JPH03185656A - Rotary head cylinder - Google Patents

Abstract

PURPOSE:To stabilize signal transmission of a magnetic recording and reproducing head, and a magnetic tape by non-linearly increasing the air groove cross-sectional area per unit length in the direction of an axis formed on a rotary drum in addition to the area which comes over the rotary drum of the magnetic tape as it departs further away from a fixed drum. CONSTITUTION:For an air groove 5 formed on a rotary drum 1, the air groove cross-sectional area is not only increased monotonically taking into account the linear change of the area of a magnetic tape 7 which comes over the rotary drums 1, but the air groove cross-sectional area for each unit length in the axial direction is increased non-linearly taking into account the change of the tension of the magnetic tape 7. Then, the floating height of the magnetic tape 7 can be uniformized from the enter side part to the exit side part of a rotary head cylinder. Thus, the recording and reproducing by the magnetic recording and reproducing head can be stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a rotary head cylinder in a video tape recorder (hereinafter referred to as VTR), and more particularly to the floating of a magnetic tape from a rotating drum.

BACKGROUND OF THE INVENTION In recent years, there has been an increasing demand for the development of high-density recording technology for VTRs, and it has become important to maintain good contact between the rotating head cylinder and the magnetic tape. An example of a conventional rotary head cylinder will be described below with reference to the drawings.

FIG. 3 is a front view of a conventional VTR rotary head cylinder. The zero-rotation drum 1 has a flange (
(not shown), and a magnetic recording/reproducing head 4 is attached and fixed to the lower end of the rotating drum I at a position where its tip slightly protrudes from the outer peripheral surface of the rotating drum I. Furthermore, the rotary drum 1 has a plurality of air grooves 5 carved at equal cross-sectional areas and equal pitches over the entire outer circumferential surface of the drum. The rotating drum l is rotatably supported. The fixed drum 3 supports the rotary shaft 2 and guides the magnetic tape 7 obliquely through a guide 6 formed on its outer circumferential surface.

Regarding the rotating head cylinder configured as above,
The operation will be explained below. FIG. 4 is a plan view of the rotating head cylinder. The magnetic tape 7 runs along the outer circumferential surface of the rotary head cylinder from the entry side portion A to the exit side portion B, and travels in the direction of the arrow in the figure. At the same time, the rotating drum 1 rotates in the direction indicated by the arrow in the figure.

In this state, the magnetic recording/reproducing head 4 fixed to the lower end of the rotating drum 1 scans the magnetic tape 7 to record and reproduce signals. At this time, the air flow between the magnetic tape 7 and the rotating drum 1 forms an air layer called an air film, and the magnetic tape 7 is lifted off the rotating drum 1.

FIG. 5 is a partial sectional view of the rotary head cylinder.

Code in the diagram? a, 7b, and 7c all show the floating state of the magnetic tape 7 during recording and reproduction.The relative positions of the magnetic tapes 7a to 7C with respect to the 0-rotation head cylinder are different because the magnetic tape 7 is rotating. This is because it is wound diagonally onto the outer peripheral surface of the head cylinder. 7a is the magnetic tape at the entrance side A of the rotating head cylinder.In the entrance side A of the 1-turn head cylinder, the area of the magnetic tape 7 covering the rotating drum 1 is large, and the thickness of the air film formed is large. Therefore, the flying height of the magnetic tape 7 becomes large.

On the other hand, 7C is the magnetic tape at the exit side B of the rotary head cylinder, and the thickness of the air film formed by the rotary drum 1 is small, so that the flying height of the magnetic tape 7 is small.

Further, a factor that affects the flying height of the magnetic tape 7 is the tension of the magnetic tape 7. When the tension of the magnetic tape 7 is high, the thickness of the air film is small and the flying height is small. Conversely, when the tension of the magnetic tape 7 is low, the flying height is large. [While the magnetic tape 7 is running, the magnetic tape 7
The tension increases from the entrance side part A to the exit side part B of the rotary head cylinder, so the flying height decreases from the entrance side part A to the exit side part B. As described above, due to two factors: the area of the magnetic tape 7 applied to the rotating drum 1 and the tension of the m-chip 17, the flying height of the magnetic tape 7 increases from the entrance side A to the exit side B of the rotary head cylinder. Change.

8 Problems to be Solved by the Invention In the above configuration, magnetic tape 7 is transferred from rotating drum l.
This floating changes the contact pressure and contact area between the magnetic recording/reproducing throat 4 and the magnetic tape 7, which prevents the magnetic recording/reproducing head 4 from performing sufficient recording/reproducing, especially when the track is narrowed. There was a problem. Furthermore, some air grooves 5 formed on the rotating drum l have an increased air groove cross-sectional area in consideration of the area of the magnetic tee 17 applied to the rotating drum l, but this increases the tension of the magnetic tape 7. A sufficient effect cannot be obtained against changes in flying height due to changes in .

The present invention has been made to solve the above problems, and in order to stabilize the signal transmission between the magnetic recording/reproducing head 4 and the magnetic tape 7, the flying height of the magnetic tape 7 is adjusted to the entrance side of the throat cylinder. To provide a rotary head cylinder that can be made uniform from part A to outlet part B.

Means for Solving the Problems In order to solve the above problems, the present invention provides a rotating drum having a magnetic recording/reproducing head on a rotatable drum and having a plurality of air grooves over the entire outer peripheral surface of the drum; disposed opposite to the drum to support the rotating shaft of the rotating drum;
and a fixed drum that guides the magnetic tape on its outer peripheral surface, and the cross-sectional area of the air groove per unit length in the axial direction increases non-linearly as the distance from the fixed drum increases.

