JPH0541075A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent the damage of the magnetic disk memory device by the electric discharge generated between a magneto-resistance effect type head and a conductive magnetic recording medium by the high-frequency radio waves or magnetic fields applied to the device from the outside. CONSTITUTION:The main part of the magnetic disk memory device including a conductive magnetic disk 10, an MR magnetic head element 31, a revolving shaft 56 for driving the disk, a head driving device 57, a preamplifier 62, etc., is enclosed with an outside box 51 and cap 52 consisting of a metal having at least >=0.01mm thickness, by which the influence of the above-mentioned radio waves and magnetic fields is decreased. A liquid metal is interposed in a sliding current collector 58 making an electrical connection between the revolving shaft 56 and the outside box to decrease a contact potential difference. The induced voltage between the head and the recording medium is decreased in this way and the discharge therebetween is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing device such as a magnetic disk storage device having a conductive magnetic recording medium and a magnetoresistive effect magnetic head, and more particularly to a magnetic recording / reproducing device between the recording medium and the magnetic head. The present invention relates to a magnetic recording / reproducing device that prevents discharge.

[0002]

2. Description of the Related Art Generally, an inductive recording magnetic head and a magnetoresistive effect (hereinafter abbreviated as MR) reproducing magnetic head, or a magnetic recording apparatus using a magnetic head having a combination thereof, is a digital recording apparatus, for example. It is well known because it has been commercialized as a magnetic tape storage device. In the case of a magnetic disk storage device, the combination of the recording magnetic head and the reproducing magnetic head can be designed so as to have the optimum performance, so that the performance of the entire magnetic disk storage device can be improved. That is, since the MR reproducing magnetic head has high information reproducing voltage sensitivity and low impedance, information can be reproduced at high speed. Moreover, since the information recording head is not involved in information reproduction, the number of turns of the exciting coil can be reduced. Therefore, the inductive recording magnetic head can also reduce the impedance, so that information can be recorded at high speed. A magnetic head that is a composite of an inductive recording magnetic head and an MR reproducing magnetic head applied to a magnetic disk storage device is often formed of a thin film because high dimensional accuracy is required. As a magnetic head array that combines them, a laminated structure in which they are stacked in the moving direction of the magnetic recording medium, and an integrated structure in which MR elements are arranged in a part of the magnetic core of the recording magnetic head are known.

When an alloy thin film magnetic recording medium having conductivity, which is advantageous for realizing a high recording density, is used, according to the study of the present inventors, the gap between the magnetic head and the magnetic recording medium is 0.1 μm or more. In a magnetic disk storage device having a size of 0.3 μm or less, the steady discharge withstand voltage between the medium and the magnetic head is as low as 0.8 to 1.2 V and as high as 5 to 10 V.

In the case of the conventional induction type magnetic head, at least 100 coils are provided for the magnetic core facing the recording medium.
It was easy to have a withstand voltage as high as a bolt.
Therefore, the magnetic head did not discharge to the recording medium. Nevertheless, even in the magnetic disk storage device using the conventional induction type magnetic head, the outer box surrounding the magnetic head, the magnetic disk, etc. often has an electrical shield function. This is to prevent a reproduction error caused by an external electromagnetic field penetrating the reproducing device to generate noise when reproducing information, and is necessary only during the reproducing operation of the magnetic disk storage device. This is a countermeasure against a transient phenomenon. Therefore, in the magnetic disk storage device using the conventional induction type magnetic head, the influence of the external electromagnetic field can be greatly reduced by other means. For example, when an error in the reproduced information is detected, it is possible to correctly reproduce the information by a method such as reading the information again, or providing a redundancy to logically correct the error. In addition, it is not necessary to protect against a phenomenon that is enormous but extremely infrequent, such as an error that occurs once or less per billion bits, which is acceptable as a magnetic disk storage device.

