JP2016188854A - Sensor element and gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the water resisting property of the element body of a sensor element.SOLUTION: A sensor element 101 includes: an element body 102 in the shape of a long rectangular parallelepiped, having an oxygen-ion-conductive solid electrolyte layer; an outer pump electrode 23 arranged on a first surface 102a of the element body 102; and a protective layer 84 covering at least a part of a second surface 102b opposite to the first surface 102a of the element body 102 and having at least one exposed space (lower space 92) to which the second surface 102a is exposed. The lower space 92 is optionally placed to overlap with the center of a region of the second surface 102b which is covered with the protective layer 84 when viewed from the direction perpendicular to the second surface 102b.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a sensor element and a gas sensor.

  Conventionally, a gas sensor including a sensor element that detects a concentration of a predetermined gas such as NOx in a gas to be measured such as an exhaust gas of an automobile is known. In such a gas sensor, it is known to form a protective layer on the surface of the sensor element. For example, Patent Documents 1 and 2 describe forming a protective layer on the surface of a sensor element by printing or plasma spraying. By forming this protective layer, for example, cracking of the sensor element due to adhesion of moisture in the gas to be measured can be suppressed.

JP2011-214853A Japanese Patent No. 3766572

  The sensor element of such a gas sensor has a high temperature during normal driving (for example, 800 ° C. or the like), and it has been desired to further suppress cracking of the sensor element due to rapid cooling due to moisture adhesion.

  The present invention has been made to solve such a problem, and has as its main object to improve the water resistance of the element body of the sensor element.

  The present invention employs the following means in order to achieve the main object described above.

The sensor element of the present invention is
A long rectangular parallelepiped element body provided with an oxygen ion conductive solid electrolyte layer;
An outer electrode disposed on a first surface which is one of the surfaces of the element body;
A protective layer covering at least a part of the second surface opposite to the first surface of the element body, and having one or more exposed spaces in which the second surface is exposed;
It is equipped with.

  In this sensor element, the protective layer covers at least a part of the second surface opposite to the first surface on which the outer electrode is disposed on the surface of the element body. The protective layer has one or more exposed spaces where the second surface is exposed. Thereby, since heat conduction in the thickness direction of the protective layer can be insulated by the exposed space, cooling of the element body when water adheres to the surface of the protective layer is suppressed. Therefore, the water resistance of the element body is improved.

  In the sensor element of the present invention, at least one of the exposed spaces is overlapped with a center of a region of the second surface covered by the protective layer when viewed from a direction perpendicular to the second surface. May be located. Here, the center of the region covered with the protective layer is likely to be relatively hot, and a portion far from the center (for example, a portion near the end of the second surface) is not likely to be relatively hot. Therefore, the water resistance of the element body is further improved by insulating the center of the region of the second surface covered by the protective layer with the exposed space. Note that “the center of the region covered with the protective layer in the second surface” may be the center in the short direction of the second surface of the region covered with the protective layer. The center of the second surface may be the center of the second surface in the lateral direction and the center of the longitudinal direction (that is, the center of the region covered with the protective layer).

  In the sensor element of the present invention, at least one of the exposed spaces may have an opening communicating with the outside of the protective layer. By so doing, heat in the exposed space can be released from the opening, so that overheating of the element body is suppressed. Therefore, a rapid temperature drop of the element body when water adheres to the surface of the protective layer can be suppressed, and the water resistance of the element body is improved.

  In the sensor element according to the aspect of the invention, the protective layer is located in a direction perpendicular to the second surface with respect to at least one of the plurality of exposed spaces and the plurality of exposed spaces, and the second surface is exposed. A plurality of unexposed spaces that are not exposed. When there are a plurality of such spaces in the protective layer, the strength of the protective layer is less likely to decrease than when there is one space having the same total volume. Therefore, by providing a space in the protective layer, it is possible to improve water resistance, and to suppress a decrease in the strength of the protective layer due to the presence of the space.

  In the sensor element of the present invention, the protective layer may have at least one columnar portion that supports the exposed space in a direction perpendicular to the second surface with respect to at least one of the exposed spaces. If it carries out like this, the fall of the intensity | strength of a protective layer can be suppressed because a columnar part supports exposed space.

  In the sensor element of the present invention having a columnar portion, the protective layer has a plurality of the columnar portions, and the plurality of columnar portions are viewed from a direction perpendicular to the second surface. You may arrange | position in the tendency for the density of this columnar part to become high, so that it is far from the center of the area | region coat | covered with the said protective layer among 2nd surfaces. Here, the center of the region covered with the protective layer is likely to be relatively hot, and a portion far from the center (for example, a portion near the end of the second surface) is not likely to be relatively hot. Therefore, by making the density of the columnar part tend to be higher in a part that is relatively difficult to reach a high temperature, the columnar part has a columnar part in a region that is likely to become high temperature while suppressing a decrease in the strength of the protective layer. The fall of the heat insulation effect of the exposure space by can be suppressed. Therefore, it is possible to further improve the water resistance of the element body while further suppressing the decrease in the strength of the protective layer. Here, “the tendency for the density of the columnar portions to increase” includes a tendency for the number of columnar portions per unit area to increase and a tendency for the thickness of the columnar portions to increase.

  In the sensor element of the present invention having a columnar portion, the plurality of columnar portions are located at the center of a region of the second surface covered by the protective layer when viewed from a direction perpendicular to the second surface. You may arrange | position in the tendency for the density of this columnar part to become high, so that it is near.

  In the sensor element of the present invention, the protective layer may include a plurality of the exposed spaces whose longitudinal direction is along the longitudinal direction of the second surface along the lateral direction of the second surface. A protective layer caused by a difference in thermal expansion coefficient between the protective layer and the element body when exposed to water due to the presence of a plurality of elongated exposure spaces along the short direction of the second surface along the longitudinal direction of the second surface Thus, the stress along the short direction of the second surface with respect to the element body is reduced. Therefore, the element main body becomes difficult to break when wet, and the water resistance of the element main body is further improved. In this case, the exposed space whose longitudinal direction is along the longitudinal direction of the second surface may be a rectangular parallelepiped space in which one side along the short direction of the second surface is shorter than the other two sides. .

  In the sensor element of the present invention, the protective layer may have a plurality of the exposed spaces whose longitudinal direction is along the short direction of the second surface along the longitudinal direction of the second surface. A protective layer caused by a difference in thermal expansion coefficient between the protective layer and the element body when exposed to water by having a plurality of elongated exposure spaces along the short direction of the second surface along the longitudinal direction of the second surface Thus, the stress along the longitudinal direction of the second surface with respect to the element body is reduced. Therefore, the element main body becomes difficult to break when wet, and the water resistance of the element main body is further improved. In this case, the exposed space whose longitudinal direction is along the short direction of the second surface may be a rectangular parallelepiped space in which one side along the longitudinal direction of the second surface is shorter than the other two sides. .

  In the sensor element of the present invention, the protective layer has a plurality of first exposed spaces, which are the exposed spaces whose longitudinal direction is along the longitudinal direction of the second surface, along the lateral direction of the second surface. And there are a plurality of second exposure spaces along the longitudinal direction of the second surface, the second exposure space being the exposure space that intersects with the first exposure space. You may do it. In this case, both the stress along the short side direction of the second surface from the protective layer to the element body and the stress along the longitudinal direction are caused by the difference in thermal expansion coefficient between the protective layer and the element body when wet. Reduced. Therefore, the element main body becomes difficult to break when wet, and the water resistance of the element main body is further improved.

  In the sensor element of the present invention, at least one of the exposed spaces may have a shape in which the exposed space tends to become narrower as the distance from the second surface increases. The exposure space having such a shape can suppress a decrease in the strength of the protective layer, for example, compared to a rectangular parallelepiped space having an inner surface parallel to the second surface.

  In the sensor element of the present invention, at least one of the exposed spaces may have at least two inner surfaces that are inclined toward each other as the distance from the second surface increases. The exposed space having such an inner surface can suppress a decrease in the strength of the protective layer, for example, compared to a rectangular parallelepiped space having an inner surface parallel to the second surface.

  In the sensor element of the present invention, at least one of the exposed spaces may be a curved surface with an inner surface facing the second surface curved outward. The exposed space having such an inner surface can suppress a decrease in the strength of the protective layer, for example, compared to a rectangular parallelepiped space having an inner surface parallel to the second surface.

The gas sensor of the present invention is
The sensor element according to any one of the aspects described above is provided.

  This gas sensor includes the sensor element of the present invention according to any one of the aspects described above. Therefore, the same effect as the sensor element of the present invention described above, for example, the effect of improving the water resistance of the element body can be obtained.

The perspective view which showed roughly an example of the structure of the sensor element 101 of 1st Embodiment. FIG. 3 is a cross-sectional view schematically illustrating an example of the configuration of the gas sensor 100 according to the first embodiment. BB sectional drawing of FIG. CC sectional drawing of FIG. DD sectional drawing of FIG. Sectional drawing of 101 A of sensor elements of 2nd Embodiment. EE sectional drawing of FIG. Sectional drawing of the sensor element 101B of 3rd Embodiment. FF sectional drawing of FIG. Sectional drawing of the sensor element 101C of 4th Embodiment. GG sectional drawing of FIG. Sectional drawing of sensor element 101D of 5th Embodiment. HH sectional drawing of FIG. Sectional drawing of the sensor element 101E of 6th Embodiment. II sectional drawing of FIG. Sectional drawing of the sensor element 101F of 7th Embodiment. JJ sectional drawing of FIG. KK sectional drawing of FIG. Sectional drawing of the sensor element 101G of 8th Embodiment. LL sectional drawing of FIG. Sectional drawing of the sensor element 101H of 9th Embodiment. MM sectional drawing of FIG. A sectional view of sensor element 101I of a 10th embodiment. The bottom view around the front end of the sensor element 101I. Sectional drawing of the sensor element 101J of 11th Embodiment. The bottom view around the front end of the sensor element 101J. A sectional view of sensor element 101K of a 12th embodiment. The bottom view around the front end of the sensor element 101K.

[First Embodiment]
Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view schematically showing an example of a configuration of a sensor element 101 included in the gas sensor 100 according to the first embodiment. FIG. 2 is a cross-sectional view schematically showing an example of the configuration of the gas sensor 100. 2 is a cross section taken along the line AA of FIG. 3 is a cross-sectional view taken along line BB in FIG. In FIG. 3, illustration of the inside of the cross section of the element body 102 is omitted. 4 is a cross-sectional view taken along the line CC of FIG. 5 is a cross-sectional view taken along the line DD of FIG. The sensor element 101 has a long rectangular parallelepiped shape. The longitudinal direction of the sensor element 101 (left-right direction in FIG. 2) is the front-rear direction, and the thickness direction of the sensor element 101 (up-down direction in FIG. 2) is the up-down direction. To do. The width direction of sensor element 101 (the direction perpendicular to the front-rear direction and the up-down direction) is the left-right direction.

The gas sensor 100 is attached to a pipe such as an exhaust pipe of a vehicle, for example, and is used for measuring the concentration of a specific gas such as NOx or O ₂ contained in the exhaust gas as the gas to be measured. In the present embodiment, the gas sensor 100 measures the NOx concentration as the specific gas concentration. The gas sensor 100 includes a sensor element 101. The sensor element 101 includes a sensor element body 102 and a porous protective layer 84 that covers the sensor element body 102. The sensor element body 102 refers to a part other than the protective layer 84 in the sensor element 101.

