JPH07208941A - Measuring method for spacing of magnetic head - Google Patents

Abstract

PURPOSE:To measure the dynamic characteristic of a magnetic head with high accuracy by detecting precisely the amount of change of dynamic spacing of the magnetic head in relation to a known force of vibration. CONSTITUTION:A spindle 2 with an encoder 3 for rotating a transparent disk prepared by simulating a medium, a mechanism for positioning a magnetic head, a vibration generator 23 for vibrating the magnetic head 5 and an AE sensor detecting the contact of the magnetic head 5 are provided in a chamber 6 of which the pressure can be reduced, and current introduction terminals for exchanges of signals between a mechanism system and the sensor in the chamber 6 and a personal computer 30 provided outside are provided for the chamber 6. As the result, the dynamic characteristic of the magnetic head can be estimated with high accuracy.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head spacing measuring means and method for an information storage device.

2. Description of the Related Art A conventional magnetic head spacing measuring device measures a magnetic head spacing averaged over time, or vibrates a magnetic head supporting system as described in Japanese Patent Laid-Open No. 4-131704. The dynamic characteristics of the magnetic head have been evaluated by measuring the average and dynamic variations of the magnetic head spacing in the absence of force input.

The above-mentioned prior art is to measure the magnetic head spacing levitated on a transparent disc that transmits light, and the motion generated by the excitation force due to the surface shape of the transparent disc is measured. Only the dynamic spacing variation can be measured. By the way, the surface shape of the transparent disc that transmits light is 1
Accurate measurement over the circumference is extremely difficult due to runouts and undulations of about 10 μm. That is, it is extremely difficult to understand the excitation force due to the surface shape of the transparent disk when evaluating the follow-up characteristic, that is, the dynamic characteristic of the excitation force of the magnetic head. However, it was difficult to evaluate the dynamic characteristics of the magnetic head with high accuracy.
An object of the present invention is to provide a device for measuring a magnetic head spacing, an exciter for exciting a magnetic head support system to dynamically control the magnetic head spacing, and an average control for the magnetic head spacing. In order to achieve this, a decompression device that lowers the pressure of the measurement environment is provided, and an AE sensor that can detect that the magnetic head has contacted the transparent disk is provided in the magnetic head support system or its peripheral parts, and the vibration of the vibration exciter It is an object of the present invention to provide a measuring apparatus and a testing method therefor capable of accurately evaluating dynamic characteristics of a magnetic head by controlling force, vibration frequency, environmental pressure and the like with a personal computer.

To achieve the above object, a spindle for rotating a transparent disk simulating a medium, an encoder capable of detecting a circumferential position, and a mechanism for positioning a magnetic head, An exciter for exciting the magnetic head support system and an AE sensor for detecting that the magnetic head has come into contact with the transparent disk are provided. Further, these components are provided in a chamber capable of depressurizing, and a current introducing terminal for exchanging signals between a mechanical system and a sensor in the depressurizing chamber and a personal computer provided outside is provided in the depressurizing chamber. Further, the data taken into the personal computer is processed.

The spindle for rotating the transparent disk simulating the medium, the mechanism for positioning the magnetic head, and the vibrator for exciting the magnetic head are incorporated in the decompression chamber. When the transparent disc rotates, a fluid force is generated between the magnetic head and the transparent disc, and the fluid force forms a spacing between the magnetic head and the transparent disc. If it is low, it is small, that is, the fluid force generated by the rotation of the transparent disk can be controlled, and the average magnetic head spacing can be controlled by controlling the environmental pressure during the spacing measurement. A magnetic head having a space formed between the transparent disk and the disk is kept by a so-called air spring, and if any exciting force is applied to the magnetic head, the spacing will be maintained. Fluctuates. Therefore, it is possible to dynamically control the magnetic head spacing by providing a vibration exciter in a mechanism portion for positioning the magnetic head and vibrating a support system that supports the magnetic head. The dynamic spacing variation at this time is generally larger than the spacing variation due to the surface shape of the transparent disc, although it depends on the excitation force and the like.
By using the output of the encoder to subtract the spacing variation during non-excitation from the spacing variation during excitation, the dynamic spacing variation of the magnetic head with respect to a known excitation force, that is, the response can be accurately measured. It becomes possible to evaluate, and by detecting the contact signal between the magnetic head and the transparent disk from the AE sensor, the dynamic characteristics of the magnetic head including the time of contact can be evaluated with high accuracy.

