JP2023103963A - gas sensor - Google Patents

Abstract

To provide a gas sensor element capable of making both high-precision concentration measurement in an environment with high concentration of a specific gas in a measurement target gas and high-precision concentration measurement in an environment with low concentration of the specific gas.SOLUTION: A gas sensor according to an aspect of the present invention is configured to adjust the sensor element driving temperature such that cell resistance of a main pump cell becomes a predetermined value. In a gas sensor according to an aspect of the present invention, a gradient of cell resistance of the main pump cell is greater than that of cell resistance of a measurement pump cell.SELECTED DRAWING: Figure 1

Description

The present invention relates to gas sensors.

Conventionally, in gas sensors that detect the concentration of specific gases such as oxygen and _NOx in gases to be measured such as automobile exhaust gas, a heater is embedded inside to activate the oxygen ion conductive solid electrolyte that constitutes the sensor element. A gas sensor is known which has a sensor element which is shaped as follows. For example, Patent Literature 1 listed below discloses a gas sensor having a heater embedded therein and having a sensor element for controlling the electric power of the heater so that the impedance of the pump cell for measurement is constant.

JP-A-10-318979

In the future, with the tightening of automobile exhaust gas regulations, gas sensors will not only be able to accurately measure concentrations in environments with high concentrations of specific gases in the gas to be measured, but also in environments with low concentrations of specific gases. It is expected that highly accurate concentration measurement will be required. As a result of studying from such a point of view, the inventors of the present invention have found that the conventional gas sensor having the above-described structure can perform highly accurate concentration measurement in an environment where the concentration of the specific gas in the gas to be measured is high, The inventors have found a problem that it is difficult to achieve high-precision concentration measurement in a low-concentration environment. Details will be described below.

First, the inventors of the present invention have found a problem that, in a gas sensor that measures the concentration of a specific gas in a gas to be measured, fluctuations in the offset value greatly affect the measurement accuracy in an environment where the concentration is generally low. I found something. That is, since the measured concentration changes by several ppm due to the fluctuation of the offset value, even if the fluctuation of the offset value is constant, the lower the concentration of the specific gas in the gas to be measured, the more the offset value with respect to the measurement accuracy. The effect of fluctuations in is greater. For example, if the concentration of the specific gas in the measured gas is 500 ppm, even if the offset value fluctuates by 5 ppm, the error due to the offset value fluctuation remains at 1%. On the other hand, when the concentration of the specific gas in the measured gas is 50 ppm, if the offset value fluctuates by 5 ppm, the error due to the offset value fluctuation is 10%, and the offset value fluctuation greatly affects the measurement accuracy.

Here, one of the causes of the offset value fluctuation is the temperature fluctuation of the sensor element (particularly, the electrode such as the measuring electrode) due to the set temperature of the heater, the temperature of the gas to be measured, and the like. Therefore, the inventors of the present invention have studied suppressing the fluctuation of the offset value by lowering the temperature of the sensor element, that is, by lowering the temperature of the heater.

As a result, the inventors of the present invention have found that simply lowering the temperature of the sensor element (electrode) poses a problem that the measurement accuracy may deteriorate. That is, when the temperature of the sensor element is lowered, the resistance to the reaction of the adjustment pump cell, which is an electrochemical pump cell for adjusting the oxygen concentration, increases, so it is necessary to increase the pump voltage applied to the adjustment pump cell. However, if the pump voltage applied to the adjustment pump cell is increased, the specific gas in the gas to be measured is decomposed in the adjustment pump cell, and as a result, the sensitivity to the specific gas may decrease. If it is high, there is a risk that the measurement accuracy will deteriorate.

In one aspect, the present invention has been made in view of such circumstances, and its object is to perform highly accurate concentration measurement in an environment where the concentration of a specific gas in a gas to be measured is high, and to perform measurement in an environment where the concentration is low. An object of the present invention is to provide a gas sensor element capable of achieving both high-precision concentration measurement under low pressure.

The present invention adopts the following configurations in order to solve the above-described problems.

A gas sensor according to a first aspect is a sensor element formed by stacking a plurality of oxygen ion conductive solid electrolyte layers, and is provided with an internal space into which a gas to be measured is introduced and the internal space. An electrochemical pump cell comprising a measuring electrode, an outer pumping electrode provided at a location different from the inner cavity, and the solid electrolyte layer existing between the measuring electrode and the outer pumping electrode. a measuring pump cell, an inner pump electrode formed facing the inner space, a third electrode provided in a manner exposed to an external space in contact with the outer pump electrode or the solid electrolyte layer, and the a regulating pump cell, which is an electrochemical pump cell composed of an inner pump electrode and the solid electrolyte layer present between the outer pump electrode or the third electrode; a heater unit for heating the sensor element to a predetermined temperature; a detection unit for detecting a cell resistance value of the adjustment pump cell; and a cell of the adjustment pump cell detected by the detection unit. an adjusting unit that adjusts the predetermined temperature so that the resistance value becomes a predetermined value, and the slope of the cell resistance of the adjusting pump cell with respect to the input power to the heater unit is determined by the resistance to the heater unit. It is larger than the slope of the cell resistance of the measuring pump cell with respect to the input power.

In this configuration, the predetermined temperature is adjusted, that is, the predetermined temperature is controlled so that the cell resistance value of the adjustment pump cell detected by the detection unit becomes the predetermined value. Further, the slope of the cell resistance of the adjustment pump cell with respect to the input power to the heater section is larger than the slope of the cell resistance of the measurement pump cell with respect to the input power to the heater section. That is, in this configuration, the slope of the cell resistance with respect to the input power to the heater section is larger in the adjustment pump cell than in the measurement pump cell.

By controlling the predetermined temperature and setting the cell resistance value of the adjustment pump cell to the predetermined value, the following effects can be obtained. That is, since the value of the cell resistance of the adjustment pump cell is maintained at the predetermined value, the resistance to the reaction of the adjustment pump cell does not increase, and it is necessary to increase the pump voltage applied to the adjustment pump cell. Nor. Therefore, "as a result of increasing the pump voltage applied to the adjustment pump cell, the specific gas in the gas to be measured is decomposed in the adjustment pump cell, and the measurement accuracy of the concentration of the specific gas deteriorates. It is possible to avoid the situation that the measurement accuracy deteriorates when the concentration is high.

Further, with respect to the slope of the cell resistance with respect to the input power, since the slope of the adjustment pump cell is larger than the slope of the measurement pump cell, a small input power causes the cell resistance value of the adjustment pump cell to rise to the predetermined value. value can be controlled.

Furthermore, since the slope of the cell resistance of the adjustment pump cell with respect to the input power is large, when varying the input power (that is, the predetermined temperature) so that the value of the cell resistance of the adjustment pump cell becomes a predetermined value, Moreover, the fluctuation of the predetermined temperature can be reduced. By reducing the fluctuation of the predetermined temperature, the fluctuation of the offset value can be suppressed, and highly accurate concentration measurement can be realized even when the concentration of the specific gas in the gas to be measured is low. can.

In addition, regarding the slope of the cell resistance with respect to the input power, the slope of the measurement pump cell is smaller than the slope of the adjustment pump cell. Therefore, even if the temperature (for example, the temperature of the measurement pump cell) fluctuates, the change in the cell resistance of the measurement pump cell is small and the fluctuation of the offset value can be suppressed.

As described above, the gas sensor according to the first aspect avoids a situation in which the measurement accuracy deteriorates when the concentration of the specific gas in the gas to be measured is high. Highly accurate density measurement can be achieved even when the density is low. In other words, the gas sensor according to the first aspect achieves both high-accuracy concentration measurement in an environment where the concentration of the specific gas in the gas to be measured is high and high-accuracy concentration measurement in an environment where the concentration is low. can be done. The "slope of the cell resistance with respect to the input power to the heater section" is, for example, the "slope of the cell resistance with respect to the input power to the heater section in the atmosphere".

A gas sensor according to a second aspect is the gas sensor according to the first aspect, wherein the slope of the cell resistance of the adjustment pump cell with respect to the input power to the heater section is the measured It may be 1.5 times to 1000 times the slope of the cell resistance of the pump cell. In this configuration, the slope of the cell resistance of the adjustment pump cell with respect to the power applied to the heater section is 1.5 to 1000 times the slope of the cell resistance of the measurement pump cell with respect to the power applied to the heater section. is. As described above, in order to achieve both high-accuracy concentration measurement under high concentration and high-accuracy concentration measurement under low concentration, the slope of the cell resistance of the adjustment pump cell with respect to the input power is determined by the input power. is preferably greater than the slope of the cell resistance of the measuring pump cell with respect to . The inventor of the present invention has determined through experiments that the slope of the cell resistance of the adjustment pump cell with respect to the input power is preferably 1.5 to 1000 times the slope of the cell resistance of the measurement pump cell with respect to the input power. It was confirmed. Therefore, in the gas sensor according to the second aspect, the slope of the cell resistance with respect to the input power is such that the adjustment pump cell and the measurement pump cell satisfy the above-described relationship, so that both under high concentration and under low concentration, Highly accurate concentration measurement can be realized.

A gas sensor according to a third aspect is the gas sensor according to the first or second aspect, wherein the area of the measurement electrode may be larger than the area of the inner pump electrode. In such a configuration the area of the measuring electrode is larger than the area of the inner pump electrode. As described above, in order to achieve both high-accuracy concentration measurement under high concentration and high-accuracy concentration measurement under low concentration, the slope of the cell resistance of the adjustment pump cell with respect to the input power is determined by the input power. is preferably greater than the slope of the cell resistance of the measuring pump cell with respect to . Through experiments, the inventors of the present invention have found that the area of the measurement electrode must be increased to make the slope of the cell resistance of the adjustment pump cell with respect to the input power larger than the slope of the cell resistance of the measurement pump cell with respect to the input power. It has been found useful to have a larger area than the inner pump electrode. Therefore, in the gas sensor according to the third aspect, by making the area of the measurement electrode larger than the area of the inner pump electrode, highly accurate concentration measurement can be realized in both high and low concentrations. can.

A gas sensor according to a fourth aspect is the gas sensor according to the first or second aspect, wherein the measurement electrode may be thicker than the inner pump electrode. In such a configuration, the thickness of the measurement electrode is greater than the thickness of the inner pump electrode. As described above, in order to achieve both high-accuracy concentration measurement under high concentration and high-accuracy concentration measurement under low concentration, the slope of the cell resistance of the adjustment pump cell with respect to the input power is determined by the input power. is preferably greater than the slope of the cell resistance of the measuring pump cell with respect to . Through experiments, the inventors of the present invention have found that the thickness of the measurement electrode is required to make the slope of the cell resistance of the adjustment pump cell with respect to the input power larger than the slope of the cell resistance of the measurement pump cell with respect to the input power. have found it useful to make it thicker than the thickness of the inner pump electrode. Therefore, in the gas sensor according to the fourth aspect, by making the thickness of the measurement electrode thicker than the thickness of the inner pump electrode, highly accurate concentration measurement can be realized both under high concentration and under low concentration. can be done.

A gas sensor according to a fifth aspect is the gas sensor according to any one of the first to fourth aspects, wherein the measurement electrode may have a lower porosity than the inner pump electrode. In such a configuration, the porosity of the measurement electrode is lower than that of the inner pump electrode. As described above, in order to achieve both high-accuracy concentration measurement under high concentration and high-accuracy concentration measurement under low concentration, the slope of the cell resistance of the adjustment pump cell with respect to the input power is determined by the input power. is preferably greater than the slope of the cell resistance of the measuring pump cell with respect to . Through experiments, the inventors of the present invention have found that the porosity of the measurement electrode is required to make the slope of the cell resistance of the adjustment pump cell with respect to the input power larger than the slope of the cell resistance of the measurement pump cell with respect to the input power. was found to be useful to have a lower than the porosity of the inner pump electrode. Therefore, in the gas sensor according to the fifth aspect, by making the porosity of the measurement electrode lower than the porosity of the inner pump electrode, high-accuracy concentration measurement can be achieved both under high and low concentrations. can do.

A gas sensor according to a sixth aspect is the gas sensor according to any one of the first to fifth aspects, wherein the measurement electrode and the inner pump electrode are cermet electrodes of zirconia and a noble metal, and , the ratio of noble metal to zirconia may be higher than the ratio of noble metal to zirconia in the inner pump electrode. In that arrangement, the measuring electrode and the inner pump electrode are cermet electrodes of zirconia and noble metal, and the ratio of noble metal to zirconia is higher in the measuring electrode than in the inner pump electrode. As described above, in order to achieve both high-accuracy concentration measurement under high concentration and high-accuracy concentration measurement under low concentration, the slope of the cell resistance of the adjustment pump cell with respect to the input power is determined by the input power. is preferably greater than the slope of the cell resistance of the measuring pump cell with respect to . Through experiments, the inventors of the present invention have found that the ratio of noble metal to zirconia is necessary to make the slope of the cell resistance of the adjustment pump cell with respect to the input power larger than the slope of the cell resistance of the measurement pump cell with respect to the input power. We have found it useful to have a higher ratio at the measuring electrode than at the inner pump electrode. Therefore, in the gas sensor according to the sixth aspect, by making the ratio of noble metal to zirconia higher in the measurement electrode than in the inner pump electrode, high accuracy can be achieved both under high concentration and under low concentration. Densitometry can be achieved.

A gas sensor according to a seventh aspect is the gas sensor according to any one of the first to sixth aspects, even if the Au content of the measurement electrode is lower than the Au content of the inner pump electrode. good. In such a configuration, the Au content of the measuring electrode may be lower than the Au content of the inner pump electrode, for example the Au content of the measuring electrode may be 0%, i.e. the measurement The electrodes may not contain Au. Even if the measurement electrode contains Au, the Au content of the measurement electrode is lower than the Au content of the inner pump electrode. As described above, in order to achieve both high-accuracy concentration measurement under high concentration and high-accuracy concentration measurement under low concentration, the slope of the cell resistance of the adjustment pump cell with respect to the input power is determined by the input power. is preferably greater than the slope of the cell resistance of the measuring pump cell with respect to . Through experiments, the inventors of the present invention have found that the following measurement electrodes are required to make the slope of the cell resistance of the adjustment pump cell with respect to the input power larger than the slope of the cell resistance of the measurement pump cell with respect to the input power. It was confirmed that it is useful to configure That is, it was confirmed that it is useful to make the Au content of the measurement electrode lower than the Au content of the inner pump electrode. That is, it was confirmed that it is useful to include Au in the inner pump electrode and not include Au in the measurement electrode. Further, it was confirmed that even when the measurement electrode contains Au, it is useful to make the Au content of the measurement electrode lower than the Au content of the inner pump electrode. Therefore, in the gas sensor according to the seventh aspect, the content of Au in the measurement electrode is lower than the content of Au in the inner pump electrode, so that the concentration can be obtained with high precision regardless of whether the concentration is high or low. measurements can be realized.

A gas sensor according to an eighth aspect is the gas sensor according to any one of the first to seventh aspects, wherein the distance between the measurement electrode and the outer pump electrode is equal to the distance between the inner pump electrode and the outer pump electrode. Alternatively, it may be smaller than the distance from the third electrode. In such an arrangement the distance between the measuring electrode and the outer pump electrode is smaller than the distance between the inner pump electrode and the outer pump electrode or the third electrode. As described above, in order to achieve both high-accuracy concentration measurement under high concentration and high-accuracy concentration measurement under low concentration, the slope of the cell resistance of the adjustment pump cell with respect to the input power is determined by the input power. is preferably greater than the slope of the cell resistance of the measuring pump cell with respect to . The inventors of the present invention have found through experiments that the slope of the cell resistance of the adjustment pump cell with respect to the input power is larger than the slope of the cell resistance of the measurement pump cell with respect to the input power, in order to It has been found useful to make the distance between the pump electrodes smaller than the distance between the inner pump electrode and the outer pump electrode or the third electrode. Therefore, in the gas sensor according to the eighth aspect, the distance between the measurement electrode and the outer pump electrode is made smaller than the distance between the inner pump electrode and the outer pump electrode or the third electrode. As a result, highly accurate concentration measurement can be achieved in both high and low concentrations.

As another aspect of the gas sensor according to each of the above aspects, one aspect of the present invention may be an information processing method or a program that realizes all or part of each of the above configurations. However, it may be a storage medium that stores such a program and is readable by a computer, other device, machine, or the like. Here, a computer-readable storage medium is a medium that stores information such as a program by electrical, magnetic, optical, mechanical, or chemical action. An information processing method that implements all or part of each of the above configurations may be called, for example, a gas sensor control method or the like, depending on the content of calculations involved. Similarly, a program that implements all or part of each of the above configurations may be referred to as, for example, a gas sensor control program.

For example, a method for controlling a gas sensor according to a ninth aspect is a sensor element formed by laminating a plurality of oxygen ion conductive solid electrolyte layers, wherein an internal cavity into which a gas to be measured is introduced; an external pump electrode provided at a location different from the internal space; and the solid electrolyte layer existing between the measurement electrode and the external pump electrode. a measuring pump cell which is a chemical pump cell; an inner pump electrode formed facing the internal space; a regulating pump cell which is an electrochemical pump cell composed of three electrodes and the solid electrolyte layer present between the inner pump electrode and the outer pump electrode or the third electrode; a control method for a gas sensor including a sensor element embedded in a gas sensor for heating the sensor element to a predetermined temperature, the method comprising: a detection step of detecting a cell resistance value of the adjustment pump cell; and an adjusting step of adjusting the predetermined temperature so that the cell resistance value of the adjusting pump cell detected in the detecting step becomes a predetermined value. The slope of the cell resistance of the adjustment pump cell with respect to the input power is greater than the slope of the cell resistance of the measurement pump cell with respect to the power input to the heater section.

According to the present invention, it is possible to provide a gas sensor element capable of both highly accurate concentration measurement under an environment where the concentration of a specific gas in a gas to be measured is high and highly accurate concentration measurement under an environment where the concentration is low. can be done.

FIG. 1 is a diagram schematically showing an example of the configuration of a gas sensor, including a vertical cross-sectional view along the longitudinal direction of the sensor element. 2 is a diagram showing an example of a functional configuration of a controller included in the sensor of FIG. 1. FIG. FIG. 3 is a diagram showing the slope of the cell resistance of each of the main pump cell and the measurement pump cell with respect to the input power to the heater section in the sensor of FIG. FIG. 4 shows an example of numerical values for each of the electrode area, thickness, porosity, ratio of noble metal to zirconia, Au content, and distance between electrodes for the main pump cell and the measuring pump cell of the sensor in FIG. It is a figure which shows. FIG. 5 shows numerical values for each of the electrode area, thickness, porosity, ratio of noble metal to zirconia, Au content, and distance between electrodes for the main pump cell and the measurement pump cell of the sensor according to the modification. It is a figure which shows an example. FIG. 6 is a diagram showing an organized summary of experiments conducted by the inventors of the present invention.

Hereinafter, an embodiment (hereinafter also referred to as "this embodiment") according to one aspect of the present invention will be described based on the drawings. However, this embodiment described below is merely an example of the present invention in every respect. It goes without saying that various modifications and variations can be made without departing from the scope of the invention. That is, in implementing the present invention, a specific configuration according to the embodiment may be appropriately employed.

The gas sensor according to the present embodiment is a sensor that detects _NOx by a sensor element in which a heater section for heating the sensor element to a predetermined temperature is embedded and measures the concentration of NOx. The sensor element comprises an adjustment pump cell which is an electrochemical pump cell, and an electrochemical pump cell into which the gas to be measured is introduced after oxygen contained in the gas to be measured is pumped in the adjustment pump cell. and a pump cell for The gas sensor according to this embodiment detects the cell resistance value of the adjustment pump cell, and adjusts the predetermined temperature so that the detected cell resistance value becomes a predetermined value. The slope of the cell resistance of the adjustment pump cell with respect to the power applied to the heater section is greater than the slope of the cell resistance of the measurement pump cell with respect to the power applied to the heater section.

In the gas sensor according to the present embodiment, the predetermined temperature is controlled to set the cell resistance of the adjustment pump cell to a predetermined value. There is no need to increase the pump voltage applied to the adjustment pump cell. Therefore, in the gas sensor according to the present embodiment, "as a result of increasing the pump voltage applied to the adjustment pump cell, NO _x in the gas to be measured is decomposed in the adjustment pump cell, and the measurement accuracy of the NO _x concentration deteriorates." However, it is possible to avoid the situation that the measurement accuracy deteriorates especially when the concentration of NO _x is high. In addition, since the slope of the cell resistance of the adjustment pump cell with respect to input power is larger (than the slope of the cell resistance of the measurement pump cell with respect to input power), the cell resistance of the adjustment pump cell increases with a small input power. It can be controlled to have a predetermined value. Furthermore, since the slope of the cell resistance of the adjustment pump cell with respect to the input power is large, when changing the input power (that is, the predetermined temperature) so that the value of the cell resistance of the adjustment pump cell becomes a predetermined value, Fluctuations in the predetermined temperature can be reduced. By reducing the fluctuation of the predetermined temperature, the fluctuation of the offset value can be suppressed, and highly accurate concentration measurement can be realized even when the concentration of NO _x in the gas to be measured is low. .

_INDUSTRIAL APPLICABILITY As described above, the gas sensor according to one aspect of the present invention avoids a situation in which the measurement accuracy deteriorates when the concentration of NO _x in the gas to be measured is high. High-precision concentration measurement can be achieved even when the is low. In other words, the gas sensor according to one aspect of the present invention achieves both high-precision concentration measurement in an environment where the concentration of NO _x in the gas to be measured is high and high-precision concentration measurement in an environment where the concentration is low. can be done. An example of a gas sensor having these configurations will be described below.

