JPH0417923Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a lens barrel, and more particularly to the structure of a cylindrical member in which a holding member for holding an optical member is housed.

(Prior Art) Conventionally, the main parts of this type of lens barrel have been made of metal. These metal materials have the disadvantages of being expensive, requiring high processing costs, and being heavy. Attempts have been made to use plastic molding materials to overcome these drawbacks, but holding tubes that hold a movable lens frame inside, such as zoom lenses, are particularly difficult to use because they have cam grooves. , the wall thickness of the material becomes extremely uneven, the amount of shrinkage varies depending on the location when molded with plastic, and the dimensional accuracy of the cylinder's roundness and the groove width of the cam groove is considerably lower than that of metal materials. It was inferior and could not be put to practical use.

In a conventional lens barrel, the fitting structure between a cylindrical member such as a fixed cylinder that houses the holding member and the holding member is such that the entire circumference of the outer cylindrical surface of the holding member is in contact with the entire circumference of the inner circumferential surface of the cylindrical member. It was hot. Therefore, if the cylindrical member is made of plastic material, the perfect circular shape of the cylindrical member will collapse and deform during the molding process, during the cooling process after molding, or due to changes over time, resulting in deformation into an ellipse, rice ball shape, etc.
As a result, displacement of the axis of the optical member and problems with the sliding properties of the holding member have occurred. Conventionally, in the above case, the mold was corrected and the mold was machined so that the molded cylindrical member maintained a perfect circle, but as is well known, mold machining requires ultra-precise precision, which increases the processing cost of the product. There were problems such as price increases.

(Objective of the invention) The present invention provides a lens barrel that solves the problems of the plastic cylinder member described above.

Particularly, the present invention provides a cylindrical member structure that can solve the above-mentioned problems when a cylindrical member housing a holding member for holding an optical member is made by molding a plastic material.

Furthermore, the present invention provides a lens barrel that prevents the reflection of light rays by utilizing the structure of the cylinder member and does not cause flare or the like.

Furthermore, the present invention provides a lens barrel that takes measures against leakage of lubricating oil applied to the sliding surfaces of the holding member and the cylindrical member.

(Example of idea) 1 and 2 show an embodiment of the present invention.

In the figure, 1 is a fixed barrel that constitutes a lens barrel, and the fixed barrel 1 has three protruding sliding contact parts 1a ₁ , 1a ₂ , and 1a ₃ extending in a direction parallel to the optical axis on the inner peripheral surface. , guide grooves 1b ₁ , 1b ₂ , 1b ₃ are provided in the protruding sliding contact portions 1a ₁ , 1a ₂ , 1a ₃ in a direction parallel to the optical axis. Inner peripheral surface 1 other than the protruding sliding contact portions 1a ₁ , 1a ₂ , 1a ₃
Antireflection portions in the shape of uneven surfaces, sawtooth surfaces, etc. are applied to c ₁ , 1c ₂ , and 1c ₃ .

The cylindrical member 1 is made of a plastic material, such as polycarbonate, by molding.

Reference numeral 2 denotes a holding member that holds an optical element _l1 such as a lens or filter, and is fitted inside the fixed cylinder 1.

The outer peripheral surface of the holding member 2 is in sliding contact with the protruding sliding contact portion of the fixed tube 1, and the other inner peripheral surface, that is, the surface provided with anti-reflection is not in sliding contact. Reference numeral 4 denotes a rotating member fitted on the outside of the fixed cylinder 1, and the rotating member 4 has cam grooves 4a ₁ , 4a ₂ , which intersect with the guide grooves _{1b 1} , 1b 2 , 1b ₃ .
4a ₃ (not shown) is formed. 6 is the straight groove 1b ₁ ,
These are engagement pins that are implanted in the holding member 2 and are engaged with the intersections of 1b ₂ and 1b ₃ and the cam grooves 4a ₁ , 4a ₂ , and 4a ₃ . Projected sliding contact portions 1a ₁ , 1a ₂ , 1 of the cylindrical member 1
On one end side of _a3 , there are grooves 1d ₁ , 1d 2 , 1d ₂ in the direction around the optical axis.
1d ₃ (not shown).

In the lens barrel configured as described above, when the rotary member 4 is rotated around the optical axis, the engagement pin 6 moves in a direction parallel to the optical axis, and accordingly, the optical element also moves.

The holding member 2 has the protruding sliding contact portions 1a ₁ , 1a ₂ , 1
a ₃ , and apply lubricating oil such as grease between the two. The excess amount of lubricating oil accumulates in the grooves 1d ₁ , 1d ₂ , and 1d ₃ .

