JPH08304688A - Backlash prevention mechanism for lens barrel - Google Patents

Abstract

(57) [Abstract] [Purpose] Prevents looseness in the optical axis direction between a pair of helicoid-joined cylinders, and prevents fluctuations in load when rotating one cylinder, and (EN) A rattling prevention mechanism capable of simultaneously preventing rattling. [Structure] The other cylinder 6 that is helicoidally coupled to one cylinder 3 that is rotationally operated is composed of first and second cylinders 61 and 62 that are divided in the optical axis direction. The first and second cylindrical portions are connected in the optical axis direction by a connecting member 7 having an elastic force in the optical axis direction. Due to the elastic force of the connecting member 7, the first and second cylindrical body portions 61 and 62 come into contact with the respective one cylindrical body 3 in different optical axis directions, and play in the optical axis direction is prevented. To be done. In addition, since the biasing forces of the first and second cylindrical bodies are offset, the fluctuation of the load when the one cylindrical body is rotated in the forward and reverse directions is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has relative rotating cylinders screwed together by a helicoid, and one cylinder is rotated forward or backward in the direction around the optical axis to move the other cylinder to the optical axis. More particularly, the present invention relates to a lens barrel that moves back and forth in a direction, and more particularly to a mechanism that prevents play between the two barrels.

[0002]

2. Description of the Related Art As a mechanism for changing the focus and the focal length of a camera lens, a pair of cylinders are screwed together by a helicoid, and one cylinder is rotatable around an optical axis,
The structure of the lens barrel is configured so that the other cylinder is regulated so as not to rotate around the optical axis, and by rotating one cylinder on the other cylinder, the other cylinder is moved back and forth along the optical axis direction. It is provided. However, in this helicoid, since there are tolerances and manufacturing errors between the two cylinders, rattling is likely to occur in the optical axis direction and the radial direction.
In particular, looseness in the optical axis direction causes so-called backlash when changing the rotation direction of one cylinder between forward rotation and reverse rotation, and causes a deviation in the relative rotational positional relationship between both cylinders. Let

Normally, in a lens barrel of a camera lens, the focal position and focal length of the lens are detected based on the advance / retreat position of the other cylinder, but normally, the moving position of this retracted cylinder is detected. Instead of detecting, the detection is performed by detecting the rotational angle position of one of the cylinders that is closely related to the advance / retreat position of the other cylinder. For this reason,
If backlash or backlash occurs between the rotational position and the retracted position of the cylindrical body, the above-mentioned detection accuracy is lowered, and along with this, the accuracy of the focusing and automatic setting of the focal length in the camera is lowered. Further, the radial play causes the position of the optical axis of the lens to be unstable, and in any case, causes deterioration of the lens performance of the camera.

Therefore, a mechanism for preventing this kind of looseness has been conventionally proposed. For example, actual Kaihei 4-10461
In Japanese Patent Laid-Open No. 2 and Japanese Utility Model Laid-Open No. 3-6614, the other cylinder in the helicoid portion is urged in the optical axis direction by an elastic member to urge the other cylinder that is moved forward and backward in the optical axis direction. The body is pressed against one of the cylinders to prevent backlash in the optical axis direction. Further, in Japanese Patent Laid-Open No. 2-207207, by inserting an elastic material between the radial directions of the two lens barrels, the two barrels are pressed in the radial direction to prevent backlash in the radial direction. I am trying to

[0005]

However, each of the conventional rattling prevention mechanisms proposed in the above publications has a structure for preventing rattling in either the optical axis direction or the radial direction. It is difficult to prevent backlash at the same time. For this reason, in order to prevent backlash in both directions, it is necessary to independently provide each structure in the lens barrel, which complicates the structure and increases the number of parts, thus reducing the size of the lens barrel. It is not preferable for the purpose.

Further, in order to prevent backlash in the optical axis direction,
In the above-mentioned publication, since the tubular body that is moved forward and backward is urged in one direction of the optical axis, elastic force is constantly applied to this tubular body in the optical axis direction. Therefore, when the cylinder is moved back and forth, the load, that is, the torque, of one cylinder in the direction around the optical axis is changed depending on whether the cylinder is moved in the urging direction or the opposite direction. become. When the lens barrel is manually moved back and forth, such a fluctuation in torque causes the operating force of the rotating barrel to differ depending on the direction of the lens barrel. The operability of the cylinder or the entire camera is reduced. Further, in an autofocus camera that moves a lens barrel forward and backward by a motor or the like or a camera that employs a power zoom mechanism, the control characteristics of the motor vary due to the difference in torque described above, which makes quick and highly accurate control difficult. It also becomes a cause.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a rattling prevention mechanism in which the load does not fluctuate when the cylinder is operating. Another object of the present invention is to provide a rattling prevention mechanism capable of simultaneously preventing rattling in the optical axis direction and rattling in the radial direction.

