JP3261934B2 - Estimation device for wear coefficient of magnetic head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head wear coefficient estimating apparatus capable of estimating the wear coefficient of a magnetic head in a short time without actually measuring the wear amount.

[0002]

2. Description of the Related Art In recent years, an apparatus for recording and reproducing information by contacting and running a magnetic head such as a VTR and a magnetic tape has been improved in image quality, long-time recording and downsizing. For example, in order to achieve high image quality and downsizing, a conventional magnetic head is made of single-crystal ferrite. A method of improving the magnetic characteristics of a magnetic head by improving the characteristics or bonding a thinned head material has been implemented. On the other hand, in a magnetic tape, a contact state with a magnetic head is improved by improving a surface state of the magnetic tape, or a magnetic property of a magnetic material applied to the magnetic tape is improved. Is changed from iron oxide to non-iron oxide to improve magnetic properties. Further, in order to realize long-time recording and downsizing, a method such as thinning a magnetic tape has been implemented.

However, all of these approaches change the form of friction and wear between the magnetic head and the magnetic tape from conventional ones. As a result, in developing such a magnetic head or magnetic tape, it has become essential to develop a method that can evaluate the wear characteristics of the magnetic head and the magnetic tape in a short time. Conventionally, the wear characteristics of a magnetic head and a magnetic tape are evaluated by a method in which the magnetic head and the magnetic tape are actually brought into contact for a certain period of time and then measured, for example, by measuring the shape of the magnetic head or measuring the mass of the magnetic head. I have been.

On the other hand, as a method of calibrating an output signal of a piezoelectric element, a method of dropping a hard sphere having a known mass and calibrating it by using its collision energy, and a method of using a release energy when bending the lead of a mechanical pencil are used. Calibration methods and the like have been performed.

[0005]

In such a conventional method for evaluating wear characteristics, in order to maintain sufficient measurement accuracy,
A long-term wear test had to be performed, and a large number of evaluations had to be performed due to the large individual differences in the form of wear.
Therefore, there has been a problem that a large amount of magnetic tape is required, and a large cost is required for evaluation. Also, in the conventional method of calibrating the output signal of the piezoelectric element, a new device is required for calibration, and when the input portion of the signal is very small like a magnetic head and the mechanical strength is small, There was a problem that it was very difficult.

The present invention has been made in view of the above points, and provides a magnetic head wear coefficient estimating apparatus capable of easily and quickly evaluating the wear characteristics of a magnetic head and a magnetic tape. The purpose is to do.

[0007]

In order to achieve the above object, the present invention provides a rotating cylinder having at least one magnetic head, and a tape running spirally wound around the rotating cylinder at a certain angle. A piezoelectric element mounted near the magnetic head or on a rotating cylinder, a signal transmitting means for extracting a signal from the piezoelectric element to the outside of the rotating cylinder, and an effective value measuring means for obtaining an effective value of an output voltage of the piezoelectric element. The effective value of the output voltage of the piezoelectric element and the hardness of the magnetic head, the perpendicular force applied to the magnetic head, the wear volume of the magnetic head, and the wear coefficient of the magnetic head obtained from the sliding distance between the magnetic head and tape The wear coefficient of the magnetic head is determined from the correlation diagram of FIG.

The present invention is also directed to a rotating cylinder having at least one magnetic head, a tape helically wound around the rotating cylinder at a predetermined angle and running, and a piezoelectric element mounted near the magnetic head or mounted on the rotating cylinder. When,
A rotating magnetic body made of a soft magnetic material that rotates integrally with the rotating cylinder and is wound with a first coil on a concentric circle with the rotation center of the rotating cylinder; and a predetermined gap between the rotating magnetic body and the rotating magnetic body. A fixed side magnetic body made of a soft magnetic material in which a second coil is wound and disposed at a position facing the first coil, and an effective value measuring means for obtaining an effective value of an output voltage of the piezoelectric element. Then, the effective value of the output voltage of the piezoelectric element and the hardness of the magnetic head, the perpendicular force applied to the magnetic head, the wear volume of the magnetic head, and the sliding distance between the magnetic head and the tape, which are determined in advance, are used. The wear coefficient of the magnetic head is determined from the correlation diagram with the wear coefficient.