As shown in FIG. 2, the sensor element 101 includes a first substrate layer 1, a second substrate layer 2, and a third substrate layer 3 each made of an oxygen ion conductive solid electrolyte layer such as zirconia (ZrO ₂ ). The first solid electrolyte layer 4, the spacer layer 5, and the second solid electrolyte layer 6 are elements having a structure in which the layers are laminated in this order from the bottom in the drawing. The solid electrolyte forming these six layers is dense and airtight. The sensor element 101 is manufactured, for example, by performing predetermined processing and circuit pattern printing on a ceramic green sheet corresponding to each layer, stacking them, and firing and integrating them.

  One end portion (front end portion) of the sensor element 101, and between the lower surface of the second solid electrolyte layer 6 and the upper surface of the first solid electrolyte layer 4, the gas inlet 10 and the first diffusion In a mode in which the rate-limiting portion 11, the buffer space 12, the second diffusion-controlling portion 13, the first internal space 20, the third diffusion-controlling portion 30, and the second internal space 40 are communicated in this order. Adjacently formed.

  The gas introduction port 10, the buffer space 12, the first internal space 20, and the second internal space 40 are provided on the lower surface of the second solid electrolyte layer 6 with the upper portion provided in a state in which the spacer layer 5 is cut out. The space inside the sensor element 101 is defined by the lower part being the upper surface of the first solid electrolyte layer 4 and the side parts being the side surfaces of the spacer layer 5.

  Each of the first diffusion rate controlling unit 11, the second diffusion rate controlling unit 13, and the third diffusion rate controlling unit 30 is provided as two horizontally long slits (the opening has a longitudinal direction in a direction perpendicular to the drawing). . In addition, the site | part from the gas inlet 10 to the 2nd internal space 40 is also called a gas distribution part.

  Further, at a position farther from the front end side than the gas circulation part, the side part is partitioned by the side surface of the first solid electrolyte layer 4 between the upper surface of the third substrate layer 3 and the lower surface of the spacer layer 5. The reference gas introduction space 43 is provided at the position. For example, the atmosphere is introduced into the reference gas introduction space 43 as a reference gas when measuring the NOx concentration.

  The air introduction layer 48 is a layer made of porous ceramics, and a reference gas is introduced into the air introduction layer 48 through the reference gas introduction space 43. The air introduction layer 48 is formed so as to cover the reference electrode 42.

  The reference electrode 42 is an electrode formed in such a manner that it is sandwiched between the upper surface of the third substrate layer 3 and the first solid electrolyte layer 4. As described above, the reference electrode 42 leads to the reference gas introduction space 43. An air introduction layer 48 is provided. Further, as will be described later, it is possible to measure the oxygen concentration (oxygen partial pressure) in the first internal space 20 and the second internal space 40 using the reference electrode 42.

  In the gas circulation part, the gas inlet 10 is a part opened to the external space, and the gas to be measured is taken into the sensor element 101 from the external space through the gas inlet 10. The first diffusion control unit 11 is a part that provides a predetermined diffusion resistance to the gas to be measured taken from the gas inlet 10. The buffer space 12 is a space provided to guide the gas to be measured introduced from the first diffusion rate controlling unit 11 to the second diffusion rate controlling unit 13. The second diffusion rate limiting unit 13 is a part that imparts a predetermined diffusion resistance to the gas to be measured introduced from the buffer space 12 into the first internal space 20. When the gas to be measured is introduced from the outside of the sensor element 101 to the inside of the first internal space 20, the pressure fluctuation of the gas to be measured in the external space (exhaust pressure pulsation if the gas to be measured is an automobile exhaust gas) ), The gas to be measured that is suddenly taken into the sensor element 101 from the gas inlet 10 is not directly introduced into the first internal space 20, but the first diffusion control unit 11, the buffer space 12, the second After the concentration variation of the gas to be measured is canceled through the diffusion control unit 13, the gas is introduced into the first internal space 20. As a result, the concentration fluctuation of the gas to be measured introduced into the first internal space 20 becomes almost negligible. The first internal space 20 is provided as a space for adjusting the partial pressure of oxygen in the gas to be measured introduced through the second diffusion rate limiting unit 13. The oxygen partial pressure is adjusted by the operation of the main pump cell 21.

  The main pump cell 21 includes an inner pump electrode 22 having a ceiling electrode portion 22a provided on substantially the entire lower surface of the second solid electrolyte layer 6 facing the first internal space 20, and an upper surface of the second solid electrolyte layer 6. An electrochemical pump cell comprising an outer pump electrode 23 provided in a manner exposed to the external space in a region corresponding to the ceiling electrode portion 22a, and a second solid electrolyte layer 6 sandwiched between these electrodes. is there.

  The inner pump electrode 22 is formed across the upper and lower solid electrolyte layers (the second solid electrolyte layer 6 and the first solid electrolyte layer 4) that define the first inner space 20, and the spacer layer 5 that provides side walls. Yes. Specifically, a ceiling electrode portion 22a is formed on the lower surface of the second solid electrolyte layer 6 that provides the ceiling surface of the first internal space 20, and a bottom portion is formed on the upper surface of the first solid electrolyte layer 4 that provides the bottom surface. Spacer layers in which the electrode portions 22b are formed and the side electrode portions (not shown) constitute both side walls of the first internal space 20 so as to connect the ceiling electrode portions 22a and the bottom electrode portions 22b. 5 is formed on the side wall surface (inner surface), and is disposed in a tunnel-shaped structure at the portion where the side electrode portion is disposed.

The inner pump electrode 22 and the outer pump electrode 23 are formed as a porous cermet electrode (for example, a cermet electrode of Pt and ZrO ₂ containing 1% of Au). The inner pump electrode 22 in contact with the gas to be measured is formed using a material that has a reduced reduction ability for the NOx component in the gas to be measured.

  In the main pump cell 21, a desired pump voltage Vp 0 is applied between the inner pump electrode 22 and the outer pump electrode 23, and the pump current is positive or negative between the inner pump electrode 22 and the outer pump electrode 23. By flowing Ip0, oxygen in the first internal space 20 can be pumped into the external space, or oxygen in the external space can be pumped into the first internal space 20.

  Further, in order to detect the oxygen concentration (oxygen partial pressure) in the atmosphere in the first internal space 20, the inner pump electrode 22, the second solid electrolyte layer 6, the spacer layer 5, and the first solid electrolyte layer 4. The third substrate layer 3 and the reference electrode 42 constitute an electrochemical sensor cell, that is, a main pump control oxygen partial pressure detection sensor cell 80.

  By measuring the electromotive force V0 in the main pump control oxygen partial pressure detection sensor cell 80, the oxygen concentration (oxygen partial pressure) in the first internal space 20 can be known. Further, the pump current Ip0 is controlled by feedback-controlling the pump voltage Vp0 of the variable power source 25 so that the electromotive force V0 is constant. Thereby, the oxygen concentration in the first internal space 20 can be kept at a predetermined constant value.

  The third diffusion control unit 30 provides a predetermined diffusion resistance to the gas under measurement whose oxygen concentration (oxygen partial pressure) is controlled by the operation of the main pump cell 21 in the first internal space 20, and the gas under measurement is supplied to the gas under measurement. This is the part that leads to the second internal space 40.

  The second internal space 40 is provided as a space for performing a process related to the measurement of the nitrogen oxide (NOx) concentration in the gas to be measured introduced through the third diffusion control unit 30. The NOx concentration is measured mainly in the second internal space 40 in which the oxygen concentration is adjusted by the auxiliary pump cell 50, and further by measuring the pump cell 41 for measurement.

  In the second internal space 40, after the oxygen concentration (oxygen partial pressure) is adjusted in advance in the first internal space 20, the auxiliary pump cell 50 is further supplied to the gas to be measured introduced through the third diffusion control unit 30. The oxygen partial pressure is adjusted by the above. Thereby, since the oxygen concentration in the second internal space 40 can be kept constant with high accuracy, the gas sensor 100 can measure the NOx concentration with high accuracy.

  The auxiliary pump cell 50 includes an auxiliary pump electrode 51 having a ceiling electrode portion 51a provided on substantially the entire lower surface of the second solid electrolyte layer 6 facing the second internal space 40, and an outer pump electrode 23 (outer pump electrode 23). The auxiliary electrochemical pump cell is configured by the second solid electrolyte layer 6 and a suitable electrode outside the sensor element 101 is sufficient.

  The auxiliary pump electrode 51 is disposed in the second internal space 40 in the same tunnel configuration as the inner pump electrode 22 provided in the first internal space 20. That is, the ceiling electrode portion 51 a is formed on the second solid electrolyte layer 6 that provides the ceiling surface of the second internal space 40, and the first solid electrolyte layer 4 that provides the bottom surface of the second internal space 40 is formed on the first solid electrolyte layer 4. The bottom electrode part 51b is formed, and the side electrode part (not shown) connecting the ceiling electrode part 51a and the bottom electrode part 51b is provided on the spacer layer 5 that provides the side wall of the second internal space 40. It has a tunnel-type structure formed on both wall surfaces. Note that the auxiliary pump electrode 51 is also formed using a material having a reduced reducing ability with respect to the NOx component in the gas to be measured, like the inner pump electrode 22.

  In the auxiliary pump cell 50, by applying a desired voltage Vp1 between the auxiliary pump electrode 51 and the outer pump electrode 23, oxygen in the atmosphere in the second internal space 40 is pumped to the external space, or It is possible to pump into the second internal space 40 from the space.

  Further, in order to control the oxygen partial pressure in the atmosphere in the second internal space 40, the auxiliary pump electrode 51, the reference electrode 42, the second solid electrolyte layer 6, the spacer layer 5, and the first solid electrolyte. The layer 4 and the third substrate layer 3 constitute an electrochemical sensor cell, that is, an auxiliary pump control oxygen partial pressure detection sensor cell 81.

  The auxiliary pump cell 50 performs pumping by the variable power source 52 that is voltage-controlled based on the electromotive force V1 detected by the auxiliary pump control oxygen partial pressure detection sensor cell 81. Thereby, the oxygen partial pressure in the atmosphere in the second internal space 40 is controlled to a low partial pressure that does not substantially affect the measurement of NOx.

  At the same time, the pump current Ip1 is used to control the electromotive force of the oxygen partial pressure detection sensor cell 80 for main pump control. Specifically, the pump current Ip1 is input as a control signal to the main pump control oxygen partial pressure detection sensor cell 80, and the electromotive force V0 is controlled, so that the third diffusion rate limiting unit 30 controls the second internal space. The gradient of the oxygen partial pressure in the gas to be measured introduced into the gas 40 is controlled so as to be always constant. When used as a NOx sensor, the oxygen concentration in the second internal space 40 is maintained at a constant value of about 0.001 ppm by the action of the main pump cell 21 and the auxiliary pump cell 50.

  The measurement pump cell 41 measures the NOx concentration in the gas to be measured in the second internal space 40. The measurement pump cell 41 includes a measurement electrode 44 provided on a top surface of the first solid electrolyte layer 4 facing the second internal space 40 and spaced from the third diffusion rate-determining portion 30, an outer pump electrode 23, The electrochemical pump cell is constituted by the second solid electrolyte layer 6, the spacer layer 5, and the first solid electrolyte layer 4.

  The measurement electrode 44 is a porous cermet electrode. The measurement electrode 44 also functions as a NOx reduction catalyst that reduces NOx present in the atmosphere in the second internal space 40. Further, the measurement electrode 44 is covered with a fourth diffusion rate controlling part 45.

  The 4th diffusion control part 45 is a film | membrane comprised with a ceramic porous body. The fourth diffusion control unit 45 plays a role of limiting the amount of NOx flowing into the measurement electrode 44 and also functions as a protective film for the measurement electrode 44. In the measurement pump cell 41, oxygen generated by the decomposition of nitrogen oxides in the atmosphere around the measurement electrode 44 can be pumped out, and the generated amount can be detected as the pump current Ip2.

