JPH02265055A - Controller for distance between magnetic head and disk - Google Patents

Abstract

PURPOSE:To improve the recording and reproducing characteristic and to execute the switching at a high speed by providing a driving mechanism for executing a control so that a distance to the magneto-optical recording medium surface of a head can be kept constant, based on a distance detected by a sensor. CONSTITUTION:A shaft 15 is attached to a magnetic head/sensor fixed part 14 to which a magnetic head 11 and reflection type sensors 12, 13 are attached, and this shaft 15 is held by plate springs 16 of two plates. To the shaft 15 between the plate springs 16, a coil 17 is attached, and by combining a permanent magnet 18 and a yoke 19 so as to surround the coil 17, a magnetic circuit is formed. When the gap of the magnetic circuit is opened toward the upper side, it becomes a closed magnetic path to a disk 10 side. By placing the coil 17 in the gap, and controlling a supply current to the coil 17 by using the outputs of the sensors 12, 13, the magnetic head 11 is driven in the vertical direction. In such a way, the distance to the disk 10 of the head 11 can always be kept constant.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic head-disk distance control device, and in particular to a high-frequency magnetic head-disk distance control device that allows information to be overwritten on a magneto-optical recording medium by a magnetic field modulation recording method. The present invention relates to a magnetic head-disk distance control device suitable for a magneto-optical disk device using a modulated magnetic field generating device.

[Conventional technology]

Magneto-optical disk memory using a magneto-optical recording medium takes advantage of various features of optical disk memory, such as high density, large capacity, interchangeable media, and random access, and also has the advantage of being rewritable. This is a file device that is attracting attention.

When rewriting information in a magneto-optical disk device using such a disk, if the commonly used optical modulation recording method is used, the problem is that the data transfer speed is slow because overwriting is not possible. occurs. This is because in a magneto-optical disk device that uses optical modulation recording, when rewriting information, it is necessary to perform a -degree erasure before recording, which effectively reduces the transfer speed during recording. It is from.

If override is possible in a magneto-optical disk device, recording and reproduction can be performed at the same transfer speed, thereby improving data transfer speed and making it applicable to a wider range of fields.

Therefore, several methods have been proposed so far to enable overriding. One of the methods is to continuously irradiate laser light during recording.
There is a magnetic field modulation recording method that switches the polarity of an applied magnetic field.

As a magnetic field modulation recording magnetic head that can be used in this method, one possible method is to use a floating magnetic head, such as in a hard magnetic disk device. However, in this method using a flying magnetic head, since the flying height of the magnetic head is small, on the order of several μm, there is a risk of head crash. Furthermore, since it is affected by dust on the disk, it becomes necessary to adopt a sealed dust-proof structure like a hard magnetic disk drive, and the media interchangeability, which is one of the characteristics of magneto-optical disks, cannot be maintained. there is a possibility.

Therefore, as a further countermeasure against this point, it is conceivable to apply a bulk type magnetic field modulation head that maintains a spacing that is not affected by dust on the disk. in this case,
Since it is impossible for the magnetic head to float in the air, the magnetic head is fixed at a position perpendicular to the disk at such a position that it will not come into contact even with surface runout.

FIGS. 4(a) and 4(b) show a top view and a sectional view of such a bulk type magnetic head, and here, as its specific structure, a ferrite yoke 21 as shown in FIG. Consider a bulk type magnetic field modulation magnetic head having a structure consisting of a coil 22 and a coil 22. When such a bulk type magnetic head is used as a magnetic field modulation head, it is fixedly placed at a predetermined position selected from the above-mentioned viewpoint in the direction perpendicular to the disk.

[Problems to be Solved by the Invention] However, when trying to apply a bulk type magnetic head that enables overriding and also solves the above-mentioned problems when using a floating magnetic head, the following problems arise. Problems such as recording/reproducing characteristics pose a practical obstacle.

That is, when using the above-mentioned bulk type magnetic field modulation head, the position of the magnetic head in the direction perpendicular to the disk is fixed, and as a result, the distance between the magnetic head and the disk due to surface runout of the disk. changes. When such surface wobbling occurs in the disk used during recording and reproduction, the magnetic field strength on the surface of the recording medium changes if the magnetic head is always driven with the same current.

FIG. 5 shows simulation results of changes in magnetic field strength with respect to distance from the end face on the central axis of the magnetic head in the magnetic head of FIG. 4.

From the results shown in Fig. 5, for example, if the required applied magnetic field strength on the recording medium surface is 3000e, the distance between the magnetic head and the disk will be 0.25 mm, but there will be surface runout of the disk as described above. Therefore, due to the surface runout, the distance between the magnetic head and the disk cannot be kept constant at 0.25 mm, and therefore the required applied magnetic field strength, in this case 3000e, cannot be maintained.

Specifically, according to FIG. 5, if the amount of surface runout of the disk is about 200 μm pp, the magnetic field strength on the recording medium surface will be ± between 2000e and 4000e.
It is shown that the change is about 1000e.

