JP2014029349A - Gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas sensor capable of stably maintaining measurement accuracy even with adhesion of water to a tip of a sensor element.SOLUTION: A gas sensor has a sensor element including oxygen ion conductive solid electrolyte as a main component, and is configured to detect a specified gas component in a measurement target gas. The sensor element has: an aperture which opens to an external space; an external communication part that introduces the measurement target gas under a predetermined diffusion resistance from the external space; a buffer space that communicates the external communication part; a first internal space that communicates the buffer space under a predetermined diffusion resistance; a second internal space that communicates the first internal space under a predetermined diffusion resistance; and a pumping cell capable of pumping out oxygen in each internal space through adding a predetermined voltage between an internal electrode formed on a surface of each internal space and an external electrode formed in a space different from each internal space. A width of the external communication part is 5%-60% of a width of the first internal space, and a thickness thereof is 50%-100% of the first internal space.

Description

  The present invention relates to a gas sensor that includes a sensor element and measures a predetermined gas component in a gas component to be measured.

Conventionally, various measuring devices have been used to know the concentration of a desired gas component in a gas to be measured. For example, as an apparatus for measuring the NOx concentration in a gas to be measured such as combustion gas, an electric device configured by forming a Pt electrode and an Rh electrode on a solid electrolyte layer having oxygen ion conductivity such as zirconia (ZrO ₂ ) Gas sensors having chemical pump cells are known. Such a gas sensor takes in the gas to be measured from the external space into the sensor element, and diffuses in communication with the external space so as to provide the gas to be measured with a diffusion resistance suitable for measuring the desired gas component concentration. A rate-limiting part is formed.

  For example, a gas sensor that has an opening communicating with an external space at the tip of a sensor element and includes a diffusion rate-limiting portion formed as a horizontally long slit is known (for example, see Patent Document 1). Further, Patent Document 1 discloses a gas sensor that further includes a gas introduction space in front of the slit-shaped diffusion rate controlling portion described above. Further, when the measurement gas is taken into the sensor element from the external space by filling the introduction portion of the measurement gas from the external space of the sensor element with the porous body, the desired gas is supplied to the measurement gas. A gas sensor sensor provided with a diffusion rate-determining unit that imparts a diffusion resistance suitable for measurement of the component concentration is known (for example, see Patent Document 2).

Japanese Patent No. 3701124 Japanese Patent No. 3176890

  A gas sensor as disclosed in Patent Document 1 and Patent Document 2 is provided, for example, in an exhaust pipe of an internal combustion engine such as an automobile engine, and is used for measuring the concentration of a desired gas component contained in exhaust gas. In such an internal combustion engine, when the driving is stopped, the water vapor contained in the exhaust gas may be condensed into water droplets. Such water droplets accumulate in the exhaust pipe and adhere to the gas sensor.

  In general, the gas sensor is mounted in the exhaust pipe so as to be substantially perpendicular to the flow of the exhaust gas in a state where a protective cover having a gas introduction hole through which gas can freely enter and exit is provided on the outside of the sensor element. When water droplets adhere to the inside of the protective cover, some of the water droplets are discharged from the gas introduction hole, but the water droplets stay on the bottom of the protective cover. Since the bottom of the protective cover is close to the tip of the sensor element, when the internal combustion engine is re-driven, a considerable amount of water droplets staying at the bottom of the protective cover adhere to the tip of the sensor element. It becomes. In addition to this, water droplets staying in the exhaust pipe may be scattered in the protective cover and adhere to the tip of the sensor element.

  Then, since only the tip portion is partially cooled by the attachment of water droplets, in the sensor element, a temperature gradient is generated between the tip portion and the inside. Furthermore, cracks may occur due to thermal stress generated due to the temperature gradient.

  In addition, water adhering to the tip of the sensor element may reach the inside space through a slit-shaped diffusion rate-limiting part formed at the tip of the sensor element due to capillary action. When the internal combustion engine is driven in this state, water rapidly evaporates in the internal space, and the sensor element is cracked.

  Thus, if a crack occurs in the sensor element, the diffusion resistance imparted to the gas to be measured changes greatly, which is not preferable because the measurement accuracy decreases.

  The present invention has been made in view of the above problems, and an object thereof is to provide a gas sensor in which measurement accuracy is stably maintained.

  The invention of claim 1 is a gas sensor having a sensor element composed mainly of a solid electrolyte having oxygen ion conductivity, and detecting a predetermined gas component in a gas to be measured, wherein the sensor element is an external space. An external communication part that introduces the gas to be measured under a predetermined diffusion resistance from the external space, a buffer space that communicates with the external communication part, and the buffer space and a predetermined diffusion resistance A first internal space communicating with the first internal space, a second internal space communicating with the first internal space under a predetermined diffusion resistance, and the first internal space. By applying a predetermined voltage between the first internal electrode formed on the surface and the external electrode formed in a space different from the first internal space, oxygen in the first internal space A main pumping cell provided so as to be pumped and a table of the second internal space By applying a predetermined voltage between the second internal electrode formed in the second electrode and the external electrode formed in a space different from the second internal space, oxygen in the second internal space is formed. An auxiliary pumping cell provided so as to be able to pump out, and the external communication part has one opening on each of two side parts along the longitudinal direction of the sensor element, and the longitudinal communication part. A space having a uniform width along a direction perpendicular to the direction, wherein the width of the external communication portion is 5% or more and 60% or less with respect to the width of the first internal space, and the external communication portion Is 50% or more and 100% or less with respect to the thickness of the first internal space.

