JP2532713Y2 - Zoom lens cam mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a cam mechanism of a zoom lens, and more specifically, controls movement of a lens optical system in an optical axis direction by a cam member and a cam follower. The present invention relates to a cam mechanism of a zoom lens.

[Conventional technology]

Conventionally, in performing a zooming operation of a zoom lens, a cam mechanism for moving the lens optical system in the optical axis direction includes a cam follower implanted in the lens optical system formed on a cylindrical cam member. This is performed by so-called one-sided cam means which is pressed against the cam surface of the shape by, for example, a spring urging force, and the cam follower spring-contacted the cam surface is moved in the optical axis direction by the rotation of the cam member.

[Problems to be Solved by the Invention] By the way, in the spring contact of the cam follower to the cam surface, the spring contact force of the cam follower to the cam surface changes due to the movement of the cam follower in the optical axis direction accompanying the rotation of the cam member. However, as a result, the load force applied to the cam member fluctuates, and the movement of the lens optical system cannot be performed smoothly.

As a means for reducing the above-mentioned change in the spring contact force, the problem can be solved by using a relatively long spring member. However, in such a case, the space occupied by the spring member becomes large and the size of the camera is reduced. Disadvantageous.

Therefore, as a device devised to solve the above problem, for example, there is a cam mechanism of a zoom lens disclosed in Japanese Utility Model Laid-Open No. 98805/1985.

That is, this cam mechanism is such that the cam follower of the moving optical system that moves in the optical axis direction is pressed against the cam portion of the cam member by the press contact means. With respect to the movement in the optical axis direction, the pressing force of the cam follower by the pressing means of the cam follower does not change so much, so that the moving optical system can be moved smoothly. Basically, it is a proposal for an integral cam configuration, and it is difficult to mold a cam member. Further, in a so-called multipoint cam in which the cam member is supported by a plurality of cam followers, the number of parts inevitably increases, and the cost increases accordingly.

As another solution, for example, a zoom lens described in Japanese Patent Publication No. 52-20136 has been proposed, but in the case of this conventional example, the configuration is extremely complicated, the number of parts is large, and The disadvantage is that it takes a lot of time and effort to assemble, and is therefore expensive.

This invention has been made to solve the above-mentioned problems, and its purpose is to reduce the number of parts as well as to reduce the fluctuation of the spring pressing force of the cam follower to the cam surface. It is another object of the present invention to provide a cam mechanism for a zoom lens which has a simplified configuration and enables molding.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a cam mechanism of a zoom lens that controls movement of a lens optical system in the optical axis direction by a cam member and a cam follower, and has a cam follower and holds the lens optical system. A lens holding frame, a fixed cylindrical body that supports the lens holding frame movably in the optical axis direction, a drive cam member that is rotationally driven by a drive motor and has a cam surface of a predetermined shape on at least one end surface, and the drive cam A driven cam member having a cam surface substantially equivalent to the cam surface of the member, and moving in the optical axis direction while rotating in synchronization with the drive cam member while sandwiching the cam follower between the cam surface of the drive cam member and And a spring member for urging the cam follower against the cam surface of the drive cam member via the driven cam member.

[Action]

The cam mechanism of the zoom lens according to the present invention always presses the cam follower against the cam surface of the driving cam member through a driven cam member having a cam surface equivalent to the cam surface of the driving cam member by the spring force of the spring member. , The pressure of the cam follower against the cam surface can be kept substantially constant against the movement of the cam follower in the optical axis direction accompanying the rotation of the driving cam member. Axial movement can be performed smoothly.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

1 and 2 are a cross-sectional view and an external view showing the configuration of an embodiment of a cam mechanism of a zoom lens according to the present invention.

In both figures, reference numeral 1 denotes a fixed cylindrical body fixed to a camera body (not shown). Straight guide grooves 2 extending in the optical axis O direction are formed at positions facing the peripheral wall of the fixed cylindrical body 1. A lens holding frame 3 for holding the lens groups 4, 4 is fitted into the fixed cylindrical body 1. The lens holding frame 3 has two cam followers 5, 5 planted on the outer peripheral surface thereof. Cylinder 1
Are respectively engaged with the straight guide grooves 2, and are movable in the optical axis O direction.

A drive cam member 6 made of a cylindrical body is fitted around the outer periphery of the fixed cylinder 1 so as to be rotatable about an optical axis O. The drive cam member 6 is driven by a drive source such as a motor (not shown). The force is transmitted via a speed reduction mechanism to rotate. Also,
One end face of the drive cam member 6 (left end face in FIG. 2)
As is apparent from the perspective view shown in FIG. 3, two cam surfaces 7, 7 having the same shape are shifted from each other by 180 °, and these cam surfaces 7, 7 are outside the straight guide groove 2. The cam followers 5 and 5 that protrude are engaged (abutting).

