SENSOR ELEMENT AND GASS SENSOR

Abstract

A sensor element serves to detect the concentration of a specific gas in a sample gas. The sensor element comprises an element body that has an internal sample gas flow section, which introduces the sample gas from a gas inlet and causes the sample gas to flow in a front-to-back direction, and a diffusion control section 11a located in the sample gas flow section, which exerts a diffusion resistance on the sample gas introduced from the gas inlet. The diffusion control section 11a comprises a first porous body 87a and a first spatial section 85a, which are provided in at least a portion of the diffusion control section 11a in the front-to-back direction.The first porous body 87a is provided such that it occupies part of a cross-section of the diffusion control section 11a perpendicular to the front-back direction and allows the gas of the object to pass through it, and the first space section 85a comprises part of the cross-section that is not occupied by the porous body 87a and allows the gas of the object to pass through it.

Description

Technical field

[0001] The present invention relates to a sensor element and a gas sensor. State of the art

[0002] A gas sensor is known that detects the concentration of a specific gas, such as NOx, in a sample gas, such as the exhaust gas of an internal combustion engine. For example, PTL 1 describes a gas sensor comprising a sensor element that includes an element body, a main pump cell, an auxiliary pump cell, and a measuring pump cell. The element body comprises an oxygen-ion-conducting solid electrolyte layer and has an internal sample gas flow section that introduces the sample gas and causes it to flow. The main pump cell comprises an inner main pump electrode located in a first inner cavity of the sample gas flow section and an outer main pump electrode located on the outside of the element body, exposed to the sample gas.The auxiliary pump cell comprises an inner auxiliary pump electrode located in a second inner cavity downstream of the first inner cavity in the sample gas flow section, and an outer auxiliary pump electrode located on an outer surface of the element body exposed to the sample gas. The measuring pump cell comprises an inner measuring pump electrode located in a measuring chamber downstream of the second inner cavity in the sample gas flow section, and an outer measuring pump electrode located on an outer surface of the element body exposed to the sample gas. When this sensor element is used to detect NOx concentrations, the oxygen concentration in the sample gas in the first and second inner cavities is set by the main pump cell and the auxiliary pump cell.Next, NOx in the sample gas is reduced by the set oxygen concentration in the measuring chamber. The NOx concentration in the sample gas is then measured based on the pump flow rate when the measuring pump cell pumps out the oxygen produced by the NOx reduction. Document listPatent documents

[0003] PTL 1: Japanese unexamined patent application with publication number 2017-181499 A Summary of the invention: Technical problem

[0004] In such a gas sensor, even if the composition of the gas being measured is identical, the operation of a pump cell (e.g., the value of a pump current flowing through a pump cell of the sensor element) can differ if the dynamic pressure of the gas being measured differs. As a result, the dynamic pressure of the gas being measured can affect the accuracy of the measurement of the concentration of a specific gas. Therefore, the effect of the dynamic pressure of the gas being measured on the pump cell should be reduced.

[0005] The present invention was made to solve this problem, and a main objective is to reduce the effect of the dynamic pressure of the gas in the measuring object on the pump cell. Solution to the problem

[0006] The present invention uses the following device to solve the main problem described above.

[0007] [1] A sensor element according to the present invention is a sensor element for detecting a concentration of a specific gas in a sample gas, wherein the sensor element comprises: an element body having an oxygen-ion-conducting solid electrolyte layer and an internal sample gas flow section which introduces the sample gas from a gas inlet and causes the sample gas to flow in a first direction; a pump cell comprising an inner electrode provided in an inner cavity of the sample gas flow section and an outer electrode provided on an outer surface of the element body; and a diffusion control section located upstream of the inner cavity in the sample gas flow section which exerts a diffusion resistance on the sample gas introduced from the gas inlet.wherein the diffusion control section comprises a porous body and a space section or free space section, which are provided in at least a part of the diffusion control section in the first direction, wherein the porous body is provided such that it occupies a part of a cross-section of the diffusion control section perpendicular to the first direction and allows the gas of the sample to pass through it, and the space section comprises a part of the cross-section that is not occupied by the porous body and allows the gas of the sample to pass through it.

[0008] This sensor element includes a diffusion control section, which is part of the sample gas flow section and causes the sample gas to flow in the first direction. The diffusion control section comprises the porous body and the spatial section, which are provided in at least a portion of the diffusion control section in the first direction. The porous body is positioned to occupy a portion of the cross-section of the diffusion control section perpendicular to the first direction. The spatial section comprises a portion of the cross-section not occupied by the porous body. As a result, the flow velocity of the sample gas passing through the porous body can be differentiated from the flow velocity of the sample gas passing through the spatial section in the cross-section of the diffusion control section perpendicular to the first direction.This can cause turbulence in the sample gas after passage and an increase in the pressure drop of the sample gas. Therefore, the effect of the dynamic pressure of the sample gas on the pump cell, which includes the inner electrode located downstream of a diffusion control section, can be reduced.

