JP4302611B2 - Combustible gas detection device and combustible gas detection method - Google Patents

Description

  The present invention relates to a flammable gas detection device and a flammable gas detection method for detecting a flammable gas in an atmosphere to be detected.

Conventionally, in this type of combustible gas detection device, there is a hydrogen gas sensor for a fuel cell vehicle disclosed in Non-Patent Document 1 below. This hydrogen gas sensor detects the degree of influence of humidity from the difference between detection values of both thermistors controlled to different temperatures, and detects hydrogen gas by correcting the humidity component.
Masaaki Tada and three others, "Hydrogen Sensor for Fuel Cell Vehicles", SAE-2003-01-1137, p7-p8

  By the way, in the hydrogen gas sensor, even if the concentration of hydrogen gas in the atmosphere to be detected is the same, the phenomenon that the thermal conductivity of the entire atmosphere to be detected fluctuates due to a change in humidity in the atmosphere to be detected is considered. As a result, the hydrogen gas detection accuracy is low.

  Therefore, in order to cope with the above, the present invention takes into account that the concentration of the combustible gas in the detected atmosphere varies based on the humidity in the detected atmosphere, and accurately detects the combustible gas. An object of the present invention is to provide a combustible gas detection device and a combustible gas detection method that detect the above.

  In solving the above-described problems, the combustible gas detection device according to the present invention includes a plurality of heating resistors (211, 221, 330) exposed to the detected atmosphere.

In the combustible gas detection device, the two heating resistors so as to maintain the resistance values of the two heating resistors (211) among the plurality of heating resistors at respective values corresponding to different constant temperatures. Energization control means (230, 240, 480) for energization control of
Temperature detection means (390) for detecting the environmental temperature in the atmosphere to be detected;
Voltage difference calculation means (420, 430) for calculating a difference between the terminal voltages of the two heating resistors generated in the energization control state by the energization control means as a voltage difference;
Voltage ratio determining means (431) for determining, as a voltage ratio, a ratio of the respective terminal voltages of the two heating resistors generated in the energization control state by the energization control means;
Humidity determining means (432) for determining the humidity in the detected atmosphere based on the relationship between the voltage ratio determined by the voltage ratio determining means and the detected environmental temperature by the temperature detecting means;
Concentration calculating means (433, 434, 440) for calculating the concentration of the combustible gas in the detected atmosphere based on the relationship between the voltage difference calculated by the voltage difference calculating means, the humidity determined by the humidity determining means, and the detected environment temperature. )
The combustible gas is detected based on the calculated concentration of the concentration calculating means.

  According to this, the difference between the terminal voltages of the two heating resistors generated in the energization control state is calculated as a voltage difference, and the ratio of the terminal voltages of the two heating resistors generated in the energization control state is the voltage. The humidity in the detected atmosphere is determined based on the relationship between the determined voltage ratio and the detected environment temperature. Then, the concentration of the combustible gas in the detected atmosphere is calculated based on the relationship between the calculated voltage difference, the determined humidity, and the detected environment temperature, and the combustible gas is detected based on the calculated concentration.

  Thereby, considering that the thermal conductivity of the atmosphere to be detected fluctuates according to the humidity in the atmosphere to be detected, it is possible to detect combustible gas by processing to eliminate this fluctuation, This detection accuracy can be secured high.

  According to the second aspect of the present invention, the combustible gas detection device includes the heating resistor (211, 221 and 330) exposed to the detected atmosphere.

In the combustible gas detection device, energization control means (214) for intermittently energizing the heat generating resistor so as to maintain the resistance value of the heat generating resistor at different values corresponding to different constant temperatures at different times. 215, 216, 231, 290, 481), and
Temperature detecting means (500, 390) for detecting the environmental temperature in the detected atmosphere;
Voltage difference calculation means (420, 430) for calculating a difference between the terminal voltages of the heating resistors generated at different times in the intermittent energization control state by the energization control means, as a voltage difference;
A voltage ratio determining means (431) for determining, as a voltage ratio, a ratio of each terminal voltage of the heating resistor generated at different times in the intermittent energization control state by the energization control means;
Humidity determining means (432) for determining the humidity in the detected atmosphere based on the relationship between the voltage ratio determined by the voltage ratio determining means and the detected environmental temperature by the temperature detecting means;
Concentration calculating means (433, 434) for calculating the concentration of the combustible gas in the detected atmosphere based on the relationship between the voltage difference calculated by the voltage difference calculating means, the humidity determined by the humidity determining means, and the detected environment temperature. 440), and
The combustible gas is detected based on the calculated concentration of the concentration calculating means.

  According to this, the difference between the terminal voltages of the heating resistors generated at different times in the intermittent energization control state is calculated as a voltage difference, and the heat generated at different times in the intermittent power control state. The ratio of the terminal voltages of the resistors is determined as the voltage ratio, and the humidity in the detected atmosphere is determined based on the relationship between the determined voltage ratio and the detected environment temperature. Then, the concentration of the combustible gas in the detected atmosphere is calculated based on the relationship between the calculated voltage difference, the determined humidity, and the detected environment temperature, and the combustible gas is detected based on the calculated concentration.

  Thus, even if the number of heating resistors is single, the difference and ratio of the terminal voltages of the heating resistors that occur at different times in the intermittent energization control state are the voltage difference and voltage ratio. As a result, the configuration of the gas detection device can be further reduced in size and the power consumption of the detection element can be further suppressed, and the same effect as that of the first aspect of the invention can be achieved.

Moreover, according to the description of claim 3, the combustible gas detection device according to the present invention is
A semiconductor substrate (310) formed by forming a plurality of recesses (311) from the back side at intervals, an insulating layer (320) formed on the surface of the semiconductor substrate, and the recesses on the surface of the insulating layer A plurality of heating resistors (211, 221, 330) formed corresponding to, and a protective layer (350, 360) formed on the surface of the insulating layer so as to cover these heating resistors, A detection element (300) disposed in the atmosphere to be detected;
Energization control for energizing the two heating resistors so as to maintain the resistance values of the two heating resistors (211 and 221) among the plurality of heating resistors at respective values corresponding to different constant temperatures. Means (230, 240, 480);
Temperature detection means (390) for detecting the environmental temperature in the atmosphere to be detected;
Voltage difference calculation means (420) for calculating a difference between the terminal voltages of the two heating resistors generated in the energization control state by the energization control means as a voltage difference;
Voltage ratio determining means (431) for determining, as a voltage ratio, a ratio of the respective terminal voltages of the two heating resistors generated in the energization control state by the energization control means;
Humidity determining means (432) for determining the humidity in the detected atmosphere based on the relationship between the voltage ratio determined by the voltage ratio determining means and the detected environmental temperature by the temperature detecting means;
Concentration calculating means (440) for calculating the concentration of the combustible gas in the detected atmosphere based on the relationship between the voltage difference calculated by the voltage difference calculating means, the humidity determined by the humidity determining means, and the detected environment temperature; And
The combustible gas is detected based on the calculated concentration of the concentration calculating means.

  According to this, unlike the invention according to claim 1, the combustible gas detection device having the detection element having the above-described configuration can also achieve the same operational effects as the invention according to claim 1.

Moreover, according to the description of Claim 4, the combustible gas detection apparatus which concerns on this invention
A semiconductor substrate (310) formed with a recess (311) from the back side, an insulating layer (320) formed on the surface of the semiconductor substrate, and formed on the surface of the insulating layer corresponding to the recess. A detection element that includes a heating resistor (211, 221 and 330) and a protective layer (350, 360) formed on the surface of the insulating layer so as to cover the heating resistor and is arranged in a detection atmosphere. (300),
Energization control means (214, 215, 216, 231 and 290) for intermittently energizing the heating resistor so as to maintain the resistance value of the heating resistor at different values corresponding to different constant temperatures at different times. 481),
Temperature detecting means (500, 390) for detecting the environmental temperature in the detected atmosphere;
Voltage difference calculation means (420, 430) for calculating a difference between the terminal voltages of the heating resistors generated at different times in the intermittent energization control state by the energization control means, as a voltage difference;
A voltage ratio determining means (431) for determining, as a voltage ratio, a ratio of each terminal voltage of the heating resistor generated at different times in the intermittent energization control state by the energization control means;
Humidity determining means (432) for determining the humidity in the detected atmosphere based on the relationship between the voltage ratio determined by the voltage ratio determining means and the detected environmental temperature by the temperature detecting means;
Concentration calculating means (433, 434, 440) for calculating the concentration of the combustible gas in the detected atmosphere based on the relationship between the voltage difference calculated by the voltage difference calculating means, the humidity determined by the humidity determining means, and the detected environment temperature. )
The combustible gas is detected based on the calculated concentration of the concentration calculating means.

  According to this, unlike the invention described in claim 2, the combustible gas detection device having the detection element having the above-described configuration can achieve the same operational effects as the invention described in claim 2.

  In addition, in the invention according to any one of claims 1 to 4, the humidity determining means is based on the approximate linear relationship established between the voltage ratio and the humidity at each environmental temperature, from the determined voltage ratio. The humidity may be determined.

  Further, in the invention according to claim 2 or 4, the terminal voltage generated in advance among the terminal voltages of the heating resistor generated at different times in the intermittent energization control state by the voltage ratio determining means. The ratio obtained by dividing the voltage by the terminal voltage generated subsequently is defined as a voltage ratio, and the humidity determination by the humidity determination means is performed only when the voltage ratio is larger (or smaller) than 1. Good.

