JPH1183796A - Exhaust gas sensor and exhaust gas sensor system using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas sensor which can selectively detect a specific hydrocarbon component and obtain information related to concentrations of different components or component groups separately. SOLUTION: Two elements 3, 4, one functioning as an oxygen concentration cell element and the other functioning as an oxygen pump element, are set to face each other via a gap 15. Electrodes 10-13 of different oxidation catalyst activation differences are arranged at both faces of each element 3, 4. An exhaust gas is introduced to both sides of the element functioning as the oxygen concentration cell element. A difference of oxygen consumption amounts is brought about at both sides of the oxygen concentration cell element due to oxidation (burning) of a component to be detected of the exhaust gas, whereby a concentration cell electromotive force is generated. The element functioning as the oxygen pump element sucks in or out the oxygen to the gap so as to make the concentration cell electromotive force constant. A concentration of the component to be detected in the exhaust gas is detected from a current value of the oxygen pump.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas sensor for detecting a target component contained in exhaust gas and an exhaust gas sensor system using the same.

[0002]

2. Description of the Related Art As a sensor for detecting components to be detected such as hydrocarbons (hereinafter, also referred to as HC), CO, and nitrogen oxides (hereinafter, also referred to as NOX) contained in exhaust gas of automobiles and the like, For example, a resistance type sensor is known. In this method, an oxide semiconductor such as SnO ₂ is used as a detecting element, and the content of the detected component in the exhaust gas is detected based on a change in resistance of the oxide semiconductor accompanying the adsorption of the detected component. .

[0003]

The above-mentioned resistance type exhaust gas sensor has a characteristic that the output of the detection element made of an oxide semiconductor changes depending on the concentration of oxygen contained in the exhaust gas. Therefore, there is a problem that the detected output value varies depending on the oxygen concentration in the exhaust gas even for the same pollutant concentration. Then, for example, Japanese Patent Application Laid-Open No.
As disclosed in U.S. Pat. No. 94 or the like, oxygen is sent into exhaust gas by a pump element using a solid electrolyte to increase the concentration thereof, and the detection accuracy is improved by reducing the relative fluctuation of the oxygen concentration in the gas. A proposal has been made. However, when the concentration of oxygen in the exhaust gas changes significantly, the effect of suppressing the relative concentration fluctuation due to the introduction of oxygen from the pump element becomes insufficient, and there is a disadvantage that satisfactory detection accuracy cannot be obtained.

In addition, in the conventional exhaust gas sensor described above, when detecting the HC concentration, a specific hydrocarbon component (for example, methane) is selectively selected even if information on the total concentration of various hydrocarbons is obtained. Or the concentrations of a plurality of types of components cannot be individually detected.

According to the present invention, even if the oxygen concentration in the exhaust gas changes, the concentration of the detected component can be detected with high accuracy, and when a plurality of types of the detected component are present, a specific hydrocarbon component can be detected. An object of the present invention is to provide an exhaust gas sensor capable of selectively detecting or individually obtaining information on the concentrations of components or component groups different from each other, and an exhaust gas sensor system using the same.

[0006]

Means for Solving the Problems and Action / Effect In order to solve the above-mentioned problems, an exhaust gas sensor according to the present invention is characterized in that it is configured as follows. That is, the exhaust gas sensor is composed of an oxygen ion-conductive solid electrolyte, electrodes are formed on both surfaces, and the first element has different oxidation catalytic activities of the electrodes with respect to a component to be detected in the exhaust gas. Electrodes are formed on both surfaces formed of a solid electrolyte, and are disposed opposite to the first element so as to form a predetermined amount of clearance in which the flow of exhaust gas from the atmosphere to be measured is allowed. The oxidation catalyst activities of the electrodes with respect to the component to be detected were different from each other, and the difference in the oxidation catalyst activities between the electrodes on both surfaces was adjusted to be larger than the difference in the oxidation catalyst activities between the electrodes on both surfaces of the first element. A second element. One of the first element and the second element functions as an oxygen concentration cell element, and the other pumps oxygen into the gap in a direction in which the absolute value of the concentration cell electromotive force generated in the oxygen concentration cell element decreases. A first mode in which the first element becomes an oxygen concentration cell element and the second element becomes the oxygen pump element, and a second mode in which the first element becomes the oxygen pump element, and vice versa. It is possible to switch between them.

Further, an exhaust gas sensor system of the present invention using the above exhaust gas sensor is characterized by having the following requirements. Exhaust gas sensor: equipped with the following two elements. (a) First element: composed of an oxygen ion conductive solid electrolyte, electrodes are formed on both sides, and the oxidation catalytic activities of the electrodes for components to be detected in exhaust gas are different from each other. (b) Second element: The first element is formed of an oxygen ion conductive solid electrolyte, electrodes are formed on both sides, and a first element is formed so as to form a predetermined amount of gap that allows the flow of exhaust gas from the atmosphere to be measured. And the oxidation catalyst activities of the electrodes with respect to the components to be detected in the exhaust gas are different from each other, and the difference in the oxidation catalyst activities between the electrodes on both surfaces is caused by the oxidation between the electrodes on both surfaces of the first element. It is set to be larger than the catalyst activity difference. Element control means: one of the first element and the second element is an oxygen concentration cell element, and the other is pumping oxygen into or from the gap in a direction in which the absolute value of the concentration cell electromotive force decreases. It functions as an oxygen pump element to pump out. Control mode switching means: The control mode by the element switches between a first mode in which the first element becomes the oxygen concentration cell element and the second element becomes the oxygen pump element, and a second mode in which the second element becomes the oxygen pump element.

In the exhaust gas sensor and the exhaust gas sensor system described above, one is an oxygen concentration cell element, and the other is an oxygen pump element. And exhaust gas is introduced to both sides of the oxygen concentration cell element. On both sides of the oxygen concentration cell element, there is a difference in oxygen consumption due to oxidation (combustion) of the component to be detected in the exhaust gas, and a concentration cell electromotive force is generated. For example, if oxygen is pumped into or out of the gap by the oxygen pump element so that the electromotive force of the concentration cell becomes constant, for example, the detected value in the exhaust gas is determined by the oxygen pump current value (or voltage value) at that time. The concentration of the component can be known. In this case, even if the oxygen concentration changes, the concentration of the component to be detected in the exhaust gas can be accurately detected.

Further, in the exhaust gas sensor or the exhaust gas sensor system according to the present invention, the first mode in which the oxidation catalyst activity difference between the electrodes on both surfaces is small is the oxygen concentration cell element, and the oxidation catalyst activity difference is also large. The second device side can be appropriately switched and used between a second mode in which the oxygen concentration cell device is used as the oxygen concentration cell device. This makes it possible to obtain different density information of the detected component in the two modes. For example, when the detected components include two or more detected components having different activities with respect to the oxidation reaction, the activity on the oxidation reaction is relatively small in the first mode on both surfaces of the oxygen concentration cell element (that is, combustion). A difference occurs in the oxidation amount (combustion amount) of the component (which is difficult to perform). On the other hand, in the second mode, a difference also occurs in the oxidation amount of the component having a relatively large activity for the oxidation reaction. Therefore, based on the sensor outputs of both modes, it is possible to selectively detect a specific hydrocarbon component, or to individually obtain information on the concentrations of different components or component groups.

In the exhaust gas sensor, as described above, the gap, the first element and the second element, which are to be oxygen concentration cells (hereinafter simply referred to as oxygen concentration cells)
The exhaust gas containing the component to be detected and oxygen can be introduced into a space opposite to the gap (hereinafter referred to as an opposite space) across the gap. In this case, the electrode on the gap side of the oxygen pump element (hereinafter, simply referred to as oxygen pump element) among the first element and the second element is the first electrode, and the electrode on the gap side of the oxygen concentration cell element is the second electrode. The electrode on the opposite space side of the oxygen concentration cell element as the third electrode,
The component to be detected in the exhaust gas introduced into the gap and the opposite space reacts with oxygen in the exhaust gas using at least one of the first to third electrodes as an oxidation catalyst in at least one of the gap and the opposite space. So that there is a difference in the amount of the component to be detected due to the reaction with oxygen between the gap and the opposite space.
The oxidation catalytic activity of the third electrode can be adjusted. Then, information that reflects the current value flowing through the oxygen pump element when the concentration cell electromotive force of the oxygen concentration cell element reaches a predetermined electromotive force target value EC is used as the concentration detection information of the detected component in the exhaust gas. And the difference between the oxidation catalyst activity between the electrodes on both surfaces of the first element and the difference between the oxidation catalyst activities between the electrodes on both surfaces of the second element are different from each other based on the difference between the first mode and the second mode. Depending on the mode, different density detection information is output. In the corresponding exhaust gas sensor system, the function of outputting concentration detection information having different contents in the first mode and the second mode is realized by the concentration detection information output means.

In the exhaust gas sensor configured as described above, the exhaust gas containing the component to be detected and oxygen is introduced into the space opposite to the gap with the oxygen concentration cell element interposed therebetween.
The first and second electrodes disposed on the side facing the gap, and the activity of the third electrode disposed on the opposite space side as an oxidation catalyst, due to the oxidation of the component to be detected on the gap side and the opposite space side. The amount of consumption is adjusted so as to cause a difference, and oxygen is consumed more on the side where the detected component is consumed more. As a result, an oxygen concentration difference occurs on both sides of the oxygen concentration cell element, and a concentration cell electromotive force is generated based on the difference. The oxygen pump element pumps oxygen into the gap when the gap side is on the low oxygen concentration side, and conversely pumps oxygen from the gap when the gap side is on the high oxygen concentration side,
The concentration cell electromotive force is controlled to be equal to the electromotive force target value EC.

Then, the concentration cell electromotive force is equal to the electromotive force target value E.
The current flowing through the oxygen pump element when it reaches C (hereinafter referred to as the pump current) is a value that substantially reflects the concentration value of the detected component in the exhaust gas. The concentration can be detected. Also, the value of the pump current is hardly affected by the oxygen concentration in the exhaust gas unless the concentration of the component to be detected in the exhaust gas changes, and the value of the pump current with respect to the change in the concentration of the component to be detected. The change is almost linear. Thus, even if the oxygen concentration changes within a predetermined range, the concentration of the component to be detected in the exhaust gas can be accurately detected.

[0013] In the exhaust gas sensor and the exhaust gas sensor system, the first element is arranged so that one of the two electrodes having high oxidation catalytic activity faces the gap, and the second element is the one having the oxidation catalytic activity of the two electrodes. The tall ones can be arranged to face the gap. Thereby, in any mode, it is possible to surely cause a difference in the amount of consumption of the detected component due to oxidation between the gap side and the opposite space side of the oxygen concentration cell element, and thus the detection sensitivity of the detected component. Can be enhanced.

The oxidation catalytic activities of the electrodes facing the gap between the first and second elements may be the same or different from each other. When the oxidation catalytic activities of both electrodes are substantially the same, the oxidation consumption of the component to be detected near the gap side electrode (that is, the second electrode) of the oxygen concentration cell element is substantially the same in both modes. Therefore, the sensor output obtained in both modes, that is, the reference level of the density detection information can be matched, and by comparing the two density detection information as described later, the density information of a specific detected component can be relatively easily obtained. Will be able to gain. In this case, in order to make the oxidation catalyst activity of the electrode facing the gap of the first element and the electrode facing the gap of the second element substantially the same,
It can be said that it is desirable that both electrodes are made of the same material.

As an example of a specific combination of electrode materials, an electrode not facing the gap of the first element is formed of Pt-Pd
An electrode, and an electrode facing the gap is also a Pt electrode,
A configuration in which the electrode facing the gap of the second element is a Pt electrode and the electrode not facing the gap is an Au electrode can be exemplified. According to this configuration, for example, when the component to be detected is HC, there is an advantage that methane as a specific component can be detected with high sensitivity in the first mode and the total amount of HC can be detected with high sensitivity in the second mode.

The above-mentioned exhaust gas sensor obtains the concentration detection information obtained in the first mode and the concentration detection information obtained in the second mode when the exhaust gas contains two or more detected components having different activities with respect to the oxidation reaction. Based on the density detection information, it is possible to obtain information on the density of a specific one of the two or more detected components. Further, in the exhaust gas sensor system, based on the concentration detection information obtained in the first mode and the concentration detection information obtained in the second mode, information on the concentration of a specific one of the two or more detected components is generated. Then, a specific component detection information generating / outputting means for outputting the same can be provided. With this configuration, it is possible to obtain concentration information of a specific component to be detected, which cannot be obtained only by the concentration detection information in each mode, based on a combination of the concentration detection information in both modes, and thus to detect a detectable detected component. The types of components can be increased.

More specifically, in the first mode, density detection information relating to the density of a specific one of the two or more detected components is output, and in the second mode, all of the two or more detected components are output. Can be output. Further, based on a difference between the output of the density detection information obtained in the second mode and the output of the density detection information obtained in the first mode, a residual obtained by removing one specific component from the two or more detected components. The information on the total concentration of the components can be obtained. For example, one specific component of the detected components can be methane, and the other detected components can be non-methane hydrocarbons. In this case, the combination of the electrode materials is such that the electrode not facing the gap of the first element is a Pt-Pd electrode, the electrode facing the gap is a Pt electrode, and the electrode facing the gap of the second element is the same. It is preferable that the Pt electrode is used, and the electrode not facing the gap is the Au electrode.

Hereinafter, various contents that can be added to the exhaust gas sensor and the exhaust gas sensor system of the present invention will be described. First, in the exhaust gas sensor, the first element and the second element can be configured as an integrated fired body that is stacked on each other in a state where a gap is formed. According to this, since the first element and the second element are configured as an integrated fired body laminated on each other, the following effects are achieved. Since the first element and the second element are integrated at the same time as firing, the assembly process after firing can be omitted or simplified, and the manufacturing efficiency of the sensor is increased. For example, in the case of a structure in which the first element and the second element are separately fired, and integrated by bonding or the like after the firing, it is difficult to keep the gap formation constant due to deformation during firing of the element. In some cases, the output level varies between individual sensors. However, in the structure integrated by the above-described firing, such a problem is unlikely to occur because the formation amount of the gap is easy to control. The first element and the second element have a thin plate shape (for example, a thickness of 1 mm or less, specifically,
When it is formed to a thickness of about 0.4 mm), in a configuration in which the elements are integrated by bonding or the like after firing, mechanical strength, for example, impact resistance is insufficient, and cracks and cracks may easily occur in the element. However, by integrating them by firing, the elements reinforce each other, and the mechanical strength can be improved.

The integrated structure as described above can be efficiently obtained by, for example, the following manufacturing method. First, on both sides of the first ceramic powder compact to be the first element,
An electrode pattern to be an electrode is formed by printing using an electrode material powder paste, and an electrode pattern is similarly formed by printing on both surfaces of a second ceramic powder compact to be a second element. Next, the first and second ceramic powder compacts are formed so that the electrode patterns to be the first electrode and the second electrode face each other, and a gap is formed between the facing electrode patterns. Laminate each other. And
By firing the laminated body, a first element and a second element integrated with each other are obtained.

The solid electrolyte constituting the first element and the second element is ZrO ₂ in which Y ₂ O ₃ or CaO is dissolved.
Is a typical one, but a solid solution of an oxide of another alkaline earth metal element or a rare earth metal element and ZrO ₂ may be used. Further, ZfO _{2 serving as} a base may contain HfO ₂ .

The size of the gap formed between the first element and the second element is preferably set to, for example, 1 mm or less. If the size of the gap exceeds 1 mm, the effect of restricting the flow of new exhaust gas due to the gap becomes small, and the detection accuracy of the sensor may decrease.

In the exhaust gas sensor having the above structure, the absolute value of the concentration cell electromotive force of the oxygen concentration cell element is 10%.
The value of the current flowing through the oxygen pump element when it reaches the target electromotive force value EC set at mV or less can be extracted as information reflecting the concentration of the detected component in the exhaust gas.

On the other hand, when a test gas containing 1% by volume or more of oxygen and substantially not containing a component which reacts with oxygen at the operating temperature of the sensor is introduced into the gap and the opposite space, the oxygen concentration cell element is generated. The absolute value of the offset electromotive force is set to EOS (unit: mV), and in response to this, the electromotive force target value EC is set within the range of (EOS-5) mV or more and (EOS + 5) mV or less, and the oxygen concentration battery The value of the current flowing through the oxygen pump element when the absolute value of the concentration cell electromotive force of the element reaches the electromotive force target value EC can also be extracted as information reflecting the concentration of the component to be detected in the exhaust gas.

