JPH0640360B2 - Gas response device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a gas response device that can be maintained with extremely small electric power.

[Conventional technology]

Gas alarm devices that are currently in practical use need to keep the gas detection element at a predetermined high temperature (for example, 300 ° C. or higher in the case of methane and propane) due to problems such as gas detection sensitivity and gas response characteristics. High power consumption. For this reason, a household gas alarm requires an AC cord, and an industrial detection alarm requires a power cable for the detection section.
There are many inconveniences in installation and handling.

In order to improve this, measures such as reducing the power consumption other than the gas detecting element, intermittently using the gas detecting element, and increasing the power efficiency by a pulse power source are taken.

[Problems to be solved by the invention]

In these conventional examples, even though the power consumption is reduced, it does not become so small that the purpose can be achieved for the intended time, and in intermittent use, the gas response characteristic of the gas detection element causes the intermittent power consumption. It is necessary to increase the frequency, and therefore, there is a problem in that when the battery is driven, it is limited to be maintained for about one year.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a gas responsive device that enables the realization of a cordless alarm and that does not require troublesome power supply wiring or expensive cave construction. .

[Means for solving problems]

This invention, when the gas sensing element is used at a temperature lower than a predetermined high temperature (hereinafter referred to as high temperature) (hereinafter referred to as low temperature),
Focusing on the fact that it has gas detection sensitivity while also deteriorating characteristics such as gas response characteristics and gas detection sensitivity, it was heated to a low temperature at all times, and a low concentration gas (hereinafter referred to as trigger gas) was monitored and detected. Only at this time, the gas is heated to a high temperature to monitor and detect a gas having a higher concentration (hereinafter referred to as a target gas), which is the original detection purpose.

1st invention concerning this invention WHEREIN: The trigger gas detection circuit which has the low temperature gas detection element which detects a trigger gas at low temperature, and the high temperature gas which is normally kept at ambient temperature (henceforth normal temperature) and is heated to high temperature at the time of trigger gas detection. It is composed of a target gas detection circuit having a detection element, and a heating means which operates by the output of the trigger gas detection circuit and heats the high temperature gas detection element.

A second aspect of the present invention allows the same gas detecting element to perform the roles of the low temperature gas detecting element and the high temperature gas detecting element.

[Action]

1st and 2nd invention concerning this invention WHEREIN: Only when the low temperature gas detection element of a trigger gas detection circuit detects a trigger gas, a target gas detection circuit is operated and a high temperature gas detection element is heated and a target gas is detected. Since it is in a monitoring state that can
Normally, it operates with enough power to operate only the trigger gas detection circuit that consumes extremely little power.

〔Example〕

FIG. 1 shows an embodiment of the first invention according to the present invention. In this figure, e ₁ is a low-temperature gas detection element, and here a semiconductor gas detection element whose resistance value decreases when gas is detected is used, and it is normally heated by only the current flowing between the electrodes eh-e ₀ Kept in.

As will be described later, when the low temperature gas detection element e ₁ detects a gas at a low temperature, it has a poor gas emission characteristic. Therefore, the low temperature gas detection element e ₁ is periodically heated to a high temperature during this period to release the adsorbed gas (hereinafter referred to as purge) before use. ing. Needless to say, this function is not necessary when a detection element whose emission characteristic does not matter is used as a low temperature gas detection element. R ₁ is a load resistance of the low temperature gas detection element. e ₂ is a high temperature gas detecting element, which is not supplied with electric power at all times and is inoperative at room temperature, and is heated and activated only when detection of the target gas is necessary. e
Reference numeral ₃ denotes a compensating element for the high temperature gas detecting element e ₂ , which also serves as a load resistance. Here, the high temperature gas detection element e ₂ uses the catalytic combustion type gas detection element that requires the compensation element e ₃ . Q _{1, Q 1} is a _transistor, IC 1, IC ₂ are comparative amplifier, the non-inverting input of the comparison amplifier IC ₁ 'is connected to the load resistor _{R 1,} the input is the output voltage _{V 1} of the cold gas sensing element _{e 1} The inverting input is connected to the resistors R ₂ and R ₃ , and the comparison voltage V ₂ is input. The non-inverting input of the comparison amplifier IC ₂ is connected to the compensating element e ₃ , the output voltage V ₄ of the high temperature gas detecting element is input, and the inverting input is the variable resistor VR.
And the comparison voltage V ₅ is input. R _{2 to} R ₇ are resistors, VR is a variable resistor, C ₀ is a capacitor, LED
Is a light emitting diode, E is a power supply, and TM is a timer circuit, which constantly outputs a high level voltage and outputs V _{3 of the} comparison amplifier IC _1.
Becomes high level and is activated, and a one-shot low level voltage is output to the capacitor C ₀ at regular intervals. Further, DD is a diode, P ₁ is a node indicating the output terminal of the comparison amplifier IC ₂ , and P ₂ is a node indicating the ground potential point.