Moreover, according to the description of Claim 5, this invention WHEREIN: In the combustible gas detection apparatus as described in any one of Claims 1-4,
The voltage difference is an independent variable, the concentration of the combustible gas is a dependent variable, and the determination is performed using a predetermined relationship between an intercept of a linear function equation established with the humidity and the environmental temperature as parameters, and the humidity. Intercept determining means (433) for determining the intercept based on humidity;
Gradient determining means (434) for determining the gradient of the linear function equation based on the detected ambient temperature,
The concentration calculating means uses both the determined intercept by the intercept determining means and the determined gradient by the gradient determining means in place of the determined humidity and the detected environmental temperature, and the combustibility based on the linear function equation according to the calculated voltage difference. The gas concentration is calculated.

  According to this, the voltage difference of each terminal voltage of the heating resistor generated in the energization control state by the energization control means is an independent variable, the concentration of the combustible gas in the detected atmosphere is the dependent variable, the humidity and the environment A linear function formula that assumes temperature as a parameter is assumed.

  Under such a premise, the intercept of the linear function equation is determined based on the determined humidity using a predetermined relationship established between the intercept of the linear function equation and the humidity, and the linear function The slope of the equation is determined based on the detected ambient temperature.

  Then, the concentration of the combustible gas is calculated based on the linear function equation using the voltage difference of each terminal voltage of the heating resistor generated in the energization control state, the determined intercept and the determined gradient, and the calculated concentration Based on the above, combustible gas is detected.

  Accordingly, in consideration of the fact that the concentration of the combustible gas in the atmosphere to be detected fluctuates according to the humidity in the atmosphere to be detected, the combustible gas is detected by processing to eliminate this fluctuation. Therefore, this detection accuracy can be further ensured.

  According to a sixth aspect of the present invention, in the combustible gas detection device according to any one of the first to fifth aspects, the temperature detecting means is a temperature measuring device disposed in the detected atmosphere. The resistor is a resistance temperature detector that detects an environmental temperature in the atmosphere to be detected in accordance with a change in the resistance value.

  Thus, even if the resistance temperature detector disposed in the atmosphere to be detected is employed as the temperature detecting means, the same effect as that of the invention according to any one of claims 1 to 5 can be achieved.

According to a seventh aspect of the present invention, in the combustible gas detection device according to the third or fourth aspect, the temperature detection means is a thin film resistor formed on the surface of the semiconductor substrate. ,
The thin film resistor is a thin film resistor that detects an environmental temperature in the detected atmosphere based on a change in the resistance value.

  As described above, since the thin film resistor formed on the surface of the semiconductor substrate is employed as the temperature detecting means, the resistance value of the thin film resistor can change rapidly with the change in the environmental temperature. Therefore, the same effect as that of the invention of claim 3 or 4 can be achieved with higher accuracy.

In the combustible gas detection method according to the present invention, according to the description of claim 8,
Energizing and controlling the heating resistors so as to maintain the resistance values of the heating resistors (211, 221 and 330) exposed to the detected atmosphere at respective values corresponding to different constant temperatures;
Determining the humidity in the detected atmosphere based on the relationship between the voltage ratio of each terminal voltage of both heating resistors generated in the energization control state in the detected atmosphere and the environmental temperature in the detected atmosphere;
The combustible gas is detected by calculating the concentration of the combustible gas in the detected atmosphere based on the voltage difference between the terminal voltages of the two heating resistors, the humidity, and the environment temperature.

  According to this, it is possible to provide a combustible gas detection method capable of achieving the same function and effect as the first aspect of the invention.

Further, in the combustible gas detection method according to the present invention, according to the description of claim 9,
The heating resistor is subjected to intermittent energization control so that the resistance value of the heating resistor exposed to the detected atmosphere is maintained at different times corresponding to different constant temperatures,
The humidity in the detected atmosphere is determined based on the relationship between the voltage ratio of each terminal voltage of the heating resistor generated in the intermittent energization control state in the detected atmosphere and the environmental temperature in the detected atmosphere. ,
The combustible gas is detected by calculating the concentration of the combustible gas in the detected atmosphere based on the voltage difference between the terminal voltages of the heating resistor, the humidity, and the environmental temperature.

  According to this, it is possible to provide a combustible gas detection method capable of achieving the same effect as that of the invention described in claim 2.

According to the description of claim 10, the present invention provides the combustible gas detection method according to claim 8 or 9,
Calculation of the above flammable gas is
Predetermined relationship between the humidity and the intercept of a linear function equation established with the voltage difference as an independent variable, the concentration of the combustible gas in the detected atmosphere as a dependent variable, and the humidity and the environmental temperature as parameters To determine the intercept based on the determined humidity,
Using the gradient of the linear function equation determined based on the environmental temperature, the intercept, and the voltage difference, the concentration of the combustible gas is calculated based on the linear function equation. To do.

  Thereby, the effect of the invention of Claim 8 or 9 can be improved further.

  It should be noted that each of the relationships described in claims 1, 2, 3, 4, 8 or 9 or the predetermined relationship and linear function equation described in claims 5 or 10 may be stored in advance in a memory as data. Good. Moreover, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

Hereinafter, each embodiment of the present invention will be described with reference to the drawings.
(First embodiment)
1 and 2 show a first embodiment of a combustible gas detection device according to the present invention, and this combustible gas detection device is used, for example, to detect hydrogen gas leaking from a fuel cell.

  The combustible gas detection device includes an apparatus unit 100 (see FIG. 1) and a control circuit 200 (see FIG. 2). As shown in FIG. 1, the device unit 100 includes a casing 110, a lid 120, and a connector 130. The casing 110 has both casing members 111 and 112, and both the casing members 111 and 112 are fitted to each other at their respective openings to constitute the casing 110.

  Here, the casing member 111 includes a gas introduction tube 113, and this gas introduction tube 113 extends cylindrically outward from the center of the bottom wall of the casing member 111, and is It opens to the direction. In FIG. 1, reference numeral 115 denotes an O-ring. This O-ring may be abolished depending on the attachment location of the combustible gas detection device.

  As shown in FIG. 1, the lid 120 is coaxially fitted from the inside of the casing member 111 into the gas introduction tube 113, and the lid 120 is a cylinder as shown in FIGS. 1 and 3. A member 121 is provided. As shown in FIG. 1, the cylindrical member 121 is coaxially fitted in the small diameter hole portion of the gas introduction tube 113 at the bottom wall side cylindrical portion, and the cylindrical member 121 has an annular bottom wall. At 122 (refer to FIG. 3), the gas inlet 114 is seated from the inner surface side. The cylindrical member 121 is opened outward through the gas inlet 114 in the hollow portion of the annular bottom wall 122.

  The cylindrical member 121 is hermetically sealed with an adhesive through an annular seal (not shown) such as packing in a large-diameter hole formed on the proximal end side of the gas introduction tube 113 at the proximal end-side annular flange portion 123. It is adhesively fitted. Note that instead of adhering with an adhesive via an annular seal as described above, welding may be used.

  Further, the lid 120 includes a water repellent filter 124 and a metal mesh 125 provided in the cylindrical member 121. The water repellent filter 124 is sandwiched between the annular bottom wall 122 of the cylindrical member 121 and the annular plate spacer 126 at the outer peripheral portion thereof. The water repellent filter 124 includes the gas inlet 114 and the cylindrical member. Intrusion of water droplets and intrusion of dust from the hollow portion of the annular bottom wall 122 into the spacer 126 is prevented.

  The metal mesh 125 is sandwiched between the annular plate spacer 126 and the annular bottom wall of the cylindrical spacer 127 at the outer periphery thereof. The metal mesh 125 plays the following role. That is, when a heating resistor 330 (see FIG. 4), which will be described later, is energized, a current flows through the heating resistor and the temperature of the heating resistor exceeds the lower limit explosion temperature of hydrogen gas. When ignited inside, the wire mesh 125 prevents a fire from escaping from the inside of the spacer 127 to the outside.

  The spacer 127 is coaxially press-fitted into the cylindrical portion of the cylindrical member 121, and the metal mesh 125, the annular spacer 126, and the water repellent filter 124 are connected to the annular bottom wall of the cylindrical member 121. It is fixed on the inner surface of 122.

  The connector 130 is assembled to the right side wall of the casing member 111 shown in FIG. 1, and the connector 130 is connected to the casing 111 by a plurality of connector pins 131 (only one connector pin is shown in FIG. 1). It is electrically connected to a wiring pattern portion (not shown) of the wiring board 180 through the right side wall. The connector 130 may be integrated with the casing member 111.

  As shown in FIGS. 1 and 3, the apparatus unit 100 includes a detection element 300, a laying plate 140, and a mounting plate 150, and the detection element 300 includes a laying plate 140 as shown in FIGS. 1 and 3. Along with the mounting plate 150, the cylindrical member 121 is supported. As shown in FIG. 3, the attachment plate 150 is coaxially and airtightly fixed in the annular flange portion 123 of the cylindrical member 121 at the outer peripheral portion 151 having an L-shaped cross section. The laying plate 140 is made of a material having a low thermal conductivity, and this laying plate 140 is bonded to the central portion of the outer surface (the surface on the spacer 127 side) of the mounting plate 150 with an adhesive. The detection element 300 is adhered to the outer surface (surface on the spacer 127 side) of the laying plate 140 with an adhesive, and is exposed in the spacer 127.

