JPS59129962A - Rotary head assembly - Google Patents

Abstract

PURPOSE:To improve an input/output characteristic of a signal with respect to an all winding angle of a tape of a rotary head by providing an air pressure leak groove extending from the vicinity of the center of the outside circumferential surface of an upper rotary cylinder to the upper end face, and adjusting the floating amount of the tape. CONSTITUTION:When a rotary cylinder 10 rotates, dynamic pressure is generated by a spiral groove formed on the lower end face of the cylinder 10, and a magnetic tape 13 floats up a little on the cylinder. When an air pressure leak groove 11 provided on the cylinder 10 and a head fitting window 15 are positioned in the vicinity of the entry of a tape, the greater part of the leak groove 11 is covered with the vicinity of the upper end of the tape 13, but when they are at an intermediate position of the entry and the delivery of the tape, the leak groove 11 is nearly exposed. Accordingly, only when a head passes through the vicinity of the entry, a floating amount of a tape by the leak groove 11 is reduced, the head contacts with the tape in a good condition, and a signal input/ output characteristic can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a rotary head assembly for a video tape recorder (hereinafter abbreviated as "VTR").

A VH3 type VTR will be described as a representative example of a conventional configuration and its problems. A conventional rotary head assembly, as shown in FIG.
This is supported by a rotating cylinder 2 that rotates and slides at 1800 rpm and a fixed cylinder 3 that does not rotate and slide. A lead 4 is provided on the fixed cylinder 3 for the purpose of regulating the position of the tape 10 when it runs. The magnetic head 5 mounted on the rotary cylinder 2 accurately helically scans the tape 1, thereby realizing reliable input/output of video signals via the tape 1. However, since the tape 1 travels in the fixed cylinder 3 while almost sliding in contact with the cylinder 3, the tape 1 is subjected to dynamic frictional force. Particularly when the VTR is used in a high humidity atmosphere or under conditions of rapid temperature changes, microscopic water droplets may
Condensation occurs between the fixed cylinder 3 and the fixed cylinder 3, and a thin water film of several hundred to several thousand angstroms is formed. Due to the viscous resistance of water caused by the presence of this water film, the tape 1 and fixed cylinder 3 may completely adhere to each other, or a type of self-excited vibration may be excited on the tape side due to intermittent adhesion phenomenon. many. In the above case, accurate input/output of video and audio signals via the tape cannot be expected, and the performance of the VTR is significantly degraded or becomes completely unusable.

In addition, in FIG. 1, 6 is a tape running guide post;
Arrow A indicates the tape running direction, and arrow B indicates the rotation direction of the rotary cylinder 2. (Arrows A and B are common to each figure.) On the other hand, due to the need to develop a small and lightweight VTR, an increase in magnetic recording density is required on the tape side. In other words, the tape ranges from conventional ferrite or chromium dioxide magnetic powder coated with a resin binder to nickel on a resin base.

There is a trend toward metal tapes coated with vapor-deposited or coated cobalt alloys. In this case, the metal tape is
The sliding state with the mating cylinder becomes metal-to-metal sliding, and the relative coefficient of friction becomes higher, making it difficult to ensure stable tape running.

Therefore, in order to eliminate the above-mentioned drawbacks, the present inventors developed a second
．． A new type of rotary head assembly having the configuration shown as a representative example in FIG. 3 has already been proposed. This is because the spiral group 6 provided in a specific part of the rotary cylinder 2 or the fixed cylinder 3 is actuated by the rotation of the rotary cylinder 2 and generates dynamic pressure, which causes the tape to be drawn on the rotary cylinder 2 and the fixed cylinder 3. 1 is a minute amount (approximately 6 to 1 o/
It was designed so that only the magnetic head 5 came into contact with the tape 1 while floating (1 m). This invention greatly improves the tape sliding characteristics of the rotating head assembly, thereby stabilizing tape running, eliminating self-excited vibrations, running under environmentally resistant conditions, and improving signal characteristics. This has the remarkable effect of suppressing wear and deterioration of both.

In addition, in FIG. 2, 7 is a rotating shaft, and 8 is a bearing.

However, when the tape is held floating in the rotating head assembly of the above new configuration, especially at position 9 (hereinafter referred to as the entrance side) where the tape starts to wrap around the rotating head assembly, the tape surface is Most of the tape is hung on the rotating nolinder 2, and the tape runs along a small portion of the fixed cylinder. In this part, the magnetic head is pushed upward from below at the lower end in the width direction of the tape, so that the floating tape is easily tilted and deformed, making it impossible to ensure proper contact between the head and the tape. For this reason, the signal input/output characteristics on the input side of the rotating head assembly deteriorate. On the other hand, at the end of winding the tape around the rotary head assembly (hereinafter referred to as the exit side), most of the tape is hung on the fixed cylinder, and the head passes through the upper end in the tape width direction and leaves the tape. In this case, the signal input/output characteristics on the output side of the rotary head assembly deteriorate, but normally the degree of deterioration on the input side is not so bad. This difference is considered to be due to the difference in mechanism between when the head enters into contact with the tape from the air and when it leaves the contact state.

