JP6438851B2 - Gas sensor element and gas sensor - Google Patents

Description

  The present invention relates to a gas sensor element and a gas sensor that are suitably used for detecting the gas concentration of a specific gas contained in combustion gas or exhaust gas of, for example, a combustor or an internal combustion engine.

Conventionally, a gas sensor for detecting the concentration of a specific component (oxygen or the like) in exhaust gas of an internal combustion engine has been used. This gas sensor has a gas sensor element inside itself, and the gas sensor element is formed by stacking an oxygen concentration detection cell and an oxygen pump cell each composed of a solid electrolyte body and a pair of electrodes (see Patent Document 1). The oxygen concentration detection cell and the oxygen pump cell are provided in a measurement chamber that forms an internal space of the gas sensor element. Then, oxygen in the measurement chamber is pumped by the oxygen pump cell so that the voltage (electromotive force) generated between the electrodes of the oxygen concentration detection cell in accordance with the oxygen concentration of the exhaust gas in the measurement chamber becomes a predetermined value. The oxygen concentration is adjusted, and the oxygen concentration in the exhaust gas corresponding to the pumping current flowing through the oxygen pump cell is detected linearly.
Further, there is a gas sensor (typically a NOx sensor) in which a second measurement chamber is provided in communication with the measurement chamber and a second pump cell is disposed so as to face the second measurement chamber. In this gas sensor, the exhaust gas whose oxygen concentration has been adjusted by operating the oxygen pump cell as described above is introduced into the second measurement chamber, and the NOx concentration is detected by measuring the current flowing through the second pump cell.

By the way, in order to reduce the power consumption of the gas sensor, it is desired to reduce the voltage applied to the oxygen concentration detection cell and the oxygen pump cell, that is, to reduce the thickness of the solid electrolyte body of each cell. Further, when the thickness of the solid electrolyte body is reduced, the internal resistance of the cell is reduced and the responsiveness is improved. Furthermore, the lower the voltage applied to the cell, the more the characteristic deterioration of the solid electrolyte body called blackening can be suppressed. Blackening is a phenomenon in which the metal oxide in a solid electrolyte body is reduced due to oxygen deficiency in the solid electrolyte body in a state where an electrode reaction occurs through the solid electrolyte body. When blackening occurs, the characteristics (ion conductivity) of the solid electrolyte body deteriorate, and the pumping performance decreases.
On the other hand, since the oxygen ion conductivity of the solid electrolyte body, and consequently the detection output of the oxygen concentration detection cell, changes depending on the temperature of the solid electrolyte body, the oxygen concentration detection cell (solid electrolyte body) is required to improve detection accuracy. It is necessary to keep at a predetermined temperature. As shown by a curve C1 in FIG. 5, since there is a correlation between the temperature of the solid electrolyte body and the internal resistance (internal impedance) Rpvs, the internal resistance Rpvs of the solid electrolyte body of the oxygen concentration detection cell is a predetermined value. The heater is heated so as to have a value, and the temperature of the gas sensor element is controlled.

JP 2013-7642 A

However, when the thickness of the solid electrolyte body of the oxygen concentration detection cell is reduced, the temperature change of the internal resistance Rpvs of the solid electrolyte body increases, and the curve C1 in FIG. 5 becomes a flat curve C2 closer to the temperature axis of the solid electrolyte body. Become. For this reason, when the internal resistance Rpvs varies by ΔR, the temperature fluctuation Δ2 of the curve C2 becomes larger than the temperature fluctuation Δ1 of the curve C1. Then, even if the heater is heated so that the internal resistance Rpvs becomes a predetermined value and the internal resistance Rpvs can be controlled within the range of ΔR, the temperature fluctuation in the curve C2 is larger than that in the curve C1, so the gas sensor by the heater There is a problem that it becomes difficult to control the temperature.
Therefore, an object of the present invention is to provide a gas sensor element and a gas sensor that reduce power consumption and improve oxygen pumping responsiveness, and suppress a decrease in blacking and detection accuracy of a gas to be measured.