[Configuration example]
FIG. 1 is a diagram schematically showing an example of the configuration of a gas sensor S, including a vertical cross-sectional view along the longitudinal direction of a gas sensor element 100 according to this embodiment. The gas sensor S includes a gas sensor element 100 and a controller 110, as shown in FIG. The gas sensor element 100 has, for example, an elongated plate-like shape extending in the longitudinal direction (axial direction), and is formed, for example, in the shape of a rectangular parallelepiped. The gas sensor element 100 illustrated in FIG. 1 has a front end and a rear end as ends in the longitudinal direction. In the following description, the front end will be referred to as the left end in FIG. 1, and the trailing edge is the right edge (ie, the trailing edge) in FIG. However, the shape of the gas sensor element 100 is not limited to such an example, and may be appropriately selected according to the embodiment. 1 is the right side of the gas sensor element 100, and the front side of the paper is the left side of the gas sensor element 100 in the following description. The controller 110 also includes a detection unit 111, a temperature setting unit 112, and a heater control unit 113 as functional configurations. Details of each of the gas sensor element 100 and the controller 110 will be described below.

<Gas sensor element>
As illustrated in FIG. 1, the gas sensor element 100 includes a first substrate layer 1, a second substrate layer 2, a third substrate layer 3, a first solid electrolyte layer 4, a spacer layer 5, and a second solid electrolyte layer 6. A laminated body is provided which is formed by laminating layers in order from the lower side. Each layer 1-6 is composed of a solid electrolyte layer having oxygen ion conductivity such as zirconia (ZrO2). The solid electrolyte forming each layer 1-6 may be dense. Dense refers to having a porosity of 5% or less.

The gas sensor element 100 is manufactured by, for example, performing processes such as predetermined processing and wiring pattern printing on ceramic green sheets corresponding to each layer, laminating them, and then firing and integrating them. As an example, gas sensor element 100 is a laminate of a plurality of ceramic layers. In this embodiment, the upper surface of the second solid electrolyte layer 6 forms the upper surface of the gas sensor element 100, the lower surface of the first substrate layer 1 forms the lower surface of the gas sensor element 100, and the side surfaces of the layers 1 to 6 , constitute each side of the gas sensor element 100 .

In the present embodiment, one end of the gas sensor element 100 is provided between the lower surface 62 of the second solid electrolyte layer 6 and the upper surface of the first solid electrolyte layer 4 so as to receive the gas to be measured from the external space. A configured interior space is provided. The internal space according to the present embodiment includes a gas introduction port 10, a first diffusion control section 11, a buffer space 12, a second diffusion control section 13, a first internal space 15, a third diffusion control section 16, and a second internal space. The place 17, the fourth diffusion rate-limiting portion 18, and the third internal cavity 19 are configured to be adjacently formed in a manner communicating with each other in this order. That is, the internal space according to this embodiment has a three-chamber structure (first internal space 15, second internal space 17 and third internal space 19).

In one example, this internal space is provided in the form of hollowing out the spacer layer 5 . The upper portion of the internal space is defined by the lower surface 62 of the second solid electrolyte layer 6 . A lower portion of the internal space is defined by the upper surface of the first solid electrolyte layer 4 . The sides of the interior space are defined by the sides of the spacer layer 5 .

The first diffusion rate-controlling part 11 is provided as two horizontally long slits (the opening has a long side direction in a direction perpendicular to the drawing). In addition, the second diffusion rate-controlling part 13, the third diffusion rate-controlling part 16, and the fourth diffusion rate-controlling part 18 have lengths extending in the direction perpendicular to the drawing that are equal to the first internal space 15 and the second internal space, respectively. 17, and third internal cavity 19, respectively.

As illustrated in FIG. 1, each of the second diffusion rate-controlling portion 13 and the third diffusion rate-controlling portion 16 has two laterally long (openings are elongated in the direction perpendicular to the drawing) like the first diffusion rate-controlling portion 11. It may be provided as a slit with a side direction). On the other hand, the fourth diffusion rate-controlling part 18 is provided as one horizontally long slit (the opening has a longitudinal direction in the direction perpendicular to the drawing) formed as a gap with the lower surface of the second solid electrolyte layer 6. may be In other words, the fourth diffusion control section 18 may be in contact with the upper surface of the first solid electrolyte layer 4 . Each of the second diffusion rate-controlling section 13, the third diffusion rate-controlling section 16, and the fourth diffusion rate-controlling section 18 will be described later in detail. A portion (internal space) from the gas introduction port 10 to the third internal space 19 is referred to as a measured gas flow portion 7 .

A side surface of the first solid electrolyte layer 4 between the upper surface of the third substrate layer 3 and the lower surface of the spacer layer 5 and at a position farther from the tip side (the front side of the gas sensor element 100) than the gas flow portion 7 to be measured is located. A reference gas introduction space 43 is provided at a position partitioned by . A reference gas such as air is introduced into the reference gas introduction space 43 . However, the configuration of the gas sensor element 100 need not be limited to such an example. As another example, the first solid electrolyte layer 4 may be configured to extend to the rear end of the gas sensor element 100, and the reference gas introduction space 43 may be omitted. In this case, the atmosphere introduction layer 48 may be configured to extend to the rear end of the gas sensor element 100 .

An atmosphere introduction layer 48 is provided on a portion of the upper surface of the third substrate layer 3 adjacent to the reference gas introduction space 43 . The atmosphere introduction layer 48 is made of porous alumina and configured to introduce a reference gas through the reference gas introduction space 43 . In addition, an atmosphere introduction layer 48 is formed to cover the reference electrode 42 .

The reference electrode 42 is formed so as to be sandwiched between the upper surface of the third substrate layer 3 and the first solid electrolyte layer 4, and is surrounded by an atmosphere introduction layer 48 connected to the reference gas introduction space 43. ing. The reference electrode 42 is used to measure the oxygen concentration (oxygen partial pressure) within the first internal cavity 15 and the second internal cavity 17 . Details will be described later.

The gas introduction port 10 is a portion of the measured gas circulation portion 7 that opens to the external space. The gas sensor element 100 is configured to take in the gas to be measured from the external space through the gas inlet 10 . In this embodiment, as illustrated in FIG. 1 , the gas introduction port 10 is arranged on the tip surface (front surface) of the gas sensor element 100 . In other words, the measured gas circulation portion 7 is configured to have an opening at the tip surface of the gas sensor element 100 . However, it is not essential that the measured gas circulation section 7 is configured to have an opening at the tip surface of the gas sensor element 100 , that is, that the gas introduction port 10 is arranged at the tip surface of the gas sensor element 100 . The gas sensor element 100 only needs to be able to take in the gas to be measured from the external space into the inside of the gas-to-be-measured flow section 7, and the gas introduction port 10 can be arranged, for example, on the right side or the left side of the gas sensor element 100. You may

The first diffusion control portion 11 is a portion that imparts a predetermined diffusion resistance to the gas to be measured introduced from the gas inlet 10 .

The buffer space 12 is a space provided for guiding the gas to be measured introduced from the first diffusion rate controlling section 11 to the second diffusion rate controlling section 13 .

The second diffusion control portion 13 is a portion that imparts a predetermined diffusion resistance to the gas to be measured introduced from the buffer space 12 into the first internal space 15 .

When the gas to be measured is introduced from the outer space of the gas sensor element 100 into the first inner space 15, the pressure fluctuation of the gas to be measured in the outer space (if the gas to be measured is the exhaust gas of an automobile, the exhaust pressure pulsation), the gas may be suddenly taken into the inside of the gas sensor element 100 from the gas introduction port 10 . Even in this case, in this configuration, the gas to be measured that is taken in is not introduced directly into the first internal space 15, but instead flows through the first diffusion rate-controlling section 11, the buffer space 12, and the second diffusion rate-controlling section 13. After the change in the concentration of the gas to be measured is canceled out, the gas is introduced into the first internal cavity 15 . As a result, the change in the concentration of the gas to be measured introduced into the first internal space 15 is almost negligible.

The first internal space 15 is provided as a space for adjusting the oxygen partial pressure in the gas to be measured introduced through the second diffusion control section 13 . The oxygen partial pressure is adjusted by operating the main pump cell 21 .

The main pump cell 21 is an electrochemical pump cell composed of an inner pump electrode 22, an outer pump electrode 23, and a second solid electrolyte layer 6 sandwiched between these electrodes. The inner pump electrode 22 has a ceiling electrode portion 22 a provided on substantially the entire lower surface 62 of the second solid electrolyte layer 6 adjacent to (facing) the first internal cavity 15 . The outer pump electrode 23 is provided in a region of the upper surface 63 of the second solid electrolyte layer 6 corresponding to the ceiling electrode portion 22a in a manner adjacent to the external space. The main pump cell 21 is an example of a "adjusting pump cell".

The inner pump electrode 22 is formed across the upper and lower solid electrolyte layers (second solid electrolyte layer 6 and first solid electrolyte layer 4) that partition the first internal cavity 15 and the spacer layer 5 that provides side walls. . Specifically, the ceiling electrode portion 22a is formed on the lower surface 62 of the second solid electrolyte layer 6 that provides the ceiling surface of the first internal cavity 15, and the upper surface of the first solid electrolyte layer 4 that provides the bottom surface of the first internal cavity 15. A bottom electrode portion 22b is formed. Side electrode portions (not shown) are side wall surfaces (inner surfaces) of the spacer layer 5 forming both side wall portions of the first internal space 15 so as to be connected to the ceiling electrode portion 22a and the bottom electrode portion 22b. is formed in In other words, the inner pump electrode 22 is arranged in a tunnel-like structure at the position where the side electrode portion is arranged. The inner pump electrode 22 is an example of "an inner pump electrode formed to face the internal cavity (measurement gas flow part 7)".

The inner pump electrode 22 and the outer pump electrode 23 are formed as porous cermet electrodes (for example, cermet electrodes composed of Pt and ZrO ₂ containing 1% Au). The inner pump electrode 22, which contacts the gas to be measured, is made of a material having a weakened ability to reduce nitrogen oxides (NO _x ) in the gas to be measured.

The gas sensor element 100 applies a desired pump voltage Vp0 between the inner pump electrode 22 and the outer pump electrode 23 in the main pump cell 21, and a positive or negative voltage is applied between the inner pump electrode 22 and the outer pump electrode 23. By applying the pump current Ip0, the oxygen in the first internal space 15 can be pumped out to the external space, or the oxygen in the external space can be pumped into the first internal space 15 .

In order to detect the oxygen concentration (oxygen partial pressure) in the atmosphere in the first internal space 15, the inner pump electrode 22, the second solid electrolyte layer 6, the spacer layer 5, the first solid electrolyte layer 4, the third The substrate layer 3 and the reference electrode 42 constitute a main pump control oxygen partial pressure detection sensor cell 80 (that is, an electrochemical sensor cell).

The gas sensor element 100 is configured to be able to identify the oxygen concentration (oxygen partial pressure) in the first internal space 15 by measuring the electromotive force V0 in the oxygen partial pressure detection sensor cell 80 for controlling the main pump. Furthermore, the pump current Ip0 is controlled by feedback-controlling Vp0 so that the electromotive force V0 is constant. Thereby, the oxygen concentration in the first internal space 15 can be maintained at a predetermined constant value.

The third diffusion rate control section 16 applies a predetermined diffusion resistance to the gas under measurement whose oxygen concentration (oxygen partial pressure) is controlled by the operation of the main pump cell 21 in the first internal cavity 15, thereby reducing the gas under measurement. This is a portion that leads to the second internal space 17 .

The second internal space 17 is provided as a space for further adjusting the oxygen partial pressure in the gas to be measured introduced through the third diffusion control section 16 . Such oxygen partial pressure is adjusted by operating the auxiliary pump cell 50 .

The auxiliary pump cell 50 is composed of an auxiliary pump electrode 51 , an outer pump electrode 23 (not limited to the outer pump electrode 23 , but any appropriate electrode outside the gas sensor element 100 ), and a second solid electrolyte layer 6 . is an auxiliary electrochemical pump cell. The auxiliary pump electrode 51 has a ceiling electrode portion 51a provided over substantially the entire lower surface of the second solid electrolyte layer 6 facing the second internal space 17 . The auxiliary pump cell 50 is an example of an "adjusting pump cell." Moreover, the above-mentioned "appropriate electrode outside the gas sensor element 100" is an example of "the third electrode provided in a manner of being in contact with the solid electrolyte layer and exposed to the external space".

The auxiliary pump electrode 51 is arranged in the second internal space 17 in a tunnel-like structure similar to the inner pump electrode 22 provided in the first internal space 15 . That is, the ceiling electrode portion 51a is formed on the lower surface 62 of the second solid electrolyte layer 6 that provides the ceiling surface of the second internal space 17, and the first solid electrolyte layer provides the bottom surface of the second internal space 17. 4 is formed with a bottom electrode portion 51b. Side electrode portions (not shown) connecting the ceiling electrode portion 51a and the bottom electrode portion 51b are formed on both wall surfaces of the spacer layer 5 that provide side walls of the second internal space 17, respectively. Accordingly, the auxiliary pump electrode 51 has a tunnel-like structure. The auxiliary pump electrode 51 is an example of "an inner pump electrode formed to face the internal space (measured gas flow section 7)".

As with the inner pump electrode 22, the auxiliary pump electrode 51 is also made of a material having a weakened ability to reduce nitrogen oxides in the gas to be measured.

By applying a desired voltage Vp1 between the auxiliary pump electrode 51 and the outer pump electrode 23 in the auxiliary pump cell 50, the gas sensor element 100 pumps out oxygen in the atmosphere in the second internal cavity 17 to the external space, Alternatively, it is configured such that it can be pumped into the second internal space 17 from the external space.

In order to control the oxygen partial pressure in the atmosphere inside the second internal space 17, the auxiliary pump electrode 51, the reference electrode 42, the second solid electrolyte layer 6, the spacer layer 5, the first solid electrolyte layer 4, and The third substrate layer 3 constitutes an auxiliary pump control oxygen partial pressure sensor cell 81 (that is, an electrochemical sensor cell).

The auxiliary pump cell 50 performs pumping with the variable power source 52 whose voltage is controlled based on the electromotive force V1 detected by the oxygen partial pressure detecting sensor cell 81 for controlling the auxiliary pump. As a result, the partial pressure of oxygen in the atmosphere inside the second internal space 17 is controlled to a low partial pressure that does not substantially affect the measurement of _NOx .

Along with this, the pump current Ip1 is used to control the electromotive force of the oxygen partial pressure detection sensor cell 80 for main pump control. Specifically, the pump current Ip1 is input as a control signal to the oxygen partial pressure detection sensor cell 80 for controlling the main pump, and the electromotive force V0 thereof is controlled, whereby the current from the third diffusion rate-determining section 16 to the second internal space is The gradient of the oxygen partial pressure in the gas to be measured introduced into 17 is controlled so as to be constant at all times. When used as a NO _x sensor, the main pump cell 21 and the auxiliary pump cell 50 work to keep the oxygen concentration in the second internal space 17 at a constant value of about 0.001 ppm.

The fourth diffusion rate control section 18 applies a predetermined diffusion resistance to the gas under measurement whose oxygen concentration (oxygen partial pressure) is controlled by the operation of the auxiliary pump cell 50 in the second internal space 17, thereby reducing the gas under measurement. This is a portion that leads to the third internal space 19 .

The third internal space 19 is provided as a space for performing processing related to measurement of nitrogen oxide (NO _x ) concentration in the gas to be measured introduced through the fourth diffusion control section 18 . The NO _x concentration is measured by operating the measuring pump cell 41 . In this embodiment, after the oxygen concentration (oxygen partial pressure) is adjusted in advance in the first internal space 15, in the second internal space 17, for the gas to be measured introduced through the third diffusion control section, Further adjustment of the oxygen partial pressure by the auxiliary pump cell 50 is performed. Thereby, the oxygen concentration of the gas to be measured introduced from the second internal space 17 to the third internal space 19 can be kept constant with high accuracy. Therefore, the gas sensor element 100 according to this embodiment can measure the NO _x concentration with high accuracy.

The measuring pump cell 41 measures the nitrogen oxide concentration in the gas to be measured in the third internal space 19 . The measuring pump cell 41 is an electrochemical pump cell composed of the measuring electrode 44 , the outer pumping electrode 23 , the second solid electrolyte layer 6 , the spacer layer 5 and the first solid electrolyte layer 4 . In one example of FIG. 1 , the measurement electrode 44 is provided on the upper surface of the first solid electrolyte layer 4 adjacent (facing) the third internal cavity 19 .

The measurement electrode 44 is a porous cermet electrode. The measurement electrode 44 also functions as a NO _x reduction catalyst that reduces NO _x present in the atmosphere inside the third internal cavity 19 . In one example of FIG. 1, the measuring electrode 44 is exposed within the third internal cavity 19 . In another example, the measurement electrode 44 may be coated with a diffusion limiter. The diffusion control section may be composed of a porous film containing alumina (Al ₂ O ₃ ) as a main component. The diffusion control section plays a role of limiting the amount of NO _x flowing into the measurement electrode 44 and also acts as a protective film for the measurement electrode 44 .

The gas sensor element 100 is configured to pump oxygen generated by decomposition of nitrogen oxides in the atmosphere around the measurement electrode 44 in the measurement pump cell 41 and detect the amount of oxygen generated as a pump current Ip2.

In addition, in order to detect the oxygen partial pressure around the measurement electrode 44, the second solid electrolyte layer 6, the spacer layer 5, the first solid electrolyte layer 4, the third substrate layer 3, the measurement electrode 44, and the reference electrode 42 , an oxygen partial pressure detection sensor cell 82 for controlling a measuring pump (that is, an electrochemical sensor cell). The variable power supply 46 is controlled based on the voltage (electromotive force) V2 detected by the oxygen partial pressure detection sensor cell 82 for controlling the measuring pump.

The measured gas guided into the third internal space 19 reaches the measuring electrode 44 under the condition that the oxygen partial pressure is controlled. Nitrogen oxides in the gas to be measured around the measuring electrode 44 are reduced (2NO→N ₂ +O ₂ ) to generate oxygen. The generated oxygen is pumped by the measuring pump cell 41. At this time, the variable power supply is controlled so that the control voltage V2 detected by the measuring pump control oxygen partial pressure detecting sensor cell 82 is constant. is controlled. Since the amount of oxygen generated around the measuring electrode 44 is proportional to the concentration of nitrogen oxides in the gas to be measured, the pump current Ip2 in the pump cell 41 for measurement is used to measure the nitrogen oxides in the gas to be measured. The concentration will be calculated.

In addition, by combining the measuring electrode 44, the first solid electrolyte layer 4, the third substrate layer 3, and the reference electrode 42 to constitute an oxygen partial pressure detecting means as an electrochemical sensor cell, the measuring electrode 44 An electromotive force corresponding to the difference between the amount of oxygen generated by the reduction of the NO _x component in the ambient atmosphere and the amount of oxygen contained in the reference atmosphere can be detected. Thereby, it is also possible to obtain the concentration of the nitrogen oxide component in the gas to be measured.

An electrochemical sensor cell 83 is composed of the second solid electrolyte layer 6 , the spacer layer 5 , the first solid electrolyte layer 4 , the third substrate layer 3 , the outer pump electrode 23 and the reference electrode 42 . The gas sensor element 100 is configured to be able to detect the oxygen partial pressure in the gas to be measured outside the sensor using the electromotive force Vref obtained by the sensor cell 83 .

By operating the main pump cell 21 and the auxiliary pump cell 50 in the gas sensor element 100 having the above configuration, the oxygen partial pressure was always kept at a constant low value (a value that does not substantially affect the measurement of NO _x ). A gas to be measured can be supplied to the measuring pump cell 41 . Therefore, the gas sensor element 100 is approximately proportional to the concentration of nitrogen oxides in the gas to be measured, and based on the pump current Ip2 that flows when the oxygen generated by the reduction of NO _x is pumped from the measuring pump cell 41, It is configured to be able to specify the concentration of nitrogen oxides in the gas to be measured.

Furthermore, the gas sensor element 100 is provided with a heater 70 that plays a role of temperature adjustment for heating and keeping the gas sensor element 100 warm in order to increase the oxygen ion conductivity of the solid electrolyte. The heater 70 includes heater electrodes 71 (eg, 71a, 71b, 71c, not shown), heater elements 72, heater leads 72a (eg, 72a1, 72a2, not shown), through holes 73, and a heater insulating layer 74. and a heater resistance detection lead 76 (FIG. 2), not shown in FIG. Also, in the example of FIG. 1, the heater 70 further includes pressure dissipation holes 75 .

The heater 70 is embedded in the base portion of the gas sensor element 100 except for the heater electrode 71 . In this embodiment, the heater 70 is arranged at a position closer to the lower surface of the gas sensor element 100 than the upper surface of the gas sensor element 100 in the thickness direction (vertical direction/stacking direction) of the gas sensor element 100 . However, the arrangement of the heater 70 is not limited to such an example, and may be appropriately selected according to the embodiment.

The heater electrode 71 is an electrode formed so as to be in contact with the lower surface of the first substrate layer 1 (the lower surface of the gas sensor element 100). By connecting the heater electrode 71 to an external power source, power can be supplied to the heater 70 from the outside.

The heater element 72 is an electric resistor sandwiched between the second substrate layer 2 and the third substrate layer 3 from above and below. It is a resistance heating element provided in. The heater element 72 is supplied with power from a heater power source 77 (FIG. 2) provided outside the gas sensor element 100, not shown in FIG. As a result, heat is generated, and the solid electrolyte forming the gas sensor element 100 is heated and kept warm. The heater element 72 is made of Pt or made mainly of Pt. The heater element 72 is embedded in a predetermined range on the side of the gas sensor element 100 on which the measured gas flow section 7 is provided so as to face the measured gas flow section 7 in the element thickness direction. The heater element 72 is provided so as to have a thickness of, for example, approximately 10 μm to 20 μm.

