JP5148551B2 - Gas detection device, combustion equipment equipped with this gas detection device, and gas alarm - Google Patents

Description

  The present invention is provided inside a housing, and includes a gas detection unit whose electric resistance value changes in response to a detection target gas, a heating unit that heats the gas detection unit, a high temperature operation state and a low temperature The operation of the heating unit is controlled so as to alternately and repeatedly switch to the operating state or only in the high temperature operating state, and combustible as a detection target gas based on the first electric resistance value of the gas detecting unit in the high temperature operating state The present invention relates to a gas detection device including a control unit for detecting a sexual gas, a combustion device including the gas detection device, and a gas alarm.

The gas detection device is configured to control the operation of the heating unit so that the gas detection unit is alternately and repeatedly switched between a high temperature operation state and a low temperature operation state, or only in a high temperature operation state. And detects incomplete combustion gas in the low-temperature operating state if necessary, and detects incomplete combustion based on this detection information. (For example, refer to Patent Document 1).
And in the gas detection apparatus of patent document 1, it is possible to eliminate the influence of hydrogen gas etc. as miscellaneous gas (non-detection target gas) and to improve the detection accuracy of methane gas as combustible gas. The configuration is adopted.
Specifically, the electric resistance value of the gas detection unit immediately before the end of the high temperature operation state is set to an electric resistance value A (described as the first electric resistance value in Patent Document 1), and the high temperature operation state is stabilized from the low temperature operation state. The electrical resistance value in the intermediate state is detected as an electrical resistance value B (described as the second electrical resistance value in Patent Document 1), and the increase / decrease direction of the electrical resistance value A and the increase / decrease direction of the electrical resistance value B or the electrical resistance value Whether a coordinate point determined by the electrical resistance value A and the comparison value or the electrical resistance value B exists in a predetermined region in the two-dimensional orthogonal coordinate space defined by the increase / decrease direction of the comparison value of A and the electrical resistance value B Based on whether or not, the influence of the non-detection target gas is excluded and the presence of methane gas is determined.

JP 2007-271440 A

  The gas detection device as described above is provided, for example, in a combustion device such as a gas fan heater used in the home or a device such as a gas alarm. It is used to detect the generation of incomplete combustion gas due to combustion.

Here, a siloxane compound is included for some reason, for example, by a dew condensation prevention spray, a silicon spray, a hair spray, or the like, in the vicinity where such a combustion device such as a gas fan heater or a device such as a gas alarm is installed. When the substance is sprayed, the siloxane compound is prevented from adhering to or coming into contact with the gas detection unit in the casing of the gas detection device mounted on the combustion device or the gas alarm device. Adsorbed to the filter. Here, the siloxane compound is an organic polymer having a siloxane bond of “Si—O—Si” in the skeleton, such as (CH ₃ ) ₈ (SiO) ₄ or (CH ₃ ) ₁₀ (SiO) _5. There is.
In such a situation, when heating of the gas detection unit by the heating unit is started in the gas detection device, the gas detection unit repeats a high temperature operation state and a low temperature operation state, or enters a high temperature operation state. Then, it is heated to a high temperature necessary for detecting the combustible gas (for example, about 400 ° C. when the combustible gas is methane gas). As a result, the temperature of the gas detection part to which the siloxane compound is attached becomes high, and the siloxane compound is decomposed and deposited on the surface of the gas detection part (for example, a sintered body of a metal oxide semiconductor). In some cases, an object is covered, or an insulating film of SiO ₂ is formed on the surface of the gas detection unit. If there is a siloxane compound adsorbed on the filter, it is desorbed by the heating and adheres to the gas detection unit, and the surface of the gas detection unit covers the surface of the gas detection unit with the siloxane compound or a decomposition product thereof as described above. Alternatively, an insulating film of SiO ₂ may be formed on the surface of the gas detection unit.

Thus, the presence of a siloxane compound or a decomposition product thereof, and an insulating film of SiO _{2 on} the surface of the gas detection unit changes the electrical characteristics of the detected gas detection unit. For example, FIG. As shown in FIG. 9, the electrical resistance value as an electrical characteristic of the gas detection unit in the air is lowered (so-called sensitization) in the high temperature operation state, while it is not in the low temperature operation state as shown in FIG. 9. When the complete combustion gas is detected, the electric resistance value of the gas detection unit increases (so-called blunting) (hereinafter referred to as siloxane poisoning).
Therefore, when flammable gas is detected in a high temperature operating state, it may be determined that flammable gas is present even though flammable gas is not present or is present only at a low concentration. When the complete combustion gas is detected, it may be determined that the incomplete combustion gas does not exist even though the incomplete combustion gas exists at a high concentration. In other words, the presence of flammable gas or incomplete combustion gas that actually exists cannot be accurately detected, and further, an alarm may be issued based on the erroneous detection result.
Such a state where the gas detection unit is poisoned with siloxane is in a normal state even when the gas detection unit is repeatedly heated between a high temperature operation state and a low temperature operation state or exposed to clean air. Therefore, it can be said that the gas detection unit or the gas detection device is out of order, and it is desirable to replace these gas detection devices at an early stage.
Therefore, the gas detector accurately determines that siloxane poisoning has occurred, accurately detects the presence of flammable gas and incomplete combustion gas, and detects and alarms for flammable gas and incomplete combustion gas. It is necessary to be able to determine the failure state of the gas detection device.

  The present invention has been made in view of such circumstances, and an object of the present invention is to detect whether a gas detection unit is in a siloxane poisoning state by a siloxane compound and to detect the presence of a detection target gas having a predetermined concentration. Another object of the present invention is to provide a gas detection device capable of accurately performing an alarm and recognizing a sensor failure due to siloxane poisoning at an early stage, a combustion device equipped with the gas detection device, and a gas alarm.

In order to achieve the above object, a gas detection device according to the present invention is provided inside a casing and has a gas detection unit that changes its electric resistance in response to a detection target gas, and heats the gas detection unit. The gas in the high temperature operation state is controlled while the heating unit and the gas detection unit are alternately and repeatedly switched between a high temperature operation state and a low temperature operation state, or only in a high temperature operation state. And a control unit that detects a combustible gas as the detection target gas based on the first electric resistance value of the detection unit, the characteristic configuration of which is
The siloxane compound present in the atmosphere of the gas detection unit may poison the gas detection unit when the temperature of the gas detection unit heated by the operation control of the heating unit by the control unit is in the high temperature operation state. It is determined that the surface of the gas detection unit is poisoned by the siloxane compound when a reduced state in which the first electrical resistance value detected by the control unit decreases for a predetermined period at a certain temperature. It is in the point provided with the judgment part.

According to this characteristic configuration, the control unit may poison the gas detection unit with the temperature of the gas detection unit heated by the heating unit in a high temperature operating state, and the siloxane compound present in the atmosphere of the gas detection unit. It is configured to be able to be heated to a temperature, and when the determination unit continues the lowering state in which the first electric resistance value detected by the control unit decreases for a predetermined period, the surface of the gas detection unit is covered with a siloxane compound or a decomposition product thereof. Since the gas detection unit is poisoned by a siloxane compound such as a cover or a SiO ₂ insulating film is formed on the surface of the gas detection unit, 1 The electric resistance value is reduced (so-called sensitization), and it can be recognized that there is a possibility that the detection and alarm of the flammable gas may be made erroneously. It can be determined that it is a failure.
That is, for example, as shown in FIG. 6, in the case where heating is started by the heating unit and it is in a high temperature operating state, when gas or methane gas as a flammable gas with a predetermined concentration exists in the air, the gas detection unit The first electric resistance value shows a behavior that stabilizes at a predetermined electric resistance value as the number of days elapses, although the electric resistance value initially decreases (normal state). On the other hand, as shown in FIG. 7, in the siloxane-poisoned state, the first electric resistance value when air is present is sequentially increased with the passage of days despite the absence of methane gas as a combustible gas. Even after the cyclic siloxane (an example of a siloxane compound) is eliminated from the atmosphere and exposed to clean air, the first electric resistance value remains lowered. In addition, even when methane gas having a predetermined concentration is present, when the siloxane poisoning is performed, the first electric resistance value of the gas detection unit is relatively greatly reduced and is not stabilized, and cyclic siloxane is generated from the atmosphere. After being removed and exposed to clean air, it will finally stabilize. The predetermined period is a relatively long period. For example, a period of at least about 10 days to several tens of days is assumed.
Therefore, according to this feature configuration, for example, by detecting a decrease state of the first electric resistance value in a predetermined period as shown in FIG. 7, it is determined whether or not the gas detection unit is poisoned with siloxane. Whether or not a sensor failure has occurred can be determined. In addition, if it is determined that it is not siloxane poisoning, the presence of flammable gas can be accurately detected, so that it is flammable when it is in a siloxane poisoning state (the gas detector may be sensitive). It is possible to prevent the gas from being detected, and it is detected or alarmed that the flammable gas of a predetermined concentration is present even though the flammable gas is not present or is present only at a low concentration. It is possible to prevent going.
Therefore, it is possible to determine whether or not the gas detection unit is in a siloxane poisoning state by the siloxane compound, and to accurately detect and alarm the presence of the detection target gas having a predetermined concentration. A gas detection device capable of recognizing a sensor failure at an early stage can be provided.