  In order to detect the oxygen partial pressure around the measurement electrode 44, an electrochemical sensor cell, that is, a first solid electrolyte layer 4, a third substrate layer 3, a measurement electrode 44, and a reference electrode 42, that is, A measurement pump control oxygen partial pressure detection sensor cell 82 is configured. The variable power supply 46 is controlled on the basis of the electromotive force V2 detected by the measurement pump control oxygen partial pressure detection sensor cell 82.

The gas to be measured introduced into the second internal space 40 reaches the measurement electrode 44 through the fourth diffusion rate-determining unit 45 under the condition where the oxygen partial pressure is controlled. Nitrogen oxide in the gas to be measured around the measurement electrode 44 is reduced (2NO → N ₂ + O ₂ ) to generate oxygen. The generated oxygen is pumped by the measurement pump cell 41. At this time, the variable power source is set so that the electromotive force V2 detected by the measurement pump control oxygen partial pressure detection sensor cell 82 is constant. 46 voltage Vp2 is controlled. Since the amount of oxygen generated around the measurement electrode 44 is proportional to the concentration of nitrogen oxide in the gas to be measured, the nitrogen oxide in the gas to be measured using the pump current Ip2 in the measurement pump cell 41. The concentration will be calculated.

  In addition, if the measurement electrode 44, the first solid electrolyte layer 4, the third substrate layer 3, and the reference electrode 42 are combined to form an oxygen partial pressure detecting means as an electrochemical sensor cell, The electromotive force according to the difference between the amount of oxygen generated by the reduction of the NOx component in the surrounding atmosphere and the amount of oxygen contained in the reference atmosphere can be detected, thereby the concentration of the NOx component in the gas to be measured Is also possible.

  The second solid electrolyte layer 6, the spacer layer 5, the first solid electrolyte layer 4, the third substrate layer 3, the outer pump electrode 23, and the reference electrode 42 constitute an electrochemical sensor cell 83. The oxygen partial pressure in the gas to be measured outside the sensor can be detected by the electromotive force Vref obtained by the sensor cell 83.

  In the gas sensor 100 having such a configuration, by operating the main pump cell 21 and the auxiliary pump cell 50, the oxygen partial pressure is always kept at a constant low value (a value that does not substantially affect the measurement of NOx). A gas to be measured is supplied to the measurement pump cell 41. Therefore, the NOx concentration in the measurement gas is determined based on the pump current Ip2 that flows when oxygen generated by the reduction of NOx is pumped out of the measurement pump cell 41 in proportion to the NOx concentration in the measurement gas. You can know.

  Furthermore, the sensor element 101 includes a heater unit 70 that plays a role of temperature adjustment for heating and maintaining the sensor element 101 in order to increase the oxygen ion conductivity of the solid electrolyte. The heater unit 70 includes a heater connector electrode 71, a heater 72, a through hole 73, a heater insulating layer 74, and a pressure dissipation hole 75.

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

  The heater 72 is an electric resistor formed in a form sandwiched between the second substrate layer 2 and the third substrate layer 3 from above and below. The heater 72 is connected to the heater connector electrode 71 through the through-hole 73, and generates heat when power is supplied from the outside through the heater connector electrode 71, thereby heating and keeping the solid electrolyte forming the sensor element 101. .

  The heater 72 is embedded over the entire area from the first internal space 20 to the second internal space 40, and the entire sensor element 101 can be adjusted to a temperature at which the solid electrolyte is activated. ing.

  The heater insulating layer 74 is an insulating layer formed on the upper and lower surfaces of the heater 72 by an insulator such as alumina. The heater insulating layer 74 is formed for the purpose of obtaining electrical insulation between the second substrate layer 2 and the heater 72 and electrical insulation between the third substrate layer 3 and the heater 72.

  The pressure dissipating hole 75 is a portion that is provided so as to penetrate the third substrate layer 3 and communicate with the reference gas introduction space 43, and is for the purpose of alleviating the increase in internal pressure accompanying the temperature increase in the heater insulating layer 74. Formed.

  The element body 102 is partially covered with a protective layer 84 as shown in FIGS. Here, since the sensor element 101 is a rectangular parallelepiped, as shown in FIGS. 1 to 3, as the outer surface of the solid electrolyte layer of the sensor element 101, the first surface 102 a (upper surface), the second surface 102 b (lower surface), There are six surfaces: a third surface 102c (left side surface), a fourth surface 102d (right side surface), a fifth surface 102e (front end surface), and a sixth surface 102f (rear end surface). The protective layer 84 is a porous body, and is formed on each of the five surfaces (first to fifth surfaces 102a to 102e) of the six surfaces (first to sixth surfaces 102a to 102f) of the element body 102. First to fifth protective layers 84a to 84e are provided. The first to fifth protective layers 84a to 84e are collectively referred to as a protective layer 84. Each of the first to fourth protective layers 84a to 84d has a region from the front end surface of the element body 102 to the distance L (see FIG. 2) to the rear of the surface of the element body 102 on which the first to fourth protective layers 84a to 84d are formed. All covered. The first protective layer 84a also covers the portion of the first surface 102a where the outer pump electrode 23 is formed (see FIGS. 2 and 3). The fifth protective layer 84e also covers the gas inlet 10, but since the fifth protective layer 84e is a porous body, the gas to be measured can reach the gas inlet through the inside of the protective layer 84e. is there. The protective layer 84 covers a part of the element body 102 (a part from the front end surface to the distance L including the front end surface of the element body 102) to protect the part. The protective layer 84 plays a role of suppressing the occurrence of cracks in the element body 102 due to, for example, moisture in the gas to be measured attached thereto. The distance L is (0 <distance L <length in the longitudinal direction of the element body 102) based on the range in which the element body 102 is exposed to the gas to be measured in the gas sensor 100, the position of the outer pump electrode 23, and the like. It is determined by the scope.

  In the present embodiment, as shown in FIG. 1, the element body 102 has a length in the front-rear direction, a width in the left-right direction, and a thickness in the vertical direction, and length> width> thickness. Yes. The distance L is assumed to be larger than the width and thickness of the element body 102.

  As shown in FIGS. 2 to 5, the protective layer 84 has a space 90 inside. Specifically, the first protective layer 84a has the upper space 91, the second protective layer 84b has the lower space 92, the third protective layer 84c has the left space 93, and the fourth protective layer 84d. Has a right space 94. These spaces 91 to 94 are collectively referred to as a space 90.

  The upper space 91 is an exposed space in which the first surface 102a is exposed, and is formed in a substantially rectangular parallelepiped shape. As shown in FIG. 4, the upper space 91 is a region covered with the protective layer 84 (the first protective layer 84 a) of the first surface 102 a when viewed from the direction perpendicular to the first surface 102 a, that is, in a top view. It is located so as to include the center of (the region from the front end surface to the distance L in the first surface 102a). That is, the center of the region covered with the protective layer 84 (first protective layer 84a) in the first surface 102a is exposed in the upper space 91. In addition, the center of the area | region covered with the protective layer 84 among the 1st surfaces 102a means the center of the front-back direction of the area | region, and the center of the left-right direction. Further, the upper space 91 may be positioned such that at least a part of the upper space 91 overlaps at least a part of the outer pump electrode 23 when viewed from above. In the present embodiment, as shown in FIG. 4, when viewed from above, the upper space 91 is positioned so as to overlap the entire outer pump electrode 23 (the upper space 91 includes the entire outer pump electrode 23). That is, the entire outer pump electrode 23 is exposed in the upper space 91.

  Unlike the upper space 91, the lower space 92, the left space 93, and the right space 94 are exposed to the second surface 102b, the third surface 102c, and the fourth surface 102d, respectively, but have the same shape as the upper space 91. doing. The positional relationship of the lower space 92, the left space 93, and the right space 94 with respect to the second surface 102b, the third surface 102c, and the fourth surface 102d is the same as the positional relationship of the upper space 91 with respect to the first surface 102a. The upper space 91 and the lower space 92 have a vertically symmetrical shape and arrangement. The left space 93 and the right space 94 have a symmetrical shape and arrangement.

  Specifically, the lower space 92 is an exposed space in which the second surface 102b is exposed, and is formed in a substantially rectangular parallelepiped shape. As shown in FIG. 5, the lower space 92 is a region covered with the protective layer 84 (second protective layer 84b) of the second surface 102b when viewed from the direction perpendicular to the second surface 102b, that is, from below. It is located so as to include the center of the second surface 102b from the front end surface to the distance L. That is, the center of the region covered with the protective layer 84 (second protective layer 84 b) in the second surface 102 b is exposed in the lower space 92. In addition, the center of the area | region covered with the protective layer 84 among the 2nd surfaces 102b means the center of the front-back direction of the area | region, and the center of the left-right direction.

  The left space 93 has the third surface 102c exposed, and is covered by the protective layer 84 (third protective layer 84c) of the third surface 102c when viewed from the direction perpendicular to the third surface 102c, that is, from the left. Is located so as to include the center of the region (region of the third surface 102c from the front end surface to the distance L). The right space 94 has the fourth surface 102d exposed, and is covered by the protective layer 84 (fourth protective layer 84d) of the fourth surface 102d when viewed from the direction perpendicular to the fourth surface 102d, that is, from the right side. Is located so as to include the center of the region (the region from the front end surface to the distance L of the fourth surface 102d).

  The protective layer 84 is made of a porous material such as an alumina porous material, a zirconia porous material, a spinel porous material, a cordierite porous material, a titania porous material, or a magnesia porous material. In the present embodiment, the protective layer 84 is made of an alumina porous body. Although it does not specifically limit, the film thickness of the protective layer 84 is 100-1000 micrometers, for example, and the porosity of the protective layer 84 is 5 volume%-85 volume%, for example.

  A method for manufacturing the gas sensor 100 thus configured will be described below. In the manufacturing method of the gas sensor 100, the element body 102 is first manufactured, and then the protective layer 84 is formed on the element body 102 to manufacture the sensor element 101.

  A method for manufacturing the element body 102 will be described. First, six green ceramic green sheets are prepared. And each corresponding to each of the 1st substrate layer 1, the 2nd substrate layer 2, the 3rd substrate layer 3, the 1st solid electrolyte layer 4, the spacer layer 5, and the 2nd solid electrolyte layer 6, A pattern such as an electrode, an insulating layer, and a resistance heating element is printed on the ceramic green sheet. After forming various patterns in this way, the green sheet is dried. Then, they are laminated to form a laminate. The laminated body thus obtained includes a plurality of element bodies 102. The laminated body is cut and cut into the size of the element body 102 and fired at a predetermined firing temperature to obtain the element body 102.

  Next, a method for forming the protective layer 84 on the element body 102 will be described. The protective layer 84 can be formed by various methods such as gel casting, screen printing, dipping, and plasma spraying. The space 90 in the protective layer 84 can be formed using a disappearing material (for example, carbon, theobromine, etc.) that disappears by combustion.

  The gel casting method is a method in which a slurry is solidified by a chemical reaction of the slurry itself to form a molded body. For example, a part of the element body 102 (the part to be covered) is exposed inside the mold, and the slurry is poured into the gap between the mold and the element body 102 to be solidified. As a slurry used for the gel casting method, for example, a slurry containing raw material powder (such as ceramic particles) of the protective layer 84, a sintering aid, an organic solvent, a dispersant, and a gelling agent can be used. The gelling agent is not particularly limited as long as it contains at least two kinds of polymerizable organic compounds, and examples thereof include those containing two kinds of organic compounds capable of urethane reaction. Examples of such two types of organic compounds include isocyanates and polyols. In preparing the slurry, first, a raw material powder, a sintering aid, an organic solvent, and a dispersing agent are added at a predetermined ratio and mixed for a predetermined time to prepare a slurry precursor. And just before using a slurry, it is set as a slurry by adding a gelling agent to the slurry precursor, and mixing. In addition, any one or two of isocyanates, polyols and catalysts constituting the gelling agent are added to the slurry precursor, and then the remaining components may be added when preparing the slurry. Good. The slurry after adding the gelling agent to the slurry precursor is preferably poured quickly into the mold because the chemical reaction (urethane reaction) of the gelling agent starts to progress over time.