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a block diagram showing an embodiment of a magnetic head spacing measuring device of the present invention. Decompression chamber 6
Includes a spindle 2 for rotating the transparent disc 4,
Encoder 3 that can detect the circumferential position and magnetic head 5
Stage 9 for loading the magnetic head 5, and XY for positioning the magnetic head 5.
A stage a11, an exciter 23 for exciting the magnetic head, and a vacuum gauge 7 are provided. An AE sensor 20 is attached to the shaker, and an AE preamplifier 21 is also provided in the decompression chamber. In addition, XY for positioning corresponding to the magnetic head position so that interference fringes generated between the magnetic head and the transparent disk can be detected through the optical window 18.
A measurement optical system formed by the camera 13, the light source 14, the interference filter 15, the beam splitter 16, and the lens 17 is provided on the stage b12. The gonio stage, the Z-axis stage, the XY stage a, and the XY stage b are connected to the stage driver 8, the AE preamplifier is connected to the AE main amplifier, and the piezoelectric actuator 24, which is a component of the vibrator, is connected to the power amplifier 26. The acceleration sensor 27 attached to the vibration exciter is connected to the acceleration amplifier 28, and each device in the decompression chamber is connected to an external device.
For example, current terminal 954-797 manufactured by Nichiden Anelva Co., Ltd.
0 or the like can be used. The personal computer 30
Controls each device and captures signals from each device.
The personal computer is connected to the spindle driver 1, the stage driver 8, the function synthesizer 25, and the oscilloscope 22 by using the GPIB terminal, and the personal computer can set and control each device. Here, the GPIB terminal does not necessarily have to be connected, and it depends on the control terminal of each device.
You may connect with a 232C terminal. In addition, the analog / digital converter 29 connected to the personal computer
An encoder 3, a vacuum gauge 7, a camera 13, an AE main amplifier 19, and an acceleration amplifier 28 are connected to (hereinafter referred to as an A / D converter), and an analog signal from each device can be taken into a personal computer as a digital signal. Similarly, the oscilloscope 22 has an encoder 3, a camera 1
3. The AE main amplifier 19 is connected to monitor high speed phenomena. Here, if a digital oscilloscope capable of data storage is used for the oscilloscope, the signals of the encoder, the camera, and the AE main amplifier can be stored, and the data can be taken into the personal computer. FIG. 2 shows an explanatory diagram of the spacing measurement flow of the present invention. A case where the spacing measuring device of the present invention is applied to a magnetic head of a magnetic disk will be described as an example. In order to perform the spacing measurement, first the spindle 2 is started. The rising acceleration, rotation speed, and start of the spindle are set and executed by the personal computer 30 through GPIB. Then, after a suitable time has passed,
For example, immediately after reaching steady rotation, the magnetic head 5 is moved to the transparent disc 4
Load on top. Loading is performed by rotation of the goniometer stage 9 or movement of the Z-axis stage 10, and the GPIB from the personal computer 30 is loaded.
The command is transmitted to the stage driver via the and executed. Although there is no limitation on the loading position, the loading is performed at the outer peripheral position than the measurement region in order to avoid damage to the transparent disc in the spacing measurement region. After the magnetic head 5 finishes loading, the magnetic head position is changed by the XY stage a in order to set the yaw angle, which is the angle between the flying position of the magnetic head and the rotational tangential direction of the magnetic head, to the set value. If the spindle rotation speed at the time of loading is different from the spindle rotation speed at the time of measurement, the spindle 2 is controlled to change the rotation speed. Further, the spacing measurement optical system also moves the XY stage b12 according to the position of the magnetic head to prepare for measurement. Magnetic head 5
When the preparation for measurement is completed, the oscilloscope 22 can capture the encoder signal, the AE signal, and the signal from the camera through the GPIB from the personal computer 30 so that the AE signal from the AE sensor 20 attached to the shaker 23 can be measured. The measurement condition is set to and the AE signal is set as the trigger signal of the data storage. As a result, each signal can be captured at high speed when the AE signal reaches a certain level. Further, the A / D converter 29 is also set by the personal computer 30 after setting the measurement conditions, and then the encoder signal, the AE signal, the signal from the vacuum gauge, and the signal from the camera are taken in. Although the digital storage oscilloscope and the A / D converter have basically the same functions, the oscilloscope is generally high-speed but has a small memory capacity and a low conversion resolution. For example, Ermec EC-23 Co., Ltd.
If the 98H-4 is used, the sampling rate is 1 word / microsecond or less, but a large amount of memory of several tens of megabytes or more and 12-bit resolution can be obtained. Therefore, when AE
Whether or not a signal is generated is detected by the A / D converter 29, and the AE signal can be grasped with high accuracy by the oscilloscope 22. At this time, the spacing variation of the magnetic head 5 depending on the surface shape of the transparent disc 4 is measured by the luminance signal of the interference fringes from the camera, which is taken into the A / D converter. Next, when the pressure in the decompression chamber is reduced, that is, when the average flying height of the magnetic head is reduced, decompression is performed, and otherwise, the following operation is performed. The shaker is, for example, Japanese Patent Application No. 05-05161.
The multidimensional vibration test apparatus described in Japanese Patent No. 7 is used. The input to the piezoelectric actuator 24 is the output of the function synthesizer 25 capable of generating an arbitrary waveform set by the personal computer, and the power amplifier 26.
Using the signal amplified by
The amount of spacing variation at the time of vibration is measured by loading it into a personal computer with a / D converter. If the output of the function synthesizer is started by a signal from, for example, an I / O port of a personal computer, the excitation start time can be analyzed from the data by sampling this with both the A / D converter and the oscilloscope. A first explanatory view of the test method of the present invention is shown in FIG. The measurement result of the spacing variation during vibration includes the spacing variation due to the excitation force depending on the surface shape of the transparent disk and the excitation force depending on the air flow, that is, the spacing variation during non-excitation. Encoder signal A phase or B
Phase and 1-per-cycle Z-phase pulse match the circumferential position of the transparent disk while subtracting the amount of spacing variation during non-excitation from the amount of spacing variation during excitation The response to force can be sought. Here, the data to be subtracted may be one round of data, or may be subtracted between the averaged data of several rounds. As a result, the dynamic characteristics of the magnetic head can be evaluated with higher accuracy than before. Further, for example, the seek operation at the time of data retrieval of the magnetic disk device, the movement from the contact / start / stop area to the data area, or the exciting force to the magnetic head generated at the time of retraction is measured by using another accelerometer or the like. Then, by reproducing this data with a function synthesizer capable of generating an arbitrary waveform, the variation amount of the magnetic head spacing in the actual device can be measured in a simulated manner. Further, by generating a theoretical excitation force to be simulated at the time of designing the magnetic head with the function synthesizer, the validity of the simulation can be verified or the actual dynamic characteristics of the magnetic head can be verified. Second test method of the present invention
FIG. 4 shows an explanatory view of the above. When the exciting force is being input to the magnetic head, the spacing variation is larger than in the state where no exciting force is applied, and therefore it is quite possible that the magnetic head contacts the transparent disk. This is constantly monitored by the AE sensor, and the oscilloscope 22 and the A / D converter 29 simultaneously capture the AE signal for detecting contact and the intensity signal of the interference fringes between the head transparent discs. The main component of the spacing variation of the magnetic head is about several tens of kHz, whereas the main component of the AE signal is several hundreds of kHz or more, so the spacing change is evaluated by the A / D converter and the AE signal is evaluated by the oscilloscope. In addition, since the data captured by the A / D converter can be evaluated by subtracting the amount of spacing variation during non-excitation, only the spacing variation due to contact can be evaluated, and the magnetic head during contact can be evaluated. Dynamic characteristics can be evaluated with high accuracy. Also, the data captured by the oscilloscope is A
It is suitable for evaluation of E signal, and can accurately evaluate the magnitude of the amplitude of the AE signal, which is correlated with the magnitude of the contact force between the magnetic head and the transparent disc. When the above measurement is completed, if the experiment conditions are changed, change the corresponding part and perform the experiment again.For example, abrasion of the protrusion may be considered when measuring the magnetic head behavior when it is in contact with the protrusion, so leave it as it is. After a certain period of time, measure the spacing again,
Evaluate changes in spacing variation. After a series of measurements, if vibrating, stop the vibration exciter, and if depressurizing, return the environment inside the decompression chamber to atmospheric pressure, load off the magnetic head, stop the spindle, and measure all spacing. Is completed. The case where the magnetic head of the magnetic disk device is applied has been described above. For example, in the case of a floppy disk device, a plastic transparent disk can be used to measure the spacing variation amount in the same manner. Also, when a recording medium is used instead of the transparent disk, it is possible to measure the dynamic spacing variation amount of the magnetic head from the variation of the read output of the magnetic head by adding a read / write circuit.
The dynamic characteristics of the magnetic head can be evaluated with high accuracy by using the above measuring device.

