JPH09105848A - Lens driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a shock receiving part on a rack member and to improve shock resistance by turning the rack member on a plane orthogonal to an optical axis and forming a rack tooth part meshing with a feed screw shaft to have curvature on the plane orthogonal to the optical axis. SOLUTION: The rack member 4 is turnably supported with the through-hole if of a moving mirror frame 1 as an axis so as to follow up positional deviation between the shaft 6 and the member 4, without changing the pinching pressure of a spring 4c. Furthermore, by providing a curvature part which is not coaxial to the center of rotation of the shaft 6 in the rack tooth, its relative amount with the shaft 6 is increased. Thus, load imposed on the shaft 6 is kept constant, so that allowance to the dispersion of the dimensional accuracy of parts becomes large, and stable driving performance is obtained. Since the relative amount of the rack tooth to a screw thread is increased, the shock resistance performance is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens driving device for driving a moving lens group such as a zoom lens.

[0002]

2. Description of the Related Art FIG. 6 shows a first conventional lens driving device disclosed in, for example, Japanese Unexamined Patent Publication (Kokai) No. 4-46307, in which a master lens 51 is mounted on a resin lens frame 52 by means such as heat caulking. Is held. This lens frame 5
2 is a guide bar 54, 55 arranged inside the fixed lens barrel.
Is held slidably in the optical axis direction XX.

A groove (not shown) is provided in the upper portion of the lens frame 52, and a notch nut 58 screwed into the feed screw shaft 57 of the motor 56 by a cylinder angle of 120 ° is provided in the groove.
The leg portion 58b of the driven body 58 made of a is inserted and supported. This groove has no gap in the optical axis direction when the leg portion 58b of the driven body 58 is inserted, and has a slight gap in the direction perpendicular to the optical axis.

Further, the driven body 58 having the notch nut 58a passes through the hole 58d, and one end of the driven body 58 is parallel to the feed screw shaft 57.
It is held so that it can slide and rotate. An arm 58 for sandwiching the feed screw shaft 57 in the driven body 58.
c is formed, the guide bar 61 is used as a fulcrum, and the feed screw 57a of the feed screw shaft 57 is pressed and biased so that the notch nut 58a and the feed screw 57a are screwed together without a gap.

Next, the operation will be described. When the feed screw shaft 57 is rotationally driven by the motor 56, the driven body 58 having the notched nut 58a screwed onto the feed screw shaft with a small clearance slides on the guide bar 61 and moves in the optical axis direction. The lens barrel 52 engaged with the driven body 58 obtains a predetermined moving distance with respect to the rotation angle of the motor 56 to perform the focusing operation of the master lens 51.

FIG. 7 shows a second conventional lens moving device disclosed in Japanese Unexamined Patent Publication No. 3-294808, in which a focusing lens (not shown) is heat caulked on a lens holding frame 72 made of resin. It is fixed by means of. Fixed barrel 73
A guide bar 74 is provided inside the lens, and the lens holding frame 72 slidably engages with the guide bar 74 to move the focusing lens (not shown) in the direction of the optical axis X-X. It has a simple structure. A rack unit (rack member) 75 is fixed to the lens holding frame 72 with screws 76, and the tip of the rack unit 75 is engaged with a feed screw 78 of a stepping motor 77. Feed screw 7
8 is held by a metal bearing 79 of a stepping motor 77 and a thrust bearing 81 provided on a guide plate 80, and a thrust bearing 81 is provided by a leaf spring (not shown) provided inside the stepping motor 77.
By biasing the feed screw shaft 78 in the direction of, the rattling of the feed screw shaft 78 in the thrust direction is prevented. The stepping motor 77 uses screws 83,
It is fixed to the fixed barrel 73 by 84.

Next, the operation will be described. When the stepping motor 77 rotates, the feed screw shaft 78 also rotates, the rack portion 85 engaged with the feed screw shaft 78 moves, and the focusing lens also moves in the optical axis XX direction. Therefore, by rotating the stepping motor 77 in the forward and reverse directions, the focusing lens also moves forward and backward, and the focusing operation can be performed.