  For example, when forming the protective layer 84, it carries out as follows. First, the vanishing material is applied and dried on the surface of the element body 102 to form a vanishing body in the shape of the upper space 91, the lower space 92, the left space 93, and the right space 94. Application | coating of a loss | disappearance material can be performed by screen printing, gravure printing, inkjet printing, etc., for example. Moreover, you may form a loss | disappearance body by repeating application | coating and drying several times. Next, a protective layer 84 is formed on the surface of the element body 102. Thereby, the protective layer 84 provided with the vanishing body in the shape of the space 90 is formed. Thereafter, the lost body is lost by combustion. Thereby, the lost body part becomes the space 90, and the protective layer 84 having the space 90 inside is formed. In this way, the protective layer 84 is formed on the element body 102 to obtain the sensor element 101. When the protective layer 84 is formed by gel casting, screen printing, or dipping, the slurry that becomes the protective layer 84 is solidified or dried, and then the slurry is fired to form the protective layer 84. In this case, firing of the protective layer 84 and burning of the lost body may be performed simultaneously. Further, when the protective layer 84 is formed by plasma spraying, the lost body may be lost by combustion after the protective layer 84 is formed.

  When forming the protective layer 84 (or the protective layer 84 before firing) having the disappearance body in the shape of the space 90, the formation of a part of the protection layer 84 and the formation of a part of the disappearance body are repeated. Then, the protective layer 84 and the disappearing body may be formed by gradually laminating in the thickness direction from the surface of the element body 102. The protective layer 84 may be formed by collectively forming the first to fifth protective layers 84a to 84e, or by forming the first to fifth protective layers 84a to 84e one by one. Also good.

  When the sensor element 101 is obtained in this manner, the gas sensor 100 is obtained by being housed in a predetermined housing and incorporated in the main body (not shown) of the gas sensor 100.

  When the gas sensor 100 configured in this way is used, the gas to be measured in the pipe reaches the sensor element 101, passes through the protective layer 84, and flows into the gas inlet 10. The sensor element 101 detects the NOx concentration in the gas to be measured that has flowed into the gas inlet 10. At this time, moisture contained in the measurement gas may adhere to the surface of the protective layer 84. The element body 102 is adjusted to a temperature (for example, 800 ° C.) at which the solid electrolyte is activated by the heater 72 as described above, and when moisture adheres to the element 102, the temperature rapidly decreases and cracks occur in the element body 102. May occur. Here, the protective layer 84 of the present embodiment has a space 90 inside. Thereby, heat conduction in the thickness direction of the protective layer 84 (direction from the outer peripheral surface of the protective layer 84 toward the element main body 102) can be insulated by the space 90, so that the element when water adheres to the surface of the protective layer 84 Cooling of the main body 102 is suppressed. Specifically, each of the upper space 91, the lower space 92, the left space 93, and the right space 94 is present, so that water adheres to the upper, lower, left, and right surfaces of the protective layer 84. In this case, the cooling of the element body 102 can be suppressed. Therefore, in this embodiment, the water resistance of the element body 102 is improved.

  Here, the correspondence between the components of the present embodiment and the components of the present invention will be clarified. The element body 102 of this embodiment corresponds to the element body of the present invention, the outer pump electrode 23 corresponds to the outer electrode, the lower space 92 corresponds to the exposed space, and the protective layer 84 corresponds to the protective layer.

  According to the gas sensor 100 of the present embodiment described in detail above, the sensor element 101 includes the long rectangular parallelepiped element body 102 including the oxygen ion conductive solid electrolyte layer and the first surface 102 a of the element body 102. One or more exposed spaces (lower spaces) that cover the arranged outer pump electrode 23 and at least a part of the second surface 102b opposite to the first surface 102a of the element body 102 and expose the second surface 102b. 92). Accordingly, heat conduction in the thickness direction of the protective layer 84 (particularly heat conduction upward from the lower surface of the second protective layer 84b) can be insulated by the lower space 92, so that water is applied to the surface of the protective layer 84. Cooling of the element main body 102 when adhering is suppressed. Therefore, the water resistance of the element body 102 is improved. In the present embodiment, as shown in FIG. 2, the heater 72 is disposed below the center of the element body 102 in the vertical direction. That is, the heater 72 is disposed closer to the second surface 102b than the first surface 102a. For this reason, the second surface 102b tends to be relatively hot. Therefore, it is highly significant that the protective layer 84 includes the lower space 92 on the second surface 102b side. In addition, since each of the upper space 91, the left space 93, and the right space 94 exists, the element main body 102 when water adheres to the surfaces of the first, third, and fourth protective layers 84a, 84c, and 84d. Therefore, the water resistance of the element body 102 is further improved.

  Further, the lower space 92 is positioned so as to overlap the center of the region covered with the protective layer 84 of the second surface 102b when viewed from the direction perpendicular to the second surface 102b. Here, the center of the region covered with the protective layer 84 is likely to be relatively hot, and a portion far from the center (for example, a portion near the end of the second surface 102b) is not likely to be relatively hot. Therefore, the water resistance of the element body 102 is further improved by insulating the center of the region of the second surface 102b covered with the protective layer 84 with the lower space 92.

[Second Embodiment]
FIG. 6 is a cross-sectional view of the sensor element 101A of the second embodiment. 7 is a cross-sectional view taken along line EE in FIG. In the sensor element 101A, the protective layer 84 includes a space 90A different from the space 90, and the other points are the same as the sensor element 101 of the first embodiment.

  The space 90A has an upper space 91A, a lower space 92A, a left space 93A, and a right space 94A. The upper space 91A is the same as the upper space 91 of the first embodiment except that the upper space 91A further includes a communication hole H1 that opens to the upper surface of the first protective layer 84a. Similarly, each of the spaces 92A to 94A is the same as each of the spaces 92 to 94 of the first embodiment except that the spaces 92A to 94A further include communication holes H2 to H4 that open to the outer surface of the protective layer 84.

  The communication hole H <b> 2 is a rectangular parallelepiped space opened in a substantially square shape on the lower surface of the protective layer 84. However, the present invention is not limited to this, and the opening may be circular, for example. The lower space 92A communicates with the outside of the protective layer 84 through the communication hole H2. The position of the communication hole H2 may be the center in the front-rear direction of the region of the second surface 102b covered with the protective layer 84 when viewed from the direction perpendicular to the second surface 102b, or the center in the left-right direction. Alternatively, it may be the center (center of front, back, left, and right).

  The positional relationship and shape of the communication holes H1, H3, and H4 with respect to the corresponding first, third, and fourth surfaces 102a, 102c, and 102d are the same as the positional relationship and shape of the communication hole H2 with respect to the second surface 102b. . In the present embodiment, the upper space 91A and the lower space 92A have a vertically symmetrical shape and arrangement. The left space 93A and the right space 94A have a symmetrical shape and arrangement.

  Similarly to the sensor element 101, the sensor element 101 </ b> A described above is further improved in water resistance of the element body 102 due to the presence of the spaces 91 </ b> A to 94 </ b> A. The lower space 92A has an opening (opening of the communication hole H2) that communicates with the outside of the second protective layer 84b. Thereby, since heat in the lower space 92A can be released from the opening, overheating of the element body 102 is suppressed. Therefore, a rapid temperature drop of the element body 102 when water adheres to the surface of the protective layer 84 can be suppressed, and the water resistance of the element body 102 is improved. Similarly, each of the spaces 91A, 93A, 94A has the openings of the communication holes H1, H3, H4, so that the water resistance of the element body 102 is improved.

[Third Embodiment]
FIG. 8 is a cross-sectional view of the sensor element 101B of the third embodiment. 9 is a cross-sectional view taken along line FF in FIG. The sensor element 101B includes a space 90B in which the protective layer 84 is different from the space 90, and is otherwise the same as the sensor element 101 of the first embodiment.

  The space 90B has an upper space 91B, a lower space 92B, a left space 93B, and a right space 94B. The lower space 92B is a plurality of exposed spaces 95B2 where the second surface 102b is exposed, and a plurality of exposed spaces 95B2 which are shifted in a direction (downward) perpendicular to the second surface 102b with respect to the exposed space 95B2 and where the second surface 102b is not exposed. Non-exposed space 96B2. The exposed space 95B2 is a substantially rectangular parallelepiped space. As shown in FIG. 9, there are a total of 12 exposure spaces 95B2 in the left-right direction and four in the front-rear direction, and they are arranged in a grid pattern in the bottom view. The non-exposed space 96B2 is a substantially rectangular parallelepiped space. As shown in FIG. 9, there are a total of 20 non-exposed spaces 96B2 in the left-right direction and five in the front-rear direction, and they are arranged in a lattice pattern in the bottom view. The plurality of exposed spaces 95B2 have the same vertical length. The plurality of non-exposed spaces 96B2 have the same vertical length and the same vertical position. That is, the plurality of exposed spaces 95B2 and the plurality of non-exposed spaces 96B2 are arranged in two upper and lower stages.

  The plurality of exposed spaces 95B2 and the plurality of non-exposed spaces 96B2 are positioned at a height apart from each other so that their positions do not overlap when viewed from a direction perpendicular to the vertical direction. Further, the plurality of exposure spaces 95B2 and the plurality of exposure spaces 96B2 are arranged at positions shifted in the left-right direction and positions shifted in the front-rear direction.

  The upper space 91B is a plurality of exposed spaces 95B1 in which the first surface 102a is exposed, and a plurality of exposed spaces 95B1 that are shifted in a direction (upward) perpendicular to the first surface 102a with respect to the exposed space 95B1 and the first surface 102a is not exposed. A non-exposed space 96B1. The left space 93B is a plurality of exposed spaces 95B3 in which the third surface 102c is exposed, and a plurality of exposed spaces 95B3 that are shifted in a direction perpendicular to the third surface 102c (leftward) with respect to the exposed space 95B3 and in which the third surface 102c is not exposed. Non-exposed space 96B3. The right space 94B is a plurality of exposed spaces 95B4 in which the fourth surface 102d is exposed, and a plurality of exposed spaces 95B4 that are shifted in a direction perpendicular to the fourth surface 102d (rightward) with respect to the exposed space 95B4 and in which the fourth surface 102d is not exposed. Non-exposed space 96B4. The positional relationship and shape of each exposed space 95B1, 95B3, 95B4 and each non-exposed space 96B1, 96B3, 96B4 with respect to the corresponding first, third, and fourth surfaces 102a, 102c, and 102d are the exposure to the second surface 102b. The positional relationship and shape of the space 95B2 and the non-exposed space 96B2 are the same. In the present embodiment, there are four exposure spaces 95B3 and 95B4, one in the vertical direction and four in the front-rear direction. The non-exposed spaces 96B3 and 96B4 are 10 in total, two in the vertical direction and five in the front-rear direction. In the present embodiment, the upper space 91B and the lower space 92B have a vertically symmetrical shape and arrangement. The left space 93B and the right space 94B have a symmetrical shape and arrangement.

