JPH0316698B2 - - 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. This is due to permanent deformation of the tape material, which 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 large material with low breaking strength, it is extremely unlikely that the tape will break due to abnormal tension as described above. Therefore, even if a breakage 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 wave-like trouble. Also
In magnetic tape devices such as VTRs, the tape running section is usually located in a hidden location inside the main body case. For this reason, it has been difficult to directly visually detect the wavy deformation of the tape. Furthermore, even if you try to find a wavy deformation problem from changes in the reproduced image or audio in a VTR device, etc., if the wavy deformation is small, it is difficult to determine whether or not the image change is caused by the wavy deformation of the tape. It was extremely difficult. Further, such judgment means based on images cannot be directly monitored 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 wave-like 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 the occurrence of wave-like deformation of a tape 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 best to place the piezoelectric element detector _U1 near the tape outlet of a mechanical part where wave-like deformation of the tape is likely to occur; in the case of a VTR device, place it near the tape outlet of the tape guide shaft or rotating head cylinder. be done. 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 ,
Monitoring circuit systems U _a and U _b that can detect mainly two types of abnormal conditions occurring on the tape T are provided. That is, one of them is a monitoring circuit system U _a that detects seaweed-like waveform deformation, and the other one is a monitoring circuit system U _b that detects intermittent deformation such as folds.

When wakame-like wavy deformation occurs, the output signal obtained from the piezoelectric element detector U ₁ when the tape is running has a uniform frequency that is higher than the output signal obtained when the tape is running normally. It is a change signal. On the other hand, the abnormal state of the tape is not only wavy deformation, but also intermittent abnormal deformation such as wrinkles and creases. The output signal when such intermittent deformation such as a crease occurs is not a uniform frequency change signal as described above, but an amplitude change signal with a large amplitude, and is a pulse-like signal with such a large amplitude. is output intermittently. Therefore, in order to appropriately process such intermittent amplitude change signals, the present invention is also separately provided with a monitoring circuit system U _b for detecting intermittent deformation.

First, let's talk about the waveform deformation monitoring circuit system U _a .
A waveform shaping circuit U ₂ is installed after the common amplifier AMP.
Retriggerable monostable multivibrator MM ₁ ,
Low pass filter LPF and level detector U ₃
are connected sequentially. The retriggerable monostable multivibrator MM ₁ has its circuit constant set to a predetermined value, so that the return time 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,
The metastable state continues to be maintained.

This invention determines that the tape is abnormal when this quasi-stable state continues for a certain period of time, in other words, when the wave-like deformation continues for a certain length or _more . prepared for use. level detector
_U3 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.

Next, the intermittent deformation monitoring circuit system U _b will be explained. This monitoring circuit system U _b determines whether the tape is abnormal or not based on how many large-amplitude pulse signals are output within a predetermined time based on tape folds, etc., and the output line of the amplifier AMP is This branch line is led to one input terminal of the level comparison circuit _U4 . U ₅ is a reference voltage generation circuit, MM ₂ is a monostable multivibrator, AND is an AND circuit, U ₆
is a counter, monostable multivibrator MM ₂
The circuit constant is set to a predetermined value, and the output signal opens the AND circuit AND for a predetermined time.

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.

