JPH0769505B2 - Motion transmission member of lens drive system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a focusing lens feeding mechanism for a camera lens, wherein an inner cylinder having the focusing lens fixed therein is slid back and forth by rotating a distance ring.
That is, the present invention relates to a motion transmitting member for converting rotational motion into linear motion and transmitting the linear motion.

(Prior Art) Conventionally, focusing of a camera lens is performed by rotating a distance ring (focus ring) outside the lens barrel to move a built-in focusing lens position by a predetermined amount in the optical axis direction to change a focus position. It is configured to do.

As a mechanism for moving the focusing lens position by rotating the distance ring in this way, a male screw is formed on the outer circumference of the inner cylinder to which the focusing lens is fixed, and a guide groove is formed in the optical axis direction to form the inner cylinder. , A guide plate that is rotatably attached to the lens mount or the camera body and is screwed into a distance ring with an internal thread formed on the inner circumference, and a guide plate installed immovably with the lens mount or the camera body A so-called straight helicoid mechanism in which the inner cylinder, which is slidably fitted to the shaft and whose rotation is restricted by the guide plate when the distance ring is rotated, slides in the optical axis direction along the guide groove. Depends on. In this case, the slide amount (length) of the inner cylinder for one rotation of the distance ring
Is called the lead.

This straight advancing helicoid type has a complicated structure and requires high-precision machining of parts and a wide mechanism space, so that it cannot meet the demands for size reduction, weight reduction and cost reduction.

Therefore, as a modification of the above mechanism, a guide slit in the optical axis direction is formed in the outer cylinder fixed to the lens mount or the camera body, and the inner cylinder fixed with the focusing lens is fitted in the outer cylinder and the outer cylinder is fitted. A cylindrical roller made of synthetic resin or the like with a small friction coefficient is fixed to the outer surface of the inner cylinder through the guide slit, and the upper end of the roller protruding from the outer surface of the outer cylinder is formed on the inner circumference of the distance ring. (Helicoid) is slidably fitted, and when the distance ring is rotated, the roller whose slide direction is regulated by the guide slit moves back and forth according to the change in the front and rear position of the screw groove, and slides the inner cylinder back and forth. There is something I did. That is, one roller has two functions of the male screw and the guide plate in the straight-moving helicoid type.

(Problems of the prior art) However, in the above-mentioned conventional mechanism, the roller that converts the rotational movement of the distance ring into the front-back movement of the inner cylinder is in line contact with the side surface of the spiral groove of the distance ring. Because of this, the stress is concentrated, and the inner cylinder is deformed by a relatively weak external force. Further, since the contact sliding position between the roller and the side surface of the spiral groove is always constant, the contact portion is significantly worn, and as a result, play is generated between the roller and the spiral groove. There is a fatal problem that backlash causes the lens position fixed to the inner cylinder to move, which makes it impossible to maintain the predetermined optical performance. There was a drawback that it deteriorated the sex and interfered with the shooting.

Further, the contact between the roller and the guide slit formed on the outer cylinder is the same as the line contact and the abutting sliding at the same position, so that there is a similar drawback. There is a backlash due to a fitting error between the inner diameter of the outer cylinder and the outer diameter of the inner cylinder. As a result, the above two errors are synergistically added to make a larger error, which further deteriorates the optical performance and deteriorates the feeling of use due to backlash.

In order to prevent such a state, the fitting clearance between the inner cylinder and the outer cylinder is reduced, multiple thread grooves are formed in the distance ring, the number of rollers is increased, and the guide slit 1 of the outer cylinder is formed. Two rollers are attached to the inner cylinder with respect to the strip, and either one of the rollers is projected from the upper surface of the outer cylinder so as to be fitted in the thread groove of the distance ring. Regarding the radial play of the cylinder, it is considered to prevent the play from occurring by the mounting interval of the two rollers.

However, in the case of such a configuration, the number of parts increases, and it is necessary to process and assemble each part with high precision, and as a result, the manufacturing cost increases.

Therefore, in the part where this mechanism is actually used, the focusing lens that moves by rotation of the range ring is lightweight, and external force from the outside is not directly applied, that is, the user can touch it. It is limited to a lens for inner focus that does not exist.

(Object of the Invention) The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a lens which has high durability and can be used in a portion to which an external force is applied, and which has a simple structure and high productivity. A motion transmission member of a drive system is provided.