In order to solve the above problems, a gas sensor element of the present invention has a first solid electrolyte body, a detection electrode and a reference electrode arranged on the first solid electrolyte body, and introduces a gas to be measured in communication with the outside. The detection electrode is arranged facing the measurement chamber, and the oxygen concentration detection cell that generates electromotive force according to the oxygen concentration in the measurement chamber, the second solid electrolyte body, and the second solid electrolyte body An oxygen pump cell that pumps oxygen in the measurement chamber such that one of the pair of electrodes is disposed facing the measurement chamber and the electromotive force is constant. The thickness t2 of the second solid electrolyte body is thinner than the thickness t1 of the first solid electrolyte body.
According to this gas sensor element, the voltage applied to the oxygen pump cell having the second solid electrolyte body is reduced, and the power consumption of the gas sensor can be reduced. In addition, the responsiveness of the oxygen pump cell is improved and blackening of the oxygen pump cell can be suppressed.
On the other hand, since the thickness t1 of the first solid electrolyte body is maintained thicker than the second solid electrolyte body, the temperature control of the gas sensor element based on the internal resistance Rpvs of the first solid electrolyte body can be accurately performed. The detection accuracy of the oxygen concentration by the oxygen concentration detection cell can be improved.
When the oxygen concentration detection cell and the oxygen pump cell are stacked, a spacer that forms a measurement chamber facing the detection electrode of the oxygen concentration detection cell is stacked with the oxygen concentration detection cell (and oxygen pump cell if necessary). .

The gas sensor element of the present invention further includes a heater part having a heating element that generates heat when energized in an insulating ceramic body, and the heater part is controlled based on an internal resistance value Rpvs of the first solid electrolyte body. Also good.
In the gas sensor element of the present invention, it is preferable that the thickness t2 of the second solid electrolyte body exceeds 20 μm.
When the thickness t2 of the second solid electrolyte body is 20 μm or less, the second solid electrolyte body is broken due to thermal stress applied to the second solid electrolyte body due to the temperature gradient of the gas sensor element when the temperature rises. The durability of the pump cell may be reduced. Therefore, when the thickness t2 of the second solid electrolyte body exceeds 20 μm, the durability of the cell can be improved.

The gas sensor element of the present invention according to claim 1 further includes a heater portion having a heating element that generates heat when energized in an insulating ceramic body, and the heater portion is positioned in the stacking direction more than the second solid electrolyte body. The first solid electrolyte body may be disposed close to the first solid electrolyte body.
In the gas sensor element according to the second aspect of the present invention, the heater section may be disposed closer to the first solid electrolyte body than the second solid electrolyte body in the stacking direction.
In the oxygen concentration detection cell having the first solid electrolyte body that is thicker than the second solid electrolyte body, the thermal conductivity from the heater portion is inferior to that of the oxygen pump cell, so that the responsiveness tends to be lower than that of the oxygen pump cell. is there. Therefore, by bringing the heater portion closer to the second solid electrolyte body in the stacking direction, the thermal conductivity from the heater portion to the oxygen pump cell can be improved, and the responsiveness of the oxygen pump cell can also be improved.

In the gas sensor element of the present invention, at least a part of the oxygen pump cell and the oxygen concentration detection cell may overlap in the stacking direction to form an overlapping portion.
According to this gas sensor element, by forming the overlapping portion, the oxygen pump cell and the oxygen concentration detection cell are adjacent to each other in the plane direction (direction perpendicular to the stacking direction) in which the gas to be measured flows. For this reason, both cells can be exposed to almost the same environment against changes in the atmosphere (oxygen concentration) and temperature of the gas to be measured introduced into the measurement chamber, further improving the accuracy of oxygen concentration detection by the oxygen concentration detection cell. Can be made.

In the gas sensor element of the present invention, at least one of the first solid electrolyte body and the second solid electrolyte body is embedded in a portion where an insulating substrate having a higher thermal conductivity than the solid electrolyte body is cut out. May be.
According to this gas sensor element, the heat of the heater portion and the like is easily transmitted to the solid electrolyte body through the insulating substrate having a high thermal conductivity, so that the power consumption of the gas sensor can be further reduced.

  The gas sensor of the present invention is a gas sensor comprising a sensor element that detects the concentration of a specific gas component in a gas to be measured and a housing that holds the sensor element, wherein the sensor element uses the gas sensor element. To do.

  According to the present invention, the power consumption of the gas sensor can be reduced to improve the response of oxygen pumping, and blacking and a decrease in detection accuracy of the gas to be measured can be suppressed.

It is sectional drawing which follows the longitudinal direction of the gas sensor (oxygen sensor) which concerns on embodiment of this invention. It is a disassembled perspective view of a gas sensor element. It is a schematic cross section orthogonal to the axial direction of a gas sensor element. It is sectional drawing which follows the longitudinal direction of the gas sensor element as a NOx sensor element. It is a figure which shows the relationship between the temperature of a solid electrolyte body, and internal resistance (internal impedance) Rpvs.