Further, according to the present invention, a plurality of tapes having different abrasiveness are brought into contact with a magnetic head, and the effective value of the signal voltage of the piezoelectric element and the hardness of the magnetic head at that time, the perpendicular force applied to the magnetic head, Using the wear volume of the magnetic head and the wear coefficient obtained from the sliding distance between the magnetic head and the tape, a calibration formula for the effective value of the signal voltage of the piezoelectric element and the wear coefficient of the magnetic head is obtained, and the wear coefficient of the magnetic head is calculated. presume.

The present invention is also directed to a magnetic head, in which the same tape is repeatedly contacted and run a plurality of times, at which time the effective value of the signal voltage of the piezoelectric element and the hardness of the magnetic head, the perpendicular force applied to the magnetic head, and the magnetic head Using the wear volume of the magnetic head and the wear coefficient obtained from the sliding distance between the magnetic head and the tape, a calibration formula for the effective value of the signal voltage of the piezoelectric element and the wear coefficient of the magnetic head is obtained, and the wear coefficient of the magnetic head is estimated. .

Further, according to the present invention, the same tape is run in contact with a magnetic head in a plurality of humidity environments, and the effective value of the signal voltage of the piezoelectric element and the hardness of the magnetic head at that time, the perpendicular force applied to the magnetic head, Using the wear volume of the magnetic head and the wear coefficient obtained from the sliding distance between the magnetic head and the tape, a calibration formula for the effective value of the signal voltage of the piezoelectric element and the wear coefficient of the magnetic head is obtained, and the wear coefficient of the magnetic head is calculated. presume.

[0012]

With the magnetic head wear coefficient estimating apparatus of the present invention, it is possible to quickly and easily estimate the magnetic head wear coefficient without directly measuring the shape or mass of the magnetic head.

[0013]

【Example】

(Embodiment 1) An apparatus for estimating a wear coefficient of a magnetic head according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a principle diagram of an apparatus for estimating a wear coefficient of a magnetic head according to a first embodiment of the present invention. The head base 4 on which the magnetic head 2 is mounted is mounted on a rotary cylinder 5. FIG. 2 is a detailed view of the vicinity of the mounting portion of the piezoelectric element 1. Here, as shown in FIG. 2, the case where the piezoelectric element 1 is mounted on the head base 4 will be described. The piezoelectric element is an element that converts an applied pressure into an electric signal, such as an AE sensor (Acoustic emission sensor). The magnetic head 2 mounted on the head base 4 includes a rotary cylinder 5
The tape 3 protrudes from the outer peripheral surface 5a by several microns to several tens of microns, and the tape 3 is spirally wound around the rotary cylinder 5 and the fixed cylinder 6 at a predetermined angle, for example, 180 degrees. A slip ring support 7 is mounted on the upper surface of the rotary cylinder 5. A slip ring 8 having two or more channels is attached to the slip ring support 7 so that output from at least one piezoelectric element 1 can be taken out. A brush 9 having two or more channels is pressed against the slip ring 8 as in the case of the slip ring 8, so that the electric signal can be stably transmitted to the outside of the rotary cylinder 5 even when the rotary cylinder 5 rotates. It has become. If necessary, an effective value meter 13 as an effective value measuring means is connected via a high band amplifier 11 as a signal amplifying means and a filter 12 as a frequency limiting means. For example, a correlation diagram between the effective value of the output voltage of the piezoelectric element 1 and the wear coefficient of the magnetic head 2 as shown in FIG. 3 is prepared in advance. With the above configuration, the tape 3 is running by cooperation of a capstan shaft (not shown) and a pinch roller (not shown). Then, the rotating cylinder 5 on which the magnetic head 2 is mounted rotates with the rotation of the rotating shaft 10 so that the magnetic head 2 and the tape 3 slide. At this time, since the piezoelectric element 1 is mounted on the head base 4, the voltage according to the magnitude of the elastic wave generated in the magnetic head 2 due to the sliding of the magnetic head 2 and the tape 3 is output from the piezoelectric element 1. It occurs between terminals. This elastic wave is generated when, for example, wear particles fall off the sliding surface of the magnetic head 2 with the tape 3. An electric signal generated in the piezoelectric element 1 is guided to the slip ring 8. When extracting electric signals from a plurality of piezoelectric elements 1, it is sufficient that there are channels of the number obtained by multiplying the number of piezoelectric elements 1 by two. However, it is possible to use a common ground wire, so that the number of channels obtained by adding 1 to the number of piezoelectric elements 1 is sufficient. The wear coefficient of the magnetic head 2 can be estimated by reading the effective value of the signal voltage taken out by the slip ring 8 with the effective value meter 13 and comparing the value with, for example, a correlation diagram as shown in FIG. However, since this correlation diagram differs depending on the configuration of the present apparatus, it is necessary to obtain a specific one for the apparatus in advance. In the present embodiment, the case where the piezoelectric element 1 is mounted on the head base 4 has been described, but the mounting position of the piezoelectric element 1 is set to the position of the rotary cylinder 5 as long as the elastic wave generated in the magnetic head 2 can be observed. There is no problem even on the top surface. Although the method using the slip ring 8 and the brush 9 as the signal transmitting means has been described, any means may be used as long as a signal can be transmitted from the rotary cylinder 5 to the outside. Regarding the magnetic head 2 to be mounted, there is no problem in the function of the device even if a plurality of magnetic heads 2 are mounted. For example, a plurality of magnetic heads 2 are mounted, and the wear of each magnetic head 2 can be estimated by mounting the piezoelectric element 1 only on the magnetic head 2 for which the wear coefficient needs to be estimated. Generally, a plurality of magnetic heads are mounted on a rotating cylinder that actually records a video signal or the like. For it,
In particular, by mounting only one magnetic head 2 on the rotary cylinder 5, the following effects can be obtained. That is, since there is only one magnetic head 2, the piezoelectric element 1 does not detect an elastic wave caused by sliding of the tape 3 with another magnetic head 2. Therefore, there is an effect that the accuracy of estimating the wear coefficient of the magnetic head 2 is improved.