See also Figures 3A to 3E for waveform deformation monitoring circuit system.
I will explain from U _a . As shown by T' in FIG. 2, a seaweed-like wavy deformation part occurs in the tape T, which is an abnormal state, and this wavy deformation part T' causes the piezoelectric element detector U ₁ to slide against the sliding contact 3. When the leaf spring 1 travels in contact with the vehicle, the leaf spring 1 bends following the change in the wave-like deformation portion T'. This deflection applies stress to the piezoelectric element 2, and a vibration signal corresponding to the wave-like deformation portion T' is generated between both ends of the piezoelectric element 2, which is amplified to a required level by the amplifier AMP (FIG. 3A). Next, this vibration signal is shaped by the waveform shaping circuit _U2 as shown in FIG. 3B, and this is input as a trigger signal to the retriggerable monostable multivibrator _MM1 . At this time, the time for the monostable multivibrator MM ₁ to return to a stable state is set to be longer than the vibration period of the vibration signal e ₁ corresponding to the wave-like deformation part _T ', so While the shaping signal is being input as a trigger signal, the multivibrator _MM1 is in a quasi-stable state and continuously outputs an "H" level signal _e2 . When the “H” level signal _e2 is input to the low pass filter LPF, this low pass filter
After a predetermined time defined by the time constant of the LPF, a predetermined level signal _e3 appears at its output (FIG. 3D). This predetermined level signal e ₃ turns the transistor in the level detector U ₃ ON, and its output becomes “H”.
A level signal _e4 is generated, which appears at the output terminal 5 via the OR circuit OR, and it is accurately detected that a tape abnormality due to the waveform deformation T' 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 operation of the intermittent deformation monitoring circuit system _Ub will be explained with reference to FIGS. 4A to 4C. If intermittent abnormal deformation such as wrinkles or creases occurs in the tape T, a large-amplitude pulse-like signal is generated intermittently from the piezoelectric element detector _U1 , and from the amplifier AMP, the signal shown in Fig. 4A is generated. An irregular vibration signal e ₅ appears. This vibration signal
e ₅ is the level comparison circuit U ₄ and the reference voltage generation circuit U ₅
is compared with a reference voltage e ₆ from , and a comparison output e ₇ is obtained. This comparison output e ₇ is one of the AND circuits
Direct input to AND, and the other input to monostable multivibrator MM ₂ . The monostable multivibrator MM ₂ is triggered by the initial pulse signal at the comparison output e ₇ and turns into a quasi-stable state, outputs an "H" level for a predetermined time specified by the circuit constants, and opens the AND circuit AND. . Therefore, the comparison output _e7 is input to the counter _U6 only for a predetermined period of time and is counted. When the number of counts within this predetermined time exceeds a predetermined number, an output is obtained from counter U ₆ , and this is the OR circuit OR
The tape appears at the output terminal 5 through the tape, and it is detected that an abnormality in the tape due to intermittent deformation such as wrinkles has occurred.

As described in detail above, according to the present invention, there is provided a piezoelectric element detector that comes into sliding contact with the running tape and outputs a vibration signal corresponding to the wave-like deformation of the tape, and a piezoelectric element detector that is set at a predetermined time for a return time, and that returns within the predetermined time. A monostable multivibrator that is retriggered by a trigger signal is provided, and a signal related to the vibration signal is introduced into the monostable multivibrator as a trigger signal, and when the time width of the output pulse signal is greater than a predetermined width,
Since tape abnormalities are detected using this signal, it is possible to accurately detect tape abnormalities caused by wave-like deformation while the tape is running, regardless of whether it is during recording or playback, and tape damage can be kept to a minimum. Effects can be obtained.

[Brief explanation of drawings]

1 to 4 A, B, and C show an embodiment of the tape running monitoring device according to the present invention, FIG. 1 is a block diagram, and FIG. 2 is an enlarged view showing the piezoelectric element detector. The perspective view and FIGS. 3A to 3E are signal waveform diagrams for explaining the operation of the waveform deformation monitoring circuit system.
Figures A, B, and C are signal waveform diagrams for explaining the operation of the intermittent deformation monitoring circuit system. 2: piezoelectric element, 3: sliding contact, AMP: amplifier,
LPF: Low pass filter, MM ₁ : Retriggerable monostable multivibrator, T: Tape,
T′: Wave-like deformation part, U _a : Wave-like deformation monitoring circuit system,
U _b : Intermittent deformation monitoring circuit system, U ₁ : Piezoelectric element detector,
U ₂ : Waveform shaping circuit, U ₃ : Level detector.

Claims (1)

[Scope of Claims] 1. A piezoelectric element detector that slides on a running tape to detect wave-like deformation of the running tape and outputs a vibration signal corresponding to the wave-like deformation, and a piezoelectric element detector that returns to a stable state at a predetermined time. set,
A retrigger operation is performed by the trigger signal within this predetermined time,
It is characterized by comprising a monostable multivibrator that introduces a signal related to the output signal of the piezoelectric element detector as a trigger signal and detects a tape abnormality when the time width of the output pulse signal is equal to or larger than a predetermined width. Tape running monitoring device.