JPH04310613A - Height adjusting method of magnetic head - Google Patents

Abstract

PURPOSE:To provide a method to be able to adjust the head height of a magnetic head fixed at the cylinder quickly and with high accuracy without changing by the mechanical vibration and the temperature change. CONSTITUTION:A head base 1 to stick a head chip 3 is fixed to an upper cylinder 1, and the magnetic head height before adjustment is measured by using an objective lens 6 while the upper cylinder is rotated by the regular number of rotation. The cylinder is rotated by the number of rotation lower than the regular number of rotation, near the part to stick the head chip 3 of the head base 1 is irradiated with laser light 11 synchronized to the rotation, the head base 1 is deformed to the irradiation side and the head height of the head chip 3 is adjusted so as to become the prescribed value.

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. 2) between the reference plane 5 of the lower cylinder 2 shown in FIG. 2 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. 3
) will be explained below. However, (Figure 3) is (Figure 2
) 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. 4 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.

[0009]Actual VTRs have various elements that cause vibrations, 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 cannot be avoided. do not have.

[0010]Currently, in an attempt to minimize the influence of these variable factors, screw loosening preventive agents (resin that sticks at room temperature) are used for insect screws, but the effect is not sufficient and many The head height changed on the order of microns.

Furthermore, when a hydrodynamic bearing is used as a bearing for a rotating cylinder, the relative position of the rotating upper cylinder to the lower cylinder changes greatly depending on whether or not the shaft is rotating. Therefore, it is difficult to ensure sufficient accuracy, and in the end, adjustment work has 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 head attached to a rotating cylinder in which the cylinder is rotated at a lower rotational speed than the rotational speed at which recording and reproduction are actually performed. The head base of the magnetic head attached to the cylinder is partially deformed by irradiating a laser beam in synchronization with the rotation of the cylinder near the part where the head chip is attached. This is to adjust the head height.

[0015]

[Operation] According to the present invention, the head height is adjusted by plastic deformation of the head base due to laser beam irradiation, so the adjusted head height is not easily affected by mechanical vibrations or temperature changes. Since the head base can be deformed without contact, adjustments can be made while the cylinder is rotating. Further, since the laser beam is irradiated in synchronization with a rotational speed lower than the rotational speed at which actual recording and reproduction is performed, the synchronization accuracy does not need to be very high.

[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 transmit the laser beam while rotating, the laser oscillation must be synchronized with the rotation of the upper cylinder 1.

On the other hand, the diameter of the upper cylinder used in this example is 62 mm, and the through hole 9 provided is on a circumference of 50 mm in diameter. Therefore, the normal rotation speed (180 per minute
0 rotation), the speed when the through hole 9 is on the optical axis of the laser beam is 4.7 m/sec. This ultimately means that if the laser oscillation deviates from rotational synchronization by 0.35 msec or more, the laser beam will hit the upper cylinder, making it impossible to control the deformation of the head base with high precision.

Therefore, in this embodiment, in consideration of the timing accuracy of laser oscillation, the rotational speed is lowered to an extent that no shaft vibration occurs. The rotation speed at that time was 1000 revolutions per minute. By lowering the rotation speed of the cylinder using a hydrodynamic bearing, the upper cylinder approaches the lower cylinder in the height direction, but this does not affect the amount of deformation of the head base itself.

Under the conditions described above, a dummy head base was deformed by laser light as a preliminary experiment;
It was deformed to the irradiation side by 0.5 μm per pulse. Furthermore, since the total amount of deformation was proportional to the total number of pulses of the irradiated laser beam, the amount of deformation was adjusted using the total number of pulses of the laser beam.

Actually, since the required deformation amount was 12.3 μm, the total number of pulses was set to 25, and the laser beam was applied at 1000 pulses.
Irradiation was performed 25 times in synchronization with the rotation of the cylinder at rpm. As a result, the head base was deformed by 12.7 μm toward the irradiation side, and a highly accurate adjustment was achieved with a deviation of 0.4 μm from the target head height. Further, the time required for adjustment was only 1.5 seconds.

[0023] Also, 1 in the range of -40°C to 80°C
Even after the 0 hour heat shock test, the amount of deformation remained stable with no change.

In this embodiment, the amount of deformation is adjusted by controlling the number of laser beam pulses, but the power of the laser beam may also be controlled. Further, although a Nd:YAG laser was used as a laser light source, other light sources may be used. For example, carbon dioxide laser, Ar gas, excimer laser, etc. may be used. Furthermore, the present invention can be applied to head bases made of materials other than brass by changing the laser irradiation conditions.

In addition, in this embodiment, the height adjustment was explained with one head chip bonded to the head base, but this also applies when multiple head chips are bonded to one head base. The invention can be applied and furthermore,
If a plurality of such head bases are fixed to the cylinder, the present invention can be similarly applied to all of them.

In this embodiment, welding deformation by laser beam irradiation using optical energy was used, but in principle, any method that can perform local heating may be used. Examples include arc welding and electron beam welding using electrical energy, ultrasonic welding using ultrasonic energy, and gas welding using chemical energy.

[0027]

Effects of the Invention As described in the embodiments above, according to the present invention, the head height can be adjusted while the cylinder is rotating, and the cylinder rotational speed at the time of adjustment is Since the head height can be set low, the head height can be adjusted with high precision using a relatively inexpensive laser device. Therefore, in addition to cost reduction benefits such as reducing the number of parts in the manufacturing process of current VTRs and streamlining adjustment work, it also enables the mass production of VTRs with higher image quality.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram for explaining one embodiment of the present invention using a cross section of a cylinder and a laser beam.

FIG. 2 is an explanatory diagram for explaining the definition of head height.

FIG. 3 is a sectional view of the upper cylinder illustrating a conventional head height adjustment method.

FIG. 4 is an enlarged view of the main part of the upper cylinder in FIG. 3;

[Explanation of symbols]

1 Upper cylinder 2 Lower cylinder 3 Head chip 4 Head base 5 Reference plane 6 Objective lens 7. Bug screw 10. Focusing lens 11 Laser light

Claims (1)

[Claims] 1. In a magnetic head attached to a rotating cylinder, the head base of the magnetic head attached to the cylinder is rotated at a rotation speed lower than the rotation speed for actual recording and reproduction. A method for adjusting the height of a magnetic head, in which the height of the head is adjusted by partially deforming the head base by irradiating a laser beam in synchronization with the rotation of the cylinder near the part to which the head chip is attached.