JP2002006196A - Structure of cam of lens barrel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an accurate line contact between the cam surface of a convex cam part and cam follower parts and improve the precision of positioning the cam without raising the cost of a metal mold. SOLUTION: The structure is provided with cam projections 5c formed by molding process on the outer surface of a cam annulus 5, and a plurality of cam followers 6b and 6c formed by molding process on the inner surface of a cylinder-shaped part 6, into which the cam annulus 5 is inserted so that each cam projection 5c is nipped by cam followers 6b and 6c along the direction of the optical axis. In the molding process of the cam followers 6b and 6c, the mold to form the surface holding the cam projections 5c is taken off in the direction of the optical axis having no inclination in the radial direction of the cylinder-shape part 6. In the molding process of the cam projections 5c, the mold to form the cam surface coming into contacting with the cam followers 6b and 6c is taken off in the direction of the optical axis having no inclination in the radial direction of the cam annulus 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cam structure of a lens barrel having a convex cam portion and a cam follower portion formed by molding.

[0002]

2. Description of the Related Art Conventionally, the cam structure of a zoom lens barrel is as follows.
When the cam member is metal, a cam groove penetrating from the outside of the cam member is provided by machining, or an inner cam that does not penetrate from the inner diameter side of the cam member to the outside of the cam cylinder is provided by machining. .

On the other hand, when both the cam member and the cam follower are made of synthetic resin, as described in Japanese Patent Publication No. 6-130268, a convex cam is provided on the inner diameter side of the cam member to sandwich the convex cam. The cam follower was provided outside the separate member. Further, as described in Japanese Patent Publication No. 8-146278, a convex cam is provided on the outer diameter side of the cam member, and a cam follower for sandwiching the convex cam is provided inside another member.

[0004]

However, the method of forming a plurality of cams on a metal cam member by machining is higher in cost than forming a cam member with a synthetic resin, and the processing of a plurality of cams is expensive. Unless an appropriate interval is provided, there is a problem that deformation due to processing occurs.

On the other hand, when the cam member is made of synthetic resin, the convex cam described in Japanese Patent Publication No. 6-130268 or Japanese Patent Publication No. 8-146278 has been molded by a die-cutting mold in the optical axis direction. Further, a plurality of cam followers sandwiching these convex cams are provided so that the angular directions are paired at the same position. For this reason, the cam follower is provided with a radial die-cutting mold (Japanese Patent Publication No.
In the case of -130268, radial outward direction, Tokuhei 8
In the case of -146278, it was a structure molded in the radial inner direction.

In either case, since the cam follower is die-cut in the radial direction and molded, it is inevitable that the cam follower has a draft. on the other hand,
Since the convex cam portion is molded by a die-cutting mold in the optical axis direction, it can be molded without a cam surface gradient. Therefore, the cam follower and the cam surface of the convex cam are not properly in line contact. For this reason, there was a problem that the position accuracy by the cam was poor. In addition, since the cam follower is divided into the inner molds, there is a problem that the mold cost is increased.

An object of the present invention is to provide a cam structure of a lens barrel capable of improving the positional accuracy of a cam by making the cam surface of a convex cam portion and a cam follower portion come into linear contact without increasing the mold cost. To provide.

[0008]

According to a first aspect of the present invention, a convex cam portion (5c) formed by molding on the outer surface of an inner cylinder (5) is provided. And a plurality of cam forward portions (6b, 6c) formed by molding on the inner surface of the outer cylinder (6) to sandwich the convex cam portion in the optical axis direction. Cam follower part (6b, 6
(c) a cam of the lens barrel, characterized in that a surface sandwiching the convex cam portion (5c) is molded by a die-cut mold in the optical axis direction having no radial gradient in the outer cylinder (6). Structure.

According to a second aspect of the present invention, in the cam structure of the lens barrel according to the first aspect, the convex cam portion (5c) is provided.
Is a lens barrel characterized in that a cam surface in contact with said cam follower portions (6b, 6c) is molded by a die-cutting mold in the optical axis direction in the inner cylinder (5) having no radial gradient. Cam structure.

[0010] The invention of claim 3 is claim 1 or claim 2.
Wherein the plurality of cam follower portions (6b, 6c) are provided in pairs with the plurality of cam surfaces of the convex cam portion (5c),
The pair (6b, 6c) has a cam structure of a lens barrel, characterized in that there is a shift in the optical axis direction in the angular direction that is greater than the width of the cam follower portion.

According to a fourth aspect of the present invention, in the cam structure of the lens barrel according to the third aspect, the convex cam portion (5c) is provided.
Is a cam structure for a lens barrel, wherein the plurality of cam surfaces are shifted back and forth in the optical axis direction in accordance with the angular displacement of the plurality of cam follower portions.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment of the present invention will be described in more detail. (Lens Barrel) FIG. 1 is a sectional view showing a lens barrel having a cam structure according to an embodiment of the present invention. The fixed mount 1 is a male mount for mounting on a female mount on the camera side, and has a bayonet portion 1a and the like.