For example, if oxygen is pumped into or out of the gap by the oxygen pump element so that the oxygen concentration on the gap side and the space on the opposite side across the oxygen concentration cell element are equal to each other, Since the pump current directly corresponds to the difference in the consumption of the detected component between the two spaces, the concentration of the detected component can be detected with higher accuracy, and the analysis of the detection result can be performed. It will be easier. In this case, if the oxygen concentration on both sides of the oxygen concentration cell element becomes equal, the concentration cell electromotive force is theoretically 0. Therefore, the oxygen pump element causes oxygen in the gap so that the concentration cell electromotive force becomes 0. Pumping or pumping will be performed. However, even when the oxygen concentration on both sides of the oxygen concentration cell element becomes equal, the electromotive force of the oxygen concentration cell element usually does not become 0, and a constant offset electromotive force often remains.

The present inventors have found that the absolute value of the offset electromotive force of most commonly used oxygen ion conductive solid electrolytes when an oxygen concentration cell element is constituted by the solid electrolytes falls within the range of 10 mV or less. At the same time, in the exhaust gas sensor of the present invention, the electromotive force target value EC is set to 10 mV or less, and the oxygen pump element when the absolute value of the concentration cell electromotive force reaches the electromotive force target value EC is set. By using the flowing current value as the detection signal, it has been found that the concentration of the detected component in the exhaust gas can be accurately detected. If the oxygen concentration range of the measurement atmosphere is known, it is desirable to set the offset electromotive force at the maximum oxygen concentration in the range as the electromotive force target value.

On the other hand, the present inventors have found the following as a result of intensive studies. That is, the offset electromotive force of the oxygen concentration cell element is more likely to fluctuate as the oxygen concentration in the exhaust gas involved in the detection decreases, and when the electromotive force target value EC is set based on the offset electromotive force at an oxygen concentration equal to or less than a certain value, The sensor output is easily affected by the oxygen concentration in the exhaust gas. In order to solve this problem, an oxygen concentration cell when a test gas containing 1% by volume or more of oxygen and substantially not containing a component which reacts with oxygen at the sensor operating temperature is introduced into the gap and the opposite space. The absolute value of the offset electromotive force generated in the element is defined as EOS (unit: mV), and based on this, the electromotive force target value EC is set within the range of (EOS-5.0) mV or more and (EOS + 5.0) mV or less. It becomes effective. By setting the electromotive force target value EC within the above range, a more stable sensor output that is not affected by the oxygen concentration in the exhaust gas can be obtained. In this case, it is desirable to set the electromotive force target value EC as close as possible to EOS in order to increase the detection accuracy of the sensor. The oxygen concentration in the test gas for determining EOS is desirably 10% or more, or the atmosphere is preferably used. Further, the electromotive force target value EC is set to 10 mV as in the above-described configuration.
By setting as follows, a more stable and accurate sensor output can be obtained.

The exhaust gas sensor of the present invention may be arranged, for example, on the downstream side of an oxidation catalytic converter of a gasoline engine or a three-way catalytic converter to detect deterioration of the three-way catalyst in the converter.
In this case, the oxygen in the exhaust gas is introduced into the exhaust gas sensor in a state in which a considerable portion has been consumed for oxidation of CO or HC in the upstream catalyst.
In this case, since the oxygen concentration in the exhaust gas related to the detection is at a level of about 5000 ppm or less,
It is desirable that the exhaust gas sensor is configured to be able to accurately detect the component to be detected in the region where the oxygen concentration is low as described above. For this purpose, for example, when the oxygen concentration is 10
Q100 is the sensor output corresponding to 0 ppm, and 1000
Assuming that the sensor output corresponding to ppm is Q1000, the above-described starting rate is set so that the output change rate Δ (%) = {| Q100−Q1000 | / Q100} × 100 becomes ± 30% or less, more preferably ± 10% or less. It is preferable to set a power target value EC.

Next, in the exhaust gas sensor, a heating element is laminated on at least one of the first element and the second element on a side opposite to the gap, and the first element, the second element, and the heating element are stacked on each other. However, it can be constituted as an integral fired body laminated on each other. Thereby, the assembly process of the sensor including the heating element can be simplified, the whole sensor can be configured more compactly, and the mechanical strength of the entire sensor can be further improved by the reinforcing effect of the integrated heating element. be able to.

[0029] The sensor having the above-mentioned structure is characterized in that, in the above-described method, at least one of the first and second ceramic powder compacts is provided with a third ceramic powder compact to be a heating element on a side opposite to the gap. The first element, the second element, and the heating element integrated with each other are obtained by stacking and firing the stacked body, so that efficient manufacture can be achieved.

In the exhaust gas sensor according to the present invention, the above-mentioned gap may be configured to communicate with the outer space at a communication portion formed at a side edge of the stacked body of the first element and the second element. Thus, the exhaust gas can be smoothly introduced from the communication portion into the gap. In this case, the communicating portion can be formed of a porous ceramic body that allows gas to flow between the gap and the outer space. This makes it difficult for dirt particles such as soot and oil droplets contained in the exhaust gas to enter the gap, thereby preventing or suppressing the deterioration of the electrode facing the gap due to the adhesion of the dirt particles. Can be. In this case, as a method of forming the communicating portion by the porous ceramic body,
In the above-described method, between the first and second ceramic powder compacts, a communicating portion pattern to be the communicating portion is formed by a porous ceramic powder (for example, a porous Al ₂ O ₃ powder) or a porous ceramic body after firing. Using a paste consisting of a powder mixture, etc.
A method of integrally firing this can be exemplified.

Next, between the first element and the second element in the gap, a column for defining the interval of the gap can be formed in a state in which gas does not enter or leave the gap. For example, when the first element and the second element are formed in a plate shape, a so-called ceramic formed by kneading a ceramic powder and an organic binder into a sheet shape as the first and second ceramic powder compacts described above. Green sheets are often used. In this case, the ceramic green sheets laminated with the gap formed are deformed during firing and sag toward the gap side, and the amount of the finally formed gap varies, or in extreme cases, the gap is crushed and the upper and lower electrodes are collapsed. May cause troubles such as contact. Therefore, as described above, if a pillar portion that defines the gap interval is formed between the first element and the second element,
It is possible to stably form a gap having an expected size, and thus it is possible to make it difficult to cause a problem such as output variation between individual sensors due to variation in the gap amount.

The above-mentioned support portion can be efficiently formed by the following method. That is, in at least one of the first and second ceramic powder compacts, a pillar pattern to be a pillar is formed in the region corresponding to the gap by using ceramic powder. Next, the first and second ceramic powder compacts are stacked on each other such that a gap is formed on the side where the column pattern is formed. Then, by sintering the laminated body, a column based on the column pattern is formed between the first element and the second element. The column pattern is a ceramic powder compact (for example, a ceramic green sheet)
Or by pattern printing using a ceramic powder paste.

Specifically, the support portion may be formed in a scattered or staggered manner in the gap forming area, or may be formed in a direction intersecting the laminating direction of the first element and the second element. The gap can be formed in a partition wall shape that partitions the gap into two or more spaces. In addition, as the material of the support portion, even if it is made of the same ceramic material as the first element and the second element (that is, oxygen ion conductive solid electrolyte ceramic), a different ceramic material (for example, Al ₂
O ₃ (including a porous body) may be used, but it is particularly preferable to use a material that can be integrated with the first element and the second element by firing.

Next, the first element and the second element can be formed in a horizontally long plate shape, and can be arranged to face each other. In this case, each electrode can be formed on one end side in the plate surface longitudinal direction of the first element and the second element. Similarly, a spacer having substantially the same thickness as the gap is inserted between the first element and the second element on the other end side in the longitudinal direction of the plate surface. And the second element can be integrated with each other by firing. By arranging the spacer between the first element and the second element, a necessary gap can be easily formed, and the plate-like first element and the second element can be reinforced by integrating the spacer. Thus, the mechanical strength of the sensor can be improved.

The exhaust gas sensor having such a configuration can be efficiently manufactured by the following method. That is, in the above-described method, the first and second ceramic powder compacts are each formed in a horizontally long plate shape and arranged to face each other, and the electrode patterns are formed on the plate surfaces of the first and second ceramic powder compacts. It is formed on one end side in the longitudinal direction. Further, at the other end side in the longitudinal direction of the plate surface, a spacer molded body to be a spacer portion is interposed between the first and second ceramic powder molded bodies. Then, by firing a laminate of the spacer molded body and the first and second ceramic powder molded bodies,
The first element and the second element are joined and integrated with each other via a spacer portion based on the spacer molded body.

In this case, by forming the above-described support portion in the gap, the dimensional accuracy of the gap can be improved. Further, between the first element and the second element, an auxiliary spacer section may be interposed at a position opposite to the spacer section with respect to the gap in the longitudinal direction. With this configuration, since the gap forming portion between the first element and the second element is supported on both sides in the longitudinal direction by the spacer portion and the auxiliary spacer portion, the mechanical strength of the sensor in the gap portion is greatly improved. be able to. On the other hand, a reinforcing spacer portion is inserted between the first element and the second element so as to be part of the peripheral edge of the gap, for example, along the side edges on both sides in the plate width direction of the first element and the second element. With the integrated structure, the mechanical strength of the sensor in the gap can be similarly improved. In this configuration, the spacer section, the support section, the auxiliary spacer section, or the reinforcing spacer section can be made of the same material ceramic as the first element and the second element. In this case, it is desirable to interpose an insulating layer for preventing current leakage between the first element and the second element between them and at least one of the oxygen concentration cell element and the oxygen pump element.

On the other hand, as a simpler sensor configuration, the following can be exemplified. That is, the first element and the second element are similarly configured in the form of a horizontally long plate and arranged to face each other, and each electrode is formed on one end side of the first element and the second element in the plate surface longitudinal direction. On the other hand, between the first element and the second element in the gap, a column that defines the interval of the gap is formed in such a manner that gas does not enter and exit the gap. Further, the first element and the second element are joined and integrated with each other via an insulating layer in an area other than the gap. According to this configuration, the gap can be formed without using the spacer portion, so that the sensor can be configured more compactly. Further, since the steps of fabricating the spacer portion and stacking and disposing the spacer portion can be omitted, the sensor can be manufactured. It can be performed more efficiently.

The following is a specific example of the production method. In the method, the first and second ceramic powder compacts are each formed in a horizontally long plate shape and laminated on each other, and the electrode pattern is formed in the plate surface longitudinal direction of the first and second ceramic powder compacts. It is formed on one end side. Then, in a region scheduled in the gap between the first and second ceramic powder compacts, a pillar pattern to be a pillar portion is formed using a ceramic powder paste, and the pillar portion pattern overlaps with the pillar pattern. An auxiliary support pattern is formed in a region where the gap does not occur by using a powder paste of a material that burns or decomposes (or burns or decomposes and disappears) during firing in a region that is also planned in the gap. Further, an insulating layer pattern is formed between the first and second ceramic powder compacts in other regions except for the region scheduled for the gap. Then, by firing the laminate, a gap and a pillar based on the pillar pattern are formed between the first element and the second element, and the first element is formed in another region except the gap. And the second element are joined to each other via an insulating layer based on the insulating layer pattern. Note that the pillar pattern or the auxiliary support pattern can be formed by printing.

The support pattern and the auxiliary support pattern are
By forming the first and second ceramic powder compacts in a complementary manner by printing as described above, when the first and second ceramic powder compacts are laminated, the strut portion pattern is crushed between the two based on the reinforcing effect by the auxiliary support pattern. Is prevented or suppressed. Then, since the auxiliary support pattern is burned or decomposed and disappears by firing, a fixed amount of gap can be formed between the first element and the second element with high accuracy and extremely easily. Further, by forming the first and second ceramic powder compacts by, for example, ceramic green sheets, even if the insulating layer pattern is formed much thinner than the pillar portion pattern, the first and second ceramic powder compacts are formed. When the body is slightly bent, the two can be in close contact with each other via the insulating layer pattern, and can be integrated without any trouble by firing.

The insulating layer pattern can be formed by using a paste of insulating ceramic powder, for example, Al ₂ O ₃ powder. In this case, the strut pattern is formed by using an insulating ceramic powder having a larger particle size than the insulating layer pattern, for example, a paste of Al ₂ O ₃ porous powder, etc. Can be difficult. On the other hand, the auxiliary support pattern can be formed using, for example, a paste mainly composed of carbon powder.

Next, in the above exhaust gas sensor, the gap between the first element and the second element is made as small as possible (preferably 1 mm or less) to reduce the effect of restricting the flow of new exhaust gas by the gap. Increasing as much as possible is advantageous in improving the detection accuracy of the sensor. Conversely, if the size of the gap is too large, the reaction between HC and oxygen on the electrode having catalytic activity becomes unstable, the electromotive force of the oxygen concentration cell becomes small, and a sufficient sensor output can be obtained. It can go away. This tendency is particularly remarkable when the oxygen concentration in the exhaust gas to be measured greatly fluctuates or when the water vapor concentration in the gas is high. When a gap forming member that forms a predetermined gap (another gap) between the gap and the surface on the opposite side is arranged for at least one of the two elements, the size of the gap is made as small as possible for the same reason. (Preferably 1 mm
Less than).

However, if the gap amount between the above elements is too small, then the first element, the second element,
Alternatively, when the gap forming member is manufactured, a slight deformation at the time of firing has a great effect on the gap formation amount, and there may be a problem that the output tends to fluctuate among the individual sensors.
In order to solve this, it is effective to adopt the following sensor structure. That is, a measurement chamber is formed so as to be in contact with at least one of the electrodes of the first element and the second element, and gas is passed through the wall of the measurement chamber from the atmosphere to be measured to the measurement chamber. A communication part is formed. Then, the gas communication section is configured as a diffusion control flow section including at least one of a small hole, a slit, and a porous communication section made of porous ceramic or porous metal.

In this way, even when the size of the gap is increased to a certain degree or more, the exhaust gas flows into the measurement chamber while its diffusion is restricted from the diffusion restricting flow section, and after the exhaust gas is introduced into the measurement chamber. Similarly, the gas is discharged into the atmosphere to be measured while the diffusion is regulated by the diffusion regulating distribution section. Therefore, the residence time of the exhaust gas once introduced in the measurement chamber becomes longer, and even if the composition of the exhaust gas (particularly the amount of oxygen or water vapor) in the detected atmosphere changes during that time, the influence on the gas in the measurement chamber is not affected. Since it becomes smaller, a stable and high sensor output can be obtained, and the detection accuracy of the sensor can be improved.

Next, regarding the form of formation of the measurement chamber and the diffusion control flow portion, if it is formed on the side of the gap between the first element and the second element, it should surround the electrode facing the gap. A space surrounded by the inner surface of the wall and the opposing surfaces of the first element and the second element can be used as a measurement room. In addition, the diffusion control flow portion is formed so as to penetrate at least one of the wall, the first element, and the second element from the measured atmosphere side to the measurement chamber side. May be a slit or a small hole communicating with each other. The above-described porous ceramic (or porous metal) that allows the flow of gas between the gap and the atmosphere to be measured can also function as the diffusion-regulating flow section.

In the case where the slit is formed as the diffusion control flow portion, for example, a wall forming body constituting at least a part of the wall is disposed between the first element and the second element, and the wall is formed. The slit can be formed between the body and at least one of the first element and the second element in a form along the plate surface of the first element or the second element. Thus, the exhaust gas can be introduced into the measurement chamber through the slit smoothly and without any spatial deviation.

Next, assuming that the width (interval) of the slit is d and the dimension of the measuring chamber (hereinafter, referred to as the height of the measuring chamber) in the direction in which the first element and the second element face each other is h, d / h
Is preferably adjusted in the range of 1/100 to 1/4. d /
If h exceeds ４, the effect of restricting the diffusion of exhaust gas in the slit becomes insufficient, and a sufficient sensor output may not be obtained. If d / h is less than 1/100, the flow rate of gas into or out of the measurement chamber may be too low, and the detection accuracy of the sensor may be reduced. d / h is more desirably set in the range of 1/20 to 1/8. The ratio S / V of the area of the inner peripheral surface of the slit to the space volume V in the slit is preferably adjusted in the range of 4 to 100, preferably 20 to 50 for the same reason.

On the other hand, the absolute value of the slit width d is 0.01
It is better to adjust within the range of 1.0 mm. d is 1.0m
If m is exceeded, the effect of restricting the diffusion of the exhaust gas in the slit becomes insufficient, and a sufficient sensor output may not be obtained. On the other hand, when d is less than 0.01 mm, the flow rate of the gas into or out of the measurement chamber becomes too low, and the detection accuracy of the sensor may be rather lowered. Note that d is more desirably set in the range of 0.02 to 0.05 mm.