  The invention according to claim 2 is a gas sensor having a sensor element composed mainly of a solid electrolyte having oxygen ion conductivity, and detecting a predetermined gas component in the gas to be measured, wherein the sensor element is external space. An external communication part that introduces the gas to be measured under a predetermined diffusion resistance from the external space, a buffer space that communicates with the external communication part, and the buffer space and a predetermined diffusion resistance A first internal space communicating with the first internal space, a second internal space communicating with the first internal space under a predetermined diffusion resistance, and the first internal space. By applying a predetermined voltage between the first internal electrode formed on the surface and the external electrode formed in a space different from the first internal space, oxygen in the first internal space A main pumping cell provided so as to be pumped and a table of the second internal space By applying a predetermined voltage between the second internal electrode formed in the second electrode and the external electrode formed in a space different from the second internal space, oxygen in the second internal space is formed. An auxiliary pumping cell provided so as to be able to pump out, and the external communication portion has only one opening at the tip of the sensor element and extends from the opening along the longitudinal direction of the sensor element. A space having a uniform width, the width of the external communication portion being 5% or more and 60% or less with respect to the width of the first internal space, and the thickness of the external communication portion being the first width. It is characterized by being 50% or more and 100% or less with respect to the thickness of the internal space.

  A third aspect of the present invention is the gas sensor according to the first or second aspect, wherein the sensor element includes a measurement electrode formed on a surface of the second internal space, and the second internal space. A reference electrode formed at a location different from the measurement area, a measurement cell including the measurement electrode and the reference electrode, and a measurement cell. A porous diffusion layer that imparts a diffusion resistance of: the measurement electrode reduces the oxide gas component in the predetermined gas component to which the predetermined diffusion resistance is imparted by the porous diffusion layer, The measurement cell is configured to apply a voltage according to a reduction degree of the oxide gas component in the measurement electrode between the measurement electrode and the reference electrode, thereby causing a current flowing between the measurement electrode and the reference electrode, Provided for measurement It becomes, characterized in that.

  According to the first to third aspects of the present invention, it is possible to realize a gas sensor in which measurement accuracy is stably maintained even when water adheres to the tip of the sensor element.

  According to the inventions of claims 1 to 3, even if the gas to be measured is suddenly taken into the sensor element due to the pressure fluctuation of the gas to be measured in the external space, the concentration fluctuation of the gas to be measured Therefore, it is possible to realize a gas sensor in which is suppressed appropriately.

  In addition, according to the inventions of claims 1 to 3, it is possible to realize a gas sensor in which infiltration of water adhering to the tip of the sensor element into the sensor element due to capillary action is suppressed.

It is the perspective view which showed roughly an example of the structure of the sensor element of the gas sensor which concerns on 1st Embodiment. It is the cross-sectional schematic diagram which showed schematically the cross section of the sensor element of the gas sensor which concerns on 1st Embodiment. It is the cross-sectional schematic diagram which illustrated the structure of the gas sensor which concerns on 1st Embodiment. It is the cross-sectional schematic diagram which showed schematically the cross section of the sensor element of the gas sensor which concerns on 2nd Embodiment. It is the perspective view which showed roughly an example of the structure of the sensor element of the gas sensor which concerns on 3rd Embodiment. It is the cross-sectional schematic diagram which showed schematically the cross section of the sensor element of the gas sensor which concerns on 3rd Embodiment. It is the perspective view which showed roughly an example of the structure of the sensor element of the gas sensor which concerns on 4th Embodiment. It is the cross-sectional schematic diagram which showed schematically the cross section of the sensor element of the gas sensor which concerns on 4th Embodiment. It is the cross-sectional schematic diagram which showed the modification of the gas sensor which concerns on this invention. It is the figure which showed the relationship between the structure of an external communication part, and fracture strength. It is the figure which showed the relationship between the width | variety and external strength of the external communication part of the gas sensor which concerns on the Example equivalent to 1st Embodiment. It is the figure which showed the relationship between the thickness of the external communication part of the gas sensor which concerns on the Example equivalent to 2nd Embodiment, and fracture strength. It is the figure which showed the relationship between the thickness of the external communication part of the gas sensor which concerns on the Example equivalent to 3rd Embodiment, and fracture strength. It is the figure which showed the relationship between the width | variety and external strength of the external communication part of the gas sensor which concerns on the Example equivalent to 4th Embodiment. It is a figure which shows the result of having measured the response time of the gas sensor which concerns on an Example and a comparative example.

<First Embodiment>
<Schematic configuration of gas sensor>
First, a schematic configuration of the gas sensor 100 will be described.

  FIG. 1 is an external perspective view schematically showing an example of the configuration of the sensor element 101 of the gas sensor 100. FIG. 1 shows right-handed xyz coordinates with the longitudinal direction of the sensor element 101 as the x-axis (the same applies hereinafter). FIG. 2 is a schematic cross-sectional view schematically showing a cross section of the sensor element 101 at each position shown in FIG. 1 in order to explain the structure of the gas flow part 111. In FIG. 2, the configuration other than the gas circulation unit 111 is omitted for simplification. FIG. 2A is a cross-sectional view taken along the line AA ′ in FIG. FIG. 2B is a cross-sectional view taken along line BB ′ of FIG. FIG. 2C is a cross-sectional view taken along the line CC 'in FIG. FIG. 3 is a schematic cross-sectional view illustrating a more detailed configuration of the gas sensor 100.

