JPH04310617A - Height adjusting method of magnetic head - Google Patents

Abstract

PURPOSE:To provide a method to adjust the height of a head fitted at a rotating cylinder without being influenced with the mechanical vibration and the temperature change while the cylinder is rotated with high accuracy and non-contact, in a magnetic recording and reproducing device with the rotating cylinder. CONSTITUTION:An upper cylinder 1 is rotated by the number of rotation at the time of using it as a VTR actually, the distance (head height) of the head gap edge of a head chip 3 and a reference surface 5 of a lower cylinder 2 is measured by using an objective lens 6 and the deforming quantity of the head base necessary to form the prescribed head height is calculated. Next, while the upper cylinder is rotated, a laser beam 11 is allowed to irradiate near the part to stick the head chip 3 of a head base 4, only the prescribed quantity of the head base is deformed by the welding deformation and the head height is adjusted. The adjustment of the deforming quantity is performed by the control (control of irradiation distance (d) in the figure) of the focus condition of the laser beam on a head base surface 12 to which the laser beam is radiated.

Description

[Detailed description of the invention]

0001

TECHNICAL FIELD This invention relates to a method for adjusting the height of a magnetic head in a magnetic storage device using a rotating cylinder.

0002

2. Description of the Related Art The positioning accuracy of a magnetic head used in a magnetic recording/reproducing device is an important accuracy that determines the format of information recorded on a medium.

[0003] For example, in a video tape recorder that is widely used for home use, the rotating cylinder has a 180°
Two pairs of magnetic heads mounted facing each other record and reproduce image and audio information while sequentially scanning the magnetic tape diagonally. The track pitch actually recorded on a magnetic tape is very narrow, 60 μm in the 2-hour mode and 20 μm in the 6-hour mode.

If the two pairs of magnetic heads described above cannot accurately scan these tracks, recorded information cannot be accurately reproduced, and the quality of the reproduced image will be significantly degraded. To prevent this, it is necessary to precisely match the scanning pitch of the magnetic head to the above-mentioned track pitch, and an important factor that determines this scanning pitch is the height of the magnetic head.

The height of the magnetic head is the distance (H in FIG. 3) between the reference plane 5 of the lower cylinder 2 shown in FIG. 3 and the end of the gap of the head fixed to the upper cylinder 1. It is.

Regarding the conventional head height adjustment method (Fig. 4
) will be explained below. However, (Fig. 4)
) is a diagram showing a cross section of the upper cylinder part in the middle.

First, a spacer (not shown) of a predetermined thickness is inserted between the upper cylinder 1 and the head base 4 to which the head chip 3 is attached to make a rough adjustment, and then the head height is adjusted using the objective lens 6. While observing this, screw in the insect screw 7 that is touching a part of the head base 4 by the necessary amount of adjustment in the direction of the arrow 8 in (Fig. 5) to partially deform the head base and set the desired head. Adjust the height.

[0008]

The basic principle of adjustment using a conventional insect screw is to utilize the deformation of the head base due to the pushing force of the insect screw within the limit of the elastic deformation of the head base. In such a case, if the amount of push-in of the insect screw changes due to mechanical vibration or temperature change, the amount of deformation of the head base will change by that amount, and there is a possibility that the head height will eventually change.

In actual VTRs, there are various factors that generate vibration, such as cylinder rotation and tape transport, and temperature changes due to changes in the heat generated from these drive systems over time and changes in the usage environment must be avoided. I can't do it.

[0010]Currently, in an attempt to minimize the effects of these factors, screw loosening agents (resin that sticks at room temperature) are used for insect screws, but the effect is not sufficient; The head height had changed depending on the order. This change in head height is one of the important factors that affects the image quality of a VTR.

[0011] Furthermore, when a hydrodynamic bearing is used for the bearing of the rotating cylinder, the relative position of the rotating upper cylinder to the lower cylinder changes as the shaft rotates, so the conventional method of adjustment in a stationary state can ensure sufficient accuracy. It was difficult to do so, and in the end, adjustment work had to be a trial and error process.

[0012] Moreover, the actual adjustment work using the insect screws was done manually and was quite complicated.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method that can solve the above problems and adjust the head height of a magnetic head with high precision and high efficiency without being affected by vibrations or temperature changes. .

[0014]

[Means for Solving the Problems] In order to achieve this object, the present invention provides a magnetic recording/reproducing device having a rotating cylinder, in which a laser beam is irradiated near a head chip attachment portion of a head base attached to the rotating cylinder. By controlling the focus state of the laser beam in the laser irradiation section of the head base, the amount of deformation of the head base is controlled and the height of the magnetic head is adjusted.

[0015]

[Operation] By using laser processing that can deform the head base without contact, the head height can be adjusted even when the upper cylinder is rotated.
Moreover, by adjusting the focus of the laser beam, the energy density in the irradiated part of the head base is controlled, and the amount of deformation of the head base is adjusted, so high-precision adjustments can be made quickly under laser processing conditions that provide stable laser output. It has this effect.

[0016]

[Embodiment] An embodiment of the height adjustment of a magnetic head according to the present invention will be described with reference to (FIG. 1). A head base 4 made of brass with a thickness of 1.5 mm to which a head chip 3 is attached is attached to the upper cylinder 1;
was fixed to the lower cylinder 2 by a fluid bearing (not shown). Next, the head height was measured using the objective lens 6 while rotating the upper cylinder 1 at the regular rotation speed, and it was found that a deformation adjustment of 12.3 μm was required to reach the predetermined head height.