A pair of heater leads (for example, a heater lead 72a1 and a heater lead 72a2, not shown) connected to both ends of the heater element 72 have substantially the same shape, that is, both have the same resistance value. So it is provided. Heater leads 72a1 and 72a2 are connected to different heater electrodes 71a and 71b (not shown) through corresponding through holes 73, respectively.

Further, a heater resistance detection lead 76 is provided so as to be pulled out from a connecting portion between the heater element 72 and one heater lead 72a2. It is assumed that the resistance value of the heater resistance detection lead 76 can be ignored. The heater resistance detection lead 76 is connected to the heater electrode 71c (not shown) through the corresponding through hole 73. As shown in FIG.

Further, the heater element 72 can adjust the temperature of the entire gas sensor element 100 to a temperature at which the solid electrolyte is activated. That is, in the gas sensor element 100, by causing the heater element 72 to generate heat by passing a current through the heater element 72 through the heater electrode 71, each part of the gas sensor element 100 can be heated to a predetermined temperature and kept warm. It's becoming Specifically, the gas sensor element 100 is heated so that the temperature of the solid electrolyte and electrodes in the vicinity of the measured gas flow section 7 is, for example, about 700° C. to 900° C. (or 750° C. to 950° C.). . Such heating increases the oxygen ion conductivity of the solid electrolyte forming the base portion of the gas sensor element 100 . The heating temperature by the heater element 72 when the gas sensor S is used (when the gas sensor element 100 is driven) is sometimes referred to as the sensor element driving temperature.

The degree of heat generation by the heater element 72 is determined by the magnitude of the resistance value (heater resistance) of the heater element 72 . A heater resistance detection lead 76 is provided for such heater resistance measurement.

The heater insulating layer 74 is an insulating layer formed to cover the heater element 72. For example, the heater insulating layer 74 is an insulating layer formed on the upper and lower surfaces of the heater element 72 with an insulator such as alumina. The heater insulating layer 74 is formed for the purpose of providing electrical insulation between the second substrate layer 2 and the heater element 72 and electrical insulation between the third substrate layer 3 and the heater element 72 . The heater insulating layer 74 has a thickness of about 70 μm to 110 μm, and is provided at a position spaced apart from the tip surface and side surface of the gas sensor element 100 by about 200 μm to 700 μm. However, the thickness of the heater insulating layer 74 does not need to be constant, and may differ between the portions where the heater elements 72 are present and the portions where the heater elements 72 are not present.

The pressure dissipation hole 75 is a portion that penetrates the third substrate layer 3 and is provided so as to communicate with the reference gas introduction space 43. The pressure dissipation hole 75 is provided for the purpose of alleviating an increase in internal pressure accompanying a temperature increase in the heater insulating layer 74. formed. However, providing the pressure dissipation hole 75 is not essential, and the pressure dissipation hole 75 may not be provided.

<Controller>
Next, functions of the controller 110 will be described in detail. The controller 110 controls the operation of each part of the gas sensor S, specifies the NO _x concentration based on the pump current Ip2 flowing through the gas sensor element 100, and maintains the gas sensor element 100 at a "predetermined temperature (sensor element driving temperature)”. The controller 110 is implemented by a general-purpose or dedicated computer, and functional components implemented by its CPU, memory, etc. include a detection unit 111 and a temperature setting unit 112, as illustrated in FIG. (adjustment unit) and a heater control unit 113 . When the gas sensor S detects and measures NO _x contained in exhaust gas from an automobile engine, and the gas sensor element 100 is attached to the exhaust path, part or all of the functions of the controller 110 are It may be implemented by an ECU (electronic control unit) mounted on an automobile.

In addition, in FIG. 1 and the like, the detection unit 111, the temperature setting unit 112, and the heater control unit 113 are listed as functional blocks provided in the controller 110, but the controller 110 includes functional blocks other than these functional blocks. may be Controller 110 may include, for example, functional blocks for NO _x sensing, concentration calculations, and the like. Specifically, the controller 110 may further include a functional block for controlling the operation of each pump cell, a functional block for calculating the _NOx concentration, and a functional block for comprehensively controlling the operation of each part of the controller 110. good.

The detection unit 111 measures (detects) the cell resistance (impedance) value of the main pump cell 21 and notifies the temperature setting unit 112 of the measured cell resistance value of the main pump cell 21 . The detection unit 111 supplies, for example, an alternating current between the inner pump electrode 22 and the outer pump electrode 23 of the main pump cell 21, and converts the alternating current signal generated between them into a voltage having a level corresponding to the impedance therebetween. can be converted into a signal.

Specifically, the detection unit 111 is inserted and connected between the inner pump electrode 22 and the outer pump electrode 23 of the main pump cell 21, and detects the impedance between the inner pump electrode 22 and the outer pump electrode 23. It may be an impedance detection circuit. The detection unit 111 generates an alternating current generation circuit that supplies an alternating current between the inner pump electrode 22 and the outer pump electrode 23, and a voltage signal having a level corresponding to the impedance generated between the two by supplying the alternating current between them. and a signal detection circuit for detecting. The signal detection circuit provided in the detection unit 111 converts the AC signal generated between the inner pump electrode 22 and the outer pump electrode 23 into a voltage signal whose level corresponds to the impedance between the inner pump electrode 22 and the outer pump electrode 23 . It may be configured by a filter circuit (for example, a low-pass filter, a band-pass filter, etc.) that converts to . Note that the detection unit 111 may detect the cell resistance as follows. That is, for example, the detection unit 111 measures the IV curve in the atmosphere, calculates the slope from the current value when the voltage is swept at 5 mV / s between 0 and 50 mV, and the cell You can ask for resistance.

The temperature setting unit 112 (adjusting unit) sets a “predetermined temperature (sensor element driving temperature)” to which the gas sensor element 100 reaches by being heated by the heater 70 . In particular, the temperature setting unit 112 sets the sensor element drive temperature based on the “cell resistance value of the main pump cell 21 ” detected by the detection unit 111 . Specifically, temperature setting unit 112 acquires reference impedance 115 by referring to storage unit 114 when “value of cell resistance of main pump cell 21 ” is notified from detection unit 111 . The temperature setting unit 112 then calculates the difference between the acquired reference impedance 115 and the cell resistance value of the main pump cell 21 notified from the detection unit 111 . The reference impedance 115 is, for example, a preset value as a value of cell resistance that the main pump cell 21 in the gas sensor S should exhibit. The temperature setting unit 112 sets the sensor element drive temperature based on the calculated "difference between the reference impedance 115 and the cell resistance of the main pump cell 21". Specifically, the temperature setting unit 112 sets the sensor element drive temperature so that the "difference between the reference impedance 115 and the cell resistance of the main pump cell 21" becomes small. That is, the temperature setting unit 112 sets the sensor element drive temperature so that the reference impedance 115 and the cell resistance of the main pump cell 21 are equal.

For example, when the cell resistance value of the main pump cell 21 is smaller than the reference impedance 115, the temperature setting unit 112 increases the cell resistance value of the main pump cell 21 so that it becomes equal to the reference impedance 115 by that time. Lower the sensor element driving temperature. The temperature setting unit 112 notifies the heater control unit 113 of a new sensor element drive temperature that is lowered so that the cell resistance of the main pump cell 21 becomes equal to the reference impedance 115 .

For example, if the cell resistance value of the main pump cell 21 is greater than the reference impedance 115, the temperature setting unit 112 reduces the cell resistance value of the main pump cell 21 so that it becomes equal to the reference impedance 115 by that time. Increase the sensor element driving temperature. The temperature setting unit 112 notifies the heater control unit 113 of a new sensor element drive temperature that is increased so that the cell resistance of the main pump cell 21 becomes equal to the reference impedance 115 .

The heater control section 113 controls the operation of the heater 70 based on the sensor element driving temperature notified from the temperature setting section 112 . For example, the heater control unit 113 sets the value of the heater resistance (resistance of the heater element 72) obtained as the resistance value between the heater resistance detection lead 76 and the heater lead 72a to the predetermined temperature set by the temperature setting unit 112. The heater voltage applied to the heater power supply 77 is controlled so as to have a value corresponding to . Thereby, the heater control unit 113 controls power supply to the heater 70 , that is, controls input power to the heater 70 . The heater element 72 generates heat in accordance with the heater resistance controlled in such a manner. The heater control unit 113 controls the value of the heater resistance according to the "predetermined temperature set by the temperature setting unit 112", whereby the gas sensor element 100 is heated by the heater 70 to the "predetermined temperature set by the temperature setting unit 112". "predetermined temperature" is reached. The input power to the heater 70 is the product of the voltage applied to the heater 70 (that is, the voltage that is applied between the heaters) and the current that flows through the heater 70 (that is, the current that flows between the heaters).

<Constant Impedance Control of Auxiliary Pump Cell>
FIG. 2 is a diagram showing an outline of constant impedance control in the gas sensor S. As shown in FIG. Impedance constant control is control (processing) for keeping the cell resistance (impedance) of the auxiliary pump cell (for example, the main pump cell 21 in the example shown in FIG. 2) constant. As illustrated in FIG. 2, in constant impedance control, the detection unit 111 first measures (detects) the cell resistance (impedance) value of the main pump cell 21, for example, the inner pump electrode 22 and the outer pump electrode 23. (detection step). The detection unit 111 notifies the temperature setting unit 112 of the detected "cell resistance value of the main pump cell 21".

Based on the "value of the cell resistance of the main pump cell 21" notified from the detection unit 111, the temperature setting unit 112 sets the "predetermined temperature" to which the gas sensor element 100 reaches by being heated by the heater 70, that is, the sensor temperature. Set the device drive temperature. In particular, the temperature setting unit 112 sets the sensor element drive temperature so that the reference impedance 115 and the cell resistance of the main pump cell 21 are equal (adjustment step).

When the cell resistance value of the main pump cell 21 detected by the detection unit 111 is equal to the reference impedance 115, the temperature setting unit 112 sets the sensor element drive temperature to the same temperature as the sensor element drive temperature set at that time. You can set the temperature. The temperature setting unit 112 notifies the heater control unit 113 of the set sensor element driving temperature.

The heater control section 113 controls the operation of the heater 70 based on the sensor element driving temperature notified from the temperature setting section 112 . For example, the heater control unit 113 controls the heater voltage applied to the heater power supply 77 so that the value of the heater resistance (resistance of the heater element 72) becomes a value corresponding to the sensor element driving temperature notified from the temperature setting unit 112. to control. Heater control section 113 controls the input power (feeding power) from heater power source 77 to heater 70 , and heater 70 controls the temperature of gas sensor element 100 so that the temperature of gas sensor element 100 reaches the sensor element drive temperature set by temperature setting section 112 . The element 100 is heated.

It should be noted that although an example in which the adjustment pump cell whose cell resistance (impedance) value is detected by the detection unit 111 is the main pump cell 21 has been described so far, the adjustment pump cell whose cell resistance value is detected by the detection unit 111 has been described. may be the auxiliary pump cell 50 . That is, the detection unit 111 measures (detects) the cell resistance value of the auxiliary pump cell 50 as the cell resistance (impedance) value of the adjustment pump cell, and sets the measured cell resistance value of the auxiliary pump cell 50 to the temperature setting unit 112. may be notified to The detection unit 111 supplies, for example, an alternating current between the auxiliary pump electrode 51 of the auxiliary pump cell 50 and the outer pump electrode 23 (or the third electrode), and detects the alternating current signal generated between them as the impedance between them. may be converted into a voltage signal having a level corresponding to . Specifically, the detection unit 111 is inserted and connected between the auxiliary pump electrode 51 of the auxiliary pump cell 50 and the outer pump electrode 23, and detects the impedance between the auxiliary pump electrode 51 and the outer pump electrode 23. It may be an impedance detection circuit. Since the method for detecting the cell resistance value of the auxiliary pump cell 50 by the detection unit 111 is the same as the method for detecting the cell resistance value of the main pump cell 21 by the detection unit 111, the details will be omitted.

Similarly, the auxiliary pump cell 50 may be the adjustment pump cell whose cell resistance value becomes equal to the reference impedance 115 by adjusting (controlling) the sensor element driving temperature by the temperature setting unit 112 . That is, the temperature setting unit 112 may set the sensor element drive temperature so that the reference impedance 115 and the cell resistance of the auxiliary pump cell 50 are equal. In this case, the reference impedance 115 is a value set in advance as a cell resistance value that the auxiliary pump cell 50 should exhibit in the gas sensor S, for example.

Furthermore, the detection unit 111 may measure (detect) the cell resistance value of each of the main pump cell 21 and the auxiliary pump cell 50 as the cell resistance (impedance) value of the adjustment pump cell. In this case, the detection unit 111 notifies the temperature setting unit 112 of the measured cell resistance values of the main pump cell 21 and the auxiliary pump cell 50 . Then, the temperature setting unit 112 sets the value of the cell resistance of the main pump cell 21 equal to the "reference impedance 115 preset as the value of the cell resistance that the main pump cell 21 should exhibit in the gas sensor S", and The sensor element driving temperature may be set so that the "reference impedance 115 preset as the cell resistance value that the auxiliary pump cell 50 should exhibit in the gas sensor S" and the cell resistance value of the auxiliary pump cell 50 are equal. .

That is, in the gas sensor S, the cell resistance value of at least one of the main pump cell 21 and the auxiliary pump cell 50 is detected as the cell resistance value of the adjustment pump cell. Then, the sensor element driving temperature is adjusted so that the detected cell resistance value of the adjustment pump cell becomes equal to the "preset reference impedance 115 as the cell resistance value that the adjustment pump cell should exhibit in the gas sensor S". set.

<Inclination of Cell Resistance of Measurement Pump Cell and Adjustment Pump Cell with respect to Input Power>
FIG. 3 is a diagram showing an example of an image of the slope of the cell resistance of each of the measuring pump cell 41 and the main pump cell 21 with respect to the input power (power supply) to the heater 70 in the gas sensor S. The "slope of the cell resistance with respect to the input power to the heater 70" is, for example, the "slope of the cell resistance with respect to the input power to the heater 70 in the air".

As illustrated in FIG. 3, in the gas sensor S, the slope of the cell resistance (impedance) [ohm] of the measurement pump cell 41 with respect to the input power [W] to the heater 70 is 11.5 ” to “13.5”, it is about “10 [ohm/W]”. That is, the impedance between the measuring electrode 44 and the outer pump electrode 23 with respect to the input power to the heater 70 is approximately "10 [ohm/ W]”.

On the other hand, in the gas sensor S, the slope of the cell resistance (impedance) [ohm] of the main pump cell 21 with respect to the input power [W] to the heater 70 is from "11.5" to "13 In the range up to .5”, it is about “600 [ohm/W]”. That is, the impedance between the inner pump electrode 22 and the outer pump electrode 23 with respect to the input power to the heater 70 is about 600 [ohms] in the input power range from "11.5" to "13.5". /W]”.

Therefore, in the gas sensor S, the slope of the cell resistance of the main pump cell 21 with respect to the input power to the heater 70 is greater than the slope of the cell resistance of the measurement pump cell 41 with respect to the input power to the heater 70 .

As described above, in the gas sensor S, the sensor element drive temperature is adjusted so that the cell resistance value of the main pump cell 21 (adjustment pump cell) detected by the detection unit 111 becomes a predetermined value (reference impedance 115). , the sensor element drive temperature is controlled. Also, the slope of the cell resistance of the main pump cell 21 with respect to the input power to the heater 70 is greater than the slope of the cell resistance of the measurement pump cell 41 with respect to the input power to the heater 70 . That is, in this configuration, the slope of the cell resistance with respect to the input power to the heater 70 is larger for the main pump cell 21 than for the measurement pump cell 41 .

By controlling the sensor element drive temperature and setting the cell resistance of the main pump cell 21 to a predetermined value, the following effects are obtained. That is, since the cell resistance value of the main pump cell 21 is maintained at a predetermined value, the resistance to the reaction of the main pump cell 21 does not increase, and the pump voltage applied to the main pump cell 21 does not need to be increased. Therefore, "as a result of increasing the pump voltage (pump voltage Vp0) applied to the main pump cell 21, the main pump cell 21 decomposes NO _x in the gas to be measured, degrading the measurement accuracy of the concentration of NO _x . It is possible to avoid the situation that the measurement accuracy deteriorates when the concentration of _x is high.

Regarding the slope of the cell resistance with respect to the input power to the heater 70, since the slope of the main pump cell 21 is larger (than the slope of the measurement pump cell 41), the cell resistance of the main pump cell 21 can be adjusted to a predetermined value with a small input power. can be controlled to be the value of

Furthermore, since the slope of the cell resistance of the main pump cell 21 with respect to the input power to the heater 70 is large, when changing the input power (that is, the sensor element driving temperature) so that the cell resistance value of the main pump cell 21 becomes a predetermined value, Moreover, fluctuations in sensor element drive temperature can be reduced. By reducing the fluctuation of the sensor element driving temperature, the fluctuation of the offset value can be suppressed, and highly accurate concentration measurement can be realized even when the concentration of NO _x in the gas to be measured is low. .

As described above, the gas sensor S avoids _a situation in which the measurement accuracy deteriorates when the NO _x concentration in the gas to be measured is high. Accurate concentration measurement can be realized. That is, the gas sensor S can achieve both high-precision concentration measurement in an environment where the NO _x concentration in the gas to be measured is high and high-precision concentration measurement in an environment where the concentration is low.

The cell resistance value of the measurement pump cell 41 may be measured using, for example, the following impedance detection circuit. That is, using an impedance detection circuit that is inserted and connected between the measurement electrode 44 and the outer pump electrode 23 of the measurement pump cell 41 and that detects the impedance between the measurement electrode 44 and the outer pump electrode 23, the measurement A value of the cell resistance of the pump cell 41 may be measured. Such an impedance detection circuit includes an alternating current generation circuit that supplies an alternating current between the measuring electrode 44 and the outer pump electrode 23, and a voltage level corresponding to the impedance generated between the two by the alternating current supply between them. A signal detection circuit for detecting a signal may be provided. Such a signal detection circuit is a filter that converts an AC signal generated between the measuring electrode 44 and the outer pump electrode 23 into a voltage signal whose level corresponds to the impedance between the measuring electrode 44 and the outer pump electrode 23. It can be configured by a circuit (for example, a low-pass filter, a band-pass filter, etc.).

An example in which the adjustment pump cell is the main pump cell 21 has been described so far as the adjustment pump cell whose slope of the cell resistance (impedance) with respect to the input power to the heater 70 is larger than that of the measurement pump cell 41 . However, the auxiliary pump cell 50 may be the adjustment pump cell that exhibits a larger cell resistance gradient (cell resistance gradient with respect to the input power to the heater 70 ) than the measurement pump cell 41 . That is, the slope of the cell resistance of the auxiliary pump cell 50 with respect to the input power to the heater 70 may be larger than the slope of the cell resistance of the measurement pump cell 41 with respect to the input power to the heater 70 .

Moreover, both the main pump cell 21 and the auxiliary pump cell 50 may have a slope of cell resistance (impedance) with respect to the input power to the heater 70 that is larger than that of the measuring pump cell 41 . That is, both the slope of the cell resistance of the main pump cell 21 with respect to the input power to the heater 70 and the slope of the cell resistance of the auxiliary pump cell 50 with respect to the input power to the heater 70 are both It may be larger than the slope of the cell resistance.

In the gas sensor S, the slope of the cell resistance of at least one of the main pump cell 21 and the auxiliary pump cell 50 (the slope of the cell resistance with respect to the input power to the heater 70 ) should be greater than the slope of the cell resistance of the measurement pump cell 41 .

<Ratio between the slope of the cell resistance of the pump cell for measurement and the slope of the cell resistance of the pump cell for adjustment>
As described above, in the gas sensor S, the slope of the cell resistance [ohm] of the measurement pump cell 41 with respect to the input power [W] to the heater 70 is from "11.5" to "13.5". up to about 10 [ohm/W]. The slope of the cell resistance [ohm] of the main pump cell 21 with respect to the input power [W] to the heater 70 is approximately " 600 [ohm/W]".

Therefore, in the gas sensor S, the slope of the cell resistance of the main pump cell 21 with respect to the input power to the heater 70 is approximately "60" times the slope of the cell resistance of the measurement pump cell 41 with respect to the input power to the heater 70 . That is, in the gas sensor S, the slope of the cell resistance of the main pump cell 21 with respect to the input power to the heater 70 is 1.5 to 1000 times the slope of the cell resistance of the measurement pump cell 41 with respect to the input power to the heater 70. value.

As described above, in order to achieve both high-accuracy concentration measurement in an environment where the concentration of NO _x in the gas to be measured is high and high-accuracy concentration measurement in an environment where the concentration is low, the input power to the heater 70 must be It is desirable to make the slope of the cell resistance of the adjustment pump cell (for example, the main pump cell 21) larger than the slope of the cell resistance of the measurement pump cell 41 with respect to the input power. In particular, the inventors of the present invention have experimentally determined that the slope of the cell resistance of the adjustment pump cell with respect to the input power to the heater 70 is from 1.5 times the slope of the cell resistance of the measurement pump cell 41 with respect to the input power to the heater 70. It was confirmed that 1000 times is desirable. For example, it is desirable that the slope of the cell resistance of the main pump cell 21 with respect to the input power to the heater 70 is 1.5 to 1000 times the slope of the cell resistance of the measurement pump cell 41 with respect to the input power to the heater 70. It was confirmed.

As described above, in the gas sensor S, the slope of the cell resistance of the main pump cell 21 with respect to the input power to the heater 70 is approximately "60" times the slope of the cell resistance of the measurement pump cell 41 with respect to the input power to the heater 70. there is Therefore, in the gas sensor S, the slope of the cell resistance of the main pump cell 21 is 1.5 times to 1000 times the slope of the cell resistance of the measurement pump cell 41 with respect to the input power to the heater 70. High-precision concentration measurement can be achieved even under low-concentration or low-concentration conditions.