The sensor element 101 includes a first substrate layer 1, a second substrate layer 2, a third substrate layer 3, and a first solid electrolyte layer 4 each made of an oxygen ion conductive solid electrolyte layer such as zirconia (ZrO ₂ ). The spacer layer 5 and the second solid electrolyte layer 6 are elongated and long plate-like elements having a structure in which they 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, for example, laminated on ceramic green sheets corresponding to each layer after performing predetermined processing and circuit pattern printing, and cutting the obtained laminate into element units. Manufactured by firing and integrating.

  One end 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 external communication portion 11, the first internal space 20, and the first The 1 diffusion control part 30 and the 2nd internal space 40 are adjacently formed in the aspect connected in this order.

  The external communication portion 11 is a space inside the sensor element 101 provided in a form in which the spacer layer 5 is cut out. The external communication portion 11 has an upper portion on the lower surface of the second solid electrolyte layer 6 or the inner surface 5 a of the spacer layer 5, a lower portion on the upper surface of the first solid electrolyte layer 4 or the inner surface 5 b of the spacer layer 5, and a side portion on the spacer layer 5. It is provided by being partitioned by the side surfaces 5c and 5d. However, in more detail, as will be described later, the position where the external communication portion 11 is formed is adjusted according to the degree of diffusion resistance suitable for the measurement of nitrogen oxide (NOx) concentration.

  The first internal space 20 and the second internal space 40 are also spaces inside the sensor element 101 provided in a form in which the spacer layer 5 is cut out. The first internal space 20 and the second internal space 40 are partitioned by the lower surface of the second solid electrolyte layer 6 at the upper portion, the upper surface of the first solid electrolyte layer 4 at the lower portion, and the side surface of the spacer layer 5 at the side portion. Is provided.

  The first diffusion control unit 30 is provided as two horizontally long slits (the opening has a longitudinal direction in the y-axis direction). A portion from the external communication portion 11 to the second internal space 40 is also referred to as a gas circulation portion 111.

  Further, on the other end side of the sensor element 101 and at a position farther from the element tip 101a than the gas flow part 111, it is between the upper surface of the third substrate layer 3 and the lower surface of the spacer layer 5. A reference gas introduction space 43 is provided at a position where the side portion is partitioned by the side surface of the first solid electrolyte layer 4. For example, the atmosphere is introduced into the reference gas introduction space 43 as a reference gas when measuring the NOx concentration.

  The atmosphere introduction layer 48 is a layer made of porous alumina, and the reference gas is introduced into the atmosphere 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 described later, it is possible to measure the oxygen concentration (oxygen partial pressure) in the internal space using the reference electrode 42.

<Details of Gas Distribution Department and related parts>
The external communication portion 11 imparts a predetermined diffusion resistance suitable for measurement of nitrogen oxide (NOx) concentration to the gas to be measured introduced from the external space through the opening portion 11a formed in the sensor element tip portion 101a. In addition, it is a part that guides the gas to be measured to the first internal space 20 that communicates with the communication part 11b.

  The width a in the y-axis direction and the thickness b in the z-axis direction of the external communication portion 11 depend on the degree of diffusion resistance to be applied to the gas to be measured introduced into the first internal space 20 from the opening 11a. It is prescribed.

  However, the external communication portion 11 has a thickness b of 50% to 100% with respect to a thickness (vacancy thickness) d in the z-axis direction of the first internal space 20, and a width a is the first internal space. It is preferable that it is 5% to 60% (desirably 10% to 40%) with respect to the width (vacant width) c of 20 in the y-axis direction.

  When the thickness b is less than 50% with respect to the thickness d, the opening area of the opening 11a becomes small, and water adhering to the sensor element tip 101a is likely to enter the first internal space 20 due to capillary action. It is not preferable. Further, when the width a is less than 5% with respect to the width c, the opening area of the opening 11a becomes small, and the water adhering to the sensor element tip 101a easily enters the first internal space 20 due to capillary action. Therefore, it is not preferable. On the other hand, when the width a exceeds 60% with respect to the width c, it becomes difficult to impart diffusion resistance suitable for measurement of nitrogen oxide (NOx) concentration to the gas to be measured.

  Thus, in the gas sensor 100, the width a and the thickness b of the external communication portion 11 are defined within the above-described range, so that the water adhering to the sensor element tip portion 101a enters the first internal space 20. Infiltration is suppressed.

  The first internal space 20 is provided as a space for adjusting the oxygen partial pressure in the measurement gas introduced through the external communication portion 11. 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 porous cermet electrodes (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 or no reducing ability for the NOx component in the measured gas.

  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.

  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 6, the spacer layer 5, the first solid electrolyte 4, The third substrate layer 3 and the reference electrode 42 constitute an electrochemical sensor cell, that is, an oxygen partial pressure detection sensor cell 80 for main pump control.

  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 control of Vp0 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 first diffusion control unit 30 provides a predetermined diffusion resistance to the gas to be measured 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 to be measured is supplied to the gas to be measured. 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 first 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 the first internal space 20 in advance, the auxiliary pump cell 50 is further supplied to the gas to be measured introduced through the first 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 the sensor element 101 and an appropriate electrode on the outside.