On the other hand, in the magnetic disk storage device using the MR type magnetic head, the discharge withstand voltage is low because the MR element is exposed at the tip of the magnetic head. In addition, since the MR element is connected to a low-impedance power source in order to detect the resistance change of the MR element, once the discharge starts at a voltage exceeding the withstand voltage (discharge starting voltage), a voltage lower than that (discharge At the sustain voltage), a large current flows from the low impedance power source through the MR element into the magnetic recording medium (that is, a large amount of energy is injected). Therefore, the discharge between the magnetic head and the magnetic recording medium damages both or either. Therefore, in order to realize a highly reliable magnetic disk storage device, it is necessary to set the potential between the MR element and the recording medium to 0.8 V or less, for example. Further, while the magnetic disk storage device is stopped, the magnetic recording medium and the magnetic head are left in contact with each other. In such a case, when a current flows between the magnetic recording medium and the MR element due to the influence of a small amount of ions contained in the lubricating material applied to the surface of the magnetic recording medium, either one of them is subject to electrolytic corrosion. Occur.

Conventionally, for example, US Pat. No. 4,879,610
As can be seen in the specification, it has been proposed to devise a drive circuit for the MR element to reduce the problem of such discharge. In this proposal, the operation center level of the MR element is made to coincide with the ground potential of the signal processing system connected to the MR element to prevent discharge between the MR element and the conductive magnetic recording medium.

[0007]

Usually, the DC resistance of the MR element is at most about 10 to 20Ω, and the driving current thereof is about 10 mA. Therefore, the prior art according to the above-mentioned U.S. Pat. No. 5,837,088 only provides the effect of operating an MR element operating at 0 to 200 millivolts at -100 millivolts to +100 millivolts. For this reason, the technique of the above-mentioned U.S. Pat.

According to the research conducted by the present inventors, it is clear that in the magnetic disk storage device, a voltage higher than the voltage provided by the MR element drive circuit may be applied between the magnetic recording medium and the MR type magnetic head. Became. That is, the following two factors are major factors.

The first is a high frequency electric field or magnetic field applied from the outside. When an electric field is applied to the MR type magnetic head and the electric wiring connected to the MR type magnetic head, a voltage is induced between the magnetic recording medium and the magnetic head. In addition, the above electric wiring,
When a high-frequency magnetic field penetrates a mostly closed electric loop composed of a ground plane, a conductive shaft for rotating the magnetic recording medium, a conductive magnetic recording medium, etc., a voltage is induced in the electric loop. Therefore, a voltage is generated between the magnetic recording medium and the magnetic head.

The second cause is imperfect electrical connection between the rotary shaft and a fixed portion supporting the rotary shaft. In order to ground the rotating shaft, a sliding current collector must be used, but the sliding current collector has a metal interface, which causes a contact potential difference. This potential difference is 0.1 even for minute currents.
A potential difference of about 0.3 V or about 0.8 V may occur when the current density increases. Since such a phenomenon occurs even when a commutator of an electric motor or a switch is contacted, it is a problem widely known to electric engineers. Therefore, it is shown that the magnetic recording medium may be charged within a range of about ± 0.3 V with respect to the ground potential. For this reason, MR
It can be seen that when the element has a potential of about ± 0.5 V with respect to the ground potential, there is a possibility of discharging between the element and the recording medium.

Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, and an MR type magnetic head or a composite magnetic head with the MR type magnetic head (the "MR type magnetic head" of the present invention includes a composite magnetic head. ) And a conductive magnetic recording medium, a magnetic disk storage device based on an external electric field or magnetic field, or an imperfect electrical connection between a rotating shaft for driving the recording medium and a fixed portion. An object of the present invention is to provide a highly reliable magnetic recording / reproducing apparatus by preventing discharge between the magnetic head and the magnetic recording medium.

[0012]

In order to achieve the above object, the present invention roughly provides the following two solutions.

As a first solution, the present invention is a magnetic recording / reproducing apparatus having a conductive magnetic recording medium and a magnetoresistive effect magnetic head, and an external electric field perpendicular to the surface of the magnetic recording medium or the magnetic recording medium. Means for shielding an external magnetic field parallel to the plane of the. As a shield means
Specifically, the magnetic recording medium, a member for mounting and rotating the magnetic recording medium, and a shield box containing the magnetoresistive effect magnetic head (including its preamplifier if necessary) are used. This shield box is composed of at least two constituent elements, and the boundaries of the respective constituent elements are connected to each other via a conductive elastic body.

As a second means for solving the problems, the present invention provides a conductive magnetic recording medium, a rotating member for mounting and rotating the magnetic recording medium so as to be electrically joined to the magnetic recording medium, and a magnetoresistive effect. Type magnetic head, a conductive fixing member to which the magnetoresistive effect type magnetic head is attached so as to be electrically joined to the magnetoresistive effect type magnetic head, and between the rotating member and the fixing member. And a liquid metal that is electrically joined.

[0015]

The operation based on the above configuration will be described.

According to the first solution of the present invention, in a magnetic recording / reproducing apparatus in which a conductive magnetic storage medium and a magnetoresistive effect magnetic head are combined, an external magnetic field perpendicular to the surface of the recording medium or an external magnetic field parallel to the magnetic recording / reproducing apparatus is used. Since a shield means such as a shield box for shielding the magnetic field is provided, regardless of whether the magnetic recording / reproducing apparatus is operating or stopped,
Powerful electromagnetic waves such as lightning, broadcast radio waves, microwave heating devices, and radar always enter the magnetic recording / reproducing device to generate an induced voltage between the magnetic effect type magnetic head and the conductive magnetic recording medium. Therefore, it is possible to prevent discharge or current flow between the magnetic head and the magnetic recording medium, and prevent permanent damage to the magnetic head and the magnetic recording medium.

According to the second solving means of the present invention,
Since the liquid metal was interposed as a current collector between the rotating part where the conductive magnetic recording medium was mounted and rotated and the fixed part where the magnetic effect type magnetic head was mounted, the contact potential difference between the rotating part and the fixed part was reduced. To thereby ensure an electrical connection between the magnetic recording medium and the magnetic head and to ensure their grounding, further preventing the generation of a voltage between this magnetic head and the magnetic recording medium, It is possible to further prevent these permanent damages by eliminating discharge or energization between them.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an MR type information reproducing dedicated magnetic head 30 and an induction type information writing dedicated magnetic head 20 which are applied to the apparatus of the present invention.
FIG. 1 shows an example of a composite magnetic head for a magnetic disk storage device, which is composited within 0, and the basic structure of such a composite magnetic head is shown, for example, in US Pat. No. 3,908,194. Further, the magnetic disk 10 is formed by depositing a magnetic recording layer 13 such as an alloy containing cobalt as a main component on a base 12 made of, for example, an aluminum base 11 or nickel phosphorus or chrome by a method such as sputtering, and the surface thereof. A protective film 14 such as a carbon film and a lubricant 15 such as fluorocarbon oil and fat are applied to Since the lubricant 15 has an average thickness of about several tens to several hundreds angstroms and has many pinholes, the film 15 cannot be expected to electrically insulate the surface of the protective film 14. When the magnetic disk 10 is rotating at a predetermined speed, the floating structure 40 is configured to float above the surface of the magnetic disk 10 at a predetermined gap h. This gap h is 0.1 to 0.3 μm in a magnetic disk storage device currently in practical use.
Although it is a degree, it has to be reduced in inverse proportion to the increase of the recording density, so that it is expected to decrease to about 0.05 μm in the near future.

A coil 24 is provided in the inductive write magnetic head 20 so as to penetrate a magnetic circuit including a magnetic gap 21 and magnetic yokes 22 and 23. In addition, an insulating film 25, between the coil 24 and the magnetic yokes 22 and 23,
26, a gap of 1 μm or more is provided. Since these insulating films 25 and 26 have a withstand voltage of 2 to 4 million volts per centimeter (200 to 400 volts per 1 μm), the magnetic yoke 22 and
It is easy to set the discharge withstand voltage between the coil 23 and the coil 24 to 200 V or more.