In this embodiment, Nd is used as the laser beam 11.
: Short pulse oscillation of a YAG laser (wavelength: 1.06 μm) was used. In addition, the pulse width of the excitation flash light was set to 1 m.
sec, and the excitation voltage was 450 volts, the laser energy obtained was about 1 joule per pulse.

The upper cylinder is provided with a through hole 9 through which laser light passes. This through hole has a circular arc shape extending in the rotational direction of the arrow in the figure and has a length of 8 mm. In order to actually pass the laser beam while rotating, the laser oscillation was synchronized with the rotation of the upper cylinder 1.

Actual laser light 11 under the conditions described above
The following describes the modification of the head base.

FIG. 2 is a graph showing the relationship between the irradiation distance d and the amount of deformation of the head base, which was obtained through an experiment conducted in advance using a dummy head base made of the same material and having the same shape. As is clear from this figure, there is a proportional relationship between the irradiation distance d and the amount of deformation of the head base.

Therefore, based on this result, the irradiation distance d was changed to 3.
When an actual head base was deformed with a diameter of 9 mm, the amount of deformation obtained was 12.0 μm, which was a deviation of only 0.5 μm from the target.

[0022] In another embodiment, the required deformation amount is 1.
For the one with a diameter of 5.7 μm, the distance d was divided into multiple steps and the laser irradiation position was shifted by 0.1 mm at each step. The reason for dividing the welding into multiple stages is to take advantage of the additivity of welding deformation and take measurements at any time to re-ascertain the desired amount of deformation and deform more accurately. In addition, the irradiation position was shifted by 0.1 mm,
This is to prevent the absorption rate of laser energy from changing due to changes in surface properties after irradiation.

Actually, the first deformation was performed with the irradiation distance d set to 29 mm, and as a result, the amount of deformation was 9.3 μm. Therefore, the remaining required deformation amount is 6.4 μm, and then the irradiation position is shifted by 0.1 mm in the direction of the rotation center.
A second deformation was performed at an irradiation distance d of 17 mm. The amount of deformation at this time was 4.2 μm, which was still 2.2 μm short. Therefore, the third deformation was performed with the irradiation distance d set to 7.5 mm, and the result was 2.1 μm. The final amount of deformation was 15.0 μm, which was 0.1 μm away from the target.
It was 6 μm.

[0024] Such highly accurate deformation is possible because it is possible to gradually reduce the amount of deformation with little error under stable laser emission conditions.

The above-described head height adjustment according to the present invention does not use insect screws and is based on plastic deformation of the head base, so it is completely free from the effects of mechanical vibration and temperature changes that were problems in the past. I don't accept it. Actually, -40℃
A heat shock test was conducted by repeatedly heating the head to 80°C, and the amount of deformation of the head base before and after the test was 0.1μ.
There was no change with an accuracy of m or less.

In this embodiment, a hydrodynamic bearing was used, so the head height was adjusted while rotating the cylinder. However, according to the present invention, a bearing other than a hydrodynamic bearing, for example, using a bearing, can be used. The head height can be adjusted with the cylinder stationary.

In addition, in this embodiment, the irradiation distance d was changed as focus control, but even if the irradiation distance is not changed, the focal position of the lens system can be changed to achieve the same effect as when the irradiation distance d is changed. It is clear that this effect can be obtained.

Furthermore, it is also possible to automate the laser irradiation and the driving system of the focusing lens and the measurement system by computer-controlling the relationship between the irradiation distance d and the amount of deformation as data. By automating this series of adjustment work, it will be possible to incorporate it into the actual VTR mass production line, and it will be possible to perform head height adjustment more quickly and with higher precision and reliability than ever before. It's obvious.

[0029]

[Effects of the Invention] As described in the embodiments above, the present invention has the advantage that highly accurate head height adjustment can be performed while the cylinder is rotating by simply controlling the focus state of the laser beam. , by automating VT
It becomes possible to incorporate it into the R mass production line, and its productivity improves dramatically. Further, according to the present invention, since the head height is not affected by mechanical vibrations or temperature changes, it is easy to realize a high-quality VTR by narrowing the tracks.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram illustrating main cross sections of upper and lower cylinders and a head height adjustment mechanism using laser light according to an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the irradiation distance d and the amount of deformation of the head base in the present invention.

FIG. 3 is an explanatory diagram for explaining the definition of head height.

FIG. 4 is a sectional view of the upper cylinder illustrating a conventional head height adjustment method.

FIG. 5 is an enlarged view of the main part of the upper cylinder in FIG. 4;

[Explanation of symbols]

1 Upper cylinder 2 Lower cylinder 3 Head chip 4 Head base 5 Reference plane 6 Objective lens 7. Bug screw 8 Screwing direction of insect screw 9 Through hole 10. Focusing lens 11 Laser light 12 Head base surface

Claims (2)

[Claims] 1. In a magnetic recording/reproducing device having a rotating cylinder, the head height is adjusted by irradiating a laser beam near a head chip attachment portion of a head base attached to the rotating cylinder to deform the head base. A method for adjusting the height of a magnetic head, the method comprising: adjusting the amount of deformation of the head base by controlling a focus state of the laser beam in a laser irradiation section of the head base. 2. The method for adjusting the height of a magnetic head according to claim 1, wherein the head base is deformed in multiple stages by changing the position where the laser beam is irradiated.