JP2590348Y2 - Oil splash prevention device for 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 lens barrel for performing focusing, zooming, and the like through a gear train mechanism, and more particularly to an oil splash prevention device for preventing lubricating oil in the gear train from scattering around.

[0002]

2. Description of the Related Art In a lens barrel having an AF (auto focus) mechanism, a PZ (power zoom) mechanism, and the like, a gear train mechanism is used as a driving mechanism. Some gears of this gear train mechanism rotate at high speed, and a small amount of lubricating oil is often used for smooth operation. This lubricating oil may scatter around when the gear rotates at high speed. On the other hand, in an interchangeable lens that is required to be as small as possible, many components are arranged in a narrow space, and the scattered oil may adversely affect the lens performance. For example, if oil adheres to the diaphragm blade or its operating mechanism parts, smooth operation becomes impossible due to the viscosity of the oil, and if it adheres to the lens, optical performance deteriorates.

[0003]

The object of the present invention is to provide an oil splash prevention device which does not adversely affect the aperture mechanism (aperture block) of the lens barrel even if the lubricating oil used for gears scatters, based on the awareness of such problems. Aim.

[0004]

SUMMARY OF THE INVENTION According to the present invention, an aperture block having a plurality of aperture blades for changing the size of an aperture centered on an optical axis, and at least one of constituent lens groups are light-transmitted through a gear train mechanism. A lens driving mechanism having a lens driving mechanism for moving in the axial direction, wherein at least one of the gears constituting the gear train mechanism and not having the optical axis as the center of rotation covers at least the outer periphery of the gear on the optical axis side; An oil splash prevention cover is provided to prevent lubricating oil adhering to the row mechanism from scattering toward the throttle block. Generally, lubricating oil is often applied to a large gear whose rotation center is the optical axis. For this reason, it is most preferable that the oil splash prevention cover is provided on a gear that always meshes with the gear having the optical axis as the center of rotation.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An interchangeable lens barrel 1 in which switching between AF and MF (manual focus) is made possible on the lens side.
The illustrated embodiment in which the present invention is applied to FIG. The interchangeable lens barrel 10 is of a two-group type that includes a front lens group L1 and a rear lens group L2, and performs focusing by adjusting the position of the rear lens group L2 in the optical axis direction. Front group lens L
Reference numeral 1 is fixed to a fixed lens barrel 12 provided at the rear end with a connection mount 11 for connection to a camera body. The fixed lens barrel 12 has an AF-MF switching ring 13 supported on its front outer periphery so as to be movable in the optical axis direction, and a distance scale ring 14 rotatably supported on its rear inner periphery. The AF-MF switching ring 13 also serves as a manual focusing ring. In addition, the fixed lens barrel 12
Has a fixed inner tube 12a, a lead ring 15 is rotatably fitted to the outer periphery of the inner fixed tube 12a, and a movable lens barrel 16 is fitted to the inner periphery. Distance scale ring 14 and lead ring 15
Are connected by a connecting member 17 and always rotate the same. A distance scale (not shown) is provided on the outer circumference of the distance scale ring 14, and the distance scale is fixed to the fixed barrel 12.
At the distance scale window (not shown).

A straight guide groove 19 extending in a direction parallel to the optical axis is formed in the inner fixed cylinder 12a, and a lead groove 20 is formed in the lead ring 15. The radial pin 22 implanted in the movable barrel 16 is inserted through the straight guide groove 19 and the lead groove 20, and when the lead ring 15 rotates, the radial pin 22 follows the straight guide groove 19 and the lead groove 20 and moves. Moves straight in the optical axis direction. The movable lens barrel 16 includes a rear lens group L
2 and the stop block 50 are supported. Therefore, when the lead ring 15, that is, the distance scale ring 14 is rotationally driven, the rear lens group L2 moves in the optical axis direction to perform focusing.

The AF mechanism comprising a gear train mechanism is a mechanism for electrically driving and rotating the distance scale ring 14. The distance scale ring 14 has a lens driving inner gear 23 centered on the optical axis on its inner periphery. Is formed. On the other hand, a joint gear 25 is rotatably supported by the connection mount 11 and the bearing plate 26 . The joint gear 25 has a joint 25a at the rear end coupled to a joint gear of the camera body, and has a gear 25b at the front end. The gear 25b meshes with a gear 27 supported by the bearing plate 24 and the bearing plate 26, and a small gear 27a coaxially integrated with the gear 27 always meshes with a clutch gear 29 integrated with the switching shaft 28.