On the other hand, a driven cam member 8 made of a cylindrical body is fitted around the outer periphery of the fixed cylindrical body 1 on the front side of the driving cam member 6 so as to be rotatable about the optical axis O and movable in the optical axis O direction. On one end surface (right end surface in FIG. 2) of the driven cam member 8, there are provided cam surfaces 9, 9 substantially equivalent to the cam surfaces 7, 7 of the driving cam member 6, respectively. 9 and cam surface 7,7
And sandwich the cam followers 5,5 respectively.

Further, the driving cam member 6 and the driven cam member 8 engage with the protruding piece 6a provided on the driving cam member 6 so as to have a slight gap (play) with a notch 8a formed on the driven cam member 8. Thus, the rotation of the driven cam member 8 synchronized with the rotation of the driving cam member 6 can be realized.

Reference numeral 10 denotes a spring member interposed between a flange portion 1a formed at the front end of the fixed cylindrical body 1 and the driven cam member 8, and this spring member 10 is partially cut as shown in FIG. The cam follower 5 is always pressed against the cam surface 7 of the driving cam member 6 by the spring biasing force of the spring member 10 via the driven cam member 8 with an appropriate pressing force. ing.

Next, the operation of the cam mechanism of the zoom lens according to the present invention will be described.

When the driving cam member 6 rotates either clockwise or counterclockwise from a driving source (not shown) via a deceleration mechanism by starting the zooming operation, the cam surface 7 is pressed against the driven cam member 8 via the driven cam member 8. The cam follower 5 advances and retreats along the rectilinear guide groove 2 due to the rotational movement of the cam surface 7, and the lens group 4 moves forward or backward in the optical axis O direction together with the lens holding frame 3 to perform a zoom operation.

In the above operation, the driven cam member 8 rotates in synchronization with the rotation of the driving cam member 6, so that the intervals between the cam surfaces 7 and 9 of the driving member 6 and the driven cam member 8 are kept substantially constant. The spring force of the spring member 10 is kept substantially constant.
Accordingly, the cam follower 5 moves forward and backward along the guide groove 2 in a state where the cam follower 5 is sandwiched by the cam surfaces 7 and 9 of the driven cam member 8 with a substantially constant pressing force.

That is, despite the movement of the cam follower 5 in the optical axis direction, the spring member 10 hardly expands and contracts, and the pressing force between the cam follower 5 and the cam surface 7 hardly changes. By rotating the lens 6 with a constant rotational force, the movement of the lens optical system in the optical axis direction can be performed smoothly.

Further, since the projecting piece 6a of the driving cam member 6 and the notch 8a of the driven cam member 8 are engaged so as to cause some play, an error generated on the cam surfaces 7, 9 of the two cam members 6, 8 is reduced. The two cam followers 5,5 can be evenly pressed against the cam surfaces 7,7 by absorption.

The present invention is not limited to only the above-described embodiment, and various modifications can be made without departing from the scope of the invention.

For example, in the embodiment, two cam followers 5 are provided.
Although the case of a so-called two-point cam has been described, the same operation can be obtained in the case of a three-point cam or a one-point cam. In the case of a one-point cam, play between the protruding piece 6a of the driving cam member 6 and the cutout portion 8a of the driven cam member 8 is unnecessary.

In addition, although the example in which the engagement portion between the protruding piece 6a and the cutout portion 8a is provided at one location has been described, the number of engagement locations may be provided according to the number of multipoint cams.

[Effect of the invention]

As described above, according to the present invention, the fluctuation of the pressing force of the cam follower against the cam surface can be reduced to smoothly move the lens optical system in the optical axis direction, and the number of parts can be reduced. Since the entire structure can be simplified and the molding of the cam member can be performed, there is little secondary processing, and there is an effect that it can be manufactured inexpensively.

[Brief description of the drawings]

1 and 2 are a sectional view and an external view, respectively, showing the configuration of an embodiment of a cam mechanism of a zoom lens according to the present invention, and FIG. 3 is a drive cam member and a driven cam according to the embodiment. FIG. 4 is a perspective view of a member, and FIG. 4 is a perspective view of a spring member applied to the embodiment. DESCRIPTION OF SYMBOLS 1 ... Fixed cylindrical body, 2 ... Straight guide groove, 3 ... Lens holding frame, 4 ... Lens group, 5 ... Cam follower, 6 ...
Driving cam member, 6a Projecting piece, 7 Cam surface, 8 Followed cam member, 8a Notch, 9 Cam surface, 10 Spring member, O Optical axis.

Claims (1)

(57) [Scope of request for utility model registration] A cam mechanism and a cam follower for controlling the movement of a lens optical system in an optical axis direction by a cam member and a cam follower. A lens holding frame having a cam follower and holding a lens optical system, and the lens A fixed cylindrical body that supports the holding frame so as to be movable in the optical axis direction, a drive cam member that is rotated and driven by a drive motor and has a cam surface of a predetermined shape on at least one end surface, and is substantially equivalent to the cam surface of the drive cam member A driven cam member having an appropriate cam surface and moving in the optical axis direction while rotating in synchronization with the drive cam member with the cam follower interposed between the driven cam member and the driven cam member; And a spring member for urging the cam follower against the cam surface of the driving cam member.