JPH03210543A - Lens driving device - Google Patents

Abstract

PURPOSE:To absorb the deviation of parallelism between the guide bar of a moving lens frame and a screw shaft by engaging the spherical part of the moving lens frame with the forked locking part of a nut member to spherically join the frame with the nut member. CONSTITUTION:The lens driving device is provided with a motor 68, the screw shaft 76, the nut member 78 screwed with the screw shaft 76 and provided with the forked locking part 80, the spherical part engaged with the locking part 80 so as to be spherically contacted, and a moving lens 34 to be guided by the guide bar 42. Since the nut member 78 is engaged with the moving lens frame without using a twisted spring and respective faces are spherically joined, the deviation of parallelism between the guide bar of the moving lens frame and the screw shaft can be absorbed. Thus, the lens driving device with the simple construction can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a lens driving device, and more particularly to a focusing lens driving device incorporated in a photographing lens barrel of a video camera or the like.

[Conventional technology]

An autofocus type focus lens is driven by a motor based on an AP signal to focus. In such an autofocus drive mechanism, for example, a motor output shaft is connected to a screw shaft, and a nut member is threaded onto the screw shaft. In such a structure, when the screw shaft tries to rotate, the nut member also tries to rotate at the same time as the screw shaft, so it is necessary to prevent rotation. An example of such rotation restriction is a nut member in which a pin is formed protrudingly from the nut member, and this pin is inserted into a long groove on the main body side to prevent rotation.

On the other hand, if there is play in the joint between the nut member and the lens frame, accurate feeding cannot be achieved. However, if there is no backlash to some extent, positional accuracy such as parallelism between the lens frame and the nut member is required. This becomes more severe as the amount of movement increases. One method is to use a torsion coil spring to shift the looseness to one side, thereby absorbing misalignment between the lens frame and the nut member and allowing accurate feeding.

In such a structure, when the screw shaft rotates, the nut member moves back and forth, and accordingly, the movable lens frame moves back and forth along the guide bar. The nut member and the movable lens frame are engaged with each other with the pin and protrusion in contact with each other, so the screw shaft and
Any deviation in parallelism between the movable lens frame and the guide bar can be absorbed.

[Problem to be solved by the invention]

However, since the conventional lens driving device requires a torsion spring, there is a problem in assembly.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to propose a lens drive device with a simple structure that does not use a torsion spring.

[Means to solve problems]

In order to achieve the above object, the present invention includes a motor, a screw shaft connected to the motor, a nut member screwed onto the screw shaft and provided with a fork-like locking portion, and a screw shaft of the nut member. It is characterized by comprising a movable lens frame that is provided with a spherical part that fits into the forked locking part in spherical contact and is guided by a guide bar.

[Effect]

In the present invention, the spherical portion of the movable lens frame fits into the forked locking portion of the nut member. Therefore, the nut member and the movable lens frame are engaged without using a torsion spring, and since the surfaces are also in spherical contact, it is possible to absorb the deviation in parallelism between the guide bar of the movable lens frame and the screw shaft. Further, the rotation of the nut member is also stopped by the engagement between the forked locking portion and the movable lens frame.

〔Example〕

Preferred embodiments of the lens driving device according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows a zoom lens barrel to which the present invention is applied. In FIG. 1, the fixed barrel 10 includes, from the front, a first fixed lens group 12, a first zoom movable lens group 14, a second zoom movable lens group 16, a focus movable lens group 18,
Five lens groups of the second fixed lens group 20 are arranged.

In addition, an aperture plate 17 is provided at the front of the second zoom movable lens group 16.
is provided.

The first fixed lens group 12 has a lens frame 2 at the front of the fixed barrel 10.
It is fixed via 2. A cam cylinder 24 is rotatably supported inside the center of the fixed cylinder 10.
4 is adapted to receive rotational driving force from a motor (not shown) via a gear 26 provided at its rear end.