When the recording magnetic field strength changes as described above, the recording conditions change and the recording and reproducing characteristics change. For example, looking at the unerasable characteristics of a magneto-optical disk with respect to magnetic field strength,
Comparing the residual characteristics when the magnetic field strength is 2000e and 40000e, there is a difference of about 5 dB in the residual characteristics, which leads to deterioration of the recording and reproducing characteristics. In particular, one of the reasons for adopting the magnetic field modulation method is to enable overwriting, that is, to enable overwriting, rather than separately performing -degree erasing and then recording. It turns out that the occurrence of instability in erasure, such as the "double series", due to changes in magnetic field strength due to surface runout is a major problem.

An object of the present invention is to make it possible to always keep the magnetic field strength on the recording medium constant when applying a recording magnetic field onto the surface of a magneto-optical recording medium using a magnetic field modulation recording method, and to improve recording and reproducing characteristics. Moreover, it is an object of the present invention to provide a magnetic head-disk distance control device that has excellent performance such as high-speed switching operation.

[Means to solve the problem]

A magnetic head-disk distance control device of the present invention includes: a head that applies a recording magnetic field onto the surface of a magneto-optical recording medium using a magnetic field modulation recording method; a sensor that detects the distance of the head to the surface of the magneto-optical recording medium; and a sensor. The present invention is characterized by comprising a drive mechanism that controls the distance of the head to the magneto-optical recording medium surface to maintain a constant distance based on the distance detected by.

[Effect]

According to the present invention, it is possible to always keep the magnetic field strength on the recording medium surface constant by detecting the distance of the magnetic head for magnetic field modulation from the recording medium surface and controlling the distance to be kept constant. It is.

〔Example〕

Next, the present invention will be explained with reference to the M plane.

FIG. 1 is a perspective view showing an embodiment of the present invention.

As shown in FIG. 1, the magnetic head-disk distance control device of this embodiment includes an optical system, that is, an optical system that includes a lens and the like that irradiates a laser beam onto the disk 10 as a magneto-optical recording medium, with a disk 10 in between. A high frequency modulated magnetic field generator is placed on the opposite side of the system.

The high frequency modulated magnetic field generating device is a bulk type magnetic field modulating magnetic field generating head that applies a recording magnetic field to the disk 10 using a magnetic field modulation recording method, and in the illustrated example, the device is a bulk type magnetic field modulating magnetic field generator consisting of a ferrite yoke 21 and a coil 22 shown in FIG. It has a magnetic head 11 for use.

In this embodiment, in addition to this, the disk 10 of the magnetic head 11
A reflective sensor is provided as a sensor for detecting the distance between the magnetic head 11 and the disk 10, and a drive mechanism that controls the magnetic head 11 to maintain a constant distance from the disk 10 based on the detection output of the sensor.

In the illustrated example, the reflective sensors include two reflective sensors 12.
．． As shown in FIG. 1, these two reflective sensors 12 and 13 are placed on both sides of a magnetic head 11 for magnetic field modulation recording as shown in FIG. Specifically, the magnetic head/sensor fixing part 14 is used, and the magnetic head 11 and the reflective sensors 12, 13 are attached thereto.As will be described later, each reflective sensor 12.
13 is installed so as to be shifted in the vertical direction so that the distance from the disk 1o is slightly different.

In this embodiment, the drive mechanism has a shaft 15, a leaf spring 16, a coil 17, a permanent magnet 18, and a yoke 19, and further includes a support portion 2o for supporting these.

An example of a method for driving the magnetic head 11 against surface runout of the disk 10 will be described in more detail based on the configuration shown in FIG. 1 as follows.

That is, the shaft 15 is attached to the magnetic head/sensor fixing part 14 to which the magnetic head port and the reflective sensor 2, 13 are attached.
is attached, and this shaft 15 is held by two leaf springs 16. A coil 17 is attached to the shaft 15 between two leaf springs 16. Furthermore, a permanent magnet 18 and a yoke 19 are combined to form a magnetic circuit so as to surround the coil 17.

These magnetic circuits and one end side of the leaf spring 16 are attached to the support part 20, but in this case, regarding the magnetic circuits,
As shown in the embodiment of FIG.
By creating a closed magnetic circuit on the disk 1o side, the magnetic circuit consisting of
o You can prevent it from appearing on the screen. However, if the gap in the magnetic circuit is formed so as to open upward in the figure as shown in FIG. 1, a closed magnetic path can be created on the disk 1o side. It is possible to prevent the influence of the circuit from appearing on the disk 10. Then, a coil 17 is placed in the gap, and this coil 1
By controlling the current supplied to 7 using the outputs of the reflective sensors 12 and 13, the magnetic head sensor fixing part 14 and, therefore, the magnetic head 11 are driven to move in the vertical direction in the figure via the shaft 15. do.

As described above, the magnetic node-to-disk distance control device of this embodiment includes a magnetic head 11 that applies a recording magnetic field by a magnetic field modulation recording method onto the surface of the disk 10, which is a magneto-optical recording medium, and reflective sensor 12.1 as a sensor for detecting the distance to the recording medium surface;
3, and a drive mechanism that controls the distance of the magnetic head 11 to the recording medium surface to be kept constant based on the detected distance, and the distance of the magnetic head 11 to the recording medium surface is always maintained constant. Let it drip.