It should be noted that, until now, the pump cell for adjustment "shows a slope of the cell resistance that is 1.5 to 1000 times greater than the slope of the cell resistance of the measurement pump cell 41 (the slope of the cell resistance with respect to the input power to the heater 70)". , an example in which the adjustment pump cell is the main pump cell 21 has been described. However, the auxiliary pump cell 50 may be the adjustment pump cell that "shows a cell resistance slope that is 1.5 to 1000 times as large as the cell resistance slope of the measurement pump cell 41 ." That is, the slope of the cell resistance of the auxiliary pump cell 50 with respect to the input power to the heater 70 may be 1.5 to 1000 times the slope of the cell resistance of the measurement pump cell 41 with respect to the input power to the heater 70 .

Moreover, the slope of the cell resistance of both the main pump cell 21 and the auxiliary pump cell 50 (the slope of the cell resistance with respect to the input power to the heater 70) is 1.5 to 1000 times the slope of the cell resistance of the measurement pump cell 41. There may be. That is, both the slope value of the cell resistance of the main pump cell 21 with respect to the input power to the heater 70 and the slope value of the cell resistance of the auxiliary pump cell 50 with respect to the input power to the heater 70 are measured with respect to the input power to the heater 70. The value may be 1.5 to 1000 times the slope of the cell resistance of the pump cell 41 for use.

In the gas sensor S, the slope of the cell resistance of at least one of the main pump cell 21 and the auxiliary pump cell 50 (the slope of the cell resistance with respect to the input power to the heater 70) is 1.5 times the slope of the cell resistance of the measurement pump cell 41. A value of 1000 times from .
<Various parameters related to the pump cell for measurement and the pump cell for adjustment>
FIG. 4 shows an example of numerical values for each of the electrode area, thickness, porosity, ratio of noble metal to zirconia, Au content, and distance between electrodes for the gas sensor S, the measurement pump cell 41, and the main pump cell 21. It is a figure which shows.

(Regarding electrode area)
As illustrated in FIG. 4, in the gas sensor S, the electrode area of the main pump cell 21, that is, the area [mm ² ] of the inner pump electrode 22 (in particular, the surface exposed to the gas to be measured) is 1.5. is. On the other hand, the electrode area of the measurement pump cell 41, that is, the area [mm ² ] of the measurement electrode 44 (in particular, the surface exposed to the gas to be measured) is "7.5". Therefore, in the gas sensor S, the area of the measurement electrode 44 (the surface exposed to the gas to be measured) is larger than the area of the inner pump electrode 22 (the surface exposed to the gas to be measured).

As described above, in order to achieve both high-accuracy concentration measurement in an environment where the concentration of NO _x in the gas to be measured is high and high-accuracy concentration measurement in an environment where the concentration is low, the input power to the heater 70 must be It is desirable to make the slope of the cell resistance of the adjustment pump cell (for example, the main pump cell 21) larger than the slope of the cell resistance of the measurement pump cell 41 with respect to the input power. The inventors of the present invention have found through experiments that the area of the measurement electrode 44 is required to make the slope of the cell resistance of the main pump cell 21 with respect to the input power to the heater 70 larger than the slope of the cell resistance of the measurement pump cell 41 with respect to the input power. is larger than the area of the inner pump electrode 22. Therefore, in the gas sensor S, since the area of the measurement electrode 44 is larger than the area of the inner pump electrode 22, highly accurate concentration measurement can be achieved both under high and low concentrations.

(Regarding electrode thickness)
As illustrated in FIG. 4, in the gas sensor S, the thickness of the electrode of the main pump cell 21, that is, the thickness [μm] of the inner pump electrode 22 is "15". On the other hand, the thickness of the electrode of the measuring pump cell 41, that is, the thickness [μm] of the measuring electrode 44 is "25". Therefore, in the gas sensor S, the measurement electrode 44 is thicker than the inner pump electrode 22 .

As described above, in order to achieve both high-accuracy concentration measurement in an environment where the concentration of NO _x in the gas to be measured is high and high-accuracy concentration measurement in an environment where the concentration is low, the input power to the heater 70 must be It is desirable to make the slope of the cell resistance of the adjustment pump cell (for example, the main pump cell 21) larger than the slope of the cell resistance of the measurement pump cell 41 with respect to the input power. The inventors of the present invention have found through experiments that the thickness of the measurement electrode 44 is required to make the slope of the cell resistance of the main pump cell 21 with respect to the input power to the heater 70 greater than the slope of the cell resistance of the measurement pump cell 41 with respect to the input power. is thicker than the thickness of the inner pump electrode 22. Therefore, in the gas sensor S, the thickness of the measuring electrode 44 is thicker than the thickness of the inner pump electrode 22, so that highly accurate concentration measurement can be realized both under high and low concentrations.

(Regarding electrode porosity)
As illustrated in FIG. 4, in the gas sensor S, the porosity of the electrode of the main pump cell 21, that is, the porosity [%] of the inner pump electrode 22 is "10". On the other hand, the porosity of the electrode of the measurement pump cell 41, that is, the porosity [%] of the measurement electrode 44 is "5". Therefore, in the gas sensor S, the porosity of the measurement electrode 44 is lower than the porosity of the inner pump electrode 22 .

As described above, in order to achieve both high-accuracy concentration measurement in an environment where the concentration of NO _x in the gas to be measured is high and high-accuracy concentration measurement in an environment where the concentration is low, the input power to the heater 70 must be It is desirable to make the slope of the cell resistance of the adjustment pump cell (for example, the main pump cell 21) larger than the slope of the cell resistance of the measurement pump cell 41 with respect to the input power. The inventors of the present invention have found through experiments that the cell resistance of the main pump cell 21 with respect to the input power to the heater 70 should be greater than the cell resistance of the measurement pump cell 41 with respect to the input power. It has been found useful to make the porosity lower than the porosity of the inner pump electrode 22 . Therefore, in the gas sensor S, since the porosity of the measuring electrode 44 is lower than that of the inner pump electrode 22, highly accurate concentration measurement can be achieved both under high and low concentrations.

The porosity of the inner pump electrode 22, the measurement electrode 44, the auxiliary pump electrode 51, etc. in the gas sensor S is determined by scanning the inner pump electrode 22, the measurement electrode 44, the auxiliary pump electrode 51, etc. with a scanning electron microscope (SEM). It is a value measured by analyzing an SEM image obtained by observing at.

(Regarding the ratio of noble metal and zirconia in the electrode)
In the gas sensor S, the inner pump electrode 22 and the measurement electrode 44 are both zirconia and noble metal cermet electrodes. As illustrated in FIG. 4, in the gas sensor S, the ratio of noble metal to zirconia in the electrodes of the main pump cell 21, i.e., the ratio of noble metal to zirconia in the inner pump electrode 22 is "(noble metal) 85 to (zirconia) 15”. On the other hand, the ratio of noble metal to zirconia in the electrodes of the measuring pump cell 41, that is, the ratio of noble metal to zirconia in the measuring electrode 44 is "(noble metal) 85:(zirconia) 15". Therefore, in the gas sensor S, the ratio of noble metal to zirconia in the measurement electrode 44 is the same as the ratio of noble metal to zirconia in the inner pump electrode 22 .

As described above, in order to achieve both high-accuracy concentration measurement in an environment where the concentration of NO _x in the gas to be measured is high and high-accuracy concentration measurement in an environment where the concentration is low, the input power to the heater 70 must be It is desirable to make the slope of the cell resistance of the adjustment pump cell (for example, the main pump cell 21) larger than the slope of the cell resistance of the measurement pump cell 41 with respect to the input power. The inventors of the present invention have found through experiments that the ratio of noble metal to zirconia is necessary to make the slope of the cell resistance of the main pump cell 21 with respect to the input power to the heater 70 greater than the slope of the cell resistance of the measurement pump cell 41 with respect to the input power. It has been found useful to have a higher ratio at the measuring electrode 44 than at the inner pump electrode 22 for . Therefore, in the gas sensor S, when the ratio of noble metal to zirconia in the measuring electrode 44 is set higher than the ratio in the inner pump electrode 22, highly accurate concentration measurement can be realized both under high concentration and under low concentration. .

(Regarding the Au content of the electrode)
As illustrated in FIG. 4, in the gas sensor S, the Au content rate of the electrode of the main pump cell 21, that is, the Au content rate [wt%] of the inner pump electrode 22 is "0". On the other hand, the Au content of the electrode of the measurement pump cell 41, that is, the Au content [wt%] of the measurement electrode 44 is "0". Therefore, in the gas sensor S, the Au content of the measurement electrode 44 is the same as the Au content of the inner pump electrode 22 .

As described above, in order to achieve both high-accuracy concentration measurement in an environment where the concentration of NO _x in the gas to be measured is high and high-accuracy concentration measurement in an environment where the concentration is low, the input power to the heater 70 must be It is desirable to make the slope of the cell resistance of the adjustment pump cell (for example, the main pump cell 21) larger than the slope of the cell resistance of the measurement pump cell 41 with respect to the input power. Through experiments, the inventors of the present invention determined that the measurement electrode 44 should be adjusted as follows in order to make the slope of the cell resistance of the main pump cell 21 with respect to the input power to the heater 70 larger than the slope of the cell resistance of the measurement pump cell 41 with respect to the input power. It was confirmed that it is useful to configure as follows. That is, it was confirmed that it is useful to make the Au content of the measurement electrode 44 lower than the Au content of the inner pump electrode 22 . That is, it was found useful to include Au in the inner pump electrode 22 and not include Au in the measurement electrode 44 . Further, it was confirmed that even when the measurement electrode 44 contains Au, it is useful to make the Au content of the measurement electrode 44 lower than the Au content of the inner pump electrode 22 . Therefore, when the Au content of the measurement electrode 44 is set lower than the Au content of the inner pump electrode 22, the gas sensor S can achieve highly accurate concentration measurement under both high and low concentrations. .

(Regarding the distance between electrodes)
As illustrated in FIG. 4, in the gas sensor S, the inter-electrode distance of the main pump cell 21, that is, the distance [μm] between the inner pump electrode 22 and the outer pump electrode 23 is "0.4". On the other hand, the inter-electrode distance of the measuring pump cell 41, that is, the distance [μm] between the measuring electrode 44 and the outer pump electrode 23 is "0.2". Therefore, in the gas sensor S, the inter-electrode distance of the measuring pump cell 41 (the distance between the measuring electrode 44 and the outer pump electrode 23) is equal to the inter-electrode distance of the main pump cell 21 (the distance between the inner pump electrode 22 and the outer pump electrode 23). smaller (shorter) than the distance between

As described above, in order to achieve both high-accuracy concentration measurement in an environment where the concentration of NO _x in the gas to be measured is high and high-accuracy concentration measurement in an environment where the concentration is low, the input power to the heater 70 must be It is desirable to make the slope of the cell resistance of the adjustment pump cell (for example, the main pump cell 21) larger than the slope of the cell resistance of the measurement pump cell 41 with respect to the input power. Through experiments, the inventors of the present invention have found that the slope of the cell resistance of the main pump cell 21 with respect to the input power to the heater 70 is larger than the slope of the cell resistance of the measurement pump cell 41 with respect to the input power. It has been found useful to make the inter-electrode distance smaller (shorter) than the inter-electrode distance of the main pump cell 21 . Therefore, in the gas sensor S, the inter-electrode distance of the measuring pump cell 41 is smaller than the inter-electrode distance of the main pump cell 21, so that highly accurate concentration measurement can be achieved both under high and low concentration conditions.

[feature]
As described above, the gas sensor S according to this embodiment includes the gas sensor element 100 , the detection section 111 and the temperature setting section 112 . The gas sensor element 100 is a sensor element composed of six oxygen ion conductive solid electrolyte layers. The gas sensor element 100 includes an internal space (measurement gas circulation portion 7) into which the gas to be measured is introduced, a measurement pump cell 41, and a heater 70 (heater portion). and at least one of the auxiliary pump cell 50 . The measurement pump cell 41 includes a measurement electrode 44 provided in the measured gas circulation portion 7, an outer pump electrode 23 provided in a different portion from the measured gas circulation portion 7, and the measurement electrode 44 and the outer pump electrode 23. and a solid electrolyte layer (second solid electrolyte layer 6, spacer layer 5, and first solid electrolyte layer 4) present therebetween. The heater 70 is embedded inside the gas sensor element 100 and heats the gas sensor element 100 to a predetermined temperature (sensor element driving temperature).

The adjustment pump cell provided in the gas sensor element 100 includes an inner pump electrode (inner pump electrode 22 or auxiliary pump electrode 51) formed facing the internal space of the gas sensor element 100 (that is, the measured gas flow portion 7), and an outer pump cell. between the inner pump electrode and the outer pump electrode 23 or the third electrode provided in a manner exposed to the external space in contact with the pump electrode 23 or at least one of the solid electrolyte layers 1-6; and a solid electrolyte layer present in the electrochemical pump cell.

Specifically, the main pump cell 21 includes an inner pump electrode 22 formed facing the gas flow part 7 to be measured, an outer pump electrode 23 , and a second electrode sandwiched between the inner pump electrode 22 and the outer pump electrode 23 . It is an electrochemical pump cell composed of two solid electrolyte layers 6 . The auxiliary pump cell 50 includes an auxiliary pump electrode 51, an outer pump electrode 23 (or a suitable electrode outside the gas sensor element 100 in contact with at least one of the solid electrolyte layers 1-6), and a solid electrolyte sandwiched between them. It is an electrochemical pump cell constituted by a layer (for example, a second solid electrolyte layer 6). A "suitable electrode outside the gas sensor element 100 in contact with at least one of the solid electrolyte layers 1-6" is also referred to as a third electrode.

The detection unit 111 detects the value of the cell resistance (impedance) of the adjustment pump cell provided in the gas sensor element 100 . That is, the detection unit 111 detects the cell resistance value of at least one of the main pump cell 21 and the auxiliary pump cell 50 .

The temperature setting unit 112 (adjusting unit) adjusts the predetermined temperature (sensor element driving temperature ) is adjusted (set). That is, temperature setting unit 112 sets the sensor element driving temperature such that the cell resistance value of at least one of main pump cell 21 and auxiliary pump cell 50 is equal to reference impedance 115 .

In the gas sensor S, the slope of the cell resistance of the adjustment pump cell (the slope of the cell resistance with respect to the input power to the heater 70 ) is greater than the slope of the cell resistance of the measurement pump cell 41 . That is, in the gas sensor S, the slope of the cell resistance of at least one of the main pump cell 21 and the auxiliary pump cell 50 (the slope of the cell resistance with respect to the input power to the heater 70 ) is greater than the slope of the cell resistance of the measurement pump cell 41 .

Further, the gas sensor control method according to the present embodiment is a control method for a gas sensor including the gas sensor element 100, and is an information processing method for executing a detection step and an adjustment step.

The detection step detects the value of the cell resistance (impedance) of the adjustment pump cell provided in the gas sensor element 100 . That is, the detection step detects the cell resistance value of at least one of the main pump cell 21 and the auxiliary pump cell 50 .

The adjustment step adjusts (sets) a predetermined temperature (sensor element drive temperature) so that the cell resistance (impedance) of the adjustment pump cell detected in the detection step becomes the reference impedance 115 (predetermined value). . That is, the adjusting step sets the sensor element drive temperature such that the cell resistance value of at least one of the main pump cell 21 and the auxiliary pump cell 50 becomes equal to the reference impedance 115 .

In the gas sensor control method according to the present embodiment, the slope of the cell resistance of the adjustment pump cell (the slope of the cell resistance with respect to the input power to the heater 70 ) is greater than the slope of the cell resistance of the measurement pump cell 41 . That is, in the gas sensor control method according to the present embodiment, the slope of the cell resistance of at least one of the main pump cell 21 and the auxiliary pump cell 50 (the slope of the cell resistance with respect to the input power to the heater 70) is the cell resistance of the measuring pump cell 41. is greater than the slope of

In this configuration, the sensor element drive temperature is adjusted so that the cell resistance value of the adjustment pump cell (at least one of the main pump cell 21 and the auxiliary pump cell 50) detected by the detection unit 111 (detection step) becomes a predetermined value. , that is, the sensor element driving temperature is controlled. Also, the slope of the cell resistance of the adjustment pump cell with respect to the input power to the heater 70 is greater than the slope of the cell resistance of the measurement pump cell 41 with respect to the input power to the heater 70 . That is, in this configuration, the slope of the cell resistance with respect to the input power to the heater 70 is larger for the adjustment pump cell than for the measurement pump cell 41 .

By controlling the sensor element driving temperature and setting the cell resistance of the adjustment pump cell to a predetermined value, the following effects are obtained. That is, since the value of the cell resistance of the adjustment pump cell is maintained at a predetermined value, the resistance to the reaction of the adjustment pump cell does not increase, and the pump voltage applied to the adjustment pump cell (that is, the pump voltage Vp0 and the voltage At least one of Vp1) need not be increased. Therefore, "as a result of increasing the pump voltage applied to the adjustment pump cell, the specific _NOx gas in the gas to be measured is decomposed in the adjustment pump cell, and the measurement accuracy of _{the NOx} concentration deteriorates. It is possible to avoid the situation that the measurement accuracy deteriorates when the is high.

As for the slope of the cell resistance with respect to the input power to the heater 70, since the slope of the adjustment pump cell is larger than the slope of the measurement pump cell 41, the cell resistance of the adjustment pump cell can be set to a predetermined value with a small input power. can be controlled so that

Furthermore, since the slope of the cell resistance of the adjustment pump cell with respect to the input power to the heater 70 is large, when changing the input power (that is, the sensor element driving temperature) so that the cell resistance value of the adjustment pump cell becomes a predetermined value, Moreover, fluctuations in sensor element drive temperature can be reduced. By reducing the fluctuation of the sensor element driving temperature, the fluctuation of the offset value can be suppressed, and highly accurate concentration measurement can be realized even when the concentration of NO _x in the gas to be measured is low. .

In addition, regarding the slope of the cell resistance with respect to the input power to the heater 70, the slope of the measurement pump cell 41 is smaller (than the slope of the adjustment pump cell). Therefore, even if the temperature (for example, the temperature of the measurement pump cell 41) fluctuates, the change in the cell resistance of the measurement pump cell 41 is small and the fluctuation of the offset value can be suppressed.

As described above, the _gas sensor S avoids a situation in which the measurement accuracy deteriorates when the concentration of NO _x in the gas to be measured is high. Accurate concentration measurement can be realized. That is, the gas sensor S can achieve both high-precision concentration measurement in an environment where the concentration of _NOx in the gas to be measured is high and high-precision concentration measurement in an environment where the concentration is low.

In the gas sensor S, the slope of the cell resistance of the adjustment pump cell with respect to the power applied to the heater 70 is 1.5 to 1000 times the slope of the cell resistance of the measurement pump cell 41 with respect to the power applied to the heater 70 . In this configuration, the slope of the cell resistance of the adjustment pump cell with respect to the power applied to the heater 70 is 1.5 to 1000 times the slope of the cell resistance of the measurement pump cell 41 with respect to the power applied to the heater 70 . As described above, in order to achieve both high-accuracy concentration measurement under high concentration and high-accuracy concentration measurement under low concentration, the slope of the cell resistance of the adjustment pump cell with respect to the input power to the heater 70 is determined by the heater It is desirable to make it larger than the slope of the cell resistance of the measuring pump cell 41 with respect to the input power to 70 . The inventor of the present invention has experimentally determined that the slope of the cell resistance of the adjustment pump cell with respect to the power applied to the heater 70 is 1.5 to 1000 times the slope of the cell resistance of the measurement pump cell 41 with respect to the power applied to the heater 70. It was confirmed that it is desirable to Therefore, the gas sensor S sets the slope of the cell resistance of the adjustment pump cell (the slope of the cell resistance with respect to the input power to the heater 70) to a value 1.5 to 1000 times the slope of the cell resistance of the measurement pump cell 41. As a result, highly accurate density measurement can be achieved in both high and low densities.

[Modification]
Although the embodiments of the present invention have been described above, the description of the embodiments up to the above is merely an illustration of the present invention in every respect. Various modifications and variations may be made to the above embodiments. Omission, replacement, and addition of components may be made as appropriate for each component of the above-described embodiment. Also, the shape and size of each component of the above embodiment may be changed as appropriate according to the embodiment. For example, the following changes are possible. In addition, below, the same code|symbol is used about the component similar to the said embodiment, and description is abbreviate|omitted suitably about the point similar to the said embodiment. The following modified examples can be combined as appropriate.

(I) Configurations of measurement pump cell and main pump cell FIG. 5 shows the electrode area, thickness, porosity, ratio of noble metal to zirconia, and Au for the measurement pump cell 41 and the main pump cell 21 of the gas sensor S1 according to the modification. It is a figure which shows an example of the numerical value about each of a content rate and an inter-electrode distance.

(Regarding electrode area)
As illustrated in FIG. 5, in the gas sensor S1, the electrode area of the main pump cell 21, that is, the area [mm ² ] of the inner pump electrode 22 (especially the surface exposed to the gas to be measured) is "1". . On the other hand, the electrode area of the measurement pump cell 41, that is, the area [mm ² ] of the measurement electrode 44 (in particular, the surface exposed to the gas to be measured) is "12". Therefore, in the gas sensor S1, the area of the measurement electrode 44 (the surface exposed to the gas to be measured) is larger than the area of the inner pump electrode 22 (the surface exposed to the gas to be measured).