The cylindrical member 1 is made by molding a plastic material. The molding process is performed by injecting a plastic material into a cavity in a mold consisting of an outer mold and an inner mold, and solidifying the plastic material. The inside of the cylindrical member 1 is formed by the outer peripheral surface of an inner mold (male mold), and the outside of the cylindrical member 1 is formed by the inner peripheral surface of an outer mold (female mold). The protruding sliding contact portions 1a ₁ , 1a ₂ , 1 of the cylindrical member 1
a ₃ is formed by the recess 8a of the male die 8 as shown in FIG.

The concave portion 8a of the male die 8 is cut to obtain a perfect circle of the cylindrical member 1, particularly the outer surface of the protruding sliding contact portion. In this case, the protruding sliding contact portions 1a ₁ , 1a ₂ ,
In order to accurately correct the mold (male mold), it is preferable that the width x in the circumferential direction of 1a ₃ is as short as possible because the processing area becomes smaller.

Guide grooves 1 formed in sliding contact parts 1a ₁ , 1a ₂ , 1a ₃
The width y of b ₁ , 1b ₂ , and 1b ₃ is determined by the diameter of the engagement pin 6.

The effective sliding width dimension of the protruding sliding contact portion that actually slides in sliding contact with the holding member 2 is the dimension xy, and the width dimension z on one side is 1/2 of that.

In the embodiment of the present invention, by making the dimension z approximately equal to the thickness of the thin wall portion of the cylindrical member 1, the sliding of the holding member 2 is improved in terms of workability such as molding of the cylindrical member. We were also able to obtain very favorable results in terms of gender.

Lens barrels For example, polycarbonate is used in the case of interchangeable lens barrels for single-lens reflex cameras, but when molding polycarbonate to make the tube member 1 shown in Figure 2, the wall thickness is preferably about 1.4 mm to 1.5 mm. . This is a size that is close to the limit for strength as a lens barrel and for preventing "sink" and "distortion" due to cooling during molding and aging. By making the dimension z of the cylindrical member 1 of the present invention approximately equal to the thickness dimension t (for example, 1.4 mm) of the thin portion, the protruding sliding contact portions 1a ₁ , 1a ₂ , 1a ₃ "sink", " It was possible to suppress the occurrence of "distortion" and maintain the accuracy of the correction processing of the recessed part of the male mold.

1e ₁ and 1e ₂ shown in Fig. 1 indicate oil sump grooves,
These grooves 1e ₁ , 1e ₂ correspond to the protruding sliding contact portions 1a ₁ , 1
It is used in place of the grooves 1d ₁ , 1d ₂ , 1d ₃ provided on one end _side of a 2 , 1a ₃ , and the protruding sliding contact portion 1
It is provided in the anti-reflection section along the a ₁ , 1 _{a 2} , and 1 a ₃ in a direction parallel to the optical axis, or it is provided so as to surround the periphery of the anti-reflection section. The guide grooves 1b ₁ , 1b ₂ , and 1b ₃ are illustrated as straight grooves running parallel to the optical axis, but if the holding member 2 is to be moved in a nonlinear manner, they are nonlinear guide grooves.

The cylindrical member of the lens barrel of the present invention described above has a protruding sliding contact portion formed on the inner diameter surface along the guide groove, and is in sliding contact with the holding member on the inner diameter side through this protruding sliding contact portion. Therefore, it has become possible to perform molding using a synthetic resin material in place of cutting using a metal material, and it has become possible to satisfy accuracy and reduce manufacturing costs. In particular, the positional relationship between the cam follower provided on the holding member and the guide groove of the cylindrical member, which requires high precision, can also be improved by forming the protruding sliding contact portion along the guide groove. Movement of the holding member can be obtained.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the lens barrel, Fig. 2 is a perspective view of the main parts of the lens barrel, Fig. 3 is a sectional view of the main parts of the molding die, 1...tube member, 2...holding member, 1a ₁ , 1a ₂ ,
1a ₃ ... protruding sliding contact portion, 1b ₁ , 1b ₂ , 1b ₃ ... guide groove, 4 ... rotating member.

Claims (1)

[Claims for Utility Model Registration] (1) A cylindrical member that movably supports a holding member that holds an optical member on the inner diameter side thereof, and a plurality of cam followers provided on the holding member are inserted. In a lens barrel in which a guide groove is formed in the cylindrical member, along the guide groove on the inner diameter surface of the cylindrical member,
A lens barrel characterized in that a plurality of protruding sliding contact portions are formed in sliding contact with an outer diameter portion of the holding member. (2) The lens barrel according to claim 1, wherein an anti-reflection structure is provided in a portion of the inner diameter surface of the cylindrical member other than the protruding sliding contact portion. (3) The lens barrel according to claim 1 or 2, wherein a groove is formed at an end position of the protruding sliding contact portion on the inner diameter surface of the cylindrical member.