JPH0210450Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas leak detector that outputs a signal voltage depending on the level of gas concentration.

Conventionally, this type of gas leak detector was generally powered by a commercial AC 100V, with 6 volts under normal monitoring conditions, 12 volts when the surrounding gas concentration exceeded the specified value, and the power turned off. It is configured to output a signal voltage of 0 volts in the event of a fault, and by determining the signal voltage from multiple gas leak detectors with a receiver, it can concentrate on eight states: normal, gas leak, and fault occurrence. I am able to monitor it.

By the way, in addition to the gas leak alarm, such a gas leak centralized monitoring device also activates a gas emergency shutoff valve installed in the gas lead-in pipe to the building in conjunction with the gas leak detection. is considered.

However, there is a risk that the gas emergency valve may be closed due to a false alarm from the gas leak detector, and to prevent this, it may be possible to set the gas detection concentration that outputs the gas leak signal to a higher value. However, there was a problem in that increasing the gas leak detection concentration caused a significant detection delay, making it easier to cause accidents due to gas leaks.

The present invention was developed by focusing on these conventional problems, and divides gas leak detection into two stages, low concentration and high concentration, depending on the gas concentration. The purpose of the present invention is to provide a gas leak detector that outputs a signal voltage that can be identified by a gas leak detector, which ensures a gas leak alarm, and which enables operations such as gas emergency shutoff and valve shutoff linked to gas leak detection. do.

The present invention will be explained below based on the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

First, to explain the configuration, in the gas leak detector 10 of the present invention, 12 has a power supply circuit that is supplied with commercial AC 100V or DC 24V from the outside, and 14 has a gas sensor, and a detection signal according to the gas concentration is sent from the sensor. 16 is a switching circuit that outputs an output when the detected concentration of the gas concentration detecting circuit 14 reaches the first detected concentration;
8 is a switching circuit that outputs an output when the detected concentration of the gas concentration detection circuit 14 reaches a second detected concentration that exceeds the first detected concentration; 15 is a switching circuit that performs switching in a transient state when power is applied to the power supply circuit 12; an initial reset circuit that outputs a signal that prohibits the operation of the circuits 16 and 18 for a certain period of time; 2;
0 is the output signal from switching circuits 16 and 18
e ₁ , e ₂ , and also output signal voltages corresponding to each of the normal conditions when the power supply circuit 16 and 18 are not outputting power and the power supply voltage is applied from the power supply circuit 12. 22 is an alarm circuit that sounds a buzzer or the like based on the output of the switching circuit 18; 24 is an alarm circuit that sounds a buzzer, etc.;
This is a display circuit equipped with display means that lights up according to the outputs of switching circuits 16 and 18.

FIG. 2 is a circuit diagram showing a specific embodiment of the signal output circuit 20 in the embodiment of FIG. 1.

The signal output circuit 20 has a logic circuit consisting of a NOR gate 26, an inverter 28, and an AND gate 30, and includes switching circuits 16 and 18 (see FIG. 1).
The outputs e ₁ and e ₂ of are input to the NOR gate 26, and the AND gate 30 receives the output signal e ₁ from the switching circuit 16 and the output signal e ₂ from the switching circuit 18.
An oscillation circuit 32 outputting a signal inverted by an inverter 28 and a clock pulse of a predetermined frequency.
The output of is added. The output of the NOR gate 26 is connected to the base of the transistor Tr ₁ through a resistor R ₁ , and on the collector side of the transistor Tr ₁ is connected to the base of the transistor Tr ₃ through a Zener diode ZD with a Zener voltage Vz = 6 volts. ing.

On the other hand, the output of the AND gate 30 is a transistor
It is connected to the base of transistor Tr ₂ connected in series with Tr ₃ , and the power supply voltage +12 volts is connected to the transistor.
It is taken out from the output end via Tr ₂ , Tr ₃ and diode D ₁ .

Next, referring to the signal waveform diagram in Figure 3,
The operation of the gas leak detector of the present invention shown in the figure will be explained.

