JPH08287630A - Magnetic disk device - Google Patents

Abstract

PURPOSE: To satisfactorily miniaturize a magnetic disk device without increasing the electric power consumption by suppressing deterioration of magnetic flux density in a gap in a magnetic field device even when the device is miniaturized. CONSTITUTION: With regard to a movable coil type actuator of the magnetic disk device, an intermediate yoke 3 consisting of a magnetic body in a thin-plate shape is provided in the middle of a magnetic gap of the field device consisting of permanent magnetss 1A, 1B, 1C and 1D and yokes 8A and 8B, and then an upper movable coil part 2A and a lower movable coil part 2B are provided above and below the intermediate yoke 3. Thus, since magnetic permeability of the intermediate yoke 3 is high, leakage flux in end parts of the magnetic gap can be reduced, and as a result of it, the magnetic flux density is increased to obtain a large driving force, so that miniaturization is feasible, and also a high responsiveness can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk device using a movable coil type actuator as an actuator for positioning a magnetic head.

[0002]

2. Description of the Related Art As is well known, in recent years, a magnetic disk device called a hard disk device has been used as a storage device for a personal computer (personal computer) or the like, and particularly an external storage device having a large capacity. Has been widely used as.

An example of this magnetic disk device will now be described with reference to FIG. 10. This device generally has a magnetic disk 5 for recording, a magnetic head 6, a head arm 7, and a head positioning actuator, as shown in the drawing. As shown in FIG. 11, the actuator A is generally composed of four plate-shaped permanent magnets 1A, 1B, 1C, 1D, a coil 2, and a yoke 8A. , 8B.

The permanent magnets 1A, 1B, 1C and 1D and the yokes 8A and 8B constitute a field device of a movable coil type actuator, and therefore, the permanent magnets 1A, 1B and 1D.
C and 1D are attached to the two yokes 8A and 8B located in the upper and lower sides in the drawing with polarities as shown in FIG. 12, whereby the gap G is formed as shown by the arrow B. The magnetic flux B flows therethrough, and a magnetic field having a predetermined strength is formed in the gap G.

The coil 2 includes permanent magnets 1A, 1B, 1C,
It is attached to the head arm 7 so as to be located in the gap G between 1D.
As shown in FIG. 10, the end to which the magnetic head 6 is attached is rotatably held as shown by an arrow P about the rotation shaft 7A, and the magnetic head 6 is The coil 2 is attached to the end opposite to the attached end.

Therefore, an electromagnetic force indicated by an arrow F in FIG. 12 is generated in the coil 2 depending on the direction of the current flowing through the coil 2, and as a result, the magnetic head 6 of the head arm 7 is attached. The magnetic head 6 can be positioned on a predetermined recording track of the magnetic disk 5 by moving the end portion as shown by an arrow P in FIG.

By the way, such an actuator is
The electromagnetic force acting on the coil 2 causes the coil 2 itself to move, that is, it is a movable coil. Therefore, as described above, it is called a movable coil actuator.
Furthermore, since the head arm rotates by being supported by the rotating shaft, it is also called a rotary actuator.

An example of this type of conventional device is the device described in Japanese Patent Laid-Open No. 4-258855.

[0009]

It cannot be said that the prior art described above takes into consideration the decrease in the air gap magnetic flux density due to the miniaturization of the device, and it is difficult to obtain the necessary driving force, and the positioning response is improved. There is a problem that the power consumption decreases and the power consumption increases. That is, in the case of downsizing, the air gap relatively expands, and as a result, it becomes difficult to obtain the necessary driving force, or the coil current needs to be increased and the power consumption increases. Of.

The object of the present invention is to suppress the reduction of the air gap magnetic flux density in the field device even when the device is downsized, and as a result, it is possible to sufficiently downsize without increasing the power consumption. It is to provide a magnetic disk device.

[0011]

As a field device of a movable coil type actuator, one having a thin plate-shaped magnetic body held substantially in the middle of an air gap is used, and the thin plate-shaped magnetic body is used as a movable coil. A portion divided into a conductor group positioned between one surface of the plate-shaped permanent magnet and one surface of the plate-shaped permanent magnet, and a conductor group positioned between the other surface of the thin plate-shaped magnetic body and the other surface of the plate-shaped permanent magnet. It is achieved by using the one configured as follows.

