JPH04337573A - Rotary actuator - Google Patents

Abstract

PURPOSE:To reduce the maximum magnetic flux density of upper and lower yokes, to prevent the yokes from being saturated and to enable the improvement of efficiency and high speed access by connecting the upper and lower yoks with side yokes and an auxiliary yoke in the direction of circumference and at the outer peripheral side. CONSTITUTION:By connecting the upper and lower yokes 26, 27 with a horseshoe yoke 23 obtd. by connecting integrally the side yokes 22 and a rear yoke 21, the way back of the magnetic flux after the magnetic flux is arrived at the upper yoke 26 is led to the side of the rear yoke 21 and the side yokes 22 and the magnetic flux from the north pole of the magnet 25 is considerably increased. Thus, since the maximum magnetic flux density of the upper and lower yokes 26, 27 is reduced, the magnetic saturation of the hoke is prevented and also magnetic reluctance is reduced and high efficiency is attained effectively.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary actuator, and more particularly to a rotary actuator for head access of a magnetic disk device widely used as an external storage device for computer systems. In recent years, the capacity of magnetic disk drives has significantly increased, and as a result, it has become important to improve the positioning accuracy of magnetic heads. At the same time, there is also a strong demand for faster access and lower power consumption, creating a need for highly efficient access motors. In addition, with the improvement in recording density, the size of the entire device has been significantly reduced, and recently there has been a strong demand for thinner devices. In response to such demands, there is a problem in that miniaturization makes it difficult to increase efficiency, and conversely, increasing efficiency goes against miniaturization, so a small and efficient rotary actuator is desired.

0002

2. Description of the Related Art FIG. 8 shows a conventional flat coil rotary actuator 80 for accessing a magnetic head for reading and writing information in a magnetic disk device. This rotary actuator 80 has a rotor 84 which is equipped with an arm 81 having a magnetic head H at its tip on one side, a flat coil 82 on the opposite side, and which can swing around a rotating shaft 83. The rotor 84 is configured to swing using the magnetic force of a magnet 85 provided on the opposite surface of the flat coil 82. And this magnet 85
is mounted on the lower yoke 87 and inserted under the flat coil 82 in parallel with the flat coil 82.
2, an upper yoke 86 is attached to a boss 88 protruding from a lower yoke 87 with screws 89 to form a magnetic circuit. As shown in the figure, the magnetic circuit of the rotary actuator 80 includes a pair of fan-shaped planar magnets 85 and upper and lower yokes 86 and 87.

FIG. 9 shows the rotary actuator 80 of FIG.
This figure shows a cross section of a magnetic circuit, and shows the flow of magnetic flux in this magnetic circuit. In the figure, 91 is a gap, and the flat coil 82 is located in this gap 91. Also, 85N is the N pole of the magnet 85, and 85S is the N pole of the magnet 8.
5, h is the thickness of the upper yoke 86, and L is the thickness of the upper yoke 86.
s indicates the length of the magnet.

Actuator 8 configured as above
0, if you try to perform high-speed access,
The gap 9 can be reduced by changing the magnet 85 to one with a high energy product.
It is common practice to increase the magnetic flux density of 1.

[0005]

[Problem to be solved by the invention] However, the magnet 8
When the energy of the upper yoke 86 is increased, the magnetic flux of the yokes 86 and 87 tends to become saturated, which is becoming a major problem especially when an attempt is made to reduce the thickness h of the upper yoke 86 to make it thinner. In such cases, there is a method of using high saturation magnetic flux density materials (permendur, etc.), but this only increases the saturation magnetic flux density by 20 to 30%, and on the other hand, it significantly deteriorates workability, increases cost, etc. The problem is that it has major disadvantages and is not a good idea.

Therefore, the present invention aims to increase the gap magnetic flux density by avoiding saturation of this yoke within limited dimensions and without using special materials, thereby achieving more efficient and high-speed access. The purpose is to provide actuators.

