JPH11110927A - Information recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a head positioning highly accurate by allowing a head positioning mechanism to be provided with the head carriage supported freely rotatably around a prescribed rotary shaft and a driving force imparting mechanism imparting a driving force on the head carriage and generating forces of a rotational direction and a radial direction with respect to the head carriage. SOLUTION: A rotational torque is applied to a head carriage 10 by a driving resultant force F0 to generate a rotational acceleration in the carriage and the position signal preliminarily recorded on a magnetic disk 1 is detected with a magnetic head 2 and the magnetic head 2 is positioned to a desired recording track by controlling a current to be applied to a coil 21 with a control circuit. Thus, since the direction of the resultant force F0 is always made coincide with a straight line connecting the rotational center and the magnetic head 2, the direction of a vibration by the exciting force of a translating method becomes roughly perpendicular to the tracking direction shown with the arrow Q and even when vibrations are generated, the vibrations become non-interference in the direction of the head positioning.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording / reproducing apparatus used for recording / reproducing information, and more particularly to a head positioning mechanism for positioning a head on a recording track of a recording medium.

[0002]

2. Description of the Related Art In recent years, devices using a disk-shaped recording medium, such as a magnetic disk device and an optical disk device, have become widespread as information recording / reproducing devices. Above all, magnetic disk devices are widely used as external storage devices for personal computers, taking advantage of the high speed of data transfer. In general, a magnetic disk device generally has a configuration in which concentric recording tracks are provided on a magnetic disk, and information is recorded / reproduced by positioning a magnetic head on a desired track of the magnetic disk by an oscillating head positioning mechanism. Has become.

An oscillating type head positioning mechanism is such that a head carriage is rotatably mounted on a base by a ball bearing or the like, and a head is transferred and positioned in a radial direction of a recording medium by a driving force applying mechanism called a voice coil motor. It is. This oscillating head positioning mechanism is widely used in small magnetic disk drives because of its simple structure and less susceptibility to disturbance vibration.

As a driving force applying mechanism in a conventional head positioning mechanism, a flat coil type voice coil motor is mainly used. As disclosed in, for example, Japanese Patent Application Laid-Open No. 6-243604, a flat coil type voice coil motor includes a fan-shaped coil provided in a plane substantially orthogonal to the rotation center axis of the head carriage, and a radius of the coil. A permanent magnet facing only the side in the direction is provided, and a tangential force, that is, a torque is generated by an interaction between a current flowing in the radial side of the coil and a magnetic flux interlinked with the current.

In recent years, various proposals have been made for the purpose of improving the performance of a swing type head positioning mechanism. Among them, a driving method for reducing the quasi-rigid mechanical vibration of the head carriage has been proposed for the purpose of improving the head positioning accuracy.

One is a method in which a driving force is generated in a head carriage in a direction substantially perpendicular to the direction in which the magnetic head is positioned. (Hereinafter, this is referred to as an orthogonal driving method.) As a method for realizing the orthogonal driving method, for example, Japanese Patent Laid-Open Publication No. Hei.
Japanese Patent No. 80475 discloses a configuration in which a voice coil motor is provided on a side portion of a head carriage. According to the orthogonal drive method, since the direction of the quasi-rigid mechanical vibration caused by the translational excitation force acting on the rotation axis is substantially orthogonal to the head positioning direction, the influence of the quasi-rigid mode is suppressed,
The positioning accuracy of the magnetic head is significantly improved.

Another driving method is a method in which the head carriage is driven by a couple with respect to the rotation center axis. (Hereinafter, this will be referred to as a symmetric drive system.) As an embodiment of the symmetric drive system, for example, in U.S. Pat. Is disclosed. According to the symmetric drive system, since no translational excitation force acts on the rotation axis, quasi-rigid mechanical vibration of the head carriage does not occur, and the positioning accuracy of the magnetic head is significantly improved.

[0008]

However, Japanese Patent Application Laid-Open No. 3-80475 or U.S. Pat.
The conventional swinging head positioning mechanism disclosed in the specification of Japanese Patent No. 252 has a problem that the geometrical position of the driving force applying mechanism with respect to the head carriage is defined.

In other words, the swinging head positioning mechanism disclosed in Japanese Patent Application Laid-Open No. 3-80475 requires that a coil be disposed in a direction perpendicular to the magnetic head with respect to the rotation center axis of the head carriage. In addition, it is necessary to provide a magnetic circuit on a base opposed thereto.