[0012]

The thin plate-shaped magnetic body forms an intermediate yoke in the air gap to provide a magnetic path with a low magnetic resistance to the magnetic flux passing through the air gap, so that the magnetic flux that tries to leak from the periphery of the air gap to the outside Work to induce. As a result, the leakage magnetic flux is suppressed, so that the magnetic flux passing through the air gap increases, the magnetic flux density increases, and the electromagnetic force acting on the moving coil becomes stronger. As a result, it is necessary to reduce the size. The driving force can be easily obtained.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic disk device according to the present invention will be described in detail below with reference to embodiments shown in the drawings. 1 and 2
Shows an embodiment of the movable coil type actuator A in the present invention. In these figures, 3 is an intermediate yoke, and the others are the same as the conventional example described in FIG. The example is different from the above-described conventional example in that the movable coil 2 is divided into an upper movable coil portion 2A and a lower movable coil portion 2B.

The intermediate yoke 3 is made of a thin plate of a magnetic material having a high magnetic permeability, such as a nickel-iron alloy, and a plate-shaped permanent magnet 1 on the upper side in the figure by a holding member (not shown).
It is held almost in the middle of the magnetic gap G formed between A and 1C and the plate-like permanent magnets 1B and 1D on the lower side.

Corresponding to the fact that the intermediate yoke 3 is provided substantially in the middle of the magnetic gap G as described above, the upper movable coil portion 2A is first provided on one surface of the intermediate yoke 3.
That is, it is attached to the end of the head arm 7 (FIG. 10) so that it is located between the upper surface in the figure and one of the plate-shaped permanent magnets, that is, between the plate-shaped permanent magnets 1A, 1C in these figures. Next, the lower movable coil portion 2B includes the other surface of the intermediate yoke 3, that is, the lower surface in the drawing, and the other of the plate-shaped permanent magnets.
That is, in the figure, it is mounted between the permanent magnets 1B and 1D at the end of the head arm 7 as well.

Next, the operation of this embodiment will be described. As is apparent from FIG. 2, in the magnetic gap G, the permanent magnets 1A and 1C on the upper side and the permanent magnet 1 on the lower side are included.
By B and 1D, a magnetic flux exists as shown by an arrow B, and a magnetic field is formed in the vertical direction of the figure. Since the upper moving coil portion 2A and the lower moving coil portion 2B exist in this magnetic field, these moving coil portions 2A, 2
When a current is supplied to B, an electromagnetic force directed in the left-right direction in the figure is generated by the interaction between the current of this coil and the magnetic field formed in the magnetic gap G, as shown by an arrow F, It occurs in 2A and 2B. The moving direction at this time is determined by the direction of the current supplied to the coil.

As a result, the head arm 7 has a rotating shaft 7A.
A rotational driving force (torque) appears, and the magnetic head 8 attached to the other end is moved as shown by an arrow P in FIG. 10 to move it to an arbitrary position on the recording surface of the magnetic disk 5, Can be positioned on the recording track, and therefore, a function as a head driving actuator of the magnetic disk device can be obtained.

Next, the function of the intermediate yoke 3 in this embodiment will be described. The intermediate yoke 3 is made of a magnetic material having a high magnetic permeability as described above, and it has a magnetic gap G. Since it is located in the middle, as shown in FIG. 2, at the end portions of the magnetic gap G, that is, the left and right end portions in the figure, a path having a small magnetic resistance to the magnetic flux.
(Magnetic path) is formed.

As a result, as shown in the figure, the magnetic flux (leakage magnetic flux) which is about to leak to the outside flows into the intermediate yoke 3,
The magnetic flux is introduced into the magnetic air gap G, the magnetic flux passing through the magnetic air gap G increases, and the magnetic flux density in the magnetic air gap G increases.