(Means for Solving Problems) In order to solve the above problems, the motion transmitting member of the lens drive system according to the present invention is slidably fitted to the inner circumference of the outer cylinder fixed to the lens mount or the camera body. Is fitted to a guide slit formed in the outer cylinder so as to extend linearly along the axial direction, and restricts the sliding direction of the inner cylinder along the axial direction. Slidingly fits a lead groove formed to extend linearly in a distance ring that is relatively rotatably fitted to the outer circumference of the cylinder, and converts the rotational movement of the distance ring into a longitudinal movement of the inner cylinder. In the motion transmitting member, a base portion that is fitted in the guide slit and extends along the axial direction, and both end portions of both side surfaces of the base portion along the axial direction are formed, and The first contact which comes into surface contact with both sides of the guide slit of the cylinder A recess formed between the sliding surface and both end portions of both side surfaces of the base along the axial direction, and a recess integrally formed on one end portion of the base portion, in the lead groove of the distance ring. At the one end portion of the base portion, a protruding portion to be fitted, a second sliding surface which is respectively formed on both side surfaces of the protruding portion and is in surface contact with both side surfaces of the lead groove of the distance ring, respectively. One of the mounting holes is formed so as to penetrate through in the thickness direction together with the protruding portion, and the other mounting hole is formed at the other end of the base portion so as to penetrate through in the thickness direction. There is.

(Example) FIG. 1 shows a guide piece as an example of a motion transmitting member of a lens drive system according to the present invention.
The figure shows a camera lens constructed using it.

As shown in FIG. 2, the lens 100 has a lens barrel 5 as an inner cylinder, a fixed barrel 6 as an outer cylinder, and a distance ring 7 as main components. Then, it is connected and fixed to a camera body (not shown) through a mount flange 8 fixed to the rear end of the fixed barrel 6, and is configured to rotate the distance ring 7 to change the focus position and perform focusing. There is.

The lens barrel 5 has a substantially cylindrical shape, and a focusing lens group that moves in the optical axis direction to change the focus position among the lens groups of the optical system that configures the lens 100 in its inner diameter portion.
51 and 52 are fixed, and the outer diameter is slidably fitted to the inner diameter of the fixed cylinder 6 with a predetermined tolerance. The guide pieces 1 ... As a motion transmitting member are fixed by screws 101, 101, respectively, at three locations on the outer circumference, which are allocated at equal angles.

The fixed barrel 6 has a cylindrical shape and is configured to be coupled to the camera body via the mount flange 8 fixed to the rear end as described above, and the fixed lens group 53 is fixed inside and the outer periphery is Three guide slits 61 at equal angular positions ...
Are linearly formed with a predetermined width in a direction parallel to the optical axis.

The guide slits 61 ... Are formed to have a length corresponding to the amount of movement of the focusing lens groups 51 and 52 necessary for focusing, and the guide piece 1 is formed through the guide slits 61.
Are fixed to the outer surface of the lens barrel 5.

The guide piece 1 is formed by injection-molding a glass fiber-containing polycarbonate resin integrally with a plate-shaped base portion 10 that is long in the front-rear direction and a protrusion 20 that protrudes to the upper surface of one end of the base portion 10. Further, mounting holes 3.3 for fixing to the lens barrel (inner cylinder) 5 are opened by screws 101, 101, respectively.

The base portion 10 includes left and right side surfaces 11 at both ends in the longitudinal direction.
The width A of the sliding surface defined by 11 is formed with a predetermined tolerance and a predetermined parallelism so that the guide slit 61 of the fixed cylinder 6 can be slidably fitted without rattling, and the surface thereof is also formed with a predetermined accuracy. Has been done. Further, the thickness is formed to be less than or equal to the wall thickness of the fixed cylinder 6, and the planar shape of both ends is a semicircle having the same diameter as the width A.

The protruding portion 20 is formed in a substantially rhombic shape on the upper surface of one end of the base portion 10, and is a side surface on the side parallel to the left and right side surfaces 11 of the base portion 10.
21 and 21 are continuous so that they are flush with the left and right side faces 11 and 11, and the other two side faces have a predetermined angle α with respect to a straight line orthogonal to the left and right side faces 11 and 11 of the base part 10. Parallel sliding surfaces
22 ・ 22 is formed. This angle α is the same as the lead angle α of the spiral grooves 71 ... As the lead groove formed on the inner circumference of the distance ring 7 described later.

