JP2005276319A - Method and device for erasing magnetic information recorded on magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for simply and certainly erase magnetic information recorded in after use magnetic recording medium especially, a magnetic disk device (hard disk device), and preventing the magnetic information recorded from leaking to a third party at the time of discarding the above devices. <P>SOLUTION: The device has a core having a shape which is a part of closed curve excised in terms of a front shape as a whole, a gap formed between the end faces of the excised core, an electrical insulation layer from the near position of the both end faces to the position near the middle point of the core respectively, and includes an electrical magnetic field generation means equipped with two coils formed by winding a lead wire which can make the current conductive for the inside of the layer. It is characterized in that the magnetic information recorded on the magnetic recording medium is erased by the magnetic force moving through the gap by placing the magnetic recording medium which is a demagnetized object in the gap field. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention applies a magnetic force generated by an electromagnet to a magnetic recording medium, erases the recorded information on the magnetic recording medium, and discards the magnetic recording medium that is no longer needed. The present invention relates to a method and apparatus for erasing magnetic information on a magnetic recording medium for preventing leakage and safely discarding.

  Conventionally, when discarding a magnetic recording medium used by a company or an individual, especially a magnetic disk storage device (hereinafter simply referred to as an HDD), it is connected to a computer so that the recorded information is not disclosed to a third party. In this state, the recorded magnetic information is erased after being formatted by the operating system. However, in this format by the operating system, only the management area that manages the arrangement of the magnetic information, etc., is erased from the recorded information in the HDD, so that the magnetic information is apparently erased. However, the magnetic information remaining on the disk is analyzed by using HDD analysis software or the like, and there is a problem that confidential documents etc. are leaked.

  In view of such circumstances, in order to erase magnetic information recorded on various magnetic recording media, methods have been provided for erasing magnetic information that has been recorded by applying magnetism to the magnetic recording medium from the outside. For example, a method of erasing magnetism by inserting a recording medium such as a cassette tape or a magnetic disk into a cylindrical magnetic coil (see, for example, Japanese Patent Laid-Open No. 60-129909), or a part of a magnetic disk device in a magnetic field. There is a method of erasing information recorded on a disk storage medium inserted and stored in the apparatus (see, for example, Japanese Patent No. 3063860).

  The latter erasing method is intended to erase magnetic information recorded in a so-called hard disk device (hereinafter simply referred to as HDD). In this erasing method, permanent magnets having polarities repelling each other are arranged at opposing positions, the HDD is inserted into a magnetic field generated by the opposing permanent magnets and having magnetic field lines in the vertical or horizontal direction, and the HDD is inserted into the HDD. A magnetic force is applied to the stored magnetic disk to erase the record.

  When opposing magnets are placed and a magnetic field is generated in the gap (in this technique, a magnetic field in the vertical direction is indicated), if there is no magnetic material in the gap, the magnet reaches one magnet from the other. Although a magnetic force is generated, when a magnetic material exists in the gap, the magnetic force is attracted to the magnetic material. In order for the magnetic force to pass through the magnetic material to the opposing magnetic pole, a magnetic material having a length proportional to the distance corresponding to the gap is required, and if a sufficiently long magnetic material cannot be secured, it is attracted. The applied magnetic force causes a sudden decay, and as a result, the magnetic force reaches the magnetic body, but does not reach the opposing magnetic pole. In addition, a magnetic body that attracts magnetic force and cannot escape magnetic force to the opposing magnetic pole has a magnet-like effect, so that the attracted magnetic force and the opposite pole state are obtained, and the attracted magnetic force returns to the permanent magnet. For this reason, when the magnetic disk is arranged in the gap between the opposing permanent magnets as in the latter technique, the magnetic force generated from the upper or lower permanent magnet is the same as that of the upper magnetic side of the uppermost magnetic disk or the lower magnetic disk. The magnetic material applied to the lower magnet surface will reach the magnetic material, but the length of the magnetic material existing between the magnetic poles is only the thickness applied to the surface of the magnetic disk. After reaching the surface magnetic body, it returns to the original permanent magnet.

  In this way, when the permanent magnets are arranged above and below so as to sandwich the front and back surfaces of the magnetic disk, the magnetic force reaches the magnetic disk surface on the side where the permanent magnet exists, but the magnetic force does not reach the back surface. If there are, for example, three magnetic disks in the HDD, the magnetic force applied to the magnetic body applied to the outer surface of the magnetic disk located outside does not reach the end, and as a result, the back surface of the magnetic disk located outside. In addition, the magnetic force does not reach a total of four surfaces on the front and back surfaces of the second magnetic disk located in the middle. Therefore, when such a method is used, it is difficult to erase magnetic information recorded on the HDD.

