JPS6346647A - Processing method for rotary magnetic head cylinder - Google Patents

Abstract

PURPOSE:To prevent vibration at the exit of a tape by processing a slight projection in the vicinity of a part where a tape is parted from a lower cylinder in matching at the processing of a tape running face and a tape guide face so as to lower the face pressure between the tape and the video head. CONSTITUTION:A magnetic tape 11 is wound over nearly 180 deg. around a rotary cylinder 3 by guide pins 12, 13. A projection 25 is provided at the upper end of a peripheral of the lower cylinder 21 at the end of winding of the magnetic tape 11, which is parted from the rotary cylinder 3 at the projection 25. The contact pressure between a magnetic head 6 and the magnetic tape 11 is decreased at the projection 25 and when the magnetic head 6 is parted from the magnetic tape 11 in this state, the shock of the magnetic head 6 parted from the tape 11 is small and no waving is caused in the tape 11. The projection 25 is formed simply by leaving the projection 25 slightly in applying cutting processing to the lower cylinder 21.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to a rotating magnetic head cylinder suitable for vibrations generated when a video head attached to the rotating cylinder separates from a magnetic tape in a helical scan video tape recorder. Regarding processing methods.

[Background of the invention]

In a helical scan video tape recorder, a magnetic tape is wound approximately 180 degrees around a rotating cylinder, and a rotating magnetic head records and reproduces video signals obliquely to the longitudinal direction of the magnetic tape. In this case, the tip of the magnetic head protrudes from the outer peripheral surface of the rotating cylinder.

Therefore, when the magnetic head is in contact with the magnetic surface of the magnetic tape, the magnetic tape is lifted away from the outer peripheral surface of the rotating cylinder by the magnetic head, and a large pressure is created between the magnetic head and the magnetic tape. It's working. Then, when the magnetic head separates from the magnetic tape, this pressure is suddenly removed, and the impact generated at that time causes vibrations in the magnetic tape, and the vibrations of the tape cause jitter during reproduction.

The occurrence of this jitter will be explained below using figures. FIG. 6 is a perspective view of a conventional rotating magnetic head cylinder device. In FIG. 6, 3 is a rotating cylinder, and the cylinder 3 is divided into an upper cylinder 20 and a lower cylinder 21, and a magnetic head 6 is disposed between the upper cylinder 20 and the lower cylinder 21. The magnetic tape 11 has two guide pins 1
2° 13, the tape is wound in a spiral shape over approximately 180 degrees around the outer periphery of the cylinder 3, and runs along a tape guide surface 22 provided on the outer periphery of the lower cylinder 21. The magnetic head 6 rotates alone or together with the upper cylinder 20, and the rotation method is in the direction shown by arrow A, and the magnetic head 6 starts contacting the magnetic tape 11 from the lower end,
The magnetic tape 11 is brought into contact with the magnetic tape 11 so that the tape comes out from the upper end of the magnetic tape 11. FIG. 9 is a sectional view of a part of this cylinder part, and the magnetic head 6 is attached to the upper cylinder 20 via the head plate 23 and rotates together with the upper cylinder 20. The leading end of the magnetic head 6 projects outward from the outer circumferential surfaces of the upper cylinder 20 and lower cylinder 21, thereby separating the magnetic tape 11 from the outer circumferential surfaces of the cylinders 20, 21.

In such a device, when recording a video signal on a magnetic tape by running a magnetic tape and rotating a magnetic head, or when reproducing a video signal on a magnetic tape, the magnetic head is rotated as shown in Fig. 6. 6 starts contacting from the lower end of the magnetic tape 11 and exits from the upper end of the magnetic tape 11. When the magnetic head 6 and the magnetic tape 11 are in contact with each other, pressure is applied between the magnetic head 6 and the magnetic tape 11, and when the magnetic head 6 is pulled out from the upper end of the magnetic tape 11, this pressure is released. It suddenly disappears, and the impact at that time generates vibrations in the upper end portion C (FIG. 6) of the magnetic tape 11. When vibrations occur in the tape 11 in this way, as shown in FIG. 7 during playback, on the television monitor 14, for example, the line E, which should be a single straight line, undulates at the portion D, resulting in an unsightly screen. Such screen curvature is generally called jitter, and FIG. 8 shows the results of spectrum analysis of this jitter.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a rotating magnetic head cylinder that eliminates the above-mentioned drawbacks.

