JP4461244B2 - Lens moving device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lens moving device that moves a lens in an optical axis direction using a cam mechanism.
[0002]
[Prior art]
2. Description of the Related Art A lens moving device that performs zooming by moving a lens in the optical axis direction using a cam cylinder is known. As shown in FIG. 6, such a lens moving device generally has a lens moving cylinder provided with a straight guide opening 11 provided in the fixed cylinder 10, a cam groove 13 provided in the cam cylinder 12, and a cam follower 14. 15. The movable cylinder 15 is rotatably supported on the inner periphery of the fixed cylinder 10, and a lens group 16 constituting a photographing lens is held therein. The cam cylinder 12 is rotatably supported on the outer periphery of the fixed cylinder 10 and is rotated at the time of zooming. The cam follower 14 is provided near the outer peripheral rear end (imaging surface 17 side) of the movable cylinder 15 and is engaged with the cam surface 13 a of the cam groove 13 while being inserted through the rectilinear guide opening 11. . When the cam cylinder 12 is rotated, the cam follower 14 is guided by the movement of the intersection of the cam surface 13 a and the rectilinear guide opening 11, and the moving cylinder 15 moves in the direction of the optical axis O with respect to the fixed cylinder 10. In order to smoothly move the movable cylinder 15, the cam groove 13, the cam follower 14, and the rectilinear guide opening 11 are respectively provided at three circumferential positions around the optical axis O.
[0003]
By the way, a lens barrel used for a compact camera or the like is die-molded with a plastic material in order to reduce the cost compared to metal cutting and molding. When the cam cylinder 12 is molded, it is necessary to consider the draft for the cam groove 13. For this reason, the cam surface 13a becomes a taper taper surface, and accordingly, the outer periphery 14a of the cam follower 14 that engages with the cam surface 13a also needs to be a taper surface.
[0004]
[Problems to be solved by the invention]
As shown in FIG. 6, when the movable cylinder 15 is fully extended, the movable cylinder 15 is supported by the fixed cylinder 10 on the rear end side, so that the movable cylinder 15 is easily inclined with respect to the optical axis O. For the above-mentioned reasons, the cam groove 13 and the cam follower 14 have tapered tapered surfaces, so that an external force is applied to the distal end of the movable cylinder 15 and the rear end is slightly deformed while the cam groove 13 and the cam follower 14 are At the moment of tilting beyond the engagement depth A, the cam follower 14 comes out of the cam groove 13 completely. If the moving cylinder 15 is displaced at this time, even if the external force disappears, the cam follower 14 cannot be properly engaged with the cam groove 13 and may remain detached.
[0005]
The present invention has been made in consideration of the above-described circumstances, and provides a lens moving device capable of maintaining stable engagement between the cam groove and the cam follower while having a tapered tapered surface shape. The purpose is to do.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, in the lens moving device according to claim 1, the cam follower is wider than the straight guide opening between the first engagement portion and the second engagement portion of the cam follower, and the cam. A third engaging portion that abuts against the circumferential surface of the linear guide cylinder by the thickness of the second engaging portion that is thicker than the gap between the cylinder and the linear guide cylinder and prevents the cam follower from coming out of the cam groove. Is provided. In the lens moving device according to the second aspect, the cam groove has a bottom. According to a third aspect of the present invention, the cam follower comprises a cam roller rotatably attached to a pin fixed to the lens holding frame.
[0007]
According to a fourth aspect of the present invention, the third engaging portion is constituted by an end face formed from the rear end edge of the second engaging portion having the tapered shape toward the first engaging portion. Further, in the lens moving device according to claim 5, the third engaging portion is formed by a protrusion protruding along the cam groove from the rear end portion of the tapered second tapered engaging portion and exceeding the width of the straight guide opening. Is configured.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
1 and 2 show a zoom lens using the lens moving device of the present invention. The zoom lens is composed of two groups of a first lens group 18 and a second lens group 19 in order from the subject side, and these include a fixed cylinder 20, a cam cylinder 21, a first lens moving cylinder 22, and a second lens moving frame. 23 is supported so as to be movable in the direction of the optical axis O.
[0009]
The first lens moving cylinder 22 includes a lens holding frame 24 inside the tip. 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 25 extending in parallel with the optical axis O is formed in the fixed cylinder 20. 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, respectively.
[0010]
The cam cylinder 21 rotates on the outer periphery of the fixed cylinder 20 by using the drive of the zooming motor 28. The first lens moving cylinder 22 is formed with a long length in the direction of the optical axis O so that the first lens moving cylinder 22 is fully extended toward the subject at the telephoto end. The lens holding frame 24 is coupled to the first lens moving cylinder 22 by a helicoid 29 and is rotatable with respect to the first lens moving cylinder 22. A first cam follower 30 is provided at the outer peripheral rear end of the first lens moving cylinder 22. The first cam follower 30 is engaged with the first cam groove 26 through the rectilinear guide opening 25.
