JPH02249117A - Magnetic head position measuring method - Google Patents

Abstract

PURPOSE:To measure the azimuth angle and the effective core width of a head to be measured simultaneously by preparing a graph, and reproducing four reference signals by the head to be measured, and plotting computed results computed by reproducing output on the graph. CONSTITUTION:A magnetic disk medium having the reference signals (wavelength lambda) A-D written on a prescribed concentric circle on a recording medium by varying the angles of a magnetic head, respectively is prepared, and the reproducing output from the magnetic disk by the magnetic head is expressed in equation I. In equation I, theta represents the azimuth of the magnetic head 24, and (w) represents the effective core width of the magnetic head 24 i.e. the length of a part where the core of the magnetic head 24 and a signal write part are superimposed, which corresponds to a radius direction position error 25. Then, the signals A-D are found from a prescribed range of angle and the effective core width, respectively, and the graph is generated by plotting theta and (w) on a coordinate setting A/B and a D/C as intersecting coordinate axes. Furthermore, the four reference signals by the head to be measured are reproduced, and A/B and D/C are computed and are plotted on the graph. In such a way, the tilt angle and the effective core width of the head to be measured can be obtained simultaneously.

Description

TECHNICAL FIELD The present invention relates to a method for measuring the position of a magnetic head, and more particularly to a method for measuring the tilt angle and effective core width of a magnetic head.

PRIOR ART As a conventional method for measuring the position of a magnetic head, there is a method of detecting the state of inclination of the head to be measured using a reference magnetic disk as shown in FIG. 3, and determining whether it is good or bad.

Referring to FIG. 4, on the reference magnetic disk 10, there is a magnetic field (not shown) at the center line 9 of a certain track.
Reference signal 5 written at an angle of -a with respect to the reference position
, a reference signal 6 written at an angle of b degrees, a reference signal 7 written at an angle of -b degrees, and a reference signal 8 written at an angle of a degree are recorded in advance.

When this reference magnetic disk is read and reproduced by a magnetic head to be measured, output waveforms as shown in FIGS. 5 to 7 will be obtained depending on the inclination of the head to be measured.

That is, when the inclination of the head to be measured is 0 degrees (no inclination), among the four reference signals shown in FIG. Readings are made at a relative tilt of a10Q) degrees. Similarly, for signal 6 written with a slope of b degrees, the relative slope is (b + 0) degrees, and for signal 7 written with a slope of -b degrees, it is (- With a relative inclination of (10) degrees, the signal 8 written with an inclination of a degrees will be read with a relative inclination of (a+0) degrees.

These reproduction output voltages A-D (corresponding to reference signals 5 to 8, respectively) are as shown in FIG. 5, where B=C.

It becomes A-D. For example, the signal written with the magnetic head tilted by -48 minutes is the reference signal 5 in Fig. 4, the signal written with the magnetic head tilted by 24 minutes is the reference signal 6, and the signal written with the magnetic head tilted by -2 minutes is the reference signal. 8, and when reading is performed with a magnetic head tilted by 12 minutes, an output waveform as shown in FIG. 6 is obtained. At this time, it becomes AB.

Similarly, if the same reference signal is read with a magnetic head tilted by -12 minutes, the output waveform will be as shown in FIG. 7, and C=D.

In this way, by comparing waveforms A and B and waveforms C and D shown in FIGS. 5 to 7, the tilt of the magnetic head is within the range of 112 minutes to 12 minutes. , it is possible to judge whether it is good or bad.

In the conventional magnetic head position measuring method described above, only the quality determination is made by comparing the output voltages of the output waveforms, and it is not possible to determine whether the product is good or defective. In other words, in the case of a defective product, we do not know how much to adjust the angle of the head in the direction of to make it a good product.
Adjustment of the magnetic head is difficult during manufacturing. Furthermore, the conventional method described above does not take into account the positional error (corresponding to the effective core width) of the magnetic head in the radial direction of the magnetic disk, so it is not possible to simply compare voltages based on the output waveform. There is a risk of making a mistake in determining the tilt angle and manufacturing a defective magnetic head.

Purpose of the Invention Therefore, the present invention has been made to solve the drawbacks of the conventional ones, and its purpose is to simultaneously measure the effective core width as well as the inclination angle of the magnetic head to be measured. An object of the present invention is to provide a method for measuring the position of a magnetic head.

Structure of the Invention A magnetic head position measuring method according to the present invention uses four reference signals (wavelength λ) A written on predetermined concentric circles on a recording medium while changing the angle of the magnetic head.

Prepare a magnetic disk medium having B, C, and D (A-D in the rotational direction of the recording medium), and determine the inclination angle θ (radian) of the magnetic head, the effective core width w1, and the wavelength λ. The playback output formula % is calculated using the predetermined range of the angle and the predetermined range of the effective core width to obtain A-D, and from the obtained results A/B and D/C. A graph is created by plotting θ and W on coordinate axes that are orthogonal to each other, and the four reference signals from the head to be measured are reproduced, and the reproduced output is used to determine A/B, D/C. The special feature is that the inclination angle and effective core width of the Rad to be measured are obtained by calculating the calculation result and plotting the calculation result on the graph.

