JP2001042189A - Lens moving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a cam follower from falling off from a cam groove having a tapered cam surface. SOLUTION: The cam follower 30 is engaged with a straight advance guide aperture 25 provided in a fixed barrel and the cam groove 26 provided in a cam barrel and having a trapezoidal cross section. The cam groove 26 is formed so that the maximum width of the trapezoidal cross section may be larger than the width of the aperture 25. The cam follower 30 is constituted in the two-stage shape of a large-diameter part 34 which is formed to have the trapezoidal cross section so that its outer periphery may be engaged with the groove 26 and a small-diameter part 33 whose outer periphery is engaged with the aperture 25. A step part 34b between the large-diameter part 34 and the small- diameter part 33 is caught by the edge of the aperture 25, whereby the cam follower 30 is prevented from falling off.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens moving device for moving a lens in an optical axis direction using a cam mechanism.

[0002]

2. Description of the Related Art There is known a lens moving device which performs zooming by moving a lens in an optical axis direction using a cam cylinder. Such a lens moving device generally includes a straight guide opening 11 provided in a fixed barrel 10 and a cam barrel 1 as shown in FIG.
2 and a lens moving barrel 15 provided with a cam follower 14. Moving cylinder 15
Is rotatably supported on the inner periphery of the fixed barrel 10 and holds therein a lens group 16 constituting a photographic lens. The cam cylinder 12 is rotatably supported on the outer periphery of the fixed cylinder 10 and is rotated during zooming. The cam follower 14 is provided near the rear end of the outer periphery of the movable barrel 15 (on the side of the imaging surface 17), and is engaged with the cam surface 13 a of the cam groove 13 while being inserted through the straight guide opening 11. . When the cam cylinder 12 is rotated, the cam surface 13a and the straight guide opening 1
The cam follower 14 is guided by the movement of the intersection with 1, and the movable barrel 15 moves in the direction of the optical axis O with respect to the fixed barrel 10. Note that, in order to smoothly move the movable barrel 15,
The cam groove 13, the cam follower 14, and the rectilinear guide opening 11 are respectively provided at three divided positions in the circumferential direction around the optical axis O.

[0003] By the way, a lens barrel used for a compact camera or the like is molded from a plastic material in a mold in order to reduce the cost as compared with molding by cutting metal. When the cam cylinder 12 is molded, it is necessary to consider the draft of the cam groove 13. For this reason, the cam surface 13a
Becomes a tapered surface, and the cam follower 1
It is necessary that the outer periphery 14a of the four which engages with the cam surface 13a also has a tapered surface.

[0004]

When the movable barrel 15 is fully extended as shown in FIG. 6, the movable barrel 15 is supported by the fixed barrel 10 at its rear end.
5 is easily inclined with respect to the optical axis O. Further, for the above-mentioned reason, since the cam groove 13 and the cam follower 14 have tapered surfaces, an external force is applied to the leading end of the moving cylinder 15 and the trailing end is slightly deformed while the cam groove 13 and the cam follower 14 are slightly deformed. The cam follower 14 is completely removed from the cam groove 13 at the moment when the cam follower 14 is inclined beyond the engagement depth A. If a displacement is applied to the moving cylinder 15 at this time, even if the external force is lost, the cam follower 14 moves the cam groove 1.
3 cannot be correctly engaged, and may remain disengaged.

The present invention has been made in consideration of the above circumstances, and has a cam groove and a cam follower formed into a tapered tapered surface, while maintaining a stable engagement between the two. It is intended to provide a device.

[0006]

In order to achieve the above object, in the lens moving device according to the first aspect, a straight guide opening is provided between the first engaging portion and the second engaging portion of the cam follower. The third engagement portion is wider than the width, and is provided in contact with the peripheral surface of the linear guide cylinder to prevent the cam follower from coming out of the cam groove. In the lens moving device according to the second aspect, the cam groove has a bottom. Further, in the lens moving device according to the third aspect, the cam follower is constituted by a cam roller rotatably attached to a pin fixed to the lens holding frame.

According to a fourth aspect of the present invention, in the lens moving device, the third engaging portion is formed by an end face formed from the rear end edge of the tapered tapered second engaging portion toward the first engaging portion. It is. Further, in the lens moving device according to the fifth aspect, the third engaging portion is formed by a projection protruding from the rear end portion of the tapered second engaging portion along the cam groove and beyond the width of the linear guide opening. It is what constituted.

[0008]

1 and 2 show a zoom lens using a lens moving device according to the present invention. The zoom lens is composed of two groups, a first lens group 18 and a second lens group 19, in that order from the subject side. These are a fixed barrel 20, a cam barrel 21, a first lens movable barrel 22, and a second lens movable frame. 2
3 movably supports in the direction of the optical axis O.

The first lens moving barrel 22 has a built-in lens holding frame 24 inside the distal end. The first lens group 18 is fixed to the lens holding frame 24. The second lens group 19 is fixed to the second lens moving frame 23. A straight guide opening 2 extending parallel to the optical axis O is provided in the fixed cylinder 20.
5 are formed. A first cam groove 26 for moving the first lens group 18 and a second cam groove 27 for moving the second lens group 19 are formed on the inner periphery of the cam cylinder 21.

