JPS5936343B2 - 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 that allows easy and accurate creation of leads for regulating the running position of a magnetic tape.

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

That is, the magnetic tape 1 is inserted through the guide posts 2a and 2b so that the edge of the magnetic tape follows the tape guide step 4 (hereinafter referred to as a lead) provided on the outer peripheral surface of the lower fixed cylinder 3. Then, it is wound spirally around the outer peripheral surfaces of the upper rotating cylinder 5 and the lower fixed cylinder 3, 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, which is made up of the outer peripheral surface of the lower fixed cylinder 3 and the leads 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 be incorrect. It becomes stable, and unevenness occurs 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, for the lower fixed cylinder 3 which is fixed to the lathe main spindle T and rotates at a constant speed, the cutting tool 9 fixed to the tool rest 8 is moved in the direction of the arrow in the figure (in the direction of the lathe main spindle T) in synchronization with the rotation of the lathe main spindle 7. direction). Therefore, the positional transition of the tool post 8 during its reciprocating motion must match the shape of the lead 4. FIG. 3 shows a developed view of the lead shape on the outer peripheral surface of a conventional lower fixed cylinder.

The magnetic tape 1 is wound around the lower cylinder and runs in a section from 00 to 1800, and 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 changes in displacement, velocity, and acceleration of the motion required of the tool post 8 when machining a lead having such a shape using a lathe as described above. S' in the figure
, V, and A indicate the displacement, speed, and acceleration of the tool rest 8, respectively. In the shape of the lead, the acceleration is discontinuous at the connection between the straight part and the circular arc part, and the absolute value of the acceleration is also large, which is extremely inconvenient from a mechanical point of view. I will be joining. This causes vibrations that are harmful to the machine tool, leading to deterioration of the machining accuracy of the lead shape and deterioration of the roundness of the cylinder, which prevents the designated tape from being guided correctly, resulting in poor quality of the VTR's playback image. This results in unevenness. The present invention solves the above-mentioned conventional drawbacks, and the reed shape is such that its acceleration curve is continuous, that is, the shape of the guide step 4 on the drum outer periphery is shaped in the circumferential direction of the drum. The coordinates are constructed by lines whose second-order differential coefficients are continuous over the entire circumference, and examples thereof will be described below.

Fig. 5a shows an example in which a modified trapezoidal curve called a cam curve is applied, in which the acceleration continuously changes in the section of 180° to 360° that does not contact the magnetic tape other than the linear part where the magnetic tape of the lead comes into contact. This shows that.

Changes in acceleration V and acceleration A at this time are shown in FIG. 5b. Compared to the acceleration curve (FIG. 4) based on the conventional lead shape, according to the present invention (1) since the acceleration changes continuously, harmful vibrations to the machine tool can be suppressed.

(2) Since the acceleration and deceleration sections are widened and the maximum absolute value of acceleration is smaller than in FIG. 4, the followability of the movement of the cutting tool, tool rest, etc. is improved.

Due to these advantages, the roundness of the cylinder and the machining 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 rest 8 is generated by a cam mechanism or the like, as is usually done, it is also effective in reducing wear on the gum surface.

In addition, as the above-mentioned embodiment of the present invention, the force shown in the case where a modified trapezoidal curve is used for the reed shape, such as a cycloid curve, a composite sine curve, a modified sine curve, a parabolic sine curve, etc.
It is clear that a curve in which the acceleration changes continuously will have the same effect.

Additionally, in general, due to the head scanning method, the lead must be located extremely close to the height H of the lower fixed cylinder at around 0° in Figure 5a, so in order to satisfy this constraint, For this purpose, an asymmetric deformed trapezoidal curve in which the absolute values of the maximum and minimum values of the second-order differential coefficients are not equal, or an asymmetric curve such as a trapecloid may be used.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an outline of the cylinder section of a conventional VTR, Fig. 2 is an explanatory view of the processing method for the lead part for the lower cylinder tape guide, and Fig. 3 is a developed view showing the conventional lead shape.
Fig. 4 is a curve diagram of changes in displacement, speed, and acceleration of the tool rest in a conventional lead shape, Fig. 5a is a developed view showing an embodiment of the lead shape according to the present invention, and Fig. 5b is a lead according to the present invention. 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 step part for tape guide, 5 ・・・・・・
Upper rotating cylinder, 6...Magnetic head.

Claims (1)

[Scope of Claims] 1. In a tape guide for a rotary head type magnetic recording/reproducing device comprising a drum having a guide step on the outer periphery for keeping the running position of the magnetic tape constant, the shape of the guide step on the outer periphery of the drum. A tape guide for a rotary head type magnetic recording/reproducing device, characterized in that the tape guide is constituted by a line whose second-order differential coefficient is continuous over the entire circumference with respect to coordinates taken in the circumferential direction of the drum. . 2. Claim 1, characterized in that the shape of the guide stepped portion on the outer periphery of the drum is constituted by a line in which the absolute values of the maximum and minimum values of the second-order differential coefficients are not equal. A tape guide for a rotating head type magnetic recording/playback device described in .