  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 reduction ability or no reduction 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 to the main pump control oxygen partial pressure detection sensor cell 80 as a control signal, and the electromotive force V0 is controlled, so that the first 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.

  That is, in the gas sensor 100, 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).

  Thus, the NOx concentration of the gas to be measured whose oxygen concentration is adjusted in the second internal space 40 is measured by the measurement pump cell 41 operating. The measurement pump cell 41 includes a measurement electrode 44 provided on the upper surface of the first solid electrolyte layer 4 facing the second internal space 40, the outer pump electrode 23, the second solid electrolyte layer 6, and the spacer layer 5. An electrochemical pump cell constituted by 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 second diffusion rate controlling part 45.

The second diffusion rate controlling part 45 is a film composed of a porous body mainly composed of alumina (Al ₂ O ₃ ). The second 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 layer 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 partial pressure of oxygen around the measurement electrode 44, the second solid electrolyte layer 6, the spacer layer 5, the first solid electrolyte layer 4, the third substrate layer 3, the measurement electrode 44, The reference electrode 42 constitutes an electrochemical sensor cell, that is, a measurement pump control oxygen partial pressure detection sensor cell 82. 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.

As described above, the gas to be measured guided into the second internal space 40 reaches the measurement electrode 44 through the second 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 control voltage V2 detected by the measurement pump control oxygen partial pressure detection sensor cell 82 becomes constant. The 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.

  That is, in the gas sensor 100, the gas to be measured is based on the pump current Ip2 that flows when the oxygen generated by the reduction of NOx is pumped out of the measurement pump cell 41 in proportion to the concentration of NOx in the gas to be measured. The NOx concentration inside can be known.

  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.

<Heater part>
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 electrode 71, a heater 72, a through hole 73, a heater insulating layer 74, and a pressure dissipation hole 75.

  The heater 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 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 electrode 71 through the through-hole 73, generates heat when power is supplied from outside through the heater electrode 71, and heats and keeps 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.

  As described above, in the gas sensor 100 according to the present embodiment, the water adhering to the sensor element tip 101a is suitably determined by determining the size of the external communication part 11 having the opening 11a at the tip 101a of the sensor element 101. Is prevented from entering into the internal space by capillary action. As a result, it is suppressed that the sensor element 101 is cracked due to the rapid evaporation of water in the internal space.

  Therefore, in the gas sensor 100 according to the present embodiment, a decrease in measurement accuracy due to a crack generated in the sensor element 101 is suitably suppressed. In other words, even if water adheres to the sensor element tip 101a during the gas sensor operation, the measurement accuracy is stably maintained.

  The sensor element 101 is formed in the spacer layer 5 in the green sheet process described above if the thickness b of the external communication portion 11 is the same as the thickness d of the first internal space 20. When the opening corresponding to the first internal space 20 or the second internal space 40 is formed in the corresponding ceramic green sheet by punching, the opening corresponding to the external communication portion 11 is also formed, and thereafter the above-mentioned It is realizable by going through the same process as.

  If the thickness b of the external communication portion 11 is smaller than the thickness d of the first internal space 20, the first solid electrolyte layer 4 and the spacer layer are separated from the green sheets corresponding to the six layers described above. After the green sheet laminated between the spacer layer 5 and the second solid electrolyte layer 6 is prepared and the corresponding notch is formed in the ceramic green sheet by punching in the green sheet process described above Then, the lamination including the green sheet is performed, and thereafter, the same process as described above may be performed.

  Alternatively, in the above-described green sheet process, when a predetermined circuit pattern is printed on the ceramic green sheet corresponding to each layer, the external communication portion 11 is connected to the first solid electrolyte layer 4 or the spacer layer 5. A corresponding sublimation paste may be printed. In such a case, the external communication part 11 is formed by sublimating the paste during firing.

  As described above, according to the present embodiment, by providing the external communication portion with a predetermined size at the sensor element tip 101a, even if water adheres to the sensor element tip 101a during operation, the measurement accuracy Can be realized in a stable manner.

<Second Embodiment>
In 2nd Embodiment, the aspect from which the structure of a gas distribution part differs from the gas sensor 100 which concerns on 1st Embodiment is demonstrated.

  In addition, since the external perspective view which shows an example of a structure of the sensor element 201 of the gas sensor 200 which concerns on 2nd Embodiment is the same as that of the gas sensor 100 which concerns on 1st Embodiment, FIG. 1 is quoted. .

  FIG. 4 is a schematic cross-sectional view schematically showing a cross section of the sensor element 201 at each position shown in FIG. 1 in order to explain the structure of the gas flow part 112. In FIG. 4, the configuration other than the gas circulation unit 112 is omitted for simplification. FIG. 4A is a cross-sectional view taken along line AA ′ of FIG. FIG. 4B is a cross-sectional view taken along line BB ′ of FIG. FIG. 4C is a cross-sectional view taken along the line CC ′ in FIG. In addition, about the structure similar to the gas sensor 100 which concerns on 1st Embodiment, the same code | symbol is attached | subjected and the description and illustration are abbreviate | omitted.

  The sensor element 201 has a configuration in which a buffer space 91 and a third diffusion control part 92 are provided between the external communication part 11 and the first internal space 20 of the sensor element 101 according to the first embodiment. . In the present embodiment, a part from the external communication part 11 to the second internal space 40 is also referred to as a gas circulation part 112.

