JP2003090819A - Method for detecting gas concentration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas concentration detecting method of excellent response. SOLUTION: In a gas sensor element 1 for detecting the specified gas concentration in a gas to be measured, the sensor output after a predetermined time is estimated and the specified gas concentration is detected by using the time derivative A(t) of the sensor output Y(t) in the gas sensor element 1, and the time derivative B(t) of A(t).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an exhaust system of an internal combustion engine,
The present invention relates to a gas concentration detection method used for detecting NOx and the like.

[0002]

2. Description of the Related Art Air pollution caused by exhaust gas emitted from an internal combustion engine for automobiles poses a serious problem in modern society, and purification standards for pollutants in exhaust gas are becoming stricter year by year. Nitrogen oxides in exhaust gas (NO
x) It is considered that the exhaust gas can be purified more efficiently by detecting the concentration and feeding back the detection result to the engine combustion control monitor, the catalyst monitor, or the like. Against this background, there has been a demand for a gas sensor element capable of accurately detecting the NOx concentration in exhaust gas.

By the way, as a conventionally well-known gas sensor element, there is a configuration as shown in FIG. In the gas sensor element 1, the oxygen pump cell 92 is arranged so as to face the first measured gas chamber 971, and by applying a voltage to the oxygen pump cell 92, the first measured gas chamber 9
Oxygen in 71 is pumped to the outside of the device. Or first
Oxygen from outside the element is pumped into the measured gas chamber 97.

Further, the gas sensor element 1 has an oxygen monitor cell 93 capable of detecting the oxygen concentration in the first measured gas chamber 971, and the oxygen in the first measured gas chamber 971 detected by the oxygen monitor cell 93. The oxygen pump cell 92 is feedback-controlled by the oxygen monitor cell 93 so that the concentration becomes constant. Second measured gas chamber 9
A sensor cell 94 that can measure the NOx concentration by measuring oxygen ions generated from NOx is provided at 72. As described above, the first measured gas chamber 971 is provided.
Since the oxygen concentration inside is controlled to be constant, the oxygen concentration inside the second measured gas chamber 972 is also constant.

Therefore, the amount of oxygen ions moving in the sensor cell 94, that is, the magnitude of the oxygen ion current in the sensor cell 94 corresponds to the NOx concentration. This makes it possible to accurately measure the NOx concentration regardless of the increase or decrease in the oxygen concentration in the exhaust gas.

[0006]

[Problems to be Solved] However, conventional NOx
Since the sensor has a long diffusion path of the gas to be measured up to the sensor cell 94 for detecting NOx inside the element,
There was a problem that the response speed was slow.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a method of detecting gas concentration having excellent responsiveness.

[0008]

According to a first aspect of the present invention, in a gas sensor element for detecting a specific gas concentration in a gas to be measured, a time differential value A of a sensor output Y (t) in the gas sensor element is obtained.
(T) and a time differential value B (t) of A (t) are used to predict a sensor output after a predetermined time, and a specific gas concentration is detected. Claim 1).

In the present invention, the specific gas concentration can be estimated from the differential value of the sensor output, paying attention to the fact that there is a correlation between the specific gas concentration to be detected and the changing speed of the sensor output of the gas sensor element. Here, FIG. 6 is a diagram schematically showing the relationship between the sensor output and the elapsed time. A broken line a shown in the figure shows a relationship when the gas concentration changes from a certain gas concentration to a high gas concentration, and a solid line b shows a relationship when the gas concentration changes to a lower gas concentration than that of the broken line a.

Consider a case where the specific gas concentration changes from a certain concentration to a higher concentration. That is, in FIG. 6, the change amount of the gas concentration at time Δt (from time t to time t + Δt) in the portion where the gas concentration is gradually increasing is Ya (t + Δt) −Ya (t) in the case of the broken line a, and the solid line In the case of b, it is Yb (t + Δt) −Yb (t). The functions Ya (t) and Yb (t) are represented by broken lines a and
It is a function of the sensor output in the vicinity of time t to time t + Δt on the solid line b.

