

According to this configuration of the present invention, the above-mentioned first
Unlike the conventional example, it is not necessary to screw the nut 17 into the lead screw 10 from the tip thereof, and the lead screw 10 can be quickly set at the desired position in the lateral direction. Further, in this set state, the carriage portion 40 is in a state in which the backlash has been eliminated by the effect of the lead screw pressing portion 4 as described above, and the carriage portion 40 is then attached to the moving lens frame 11. Should be connected. A detailed view of the connecting portion is shown in FIG.

In FIG. 3, connecting locking portions 13a and 13b provided on the bush 12 which is a part of the movable lens frame 11.
The carriage connecting legs 5a and 5b may be inserted in the same, and at the same time, the carriage rotation stopping part 6 may be inserted into the rotation locking parts 14a and 14b also provided in the bush 12.
The dimension A is set to be slightly longer than the dimension B, and the carriage connecting legs 5a and 5b are elastically deformed and set in the optical axis direction at the time of insertion. Axial direction (guide bars 31, 32
There is no play in the axial direction). Further, the dimension C is set to be slightly smaller than the dimension D, and even after the carriage portion rotation stopping portion 6 is inserted into the rotation locking portions 14a and 14b, the carriage portion 40 serves only as a rotation stopper, and thus the carriage portion 40 does not rotate. The bush 12 is designed so that it will not be forced.

This is a point different from the above-mentioned second conventional example. In the second conventional example, first, the clamper composed of the meshing body 18 and the leaf spring 19 is connected by the movable lens frame 11 and the connecting member 20. After that, the lead screw 10 is engaged with the clamper in the order of assembling. However, since the connecting member 20 between the moving lens frame 11 and the clamper is a leaf spring, the lead screw 10 and the guide bars 31, 32 are not connected to each other. If not strictly parallel, the leaf spring which is the connecting member 20 is twisted and a large force is applied to the clamper and the bush 12 to increase the driving resistance. However, in the case of the configuration of the present invention, the direction of the optical axis (guide bar) is increased. 31,
There is no restraint element other than the (32 axis direction), and the drive resistance does not increase even if the parallelism between the lead screw 10 and the guide bars 31 and 32 is slightly different. Therefore, the movable lens frame 11 moves smoothly without backlash and without generating vibration or noise.

Next, as shown in FIG. 3, the carriage connecting legs 5a and 5b and the connecting locking portion 1 provided on the movable lens frame.
The clearance with 3a and 13b is described.

As described above, the carriage connecting leg 5
a and 5b are elastically deformed in the direction of the optical axis so that the connection locking portion 13
a, 13b, wherein the carriage connecting legs 5a, 5b are not elastically deformed, and the connecting locking portions 13a, 13b form a clearance a satisfying the following formula in the optical axis direction. In the case where they are detachably engaged, the following advantages are obtained.

If the clearance is not provided, the carriage 40 vibrates due to the rotation of the lead screw, whereas if the clearance is provided, this vibration is difficult to be directly transmitted to the moving lens frame, and the image due to the vibration of the moving lens frame is generated. Disturbance, noise, and vibration of the entire lens barrel can be prevented. That is, when these problems finally become problems as a product, the carriage connecting legs 5a, 5b
Does not elastically deform and has a clearance with the connecting locking portion 13
It is recommended to set to a and 13b. However, if the clearance is too large, it will rattle and precise control will not be possible.

L: lead of lead screw δ: rotation angle of drive source (stepping motor) in one pulse a <L · δ / 360 ° Further, A of FIG. 3A and B of FIG. 3C. The difference, B−A, corresponds to the clearance a, and in the embodiment, L · δ / 360
= 0.015 mm (15 μm) and the clearance a
Is less than L · δ / 360, taking into account variations, 10
μm or less.

Referring to FIG. 1, in the present invention, the axial direction of the guide bar 31 is the Z axis, and there is almost no effect on the parallel displacement of the lead screw 10 in the Y direction and the rotational displacement of the φ direction. It only slightly affects the parallel displacement in the X direction and the rotational displacement in the θ direction. In the second conventional example, all of these four positional deviations had a great influence on the driving. This requires less process control at the production site and is very advantageous in terms of cost.