  Similarly to the sensor element 101, the sensor element 101B described above is further improved in water resistance of the element body 102 due to the presence of the spaces 91B to 94B. In addition, the second protective layer 84b is shifted in a direction perpendicular to the second surface 102b with respect to at least one of the plurality of exposed spaces 95B2 and the plurality of exposed spaces 95B2, and the second surface 102b is not exposed. And an unexposed space 96B2. When there are such a plurality of spaces in the second protective layer 84b, the strength of the second protective layer 84b is less likely to decrease than when there is one space having the same total volume. Therefore, by providing a space in the second protective layer 84b, it is possible to improve the water resistance of the element body 102, and to suppress a decrease in strength of the second protective layer 84b due to the presence of the space. Further, since there are a plurality of non-exposure spaces 96B2 that are shifted in a direction perpendicular to the plurality of exposure spaces 95B2, a plurality of spaces having the same shape and number are all shifted in a direction parallel to the second surface 102b. Compared with the case where it is located (it is not shifted | deviated to the perpendicular direction), the position of space is easy to separate | separate. Therefore, a decrease in strength of the second protective layer 84b can be further suppressed. The same effect can be obtained by the same configuration for each of the spaces 91B, 93B, 94B.

[Fourth Embodiment]
FIG. 10 is a cross-sectional view of the sensor element 101C of the fourth embodiment. 11 is a cross-sectional view taken along the line GG in FIG. The sensor element 101C includes a space 90C in which the protective layer 84 is different from the space 90B, and the other points are the same as the sensor element 101B of the third embodiment.

  The space 90C has an upper space 91C, a lower space 92C, a left space 93C, and a right space 94C. The lower space 92C is a plurality of exposed spaces 95C2 in which the second surface 102b is exposed and a plurality of exposed spaces 95C2 that are shifted in a direction (downward) perpendicular to the second surface 102b with respect to the exposed space 95C2 and in which the second surface 102b is not exposed. Non-exposed space 96C2. Similarly, each space 91C, 93C, 94C has a plurality of exposed spaces 95C1, 95C3, 95C4 and a plurality of non-exposed spaces 96C1, 96C3, C4.

  The number, shape, and arrangement of the non-exposed spaces 96C2 are the same as the non-exposed spaces 96B2 of the third embodiment. Similarly, the number, shape, and arrangement of the non-exposed spaces 96C1, 96C3, 96C4 are the same as the non-exposed spaces 96B1, 96B3, 96B4 of the third embodiment.

  The plurality of exposed spaces 95C2 are displaced from the plurality of non-exposed spaces 96C2 in the direction perpendicular to the second surface 102b and in the front-rear direction, but the positions in the left-right direction are the same. This is different from the positional relationship between the exposed space 95B2 and the non-exposed space 96B2 in the third embodiment. As shown in FIG. 11, the exposure space 95C2 has a total of 16 exposure spaces, 4 in the left-right direction and 4 in the front-rear direction, and is arranged in a lattice shape in a bottom view.

  Similarly, the plurality of exposed spaces 95C1, 95C3, and 95C4 have the same left-right position as the corresponding non-exposed spaces 96C1, 96C3, and 96C4. The positional relationship and shape of the exposure spaces 95C1, 95C3, and 95C4 with respect to the first, third, and fourth surfaces 102a, 102c, and 102d respectively correspond to the positional relationship and shape of the exposure space 95C2 with respect to the second surface 102b. It is the same. In the present embodiment, there are eight exposure spaces 95C3 and 95C4, two in the vertical direction and four in the front-rear direction. In the present embodiment, the upper space 91C and the lower space 92C have a vertically symmetrical shape and arrangement. The left space 93C and the right space 94C have a symmetrical shape and arrangement.

  The sensor element 101C described above can obtain the same effect by the same configuration as the sensor element 101 and the sensor element 101B.

[Fifth Embodiment]
FIG. 12 is a cross-sectional view of the sensor element 101D of the fifth embodiment. 13 is a cross-sectional view taken along the line HH in FIG. The sensor element 101D includes a space 90D in which the protective layer 84 is different from the space 90, and the other points are the same as the sensor element 101 of the first embodiment.

  The space 90D has an upper space 91D, a lower space 92D, a left space 93D, and a right space 94D. The upper space 91D is the same as the upper space 91 of the first embodiment except that a plurality of columnar portions P1 that support the upper space 91D in the direction perpendicular to the first surface 102a are formed. Similarly, each of the spaces 92D to 94D is the first except that a plurality of columnar portions P2 to P4 that support each space are formed in a direction perpendicular to the corresponding second surface to fourth surface 102b to 102d. It is the same as each space 92-94 of embodiment.

  The columnar part P2 is a part of the second protective layer 84b and has a quadrangular columnar shape. The shape of the columnar part P2 is not limited to this, and may be a columnar shape, a triangular column shape, a polygonal column shape of pentagon or more. As shown in FIG. 13, when viewed from the direction perpendicular to the second surface 102b, the plurality of columnar portions P2 are farther from the center in the front-rear direction of the region covered with the protective layer 84 on the second surface 102b. It arrange | positions in the tendency for the density of the columnar part P2 to become high. More specifically, the number of columnar portions P2 per unit area increases as the distance from the center in the front-rear direction increases (the plurality of columnar portions P2 tend to be dense). In other words, the plurality of columnar portions P2 are arranged such that the number of the columnar portions P2 per unit area increases as it is closer to the front end or the rear end of the region covered with the protective layer 84 in the second surface 102b. ing.

  The positional relationship and shape of the columnar portions P1, P3, and P4 with respect to the corresponding first, third, and fourth surfaces 102a, 102c, and 102d are the same as the positional relationship and shape of the columnar portion P2 with respect to the second surface 102b. . For example, when the columnar portion P1 is viewed from a direction perpendicular to the first surface 102a, the columnar portion P1 per unit area becomes farther away from the center in the front-rear direction of the region covered with the protective layer 84 of the first surface 102a. The number of is arranged in a tendency to increase. When viewed from the direction perpendicular to the third surface 102c, the columnar portion P3 is the number of the columnar portions P3 per unit area as the distance from the center in the front-rear direction of the region covered with the protective layer 84 of the third surface 102c increases. There is a tendency to increase. When viewed from the direction perpendicular to the fourth surface 102d, the columnar portion P4 is the number of the columnar portions P4 per unit area as the distance from the center in the front-rear direction of the region covered with the protective layer 84 of the fourth surface 102d increases. There is a tendency to increase. In the present embodiment, the plurality of columnar portions P1 and the plurality of columnar portions P2 have a vertically symmetric shape and arrangement. The plurality of columnar portions P3 and the plurality of columnar portions P4 have a symmetrical shape and arrangement.

  Similarly to the sensor element 101, the sensor element 101D described above is further improved in water resistance of the element body 102 due to the presence of the spaces 91D to 94D. The second protective layer 84b has one or more columnar portions P2 that support the lower space 92D in a direction perpendicular to the second surface 102b with respect to the lower space 92D. Therefore, the columnar part P2 supports the lower space 92D, so that a decrease in strength of the second protective layer 84b can be suppressed. Further, the second protective layer 84b has a plurality of columnar portions P2, and the plurality of columnar portions P2 are columnar as the distance from the center of the region covered by the second protective layer 84b in the second surface 102b increases. It arrange | positions in the tendency for the density of the part P2 to become high. Here, the center of the region covered with the second protective layer 84b is likely to be relatively hot, and a portion far from the center (for example, a portion near the end of the second surface 102b) is not likely to be relatively hot. For this reason, the density of the columnar portion P2 tends to be higher in a portion that is relatively difficult to reach a high temperature, thereby suppressing a decrease in the strength of the second protective layer 84b by the columnar portion P2 and a region that is likely to be heated to a columnar shape. A decrease in the heat insulation effect of the lower space 92D due to the presence of the part P2 can be suppressed. Accordingly, it is possible to further improve the water resistance of the element body 102 while further suppressing the decrease in the strength of the second protective layer 84b. The same effect can be obtained with the same configuration for each of the spaces 91D, 93D, and 94D.

[Sixth Embodiment]
FIG. 14 is a cross-sectional view of the sensor element 101E of the sixth embodiment. 15 is a cross-sectional view taken along the line II of FIG. The sensor element 101E includes a space 90E in which the protective layer 84 is different from the space 90D, and the other points are the same as the sensor element 101D of the fifth embodiment.

  The space 90E has an upper space 91E, a lower space 92E, a left space 93E, and a right space 94E. The spaces 91E to 94E are the same as the spaces 91D to 94D of the fifth embodiment, except that the arrangement and number of the columnar portions P1 to P4 that support the spaces 91E to 94E are different.

  As shown in FIG. 15, the plurality of columnar portions P2 are closer to the center in the front-rear direction of the region of the second surface 102b covered with the protective layer 84 when viewed from the direction perpendicular to the second surface 102b. It arrange | positions in the tendency for the density of the columnar part P2 to become high. More specifically, the closer to the center in the front-rear direction, the greater the number of columnar portions P2 per unit area (the tendency that a plurality of columnar portions P2 are densely arranged).

  The positional relationship and shape of the columnar portions P1, P3, and P4 with respect to the corresponding first, third, and fourth surfaces 102a, 102c, and 102d are the same as the positional relationship and shape of the columnar portion P2 with respect to the second surface 102b. . For example, when the columnar portion P1 is viewed from a direction perpendicular to the first surface 102a, the columnar portion P1 per unit area is closer to the center in the front-rear direction of the region covered with the protective layer 84 of the first surface 102a. The number of is arranged in a tendency to increase. The number of columnar portions P3 per unit area is closer to the center in the front-rear direction of the region covered by the protective layer 84 in the third surface 102c when viewed from the direction perpendicular to the third surface 102c. There is a tendency to increase. The number of the columnar portions P4 per unit area is closer to the center in the front-rear direction of the region covered with the protective layer 84 in the fourth surface 102d when viewed from the direction perpendicular to the fourth surface 102d. There is a tendency to increase. In the present embodiment, the plurality of columnar portions P1 and the plurality of columnar portions P2 have a vertically symmetric shape and arrangement. The plurality of columnar portions P3 and the plurality of columnar portions P4 have a symmetrical shape and arrangement.

  Similarly to the sensor element 101, the sensor element 101E described above is further improved in water resistance of the element body 102 due to the presence of the spaces 91E to 94E. Moreover, since the columnar part P2 supports the lower space 92E, a decrease in strength of the second protective layer 84b can be suppressed. The same effect can be obtained with the same configuration for each of the spaces 91D, 93D, and 94D.

[Seventh Embodiment]
FIG. 16 is a cross-sectional view of the sensor element 101F of the seventh embodiment. 17 is a cross-sectional view taken along line JJ in FIG. 18 is a cross-sectional view taken along the line KK of FIG. In the sensor element 101F, the protective layer 84 includes a space 90F different from the space 90, and the other points are the same as the sensor element 101 of the first embodiment.

  The space 90F has an upper space 91F, a lower space 92F, a left space 93F, and a right space 94F. As shown in FIG. 17, the lower space 92F has a first exposure space 97F2 in which the longitudinal direction is the exposure space along the longitudinal direction (front-rear direction) of the second surface 102b, and the short side direction ( A plurality are provided along the horizontal direction. In addition, the lower space 92F has a longitudinal direction along the short direction of the second surface 102b and a second exposed space 98F2, which is an exposed space intersecting the first exposed space 97F2, along the longitudinal direction of the second surface 102b. Have more than one. In the present embodiment, there are two first exposure spaces 97F2 and five second exposure spaces 98F2. The plurality of second exposure spaces 98F2 are located at equal intervals in the front-rear direction.

  The first exposure space 97F2 and the second exposure space 98F2 are both substantially rectangular parallelepiped spaces. The first exposed space 97F2 has a slit shape, and one side (side in the left-right direction) along the short direction of the second surface 102b is the other two sides (side in the up-down direction and the front-rear direction). Shorter than). The second exposed space 98F2 has a slit shape, and one side (side in the front-rear direction) along the longitudinal direction of the second surface 102b is more than the other two sides (side in the up-down direction and left-right direction). short.