  Further, as shown in FIGS. 1 and 3, the device unit 100 includes a plurality of pin-shaped terminals 160 to 164 and a heater 170, and each of the terminals 160 to 164 is inserted into the mounting plate 150. . As shown in FIGS. 1 and 3, the heater 170 is electrically connected between the tip portions of both terminals 160 and 163, and the heater 170 is detected by the power supply via both terminals 160 and 163. Is heated and the condensation and impurities adhering to the detection element 300 are dried and disappeared.

  In particular, when a resistance temperature detector that detects the ambient temperature is provided on the surface of the detection element 300, the temperature detected by the resistance temperature detector is actually caused by condensation or impurities attached to the surface of the detection element 300. This has the effect of preventing the occurrence of a situation in which the temperature is lower than the ambient temperature and the temperature detection accuracy is lowered. In addition, the detection element 300 is electrically connected to each front-end | tip part of the terminals 161, 162, and 164 by wire bonding in each electrode film 370 (refer FIG. 4) mentioned later.

  The wiring board 180 is provided in the casing 110, and the wiring board 180 is supported by the opening end of the casing member 111 at the outer periphery thereof. Each terminal 160 to 164 is fitted to the wiring board 180 at its base end portion and is electrically connected to the wiring pattern portion of the wiring board 180.

  As shown in FIG. 1, the control circuit 200 is mounted on the back surface (the lower side in FIG. 1) of the wiring board 180 in the casing 110, and the control circuit 200 is connected to the wiring board 180. It is electrically connected to the connector pin 131 of the connector 130 and each of the terminals 160 to 164 via the pattern portion.

  Next, the configuration of the detection element 300 described above will be described with reference to FIGS. The detection element 300 is manufactured using a micromachining technique, and the detection element 300 includes a silicon semiconductor substrate 310 and upper and lower insulating layers 320 as shown in FIG. The upper insulating layer 320 is formed on the surface of the semiconductor substrate 310, while the lower insulating layer 320 is formed on the back surface of the semiconductor substrate 310. The upper insulating layer 320 includes a silicon oxide film 321 formed on the surface of the semiconductor substrate 310 and a silicon nitride film 322 stacked on the silicon oxide film 321. The lower insulating layer 320 includes a silicon oxide film 321 formed on the back surface of the semiconductor substrate 310 and a silicon nitride film 322 stacked on the silicon oxide film 321.

  Here, the left and right concave portions 311 shown in FIG. 4 are formed in the semiconductor substrate 310 at intervals on the back surface side of the upper insulating layer 320. In addition, the lower insulating layer 320 is removed at portions corresponding to the respective recesses 311 and formed as openings of the respective recesses 311. As a result, the upper insulating layer 320 is exposed to the outside through the opening of each recess 311 at each corresponding back surface of the back surface corresponding to each recess 311. The semiconductor substrate 310 constitutes a substrate portion 312 at a portion other than each recess 311.

  Further, as shown in FIGS. 4 and 5, the detection element 300 includes left and right heat generating resistors 330 and left, center, and right wiring films 340. The left heating resistor 330 is spirally formed on a portion of the surface of the upper insulating layer 320 corresponding to the left recess 311, while the right heating resistor 330 is formed on the right side of the surface of the upper insulating layer 320. A spiral shape is formed on a portion corresponding to the recess 311. In the first embodiment, both the heating resistors 330 are formed of a platinum resistance material together with each wiring film 340 described later.

  As shown in FIG. 4, the left wiring film 340 is located on the left side of the surface of the upper insulating layer 320 corresponding to the substrate portion 312 of the semiconductor substrate 310. As shown in FIG. It is formed so as to be integrated with one end of 330. The central wiring film 340 is located on the central portion of the surface of the upper insulating layer 320 so as to correspond to the substrate portion 312 of the semiconductor substrate 310, and has the other end of the left heating resistor 330 and one end of the right heating resistor 330. It is formed so as to be integrated. The right wiring film 340 is formed on the right side of the surface of the upper insulating layer 320 so as to correspond to the substrate portion 312 of the semiconductor substrate 310 and to be integrated with the other end of the right heating resistor 330. Has been.

  Further, as shown in FIGS. 4 and 5, the detection element 300 includes an inner protective layer 350 and an outer protective layer 360, and left, center, and right electrode films 370. It is formed on the surface of the upper insulating layer 320 so as to cover each wiring film 340 and each heating resistor 330. The outer protective layer 360 is formed on the inner protective layer 350 in a stacked form.

  Here, in the inner protective layer 350 and the outer protective layer 360, the contact holes 361 on the left side, the central side, and the right side are provided with the wiring films 340 on the left side, the central side, and the right side of the inner protective layer 350 and the outer protective layer 360, respectively. It is formed in each part corresponding to. As a result, the left, center, and right wiring films 340 are exposed outwardly through the left, center, and right contact holes 361 on the surface. The left, central and right electrode films 370 are formed on the left, central and right wiring films 340 through the left, central and right contact holes 361.

  In the first embodiment, in the detection element 300, the left heating resistor 330, the left and center wiring films 340, and the left and center electrode films 370 mainly serve as the left heat-conducting gas detection unit 380. The right heating resistor 330, the central and right wiring films 340, and the central and right electrode films 370 mainly constitute the right heat conduction type gas detection unit 380.

  Further, as shown in FIG. 5, the detection element 300 includes a resistance temperature detector 390, and the resistance temperature detector 390 is a resistance temperature detector material containing platinum (Pt). On the upper side in the figure, a thin film resistor is formed between the upper insulating layer 320 and the inner protective layer 350. Thereby, the resistance temperature detector 390 detects the temperature (hereinafter also referred to as environmental temperature) of the atmosphere to be detected in which the gas detection device is arranged. In the first embodiment, the temperature resistance coefficient of the resistance temperature detector 390 is substantially the same as the temperature resistance coefficient of both the heating resistors 330.

  Each electrode film 391 is formed on both left and right ends of the resistance temperature detector 390 in each contact hole (not shown) formed in the inner protective layer 350 and the outer protective layer 360. The resistance temperature detector 390 is connected to the wiring pattern portion of the wiring board 180 via both terminals 391 and a terminal (not shown).

  Next, the configuration of the control circuit 200 described above will be described with reference to FIG. The control circuit 200 includes both bridge circuits 210 and 220. As shown in FIG. 2, the bridge circuit 210 includes a heating resistor 211 for gas detection and fixed resistors 212, 213, and 214. It is configured to form a bridge circuit.

  In the bridge circuit 210, the gas detection heating resistor 211 is configured by a left heating resistor 330 that constitutes the left heat conduction type gas detection unit 380 of the detection element 300. Here, the heating resistor 211 is grounded at one end, and the other end of the heating resistor 211 is grounded via a fixed resistor 212, a fixed resistor 213, and a fixed resistor 214.

  Thus, the bridge circuit 210 includes a constant temperature control circuit between the common terminal (one side power supply terminal) of the heating resistor 211 and the fixed resistor 214 and the common terminal (other side power supply terminal) of the two fixed resistors 212 and 213. Operates in response to a control voltage from 230. Under this operation, the bridge circuit 210 is connected to a common terminal (one output terminal of the bridge circuit 210) of the heating resistor 211 and the fixed resistor 212 based on a change in the resistance value of the gas detection heating resistor 211. A potential difference (representing the concentration of hydrogen gas) generated between the common terminals of the fixed resistors 213 and 214 (the other output terminal of the bridge circuit 210) is output.

  The constant temperature control circuit 230 maintains the resistance value of the gas detection heating resistor 211 at a value corresponding to a constant temperature (for example, 150 (° C.)) according to the output (described later) of the operational amplifier circuit 250. The control voltage to the bridge circuit 210 is formed based on the output voltage of the built-in DC power supply (not shown). The resistance value of the heating resistor 211 (330) increases (or decreases) in accordance with the control voltage or the temperature rise (or decrease) of the heating resistor 211.

  Further, as shown in FIG. 2, the bridge circuit 220 is configured to form a Wheatstone bridge circuit with the gas detection heating resistor 221 and the fixed resistors 222, 223, and 224. In the bridge circuit 220, the gas detection heating resistor 221 is configured by a right heating resistor 330 that constitutes the right heat conduction type gas detection unit 380 of the detection element 300. Here, the heating resistor 221 is grounded at one end, and the other end of the heating resistor 221 is grounded via a fixed resistor 222, a fixed resistor 223, and a fixed resistor 224.

  Thus, the bridge circuit 220 includes the constant temperature control circuit 240 between the common terminal (one side power supply terminal) of the heating resistor 221 and the fixed resistor 224 and the common terminal (other side power supply terminal) of both the fixed resistors 222 and 223. Operates in response to a control voltage from. Under this operation, the bridge circuit 220 is connected to the common terminal (one side output terminal of the bridge circuit 220) of the heating resistor 221 and the fixed resistor 222 based on the change in the resistance value of the gas detection heating resistor 221. A potential difference (representing the hydrogen gas concentration) generated between the common terminals of the fixed resistors 223 and 224 (the other output terminal of the bridge circuit 220) is output.

  The constant temperature control circuit 240 maintains the resistance value of the gas detection heating resistor 221 at a value corresponding to a constant temperature (for example, 330 (° C.)) according to the output (described later) of the operational amplifier circuit 260. The control voltage to the bridge circuit 220 is formed based on the output voltage of the built-in DC power supply (not shown). Note that the resistance value of the heating resistor 221 increases (or decreases) in accordance with a control voltage from the constant temperature control circuit 240 or an increase (or decrease) in the temperature of the heating resistor 211. The output of each control voltage of both constant temperature control circuits 230 and 240 is started in synchronization with the power switch 281 being turned on.