[0007]

[Means for Solving the Problems] The structure of a rotary actuator according to the present invention that achieves the above object is shown in FIG. As shown in FIG. 1, the rotary actuator of the present invention includes an arm 1 equipped with a magnetic head at the tip on one side, a flat coil 2 on the other side, and a rotor that can swing around a rotating shaft 3. 4, a magnet means 5 provided on the opposing surface of the flat coil 2 to apply a magnetic force to the flat coil 2, and an upper and lower yoke 6 provided as a yoke of the magnet means 5 in the vertical direction parallel to the flat coil 2. , 7, a side yoke 8 that connects the upper and lower yokes 6 and 7 at both ends in the circumferential direction where the flat coil 2 swings, and an auxiliary yoke 9 that connects the upper and lower yokes 6 and 7 on the outer peripheral side of the magnet means 5. It is characterized by

[0008]

[Operation] According to the rotary actuator of the present invention, the magnetic flux emitted from the N pole of the magnet passes through the gap to reach the upper yoke, passes through the side yoke and the auxiliary yoke provided on the outer peripheral side of the flat coil, and passes through the lower yoke. Return to the S pole of the magnet. With such a magnetic path, the maximum magnetic flux density of the upper and lower yokes is significantly reduced, saturation of the yokes is avoided, and the gap magnetic flux density is increased. Conversely, if the yoke has not reached saturation, the magnetic resistance of the magnetic circuit decreases and the gap magnetic flux density increases.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 2 shows a rotary actuator 2 of the present invention.
2 shows the configuration of one embodiment of No. 0. The structure on the rotor side of this embodiment is the same as the structure on the rotor side shown in FIG. 8, so the same reference numerals will be used to explain it. The rotor 84 is designed to swing around a rotating shaft 83, and an arm 81 having a magnetic head H at its tip is provided on one side of the rotor 84, and a flat coil 82 is provided on the opposite side. .

On the other hand, the stator side of the rotary actuator 20 has a flat coil 82 on the upper surface of the lower yoke 27.
A pair of magnets 25 consisting of N and S poles that apply magnetic force to
are provided to face the flat coil 82, and on both sides of the attachment part of the magnet 25 of the lower yoke 27,
A side yoke 22 is provided, and a rear yoke 21 is provided on the outside of the magnet 25 on the side opposite to the insertion side of the flat coil 82. In this embodiment, these two side yokes 22 and rear yoke 21 are connected and integrally formed to form a substantially horseshoe-shaped yoke 23. 26
is an upper yoke attached above the side yoke 22 and rear yoke 21.

In this way, when the upper yoke 26 and the lower yoke 27 are connected by the substantially horseshoe-shaped yoke 23, the pair of magnets 25 and the upper and lower yokes 26, 27 are the same as in the conventional example, but The return path of the magnetic flux after reaching the yoke 26 is significantly increased. Figure 3 shows the upper yoke 2 in Figure 2.
6 shows the magnetic flux distribution inside the device. From this figure, the magnetic flux after reaching the upper yoke 26 from the N pole of the magnet 25 is:
It can be seen that the water flows inside the upper yoke 26 toward the south pole, and also flows toward the rear yoke 21 and side yokes 22.

FIG. 4 shows a circumferential cross section of the magnetic circuit shown in FIG. As can be seen from this cross-sectional view, the magnetic flux from the magnet 25 is dispersed by the magnetic path of the straight portions at both ends of the side yoke 22, and the maximum magnetic flux density of the upper and lower yokes 26 and 27 is
It will be reduced to about half of the conventional amount. FIG. 5 shows a radial cross section of the magnetic circuit of FIG. As can be seen from this cross-sectional view, the magnetic flux is divided into a magnetic flux that goes from the N pole of the magnet 25 to the adjacent S pole, and a magnetic flux that goes to the S pole on the back of the magnet itself, and a magnetic flux that goes to the S pole on the back of the magnet 25. The magnetic flux passes through the rear yoke 21 on the outer peripheral side.

In the magnetic circuit of the rotary actuator 20 shown in FIG. 2, the magnetic path as described above is formed.
The maximum magnetic flux density of the upper and lower yokes 26 and 27 (generally the N of the magnet
(at the boundary between the pole and the south pole) can be significantly reduced, and saturation of the yoke can be avoided. As a result, the gap magnetic flux density can be increased, and conversely, even if the yoke has not reached saturation, the magnetic resistance of the magnetic circuit can be lowered and the gap magnetic flux density can be increased.

FIG. 6 shows the rotary actuator 20 of FIG.
2 shows a modification of the magnetic circuit shown in FIG. 2, and the same components as those in the magnetic circuit shown in FIG. The magnetic circuit in this figure is essentially the same as in Figure 2, but
The effect as a return yoke is the magnet 2 with a pair of N and S poles.
Note that the center side of each magnet 25 is large, and the end of the magnet 25 (
The return yoke is removed at the boundary between both magnets 5). Therefore, the two side yokes 22A, 22B
Gaps 24A, 24B, and 24C are provided between the two rear yokes 23A, 23B, respectively. and,
These gaps 24A, 24B, and 24C facilitate the flow of air to the rear as the disk rotates, which has the advantage of improving air cooling conditions for the coil.