The slit may be formed in the middle of the wall forming body in the thickness direction (the laminating direction of the oxygen concentration cell element and the oxygen pump element). However, the slit may be formed in the middle part. A configuration formed between at least one of the two elements is more advantageous in manufacturing the sensor. That is, in the former case, a ceramic molded body to be a wall forming body (hereinafter, referred to as a ceramic molded body)
A gap that is to be a slit is formed in advance in the wall-forming molded body), or the ceramic molded body is formed in two portions adjacent to each other in the thickness direction, and a gap is formed between these portions. A slight increase in man-hours, such as firing in a hot state, is inevitable. On the other hand, in the latter case, a predetermined amount of gap is formed between the molded body for forming the wall portion and the ceramic molded body to be the first element or the second element (hereinafter, referred to as the molded body for element formation), and firing is performed. The exhaust gas sensor having the above structure can be easily manufactured only by performing the above operation.

The above-mentioned slit is formed, for example, by forming a layer made of a material (for example, carbon paste or the like) which is burned off by firing between the molded body for forming a wall portion and the molded body for forming an element in a region where the slit is to be formed. It can be formed by sandwiching and firing the laminated body to burn out the layer. In this case, the width of the formed slit can be freely adjusted according to the thickness of the layer to be formed.

Next, the wall forming body can be integrated with at least one of the first element and the second element by firing. By integrating these by firing, the mechanical strength of the sensor can be improved. When a slit is formed only between the wall forming body and either one of the first element and the second element, the wall forming body and the element forming forming body are formed on the side where the slit is not formed. On the side where the slit is formed, a slit is formed by partially sandwiching the sheet with respect to the lamination surface, and the wall is formed in the lamination surface region where the sheet is not interposed. A configuration in which the molded body for forming and the molded body for element formation are integrated is possible. In this case, since the oxygen pump element and the oxygen concentration cell element are integrated with each other in a portion other than the slit formation region on the slit formation side, the strength of the sensor can be further increased.

On the other hand, when the diffusion control flow portion is formed by a small hole instead of the slit, the small hole can be formed in, for example, a wall forming body. In this case, in order to allow the exhaust gas to flow evenly into the measurement chamber, it is preferable to form a plurality of small holes at predetermined intervals in, for example, the plate surface direction of the plate-like first element or the second element. Further, the small hole may be formed so as to penetrate the first element or the second element in the thickness direction. In this case, it is desirable to form a plurality of the small holes at predetermined intervals along the periphery of the electrodes formed on the elements in order to form a uniform exhaust gas inflow state.

Next, the first element and the second element can be formed in the shape of a horizontally long plate. A plurality of small hole groups can be arranged. In this way, the exhaust gas that has flowed into the measurement chamber from one of the slits or small holes is discharged from the other, so that a smooth flow of the exhaust gas is formed in the measurement chamber, and thus the sensor output can be reduced. Responsiveness can be improved.

Next, in the exhaust gas sensor, a measurement chamber may be formed on the side opposite to the side facing the gap between the first element and the second element. That is, the above-described gap forming member that forms another gap between the first element and the second element is disposed facing the first element and the second element from the side opposite to the above-described gap and facing the first element and the second element. Forming a wall so as to surround the periphery of the corresponding electrode between the gap forming member and the first element or the second element, and the inner surface of the wall, the gap forming member and the first element or the second element. The space surrounded by the facing surface is defined as a measurement room.

Also in this case, the diffusion control flow section can be formed in substantially the same manner as in the case where the measurement chamber is formed between the first element and the second element. That is, the diffusion control flow portion is formed in at least one of the wall portion and the gap forming member so as to penetrate from the measured atmosphere side to the measurement chamber side, and connects the measured atmosphere and the measurement chamber to each other. It can be configured as a slit or a small hole. Further, between the gap forming member and the first element or the second element, it is possible to arrange a wall forming body that forms at least a part of the wall, and the wall forming body and at least the first element and the second element. The slit can be formed between any one of the slit forming members and the slit forming member, the first element, or the second element along the plate surface.

The wall forming body can be integrated with at least one of the gap forming member, the first element and the second element by firing. Further, the gap forming member, the first element and / or the second element can be formed in a horizontally long plate shape, and the diffusion control flow portion is provided on both sides of the gap forming member, the first element or the second element in the plate surface width direction. Can be formed as a slit.

The material of each electrode of the first and second elements is as follows:
Those having relatively high catalytic activity for the reaction with oxygen include metals (simple or alloy) mainly containing any of Pt, Pd and Rh, Pt-Rh-based alloys, Rh-Pd
Alloys, Pd-Ag alloys, and the like (hereinafter, these are referred to as highly active metal groups) can be used. Conversely, those having relatively low catalytic activity include A
a metal (simple or alloy) mainly composed of any one of u, Ni and Ag, or a Pt-Au-based alloy, a Pt-Ni-based alloy,
Pt-Ag-based alloys, Ag-Pd-based alloys, Au-Pd-based alloys, and the like (hereinafter, these are referred to as low-active metal groups) can be used. It should be noted that a Pt-Pd-based alloy can also be used, which has a slightly lower catalytic activity than Pt, but is considerably higher than Au or the like.

When an electrode having a low oxidation catalytic activity with respect to the component to be detected is formed, at least a portion including the surface in contact with the exhaust gas is made of a material which is inactive with respect to the reaction between the component to be detected and oxygen. Can be configured. In this case, it is obvious that the entire electrode can be made of the above-mentioned catalyst-inactive material, but in the contact portion with the exhaust gas, only the surface layer may be made of the catalyst-inactive material. The body may be formed of a catalytically active material, and the surface thereof may be coated with a catalytically inactive material to obtain an electrode. Examples of the catalyst-inactive material include those belonging to a low-active metal group such as a metal mainly containing any of Au, Ni, and Ag described above, or SnO ₂ , ZnO, In ₂ O ₃ , WO ₃ , and Bi.
Oxides such as ₂ O ₃ can be exemplified.

Next, a gas holding member made of a metal mesh or a porous metal may be interposed in a gap formed between the first element and the second element. This way,
The gas holding member functions as a spacer for forming the gap, and the dimensional accuracy of the gap can be improved. In addition,
When the gas holding member is formed of a mesh, it is desirable to use a mesh having a formation density of 100 to 500 mesh.

Next, in the exhaust gas sensor system of the present invention, heat generation control means for controlling heat generation of the heating element can be provided so that the temperature of the oxygen concentration cell element approaches a predetermined temperature target value. That is, in the above sensor system, the operation of the oxygen pump element is controlled with reference to the concentration cell electromotive force generated in the oxygen concentration cell element. If the temperature of the oxygen concentration cell element changes even if the concentrations of the components to be detected are the same, the concentration cell electromotive force and, consequently, the value of the pump current serving as the concentration detection information fluctuate, leading to an increase in measurement error. However, by providing the above-described heat generation control means, the heat generation of the heating element is controlled so that the temperature of the oxygen concentration cell element approaches a predetermined temperature target value. The measurement error of the detected component can be reduced, and the measurement accuracy can be improved.

The heat generation control means includes a temperature detection means for detecting the temperature of the oxygen concentration cell element, and a heat generation means based on the temperature detection result of the temperature detection means so that the temperature of the oxygen concentration cell element approaches the temperature target value. And an energization control means for controlling energization of the element. As a result, even if the temperature of the oxygen concentration cell element may temporarily change due to a sudden change in the exhaust gas temperature or the like, the pump current information is corrected based on the detected temperature information. It is possible to maintain good component detection accuracy. In this case, the temperature of the oxygen concentration cell element may be measured by using a separately provided temperature sensor such as a thermistor or a thermocouple. However, since the value of the internal resistance of the concentration cell element changes depending on the temperature, If the temperature is measured using the above, there is no need to provide a temperature sensor, and there is an advantage that the configuration of the measurement system can be simplified.

In this case, the sensor system includes a detected component concentration information correcting means for generating temperature compensated detected component concentration information based on the temperature information detected by the temperature detecting means and the pump current information. And a corrected measurement result output means for outputting the generated detected component concentration information as a corrected measurement result.

More specifically, the detected component concentration information correction means calculates the temperature deviation-pump current correction amount that gives a relationship between the temperature deviation from the temperature target value and the correction amount (pump current correction amount) for the pump current information. Correction reference information storage means for storing relation information as correction reference information; and a pump current for determining a pump current correction amount corresponding to a difference between the temperature detected by the temperature detection means and the temperature target value with reference to the correction reference information. It can be configured to include a correction amount determining unit and a correction calculating unit that performs a calculation for correcting the measured pump current information based on the determined pump current correction amount. According to this, since the pump current information can be corrected by converting the temperature deviation from the target temperature into a pump current correction amount, the algorithm of the correction process can be simplified, and the correction output of the detected component concentration measurement result can be simplified. Responsiveness can be improved.

In this case, the detected component concentration information correcting means can be provided with a pump current information-detected component concentration information converting means for converting the pump current information into the detected component concentration information, and outputting the corrected measurement result. The means may output the converted detected component concentration information as temperature-compensated detected component concentration information. In addition, the pump current information-detected component concentration information conversion unit specifically stores a pump current value-detected component concentration relationship information indicating a relationship between the pump current value and the detected component concentration, and With reference to the stored pump current value-detected component concentration relationship information, a detected component concentration calculating means for calculating a detected component concentration indicated by the corrected pump current information can be configured as: The correction measurement result output means may be configured to output the calculation result. On the other hand, the corrected pump current information may be directly output to the outside.

On the other hand, the detected component concentration information correction means stores the relationship between the pump current value and the detected component concentration value for each temperature, and stores pump current information-detected component concentration relationship information as correction reference information. Based on the corrected reference information storage means and the information on the temperature detected by the temperature detecting means and the measured pump current information, a reference is made to the corrected reference information, whereby the detected component corresponding to the temperature and the pump current value is detected. A correction density information generating means for generating the density value as temperature-compensated detected component density information may be provided. According to this configuration, it is necessary to prepare pump current information-detected component concentration relationship information for each temperature, but without calculating the pump current correction amount from the detected temperature, the measured temperature and the pump current can be used. The corresponding detected component concentration can be directly determined, and the response in the detected component concentration output can be further improved.

Next, the temperature detecting means includes an internal resistance measuring means for measuring the internal resistance of the oxygen concentration cell element, and temperature information for generating information on the temperature of the oxygen concentration cell element based on the measured internal resistance value. It can be configured to include a generation unit and a temperature information output unit that outputs information of the generated temperature. As described above, according to this configuration, there is no need to separately provide a temperature sensor or the like, and there is an advantage that the device configuration can be simplified.

The internal resistance measuring means includes, specifically, an internal resistance detection current supplying means for supplying a constant internal resistance detection current to the oxygen concentration cell element, and an oxygen concentration battery when the internal resistance detection current is supplied. Voltage information detecting means for detecting information (voltage information) reflecting a voltage applied to the element, and measuring an internal resistance value of the oxygen concentration cell element based on the detected voltage information. it can. According to this, the internal resistance of the oxygen concentration cell element can be easily measured from the applied voltage when the constant current is applied.

If there is a difference in oxygen concentration on both sides of the oxygen concentration cell element, a concentration cell electromotive force is generated in the oxygen concentration cell element, and the detected voltage information includes information on the concentration cell electromotive force. May not be included or may be superimposed and cause an error. In this case, when measuring the internal resistance of the oxygen concentration cell element, the voltage applied to the oxygen concentration cell element is increased by setting the internal resistance detection current to be larger than a certain value, and the influence of the concentration cell electromotive force is relatively reduced. Reducing the size is effective in increasing the accuracy of the internal resistance measurement. On the other hand, the following method is also effective for removing or reducing the influence of the superimposed or included concentration cell electromotive force. That is, in the state where the internal resistance detection current is not passed through the oxygen concentration battery element to the internal resistance measuring means,
Concentration cell electromotive force measurement means for measuring the concentration cell electromotive force of the oxygen concentration cell element, and voltage information correction means for correcting the content of the detected voltage information based on the measured concentration cell electromotive force information; Is provided. Specifically, the influence of the concentration cell electromotive force component can be effectively removed by subtracting the measurement result of the concentration cell electromotive force by the concentration cell electromotive force measurement means from the detection result of the voltage information.

Next, when a current for measuring the internal resistance is applied to the oxygen concentration cell element, oxygen is transported in the oxygen concentration cell element in a direction opposite to the direction of the current supply (ie, it functions as an oxygen pump). Changes in the oxygen concentration. As a result, when returning to the measurement of the concentration of the detected component by the exhaust gas sensor, the change in the oxygen concentration may cause an error in the measurement accuracy of the concentration of the detected component. In addition, when the internal resistance value of the oxygen concentration cell element is high, oxygen ions in the oxygen concentration cell element are difficult to move,
Polarization may occur with the passage of current. Then, after the internal resistance detection current is supplied to the oxygen concentration cell element by the correction current supply means and the internal resistance is measured, the correction current is supplied to the oxygen concentration cell element in a direction opposite to the internal resistance detection current. If this is done, oxygen is transported in the opposite direction to the above by the energization, so that the changed oxygen concentration approaches the state before the internal resistance measurement, and the measurement accuracy of the concentration of the detected component after the return is increased. At the same time, the polarization state of the oxygen concentration cell element can be eliminated. In this case, the magnitude and energizing time of the correction current are set so that approximately the same amount of oxygen that is considered to be transported when the internal resistance detection current is applied is reversely transported by the application of the correction current. For example, it is preferable to supply a current having substantially the same magnitude as the internal resistance detection current for approximately the same time as the internal resistance detection current.

Next, the concentration cell electromotive force of the oxygen concentration cell element is compared with a predetermined control reference value, and a pump current corresponding to the difference between the concentration cell electromotive force and the target electromotive force EC is directed to the oxygen pump element. Pump current control means for outputting the output. As a result, the concentration cell electromotive force becomes the electromotive force target value E
The pump current value is controlled so as to approach C. Here, the internal resistance measuring means includes a pump current interrupting means for interrupting the output of the pump current to the oxygen pump element by the pump current controlling means at a predetermined timing, and the internal resistance detecting current supplying means includes a pump It can be configured such that the internal resistance detection current is supplied to the oxygen concentration cell element in a state where the current output is cut off. As a result, the interference between the internal resistance detection current and the pump current is prevented, and the internal resistance of the oxygen concentration cell element can be accurately detected.

In this case, if the output of the pump current is cut off for a long time, the electromotive force of the concentration cell deviates from the electromotive force target value EC and becomes unstable. The original purpose of the device may be impaired. Therefore, in the internal resistance measuring means, the pump current interrupting means periodically interrupts the output of the pump current by the pump current control means at predetermined time intervals, whereby the internal resistance measuring means It can be configured to periodically measure the internal resistance of the oxygen concentration cell element in response to the interruption of the current output. As a result, the frequency of the internal resistance measurement can be increased without continuously interrupting the output of the pump current for a long time, and the temperature can be more accurately compensated for the concentration measurement result of the component to be detected. In addition, it is possible to improve the accuracy of the temperature control of the heat generating element by the heat control means using the internal resistance value as the temperature information.

[0071]

Embodiments of the present invention will be described below with reference to embodiments shown in the drawings. FIG. 1 shows an exhaust gas sensor 1 as one embodiment of the present invention. That is, in the exhaust gas sensor 1, a first heater 2 (heating element), a first element 3, a second element 4, and a second heater 5 (heating element) each formed in a horizontally long plate shape are laminated in this order. It is configured as something. The first element 3 and the second element 4 are made of a solid electrolyte having oxygen ion conductivity. As such a solid electrolyte, Y ₂ O ₃
Although ZrO ₂ containing CaO as a solid solution is typical, a solid solution of an oxide of another alkaline earth metal or rare earth metal and ZrO ₂ may be used. Also,
ZrO _{2 serving} as a base may contain HfO ₂ . In the present embodiment, Z in which Y ₂ O ₃ or CaO
It is assumed that rO ₂ solid electrolyte ceramic is used. On the other hand, the first and second heaters 2 and 5 are constituted by known ceramic heaters.