The fixed part 2 is an integral part of the fixed mount 1, and has three straight key parts 2a protruding from the inner diameter part.
And a guide groove 2b provided around the optical axis and provided with an angle groove covering the zooming range, and a guide groove 2c provided at the distal end portion of the fixed portion 2.

The zoom ring 3 is a member for performing zooming by rotating in the direction of the optical axis, protruding toward the inner diameter side, and three pins 3a engaging with the guide grooves 2b, and a front end of the zoom ring 3. And a straight key portion 3b protruding toward the inner diameter side of the portion.

After the assembly and adjustment, the adjustment member 4 is
The member is fixed to the zoom ring 3 by an adhesive tape 15 so as to rotate integrally with the zoom ring 3, and includes a female helicoid screw 4a provided on the inner diameter side.

The cam ring 5 is a member for controlling the movement of the first lens unit L1, and includes a straight guide groove 5 provided on the right outside.
a, a male helicoid screw 5b provided on the outer diameter side, and a cam projection 5c provided on the left outer peripheral portion of the cam ring 5 (FIG. 2).
And FIG. 5), and a concave cam groove 5d (see FIGS. 3 and 5) provided in the inner diameter portion.

The tubular member 6 is a male helicoid member, and includes a helicoid screw 6a provided on the left portion of the outer diameter, cam followers 6b and 6c provided on the inner diameter portion (see FIGS. 4 and 5), and an outer diameter. Straight guide groove 6 provided on the right side of
d and the like.

The holding frame 7 is a member for holding the first group lens L1, and is provided with a female helicoid screw 7 provided on the inner diameter portion.
a and a key portion 7b for engagement provided on a right side portion of the outer diameter.
And the like.

The drive ring 8 is a member that is rotated around the optical axis by a drive gear (not shown). The drive ring 8 is provided integrally with the drive ring 8 in the optical axis direction, and is provided on the inner diameter portion. And a driving gear 8b.

The straight-moving interlocking key 10 has a screw 12
It is a member that is positioned and fixed by. Holding member 11
Is a member for holding the second group lens L2, which is provided on the outer diameter portion and engages with the cam groove 5d.
And a guide groove 11b engaged with the straight-moving interlocking key 10. The adhesive tape 15 includes the zoom ring 3 and the adjustment member 4.
Is a member that is fixed after adjustment. The rubber ring 20 is a ring that covers the zoom ring 3 and the adjustment member 4 after being fixed with the adhesive tape 15.

(Cam Structure) Next, the detailed structure of the cam structure of the lens barrel according to the present embodiment will be described in more detail. 2 to 4 are developed views showing a cam portion of the cam structure according to the present embodiment. FIG. 5 is a perspective view showing a cam cylinder and a tubular member having a cam structure according to the present embodiment.

The cam ring (inner cylinder) 5 is provided with a cam projection 5c on the left outer peripheral portion thereof as shown in the developed views of FIGS. 2 and 4, and the cam projection (convex cam portion) 5c Followers (cam follower portions) 6b, 6c. The cylindrical member (outer cylinder) 6 is a helicoid member that controls the movement of the first lens unit L1. As shown in a developed view of FIG. 4, a helicoid screw 6a is provided on an outer left portion, and an inner diameter portion thereof is provided. Cam followers 6b and 6c are provided.

The cam followers 6b and 6c are provided as a pair, and the angular position in the optical axis direction is shifted at least by the width of each of the cam followers 6b and 6c. It is arranged to become.
The cam followers 6b and 6c are formed so that the surfaces sandwiching the cam protrusions 5c have no gradient in the radial direction of the tubular member 6.

On the other hand, as shown in FIG. 2, the cam surface of the cam projection 5c is shifted in the angular direction before and after the optical axis in accordance with the cam followers 6b and 6c. Similarly to the cam followers 6b and 6c, the cam projections 5c are also arranged so as to enable die-molding in the optical axis direction, so that the cam surface has no gradient in the cam ring 5 in the radial direction. Molded into

The inner diameter of the cylindrical member 6 of the cam cylinder 5 and the cylindrical member 6 is larger than the outer diameter of the cam cylinder 5. As shown in FIG. 5, both of the cam followers 6b and 6c (3
The cam cylinder 5 is inserted into the tubular member 6 such that the cam projections 5c sandwich the cam projections 5c (three locations). In FIG. 5, the helicoid screw 6a is omitted.