The cam cylinder 21 rotates around the outer periphery of the fixed cylinder 20 by using the driving of the variable power motor 28. The first lens moving barrel 22 is formed to have a longer length in the direction of the optical axis O so that the first lens moving barrel 22 is fully extended toward the subject at the telephoto end. The lens holding frame 24 is connected to the first lens moving cylinder 22.
Are connected by a helicoid 29 and are rotatable with respect to the first lens moving barrel 22. A first cam follower 3 is provided at the outer rear end of the first lens moving barrel 22.
0 is provided. The first cam follower 30 is engaged with the first cam groove 26 through the straight guide opening 25.

Since the second lens moving frame 23 moves inside the fixed barrel 20, the length of the second lens moving frame 23 in the direction of the optical axis O is shorter than that of the first lens moving barrel 22. A second cam follower 31 is provided on the outer periphery of the second lens moving frame 23. The second cam follower 31 has a linear guide opening 2
5 and is engaged with the second cam groove 27.

The first cam groove 26 is a groove with a bottom, and has a trapezoidal cross section due to a draft angle when the cam cylinder 21 is molded. In the first cam groove 26, two non-parallel sides of the four sides forming the trapezoidal cross section form a cam surface on which the first cam follower 30 slides. These cam surfaces are tapered surfaces that are inclined so as to spread from the bottom of the cam groove 26 toward the linear guide opening 25.

The first cam follower 30 is a cam roller formed of a resin, an elastic material, or the like, and rotatably attached to the shaft 22a. The shaft 22a is fixed to the first lens moving barrel 22. As a method of fixing the shaft 22a, the shaft 22a may be press-fitted into the first lens moving barrel 22, or may be formed integrally with the first lens moving barrel 22. As a method of attaching the first cam follower 30 to the shaft 22a, the first cam follower 30 may be simply covered or may be screwed.

The first cam follower 30 has a small diameter portion 33 corresponding to a first engagement portion and a large diameter portion 3 corresponding to a second engagement portion.
4 and are integrally formed in a two-stage shape having a different diameter. The large diameter portion 34 has a larger diameter than the small diameter portion 33. The outer periphery of the small diameter portion 33 is engaged with the straight guide opening 25, and has a diameter substantially equal to the width of the straight guide opening 25. The large diameter portion 34 has a truncated cone shape (truncated cone shape), and a tapered surface 34 a on the outer periphery slides on the cam surface of the first cam groove 26.

The maximum diameter of the large diameter portion 34 is larger than that of the small diameter portion 33. Therefore, the step 34b between the large diameter portion 34 and the small diameter portion 33 is caught on the edge of the straight guide opening 25,
The first cam follower 30 is prevented from dropping from the first cam groove 26. The step portion 34b is an end face formed from the rear edge of the large-diameter portion 34 toward the small-diameter portion 33, and corresponds to a third engagement portion of the present invention.

The first cam groove 26 is formed so that the edge thereof is wider than the width of the straight guide opening 25 in accordance with the two-step shape of the first cam follower 30. The first lens moving cylinder 22
And to smoothly move the second lens frame 23,
The first and second cam grooves 26 and 27, the first and second cam followers 30 and 31, and the straight guide opening 25 are formed along the optical axis O.
Are provided at three divided positions in the circumferential direction around the center.

Next, the operation of the above configuration will be described. In the zoom lens, the state shown in FIG. 1 is at the wide end. The first cam follower 30, as shown in FIG.
4 is engaged with the opposed cam surface 26a of the first cam groove 26, and the outer periphery of the small diameter portion 33 is engaged with the opposed inner wall 25a of the straight guide opening 25.

At the time of zooming, the cam cylinder 21 is rotated. When the cam cylinder 21 rotates, an overlapping portion (intersection) between the straight guide opening 25 and the first cam groove 26 moves in the direction of the optical axis O,
The first cam follower 30 is guided by this movement of the intersection, and the first lens moving barrel 22 is moved in the direction of the optical axis O.

The rotation of the cam cylinder 21 also moves the intersection between the straight guide opening 25 and the second cam groove 27.
The lens frame 23 also moves in the direction of the optical axis O. First and second
The cam grooves 26 and 27 are shaped so as to move the first and second lens groups 18 and 19 so that the interval changes according to the magnification position. As a result, the first and second lens groups 18 and 19 move in the direction of the optical axis O so that the distance between them changes, and the focal length of the zoom lens changes.

At the time of focusing, the lens frame 24 is rotated by driving a focusing motor (not shown). Lens frame 24
Rotates, the lens frame 24 moves in the direction of the optical axis O with respect to the first lens moving barrel 22 according to the lead of the helicoid 29. As a result, the first lens group 18 moves to a focus position determined by the zoom position and the subject distance as a result of the distance measurement.

When the first lens moving barrel 22 is at the telephoto end,
When an external force is applied to the tip, the impact is transmitted to the first cam follower 30, and the first cam follower 30 tries to escape from the first cam groove 26. However, the step portion 34b of the first cam follower 30 moves straight. The first cam follower 30 is in contact with the edge of the opening 25 and acts as a stopper.
Can surely be prevented from falling off.