[0009] [2] In the sensor element described above (the sensor element according to the preceding [1]), the porous body can be provided in the diffusion control section in such a way that it occupies 30% to 70% of the cross-section.

[0010] [3] In the sensor element described above (the sensor element according to [1] or [2] above), the porosity of the porous body can be 15% or less. In this way, the flow velocity of the gas passing through the porous body can be made more different from the flow velocity of the gas passing through the space section, and the pressure drop of the gas after passing through can be further increased.

[0011] [4] In the sensor element described above (the sensor element according to one of the preceding [1] to [3]), the porous body can be provided in a plurality, so that parallel flow paths are formed in the cross-section.

[0012] [5] In the sensor element described above (the sensor element according to one of the preceding [1] to [4]), the element body can have a longitudinal direction and can be a layered body composed of several layers stacked in a layering direction perpendicular to the longitudinal direction; the cross-sectional shape of the space section can be a predetermined shape with a longer outer perimeter than a reference rectangle; the reference rectangle can be a rectangle having the same area as the cross-section of the space section; the reference rectangle can be a rectangle formed by deforming the circumscribed rectangle of the cross-section, which is constructed from two sides parallel to the layering direction and two sides parallel to a second direction perpendicular to the layering direction, such that short sides become shorter while maintaining the length of long sides; or a rectanglewhich is formed by deforming the circumscribed rectangle while maintaining a ratio of each side, or a rectangle formed by changing the length of each side of the circumscribed rectangle such that the overlap area with the cross-section is maximized. In this way, the portion of the spatial section of the diffusion control section with the cross-sectional shape perpendicular to the first direction, which is the predetermined shape, has a smaller hydraulic diameter than the reference rectangle. Consequently, the pressure drop of the sample gas passing through the spatial section is higher. This shape can also reduce the effect of the sample gas's dynamic pressure on the pump cell, which includes the inner electrode located downstream of a diffusion control section.

[0013] [6] In the sensor element described above (the sensor element according to the preceding [5]), the outer circumference of the specified shape can comprise a first section and a second section, each directed towards each other in the layering direction and extending along the second direction, and at least a part of the first section and / or at least a part of the second section can each have a curved shape.

[0014] [7] In the sensor element described above (the sensor element according to [5] or [6] above), the outer circumference of the specified shape may comprise a first section and a second section, each directed towards each other in the layering direction and extending along the second direction, and at least a part of the first section and / or at least a part of the second section may each have a polygonal line shape.

[0015] [8] In the sensor element described above (the sensor element according to [6] or [7] above), the first section and the second section can each have a convex shape on the same side in the layering direction.

[0016] [9] In the sensor element described above (the sensor element according to [6] or [7] above), the first section and the second section can each have a convex shape on a side where they approach each other or on a side where they are separated from each other in the layering direction.

[0017]

[10] In the sensor element described above (the sensor element according to one of the preceding [5] to [9]), the diffusion control section can have a plurality of spatial sections and each of the plurality of spatial sections can have a cross-sectional shape which is the specified shape.

[0018]

[11] In the sensor element described above (the sensor element according to one of the preceding [1] to

[10] ), the diffusion control section can be configured such that the cross-sectional area of ​​a cross-section perpendicular to the first direction is smaller in at least a part of a downstream side of an upstream end than in the upstream end. This increases the pressure drop of the gas of the sample passing through a part of the space section with a smaller cross-sectional area than the upstream end. This configuration also reduces the effect of the dynamic pressure of the gas of the sample on the pump cell, which includes the inner electrode located downstream of a diffusion control section.

[0019]

[12] In the sensor element described above (the sensor element according to the preceding

[11] ), the diffusion control section can have an outline of the cross-section parallel to the first direction and the outline can extend such that it is curved with respect to the first direction.