On the other hand, the MR type information reproducing magnetic head 30 is provided with an MR element 31 and a magnetic shield 32 for sandwiching the MR 31 and enhancing the resolution of information reproduction.
Further, the MR element 31 is connected to an electric circuit (not shown) for detecting the resistance change of the MR element 31, and the lead wire 3 is provided.
Connected to 3. The tip of the MR element 31 is exposed on the surface of the floating structure 40 facing the magnetic recording medium 13. Therefore, the discharge breakdown voltage between the MR element 31 and the protective film 14 or the conductive magnetic recording medium 13 becomes a small value of 1 volt or less as described above.

Next, referring to FIG. 2, an HDA (Head Disk) of a magnetic disk storage device according to an embodiment of the present invention will be described.
The configuration inside the assembly will be described.

The magnetic disk 10 is fixed to a conductive rotating shaft 56, and the rotating shaft 56 is rotated at a high speed of about 3600 rpm by an electric motor 70 having the rotating shaft 56 as a part of a rotor. The electric motor 70 is fixed to a conductive outer box 51 via a fixed shaft 71. The conductive floating structure 40 is close to the magnetic disk 10 and is supported by a conductive load spring 41 attached to the conductive head arm 42, and at the same time, a load is applied from the spring 41. When the magnetic disk 10 rotates, a levitation force is generated in the levitation structure 40 by the air flow generated on the surface thereof. Due to the balance between the levitation force and the load of the spring 41, the levitation structure 40 is levitated with a small gap as described above. In addition, the floating structure 4
0 indicates the head arm 4 by the magnetic head driving device 57.
2. Through the spring 41, it can be moved so as to coincide with an arbitrary information track position on the magnetic disk 10. Normally, the head arm 42 is grounded to the outer box 51 via a flexible electric wire 43.

MR element 3 incorporated in the floating structure 40
The constant current source 60 supplies a predetermined constant current to 1. Information of the magnetic recording medium is the MR element 31.
The minute resistance change of about 1 to 2% that causes
A voltage change is generated between both terminals of the element 31. This voltage change is amplified by the preamplifier 62 through the capacitor 61, and then guided to the connection connector 65 through the hole 55 of the outer box 51 by the flexible printed wiring board 63. Reference numeral 64 is a ground wire of the printed wiring board 63, and 67 is a ground wire. From the connection connector 65, it is further led to a signal processing circuit (not shown). The magnetic disk 10 is mechanically fixed to the rotating shaft 56 and electrically coupled thereto. The rotating shaft 56 has a slip contact 58 so that the outer box 51
Electrically connected to. A liquid metal 59 such as mercury amalgam is provided at the contact portion of the slip contact 58 with the rotary shaft 56, and this maintains electrical contact. In the above description, the case where the outer box 51 has conductivity has been described. When the outer box 51 is made of a non-conductive material, a conductive wire may be provided to connect the slip contact 58 and the ground wires 43 and 64 to each other. In the recent magnetic disk storage device, the flying gap h between the magnetic recording medium 10 and the slider (flying structure) 40 is 0.3 μm as described above.
The packing gasket 54 is sandwiched between the outer box 51 and the lid 52, and these are fastened with, for example, screws 53 in order to prevent dust from entering the gap.

Consider the influence of an external high frequency electric field and magnetic field.

The MR element has a ground wire 67 as shown in FIG.
Since it is grounded to the outer box 51 through the grounding wire 64 together with the preamplifier 62, the influence of the low-frequency electric field and magnetic field does not reach the voltage for generating the above-mentioned discharge. However, when the frequency of the external electromagnetic field increases, a high voltage is induced between the magnetic disk 10 and the MR element 40 due to the inductance (self-induction) of the conductor included in the printed wiring board 63 and the generation of a standing wave. Like There are thunder, medium wave (that is, in the range of about 0.5 MHz to 2 MHz) broadcasting, microwave heating devices, radar, and the like that generate high electric fields and magnetic fields at high frequencies. Some medium wave broadcasts have a transmission power of 100 kilowatts. Since this frequency band has a wavelength of several tens of meters and is sufficiently longer than the size of the magnetic disk device, its influence can be calculated as a uniform parallel electric field. When the transmitter output impedance is 50Ω and the antenna height is 65 meters, the peak amplitude (0-peak) value of the electric field is about 49 volts / meter just below the antenna. When the gap between the printed wiring board 63 and the outer casing 51 is, for example, 5 cm, the direction of the electric field is substantially perpendicular to the printed wiring board 63, the spring 41, or the like, and the plate surface of the magnetic disk 10, the MR element. A maximum voltage of 2.4 V is induced between the tip of 31 and the outer box 51. With a transmitting antenna,
If a conductive object is present between the magnetic disk storage devices, a higher voltage will be applied to the MR element 31 due to the disturbance of the electric field.
The possibility of being induced by Therefore, 1
If a safety factor of 0 times is expected, the conductive magnetic recording medium 13
In the case of the magnetic disk storage device including the MR element and the MR element, a shield having an attenuation capability of at least 1/30 (-30 dB) with respect to the medium-wave electromagnetic field is required.

