JPH0572550B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field] The present invention relates to a gas leak alarm device.

[Background Art] A metal oxide semiconductor whose electrical resistance changes by adsorbing a predetermined gas is used as a gas detection element, and this gas detection element is alternately subjected to low-temperature heating and high-temperature heating. It's repeating. This is designed to detect gas during low-temperature heating and release the adsorbed gas during high-temperature heating.

By the way, in order to improve the reliability of gas leak detection, it is necessary to detect a disconnection of the gas detection element or a disconnection of the heating means.

As a means for notifying a receiver of the occurrence of a disconnection when a gas detection element is disconnected, there is a known method that uses a dedicated disconnection signal line to notify the disconnection state. However, this has the disadvantage that a new signal line must be laid.

In order to overcome this drawback, it is conceivable to make the frequency of the disconnection signal different from the frequency of the alarm signal and to send the alarm signal and the disconnection signal through the same signal line.

[Problems with Background Art] In the above case, it is necessary to provide an oscillation circuit of a predetermined frequency as a disconnection signal and a reception determination circuit thereof, which causes a problem that the entire circuit becomes complicated.

[Object of the Invention] The present invention has been made by focusing on the problems of the above-mentioned background art.In a gas leak alarm device, a disconnection signal generated when a gas detection element or its heating means is disconnected is transmitted to a receiver. The purpose of this invention is to provide a gas leak alarm device with a simplified circuit configuration.

[Summary of the Invention] The present invention provides a heating means for heating a gas detection element, a power supply line for supplying current from a receiver to the heating means, and at least one of the heating means and the gas detection element. Disconnection detection means for detecting a disconnection is provided, and when the disconnection detection means detects a disconnection, a disconnection signal sending means is provided for transmitting a disconnection signal to the receiver via the power supply line, and the polarity of the power supply with respect to the power supply line is determined. When the reverse occurs, the receiver receives a disconnection signal.

[Embodiment of the Invention] FIG. 1 is a block diagram showing an embodiment of the present invention.

First, between the receiver R and the gas detector D, there are power lines L1, L2, and a signal line L3, which sends an alarm signal.
L4 is provided.

The receiver R includes a heating control circuit 1 that controls the heating operation of a heater HE that heats the gas detection element GS.
0, a disconnection signal detection circuit 40 that detects a disconnection signal received from the gas detector D, a disconnection display circuit 50 that displays the disconnection state, and switches S1 and S2 for reversing the polarity of the power lines L1 and L2. is provided. The receiver R also includes an alarm signal detection circuit 80 that detects an alarm signal from the gas detector D;
A gas leak alarm circuit 90 is provided.

On the other hand, the gas detector D includes a gas detection element GS,
A heating means disconnection detection circuit 20a that detects a disconnection in a heating means such as a heater HE, and a gas detection element disconnection detection circuit 20 that detects a disconnection in a gas detection element GS.
b, a gas leak detection circuit 60, and an alarm signal sending circuit 70.

The gas detection element GS is made of a metal oxide semiconductor whose electrical resistance changes by adsorbing a predetermined gas.

The heating control circuit 10 alternately heats the heater HE at a low temperature suitable for detecting gas and at a high temperature suitable for releasing the adsorbed gas. The high temperature heating is achieved by turning on the switch 10S, and the low temperature heating is achieved by turning off the switch 10S.

Next, the operation of the embodiment shown in FIG. 1 will be explained.

First, a description will be given of the case where disconnection detection is not performed for the heater HE or the gas detection element GS.
In this case, manually switch both switches S1 and S2 to contact a (switches S1 and S2
). The heating control circuit 10 is operated by the power source E1. The heating control circuit 10 generates a pulse having a predetermined time width, the switch 10S is turned on in synchronization with the generation of this pulse, and the switch 10S is turned off when the pulse is not generated.

When the switch 10S is turned on, the power lines L1 and L
2, the heater HE operates, and the heat causes the gas detection element GS to be activated.
is heated and releases the gas adsorbed there.
On the other hand, when the switch 10S is turned off, the gas detection element GS adsorbs surrounding gas, and the resistance value changes depending on the amount of the adsorbed gas. Based on this change in resistance value, the gas leak detection circuit 6
0 performs gas leak detection.

If a gas leak occurs, the alarm signal sending circuit 70 sends a predetermined alarm signal to the receiver R.
send to Then, in the receiver R, the alarm signal detection circuit 80 detects the alarm signal, and based on this, the gas leak alarm circuit 90 issues an alarm using a buzzer or the like.

In the above case, the wire breakage signal detection circuit 40 does not receive any signal and therefore does not operate, and the wire breakage display circuit 50 also does not display a wire breakage.

