JPS6050736A - Rotary head assembly - Google Patents

Abstract

PURPOSE:To improve both the driving stability and the signal input/output characteristics for the rotary head of a VTR by forming a pump-out type spiral group on the counter surface of a rotary member set opposite to a fixed member, and at the same time omitting the spiral group set at the upstream side of a magnetic head attachment window formed on the rotary member. CONSTITUTION:A magnetic head attachment part 6a including a magnetic head attachment window 6 mounted with a magnetic head 5 is provided on the bottom surface of a rotary member 7, and spiral groups 11 and lands 12 are provided alternately in other nearly concentric areas of the member 7. No group 11 exists at all and only lands 12 exist in an area within a revolving angle theta1 (7 deg.) measured from the vertical edge 6b at the upstream side of the window 6 toward the upstream side of a revolving direction of the member 7 when viewed from the window 6. Therefore a tape 1 floats up by a slight amount over the entire circumference on a rotary head assembly. However this floating amount of the tape is locally reduced at the area of theta1 where the groups 11 are omitted. Thus a satisfactory contact is secured between the head 5 and the tape 1.

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 VH8 type VTR will be described as a representative example of a conventional configuration and its problems. The conventional rotary head assembly, as shown in FIG. 1, has a rotating member 2 that rotates and slides at 1000 to 200 Orpm, and a non-rotating member 2 that rotates and slides with respect to a magnetic tape (hereinafter abbreviated as "tape") 1. The structure is such that stiffness is maintained by the sliding fixed portion 4'A3. A lead 4 is provided at the fixed portion 3-1 at t:1 for regulating the position of the tape 1 during running.

The magnetic head 5 mounted on the rotary section 4'' 2L accurately helically scans the tape 1-, thereby realizing reliable input/output of video signals via the tape 1. Note that this is a 6-digit magnetic head mounting window. The magnetic head 6 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 wear that occurs here as well, and these abrasion particles move on the rotating member in a partially attached state. These wear particles accumulate in a specific region on the wide rotating member, which has a diameter of several microns at most in the initial stage of generation, 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 peripheral speed of the rotating member), and the wear powder on the rotating member forms a kind of built-up edge that slides relative to the tape at a high speed (the outermost peripheral speed of the rotating member). This can cause significant damage including peeling of the magnetic layer. As a practical matter, if the abrasion powder accumulates on the rotating member, the tape damage phenomenon described above will be eliminated. Below 1-
．． As a way to solve the problems of
As shown in FIGS. 2 and 3, the rotating part 4]7 and the rigid 'Ii',
A spiral group 9 is formed between the rotating part IA8 and the rotational force of the rotating part A7 is used to generate dynamic pressure (air pressure) to spread the tape around the entire circumference of the rotating head assembly. :(6~201im) Float-1-Hold Mi
We have already proposed a rotating head assembly with the following configuration:
Since the tape is basically held floating in the direction away from the head by the rotating head assembly 1-, it has a great effect on tape running performance and tape life, but on the other hand, the signal flow through the tape is reduced. Problem No. 1''J arises in that the stability deteriorates and the envelope output becomes difficult to output.

OBJECTS OF THE INVENTION Present Invention Ke 1: In view of the above-mentioned drawbacks, a pump out J14 is provided on the opposing surface of the rotating part that is close to the fixed member and faces lj!
71. to the rotating head assembly forming a spiral group. -Magnetic head mounting window 1- on the rotating member-
By omitting the 1ull spiral group, a rotary head assembly with stable running performance and high signal input/output characteristics is provided.

Structure of the Invention The present invention provides a fixing part (i) having a fixed cylindrical part, and a fixing part (a) having approximately the same diameter as the fixing member, which is disposed close to the fixing member on the same axis, and holds a magnetic head. a rotating member that rotates itself; a magnetic head mounting portion that is provided on the rotating member and 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 group is provided on the rotating member at a portion facing the fixed member, and of the spiral group, the spiral group is provided on the upstream side in the rotational direction when viewed from the upstream end in the rotational direction of the magnetic head mounting window. The spiral group is omitted in some areas of the tape, keeping it floating above the tape full-rotation head assembly to ensure stable running, while improving contact between the magnetic head and the tape for image signal input/output. It has the unique effect of significantly improving properties.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described and explained below with reference to the drawings. 4th Mlt is a bottom view showing the spiral group provided on the bottom surface of the rotating member 71 in the first embodiment of the present invention. A magnetic head mounting window 6 is included on the bottom surface of the rotating member 7 to mount the l':1-1 magnetic head 5.
Spiral groups 11 and lands 12 are alternately provided in the other concentric areas where the air head attachment portion 6a is provided.

111. from the magnetic head mounting window. The direction of rotation of the rotating member is 1 - toward the stream side.In the area within the rotation angle 01 of 4 rivers from the upstream vertical edge 6b of the window with IR head, there is no spiral group 11, and the area is entirely composed of lands 12. has been done. Figure 5 1.2 shows the local deformation behavior of the tape, especially in the vicinity of the magnetic head, on a rotary head assembly having a spiral group configured as shown below, based on actual data measured by a photon sensor. Explanation of operation: When the spiral group has a velocity relative to the opposing plane set in the qf row in close proximity, it exhibits a non-uniform discharge air pressure distribution as shown in FIG. Therefore, the amount of tape floating deformation at the spiral group 11 position is larger than that at the land 12 position. On the other hand, in the magnetic henode 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 6 when a conventional spiral group is provided. Since the spiral group 11 is provided near the upstream end 6b of the magnetic head mounting window, the tape may partially float near the tip of the magnetic head 6.
1- As a result, the contact between the magnetic head 6 and the tape 1 is poor, resulting in a defective envelope output. One-way solution 6 Figure 2
17 shows the tape deformation behavior when the rotating member of the embodiment of the present invention is used, and the spiral group 11 in the region of θ
By omitting the magnetic head 5, the tape flying height at this portion is locally reduced, and 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. Let's talk about the specific size of 60. FIG. 6 is a partially enlarged view of the vicinity of the magnetic head for explaining the determination of the 1θ value. As mentioned earlier, the floating blade is lost at the magnetic head mounting window for tape 1 it. If the tape 1 then comes into geometrical contact with the rotating element 7, wear may actually occur between the tape and the rotating element 7. If the tape 1 is stretched at the tip of the pin 14 that protrudes in the radial direction by δ from the cylindrical portion 13 with radius H, the tape 1 will be in geometric contact with the cylindrical surface 13 using the point where the pin stands as a reference point. This is the tipping point V. At this time, the rotation angle at the point V dimension is 1θ, , = cos '(R/(R+δ)
) of the magnetic head as V1δ, which is given by
The protrusion of l (1Hδ) and the floating oil H1 of the tape exist as shown in Fig. 7. Therefore, at this time, as θ, θ= c
os' (R/ (R-1-I(δ)) + Cog
'(R/(R-1-J)). For example, when considering a small 8'yn video, R=20ffM, H
When δ=O, OF5MM and Hj=0.02111W, θ is 1° and 7°. As mentioned above, if θ is properly set i
The envelope waveform that causes the spiral group to be missing on the upstream side of the magnetic head mounting window due to N constant 17 is not shown in Figure 8a.
Figure 8 shows the envelope waveform produced by a rotary head assembly with a conventional spiral group configuration. Therefore, the effect of the rotary head assembly itself on tape running performance is maintained as before.

Advantages of the Invention As described above, the present invention provides a structure between 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 group is provided on the rotating member side of the opposing part of the rotating member, and the spiral group is missing in a part of the upstream side of the rotating member when viewed from the upstream side of the magnetic head mounting window of 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 stably floating around the entire circumference above the rotating head assembly. Friction and abrasion due to contact between the tape and the tape can be avoided, and its practical effects are significant.

[Brief explanation of drawings]

Figure 1 is a perspective view of a conventional rotary head assembly, Figure 2 is a sectional view of a rotary head assembly with C1, v1 configuration, and Figure 3
Figure V1 is a bottom view of the rotating member in the same rotating head assembly.
4', A bottom view, 5th sill 1 (1), (2) describes the tape deformation behavior near the magnetic head nozzle mounting window, a sectional view for clarity, and Figure 6 shows the geometry of the tape and the rotating member. Fig. 7 is a schematic diagram for explaining the physical contact of Fig. 6.
FIGS. 8(a) and 8(b) are schematic diagrams showing envelope output. 1...Tape, 6...Magnetic head, 6...
...Magnetic head mounting window, 6b...Magnetic head mounting window upstream end, 7...Rotating member, 8...Fixing member, 11...Spiral group. Name of representative PII Patent attorney Toshio Nakao and one other person Figure 1 → Figure 2 Figure 4

Claims (2)

[Claims] (1) A fixed part having a fixed cylindrical part, which has approximately the same diameter as this fixed member, is provided close to the fixed member on the same axis, and rotates while holding a magnetic head. The rotating member includes: a rotating member; a magnetic head mounting portion that is provided on the rotating member and 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 group is provided in a portion facing the fixed portion, and a part of the spiral group 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 missing spiral group. (2) Regarding the missing portion of the spiral group on the upstream side in the rotation direction of the rotating member, at the rotation angle θ defined from the upstream end in the rotation direction of the magnetic head 2-7 to the -1-stream side, θ is [Claim 1] - A rotary head assembly according to claim 1, in which the spiral group is omitted in an area within 7 degrees.