JPH0446326A - Lens driving device - Google Patents

Abstract

PURPOSE:To rotate the motor shaft of a stepping motor and to move a moving lens frame in an optical axis direction by holding a rack and providing a spring body which energizes the rack toward a threaded part in such a manner that the rack presses the threaded part on the moving lens frame. CONSTITUTION:A guide hole 9 of the lens driving device is coupled to the motor shaft 11 of the stepping motor 10 and the rack 13 which presses the threaded part 12 is engaged and, therefore, the force to turn the moving lens frame 1 around the motor shaft as the center of rotation is no longer generated. Consequently, the friction force is much lower than heretofore in the relation between the guide hole 7 for regulating the movement and a 1st guide pole 4 and, therefore, the hysteresis by a difference in the driving direction generated by the delayed movement of the support 6 side for regulating the movement than the support 8 side for guiding the moving lens frame 1 when the moving lens frame 1 is moved in the optical axis direction of the moving lens group 2 by rotating the motor shaft 11 is extremely lessened. The problem that the feed accuracy at the time of the movement of the moving lens frame 1 degrades is no longer generated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a lens driving device used in an imaging device such as a video camera or an electronic still camera.

2. Description of the Related Art Conventionally, as an example of a lens drive device used in a lens barrel device that performs focusing, zooming, etc. in an imaging device, a stepping motor is used, in which a screw for transmitting driving force is formed on the side cylinder surface of a rotating motor shaft. There is one in which a movable lens group attached to the rack is moved by a drive transmission means consisting of a rack that engages with the screw.

Below, an example of the lens driving device is shown in Figures 3 and 4.
This will be explained with reference to the figures.

In the figure, 1 is a movable lens frame that holds a movable lens group 2 consisting of at least one lens, and the movable lens frame 1 is attached to a fixed lens support 3 to which a fixed lens group (not shown) is attached. It is movably arranged. 4 is a first guide pole as a first moving track means attached to the fixed lens support 3, and the first guide pole 4 is located below the side peripheral surface of the movable lens frame 1, and , are arranged parallel to the optical axis of the moving lens group 2. Reference numeral 6 denotes a second guide pole as a second movement track means attached to the fixed lens support 3 so as to be located above the side peripheral surface of the movable lens frame 1;
The guide pole 5 is provided with the movable lens frame 1 positioned midway between the guide pole 5 and the first guide pole 4. and the second guide pole 5. First guide pole4. The optical axes of the movable lens group 2 are arranged so as to face each other and to be located on the same plane A. Reference numeral 6 denotes a movement regulating support body extending downward from the side peripheral surface of the movable lens frame 1, and the free end of the movement regulating support body 6 has a notch shape such as a U-shape for movement regulating purpose. A guide hole 7 is formed as a movement restricting means. The rotation prevention guide hole 7 has its longitudinal direction substantially parallel to the plane A so that the movement of the movable lens frame 1 can be restricted when the movable lens frame 1 is rotated about the second guide pole 6. It may also be in the form of a long hole or the like. The movement regulating guide hole 7 is engaged with the first guide pole 4 so as to be movable in the thrust axis direction of the first guide pole 4. Reference numeral 8 denotes a pair of guide supports extending upward from the side peripheral surface of the movable lens frame 1, each of which guide supports 8 having a guide hole 9 formed therein. The guide hole 9 is engaged with the second guide pole 5 so as to be movable in the thrust axis direction of the second guide pole 5.

Reference numeral 1o denotes a stepping motor attached to the fixed lens support 3, and the motor shaft 11 of the stepping motor 10 is arranged so as to be located substantially on the same plane A above the second guide pole 5. The motor shaft 11
A spiral threaded portion 12 is formed on the side peripheral surface of the rack, and the threaded portion 12 engages with a rack 13 disposed on the side thereof. The rack 13 is a first rack provided on the movable lens frame 1.
It is held by the first elastic support 14 and is always urged to abut against the threaded portion 12 by the first elastic support 14 . Reference numeral 16 denotes a dummy rack that faces the rack 13 via the threaded portion 12, and the dummy rack has a shape that does not mesh with the threaded portion 12 so that the driving force of the threaded portion 15 is not transmitted. The dummy rack 1
6 is a second elastic support body 16 provided on the movable lens frame 1
and is always urged by the second elastic support member 16 so as to come into contact with the threaded portion 12 . The biasing force of the first elastic support 14 via the rack 13 and the biasing force of the second elastic support 16 via the dummy rack 15 against the threaded portion 12, that is, the motor shaft 11, are equal so as to cancel each other out. This prevents the movable lens frame 1 from rotating about the second guide pole 6.

