JPH02246764A - Linear actuator for disc drive - Google Patents

Abstract

PURPOSE:To obtain a practical linear actuator for disc drive by arranging a permanent thrust magnet producing lines of magnetic force radially, a side yoke for supporting a rod guide and a permanent magnet for floating a carriage around a cylindrical central shaft. CONSTITUTION:Permanent thrust magnets 3a, 3b are arranged at the opposite ends of a cylindrical carriage 2 and a drive coil 6 is wound around a guide 7 so that the flux of the permanent magnets 3a, 3b crosses perpendicularly with the coil 6. A floating permanent magnet 13 is arranged in an outer yoke, in parallel with the guide 7, while being covered by a non-magnetic bracket 20. The floating permanent magnet 13 repels the thrust permanent magnets 3a, 3b thus floating the carriage 2 without contacting with the guide 7 and the drive coil 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a linear actuator for a disk device for head positioning used in a magnetic disk device or the like.

[Conventional technology]

In general, actuators for magnetic disk drives must satisfy the following technical requirements in order to ensure high performance and high reliability.

(1) It must be small and lightweight to improve access speed.

In order to improve positioning accuracy, it must be supported with high rigidity in all directions except the access direction.

(3) To prevent damage to the magnetic head and magnetic disk, no dust should be generated.

(This will interfere with the recording and reproducing operation of 41M1 recorded information.

(5) Low power consumption required for access and no electromagnetic noise.

Actuators that meet the above requirements can be roughly divided into swing arm type actuators that position the magnetic head by rotational movement around a pivot axis, and linear type actuators that position the magnetic head by linear movement along a guide. Among these, the swing arm method is based on rotational movement, so the converted mass of the movable part can be smaller than that of the linear method, making it suitable for high-speed access. but,
Since minute bending vibrations occur in the actuator due to the action of acceleration during rotational movement, it takes time to position after access, and the recording and reproducing time of magnetically recorded information ends up being longer than in the linear method. For this reason, in cases where high speed and high precision are particularly required, such as in large-scale equipment, the linear method has traditionally been widely adopted.

The problem with the linear method is that since it is a linear motion, the entire actuator moves and the mass of the movable part is large, and a large amount of electric power is required for high-speed access. Examples include scattering of lubricating grease and generation of dust due to wear at the transfer points between the roller guide and the guiding guide rail.

In order to solve the above problems, various types of linear actuators have been devised. Among them, JP-A-57-113767 and JP-A-58-8887 have an actuator floating on an air bearing to eliminate the need for roller guides, thereby reducing weight and preventing dust generation.
No. 7, JP-A-61-59669, JP-A-59-104
No. 762, JP-A-59-210575, etc. There is also an example disclosed in Japanese Patent Laid-Open No. 57205868 in which the actuator is similarly levitated using a magnetic bearing instead of an air bearing.

[Problem to be solved by the invention]

Despite the various inventions mentioned above,
Currently, there are no examples of air bearings or magnetic bearings being used in practical, commercial magnetic disk drives. This is because the rigidity is lower than the bearings used, and a slight vibration or other disturbance causes the actuator to change its posture significantly, which is a fatal drawback in that positioning accuracy decreases. Furthermore, in the case of air bearings, a compressor is required to constantly feed high-pressure air into the bearing, and it is difficult to supply air at a stable pressure.In the case of magnetic bearings, the actuator drive In addition to the magnetic circuit used in the voice coil motor for the Another major factor is that there are many implementation constraints such as negative effects. Furthermore, both bearings must have a complicated shape in order to stably support the actuator, and the air bearing in particular requires a dense design for air pressure distribution.

In order to solve the above-mentioned problems, the following measures have also been taken. First, regarding the low rigidity of buoyant type bearings, it is effective to make the actuator extremely lightweight. This is because if the mass of the actuator movable part supported by the bearing becomes smaller, it is equivalent to relatively increasing the rigidity of the bearing.

However, in examples using air bearings such as JP-A-57-113767 and JP-A-57-176514, although the actuator itself is made small and lightweight, it takes a long time to obtain high rigidity. Since a high-pressure air supply is required and the air is taken in from outside the device, other technical problems arise, such as dust entering the device and temperature control. Furthermore, due to extreme weight reduction, the actuator becomes too small, and the magnetic circuit for driving the actuator ends up penetrating close to the surface of the magnetic disk. In order to support the actuator with only air bearings, the weight must be reduced to compensate for the reduced rigidity. For this reason, during recording and reproducing with the magnetic head, the leakage magnetic flux has an adverse effect, and there is a high probability that a failure will occur.

