JP2003004698A - Flammable gas detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve improved selectivity in oxygen, selectively measure the concentration of a hydrogen gas, simultaneously measure the concentration of a flammable gas other than the oxygen gas, and simultaneously achieve low cost and high reliability. SOLUTION: The flammable gas detector 100 comprises first and second sensors 110 and 210 as a gas concentration detection means consisting of a gas diffusion speed-controlling section, an ion-conductive solid electrolyte body, and an electrode, and a gas concentration operating means which sets different detection sensitivities to them, and operates the concentration of at least two types of specific gases based on the detection values of the first and second sensors 110 and 210, thus measuring for example the concentration of oxygen and carbon monoxide simultaneously and accurately.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustible gas detection device having excellent selectivity for a combustible gas as a gas to be measured.

As a sensor using an oxygen ion conductive solid electrolyte body, there are an oxygen sensor for detecting the oxygen concentration in the exhaust gas of an automobile and an air-fuel ratio sensor for obtaining the air-fuel ratio from the oxygen concentration. It is known that such a conventional sensor also reacts with combustible gases such as hydrogen and carbon monoxide.

The sensor element of the sensor is constructed so that the gas to be measured can reach the gas diffusion chamber by diffusion through the diffusion rate controlling portion. Further, the oxygen pump cell is formed of an oxygen ion conductive solid electrolyte body and outer and inner electrodes arranged on both surfaces thereof. Further, the oxygen detection cell is formed of an oxygen ion conductive solid electrolyte body and oxygen reference electrodes and oxygen measurement electrodes arranged on both surfaces thereof, and the oxygen pump cell and the oxygen detection cell are sensor-controlled with an operational amplifier. Each connected to the circuit. Furthermore, a heater unit for controlling the sensor element to the activation temperature is provided.

The sensor element having such a structure is disclosed in, for example, SAE paper (No. 850378), automobile technology (Vol. 41, No. 12, 1987), or Japanese Patent Laid-Open No.
No. 00-9685.

[0005]

The sensor element of such a conventional sensor has a gas diffusion rate controlling part for limiting the diffusion amount of the gas to be measured, and a gas diffusion chamber for diffusing gas passing through the gas diffusion rate controlling part. An oxygen detection cell for measuring the oxygen partial pressure of the gas diffusion chamber, and an oxygen pump cell having an action of pumping oxygen into the gas diffusion chamber based on the output of the oxygen detection cell and an action of pumping oxygen out of the gas diffusion chamber, Since the pump current Ip flowing through the oxygen pump cell is measured to obtain the oxygen concentration and the hydrogen concentration, the reaction component gas in the measured gas is continuously diffused into the gas diffusion chamber based on each diffusion coefficient. Will come.

That is, the measured pump current Ip is the sum of all these reaction components, and the pump current Ip for each reaction component could not be extracted. That is,
When multiple combustible gases coexist, the reaction components are:
Although there are combustible gases such as various hydrocarbons such as oxygen, carbon monoxide, hydrogen and methane, and various alcohols, it is difficult to detect a specific gas because the conventional sensor lacks gas selectivity. .

For example, in combustion in a gasoline engine, when the amount of fuel is larger than the stoichiometric air-fuel ratio, that is, in the case of so-called rich combustion, carbon monoxide is present in about 3 times that of several% of hydrogen. Further, in a fuel cell system in which hydrogen is taken out from various fuels and electric power is generated from the hydrogen and oxygen (air), combustible gases other than hydrogen such as carbon monoxide may exist in the process of reforming the fuel. is there.

In this fuel cell system, the emergence of a sensor capable of selectively detecting hydrogen and carbon monoxide is strongly desired from the viewpoint of improving the efficiency of power generation and improving the reliability of the fuel cell system. However, it has been a conventional problem to solve this problem.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and provides a combustible gas detection device which is excellent in hydrogen selectivity and which can selectively measure the hydrogen gas concentration. The purpose is to do. In addition, in the subordinate concept of the present invention, in addition to this, the concentration of combustible gas other than hydrogen gas can be measured at the same time. For example, in a fuel cell system, a high concentration of reactive components other than hydrogen can be measured. In case of carbon monoxide only, it is possible to measure hydrogen concentration and carbon monoxide concentration at the same time, and
To provide a combustible gas detection device that can realize low cost and high reliability at the same time by using an oxygen ion conductive solid electrolyte that has been widely used as a sensor for engine control and has a proven track record in durability and reliability. Has an aim.