Further, a detailed explanation will be given with reference to FIGS. 2 and 3.

The above-mentioned reflective sensor 12 used as a distance detection sensor.
Reference numeral 13 is composed of a light source and a light receiving section, and the output changes depending on the distance between the sensor and the reflecting plate.

FIG. 2 shows the relationship between the output and the distance between the end face of the reflective sensor and the reflector.

As mentioned above, these two reflective sensors are mounted so that the respective sensors 12 and 13 are shifted in the vertical direction so that the distances between the sensors and the disk 10 are slightly different, as shown in FIG. However, when shifted in this way, the output of each reflective sensor relative to the distance from the fouling plate becomes as shown in FIG. That is, in the figure, the characteristic j2+2 is the characteristic of the reflective sensor 12! , 3 indicate the respective output characteristics of the reflective sensor 13.

FIG. 3 shows the differential signals of the outputs obtained from the two reflective sensors 1213 at this time. At the point where this differential signal crosses zero, the magnetic head 11 and the disk 1
By installing the magnetic head 11 so that the distance from
can always be controlled to an optimal position in the direction perpendicular to the disk 10.

That is, as described above, by applying current to the coil 17, the magnetic head 11 is driven vertically up and down with respect to the disk 10, so that the differential output of the two reflective sensors 12 and 13 described above is By controlling the current flowing through the coil 17 based on the obtained error signal, the distance between the magnetic head 11 and the disk 10 can be kept constant.

In this manner, in the configuration shown in FIG. 1, the distance of the magnetic head 11 for magnetic field modulation from the disk 10 surface is detected, and by controlling the distance to be kept constant, the magnetic field strength on the disk 10 surface is adjusted. It can be kept constant at all times, and the recording and reproducing characteristics can be improved.

This eliminates the instability of the unerased characteristics and is suitable for overriding.

In addition, when the configuration shown in Figure 1 is not adopted, in the case of a bulk type magnetic head, the distance between the magnetic head and the disk should be 0.3 mm, taking into account the risk of contact due to surface runout of the disk used. However, according to the present invention, the distance between the recording medium surface and the magnetic nodule 11 can always be kept constant even with a bulk type, so that the magnetic head 11 can be It becomes possible to move the disk closer to the disk 10. This makes it possible to obtain the necessary applied magnetic field with an even smaller current, making it possible to meet high-speed switching and to provide excellent practicality.

That is, when trying to prevent changes in the magnetic field strength due to surface runout of the disk 10, by changing the drive current of the magnetic head with respect to the distance between the disk and the magnetic head, which changes due to the surface runout of the disk, It is also possible to control the magnetic field strength on the disk so that it is always constant.
This may be considered as one of the solutions, but at present, the inductance of the applied magnetic head is several μ11.
Because of the large size, high-speed switching operation (as mentioned above, in the magnetic field modulation recording method, in order to enable override, the polarity of the applied magnetic field is switched while the laser beam is continuously irradiated during recording. (required), this current control type method is practically uncontrollable, whereas the configuration shown in FIG. 1 does not interfere with high-speed switching operation.

In this way, the distance between the recording medium surface and the magnetic head 11 can be kept constant, which not only improves recording and reproducing characteristics, but also allows the magnetic head 11 to be brought closer to the disk 10. This makes it possible to obtain the necessary applied magnetic field with a small amount of current.
There are also advantages such as high-speed switching being possible and temperature rise of the magnetic head 11 being suppressed.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to detect the distance of the magnetic head for magnetic field modulation to the recording medium surface and control the distance to be kept constant, thereby increasing the magnetic field strength on the recording medium surface. can be kept constant at all times, which has the effect of improving recording and reproducing characteristics.

In addition to this, there are other effects such as being able to obtain the necessary applied magnetic field with less current, enabling high-speed switching, and suppressing the rise in temperature of the magnetic head.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention, FIG. 2 is a diagram showing an example of the relationship between the output of the reflective sensor and the distance to the foul plate, and FIG. 3 is a diagram showing the relationship between the output of the two reflective sensors and A diagram showing an example of differential output. Figures 4(a) and (b) are top views and cross-sectional views of the bulk type magnetic head. Figure 5 shows changes in magnetic field strength with respect to distance from the end surface of the bulk type magnetic head. FIG. 10... Disk 11... Magnetic heads 12, 13... Reflective sensor 14... Magnetic head/sensor fixing part 15...
・Shaft 16...Plate springs 17, 22...Coil 18...Permanent magnet 19...Yoke 20...Support part 21...Ferrite yoke

Claims (1)

[Claims] (1) A head that applies a recording magnetic field onto the surface of a magneto-optical recording medium using a magnetic field modulation recording method, a sensor that detects the distance of the head to the surface of the magneto-optical recording medium, and a sensor that detects the distance of the head based on the distance detected by the sensor. A magnetic head-disk distance control device comprising: a drive mechanism that controls the distance to the magneto-optical recording medium surface to maintain a constant distance.