Hereinafter, embodiments of the present invention will be described.
FIG. 1 is a sectional view taken along the longitudinal direction (axis L direction) of a gas sensor (oxygen sensor) 1 according to a first embodiment of the present invention, and FIG. 2 is a schematic exploded perspective view of a gas sensor element 100 (detection element 300 and heater 200). FIG. 3 and FIG. 3 are cross-sectional views orthogonal to the direction of the axis L of the detection element 300.

  As shown in FIG. 1, the gas sensor 1 includes a gas sensor element (oxygen sensor element) 100 including a detection element unit 300 and a heater unit 200 stacked on the detection element unit 300, a main body that holds the gas sensor element 100 and the like inside. A metal fitting (housing) 30 and a protector 24 attached to the tip of the metal shell 30 are included. The gas sensor element 100 is arranged so as to extend in the direction of the axis L.

  As shown in FIG. 2, the heater unit 200 includes a first base 101 and a second base 103 mainly composed of alumina, and a heating element 102 mainly composed of platinum sandwiched between the first base 101 and the second base 103. have. The heating element 102 has a heating part 102a located on the tip side and a pair of heater lead parts 102b extending from the heating part 102a along the longitudinal direction of the first base 101. The terminal of the heater lead portion 102b is electrically connected to the heater side pad 120 via a conductor formed in the heater side through hole 101a provided in the first base 101. A laminate of the first substrate 101 and the second substrate 103 corresponds to the insulating ceramic body.

The detection element unit 300 includes an oxygen concentration detection cell 130 and an oxygen pump cell 140.
The oxygen concentration detection cell 130 is formed of a first solid electrolyte body 105c and a first electrode 104 and a second electrode 106 formed on both surfaces of the first solid electrolyte body 105c. In addition, the front end side of the first support body 105 mainly composed of alumina is cut out in a rectangular shape, and the first solid electrolyte body 105c is embedded in the cut-out portion. The outer dimensions of the first support 105 are the same as those of the gas sensor 1, and one first through hole 105 a is provided on the rear end side of the first support 105.
The first electrode 104 is formed by a first electrode portion 104 a and a first lead portion 104 b extending from the first electrode portion 104 a along the longitudinal direction of the first support 105. The second electrode 106 is formed by a second electrode portion 106 a and a second lead portion 106 b extending from the second electrode portion 106 a along the longitudinal direction of the first support 105.
The first electrode 104 and the second electrode 106 correspond to “reference electrode” and “detection electrode” in the claims, respectively. The first support 105 corresponds to an “insulating substrate” in the claims.

  The terminals of the first lead portion 104b are connected to the first through hole 105a, the second through hole 107a provided in the insulating layer 107 described later, the fourth through hole 109a provided in the second solid electrolyte body 109, and the protective layer 111. It electrically connects with the detection element side pad 121 through a conductor formed in each of the sixth through holes 111a provided. On the other hand, the end of the second lead portion 106b is a third through hole 107b provided in the insulating layer 107 described later, a fifth through hole 109b provided in the second support 109 described later, and a seventh through hole provided in the protective layer 111. The detection element side pad 121 is electrically connected through a conductor formed in each of the holes 111b.

On the other hand, the oxygen pump cell 140 is formed of a second solid electrolyte body 109c, and a third electrode 108 and a fourth electrode 110 formed on both surfaces of the second solid electrolyte body 109c. Note that the tip end side of the second support 109 mainly composed of alumina is cut out in a rectangular shape, and the second solid electrolyte body 109c is embedded in the cut-out portion. The external dimensions of the second support 109 are the same as those of the gas sensor 1, and the fourth through hole 109 a and the fifth through hole 109 b are provided on the rear end side of the second support 109.
The third electrode 108 is formed of a third electrode portion 108 a and a third lead portion 108 b extending from the third electrode portion 108 a along the longitudinal direction of the second support 109. The fourth electrode 110 is formed of a fourth electrode portion 110 a and a fourth lead portion 110 b extending from the fourth electrode portion 110 a along the longitudinal direction of the second support 109.
The third electrode 108 and the fourth electrode 110 correspond to “a pair of electrodes” in the claims, and the third electrode 108 corresponds to “one electrode” in the claims. The second support 109 corresponds to an “insulating substrate” in the claims.

  Then, the terminal of the third lead portion 108b is electrically connected to the detection element side pad 121 via a conductor formed in each of the fifth through hole 109b and the seventh through hole 111b provided in the protective layer 111. On the other hand, the terminal of the fourth lead portion 110b is electrically connected to the detection element side pad 121 via a conductor formed in an eighth through hole 111c provided in the protective layer 111 described later. The second lead portion 106b and the third lead portion 108b are at the same potential.