[0010]

A combustible gas detection device according to the present invention, as set forth in claim 1, has a gas diffusion rate controlling section for limiting the diffusion amount of a gas to be measured and a gas diffusion rate controlling section. At least 2 gas concentration detecting means comprising an ion conductive solid electrolyte body that generates a voltage or current by reacting with the gas to be measured that has passed therethrough, and an electrode that supplies or takes out voltage or current to or from the ion conductive solid electrolyte body. In addition to the above, different gas sensitivities are set for the respective gas concentration detecting means, and gas concentration calculating means for calculating the concentrations of at least two kinds of specific gases based on the detection values of the respective gas concentration detecting means are provided. It is characterized by that.

Further, in the combustible gas detecting device according to the present invention, as described in claim 2, the gas concentration calculating means determines the sensitivity of one gas concentration detecting means to one specific gas K1. , The ratio (K1 ′ / K1) of the sensitivity K1 for one specific gas and the sensitivity K1 ′ for the other specific gas is Z1, and the detected value of the concentration is Ip1,
Regarding the other gas concentration detecting means, the sensitivity to one specific gas is K2, and the ratio of the sensitivity K2 to one specific gas and the sensitivity K2 'to the other specific gas (K1' / K1).
Is Z2 and the detected value of the concentration is Ip2, the concentration X (a) of one specific gas and the concentration X of the other specific gas
(B) is expressed by the following formula X (a) = (K1 · Ip2-K2 · Ip1) / K1 · K2 (Z2-Z1) X (b) = (K2 · Z2 · Ip1−K1 · Z1 · Ip2) / K1 · K2 (Z2
-Z1).

Similarly, in the combustible gas detection device according to the present invention, as described in claim 3, detection sensitivity setting for setting the detection sensitivity of at least one type of specific gas detected by the gas concentration detection means. Means may be provided.

Similarly, in the flammable gas detection device according to the present invention, as described in claim 4, the detection sensitivity setting means is such that the diffusion resistance of the gas diffusion rate controlling portion is large (for example, of a porous body). It may be a means for setting the detection sensitivity by the size and length of the pores.

Similarly, in the flammable gas detection device according to the present invention, as described in claim 5, the detection sensitivity setting means can be a gas adsorbent for adsorbing a specific gas. .

Similarly, in the combustible gas detection device according to the present invention, as described in claim 6, the gas adsorbent may adsorb at least one of carbon monoxide and hydrocarbon. it can.

Similarly, the combustible gas detection device according to the present invention may be provided with an oxygen dope means for refreshing the gas adsorbent having adsorbed the specific gas, as described in claim 7. it can.

Similarly, in the combustible gas detection device according to the present invention, as described in claim 8, the detection sensitivity setting means is a means for setting the detection sensitivity by the temperature of the ion conductive solid electrolyte body. It can be.

Similarly, in the combustible gas detecting device according to the present invention, as described in claim 9, the ion conductive solid electrolyte body of one of the gas concentration detecting means is an oxygen ion conductive solid electrolyte body. The ion conductive solid electrolyte body of the other gas concentration detecting means can be a hydrogen ion (proton) conductive solid electrolyte body.

Similarly, in the combustible gas detection device according to the present invention, as described in claim 10, a plurality of gas concentration detection means may be integrally provided on the same element. it can.

Similarly, in the combustible gas detection device according to the present invention, as described in claim 11, the specific gas is hydrogen and at least one of carbon monoxide and hydrocarbon. You can

[0021]

According to the combustible gas detection device of the first aspect of the present invention, at least two gas concentration detection means having different detection sensitivities are provided, and at least two types are detected based on the detection value of each gas concentration detection means. When a plurality of combustible gases, that is, specific gases coexist in the measured gas, for example, high concentration hydrogen in the fuel cell system and low concentration However, even in the presence of carbon monoxide of several percent or more, which cannot be ignored, hydrogen selectivity is excellent, and the respective concentrations can be detected simultaneously and accurately.

According to the combustible gas detection device of the second aspect of the present invention, the same effect as that of the first aspect can be obtained, and even when hydrocarbons coexist as a specific gas in the measured gas. By specifying the kind of the hydrocarbon (for example, methane or the average composition of the hydrocarbon), the concentration of the hydrocarbon can be accurately detected like hydrogen and carbon monoxide. Further, low cost and high reliability can be realized at the same time by using the ion conductive solid electrolyte body which is widely used as an engine control sensor and has a proven track record in durability and reliability. Further, in the gas concentration calculating means for calculating the concentration of the specific gas based on the detection values from the respective gas concentration detecting means having different detection sensitivities, by setting the equations for calculating the concentrations of one and the other specific gas, And the respective concentrations of the other gas can be derived simultaneously and accurately.

According to the combustible gas detecting device of the third aspect of the present invention, the same effects as those of the first and second aspects can be obtained, and at least one kind of specific gas detected by the gas concentration detecting means. By adopting the detection sensitivity setting means that sets the detection sensitivity of, it is possible to set the detection sensitivity ratio between multiple specified gases, and only the gas component (unknown number) that you want to measure in the measured gas If the gas concentration detecting means is provided, it is possible to derive a plurality of concentrations of the specific gas to be measured.