(Embodiment 2) Next, a second embodiment will be described. In this embodiment, the filter 12 of FIG. 1 is of a high-frequency pass type having a cutoff frequency of 1 kHz or more. Piezoelectric element 1
In addition to the original signal, there are many noise signals in addition to the original signal. Since the noise component is particularly large in a low frequency range of 1 kHz or less, the cutoff frequency of the filter 12 is 1 kHz or more in the present invention. In this case, the noise component can be sufficiently attenuated and the S / N ratio can be improved. By such means, the S / N of the apparatus can be improved, and the accuracy of estimating the wear coefficient of the magnetic head 2 can be improved.

(Embodiment 3) Next, a third embodiment will be described. FIG. 4 is a principle diagram of the magnetic head wear coefficient estimating apparatus of the present embodiment. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. The difference from the first embodiment is that, in order to transmit an electric signal generated in the piezoelectric element 1 to the outside of the rotary cylinder 5, it rotates integrally with the rotary cylinder 5 and is coaxial with the rotation center of the rotary cylinder 5. A rotating magnetic body 14a made of a soft magnetic material on which a first coil is wound, facing the rotating magnetic body 14a with a predetermined gap, and a second coil at a position facing the first coil. -Side magnetic body 14 made of a soft magnetic material and wound around
b. The rotating magnetic body 14a and the fixed magnetic body 14b have two or more channels so that the output from at least one piezoelectric element can be transmitted. In the case of extracting signals from a plurality of piezoelectric elements, it is sufficient that there are channels of the number obtained by multiplying the number of piezoelectric elements by two.
However, since a common ground can be used, the number of channels obtained by adding 1 to the number of piezoelectric elements is sufficient.

Here, the use of the rotating side magnetic body 14a and the fixed side magnetic body 14b has the following advantages. That is, since the signal is not transmitted by sliding like the slip ring and the brush used in the description of the first embodiment, no sliding noise is generated and the S / N of the signal is good. Further, depending on the turn ratio of the coils of the rotating magnetic body 14a and the fixed magnetic body 14b, the rotating magnetic body 14a and the fixed magnetic body 14b are determined.
Can have a signal voltage amplifying function. For example, if the winding ratio of the coil of the rotating side magnetic body 14a and the fixed side magnetic body 14b is set to one to two, the voltage can be doubled by the rotating side magnetic body 14a and the fixed side magnetic body 14b. That is, it is possible to set the amplification factor of the high-band amplifier 11 to be small, or not to use the high-band amplifier 11. In addition, since the rotation side magnetic body 14a and the fixed side magnetic body 14b have an effect of attenuating a signal in a low frequency range due to their characteristics, the filter 12 may be omitted depending on conditions such as measurement accuracy.

