CN113495093A

CN113495093A - Gas sensor

Info

Publication number: CN113495093A
Application number: CN202110288161.5A
Authority: CN
Inventors: 市川大智; 近藤裕一郎; 森伸彦
Original assignee: NGK Insulators Ltd
Current assignee: NGK Insulators Ltd
Priority date: 2020-03-19
Filing date: 2021-03-17
Publication date: 2021-10-12
Anticipated expiration: 2041-03-17
Also published as: CN113495093B; JP2021152520A

Abstract

A gas sensor (10) measures the concentrations of a first target component and a second target component, and comprises: a first switch (SW1) for ON/OFF-controlling the driving of the first preliminary adjustment pump unit (80A); a second switch (SW2) for ON/OFF-controlling the driving of the second preliminary adjustment pump unit (80B); and a switch control mechanism (101) for controlling the switching of the first switch (SW1) and the second switch (SW 2).

Description

Gas sensor

Technical Field

The present invention relates to a gas sensor capable of measuring the concentration of each of a plurality of target components in a gas to be measured.

Background

Monitoring NOx and NH has been known in the past₃The gas sensor of (1) (see, for example, Japanese patent laid-open No. 2001-133447). That is, Japanese patent application laid-open No. 2001-133447 describes the following: in monitoring NOx and NH₃In this case, a first gas sensor having a pump in an ON state and a second gas sensor having a pump in an OFF state are used.

Disclosure of Invention

However, as disclosed in japanese patent application laid-open No. 2001-133447, when a first gas sensor having a pump that is always in an ON state and a second gas sensor having a pump that is always in an OFF state are used, the electrode of the first gas sensor having a pump that is always in an ON state is further deteriorated than the second gas sensor, and the lifetime of the gas sensor may be shortened overall.

The purpose of the present invention is to provide a method for measuring, with good accuracy over a long period of time, a plurality of components (for example, NO) coexisting in an environment where an unburned component such as exhaust gas and oxygen exist₂、NH₃) The concentration of (a).

The gas sensor according to one aspect of the present invention measures the concentrations of a first target component and a second target component,

the gas sensor includes:

1 or more sensor elements;

a temperature control mechanism that controls a temperature of the sensor element;

1 or more oxygen concentration control means; and

a target component concentration acquisition means for acquiring the concentration of the target component,

the sensor element has: a structure containing at least an oxygen ion conductive solid electrolyte; and 1 or more sensor cells formed on the structural body,

the sensor unit includes a gas inlet, a first diffusion rate controller, a first chamber, a second diffusion rate controller, a second chamber, a third diffusion rate controller, and a measuring chamber facing the gas inlet,

the measuring chamber of the 1 or more sensor units is provided with a target component measuring pump unit,

the oxygen concentration control means controls the oxygen concentration in the first chamber and the second chamber of the 1 or more sensor cells,

the target component concentration acquisition means acquires the concentration of the second target component based on a difference between a current value flowing through one of the target component measurement pump cells and a current value flowing through the other of the target component measurement pump cells,

measuring a current value flowing through the pump cell based on the other target component to obtain a total concentration of the first target component and the second target component,

the concentration of the first target component is obtained by subtracting the concentration of the second target component from the total concentration.

According to the gas sensor of the present invention, it is possible to measure unburned components such as exhaust gas and a plurality of components (for example, NO and NO) coexisting in an environment where oxygen is present with good accuracy over a long period of time₂、NH₃) The concentration of (c).

The above objects, features and advantages can be more easily understood by the following description of the embodiments with reference to the accompanying drawings.

Drawings

Fig. 1 is a sectional view showing a structural example of the gas sensor according to the present embodiment (sectional view taken along line I-I in fig. 2 and 3: hatching is omitted).

Fig. 2 is a sectional view (sectional view on line II-II in fig. 1) showing a structural example of the first sensor unit of the gas sensor.

Fig. 3 is a sectional view (sectional view on the line III-III in fig. 1) showing a structural example of the second sensor unit of the gas sensor.

Fig. 4 is a structural view schematically showing the gas sensor.

Fig. 5 is an explanatory view schematically showing reactions in the first preliminary adjustment chamber, the first oxygen concentration adjustment chamber, and the first measurement chamber of the first sensor unit, and the second preliminary adjustment chamber, the second oxygen concentration adjustment chamber, and the second measurement chamber of the second sensor unit, in a case where the first preliminary adjustment pump unit is ON and the second preliminary adjustment pump unit is OFF.

Fig. 6 is an explanatory view schematically showing reactions in the first preliminary adjustment chamber, the first oxygen concentration adjustment chamber, and the first measurement chamber of the first sensor unit, and the second preliminary adjustment chamber, the second oxygen concentration adjustment chamber, and the second measurement chamber of the second sensor unit, in a case where the first preliminary adjustment pump unit is OFF and the second preliminary adjustment pump unit is ON.

Fig. 7 is a diagram showing a map used in the gas sensor in the form of a graph.

Fig. 8 is an explanatory diagram showing a map used in the gas sensor in the form of a table.

Fig. 9 is an explanatory diagram showing measurement results for confirming the accuracy of the mapping in the form of a table.

Fig. 10A is a timing chart showing the start and end of operation of the vehicle and the like at the first switching timing. Fig. 10B is a timing chart showing the ON/OFF switching timing of the first preliminary adjustment pump unit and the second preliminary adjustment pump unit, and fig. 10C is a block diagram of the switching control.

Fig. 11 is a flowchart showing the ON/OFF switching timings of the first preliminary adjustment pump unit and the second preliminary adjustment pump unit at the first switching timing.

Fig. 12A is a timing chart showing the start and end of operation of the vehicle and the like at the second switching timing, fig. 12B is a timing chart showing the ON/OFF switching timing of the first preliminary adjustment pump unit and the second preliminary adjustment pump unit, and fig. 12C is a block diagram of the switching control.

Fig. 13 is a flowchart showing the ON/OFF switching timings of the first preliminary adjustment pump unit and the second preliminary adjustment pump unit at the second switching timing.

Fig. 14A is a timing chart showing the start and end of operation of the vehicle and the like at the third switching timing, fig. 14B is a timing chart showing the ON/OFF switching timing of the first preliminary adjustment pump unit and the second preliminary adjustment pump unit, and fig. 14C is a block diagram of the switching control.

Fig. 15 is a flowchart showing the ON/OFF switching timings of the first preliminary adjustment pump unit and the second preliminary adjustment pump unit at the third switching timing.

Fig. 16A is a timing chart showing the start and end of operation of the vehicle and the like at the fourth switching timing, fig. 16B is a timing chart showing the ON/OFF switching timing of the first preliminary adjustment pump unit and the second preliminary adjustment pump unit, and fig. 16C is a block diagram of the switching control.

Fig. 17 is a flowchart showing the ON/OFF switching timings of the first preliminary adjustment pump unit and the second preliminary adjustment pump unit at the fourth switching timing.

Fig. 18 is a sectional view showing a structural example of the gas sensor according to the first modification.

Fig. 19 is a sectional view showing a structural example of a gas sensor according to a second modification.

Detailed Description

Hereinafter, a metal terminal according to the present invention will be described in detail with reference to the accompanying drawings by referring to preferred embodiments.

First, a basic configuration example and a measurement principle of the gas sensor 10 according to the present embodiment will be described below.

As shown in fig. 1 to 3, the gas sensor 10 includes a sensor element 12. The sensor element 12 has: a structure 14 containing an oxygen ion conductive solid electrolyte; and a first sensor cell 15A and a second sensor cell 15B formed in the structural body 14. Of course, 2 structures 14 may be configured such that the first sensor unit 15A is formed in one structure 14 and the second sensor unit 15B is formed in the other structure 14. This is explained below.

Here, if the thickness direction of the structural body 14 is defined as the longitudinal direction and the width direction of the structural body 14 is defined as the lateral direction, the first sensor unit 15A and the second sensor unit 15B are provided in the structural body 14 in a state of being arranged along the lateral direction.

As shown in fig. 1 and 2, the first sensor unit 15A includes: a first gas inlet 16A formed in the structural body 14, into which the gas to be measured is introduced 16A; a first oxygen concentration adjustment chamber 18A formed in the structure 14 and communicating with the first gas introduction port 16A; and a first measurement chamber 20A formed in the structure 14 and communicating with the first oxygen concentration adjustment chamber 18A.

The first oxygen concentration adjustment chamber 18A has: a first main regulation chamber 18Aa communicating with the first gas introduction port 16A; and a first sub regulation chamber 18Ab that communicates with the first main regulation chamber 18 Aa. The first measurement chamber 20A communicates with the first sub-regulation chamber 18 Ab.

Further, the first sensor unit 15A has a first preliminary adjustment chamber 22A, and the first preliminary adjustment chamber 22A is provided between the first gas introduction port 16A and the first main adjustment chamber 18Aa in the structural body 14, and communicates with the first gas introduction port 16A.

On the other hand, as shown in fig. 1 and 3, the second sensor unit 15B includes: a second gas inlet 16B formed in the structure 14, into which the gas to be measured is introduced 16B; a second oxygen concentration adjustment chamber 18B formed in the structure 14 and communicating with the second gas inlet 16B; and a second measurement chamber 20B formed in the structure 14 and communicating with the second oxygen concentration adjustment chamber 18B.

The second oxygen concentration adjustment chamber 18B has: a second main adjustment chamber 18Ba communicating with the second gas inlet 16B; and a second sub regulation chamber 18Bb that communicates with the second main regulation chamber 18 Ba. The second measurement chamber 20B communicates with the second sub regulation chamber 18 Bb.

The second sensor unit 15B further includes a second preliminary adjustment chamber 22B, and the second preliminary adjustment chamber 22B is provided between the second gas inlet 16B and the second main adjustment chamber 18Ba in the structural body 14 and communicates with the second gas inlet 16B.

As shown in fig. 2 and 3, the structure 14 is configured such that: six layers of the first substrate layer 26a, the second substrate layer 26b, the third substrate layer 26c, the first solid electrolyte layer 28, the separation layer 30, and the second solid electrolyte layer 32 are stacked in this order from the lower side in the drawing. Each layer is made of zirconium oxide (ZrO)₂) A plasma ion conductive solid electrolyte layer.

As shown in fig. 2, the first sensor unit 15A includes a first gas introduction port 16A, a first diffusion rate control portion 34A, a first preliminary adjustment chamber 22A, a second diffusion rate control portion 36A, a first oxygen concentration adjustment chamber 18A, a third diffusion rate control portion 38A, and a first measurement chamber 20A on the tip end portion side of the sensor element 12 between the lower surface of the second solid electrolyte layer 32 and the upper surface of the first solid electrolyte layer 28. Further, a fourth diffusion rate control portion 40A is provided between the first main adjustment chamber 18Aa and the first sub adjustment chamber 18Ab that constitute the first oxygen concentration adjustment chamber 18A.

The first gas introduction port 16A, the first diffusion rate controller 34A, the first preliminary adjustment chamber 22A, the second diffusion rate controller 36A, the first main adjustment chamber 18Aa, the fourth diffusion rate controller 40A, the first sub-adjustment chamber 18Ab, the third diffusion rate controller 38A, and the first measurement chamber 20A are adjacently formed so as to communicate in this order. A portion from the first gas introduction port 16A to the first measurement chamber 20A is also referred to as a first gas flow portion.