First, under normal conditions when the output of the gas concentration detection circuit 14 is 0 volts, the switching circuits 16,
18 output signals e ₁ and e ₂ are both 0 volts,
Each of the signals e ₁ and e ₂ to the signal output circuit shown in FIG. 2 is at L level. For this reason, Noah Gate 26
The input becomes (L, L) to produce an H level output, turning on the transistor Tr ₁ via the resistor R ₁ . When the transistor Tr ₁ is turned on, the Zener diode ZD connected to the base of the transistor Tr ₃ is turned on, and the voltage determined by the Zener voltage Vz of this Zener diode ZD = 6 volts is output via the transistor Tr ₃ and the diode D ₁ . Become so. At this time, the AND gate ₃₀
Forbidden by level, and gate 30
The output of transistor Tr2 becomes L level, and the base current flows from the base of transistor _Tr2 .
Tr ₂ is in the on state, and the operation of the transistor Tr ₃ makes it possible to send out an output voltage of 6 volts (first signal voltage).

Next, when the surrounding gas concentration reaches the first detection concentration set in the switching circuit 16, the switching circuit 16 outputs an output signal _e1 which becomes H level. Therefore, the inputs of the NOR gate 26 shown in FIG. 2 become (H, L), and the NOR gate 26
The output of transistor Tr 6 becomes L level, transistor Tr ₁ is turned off, and Zener diode ZD becomes non-conductive.

On the other hand, in response to the input of the AND gate 30, the output signal _e2 of the switching circuit 18 is output to the inverter 28.
Since the output signal _e1 of the switching circuit 16 is also at the H level, the AND gate 30 is in the allowable state, and the oscillation pulse from the oscillation circuit 32 is passed through the AND gate 30. Applied to the base of transistor Tr ₂ . Therefore, the transistor Tr ₂ is turned on and off in response to the oscillation pulse of the oscillation circuit, and as shown in Figure 3b, a rectangular pulse signal of a predetermined frequency varying between the power supply voltage +12 volts and 0 volts is transmitted by the resistor R ₂ . Transistor Tr ₃ biased and in the on state
and will be output via _D1 .

Furthermore, the surrounding gas concentration increases, and the detected concentration from the gas concentration detection circuit 14 changes to the switching circuit 18.
If it exceeds the second detection concentration set to
The switching circuit 18 outputs, and the output signal e ₂ is also high.
level. The output of this switching circuit 18 is fed to an alarm circuit 22 to sound a buzzer or the like to notify gas leakage, and is also fed to a display circuit 24 to indicate that the detected gas concentration has reached a specified high concentration. do. Furthermore, since each of the signals e ₁ and e ₂ to the signal output circuit 20 becomes H level, the output signal e ₂ is inverted by the inverter 28 and becomes L level in the signal output circuit shown in FIG. is prohibited, and the output of the AND gate 30 becomes L level. At this time, the output of the NOR gate 26 is also at L level, and the transistor Tr ₁ is in an off state. Therefore, the oscillation circuit 3
The output pulse of 2 is inhibited by AND gate 30,
The transistor Tr ₂ is turned on by the L level output of the AND gate 30, and the transistor Tr ₃ is turned on by the bias of the resistor R ₂ , so that the power supply voltage of 12 volts (second signal voltage) is output as is through the diode D ₁ . Become.

Furthermore, the power supply circuit 12 is malfunctioning or the power supply circuit 12
In the event of a power outage in which the commercial AC 100V or DC 24V applied to the gas leak detector is cut off, the application of the power supply voltage +12V to the signal output circuit 20 is cut off, so the output voltage of the signal output circuit becomes 0 volts, and the gas leak detector 10 will notify you that a failure has occurred.

In this way, the gas leak detector of the present invention uses a rectangular pulse that has a peak value of 6 volts during normal operation, 12 volts when the gas leak detection concentration reaches the first stage, and a rectangular pulse that has a peak value of 12 volts when the gas leak detection concentration reaches the second stage. Since the signal voltage is sent out to be 12 volts when the voltage reaches 12 volts, and 0 volts when there is a fault, for example, a gas leak alarm is displayed in the first stage of gas leak detection (square pulse signal), and then in the second stage. When a gas leak detection signal (12 volts) is output, it is determined that a gas leak has definitely occurred, and the gas emergency valve, etc., is closed in conjunction with the second stage gas leak. can do.

