JPH0769506B2 - Lens barrel - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a lens barrel in an optical device, and more particularly, to a lens having a structure in which an outer helicoid body and an inner helicoid body are screwed with each other via a helicoid screw. Regarding the lens barrel.

[Prior Art] In recent years, in a manufacturing technology such as a VTR, a lens barrel configured by combining an outer helicoid body and an inner helicoid body in a state of being screwed with each other via a helicoid screw is
For example, in order to reduce the manufacturing cost, it is made of synthetic resin. Here, the backlash that occurs when the outer helicoid body and the inner helicoid body are fitted to each other has a serious influence on the performance and characteristics of an optical device such as a VTR in which a lens barrel configured by combining them is mounted. To exert. That is, such fitting backlash causes a fatal defect in the optical device as a product as described below.

a) Poor resolution due to misalignment of the optical axis b) Malfunction of inward liquid body c) Flange back defect.

In order to solve these problems, conventionally, for example,
The technique disclosed in JP-A-56-9710 has been proposed. In this publication, the pitch and lead angle of a helicoid screw are set differently from those of other helicoid screws; the helicoid thread shape is set differently from other helicoid thread shapes; It is disclosed that a groove is provided along the lead in the portion.

The techniques disclosed in this publication are all aimed at preventing thrust play in the helicoid screw fitting portion. However, as shown in and, even if the helicoid screw thread shape and the like are made different from the other portions, the helicoid screws will slide relative to each other in accordance with the feeding and feeding of the inner helicoid body. For this reason, the helicoid screw thread is worn, and it is impossible to prevent the backlash of the fitting portion due to the helicoid screw.

Further, the groove is formed in the helicoid screw thread to add elasticity to the helicoid screw thread so as to absorb the thrust play of the helicoid screw fitting portion. However, since the helicoid screw thread fits and slides while leaning against the mating member, the rotation torque is increased,
The rotation torque cannot be kept constant, which causes uneven rotation. Also, the helicoid thread
It has been pointed out that the synthetic resin is deformed due to shrinkage during molding, which makes it extremely difficult to set the rotational torque.

As described above, in this conventional technique, it is very difficult to provide a lens barrel provided with a helicoid screw that does not have thrust backlash and can maintain a rotating torque at a constant and appropriate value. . Therefore, in order to solve the problems of JP-A-56-9710, JP-A-57-210304 and JP-A-57-210305 have been proposed.

In Japanese Patent Laid-Open No. 57-210304, a protrusion having elasticity is provided on the outer peripheral portion of the inner helicoid body to prevent radial play when the inner helicoid body and the outer helicoid body are fitted to each other. Is configured.
Further, in JP-A-57-210305, a lightening portion is formed at the bottom of the helicoid screw thread of the inner helicoid body, and the helicoid screw thread itself is made to have elasticity, and this helicoid screw thread is pressed against a mating member. Is configured.
With such a configuration, the thrust and radial play at the time of fitting can be prevented by the action / reaction force generated at the time of pressing.

[Problems to be Solved by the Invention] However, in the techniques disclosed in these two publications, the elastic member provided on the inner helicoid body always fits and slides while being pressed against the mating member. Therefore, it has been pointed out that the rotational torque is heavy, and the rotational torque is different depending on when the inner helicoid body is extended and when it is extended. Further, since the inner helicoid body integrally provided with such an elastic member is molded with a synthetic resin by using an injection molding die, due to defective release of the elastic member, deformation from the design shape, insufficient dimension, etc. The shape of the elastic member is not stable. Therefore, it becomes very difficult to set the elastic coefficient of the elastic member,
It has been pointed out that there are problems such as a decrease in yield during molding and a difficulty in setting the rotational torque.

The present invention has been made in view of the above-described problems, and an object of the present invention is to improve the wear resistance of a helicoid screw while reducing the radial play when fitting the inner helicoid body and the outer helicoid body. In this way, it is possible to provide a lens barrel made of synthetic resin that can improve the reliability of the optical system by eliminating the deviation of the optical axis.