[0011]
Since the second lens moving frame 23 moves inside the fixed cylinder 20, the length in the direction of the optical axis O is shorter than that of the first lens moving cylinder 22. A second cam follower 31 is provided on the outer periphery of the second lens moving frame 23. The second cam follower 31 is engaged with the second cam groove 27 through the rectilinear guide opening 25.
[0012]
The first cam groove 26 is a bottomed groove, and has a trapezoidal cross section due to a draft when the cam cylinder 21 is molded. In the first cam groove 26 , two non-parallel sides of the four sides constituting the trapezoidal cross section are cam surfaces 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 first cam groove 26 toward the straight guide opening 25.
[0013]
The first cam follower 30 is a cam roller that is formed of a resin, an elastic material, or the like, and is rotatably attached to the shaft 22a. The shaft 22 a is fixed to the first lens moving cylinder 22. As a method for fixing the shaft 22 a, the shaft 22 a may be press-fitted into the first lens moving cylinder 22 or formed integrally with the first lens moving cylinder 22. As a method of attaching the first cam follower 30 to the shaft 22a, it may be simply covered or may be screwed.
[0014]
The first cam follower 30 is integrally formed in a two-stage shape having different diameters of a small diameter portion 33 corresponding to the first engagement portion and a large diameter portion 34 corresponding to the second engagement portion. The large diameter portion 34 is thicker than the small diameter portion 33. The small diameter portion 33 has an outer periphery engaged with the rectilinear guide opening 25 and has a diameter substantially the same as the width of the rectilinear guide opening 25. The large-diameter portion 34 has a truncated cone shape (a truncated cone shape), and a tapered surface 34 a on the outer periphery thereof slides on the cam surface of the first cam groove 26.
[0015]
The maximum diameter of the large diameter portion 34 is larger than that of the small diameter portion 33. Accordingly, the step portion 34 b between the large diameter portion 34 and the small diameter portion 33 is caught on the edge of the rectilinear guide opening 25, and the first cam follower 30 is prevented from falling off from the first cam groove 26. The stepped portion 34b is an end surface formed from the rear end edge of the large diameter portion 34 toward the small diameter portion 33, and this corresponds to the third engagement portion of the present invention.
[0016]
Along with the two-stage shape of the first cam follower 30, the first cam groove 26 has an edge wider than the width of the rectilinear guide opening 25. In order to smoothly move the first lens moving cylinder 22 and the second lens moving 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 respectively provided at three divided positions in the circumferential direction around the optical axis O.
[0017]
Next, the operation of the above configuration will be described. The zoom lens has the wide end in the state shown in FIG. As shown in FIG. 3, the first cam follower 30 has a tapered surface 34a on the outer periphery of the large-diameter portion 34 engaged with the cam surface 26a facing the first cam groove 26, and the outer periphery of the small-diameter portion 33 is a straight guide. The opening 25 is engaged with the opposing inner wall 25a.
[0018]
At the time of zooming, the cam cylinder 21 is rotated. When the cam cylinder 21 rotates, the overlapping portion (intersection point) between the rectilinear guide opening 25 and the first cam groove 26 moves in the direction of the optical axis O, and the first cam follower 30 is guided by the movement of this intersection point to the first. The lens moving cylinder 22 is moved in the direction of the optical axis O.
[0019]
In addition, since the intersection of the rectilinear guide opening 25 and the second cam groove 27 is moved by the rotation of the cam barrel 21, the second lens moving frame 23 is also moved in the direction of the optical axis O. The first and second cam grooves 26 and 27 are shaped to move the first and second lens groups 18 and 19 so that the interval changes according to the zoom 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.
[0020]
At the time of focusing, the lens holding frame 24 is rotated by driving a focusing motor (not shown). When the lens holding frame 24 rotates, the lens holding frame 24 moves in the direction of the optical axis O according to the lead of the helicoid 29 with respect to the first lens moving cylinder 22. As a result, the first lens group 18 moves to a focus position determined by the zoom position and the subject distance of the distance measurement result.
[0021]
When an external force is applied to the tip of the first lens moving cylinder 22 at the tele end, the impact is transmitted to the first cam follower 30 and the first cam follower 30 tends to come out of the first cam groove 26. Since the step 34b of the first cam follower 30 abuts against the edge of the rectilinear guide opening 25 and acts to prevent the first cam follower 30 from falling off, the first cam follower 30 can be reliably prevented from falling off.