[0008]

The rattling prevention mechanism of the present invention is such that when one of the pair of helicoidally connected cylinders is rotationally operated, it is moved in the direction of the optical axis. The other tubular body is composed of first and second tubular bodies divided in the optical axis direction, and the first and second tubular bodies are biased in different directions along the optical axis. And are connected to each other in the optical axis direction.

For example, the first and second cylindrical bodies are connected by a connecting member having an elastic force in the optical axis direction. In addition, this connecting member urges the first and second tubular portions, for example, in a direction in which they are separated from each other in the optical axis direction. Further, the first and second cylindrical body portions are connected by the connecting members at a plurality of circumferential positions of the edges facing each other in the optical axis direction.

Further, in the backlash preventing mechanism of the present invention, the connecting member integrally has an elastic piece portion having an elastic force toward the inner diameter direction, and the elastic piece portion is radially arranged on the outer peripheral surface of the one cylindrical body. It is preferable that the structure is elastically contacted with.

[0011]

Next, the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment in which the present invention is applied to a focusing mechanism for a lens barrel, and is a vertical cross-sectional view of the lens barrel above the optical axis. In the figure, the rear lens group L2 is attached to the inside of the fixed barrel 1 having a bayonet mount 2 attached to and detached from the camera body at its base end, and at the position on the tip side in the optical axis direction. The helicoid cylinder 3 is coaxially installed. The circular flange 3a provided at the base end portion of the helicoid cylinder 3 is fitted into the circumferential groove 1a on the inner surface of the fixed cylinder 1, so that the helicoid cylinder 3 does not move in the optical axis direction and moves around the optical axis. It is configured to be rotatable. Further, a drive pin 4 which is radially penetrated through the circumferential groove 1a of the fixed barrel 1 is fixed to a part of the circumference of the circular flange 3a, and the drive pin 4 is fitted on the outer side of the fixed barrel 1. By engaging the combined distance operation ring 5, the helicoid cylinder 3 can be rotated around the optical axis by rotating the distance operation ring 5.

In the radial gap between the fixed barrel 1 and the helicoid barrel 3, a movable barrel 6 which is divided and formed in the optical axis direction is arranged. 2 shows the appearance of the moving barrel 6, and FIG. 3 shows a developed view in the circumferential direction thereof, the moving barrel 6 is divided into a first moving barrel portion 61 and a second moving barrel portion 62. Although the first moving barrel portion 61 and the second moving barrel portion 62 have different lengths in the optical axis direction, they have the same inner diameter and outer diameter dimension, and the inner surface thereof has the helicoid groove 61a. , 62a are formed and screwed to the outside of the helicoid cylinder 3. The first moving barrel portion 61 arranged at the base end side of the lens barrel is integrally formed with a key portion 63 protruding in the radial direction on a part of the circumference thereof. It is fitted into a key groove 1b provided in the inner surface of the optical axis direction, and thereby the first moving tubular portion 61 is restricted from rotating around the optical axis. In addition, the second lens disposed on the tip side of the lens barrel
A front lens group L1 is attached to the movable barrel portion 62 for focusing in cooperation with the rear lens group L2.

Further, the first and second moving barrel portions 6
Reference numerals 1 and 62 denote rectangular notches 64 formed by cutting out a part of the front surface side of each cylinder at a plurality of circumferential positions at opposite ends, in this example, at positions equally divided into three in the circumferential direction. , 6
5 is formed in the optical axis direction. The connecting member 7 is fitted between the notches that are opposed to each other, and the connecting member 7 allows the first and second moving tubular portions 61 and 62 to move in the optical axis direction and the optical axis direction. Each is integrated. FIG. 4A is a plan view of this connecting member, and FIG. 5B is a vertical sectional view thereof. The connecting member 7 is composed of an elongated substantially rectangular connecting piece portion 71 and an elastic piece portion 72 integrally provided on the inner surface of the connecting piece portion 71, and is formed by, for example, resin molding.

The connecting piece portion 71 is formed to have the same width dimension as the notches 64 and 65 provided in the moving cylinder portions 61 and 62, and a frame-like portion 73 is formed at one end thereof. In this frame-shaped portion 73, elastic force in the lengthwise direction is applied. And this frame-shaped portion 7
3 and the other end are fitted into the notches 65 and 64 of the respective moving cylinders 62 and 61 in a press-fitted state. In this fitted state, the first and second moving tubular portions 61 and 62 are in a connected state, and the frame-shaped portion 73 is elastically deformed in the longitudinal direction by the projection 73a provided at the tip of the frame-shaped portion 73. Configured to let. In addition, the elastic piece 7
2 has a base end portion protruding from the inner surface of the connecting piece portion 71 and extends along the inside of the connecting piece portion 71, and has a tip portion 72a curved inward. As a result, the elastic piece portion 72 imparts elasticity to the connecting piece portion 71 in the thickness direction thereof.