The first solid electrolyte body 105c and the second solid electrolyte body 109c are partially stabilized zirconia sintered bodies obtained by adding yttria (Y ₂ O ₃ ) or calcia (CaO) as a stabilizer to zirconia (ZrO ₂ ). It is composed of

  The heating element 102, the first electrode 104, the second electrode 106, the third electrode 108, the fourth electrode 110, the heater side pad 120, and the detection element side pad 121 can be formed of a platinum group element. Pt, Rh, Pd etc. can be mentioned as a suitable platinum group element which forms these, These can also be used individually by 1 type, and can also use 2 or more types together.

  However, the heating element 102, the first electrode 104, the second electrode 106, the third electrode 108, the fourth electrode 110, the heater side pad 120, and the detection element side pad 121 are mainly composed of Pt in consideration of heat resistance and oxidation resistance. It is even more preferable to form it. Furthermore, the heating element 102, the first electrode 104, the second electrode 106, the third electrode 108, the fourth electrode 110, the heater side pad 120, and the detection element side pad 121 include ceramic components in addition to the main platinum group element. It is preferable to contain. This ceramic component is preferably the same component as the main component on the laminated side (for example, the main component of the first solid electrolyte body 105c and the second solid electrolyte body 109c) from the viewpoint of fixation. .

  An insulating layer 107 is formed between the oxygen pump cell 140 and the oxygen concentration detection cell 130. The insulating layer 107 includes an insulating portion 114 and a diffusion rate controlling portion 115. In the insulating part 114 of the insulating layer 107, a hollow measurement chamber 107c is formed at a position corresponding to the second electrode part 106a and the third electrode part 108a. The measurement chamber 107c communicates with the outside in the width direction of the insulating layer 107, and a diffusion rate-determining unit 115 that realizes gas diffusion between the outside and the measurement chamber 107c under a predetermined rate-limiting condition. Is arranged.

  The insulating part 114 is not particularly limited as long as it is an insulating ceramic sintered body, and examples thereof include oxide ceramics such as alumina and mullite.

  The diffusion control part 115 is a porous body made of alumina. The diffusion rate-determining unit 115 performs rate-limiting when the gas to be measured flows into the measurement chamber 107c.

  A protective layer 111 is formed on the surface of the second solid electrolyte body 109c so as to sandwich the fourth electrode 110. The protective layer 111 sandwiches the fourth electrode portion 110a, sandwiches the porous electrode protection portion 113a for protecting the fourth electrode portion 110a from poisoning, and the fourth lead portion 110b. It consists of a reinforcing part 112 for protecting the second solid electrolyte body 109c. In the gas sensor element 100 of the present embodiment, the current flowing between the electrodes of the oxygen pump cell 140 so that the voltage (electromotive force) generated between the electrodes of the oxygen concentration detection cell 130 becomes a predetermined value (for example, 450 mV). The direction and size of the gas are adjusted, and oxygen in the measurement chamber 107c is pumped. The gas sensor element 100 constitutes an oxygen sensor element that linearly detects the oxygen concentration in the gas to be measured corresponding to the current flowing through the oxygen pump cell 140.

  Returning to FIG. 1, the metal shell 30 is made of SUS430, and has a male screw portion 31 for attaching the gas sensor to the exhaust pipe, and a hexagonal portion 32 to which an attachment tool is applied at the time of attachment. Further, the metal shell 30 is provided with a metal side step portion 33 protruding radially inward, and this metal side step portion 33 supports a metal holder 34 for holding the gas sensor element 100. . Inside the metal holder 34, a ceramic holder 35 and a talc 36 are arranged in this order from the tip side. The talc 36 includes a first talc 37 disposed in the metal holder 34 and a second talc 38 disposed over the rear end of the metal holder 34. The gas sensor element 100 is fixed to the metal holder 34 by compressing and filling the first talc 37 in the metal holder 34. Further, the second talc 38 is compressed and filled in the metal shell 30, so that a sealing property between the outer surface of the gas sensor element 100 and the inner surface of the metal shell 30 is ensured. An alumina sleeve 39 is disposed on the rear end side of the second talc 38. The sleeve 39 is formed in a multi-stage cylindrical shape, is provided with a shaft hole 39a along the axis, and the gas sensor element 100 is inserted through the shaft hole 39a. The caulking portion 30 a on the rear end side of the metal shell 30 is bent inward, and the sleeve 39 is pressed to the front end side of the metal shell 30 through the stainless steel ring member 40.

