JPS5914121A - Magnetic head for detecting of head clogging - Google Patents

Abstract

PURPOSE:To detect accurately a lost part of video signals, by applying winding to a head chip having an azimuth angle equal to the gap azimuth angle of a video track on a magnetic tape. CONSTITUTION:The video signal recorded on a magnetic tape 10 traveling toward an arrow mark is reproduced by a fixed magnetic head 8 having an azimuth angle equal to the azimuth of a magnetized pattern 11. The pattern 11 on the tape 10 has a gap azimuth theta1 and track width W1. The head 8 is connected with a yoke 15 containing a winding 14 with a terminal 13 wound around a head chip 12 having an azimuth theta1 (equal to the gap azimuth) and then put into a housing 16 which serves also as a shielding case. In such a way, the lost part of video signals can be detected accurately. This head ensures accurate detection of clogging of the video head.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic head for detecting clogging of a video head in a helical scan video tape recorder.

Structure of a conventional example and its problems A conventional helical scan type video tape recorder will be explained with reference to FIGS. 1 and 2.

On the disk (1), there is a video head (2) (:l) that actually records the video signal, and each of these video heads (
2) (3) A clogging detection head (JJ i5) that rotates following f is installed, and the disk (
As the tape (6) rotates and the tape (6) runs, the clogging detection head (4) scans and reproduces the no.f turn recorded by the video head (2), thereby monitoring the quality of the recording. do.

Similarly, the clogging detection head (5) scans and monitors the pattern recorded by the video head (3).

That is, to explain using the magnetization pattern shown in FIG. 2, a clogging detection head whose height is corrected according to the distance from the video head (2) moves over the pattern (7) recorded by the video head (2). (The four heads scan and reproduce the same trajectory. However, in this type of system, the video head (2) (3) that actually records the video signal and the head (4) (5) for clogging detection are close to each other. Therefore, the clogging detection head (4) (5) not only reproduces the signal on the tape (6), but also directly picks up the recording signal of the video head f2) (3) by magnetic coupling, causing the tape (6
) If there is a defective part in pattern (7)I, the defective part cannot be detected accurately and the video head (
2) There is a problem in that it is only possible to reliably detect the clogging in (3).

OBJECTS OF THE INVENTION The present invention solves the above-mentioned conventional drawbacks, and an object of the present invention is to provide a video head (a magnetic head for head clogging detection that can accurately detect defective portions of a video signal recorded in fragments).

SUMMARY OF THE INVENTION In order to achieve the above object, the magnetic head for head clogging detection of the present invention seals an azimuth angle equal to the gap azimuth angle of a video track f on a magnetic tape recorded by a helical scan type HD tape recorder. The head chip is wound with a wire and housed in a housing.

DESCRIPTION OF EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described based on the drawings.

In Fig. 8, (8) is a head clogging detection magnetic head (hereinafter referred to as magnetic head) having a spacing gap (9), αQ is a magnetic tape, and 0υ is a video recorded on the magnetic tape OQ. This is the magnetization pattern of the signal, and the video signal recorded on the magnetic tape Q0 traveling in the direction of the arrow ζ is reproduced by a fixed magnetic head (8) having an azimuth equal to the azimuth of the magnetization pattern Qυ. Magnetization pattern on FJσ magnetic tape QO (
B) is the gap azimuth θ1 and the track width W1 as shown in FIG. As shown in Fig. 5, the HITi self-adjustable head (8) has a head chip @ (here, a yoke around which a winding Q ) and housed in a housing that also serves as a shield case. = The track width W of the head chip (b) in V must be approximately equal to the track width W1 on the magnetic tape OQ, so in current VTRs it is about 20~'IOItm, which is weak in strength and prone to cracks. Chips, etc. occur. Therefore, as shown in Fig. 6, by making the head chip Q7) a glass-reinforced type, that is, by reinforcing the area near the gap with glass, the thickness of the head chip Q7 can be made several hundred μm. possible and easy to manufacture.