The swing type head positioning mechanism disclosed in US Pat. No. 4,620,252 requires that two coils be disposed at point-symmetric positions with respect to the rotation center axis of the head carriage. is there. In addition, it is necessary to provide a magnetic circuit on a base opposed thereto.

Defining the geometrical position of the driving force applying mechanism with respect to the head carriage imposes the following two design restrictions.

The first limitation is a limitation on the external dimensions of the drive. 2. Description of the Related Art In a magnetic disk drive, the housing dimensions of a magnetic disk drive generally called a form factor are substantially standardized. However, in the above-described conventional swing type head positioning mechanism, the rotation center axis of the head carriage needs to be largely separated from the disk in order to avoid mechanical and magnetic interference between the driving force applying mechanism and the disk. It is difficult to accommodate the head positioning mechanism within the dimensions.

The second constraint relates to the mass balance of the movable body. In order to reduce the influence of disturbance vibration in the oscillating head positioning mechanism, it is necessary to make the center of mass of the movable part coincide with the rotation center axis as much as possible. However, in the above-described conventional swinging head positioning mechanism, it is difficult to balance the mass of the entire movable part because the position of the coil mounted on the movable part is defined.

In order to balance the mass, it is necessary to add a counter balance, which has a problem that the moment of inertia of the movable portion is increased and the head transfer speed is reduced. Also, the requirement that the rotation center axis be largely separated from the disk leads to an increase in the length of the head arm, which similarly causes an increase in the moment of inertia.

As described above, in the conventional oscillating head positioning mechanism, the geometric position of the driving force imparting mechanism is defined to realize the orthogonal drive system or the symmetric drive system, so that the speed is increased and the size is reduced. There was a problem of wanting to give restrictions to the conversion.

In view of the above problems, the present invention realizes orthogonal driving and symmetric driving without restricting the geometrical position of the driving force applying mechanism. The goal is to achieve

[0017]

In order to achieve the above object, an information recording / reproducing apparatus according to the present invention comprises a recording medium on which recording tracks are formed, and a head for recording or reproducing information on or from the recording medium. An information recording / reproducing apparatus including a head positioning mechanism for positioning the head on a predetermined track of the recording medium, the head positioning mechanism being a head carriage rotatably supported around a predetermined rotation axis, A driving force applying mechanism for applying a driving force to the head carriage, wherein the driving force applying mechanism generates a rotational force on the head carriage; and a radial force on the head carriage. Is provided.

With this configuration, mechanical vibration of the head carriage can be suppressed, precise head positioning can be achieved, and the size and speed of the apparatus can be reduced.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) Hereinafter, a first embodiment of the information recording / reproducing apparatus according to the present invention will be described with reference to FIGS.

FIG. 1 shows a first embodiment of the present invention.
3 is a plan view of a main part of the information recording / reproducing apparatus of FIG. FIG. 2 shows FIG.
FIG. 3 is a detailed view of a driving force applying mechanism in FIG. In FIG. 1, reference numeral 1 denotes a magnetic disk provided with concentric recording tracks, and reference numeral 3 denotes a spindle motor for rotating the magnetic disk 1 at a constant angular velocity.

Reference numeral 2 denotes a magnetic head for recording and reproducing information on and from the magnetic disk 1. Reference numeral 5 denotes a head positioning mechanism for positioning the magnetic head 2 on an arbitrary recording track of the magnetic disk 1. The head positioning mechanism includes a head carriage 10 and a driving force applying mechanism 20.
The head carriage 10 is rotatably mounted by a ball bearing 7 mounted on a shaft 6 fixed to the base 4. A magnetic head 2 is supported at the tip of a head arm 12 provided on the head carriage 10 by a leaf spring-shaped suspension 11 close to the recording surface of the magnetic disk 1.

Head arm 12 of head carriage 10
The coil 21 is fixed to the opposite side. Coil 21
Is opposed to the magnet 23 via a slight gap.
The magnet 23 is attached to the base 4 via a yoke 24. A back yoke (not shown) is similarly provided on a side of the coil 21 opposite to the magnet 23 with a slight gap therebetween, thereby forming a closed magnetic circuit. Reference numeral 16 denotes a balancer. The center of mass of the head carriage 10 coincides with the center axis of the shaft 6.