[0020]

[13] A gas sensor according to the present invention comprises the sensor element according to any one of the preceding [1] to

[12] . Consequently, the gas sensor produces the same advantageous effects as those produced by the preceding sensor element. For example, an advantageous effect is the reduction of the effect of the dynamic pressure of the gas in the sample on the pump cell. Brief description of the drawings Fig. Figure 1 is a schematic cross-sectional view that schematically shows an example of the construction of a gas sensor 100. Fig. 2 is a view along arrow A in the Fig. 1. Fig. Figure 3 is a cross-sectional view along line BB in the Fig. 1. Fig. Figure 4 is a block diagram showing a block diagram between a control device 95 and relevant elements, including cells. Fig. Figure 5 is a cross-sectional view along line CC in the Fig. 3. Fig. Figure 6 is a partial cross-sectional view showing a process for producing a diffusion adjustment section 11a. Fig. Figure 7 is an explanatory diagram showing a diffusion adjustment section 11a according to a modification. Fig. Figure 8 is an explanatory diagram showing a diffusion adjustment section 11a according to a modification. Fig. Figure 9 is an explanatory diagram showing a reference rectangle S1. Fig. Figure 10 is an explanatory diagram showing a reference rectangle S2. Fig. Figure 11 is a partial cross-sectional view showing a process for producing the diffusion control section 11a in the Fig. 8 shows. Fig. Figure 12 is an explanatory diagram showing a diffusion adjustment section 11a according to a modification. Fig. Figure 13 is an explanatory diagram showing a diffusion adjustment section 11a according to a modification. Fig. Figure 14 is an explanatory diagram showing a diffusion adjustment section 11a according to a modification. Fig. Figure 15 is an explanatory diagram showing a diffusion adjustment section 11a according to a modification. Fig. Figure 16 is an explanatory diagram showing a diffusion adjustment section 11a according to a modification. Fig. Figure 17 is an explanatory diagram showing a diffusion adjustment section 11a according to a modification. Fig. Figure 18 is an explanatory diagram showing a diffusion adjustment section 11a according to a modification. Fig. Figure 19 is an explanatory diagram showing a diffusion adjustment section 11a according to a modification. Fig. Figure 20 is an explanatory diagram showing a diffusion adjustment section 11a according to a modification. Fig. Figure 21 is an explanatory diagram showing a diffusion adjustment section 11a according to a modification. Fig. Figure 22 is an explanatory diagram showing a diffusion adjustment section 11a according to a modification. Fig. Figure 23 is a schematic cross-sectional view showing a first diffusion adjustment section 211 according to a modification. Fig. Figure 24 is a cross-sectional view along line DD in the Fig. 23. Fig. Figure 25 is a cross-sectional view along line EE in the Fig. 24. Description of embodiments

[0021] Next, an embodiment of the present invention will be described with reference to the drawings. Fig. Figure 1 is a schematic cross-sectional view that schematically shows an example of the construction of the gas sensor 100, which is an embodiment of the present invention. Fig. 2 is a view along arrow A in the Fig. 1. The Fig. Figure 3 is a cross-sectional view along line BB in the Fig. 1. The Fig. Figure 4 is a block diagram showing an electrical connection relationship between a control device 95, cells, and a heating device 72. Fig. Figure 5 is a cross-sectional view along line CC in the Fig. 3. The Fig. Figure 5 is a schematic cross-sectional view that schematically shows an area around a first spatial section or free space section 85a of a first diffusion control section 11. The gas sensor 100 is installed, for example, in a pipe, such as the exhaust pipe of an internal combustion engine. The gas sensor 100 uses the exhaust gas from an internal combustion engine as the gas to be measured and detects the concentration of a specific gas, which is the concentration of a specific gas, such as NOx or ammonia, in the gas to be measured. In the present embodiment, the gas sensor 100 measures an NOx concentration as the concentration of a specific gas.The gas sensor 100 comprises a sensor element 101, which includes a long rectangular parallelepiped element body 102, cells 21, 41, 50, 80 to 83 incorporated into the sensor element 101, a heating element section 70 provided within the sensor element 101, and a control device 95 comprising variable power supplies 24, 46, 52 and a heating element power source 76, and which controls the entire gas sensor 100. In the present embodiment, as shown in . Fig. As shown in Figures 1 to 3, the longitudinal direction of the element body 102 of the sensor element 101 is defined as the front-back direction (longitudinal direction), the layering direction (thickness direction) of each layer 1 to 6 of the element body 102 is defined as the top-bottom direction, and the direction perpendicular to the front-back direction and the top-bottom direction is defined as the left-right direction (lateral direction). Fig. 5 is for illustrative purposes compared to the Fig. 2 is represented with an elongated top-bottom length.

[0022] The element body 102 is a layered body in which six layers, i.e., a first substrate layer 1, a second substrate layer 2, a third substrate layer 3, a first solid electrolyte layer 4, a spacer layer 5, and a second solid electrolyte layer 6, each formed from an oxygen-ion-conducting solid electrolyte layer made of zirconium oxide (ZrO2) or the like, are laminated in this order from a bottom side in the drawing. The solid electrolyte forming these six layers has a high density and is airtight. The element body 102 is manufactured, for example, by applying a predefined processing step, printing a circuit structure, and the like onto a ceramic green layer corresponding to each layer, then laminating these layers, and subsequently firing the layers to integrate them.

