JPH0467365A - Magnetic head actuator - Google Patents

Abstract

PURPOSE:To realize the actuator of satisfactory responsibility and to improve a dynamic characteristic by forming the circuit pattern of conductive foil on an insulating bendable film and shaping the pattern in a cylinder shape in a form following an air gap part to constitute a voice coil. CONSTITUTION:The voice coil 14 is constituted by winding the film 15 formed by an insulating material round so that a diameter comes to a prescribed one and spiral circuit patterns 16B and 16C forming a rectangular form, which is shown in (B) and (C) are formed on the surface and back of the film 15. Consequently, the bobbin of an electromagnetic coil is formed by the insulating bendable film and the coil is formed on the film 15 as conductive foil. Thus, the coil which appropriately functions against the arrangement of permanent magnet and a yoke can be held by holding light weight and sufficient strength. Thus, the dynamic characteristic can considerably be improved by narrowing the interval of the air gap part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic head actuator for moving a magnetic head to perform a tracking operation.

[Prior Art] Conventionally, as an actuator for a magnetic head, one that utilizes a voice coil and is shown in FIG. 11A is known. In the figure, LA and IB are permanent magnets, 2 is an inner yoke, and 3A, 3B, and 3C are outer yokes, and the permanent magnets IA and IB and the inner yoke 2 are formed concentrically with the same diameter. A voice coil 4 as shown in FIG. 1 is movably held along an air gap 5 between the inner yoke 2 and the outer yoke 3B.

6A and 6B are gimbal springs that support the voice coil 4 movably in the direction of its central axis; 7 is a coil holder IIIA; and 7 is attached to a head support portion 8C extending from the lower coil holder 8B. magnetic head, 9
AJ5 and 9B are wiring drawn out from the voice coil 4 and the magnetic head 7, and 1o is a shield case covering the outside.

The voice coil 4 is also provided with a cylindrical thin bobbin I4 made of a resin material, for example, as shown in the first IB.
For example, a coil of copper wire 15 coated with polyester or the like has been used.

In the magnetic head actuator configured in this way,
Since the permanent magnets IA and IB are provided with the same magnetic poles (in this example, N poles) facing each other, the magnetic flux from both magnets IA and IB is transferred from the inner yoke 2 to the air gap portion 5, respectively. A loop is formed that returns to the S pole of each magnet via the outer yoke 3B and further via the outer yokes 3A and 3G. Therefore, a radial magnetic field is formed in the air gap portion 5 from the inner yoke 2 toward the outer yoke 3B.

Now, when current is applied to the voice coil 4, a force is generated in a direction that crosses the magnetic flux formed in the air gap portion 5, and as a result, the voice coil 4 supported by the gimbal springs 6A and 6B is affected by the reaction force of the springs. Displaced in its axial direction until it is in balance. Therefore, this displacement can be used to function as an actuator for the magnetic head 7.

[Problems to be Solved by the Invention] However, in the above conventional example, the two magnets IA and I
By arranging the magnetic poles of B to face each other, a unidirectional magnetic field is formed in the air gap portion 5, so
Almost all the magnetic flux passes through the outer yoke 3A or 3C. On the other hand, a head support part 8C for fixing the magnetic head 7 from the voice coil 4 extends outward from the holder 8B, and it is also necessary to take out the wiring 9A and 9B to the magnetic head 7 and the voice coil 4. Therefore, it is necessary to provide a notch 11 in the outer yoke 3B. Therefore, leakage of magnetic flux from these notches 11 is likely to occur.

In addition, in the above conventional example, since the voice coil 4 is made of a bobbin 14 made of a resin-based material and a coated copper wire 15 wound around the bobbin 14, the dynamic characteristics of the actuator are improved in the following ways. There were obstacles in doing so.

That is, 1) The thickness of the bobbin is determined by the strength required as a resin-based structure, so it cannot be made very thin.

2) The thickness of the coating is set based on the required electrical insulation, so the thinner the wire used, the greater the proportion of the coating material.

3) Even if the windings are wound in alignment, it is difficult to control the shape accuracy.

For these reasons, the radial dimension of the voice coil 4,
Furthermore, it is not only impossible to reduce the interval between the air gap portions 5 in which the voice coil 4 is movably disposed, making it impossible to increase the magnetic flux density, but also making it difficult to improve heat dissipation, and furthermore, the inertia of the voice coil itself Because it is difficult to reduce mass,
It was difficult to improve dynamic characteristics.