  The operational amplifier circuit 250 amplifies a potential difference generated between both output terminals of the bridge circuit 210 and outputs the amplified potential difference to the constant temperature control circuit 230 and the microcomputer 270. The operational amplifier circuit 260 amplifies a potential difference generated between both output terminals of the bridge circuit 220 and outputs the amplified potential difference to the constant temperature control circuit 240 and the microcomputer 270.

  The microcomputer 270 operates with power supplied from the DC power supply 280 via the power switch 281 and executes the computer program according to the flowchart shown in FIG. During this execution, the microcomputer 270 performs various processes necessary for calculating the hydrogen gas concentration based on the detected environment temperature of the resistance temperature detector 390 and the output potential differences of the two operational amplifier circuits 250 and 260. The computer program is stored in the ROM of the microcomputer 270 so as to be readable by the microcomputer.

  In this 1st Embodiment comprised as mentioned above, the apparatus unit 100 of the said combustible gas detection apparatus shall be arrange | positioned in to-be-detected atmosphere. In this state, when hydrogen gas leaking into the detected atmosphere flows into the gas introduction tube 113 of the apparatus unit 100 from the gas introduction port 114, the hydrogen gas is removed from the water repellent filter 124 and the wire mesh. 125 and flows into the cylindrical spacer 127, and then reaches the detection element 300. Accordingly, the hydrogen gas flows near the surface of the outer protective layer 360 so as to come into contact with the detection element 300.

  In such a state, when the power switch 281 is turned on and the microcomputer 270 is supplied with power from the DC power supply 280, the microcomputer 270 starts executing the computer program according to the flowchart of FIG. With this start, in step 400, a soft timer built in the microcomputer 270 is activated. Therefore, the soft timer starts timing by the reset activation.

  Next, the determination of NO is repeated in step 410 until the time measured by the soft timer has exceeded a predetermined waiting time. The predetermined waiting time is the temperature of the heating resistor 211 is controlled to be the constant temperature (150 (° C.)) under the control of the constant temperature control circuit 230 and the heating resistance is controlled under the control of the constant temperature control circuit 240. The time (for example, 0.5 (second)) required for the body 221 to reach the constant temperature (330 (° C.)) is set.

  Further, in synchronization with the power switch 281 being turned on, the output of each control voltage by the two constant temperature control circuits 230 and 240 is started. Accordingly, when the constant temperature control circuit 230 outputs a control voltage between both power supply terminals of the bridge circuit 210, the bridge circuit 210 is energized with the control voltage. The potential difference output from both output terminals of the bridge circuit 210 is amplified by the operational amplifier circuit 250 and fed back to the constant temperature control circuit 230. Accordingly, the heating resistor 211 is controlled at a constant temperature so that the resistance value of the heating resistor 211 maintains a value corresponding to the constant temperature (150 (° C.)) while the determination of NO in step 410 is repeated. The energization is controlled by the circuit 230.

  When the constant temperature control circuit 240 outputs a control voltage between both power supply terminals of the bridge circuit 220, the bridge circuit 220 is energized with the control voltage. The potential difference output from both output terminals of the bridge circuit 220 is amplified by the operational amplifier circuit 260 and fed back to the constant temperature control circuit 240. Therefore, during the repetition of the determination of NO in step 410, the heating resistor 221 is controlled at a constant temperature so that the resistance value of the heating resistor 221 maintains a value corresponding to the constant temperature (330 (° C.)). The energization is controlled by the circuit 240.

  Thereafter, when the time measured by the soft timer has passed the predetermined waiting time, YES is determined in step 410 and the variable N = 0 is cleared in the next step 411. Next, in step 420, input processing of the respective amplified potential differences of the operational amplifier circuits 250 and 260 and the environmental temperature (hereinafter referred to as environmental temperature T) detected by the resistance temperature detector 390 is performed.

  Next, in step 430, the voltage difference Vd is calculated. Here, the voltage difference Vd refers to a difference between the terminal voltage of the heating resistor 221 and the terminal voltage of the heating resistor 211. In the calculation process in step 430, the voltage difference Vd is calculated based on the difference between the amplified potential difference from the operational amplifier circuit 260 and the amplified potential difference from the operational amplifier circuit 250.

  Thereafter, in step 431, the voltage ratio Rv is calculated. Here, the voltage ratio Rv refers to the ratio of the terminal voltage of the heating resistor 221 to the terminal voltage of the heating resistor 211. In the processing of step 431, the voltage ratio Rv is calculated based on the ratio of the amplified potential difference from the operational amplifier circuit 260 to the amplified potential difference from the operational amplifier circuit 250.

  When the calculation of the voltage ratio is completed in this way, in the next step 432, the relative humidity H in the detected atmosphere is calculated. In this calculation process, the relative humidity H at each environmental temperature is based on a characteristic (hereinafter also referred to as a relative humidity-voltage ratio characteristic) representing an approximate linear relationship between the relative humidity H and the voltage ratio Rv shown in FIG. Calculated from Rv.

  In the present embodiment, the approximate relationship increases in accordance with an increase in the relative humidity in the detected atmosphere and an increase in the environmental temperature (or a decrease in the relative humidity in the detected atmosphere and a decrease in the environmental temperature). (Or decrease). In other words, the above approximate relationship is a relationship in which the relative humidity in the detected atmosphere increases (or decreases) in response to an increase in the voltage ratio and an increase in the environmental temperature (or a decrease in the voltage ratio and a decrease in the environmental temperature). Say. However, the relative humidity-voltage ratio characteristic is stored in advance in the ROM of the microcomputer 270 as data together with a linear function equation and map data described later. Note that the storage of the data is not limited to the ROM, and may be performed by an appropriate memory.

  Here, the grounds for introducing the relative humidity-voltage ratio characteristic will be described. The detection element 300 is arranged in the detection atmosphere, and the hydrogen gas concentration D (hereinafter also referred to as hydrogen gas concentration D) contained in the detection atmosphere is the terminal voltage of the right heating resistor 330 of the detection element 300. The relative humidity in the detected atmosphere is related to the voltage difference Vd with respect to the terminal voltage of the left heating resistor 330 (hereinafter also referred to as the voltage difference Vd between the two heating resistors 330). Measurement was performed using H as a parameter. However, the environmental temperature T of the detected atmosphere is, for example, 80 (° C.). In addition, the temperature of the left heating resistor 330 is maintained at 150 (° C.), while the temperature of the right heating resistor 330 is maintained at 330 (° C.).

  As a result of the measurement, a plurality of graphs were obtained using relative humidity H as a parameter, as illustrated in FIG. However, in FIG. 8, the graph 1 shows the relationship between the voltage difference Vd between the two heating resistors 330 and the hydrogen gas concentration D when the relative humidity H = 0 (% RH). Graph 2 shows the relationship between the voltage difference Vd between the heating resistors 330 and the hydrogen gas concentration D when the relative humidity H = 45 (% RH), and graph 3 shows the relative humidity H = 100 (% The relationship between the voltage difference Vd between the two heating resistors 330 and the hydrogen gas concentration D at the time of (RH) is shown. Note that such a relationship can be obtained substantially similarly at relative humidity other than H = 0 (% RH), 45 (% RH), and 100 (% RH).

  Therefore, according to each graph of FIG. 8, the relationship between the voltage difference Vd between the two heating resistors 330 and the hydrogen gas concentration D is based on the relative humidity H as a parameter under the environment temperature T = 80 (° C.). It can be seen that this is represented by a linear graph that translates along the vertical axis of the orthogonal coordinate plane of FIG. In other words, it can be seen that the voltage difference Vd between the two heating resistors 330 is directly proportional to the hydrogen gas concentration D, although the relative humidity H is a parameter.

  Here, in FIG. 8, the gradients of the respective graphs are the same, and are mainly determined by the environmental temperature T in the detected atmosphere. Therefore, if this gradient is A, each graph can be expressed by a linear function equation Vd = A · D + B. However, Vd is an independent variable of the said linear function formula, D is a dependent variable of the said linear function formula, B shows the intercept of the said linear function formula. This intercept B represents the intersection of the linear function equation with the vertical axis of the orthogonal coordinate plane of FIG. 8, that is, the voltage difference between the two heating resistors 330 when D = 0 (%).

  Further, on the assumption of each graph of FIG. 8, the relative humidity H in the detected atmosphere is a voltage ratio Rv of the terminal voltage of the left heating resistor 330 to the terminal voltage of the right heating resistor 330 (hereinafter, both heating resistors). And a voltage ratio Rv of 330). As a result of this measurement, the graph 4 shown in FIG. 7 was obtained. According to this graph 4, it can be seen that the relative humidity H has an approximate linear relationship with the voltage ratio Rv of both the heating resistors 330.

  Therefore, the relationship between the relative humidity H specified in the graph of FIG. 7 and the voltage ratio Rv of both the heating resistors 330 is the voltage difference Vd between the heating resistors 330 specified in each graph of FIG. The relationship between the concentration D and the concentration D was examined.

  According to FIG. 8, the relationship between the voltage difference Vd between the two heating resistors 330 and the hydrogen gas concentration D parameters the relative humidity H. Therefore, the intercept B, which is the intersection of the graphs 1, 2, and 3 with the vertical axis of FIG. Here, the intercept B and the relative humidity H have a cubic function relationship and cannot be easily derived. However, the relationship between the intercept B and the relative humidity H is obtained as map data by actual measurement.

  Further, as can be seen from the graph 4 in FIG. 7, the relative humidity H is uniquely determined by the environmental temperature T and the voltage ratio Rv of both the heating resistors 330. Therefore, it can be seen that the intercept B corresponding to the determined relative humidity H is uniquely determined from the map data.