According to the combustible gas detecting device of the fourth aspect of the present invention, the same effect as that of the third aspect can be obtained, and in the detection sensitivity setting means, the diffusion resistance of the gas diffusion rate controlling portion is large. By setting the detection sensitivity according to this, the diffusion rate of the specific gas to be measured can be adjusted relatively easily, and as a result, the sensitivity ratio of the specific gas to be measured, for example, the sensitivity ratio of hydrogen and carbon monoxide is desired. Can be set to the value of.

According to the combustible gas detection device of the fifth aspect of the present invention, the same effect as that of the third aspect can be obtained, and the detection sensitivity setting means adopts the gas adsorbent. When one gas concentration detecting means is provided with an adsorbent for one specific gas, the detection sensitivity of the specific gas is remarkably reduced, which makes it possible to obtain a large sensitivity ratio with the other gas concentration detecting means. It is possible to improve the accuracy of calculating the concentration of the specific gas.

According to the combustible gas detecting device of the sixth aspect of the present invention, the same effect as that of the fifth aspect can be obtained and, in addition, for example, one of the gas concentration detecting means is provided with a carbon monoxide adsorbent. When provided, the detection sensitivity of carbon monoxide can be significantly reduced, and when a hydrocarbon adsorbent is provided,
The detection sensitivity of hydrocarbons can be remarkably reduced, and thereby the sensitivity ratio with the other gas concentration detection means can be increased, so that the accuracy of the concentration calculation of the specific gas can be further improved.

According to the combustible gas detection device of claim 7 of the present invention, the same effects as those of claims 4 and 5 can be obtained, and at the same time, the oxygen dope for refreshing the gas adsorbent adsorbing the specific gas is refreshed. By adopting the means,
The function of the gas adsorbent, which is the detection sensitivity setting means, can be permanently obtained, and the capacity of the gas adsorbent can be reduced by setting the control timing of the oxygen dope means to a relatively short cycle, and the flammability can be reduced. This can also contribute to further downsizing of the volatile gas detection device.

According to the combustible gas detector of the eighth aspect of the present invention, the same effect as that of the third aspect can be obtained, and the detection sensitivity is set by the temperature of the ion conductive solid electrolyte body. By adopting the sensitivity setting means, the detection sensitivity can be set relatively easily.

According to the combustible gas detecting device of the ninth aspect of the present invention, the same effects as those of the first to third aspects can be obtained, and at the same time, the ion conductive solid electrolyte body of one gas concentration detecting means. Is an oxygen ion conductive solid electrolyte body, and the other ion conductive solid electrolyte body of the gas concentration detecting means is a hydrogen ion conductive solid electrolyte body, so that the hydrogen ion conductive solid electrolyte body is particularly excellent in hydrogen selectivity. Therefore, the accuracy of calculating the concentration of the specific gas can be further improved.

According to the combustible gas detecting device of the tenth aspect of the present invention, the same effects as those of the first to ninth aspects can be obtained, and a plurality of gas concentration detecting means are integrated on the same element. By providing the above, it is possible to detect a plurality of specific gases to be measured at the closest position temporally and spatially, and it is possible to improve the accuracy of the concentration calculation of each specific gas. In addition, further miniaturization and weight reduction can be realized, and cost reduction can be realized, which makes the device even more practical.

According to the combustible gas detection device of the eleventh aspect of the present invention, the same effects as those of the first to tenth aspects can be obtained, and hydrogen, carbon monoxide and hydrocarbons are other components. An extremely useful combustible gas detection device can be provided for a fuel cell system having a relatively higher concentration and coexisting state.

[0032]

EXAMPLES Hereinafter, the flammable gas detection device according to the present invention will be described in detail based on examples, but it goes without saying that the present invention is not limited to the following examples. Also,
It goes without saying that what is shown in the drawings of this embodiment does not represent the actual size and shape of the sensor element such as the size and aspect ratio, but is for the purpose of easily explaining the configuration and operation. .

(Embodiment 1) FIGS. 1 to 5 are views for explaining an embodiment of a combustible gas detection device according to the present invention.
In this embodiment, the combustible gas detection device applied to the fuel cell system shown in FIG. 3 is taken as an example.