(Embodiment 4) Next, a method for calibrating a piezoelectric element in the apparatus for estimating a wear coefficient of a magnetic head according to the present invention will be described. FIG. 5 is a graph showing the read value of the effective value meter 13 when the tape 3 having a different abrasiveness is run using the apparatus having the above-described configuration on the vertical axis, and the magnetic value obtained from the actually measured wear amount of the magnetic head 2. Head 2 wear coefficient k and tape 3
Is a graph plotting the square root of the product kNv of the vertical force N applied to the magnetic head 2 and the sliding speed v between the magnetic head 2 and the tape 3 on the horizontal axis. Thus, it can be seen that the two have a linear relationship. That is, if the relationship between the two is expressed by an equation,

[0018]

(Equation 1)

Is as follows. In (Equation 1), α is the slope of the straight line, and β is the intercept of the vertical axis. Once such a device is calibrated, the normal force N applied to the magnetic head 2 by the tape 3 at that time and the sliding of the tape 3 and the magnetic head 2 will no matter what kind of abrasive tape 3 is run thereafter. By knowing the speed v, the wear coefficient k of the magnetic head 2 can be estimated. Here, the normal force N applied by the tape 3 to the magnetic head 2 can be measured using a strain gauge or the like. Further, even if the magnetic head 2 is different from that at the time of calibration, the hardness can be converted by measuring the hardness with a Vickers hardness tester or the like and measuring the attenuation rate of the elastic wave in the magnetic head 2 using ultrasonic waves or the like. .

First, a method for calibrating the piezoelectric element 1 in the apparatus for estimating a wear coefficient of a magnetic head according to the fourth embodiment of the present invention will be described. The device used for the calibration is the same as in the first embodiment.
It is assumed that the apparatus for estimating the wear coefficient of the magnetic head described in the above items 3 to 3 is used. Using the above apparatus, two types of tapes 3 having different polishing properties are caused to contact and run on the magnetic head 2.
At this time, the effective value of the signal voltage of each piezoelectric element 1 is read by the effective value meter 13. In addition, the actual wear amount of the magnetic head 2 caused by running each tape 3 is measured, and the wear coefficient of the magnetic head 2 is calculated. At this time, the amount of wear of the magnetic head 2 is measured based on a change in the shape of the magnetic head before and after the wear, a change in the mass, and the like. Thus, in (Equation 1), if there are two types of tapes 3, α and β can be obtained by solving simultaneous equations. The tape 3 may be of three or more types, and α and β that best satisfy the respective data can be obtained by a method of drawing an approximate straight line on a graph or the like. By using as many tapes 3 with different abrasive properties as possible, it is possible to improve the accuracy of α and β to be obtained. Of course, when the calibration is performed in a short time, two types of tapes 3 having different abrasiveness may be used. The calibration method of the present invention uses the piezoelectric element 1
It is not necessary to prepare a special device for the calibration of the piezoelectric element 1, and the calibration of the piezoelectric element 1 can be performed at low cost and in a short time.

(Embodiment 5) A piezoelectric element 1 in a wear coefficient estimating apparatus for a magnetic head according to a fifth embodiment of the present invention.
Will be described. The equipment used for calibration is
The apparatus for estimating the wear coefficient of a magnetic head described in the first to third embodiments is used. The same tape 3 is caused to contact and run a plurality of times with the magnetic head 2 using the above-described device. The present invention utilizes the fact that the wear coefficient of the magnetic head 2, that is, the abrasiveness of the tape 3, decreases as the running is repeated as shown in FIG. At this time, the effective value of the signal voltage of the piezoelectric element 1 at each running frequency is read by the effective value meter 13. Further, the actual wear amount of the magnetic head 2 due to the tape 3 at each run is measured, and the wear coefficient of the magnetic head 2 is calculated. At this time, the amount of wear of the magnetic head 2 is measured based on a change in the shape of the magnetic head before and after the wear, a change in the mass, and the like.
Thus, in (Equation 1), if the number of runs of the tape 3 is two, α and β are obtained by solving simultaneous equations. If the number of runs is three or more, α and β satisfy the respective data best. β can be obtained by a method of drawing an approximate straight line on a graph or the like. The accuracy of α and β to be obtained can be improved by conducting as many experiments as possible. Of course, if you want to calibrate in a short time,
The tape 3 need only be run twice. Further, it is also possible to use only the first and fifth data, for example, without using the data of the continuous number of times. According to the present invention, only one type of tape 3 is required, and the piezoelectric element 1 can be calibrated at low cost.