In view of the conventional problems as mentioned above, the object of the present invention is to
An object of the present invention is to provide a magnetic head actuator that can improve dynamic characteristics by reducing the weight of a coil bobbin and increasing the density of magnetic flux in an air gap.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a plurality of permanent magnets and a yoke provided concentrically with an air gap between the plurality of permanent magnets.

A magnetic head actuator is provided with an electromagnetic coil movably supported in the air gap portion, and is capable of driving a magnetic head by excitation of the electromagnetic coil. The electromagnetic coil is characterized in that the electromagnetic coil is constructed by winding a flexible film into a shape corresponding to the air gap portion.

[Function] According to the present invention, the bobbin of the electromagnetic coil is formed of an insulating flexible film, and the coil is formed as a conductive foil on the film. This means that a coil that functions properly even when the coil is lightweight and has sufficient strength can be obtained, and by narrowing the distance between the air gaps, it can significantly contribute to improving dynamic characteristics.

[Examples] Examples of the present invention will be described below in detail and specifically based on the drawings.

1 to 4 show a first embodiment of the present invention. In these figures, IA-IC is a permanent magnet, 2A and 2B are inner yokes, and 3A to 3C are outer yokes. The three permanent magnets IA to IC are connected to an inner yoke 2A interposed between them.
, 2B and the same diameter, and are stacked in the axial direction with the same poles facing each other, kept concentrically, and fixed with adhesive or the like. Furthermore, these three magnets LA, IB, IC
Among them, the thickness of the center magnet IB is the same as that of the magnets LA at both ends,
It is set to about twice that of IC, and the inner yoke 2A,
The thickness of 2B is set so that the magnetic flux density within the near gap portion 5 is maximized within a range in which demagnetization of the permanent magnet does not occur.

Further, in this embodiment, the voice coil 14 is configured as shown in FIG. That is, (A) in FIG. 5 shows the finished state, and (B) shows the voice coil 14 in this example.
The film 15 made of an insulating material as shown in (B) and (C) is rolled into a circle (rolled) to a predetermined diameter, and the front and back surfaces of the film 15 are
) A spiral circuit pattern 1 with a rectangular shape as shown in
6B and 16G are formed.

Furthermore, in (A) to (C) of FIG. 5, 17 is a terminal portion extending from the film 15, and on the front surface (B) side, it is rotated counterclockwise from one terminal 17A formed on the terminal portion 17. The circuit pattern 16B is formed in a state of being rolled inward in the direction of.

160 is a through hole, and the circuit led to the through hole 160 on the front side is
is connected to the circuit pattern 16C on the back side through ((C
) See figure) From here, it is unwound outward in a clockwise direction and guided to the other terminal 17B of the terminal portion 17.

In the voice coil 14 configured in this way, one terminal 1
7A flows in the direction of arrow A in the upper half 14A of the circuit pattern 16B and in the direction of arrow B in the lower half 14B, and also in the circuit pattern 16C on the back side. In the half portion 14B, the flow flows in the same direction corresponding to the surface. On the other hand, the upper half of the coil 1
4A is provided corresponding to the upper air gap portion 5A in FIG. 1, and the lower coil half portion 14B is provided corresponding to the lower air gap portion 5B.
Since the direction of the magnetic flux is opposite between the coil upper half 14 and
The same axial force is generated in A and lower half 14B.

In addition, in this embodiment, since the terminal portion 17 is formed by appropriately extending a part of the film 15, it is easy to connect the wires after assembly, and a plurality of such coil elements can be made from one sheet of film. It is possible to select a shape that does not produce waste when cutting out the body, contributing to a reduction in manufacturing costs. In addition, by configuring the voice coil 14 as in this embodiment, the accuracy of the wiring position and shape is improved compared to conventional voice coils, and it is also extremely lightweight, which greatly improves the dynamic characteristics of the actuator. I can contribute.

In forming the above-mentioned circuit patterns 16B and 16G, for example,
It is possible to use a method such as etching a copper foil with a thickness of about μ-1, but it is not limited to copper foil, but an appropriately lightweight and conductive material such as aluminum foil or plated material can be used. In particular, by using a conductor with a low specific gravity such as aluminum, it is possible to form a significantly lightweight coil.