The width B between the sliding surfaces 22 and 22 is formed to have a predetermined tolerance and a predetermined parallelism so as to be slidably fitted to the lead grooves 71 formed on the inner circumference of the distance ring 7 without any play. The surface is also formed with a predetermined accuracy.

The thickness of the protruding portion 20 including the base portion 10 is equal to that of the lens barrel 5.
It is less than the distance from the outer surface to the bottom surface of the lead groove 71 of the distance ring 7.

Further, the center of the left and right side surfaces 11 and 11 of the base portion 10 (that is, the side surface
The recesses 11a ・ 1
1a is formed.

By adopting the configuration including the recesses 11a, 11a in this way, the guide slits 61 of the fixed cylinder 6 are slidably fitted at the front and rear ends of the base portion 10, and the configuration accuracy such as the amount of backlash is configured. The amount of fitting (length) can be shortened while maintaining. Therefore, its narrow fitting range (X in the figure
It is sufficient to manage the dimensional accuracy and the plane accuracy of X), which facilitates production and management. In addition, the concave portions 11a, 11a serve as grease supply, and the grease can be stably supplied, which enables smooth motion transmission drive.

The distance ring 7 has a cylindrical shape, and the inner peripheral surface thereof has lead grooves 71 ... Formed in a spiral shape with a groove having a predetermined width and depth having a predetermined lead angle α with respect to the circumferential direction. Three lines are formed at intervals. This lead angle α is determined by the inner diameter of the distance ring 7 and the lead groove.
71 is defined by the distance (lead) that makes one rotation on the inner circumference of the distance ring 7, and the lead is based on the lens operability, the distance ring 7, the rotation angle, and the amount of movement of the lens barrel (that is, the focus lens). The amount of movement).

The distance ring 7 is fitted into the outer diameter of the fixed barrel 6 so as to be relatively rotatable with a predetermined fitting tolerance, and the guide piece 1 fixed to the outer surface of the lens barrel 5 is projected onto the outer face of the fixed barrel 6. The width B formed by the sliding surfaces 22 of the protruding portion 20 is fitted into the lead groove 71, and the rear end (camera body side) is brought into contact with the large diameter portion 62 formed in the fixed ring 6. At the same time, the front end is regulated by a ring nut 63 screwed onto the outer periphery of the fixed barrel 6 and installed on the outer periphery of the fixed barrel 6.

That is, the distance ring 7 is installed so as to be relatively rotatable with respect to the fixed cylinder 6 and not relatively slidable forward and backward.

Thus, in the configuration as described above, when the distance ring 7 is rotated, the guide pieces 1 ... Fixed to the lens barrel 5 also try to rotate accordingly. However, the fixed cylinder 6
Since the guide slits 61 are restricted by the guide slits 61 and cannot rotate, they are moved forward and backward along the guide slits 61 by the component force in the front-rear direction generated by the lead angle α. That is,
The guide pieces 1 act as both the male screw and the guide plate in the straight helicoid, and as a result, the distance ring 7
The lens barrel 5 is moved back and forth by rotating.

The focusing lens group 51 fixed to the lens barrel 5 by moving the lens barrel 5 back and forth.
-The 52 position moves back and forth, and the focus position changes.

At this time, the contact between the guide slits 61 and the lead grooves 71 and the guide pieces 1 is a surface contact, and the pressure applied per unit area is significantly smaller than that in the conventional line contact.
Therefore, deformation and wear due to stress concentration are reduced, and the contact with a certain width reduces the occurrence of backlash in the gap of the sliding portion.

The side surfaces of the lead grooves 71 ... Inside the distance ring 7 are precisely curved surfaces with a constant rate of change, and the sliding surfaces 22, 22 of the guide pieces 1 that come into contact with the side surfaces of the lead grooves 71. Should have similar curved surfaces, but since the contact length is smaller than the inner diameter of the distance ring 7, it can be handled by an approximate plane.

Further, since the guide pieces 1 are made of a glass fiber-containing polycarbonate resin having a thermal expansion coefficient substantially equal to that of the outer cylinder 7 and the distance ring 6 formed of an aluminum alloy, the guide pieces 1 ... The combined state can be maintained, and the operating force (rotation torque of the range ring 7) can be made constant. Further, since the contact portion is in surface contact, the distance ring 6 rotates due to the external force applied to the inner cylinder 5 and the weight of the component and the camera when the lens optical axis direction is the same as the gravity direction. It is also possible to prevent the occurrence of a phenomenon called so-called self-weight loss.