As is known from FIG. 6, the higher the gas concentration, the larger the amount of change in the sensor output per unit time. Therefore, the average rate of change per unit time is higher when the gas concentration is higher, and the output of the specific gas concentration can be predicted from the differential value obtained by differentiating the function of the sensor output with respect to time. If a response delay occurs when the gas concentration is measured using the gas sensor element, the sensor output predicted value obtained from the differential value of the current sensor output should be provisionally used as described above. You can

Therefore, for example, when the gas concentration is detected and the detected value is used as a reference value or the like in arbitrary control, the predicted value described above is tentatively passed to the next process to perform control. Can be realized by using the gas concentration detecting method according to the present invention.

As described above, according to the present invention, it is possible to provide a gas concentration detecting method having excellent responsiveness.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The time differential value of the sensor output of the first invention (claim 1) and the further time differential value of the time differential value (that is, the time differential value of the second floor by t of the sensor output) are , The initial concentration and the change rate of the sensor output with time are measured and calculated from the map diagram etc. that shows the relationship between the two stored in the computer beforehand. At this time, information such as the oxygen concentration in the measured gas, the temperature, the flow velocity of the measured gas, the pressure, etc., which influences the map diagram showing the relationship between the temporal speed of output change and the specific gas concentration (for example, an automobile engine In the case of a gas sensor element installed in the exhaust system, it is possible to correct the calculated value of the specific gas concentration described above by obtaining it). The details of the prediction method will be described later.

Further, the detection method according to the present invention, for example, from the exhaust gas flowing in the combustion exhaust system of an automobile internal combustion engine, N
It can be used when measuring Ox, HC, CO, oxygen concentration, etc. As an element to which this detection method is applied, a gas sensor element having a plurality of electrochemical cells and the like can be mentioned. The electrochemical cell in this case is a cell of a limiting current type or a concentration electromotive force type consisting of a solid electrolyte plate and a pair of electrodes, and is a gas from the current value flowing in the cell or the electromotive force between the electrodes in the cell. Detect the concentration. As for the shape of the element, not only the laminated type described in the present embodiment but also a cup type element can be applied. Also, the detection method of the present invention can be realized by using a semiconductor gas sensor element.

The sensor output Y (t) at time t
In contrast, the sensor output Y (t + Δ at time t + Δt
t) is the time differential value A (t) of the sensor output Y (t),
It is preferable to use the time differential value B (t) of A (t) to calculate based on the following (Equation 3) and (Equation 4) (claim 2).

[0017]

[Equation 3]

[0018]

[Equation 4]

This makes it possible to more accurately predict the sensor output, that is, the specific gas concentration.

Further, the measured gas chamber into which the measured gas is introduced under a predetermined diffusion resistance, an electrode provided on the surface of a solid electrolyte plate having oxygen ion conductivity, and the electrode are paired to constitute the above measured target. An oxygen pump cell, which is composed of electrodes facing the gas chamber, is configured to introduce or discharge oxygen into the gas chamber to be measured by energizing these electrodes, and adjust the oxygen concentration in the gas chamber to be measured; Of a specific gas concentration in the measured gas chamber from the ion current generated between these electrodes, and an electrode provided on the surface of a solid electrolyte plate and formed in a pair with the electrode and facing the measured gas chamber. It is preferable to use a gas sensor element configured to detect (Claim 3).

In this case, the specific gas concentration can be detected without being affected by the oxygen concentration in the measured gas,
The detection accuracy is improved.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) In the detection method of this embodiment, the time differential value A (t) of the sensor output Y (t) in the gas sensor element and A
Using the time differential value B (t) of (t), the sensor output after a predetermined time is predicted and the specific gas concentration is detected. At this time, with respect to the sensor output Y (t) at time t, the time t
The sensor output Y (t + Δt) at + Δt is described above using the time differential value A (t) of the sensor output Y (t) and the time differential value B (t) of A (t). The sensor output after a predetermined time is predicted based on 1) and (Equation 2).

The gas sensor element 1 used in the gas concentration detecting method described in this example will be described. As shown in FIGS. 1 and 2, the gas sensor element 1 has a measured gas chamber 7 into which a measured gas is introduced under a predetermined diffusion resistance, and is provided on the surface of an oxygen ion conductive solid electrolyte plate 5. The electrode 22 and the electrode 21 that is paired with the electrode 22 and faces the gas chamber 7 to be measured.
The oxygen pump cell 2 is configured to introduce or discharge oxygen into the measured gas chamber 7 by energizing the measured gas chambers 1 and 22 to adjust the oxygen concentration in the measured gas chamber 7.