The first element 3 is formed in a horizontally long plate shape, and porous electrodes 10 and 11 having oxygen molecule dissociation ability are formed on both surfaces near one end in the longitudinal direction. The second element 4 (which also functions as a temperature detecting means) has the same porous electrodes 12, 1 on both surfaces thereof at positions corresponding to the electrodes 10, 11 of the first element 3.
3 are formed. Except for the portions where the electrodes 10 to 13 are formed, a plate-shaped spacer portion 200 made of a solid electrolyte ceramic of the same material as the elements is interposed between the first element 3 and the second element 4. Al ₂ O ₃
The two surfaces are integrated with the first element 3 and the second element 4 by baking through insulating layers 201 and 202 made of the same. Thereby, a gap 15 is formed between the electrode 11 of the first element 3 and the electrode 12 of the second element 4. In the gap 15, between the second element 4 and the first element 3, an elongated reinforcing spacer 2 integral with the spacer 200 so as to be along the side edges on both sides in the plate width direction.
03 is interposed and integrated. And the gap 15
In the end faces of the second element 4 and the first element 3, the exhaust gas can flow in and out by communicating with the outside space by using the opening 204 opened between the reinforcing spacers 203 as a communication part.

On the other hand, between the first heater 2 and the first element 3 and between the second element 4 and the second heater 5, spacers 6 made of glass, cement, or the like are respectively provided.
And 8 (FIG. 2) are interposed, and a predetermined amount of gaps 14 and 16 are formed between the respective elements. In addition,
The gap 15 corresponds to a gap between the first element and the second element, and the gaps 14 and 16 also correspond to opposite spaces. In addition, the second heater 5 plays a role of a gap forming member.

The electrodes 10 and 11 of the first element 3 are made of materials having different oxidation catalytic activities with respect to hydrocarbons as components to be detected. 15 are arranged. The electrodes 12 and 13 of the second element 4 are also made of materials having different oxidation catalytic activities with respect to hydrocarbons as components to be detected. A material which is larger than the difference in the oxidation catalyst activity between the electrodes 10 and 11 on both surfaces of one element 3 is used, and a material (12) having a high oxidation catalyst activity is arranged so as to face the gap 15. The electrodes 11 and 12 of the first element 3 and the second electrode 4 that face the gap 15 are
They are made of the same material.

In this embodiment, the electrode 10 not facing the gap 15 of the first element 3 is a Pt-Pd electrode, and the electrode 11 facing the gap 15 is also a Pt electrode. The electrode 12 facing the gap 15 is a Pt electrode, and the electrode 13 not facing the gap 15 is an Au electrode. The Pd content in the Pt-Pd electrode is adjusted, for example, in the range of 1 to 50% by weight. When the Pd content is less than 1% by weight, the difference in oxidation catalyst activity between the electrode 10 and the electrode 10 becomes too small, and the sensitivity of detecting methane concentration in the first mode described later may be insufficient. On the other hand, if the Pd content exceeds 50% by weight, the adhesion between the Pt-Pd alloy and the solid electrolyte ceramic becomes insufficient, and the electrode may be peeled off. Pd content is desirably 2-1.
It is preferable to adjust it in the range of 4% by weight.

The first element 3 and the second element 4
One of them functions as an oxygen concentration cell element, and the other pumps oxygen into the gap 15 in the direction in which the absolute value of the concentration cell electromotive force generated in the oxygen concentration cell element decreases, or
Will function as an oxygen pump element that pumps oxygen from the fuel cell. Then, a control mode switching mechanism (control mode switching means) described later switches between a first mode in which the first element 3 becomes an oxygen concentration cell element and the second element 4 becomes an oxygen pump element, and a second mode in which the first element 3 becomes an oxygen pump element. It is used by appropriately switching between them.

FIG. 2 is a view in which the spacer section 200 and the auxiliary spacer section 203 are omitted to show the internal structure of the exhaust gas sensor 1. From each of the porous electrodes 10 and 11 of the first element 3, an electrode lead portion 1 extending toward the mounting base end side of the exhaust gas sensor 1 along the longitudinal direction of the element 3.
The first element 3 has one end of each of the connection terminals 10b and 11b embedded at the base end side. Then, for example, the connection terminal 10
As shown in FIG. 2B, b and 11b are formed by conducting portions 10f formed by sintering a metal paste.
It is electrically connected to the ends of the electrode leads 10a, 11a. Further, each of the porous electrodes 12 of the second element 4,
Similarly, the electrode lead portions 12a and 13a are integrally formed on the connector 13, and connection terminals 12b and 13b are attached to the electrode lead portions 12a and 13b, respectively.

FIG. 3A shows an example of the overall configuration of the exhaust gas sensor 1, and FIG. 3B shows the internal structure thereof. That is, a main part of the exhaust gas sensor 1 is a laminate 31 including the first heater 2, the first element 3, the second element 4, and the second heater 5 shown in FIGS. Through hole 3
A ceramic stopper 30 having 0 a is fitted to the laminate 31 from the outside. The laminated body 31 has electrodes 10 inside the ceramic porcelain tube 32 having one end open and a bottom 32b having a through hole 32a formed on the other end.
Ends (hereinafter, referred to as detection ends) 31 formed with １３13
a is disposed so as to protrude from the through hole 32a, and the space between the insulator tube 32 and the laminate 31 is filled with glass G. The end surface of the ceramic stopper 30 contacts the inner surface of the bottom 32b of the porcelain tube 32,
It also plays a role in defining the amount of protrusion of the laminate 31 from the insulator tube 32.

The outside of the insulator tube 32 is a metal outer cylinder 3.
3 and a metal shell 34 integrated with the outer cylinder 33 by a caulking connection portion 34a. Metal shell 34
A male screw portion 34b for attaching the sensor 1 to an attachment portion (not shown) such as an exhaust pipe is formed on the outer peripheral surface of the sensor, and an opening 34c formed on the tip side thereof detects the above-described laminate 31. The end 31a is projected. An annular protector mounting sleeve 34d is formed integrally with the periphery of the opening 34c of the metal shell 34. A large number of through holes 3 cover the detection end 31a and allow the exhaust gas to flow to the detection end 31a.
A cylindrical protector 35 having 5a is fitted to the protector mounting sleeve 34d from the outside, and further joined and integrated by spot welding or the like. On the other hand, in the space formed between the metal shell 34 and the intermediate portion of the insulator tube 32, a caulking fitting 3 for receiving the working force at the time of caulking is provided on the side close to the caulking joint 34a.
6, and the remaining space is filled with a filler 80.

On the other hand, each of the elements 2 to 5 constituting the laminate 31
A lead wire 37 is joined to the connection terminal (FIG. 1 etc.) by welding or the like.
Extending outward from the end. The intermediate portion of the lead wire 37 is a sealing member 38 made of an elastic material such as rubber.
, And a protective outer cylinder 39 made of metal is fitted further outside. Then, the protective outer cylinder 39
Is integrated with the outer cylinder 33 by caulking.

The exhaust gas sensor 1 is attached to, for example, an attachment portion provided in an exhaust pipe such that the protector 35 is located in the exhaust pipe. For example, in the second mode in which the first element 3 is an oxygen pump element and the second element 4 is an oxygen concentration cell element, the following is performed. That is,
As shown in FIG. 4, a voltage is applied to the first element 3 serving as an oxygen pump element via the above-described lead wire 37 (FIG. 3) such that one of the porous electrodes 10 and 11 is positive and the other is negative. Is applied. Then, in the porous electrode having a positive polarity, oxygen molecules in the exhaust gas in contact with the porous electrode are dissociated on the electrode, and the dissociated oxygen is in the form of ions by the applied voltage serving as a driving force. It is sent into the element 3. Also,
Oxygen ions transported in the element 3 by the application of the voltage receive electrons on the porous electrode having a negative polarity, are recombined with oxygen molecules, and are released into the atmosphere.

The second element 4 serving as an oxygen concentration cell element
In the above, no voltage is applied to the porous electrodes 12 and 13, and oxygen molecules in the exhaust gas in contact with the electrodes 12 and 13 are dissociated on the electrodes 12 and 13, respectively. Spreads in. And electrode 1
If there is a difference in oxygen concentration between the second side and the thirteenth side, the element 4
A concentration gradient of oxygen ions is generated inside the cell, and a concentration cell electromotive force corresponding to the concentration gradient is generated between the two electrodes 12 and 13. In the following, regarding the gap 15 formed between the oxygen pump element and the oxygen concentration cell element, the porous electrode 11 facing the gap 15 of the first element 3 faces the first electrode and the gap 15. The porous electrode 12 of the second element 4 is called a second electrode, and the porous electrode 13 not facing the gap 15 is called a third electrode.

On the other hand, among the porous electrodes 10 to 13,
At least a part of the component has a role of dissociating or recombining oxygen molecules as described above, and also has a binding reaction between a hydrocarbon-based target component and oxygen in exhaust gas in contact therewith, that is, combustion of the target component. It also functions as an oxidation catalyst for accelerating the reaction. Then, in the exhaust gas sensor 1 of the present embodiment, the first electrode 11 and the second electrode 12
Is composed of Au. Thus, the activity of the oxidation catalyst for the detected component is adjusted such that a difference occurs in the consumption of the detected component due to the reaction with oxygen on both sides of the second element 4 (that is, on the gap 15 side and the gap 16 side). (In this case, the consumption increases on the gap 15 side). The size of each of the gap 15 and the gap 16 is adjusted within a range of 1 mm or less. On the other hand, the area Sp of the first electrode 11 is set equal to or larger than the area SS of the second electrode 12.

On the other hand, in the first mode, the first element 3 becomes an oxygen concentration cell element, and the second element 4 becomes an oxygen pump element. In this case, the electrode 12 made of Pt is the first electrode, the electrode 11 is the second electrode, and the electrode 10 made of the Pt-Pd alloy is the third electrode. Also in this case, the oxidation catalyst activity for the detected component is different in the consumption of the detected component due to the reaction with oxygen on both sides of the oxygen concentration cell element (first element 3) (that is, on the gap 14 side and the gap 15 side). (In this case, the consumption increases on the gap 14 side).

Hereinafter, a method of integrally firing the first element 3 and the second element 4 will be described with reference to FIG. That is, the unfired assembly 310 for forming the integrally fired body
Are a first part 211 (corresponding to a first ceramic powder compact) for forming the first element 3 and a second part 212 (corresponding to the second ceramic powder compact) for forming the second element 4. And a third portion 213 for forming the gap 15. First, the first part 211
Is formed using a green body obtained by kneading ZrO ₂ powder together with an organic binder, and is to be a main body of the first element 3.
rO ₂ green sheet 220 is included. The ZrO ₂
The electrodes 10 and 11 on both sides of the green sheet 220 (FIG. 2)
And the like, except for the portion where the formation of
The insulating coats (insulating layer patterns) 221 and 222 for insulating between the first element 3 and the first element 3 are made of Al ₂ O _3.
It is formed using a paste or the like. Those insulating coats 22
After forming the electrodes 1 and 222, an electrode pattern 223 for forming the electrodes 10, 11 and the leads 10a, 11a is formed.
And 224 are formed by printing using a Pt paste or the like. An overcoat 225 for protection is formed on the electrode pattern 223 on the side to be the outer electrode 10 by using an Al ₂ O ₃ paste or the like.

On the other hand, similarly, the second portion 212 has insulating coats (insulating layer patterns) 231 and 232 on both surfaces of the ZrO ₂ green sheet 230 to be the main body of the second element 4.
Is formed. Here, an electrode pattern 233 for forming the electrode 12 and its lead portion 12a is formed on the insulating coat 231 side.
Since the (third electrode) has a low melting point and cannot be integrally baked with ZrO ₂ , only the electrode lead portion pattern 234 for forming the lead portion 13a is formed on the insulating coat 232 side, and Al is formed thereon. _A protective overcoat 235 is applied with ₂ O ₃ paste.

Next, the third portion 213 includes the spacer portion 20.
A ZrO ₂ green sheet 240 in which a portion 200a (spacer molded body) to be 0 and a portion 203a to be a reinforcing spacer portion 203 are integrally formed is mainly constituted, and both surfaces thereof are bonded coats 241 and 242. Are formed using an Al ₂ O ₃ paste or the like. These bonding coats 241 and 242, together with the above-mentioned insulating coats 222 and 231, become insulating layers 201 and 202 by firing, respectively, and connect the spacer 200 and the reinforcing spacer 203 with the first element 3 and the second element 4 to each other. Plays the role of joining.

The first portion 211 and the third portion 213 are laminated on each other, and Pt- for forming the terminals 10b and 11b (FIG. 2) corresponding to the ends of the leads 10a and 11a. One end side of each of the Rh alloy wires 243a and 243b is sandwiched. A through hole 220a is formed at a position corresponding to the end of the lead portion 10a of the ZrO ₂ green sheet 220.
2a, the paste is filled therein, and as shown in FIG. 2 (b), the filled paste is sintered by firing to become a conductive portion 10f, and the terminal 10f is formed.
b (Pt-Rh alloy wire 243b) and the lead portion 10b are electrically connected. On the other hand, the pattern of the lead portion 11a, and the Pt-Rh alloy wires 243a, in direct contact with pinched between the ZrO ₂ green sheets 220 and 240.

The second portion 212 is also laminated on the third portion 213 from the side opposite to the first portion 211, and forms terminals 12b and 13b (FIG. 2) corresponding to the ends of the leads 12a and 13a. -Pt-Rh alloy wire 24
One end side of each of 4a and 244b is sandwiched,
The green assembly 310 is completed. At a position corresponding to the end of the lead portion 13a of the ZrO ₂ green sheet 230, a through-hole 230a is formed like the through-hole 220a of the first portion 211, and a conductive portion based on the paste filled therein is formed. Accordingly, the terminal 13b and the lead portion 13a are electrically connected. Further, the pattern of the lead portion 12a and the Pt-Rh alloy wire 244 serving as the terminal 12b are used.
a is sandwiched between the ZrO ₂ green sheets 240 and 230 and is in direct contact therewith.

Then, the unfired assembly 310 is fired to form an integrally fired product of the first element 3 shown in FIGS. 1 and 2 and the second element 4 in which the third electrode 13 is not formed. can get. Then, as shown in FIG. 5, a pattern 245 is paste-printed at a position corresponding to the second element 4 using an Au powder paste, and further baked at a temperature lower than the firing temperature of the ceramic (for example, 850 to 1000 ° C.). By performing the next metallizing process, the third electrode 13 is formed, and the main part of the exhaust gas sensor is completed.

The outline of the operation principle of the exhaust gas sensor 1 is as follows. As shown in FIG. 4, the exhaust gas sensor 1 is attached to an exhaust pipe, and a gap 15 between the first element 3 and the second element 4 and a gap 16 between the second element 4 and the heater 5 (opposite space). At this time, an exhaust gas containing a hydrocarbon-based component to be detected and oxygen is introduced. First, in the first mode, the electrodes 11 and 12 located on the gap 15 side are both formed of Pt, and the electrodes 10 and 12 located on the gap 14 side are
Is composed of a Pt-Pd alloy, the amount of the component to be detected in the exhaust gas due to oxidation is greater on the gap 15 side than on the gap 14 side. On the side where the consumption of the detected component is large, the consumption of oxygen in the exhaust gas EG is also large, so that the oxygen concentration in the gap 14 is higher than that in the gap 15 and the oxygen concentration cell element A concentration cell electromotive force with the gap 14 being positive is generated in the first element 3.

When oxygen is pumped from the gap 16 to the gap 15 by the second element 4 serving as an oxygen pump element so that the absolute value of the electromotive force of the concentration cell becomes a constant value of, for example, 10 mV or less. The current flowing through the second element 4 (hereinafter, referred to as
The oxygen pump current or the pump current) is a value reflecting the amount of oxygen consumed for oxidizing the component to be detected. When the concentration of the detected component in the exhaust gas EG increases,
The amount of oxygen consumed by the oxidation increases, and as a result, the pump current also increases. Therefore, by measuring the pump current, the concentration of the detected component in the exhaust gas EG can be known.

On the other hand, in the second mode, the electrodes 11 and 12 located on the gap 15 side are both made of Pt.
Since the electrode 13 located on the gap 16 side is made of Au, the amount of the component to be detected in the exhaust gas due to oxidation is larger on the gap 15 side than on the gap 16 side. As a result, the oxygen concentration in the gap 16 becomes higher than that in the gap 15, and a concentration cell electromotive force with the gap 16 side being positive is generated in the second element 4 serving as the oxygen concentration cell element.