[0022]
In the above-described embodiment, the bottomed cam groove is used. However, the present invention is not limited to this, and a cam groove having no bottom may be used as long as the opposing wall surface forming the cam groove is a tapered tapered slope. However, the bottom is preferable because the strength of the cam cylinder 21 can be obtained. Further, the overlapping order of the cam cylinder 21 and the fixed cylinder 20 may be reversed. In this case, the first lens moving cylinder 22 is overlapped on the outermost periphery, and the first cam follower 30 may be provided on the inner peripheral surface of the first lens moving cylinder 22 so as to protrude toward the optical axis O. Moreover, in the said embodiment, although the rectilinear guide opening 25 is provided in the fixed cylinder 20, in this invention, it is good not only as this but the structure which provided the rectilinear guide cylinder separately.
[0023]
FIG. 4 shows an embodiment in which the cam groove 40 is formed with the same width as the rectilinear guide opening 41. The cam follower 42 includes a second engagement portion 43, a first engagement portion 44, and a pair of protrusions 45 corresponding to the third engagement portion. The second engaging portion 43 has a tapered tapered slope so as to engage with the cam groove 40. The first engagement portion 44 has a columnar shape formed with the same diameter as the outer periphery of the large diameter of the second engagement portion 43 and engages with the rectilinear guide opening 41.
[0024]
The pair of protrusions 45 are formed on the outer periphery of the second engagement part 43 so as to protrude in opposite directions. These protrusions 45 are formed along the cam groove 40 and beyond the width of the straight guide opening 41. These two protrusions 45 reliably prevent the second engagement portion 43 from dropping from the cam groove 40. Only one protrusion 45 may be provided.
[0025]
FIG. 5 shows an example of a structure in which the first cam follower 30 is put on the shaft 22a. In this case, the shaft 22 a can be prevented from coming out of the first cam follower 30 by making the shaft 22 a engage with the large diameter portion 34 and the small diameter portion 33. When the first cam follower 30 is screwed to the shaft 22a, the stepped portion 34b of the first cam follower 30 abuts against the edge of the straight guide opening 25 to prevent the first cam follower 30 from coming off. It is possible to reliably prevent the 30 from falling off and the rear end of the first lens moving cylinder 22 from being inclined by an external force.
[0026]
【The invention's effect】
As described above, in the present invention, the first engaging portion that engages with the rectilinear guide opening and the tapered taper shape that engages with the cam groove and more than the gap between the cam cylinder and the rectilinear guide cylinder. Since the third engaging portion wider than the width of the straight guide opening is provided between the thick second engaging portion, when the cam follower comes out of the cam groove, the second engaging portion has a second thickness. It is possible to reliably prevent the three engaging portions from coming out by coming into contact with the circumferential surface of the straight guide tube .
[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 cross-sectional view showing a zoom lens at a telephoto end.
FIG. 3 is a perspective view showing a main part of the cam follower.
FIG. 4 is a perspective view showing another embodiment in which the cam groove and the rectilinear guide opening have the same width.
5 is a cross-sectional view showing an example of a covered structure of Kamufo lower over the shaft.
FIG. 6 is a cross-sectional view showing a zoom lens described in the prior art.
[Explanation of symbols]
10, 20 Fixed cylinder 11, 25 Straight guide opening 12, 21 Cam cylinder 15, 22 Lens moving cylinder 13, 26, 27 Cam groove 14, 30, 31 Cam follower 33 Small diameter portion 34 Large diameter portion 34b Stepped portion

Claims (5)

A rectilinear guide tube having a rectilinear guide opening parallel to the optical axis;
A cam cylinder in which the opposing wall surface forming the cam groove is a tapered tapered slope;
Holding the lenses and is attached to the lens holding frame to move in the optical axis direction by the rotation of the cam barrel, a first engagement portion engaged with the rectilinear guide opening, tapered engaging said cam groove A taper-shaped second engagement portion that is thicker than a gap between the cam cylinder and the rectilinear guide cylinder, and is provided between the first engagement section and the second engagement section. A cam follower having a third engagement portion that is wider than the width of the straight guide opening ;
With
The third engaging portion, the lens in which the cam follower by abutting the peripheral surface of the rectilinear guide tube by the thickness of the second engaging portion, wherein the benzalkonium be prevented from being withdrawn from the cam groove Mobile equipment.   The lens moving device according to claim 1, wherein the cam groove has a bottom.   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. The third engaging portion is tapered from the rear edge of the second engagement portion which is tapered according to claim 1 or 3, wherein that the end surface formed toward the first engagement portion and Features Lens moving device. The first engagement portion and the second engagement portion are formed with the same diameter, and the third engagement portion extends along the cam groove from the rear end portion of the tapered second engagement portion. The lens moving device according to claim 1, wherein the lens moving device protrudes beyond the width of the straight guide opening.

Images