  The buffer space 91 is a space inside the sensor element 101 that is provided in a manner in which the spacer layer 5 is cut out, similarly to the external communication portion 11. In other words, the buffer space 91 is also provided by partitioning the upper portion with the lower surface of the second solid electrolyte layer 6, the lower portion with the upper surface of the first solid electrolyte layer 4, and the side portions with the side surfaces of the spacer layer 5. However, the buffer space 91 is provided such that the width w in the y-axis direction is larger than the width a of the external communication portion 11.

  By providing such a buffer space 91, in the sensor element 201, when the gas to be measured is introduced from the outside of the sensor element 201 to the inside of the first internal space 20, the pressure fluctuation of the gas to be measured in the external space (the gas to be measured) If the measurement gas is an automobile exhaust gas, the influence of exhaust pressure pulsation) is reduced. In other words, even if the gas to be measured is rapidly taken in along with the pressure fluctuation, the concentration fluctuation of the gas to be measured introduced into the first inner space 20 is almost negligible.

  The third diffusion rate-determining unit 92 is a part that imparts a predetermined diffusion resistance to the gas to be measured introduced from the buffer space 91 into the first internal space 20, and has two horizontally long (open in the y-axis direction). Is provided as a slit).

  In the sensor element 201, nitrogen oxide (NOx) is measured against the gas to be measured introduced into the second internal space 20 from the opening 11 a by the entirety of the external communication portion 11, the buffer space 91, and the third diffusion rate-limiting portion 92. ) A predetermined diffusion resistance suitable for concentration measurement is given.

  Therefore, the values of the width a and the thickness b that define the value of the diffusion resistance provided in the external communication portion 11 may be determined based on the relationship with the diffusion resistance provided in the third diffusion rate-limiting unit 92. However, also in the present embodiment, as in the first embodiment, the external communication portion 11 has a thickness b of 50% to 100% with respect to the thickness d in the z-axis direction of the first internal space 20. The width a is preferably 5% to 60% (desirably 10% to 40%) with respect to the width c of the first internal space 20 in the y-axis direction. Thereby, the occurrence of capillary action is suppressed.

  As described above, according to the present embodiment, as in the first embodiment, even if water adheres to the sensor element tip 201a during operation, the measurement accuracy is stably maintained, By providing the buffer space 91 and the third diffusion rate-determining unit 92, even if the gas to be measured is suddenly taken into the sensor element 201 due to the pressure fluctuation of the gas to be measured in the external space, the gas to be measured It is possible to realize a gas sensor in which concentration fluctuations are suitably suppressed.

<Third Embodiment>
In 3rd Embodiment, the aspect in which an external communication part is provided in the position different from the gas sensor 100 which concerns on 1st Embodiment is demonstrated.

  FIG. 5 is an external perspective view schematically showing an example of the configuration of the sensor element 301 of the gas sensor 300 according to the third embodiment. FIG. 6 is a schematic cross-sectional view schematically showing a cross section of the sensor element 301 at each position shown in FIG. 5 in order to explain the structure of the gas flow part 113. In FIG. 6, the configuration other than the gas circulation unit 113 is omitted for simplification. FIG. 6A is a cross-sectional view taken along line AA ′ of FIG. FIG. 6B is a cross-sectional view taken along line BB ′ of FIG. FIG.6 (c) is sectional drawing which cut | disconnected CC 'of FIG. 5 along the arrow. In addition, about the structure similar to the gas sensor 100 which concerns on 1st Embodiment, and the gas sensor 200 which concerns on 2nd Embodiment, the same code | symbol is attached | subjected and the description and illustration are abbreviate | omitted.

  The sensor element 301 is provided with the external communication portion 12 on the sensor element side portion 301b in place of the external communication portion 11 provided on the sensor element tip portion 101a in the sensor element 101 according to the first embodiment. . In the present embodiment, a part from the external communication part 12 to the second internal space 40 is also referred to as a gas circulation part 113.

  Similar to the external communication portion 11, the external communication portion 12 is a space inside the sensor element 301 provided in a form in which the spacer layer 5 is cut out. The external communication portion 12 has an upper portion on the lower surface of the second solid electrolyte layer 6 or the inner surface 5 a of the spacer layer 5, a lower portion on the upper surface of the first solid electrolyte layer 4 or the inner surface 5 b of the spacer layer 5, and a side portion on the spacer layer 5. It is provided by being partitioned by the side surfaces 5e and 5f. However, in more detail, the position where the external communication portion 12 is formed is adjusted according to the degree of diffusion resistance suitable for measurement of nitrogen oxide (NOx) concentration.

  The width e in the x-axis direction and the thickness f in the z-axis direction of the external communication portion 12 depend on the degree of diffusion resistance to be imparted to the gas to be measured introduced into the first internal space 20 from the opening 12a. It is prescribed.

  However, as with the external communication portion 11, the external communication portion 12 has a thickness f of 50% to 100% with respect to the thickness d in the z-axis direction of the first internal space 20, and the width e is the first. The inner space 20 is preferably 5% to 60% (desirably 10% to 40%) with respect to the width c in the y-axis direction.

  As described above, in the gas sensor 300, the width e and the thickness f of the external communication portion 12 are defined within the above-described range, so that the water adhering to the sensor element side portion 301b enters the first internal space 20. Infiltration is suppressed.