Then, oxygen is pumped from the gap 14 side to the gap 15 side by the first element 3 serving as an oxygen pump element so that the absolute value of the electromotive force of the concentration cell becomes a constant value of, for example, 10 mV or less. The current flowing through the first element 3 (hereinafter, referred to as
The oxygen pump current or the pump current) is a value reflecting the amount of oxygen consumed for oxidizing the component to be detected. When the concentration of the detected component in the exhaust gas EG increases,
The amount of oxygen consumed by the oxidation increases, and as a result, the pump current also increases. Therefore, by measuring the pump current, the concentration of the detected component in the exhaust gas EG can be known.

Here, in the above two modes, when the detected component to be detected is, for example, HC, the detected density information is different from each other. That is, as shown in FIG. 36, in the exhaust gas, various HC components other than methane such as methane (CH ₄ ), ethane (C ₂ H ₆ ), and propane (C ₃ H ₈ ) (hereinafter referred to as non-methane) are included. Methane HC component)
Are mixed. Of these, methane has relatively low activity for oxidation (ie, combustion),
Generally, various non-methane HC components have a higher activity for oxidation than methane, that is, they have a property of easily burning. Here, in the first mode, the first element 3 is an oxygen concentration cell element, but the Pt-Pd alloy constituting the electrode 10 is H
Although the oxidation catalyst activity for C is slightly lower than that of Pt, it is considerably higher.
The combustion of the components will generally proceed well. On the other hand, Pt constituting the electrode 11 has a higher oxidation catalyst activity than the Pt-Pd alloy. Therefore, in the electrode 11, for example, combustion of non-methane HC components proceeds almost equally to the electrode 10 side, but the amount of methane combustion is slightly larger than that of the electrode 10 side. Therefore, a concentration cell electromotive force is generated on both sides of the first element 3 mainly based on the difference in the amount of methane combustion, and the methane concentration CHCA can be known from the pump current value of the second element 4 at this time.

On the other hand, in the second mode, the second element 4 becomes an oxygen concentration cell element, but Au constituting the electrode 13 is almost inactive against the oxidation of HC, and H on the electrode 13 side.
The combustion of the C component hardly proceeds. On the other hand, the electrode 12 is made of Pt similarly to the electrode 11, and combustion of HC actively proceeds. Accordingly, the concentration cell electromotive force generated in the second element 4 in this mode reflects the concentration of all HC including methane, and the total HC concentration CHCB is known from the pump current value of the first element 3 at this time. be able to. Furthermore, if the difference CHCC = CHCB-CHCA of the CHCA and CHCB obtained in the first mode and the second mode, respectively, is obtained, the total concentration of non-methane HC components can be known from the CHCC.
In addition, if the oxidation catalyst activity is adjusted to a condition different from the above by changing the material of each of the electrodes 10 to 13, it is also possible to obtain concentration information of the detected component other than the above.

Next, in the exhaust gas sensor 1,
As shown in FIG. 6, a pillar portion 210 that defines an interval between the second element 4 and the first element 3 in the gap 15 in a state in which gas does not flow in and out of the gap 15 in the gap 15.
Can be formed. In the example shown in FIG. 6, the column portion 210 is formed of a solid electrolyte ceramic of the same material as the first element 3 and the second element 4 in a partition wall shape that divides the gap 15 into two parts at a middle position in the longitudinal direction. ing. An auxiliary spacer 215 is interposed and integrated with the gap 15 on the side opposite to the spacer 200. The gap 15 is communicated with the outer space by using the openings 204 formed on both sides of the column 210 as communication parts on both side surfaces in the width direction of the stacked body of the first element 3 and the second element 4. Exhaust gas can enter and exit.

The support 210 can be integrally formed with the first element 3 and the second element 4 by firing the unfired assembly 310 shown in FIG. Green assembly 310 of FIG.
Is configured exactly the same as that shown in FIG. 5 except for the third portion 213. In the third portion 213, a spacer molded body 200 a for forming the spacer portion 200 and an auxiliary spacer portion 215 disposed on the opposite side of the space scheduled for the gap 15 are formed. Of the auxiliary spacer molded body 215a, and a pillar molded body 21 as a pillar pattern disposed therebetween.
0a is formed using the ZrO ₂ green sheet 240, and the first portion 211 and the second portion 2 are formed on both sides thereof.
12 are stacked.

Then, by firing this, between the second element 4 and the first element 3, the above-mentioned support column molded body 210 is formed.
The support part 210 based on a is formed. By interposing the support portion molded body 210a at the time of firing, the ZrO ₂ green sheets laminated in a state where a gap is formed are prevented from being deformed at the time of firing and hanging down to the gap side, and a gap having an intended size is prevented. 15 can be formed stably. In the example shown in FIG. 6, the column portion 210 is formed so as to cross the electrodes 11 and 12 in the width direction. However, the column portion 210 is formed at a position where it does not interfere with the electrodes 11 and 12, as shown in FIG. You may do so. In FIG.
A plurality of reference numerals 10 are arranged at predetermined intervals on both sides in the width direction of the second element 4 and the first element 3 along the longitudinal direction thereof. On the other hand, the gap 15
When the length in the longitudinal direction between the second element 4 and the first element 3 is not so large, as shown in FIG.
It is also possible to adopt a configuration in which 0 is omitted.

Further, for the second element 4 and the first element 3,
At least one of the first and second heaters 2 and 5 may be integrated by firing. FIG. 10 shows an example thereof, in which the first heater 2 is stacked on the first element 3 on the side opposite to the gap 15, and the first element 3, the second element 4, and the first heater 2 are Are formed as an integral fired body laminated on each other. The second heater 5
Has been omitted. Here, a gap 14 is formed between the first heater 2 and the outer electrode 10.
In regions other than region 4, the first heater 2 and the first element 3 are joined via an insulating layer 2c made of Al ₂ O ₃ or the like.

The above sensor structure has a structure as shown in FIG.
Basically, in the unfired assembly shown in FIG. 7, a fourth portion (third ceramic powder compact) to be the first heater 2 from the side opposite to the third portion 213 with respect to the first portion 211. 214, and is obtained by firing the unfired assembly 310 obtained as a laminate. Hereinafter, the differences from FIG. 7 will be described.
1 to 7 are omitted, and a Pt-Rh alloy wire 2 serving as heater energizing terminals 2a and 2b (FIG. 10) is provided from a side closer to the electrode pattern 223.
57a, 257b, bonding coat 256 (using Al ₂ O ₃ paste or the like), auxiliary support pattern 255 for gap formation
(By carbon paste etc.), overcoat 254
(Using Al ₂ O ₃ paste, etc.), heater pattern 253
(Using Pt paste or the like), insulating coat 252 (Al ₂
O ₃ by paste or the like), ZrO ₂ green sheet 251
(To be the heater body) and overcoat 250 (A
l by ₂ O ₃ paste or the like) is the fourth part 214 are laminated in this order is formed. In addition, the support part 210 is shown in FIG.
Are omitted in the same manner as in the above configuration. Here, the gap-forming auxiliary support pattern 255 is selectively formed in a region corresponding to the outer electrode 10 with respect to the electrode pattern 223, disappears at the time of firing, and is formed on the ZrO ₂ green sheet 251 as shown in FIG. The gap 14 is formed between the heater element 2 and the first element 3 based on the above.

FIG. 12 shows a configuration example of an exhaust gas sensor that does not use a spacer portion as a simpler configuration. That is, in the exhaust gas sensor 1, the first element 3 and the second element 4 are each formed in a horizontally long plate shape and arranged to face each other, and the electrodes 10 to 13 are connected to the first element 3 and the second element 4 respectively. Is formed on one end side in the longitudinal direction of the plate surface. And, in the gap 15, between the first element 3 and the second element 4,
On the other hand, the first element 3 and the second element 4 are joined and integrated with each other via an insulating layer 260 having a thickness smaller than the height of the support portion 210 in a region excluding the gap 15 while 0 is formed. . Although at least one of the first and second heaters 2 and 5 is provided, FIG. 12 omits this.

The gap 15 is open to both sides in the width direction of the stacked body of the first element 3 and the second element 4 to form a communication part 261 through which exhaust gas can enter and exit. Each electrode 1
The terminals 10b, 11b, 13b of 0 to 13 are connected to the first element 3
On the end face side in the longitudinal direction of the second element 4, the base end side projects so as to be sandwiched between them. The connection form of the terminals 10b and 13b to the electrodes 10 and 13 is the same as that shown in FIG. Further, since the electrodes 11 and 12 are commonly grounded as described later, the terminal 11b is shared between the electrodes 11 and 12, and the terminal 12b in the configuration of FIG. 2 is omitted. Also,
As shown in FIG. 12 (c), the support portion 210 has a rectangular cross section formed in a scattered or staggered shape, but may be formed in a circular cross section as shown in FIG. Alternatively, as shown in FIG. 11E, the components may have a rectangular cross section having different lengths.

FIG. 13 shows a method of manufacturing the above sensor structure.
This will be described with reference to FIG. Also in this case, basically, the unfired assembly 31 including the first portion 211 and the second portion 212 described above.
0. However, there is a difference in the following manufacturing method from the sensor structure shown in FIG. First, the third portion including the ZrO ₂ green sheet for forming the spacer portion is omitted, and instead, the ceramic powder is provided in a region scheduled for the gap 15 on each of the opposing surfaces of the first portion 211 and the second portion 212. Using a paste (for example, a porous Al ₂ O ₃ powder paste),
Support column patterns 266a and 266b to be 10 are formed. In addition, the strut portion patterns 266a and 266a
66b at a position where it does not overlap with 66b.
The auxiliary support patterns 267a and 267b are formed in a region designated as No. 5 by a powder paste (for example, carbon paste) of a material which burns or decomposes during firing. Further, a bonding coat 269 as an insulating layer pattern is provided on the other area except the area planned for the gap 15.
It is formed by l ₂ O ₃ powder paste or the like with a thickness smaller than the total height of the pillar patterns 266a and 266b.

By firing the unfired assembly 310, as shown in FIG. 15, between the second element 4 and the first element 3, the auxiliary support patterns 267a and 267 are provided.
b disappears, and the above-mentioned strut pattern 266a,
The support portion 210 is formed by integrating the 266b by firing, and the gap 15 is formed in a form in which the size is defined by the support portion 210. On the other hand, in the other region except the gap 15, the second element 4 and the first element 3 are bonded to each other via an insulating layer 260 based on the bonding coat 269.

Here, as shown in FIG. 14, the support portion patterns 266a and 266b and the auxiliary support patterns 267 are provided.
a and 267b are formed complementarily so as to almost completely fill the plane, and when the first portion 211 and the second portion 212 are stacked, based on the reinforcing effect of the auxiliary support patterns 267a and 267b, the support portion patterns 266a and 267b are formed. 266b is prevented or suppressed from being crushed between them. Also,
The main part of the first part 211 and the second part 212 is Zr
Because O ₂ has been formed in the green sheets 220 and 230, as shown in exaggerated in FIG. 15 (a), even laminating coat 269 266a, were considerably thinner than the total thickness of the 266b, ZrO _{When the two} green sheets 220 and 230 are slightly bent, they can be adhered to each other via the bonding coat 269, and can be integrated without any trouble by firing.

FIG. 16 shows a modification of the sensor structure obtained by a manufacturing method similar to that shown in FIG. In this configuration, the communicating portion of the gap 15 is not an open portion,
Porous ceramic body 270 made of porous Al ₂ O ₃ fired body
Is configured as Further, the support portion 210 is not formed.

A method of manufacturing the above structure will be described with reference to FIG. 17 focusing on differences from FIG. First, FIG.
Communication part pattern 2 for forming the porous ceramic body 270 in place of the pillar part patterns 266a and 266b of FIG.
The gap forming portions 71a and 271b are formed of a porous Al ₂ O ₃ powder paste, and the gap forming auxiliary support patterns 272a and 272b of carbon paste are formed in the gap forming portion as in FIG. By firing this, the communication portion patterns 271a and 271b are integrated into a porous ceramic body 270, and the gap-forming auxiliary support patterns 272a and 272b disappear to form the gap 15.

Hereinafter, a sensor system using the exhaust gas sensor will be described. FIG. 18 is a block diagram showing an electrical configuration of an example of a sensor system using the exhaust gas sensor 1. That is, the sensor system 50
Are the exhaust gas sensor 1 and the microprocessor 51
And the exhaust gas sensor 1 and the microprocessor 51
And a peripheral circuit 50a for connecting the two. Note that the CPU 53 of the microprocessor 51 has a ROM 5
5, the element control means, the density detection information output means, the specific component detection information generation /
Output means, detected component concentration information correction means, conduction control means, pump current correction amount determination means, correction calculation means, correction concentration information generation means, internal resistance measurement means, temperature information generation means, concentration cell electromotive force measurement means, and voltage It is the main body of information correction means and the like.

The second element 4 of the exhaust gas sensor 1 is
2 is grounded, while the electrode 13 is connected to the switch Sw of the analog switch circuit 500 as a control mode switching means.
When the switch 5 is on, it is connected to the output side of the operational amplifier 61. Similarly, when the switch Sw4 is on, the operational amplifier 61 is connected via the switch Sw1 of the analog switch circuit 60.
(Pump current control means) is connected to the negative terminal side (where Sw4 and Sw5 are always turned off when one is turned on). The electrode 11 side of the first element 3 is commonly grounded to the electrode 12 of the second element 4, but the electrode 10 is connected to the switch Sw6 of the switch circuit 500.
Is connected to the output side of the operational amplifier 61 when
Similarly, when the switch Sw7 is on, the switch circuit 6
The switch Sw1 of 0 is connected to the negative terminal side of the operational amplifier 61 (pump current control means) (here, when one of Sw4 and Sw5 is turned on, the other is always turned off).

The operation of the switch circuit 500 is controlled by a control signal from the microprocessor 51. Then, the microprocessor 51 transmits a switch signal to the switch circuit 500 via the switch control unit 501 by using one of the H and L signals corresponding to the first mode and the second mode, respectively. This signal is transmitted to, for example, the buffer 502 (which may be omitted)
Non-inverted input to w4 and Sw6, and inverter 503
, And are inverted and input to Sw5 and Sw7. This allows
As for the set of Sw4 and Sw6 and the set of Sw5 and Sw7, those in the set are turned on or off at the same time, and if one set is turned on between the sets, the other set is always turned off. When Sw5 and Sw7 are on, the first mode becomes the first mode in which the first element 3 becomes the oxygen concentration cell element and the second element 4 becomes the oxygen pump element, and when Sw4 and Sw6 are on, It becomes the opposite second mode.

A power supply circuit 65 for providing a target electromotive force value EC is connected to the positive terminal side of the operational amplifier 61.
The power supply circuit 65 is configured so that the set value of the electromotive force target value EC can be changed within a certain range. For example, in the example shown in the figure, the bridge circuit 66 includes three fixed resistors 66a to 66c and one variable resistor 66d on each side, and a power supply 67 connected thereto. When the resistance range of the variable resistor 66d is Rmin to Rmax, Rmin <
The resistance values of the fixed resistors 66a to 66c are adjusted so that the bridge is balanced at a certain resistance value Re satisfying Re <Rmax, and the output voltage to the terminal of the operational amplifier 61 becomes zero. By shifting the resistance value of the variable resistor 66d from Re to the Rmin or Rmax side, the electromotive force target value EC can be changed within a certain range on both the positive and negative sides of 0V.

The operational amplifier 61 includes peripheral resistors 61a to 61a.
61d constitutes a differential amplifier, the output side of which is connected via a current detecting resistor 62 to the side of the first and second elements 3 and 4 which does not face the gap 15 of the element to be an oxygen pump element. (That is, the electrode 13 in the first mode and the electrode 10 in the second mode). On the other hand, on the negative terminal side of the input, the electrode on the side of the first and second elements 3 and 4 that does not face the gap 15 of the element to be an oxygen concentration cell element (that is, the electrode 10 and the second electrode in the first mode). In the mode, it is connected to the electrode 13). Thereby, the operational amplifier 6
1 is a concentration cell electromotive force input Em of the oxygen concentration cell element,
The difference voltage Em−EC from the electromotive force target value EC is inverted and amplified,
The output voltage is applied to the electrode not facing the gap 15 of the oxygen pump element.

For example, in the second mode, as shown in FIG. 19, if Em> EC, Em−EC> 0, so that the output voltage −A1 (Em−EC) of the operational amplifier 61 becomes negative and the first element A voltage is applied to the first element 3 so that the first electrode 11 side becomes negative, and a pump current Ip flows through the first element 3 in a direction to pump oxygen into the gap 15. The pump current Ip is represented by a voltage difference between both ends of the current detecting resistor 62 (resistance value R3).
It is taken out as a voltage signal by an operational amplifier 64 constituting a differential amplifier together with the peripheral resistors 64a to 64d,
Further, as shown in FIG. 18, the data is digitized by a dipolar A / D converter 70 and input to the microprocessor 51.