The first gas introduction port 16A, the first preliminary adjustment chamber 22A, the first main adjustment chamber 18Aa, the first sub adjustment chamber 18Ab, and the first measurement chamber 20A are internal spaces provided so that the partition layer 30 is pierced through them. The first preliminary adjustment chamber 22A, the first main adjustment chamber 18Aa, the first sub-adjustment chamber 18Ab, and the first measurement chamber 20A are each formed by a lower surface section of the second solid electrolyte layer 32, a lower portion section of each of the first solid electrolyte layer 28, and a side portion section of each of the isolation layers 30.

As shown in fig. 3, the second sensor unit 15B also includes a second gas introduction port 16B, a first diffusion rate controller 34B, a second preliminary adjustment chamber 22B, a second diffusion rate controller 36B, a second oxygen concentration adjustment chamber 18B, a third diffusion rate controller 38B, and a second measurement chamber 20B on the distal end side of the sensor element 12 and between the lower surface of the second solid electrolyte layer 32 and the upper surface of the first solid electrolyte layer 28. Further, a fourth diffusion rate control portion 40B is provided between the second main adjustment chamber 18Ba and the second sub adjustment chamber 18Bb constituting the second oxygen concentration adjustment chamber 18B.

The second gas introduction port 16B, the first diffusion rate controller 34B, the second preliminary adjustment chamber 22B, the second diffusion rate controller 36B, the second main adjustment chamber 18Ba, the fourth diffusion rate controller 40B, the second sub-adjustment chamber 18Bb, the third diffusion rate controller 38B, and the second measurement chamber 20B are adjacently formed so as to communicate with each other in this order. A portion from the second gas inlet 16B to the second measurement chamber 20B is also referred to as a second gas flow portion.

The second gas introduction port 16B, the second preliminary adjustment chamber 22B, the second main adjustment chamber 18Ba, the second sub adjustment chamber 18Bb, and the second measurement chamber 20B are internal spaces provided so as to pierce the partition layer 30. The second preliminary adjustment chamber 22B, the second main adjustment chamber 18Ba, the second sub-adjustment chamber 18Bb, and the second measurement chamber 20B are each formed by a lower surface section of the second solid electrolyte layer 32, a lower portion section of each of the second preliminary adjustment chamber, the second main adjustment chamber, the second sub-adjustment chamber, and the second measurement chamber, respectively, being formed by an upper surface section of the first solid electrolyte layer 28, and a side portion section of each of the second preliminary adjustment chamber, the second main adjustment chamber, the second sub-adjustment chamber, and the second measurement chamber 20B being formed by a side surface section of the separator 30.

In the first sensor cell 15A and the second sensor cell 15B, the first diffusion rate control sections (34A, 34B), the third diffusion rate control sections (38A, 38B), and the fourth diffusion rate control sections (40A, 40B) are each provided with 1 or 2 horizontally long slits (the direction perpendicular to the drawing is the longitudinal direction of the opening). The second diffusion rate control sections (36A, 36B) are provided with 1 or 2 horizontally long slits (the direction perpendicular to the drawing is the longitudinal direction of the opening).

Further, a reference gas introduction space 41 common to the first sensor cell 15A and the second sensor cell 15B is provided between the upper surface of the third substrate layer 26c and the lower surface of the separation layer 30 and at a position further from the end side than the first gas flow portion and the second gas flow portion, respectively. The reference gas introduction space 41 is an internal space whose upper portion is defined by the lower surface of the separator 30, whose lower portion is defined by the upper surface of the third substrate layer 26c, and whose side portion is defined by the side surface of the first solid electrolyte layer 28. For example, oxygen or the atmosphere is introduced as the reference gas into the reference gas introduction space 41.

The first gas introduction port 16A and the second gas introduction port 16B are portions opened to the outside space, and the gas to be measured enters the first sensor unit 15A and the second sensor unit 15B from the outside space through the first gas introduction port 16A and the second gas introduction port 16B.

The first diffusion rate control portion 34A of the first sensor unit 15A is: a portion where a predetermined diffusion resistance is applied to the gas to be measured introduced from the first gas introduction port 16A into the first preliminary adjustment chamber 22A. The first diffusion rate control section 34B of the second sensor cell 15B is: a portion that applies a predetermined diffusion resistance to the gas to be measured introduced from the second gas introduction port 16B into the second preliminary adjustment chamber 22B. Hereinafter, the first preliminary adjustment chamber 22A and the second preliminary adjustment chamber 22B will be described.

The second diffusion rate control portion 36A of the first sensor unit 15A is: a portion where a predetermined diffusion resistance is applied to the gas to be measured introduced from the first preliminary adjustment chamber 22A into the first main adjustment chamber 18 Aa. The second diffusion rate control section 36B of the second sensor cell 15B is: a portion where a predetermined diffusion resistance is applied to the gas to be measured introduced from the second preliminary adjustment chamber 22B into the second main adjustment chamber 18 Ba.

The first main regulation chamber 18Aa is provided: a space for adjusting the oxygen partial pressure in the gas to be measured introduced from the first gas introduction port 16A. The first main pump unit 42A described later operates to adjust the oxygen partial pressure. Likewise, the second main regulation chamber 18Ba is provided: a space for adjusting the oxygen partial pressure in the gas to be measured introduced from the second gas introduction port 16B. The second main pump unit 42B described later operates to adjust the oxygen partial pressure.

The first main pump unit 42A is: the electrochemical pump cell is configured as a first electrochemical pump cell (main electrochemical pump cell) including a first main inner pump electrode 44A, an outer pump electrode 46 common to the first sensor cell 15A and the second sensor cell 15B, and an oxygen ion conductive solid electrolyte sandwiched between the electrodes. The first main inner pump electrode 44A is provided at: the upper surface of the first solid electrolyte layer 28, the lower surface of the second solid electrolyte layer 32, and the side surfaces of the separator 30 that define the first main adjustment chamber 18Aa are substantially all divided. The common outer pump electrode 46 is provided from a region corresponding to the first main inner pump electrode 44A to a region corresponding to the second main inner pump electrode 44B (second sensor cell 15B) on the upper surface of the second solid electrolyte layer 32 so as to be exposed to the external space.

The first main pump unit 42A is configured to: by applying the first pump voltage Vp1 by the first variable power supply 48A for the first sensor unit provided outside the sensor element 12 and causing the first pump current Ip1 to flow between the common outer pump electrode 46 and the first main inner pump electrode 44A, it is possible to draw oxygen in the first main regulation chamber 18Aa to the outside space or to draw oxygen in the outside space into the first main regulation chamber 18 Aa.

In addition, the first sensor cell 15A has a first oxygen partial pressure detection sensor cell 50A as an electrochemical sensor cell. The first oxygen partial pressure detection sensor unit 50A includes: a first main inner pump electrode 44A; a common reference electrode 52 sandwiched by the upper surface of the third substrate layer 26c and the first solid electrolyte layer 28; and an oxygen ion conductive solid electrolyte sandwiched by these electrodes. The common reference electrodes 52 are: and an electrode having a substantially rectangular shape in plan view, which is made of porous cermet similar to the common outer pump electrode 46 and the like. Further, around the common reference electrode 52, there are provided: and a common reference gas introduction layer 54 made of porous alumina and communicating with the common reference gas introduction space 41. That is, the reference gas in the reference gas introduction space 41 is introduced to the surface of the reference electrode 52 through the reference gas introduction layer 54. The first oxygen partial pressure detection sensor unit 50A generates a first electromotive force V1 between the first main inner pump electrode 44A and the reference electrode 52 due to the difference in oxygen concentration between the atmosphere in the first main adjustment chamber 18Aa and the reference gas in the reference gas introduction space 41.

The first electromotive force V1 generated in the first oxygen partial pressure detection sensor unit 50A changes in accordance with the oxygen partial pressure of the atmosphere existing in the first main regulation chamber 18 Aa. The first sensor unit 15A feedback-controls the first variable power supply 48A of the first main pump unit 42A using the first electromotive force V1 described above. Thus, the first pump voltage Vp1 applied by the first variable power supply 48A to the first main pump unit 42A can be controlled in accordance with the oxygen partial pressure of the atmosphere in the first main regulation chamber 18 Aa.

The fourth diffusion rate controller 40A is: the oxygen concentration (oxygen partial pressure) of the gas to be measured is controlled by the operation of the first main pump unit 42A in the first main adjustment chamber 18Aa while applying a predetermined diffusion resistance to the gas to be measured and introducing the gas to be measured to a portion of the first sub adjustment chamber 18 Ab.

The first sub-regulation chamber 18Ab is provided as a space for performing the following processes: the oxygen concentration (oxygen partial pressure) is adjusted in the first main adjustment chamber 18Aa in advance, and then the oxygen partial pressure of the gas to be measured introduced through the fourth diffusion rate control portion 40A is adjusted by the first auxiliary pump unit 56A described later. This makes it possible to accurately maintain the oxygen concentration in the first sub-regulation chamber 18Ab constant, and therefore, the first sensor unit 15A can accurately measure the NOx concentration.

The first auxiliary pump cell 56A is an electrochemical pump cell, and includes a first auxiliary pump electrode 58A, a common outer pump electrode 46, and the second solid electrolyte layer 32, wherein the first auxiliary pump electrode 58A is provided at: substantially the entire region of the lower surface of the second solid electrolyte layer 32 that faces the first sub-regulation chamber 18 Ab.

The first auxiliary pump electrode 58A is also formed of a material that can reduce the reducing ability for the NOx component in the measurement gas, similarly to the first main inner pump electrode 44A.

The first auxiliary pump unit 56A is configured to: by applying a desired second voltage Vp2 between the first auxiliary pump electrode 58A and the outer pump electrode 46, oxygen in the atmosphere in the first auxiliary adjustment chamber 18Ab can be sucked into the external space or oxygen can be sucked into the first auxiliary adjustment chamber 18Ab from the external space.

In order to control the oxygen partial pressure in the atmosphere in the first sub-regulation chamber 18Ab, the second oxygen partial pressure detection sensor cell 50B for controlling the first auxiliary pump, which is an electrochemical sensor cell, is configured to include the first auxiliary pump electrode 58A, the reference electrode 52, the second solid electrolyte layer 32, the separator 30, and the first solid electrolyte layer 28.

The first auxiliary pump unit 56A pumps the fluid by the second variable power source 48B, and controls the voltage of the second variable power source 48B based on the second electromotive force V2 detected by the second oxygen partial pressure detection sensor unit 50B. Thereby, the oxygen partial pressure in the atmosphere in the first sub-regulation chamber 18Ab is controlled to a low partial pressure that does not substantially affect the measurement of NOx.

In addition, at the same time, the second pump current value Ip2 of the first auxiliary pump cell 56A is used to control the second electromotive force V2 of the second oxygen partial pressure detecting sensor cell 50B. Specifically, the second pump current Ip2 is controlled in the following manner: the second electromotive force V2 is input as a control signal to the second oxygen partial pressure detection sensor unit 50B and controlled, so that the gradient of the oxygen partial pressure in the gas to be measured introduced into the first sub-regulation chamber 18Ab by the fourth diffusion rate control unit 40A is always constant. In addition, if the first variable power supply 48A of the first main pump unit 42A is feedback-controlled so that the second pump current value Ip2 is constant, the accuracy of the oxygen partial pressure control in the first sub-regulation chamber 18Ab is further improved. When the first sensor unit 15A is used as a NOx sensor, the oxygen concentration in the first sub-regulation chamber 18Ab is accurately maintained at the predetermined value for each condition by the operation of the first main pump unit 42A and the first auxiliary pump unit 56A.