  The external communication portion 12 has a distance t1 in the x-axis direction from the end of the first internal space 20 on the element front end side to the communication portion 12b in the x-axis direction of the first internal space 20. It is preferable that it is 20% or less with respect to the length t2. If the distance t1 exceeds 20%, it becomes difficult to adjust the oxygen partial pressure in the measurement gas described above in the first internal space 20. T1 may be 0. This is because the oxygen partial pressure can be adjusted more effectively.

  As described above, in the gas sensor 300 according to the present embodiment, by providing the external communication portion 12 having the opening 12a on the side portion 301b of the sensor element 301, water attached to the sensor element tip portion 301a is caused by capillary action. Infiltration into the inside is suppressed. Furthermore, by suitably determining the size of the external communication portion 12, the water adhering to the sensor element side portion 301b is also prevented from entering the inside due to capillary action. As a result, it is possible to prevent the sensor element 301 from cracking due to the rapid evaporation of water in the internal space.

  In addition, in the gas sensor 300 according to the present embodiment, by providing the external communication portion 12 having the opening 12a on the sensor element side portion 301b instead of the external communication portion having the opening at the sensor element tip portion 301a, The strength in the vicinity of the sensor element tip 301a is improved. As a result, the sensor element 301 is prevented from cracking due to thermal stress generated by water adhering to the sensor element tip 301a.

  Therefore, in the gas sensor 300 according to the present embodiment, a decrease in measurement accuracy due to a crack generated in the sensor element 301 is suitably suppressed. In other words, even if water adheres to the sensor element tip 301a during the gas sensor operation, the measurement accuracy is stably maintained.

  As described above, according to the present embodiment, by providing the external communication portion with a predetermined size on the sensor element side portion 301b, even if water adheres to the sensor element tip portion 301a during operation, measurement accuracy is improved. Can be realized in a stable manner.

<Fourth embodiment>
In 4th Embodiment, the aspect from which the structure of a gas distribution part differs from the gas sensor 300 which concerns on 3rd Embodiment is demonstrated.

  FIG. 7 is an external perspective view schematically showing an example of the configuration of the sensor element 401 of the gas sensor 400 according to the fourth embodiment. FIG. 8 is a schematic cross-sectional view schematically showing a cross section of the sensor element 401 at each position shown in FIG. 7 in order to explain the structure of the gas flow part 114. In FIG. 8, the configuration other than the gas circulation unit 114 is omitted for simplification. FIG. 8A is a cross-sectional view taken along line AA ′ of FIG. FIG. 8B is a cross-sectional view taken along the line BB ′ in FIG. FIG.8 (c) is sectional drawing which cut | disconnected CC 'of FIG. 7 along the arrow. In addition, about the structure similar to the gas sensor 100 which concerns on 1st Embodiment thru | or the gas sensor 300 which concerns on 3rd Embodiment, the same code | symbol is attached | subjected and the description and illustration are abbreviate | omitted.

  The sensor element 401 has a configuration in which a buffer space 91 and a third diffusion limiting part 92 are provided between the external communication part 12 and the first internal space 20 of the sensor element 301 according to the third embodiment. . In the present embodiment, a part from the external communication part 12 to the second internal space 40 is also referred to as a gas circulation part 114. In the present embodiment, the buffer space 91 is provided such that the width t4 in the x-axis direction is larger than the width e of the external communication portion 12. Thereby, the buffer effect similar to 2nd Embodiment is acquired.

  In the sensor element 401, nitrogen oxide (NOx) is measured against the gas to be measured introduced into the second internal space 20 from the opening 12 a by the entirety of the external communication portion 12, the buffer space 91, and the third diffusion rate-limiting portion 92. ) A predetermined diffusion resistance suitable for concentration measurement is given.

  Therefore, the values of the width e and the thickness f that define the value of the diffusion resistance applied at the external communication portion 12 may be determined based on the relationship with the diffusion resistance applied at the third diffusion rate limiting portion 92. However, also in the present embodiment, as in the third embodiment, the external communication portion 12 has a thickness f of 50% to 100% with respect to the thickness d of the first internal space 20 in the z-axis direction. The width e is preferably 5% to 60% (desirably 10% to 40%) with respect to the width c of the first internal space 20 in the y-axis direction. Thereby, generation | occurrence | production of a capillary phenomenon is suppressed.

  In the external communication portion 12, the distance t3 in the x-axis direction from the end of the buffer space 91 to the communication portion 12b is equal to the length t4 of the buffer space 91 in the x-axis direction. It is preferable that it is 50% or less. When the distance t3 exceeds 50%, it becomes difficult to cancel the rapid change in the concentration variation of the gas to be measured described above in the buffer space 91.

  As described above, according to the present embodiment, as in the third embodiment, even if water adheres to the sensor element tip 401a during operation, the measurement accuracy is stably maintained, By providing the buffer space 91 and the third diffusion rate limiting unit 92, even if the gas to be measured is suddenly taken into the sensor element 401 due to the pressure fluctuation of the gas to be measured in the external space, the gas to be measured It is possible to realize a gas sensor in which concentration fluctuations are suitably suppressed.

<Modification>
In the above description, the mode in which the first diffusion rate controlling unit 30 and the third diffusion rate controlling unit 92 are formed as horizontally long slits has been described. However, the application of the present invention is not limited to this, and other shapes are used. It may be formed.

