JPH0529244B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field to which the Invention Pertains] The present invention relates to a magnetic disk that exists on the surface of a magnetic disk used in a fixed magnetic disk device, and that may cause trouble when writing or reading data to or from the disk, or may damage the magnetic head. This invention relates to a method for measuring the height of protrusions that may cause damage.

[Prior art and its problems]

Magnetic disks are manufactured by plating a magnetic layer, protective lubricant layer, etc. on the surface of a disk-shaped substrate and forming them using various methods such as sputtering and coating.
If the roughness of the substrate surface is not sufficiently uniform and protrusions are present, or if impurities are mixed in during the formation of each layer, protrusions may occur on the surface of the magnetic disk. Fixed magnetic disk drives use the CSS method, but even when the magnetic head writes and reads data while moving slightly above the magnetic disk surface, the presence of such protrusions can cause errors. If the protrusion is high, the magnetic head may collide with the protrusion and be damaged. In addition, in the CSS method, when the device starts to drive, the magnetic head slides from a state in contact with the magnetic disk surface and enters a floating running state, and when the device stops, the magnetic head slides in contact with the magnetic disk surface from the floating state and stops. . At this time,
If a protrusion exists, a collision with the magnetic head will occur,
Both will be damaged to some extent. Therefore, it is preferable that the number of protrusions is as small as possible, and the height thereof is preferably as low as possible.

The acoustic emission (hereinafter abbreviated as AE) method is conventionally known as a method for determining the number and height of protrusions. This method involves attaching an AE sensor to the slider arm of the magnetic head.
The magnetic disk is rotated at a predetermined rotational speed to cause the magnetic head to fly and travel. When the protrusion comes into contact with the magnetic head, the slider arm vibrates and a peak voltage is generated in the output signal voltage of the AE sensor. The number of protrusions and their heights are determined from this peak voltage. By moving the magnetic head over the entire radial direction of the magnetic disk, information on the protrusions on the entire surface of the magnetic disk can be obtained.

However, although the number of protrusions can be easily determined by counting the number of peak voltages,
In order to find out the height, it was necessary to repeat the measurement by changing the number of rotations of the magnetic disk for each protrusion. In other words, as the rotational speed of the magnetic disk is increased for the protrusion whose height is to be measured, the flying height of the magnetic head increases and it no longer comes into contact with the protrusion, and the peak voltage no longer appears in the output signal voltage of the AE sensor. The rotational speed that corresponds to the noise level is measured, and the traveling speed of the magnetic head is calculated. Since the relationship between the traveling speed of the magnetic head and the flying height is known (based on white light interferometry using a glass substrate),
If you know the traveling speed of the magnetic head when the peak voltage occurs in the output signal voltage of the AE sensor and when that peak voltage disappears and becomes the noise level, you can find out the flying height of each magnetic head and calculate the difference. The protrusion height can be found as . However, it is very time-consuming to perform such measurements for each protrusion.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a protrusion height measuring method that eliminates the above-mentioned drawbacks and allows the height of protrusions to be easily determined.

[Key points of the invention]

According to the present invention, when a magnetic disk is rotated at a predetermined rotation speed and a magnetic head running at a small gap from the disk surface contacts a protrusion existing on the disk surface, the slider of the magnetic head The peak voltage Vp of the output signal voltage generated by the AE sensor attached to the arm and the distance R from the disk rotation center to the protrusion that generated the peak voltage
Calculate the product Vp・R of , and use the relationship diagram between the Vp・R value and the protrusion height when the previously determined magnetic disk is rotated at the predetermined rotation speed,
The above objective is achieved by knowing the height of the protrusion that gives the calculated Vp.R value.

[Embodiments of the invention]

FIG. 2 is a conceptual diagram of an example of a device for performing measurements according to the present invention, in which a magnetic disk 1 to be measured is attached to a rotating shaft 2, and a magnetic disk 1 to be measured is attached to a rotating shaft 2.
A magnetic head 3, which is placed opposite to the surface of the magnetic head 3, is attached to a slider arm 5 via a leaf spring 4.
An AE sensor 6 is attached to the slider arm 5, which converts minute vibrations of the magnetic head into a signal.The output signal is amplified by an amplifier 7, read by an effective value (RMS) voltmeter 8, and read by an oscilloscope 9. output a voltage waveform. The slider arm 5 allows the magnetic head 3 to move over the entire radial direction of the surface of the disk 1, and can be adjusted so that the magnetic head 3 is at an appropriate position on the surface of the disk 1.

