JPS6032269B2 - detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a detection device for detecting the running speed and/or tension of a recording medium when the recording medium runs in a magnetic tape device or a film device.

In general, in devices that use tapes, films, etc. as media, it is necessary to control the running speed and tension of the tape, film, etc., and various measures have been taken to manage it, but the most difficult one is to control the running speed of the tape, film, etc. This is a detection unit that faithfully picks up tension, and the present invention relates to this detection unit.

The content of the present invention will be explained below using a VT which is a typical example of a magnetic tape device.
The R will be explained as an example, and in particular, the case where it is incorporated into the parallel M-type loading system adopted in the V-ship type Kyo-inch female control will be explained. FIG. 1 is a diagram showing a conventional parallel M type loading system, and FIG. 2 is a detailed diagram showing the tension brake section of FIG. 1.

In FIG. 1, 1 is a rotating drum, la and lb are fixed to the neck of the rotating drum 1 with a slight protrusion.
This is a video head that rotates at high speed.

The two heads la, lb are indexed at exactly 180° relative to the center of the drum.

2a, 2b, 2c are loading tape guides on the supply side, and 2a', 2b', 2c' are loading tape guides on the take-up side.
It has the function of stably supporting the rhombus.

4a is a guide low-foot on the supply side, 4b is a guide low-foot on the tie-up side, and 4b is a guide roller on the tie-up side. These are impedance rollers that reduce tape vibration and jitter.

Reference numeral 5 designates a full erase head, 6 a tape guide, 7 a tension pole for keeping the back tension of the tape constant, and 8 a tension arm to which the tension pole is fixed and which moves in the rotational direction about a rotation center 8a.

Reference numeral 9 denotes an audio erasing head, and 1 an audio/control signal head. Generally, the audio erasing head 9 and the audio/control signal head 1 are integrated to provide mechanical precision.

11 is a tape guide. 12 is pinch lohu, 1
3 is a cap stan, and the magnetic tape 3 is sandwiched between a pinch roller 12 and a cap stan 13, and can be advanced at a constant speed by the rotation of the cap stan 13.

Reference numeral 14 denotes the magnetic tape 3 and a stored cassette.

Reference numerals 15 and 16 are tape guides that are present in the cassette and are used to smoothly supply and wind up the stored tape. 17
18 is a supply reel in the cassette, and 19 is a take-up reel in the cassette.

In the tape running section constructed as described above, the tape 3 runs at a constant speed in the direction of the missing mark shown at 3 in FIG. 1, and the recording signal is reproduced on the tape by the rotary heads la, 1M.

In order for the tape running section to operate smoothly and for recording and reproducing operations to be performed according to a fixed tape format, the tension and tape speed must be constant at each point in the tape running path. Generally, the tension of the tape varies greatly depending on the supply reel hub, so a back tension mechanism is required as shown in FIG. FIG. 2 shows details of the conventionally used tape back tension mechanism shown in FIG.

The tension pole 7 is fixed to the tension arm 8,
The other end of this tension arm is pulled against a portion 21 of the main deck section by a spring. The tension arm is fixed to the deck by a center 8a, and has a structure in which it rotates in the direction of the arrow shown by the dashed line with the center 8a as the rotation center. Therefore, if the magnetic tape 3 is not present or the tension of the tape is reduced, the tension pole will move in the left direction of the arrow. On the other hand, a tension band 17 is provided on this tension arm 8 from a fixed point 8b. The tension band is generally made of a flexible material such as a phosphor bronze plate, and surrounds the outer cover of the pillar portion 22a of the saffray reel disk 22, and the inside of the tension band is made of felt-like material to increase friction. It is now 17a. Reference numeral 23 denotes a mounting portion for fixing the other end of the tension band to the main deck portion.

Here, if the tension pole rotates to the left as indicated by the dashed-dotted line as described above, the fixed point 8b in the tension arm also rotates to the left, so the tension band 17 is also pulled to the left, and the other end is fixed at the attachment part, so the felt part 17a of the tension band 17
comes into close contact with the outer surface of the center column portion 22a of the supply reel disk, thereby applying a brake to the rotational movement of the supply reel disk. Conversely, when the tension pole rotates in the right direction of the arrow, the tension band 17 moves to the right, the brake is released, and the supply reel disc rotates slightly.
Here, between the peeling tension P, the torque T and the reel radius r, the skin P:;

Therefore, if you use a tape cassette wound around a supply reel hub with a large diameter, or if a large amount of magnetic tape is wound around the supply reel hub (see Figure 1, Figure 3).
In case a), the radius r is large and the torque T is constant, so the tension P is equal to 4.

Therefore, the elastic force of the spring is overcome by the tape tension, and the tension pole 7 moves to the left of the arrow shown by the dotted chain line, and the tension band 17 comes into contact with the pillar portion 22a of the supply reel disk, and the brake is activated. Then, the torque T increases and the tension P increases again according to the above-mentioned relational expression. On the other hand, when a small amount of tape is wound around a supply reel with a small diameter (as shown in Fig. 1, 3c), the tension becomes large, the tension pole 7 moves to the right of the arrow, and the tension band 17 moves toward the supply reel. Pillar portion 22 of the reel disc
It separates from a and the braking force is lost. Then, the torque T decreases and the tension decreases. That is, the conventionally used first
According to the back tension mechanism shown in FIGS. 2 and 2, the tape tension can be kept constant regardless of the diameter of the supply reel hub or the amount of tape wound around it.
However, the back tension mechanism as described above has the following drawbacks. 1 The tape tension can be kept almost constant regardless of the supply reel hub or the amount of tape wound around it, but because it is a mechanical system, fine control is not possible. A slight difference occurs at the end of winding 3c, and a skew phenomenon usually occurs during playback.

2. Since it is a mechanical system, especially friction between the tension bath 17 and the IJ roll disk 22, there are large fluctuations due to changes over time.

3. In the case of the conventional example, only the tape tension is controlled and the tape speed is not controlled.

The present invention eliminates the above-mentioned drawbacks of the prior art and provides a detection device for detecting tape tension or tape speed when the tape tension or tape speed is kept constant.

Recently, high-density recording on tapes has progressed, requiring fine control of tape speed and tension, and drive motors are often provided for each of the supply reel disk and take-up reel disk. (Traditionally, the supply reel disk and take-up reel disk were driven by belts, idlers, etc., but recently direct drive motors are often used.) In this case, how is the tape speed and tension detected and converted into electrical signals? The biggest question is whether to do so. This electric signal drives the supply reel rotation motor and the take-up reel rotation motor. An embodiment of the present invention will be described below with reference to FIG. Third
In the figures, the same numbers as those shown in Figure 1 are the same.
“or a significant portion shall be indicated.

7 is new and shows a tension pole, and the tension band 17 shown in FIG. 1 has been removed.

The running system of the magnetic tape device 3 is exactly the same; the magnetic tape 3 stored in a supply reel disk is stacked around a rotating drum 1 and is run by a capstan shaft 13 and a pinch roller 12. FIG. 4 is a detailed configuration diagram of the detection section of FIG. 3, and FIG. 5 is a side sectional view of a part of FIG. 4. In Figures 4 and 5, 7 is a tension pole consisting of a rotating body with radial wings, 7a is the center of the rotating body, and 8 is a tension arm that supports the entirety of 7 and 7a, and is a rotating body. It rotates in the direction of the dashed line arrow about the center 8a. 20 is a spring, and 21 is a light sensor, such as a phototransistor or photodiode, which is provided on the main deck and is located on the locus of the tension pole 7 that rotates around the rotation center 8a. On the other hand, since the magnetic tape 3 runs in contact with the outer surface of the tension pole 7 having radial wings, the tension ball 7 is rotated as the magnetic tape 3 travels. Here, as shown in FIG. 4B, light is applied to the optical sensor 21 from the top surface, for example, by external light or light from a light source such as a lamp. The directivity of the optical sensor should be narrow and sharp, and it is desirable that it only detects light from directly above the optical sensor. Now, the relative positional relationship between the tension pole 7 and the optical sensor 21 is such that when the optical sensor 21 is located approximately at the center of the length of the radial type blade of the tension pole 7, the time for light to be irradiated to the optical sensor 21 and the radial type blade Since the time blocked by the light is equal, the output electrical signal of the optical sensor 21 becomes as shown in FIG.