Further, a magnetic bearing such as that disclosed in Japanese Patent Application Laid-Open No. 57-205868 also has similar problems. In other words, although the rigidity of the bearing itself is greater than that of an air bearing, the actuator must also be provided with a permanent magnet for levitation, so the mass of the bearing itself is large, and as a result, it is difficult to support the actuator stably like an air bearing. I can't. Therefore,
The key to achieving a practical magnetic levitation actuator is to reduce the weight of the actuator. In the conventional example, the magnetic bearing itself is large and heavy. This is because the attitude of the actuator is maintained only by the magnetic bearing. That is, if the positioning direction of the actuator (direction of movement of the head and throat) is the X-axis direction, the following can be said in the xyz orthogonal coordinate system. In other words, except for the positioning direction/X,
The actuator has five degrees of freedom: translation in the X direction perpendicular to the X direction, translation in two directions, and rolling, yawing, and pitching, which are rotations about the X, y, and Z axes. . If we try to restrain these five degrees of freedom using only magnetic bearings according to the prior art, at least four permanent magnets are provided in the actuator, and the four permanent magnets are repelled by the four permanent magnets provided in the actuator. Must be installed on the guide side. In addition to this, it is necessary to separately provide a coil or a permanent magnet for driving the actuator. In this case, the mass of the movable part of the actuator becomes too large.

The present invention was made in view of the problems of the prior art described above, and an object of the present invention is to provide a practical linear actuator for a disk device.

[Means to solve the problem]

The linear actuator for a disk device of the present invention has a substantially cylindrical hole provided parallel to the direction in which the head is positioned and driven, and a propulsion device that emits lines of magnetic force radially and perpendicular to the central axis of the substantially cylindrical hole. a carriage formed to hold a head; a bar-shaped guide that penetrates the substantially cylindrical hole with a certain gap and around which a driving coil is wound; a side yoke that supports the guide; and a levitation permanent magnet that emits lines of magnetic force in the opposite direction to the lines of magnetic force radiated from the propulsion permanent magnet and levitates the carriage by a repulsive force acting between the propulsion permanent magnet and the side yoke; It is characterized by being composed of.

[For production]

The basic operation of the linear actuator for a disk device according to the present invention is as follows. That is, the carrier is levitated by the repulsive force generated by the propulsion permanent magnet and the levitation permanent magnet.

Then, by energizing the drive coil, the propulsion permanent magnet receives a force in the direction of movement of the head and moves based on the magnetic flux formed by the propulsion permanent magnet and the current flowing through the drive coil, according to the so-called left-hand rule. .

The linear actuator for a disk device of the present invention is constructed based on the following concept.

That is, in the present invention, when the positioning direction of the actuator is the X direction of the xyz coordinate system, the direction (degree of freedom) constrained by the carriage is translation in the y direction, which is a displacement occurring in a plane parallel to the disk. It is configured such that only yawing, which is rotation around two axes, is restricted, and the other three directions (degrees of freedom; translation, rolling, and pitching in two directions) are constrained by the head itself.

Further, the propulsion permanent magnet is configured to be used for both floating the carriage and moving the carriage. Therefore, at least one permanent magnet is required to be provided on the carriage, and a significant reduction in mass can be achieved.

Next, the reason why the head itself can restrain the other three directions will be explained. That is, in the present invention, the air bearing effect that the head itself receives from the high-speed air flow on the surface of the magnetic disk is actively utilized. Generally, the head flies with an extremely small gap of 0.2 to 0.3 μl relative to the disk, and if the head is pressed against the disk surface with a force of several tens to 100 g, there will be a gap between the magnetic disk surface and the above. It is possible to follow the unevenness of the surface of the magnetic disk while maintaining a small gap. The force that maintains the minute gap against the pressing force is obtained by the pressure increase that occurs when the high-speed airflow flowing over the surface of the magnetic disk penetrates between the disks with the head. Therefore, the head itself becomes a high-performance air bearing. Since the head follows the disk surface and is positioned in a self-centering manner, the out-of-plane translation (two directions), which is displacement perpendicular to the disk surface, and rolling and pitching are independent of the head itself. It is possible to leave it to the restraint force.The magnetic bearing only needs to have a support for the remaining two directions, namely, in-plane translation (y direction) and yawing restraint.

Moreover, in a disk drive, in-plane displacement of the disk (displacement in the tangential direction of the trunk) does not pose much of a problem in practice, so highly accurate positioning is not necessary (as long as the magnetic head does not shift significantly). good.