As described above, by making the area of the measurement electrode 44 larger than the area of the inner pump electrode 22, the slope of the cell resistance of the main pump cell 21 (the slope of the cell resistance with respect to the input power to the heater 70) can be measured by the measurement pump cell 41. can be greater than the slope of the cell resistance of By making the slope of the cell resistance of the main pump cell 21 larger than the slope of the cell resistance of the measurement pump cell 41, high-accuracy concentration measurement under an environment where the concentration of NO _x in the gas to be measured is high and It is possible to achieve both high-precision concentration measurement under a low environment.

Therefore, in the gas sensor S1, since the area of the measurement electrode 44 is larger than the area of the inner pump electrode 22, highly accurate concentration measurement can be achieved both under high and low concentrations.

(Regarding electrode thickness)
As illustrated in FIG. 5, in the gas sensor S1, the thickness of the electrode of the main pump cell 21, that is, the thickness [μm] of the inner pump electrode 22 is "15". On the other hand, the thickness of the electrode of the measuring pump cell 41, that is, the thickness [μm] of the measuring electrode 44 is "15". Therefore, in the gas sensor S<b>1 , the thickness of the measurement electrode 44 is the same as the thickness of the inner pump electrode 22 .

As described above, by making the thickness of the measurement electrode 44 larger than the thickness of the inner pump electrode 22, the slope of the cell resistance of the main pump cell 21 (the slope of the cell resistance with respect to the power input to the heater 70) can be obtained from the measurement pump cell. 41 cell resistance slope. By making the slope of the cell resistance of the main pump cell 21 larger than the slope of the cell resistance of the measurement pump cell 41, high-accuracy concentration measurement under an environment where the concentration of NO _x in the gas to be measured is high and It is possible to achieve both high-precision concentration measurement under a low environment.

Therefore, when the thickness of the measuring electrode 44 is made thicker than the thickness of the inner pump electrode 22, the gas sensor S1 can realize high-precision concentration measurement under both high concentration and low concentration.

(Regarding electrode porosity)
As illustrated in FIG. 5, in the gas sensor S1, the electrode porosity of the main pump cell 21, that is, the porosity [%] of the inner pump electrode 22 is "20". On the other hand, the porosity of the electrode of the measurement pump cell 41, that is, the porosity [%] of the measurement electrode 44 is "10". Therefore, in gas sensor S<b>1 , the porosity of measuring electrode 44 is lower than the porosity of inner pump electrode 22 .

As described above, by making the porosity of the measurement electrode 44 lower than the porosity of the inner pump electrode 22, the slope of the cell resistance of the main pump cell 21 (the slope of the cell resistance with respect to the input power to the heater 70) can be measured. can be made larger than the slope of the cell resistance of the pump cell 41 for use. By making the slope of the cell resistance of the main pump cell 21 larger than the slope of the cell resistance of the measurement pump cell 41, high-precision concentration measurement can be performed in an environment where the NO _x concentration in the gas to be measured is high. It is possible to achieve both high-precision concentration measurement under a low environment.

Therefore, in the gas sensor S1, since the porosity of the measuring electrode 44 is lower than that of the inner pump electrode 22, highly accurate concentration measurement can be realized both under high and low concentrations.

(Regarding the ratio of noble metal and zirconia in the electrode)
In the gas sensor S1, the inner pump electrode 22 and the measuring electrode 44 are both zirconia and noble metal cermet electrodes. As illustrated in FIG. 5, in the gas sensor S1, the ratio of noble metal to zirconia in the electrodes of the main pump cell 21, that is, the ratio of noble metal to zirconia in the inner pump electrode 22 is "(noble metal) 85 to (zirconia) 15”. On the other hand, the ratio of noble metal to zirconia in the electrodes of the measuring pump cell 41, that is, the ratio of noble metal to zirconia in the measuring electrode 44 is "(noble metal) 85:(zirconia) 15". Therefore, in the gas sensor S 1 , the ratio of noble metal to zirconia in the measurement electrode 44 is the same as the ratio of noble metal to zirconia in the inner pump electrode 22 .

As described above, regarding the ratio of noble metal to zirconia, by making the ratio of the measurement electrode 44 higher than the ratio of the inner pump electrode 22, the slope of the cell resistance of the main pump cell 21 (the slope of the cell resistance with respect to the input power to the heater 70 ) can be made larger than the slope of the cell resistance of the measuring pump cell 41 . By making the slope of the cell resistance of the main pump cell 21 larger than the slope of the cell resistance of the measurement pump cell 41, high-accuracy concentration measurement under an environment where the concentration of NO _x in the gas to be measured is high and It is possible to achieve both high-precision concentration measurement under a low environment.

Therefore, when the ratio of noble metal to zirconia in the measuring electrode 44 is set higher than the ratio in the inner pump electrode 22, the gas sensor S1 can realize highly accurate concentration measurement under both high concentration and low concentration. can.

(Regarding the Au content of the electrode)
As illustrated in FIG. 5, in the gas sensor S1, the Au content rate of the electrode of the main pump cell 21, that is, the Au content rate [wt%] of the inner pump electrode 22 is "0.5". On the other hand, the Au content of the electrode of the measurement pump cell 41, that is, the Au content [wt%] of the measurement electrode 44 is "0". Therefore, in the gas sensor S<b>1 , the Au content of the measurement electrode 44 is lower than the Au content of the inner pump electrode 22 .

As described above, by making the Au content of the measurement electrode 44 lower than the Au content of the inner pump electrode 22, the slope of the cell resistance of the main pump cell 21 (the slope of the cell resistance with respect to the input power to the heater 70 ) can be made larger than the slope of the cell resistance of the measuring pump cell 41 . By making the slope of the cell resistance of the main pump cell 21 larger than the slope of the cell resistance of the measurement pump cell 41, high-accuracy concentration measurement under an environment where the concentration of NO _x in the gas to be measured is high and It is possible to achieve both high-precision concentration measurement under a low environment.

Therefore, in the gas sensor S1, since the Au content of the measurement electrode 44 is lower than that of the inner pump electrode 22, high-precision concentration measurement can be achieved both at high concentrations and at low concentrations.

(Regarding the distance between electrodes)
As illustrated in FIG. 5, in the gas sensor S1, the distance between the electrodes of the main pump cell 21, that is, the distance [μm] between the inner pump electrode 22 and the outer pump electrode 23 is "0.2". On the other hand, the inter-electrode distance of the measuring pump cell 41, that is, the distance [μm] between the measuring electrode 44 and the outer pump electrode 23 is "0.2". Therefore, in the gas sensor S1, the inter-electrode distance of the measuring pump cell 41 (the distance between the measuring electrode 44 and the outer pump electrode 23) is equal to the inter-electrode distance of the main pump cell 21 (the distance between the inner pump electrode 22 and the outer pump electrode 23). distance between

As described above, by making the inter-electrode distance of the measurement pump cell 41 smaller (shorter) than the inter-electrode distance of the main pump cell 21, the slope of the cell resistance of the main pump cell 21 (the cell resistance with respect to the input power to the heater 70) is reduced. slope) can be larger than the slope of the cell resistance of the measuring pump cell 41 . By making the slope of the cell resistance of the main pump cell 21 larger than the slope of the cell resistance of the measurement pump cell 41, high-accuracy concentration measurement under an environment where the concentration of NO _x in the gas to be measured is high and It is possible to achieve both high-precision concentration measurement under a low environment.

Therefore, when the inter-electrode distance of the measuring pump cell 41 is made smaller than the inter-electrode distance of the main pump cell 21, the gas sensor S1 can realize highly accurate concentration measurement under both high and low concentrations.

(Notes on electrode area)
So far, an example has been described in which the adjustment pump cell is the main pump cell 21 as an adjustment pump cell having an electrode with an area smaller than that of the electrode (measurement electrode 44) of the measurement pump cell 41. FIG. That is, by making the area of the measurement electrode 44 larger than the area of the inner pump electrode 22, the slope of the cell resistance of the main pump cell 21 as the adjustment pump cell is made larger than the slope of the cell resistance of the measurement pump cell 41. We have already described examples of what can be done. However, the auxiliary pump cell 50 may be the adjustment pump cell having an electrode with an area smaller than that of the electrode (measurement electrode 44 ) of the measurement pump cell 41 . That is, the area of the measurement electrode 44 may be larger than the area of the auxiliary pump electrode 51 of the auxiliary pump cell 50 .

Also, the area of the electrodes of both the main pump cell 21 and the auxiliary pump cell 50 may be smaller than the area of the electrodes of the measurement pump cell 41 . That is, both the area of the inner pump electrode 22 and the area of the auxiliary pump electrode 51 of the auxiliary pump cell 50 may be smaller than the area of the measurement electrode 44 .

In the gas sensor according to one aspect of the present invention, the area of the measurement electrode 44 is larger than the area of at least one of the main pump cell 21 and the auxiliary pump cell 50 (for example, the area of at least one of the inner pump electrode 22 and the auxiliary pump electrode 51). should be large.

By making the electrode area of the measurement pump cell 41 larger than the electrode area of the adjustment pump cell, the slope of the cell resistance of the adjustment pump cell (the slope of the cell resistance with respect to the input power to the heater 70) can be adjusted to the measurement pump cell. 41 cell resistance slope. By making the slope of the cell resistance of the adjustment pump cell 41 larger than the slope of the cell resistance of the measurement pump cell 41, high-precision concentration measurement can be performed in an environment where the concentration of NO _x in the gas to be measured is high. It is possible to achieve both high-precision concentration measurement under a low environment.

(Notes on electrode thickness)
So far, an example in which the adjustment pump cell is the main pump cell 21 has been described as an adjustment pump cell having an electrode thinner than the thickness of the electrode (measurement electrode 44) of the measurement pump cell 41. FIG. That is, by making the measurement electrode 44 thicker than the inner pump electrode 22, the slope of the cell resistance of the main pump cell 21 as the adjustment pump cell is made larger than the slope of the cell resistance of the measurement pump cell 41. We have already described examples of what can be done. However, the auxiliary pump cell 50 may be the adjustment pump cell having an electrode thinner than the electrode (measurement electrode 44 ) of the measurement pump cell 41 . That is, the measurement electrode 44 may be thicker than the auxiliary pump electrode 51 of the auxiliary pump cell 50 .

Moreover, the thickness of the electrodes of both the main pump cell 21 and the auxiliary pump cell 50 may be thinner than the thickness of the electrode of the measurement pump cell 41 . That is, both the thickness of the inner pump electrode 22 and the thickness of the auxiliary pump electrode 51 of the auxiliary pump cell 50 may be thinner than the thickness of the measurement electrode 44 .

In the gas sensor according to one aspect of the present invention, the thickness of the measurement electrode 44 is greater than the thickness of at least one of the main pump cell 21 and the auxiliary pump cell 50 (for example, the thickness of at least one of the inner pump electrode 22 and the auxiliary pump electrode 51). should be thicker.

By making the thickness of the electrode of the measuring pump cell 41 thicker than the thickness of the electrode of the adjusting pump cell, the slope of the cell resistance of the adjusting pump cell (the slope of the cell resistance with respect to the input power to the heater 70) can be changed to that of the measuring pump cell. 41 cell resistance slope. By making the slope of the cell resistance of the adjustment pump cell 41 larger than the slope of the cell resistance of the measurement pump cell 41, high-precision concentration measurement can be performed in an environment where the concentration of NO _x in the gas to be measured is high. It is possible to achieve both high-precision concentration measurement under a low environment.

(Note regarding electrode porosity)
So far, an example in which the adjustment pump cell is the main pump cell 21 has been described as an adjustment pump cell having an electrode with a porosity higher than that of the electrode of the measurement pump cell 41 (measurement electrode 44). That is, by making the porosity of the measurement electrode 44 lower than the porosity of the inner pump electrode 22, the slope of the cell resistance of the main pump cell 21 as the adjustment pump cell is lower than the slope of the cell resistance of the measurement pump cell 41. So far we have discussed examples that can be made larger. However, the auxiliary pump cell 50 may be the adjustment pump cell having an electrode with a porosity higher than that of the electrode (measurement electrode 44 ) of the measurement pump cell 41 . That is, the porosity of the measurement electrode 44 may be lower than that of the auxiliary pump electrode 51 of the auxiliary pump cell 50 .

Moreover, the porosity of the electrodes of both the main pump cell 21 and the auxiliary pump cell 50 may be higher than the porosity of the electrodes of the measurement pump cell 41 . That is, both the porosity of the inner pump electrode 22 and the porosity of the auxiliary pump electrode 51 of the auxiliary pump cell 50 may be higher than the porosity of the measurement electrode 44 .

In the gas sensor according to one aspect of the present invention, the porosity of the measurement electrode 44 is equal to the porosity of at least one electrode of the main pump cell 21 and the auxiliary pump cell 50 (for example, the porosity of at least one of the inner pump electrode 22 and the auxiliary pump electrode 51). rate).

By making the electrode porosity of the measuring pump cell 41 lower than the electrode porosity of the adjusting pump cell, the slope of the cell resistance of the adjusting pump cell (the slope of the cell resistance with respect to the input power to the heater 70) is measured. can be made larger than the slope of the cell resistance of the pump cell 41 for use. By making the slope of the cell resistance of the adjustment pump cell larger than the slope of the cell resistance of the measurement pump cell 41, high-precision concentration measurement can be performed in an environment where the concentration of NO _x in the gas to be measured is high. It is possible to achieve both high-precision concentration measurement under a low environment.

(Note regarding the ratio of noble metal to zirconia)
So far, an example in which the adjustment pump cell is the main pump cell 21 as an adjustment pump cell having a cermet electrode having a lower ratio of the noble metal to zirconia than the ratio of the electrode (measurement electrode 44) of the measurement pump cell 41 has been described. I've been That is, regarding the ratio of noble metal to zirconia, by making the ratio of the measuring electrode 44 higher than the ratio of the inner pumping electrode 22, the slope of the cell resistance of the main pump cell 21 as the adjusting pump cell is changed to the cell resistance of the measuring pump cell 41. We have so far described examples where the slope of . However, the auxiliary pump cell 50 may be an adjustment pump cell having a cermet electrode with a ratio of noble metal to zirconia lower than the ratio of the electrode (measurement electrode 44 ) of the measurement pump cell 41 . That is, with respect to the ratio of noble metal to zirconia, the ratio of measurement electrode 44 may be higher than the ratio of auxiliary pump electrode 51 of auxiliary pump cell 50 .

Moreover, regarding the ratio of noble metal to zirconia, the ratio of the electrodes of both the main pump cell 21 and the auxiliary pump cell 50 may be lower than the ratio of the electrodes of the measurement pump cell 41 . That is, both the ratio of the noble metal to zirconia of the inner pump electrode 22 and the ratio of the auxiliary pump electrode 51 of the auxiliary pump cell 50 may be lower than the ratio of the measurement electrode 44 .

In the gas sensor according to one aspect of the present invention, regarding the ratio of noble metal to zirconia, the ratio of the measurement electrode 44 is equal to the ratio of the electrodes of at least one of the main pump cell 21 and the auxiliary pump cell 50 (for example, the inner pump electrode 22 and the auxiliary pump electrode 51). ratio of at least one of).

Regarding the ratio of the noble metal to zirconia, by making the ratio of the electrodes of the measurement pump cell 41 higher than the ratio of the electrodes of the adjustment pump cell, the slope of the cell resistance of the adjustment pump cell (the cell resistance with respect to the input power to the heater 70 slope) can be larger than the slope of the cell resistance of the measuring pump cell 41 . By making the slope of the cell resistance of the adjustment pump cell larger than the slope of the cell resistance of the measurement pump cell 41, high-precision concentration measurement can be performed in an environment where the concentration of NO _x in the gas to be measured is high. It is possible to achieve both high-precision concentration measurement under a low environment.

(Note regarding Au content)
So far, an example in which the adjustment pump cell is the main pump cell 21 has been described as an adjustment pump cell having an electrode with a higher Au content than the electrode of the measurement pump cell 41 (measurement electrode 44). That is, by making the Au content rate of the measurement electrode 44 lower than the Au content rate of the inner pump electrode 22, the slope of the cell resistance of the main pump cell 21 as the adjustment pump cell is changed to the slope of the cell resistance of the measurement pump cell 41. So far we have discussed examples where it can be larger than . However, the auxiliary pump cell 50 may be the adjustment pump cell having an electrode with a higher Au content than the electrode of the measurement pump cell 41 (measurement electrode 44 ). That is, the Au content of the measurement electrode 44 may be lower than the Au content of the auxiliary pump electrode 51 of the auxiliary pump cell 50 .

Also, the Au content in the electrodes of both the main pump cell 21 and the auxiliary pump cell 50 may be higher than the Au content in the electrodes of the measurement pump cell 41 . That is, both the Au content of the inner pump electrode 22 and the Au content of the auxiliary pump electrode 51 of the auxiliary pump cell 50 may be higher than the Au content of the measurement electrode 44 .

In the gas sensor according to one aspect of the present invention, the Au content of the measurement electrode 44 is equal to the Au content of at least one electrode of the main pump cell 21 and the auxiliary pump cell 50 (for example, the inner pump electrode 22 and the auxiliary pump electrode 51). content of at least one of Au).

By making the Au content rate of the electrode of the measurement pump cell 41 lower than the Au content rate of the electrode of the adjustment pump cell, the slope of the cell resistance of the adjustment pump cell (the slope of the cell resistance with respect to the input power to the heater 70) can be reduced. , can be greater than the slope of the cell resistance of the measuring pump cell 41 . By making the slope of the cell resistance of the adjustment pump cell larger than the slope of the cell resistance of the measurement pump cell 41, high-precision concentration measurement can be performed in an environment where the concentration of NO _x in the gas to be measured is high. It is possible to achieve both high-precision concentration measurement under a low environment.

(Note regarding the distance between electrodes)
So far, an example has been described in which the adjustment pump cell is the main pump cell 21 as an adjustment pump cell having an inter-electrode distance that is larger (longer) than the inter-electrode distance of the measurement pump cell 41 . That is, the distance between the electrodes of the measuring pump cell 41 (the distance between the measuring electrode 44 and the outer pump electrode 23) is changed to the distance between the electrodes of the main pump cell 21 (the distance between the inner pump electrode 22 and the outer pump electrode 23). So far, an example has been described in which the slope of the cell resistance of the main pump cell 21 as the adjustment pump cell can be made larger than the slope of the cell resistance of the measurement pump cell 41 by making the cell resistance smaller (shorter) than the adjustment pump cell 41. However, the auxiliary pump cell 50 may be the adjustment pump cell having an inter-electrode distance greater than the inter-electrode distance of the measuring pump cell 41 . That is, the inter-electrode distance of the measuring pump cell 41 may be smaller than the inter-electrode distance of the auxiliary pump cell 50 (the distance between the auxiliary pump electrode 51 of the auxiliary pump cell 50 and the outer pump electrode 23 or the third electrode).

Further, the inter-electrode distance of both the main pump cell 21 and the auxiliary pump cell 50 may be greater than the inter-electrode distance of the measurement pump cell 41 . That is, both the distance between the inner pump electrode 22 and the outer pump electrode 23 and the distance between the auxiliary pump electrode 51 and the outer pump electrode 23 or the third electrode are may be greater than the distance between

In the gas sensor according to one aspect of the present invention, the inter-electrode distance of the measuring pump cell 41 should be smaller than the inter-electrode distance of at least one of the main pump cell 21 and the auxiliary pump cell 50 .

By making the inter-electrode distance of the measuring pump cell 41 smaller than the inter-electrode distance of the adjusting pump cell, the slope of the cell resistance of the adjusting pump cell (the slope of the cell resistance with respect to the input power to the heater 70) can be adjusted to the measuring pump cell. 41 cell resistance slope. By making the slope of the cell resistance of the adjustment pump cell larger than the slope of the cell resistance of the measurement pump cell 41, high-precision concentration measurement can be performed in an environment where the concentration of NO _x in the gas to be measured is high. It is possible to achieve both high-precision concentration measurement under a low environment.

So far, the measurement pump cell 41 and the adjustment pump cell have been designed to make the slope of the cell resistance of the adjustment pump cell (the slope of the cell resistance with respect to the input power to the heater 70) larger than the slope of the cell resistance of the measurement pump cell 41. The following conditions 1 to 6 have been described as conditions for the configuration. That is, Condition 1 is that the electrode area of the measurement pump cell 41 is larger than the electrode area of the adjustment pump cell. Condition 2 is that the thickness of the electrode of the pump cell for measurement 41 is thicker than the thickness of the electrode of the pump cell for adjustment. Condition 3 is that the porosity of the electrode of the pump cell for measurement 41 is lower than that of the electrode of the pump cell for adjustment. Condition 4 is that the ratio of noble metal to zirconia in the electrode of the pump cell for measurement 41 is higher than the ratio of noble metal to zirconia in the electrode of the pump cell for adjustment. Condition 5 is that the Au content of the electrode of the pump cell for measurement 41 is lower than the Au content of the electrode of the pump cell for adjustment. Condition 6 is that the inter-electrode distance of the measurement pump cell 41 is smaller (shorter) than the inter-electrode distance of the adjustment pump cell.

In order to make the slope of the cell resistance of the adjustment pump cell (the slope of the cell resistance with respect to the input power to the heater 70) greater than the slope of the cell resistance of the measurement pump cell 41, all of conditions 1 to 6 must be satisfied. is not required. In order to make the slope of the cell resistance of the adjustment pump cell (the slope of the cell resistance with respect to the input power to the heater 70) greater than the slope of the cell resistance of the measurement pump cell 41, the inventors of the present invention have to satisfy conditions 1 to 6. Experiments have shown that it is useful to configure the regulating pump cell and the measuring pump cell 41 such that at least one of them is satisfied. In the above experiment, the inventors found that the slope of the cell resistance of the adjustment pump cell (the slope of the cell resistance with respect to the power applied to the heater 70) was adjusted to suppress the fluctuation of the offset value that affects the measurement accuracy. It has also been confirmed that it is desirable to set the value to be 1.5 to 1000 times the slope of the cell resistance of the pump cell 41 for measurement. Details of the experiment will be described later.