Therefore, when the first and second moving cylinders 61 and 62 connected by the connecting member 7 are screwed to the outside of the helicoid cylinder 3 as shown in FIG. 62 helicoid screw pitch dimension and connecting member 7
Due to the relationship with the length of the connecting member 7, the connecting member 7 is inserted between both the moving cylinder portions in a state of being compressed in the axial direction.
For this reason, the frame-shaped portion 73 is elastically deformed by this compression force, and a reaction force against this compression force is generated in the frame-shaped portion 73, and this reaction force is generated in the first moving tubular portion 61 and the second moving tubular portion 62.
And are applied in a direction to separate and in the axial direction. As a result, as shown in the enlarged view of FIG. 5, the first moving tubular portion 61 is pressed rightward as indicated by an arrow F1 in the drawing, and the helicoid 6 is pushed.
The right slope of the screw thread of 1a is brought into contact with the left slope of the screw thread of the helicoid cylinder 3, and the second moving cylinder portion 62 is pressed to the left as shown by an arrow F2 to the left slope of the screw thread of the helicoid 62a. Is brought into contact with the right slope of the thread of the helicoid cylinder 3.
As a result, the movable barrel portions 61, 62 are biased in mutually opposite directions, and play in the optical axis direction with respect to the helicoid barrel 3 is prevented.

At this time, since the abutting forces in the optical axis directions generated in the respective moving barrel portions 61 and 62 are opposite to each other, the moving barrel 6 as a whole is biased in the optical axis direction with respect to the helicoid barrel 3. Therefore, when the helicoid cylinder 3 is rotated, the operation force does not change due to the difference in the rotation direction, and the operation force for operating the focal length of the lens does not vary.

On the other hand, in the state of FIG. 1 in which both the moving cylinder portions 61 and 62 are screwed into the helicoid cylinder, the elastic piece portion 7 of the connecting member 7 is formed.
2 is brought into contact with the top surface of the screw thread of the helicoid cylinder 3 and is elastically deformed somewhat in the outer diameter direction. Therefore, the elastic piece 72 applies an elastic force to the screw thread in the inner diameter direction by its reaction force. Then, as shown in the cross-sectional view seen from the optical axis direction in FIG. 6, the elastic piece portions 72 of the respective connecting members 7 are located at three positions in the circumferential direction of the moving barrel 6 (61, 62).
By applying an elastic force in the inner diameter direction to the moving cylinder 6, the moving cylinder 6 is elastically held in a concentric position with the helicoid cylinder 3 due to the balance between these, and radial play between the two cylinders is prevented. Will be. The elastic piece 72
Since the tip portion 72a is curved in the outer diameter direction, even when the connecting member 7 is moved in the optical axis direction together with the moving barrel 6, the tip portion 72a does not bite into the thread of the helicoid barrel 3.

FIG. 7 is a sectional view similar to FIG. 1 showing another embodiment of the present invention, in which the helicoid cylinder 3 is connected to the motor 8 as shown in FIG.
And an example in which the reduction gear mechanism 9 is rotationally driven. That is, the internal gear 3A is formed along the inner peripheral surface of the base end of the helicoid cylinder 3, the gear of the reduction gear mechanism 9 rotationally driven by the motor 8 is meshed with the internal gear 3A, and the rotation of the motor rotates the helicoid cylinder 3A. Is rotated around the optical axis.

Also in this structure, the moving barrel 6 is composed of the first and second moving barrel portions 61 and 62 and is connected to each other by the connecting member 7, which is the same as the first embodiment. Then, the first and second moving tubular portions 61, 6
Since 2 is biased in the opposite directions in the optical axis direction,
The urging force in the optical axis direction in the entire movable barrel 6 is canceled out,
It is also the same that the torque is made uniform. Therefore, in this configuration, since the load is constant regardless of the rotation direction of the motor 8, the moving speed of the moving barrel 6 can be made uniform, and high-precision motor control can be performed.

In the above embodiment, the connecting member is fitted in the notches of the respective moving cylinders, but this may be connected by adhesion. Further, the elastic piece portion may be configured such that a part of the connecting piece portion is projected in the inner diameter direction. In addition, the connecting member may be configured to urge the first and second moving tubular portions in a direction in which they approach each other in the optical axis direction.