  Further, a metal protector 24 having a plurality of gas intake holes 24a is attached to the outer periphery on the front end side of the metallic shell 30 by covering the distal end portion of the gas sensor element 100 protruding from the distal end of the metallic shell 30 by welding. . This protector 24 has a double structure, a cylindrical outer protector 41 having a uniform outer diameter on the outer side, and an outer diameter of the rear end part 42a on the inner side from the outer diameter of the front end part 42b. An inner protector 42 having a bottomed cylindrical shape that is formed to be larger is also arranged.

  On the other hand, on the rear end side of the metal shell 30, the front end side of the outer tube 25 made of SUS430 is inserted. The outer cylinder 25 has a distal end portion 25a whose diameter is enlarged on the distal end side fixed to the metal shell 30 by laser welding or the like. A separator 50 is disposed inside the rear end side of the outer cylinder 25, and a holding member 51 is interposed in a gap between the separator 50 and the outer cylinder 25. The holding member 51 is fixed by the outer cylinder 25 and the separator 50 by engaging a protrusion 50 a of the separator 50 described later and caulking the outer cylinder 25.

  The separator 50 is provided with through holes 50b for inserting the lead wires 11 to 15 for the detection element unit 300 and the heater unit 200 from the front end side to the rear end side (note that the lead wires 14, 15 is not shown). The connection holes 16 that connect the lead wires 11 to 15 to the detection element side pads 121 of the detection element unit 300 and the heater side pads 120 of the heater unit 200 are accommodated in the through holes 50b. Each lead wire 11-15 is connected to a connector (not shown) outside. Electric signals are input and output between the external devices such as the ECU and the lead wires 11 to 15 through this connector. Moreover, although not shown in detail in each lead wire 11-15, it has the structure which showed the conducting wire with the insulating film which consists of resin.

  Further, a substantially cylindrical rubber cap 52 for closing the opening 25 b on the rear end side of the outer cylinder 25 is disposed on the rear end side of the separator 50. The rubber cap 52 is fixed to the outer cylinder 25 by caulking the outer periphery of the outer cylinder 25 toward the radially inner side in a state where the rubber cap 52 is mounted in the rear end of the outer cylinder 25. The rubber cap 52 is also provided with through holes 52a for inserting the lead wires 11 to 15 from the front end side to the rear end side.

FIG. 3 is a schematic cross-sectional view orthogonal to the axis L direction of the gas sensor element 100.
As shown in FIG. 3, the thickness t2 of the second solid electrolyte body 109c is made thinner than the thickness t1 of the first solid electrolyte body 105c. For this reason, the voltage applied to the oxygen pump cell 140 having the second solid electrolyte body 109c is reduced, and the power consumption of the gas sensor can be reduced. In addition, the responsiveness of the oxygen pump cell 140 is improved and blackening of the oxygen pump cell 140 can be suppressed. Further, when the gas sensor element 100 includes the heater unit 200, the thermal conductivity from the heater unit 200 to the oxygen pump cell 140 is improved, and the oxygen pump cell 140 is heated to a predetermined temperature earlier. 140 responsiveness is improved.
On the other hand, since the thickness t1 of the first solid electrolyte body 105c is maintained thicker than the second solid electrolyte body 109c, the temperature control of the gas sensor element 100 based on the internal resistance Rpvs of the first solid electrolyte body 105c is accurately performed. Therefore, the oxygen concentration detection accuracy by the oxygen concentration detection cell 130 can be improved.

It is preferable that the thickness t2 of the second solid electrolyte body 109c exceeds 20 μm. As described above, the thickness t2 of the second solid electrolyte body 109c is preferably as small as possible. However, when the thickness t2 is 20 μm or less, the durability of the second solid electrolyte body 109c (oxygen pump cell 140) (the gas sensor element 100 by the heater unit 200) is improved. Due to the temperature gradient of the element at the time of temperature increase, there is a case where the breakdown due to the application of thermal stress to the second solid electrolyte body 109c is reduced.
When the heater unit 200 is stacked on the gas sensor element 100, as shown in FIG. 3, the heater unit 200 is disposed closer to the first solid electrolyte body 105c than the second solid electrolyte body 109c in the stacking direction. It is preferable. In the oxygen concentration detection cell 130 having the first solid electrolyte body 105c that is thicker than the second solid electrolyte body 109c, the thermal conductivity from the heater unit 200 is inferior to that of the oxygen pump cell 140, so that it responds more than the oxygen pump cell 140. Tend to be low. Therefore, by bringing the heater unit 200 closer to the second solid electrolyte body 109c in the stacking direction, the thermal conductivity from the heater unit 200 to the oxygen pump cell 140 can be improved, and the responsiveness of the oxygen pump cell 140 can also be improved. .
The thickness t2 of the second solid electrolyte body 109c is more preferably more than 20 μm and not more than 120 μm. When the thickness t2 of the second solid electrolyte body 109c exceeds 120 μm, blackening may occur due to the voltage applied for the oxygen pump. From the viewpoint of controlling the temperature of the oxygen concentration detection cell 130 using the internal resistance Rpvs of the first solid electrolyte body 105c described above, the thickness t1 of the oxygen concentration detection cell 130 is preferably 150 μm or more.