FIG. 2 shows the details of the coil 21 and the magnet 23 described above. The planar shape of the coil 21 is such that two radial portions 21 provided approximately in the radial direction with respect to the center of rotation of the head carriage 10 (that is, the center of the shaft 6).
a, 21b and an outer peripheral portion 21 provided in a substantially circumferential direction
c, the inner peripheral portion 21d, and an arc connecting them. A center line C of the coil and a straight line D connecting the rotation center of the carriage 10 and the magnetic head 2 form an angle α. In the present embodiment, α is set to 133 degrees.

The magnet 23 has the radial portions 23a and 23b, the outer peripheral portion 23c, and the inner peripheral portion 2 opposed to the radial portions 21a and 21b, the outer peripheral portion 21c, and the inner peripheral portion 21d of the coil, respectively.
3d is provided. Each part of the magnet has an S pole at the radius portion 23a and the inner peripheral portion 23d and an N pole at the radius portion 23b and the outer peripheral portion 23c.
Polarized. In the present embodiment, these are configured by combining four magnets which are monopolar magnetized, but may be one in which such a magnetized pattern is formed on one magnet.

The operation of the information recording / reproducing apparatus of the present invention (first embodiment) configured as described above will be described below.

First, a driving force applying mechanism 2 will be described with reference to FIG.
The operation of 0 will be described. The coil 21 is energized by a drive circuit (not shown). An electromagnetic force is generated by the interaction between the current flowing through the coil 21 and the magnetic flux generated from the magnet 23. Now, assuming that a current flows through the coil 21 in the direction of the arrow A, the respective portions 21a, 21b, 21c,
At 21d, forces Fa, Fb, Fc, and Fd are generated. With respect to these forces, Fa and Fb are forces in the rotational direction, and Fc and Fd are radial forces with respect to the rotation center axis of the carriage 10. The resultant driving force F obtained by combining these four forces
The action line B of o forms an angle θ with respect to the center line C of the coil 21. In the present embodiment, θ is set to 47 degrees. By changing the magnitude of the current, the driving resultant force Fo and the magnitude thereof change proportionally, but the angle θ is always constant. As described above, since the angle α between the center line C of the coil and the straight line D connecting the rotation center of the carriage 10 and the magnetic head 2 is set to 133 degrees, the line of action B of the driving resultant force Fo is a straight line. It is parallel to D.

Next, the operation of precisely positioning the head by the present head positioning mechanism will be described with reference to FIG. A rotational torque is applied to the head carriage 10 by the driving resultant force Fo, and a rotational acceleration is generated. A position signal recorded in advance on the magnetic disk 1 is detected by the magnetic head 2, and based on the detected position signal, a control circuit (not shown) controls the coil 2.
The magnetic head 2 is positioned at a desired recording track by controlling the current supplied to the magnetic head 2.

Generally, as a factor that hinders the positioning accuracy of the head, there is a problem of mechanical vibration of the head positioning mechanism. Among them, as a vibration mode that regulates the control band,
A quasi-rigid mode is generally known, which is caused by the mass of the movable portion of the head positioning mechanism and the spring property of the bearing. Also in the present embodiment, a quasi-rigid vibration mode of the head carriage 10 exists due to the mass of the head carriage 10 and the resiliency of the ball bearings 7. However, as described above, since the direction of the driving force resultant force Fo always coincides with the straight line D connecting the rotation center and the magnetic head 2, the direction of vibration by the excitation force in the translation method is indicated by an arrow P. Direction
It is almost perpendicular to the tracking direction indicated by arrow Q.
Even if vibration occurs, it does not interfere in the track positioning direction. That is, the effect of the translational excitation force can be effectively removed. Therefore, the control band can be expanded, and precise head positioning can be performed.

As described above, according to the present embodiment, the rotational force and the radial force are generated by the current flowing through the coil 21 of the driving force applying mechanism 20, and the direction of the driving force Fo is always changed. , The orthogonal drive system can be realized without arranging the coils 21 at right angles. Since the angle formed by the head arm 12 and the coil 21 can be set to an obtuse angle, the mobility applying mechanism 20 does not interfere with the magnetic disk 1 and the head positioning mechanism 5 can be housed in the form factor. Also, the balancer 16 for matching the center of mass of the head carriage 10 to the center of rotation may be small, and the high-speed performance is not significantly impaired by an increase in the moment of inertia.