In the above embodiment, the bottomed cam groove is used. However, the present invention is not limited to this. If the facing wall surface forming the cam groove is a tapered tapered slope, the bottomed cam groove is not used. May be. However, the one with the bottom is the cam cylinder 21
It is preferable because the strength of the above can be obtained. Further, the order in which the cam cylinder 21 and the fixed cylinder 20 overlap may be reversed. In this case, the first lens moving barrel 22 may be superimposed on the outermost periphery, and the first cam follower 30 may be provided on the inner peripheral surface of the first lens moving barrel 22 so as to protrude toward the optical axis O. In the above embodiment, the straight guide opening 25 is provided in the fixed barrel 20. However, the present invention is not limited to this, and a configuration may be adopted in which a straight guide cylinder is separately provided.

FIG. 4 shows a cam groove 40 with a straight guide opening 41.
An embodiment formed with the same width as that of FIG. The cam follower 42 includes a first engagement portion 43, a second engagement portion 44, and a pair of protrusions 45 corresponding to the third engagement portion. The first engagement portion 43 has a tapered inclined surface so as to engage with the cam groove 40. The second engagement portion 44
The first engaging portion 43 has a columnar shape formed with the same diameter as the large-diameter outer periphery, and engages with the linear guide opening 41.

The pair of projections 45 are formed on the outer periphery of the first engagement portion 43 so as to project in opposite directions. These projections 45 are formed along the cam groove 40 and in the straight guide opening 41.
Is formed so as to protrude beyond the width. These two projections 45 reliably prevent the first engagement portion 43 from falling off from the cam groove 40. In addition, only one protrusion 45 may be provided.

FIG. 5 shows the first cam follower 30 connected to the shaft 22.
It is an example of the structure overlaid on a. In this case, the shaft 22a can be prevented from falling out of the first cam follower 30 by setting the length of the shaft 22a to engage with the large diameter portion 34 and the small diameter portion 33. Further, when the first cam follower 30 is screwed to the shaft 22a, the step portion 34b of the first cam follower 30 contacts the edge of the straight guide opening 25 to prevent the first cam follower 30 from coming off. 30 can be reliably prevented from falling and the rear end of the first lens moving barrel 22 being inclined by the external force.

[0026]

As described above, according to the present invention, between the first and second engaging portions of the cam follower, the width is wider than the width of the linear guide opening and abuts on the peripheral surface of the linear guide cylinder. Since the third engaging portion is provided, it is possible to reliably prevent the cam follower from coming out of the cam groove by contact of the third engaging portion with the peripheral surface of the straight guide cylinder.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a zoom lens using a lens moving device of the present invention, showing a lens position at a wide end.

FIG. 2 is a sectional view showing the zoom lens at the telephoto end.

FIG. 3 is a perspective view showing a main part of a cam follower.

FIG. 4 is a perspective view showing another embodiment in which a cam groove and a straight guide opening have the same width.

FIG. 5 is a sectional view showing an example of a structure in which a cam follower is put on a shaft.

FIG. 6 is a cross-sectional view illustrating a zoom lens described in the related art.

[Explanation of symbols]

 10, 20 Fixed tube 11, 25 Straight guide opening 12, 21 Cam tube 15, 22 Lens moving tube 13, 26, 27 Cam groove 14, 30, 31 Cam follower 33 Small diameter portion 34 Large diameter portion 34b Step portion

Continued on the front page (72) Inventor Eiichi Kabe 1-324 Uetakecho, Omiya-shi, Saitama Fuji Photo Optical Co., Ltd. F-term (reference) 2H044 BD08 BD09 BD10 BD20 BF03 DA02 DD03

Claims (5)

[Claims] 1. A rectilinear guide cylinder having a rectilinear guide opening parallel to an optical axis, a cam cylinder having a cam groove having a tapered sloped opposing wall surface, and a lens holding frame holding a movable lens. A cam follower having a first engaging portion engaged with the straight guide opening and a tapered second engaging portion engaged with the cam groove;
In a lens moving device configured to move a lens holding frame in an optical axis direction by rotation of a cam cylinder, a distance between a first engaging portion and a second engaging portion of the cam follower is greater than a width of the linear guide opening. And a third engaging portion that abuts against the peripheral surface of the straight guide cylinder to prevent the cam follower from coming out of the cam groove. 2. The lens moving device according to claim 1, wherein the cam groove has a bottom. 3. The lens moving device according to claim 1, wherein the cam follower is a cam roller rotatably attached to a pin fixed to the lens holding frame. 4. The apparatus according to claim 1, wherein the third engaging portion is an end face formed from a rear end edge of the second engaging portion having a tapered shape toward the first engaging portion. Item 1 or 3
The lens moving device as described in the above. 5. The third engaging portion is a projection that projects from a rear end of the tapered second engaging portion along the cam groove and beyond the width of the straight guide opening. The lens moving device according to claim 1 or 3, wherein