The fuel cell system shown in FIG. 3 is, for example, a methanol fuel reforming type, which supplies hydrogen and oxygen to the fuel cell 50 to generate electric power. That is,
In the fuel cell system, the methanol supplied from the fuel tank 51 is burned in the combustor 52 and is used as the heat source of the evaporator 53, and the methanol and water supplied from the fuel tank 51 and the water tank 54 are vaporized in the evaporator 53. And supply it to the fuel reformer 55. The fuel reformer 55 reforms the supplied mixed gas of methanol and water via a reforming catalyst, a shift catalyst, and a carbon monoxide selective catalyst, and reforms gas containing hydrogen as a main component with the fuel cell 50. Supply to. Further, oxygen (air) is supplied to the fuel cell 50 via the humidifier 56.

Here, since the reformed gas supplied to the fuel cell 50 contains a reducing gas such as carbon monoxide, which causes a decrease in cell performance, in addition to hydrogen, the reformed gas contains the monoxide. It is necessary to measure the concentration of carbon, etc. Further, the exhaust gas from the fuel cell 50 is a combustible gas containing hydrogen,
This gas can be used as the fuel gas in the combustor 52, but at this time, it is necessary to measure the hydrogen concentration in feedback control of the amount of the fuel component in the combustor 52. Therefore, in the above fuel cell system,
A combustible gas detection device 100 is provided in a hydrogen (reformed gas) supply path and an exhaust path for the fuel cell 50.

As shown in FIG. 1, the combustible gas detecting device 100 is provided with two gas concentration detecting means, a first sensor 110 and a second sensor 210, in the middle of a supply passage (or an exhaust passage) 60. There is. First and second sensor 11
0 and 210 are sensor bodies 110A and 210A
And sensor control circuits 110B and 21 which are output units of detection values
It consists of 0B. In addition, the combustible gas detection device 10
0 is a gas concentration calculation means 101 for calculating the concentrations of at least two kinds of specific gases based on the detection values of both sensor control circuits 110B and 210B, and a calculation for setting a constant at the time of calculation for the gas concentration calculation means 101. Constant setting means 102
Is equipped with. The specific gases to be measured in this example are hydrogen and carbon monoxide.

First and second sensors 110, 210
Is a gas diffusion rate controlling part for limiting the diffusion amount of the measured gas,
It is equipped with an ion conductive solid electrolyte body that generates a voltage or current by reacting with the gas to be measured that has passed through the gas diffusion rate controlling part, and an electrode that supplies or takes out voltage or current to the ion conductive solid electrolyte body. Has the configuration shown in FIG.

In the sensor element 10 housed in each of the sensor bodies 110A and 210A, as shown in FIG. 2, the gas to be measured, which is a combustible gas, passes through the gas diffusion rate controlling portion 10a,
The gas diffusion chamber 12 can be diffused and reached. The oxygen pump cell 11 is an oxygen ion conductive solid electrolyte body (zirconia having a property of selectively transmitting oxygen) 1
1a and outer electrodes (platinum) 11b arranged on both sides thereof
And the inner electrode (platinum) 11c. The oxygen detection cell 13 has an oxygen ion conductive solid electrolyte body 13a.
And an oxygen reference electrode 13b and an oxygen measuring electrode 13c arranged on both sides thereof. Oxygen reference electrode 13
b is a sensor control circuit 110B including the operational amplifier 21.
(210B), respectively.

Further, the sensor element 10 is provided with a heater section 15 for controlling the element to an activation temperature. The heater section 15 is configured by disposing a heater 15b in a ceramic substrate 15a and connecting it to a heater control circuit 15c. The space formed by the solid electrolyte 11a and the solid electrolyte 13a via the spacer 12a is used as the gas diffusion chamber 12 described above, and
The oxygen reference chamber 14 is a space formed by the solid electrolyte 13a and the ceramic substrate 15a via the spacer 14a.

In such a sensor element 10, the gas diffusion rate controlling part 10a for limiting the diffusion amount of the gas to be measured and the gas diffusion chamber 12 for diffusing the gas passing through the gas diffusion rate controlling part 10a.
And the oxygen detection cell 13 for measuring the oxygen partial pressure of the gas diffusion chamber 12, and the gas diffusion chamber 1 based on the output of the oxygen detection cell 13.
2 is provided with an oxygen pump cell 11 having a function of pumping oxygen and a function of pumping oxygen from the gas diffusion chamber 12, and the pump current Ip flowing through the oxygen pump cell 11 is measured to obtain the oxygen concentration and the hydrogen concentration. There is.

At this time, the reaction component gas in the gas to be measured is continuously diffused into the gas diffusion chamber 12 based on each diffusion coefficient. That is, the measured pump current Ip is the value of the sum of all these reaction components. Therefore, it is difficult to extract the pump current Ip for the hydrogen gas with only one sensor.