In the above embodiment, a rectangular pulse signal having a peak value of 12 volts is sent when the gas leak detection concentration reaches the first stage, and a signal voltage of 12 volts is sent when the gas leak detection concentration reaches the second stage. However, when the gas leak detection concentration reaches the first stage, it is 12 volts, and when it reaches the second stage, it is 12 volts.
Of course, a signal voltage that is a rectangular pulse signal having a peak value of volts may be transmitted.

In addition, the gas leak detector of the present invention can output four types of states: normal, gas leak first stage, gas leak second stage, and fault by signal voltages on a pair of signal lines, and the receiver detects gas leaks. It also has the advantage that signal line connections can be simplified when centrally monitoring the detector.

FIG. 4 is a block diagram showing an embodiment of a gas leak central monitoring system using a plurality of gas leak detectors according to the present invention and centrally monitoring the gas leak with a central receiver.

First, to explain the configuration, a plurality of gas leak detectors 10a, 10b, . . . of the present invention shown in FIGS. 1 and 2 are provided, and each gas leak detector 10a, 10
A pair of signal lines 38 are drawn out from each of the repeaters 34a, 34b, . . . and connected to each of the repeaters 34a, 34b, . It is connected to a receiver 36 installed in a room or the like.

FIG. 5 shows a repeater 34 used in the embodiment of FIG.
This shows an example in which a 4-wire connection is made to the receiver 36 through a power line 44, a common line 44', a calling line 46, and a response line 48, and a signal from a gas leak detector is connected to the receiver 36. is input to the transistor Tr ₄ via a series circuit of a resistor R ₄ and a diode D ₁ , and a resistor R ₃ connected in parallel to the series circuit. A capacitor C _{1 is connected to the base side of the transistor Tr 4 ,} and the resistor R ₄ , diode D ₁ and capacitor C ₁ form an integrating circuit. The emitter of the transistor Tr ₄ connected to the resistor R ₅ is connected to a response line 48 via an analog switch 40, and the analog switch 40 is switched on by a frequency discrimination circuit 42 which receives and outputs a frequency signal from a calling line 46. It is configured as follows. As the frequency identification circuit 42, for example, a PLL etc. is used,
When a frequency signal pre-assigned to each repeater is received, an identification output is generated and the analog switch 40 is turned on.

Next, the operation will be explained with reference to the embodiments shown in FIGS. 4 and 5.

The receiver 36 uses the calling line 46 to transmit frequencies f ₁ , f ₂ , ..., f ₃₀ that are pre-assigned to each repeater as shown in the time chart of FIG.
So-called boring is carried out in which frequency signals of If a two-stage gas leak detector is output, these gas leak detectors 10a, 1
Each repeater 34a, 34b,... according to the output of 0b...
In response to the call of the frequency signals f ₁ , f ₂ , . . . _for each of 48 and a predetermined signal voltage V ₂ from the relay 34b of the gas leak detector 10b which outputs the first stage gas leak detection output, that is, the oscillation pulse signal, and further a second stage gas signal (not shown). A predetermined voltage _V3 is now output from the repeater 34c receiving the leakage detection output.

The response line output voltages from these repeaters 34a, 34b, .
a is normal, the gas leak detector 10b is in the first stage gas leak detection state, and the gas leak detector 10c is in the second stage gas leak detection state,
For example, in conjunction with the reception and detection of the gas leak detection output in the second stage, an activation signal for a gas emergency, valve shutoff, etc. is output.

Here, for the first stage of gas leak detection, the first,
Since the embodiment of the present invention shown in FIG. 2 outputs a rectangular pulse, if this rectangular pulse signal is input to the repeater 34 shown in _FIG . Diode D ₁
and is smoothed by an integrating circuit consisting of capacitor _C1 ,
Normal output 6 volts and second stage gas leak detection output
It is converted to a predetermined voltage _V2 between 12 volts.

Due to the smooth output of rectangular pulses in the repeater 34, the normal output of 6 volts, the first stage gas leak detection output (rectangular pulse) and the second stage gas leak detection output can be achieved without the need for a special voltage conversion circuit etc. Three types of input signals of 12 volts output and four types of input signals of 0 volts for failure output when the power is cut off are converted into different signal voltages by a simple circuit configuration and sent via analog switch 40 in response to a call from the receiver. It can be made to output.

