JP2004309172A - Electrostatic sensor using magnetoresistive head - Google Patents

Abstract

An object of the present invention is to measure the amount of electrostatic discharge generated by charging a magnetic recording medium with high accuracy under the same conditions as during actual reproduction.
An amount of electrostatic discharge generated by charging the magnetoresistive magnetic head by actually sliding the magnetic recording medium through a magnetoresistive element, amplifying the amount, and identifying it. For this purpose, the magnetoresistive head is slid over the magnetic recording medium, and the current flowing through the resistance of the magnetoresistive element of the magnetoresistive head is extracted as a voltage using at least an amplifier circuit and a feedback resistor. The amount of electrostatic discharge generated by charging the magnetic recording medium is identified based on the extracted voltage.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is directed to an electrostatic sensor using a magnetoresistive magnetic head for measuring the amount of static electricity generated by charging of a magnetic recording medium, a method for detecting the amount of electrostatic discharge, and thermal noise in the magnetoresistive magnetic head. The present invention relates to an apparatus and a method for measuring a thermal noise of a magnetoresistive magnetic head to be measured.
[0002]
[Prior art]
For example, in a recording / reproducing apparatus using a magnetic tape as a recording medium, such as a video tape recorder or a digital data recorder, generally, the magnetic head is obliquely slid with respect to the magnetic tape running based on the helical scan method. To write and read signals.
[0003]
In such a recording / reproducing apparatus, high-density recording by shortening the wavelength of a recording signal has been actively promoted for the purpose of expanding data storage capacity and the like. In order to cope with such high-density recording, attempts have been made to apply a magneto-resistance effect type magnetic head (hereinafter referred to as an MR head) capable of obtaining high reproduction sensitivity as a reproduction head. Incidentally, this MR head has been widely used in a hard disk drive in which the head and the disk do not contact each other than before.
[0004]
This MR head has a structure in which a magneto-resistance effect element (hereinafter, referred to as an MR element) that exhibits a magneto-resistance effect is exposed from a surface facing a magnetic tape as a recording medium, and a signal from the magnetic tape is provided. The magnetic field is directly detected by this MR element. (For example, refer to Patent Document 1.)
[Patent Document 1]
JP 07-176018 A
[Problems to be solved by the invention]
By the way, in the above-mentioned recording / reproducing apparatus, since the MR head comes into contact with the magnetic tape running inside the apparatus, if an MR head having a structure in which the MR element is exposed on the recording medium side is applied as a reproducing head, Static electricity is generated on the magnetic tape due to friction, contact, peeling, and the like between the MR head and the tape. The accumulation of static electricity on the magnetic tape causes an electrostatic discharge (hereinafter referred to as ESD) between the magnetic tape and the MR head. Alternatively, externally generated ESD discharges to the MR head through the magnetic tape. In particular, when the MR head is handled while mounted on a head base, the terminals are open, and there is a problem that charges based on such static electricity are easily accumulated and are destroyed. In addition, there is a problem that heat is generated in the MR head by the generated static electricity, and so-called thermal noise is generated in a signal to be reproduced.
[0006]
For this reason, it is necessary to analyze the factor of the generation of static electricity by measuring the amount of electrostatic discharge generated by charging on the order of nanoampere, and to take measures for suppressing the above-described electrostatic breakdown and thermal noise.
[0007]
However, it has been difficult to measure the amount of electrostatic discharge generated by charging the magnetic tape on the order of nanoamps by sliding the MR head actually mounted on the rotating drum on the magnetic tape. In particular, high-precision data measured under the same conditions as during actual reproduction could not be obtained.
[0008]
The present invention has been devised in view of the above-described problems, and has as its object the purpose of making it possible to accurately measure the amount of electrostatic discharge generated by charging a magnetic recording medium under the same conditions as during actual reproduction. Sensor using magnetoresistive effect type magnetic head, method for detecting electrostatic discharge amount, and magnetoresistive effect for measuring thermal noise in magnetoresistive effect type magnetic head with high accuracy under the same conditions as during actual reproduction And a method of measuring thermal noise of a magnetic head.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventor has proposed a magneto-resistance effect type magnetic head, in which the amount of electrostatic discharge discharged to the head from the charging of the tape by actually sliding on the magnetic recording medium is changed to the magneto-resistance effect element. The present invention has invented an electrostatic sensor and an electrostatic discharge amount detecting method using a magneto-resistance effect type magnetic head which is taken out via a magnetic head and amplified and identified.
[0010]
That is, an electrostatic sensor using a magnetoresistive magnetic head to which the present invention is applied is composed of a magnetoresistive magnetic head sliding on a magnetic recording medium, at least an amplifier circuit and a feedback resistor, and is connected. Current-voltage conversion means for extracting a current flowing through the resistance of the magneto-resistance effect element of the magneto-resistance effect type magnetic head as a voltage; and static electricity generated by charging of a magnetic recording medium based on the voltage extracted by the current-voltage conversion circuit. And an identification means for identifying the amount of discharge.