(Zooming operation) According to the above structure,
When the zoom ring 3 is rotated around the optical axis, the adjustment member 4 and the cam barrel 5 fixed integrally with the zoom ring 3 rotate around the optical axis. Then, since the cam projection 5c rotates around the optical axis, the cam followers 6b and 6c engaged so as to sandwich the cam projection 5c and the rectilinear groove 6d engaged with the rectilinear key 2a of the fixed portion 2 are formed. By the action, the tubular member 6 moves back and forth in the optical axis direction. For this reason, the holding frame 7 of the first group lens L1 which is screw-engaged with the tubular member 6 also moves integrally in the optical axis direction.

On the other hand, the interlocking projection 11a (FIGS. 1 and 2) of the second lens group holding frame 11 which engages with the inner diameter cam groove 5d of the cam cylinder 5, and the guide groove 11b which engages with the linearly interlocking key 10
When the cam barrel 5 is rotated by the action described above, the second lens unit L2 moves zooming in the optical axis direction.

The first lens unit L1 is also a focusing lens unit, and when the holding frame 7 rotates, the helicoid screws 7a, 6a
The optical axis is moved in the optical axis direction by the driving action of, and a focusing operation is performed. Then, the key portion 7b for engagement is rotationally linked with the key portion 8a for interlocking of the drive ring 8, so that the drive ring 8 rotates when performing a focusing operation. The drive ring 8 is restricted by the guide groove 2c of the fixed portion 2 so as to be rotatable only around the optical axis. When the drive ring 8 is driven by a motor and gears for AF, the drive ring 8 is rotated around the optical axis by a gear 8b provided on the drive ring 8 and a drive gear (not shown).

(Flange Back Adjustment) Next, the flange back adjustment of the lens barrel according to the present embodiment will be described.
In a zoom lens, there is a possibility that an error occurs in the focus position of the optical system due to manufacturing variations of parts. In order to eliminate this error, the position of the focusing lens (in this case, the first lens unit L1) is adjusted in the optical axis direction by shifting the washer adjustment and the rotation limit position before the flange back adjustment (the structure is as follows). (Not shown), the focus is adjusted so as not to cause the focus shift on the wide side and the tele side. When this focus movement adjustment is performed, the flange back of the entire optical system shifts.

In this embodiment, in order to adjust the flange back, when the adjusting member 4 is rotated around the optical axis,
By the action of the helicoid screw 5b of the cam cylinder 5 engaging with the helicoid screw 4a of the adjusting member 4 and the linear key portion 3b of the zoom ring 3 engaging with the linear groove 5a of the cam cylinder 5, the cam cylinder 5 is moved to the zoom ring 3. On the other hand, the movement of the optical axis is adjusted while the rotation is interlocked. The cam barrel 5 holds the entire optical system.

As described above, by rotating the adjustment member 4, the flange back can be adjusted. After the flange back is adjusted, the zoom ring 3 and the adjustment member 4 are fixed by the adhesive tape 15, and the rubber ring 20 is put on the zoom ring 3 and the adjustment member 4.

(Mold Structure) FIGS. 6 to 8 are explanatory views showing the mold structure when the cam follower of the cam structure according to the present embodiment is molded by a die-cutting mold in the optical axis direction.
9 and 10 are explanatory views showing a mold structure (comparative example) in the case where the cam follower is molded by a radial die-cutting mold.

This mold structure, as shown in FIG. 6, nests a fixed mold 100 and a movable mold 101 to form the cam followers 6b and 6c on the inner diameter side of the cylindrical member 6. It has a structure. FIG. 7 is a cross-sectional view showing a case viewed in the cross-sectional AA direction of FIG. In this mold structure, a gate 103 is provided on a fixed mold 100. The movable mold 101 is configured to move to the arrow side C in the optical axis direction. The outer mold 102 is configured to divide in the radial direction and slide in the direction of arrow D.

FIG. 8 is a cross-sectional view as viewed in the direction of the section BB in FIG. Since the side surfaces of the cam followers 6b and 6c are cut out in the optical axis direction, they are molded without a gradient.

FIG. 9 shows a comparative example in which the cam followers 60b and 60c are provided at the same angular position. In such a case, Japanese Patent Publication No. Sho 59-14333 discloses a mold structure in which the mold is narrowed toward the inner diameter side even when there is an inner diameter undercut in order to mold the cam followers 60b and 60c having the inner diameter. Like that.

Such a mold structure is generally called a collapsible core. The details are described in the above publication, but will be briefly described with reference to FIG. The mold of the inner diameter portion is mainly composed of three types of parts. At the center of the mold, a conical core rod 110 is provided, and on the outside thereof, the same number of movable cores 111 and 112 arranged alternately in the circumferential direction are provided. In this case, an angle α is provided between the conical inclination of the core rod 110 and the movable core 111, and an angle β is provided between the conical inclination of the core rod 110 and the movable core 112.
Is provided. Then, it is necessary to set α> β (α is set to about twice β in an actual structure), and the movable cores 111 and 112 are
It has a configuration that can guide along zero.