  As described above, the hydrogen gas concentration D can be calculated by using the equation D = (Vd−B) / A converted from the linear function equation Vd = A · D + B. Here, if Va = (Vd−B), D is directly proportional to Va. Therefore, D is calculated based on Va from D = Va / A, and the graph shown in FIG. 9 is obtained. . Therefore, the relative humidity-voltage ratio characteristic specified in the graph of FIG. 7 was introduced.

  As described above, when the calculation of the voltage ratio Rv and the voltage difference Vd is completed in step 430 and step 431, the relative humidity H is calculated in step 432. In this calculation process, the relative humidity H is calculated based on the voltage ratio Rv using the relative humidity-voltage ratio characteristics (stored in the ROM) of FIG.

  Next, in step 433, the intercept B is determined from the calculated relative humidity H in step 432 based on the map data (stored in the ROM). In step 434, the gradient A is calculated based on the environmental temperature T in step 420. However, the gradient A has a certain relationship with the environmental temperature. The gradient A is preferably calculated in consideration of the type of detection gas.

  Thereafter, in step 440, the voltage difference Vd, the gradient A, and the intercept B are obtained by using the equation D = (Vd−B) / A, in which the hydrogen gas concentration D is converted from the linear function equation Vd = A · D + B. Calculated based on The conversion formula D = (Vd−B) / A is stored in advance in the ROM of the microcomputer 270.

  Next, in step 450, N = N + 1 = 1 is added and updated. In step 460, it is determined whether or not the variable N = predetermined number of times. Since N = 1 at the current stage, NO is determined in step 460 based on N = 1 <No (= 10), and the computer program returns to step 420.

  Thereafter, the cyclic process through steps 420 to 460 is repeated until the addition update value of the variable N in step 450 becomes N = No. Thereafter, if N = No and the determination in step 460 is YES, in the next step 470, the average value of all the hydrogen gas concentrations calculated in step 440 is calculated and output as the detected hydrogen gas concentration. .

  As described above, according to the first embodiment, the voltage difference Vd between the terminal voltage of the heating resistor 211 and the terminal voltage of the heating resistor 221 generated in the above-described energization control state by the constant temperature control circuits 230 and 240. Is assumed to be an independent variable, the concentration D of the combustible gas in the atmosphere to be detected is a dependent variable, and a linear function equation Vd = A · D + B that is established with the relative humidity H and the environmental temperature T as parameters is assumed.

  Further, in addition to the map data representing the cubic function relationship established between the intercept B of the linear function equation and the relative humidity H, the heating resistor generated in the energization control state by the constant temperature control circuits 230 and 240 The approximate linear relationship (see FIG. 7) established at the ambient temperature T between the voltage ratio Rv of the terminal voltage 221 to the terminal voltage of the heating resistor 211 and the relative humidity H in the atmosphere to be detected is also used. The humidity H is calculated from the approximate linear relationship based on the determined voltage ratio Rv, the intercept B of the linear function equation is determined from the map data based on the determined relative humidity H, and the gradient A of the linear function equation is It is calculated based on the environmental temperature T.

  The concentration D of the combustible gas is the voltage difference Vd between the terminal voltage of the heating resistor 221 and the terminal voltage of the heating resistor 211 generated in the energization controlled state by the constant temperature control circuits 230 and 240, and the determined intercept B. And based on the linear function equation using the calculated gradient A, combustible gas is detected based on the calculated concentration.

From the above, considering that the thermal conductivity of the atmosphere to be detected fluctuates according to the relative humidity in the atmosphere to be detected, combustible gas is detected by processing so as to eliminate the influence of this fluctuation. As a result, high detection accuracy can be secured. Here, since the temperature resistance coefficients of the two heating resistors 211 and 221 are substantially the same as the temperature resistance coefficient of the temperature measuring resistor 390 as described above, the resistance values and the temperature measuring resistors of the two heating resistors 211 and 221 are the same. The resistance value of 390 shows almost the same change characteristic at the common environmental temperature. Accordingly, calculation and detection of the combustible gas concentration can be performed with higher accuracy. In addition, since the resistance temperature detector 390 is a thin film resistor, the resistance value of the thin film resistor can change rapidly as the environmental temperature changes.
(Second Embodiment)
10 and 11 show a second embodiment of the combustible gas detection device according to the present invention. In the second embodiment, as shown in FIG. 10, the microcomputer 270 replaces the constant temperature control circuit 230 with the output control voltage of the constant temperature control circuit 230 in the bridge circuit 210 in the first embodiment. In addition to direct output, the output control voltage of the constant temperature control circuit 240 is directly output to the bridge circuit 220 instead of the constant temperature control circuit 240. Accordingly, both constant temperature control circuits 230 and 240 are abolished in the second embodiment.

  In the second embodiment, the microcomputer 270 is changed to execute the computer program according to the flowchart shown in FIG. 11 instead of the flowchart of FIG. Other configurations are the same as those in the first embodiment.

  In the second embodiment configured as described above, it is assumed that the combustible gas detection device is disposed in the detected atmosphere as described in the first embodiment.

  In such a state, when the power switch 281 is turned on and the microcomputer 270 is supplied with power from the DC power supply 280, the microcomputer 270 starts executing the computer program according to the flowchart of FIG. Along with this start, in step 480, constant temperature control processing of both the heating resistors 211 and 221 is performed.

  In this constant temperature control process, the control voltage maintains the resistance value of the gas detection heating resistor 211 at a value corresponding to a constant temperature (for example, 150 (° C.)) according to the output of the operational amplifier circuit 250. Then, it is formed based on the output voltage of the DC power supply 280 and is output to the bridge circuit 210. Further, in accordance with the output of the operational amplifier circuit 260, another control voltage is controlled so as to maintain the resistance value of the gas detection heating resistor 221 at a value corresponding to a constant temperature (eg, 330 (° C.)). Based on the output voltage of the power source 280, it is formed and output to the bridge circuit 220.

  Accordingly, the heating resistor 211 is maintained at the constant temperature (for example, 150 (° C.)) and the heating resistor 221 is maintained at the constant temperature (for example, 330 (° C.)).

In such a state, the following processing from step 411 is performed in the same manner as in the first embodiment. As a result, the same effect as the first embodiment can be achieved.
(Third embodiment)
FIGS. 12-18 has shown 3rd Embodiment of the combustible gas detection apparatus based on this invention. In the third embodiment, in the detection element 300 (see FIGS. 4 and 5) described in the first embodiment, a temperature measuring resistor 500 is used instead of the right heating resistor 330. (See FIGS. 12 and 13). Accordingly, in the third embodiment, the resistance temperature detector 390 described in the first embodiment is abolished.

  The resistance temperature detector 500 has a serpentine shape with a resistance temperature material containing platinum (Pt) on a portion corresponding to the right recess 311 in the surface of the upper insulating layer 320 described in the first embodiment. Is formed. Thereby, the resistance temperature detector 500 detects the environmental temperature of the atmosphere to be detected in which the gas detection device is arranged, similarly to the resistance temperature detector 390 described in the first embodiment.

  Here, the temperature measuring resistor 500 is formed at both ends so as to be integrated with both the central and right wiring films 340 described in the first embodiment. In the third embodiment, the temperature resistance coefficient of the resistance temperature detector 500 is substantially the same as the temperature resistance coefficient of the left heating resistor 330 described in the first embodiment.

  In the third embodiment, a control circuit shown in FIG. 14 is employed instead of the control circuit 200 described in the first embodiment. This control circuit employs a temperature control circuit 231 instead of the constant temperature control circuit 230 described in the first embodiment, and also includes a bridge circuit 220 and a constant temperature control circuit 240 described in the first embodiment. The operational amplifier circuit 260 is abolished.

  The temperature control circuit 231 is configured to generate a pulsed control voltage (see FIG. 16) at a predetermined pulse period under the control of the microcomputer 270. Here, the control voltage becomes a low level L (> 0) in the first half of the pulse period (for example, t = t0 to t1 in FIG. 16), and the second half of the pulse period (for example, in FIG. 16). At t = t1 to t2), the high level H (> L) is generated. The pulse period is, for example, 20 (seconds), and the first half and the second half of the pulse period are 10 (seconds), respectively. The reason why the level of the control voltage is equal to or higher than the low level L (> 0) is to keep the heating resistor 211 in an energized state as will be described later. This is useful for facilitating failure detection such as disconnection or short circuit of the heating resistor 211.

  In the third embodiment, the microcomputer 270 described in the first embodiment is changed to execute the computer program in accordance with the flowchart shown in FIG. 15 instead of the flowchart in FIG. Yes. Here, the flowchart of FIG. 15 is a modification of the flowchart (see FIG. 11) described in the second embodiment.

  In the third embodiment, in the bridge circuit 210 (see FIG. 2) described in the first embodiment, both fixed resistors 215 and 216 and an analog changeover switch 290 are additionally provided as shown in FIG. The adopted structure is adopted.

  As shown in FIG. 14, the analog changeover switch 290 includes a movable contact 291 and fixed contacts 292, 293, and 294 that selectively switch on the movable contact 291. Here, the movable contact 291 is grounded via the fixed resistor 213, the fixed resistor 212, and the fixed resistor 211 described in the first embodiment. The fixed contact 292 is grounded via a fixed resistor 214. The fixed contact 293 is grounded via the fixed resistor 215, and the fixed contact 294 is grounded via the fixed resistor 216.