FIG. 7 is a sectional view showing the structure of another embodiment of the rotary actuator of the present invention. In order to reduce the thickness of the rotary actuator 30 of this embodiment,
An iron base 37 and an iron cover 36 are used for the upper and lower yokes. A rotating shaft 83 is provided between the iron base 37 and the iron cover 36, and the rotor 84 is rotatably attached to the rotating shaft 83. An arm 81 having a magnetic head at its tip is provided on one side of the rotor 84, and a flat coil 82 is provided on the opposite side. There is a magnet 25 on the base 37 facing the flat coil 82. The horseshoe-shaped yoke 33 may have the same shape as shown in FIG.
, and is used as a spacer between the covers 36. Therefore, the horseshoe-shaped yoke 33 of this embodiment also functions as a reinforcing material for the thin base 37 and the cover 36.
This increases the natural frequency of the cover 36 and contributes to improving head positioning accuracy.

As described above, according to the rotary actuator of the present invention, the maximum magnetic flux density between the upper and lower yokes can be significantly reduced, saturation of the yoke can be avoided, and as a result, the gap magnetic flux density can be increased. . vice versa,
Even when the yoke has not reached saturation, the magnetic resistance of the magnetic circuit can be lowered and the gap magnetic flux density can be increased, resulting in lower power consumption.

[0017]

[Effects of the Invention] As explained above, according to the present invention, a high magnetic flux density can be obtained in a narrow space, and a magnetic disk device that is smaller, has faster access, and has lower power consumption can be realized. be.

[Brief explanation of drawings]

FIG. 1 is a principle configuration diagram showing the configuration of a rotary actuator according to the present invention.

FIG. 2 is a perspective view showing the configuration of an embodiment of the rotary actuator of the present invention.

FIG. 3 is an explanatory diagram showing the magnetic flux distribution within the upper yoke of FIG. 2;

FIG. 4 is a cross-sectional view showing the circumferential magnetic flux distribution of the magnetic circuit shown in FIG. 2;

FIG. 5 is a cross-sectional view showing the radial magnetic flux distribution of the magnetic circuit of FIG. 2;

FIG. 6 is a perspective view showing the configuration of a modification of the magnetic circuit shown in FIG. 2;

FIG. 7 is a sectional view of another embodiment of the rotary actuator of the present invention.

FIG. 8 is a perspective view showing the configuration of a conventional rotary actuator.

9 is a cross-sectional view of the magnetic circuit of the rotary actuator of FIG. 8. FIG.

[Explanation of symbols]

1...Arm 2...Flat coil 3...Rotating shaft 4...Rotor 5...Magnet 6...Upper yoke 7...Lower yoke 8...Side yoke 9...Auxiliary yoke 20...Rotary actuator of the present invention 21...Rear yoke 22...Side yoke 23... Horseshoe-shaped yokes 24A, 24B, 24C... Gap 25... Magnet 26... Upper yoke 27... Lower yoke 81... Arm 82... Flat coil 83... Rotating shaft 84... Rotor

Claims (3)

[Claims] Claim 1: A rotary actuator for accessing a magnetic head for reading and writing information in a magnetic disk device, comprising an arm (1) with a magnetic head at the tip on one side and a flat coil (2) on the other side. , a rotor (4) that can swing around a rotating shaft (3), and a magnet means (5) provided on the opposing surface of the flat coil (2) to apply a magnetic force to the flat coil (2).
As yokes of this magnet means (5), upper and lower yokes (6) and (7) are provided vertically parallel to the flat coil (2), and these upper and lower yokes (6) and (7)
) are connected to each other at both ends in the circumferential direction of the flat coil (2), and an auxiliary yoke is connected to the upper and lower yokes (6), (7) at the outer circumferential side of the magnet means (5). (9) A rotary actuator comprising: and. 2. The lower yoke (7) is a base of the disk device, the upper yoke (6) is a cover for sealing the disk device, and the auxiliary yoke (9) is located between the base and the cover. The rotary actuator according to claim 1, wherein the rotary actuator is sandwiched. 3. The auxiliary yoke (9) is arranged in the center of the magnet means (5) and the side yoke (8)
) The rotary actuator according to claim 1, wherein a gap is provided between the rotary actuator and the rotary actuator.