JPS6148757B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metal object destruction detection sensor, which includes a piezoelectric element 2 fixed to a metal object 1 to be destroyed so as to detect vibrations of the metal object 1 to be destroyed, and a sensor for detecting the destruction of a metal object 1. A low frequency filter 3 receives the output and passes a signal with a frequency of about 100Hz to 1KHz, a high frequency filter 4 receives the output of the piezoelectric element 2 and passes a signal with a frequency of about 10KHz to 30KHz, and both filters 3 . Related to detection sensor.

Conventionally, there have been metal object destruction detection sensors that use piezoelectric elements to detect vibrations caused by the destruction of safes, lockers, etc. with drills, hammers, saws, etc.; The problem was that even if you hit the device with your foot or hand and vibrated it, it would malfunction.

The present invention was made in view of this drawback, and its purpose is to provide a metal object destruction detection sensor that can detect the actual destruction of a safe, locker, etc. and reduces malfunctions. It is in.

The present invention will be explained below. Figures 1a and 1b show the spectrum of vibrations when a safe or locker, which is a metal object to be destroyed, is subjected to an impact with various objects to generate vibrations. In other words, Figure 1a shows the spectrum when vibrations and shocks are applied with metal tools such as drills, hammers, and hacksaws, and Figure 1b shows the spectrum when vibrations and shocks are applied with hands and feet. Although the frequencies that occur in both are equivalent,
It can be seen that the level ratio of low frequencies and high frequencies is different. By detecting this frequency and level ratio, the present invention is capable of detecting only the impact of destructive objects (drills, hammers, etc.) without causing malfunctions due to impacts from hands, feet, etc. The figure shows an electrical circuit block diagram of the embodiment. As shown in FIG. 3, the piezoelectric element 2 is fixed to the inner wall surface of a metal object 1 to be destroyed, such as a safe or locker, so that vibrations can be detected, and connected to a circuit provided outside via a lead wire l. The detection signal is input to a low frequency filter 3 and a high frequency filter 4.
The low frequency filter 3 corresponds to the low frequencies having the peaks shown in Figures 1a and b, and allows only signals with frequencies between 100Hz and 1KHz to pass, for example, and the high frequency filter 4 corresponds to the low frequencies having the peaks shown in Figures 1a and b. It corresponds to high frequencies with peaks, and allows signals with frequencies of, for example, 10 KHz to 300 KHz to pass through. The outputs of both filters 3 and 4 are input to a signal processing circuit 5. The signal processing circuit 5 is composed of a circuit as shown in FIG. 4, for example, and inputs the signals inputted from both filters 3 and 4 to level detectors 6 and 7, respectively, so that the signal levels correspond to predetermined levels. It detects whether or not the level is above the level, and if each signal is above a predetermined level, the signal is further output to the level comparator 8, and the output from the high frequency filter 4 side is sent to the low frequency filter 3. Furthermore, the outputs of both level detectors 6 and 7 are AND gated by an AND circuit 9, and this gate output is combined with the output signal of the level comparator 8. is AND gated by an AND circuit 10, and the gate output is output as a detection signal. In the figure, 11 is the switching circuit and the fourth
As shown in the figure, it is made up of a transistor Tr, which is turned on when the detection signal is input to drive a notification means 12 consisting of a bell or a lamp.

Therefore, if the metal object 1 to be destroyed is currently in a state where no impact is applied, no output is generated in the level detectors 6 and 7 of the signal processing circuit 5, and as a result, the output of the AND circuit 9 is "L". Therefore, the AND circuit 10 does not output a detection signal, which is a gate output, and the notification means 12 is not driven. Next, if a strong impact is applied to the metal object 1 by a limb or the like, a signal having the spectrum shown in FIG. The signal passes through and is input to the signal processing circuit 5.
In this case, if the input signal of each level detector 6, 7 exceeds a predetermined level, both level detectors 6, 7
The signals are outputted from 7 and sent to a level comparator 8.
The signals are also input to the AND circuit 9, respectively. The two inputs of the AND circuit 9 become "H" and produce a gate output, but in the case of the level comparator 8, as is clear from the spectrum in Figure 1b, the level of the low frequency signal is the level of the high frequency signal. Since it is higher, no output is generated from the level comparator 8, and no detection signal, which is the gate output of the AND circuit 10, is generated. Therefore, the switching circuit 11 also does not operate, and the notification means 12 is not driven.

Furthermore, when the metal object 1 to be destroyed is attempted to be destroyed with a tool such as a hammer, drill, or saw, the piezoelectric element 2
A signal with the spectrum shown in Figure 1a is generated,
This signal is input to level detectors 6 and 7 via a low frequency filter 3 and a high frequency filter 4, respectively. At this time, if the level of the signal input to each is above a predetermined level, the level detectors 6 and 7
A signal is outputted from and input to an AND circuit 9 and a level comparator 8, respectively, and the AND circuit 9 generates a gate output. On the other hand, in the level comparator 8, since the signal spectrum is as shown in FIG. 1a, the level of the high frequency signal is higher than the level of the low frequency signal, so a comparison output is generated.
Therefore, the AND circuit 10 outputs a detection signal as a gate output. Switching circuit 11
is turned on by the detection signal, drives the notification means 12, and gives a warning that the metal object 1 to be destroyed is being destroyed by a tool such as a hammer, drill, or saw.

The present invention includes a piezoelectric element fixed to a metal object to be destroyed so as to detect vibrations of the metal object to be destroyed, and a low frequency filter that inputs the output of this piezoelectric element and passes signals with a frequency of about 100Hz to 1KHz. , has a high frequency filter that inputs the output of the piezoelectric element and passes a signal with a frequency of about 10KHz to 30KHz, so it can detect vibrations generated by the impact applied to the metal object to be destroyed, and also detect vibrations in the vibration spectrum. It is capable of extracting high-level frequency component signals, and outputs an output signal only when the outputs of both filters are above a predetermined level and the output value of the high-frequency filter is greater than the output value of the low-frequency filter. It has a signal processing circuit that can distinguish and detect vibrations when a metal object is being destroyed by a tool such as a drill, hammer, or saw, and impact vibrations caused by limbs, etc. This method has the effect of being able to perform stable detection even if the mounting position of the piezoelectric element or the fracture position is different, compared to a method that detects only when the high-frequency vibration is at a predetermined level or higher.

[Brief explanation of the drawing]

Figures 1a and b are diagrams explaining the principle of the present invention, Figure 2 is an electric circuit block of an embodiment of the present invention, Figure 3 is a layout diagram of a piezoelectric element, and Figure 4 is a detailed diagram of the main parts of the same. In the circuit diagram, 1 is a metal object to be destroyed, 2 is a piezoelectric element, 3 is a low frequency filter, 4 is a high frequency filter, and 5 is a signal processing circuit.

Claims (1)

[Claims] 1 A piezoelectric element fixed to the metal object to be destroyed so as to detect vibrations of the metal object to be destroyed, a low frequency filter that inputs the output of this piezoelectric element and passes signals with a frequency of approximately 100Hz to 1KHz, and the piezoelectric element. A high frequency filter that inputs the output of the filter and passes a signal with a frequency of about 10KHz to 30KHz, and the output of each of the filters is above a predetermined level, and the output value of the high frequency filter is greater than the output value of the low frequency filter. A metal object destruction detection sensor equipped with a signal processing circuit that outputs an output signal only at certain times.