JPH02282911A - Effective gap range finding method for magnetic head - Google Patents

Abstract

PURPOSE:To improve accuracy by setting a recording frequency equal to a frequency when a magnetic head is used in a floppy disk drive, performing recording and reproduction by varying a rotational frequency, and finding the effective gap range of the magnetic head from the rotational frequency of a floppy disk in which the minimum reproducing output can be obtained. CONSTITUTION:The recording frequency is fixed at the frequency when the magnetic head 101 is used in the floppy disk drive, and the recording and repro duction are performed at every varying of the rotational frequency of the floppy disk 102 by a rotational frequency setting circuit 104, and the effective gap range is found from the rotational frequency of the floppy disk 102 in which the minimum reproducing output can be obtained based on a prescribed equation. In such a manner, the rising of a recording current can be accelerated, and measurement with high accuracy can be easily performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a method for measuring the effective gap length of a magnetic head for a magnetic storage device using a flexible disk.

[Conventional technology]

In recent years, the storage capacity of magnetic storage devices using flexible disks has increased, and the recording and reproducing gap lengths of the magnetic heads used in these devices have entered the submicron range. A measurement method that can accurately measure the effective gap length is desired.

Conventionally, the measuring method used to measure the effective gap length of this type of magnetic head is to rotate a magnetic head 201, a floppy disk 202 used for recording and reproducing information, and a floppy disk, as shown in FIG. A spinstand 206, a rotational frequency setting circuit 204 that sets the rotational frequency of the spinstand, an oscillator 209 that generates a recording signal having a recording frequency, and an oscillator 209 that is used to record information on the floppy disk 202 by the magnetic head 201. Recording circuit 208 and the magnetic head 201
A reproduction circuit 205 that amplifies the reproduction output of the reproduced image, a spectro analyzer 206 that extracts the recording frequency component from the output of the reproduced image, and a spectro analyzer 206 that sets and controls the recording frequency and determines the characteristics of the magnetic head from the recording frequency characteristics of the output of the spectro analyzer 206. Computer 2 to find effective gap length
It consists of 07 configurations.

Here, the rotation frequency of the floppy disk 202 is set by the rotation frequency setting circuit 204 to the rotation frequency of the floppy disk 2020 when the magnetic head 201 is used in a floppy disk drive.

FIG. 8 is a flowchart of an example of a conventional effective gap length measuring method, and the measurement is performed in the following steps. First, the rotational frequency of the floppy disk of the floppy disk drive in which the magnetic head is mounted is set, and a recording signal having the recording frequency set by the combiator is IE'd by the oscillator to perform recording and reproduction on the floppy disk. A spectrum analyzer extracts only the recording frequency component from the reproduced output, digitizes the recording frequency component, and imports it into the memory of the computer. The above-mentioned recording frequency setting, recording, and reproduction are repeated until the recording frequency at which the reproduction output becomes minimum is determined. Once the recording frequency at which the reproduction output is minimum is determined, the effective gap length of the magnetic head is determined by a computer using the relational expression shown below. From the rotational frequency of the floppy disk and the recording frequency at which the reproduction output becomes minimum, the wavelength of the continuous magnetization reversal pattern recorded on the floppy disk medium at which the reproduction output becomes minimum is determined by the following equation (1).

/l m= 2 x r f r / fmix
--- (1) Here, r is the distance from the center of the floppy disk to the recording/reproducing gap of the magnetic head, fr is the rotational frequency of the floppy disk, f
min.

λ is the recording frequency at which the reproduction output is minimum, and the continuous magnetization reversal pattern wavelength on the floppy disk medium.

Furthermore, from the linear theory of recording and reproduction applying the reciprocity theorem regarding recording and reproduction, the effective gap length g i tr and Am are determined as got t ”0.89Xλmin
- (2), and from the above equations (1) and (2), the effective gap length is g e r t ”0.89X2πr f r/ f7
・=(3) is found. Here, 0.89 is a coefficient derived from the linear theory of recording and reproduction applying the reciprocity theorem.

FIG. 9 is a conceptual diagram of the recording frequency characteristics of the reproduction output when recording and reproduction are performed each time the recording frequency is changed and reproduction output data is taken using the conventional method of measuring the effective gap of a floppy magnetic head. .

[Problem to be solved by the invention]

However, in the conventional method for measuring the effective gap length of a magnetic head, at the recording frequency of a floppy disk drive shown in FIG. 4(a), the recording current rises sufficiently early (rises); ), the rise of the recording current is delayed due to the inductance of the recording coil of the magnetic head.
A phenomenon occurred in which the recording current switching time for the two recording coils came before the set current was reached.

As a result, near the above recording frequency, the magnetization reversal of the continuous magnetization reversal pattern recorded on the floppy disk medium does not reach deep enough into the medium.
Insufficient playback output, playback output to noise ratio (S/N)
There was a problem in that the measurement accuracy of the effective gap length obtained from the wavelength was poor.

The present invention has been made to address the above-mentioned problems, and an object of the present invention is to provide a method for measuring the effective gap length of a magnetic head that can measure the effective gap length of a magnetic head with sufficient accuracy.