The gas sensor element 1 comprises an electrode 42 provided on the surface of an oxygen ion conductive solid electrolyte plate 6 and an electrode 41 which is paired with the electrode 42 and faces the gas chamber 7 to be measured. The sensor cell 4 is configured to detect the specific gas concentration in the measured gas chamber 7 from the ion current generated between the electrodes 41 and 42 of the.

The details will be described below. The gas sensor element of this example is a composite type element that is installed in the exhaust system of an automobile engine, measures the NOx concentration in the exhaust gas of the engine, and is used for controlling combustion of the engine.

As shown in FIGS. 1 and 2, the gas sensor element 1 of this example is a sheet-shaped solid electrolyte plate 5 for forming an oxygen pump cell 2, a sheet-shaped solid electrolyte plate 5 for forming an oxygen monitor cell 3, and a sensor cell 4. Solid electrolyte plate 6 and a sheet-like spacer 8 for forming a gas chamber 7 to be measured,
A sheet-shaped spacer 9 for forming the reference gas chamber 100 and a heater 10 for heating these are sequentially laminated and configured.

The gas to be measured chamber 7 is a small chamber into which the gas to be measured is introduced from the atmosphere in which the gas to be measured spreads outside the element, and is located between the solid electrolyte plates 5 and 6 as shown in FIG. It is formed by the holes 81 and 82 provided in the spacer 8. Then, in the gas chamber 7 to be measured, with the narrowed narrowed portion 83 as a boundary between the holes 81 and 82, holes are sequentially drawn from the tip side (left side in FIGS. 1 and 2) of the gas sensor element 1. The first measured gas chamber 71 is constituted by 81, and the second measured gas chamber 72 is constituted by the hole 82.
The narrowed portion 83 serves as a diffusion resistance passage 73 that limits the rate of the gas to be measured that is directed from the first gas chamber 71 to be measured to the second gas chamber 72 to be measured.

The first measured gas chamber 71 has a pinhole 11 as a diffusion resistance means penetrating the solid electrolyte plate 5.
Through the outside of the device, which is the atmosphere on the measured gas side. The size of the pinhole 11 is appropriately set so that the diffusion speed of the gas under measurement introduced through the first gas under measurement chamber 71 and the second gas under measurement chamber 72 through the pinhole 11 becomes a predetermined speed. To be done.

A solid protective layer 12 made of porous alumina or the like is formed on the solid electrolyte plate 5 so as to cover the pinhole 11 from the atmosphere to be measured gas. Poisoning of the positioned electrodes 21, 31, 41 and clogging of the pinhole 11 are prevented. In addition,
As the diffusion resistance means, in addition to the pinhole, a porous body capable of being ventilated may be provided at the position where the pinhole 11 is formed.

In the reference gas chamber 100, the atmosphere as the reference oxygen concentration gas having a constant oxygen concentration is introduced, and the vent hole 91 provided in the spacer 9 laminated below the solid electrolyte plate 6 is provided.
Formed in. The hole 91 is formed in the gas sensor element 1
Has a passage portion 92 as a groove extending in the longitudinal direction, and the atmosphere is introduced through the passage portion 92.

The spacers 8 and 9 are made of an insulating material such as alumina. Solid electrolyte plates 5, 6 for constructing an oxygen pump cell 2, an oxygen monitor cell 3, and a sensor cell 4.
Consists of an electrolyte having oxygen ion conductivity such as zirconia or ceria.

The oxygen pump cell 2 includes a solid electrolyte plate 5 and
It is composed of a pair of electrodes 21 and 22 arranged so as to face each other so as to sandwich the solid electrolyte plate 5. One electrode 21 of the pair of electrodes 21, 22 is provided in contact with the solid electrolyte plate 5 facing the first measured gas chamber 71 located on the gas flow upstream side in the measured gas chamber 7, and the other electrode 21 is provided. The electrode 22 is provided in contact with the solid electrolyte plate 5 so as to face the measured gas existing space. Further, the oxygen pump cell 2 is connected to a pump circuit 240 having a power supply 25.

