JPH11215795A - Control actuator with magnetosensitive element, and lens mirror cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce external disturbance magnetic field to a magnetosensitive element, and realize miniaturization and improvement in reliability, by adding a permanent magnet for reducing the external disturbance magnetic field, when linear motor and a magnetosensitive element for position control are used. SOLUTION: This control actuator is equipped with a linear motor 1 and a magnetosensitive element 20 for position detection, and a permanent magnet for reducing external disturbance magnetic field 30 is arranged between the linear motor 1 and the magnetosensitive element 20. The permanent magnet 30 generates a magnetic field having a direction which cancels at least a magnetic field component which affect the magnetic detection operation of the magnetosensitive element 20, from the disturbance magnetic field containing leakage flux from the linear motor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control actuator with a magnetically sensitive element and a lens barrel used for driving a driven body such as a lens and a mirror at a high speed.

[0002]

2. Description of the Related Art Conventionally, a lens barrel that moves a movable lens system using a rotary actuator such as a stepping motor has been proposed.

In addition, Japanese Patent Application Laid-Open No. 8-149777 proposes an optical device that moves a movable lens system using a linear motor and controls position using a magnetically sensitive element.

[0004]

When moving a lens at high speed in a lens barrel of a video camera or the like, it is necessary to use a linear motor or the like, and further, it is necessary to use a magnetic sensing element or the like for controlling the position of the lens. was there. In an attempt to reduce the size in such a situation, in a device using a linear motor and a magnetically sensitive element, there is a problem that the leakage magnetic flux of the linear motor greatly affects the magnetically sensitive element and it is difficult to reduce the size.

In a general magnetic shield as means for reducing the leakage magnetic flux, there is a restriction on the structure of the linear motor, and it is difficult to completely suppress the leakage magnetic flux. This is an obstacle to miniaturization.

In view of the above, the present invention reduces the disturbance magnetic field to the magnetic sensing element by adding a disturbance magnetic field reducing permanent magnet in a configuration using a linear motor and a position control magnetic sensing element. It is an object of the present invention to provide a control actuator with a magnetically sensitive element and a lens barrel, which achieve miniaturization of the device and improve the reliability of the position control operation.

[0007] Other objects and novel features of the present invention will be clarified in embodiments described later.

[0008]

In order to achieve the above object, a control actuator with a magnetically sensitive element according to the present invention comprises:
In a configuration having a linear motor and a magnetic sensing element for position detection, in a disturbance magnetic field including a leakage magnetic field from the linear motor, at least a magnetic field in a direction to cancel a magnetic field component that affects a magnetic detection operation of the magnetic sensing element is removed. A permanent magnet for reducing a disturbance magnetic field generated is provided.

In the control actuator with a magnetically sensitive element, the permanent magnet for reducing a disturbance magnetic field may be arranged between the linear motor and the magnetically sensitive element.

The lens barrel according to the present invention is configured such that a movable lens system is driven by a control actuator having a magnetically sensitive element having a linear motor and a magnetically sensitive element for position detection, and wherein a disturbance including a leakage magnetic field from the linear motor is provided. It is characterized in that a disturbance magnetic field reducing permanent magnet that generates a magnetic field in a direction that cancels out a magnetic field component that affects at least the magnetic detection operation of the magnetically sensitive element in the magnetic field is provided.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a control actuator with a magnetically sensitive element and a lens barrel according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a control actuator with a magnetically sensitive element according to a first embodiment of the present invention. In this figure, reference numeral 1 denotes a linear motor, in which a permanent magnet 3 for a linear motor is fixed inside a magnetic yoke 2, and a movable coil (not shown) is provided around a field section 4 formed by a part of the magnetic yoke 2.
Are provided movably. The linear motor 1 is configured to linearly move the movable coil along the field portion 4 by energizing the movable coil. A driven body to be driven by the linear motor 1 is connected to the movable coil.

Reference numeral 10 denotes a magnetic scale, which is formed by alternately magnetizing minute magnetic poles N and S in a longitudinal direction, and is fixed to a driven body driven linearly by a linear motor 1, for example. When the driven body is a lens barrel of a camera or a video camera, the driven body is a lens and a holding frame integrated with the lens.