And A is a trigger gas detection circuit, e ₁ , R ₁ ~
It is composed of R ₃ , IC _{1, and the} like. B is a target gas detection circuit, which is composed of e ₂ , e ₃ , R ₅ , R ₆ , VR, IC _{2, and the} like. C is a heating means, which is composed of Q ₂ , R _{4 and the} like. D
Is an alarm display circuit composed of LEDs, R _7, etc., and F is a purge circuit composed of C _O , Q ₁ , eh, etc.

Next, the operation will be described.

When the power supply E is turned on, a charging current flows through the capacitor C ₀ through the light emitting diode LED and the resistor R ₇ to turn on the light emitting diode LED and the transistor Q ₁
The Toranajisuta Q ₁ flows into the base turned on to heat the same element current flows into the electrode and the heater eh cold gas sensing element e ₁ to a high temperature. As a result, the low temperature gas detection element e
₁ is purged. When the capacitor C ₀ is charged, the charging current disappears, the transistor Q ₁ is turned off, the purge is completed, and the light emitting diode LED is turned off. The low-temperature gas detection element e ₁ is no longer heated by the heater current, and is heated only by the current between the electrodes eh-e ₀ to have a low temperature.

Then, when the trigger gas is not detected, the resistance value of the low temperature gas detection element e ₁ is high, the voltage V ₁ is lower than the comparison voltage V ₂ , and the output V ₃ of the comparison amplifier IC ₁ is at a low level. During this time, the base current of the transistor Q ₂ is cut off, Q ₂ remains off, the high temperature gas detection element e ₂ is not supplied with power, is kept at room temperature, and is inoperative.

When the low temperature gas detection element e ₁ detects the trigger gas, the resistance value of the low temperature gas detection element e ₁ decreases, the output voltage V ₁ increases, and when the comparison voltage V ₂ is exceeded, the output V ₃ of the comparison amplifier IC ₁ becomes high. It becomes a level. That is, the trigger gas detection circuit A outputs an output to the heating means C. At this time, the timer circuit TM is activated. The transistor Q ₂ is a resistor R ₄
Then, the base current flows through the device and turns on, power is supplied from the power source E to the target gas detection circuit B through the transistor Q ₂ , and the high temperature gas detection element e ₂ and the compensating element e ₃ are heated to a high temperature and brought into an operating state. At this time, when there is no target gas, the comparison voltage V ₅ is the output V of the high temperature gas detection element e ₂ .
_Since it is lower than _{4 and} is initially set by the invariable resistor VR, the output V ₀ of the comparison amplifier IC ₂ is at a high level.

When the high temperature gas detecting element e ₂ detects the target gas, the output voltage V ₄ decreases and becomes lower than the comparison voltage V ₅ , the output V ₀ of the comparison amplifier IC ₂ becomes low level, that is, the node P ₁ changes to the node P _{1. 2} becomes the same ground potential (specifically, a ground terminal (not shown) of the comparison amplifier IC ₂ and the node P
Since ₁ and are connected), the electric charge charged in the capacitor _{C 0,} the light emitting diode DD from node _P 1, _{P 2}
To discharge. On the other hand, the voltage of the power source E is applied to both ends of the series circuit of the light emitting diode LED and the resistor R ₇ to light the light emitting diode LED and display an alarm. If the target gas disappears, the output voltage V ₄ becomes higher than the comparison voltage V ₅ ,
The output V ₀ of the comparison amplifier IC ₂ returns to the high level, and the light emitting diode LED is turned off. The capacitor C ₀ starts charging, and a charging current flows through the base of the transistor Q ₁ to turn it on, and a heater current is supplied to the low temperature gas detection element e ₁ to heat it to a high temperature and purge it. As a result, the adsorbed gas of the low temperature gas detection element e ₁ having a slow gas response characteristic is released. Upon completion of charging the capacitor C _0, the transistor Q
₁ is turned off, and the low temperature gas detection element e ₁ is no longer heated by the heater current and returns to the low temperature state. There is no target gas,
While the output of the comparison amplifier IC ₁ is high level, the timer circuit T
Since a one-shot low-level voltage is output from M at regular time intervals, that is, the node P ₁ changes to the node P _{2 at} constant time intervals.
Since it becomes the same ground potential as the above, the state becomes exactly the same as when the low level voltage is output from the comparator IC ₂ described above, and the low temperature gas detection element e ₁ is purged along with the discharge of the capacitor C _{0 in} this cycle. That is, the same element is provided with a constant gas release characteristic, and the trigger gas detection and target gas detection circuit B is performed.
To operate effectively.