JP 60-129909 A Japanese Patent No. 3063860

  The present invention can easily and reliably erase magnetic information recorded on a used magnetic recording medium, particularly a magnetic disk device (hard disk device), and be recorded by a third party when the device is discarded. It is an object of the present invention to provide a method and an apparatus for preventing information from leaking.

  In order to solve the above-mentioned problems, the present invention adopts a structure in which a gap is formed between a core having a shape in which the front shape is cut as a whole and a part of the closed curve is cut off, and an end face of the core cut out. Including an electric magnetic field generating means having two coils formed by winding a conductive wire having an electric insulation layer from the vicinity position to a position near the midpoint of the core and capable of conducting a current inside the core. A magnetic recording medium that is an object to be demagnetized is present, and magnetic information recorded on the magnetic recording medium is erased by a magnetic force that moves through a gap.

  The core is formed in a shape in which the end surfaces are arranged substantially opposite to each other while forming a gap between the end surfaces formed by cutting and removing a part of the substrate whose front shape is a closed curve.

  The shape formed by cutting out a part of the closed curve as a whole is substantially U-shaped or substantially C-shaped.

  The base material is composed of a grain-oriented electrical steel sheet as a main material.

  The closed curved base is a wound iron core formed by winding a grain-oriented electrical steel sheet.

  The front shape of the part forming the coil of the core is a linear shape.

  The inner peripheral surface of the coil forming portion of the core has a planar shape, and the planar inner peripheral surfaces of the two coil forming portions are parallel to each other.

  Both end surfaces are formed with protrusions protruding opposite to each other from the inner end of the coil forming portion of the core.

  The narrow angle between the protruding portion and the coil forming portion is substantially a right angle.

  The end surfaces are formed in parallel, or the end surfaces on the outer peripheral surface side of the base material at the end surfaces are widened, the end portions on the inner peripheral surface side are narrowed, and the end surfaces are slightly parallel to each other. It is characterized by being formed in an outwardly opening shape.

  A core having a shape obtained by cutting a part of a closed curve as a whole is characterized by comprising at least two pieces.

  The current flowing through the coil is direct current or alternating current, and in any case, the current is conducted to each coil so that the magnetic fields excited at both ends of the core are in phase.

  The current flowing through the coil is supplied intermittently for a preset time, and the magnetic field is generated and stopped periodically.

  A driving power is supplied to the magnetic disk storage device, and the magnetic disk housed in the device is rotated.

  The magnetic storage medium is provided with positioning means for facilitating the influence of the magnetic force generated by the electric magnetic field generator.

  According to the present invention, magnetic information recorded on a used magnetic recording medium, in particular, a magnetic disk storage device can be easily and reliably erased in a short time. Even if the information is transferred to a third party, the magnetic information recorded during use is not read out, and the magnetic disk storage device can be discarded without worrying about information leakage.

字形で平坦な正面を有し、この面を該面に対して垂直に所定量引き延ばして得られる立体形状に形成され主として二つのコイル形成部(2a)(2a)と、このコイル形成部(2a)(2a)の一端同士を繋ぐ略円弧形状部(５)と、該コイル形成部(2a)(2a)の他端それぞれに形成される計二つの突条部(６)(６)と、これら二つの突条部(６)(６)それぞれの先端である計二つの端面(４)(４)と、この端面(４)(４)間に形成されるギャップ(７)とからなる。尚、該ギャップ(７)の幅は、被消磁対象物を載置可能な幅であれば良く、特に限定されるものではない。又、図１０に示すように端面(４)における基材の外周面側の端部間(ｄ)を広くし、内周面側の端部間(ｄ')を狭くして、両端面(４)間を平行よりも若干外開き状に形成しても良い。 A method for erasing magnetic information recorded on a magnetic recording medium according to the present invention, particularly a magnetic disk storage device (hereinafter simply referred to as HDD), will be described in detail with reference to the drawings. FIG. 1 is a schematic circuit diagram of an apparatus according to the erasing method of the present invention. (1) is an electric magnetic field generator, and the front shape having two end faces (4) and (4) is a part of a closed curve as a whole. A coil (3) is wound around a core (2) having a shape obtained by cutting off a wire. The core (2) is made of a ferromagnetic base material and has a substantially frontal shape.