Therefore, in the flammable gas detection device 100, the first and second sensors 110 and 210 are provided and different detection sensitivities are set to them. Figure 4
(A) is a detection characteristic of hydrogen and carbon monoxide detected by the first sensor 110, showing a sensitivity K1 for hydrogen and a sensitivity K1 'for carbon monoxide, and its ratio (K1').
/ K1) is Z1. In addition, FIG.
The detection characteristics of hydrogen and carbon monoxide detected by the sensor 10 indicate the sensitivity K2 for hydrogen and the sensitivity K2 ′ for carbon monoxide, and the ratio (K2 ′ / K2) is Z2. That is, the first sensor 110 and the second sensor 21
At 0, the slopes of the graph shown in FIG. 4, that is, the detection sensitivities are different from each other. Then, the hydrogen concentration X (a) and the carbon monoxide concentration X (b) can be obtained from the detection characteristics of both by the following equations.

X (a) = (K1 · Ip2-K2 · Ip1) / K1 · K2 (Z2-Z1) Equation 1 X (b) = (K2 · Z2 · Ip1−K1 · Z1 · Ip2) / K1 · K2 (Z2-Z1) ... Equation 2 Here, K1, K2, Z1, and Z2 are constants obtained in advance, and Ip1 is a detection value of the first sensor 110 (Ip1 =
K1 · X (a) + K1 · Z1 · X (b)), and Ip
2 is the detection value of the second sensor 210 (Ip2 = K2 · X
(A) + K2 · Z2 · X (b)).

At this time, in the first sensor 110 and the second sensor 210, as shown in FIG. 4, hydrogen detection sensitivities K1 and K2 are detected.
, Hydrogen sensitivity K1, K2 and carbon monoxide sensitivity K1 ',
Since the ratios Z1 and Z2 of K2 'are set to different values, the above equations 1 and 2 can be solved. The detection value I of the first and second sensors 110 and 210
Both p1 and Ip2 may be the sum of the hydrogen content and the carbon monoxide content as long as the effects of combustible gas components other than hydrogen and carbon monoxide can be ignored.

In this way, the first and second sensors 11
Since the ratios Z1 and Z2 of the sensitivities K1 and K2 of hydrogen of 0 and 210 and the sensitivities K1 ′ and K2 ′ of carbon monoxide are different,
In the gas concentration calculation means 101, each sensor 110, 2
10 detected values Ip1, Ip2 and constants K1, K2, Z
The hydrogen concentration X (a) and the carbon monoxide concentration X (b) are calculated by solving the simultaneous binary linear equations using 1, Z2.

FIG. 5 is a flow chart for explaining the processing steps of the combustible gas detection device 100. First, in step S1, a constant determined in advance, that is, the sensitivity K1 of hydrogen in the first and second sensors 110 and 210,
Ratio of sensitivity of K2 and hydrogen to sensitivity of carbon monoxide Z1, Z
2 is read, and in step S2, the first and second
The heater unit 15 of each of the sensors 110 and 210 is turned on, and in step S3, the sensor element 10 is in an active state (state in which the element temperature is about 500 to 800 ° C.), that is, the first
Then, it is determined whether or not the second sensors 110 and 210 are in a measurable state.

Then, the first and second sensors 110,
When the 210 is ready for measurement, step S
4, the output values Ip1 and Ip2 of the first and second sensors 110 and 210 are read, and in step S5, the hydrogen concentration X (a) is calculated by the above equation 1, and then in step S6, the above equation is calculated. The carbon monoxide concentration X (b) is calculated from 2. These calculations are performed by the gas concentration calculation means 101.

Thereafter, in step S7, the hydrogen concentration X (a) and the carbon monoxide concentration X (b), which are the calculation results, are obtained.
Is output to an external device, and in step S8, it is determined whether or not the measurement is ended. If it is not ended, the process returns to step S3, and if it is ended, the measurement is ended in step S9.

As described above, in the combustible gas detection device 100 described in the above embodiment, the calculation flow can be easily constructed, and the sensor which is the gas concentration detection means does not have special gas selectivity. In addition, the concentrations of hydrogen and carbon monoxide, which are specific gases, can be measured simultaneously and accurately. In this embodiment, the first and second sensors 1
The case where two types of specific gas concentrations are measured using 10 and 210 has been described, but as shown in FIG.
It is also possible to measure three types of specific gas concentrations using one sensor 110 to 310.

(Embodiment 2) FIG. 7 is a view for explaining another embodiment of the combustible gas detecting device according to the present invention. In addition,
The same parts as those in the previous embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

Combustible gas detection device 400 of this embodiment
Means two gas concentration detecting means 41 on one sensor element.
0, 510 are integrally provided. That is, in the first embodiment, the first and second sensors 11 are
Although 0 and 210 have been described as the gas concentration detecting means, respectively,
In the second embodiment, one sensor includes two gas concentration detecting means 410, 510.
Although not shown in the drawings, the sensor control circuit (see FIG. 2) and the gas concentration calculating means (see FIG. 1), which are the output units of the detected values, are also provided in this embodiment.