[0011]
Further, the method for detecting the amount of electrostatic discharge to which the present invention is applied is characterized in that the magneto-resistance effect type magnetic head is slid on a magnetic recording medium and the magneto-resistance effect type magnetic head uses at least an amplifier circuit and a feedback resistor. The current flowing through the resistance of the effect element is extracted as a voltage, and the amount of static electricity generated by charging the magnetic recording medium is identified based on the extracted voltage.
[0012]
In order to solve the above-mentioned problems, the present inventor has proposed a magnetic resistance effect type magnetic head, in which thermal noise generated by sliding on a magnetic recording medium that actually travels is extracted through a magnetoresistive effect element. A device and method for measuring the thermal noise of a resistance effect type magnetic head have been invented.
[0013]
That is, the thermal noise measuring device for a magnetoresistive magnetic head to which the present invention is applied is composed of a magnetoresistive magnetic head that slides on a magnetic recording medium, at least an amplifier circuit and a feedback resistor, and is connected. Current-voltage converting means for extracting a current flowing through the resistance of the magneto-resistance effect element of the magneto-resistance effect type magnetic head as a voltage; Measuring means for measuring noise.
[0014]
The method for measuring the thermal noise of a magneto-resistance effect type magnetic head to which the present invention is applied is such that the magneto-resistance effect type magnetic head is slid on a magnetic recording medium, and at least an amplifier circuit and a feedback resistor are used. The current flowing through the resistance of the magnetoresistive element of the magnetic head is extracted as a voltage, and the thermal noise in the magnetoresistive head is measured based on the extracted voltage.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0016]
The present invention is applied to, for example, an electrostatic discharge amount measuring device 1 as shown in FIG. The electrostatic discharge amount measuring apparatus 1 generally includes a magneto-resistance effect type magnetic head (hereinafter, referred to as an MR head) 12 for reproducing a signal recorded on a magnetic tape 10 by a so-called helical scan method, and at least a magnetic tape. An electrostatic discharge amount measuring system 4 for measuring the amount of electrostatic discharge from the magnetic head 10 to the MR head 12 is provided. The rotating drum 11 of the electrostatic discharge amount measuring system 4 supports the magnetic tape 10 while traveling in the direction of arrow A in FIG. 1 is rotated through a shaft 15 in the direction of arrow B in FIG. 1, and a read-only MR head 12 mounted on the rotary drum 11 reproduces signals while sliding on the magnetic tape 10. I have.
[0017]
A fixed drum 13 is provided at a position facing the rotating drum 11 to form a so-called two-layer type drum. The rotating drum 11 has a current-voltage conversion circuit 17 connected to an MR head. Further, one end of a slip ring 18 connected to the current-voltage conversion circuit 17 is disposed on the support shaft 15, and an oscilloscope 19 is connected to the other end of the slip ring 18.
[0018]
The rotating drum 11 is formed in a substantially disk shape with a metal material such as aluminum, and is arranged so that the center thereof is fixed to the support shaft 15 and is rotatable. The rotating drum 11 is formed such that the thickness of the support shaft in the axial direction is about の of the tape width of the magnetic tape 10. The rotating drum 11 is provided with one or more MR heads 12 with their tips slightly projecting outward from openings provided in the outer peripheral surface.
[0019]
The MR head 12 reads a signal recorded on the magnetic tape 10 by using a magnetoresistance effect of a magnetoresistance effect element (hereinafter, referred to as an MR element). An MR element is a type of resistance element, and its electric resistance changes according to a change in an external magnetic field such as a signal magnetic field recorded on a magnetic recording medium. That is, the MR head 12 reads a signal recorded on the magnetic recording medium by utilizing the fact that a current flows through the MR element and the value of the current flowing through the MR element changes according to the signal magnetic field from the magnetic recording medium. . Since the MR element has high sensitivity to the amount and direction of the magnetic flux, the MR head 12 can read signals at a high linear density.
[0020]
The fixed drum 13 is formed by molding a metal material such as aluminum into a substantially disk shape having a predetermined thickness. Further, a tape guide groove (not shown) for maintaining a posture when the magnetic tape 10 slides is formed on the outer peripheral surface. Since the magnetic tape 10 is wound around the outer peripheral surfaces of the rotating drum 11 and the fixed drum 13 along the tape guide groove, the magnetic tape 10 can run at a predetermined angle with respect to a direction orthogonal to the support shaft 15. it can.
[0021]
The current-voltage conversion circuit 17 extracts a current flowing through the MR element of the MR head 12 as a voltage, and amplifies the voltage. As shown in FIG. 2, for example, the current-voltage conversion circuit 17 includes an amplifier 31 having an input terminal connected to the MR head 12, a feedback resistor 32 connected in parallel to the amplifier 31, an output terminal of the amplifier 31, and a feedback terminal. A buffer circuit 33 connected to the resistor 32.
[0022]
That is, by controlling the resistance value of the feedback resistor 32 in the current-voltage conversion circuit 17, even if the current flowing through the resistor 30 of the MR element is on the order of nanoampere, it can be amplified and converted into a voltage. Incidentally, the feedback resistor 32 may be freely controlled by the user himself according to the amount of electrostatic discharge to be measured.
[0023]
The slip ring 18 is a device for transmitting a signal between the amplifier 17 inscribed in the rotating drum 11 as a rotating body and an oscilloscope 19 as a fixed body.
[0024]
The oscilloscope 19 is a device for allowing a user to identify a temporal change in a signal transmitted through the slip ring 18. In the oscilloscope 19, by applying a voltage based on the transmitted signal to the coil, the irradiated electron beam can be deflected, and a signal waveform can be displayed on a screen. As an alternative to the oscilloscope 19, another voltmeter or the like may be used.
[0025]
The magnetic tape 10 includes a linear track on which management information and the like are recorded, and a helical track on which information signals such as video to be reproduced are recorded. Incidentally, in order to use the magnetic tape 10 only as a sample for comparing the detected electrostatic discharge amount, for example, a plurality of types of tapes having different surface resistances may be used.
[0026]
Next, the operation of the electrostatic discharge measuring device 1 to which the present invention is applied will be described with reference to FIG.
[0027]
First, the rotating drum 11 of the electrostatic discharge amount measuring system 4 is rotationally driven in the direction of arrow B in FIG. 3 by running the magnetic tape 10 in the direction of arrow A in FIG. Since the MR head 12 protruding from the outer peripheral surface of the rotating drum 11 contacts the running magnetic tape 10 and slides obliquely, the friction, contact, separation, etc. between the MR head 12 and the magnetic tape 10 cause Static electricity is charged on the tape 10, and furthermore, based on the static electricity, an electrostatic discharge (hereinafter, referred to as ESD) occurs between the magnetic tape 10 and the MR head 12. Further, a current i flows through the resistor 30 of the MR element in the MR head 12 due to the ESD.
[0028]
Therefore, in the electrostatic discharge amount measuring apparatus 1 to which the present invention is applied, the current flowing through the resistor 30 of the MR element is taken out as a voltage and identified to measure the amount of electrostatic discharge generated by charging the magnetic tape 10. I do. That is, the current-voltage conversion circuit 17 amplifies the discharge amount i until the current value becomes imr, converts this to current-voltage, and displays it on the screen of the oscilloscope 19, thereby obtaining a peak as shown in FIG. . By analyzing this peak, the voltage value obtained by the current-voltage conversion can be identified with high accuracy, and the amount of electrostatic discharge generated by charging the magnetic tape 12 can be identified.
[0029]
As described above, according to the present invention, by mounting the MR head 12 used for normal reproduction on the rotating drum 11, the amount of electrostatic discharge can be measured under the same conditions as during actual reproduction. Therefore, according to the present invention, the amount of electrostatic discharge generated by charging the magnetic tape 10 during the actual reproduction of the reproducing apparatus, and hence the amount of electrostatic discharge, can be obtained with high accuracy.
[0030]
In particular, in the present invention, the resistance value of the feedback resistor 32 constituting the current-voltage conversion circuit 17 can be freely controlled. For this reason, since the amount of electrostatic discharge generated by charging is very small, even when only nanoampere-order ESD occurs, it can be extracted and measured with high precision, and the mechanism of ESD generation Can be analyzed.
[0031]
The present invention is not limited to the above-described embodiment. For example, as shown in FIG. 4, when measuring the amount of electrostatic discharge, the magnetic tape 10 is connected to a metal guide 42 connected to a power supply 41. The contact may be performed after the surface of the magnetic tape 10 is charged in advance. This makes it possible to compare the amount of electrostatic discharge measured with the magnetic tape that is not charged.
[0032]
Further, in the above-described embodiment, the magnetic tape 10 has been described as an example of the magnetic recording medium. However, the present invention may be applied to a magnetic head for executing a reproducing process of another recording medium such as a magnetic disk.
[0033]
Further, in the present invention, by measuring the ESD at the same time as the normal reproduction, the ESD during the reproduction may be monitored in real time. In such a case, when the discharge amount based on the ESD exceeds a certain value, an alarm may be issued to alert the user.
