JPH0481274B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a video tape recorder (hereinafter referred to as "VTR").
It is abbreviated as. ) of the rotary head assembly.

Conventional configuration and its problems As a representative example, a VHS type VTR will be explained. As shown in FIG. 1, the conventional rotary head assembly has a rotating member 2 that rotates and slides at 1000 to 2000 rpm, and a non-rotating member 2 that rotates and slides at 1000 to 2000 rpm with respect to a magnetic tape (hereinafter abbreviated as "tape") 1. This is supported by a sliding fixing member 3. A lead 4 is provided on the fixing member 3 for the purpose of regulating the position of the tape 1 during running. A magnetic head 5 mounted on a rotating member 2 is connected to a tape 1.
By performing a helical scan accurately on the tape 1, reliable input and output of the video signal can be realized through the tape 1. Note that 6 is a magnetic head mounting window. The magnetic head 5 is held so as to protrude outward from the outer peripheral surface of the rotating member 2 by approximately several tens of microns. When inputting and outputting video signals, the magnetic head on the rotating member rotates at high speed and comes into contact with the tape, causing abrasion between the surface of the magnetic head and the tape and producing abrasion particles. On the other hand, the tape also comes into contact with a part of the rotating member, and abrasion particles are generated due to the abrasion that occurs here as well.
These wear particles move on the rotating member in a partially attached state. At the initial stage of generation, these wear particles have a diameter of several microns at most, but they accumulate in a specific area on the rotating member and grow to a diameter of 10 microns or more. The abrasion powder on the rotating member that has grown through these steps forms a kind of built-up edge that slides relative to the tape at high speed (the outermost circumferential speed of the rotating member), and has magnetic properties against the tape. This can cause significant damage including delamination of layers. In practice, if wear debris does not accumulate on the rotating member, the tape damage phenomenon described above is eliminated. As a method to solve the above problems, one of the authors proposed a rotating member 7 as shown in FIGS. 2 and 3.
A spiral groove 9 is formed between the tape and the fixed member 8, and the dynamic pressure (air pressure) generated by the rotational force of the rotating member 7 is used to spread the tape in a minute amount (5 to 20 μm) over the entire circumference of the rotating head assembly. We have already proposed a rotating head assembly with a new configuration that keeps it floating. However, since the tape is basically held floating on the rotating head assembly in the direction away from the head, this has a great effect on tape running performance and tape life, but on the other hand, the input/output characteristics of signals via the tape deteriorate. A problem arises in that the envelope output becomes difficult to output.

OBJECTS OF THE INVENTION In view of the above drawbacks, the present invention provides a rotating head assembly in which a pump-out type spiral groove is formed on the opposing surface of a rotating member that closely faces a fixed member. By omitting the spiral groove in the rotary head assembly, a rotary head assembly with stable running performance and high signal input/output characteristics is provided.

Structure of the Invention The present invention includes a fixing member having a fixed cylindrical portion, a fixing member having approximately the same diameter as the fixing member, and a magnetic head that is disposed on the same axis in close proximity to the fixing member and that holds a magnetic head. It consists of a rotating rotating member, a magnetic head mounting part provided on the rotating member and containing the magnetic head, and a magnetic head mounting window sharing an outer peripheral surface of the rotating member with the magnetic head mounting part, A pump-out type spiral groove is provided on the rotating member at a portion facing the fixed member, and a portion of the spiral groove on the upstream side in the rotational direction when viewed from the upstream end in the rotational direction of the magnetic head mounting window is provided on the rotating member. The tape is constructed by omitting a spiral groove in the rotating head assembly, ensuring stable running by keeping the tape floating above the rotating head assembly, while improving contact between the magnetic head and the tape and greatly improving the input/output characteristics of image signals. It has the unique effect of improving

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 4 is a bottom view showing the position of the spiral groove provided on the upper bottom surface of the rotating member 7 in the first embodiment of the present invention. A magnetic head mounting portion 6a including a magnetic head mounting window 6 for mounting the magnetic head 5 is provided on the bottom surface of the rotating member 7, and spiral grooves 11 and lands 12 are alternately provided in the other approximately concentric area. There is.
Rotation direction A of the rotating member viewed from the magnetic head mounting window
There is no spiral groove 11 in the area within a rotation angle θ ₁ measured from the vertical edge 6b on the upstream side of the magnetic head mounting window in the upstream direction of the magnetic head mounting window, and the area is entirely composed of lands 12. On the rotary head assembly having the spiral groove configured as described above, the local deformation behavior of the tape especially in the vicinity of the magnetic head is shown in Figures 1 and 2 based on the data measured by a photonic sensor, and the operation is explained. do. When the spiral groove has a velocity relative to the opposing plane that is set close to and parallel to the spiral groove, a non-uniform discharge air pressure distribution as shown in FIG. 6 is exhibited. Therefore, the amount of tape floating deformation at the spiral groove 11 position is larger than that at the land 12 position. On the other hand, in the magnetic head mounting portion 6a, unless the rotating member 7 is completely aerodynamically shielded, an air leakage phenomenon is observed, and the pressure locally decreases to the same level as atmospheric pressure. FIG. 5 shows tape deformation behavior in the vicinity of the magnetic head 5 when a conventional spiral groove is provided. Since the spiral groove 11 is provided near the upstream end 6b of the magnetic head mounting window, the tape locally floats near the tip of the magnetic head 5, resulting in poor contact between the magnetic head 5 and the tape 1. This causes envelope output failure. On the other hand, FIG. 5 2 shows the tape deformation behavior when the rotating member according to the embodiment of the present invention is used. Since the spiral groove 11 is omitted in the region of θ, the tape flying height in this area is localized. As a result, sufficient contact between the magnetic head 5 and the tape 1 is ensured. Therefore, the envelope output in this case is necessarily ensured sufficiently. The specific size of θ will be described. FIG. 6 is a partially enlarged view of the vicinity of the magnetic head for explaining the process of determining the θ value. As mentioned above, the tape 1 loses its floating force at the magnetic head mounting window. At this time, the tape 1 is
In practice, wear may occur between the tape and the rotating member 7 if there is geometrical contact with the tape. If the tape 1 is stretched at the tip of the pin 14 that protrudes in the radial direction by δ from the cylindrical surface 13 with radius R,
A point M is where the tape 1 geometrically contacts the cylindrical surface 13 with reference to the point where the pin stands. At this time, the rotation angle θ ₀ to point M is θ ₀ = cos ^-1 (R/(R
+δ)). Specifically, as δ, the protruding amount H of the shoulder of the magnetic head and the flying height _Ht of the tape exist as shown in FIG. Therefore, at this time,
As θ, θ=cos ^-1 (R/(R+H〓))+cos ^-1 (R/
(R+H _t )). For example, when considering a small 8m/m video, R = 20mm, H = 0.05mm, H _t =
If it is 0.02mm, θ will be approximately 7°. As above,
By appropriately selecting θ, the envelope waveform that eliminates the spiral groove on the upstream side of the magnetic head mounting window can be greatly improved as shown in FIG. 8a. FIG. 8b shows an envelope waveform produced by a conventional rotary head assembly having a spiral groove configuration. Furthermore, since the tape has been floated in the area where the spiral groove is provided, the effect of the rotary head assembly itself on tape running properties is maintained as before.

Effects of the Invention As described above, the present invention comprises a fixed member having a fixed cylindrical portion, and a rotating member that is provided on the same axis in close proximity to the fixed member and rotates while holding a magnetic head. A pump-out type spiral groove is provided on the rotating member side of the opposing part between the two, and the spiral groove is missing in a part of the upstream side in the rotational direction when viewed from the upstream side of the magnetic head mounting window on the rotating member. In addition to improving the contact with the tape and greatly improving the input/output characteristics of signals via the tape on the rotating head assembly, the tape is kept floating stably on the entire circumference of the rotating head assembly, making the rotating head assembly Friction and abrasion caused by contact between the tape and the tape can be avoided, and this has a great practical effect.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a conventional rotary head assembly, FIG. 2 is a sectional view of a newly configured rotary head assembly, FIG. 3 is a bottom view of the rotary member in the same rotary head assembly, and FIG. 4 is an embodiment of the present invention. A bottom view of the rotating member in the example, FIGS. 5 1 and 2 are sectional views for explaining the tape deformation behavior near the magnetic head mounting window,
Figure 6 is a schematic diagram explaining the geometrical contact between the tape and the rotating member, Figure 7 is a schematic diagram embodying Figure 6, and Figures 8 a and b are diagrams showing envelope output. It is a diagram. DESCRIPTION OF SYMBOLS 1... Tape, 5... Magnetic head, 6... Magnetic head mounting window, 6b... Upstream end of magnetic head mounting window, 7... Rotating member, 8... Fixed member, 11...
spiral groove.

Claims (1)

[Scope of Claims] 1. A fixing member having a fixed cylindrical portion, which has approximately the same diameter as the fixing member, is provided on the same axis in close proximity to the fixing member, and holds a magnetic head and is self-contained. a rotating member; a magnetic head mounting portion provided on the rotating member that includes the magnetic head; and a magnetic head mounting window that shares an outer peripheral surface of the rotating member with the magnetic head mounting portion; A pump-out type spiral groove is provided on the rotating member at a portion facing the fixed member, and a part of the spiral groove is located on the upstream side in the rotational direction when viewed from the upstream end in the rotational direction of the magnetic head mounting window. A rotating head assembly with a spiral groove missing. 2 Regarding the missing portion of the spiral groove on the upstream side in the rotational direction of the rotating member, at the rotation angle θ defined from the upstream end in the rotational direction of the magnetic head to the upstream side, the spiral groove is missing in an area where θ is within 7°. A rotary head assembly according to claim 1.