  Accordingly, the analog changeover switch 290 controls the movable contact 291 to each of the fixed contacts 292, 293, and 294 in synchronization with the level change of the control voltage under the control of the microcomputer 270 described in the first embodiment. Switch to one of the following. It should be noted that, hereinafter, the input state of the movable contact 291 to the fixed contact 292 is referred to as a first input state, and the input state of the movable contact 291 to the fixed contact 293 is referred to as a second input state, to the fixed contact 294 of the movable contact 291. The input state is referred to as a third input state.

  Here, when the control voltage is at the low level L, the analog changeover switch 290 is controlled by the microcomputer 270 so as to be in the first on state. Accordingly, in the bridge circuit 210, the fixed resistor 214 among the fixed resistors 214 to 216 is connected in series to the fixed resistor 213.

  When the control voltage changes from the low level L to the high level H, the analog changeover switch 290 is controlled by the microcomputer 270 so as to switch to either the second or third input state. Accordingly, in the bridge circuit 210, either one of the fixed resistors 215 and 216 is connected in series to the fixed resistor 213.

  In the third embodiment, in the bridge circuit 210, the resistance values of the fixed resistors 214 to 216 are set as follows. That is, when the fixed resistor 214 is connected in series to the fixed resistor 213 in the low level state of the control voltage, the temperature of the heating resistor 211 (hereinafter also referred to as resistor temperature C) is C = C1 (see FIG. 17). The resistance value of the fixed resistor 214 (hereinafter also referred to as the resistance value R1) is set so that a current maintained at () (hereinafter also referred to as the current I1) flows through the heating resistor 211.

  Further, when the fixed resistor 215 is connected in series to the fixed resistor 213 in the high level state of the control voltage, a current that maintains the resistor temperature C at C = C2 (see FIG. 17) (hereinafter also referred to as a current I2). The resistance value of the fixed resistor 215 (hereinafter, also referred to as the resistance value R2) is set so as to flow through the heating resistor 211.

  Further, when the fixed resistor 216 is connected in series to the fixed resistor 213 in the high level state of the control voltage, a current that maintains the resistor temperature C at C = C3 (see FIG. 17) (hereinafter also referred to as a current I3). The resistance value of the fixed resistor 216 (hereinafter, also referred to as the resistance value R3) is set so as to flow through the heating resistor 211.

  Here, the resistance values of the fixed resistors 214 to 216 have a relationship of R1 <R3 <R2. Therefore, the resistor temperature C has a relationship of C1 <C3 <C2 as shown in FIG.

  The resistor temperature C = C1 is higher than 100 (° C.). As described above, the temperature of the heating resistor 211 is maintained higher than 100 (° C.) by always energizing the heating resistor 211 by setting the control voltage level to the low level L (> 0) or more. In order to prevent moisture from adhering to the heating resistor 211, such as condensed water. This prevention is useful for smoothing the temperature rise of the heating resistor 211. Other configurations are the same as those in the first embodiment.

  In the third embodiment configured as described above, it is assumed that the combustible gas detection device is disposed in the detected atmosphere as described in the first embodiment.

  In such a state, when the power switch 281 is turned on and the microcomputer 270 is supplied with power from the DC power supply 280, the microcomputer 270 starts executing the computer program according to the flowchart of FIG. With this start, in step 412, the variable N = 0 is cleared. At this time, it is assumed that time t = t0.

  Next, the circulation processing of both step 481 and step 413 is performed. That is, in step 413, it is determined whether or not the temperature cycle τ has elapsed. In the third embodiment, the temperature period τ corresponds to twice the pulse period of the control voltage (for example, t = t0 to t4). Thus, until the temperature cycle τ elapses, the determination of NO is repeated in step 413, so that the circulation processing in both steps 481 and 413 is performed as described above.

  During such circulation processing, in step 481, the temperature control processing of the heating resistor 211 of the bridge circuit 210 in the third embodiment is performed. Specifically, the temperature control circuit 231 is controlled by the microcomputer 270 to generate a control voltage in a pulse shape with the above pulse period. Here, the control voltage maintains a low level L at t = t0 to t1, maintains a high level H at t = t1 to t2, maintains a low level L at t = t2 to t3, It changes so as to maintain the high level H from t = t3 to t4.

  The analog changeover switch 290 switches the movable contact 291 to any one of the fixed contacts 292 to 294 in synchronization with the level change of the control voltage under the control of the microcomputer 270. Specifically, the analog changeover switch 290 enters the first on state at time t = t0, enters the second on state at t = t1, enters the first on state at t = t2, and sets t = t3. The third charging state is set at t1, and the first charging state is set at t = t4.

  Thus, as described above, when t = t0, the analog changeover switch 290 enters the first input state, and when the control voltage from the temperature control circuit 231 is output to the bridge circuit 210 at the low level L, the bridge In the circuit 210, the fixed resistor 214 is connected in series with the fixed resistor 213, and the current I1 flows through the heating resistor 211 to maintain the temperature of the heating resistor at C = C1.

  Next, as described above, when the analog changeover switch 290 enters the second input state at time t = t1 and the fixed resistor 215 is connected in series to the fixed resistor 213 in the bridge circuit 210, the temperature control circuit 231 The control voltage is output to the bridge circuit 210 at the high level H, and the current I2 flows through the heating resistor 211 to maintain the temperature of the heating resistor at C = C2.

  Here, as described above, when the control voltage from the temperature control circuit 231 is output to the bridge circuit 210 at the high level H, the bridge circuit 210 includes the common terminals of the fixed resistors 213 and 215, the fixed resistors 212, and A potential difference V1 (see t = t1 to t2 in FIG. 18) is output from the common terminal of the heating resistor 211 based on the resistance value R2 of the fixed resistor 215 and the resistance value of the heating resistor 211. Then, this potential difference V1 is amplified by the operational amplifier circuit 250 and output to the microcomputer 270 as the amplified potential difference VA1. Thus, the amplified potential difference VA1 output to the microcomputer 270 is stored in the RAM of the microcomputer 270 during the next t = t2 to t3.

  Thereafter, as described above, at time t = t2, the analog changeover switch 290 enters the first input state, and when the fixed resistor 214 is again connected in series to the fixed resistor 213 in the bridge circuit 210, the temperature control circuit The control voltage from H.231 is output to the bridge circuit 210 at the low level L, and the current I1 flows through the heating resistor 211 to maintain the temperature of the heating resistor at C = C1.

  Next, as described above, at time t = t3, the analog changeover switch 290 enters the third input state, and when the fixed resistor 216 is connected in series to the fixed resistor 213 in the bridge circuit 210, the temperature control circuit 231 The control voltage is output to the bridge circuit 210 at the high level H, and the current I3 flows through the heating resistor 211 to maintain the temperature of the heating resistor at C = C3.

  Here, as described above, when the control voltage from the temperature control circuit 231 is output to the bridge circuit 210 at the high level H at time t = t3, the bridge circuit 210 is common to both the fixed resistors 213 and 216. A potential difference V2 (see t = t3 to t4 in FIG. 18) between the terminal and the common terminal of the fixed resistor 212 and the heating resistor 211 based on the resistance value R3 of the fixed resistor 216 and the resistance value of the heating resistor 211. ) Is output. Then, this potential difference V2 is amplified by the operational amplifier circuit 250 and output to the microcomputer 270 as the amplified potential difference VA2. Thus, the operational amplification voltage VA2 output to the microcomputer 270 is stored in the RAM of the microcomputer 270 between t = t4 and t5. At this stage, as shown in FIG. 18, since the potential difference V1> the potential difference V2, the amplified potential difference VA1> the amplified potential difference VA2.

  Thereafter, when the determination in step 413 becomes YES as the temperature cycle τ elapses, in the next step 420, both amplified potential difference read processing and environmental temperature T input processing are performed.

  In this read processing and input processing, instead of the amplified potential differences from the two operational amplifier circuits 250 and 260 described in the first embodiment, the operations stored in the RAM of the microcomputer 270 in step 481 as described above. Both amplified potential differences VA 1 and VA 2 from the amplifier circuit 250 are read out, and the environmental temperature T detected by the resistance temperature detector 500 is input to the microcomputer 270.

  Next, in step 430, the voltage difference Vd is calculated. In this calculation process, instead of the difference between the amplified potential differences from the two operational amplifier circuits 250 and 260 described in the first embodiment, the difference between the amplified potential differences VA1 and VA2 read out at step 420 (VA1- VA2) is calculated.

  When the processing in step 430 is completed in this way, in step 431, the voltage ratio Rv is determined. In this determination process, the ratio (VA1 / VA2) of the amplified potential difference VA1 to the amplified potential difference VA2 is set to the voltage ratio Rv instead of the ratio of the amplified potential differences from the two operational amplifier circuits 250 and 260 described in the first embodiment. Is calculated as

  Then, in the next step 490, it is determined whether or not Rv> 1 is satisfied. At the present stage, as described above, since VA1> VA2, Rv> 1 is established. Therefore, the determination in step 490 is YES. If Rv ≦ 1 holds, the processing after step 481 is performed again.

  As described above, with the determination of YES in step 490, the processing after step 432 is performed in the same manner as in the first embodiment. Then, the processing after step 481 is performed in the same manner as described above after t = t4 to t8 until the determination in step 460 becomes YES.

  That is, the control voltage from the temperature control circuit 231 maintains the low level L from t = t4 to t5, maintains the high level H from t = t5 to t6, and low level L from t = t6 to t7. And changes so as to maintain the high level H from t = t7 to t8.