  In the gas detector according to the present invention, in the determination of the poisoning state by the siloxane compound, the determination unit detects the first electric resistance value detected with respect to the initial value of the first electric resistance value in a normal state. Based on the ratio of the electrical resistance values, when the state where the ratio is lower than the predetermined determination ratio continues for a predetermined period, the surface of the gas detection unit is determined to be poisoned by the siloxane compound. is there.

According to this characteristic configuration, in determining the poisoning state by the siloxane compound, the determination unit determines the ratio based on the ratio of the detected first electric resistance value to the initial value of the first electric resistance value in the normal state. When the state in which the gas flow rate is lower than the predetermined determination ratio continues for a predetermined period, it is determined that the surface of the gas detection unit is poisoned by the siloxane compound. With reference to the initial value of the first electrical resistance value at the base, it is possible to more easily recognize the detected decrease in the first electrical resistance value and more easily determine whether the gas detection unit is in a siloxane poisoning state or not. can do.
Therefore, it is possible to more easily and reliably determine whether or not the gas detection unit is poisoned with siloxane, and to easily and reliably recognize a sensor failure.

  A further characteristic configuration of the gas detection device according to the present invention is that the predetermined determination ratio of the detected first electric resistance value with respect to the initial value is 0.5.

  According to this characteristic configuration, it is possible to more reliably and early recognize whether or not the reduced state in which the first electric resistance value of the gas detection unit is reduced is more reliable and early and to recognize whether or not siloxane poisoning has occurred. it can. For example, as shown in FIG. 10, the change in the first electric resistance value in the normal state at the high temperature operating state is that the ratio of the first electric resistance value to the initial value of the first electric resistance value is about 0.9. However (when about 100 days have elapsed), the siloxane poisoning state decreases to about 0.2 (when about 100 days have elapsed). In such a state of being lowered to about 0.2, the combustible gas cannot be accurately detected. Therefore, the combustible gas can be detected to some extent before the ratio is reduced to about 0.2. Adopting a possible ratio (for example, about 0.5, which is the ratio when about 35 days have passed) as a predetermined judgment ratio, siloxane poisoning earlier and more reliably before the detection capability of combustible gas decreases It can be determined whether or not. In addition, when the gas detection unit can detect incomplete combustion gas, a predetermined determination ratio that can determine whether or not the siloxane poisoning state is maintained while maintaining the detection capability of incomplete combustion gas. Can be set.

  A further characteristic configuration of the gas detection device according to the present invention is that when determining the poisoning state by the siloxane compound, the first electric resistance value gives an alarm when a predetermined concentration of flammable gas is generated. When the state where the electric resistance value is lower than the predetermined electric resistance value set to a multiple of the flammable gas alarm point is continued for a predetermined period, the determination unit is configured such that the surface of the gas detection unit is the siloxane compound. It is in the point of judging that it is poisoning state by.

According to this characteristic configuration, in determining the poisoning state by the siloxane compound, the first electric resistance value is an electric resistance value for issuing an alarm when a predetermined concentration of the combustible gas is generated. The determination unit determines that the surface of the gas detection unit is poisoned by the siloxane compound when the state of lowering the predetermined electrical resistance value set to a multiple of the alarm point continues for a predetermined period. By appropriately setting the gas alarm point and its multiple, it is possible to more easily recognize the detected decrease in the first electric resistance value based on this multiple, and the gas detector can be more easily poisoned with siloxane. It can be determined whether or not it is in a state. The flammable gas alarm point is an electric resistance value corresponding to the detection voltage detected by the gas detection unit when a predetermined concentration of flammable gas is present, and when an alarm is issued as a result of fuel leakage. It is set as a standard for For example, when the flammable gas alarm point is set to an electric resistance value (about 1.1 kΩ) when methane gas as a flammable gas of 3000 ppm is present, the electric resistance value is increased from about 2 to 6 times. It can be set (3 times in FIG. 7).
Therefore, it is possible to more easily and reliably determine whether or not the gas detection unit is poisoned with siloxane, and to easily and reliably recognize a sensor failure.

  According to a further characteristic configuration of the gas detection device according to the present invention, the determination unit corrects the first electric resistance value corresponding to an ambient temperature condition, and corrects the first electric resistance value instead of the first electric resistance value. The determination is made using the first electric resistance value.

  According to this characteristic configuration, the first electric resistance value is corrected in accordance with the temperature condition around the gas detection unit, and it is determined whether or not the siloxane poisoning state is based on the corrected first electric resistance value. Therefore, even if the temperature conditions in the atmosphere of the gas detection unit may fluctuate and the first electric resistance value may fluctuate, it is possible to accurately determine whether or not the siloxane poisoning state is achieved with the effect of this fluctuation reduced. Can be determined.

  The gas detector according to the present invention is further characterized in that the control unit detects incomplete combustion gas as the detection target gas based on a second electric resistance value of the gas detection unit in the low temperature operation state. In the configuration, the determination unit determines that the surface of the gas detection unit is poisoned by the siloxane compound when the second electric resistance value exceeds a predetermined electric resistance value. .

According to this characteristic configuration, the control unit detects the incomplete combustion gas as the detection target gas based on the second electric resistance value of the gas detection unit in the low temperature operating state, and the first electric resistance value In addition to the determination, the determination unit determines that the surface of the gas detection unit is poisoned by the siloxane compound when the second electric resistance value exceeds a predetermined electric resistance value. The surface of the gas detection unit is covered with a siloxane compound or a decomposition product thereof, or the SiO ₂ film is formed on the surface of the gas detection unit, and the second electric resistance value of the gas detection unit is increased (so-called blunting). It is possible to more reliably recognize that the detection and alarm of incomplete combustion gas may be erroneously performed, and it is possible to more reliably determine sensor failure due to siloxane poisoning.
That is, for example, as shown in FIG. 8, when heating by the heating unit is stopped and in a low temperature operation state, when air or carbon monoxide gas as a partial concentration of incomplete combustion gas exists in the air, The second electric resistance value of the gas detection section shows a behavior that stabilizes at a predetermined electric resistance value as the number of days elapses although the electric resistance value decreases in the initial stage (normal state). On the other hand, as shown in FIG. 9, in the siloxane-poisoned state, the second electrical resistance value when air is present is stabilized at a predetermined value even if the number of days elapses as in the normal state. In an environment where a predetermined concentration of carbon monoxide gas is present, the second electrical resistance value of the gas detector increases with the passage of days (so-called blunting), and after removing cyclic siloxane from the atmosphere and exposing it to clean air However, it stabilizes with the increased electrical resistance value.
Therefore, according to this characteristic configuration, the second electric resistance value exhibiting the above behavior is detected by detecting that the second electric resistance value exceeds a predetermined electric resistance value, so that the gas detection unit can It is possible to more accurately and reliably determine whether or not the vehicle is poisoned, and to determine whether or not the sensor is malfunctioning more accurately and reliably.

  In the gas detector according to the present invention, the predetermined electrical resistance value gives an alarm when incomplete combustion gas having a predetermined concentration is generated in determining the poisoning state by the siloxane compound. When the incomplete combustion gas alarm point, which is an electrical resistance value for, is set to a multiple of the alarm point, and the second electrical resistance value has increased to an electrical resistance value that exceeds the multiple, It exists in the point determined to be a poisoning state by a siloxane compound.

  According to this characteristic configuration, in determining the poisoning state by the siloxane compound, the predetermined electric resistance value is an electric resistance value for issuing an alarm when an incomplete combustion gas having a predetermined concentration is generated. Since it is set to a multiple of the combustion gas alarm point, the second electric resistance value is increased by appropriately setting a criterion for determining whether or not the second electric resistance value of the gas detector is increased. Can be recognized more easily, and whether or not the siloxane is in a poisoned state can be more easily recognized. The incomplete combustion gas alarm point is an electric resistance value corresponding to the detection voltage detected by the gas detection unit when incomplete combustion gas of a predetermined concentration exists, and it is alarmed that incomplete combustion has occurred. It is set as a reference when issuing. For example, when the incomplete combustion gas alarm point is set to an electric resistance value (about 14.9 kΩ) when carbon monoxide gas as incomplete combustion gas of 150 ppm is present, the electric resistance value is five times the electric resistance value. To 30 times (20 times in FIG. 11).

  According to a further characteristic configuration of the gas detection device according to the present invention, the determination unit determines a decrease state in which the detected first electric resistance value decreases, and the detected second electric resistance value is the predetermined value. When the first electrical resistance value is in a lowered state and the second electrical resistance value exceeds the predetermined electrical resistance value in a configuration for determining whether or not the electrical resistance value is exceeded When the failure count becomes a predetermined count by repeating these determinations, the reduced state in which the first electric resistance value decreases and the second electric resistance value exceeds the predetermined electric resistance value. It is in the point determined to be a poisoned state by the siloxane compound as a state in which the siloxane compound continues for a predetermined period.

