JPS60417A - Lens driving device - Google Patents

Abstract

PURPOSE:To make a titled device small-sized by supporting a cylindrical rotary magnet from a parallel 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 through ball bearings 15a, 15b by the yokes 8, 9. Grooves 11a, 11b for placing the bearings 15a, 15b are provided on both side end faces of the magnet 11. The yokes 8, 9 are provided by being 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 photographic lens driving device for a still camera, cine camera, television camera, etc., and in particular has a built-in motor for autofocus (automatic focus adjustment) and autozoom (automatic magnification change). The lens is driven by a motor.

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 had an unusual shape with partial protrusions. It is expensive because it requires a large number of parts to be machined into the fixed tube of the lens barrel in order to attach the motor, gear trains, and other parts. 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, JP-A-5E is considered to be the most advanced! The device disclosed in Japanese Patent No. 147132 has a simple structure because it does not have gears or the like, 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. Further, a stator is attached to the lens barrel, and a rotor is attached to the lens barrel via a bearing. Therefore, the relative position accuracy of the stator and rotor deteriorates, resulting in eccentric rotation and torque unevenness. In severe cases, a hit or a de-adjustment phenomenon may occur. Furthermore, the assembly procedure becomes difficult, resulting in poor assembly efficiency.

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 mechanism for moving a lens in the optical axis direction is driven by a step motor. The lens driving device is characterized in that the moving mechanism is formed by the rotor of the held hollow motor.

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 barrel incorporating a lens driving device to which the present invention is applied. Lenses G, ψG5, and G6 are built into the lens barrel 1, of which the lens G5 is moved in the optical axis direction for focusing. The fixed cylinder 3 holds the lenses G1, G2, G3, G4, 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 consists of a plastic magnet (11). The rotor 11 is connected to the pole bearing 15a by the yokes 8 and 9.
It is supported through b.

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 1 plays the role of a rotating cam, and is provided with a bottomed cam groove 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, grooves 11a in which bearings 15a are arranged on both end surfaces of the rotor 11.
A groove 11b (indicated by a dotted line) is provided in which the bearing 15b is placed.

A bearing groove 8a (shown by dotted lines) is provided on the inner surface of the stake 8 at a position facing the groove 11a, and a bearing groove 9a is provided on the inner surface of the stator 9 at a position facing the groove 11b. Hair rings 15a are attached to the gates of these grooves 8a and lla.
A hair ring 15b is inserted between lb.

Therefore, as shown in FIG. 3, the yokes 8 and 9 are arranged in a direction parallel to the optical axis. A rotor magnet ( ) 11 is placed in the space where both of them are formed. Yoke 8 is hollow part 1
6, and the coil 6 is wound inside the hollow part 16. Comb south yokes 16a and 16b are formed alternately from the hollow part 16, so that the generated magnetic field has opposite polarity.
,)ru.

Similarly, the yoke 9 has a coil 7 wound inside the hollow part 17, and has comb-toothed yokes 17a and 1 that generate magnetic fields of opposite polarity.
6b is formed. Comb teeth 16a of each of yokes 8 and 9
The skewers 16b and 17a, 17b 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. York 9
are also positioned and held using a similar configuration. Cam groove 11c
is engaged with a guide roller 14 that is pivotally supported by the movable barrel 13c that holds the focusing lens G5, and the roller 14 engages with the fixed barrel 3.
It slidably passes through a guide hole 3c that is long in the optical axis direction and is provided in the inner tube 3a.

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. LX, L2, L3, and L correspond to the field coil 6-7 (FIG. 1). E is a driving power battery.

In the step motor having the above configuration, when an input signal having the illustrated pulse waveform is sent to the input terminal of the ring counter 54, power is supplied to the field coil L1, and the field yoke corresponding to the coil L1 is excited. Assuming that there are 11 magnetized magnetic poles or S poles corresponding to the field yoke, when the generated magnetic pole of the yoke becomes the S pole, they repel each other, and the yoke
Attract each other with poles. The cam cylinder 11, which is a rotor magnet repeatedly magnetized as described above, for energizing each of the magnetic field coils L and -L4 in response to 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 rotating bearing that is the moving mechanism, the cam, and the magnetite that is the rotor of the motor are integrated, and the rotor and stator are directly connected by the bearing. There is no inertia during rotation, quick response rotation, good controllability, and no gear noise.

Since it can be assembled and assembled into the lens barrel using only a motor, assembly is easy and costs can be reduced.

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.

FIG. 5 is a diagram showing another embodiment of the bearing receiver for the rotor 11. In the figure (a), a plurality of integral protrusions 23 are provided on the rotor 11, which is a cam cylinder. A pawl sliding raceway groove 24 is formed between each protrusion, and the pawl bearing rolls only between the protrusions. The protrusions therefore act as pole retainers.

Figure (b) shows pole holding parts 25 on both end surfaces of the rotor 11.
is provided, and a pole is rotatably embedded.

A helicoidal screw may be provided instead of the cam as the lens moving mechanism. In addition to the two-phase stencil motor, a multi-layer stencil motor may also be used in view of controllability and 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 zooming movement mechanism, an autofocus/zoom lens focusing movement mechanism, and a zooming 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. The block diagram, FIG. 5, is a partial shoulder circumference of another embodiment of the rotor. J is the lens barrel, 3 is the fixed barrel, 6 and 7 are the field coils, 8
・9 is the field yoke, 11 is the rotor magnet, 11a@
llb is a groove for a bearing receiver, 11c is a cam groove, 14 is a guide roller, and 15a-15b are bearings. (Voluntary) Procedural Amendment July 23, 1980 1, Indication of Case 1989 Patent Application No. 89783 2, Name of Invention Lens Drive Device 3, Person Making Amendment Relationship to Case Patent Name of Applicant (1oo) Canon Co., Ltd. 4, Agent Kimura Building 5, 2-11-12 Yoyogi, Shibuya-ku, Tokyo, Subject of amendment Specification "Claims" ・ "Detailed Description of the Invention" column, Drawings 6 , Contents of correction (2) [On the lens barrel] on page 3 of the specification, lines 12 to 15
The phrase "...formed..." has been corrected as follows. A cylindrical rotating magnet arranged in a direction parallel to the optical axis direction is rotatably supported from a direction parallel to the optical axis direction with respect to a coil attached to a fixed tube of the lens barrel, and is attached to the coil. A comb-tooth yoke that 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 comb-toothed yoke that attracts the magnetic field generated from the coil and the optical axis direction provided on the fixed cylinder are connected to each other. an engaging member that engages with a guide hole parallel to the
The fact that it was attached to a movable lens holding cylinder... (3) Similarly, the specification should be corrected as follows. Page Line Wrong Correct 417 - Body Cylindrical 55 Stator 56 on the field yoke 8 side of the stator 9 Stator 67-813c13 68 on the field yoke 9 side of the stator 9 7 13 11'b 1lc (4) The code “8” in Figure 3 of the drawing has been replaced with “7” as shown in red on the attached sheet.
”. 1. A lens driving device in which a mechanism for moving a lens in the optical axis direction is driven by a step motor, characterized by the following features.

Claims (1)

[Claims] (1) In a lens drive device in which a step motor drives a mechanism for moving a lens in the optical axis direction. 1. A lens driving device characterized in that the moving mechanism is formed by a hollow motor having a rotor held by a stator via a bearing on a stator fixedly held relative to a lens barrel.