JPH0425603B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a drum device for a helical scan video tape recorder (hereinafter abbreviated as VTR).

[Prior art]

FIG. 1 is a plan view showing a tape running system of a helical scan VTR using a conventional drum device. FIG. 2 is an exploded perspective view showing a conventional drum device, and FIG. 3 is a sectional view thereof.

First, a conventional helical scan type VTR will be briefly explained with reference to FIG. Magnetic tape 3 wound on supply reel 2 of cassette 1
is pulled out from the cassette 1 by guide rollers 4 and 5 on the entrance side and guide rollers 6 on the exit side.
The pulled-out magnetic tape 3 comes into contact with the full-width erasing head 7 and the impedance roller 8, and then is wound around the drum device 9. Thereafter, the magnetic tape 3 contacts the impedance roller 10, the audio erasing head 11, and the audio control head 12, and then
It is sandwiched between the capstan 13 and the pinch roller 14. Capstan 13 is rotating at a predetermined speed. Therefore, the magnetic tape 3 sandwiched and pressed between the capstan 13 and the pinch roller 14 runs at a predetermined speed in accordance with the rotation of the capstan 13. In this way, tape running for recording and playback becomes possible. The magnetic tape 3 is
Thereafter, it is wound onto a take-up reel 15 within the cassette 1.

Next, referring to FIG. 2, the drum device 9 includes a pair of rotating drum 16 disposed at the top and a fixed drum 17 disposed at the bottom. The rotating drum 16 has a built-in video head 18, and signals picked up from the video head 18 are transmitted to the fixed drum 17. A more specific structure will be explained. The rotating drum 16 rotates integrally with a drum shaft 19 and a flange 20 fixed to the drum shaft 19 by, for example, press fitting. A rotating rotary transformer 21 is fixed to the flange 20 by, for example, adhesive. On the other hand, a fixed rotary transformer 22 disposed opposite to the rotating rotary transformer 21 is fixed to the drum 17 by, for example, adhesive. The gap between the rotating rotary transformer 21 and the fixed rotary transformer 22 is approximately 80 μm. The fixed drum 17 has a lead groove 23 on its outer peripheral surface, and the magnetic tape runs on this lead groove 23.

Referring to FIG. 3, signals from the video head 18 attached to the rotating drum 16 are transmitted via lead wires 24 to a printed circuit board 25 (not shown in FIG. 2) attached to the rotating drum 16. (is being carried out). Furthermore, this signal is transmitted from the printed circuit board 25 to the rotating rotary transformer 21 via the lead wire 26. As described above, this rotating rotary transformer 21 is electromagnetically coupled to the fixed rotary transformer 22 with a gap of approximately 80 μm. Therefore, the rotating video head 18
The signal picked up by the printed circuit board 2
5. The signal is transmitted to the electric circuit section through a path consisting of a rotating rotary transformer 21 and a fixed rotary transformer 22. In addition, the part indicated by reference number 27 in the figure is
This is the motor unit that drives the drum. Although the figure shows a so-called DD system in which the motor shaft and the drum shaft are directly connected, the system is not limited to this system, and there are also systems in which the drum is driven via a belt or the like.

The conventional VTR drum device constructed as described above has the following drawbacks. In other words, it is constructed with a structure in which weak signals from the magnetic tape are routed through lead wires, and a coil is wound in a ring around a rotary transformer made of a flat ferrite core, making it immune to electrostatic and electromagnetic interference. Extremely weak. To give an example, VTR
If placed on top of or close to a CTV, it may be subject to high-voltage interference from the CTV, the magnetic flux leaking from the deflection yoke may cause beats in the reproduced image, or
Beats can also occur in the VTR itself due to magnetic flux leakage from the internal transformer. In addition, radio waves from radio broadcasts, called medium wave interference, enter the rotary transformer and cause beats, so in some areas it may be necessary to surround the entire VTR with a metal enclosure. For this reason, current VTRs are provided with a shield case housing internally in order to eliminate the above-mentioned disadvantages.