The third diffusion rate control unit 38A is: the oxygen concentration (oxygen partial pressure) of the gas to be measured is controlled by the operation of the first auxiliary pump unit 56A in the first auxiliary adjustment chamber 18Ab while applying a predetermined diffusion resistance to the gas to be measured and introducing the gas to be measured into a portion of the first measurement chamber 20A.

In the first sensor unit 15A, the NOx concentration is measured mainly by the operation of the first measurement pump unit 60A provided in the first measurement chamber 20A. As shown in fig. 2, the first measurement pump cell 60A is an electrochemical pump cell configured to include a first measurement electrode 62A, a common outer pump electrode 46, a second solid electrolyte layer 32, a separator 30, and a first solid electrolyte layer 28. The first measurement electrode 62A is a porous cermet electrode that is provided directly on, for example, the upper surface of the first solid electrolyte layer 28 in the first measurement chamber 20A and is made of a material having a higher reduction ability for NOx components in the measurement target gas than the first main inner pump electrode 44A. The first measurement electrode 62A also functions as an NOx reduction catalyst that reduces NOx present in the atmosphere on the first measurement electrode 62A.

The first measurement pump unit 60A is configured to: oxygen generated by decomposition of nitrogen oxides in the atmosphere around the first measurement electrode 62A (in the first measurement chamber 20A) can be drawn out, and the amount of oxygen generated can be detected as the first pump current value Ip3, i.e., the sensor output (first measurement pump current value Ip3) of the first sensor cell 15A.

In order to detect the oxygen partial pressure around the first measurement electrode 62A (in the first measurement chamber 20A), the third oxygen partial pressure detection sensor cell 50C for a measurement pump control, which is an electrochemical sensor cell, is configured to include the first solid electrolyte layer 28, the separator 30, the first measurement electrode 62A, and the reference electrode 52. The third variable power supply 48C is controlled based on the third electromotive force V3 detected by the third oxygen partial pressure detection sensor unit 50C.

The gas to be measured introduced into the first sub-regulation chamber 18Ab passes through the third diffusion rate controller 38A while the oxygen partial pressure is controlled, and reaches the first measurement electrode 62A in the first measurement chamber 20A. The nitrogen oxide in the measurement target gas around the first measurement electrode 62A is reduced to generate oxygen. The generated oxygen is pumped by the first measurement pump unit 60A. At this time, the third voltage Vp3 of the third variable power supply 48C is controlled so that the third electromotive force V3 detected by the third partial pressure detection sensor unit 50C is constant. The amount of oxygen generated around the first measurement electrode 62A is proportional to the concentration of nitrogen oxide in the measurement gas. Therefore, the nox concentration in the measurement gas can be calculated using the first measurement pump current value Ip3 of the first measurement pump cell 60A. That is, the first measurement pump unit 60A measures the concentration of the specific component (NO) in the first measurement chamber 20A.

Further, the first heater 72A is formed in the first sensor cell 15A so as to be sandwiched between the second substrate layer 26b and the third substrate layer 26c from above and below. The first heater 72A is supplied with power from the outside through a heater electrode, not shown, provided on the lower surface of the first substrate layer 26a, and generates heat. The oxygen ion conductivity of the solid electrolyte constituting the first sensor cell 15A is improved by the heat generation of the first heater 72A. The first heater 72A is buried in the entire areas of the first preliminary adjustment chamber 22A, the first oxygen concentration adjustment chamber 18A, and the first measurement chamber 20A, and can heat a predetermined position of the first sensor unit 15A to a predetermined temperature and maintain the temperature. In addition, a first heater insulating layer 74A made of alumina or the like is formed on the upper and lower surfaces of the first heater 72A for the purpose of obtaining electrical insulation with respect to the second substrate layer 26b and the third substrate layer 26 c.

The first sensor unit 15A includes a first switch SW1, and the first switch SW1 ON/OFF-controls the operation of a first preliminary adjustment pump unit 80A described later. The first preliminary adjustment chamber 22A functions as a space for adjusting the oxygen partial pressure in the gas to be measured introduced from the first gas introduction port 16A. The first preliminary adjustment pump unit 80A operates to adjust the oxygen partial pressure.

The first preliminary adjustment pump unit 80A is a preliminary electrochemical pump unit that operates by turning ON the first switch SW 1. The first preliminary adjustment pump unit 80A is configured to include a first preliminary pump electrode 82A, the outer pump electrode 46, and the second solid electrolyte layer 32, wherein the first preliminary pump electrode 82A is provided at: substantially the entire area of the lower surface of the second solid electrolyte layer 32 that faces the first preliminary conditioning chamber 22A.

The first preliminary pump electrode 82A is also formed of a material that can reduce the reducing ability for the NOx component in the measurement gas, similarly to the first main inner pump electrode 44A. Specifically, for example, two components of Pt and Au are contained, and the composition ratio Au/(Pt + Au) is 4% to 20%. These components constitute a porous cermet.

The first preliminary adjustment pump unit 80A is configured to: by applying a desired first preliminary voltage Vpa between the first preliminary pump electrode 82A and the outer pump electrode 46, oxygen in the atmosphere in the first preliminary adjustment chamber 22A can be sucked into the external space, or oxygen can be sucked into the first preliminary adjustment chamber 22A from the external space.

In order to control the oxygen partial pressure in the atmosphere in the first preliminary adjustment chamber 22A, the first sensor unit 15A includes a first preliminary oxygen partial pressure detection sensor unit 84A for controlling the first preliminary pump. The first preliminary oxygen partial pressure detection sensor cell 84A has a first preliminary pump electrode 82A, a reference electrode 52, a second solid electrolyte layer 32, a separator 30, and a first solid electrolyte layer 28.

The first preliminary adjustment pump unit 80A pumps by the first preliminary variable power supply 86A, and controls the voltage of the first preliminary variable power supply 86A based on the first preliminary electromotive force Va detected by the first preliminary oxygen partial pressure detection sensor unit 84A. Thereby, the oxygen partial pressure in the atmosphere in the first preliminary adjustment chamber 22A is controlled to: a lower partial pressure that has substantially no effect on the determination of NOx.

At the same time, the first preliminary pump current value Ipa is used to control the electromotive force of the first preliminary oxygen partial pressure detection sensor unit 84A. Specifically, the first preliminary pump current Ipa is controlled in such a manner that: the first preliminary electromotive force Va is controlled by inputting a control signal to the first preliminary oxygen partial pressure detection sensor unit 84A, so that the gradient of the oxygen partial pressure in the gas to be measured introduced from the first diffusion rate control unit 34A into the first preliminary adjustment chamber 22A is always constant.

The first preliminary adjustment chamber 22A also functions as a buffer space. That is, it is possible to eliminate the change in the concentration of the gas to be measured caused by the change in the pressure of the gas to be measured in the external space (pulsation of the exhaust pressure in the case where the gas to be measured is the exhaust gas of an automobile).

On the other hand, as shown in fig. 3, the second sensor unit 15B has substantially the same configuration as the first sensor unit 15A described above, and includes a second main pump unit 42B, a second auxiliary pump unit 56B, a fourth oxygen partial pressure detection sensor unit 50D, a fifth oxygen partial pressure detection sensor unit 50E, and a sixth oxygen partial pressure detection sensor unit 50F.

Similarly to the first main pump element 42A, the second main pump element 42B is a second electrochemical pump element (main electrochemical pump element) including a second main inner pump electrode 44B, a common outer pump electrode 46, and an oxygen ion conductive solid electrolyte sandwiched between these electrodes.

By applying the fourth pump voltage Vp4 by the fourth variable power supply 48D for the second sensor cell 15B and passing the fourth pump current Ip4 between the common outer pump electrode 46 and the second main inner pump electrode 44B, it is possible to suck oxygen in the second main regulation chamber 18Ba into the external space or to suck oxygen in the external space into the second main regulation chamber 18 Ba.

Like the first auxiliary pump cell 56A described above, the second auxiliary pump cell 56B is an electrochemical pump cell, and includes a second auxiliary pump electrode 58B, the common outer pump electrode 46, and the second solid electrolyte layer 32, wherein the second auxiliary pump electrode 58B is provided at: substantially the entire area of the lower surface of the second solid electrolyte layer 32 that faces the second sub regulation chamber 18 Bb.

The second auxiliary pump unit 56B is configured to: by applying a desired fifth voltage Vp5 between the second auxiliary pump electrode 58B and the outer pump electrode 46, oxygen in the atmosphere in the second sub regulation chamber 18Bb can be sucked into the external space or oxygen can be sucked into the second sub regulation chamber 18Bb from the external space.

Like the first oxygen partial pressure detection sensor cell 50A, the fourth oxygen partial pressure detection sensor cell 50D is configured to include the second main inner pump electrode 44B, a common reference electrode 52 sandwiched between the upper surface of the third substrate layer 26c and the first solid electrolyte layer 28, and an oxygen ion conductive solid electrolyte sandwiched between these electrodes.

The fourth oxygen partial pressure detection sensor unit 50D generates a fourth electromotive force V4 between the second main inner pump electrode 44B and the reference electrode 52 due to the difference in oxygen concentration between the atmosphere in the second main adjustment chamber 18Ba and the reference gas in the reference gas introduction space 41.

The fourth electromotive force V4 generated in the fourth oxygen partial pressure detection sensor unit 50D changes in accordance with the oxygen partial pressure of the atmosphere existing in the second main regulation chamber 18 Ba. The second sensor unit 15B feedback-controls the fourth variable power supply 48D of the second main pump unit 42B using the fourth electromotive force V4 described above. Thus, the fourth pump voltage Vp4 applied by the fourth variable power supply 48D to the second main pump unit 42B can be controlled in accordance with the oxygen partial pressure of the atmosphere in the second main regulation chamber 18 Ba.

In order to control the oxygen partial pressure in the atmosphere in the second sub-regulation chamber 18Bb, a fifth oxygen partial pressure detection sensor cell 50E for controlling a second auxiliary pump, which is an electrochemical sensor cell, is configured to include the second auxiliary pump electrode 58B, the reference electrode 52, the second solid electrolyte layer 32, the separator 30, and the first solid electrolyte layer 28.

The second auxiliary pump unit 56B pumps the liquid by the fifth variable power supply 48E, and controls the voltage of the fifth variable power supply 48E based on the fifth electromotive force V5 detected by the fifth oxygen partial pressure detection sensor unit 50E. Thereby, the oxygen partial pressure in the atmosphere in the second sub regulation chamber 18Bb is controlled to: a lower partial pressure that has substantially no effect on the determination of NOx.

At the same time, fifth pump current value Ip5 for second auxiliary pump cell 56B is used to: the fifth electromotive force V5 of the fifth oxygen partial pressure detection sensor unit 50E is controlled. Namely, it is controlled to: the gradient of the oxygen partial pressure in the gas to be measured introduced into the second sub regulation chamber 18Bb is made constant at all times.