The sensor cell 4 comprises a solid electrolyte plate 6 and a pair of electrodes 4 arranged to face each other so as to sandwich the solid electrolyte plate 6.
1 and 42. One electrode 41 of the pair of electrodes 41, 42 is provided in contact with the solid electrolyte plate 6 facing the second measured gas chamber 72 located on the gas flow downstream side in the measured gas chamber 7, and the other electrode 41 is provided. The electrode 42 is provided facing the reference gas chamber 100 and in contact with the solid electrolyte plate 6. Further, the sensor cell 4 is connected to a sensor circuit 440 including a power supply 45 and an ammeter 46.

The oxygen monitor cell 3 includes a solid electrolyte plate 6 and
It is composed of a pair of electrodes 31 and 32 arranged so as to face each other so as to sandwich the solid electrolyte plate 6. One electrode 31 of the pair of electrodes 31, 32 is provided in contact with the solid electrolyte plate 6 facing the second measured gas chamber 72 located downstream of the gas flow in the measured gas chamber 7, and the other electrode 31 is provided. The electrode 32 is provided facing the reference gas chamber 100 and in contact with the solid electrolyte plate 6. Further, the oxygen monitor cell 3 includes a power source 35 and an ammeter 36.
Is connected to the monitor circuit 340. Further, a circuit for feedback-controlling the power supply 25 from the value of the ammeter 36 is provided.

Here, NO in the gas to be measured is applied to one electrode 21, 31 of the oxygen pump cell 2 and the oxygen sensor cell 3.
In order to suppress the decomposition of x, it is preferable to use an electrode having a low NOx decomposition activity. Specifically, Pt and A as main components
A porous cermet electrode containing u is preferably used. At this time, the content of Au in the metal component is preferably about 1 to 10% by weight.

Further, as one electrode 41 of the sensor cell 4, it is preferable to use an electrode having a high NOx decomposition activity in order to decompose NOx in the gas to be measured. Specifically, a porous cermet electrode containing Pt and Rh as main components is preferably used. At this time, the content of Rh in the metal component is preferably about 10 to 50% by weight. Oxygen pump cell 2, oxygen monitor cell 3, electrode 22 of sensor cell 4,
Pt porous cermet electrodes are suitably used for 32 and 42, for example.

Further, as shown in FIG.
Leads 23, 24, 33, 34, 43, 44 for extracting electric signals from the electrodes 21, 22, 31, 32, 41, 42 are provided on the 1, 22, 31, 32, 41, 42.
Are integrally formed. Here, the solid electrolyte plates 5, 6
It is preferable to form an insulating layer (not shown) of alumina or the like between the solid electrolyte plates 5, 6 and the leads 23 and the like in the portions other than the electrodes 21 and the like, particularly the portions where the leads and the like are formed.
The heater 10 is formed by patterning a heating element 14 that generates heat when energized on the upper surface of a heater sheet 13 made of alumina, and the heating element 14 has an upper surface (a surface on the spacer 9 side)
An alumina layer 15 for insulation is formed.

As the heating element 14, a cermet made of Pt and ceramics such as alumina is used. This heater 10 causes the heating element 14 to generate heat by external power supply,
The cells 2, 3 and 4 are heated to the activation temperature. In addition, as shown in FIG. 2, the heating element 14 and the electrodes 21 of the cells 2, 3 and 4 are connected to the leads 23, respectively.
Etc., and through the through holes 130 formed in the sheets 5, 8, 9, 15, and 13 are electrically connected to the terminals 140.

A lead wire is connected to the terminal 140 through a connector by crimping, brazing, etc., so that an electric signal can be exchanged between the external circuit and each of the cells 2, 3, 4 and the heater 10. (Not shown).

In manufacturing the gas sensor element 1 shown in this example, solid electrolyte plates 5 and 6, spacers 8 and 9,
The alumina layer 15 and the heater sheet 13 can be formed of a green sheet formed into a sheet shape by a doctor blade method, an extrusion molding method, or the like. The electrodes 21, etc., the leads 23, etc., and the terminals 140 can be formed on the green sheet by screen printing or the like. Then, the green sheets are laminated and fired to be integrated into the gas sensor element 1.