According to the present invention, the dynamic fluctuation amount of the magnetic head spacing on the transparent disk is obtained in the form of a response to a known input, so that the dynamic characteristics of the magnetic head can be evaluated with high accuracy. . Further, since the contact signal between the magnetic head and the transparent disk can be measured at the same time, it is possible to evaluate the dynamic characteristics of the magnetic head including the time of contact.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a magnetic head spacing measuring device of the present invention.

FIG. 2 is an explanatory diagram of a spacing measurement flow of the present invention.

FIG. 3 is an explanatory diagram of a first test method of the present invention.

FIG. 4 is an explanatory diagram of a second test method of the present invention.

[Explanation of symbols]

 1 spindle driver 2 spindle 3 encoder 4 transparent disk 5 magnetic head 6 decompression chamber 7 vacuum gauge 8 stage driver 9 goniometer stage 10 Z-axis stage 11 XY stage a 12 XY stage b 13 camera 14 light source 15 interference filter 16 beam splitter 17 lens 17 Optical Window 18 AE Main Amplifier 19 AE Sensor 20 AE Pre-Amplifier 21 Oscilloscope 23 Exciter 24 Piezoelectric Actuator 25 Function Synthesizer 26 Power Amplifier 27 Acceleration Sensor 28 Acceleration Amplifier 29 Analog / Digital Converter 30 Personal Computer

Claims (1)

[Claims] 1. The spacing of a magnetic head is optically measured from the intensity of interference fringes formed between a magnetic head and a transparent disk simulating a recording medium and the change in the intensity to measure the spacing of the magnetic head. A magnetic head spacing test method characterized in that a support system of a magnetic head is vibrated in a multidimensional manner during measurement, and an average spacing amount and a dynamic variation amount between the magnetic head and the transparent disk are measured.