The case where the wavelength of the electromagnetic field is close to the size of the magnetic disk storage device or the length of the conducting wire or the like included in the device will be described. When the length of the conductor whose one end is grounded is ¼ of the wavelength of the electromagnetic field, the resonance phenomenon induces a large voltage near the electric field of the electromagnetic field at the other end of the conductor.

For example, the length from the tip of the MR element 31 to the ground line 64 via the printed wiring board 63 is 1
It is assumed to be 5 cm. At this time, 4 of that length
When an electromagnetic wave having a double wavelength, that is, a wavelength of 60 centimeters (that is, a frequency of about 500 MHz) is applied, the efficiency as a receiving antenna is increased, and more power is added to the MR element. The above-mentioned frequency is in the UHF band, and there are few sources of large output, but as described above, a large voltage may be generated between the MR 31 and the magnetic disk 10 even with an output of, for example, about 100 watts.

Next, consider the example of a radar. Some radars for aircraft route monitoring have a frequency of 1.3 GHz and a transmission output of 2 Mwatts. The wavelength of this electromagnetic wave is about 23 cm, and the quarter wavelength is 5.8 cm. Resonance also occurs for odd multiples of 1/4 such as 3/4 wavelength, so conductors of these lengths (for example, 3/4 wavelength is 17.3 cm at the above frequencies). Also be careful. The power is 100 area
If we radiate from a square meter (5.6 meters diameter) antenna, we get 200 watts of power per 100 square centimeters. If the conductor is an antenna having an impedance of 50Ω, the voltage at its tip is 100 volts.

Therefore, a magnetic disk storage device including the magnetic disk 10 having conductivity and the MR element 31 is several hundred MH.
A shield of at least 1/1000 (-60 dB) or more is required for an electromagnetic field having a frequency of z or higher.

Since lightning is an impulse-shaped electromagnetic field,
Since it has a component in a wide frequency band, it can be considered in the same manner as the measures described so far.

Next, the influence of the magnetic field will be described. MR element 31, head arm 42, ground wire 43, outer case 51, slip contact 58, rotating shaft 56, magnetic disk 10
Forms a closed electric loop except between the disk 10 and the MR element 31. Therefore, a voltage proportional to the time change rate of the magnetic flux penetrating this loop is applied to the magnetic disk 10.
And the MR element 31. For example, a magnetic flux having an amplitude of 1 oersted (100 microtesla) and a frequency of 320 kHz causes a voltage of about 1 volt in the loop. With a high frequency magnetic flux of the same amplitude and a frequency of 1 MHz, a voltage of about 3.1 volts is generated in the loop. Modern switching power supplies are 100 kHz to 50
Since there are some that operate at a pulse frequency of 0 kHz, magnetic disk storage devices are likely to be exposed to noise flux at these frequencies. Therefore, the high frequency magnetic field is 1/1
A shield function that reduces 0 to 1/30 or more is required.

However, unlike a radio wave, a magnetic field has no directivity, and therefore, it is exponentially attenuated exponentially in inverse proportion to the distance from the magnetic field source. For this reason, it suffices to consider only the magnetic field source installed in the immediate vicinity as the shield means for the magnetic field.

The operation of the slip contact 58 is as described above.