In addition, as shown in FIG. 3, it is preferable that at least a part of the oxygen pump cell 140 and the oxygen concentration detection cell 130 overlap in the stacking direction to form an overlapping portion S1. By forming the overlapping portion S1, the oxygen pump cell 140 and the oxygen concentration detection cell 130 are adjacent to each other in a plane direction (a direction perpendicular to the stacking direction) in which the measurement gas flows. For this reason, both cells can be exposed to substantially the same environment with respect to fluctuations in the atmosphere (oxygen concentration) and temperature of the gas to be measured introduced into the measurement chamber 107c, and the oxygen concentration detection cell 130 can detect the oxygen concentration. Further improvement can be achieved.
The overlapping portion S1 is defined as follows. First, the outer edge of the overlapping portion in the stacking direction of each component (second solid electrolyte body 109c, third electrode 108, and fourth electrode 110) of the oxygen pump cell 140 is regarded as the outer edge of the oxygen pump cell 140. Similarly, the outer edge of the overlapping portion in the stacking direction of each component (first solid electrolyte body 105 c, first electrode 104, second electrode 106) of the oxygen concentration detection cell 130 is regarded as the outer edge of the oxygen concentration detection cell 130. A portion where the outer edges of the oxygen pump cell 140 and the oxygen concentration detection cell 130 overlap in the stacking direction is defined as an overlapping portion S1.

  The present invention is not limited to the above embodiment, but can be applied to any gas sensor (gas sensor element) having an oxygen pump cell and an oxygen concentration detection cell, and can be applied to the oxygen sensor (oxygen sensor element) of the present embodiment. However, it is needless to say that the present invention is not limited to these uses, and includes various modifications and equivalents included in the concept and scope of the present invention. For example, the present invention may be applied to a NOx sensor (NOx sensor element) that detects the NOx concentration in the gas to be measured.

FIG. 4 is a cross-sectional view along the longitudinal direction of the gas sensor element 100C as the NOx sensor element.
The gas sensor element (NOx sensor element) 100C has an elongated and long plate shape, and has three layers of plate-like solid electrolyte bodies 109Z, 105Z, 151, and insulators 180, 185 made of alumina or the like between them. The layered structure is sandwiched between these layers, and these stacked structures constitute the detection element portion 300C. In addition, sheet-like insulating layers 103C and 101C mainly composed of alumina are laminated on the outer layer (the lower side in FIG. 4) on the solid electrolyte body 151 side, and a heat generating portion 102C composed of a heater pattern mainly composed of Pt therebetween. A heater portion 200C in which is embedded is provided.

The detection element unit 300C includes the following oxygen pump cell (Ip1 cell) 140C, oxygen concentration detection cell (Vs cell) 130C, and second pump cell (Ip2 cell) 150.
The oxygen pump cell 140C is formed of the second solid electrolyte body 109Z and the third electrode 108C and the fourth electrode 110C formed on both surfaces thereof. The oxygen concentration detection cell 130C is formed of a first solid electrolyte body 105Z and a first electrode 104C and a second electrode 106C formed on both surfaces thereof. Further, a hollow measurement chamber 107c2 as a small space is formed between the solid electrolyte body 109Z and the solid electrolyte body 105Z, and the second electrode 106C and the third electrode 108C are arranged in the measurement chamber 107c2. . The measurement chamber 107c2 communicates with the outside on the distal end side, and a diffusion rate controlling portion 115C is disposed at the communicating portion.
A protective layer 111Z is formed on the surface of the second solid electrolyte body 109Z so as to sandwich the fourth electrode 110C. In addition, a portion of the protective layer 111Z that covers the fourth electrode portion 110C is cut out to embed a porous electrode protective portion 113C.

Since the oxygen concentration detection cell 130C and the oxygen pump cell 140C have the same functions as the oxygen concentration detection cell 130 and the oxygen pump cell 140 in the oxygen sensor element 100 described above, description thereof is omitted. The oxygen concentration detection cell 130C generates an electromotive force in accordance with an oxygen partial pressure difference between the measurement chamber 107c2 and a reference oxygen chamber 170 described later.
In the example of FIG. 4, the external dimensions of the solid electrolyte bodies 109Z, 105Z, 151 are the same as those of the gas sensor 1, and the support body is not cut out and embedded as in the oxygen sensor element 100 described above. .