In order to detect the oxygen partial pressure around the second measurement electrode 62B (in the second measurement chamber 20B), the sixth oxygen partial pressure detection sensor cell 50F for a measurement pump control, which is an electrochemical sensor cell, is configured to include the first solid electrolyte layer 28, the separator 30, the second measurement electrode 62B, and the reference electrode 52. The sixth variable power supply 48F is controlled based on the sixth electromotive force V6 detected by the sixth oxygen partial pressure detection sensor unit 50F.

The gas to be measured introduced into the second sub regulation chamber 18Bb passes through the third diffusion rate controller 38B under the condition that the oxygen partial pressure is controlled, and reaches the second measurement electrode 62B in the second measurement chamber 20B. The nitrogen oxide in the gas to be measured around the second measurement electrode 62B is reduced to generate oxygen. The generated oxygen is pumped by the second measurement pump unit 60B. At this time, the sixth voltage Vp6 of the sixth variable power supply 48F is controlled so that the sixth electromotive force V6 detected by the sixth oxygen partial pressure detection sensor unit 50F is constant. The amount of oxygen generated around the second measurement electrode 62B is proportional to the concentration of nitrogen oxide in the measurement gas. Therefore, the concentration of nitrogen oxides in the measurement gas can be calculated by the second measurement pump current value Ip6 of the second measurement pump cell 60B. That is, the second measurement pump unit 60B measures the concentration of the specific component (NO) in the second measurement chamber 20B.

The second sensor cell 15B includes an electrochemical oxygen detection cell 70. The oxygen detecting cell 70 has the second solid electrolyte layer 32, the separation layer 30, the first solid electrolyte layer 28, the third substrate layer 26c, the outer pump electrode 46, and the reference electrode 52. The partial pressure of oxygen in the gas to be measured outside the sensor element 12 can be detected from the electromotive force Vr obtained by the oxygen detection means 70.

In the second sensor cell 15B, a second heater 72B similar to the first heater 72A is formed so as to be sandwiched between the second substrate layer 26B and the third substrate layer 26c from above and below. The second heater 72B is embedded in the entire area of the second preliminary adjustment chamber 22B, the second oxygen concentration adjustment chamber 18B, and the second measurement chamber 20B, and can heat a predetermined position of the second sensor unit 15B to a predetermined temperature and maintain the temperature. In addition, a second heater insulating layer 74B made of alumina or the like is also formed on the upper and lower surfaces of the second heater 72B for the purpose of obtaining electrical insulation with respect to the second substrate layer 26B and the third substrate layer 26 c. In addition, the first heater 72A and the second heater 72B may be constituted by 1 heater in common, and in this case, the first heater insulating layer 74A and the second heater insulating layer 74B are also in common.

As shown in fig. 3, the second sensor unit 15B further includes a second switch SW2, and the second switch SW2 controls ON/OFF operation of a second preliminary adjustment pump unit 80B described later. The second preliminary adjustment chamber 22B functions as a space for adjusting the oxygen partial pressure in the gas to be measured introduced from the second gas introduction port 16B. The second preliminary adjustment pump unit 80B operates to adjust the oxygen partial pressure.

The second preliminary adjustment pump unit 80B is a preliminary electrochemical pump unit that operates by turning ON the second switch SW 2. The second preliminary adjustment pump cell 80B is a preliminary electrochemical pump cell configured to include a second preliminary pump electrode 82B, the outer pump electrode 46, and the second solid electrolyte layer 32, wherein the second preliminary pump electrode 82B is provided at: substantially the entire area of the lower surface of the second solid electrolyte layer 32 that faces the second preliminary conditioning chamber 22B.

Similarly to the first preliminary pump electrode 82A (see fig. 2), the second preliminary pump electrode 82B is also formed of a material that can reduce the reducing ability for the NOx component in the measurement target gas. Specifically, for example, two components of Pt and Au are contained, and the composition ratio Au/(Pt + Au) is 4% to 20%. These components constitute a porous cermet.

The second preliminary adjustment pump unit 80B is configured to: by applying a desired second preliminary voltage Vpb between the second preliminary pump electrode 82B and the outer pump electrode 46, oxygen in the atmosphere in the second preliminary adjustment chamber 22B can be sucked into the external space, or oxygen can be sucked into the second preliminary adjustment chamber 22B from the external space.

In order to control the oxygen partial pressure in the atmosphere in the second preliminary adjustment chamber 22B, the second sensor unit 15B includes a second preliminary oxygen partial pressure detection sensor unit 84B for controlling a second preliminary pump. The second preliminary oxygen partial pressure detection sensor cell 84B has a second preliminary pump electrode 82B, a reference electrode 52, a second solid electrolyte layer 32, a separator 30, and a first solid electrolyte layer 28.

The second preliminary adjustment pump unit 80B pumps the liquid by the second preliminary variable power supply 86B, and controls the voltage of the second preliminary variable power supply 86B based on the second preliminary electromotive force Vb detected by the second preliminary oxygen partial pressure detection sensor unit 84B. Thereby, the oxygen partial pressure in the atmosphere in the second preliminary adjustment chamber 22B is controlled to: a lower partial pressure that has substantially no effect on the determination of NOx.

At the same time, second preliminary pump current value Ipb is used to: the electromotive force of the second preliminary oxygen partial pressure detection sensor unit 84B is controlled. Specifically, the second preliminary pump current Ipb is controlled in the following manner: the second preliminary electromotive force Vb is input as a control signal to the second preliminary oxygen partial pressure detection sensor unit 84B and controlled so that the gradient of the oxygen partial pressure in the gas to be measured introduced into the second preliminary adjustment chamber 22B from the first diffusion rate control portion 34B is always constant.

The second preliminary adjustment chamber 22B also functions as a buffer space. That is, it is possible to eliminate the change in the concentration of the gas to be measured caused by the change in the pressure of the gas to be measured in the external space (pulsation of the exhaust pressure in the case where the gas to be measured is the exhaust gas of an automobile).

Further, as schematically shown in fig. 4, the gas sensor 10 has a temperature control mechanism 100, a switching control mechanism 101, a first oxygen concentration control mechanism 102A, a second oxygen concentration control mechanism 102B, and a target component concentration acquisition mechanism 104.

The temperature control mechanism 100 controls the temperatures of the first sensor unit 15A and the second sensor unit 15B by controlling the energization of the first heater 72A and the second heater 72B of the sensor element 12.

The switch control means 101 performs switch control of the first switch SW1 and the second switch SW 2. For example, when the first preliminary adjustment pump unit 80A is operated, the first switch SW1 is turned ON, and the second switch SW2 is turned OFF. Conversely, when the second preliminary adjustment pump unit 80B is operated, the first switch SW1 is turned OFF, and the second switch SW2 is turned ON.

The first oxygen concentration control mechanism 102A has: a first oxygen concentration control portion 106A that controls the oxygen concentration in the first oxygen concentration adjustment chamber 18A of the first sensor unit 15A; and a first preliminary oxygen concentration control unit 108A that controls the oxygen concentration in the first preliminary adjustment chamber 22A of the first sensor unit 15A.

The second oxygen concentration control mechanism 102B has: a second oxygen concentration control portion 106B that controls the oxygen concentration in the second oxygen concentration adjustment chamber 18B of the second sensor unit 15B; and a second preliminary oxygen concentration control unit 108B that controls the oxygen concentration in the second preliminary adjustment chamber 22B of the second sensor unit 15B.

The target component concentration acquiring means 104 acquires the concentration of the first target component (NO) and the second target component (NH) based on the difference (change amount Δ Ip) between the first measured pump current value Ip3 flowing through the first measuring pump cell 60A of the first sensor cell 15A and the second measured pump current value Ip6 flowing through the second measuring pump cell 60B of the second sensor cell 15B, the second measured pump current value Ip6 (total concentration), and the map 110 described later₃) The concentration of (c).

The temperature control means 100, the switching control means 101, the first oxygen concentration control means 102A, the second oxygen concentration control means 102B, and the target component concentration acquisition means 104 are each constituted by 1 or more processors having, for example, 1 or more CPUs (central processing units), a storage device, and the like. The processor is as follows: a software function unit that realizes a predetermined function by executing a program stored in the storage device by the CPU. Of course, the integrated circuit may be an integrated circuit such as an FPGA (Field-Programmable Gate Array) in which a plurality of processors are connected according to functions. The map 110 may be stored in advance in the storage device, which is one of the peripheral circuits of the gas sensor, as described above. Of course, the mapping 110 (stored in the storage device described above) may be obtained using a communication mechanism.

Conventional NOx sensor with series 2-chamber configuration for NO and NH₃After all the target component (2) is converted into NO in the oxygen concentration adjusting chamber, the NO is introduced into the measuring chamber, and the total amount of the 2 components is measured. That is, the concentrations of the respective 2 target components, that is, NO and NH, could not be measured₃The respective concentrations.

On the other hand, since the gas sensor 10 includes the first sensor cell 15A, the second sensor cell 15B, the temperature control means 100, the switching control means 101, the first oxygen concentration control means 102A, the second oxygen concentration control means 102B, and the target component concentration acquisition means 104, it is possible to acquire NO and the target component concentrationNH₃The respective concentrations.

The temperature control mechanism 100 performs feedback control of the first heater 72A and the second heater 72B based on a condition of a sensor temperature set in advance and a measurement value from a temperature sensor (not shown) that measures the temperature of the sensor element 12, thereby adjusting the temperature of the sensor element 12 to a temperature that meets the condition.

The first oxygen concentration control portion 106A of the first oxygen concentration control mechanism 102A performs feedback control of the first variable power source 48A based on the preset condition of the oxygen concentration in the first oxygen concentration adjustment chamber 18A and the first electromotive force V1 generated in the first oxygen partial pressure detection sensor unit 50A (see fig. 2), thereby adjusting the oxygen concentration in the first oxygen concentration adjustment chamber 18A to a concentration that meets the above-described condition.

The second oxygen concentration control portion 106B of the second oxygen concentration control mechanism 102B performs feedback control on the fourth variable power supply 48D based on the preset condition of the oxygen concentration in the second oxygen concentration adjustment chamber 18B and the fourth electromotive force V4 generated in the fourth oxygen partial pressure detection sensor unit 50D (see fig. 3), thereby adjusting the oxygen concentration in the second oxygen concentration adjustment chamber 18B to a concentration that meets the above-described condition.

In this way, the gas sensor 10 is controlled by the first oxygen concentration control means 102A and the second oxygen concentration control means 102B or the temperature control means 100, or the first oxygen concentration control means 102A, the second oxygen concentration control means 102B and the temperature control means 100: so that NH₃To suit NH₃The measured ratio is converted to NO without decomposing NO in the first oxygen concentration adjustment chamber 18A and the second oxygen concentration adjustment chamber 18B.

The first preliminary oxygen concentration control portion 108A of the first oxygen concentration control mechanism 102A performs feedback control on the first preliminary variable power source 86A based on the condition of the oxygen concentration set in advance and the first preliminary electromotive force Va generated in the first preliminary oxygen partial pressure detection sensor unit 84A (see fig. 2), thereby adjusting the oxygen concentration in the first preliminary adjustment chamber 22A to a concentration that meets the condition. NH is controlled by the first preliminary oxygen concentration control portion 108A₃To suitIn NH₃The measured ratio is converted to NO without decomposing NO in the first preliminary adjustment chamber 22A in the first sensor unit 15A.

