JPH029015A - Rotary drum device - Google Patents

Abstract

PURPOSE:To decrease a leakage flux on a magnetic head side and to prevent the demagnetization of a magnetic tape and the generation of audio noise by placing a shielding case consisting of a magnetic material with a gap in the periphery of a magnetic head driving part, especially, so that the gap on the magnetic head side becomes the largest. CONSTITUTION:A shielding case 32 consisting of a magnetic material is provided with a gap in the periphery of first-third yokes 21, 23 and 24 of a magnetic head driving part 7 for displacing a magnetic head 16 in the vertical direction (the width direction of a magnetic tape), especially, so that the gap on the magnetic head 16 side becomes the largest. Accordingly, a magneto-resistance extending from the yokes 21-24 to the shielding case 32 becomes maximum in the direction of the magnetic head 16. Therefore, the majority of leakage flux passes through other parts J, K where the magneto-resistance is small than the direction of the magnetic head 16, reaches the shielding case 32, returns to the yokes 21, 23 and 24 again and forms a closed magnetic path. In this regard, from the shielding case 32 on the magnetic head 16 side, a magnetic flux for exerting an undesirable influence on the outside scarcely leaks.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is directed to, for example, making a magnetic head movable in the width direction of a magnetic tape to accurately trace magnetic recording traces.
e) A rotating drum device for a video tape recorder.

[Conventional technology]

FIG. 6 is a sectional view showing the main parts of a rotating drum device according to a conventional embodiment, FIG. 7 is a view taken along the ■-■ arrow in FIG. 6, and FIG. 8 is a view taken along the ■-■ arrow in FIG. , FIG. 9 is a sectional view of FIG.
Figure O is a side view of Figure 8.

In Figures 6 and 7, (1) is the lower drum, (2) is the bearing attached to this lower drum, (3) is the rotating shaft supported by this bearing and rotates, and (4) is this rotating shaft. A pedestal fitted to one end of the pedestal, (5) an upper drum attached to this pedestal using screws (6), and (7) a magnetic head attached to this upper drum using screws (8). Drive unit, (9)
is the lower transformer attached to the lower drum (1), α0) is the upper transformer attached to the pedestal (4), (11) is the wiring board attached to the upper drum (5), and (12) is the magnetic head drive A non-rotating contactor (13) for supplying a control current to the part (7) is mounted on a pedestal (
(4) is a rotating electrode provided on a part of the electrode (14).
a connecting part (16) electrically connected from 3) to the magnetic head drive part (7) via the connecting part (15) and the wiring board (11);
is the magnetic head WjA! It is a magnetic head attached to the 1111 part (7), and is electrically connected to the upper transformer (101) via the connection part (l?), the wiring board (11), and the connection part (15). (18) is a recess provided in a part of the upper drum (5) to accommodate the magnetic head drive unit (7), and is formed one size larger than the magnetic head drive unit (7) so that the position of the magnetic head (16) can be adjusted. (19) is a position adjustment hole for adjusting the position of the magnetic head (16);
0) is a magnetic tape that comes into sliding contact with the magnetic head (16).

Figures 8, 9 and 10 show the magnetic/rad drive section (7
) in more detail, (21) is a first yoke made of a magnetic material, (22) is a columnar first permanent magnet fixed to this first yoke, and (23) is a part of the inner circumference that is convex. Shape part (
23a), a second yoke made of magnetic material attached to the first yoke (21); (24) a third yoke made of magnetic material attached to this second yoke;
25) is a columnar second permanent magnet fixed to the third yoke with the same magnetic poles as those of the first permanent magnet (22) facing each other;
) is a pole piece made of a magnetic material and fixed to either one of the second permanent magnets and the first permanent magnet, and (27) is a leaf spring made of a thin non-magnetic material; ) and the second yoke (23), and its extending portion (27m) is held between the first yoke (21) and the second yoke (23).
A counter (21a) provided in the yoke (23),
It protrudes outward through (23a), and a magnetic head (16) is attached to its tip. (28) is a plate spring made of a thin non-magnetic material and is held between the second yoke (23) and the third yoke (24). (29) is a fixed member held by the leaf springs (27) and (28), respectively, and (30) has an inner circumference of the first permanent magnet (22), the second permanent magnet (25), and the pole piece (26). A bobbin (31) is fixed to the fixing member (29) at a position with a gap (F) between it and the outer circumference of the second yoke (23). Convex shaped part (23
a), there is a gap (G) over the entire circumference.

The conventional rotating drum device is constructed as described above. For example, referring to FIG. 9, the first permanent magnet (22) is connected to the pole piece (26), the second yoke (23) and the first yoke (21).
) to generate magnetic flux (D). Similarly, the second permanent magnet (25) is connected to the pole piece (26),
A magnetic flux (magnetic flux (E) in the opposite direction to DJ) is generated by a closed magnetic path created by the yoke (23) and the third yoke (24).