  Also, the analog changeover switch 290 is in the first on state at time t = t4 and in the second on state at t = t5 in synchronization with the level change of the control voltage under the control of the microcomputer 270. At t = t6, the third charging state is reached at t = t7, and the first charging state is reached at t = t8.

  Therefore, as described above, when t = t4, the analog changeover switch 290 enters the first input state, and when the control voltage from the temperature control circuit 231 is output to the bridge circuit 210 at the low level L, the bridge The fixed resistor 214 of the circuit 210 is connected in series to the fixed resistor 213, and the current I1 flows through the heating resistor 211 to maintain the temperature of the heating resistor at C = C1 (see FIG. 17).

  Next, as described above, when the analog changeover switch 290 is in the second input state at time t = t5 and the fixed resistor 215 is connected in series to the fixed resistor 213 in the bridge circuit 210, the temperature control circuit 231 The control voltage is output to the bridge circuit 210 at the high level H, and the current I2 flows through the heating resistor 211 to maintain the temperature of the heating resistor at C = C2 (see FIG. 17).

  Here, as described above, when the control voltage from the temperature control circuit 231 is output to the bridge circuit 210 at the high level H, the bridge circuit 210 includes the common terminals of the fixed resistors 213 and 215, the fixed resistors 212, and A potential difference V3 (see t = t5 to t6 in FIG. 18) is output from the common terminal of the heating resistor 211 based on the resistance value R2 of the fixed resistor 215 and the resistance value of the heating resistor 211. Then, this potential difference V3 is amplified by the operational amplifier circuit 250 and output to the microcomputer 270 as the amplified potential difference VA3. Thus, the amplified potential difference VA3 output to the microcomputer 270 is stored in the RAM of the microcomputer 270 during the next t = t6 to t7.

  Thereafter, as described above, at time t = t6, the analog changeover switch 290 enters the first input state, and when the fixed resistor 214 is again connected in series to the fixed resistor 213 in the bridge circuit 210, the temperature control circuit The control voltage from H.231 is output to the bridge circuit 210 at the low level L, and the current I1 flows through the heating resistor 211 to maintain the temperature of the heating resistor at C = C1 (see FIG. 17).

  Next, as described above, at time t = t7, when the analog changeover switch 290 is in the third input state and the fixed resistor 216 is connected in series to the fixed resistor 213 in the bridge circuit 210, the temperature control circuit 231 The control voltage is output to the bridge circuit 210 at the high level H, and the current I3 flows through the heating resistor 211 to maintain the temperature of the heating resistor at C = C3 (see FIG. 17).

  Here, as described above, when the control voltage from the temperature control circuit 231 is output to the bridge circuit 210 at the high level H at time t = t7, the bridge circuit 210 is common to both the fixed resistors 213 and 216. Based on the change in resistance value R3 of the fixed resistor 216 and the resistance value of the heating resistor 211 from between the terminal and the common terminal of the fixed resistor 212 and the heating resistor 211 (see t = t7 to t8 in FIG. 18). ) Is output. Then, this potential difference V1 is amplified by the operational amplifier circuit 250 and output to the microcomputer 270 as the amplified potential difference VA1. Thus, the operational amplification voltage VA1 output to the microcomputer 270 is stored in the RAM of the microcomputer 270 between t = t8 and t9. At this stage, as shown in FIG. 18, since the potential difference V3> the potential difference V1, the amplified potential difference VA3> the amplified potential difference VA1.

  Thus, when a determination of YES is made in step 413 as the temperature period τ corresponding to t = t4 to t8 elapses, in step 420, as described above, the data stored in the RAM of the microcomputer 270 is stored in step 481. Both amplified potential differences VA3 and VA1 are read from the operational amplifier circuit 250, and the ambient temperature T detected by the resistance temperature detector 500 is input to the microcomputer 270. Next, in step 430, the difference (VA3-VA1) between the two amplified potential differences VA3 and VA1 read in step 420 is calculated. Thereafter, in step 431, the ratio (VA3 / VA1) of the amplified potential difference VA3 to the amplified potential difference VA1 is calculated as the voltage ratio Rv.

  Therefore, at the present stage, as described above, since VA3> VA1, since Rv> 1 is established, the determination in step 490 is YES. Accordingly, the processing after step 432 is performed in the same manner as described above.

  As described above, in the third embodiment, the bridge circuit 220, the constant temperature control circuit 240, and the operational amplifier circuit 260 described in the first embodiment are eliminated, and the bridge circuit 210 is used as the first circuit. The bridge circuit 210 described in the embodiment employs a configuration in which the analog changeover switch 290 and the fixed resistors 215 and 216 are added as described above, and the temperature control circuit 231 is controlled by the constant temperature control described in the first embodiment. The circuit 230 is used instead. Then, the bridge circuit 210 and the temperature control circuit 231 according to the third embodiment are controlled by the microcomputer 270 as described above according to the flowchart of FIG. And the analog changeover switch 290 are changed over and driven.

  As a result, the bridge circuit and the heating resistor are made single with the bridge circuit 210 and the heating resistor 211, respectively, so that the detection element 300 can be reduced in size and power consumption can be suppressed, and the same as in the first embodiment. An effect can be achieved.

  Next, a modification of the third embodiment will be described. In the third embodiment, as described above, an example is shown in which processing accompanying the calculation of the concentration of hydrogen gas is performed with the establishment of the voltage ratio Rv> 1 every time the temperature cycle τ elapses. However, the present invention is not limited to this, and the third embodiment may be modified as follows.

  That is, instead of “whether the temperature cycle τ has passed” as the determination criterion in step 413, “whether the control voltage pulse cycle has passed” is adopted. Here, the progress of the pulse cycle corresponds to, for example, the first half of the temperature cycle τ, the second half of the temperature cycle τ, or the first half of the subsequent temperature cycle τ.

  Under such a premise, every time YES is determined in step 413 as the pulse period elapses, the processing after step 420 is repeated as follows.

  As described in the third embodiment, for example, the microcomputer 270 is between t = t2 and t3, between t = t4 and t5, between t = t6 and t7, and between t = t8 and t9. Among the amplified potential differences VA1, VA2, VA3, and VA1 sequentially stored in the RAM, the amplified potential differences VA1, VA2, both amplified potential differences VA2, VA3, and both amplified potential differences VA3, VA1 are sequentially set together with the environmental temperature T in step 420. Read out.

  Then, the two amplified potential differences VA1 and VA2, the two amplified potential differences VA2 and VA3, and the two amplified potential differences VA3 and VA1 that are sequentially read out in this way are sequentially calculated as a voltage difference Vd in step 430. Next, the two amplified potential differences VA1 and VA2, the two amplified potential differences VA2 and VA3, and the two amplified potential differences VA3 and VA1 that are sequentially read out as described above are sequentially converted into voltage ratios Rv = VA1 / VA2, VA2 / VA3, and VA3, respectively. It is determined in step 431 as / VA1.

  Here, Rv = VA1 / VA2> 1, Rv = VA2 / VA3 <1 and Rv = VA3 / VA1> 1 (see FIG. 18). Therefore, in step 490, YES is determined when Rv = VA1 / VA2> 1, NO is determined when Rv = VA2 / VA3 <1, and YES is determined when Rv = VA3 / VA1> 1.

  For this reason, the processing after step 432 is performed only when the determination in step 490 is YES. Also by this, the same effect as the third embodiment can be achieved.

In carrying out the present invention, the following various modifications are possible without being limited to the above embodiments.
(1) As a material for forming the heating resistor 330 and the wiring film 340, it is desirable that the chemical durability is high at a high temperature and the temperature resistance coefficient is large.
(2) The present invention may be applied not only to hydrogen gas but also to concentration detection of combustible gas such as city gas and leakage detection of the gas.
(3) The number of heating resistors in each of the above embodiments is not limited to two, and may be three or more.
(4) The resistance thermometer 390 or 500 is not limited to a thin film resistor, and may be various resistors such as a thermistor capable of detecting temperature.
(5) Instead of the resistance temperature detector 390 or 500, a temperature resistance resistor or other temperature sensor separate from the detection element 300 may be employed. In this case, it is desirable that the temperature sensor is disposed in a detection atmosphere in which the detection element 300 is disposed.
(6) Unlike the above-described embodiment, the heating resistors 211 and 221 (330) generate heat in which the resistance value is changed so as to decrease (or increase) in accordance with an increase (or decrease) in the temperature of the heating resistor. A resistor may be used. In this case, the voltage difference Vd and the voltage ratio Rv described in the above embodiment are calculated on the basis of the larger resistance value of both the heating resistors 211 and 221.
(7) The predetermined waiting time, which is the determination criterion in step 410 of FIG. 6, is not limited to 0.5 (seconds), and may be changed as appropriate. In short, both the heating resistors 211 and 221 have their constant temperatures. Any time may be used as long as the temperature can be set to the corresponding constant temperature by the control.
(8) The temperature resistance coefficients of the two heating resistors 211 and 221 may not necessarily be the same as the temperature resistance coefficient of the resistance temperature detector 390 or 500.
(9) In the third embodiment, the determination criterion in step 490 (see FIG. 15) is not limited to Rv> 1, but may be Rv <1.
(10) In the third embodiment, prior to the processing of step 412 in the flowchart of FIG. 15, the same processing as both steps 400 and 410 of the flowchart (see FIG. 6) described in the first embodiment is performed. It may be.