First and second gas concentration detecting means 41
0 and 510 are first and second oxygen detection cells 413 and 513 for measuring the oxygen concentration in the gas diffusion chambers 412 and 512 with reference to the oxygen concentration in the atmosphere (about 20.9%).
First and second oxygen pump cells 411, 511 driven based on the measurement results of the first and second oxygen detection cells 413, 513 are formed so as to sandwich the gas diffusion chambers 412, 512.

The first oxygen detection cell 413 has a structure in which a pair of electrodes (platinum) having a catalytic action are provided on both surfaces of an oxygen ion conductive solid electrolyte body (zirconia having a property of selectively transmitting oxygen) 413a. It has become. One of the pair of electrodes is an oxygen reference electrode 413c facing the oxygen reference chamber 14 communicating with the atmosphere, and the other is a gas diffusion chamber 412.
Oxygen measuring electrode 413b facing the.

Like the first oxygen detection cell 413, the first oxygen pump cell 411 has a structure in which a pair of electrodes having a catalytic action are provided on both surfaces of the oxygen ion conductive solid electrolyte body 411a. At this time, one of the pair of electrodes is
Oxygen pump outer electrode 4 facing the outside of the gas diffusion chamber 412
11c and the other is the oxygen pump inner electrode 411b facing the gas diffusion chamber 412.

The second oxygen sensing cell 513 and the second oxygen sensing cell 513
The basic structure of the oxygen pump cell 511 is similar to that of the first one, and each oxygen ion conductive solid electrolyte body 511a,
Oxygen reference chamber 1 equipped with 513a and communicating with the atmosphere
4 facing the oxygen reference electrode 513c and the gas diffusion chamber 51
2 and the oxygen measuring electrode 513b facing the No. 2 and the oxygen pump outer electrode 511c facing the outside of the gas diffusion space 512.
And an oxygen pump inner electrode 511b facing the gas diffusion space 512. The second cells 513,
511 oxygen-ion conductive solid electrolyte body 511a, 51
3a is given a different sign from the oxygen ion conductive solid electrolyte bodies 411a and 413a of the first cells 413 and 411, but it goes without saying that both may be common members.

Here, the difference between the first gas concentration detecting means 410 and the second gas concentration detecting means 520 is the configuration of the gas diffusion rate controlling parts 410a and 510a for limiting the diffusion amount of gas. The diffusion resistance of the second gas diffusion controlling section 510a is set to be larger than the diffusion resistance of the diffusion controlling section 410a. That is, as the detection sensitivity setting means for setting the detection sensitivity of at least one type of specific gas detected by the gas concentration detection means, the first and second gas diffusion rate controlling sections 410 are provided.
a, 510a is formed of a porous body, and the length of the porous body forming the second gas diffusion rate controlling portion 510a is longer than the length (diffusion effective distance) of the porous body forming the first gas diffusion rate controlling portion 410a. Is getting bigger. In addition, the diffusion resistance can be made different by making the pore diameter of the porous body different.

The above-described combustible gas detection device 400 can obtain the same effects as those of the previous embodiment, and at the same time, the first and second gas concentration detection means 41 can be provided on one sensor element.
Since 0, 510 is provided, it is possible to detect a plurality of specific gases to be measured at the closest position temporally and spatially, and further improve the accuracy of the concentration calculation of each specific gas, and further reduce the size. It is possible to realize weight reduction and cost reduction. Then, as the detection sensitivity setting means, the first and second gas diffusion rate controlling parts 410a and 510 are provided.
Since a is made of a porous material having a different diffusion resistance, it is possible to cause a significant difference in the detection sensitivity ratio between a plurality of specific gases, for example, the detection sensitivity ratio between hydrogen and carbon monoxide. Is further enhanced.

(Embodiment 3) FIG. 8 is a view for explaining still another embodiment of the combustible gas detecting device according to the present invention.
The combustible gas detection device 600 of this embodiment is provided with the first and second gas concentration detection means 410, 510 on one sensor element, as in the case of the second embodiment.

Further, in this embodiment, the gas adsorber 612a, which is the detection sensitivity setting means, is located at a predetermined distance from the gas diffusion rate controlling part 510a in the gas diffusion chamber 512 on the right side of the second gas concentration detecting means 510 side. It's located away from the machine. The gas adsorbent 612a is, for example, a porous body such as ZnO or SnO ₂ that selectively adsorbs carbon monoxide, and functions to selectively block carbon monoxide that enters the gas diffuser 512. As a result, a large difference occurs in the carbon monoxide detection sensitivity between the first and second gas concentration detecting means 410, 510, and the measurement accuracy is further enhanced as in the second embodiment. This effect becomes more remarkable as the temperature of the sensor element is lower.