Thus, magnetic flux (D) and magnetic flux (E) both flow in the annular gap (F
) and (G) in the same direction, and the total magnetic flux of the first permanent magnet (22) and the second permanent magnet (25) crosses the coil (31).

In this state, the coil (31) is connected to the electrode (
13), connection part (+5), and (14), the coil (31), bobbin (30), and magnetic head (1
6) moves vertically in a parallel straight line as one unit.

In this way, the magnetic head (16) is displaced in the width direction of the magnetic tape (20) and traces the magnetic recording trace with high precision.

[Problem to be solved by the invention]

In the conventional rotating drum device as described above, a part of the magnetic flux generated by the first permanent magnet (22) and the second permanent magnet (25) is transferred to the first yoke (21) and the first yoke (21) as shown in FIG. 9H and I. There is leakage (hereinafter referred to as leakage magnetic flux) to the outside over the entire circumference of the second yoke (23) and the third yoke (24), especially the magnetic head (1
There were quality problems such as the magnetic tape (20) being demagnetized due to leakage magnetic flux on the 6) side and audio noise being generated.

[Purpose of the invention]

The present invention has been made to solve these problems, and in particular, it is an object of the present invention to provide a rotating drum device that reduces leakage magnetic flux on the magnetic head side and prevents demagnetization of the magnetic tape and generation of audio noise.

[Means to solve the problem]

In the rotating drum device according to the present invention, a shield case made of a magnetic material is arranged around the first yoke, the second yoke, and the third yoke with a gap therebetween, so that the gap in the direction of the magnetic head is larger than the others. This is what I did.

[Effect]

In this invention, since leakage magnetic flux easily passes through the shield case on the side with the smaller gap, the leakage magnetic flux on the side of the magnetic head with the largest gap can be reduced.

[Embodiments of the invention]

FIG. 1 is a cross-sectional view showing the main parts of a rotating drum device showing an embodiment of the present invention, FIG. 2 is a view taken along the line II-II in FIG. 1, and FIG. 4 is a sectional view of FIG. 3, and FIG. 5 is a side view of FIG. 3.

In these figures, (1) to (31) have exactly the same configuration as the above-mentioned conventional device. (32) are the first yoke (21), the second yoke (23), and the third yoke (24).
) is housed with a gap therebetween, and is arranged so that the gap on the side of the magnetic head (16) is maximized. This shield case is divided into two parts (32m) and (32b) for easy storage and assembly, and a window (32c) is provided in (32a) to allow the extension (27m) to escape. It is being

In the rotating drum device configured as described above, the gaps between the shield case (32), the first B-ring (21), the second yoke (23), and the third yoke (24) (hereinafter referred to as yokes) are Since the gap in the direction of the magnetic head (16) is maximized without making it uniform, the yoke (2]),
The magnetic resistance from (23) and (24) to the shield case (32) is maximum in the direction of the magnetic head (1B).

For this reason, the majority of the leakage magnetic flux reaches the shield case (32) through a place with low magnetic resistance other than the magnetic field (16), as shown in Figure 4 (J) and (K). ,
Since the magnetic flux returns to the yokes (21), (23), and (24) again to form a closed magnetic path, almost no magnetic flux leaks from the shield case (32) on the magnetic head (16) side to the extent that it has an adverse effect on the outside. .

〔Effect of the invention〕

As explained above, by using a shield case in which the gap between the yoke and the magnetic head is maximized on the magnetic head side, this invention can suppress the magnetic flux leaking to the outside of the magnetic head side, thereby preventing demagnetization of the magnetic tape and A high-quality rotating drum device can be obtained without causing noise.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the main parts of a rotating drum device showing an embodiment of the present invention, FIG. 2 is a view taken along arrows ■-■ in FIG. 1, and FIG. 4 is a sectional view of FIG. 3, FIG. 5 is a side view of FIG. Figure 6 is a view from the ■-■ arrow in Figure 6, Figure 8 is a view from the ■-■ arrow in Figure 6, and Figure 9 is a view from the ■-■ arrow in Figure 6.
The figure is a sectional view of FIG. 8, and FIG. 10 is a side view of FIG. 8. In the figure, (7) is a magnetic head drive unit, (16) is a magnetic wood, and (32) is a shield case. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] A magnetic head, which is an electromagnetic transducer for recording and reproducing, a magnetic head drive unit for moving the magnetic head up and down, and a gap around the magnetic head drive unit, which is arranged so that the gap on the magnetic head side is maximized. A rotating drum device characterized by being equipped with a shield case made of a magnetic material.