JPS5815845B2 - floating head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotary scanning head that writes and reads signals by rotating a magnetic head to scan the surface of a magnetic tape as a magnetic recording medium. This invention relates to a floating head that scans while maintaining a constant minute gap between the head and the tape using a dynamic pressure air film to prevent this.

In a rotary head recording mechanism that records digital signals by rotating a magnetic head to scan the tape surface, a wedge-shaped gap is created between the head surface and the tape in order to eliminate errors in recording and playback caused by wear between the tape and the head. A grooved spherical head is used that levitates and scans the tape up to a minute and constant gap using the air film pressure generated in the air. Fig. 1 is a front view showing an example of this floating head;
The figure is a side view thereof, and FIG. 3 is an enlarged front view of the head portion.

The head 1 has a rectangular shape with a length of 5 to 6 mm and a width of 4 to 5 mm, and is installed in the center of a rotor rotor 2 having a diameter of about 90 mm and a width of 13 mm so as to protrude by about 80 μm.

Head bearing surface center land portion 1a and head bearing surface 1b
has a spherical or pseudo-spherical shape with a radius of curvature of about 20 mm.

Also, this bearing surface has a width of 150μ along the head scanning direction.
Two narrow grooves 1c are formed around m.

The vicinity of the bearing apex 1d of the central land portion 1a sandwiched between the two narrow grooves 1c is a magnetic head 3, and therefore the width of the central land portion 1a is 200 μm and 380 μm depending on the magnetic helad gap width. ing.

When this grooved spherical head is pushed into the tape by about 50 μm and scanned in the scanning direction 4 at a speed of 25 m/s, for example, air film pressure is generated in the wedge-shaped gap between the bearing surface and the tape, and As shown in Figure 3, the tape has an equal gap line A1. A2. It exhibits a floating clearance distribution represented by A3, etc.

In other words, as is well known in conventional cylindrical foil bearings, the tape floating clearance is not symmetrical with respect to the bearing apex 1d, and a minimum clearance region is formed at least 1 mm behind the bearing apex 1d, and this minimum clearance A uniform clearance region of 1.5 to 2 times the minimum clearance is formed over a range of 1.2 to 1.51E11L beyond the bearing apex 1d.

The minimum gap position and uniform gap area vary somewhat depending on the amount of head pushing into the tape, tape tension, etc., but the radius of curvature is around 20 u, and the scanning speed is 25 m /
In the case of s, the amount of variation is 0.3 to 0.4 times,
Therefore, even if variations in usage conditions are anticipated, the head gap portion 3a can be maintained at a substantially desired constant clearance.

In this way, the conventional grooved spherical head has a central land portion 1a.
The gap of the magnetic head gap installed in the
．． It has an excellent ability to maintain a nearly constant gap of 5 μm.

However, in order to meet the challenge of constructing a head capable of high-density recording with even smaller gaps and narrow recording track widths of several tens of micrometers, this type of conventional grooved spherical head has the following problems. are doing.

The first problem is the difficulty in achieving both reduction in the gap in the magnetic head gap and reliability in head wear.

In the conventional head structure as shown in Fig. 1, the tape flying clearance in the head gap is made small, for example 0.2.
To make it approximately μm, the width of the central land portion 1a should be 200 μm.
It should be about m.

However, along with this, the minimum gap also becomes smaller, and the head and tape at the minimum gap come into contact due to the surface roughness of the tape.

In other words, in conventional grooved spherical heads, the tape flying clearance at the head gap cannot be made very small in order to prevent the tape and the head from wearing out at the minimum clearance position.

This problem can be solved to some extent within the framework of the conventional head structure by shifting the head gap portion 3a backward from the bearing apex 1d and providing it near the minimum gap position.

However, as mentioned above, the minimum clearance position of the grooved spherical head varies by about 0.3 to 0.4 u depending on the amount of head pushing into the tape, tape tension, head setting error, etc.
As shown in the figure, the clearance behind the minimum clearance position increases rapidly, so in consideration of this variation in usage conditions, the head gap should be adjusted 0.2 to 0.3 times from the minimum clearance position.
Must be set in front of tnm.

