JP2733619B2 - Lens drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention uses an elastic member as a device for preventing vibration and resonance of a photographing lens system, which is converted into linear motion in conjunction with a male screw rotated and driven by a drive motor. The present invention relates to an arranged driving device.

[Prior Art] Conventionally, in the above lens driving device, FIGS.
As shown in the drawing, the driven lens frame 12 is supported by a male screw member 16a by screw fitting or the like, and the guide sleeve 12a provided on one of the driven lens frames 12 and substantially with respect to the optical axis of the driven lens frame 12. A U-shaped groove for stopping rotation is provided at 180 °, and the motor is directly driven via a female screw portion 17b integrated with the driven lens frame 12 by a guide pin 13a, 13b or a projection disposed on the mirror member 11. Rotational drive from 14 to the driven lens frame
Generally, it is configured to communicate to 12. Further, as a drive conversion to the linear movement of the driven lens frame 12, a female screw portion 17b screw-fitted to the male screw member 16a is provided, and the driven lens frame 12 is moved linearly through the female screw portion 17b. Are known.

[Problems to be solved by the invention]

If the male screw member 16a is bent, the driven lens frame 12 swings while the motor 14 is being driven to rotate, causing a so-called "image wobble" phenomenon on a photographing screen, and a problem of deterioration of the resolving power becomes a problem. In particular, in the case of a type that forms images continuously, the above-mentioned problem is more remarkable.

If each of the male screw member 16a, the guide pins 13a, 13b, and the U-shaped groove 12b is not guaranteed to be completely parallel to the optical axis, the driven lens frame 12 may be squeezed, rattled, or stopped during operation. Smooth drive is not performed. Therefore, the mirror member 11, the guide pins 13a and 13b, the U-shaped groove 12b, and the like need to be processed with high precision together with the driven lens member 12, and often pose a problem from the viewpoint of wear resistance.

Further, when the motor 14 starts rotating, the shock is transmitted to the driven lens frame 12 due to the sharp rise of the rotation, and an abnormal sound is generated. Further, when a stepping motor is used as the motor 14, the problem is further increased because the shock continues during the rotation driving.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to obtain a simple and reliable operation of the photographing lens system which is always stable and to improve the image quality.

[Means for solving the problem]

The object of the present invention is to provide a screw-type lens driving device for converting a rotational movement of a male screw member into a linear movement of a female screw member to move a driven lens in an optical axis direction, wherein the female screw is provided between the female screw member and the drive lens frame. The present invention is achieved by a lens driving device wherein a protrusion provided in a radial direction of a member transmits a drive via an elastic member having elasticity in a rotation direction of the male screw shaft.

〔Example〕

A specific embodiment of the present invention is shown in FIGS. 1 (a) and 1 (b).

However, the present invention is not limited to this embodiment.
In addition, members having the same functions as those of the prior art are denoted by the same reference numerals.

The driven lens frame 12 has two guide pins 13a and 13b of a mirror body 11 provided substantially vertically (eg, left and right) and a guide sleeve 12a provided integrally with the driven lens frame 12.
And is engaged with the U-shaped groove 12b and held as a structure movable in the optical axis direction.

Male screw member at the tip (hereinafter referred to as lead screw)
A rotary drive motor 14 having a shaft 16 provided with a portion 16a is fixed to a holder 15 having a pivot bearing 23. The tip of the shaft 16 on the motor 14 side also has a spherical shape, and is pressed in the direction of the arrow (coincident with the optical axis direction in this example) by a plate spring 14a formed integrally with the motor 14. The radial bearing 14b holds the shaft 16 provided integrally with the motor 14, and defines the position on the thrust side together with the fitting with the holder 15 and the rotating nut 21. For example, even if the pivot bearing 23 and the leaf spring 14a are exchanged and urged in the direction opposite to the direction of the arrow, no problem occurs. In this method, since the places where the pressure in the thrust direction is applied by the leaf springs 14a are all point contacts, there is very little rotary torque loss.

Also, the pivot bearing 23 is not necessarily shown in FIG.
Instead of the above type, it is also possible to abolish the pivot bearing 23 by forming the tip of the shaft 16 as shown in FIG. 1 (c). The nut receiver 22 is integral with the driven lens frame 12, and in this embodiment, it has an inverted U shape as shown in the sectional view of FIG. 2A and the front view of FIG. Although it does, it does not matter even if it has a cylindrical shape.