That is, by realizing the orthogonal drive system, it is possible to eliminate the influence of the translational exciting force acting on the head carriage 10 and achieve precise head positioning, and at the same time achieve both miniaturization and high-speed operation. .

(Second Embodiment) Hereinafter, an information recording / reproducing apparatus according to a second embodiment of the present invention will be described with reference to FIGS.

FIG. 3 shows a second embodiment of the present invention.
3 is a plan view of a main part of the information recording / reproducing apparatus of FIG. FIG. 4 shows FIG.
FIG. 3 is a detailed view of a driving force applying mechanism in FIG. 3, reference numeral 1 denotes a magnetic disk provided with concentric recording tracks, and reference numeral 3 denotes a spindle motor for rotating the magnetic disk 1 at a constant angular velocity.

Reference numeral 2 denotes a magnetic head for recording and reproducing information on the magnetic disk 1. Reference numeral 5 denotes a head positioning mechanism for positioning the magnetic head 2 on an arbitrary recording track of the magnetic disk 1. The head positioning mechanism includes a head carriage 10 and a driving force applying mechanism 20.
The head carriage 10 is rotatably mounted by a ball bearing 7 mounted on a shaft 6 fixed to the base 4. A magnetic head 2 is supported at the tip of a head arm 12 provided on the head carriage 10 by a leaf spring-shaped suspension 11 close to the recording surface of the magnetic disk 1.

Head arm 12 of head carriage 10
On the opposite side, two coils 21 and 22 are fixed. The magnets 23 face the coils 21 and 22 with a slight gap therebetween. The magnet 23 is attached to the base 4 via a yoke 24. Similarly, a back yoke (not shown) is provided on the opposite side of the coils 21 and 22 from the magnet 23 with a slight gap therebetween, thereby forming a closed magnetic circuit. Note that the center of mass of the head carriage 10 coincides with the center axis of the shaft 6.

FIG. 4 shows the coils 21 and 22 and the magnet 2 described above.
3 is shown in detail. The coil 21 and the coil 22 have the same specifications, and have the same shape, wire diameter, number of turns, and the like. Coil 2
In 1 and 22, the planar shape is the head carriage 1
The two radial portions 21a, 21b and 22a, 22b provided approximately in the radial direction with respect to the center of rotation
And outer peripheral portions 21c and 2 provided approximately in the circumferential direction.
2c, inner peripheral parts 21d and 22d, and arcs connecting them. The angle α between the center line C1 of the coil 21 and the center line C2 of the coil 22 is set to 86 degrees.

The magnet 23 is magnetized to two poles in the pattern shown in FIG. 4, with 23a being the S pole and 23b being the N pole. In the present embodiment, such a magnetized pattern is formed on one magnet, but a similar pattern may be formed by combining several magnets.

The operation of the information recording / reproducing apparatus of the present invention (second embodiment) configured as described above will be described below.

First, the operation of the driving force applying mechanism will be described with reference to FIG. A drive circuit (not shown) supplies the same amount of current to the coils 21 and 22 in the opposite direction. An electromagnetic force is generated by the interaction between the current flowing through the coils 21 and 22 and the magnetic flux generated from the magnet 23.

Now, assuming that a current is applied to the coil 21 in the direction of arrow A1 and to the coil 22 in the direction of arrow A2,
In each of the sections 21a, 21b, 21c, and 21d, F
1a, F1b, F1c, and F1d are also applied to the coil 2
2 at each of the portions 22a, 22b, 22c, and 22d.
Forces 2a, F2b, F2c and F2d are generated. Among the forces generated in the coil 21, F1a and F1b are rotational forces, and F1c and F1d are radial forces. The line of action B1 of the driving resultant force F1o of the coil 21 obtained by combining these four forces forms an angle of θ1 with the center line C1 of the coil 21. In the present embodiment, θ1 is set to 47 degrees.

Similarly, of the force generated in the coil 22, F
2a and F2b are forces in the rotation direction, and F2c and F2d are forces in the radial direction. Compared to the coil 21, the force in the rotational direction is the same, but the force in the radial direction is in the opposite direction. The driving resultant force F of the coil 22 obtained by combining these four forces is as follows.
The action line B2 of 2o is θ with respect to the central axis C2 of the coil 21.
Make two angles. In the present embodiment, θ2 is θ1
The angle is set to 47 degrees in the same manner as described above.