Here, the above-mentioned combustible gas detection device 600 is used.
Then, since the adsorption function is lost when the gas adsorbent 612a is filled with the adsorbed gas, the third oxygen pump cell 611 is provided in the vicinity of the gas adsorbent 612a as an oxygen doping means for refreshing the gas adsorbent 612a. It is provided. This third pump cell 611 is provided with an oxygen pump outer electrode 611c and an oxygen pump inner electrode 611b similarly to the first and second ones, and carbon monoxide adsorbed by the gas adsorbent 612a by the oxygen which is periodically doped. Is oxidized.

In this embodiment, the third oxygen pump cell 611 can also be used as the second oxygen pump cell 511, and the gas diffusion rate controlling portion 51 can be used.
It is also possible to configure 0a with a gas adsorbent. Further, if a hydrocarbon adsorbent such as zeolite is used for the gas adsorbent 612a, the first and second gas concentration detecting means 4 can be used.
A great difference can be caused in the detection sensitivity of hydrocarbons between 10, 510, and as a result, the measurement accuracy is improved.

(Embodiment 4) FIG. 9 is a view for explaining still another embodiment of the combustible gas detecting device according to the present invention.
The combustible gas detection device 700 of this embodiment is similar to Embodiments 2 and 3 above in that the first and second sensor elements are provided on one sensor element.
The gas concentration detecting means 410 and 710 are provided.

In this embodiment, the second gas concentration detecting means 7
10 includes a hydrogen detection cell 713. The hydrogen detection cell 713 includes a hydrogen ion (proton) conductive solid electrolyte body 713a, an outer electrode 713c and an inner electrode 713b.
Is equipped with. This hydrogen ion conductive solid electrolyte body 71
3a generates an electromotive force according to the difference in hydrogen concentration on both sides, and functions as a so-called hydrogen concentration battery.

In this combustible gas detection device 700, the oxygen concentration and the hydrogen concentration are controlled to almost zero in the vicinity of the inner electrodes 413b and 713b facing the inside of the gas diffusion chamber 412. An electromotive force Vs is generated between the outer electrode 713c, which comes into contact with high-concentration hydrogen in the gas to be measured, and the inner electrode 713b where the hydrogen concentration is substantially zero outside the 713a.
The detection is performed in 3.

The detected electromotive force Vs is based on the generally known Nernst equation, and if the concentration of one specific gas is constant, it depends on the concentration of the other specific gas (in this case, the hydrogen concentration in the measured gas). . That is, the hydrogen concentration X (a) is obtained from the electromotive force Vs.

As described in the previous embodiment, the first gas concentration detecting means 410 is the total detected value Ip1 of the combustible gas containing hydrogen. Therefore, from the hydrogen concentration X (a) detected by the second gas concentration detecting means 710, the detected value I
By deriving p2 and subtracting the detected value Ip2 from the detected value Ip1, the detected value Ip3 of the combustible gas other than hydrogen is obtained, and by applying the same calculation method as that of the first embodiment from the detected value Ip3. , The concentrations of other combustible gases can be calculated.

(Embodiment 5) FIG. 10 is a view for explaining still another embodiment of the combustible gas detecting device according to the present invention. In the combustible gas detection device 800 of this embodiment, a hydrogen pump cell 811 is added to the combustible gas detection device 700 of the above-described fourth embodiment, and a partition 812a forms a gas diffusion chamber 812 for the first gas concentration detection means 410. , And a gas diffusion chamber 412 for the second gas concentration detecting means 810.

The hydrogen pump cell 811 includes a hydrogen ion (proton) conductive solid electrolyte body 811a and an outer electrode 81.
1c and the inner electrode 811b. The related operation between the hydrogen pump cell 811 and the hydrogen detection cell 713 is as follows.
This is the same as the related operation between the oxygen pump cell 411 and the oxygen detection cell 413. Then, the second gas concentration detection means 810
Is a method of utilizing an oxygen ion conductive solid electrolyte body.
Similar to the gas concentration detecting means 410, the hydrogen concentration detecting characteristic becomes linear, and the handling such as calculation becomes easy.

As the detection sensitivity setting means for setting the detection sensitivity of at least one kind of specific gas detected by the gas concentration detection means, for example, in the second embodiment (see FIG. 7),
The case where the second gas diffusion rate controlling parts 410a and 510a are made of porous bodies having different diffusion resistances has been described, and the case where the carbon monoxide or hydrocarbon gas adsorbent 612a is used has been described in the third embodiment. However, in addition to these, it is also possible to set the detection sensitivity for the gas concentration detection means by controlling the temperature of the ion conductive solid electrolyte body. The difference in detection sensitivity becomes remarkable, and the measurement accuracy can be further improved.