(II) Others In the above embodiment, the laminate of the gas sensor element 100 is composed of six solid electrolyte layers. However, the number of solid electrolyte layers forming the laminate is not limited to such an example, and may be appropriately selected according to the embodiment.

Further, in the above embodiment, the internal space into which the gas to be measured is introduced (that is, the gas-to-be-measured flow section 7) is located at a position defined by the first solid electrolyte layer 4, the spacer layer 5, and the second solid electrolyte layer 6. provided in However, the arrangement of the measured gas circulation section 7 need not be limited to such an example, and may be appropriately selected according to the embodiment. The arrangement of the first surface, the second surface, the first pump electrode, the second pump electrode, the first lead, and the second lead may be appropriately selected according to the structure of the laminate and the internal space.

Further, in the above-described embodiment, the gas-to-be-measured circulation section 7 is configured to have a three-chamber structure. However, the configuration of the measurement target gas circulation section 7 is not limited to such an example, and may be appropriately selected according to the embodiment. In another example, the fourth diffusion control section 18 and the third internal cavity 19 may be omitted, whereby the measured gas circulation section 7 may be configured to have a two-chamber structure. In this case, the measurement electrode 44 may be provided on the upper surface of the first solid electrolyte layer 4 adjacent to the second internal cavity 17 at a position away from the third diffusion rate-limiting portion 16 .
That is, the measured gas circulation section 7 may include two empty chambers in which oxygen is pumped out or pumped in, or may include only one. Moreover, it is not essential for the gas sensor element 100 to have one or more diffusion control sections.

Also, in FIG. 1, both the inner pump electrode 22 and the outer pump electrode 23 are exposed to the space. Adjacent to the space, however, is not limited to such a form, and may be indirectly adjoined via a covering or the like. As another example, the outer pump electrode 23 may be covered with a protective member or the like.

Further, in the above embodiment, the reference gas introduction space 43 is provided. However, the configuration of the gas sensor element 100 need not be limited to such an example. In another example, the first solid electrolyte layer 4 may be configured to extend to the rear end of the gas sensor element 100, and the reference gas introduction space 43 may be omitted. In this case, the atmosphere introduction layer 48 may be configured to extend to the rear end of the gas sensor element 100 .

Further, in the above embodiment, the gas sensor element 100 is configured to measure the concentration of nitrogen oxides (NO _x ). However, the gas sensor element of the present invention need not be limited to such a gas sensor element configured to measure the concentration of _NOx . In another example, the gas sensor element of the invention may be another gas sensor element, such as a gas sensor element configured to measure the concentration of oxygen, for example. For example, by omitting the auxiliary pump cell and the measurement pump cell from the gas sensor element 100 according to the above embodiment and arranging the reference electrode below the main pump electrode, a gas sensor element for measuring the oxygen concentration can be configured. . In this case, the gas sensor element can measure the oxygen concentration in the gas to be measured by pumping oxygen with the main pump cell.

[Example]
FIG. 6 is a diagram showing an organized summary of experiments conducted by the inventors of the present invention. Specifically, FIG. 6 shows the gas sensors according to Examples 1 to 12, Comparative Example 1, and Comparative Example 2, for which the inventor confirmed the "offset value fluctuation amount (offset fluctuation rate)". Numerical values of various parameters and confirmation results are shown for each. As will be described below, the present inventor evaluated the amount of variation in the offset value of each of the gas sensors according to Examples 1 to 12, Comparative Example 1, and Comparative Example 2 (offset variation evaluation 1) and Evaluation 2 (offset fluctuation evaluation 2) was confirmed. As described above, the "fluctuation in the offset value" affects the measurement accuracy of the gas sensor. The gas sensors according to Examples 1 to 12, Comparative Examples 1, and 2 all employ the configuration shown in FIG.

As shown in FIG. 6, for the gas sensor of Example 1-10 in which the slope of the cell resistance of the adjustment pump cell is 1.5 to 1000 times the slope of the cell resistance of the measurement pump cell 41, the offset Variation evaluation 1 was "A". Although the details will be described later, "offset fluctuation evaluation 1" indicates an evaluation of the amount of fluctuation in the offset value before and after the change in gas temperature, and "A" indicates that it was "remarkably good." It shows the evaluation result. For the gas sensor of Example 1-10, the offset variation evaluation 2 representing the amount of variation in the offset value before and after the endurance test (details of which will be described later) was also "A". Also, the slope of the cell resistance of the adjustment pump cell 41 is not in the range of 1.5 to 1000 times the slope of the cell resistance of the measurement pump cell 41, but the former is greater than the latter. , its offset variation evaluation 1 was "B". "B" represents the next best evaluation result after "A", that is, represents the evaluation result of "good". For the gas sensor of Examples 11-12, the offset variation evaluation 2 was also "B". On the other hand, for the gas sensor of Comparative Example 1-2 in which the slope of the cell resistance of the adjustment pump cell is smaller than or the same as the slope of the cell resistance of the measurement pump cell 41, the offset variation evaluation 1 is It was "F". "F" indicates the lowest evaluation, that is, the evaluation result of "not good". For the gas sensor of Comparative Example 1-2, the offset fluctuation evaluation 2 was also "B".

6, the inventors of the present invention confirmed that by making the slope of the cell resistance of the adjustment pump cell larger than the slope of the cell resistance of the measurement pump cell 41, the fluctuation of the offset value can be suppressed. bottom. In particular, according to the experiment shown in FIG. 6, the present inventor found that the slope of the cell resistance of the adjustment pump cell is set to a value 1.5 to 1000 times the slope of the cell resistance of the measurement pump cell 41, thereby offsetting It was confirmed that the fluctuation of the value can be effectively suppressed. 6, the inventors found that the slope of the cell resistance of the adjustment pump cell with respect to the input power to the heater 70 was larger than the slope of the cell resistance of the measurement pump cell 41 with respect to the input power to the heater 70. Therefore, it was confirmed that it is desirable to configure the measurement pump cell 41 and the adjustment pump cell so as to satisfy at least one of the conditions 1 to 6 described above. Details of the contents shown in FIG. 6 will be described below.

Note that FIG. 6 shows an example in which the adjustment pump cell is the main pump cell 21 . That is, condition 1 in FIG. 6 means that "the area of the measurement electrode 44 is larger than the area of the inner pump electrode 22". Condition 2 means that "the thickness of the measurement electrode 44 is greater than the thickness of the inner pump electrode 22". Condition 3 means that "the porosity of the measurement electrode 44 is lower than the porosity of the inner pump electrode 22". Condition 4 means that "the ratio of noble metal to zirconia in the measurement electrode 44 is higher than the ratio of noble metal to zirconia in the inner pump electrode 22". Condition 5 means that "the content of Au in the measurement electrode 44 is lower than the content of Au in the inner pump electrode 22". Condition 6 means that "the distance between the measurement electrode 44 and the outer pump electrode 23 is smaller (shorter) than the distance between the inner pump electrode 22 and the outer pump electrode 23".

In the diagram shown in FIG. 6, the "ratio of the slope of the cell resistance to the input power to the heater (main/for measurement)" is It shows the ratio (magnification) of "the slope of the cell resistance of the main pump cell 21 with respect to the input power to the heater 70". "Main" in "area [mm ² ]" indicates the electrode area of the main pump cell 21, that is, the area [mm ² ] of the inner pump electrode 22 (in particular, the surface exposed to the gas to be measured). The "measurement" in the "area [mm ² ]" indicates the electrode area of the measurement pump cell 41, that is, the area [mm ² ] of the measurement electrode 44 (in particular, the surface exposed to the gas to be measured). . “Main” in “thickness [μm]” indicates the thickness of the electrode of the main pump cell 21 , that is, the thickness [μm] of the inner pump electrode 22 . “For measurement” in “thickness [μm]” indicates the thickness of the electrode of the pump cell 41 for measurement, that is, the thickness [μm] of the measurement electrode 44 . “Main” in “porosity [%]” indicates the porosity of the electrode of the main pump cell 21 , that is, the porosity [%] of the inner pump electrode 22 . “For measurement” in “porosity [%]” indicates the porosity of the electrode of the pump cell 41 for measurement, that is, the porosity [%] of the measurement electrode 44 . “Main” in “Au content rate [wt %]” indicates the Au content rate of the electrode of the main pump cell 21 , that is, the Au content rate [wt %] of the inner pump electrode 22 . "For measurement" in "Au content [wt%]" indicates the Au content of the electrode of the pump cell 41 for measurement, that is, the Au content of the measurement electrode 44 [wt%]. “Main” in “interelectrode distance [μm]” indicates the interelectrode distance of the main pump cell 21 , that is, the distance [μm] between the inner pump electrode 22 and the outer pump electrode 23 . "For measurement" in the "interelectrode distance [μm]" indicates the interelectrode distance of the measurement pump cell 41, that is, the distance [μm] between the measurement electrode 44 and the outer pump electrode 23. FIG. “Main” in the “noble metal/zirconia ratio” indicates the ratio (ratio) between the noble metal and zirconia in the electrode of the main pump cell 21 , that is, the ratio between the noble metal and zirconia in the inner pump electrode 22 . The “measurement” in the “noble metal/zirconia ratio” indicates the ratio (ratio) between the noble metal and zirconia in the electrode of the pump cell 41 for measurement, that is, the ratio between the noble metal and zirconia in the measurement electrode 44 .

Further, "offset variation evaluation 1" and "offset variation evaluation 2" are the "offset value variations (offset variation )” indicates the size.

Specifically, the offset fluctuation evaluation 1 is when the gas temperature is varied from "100" ° C. to "400" ° C. in an environment where NO _x is "0" ppm and O ₂ is "18"% , the magnitude of the offset variation of the gas sensor NO _x output (eg, pump current Ip2). "A" in the offset variation evaluation 1 indicates that the offset variation of the NO _x output before and after the change in gas temperature is within "±7" ppm. “B” of the offset variation evaluation 1 indicates that the offset variation of the NO _x output before and after the change in gas temperature is greater than “±7” ppm and within “±15” ppm. An “F” for offset variation evaluation 1 indicates that the offset variation of the NO _x output before and after the change in gas temperature is greater than “±15” ppm.

Further, the offset variation evaluation 2 is the magnitude of the offset variation (offset value change amount). That is, as the above-mentioned endurance test, the present inventors attached each gas sensor to the piping of the exhaust gas pipe of an automobile, and performed a 40-minute driving pattern in which the engine speed was 1500 to 3500 rpm and the load torque was 0 to 350 N m. was repeated for 2000 hours. In the endurance test, the gas temperature was 200° C. to 600° C., and the NO _x concentration was 0 to 1500 ppm. Then, for each gas sensor, the _NOx concentration was "0" ppm, the _O2 concentration was "0"%, and the _H2O concentration was "3"% before and after the endurance test. The offset value was measured when the model gas was flowed, and the amount of change was investigated. “A” in the offset variation evaluation 2 indicates that the offset variation of the NO _x output before and after the above endurance test was within “±7” ppm. “B” in the offset variation evaluation 2 indicates that the offset variation of the NO _x output before and after the endurance test was greater than “±7” ppm and within “±15” ppm. . “F” in the offset variation evaluation 2 indicates that the offset variation of the NO _x output before and after the endurance test was greater than “±15” ppm.

As described above, the smaller the offset fluctuation of the NO _x output, the smaller the influence on the measurement accuracy of the gas sensor, and the smaller the possibility that the measurement accuracy deteriorates. Then, offset variation evaluation 1 and offset variation evaluation 2 are, respectively, examples 1 to 12, comparative example 1, and comparative The amount of change in the offset value of each gas sensor according to example 2 is evaluated. Before and after such a change in conditions, it is possible to use a "method of correcting a value determined for each certain period of time", that is, time correction. Therefore, when the amount of change in the offset value before and after the change in conditions falls within the range of -15% to +15%, the above-described time correction can be effectively used, and "suppressing the change in the offset value We are able to do it.” Therefore, in each of the offset fluctuation evaluation 1 and the offset fluctuation evaluation 2, when the amount of fluctuation in the offset value before and after the change in conditions is within "±7" ppm, the result is "A (remarkably good )” was evaluated. Similarly, if the amount of change in the offset value before and after the change in conditions is greater than “±7” ppm and within “±15” ppm, the result is evaluated as “B (good)”. bottom. In addition, when the amount of variation in the offset value before and after the change in conditions was greater than "±15" ppm, the result was evaluated as "F (not good)". Note that units are omitted in the following description for simplification of description.

(About Example 1)
The electrode area (“main” of “area”) of the main pump cell 21 of Example 1 is “1.5”, and the electrode area of the measurement pump cell 41 (“measurement” of “area”) is “7 .5". That is, in Example 1, the electrode area of the measurement pump cell 41 (the area of the measurement electrode 44) is larger than the electrode area of the main pump cell 21 (the area of the inner pump electrode 22), satisfying Condition 1. The thickness of the electrode of the main pump cell 21 of Example 1 (“main” in “thickness”) is “15”, and the thickness of the electrode of the measurement pump cell 41 (“measurement” in “thickness”) is “25”. ”. That is, in Example 1, the thickness of the electrode of the measuring pump cell 41 (thickness of the measuring electrode 44) is thicker than the thickness of the electrode of the main pump cell 21 (thickness of the inner pump electrode 22), satisfying Condition 2. The porosity of the electrode of the main pump cell 21 of Example 1 (“main” in “porosity”) is “10”, and the porosity of the electrode of the measurement pump cell 41 (“measurement” in “porosity”) is “10”. is "5". That is, in Example 1, the electrode porosity of the measurement pump cell 41 (the porosity of the measurement electrode 44) is lower than the porosity of the electrode of the main pump cell 21 (the porosity of the inner pump electrode 22). meet. The Au content of the electrode of the main pump cell 21 of Example 1 (“main” in “Au content”) is “0.0”, and the Au content of the electrode of the measurement pump cell 41 (“Au The content of "for measurement") is "0.0". That is, in Example 1, the Au content rate of the electrode of the measuring pump cell 41 (the Au content rate of the measuring electrode 44) ) and does not satisfy condition 5. The inter-electrode distance of the main pump cell 21 of Example 1 (“main” in “inter-electrode distance”) is “0.4”, and the inter-electrode distance of the measurement pump cell 41 (“inter-electrode distance” is “measuring ”) is “0.2”. That is, in Example 1, the inter-electrode distance of the measuring pump cell 41 (the distance between the measuring electrode 44 and the outer pump electrode 23) is the same as the inter-electrode distance of the main pump cell 21 (the inner pump electrode 22 and the outer pump electrode 23). , and satisfies condition 6. The ratio between the noble metal and zirconia in the electrode of the main pump cell 21 of Example 1 (“main” in the “noble metal/zirconia ratio”) was “85:15”, and the ratio between the noble metal and zirconia in the electrode of the measuring pump cell 41 was “85:15”. The ratio (“measurement” of “noble metal/zirconia ratio”) is “85:15”. That is, in Example 1, the ratio of noble metal to zirconia in the electrode of the measuring pump cell 41 (the ratio of noble metal to zirconia in the measuring electrode 44) was the ratio of the noble metal to zirconia in the electrode of the main pump cell 21 (the zirconia ratio of precious metals to ) and does not satisfy condition 4.

Therefore, in Example 1, among the conditions 1 to 6, conditions 4 and 5 are not satisfied, but conditions 1, 2, 3, and 6 are satisfied. The "slope ratio of the cell resistance to the input power to the heater (main/measurement)" in Example 1 is "250". That is, in the gas sensor according to Example 1, the slope of the cell resistance of the main pump cell 21 (the slope of the cell resistance with respect to the input power to the heater 70) is 1.5 times to 1000 times the slope of the cell resistance of the measurement pump cell 41. double the value. The "offset fluctuation evaluation 1" and the "offset fluctuation evaluation 2" of the gas sensor according to Example 1 were both the highest evaluation "A".

(About Example 2)
The electrode area of the main pump cell 21 of Example 2 is "1.0", and the electrode area of the measurement pump cell 41 is "12.0". In other words, in Example 2, the electrode area of the measurement pump cell 41 (the area of the measurement electrode 44) is larger than the electrode area of the main pump cell 21 (the area of the inner pump electrode 22), satisfying Condition 1. The thickness of the electrode of the main pump cell 21 of Example 2 is "15", and the thickness of the electrode of the measurement pump cell 41 is "15". That is, in Example 2, the thickness of the electrode of the measuring pump cell 41 (thickness of the measuring electrode 44) is equal to the thickness of the electrode of the main pump cell 21 (thickness of the inner pump electrode 22), and Condition 2 is not satisfied. The porosity of the electrode of the main pump cell 21 of Example 2 is "20", and the porosity of the electrode of the measurement pump cell 41 is "10". That is, in Example 2, the electrode porosity of the measurement pump cell 41 (the porosity of the measurement electrode 44) is lower than the porosity of the electrode of the main pump cell 21 (the porosity of the inner pump electrode 22). meet. The Au content of the electrode of the main pump cell 21 of Example 2 is "0.5", and the Au content of the electrode of the measurement pump cell 41 is "0.0". That is, in Example 2, the Au content of the electrode of the measuring pump cell 41 (the Au content of the measuring electrode 44) is the same as the Au content of the electrode of the main pump cell 21 (the Au content of the inner pump electrode 22). ) and satisfies condition 5. The inter-electrode distance of the main pump cell 21 of Example 2 is "0.2", and the inter-electrode distance of the measurement pump cell 41 is "0.2". That is, in Example 2, the inter-electrode distance of the measuring pump cell 41 (the distance between the measuring electrode 44 and the outer pump electrode 23) is the same as the inter-electrode distance of the main pump cell 21 (the inner pump electrode 22 and the outer pump electrode 23). ), which does not satisfy condition 6. The ratio of noble metal to zirconia in the electrode of the main pump cell 21 of Example 2 is "85:15", and the ratio of noble metal to zirconia in the electrode of the measuring pump cell 41 is "85:15". That is, in Example 2, the ratio of noble metal to zirconia in the electrode of the measuring pump cell 41 (ratio of noble metal to zirconia in the measuring electrode 44) is the same as the ratio of noble metal to zirconia in the electrode of the main pump cell 21 (zirconia in the inner pump electrode 22). ratio of precious metals to ) and does not satisfy condition 4.

Therefore, in Example 2, among conditions 1 to 6, conditions 2, 4, and 6 are not satisfied, but conditions 1, 3, and 5 are satisfied. The "slope ratio of the cell resistance to the input power to the heater (main/measurement)" in Example 2 is "30". That is, in the gas sensor according to the second embodiment, the slope of the cell resistance of the main pump cell 21 (the slope of the cell resistance with respect to the input power to the heater 70) is 1.5 times to 1000 times the slope of the cell resistance of the measurement pump cell 41. double the value. The "offset fluctuation evaluation 1" and the "offset fluctuation evaluation 2" of the gas sensor according to Example 2 were both the highest evaluation "A".

(About Example 3)
The electrode area of the main pump cell 21 of Example 3 is "5.0", and the electrode area of the measurement pump cell 41 is "5.0". That is, in Example 3, the electrode area of the measuring pump cell 41 (the area of the measuring electrode 44) is equal to the electrode area of the main pump cell 21 (the area of the inner pump electrode 22), which does not satisfy Condition 1. The thickness of the electrode of the main pump cell 21 of Example 3 is "15", and the thickness of the electrode of the measurement pump cell 41 is "15". That is, in Example 3, the thickness of the electrode of the measuring pump cell 41 (thickness of the measuring electrode 44) is equal to the thickness of the electrode of the main pump cell 21 (thickness of the inner pump electrode 22), and Condition 2 is not satisfied. The porosity of the electrode of the main pump cell 21 of Example 3 is "15", and the porosity of the electrode of the measurement pump cell 41 is "15". That is, in Example 3, the electrode porosity of the measurement pump cell 41 (the porosity of the measurement electrode 44) is equal to the electrode porosity of the main pump cell 21 (the porosity of the inner pump electrode 22), satisfying Condition 3. not The Au content of the electrode of the main pump cell 21 of Example 3 is "1.0", and the Au content of the electrode of the measurement pump cell 41 is "0.0". That is, in Example 3, the Au content of the electrode of the measuring pump cell 41 (the Au content of the measuring electrode 44) is the Au content of the electrode of the main pump cell 21 (the Au content of the inner pump electrode 22 ) and satisfies condition 5. The inter-electrode distance of the main pump cell 21 of Example 3 is "0.2", and the inter-electrode distance of the measurement pump cell 41 is "0.2". That is, in Example 3, the inter-electrode distance of the measuring pump cell 41 (the distance between the measuring electrode 44 and the outer pump electrode 23) is the same as the inter-electrode distance of the main pump cell 21 (the inner pump electrode 22 and the outer pump electrode 23). ), which does not satisfy condition 6. The ratio of noble metal to zirconia in the electrode of the main pump cell 21 of Example 3 is "85:15", and the ratio of noble metal to zirconia in the electrode of the measuring pump cell 41 is "85:15". That is, in Example 3, the ratio of noble metal to zirconia in the electrode of the pump cell 41 for measurement (the ratio of noble metal to zirconia in the measurement electrode 44) was the ratio of the noble metal to zirconia in the electrode of the main pump cell 21 (the zirconia ratio of precious metals to ) and does not satisfy condition 4.

Therefore, in Example 3, among the above conditions 1 to 6, conditions 1, 2, 3, 4, and 6 are not satisfied, but condition 5 is satisfied. The "slope ratio of the cell resistance to the input power to the heater (main/measurement)" in Example 3 is "2". That is, in the gas sensor according to Example 3, the slope of the cell resistance of the main pump cell 21 (the slope of the cell resistance with respect to the input power to the heater 70) is 1.5 times to 1000 times the slope of the cell resistance of the measurement pump cell 41. double the value. The "offset fluctuation evaluation 1" and the "offset fluctuation evaluation 2" of the gas sensor according to Example 3 were both the highest evaluation "A".

