JPS61222077A - Method for evaluating floating property of magnetic head - Google Patents

Abstract

PURPOSE:To detect minute head touch and to improve the reliability of a device by evaluating the floating properties of a magnetic head by an output waveform of an elastic wave element provided to a fixed end of a spring arm. CONSTITUTION:The piezoelectric signals 7 from an AE element 6 is amplified and supplied to a high pass filter 9 to remove a low frequency component so that only the high frequency component is amplified by an amplifier 10 for observing the waveform. Only the higher harmonic components of the simple waveform of the vibration due to the wind produced by the high speed rotation of the disk and the complicated waveform caused by the disk impact are taken out by a high pass filter and compared with the waveform that short-circuits a filter 9 to remove the noise caused by friction with the wind to clearly detect the minute head touch. The result is the improved reliability of the device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for evaluating the flying properties of a magnetic head that can clearly detect helad touch signals.

A magnetic disk drive rotates a magnetic disk, which has a magnetic film less than 1 μm thick on a non-magnetic disk made of an aluminum alloy or the like, at high speed, and the resulting lifting force allows the magnetic head to open a minute gap of about 0.5 μm. It is a device that floats on a magnetic disk and records information on a magnetic disk or reproduces information that has already been recorded.

Here, the material for the magnetic film is iron sesquioxide (γ-Fez
03) and nickel, cobalt, phosphorus (N
Magnetic alloys such as i-Co-P) and cobalt-chromium (Co-Cr) are used, and the former is mainly produced by spin-coding, while the latter is produced by vacuum evaporation or sputtering. is being made.

However, if the thin film formation is incomplete and there are minute irregularities or dust is attached, a change in lift occurs, causing the floating magnetic head to fluctuate and come into contact with the magnetic disk medium. In extreme cases, a drop collision, that is, a head crash, may occur, causing fatal damage to the magnetic disk.

Therefore, prior to assembly into a magnetic disk device, each magnetic disk medium is subjected to rigorous evaluation tests to eliminate defective products.

On the other hand, phenomena such as head touch or head crash also occur when the shape or structure of the magnetic head is defective.
Since magnetic heads are manufactured by molding, the frequency of defective products is low.

The present invention relates to a measuring method capable of detecting minute head touches during floating inspection of magnetic disk substrates.

[Conventional technology]

In order to determine the quality of a magnetic disk medium (hereinafter simply referred to as a disk), a levitation test is required in addition to static tests such as surface roughness. A spring arm 3 holding a magnetic head 2 for recording and reproducing information has an acoustic wave element (Acoustic Em
ission element (hereinafter abbreviated as AH element) 6 is installed,
The presence or absence of a head touch is determined from the piezoelectric signal detected by this AE element.

Here, the AE element 6 is made of lead zirconate titanate (PbZr
It is a piezoelectric sensor using piezoelectric ceramics or single crystals such as 03-pb'rto (abbreviated as PZT), which detects mechanical vibrations received by a magnetic head 2 through a spring arm 3. As shown in FIG. 2, the piezoelectric signal 7 from the AE element 6 is amplified in multiple stages, thereby detecting head touches and head crashes.

However, the conventional signal obtained in this way has a lot of noise as shown in FIG. 4, and it is difficult to detect minute head touch signals.

That is, when the slice level is increased to eliminate noise and detect only the head touch signal, the head touch signal is also likely to be removed because the level of the head touch signal itself is inherently low.

For these reasons, there has been a need for a method that can detect minute head touch signals.

[Problem that the invention seeks to solve]

As mentioned above, conventionally, the piezoelectric signal generated in the AH element installed at the fixed end of the spring arm is amplified and this waveform is observed, and head touches and head crashes are detected from this voltage fluctuation, but the noise level The problem is that minute head touch signals are overlooked because of the high head touch signals.

[Means for solving problems]

The problem described above is that the levitation of the magnetic head, which flies above the disk to record and reproduce information due to the lift generated by the high-speed rotation of the disk, is affected by the output of the AE element installed at the fixed end of the spring arm equipped with the magnetic head. Furthermore, the problem can be solved by using a method for evaluating the flying properties of the magnetic head, which evaluates from the output waveform obtained through a high-pass filter.

[Effect]

The present invention was made as a result of investigating the cause of noise detected by an AE element.

In other words, the disk is rotating at approximately 360 ORPM,
This corresponds to a circumferential speed of about 50 m/sec, and the magnetic head has a speed of 0.5 m/sec due to the lift force generated by the wind.
The magnetic head is floating by about μm.

The vibrations caused by the wind hitting the spring arms, arms, etc. are naturally different from the vibrations caused by the magnetic head hitting the disk substrate.

That is, vibrations caused by friction with the wind should be repetitive vibrations with a relatively simple waveform, while vibrations caused by impact should be vibrations with a complex waveform.

Therefore, by inserting a high-pass filter (hereinafter referred to as a bypass filter), it is possible to remove all of the piezoelectric components caused by friction with the wind and the low frequency components of the piezoelectric components caused by impact, and extract only the harmonic components. I should get it.

The present invention extracts only the harmonic components of the shock wave by passing it through a bypass filter in the process of amplifying the piezoelectric signal from the AE element. [Embodiment] FIG. 1 is a block diagram of a detection circuit to which the present invention is applied, and FIG. 5 is a detection waveform using this.

The bypass filter used in this embodiment has a cutoff frequency of 100 to 200 KHz, the arrangement of the AE element 6, etc. is the same as the conventional one, and the AI! Only the measurement circuit from element 6 is different.

That is, as shown in FIG. 1, the piezoelectric signal amount 7 from the AE element 6 is amplified by an amplifier 8 and then input to a bypass filter 9 to remove low frequency components, and only high frequency components are transmitted to an amplifier 10.
The waveform was observed by amplifying the signal.

FIG. 5 shows the waveform obtained in this way, and the scale is IV/di,v.

Also, Figure 4 shown earlier shows the waveform when the bypass filter 9 is short-circuited, and by comparing the two, noise caused by friction with the wind can be removed. It can be seen that touch can be clearly detected.

〔Effect of the invention〕

By implementing the present invention, it has become possible to detect minute head touches that were easily overlooked due to the large amount of noise, and it has become possible to improve the reliability of magnetic disk drives.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a detection circuit embodying the present invention, Fig. 2 is a block diagram of a conventional detection circuit, Fig. 3 is a perspective view showing the relationship between the magnetic head and the AE element, Figs. The figure is a photograph of the detected waveform. In the figure, 1 is a magnetic disk, 2 is a magnetic head, 3 is a spring arm, 4 is an arm, 5 is a fixed end,
6 is an AE element, 7 is a piezoelectric signal, 8. 0 is an amplifier, and 9 is a bypass filter. Committee IeJ No. 3 Closed No. 44

Claims (1)

[Claims] The levitation of the magnetic head, which records and reproduces information by floating above the disk substrate due to the lift generated by high-speed rotation of the magnetic disk substrate, is controlled by the output of an acoustic wave element provided at the fixed end of a spring arm equipped with the magnetic head. A method for evaluating magnetic head flying ability, further comprising evaluating from an output waveform obtained through a high-pass filter.