In this way, in the gas leak centralized monitoring device using the gas leak detector of the present invention, the detection status of multiple gas leak detectors can be monitored by connecting the receiver and the terminal with four signal lines. can be centrally monitored.

In addition, in the above embodiment, the case where the gas detection concentration was detected in two stages was taken as an example.
The present invention is not limited to this, but it is also possible to set multiple levels of gas leakage concentrations in advance and output different signal voltages V ₁ , V ₂ , V _{3 .} . . Vn according to each detected concentration. The gas leak state can be detected with high precision, and the receiver side can more reliably grasp the gas leak state.

In addition, the gas leak central monitoring device shown in Figure 4 is
Since the equipment has the same configuration as the conventionally used one-stage gas leak detector, the conventional gas leak detector is replaced with the gas leak detector of the present invention and the interrupter shown in Fig. 5. This makes it possible to realize a gas leak centralized monitoring system that performs gas leak detection in two stages even for existing equipment.

As explained above, according to the present invention, gas leak detection is divided into two stages, low concentration and high concentration, depending on the gas concentration, and a signal that can be identified on the receiver side according to the detection stage is By outputting voltage, we are able to reliably issue a gas leak alarm, so even if a gas leak is detected due to a false alarm, the receiver can easily see what kind of detection state it is in. When the second stage gas leak detection output is received, it can be determined that a gas leak has definitely occurred, so a gas emergency valve, etc. is activated in conjunction with the second stage gas leak detection. This makes it possible to further improve the reliability and safety of the gas leakage centralized monitoring device.

Further, one of the two-stage gas leak alarm is a voltage signal, and the other is a signal obtained by pulsing the voltage signal,
The pulsed signal can be easily converted into a signal voltage between the first signal voltage and the second signal voltage by passing it through an integrating circuit, so it can be converted into a signal voltage in four states including the normal and power-off signals. can be output through a pair of signal lines, simplifying the repeater circuit and signal line connection when centrally monitoring the gas leak detector using the receiver.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a circuit diagram showing an embodiment of the signal output circuit in the embodiment of Fig. 1, and Fig. 3 is an embodiment of the invention shown in Fig. 1. Fig. 4 is a block diagram of a gas leak centralized monitoring device using the gas leak detector of the present invention, and Fig. 5 shows an embodiment of a repeater used in the device shown in Fig. 4. Circuit block diagram, No. 6
This figure is a time chart showing signal transmission in the apparatus of FIG. 4. 10, 10a, 10b...Gas leak detector, 1
2...Power supply circuit, 14...Gas concentration detection circuit, 1
6, 18...Switching circuit, 20...Signal output circuit, 22...Alarm circuit, 24...Display circuit,
26... Noah gate, 28... Inverter, 30
...And gate, 32...Oscillation circuit, 34,3
4a, 34b...Repeater, 38...Transmission line,
36...Receiver, 40...Analog switch, 4
2... Frequency identification circuit, 44... Power line, 44'
...common line, 46...calling line, 48...response line.

Claims (1)

[Scope of Claim for Utility Model Registration] A gas concentration detection circuit that is activated by power applied from a power supply circuit to detect ambient gas concentration, and an output when the detected concentration of the gas concentration detection circuit exceeds a predetermined value. a first switching circuit that outputs an output when the detected concentration exceeds another predetermined value that exceeds the predetermined value; and a second switching circuit that outputs an output when the detected concentration exceeds the predetermined value. A first signal voltage is output when the switching circuit is not outputting, and a second signal voltage different from the first signal voltage or a second signal voltage of the oscillation circuit is output when only the first switching circuit is outputting. A signal obtained by pulsing the second signal voltage is outputted, and when both the first and second switching circuits are outputting, the second signal voltage is output when only the first switching circuit is outputting. If it is outputting, the pulsed signal is outputted, and if the pulsed signal is outputted when only the first switching means is outputting, the second signal voltage is outputted, and further, the power supply circuit outputs the second signal voltage. a signal output circuit that outputs a zero voltage different from each of the signal voltages when the power is no longer applied by the gas leak detector.