By sharing the restraint of the actuator as described above, a lightweight and practical magnetic bearing structure can be realized.

〔Example〕

The present invention will be described in more detail below with reference to embodiments shown in the accompanying drawings.

FIG. 1 is an explanatory diagram showing a first embodiment of the present invention, in which magnetic heads 1 are located on the upper and lower surfaces of each magnetic disk 18, respectively. The magnetic head l is fixed to the magnetic head mounting portion 20 via a load arm 26 made of a temporary spring. The actuator that holds the counter arm 26 is
It is as follows.

That is, permanent propulsion magnets 3a, 3b are provided at both ends of the approximately cylindrical carriage 2.
A driving coil 6 is wound around the circumference of a guide 7 passing through the carriage 2, and a propulsion permanent magnet 3a.

The magnetic flux generated by 3b and the coil 6 intersect perpendicularly.

FIG. 2(a) is an explanatory yz plane sectional view around the guide 7 shown in FIG. 1, and FIG. As shown in Figures (a) and (b), the magnetization direction of the propulsion permanent magnets 3a and 3b is in the radial direction when viewed from the central axis of the guide 7, as shown in Figures 2 (a) and (bl). Yes, leakage magnetic flux from N pole 19
crosses the drive coil 6 and passes inside the iron guide 7,
It returns to the S pole of the propulsion permanent magnets 3a, 3b via the iron side yokes 5a, 5b and the iron outer yoke 4.

As described above, since a closed magnetic circuit is formed by the propulsion magnets 3a, 3b, guide 7, side yokes 5a, 5b, and outer yoke 4, magnetic flux can be passed through the drive coil 6 without waste, and the drive coil By energizing 6, a large driving force can be obtained. Further, since leakage of magnetic flux to the outside is small, it does not adversely affect the recording/reproducing operation of the magnetic head l.

In addition, as shown in FIGS. 1 and 2 (18) and (b), a levitation permanent magnet 13 is provided in the outer yoke 4 in parallel with the guide 7 and is protected by a bracket 20 made of a non-magnetic material. be. The non-magnetic bracket 20 is used because
The magnetic flux of the levitation permanent magnet 13 is prevented from adversely affecting the propulsion permanent magnets 3a, 3b via the outer yoke 4. The magnetization direction of the levitation permanent magnet 13 is as shown in FIG.
3b, and due to this repulsive force, the carriage 2 floats without contacting the guide 7 and the drive coil 6. If this continues, the carriage 2 will rotate relative to the guide 7.

However, the floating blades generated by the high-speed airflow generated by the rotation of the magnetic disk 18 act on the two magnetic heads l attached from the magnetic head attachment part 20 of the carriage 2 via the load arm 26 to be separated from the guide 7. This prevents the carriage 2 from rotating. In addition, a counter arm 17 is placed from the carriage 2 on the side opposite to the magnetic head l so that the center of gravity of the entire actuator coincides with the central axis of the guide 7.
stands out and maintains balance. Therefore, even during an access operation or when external vibrations are applied, the actuator can stably maintain its floating state.

In addition, as shown in FIG. 2 (bl), the braking permanent magnet 21
a, 21b are the side yokes 5a at both ends of the guide 7.
+5b. The magnetization direction of the braking permanent magnets 21a and 21b is the propulsion permanent magnet 3a.

3b, so when the carriage 2 moves to the end of the guide 7, a repulsive force acts on each other. Therefore, the carriage 2 is prevented from leaving the movable area and colliding with the side yokes 5a, 5b.

As shown in FIG. 1, both terminals 8.9 of the coil 6 are connected to a coil drive control circuit (not shown) via lead wires 11.12, and the terminals 8.9 of the coil 6 are connected to a coil drive control circuit (not shown) through lead wires 11.12. The position information of the actuator can be obtained from the magnetic disk 18 using one of the two magnetic heads l provided for each actuator.
It can be obtained by reading out the position information recorded in . The remaining magnetic head 1 is used exclusively for recording and reproducing magnetically recorded information.The position information detected from the 0M1 magnetic head 1 is provided at a terminal 16 by a flexible rope 14. Amplifier ICl
3, and is fed back to a coil drive control circuit (not shown). Since each actuator is driven separately while detecting position information using the method described above, the actual access time is reduced.

