JPS60415A - Lens driving device - Google Patents

Abstract

PURPOSE:To make a titled device small-sized by supporting a cylindrical rotary magnet from a radiating direction of an optical axis against a coil attached to a fixed cylinder of a lens barrel, extending a comb-tooth yoke attached to the coil to the outside circumferential part of the magnet, and engaging a moving lens holding cylinder with a cam groove of the inside circumference of the magnet. CONSTITUTION:A fixed cylinder 3 of a lens barrel 1 holds lenses G1-G4 and G6, and also holds a stator of a step-motor. The stator consists of field coils 6, 7, and field yokes 8, 9 having comb-teeth 16a, 16b and 17a, 17b. A rotor consists of a cylindrical magnet 11, and the magnet 11 is supported by ball bearings 15a, 15b against an inside cylider 3a of the fixed cylinder 3. Grooves 11a, 11b for placing the bearings 15a, 15b are provided on the inside circumferential surface of the magnet 11. The yokes 8, 9 are provided as extended to the outside circumferential part of the magnet 11. A cam groove 11C is provided on the inside circumference of the magnet 11, and the groove 11C is engaged with a guide roller 14 of a moving cylinder 13 and drives to focus a lens G5. In this way, the outside diameter of the lens barrel can be reduced, and a device having a good driving performance is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photographing lens driving device for a still camera, a cine camera, a television camera, etc., and particularly relates to an autofocus (
It has a built-in motor for automatic focus adjustment and automatic zoom (automatic magnification change), and the motor drives the lens.

In a conventional device for driving a lens in the optical axis direction, such as an autofocus lens, a drive mechanism such as a motor and a reduction gear train is built into the outside of a cylindrical lens barrel. Therefore,
The outer shape of the lens barrel (1) had an unusual shape due to partial protrusions.6 In order to attach the motor, there are many parts to be machined into the fixed barrel of the lens barrel, gear trains, etc., making it expensive. It had become a thing. In addition, there is a drawback that the noise generated from the gear train and the like when driving the lens is large. Abrasion of the motor brushes and gear tooth surfaces is unavoidable, and failures occur due to dust adhering to the tooth surfaces, so reliability in terms of performance is not desirable.

In order to improve such conventional lens driving devices,
Several proposals have been made to incorporate a motor inside the lens barrel. Among them, the one disclosed in Japanese Unexamined Patent Application Publication No. 147132/1983, which is considered to be the most advanced, has a simple structure because it does not have gears, and from this point of view it can be fairly evaluated.

However, the rotor of the motor and the rotating ring, which is the mechanism for moving the lens, are constructed separately and connected together. Therefore, these rotating parts become large-sized. Furthermore, the inertia during rotation is large, making it unsuitable for rapid autofocus shooting operations. Furthermore, since the stator is disposed outside the outer periphery of the rotor, the lens barrel becomes thick.

It is an object of the present invention to eliminate these drawbacks of conventional devices and provide a compact and inexpensive lens driving device with good driving performance.

In order to achieve this object, the present invention provides a lens drive device in which a step motor drives a mechanism for moving a lens in the optical axis direction, in which the stator coil and rotor magnet of the step motor are arranged in a direction parallel to the optical axis. The lens driving device is characterized in that the moving mechanism is formed by the rotor magnet.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of an autofocus lens mirror incorporating a lens driving device to which the present invention is applied. Lenses G1, G2-G3, G4, G5, and G6 are built into the lens barrel 1, of which lens G is moved in the direction of the optical axis for focusing. Fixed barrel 3 is lens G1-G2・G
Holds 3φG4 and G6 and also holds the stator of the step motor. The stator consists of field coils 6 and 7 and corresponding field yokes 8 and 9, respectively. The rotor is made of plastic magnet, ) 11, and is supported by an inner cylinder 3a of a fixed cylinder 3 by pole bearings 15a and 15b.

A partially enlarged view of the rotor and stator of this step motor is shown in FIG. In this figure, the field yokes 8 and 9 and the rotor magnet 11 are shown separated to make it easier to understand the structure of each part.

The plastic rotor magnet 11 is integrally formed with north and south magnetic poles alternately magnetized at a constant pitch. This rotor 11 serves as a rotating cam, and is provided with a bottomed cam groove 11c on its inner circumference. The trajectory of the cam groove lie is aligned with the movement trajectory of the focal position of the lens. Similarly, a groove 11a for arranging the bearing 15a and a groove 11b for arranging the bearing 15b (not shown in this figure) are provided on the inner peripheral surface of the rotor 11.

As shown in FIG. 3, the yokes 8 and 9 are arranged in a direction parallel to the optical axis, and the rotor magnet 11 is arranged in the space formed by the two yokes. The yoke 8 has a hollow part 16, and the coil 6 is wound inside the hollow part 16. Hollow part 1
From 6 onwards, comb tooth yokes 16a and 16b are formed alternately so that the generated magnetic fields have opposite polarities. Similarly, in the yoke 9, the coil 7 is wound inside the hollow portion 17, forming comb-toothed yokes 17a and 17b that generate magnetic fields of opposite polarity. The comb teeth 16a-16b and 17aφ17b of the yokes 8 and 9 face each other in a direction parallel to the optical axis at positions shifted by half a pitch.