(Embodiment 6) A piezoelectric element 1 in an apparatus for estimating a wear coefficient of a magnetic head according to a sixth embodiment of the present invention.
Will be described. The equipment used for calibration is
The apparatus for estimating the wear coefficient of a magnetic head described in the first to third embodiments is used. Using the above-described apparatus, the same tape 3 is caused to contact the magnetic head 2 in a plurality of environments having different humidities. In the present invention, as shown in FIG.
Is utilized, that is, the abrasion coefficient of the tape 3, that is, the abrasiveness of the tape 3 increases as the humidity increases. At this time, the effective value of the signal voltage of the piezoelectric element 1 in each humidity environment is read by the effective value meter 13. Also, the actual wear amount of the magnetic head 2 by the tape 3 in each humidity environment is measured, and the wear coefficient of the magnetic head 2 is calculated. At this time, the amount of wear of the magnetic head 2 is measured based on a change in the shape of the magnetic head before and after the wear, a change in the mass, and the like. Thus, in (Equation 1), if the humidity environment is two, α and β are obtained by solving simultaneous equations,
If there are three or more environments, α and β that best satisfy the respective data can be obtained by a method of drawing an approximate straight line on a graph or the like. The accuracy of α and β can be improved by conducting an experiment in as many humidity environments as possible and by selecting a humidity environment in which the difference in polishing properties is as large as possible. Of course, when performing calibration in a short time, the tape 3 may be run only in two environments. According to the present invention, the piezoelectric element 1 can be calibrated at a low cost by using only one type of tape 3, and a large difference in abrasiveness can be created by changing the humidity environment even with the same tape 3. The accuracy of the calibration is improved.

[0023]

According to the present invention, the magnetic head having the piezoelectric element mounted on the tape surface is caused to contact and travel, the effective value of the signal voltage generated in the piezoelectric element is measured, and the effective value of the signal voltage determined in advance is determined. The wear coefficient of the magnetic head can be estimated from the calibration diagram with the wear coefficient of the magnetic head. Therefore, according to the present invention, it is possible to provide an apparatus for estimating a wear coefficient of a magnetic head which can be applied as a part of development and improvement of a magnetic head and a tape without performing a long-time wear test and easily measuring. It becomes possible. Also, according to the present invention, no special device is required for the piezoelectric element calibration,
It is possible to provide a low cost and high efficiency magnetic head wear coefficient estimating apparatus.

[Brief description of the drawings]

FIG. 1 is a principle diagram of an apparatus for estimating a wear coefficient of a magnetic head according to a first embodiment of the present invention;

FIG. 2 is a detailed view around a piezoelectric element mounting portion according to the first embodiment of the present invention.

FIG. 3 is a calibration diagram of an effective value of a piezoelectric element signal voltage and a wear coefficient according to the first embodiment of the present invention;

FIG. 4 is a principle diagram of an apparatus for estimating a wear coefficient of a magnetic head according to a second embodiment of the present invention;

FIG. 5 shows the effective value of the piezoelectric element and the wear coefficient k of the magnetic head,
Diagram showing the relationship between the perpendicular force N applied to the magnetic head by the tape and the square root of the product kNv of the sliding speed v between the magnetic head and the tape.

FIG. 6 is a diagram showing a relationship between a wear coefficient of a magnetic head and the number of times of running in a fifth embodiment of the present invention.