Next, the structure of a magnetic disk storage device according to an embodiment of the present invention will be described with reference to FIG. In order to reduce the influence of the first object of the present invention, that is, the influence of an external high-frequency electric field or magnetic field, in this embodiment, the magnetic disk 10 and the MR element 31 are provided by the conductive outer box 51 and the conductive lid 52. The main portion such as the magnetic head slider 40 including the magnetic recording element is sealed. This embodiment has a shape generally adopted in a magnetic disk storage device using a magnetic disk having a small diameter such as 5.25 inches and 3.5 inches. That is, the base that fixes the rotary shaft 56 and the head drive device 57 also serves as the outer case 51. At this time, the lid 52 mainly covers the main part.

For example, assume that the outer box 51 or the lid 52 is made of an aluminum alloy having a thickness of 0.001 mm. Since this alloy has a resistivity of about 2.8 to 3.0 μΩ · cm, the resistance value between two opposing sides of a square plate having the above thickness is 28 to 30 mm regardless of the size of the square. Becomes Ω. Since the planar shape of the outer box 51 is a rectangle having an aspect ratio of 2 or less, it is assumed that the outer box 51 is
Alternatively, even if the lid 52 is forcibly supplied with a current of 1 amp, only a potential difference of 60 millivolts or less will occur. In addition, since the conductivity with the space is significantly different, the radio waves are transmitted from the outer box 5
1 and the surface of the lid 52. Therefore, it can be understood that the outer box 51 and the lid 52 have a good electric field shielding function even if the metal is 0.001 mm thin. This means that most of the outer box 51 and the lid 52 are made of an insulating material such as an organic resin as a strength member, and a metal film is formed on the surface of the outer electrode 51 and the lid 52 by electrodeposition or vacuum deposition. Also shows that the purpose can be satisfied.

Next, the prevention of the influence of the high frequency magnetic field will be described.

It is assumed that the outer box 51 and the lid 52 are rectangular parallelepipeds each having a six-sided rectangle. Also, consider the simplest case where the magnetic field is applied from a direction perpendicular to one plane.
When the surface of the first surface (for example, the bottom surface of the outer box and the upper surface of the lid) where the magnetic field is incident from the right angle direction is covered with a conductor, an eddy current flows in the surface of the conductor to prevent the magnetic field from entering. It is clear that this will be done. When the four surfaces (for example, the front and rear surfaces and the left and right side surfaces) that are in contact with the first surface are electrically connected to the first surface and further between the respective surfaces, the four surfaces are generated in the first surface. It becomes a current path that promotes eddy current. Therefore, the first
The above-mentioned four surfaces, which are perpendicular to the surface of, also contribute to the prevention of magnetic field penetration.

If a sufficient margin is provided and the thickness of the metal portion of the outer box and lid is 0.01 mm or more, 500 KH
All electromagnetic fields above Z can be attenuated over 30 dh.

Further, even if a conductive ring having a low resistance value and contacting the first surface is provided so as to surround the first surface, an eddy current parallel to the first surface can be generated. 4 above
The same effect as the surface can be obtained.

This method shows that the ring of conductors can be added to an already completed magnetic disk storage device.
For example, for the purpose of downsizing a device to which a magnetic disk is applied, a switching power supply (a power supply using high frequency generates high pulse noise. Not shown) and a magnetic disk storage device have to be arranged close to each other. If not obtained, for example, a tape-shaped conductor may be wound.

The packing gasket 54 provided to maintain the airtightness also uses an elastic body having conductivity. this is,
This is for surely forming the eddy current path on the first surface and the four surfaces in contact with the first surface, and for preventing the formation of an inverse antenna due to an electrical gap. That is, if there is a gap or a hole, this becomes a new radiation source, and electromagnetic waves enter into the box from here, and this is prevented. However, the material of the gasket 54 does not need to have uniform conductivity, and a conductive material may be dispersed in a cycle sufficiently shorter than the wavelength of the highest frequency electromagnetic wave to be blocked. As an example of a material satisfying this purpose, metal particles or carbon powder may be dispersed in silicone rubber, or needle-like metal pieces may be dispersed in a similar elastic body.

