JP2591774Y2 - Backlash removal mechanism for lead groove guide device of lens barrel - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead groove guiding device for a lens barrel, and more particularly to a backlash removing mechanism for the device.

[0002]

2. Description of the Related Art In a lens barrel, for example, a lead groove (including a cam groove) guide mechanism is widely used for moving a focusing lens or a zooming lens group for zooming in the optical axis direction. ing. In this guide mechanism, basically, a lead groove is provided in one (eg, a lens support ring) of two relatively rotating annular members, and a roller (roller) fitted in the lead groove is provided in the other (eg, a fixed ring). It is configured. When the lens support ring is rotated with respect to the fixed ring, the lens support ring moves in the axial direction according to the shape of the lead groove.

In this lead groove guide mechanism, backlash cannot be avoided due to the clearance between the lead groove and the roller. This backlash appears as a phenomenon of image skipping in which the focus position changes suddenly in the focusing mechanism, and as a sudden change in the focal length in the zooming mechanism. For this reason, various types of backlash removing mechanisms have been conventionally proposed. Basically, the backlash removing mechanism always contacts one roller to one side of the lead groove by urging one of the two annular members to move in the axial direction. However, in the conventional structure, this urging mechanism becomes large, and the axial position of the annular member causes
There was a problem that the biasing force changed. When the urging force changes, the rotation resistance and the like change, and stable operation cannot be obtained.

Recently, in order to reduce the cost, the annular member is being formed into a resin molded product, and the accuracy of the molded product is inferior to that of a machined product. growing. In order to minimize the backlash itself, several rollers with slightly different diameters (for example, 1/100 mm each) are prepared, and the roller with the smallest gap is selected for each lead groove. But work efficiency is very poor.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve such a conventional problem and to provide a backlash removing mechanism which is small and whose urging force does not change depending on the axial position of the annular member.

[0006]

SUMMARY OF THE INVENTION The present invention provides a groove-side annular member having a lead groove, separately from the lead groove, a pressing surface parallel to the lead groove, and a roller-side annular member on which a roller is provided. An elastic member is provided for elastically contacting and biasing the groove-side annular member toward one side in the axial direction so as to elastically contact the roller with the other side of the lead groove. According to this configuration, even if the axial position of the annular member changes, the force for urging the annular member in the axial direction does not change.

[0007]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
In this embodiment, the present invention is applied to a surveillance camera lens. As shown in FIG. 1, the surveillance camera lens includes, in order from the object side, a focusing lens group L1,
This is a four-unit configuration including a variable power lens unit L2, a compensator lens unit L3, and a master lens unit L4. Each lens group L1 to L4 includes a respective lens frame 11, 12, 1
3 and 14, respectively.
Is fixed to a focusing ring 16 rotatably fitted around the distal end of the fixed cylinder 15. The lens frames 12 and 13 are guided linearly by a fixed barrel 15,
The cam ring 17 is rotatably fitted on the inner circumference of the lens and moves in the optical axis direction. The master lens unit L4 has a fixed barrel 15
It is fixed to. The focusing ring 16 is driven to rotate via a pinion that meshes with the drive gear 23.

The lead groove guiding mechanism and its backlash removing mechanism, which are features of the present invention, are a focusing ring (groove-side annular member) 16 and a fixed cylinder (roller-side annular member) 1.
5 is provided. As is apparent from FIG. 2, the focusing ring 16 has a lead groove 18 inclined with respect to the circumferential direction, and a pressing surface 25 different from the lead groove 18 and parallel to the lead groove 18. A roller 19 fitted in the lead groove 18 is pivotally attached to the fixed cylinder 15 by a shaft 21, and an elastic member 20 elastically contacting a pressing surface 25 is fixed by a shaft 26. Each of the roller 19 and the elastic member 20 is preferably made of a molded product of a synthetic resin material. In general, a lead groove refers to a linear groove, and a cam groove refers to a non-linear groove. However, the lead groove referred to in this specification is a concept including both.

Therefore, according to the above configuration, regardless of the moving direction of the focusing ring 16, the roller 19
Due to the zero force, the lead groove 18 rotates while always elastically contacting the rear wall B with the same force. In particular, even when the focusing ring 16 changes the rotating direction, this relationship is maintained.
The phenomenon of "image jump" in which the focusing state changes rapidly does not occur. Further, the driving force when driving the focusing ring 16 via the driving gear 23 does not change.

FIGS. 3, 4, 5 and 6 show modifications of the elastic member 20. FIG. FIG. 3 shows the elastic leg 20a provided with a hollow portion 20b to increase the elastic force. FIG. 4 shows the elastic leg 2a.
A U-shaped bent portion 20c is provided at the tip of the hole 0a to increase the elastic force. FIG. 5 shows only one hollow portion 20d.
FIG. 6 shows an elastic contact portion 20e formed, and FIG. 6 shows an asymmetric shape of a pair of elastic legs 20a.

In the above embodiment, the present invention is applied to a focusing mechanism of a lens barrel. The present invention can be applied to all devices for guiding an annular member by a lead groove (including a non-linear cam groove). .

[0012]

As described above, according to the present invention, in the guide mechanism using the lead groove, the backlash caused by the play between the lead groove and the roller can be easily and surely removed by a small and space-saving device. it can. Further, even if the rotational position of the annular member changes, the urging force in the axial direction does not change. In addition, since a pressing surface parallel to the lead groove is provided separately from the lead groove on the groove-side annular member having the lead groove, a degree of freedom is obtained in the installation position of the pressing surface and the elastic member elastically contacting the pressing surface.

[Brief description of the drawings]

FIG. 1 is an upper half sectional view of a lens barrel to which a backlash removing mechanism of a lead groove guiding mechanism of the present invention is applied.

FIG. 2 is an enlarged development view as viewed from an arrow P in FIG. 1;

FIG. 3 is a plan view showing another example of the elastic member used in the present invention.

FIG. 4 is a plan view showing still another example of the elastic member used in the present invention.

FIG. 5 is a plan view showing another example of the elastic member used in the present invention.

FIG. 6 is a plan view showing another example of the elastic member used in the present invention.

[Explanation of symbols]

 Reference Signs List 11 lens frame 15 fixed cylinder (roller-side annular member) 16 focusing ring (groove-side annular member) 18 lead groove 19 roller 20 elastic member 21 shaft 25 pressing surface

Continuation of the front page (56) References JP-A-54-91322 (JP, A) JP-A-62-184512 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02B 7 / 04-7/16

Claims (1)

(57) [Scope of request for utility model registration] 1. A lead groove guide device for a lens barrel, wherein a lead groove is provided on one of two annular members which rotate relatively, and a roller is fitted on the other of the two members. The member is provided with a pressing surface parallel to the lead groove separately from the lead groove. The roller-side annular member provided with the roller is elastically contacted with the pressing surface, and the groove-side annular member is moved in one axial direction. A backlash removing mechanism for a lead groove guiding device for a lens barrel, wherein an elastic member is provided for urging the roller to resiliently contact the other side of the lead groove.