(About Example 4)
The electrode area of the main pump cell 21 of Example 4 is "5.0", and the electrode area of the measurement pump cell 41 is "12.0". In other words, in Example 4, the electrode area of the measurement pump cell 41 (the area of the measurement electrode 44) is larger than the electrode area of the main pump cell 21 (the area of the inner pump electrode 22), satisfying Condition 1. The thickness of the electrode of the main pump cell 21 of Example 4 is "15", and the thickness of the electrode of the measurement pump cell 41 is "15". That is, in Example 4, the electrode thickness of the measuring pump cell 41 (thickness of the measuring electrode 44) is equal to the electrode thickness of the main pump cell 21 (thickness of the inner pump electrode 22), which does not satisfy Condition 2. The porosity of the electrode of the main pump cell 21 of Example 4 is "20", and the porosity of the electrode of the measurement pump cell 41 is "20". That is, in Example 4, the electrode porosity of the measurement pump cell 41 (the porosity of the measurement electrode 44) is equal to the electrode porosity of the main pump cell 21 (the porosity of the inner pump electrode 22), satisfying Condition 3. not The Au content of the electrode of the main pump cell 21 of Example 4 is "0.0", and the Au content of the electrode of the measurement pump cell 41 is "0.0". That is, in Example 4, the Au content of the electrode of the measuring pump cell 41 (the Au content of the measuring electrode 44) is the Au content of the electrode of the main pump cell 21 (the Au content of the inner pump electrode 22 ) and does not satisfy condition 5. The inter-electrode distance of the main pump cell 21 of Example 4 is "0.2", and the inter-electrode distance of the measurement pump cell 41 is "0.2". That is, in Example 4, the inter-electrode distance of the measuring pump cell 41 (the distance between the measuring electrode 44 and the outer pump electrode 23) is the same as the inter-electrode distance of the main pump cell 21 (the inner pump electrode 22 and the outer pump electrode 23). ), which does not satisfy condition 6. The ratio of noble metal to zirconia in the electrode of the main pump cell 21 of Example 4 is "85:15", and the ratio of noble metal to zirconia in the electrode of the measuring pump cell 41 is "85:15". That is, in Example 4, the ratio of noble metal to zirconia in the electrode of the measuring pump cell 41 (the ratio of noble metal to zirconia in the measuring electrode 44) was the ratio of the noble metal to zirconia in the electrode of the main pump cell 21 (the zirconia ratio of precious metals to ) and does not satisfy condition 4.

Therefore, in Example 4, among the above conditions 1 to 6, conditions 2, 3, 4, 5, and 6 are not satisfied, but condition 1 is satisfied. The "slope ratio of the cell resistance to the input power to the heater (main/measurement)" in Example 4 is "2". That is, in the gas sensor according to Example 4, the slope of the cell resistance of the main pump cell 21 (the slope of the cell resistance with respect to the input power to the heater 70) is 1.5 times to 1000 times the slope of the cell resistance of the measurement pump cell 41. double the value. The "offset fluctuation evaluation 1" and the "offset fluctuation evaluation 2" of the gas sensor according to Example 4 were both the highest evaluation "A".

(About Example 5)
The electrode area of the main pump cell 21 of Example 5 is "10.0", and the electrode area of the measurement pump cell 41 is "10.0". That is, in Example 5, the electrode area of the measurement pump cell 41 (the area of the measurement electrode 44) is equal to the electrode area of the main pump cell 21 (the area of the inner pump electrode 22), and Condition 1 is not satisfied. The thickness of the electrode of the main pump cell 21 of Example 5 is "10", and the thickness of the electrode of the measurement pump cell 41 is "25". That is, in Example 5, the thickness of the electrode of the measuring pump cell 41 (thickness of the measuring electrode 44) is thicker than the thickness of the electrode of the main pump cell 21 (thickness of the inner pump electrode 22), satisfying Condition 2. The porosity of the electrode of the main pump cell 21 of Example 5 is "20", and the porosity of the electrode of the measurement pump cell 41 is "20". That is, in Example 5, the electrode porosity of the measurement pump cell 41 (the porosity of the measurement electrode 44) is equal to the electrode porosity of the main pump cell 21 (the porosity of the inner pump electrode 22), satisfying Condition 3. not The Au content of the electrode of the main pump cell 21 of Example 5 is "0.0", and the Au content of the electrode of the measurement pump cell 41 is "0.0". That is, in Example 5, the Au content of the electrode of the measuring pump cell 41 (the Au content of the measuring electrode 44) is equal to the Au content of the electrode of the main pump cell 21 (the Au content of the inner pump electrode 22) ) and does not satisfy condition 5. The inter-electrode distance of the main pump cell 21 of Example 5 is "0.2", and the inter-electrode distance of the measurement pump cell 41 is "0.2". That is, in Example 5, the inter-electrode distance of the measuring pump cell 41 (the distance between the measuring electrode 44 and the outer pump electrode 23) is the same as the inter-electrode distance of the main pump cell 21 (the inner pump electrode 22 and the outer pump electrode 23). ), which does not satisfy condition 6. The ratio of noble metal to zirconia in the electrodes of the main pump cell 21 of Example 5 is "85:15", and the ratio of noble metal to zirconia in the electrodes of the measuring pump cell 41 is "85:15". That is, in Example 5, the ratio of noble metal to zirconia in the electrode of the measuring pump cell 41 (the ratio of noble metal to zirconia in the measuring electrode 44) was the ratio of the noble metal to zirconia in the electrode of the main pump cell 21 (the zirconia ratio of precious metals to ) and does not satisfy condition 4.

Therefore, in Example 5, among conditions 1 to 6, conditions 1, 3, 4, 5, and 6 are not satisfied, but condition 2 is satisfied. The "ratio of the slope of the cell resistance to the input power to the heater (main/measurement)" in Example 5 is "1.5". That is, in the gas sensor according to Example 5, the slope of the cell resistance of the main pump cell 21 (the slope of the cell resistance with respect to the input power to the heater 70) is 1.5 times to 1000 times the slope of the cell resistance of the measurement pump cell 41. double the value. The "offset fluctuation evaluation 1" and the "offset fluctuation evaluation 2" of the gas sensor according to Example 5 were both the highest evaluation "A".

(About Example 6)
The electrode area of the main pump cell 21 of Example 6 is "10.0", and the electrode area of the measurement pump cell 41 is "10.0". In other words, in Example 6, the electrode area of the measurement pump cell 41 (the area of the measurement electrode 44) is equal to the electrode area of the main pump cell 21 (the area of the inner pump electrode 22), and Condition 1 is not satisfied. The thickness of the electrode of the main pump cell 21 of Example 6 is "15", and the thickness of the electrode of the measurement pump cell 41 is "15". That is, in Example 6, the electrode thickness of the measuring pump cell 41 (thickness of the measuring electrode 44) is equal to the electrode thickness of the main pump cell 21 (thickness of the inner pump electrode 22), which does not satisfy Condition 2. The porosity of the electrode of the main pump cell 21 of Example 6 is "15", and the porosity of the electrode of the measurement pump cell 41 is "15". That is, in Example 6, the electrode porosity of the measurement pump cell 41 (the porosity of the measurement electrode 44) is equal to the electrode porosity of the main pump cell 21 (the porosity of the inner pump electrode 22), satisfying Condition 3. not The Au content of the electrode of the main pump cell 21 of Example 6 is "0.0", and the Au content of the electrode of the measurement pump cell 41 is "0.0". That is, in Example 6, the Au content of the electrode of the measuring pump cell 41 (the Au content of the measuring electrode 44) is the Au content of the electrode of the main pump cell 21 (the Au content of the inner pump electrode 22 ) and does not satisfy condition 5. The inter-electrode distance of the main pump cell 21 of Example 6 is "0.4", and the inter-electrode distance of the measurement pump cell 41 is "0.2". That is, in Example 6, the inter-electrode distance of the measuring pump cell 41 (the distance between the measuring electrode 44 and the outer pump electrode 23) is the same as the inter-electrode distance of the main pump cell 21 (the inner pump electrode 22 and the outer pump electrode 23). , and satisfies condition 6. The ratio of noble metal to zirconia in the electrode of the main pump cell 21 of Example 6 is "85:15", and the ratio of noble metal to zirconia in the electrode of the measuring pump cell 41 is "85:15". That is, in Example 6, the ratio of noble metal to zirconia in the electrode of the measuring pump cell 41 (ratio of noble metal to zirconia in the measuring electrode 44) was the ratio of noble metal to zirconia in the electrode of the main pump cell 21 (zirconia in the inner pump electrode 22). ratio of precious metals to ) and does not satisfy condition 4.

Therefore, in Example 6, among the conditions 1 to 6, conditions 1, 2, 3, 4, and 5 are not satisfied, but condition 6 is satisfied. The "slope ratio of cell resistance to input power to heater (main/measurement)" in Example 6 is "1.8". That is, in the gas sensor according to Example 6, the slope of the cell resistance of the main pump cell 21 (the slope of the cell resistance with respect to the input power to the heater 70) is 1.5 times to 1000 times the slope of the cell resistance of the measurement pump cell 41. double the value. The "offset fluctuation evaluation 1" and the "offset fluctuation evaluation 2" of the gas sensor according to Example 6 were both the highest evaluation "A".

(About Example 7)
The electrode area of the main pump cell 21 of Example 7 is "10.0", and the electrode area of the measurement pump cell 41 is "10.0". In other words, in Example 7, the electrode area of the measurement pump cell 41 (the area of the measurement electrode 44) is equal to the electrode area of the main pump cell 21 (the area of the inner pump electrode 22), and Condition 1 is not satisfied. The thickness of the electrode of the main pump cell 21 of Example 7 is "15", and the thickness of the electrode of the measurement pump cell 41 is "15". That is, in Example 7, the electrode thickness of the measuring pump cell 41 (thickness of the measuring electrode 44) is equal to the electrode thickness of the main pump cell 21 (thickness of the inner pump electrode 22), which does not satisfy Condition 2. The porosity of the electrode of the main pump cell 21 of Example 7 is "15", and the porosity of the electrode of the measurement pump cell 41 is "15". That is, in Example 7, the electrode porosity of the measurement pump cell 41 (the porosity of the measurement electrode 44) is equal to the electrode porosity of the main pump cell 21 (the porosity of the inner pump electrode 22), satisfying Condition 3. not The Au content of the electrode of the main pump cell 21 of Example 7 is "0.0", and the Au content of the electrode of the measurement pump cell 41 is "0.0". That is, in Example 7, the Au content of the electrode of the measuring pump cell 41 (the Au content of the measuring electrode 44) is the Au content of the electrode of the main pump cell 21 (the Au content of the inner pump electrode 22) ) and does not satisfy condition 5. The inter-electrode distance of the main pump cell 21 of Example 7 is "0.2", and the inter-electrode distance of the measurement pump cell 41 is "0.2". That is, in Example 7, the inter-electrode distance of the measuring pump cell 41 (the distance between the measuring electrode 44 and the outer pump electrode 23) is the same as the inter-electrode distance of the main pump cell 21 (the inner pump electrode 22 and the outer pump electrode 23). ), which does not satisfy condition 6. The ratio of noble metal to zirconia in the electrode of the main pump cell 21 of Example 7 is "70:30", and the ratio of noble metal to zirconia in the electrode of the measuring pump cell 41 is "85:15". That is, in Example 7, the ratio of noble metal to zirconia in the electrode of the measuring pump cell 41 (the ratio of noble metal to zirconia in the measuring electrode 44) was the ratio of the noble metal to zirconia in the electrode of the main pump cell 21 (the zirconia ratio of precious metals to), and satisfies condition 4.

Therefore, in Example 7, among the conditions 1 to 6, conditions 1, 2, 3, 5, and 6 are not satisfied, but condition 4 is satisfied. Then, the "ratio of the slope of the cell resistance to the input power to the heater (main/measurement)" in Example 7 is "2.5". That is, in the gas sensor according to Example 7, the slope of the cell resistance of the main pump cell 21 (the slope of the cell resistance with respect to the input power to the heater 70) is 1.5 times to 1000 times the slope of the cell resistance of the measurement pump cell 41. double the value. The "offset fluctuation evaluation 1" and the "offset fluctuation evaluation 2" of the gas sensor according to Example 7 were both the highest evaluation "A".

(About Example 8)
The electrode area of the main pump cell 21 of Example 8 is "10.0", and the electrode area of the measurement pump cell 41 is "10.0". That is, in Example 8, the electrode area of the measuring pump cell 41 (the area of the measuring electrode 44) is equal to the electrode area of the main pump cell 21 (the area of the inner pump electrode 22), and Condition 1 is not satisfied. The thickness of the electrode of the main pump cell 21 of Example 8 is "15", and the thickness of the electrode of the measurement pump cell 41 is "15". That is, in Example 8, the thickness of the electrode of the measuring pump cell 41 (thickness of the measuring electrode 44) is equal to the thickness of the electrode of the main pump cell 21 (thickness of the inner pump electrode 22), and Condition 2 is not satisfied. The porosity of the electrode of the main pump cell 21 of Example 8 is "50", and the porosity of the electrode of the measurement pump cell 41 is "10". That is, in Example 8, the electrode porosity of the measurement pump cell 41 (the porosity of the measurement electrode 44) is lower than the porosity of the electrode of the main pump cell 21 (the porosity of the inner pump electrode 22). meet. The Au content of the electrode of the main pump cell 21 of Example 8 is "0.0", and the Au content of the electrode of the measurement pump cell 41 is "0.0". That is, in Example 8, the Au content of the electrode of the measuring pump cell 41 (the Au content of the measuring electrode 44) is the Au content of the electrode of the main pump cell 21 (the Au content of the inner pump electrode 22) ) and does not satisfy condition 5. The inter-electrode distance of the main pump cell 21 of Example 8 is "0.2", and the inter-electrode distance of the measurement pump cell 41 is "0.2". That is, in Example 8, the inter-electrode distance of the measuring pump cell 41 (the distance between the measuring electrode 44 and the outer pump electrode 23) is the same as the inter-electrode distance of the main pump cell 21 (the inner pump electrode 22 and the outer pump electrode 23). ), which does not satisfy condition 6. The ratio of noble metal to zirconia in the electrode of the main pump cell 21 of Example 8 is "85:15", and the ratio of noble metal to zirconia in the electrode of the measuring pump cell 41 is "85:15". That is, in Example 8, the ratio of noble metal to zirconia in the electrode of the measuring pump cell 41 (the ratio of noble metal to zirconia in the measuring electrode 44) was the ratio of the noble metal to zirconia in the electrode of the main pump cell 21 (the zirconia ratio of precious metals to ) and does not satisfy condition 4.

Therefore, in Example 8, among the conditions 1 to 6, conditions 1, 2, 4, 5, and 6 are not satisfied, but condition 3 is satisfied. Then, the "ratio of the slope of the cell resistance to the input power to the heater (main/measurement)" in Example 8 is "1.8". That is, in the gas sensor according to Example 8, the slope of the cell resistance of the main pump cell 21 (the slope of the cell resistance with respect to the input power to the heater 70) is 1.5 times to 1000 times the slope of the cell resistance of the measurement pump cell 41. double the value. The "offset fluctuation evaluation 1" and the "offset fluctuation evaluation 2" of the gas sensor according to Example 8 were both the highest evaluation "A".

(About Example 9)
The electrode area of the main pump cell 21 of Example 9 is "7.5", and the electrode area of the measurement pump cell 41 is "10.0". That is, in Example 9, the electrode area of the measurement pump cell 41 (the area of the measurement electrode 44) is larger than the electrode area of the main pump cell 21 (the area of the inner pump electrode 22), satisfying Condition 1. The thickness of the electrode of the main pump cell 21 of Example 9 is "15", and the thickness of the electrode of the measurement pump cell 41 is "40". That is, in Example 9, the electrode thickness of the measuring pump cell 41 (thickness of the measuring electrode 44) is thicker than the electrode thickness of the main pump cell 21 (thickness of the inner pump electrode 22), satisfying condition 2. The porosity of the electrode of the main pump cell 21 of Example 9 is "15", and the porosity of the electrode of the measurement pump cell 41 is "5". That is, in Example 9, the electrode porosity of the measurement pump cell 41 (the porosity of the measurement electrode 44) is lower than the porosity of the electrode of the main pump cell 21 (the porosity of the inner pump electrode 22). meet. The Au content of the electrode of the main pump cell 21 of Example 9 is "1.0", and the Au content of the electrode of the measurement pump cell 41 is "0.0". That is, in Example 9, the Au content of the electrode of the measuring pump cell 41 (the Au content of the measuring electrode 44) is the Au content of the main pump cell 21 electrode (the Au content of the inner pump electrode 22). ) and satisfies condition 5. The inter-electrode distance of the main pump cell 21 of Example 9 is "0.4", and the inter-electrode distance of the measurement pump cell 41 is "0.2". That is, in Example 9, the inter-electrode distance of the measuring pump cell 41 (the distance between the measuring electrode 44 and the outer pump electrode 23) is the same as the inter-electrode distance of the main pump cell 21 (the inner pump electrode 22 and the outer pump electrode 23). , and satisfies condition 6. The ratio of noble metal to zirconia in the electrode of the main pump cell 21 of Example 9 is "85:15", and the ratio of noble metal to zirconia in the electrode of the measuring pump cell 41 is "85:15". That is, in Example 9, the ratio of noble metal to zirconia in the electrode of the measuring pump cell 41 (ratio of noble metal to zirconia in the measuring electrode 44) was the ratio of noble metal to zirconia in the electrode of the main pump cell 21 (zirconia in the inner pump electrode 22). ratio of precious metals to ) and does not satisfy condition 4.

Therefore, in the ninth embodiment, out of the conditions 1 to 6, the condition 4 is not satisfied, but the conditions 1, 2, 3, 5 and 6 are satisfied. The "ratio of the slope of the cell resistance to the input power to the heater (main/measurement)" in Example 9 is "10". That is, in the gas sensor according to Example 9, the slope of the cell resistance of the main pump cell 21 (the slope of the cell resistance with respect to the input power to the heater 70) is 1.5 times to 1000 times the slope of the cell resistance of the measurement pump cell 41. double the value. The gas sensor according to the ninth embodiment was rated "A", the highest score, for both "offset variation evaluation 1" and "offset variation evaluation 2".

(About Example 10)
The electrode area (“main” of “area”) of the main pump cell 21 of Example 10 is “1.5”, and the electrode area of the measurement pump cell 41 (“measurement” of “area”) is “7 .5”. That is, in Example 10, the electrode area of the measurement pump cell 41 (the area of the measurement electrode 44) is larger than the electrode area of the main pump cell 21 (the area of the inner pump electrode 22), satisfying Condition 1. The thickness of the electrode of the main pump cell 21 of Example 10 (“main” in “thickness”) is “15”, and the thickness of the electrode of the measurement pump cell 41 (“measurement” in “thickness”) is “25”. ”. That is, in Example 10, the thickness of the electrode of the measuring pump cell 41 (thickness of the measuring electrode 44) is thicker than the thickness of the electrode of the main pump cell 21 (thickness of the inner pump electrode 22), satisfying Condition 2. The porosity of the electrode of the main pump cell 21 of Example 10 (“main” in “porosity”) is “10”, and the porosity of the electrode of the measurement pump cell 41 (“measurement” in “porosity”) is “10”. is "5". That is, in Example 10, the electrode porosity of the measurement pump cell 41 (the porosity of the measurement electrode 44) is lower than the porosity of the electrode of the main pump cell 21 (the porosity of the inner pump electrode 22). meet. The Au content of the electrode of the main pump cell 21 of Example 10 (“main” in “Au content”) is “1.0”, and the Au content of the electrode of the measurement pump cell 41 (“Au "For measurement") of "content rate of" is "0.0". That is, in Example 10, the Au content of the electrode of the measuring pump cell 41 (Au content of the measuring electrode 44) ) and satisfies condition 5. The inter-electrode distance of the main pump cell 21 of Example 10 (“main” in “inter-electrode distance”) is “0.4”, and the inter-electrode distance of the measuring pump cell 41 (“inter-electrode distance” is “measuring ”) is “0.2”. That is, in Example 10, the inter-electrode distance of the measuring pump cell 41 (the distance between the measuring electrode 44 and the outer pump electrode 23) is the same as the inter-electrode distance of the main pump cell 21 (the inner pump electrode 22 and the outer pump electrode 23). , and satisfies condition 6. The ratio between the noble metal and zirconia in the electrode of the main pump cell 21 of Example 10 (“main” in the “noble metal/zirconia ratio”) was “70:30”, and the ratio between the noble metal and zirconia in the electrode of the measuring pump cell 41 was “70:30”. The ratio (“measurement” of “noble metal/zirconia ratio”) is “85:15”. That is, in Example 10, the ratio of noble metal to zirconia in the electrode of the measuring pump cell 41 (the ratio of noble metal to zirconia in the measuring electrode 44) was the ratio of the noble metal to zirconia in the electrode of the main pump cell 21 (the zirconia ratio of precious metals to), and satisfies condition 4.

Therefore, in the tenth embodiment, all of the conditions 1 to 6 described above are satisfied. The "slope ratio of the cell resistance to the input power to the heater (main/measurement)" in Example 10 is "1000". That is, in the gas sensor according to the tenth embodiment, the slope of the cell resistance of the main pump cell 21 (the slope of the cell resistance with respect to the input power to the heater 70) is 1.5 times to 1000 times the slope of the cell resistance of the measurement pump cell 41. double the value. The "offset fluctuation evaluation 1" and the "offset fluctuation evaluation 2" of the gas sensor according to Example 10 were both the highest evaluation "A".