Example Next, the present invention will be explained in detail.

First, it is well known that the equation for reproduction output from a magnetic disk by a magnetic head is expressed by the following equation.

In other words, the playback output is 5in(π・w@tanθ/λ)/(π11w11La
oθ/λ)...(1). In the above formula (1), θ is the magnetic herad inclination (radian), and the magnetic head 24 shown in FIG.
is the slope θ. Further, W is the effective core width of the magnetic head, the length W of the overlapping part between the core of the magnetic head 24 and the signal writing section 23 shown in FIG. 3, and the radial position error 2
It corresponds to 5. λ is the wavelength of the reference signal written on the magnetic disk.

The above formula (1) is used to create a graph (Fig. 2) for use in the embodiment of the present invention, and in this example, 4
Radius R on the concentric circle 9 where two reference signals are written = 51.
537 (IIIm), and the writing frequency f ~250
(KHz), and the rotational speed of the magnetic disk is 360 (KHz).
rpm). Also, of the four write signals, the first
The signal 5 was written by tilting the magnetic head by -48 minutes, the second signal 6 by tilting it by 24 minutes, the third signal 7 by tilting it by -24 minutes, and the fourth signal 8 by tilting it by 48 minutes.

Under the above conditions, if the effective core width W of the magnetic head is in the range of 150 Cttm to 360 (μm), and the tilt angle θ of the magnetic head is in the range of 0 to 23 minutes, then The playback outputs A-D obtained by reading the reference signals 5 to 8 (in order from the disk rotation direction) of No. 4 are obtained using the above formula (1), and the reproduction outputs A-D are calculated on the coordinates with A/B and D/C as orthogonal coordinate axes. Then, by plotting these relationship values within the range of θ and W, the graph shown in FIG. 2 is obtained.

As mentioned above, the graph shown in Figure 2 is based on θ of 0.
It is created by plotting in the range of minutes to 23 minutes, but 0
The graph in the range from minutes to -23 minutes is obtained as a line-symmetric graph obtained by folding back around the line of θ-0 minutes, that is, the line of head inclination angle O (indicated by 1) as the axis of symmetry.

Therefore, the head inclination angle in the range of -23 minutes to 23 minutes and the effective core width in the range of 150 (μl11) to 360 (μm) can be measured using this graph. The measuring method will be explained below using the flowchart shown in FIG.

First, in step 100, the graph shown in FIG. 2 mentioned above is prepared. After that, in the next step 101, four reference signals 5 to 8 (
(see Figure 4), and the reproduced waveforms A-D are amplified in step 102, and then converted to A for digital processing.
The data is digitized by a /D (analog/digital) converter (step 103).

Step 1: Temporarily memorize the maximum value of this reproduced waveform A-D.
04), then A/B and D/C are calculated (step 105). The combined prices of A/B and D/C are plotted on the vertical axis 3 and horizontal axis 4 of the graph of FIG. 2, respectively (step 106). The value of θ and the value of W at the intersection obtained by extending the plot points of both axes 3 and 4 are determined as the inclination angle and effective core width of the magnetic head to be measured (
Step 10.7).

This is done for all heads to be measured, and the measurement process ends (step 108).

It is obvious that the above processing can be easily performed by digital processing using a microcomputer or the like.

Effects of the Invention As described above, according to the present invention, by preparing the graph shown in FIG. 2 in advance, the inclination angle of the Rad to be measured and the effective core width can be measured simultaneously. .

[Brief explanation of drawings]

FIG. 1 is a flowchart showing the operation of an embodiment of the present invention;
Fig. 2 is a graph for measuring θ and W used in the embodiment of the present invention, Fig. 3 is a diagram explaining θ and W, and Fig. 4 is a magnetic field on which the reference signal used in the embodiment of the present invention is written. FIGS. 5 to 7, which are diagrams showing examples of disk media, respectively show reproduction waveforms when the magnetic disk medium shown in FIG. 4 is read by magnetic heads having various tilt angles. Explanation of symbols of main parts 5 to 8...Reference signal 9...Track center line 10...Magnetic disk 23...Signal writing section 24... ...Magnetic head 25...Radial position error 26...Magnetic head center line

Claims (1)

[Claims] (1) Four reference signals (wavelength λ) A and B written on predetermined concentric circles on the recording medium by changing the angle of the magnetic head respectively.
, C, D (referred to as A to D in the order of rotational direction of the recording medium), and using the tilt angle θ (radian) of the magnetic head, the effective core width w, and the wavelength λ. The reproduction output formula sin(π・w・tanθ/λ)/(π・w・tanθ
/λ), A to D are calculated in the predetermined range of the angle and the predetermined range of the effective core width, and from the obtained results, the coordinates with A/B and D/C as perpendicular coordinate axes are calculated. Create a graph by plotting θ and w, respectively, reproduce the four reference signals from the head to be measured, calculate A/B and D/C from the reproduced output, and use the calculation results as described above. A method for measuring the position of a magnetic head, characterized in that the inclination angle and effective core width of the head to be measured are obtained by plotting them on a graph.