[Summary of the invention]

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and instead of the electromagnetic coupling type rotary transformer used in the conventional VTR drum, an optical coupling type non-contact coupler is installed. The object of the present invention is to provide a drum device that can eliminate the drawbacks of the conventional method.

[Embodiments of the invention]

FIG. 4 is an exploded perspective view showing one embodiment of the present invention, and FIG. 5 is a sectional view thereof. Figure 6 shows
FIG. 1 is a plan view showing a tape running system of a VTR using an embodiment of the present invention. In these figures, the same numbers as those used in FIGS. 1 to 3 indicate the same or corresponding parts.

Referring to FIGS. 4 and 5, in a drum device 28 according to the present invention, a circular printed circuit board 29 is fixed to a flange 20 that rotates integrally with the rotating drum 16. On one side (bottom side) of this printed circuit board 29, photo couplers 30 and 31 (both are optical elements with a built-in light emitting element and a light receiving element) each consisting of at least a light emitting element and a light receiving element are incorporated, and a regenerative amplifier ( HEAD
AMP, and the recording amplifier (REC
AMP) is included. Lead wires 32 and 33 for transmitting and receiving electrical signals are connected between the printed circuit board 29 and the video head 18 in charge of each field. Further, power supply B and GND (earth) for operating the electronic components on the printed circuit board 29 are supplied from the head and bottom of the drum shaft 19. That is, the ground piece 34 is brought into direct contact with the head of the drum shaft 19. On the other hand, a contact gap 35 is provided at the bottom of the drum shaft 19 and is insulated from the shaft, and a power supply section 36 is brought into contact with this contact gap 35. As shown in FIG. 5, a lead wire 37 is connected to the top and bottom of the drum shaft 19, and the other end of the lead wire 37 is connected to the printed circuit board 29. The lead wire 37 extending from the bottom of the drum shaft 19 is
It runs inside the drum shaft 19 toward the head. Note that, since the rotating drum 16 generally rotates at a high speed of 1800 rpm, it is often thought that the lifespan of the grounding piece 34 and the power supplying piece 36 that come into contact with the drum shaft 19 becomes a problem. However, if the center of the drum shaft 19 is used as a contact point, the sliding speed can be extremely reduced, and as a result, the life can be extended.

Inside the fixed drum 17 is a circular printed circuit board 3.
8 is completely included and fixed. On the top surface of this printed circuit board 38, there is at least a photo coupler 39 (an optical element that has a built-in light emitting element and a light receiving element; the light receiving element operates during playback and the light emitting element operates during recording) and an electronic circuit that drives it. is included. The B power supply supplied to these electronic components and the transmission and reception of signals are performed by a lead wire group 40 (not shown in FIG. 5).

A part of the inner surface of the fixed drum 17 is provided with light absorption means (for example, painted black) to absorb excess light in order to improve the S/N during signal transmission and reception. It has been devised. Referring to FIG. 6, when the video head 18 is within the angle θ of the drum 28 shown (the video head 18 is rotating at 1800 rpm), the video head 18 is attached to the magnetic tape 3. During this period, there is no need to receive light from the optical element 30 or 31 attached to the rotating drum 16. Therefore, the light receiving element 39 only needs to be able to pick up signals from the head 18 that is in contact with the magnetic tape 3. Of course, all you have to do is switch the light element 30 or 31 to light up, but
In that case, a pulse (generally called an FF pulse) that detects the drum phase must be applied to the rotating printed circuit board, and additional contact pieces are required. Therefore, it is desirable to paint the area within the angle θ black.

According to the drum device configured as described above, during recording, the recording signal on the fixed printed circuit board 38 is transmitted (that is, optically coupled) to the rotating light receiving element 30 or 31 via the light emitting element 39, and is amplified. Video head 18 from recording amplifier (REC AMP)
is applied to the tape and recorded on the tape at the optimum recording current. During reproduction, a weak signal picked up from the magnetic tape 3 by the video head 18 is amplified by a reproducing amplifier (HEAD AMP) and emitted by a light emitting element 30 or 31. The light is then received by the fixed light receiving element 39, amplified to a predetermined level by an amplifier in the fixed printed circuit board 38, and transmitted to the outside of the drum via the lead wire group 40.

Also, with reference to FIGS. 4 and 6, the inner surface (θ
Since the light absorbing means (for example, painted black) is formed within the angle of , the following unique effects are produced.

That is, with reference to FIG. 6, θ of the drum 28
Even when the video head 18 is within an angle of
31 is emitting light. However, the light receiving element 39
When the video head 18 is within the angle θ of the drum 28, there is no need to receive the light from the optical elements 30 and 31; conversely, when the video head 18 receives the light, the S/
Decrease N. Therefore, a light absorbing means (for example, painted black) was formed on the inner surface (within the angle θ) of the fixed drum 17 on the side not in contact with the magnetic tape. As a result, when the video head 18 is present within the θ angle of the drum 28, the light emitted by the optical elements 30 and 31 is absorbed by this light absorbing means and does not reach the light receiving element 39. As a result, the S/N improves.

In addition, in the above-mentioned embodiment, the photo cutter 3
0, 31, and 39 each incorporate both a light emitting element and a light receiving element, but the present invention is not limited to this, and each may be provided separately. It is also possible to improve the S/N by matching the optical wavelengths for both transmission and reception. Further, in the above-described embodiment, the portion θ inside the fixed drum 17 is painted black, but other ideas may be considered. for example,
A wall may be provided inside to block light.

〔Effect of the invention〕

As described above, according to the present invention, signals from the rotary head are transmitted and received by optical coupling, so that the interference seen in conventional drum devices is eliminated. In addition, the inside of a VTR chassis is dark and there is almost no interference from light, and the rotating drum and fixed drum (both made of aluminum) are completely surrounded by each other and are electrically grounded, so it is not possible to completely shield the chassis. be done. Since the extracted signal is amplified to a predetermined level within this shielded drum, it is extremely stable. Further, it is possible to reliably inspect each drum unit within the process of the production department. Furthermore, in conventional rotary transformers, shallow grooves were cut into a flat ferrite plate, several turns of the winding coil were housed in the grooves, and the coils were fixed with adhesive, but with this invention, these are completely unnecessary. Cost reduction is also significant.

[Brief explanation of drawings]

FIG. 1 is a plan view showing a tape running system of a helical scan VTR using a conventional drum device. FIG. 2 is an exploded perspective view showing a conventional drum device. FIG. 3 is a sectional view of the drum device shown in FIG. 2. FIG. 4 is an exploded perspective view showing an embodiment of the present invention. FIG. 5 is a sectional view showing an embodiment of the present invention. FIG. 6 uses one embodiment of the invention.
FIG. 2 is a plan view showing a tape running system of a VTR. In the figure, 16 is a rotating drum, 17 is a fixed drum, 18 is a video head, 19 is a drum shaft, 28 is a drum device, 29 is a printed circuit board, 3
0 and 31 are photo couplers, 34 is a grounding section, 35 is a contact gap, 36 is a B power supply section, 38 is a printed circuit board, and 39 is a photo coupler.

Claims (1)

[Claims] 1. A video head, a recording amplifier for driving the video head, a reproducing amplifier for amplifying the signal detected from the video head, and a main unit for transmitting and receiving signals during recording or reproduction. A rotating drum comprising a photocoupler of 1, divided into one side in contact with the magnetic tape and the other side not in contact with the magnetic tape, the inner surface of the other side being provided with light absorption means, and further comprising: , a fixed drum comprising a second photo coupler that is paired with the first photo coupler to transmit and receive signals, and the power supply to the rotating drum rotates integrally with the rotating drum. A drum unit of a videotape recorder, which is fed via a drum shaft.