JPH0573870A - Magnetic head actuator - Google Patents

Abstract

PURPOSE:To reduce the influence of a leaked magnetic flux, to miniaturize the device and to attain a high performance by fixing a magnetic head to the tip part of a projected part provided on coil bobbin supported so as to be displaced in the air gap of a magnetic route, providing a transparent hole on the middle and penetrating a part of a yoke. CONSTITUTION:A coil bobbin 4 having a voice coil 14 in the air gap in the magnetic route of permanent magnets 1A and 1B, an internal yoke 2 and external yokes 3A, 3B and 3C is supported by gimbal springs 5A and 5B. Magnetic heads 8A and 8B are fixed to the tip part of a projected part 35 fixed to the bobbin 4 of the spring 5B and a transparent hole 45 is provided on the middle. One of four projected parts 13 of the yoke 3B is penetrated through the transparent hole 45 and connected to the yoke 3C, the fixed side land part of flexible plant substrates 25A and 25B is bent 90 degrees and fixed to the yoke 3B. Thus, the influence of the leaked magnetic flux of the magnetic head is reduced, the device is miniaturized and the high performance is attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head actuator for displacing a magnetic head to perform a tracking operation in a VTR or the like.

[0002]

2. Description of the Related Art Conventionally, as a device of this type, a device utilizing a voice coil, a device utilizing a bimorph and the like have been known.

FIG. 7 shows an example using a voice coil. The figure is an axial cross-sectional view of a columnar
A, 1B are permanent magnets, 2 are inner yokes, 3A, 3B, 3C
Is an outer yoke, 8A and 8B are magnetic heads, 5A and 5B are gimbal springs, 4 is a coil bobbin, and 14 is a voice coil.

Since the two columnar permanent magnets 1A and 1B have the same magnetic poles (N poles in this example) opposed to each other, the magnetic flux emitted from both magnets is the air from the inner yoke 2 to which the voice coil 14 is arranged. It returns to the S pole through the gap portion 10, the inside of the outer yoke. That is, a radial magnetic field is formed in the air gap portion 10 from the inner yoke 2 toward the outer yoke 3B. The voice coil 14 is attached to two gimbal springs 5A and 5B arranged outside the permanent magnets 1A and 1B,
It is supported so that it can be displaced only in the axial direction. Therefore, when an electric current is passed through the voice coil 14, an electromagnetic force is generated between the voice coil 14 and the magnetic field in the air gap 10, and the voice coil 1
4 can be axially displaced to a position where it is in balance with the reaction force of the gimbal springs 5A and 5B. As shown in FIG. 8, a protrusion is provided on a part of the gimbal spring 5B fixed to the voice coil 14 to fix the magnetic heads 8A and 8B.
It is used as an actuator.

[0005]

However, in the above-mentioned conventional example, since the gimbal spring is arranged outside the diameter of the air gap portion, the outer diameter of the actuator becomes large.

Generally, the performance (amplitude, response frequency, etc.) of an actuator improves as the volume of the air gap and the magnetic flux density increase. That is, if the cross-sectional area of the magnet is reduced, the performance deteriorates, and it is difficult to reduce the size of the VT.
As R becomes smaller, it is not possible to cope with the reduction in diameter of the rotary head drum.

Further, since the rotational speed of the rotary head is increased in a digital VTR or the like, it is difficult to improve the response frequency of the actuator.

Further, since the magnetic head mounting portion is close to the cutout portion of the outer yoke, there is a drawback that it is easily affected by the leakage magnetic flux.

Furthermore, when two or more magnetic heads are to be loaded, a larger area including the wiring space is required, which may result in a large notch or insufficient rigidity.

Therefore, an object of the present invention is to provide a magnetic head actuator which solves the above problems.

[0011]

To achieve the above object, the present invention is directed to a magnetic material forming a magnetic path having an air gap, a coil bobbin located in the air gap, and the coil bobbin displaced into the air gap. An elastic support member for supporting the elastic bobbin so that the elastic bobbin is secured to the coil bobbin by a protrusion, and at least one magnetic head is fixed to the tip of the protrusion. Further, a through hole is provided in the middle of the projecting portion so as to penetrate a part of the yoke constituting the magnetic material.

[0012]

According to the present invention, the effect of the leakage magnetic flux from the magnetic material on the magnetic head is reduced by providing a through hole in the protruding portion for mounting the magnetic head and penetrating a part of the (outer) yoke. In addition, the outer shape of the (outer) yoke is reduced.

[0013]

1 to 4 show an embodiment of the present invention.
2 is an exploded perspective view, FIG. 2 is a perspective view of an assembled state, and FIGS. 3 and 4 are cross-sectional views seen from the directions of arrows a and b shown in FIG. 2, respectively.

In the figure, 1A and 1B are permanent magnets, 2 is an inner yoke, 3A, 3B and 3C are outer yokes, 4 is a coil bobbin, 5A and 5B are gimbal springs, 8A and 8B are magnetic heads, 14 is a voice coil and 25A. , 25B are coils, a flexible printed circuit board for wiring the magnetic head, and 23A, 23B are reference planes for mounting the actuator on the rotary head drum.