When the mold is opened at the time of molding, as the core rod 110 fixed to the substrate 115 is moved in the direction of arrow E, the movable cores 111 and 112 are moved in the inner diameter direction (direction of arrow F). The movable core 111 comes off from the undercut portions of the followers 60b and 60c. Shape of movable core 111 and movable core 112 (details not shown)
The movable core 112 has an arc-shaped cross section and the movable core 1
11 has a trapezoidal cross section that matches the bow curvature. And, each movable core 111, 112,
It is engaged with the core rod 110 (not shown). The mold 112 outside the component 60 has a structure in which the mold 112 is divided and moved in the radial direction.

This collapsible core structure has the advantage that molding is possible even if there is an inner diameter undercut portion. However, if the amount of undercut is large, a mold structure may not be formed. In addition, there is a problem in that processing for ensuring the accuracy of the dovetailed engagement portion between the core rod and the movable core requires extremely high processing accuracy. Further, when molding the undercut portion, the mold is moved in the inner diameter direction, so that the side surfaces of the cam followers 60b and 60c have draft angles.

[0039]

As described above in detail, the surface sandwiching the convex cam portion of the cam follower portion was molded by a die-cutting mold in the optical axis direction having no radial gradient. In addition, the cam surface of the convex cam portion that comes into contact with the cam follower portion was also formed by a die-cutting mold in the optical axis direction having no gradient in the radial direction. As a result, the cam surface of the convex cam portion and the cam follower portion are correctly in line contact with each other, and the positional accuracy by the cam is improved.

Further, since the contact between the convex cam portion and the cam follower portion keeps the line contact, it is possible to improve the impact resistance against the impact applied to the optical system and the like. Furthermore, since the cam follower portion can be configured to be cut out in the optical axis direction from the conventional radial split mold, the mold cost is particularly reduced as compared with the case where the cam follower portion is formed as the inner split mold. There is also the effect of.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a cam structure of a lens barrel according to the present invention.

FIG. 2 is a development view showing an embodiment of a cam structure of the lens barrel according to the present invention.

FIG. 3 is a development view showing an embodiment of a cam structure of the lens barrel according to the present invention.

FIG. 4 is a development view showing an embodiment of a cam structure of the lens barrel according to the present invention.

FIG. 5 is a perspective view showing an embodiment of a lens barrel cam structure according to the present invention.

FIG. 6 is an explanatory diagram showing a mold structure when a cam follower of the cam structure according to the present embodiment is molded by a die-cutting mold in the optical axis direction.

FIG. 7 is a cross-sectional view showing a case when viewed in a cross-sectional AA direction of FIG. 6;

FIG. 8 is a cross-sectional view showing the case when viewed in the direction of the cross section BB in FIG. 6;

FIG. 9 is an explanatory view showing a mold structure (comparative example) when a cam follower is molded by a radial die-cutting mold.

FIG. 10 is an explanatory view showing a mold structure (comparative example) when a cam follower is molded by a radial die-cutting mold.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed mount 2 Fixed part 3 Zoom ring 4 Adjusting member 5 Cam cylinder 5a Straight running groove 5c Cam projection 5d Cam groove 6b Cam follower 6d Straight running guide groove 7 Holding frame 7b Key portion 8 Drive ring 8a Key portion 8b Gear 10 Straight running key L1 First lens group L2 Second lens group

Claims (4)

[Claims] 1. A convex cam portion formed on the outer surface of an inner cylinder by molding, and a plurality of cam forwards formed by molding on an inner surface of the outer cylinder into which the inner cylinder is inserted, and sandwiching the convex cam portion in the optical axis direction. In the cam structure of the lens barrel comprising: a plurality of cam follower portions, the surfaces sandwiching the convex cam portion are molded by a die-cut mold in the optical axis direction in the outer cylinder having no radial gradient. A lens barrel cam structure. 2. The cam structure of a lens barrel according to claim 1, wherein said convex cam portion has a cam surface in contact with said cam follower portion in an optical axis direction having no gradient in a radial direction of said inner cylinder. The cam structure of the lens barrel, characterized by being molded by a die-cut mold. 3. The cam structure of the lens barrel according to claim 1, wherein the plurality of cam follower portions are provided in pairs with respect to a plurality of cam surfaces of the convex cam portion. The cam structure of the lens barrel, wherein each of the pairs is displaced in the optical axis direction in an angular direction greater than the width of the cam follower portion. 4. The cam structure of a lens barrel according to claim 3, wherein the convex cam portion moves the plurality of cam surfaces in an optical axis direction corresponding to an angular displacement of the plurality of cam follower portions. The cam structure of the lens barrel, which is shifted before and after.