Returning to FIG. 18, next, each of the electrodes 10 to 13
Among them, the current value I is supplied to the third electrode side (electrode 13 in the second mode, electrode 10 in the first mode) of the oxygen concentration cell element via Sw2 and Sw3 of the analog switch circuit 60.
Constant current power supply circuits 73 and 74 having different polarities at C are connected to each other. Further, the voltage signal VS on the third electrode side is digitally converted by a dipolar A / D converter 71 and input to the microprocessor 51. The switches Sw1 to Sw3 of the analog switch circuit 60 are turned on / off in response to a control signal from the microprocessor 51.

The first and second heaters 2 and 5 of the exhaust gas sensor 1 are connected to the microprocessor 51 via, for example, a common heater energizing circuit 72. FIG.
0 (a) shows an example of the heater energizing circuit 72. The heater energizing circuit 72 includes a D / A converter 80 for performing analog conversion of a heater control value provided from the microprocessor 51, and a current amplifying transistor 8 connected thereto.
The heaters 2 and 5 are connected to the transistor 82. The transistor 82 operates in the active region, and increases the current flowing through the heaters 2 and 5 according to the applied heater control value.

On the other hand, FIG. 20B shows a PWM (pulse wi)
dth modulation) Heater energizing circuit 7 adopting control method
2 shows an example. The main component of this circuit 72 is a PWM control circuit 85, which
/ A to convert the heater control value given from
A converter 86, a triangular wave (or sawtooth wave) generating circuit 87, their D / A converter 86 and a triangular wave generating circuit 8
Single-power-supply operational amplifier 8 to which outputs from 7 are input respectively
8 is included. Single power supply operational amplifier 88
Operates as a comparator that outputs either zero or a non-zero predetermined voltage V in accordance with the magnitude relationship between the heater control value and the triangular wave input value. If the value is large, zero is output). Hereinafter, the operational amplifier 88 is referred to as a comparator 88.

FIG. 20C shows a triangular wave generating circuit 8.
7 includes an operational amplifier 89 functioning as a comparator, and an integration circuit 100 including an operational amplifier 98, a resistor 97, and a capacitor 99. The operational amplifier 89 outputs positive and negative maximum voltages according to whether the voltage addition value at points A and B in the drawing is positive or negative. The output voltage of the operational amplifier 89 is a square wave having a constant value VZD of positive and negative voltages with respect to 0 V by the diode groups 92 to 95 and the Zener diode 96. Is converted to The period λ of the triangular wave (FIG. 21) can be adjusted according to the resistance value of the resistor 97 of the integrating circuit 100 and the capacitance of the capacitor 99. The generated triangular wave is amplified to a predetermined amplitude by the operational amplifier 101, and is amplified by the comparator 88 shown in FIG.
Is output to

FIG. 21 is a diagram for explaining the operation of the PWM control circuit 85. In the input of the comparator 88, the output of the comparator 88 is + V during the period when the heater control voltage Vi is smaller than the triangular wave input Vt. Otherwise, it is 0. Thereby, the comparator 8
8 has a duty ratio of {(Vi + Vmax) / 2Vmax} × λ.
(However, -Vmax ≦ Vi ≦ + Vmax, where Vmax is the maximum amplitude of the triangular wave input). This P
The transistor 82 in FIG. 20B is switched at high speed by the WM wave output, and the heaters 2 and 5 are intermittently energized by the duty ratio. Then, the heat generation of the heaters 2 and 5 is adjusted by changing the duty ratio according to the heater control voltage value Vi.

Next, the microprocessor 5 shown in FIG.
Reference numeral 1 denotes an I / O port 52 serving as an input / output interface with the peripheral circuit 50a, and a CPU 5 connected thereto.
3, a RAM 54, a ROM 55, a clock circuit 56, and the like. The RAM 53 has a CPU 53
A work area 54a and a measured value memory area 54b for storing data of various measured values taken in processing to be described later or various counter values generated in the course of control processing to be described later are formed. ROM5
5 includes a control program 55a for calculating the output value of the detected component of the sensor system 50 and controlling the output thereof.
Correction reference information 55b used by the control program 55a
(Details of which will be described later) are stored. Also,
The CPU 53 realizes a timer function for measuring time used in processing described later by counting clock pulses of a fixed period generated by the clock circuit 56.

Hereinafter, the operation of the sensor system 50 will be described with reference to the processing flow viewed from the CPU 53 of the microprocessor 51. 30 to 32 show flowcharts thereof. First, in S0 of FIG. 30, an activation process of the exhaust gas sensor 1 is performed. The purpose of the activation process is to start energization of the heaters 2 and 5 and to stabilize the first element 3 and the second element 4 at a predetermined operating temperature. Then, the element temperature is detected by measuring the internal resistance of the first element 3 or the second element 4, and the internal resistance RVS is calculated as shown in FIG.
(In the following, in the present embodiment, the internal resistance is measured using the second element 4).

FIG. 31 shows the details of the processing. That is, in S101, the desired set value Vh0 is set in the heater energizing circuit 72 as the control value Vi. At this time, all of the switches Sw1 to Sw3 of the analog switch circuit 60 are turned off, and the operational amplifier 61 is also turned off. In this state, S10
2, the heater control voltage value Vi is supplied to the heater energizing circuit 72.
By outputting the initial set value Vh0, the energization of the heater is started. Then, in step S103, when a predetermined time t0 has elapsed from the start of energization, a temperature control process is started. First S10
In step 4, Sw2 of the analog switch circuit 60 in FIG. 18 is turned on, and the activation determination counter value N is cleared in step S105 in FIG.

Then, the flow advances to S106, where the value of the voltage VS on the electrode 13 side of the second element 4 is converted to an A / D converter 71 (FIG. 18).
The internal resistance RVS of the second element 4 is calculated from the value of VS in S107. That is, since Sw1 is off and the operational amplifier 61 is also inactive, the operation of the constant current power supply 73 (current Ic: current for detecting internal resistance) forms an energization path shown in FIG. . Here, since the electrode 12 side of the second element 4 is grounded, the voltage VS on the electrode 13 side is represented by VS = IC · RVS ‥‥‥ (1), where RVS is the internal resistance of the second element 4. Is done. Further, VS has a meaning as voltage information applied to the second element 4, and the internal resistance value RVS can be obtained by RVS = (VS / IC) ‥‥‥ (2). Note that strictly speaking, the concentration cell electromotive force Em of the second element 4 is superimposed on the voltage VS. However, in this activation process, the current Ic is sufficiently large.
Since the concentration cell electromotive force Em is negligible compared to the partial pressure applied to the second element 4, the correction is not performed. However, the correction may be performed by a method described later.

As described above, as shown in FIG.
The value of RVS has a certain relation with the element temperature T of the second element 4, and this relation is used as the correction reference information 55b in the ROM 55.
(FIG. 18), the element temperature T can be calculated from the value of RVS.
Can be determined. Further, the value of RVS itself can be used as temperature information. In this embodiment, in order to make the description easy to understand, as shown in FIG. The temperature T corresponding to RVS is obtained by interpolation with reference to the map 301 (S107).
Note that the calculated value of the internal resistance RVS is stored in the measured value memory area 54b of FIG. 18, and is overwritten and updated when a new internal resistance RVS is detected and calculated.

The determined element temperature T is equal to the upper limit value Tma.
It is determined in S108 and S110 whether or not the temperature falls within the set temperature range of x and the lower limit value Tmin. When the element temperature T is higher than the upper limit value Tmax, the heater control voltage value Vi decreases by a certain value ΔVi to suppress the heat generation of the heaters 2 and 5, and conversely, when the heater control voltage value Vi is lower than the lower limit value Tmin. The heater control voltage value Vi increases by ΔVi and the heaters 2, 5
Is promoted (S109, S111). Also, T
If min ≦ T ≦ Tmax, the current value of Vi is maintained, and the activation determination counter value N is incremented (S112,
S113).

Then, the value of the activation determination counter value N becomes
For example, until the set value NS is reached, the above S106 to S1
13 is repeated at fixed time intervals ta (S114,
S115) If N reaches NS, it is considered that the element temperature T has been substantially maintained within the set temperature range, and FIG.
At the time, Sw2 of the analog switch circuit 60 is turned off.
After turning on w1 and further warming up the operational amplifier 61 for a predetermined period of time tw, the activation process ends (S116, S117).

Returning to FIG. 30, when the activation process S0 is completed, the process proceeds to S1, where Sw4 and Sw6 of the switch circuit 500 are turned on to set the mode to the second mode. And S2
The detection of the pump current Ip of the first element 3 is started. In this state, the analog switching circuit 60
Since only 1 is on, the energization path is as shown in FIG. The operation of the sensor 1 in this state will be described below.

That is, as the sensor 1 comes into contact with the exhaust gas, a hydrocarbon such as methane (hereinafter referred to as HC) as a detected component reacts with oxygen in the gap 15 to reduce the oxygen concentration. Then, a concentration cell electromotive force Em having the third electrode 13 side positive is generated in the second element 4. Here, the target electromotive force value EC input to the operational amplifier 61 is, for example, 0
Since Em−EC> 0, the output voltage −A1 (Em−EC) of the operational amplifier 61 becomes negative, and a voltage is applied to the first element 3 so that the first electrode 11 side becomes negative. Then, a pump current Ip flows through the first element 3 in a direction to pump oxygen into the gap 15. Then, the pumping of oxygen into the gap 15 by the first element 3 proceeds, and the concentration cell electromotive force Em gradually decreases, so that the oxygen pump current Ip is controlled to decrease. As a result, the oxygen pump current is finally controlled so that the concentration cell electromotive force Em approaches substantially zero, and the concentration of the detected component can be known from the equilibrium value of the oxygen pump current Ip at that time. As described above, the signal of the pump current Ip is converted into a voltage signal by taking the difference between the voltages at both ends of the current detecting resistor 62 by the operational amplifier 64, digitized by the A / D converter 70, and input to the microprocessor 51. Is done. However, the electromotive force target value EC is not always set to 0 in practice.
The reason will be described below.

First, the fact that the electromotive force of the concentration cell is 0 means that, theoretically, both sides of the second element 4 (that is, the gap 15
And 16) mean that the oxygen concentrations are equal. This also means that the pump current directly corresponds to the difference in the amount of the detected component between the gaps 15 and 16, so that the concentration of the detected component can be accurately detected, and the detection result Analysis is also easier. However, usually, even if the oxygen concentrations in the gaps 15 and 16 are equal,
The electromotive force of the second element 4 does not actually become 0, and a constant offset electromotive force often remains. In this case, the target electromotive force EC corresponding to the offset electromotive force is set to 10 mV.
By setting as a detection signal the current value flowing in the first element 3 when the absolute value of the electromotive force of the concentration cell reaches the target electromotive force value EC, the detected component in the exhaust gas is set in the following range. Can be detected more accurately.

Further, the offset electromotive force of the second element 4 is:
The lower the oxygen concentration in the exhaust gas involved in the detection becomes, the more likely it is to fluctuate. If the electromotive force target value EC is set on the basis of the offset electromotive force at an oxygen concentration equal to or less than a certain value, the sensor output will be affected by the oxygen concentration in the exhaust gas. Easier to receive. Therefore, oxygen is added to, for example, 1% by volume or more (preferably 1% by volume).
EOS (unit: mV) when a test gas containing at least 0% by volume and containing substantially no component that reacts with oxygen at the sensor operating temperature is introduced into the gaps 15 and 16, respectively. ), And the electromotive force target value EC is set to (EOS-5) mV or more (EOS +
5) It is effective to set within the range of mV or less.

The change and adjustment of the electromotive force target value EC can be performed by adjusting the variable resistor 66d of the power supply circuit 65 as described above. In addition, even if the offset electromotive force of the second element 4 has a different value for each second element 4, the same second element 4 may continue to show a stable value for a relatively long time. Many. Therefore, the variable resistor 66d is
For example, when the device 50 is shipped, if the resistance value is once adjusted according to the unique offset electromotive force of the second element 4 being used, it is sufficiently considered that the necessity of the change is eliminated. Can be In this case, it is convenient if the variable resistor 66d is constituted by a semi-fixed resistor.

Returning to FIG. 30, when the value of the pump current Ip is detected, the concentration of the detected component corresponding to the pump current Ip is determined. However, the pump current Ip
Is changed by the element temperature T, the correction is performed as follows. First, the value of the internal resistance value RVS of the second element 4 stored in the RAM 54 (FIG. 18) is read, and the corresponding temperature T is determined with reference to the aforementioned map 301 (FIG. 24) (FIG. 30: S3). The pump current correction amount ΔIp for each temperature with respect to the value of the pump current Ip
Can be experimentally determined, for example, in the form as shown in FIG. 25 (b), so that the value of each ΔIp and the element temperature T
Map 302 (FIG. 26) showing the values of
Is created on the basis of this, and stored in the ROM 55 (correction reference information storage means), each pump current correction amount ΔIp is referred to this map 302 (temperature deviation-pump current correction amount relation information). It can be determined by an interpolation method (FIG. 30: S4). As shown in FIG. 29A, a map 302a in which the internal resistance value RVS directly corresponds to the pump current correction amount ΔIp is stored, and the correction amount ΔIp is directly determined from the value of the internal resistance value RVS. You may do so.

Next, the routine proceeds to S5, where the pump current correction amount ΔI
p is added to the actually measured pump current Ip to correct the same, and the HC concentration CHCB as the detected component concentration corresponding to the corrected pump current Ip 'is determined. In this case, since the mode is the second mode, the HCCB corresponds to the total HC concentration (in the map, the HC concentration is simply described as CHC for the purpose of describing the operation of the first mode). The value of the HC concentration CHCB with respect to the value of the various pump currents Ip 'can be determined by referring to, for example, a map 304 (stored in the ROM 55) which gives a relationship between the pump current Ip' and the HC concentration CHCB as shown in FIG. , Can be determined by an interpolation method. Thus, if the HC concentration CHCB is determined, S
At 6, this is output as a temperature compensated density detection value.

As shown in FIG. 29 (b), a two-dimensional map 302b (pump current information-Pc) showing the pump current Ip and the HC concentration CHC in association with each other for various values of the element temperature T. Based on the detected component concentration relationship information), the value of the HC concentration CHCB corresponding to the combination of the detected value of the pump current Ip and the value of the element temperature T may be directly determined by two-dimensional interpolation. . Alternatively, the value of the pump current Ip which has been temperature-compensated by the above-described method may be output as it is. On the other hand, when the influence of the temperature fluctuation on the pump current Ip is not so problematic, it is possible to adopt a configuration in which the above-described temperature compensation processing by the microprocessor 51 is not particularly performed. In this case, the microprocessor 51 is omitted, and the operational amplifier 51 is omitted.
Can function as density detection information output means.

Then, the flow advances to S7 in FIG. 30, where Sw5 and Sw7 of the switch circuit 500 are turned on to set the mode to the first mode. Then, proceed to S8, and thereafter up to S12,
The oxygen pump element becomes the second element 4, the oxygen concentration cell element becomes the first element 3, and the pumping direction of oxygen by the oxygen pump element is from the gap 16 side to the gap 15 side. Then, at S8, the pump current I of the second element 4 is obtained.
The detection of p ″ is started, and the internal resistance value RV of the first element 3 is determined in S9.
S ′ is read, and a correction amount of Ip ″ is calculated in S10. From the Ip ″ corrected in S11, a CH concentration output value CHCA (corresponding to the methane concentration) is calculated, and S1 is calculated.
This is output in step 2. In S13, non-methane HC
The density value CHCC is calculated from CHCB-CHCA, and is output in S14. 27 to 29 are separately stored also for the first mode (in this case, the contents of the map are generally different from those of the second mode). Thereafter, the process returns to S1 and the following processing is repeated.

Next, after the element temperature T is set during the activation process, the control is continued in parallel with the hydrocarbon concentration detection process. FIG. 32 shows the flow of the processing. That is, the processing routine is periodically executed by the CPU 53 by time measurement based on a clock pulse (by the clock circuit 56 (FIG. 18)) as an interruption processing routine for the routine of FIG.
The cycle of the execution can be set, for example, in the range of 0.3 to 1 ms. If the execution cycle exceeds 1 ms,
In some cases, it may not be possible to sufficiently secure the accuracy of concentration measurement by the temperature measurement and by the sensor. On the other hand, when the time is less than 0.3 ms, the ratio of the temperature measurement processing to the processing time of the CPU 53 becomes too large, and the operation stop time of the oxygen pump element becomes long, so that sufficient concentration detection accuracy may not be secured. However, by using a CPU 53 that can perform high-speed processing, such as one with a high clock frequency, the execution cycle may be less than the above value. Note that FIG.
The Sw of the analog switch circuit 60 in the processing
The operation timing chart of 1 to Sw3 is shown by the second element 4 to be detected.
And the voltage signal VS on the third electrode 13 side.