Reference numeral 20 denotes a position-sensitive magnetic sensing element such as an MR element or a Hall element. When used for position control of a driven body in combination with the magnetic scale 10, a high-sensitivity MR element is generally used, and the magnetically sensitive element 20 magnetizes the minute magnetic poles N and S of the magnetic scale 10 alternately. It is fixedly arranged so as to face the longitudinal surface (for example, is fixed to an apparatus case or the like to which the magnetic yoke 2 of the linear motor 1 is fixed), and magnetically detects the movement of the magnetic scale 10, that is, the movement of the driven body. .

When a strong rare earth magnet is used as the permanent magnet 3 for the linear motor of the linear motor 1, the magnetic flux is minimized by increasing the thickness of the magnetic yoke 2 or surrounding substantially the entire permanent magnet 3 for the linear motor. However, as a result of the magnetic scale 10 and the magnetic sensitive element 20 being arranged close to the linear motor 1 with the miniaturization of various devices, the magnetic flux 10 (shown by a dotted arrow P in FIG. 1) causes A magnetic field of the order of Gauss also appears at the position of the magnetically sensitive element 20. To cancel this, a disturbance magnetic field reducing permanent magnet 30 is fixed to the outer surface of the magnetic yoke 2 between the linear motor 1 and the magnetically sensitive element 20. The permanent magnet 30 for reducing a disturbance magnetic field is preferably, for example, a sheet-like rubber magnet. In FIG. 1, a permanent magnet 30 for reducing a disturbance magnetic field is indicated by a dotted arrow Q in FIG.
FIG.

Here, the magnetic field due to the leakage magnetic flux of the linear motor 1 at the position of the magnetic sensing element 20 is changed to X, X orthogonal to each other.
When considered separately for the Y and Z axis components, the magnetic scale 10
Since the X-axis component coincident with the longitudinal direction of the magnetic scale 10 adversely affects the minute magnetic poles N and S of the magnetic scale 10, it is necessary to sufficiently cancel and suppress the magnetic field of the disturbance magnetic field reducing permanent magnet 30, and the Z-axis component is also reduced. The direction coincides with the magnetic detection axis of the magnetically sensitive element 20, which adversely affects the magnetic detection operation of the magnetically sensitive element 20. The Y-axis component has few problems even if the magnetic field remains.

According to the first embodiment, the following effects can be obtained.

(1) A magnetic field for canceling a magnetic field component that affects the magnetic detection operation of the magnetic sensing element 20 in the leakage magnetic field from the linear motor 1 is changed to a disturbance magnetic field reducing permanent magnet 3.
0, and it is possible to prevent the magnetic sensitive element 20 from being adversely affected even when the linear motor 1 and the magnetic scale 10 approach each other due to the miniaturization.

(2) By disposing the permanent magnet 30 for reducing the disturbance magnetic field at an appropriate position to remove the adverse effect due to the leakage magnetic flux of the linear motor 1, the magnetic sensitive element 2 of the magnetic scale 10 can be removed.
0 improves the reliability of the reading operation.

FIG. 2 shows a second embodiment of the present invention.
In this case, a disturbance magnetic field reducing permanent magnet 30 is disposed on the back side of the magnetically sensitive element 20 as viewed from the linear motor 1. The configuration other than the disposition of the disturbance magnetic field reducing permanent magnets 30 is the same as that of the above-described first embodiment, and the same or corresponding portions are denoted by the same reference characters and description thereof is omitted.

Also in the case of the second embodiment, the disturbance magnetic field reducing permanent magnet 30 separates the magnetic field due to the leakage magnetic flux of the linear motor 1 at the position of the magnetic sensing element 20 into X, Y and Z axis components. When considered, the arrangement is such that the X-axis component and the Z-axis component are sufficiently suppressed.

FIGS. 3 and 4 show a third embodiment of the present invention, in which a control is provided with a magnetic sensor having a linear motor 1, a magnetic sensor 20 for detecting a position, and a permanent magnet 30 for reducing a disturbance magnetic field. 4 shows a lens barrel having a structure in which a movable lens system 50 is driven by an actuator 40. In these figures, a movable lens system 50 is composed of a lens 51 and a holding frame 52 integral therewith.
Are slidably supported in parallel to the driving direction of.