Effect of the Invention With the above-described configuration, the present invention considers changes in tension of the magnetic tape in addition to changes in the area of the magnetic tape applied to the rotating drum as factors that affect the flying height of the magnetic tape, and calculates the amount per unit length in the axial direction. The cross-sectional area of the air groove increases non-linearly as it moves away from the fixed drum.At the top of the rotating drum of a 0-rotation head cylinder, air escape between the magnetic tape and the drum is improved, and the thickness of the air film is increased. In addition, in the lower part of the rotating drum, air escape between the magnetic tape and the drum is almost eliminated, and the tape flying height is maintained at 11 even when the tension of the magnetic tape is high. Therefore, although the flying height of the magnetic tape as a whole becomes quite small at the entrance side of the rotating head cylinder, a sufficient flying height can be obtained at the exiting side of the rotating head cylinder. This makes it possible to achieve uniformity from the inlet side to the outlet side of the cylinder.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a partial sectional view of a rotary head cylinder showing an embodiment of the present invention.
Air grooves 5a to 5e are formed over the entire circumference, and the cross-sectional area of each air groove has the following relationship: 5a>5b>5c>5d>5e.

Figure 2 is a graph showing the cross-sectional area of the air grooves 5a to 5e formed in the rotary head cylinder of the present invention. This shows that the air groove cross-sectional area per unit length in the rotational axis direction increases non-linearly from the bottom to the top of the rotating drum 1.

The operation of the above structure will be explained below.The air grooves 5a to 5e of the present invention allow the rotary head cylinder entry side A, that is, the magnetic tape 7 to reach the upper part of the rotary drum 1, and to maintain the tension of the magnetic tape 7. At a low position, the air grooves 5a and 5b, which have a large cross-sectional area, improve the escape of air and are effective in reducing the thickness of the air film, making it possible to reduce the flying height of the magnetic tape 7. .

Air grooves 5d, 5 with small cross-sectional areas are formed in the rotating head cylinder exit portion B, that is, in the position where the magnetic tape 7 is applied to the lower part of the rotating drum 1 and the tension of the magnetic tape 7 is high.
There is almost no effect of reducing the thickness of the air film due to e, and it is possible to secure the tape floating amount.

In other words, the air grooves 5 formed on the rotating drum 1 not only increase the cross-sectional area of the air grooves monotonically, but also increase the magnetic The cross-sectional area of the air groove per unit length in the axial direction is increased non-linearly, taking into account the change in the tension of the tape 7. It is possible to equalize the flying height. Therefore, the state of contact between the magnetic recording/reproducing head 4 and the magnetic tape 7 is almost the same from the rotary head cylinder entrance part A to the exiting part B, thereby stabilizing recording and reproduction by the magnetic recording/reproducing head 4. I can do it. Furthermore, since the magnetic tape 7 also floats on the rotary head cylinder outlet side B, there is also the effect of reducing the rotational load on the rotary drum I.

Note that the present invention is not limited to the above embodiments,
By changing the pitch of the air grooves, it is possible to obtain the effects of the present invention even if the groove cross-sectional area per unit length is increased non-linearly. Further, the groove cross-sectional area may be changed depending on the circumferential speed of the rotating drum l, the type of magnetic tape 7, etc., such as making only the lower two grooves have the same cross-sectional area.

Effects of the Invention As described above, according to the present invention, in addition to the area of the magnetic tape on the rotating drum, the tension of the magnetic tape is taken into account as a factor that affects the flying height of the magnetic tape. The cross-sectional area of the air groove per unit length in the axial direction formed was increased non-linearly as the distance from the fixed drum was increased. As a result, on the entrance side of the rotating head cylinder, air escape between the magnetic tape and the drum is improved, and the effect of reducing the thickness of the air film is increased.
At the exit side, the air escape between the magnetic tape and the drum is almost eliminated, and even when the tension of the magnetic tape is high, the tape flying height is ensured, so the flying height of the magnetic tape is reduced from the entrance side of the rotating head cylinder. It is possible to achieve uniformity even down to the outlet side. Therefore, the effect of stabilizing signal transmission between the magnetic recording/reproducing head and the magnetic tape can be obtained.

[Brief explanation of drawings]

Fig. 1 is a partial sectional view of a rotary head cylinder showing an embodiment of the present invention, Fig. 2 is an explanatory view showing an increase in the cross-sectional area of the air grooves of the rotary drum of the present invention, and Fig. 3 is a diagram showing a conventional rotary head cylinder. 4 is a front view of a conventional rotary head cylinder, and FIG. 5 is a partial sectional view of the rotary head cylinder. l... Rotating drum, 2... Rotating shaft, 3
...Fixed drum, 4...Magnetic recording/reproducing head, 5...Air groove, 6...Reed, 7...Magnetic tape, A...Rotating head cylinder inlet side part, B...Rotating head cylinder outlet side part, 12...Rotating drum outer peripheral surface, 5a
~5e...Air groove, 7a~7C...Magnetic tape.

Claims (1)

[Claims] a rotating drum having a magnetic recording/reproducing head on a rotatable drum and having a plurality of air grooves all around the outer circumferential surface of the drum; 1. A rotary head cylinder comprising: a fixed drum that guides a magnetic tape on a surface thereof, wherein a cross-sectional area of the air groove per unit length in the axial direction increases non-linearly as the distance from the fixed drum increases.