By changing the magnitude of the current,
The magnitudes of the driving resultant forces F1o and F2o change proportionally, but θ1 and θ2 are always constant. As described above, in the present embodiment, the center line C1 of the coil 21 and the coil 2
2 is set to 86 degrees, the action line B1 of F1o and the action line B2 of F2o are parallel, and the two forces are couples. Further, a straight line D connecting the rotation center axis of the head carriage 10 and the magnetic head 2 is parallel to the two action lines B1 and B2.

Next, the operation of precisely positioning the head by the present head positioning mechanism will be described with reference to FIG. A rotational torque is applied to the head carriage 10 by the aforementioned couples F1o and F2o, and a rotational acceleration is generated. The magnetic head 2 detects a position signal previously recorded on the magnetic disk 1 and controls a current supplied to the coil 21 by a control circuit (not shown) based on the detected position signal. Positioned.

As in the first embodiment, a quasi-rigid vibration mode of the head carriage 10 due to the mass of the head carriage 10 and the spring property of the ball bearings 7 also exists in the present embodiment. I do. However, as described above, since the driving force resultant force F1o of the coil 21 and the driving force resultant force F2o of the coil 22 are couples, the ball bearing 7
No translational excitation force acts on the surface. Therefore, even if the above mode exists, it is not excited. Therefore, the control band can be expanded, and precise head positioning can be performed.

As described above, according to the present embodiment, the current flowing through the coils 21 and 22 of the driving force applying mechanism 20 generates a rotating force and a radial force, respectively, so that each driving force F1o , F2o are set so that the action lines B1 and B2 form angles of θ1 and θ2 with respect to the coil center axes C1 and C2, respectively.
The angle α between 1 and C2 is

[0045]

(Equation 1)

By setting so as to satisfy the relationship, the resultant driving forces F1o and F2o of the coils 21 and 22 can act as couples, and a symmetric driving system can be realized. That is, unlike the conventional example, it is not necessary to arrange the two coils symmetrically with respect to the point, and the angle between each coil and the head arm 12 can be made obtuse. Therefore, the driving force applying mechanism 20 does not interfere with the magnetic disk 1, and the head positioning mechanism 5 can be housed in the form factor.

In order to realize the symmetric drive, (Equation 1)
However, in the present embodiment, as described above, a straight line D connecting the rotation center and the magnetic head 2 to the action lines B1 and B2 of the two driving resultant forces F1o and F2o is sufficient. Are configured to be parallel,
The head carriage can be configured in a line-symmetrical shape. Therefore, the center of mass can easily be made coincident with the center of rotation without adding a counter balance, and the inertia of the movable portion can be minimized. Therefore, a high-speed head transfer / positioning operation can be realized.

That is, by realizing the symmetric drive system, the translational excitation force is eliminated, and precise head positioning can be achieved, and both miniaturization and high-speed operation can be achieved.

In this embodiment, two coils are used, but the number of coils may be two or more. Also, each coil may have a different specification. According to the present invention, in any case, it is possible to configure so that a product obtained by combining all the forces generated in each coil becomes a couple.

The direction θ of the resultant force Fo in the first embodiment and the directions θ1 and θ2 of the resultant forces F1o and F2o in the second embodiment are set to 4 respectively.
Although set to 7 degrees, the present invention is not limited to this, and the direction of the driving resultant force can be set arbitrarily. For example, by appropriately setting the ratio between the length of the radial portion of the coil and the length of the outer peripheral portion or the inner peripheral portion, the ratio of the rotational force to the radial force can be appropriately set, and the action line of the driving resultant force can be set to a desired value. Direction can be set. Similarly, the direction of the driving resultant force can be appropriately set by appropriately setting the ratio of the amount of the magnetic flux linked to the radial portion of the coil to the amount of the magnetic flux linked to the outer peripheral portion or the inner peripheral portion. The adjustment of the amount of magnetic flux can be easily realized by the shape of the magnet facing the coil or the magnetization pattern. As described above, the ability to freely set the direction of the driving resultant force depending on the shape of the coil, the shape of the magnet, or the magnetization pattern has an effect of giving a great degree of freedom to the design of the head positioning mechanism 5.