According to this characteristic configuration, the determination unit uses the first electric resistance value and the second electric resistance value detected at each detection timing, and the first electric resistance value is in a lowered state and the second electric resistance value is detected. When the resistance value exceeds the predetermined electric resistance value, the failure count is updated by one, and when these determinations are repeated and the failure count reaches the predetermined count, the first electric resistance value decreases and the second electric resistance decreases. Assuming that the state where the value exceeds the predetermined electric resistance value continues for a predetermined period, the gas detection unit determines that the poisoning state is caused by the siloxane compound.
Thereby, at each detection timing, it is possible to determine the poisoning state by the siloxane compound using both the detected first electric resistance value and the second electric resistance value, and to improve the determination accuracy. It can be recognized accurately. In particular, the determination of whether or not the first electric resistance value decreases and the second electric resistance value exceeds a predetermined electric resistance value is repeated, and the siloxane poisoning is not determined until the condition that satisfies the condition reaches a plurality of times. Therefore, based on a plurality of determination results (determination results until the failure count reaches a predetermined count corresponding to the lapse of a predetermined period), the poisoning state by the siloxane compound can be determined more accurately. For example, it is possible to satisfactorily eliminate the influence of a transient gas such as cooking gas generated by cooking (a gas existing in units of several minutes or tens of minutes, which is a relatively short time).

In order to achieve the above object, the characteristic configuration of the combustion equipment including the gas detection device according to the present invention is as follows:
Combustion equipment comprising any one of the above-described gas detection devices,
Air outside the casing is supplied as combustion air to the combustion section through an intake port provided in a casing in which the combustion section for burning the combustible gas is housed, and the combustion gas in the combustion section is supplied. An air blowing part is provided to ventilate so as to blow out of the casing from the blowout opening provided in the casing,
The gas detector is provided at or near the intake port so as to be sensitive to combustible gas or incomplete combustion gas in the combustion air supplied through the intake port. .

  According to this characteristic configuration, the combustion device includes the gas detection device including the gas detection unit sensitive to the inflammable gas and the incomplete combustion gas, and whether or not the gas detection device is in a siloxane poisoning state by the siloxane compound. Therefore, it is possible to reliably recognize a sensor failure due to siloxane poisoning, replace the gas detection unit and the gas detection device at an early stage, and ensure safe operation of the combustion equipment. .

In order to achieve the above object, the characteristic configuration of the gas alarm device including the gas detection device according to the present invention is as follows:
A gas alarm device comprising any one of the above-described gas detection devices,
The said gas detection part is provided in the said alarm device main body so that it may respond to the combustible gas in the air supplied through the gas inflow port provided in the alarm device main body, and incomplete combustion gas. is there.

  According to this characteristic configuration, the gas alarm device includes the gas detection device including the gas detection unit sensitive to the inflammable gas and the incomplete combustion gas, and whether or not the gas detection device is in a siloxane poisoning state by the siloxane compound. Therefore, it is possible to reliably recognize the sensor failure due to siloxane poisoning, replace the gas detector and gas detector at an early stage, and ensure safe operation of the gas alarm Can do.

The block diagram of the combustion equipment provided with the gas detection apparatus which concerns on this invention The figure which shows the principal part of the gas detection apparatus which concerns on this invention FIG. 2 is a partially cutaway external view of a gas detection device according to the present invention. The figure which shows the equivalent circuit of the gas detection part which concerns on this invention 1 is a vertical right side view showing a schematic configuration of a combustion apparatus provided with a gas detection device according to the present invention. The graph which shows the relationship between the elapsed days in the normal state in a high temperature operation state, and 1st electrical resistance value The graph which shows the relationship between the elapsed days in a siloxane poisoning state in a high temperature operation state, and a 1st electrical resistance value The graph which shows the relationship between the elapsed days in a normal state in a low-temperature operation state, and a 2nd electrical resistance value The graph which shows the relationship between the elapsed days in a siloxane poisoning state in a low-temperature operation state, and a 2nd electrical resistance value The graph which shows the 1st criteria in a high temperature operation state The graph which shows the 2nd criteria in a low-temperature operation state The figure which shows the temperature correction table in the high temperature operating state The figure which shows the temperature correction table in the low temperature operation state The flowchart which concerns on 1st Embodiment in the case of performing determination operation | movement using the gas detection apparatus which concerns on this invention The flowchart which concerns on 2nd Embodiment in the case of performing determination operation | movement using the gas detection apparatus which concerns on this invention

[First Embodiment]
Hereinafter, an embodiment in which the gas detection device according to the present invention is applied to a gas fan heater as a combustion device (an example of a device including the gas detection device) will be described.
As shown in FIG. 1, the gas detection device A is electrically sensitive to a combustible gas (a methane gas that is a gas fuel in this embodiment) that is a detection target gas in a high-temperature operation state where the temperature is equal to or higher than the high-temperature sensitive temperature. The electrical resistance value changes in response to the incomplete combustion gas (carbon monoxide gas in this embodiment) that is the detection target gas in a low temperature operating state where the temperature is lower than the high temperature side sensitive temperature. A gas detection unit 1 whose value changes, a heater 2 that heats the gas detection unit 1 (an example of a heating unit), and a heater 2 that repeatedly switches the gas detection unit 1 between a high temperature operation state and a low temperature operation state. Sensor control unit 16 (an example of a control unit) that detects combustible gas in a high temperature operation state and detects incomplete combustion gas in a low temperature operation state based on the electric resistance value of the gas detection unit 1 ) Etc. It has been made.

As shown also in FIG. 2, in addition to the gas detection part 1 and the heater 2, the gas sensor S is comprised including the electrode 3 for a detection.
The heater 2 and the detection electrode 3 are embedded in the gas detection unit 1. In this embodiment, a coil-shaped heater combined electrode 4 and a center electrode 5 penetrating the center of the heater combined electrode 4 are embedded in the gas detection unit 1, and the heater combined electrode 4 and the center electrode 5 are detected. The heater electrode 4 is configured to function as the heater 3 and the heater electrode 4 is configured to function as the heater 2. Incidentally, the heater combined electrode 4 and the center electrode 5 are composed of noble metal wires such as platinum alloy wires.

The high-temperature sensitive temperature at which the gas detector 1 is in a high-temperature operating state is selected as a flammable gas compared to a change in electrical resistance when adsorbing flammable gas compared to an electric resistance when adsorbing incomplete combustion gas. The temperature at which the gas detector 1 is in a low-temperature operating state is such that the change in the electrical resistance value during incomplete combustion gas adsorption is the change in the electrical resistance value during flammable gas adsorption. Compared to the above, the temperature becomes so high that the incomplete combustion gas can be selectively detected.
Specific examples of the high temperature side sensitive temperature at which the gas detector 1 is in a high temperature operating state and the temperature at which the gas detector 1 is in a low temperature operating state are the gas detection accuracy required for combustion equipment, fuel leakage and incomplete combustion. It is set as appropriate according to the gas concentration or the like for executing a safe operation against the above. For example, the high temperature side sensitive temperature is about 300 to 400 ° C. when detecting methane gas, and the temperature at which the low temperature operation state is detected is about 80 to 100 ° C. when detecting carbon monoxide gas.

The gas detector 1 is formed of a sintered body of a metal oxide semiconductor such as tin oxide (SnO ₂ ). The gas detection unit 1 is formed in a shape such as a flat plate shape or a spherical shape (including an elliptical sphere). In this embodiment, the major axis direction has a diameter of about 0.5 mm and the minor axis direction has a diameter of about 0.3 mm. It is formed in an oval shape.
The metal oxide semiconductor carries a catalyst for reducing sensitivity to other gases other than combustible gas and incomplete combustion gas. Examples of the catalyst include Pd, W, Pt, Rh, Ce, Mo, and V. 1 type or 2 types or more of these catalysts are used.
In this embodiment, Pd is used as the catalyst. When Pd is used as the catalyst in this way, the time until the electric resistance changed by the gas adsorption is stabilized after the gas detection unit 1 adsorbs the gas is shortened. As a result, the responsiveness of the gas detector 1 is improved.

  As shown in FIGS. 2 and 3, the gas sensor S supports the gas detection unit 1 in a state where it is connected to three terminals 7a, 7b, 7c penetrating the front and back of the generally disk-shaped base 6, and the base 6 is provided with a substantially cylindrical inner case 8 having both ends opened in a state in which the gas detection unit 1 is accommodated therein, and a substantially cylindrical housing having a gas inlet 9 as an opening on one end side. 10 (an example of a housing) is provided on the back side of the base 6 so as to cover the inner case 8.

As shown in FIG. 2, both ends of the heater electrode 4 are separately connected to two heater terminals 7a, 7b of the three terminals 7a, 7b, 7c, and the remaining one detection terminal. One end of the center electrode 5 is connected to 7c.
As shown in FIG. 3, the housing 10 is longer than the inner case 8, and the housing 10 is provided with an opening on the side opposite to the gas introduction port 9 fitted to the base 6. .
A metal mesh 11 such as stainless steel is stretched at the gas inlet 9 of the housing 10, and a filter 12 is provided between the upper portion of the inner case 8 and the metal mesh 11 in the housing 10 for adsorbing and removing miscellaneous gases. ing.
The filter 12 is formed of, for example, activated carbon, silica gel, or a material that combines these activated carbon and silica gel.
Further, the filter 12 absorbs and removes miscellaneous gas (for example, gas of organic solvent such as alcohol, silicon vapor containing siloxane compound, NOx) contained in the gas flowing into the inner case 8 from the gas inlet 9. It has become.