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing an embodiment of a combustible gas detection device according to the present invention.

FIG. 2 is a sectional view illustrating details of first and second sensors shown in FIG.

FIG. 3 is an explanatory diagram showing a fuel cell system.

FIG. 4 is a graph (a) showing the detection sensitivity characteristic of the first sensor.
3 is a graph (b) showing the detection sensitivity characteristics of the second sensor.

FIG. 5 is a flowchart illustrating a processing process of the combustible gas detection device.

FIG. 6 is an explanatory diagram showing a case where three sensors are provided.

FIG. 7 is a cross-sectional view showing another embodiment of the combustible gas detection device according to the present invention.

FIG. 8 is a sectional view showing still another embodiment of the combustible gas detection device according to the present invention.

FIG. 9 is a sectional view showing still another embodiment of the combustible gas detection device according to the present invention.

FIG. 10 is a sectional view showing still another embodiment of the combustible gas detection device according to the present invention.

[Explanation of symbols]

100-800 Combustible gas detection device 10a Gas diffusion rate controlling parts 11a, 13a Ion conductive solid electrolyte body 11b, 11c Electrodes 13b, 13c Electrode 110 1st sensor (gas concentration detection means) 120 2nd sensor (gas concentration detection means) 101 gas concentration calculating means 410 to 810 gas concentration detecting means 410a, 510a gas diffusion rate controlling part (detection sensitivity setting means) 612a gas adsorber (detection sensitivity setting means) 611 third gas concentration detecting means (oxygen dope means)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G01N 27/46 331 371G 27/58 BZ F term (reference) 2G004 BB04 BD14 BL19 BM04 BM10 ZA01 5H027 AA02 BA01 KK31

Claims (11)

[Claims] 1. A gas diffusion rate controlling part for limiting a diffusion amount of a gas to be measured, an ion conductive solid electrolyte body which generates a voltage or a current by reacting with the gas to be measured which has passed through the gas diffusion rate controlling part, and ion conductivity. At least two gas concentration detecting means including electrodes for supplying or extracting voltage or current to the solid electrolyte body are provided, and different detection sensitivities are set for the respective gas concentration detecting means. A combustible gas detection device comprising gas concentration calculation means for calculating the concentrations of at least two kinds of specific gases based on the detection values of the means. 2. The gas concentration calculating means determines the sensitivity of one gas concentration detecting means to one specific gas, K1,
Let Z1 be the ratio (K1 ′ / K1) of the sensitivity K1 for one specific gas and the sensitivity K1 ′ for the other specific gas, and let the detected value of the concentration be Ip1, K2, ratio of sensitivity K2 for one specific gas and sensitivity K2 'for another specific gas (K1' / K1)
Is Z2 and the detected value of the concentration is Ip2, the concentration X (a) of one specific gas and the concentration X (b) of the other specific gas are expressed by the following formula X (a) = (K1 · Ip2−K2 · Ip1 ) / K1 ・ K2 (Z2-Z1) X (b) = (K2 ・ Z2 ・ Ip1−K1 ・ Z1 ・ Ip2) / K1 ・ K2 (Z2
-Z1) is a means for determining based on
The flammable gas detection device described in 1. 3. The flammable gas detection device according to claim 1, further comprising detection sensitivity setting means for setting detection sensitivity of at least one type of specific gas detected by the gas concentration detection means. 4. The flammable gas detection device according to claim 3, wherein the detection sensitivity setting means is a means for setting the detection sensitivity according to the size of the diffusion resistance of the gas diffusion rate controlling portion. 5. The flammable gas detection device according to claim 3, wherein the detection sensitivity setting means is a gas adsorbent that adsorbs a specific gas. 6. The combustible gas detection device according to claim 5, wherein the gas adsorbent adsorbs at least one of carbon monoxide and hydrocarbon. 7. The combustible gas detection device according to claim 4, further comprising an oxygen doping means for refreshing the gas adsorbent that has adsorbed the specific gas. 8. The flammable gas detection device according to claim 3, wherein the detection sensitivity setting means is means for setting the detection sensitivity at the temperature of the ion conductive solid electrolyte body. 9. The ion conductive solid electrolyte body of one of the gas concentration detecting means is an oxygen ion conductive solid electrolyte body, and the ion conductive solid electrolyte body of the other gas concentration detecting means is a hydrogen ion conductive solid body. It is an electrolyte body, The combustible gas detection apparatus in any one of Claims 1-3 characterized by the above-mentioned. 10. The combustible gas detection device according to claim 1, wherein a plurality of gas concentration detection means are integrally provided on the same element. 11. The combustible gas detection device according to claim 1, wherein the specific gas is hydrogen and at least one of carbon monoxide and hydrocarbon.