Using such a device, the disk 1 and rotating shaft 2 are rotated at 1500 rpm. The magnetic head 3 travels while slightly floating above the surface of the disk 1. When a protrusion exists on the surface of the disk 1 and comes into contact with the magnetic head 3, a peak voltage is generated in the output signal voltage of the AE sensor at the noise level due to the contact of the protrusion. AE seen on oscilloscope 9 in Figure 3
A typical output signal voltage waveform of the sensor is shown. Corresponding to a normal disk surface, the output waveform of the AE sensor shows a noise level similar to Vn, but if there is a protrusion and it comes into contact with the magnetic head, the output waveform will change.
A peak voltage such as Vp occurs. The peak voltage quickly decays and returns to the noise level. This peak voltage increases depending on the height of the protrusion. When the rotation speed of the disk 1 is increased, the traveling speed of the magnetic head 3 becomes faster and the flying height above the disk surface becomes larger.
The magnetic head 3 no longer contacts the protrusion, and the peak voltage Vp in FIG. 3 no longer occurs. The running speed of the magnetic head can be calculated from the rotational speed at this time and the distance from the disk rotation center to the magnetic head (this distance is equivalent to the distance to the protrusion).
The flying height of the magnetic head above the disk surface can be determined.

The difference between this flying height and the flying height when the disk rotates at 1500 rpm is the height of the protrusion, and conventionally this work was done for each individual protrusion to measure the height, but it was very time-consuming. He was stiff.

The inventors have discovered that AE due to protrusions on the disk surface
As a result of various studies on the relationship between the peak voltage of the sensor output signal and the protrusion height, we found that the product of the peak voltage Vp and the distance Rmm of the protrusion from the center of rotation of the disk at that time.
We found that the relationship between Vp・R and the height of the protrusion is a straight line when VP・R is on a logarithmic scale.
The diagram shown in the figure was created. By using such a relational diagram created in advance, the laborious work of changing the rotation speed for each protrusion and finding the rotation speed at which the peak voltage Vp of the output signal of the AE sensor disappears, as in the conventional method, can be done. It is possible to easily know the height of the protrusion from this diagram by simply reading the peak voltage.

In this example, the rotation speed of the magnetic disk is
Although the rotation speed is set at 1500 rpm, the rotation speed is not limited to this, and an appropriate rotation speed can be selected depending on the height of the protrusion that needs to be detected and the detection accuracy.

〔Effect of the invention〕

According to the present invention, the AE attached to the magnetic head
By utilizing the relationship diagram between the product Vp・R of the peak voltage Vp caused by the protrusion on the disk surface generated in the output signal voltage of the sensor and the distance Rmm of the protrusion from the disk rotation center, and the protrusion height, the predetermined value can be determined. The protrusion height can be easily determined by simply reading the peak voltage of the output signal of the AE sensor attached to the magnetic head and calculating the product Vp·R while rotating the magnetic disk at a rotation speed of . Furthermore, by performing the above measurements while moving the magnetic head over the entire radial direction of the magnetic disk, it is possible to determine the number and height of protrusions on the entire disk surface using a very simple method, which is extremely useful in practice. It is a valid measurement method.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the product of the peak voltage of the output signal of an AE sensor according to an embodiment of the present invention and the distance of the protrusion from the disk rotation center and the protrusion height, and FIG. 2 is a diagram showing the relationship between the protrusion height and the measurement according to the present invention. FIG. 3 is a conceptual diagram of an example of a device for performing this, and FIG. 3 is a voltage waveform diagram showing an example of an output signal voltage of an AE sensor. 1... Magnetic disk, 2... Rotating shaft, 3... Magnetic head, 4... Leaf spring, 5... Slider arm, 6... AE
Sensor, 7...Amplifier, 8...RMS voltmeter, 9...
oscilloscope.

[Claims]

1. A rotating device having a rotating shaft to which a subject is attached via a holder that removably attaches the subject, aligning the axes thereof, and a probe to any position on the subject, etc. It has a scanner that moves the
1. An ultrasonic measuring device that performs automatic measurement via a CPU, wherein the outer diameter of the holder is formed to a shape and size specific to a subject.