  FIG. 4 shows an equivalent circuit of the gas sensor S, Rh shows the electric resistance value of the heater combined electrode 4, and Rs shows the electric resistance of the gas detection unit 1 between the center electrode 5 and one end of the heater combined electrode 4. Indicates the value. When the combustible gas is adsorbed on the gas detection unit 1 in the high temperature operation state, or the incomplete combustion gas is adsorbed on the gas detection unit 1 in the low temperature operation state, the electric resistance Rs of the gas detection unit 1 changes. It will be.

  As shown in FIG. 1, in addition to the gas sensor S and the sensor control unit 16, the gas detection apparatus A includes a constant voltage circuit 13 that steps down and rectifies and smoothes a commercial AC power supply to obtain a DC voltage Vc, and a heater for the gas sensor S. The switching element 14 for controlling the pulse width of the voltage applied to the dual-purpose electrode 4, the load resistor 15 for dividing the output voltage of the constant voltage circuit 13 with the gas detector 1, and the like are provided.

The constant voltage circuit 13 supplies driving power to the heater 2 and the sensor control unit 16.
The positive side of the constant voltage circuit 13 is connected to the collector of the switching element 14, and one end of the heater serving electrode 4 is connected to the emitter of the switching element 14 via the heater terminal 7 a. The end is connected to the negative side of the constant voltage circuit 13 via the heater terminal 7b.
One end of the load resistor 15 is connected to the center electrode 5 of the gas sensor S via the detection terminal 7c, and the other end is connected to the + side of the constant voltage circuit 13.
Further, a resistor 17 and a thermistor 18 that detects the ambient temperature of the gas detector 1 are connected in series between the + side and the − side of the constant voltage circuit 13.

The sensor control unit 16 is configured to control the pulse width of switching of the switching element 14 and to detect fuel leakage and incomplete combustion based on the resistance change of the gas detection unit 1, and the sensor control unit 16 The drive circuit 19, the A / D conversion circuit 20, the signal processing circuit 21, the temperature signal conversion circuit 22, the output circuit 23, the memory 24, the determination unit 26, and the like are provided.
The drive circuit 19 is connected to the base of the switching element 14 via the resistor 25 and controls the switching of the switching element 14 with a pulse width.
The A / D conversion circuit 20 is connected to the center electrode 5 of the gas sensor S via the detection terminal 7c, and the voltage across the heater electrode 4 and the center electrode 5 of the gas detector 1 (hereinafter referred to as the detection voltage). A) may be A / D converted and output to the signal processing circuit 21. That is, the detection voltage (electrical characteristic) corresponds to the detection information of the combustible gas and the detection information of the incomplete combustion gas.
The temperature signal conversion circuit 22 generates a temperature signal corresponding to the ambient temperature by A / D converting the partial pressure applied to the resistor 17 and outputs the temperature signal to the signal processing circuit 21.

The signal processing circuit 21 uses the detection voltage (first electric resistance value R1, second electric resistance value R2) of the gas detection unit 1 output from the A / D conversion circuit 20 as the temperature output from the temperature signal conversion circuit 22. The fuel is corrected based on the correction coefficient K stored in the memory 24 corresponding to the signal, and based on the corrected detection voltages (corrected first electric resistance value R1 ′ and second electric resistance value R2 ′). Identify leaks and incomplete combustion. Specifically, for example, a temperature correction table as shown in FIGS. 12 and 13 is stored in the memory 24, and the correction coefficient in the high temperature operation state corresponding to the temperature signal output from the temperature signal conversion circuit 22 is stored. Using K1 and the correction coefficient K2 in the low temperature operation state, the first electric resistance value R1 is corrected by the equation (1) to obtain the corrected first electric resistance value R1 ′. Similarly, the second electric resistance value R2 is corrected by the equation (2) to obtain a corrected second electric resistance value R2 ′. The correction coefficients K1 and K2 are determined as shown in FIGS. 12 and 13, for example, based on the deviation from the temperature with the electric resistance value at 20 ° C. as a reference (for example, 1).
R1 ′ = R1 / K1 (1) R2 ′ = R2 / K2 (2) When the signal processing circuit 21 determines that the fuel leak is detected, the output circuit 23 outputs a fuel leak detection signal to be described later. When the incomplete combustion is determined by the signal processing circuit 21, an incomplete combustion detection signal is output to the main control unit 42. The output circuit 23 outputs a sensor failure signal to the main control unit 42 when the determination unit 26 determines that the gas detection unit 1 is siloxane poisoning described later.
The memory 24 includes a temperature correction table including correction coefficients K1 and K2 for correcting the detection voltage (first electric resistance value R1 and second electric resistance value R2) according to the ambient temperature, a flammable gas having a predetermined concentration, When incomplete combustion gas exists, the electrical resistance values (flammable gas alarm point Rma, incomplete combustion gas alarm point Rca) corresponding to the respective detection voltages detected by the gas detection unit 1 and a determination unit 26 described later. In FIG. 4, various determination criteria for determining whether or not the electric resistance value of the gas detection unit 1 has changed due to the influence of the insulating film or the like due to SiO ₂ (siloxane poisoning) are stored.
The determination unit 26 detects the electrical resistance value Rs detected by the gas detection unit 1 (the electrical resistance value corresponding to the detection voltage used when the signal processing circuit 21 determines fuel leakage or incomplete combustion, for example, the first electrical value). Based on the resistance value R1, the second electric resistance value R2), whether or not the gas detection unit 1 has changed in the electric resistance value of the gas detection unit 1 due to the influence of an insulating film or the like by SiO ₂ , that is, siloxane It is determined whether or not it is in a poisoned state, and the determination result is output to the output circuit 23 as a sensor failure signal and output to the main control unit 42 of the gas fan heater. Details of the operation of the determination unit 26 will be described later.

  As shown in FIGS. 1 and 5, the gas fan heater includes a burner 41 as a combustion section for burning supplied gas fuel, fuel interrupting means V for intermittently supplying gas fuel to the burner 41, fuel A gas detection device A that detects leakage and incomplete combustion of the burner 41, a main control unit 42 that controls the operation of the gas fan heater, and an operation unit 43 that commands various control commands to the main control unit 42 are provided. It is configured.

As shown in FIG. 5, the burner 41 is housed in a casing 46 having an intake port 44 on the upper side of the back surface and an outlet 45 on the lower side of the front surface. Inside the casing 46, air outside the casing sucked through the intake port 44 is supplied to the burner 41 as combustion air, and the combustion gas of the burner 41 is ventilated so as to blow out from the outlet 45 to the outside of the casing. A blower 47 is provided as a blowing means.
In the casing 46, a part of the air outside the casing sucked through the intake port 44 is supplied to the burner 41 as combustion air, and the remainder is mixed with the combustion gas of the burner 41 and led to the blowout port 45. In addition, an internal air passage 48 is formed. The blower 47 is provided in the casing 46 with the discharge portion facing the blowout port 45 in a state of sucking the intake port 44.
That is, the combustion gas of the burner 41 is mixed with the air in the space to be heated sucked through the intake port 44 to generate hot air, and the warm air is blown out from the outlet 45 to the space to be heated to heat the space to be heated. Is configured to do. An air filter 49 is provided at the intake port 44.

  And the gas sensor S is provided in the inlet 44 of the casing 46 so that the gas detection part 1 may be sensitive to the combustible gas and incomplete combustion gas in the air inhaled through the inlet 44.

The fuel supply path 52 is connected to, for example, a city gas pipe (not shown) to which city gas (gas such as 13A, which is mainly composed of methane gas (CH ₄ )) is supplied. In this embodiment, methane gas is mainly used. City gas as a component is supplied to the burner 41.
The operation unit 43 includes an operation switch 55 for commanding start and stop of operation of the gas fan heater, an alarm lamp 56 that is turned on when fuel leakage or incomplete combustion occurs, and a failure lamp that is turned on when a sensor failure occurs. 57. A temperature setting unit (not shown) for setting the heating target temperature, a display unit (not shown) for displaying various information such as the heating target temperature, the room temperature, and the like are provided.
The operation switch 55 is configured so that an operation start and an operation stop are instructed alternately every time the pressing operation is repeated.