  Similar to the lower space 92F, the upper space 91F has a plurality of first exposure spaces 97F1 and a plurality of second exposure spaces 98F1. The left space 93F has a plurality of first exposure spaces 97F3 and a plurality of second exposure spaces 98F3, like the lower space 92F. The right space 94F has a plurality of first exposure spaces 97F4 and a plurality of second exposure spaces 98F4, like the lower space 92F.

  The positional relationship and shape of each of the first exposure spaces 97F1, 97F3, 97F4 and each of the second exposure spaces 98F1, 98F3, 98F4 with respect to the corresponding first, third, and fourth surfaces 102a, 102c, 102d are the second surface. The positional relationship and shape of the first exposure space 97F2 and the second exposure space 97F2 with respect to 102b are the same. For example, the plurality of first exposure spaces 97F1, 97F3, and 97F4 are along the longitudinal direction (front-rear direction) of the first, third, and fourth surfaces 102a, 102c, and 102d corresponding to the longitudinal directions. The plurality of second exposure spaces 98F1, 98F3, and 98F4 are along the short direction of the first, third, and fourth surfaces 102a, 102c, and 102d corresponding to the longitudinal directions. Further, the plurality of first exposure spaces 97F1 and the plurality of second exposure spaces 98F1 intersect, the plurality of first exposure spaces 97F3 and the plurality of second exposure spaces 98F3 intersect, and the plurality of first exposure spaces 97F1. The exposure space 97F4 and the plurality of second exposure spaces 98F4 intersect. In the present embodiment, the upper space 91F and the lower space 92F have a vertically symmetrical shape and arrangement. The left space 93F and the right space 94F have a symmetrical shape and arrangement.

  Similarly to the sensor element 101, the sensor element 101 </ b> F described above further improves the water resistance of the element body 102 due to the presence of the spaces 91 </ b> F to 94 </ b> F. Further, the second protective layer 84b has a plurality of first exposed spaces 97F2 and a plurality of second exposed spaces 98F2. Since there are a plurality of elongated first exposed spaces 97F2 along the longitudinal direction of the second surface 102b along the short direction of the second surface 102b, the heat of the second protective layer 84b and the element body 102 when exposed to water. Stress along the short direction of the second surface 102b from the second protective layer 84b to the element body 102 due to the difference in expansion coefficient is reduced. In addition, since there are a plurality of elongated second exposed spaces 98F2 along the longitudinal direction of the second surface 102b along the short direction of the second surface 102b, the second protective layer 84b, the element main body 102, and the like when exposed to water. The stress along the longitudinal direction of the second surface 102b from the second protective layer 84b to the element body 102 due to the difference in thermal expansion coefficient is reduced. As a result, the element main body 102 is less likely to break when wet, and the water resistance of the element main body 102 is further improved. Each of the first, third, and fourth protective layers 84a, 84c, and 84d also has the same effect due to the same configuration due to the presence of the spaces 91F, 93F, and 94F.

[Eighth Embodiment]
FIG. 19 is a cross-sectional view of the sensor element 101G of the eighth embodiment. 20 is a cross-sectional view taken along line LL in FIG. In the sensor element 101G, the protective layer 84 includes a space 90G. The space 90G has an upper space 91G, a lower space 92G, a left space 93G, and a right space 94G. The upper space 91G is the same as the upper space 91F of the seventh embodiment, except that it includes a plurality of first exposure spaces 97F1 and does not include the second exposure space 98F1. Similarly, each of the spaces 92G to 94G includes a plurality of first exposure spaces 97F2 to 97F4, and each of the spaces 92F to 94F of the seventh embodiment except that the second exposure spaces 98F2 to 98F4 are not included. Is the same.

  Similarly to the sensor element 101, the sensor element 101G described above is further improved in water resistance of the element body 102 due to the presence of the spaces 91G to 94G. Further, since the second protective layer 84b includes the plurality of first exposed spaces 97F2, the difference in thermal expansion coefficient between the second protective layer 84b and the element main body 102 when exposed to water is the same as in the seventh embodiment. The stress along the short direction of the second surface 102b with respect to the element body 102 from the second protective layer 84b due to the above is reduced. Thereby, the element main body 102 becomes difficult to break when wet, and the water resistance of the element main body 102 is further improved. Each of the first, third, and fourth protective layers 8a, 84c, and 84d has the same effect because the first exposed spaces 97F1, 97F3, and 97F4 exist.

[Ninth Embodiment]
FIG. 21 is a cross-sectional view of the sensor element 101H of the ninth embodiment. 22 is a cross-sectional view taken along line MM in FIG. In the sensor element 101H, the protective layer 84 includes a space 90H. The space 90H has an upper space 91H, a lower space 92H, a left space 93H, and a right space 94H. The upper space 91H is the same as the upper space 91F of the seventh embodiment except that it includes a plurality of second exposure spaces 98F1 and does not include the first exposure space 97F1. Similarly, each of the spaces 92H to 94H includes a plurality of second exposure spaces 98F2 to 98F4, and each of the spaces 92F to 94F of the seventh embodiment except that the first exposure spaces 97F2 to 97F4 are not included. Is the same.

  Similarly to the sensor element 101, the sensor element 101H described above is further improved in water resistance of the element body 102 due to the presence of the spaces 91H to 94H. Further, since the second protective layer 84b has a plurality of second exposed spaces 98F2, the difference in thermal expansion coefficient between the second protective layer 84b and the element body 102 when exposed to water is the same as in the seventh embodiment. Due to the above, the stress along the longitudinal direction of the second surface 102b from the second protective layer 84b to the element body 102 is reduced. Thereby, the element main body 102 becomes difficult to break when wet, and the water resistance of the element main body 102 is further improved. Each of the first, third, and fourth protective layers 84a, 84c, and 84d has the same effect because the second exposed spaces 98F1, 98F3, and 98F4 exist.

[Tenth embodiment]
FIG. 23 is a cross-sectional view of the sensor element 101I according to the tenth embodiment. FIG. 24 is a bottom view around the front end of the sensor element 101I. FIG. 23 shows a state in which the sensor element 101I is viewed from the lower right rear side. The sensor element 101I includes a space 90I in which the protective layer 84 is different from the space 90, and is otherwise the same as the sensor element 101 of the first embodiment.

  The space 90I has a plurality of upper spaces 91I, lower spaces 92I, left spaces 93I, and right spaces 94I. The lower space 92I is an exposed space where the second surface 102b is exposed. The lower space 92I is a substantially triangular prism-shaped space whose longitudinal direction is along the longitudinal direction of the second surface 102b. A plurality (six in this embodiment) of the plurality of lower spaces 92I are arranged along the short direction of the second surface 102b. In the lower space 92I, as shown in FIG. 23, a cross section perpendicular to the second surface 102b (a cross section along the vertical and horizontal directions) has a triangular shape. For this reason, the lower space 92I has a shape in which the space tends to become narrower as the distance from the second surface 102b increases, that is, as it goes downward. Further, the lower space 92I has inner surfaces Sa2 and Sb2 constituting two sides of a triangle facing the second surface 102b in a cross-sectional view perpendicular to the second surface 102b. The inner surfaces Sa2 and Sb2 are inclined so as to approach each other as the distance from the second surface 102b increases.

  Each of the spaces 91I, 93I, and 94I is an exposed space in which the first, third, and fourth surfaces 102a, 102c, and 102d are exposed, like the lower space 92I. Each space 91I, 93I, 94I has an inner surface Sa1, which forms two sides of a triangle facing the corresponding surface in a cross-sectional view perpendicular to the corresponding first, third, and fourth surfaces 102a, 102c, 104d. It has Sa3, Sa4 and inner surfaces Sb1, Sb3, Sb4. The positional relationships and shapes of the spaces 91I, 93I, and 94I with respect to the corresponding first, third, and fourth surfaces 102a, 102c, and 102d are the same as the positional relationships and shapes of the lower space 92I with respect to the second surface 102b. is there. The left space 93I and the right space 94I are arranged side by side in the vertical direction. In the present embodiment, the plurality of upper spaces 91I and the plurality of lower spaces 92I have a vertically symmetrical shape and arrangement. The plurality of left spaces 93I and the plurality of right spaces 94I have a vertically symmetric shape and arrangement. Further, the outer pump electrode 23 is exposed in the four upper spaces 91I in the center in the left-right direction among the plurality of upper spaces 91.

  Similarly to the sensor element 101, the sensor element 101I described above is further improved in water resistance of the element body 102 due to the presence of the spaces 91I to 94I. Further, the lower space 92I has a shape in which the space tends to become narrower as the distance from the second surface 102b increases. The lower space 92I having such a shape has a lower strength of the second protective layer 84b than a space having a rectangular parallelepiped shape having an inner surface parallel to the second surface 102b, for example, the lower space 92 in FIG. Can be suppressed.

  Further, the lower space 92I has at least two inner surfaces Sa2 and Sb2 that are inclined in a direction of approaching each other as the distance from the second surface 102b increases. The lower space 92I having such inner surfaces Sa2 and Sb2 is, for example, a second protective layer compared to a rectangular parallelepiped space having an inner surface parallel to the second surface 102b, such as the lower space 92 in FIG. A decrease in strength of 84b can be suppressed.

  The second protective layer 84b has a plurality of lower spaces 92I whose longitudinal direction is along the longitudinal direction of the second surface 102b, along the lateral direction of the second surface 102b. Therefore, similarly to the sensor elements 101F and 101G, the shortness of the second surface 102b from the second protective layer 84b to the element main body 102 due to the difference in thermal expansion coefficient between the second protective layer 84b and the element main body 102 when wet. Stress along the hand direction is reduced. Thereby, the element main body 102 becomes difficult to break when wet, and the water resistance of the element main body 102 is further improved.

  Each of the first, third, and fourth protective layers 84a, 84c, and 84d also has the space 91I, 93I, and 94I, and thus the same effect can be obtained by the same configuration as the second protective layer 84b. .

[Eleventh embodiment]
FIG. 25 is a cross-sectional view of the sensor element 101J of the eleventh embodiment. FIG. 26 is a bottom view around the front end of the sensor element 101J. FIG. 25 shows a state in which the sensor element 101J is viewed from the lower right rear side. The sensor element 101J includes a space 90J in which the protective layer 84 is different from the space 90, and the other points are the same as the sensor element 101 of the first embodiment. The space 90J has exposed spaces 95J1 to 95J6.

  The exposed space 95J2 is a space disposed on the lower side of the element body 102, and the second surface 102b is exposed. The exposed space 95J2 is a semi-elliptical columnar space, and the inner surface (the inner surface of the protective layer 84, that is, the surface facing upward) facing the second surface 102b has a rectangular shape curved outward (downward) from the second protective layer 84b. The curved surface (a curved surface corresponding to a part of the inner peripheral surface of the cylinder). Therefore, the exposed space 95J2 has a semi-elliptical cross section (a cross section along the vertical and horizontal directions) perpendicular to the second surface 102b, and the space becomes narrower as it moves away from the second surface 102b (downward). It has a trend shape. The exposure space 95J2 has a longitudinal direction along the longitudinal direction of the second surface 102b.

  The exposed space 95J1 is a space arranged on the upper side of the element body 102, and the first surface 102a is exposed. The exposed space 95J1 is a semi-elliptical columnar space, and the inner surface (the inner surface of the protective layer 84, that is, the surface facing downward) facing the first surface 102a has a rectangular shape curved outward (upward) from the first protective layer 84a. The curved surface (a curved surface corresponding to a part of the inner peripheral surface of the cylinder). The exposure space 95J1 has a longitudinal direction along the longitudinal direction of the first surface 102a. The entire outer pump electrode 23 is exposed in the exposed space 95J1. The exposed space 95J1 has a vertically symmetrical shape and arrangement with the exposed space 95J2.