First, in S201, while Sw1 of the analog switch circuit 60 in FIG.
The voltage signal VS on the third electrode 13 side of the second element 4 is read and stored in the measured value memory area 54b of the RAM 54 as the detected value VS1. This voltage signal VS has a value corresponding to the concentration cell electromotive force Em input to the operational amplifier 61. Next, in S202, Sw1 is turned off, and Sw2 is turned on instead. Then, the current path becomes as shown in FIG. 22 and the constant current IC for detecting the internal resistance is supplied to the second element 4. Then, the voltage signal VS is read after a lapse of a fixed time t1 from the start of the supply of the constant current IC, and is read as the detected value VS2.
b (S203, S204). As described above, the voltage signal VS at this time reflects the internal resistance of the second element 4, but the voltage signal VS has a form in which the concentration cell electromotive force Em of the second element 4 is superimposed or included. I have. Therefore,
By taking the difference between VS2 and VS1, the concentration cell electromotive force E
The influence of the m component can be removed (S209).

Here, the reason why VS is measured after a lapse of a fixed time t1 from the start of the application of the constant current IC is as follows. That is, when a constant current IC is applied to the second element 4,
Oxygen is transported in the second element 4 in a direction opposite to the current flow (that is, in a direction from the gap 16 side to the 15 side), and the oxygen concentration on both sides of the second element 4 changes. As a result, as shown in FIG. 23, the value of the concentration cell electromotive force Em and thus the value of VS also change with the continuation of the current IC. Here, in order to ensure the accuracy of the internal resistance measurement, it is important that the change in VS unavoidably caused by energization is always substantially constant. Since a constant current IC is used as the current for measuring the internal resistance, if the energization time until the measurement of VS is controlled to be always t1, the oxygen transport amount, that is, both sides of the second element 4 can be controlled. The change in the oxygen concentration is also substantially constant, and the change in the electromotive force Em of the concentration cell and thus the change in VS can be substantially constant. If the switching speed of the analog switch circuit 60 is sufficiently high and the current level after the switching of the energizing path is sufficiently fast, VS may be measured immediately after the start of energization of the constant current IC.

Next, the supply of the constant current IC causes a change in the oxygen concentration on both sides of the second element 4. Another problem is that when the exhaust gas sensor 1 returns to the measurement of the hydrocarbon concentration, the oxygen concentration changes. May affect the measurement accuracy of the concentration of the detected component. When the internal resistance value of the second element 4 is high, oxygen ions in the second element 4 are difficult to move, and polarization may occur with the passage of current. In order to solve this problem, this embodiment employs the following method. That is, S205 in FIG.
In steps S208 to S208, after a certain period of time t2 has elapsed after the detection of VS, the switch SW2 is turned off to terminate the supply of the constant current IC. On the other hand, the switch Sw3 is turned on. The energizing means) energizes a correction current IA having the same magnitude in the opposite direction to IC for a time t3 substantially equal to the total energizing time t1 + t2 of IC, and then turns off Sw3. As a result, approximately the same amount of oxygen is transported in the second element 4 in the opposite direction to the above, and the oxygen pumped from the gap 16 side to the gap 15 side by IC energization is, so to speak, pumped back. It can approach the state before the internal resistance measurement. When it is determined that the influence on the oxygen concentration change on both sides of the second element 4 is small, for example, when the energizing time of the current IC for measuring the internal resistance of the second element 4 can be sufficiently shortened, as shown in FIG. In addition, it is possible to omit the constant current power supply 74 for generating the correction current IA (corresponding to this, the analog switch circuit 60 may have a smaller number of switch channels).

Referring back to FIG. 32, when the supply of the correction current IA is completed, the difference ΔVS between VS2 and VS1 is determined in S209 as described above.
Is calculated, and ΔVS is regarded as VS to calculate RVS according to the above equation (2). Hereinafter, the process from S210 to S215 for determining the element temperature T from RVS and determining the heater control voltage value Vi based on it is almost the same as the process from S107 to S112 in the sensor activation process of FIG. The description is omitted. Then, at time S216, time t4
After waiting for only this time, Sw1 is turned on in S217, and the internal resistance measurement processing ends. Thereafter, the hydrocarbon concentration measurement processing routine of FIG. 30 is executed again. The measured value of the element temperature T is updated every time the internal resistance measurement processing is performed, and the updated information of the element temperature T is always used in the hydrocarbon concentration measurement processing routine of FIG. Further, the heater temperature is also periodically corrected based on the measured value of the element temperature T.

Accordingly, the temperature of the second element 4 is accurately maintained at the set value by the heaters 2 and 5, and the measurement accuracy of the carbide concentration in the exhaust gas is improved. Also, as shown in FIG. 25, even when the exhaust gas temperature changes suddenly when the vehicle engine or the like is rapidly accelerated and decelerated, the temperature T of the second element 4 correspondingly changes suddenly, By correcting the temperature change of the oxygen pump current Ip, the element temperature T
, It is possible to continue the measurement of the carbide concentration with relatively high accuracy without waiting for the return.

The internal resistance measuring process can be executed as a subroutine of the measuring process routine instead of an interrupt routine for the hydrocarbon concentration measuring process routine. An example of a flowchart in this case is shown in FIG. Determination of S0-S14 hydrocarbon concentration
The output processing is exactly the same as that of FIG.
The difference is that the measurement counter Nm is incremented each time the process is completed by adding steps 01 to S303. Then, when Nm reaches the predetermined count number Nq in S302, the same internal resistance measurement processing as that shown in FIG. 32 is executed in S304. After execution of the internal resistance measurement processing, S301
Then, the measurement counter Nm returns to 1, and the same processing is repeated thereafter. In this method, there is no difference in that the internal resistance measurement process is performed periodically, but the feature is that the measurement process of the hydrocarbon concentration is not necessarily performed at a fixed time interval, but is performed every time a predetermined number of processes are completed. is there. This prevents the hydrocarbon concentration measurement process from being interrupted due to the internal resistance measurement process, and reduces the frequency of occurrence of errors and the like.

As shown in FIG. 28, the internal resistance RVS
The map 305 storing the value of the control voltage value Vi to be given to the heater energizing circuit 72 is stored in association with the various values of the above. By referring to this, the map 305 is determined according to the value of the internal resistance RVS (that is, the element temperature T). Thus, the value of the control voltage value Vi may be determined irrespective of the current voltage value.

Further, the constant current generating circuit shown in FIG.
Instead of using two units, 3 and 74, one unit may be used by switching the polarity as needed using a polarity switching circuit (not shown). The microprocessor 5
A circuit that can generate a current according to the current value and the polarity instructed from the one side may be used. One example is shown in FIG. That is, in this configuration, the voltage / current conversion circuit 189 is used instead of the constant current generation circuits 73 and 74.
Is used.

In this circuit 189, the current instruction voltage Vi from the microprocessor 51 is input to the operational amplifier 191 via the D / A converter (dipolar type) 190, and the current is supplied to the output side of the operational amplifier 191. A resistor 195 for detection is connected, and a voltage drop in the resistor 195 due to the output of the operational amplifier 191 is fed back via a voltage follower 192. As a result, the voltage drop at the resistor 195, that is, the current value IO is maintained at a constant value according to the input voltage Vi regardless of the connected load. In the figure, the resistance values of the resistors 193 and 194 are Rf,
If Rk and the resistance value of the resistor 195 are RS, then IO = (Vi × Rf) / (Rk × RS) ‥‥‥ (3) In this case, the current IC for measuring the internal resistance is generated by the predetermined current instruction voltage Vi, and the correction current is given a current instruction voltage Vi ′ having a polarity opposite to that of the voltage Vi, so that the current IC has a direction opposite to the current IC. It can also be generated as a current. Also, the current level to be generated and the current supply time can be freely set by changing the current instruction voltage value and the output time from the microprocessor 51 side.

Hereinafter, various modifications of the exhaust gas sensor of the present invention will be described. First, an electrode having a low oxidation catalyst activity, such as the electrode 13 in FIG. 1, as shown in FIG.
Pt, Rh, Pd, Ir, etc., which belong to the highly active metal group, form the main body 101 of the porous electrode, and a catalytically inactive material (for example, Au or Those belonging to the low activity metal group such as Ag-based metals, or SnO ₂ , ZnO, In ₂
A coating 102 of an oxide such as O ₃ , WO ₃ , Bi ₂ O ₃ ) may be applied to form a final electrode.

In this case, the coating 102 is formed by, for example, a method of applying a paste containing the above-mentioned catalyst-inactive material particles to the main body 101 and re-firing as shown in FIG. Alternatively, as shown in FIG. 3C, the film can be formed by a vapor deposition method such as vacuum evaporation or sputtering. As shown in FIGS. 37 (b) to 37 (c), the porous main body portion 1 is formed.
In FIG. 01, since a large number of voids P are formed in a complicated manner, the coating 102 may not necessarily be formed deep inside the voids P. However, the catalytic activity for the reaction between the component to be detected and oxygen is not limited. Can be made sufficiently small, such an uncoated portion may be formed.

As shown in FIG. 38, the gap 15 formed between the first element 3 and the second element 4 is made of a metal mesh or a porous metal (for example, Pt). The gas holding member 160 can be inserted. In addition,
When the gas holding member 160 is formed of a metal mesh, it is desirable to use a metal mesh having a formation density of 100 to 500 mesh.

Next, in the exhaust gas sensor 1 shown in FIG. 1 and the like, the gap 15 between the first element 3 and the second element 4
It is advantageous to improve the detection accuracy of the sensor 1 by minimizing the size (preferably 1 mm or less) and increasing the effect of restricting the flow of new exhaust gas by the gap 15 as much as possible. Conversely, if the size of the gap 15 is too large, the reaction between HC and oxygen on the electrode having catalytic activity (the second electrode 11 and the third electrode 12 in this embodiment) becomes unstable, The electromotive force of the oxygen concentration cell may become small and the sensor output may not be sufficiently obtained. However, if the amount of the gap 15 between the elements 3 and 4 is too small, the first element 3 and the second element 4
In the case of manufacturing the sensor, slight deformation at the time of firing has a great influence on the formation amount of the gap 15, and there is a case where the output varies between individual sensors. Hereinafter, a sensor structure effective to solve this problem will be described (note that parts common to the sensor structure already described are denoted by the same reference numerals and detailed description thereof is omitted).

That is, the exhaust gas sensor 4 shown in FIG.
In FIG. 00, a spacer 401 as a wall forming body is interposed between the second element 4 and the first element 3, and the spacer 401 has a thickness corresponding to the electrodes 11 and 12. A window 401a penetrating therethrough in the direction is formed. The spacer 401 forms a wall 401b surrounding the electrodes 11 and 12 by the window 401a. The space surrounded by the inner surface of the wall 401b and the opposing surfaces of the second element 4 and the first element 3 is a measurement chamber 403 (gap 15). Then, at a position corresponding to the measurement chamber 403, between the wall portion 401b and the first element 3, diffusion is provided on both sides in the width direction of the first element 3 so that the measurement chamber 403 communicates with the atmosphere to be detected outside. A slit 402 is formed as a flow restricting portion.

As shown in FIG. 39C, the slit 4
02 denotes a wall 401 on both sides of the second electrode 12 in the width direction.
b is formed in a form in which a portion on the lamination surface side of the first element 3 with the first element 3 is cut out by a constant thickness, and as shown in FIG. It extends in the longitudinal direction. Further, the width d is set smaller than the height h of the measurement chamber 403, and specifically, d / h is 1/100.
１ ／, more preferably 1/20 範 囲 1/8. The absolute value of the slit width d is 0.0
1 to 1.0 mm, more preferably 0.02 to 0.05 m
m. Further, the ratio S / V of the area of the inner peripheral surface of the slit to the space volume V in the slit 402
Is adjusted in the range of 4 to 100, preferably 20 to 50. The slit 402 may be formed between the wall 401b and the second element 4 in the same manner.

The spacer section 401 (wall section 401b)
Is formed on almost the entire lamination surface of the second element 4 and on the slit 402 of the first element 3.
Similarly, except for the formation region, almost all of the laminated surfaces are integrated by firing. Further, the first heater 2 and the second heater 5 are stacked on the first element 3 and the second element 4 via spacers 6 and 8, respectively.

An integrated laminate of the first element 3, the spacer section 401, and the second element 4, which are the main parts of the exhaust gas sensor 400, is formed by the same method as shown in FIG. , 4 by laminating and firing ceramic green sheets (compacts). At this time, the slit 402 is provided between the green sheet (ceramic molded body) to be the first element 3 and the green sheet to be the spacer.
If a layer of a predetermined thickness formed of a material (for example, carbon paste or the like) which is burned out at the firing temperature is sandwiched in a region where the formation of is formed, this layer is burned out during firing and the slit 402 can be easily formed. Can be formed.

By doing so, the height h of the measurement chamber 403
Even when the size of the gap 15 (that is, the size of the gap 15) is increased to a certain degree or more, the exhaust gas flows into the measurement chamber 403 while the diffusion is restricted by the slit 402, and
After being introduced into 3, it is discharged into the atmosphere to be measured while diffusion is also regulated through the slit 402. Therefore,
Even if the residence time of the exhaust gas once introduced in the measurement chamber 403 becomes longer and the exhaust gas composition (particularly the amount of oxygen or water vapor) in the detected atmosphere changes during that time, the influence on the gas in the measurement chamber is not affected. Since the size is reduced, the output of the sensor 400 is improved, and the detection accuracy of the sensor 400 can be improved. Further, since the first element 3 and the second element 4 are integrated via the spacer 401, the mechanical strength of the sensor 400 is increased.

Note that the measurement chamber having the same configuration is provided with the second element 4
And / or the electrode 10 of the first element 3. FIG. 40 shows an example thereof. That is, in the sensor 400 of FIG.
A gap forming ceramic plate 406 as a gap forming member is integrated through a spacer portion 404 having a spacer 04a, and the inner surface of the wall portion 404b formed by the spacer portion 404, the first element 3 or the second element 4, A measurement chamber 407 is formed by each of the surfaces facing the gap forming ceramic plate 406. In addition, a slit 405 similar to the second electrode 12 is formed between the wall portion 404b and the first element 3 or the second element 4 at a position corresponding to the measurement chamber 407. The first heater 2 and the second heater 5 are stacked on the gap forming ceramic plate 406. With this configuration, a more stable and high-output sensor can be realized.

It is to be noted that the diffusion control flow portion may be constituted by a small hole instead of the slit. For example, in the example shown in FIG. 45, a small hole 410 penetrating through the wall 401b in the plate surface direction of the first element 3 and the second element 4 extends along the circumferential direction of the first and second electrodes 11, 12. A plurality are formed at predetermined intervals. On the other hand, in the example shown in FIG. 46, a plurality of small holes 410 penetrating the second element 4 in the thickness direction are formed at predetermined intervals along the periphery of the third electrode 13.

Next, in the structure shown in FIG. 41, the spacer 401 is integrated with the second element 4 by firing, while the first element 3 is not integrated but separated. . In this case, the slit 402 is formed between the plate surface of the first element 3 and the opposing surface of the wall 401b. Further, the first heater 2, the first element 3, the second element 4, and the second heater 5 are stacked via spacers 6 to 8 to form a stacked body 31, and the rectangular through-hole 30a is formed.
The ceramic stopper 30 having the following structure is fitted to the laminate 31 from the outside. As shown in FIG. 41,
The spacer 7 is interposed between the spacer portion 401 and the first element 3 and plays a role of forming a slit 402 having a predetermined size between the two.

The assembly of the exhaust gas sensor 400 is as follows.
For example, it can be performed as follows. That is,
As shown in FIG. 42A, the elements 2 to 5 are
The laminated body 31 is formed by laminating the ceramic stoppers 8 through which the ceramic stopper 30 is fitted as shown in FIG. Subsequently, as shown in (c), a lead wire 37 made of, for example, stainless steel is joined to each connection terminal of the elements 2 to 5 by welding, and as shown in (d), the laminate 31 is connected to the insulator tube 3.
After filling the inside with glass powder, it is heated to 900 to 1000 ° C. in a predetermined furnace to melt the glass powder, and a glass seal is formed between the insulator tube 32 and the laminate 31.