Next, a case will be described in which disconnection detection is performed for the heater HE or the gas detection element GS.

In this case, both switches S1 and S2 are manually switched to contact b. As a result, the polarities of the power supply lines L1 and L2 are reversed.

Since both switches S1 and S2 are switched to contact b, current tends to flow in the opposite direction to the heater HE. At this time, the disconnection detection circuit 20a of the heating means detects the disconnection state of the heater HE (a specific example of this is shown in FIG. 2), and the disconnection detection circuit 20b of the gas detection element detects the disconnection state of the heater HE.
Detect disconnection state of GS (this specific example also applies to the second
(shown in the figure).

When the disconnection detection circuit 20a or 20b detects a disconnection, the disconnection signal sending circuit 30 connects the power lines L1 and L.
2, thereby short-circuiting the power supply lines L1 and L2.
This means that a disconnection signal was sent out. In other words,
The disconnection signal sending circuit 30 sends out a disconnection signal to the power supply lines L1 and L2 when an input signal is received, and is a type of gate. As a result, the disconnection signal detection circuit 40 of the receiver R receives the disconnection signal via the power line L1, and the disconnection display circuit 50 lights up a predetermined LED or the like to indicate the disconnection state.

In the above case, the disconnection signal is sent through the power lines L1 and L2 without providing a dedicated signal line for the disconnection signal, so the number of signal lines is small, and the frequency of the signal cannot be changed. Since there is no need for complicated circuitry for modulation, etc., there is an advantage that the overall circuit configuration is simple.

FIG. 2 is a circuit diagram showing the above embodiment in more detail. Note that the same members as those in the embodiment shown in FIG. 1 are given the same reference numerals.

First, the heating control circuit 10 includes an oscillator OSC that generates a pulse with a predetermined period and a predetermined width, a transistor Q1 that is turned on only during the generation period of this pulse, and a transistor Q1 that emits light when the transistor Q1 is turned on.
It has an LED 3 and a heater relay H that operates at this time. Note that the diode D3 is for absorbing unnecessary pulses generated by the relay H, and the resistors R4 and R5 are voltage dividing resistors.

The disconnection signal detection circuit 40 includes a thyristor Q2 that turns on when receiving a disconnection signal via the power line L1 and the switch S1, and a trouble relay T and a switch S3 connected in series with the thyristor Q2. There is. Note that the switch S3 is a recovery switch that is turned off when the thyristor Q2 is turned off after being turned on once. Further, the diode D4 is for absorbing unnecessary pulses generated by the relay T, and the resistor R9 is a resistor for detecting a disconnection signal.

The disconnection display circuit 50 includes a switch S4 that is turned on when the relay T is activated, and a switch S4 that is turned on when the relay T is activated.
4, a resistor R6, and an LED1 connected in series.

The disconnection detection circuit 20a of the heating means is connected to the heater HE.
A diode D11 is connected in series with the resistor R22, and a resistor R22 is connected in parallel with the diode D11.
, a transistor Q10 that is turned on when the heater HE is disconnected, and a photocoupler PC2 that is conductive when the transistor Q10 is turned on. Note that the diode D11 is connected to the resistor R22.
This is to prevent the heater current from decreasing due to Further, the resistor R21 cooperates with the resistor R22 to configure a voltage dividing circuit, and the diode D
12 prevents reverse current from flowing.

The disconnection detection circuit 20b of the gas detection element includes a resistor R2 that divides the voltage at the terminal GS1 of the gas detection element GS.
5, R26, a transistor Q11 that turns off when the gas detection element GS is disconnected, and a transistor Q12 that inverts the phase of the output signal of this transistor Q11. Note that the transistor Q12 is connected in series with a photocoupler PC1, which will be described later, via a resistor R28. Also,
Resistor R27 is a load resistance of transistor Q11.

The disconnection signal sending circuit 30 includes a photocoupler PC1 that is activated when the gas detection element GS or the heater HE is disconnected. This photocoupler PC1, when activated, connects the power lines L1 and L2 via a resistor R20. Note that the diode D10 prevents current from flowing in the opposite direction to the phototransistor that constitutes the photocoupler PC1.

The disconnection detection display circuit 35 is connected to the disconnection detection circuit 20a.
The circuit includes a PUT Q13 that turns on when the photocoupler PC2 of 1 is activated or when the transistor Q12 of the disconnection detection circuit 20b is turned on, and an LED 10 connected in series with the PUT Q13. In addition, resistance R2
9, R30 is voltage dividing resistor, resistor R31 is PUTQ1
This is a resistor that regulates the current flowing through the signal lines L3 and L4 to below the current value of the relay N when the relay N is turned on.