Hereinafter, control operations of the sensor control unit 16 and the main control unit 42 will be described.
The sensor control unit 16 and the main control unit 42 are both configured using a microcomputer, and are configured to be able to communicate control information with each other in a wired or wireless manner.
When the operation start is commanded by the operation switch 55, the main control unit 42 operates the blower 47. After the blower 47 is operated, the main control unit 42 operates the igniter 50 and opens the on-off valve 53 and the proportional valve 54 to open the burner 41. An ignition process is performed to ignite the igniter 50, and after the output voltage of the thermocouple 51 reaches the ignition detection level and the ignition of the burner 41 is detected, the operation of the igniter 50 is stopped.
After detecting the ignition of the burner 41, the main control unit 42 adjusts the opening of the proportional valve 54 so that the temperature detected by a room temperature sensor (not shown) for detecting the temperature of the heating target space becomes the heating target temperature. After the combustion amount adjustment control for adjusting the combustion amount of 41 is executed and the operation stop is instructed by the operation switch 55, the fire extinguishing process for closing the on-off valve 53 and the proportional valve 54 and extinguishing the burner 41 is executed. The blower 47 is configured to be stopped.
The main control unit 42 receives detection information as to whether or not fuel leakage or incomplete combustion has occurred from the sensor control unit 16 described later during execution of the ignition process and the combustion amount adjustment control. If there is no fuel leakage or incomplete combustion, the operation is continued as it is. However, if fuel leakage or incomplete combustion has occurred, the alarm lamp 56 is lit to stop the operation. It is configured.
On the other hand, when the main control unit 42 receives from the determination unit 26 of the sensor control unit 16 a sensor failure signal indicating that the gas detection unit 1 is in a siloxane poisoning state and the gas detection unit 1 has failed. The failure lamp 57 is turned on, and the operation is stopped as necessary. That is, when the gas detection unit 1 is in a siloxane poisoning state, the detection information indicating whether fuel leakage or incomplete combustion has occurred is not reliable, and the siloxane poisoning state causes the gas detection unit 1 to be hot. Even if it is exposed to the operating state or clean air, it does not return to the normal state. Therefore, it is determined that the sensor has failed, prompts the replacement of the gas detection unit 1 or the gas detection device A, etc. It is to ensure safety.

Next, the control operation of the sensor control unit 16 will be described.
When the operation start is commanded by the operation switch 55 of the gas fan heater, the main control unit 42 causes the constant voltage circuit 13 to supply driving power to the heater 2 and the sensor control unit 16. Thereby, the operation of the gas detection device A is started.
The temperature of the gas detection unit 1 is adjusted by the sensor control unit 16 so that the switching of the switching element 14 is pulse-width controlled and the energization to the heater 2 is duty controlled.
The sensor control unit 16 controls the operation of the heater 2 so that the gas detection unit 1 is alternately and repeatedly switched between the high temperature operation state and the low temperature operation state, and the high temperature operation state based on the electric resistance value of the gas detection unit 1. In this configuration, combustible gas is detected, fuel leakage is detected based on the detected information, incomplete combustion gas is detected in a low temperature operating state, and incomplete combustion of the burner 41 is detected based on the detected information.
For example, the time from the start of heating to the end of the high temperature operating state is about 5 seconds, and the time from the end of the heating by the heater 2 to the end of the high temperature operating state and the end of the low temperature operating state is the start of heating. The gas detection unit immediately before the end of the low temperature operation state is detected by detecting the fuel leakage of the methane gas using the first electric resistance value R1 of the gas detection unit 1 immediately before the end of the high temperature operation state. Carbon monoxide gas (CO gas) as incomplete combustion gas is detected using the second electric resistance value R2. Here, the time during which the operation of the heater 2 is controlled to bring the gas detection unit 1 into the high temperature operation state corresponds to the high temperature operation state, and the operation of the heater 2 is controlled to bring the gas detection unit 1 into the low temperature operation state. The time required for the operation corresponds to a low temperature operation state. In addition, the high temperature side sensitive temperature in a high temperature operation state is set to 400 degreeC, for example, and the temperature of the gas detection part 1 is adjusted to the low temperature side sensitive temperature of 80 degreeC in a low temperature operation state, for example.

Here, for example, as shown in FIG. 6, when the gas detection unit 1 is in a normal state (when siloxane poisoning has not occurred), the temperature of the gas detection unit 1 is 400 ° C., which is the high-temperature side sensitive temperature. In addition, the first electric resistance value R1air (first electric resistance value R1) of the gas detection unit 1 in the air is initially reduced, but is stabilized and hardly changes even after a relatively long number of days have passed. . Similarly, the first electric resistance value R1s (first electric resistance value R1) when methane gas is contained in the air at a predetermined concentration (1000 ppm and 3000 ppm in FIG. 6) is almost the same even if a relatively long number of days have passed. It does not change. Therefore, when the first electric resistance value R1air of the gas detection unit 1 in the air and the first electric resistance value R1s when methane gas is contained in the air at a predetermined concentration, these electric resistance values are clearly shown. Therefore, the presence of methane gas can be detected well in a high-temperature operating state.
In the detection of fuel leakage of methane gas as combustible gas, when the first electric resistance value R1s immediately before the end of the high temperature operation state is lower than the fuel leakage alarm point (methane alarm point), methane gas leaks. It is determined that In the methane alarm point, the detection voltage corresponding to the electric resistance value Rma (about 1.1 kΩ) of the gas detection unit 1 when the methane concentration in the air is the fuel leakage concentration (for example, 3000 ppm) is set as the fuel leakage detection voltage. The electrical resistance value Rma and the fuel leakage detection voltage are stored in the memory 24 of the sensor control unit 16 (see FIG. 6).
When the sensor control unit 16 is in a high temperature operating state, if the first electrical resistance value R1s falls below the electrical resistance value Rma, it detects that a fuel leak has occurred and transmits a fuel leak detection signal to the main control unit 42. Is configured to do.

On the other hand, for example, as shown in FIG. 8, when the gas detection unit 1 is in a normal state (when siloxane poisoning has not occurred), the temperature of the gas detection unit 1 is 80 ° C., which is the low-temperature side sensitive temperature. Although the electric resistance value R2air (second electric resistance value R2) of the gas detection unit 1 in the air is initially reduced, it is stabilized and hardly changes even after a relatively long period of time has passed. Similarly, the second electric resistance value R2s (second electric resistance value R2) when the CO gas is contained in the air at a predetermined concentration (100 ppm and 300 ppm in FIG. 8) is the same even if a relatively long number of days have passed. Almost no change. Therefore, when the second electric resistance value R2air of the gas detection unit 1 in the air and the second electric resistance value R2s when the CO gas is contained in the air at a predetermined concentration, these electric resistance values are Since a clear difference (sensitivity) occurs, the presence of CO gas can be detected well in a low-temperature operating state.
In the detection of incomplete combustion by CO gas as incomplete combustion gas, when the second electrical resistance value R2s immediately before the end of the low temperature operation state is lower than the carbon monoxide alarm point (CO alarm point), CO It is determined that gas is generated and incompletely combusted. The CO alarm point indicates that the detection voltage corresponding to the electric resistance value Rca (about 14.9 kΩ) of the gas detection unit 1 when the CO gas concentration in the air is the incomplete combustion detection concentration (for example, 150 ppm) is detected as incomplete combustion. The electric resistance value Rca and the incomplete combustion detection voltage are stored in the memory 24 of the sensor control unit 16 (see FIG. 11).
When the second electrical resistance value R2s is lower than the electrical resistance value Rca when the sensor control unit 16 is in a low temperature operating state, the sensor control unit 16 detects that incomplete combustion has occurred and sends an incomplete combustion detection signal to the main control unit 42. Configured to send to.

Here, in the vicinity where the gas fan heater is installed, for example, when a substance containing the siloxane compound is sprayed by, for example, dew condensation prevention spray, silicon spray, hair spray, etc., the siloxane compound is Then, it adheres to the gas detection unit 1 or is adsorbed by the filter 12 for preventing contact with the gas detection unit 1. In this state, as described above, the gas detection unit 1 is poisoned to the gas detection unit 1 by the high temperature operation state (for example, about 300 to 400 ° C.) (the siloxane compound present in the atmosphere of the gas detection unit 1). When heated to a certain temperature), the siloxane compound adhering to the gas detection unit 1 or the siloxane compound desorbed from the filter 12 is decomposed and deposited on the surface of the gas detection unit 1. The surface is covered with a siloxane compound or a decomposition product thereof, or an insulating film of SiO ₂ is formed on the surface of the gas detector 1 (siloxane poisoning). Here, the siloxane compound is an organic polymer having a siloxane bond of “Si—O—Si” in the skeleton, such as (CH ₃ ) ₈ (SiO) ₄ or (CH ₃ ) ₁₀ (SiO) _5. There is.
When the gas fan heater is used in a state where such an insulating film of SiO ₂ is formed, the electric resistance value detected by the gas detection unit 1 in the gas detection device A may fluctuate.

For example, FIG. 7 shows changes over time of the first electric resistance value R1 in a high-temperature operating state when siloxane poisoning is performed. Specifically, the first electric resistance value of the gas detection unit 1 under a condition (indicated by D5 in the figure) in which a gas containing 10 ppm of cyclic siloxane (decamethyl cyclosiloxanesilane) is present in the atmosphere (in the air). A change in R1 (about 96 days) and a change in the first electrical resistance value R1 (about 44 days) when the gas detection unit 1 is exposed to an atmosphere of clean air thereafter are shown.
As shown in FIG. 7, when the gas detection unit 1 is poisoned with siloxane, the first electric resistance value R1air of the gas detection unit 1 in the air is the number of days despite the absence of methane gas. It gradually decreases with progress (so-called sensitization), and even after the cyclic siloxane is removed from the atmosphere and exposed to clean air, the first electric resistance value R1air remains in a reduced state. Further, even when methane gas having a predetermined concentration is present, when siloxane poisoning is performed, the first electrical resistance value R1s of the gas detection unit 1 is relatively greatly reduced and is not stabilized, and cyclic siloxane is generated from the atmosphere. After being removed and exposed to clean air, it will finally stabilize. Even if the presence of methane gas is detected based on the first electric resistance value R1 of the gas detection unit 1 in such a state, the concentration of methane gas is more accurate than the detection of methane gas in the normal state shown in FIG. The alarm corresponding to the above cannot be performed, and there is a high possibility of generating a false alarm, and the sensitivity is also very low.