(About Example 11)
The electrode area (“main” in “area”) of the main pump cell 21 of Example 11 is “6.0”, and the electrode area (“measurement” in “area”) of the measurement pump cell 41 is “5.0”. .0”. In other words, in Example 11, the electrode area of the measurement pump cell 41 (the area of the measurement electrode 44) is smaller than the electrode area of the main pump cell 21 (the area of the inner pump electrode 22), and Condition 1 is not satisfied. The thickness of the electrode of the main pump cell 21 of Example 11 (“main” of “thickness”) is “10”, and the thickness of the electrode of the measurement pump cell 41 (“measurement” of “thickness”) is “20”. ”. That is, in Example 11, the thickness of the electrode of the measuring pump cell 41 (thickness of the measuring electrode 44) is thicker than the thickness of the electrode of the main pump cell 21 (thickness of the inner pump electrode 22), satisfying Condition 2. The porosity of the electrode of the main pump cell 21 of Example 11 (“main” of “porosity”) is “20”, and the porosity of the electrode of the measurement pump cell 41 (“measurement” of “porosity”) is is "20". That is, in Example 11, the electrode porosity of the measurement pump cell 41 (the porosity of the measurement electrode 44) is equal to the electrode porosity of the main pump cell 21 (the porosity of the inner pump electrode 22), satisfying Condition 3. not The Au content of the electrode of the main pump cell 21 of Example 11 (“main” in “Au content”) is “0.0”, and the Au content of the electrode of the measurement pump cell 41 (“Au "For measurement") of "content rate of" is "0.0". That is, in Example 11, the Au content of the electrode of the measuring pump cell 41 (the Au content of the measuring electrode 44) was the Au content of the electrode of the main pump cell 21 (the Au content of the inner pump electrode 22) ) and does not satisfy condition 5. The inter-electrode distance of the main pump cell 21 of Example 11 (“main” in “inter-electrode distance”) is “0.2”, and the inter-electrode distance of the measurement pump cell 41 (“inter-electrode distance” is “measuring ”) is “0.2”. That is, in Example 11, the inter-electrode distance of the measuring pump cell 41 (the distance between the measuring electrode 44 and the outer pump electrode 23) is the same as the inter-electrode distance of the main pump cell 21 (the inner pump electrode 22 and the outer pump electrode 23). ), which does not satisfy condition 6. The ratio between the noble metal and zirconia in the electrode of the main pump cell 21 of Example 11 (“main” in the “noble metal/zirconia ratio”) was “85:15”, and the ratio between the noble metal and zirconia in the electrode of the measuring pump cell 41 was “85:15”. The ratio (“measurement” of “noble metal/zirconia ratio”) is “85:15”. That is, in Example 11, the ratio of noble metal to zirconia in the electrode of the measuring pump cell 41 (the ratio of noble metal to zirconia in the measuring electrode 44) was the ratio of the noble metal to zirconia in the electrode of the main pump cell 21 (the zirconia in the inner pump electrode 22). ratio of precious metals to ) and does not satisfy condition 4.

Therefore, in the eleventh embodiment, among the conditions 1 to 6, the condition 2 is satisfied, but the conditions 1, 3, 4, 5 and 6 are not satisfied. The "slope ratio of the cell resistance to the input power to the heater (main/measurement)" in Example 11 is "1.2". That is, in the gas sensor according to Example 11, the slope of the cell resistance of the main pump cell 21 (the slope of the cell resistance with respect to the input power to the heater 70) is 1.5 times to 1000 times the slope of the cell resistance of the measurement pump cell 41. not doubled. However, in Example 11, the slope of the cell resistance of the adjustment pump cell (main pump cell 21 ) is greater than the slope of the cell resistance of the measurement pump cell 41 . The "offset fluctuation evaluation 1" and the "offset fluctuation evaluation 2" of the gas sensor according to Example 11 were both "B", although they were lower than the highest evaluation "A".

(About Example 12)
The electrode area (“main” of “area”) of the main pump cell 21 of Example 12 is “1.0”, and the electrode area of the measurement pump cell 41 (“measurement” of “area”) is “10”. .0”. In other words, in Example 12, the electrode area of the measurement pump cell 41 (the area of the measurement electrode 44) is larger than the electrode area of the main pump cell 21 (the area of the inner pump electrode 22), satisfying Condition 1. The thickness of the electrode of the main pump cell 21 of Example 12 (“main” in “thickness”) is “15”, and the thickness of the electrode of the measurement pump cell 41 (“measurement” in “thickness”) is “25”. ”. That is, in Example 12, the thickness of the electrode of the measuring pump cell 41 (thickness of the measuring electrode 44) is thicker than the thickness of the electrode of the main pump cell 21 (thickness of the inner pump electrode 22), satisfying Condition 2. The porosity of the electrode of the main pump cell 21 of Example 12 (“main” in “porosity”) is “10”, and the porosity of the electrode of the measurement pump cell 41 (“measurement” in “porosity”) is “10”. is "5". That is, in Example 12, the electrode porosity of the measurement pump cell 41 (the porosity of the measurement electrode 44) is lower than the porosity of the electrode of the main pump cell 21 (the porosity of the inner pump electrode 22). meet. The Au content of the electrode of the main pump cell 21 of Example 12 (“main” in “Au content”) is “1.0”, and the Au content of the electrode of the measurement pump cell 41 (“Au "For measurement") of "content rate of" is "0.0". That is, in Example 12, the Au content of the electrode of the measuring pump cell 41 (the Au content of the measuring electrode 44) is the Au content of the electrode of the main pump cell 21 (the Au content of the inner pump electrode 22) ) and satisfies condition 5. The inter-electrode distance of the main pump cell 21 of Example 12 (“main” in “inter-electrode distance”) is “0.4”, and the inter-electrode distance of the measuring pump cell 41 (“inter-electrode distance” is “measuring ”) is “0.2”. That is, in Example 12, the inter-electrode distance of the measuring pump cell 41 (the distance between the measuring electrode 44 and the outer pump electrode 23) is the same as the inter-electrode distance of the main pump cell 21 (the inner pump electrode 22 and the outer pump electrode 23). , and satisfies condition 6. The ratio of the noble metal to zirconia in the electrode of the main pump cell 21 of Example 12 (“main” in the “noble metal/zirconia ratio”) was “70:30”, and the ratio of the noble metal to zirconia in the electrode of the measurement pump cell 41 was “70:30”. The ratio (“measurement” of “noble metal/zirconia ratio”) is “85:15”. That is, in Example 12, the ratio of noble metal to zirconia in the electrode of the measuring pump cell 41 (the ratio of noble metal to zirconia in the measuring electrode 44) was the ratio of the noble metal to zirconia in the electrode of the main pump cell 21 (the zirconia in the inner pump electrode 22). ratio of precious metals to), and satisfies condition 4.

Therefore, in Example 12, all of the above conditions 1 to 6 are satisfied. However, the "ratio of the slope of the cell resistance to the input power to the heater (main/measurement)" in Example 12 is "2000". That is, in the gas sensor according to the twelfth embodiment, the slope of the cell resistance of the main pump cell 21 (the slope of the cell resistance with respect to the input power to the heater 70) is 1.5 times to 1000 times the slope of the cell resistance of the measurement pump cell 41. not doubled. However, in Example 12, the slope of the cell resistance of the adjustment pump cell (main pump cell 21 ) is greater than the slope of the cell resistance of the measurement pump cell 41 . The "offset fluctuation evaluation 1" and the "offset fluctuation evaluation 2" of the gas sensor according to Example 12 were both "B", although they were lower than the highest evaluation "A".

(Regarding Comparative Example 1)
The electrode area (“main” of “area”) of the main pump cell 21 of Comparative Example 1 is “12.0”, and the electrode area (“measurement” of “area”) of the measurement pump cell 41 is “1 .0”. That is, in Comparative Example 1, the electrode area of the measurement pump cell 41 (the area of the measurement electrode 44) is smaller than the electrode area of the main pump cell 21 (the area of the inner pump electrode 22), and Condition 1 is not satisfied. The thickness of the electrode of the main pump cell 21 of Comparative Example 1 (“main” in “thickness”) is “15”, and the thickness of the electrode of the measurement pump cell 41 (“measurement” in “thickness”) is “15”. ”. That is, in Comparative Example 1, the electrode thickness of the measuring pump cell 41 (thickness of the measuring electrode 44) is equal to the electrode thickness of the main pump cell 21 (thickness of the inner pump electrode 22), and Condition 2 is not satisfied. The porosity of the electrode of the main pump cell 21 of Comparative Example 1 (“main” in “porosity”) is “10”, and the porosity of the electrode of the measurement pump cell 41 (“measurement” in “porosity”) is “10”. is "20". That is, in Comparative Example 1, the electrode porosity of the measurement pump cell 41 (the porosity of the measurement electrode 44) is higher than the porosity of the electrode of the main pump cell 21 (the porosity of the inner pump electrode 22). not filled. The Au content of the electrode of the main pump cell 21 of Comparative Example 1 (“main” in “Au content”) is “0.5”, and the Au content of the electrode of the measurement pump cell 41 (“Au The content of "for measurement") is "0.0". That is, in Comparative Example 1, the Au content of the electrode of the measuring pump cell 41 (the Au content of the measuring electrode 44) is equal to the Au content of the electrode of the main pump cell 21 (the Au content of the inner pump electrode 22) ) and satisfies condition 5. The inter-electrode distance of the main pump cell 21 of Comparative Example 1 (“main” in “inter-electrode distance”) is “0.2”, and the inter-electrode distance of the measuring pump cell 41 (“inter-electrode distance” is “measuring ”) is “0.2”. That is, in Comparative Example 1, the inter-electrode distance of the measuring pump cell 41 (the distance between the measuring electrode 44 and the outer pump electrode 23) is the same as the inter-electrode distance of the main pump cell 21 (the inner pump electrode 22 and the outer pump electrode 23). ), which does not satisfy condition 6. The ratio of the noble metal to zirconia in the electrode of the main pump cell 21 of Comparative Example 1 (“main” in the “noble metal/zirconia ratio”) was “85:15”, and the ratio of the noble metal to zirconia in the electrode of the measuring pump cell 41 was “85:15”. The ratio (“measurement” of “noble metal/zirconia ratio”) is “85:15”. That is, in Comparative Example 1, the ratio of noble metal to zirconia in the electrode of the pump cell 41 for measurement (ratio of noble metal to zirconia in the measurement electrode 44) is the ratio of noble metal to zirconia in the electrode of the main pump cell 21 (zirconia ratio of precious metals to ) and does not satisfy condition 4.

Therefore, in Comparative Example 1, among the conditions 1 to 6, the condition 5 is satisfied, but the conditions 1, 2, 3, 4 and 6 are not satisfied. The ratio of the slope of the cell resistance to the input power to the heater (main/measurement) of Comparative Example 1 is 0.002. That is, in the gas sensor according to Comparative Example 1, the slope of the cell resistance of the main pump cell 21 (the slope of the cell resistance with respect to the input power to the heater 70) is 1.5 times to 1000 times the slope of the cell resistance of the measurement pump cell 41. not doubled. Further, in Comparative Example 1, the slope of the cell resistance of the adjustment pump cell (main pump cell 21 ) is smaller than the slope of the cell resistance of the measurement pump cell 41 . Both the "offset fluctuation evaluation 1" and the "offset fluctuation evaluation 2" of the gas sensor according to Comparative Example 1 were the lowest evaluation "F".

(Regarding Comparative Example 2)
The electrode area (“main” of “area”) of the main pump cell 21 of Comparative Example 2 is “5.0”, and the electrode area (“measurement” of “area”) of the measurement pump cell 41 is “5.0”. .0”. That is, in Comparative Example 2, the electrode area of the measurement pump cell 41 (the area of the measurement electrode 44) is equal to the electrode area of the main pump cell 21 (the area of the inner pump electrode 22), and Condition 1 is not satisfied. The thickness of the electrode of the main pump cell 21 of Comparative Example 2 (“main” in “thickness”) is “15”, and the thickness of the electrode of the measurement pump cell 41 (“measurement” in “thickness”) is “15”. ”. That is, in Comparative Example 2, the electrode thickness of the measuring pump cell 41 (thickness of the measuring electrode 44) is equal to the electrode thickness of the main pump cell 21 (thickness of the inner pump electrode 22), and Condition 2 is not satisfied. The porosity of the electrode of the main pump cell 21 of Comparative Example 2 (“main” in “porosity”) is “15”, and the porosity of the electrode of the measurement pump cell 41 (“measurement” in “porosity”) is “15”. is "15". That is, in Comparative Example 2, the electrode porosity of the measurement pump cell 41 (the porosity of the measurement electrode 44) is equal to the electrode porosity of the main pump cell 21 (the porosity of the inner pump electrode 22), satisfying Condition 3. not The Au content of the electrode of the main pump cell 21 of Comparative Example 2 (“main” in “Au content”) is “0.0”, and the Au content of the electrode of the measurement pump cell 41 (“Au The content of "for measurement") is "0.0". That is, in Comparative Example 2, the Au content of the electrode of the measuring pump cell 41 (the Au content of the measuring electrode 44) is the Au content of the electrode of the main pump cell 21 (the Au content of the inner pump electrode 22) ) and does not satisfy condition 5. The inter-electrode distance of the main pump cell 21 of Comparative Example 2 (“main” in “inter-electrode distance”) is “0.2”, and the inter-electrode distance of the measuring pump cell 41 (“inter-electrode distance” is “measuring ”) is “0.2”. That is, in Comparative Example 2, the inter-electrode distance of the measuring pump cell 41 (the distance between the measuring electrode 44 and the outer pump electrode 23) is the same as the inter-electrode distance of the main pump cell 21 (the inner pump electrode 22 and the outer pump electrode 23). ), which does not satisfy condition 6. The ratio of the noble metal to zirconia in the electrode of the main pump cell 21 of Comparative Example 2 (“main” in the “noble metal/zirconia ratio”) was “85:15”, and the ratio of the noble metal to zirconia in the electrode of the measurement pump cell 41 was “85:15”. The ratio (“measurement” of “noble metal/zirconia ratio”) is “85:15”. That is, in Comparative Example 2, the ratio of noble metal to zirconia in the electrode of the pump cell 41 for measurement (the ratio of noble metal to zirconia in the measurement electrode 44) is the ratio of the noble metal to zirconia in the electrode of the main pump cell 21 (the zirconia ratio of precious metals to ) and does not satisfy condition 4.

Therefore, in Comparative Example 2, all of the above conditions 1 to 6 are not satisfied. The "ratio of the slope of the cell resistance to the input power to the heater (main/measurement)" of Comparative Example 2 is "1.0". That is, in the gas sensor according to Comparative Example 2, the slope of the cell resistance of the main pump cell 21 (the slope of the cell resistance with respect to the input power to the heater 70) is 1.5 times to 1000 times the slope of the cell resistance of the measurement pump cell 41. not doubled. In Comparative Example 2, the slope of the cell resistance of the adjustment pump cell (main pump cell 21 ) is equal to the slope of the cell resistance of the measurement pump cell 41 . Both the "offset variation evaluation 1" and the "offset variation evaluation 2" of the gas sensor according to Comparative Example 2 were the lowest evaluation of "F".

As can be seen from the comparison between Example 1-12 and Comparative Example 1-2, the slope of the cell resistance of the adjustment pump cell (the main pump cell 21 in the example of FIG. 6) is greater than the slope of the cell resistance of the measurement pump cell 41. By doing so, the fluctuation of the offset value can be suppressed. That is, by making the slope of the cell resistance of the main pump cell 21 larger than the slope of the cell resistance of the measurement pump cell 41, high-precision concentration measurement under an environment where the concentration of NO _x in the gas to be measured is high, and It is possible to achieve both high-precision concentration measurement under a low environment. Therefore, the gas sensor according to the present embodiment can realize highly accurate concentration measurement both under high concentration and under low concentration. Further, as can be seen from the comparison between Examples 1-10 and 11-12, the slope of the cell resistance of the adjustment pump cell is 1.5 to 1000 times the slope of the cell resistance of the measurement pump cell 41. By setting the value to , the fluctuation of the offset value can be effectively suppressed. Further, as can be seen from Examples 1 to 12 and Comparative Example 2, in order to make the slope of the cell resistance of the adjustment pump cell larger than the slope of the cell resistance of the measurement pump cell 41, condition 1-condition It is useful to configure the conditioning pump cell and the measuring pump cell 41 such that at least one of 6 is satisfied.

(Notes on adjustment pump cells)
In order to make the slope of the cell resistance of the auxiliary pump cell 50 as the adjustment pump cell larger than the slope of the cell resistance of the measurement pump cell 41, the inventors of the present invention have determined that at least one of conditions 1 to 6 must be satisfied. It has also been confirmed that it is useful to configure the auxiliary pump cell 50 and the measuring pump cell 41 in the same manner. When the auxiliary pump cell 50 is used as the adjustment pump cell, condition 1 means that "the area of the measurement electrode 44 is larger than the area of the auxiliary pump electrode 51". Condition 2 means that "the thickness of the measurement electrode 44 is greater than the thickness of the auxiliary pump electrode 51". Condition 3 means that "the porosity of the measurement electrode 44 is lower than that of the auxiliary pump electrode 51". Condition 4 means that "the ratio of noble metal to zirconia in the measurement electrode 44 is higher than the ratio of noble metal to zirconia in the auxiliary pump electrode 51". Condition 5 means that "the content of Au in the measurement electrode 44 is lower than the content of Au in the auxiliary pump electrode 51". Condition 6 is that "the distance between the measurement electrode 44 and the outer pump electrode 23 is smaller (shorter) than the distance between the auxiliary pump electrode 51 and the outer pump electrode 23 (or the third electrode)." means conditions.

S, S1... gas sensor, 100... sensor element, 111... detector,
112... Temperature adjustment part (adjustment part), 1... First substrate layer (solid electrolyte layer),
2... Second substrate layer (solid electrolyte layer), 3... Third substrate layer (solid electrolyte layer),
4... First solid electrolyte layer (solid electrolyte layer), 5... Spacer layer (solid electrolyte layer),
6... Second solid electrolyte layer (solid electrolyte layer), 7... Gas flow part to be measured (internal space),
44... Measuring electrode, 23... Outer pump electrode, 41... Measuring pump cell,
70... heater (heater section), 22... inner pump electrode,
51... Auxiliary pump electrode (inner pump electrode), 21... Main pump cell (adjustment pump cell),
50 Auxiliary pump cell (adjustment pump cell)

Claims (9)

A sensor element formed by laminating a plurality of oxygen ion conductive solid electrolyte layers,
an internal cavity into which the gas to be measured is introduced;
a measurement electrode provided in the internal space, an outer pump electrode provided at a location different from the internal space, and the solid electrolyte layer existing between the measurement electrode and the outer pump electrode; a measuring pump cell, which is an electrochemical pump cell composed of
an inner pump electrode formed facing the inner cavity; a third electrode provided in a manner exposed to the outer space in contact with the outer pump electrode or the solid electrolyte layer; the inner pump electrode; the solid electrolyte layer present between the outer pump electrode or the third electrode; and
a heater unit embedded in the sensor element for heating the sensor element to a predetermined temperature;
a sensor element comprising
a detection unit that detects the value of the cell resistance of the adjustment pump cell;
an adjustment unit that adjusts the predetermined temperature so that the cell resistance value of the adjustment pump cell detected by the detection unit becomes a predetermined value;
with
the slope of the cell resistance of the adjustment pump cell with respect to the input power to the heater section is greater than the slope of the cell resistance of the measurement pump cell with respect to the input power to the heater section;
gas sensor. The slope of the cell resistance of the adjustment pump cell with respect to the input power to the heater section is 1.5 to 1000 times the slope of the cell resistance of the measurement pump cell with respect to the input power to the heater section.
The gas sensor according to claim 1. the area of the measurement electrode is greater than the area of the inner pump electrode;
The gas sensor according to claim 1 or 2. the thickness of the measurement electrode is greater than the thickness of the inner pump electrode;
The gas sensor according to claim 1 or 2. the porosity of the measurement electrode is lower than the porosity of the inner pump electrode;
The gas sensor according to claim 1 or 2. the measuring electrode and the inner pump electrode are cermet electrodes of zirconia and noble metal;
the ratio of noble metal to zirconia in the measurement electrode is higher than the ratio of noble metal to zirconia in the inner pump electrode;
The gas sensor according to claim 1 or 2. the Au content of the measurement electrode is lower than the Au content of the inner pump electrode;
The gas sensor according to claim 1 or 2. the distance between the measuring electrode and the outer pump electrode is less than the distance between the inner pump electrode and the outer pump electrode or the third electrode;
The gas sensor according to claim 1 or 2. A sensor element formed by laminating a plurality of oxygen ion conductive solid electrolyte layers,
an internal cavity into which the gas to be measured is introduced;
a measurement electrode provided in the internal space, an outer pump electrode provided at a location different from the internal space, and the solid electrolyte layer existing between the measurement electrode and the outer pump electrode; a measuring pump cell, which is an electrochemical pump cell composed of
an inner pump electrode formed facing the inner cavity; a third electrode provided in a manner exposed to the outer space in contact with the outer pump electrode or the solid electrolyte layer; the inner pump electrode; the solid electrolyte layer present between the outer pump electrode or the third electrode;
a heater unit embedded in the sensor element for heating the sensor element to a predetermined temperature;
In a control method of a gas sensor comprising a sensor element containing
a detection step of detecting a cell resistance value of the adjustment pump cell;
an adjustment step of adjusting the predetermined temperature so that the cell resistance value of the adjustment pump cell detected in the detection step becomes a predetermined value;
including
The slope of the cell resistance of the adjustment pump cell with respect to the input power to the heater section is greater than the slope of the cell resistance of the measurement pump cell with respect to the input power to the heater section.
Gas sensor control method.