  In the third embodiment and the fourth embodiment, the aspect in which one external communication portion is provided on each side portion of the sensor element has been described. However, the application of the present invention is limited to this. It may be an embodiment in which two or more external communication portions are provided on each side portion of the sensor element. Or the aspect by which an external communication part is provided only in one side part may be sufficient.

  When the thickness of the external communication portion is made smaller than the thickness of the first internal space, the external communication portion is located above or below the spacer layer 5 as shown in FIGS. 9 (a) and 9 (b). The aspect formed in either side may be sufficient, and the aspect formed in the approximate center of the spacer layer 5 may be sufficient as shown in FIG.9 (c).

Example 1
Examples of the gas sensor A according to the first embodiment, the gas sensor A according to the second embodiment, the gas sensor B according to the second embodiment, and the gas sensor 300 according to the third embodiment. A water droplet dropping test was performed on gas sensors C and D as examples, gas sensors E and F as examples of the gas sensor 400 according to the fourth embodiment, and gas sensor G as a comparative example.

  In the gas sensor C, the distance t1 is 0, in the gas sensor D, the distance t1 is 10% of the length t2, in the gas sensor E, the distance t3 is 0, and in the gas sensor F, the distance t3 is 10% of the length t4. The gas sensor G is a conventional gas sensor in which a slit-like external communication portion having an opening is provided at the tip of the sensor element. In the gas sensor G, the width of the external communication portion is the same as the vacancy width, and the thickness of the external communication portion is 5% of the vacancy thickness.

  In the water drop test, a water drop was dropped in the vicinity of the tip of the sensor element while driving the gas sensor while heating the sensor element at a predetermined temperature, and it was confirmed whether or not a crack occurred in the sensor element. Then, increase the amount of water drops to be dropped until a crack occurs in the sensor element, perform the same test, stop the driving of the gas sensor when the crack occurs in the sensor element, and the amount of water drops at this time It was done by measuring. The cracked water droplet amount ratio is a value represented by the ratio of the water droplet amount at which each of the gas sensor A to gas sensor F cracks to the water droplet amount at which the gas sensor G crack is generated.

  FIG. 10 shows the result of measuring the amount of cracked water droplets of the gas sensors A to F. In the gas sensor A, the width a is 20% of the width c and the thickness b is 100% of the thickness d. In the gas sensor B, the width a is 10% of the width c and the thickness b is 100% of the thickness d. The width e is 20% of the width c and the thickness f is 100% of the thickness d. In the gas sensor D, the width e is 30% of the width c and the thickness f is 50% of the thickness d. In the gas sensor F, the width e is 15% of the width c and the thickness f is 80% of the thickness d. In each of gas sensor A to gas sensor G, the number of measurements was set to 5.

  The circles in FIG. 10 indicate the average values of the measured values, and the lines above and below the circles indicate the maximum and minimum values of the measured values. As shown in FIG. 10, it was confirmed that the gas sensor A to the gas sensor F had more cracked water droplets than the gas sensor G. Such a result means that the gas sensor A to the gas sensor F have a higher breaking strength than the gas sensor G.

(Example 2)
In this example, in order to examine the relationship between the size of the external communication portion and the breaking strength, a plurality of gas sensors having different ratios of the size of the external communication portion to the size of the vacant space were prepared for each embodiment. The same water drop dropping test as in Example 1 was performed.

  FIG. 11 is a gas sensor corresponding to the first embodiment, and shows the results of measuring the amount of cracked water droplets of eight types of gas sensors having different widths a of the external communication portion 11. FIG. 12 shows the results of measuring the amount of cracked water droplets of five types of gas sensors corresponding to the second embodiment and different in the thickness b of the external communication portion 12. FIG. 13 shows the results of measuring the amount of cracked water droplets of five types of gas sensors corresponding to the third embodiment and having different thicknesses f of the external communication portion 12. Furthermore, FIG. 14 is a gas sensor corresponding to the fourth embodiment, and shows the results of measuring the amount of cracked water droplets of eight types of gas sensors having different widths e of the external communication portion 12. For each type of gas sensor, the number of measurements was five. However, the ratio of the external communication width to the vacant width in FIGS. 11 and 14 is 100%, and the ratio of the external communication thickness to the vacant thickness in FIGS. 12 and 13 is 5% in the comparative example. It is a measurement result about a certain gas sensor G.

  The circles in FIGS. 11 to 14 indicate the average value of the measurement values, and the lines above and below the circles indicate the maximum value and the minimum value of the measurement values. As shown in FIG. 11 to FIG. 14, it is confirmed that the gas sensor according to the example has more cracked water droplets than the gas sensor G according to the comparative example regardless of the width or thickness of the external communication portion. It was done. This result means that the gas sensor according to the example has a higher breaking strength than the gas sensor G according to the comparative example regardless of the width or thickness of the external communication portion. In particular, when the ratio of the external communication portion width to the vacancy width is 5% or more and 60% or less, and when the ratio of the external communication portion thickness to the vacancy thickness is 50% or more and 100% or less, water droplets causing cracks are generated. The amount is twice or more that of the gas sensor according to the comparative example. This indicates that a gas sensor having a breaking strength more than twice that of the prior art is realized by providing an external communication portion so as to satisfy these sizes.

  From the results of Example 1 and Example 2, it was confirmed that the provision of the external communication portion defined in the size according to the requirements described above is effective in improving the fracture strength. Further, in both Example 1 and Example 2, it is more effective to improve the fracture strength by providing an external communication part having an opening on the side of the sensor element (corresponding to the third and fourth embodiments). It was confirmed that there was. Such a result means that the provision of the external communication portion described above is effective in suppressing a decrease in measurement accuracy caused by a crack generated in the sensor element.