FIG. 7 is a diagram showing a relationship between a wear coefficient of a magnetic head and a humidity environment in a sixth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric element 2 Magnetic head 3 Tape 5 Rotating cylinder 7 Slip ring support 8 Slip ring 9 Brush 12 Filter 13 Effective value meter 14a Rotation side magnetic body 14b Fixed side magnetic body

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-5-296901 (JP, A) JP-A-60-251520 (JP, A) JP-A-3-6438 (JP, A) JP-A-63-1988 71626 (JP, A) JP-A-5-187993 (JP, A) JP-A-1-102716 (JP, A) JP-A-3-67149 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) G01N 3/56 G11B 5/455 JICST file (JOIS)

Claims (6)

(57) [Claims] 1. A rotary cylinder having at least one magnetic head, a tape helically wound around the rotary cylinder at a constant angle and running, and a piezoelectric element mounted near the magnetic head or mounted on the rotary cylinder. When,
Signal transmitting means for extracting the signal of the piezoelectric element to the outside of the rotary cylinder; and effective value measuring means for determining an effective value of the output voltage of the piezoelectric element, wherein the effective value of the output voltage of the piezoelectric element is determined in advance. From the correlation diagram of the hardness of the magnetic head, the normal force applied to the magnetic head, the wear volume of the magnetic head, and the wear coefficient of the magnetic head determined from the sliding distance between the magnetic head and the tape. An apparatus for estimating a wear coefficient of a magnetic head, wherein the wear coefficient of the magnetic head is obtained. 2. The magnetic head according to claim 1, further comprising means for limiting the frequency band of the output of the piezoelectric element, and which is a high-frequency pass type frequency band limiting means having a cutoff frequency of 1 KHz or more. Wear coefficient estimating device. 3. A rotary cylinder provided with at least one magnetic head, a tape wrapped around the rotary cylinder at a fixed angle and running, and a piezoelectric element mounted near the magnetic head or on the rotary cylinder. When,
A rotating magnetic body made of a soft magnetic material that rotates integrally with the rotating cylinder and has a first coil wound coaxially with the rotation center of the rotating cylinder; and a predetermined gap between the rotating magnetic body and the rotating magnetic body. A fixed-side magnetic body made of a soft magnetic material in which a second coil is wound and disposed at a position facing the first coil; and an effective value measuring means for obtaining an effective value of an output voltage of the piezoelectric element. And the effective value of the output voltage of the piezoelectric element obtained in advance, the hardness of the magnetic head, the normal force applied to the magnetic head, the wear volume of the magnetic head, and the sliding of the magnetic head and the tape. A wear coefficient estimating apparatus for a magnetic head, wherein a wear coefficient of a magnetic head is obtained from a correlation diagram with a wear coefficient of the magnetic head obtained from a distance. 4. A method in which a plurality of tapes having different abrasive properties are caused to travel in contact with a magnetic head, and the effective value of the signal voltage of the piezoelectric element and the hardness of the magnetic head at that time, the perpendicular force applied to the magnetic head, Using a wear volume obtained from a wear volume of a magnetic head and a sliding distance between the magnetic head and the tape, a calibration formula between an effective value of a signal voltage of the piezoelectric element and a wear coefficient of the magnetic head is obtained. 4. A magnetic head wear coefficient estimating device according to claim 1, wherein 5. The same tape is repeatedly run in contact with the magnetic head a plurality of times, and the effective value of the signal voltage of the piezoelectric element and the hardness of the magnetic head, the perpendicular force applied to the magnetic head, the magnetic force, Using a wear volume of a head and a wear coefficient obtained from a sliding distance between the magnetic head and the tape, a calibration formula between an effective value of a signal voltage of the piezoelectric element and a wear coefficient of the magnetic head is obtained. 4. A magnetic head wear coefficient estimating device according to claim 1, 2 or 3. 6. The same tape is run in contact with a magnetic head in a plurality of humidity environments, and the effective value of the signal voltage of the piezoelectric element, the hardness of the magnetic head, and the vertical force applied to the magnetic head in each humidity environment Determining a calibration equation between the effective value of the signal voltage of the piezoelectric element and the wear coefficient of the air head using the wear volume of the magnetic head and the wear coefficient obtained from the sliding distance between the magnetic head and the tape. 4. A magnetic head wear coefficient estimating device according to claim 1, wherein the magnetic head is a wear coefficient estimating device.