[0021]

As described above, according to the present invention, of a pair of helicoidally joined cylinders, the other cylinder, which is moved in the optical axis direction with respect to one cylinder, is divided in the optical axis direction. The first and second cylindrical body portions are connected to each other in the optical axis direction while being biased in different directions of the optical axis direction. Therefore, the first and second tubular body portions are respectively brought into contact with one of the tubular bodies in different optical axis directions,
It is possible to prevent backlash in the direction of the optical axis with respect to one of the cylinders, and since the biasing forces of the first and second cylinders are offset, a biased force may be applied to one of the cylinders. In addition, when one of the cylinders is rotated, the operability is not impaired due to the difference in the operation force in the rotation direction.

Further, since the first and second cylindrical portions are connected by the connecting member having an elastic force in the optical axis direction, it is possible to connect both cylindrical portions and simultaneously apply a biasing force to both cylindrical portions. And the structure is not complicated.

For example, the connecting member is configured so as to urge the first and second cylindrical body parts in the direction of separating the first and second cylindrical body parts from each other in the optical axis direction, so that the connecting member is mounted between the cylindrical body parts in a compressed state. By doing so, it is possible to connect the two cylindrical body parts and to apply an urging force to the two cylindrical body parts, and it is possible to simplify the connection structure between the both cylindrical body parts and the connecting member.

Further, the first and second cylindrical portions are connected by the connecting members at a plurality of circumferential positions of the edges facing each other in the optical axis direction, so that both cylindrical bodies can be evenly rotated about the optical axis. The parts can be respectively biased in the axial direction, the coaxial position with one of the cylinders is maintained, and the other cylinder can be smoothly moved along the optical axis.

Further, in the present invention, the connecting member integrally has an elastic piece portion having an elastic force toward the inner diameter, and the elastic piece portion is elastically brought into radial contact with the outer peripheral surface of one cylinder. Thus, radial play between the other cylinder and the one cylinder can be prevented.

Here, one cylinder is constructed as a helicoid cylinder which is rotated around the optical axis by a manual operation or a drive source, and the other cylinder is moved forward and backward with respect to the helicoid cylinder in the optical axis direction. By configuring as a lens barrel, there is an effect that the focal length of the lens of the camera and the focusing operation can be performed accurately and smoothly without rattling.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an upper side of an optical axis of a lens barrel to which the present invention is applied.

FIG. 2 is a perspective view of a movable barrel.

FIG. 3 is a diagram developed in a direction around an optical axis of a movable barrel.

FIG. 4 is a plan view of a connecting member and a vertical sectional view thereof.

FIG. 5 is a diagram for explaining a backlash preventing action in the optical axis direction.
It is an enlarged view of the principal part.

FIG. 6 is a cross-sectional view seen from the optical axis direction for explaining the radial backlash preventing action.

FIG. 7 is a sectional view similar to FIG. 1 in another embodiment of the present invention.

[Explanation of symbols]

 1 Fixed Cylinder 3 Helicoid Cylinder 6 Moving Cylinder 7 Connecting Member 8 Motor 9 Reduction Gear Mechanism 61 First Moving Cylinder Part 62 Second Moving Cylinder Part 61a, 62a Helicoid Screw 64, 65 Notch 71 Coupling Piece 72 72 Elastic Piece

Claims (6)

[Claims] 1. A lens constructed such that a pair of cylinders constituting a lens barrel are helicoidally coupled, and when one cylinder is rotated around the optical axis, the other cylinder is moved in the optical axis direction. In the lens barrel, the other cylindrical body is composed of first and second cylindrical body parts divided in the optical axis direction, and the first and second cylindrical body parts are respectively arranged in different directions in the optical axis direction. A mechanism for preventing rattling of a lens barrel, which is connected to each other in the optical axis direction in a biased state 2. The rattling prevention mechanism for a lens barrel according to claim 1, wherein the first and second cylindrical portions are connected by a connecting member having an elastic force in the optical axis direction. 3. A rattling prevention mechanism for a lens barrel according to claim 2, wherein the connecting member urges the first and second cylindrical portions in a direction to separate them from each other in the optical axis direction. 4. The rattling prevention mechanism for a lens barrel according to claim 2, wherein the first and second cylindrical body portions are connected by a connecting member at a plurality of circumferential positions of the edges facing each other in the optical axis direction. 5. The connecting member integrally has an elastic piece portion having an elastic force toward the inner diameter direction, and the elastic piece portion is elastically brought into radial contact with the outer peripheral surface of the one cylindrical body. 2 to 4 lens barrel play prevention mechanism. 6. The one cylinder is a helicoid cylinder rotated around an optical axis by a manual operation or a drive source,
The rattling prevention mechanism for the lens barrel according to claim 1, wherein the other tubular body is a lens barrel that is moved forward and backward with respect to the helicoid barrel in the optical axis direction.