In this embodiment, the unit of the lead screw 16a and the nut 17a including the motor 14 and the related member unit including the lens body 11 and the driven lens frame 12 are separately assembled and adjusted, and both can be attached at the final stage of assembly. Therefore, the assembly and adjustment work is extremely easy.

The nut receiver 22 is pressed against a female screw member (hereinafter, referred to as a nut) 17 which is screw-fitted to the lead screw 16a by the urging force in the thrust direction of a helical spring 19 fitted to the shaft 16. Here, the helical spring 19
May be replaced between the mirror body 11 and the lens frame 12 around the axis 13a in FIG. 1 (a). In this embodiment, the contact surface between the nut receiver 22 and the nut 17 is spherical as shown in the sectional view of FIG. 2A and the front view of FIG. The boss is provided with three or more bosses, and the boss is made of a material which is slidable with the nut 17 and has a smooth surface finish.

The damper rubber 18 which is a basic member of the present embodiment is a rubber or elastic member having the shape shown in the plan view of FIG. 3 (a) and the sectional view of FIG. 3 (b). As an example, what is shown as 18a in the plan view of FIG. 4 (a) and the sectional view of FIG. 4 (b) is also useful. Then, it is integrally attached to the nut receiver 22 (integral with the driven lens frame) at the position shown in FIGS. 1 (a) and 1 (b). A projection 17a integrated with the nut 17 is inserted into a hole provided at the center of the damper rubber 18 or 18a, and is engaged so that the rotational driving force of the shaft 16 and the lead screw 16a is transmitted.

The flywheel 20 is of the present applicant's invention (pending), and a high-viscosity fluid is injected into the fitting clearance between the flywheel 20 and the shaft 16. This is because when a stepping motor is used for the motor 14, the vibration of the lead screw 16a is not only the applied frequency component,
Since the vibration source has a high frequency component called a transient phenomenon, the purpose is to vibrate only the applied frequency component excluding the high frequency component. A flywheel stopper 21 is fixed to the shaft 16 with a certain clearance with the flywheel 20 to regulate the position of the flywheel 20 and to prevent the highly viscous fluid from flowing into the lead screw portion 16a. I have. In the present embodiment, the flywheel stopper 21 is a circular nut, and the end of the lead screw 16a set on the shaft 16 by screw fitting with the lead screw 16a is used to position the flywheel stopper 21 with the flywheel 20. It is processed so as to obtain a predetermined clearance.

Further, the flywheel stopper 21 is not limited to this configuration, and use of an O-ring or the like does not cause any problem.
When the drive motor 14 is rotated in the state of the structure of the present embodiment and the torque of the motor is T ₀ , the torque T ₁ received from the lead screw 16 a of the nut 17 is T ₁ = k ₁ · T ₀ (1) ) K ₁ = f (Qlμ ₁ ) QMAX = P + W QMIN = P−W P> W P: pressure of spring 19 W: weight of driven lens frame 12 l: screw lead μ ₁ : friction coefficient of screw You. A helical spring to eliminate the difference in posture
The pressure of 19 is set with P> W as described above. As shown in the sectional view of FIG. 2 (a) and the front view of FIG. 2 (b), when the distance from the center axis Z to the spherical boss at the tip of the nut receiver 22 is r, the nut received from the nut receiver 22 torque T ₂ of the 17 becomes the following equation.

T ₂ = −μ ₂ Q · r (2) μ ₂ : Coefficient of friction between the nut receiver 22 and the nut 17 Therefore, the nut 17 tries to rotate with the torque represented by T ₃ .

T ₃ = T ₁ + T ₂ = k ₁ T ₀ -μ ₂ Q · r (3) However, the nut 17 has a projection 17a at the tip, and the plan view of FIG. 5A and the plan view of FIG. As shown in the cross-sectional view of FIG. 6B, since the projection 17a is inserted into the hole of the damper rubber 18, if the length from the axis to the tip of the projection 17a is R, the damper rubber 18 is as shown in FIG. As shown in the plan view and the cross-sectional view of FIG. 6 (b), it deforms under the force of F = T ₃ / R. L, a, and t are the dimensions of the elastic member shown in FIGS. 5A and 5B, and Hs is the hardness of the member. Δ is the amount of deformation of the member.