It has a letter-shaped and flat front surface, and is formed into a three-dimensional shape obtained by extending this surface by a predetermined amount perpendicular to the surface, and mainly two coil forming portions (2a) (2a), and this coil forming portion (2a ) (2a), a substantially arc-shaped portion (5) that connects one ends of the two, and a total of two protrusions (6), (6) formed on the other ends of the coil forming portions (2a) (2a), The two ridges (6) and (6) are composed of two end faces (4) and (4), which are the respective tips, and a gap (7) formed between the end faces (4) and (4). The width of the gap (7) is not particularly limited as long as the object to be demagnetized can be placed thereon. Further, as shown in FIG. 10, the end surface (4) has a wide end portion (d) between the outer peripheral surface sides of the base material and a narrow end portion (d ') between the inner peripheral surface sides. 4) The gap may be formed in a slightly outward shape rather than parallel.

  (13) is a main timer for determining the total power supply time to the electric magnetic field generator (1). The main timer (13) includes a start switch (17), an energizing time setting timer (14) and a pause. The time setting timer (15) and magnet switch (16) are connected. Reference numeral (10) denotes a sub power supply that supplies drive power to the HDD (30) via the connector (20) and also supplies drive power to the magnetic sensor (18). A magnetic force meter (19) is connected to the magnetic sensor (18). (11) is a capacitor, and stores electric power to avoid this in the case where power shortage occurs when the electric magnetic field generator (1) is driven. A cooling fan (17) operates in conjunction with the main switch (8) to cool the magnetic field generator (1). In order to prevent magnetic leakage when an object to be demagnetized is placed on the device, the device is provided with a lid, and a limit switch (21) linked to opening and closing of the lid is provided. The power supply to the circuit is preferably controlled by a relay switch (12) that detects on / off.

  As described above, the electric magnetic field generator (1) has a shape in which the front surface shape is partially cut off as a whole, and excites in-phase magnetic fields on the two end surfaces (4) and (4). Therefore, the magnetic forces generated from the two end faces (4) and (4) repel each other in the gap, and almost all the magnetic flux lines emitted from the end face (4) as shown in FIG. It becomes a magnetic flux line (23) that passes through the portion (2b) and moves in parallel toward the substantially arc-shaped portion (5). By using a ferromagnetic material such as a grain-oriented electrical steel sheet as a material for forming the core, it is generated in the gap compared to the case where the core is formed by laminating steel sheets punched into an arbitrary shape as in the past. The magnetic force can be very strong.

字形に形成してなるコア(２)の一端面(４)の近傍の様子を図８に示した。この図においては、方向性電磁鋼板(Ｂ)を巻回した巻鉄心の巻数は８回巻きとなっているが勿論、巻数は方向性電磁鋼板(Ｂ)の厚み等に応じて任意に採ることが出来何等限定されない。図８に示すように、この図におけるコア(２)の端面(４)は、巻鉄心の一部を切除して有限の長さの突条部(６)を存して該端面(４)を形成して構成されるが、端面(４)は、図９に示すように突条部(６)の長さを零とするように巻鉄心の一部を切除して端面(4')を形成しても良い。つまり、突条部(６)の長さは零から所定の有限の長さに採ることが出来、その先端である切断面を端面(４)又は(4')とする。 In the present invention, a part of a wound iron core formed by winding the grain-oriented electrical steel sheet that is preferably used is cut out and substantially

FIG. 8 shows a state in the vicinity of one end face (4) of the core (2) formed in a letter shape. In this figure, the number of turns of the wound iron core around which the grain-oriented electrical steel sheet (B) is wound is eight, but of course the number of turns is arbitrarily selected according to the thickness of the grain-oriented electrical steel sheet (B). There is no limitation. As shown in FIG. 8, the end surface (4) of the core (2) in this figure has a protruding portion (6) of a finite length by cutting off a part of the wound iron core and the end surface (4). As shown in FIG. 9, the end face (4 ') is formed by cutting a part of the wound iron core so that the length of the protrusion (6) is zero, as shown in FIG. May be formed. That is, the length of the protrusion (6) can be set from zero to a predetermined finite length, and the cut surface which is the tip thereof is defined as the end surface (4) or (4 ′).

