JPH0562379A - Disk drive device - Google Patents

Abstract

PURPOSE:To prevent the adverse influence of leaked magnetic flux by attaching a magnetic sensor to a head base or a chassis with a magnetic shield plate between them and transporting the base by a linear motor. CONSTITUTION:A head base moving means A consists of a linear motor 6 consisting of permanent magnets 8a and 8b and a coil part 9, and a position detecting means B consists of magnetic sensors S1 and S2 and a magnetic scale 10 which face each other and are attached to a head base 2 and a chassis 1. When target track data is inputted with the head base 2 in the reference position, a current flows to a coil part 9 of each motor 6. Then, this current is orthogonal in the magnetic path formed by permanent magnets 8a and 8b and a yoke 7 to give an impellent force to the base 2. Sensors S1 and S2 are moved on the scale 10 by movement of the base 2 to output a sine wave, and motor is subjected to feedback control. Then, magnetic fields in the X direction in positions of sensors S1 and S2 are cancelled and are shielded by a shield plate 21, an influence of a leaked magnetic flux is eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk drive device in which a head base on which a head element is mounted is linearly movable to change the position of the head element.

[0002]

2. Description of the Related Art Disk drive devices include a rotary type and a linear type as head element moving systems. In the linear type, a head element is displaced linearly by moving a head base linearly. A linear motor is used as a drive source of the head base moving means in order to simplify the motion transmission system.

On the other hand, it has been proposed to use an optical scale and an optical sensor as a position detecting means for detecting the position of the head base. However, since the slit holes of the optical scale are formed by exposure processing with a single light source, they are all used. There is a certain limit to the measurement accuracy because the same shape is not formed at the position. Therefore, the applicant has considered using a magnetic scale and a magnetic sensor in order to obtain a measurement accuracy that can meet the demand for high-density tracks. Since the magnetic scale is formed by arranging a magnetic material in the vicinity of a single magnetic head and magnetizing the magnetic material by moving the magnetic material at a constant speed, an accurate magnetization pattern can be obtained at all positions.

[0004]

However, when the magnetic sensor is used near the linear motor, the magnetic flux is leaked from the linear motor, which adversely affects the magnetic sensor. In order to prevent this, it is possible to cover the linear motor or the magnetic sensor with a shield case. However, such a configuration has a problem that the structure becomes complicated and the cost increases.

An object of the present invention is to provide a disk drive device which can effectively prevent magnetic flux leaking from a linear motor from adversely affecting a magnetic sensor without using a shield case.

[0006]

DISCLOSURE OF THE INVENTION A disk drive device according to the present invention for achieving the above object comprises a head base moving means for moving a head base mounted with a head element with respect to a chassis, and the head base. In a disk drive device having a position detecting means for detecting a moving position of a table, the head base moving means is composed of a linear motor composed of a permanent magnet and a coil part, and the position detecting means is the head base. It is composed of a magnetic sensor and a magnescale attached to the chassis and the chassis, respectively, and
The magnetic sensor was attached to the head base or the chassis via a magnetic shield plate arranged on the back surface thereof.

[0007]

The magnetic flux leaked from the linear motor is shielded by the magnetic shield plate arranged on the back surface of the magnetic sensor, and the magnetic flux is prevented from adversely affecting the magnetic sensor.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 6 show one embodiment of the present invention. 1 to 3, a magnetic recording disk D is rotatably supported on a chassis 1.
Is rotated by the rotating force of a motor (not shown). or,
A head base 2 is arranged on the chassis 1, and the head base 2 is linearly moved by a head base moving means A described below. The head base 2 supports the base ends of two leaf springs 3, and the head element 4 is fixed to the tip of each leaf spring 3.

The head base moving means A has a rail 5 fixed to the chassis 1, and the head base 2 is slidably provided by being guided by the rail 5. The movement of the head base 2 moves the head element 4 in the radial direction of the disk D. Further, linear motors 6 are provided at symmetrical positions of the head base 2, and each linear motor 6 is composed of a fixed side and a movable side. Fixed side is chassis 1
The yoke 7 is fixed to the rail 7. The yoke 7 is arranged in the same direction as the rail 5 in the longitudinal direction. York 7
An upper plate portion 7a, a lower plate portion 7b, and a center portion 7c at the center thereof are provided in parallel in the longitudinal direction of the upper plate portion 7a at a constant interval.
Permanent magnets 8a and 8b are fixed to the lower surface of a and the upper surface of the lower plate portion 7b, respectively.

The permanent magnets 8a and 8b are vertically polarized, and the permanent magnets 8a and 8b at the upper and lower positions have the same polarity on the side of the center portion 7c. The polarities of the permanent magnets 8a and 8b at the left and right symmetrical positions of the left and right linear motors 6 are opposite to each other. That is, in this embodiment, as shown in FIG. 3, the left side permanent magnets 8a, 8b are provided with S on the side of the center portion 7c.
The poles and the right side permanent magnets 8a and 8b have N on the side of the center portion 7c.
It is made up of poles. The movable side has a coil portion 9 fixed to the head base 2, and each coil portion 9 is inserted into each center portion 7c.

The position detecting means B has a magnet scale 10 and magnetic sensors S ₁ and S ₂ . The magnescale 10 is embedded in a groove 11 formed in the rail 5 in the longitudinal direction.
The magnetic scale 10 is manufactured by arranging the magnetic material close to the single magnetic head and moving the magnetic material at a constant speed to alternately magnetize the S pole and the N pole. To do. Therefore, it is magnetized regularly at all positions, and
Even if the long-sized Magnescale 10 is manufactured, the magnetization will not be disturbed.

Magnetic sensors (eg MR elements) S ₁ , S
_As shown in FIG. 4, ₂ is fixed to a magnetic sensor support member 22 provided on the end surface of the head base 2 opposite to the head element 4 via a magnetic shield plate 21 arranged on the back surface thereof. It is located opposite to the Magnescale 10. _Two magnetic sensors S ₁ and S ₂ are provided at a constant interval in the moving direction of the head base 2, and the interval is given by considering the pitch from the N pole to the S pole of the magnet scale 10 as the magnetizing interval. It is set to 1/4. Therefore, the outputs of the _two magnetic sensors S ₁ and S ₂ are sine waves that are phase-shifted by 90 °, and the output signals are guided to a waveform processing circuit (not shown). A scale signal, a movement direction signal, etc. are formed by this waveform processing circuit, and the linear motor 6 is feedback-controlled based on this scale signal, etc. The magnetic sensors S ₁ and S ₂ may be of any type as long as they output an output signal proportional to the strength of the magnetic force. In this embodiment, a magnetic resistance type sensor is used as shown in FIG. There is. The magnetic sensors S ₁ and S ₂ of this type utilize a phenomenon in which the electric resistance value changes when a magnetic flux orthogonal to the current direction exists. It is arranged to be most sensitive. Therefore, the disturbance in the X direction is the most inconvenient component for position reading.

The operation of the above configuration will be described below.
When the target track data is input when the head base 2 is at the reference position, a current flows through the coil portion 9 of each linear motor 6 as shown in FIG. Then, this current is orthogonal to the magnetic path formed by the permanent magnets 8a and 8b and the yoke 7, so that a propulsive force is applied to the head base 2. By the movement of the head base 2, the magnetic sensors S ₁ and S ₂ move on the magnet scale 10 to output sine waves, and the linear motor 6 is feedback-controlled by this output signal.

Here, the leakage fluxes due to the left and right permanent magnets 8b at the lower positions near the magnetic sensors S ₁ and S ₂ are as shown in FIGS. 6 and 7. X at the positions of the magnetic sensors S ₁ and S ₂
As shown in FIG. 5, the left and right magnetic fluxes in the directional magnetic field are canceled in the opposite directions, and the magnetic sensors S ₁ and S ₂
Since it is shielded by the magnetic shield plate 21 arranged on the back surface of the, it is not affected by the leakage magnetic flux. Further, the leakage magnetic flux of the permanent magnets 8a at the left and right upper positions is weaker than that at the lower position, and similarly, the left and right magnetic fluxes are in opposite directions, which does not adversely affect. Therefore, the magnetic sensors S ₁ and S ₂ output accurate sine wave signals based only on the magnescale 10.
Further, in this embodiment, the leakage magnetic flux in the Z direction is also canceled in the opposite direction as shown in FIG.

In the above embodiment, the magnetic shield plate 21 is formed of a thin plate of permalloy or the like into a flat plate shape, but the magnetic shield plate 21 is bent at the peripheral edge portion 23 as shown in FIG. By mounting the magnetic sensors S ₁ and S ₂ so as to wrap around them, it is possible to prevent the leakage magnetic flux from wrapping around and provide a more complete shield effect.

Further, in the embodiment, a pair of left and right linear motors are symmetrically arranged on both left and right sides of the magnetic sensors S ₁ and S ₂ , and the polarities of the permanent magnets of these linear motors are reversed, so that the pair of left and right linear motors are separated from each other. However, as described above, it is not always necessary to arrange the pair of left and right symmetrically and to reverse the polarities of the permanent magnets.

Further, in this embodiment, the magnetic sensors S ₁ and S ₂ are provided on the head base 2 and the magnetic scale 10 is provided on the fixed side. On the contrary, the magnetic scale 10 is provided on the head base 2 and the fixed side is provided. The magnetic sensors S ₁ and S ₂ may be provided.

[0018]

As described above, according to the present invention, in the disk drive device in which the head base is linearly moved, the magnetic sensor which constitutes the position detecting means together with the magnescale is arranged on the back surface thereof. Since it is structured to be attached to the head base or chassis via the plate, the magnetic flux leakage from the linear motor can be shielded by the magnetic shield plate arranged on the back surface of the magnetic sensor, thus eliminating the need for a shield case. As a result, the structure of the disk drive device can be simplified and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a plan view of a disk drive device.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is an enlarged sectional view taken along line BB of FIG.

FIG. 4 is an exploded perspective view of a main part.

FIG. 5 is a schematic perspective view of position detecting means.

FIG. 6 is a diagram showing a state of magnetic flux leakage.

FIG. 7 is a diagram showing a state of leakage magnetic flux.

FIG. 8 is a sectional view of another embodiment.

[Explanation of symbols]

A ... Head base moving means, B ... Position detecting means, S ₁ , S ₂
... magnetic sensor, 1 ... chassis, 2 ... head base, 4 ... head element, 6 ... linear motor, 8a, 8b ... permanent magnet,
9 ... Coil part, 10 ... Magnescale, 21 ... Magnetic shield plate.

Front page continuation (72) Inventor Yoshihiro Kanda 1-21-1 Ikenohata, Taito-ku, Tokyo Aiwa Co., Ltd. (72) Inventor Takumi Usui 1-2-11 Ikenohata, Taito-ku, Tokyo Iwa Co., Ltd.

Claims (1)

[Claims] 1. A disk drive device comprising: a head base moving means for moving a head base on which a head element is mounted with respect to a chassis; and a position detecting means for detecting a moving position of the head base. The base moving means is composed of a linear motor composed of a permanent magnet and a coil portion, and the position detecting means is composed of a magnetic sensor and a magnet scale attached to the head base and the chassis so as to face each other. A disk drive device, wherein the magnetic sensor is attached to the head base or chassis via a magnetic shield plate arranged on the back surface thereof.