JPH04104112A - Movement device for lens barrel - Google Patents

Abstract

PURPOSE:To effectively prevent a cam surface from flawing even when a large impact force is applied to the lens barrel, to reduce the wear, and to move the lens barrel with high accuracy by constituting the cam part and cam follower of a cam means for moving the lens barrel so that they are in surface contact with each other. CONSTITUTION:The cam means consists of the cam part 5a provided on the inner peripheral surface of a cam cylinder 5 to be rotated or moved straight and the cam follower 7a provided to part of the lens barrel 7. The cam part 5a has a rectangular sectional shape projecting toward the center of the cam cylinder 5 and also has a constant lead and the cam follower 7a is molded in a shape along the lead of the cam part 5a and clamps the cam surface of the cam part 5a by surface contacting and faces across the cam part 5a so that the surface on the opposite side about a line crossing the moving direction of the cam part 5a at right angles leaves the cam part 5a. Thus, the sectional shape of the cam part is made rectangular to form a complete square thread shape, so size measurement is easy and the high-accuracy shape is secured. The influence of the deformation of the cam cylinder upon the projection width of the cam part is small and there is no wedge operation as compared with a trapezoid cam part, so the cam cylinder is put in operation with low torque.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a device for moving a lens barrel, and in particular, in a photographing system such as a single focal length lens or a zoom lens, the lens barrel is moved by a zooming operation or a focusing operation. A lens suitable for photo cameras, video cameras, etc. that has strong impact resistance and can be moved with high precision by using a cam means consisting of an appropriately configured cam part and cam follower when moving in the axial direction. This invention relates to a lens barrel moving device.

(Prior art) In many photographic systems, moving devices capable of high-precision movement without backlash have been used in devices that perform rotational or linear movement of the lens barrel during zooming, focusing, etc. is requested.

For example, Japanese Patent Publication No. 61-20842 proposes a lens barrel moving device that uses appropriately constructed cam means to enable highly accurate movement.

According to this publication, a cam portion is provided in a part of the lens barrel that is moved by rotational operations such as zooming and focusing operations. Then, the cam part is provided with two cam surfaces, a straight groove that intersects the cam surfaces is formed in the fixed cylinder, a key member is fitted into the straight groove, and one cam surface of the cam part is fitted to the key member. A cylindrical cam follower is fixed in contact with the cam follower, a groove is formed in the key member, and a cylindrical protrusion in contact with the other cam surface of the cam portion is engaged with the groove. Then, the cam follower and the protrusion are pulled by a spring tensioned within the housing of the key member, and the cam follower and the protrusion are respectively biased against the cam surface of the cam part, thereby creating a lens barrel with a structure that prevents rattling. We are proposing a mobile device.

(Problems to be Solved by the Invention) In the lens barrel moving device proposed in the above-mentioned Japanese Patent Publication No. 61-20842, for example, when a strong impact force is applied to the lens barrel, the cam surface of the cam portion is moved by the cam follower. There may be scratches or dents. If the cam surface is scratched or dented, the lens barrel will become loose during zooming, for example, and the optical performance will deteriorate significantly.

On the other hand, in Japanese Utility Model Publication No. 61-24969, the present applicant has developed a method of increasing the radius of the portion of the cam follower in contact with the cam surface, thereby causing scratches on the cam surface or protective wall surface when impact force is applied to the lens barrel. We are proposing a lens barrel moving device that prevents scratches.

The present invention further improves the configuration of the cam means consisting of the cam part and the cam follower in the previous lens barrel moving device by the present applicant, and the present invention is designed to further improve the structure of the cam means consisting of the cam part and the cam follower in the previous lens barrel moving device by the present applicant. A lens mirror that effectively prevents scratches on the cam surface, reduces wear on the cam means when reversing edges, and enables high-speed movement of the lens barrel. The purpose is to provide a cylinder moving device.