  FIG. 2 is a diagram showing the magnetic field generated at a certain moment when a direct current or alternating current is conducted to the electric magnetic field generating device and the magnetic field generated around the device. It was created by a simulator. A coil (3) is formed by winding a conducting wire from the upper end to the lower end of the coil forming part (2a) in a uniform manner, and each of the lines schematically described inside and outside the core (2) It represents a magnetic flux line (23). As can be seen from this figure, in the coil forming portion (2a) of the core (1), the magnetic flux lines (23) are parallel and have the highest density in the strongest magnetic field region, and then both coil forming portions. The space (2b) between (2a) and (2a) is a magnetic field region in which the magnetic flux lines (23) are parallel and considerably dense and high in intensity, and the magnetic field in the space around the outer peripheral surface of the core (2) It can be seen that the magnetic flux lines (23) are curved and have a low density and a relatively weak magnetic field. Moreover, how to wind the conducting wire in the coil forming portion (2a) is not limited in any way, and it is preferable to appropriately form the coil (3) as necessary.

字形に形成されるコア(２)が、左右同形の略Ｌ字形の二つの部片(2')から構成され、これら二つの略Ｌ字形部片(2')をそれぞれ図５に示すように対向させて全体として略

字形をなすように配置し、コイル(３)の巻き方や配線及び電流の流し方は上記説明と同等に行うのである。このようにして、一部品から構成されるコア(２)の場合とほぼ同等の磁界を生成することが出来る。 The apparatus can be configured as shown in FIG. 5 as being capable of generating a magnetic field substantially similar to the magnetic field shown in FIG. That is, the front shape is almost as a whole.

The core (2) formed in a letter shape is composed of two substantially L-shaped pieces (2 ') having the same left and right shape, and these two substantially L-shaped pieces (2') are respectively shown in FIG. Opposite as a whole

They are arranged in a letter shape, and the winding method of the coil (3), the wiring, and the current flow method are carried out in the same manner as described above. In this way, it is possible to generate a magnetic field substantially equivalent to the case of the core (2) composed of one component.

  As for the current supplied to the coil (3), AC power is supplied in the illustrated case, but it is also possible to supply DC power. Even when either AC or DC power is supplied, the directional magnetic steel sheet is used for the electric magnetism generator as described above, so the maximum magnetic force can be generated immediately after the power supply. In addition, it is possible to instantaneously and greatly affect the HDD to be erased. Thus, by using the present invention, the magnetic information recorded on the HDD can be erased in one second to several seconds. In addition, since the power supply time to the coil (3) can be set from 1 second to several seconds by the main timer (13), there is no waste of supplying more power than necessary, and the recording information can be saved with less power consumption. Can be erased.

  Hereinafter, an erasing method for a magnetic disk storage device (HDD) will be described as an erasing method of a magnetic recording medium using the erasing device of the present invention. First, as shown in FIGS. 3 and 4, the magnetic disk (31) housed in the HDD is placed so as to come in the gap (8) of the electric magnetic field generator (1). Preferably, the spindle motor (33) formed at the center of the magnetic disk (31) is placed so as to be substantially at the same position as the outer peripheral surface of the core. At the same time, it is desirable to connect the power connector (20) to supply drive power to the HDD so that the HDD is in the drive state (the magnetic disk is rotating).

  After the HDD is placed in the gap and it is confirmed that the HDD is placed at an appropriate position with respect to the magnetic field generator (1), the pilot lamp (9) is turned on by turning on the main switch (8). Electric power is supplied to the sub power source (10), the capacitor (11), and the relay switch (12), and the HDD and the cooling fan are in operation. Therefore, in this state, no power is supplied to the magnetic field generator (1) and the HDD is not affected by the magnetic force. For example, if the relay switch (12) senses the opening / closing of the magnetic shielding cover of the device, it can supply power to the subsequent circuit only when the cover is closed, preventing magnetic leakage from the device and ensuring safety. Can be considered. The capacitor (11) is for absorbing and complementing the voltage drop at the start of operation of the magnetic field generator (1), fluctuations in the power supply voltage, etc., and supplying stable power to the magnetic field generator (1). (13) is a main timer, which sets the total operating time for erasure. (14) is a pause timer, and (15) is an energization timer, which controls the power supply OFF and ON times to the electric magnetic field generator (1). (16) is a magnet switch, which controls the power supply to the magnetic field generator (1) according to the energization time controlled by each timer.