From the above description, as shown in FIG. 3, the magnetic disk 10, the rotating shaft 56 of the magnetic disk, and the electric motor 7 are shown.
0, the magnetic head 40, the magnetic head driving device 57, the recording / reproducing electronic circuit 75 connected to the magnetic head, and other main parts of the magnetic disk storage device by an outer box 51, a lid 52, and a packing gasket 54. It can be understood that it can be magnetically sealed.

Next, the rotating shaft 56 of the magnetic disk is attached to the outer box 51.
Next, a specific method of connecting with a small potential difference will be described.
FIG. 4 shows a sectional view of an assembly of a magnetic disk and an electric motor of the first embodiment.

In FIG. 4, the metal hub 106 also serves as the rotating shaft 56 of FIG. 3 and a part of the rotor of the electric motor 70. Magnetic disk 10 and metal spacer 12 on the hub
1 are stacked alternately, and the metal clamp 123 and the screw 124
Fixed in. The upper and lower two bearings 102 and 102a and the fixed shaft 100 support the hub 106. In addition, the fixed shaft 10
0 is provided with a stator core 103 and an electric winding 104, and a permanent magnet 105 fixed to a hub 106 is used to connect the hub 1 to the hub 1.
An electric motor 70 that rotates 06 is configured. Fixed shaft 1
00 has its lower end fixed to the conductive outer box 51.
An annular groove 130 is formed in the outer box 51 so as to surround the vicinity of the fixed shaft 100, and the liquid metal 132 is put in the groove 130 in the range of 5 to 50 degrees Celsius, for example. Reference numeral 109 is a cylindrical metal bearing holder mounted between the hub 106 and the bearing 102a so as to rotate together with the hub 106 coaxially with the hub 106.
An annular electrode 131 is provided so as to be in contact with the liquid metal 132 while being fixed to the inner circumference below 9. Liquid metal materials that satisfy the above conditions include mercury, amalgam, and gallum. By doing so, the outer box 51 and the annular electrode 131
It is clear that the contact potential difference between the two can be as low as 1 millivolt. These metals easily evaporate even at room temperature. Further, when these metals condense and adhere to each other, corrosion of other metals is promoted. Therefore, by the magnetic fluid seal using the magnetic fluid 108 and the permanent magnet 107 with a metal plate, the vapor of these metals is discharged from the space 151 of the electric motor to the magnetic disk. It is desirable to prevent diffusion into the space 152 including

When the number of revolutions of the electric motor is increased to, for example, 5400 revolutions per minute, the frictional force of the annular electrode 131 or the scattering of the liquid metal 132 due to the centrifugal force may be a problem. FIG. 5 shows an embodiment for dealing with such a problem. In FIG. 5, the metal rotating shaft 101 fixed to the metal hub 106 is provided, the metal case 133 having the groove 130 is attached to the outer box 51, the liquid metal 132 is put in the groove 130, and the rotating shaft 101 is almost at the center. The needle-shaped electrode (ground pin) 134 provided at the contact point is brought into contact with the liquid metal 132 to short-circuit the MR type magnetic head and the magnetic disk, thereby improving the above-mentioned problems for high-speed rotation. .. Other configurations are the same as those in FIG. 4, and the same reference numerals are given.

According to the present embodiment, inside the space surrounded by the outer box 51 and the lid 52, an electromagnetic field of 500 kHz or more and a magnetic field of 320 kHz or more are applied to the outside with a strength of 1%.
/ 30 or less. Further, by improving the sliding current collector, the potential difference between the rotating shaft 56 of the magnetic disk and the outer case 51 can be reduced. As a result, discharge or current flow between the magnetoresistive magnetic head and the magnetic disk having the conductive magnetic recording medium can be prevented during the operation of the magnetic disk storage device and at the time of stop thereof. And prevent permanent damage to the magnetic disk.