Problems to be Solved by the Invention However, in the lens driving device having the above-mentioned configuration, when a plurality of units are produced, the first elastic support 14 and the second elastic support 1e have elastic force and size, respectively. Since variations always occur, the biasing forces of the first elastic support 14 and the second elastic support 16 against the motor shaft 11 are almost never equal. Therefore, the movable lens frame 1 rotates around the second guide pole 6, and the frictional force between the movement restriction guide hole 7 of the movement restriction support 6 and the first guide pole 4 increases. was. As a result, when rotating the motor shaft 11 to move the movable lens frame 1 in the optical axis direction of the movable lens group 2 for focusing, zooming, etc., the guide support 8 side above the movable lens frame 1 Lower movement regulating support e of the delayed moving lens frame 1
Since the side of the movable lens frame 1 moves, a problem arises in that hysteresis occurs due to the difference in driving direction, and the feeding accuracy during movement of the movable lens frame 1 is deteriorated.

In order to solve this problem, all of the first elastic supports 14 and second elastic supports 16 are inspected for the above-mentioned variations, and those with the least variation are used to assemble the lens drive device. However, the problem of increasing costs and always deteriorating the feed accuracy during movement of the movable lens frame 1 could not be solved satisfactorily.

The present invention solves these problems and provides a lens driving device that is inexpensive and has improved feeding accuracy when moving the movable lens frame 1.

Means for Solving the Problems The lens driving device of the present invention is provided with a movable lens frame for holding a movable lens group, and the lens frames are positioned in the middle and face each other, and the optical axis of the movable lens group is A motor shaft of a nutepping motor and a moving track means are respectively provided so as to be parallel to each other, and a guiding support body having a guide hole that engages movably along the motor shaft is provided so as to protrude from the moving lens frame. , a movement regulating support member formed with a movement regulating means that engages with the moving track means so as to move along the moving track means is provided protruding from the movable lens frame; A rack is provided at a position on the side of the threaded part so as to engage with the threaded part formed in the threaded part, and a spring is provided for holding the rack and biasing the rack in the direction of the threaded part so that the rack presses the threaded part. By providing a body on the movable lens frame, the movable lens frame is configured to be moved in the optical axis direction when the motor shaft of the nutepping motor is rotated.

Function: The lens driving device of the present invention has the above-described configuration, so that the rack biased by the spring body is pressed against the motor shaft of the stevening motor, which is movably engaged with the guide hole of the guide support. Since the movable lens frame is not rotated about the motor shaft, the frictional force between the movement regulating guide hole of the movement regulating support and the moving track means is reduced. . As a result, when the movable lens frame is moved in the optical axis direction of the movable lens group by rotating the motor shaft, the movement regulating support side moves later than the guiding support side of the movable lens frame. Since the hysteresis caused by the difference in the drive direction that occurs is much smaller than in the past, the movement of the movable lens frame from the guide support side to the point where it deteriorates the feeding accuracy during movement of the movable lens frame and causes problems. This prevents the movement regulating support from moving with delay.

Example Below, the first example of a lens driving device according to an example of the present invention will be described.
This will be explained with reference to the figures and FIG.

It should be noted that the same parts as in the prior art are given the same reference numerals as in FIGS. 3 and 4, and their explanation will be omitted.

In FIGS. 1 and 2, a movable lens frame 1 holding a movable lens group 2 is movably arranged relative to a fixed lens support 3, and is moved downward on the side cylinder surface of the movable lens frame 1. A first guide pole 4 parallel to the optical axis of the lens group 2
is provided as the first moving track means. A nutepping motor 1o, which is a drive source, has a spiral threaded portion 12 formed on the side cylinder surface of a motor shaft 11, and is attached to the fixed lens support 3 so as to be located above the side cylinder surface of the movable lens frame 1. There is. The motor shaft 11 of the nutepping motor 1o is located approximately on the same plane A as the first guide pole 4 and the optical axis of the movable lens group 2 so as to serve as a second moving track means and a driving source, and They are arranged parallel to each other and facing each other. A movement restriction guide hole 7 as movement restriction means is formed at the free end of the movement restriction support 6 extending downward from the side cylinder surface of the movable lens frame 1; Seven lanuts of the first guide pole 4 are engaged with the first guide pole 4 so as to be movable in the axial direction. A guide hole 9 is formed in each of the pair of guide supports 8 extending upward from the side cylinder surface of the movable lens frame 1, and the guide hole 9 is formed in the axial direction of the motor shaft 11 of the stepping motor 1o. The motor shaft 11 is movably engaged with a threaded portion 12 of the motor shaft 11. On the side of the threaded part 12 is a motor shaft 1.
A rack 13 that transmits the rotational force of lens frame 1 is positioned while meshing with the threaded portion 12, and the rack 13 is held by a first elastic support 14 provided on the movable lens frame 1 so as to bias it in the direction of the threaded portion 12. ing. The elastic support 14 allows the rack 13 to always press the threaded portion 12 to maintain the engagement, so that the rotational force of the motor shaft 11 is reliably used as a driving force in the optical axis direction of the movable lens group 2 to connect the rack 13 with the elastic force. The signal is transmitted to the movable lens frame 1 via the support 14, and the movable lens frame 1 is moved in the optical axis direction by the transmission.