  The main timer (13), pause timer (14), and energization timer (15) are set to 30 seconds, 6 seconds, and 1 second as initial settings, and the energization / pause process is repeated about 5 times. The magnetic field generator (1) of the present invention can instantaneously generate a large magnetic force and affect the magnetic disk (31), and the magnetic disk is in a rotating state. The recording surface passes through the magnetic field about 60 times, and it is possible to erase the recorded data by energizing for 1 second, but the magnetic data will return to the state it had before receiving the magnetic force with time. In order to prevent this, the time setting is suitable for generating magnetic force about five times and completely erasing the data of the magnetic material. Needless to say, these set times can be arbitrarily set again.

  In the erasing procedure, after the HDD is completely installed and the device cover (not shown) is closed, the main switch (8) is turned on and the start switch (17) is pushed. Receiving this, the main timer (13) performs an ON operation for a preset time (for example, 30 seconds), and power is supplied to the pause timer (14). Since the pause timer repeats ON / OFF every set time (for example, 6 seconds), power is supplied to the energization timer (15) only when it is ON. The energization timer performs an energization operation for a set time (for example, 1 second) after power is supplied. With these combinations, the magnet switch (16) is energized in a cycle of 1 second → 5 seconds of rest → 1 second of energization and 6 seconds cycle for 30 seconds, a total of 5 times. According to the operation of the magnet switch (16), generation of magnetic force is periodically repeated to apply magnetic force to the HDD.

As shown in FIG. 2, the magnetic field generator (1) that is energized by the ON operation of the magnet switch (16) has a magnetic force released from one core end face (4) released from the opposite core end face. After repulsion near the center of the gap with the magnetic force, almost all the magnetic force passes through the central space portion (2b) of the core and generates a magnetic flux line (23) that moves in parallel toward the substantially arc-shaped portion (5). In this embodiment, since the AC power is supplied to the magnetic field generator (1), the direction of the magnetic force generated in the gap (7) is reversed in accordance with the frequency. Even if it exists, the shape of the magnetic force generated is the same. The magnetic force generated in the gap has the property that if a substance having a magnetizing property such as a magnetic substance exists, it passes through the material as a path while affecting the substance, and flows to the other magnetic pole. For this reason, the magnetic force released from the end face (4) is attracted to the magnetic material applied to the surface of the magnetic disk (31) housed in the HDD (30), passes through the magnetic material, and then enters the core space. After that, it flows to the core facing the gap.

  As described above, the magnetic flux line repels the magnetic force emitted perpendicularly from the end face in the vicinity of the gap (7), and the central space portion (2b) has a substantially arc-shaped portion (parallel to the coil forming portion (2a)). The shape is suitable for 5). Therefore, taking the (A) part of the magnetic disk (31) in FIG. 3 as an example, the magnetic material in the vicinity of the spindle motor (32) of the magnetic disk (31) is placed on the disk surface released from the end face (4). On the other hand, the magnetic body in the vicinity of the outer periphery is affected by the magnetic force in the direction parallel to the disk surface. Further, in the middle periphery between the inner periphery and the outer periphery, the magnetic disk surface is affected by the magnetic force flowing inclined from the end surface. Furthermore, since the drive power is supplied to the HDD (20), the magnetic disk (21) is rotating. Accordingly, the part (A) moves to the part (A ') after a certain time, and here, both the vicinity of the inner periphery and the vicinity of the outer periphery are affected by the magnetic force in a direction substantially perpendicular to the magnetic disk surface. As described above, the magnetic body is affected by the magnetic force in the direction of constantly changing in the vertical, inclined, and horizontal directions with respect to the magnetic disk surface as the disk rotates at all locations on the magnetic disk. The vicinity of the spindle motor always receives a magnetic force in the direction perpendicular to the disk surface, but the magnetic material for recording magnetic information does not exist in this vicinity, and exists from a position slightly moved in the circumferential direction. Yes. Therefore, even a magnetic body existing near the center does not always receive a vertical magnetic force but receives a magnetic force from various directions such as vertical, inclined, and horizontal.

  The amount of magnetic force generated in the gap (7) varies depending on the amount of a magnetized substance such as a magnetic material existing in the space. When the permanent magnets facing each other are arranged as in the prior art, and the magnetic disk is arranged between the magnets, there is a magnetic material that becomes the path of magnetic force only for the thickness applied to the front and back of the disk. Therefore, the flowing magnetic force is very small. On the other hand, by arranging the magnetic disk in the gap (7) as in the present invention, a magnetic body having a distance comparable to the disk radius from the center of the magnetic disk to the circumference serves as a magnetic force flow path. A large amount of magnetism flows with little loss. As a result, the magnetic material applied to the surface of the magnetic disk by a large amount of magnetic force is greatly affected.