On the other hand, a clutch gear 30 is fitted on the switching shaft 28 so as to be relatively rotatable and movable in the axial direction. The clutch gear 30 is rotatably supported by a bearing plate 31 fixed to the inner surface of the fixed lens barrel 12, and always meshes with the inner gear 23 of the distance scale ring 14. Each of the clutch gear 29 and the clutch gear 30 has a clutch tooth 29
a and 30a are formed. Although the shape of the clutch teeth 29a is not clear in the drawing, it is the same as that of the clutch teeth 30a, and the clutch gear 29 and the clutch gear 30 rotate together when both approach and the two clutch teeth 29a and 30a are engaged. I do. All of the gears other than the lens drive inner gear 23 are small gears located around the lens barrel and not having the optical axis as the center of rotation.

The distal end of the switching shaft 28 is supported by a guide plate 34 fixed to the fixed lens barrel 12 by a fixing screw 33. The compression coil spring 3 inserted through the switching shaft 28
5 and washer 36, and C fixed to the tip of switching shaft 28
The ring 37 allows the clutch teeth 29a of the clutch gear 29 to move forward, that is, the clutch teeth 30 of the clutch gear 30.
It is urged to move in the direction engaging with a.

On the guide plate 34, an AF-MF detection switching plate 38 is supported. The AF-MF detection switching plate 38 includes a long hole 38 a corresponding to the fixing screw 33, a pressed protrusion 38 b engaging with the pressing protrusion 13 a of the AF-MF switching ring 13, and a step switching shaft of the switching shaft 28. It has an engaging portion 38c with the switching shaft 28, is movable in the same direction as the switching shaft 28, and is urged forward by a tension coil spring 39 stretched between the switching shaft 28 and the guide plate 34. ing. The AF-MF detection switching plate 38 has a brush 41 that comes into contact with a code plate 40 fixed to the fixed lens barrel 12. When the brush 41 changes the contact position, the code plate 40 switches between AF and MF. To the camera body. The engaging portion 38c is provided with a pressing protrusion 13a of the AF-MF switching ring 13.
When the AF-MF detection switching plate 38 is operated to move backward, the switching shaft 28 is moved backward.

As is well known, the aperture block 50 sandwiches a plurality of aperture blades 53 between an aperture opening / closing ring 51 and an aperture support ring 52, and reduces the drive dowel 53 a planted on one surface of the aperture blade 53. A squeezing dowel 53b planted on the other surface is inserted into a support hole 52a of the squeezing support ring 52 in a squeezing opening / closing cam groove (not shown) of the opening / closing ring 51. The aperture support ring 52 is fixed to the fixed lens barrel 12, and the aperture opening / closing ring 51 is rotatable. The aperture ring 51
The diaphragm driving rod 55 extends in a direction parallel to the optical axis. The diaphragm driving rod 55 is driven by a diaphragm driving arm 56. The iris drive arm 56 is pivotally attached to the fixed lens barrel 12 by a shaft 57. A driven portion 56a at the rear end faces the rear portion of the connection mount 11, and a linking pin 56b at the front end is connected to the iris drive rod 55. Engage. The shaft 57 is provided on a support plate 59 fixed to the fixed lens barrel 12 with a fixing screw 58. The driven portion 56a is rotated by, for example, a predetermined angle by an aperture driving member on the camera body side.
The aperture diameter formed in 3 changes in size.

In the interchangeable lens barrel 10 having the above structure, a small amount of lubricating oil is applied to the inner gear 23 of the distance scale ring 14, which is a large gear centered on the optical axis. The lubricating oil may transfer to the clutch gear 30 which always meshes with the lubricating oil. When the clutch gear 30 rotates at a high speed, the lubricating oil scatters around. The aperture block 50 is a clutch gear 3
In particular, at the infinity photographing position where the rear lens group L2 (moving lens barrel 16) is most retracted, it is closest to the clutch gear 30. If oil is applied to the aperture block 50 and the oil adheres to the aperture blades 53, for example, the operation of the oil becomes worse due to the viscosity of the oil, and the attached oil shines, causing internal reflection. Furthermore, if oil adheres to the surface of the constituent lens of the rear lens group L2, the image performance deteriorates, and similarly causes internal reflection.

