JPS5936342B2 - Tape guide for rotating head type magnetic recording/playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tape guide for a rotary head type magnetic recording/reproducing device (VTR), and provides a structure in which a lead for regulating the running position of a magnetic tape can be easily created with high accuracy. be.

The head cylinder section of a helical scan type VTR has the structure shown in FIG.

That is, the magnetic tape 1 is arranged such that the edge of the magnetic tape 1 is aligned with the tape guide step 4 (hereinafter referred to as a lead) provided on the outer peripheral surface of the lower fixed cylinder 3 via the guide pins 2a and 2b. Then, it is wound around the outer peripheral surfaces of the upper rotating cylinder 5 and the lower fixed cylinder 3 in a threaded manner and travels at a constant speed.

The magnetic head 6 is attached to the upper rotating cylinder 5 and runs diagonally across the magnetic tape 1 to record and reproduce signals. Therefore, the upper rotating cylinder 5
If the tape guide device, which is composed of the outer peripheral surface of the lower fixed cylinder 3 and the lead 4 provided on the lower fixed cylinder 3, is not manufactured and assembled correctly, the contact state between the magnetic tape 1 and the magnetic head 6 may deteriorate. This results in instability and unevenness in the reproduced image of the VTR.

On the other hand, the lead 4 of the lower fixed cylinder 3 is usually machined using a lathe, as shown in FIG.

In other words, the lower fixed cylinder 3 is fixed to the lathe main shaft T and rotates at a constant speed, while the cutting tool 9 fixed to the tool rest 8 is moved in the direction of the arrow in the figure (the lathe main shaft T) in synchronization with the rotation of the lathe main shaft T.
is created by making a reciprocating motion in the direction of Therefore, the positional transition of the tool post 8 during its reciprocating motion must match the shape of the lead 4. Third
The figure shows a developed view of the lead shape on the outer peripheral surface of a conventional lower fixed cylinder.

Magnetic tape 1 is in the range 00-1800, lower cylinder 3
The lead 4 in this section is linear. Since the section from 1800 to 3600 is not directly related to the running of the tape, conventionally the section has been formed by appropriately combining straight lines and circular arcs, as shown in the figure.

FIG. 4 shows the displacement of the movement required of the tool post 8 when machining a lead with such a shape using a lathe as described above.
This shows changes in velocity and acceleration.

In the figure, S, V, and A indicate the displacement, speed, and acceleration of the tool rest 8, respectively. Due to the shape of the lead, in the straight sections other than the circular arc, the acceleration is o, but in the circular arc sections, a considerably large acceleration must be generated on the tool rest, and unreasonable force is applied to the tool rest. become. This causes vibrations that are harmful to the machine tool, leading to a deterioration in the machining accuracy of the lead shape and deterioration of the roundness of the cylinder, which prevents the tape from being correctly guided to the specified position and causing damage to the VTR.
This results in unevenness in the reproduced image. The present invention solves the above-mentioned conventional drawbacks, and consists in making the lead shape other than the part around which the tape wraps a parabola, thereby suppressing the acceleration applied to the tool post 8 to a smaller level. Examples of the present invention will be described below.

Figure 5a shows that the magnetic tape of the lead is in an area of 180° to 360° that does not contact the magnetic tape other than the straight part where it comes into contact.
This shows an example in which a downwardly convex parabola C1 and an upwardly convex parabola C2 are applied.

Changes in the velocity (V) and acceleration (A) of the tool post 8 at this time are shown in FIG. 5b. It can be seen that compared to the acceleration curve (FIG. 4) with the conventional lead configuration, the acceleration value is significantly reduced according to the invention. If we consider the motion of the turret 8 from an energetic perspective, (1) the integrated value of the acceleration is 0.
Must.

(2) The value obtained by integrating the absolute value of acceleration must have a constant value. This is explained by this.

In the present invention, as described above, the acceleration required for the tool rest 8 can be suppressed to a smaller value than in the past, so the tool rest can easily follow the movement, and harmful vibrations of the machine tool can be reduced. The roundness of the cylinder and the processing accuracy of the lead shape are dramatically improved, the carding accuracy of the tape is improved, and the occurrence of unevenness in VTR reproduced images is effectively reduced.

Furthermore, when the reciprocating motion of the tool post is generated by a cam mechanism or the like, as is usually done, it is also effective in reducing wear on the cam surface.

In the above-described embodiment of the present invention, an example was shown in which the lead shape in the section not in contact with the magnetic tape was constructed by connecting two parabolas, but as shown in FIG. It is clear that the same effect can be obtained by connecting parabolas.

[Brief explanation of drawings]

Figure 1 is a perspective view showing the outline of the cylinder center of the VTR, Figure 2
The figure is an explanatory diagram of the processing method for the lead part for the VTR lower cylinder tape guide, and Figure 3 is a developed view showing the conventional lead shape.
FIG. 4 is a curve diagram showing changes in displacement, velocity, and acceleration of the tool rest in a conventional lead shape, FIG. 5 a is a developed diagram showing an example of the lead shape according to the present invention, and FIG. FIG. 6a is a developed diagram showing another embodiment of the lead shape according to the present invention, and FIG. FIG. 3 is a curve diagram showing changes in speed and acceleration of the tool rest depending on the shape. 1...Magnetic tape, 2a, 2b...
Guide pin, 3...Lower fixed cylinder, 4...
. . . Guide stepped portion for tape guide, 5 . . . Upper rotating cylinder, 6 . . . Magnetic head.

Claims (1)

[Claims] 1. In a tape guide for a rotary head type magnetic recording/reproducing device which is composed of a drum having a guide step on the outer periphery that keeps the running position of the magnetic tape constant, a part of the guide step that does not directly contact the magnetic tape on the outer periphery of the drum. A tape guide for a rotary head type magnetic recording and reproducing device, characterized in that the shape of is formed by connecting a plurality of parabolas.