  When the electric magnetic field generator (1) is wound with a strip-shaped directional electromagnetic steel sheet, it is generated on the end face (4) even when there is no magnetic material in the air gap. The magnetic force emitted from the end face is very small, and almost all the magnetic force is emitted toward the center of the gap. Therefore, compared with a conventional erasing apparatus using a permanent magnet, the magnetic material applied to the magnetic disk (31) is greatly affected. Although the direction of the magnetic force always changes due to AC power, the same effect can be obtained when a magnetic force generated in the opposite direction flows.

  As described above, since power is supplied to the HDD (30) via the connector (20) to bring the HDD (30) into operation and the magnetic disk (31) is rotated, the magnetic disk (31) is rotated. The magnetic material can pass through a magnetic field having magnetic forces in various directions such as perpendicular, inclined, and horizontal with respect to the disk surface, and some of the magnetic materials on the magnetic disk (31) are affected by the magnetic force. It does not receive and does not retain magnetic information. Since the HDD normally rotates at about 3000 to 7000 rpm, it passes through the magnetic field about 50 to 110 times per second. Further, since the magnetic disk (31) is rotating, the direction of the magnetic force applied to the magnetic material applied to the magnetic disk (31) differs depending on the rotational position. In the vicinity of the gap (7), a magnetic force perpendicular to the disk surface is received. However, when the gap is subsequently rotated and the core space is reached, a magnetic force horizontal to the disk surface in the direction of the center → circumference is received. It will be. Also, depending on the location, the magnetic body is affected by the magnetic force from various directions, such as receiving a magnetic force that is inclined with respect to the disk surface. It will be in the state of facing. That is, it is possible to erase the recorded information according to the present invention regardless of the recording method regardless of the recording method of the HDD (perpendicular magnetic recording method, horizontal magnetic recording method, etc.).

  The magnetic field generator (1) that generates the magnetic force is a large magnet as a whole, and a magnetic force that repels the gap is generated. Therefore, the HDD (30) placed in the gap causes an amplitude motion. . Therefore, it is preferable to provide means for suppressing the amplitude of the HDD. However, this presser means may be one that completely fixes the HDD so as not to swing it, but it preferably leaves the gap while allowing a slight amplitude operation in the gap portion (7). There may be no fixing method. With this configuration, the magnetic disk receives a magnetic force in a direction perpendicular to the disk surface and a magnetic force in a horizontal direction, and when the disk surface is inclined with respect to the end surface, the magnetic disk is In a scene that is affected by the magnetic force of the magnetic field, the timing of receiving a magnetic force in a slightly tilted direction other than perpendicular occurs, and as a result, the magnetic material is affected by the magnetic force from countless directions, and the previously recorded magnetic field The information will be completely erased.

  In the electric magnetic generator (1) of the present invention, almost all of the magnetic force released from the end surface of the core is guided to the space in the core and there is almost no magnetic force to leak, but no magnetic leakage occurs to the surroundings. For this reason, it is desirable to take anti-magnetic measures around the device. For example, an intermediate plate (35) having a non-magnetic property such as a wooden board as shown in FIG. 11 is sandwiched between an inner plate (34a) and an outer surface plate (34b) having a magnetic property, such as an iron plate. It is preferable to make a three-layer structure in which is covered with an upper plate (36) having a magnetic property such as iron. The lower end of the housing panel (33) has a structure in which the outer plate (34b) is bent toward the inner plate (34a), and even if the outer plate (34b) becomes magnetized, it is released from the end. The magnetic force is released in the device housing direction.

  Even if a strong magnetic force is released by the electric magnetic field generator (1) by using the casing panel for each side, top, bottom, back and cover of the apparatus, almost no magnetic force is generated outside the casing. Leakage does not occur, and it is possible to achieve magnetic leakage lower than the magnetic shielding standard defined in household equipment such as televisions and microwave ovens. Therefore, it is possible to carry this apparatus and erase the magnetic recording information of the HDD at an arbitrary place.