That is, a pulse signal with a duty ratio of 50:50 is obtained. Furthermore, when the tape speed is slow, a pulse signal with a low frequency as shown in FIG. 6a is obtained, and when the tape speed is long, a pulse signal with a high frequency as shown in FIG. 6b is obtained. Therefore, first the tape speed is easily detected. Furthermore, as described in the conventional example shown in FIGS. 1 and 2, due to the fluctuation of the tape tension, the entire position of the tension pole 7 is moved by the tension arm 8 and the sprocket IJ ring 20 onto the dot-dashed line with the center of rotation 8a as the center. Move left or right. (This principle has already been described in detail.) Assume that the optical sensor 21 is positioned approximately at the center of the length of the radial wing of the tension pole 7, and that the tape is running at a predetermined magnetic tape speed. The optical sensor output signals of Fig. 6a and Fig. 6c
shall be. Next, magnetic tape 3 on the supply reel disk
If the outer diameter of the winding is large, the tension pole 7 moves to the left on the dashed line as described in the conventional example shown in FIGS. 1 and 2. Therefore, the period during which the radiation-type wings block the light from the optical sensor 21 is shortened, so that an output electrical signal as shown in FIG. 6d can be obtained from the optical sensor 21. That is, the frequency is the 6th
Similar to Figures a and c, these are pulse signals with different duties.
Conversely, the tension pole 7, which has a small winding outer diameter of the magnetic tape 3 on the supply reel disk, moves to the right on a one-point head line and blocks the light for a longer period of time, so a pulse signal as shown in Figure 6e is obtained. It will be done. In the above description, the optical sensor 21 was taken as an example, but it goes without saying that various other sensors such as a magnetic head and a capacitance change detector can be considered.

Further, although the description has been made using a VTR as a representative example of a magnetic tape device, the speed and tension detector of the present invention can be widely used in other devices using paper tape or film as a medium. As is clear from the above description, the detection device of the present invention can easily detect the speed or tension of the medium and easily convert it into an electrical signal, so electrical control can be performed based on this electrical signal. The above-mentioned conventional drawbacks can be completely eliminated.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing the entire tape running system of a conventional VTR device, FIG. 2 is a diagram showing the tape back tension mechanism of FIG. 1, and FIG. 3 is an overall configuration diagram showing an embodiment of the present invention.
4 is a detailed view of the detecting section of FIG. 3, FIG. 5 is a side sectional view of a part of FIG. 4, and FIG. 6 is an operation waveform diagram for explaining the operation of FIG. 3. In the figure, 1 is a rotating drum, 2 is a tape guide, 3 is a magnetic tape, 4 is a guide low-foot, 5 is a full erase head, 6 is a tape guide, 7 is a tape tension pole, and 8
is a tension arm, 9 is an audio erasing head, 10 is an audio and control signal head, TI is a tape guide, 12
13 is a cap stan, 14 is a cassette, 15 is a tape guide, 16 is a tape guide, 17
is a tension band, 18 is a supply reel, 19 is a take-up reel, 20 is a spring, and 21 is a sensor. In the drawings, the same reference numerals indicate the same or corresponding parts. Figure 1 Figure 6 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1. A rotating body having radial wings that rotates when it comes into contact with a traveling medium, and a movable mounting that moves the entire position of the rotating body in a plane direction with respect to the rotation axis by the medium. The device is equipped with a sensor that detects a certain position through which the radial vanes of the rotating body rotate, and brings a traveling medium into contact with a part of the rotating body, and electrically controls at least one of the speed and tension of the rotating medium. A detection device characterized by detecting. 2. The detection device according to claim 1, wherein both the velocity of the medium and the tension of the medium are electrically detected. 3. The detection device according to claim 1, which uses a magnetic tape as the medium.