The rear end side portion of the distance ring 7 is covered with a cylindrical cover 9 fixed to the fixed barrel 6, which enables the lens 100 to be supported and held by the camera without directly contacting the distance ring 7. It is configured to prevent dust from entering the optical system. Then, knurling is applied to the outer periphery of the tip portion that protrudes forward from the front end of the cover 9 to operate
Is formed, and the operating portion 73 is rotated to perform focusing.

In the above embodiment, the guide pieces 1 are installed at three locations on the circumference of the lens barrel 5 (that is, the guide slits 61 of the outer cylinder 6 into which the motion transmitting member 1 fits and the distance ring 7). Each of the lead grooves 71 ... Is composed of three strips), but it is needless to say that any number of them may be installed.

(Effects of the Invention) By configuring the motion transmission member of the lens drive system according to the present invention as described above, the contact portion of the motion transmission member with the slide guide of the fixed cylinder and the contact portion with the lead groove of the distance ring. Is configured to slide in surface contact with each other, and the load per unit area is drastically reduced as compared with the conventional line contact by rollers.

Therefore, when the range ring is operated or when an external force is applied to the inner cylinder, the deformation of the motion transmitting member due to the concentrated stress generated in the contact portion is prevented, the wear amount due to friction is reduced, and the durability is improved. is there.

Also, even with the same fitting error, the amount of backlash is reduced compared to line contact, so fitting accuracy can be relaxed, and the number of parts is reduced due to the single member configuration. The assembling work of the lens body can be simplified and the cost can be reduced.

That is, it is possible to obtain a motion transmitting member which has high durability, can stably maintain accuracy, and has good productivity.

Furthermore, by using this motion transmitting member, it becomes possible to adopt the above-mentioned extension mechanism even in the extension part (front group focus etc.) to which an external force is applied, which could not be used conventionally, which contributes to downsizing of the lens body. Is.

[Brief description of drawings]

1 is a perspective view showing the configuration of an embodiment of a motion transmitting member of a lens drive system according to the present invention, FIG. 2 is a sectional view of a lens using the motion transmitting member shown in FIG. 1, and FIG. FIG. 3 is a conceptual plan view of the lens shown in FIG. In the figure, 1 ... Guide piece (motion transmitting member) 3 ... Mounting hole 10 ... Base part 11 ... Left and right side surfaces (sliding surface that makes surface contact with the guide slit side surface of the inner cylinder) 11a. Projection 22 …… Sliding surface (sliding surface that makes surface contact with the side of the lead groove of the distance ring) 5 …… Lens barrel (inner tube) 6 …… Fixed tube (outer tube) 61 …… Guide slit 7 …… Distance ring 71 ... Lead groove 8 ... Lens mount.

Claims (1)

[Claims] 1. A lens mount or an outer cylinder fixed to a camera body, which is fixed to an inner cylinder slidably fitted to the inner circumference of the outer cylinder and is formed to extend linearly in the outer cylinder along the axial direction. A lead groove formed by fitting with a guide slit to regulate the sliding direction of the inner cylinder along the axial direction and extending linearly in a distance ring fitted relatively rotatably to the outer circumference of the outer cylinder. A motion transmitting member that slidably fits with the distance ring and converts the rotational motion of the distance ring into the longitudinal motion of the inner cylinder, and is fitted into the guide slit and extends along the axial direction. A base portion; first sliding surfaces which are respectively formed at both end portions of both side surfaces of the base portion along the axial direction and which are in surface contact with both side surfaces of the guide slit of the outer cylinder; and the shaft of the base. The recesses formed between both ends of both sides along the direction, Protrusions that are integrally formed on one end of the base portion and that fit into the lead grooves of the distance ring; and both side surfaces of the lead groove of the distance ring that are formed on both side surfaces of the protrusion portion, respectively. A second sliding surface that is in surface contact with each other, one mounting hole formed in the one end portion of the base portion in the thickness direction together with the projecting portion, and the other end portion of the base portion, A motion transmitting member for a lens drive system, comprising: the other mounting hole formed so as to penetrate in the thickness direction.