In addition, when shaping as shown in FIG. 5 (A),
Circuit pattern 16B on the front side and circuit pattern 16G on the back side
Since they come into contact with each other, it is necessary to insulate the space between them, which can be done by sandwiching another insulating film or by applying an insulating agent.

In addition, in the first embodiment described above, the central magnet IH
Although the thickness of the magnets LA and IC at both the upper and lower ends is approximately twice that of the magnets LA and IC, it is also possible to use two magnets IB with the same shape as IA and IC, stacked together, and in this case, only one type of magnet shape is used. can be unified.

A second embodiment of the present invention is shown in FIG. 6. In this embodiment, two cylindrical magnets IA and IB are magnetized in opposite radial directions, and are integrated with one outer yoke 3A. By providing the yoke portion 2, an air gap portion 5 is formed between the inner yoke portion 2 and the magnets LA and IB.

According to such a configuration, a part of the magnetic flux guided from the magnet IA to the inner yoke part 2 via the air gap part 5 reaches the magnet IH via the air gap part 5 again, and the remaining magnetic flux is transferred to the outer yoke 3A, Return to magnet IA via 3B. Further, approximately the same amount of magnetic flux as the magnetic flux guided from magnet IA to IB through inner yoke portion 2 is guided from magnet IB to magnet IA through outer yoke 3B. Three magnetic paths are formed in this way, and magnetic flux is generated at a ratio according to the permeance of each path, so
In the case of this embodiment, when the length of the magnet in the axial direction is increased, the cross-sectional area of the air gap portion 5 traversed by the magnetic flux can be changed accordingly.

However, in the case of this example, the cross-sectional area of the inner yoke portion 2 is constant regardless of the length of the magnet in the axial direction. Therefore, in this example, it is desirable to set the length of the magnet so that both of the two magnetic paths passing through the inner yoke portion 2 described above are not saturated.

According to the present embodiment, since the magnets IA and 1B are provided outside the air gap portion 5, the cross-sectional area of both magnets can be increased compared to the first embodiment. It is possible to maintain a higher transverse magnetic flux density, and the dynamic characteristics of the actuator can be further improved.

Reference numeral 14 denotes a voice coil used in this embodiment.1 The flow of magnetic flux in the air gap portion 5 of this embodiment is similar to that of the first embodiment, and in the upper half air gap portion 5A, the N of the magnet IA is A magnetic flux flows from the pole toward the inner yoke portion 2, and a loop of the magnetic flux flows from the inner yoke portion 2 to the S pole of the magnet IB in the lower air gap portion 5B. Therefore, the voice coil 14 shown in FIG. 5 can be used as it is.

FIG. 7 shows a third embodiment of the present invention. In this embodiment, the number of magnets is increased to IA to ID compared to the second embodiment, and the form of the voice coil is changed accordingly. It is structured as follows. Since the structure and operation of the actuator itself is similar to the second embodiment, the explanation thereof will be omitted.It goes without saying that according to this embodiment, leakage of magnetic flux is further suppressed.

Now, in this embodiment, (A) in FIG. 8 shows the finished state of the voice coil 24, and (B) 8
and (C) show the front and back sides of the film 15 in the unfolded state, that is, the circuit pattern 26B on the front side.
is once formed counterclockwise inwardly as shown in (B), then connected to the back side via the through hole 26D, and then wound clockwise outwardly as shown in (C). After being folded downward and formed clockwise inward from here, it is again connected to the surface side through the through hole 26E. From here, the terminal is formed in an outward winding counterclockwise direction, and the terminal is guided to the terminal portion 27.

Therefore, the current flows through the circuit patterns 26B, 26C, in the direction of arrow A in the coil parts 24AJ and 24G, and in the direction of arrow B in the coil parts 24B and 24D.
These coil portions 24A to 2
Since the magnets 4D are arranged corresponding to the magnets IA to ID, it is possible to generate force in the same direction in the voice coil 24.

FIG. 9 shows the fourth embodiment of the present invention, and FIG. 10 shows the fourth embodiment of the present invention.
The structure of the voice coil according to an example is shown.

In the fourth embodiment, both outer yokes 3A and 3C are made of non-magnetic material.