In the lens driving device configured as described above, the guide hole 9 is engaged with the motor shaft 11 of the stepping motor 10, and the rack 13 that presses the threaded portion 12 is engaged, so that the motor shaft is the rotation center. As a result, no force is generated to rotate the movable lens frame 1. As a result, the relationship between the movement regulating guide hole 7 and the first guide ball 4 has much less frictional force than before, so the motor shaft 11 is rotated to move the movable lens frame 1 to the movable lens group 2. When moving in the optical axis direction, hysteresis due to the difference in drive direction that often occurs due to the movement of the guide support 8 side of the movable lens frame 1 and the movement regulating support θ side being delayed compared to the conventional case. Therefore, the problem of deteriorating the feeding accuracy during the movement of the movable lens frame 1 does not occur.

In addition, in this embodiment, as the structure of engagement between the first moving track means and the movement regulating means, a structure in which the first guide ball 4 is inserted into the movement regulating guide hole 7 has been described.
It goes without saying that the engagement structure may be based on conventionally known techniques. For example, the movement restriction guide hole 7 may be abolished, a groove in the optical axis direction may be provided on either the movement restriction support 6 or the first guide ball 4, and the other may be engaged with the groove. In addition to providing the convex portion, the formation of the groove and the convex portion may be set so that the range in which the engagement is maintained is at least the movement range of the movable lens frame 1.

Further, in this embodiment, the outer diameter of the threaded portion 12 of the motor shaft 11 and the inner diameter of the guide hole 9 are configured to slidably engage with each other. It goes without saying that the side face of 11 and the guide hole 9 may be slidably engaged with each other.

Effects of the Invention As described above, the lens driving device of the present invention movably engages the guide hole of the guide support with the motor shaft of the stepping motor, and performs stepping while pressing the side shaft surface of the motor shaft. Since the rack, which is biased by a spring body, is pressed and engaged with the motor shaft of the motor, the movable lens frame does not rotate about the motor shaft, and the engaged movement restriction is prevented. The frictional force between the movement regulating means of the support body and the movement track means can be reduced. As a result, when the movable lens frame is moved in the optical axis direction of the movable lens group by rotating the motor shaft, the movement regulating support side moves later than the guiding support side of the movable lens frame. Since the hysteresis caused by the difference in the driving direction that occurs is much smaller than in the past, the movement of the movable lens frame from the guiding support side to the point where it deteriorates the feeding accuracy during movement of the movable lens frame and causes problems. It was possible to eliminate the delay in movement of the movement regulating support side.

[Brief explanation of drawings]

FIG. 1 is a side view of a lens driving device according to an embodiment of the present invention, FIG. 2 is a partially cutaway front sectional view taken along line B-B in FIG. 1 in the direction of the arrow, and FIG. 3 is a conventional lens. A side view of the drive device, FIG. 4 is a partially cutaway front sectional view seen from the arrow direction at A and A14 in FIG. 3. 1...Moving lens frame, 2...Moving lens group, 3...Fixed lens support, 4...First guide ball, 6... Support for movement control, 7.
... Guide hole for movement regulation, 8 ... Guide support, 9 ... Guide hole, 10 ... Stepping motor, 11 ... - Motor shaft , 12...
Threaded portion, 13... Rack, 14... Elastic support. Name of agent: Patent attorney Shigetaka Awano and one other person

Claims (1)

[Claims] a movable lens frame that holds a movable lens group and is movable in the optical axis direction of the movable lens group; a stepping motor that is disposed such that a motor axis faces the optical axis;
A threaded portion formed on the side cylinder surface of the motor shaft, a rack disposed on the side of the threaded portion so as to engage with the threaded portion, and the rack is held and the rack engages the threaded portion. a spring body provided on the movable lens frame so as to press it in the direction of the screw portion; a guiding support body provided on the movable lens frame so as to protrude in the direction of the motor shaft; The movable lens frame is positioned between a guide hole formed in the guide support that engages with the shaft and is movable along the motor shaft, and the movable lens frame so as to restrict the moving direction of the movable lens frame. a moving track means provided opposite to the motor shaft; a movement regulating support provided on the moving lens frame so as to protrude in the direction of the moving track means; a movement regulating means formed on the movement regulating support so as to be movably engaged with the track means, and the movable lens frame is moved in the optical axis direction by rotating a motor shaft of a stepping motor. A lens driving device characterized by: