JPH0316699B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tape running monitoring device for a magnetic tape device such as a VTR.

Conventional tape running monitoring device replaced with cassette type VTR
This will be explained using as an example. this species
In a VTR, a supply reel and a take-up reel are installed in a cassette, and the tape pulled out from the cassette is guided by a tape guide shaft or guide roller and mounted on a rotating head cylinder to form the required running path. Ru. By the way, in such VTRs, especially during tape loading, the tape does not align properly with the tape guide axis.
Therefore, the lead surface of the rotary head cylinder may not be properly aligned. If a transition is made to the steady running mode in such a state, an abnormal tension may be generated in the running tape, and the tape may be deformed into a so-called wavy shape. Moreover, not only such wavy deformation but also intermittent abnormal deformation such as wrinkles and creases may occur due to improper equipment operation or tape handling. The tape deformation described above is due to permanent deformation of the tape material, and is a serious problem for tape devices.

However, conventionally it has been very difficult to discover this type of trouble. The reason is,
Since the tape is made of a material with a fairly high breaking strength, it is extremely unlikely that the tape will break due to equipment operation or improper tape handling as described above. Therefore, even if a tape deformation problem occurs, the tape continues to run without falling off the rotating head cylinder or tape guide shaft. For this reason, the rotation detection mechanism, which is one type of conventional tape running monitoring device, has not been able to appropriately detect the above-mentioned tape deformation. Also
In magnetic tape devices such as VTRs, the tape running section is usually located in a hidden location within the main body case. For this reason, it has been difficult to directly visually detect tape deformation problems. Furthermore, even if you try to find a tape deformation problem from changes in the reproduced image or audio in a VTR device, etc., if the degree of deformation is small, it is necessary to determine whether or not the image change is caused by tape deformation. was extremely difficult. In addition, such image-based judgment means cannot be used for monitoring during recording, and this would not be possible without a monitor device. As described above, there has been a problem in that none of the conventional mechanisms or means can adequately monitor the occurrence of tape deformation.

The present invention was made in view of these conventional problems, and it is an object of the present invention to provide a tape running monitoring device that can detect tape deformation troubles at an early stage and minimize tape damage. The purpose is

The present invention will be explained below based on the drawings. 1st
FIG. 2 is a diagram showing an embodiment of the present invention.

First, to explain the configuration, the symbol T in the figure is a tape;
U ₁ is a piezoelectric element detector, and this piezoelectric element detector U ₁
A piezoelectric element 2 is attached to a strip-shaped leaf spring 1.
is provided. The piezoelectric element 2 is made of a piezoelectric material such as piezoelectric ceramic. A sliding contact 3 is attached to the tip of the leaf spring 1, and a fixing member 4 is attached to the rear end.
It is fixed to the main body of the device (not shown) via.
It is preferable that the piezoelectric element detector _U1 is placed near the tape outlet in a mechanical part where the tape T is likely to be deformed.
In the case of a VTR device, it is arranged near the tape outlet of the tape guide shaft or rotating head cylinder. Further, the sliding contact 3 may be arranged in such a manner that it comes into contact with either the front or back surface of the running tape T.

And after such a piezoelectric element detector U ₁ ,
Separate monitoring circuit systems are provided for detecting two main types of abnormal conditions that occur on the tape T. That is, one of them is a monitoring circuit system U _a that detects intermittent deformations such as creases, and the other is a monitoring circuit system U _b that detects wakame-like wavy deformations.

When wakame-like wavy deformation occurs, the output signal obtained from the piezoelectric element detector U ₁ when the tape is running is a one-dimensional vibration change in which the frequency is higher than the output signal obtained when the tape is running normally. It's a signal. On the other hand, in the case of intermittent deformations such as creases that are the object of detection in this invention, the output signal is not a unified frequency change signal as described above, but an amplitude change signal with a large amplitude level. A large-amplitude pulse-like signal is intermittently output. Therefore, in order to appropriately process the output signals from both the above-mentioned transformations, both monitoring circuit systems U _a ,
There is a _Ub attached.

First, the intermittent deformation monitoring circuit system U _a will be explained. This monitoring circuit system U _a determines whether there is an abnormality in the tape T or not based on how many large-amplitude pulse-like signals are output within a predetermined time based on the folds of the tape, etc., and it uses a common amplifier. The output line of the AMP is led to one input terminal of the level comparison circuit _U2 .
U ₃ is a reference voltage generation circuit, MM ₁ is a monostable multivibrator, AND is an AND circuit, and U ₄ is a counter. The monostable multivibrator MM ₁ has a circuit constant set to a predetermined value, and the circuit constant is set to a predetermined value, and the circuit constant is set to a predetermined value. AND circuit AND with its output signal
is opened for a predetermined period of time. In addition, the level comparison circuit
A waveform shaping circuit may be interposed at the next stage of _U2 , and the waveform-shaped signal may be introduced into the monostable multivibrator _MM1 or the like.

Next, the waveform deformation monitoring circuit system U _b will be described.
The output line of the amplifier AMP is branched, and this branch line is equipped with a waveform shaping circuit _U5 , a retriggerable monostable multivibrator _MM2 , a low-pass filter LPF,
and level detector U ₆ are connected in sequence.
Retriggerable monostable multivibrator MM ₂
By defining the circuit constants to predetermined values, the time for returning to a stable state is set to a predetermined time. Here, the predetermined time is a time interval set to be larger by an appropriate amount than the vibration period of the signal output from the piezoelectric element detector _U1 in an abnormal state where wave-like deformation occurs. After transitioning to a metastable state with the initial trigger signal, if the next trigger signal is input within a predetermined time, that is, while in this metastable state, it will be retriggered by this next trigger signal and enter a new metastable state. transition, and a metastable state is maintained. Wave deformation monitoring circuit system
When this metastable state continues for a certain period of time, U _b is
In other words, when the wave-like deformation continues for a certain length or more, it is determined that the tape is abnormal, and the low-pass filter LPF and level detector _U6 are provided for this abnormality determination. Level detector U ₆
has a built-in transistor element, for example, and when the output from the low-pass filter LPF is above a predetermined level, it turns ON and outputs an "H" level.