Control actuator 40 with magnetic sensing element
Is substantially the same as that of the first embodiment described above, and the movable frame 5 linearly moving along the field portion 4 of the linear motor 1 is provided with a holding frame 52 of a movable lens system 50 as a driven body. Are fixed and integrated. The magnetic scale 10 is fixed to the upper part of the holding frame 52, and the magnetically sensitive element 20 is fixedly arranged on the case side of the lens barrel so as to face the longitudinal surface where the minute magnetic poles N and S of the magnetic scale 10 are alternately magnetized. Have been. In addition, the permanent magnet 30 for reducing a disturbance magnetic field includes a magnetic yoke 2 between the linear motor 1 and the magnetic sensing element 20.
It is fixed to the outer surface.

The configuration other than the movable lens system 50 and the mechanism for supporting the movable lens system 50 is the same as that of the first embodiment described above, and the same or corresponding parts are denoted by the same reference characters and description thereof is omitted.

Also in the case of the third embodiment, the disturbance magnetic field reducing permanent magnet 30 separates the magnetic field due to the leakage magnetic flux of the linear motor 1 at the position of the magnetic sensing element 20 into X, Y, and Z axis components. When considered, the arrangement is such that the X-axis component and the Z-axis component are sufficiently suppressed.

Incidentally, the disturbance magnetic field may include a magnetic field generated by a magnetic source other than the leakage magnetic flux of the linear motor 1.
In any case, among the disturbance magnetic fields including the leakage magnetic field from the linear motor 1, a magnetic field in a direction to cancel at least a magnetic field component affecting the magnetic detection operation of the magnetic sensing element 20 is generated by the disturbance magnetic field reducing permanent magnet 30. Just set it.

The magnetic scale 10 is a linear motor 1
Is fixed to the driven body that is driven linearly by
The present invention is applicable even if the driven body is driven by another driving source.

Although the embodiments of the present invention have been described above, it is obvious to those skilled in the art that the present invention is not limited to the embodiments and various modifications and changes can be made within the scope of the claims. There will be.

[0029]

As described above, according to the present invention,
When using a magnetically sensitive element for position control in applications that drive lenses and mirrors at high speeds, it was difficult to design a compact design due to the effects of leakage flux from the linear motor, but by adding a permanent magnet for reducing disturbance magnetic fields, The adverse effect of the disturbance magnetic field on the magnetic sensing element can be removed, and the size can be reduced. Further, the reliability of the magnetic sensing operation of the magnetic sensing element is also improved. Therefore, a device such as a lens barrel of a small camera or a video camera can be realized.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a control actuator with a magnetically sensitive element according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a main part of a control actuator with a magnetically sensitive element according to a second embodiment of the present invention.

FIG. 3 is a front view showing a lens barrel using a control actuator with a magnetically sensitive element according to a third embodiment of the present invention.

FIG. 4 is a side sectional view of FIG. 3;

DESCRIPTION OF SYMBOLS 1 Linear motor 2 Magnetic yoke 3 Permanent magnet for linear motor 4 Field part 5 Moving coil 10 Magnetic scale 20 Magnetic sensing element 30 Permanent magnet for reducing disturbance magnetic field 40 Control actuator with magnetic sensing element 50 Moving lens system 51 Lens 52 Holding frame 53 Guide shaft

Claims (3)

[Claims] 1. A control actuator with a magnetic sensing element having a linear motor and a magnetic sensing element for position detection, wherein at least one of a disturbance magnetic field including a leakage magnetic field from the linear motor affects a magnetic detection operation of the magnetic sensing element. A control actuator with a magnetically responsive element, comprising: a permanent magnet for reducing a disturbance magnetic field, which generates a magnetic field in a direction to cancel a magnetic field component that exerts a force. 2. The permanent magnet for reducing a disturbance magnetic field is disposed between the linear motor and the magnetically sensitive element.
A control actuator with a magnetically sensitive element according to the above. 3. A lens barrel for driving a movable lens system with a control actuator having a magnetically sensitive element having a linear motor and a magnetically sensitive element for position detection, wherein at least one of disturbance magnetic fields including a leakage magnetic field from the linear motor is provided. A lens barrel, further comprising: a disturbance magnetic field reducing permanent magnet that generates a magnetic field in a direction to cancel a magnetic field component affecting a magnetic detection operation of the magnetic sensing element.