JPS6120252A - Rotary head assembly - Google Patents

Abstract

PURPOSE:To float the entire body of a tape from a rotary cylinder and, at the same time, to stably run the tape without leading the tape, by making the barrel section of the rotary cylinder longer and giving a prescribed diameter difference between its upper and lower parts. CONSTITUTION:The barrel section of a rotary cylinder 15 is formed longer so that it can reach the vicinity of the base of a fixing cylinder 16 and the cylinder diameter at the upper part is made larger than that at the lower part in the vicinity of the recording and reproducing head fitting height. A recording and reproducing head 4 is fitted to the rotary cylinder 15 so that a prescribed quantity of the head 4 can be projected from the opening 17 of the cylinder 15. As a result, a tape can be run under a condition where the tape is wound around the barrel section of the cylinder 15 and around a rotary head assembly with an air film between the tape and assembly. By chaning the diameter of the barrel section in such a way, a downward component of force is applied to the tape and, on the othr hand, force moving the tape upward is always applied to the tape from the contact between the head projected from the rotary cylinder 15 and the tape. Therefore, the tape can be run stably without leading the tape, when the diameter difference is properly selected so as to balance the two force with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a rotary head assembly for a video tape recorder (VTR) or the like that requires high-speed and highly accurate rotational transmission.

[Prior art]

The rotary head assembly of a conventional VTR has a structure as shown in FIG. 1 (however, the drive motor is not shown). In Fig. 1, 1 is a rotating cylinder, 2 is a rotating shaft, and 3 is a flange for directly connecting the rotating cylinder 1 and the rotating shaft 2, and is fixed to the rotating shaft 2 by a method such as press fitting or shrink fitting. . Reference numeral 4 denotes a head for recording and reproducing information on a video tape, which is attached to the rotary cylinder 1. 5 is a fixed cylinder, and the upper part inside the cylinder 5.

A ball bearing 6.7 is housed in the lower part, and a lead 8 for guiding the running of the tape is formed on the outer peripheral surface of the ball bearing 6.7.

Further, 9 and 10 are a rotary transformer on the rotating side and a rotary transformer on the stationary side for transmitting and receiving signals from the spatula 4 and for increasing the width, and 11 is a spring for applying preload to the bearing retainer 12, which is the end ring. 13 to apply preload to the ball bearing 7. 14 is a set screw for fixing the end ring.

By the way, generally speaking, in a VTR rotating head assembly,
The tape is wound and travels around the rotating head assembly at a predetermined inclination (lead angle) (this is called a helical scan). At this time, the rotary cylinder 1 draws air and enters between the tape and the rotary cylinder 1, so that an air film is created between the rotary cylinder and the tape. Only the head 4, which is attached so as to protrude from the rotating cylinder 1, is in contact with the tape. On the other hand, on the fixed cylinder 5 side, the tape runs on the tape running lead 8 of the fixed cylinder 5, and the tape slides on the side surface of the fixed cylinder. Therefore, the tape tension increases from the tape inlet to the tape outlet of the rotary head assembly by an amount corresponding to this sliding frictional resistance.

Now, suppose that the tape winding angle of the rotating hend assembly is θ(
rad), the coefficient of friction between the fixed cylinder side surface and the tape is μ, the tape tension at the tape entrance to the rotating hend assembly is Tl (gr), and the tape tension at the exit is 72 (gr), then the tension increases. The rate is as follows.

T 2 /T I -e" Now, if θ-190' and μm0.2, the tension increase rate will be T 2 /T 1 = 1.94. If the tension at the entrance is 71-37.5 gr. , the tension at the exit increases to T2-Tle"-72.8gr. Recently, rotary head assemblies have emerged that have a small-diameter rotary cylinder, increase the number of rotations, and increase the tape winding angle to ensure compatibility.

In such a rotating head assembly, θ-280
°, μ=0.2, the tension increase rate is T 2
/ T 1 = 2.66, T 2 - 99.8 gr.

In the rotating head assembly of a VTR, it is extremely important to maintain stable contact between the tape and the head, and one of the factors for stabilizing this contact is tape tension. However, at the tension increase rate mentioned above,
The head contact conditions differ between the tape entrance and tape exit, and it may even occur that stable head contact cannot be obtained. Further, at such a tension increase rate, the tape drive torque of the tape drive system, that is, the capstan becomes large, and a capstan with a large capacity is required. Further, the lead 8 of the fixed cylinder 5 is required to have extremely strict linearity as a tape running guide. For this reason, the processing machines and measuring instruments for the fixed cylinder 5 are also required to be highly accurate, and processing and measurement of the fixed cylinder are extremely expensive compared to other parts.

[Summary of the invention]

The present invention has been made in view of the above-mentioned problems of the conventional art. By creating a predetermined diameter difference between the upper and lower parts near the installation height of the head, the entire tape can be floated above the rotating cylinder, and the tape can be held without a lead due to the difference in diameter of the rotating cylinder. The object of the present invention is to provide a rotary head assembly that can run stably and at a low cost.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 2 shows a rotary hend assembly according to one embodiment of the invention. In FIG. 2, reference numeral 15 denotes a rotating cylinder, the body of which is elongated so as to reach near the bottom of the fixed cylinder 16. Further, this rotary cylinder 15 has a diameter difference between the upper and lower parts near the mounting height of the recording/reproducing head, and at this time, the cylinder diameter in the upper part is larger than that in the lower part. It is formed like this. 18 indicates the diameter difference portion.

2 is a rotating shaft, and 3 is a flange for directly connecting the rotating cylinder 15 and the rotating shaft 2, which is fixed to the rotating shaft 2 by a method such as press fitting or shrink fitting. 17 is a rotating cylinder 15
An opening 4 formed in the outer surface of the body is a head for recording and reproducing information on a video tape, and this head is attached to the rotating cylinder 15 so as to protrude from the opening 17 by a required amount. Upper and lower ball bearings 6, 7 are housed within the fixed cylinder 1G. Reference numerals 9 and 10 designate a rotary transformer on the rotating side and a rotary transformer on the stationary side for transmitting, receiving, and amplifying signals of the end 4, respectively; 11 represents a spring for applying preload to the bearing retainer 12, which is positioned by an end ring 13; This applies a preload to the ball bearing 7. 14 is a set screw for fixing the end ring.

As described above, in the rotary head assembly of this embodiment, the body of the rotary cylinder 15 is longer than the conventional one, and the fixed cylinder 16 has no part that contacts the tape, and is different from the conventional one. There is also no equivalent lead formed on the fixed cylinder.

Next, the effects will be explained.

In the rotary head assembly according to this embodiment, the tape is wound around the rotary head assembly and travels in the same manner as in the past, but in the past, the tape came into contact with the side surface of the fixed cylinder and ran on the lead. Therefore, by extending the body of a rotary cylinder to replace the part that corresponds to the tilted surface of the conventional fixed cylinder, and by winding the tape around the body of the rotary cylinder and running it, the tape can be passed through an air film. It can be rotated and wound around a 7-door assembly and run. Since the coefficient of friction between the air and the tape is so small as to be almost negligible, the rotational joint assembly according to this embodiment can almost eliminate an increase in tension. As a result, the driving force of the capstan of the tape drive system can be reduced, and secondary reductions in size, weight, and power consumption of the VTR can be achieved.

In addition, by changing the diameter of the body of the rotating cylinder, a difference occurs in the floating height of the tape between the upper and lower parts of the rotating cylinder, so the tape deforms in the middle direction and is wound helically around the rotating head assembly. do. When the tape is deformed in the direction of the tape and travels while receiving tensilan, a downward force is applied to the tape. Furthermore, due to the contact between the tape and the head protruding from the rotating cylinder, the tape is constantly subjected to a force that moves it upward. By selecting a diameter difference that balances this downward force and upward force, it becomes possible to run the tape stably without a lead.

As a secondary benefit, fixed cylinders do not require leads, so they do not require the high-precision processing machines and measuring machines that are currently available, and the processing methods can be applied not only to cutting but also forging, molding, etc. The range is widened, and the rotary head assembly can be supplied at low cost.

FIG. 3 shows another embodiment of the present invention, in which a rotating cylinder is attached to an upper rotating cylinder 19 and a lower rotating cylinder 2 that is detachably attached to the upper rotating cylinder 19.
Constructed and processed by 0.

It is designed to be easy to assemble. Also in this case, the cylinder diameter of the upper rotary cylinder 19 is made larger so that a difference in diameter occurs between the upper rotary cylinder 19 and the lower rotary cylinder 20, as in the above embodiment. In this embodiment, the recording/reproducing head may be attached to either the upper or lower rotating cylinder. In addition, other configurations are described in the second section above.
It is similar to the embodiment shown in the figure.

(Effects of the Invention) As described above, according to the present invention, the body of the rotating cylinder is formed to be long so as to reach near the bottom of the fixed cylinder, and the body is formed near the height of the recording/reproducing head. hand,
Since it is configured so that a predetermined diameter difference occurs between the upper and lower parts, the entire tape can be run while floating above the rotating cylinder, and the tape can be run stably without providing a lead on the fixed cylinder. This has the effect of reducing the cost of the entire device. Further, a VTR using such a rotary head assembly can be made smaller and lighter, and it also has the effect of reducing power consumption.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional rotary head assembly, FIG. 2 is a sectional view of a rotary head assembly according to an embodiment of the present invention, and FIG. 3 is a diagram showing another embodiment of the present invention. 4... Recording/reproducing head, 6... Upper ball bearing, 7...
・Lower ball bearing, 15... Rotating cylinder, 16... Fixed cylinder, 17... Head opening, 18... Diameter difference part, 19... Upper rotating cylinder, 20... Lower rotating cylinder . Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (4)

[Claims] (1) A rotating head assembly for a magnetic recording/reproducing device comprising a rotating cylinder that supports a recording/reproducing head and a fixed cylinder containing a bearing mechanism that supports rotation of the rotating cylinder, wherein the rotating cylinder is attached to the fixed cylinder. The cylinder has a body that reaches near the bottom of the cylinder, and the body has an opening on its outer peripheral surface for allowing the recording/reproducing head to protrude a predetermined length from the outer peripheral surface. A rotary head assembly characterized in that an upper cylinder diameter near the mounting height of the recording/reproducing head is formed larger than a lower cylinder diameter so that the running of the tape is guided by the difference in diameter. (2) The rotating cylinder is characterized by comprising an upper rotating cylinder and a lower rotating cylinder that is detachably attached to the upper rotating cylinder and has a cylinder diameter smaller than the cylinder diameter of the upper rotating cylinder. A rotary head assembly according to claim 1. (3) The rotary head assembly according to claim 2, wherein the recording/reproducing head is supported by an upper rotary cylinder of the rotary cylinder. (4) The rotary head assembly according to claim 2, wherein the recording/reproducing head is supported by a lower rotary cylinder of the rotary cylinder.