Further, for example, FIG. 9 shows a change over time of the second electric resistance value R2 in the low temperature operation state when siloxane poisoning is performed. Specifically, a change in the second electric resistance value R2 of the gas detection unit 1 (about 96 days) under a condition in which a gas containing 10 ppm of cyclic siloxane exists in the atmosphere (in the air), and thereafter The change (about 44 days) of 2nd electrical resistance value R2 when the gas detection part 1 is exposed to the atmosphere of clean air is shown.
As shown in FIG. 9, when the gas detection unit 1 is poisoned with siloxane, the second electrical resistance value R2air of the gas detection unit 1 in the air has the same number of days as in the normal state (see FIG. 8). Even if it passes, it is stabilized at a predetermined value. On the other hand, in the case where CO gas of a predetermined concentration is present and the siloxane is poisoned, the second electric resistance value R2s of the gas detector 1 increases with the passage of days (so-called blunting), and in the atmosphere Even after the cyclic siloxane is removed from the product and exposed to clean air, it is stabilized with the increased electrical resistance value. Even if the presence of the CO gas is detected based on the second electric resistance value R2 of the gas detection unit 1 in such a state, the CO gas is detected as compared with the detection of the CO gas in the normal state shown in FIG. An alarm that accurately corresponds to the concentration cannot be performed, and there is a high possibility of generating a false alarm, and the sensitivity is also very low.

  Therefore, in the gas detection apparatus A of the present application, the sensor control unit 16 determines whether or not the gas detection unit 1 is in a siloxane poisoning state and a sensor failure in which the electric resistance value of the gas detection unit 1 fluctuates. The following processing is performed by the determination unit 26 provided. In addition, the determination of the sensor failure by the determination unit 26 is performed every time the operation of the gas fan heater is started.

The determination unit 26 determines whether the gas detection unit 1 is in a siloxane poisoning state based on the electric resistance value detected by the gas detection unit 1, that is, whether the sensor is in a sensor failure state. The result is output to the output circuit 23 and output to the main control unit 42 of the gas fan heater.
In this determination, the determination unit 26 basically includes the first electrical resistance value R1 immediately before the end of the high temperature operation state detected by the sensor control unit 16 (for example, when 5 seconds have elapsed from the start of heating), the low temperature operation state. The second electric resistance value R2 immediately before the end (for example, when 25 seconds have elapsed from the start of heating) is used.

First, the determination unit 26 has an initial value R0 (for example, the elapsed days stored in the memory 24) of the first electric resistance value R1air (first electric resistance value R1) of the gas detection unit 1 in the air in a high temperature operating state. The ratio of the first electric resistance value R1 to the first electric resistance value R1air on day 0 is used as the first determination criterion.
As shown in FIG. 10, in the normal state, the first electric resistance value R1air in the air is stabilized at a predetermined electric resistance value even if the number of days elapses. The value decreases sequentially. Therefore, when the ratio of the first electric resistance value R1air to the initial value R0 of the first electric resistance value R1air in the normal state is lower than a predetermined determination ratio, it is determined that the siloxane poisoning state is present. At this time, the first electric resistance value R1air is corrected by the correction coefficient K1 according to the temperature in the atmosphere to become the first electric resistance value R1air ′.
That is, as shown in FIG. 10, the determination unit 26 determines that the ratio (R1air ′ / R0) of the first electric resistance value R1air ′ to the initial value R0 of the first electric resistance value R1air is (R1air ′ / R0) <0. .5 relationship (first determination criterion) is satisfied (indicated by a hatched area in FIG. 10), the gas detector 1 may be in a siloxane poisoning state and the gas detector 1 may be sensitized. The failure count is added to the memory 24.
As described above, in the first determination criterion, the ratio is smaller than 0.5 in the CO alarm concentration (300 ppm) of the gas alarm inspection regulations for city gas issued by the Japan Gas Appliances Inspection Association. The number of days that the alarm cannot be issued (in FIG. 11, when the CO concentration is 300 ppm, the number of days when the second electric resistance value R2s exceeds the CO alarm point) is about the 42nd day. After that, since the second electric resistance value R2s in the siloxane poisoning state becomes higher than the CO alarm point, the number of days before this number of days, that is, the number of days when the CO gas detection ability is lowered and the alarm cannot be issued. The number of days before (for example, 35 days) is set, and the ratio (about 0.5) on the 35th day in FIG. 10 is used as a reference. By setting in this way, it is possible to determine whether or not siloxane is poisoned before the detection accuracy decreases for both detection of fuel leakage of methane gas and detection of generation of CO gas due to incomplete combustion. .

And the determination part 26 updates the failure count memorize | stored in the memory 24 sequentially, and when the determination (failure count) which satisfy | fills such 1st determination criteria continues more than 100 times (for example, by determination days) When about 30 days have passed), it is determined that the gas detector 1 is in a siloxane poisoning state, assuming that the decreasing state of the first electric resistance value R1 continues for a predetermined period. Here, the reason for continuing more than 100 times is that the above determination made every time the operation of the gas fan heater (operation of the gas detection device A) is started exceeds 100 times. Assuming that the average number of uses is 3 to 4 times a day, it corresponds to about 30 days. Therefore, when the first criterion is satisfied over such a long period of time, it is not an influence of a transient gas, etc. It can be recognized that the first electric resistance value R1 cannot be recovered due to siloxane poisoning. The transient gas is, for example, a gas that temporarily comes into contact with the gas detection unit 1 to change the electric resistance value, and includes, for example, a cooking gas that is generated during cooking.
Therefore, it is possible to determine whether or not the gas detection unit 1 is poisoned with siloxane by a siloxane compound by using the first determination criterion.

Here, in order to make the determination based on the first determination criterion more accurate, the determination unit 26 determines the second electric resistance value R2s (2) of the gas detection unit 1 when a predetermined concentration of CO gas is present in the low temperature operation state. Whether or not the second electrical resistance value R2) exceeds a multiple (for example, 20 times) of the CO alarm point (for example, the electrical resistance value Rca corresponding to 150 ppm) is used as the second determination criterion.
As shown in FIG. 11, in the normal state, the second electric resistance value R2s when the CO gas is present at a predetermined concentration is stabilized at the predetermined electric resistance value even if the number of days elapses. If so, the electrical resistance value increases sequentially. Therefore, when the second electrical resistance value R2s is larger than a multiple (for example, 20 times) of the CO alarm point (indicated by a broken line region in FIG. 11), it is determined that the siloxane poisoning state is present. At this time, the second electric resistance value R2s is corrected by the correction coefficient K2 according to the temperature in the atmosphere to become the second electric resistance value R2s ′.
That is, as shown in FIG. 11, when the second electric resistance value R2s ′ satisfies the relationship of R2s ′> CO alarm point × 20 (second determination criterion), the determination unit 26, as shown in FIG. It is determined that 1 is in a siloxane poisoning state and the gas detection unit 1 is slowed down. Here, when a transient gas is present in the atmosphere of the gas detection unit 1, the second electrical resistance value R2s ′ is temporarily reduced in the presence of the transient gas, and the second Although the determination criteria are not met, the siloxane poisoning is not recoverable, so when the transient gas is removed by a ventilation fan or the like and no longer exists in the atmosphere, the second electric resistance value R2s ′ increases again and increases. 2 criteria will be satisfied. Therefore, even when the second electric resistance value R2s ′ of the gas detection unit 1 is reduced due to the influence of the transient gas, it can be clearly distinguished from the case of siloxane poisoning.
In order to determine whether or not the siloxane poisoning state is earlier, the relationship of R2s ′> CO alarm point × 20 (second determination criterion) is a multiple smaller than 20 times the CO alarm point, etc. For example, it is possible to set R2s ′> (CO alarm point × 5 to 30 times).
Therefore, by using the second determination criterion, it can be more accurately determined whether or not the gas detection unit 1 is poisoned with siloxane by a siloxane compound.

Next, the determination operation in the determination unit 26 will be described based on the flowchart shown in FIG.
When the start of operation is instructed by the operation switch 55 of the gas fan heater, the main control unit 42 executes ignition processing and combustion amount adjustment control, and supplies driving power from the constant voltage circuit 13 to the heater 2 and the sensor control unit 16. Let Thereby, the operation of the gas detection device A is started (step # 1), and the heater 2 is energized by the sensor control unit 16, and the gas detection unit 1 is alternately and repeatedly switched between the high temperature operation state and the low temperature operation state. Thus, the operation of the heater 2 is controlled (step # 2). The electrical resistance value Rma (methane alarm point) corresponding to the fuel leak detection voltage value of methane gas and the electrical resistance value Rca (CO alarm point) corresponding to the incomplete combustion detection voltage value of CO gas are stored in the memory 24 in advance. What has been set may be used, or newly set may be used.