The first zoom movable lens group 14 is mounted on a first lens frame 28, and a driven pin 3 is inserted from the top of the first lens frame 28.
0 is provided in a protruding manner, and this driven pin 30 is fitted into a cam groove 32 of the cam cylinder 24. On the other hand, the second zoom movable lens group 16 is attached to a second lens frame 34 , and a driven pin 36 is protruded from the lower part of the second lens frame 34 . It is inserted inside.

A first guide bar 40 is provided at the top of the fixed barrel 10 in the axial direction of the fixed barrel 10, and a second guide bar 42 is further provided at the bottom of the fixed barrel 10.

The front end of the first guide bar 40 is inserted into a hole 46 of a support piece 44 provided at the upper front surface of the fixed cylinder 10 and is supported.
A rear end portion of the first guide bar 40 is inserted into a hole 48 formed in a stepped portion of the fixed cylinder 10 and is supported. Further, the front end of the second guide bar 42 is supported by a hole 52 of a support piece 50 formed at the front lower part of the fixed cylinder lO, and the rear end of the second guide bar 42 is formed at the rear end of the fixed cylinder 10. hole 5
Supported by 4. Support pieces 44.50 of the guide bar 40.42 formed on the fixed cylinder 10 are formed above and below the fixed cylinder 10, as shown in FIG. 2, and form fixed aperture pieces. This prevents unnecessary light from entering and reflection of so-called shiny objects such as the guide bar 40.42 and the driven pin 30.36.

FIG. 3 shows the relationship between the first zoom lens frame 28, the second zoom lens frame 34, and the first and second guide bars 40, 42. That is, the first guide bar 40 is fitted into the guide hole 56 formed at the upper part of the second lens frame 28 and is guided in the front-rear direction, and the steady rest recess 58 formed at the lower part of the second lens frame 34 has a second guide bar 40 fitted therein. 2 guide bar 42 is inserted into the first
The zoom lens frame 28 is stabilized. Therefore, when the cam barrel 24 rotates in this state, the first zoom lens frame 28
will move back and forth while being guided by guide bars 40 and 42. On the other hand, a guide hole 60 is formed in the lower part of the second zoom lens frame 34 , and the second guide bar 42 is fitted into this guide hole 60 .
A steady rest recess 62 is formed in the upper part of the recess 6.
2 has a first guide bar 40 fitted therein. Therefore, if the cam cylinder 24 rotates in this state,! 2 zoom lens frame 3
4 moves back and forth while being guided by guide bars 40 and 42. In this way, the first guide bar 40
It fits into the guide hole 56 of the zoom lens frame 28 to guide the first zoom lens frame 28, and is located in the recess 62 of the second zoom lens frame 34 to prevent the second zoom lens frame 34 from steadying. The second guide bar 42 guides the hole 60 of the second zoom lens frame 34 and also serves as a steady rest for the first zoom lens frame 28, so the number of parts and processing steps are reduced compared to conventional zoom lens barrels. effective.

As shown in FIG. 1, the focus moving lens group 18 is attached to a lens frame 63, and the second guide bar 42 is fitted into a guide hole 64 at the bottom of this lens frame 63. Further, a recess 66 is formed in the upper part of the focus lens frame 63, and the first guide bar 40 is fitted into the recess 66 to prevent the lens frame 63 from steadying. In this way, since the focus lens frame 63 shares the guide bars 40 and 42 of the zoom lens system, it becomes easy to adjust the alignment of the optical axes of the zoom lens system and the focus lens system, and the number of parts is reduced. be.

Next, the drive mechanism of the focus lens will be explained.

As shown in FIG. 4, a pulley 70 is provided on the output shaft of the focus motor 68 attached to the fixed cylinder 1o, a belt 72 is stretched around the pulley 7o, and this belt 72 rotates a pulley 74. A screw shaft 76 is fixed to the pulley 74, and a nut member 78 is screwed onto the screw shaft 76. As shown in FIGS. 5 and 6, the nut member 78 is formed with a pair of forked locking portions 8o.