As shown in Fig. 1, if the drive direction of the actuator is defined as the X direction, and the directions perpendicular to this are defined as the , both are in a direction such that the flying height of the magnetic head l relative to the magnetic disk 18 varies. Displacement in these two directions, rolling and pitching are
The magnetic head l can be restrained by a floating blade received from a high-speed airflow flowing over the surface of the rotating magnetic disk 18.

That is, the magnetic head l receives buoyancy from the high-speed airflow generated by the rotation of the magnetic disk 18, and is restrained at a certain distance above the surface of the magnetic disk 18.

Therefore, even if the carriage 2 is displaced in two directions, rolling, or pitching, the vibration is absorbed by the load arm 26 formed from a leaf spring.
This does not affect the flying attitude of the magnetic head l.

Further, the remaining translation and yawing in the X direction are restrained by the repulsive force between the levitation permanent magnet 13 and the propulsion magnets 3a and 3b.

FIG. 3 is a cross-sectional explanatory diagram illustrating the state of repulsion between the propulsion permanent magnets 3a, 3b and the levitation permanent magnet 13 described above. As shown in FIG. 3, since the S pole of the levitation magnet 13 and the S poles of the propulsion permanent magnets 3a and 3b are opposed to each other, the lines of magnetic force 22 coming from the S pole of the levitation permanent magnet 13 are sharply bent. Similarly, it is pushed back to the north pole of the levitation magnet 13. In addition, the magnetic force 4119 emitted from the S poles of the propulsion permanent magnets 3a and 3b is pushed by the S pole of the levitation permanent magnet 13 and bent, enters the outer yoke 4, and enters the side yoke 5a,
5b and the guide 7, become lines of magnetic force that perpendicularly cross the drive coil 6, and enter the N poles of the propulsion permanent magnets 3a and 3b. (See FIG. 2 (bl)) Since the levitation permanent magnet 13 and the propulsion permanent magnet 3 a + 3 b repel each other as described above, the carriage 2 can levitate without contacting the drive coil 6.

FIG. 4 is an explanatory diagram showing a second embodiment of the present invention,
FIG. 5 is an explanatory cross-sectional view showing the area around the guide 7 in the xz plane of the embodiment shown in FIG. The second embodiment shown in FIG. 4 is different from the first embodiment shown in FIG. This is the point that

Further, as shown in FIG. 5, the propulsion permanent magnets 3a and 3b are magnetized in the opposite direction to that of the first embodiment shown in FIG. The lines of magnetic force pass through the guide 7 and enter the N pole of the propulsion permanent magnet 3b. Further, the outer peripheral sides of the levitation permanent magnets 3a and 3b are magnetically short-circuited by a cylindrical carriage 2 made of ferromagnetic material, thereby increasing the efficiency of the magnets.

Since the magnetization directions of the propulsion permanent magnets 3a and 3b are opposite to each other, the winding direction of the coils is opposite to that of the corresponding drive coils 6a and 6b, and when energized, they generate driving force in the same direction. It looks like this.

FIG. 6 is an explanatory diagram showing the third embodiment of the present invention, FIG. 7 fal is an explanatory y2 plane sectional view around the guide 7 shown in FIG. B shown in Figure 7 (i)
-B cross-sectional explanatory diagram. Figure 6, Figure 7 (a), (b
), in the third embodiment, the carriage 2 shown in FIG. Is possible.

In addition, the above-mentioned 1. Second. In the third embodiment, if a ferromagnetic and electrically conductive material such as iron is used as the material of the drive coil 6, the propulsion magnets 3a, 3b
Because the lines of magnetic force coming out from the propulsion magnet 3a,
Even if a small magnet is used for 3b, a large driving force can be obtained.

Furthermore, if a low-temperature superconductor or a high-temperature superconductor is used as the material for the same drive coil 6, and the material is used under conditions where it becomes superconducting, the lines of magnetic force coming out of the propulsion permanent magnets 3a and 3b will be the same as that of the superconductor. Drive coil 6 due to diamagnetic effect
As a result, the propulsion permanent magnets 3a, 3b are repelled by the drive coil 6 and float.

Therefore, the floating permanent magnet 13 is not required, resulting in a simpler structure.

As is clear from the above explanation, the above 1. According to the second and third embodiments, each linear actuator consists of an actuator body whose main component is a permanent magnet magnetized in the radial direction, and the permanent magnet functions to both support and propel the actuator. They have the common advantage of being extremely lightweight, and even magnetic bearings with low support rigidity can provide sufficient positioning support. By magnetizing the permanent magnet that is the actuator body in the radial direction, it is possible to achieve the above-mentioned reduction in weight and size.