(Example 3)
In this example, the responsiveness of each gas sensor of Example 1 was examined. In the response test, when the air-fuel ratio of the gas to be measured (oxygen concentration in the gas to be measured) is changed from λ = 0.9 to λ = 1.1, the air-fuel ratio λ = 0. The sensor output (Ip2) when substantially substituted with the measured gas of 9 is set to 0%, and the sensor output (Ip2) when the sensor element is almost replaced with the measured gas with the air-fuel ratio λ = 1.1 is set to 100%. Then, the time from when the sensor output (Ip2) corresponding to 33% is detected to the time when the sensor output (Ip2) corresponding to 66% is detected is measured three times for each gas sensor. I went there.

  FIG. 15 shows the results of measuring the response times of the gas sensors A to G. In each of gas sensor A to gas sensor F, the relationship between the width and width c of the external communication portion and the relationship between the thickness and thickness d of the external communication portion are the same as those of the gas sensor used in the water drop test shown in FIG. did.

  The circles in FIG. 15 indicate the average values of the measured values, and the lines above and below the circles indicate the maximum and minimum values of the measured values. As shown in FIG. 15, no significant difference was found between the response times of the gas sensors A to F and the response time of the gas sensor G.

  From the above results, it was confirmed that the same responsiveness as that of the conventional gas sensor can be obtained even in the gas sensors A to F provided with the external communication portion in accordance with the above-described requirements.

DESCRIPTION OF SYMBOLS 1 1st board | substrate layer 2 2nd board | substrate layer 3 3rd board | substrate layer 4 1st solid electrolyte layer 5 Spacer layer 5
6 Second solid electrolyte layer 11, 12 External communication portion 20 First internal space 30 First diffusion rate controlling portion 40 Second internal space 44 Measuring electrode 91 Buffer space 92 Third diffusion rate controlling portion 100 Gas sensor 101 Sensor element

Claims (3)

A gas sensor having a sensor element composed mainly of an oxygen ion conductive solid electrolyte and detecting a predetermined gas component in a gas to be measured,
The sensor element is
An external communication portion having an opening portion opened in the external space, and introducing the gas to be measured under a predetermined diffusion resistance from the external space;
A buffer space communicating with the external communication part;
A first internal space communicating with the buffer space under a predetermined diffusion resistance;
A second internal space that communicates with the first internal space under a predetermined diffusion resistance;
By applying a predetermined voltage between the first internal electrode formed on the surface of the first internal space and the external electrode formed in a space different from the first internal space, A main pumping cell provided so as to be able to pump oxygen in the internal space of 1;
By applying a predetermined voltage between the second internal electrode formed on the surface of the second internal space and the external electrode formed in a space different from the second internal space, An auxiliary pumping cell provided to be able to pump out oxygen in the second internal cavity;
With
The external communication portion has one opening on each of two side portions along the longitudinal direction of the sensor element, and a space having a uniform width along a direction perpendicular to the longitudinal direction. And
The width of the external communication portion is 5% or more and 60% or less with respect to the width of the first internal space,
The thickness of the external communication portion is 50% or more and 100% or less with respect to the thickness of the first internal space.
A gas sensor characterized by that. A gas sensor having a sensor element composed mainly of an oxygen ion conductive solid electrolyte and detecting a predetermined gas component in a gas to be measured,
The sensor element is
An external communication portion having an opening portion opened in the external space, and introducing the gas to be measured under a predetermined diffusion resistance from the external space;
A buffer space communicating with the external communication part;
A first internal space communicating with the buffer space under a predetermined diffusion resistance;
A second internal space that communicates with the first internal space under a predetermined diffusion resistance;
By applying a predetermined voltage between the first internal electrode formed on the surface of the first internal space and the external electrode formed in a space different from the first internal space, A main pumping cell provided so as to be able to pump oxygen in the internal space of 1;
By applying a predetermined voltage between the second internal electrode formed on the surface of the second internal space and the external electrode formed in a space different from the second internal space, An auxiliary pumping cell provided to be able to pump out oxygen in the second internal cavity;
With
The external communication portion is a space having only one opening at the tip of the sensor element and having a uniform width from the opening along the longitudinal direction of the sensor element.
The width of the external communication portion is 5% or more and 60% or less with respect to the width of the first internal space,
The thickness of the external communication portion is 50% or more and 100% or less with respect to the thickness of the first internal space.
A gas sensor characterized by that. The gas sensor according to claim 1 or 2, wherein
The sensor element is
A measurement electrode formed on the surface of the second internal cavity;
A reference electrode formed at a site different from the second internal space;
A measurement cell comprising the measurement electrode and the reference electrode;
A porous diffusion layer provided on the measurement electrode and imparting a predetermined diffusion resistance to the gas to be measured;
Further comprising
The measurement electrode reduces an oxide gas component in the predetermined gas component to which the predetermined diffusion resistance is imparted by the porous diffusion layer,
The measurement cell is configured to apply a voltage according to a reduction degree of the oxide gas component in the measurement electrode between the measurement electrode and the reference electrode, thereby causing a current flowing between the measurement electrode and the reference electrode, Provided to be measurable,
A gas sensor characterized by that.

Images