If the trigger gas is exhausted, the output V of the low temperature gas detection element e _1
1 becomes smaller than the comparison voltage V _2, the output V ₃ of the comparison amplifier IC ₁ is low level, the transistor Q ₂ is off,
The target gas detection circuit B is again deactivated and only the trigger gas detection circuit A continues to monitor the trigger gas.

In this way, only when the low temperature gas detection element e ₁ detects gas and the trigger gas detection circuit A outputs, the heating means C is operated to heat the high temperature gas detection element e ₂ and the target gas detection circuit. While B is in an operable state and there is no target gas and the trigger gas is being detected, the low temperature gas detection element e ₁ is regularly purged to more effectively detect the trigger gas.

FIG. 2 shows an embodiment of the second invention according to the present invention. Using one of the gas detecting elements e, the low temperature detecting element e ₁ and the high temperature gas detecting element e of the embodiment of FIG. 1 are used. _It is also used as ₂ . That is, the gas detection element e has the same structure and composition as the low temperature detection element e 1 of FIG. ₁ , but as described later, heating is divided into high and low heating.

A hot-wire type semiconductor gas detection element having a characteristic that its resistance value becomes small when gas is detected is used. The circuit configuration is different from that of the embodiment shown in FIG. 1, but the names of the respective parts are the same.

To explain its operation, the light emitting diode LED power supply E is turned on, the resistor through R _7, a charging current flows into the capacitor C _0, along with lighting the light emitting diodes LED, a transistor Q ₂ flows into the base of the transistor Q ₂ Is turned on, the base current of the transistor Q ₁ is cut off and turned off, the heater current does not flow, the heater is heated only by the current between the electrodes eh-e ₀ of the gas detection element e, and the low temperature gas detection element (detection element depending on the state below is used. It uses as the name).

Output V of low temperature gas detection element when trigger gas is not detected
_{Since 1} is lower than the comparison voltage V _{2 and} set by the resistors R ₃ and R ₄ , the output V ₃ of the comparison amplifier IC ₁ is at a low level, and after the charging of the capacitor C ₀ is completed, the light emitting diode LED is turned off. However, since the base current of the transistor Q ₁ is cut off even when the transistor Q ₂ is turned off,
This state is retained.

When the low temperature gas detection element e detects the trigger gas, its resistance value becomes low, and when the output voltage V ₁ exceeds the comparison voltage V ₂ , the output V ₃ of the comparison amplifier IC ₁ becomes a high level voltage and the transistor Q ₁ is turned on, and the electrode Also, an electric current is passed through the heater eh to heat the low temperature gas detection element e to a high temperature. As a result, the element operates as a hot gas detecting element. Further, the timer circuit TM is activated.

Since the temperature rises and the resistance value of the high temperature gas detecting element e becomes lower than that when operating at a low temperature, the output voltage V ₁ further rises and the transistor Q ₁ maintains the ON state, whereby the high temperature gas detecting element e The operating state is maintained.

When there is no target gas, the output V ₄ of the high temperature gas detection element e is lower than the comparison voltage V ₅ and is set by the variable resistor VR, so the output of the comparison amplifier IC ₂ is at a high level,
The LED is off.

When the target gas is detected, the resistance value between a and b of the electrode / heater eh decreases, and when the output voltage V ₄ exceeds the comparison voltage V ₅ , the output of the comparison amplifier IC ₂ becomes low level. That is, since the node P ₁ has the same ground potential as the node P ₂ (specifically, the ground terminal (not shown) of the comparison amplifier IC ₂ and the node P ₁ are connected), the capacitor C ₀ is charged. The electric charge that is generated is from the nodes P ₁ and P ₂ to the diode D.
It discharges via D. On the other hand, the voltage of the power supply E is applied to both ends of the series circuit of the light emitting diode LED and the resistor R ₇ , and the light emitting diode LED is turned on to display an alarm.