[0048]

As described in detail above, according to the present invention, in a magnetic recording / reproducing apparatus including a conductive magnetic recording medium and a magnetoresistive effect magnetic head, an external magnetic field perpendicular to the surface of the magnetic recording medium or Since the shield means such as a shield box for shielding the parallel external magnetic field is provided, the external magnetic field penetrates into the device to generate an induced voltage by the external magnetic field between the magnetic head and the magnetic recording medium, and discharge occurs between them. It is prevented from occurring. As a result, permanent damage to the magnetic head and the magnetic recording medium can be prevented.

Further, the electrically conductive fixed portion on which the electrically conductive magnetic recording medium is mounted and rotated and the electrically conductive fixed portion on which the magnetic effect type magnetic head is mounted are electrically connected by liquid metal. Therefore, there is an effect that it is possible to more reliably prevent the generation of a voltage between the magnetic head and the magnetic recording medium, and therefore the damage due to the electric discharge during that period.

[Brief description of drawings]

FIG. 1 is a cross-sectional perspective view of a magnetic head and a recording medium applied to the present invention.

FIG. 2 is a schematic sectional view of a magnetic disk storage device according to an embodiment of the present invention.

FIG. 3 is a perspective view of a magnetic disk storage device according to an embodiment of the present invention.

FIG. 4 is a sectional view of an example of an assembly of a magnetic disk and an electric motor applied to the present invention.

FIG. 5 is a sectional view of another embodiment of the assembly of the magnetic disk and the electric motor applied to the present invention.

[Explanation of symbols]

 10 magnetic disk 11 base 12 underlayer 13 magnetic recording layer 14 protective film 15 lubricant 20 induction type magnetic recording head 21 magnetic gap 22 lower yoke 23 upper yoke 24 coil 25, 26 insulating film 30 MR type magnetic head 31 MR element 32 magnetic shield 33 Lead Electrode (Lead Wire) 40 Floating Structure (Slider) 41 Load Spring 42 Head Arm 43 Head Arm Grounding Wire 51 Housing (Outer Box) 52 Lid 53 Screw 54 Packing Gasket 55 Through Hole 56 Rotation Shaft 57 Head Drive 58 Slip contact 59 Liquid metal 60 Constant current source 61 Capacitor 62 Preamplifier 63 Flexible printed board (printed wiring board) 64 Ground wire 65 Connector 67 Ground wire 70 Electric motor 71 Fixed shaft 75 Recording / reproducing electronic circuit 100 Fixed shaft 101 times Shaft 102, 102a Bearing 103 Stator 104 Motor winding 105 Permanent magnet 106 Hub 107 Permanent magnet with metal disk 108 Magnetic fluid 109 Bearing holder 121 Spacer 123 Clamp 124 Screw 130 Groove 131 Ground ring 132 Liquid metal 133 Case 134 Ground pin (needle) Electrode) 141 screw 151,152,153 space

Claims (5)

[Claims] 1. A magnetic recording / reproducing apparatus having a conductive magnetic recording medium and a magnetoresistive effect magnetic head, characterized in that it comprises means for shielding an external electric field perpendicular to the surface of the recording medium. apparatus. 2. A magnetic recording / reproducing apparatus having a conductive magnetic recording medium and a magnetoresistive effect type magnetic head, characterized by including means for shielding an external magnetic field parallel to the surface of the magnetic recording medium. Playback device. 3. The shield means comprises a shield box for shielding an external electric field or an external magnetic field, and the magnetic recording medium, a member for mounting and rotating the magnetic recording medium, and the magnetoresistive magnetic head in the shield box. The magnetic recording / reproducing apparatus according to claim 1, wherein the magnetic recording / reproducing apparatus is configured to be housed. 4. The shield box is composed of at least two constituent elements, and the boundaries between the constituent elements are configured to be coupled via a conductive elastic body.
The magnetic recording / reproducing apparatus described. 5. A conductive magnetic recording medium, a rotating member for mounting and rotating the magnetic recording medium so as to be electrically joined to the magnetic recording medium, a magnetoresistive effect magnetic head, and the magnetoresistive effect type. A conductive fixing member for mounting the magnetoresistive head so as to be electrically joined to the magnetic head, and a liquid metal for electrically connecting the rotating member and the fixing member are provided. A magnetic recording / reproducing apparatus characterized by the above.