Although the above embodiment has been described using a magnetic disk as an example, the present invention is not limited thereto, and can be applied to, for example, a magnetic drum device.

〔Effect of the invention〕

According to the present invention, the following effects can be obtained.

(1) Since the actuator is supported using a propulsion permanent magnet that drives the actuator, there is no need to provide a special support mechanism on the actuator side, and the weight of the moving parts can be reduced, so magnetic bearings are used. Stable support is possible even when Furthermore, since the actuator is small and lightweight, high-speed access is possible with little energy loss.

(2) Since no mechanical contact points are required to support the actuator, there is no dust generation due to wear etc., and high reliability can be achieved.

(3) Since the permanent magnet is provided on the movable side and the drive coil is provided on the stator side, it is easy to supply power to the drive coil. Moreover, breakage due to fatigue of the power supply line does not occur. Furthermore, even when a large amount of current is passed through the drive coil, heat is quickly transferred through the guide, so the temperature of the drive coil can be kept low.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the first embodiment of the present invention, and FIG. 2 (
al is a yz plane cross-sectional explanatory diagram around the guide shown in FIG.
Figure 2 (bl is an explanatory diagram of the A-A cross section shown in Figure 2 (a),
FIG. 3 is an explanatory cross-sectional view showing a situation in which the propulsion permanent magnet and the levitation permanent magnet shown in FIG. 1 repel each other, FIG. 4 is an explanatory view showing the second embodiment of the present invention, and FIG. The second part shown in Figure 4
FIG. 6 is an explanatory diagram showing the third embodiment of the present invention, and FIG.
FIG. 7(a) is a yz plane sectional explanatory view of the guide and its surroundings shown in FIG. 6, and FIG. 7(b) is a BB sectional view shown in FIG. 7(a). ■...Magnetic head, 2...Carriage, 3a, a
b...Permanent magnet for propulsion, 4...Outer yoke, 5a
, 5b...side yoke, 6.6a, 6b...
Drive coil, 7... Guide, 8.9... Drive coil terminal, 10... Center yoke, 11, 12... Lead wire, 13... Permanent magnet for levitation, 14... Flexible Lead wire, 15... Amplifier Ic, 16... Terminal, 17... Counter arm, 18... Magnetic disk, 20... Magnetic head mounting portion, 21a, 2
1t)...Permanent magnet for braking. Agent Patent Attorney Tadashi Akimoto Actual Diagram Diagram

Claims (1)

[Claims] 1. A permanent propulsion device having a substantially cylindrical hole provided parallel to the direction in which the head is positioned and driven, and radiating lines of magnetic force perpendicular to and radially with respect to the central axis of the substantially cylindrical hole. a carriage equipped with a magnet and formed to hold a head; a rod-shaped guide that penetrates the substantially cylindrical hole with a certain gap and around which a driving coil is wound; a supporting side yoke; and a levitation permanent magnet that emits lines of magnetic force in the opposite direction to the lines of magnetic force radiated from the propulsion permanent magnet and levitates the carriage by a repulsive force acting between the propulsion permanent magnet and the propulsion permanent magnet. A linear actuator for a disk device, characterized in that: 2. The linear actuator for a disk device according to claim 1, wherein the floating permanent magnet is provided on the outer peripheral side of the substantially cylindrical carriage. 3. The guide and side yoke are made of ferromagnetic material,
Furthermore, an outer yoke formed of a ferromagnetic material is provided, which is magnetically short-circuited to the side yokes and arranged to surround the levitation permanent magnet in a state of being magnetically shielded from the levitation permanent magnet. Claim 2, wherein lines of magnetic force radiated from the magnet form a closed magnetic circuit consisting of the guide, a side yoke, and an outer yoke.
The linear actuator for the described disk device. 4. The levitation permanent magnet is fixed to the guide and is equiangular in a direction perpendicular to the central axis of the approximately cylindrical hole.
2. The linear actuator for a disk device according to claim 1, wherein at least three linear actuators are provided. 5. The propulsion permanent magnet surrounds the guide,
The linear actuator for a disk device according to claim 1, characterized in that it is formed in a cylindrical shape. 6. The linear actuator for a disk device according to claim 1, wherein at least three levitating permanent magnets are provided at equal angles in a direction perpendicular to the central axis of the substantially cylindrical hole. 7. The linear actuator for a disk device according to claim 1, wherein the center of gravity of the movable portion comprising the head and the carriage substantially coincides with the central axis of the substantially cylindrical hole.