The gas leak detection circuit 60 includes a comparator COM that outputs a Hi signal when the voltage at the terminal GS1 of the gas detection element GS is equal to or higher than the reference voltage.
Note that resistors R32 and R33 are voltage dividing resistors for obtaining a reference voltage.

The alarm signal sending circuit 70 includes a comparator COM
The AND circuit 71 receives the output signal at one input terminal, the photocoupler PC3 becomes non-conductive during low-temperature heating and supplies a Hi signal to the other input terminal of the AND circuit 71, and the AND circuit 71 outputs a Hi signal. The receiver R includes a thyristor Q14 for causing a large amount of current to flow from the power source E2 of the receiver R when this happens, and an LED 11 connected in series with the thyristor Q14. In addition, resistor R34 is a photocoupler PC
3, the diode D13 prevents reverse current from flowing, and the resistor R
24 is a current regulating resistor, and resistors R35, R
36 is a voltage dividing resistor, and R37 is a current regulating resistor.

The alarm signal detection circuit 80 includes an alarm signal receiving relay N that turns on switches S5 and S6 and maintains the state only when a large current flows, a switch S3a that operates in conjunction with switch S3, and a self-contained It also has a recovery switch S7 for releasing the hold. Note that the diode D5 is for pulse absorption, and the resistor R11 is for the switch S5.
This is to generate the voltage necessary to keep the LED 11 of the alarm signal sending circuit 70 of the detector D lit when the relay N is self-held by turning on.

Further, the gas leak alarm circuit 90 includes a switch S6 that is turned on when the relay N of the alarm signal detection circuit 80 is activated, and an LED 2 and a buzzer B that are connected in series with the switch S6. . Note that the resistor R10 is a current regulating resistor.

Next, the operation of the embodiment shown in FIG. 2 will be explained.

First, the heater HE or gas detection element GS
The following describes the case where disconnection detection is not performed. In this case, both switches S1 and S2 are manually switched to contact a. The heating control circuit 10 is operated by the power source E1.

That is, the oscillator OSC generates a pulse having a predetermined time width, the switch 10S is turned on in synchronization with the generation of this pulse, and the switch S1, power line L1, heater HE, diode D11, power line L2, and switch S2 are turned on. A current flows in the loop, and the heater HE generates heat, so the gas detection element GS is heated to a high temperature. When this high-temperature heating is being performed, the LED 3 lights up to indicate that high-temperature heating is being performed. On the other hand, when the pulse is not generated, the heater HE does not generate heat, so the gas detection element GS is heated at a low temperature.

During this low-temperature heating, the gas detection element GS adsorbs gas around it, and its resistance value changes depending on the amount of adsorbed gas. Based on this change in resistance value, the gas leak detection circuit 60 detects gas leak.

If a gas leak occurs, the resistance value of the gas detection element GS will drop, the potential of terminal GS1 will rise, and the high potential of terminal GS1 will be transferred to the converter.
Since it is applied to the non-inverting terminal of COM, the comparator COM outputs a Hi signal. By this,
This means that the gas leak detection circuit 60 has detected a gas leak.

On the other hand, in the above case, since no voltage is applied to the power lines L1 and L2, the photocoupler PC3 does not operate and the AND circuit 71 outputs a Hi signal. Therefore, thyristor Q14 is turned on, and a large current flows through this thyristor Q14. This large current becomes an alarm signal, and this alarm signal is sent to the receiver R. Furthermore, the LED 11 lights up to indicate that the gas detector D has detected a gas leak.

Then, in receiver R, relay N operates to turn on switches S5 and S6. By turning on switch S6 in this way, LED2
lights up and buzzer B sounds, so the receiver R issues a gas leak alarm. In this case, switch S3
It is assumed that the switch a has already been turned on in conjunction with the switch S3, and the switch S7 has also been manually turned on.

To restore the initial state, switch S7
It is sufficient to turn off the switch S7 once, and then turn on the switch S7 in order to detect gas leakage again.

In the above case, the wire breakage signal detection circuit 40 does not receive any signal and therefore does not operate, and the wire breakage display circuit 50 also does not display a wire breakage.

Next, a case will be described in which disconnection detection is performed for the heater HE or the gas detection element GS.

In this case, both switches S1 and S2 are manually switched to contact b.

Since both switches S1 and S2 are switched to contact b, current flows in the heater HE in the opposite direction. At this time, the disconnection detection circuit 20 of the heating means
a detects the disconnection state of the heater HE, and the disconnection detection circuit 20b of the gas detection element detects the disconnection state of the gas detection element.
Detects disconnection of GS.