It is sectional drawing of the apparatus unit in 1st Embodiment of the combustible gas detection apparatus which concerns on this invention. It is a block diagram which shows the control circuit in the said 1st Embodiment. It is sectional drawing which shows the assembly | attachment structure of the detection element with respect to the cover body of FIG. It is sectional drawing of the detection element of FIG. It is a top view of the detection element of FIG. It is a flowchart which shows the effect | action of the microcomputer of FIG. It is a graph which shows the relationship between the relative humidity in the to-be-detected atmosphere in the said 1st Embodiment, and a voltage ratio. It is the graph which made the relative humidity which shows the relationship between the voltage difference and hydrogen gas concentration in the said 1st Embodiment a parameter. It is a graph which shows the relationship between the hydrogen gas concentration and Va (= voltage difference-intercept) in the said 1st Embodiment. It is a control circuit diagram in a 2nd embodiment of the present invention. It is a flowchart which shows the effect | action of the microcomputer of FIG. It is sectional drawing which follows a 12-12 line in FIG. It is a top view of the detection element in 3rd Embodiment of this invention. It is a control circuit diagram in the third embodiment. It is a flowchart which shows the effect | action of the microcomputer of FIG. It is a timing chart which shows the output waveform of the temperature control circuit in the said 3rd Embodiment. It is a timing chart which shows the time change of the temperature of the exothermic resistor in the 3rd embodiment of the above. It is a timing chart which shows the time change of the terminal voltage of the exothermic resistor in the 3rd embodiment of the above.

Explanation of symbols

211, 221 and 330 ... exothermic resistors, 214 to 216 ... fixed resistors,
230, 240 ... constant temperature control circuit, 231 ... temperature control circuit, 280 ... DC power supply,
250, 260 ... operational amplification circuit, 270 ... microcomputer,
290 ... analog changeover switch circuit, 300 ... detection element, 310 ... semiconductor substrate,
311: Recess, 320 ... Insulating layer, 350 ... Inner protective layer, 360 ... Outer protective layer,
390, 500 ... Resistance temperature detector.

Claims (10)

In the combustible gas detection device comprising a plurality of heating resistors exposed to the atmosphere to be detected,
Energization control means for energizing the two heating resistors so as to maintain the resistance values of the two heating resistors among the plurality of heating resistors at respective values corresponding to different constant temperatures;
Temperature detecting means for detecting an environmental temperature in the detected atmosphere;
Voltage difference calculating means for calculating a difference between the terminal voltages of the two heating resistors generated in the energization control state by the energization control means as a voltage difference;
Voltage ratio determining means for determining, as a voltage ratio, a ratio of the terminal voltages of the two heating resistors generated in the energization control state by the energization control means;
Humidity determining means for determining the humidity in the detected atmosphere based on the relationship between the voltage ratio determined by the voltage ratio determining means and the detected environment temperature by the temperature detecting means;
Concentration calculating means for calculating the concentration of the combustible gas in the detected atmosphere based on the relationship between the voltage difference calculated by the voltage difference calculating means, the humidity determined by the humidity determining means, and the detected environmental temperature. ,
The combustible gas detection apparatus, wherein the combustible gas is detected based on the calculated concentration of the concentration calculation means. In a flammable gas detection device comprising a heating resistor exposed to the atmosphere to be detected,
Energization control means for intermittently energizing the heating resistor so as to maintain the resistance value of the heating resistor at different values corresponding to different constant temperatures at different times; and
Temperature detecting means for detecting an environmental temperature in the detected atmosphere;
A voltage difference calculating means for calculating a difference between the terminal voltages of the heating resistors generated at different times in the intermittent energization control state by the energization control means;
Voltage ratio determining means for determining, as a voltage ratio, a ratio of each terminal voltage of the heating resistor that occurs at different times in the intermittent energization control state by the energization control means;
Humidity determining means for determining the humidity in the detected atmosphere based on the relationship between the voltage ratio determined by the voltage ratio determining means and the detected environment temperature by the temperature detecting means;
Concentration calculating means for calculating the concentration of the combustible gas in the detected atmosphere based on the relationship between the voltage difference calculated by the voltage difference calculating means, the humidity determined by the humidity determining means, and the detected environmental temperature. ,
The combustible gas detection apparatus, wherein the combustible gas is detected based on the calculated concentration of the concentration calculation means. A semiconductor substrate formed with a plurality of recesses from the back side at intervals, an insulating layer formed on the surface of the semiconductor substrate, and a plurality of recesses formed on the surface of the insulating layer corresponding to the recesses A heating element, and a detection element disposed in the atmosphere to be detected, including a protective layer formed on the surface of the insulating layer so as to cover the heating resistor;
Energization control means for energizing the two heating resistors so as to maintain the resistance values of the two heating resistors among the plurality of heating resistors at respective values corresponding to different constant temperatures;
Temperature detecting means for detecting an environmental temperature in the detected atmosphere;
Voltage difference calculating means for calculating a difference between the terminal voltages of the two heating resistors generated in the energization control state by the energization control means as a voltage difference;
Voltage ratio determining means for determining, as a voltage ratio, a ratio of the terminal voltages of the two heating resistors generated in the energization control state by the energization control means;
Humidity determining means for determining the humidity in the detected atmosphere based on the relationship between the voltage ratio determined by the voltage ratio determining means and the detected environment temperature by the temperature detecting means;
Concentration calculating means for calculating the concentration of the combustible gas in the detected atmosphere based on the relationship between the voltage difference calculated by the voltage difference calculating means, the humidity determined by the humidity determining means, and the detected environmental temperature. ,
A combustible gas detection apparatus that detects the combustible gas based on the calculated concentration of the concentration calculation means. A semiconductor substrate formed with a recess from the back side, an insulating layer formed on the surface of the semiconductor substrate, a heating resistor formed on the surface of the insulating layer corresponding to the recess, and the heating resistor And a protective layer formed on the surface of the insulating layer so as to cover the detection element, and a detection element disposed in the detection atmosphere;
Energization control means for intermittently energizing the heating resistor so as to maintain the resistance value of the heating resistor at different values corresponding to different constant temperatures at different times; and
Temperature detecting means for detecting an environmental temperature in the detected atmosphere;
A voltage difference calculating means for calculating a difference between the terminal voltages of the heating resistors generated at different times in the intermittent energization control state by the energization control means;
Voltage ratio determining means for determining, as a voltage ratio, a ratio of each terminal voltage of the heating resistor that occurs at different times in the intermittent energization control state by the energization control means;
Humidity determining means for determining the humidity in the detected atmosphere based on the relationship between the voltage ratio determined by the voltage ratio determining means and the detected environment temperature by the temperature detecting means;
Concentration calculating means for calculating the concentration of the combustible gas in the detected atmosphere based on the relationship between the voltage difference calculated by the voltage difference calculating means, the humidity determined by the humidity determining means, and the detected environmental temperature. ,
A combustible gas detection apparatus that detects the combustible gas based on the calculated concentration of the concentration calculation means. The voltage difference is an independent variable, the concentration of the combustible gas is a dependent variable, and the determination is performed using a predetermined relationship between an intercept of a linear function equation established with the humidity and the environmental temperature as parameters, and the humidity. Intercept determining means for determining the intercept based on humidity;
Gradient determining means for determining the gradient of the linear function equation based on the detected ambient temperature,
The concentration calculating means uses both the determined intercept by the intercept determining means and the determined gradient by the gradient determining means in place of the determined humidity and the detected environmental temperature, and based on the linear function formula according to the calculated voltage difference. The combustible gas detection device according to any one of claims 1 to 4, wherein the concentration of the combustible gas is calculated.   The temperature detection means is a resistance temperature detector that is disposed in the detected atmosphere and detects an environmental temperature in the detected atmosphere in accordance with a change in the resistance value thereof. The combustible gas detection device according to any one of claims 1 to 5. The temperature detecting means is a thin film resistor formed on the surface of the semiconductor substrate,
The combustible gas detection device according to claim 3 or 4, wherein the thin film resistor detects an environmental temperature in the detected atmosphere based on a change in the resistance value thereof. Energizing and controlling the two heating resistors to maintain the resistance values of the two heating resistors exposed to the detected atmosphere at respective values corresponding to different constant temperatures,
The humidity in the detected atmosphere is determined based on the relationship between the voltage ratio between the terminal voltages of the two heating resistors generated in the energization control state in the detected atmosphere and the environmental temperature in the detected atmosphere. ,
The combustible gas is detected by calculating the concentration of the combustible gas in the detected atmosphere based on the voltage difference between the terminal voltages of the two heating resistors, the humidity, and the environment temperature. Combustible gas detection method. The heating resistor is subjected to intermittent energization control so that the resistance value of the heating resistor exposed to the detected atmosphere is maintained at different times corresponding to different constant temperatures,
The humidity in the detected atmosphere is determined based on the relationship between the voltage ratio of each terminal voltage of the heating resistor generated in the intermittent energization control state in the detected atmosphere and the environmental temperature in the detected atmosphere. And
The combustible gas is detected by calculating the concentration of the combustible gas in the detected atmosphere based on the relationship between the voltage difference of each terminal voltage of the heating resistor, the humidity, and the environmental temperature. Flammable gas detection method. The calculation of the combustible gas is as follows:
The voltage difference is an independent variable, the concentration of the combustible gas in the detected atmosphere is a dependent variable, and a predetermined relationship between the humidity and the intercept of a linear function equation established using the humidity and the environmental temperature as parameters To determine the intercept based on the determined humidity,
Using the gradient of the linear function equation determined based on the environmental temperature, the intercept and the voltage difference, the concentration of the combustible gas is calculated based on the linear function equation. The combustible gas detection method according to claim 8 or 9.

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