  Then, when the gas detection unit 1 is switched from the low temperature operation state to the high temperature operation state and a predetermined time has passed (about 5 seconds have elapsed) from when the gas detection unit 1 is switched to the high temperature operation state (the temperature of the gas detection unit 1 is about 400 ° C.). The first electric resistance value R1air of the gas detection unit 1 in the air is detected (step # 3), and the heating operation of the heater 2 is stopped. The first electric resistance value R1air is temperature-corrected to R1air ′ by a correction coefficient K1 corresponding to the ambient temperature of the gas detector 1 (step # 4). The first electric resistance value R1air ′ is also used as detection information for determining whether or not methane gas is leaking fuel.

Next, in the determination unit 26, the initial value R0 (for example, the first value when the number of elapsed days is 0 days) of the first electric resistance value R1air ′ (first electric resistance value R1) of the gas detection unit 1 in the air in the high temperature operating state. A ratio of the first electric resistance value R1air ′ to the electric resistance value R1) is obtained, and it is determined whether or not the ratio is smaller than 0.5 as a first criterion (step # 5). When the ratio is 0.5 or more (step # 5: No), it is assumed that there is no sensor failure (no siloxane poisoning), and no failure count is added (step # 12), and the sensor control unit 16 The normal operation is repeated to repeat the fuel leak and incomplete combustion detection operation (step # 13).
On the other hand, when the ratio is smaller than 0.5 (step # 5: Yes), a failure count is added once and stored in the memory 24 as a sensor failure (siloxane poisoning) ( Step # 6). Then, the process proceeds to step # 7, and it is determined whether or not the failure count exceeds 100 (step # 7). If it has not exceeded 100 times, a normal operation is repeated in which the sensor controller 16 repeats the detection of fuel leakage and incomplete combustion (step # 13). When the number of times exceeds 100, the determination is made based on the second determination criterion that further improves the determination accuracy.

  Then, the determination unit 26 detects the second electric resistance value R2s immediately before the end of the low-temperature operation state (about 25 seconds after the start of heating by the heater 2) (step # 8), and starts the operation of the heater 2. . The second electric resistance value R2s is temperature-corrected to R2s ′ by a correction coefficient K2 corresponding to the ambient temperature of the gas detector 1 (step # 9). The second electric resistance value R2s ′ is also used as detection information for determining whether incomplete combustion gas is generated and CO gas is present.

Next, the determination unit 26 determines whether or not the second electric resistance value R2s ′ is larger than 20 times the CO alarm point (step # 10). If this relationship is not satisfied (step # 10: No), a normal operation is repeated in which the sensor control unit 16 repeats the detection of fuel leakage and incomplete combustion, assuming that there is no sensor failure (no siloxane poisoning). (Step # 13).
On the other hand, when this relationship is satisfied (step # 10: Yes), it is determined that the gas detection unit 1 is in a sensor failure (in a siloxane poisoning state) and the gas detection unit 1 is slowing down (step). # 11).
In this case, a sensor failure signal indicating a sensor failure is output to the main control unit 42 by the output circuit 23, and the main control unit 42 turns on the sensor failure lamp 57 of the gas fan heater to stop the operation. it can.

[Second Embodiment]
Compared with the first embodiment, the configuration of the gas detection device A and the combustion equipment is the same, but in the second embodiment, the determination operation in the determination unit 26 can be changed as follows. The determination operation of the determination unit 26 according to the second embodiment will be described based on the flowchart shown in FIG.

  When the start of operation is instructed by the operation switch 55 of the gas fan heater, the main control unit 42 executes ignition processing and combustion amount adjustment control, and supplies driving power from the constant voltage circuit 13 to the heater 2 and the sensor control unit 16. Let As a result, the operation of the gas detection device A is started (step # 21), and the heater 2 is energized by the sensor control unit 16, and the gas detection unit 1 is alternately and repeatedly switched between the high temperature operation state and the low temperature operation state. Thus, the operation of the heater 2 is controlled (step # 22). The electrical resistance value Rma (methane alarm point) corresponding to the fuel leak detection voltage value of methane gas and the electrical resistance value Rca (CO alarm point) corresponding to the incomplete combustion detection voltage value of CO gas are stored in the memory 24 in advance. What has been set may be used, or newly set may be used.

  Then, when the gas detection unit 1 is switched from the low temperature operation state to the high temperature operation state and a predetermined time has passed (about 5 seconds have elapsed) from when the gas detection unit 1 is switched to the high temperature operation state (the temperature of the gas detection unit 1 is about 400 ° C.). The first electric resistance value R1air of the gas detector 1 in the air at is detected (step # 23), and the heating operation of the heater 2 is stopped. The first electric resistance value R1air is temperature-corrected to R1air ′ by a correction coefficient K1 corresponding to the ambient temperature of the gas detector 1 (step # 24). The first electric resistance value R1air ′ is also used as detection information for determining whether or not methane gas is leaking fuel.

Next, in the determination unit 26, the initial value R0 (for example, the first value when the number of elapsed days is 0 days) of the first electric resistance value R1air ′ (first electric resistance value R1) of the gas detection unit 1 in the air in the high temperature operating state. A ratio of the first electric resistance value R1air 'to the electric resistance value R1) is obtained, and it is determined whether or not the ratio is smaller than 0.5 as a first criterion (step # 25). If the ratio is 0.5 or more (step # 25: No), it is determined that there is no sensor failure (no siloxane poisoning), and no failure count is added (step # 26), and the sensor control unit 16 The normal operation is repeated to repeat the fuel leak and incomplete combustion detection operation (step # 27).
On the other hand, when the ratio is smaller than 0.5 (step # 25: Yes), the determination based on the second determination criterion with further improved determination accuracy is performed.

  The determination unit 26 detects the second electric resistance value R2s immediately before the end of the low temperature operation state (at the time when about 25 seconds have elapsed from the start of heating by the heater 2) (step # 28), and starts the operation of the heater 2. The second electric resistance value R2s is temperature-corrected to R2s ′ by a correction coefficient K2 corresponding to the ambient temperature of the gas detector 1 (step # 29). The second electric resistance value R2s ′ is also used as detection information for determining whether incomplete combustion gas is generated and CO gas is present.

Next, the determination unit 26 determines whether or not the second electric resistance value R2s ′ is larger than 20 times the CO alarm point (step # 30). If this relationship is not satisfied (step # 30: No), it is assumed that there is no sensor failure (no siloxane poisoning), and no failure count is added (step # 31), fuel leakage by the sensor control unit 16 and A normal operation that repeats the incomplete combustion detection operation is performed (step # 27).
On the other hand, if this relationship is satisfied (step # 30: Yes), a failure count is added once and stored in the memory 24 (step # 32) assuming that there is a sensor failure (siloxane poisoning). Then, the process proceeds to step # 33, and it is determined whether or not the failure count exceeds 100 (step # 33). If it has not exceeded 100 times, normal operation is repeated in which the sensor control unit 16 repeats the detection operation of fuel leakage and incomplete combustion (step # 27). If it has exceeded 100 times, it is determined that the gas detection unit 1 has a sensor failure (in a siloxane poisoning state) (step # 34). Thereby, the poisoning state by the siloxane compound is determined by using both the first electric resistance value R1air ′ and the second electric resistance value R2s ′ detected at each detection timing (at the start of operation of the gas fan heater). Accuracy can be improved and sensor failure can be recognized more accurately. In particular, the determination of whether the first electric resistance value R1air ′ is reduced and whether the second electric resistance value R2s ′ exceeds a predetermined electric resistance value is repeatedly performed every time the gas fan heater is started. Since it is not determined to be siloxane poisoning until the state to be satisfied reaches a plurality of times (for example, until it exceeds 100 times), a determination result of a plurality of times (a determination result until the failure count reaches a predetermined count corresponding to the passage of a predetermined period) Based on the above, it is possible to more accurately determine the poisoning state by the siloxane compound. For example, it is possible to satisfactorily eliminate the influence of a transient gas such as cooking gas generated by cooking (a gas existing in units of several minutes or tens of minutes, which is a relatively short time).
If the sensor failure is determined, a sensor failure signal indicating that the sensor has failed is output from the output circuit 23 to the main control unit 42. In the main control unit 42, the sensor failure lamp 57 of the gas fan heater is turned on to operate. Can be stopped.

[Another embodiment]
(1) In the above-described embodiment, the determination based on the first determination criterion is performed in Step 5 and the determination based on the second determination criterion is performed in Step 10, but both steps are performed depending on the required detection accuracy. It is possible to appropriately select whether to perform only one. For example, in order to make a simple configuration while determining siloxane poisoning, a configuration in which only determination based on the first determination criterion can be adopted.