(Means for Solving the Problems) A lens barrel moving device of the present invention is a lens barrel moving device that moves a lens barrel using a cam means, in which the cam means is rotatable or linearly movable. The cam portion has a cam portion provided on the inner peripheral surface of the cam tube and a cam follower provided on a part of the lens barrel, and the cam portion has a rectangular cross-sectional shape protruding toward the center of the cam tube; The cam follower is formed in a shape that follows the groove of the cam part, and also holds the cam surface of the cam part in surface contact, and is opposed to the cam part with the cam part in between. , and the surface opposite to a line perpendicular to the moving direction of the cam section is formed in a direction away from the cam section.

(Example) Fig. 1 is a schematic cross-sectional view of the main part of the first embodiment when the present invention is applied to a zoom lens, Fig. 2 is a perspective view of the main part of the cam barrel shown in Fig. FIG. 1 is a perspective view of a main part of the lens barrel, and FIG. 4 is an enlarged schematic diagram of a portion of FIG. 3.

In the figure, 1 is a lens mount section, which is attached to the camera body (not shown). Reference numeral 2 designates a fixed cylinder, in which a part is provided with a bayonet claw 2a, a key groove 2b into which a key member parallel to the optical axis is fitted, and a nip hole 2C into which a pin d provided along the circumferential direction is fitted. It is being A key member 3 is fixed to the lens mount portion 1 and extends in the optical axis direction. Reference numeral 4 denotes a zooming operation tube, which is rotatably supported with respect to the fixed tube 2, and a part of it has a zooming operation tube 6.
has been planted. A cam cylinder 5 is made of plastic and is held rotatably within a predetermined angular range by a bayonet claw 2a inside the fixed cylinder 2. Further, a lens barrel 7 that moves in the optical axis direction is loosely inserted into the inside thereof via a cam means to be described later.

A cam portion 5a has a rectangular cross-section, and is provided on the inner wall of the cam cylinder 5 so as to protrude toward the center and have a certain lead. 5b is a groove, which is provided on the outer periphery of the cam cylinder 5, and which connects the bayonet pawl 2 provided on the fixed cylinder 2.
A is inserted.

The aforementioned dowel 6 connects the cam barrel 5 and the zooming operation barrel 4 through the nip hole 2c of the fixed barrel 2, and transmits the rotational force of the zooming operation barrel 4 to the cam barrel 5.

7 is a lens barrel, which is movable in the optical axis direction. 7a is a cam follower, which is integrally provided on the outer periphery of the lens barrel 7. The cam portion 5a and the cam follower 7a constitute one element of cam means. Reference numeral 7b denotes a key groove, which is provided on the outer circumference of the lens barrel 7 in a direction parallel to the optical axis, into which the key member 3 extending from the mount 1 is fitted. L+, L2, and L3 are lens groups constituting a zoom lens, and each is held by a lens holding frame.

In this embodiment, the zooming operation barrel 4 is rotated in such a configuration. Then, the cam barrel 5 connected to the zooming operation barrel 4 by a dowel 6 rotates around the optical axis. The lens barrel 7 is held inside the cam barrel 5, the three cam portions 5a are sandwiched between cam followers 7a, and the key member 3 is fitted into the keyway 7b. Therefore, when the cam barrel 5 rotates, the lens barrel 7 is guided by the key member 3 and moves a predetermined amount in the optical axis direction in accordance with the amount of rotation.

At this time, the cam portion 5a of the cam barrel 5 is engaged with the cam follower 7a of the lens barrel 7, and the lens barrel 7 is held at a certain level.
to move in the direction of the optical axis. This performs zooming operations.

In this embodiment, the cam portion 5a has a rectangular cross-sectional shape, and its side surfaces 5al are the side surfaces 7a2 and 7a of the groove portion 7al of the cam follower 7a, as shown in FIG.
It is configured so that it makes surface contact with 3.

In this way, the cam follower 7a holds the cam surface 5al in surface contact. Also, the side surfaces of the cam follower 7a are opposite to each other with the cam portion 5a in between, and the moving direction 5al of the cam portion 5a is
The surface 7a4.7a5 on the opposite side to the line 5a2 orthogonal to
are each formed of a slope (plane or curved surface) having a predetermined angle θ in the direction away from the cam portion 5a.