Therefore, the clearance in the head gap portion must be at least 0.1 μm larger than the minimum clearance.

A second problem with conventional grooved spherical heads is the difficulty in miniaturizing the recording track width of the magnetic head.

Conventional magnetic heads have a central land in the center for ease of processing, and therefore the gap width of the magnetic head is equal to the width of the central land.

On the other hand, since the tape floating gap is mainly determined by the center land width, the floating gap is also uniquely determined according to the recording track width.

In order to satisfy these two conditions of flying clearance and track width, in conventional heads, the head bearing surface is not made into a spherical surface with a single radius of curvature, but the vicinity of the apex of the head is modified into an ellipsoidal surface, and an appropriate flying clearance is achieved. I was controlling it so that it would happen.

However, the change in the gap due to this modification is slight; for example, when making a head with a track width of 50 μm, if the central land width is set to 50 μm, the tape and the head will come into contact and wear out no matter what modification is performed.

Therefore, based on the design concept of conventional head bearings,
A magnetic head with a width of 50 μm is buried in a land portion with a width of 200 to 300 μm.

However, processing a head with such a structure requires a considerable number of man-hours, and also tends to create a step in the adhesive layer between the magnetic head and the central land, which often has an adverse effect on the tape flying clearance.

In view of the above-mentioned points, the present invention provides a floating head which is designed to solve these problems and eliminate such drawbacks, in which the surface facing the magnetic recording medium has a spherical or pseudo-spherical shape. A magnetic head gap having a recording track width narrower than that of the central land is provided at the trailing edge on the outflow side of the air bearing surface of the central land, which is sandwiched in-plane by two narrow grooves along the head scanning direction; Also, no surface with a floating function is provided behind the head gap,
The head scanning speed is set to zero under the conditions of the head bearing curvature radius using the bearing outflow side length from the bearing apex of the central land portion to the magnetic head gap, the amount of head depression into the magnetic recording medium, and the tension of the magnetic recording medium. The magnetic head gap is made small enough to come into contact with the surface of the magnetic recording medium.

The floating head according to the present invention will be explained in detail below with reference to the drawings.

- FIG. 4 is a front view showing an embodiment of the floating head according to the present invention, and FIG. 5 is a side view of the floating head shown in FIG. 4.

5 is a floating head bearing, and a central land portion 5a sandwiched between two narrow grooves 5a and a bearing surface 5c located outside the narrow grooves 5a are within the same spherical surface or pseudo-spherical surface.

6 is a C-shaped magnetic core, 6a is a head gap, and 7 is a winding.

The C-shaped magnetic core 6 is made of a high magnetic permeability material such as ferrite, and the rear end of the central land is also made of a high magnetic permeability material.

In this case, the entire head bearing or the entire central land portion may be made of a high magnetic permeability material.

And the shape of this head bearing is. In order to form the necessary minute gap in the head gap 6a, the following features are provided.

First, the length 11 of the inflow side bearing from the bearing apex 5d to the front end of the head bearing 5 is such that there is enough air to fill the wedge-shaped gap between the tape and the bearing surface during rotational scanning; Have the required length.

For this purpose, it is necessary to make the clearance δ1 between the leading edge of the bearing and the tape 50 μm or more. Therefore, for example, in a spherical bearing with a radius of curvature r = 20 im, and the amount of head depression into the tape δ2 is 50 μm, , 11 = JΣ77, which requires more than 7 "6" - 2 words.

On the other hand, the outflow side bearing length 12 from the bearing apex 5d to the rear end of the bearing is considerably smaller than the above 11, which is one of the features of the present invention.

The upper limit of 12 in the head bearing 5 of the present invention is determined at the center land under the conditions of the head curvature radius and scanning speed used, and within the range of the head pushing amount into the tape used and variations in tape tension. Set the maximum value so that the trailing edge of 5b always has the minimum clearance.

Determined by

According to experiments, this value for a grooved spherical head used at a scanning speed of around 25 m/s indicates that, under the conditions of the tape tension used and the amount of head pushing into the tape, when the head scanning speed is zero, the head bearing The relationship is approximately equal to 1/2 of the major axis of the elliptical contact area between the surface and the tape.