Rotate and balance up to θ. That is, the driven lens frame 12 follows the rotation of the motor 14 with a phase delay of θ. Let the backlash allowed in this system be ε Each constant is determined so that

With this setting, when the motor 14 suddenly starts to rotate, the rotational impact force can be absorbed by using the deflection of θ, and the lead screw 16a, which is a vibration source, can be absorbed.
The rotation of the lead screw 16a can be converted into the linear movement of the lens frame 12 without transmitting the vibration of the lens frame 12 to the lens frame 12. In particular, when a stepping motor is used as the motor 14, the above-described impact force is continuously maintained, which is particularly effective. In addition, when a stepping motor is used, vibration due to the applied frequency is given to the damper rubber 18, but it is particularly important that the resonance frequency of the damper rubber 18 is always lower than the applied frequency.

Further, since the lead screw 16a, which is a vibration source, is in contact with the holder 15 via the pivot bearing 23, the holder 15 may also be a vibration source. When this holder 15 is fixed directly to the mirror 11, vibration is transmitted to the mirror 11.
When the vibration is also a problem because the vibration 12 may be caused by the vibrations 13a and 13b, it is effective to attach the holder 15 to the mirror 11 via an elastic body such as rubber.

In recent years, the mirror body 11 has been increasingly made of plastic, but is very weak against external force due to the nature of the plastic. However, if a metal plate is used for the holder 15, it can be used to reinforce the mirror body 11. In addition, as shown in FIG. 1 (d), the lead screw 16a, which is the vibration source, has no portion in contact with the holder 15, so that the vibration is not transmitted to the holder 15, and the holder 15 is made of an elastic material such as rubber as described above. Although it is useful for preventing vibration without being attached via a body member, it is disadvantageous in that it is very weak against the radial force of the shaft 16. The damper rubber 18 is the nut 17
Since the purpose is to provide elasticity in the rotational direction of FIG. 3, not only the shape shown in FIG. 3A but also the shape shown in FIG.

〔The invention's effect〕

Since the present invention is configured as described above, it absorbs and alleviates the impact of the rotation of the driving motor, and uses a relatively low-torque motor while preventing "image shaking" and abnormal noise of the photographing lens system caused by resonance and chatter. However, since stable drive rotation transmission can be obtained, there is an effect that the image quality is improved and the space and the manufacturing cost are advantageous.

[Brief description of the drawings]

FIG. 1 (a) is a sectional view parallel to the optical axis of one embodiment of the present invention. FIG. 1B is a partial sectional view at right angles to the optical axis of one embodiment of the present invention. FIGS. 1 (c) and 1 (d) are sectional views parallel to the optical axis showing another embodiment of the present invention. FIG. 2A is a sectional view of a nut receiver. FIG. 2 (b) is a front view of the nut receiver. 3 (a) and 4 (a) are plan views of the elastic member. 3 (b) and 4 (b) are cross-sectional views of the elastic member. FIG. 5A is a plan view of the nut and the elastic member at rest. FIG. 5 (b) is a front view. FIG. 6 (a) is a plan view of the initial rotation of the nut with respect to the elastic member. FIG. 6B is a front view. 7 and 8 are sectional views parallel to the optical axis of a conventional lens driving device. 11 mirror body 12 driven lens frame 12a guide sleeve 12b guide U-shaped groove 13a 13b guide pin 14 drive motor 14a leaf spring 14b 14c ... Radial shaft 15 ... Holder, 16 ... Motor shaft 16b ... Lead screw (male screw member) 17 ... Nut (female screw member) 17a ... Nut protrusion, 17b ... Female screw part 18, 18a ... Damper rubber (Elastic member) 19… helical spring, 20… flywheel 21… flywheel stopper 22… nut receiver, 23… pivot bearing

Claims (1)

(57) [Claims] 1. A screw-type lens driving device for converting a rotational motion of a male screw member into a linear motion of a female screw member to move a driven lens in an optical axis direction, wherein a driving lens frame is provided between the female screw member and the driving lens frame. A lens drive device, wherein a protrusion provided in a radial direction of the female screw member transmits a drive via an elastic member having elasticity in a rotation direction of the male screw shaft.