Further, on the rear end side of the gas sensor element 100C of the measurement chamber 107c2, a second diffusion resistor that adjusts gas diffusion as a partition between the opening 181 connected to the second measurement chamber (NOx measurement chamber) 160 and the measurement chamber 107c2. A portion 117 is provided. A second pump cell 150 is formed from the third solid electrolyte body 151, the fifth electrode 152, and the sixth electrode 153. Here, the third solid electrolyte body 151 is disposed so as to face the solid electrolyte body 105C with the insulator 185 interposed therebetween. Further, the insulator 185 is not disposed at the position where the fifth electrode 152 is formed, and a reference oxygen chamber 170 is formed as an independent space. In the reference oxygen chamber 170, the first electrode 104C of the oxygen concentration detection cell 130C is also arranged. The reference oxygen chamber 170 is filled with a ceramic porous body. Also, the insulator 185 is not disposed at the position where the sixth electrode 153 is formed, and the insulator 185 is separated from the reference oxygen chamber 170, and the hollow second measurement chamber 160 as an independent small space is provided. Is formed. The solid electrolyte body 105Z and the insulator 180 are provided with openings 125 and 181 so as to communicate with the second measurement chamber 160. As described above, the measurement chamber 107c2 and the opening 181 are connected to each other. The second diffused resistor 117 is interposed between them.
The second pump cell 150 can pump oxygen between the reference oxygen chamber 170 and the second measurement chamber 160 separated by the insulator 185.

In addition, it is preferable that at least a part of the oxygen pump cell 140C and the oxygen concentration detection cell 130C overlap in the stacking direction to form the overlapping portion S2. By forming the overlapping portion S2, the oxygen pump cell 140C and the oxygen concentration detection cell 130C are adjacent to each other in the plane direction (direction perpendicular to the stacking direction) in which the measurement gas flows. For this reason, both cells can be exposed to almost the same environment with respect to fluctuations in the atmosphere (oxygen concentration) and temperature of the gas to be measured introduced into the measurement chamber 107c2, and the oxygen concentration detection cell 130C can detect the oxygen concentration accurately. Further improvement can be achieved.
The overlapping portion S2 is defined as follows in the same manner as the overlapping portion S1. First, the outer edge of the overlapping portion in the stacking direction of each component (second solid electrolyte body 109Z, third electrode 108C, and fourth electrode 110C) of the oxygen pump cell 140C is regarded as the outer edge of the oxygen pump cell 140C. Similarly, the outer edge of the overlapping portion in the stacking direction of each component (first solid electrolyte body 105Z, first electrode 104C, second electrode 106C) of the oxygen concentration detection cell 130C is regarded as the outer edge of the oxygen concentration detection cell 130C. A portion where the outer edges of the oxygen pump cell 140C and the oxygen concentration detection cell 130C overlap in the stacking direction is defined as an overlapping portion S2.

In the NOx sensor element 100C, similarly to the oxygen sensor element 100 described above, pumping is performed by controlling the current flowing through the oxygen pump cell 140C so that the output voltage of the oxygen concentration detection cell 130C becomes a constant value. The exhaust gas whose oxygen concentration is adjusted in this way is introduced into the second measurement chamber 160 via the second diffusion resistance unit 117 and flows through the second pump cell when a constant voltage is applied to the second pump cell 150. The NOx concentration is detected by measuring the current.
Specifically, the exhaust gas in the second measurement chamber 160 is decomposed (reduced) into N ₂ and O ₂ using the sixth electrode 153 of the second pump cell 150 as a catalyst. The decomposed oxygen receives electrons from the sixth electrode 153, flows as oxygen ions in the third solid electrolyte body 151, and moves to the fifth electrode 152. At this time, the residual oxygen remaining in the measurement chamber 107c2 is also moved into the reference oxygen chamber 170 by the Ip2 cell 150. For this reason, the current flowing through the Ip2 cell 150 is a current derived from NOx and a current derived from residual oxygen.
Here, since the concentration of residual oxygen remaining in the measurement chamber 107c2 is adjusted to a predetermined value as described above, the current derived from the residual oxygen can be considered to be substantially constant, and the fluctuation of the current derived from NOx. The current flowing through the Ip2 cell 150 is proportional to the NOx concentration.