(2) In the above embodiment, in the first determination criterion, the ratio of the first electric resistance value R1air ′ to the initial value R0 of the first electric resistance value R1air of the gas detection unit 1 in the air in the high temperature operating state is the determination ratio. A relationship that is smaller than 0.5 is used. However, if the configuration can be understood that the first electric resistance value R1air ′ is decreasing with the passage of days, the configuration is not limited to this configuration. Can do. For example, the determination ratio can be set to about 0.7 to 0.3.
Further, as the first determination criterion, any structure can be adopted as long as the first electric resistance value R1air ′ is found to decrease with the passage of days. For example, the first electric resistance value R1air ′ is It can also be determined that the siloxane poisoning occurs when the electric resistance value is smaller than a predetermined multiple of the methane alarm point Rma (for example, about 2 to 6 times the methane alarm point Rma) as one criterion. In FIG. 7, it is 3 times).

(3) In the above embodiment, in the second determination criterion, the second electrical resistance value R2s ′ uses the relationship of whether or not the multiple of the CO alarm point Rca is used. Any configuration can be adopted as long as it is understood that R2s ′ increases with the number of days. For example, a multiple of the initial value R20 of the second electrical resistance value R2s ′ (for example, the second electrical resistance value R2 when the number of elapsed days is 0) is used, and the second electrical resistance value R2s is the multiple (for example, the initial value R20). It is also possible to determine that it is siloxane poisoning when it becomes larger than 2 times to 8 times.

(4) In the above embodiment, an example in which the gas detection device according to the present invention is applied to a gas fan heater has been shown. However, the gas detection device A according to the present invention detects and warns of fuel leakage or incomplete combustion. It can also be applied to gas alarms. In this case, in steps # 6 and # 7 of FIG. 14, when the gas fan heater detects a failure count exceeding 100 times, it is determined that the possibility of sensor failure is high and the process proceeds to the second criterion. When the gas detector A is used for a gas alarm device, if the state satisfying the first determination criterion continues for 10 days or more, it is determined that the possibility of sensor failure is high and the process proceeds to the second determination criterion. It can also be configured. Similarly, in steps # 32 and # 33 of FIG. 15, if the gas fan heater detects a failure count exceeding 100 times, it is determined that a sensor failure has occurred, but the gas detection device A is used as a gas alarm. When used, it may be configured to determine that a sensor failure occurs when a state that satisfies both the first determination criterion and the second determination criterion continues for 10 days or more.

(5) The gas detection device according to the present invention is applied to gas detection devices for various combustion devices such as a gas stove, an oil fan heater, an oil stove, and a hot water supply device in addition to the gas fan heater exemplified in the above embodiment. can do.

(6) In the above embodiment, the case where the sensor control unit 16 and the main control unit 42 are configured separately is illustrated. However, the sensor control unit 16 and the main control unit 42 are configured as a single unit using a microcomputer. You may comprise as.

(7) The installation location of the gas sensor S is not limited to the intake port 44 of the casing 46 illustrated in the above embodiment, and may be, for example, near the intake port 44.

(8) In the above embodiment, the case where the present invention is applied to a gas detection device for combustion equipment that uses gas fuel as fuel has been exemplified. However, the present invention is applied to a gas detection device for combustion equipment that uses liquid fuel as fuel. In this case, the gas detector 1 detects a gas obtained by vaporizing the liquid fuel as a combustible gas.
In addition, when the present invention is applied to a gas detection device for a combustion device that uses gas fuel as fuel, the gas fuel is not limited to city gas mainly composed of methane, and may be propane gas, for example.

(9) The gas detection device according to the present invention can be applied to a gas alarm device that detects and warns of fuel leakage or incomplete combustion in addition to the gas fan heater as the combustion device exemplified in the above embodiment. . For example, the gas detection unit of the gas detection device is provided in the alarm body so as to be sensitive to inflammable gas and incomplete combustion gas in the air supplied through the gas inlet provided in the alarm body. It can also be set as the gas alarm of composition. Accordingly, the gas alarm device includes a gas detection device having a gas detection unit sensitive to flammable gas and incomplete combustion gas, and in this gas detection device, it is ensured that the gas detection unit is poisoned by the siloxane compound. Therefore, it is possible to accurately detect and alarm the presence of the detection target gas having a predetermined concentration, and to ensure safe operation of the gas alarm device.

(10) In the above embodiment, the sensor control unit 16 controls the operation of the heater 2 so as to alternately and repeatedly switch the gas detection unit 1 between the high temperature operation state and the low temperature operation state. However, the present invention is limited to this configuration. Instead, for example, the sensor control unit 16 may control the operation of the heater 2 so that the temperature of the gas detection unit 1 is only in the high temperature operation state. In this case, it becomes the structure which detects a combustible gas in a high temperature operation state.

  As described above, it is possible to determine whether the gas detection unit is in a siloxane poisoning state with a siloxane compound, accurately detect the presence of a detection target gas having a predetermined concentration, and perform an alarm. It was possible to provide a gas detection device capable of recognizing sensor failure due to siloxane poisoning at an early stage, a combustion device equipped with the gas detection device, and a gas alarm.

1 Gas detection unit 2 Heater (heating unit)
10 Housing (housing)
16 Sensor control unit (control unit)
26 Judgment part A Gas detection device

Claims (11)

A gas detection unit that is provided inside the housing and changes its electric resistance value in response to a detection target gas, a heating unit that heats the gas detection unit, and a high temperature operation state and a low temperature operation state of the gas detection unit As the detection target gas based on the first electric resistance value of the gas detection unit in the high-temperature operation state, the operation of the heating unit is controlled only in a high-temperature operation state. A gas detection device comprising a control unit for detecting flammable gas,
The siloxane compound present in the atmosphere of the gas detection unit may poison the gas detection unit when the temperature of the gas detection unit heated by the operation control of the heating unit by the control unit is in the high temperature operation state. A certain temperature,
A determination unit configured to determine that the surface of the gas detection unit is poisoned by the siloxane compound when the reduced state of the first electric resistance value detected by the control unit continues for a predetermined period; Gas detection device.   In determining the poisoning state due to the siloxane compound, the determination unit determines that the ratio is a predetermined value based on a ratio of the detected first electric resistance value to an initial value of the first electric resistance value in a normal state. The gas detection device according to claim 1, wherein the surface of the gas detection unit is determined to be poisoned by the siloxane compound when the state of lower than the determination ratio continues for a predetermined period.   The gas detection device according to claim 2, wherein the predetermined determination ratio of the detected first electric resistance value with respect to the initial value is 0.5.   In determining the poisoning state by the siloxane compound, the first electric resistance value is a multiple of the combustible gas alarm point that is an electric resistance value for generating an alarm when a predetermined concentration of combustible gas is generated. 2. The determination unit according to claim 1, wherein the determination unit determines that the surface of the gas detection unit is poisoned by the siloxane compound when a state in which the electric resistance value is lower than a predetermined electric resistance value continues for a predetermined period. Gas detection device.   The determination unit corrects the first electrical resistance value corresponding to an ambient temperature condition, and performs the determination using the corrected first electrical resistance value instead of the first electrical resistance value. The gas detection device according to any one of 1 to 4. In the configuration in which the control unit detects incomplete combustion gas as the detection target gas based on a second electric resistance value of the gas detection unit in the low temperature operation state,
6. The method according to claim 1, wherein the determination unit determines that the surface of the gas detection unit is poisoned by the siloxane compound when the second electric resistance value exceeds a predetermined electric resistance value. The gas detection device according to claim 1.   In determining the poisoning state by the siloxane compound, the predetermined electric resistance value is an electric resistance value for issuing an alarm when an incomplete combustion gas having a predetermined concentration is generated. 7. When the second electric resistance value is set to a multiple and increases to an electric resistance value exceeding the multiple, it is determined that the surface of the gas detection unit is poisoned by the siloxane compound. The gas detection device described in 1.   A configuration in which the determination unit determines whether or not the detected first electric resistance value is lowered and determines whether the detected second electric resistance value exceeds the predetermined electric resistance value. When the first electric resistance value is in a lowered state and the second electric resistance value is in a state exceeding the predetermined electric resistance value, the failure count is updated by one, and these determinations are repeated. When the failure count reaches a predetermined count, the reduced state in which the first electric resistance value decreases and the state in which the second electric resistance value exceeds the predetermined electric resistance value continue for a predetermined period, The gas detection device according to claim 6, wherein the gas detection device is determined to be poisoned by a siloxane compound.   The said determination part correct | amends the said 2nd electrical resistance value corresponding to ambient temperature conditions, and performs the said determination using the corrected 2nd electrical resistance value instead of the said 2nd electrical resistance value. The gas detection device according to any one of 6 to 8. A combustion apparatus comprising the gas detection device according to any one of claims 1 to 9,
Air outside the casing is supplied to the combustion section as combustion air via an intake port provided in a casing in which a combustion section for burning combustible gas is stored, and the combustion gas in the combustion section is supplied to the combustion section. An air blowing part is provided to ventilate so as to blow out of the casing from the blowout opening provided in the casing,
A combustion device provided at or near the intake port so that the gas detector is sensitive to combustible gas or incomplete combustion gas in the combustion air supplied via the intake port. A gas alarm device comprising the gas detection device according to any one of claims 1 to 9,
Gas alarm provided in the alarm body so that the gas detector is sensitive to inflammable gas and incomplete combustion gas in the air supplied through the gas inlet provided in the alarm body vessel.

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