[0034]
Further, the present invention is not limited to the above-described embodiment, and may be applied as a thermal noise measuring device and method for measuring thermal noise generated in an MR head based on the amount of electrostatic discharge measured as described above. Good. Since this thermal noise is based on heat due to static electricity generated on the MR head 12, the relationship between the amount of electrostatic discharge and the thermal noise is measured in advance and measured in the nanoamp order by the above-described method. Thermal noise can be determined from the amount of electrostatic discharge generated. For this reason, it is possible to measure the thermal noise generated under the same conditions as in the actual reproduction with high accuracy, and it is possible to easily analyze the mechanism of the thermal noise generation.
[0035]
【The invention's effect】
As described above in detail, in the electrostatic sensor and the electrostatic discharge amount detecting method using the magnetoresistive effect magnetic head to which the present invention is applied, the magnetoresistive effect magnetic head is actually slid on the magnetic recording medium. As a result, the electrostatic discharge generated by charging is taken out through the magnetoresistive element, and amplified and identified.
[0036]
Thus, the apparatus and method for measuring the amount of electrostatic discharge of a magnetoresistive magnetic head to which the present invention is applied can measure the amount of electrostatic discharge generated by charging the magnetic recording medium under the same conditions as during actual reproduction. It is possible to analyze the generated ESD on the order of nanoamperes.
[0037]
As described above in detail, the apparatus and method for measuring the thermal noise of a magnetoresistive magnetic head to which the present invention has been applied can be performed by sliding the magnetoresistive magnetic head on a magnetic recording medium that actually travels. The generated thermal noise is extracted through the magnetoresistive element.
[0038]
Thus, the apparatus and method for measuring the amount of electrostatic discharge of a magnetoresistive magnetic head to which the present invention is applied can measure the amount of electrostatic discharge generated by charging the magnetic recording medium under the same conditions as during actual reproduction. Therefore, the generated thermal noise can be analyzed on the order of nanoamps.
[Brief description of the drawings]
FIG. 1 is a diagram for describing a configuration of an electrostatic discharge amount measuring device to which the present invention is applied.
FIG. 2 is a diagram illustrating details of a block configuration of an amplifier circuit.
FIG. 3 is a diagram for explaining an operation of the electrostatic discharge amount measuring device to which the present invention is applied.
FIG. 4 is a diagram for explaining another configuration of the electrostatic discharge amount measuring device to which the present invention is applied.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 electrostatic discharge measuring device, 10 magnetic tape, 11 rotating drum, 12 magnetoresistive magnetic head, 13 fixed drum, 15 spindle, 17 current-voltage conversion circuit, 18 slip ring, 19 oscilloscope

Claims (10)

A magnetoresistive head that slides on a magnetic recording medium;
Current-voltage conversion means, which comprises at least an amplifier circuit and a feedback resistor, and extracts a current flowing through the resistance of the magnetoresistive element of the connected magnetoresistive magnetic head as a voltage,
An identification means for identifying an amount of electrostatic discharge generated by charging of the magnetic recording medium based on a voltage taken out by the current-voltage conversion circuit. Sensors. 2. The magnetoresistive head according to claim 1, wherein said magnetoresistive head is mounted on a rotating drum and slides obliquely on a magnetic recording medium running based on a helical scan method. Was a static sensor. 2. The electrostatic sensor according to claim 1, wherein the amplification circuit has a variable amplification factor. 2. An electrostatic sensor according to claim 1, wherein said identification means identifies an amount of electrostatic discharge based on static electricity generated by said charging. The magneto-resistance effect type magnetic head is slid on the magnetic recording medium, and the current flowing through the resistance of the magneto-resistance effect element of the magneto-resistance effect type magnetic head is taken out as a voltage by using at least an amplifier circuit and a feedback resistor.
A method for detecting an amount of electrostatic discharge, characterized by identifying an amount of electrostatic discharge generated by charging the magnetic recording medium based on the extracted voltage. 6. A method according to claim 5, wherein said magnetoresistive head mounted on a rotating drum is slid obliquely on a magnetic recording medium running on the basis of a helical scan method. 6. The electrostatic discharge amount detecting method according to claim 5, wherein an amplification factor of the amplifier circuit is controlled according to a detected electrostatic discharge amount. 6. The method according to claim 5, wherein an amount of electrostatic discharge based on the static electricity generated by the charging is identified. A magnetoresistive head that slides on a magnetic recording medium;
Current-voltage conversion means, which comprises at least an amplifier circuit and a feedback resistor, and extracts a current flowing through the resistance of the magnetoresistive element of the connected magnetoresistive magnetic head as a voltage,
Measuring means for measuring thermal noise in the magnetoresistive head based on the voltage extracted by the current-to-voltage conversion circuit. Slide the magnetoresistive magnetic head over the magnetic recording medium,
Using at least an amplifier circuit and a feedback resistor, the current flowing through the resistance of the magnetoresistive element of the magnetoresistive head is taken out as a voltage,
A method for measuring thermal noise in a magnetoresistive magnetic head, comprising measuring thermal noise in the magnetoresistive magnetic head based on the extracted voltage.

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