Also in the NOx sensor element 100C of FIG. 4, since the thickness t2 of the second solid electrolyte body 109Z is made thinner than the thickness t1 of the first solid electrolyte body 105Z, the power consumption of the gas sensor can be reduced. In addition, the responsiveness of the oxygen pump cell 140C can be improved, and blackening of the oxygen pump cell 140C can be suppressed. Furthermore, the temperature control of the gas sensor element 100 can be performed with high accuracy, and the detection accuracy of the oxygen concentration by the oxygen concentration detection cell 130C can be improved.
In the NOx sensor element 100C, the thickness t3 of the third solid electrolyte body 151 of the second pump cell 150 may also be made thinner than the thickness t1 of the first solid electrolyte body 105Z. In this case, the power consumption of the second pump cell 150 is reduced, the responsiveness of the second pump cell 150 is improved, and blackening can be suppressed.

The plate-like gas sensor element (oxygen sensor element) 100 shown in FIGS. 1 to 3 was manufactured, and the voltage shown in Table 1 was applied between both electrodes 108 and 110 of the oxygen pump cell 140. If the durability of the second solid electrolyte body 109c (oxygen pump cell 140) is low, the solid electrolyte body 109c is destroyed by applying a voltage. Therefore, the second solid electrolyte body 109c is visually observed after voltage application to determine the presence or absence of cracks. . The test was performed 10 times for the same voltage, and the case where cracking was confirmed even once was evaluated as x.
The obtained results are shown in Table 1.

  As is clear from Table 1, when the thickness t2 of the second solid electrolyte body 140c exceeds 20 μm, the second solid electrolyte body 140c is cracked even when a voltage of 16V corresponding to actual use of a vehicle or the like is applied. There wasn't. From this, it is preferable that the thickness t2 of the second solid electrolyte body 140c exceeds 20 μm.

DESCRIPTION OF SYMBOLS 1 Gas sensor 30 Housing 100, 100C Gas sensor element 101, 103, 101C, 103C Insulating ceramic body (1st base | substrate and 2nd base | substrate)
102, 102C Heating element 104, 104C Reference electrode (first electrode)
105, 109 Insulating substrate (first support, second support)
106, 106C Detection electrode (second electrode)
Pair of electrodes 105c, 105Z First solid electrolyte body 109c, 109Z Second solid electrolyte body 107c, 107c2 Measurement chamber 108, 110, 108C, 110C Pair of electrodes (third electrode and fourth electrode)
108, 108C One electrode (third electrode)
130, 130C Oxygen concentration detection cell 140, 140C Oxygen pump cell 200, 200C Heater part t1 First solid electrolyte body thickness t2 First solid electrolyte body thickness S1, S2 Overlapping part

Claims (8)

The detection electrode has a first solid electrolyte body, a detection electrode and a reference electrode arranged on the first solid electrolyte body, and faces the measurement chamber that communicates with the outside and into which the gas to be measured is introduced. An oxygen concentration detection cell that generates an electromotive force according to the oxygen concentration in the measurement chamber;
A second solid electrolyte body and a pair of electrodes disposed on the second solid electrolyte body, wherein one of the pair of electrodes faces the measurement chamber, and the electromotive force is constant An oxygen pump cell for pumping oxygen in the measurement chamber so that
A gas sensor element formed by laminating
A gas sensor element in which a thickness t2 of the second solid electrolyte body is thinner than a thickness t1 of the first solid electrolyte body. A heater part having a heating element that generates heat when energized is further laminated on the insulating ceramic body,
The gas sensor element according to claim 1, wherein the heater section is controlled based on an internal resistance value Rpvs of the first solid electrolyte body. A heater part having a heating element that generates heat when energized is further laminated on the insulating ceramic body,
2. The gas sensor element according to claim 1 , wherein the heater unit is disposed closer to the first solid electrolyte body than the second solid electrolyte body in the stacking direction. The gas sensor element according to claim 2 , wherein the heater unit is disposed closer to the first solid electrolyte body than the second solid electrolyte body in the stacking direction . The gas sensor element according to any one of claims 1 to 4, wherein a thickness t2 of the second solid electrolyte body exceeds 20 µm . The gas sensor element according to any one of claims 1 to 5, wherein at least a part of the oxygen pump cell and the oxygen concentration detection cell overlap in a stacking direction to form an overlapping portion .   The at least one solid electrolyte body of the first solid electrolyte body and the second solid electrolyte body is embedded in a portion where an insulating substrate having a higher thermal conductivity than the solid electrolyte body is cut out. The gas sensor element according to any one of the above.   In a gas sensor comprising a sensor element that detects the concentration of a specific gas component in a gas to be measured, and a housing that holds the sensor element,
  The gas sensor according to claim 1, wherein the sensor element is the gas sensor element according to claim 1.

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