In this way, when a configuration is adopted in which the tape is held floating on a rotating head assembly provided with a spiral croup, it is necessary to locally reduce the tape flying height from the viewpoint of head touch on the tape.

Purpose of the Invention In view of the above-mentioned drawbacks, the present invention provides a pressure leak structure locally on the rotating head assembly to control the tape flying height, and improves signal input/output characteristics over the entire tape wrapping angle on the rotating head assembly. A rotary head assembly having a smoothing configuration is provided.

Structure of the Invention The present invention provides a lower fixed cylinder, an upper rotary cylinder having approximately the same diameter as the lower fixed cylinder and coaxially arranged with a gap therebetween, and a rotary cylinder fixed near the outer periphery of the upper rotary cylinder. , in the gap, the lower fixed cylinder and a magnetic head rotating about the same axis, and at least the magnetic head is mounted on the outer circumferential surface of the upper rotary cylinder, and the magnetic head is attached to the outer circumferential surface of the upper rotary cylinder. It has an air pressure leak groove from near the center of the outer peripheral surface of the rotating cylinder to the upper end surface, and can reduce the flying height of the magnetic tape only near the entrance side, where it is relatively difficult to ensure contact between the magnetic head and the magnetic tape. This has the unique effect of improving the tightness between the magnetic head and magnetic tape and improving the signal input/output characteristics.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 6 shows a perspective view of a rotary head assembly in a first embodiment of the present invention. In Figure 5, 1
0 is a rotating cylinder, 11 is a pneumatic leak groove provided on the rotating cylinder 1Q, 12 is a fixed cylinder, and 13 is a magnetic tape. A spiral group is formed on the lower end surface of the rotary cylinder 1o as in the conventional example shown in FIGS. tape 13
It has a structure that promotes floating from the cylinder. Note that the air pressure leak groove 11 is formed above the vicinity of the center of the outer peripheral surface of the rotary cylinder 10 directly above the head mounting window 15.

Regarding the rotating head assembly configured as above,
The operation will be explained below.

As the rotary cylinder 1o rotates, the spiral group formed on the lower end surface of the rotary cylinder 1o has a relative speed with the opposing surface, and dynamic pressure is generated here, and the magnetic tape 13 is moved several times from the top of the cylinder. Although the air pressure leak groove 11 provided directly above the head mounting window 15 is partially exposed to the magnetic tape 13, the magnetic tape 13 and the tape running surfaces of the rotary cylinder 10 and the fixed cylinder 12 are suspended. In order to release the air trapped between the two to the atmosphere, the air pressure that makes the magnetic tape 13 levitate decreases,
The amount of floating can be reduced. 6 and 7 are explanatory views showing the relative positional relationship between the air pressure leak groove 11 and the magnetic tape 13 in the first embodiment of the present invention. 6 is a top view of the rotating cylinder 10 and the magnetic tape 13, FIG. 7(a) is a view taken from arrow C in FIG. 6, and FIG. It is a diagram seen from the direction of the arrow.

As shown in FIGS. 7(a) and 7(b), when the air pressure leak groove 11 and the head mounting window 15 are located near the entrance side, the air pressure IJ groove 1 is located near the upper end of the magnetic tape 13.
However, when the air pressure IJ groove 11 and the head mounting window 15 are located near the intermediate position between the entrance and exit sides of the tape winding part, the air pressure leak groove 11 is
It is located above the upper end of the magnetic tape 13. Therefore, the reduction in tape flying height due to the air pressure leak groove 11 occurs only when the head passes near the entrance side. Note that the arrow E in FIG. 7 (-) indicates the direction of air.

As described above, according to this embodiment, the air pressure leak groove 11 is formed directly above the head mounting window 15 on the outer peripheral surface of the rotating cylinder 1o.
By providing a length extending from the upper end of the rotating cylinder 10 to the vicinity of the center, when the magnetic head passes near the entrance side, the tape flying height is maintained only near the entrance side, where contact between the magnetic head and the magnetic tape is relatively difficult to ensure. It is possible to improve the contact between the magnetic head and the magnetic tape and improve the signal input/output characteristics.

