JPS59186114A - Magnetic head - Google Patents

Abstract

PURPOSE:To obtain a head of a long service life by providing plural grooves in parallel with a recording track to a sliding face of the magnetic head so as to decrease the spacing between the head and a tape. CONSTITUTION:To the sliding face of the magnetic head, >=2 grooves in parallel with the recording track are provided. Since the air placed between the tape and the sliding face of the head is moved as shown in arrows 4-6 and most of the air enters the grooves or passes through the head side face, the spacing between the head and tape is decreased. Although the depth of gap of the head is decreased because the sliding face is worn as being operated long, the effect of the grooves is kept until the service life of the head ends by making the depth of the grooves deeper than the depth of the gap.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a recording/reproducing apparatus using a magnetic tape, and particularly to a magnetic head.

[Background of the invention]

In a recording/reproducing apparatus using a magnetic tape, recording is performed by forming a magnetization pattern on the magnetic tape using a leakage magnetic field generated in a gap (hereinafter referred to as a gap) of a magnetic head shown in FIG. During playback, a magnetic field enters the helad core from the magnetization pattern on the tape through the gap in the magnetic head, and current flows through the coil wound around the magnetic head based on the principle of electromagnetic induction, which is amplified to obtain a playback signal.

It is well known that the characteristics of such magnetic recording and reproducing are mountain-shaped with respect to frequency. FIG. 2 1 shows the frequency characteristics of the reproduced output when the relative speed between the tape and the head is 5.8 m/sec. This is due to the fact that, although the frequency at which the reproduction output is high becomes smaller, various losses during recording and reproduction still increase at the frequency (short wavelength recording). These losses include self-demagnetization loss, write demagnetization loss, write spacing loss, read spacing loss, head read efficiency, and gap loss. The magnitude of these losses is shown in FIG. 2, and it can be seen that among them, the recording spacing loss and the reproduction spacing loss are the causes that reduce the reproduction output the most.

If this spacing loss is formulated, it can be expressed as E, where E is the reproduction output. Here, λ is the recording wavelength, and d is the spacing between the head and the tape. As can be seen from this equation, the town output is exponen for the spacing d.
It attenuates to t i al. Particularly when performing high-density recording, that is, short wavelength recording, this spacing loss becomes an extremely large factor in reducing reproduction output.

The reduction in reproduction power due to such spacing reduces the signal-to-noise ratio, and is a major cause of impairing the reliability of the angular raw signal. In particular, in digital VTRs that convert video signals into rtJIOj codes and record and reproduce them,
In order to record and reproduce large amounts of image data, high-density recording with a short recording wavelength is performed. Therefore, a decrease in the high frequency component of the raw angle signal causes an error in determining "1" or "0" during reproduction9, and further deteriorates the quality of the reproduced image. Therefore, reducing the spacing loss is extremely important in improving the reliability of reproduced images.

There are three possible causes of such spacing between the tape and head: the roughness of the magnetic particles on the tape surface, the roughness of the head surface, and the floating of the tape when running at high speed. . However, this amount of spacing is quite large compared to the roughness of the tape surface and the roughness of the head surface.
The amount of spacing is shown relative to the relative speed of the head, and as the speed increases, the amount of spacing tends to increase.

From these facts, the main cause of spacing is air entering between the tape and the head sliding surface.
It is generally said that this is because the tape floats to the surface.

There are two possible ways to reduce this spacing: increasing the tape tension, or decreasing the contact area of the head to increase the contact stress at the gap. However, the method of increasing the tape tension does not actually improve the spacing, as the playback output tends to remain unchanged and become saturated once the tape tension reaches a certain level. Furthermore, when considering the deformation and strain of the tape due to tension, it is not possible to obtain an increase in contact pressure corresponding to an increase in tape tension. The method of reducing the contact area of the head requires reducing the core thickness of the head, which has the disadvantage of accelerating wear of the head and shortening its life.

[Purpose of the invention]

In consideration of the above points, the present invention provides a head structure that has a long life and reduces spacing loss between the head and the tape.

[Summary of the invention]

In the present invention, by providing a groove parallel to the recording track on the sliding surface of the magnetic head, the glyphs that fit between the head and the tape are ejected through the groove, thereby suppressing the floating of the tape and reducing the spacing. be. Another feature is that the life of the head is extended by keeping the sliding area of the head in contact with the tape the same as before or making it thicker.

The present invention will be explained in detail below.

It is believed that the life of the head is approximately inversely proportional to the stress of the tape applied to the sliding surface of the head. If the stress is denoted by Q, it is expressed as Q=αT/W. Here, α is a proportionality constant including the coefficient of friction between the tape and the head, T is the tape tension and force, and W is the head sliding area. As can be seen from this equation, the stress Q is inversely proportional to the head sliding area. Therefore, by increasing the core thickness, the sliding area increases, stress decreases, and head life increases. Moreover, this sliding surface has the characteristic that it is not related to the shape but only to the contact area.

On the other hand, FIG. 4 shows the spacing amount with respect to the head core thickness. From this figure, it can be seen that the smaller the core thickness, the smaller the spacing amount, and the greater the effect.

In view of the above, the present invention creates grooves parallel to the recording track on the sliding surface of the head to divide the sliding motion, thereby providing an effect when the core thickness is thin in terms of spacing.
Regarding the lifespan, it is designed to have an effect when the core thickness is large.

[Embodiments of the invention]

FIG. 5 is a diagram illustrating the structure of a head according to the present invention, in which two grooves are provided at both ends of all recording tracks. Figure 2
The portion shown in is the groove of the present invention.

In the case of a narrow track head where the recording track width is less than 1/3 of the core thickness and the number of grooves is 2, the tape flying height will be small if the groove is located at 1/3.2/3 of the core thickness. Become.

FIG. 6 is a diagram showing the head sliding surface of FIG. 5. The portion shown in FIG. 3 is the groove, and the arrows shown at 4 and 5.6 indicate the movement of air. As can be seen from the figure, most of the air sandwiched between the tape and the head sliding surface enters the groove or passes through the side surface of the head. Therefore, the flying height of the tape due to air is the same as the spacing amount shown in FIG. 4, where the thickness of the portion surrounded by the groove is the core thickness.

As the head is used, the sliding movement is worn out and the gap depth becomes smaller. Therefore, if the depth of the groove is made larger than the gap depth, the effect of the groove will be maintained in the trench where the life of the head will be exhausted.

FIG. 7 shows the head sliding surface when the width of the groove is made thinner on the side where the head hits the tape first (in the head running direction) and thicker on the side where it hits the tape later. In the figure, the shaded area indicates the groove. With such a groove shape, the air in the groove that is separated between the tape and the head when running is V? while passing through the groove. :#The air pressure becomes smaller than the outside air pressure. The air that enters the area shown in Figure 7 after the break is the same as the outside pressure, but the cross-sectional area of the groove is larger at the rear of the head (in the direction shown in Figure 8), so the air expands. Air pressure drops. Therefore, the air trapped between the tape and the head is sucked into this groove, and a force is exerted that presses the head sliding surface against the tape. Therefore, there is an effect that the spacing amount is smaller than that of the groove shown in FIG. 6, which has a uniform groove shape.

FIG. 8 shows a side view of the head when the depth of the groove of the head is shallower on the side that contacts the tape first and deeper on the side that contacts the tape later. The broken line in FIG. 9 represents the depth of the groove. This is based on the same principle as the head shown in FIG. 7, and the air pressure passing through the groove is lower than the outside air pressure, improving the adhesion between the tape and the head.

〔Effect of the invention〕

As described above, since the present invention provides grooves parallel to the recording tracks on the sliding surface of the magnetic head, spacing loss can be greatly reduced.

[Brief explanation of drawings]

Figure 1 shows the structure of a conventional magnetic head, Figure 2 shows the frequency characteristics of the reproduced output, and also shows various losses. Figure 3 shows the amount of spacing versus the relative speed of the tape and head. Figure 4 shows the total amount of spacing relative to the core thickness, Figure 5 is a diagram of the head structure when the present invention is applied, and Figure 6 shows the effect of the present invention in air. A diagram of the head sliding surface explained from the flow. Figure 7 is a diagram of the head sliding surface when the width of the head groove is narrower on the side that hits the tape first and wider on the side that hits the tape later. Figure 8 is a diagram of the head groove. FIG. 7 is a top view of the head when the depth is set to be shallower on the side that hits the tape first and deeper on the side that hits the tape later. (10) Vi 1 Figure Z Number of people for Figure (M) l, K) Y 3 (2) @ Village Ryo L (-i bush) Figure 4 Core thickness (μ) Figure 5 vi6 Figure ￥J ″ 7 Figure η δ Continuation of figure 1 page 0 Inventor: Morito Rokuta, Hitachi, Ltd. Tokai Plant, 1410 Oaza Inada, Katsuta City 0 Inventor: Takagi, Hitachi, Ltd., Hitachi, Ltd. Tokai Plant, 1410 Oaza Inada, Katsuta City 0 Applicant Hitachi Electronics Co., Ltd. 1-23-2 Kanda Suda-cho, Chiyoda-ku, Tokyo

Claims (1)

[Claims] 1. A magnetic head for recording and reproducing using a magnetic tape, characterized in that a sliding surface of the magnetic head has grooves parallel to recording tracks. 2. The magnetic head according to claim 1, wherein the depth of the groove of the magnetic head is greater than the depth of the head gap. 3. The magnetic head according to claim 1, wherein the number of grooves in the magnetic head is two or more in total on the left and right sides of the recording track. 4. The magnetic head according to claim 1, wherein the width of the groove of the magnetic head is made thicker on the side that hits the tape earlier than on the side that hits the tape later. 5. The magnetic head 1- according to claim 1, wherein the depth of the groove of the magnetic head is made deeper on the side that hits the tape later than on the side that hits the tape first.