Further, since the intermediate yoke 3 is located in the magnetic gap G, it serves to lower the magnetic resistance in the entire magnetic gap G, and as a result, the magnetic flux density in the magnetic gap G is high. Become.

By the way, the response of the magnetic disk device is
It is determined by the time required for positioning the magnetic head with respect to the required recording track, but in order to shorten this time, the driving force of the head driving actuator may be increased. This is because the greater the driving force, the faster the moving speed.

Here, as described above, the driving force of the movable coil actuator is determined by the product of the current supplied to the coil and the magnetic flux density in the magnetic gap G. May increase either the current or the magnetic flux density, or both of them.

According to this embodiment, since the magnetic flux density in the magnetic gap G is increased by the action of the intermediate yoke 3 as described above, when the coil current is the same, a driving force larger than that of the prior art is obtained. As a result, the response of the magnetic disk device can be improved,
It is possible to easily compensate for the decrease in responsiveness due to miniaturization.

By the way, as described above, the driving force of the movable coil actuator can also be increased by increasing the current supplied to the coil. However, in this case, the power consumption increases.

In such a magnetic disk device, the power consumption by the actuator accounts for a large proportion of the total power consumption. Therefore, increasing the coil current immediately increases the total power consumption. It will be connected.

However, according to this embodiment, since the magnetic flux density in the magnetic gap G is increased, high responsiveness can be easily obtained without increasing the coil current, and the same responsiveness can be obtained. With, it is possible to reduce power consumption and save energy.

FIG. 3 shows an example of the torque (driving force) obtained in an embodiment of the present invention in comparison with that of the conventional example. As is clear from this figure, in this example, It can be seen that a torque increase of approximately 6% is obtained as a whole. In this figure, the horizontal axis indicates the "rotation angle of the coil".
Is the rotation angle of the head arm 7 (FIG. 10).

Next, another embodiment of the present invention will be described. As described above, the intermediate yoke 3 according to the present invention is located in the magnetic gap G and forms a part of the magnetic flux path.
Therefore, in the following embodiments, this is utilized to control the distribution of the magnetic flux density in the magnetic gap G.

As is apparent from FIG. 3, in such a movable coil type actuator, the torque changes considerably depending on the rotation angle of the arm, and the torque decreases on both sides of the rotation range. I understand.

Therefore, first, in the embodiment shown in FIG. 4, the planar shape of the intermediate yoke 3 is changed so that the dimension in the direction perpendicular to the moving direction of the moving coil, that is, its width, is changed according to the position in the moving direction of the moving coil. To different dimensions, as shown,
At the center C of the moving range of the coil, the width of the intermediate yoke 3 is made smaller than at both ends.
In this embodiment, a diamond-shaped opening (through hole) 10 is provided at the center of the moving range of the coil of the intermediate yoke 3.

The aim of the embodiments shown in FIGS. 4 and 5 is to change the portion where the intermediate yoke 3 actually exists in the magnetic gap G within the moving range of the coil, and to approach the center of the moving range of the coil. The part where the intermediate yoke 3 is present is reduced.

As described above, since the intermediate yoke 3 is made of a material having a high magnetic permeability, its presence serves to increase the magnetic flux density in the magnetic gap G. Therefore, when the intermediate yoke 3 according to the embodiment of FIGS. 4 and 5 is used, the increase of the magnetic flux density at the center of the moving range of the coil can be suppressed, and as a result, as shown in FIG.
As shown in, the torque fluctuation due to the change in the rotation angle of the coil is reduced, and a more uniform torque can be obtained. Therefore, it is possible to obtain the effect of easily maintaining the positioning control accuracy.

In FIG. 6, what is referred to as the first embodiment is the characteristic of the embodiment described with reference to FIGS. 1 and 2.
The second embodiment shows the characteristics according to the embodiments of FIGS. 4 and 6, but these characteristics can be arbitrarily selected according to the width dimension of the intermediate yoke 3 and the size of the opening. You can

Next, FIG. 7 shows a modification of the embodiment of FIG.
Several slits 11 are provided as openings, and the length of each of these slits 11 is changed according to the position so that the magnetic flux density has a desired distribution state. FIG. 8 is also a modification of the embodiment of FIG. 5, in which a plurality of small holes 12 are provided, and the magnetic flux density is desired by changing the distribution state of these small holes 12. The distribution state is set to.