[0008]

However, in the first embodiment described above, in order to assemble the female screw of the notch nut 58a to the feed screw shaft 57, it is necessary to assemble from the tip of the feed screw, and the assemblability is improved. 5, the female screw of 180 ° or less is engaged with the feed screw 57a. However, when the female screw and the feed screw 57a are meshed with each other, due to variations in respective positions, the feed screw 57a
The load on the machine varies and stable feed performance,
That is, the driving performance of the lens cannot be obtained. In addition, there is a problem in that high impact resistance cannot be obtained because the spring pressure that presses the female screw suppresses tooth jumping due to impact resistance.

In the second conventional example, the position-preventing rack teeth 86 are located at positions opposed to the rack teeth 85 that mesh with the feed screw.
By providing the, the impact resistance is improved,
There is a problem that a sufficient impact resistance cannot be obtained due to a small impact portion, particularly a fine screw pitch.

The present invention has been made to solve the above problems, and it is an object of the present invention to improve the shock resistance by increasing the number of portions of the rack member that receive a shock.

[0011]

According to another aspect of the present invention, there is provided a lens driving device including a movable lens frame for holding a movable lens group, and a rack member provided on the movable lens frame in parallel with an optical axis. In a lens driving device having this rack member and a feed screw shaft which is rotationally driven by an engagement drive source to move the movable lens frame in the optical axis direction, the rack member is rotatable on a plane orthogonal to the optical axis. Further, the rack tooth portion that meshes with the feed screw shaft has a shape having a curvature in a plane orthogonal to the optical axis.

According to a second aspect of the present invention, there is provided a lens driving device, wherein a movable lens frame for holding the movable lens group, a rack member provided on the movable lens frame in parallel with the optical axis, and an engagement drive with the rack member. In a lens driving device having a feed screw shaft that is rotationally driven by a light source to move the movable lens frame in the optical axis direction, the rack member is rotatable on a plane orthogonal to the optical axis, and the feed screw is provided. A rack tooth portion that meshes with the shaft and an auxiliary tooth portion that is located opposite to the rack tooth portion with the feed screw shaft interposed therebetween, and the rack tooth portion and the auxiliary tooth portion have a curvature in a plane orthogonal to the optical axis. It is characterized by

[0013]

Embodiments of the present invention will be described below.

FIG. 1 is an exploded perspective view showing the basic structure of the present invention, and FIG. 2 is an enlarged perspective view of the essential part thereof. In FIG. 1, 1 is a movable lens frame holding a movable lens group 1a. , One surface of which is provided with a sleeve 1b protruding in the optical axis direction,
Further, a detent engagement concave portion 1c is provided at a position symmetrical with the sleeve 1b about the optical axis. Reference numerals 2 and 3 denote guide bars that hold the movable lens frame 1 movably in the optical axis direction. The guide bar 2 is inserted into the sleeve 1b, and the guide bar 3 is engaged with the detent engagement recess 1c. Reference numeral 4 is a rack member that engages with the feed screw shaft 6 and drives the movable lens frame 1 in the optical axis direction. As shown in FIGS. 2 to 4, the rack member 4 includes a rack tooth portion 4a that meshes with the feed screw shaft 6, and an auxiliary tooth 4b that prevents the rack tooth portion 4a and the feed screw shaft 6 from being disengaged from each other by an impact. , And a spring portion 4c that engages the feed screw shaft 6 and the rack tooth portion 4a by the spring force of the spring 5.

A pair of support arms 1d and 1d are provided on the outer surface of the sleeve 1b of the movable lens frame 1 with a space for supporting the rack member 4 therebetween.
e is formed in the optical axis direction, the support arm 1d is provided with a through hole 1f with which the shaft end 4e of the rack member 4 engages, and the support arm 1e is provided with a conical portion 4d of the rack member 4 by a spring 5. A through hole 1g to be pressed is provided, and the rack member 4 is supported between the pair of support arms 1d and 1e. The spring 5 is wound around the base of the shaft end 4e, one end of which is locked to the rack member 4 and the other end of which is locked to the spring 4c.