Next, the operating principle of the gas sensor element 1 will be described. In FIG. 1, the gas to be measured passes through the porous protective layer 12 and the pinhole 11 and then passes through the first gas chamber 71 to be measured.
Will be introduced to. The amount of gas introduced is the porous protective layer 1
2, determined by the diffusion resistance of the pinhole 11. Further, the measured gas is introduced into the second measured gas chamber 72.
When a voltage is applied to the pair of electrodes 21, 22 of the oxygen pump cell 2 so that the electrode 22 becomes a positive electrode, the oxygen in the measurement gas is reduced on the electrode 21 on the side of the first measurement gas chamber 71 to generate oxygen. It becomes an ion and the electrode 22 is generated by the pumping action.
Discharged to the side.

On the contrary, the electrode 21 on the side of the first measured gas chamber 71
When a voltage is applied so that the voltage becomes a positive pole, oxygen and water vapor in the gas to be measured are reduced on the electrode 22 to become oxygen ions, which are discharged to the electrode 21 side by the pumping action. The oxygen concentration in the measured gas chamber 7 can be controlled by this oxygen pump action.

A pair of electrodes 31, 32 of the oxygen monitor cell 3
Then, when a predetermined voltage (for example, 0.40 V) is applied so that the electrode 32 on the side of the reference gas chamber 100 becomes a positive electrode, the measured gas on the electrode 31 on the side of the second measured gas chamber 72 is Oxygen is reduced to oxygen ions, which are discharged to the electrode 32 side by the pumping action.

The electrode 31 is made of Pt which is inert to NOx decomposition.
Since it is an Au cermet electrode, the oxygen ion current flowing between the electrodes 31 and 32 passes through the porous protective layer 12, the pinhole 11, the first measured gas chamber 71, etc.
It depends on the amount of oxygen in the gas to be measured that reaches to, and not on the amount of NOx. Therefore, so that the current value between the electrodes 31 and 32 becomes a predetermined constant value (for example, 0.5 μA),
By controlling the applied voltage between the electrodes of the oxygen pump cell 2, the oxygen concentration in the second measured gas chamber 72 can be controlled to be constant.

On the pair of electrodes 41, 42 of the sensor cell 4,
A predetermined voltage (for example, 0.40 V) is applied so that the electrode 42 on the reference gas chamber 100 side becomes a positive electrode. Electrode 41
Is a Pt-Rh cermet electrode that is active in decomposing NOx, so oxygen and NOx in the gas to be measured are reduced to oxygen ions on the electrode 41 on the side of the second gas chamber 72 to be measured, and become oxygen ions by the pumping action. It is discharged to the electrode 42 side.
In this example, the oxygen pump cell 2 is controlled so that the current value between the electrodes 31 and 32 of the oxygen monitor cell 3 becomes a constant value (for example, 0.5 μA).
The current value between 1 and 42 is also controlled to a constant value (for example, 0.5 μA). On the other hand, if NOx exists in the measured gas,
Since the current value increases according to the NOx concentration, the NOx concentration in the measured gas can be detected by this.

Next, the gas concentration detecting method according to this embodiment will be described in detail. FIG. 3 is a block diagram showing a method for measuring the NOx concentration in the exhaust gas. The sensor control unit S2 of the sensor control circuit S1 drives the gas sensor element 1 by giving a control signal, receives the sensor signal from the gas sensor element 1, and outputs the sensor output Y.
(T) S3 is output to the differential operation section S4.

In the differential operation section S4, the sensor output Y (t)
The time differential value A (t) S5 of S3 is calculated. Furthermore A
(T) The differential value B (t) S6 of S5 is calculated to obtain A
(T) and B (t) are output to the integral calculation unit S7. In the integration calculation unit S7, calculation is performed based on the following (Equation 5) and (Equation 6), and the sensor output Y (t
+ Δt), that is, the expected output S8 at time t + Δt is calculated.

[0048]

[Equation 5]

[0049]

[Equation 6]

Further, the expected output S8 at the above time t + Δt
Is output to the differential calculation unit S4 and repeated calculation is performed, whereby the sensor output after a predetermined time can be predicted.
As a result, the reached value of the sensor output at a certain gas concentration, that is, the specific gas component concentration can be predicted before the sensor output actually responds, so that a gas sensor element with excellent responsiveness can be obtained.