[Summary of the invention]

In order to reduce the vibration of the tape that occurs when the video head leaves the tape exit side, a slight protrusion is formed near the part where the tape leaves the lower cylinder during machining of the tape running surface and the tape guiding surface. This reduces the surface pressure between the tape and the video head, reduces the impact force on the tape, and prevents vibrations on the exit side of the tape.

[Embodiments of the invention]

First, FIG. 1 is a plan view of a rotating magnetic head cylinder, which is the premise of the present invention, and FIG.
-x' sectional view. In the figure, 1.2 is a ball bearing, 21
is the lower cylinder, 4 is the shaft, and ball bearings 1 and 2 are installed in the lower cylinder 21.
A disk 5 is fitted to the upper end of the shaft 4. An upper cylinder 2o to which a video head 6 is fixed is fixed to the disk 5, and a rotary transformer 8 is fixed in close contact with the other end surface of the disk 5. Further, a rotor magnet 9 for driving is fixed to the lower end of the shaft 4, and a driving force (rotational force) is obtained by a stator 1o around which a coil is wound. The video head 6 projects slightly from the tape sliding surface of the upper cylinder 20, and performs recording and reproduction by bringing it into contact with the magnetic tape 11. Also, the rotation method of the one-turn cylinder is in the direction of arrow A, and the magnetic tape is wound from the starting side oo.

90', 180', and 270', and will be described below.

FIG. 3 is a perspective view of the rotary cylinder device of the present invention, and FIG. 4 is a sectional view of the main part of the cylinder. In FIGS. 3 and 4, the magnetic tape 11 is wrapped approximately 180 degrees around the rotating cylinder 3 by means of guide pins 12.13. A protrusion 25 is provided at the upper end of the outer circumference of the lower cylinder 21 where the winding of the magnetic tape 11 ends.

The magnetic tape 11 is wound onto this protrusion 25 and leaves the rotary cylinder 3 at the protrusion 25 .

With this configuration, the magnetic tape 11 wound around the outer periphery of the rotary cylinder 3 separates from the center of the rotary cylinder 3 at the protrusion 25, so the contact pressure between the magnetic head 6 and the magnetic tape 11 is reduced by the protrusion 25. It gets smaller at 25. Therefore, if the magnetic head 6 moves away from the magnetic tape 11 in this state, the impact when the magnetic head 6 separates from the magnetic tape 11 becomes smaller, and no waviness of the magnetic tape 11 occurs).

Next, FIG. 5 shows the results of spectrum analysis of jitter according to the present invention. The vertical axis shows jitter (dB), and the horizontal axis shows frequency [KHz
), and as can be seen from the comparison with the conventional jitter shown in FIG. 8, the jitter is reduced in the frequency region around 2Kliz. FIG. 11 shows a diagram regarding the tape winding angle position and the amount of tape vibration. In the case of the conventional example, as shown by the line (c), intense vibration occurs in the construction area (near the end of tape winding), and the effect of this vibration causes the undulations in the playback screen as described above. . However, according to the present invention, as shown in the song I (b) in FIG. 10, the tape winding end portion (18
Since a slight protrusion 25 is provided near 0'), 1
The surface pressure between the head 6 and the tape 11 can be reduced near 80 degrees. In other words, as shown by track a (d) in FIG. 11, since the impact when the head separates from the tape is reduced, there is almost no vibration, and no waviness occurs on the screen. Curve (a) in FIG. 10 shows the surface pressure characteristics applied to the head in a conventional cylinder. Furthermore, the fourth section regarding the comparison of the surface pressure between the head 6 and the tape 11.
This will be explained in detail with reference to the drawings and the cross-sectional model shown in FIG. Although FIG. 9 shows a conventional example, assuming that the surface pressure applied to the tip of the video head 6 is P1, in the embodiment of the present invention shown in FIG. Obviously, P2<PL.