[Means for Solving the Problems] In order to solve the above-mentioned problems and to achieve the object, a lens barrel of the present invention has an inner helicoid body molded from a synthetic resin and a screw engagement with the inner helicoid body. A possible outer helicoid body, and a plurality of helicoid thread portions formed in a state of being separated from each other along one of the circumferential surfaces of the inner helicoid body and the outer helicoid body facing each other along the circumferential direction, and the circumference. A helicoid thread groove formed on the other of the surfaces, into which the helicoid thread portion is screwed, and a circumferential surface of the inner helicoid body and the outer helicoid body that face each other in a state of being located between the adjacent helicoid thread portions. A first protrusion that is formed on one side and slides on a portion of the other peripheral surface where the helicoid screw groove is formed, and a corresponding helicoid screw on the protruding face of the helicoid screw thread portion. A second protrusion having a top proximate the bottom surface of the groove.

[Operation] In the lens barrel configured as described above, when the inner helicoid body is rotated with respect to the outer helicoid body, the inner helicoid body is disposed between the helicoid thread portions on the peripheral surface where the helicoid thread groove is formed. The first protrusions that are slid on are in sliding contact with each other, and the tops of the second protrusions are in slidable contact with the groove bottom surface of the helicoid screw groove, so that rattling along the radial direction is prevented and the resolution is improved. At least the inner helicoid body can be molded with synthetic resin.

[Embodiment] A configuration of an embodiment of the lens barrel according to the present invention, in which the inner helicoid is molded using a synthetic resin, will be described in detail below with reference to the accompanying drawings.

As shown in FIG. 1, the lens barrel 10 of this embodiment is
It is provided with an outer helicoid body 12 that is driven by a motor or is held and rotated by an operator of the camera, and an inner helicoid body 14 that is housed inside the outer helicoid body 12 and screwed into the outer helicoid body 12. . This outer helicoid body 12 is
Although it has several steps on its outer and inner surfaces, it is basically composed of a tapered, substantially cylindrical body. Then, the inner peripheral surface 12 at the intermediate position of the outer helicoid body 12
A helicoid thread groove 16 having a predetermined lead is continuously formed in a over the entire circumference.

Here, the focal length of the lens barrel 10 as a whole is
It is defined by a first lens system 18 and a second lens system 24, which are held by an inner helicoid body 14 and an outer helicoid body 12, respectively, which will be described later. This focal length is variably set by moving along the axial direction.

On the other hand, like the outer helicoid body 12, the inner helicoid body 14 also has some steps on its outer surface and inner surface, but is basically composed of a substantially cylindrical body having a tapered shape. The inner helicoid body 14 has the above-mentioned helicoid thread groove 16 on the outer peripheral surface of the intermediate portion 14a.
It is disposed so as to be movable along the optical axis direction via a helicoid screw portion 20 that is screwed into.

A holding mechanism 22 for holding the lens system 18 is formed on the inner circumference of the inner helicoid body 14. On the other hand, outer helicoid body
A second lens holding a second lens system 24 is provided on the inner circumference behind the second lens 12.
The holding mechanism 25 is formed. Here, the outer peripheral surface of the front portion 14b of the inner helicoid body 14 is set to be spaced apart from the inner peripheral surface of the front portion 12b of the outer helicoid body 12 by a small distance. On the outer peripheral surface of the front portion 14b of the inner helicoid body 14, a plurality of sliding contact ribs 28 are formed integrally along the circumferential direction at equal intervals so as to extend along the axial direction.
Each of the sliding contact ribs 28 is formed in a semicircular shape in cross section, and is set to be in sliding contact with the outer peripheral surface of the outer helicoid body 12 by line contact.

Further, as shown in FIG. 2, the helicoid screw portion 20 formed on the outer peripheral surface of the inner helicoid body 14 is formed with a lead corresponding to the helicoid screw groove 16, and extends along the circumferential direction. Helicoid thread 20a divided into 3 intervals
It consists of ~ 20c. Each helicoid thread 20a-20
The c has a plurality of screw thread portions 26 protruding from the outer peripheral surface of the inner helicoid body 14 by a predetermined thickness in a state of being arranged in parallel in the axial direction.