In other words, as shown in FIG. 6, the rear end of the head bearing of the present invention is equal to or more than the rear tangent line 9a of the elliptical area 8 where the tape and the head bearing 5 are in contact during non-scanning. It is necessary to be by your side.

On the other hand, the lower limit value of 12 is determined as the minimum value in the range in which the tape flying clearance on the bearing surface increases monotonically from the trailing edge of the head bearing surface toward the front under the usage conditions.

The rear edge of the bearing at this minimum distance is shown at 9b in FIG.

According to experiments, the position of the bearing trailing edge 9b is such that, under the conditions of the amount of head pushing into the tape used and the tape tension, the contact area between the bearing and the tape is at the sixth position when the scanning speed is zero. As shown in the figure, this is approximately the limit position that can maintain a monotonous elliptical shape.

That is, the trailing edge of the head bearing must be designed to be sandwiched between the rear tangent 9a of the elliptical area 8 in FIG.
For a head bearing with a scanning speed of 25 m/s, the head indentation amount is 40-60 μm, the tape tension is 0.005-0
．． Within the range of 011kg/mt, 12max=1・IW
11912min=0・711E0 In this case, for example, if you design 12=0.6am, the head pushing amount will be 6
When the size is about 0 μm, the contact area between the tape and the head during non-scanning is shown in FIG. 7 by the equal gap line A1. A2. As shown by A3, the tape is not part of a monotonous ellipse, but separates from the bearing surface before the trailing edge of the head bearing, and the tape comes into strong contact with the trailing edge of the bearing, causing unnatural deformation.

Also, the tape floating gap during head scanning is shown in Figure 7 A1.
As shown by A2 and A3, it becomes locally large in front of the trailing edge of the central land.

Next, the width of the central land portion 5b is determined so that the gap at the trailing edge becomes a desired value.

For example, in order to set the gap at the trailing edge of the center land to 0.2 μm under the above usage conditions, the width should be 250 to 300 μm.
It is appropriate to set it to m.

On the other hand, the width and depth of the two narrow grooves 5a are suitably about 100 μm, since they do not significantly affect the tape flying clearance characteristics.

As mentioned above, in conventional grooved spherical heads, the center land width was determined by the recording track width rather than the tape flying clearance characteristics, so in order to obtain an appropriate flying clearance, the spherical head bearing surface was It was necessary to modify the ellipsoidal surface again.

However, it should be noted that the head bearing of the present invention can be perfectly spherical and the flying clearance can be determined only by the central land width.

Next, the shape of the magnetic head installed at the rear end of the head bearing is as follows.
The head gap is determined to be equal to the recording track width and the C-shaped magnetic core 6 does not affect the tape flying clearance characteristics.

That is, as shown in Fig. 4, the length of the surface 6b of the C-shaped magnetic core 6 connected to the central land is 0.1 mm or less so as not to affect the floating clearance of the tape, and the rear part of the C-shaped magnetic core 6 is not more than 0.1 mm. It is chamfered with a curved angle so that it does not touch.

Further, the width of the head gap 6a at the gap abutting portion between the rear end surface of the center land and the C-shaped magnetic core 6 is processed to be equal to the desired track width.

In this case, in order to improve head efficiency, it is desirable that the trailing edge of the central land forming the head gap is also machined to have a length of 20 to 30 .mu.m and be equal to the track width, as shown in FIGS. 9a and 9b.

In the embodiment shown in FIG. 9, the width is 300~
After adhering the C-shaped magnetic core 6 of 400 μm, a local notch is made in the vicinity of the head gap meeting portion so as to be equal to the track width.

There are various methods for processing such a head gap portion, and it goes without saying that the present invention is not concerned with any processing method for forming the head gap portion to be equal to the track width.

In this way, a central groove is formed at the trailing edge of the air bearing surface of the central land portion 5b sandwiched between the two thin wires 5a.

A magnetic head gap 6a having a recording track width narrower than that of the land portion 5b is provided, and the magnetic head gap 6 is
The configuration is such that no surface with a floating function is provided behind a.