The protrusion 25 provided on the lower cylinder 21 of the rotating magnetic head cylinder of the present invention can be easily made by leaving a slight portion of the protrusion 25 uncut when cutting the lower cylinder 21. .

FIG. 12 shows a perspective view of a concrete rotary magnetic head cylinder device of the present invention including a lower cylinder made by this process. The same parts as in Figure 3 are given the same symbols. Here, the protrusion 25 is drawn slightly larger to emphasize its shape. FIG. 13 (σ) is an enlarged front view of the main part of the lower cylinder 21 including the protrusion 25, and FIG.
FIG. 3 is an enlarged sectional view taken along line d-4 in FIG. 3 (σ). Conventionally, the lower cylinder IJ cylinder 21 has a tape running surface 24 that is parallel to the outer peripheral surface of the lower cylinder 21, and a tape running surface 24 that is parallel to the outer peripheral surface of the lower cylinder 21.
It has a tape guide surface 22 located at the lower end thereof and extending to the outer peripheral surface of the tape at right angles to the tape running surface 24. When cutting the lower cylinder 21, cut from the outer periphery and upper side of the cylinder with a cutting tool to make the tape running surface 24 sequentially facing the bottom of the cylinder, and the lower end of the tape running surface 24 is cut with a cutting tool from the upper side. The tape guide surface 22 is cut into a surface perpendicular to the surface 24. The protrusion 25 of the present invention is made by leaving a small amount of material uncut at the time of cutting the outer periphery of the cylinder, so the protrusion forms an arc along the shape of the tape guide surface 22. The peripheral surface surrounded by the surface 25σ and the upper surface 25b of the cylinder, and the tape running surface 2
4 and a bulge surface that is parallel to the cylinder and projects 50 microns in the direction of the outer peripheral surface of the cylinder.

An example of the processing method according to the first embodiment of the present invention will be explained in detail below using the drawings. FIG. 14 is a schematic diagram of the machining section of a hydraulic copying cam type numerically controlled lathe that is generally used when machining the lower cylinder 21. Such a lathe is known, for example, as model DPL-5 manufactured by Hitachi Seiko Co., Ltd.

The lower cylinder 21 is held with high precision by having its circumferential protrusion 21a sandwiched between slidable claws 29 against a chuck 28 fixed to a cam 26 fixed to the main shaft 27.
Rotates in the same direction as the rotational direction of the main shaft.

On the other hand, the cam follower 33 is rotatably attached to the lead turner 34, and as the main shaft 27 rotates, the cam 26
By reciprocating as shown by arrow F following the cam surface 26σ of The movement follows the shape of 26σ. This cam surface 26I7 has a shape similar to that of the cylinder 21.
The tape guide surface 22 is set in advance to have a desired shape.

A method of processing the protrusion 25 using this apparatus will be explained in comparison with a conventional example. FIG. 17 shows a method of controlling the cutting tool 30 when processing the conventional example, and FIG.
7 is an enlarged sectional view taken along the line YY of the lower cylinder 21 in FIG. 7. FIG. The cutting depth T of the cutting tool 3o is set by the X-axis numerical control system 35 in FIG. 14, and the feed length of the cutting tool 30 is set by the Y-axis hydraulic control system 36. As a result, the cutting tool 3o in FIG.
b, and moves in the direction of the arrow in FIG. 17 following the shape of the cam surface 26σ of the cam 26 in FIG.
It moves in the L direction at a pitch of microns, moves by the feed length L and stops, and then the other cutting tool 37 in FIG.
4 and the tape guide surface 22 can be cut.