Similarly, the second preliminary oxygen concentration control portion 108B of the second oxygen concentration control mechanism 102B performs feedback control on the second preliminary variable power supply 86B based on the condition of the oxygen concentration set in advance and the second preliminary electromotive force Vb generated in the second preliminary oxygen partial pressure detection sensor unit 84B (see fig. 3), thereby adjusting the oxygen concentration in the second preliminary adjustment chamber 22B to a concentration that meets the condition. NH is controlled by the second preliminary oxygen concentration control portion 108B₃To be used for NH₃The measured ratio is converted to NO without decomposing NO in the second preliminary adjustment chamber 22B in the second sensor unit 15B.

Here, the processing operation of the gas sensor 10 will be described with reference to fig. 5 and 6.

First, as shown in fig. 5, in the first sensor unit 15A, the first preliminary adjustment pump unit 80A is turned ON, and therefore, NH introduced into the first preliminary adjustment chamber 22A through the first gas introduction port 16A₃NH is generated in the first preliminary adjustment chamber 22A₃Oxidation reaction of → NO, NH introduced through the first gas introduction port 16A₃All converted to NO. Thus, NH₃By NH₃Diffusion coefficient of 2.2cm²The diffusion rate of NO is 1.8cm at/sec after the first diffusion rate control part 34A and the second diffusion rate control part 36A on the back side of the first preliminary adjustment chamber 22A²And/sec toward the first measuring chamber 20A.

On the other hand, in the second sensor unit 15B, since the second preliminary adjustment pump unit 80B is in the OFF state, NH introduced through the second gas introduction port 16B is introduced₃To the second oxygen concentration adjustment chamber 18B. In the second oxygen concentration adjustment chamber 18B, NH is controlled by the second oxygen concentration control means 102B (see fig. 4)₃All of which are converted into NO, and therefore, NH flowed into the second oxygen concentration adjusting chamber 18B₃NH is generated in the second oxygen concentration adjustment chamber 18B₃Oxidation reaction of → NO, NH in the second oxygen concentration adjusting chamber 18B₃All transformationIs NO. Therefore, NH introduced through the second gas introduction port 16B₃By NH₃Diffusion coefficient of 2.2cm²The second diffusion rate is converted to NO in the second oxygen concentration adjustment chamber 18B by the first diffusion rate controller 34B and the second diffusion rate controller 36B, and the diffusion coefficient of NO is 1.8cm²The/sec passes through the third diffusion rate controller 38B and moves into the adjacent second measurement chamber 20B.

That is, in the first sensor cell 15A, NH occurs₃The oxidation reaction of (1) is performed in the first preliminary adjustment chamber 22A, and NH is generated in the second sensor cell 15B₃The oxidation reaction site of (2) is the second oxygen concentration adjustment chamber 18B. NO, NH₃Has different diffusion coefficients, and therefore, NO passes through the second diffusion rate control parts (36A, 36B) or NH₃The difference in the second diffusion rate control units (36A, 36B) corresponds to the difference in the amount of NO flowing into the first measurement chamber 20A and the second measurement chamber 20B. This causes a difference between the first measured pump current value Ip3 of the first measuring pump cell 60A and the second measured pump current value Ip6 of the second measuring pump cell 60B. However, the second measurement pump current value Ip6 of the second measurement pump cell 60B corresponds to NH in the measurement target gas₃The total of the concentration and the NO concentration.

The amount of change Δ Ip between the first measured pump current value Ip3 and the second measured pump current value Ip6 is dependent on NH in the gas to be measured₃Is varied. Therefore, the second measurement pump current value Ip6(NO and NH) flows through the second measurement pump cell 60B₃Total concentration of (d), and the amount of change Δ Ip (NH)₃Concentration of) capable of capturing NO and NH₃The respective concentrations.

Therefore, in the target component concentration acquisition means 104 (see fig. 4), NO and NH are acquired based on the amount of change Δ Ip between the first measured pump current value Ip3 and the second measured pump current value Ip6, the second measured pump current value Ip6, and, for example, the map 110 (see fig. 7)₃The respective concentrations.

When expressed in the form of a graph, as shown in fig. 7, map 110 is a graph in which the horizontal axis is set to second measured pump current value Ip6(μ a) and the vertical axis is set to change amount Δ Ip (μ a) between first measured pump current value Ip3 and second measured pump current value Ip 6. In fig. 7, there are representatively shown: the first characteristic line L1 and the second characteristic line L2, and the first plot group P1, the second plot group P2, and the third plot group P3 of the variation Δ Ip in the series of 100ppm, the series of 50ppm, and the series of 25ppm in terms of NO concentration.

The first characteristic line L1 shows: when the converted value of the concentration of NO is 0ppm, that is, when NO is not contained in the gas to be measured, NH is caused to be present₃The concentration conversion value of (B) is changed to 0ppm, 25ppm, 50ppm, 75ppm and 100 ppm.

The second characteristic line L2 shows: NH (NH)₃When the concentration conversion value of (A) is 0ppm, that is, the gas to be measured does not contain NH₃The reduced NO concentration values were changed to 0ppm, 25ppm, 50ppm, 75ppm and 100 ppm.

The graph of fig. 7 is expressed in a table form for easy understanding, and the content shown in fig. 8 is obtained. These contents can be found by carrying out experiments 1 to 5 described later, for example.

In the table of FIG. 8, the first column [1]]Corresponds to the first characteristic line L1 in FIG. 7, and the second column [2]]Corresponds to the second characteristic line L2 in fig. 7. Through [1]]And [2]The comparison of (A) shows that: NH (NH)₃With a sensitivity of 1.14 times that of NO. This is based on NH₃The difference in diffusion coefficient from NO appears to depend on the temperature of the sensor element 12, the oxygen concentration in the internal cavity. In addition, in the table of FIG. 8, the third column [3]]Corresponds to the first drawing group P1 in FIG. 7, fourth column [4]]Corresponds to the second drawing group P2 in FIG. 7, and the fifth column [5]]Corresponds to the third drawing group P3 in fig. 7.

In Table 1 of FIG. 8, the third column [3] is referred to]Fourth column [4]]And the fifth column [5]]Based on the second measured pump current value Ip6, the total concentration (NO equivalent), that is, any of the 100ppm series, 50ppm series, and 25ppm series is estimated, and NH is obtained based on the change amount Δ Ip₃Concentration, subtracting NH from the total concentration₃Concentration to obtain the NO concentration.

For example, when the second measured pump current value Ip6 is 0.537 (. mu.A), it is shown in the fifth column [5] of Table 1 in FIG. 8]The total concentration was estimated to be in the 25ppm range. Then, when the variation Δ Ip is 0.041(μ A), the fifth column [5] of Table 1 in FIG. 8 is followed]Known as NH₃The concentration was 4.4 ppm. Thus, NH is considered₃The sensitivity to NO was poor, with NO concentration 25-4.4 × 1.14 to about 20.0 ppm.

In the case where the change amount Δ Ip does not exist in the map 110, the closest change amount Δ Ip is determined in the map 110, the total concentration is estimated, and NH is solved by, for example, a known approximate calculation₃And (4) concentration. Then, the estimated total concentration is subtracted by NH determined by approximation calculation₃The concentration of NO may be determined. Alternatively, it may be based on NH₃And NO, respectively, and Δ Ip and Ip6 to calculate a second target component NH₃And the concentration of the second target component is subtracted from the total concentration to calculate the concentration of the first target component NO.

Here, an experimental example for obtaining the map 110 will be described.

(1) The sensor element 12 is manufactured, metal parts are assembled to form a sensor shape, and the sensor element 12 is mounted on a sample gas measuring apparatus, and the sensor element 12 is heated to approximately 800 ℃ by the first heater 72A and the second heater 72B incorporated in the sensor element 12.

(2) The voltage applied between the first main inner pump electrode 44A and the outer pump electrode 46 and the voltage applied between the second main inner pump electrode 44B and the outer pump electrode 46 are feedback-controlled so that the electromotive force between the first main inner pump electrode 44A and the reference electrode 52 of the first sensor cell 15A and the electromotive force between the second main inner pump electrode 44B and the reference electrode 52 of the second sensor cell 15B reach 230 mV.

(3) Next, the voltage applied between the first main inner pump electrode 44A and the outer pump electrode 46 and the voltage applied between the second main inner pump electrode 44B and the outer pump electrode 46 are feedback-controlled so that the electromotive force between the first auxiliary pump electrode 58A and the reference electrode 52 of the first sensor cell 15A and the electromotive force between the second auxiliary pump electrode 58B and the reference electrode 52 of the second sensor cell 15B reach 385 mV.

(4) Further, the voltage applied between the first measurement electrode 62A and the outer pump electrode 46 and the voltage applied between the second measurement electrode 62B and the outer pump electrode 46 are feedback-controlled so that the electromotive force between the first measurement electrode 62A and the reference electrode 52 of the first measurement pump unit 60A of the first sensor unit 15A and the electromotive force between the second measurement electrode 62B and the reference electrode 52 of the second measurement pump unit 60B of the second sensor unit 15B reach 400 mV.

(5) The first switch SW1 is turned ON to put the first preliminary adjustment pump unit 80A of the first sensor unit 15A in an ON state, and the second switch SW2 is turned OFF to put the second preliminary adjustment pump unit 80B of the second sensor unit 15B in an OFF state. Then, the voltage applied between the first preliminary pump electrode 82A and the outer pump electrode 46 is feedback-controlled so that the electromotive force between the first preliminary pump electrode 82A of the first preliminary adjustment pump unit 80A and the reference electrode 52 becomes a predetermined voltage.

(6) Next, N is added₂And 3% of H₂O was caused to flow into the sample gas measuring apparatus at a flow rate of 120L/min as a base gas, and the currents flowing through the first measuring pump unit 60A and the second measuring pump unit 60B were measured, and as a result, the offset current flowing through the first measuring pump unit 60A and the second measuring pump unit 60B was 0.003 μ a.

(7) Next, N is added₂And 3% of H₂O as a base gas was caused to flow into the sample gas measuring apparatus at a flow rate of 120L/min, and NH was added in an amount of 25ppm, 50ppm, 75ppm, and 100ppm while maintaining a total gas flow rate of 120L/min₃The first measurement pump current Ip3 and the second measurement pump current Ip6 flowing through the first measurement pump cell 60A and the second measurement pump cell 60B were measured (see experiment 1: the first characteristic line L1 in FIG. 7, the first column [1] of Table 1 in FIG. 8])。

(8) Next, N is added₂And 3% of H₂O as a base gas was caused to flow into the sample gas measuring apparatus at a flow rate of 120L/min, and 25ppm, 50ppm, 75ppm and 100ppm of NO were added in stages while maintaining a total gas flow rate of 120L/min, and the first measurement pump current Ip3 and the second measurement pump current Ip6 flowing through the first measurement pump cell 60A and the second measurement pump cell 60B were measured (see experiment 2: the second characteristic line L2 in FIG. 7, and the second column [2] of Table 1 in FIG. 8])。

(9) Next, N is added₂And 3% of H₂O was used as a base gas, and was caused to flow into a sample gas measuring apparatus at a flow rate of 120L/min, so that the NO concentrations were gradually decreased so that NO became 100ppm, 80ppm, 60ppm, 40ppm, 20ppm, and 0ppm, and NH was added to the gas with respect to the respective NO concentrations of NO 80ppm, 60ppm, 40ppm, 20ppm, and 0ppm₃The second measurement pump current value Ip6 of the second measurement pump unit 60B at which NO is 100ppm is maintained at 2.137 μ a. At this time, the flow rate of the base gas was adjusted so that the total gas flow rate was maintained at 120L/min. In each gas atmosphere, the first measurement pump current Ip3 flowing through the first measurement pump unit 60A was measured (experiment 3). From the first drawing group P1 in FIG. 7, the third column [3] of Table 1 of FIG. 8]Show respective NO and NH₃The first measured pump current value Ip3 and the second measured pump current value Ip6, and the difference (change amount Δ Ip) between the first measured pump current value Ip3 and the second measured pump current value Ip 6.

(10) Next, N is added₂And 3% of H₂O was used as a base gas, and was caused to flow into a sample gas measuring apparatus at a flow rate of 120L/min, so that the NO concentrations were gradually decreased so as to become NO at 50ppm, 40ppm, 30ppm, 20ppm, 10ppm, and 0ppm, and NH was added to the gas with respect to the respective NO concentrations of NO at 40ppm, 30ppm, 20ppm, 10ppm, and 0ppm₃The second measurement pump current value Ip6 of the second measurement pump unit 60B when NO is 50ppm is maintained at 1.070 μ a. At this time, the flow rate of the base gas was adjusted so that the total gas flow rate was maintained at 120L/min. In each gas atmosphere, the first measurement pump current Ip3 flowing through the first measurement pump unit 60A was measured (experiment 4). From the second drawing group P2, fig. 7Column four of Table 1 [4] 8]Show respective NO and NH₃The first measured pump current value Ip3 and the second measured pump current value Ip6, and the difference (change amount Δ Ip) between the first measured pump current value Ip3 and the second measured pump current value Ip 6.

(11) Next, N is added₂And 3% of H₂O was used as a base gas, and was caused to flow into a sample gas measuring apparatus at a flow rate of 120L/min, so that the NO concentrations were gradually decreased so as to become NO 25ppm, 20ppm, 15ppm, 10ppm, 5ppm, and 0ppm, and NH was added to the gas with respect to the respective NO concentrations of NO 20ppm, 15ppm, 10ppm, 5ppm, and 0ppm₃The second measurement pump current value Ip6 of the second measurement pump unit 60B when NO is 25ppm is maintained at 0.537 μ a. At this time, the flow rate of the base gas was adjusted so that the total gas flow rate was maintained at 120L/min. In each gas atmosphere, the first measurement pump current Ip3 flowing through the first measurement pump unit 60A was measured (experiment 5). From the third drawing group P3 in FIG. 7, the fifth column [5] of Table 1 of FIG. 8]Show respective NO and NH₃The first measured pump current value Ip3 and the second measured pump current value Ip6, and the difference (change amount Δ Ip) between the first measured pump current value Ip3 and the second measured pump current value Ip 6.

(12) The map 110 shown in fig. 7 corresponding to the first sensor unit 15A is created using the data obtained in experiments 1 to 5. To confirm the accuracy of the obtained map 110, NO and NH at concentrations different from those of experiments 1 to 5 were applied₃The first measured pump current value Ip3 and the second measured pump current value Ip6 in the mixed gas, and the difference (change amount Δ Ip) between the first measured pump current value Ip3 and the second measured pump current value Ip6 were measured, and as a result, the results shown in table 2 of fig. 9 were obtained. The results of table 2 are plotted as a graph (denoted by Δ) in fig. 7, and as a result, it was found that there is good agreement with the concentration estimated from the map 110.

(13) Next, the first switch SW1 is set to OFF and the second switch SW2 is set to ON, so that the first preliminary adjustment pump unit 80A of the first sensor unit 15A is in an OFF state and the second preliminary adjustment pump unit 80B of the second sensor unit 15B is in an ON state. Then, the second sensor unit 15B is subjected to an experiment in the same order as in (1) to (5) above, and the voltage applied between the second preliminary pump electrode 82B and the outer pump electrode 46 is feedback-controlled so that the electromotive force between the second preliminary pump electrode 82B and the reference electrode 52 of the second preliminary adjustment pump unit 80B becomes a predetermined voltage.

(14) Then, the same experiment as in (6) to (11) described above is performed to create a map corresponding to the second sensor unit 15B. Since the content of the map is substantially the same as the map 110 shown in fig. 7, the map 110 is used as a map for the first sensor unit 15A and the second sensor unit 15B.

However, for example, if only the first preliminary adjustment pump unit 80A is turned ON, only the first preliminary pump electrode 82A of the first preliminary adjustment pump unit 80A is deteriorated. Therefore, by switching ON/OFF of the first preliminary adjustment pump unit 80A and the second preliminary adjustment pump unit 80B, the durability of the entire first sensor unit 15A and the second sensor unit 15B is improved.

Here, a preferred ON/OFF switching timing (switching control) of the first preliminary adjustment pump unit 80A and the second preliminary adjustment pump unit 80B will be described with reference to fig. 10A to 17.

First, fig. 10A, 12A, 14A, and 16A are timing charts showing the start and end of operation of a vehicle or the like having an engine mounted thereon, and fig. 10B, 12B, 14B, and 16B are timing charts showing the ON/OFF switching timing of the first preliminary adjustment pump unit 80A and the second preliminary adjustment pump unit 80B. Fig. 10C, 12C, 14C, and 16C are block diagrams of the switching control, and fig. 11, 13, 15, and 17 are flowcharts showing the ON/OFF switching timing of the first preliminary adjustment pump unit 80A and the second preliminary adjustment pump unit 80B.

[ first switching timing ]

As shown in fig. 10A and 10B, the first switching timing is as follows: the first preliminary adjustment pump unit 80A and the second preliminary adjustment pump unit 80B are switched ON/OFF substantially in synchronization with the start of operation of, for example, an engine (see fig. 10C and the like) as a drive source.

That is, as shown in fig. 10C, the switching control means 101 performs ON/OFF switching of the first preliminary adjustment pump unit 80A and the second preliminary adjustment pump unit 80B based ON an engine operation start signal Sa from, for example, the engine ECU 200.

To explain this based on the flowchart of fig. 11, first, in step S1, switch control section 101 determines whether or not engine operation start signal Sa is input from, for example, engine ECU 200. When the engine operation start signal Sa is input, the switching control means 101 switches ON/OFF of the first preliminary adjustment pump unit 80A and the second preliminary adjustment pump unit 80B in step S2.

For example, if the first preliminary adjustment pump unit 80A is in the ON state and the second preliminary adjustment pump unit 80B is in the OFF state, the first preliminary adjustment pump unit 80A is switched OFF and the second preliminary adjustment pump unit 80B is switched ON. Of course, if the first preliminary adjustment pump unit 80A is in the OFF state and the second preliminary adjustment pump unit 80B is in the ON state, the first preliminary adjustment pump unit 80A is switched ON and the second preliminary adjustment pump unit 80B is switched OFF. The same applies hereinafter.

Then, in step S3, switch control means 101 determines whether or not there is a request for termination (power off, maintenance, etc.) from engine ECU200, for example. If there is no end request, the processing from step S1 onward is repeatedly executed, and if there is an end request, the processing in the switch control means 101 is ended.

[ second switching timing ]

As shown in fig. 12A and 12B, the second switching timing is as follows: the first preliminary adjustment pump unit 80A and the second preliminary adjustment pump unit 80B are switched ON/OFF every time a predetermined fixed time Ta elapses, regardless of the start and end of the operation of the engine.

That is, as shown in fig. 12C, the switching control means 101 switches ON/OFF of the first preliminary pump unit 80A and the second preliminary pump unit 80B based ON the input of a signal Sb indicating that a certain time Ta has elapsed from, for example, the engine ECU 200.

To explain this with reference to the flowchart of fig. 13, first, in step S101, the switch control means 101 determines whether or not a signal Sb indicating that a fixed time Ta has elapsed has been input from, for example, the engine ECU 200. When the signal Sb is input, the switch control means 101 switches ON/OFF of the first preliminary adjustment pump unit 80A and the second preliminary adjustment pump unit 80B in step S102.

Then, in step S103, the switch control means 101 determines whether or not there is an end request (power off, maintenance, etc.) from the engine ECU200, for example. If there is no end request, the processing from step S101 is repeatedly executed, and if there is an end request, the processing in the switch control means 101 is ended.

[ third switching timing ]

As shown in fig. 14A and 14B, the third switching timing is as follows: after a predetermined time Tb has elapsed from the start of operation, the first and second preliminary

adjustment pump units

80A and 80B are switched ON/OFF at the start of the next operation.

That is, as shown in fig. 14C, the switch control means 101 waits for the input of the signal Sd indicating the start of the next operation from the engine ECU200, based on the input of the signal Sc indicating the elapse of the predetermined time Tb from the operation start time from the engine ECU200, for example. Then, ON/OFF switching of the first preliminary adjustment pump unit 80A and the second preliminary adjustment pump unit 80B is performed based ON input of a signal Sd indicating start of operation.

To explain this based on the flowchart of fig. 15, first, in step S201, the switch control means 101 determines whether or not the signal Sc indicating that the predetermined time Tb has elapsed since the start of operation has been input from, for example, the engine ECU 200. When the signal Sc is input, the process proceeds to step S202, and the switch control means 101 waits for the input of the signal Sd indicating the start of the next operation from the engine ECU 200. When the signal Sd indicating the start of the next operation is input, the flow proceeds to step S203, and the switching control means 101 switches ON/OFF of the first preliminary adjustment pump unit 80A and the second preliminary adjustment pump unit 80B.

Then, in step S204, switch control unit 101 determines whether or not there is a request for termination (power off, maintenance, etc.) from engine ECU200, for example. If there is no end request, the processing from step S201 is repeatedly executed, and if there is an end request, the processing in the switch control means 101 is ended.

[ fourth switching timing ]

The third switching timing is substantially the same as the third switching timing described above, but is different in that: as shown in fig. 16A and 16B, the operation time is not after the predetermined time Tb has elapsed from the operation start time, but the previous operation time is taken as a reference. That is, the fourth switching timing is as follows: after the same time as the previous operation time has elapsed since the current operation start time, the first and second preliminary

adjustment pump units

80A and 80B are switched ON/OFF at the next operation start time.

That is, as shown in fig. 16C, engine ECU200 maintains the time from the start of operation to the end of operation as the previous operation time. Then, the signal Se is output at the time when the previous operation time has elapsed since the operation start time of this time. Further, as in the case of the third switching timing, a signal Sd indicating the start of the next operation is output.

The switching control means 101 waits for the input of a signal Sd indicating the start of the next operation from the engine ECU200 based ON the input state of the signal Se from the engine ECU200, for example, and performs ON/OFF switching of the first preliminary adjustment pump unit 80A and the second preliminary adjustment pump unit 80B based ON the input signal Sd.

To explain this operation based on the flowchart of fig. 17, first, in step S301, the switch control means 101 determines whether or not a signal Se indicating that the last operation time has elapsed since the start of the current operation is input from, for example, the engine ECU 200. When signal Se is input, the process proceeds to step S302, and switch control unit 101 waits for input of signal Sd indicating the start of the next operation from engine ECU 200. When the signal Sd indicating the start of the next operation is input, the flow proceeds to step S303, and the switching control means 101 switches ON/OFF of the first preliminary adjustment pump unit 80A and the second preliminary adjustment pump unit 80B.

Then, in step S304, switch control unit 101 determines whether or not there is an end request (power off, maintenance, etc.) from engine ECU200, for example. If there is no end request, the processing from step S301 is repeatedly executed, and if there is an end request, the processing in the switch control means 101 is ended.

[ invention obtained according to the embodiment ]

The above embodiments are summarized below.

[1] The gas sensor 10 according to the present embodiment is a gas sensor for measuring concentrations of a first target component and a second target component, and includes:

1 or more sensor elements (12, 12A, 12B);

a temperature control mechanism 100 that controls the temperature of the sensor element;

1 or more oxygen concentration control means (102A, 102B); and

the target component concentration acquisition means 104 acquires the target component concentration,

the sensor element has: a structure 14 containing at least an oxygen ion conductive solid electrolyte; and 1 or more sensor units (15A, 15B) formed on the structure body 14,

the sensor unit is provided with gas introduction ports (16A, 16B), first diffusion rate control sections (34A, 34B), first chambers (22A, 22B), second diffusion rate control sections (36A, 36B), second chambers (18A, 18B), third diffusion rate control sections (38A, 38B), and measurement chambers (20A, 20B) facing the direction of introduction of the gas,

the measuring chamber of 1 or more sensor units is provided with target component measuring pump units (60A, 60B),

the oxygen concentration control means controls the oxygen concentrations in the first chamber and the second chamber of 1 or more sensor units,

the target component concentration acquisition means 104 acquires the concentration of the second target component based on the difference between the current value flowing in one target component measurement pump cell and the current value flowing in the other target component measurement pump cell,

measuring the current value flowing through the pump unit based on the other target component to obtain the total concentration of the first target component and the second target component,

the concentration of the second target component is subtracted from the total concentration to obtain the concentration of the first target component.

As described above, since the first oxygen concentration control means 102A controls the oxygen concentrations in the first chamber 22A and the second chamber 18A of the first sensor unit 15A and the second oxygen concentration control means 102B controls the oxygen concentrations in the first chamber 22B and the second chamber 18B of the second sensor unit 15B, it is possible to measure the respective concentrations of a plurality of target components in the gas to be measured, and to measure an unburned component such as an exhaust gas and a plurality of components (for example, NO and NH) coexisting in an environment in which oxygen is present with good accuracy over a long period of time₃) The concentration of (c).

Further, the gas sensor 10 can easily measure NO and NH that have not been realized conventionally by changing software of a control system of the gas sensor 10 without separately adding various measurement devices as hardware or the like₃The treatment of each concentration of (1). As a result, the accuracy of the control and the failure monitoring for the NOx purification system can be improved. In particular, NO and NH in the exhaust gas downstream of the SCR system can be converted₃The difference contributes to precise control of the urea injection amount and degradation monitoring of the SCR system.

[2] In the present embodiment, 1 sensor element 12 may be provided, and the sensor element 12 may include the first sensor unit 15A and the second sensor unit 15B. This makes it possible to measure the concentration of each of the plurality of target components in the gas to be measured using 1 sensor element 12, and to reduce the size of the measurement system.

[3] In the present embodiment, 2

sensor elements

12A and 12B may be provided, one sensor element 12A may have a first sensor unit 15A, and the other sensor element 12B may have a second sensor unit 15B. Accordingly, the first sensor element 12A and the second sensor element 12B can be provided so that the respective distal end portions (the first gas introduction port 16A and the second gas introduction port 16B) of the first sensor element 12A and the second sensor element 12B can be provided so as to face each other, and the measurement target region can be flexibly dealt with.

[4] In the present embodiment, the present invention includes: a first preliminary adjustment pump unit 80A disposed on the first chamber 22A side of the first sensor unit 15A; a first oxygen concentration adjustment pump unit 42A disposed on the second chamber 18A side of the first sensor unit 15A; a second preliminary adjustment pump unit 80B disposed on the first chamber 22B side of the second sensor unit 15B; and a second oxygen concentration adjustment pump unit 42B disposed on the second chamber 18B side of the second sensor unit 15B,

the first oxygen concentration control mechanism 102A includes:

a first preliminary oxygen concentration control unit 108A that controls the first preliminary adjustment pump unit 80A to control the oxygen concentration in the first chamber 22A of the first sensor unit 15A; and

a first oxygen concentration control portion 106A that controls the oxygen concentration of the second chamber 18A of the first sensor unit 15A by controlling the first oxygen concentration adjustment pump unit 42A,

the second oxygen concentration control mechanism 102B includes:

a second preliminary oxygen concentration control unit 108B that controls the second preliminary adjustment pump unit 80B to control the oxygen concentration in the first chamber 22B of the second sensor unit 15B; and

and a second oxygen concentration control unit 106B that controls the second oxygen concentration adjustment pump unit 42B to control the oxygen concentration in the second chamber 18B of the second sensor unit 15B.

Thus, it is not necessary to use a gas sensor having a pump that is always in an ON state and a gas sensor having a pump that is always in an OFF state. That is, the electrode of the gas sensor having the pump which is always ON can be prevented from being deteriorated more than other gas sensors which are not so deteriorated, and the life of the gas sensor which can measure a plurality of components can be extended.

[5] The present embodiment includes: a first switch SW1 that ON/OFF controls the driving of the first preliminary adjustment pump unit 80A; a second switch SW2 that ON/OFF controls the driving of the second preliminary adjustment pump unit 80B; and a switch control means 101 for controlling switching of the first switch SW1 and the second switch SW 2.

By switching and controlling the first switch SW1 and the second switch SW2 by the switch control means 101, the driving of the first preliminary adjustment pump unit 80A and the driving of the second preliminary adjustment pump unit 80B can be ON/OFF controlled.

[6] In the present embodiment, the switch control mechanism 101 can perform switching control of the first switch SW1 and the second switch SW2 substantially in synchronization with the start of operation of the drive source.

[7] In the present embodiment, the switch control mechanism 101 can perform switching control of the first switch SW1 and the second switch SW2 each time a predetermined fixed time Ta elapses, regardless of the start and end of the operation of the drive source.

[8] In the present embodiment, the switch control mechanism 101 may perform switching control of the first switch SW1 and the second switch SW2 at the start of the next operation after a predetermined time Tb has elapsed from the start of the operation of the drive source. In this case, since the variation in the ON time is reduced, it is effective in extending the life of the gas sensor.

[9] In the present embodiment, the switch control mechanism 101 may perform switching control of the first switch SW1 and the second switch SW2 at the start of the next operation after the same time as the previous operation time has elapsed from the start of operation of the drive source. In this case, similarly, the variation in ON time is also reduced, and therefore, it is effective in extending the life of the gas sensor.

[10] In the present embodiment, the second chamber 18A of the first sensor unit 15A may have: a first main regulation chamber 18Aa communicating with the first chamber 22A of the first sensor unit 15A; and a first sub regulation chamber 18Ab communicating with the first main regulation chamber 18Aa, the second chamber 18B of the second sensor unit 15B having: a second main regulation chamber 18Ba communicating with the first chamber 22B of the second sensor unit 15B; and a second sub regulation chamber 18Bb communicating with the second main regulation chamber 18Ba, the first measurement chamber 20A of the first sensor unit 15A communicating with the first sub regulation chamber 18Ab, and the second measurement chamber 20B of the second sensor unit 15B communicating with the second sub regulation chamber 18 Bb.

[11] In the present embodiment, fourth diffusion

rate control portions

40A and 40B may be provided between the first main adjustment chamber 18Aa and the first sub adjustment chamber 18Ab, and between the second main adjustment chamber 18Ba and the second sub adjustment chamber 18Bb, respectively.

[12] In the present embodiment, it is preferable that the first chamber 22A of the first sensor unit 15A and the first chamber 22B of the second sensor unit 15B have the

pump electrodes

82A and 82B, respectively, the second chamber 18A of the first sensor unit 15A and the second chamber 18B of the second sensor unit 15B have the

pump electrodes

44A and 44B, respectively, the first measurement chamber 20A of the first sensor unit 15A and the second measurement chamber 20B of the second sensor unit 15B have the

measurement electrodes

62A and 62B, respectively, and each pump electrode is made of a material having lower catalytic activity than each measurement electrode.

[13]In the present embodiment, the first target component may be NO and the second target component may be NH₃。

[14]In the present embodiment, the first preliminary oxygen concentration control portion 108A may be formed to convert NH into NH₃The oxygen concentration in the first chamber 22A is controlled under the condition that NO in the first chamber 22A of the first sensor unit 15A is not decomposed by oxidation, and the second preliminary oxygen concentration control portion 108B controls NH₃The condition of oxidizing but not decomposing NO in the second chamber 22B of the second sensor unit 15B controls the oxygen concentration in the second chamber 22B.

[15]In the present embodiment, the target component concentration acquisition means 104 may use a map 110 obtained by using a map 110 in which the NO concentration and the NH concentration are determined based on a current value Ip6 flowing through the second target component measurement pump cell 60B, a difference Δ Ip between a current value Ip3 flowing through the first target component measurement pump cell 60A and a current value Ip6 flowing through the second target component measurement pump cell 60B, which are experimentally measured in advance, and the map 110 is obtained by determining the NO concentration and the NH concentration, respectively₃The concentration relationship is obtained by measuring the current value Ip6 flowing through the pump cell 60B for the second target component in actual useAnd the difference Δ Ip between the current value Ip3 flowing through the first target component measurement pump cell 60A and the current value Ip6 flowing through the second target component measurement pump cell 60B is compared with the map 110, thereby obtaining NO and NH₃The respective concentrations.

[16] In the present embodiment, an oxygen concentration detection means 70 may be provided for measuring the oxygen concentration based on the pump current value flowing through the second oxygen concentration adjustment pump unit 42B.

[17] In the present embodiment, the first outer pump electrode 46A disposed outside at least the second chamber 18A of the first sensor unit 15A and the second outer pump electrode 46B disposed outside at least the second chamber 18B of the second sensor unit 15B can be used in common. This can reduce the number of wires, and facilitate installation in various vehicles and the like.

[18] In the present embodiment, the first target component measurement pump unit 60A may include: a first measurement electrode 62A disposed in the first measurement chamber 20A of the first sensor unit 15A; and a first reference electrode 52 disposed in the reference gas introduction space 41 of the sensor element 12, and the second target component measurement pump unit 60B includes: a second measurement electrode 62B disposed in the measurement chamber 20B of the second sensor unit 15B; and a second reference electrode 52 disposed in the reference gas introduction space 41 of the sensor element 12, the first reference electrode 52 and the second reference electrode 52 being common (the reference electrode 52 (see fig. 1)). In this case as well, the number of wires can be reduced, so that the mounting in an automobile or the like becomes easy.

[19] As shown in a modification (gas sensor 10a) of fig. 18, the first sensor cell 15A and the second sensor cell 15B may be arranged to substantially face each other in the thickness direction of the sensor element 12.

The gas sensor according to the present invention is not limited to the above-described embodiments, and various configurations may be adopted without departing from the spirit of the present invention.

In the above example, the first sensor unit 15A is provided with the first measurement chamber 20A adjacent to the first sub adjustment chamber 18Ab, and the first measurement chamber 20A is provided thereinAlthough the first measurement electrode 62A is provided, in addition to this, although not shown, the first measurement electrode 62A may be disposed in the first sub-regulation chamber 18Ab, and alumina (Al) may be formed as the third diffusion rate control unit 38A so as to cover the first measurement electrode 62A₂O₃) And the like. In this case, the periphery of the first measurement electrode 62A functions as the first measurement chamber 20A.