FIG. 7 shows another embodiment, in which a wear-resistant large non-magnetic block eυ is bonded to both end faces in the thickness direction of the head chip (), and this is housed in the housing (). ing. In this case, wear resistance improves. In addition, although the shielding effect is slightly reduced, compared to the conventional rotary clogging detection head, the installation location can be far away from the video head, so recording signals are not directly read from the video head.

8 and 9 show still another embodiment, in FIG. 8, magnetic tape, (24a), (24b)
is a magnetization pattern recorded by a pair of azimuthal video heads, and θ2. θ is the gap azimuth of the magnetization patterns (24a) and (24b), respectively.

In this example, as shown in FIG. 9, the magnetization pattern (24a
) and a head chip (25a) having a gap azimuth equal to the gap azimuth θ2 of
A head chip (25b) having a gap azimuth equal to the gap azimuth v3 in b) is fitted with a shield block (via a spacer □□□ made of a non-magnetic material) and housed in a housing (c). be. According to this configuration, it is possible to detect a missing portion of a video signal recorded azimuthally by a pair of video heads.

In each of the above embodiments, clogging of the video head can be detected more accurately by using the high magnetic permeability material 'C1 as the material for the housing μQ.

Furthermore, since the magnetic head for head clogging detection according to the present invention is a fixed head, the relative speed with respect to the magnetic tape is lower than that of the conventional rotary type clogging detection head, so the head output is small. In this case, it is easy to increase the number of turns of the winding, so increasing the number of turns can eliminate the decrease in output.

Effects of the Invention As described above, according to the present invention, the following effects can be obtained.

■Since it can be installed at a position optically separated from the video head that records the video signal, it reproduces only the signals recorded on the magnetic tape, without directly reading the signal from the video head, and accurately reproduces the signal recorded on the magnetic tape. can detect signal loss areas;
Therefore, clogging of the video head can be detected reliably.

■In the conventional rotary clogging detection head, in order to follow the trajectory of the recording video head that scanned in advance,
It is necessary to accurately match the track height and gap position of the clogging detection head, and extremely high precision is required for assembly into the cylinder. Since high precision is not required, manufacturing is easy.

(2) The conventional rotary type clogging detection head has a high relative speed with the magnetic tape and wears out quickly, whereas the magnetic head for head clogging detection according to the present invention is of a fixed type and therefore has little wear.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a disk portion of a conventional helical scan video tape recorder, FIG. 2 is an explanatory diagram of a magnetization pattern on a magnetic tape, and FIGS. 8 to 5 show an embodiment of the present invention. Figure KA8 is an explanatory diagram of the principle, Figure 4 is an explanatory diagram of the magnetization pattern on the magnetic tape, Figure 5 is an exploded perspective view of the magnetic head, Figure 6 is a perspective view of a modified example of the head chip, and Figure 7 is an exploded perspective view of the magnetic head. The figure is a perspective view of a magnetic head in another embodiment, FIGS. 8 and 9 show still another embodiment, FIG. 8 is an explanatory diagram of a magnetization pattern on a magnetic tape, and FIG. 9 is a diagram of a magnetic head. It is a front view. (8) -°°head magnetic head for detecting eye deviation, (9)
(G)°...Head gap, αQ)...Magnetic tape, Qυ(24aX24b)...Magnetization pattern, aJ
aη) (25a) (25b)...Head chip, Q◆
...Winding, to 01)...Housing agent Yoshihiro GunmotoFigure 2C Figure 3Figure 4

Claims (1)

[Claims] 1. A head chip in which a head chip having an azimuth angle equal to the gap azimuth angle of a video track on a magnetic tape recorded by a helical scan video tape recorder is wound and housed in a housing. Magnetic head for detecting blockages. 2. Winding wires are applied to a plurality of head chips with different azimuth angles, and these are housed in a housing.
- A magnetic head for head clogging detection according to claim 1. 8. Both sides of the head chip in the thickness direction are sandwiched between large wear-resistant blocks, and these are housed in a housing.
F1: A magnetic head for head clogging detection according to claim 1. 4. A magnetic head for detecting head clogging according to any one of claims 1 to 8, wherein a high permeability magnetic material is used as the material of the housing.