The rack member 4 includes a through hole 1f of the movable lens frame 1,
It is rotatably supported about a line XX (a line parallel to the optical axis) connecting the centers of 1 g, and the positional deviation between the feed screw shaft 6 and the rack member 4 is detected by the scissors of the spring portion 4c. It can be followed without changing the pressure.

FIG. 5 is a view showing details of the rack shape.
In the figure, the outer diameter D and the root diameter d of the feed screw shaft 6 and the distance A between the rack teeth 4a and the auxiliary teeth 4b have a relationship of d ≦ A <D, which prevents tooth jump due to impact. However, a curvature portion R that is not coaxial with the rotation center of the feed screw shaft 6
By providing ₁ and R ₂ on the rack teeth 4a and the auxiliary teeth 4b, the amount of engagement with the feed screw shaft 6 is increased.

Next, the operation will be described. When the screw shaft 6 is driven by the motor 7 as a drive source, the movable lens barrel 1 is moved in the optical axis direction via the rack teeth 4a, the rack member 4, and the support arms 1d and 1e according to the rotation direction of the screw shaft 6. Move to. In this case, the feed screw shaft 6 has the curvature portion R of the rack tooth 4a.
Engagement is surely performed with ₁ . Also, the engagement is more reliable by pressing the curvature portion R ₂ of the auxiliary tooth 4b or the spring portion 4c.

[0019]

As described above, according to the present invention, the rack member that meshes with the feed screw shaft can be rotated on the plane orthogonal to the optical axis, and the load applied to the feed screw shaft can be kept constant. Since it is configured such that it is possible to increase the allowable amount with respect to variations in dimensional accuracy among components, stable driving performance can be obtained. Further, even for a fine feed screw thread, the amount of interaction between the screw thread and the rack tooth can be increased, so that the impact resistance performance can be improved even if the moving disassembly performance of the moving lens group is improved. There is.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a basic configuration of the present invention.

FIG. 2 is an enlarged perspective view showing a main part thereof.

FIG. 3 is a diagram illustrating a rack portion of the present invention.

FIG. 4 is a diagram illustrating a rack tooth portion of the present invention.

FIG. 5 is a diagram illustrating a rack tooth portion of the present invention.

FIG. 6 is a perspective view showing a conventional first lens driving device.

FIG. 7 is a perspective view showing a second conventional lens driving device.

[Explanation of symbols]

 1 Moving lens frame 4 Rack member 4a Rack tooth part 4b Auxiliary tooth 4c Spring part 6 Feed screw shaft

Claims (2)

[Claims] 1. A movable lens frame holding a movable lens group, a rack member provided on the movable lens frame in parallel with the optical axis, and rotationally driven by a driving source engaging with the rack member to move the movable lens frame. In a lens driving device having a feed screw shaft that moves in the optical axis direction, the rack member is rotatable on a plane orthogonal to the optical axis, and a rack tooth portion meshing with the feed screw shaft is a plane orthogonal to the optical axis. A lens driving device characterized by having a shape having a curvature. 2. A movable lens frame holding a movable lens group, a rack member provided on the movable lens frame in parallel with the optical axis, and rotationally driven by a drive source engaging with the rack member to move the movable lens frame. In a lens driving device having a feed screw shaft that moves in the optical axis direction, the rack member is rotatable on a plane orthogonal to the optical axis, and a rack tooth portion that meshes with the feed screw shaft and the feed screw shaft. A lens driving device comprising: an auxiliary tooth portion at a position facing the rack tooth portion with the rack tooth sandwiched therebetween, and the rack tooth portion and the auxiliary tooth portion have a shape having a curvature in a plane orthogonal to the optical axis.