That is, helicoid threads that are adjacent to each other in the circumferential direction.
20a to 20c are arranged in a state of being separated from each other by a predetermined distance, and in this separated portion, as shown in FIG. 3, only a predetermined height is provided radially outward from the outer peripheral surface of the inner helicoid body 14. A projecting portion 30 is integrally formed. Where each protrusion
The height of 30 is set so that the surface thereof comes into sliding contact with the inner circumferential surface of the outer helicoid body 12 on which the helicoid thread groove 16 is threaded.

Also, as shown in FIGS. 4 and 5, each thread portion 26
In the above, a plurality of recesses 32 are formed at predetermined intervals on both side surfaces 26a, 26b in the middle thereof. This recess 32 is
It will function as a so-called oil sump. Further, as shown in FIG. 4, a plurality of protrusions 34 are formed at predetermined intervals on the protruding surface of each thread portion 26. Each convex portion 34
Are projected radially outward from the projecting surface of the thread portion 26 by a predetermined height.

Here, the predetermined height is set so that the protruding surface of the convex portion 34 is provided close to the bottom surface of the corresponding helicoid screw groove 16. In other words, in a state where the inner helicoid body 14 is slightly tilted in the radial direction, the projecting surfaces of these convex portions 34 and the bottom surface of the helicoid thread groove 16 are in contact with each other, and further tilt, that is, radial backlash is prevented. Is set to.

The operation of the lens barrel 10 configured as described above will be described below.

First, the lens barrel 10 is configured in a state where the inner helicoid body 14 and the outer helicoid body 12 are combined. In the lens barrel 10 thus configured, when the outer helicoid body 12 is rotationally driven, a sliding state occurs between the outer helicoid body 12 and the inner helicoid body 14. Here, as described above, since the threaded portion 26 of the helicoid threaded portion 20 is formed with the recessed portion 32 that functions as an oil reservoir, this sliding state causes the lubricating oil stored in each recessed portion 32 to Will be carried out smoothly through.

On the other hand, the outer helicoid 1 is attached to the outer peripheral surface of the intermediate portion 14a of the inner helicoid 14 which is smoothly slid through the lubricating oil in this manner.
A projection 30 is formed between the inner helicoid 2 and the inner helicoid 14 to prevent radial play. On the other hand, for the same purpose, a plurality of protrusions 34 are formed on the protruding surface of each thread portion 26. In this way, these protrusions 30 and protrusions 34
By the action, the radial backlash of the inner helicoid body 14 is prevented, and the deviation of the optical axis is eliminated. In this way, in this embodiment, the resolution failure due to the deviation of the optical axis is surely prevented.

First, in one embodiment described above, the inner helicoid body 14
Is supported at both ends by screwing the helicoid screw groove 16 and the helicoid screw portion 20 to the outer helicoid body 12, and sliding contact between each sliding contact rib 28 and the inner peripheral surface of the outer helicoid 12. Will be done.

That is, in the conventional case, since the sliding contact rib 28 is not provided, the inner helicoid body 14 is not provided with the outer helicoid body 12.
When the helicoid screw groove 16 and the helicoid screw portion 20 are screwed with respect to each other, the length of the screwed portion of the helicoid screw groove 16 is set to be short. Therefore, the inner helicoid body 14 becomes the outer helicoid body.
It becomes a cantilevered state with respect to 12, and due to its own weight, it tilts down in the radial direction by the amount of the above-mentioned gap provided. As a result, the optical axis of the first lens system 18 may tilt from the predetermined optical axis.

However, even in this extended state, in this one embodiment, as described above, the outer periphery of the front portion 14b of the inner helicoid body 14 has the inner peripheral surface of the outer helicoid body 12 via the sliding rib 28. Since the inner helicoid body 14 is slidably in contact with the outer helicoid body 12, the optical axis of the first lens system 18 is favorably held at a predetermined position without falling down with respect to the outer helicoid body 12. Further, since the inner helicoid body 14 does not fall down with respect to the outer helicoid body 12, the screwed state of the helicoid screw groove 16 and the helicoid screw portion 20 is maintained well. That is, according to this embodiment, the poor resolution and the unnecessary operation due to the collapse of the inner helicoid body 14 will not occur.

It goes without saying that the present invention is not limited to the configuration of the above-described embodiment and can be variously modified without departing from the scope of the present invention.

For example, in the configuration of the above-described embodiment, the concave portion 32 that functions as an oil sump is formed on both side surfaces 26a and 26b of the thread portion 26.
It is described as being formed. However, the present invention is not limited to such a configuration, and as shown in FIG. 6 and FIG. 7 as a modified example, the recess 32 ′ is formed not only on both side surfaces of the thread portion 26 but also on the projecting surface. You may comprise so that it may be formed across. By forming the recess 32 'in this way, the capacity that functions as an oil sump is set to a large value, and the lubricating effect is more reliably achieved.

Further, in the configuration of the above-described embodiment, it has been described that the outer peripheral surface of the inner helicoid body 14 is formed with a helicoid screw thread, and the outer peripheral surface of the outer helicoid body 12 is formed with the helicoid thread groove 16. However, the present invention is not limited to such a configuration, and forms a helicoid screw groove on the outer peripheral surface of the inner helicoid body 14 and forms a helicoid screw thread on the inner peripheral surface of the outer helicoid body 12. Even with the above configuration, the same effect can be obtained.

[Effects of the Invention] As described in detail above, according to the present invention, the wear resistance of the helicoid screw is improved, and the radial rattling when the inner helicoid body and the outer helicoid body are fitted to each other is reduced. It is possible to provide a lens barrel made of synthetic resin that can improve the reliability of an optical system by eliminating axial misalignment.

[Brief description of drawings]

1 is a sectional view showing the construction of an embodiment of a lens barrel according to the present invention; FIG. 2 is a perspective view showing the construction of an inner helicoid body; FIG. 3 is a sectional view showing the shape of the inner helicoid body; 4 and 5 are perspective views and sectional views showing recesses and protrusions formed in the thread portion; and FIGS. 5 and 6 are perspective views and sectional views showing modified examples of the recesses; 7 is a cross-sectional view taken along the line VI-VI in FIG. In the figure, 10 ... Lens barrel, 12 ... Outer helicoid body, 12a
…… Inner surface, 12b …… Middle part, 12c …… Front part, 14…
… Inside helicoid body, 14a …… Intermediate part, 14b …… Front part, 16 …… Helicoid thread groove, 18 …… First lens system,
20 ... Helicoid screw part, 20a to 20c ... Helicoid screw thread, 22 ... Holding mechanism, 24 ... Second lens system, 25 ... Second holding mechanism, 26 ... Thread part, 26a; 26b ...... Side, 2
8 …… Sliding contact rib, 30 …… Projection, 32; 32 ′ …… Recess, 34 ……
It is a convex part.

Claims (3)

[Claims] 1. An inner helicoid body formed of a synthetic resin, an outer helicoid body screwable with the inner helicoid body, and one of the peripheral surfaces of the inner helicoid body and the outer licoid body facing each other. A plurality of helicoid screw thread portions formed in a state of being separated from each other along the direction, helicoid screw grooves formed on the other side of the peripheral surface, into which the helicoid screw thread portions are screwed, and adjacent helicoid screw threads A first protrusion that is formed on one of the opposing peripheral surfaces of the inner helicoid body and the outer helicoid body and is in sliding contact with the portion of the other peripheral surface where the helicoid thread groove is formed, while being located between the mountain portions. And a second protrusion having a top portion adjacent to the bottom surface of the corresponding helicoid screw groove on the protrusion surface of the helicoid screw thread portion. 2. The outer peripheral surface of the inner helicoid body is provided with a plurality of sliding contact ribs which are in sliding contact with the inner peripheral surface of the outer helicoid body. Lens barrel. 3. The two sides of the helicoid thread portion are
The lens barrel according to claim 1 or 2, wherein a recess functioning as an oil reservoir is formed between the second protrusions.