A pair of elongated holes 82.
82 is formed, and locking pieces 84, 84 are formed to be elastically deformable. This forked locking portion 82 is engaged with a connecting piece 86 that is integral with the focus lens frame 63 shown in FIGS. 5 and 6. That is, the connecting piece 86 is formed from pins 88, 88 on both sides and a spherical piece 90. To attach the connecting piece 86, insert the pin 88.88 into the elongated hole 82.82 between the pair of forked locking parts 80, and insert the spherical piece 90 into the groove between the locking pieces 84.84. insert. The connection structure assembled in this way is shown in No. 51!1.

In such a connection structure, the rotational force from the motor 68 is transmitted to the screw shaft 76, thereby causing the nut member 78 to move back and forth. When the nut member 78 moves back and forth, the nut member 78 and the focus lens frame 63 are connected through a spherical structure.

Therefore, the deviation in parallelism between the screw shaft 76 and the guide bar 40, 42 can be absorbed by this spherical contact portion, and the movement of the nut member 78 is not hindered. Further, since the pins 88.88 are fitted into the elongated holes 82.82, the nut member 78 is prevented from rotating.

FIGS. 7(A) and 7(B) show another embodiment according to the present invention, in which a member 100 integrated with the focus lens frame 63 has a ball 1.
02 is formed. This ball 102 is connected to the nut member 78
It fits into a bifurcated portion 104 that is integrally formed with.

The nut member 780 is prevented from rotating by fitting the pin 106 from the nut member 78 into the long groove 108 of the main body 110.

In this embodiment as well, the deviation in parallelism between the screw shaft 76 and the guide bar 42 can be absorbed by the spherical joint.

8(A) and 8(B) show another embodiment according to the present invention, in which a window 112 is formed in the main body 110. The forked portion 104 of the nut member 78 is located in this window 112 and is prevented from rotating. Other structures are shown in Figures 7 (A) and (B).
) is similar to the structure of the embodiment. That is, the ball 102 and the forked portion 104 of the nut member 78 can absorb the deviation in parallelism between the screw shaft 76 and the guide bar 42.

Behind the focus moving lens 18, a second fixed lens group 20 is fixed to the fixed barrel 10 via a lens frame 79.

As shown in FIG. 1, a low-pass filter 92 is provided at the rear of the fixed cylinder 10, and a CCD 94 is provided behind the low-pass filter 92.

In the lens barrel according to the present invention configured as described above, the zoom lens group 14 is rotated by the rotation of the cam barrel 24.
．． 16 moves as shown by the dashed line in FIG. 1 to perform zooming.

Also, the motor 68 rotates and the focus lens frame 6
3 moves to adjust the focus.

The photographed image light passes through a low-pass filter 92 and enters the CCD 94.
will be imaged.

〔Effect of the invention〕

In the present invention, the spherical part of the movable lens frame fits into the forked locking part of the nut member, and the nut member and the movable lens frame are in spherical contact, so that the movable lens frame can be moved without using a torsion spring. It is possible to absorb deviations in parallelism between the guide bar and the screw shaft.

[Brief explanation of drawings]

1 is a sectional view showing the structure of a zoom lens barrel to which the present invention is applied; FIG. 2 is a sectional view showing the shape of the front surface of the zoom lens barrel taken along the line ■-■ in FIG. 3 is a perspective view showing the relationship between the zoom lens frame and the guide bar, FIG. Fig. 6 is a perspective view showing the structure of the connection part of the drive mechanism of the four force lens, Fig. 7 (A), (B), jl
E8rI! J(A) and (B) are drawings showing other embodiments according to the present invention. 18...Focus lens, 40.42...Guide bar 68...Motor, 76
...Screw shaft, 78...Nut member, 80
...Forked part, 86... Connection piece, 90...
・Spherical top.

Claims (1)

[Claims] (1) A motor, a screw shaft connected to the motor, a nut member screwed onto the screw shaft and provided with a forked locking portion, and a spherical surface in contact with the forked locking portion of the nut member. A lens driving device comprising: a movable lens frame having a spherical part that fits with the frame and guided by a guide bar;