  The exposed space 95J4 is a space arranged at the lower left of the element body 102, and the second surface 102b and the third surface 102c are exposed. The exposed space 95J4 has a shape in which a part of a cylinder is cut out. The exposed space 95J4 has a curved surface (a part of the inner peripheral surface of the cylinder) whose inner surface (the surface facing upward) facing the second surface 102b is a rectangle curved outward (downward) from the second protective layer 84b. Curved surface). For this reason, the exposed space 95J4 has a shape in which the space tends to become narrower as the distance from the second surface 102b increases. Further, the exposed space 95J4 has a curved surface (an inner peripheral surface of the cylinder) whose inner surface (the surface facing right) facing the third surface 102c is curved to the outside (left) of the third protective layer 84c. A curved surface corresponding to a part). Therefore, the exposed space 95J4 has a shape in which the space tends to become narrower as it is farther from the third surface 102c (toward the left). The exposure space 95J4 has a longitudinal direction along the longitudinal direction of the second surface 102b and the third surface 102c.

  The exposed space 95J3 is a space arranged at the upper left of the element body 102, and the first surface 102a and the third surface 102c are exposed. The exposed space 95J3 has a vertically symmetrical shape and arrangement with the exposed space 95J4. The exposure space 95J5 is a space arranged on the upper right side of the element body 102, and the first surface 102a and the fourth surface 102d are exposed. The exposed space 95J5 has a symmetrical shape and arrangement with the exposed space 95J3. The exposed space 95J6 is a space arranged at the lower right of the element body 102, and the second surface 102b and the fourth surface 102d are exposed. The exposed space 95J6 has a shape and arrangement that is symmetrical with the exposed space 95J4, and has a shape and arrangement that is symmetrical with the exposed space 95J5.

  The exposure spaces 95J1, 95J3, and 95J5 are arranged along the short side direction of the first surface 102a. The exposure spaces 95J2, 95J4, and 95J6 are arranged along the short direction of the second surface 102b. The exposure spaces 95J3 and 95J4 are arranged along the short direction of the third surface 102c. The exposure spaces 95J5 and 95J6 are arranged along the short side direction of the fourth surface 102d.

  Similarly to the sensor element 101, the sensor element 101J described above is further improved in water resistance of the element body 102 due to the presence of the exposed spaces 95J1 to 95J6. In addition, the exposed spaces 95J2, 95J4, and 95J6 have a shape in which the space tends to become narrower as the distance from the second surface 102b increases. Further, the exposed spaces 95J2, 95J4, and 95J6 are curved surfaces whose inner surfaces facing the second surface 102b are curved outward. The space having such a shape can suppress a decrease in strength of the second protective layer 84b as compared with a rectangular parallelepiped space having an inner surface parallel to the second surface 102b, for example, the lower space 92 in FIG. .

  In addition, the protective layer 84 has exposed spaces 95J2, 95J4, and 95J6, which are a plurality of exposed spaces whose longitudinal direction is along the longitudinal direction of the second surface 102b, arranged side by side along the lateral direction of the second surface 102b. Yes. Therefore, similarly to the sensor elements 101F and 101G, the shortness of the second surface 102b from the second protective layer 84b to the element main body 102 due to the difference in thermal expansion coefficient between the second protective layer 84b and the element main body 102 when wet. Stress along the hand direction is reduced. Thereby, the element main body 102 becomes difficult to break when wet, and the water resistance of the element main body 102 is further improved.

  The exposed spaces 95J1, 95J3, and 95J6 for the first surface 102a, the exposed spaces 95J3 and 95J4 for the third surface 102c, and the exposed spaces 95J5 and 95J6 for the fourth surface 102d are also exposed spaces 95J2, 95J4, and 95J6 for the second surface 102b. The same effect can be obtained by the same configuration.

[Twelfth embodiment]
FIG. 27 is a cross-sectional view of the sensor element 101K of the twelfth embodiment. FIG. 28 is a bottom view around the front end of the sensor element 101K. FIG. 27 shows the sensor element 101K as viewed from the lower right rear. The sensor element 101K includes a space 90K in which the protective layer 84 is different from the space 90, and the other points are the same as the sensor element 101 of the first embodiment. The space 90K has exposure spaces 95K1 to 95K4.

  The exposure spaces 95K1 and 95K2 are the same spaces as the exposure spaces 95J1 and 95J2 of the sensor element 101J, respectively.

  The exposed space 95K3 is a space disposed over the upper side, the lower side, and the left side of the element body 102, and the first surface 102a, the second surface 102b, and the third surface 102c are exposed. The exposed space 95K3 has a shape in which a part of an elliptic cylinder is cut out. The exposed space 95K3 has a curved surface (a part of the inner peripheral surface of the cylinder) whose inner surface (the surface facing downward) facing the first surface 102a is a rectangle curved outward (upward) from the first protective layer 84a. Curved surface). Therefore, the exposed space 95K3 has a shape in which the space tends to become narrower as the distance from the first surface 102a increases. The exposed space 95K3 corresponds to a curved surface (a part of the inner peripheral surface of the cylinder) whose inner surface (surface facing upward) facing the second surface 102b is a rectangle curved outward (downward) from the second protective layer 84b. Curved surface). Therefore, the exposed space 95K3 has a shape in which the space tends to become narrower as the distance from the second surface 102b increases. Further, the exposed space 95K3 has a curved surface (an inner peripheral surface of the cylinder) whose inner surface (the surface facing right) facing the third surface 102c is a rectangle curved outward (left) of the third protective layer 84c. A curved surface corresponding to a part). Therefore, the exposed space 95K3 has a shape in which the space tends to become narrower as the distance from the third surface 102c increases (toward the left). The exposure space 95K3 has a longitudinal direction along the longitudinal direction of the first surface 102a, the second surface 102b, and the third surface 102c.

  The exposure space 95K4 is a space arranged over the upper side, the lower side, and the right side of the element body 102, and the first surface 102a, the second surface 102b, and the fourth surface 102d are exposed. The exposure space 95K4 has a symmetrical shape and arrangement with the exposure space 95K3.

  The exposure spaces 95K1, 95K3, and 95K4 are arranged along the short side direction of the first surface 102a. The exposure spaces 95K2, 95K3, and 95K4 are arranged along the short side direction of the second surface 102b.

  Similarly to the sensor element 101, the sensor element 101K described above has the exposed spaces 95K1 to 95K4 so that the water resistance of the element body 102 is further improved. In addition, the exposed spaces 95K2, 95K3, and 95K4 have a shape in which the space tends to become narrower as the distance from the second surface 102b increases. Further, the exposed spaces 95K2, 95K3, and 95K4 are curved surfaces whose inner surfaces facing the second surface 102b are curved outward. The space having such a shape can suppress a decrease in strength of the second protective layer 84b as compared with a rectangular parallelepiped space having an inner surface parallel to the second surface 102b, for example, the lower space 92 in FIG. . The exposed spaces 95K1, 95K3, and 95K4 for the first surface 102a, the exposed space 95K3 for the third surface 102c, and the exposed space 95K4 for the fourth surface 102d are the same as the exposed spaces 95K2, 95K3, and 95K4 for the second surface 102b. Thus, the same effect, that is, the effect of suppressing the strength reduction of the first, third, and fourth protective layers 84a, 84c, and 84d can be obtained.

  In addition, the protective layer 84 has exposed spaces 95K1, 95K3, and 95K4, which are a plurality of exposed spaces whose longitudinal direction is along the longitudinal direction of the first surface 102a, arranged side by side along the lateral direction of the first surface 102a. Yes. Therefore, similarly to the sensor elements 101F and 101G, the shortness of the first surface 102a with respect to the element body 102 from the first protection layer 84a due to the difference in thermal expansion coefficient between the first protection layer 84a and the element body 102 when wet. Stress along the hand direction is reduced. Thereby, the element main body 102 becomes difficult to break when wet, and the water resistance of the element main body 102 is further improved. Furthermore, the protective layer 84 has exposed spaces 95K2, 95K3, and 95K4, which are a plurality of exposed spaces whose longitudinal direction is along the longitudinal direction of the second surface 102b, arranged side by side along the lateral direction of the second surface 102b. Yes. Therefore, similarly to the sensor elements 101F and 101G, the stress along the short direction of the second surface 102b from the second protective layer 84b to the element body 102 is reduced. Thereby, the element main body 102 becomes difficult to break when wet, and the water resistance of the element main body 102 is further improved.

  In addition, about each space in the protective layer 84 of 2nd-12th embodiment mentioned above, it can form by using the loss | disappearance material which lose | disappears by combustion similarly to 1st Embodiment.

  It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

  For example, in the first embodiment described above, the lower space 92 overlaps with the center of the region covered with the protective layer 84 of the second surface 102b when viewed from the direction perpendicular to the second surface 102b. It was located, but is not limited to this. For example, the lower space 92 overlaps with the center in the front-rear direction of the region covered by the protective layer 84 of the second surface 102b when viewed from the direction perpendicular to the second surface 102b, and is the center in the left-right direction. It may not overlap, it may overlap with the center in the left-right direction, it may not overlap with the center in the front-rear direction, or it may not overlap with the center in the front-rear direction as well as the center in the left-right direction. Good.

  In the first embodiment described above, the highest temperature region in the second surface 102b in a state where the element main body 102 is heated to the normal driving temperature (for example, 800 ° C.) by the heater 72 is defined as the highest temperature region. The side space 92 may be positioned so as to overlap with the maximum temperature region when viewed from a direction perpendicular to the second surface 102b. By so doing, the region of the second surface 102b that is at the highest temperature when the sensor element 101 is used can be insulated by the lower space 92, so that the moisture resistance of the element body is further improved.

  In the second embodiment described above, each of the spaces 91A to 94A has one communication hole H1 to H4, but the present invention is not limited to this. One space may have a plurality of communication holes. In addition, when the protective layer 84 has a plurality of spaces, there may be a space that opens to the outside and a space that does not open.

  In the third embodiment described above, the exposed space 95B2 and the non-exposed space 96B2 are positioned at a height that is separated vertically so that the positions do not overlap each other when viewed from a direction perpendicular to the vertical direction. However, the position is not limited to this, and the positions may partially overlap when viewed from the direction perpendicular to the vertical direction. Further, although the exposure space 95B2 and the non-exposure space 96B2 are shifted in the front-rear direction, the positions in the front-rear direction may be the same. For example, the front / rear / left / right positions may be the same, except that the exposed space 95B2 and the non-exposed space 96B2 are vertically displaced. In addition, the space 90B has a space (for example, an exposure space 95B2 and a non-exposure space 96B2) arranged in two stages of the inner side and the outer side, but is not limited thereto, and has a space arranged in three or more stages. It may be. Moreover, the vertical height may be different between the plurality of non-exposed spaces 96B2. In the third embodiment, the protective layer 84 may not include the non-exposed spaces 96B1 to 96B4. In the third embodiment, when viewed from the direction perpendicular to the second surface 102b, the exposed space 95B2 tends to have a higher density as it is closer to the center of the region of the second surface 102b covered with the protective layer 84. Alternatively, a non-exposed space 96B2 may be disposed. By doing so, it is possible to improve the heat insulation of the portion that is likely to become relatively high temperature, and the water resistance of the element body 102 is improved. Note that “the tendency for the density of the space to increase” includes a tendency for the number of spaces per unit area to increase and a tendency for the space to increase. The above modification can be similarly applied to the fourth embodiment.

  In the fifth and sixth embodiments described above, the density of the columnar portions P2 is changed by changing the number of the plurality of columnar portions P2 per unit area. However, the present invention is not limited to this, and the thickness of the columnar portions P2 is changed. By doing so, the density of the columnar part P2 may be changed. Further, the density of the columnar part P2 may not be changed depending on the location.