[Means to solve the problem]

In the present invention, the recording frequency is set and fixed at the recording frequency when the magnetic head is installed in a floppy disk drive and used, and the rotation frequency setting circuit of the spindle stand is controlled by a computer to rotate the floppy disk. A narrowband filter 106 whose frequency is variable and whose center frequency is the recording frequency, and an A-D converter 1 which converts the output of the narrowband filter from analog to digital.
07, the recording frequency is set equal to the recording frequency when the magnetic head is used in a floppy disk drive, recording and reproduction are performed each time the rotational frequency of the floppy disk is changed, and the output of the floppy disk becomes smaller. The purpose is to measure the effective gap length of a magnetic head from the rotational frequency.

〔Example〕

FIG. 1 is a circuit block diagram showing a method for measuring the effective gap length of a magnetic head according to the present invention, and shows a rotation frequency setting circuit 1 controlled by a magnetic head 101 and a computer 108.
04, a spinstand 106 that rotates a floppy disk 102, an oscillator 110 with a fixed recording frequency, a recording circuit 109, a reproducing circuit 105, a narrowband filter 106, and an A-D converter 10.
7. Consists of the configuration of a computer 108.

Here, the recording frequency is set to the recording frequency when the magnetic head is used in a floppy disk drive.
The rotational frequency of the floppy disk is fixed, and recording and playback are performed each time the rotational frequency of the floppy disk is changed. From the rotational frequency of the floppy disk at which the playback output becomes minimum, the following relational expression (4) is obtained.
Based on this, the effective gap length can be determined.

g e t t =0.89 X 2πr f rmi
n/f - (4) where gaff is the effective gap length, 0.89 is a coefficient derived from the linear theory of recording and reproduction applying the reciprocity theorem, and r is the recording and reproduction gap portion of the floppy magnetic head. is the distance from the center of the floppy disk, frmin is the rotational frequency of the floppy disk at which the playback output is minimum, and f is the recording frequency.

FIG. 3 shows the method for measuring the effective gap length of a floppy magnetic head according to the present invention, and the concept of the rotational frequency characteristics of the reproduction output when recording and reproduction are performed each time the rotational frequency is changed and reproduction output data is taken. It is a diagram.

FIG. 5 is a schematic diagram of the recording wavelength λ characteristics of continuous magnetization reversal patterns on the media of reproduction output/noise by the method of measuring the effective gap length of a floppy magnetic head according to the present invention (solid line) and the conventional method (broken line). .

Since the reproduction output of the floppy magnetic head using the measurement method of the present invention can be larger than that of the conventional one, the measurement accuracy of the recording wavelength of the continuous magnetization reversal pattern on the media where the reproduction output is minimal is OdB of the reproduction output/noise. Comparing the levels, the measurement accuracy of the recording wavelength using the measurement method of the present invention is several times higher than that of the conventional method.

FIG. 6 shows an example of actual measurement using the method for measuring the effective gap length of a floppy magnetic head according to the present invention.
This is the recording wavelength characteristic of a continuous magnetization reversal pattern on the medium of the reproduction output of a 2MB floppy magnetic head. The effective gap length was found to be 0.91±0.02μ, which is considered to have sufficient measurement accuracy. By the way, the recording frequency is 25
It is 0 kHz.

〔Effect of the invention〕

As shown in the above detailed explanation, in the method for measuring the effective gap length of a floppy magnetic head according to the present invention, the effective gap length of the magnetic head is measured when the magnetic head is used in a floppy disk drive. Since it can be performed at the recording frequency, in order to improve the rise of the recording current, we have specially prepared a magnetic head with the number of turns of the recording coil reduced to about 1/3 of that of a practical magnetic head, and a spectrum analyzer. The effective gap length of the magnetic head can be measured using an electron microscope, etc., and the increase from the gap length can be investigated without using expensive measuring instruments such as
This has the effect of facilitating feedback to the glass bonding conditions for forming the gear part.

Furthermore, the present invention can also be applied to magnetic heads for hard disk drives, magnetic heads for video, etc., and has the effect of facilitating feedback to the glass bonding conditions for forming gear parts, similar to floppy magnetic heads. have.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram of an effective gap measuring method showing an embodiment of the present invention, FIG. 2 is a flowchart of an effective gap length measuring method showing an embodiment of the present invention, and FIG. 3 is a circuit block diagram of an effective gap measuring method showing an embodiment of the present invention. 4(a) and 4(b) are graphs showing the time dependence of the recording current flowing through the recording coil of the magnetic head, and FIG. Figure 6 shows an actual measurement example measured by the present invention. Fig. 7 is a circuit block diagram of an example of a conventional effective gap measurement method, Fig. 8 is a flowchart of an example of a conventional effective gear measurement method, and Fig. 9 shows a reproduction output vs. when measured using the conventional method. This is a conceptual diagram of the recording frequency characteristics. Figure 1, Figure 3, Figure 4 (a) Figure 5, 0.70 0,90 1+o t, 30-. Figure 8, Figure 6, Figure 7

Claims (1)

[Claims] In a method for measuring the effective gap length of a magnetic head for a magnetic storage device using a flexible disk, the recording frequency of the magnetic head is set to the recording frequency during normal use, the rotational frequency of the flexible disk is made variable, and the rotational frequency is changed. Recording and reproduction are performed on the flexible disk according to the rotational frequency and the recording frequency, and the wavelength of the recorded continuous magnetization reversal pattern at which the reproduction output is minimal is determined from the rotational frequency and the recording frequency, and the effective gap length is measured by performing arithmetic processing from the wavelength. A method for measuring an effective gap length of a magnetic head, characterized in that: