JP6363500B2 - Gas sensor control device - Google Patents

Description

  The present invention relates to a gas sensor control device including a gas sensor element for detecting a specific gas contained in a measurement target gas (a gas to be measured) and a control unit for controlling the temperature of the gas sensor element.

  Conventionally, a gas sensor element for detecting a specific gas (for example, NOx or the like) contained in a gas to be measured (for example, exhaust gas), and a gas sensor including such a gas sensor element are known.

Some gas sensor elements include a plurality of cells each having a plate-type solid electrolyte body and a pair of electrodes formed on the outer surface of the solid electrolyte body (see Patent Document 1).
For example, as shown in FIG. 14A, the gas sensor element that detects NOx includes, as cells, a first pump cell 901, an oxygen concentration detection cell 902, a second pump cell (NOx detection cell) 903, and the like. Are stacked via insulating layers 910, 920 and the like.

  Among these, the first pump cell 901 pumps and pumps (pumps) oxygen in the gas to be measured (exhaust gas or the like) to adjust the oxygen concentration of the gas to be measured. The oxygen concentration detection cell 902 detects the oxygen concentration of the measurement target adjusted by the first pump cell 901. In the second pump cell 903, a second pumping current corresponding to the NOx concentration contained in the gas to be measured whose oxygen concentration is adjusted flows. Based on the second pumping current, the NOx concentration in the gas to be measured can be detected.

  Separately, a current of a predetermined current value is passed between the detection electrode and the reference electrode arranged in the oxygen concentration detection cell, and the voltage value between the detection electrode and the reference electrode at this time A technique for obtaining a resistance value (that is, an internal resistance of an oxygen concentration detection cell) between the detection electrode and the reference electrode based on the current value and detecting the temperature of the oxygen concentration detection cell based on the resistance value is disclosed. (See Patent Document 2).

  In this technology, the voltage applied to the heater is controlled based on the temperature of the oxygen concentration detection cell, so that the temperature of the gas sensor element is suitable for gas detection, that is, the first and second pump cells and the oxygen concentration detection cell function. The activation temperature is controlled so that

JP 2010-122187 A JP 2003-185626 A

  However, in the above-described conventional technique for controlling the temperature of the heater, if the position where the temperature is measured and the position where the NOx concentration is detected are different in the longitudinal direction of the gas sensor element, the measurement accuracy of the gas sensor may decrease. there were.

For example, as shown in FIG. 14A, a position for measuring temperature (for example, a position where the detection electrode 902a of the oxygen concentration detection cell 902 and the reference electrode 902b face each other) P1, and a position that contributes to the detection of NOx concentration ( For example, there is a gas sensor in which the position of the second inner electrode 903a in contact with the gas to be measured for detection of NOx concentration (P2) differs in the longitudinal direction of the gas sensor element (the left-right direction in the figure).

  When this gas sensor is attached to, for example, an exhaust pipe and the NOx concentration in the exhaust gas is detected, for example, as shown in FIG. 14B due to the influence of the metal fitting of the gas sensor, the influence of the exhaust gas flow velocity, or the like. In addition, the gradient of the temperature gradient from the front end side to the rear end side of the gas sensor element may change.

  FIG. 14B shows the temperature gradient of the gas sensor element depending on the position of the gas sensor element. The left side of the drawing shows the front end side of the gas sensor element, and the right side of the drawing shows the rear end side of the gas sensor element. ◯, △, and ◇ indicate the same gas sensor element, for example, while the temperature gradient of a certain gas sensor element is ◯, the difference in the degree of influence of the metal fitting of the gas sensor or the influence of the exhaust gas flow velocity, etc. As a result, the temperature gradient may change like Δ or ◇ around the position P1.

  That is, as shown in FIG. 14B, since the temperature of the gas sensor element is controlled based on the temperature of the oxygen concentration detection cell 902 at the position P1, the temperatures of the gas sensor elements of ◯, Δ, and ◇ respectively. Although the temperature is almost the same, the gradient of the temperature gradient from the front end side to the rear end side of the gas sensor element changes due to the influence of the metal fittings of the gas sensor and the influence of the exhaust gas flow velocity. In the position P2, the temperature of the gas sensor element may vary.

  That is, when the position P1 for measuring the temperature and the position P2 contributing to the detection of the NOx concentration are different in the longitudinal direction of the gas sensor element, the temperature at the position P2 contributing to the detection of the NOx concentration varies from the target temperature. Sometimes.

  The temperature variation of the position P2 contributing to the detection of the NOx concentration, that is, the temperature variation of the second pon cell (NOx detection cell) 903 comprising the solid electrolyte body and the pair of electrodes is not the electrode activity or the specific gas in the gas to be measured. This may cause variations in the amount of gas dissociation, the internal resistance of the solid electrolyte body, etc., and thereby the second pumping current may vary. As a result, the NOx concentration detection accuracy may be reduced.

  Therefore, an object of the present invention is to provide a gas sensor control device including a gas sensor element with high detection accuracy of a specific gas, and to provide a gas sensor control device including a gas sensor having such a gas sensor element. .

  (1) The gas sensor control apparatus in the 1st aspect of this invention has a gas sensor element and a control part. Among these, the gas sensor element is formed by laminating three or more ceramic layers, and includes a first measurement chamber, a second measurement chamber, an introduction path, a first pump cell, an oxygen concentration detection cell, and a second pump cell. Have

The first measurement chamber is formed between two ceramic layers among three or more ceramic layers, and a gas to be measured is introduced from the outside.
The second measurement chamber is formed between two ceramic layers different from the layers forming the first measurement chamber, and at least a part of the first measurement chamber overlaps in the stacking direction of the ceramic layers.

The introduction path passes through the ceramic layer disposed between the first measurement chamber and the second measurement chamber in the stacking direction, and communicates the first measurement chamber and the second measurement chamber.
The first pump cell includes a ceramic layer adjacent to the first measurement chamber, a first inner electrode provided on the ceramic layer and exposed to the first measurement chamber, and a first counter electrode paired with the first inner electrode. It has. The first pump cell pumps oxygen contained in the gas to be measured in the first measurement chamber.

  The oxygen concentration detection cell is arranged downstream of the first pump cell in the introduction direction of the gas to be measured. The oxygen concentration detection cell includes a ceramic layer adjacent to the first measurement chamber, a detection electrode provided on the ceramic layer and exposed to the first measurement chamber, and a reference electrode paired with the detection electrode. . This oxygen concentration detection cell measures the oxygen concentration in the gas to be measured.

The second pump cell is disposed downstream of the oxygen concentration detection cell in the introduction direction of the gas to be measured. The second pump cell has the same ceramic layer adjacent to the second measurement chamber, the second inner electrode provided on the ceramic layer and exposed to the second measurement chamber, and the ceramic layer provided with the second inner electrode. And a second counter electrode provided on the surface and paired with the second inner electrode. In the second pump cell, a current (second pumping current) corresponding to the specific gas concentration in the gas to be measured in the second measurement chamber flows.

On the other hand, the control unit controls the temperature of the gas sensor element based on the internal resistance of the oxygen concentration detection cell.
In the oxygen concentration detection cell, at least a part of the detection electrode and the reference electrode are opposed to each other via a ceramic layer, and at least a part of each of the second inner electrode and the second counter electrode is a gas sensor element. Are arranged so as to overlap a specific region surrounded by the outermost periphery of the opposing region where the detection electrode and the reference electrode face each other. Furthermore, the reference electrode and the second counter electrode are arranged in a reference gas introduction part into which a reference gas is introduced.

  Thus, in the gas sensor control device of the first aspect, at least a part of the second inner electrode and at least a part of the second counter electrode of the second pump cell (used for detection of the specific gas) have the gas sensor elements in the stacking direction. When viewed, it is placed so as to overlap a specific area surrounded by the outermost periphery of the opposed area where the sensing electrode and reference electrode of the oxygen concentration sensing cell (where the internal resistance used to control the temperature of the gas sensor is detected) are opposed to each other Therefore, there is an effect that the detection accuracy of the specific gas in the gas to be measured is high.

  That is, in the gas sensor control device of the first aspect, the position where the second inner electrode and the second counter electrode for detecting the specific gas are arranged (hereinafter also referred to as gas detection position) is the internal resistance of the oxygen concentration detection cell. Is overlapped with a position (hereinafter also referred to as a temperature control position) to detect the gas, the gas detection position is hardly affected by temperature variations of conventional gas sensor elements.

  That is, when detecting a specific gas, a reaction of a specific gas or the like at the gas detection position (reaction for detecting a specific gas) using the temperature of the gas sensor element based on the internal resistance detected at the temperature control position. When the specific gas is detected based on the current flowing through the second pump cell, the temperature control position and the gas detection position are close to each other in the gas sensor control device of the first aspect. Less susceptible to temperature variations. That is, since the variation of the second pumping current is unlikely to occur, there is a remarkable effect that the detection accuracy of the specific gas in the gas to be measured is high.

  In particular, the second pumping current flowing between the second inner electrode and the second counter electrode used for detection of the specific gas may be a minute current on the order of μA. The influence on the detection of a specific gas is great. Therefore, the arrangement of the temperature control position and the gas detection position described above is important.

Further, in the gas sensor element of the first aspect, the reference electrode and the second counter electrode are arranged in the reference gas introduction part into which the reference gas is introduced, so that the detection accuracy of the specific gas is also high from that point. There are advantages.

  That is, the reference electrode used for detecting the oxygen concentration and the second counter electrode used for detecting the specific gas are both in contact with the reference gas (that is, the gas having the same oxygen concentration) in the same reference gas introduction section. Therefore, there is an advantage that detection accuracy is high.

Here, “detection of specific gas” includes detection of the presence or absence of specific gas or detection of the concentration of specific gas.
In the oxygen concentration detection cell, all of the detection electrodes and all of the reference electrodes may face each other, or part of the detection electrodes and part of the reference electrode may face each other. Further, all of the second inner electrode and all of the second counter electrode may overlap with the specific region, respectively, or part of the second inner electrode and part of the reference electrode may overlap with the specific region, respectively. It may be.

  (2) In the gas sensor control device according to the second aspect of the present invention, when the gas sensor element is viewed in the stacking direction, the detection electrode and the reference electrode are at least upstream of the gas to be measured in the introduction direction and the target electrode from the introduction path, respectively. The introduction path may be provided on the ceramic layer on the downstream side in the measurement gas introduction direction so as to surround the introduction path, and the introduction path may be provided so as to at least partially overlap the specific region.

  In the gas sensor control device of the second aspect, the positions of the detection electrode and reference electrode of the oxygen concentration detection cell (temperature control position), the introduction path into which the gas to be measured is introduced, and both electrodes of the second pump cell are close to each other. By being set, there is an effect that the detection accuracy of the gas to be measured in the specific gas is high, which is less susceptible to temperature variations.

  In addition, the gas to be measured introduced into the introduction path is a specific gas contained in the gas to be measured introduced into the second measurement chamber depending on the position (for example, around the opening of the introduction path) in contact with the detection electrode. The proportion may vary. On the other hand, in the gas sensor control device of the second aspect, the detection electrode of both electrodes is at least on the ceramic layer on the upstream side in the introduction direction of the gas to be measured and on the downstream side in the introduction direction of the gas to be measured with respect to the introduction path. Since it arrange | positions so that an introduction path may be enclosed, the dispersion | variation in the ratio of the specific gas contained in the to-be-measured gas introduced into a 2nd measurement chamber can be suppressed, and the density | concentration of a specific gas can be detected accurately.

  It should be noted that the range in which each electrode surrounds the introduction path is preferably large, but at least the measurement gas introduction direction upstream (that is, the first pump cell side) and the measurement gas introduction direction downstream from the introduction path. It is preferable to include (the same applies hereinafter).

  (3) A gas sensor control device according to a third aspect of the present invention is a gas sensor control device including a gas sensor having a gas sensor element that detects a specific gas contained in a gas to be measured. A gas sensor element according to the second aspect is provided.

  As described above, the control device for the gas sensor including any one of the gas sensor elements described above has an effect that the detection accuracy of the specific gas is high.

  According to the gas sensor control device of the present invention, there is an effect that the detection accuracy of the specific gas in the gas to be measured is high.

It is sectional drawing which shows the state which fractured | ruptured the NOx sensor of 1st Embodiment along the axial direction. It is a perspective view which shows the external appearance of the gas sensor element of 1st Embodiment. It is a perspective view which decomposes | disassembles and shows the gas sensor element of 1st Embodiment. It is a top view which shows a part of gas sensor element of 1st Embodiment. It is sectional drawing which fractures | ruptures and expands along a Z-axis direction typically, and shows the structure of the vicinity of the introduction path of the gas sensor element of 1st Embodiment. It is a top view which shows the arrangement | positioning of each electrode of the oxygen concentration detection cell in a gas sensor element of 1st Embodiment, and a 2nd pump cell so that it may overlap, seeing in the Z-axis direction. It is explanatory drawing which fractures | ruptures the gas sensor element of 1st Embodiment in the Z-axis direction along the Y-axis direction, and shows typically the internal structure and the structure of a control part in the front end side. It is explanatory drawing regarding the manufacturing method of the molded object of the gas sensor element of 1st Embodiment. (A) Cross-sectional view schematically showing a configuration in the vicinity of the introduction path of the gas sensor element of the second embodiment broken and expanded along the Z-axis direction, and (b) shows the oxygen concentration detection cell and the second pump cell. It is a top view which overlaps and shows arrangement | positioning of each electrode of this so that it may see in the Z-axis direction. (A) Cross-sectional view schematically showing a configuration in the vicinity of the introduction path of the gas sensor element of the third embodiment by breaking and expanding along the Z-axis direction, and (b) showing the oxygen concentration detection cell and the second pump cell. It is a top view which shows the arrangement | positioning of each electrode so that it may overlap, as seen in the Z-axis direction. It is a perspective view which decomposes | disassembles and shows the gas sensor element of 4th Embodiment. It is a top view which shows a part of gas sensor element of 4th Embodiment. It is sectional drawing which fractures | ruptures and expands along a Z-axis direction typically, and shows the structure of the vicinity of the introduction path of the gas sensor element of 4th Embodiment. (A) is sectional drawing of the conventional gas sensor element, (b) is a graph which shows the temperature dispersion | variation in the longitudinal direction of the gas sensor element.

Embodiments to which the present invention is applied will be described below with reference to the drawings.
In the embodiment described below, a gas sensor control device including a NOx sensor which is a kind of gas sensor is taken as an example. Specifically, a gas sensor control device including a gas sensor mounted on an exhaust pipe in an automobile or various internal combustion engines, which detects a specific gas (nitrogen oxide: NOx) in exhaust gas to be measured. A gas sensor control device provided with a NOx sensor constructed by assembling (detection element) will be described as an example.

[1. First Embodiment]
[1-1. Overall configuration of NOx sensor]
First, the overall configuration of the NOx sensor in which the gas sensor element of the first embodiment is used will be described with reference to FIG.

  As shown in FIG. 1, the NOx sensor 1 according to the first embodiment includes a cylindrical metal shell 5 having a screw portion 3 formed on the outer surface for fixing to an exhaust pipe, and an axis O direction (of the NOx sensor 1). A plate-shaped gas sensor element 7 extending in the longitudinal direction (vertical direction in FIG. 1), a cylindrical ceramic sleeve 9 disposed so as to surround the circumference of the gas sensor element 7 in the radial direction, and a through-hole penetrating in the direction of the axis O 11 is disposed in a state in which the inner wall surface of the gas sensor element 7 surrounds the rear end portion of the gas sensor element 7, and six (2 in FIG. 1) are disposed between the gas sensor element 7 and the first separator 13. The connection terminal 15 is mainly provided.

  As will be described in detail later, the gas sensor element 7 is formed in a rectangular parallelepiped shape (plate shape) extending in the longitudinal direction, and detects a specific gas (in this case, NOx) contained in the gas to be measured at the tip side thereof. A detection unit 17 is provided. In addition, the gas sensor element 7 has electrode pads 25 on the first main surface 21 and the second main surface 23 that are in a positional relationship of the front and back of the outer surface on the rear end side (upper side in FIG. 1: rear end portion in the longitudinal direction). 26, 27, 28, 29, and 30 (refer to FIGS. 2 and 3 for details) are formed.

  The connection terminal 15 is electrically connected to the electrode pads 25, 26, 27, 28, 29, and 30 of the gas sensor element 7, and is also electrically connected to the lead wire 35 disposed inside the NOx sensor 1 from the outside. Connected. As a result, a current path for current flowing between the external device to which the lead wire 35 is connected and the electrode pads 25, 26, 27, 28, 29, 30 is formed.

  The metal shell 5 has a through-hole 37 that penetrates in the direction of the axis O, and has a substantially cylindrical shape having a shelf 39 that protrudes radially inward of the through-hole 37. In the metal shell 5, the detection unit 17 is disposed on the front end side with respect to the front end of the through hole 37, and the electrode pads 25, 26, 27, 28, 29, and 30 are disposed on the rear end side with respect to the rear end of the through hole 37. In this state, the gas sensor element 7 inserted through the through hole 37 is held.

  An annular ceramic holder 41, talc rings 43 and 45, and the above-described ceramic sleeve 9 are arranged in this order in the through hole 37 of the metal shell 5 so as to surround the periphery of the gas sensor element 7 in the radial direction. It is laminated from the side to the rear end side.

  A caulking packing 49 is disposed between the ceramic sleeve 9 and the rear end portion 47 of the metal shell 5, while a talc ring 43, between the ceramic holder 41 and the shelf 39 of the metal shell 5 is provided. 45 and a metal holder 51 for holding the ceramic holder 41 are arranged. The rear end portion 47 of the metal shell 5 is crimped so as to press the ceramic sleeve 9 against the distal end side via a crimping packing 49.

  Further, a metal double protector 55 (for example, stainless steel) covering the protruding portion of the gas sensor element 7 is attached to the outer periphery of the distal end portion 53 of the metal shell 5 by welding or the like.

  On the other hand, an outer cylinder 57 is fixed to the outer periphery on the rear end side of the metal shell 5, and a grommet 59 is disposed in an opening on the rear end side of the outer cylinder 57. In this grommet 59, lead wires are inserted, through which six lead wires 35 (two are shown in FIG. 1) electrically connected to the electrode pads 25, 26, 27, 28, 29, 30 are inserted. A hole 61 is formed.

  A flange 63 is formed on the outer periphery of the first separator 13, and the flange 63 is fixed to the outer cylinder 57 via a holding member 65. A second separator 67 sandwiched between the first separator 13 and the grommet 59 is disposed on the rear end side of the first separator 13, and the rear end side of the connection terminal 15 is inserted into the second separator 67. ing.

[1-2. Configuration of gas sensor element]
Next, the configuration of the gas sensor element 7 will be described with reference to FIGS.
In FIG. 2, the longitudinal direction is along the direction of the axis O of the gas sensor. Further, the Z-axis direction in FIG. 2 is a stacking direction perpendicular to the longitudinal direction (hereinafter also referred to as a plan view), and the X-axis direction is a width direction perpendicular to the longitudinal direction and the stacking direction. 3 and 4, the left direction is the front end side of the gas sensor element 7, and the right direction is the rear end side of the gas sensor element 7.

<Overall configuration of gas sensor element>
As shown in FIG. 2, the gas sensor element 7 is a long, rectangular parallelepiped plate material extending in the longitudinal direction (Y-axis direction).

The gas sensor element 7 is configured by laminating a plate-shaped element portion 71 extending in the longitudinal direction and a plate-shaped heater 73 extending in the longitudinal direction. Moreover, the gas sensor element 7 includes a detection unit 17 that detects a specific gas contained in the gas to be measured on the tip side.

  That is, as shown in FIG. 3, the gas sensor element 7 is disposed on one side (upper side in FIG. 3) in the stacking direction (up and down direction in FIG. 3) and extends in the longitudinal direction, A plate-like heater 73 is disposed on the opposite side (back side) of the element portion 71 and extends in the longitudinal direction.

The element unit 71 includes a first pump cell 75, an oxygen concentration detection cell 77, and a second pump cell 79, as will be described later.
<Configuration of element part and heater>
The element unit 71 has a structure in which a first insulating layer 81, a first ceramic layer 83, a second insulating layer 85, a second ceramic layer 87, a third insulating layer 89, and a third ceramic layer 91 are laminated in this order. The heater 73 has a structure in which a fourth insulating layer 93 and a fifth insulating layer 95 are stacked in this order.

The first to third ceramic layers 83, 87, 91 are plate-shaped extending in the longitudinal direction of the gas sensor element 7.
A first measurement chamber 97 is formed between the first ceramic layer 83 and the second ceramic layer 87. The front end side region of the first measurement chamber 97 is connected to the outside via two diffusion resistors 99, and the gas to be measured (exhaust gas) that is outside air from the outside is connected to the gas sensor element 7 via the diffusion resistors 99. Introduced inside. The first measurement chamber 97 is connected to the second measurement chamber 103 formed in the third insulating layer 89 via the introduction path 101 formed in the second ceramic layer 87 in the rear end region.

  The shape of the introduction path 101 is, for example, circular when viewed in the stacking direction (that is, when viewed in the same direction as the stacking direction (in plan view)). That is, the introduction path 101 is formed as a cylindrical space.

  A heating resistor 105 formed of a conductor such as tungsten is provided between the fourth and fifth insulating layers 93 and 95. The heating resistor 105 is provided as a part of the heater 73.

  The heater 73 heats up the gas sensor element 7 (in particular, the element unit 71) to a predetermined activation temperature when the heating resistor 105 generates heat by electric power supplied from the outside, and conducts oxygen ions in the solid electrolyte body. Is used to stabilize the operation.

  The first to third ceramic layers 83, 87, 91 are each formed using, for example, zirconia, which is a solid electrolyte having oxygen ion conductivity, as a main component. In addition, the first to fifth insulating layers 81, 85, 89, 93, and 95 are formed using, for example, alumina, which is an electrical insulating material, as a main component, and can prevent permeation (circulation) of fluid such as gas. It is densely formed to the extent. The diffusion resistor 99 is formed using a porous material such as alumina, and gas can be circulated.

  Here, the main component means that “the content of the main material in the ceramic layer is 50 wt% or more”. For example, the first to third ceramic layers 83, 87, 91 contain 50 wt% or more of zirconia. Has been.

<Configuration of each cell>
As shown in FIGS. 3 and 4, the element unit 71 includes a first pump cell 75, an oxygen concentration detection cell 77, and a second pump cell 79.

  The first pump cell 75 includes a first ceramic layer 83 made of a solid electrolyte body, and a pair of rectangular electrodes arranged so as to sandwich the first ceramic layer 83, that is, a first inner electrode 111 and a first counter electrode 113. Yes. The first inner electrode 111 faces the first measurement chamber 97.

  The first counter electrode 113 is covered with a porous portion 117 (for example, alumina) embedded in a portion (opening 115) of the first insulating layer 81 that faces the first counter electrode 113. The porous part 117 is configured to allow gas (for example, oxygen) to pass therethrough.

  The oxygen concentration detection cell 77 includes a second ceramic layer 87 made of a solid electrolyte body, and a pair of annular electrodes arranged so as to sandwich the layer, that is, a detection electrode 119 and a reference electrode 121. The second ceramic layer 87 is provided with an introduction path 101 that penetrates the second ceramic layer 87 in the thickness direction at the center (in plan view) of the detection electrode 119 and the reference electrode 121. The introduction path 101 is circular in plan view.

  A reference oxygen chamber 123 as a space portion penetrating in the thickness direction of the third insulating layer 89 is formed in a portion of the third insulating layer 89 in contact with the reference electrode 121. In the reference oxygen chamber 123, a porous portion 125 (see FIG. 7) is disposed on the third ceramic layer 91 side, and a space is formed on the second ceramic layer 87 side. In addition, the reference oxygen chamber 123 is formed in an annular shape (that is, a C shape) lacking, for example, one place in a plan view.

  In the third insulating layer 89, a second measurement chamber 103 is formed as a space portion penetrating in the thickness direction of the third insulating layer 89 in the center (plan view) of the reference oxygen chamber 123. The second measurement chamber 103 is circular in plan view.

  The annular reference oxygen chamber 123 and the circular second measurement chamber 103 are formed concentrically via an annular partition 127, and the annular partition 127 is provided so as to cross the reference oxygen chamber 123. The linear partition wall 129 is connected to the outer peripheral side of the reference oxygen chamber 123 (see FIG. 4D).

  With respect to the oxygen concentration detection cell 77, oxygen flows into the reference oxygen chamber 123 from the first measurement chamber 97 through the oxygen concentration detection cell 77 by passing a predetermined weak constant current. The oxygen concentration in the reference oxygen chamber 123 is maintained at a predetermined concentration. Thereby, the reference oxygen chamber 123 is used as a reference for the oxygen concentration.

  The second pump cell 79 includes a third ceramic layer 91 made of a solid electrolyte, a second inner electrode 131 disposed on the surface of the third ceramic layer 91 facing the second measurement chamber 103, and a reference oxygen chamber 123. And a second counter electrode 133 disposed on the facing surface.

  Among these, the 2nd inner side electrode 131 is circular by planar view, and is arrange | positioned in the position which overlaps with the introduction path 101 (namely, directly under the introduction path 101: FIG. 5). In addition, the second counter electrode 133 is arranged to surround the outer peripheral side of the second inner electrode 131, and is a partly cut annular shape (that is, a C shape: see FIG. 4C). The surface of the counter electrode 133 is covered with the porous portion 125 (see FIG. 7).

  Three electrode pads 25, 26, and 27 are formed on the outer surface on the rear end side of the first insulating layer 81, and three electrode pads 28 are also formed on the outer surface on the rear end side of the fifth insulating layer 95. , 29, 30 are formed.

Each of the electrodes 111, 113, 119, 121, 131, 133 and the electrode pads 25, 26, 27, 28, 29, 30 is formed mainly of platinum. Moreover, each electrode 111,113,119,121,131,133 is formed in the porous form which can distribute | circulate a gas inside, in order to maintain an electrode reaction favorably. In other words, it is formed in a porous shape that can satisfactorily form a three-phase interface where the gas to be measured (gas phase such as oxygen or NOx), the electrode (catalyst phase), and the solid electrolyte (oxygen ion conduction phase) are in contact. ing.

  Further, as shown in FIG. 3, each of the electrodes 111, 113, 119, 121, 131, 133 and the heating resistor 105 is connected to the corresponding electrode pad 25, by the wiring units L1, L2, L3, L4, L5, L6. 26, 27, 28, 29, 30 are electrically connected.

  Specifically, the first electrode pad 25 is electrically connected to the first counter electrode 113 by the first wiring unit L1. The second electrode pad 26 is electrically connected to the reference electrode 121 by the second wiring unit L2. The third electrode pad 27 is electrically connected to the first inner electrode 111, the detection electrode 119, and the second inner electrode 131 by the third wiring unit L3. The fourth electrode pad 30 is electrically connected to the second counter electrode 133 by the fourth wiring unit L4.

  The first heater electrode pad 28 is electrically connected to the heating resistor 105 by the first heater wiring unit L5. The second heater electrode pad 29 is electrically connected to the heating resistor 105 by the second heater wiring unit L6.

  Of the wiring units L1, L2, L3, L4, L5, and L6, the first wiring unit L1 has a first lead portion L1a and a first through-hole conductor portion L1b. The first through hole conductor portion L1b is formed by the through hole H1. The first through-hole conductor portion L1b is created by forming a conductor on the inner surface of the through-hole H1 (the same applies to the formation of conductors in other through-hole conductor portions).

  The second wiring unit L2 has a second lead portion L2a and a second through-hole conductor portion L2b. The second through-hole conductor portion L2b is formed by the through holes H2, H3, H4, and H5.

  The third wiring unit L3 includes a third a lead portion L3a, a third b lead portion L3b, a third c lead portion L3c, and a third through-hole conductor portion L3d. The third through-hole conductor portion L3d is formed by the through holes H6, H7, H8, H9, and H10.

As described above, the first inner electrode 111, the detection electrode 119, and the second inner electrode 131 are electrically connected to the common third electrode pad 27.
The fourth wiring unit L4 includes a fourth lead portion L4a and a fourth through-hole conductor portion L4b. The fourth through hole conductor portion L4b is formed by the through holes H11, H12, and H13.

  The first heater wiring unit L5 includes a first heater lead L5a and a first heater through-hole conductor L5b. The first heater through-hole conductor L5b is formed by the through hole H14.

  The second heater wiring unit L6 includes a second heater lead L6a and a second heater through-hole conductor L6b. The second heater through-hole conductor L6b is formed by the through hole H15.

In addition, each wiring unit L1-L6 is comprised from the material which has platinum as a main component and contains ceramics (for example, alumina).
<Configuration around the introduction path>
Next, the arrangement of the electrodes 119, 121, 131, 133 around the introduction path 101, which is the main part of the present embodiment, will be described in detail with reference to FIGS.

  As shown in FIGS. 5 and 6, an annular detection electrode 119 is arranged on the upper surface of the second ceramic layer 87 so as to surround the introduction path 101, and on the lower surface of the second ceramic layer 87, An annular reference electrode 121 is disposed so as to surround the introduction path 101.

  Since the width of the detection electrode 119 is larger than the width of the reference electrode 121, the reference electrode 121 is disposed so as to overlap within the range of the detection electrode 119 in plan view. That is, the reference electrode 121 is disposed in the projection region of the detection electrode 119 and overlaps with a predetermined annular facing region R1 (that is, a region matching the reference electrode 121).

  Further, the third insulating layer 89 is provided with a circular second measurement chamber 103 immediately below the introduction path 101 (downward in FIG. 5), and a reference oxygen chamber 123 is C-shaped on the outer peripheral side thereof. (See FIG. 4C).

  Further, on the upper surface of the third ceramic layer 91, a circular second inner electrode 131 is disposed in the second measurement chamber 103 immediately below the introduction path 101, and on the outer peripheral side of the second inner electrode 131. A C-shaped second counter electrode 133 is arranged in the reference oxygen chamber 123.

  In particular, in the first embodiment, in a plan view, the second region is within a range (specific region R2: a range surrounded by a dotted line in FIG. 6) inside the annular outer periphery (the outermost periphery described later) GS of the reference electrode 121. The entire inner electrode 131 and second counter electrode 133 are arranged.

  That is, in the first embodiment, at least a part of the second inner electrode 131 and at least a part of the second counter electrode 133 are arranged on the outermost periphery of the facing region R1 where the detection electrode 119 and the reference electrode 121 are opposed (here, (It is the same as the outer periphery GS of the reference electrode 121) and is disposed so as to overlap the specific region R2 surrounded by the same. Further, the reference electrode 121 and the second counter electrode 133 are disposed in the reference oxygen chamber 123 into which the reference gas is introduced.

  Further, the detection electrode 119 and the reference electrode 121 are respectively provided around the introduction path 101 (that is, so as to surround the entire outer periphery of the introduction path), and the introduction path 101 at least partially overlaps the specific region R2. It is provided as follows. Note that the second inner electrode 131 is disposed immediately below the introduction path 101 (that is, in the axial direction of the introduction path 101).

[1-3. Configuration of gas sensor control device]
Next, the overall configuration of the gas sensor control device will be described with reference to FIG.
As shown in FIG. 7, the gas sensor control device 141 of the first embodiment includes the gas sensor element 7 described above and a control unit 143 that controls the operation of the gas sensor element 7.

The control unit 143 includes a microcomputer 145, an electric circuit unit 147, and the like.
The microcomputer 145 includes a CPU 149 that executes various calculations, a RAM 151 that stores calculation results, and a ROM 153 that stores programs executed by the CPU 149. In addition, the A / D converter 155 is connected to the electric circuit unit 147 through the A / D converter 155, and the signal input / output unit 159 communicates with an electronic control unit (hereinafter referred to as ECU) 157. And a timer clock (not shown).

The electric circuit unit 147 includes a reference voltage comparison circuit 161, an Ip1 drive circuit 163, a Vs detection circuit 165, an Icp supply circuit 167, an Rpvs detection circuit 169, an Ip2 detection circuit 171, a Vp2 application circuit 173, and a heater drive circuit 175. Microcomputer 14
Under the control of 5, the NOx concentration in the exhaust gas is detected using the gas sensor element 7.

  The first inner electrode 111 on the first measurement chamber 97 side of the first pump cell 75, the detection electrode 119 on the first measurement chamber 97 side of the oxygen concentration detection cell 77, and the second measurement chamber 103 side of the second pump cell 79 on the second measurement chamber 103 side. The two inner electrodes 131 are connected to a reference potential.

  The Icp supply circuit 167 supplies a current Icp between the detection electrode 119 and the reference electrode 121 of the oxygen concentration detection cell 77 and pumps out oxygen from the first measurement chamber 97 into the reference oxygen chamber 123.

The Vs detection circuit 165 is a circuit for detecting the voltage Vs between the detection electrode 119 and the reference electrode 121, and outputs the detection result to the reference voltage comparison circuit 161.
The reference voltage comparison circuit 161 is a circuit for comparing the voltage Vs between the detection electrode 119 and the reference electrode 121 detected by the Vs detection circuit 165 with a reference voltage (for example, 425 mV) as a reference. The result is output to the Ip1 drive circuit 163.

  The Ip1 drive circuit 163 is a circuit for supplying a current (first pumping current) Ip1 between the first inner electrode 111 and the first counter electrode 113 of the first pump cell 75. The magnitude and direction of the current Ip1 is preset based on the voltage comparison result between the detection electrode 119 and the reference electrode 121 by the reference voltage comparison circuit 161. It is adjusted so as to substantially match the reference voltage.

  As a result, the first pump cell 75 pumps out oxygen from the first measurement chamber 97 to the outside of the gas sensor element 7 or pumps oxygen into the first measurement chamber 97 from the outside of the gas sensor element 7. In other words, the first pump cell 75 adjusts the oxygen concentration in the first measurement chamber 97 so that the voltage between the detection electrode 119 and the reference electrode 121 is maintained at a constant value (reference voltage value). ing.

  Further, the Vp2 application circuit 173 is a circuit for applying a voltage Vp2 (for example, 450 mV) between the second inner electrode 131 and the second counter electrode 133 of the second pump cell 79, whereby the second measurement chamber Oxygen is pumped from the inside 103 to the reference oxygen chamber 123.

The Ip2 detection circuit 171 is a circuit that detects the value of the current (second pumping current) Ip2 flowing from the second inner electrode 131 to the second counter electrode 133.
The Rpvs detection circuit 169 instantaneously supplies a current Ir between the detection electrode 119 and the reference electrode 121 of the oxygen concentration detection cell 77, and between the detection electrode 119 and the reference electrode 121 generated by the supplied current Ir. The voltage Vr is detected. The detected voltage Vr is output to the microcomputer 145.

  In the microcomputer, the internal resistance Rpvs (pulse resistance) of the oxygen concentration detection cell 77 is calculated based on the current Ir and the voltage Vr. Since the internal resistance Rpvs corresponds to the temperature of the oxygen concentration detection cell 77, the temperature of the oxygen concentration detection cell 77 can be obtained from the internal resistance Rpvs as is well known.

  The heater drive circuit 175 is controlled by the CPU 149 to apply a voltage to the heating resistor 105 of the heater 95, and the first pump cell 75, the oxygen concentration detection cell 77, and the second pump cell 79 (that is, the solid of each cell 75, 77, 79). This is a circuit for heating the electrolyte) and maintaining the temperature of the solid electrolyte at a predetermined temperature.

[1-4. Operation of gas sensor element]
Next, an example of the operation of the gas sensor element 7 will be described.
First, when the control unit 143 is activated by starting the engine, the control unit 143 supplies power to the heater 73. The heater 73 heats the first pump cell 75, the oxygen concentration detection cell 77, and the second pump cell 79 to the activation temperature.

Here, control of the heater 73 will be described.
As described above, the microcomputer 149 controls the operation of the heater drive circuit 175 on the basis of the temperature of the oxygen concentration detection cell 77 obtained from the internal resistance Rpvs of the oxygen concentration detection cell 77, so that the first pump cell 75, oxygen The concentration detection cell 77 and the second pump cell 79 are heated to control the temperature of each cell 75, 77, 79 to a predetermined temperature.

  That is, in the heater drive circuit 175, the heating resistance is set so that the solid electrolyte of each of the cells 75, 77, and 79 (specifically, the solid electrolyte of the oxygen concentration detection cell 77 in the first embodiment) has a target temperature. The body 105 is subjected to PWM energization control so that a voltage is applied to the heating resistor 105.

  When each cell 75, 77, 79 is heated to the activation temperature under the control of the heater 73 described above, the control unit 143 causes a current (first pumping current) Ip 1 to flow through the first pump cell 75. As a result, the first pump cell 75 moves oxygen between the first inner electrode 111 and the first counter electrode 113 via the solid electrolyte, so that the gas to be measured (exhaust gas) flowing into the first measurement chamber 97 is obtained. ) Oxygen is pumped in and out.

  The control unit 143 controls the first pumping current Ip1 that is supplied to the first pump cell 75 so that the interelectrode voltage (interterminal voltage) of the oxygen concentration detection cell 77 becomes a constant voltage V1 (for example, 425 mV). The voltage of the oxygen concentration detection cell 77 is a value corresponding to the oxygen concentration in the detection electrode 119 with the oxygen concentration in the reference oxygen chamber 123 as a reference. By this control, the oxygen concentration in the first measurement chamber 97 is adjusted to such an extent that NOx is not decomposed.

The gas to be measured whose oxygen concentration is adjusted in the first measurement chamber 97 further flows toward the second measurement chamber 103 through the introduction path 101 of the oxygen concentration detection cell 77.
The controller 143 applies an interelectrode voltage (interterminal voltage) to the second pump cell 79. This voltage is set to a constant voltage such that the NOx gas in the gas to be measured is decomposed into oxygen and nitrogen gas (a voltage higher than the control voltage value of the oxygen concentration detection cell 77, for example, 450 mV). Thereby, NOx in the measurement gas is decomposed into nitrogen and oxygen.

  The control unit 143 causes a current (second pumping current) Ip2 to flow through the second pump cell 79 so that oxygen generated by the decomposition of NOx is pumped from the second measurement chamber 103. Since there is a proportional relationship between the second pumping current Ip2 and the NOx concentration, the NOx concentration in the gas to be measured can be detected by detecting the current value of the second pumping current Ip2.

  The gas sensor element 7 is connected to an external device (EUC157) via the connection terminal 15 and the lead wire 35. The control unit 143 supplies power for heating to the heater 73 and transmits / receives signals to / from each cell (first pump cell 75, oxygen concentration detection cell 77, second pump cell 79) of the element unit 71. The gas sensor element 7 is controlled.

[1-5. Manufacturing method of gas sensor]
Next, a method for manufacturing the NOx sensor 1 of the first embodiment will be described with reference to FIGS.

When manufacturing the gas sensor element 7, first, a known material for the gas sensor element 7 is prepared.
Specifically, an unsintered solid electrolyte sheet serving as the solid electrolyte body of each cell 75, 77, 79 of the element unit 71, an unsintered insulating sheet serving as the first insulating layer 81 of the element unit 71, and the second of the element unit 71. , A material of an unsintered insulating part (unsintered insulating part formed by screen printing) to be the third insulating layers 85 and 89, an unsintered insulating sheet to be the fourth and fifth insulating layers 93 and 95 of the heater 73, and the like. Make it.

  Among these, for example, when forming an unfired solid electrolyte sheet, first, alumina powder or butyral resin is added to ceramic powder mainly composed of zirconia, and a mixed solvent (toluene and methyl ethyl ketone) is further mixed. To produce a slurry. The slurry is made into a sheet by the doctor blade method, and the mixed solvent is volatilized to produce an unfired solid electrolyte sheet.

  When forming an unsintered insulating sheet, first, butyral resin and dibutyl phthalate are added to ceramic powder mainly composed of alumina, and a mixed solvent (toluene and methyl ethyl ketone) is further mixed to produce a slurry. To do. The slurry is made into a sheet by a doctor blade method, and the mixed solvent is volatilized to produce an unfired insulating sheet. Note that, as the material for the unfired insulating portion, a slurry similar to the material for forming the unfired insulating sheet is prepared.

  Further, when forming an unfired porous portion that becomes the diffusion resistor 99, the porous portion 117, and the porous portion 125 after firing, first, 100% by mass of alumina powder, a heat-dissipated material (for example, carbon) and the like A porous slurry in which a plasticizer is dispersed by wet mixing is produced. The plasticizer has a butyral resin and DBP.

Then, using these sheets and materials, an uncompressed laminated body that becomes the gas sensor element 7 after firing is produced in the following procedure, for example, as in the conventional case.
For example, when laminating in order from the lower layer of FIG. 3, first, an unfired insulating sheet to be the fifth insulating layer 95 is disposed, and a platinum paste to be the heating resistor 105 is screen-printed on the upper surface thereof. To form a heater pattern.

Next, an unfired insulating sheet to be the fourth insulating layer 93 is laminated on the unfired insulating sheet to be the fifth insulating layer 95 so as to cover the heater pattern.
Next, an unsintered solid electrolyte sheet to be the third ceramic layer 91 is laminated on the upper surface of the unsintered insulating sheet to be the fourth insulating layer 93.

  Next, an electrode pattern to be the second inner electrode 131 and the second counter electrode 133 is formed on the upper surface of the unfired solid electrolyte sheet to be the third ceramic layer 91 by screen printing using platinum metallized ink. Moreover, the lead pattern used as the 3c lead part L3c and the 4th lead part L4a is formed by screen printing using the paste which added the alumina to platinum.

  Next, screen printing is performed on the upper surface of the unfired solid electrolyte sheet to be the third ceramic layer 91 using the slurry of the unfired insulating portion to form the unfired insulating portion to be the third insulating layer 89. The reference oxygen chamber 123 of the unfired insulating portion is filled with a porous slurry that becomes the porous portion 125, and a carbon paste is filled thereon.

Next, an unfired solid electrolyte sheet to be the second ceramic layer 87 is laminated on the upper surface of the unfired insulating portion to be the third insulating layer 89. In this unfired solid electrolyte sheet, a through-hole serving as the introduction path 101 is formed in advance. In addition, on the upper and lower surfaces of the unfired solid electrolyte sheet, electrode patterns to be the reference electrode 121 and the detection electrode 119 are formed in the same manner as described above, and the lead patterns to be the second lead portion L2a and the third b lead portion L3b are formed. It is formed in the same manner as described above.

Next, screen printing is performed on the upper surface of the unsintered solid electrolyte sheet to be the second ceramic layer 87 using the slurry of the unsintered insulating part to form the unsintered insulating part to be the second insulating layer 85.
In addition, the porous slurry is screen-printed in the opening that becomes the diffusion resistor 99 in the unsintered insulating portion. A carbon paste is screen-printed in the opening that becomes the first measurement chamber 97.

  Next, an unsintered solid electrolyte sheet to be the first ceramic layer 83 is laminated on the upper surface of the unsintered insulating part to be the second insulating layer 85. On the upper and lower surfaces of the unfired solid electrolyte sheet, an electrode pattern to be the first inner electrode 111 and the first counter electrode 113 is formed in advance in the same manner as described above, and the first lead portion L1a and the third a lead portion L3a A lead pattern is formed in the same manner as described above.

  Next, an unfired insulating sheet to be the first insulating layer 81 is laminated on the upper surface of the unfired solid electrolyte sheet to be the first ceramic layer 83. In this unfired insulating sheet, a through-hole that becomes the opening 115 is made in advance. And the slurry for the porous used as the porous part 117 is screen-printed in this through-hole.

In this way, an uncompressed laminate is formed. In addition, unfired electrode pads to be the electrode pads 25, 26, 27, 28, 29, 30 and the like are formed in this non-bonded laminate.
And by pressing this uncompressed laminated body at 1 MPa, a compacted molded body 181 as shown in FIG. 8 is obtained.

Then, the green body 181 obtained by pressurization is cut into a predetermined size to obtain a plurality (for example, 10) of unfired laminated bodies having the same size as the gas sensor element 7.
Thereafter, the unfired laminate is removed from the resin, and further fired at a firing temperature of 1500 ° C. for 1 hour to obtain a gas sensor element 7 as shown in FIG.

After obtaining the gas sensor element 7 in this way, an assembling step for assembling the gas sensor element 7 to the metal shell 5 is performed.
That is, in this step, the gas sensor element 7 produced by the above manufacturing method is inserted into the metal holder 51, and the gas sensor element 7 is fixed by the ceramic holder 41 and the talc ring 43, thereby producing an assembly. Thereafter, the assembly is fixed to the metal shell 5, and the rear end side of the gas sensor element 7 in the direction of the axis O is inserted into the talc ring 45 and the ceramic sleeve 9, and these are inserted into the metal shell 5.

Then, the ceramic sleeve 9 is caulked at the rear end portion 47 of the metallic shell 5 to produce a lower assembly. A protector 55 is attached to the lower assembly in advance.
On the other hand, the outer cylinder 57, the separator 13, the grommet 61, and the like are assembled to produce an upper assembly. Then, the lower assembly and the upper assembly are joined to obtain the NOx sensor 1.

[1-6. effect]
(1) In the gas sensor control device 141 of the first embodiment, at least a part of each of the second inner electrode 131 and the second counter electrode 133 of the second pump cell 79 used for the detection of NOx has the gas sensor element 7 in the stacking direction. Is disposed so as to overlap with the specific region R2 surrounded by the outermost periphery SG of the opposing region R1 where the detection electrode 119 and the reference electrode 121 of the oxygen concentration detection cell 77 face each other. There is an effect that the detection accuracy of NOx is high.

  That is, the position (gas detection position) where the second inner electrode 131 and the second counter electrode 133 of the second pump cell 79 that detects NOx are arranged is the position (temperature control position) where the internal resistance of the oxygen concentration detection cell 77 is detected. ), The gas detection position is less susceptible to temperature variations in the longitudinal direction of the gas sensor element 7.

  That is, when the temperature control position and the gas detection position are close to each other, the second pumping current Ip2 is not easily affected by temperature variations when detecting the NOx concentration, so that the detection accuracy of NOx is high. Has an effect.

  In the first embodiment, since the reference electrode 121 and the second counter electrode 133 are disposed in the same reference oxygen chamber 123, the reference gas is the same, and the detection accuracy of NOx is also from that point. There is an advantage of high.

  Furthermore, since the second measurement electrode 131 is disposed immediately below the introduction path 101, the gas to be measured introduced from the introduction path 101 can easily come into contact with the second measurement electrode, and the NOx detection accuracy is high. is there.

  (2) In the first embodiment, the positions of the detection electrode 119 and the reference electrode 121 of the oxygen concentration detection cell 77, the introduction path 101, and the second pump cell 79 are close to each other (that is, overlap in the stacking direction). Position), there is an effect that the NOx detection accuracy is high.

  In addition, the gas to be measured introduced into the introduction path 101 is included in the gas to be measured introduced into the second measurement chamber 103 depending on the position in contact with the detection electrode 119 (for example, around the opening of the introduction path 101). The ratio of NOx that is generated may vary. On the other hand, in the first embodiment, the detection electrode 119 and the reference electrode surround the introduction path 101 on the second ceramic layer 87 at least upstream in the introduction direction of the measurement gas and downstream in the introduction direction of the measurement gas. Therefore, the variation in the ratio of NOx contained in the gas to be measured introduced into the second measurement chamber 103 can be suppressed, and the concentration of NOx can be detected with high accuracy.

[1-7. Correspondence with Claims]
Here, the correspondence relationship of the words in the claims and the first embodiment will be described.
The NOx sensor 1, the gas sensor element 7, the first pump cell 75, the oxygen concentration detection cell 77, and the second pump cell 79 correspond to examples of the gas sensor, the gas sensor element, the first pump cell, the oxygen concentration detection cell, and the second pump cell, respectively.

The first measurement chamber 97, the introduction path 101, and the second measurement chamber 103 correspond to examples of the first measurement chamber, the introduction path, and the second measurement chamber, respectively.
The ceramic layers 83, 87, and 91 correspond to an example of a ceramic layer. The first inner electrode 111, the first counter electrode 113, the detection electrode 119, the reference electrode 121, the reference oxygen chamber 123, the second inner electrode 131, The two counter electrodes 133 correspond to examples of a first inner electrode, a first counter electrode, a detection electrode, a reference electrode, a reference gas introduction part, a second inner electrode, and a second counter electrode, respectively.

[2. Second Embodiment]
Next, although the gas sensor control apparatus of 2nd Embodiment is demonstrated, description of the content similar to the said 1st Embodiment is abbreviate | omitted. In addition, about the number of the structure similar to 1st Embodiment, the number similar to 1st Embodiment is used.

In the gas sensor control device of the second embodiment, as shown in FIG. 9A, the second ceramic layer of the oxygen concentration detection cell 77 is formed from the upper side (upper side of FIG. 9A) as in the first embodiment. 87,
A third insulating layer 89, a third ceramic layer 91 of the second pump cell 79, and the like are disposed.

  An annular detection electrode 119 is disposed on the upper surface of the second ceramic layer 87, and an annular reference electrode 121 is disposed concentrically on the lower surface of the second ceramic layer 87. Further, a circular second inner electrode 131 and a C-shaped second counter electrode 133 are disposed on the upper surface of the third ceramic layer 91. Each electrode 119, 121, 131, 133 has a shape in plan view (the same applies hereinafter).

The second inner electrode 131 is disposed in the second measurement chamber 103, and the reference electrode 121 and the second counter electrode 133 are disposed in the reference oxygen chamber 123.
Also in the second embodiment, the reference electrode 121 is disposed in the projection region of the detection electrode 119, and the reference electrode 121 and the detection electrode 119 are in a predetermined annular facing region R1 (that is, the reference electrode 121) in plan view. In the same area). In addition, a second inner electrode 131 is disposed immediately below the introduction path 101.

  Furthermore, in plan view, the second inner electrode 131 and the second inner electrode 131 and the second inner electrode 131 are located in a range (specific region R2: a range surrounded by a dotted line in FIG. 9B) inside the outer circumference of the reference electrode 121 (and hence the outermost circumference) GS. A counter electrode 133 is disposed.

  In the second embodiment, since the outer diameter of the second counter electrode 133 is larger than the outer diameter of the reference electrode 121 in plan view, the outer periphery GS of the reference electrode 121 is between the inner periphery and the outer periphery of the second counter electrode 133. Is located.

In the second embodiment, the same effects as in the first embodiment can be obtained.
[3. Third Embodiment]
Next, the gas sensor control device of the third embodiment will be described, but the description of the same contents as the first embodiment will be omitted. In addition, about the number of the structure similar to 1st Embodiment, the number similar to 1st Embodiment is used.

  In the gas sensor control device of the third embodiment, as shown in FIG. 10 (a), the second ceramic layer of the oxygen concentration detection cell 77 from the upper side (upper side of FIG. 10 (a)) as in the first embodiment. 87, the third insulating layer 89, the third ceramic layer 91 of the second pump cell 79, and the like are disposed.

  An annular detection electrode 119 is disposed on the upper surface of the second ceramic layer 87, and an annular reference electrode 121 is disposed concentrically on the lower surface of the second ceramic layer 87. A circular second inner electrode 131 and a C-shaped second counter electrode 133 are disposed on the upper surface of the third ceramic layer 91.

The second inner electrode 131 is disposed in the second measurement chamber 103, and the reference electrode 121 and the second counter electrode 133 are disposed in the reference oxygen chamber 123.
In the third embodiment, the reference electrode 121 and the detection electrode 119 overlap each other in a predetermined annular facing region R1 in plan view. In addition, a second inner electrode 131 is disposed immediately below the introduction path 101.

  Further, in plan view, the second inner electrode 131 and the second inner electrode 131 are disposed in a range (specific region R2: a range surrounded by a dotted line in FIG. 10B) inside the outer periphery (and hence the outermost periphery) GS of the detection electrode 119. At least a part of the counter electrode 133 is disposed.

In the third embodiment, since the outer diameter of the reference electrode 121 is larger than the outer diameter of the detection electrode 119 in plan view, the outer periphery GS of the detection electrode 119 is located between the inner periphery and the outer periphery of the reference electrode 121. ing.

The third embodiment also has the same effect as the first embodiment.
[4. Fourth Embodiment]
Next, although the gas sensor control apparatus of 4th Embodiment is demonstrated, description of the content similar to the said 1st Embodiment is abbreviate | omitted. In addition, about the number of the structure similar to 1st Embodiment, the number similar to 1st Embodiment is used.

In the fourth embodiment, the configuration of the detection electrode, the reference electrode, the second inner electrode, the second counter electrode, and the vicinity thereof is greatly different from that of the first embodiment.
<Configuration of gas sensor element>
First, the configuration of the gas sensor element 7 in the gas sensor control device of the fourth embodiment will be described with reference to FIGS. 11 and 12. Except for the gas sensor element 7, it is the same as in the first embodiment.

  The gas sensor element 7 of the fourth embodiment includes an element unit 71 and a heater 73, and the element unit 71 includes a first pump cell 75, an oxygen concentration detection cell 77, and a second pump cell 79.

  Among these, the 1st pump cell 75 is provided with the 1st inner side electrode 111 and the 1st counter electrode 113 on both sides of the 1st ceramic layer 83 which consists of a solid electrolyte body. A first insulating layer 81 having a porous portion 117 is provided on the upper surface side of the first pump cell 75, and a second insulating layer 85 having a first measurement chamber 97 is provided on the lower surface side.

The oxygen concentration detection cell 77 includes a detection electrode 119 and a reference electrode 121 on both sides of a second ceramic layer 87 having an introduction path 101 and made of a solid electrolyte body.
The second pump cell 79 includes a second inner electrode 131 and a second counter electrode 133 on the upper surface of the third ceramic layer 91 made of a solid electrolyte body.

Between the oxygen concentration detection cell 77 and the second pump cell 79, a third insulating layer 89 composed of an upper layer 89a and a lower layer 89b is disposed.
Specifically, as shown in FIG. 12, the upper layer 89a is formed with a circular through-hole 123a that constitutes a part of the reference oxygen chamber 123 (upper part of FIG. 13), and the lower layer 89b has the reference oxygen chamber 123. A circular through hole 123b constituting a part (lower part of FIG. 13) is formed.

  Further, a rectangular through hole 103a constituting a part of the second measurement chamber 103 (upper part of FIG. 13) is formed in the upper layer 89a, and a part of the second measurement chamber 103 (FIG. 13) is formed in the lower layer 89b. A rectangular through-hole 103b is formed. The through hole 103b in the lower layer 89b is configured to extend longer to the tip side than the through hole 103a in the upper layer 89a.

The heater 73 includes a heating resistor 105 between the fourth insulating layer 93 and the fifth insulating layer 95.
<Configuration around the introduction path>
Next, the configuration around the introduction path 101, which is the main part of the fourth embodiment, will be described in detail with reference to FIGS.

As shown in FIGS. 12 and 13, the detection electrode 119 of the oxygen concentration detection cell 77 has a rectangular shape, and the reference electrode 121 has a shape in which one corner of the rectangular shape is recessed.
Further, the dimensions of the detection electrode 119 and the reference electrode 121 in the longitudinal direction of the gas sensor element 7 (left and right direction in FIGS. 12 and 13) are the same, and the width direction of the detection electrode 119 and the reference electrode 121 (up and down in FIG. 12). The dimension in the direction) is set so that the detection electrode 119 is longer than the reference electrode 121.

  Furthermore, the detection electrode 119 and the reference electrode 121 are arranged so that the reference electrode 121 is included in the projection region of the detection electrode 119 in plan view. In FIG. 13, the outer periphery (and hence the outermost periphery) GS of the reference electrode 121 is indicated by a dotted line.

The second inner electrode 131 and the second counter electrode 133 have a rectangular shape, and are arranged in parallel along the width direction in order from the rear end side (the right side in FIG. 13) of the gas sensor element 7.
In plan view, the second inner electrode 131 is formed within the range of the through hole 103b of the second measurement chamber 103, and the second counter electrode 133 is formed to include the entire reference oxygen chamber 123. Yes.

  That is, in the fourth embodiment, the reference electrode 121 and the detection electrode 119 overlap each other in a predetermined facing region R1 (that is, the same region as the reference electrode 121) in plan view. In addition, a part of the second inner electrode 131 is disposed immediately below the introduction path 101.

  Furthermore, in plan view, a part of the second inner electrode 131 and the entire second counter electrode 133 are within a range inside the outer periphery GS of the reference electrode 121 (specific region R2: a range surrounded by a dotted line in FIG. 12). Has been placed.

Accordingly, here, the facing region R1 and the specific region R2 are in the same range.
In the fourth embodiment, the same effects as those of the first embodiment are obtained.
As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, In the range which does not deviate from the summary of this invention, it is possible to implement in various aspects.

(1) For example, the planar shape of the introduction path may be a circle, but may be other shapes such as a polygon or an ellipse.
(2) The planar shape of the detection electrode and the reference electrode includes an annular shape, but may be various other annular shapes. Moreover, it does not need to be annular.

(3) The planar shape of the second inner electrode includes a circle, but may be other shapes such as a polygon or an ellipse.
(4) The planar shape of the second counter electrode includes an annular shape (for example, a C shape) with a part cut away, but may be other various annular shapes. Moreover, it does not need to be annular.

(5) The planar shape of the reference oxygen chamber may be an annular shape with a part cut away (for example, a C shape), but may have other annular shapes such as a polygon or an ellipse. May be.
Further, as the reference oxygen chamber, a space whose periphery is sealed can be adopted, but it may be configured to communicate with the atmosphere, for example.

  (6) The first pump cell 75 is formed using the first ceramic layer 83 in each of the above embodiments, but may be formed using the second ceramic layer 87, for example. Specifically, the first pump cell 75 may be disposed on the tip side of the oxygen concentration detection cell 77 of the second ceramic layer 87. That is, in this case, the second ceramic layer 87 serves as both the ceramic layer of the first pump cell 75 and the ceramic layer of the oxygen concentration detection cell 77.

  (7) In the above embodiment, the NOx sensor is exemplified as the gas sensor, but the present invention can also be applied to other gas sensors such as an ammonia sensor.

  DESCRIPTION OF SYMBOLS 1 ... Gas sensor, 7 ... Gas sensor element, 75 ... 1st pump cell, 77 ... Oxygen concentration detection cell, 79 ... 2nd pump cell, 83, 87, 91 ... Ceramic layer, 97 ... 1st measurement chamber, 101 ... Introduction path, 103 ... second measurement chamber, 111 ... first inner electrode, 113 ... first counter electrode, 119 ... detection electrode, 121 ... reference electrode, 123 ... reference oxygen chamber, 131 ... second inner electrode, 133 ... second counter electrode

Claims (3)

It is a gas sensor element formed by laminating three or more ceramic layers,
A first measurement chamber formed between two ceramic layers among the three or more ceramic layers, and a gas to be measured is introduced from the outside;
A second measurement chamber formed between two ceramic layers different from the interlayer forming the first measurement chamber, and at least a part of which overlaps with the first measurement chamber in the stacking direction;
An introduction path that passes through the ceramic layer disposed between the first measurement chamber and the second measurement chamber in the stacking direction and communicates the first measurement chamber and the second measurement chamber;
A first pump cell for pumping oxygen contained in the gas to be measured in the first measurement chamber; the ceramic layer adjacent to the first measurement chamber; the ceramic layer provided on the ceramic layer; and exposed to the first measurement chamber A first pump cell comprising a first inner electrode and a first counter electrode paired with the first inner electrode;
An oxygen concentration detection cell that is arranged downstream of the first pump cell in the introduction direction of the gas to be measured and measures the oxygen concentration in the gas to be measured; a ceramic adjacent to the first measurement chamber; and the ceramic layer An oxygen concentration detection cell comprising a detection electrode provided above and exposed to the first measurement chamber; and a reference electrode paired with the detection electrode;
A second pump cell that is arranged downstream of the oxygen concentration detection cell in the introduction direction of the gas to be measured, and in which a current corresponding to a specific gas concentration in the gas to be measured flows in the second measurement chamber; A ceramic layer adjacent to the ceramic layer, a second inner electrode provided on the ceramic layer and exposed to the second measurement chamber, and provided on the same surface of the ceramic layer provided with the second inner electrode, A gas sensor element comprising: a second pump cell comprising a second counter electrode paired with a second inner electrode;
A control unit for controlling the temperature of the gas sensor element based on the internal resistance of the oxygen concentration detection cell;
A gas sensor control device comprising:
In the oxygen concentration detection cell, at least a part of the detection electrode and the reference electrode are opposed via the ceramic layer,
At least a part of each of the second inner electrode and the second counter electrode of the second pump cell is a facing region where the detection electrode and the reference electrode face each other when the gas sensor element is viewed in the stacking direction. It is arranged so as to overlap a specific area surrounded by the outermost periphery of
The gas sensor control device is characterized in that the reference electrode and the second counter electrode are arranged in a reference gas introduction part into which a reference gas is introduced.   When the gas sensor element is viewed in the stacking direction, the detection electrode and the reference electrode are at least upstream of the introduction direction of the measurement gas and downstream of the introduction direction of the measurement gas with respect to the introduction path, respectively. The said introduction path is provided on the said ceramic layer so that the said introduction path may be enclosed, and the said specific path is provided so that at least one part may overlap. Gas sensor control device. A gas sensor control device including a gas sensor having a gas sensor element for detecting a specific gas contained in a gas to be measured,
A gas sensor control device comprising the gas sensor element according to claim 1 or 2 as the gas sensor element.