A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 8 shows a second embodiment of the invention. In FIG. 8, reference numeral 16 denotes an air pressure leak groove provided over the entire circumference above the center of the outer peripheral surface of the rotary cylinder 1o. The pneumatic leak groove 16 is provided as a replacement for the pneumatic leak groove 11 in the first embodiment, and the other constructions are completely the same as in the first embodiment.

Regarding the rotating head assembly configured as above,
The operation will be explained below.

FIG. 9 is an explanatory diagram showing the relative positional relationship between the air pressure leak groove 16 and the magnetic tape 13 in the second embodiment of the present invention. 9(,) is a view seen from arrow C in FIG. 6, and FIG. 9 (■) is a view seen from arrow C in FIG. 6. As can be seen from FIGS. 9(a) and 9(b), the air pressure leak groove 16 covers the magnetic tape 13 near the entrance side, but the air pressure leak groove 16 covers the magnetic tape 13 near the entrance side, but from around the intermediate position between the entrance side and the exit side at the tape winding part. Towards the output side, the air pressure leak groove 16 is located above the upper end surface of the magnetic tape 13. Therefore, in order to release the air trapped between the magnetic tape 13 and the tape running surfaces of the rotary cylinder 10 and fixed cylinder 12 to the atmosphere near the entrance side, the magnetic tape 13
The floating air pressure can be reduced and the floating height can be reduced.

Note that, compared to the air pressure leak groove 11 in the first embodiment, the air pressure leak groove 16 reduces floating of the tape near the entry side not only when the head mounting window 15 passes near the entry side but also at all times. However, since it is formed around the entire outer periphery, processing is easy. Note that it is appropriate that the air pressure leak groove be provided at a position within one quarter of the width of the magnetic tape from the upper end of the magnetic tape on the input side.

As described above, according to the present embodiment, the air pressure leak groove 16 is formed over the entire circumference of the rotary cylinder 1° from near the center to the upper part of the outer circumference.
By providing this, it is possible to reduce the tape flying height only near the input side, where it is relatively difficult to ensure contact between the magnetic head and the tape, and improve signal input/output characteristics.

Effects of the Invention As described above, the present invention forms a pneumatic leak groove at a predetermined position on the outer circumferential surface of a rotating cylinder, thereby improving the tape performance only near the entrance side, where it is relatively difficult to ensure contact between the magnetic head and the chi. The flying height can be reduced, the contact between the magnetic head and the magnetic tape can be improved, and signal input/output characteristics can be improved.

[Brief explanation of drawings]

Figure 1 is a perspective view of a conventional rotary head assembly, Figure 2 is a sectional view of a conventional air-discharge tape floating type rotary head assembly, Figure 3 is a perspective view of a rotary cylinder, and Figure 4 is a conventional FIG. 5 is a perspective view of the rotary head assembly according to the first embodiment of the present invention, FIG. 6 is a plan view of the same, and FIGS. 7(a) and (b)
8 is a front view of the rotary head assembly showing the relative positional relationship between the air pressure leak grooves near the entrance and exit sides and the tape in the first embodiment of the present invention, and FIG. 8 is a front view of the rotary head assembly in the second embodiment of the invention. Perspective view of rotating head assembly, Figure 9)
. (b) is a cross-sectional view of the rotary head assembly showing the relative positional relationship between the tape and the air pressure leak grooves near the entrance and exit sides of the rotary head assembly in the second embodiment of the present invention. 10... Rotating cylinder, 11... Air pressure leak groove, 12... Fixed cylinder, 13...
...magnetic tape, 14...gap section, 15.
...Head mounting window, 16...Pneumatic leak groove. Name of agent Patent attorney Toshio Nakao and 1 other person4 Figure 2 Figure 4 Figure 5 Figure 7 Figure 8

Claims (2)

[Claims] (1) a lower fixed cylinder, a 1F rotating cylinder having approximately the same diameter as the lower fixed cylinder and coaxially arranged with a gap; fixed near the outer periphery of the upper rotating cylinder; The lower fixed cylinder and a magnetic head rotating around the same axis are arranged in the gap, and at least the magnetic head is mounted on the outer circumferential surface of the upper rotating cylinder at the center of the outer circumferential surface of the upper rotating cylinder. A rotating head assembly having an air pressure leak groove from the vicinity to the upper end surface. (2) 4 of the magnetic tape width from the upper end of the magnetic tape at the magnetic tape winding start portion on the outer peripheral surface of the upper rotating cylinder;
2. The rotary head assembly according to claim 1, wherein the rotary head assembly has an air pressure leak groove over the entire circumference at a position within 1/2.