The structure of the connecting portion is not limited to this, and there is a method in which the carriage connecting legs 5a and 5b also serve as the carriage rotation stopper 6, as shown in FIG. That is, the coupling locking portions 13a, 13 provided on the bush 12
In place of the rotation locking portions 14a and 14b, the rotation locking portion 1
3c and 13d are provided, and the carriage connecting leg 5
In the example in which the width of a and 5b is the dimension C as shown in (b),
The relationship among the dimensions A, B, C and D is the same as in the first embodiment described with reference to FIGS. Carriage part connecting foot 5a,
It goes without saying that the shape of 5b is not limited to this shape as long as the object is achieved.

As another embodiment, as shown in FIG. 5, the bush 12 is connected to the connecting locking portions 13a, 13 of FIGS.
b, the carriage unit connecting legs 5a, 5 without newly providing the rotation locking units 14a, 14b, 13c, 13d.
As shown in the figure, b is 4 pieces of 5a, 5b, 5c, 5d,
There is also a method in which the inner walls 12a and 12b of the bush 12 are also used as the connection locking portions and the inner walls 12c and 12d of the bush 12 are also used as the rotation locking portions. In this case, the guide bar 31
In the very vicinity of the passage hole portion of the guide bar 31 of the bush 12 where the frictional force between the carriage portion connecting foot portions 5a, 5b,
Since 5c and 5d are to be inserted, the bush 12
Is very effective in reducing the moment of rotation, and it requires considerably less total space.

Further, as can be seen from the above description, in the lens driving device of the present invention, a conversion mechanism for converting the rotational movement of the lead screw 10 into a linear movement parallel to the optical axis (parallel to the guide bars 31, 32). , Moving lens frame 11
Means that when the guide bars 31 and 32 are detached from the movable lens frame 11, it is detachable, which makes it possible to assemble easily and reduce the assembly cost.

[0034]

As described above, according to the present invention, it is possible to smoothly move a lens barrel by using a driving source having a moving lens frame, without backlash, and without generating vibration or noise. Further, it is possible to provide a lens driving device having a simple structure, easy to assemble, and thus low in cost, and further capable of downsizing the lens barrel.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of an entire embodiment according to the present invention.

FIG. 2 is a view of a carriage portion that engages with the lead screw of the main portion of the present invention.

FIG. 3 is a view of a connecting portion for connecting the carriage portion to the moving lens frame of the main portion of the present invention.

FIG. 4 is a diagram of a main part of another embodiment according to the present invention.

FIG. 5 is a diagram of a main part of still another embodiment according to the present invention.

FIG. 6 is a diagram showing projected images of three pressure contact points according to the embodiment of the present invention.

FIG. 7 is a central sectional view and a front view of a conventional example.

FIG. 8 is a perspective view and a front view of another conventional example.

FIG. 9 is a view showing a carriage holding mechanism of still another conventional example.

[Explanation of symbols]

 1a, 1b Carriage part screw part 4 Lead screw pressing part 5a, 5b, 5c, 5d Carriage part connecting foot part 6 Carriage part rotation stopping part 7a, 7b Lead screw abutting part 10 Lead screw 11 Moving lens frame 12 Bushing 12a, 12b , 12c, 12d Inner wall 13a, 13b Connection locking part 13c, 13d, 14a, 14b Rotation locking part 21 Stepping motor 31, 32 Guide bar 40 Carriage part P1, P2, P3 Projected image

Claims (6)

[Claims] 1. In a lens driving device, a moving lens frame holding a lens, a guide member for guiding the moving lens frame in the optical axis direction, and a lead screw for moving the moving lens frame in the optical axis direction. And a drive unit for rotating the lead screw, and a carriage unit for converting rotational movement of the lead screw by the drive source into linear movement in a direction parallel to the guide member. A lens driving device characterized in that, when the pressure contact point between the carriage portion and the lead screw is projected onto a plane orthogonal to the rotation axis of the lead screw, the projected images of the pressure contact point are at least three points. 2. The lens driving device according to claim 1, wherein the angles of the projected images of the two adjoining projected images of the three press-contacted parts are less than 180 degrees. 3. The carriage unit and the movable lens frame are detachably engaged with each other.
The lens driving device according to. 4. The lens driving device according to claim 1, wherein the carriage portion has a connecting member that is elastically deformable in the optical axis direction. 5. The lens driving device according to claim 4, wherein the movable lens frame has a connection locking portion for engaging the connection member. 6. The lens driving device according to claim 5, wherein a clearance a between the connecting member and the connecting locking member satisfies the following expression. a <L · δ / 360 ° where L: lead of the lead screw δ: rotation angle of the drive source per pulse (°)