The target gas is exhausted, and the output of the comparison amplifier IC ₂ is "high".
After returning to level, the flow transistor Q ₂ turns on the charging current of the capacitor C ₀ is the base of the transistor Q _2, the transistor Q ₁ is longer flows current becomes the electrode and the heater eh off, the hot gas sensing element e is cold gas The process moves to the detection element e. When the target gas is not detected, the one-shot low-level voltage is output from the timer circuit TM at regular intervals while the output of the comparison amplifier IC ₁ is at a high level. Therefore, the capacitor C ₀ is discharged and charged in this cycle. The transistor Q ₁ is turned off at the same time as the transistor Q ₂ is turned on and off, that is, the heater current of the high temperature gas detection element e is cut off to operate as a low temperature gas detection element. At this time, if the trigger gas is not detected, the comparison amplifier IC ₁
Output V ₃ becomes low level, and the transistor Q ₁ is kept off and the heater current continues to be cut off.
Return to the operating state as.

The trigger gas in the above is not only a low concentration of the target gas, but of course, it can be used including various gases and water vapor. Further, the gas detection elements e ₁ , e ₂ , e, etc. may be not only the gas detection elements described above but also other types of gas detection elements.

〔The invention's effect〕

As described in detail above, the first and second inventions according to the present invention are provided with the trigger gas detection circuit and the target gas detection circuit, and normally, only the trigger gas detection circuit that consumes less power is activated and the trigger gas is removed. Since the target gas detection circuit that consumes a large amount of power is operated only when it is detected, it is possible to significantly reduce the wasted power consumed when there is no gas, as in the conventional case.

Further, the target gas detection circuit responds frequently by the trigger gas detection in the presence of the gas atmosphere, and does not operate in the absence of the gas atmosphere, which is a very rational operation as a gas response device.

And since the time for the high temperature gas detection element to reach a high temperature is much shorter than before, it is possible to reduce fatigue.
The life can be dramatically extended.

Further, the battery life as a power source can be extended to 5 years or more.

Further, in the second invention, the gas emission characteristic of the low temperature gas detecting element at the time of detecting the trigger gas does not pose a problem, and since one gas detecting element is used, the consumption at the time of detecting the target gas and the time of detecting the trigger gas is reduced. It has a great advantage in that the electric power is small, the life when the battery is used as a power source can be further extended, and the electric circuit is simplified.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing an embodiment of the second invention of the present invention. In the figure, e is a gas detection element, e ₁ is a low temperature gas detection element, e
₂ is a high temperature gas detection element, e ₃ is a compensation element, Q ₁ and Q ₂ are transistors, IC ₁ and IC ₂ are comparison amplifiers, and R _{1 to} R
₁₁ is a resistor, VR is a variable resistor, C ₀ is a capacitor,
LED is a light emitting diode, E is a power supply, A is a trigger gas detection circuit, B is a target gas detection circuit, and C is a heating means.

Claims (2)

[Claims] 1. A trigger gas detection circuit having a low temperature gas detection element for detecting gas at a low temperature, which outputs an output signal when the low temperature gas detection element detects a low concentration gas, and is always in an inoperative state, A target gas detection circuit that emits a gas detection output signal when the high temperature gas detection element detects a gas and has a high temperature gas detection element that is heated when the output signal of the trigger gas detection circuit is emitted; And a heating unit that is electrically coupled to the trigger gas detection circuit and the target gas detection circuit and that heats a high temperature gas detection element of the target gas detection circuit when an output signal of the trigger gas detection circuit is emitted. Characterized gas response device. 2. A gas detection element for performing gas detection, a trigger gas detection circuit for holding the gas detection element at a low temperature to perform gas detection as a low temperature gas detection element, and issuing an output signal when a low concentration gas is detected, When an output signal of the trigger gas detection circuit is issued, a heating means for heating the gas detection element and a normally inactive state, and when the output signal of the trigger gas detection circuit is issued, the heating means A gas response device comprising: a heated gas detection element as a high temperature gas detection element to detect gas, and a target gas detection circuit that outputs a gas detection output signal when gas is detected.