  In the fifth embodiment described above, the plurality of columnar portions P2 are far from the center in the front-rear direction of the region covered with the protective layer 84 on the second surface 102b when viewed from the direction perpendicular to the second surface 102b. The density of the columnar part P2 is arranged so as to increase, but not limited to this, the columnar part P2 may be arranged so that the density of the columnar part P2 increases as the distance from the center in the left-right direction increases. It may be arranged so that the density of the columnar part P2 increases as the distance from the object increases. Similarly, regarding the arrangement of the columnar portions P2 in the sixth embodiment, the density may be changed not only in the front-rear direction but also in the left-right direction.

  In the seventh embodiment described above, the first exposed space 97F2 has one side along the short direction of the second surface 102b shorter than the other two sides, but is not limited to this, the first exposed space 97F2 The longitudinal direction should just be along the longitudinal direction of the 2nd surface 102b. Similarly, in the seventh embodiment, the second exposed space 98F2 has one side shorter than the other two sides along the longitudinal direction of the second surface 102b, but is not limited thereto. The longitudinal direction of the second exposure space 98F3 only needs to be along the short side direction of the second surface 102b.

  In the eleventh embodiment described above, the exposed space 95J4 is disposed across the lower side and the left side of the element body 102, but is not limited thereto. For example, the protective layer 84 has a semi-elliptical columnar space disposed on the lower side of the element body 102 and a semi-elliptical columnar space disposed on the left side of the element body 102 instead of the exposed space 95J4. It may be. The same applies to the exposure spaces 95J3, 95J5, 95J6 and the exposure spaces 95K3, 95K4 of the twelfth embodiment.

  In the tenth to twelfth embodiments described above, the spaces provided in the protective layer 84 have the longitudinal direction along the front-rear direction, but are not limited thereto. If the exposed space in which the second surface 102b is exposed has a shape in which the space tends to become narrower as the distance from the second surface 102b increases, an effect of suppressing the strength reduction of the second protective layer 84b can be obtained. For example, the lower space 92I in FIG. 23 may have a triangular pyramid shape. The exposed space 95J2 in FIG. 25 may have a hemispherical shape.

  In the first to twelfth embodiments described above, the space located on the upper side of the element body 102 and the space located on the lower side are vertically symmetrical, and the space located on the left side and the space located on the right side of the element body 102 Is symmetrical, but is not limited to this. In the first to twelfth embodiments described above, each of the first to fourth protective layers 84a to 84d has a space. However, the present invention is not limited to this. The protective layer 84 only needs to have one or more exposed spaces where the second surface 102b is exposed. For example, in the first embodiment, the protective layer 84 only needs to have the lower space 92, and may not have one or more of the upper space 91, the left space 93, and the right space 94. Further, the fifth protective layer 84e may have a space in the same manner as the first to fourth protective layers 84a to 84d.

  In 1st-12th embodiment mentioned above, although the protective layer 84 had the 1st-5th protective layers 84a-84e, it is not restricted to this. The protective layer 84 only needs to include at least the second protective layer 84b. The second protective layer 84b only needs to cover at least part of the second surface 102b.

In the embodiment described above, the size of each space included in the protective layer 84 has not been particularly described, but each space may be a size that can be distinguished from the pores of the protective layer 84. For example, the volume of each space may be 12500 μm ³ or more. Further, when the volume ratio of the space is represented by volume ratio = (total volume of the space provided in the protective layer 84) / (volume of the protective layer 84) × 100, the volume ratio may be 60% or less. The “volume of the protective layer 84” is a value including the volume of the space provided in the protective layer 84.

Although not described in the above-described first to twelfth embodiments, the total volume of one or more spaces existing below the second surface 102b is preferably 0.03 mm ³ or more. In this case, the effect of improving the water resistance of the element body can be more reliably obtained by the one or more spaces. For example, in the first to tenth embodiments described above, the total volume of each of the lower spaces 92, 92A to 92I is preferably 0.03 mm ³ or more. In the eleventh embodiment, the total volume of the exposed space 95J2, the portion of the exposed space 95J4 that is located below the second surface 102b, and the portion of the exposed space 95J6 that is located below the second surface 102b. Is preferably 0.03 mm ³ or more. In the twelfth embodiment, the total volume of the exposed space 95K2, a portion of the exposed space 95K3 that is located below the second surface 102b, and a portion of the exposed space 95K4 that is located below the second surface 102b. Is preferably 0.03 mm ³ or more. Similarly, the total volume of the one or more spaces existing above the first surface 102a is preferably 0.03 mm ³ or more. The total volume of the one or more spaces existing to the left of the third surface 102c is preferably 0.015 mm ³ or more. The total volume of the one or more spaces existing to the right of the fourth surface 102d is preferably 0.015 mm ³ or more. Note that “below the second surface 102b” is not limited to being directly below the second surface 102b, and includes, for example, the lower left and the lower right. Similarly, “above the first surface 102a” is not limited to just above the first surface 102a. The same applies to “leftward from the third surface 102c” and “rightward from the fourth surface 102d”.

Although not described in the above-described first to twelfth embodiments, when there is one or more spaces that span two adjacent surfaces (surfaces sharing one side), the total volume of the one or more spaces is: It is preferable that it is 0.002 mm ³ or more. In this case, the effect of improving the water resistance of the element body can be more reliably obtained by the one or more spaces. For example, in the eleventh embodiment, the volume of the exposed space 95J3 that spans the first surface 102a and the third surface 102c is preferably 0.002 mm ³ or more. Similarly, an exposed space 95J4 that spans the second surface 102b and the third surface 102c, an exposed space 95J5 that spans the first surface 102a and the fourth surface 102d, and an exposed space 95J6 that spans the second surface 102b and the fourth surface 102d. Also, it is preferable that each volume is 0.002 mm ³ or more. Note that “a space extending over two adjacent surfaces” means a space that exists in any direction perpendicular to each of the two surfaces. For example, the exposed space 95J4 exists in both the direction perpendicular to the second surface 102b (downward) and the direction perpendicular to the third surface 102c (left), and the second surface 102b and the third surface 102c. It is a space that straddles.

  The protective layer 84 may include a combination of two or more of the spaces 90, 90A to 90K of the first to twelfth embodiments described above and the spaces of the modifications thereof as appropriate. The combination in this case includes a case where the protective layer 84 includes different types of spaces, and a case where the protective layer 84 includes spaces having the above-described characteristics regarding the shape and arrangement of different types of spaces.

For example, one or more of the spaces other than the second embodiment may have an opening communicating with the outside of the protective layer 84. When the opening is provided in the space, a communication hole that communicates the space and the outside may be provided like the communication holes H1 to H4 of the second embodiment, or the space is extended to the surface of the protective layer 84 and the space is left as it is. You may make it open outside. In addition, it is preferable that the opening of the space is appropriately sized so that water can be prevented from directly entering the inside and heat in the space can be released from the opening. For example, it may be an open area as 100μm ² ~1000μm ^2.

  For example, in each of the spaces other than the first embodiment, at least one of the exposed spaces is covered with the protective layer 84 of the second surface 102b when viewed from the direction perpendicular to the second surface 102b. You may be located so that it may overlap with the center of a field.

  DESCRIPTION OF SYMBOLS 1 1st board | substrate layer, 2nd board | substrate layer, 3rd board | substrate layer, 4th 1st solid electrolyte layer, 5 spacer layer, 6 2nd solid electrolyte layer, 10 gas inlet, 11 1st diffusion control part, 12 buffer Space, 13 Second diffusion limiting part, 20 First internal space, 21 Main pump cell, 22 Inner pump electrode, 22a Ceiling electrode part, 22b Bottom electrode part, 23 Outer pump electrode, 25 Variable power supply, 30 Third diffusion limiting part , 40 2nd internal space, 41 Measurement pump cell, 42 Reference electrode, 43 Reference gas introduction space, 44 Measurement electrode, 45 4th diffusion control part, 46 Variable power supply, 48 Air introduction layer, 50 Auxiliary pump cell, 51 Auxiliary pump Electrode, 51a Ceiling electrode part, 51b Bottom electrode part, 52 Variable power supply, 70 Heater part, 71 Heater connector electrode, 72 Heater, 73 Through hole, 74 Heat Insulating layer, 75 pressure release hole, 80 oxygen partial pressure detection sensor cell for main pump control, 81 oxygen partial pressure detection sensor cell for auxiliary pump control, 82 oxygen partial pressure detection sensor cell for measurement pump control, 83 sensor cell, 84 protective layer, 84a -84e 1st-5th protective layer, 90,90A-90K space, 91,91A-91I upper space, 92,92A-92I lower space, 93,93A-93I left space, 94,94A-94I right space, 95B1-95B4, 95C1-95C4, 95J1-95J6, 95K1-95K4 exposed space, 96B1-96B4, 96C1-96C4 non-exposed space, 97F1-97F4 first exposed space, 98F1-98F4 second exposed space, 100 gas sensor, 101, 101A to 101K sensor element, 102 element body, 10 The first surface to the sixth surface a~102f, H1~H4 hole, P1 to P4 columnar portion, Sa1~Sa4, Sb1~Sb4 surface.

Claims (14)

A long rectangular parallelepiped element body provided with an oxygen ion conductive solid electrolyte layer;
An outer electrode disposed on a first surface which is one of the surfaces of the element body;
A protective layer covering at least a part of the second surface opposite to the first surface of the element body, and having one or more exposed spaces in which the second surface is exposed;
A sensor element comprising: At least one of the exposed spaces is positioned so as to overlap a center of a region of the second surface covered by the protective layer when viewed from a direction perpendicular to the second surface.
The sensor element according to claim 1. At least one of the exposed spaces has an opening communicating with the outside of the protective layer.
The sensor element according to claim 1 or 2. The protective layer includes a plurality of the exposed spaces, and a plurality of non-exposed spaces where the second surface is not exposed by being displaced in a direction perpendicular to the second surface with respect to at least one of the plurality of exposed spaces. ,have,
The sensor element according to claim 1. The protective layer has at least one columnar portion that supports the exposed space in a direction perpendicular to the second surface with respect to at least one of the exposed spaces.
The sensor element of any one of Claims 1-4. The protective layer has a plurality of the columnar parts,
When viewed from a direction perpendicular to the second surface, the plurality of the columnar portions tend to have a higher density of the columnar portions as they are farther from the center of the region of the second surface covered by the protective layer. Arranged,
The sensor element according to claim 5. The protective layer has a plurality of the columnar parts,
When viewed from a direction perpendicular to the second surface, the plurality of the columnar portions tend to have a higher density of the columnar portions as they are closer to the center of the region of the second surface covered by the protective layer. Arranged,
The sensor element according to claim 5. The protective layer has a plurality of the exposed spaces whose longitudinal direction is along the longitudinal direction of the second surface along the lateral direction of the second surface.
The sensor element of any one of Claims 1-7. The protective layer has a plurality of the exposed spaces whose longitudinal direction is along the short direction of the second surface along the longitudinal direction of the second surface.
The sensor element according to claim 1. The protective layer has a plurality of first exposed spaces, the longitudinal direction of which is the exposed space along the longitudinal direction of the second surface, along the lateral direction of the second surface, and the longitudinal direction. Has a plurality of second exposed spaces along the longitudinal direction of the second surface, which are the exposed spaces that intersect the first exposed space along the short direction of the second surface.
The sensor element of any one of Claims 1-9. At least one of the exposed spaces has a shape in which the exposed space tends to become narrower as the distance from the second surface increases.
The sensor element of any one of Claims 1-10. At least one of the exposed spaces has at least two inner surfaces that are inclined so as to approach each other as the distance from the second surface increases.
The sensor element according to claim 1. At least one of the exposed spaces is a curved surface with an inner surface facing the second surface curved outward.
The sensor element according to claim 1.   The gas sensor provided with the sensor element of any one of Claims 1-13.

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