In this embodiment, the clutch gear 30 which always meshes with the inner gear 23 is provided with an oil splash prevention cover 45 for preventing oil from scattering toward the optical axis. The oil splash prevention cover 45 is fixed to a bearing plate 31 fixed to the fixed lens barrel 12 by a fixing screw 46 as shown in FIGS. The arc-shaped covering portion 45a to be covered and the insertion groove 4 of the switching shaft 28
5b. The oil splash prevention cover 45 has its arc-shaped cover portion 45a directed toward the optical axis O (the aperture block 50 side) and its open portion 45c directed radially outward. The oil splash prevention cover 45 is not shown in FIG.

Therefore, if the oil splash prevention cover 45 is provided, lubricating oil which may be scattered around when the clutch gear 30 rotates at a high speed adheres to the aperture block 50 or the constituent lens of the rear group lens L2. Can be eliminated.

The clutch gear 30 rotates at a high speed in the AF state in which the AF-MF switching ring 13 is at the forward moving end as shown in FIG. 1 and the clutch teeth 29a and the clutch teeth 30a are engaged. At this time, rotation is given to the joint gear 25 via the joint shaft of the camera body, and this rotation is applied to the clutch gear 30 via the above-mentioned gear train mechanism and further to the distance scale ring 1 from the inner gear 23.
4, transmitted to the lead ring 15, and the movable lens barrel 16. On the other hand, when the AF-MF switching ring 13 is moved backward,
The pressing protrusion 13a presses the pressed protrusion 38b, and the engaging portion 38
Then, the switching shaft 28 and the clutch gear 29 are retracted via c, and the engagement between the clutch teeth 29a and the clutch teeth 30a is released. At the same time, the AF-MF switching ring 13 is coupled to the distance scale ring 14 so as to rotate integrally with the distance scale ring 14 by an engagement mechanism (not shown). Therefore, MF is performed by rotating the AF-MF switching ring 13.

In the above, the AF lens is shown as an interchangeable lens having a gear train mechanism.
The same applies to the Z lens. That is, when the variable power lens group is driven via a gear train, an oil splash prevention cover is similarly provided on at least a part of the constituent gears. Also in this case, it is most effective to provide a small gear that always meshes with the lens drive gear about the optical axis as a rotation center with an oil splash prevention cover for an aperture block having a plurality of aperture blades.

[0017]

As described above, according to the present invention, the aperture block having a plurality of aperture blades for changing the size of the aperture aperture centered on the optical axis and at least one of the constituent lens groups are formed by a gear train mechanism. In a lens barrel having a lens driving mechanism that moves in the optical axis direction via a, a gear train mechanism, at least one of the gears that do not have the optical axis as the center of rotation,
An oil splash prevention cover is provided to cover at least the outer periphery of the gear on the optical axis side and to prevent the lubricating oil adhering to the gear train mechanism from scattering to the throttle block side. It is possible to eliminate the possibility that the components such as the aperture block aperture blades scattered on the shaft side are contaminated.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of an apparatus for preventing oil splashing of a lens barrel according to the present invention.

FIG. 2 is a perspective view of the main part.

FIG. 3 is a perspective view of a main part including the throttle block.

FIG. 4 is an exploded perspective view of a main part of an AF-MF switching mechanism.

[Explanation of symbols]

 Reference Signs List 10 interchangeable lens barrel 12 fixed barrel 13 AF-MF switching ring 14 distance scale ring 15 lead ring 16 movable barrel 17 coupling member 19 straight guide groove 20 lead groove 22 radial pin 23 lens drive inner gear 24 26 31 bearing plate 25 Joint gear 27 27a Gear 28 Switching shaft 29 30 Clutch gear 29a 30a Clutch teeth 45 Oil splash prevention cover 50 Throttle block 51 Throttle opening / closing ring 52 Throttle support ring 53 Throttle blade 55 Throttle drive rod 56 Throttle drive arm

Claims (2)

(57) [Scope of request for utility model registration] 1. The size of a stop aperture centered on the optical axis is changed.
A diaphragm block having a plurality of diaphragm blades to be
At least one of the lens groups is moved in the optical axis direction via a gear train mechanism.
In the lens barrel and a lens drive mechanism for moving the direction, constituting the gear train mechanism, the at least one gear without the optical axis as the center of rotation, cover the optical axis side outer circumference of at least the gear, the Lubricating oil adhering to the gear train mechanism
An oil spill prevention device for a lens barrel, comprising an oil spill prevention cover for preventing the oil from splattering toward the lens barrel. 2. The oil jumping device for a lens barrel according to claim 1, wherein the gear having an oil splash prevention cover is a gear that always meshes with a lens driving gear whose rotation axis is the optical axis. Oil splash prevention device for cylinders.