Then, as shown in FIG. 43 (a), the porcelain tube 32 in which the laminated body 31 is integrated is disposed in the metal shell 34, and the caulking metal 36 is interposed between the porcelain tube 32 and the metal shell 34. Then, the outer tube 33 is put on the exposed portion of the insulator tube 32 from the metal shell 34, and then the metal shell 34 is
By caulking while heating toward 3, a caulked joint 34a is formed, and the metal shell 34 and the outer cylinder 33 are integrated. Subsequently, as shown in FIG. 2B, another lead wire group 37a in which the seal member 38 and the protective outer tube 39 are integrated is welded to the corresponding lead wires 37 (hereinafter, integrated). The reference numeral 37 is newly assigned to both the lead wires. Then, the sealing member 38 and the protective outer cylinder 39 are slid over the lead wire 37, and the end is inserted into the outer cylinder 33, and the two are caulked to form the state shown in FIG. 43 (c). Further, if the protector 35 is attached to the metal shell 34 by welding, the assembly of the exhaust sensor 400 is completed as shown in FIG.

In this case, as shown in FIG. 44, a configuration in which the measurement chamber 407 is formed on the electrode 10 to the electrode 13 side is also possible. That is, in the sensor 400 shown in the figure, the spacer 404 for forming the measurement chamber 407 is integrated on the electrode 10 to the electrode 13 side, and the inner surface of the wall 404b by the spacer 404 and the first element 3 to A measurement chamber 407 is formed by the second element 4 and the opposing surfaces of the first heater 2 to the second heater 5. A slit 405 is formed between the spacer section 404 and the first to second heaters 2 to 5. In this configuration, the first heater 2 or the second heater 5 plays the role of a gap forming member.

[Brief description of the drawings]

FIG. 1 is a plan view, a side view, and an AA cross-sectional view showing a main part of an example of an exhaust gas sensor of the present invention.

FIG. 2 is an explanatory diagram showing a detailed structure thereof.

FIG. 3 is an explanatory view showing an example of the assembly structure.

FIG. 4 is a diagram illustrating the operation of the sensor.

FIG. 5 is an exploded perspective view showing a method for manufacturing the exhaust gas sensor of FIG. 1;

FIG. 6 is a plan view, a side view, a sectional view taken along the line AA and a sectional view taken along the line BB showing a first modified example of the exhaust gas sensor shown in FIG. 1;

FIG. 7 is an exploded perspective view showing a method for manufacturing the exhaust gas sensor of FIG. 6;

FIG. 8 is a plan view, a side view, a sectional view taken along the line AA and a sectional view taken along the line BB showing a second modified example of the exhaust gas sensor of FIG. 1;

FIG. 9 is a plan view, a side view, and sectional views AA and BB of the third modified example.

FIG. 10 is a plan view, a side view, and an AA cross-sectional view showing a fourth modified example.

FIG. 11 is an exploded perspective view showing a method for manufacturing the exhaust gas sensor of FIG. 10;

FIG. 12 is a plan view, a side view, a cross-sectional view taken along the line BB, and a cross-sectional view showing some modified examples of the support portion of the fifth modified example of the exhaust gas sensor of FIG. 1;

13 is an exploded perspective view showing a method for manufacturing the exhaust gas sensor of FIG.

FIG. 14 is an explanatory view schematically showing an arrangement relationship between the support portion pattern and the auxiliary support pattern.

FIG. 15 is a diagram illustrating the operation of the auxiliary support pattern.

FIG. 16 is a plan view, a side view, and an AA cross-sectional view showing a sixth modification of the exhaust gas sensor of FIG. 1;

FIG. 17 is an exploded perspective view showing the method for manufacturing the exhaust gas sensor of FIG. 16;

FIG. 18 is a block diagram showing an electrical configuration of an example of an exhaust gas sensor system according to the present invention using the sensor.

FIG. 19 is a hydrocarbon concentration measurement mode (second mode)
FIG. 2 is a block diagram showing a circuit operation system in FIG.

FIG. 20 is a block diagram showing some examples of a heater energizing circuit.

FIG. 21 is an explanatory diagram of PWM control of a heater.

FIG. 22 is a block diagram showing a circuit operating system when measuring the internal resistance of the oxygen concentration cell element.

FIG. 23 is an operation timing chart of each switch when measuring the internal resistance of the oxygen concentration cell element.

FIG. 24 is a conceptual diagram of a graph showing an example of the relationship between the element temperature and the internal resistance of the oxygen concentration cell element, and a map showing the relation between the internal resistance of the oxygen concentration cell element and the element temperature.

FIG. 25 is a graph showing an example of a measurement example of a pump current change accompanying rapid acceleration or deceleration of an engine, and a graph showing an example of a relationship between an element temperature and a corrected pump current value.

FIG. 26 is a conceptual diagram of a map showing a relationship between an element temperature and a corrected pump current value.

FIG. 27 is a conceptual diagram of a map showing a relationship between a pump current value and an HC concentration.

FIG. 28 is a conceptual diagram of a map showing a relationship between an internal resistance value of the oxygen concentration cell element and a heater control voltage.

FIG. 29 is a conceptual diagram of a map showing the relationship between the internal resistance value of the oxygen concentration cell element and the corrected pump current value, and a conceptual diagram of a two-dimensional map showing the relationship between the element temperature, the pump current value, and the HC concentration.

FIG. 30 is a flowchart showing a control flow on the microprocessor side in the exhaust gas sensor system of FIG. 18;

FIG. 31 is a flowchart showing details of the sensor activation process.

FIG. 32 is a flowchart showing details of an internal resistance measurement process.

FIG. 33 is a flowchart showing the flow of another control mode on the microprocessor side in the exhaust gas sensor system of FIG. 18;

FIG. 34 illustrates the exhaust gas sensor system of FIG.
FIG. 4 is a block diagram in a case where a power supply for supplying a correction current is omitted.

FIG. 35 illustrates the exhaust gas sensor system of FIG.
FIG. 4 is a block diagram showing an example in which a constant current power supply for measuring internal resistance and supplying a correction current is replaced with a voltage-current conversion circuit.

FIG. 36 is an explanatory diagram of the operation of the first mode and the second mode of the exhaust gas sensor of the present invention.

FIG. 37 is an explanatory view of a method for producing a catalyst-inactive electrode by coating.

FIG. 38 is a schematic view showing an example in which a gas holding member is interposed between an oxygen pump element and an oxygen concentration cell element.

FIG. 39 is a plan view, a side view, and an AA sectional view showing an example of a sensor having a structure in which exhaust gas is introduced into a measurement chamber through a slit.

FIG. 40 is a plan view, a side view, and an AA sectional view showing the first modification.

FIG. 41 is a plan view, a side view, and an AA cross-sectional view showing the second modified example.

FIG. 42 is a process explanatory view showing an example of a method of assembling the sensor of FIG. 41;

FIG. 43 is an explanatory view of the step following FIG. 42;

FIG. 44 is a plan view, a side view, and an AA cross-sectional view showing a third modified example of the sensor of FIG. 39.

FIG. 45 is a partial plan view showing an example of a sensor having a structure in which exhaust gas is introduced into a measurement chamber through a small hole, and a BB cross-sectional view thereof.

FIG. 46 is a partial plan view and a bottom view showing the modification.

[Explanation of symbols]

1,400 exhaust gas sensor 3 first element 4 second element 10-13 electrode 15 gap 14,16 gap (opposite space) 50 sensor system 51 microprocessor 53 CPU (element control means, concentration detection information output means,
Specific component detection information generation / output means, detected component concentration information correction means, energization control means, pump current correction amount determination means,
Correction calculation means, correction density information generation means, internal resistance measurement means, temperature information generation means, concentration cell electromotive force measurement means and voltage information correction means) 55 ROM (correction reference information storage means) 55a correction reference information 61 operational amplifier (pump current) Control means) 74 constant current power supply (correction current applying means) 200 spacer section 201, 202 insulating layer 204 opening section 210 support section 211 first portion (first powder compact) 212 second portion (second powder compact) 213 Third part 240 ZrO ₂ green sheet (spacer molded body) 241, 242 Laminating coat (insulating pattern) 266 a, 266 b Strut pattern 302 Map (temperature deviation-pump current correction amount relation information) 302b map (pump current information- Detection component concentration-related information) 401, 404 Spacer portion (wall portion forming body) 401b, 404b wall 402 and 405 slits (diffusion regulating circulating unit) 403, 407 measurement chamber 410 small hole (diffusion regulating circulation portion) 500 switching circuit (control mode switching means)

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Takafumi Oshima 14-18 Takatsuji-cho, Mizuho-ku, Nagoya-shi, Aichi Japan Special Ceramics Co., Ltd.

Claims (12)

[Claims] An exhaust gas sensor for detecting a component to be detected contained in exhaust gas, comprising an oxygen ion conductive solid electrolyte, electrodes formed on both sides, and a component to be detected in exhaust gas. A first element having different oxidation catalytic activities of the electrodes with respect to each other, and an electrode formed on both surfaces composed of an oxygen ion-conducting solid electrolyte, and a predetermined amount of gap in which the flow of exhaust gas from the atmosphere to be measured is allowed is provided. While being arranged to face the first element so as to be formed, the oxidation catalyst activities of the electrodes with respect to the component to be detected in the exhaust gas are different from each other, and the difference in the oxidation catalyst activities between the electrodes on both surfaces is A second element adjusted to be larger than a difference in oxidation catalyst activity between the electrodes on both surfaces of the first element, wherein one of the first element and the second element is an oxygen concentration cell element. And the other functions as an oxygen pump element that pumps oxygen into or out of the gap in a direction in which the absolute value of the concentration cell electromotive force generated in the oxygen concentration cell element decreases. And that the first element is the oxygen concentration cell element and the second element can be switched between a first mode that is the oxygen pump element and a reverse second mode. A characteristic exhaust gas sensor. 2. A space (hereinafter, referred to as an oxygen concentration cell element) opposite to the gap with respect to the gap and an element (hereinafter, simply referred to as an oxygen concentration cell element) serving as the oxygen concentration cell element among the first element and the second element. Exhaust gas containing the component to be detected and oxygen is introduced into the opposite space, respectively, and the first element and the second element that become the oxygen pump element (hereinafter simply referred to as the oxygen pump element) The gap-side electrode as a first electrode, the gap-side electrode of the oxygen concentration cell element as a second electrode, and the opposite space side electrode of the oxygen concentration cell element as a third electrode, The detected component in the exhaust gas introduced into the opposite space is at least one of the gap and the opposite space, and at least one of the first to third electrodes is used as an oxidation catalyst in the exhaust gas. Oxidation catalysts of the first to third electrodes so as to be consumed by reacting with the element and to cause a difference in consumption of the detected component due to reaction with oxygen between the gap and the opposite space. The activity is adjusted, and information reflecting a current value flowing through the oxygen pump element when the concentration cell electromotive force of the oxygen concentration cell element reaches a predetermined electromotive force target value EC is stored in the exhaust gas. And the difference in the oxidation catalyst activity between the electrodes on both surfaces of the first element and the difference in the oxidation catalyst activity between the electrodes on both surfaces of the second element. 2. The exhaust gas sensor according to claim 1, wherein the first mode and the second mode output concentration detection information having different contents based on the difference. 3. The first element is arranged such that one of the two electrodes having a high oxidation catalyst activity faces the gap, and the second element is one of the two electrodes having a high oxidation catalyst activity. The exhaust gas sensor according to claim 1, wherein an object is arranged so as to face the gap. 4. The exhaust gas sensor according to claim 3, wherein the electrode of the first element facing the gap and the electrode of the second element facing the gap are made of the same material. 5. An electrode of the first element not facing the gap is a Pt-Pd electrode, and an electrode facing the gap is also a Pt electrode, while facing the gap of the second element. The exhaust gas sensor according to claim 4, wherein the electrode is a Pt electrode, and the electrode not facing the gap is an Au electrode. 6. When the exhaust gas contains two or more detected components having different activities with respect to an oxidation reaction,
The information on the density of a specific one of the two or more detected components is obtained based on the density detection information obtained in the first mode and the density detection information obtained in the second mode. 6. The exhaust gas sensor according to any one of 2 to 5. 7. In the first mode, density detection information relating to a density of a specific one of the two or more detected components is output. In the second mode, the two or more detected components are output. It is assumed to output the density detection information on the total density of all of the, based on the difference between the output of the density detection information obtained in the second mode and the output of the density detection information obtained in the first mode, 6. The exhaust gas sensor according to claim 5, wherein information on the total concentration of the remaining components excluding the specific one component from the two or more detected components is obtained. 8. The exhaust gas sensor according to claim 7, wherein the specific one of the detected components is methane, and the other detected components are non-methane hydrocarbons. 9. An exhaust gas sensor system for detecting a component to be detected contained in exhaust gas, comprising an oxygen ion conductive solid electrolyte, electrodes formed on both sides, and detection in the exhaust gas. A first element having different oxidation catalytic activities of the electrodes with respect to the components, and a predetermined amount of gap formed of an oxygen ion conductive solid electrolyte, having electrodes formed on both sides thereof, and allowing the flow of exhaust gas from the atmosphere to be measured. Is formed so as to face the first element, the oxidation catalyst activities of the electrodes are different from each other with respect to the component to be detected in the exhaust gas, and the difference between the oxidation catalyst activities of the electrodes on both surfaces is An exhaust gas sensor comprising: a second element set to be larger than a difference in oxidation catalyst activity between the electrodes on both surfaces of the first element; and the first element and the second element. Element control means for functioning one of the above as an oxygen concentration cell element and the other as an oxygen pump element to pump oxygen into or out of the gap in a direction in which the absolute value of the concentration cell electromotive force decreases. And a control mode in which the control mode by the element switches between a first mode in which the first element becomes the oxygen concentration cell element and the second element becomes the oxygen pump element and a second mode in which the first element becomes the oxygen pump element. An exhaust gas sensor system comprising: switching means. 10. A space (hereinafter, simply referred to as an oxygen concentration battery element) opposite to the gap with respect to the gap and the first element and the second element that serve as the oxygen concentration cell element (hereinafter, simply referred to as an oxygen concentration cell element). Exhaust gas containing the component to be detected and oxygen is introduced into the opposite space, respectively, and the first element and the second element that become the oxygen pump element (hereinafter simply referred to as the oxygen pump element) The gap-side electrode as a first electrode, the gap-side electrode of the oxygen concentration cell element as a second electrode, and the opposite space side electrode of the oxygen concentration cell element as a third electrode, The component to be detected in the exhaust gas introduced into the opposite space is at least one of the gap and the opposite space, and at least one of the first to third electrodes is used as an oxidation catalyst in the exhaust gas. Oxidation catalysts of the first to third electrodes so that they are consumed by reacting with oxygen and a difference occurs in the amount of the component to be detected due to the reaction with oxygen between the gap and the opposite space. The activity is adjusted, and the element control means controls the operation of the oxygen pump element so that the concentration cell electromotive force of the oxygen concentration cell element approaches a predetermined electromotive force target value EC. ,
Further, information reflecting a current value flowing through the oxygen pump element when the concentration cell electromotive force reaches the electromotive force target value EC is output as concentration detection information of the detected component in the exhaust gas. The difference between the oxidation catalyst activity between the electrodes on both surfaces of the first element and the difference between the oxidation catalyst activities between the electrodes on both surfaces of the second element, based on the difference between the first mode and the second mode. 10. The exhaust gas sensor system according to claim 9, further comprising density detection information output means for outputting density detection information having different contents. 11. When the exhaust gas contains two or more detected components having different activities with respect to an oxidation reaction, the concentration detection information obtained in the first mode;
Based on the density detection information obtained in the second mode, specific component detection information generating / outputting means for generating information relating to the density of a specific one of the two or more detected components and outputting the information; Claim 9 or 10
An exhaust gas sensor system according to item 1. 12. The concentration detection information output means, based on a concentration cell electromotive force of the oxygen concentration cell element in the first mode, a concentration relating to a concentration of a specific one of the two or more detected components. In the second mode, density detection information on the total density of all of the two or more detected components is output, and the specific component detection information generation / The output unit is configured to determine the specific one of the two or more detected components based on a difference between an output of the density detection information obtained in the second mode and an output of the density detection information obtained in the first mode. The exhaust gas sensor system according to claim 11, wherein the system generates and outputs information on the total concentration of the remaining components excluding the components.