Further, in this embodiment, circuit patterns 36B and 36C as shown in (B)j5 and (C) of FIG. Similarly, through hole 36D
Connect via J5 and 36E. (Thus, in this embodiment, in the coil portions 34A, 34B, and 34G,
For example, it is possible to obtain currents in the directions indicated by arrows B, A, and arrow B, and it is possible to flow currents corresponding to each direction of magnetic flux in the gap portion 5.

In addition, in the actuator configured in this way,
The magnetic flux passing through the outer yokes 3A and 3G disappears, and most of the magnetic flux emitted from each magnet reciprocates across the air gap portion 5, so it is possible to suppress the leakage of magnetic flux to a sufficiently low level simply by providing the thin shield case 10. can.

Further, in each of the embodiments described above, the air gap portion 5 is filled with a magnetic fluid (not shown) to increase the magnetic flux density and the heat dissipation of the coil, thereby further improving the dynamic characteristics. is possible. In such a case, the surface of the present invention is smoother than that of a conventional coil bobbin, so there is less resistance to the fluid during operation, and there is less fear of the magnetic fluid scattering, which is preferable.

In the embodiments described above, the magnetic head actuator is arranged in consideration of the relationship between the permanent magnet and the yoke so that the loop of magnetic flux crosses the air gap twice, thereby increasing the magnetic flux density. However, the application of the present invention is not limited to these (the present invention can be widely applied to general magnetic head actuators in which a voice coil is movably supported in an air gap between a magnet and a yoke). Needless to say.

[Effects of the Invention] As explained above, according to the present invention, a circuit pattern of conductive foil is appropriately formed on an insulating flexible film in response to the magnetic flux crossing the air gap portion, and the circuit pattern is formed across the air gap portion. By forming the voice coil into a cylindrical shape along the section, we are able to create an actuator with good responsiveness.Furthermore, by using a material with low specific gravity such as aluminum for the conductor foil, Dynamic characteristics can be further improved. Furthermore, by filling the air gap with magnetic fluid, an actuator with even better responsiveness can be obtained.

[Brief explanation of the drawing]

1 is a sectional view showing the configuration of the first embodiment of the present invention, FIG. 2 is a view taken along the line A-A in FIG. 1, FIG. 3 is a view taken along the line B-B in FIG. 1, Fig. 4 is an external side view of the first embodiment, Fig. 5 is a configuration diagram of the coil according to the first embodiment, Section 6 is a sectional view showing the structure of the second embodiment of the present invention, and Fig. 7 is a main body. 8 is a sectional view showing the structure of a coil according to the third embodiment, FIG. 9 is a sectional view showing the structure of a fourth embodiment of the invention, and FIG. Block diagram of the coil according to the fourth embodiment, No. 11A
Figure 22 is a sectional view showing the configuration of a conventional example. 11B is a perspective view IA showing the coil of FIG. 11A taken out.
, 1B, IC, 10... Magnet, 2, 2A, 2B
, 2C...inner yoke, 3A, 3B, 3G...
Outer yoke, 14, 24.34...Voice coil, 14
A, 14B, 24A, 24B, 24G, 24D, 34A
, 34B, 34C...Coil, 5.5A, 5B...Air gap part, 6A, 6B・
...Gimbal spring, 7.Magnetic head, 8A, 8B..Coil holder, 8C..Head support part, 9A, 9B..Wiring, 10..Shield case, 11..Notch. Part, 15... Film, 16B, 16C, 26B, 26C, 36B, 36C...
・Circuit pattern, 16D, 26D, 26E, 36
D, 36E...Through hole. It is a diagram. Figure 1 of Hayabusa's B-B bride-to-be's prisoner Figure 3 Figure 1 of A-A Entenshiden Figure 2, $ - August 3rd Urasai period, 1st evening of 1st month 11 prisoners figure 7

Claims (1)

[Claims] 1) A plurality of permanent magnets, a yoke concentrically provided between the plurality of permanent magnets via an air gap, and an electromagnetic coil movably supported by the air gap. In a magnetic head actuator that is capable of driving a magnetic head by excitation of the electromagnetic coil, an insulating flexible film on which a coil circuit pattern is formed using conductive foil is wound in a shape corresponding to the air gap portion. A magnetic head actuator, characterized in that the electromagnetic coil is formed by rotating the magnetic head. 2) The magnetic head actuator according to claim 1, wherein the circuit pattern of the conductive foil is formed of aluminum or an alloy thereof.