The figure which shows the circuit schematic of the erasing apparatus of this invention Diagram showing magnetic field distribution The figure which shows the positional relationship of a magnetic field generator and HDD Diagram showing relationship between HDD and magnetic field Diagram showing one deformation of the core The figure which shows how to wind insulation covering conducting wire and the wiring method of this conducting wire FIG. 6 shows a variation of FIG. Front enlarged view of the vicinity of one end face of a core formed by winding a grain-oriented electrical steel sheet The figure which shows the deformation | transformation of FIG. Diagram showing one deformation of the core end face Sectional view of the housing panel

Explanation of symbols

(1) Electric magnetic field generator
(2) Core
(2 ') Core
(2a) Coil winding part
(2b) Central space
(3) Coil
(4) End face
(4 ') end face
(5) Substantially arc-shaped part
(6) Projection
(7) Gap
(8) Main switch
(9) Pilot lamp
(10) Sub power supply
(11) Capacitor
(12) Relay switch
(13) Main timer
(14) Pause timer
(15) Energization timer
(16) Magnet switch
(17) Cooling fan
(18) Magnetic sensor
(19) Magnetic field indicator
(20) Power connector
(21) Limit switch
(30) Hard disk device
(31) Magnetic disk
(32) Spindle motor
(34) Device housing panel
(34a) Inner plate
(34b) External plate
(35) Intermediate plate
(36) Upper cover
(B) Oriented electrical steel sheet

Claims (37)