The yoke 8 is held in position by a positioning protrusion 16d fitted into a positioning groove 3d provided on the outer periphery of the inner cylinder of the fixed cylinder 3. The yoke 9 is also positioned and held in a similar configuration. A guide roller 14 pivotally supported by a movable barrel 13c that holds the focusing lens G5 is engaged with the cam groove lie, and the roller 14 is a long guide provided in the inner barrel 3a of the fixed barrel 3 in the optical axis direction. It passes through the hole 3C in a slidable manner.

In addition, in FIG. 1, 17 is an aperture unit, 19 is a ring for operating the aperture, and 21 is a mount connected to the camera body.

FIG. 4 is a block circuit diagram for controlling the drive of the step motor. 50 is a focus detection section, 52 is a signal processing calculation section, and 54 is a ring counter. Various types of circuits can be applied within each block. L,,L2. L3. L4 corresponds to the field coils 6 and 7 (FIG. 1). E is a driving power battery.

In the step motor having the above configuration, the ring counter 54
When an input signal having the illustrated pulse waveform is sent to the input terminal of the coil L1, power is supplied to the field coil L, and the field yoke corresponding to the coil L1 is excited. Assuming that the magnetized magnetic pole of the magnet 11 corresponding to the field yoke is the S pole, when the generated magnetic pole of the yoke becomes the S pole, they repel each other and the yoke attracts the adjacent N pole. The cam cylinder 11, which is a rotor magnet, is repeatedly magnetized as described above to energize each of the magnetic field coils L1 to L4 in accordance with the input of a pulse from the ring counter 54.
rotates around the optical axis.

The rotation of the cam groove 11b causes the focusing lens G5 to move in the optical axis direction, thereby performing a focusing operation. This operation is accurate and compact because the rotation bearing that is the moving mechanism, the cam, and the magnet that is the rotor of the motor are integrated. There is no inertia during rotation, quick response rotation, good controllability, and no gear noise. It also helps reduce costs.

In the configuration of the present invention, the main components of the rotor and stator are arranged in a direction parallel to the optical axis, and only a thin comb-toothed yoke is arranged around the outer circumference of the rotor, so the outer diameter of the lens barrel can be reduced. can. In addition, the stator coils are wound using the put space of the lens barrel where the rotor is placed, which also contributes to compactness.

In the above embodiment, the plastic magnet is made of a plastic material mixed with metal powder such as ferrite. As a result, the strength is improved compared to conventional plastic molded products mixed with glass fiber, etc., and the cam lift error and groove width uniformity are molded with high precision, and there is little deviation due to temperature changes, etc. It is something.

A helicoidal screw may be provided instead of the cam as the lens moving mechanism. In addition to the two-phase step motor, a multi-layer step motor may also be used in view of control accuracy.

Although the above embodiment describes the focusing movement mechanism of an autofocus lens, the present invention is not limited to this, and can be applied to a zoom lens zoom lens focusing movement mechanism, an autofocus Φ zoom lens focusing movement mechanism, and a zoom movement mechanism. can also be applied.

[Brief explanation of the drawing]

Fig. 1 is a partially sectional side view of an autofocus lens equipped with a drive device of the present invention, Fig. 2 is an exploded perspective view of the main parts of the same, Fig. 3 is a partially sectional perspective view of the same, and Fig. 4 is a drive circuit. It is a block diagram. l is the lens barrel, 3 is the fixed barrel, 6 and 7 are the field coils, 8
- 9 is a field yoke, 11 is a rotor magnet, lla is a bearing receiver groove, flb is a cam groove, 14 is a guide roller, and 15a-15b are bearings. Patent Applicant Canon Co., Ltd. 61 (Voluntary) Procedural Amendment July 23, 1980 Commissioner of the Patent Office Manabu Shiga 1988 Patent Application No. 89781 2 Name of the invention Lens drive device 3 Person making the correction Relationship to the case Patent Applicant name (100) Canon Co., Ltd. 4, Agent 2-11-12 Yoyogi, Shibuya-ku, Tokyo Telephone 370-
642Ei (main) 59. Target of amendment Specification “Claims” ・ “
"Detailed Description of the Invention" column. (2) On page 3 of the specification, lines 7 to 10, “…”
The phrase "...formed..." has been corrected as follows. In the description, a cylindrical rotating magnet arranged in a direction parallel to the optical axis is rotatably supported from a radial direction of the optical axis with respect to a coil attached to a fixed barrel of a lens barrel. ,
A comb-tooth yoke attached to the coil and which attracts the magnetic field generated from the coil is extended to the outer periphery of the cylindrical rotating magnet, and a rotating cam groove provided on the inner periphery of the cylindrical rotating magnet and a rotating cam groove provided on the fixed cylinder. The engaging member that engages with the guide groove parallel to the optical axis direction is attached to the movable lens holding cylinder...
(3) Similarly, the specification is amended as follows. Page Line Wrong Correct 43 It becomes solid. The rotor magnet 11 is hard 44, ball 3a is pole 45, so
Therefore, the engaging member is cylindrical in the radial direction of the optical axis of the lens, claim 1, moving the lens in the optical axis direction. A lens driving device in which a mechanism is driven by a step motor, the lens driving device being characterized in that the mechanism is driven by a step motor.

Claims (1)

[Claims] (1) In a lens drive device in which a step motor drives the mechanism for moving the lens in the optical axis direction, the stator coil and rotor magnet of the step motor are arranged in a direction parallel to the optical axis, and the rotor magnet and rotor magnet are arranged in a direction parallel to the optical axis. A lens driving device characterized in that the moving mechanism is formed by: