JPH09213026A - Voice coil motor and magnetic circuit used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of parts in a yoke part constituting a magnetic circuit for voice coil motor. SOLUTION: The magnetic circuit 20 has a magnetic 21 magnetized in the direction of board thickness and the yoke part. The yoke part extends along a driving shaft and it has a center yoke 22 passing through the voice coil and a back yoke 23. The back yoke 23 has a main face 23a which is arranged separatedly from the center yoke 22 in parallel with it and opposedly to it. Both end parts 23b are bent almost at a right angle to the main face 23a with press work. The end parts 23b are brought into contact with the end parts of the center yoke 22. The magnet 21 is brought into contact with the main free 23a of the back yoke 23. The center yoke 22 and the back yoke 23 are constituted of steel plates whose board thickness are 3mm or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic circuit for a voice coil motor used for driving a carriage of a magnetic recording / reproducing apparatus in a radial direction with respect to a magnetic recording medium.

[0002]

2. Description of the Related Art As is well known, a flexible disk driver is a device for driving a flexible disk. In recent years, the capacity of a flexible disk has been increased, and a storage capacity of 150 Mbytes (hereinafter, referred to as large capacity) has been increased to a storage capacity of 1 M to 2 Mbytes (hereinafter, referred to as normal capacity). What you have is being developed. Along with this, a flexible disk driver capable of driving such a large-capacity flexible disk has been developed.

In the following, a flexible disk driver capable of driving only a large-capacity flexible disk is called a high-density dedicated flexible disk driver,
A normal density dedicated type flexible disk driver capable of driving only a normal capacity flexible disk will be referred to. Further, a flexible disk driver capable of driving both large capacity and normal capacity flexible disks will be referred to as a high density / normal density combined type flexible disk driver. If the high-density dedicated flexible disk driver and the high-density / normal density dual-purpose flexible disk driver are not distinguished, simply:
It is called a high-density flexible disk driver.

Now, one of the mechanical differences between the normal-density dedicated type flexible disk driver and the high-density type flexible disk driver is that the carriage holding the magnetic head is attached to the flexible disk inserted in the driver. The drive means is configured to be moved along a predetermined radial direction. That is, the normal density dedicated type flexible disk driver uses a stepping motor as the driving means, whereas the high density flexible disk driver uses a linear motor such as a voice coil motor (VCM) as the driving means. There is.

The voice coil motor used as the driving means of the high density type flexible disk driver will be described in detail below. The voice coil motors are arranged on both rear sides of the carriage and are wound around a drive shaft parallel to a predetermined radial direction, and a magnetic circuit for generating a magnetic field intersecting with a current flowing through the voice coil. Have and.

FIG. 4 shows a magnetic circuit of a conventional voice coil motor. The conventional magnetic circuit has a magnet 21 magnetized in the plate thickness direction and a yoke portion. The yoke portion extends along the drive shaft and penetrates through a voice coil (not shown), and a back yoke 23 ′ that is arranged in parallel with and spaced apart from the center yoke.
It is composed of a pair of side yokes 24 'arranged between both ends of the center yoke 22 and both ends of the back yoke 23'. The magnet 21 is in contact with one surface of the back yoke 23 'on the surface side facing the center yoke 22.
Each of the center yoke 22, the back yoke 23 ', and the side yoke 24' is made of a steel plate having a plate thickness of 3 mm or more.

With such a structure, the center yoke 2
A magnetic field is generated in the space between 2 and the back yoke 23 '. By passing a current through the voice coil in a direction intersecting with the magnetic field, a driving force is generated in the extending direction of the drive shaft (center yoke 22) based on the interaction between the current and the magnetic field. With this driving force, the voice coil motor moves the carriage along a predetermined radial direction.

[0008]

As shown in FIG. 4, in the conventional voice coil motor magnetic circuit, the yoke portion is composed of the center yoke 22, the back yoke 23 'and the pair of side yokes 24'. However, there is a problem that the number of components is increased.

Therefore, in view of the above-mentioned conventional problems, an object of the present invention is to provide a voice coil motor and its magnetic circuit, which can reduce the number of parts of the yoke portion constituting the magnetic circuit.

[0010]

According to the present invention, in a voice coil motor used for driving a carriage of a magnetic recording / reproducing apparatus along a predetermined radial direction with respect to a magnetic recording medium, said carriage Placed on both sides,
A voice coil wound around a drive shaft parallel to the predetermined radial direction, a center yoke extending along the drive shaft and penetrating through the voice coil, and spaced apart in parallel to the center yoke. And have the main surfaces arranged opposite to each other,
A voice coil motor can be obtained in which both ends are bent substantially at right angles to the main surface, and both ends are in contact with both ends of the center yoke.

Further, according to the present invention, in a magnetic circuit for a voice coil motor having a voice coil, a center yoke that penetrates through the voice coil and a main unit that is arranged opposite to and parallel to the center yoke. A magnetic circuit for a voice coil motor having a surface, a back yoke having both ends bent at substantially right angles to the main surface, and the both ends being in contact with both ends of the center yoke is obtained.

[0012]

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

A magnetic recording / reproducing apparatus to which the voice coil motor according to the present invention is applied will be described with reference to FIGS. 2 and 3. 2 is a plan view of the magnetic recording / reproducing apparatus, FIG. 3 is a view showing a voice coil motor portion in FIG. 2, (a) is a rear view, (b) is a front view, and (c) is ( It is sectional drawing seen from the AA 'line of a).

The illustrated magnetic recording / reproducing apparatus is a flexible disk drive (FDD), and is an apparatus for recording / reproducing a flexible disk (not shown). The flexible disk is inserted into the flexible disk drive from the direction shown by arrow A in FIG. The inserted flexible disc is rotatably supported on the surface of the main frame 11 by a disc table assembly 12
They are held on top of each other with their central axes aligned. The disk table assembly 12 is rotationally driven by a motor (not shown) provided on the back surface of the main frame 11, whereby the flexible disk rotates. A substrate (not shown) on which a number of electronic components are mounted is attached to the back surface of the main frame 11.

The flexible disk drive has a magnetic head (not shown) for reading / writing data from / to the flexible disk. Magnetic head 13
Are held by the carriage 15 via the gimbal 14. A combination of the magnetic head 13, the gimbal 14, and the carriage 15 is called a carriage assembly. The carriage 15 is arranged on the surface of the main frame 11 so as to be separated from the main frame 11, and allows the magnetic head to move along a predetermined radial direction (direction shown by arrow B in FIG. 2) with respect to the flexible disk. keeping.

The carriage 15 is supported and guided at its lower ends by a pair of guide bars 16 extending parallel to a predetermined radial direction B.

The carriage 15 is moved in a predetermined radial direction B by a voice coil motor as described in detail below.
Is driven along. More specifically, the voice coil motor is disposed behind the carriage 15, and has a pair of voice coils 17 wound around a drive shaft parallel to a predetermined radial direction B, and intersects a current flowing through the boil coil 17. And a magnetic circuit 20 for generating a magnetic field.

Referring also to FIG. 1, the magnetic circuit 20 has a magnet 21 magnetized in the plate thickness direction and a yoke portion according to the present invention. The yoke portion extends along the drive shaft,
Center yoke 22 penetrating through voice coil 17
And a back yoke 23. The back yoke 23 has a main surface 23a which is arranged parallel to and spaced apart from the center yoke 22 and is opposed to the main surface. Both ends 23 b are in contact with both ends of the center yoke 22. The magnet 21 is a back yoke 23.
Is in contact with the main surface 23a. Each of the center yoke 22 and the back yoke 23 is made of a steel plate having a plate thickness of 3 mm or more.

That is, both ends 23 of the back yoke 23
b acts as a conventional side yoke 24 '(Fig. 4). In other words, the back yoke 23 is formed by integrating the conventional back yoke 23 'and the side yoke 24' shown in FIG.

The main frame 11 has the magnetic circuit 20.
Has four pedestals 30 for arranging the space away from the main surface 11a of the main frame 11. Each pedestal 30 has a protrusion 31 projecting upward. The height of each projection 31 is smaller than the thickness of the center yoke 22. The center yoke 22 has cutouts 22a at both ends into which the projections 31 are fitted. Therefore, the protrusion 31 of the pedestal 30 functions as a positioning means for positioning the center yoke 22. Further, both end portions 23b of the back yoke 23 have the cutout portions 22a.
Has a convex portion 23c that fits in the. The height of the convex portion 23c depends on the thickness of the center yoke 22 and the protrusion portion 3 of the pedestal 30.
It is specified to be approximately equal to the value obtained by subtracting the height of 1. That is, the notch 22a of the center yoke 22 functions as a positioning unit for positioning the back yoke 23.

Since the magnetic circuit of the voice coil motor is constructed as described above, the number of parts of the yoke portion can be reduced.

In the voice coil motor having such a structure, a magnetic field is generated in the space between the center yoke 22 and the back yoke 23. By passing a current through the voice coil 17 in a direction crossing the magnetic field, a drive shaft (center yoke 22) is formed based on the interaction between the current and the magnetic field.
A driving force is generated in the extending direction of. With this driving force, the voice coil motor moves the carriage 15 in a predetermined radial direction.

The present invention is not limited to the above-described embodiments, and it is needless to say that various changes and modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, an example in which it is applied to a flexible disk drive is described, but it is also applicable to other magnetic recording / reproducing devices.

[0024]

As is apparent from the above description, according to the present invention, the yoke portion which constitutes the magnetic circuit for the voice coil motor is constituted by the center yoke and the back yoke whose both ends are bent substantially at right angles. It is possible to reduce the number of component parts of the voice coil motor. Therefore, the number of steps for assembling the voice coil motor can be reduced, and the voice coil motor can be provided at a low cost.

[Brief description of drawings]

FIG. 1 is a perspective view showing a magnetic circuit for a voice coil motor according to an embodiment of the present invention.

FIG. 2 is a plan view showing the configuration of a flexible disk drive (magnetic recording / reproducing apparatus) to which the voice coil motor according to the present invention is applied.

3A and 3B are diagrams showing a voice coil motor portion in FIG. 2, in which FIG. 3A is a rear view, FIG. 3B is a front view, and FIG.
3 is a cross-sectional view as seen from the line AA ′ of FIG.

FIG. 4 is a perspective view showing a conventional magnetic circuit for a voice coil motor.

[Explanation of symbols]

 17 voice coil 20 magnetic circuit 21 magnet 22 center yoke 22a notch 23 back yoke 23a main surface 23b both ends 23c convex 30 pedestal 31 protruding

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshinori Tanki 1601 Sakai, Atsugi, Kanagawa Mitsumi Electric Co., Ltd. Atsugi Plant

Claims (6)

[Claims] 1. A voice coil motor used to drive a carriage of a magnetic recording / reproducing apparatus along a predetermined radial direction with respect to a magnetic recording medium, the voice coil motor being disposed on the carriage and parallel to the predetermined radial direction. A voice coil wound around a drive shaft, a center yoke extending along the drive shaft and penetrating through the voice coil, and a main coil arranged opposite to and spaced from the center yoke in parallel. A voice coil motor having a surface, a back yoke having both ends bent substantially at right angles to the main surface, and the both ends contacting both ends of the center yoke. 2. The voice coil motor according to claim 1, wherein both ends of the back yoke are bent by press working. 3. The voice coil motor according to claim 1, wherein each of the center yoke and the back yoke has a plate thickness of 3 mm or more. 4. A magnetic circuit for a voice coil motor having a voice coil, comprising: a center yoke that penetrates through the voice coil; and a main surface that is arranged opposite to and parallel to the center yoke. A magnetic circuit for a voice coil motor, comprising: a back yoke, both ends of which are bent substantially at right angles to a surface, the both ends being in contact with both ends of the center yoke. 5. The magnetic circuit for a voice coil motor according to claim 4, wherein both ends of the back yoke are bent by press working. 6. The magnetic circuit for a voice coil motor according to claim 4, wherein each of the center yoke and the back yoke has a plate thickness of 3 mm or more.