The respective parts are assembled in the axial direction as shown in FIG. 1 and joined by an appropriate method such as bonding, but the outer yoke 3
One of the four protrusions 13 in the axial direction from B penetrates through the through hole 45 provided in the flat protrusion 35 of the gimbal spring 5B on which the magnetic heads 8A and 8B are mounted and engages with the outer yoke 3C. It is designed to meet.

The land portion on the fixed side of the flexible printed boards 25A and 25B for wiring is bent 90 ° and fixed to the side surface of the outer yoke 3B. This board 2
It is obvious that the shapes and fixing methods of the fixed sides of 5A and 25B can be variously changed depending on the method and arrangement of external connection or the convenience of handling the actuator, and are not directly related to the gist of the present invention.

By adopting such a configuration,
The sectional view seen from the direction of arrow a (FIG. 3) and the sectional view seen from the direction of arrow b (FIG. 4) are very different.
That is, in the cross-sectional view of FIG. 3 which corresponds to the radial direction when the magnetic head 8A and 8B are installed in the rotary head drum, the outer shape of the outer yoke is slightly larger than the diameter of the permanent magnet (φ2). Outer yoke 3B even if they are brought close to each other
Since there is a small amount of leakage flux due to the protruding portion 13, the influence is small. Therefore, even if the diameter of the rotary head drum is small, it can be incorporated. Further, if a rotary head drum having the same diameter can use a larger permanent magnet, the performance of the actuator (maximum displacement and response frequency) can be improved.

On the other hand, in the sectional view of FIG. 4 which is in the circumferential direction of the rotary head drum, the outer shape (φ1) is considerably larger than the diameter of the permanent magnet as in the outer shape of the conventional example. this is,
This is because a space for arranging the gimbal spring 5B is required. However, in practice, when the rotary head drum 110 is assembled, the centering and height when the rotary head drum 110 is assembled to the shaft are provided in the region 120 near the central axis shown by hatching in the schematic view of FIG. Since the reference plane for determination must be set as wide as possible, the actuator must be placed in a donut-shaped area outside the actuator, so there is more space in the circumferential direction than in the radial direction, and φ1 is larger than φ2. Big things don't really matter. Rather, as described above, it can be seen that the permanent magnet having the maximum diameter can be used for the radial dimension where space is tight.

[Other Embodiments] FIG. 6 is a view showing a second embodiment of the present invention, wherein the symbols are the same as those of the first embodiment. This example has the same internal structure as the first example described above, but the outer yokes 3a, 3
This is the case where the outer shapes of b and 3c are rectangular. Along with this, the through hole 4 provided in the protruding portion 35 of the gimbal spring 5B.
5 and the shape of the protruding portion 13 of the outer yoke 3b are different, but the functions are the same.

Although the above-mentioned two examples show the case where the columnar permanent magnet is used, it goes without saying that the present invention can be similarly applied to the case of using a rectangular parallelepiped or oblong column-shaped permanent magnet.
The point is that a discontinuous portion of the magnetic path is separated from the vicinity of the magnetic head by providing a through hole in a movable member on which the magnetic head is mounted and penetrating a part of the outer yoke. There are features.

[0021]

As described above, according to the present invention, by providing a through hole in the projecting portion for mounting the magnetic head and penetrating a part of the (outer) yoke, the influence of the leakage magnetic flux on the magnetic head. In addition, since the size of the rotary head drum can be reduced and the size in the diameter direction can be reduced when the rotary head drum is assembled, the magnetic head actuator can be mounted on a rotary head drum having a smaller diameter, and a magnetic head actuator with higher performance can be realized.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a magnetic head actuator according to an embodiment of the present invention.

FIG. 2 is a perspective view showing an assembled state of the actuator.

3 is a cross-sectional view of the same actuator as seen from the direction of the arrow A in FIG.

FIG. 4 is a cross-sectional view of the same actuator as seen from the direction of arrow B in FIG.

FIG. 5 is a plan view showing a state in which the rotary head drum is assembled.

FIG. 6 is a plan view of the second embodiment of the present invention.

FIG. 7 is a sectional view of an example of a conventional magnetic head actuator.

8 is a plan view of a gimbal spring of the actuator of FIG.

[Explanation of symbols]

 1A, 1B Permanent magnet 2 Inner yoke 3A, 3B, 3C Outer yoke 13 Projection part 4 Coil bobbin 14 Voice coil 5A, 5B Gimbal spring 35 Projection part 45 Through hole

Claims (1)

[Claims] 1. A magnetic material forming a magnetic path having an air gap, a coil bobbin located in the air gap, and an elastic support member movably supporting the coil bobbin in the air gap, A portion of the elastic supporting member that is fixed to the coil bobbin is provided with a protrusion, at least one magnetic head is fixed to the tip of the protrusion, and a through hole is provided in the middle of the protrusion. A magnetic head actuator, wherein the magnetic head actuator is provided so as to penetrate a part of a yoke constituting the magnetic material.