The effects of the embodiments shown in FIGS. 7 and 8 are as follows.
Both are almost the same as those of the embodiment shown in FIGS. 4 and 5, but the reduction in strength of the intermediate yoke 3 is small, and in the embodiment of FIG. 8, only small holes are removed, so that good workability can be obtained. There is an advantage to say.

Next, in the embodiment shown in FIG. 9, the magnetic flux density distribution is changed by changing the magnetic permeability of the material itself instead of changing the size. Is composed of a portion 13 made of a material having a low magnetic permeability and a portion 14 made of a material having a high magnetic permeability. Therefore, in the embodiment of FIG. 9 as well, substantially the same effects as those of the embodiments shown in FIG.
There is an advantage that sufficient strength is obtained and it is strong against deformation.

[0037]

According to the present invention, since the leakage magnetic flux can be suppressed and the magnetic flux density in the magnetic air gap can be increased correspondingly by the simple structure of only providing the intermediate yoke, the power consumption is not increased. It is possible to easily and surely provide a magnetic disk device which can be sufficiently miniaturized. Further, according to the present invention, since the magnetic flux density distribution in the magnetic gap can be easily controlled, it is possible to easily provide a magnetic disk device having good control characteristics.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a movable coil type actuator in a magnetic disk device according to the present invention.

FIG. 2 is an explanatory view showing a cross section of an embodiment of the present invention.

FIG. 3 is a characteristic diagram showing torque characteristics according to an embodiment of the present invention.

FIG. 4 is an explanatory diagram showing an example of an intermediate yoke according to the present invention.

FIG. 5 is an explanatory view showing another embodiment of the intermediate yoke in the present invention.

FIG. 6 is a characteristic diagram showing torque characteristics according to another embodiment of the present invention.

FIG. 7 is an explanatory view showing another embodiment of the intermediate yoke in the present invention.

FIG. 8 is an explanatory view showing another embodiment of the intermediate yoke in the present invention.

FIG. 9 is an explanatory view showing still another embodiment of the intermediate yoke according to the present invention.

FIG. 10 is a configuration diagram showing an example of a magnetic disk device.

FIG. 11 is a perspective view showing a conventional example of a movable coil type actuator in a magnetic disk device.

FIG. 12 is an explanatory view showing a cross section of a conventional example of a movable coil type actuator.

[Explanation of symbols]

 1A-1D Plate-shaped permanent magnet 2 Moving coil 2A Upper moving coil portion 2B Lower moving coil portion 3 Intermediate yoke 5 Magnetic disk 6 Magnetic head 7 Head arm 7A Rotating shaft 8A, 8B Yoke

Claims (4)

[Claims] 1. A field device composed of two plate-shaped permanent magnets arranged with a predetermined air gap interposed therebetween, and movable by the field device in a direction perpendicular to a direction of a magnetic field formed in the air gap. In a magnetic disk device in which a movable coil actuator composed of a movable coil held in the gap is used to position a magnetic head by the actuator, the field device is held approximately in the middle of the gap. A thin plate-shaped magnetic body, wherein the movable coil includes a conductor group located between one surface of the thin plate-shaped magnetic body and one of the plate-shaped permanent magnets, and the thin-plate magnetic body. A magnetic disk device comprising: the other surface of the body and a portion formed of a conductor group located between the other surface of the plate-shaped permanent magnet. 2. The invention according to claim 1, wherein a dimension of the thin plate-shaped magnetic body in a direction perpendicular to a moving direction of the moving coil is made different according to a position of the moving coil in the moving direction. A magnetic disk device characterized in that 3. The magnetic disk device according to claim 1, wherein the thin plate-shaped magnetic body has at least one of a slit and a through hole. 4. The magnetic disk device according to claim 1, wherein the thin plate-shaped magnetic body is made of a material having different magnetic permeability according to a moving direction of the movable coil.