FIG. 4 and FIG. 5 are graphs showing the response characteristics of the sensor when the NOx concentration in the exhaust gas which is the gas to be measured is changed. It shows the relationship between the sensor output and the response time by the detection method according to the related art and this example. FIG. 4 is a relationship diagram when switching from a state where the oxygen concentration in the exhaust gas is 5% and NO concentration is 0 to a state where the oxygen concentration is 5% and NO is 100 pm. In contrast, FIG. 5 is a relationship diagram when the oxygen concentration is 5% and the NO concentration is 100 pm, and the oxygen concentration is 5% and the NO concentration is 0.

As can be seen from the figure, in this example, the predicted value of the sensor output after a predetermined time is always output, so it can be seen that the response speed is obviously higher than in the conventional example.

The present invention is not limited to the gas sensor element of the above-mentioned embodiment, and the present invention is not limited to the gas sensor element 1 having the structure shown in the conventional example of FIG. The gas concentration according to the invention can be detected. In the gas sensor element 1 of FIG. 7, an oxygen monitor cell 93 is connected to a monitor circuit equipped with a voltmeter.

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view of a gas sensor element according to a first embodiment.

FIG. 2 is a perspective development view of the gas sensor element according to the first embodiment.

FIG. 3 is a block diagram showing a method of predicting a sensor output Y (t + Δt) at time t + Δt in the first embodiment.

FIG. 4 is a diagram showing the relationship between sensor output and time according to the present invention in the first embodiment.

FIG. 5 is a diagram showing the relationship between sensor output and time according to the present invention in the first embodiment.

FIG. 6 is a diagram showing a relationship between elapsed time and sensor output.

FIG. 7 is an explanatory diagram of a conventional gas sensor element.

[Explanation of symbols]

1. ． ． Gas sensor element, 100. ． ． Reference gas chamber, 2. ． ． Oxygen pump cell, 21, 22, 31, 32, 41, 42. ． ． electrode, 3. ． ． Oxygen monitor cell, 4. ． ． Sensor cell, 5,6. ． ． Solid electrolyte plate, 7. ． ． Measured gas chamber,

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Daisuke Makino             14 Iwatani Shimohakaku-cho, Nishio-shi, Aichi Stock Association             Company Japan Auto Parts Research Institute (72) Inventor Kenji Kanehara             14 Iwatani Shimohakaku-cho, Nishio-shi, Aichi Stock Association             Company Japan Auto Parts Research Institute (72) Inventor Shigeki Ohmichi             14 Iwatani Shimohakaku-cho, Nishio-shi, Aichi Stock Association             Company Japan Auto Parts Research Institute (72) Inventor Akio Tanaka             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO F-term (reference) 2G060 AA03 AB05 AB08 AB10 AB16                       AB19 AE19 AF06 AG11 BA01                       BB09 HC11 KA01

Claims (3)

[Claims] 1. A gas sensor element for detecting a specific gas concentration in a gas to be measured, the time differential value A (t) and A (t) of a sensor output Y (t) in the gas sensor element.
A method for detecting a gas concentration, which comprises predicting a sensor output after a predetermined time by using a time differential value B (t) of the above, and detecting a specific gas concentration. 2. The sensor output Y (t) at time t, wherein the sensor output Y (t + Δt) at time t + Δt is the time differential value A (t) of the sensor output Y (t). ) And the time derivative B (t) of A (t),
A method for detecting gas concentration, which is calculated based on the following (Equation 1) and (Equation 2). [Equation 1] [Equation 2] 3. The measured gas chamber for introducing a measured gas under a predetermined diffusion resistance, an electrode provided on the surface of a solid electrolyte plate having oxygen ion conductivity, and a pair of the electrode according to claim 1 or 2. And oxygen arranged to adjust the oxygen concentration in the measured gas chamber by introducing or discharging oxygen into the measured gas chamber by energizing these electrodes. A pump cell, an electrode provided on the surface of a solid electrolyte plate having oxygen ion conductivity, and an electrode which is paired with the electrode and faces the gas chamber to be measured. The ionic current generated between these electrodes is used to measure the gas to be measured. A method for detecting gas concentration, comprising using a gas sensor element having a sensor cell configured to detect a specific gas concentration in a chamber.