This configuration enables smooth zooming operations and effectively prevents the cam surface from being damaged by the impact force of the lens barrel 7.

FIGS. 5 and 6 show the second part of the cam follower according to the present invention. FIG. 7 is a schematic diagram of main parts of a third embodiment.

In the second embodiment shown in FIG. 5, a surface 7 corresponding to the two surfaces 7a4 and 7a5 shown in FIG. 4 among the side surfaces of the cam follower 7a.
46, 7a7 are made up of curved surfaces. The other configuration is the same as the cam follower shown in FIG.

In the third embodiment shown in FIG. 6, a surface 7 corresponding to the two surfaces 7a4 and 7a5 shown in FIG. 4 among the side surfaces of the cam follower 7a.
The angles θ of a8 and 7a9 are increased so that they are parallel to the optical axis. As a result, for example, when the cam follower 7a is molded from plastic, as shown by diagonal lines in the figure, the surfaces 7a2 and 7a3 that contact the cam surface of the cam follower 7a can be molded using a movable mold that opens in the optical axis direction and a fixed mold, respectively. That's what I do.

In the above embodiments, the present invention is applied to a lens barrel that is moved by a zooming operation, but it can be similarly applied to a lens barrel that is moved by a focusing operation.

(Effects of the Invention) According to the present invention, by configuring the cam part as a cam means for moving the lens barrel and the cam follower to be in surface contact as in the above-described shape, the cam can withstand strong impact applied to the cam follower. It is possible to achieve a lens barrel moving device capable of smooth and highly accurate movement without damaging the surface and resistant to abrasion of the cam follower.

In addition, because the cross-sectional shape of the cam section was conventionally trapezoidal, the width of the cam section changed significantly due to deformation of the cam cylinder, making it difficult to maintain the accuracy of the cam section, and the entire mold for forming the cam surface and the molded product. It was difficult to measure the lift dimension of the cam surface.

On the other hand, according to the present invention, by making the cross-sectional shape of the cam part square, it can be molded into a perfect square screw shape, so it is easy to measure the dimensions of the entire molded product and the cam surface of the molded product, for example. High precision shape is guaranteed. In addition, the effect of deformation of the cam cylinder on the width of the protrusion of the cam part is small, and compared to a trapezoidal cam part, there is no wedge action, so the cam cylinder can be operated with low torque.

In addition, when molding a cam follower integrally with a lens barrel, it is usually molded with a slide mold that releases the mold in a direction perpendicular to the optical axis, but in the case of a completely square cam part, the twist caused by the lead of the cam part Undercuts are formed in the mold release direction, making it impossible to release the mold. In contrast, the present invention has features such as being able to be molded by removing the twisted portion from the cam portion at a predetermined angle.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of the main parts of the first embodiment when the present invention is applied to a zoom lens, FIG. 2 is a perspective view of the main parts of the cam barrel shown in FIG. 1, and FIG. 3 is the lens shown in FIG. 1. FIG. 4 is an enlarged schematic diagram of a portion of the cam follower shown in FIG. 3; FIG. FIG. 6 shows the second cam follower according to the present invention. It is an enlarged schematic diagram of a 3rd example. In the figure, 1 is a lens mount part, 2 is a fixed cylinder, 3 is a key member, 4 is a zooming operation cylinder, 5 is a cam cylinder, 5a is a cam part, 5al is a cam surface, 5b is a groove part, 6 is a pin, 7 is a lens barrel, 7a is a cam follower, and 7b is a keyway. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6/65

Claims (1)

[Claims] (1) In a lens barrel moving device that uses a cam means to move a lens barrel, the cam means connects a cam portion provided on the inner peripheral surface of the cam barrel to be rotated or linearly moved. The cam follower is provided in a part, and the cam part has a rectangular cross-sectional shape protruding toward the center of the cam cylinder and has a constant lead, and the cam follower is attached to the lead of the cam part. The cam surface of the cam part is held in surface contact with the cam part, and the cam parts are opposed to each other while sandwiching the cam part.
A lens barrel moving device characterized in that the surface opposite to a line perpendicular to the moving direction of the cam section is formed in a direction away from the cam section.