JPH04103087A - Instrument for measuring floating variable of floating magnetic head - Google Patents

Abstract

PURPOSE:To make it possible to accurately measure a floating variable even when the variable is >= 2mum by forming a magnetic coil having an opened magnetic path forming an opened end opposed to a disk on a floating slider and detecting the impedance of the coil. CONSTITUTION:A measuring floating magnetic head H is constituted of a floating slider S consisting of non-magnetic ceramics and a solenoid-like magnetic coil C. When a sine wave current is supplied to the winding W2 of the coil C, an induced voltage having frequency equal to that of the current is generated on a winding W1. The level of the induced voltage is determined by the quantity M of magnetic flux passing the winding W1 out of magnetic flux generated by the current supplied to the winding W2. Especially, the quantity M sharply depends upon a distance between the opened end of the coil C and a conductor. When a conductive disk D is used, the distance between the head H and the disk D and its time variation can be detected at high sensitivity by the induced voltage generated on the winding W1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flying height measuring device for a flying magnetic head for a magneto-optical disk or a hard disk.

[Prior art 1] Conventionally, magnetic disks (
hard disks) have been put into practical use.

The signal recorder/reproducing magnetic head of a hard disk is a floating magnetic head, and is capable of flying while maintaining a distance of 05 μm or less from the surface of the disk, which is a recording medium.

By the way, when a flying magnetic head comes into contact with the disk surface (head crash) due to vibrations applied from the outside, scratches occur on the disk surface and normal signal recording and reproduction becomes impossible. On the other hand, in order to record and reproduce signals at high density, the flying height of the magnetic head should be small, which increases the risk of head crash. For this reason, there is a need for a flying slider that has a low flying height, is capable of stable flying motion, and does not cause head crashes.

The development of such a flying slider requires technology to accurately measure the flying height. In response to such demands, a flying height measuring device for a flying magnetic head for a hard disk has been developed and has already been put into practical use. This device uses laser light interference to measure the distance between flying slider disks, and is capable of measuring flying heights of 1 μm or less.

However, in recent years, a system has been proposed in which a floating magnetic head is used as a signal recording magnetic head for magneto-optical disks, similar to hard disks. For example, JP-A-1
-199301 is one example. Unlike hard disks, in this magneto-optical disk, a floating magnetic head is attached to the disk at a single point for high-density signal recording.
There is no need to place the disks close to each other within μm or less, and conversely, the surface runout of disks is larger than that of hard disks, and since hard disks are different and disks can be replaced, it is easy for dust to enter the device, so there is a risk of head crash. In order to avoid this, a flying height of 2 μm or more is required.

[Problem that the invention is trying to solve]

However, as mentioned above, the conventional flying height measuring device for a flying magnetic head for a hard disk cannot measure a flying height of 1 μm or more. Therefore, 2
For floating magnetic heads with a flying height of μm or more,
There was no technology to accurately measure the flying height, which was an obstacle in the development of flying magnetic heads.

[Summary of the Invention] The present invention provides a magnetic coil for distance detection on a flying slider, and the impedance of the magnetic coil (or the amount of magnetic flux passing through the magnetic coil) changes depending on the distance between the magnetic coil and the conductive disk. By providing a device that measures the flying height of a levitating magnetic head by utilizing the properties of the levitating magnetic head, it is possible to accurately measure even when the flying height of a levitating magnetic head is 2 μm or more. This solves problems in head development.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 shows the overall configuration of a flying height measuring device according to the present invention.

D is a disk and is a conductive substrate such as aluminum, or
A metal film is formed on the surface of a non-conductive substrate such as glass. The surface of the disk D is mirror-finished like a normal magneto-optical disk, and if necessary, a protective film of carbon, silicon nitride, etc. is formed thereon. M is a motor for rotating the disk D at high speed. H is a floating magnetic head for measurement, which is made up of a floating slider S made of non-magnetic ceramic and a solenoid-shaped magnetic coil C provided with one open end facing the disk D, as shown in detail in Figure 2. Become. The magnetic coil C has a rod-shaped core made of a high permeability magnetic material such as ferrite, and two windings W1 and W2 are provided on the core.

The size of the core is, for example, 0.6mm (width) xo, 6mm
(Width) Xl, smm (Length), number of windings is winding W1
, W2 are both 20 to 30 times.

The materials constituting these floating magnetic heads H for measurement are all the same as those of the floating magnetic head in the magneto-optical disk disclosed in JP-A-1-199301, and the manufacturing process can also be the same. In addition to a floating magnetic head for measurement having the same configuration as a floating magnetic head for a magnetic disk, any configuration other than the illustrated configuration can be manufactured. The measurement flying magnetic head H is held by a suspension SUS so as to be pressed against the disk surface with a load of several grams.

The electric circuit section for measuring the flying height consists of a sine wave oscillation circuit 2 and an amplitude stabilizing circuit 1 connected to the winding W2, a detection circuit 3, an amplifier circuit 4, and a filter circuit 5 connected to the winding Wl.

Next, the operating principle of the flying height measuring device according to the present invention will be explained.

The sine wave oscillation circuit 2 generates a sine wave voltage with a frequency of about 10 MHz. The amplitude stabilizing circuit 1 performs amplitude stabilization on the output of the sine wave oscillation circuit 2, and then supplies a sine wave current with a constant amplitude to the winding W2 of the magnetic coil C.

At this time, the winding W1 of the magnetic coil C generates an induced voltage having a frequency equal to the frequency of the current supplied to the winding W2. The magnitude (amplitude) of the induced voltage at this time is determined by the amount of magnetic flux M that flows through the winding W1 out of the magnetic flux generated by the current supplied to the winding W2. When there is a conductor (metal) nearby, the amount M of magnetic flux passing through the winding W1 is also affected by the eddy current induced on its surface.In particular, the amount M of magnetic flux is determined by the amount M between the open end of the magnetic coil C and the conductor. By using a conductive disk D, it is possible to detect the distance between the floating magnetic head H for measurement and the disk 0 and its time variation with high sensitivity using the induced voltage generated by the winding W1. It is.

The amplitude signal of the induced voltage generated by the winding Wl is extracted by the detection circuit 3, and then sent to the amplifier circuit 4 and the filter circuit 5.
The signal components in the required band are extracted with the required level sensitivity.

According to experiments, when the band is DC-10K Hz signal is 8
When extracted with a sensitivity of 0 mV/μm, the noise level was 20 mVp-p or less, and the output characteristics were almost linear over the flying height O to 50 μm, and sufficient accuracy for practical use was obtained.

Note that the configuration of the electric circuit is not limited to the one described above, and various methods can be applied, such as a method of extracting the output as an induced current instead of an induced voltage.

In the above embodiment, the magnetic coil C is wound twice, one for current supply and the other for voltage detection, enabling efficient detection. 20～
It is also possible to detect the amount M of magnetic flux passing through the magnetic coil C by supplying a current of about 10 MHz for 30 times. Electrically, the impedance Z of the magnetic coil C may be detected directly or indirectly.

An embodiment in this case will be explained with reference to FIG.

In the figure, the same components as in FIG. 1 are given the same reference numerals and their explanations will be omitted. The winding W is connected to an amplitude stabilizing circuit 1' and a detection circuit 3. The output of the sine wave oscillation circuit 2 is subjected to amplitude stabilization by the amplitude stabilizing circuit 1', and then outputs a voltage with a constant amplitude. Here, 6 is a capacitor used to cause a resonance phenomenon with the inductance component in the impedance Z of the magnetic coil C. The resonance frequency is set slightly higher or lower than the frequency of the output signal of the sine wave oscillation circuit 2. A change in the amount M of magnetic flux results in a change in the impedance Z of the magnetic coil C, resulting in a change in the resonant frequency. This effect appears as a change in the current flowing through the magnetic coil C, and is further detected as a voltage change across the magnetic coil C. Thereafter, the amplifier circuit 4 and filter circuit 5 are the same as those in the previous embodiment.

As described above, it is possible to detect the flying height even if the winding W is single-layered. Note that this embodiment is an example of an efficient detection method, and various other efficient methods can be applied to detect the impedance 2 of the magnetic coil C.

Furthermore, by providing two or more magnetic coils C on the flying slider S, it is possible to not only measure the flying height of the flying magnetic head H for measurement, but also to measure changes in the posture of the flying magnetic head H for measurement such as rolling and pitching. It is possible to measure. For example, as shown in Fig. 4, by arranging a total of three magnetic coils 01 to C3 on the front, rear, left and right sides of the floating slider S, and comparing the signals detected by the individual magnetic coils Cl-C5, the low link It is possible to measure fluctuations in levitation posture such as , pitching, etc.

〔Effect of the invention〕

As explained above, the flying height measurement device for a flying magnetic head according to the present invention is capable of measuring the flying height of a flying magnetic head with sufficient accuracy and has a wide measurement range of 0 to 50 μm.
It is possible to measure the flying height of a magneto-optical disk flying head, which has a larger flying height than a conventional hard disk flying head.

In addition, the material and shape of the floating slider magnetic coil, etc. of the floating magnetic head for measurement are the same as those of commonly used floating magnetic heads for magneto-optical disks, so it can be easily adjusted in the same process as the floating magnetic head for normal magneto-optical disks. It is possible to create a floating magnetic head for measurement with a shape of .

Furthermore, by installing two or more magnetic coils on the floating slider, rolling, pitching, etc. of the floating magnetic head can be measured.

The present invention is applicable not only to floating magnetic heads for magneto-optical disks but also to conventional floating magnetic heads for hard disks.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a flying height measuring device for a flying magnetic head according to the present invention, FIG. 2 is a diagram showing the configuration of a measuring flying magnetic head of the flying height measuring device for a flying magnetic head according to the present invention, and FIG. This figure is a diagram showing the configuration of a measuring device in another embodiment, and FIG. 4 is a diagram showing the configuration of a measuring flying magnetic head in another embodiment. D... Disk H... Flying magnetic head for measurement C... Magnetic coil W... Winding S... Flying slider

Claims (3)

[Claims] (1) A disk that is driven to rotate at high speed and has a conductive layer provided on the surface of a conductive substrate or a non-conductive substrate, a floating slider that can fly while keeping a small gap between the surface of the disk, and the surface of the floating slider. 1. A flying height measuring device for a flying magnetic head, comprising: a magnetic coil having an open magnetic path and having an open end facing the disk; and means for detecting impedance of the magnetic coil. (2) A disk that is driven to rotate at high speed and has a conductive layer provided on the surface of a conductive substrate or a non-conductive substrate, and a floating slider that can fly while maintaining a minute gap between the disk surface and the surface of the floating slider. An open magnetic path with an open end facing the disk, and supplying an alternating current to a magnetic coil with double windings and one of the windings of the coil. 1. A flying height measuring device for a flying magnetic head, comprising: means for detecting an induced voltage or an induced current generated in the other winding. (3) Claim (1) or (2) characterized in that two or more magnetic coils are provided on the floating slider.
) A flying height measuring device for a flying magnetic head as described in item 2.