In the second sensor cell 15B, similarly, the second measurement electrode 62B may be disposed in the second sub regulation chamber 18Bb, and alumina (Al) may be formed as the third diffusion rate control portion 38B so as to cover the second measurement electrode 62B₂O₃) And the like. In this case, the periphery of the second measurement electrode 62B functions as the second measurement chamber 20B.

In addition, the above examples show NH as the second target component in the

preliminary adjustment chambers

22A, 22B₃Or NO₂Examples of conversion to NO at 100% conversion, however, NH₃The conversion of (b) is not necessarily 100%, and may be based on the NH content of the gas to be measured₃The conversion rate is set arbitrarily within a range in which a good reproducibility is achieved by the concentration.

The drive of the first preliminary oxygen concentration control unit 108A and the second preliminary oxygen concentration control unit 108B may be in the direction of sucking oxygen from the inside of the first preliminary adjustment chamber 22A and the inside of the second preliminary adjustment chamber 22B, or in the direction of sucking oxygen, as long as the second target component is NH₃The presence of (3) may be sufficient to change the measurement pump currents Ip3, Ip6 as the outputs of the measurement pump cells with good reproducibility.

As shown in fig. 1 and 18, the

gas sensors

10 and 10a have a structure in which a plurality of sensor cells (for example, a first sensor cell 15A and a second sensor cell 15B) are formed in 1 structure 14 constituting a sensor element 12.

For example, as shown in fig. 19, the gas sensor 10 may have a plurality of sensor elements (e.g., a first sensor element 12A and a second sensor element 12B). In the gas sensor 10 shown in fig. 19, 1 first sensor cell 15A is formed in 1 first structure 14A constituting the

first sensor element

12A, and 1 second sensor cell 15B is formed in 1 second structure 14B constituting the second sensor element 12B. Further, as the reference electrode, a first reference electrode 52A is formed for the first sensor element 12A, and a second reference electrode 52B is formed for the second sensor element 12B.

A first outer pump electrode 46A is formed on the upper surface of the second solid electrolyte layer 32 of the first structure 14A (see fig. 2) from a region corresponding to the first main adjustment chamber 18Aa to a region corresponding to the first sub adjustment chamber 18 Ab. Similarly, a second outer pump electrode 46B is formed on the upper surface of the second solid electrolyte layer 32 of the second structure 14B (see fig. 3) from a region corresponding to the second main adjustment chamber 18Ba to a region corresponding to the second sub adjustment chamber 18 Bb.

In addition, in carrying out the present invention, various mechanisms for improving the reliability of automobile parts may be added within a range not to impair the concept of the present invention.

Claims

1. A gas sensor for measuring the concentrations of a first target component and a second target component,

the gas sensor is characterized by comprising:

1 or more sensor elements (12, 12A, 12B);

a temperature control mechanism (100) that controls the temperature of the sensor element;

1 or more oxygen concentration control means (102A, 102B); and

a target component concentration acquisition means (104),

the sensor element has: a structure (14) containing at least an oxygen ion conductive solid electrolyte, and 1 or more sensor cells (15A, 15B) formed on the structure (14),

the sensor unit is provided with gas introduction ports (16A, 16B), first diffusion rate control sections (34A, 34B), first chambers (22A, 22B), second diffusion rate control sections (36A, 36B), second chambers (18A, 18B), third diffusion rate control sections (38A, 38B), and measurement chambers (20A, 20B) facing the gas introduction direction,

the measurement chamber of the 1 or more sensor units is provided with target component measurement pump units (60A, 60B),

the oxygen concentration control means (102A, 102B) controls the oxygen concentration in the first chamber (22A, 22B) and the second chamber (18A, 18B) of the 1 or more sensor units (15A, 15B),

the target component concentration acquisition means (104) acquires the concentration of the second target component based on the difference between the current value flowing through one of the target component measurement pump units (60A) and the current value flowing through the other target component measurement pump unit (60B),

measuring the current value flowing through the pump unit (60B) based on the other target component to obtain the total concentration of the first target component and the second target component,

2. The gas sensor according to claim 1,

having 1 of said sensor elements (12),

the sensor element (12) has a first sensor unit (15A) and a second sensor unit (15B).

3. The gas sensor according to claim 1,

having 2 said sensor elements (12A, 12B),

one of the sensor elements (12A) has a first sensor unit (15A),

the other sensor element (12B) has a second sensor unit (15B).

4. The gas sensor according to claim 2,

the disclosed device is provided with: a first preliminary adjustment pump unit (80A) disposed on the first chamber (22A) side of the first sensor unit (15A); a first oxygen concentration adjustment pump unit (42A) disposed on the second chamber (18A) side of the first sensor unit (15A); a second preliminary adjustment pump unit (80B) disposed on the first chamber (22B) side of the second sensor unit (15B); and a second oxygen concentration adjustment pump unit (42B) disposed on the second chamber (18B) side of the second sensor unit (15B),

the first oxygen concentration control means (102A) is provided with:

a first preliminary oxygen concentration control unit (108A) that controls the first preliminary adjustment pump unit (80A) to control the oxygen concentration in the first chamber (22A) of the first sensor unit (15A); and

a first oxygen concentration control portion (106A) that controls the oxygen concentration of the second chamber (18A) of the first sensor unit (15A) by controlling the first oxygen concentration adjustment pump unit (42A),

the second oxygen concentration control mechanism (102B) is provided with:

a second preliminary oxygen concentration control unit (108B) that controls the oxygen concentration in the first chamber (22B) of the second sensor unit (15B) by controlling the second preliminary adjustment pump unit (80B); and

and a second oxygen concentration control unit (106B) that controls the second oxygen concentration adjustment pump unit (42B) to control the oxygen concentration in the second chamber (18B) of the second sensor unit (15B).

5. The gas sensor according to claim 4, characterized by having:

a first switch (SW1) that ON/OFF-controls the driving of the first preliminary adjustment pump unit (80A);

a second switch (SW2) that ON/OFF-controls the driving of the second preliminary adjustment pump unit (80B); and

and a switch control means (101) for controlling the switching of the first switch (SW1) and the second switch (SW 2).

6. The gas sensor according to claim 5,

the switch control mechanism (101) performs switching control of the first switch (SW1) and the second switch (SW2) substantially in synchronization with the start of operation of the drive source.

7. The gas sensor according to claim 5,

the switch control mechanism (101) performs switching control of the first switch (SW1) and the second switch (SW2) each time a predetermined fixed time (Ta) elapses, regardless of start and end of operation of the drive source.

8. The gas sensor according to claim 5,

after a predetermined time (Tb) has elapsed from the start of operation of the drive source, the switch control mechanism (101) controls the switching of the first switch (SW1) and the second switch (SW2) at the start of the next operation.

9. The gas sensor according to claim 5,

after the same time as the previous operation time has elapsed from the operation start time of the drive source, the switch control mechanism (101) controls the first switch (SW1) and the second switch (SW2) to switch at the start of the next operation.

10. The gas sensor according to any one of claims 2 to 9,

the second chamber (18A) of the first sensor unit (15A) has: a first main regulation chamber (18Aa) that communicates with the first chamber (22A) of the first sensor unit (15A); and a first sub regulation chamber (18Ab) communicating with the first main regulation chamber (18Aa),

the second chamber (18B) of the second sensor unit (15B) has: a second main regulation chamber (18Ba) communicating with the first chamber (22B) of the second sensor unit (15B); and a second sub regulation chamber (18Bb) communicating with the second main regulation chamber (18Ba),

the measurement chamber (20A) of the first sensor unit (15A) communicates with the first sub-regulation chamber (18Ab),

the measurement chamber (20B) of the second sensor unit (15B) communicates with the second sub-regulation chamber (18 Bb).

11. The gas sensor according to claim 10,

fourth diffusion rate control sections (40A, 40B) are provided between the first main adjustment chamber (18Aa) and the first sub adjustment chamber (18Ab), and between the second main adjustment chamber (18Ba) and the second sub adjustment chamber (18Bb), respectively.

12. The gas sensor according to claim 11,

pump electrodes (82A, 82B) are provided in the first chamber (22A) of the first sensor unit (15A) and the first chamber (22B) of the second sensor unit (15B), respectively,

pump electrodes (44A, 44B) are provided in the second chamber (18A) of the first sensor unit (15A) and the second chamber (18B) of the second sensor unit (15B), respectively,

measurement electrodes (62A, 62B) are provided in the measurement chamber (20A) of the first sensor unit (15A) and the measurement chamber (20B) of the second sensor unit (15B), respectively,

each of the pump electrodes is made of a material having a lower catalytic activity than each of the measurement electrodes.

13. The gas sensor according to claim 12,

the first target component is NO, and the second target component is NH₃。

14. The gas sensor according to claim 13,

the first preliminary oxygen concentration control section (108A) is configured to control NH₃Controlling the oxygen concentration in the first chamber (22A) under conditions that oxidize but do not decompose NO in the first chamber (22A) of the first sensor unit (15A),

the second preliminary oxygen concentration control part (108B) for controlling NH₃The oxygen concentration in the second chamber (22B) is controlled under conditions that oxidize but do not decompose NO in the second chamber (22B) of the second sensor unit (15B).

15. The gas sensor according to claim 13,

the target component concentration acquisition means (104) uses a map (110),

the map (110) is obtained in the following manner: the NO concentration and NH are determined based on the current value (Ip6) flowing through the other target component measurement pump cell (60B) and the difference (Δ Ip) between the current value (Ip3) flowing through the one target component measurement pump cell (60A) and the current value (Ip6) flowing through the other target component measurement pump cell (60B) which are measured experimentally in advance₃The relationship between the concentration of the active carbon and the concentration of the active carbon,

the current value (Ip6) flowing through the other target component measurement pump cell (60B) in actual use, and the difference between the current value (Ip3) flowing through the one target component measurement pump cell (60A) and the current value (Ip6) flowing through the other target component measurement pump cell (60B) are compared with the map (110), thereby determining NO and NH₃The respective concentrations.

16. The gas sensor according to claim 4,

the oxygen concentration detection means (70) is provided for measuring the oxygen concentration on the basis of the pump current value flowing through the second oxygen concentration adjustment pump unit (42B).

17. The gas sensor according to claim 12,

a first outer pump electrode (46A) disposed outside at least the second chamber (18A) of the first sensor unit (15A) and a second outer pump electrode (46B) disposed outside at least the second chamber (18B) of the second sensor unit (15B) are common.

18. The gas sensor according to claim 2,

one of the target component measurement pump units (60A) has: a first measurement electrode (62A) disposed in the measurement chamber (20A) of the first sensor unit (15A); and a first reference electrode (52) disposed in a reference gas introduction space (41) of the sensor element (12),

the other target component measurement pump unit (60B) has: a second measurement electrode (62B) disposed in the measurement chamber (20B) of the second sensor unit (15B); and a second reference electrode (52) disposed in the reference gas introduction space (41) of the sensor element (12),

the first reference electrode (52) and the second reference electrode (52) are common.

19. The gas sensor according to claim 2,

the first sensor unit (15A) and the second sensor unit (15B) are arranged substantially opposite to each other in the thickness direction of the sensor element (12).