Finally, the head bearing surface and the C-shaped magnetic core surface 6b connected thereto are finished into the same spherical surface.

Since the grooved spherical head of the present invention has such structural dimensions, when it is used as a rotary scanning head, the first
The tape exhibits a floating gap distribution represented by equal gap lines as shown in Figure 0.

That is, as mentioned above, the length 12 of the outflow side bearing from the apex to the rear end of the head bearing is set to a suitably small value, so even if the tape tension and the amount of head pushing into the tape change slightly during use, The minimum gap is always formed at the head gap portion at the trailing edge of the central land.

In addition, since this value 12 is not extremely small, the tape floating clearance on the central land surface increases monotonically toward the bearing end, and the tape does not undergo unnatural local deformation at the rear end of the bearing. Tape wear and fatigue reliability is guaranteed.

In the present invention, a magnetic head gap 6a is provided at the trailing edge on the outflow side of the central land portion 5b of the air bearing surface, and a surface having a flying function is not provided behind the magnetic head gap 6a on the outflow side. Therefore, compared to conventional heads of this type, there is an advantage in that head shape errors and setting errors can be tolerated considerably, and there is also an advantage in that the setting margin of the head can be greatly improved.

Note that the floating head of the present invention can be used not only in a rotary head recording device but also as a head in, for example, a disk device using a flexible medium.

As explained above, according to the floating head according to the present invention, a magnetic head gap is provided at the trailing edge on the outflow side of the central land portion of the air bearing surface, and a floating function is provided behind the magnetic head gap on the outflow side. Since there is no surface to hold the head, head shape errors and setting errors can be tolerated considerably compared to conventional heads of this type, and the setting margin of the head can be greatly improved, making it suitable for practical use. The above effect is extremely dogmatic.

In addition, the gap between the magnetic recording medium and the head can be reduced to the minimum allowable gap where wear due to sliding does not become a problem. Since the head gap width can be designed to a different value independently, it is extremely effective in easily realizing a rotary scanning head for high-density recording that satisfies the conditions of a minute tape flying gap and a narrow track width.

[Brief explanation of drawings]

FIG. 1 is a front view of a conventional floating rotary scanning head, FIG. 2 is a side view of FIG. 1, and FIG. 3 is a distribution of the tape flying clearance on the conventional head bearing surface. FIG. 4 is a front view showing an embodiment of the floating head according to the present invention, and FIG. 5 is a side view of FIG. 4. Fig. 6 is a plan view used to determine the rear end position of the head bearing surface of the present invention, and Fig. 7 shows the difference between the tape and the bearing surface that occurs when the outflow side bearing length is too short and the scanning speed is zero. A plan view showing a typical example of the gap line, Figure 8 is a plan view showing the equal gap line between the tape and the bearing surface during scanning when the outflow side bearing length is too short, and Figure 9 is a plan view showing the trailing edge of the center land. FIG. 10 is a plan view showing a typical example of the tape flying gap distribution of the head of the present invention. 5... Head bearing, 5a... Thin groove, 5b... Central land portion, 5c... Bearing surface, 5d... Bearing apex, 6
...C-shaped magnetic core, 6a...head gap, 7.
... Winding wire, 8... Contact area between the tape and the head bearing surface.

Claims (1)

[Claims] 1. In a floating head in which the surface facing the magnetic recording medium has a spherical or pseudo-spherical shape and has two narrow grooves along the head scanning direction within this surface, a central land sandwiched between the two narrow grooves. A magnetic rad gap having a recording track width narrower than the central land portion is provided at the trailing edge of the outflow side of the air bearing surface, and no surface having a flying function is provided behind the head gap. , the radius of curvature of the head bearing using the length of the outflow side of the bearing from the bearing apex of the central land portion to the magnetic Rad gap, the amount of head pushing into the magnetic recording medium, and the head scanning speed under the conditions of the tension of the magnetic recording medium. 1. A floating head, characterized in that the magnetic head gap is made small enough to come into contact with the surface of a magnetic recording medium when the magnetic head gap is set to zero.