In the embodiments of the present invention, the magnetic disk device is taken as an example. However, the present invention is not limited to the recording / reproducing method. For example, the present invention relates to a recording / reproducing apparatus for performing recording / reproducing using light. There may be. Similarly, the form of the recording medium is not limited. For example, an information reproducing apparatus using a tape-shaped or card-shaped recording medium may be used. INDUSTRIAL APPLICABILITY The present invention can be applied to all information recording / reproducing apparatuses that perform positioning of a head on a recording track on a recording medium by a swing type head positioning apparatus.

[0052]

As described above, according to the present invention, a recording medium having a recording track formed thereon, a head for recording or reproducing information on or from the recording medium, and the head mounted on a predetermined track of the recording medium. An information recording / reproducing apparatus including a head positioning mechanism for positioning, wherein the head positioning mechanism includes a head carriage rotatably supported around a predetermined rotation axis, and a driving force application for applying a driving force to the head carriage. A mechanism for generating a rotational force on the head carriage, and a means for generating a radial force on the head carriage. In addition to suppressing mechanical vibration and achieving precise head positioning, it is possible to reduce the size and speed of the apparatus.

[Brief description of the drawings]

FIG. 1 is a plan view of a main part of an information recording / reproducing apparatus according to a first embodiment of the present invention.

FIG. 2 is a detailed view of a driving force applying mechanism in FIG.

FIG. 3 is a plan view of a main part of an information recording / reproducing apparatus according to a second embodiment of the present invention;

FIG. 4 is a detailed view of a driving force applying mechanism in FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic disk 2 Magnetic head 3 Spindle motor 4 Base 5 Head positioning mechanism 6 Shaft 7 Ball bearing 10 Head carriage 11 Suspension 12 Head arm 16 Balancer 20 Driving force giving mechanism 21, 22 Coil 23 Magnet 24 Yoke

Continued on the front page (72) Inventor Toshiyuki Wada 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (7)

[Claims] 1. A recording medium on which a recording track is formed,
An information recording / reproducing apparatus comprising: a head for recording or reproducing information on or from the recording medium; and a head positioning mechanism for positioning the head on a predetermined track of the recording medium, wherein the head positioning mechanism has a predetermined rotation axis. A head carriage rotatably supported about the head carriage, and a driving force applying mechanism for applying a driving force to the head carriage, wherein the driving force applying mechanism generates a rotational force on the head carriage. Means for generating a radial force on the head carriage. 2. A driving force applying mechanism comprising: a coil; and a magnetic flux generating means facing the coil, wherein one of the coil or the magnetic flux generating means is attached to a head carriage and the other is attached to a base. Is composed of two radial portions provided substantially in the radial direction with respect to the rotation center axis of the head carriage, and an inner circumferential portion and an outer circumferential portion provided in the substantially circumferential direction. 2. The information recording / reproducing apparatus according to claim 1, wherein a force in a radial direction is generated by at least one of an outer peripheral portion and an inner peripheral portion of the coil. 3. The method according to claim 1, wherein the direction of the resultant force of the rotational force and the radial force generated by the driving force applying mechanism substantially coincides with a straight line connecting the rotation center of the head carriage and the head. Item 3. The information recording / reproducing device according to item 1 or 2. 4. The information recording / reproducing apparatus according to claim 1, wherein a combination of a rotational force generated by the driving force applying mechanism and a radial force is substantially a couple. . 5. A driving force applying mechanism comprising two coils, wherein the angle between the line of action of the resultant force of the first coil and the center line of the first coil is θ1, and the angle of the second coil is θ2. The angle between the line of action of the resultant force of the coil and the center line of the second coil is θ2, and the center line of the first coil and the second line is
When the angle between the center lines of the coils of α is α, θ1 and θ
The information recording / reproducing apparatus according to claim 4, wherein the sum of 2 and α is 180 degrees. 6. The information recording / reproducing apparatus according to claim 4, wherein the coils are arranged symmetrically with respect to a straight line connecting the rotation center of the head carriage and the head. 7. An angle between a straight line connecting the center of rotation of the head carriage and the head and a straight line connecting the center of rotation and the center of the coil is greater than 90 degrees.
Or the information recording / reproducing apparatus according to 4.