The output lines of both the monitoring circuit systems U _a and U _b are individually led to an OR circuit OR, and a common output terminal 5 is led out.

Next, the action will be explained.

Intermittent deformation monitoring circuit system with reference to Figures 3 A to C.
Let's start with the operation of U _a . Intermittent abnormal deformation T' such as wrinkles and creases occurs in the tape T, and when this abnormal deformation T' travels through the installation position of the piezoelectric element detector _U1 while slidingly contacting the sliding contact 3, The leaf spring 1 bends following this intermittent abnormal deformation T'. This deflection applies stress to the piezoelectric element 2, and a large-amplitude pulse-like signal corresponding to the abnormal deformation is generated intermittently between both ends of the piezoelectric element 2, and the amplifier AMP generates an irregular vibration signal e as shown in FIG. 3A. ₁ appears. This vibration signal e ₁
is compared with the reference voltage _{e 2 from} the reference voltage generation circuit U 3 in the level comparison circuit U ₂ and a comparison output (abnormal signal) e ₃ is obtained. One side of this comparison output _e3 is directly input to the AND circuit AND, and the other side is input to the monostable multivibrator _MM1 . The monostable multivibrator MM ₁ is triggered by the initial pulse signal at the comparison output e ₃ into a metastable state,
The AND circuit AND is opened by outputting the "H" level for a predetermined period of time defined by the circuit constants. Therefore, counter _U4 has a comparative output only for a predetermined period of time.
e ₃ is entered and this is counted. Then, when the count number within this predetermined time interval is greater than or equal to a predetermined number, a signal corresponding to the tape abnormality is obtained from the counter U ₄ , which appears at the output terminal 5 via the OR circuit OR, and is caused by intermittent deformation such as wrinkles. It is detected that a tape error has occurred. Once a tape abnormality is detected, measures such as stopping equipment operation are taken to prevent further damage to the tape.

Next, the waveform deformation monitoring circuit system U _b will be explained with reference also to FIGS. 4A to 4E. At this time, a vibration signal corresponding to the wave-like deformation is generated from the piezoelectric element detector _U1 . This vibration signal is then passed through the waveform shaping circuit _U5 as shown in Figure 4B.
This is input to the retriggerable monostable multivibrator MM ₂ as a trigger signal. At this time, the monostable multivibrator
Since the time for MM ₂ to return to a stable state is set to be longer than the vibration period of vibration signal e ₄ corresponding to waveform deformation, a shaping signal corresponding to this vibration signal e ₄ is input as a trigger signal. During this period, the multivibrator MM ₂ is in a metastable state and becomes “H”.
The level signal is continuously output. When the "H" level signal _e5 is input to the low pass filter LPF, a predetermined level signal _e6 appears at its output (FIG. 4D) after a predetermined time defined by the time constant of the low pass filter LPF. This predetermined level signal _e6 turns on the transistor in the level detector _U6 , and an "H" level signal _e7 is generated at its output, which appears at the output terminal 5 via the OR circuit OR, causing the tape to be deformed in a waveform. It is detected that an abnormality has occurred.

As described in detail above, according to the present invention, there is provided a piezoelectric element detector that slides in contact with the running tape and outputs a signal with an amplitude level corresponding to the tape deformation, and an output signal from the piezoelectric element detector that is introduced into the piezoelectric element detector to generate a predetermined signal. a level comparison circuit that compares the voltage with a reference level voltage of the tape and outputs an abnormal signal corresponding to abnormal deformation, and a counter that counts the abnormal signal within a predetermined time interval and outputs a tape abnormal signal when the number is equal to or greater than a predetermined number. With this provision, abnormal deformation of the tape can be accurately detected while the tape is running, regardless of whether it is during recording or playback, and tape damage can be minimized.

[Brief explanation of the drawing]

1 to 4 A to 4E show an embodiment of the tape running monitoring device according to the present invention, in which FIG. 1 is a block diagram and FIG. 2 is an enlarged perspective view showing the piezoelectric element detector. , FIGS. 3A to 3C are signal waveform diagrams for explaining the operation of the intermittent deformation monitoring circuit system, and FIG. 4A
-E are signal waveform diagrams for explaining the operation of the waveform deformation monitoring circuit system. 2: piezoelectric element, 3: sliding contact, AND: AND circuit, AMP: amplifier, MM ₁ : monostable multivibrator, T: tape, T': intermittent abnormal deformation,
U _a : Intermittent deformation monitoring circuit system, U _b : Waveform deformation monitoring circuit system, U ₂ : Level comparison circuit, U ₃ : Reference voltage generation circuit, U ₄ : Counter.

Claims (1)

[Claims] 1. A piezoelectric element detector that slides against a running tape to detect deformation of the tape and outputs a signal with an amplitude level corresponding to the deformation, and an output signal of the piezoelectric element detector is introduced. a level comparison circuit that compares the voltage with a predetermined reference level voltage and outputs an abnormal signal corresponding to abnormal deformation; 1. A tape running monitoring device comprising: a counter that outputs a tape abnormality signal when the tape is running.