  A gap is formed between the core having a shape in which a part of the closed curve is cut as a whole and a cut end surface of the core, and electrical insulation is performed from a position near the both end faces to a position near the midpoint of the core. Including an electric magnetic field generating means having two coils formed by winding a conducting wire capable of conducting an electric current inside the layer, wherein a magnetic recording medium which is an object to be demagnetized exists in the gap, and the gap is formed A method for erasing magnetic information recorded on a magnetic recording medium, wherein magnetic information recorded on the magnetic recording medium is erased by a magnetic force moving through the magnetic recording medium.   The core is formed in a shape in which the end surfaces are arranged substantially opposite to each other while forming a gap between end surfaces formed by cutting and removing a part of a base material whose front shape is a closed curve. A method for erasing magnetic information recorded on a magnetic recording medium according to 1.   3. The method for erasing magnetic information recorded on a magnetic recording medium according to claim 1, wherein the shape formed by cutting out a part of the closed curve as a whole is substantially U-shaped.   3. The method for erasing magnetic information recorded on a magnetic recording medium according to claim 1, wherein the shape formed by cutting out a part of the closed curve as a whole is substantially C-shaped.   5. The method for erasing magnetic information recorded on a magnetic recording medium according to claim 1, wherein the base material is composed of a grain-oriented electrical steel sheet as a main material.   6. The magnetic information recorded on the magnetic recording medium according to claim 1, wherein the closed curved base is a wound iron core formed by winding a grain-oriented electrical steel sheet. Way for.   The method for erasing magnetic information recorded on a magnetic recording medium according to claim 1, wherein the front shape of the portion forming the coil of the core is a linear shape.   8. The magnetism according to claim 1, wherein the inner peripheral surface of the coil forming portion of the core has a planar shape, and the inner peripheral surfaces of the two coil forming portions are parallel to each other. A method for erasing magnetic information recorded on a recording medium.   The magnetic recording medium according to any one of claims 1 to 8, wherein both end faces are formed with ridges projecting from the inner end of the coil forming portion of the core so as to face each other. A method for erasing recorded magnetic information.   10. The method for erasing magnetic information recorded on a magnetic recording medium according to claim 1, wherein the narrow angle between the protrusion and the coil forming portion is substantially a right angle.   The method for erasing magnetic information recorded on a magnetic recording medium according to claim 1, wherein the end faces are formed in parallel.   The gap between the end portions on the outer peripheral surface side of the base material on the end surface is widened, the end portion on the inner peripheral surface side is narrowed, and the gap between both end surfaces is formed to be slightly outwardly open rather than parallel. Item 11. A method for erasing magnetic information recorded on a magnetic recording medium according to any one of Items 1 to 10.   The magnetic information recorded on the magnetic recording medium according to any one of claims 1 to 12, wherein the core formed by cutting a part of the closed curve as a whole is composed of at least two pieces. A way to erase.   14. The method for erasing magnetic information recorded on a magnetic recording medium according to claim 1, wherein the current passed through the coil is a direct current.   14. The method for erasing magnetic information recorded on a magnetic recording medium according to claim 1, wherein the current flowing through the coil is an alternating current.   The magnetic recording medium according to any one of claims 1 to 15, wherein a current flowing through the coil is intermittently supplied for a preset time to generate and stop a magnetic field periodically. A method for erasing recorded magnetic information.   17. A method for erasing magnetic information recorded on a magnetic recording medium according to claim 1, wherein the magnetic recording medium is a magnetic disk storage device (hard disk device).   18. To erase magnetic information recorded on a magnetic recording medium according to claim 17, wherein driving power is supplied to the magnetic disk storage device, and the magnetic disk stored in the device is rotated. the method of.   19. The magnetic recording medium according to claim 1, further comprising positioning means for making the magnetic storage medium susceptible to a magnetic force generated by an electric magnetic field generator. A method for erasing magnetic information.   A gap is formed between the core having a shape in which a part of the closed curve is cut as a whole and a cut end surface of the core, and electrical insulation is performed from a position near the both end faces to a position near the midpoint of the core. Including an electric magnetic field generating means having two coils formed by winding a conducting wire capable of conducting an electric current inside the layer, wherein a magnetic recording medium which is an object to be demagnetized exists in the gap, and the gap is formed An apparatus for erasing magnetic information recorded on a magnetic recording medium, wherein magnetic information recorded on the magnetic recording medium is erased by a magnetic force moving through the magnetic recording medium.   The core is formed in a shape in which the end surfaces are arranged substantially opposite to each other while forming a gap between end surfaces formed by cutting and removing a part of a base material whose front shape is a closed curve. An apparatus for erasing magnetic information recorded on the magnetic recording medium according to 20.   The apparatus for erasing magnetic information recorded on a magnetic recording medium according to claim 20 or 21, wherein the shape formed by cutting out part of the closed curve as a whole is substantially U-shaped.   The apparatus for erasing magnetic information recorded on a magnetic recording medium according to claim 20 or 21, wherein the shape formed by cutting out part of the closed curve as a whole is substantially C-shaped.   The method for erasing magnetic information recorded on a magnetic recording medium according to any one of claims 20 to 23, wherein the base material is composed of a grain-oriented electrical steel sheet as a main material.   25. The magnetic information recorded on the magnetic recording medium according to claim 20, wherein the closed curved base is a wound iron core formed by winding a grain-oriented electrical steel sheet. Way for.   The method for erasing magnetic information recorded on a magnetic recording medium according to any one of claims 20 to 25, wherein a front shape of a portion of the core forming the coil is a linear shape.   27. The magnetism according to claim 20, wherein the inner peripheral surface of the coil forming portion of the core has a planar shape, and the inner peripheral surfaces of the two coil forming portions are parallel to each other. A method for erasing magnetic information recorded on a recording medium.   The magnetic recording medium according to any one of claims 20 to 27, wherein both end faces are formed with protruding ridges protruding opposite to each other from the inner end of the coil forming portion of the core. A method for erasing recorded magnetic information.   29. A method for erasing magnetic information recorded on a magnetic recording medium according to any one of claims 20 to 28, wherein the narrow angle between the protrusion and the coil forming portion is substantially a right angle.   30. The method for erasing magnetic information recorded on a magnetic recording medium according to claim 20, wherein the end faces are formed in parallel.   The gap between the end portions on the outer peripheral surface side of the base material on the end surface is widened, the end portion on the inner peripheral surface side is narrowed, and the gap between both end surfaces is formed to be slightly outwardly open rather than parallel. Item 31. A method for erasing magnetic information recorded on a magnetic recording medium according to any one of Items 20 to 30.   32. The magnetic information recorded on the magnetic recording medium according to claim 20, wherein the core having a shape obtained by cutting out a part of the closed curve as a whole is composed of at least two pieces. A way to erase.   33. A method for erasing magnetic information recorded on a magnetic recording medium according to any one of claims 20 to 32, wherein the current passed through the coil is a direct current.   34. A method for erasing magnetic information recorded on a magnetic recording medium according to claim 20, wherein the current passed through the coil is an alternating current.   The magnetic recording medium according to any one of claims 20 to 34, wherein a current flowing through the coil is intermittently supplied with power for a preset time period to periodically generate and stop a magnetic field. A method for erasing recorded magnetic information.   36. A method for erasing magnetic information recorded on a magnetic recording medium according to claim 20, further comprising a sub power source for supplying driving power to the magnetic disk storage device. 37. The magnetic recording medium according to claim 20, further comprising positioning means for making the magnetic storage medium susceptible to a magnetic force generated by an electric magnetic field generator. A method for erasing magnetic information.

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