That is, when the heater HE is disconnected, the potential at the connection point HE1 between the resistor R22 and the diode D12 increases. For this purpose, transistor Q1
0 turns on and photocoupler PC2 operates, so
A photocoupler PC1 provided in series with this is activated. The fact that photocoupler PC1 is activated means that
This means that the disconnection detection circuit 20a has detected the disconnection of the heating means.

On the other hand, if the gas detection element GS is disconnected,
Since the potential of the terminal GS1 decreases, the transistor Q11 is turned off, and the transistor Q12 is turned on, so that the photocoupler PC1 is activated. The fact that the photocoupler PC1 is activated at this time means that the disconnection detection circuit 20b has detected the disconnection of the gas detection element.

In this way, the disconnection detection circuit 20a or 20b
detects a disconnection, the photocoupler is activated as described above.
As PC1 operates, diode D10,
A current flows from the power line L2 to L1 via the resistor R20. This current is a disconnection signal.

As a result, the disconnection signal detection circuit 40 of the receiver R receives the disconnection signal via the switch S1, and the disconnection display circuit 50 lights up a predetermined LED or the like to indicate the disconnection state. That is, since a disconnection signal is sent to the gate of thyristor Q2, thyristor Q2 is turned on, relay T is activated, and switch S4 is turned on.
turns on. As a result, LED1 lights up,
Heater HE or gas detection element in gas detector D
Displays that GS is disconnected.

In addition, in the detector D, when the photocoupler PC2 is activated or the transistor Q12 is turned on, PUT Q13 of the disconnection detection display circuit 35 is turned on and LED1 is turned on.
0 is lit, and a disconnection is also displayed on the detector D side.

In the above case, the disconnection signal is sent through the power lines L1 and L2, so the number of signal lines is small, and there is no need for complicated circuits to change the signal frequency or perform modulation. , the advantage that the overall circuit configuration is simple is the same as in the case of FIG.

Note that at least one of the heating means disconnection detection circuit 20a and the gas detection element disconnection detection circuit 20b may be provided. Also, the heater HE
Other heating means may also be used. Further, a plurality of gas detectors D may be provided, and one receiver R may control these plurality of gas detectors D. In this case, if a disconnection signal of a different frequency is generated for each gas detector D, it is easy to distinguish which gas detector's heater or gas detection element is disconnected.

[Effects of the Invention] According to the present invention, the disconnection of the gas detection element or its heating means is monitored using the power supply line of the heating means. This has the advantage that a dedicated signal line is not required and the overall circuit configuration can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is a circuit diagram showing the above embodiment in more detail. 10... Heating control circuit, 20a... Disconnection detection circuit for heating means, 20b... Disconnection detection circuit for gas detection element, 30... Disconnection signal sending circuit, 40... Disconnection signal detection circuit, 50... Disconnection display circuit , 60...
... Gas leak detection circuit, 70 ... Alarm signal sending circuit, 80 ... Alarm signal detection circuit, 90 ... Gas leak alarm circuit, R ... Receiver, D ... Gas detector,
L1, L2...Power line, HE...Heater, GS...
Gas detection element.

Claims (1)

[Claims] 1. A gas detector comprising a gas detection element made of a metal oxide semiconductor whose electrical resistance changes by adsorbing a predetermined gas, and a heating means for heating the gas detection element. In the gas leak alarm device connected to the receiver, the gas detection element alternately repeats low-temperature heating suitable for detecting the gas and high-temperature heating suitable for releasing the adsorbed gas; A pair of power supply wires are provided for supplying current to the heating means, the gas detector has a disconnection detection means and a disconnection signal sending means, and the receiver detects the polarity of the pair of power supply wires. It has a polarity reversal means for reversing the polarity, and a disconnection signal detection means, and the disconnection detection means detects the current flowing through the heating means and the current flowing through the gas detection element when the polarity reversal of the power supply line is reversed by the polarity reversing means. means for detecting a disconnection in at least one of the heating means and the gas detection element by detecting a change in the current of at least one of them; When the polarity of the power supply line is reversed and the disconnection detection means detects a disconnection, a disconnection signal is generated between the power supply lines, and the disconnection signal is received through the power supply line whose polarity has been reversed. and the polarity reversing means is means for connecting the disconnection signal sending means and the disconnection detection means to the pair of power supply lines when the polarity of the power supply line is reversed. The gas leak alarm device is characterized in that the disconnection signal detection means is connected to the power supply line and detects the disconnection signal when the polarity of the power supply line is reversed by the polarity inversion means. 2. In claim 1, the wire breakage signal sending means generates the wire breakage signal by lowering the impedance between the power supply lines, and sends the wire breakage signal to the receiver. A gas leak alarm device characterized by: 3. The gas leak alarm device according to claim 1, wherein a plurality of the gas detection elements are provided, and the plurality of gas detection elements are controlled by one receiver.