Next, FIG. 15 shows a method of controlling the cutting tool when machining this embodiment, and FIG. 16 shows an enlarged sectional view Z--Z along the line of the lower cylinder 21 in FIG. 15. X-axis numerical control system 3 in Figure 14
5, in order to obtain a predetermined height of the protrusion 25, the cylinder 2
Set the depth of cut L2 from the outer peripheral surface of No. 1, and set Y in Fig. 14.
The shaft hydraulic control system 36 controls machining of the protrusion 25 to a predetermined length Q.

After machining the predetermined length 2□, the X-axis hydraulic control system 35 and Y-axis hydraulic control system 36 shown in FIG. By processing, protrusions 25 as shown in FIGS. 15 and 16 can be provided.

The shape of the outer peripheral surface of the protrusion 25 obtained by such a processing method is characterized in that it has the same shape as the tape guide surface 22, and can be processed with high precision with little variation in shape.

As described above, the protrusions of the present invention can be provided easily and with high precision by simply making cuts at predetermined timings when cutting the tape running surface 24 and the tape guide surface 22, so they are convenient. It is.

〔Effect of the invention〕

According to the present invention, the protrusion that reduces jitter caused by vibration near the end of tape winding is simply machined at the same time as the tape running surface and tape guiding surface of the fixed cylinder. This has the effect of enabling highly accurate positioning at low cost.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a rotating magnetic cylinder according to the present invention, and FIG.
The figures are a sectional view taken along the line xx' in FIG. 1, FIG. 3 is a perspective view of the rotating cylinder of the magnetic recording and reproducing apparatus of the present invention, FIG. Spectrum diagram, Figure 6 is a perspective view of a conventional rotating magnetic head cylinder,
Fig. 7 is a schematic diagram of a conventional monitor screen, Fig. 8 is a conventional jitter spectrum diagram, Fig. 9 is a sectional view of the main parts of a conventional rotating magnetic head cylinder, and Fig. 10 is a characteristic diagram of head surface pressure. , FIG. 11 is a characteristic diagram of the amount of tape vibration, FIG. 12 is a perspective view of a concrete rotating magnetic head cylinder of the present invention, and FIG. 13 (σ) is an enlarged front view of the main part of the lower cylinder including the protrusion. 13(b) is an enlarged sectional view taken along the line d-4 in FIG. 13(σ), and FIG. 14 is a schematic diagram of the machining part of a hydraulic profiling cam type numerically controlled lathe, Fig. 15 is a diagram showing the relationship between the lower cylinder and the cutting tool of the present invention, Fig. 16 is an enlarged sectional view taken along the line Z-7 in Fig. 15, and Fig. 17 is a diagram showing the relationship between the lower cylinder and the cutting tool in the conventional art. FIG. 18 is an enlarged sectional view taken along the line YY in FIG. 17. 3... Rotating cylinder, 11... Magnetic tape, 20...
・Upper cylinder, 21...Lower cylinder, 22...
・Tape guide surface, 24...Tape running surface, 25...
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Claims (1)

[Scope of Claims] 1. A rotary cylinder equipped with at least one video head, a tape running surface that is parallel to the inside of the outer peripheral surface of the cylinder, and a tape running surface that is located at the lower end of the tape running surface and perpendicular to the tape running surface. In a rotating magnetic head cylinder equipped with a fixed cylinder having a tape guide surface extending on the outer peripheral surface of the tape, on the tape release side of the tape running surface of the fixed cylinder,
A rotating magnetic head cylinder characterized in that when the outer periphery of the fixed cylinder is cut to create the tape running surface and the tape guide surface, a slight portion is left uncut to form a protrusion for preventing vibration of the tape. processing method. 2. In claim 1, the protrusion is located at an upper end of the fixed cylinder opposite to the tape guide surface, and is parallel to the tape guide surface and protrudes toward the outer peripheral surface of the fixed cylinder. A method of manufacturing a rotating magnetic head cylinder using a bulge surface.