[0023] On the side of a tip end section of the sensor element 101 (of the element body 102) (side of the left end section in the Fig. 1) a gas inlet opening 10, a first diffusion control section 11, a buffer chamber 12, a second diffusion control section 13, a first inner cavity (an oxygen concentration control chamber) 20, a third diffusion control section 30, a second inner cavity (an oxygen concentration control chamber) 40, a fourth diffusion control section 60 and a third inner cavity (a measuring chamber) 61 are formed adjacent to one another in such a way that they are connected to each other in this order between the lower surface of the second solid electrolyte layer 6 and the upper surface of the first solid electrolyte layer 4.

[0024] The gas inlet opening 10, the buffer chamber 12, the first inner cavity 20, the second inner cavity 40 and the third inner cavity 61 are spaces whose upper parts, lower parts and side parts, provided by hollowing out the spacer layer 5, are each defined by the lower surface of the second solid electrolyte layer 6, the upper surface of the first solid electrolyte layer 4 and the side surface of the spacer layer 5 within the sensor element 101.

[0025] Each of the first diffusion adjustment section 11, the second diffusion adjustment section 13 and the third diffusion adjustment section 30 is provided as two laterally elongated slots (openings whose longitudinal direction is a direction perpendicular to the drawing). Fig. 2 and Fig. Figure 5 shows the shapes of the diffusion control section 11a and the diffusion control section 11b, which form the two slots of the first diffusion control section 11. The fourth diffusion control section 60 is provided as a single laterally elongated slot (an opening whose longitudinal direction is perpendicular to the drawing), which forms the space between the lower surface of the second solid electrolyte layer 6 and the surface of the second solid electrolyte layer. A portion from the gas inlet opening 10 to the third inner cavity 61 is also referred to as the sample gas flow section.

[0026] The sensor element 101 (element body 102) comprises a reference gas introduction section 49, which allows the reference gas to flow from outside the sensor element 101 to a reference electrode 42 during the measurement of the NOx concentration. The reference gas introduction section 49 has a reference gas introduction chamber 43 and a reference gas introduction layer 48. The reference gas introduction chamber 43 is a chamber provided inward from a rear end face of the sensor element 101. The reference gas introduction chamber 43 is located between the upper surface of the third substrate layer 3 and the lower surface of the spacer layer 5 and has lateral sides provided by the side surfaces of the first solid electrolyte layer 4. The reference gas introduction chamber 43 has an opening at the rear end face of the sensor element 101.This opening acts as inlet 49a of the reference gas introduction section 49. The reference gas is introduced through inlet 49a into the reference gas introduction chamber 43. The reference gas introduction section 49 introduces the reference gas to the reference electrode 42 while a predetermined diffusion resistance is exerted on the reference gas being drawn in through inlet 49a. In the present embodiment, the reference gas is ambient air.

[0027] The reference gas introduction layer 48 is located between the upper surface of the third substrate layer 3 and the lower surface of the first solid electrolyte layer 4. The reference gas introduction layer 48 is a porous body composed of a ceramic material, such as aluminum oxide. A portion of the upper surface of the reference gas introduction layer 48 is exposed within the reference gas introduction chamber 43. The reference gas introduction layer 48 is positioned above the reference electrode 42. The reference gas introduction layer 48 allows the reference gas to flow from the reference gas introduction chamber 43 to the reference electrode 42.

[0028] The reference electrode 42 is an electrode configured such that it is surrounded by the upper surface of the third substrate layer 3 and the first solid electrolyte layer 4. As described above, the reference gas inlet layer 48, which communicates with the reference gas inlet chamber 43, is provided around the reference electrode 42. As described below, an oxygen concentration (an oxygen partial pressure) in the first inner cavity 20, an oxygen concentration (an oxygen partial pressure) in the second inner cavity 40, and an oxygen concentration (an oxygen partial pressure) in the third inner cavity 61 can be measured using the reference electrode 42. The reference electrode 42 is configured as a porous cermet electrode (for example, a cermet electrode made of Pt and ZrO2).

[0029] In the sample gas flow section, the gas inlet opening 10 is a section open to an external space, and a sample gas is drawn from the external space through the gas inlet opening 10 into the sensor element 101. The first diffusion control section 11 is a section that exerts a predetermined diffusion resistance on a sample gas drawn through the gas inlet opening 10. In the present embodiment, a front end of the first diffusion control section 11 is the gas inlet 10. As shown in Fig. 1 and Fig. As shown in Figure 2, the diffusion-adjusting section 11a of the first diffusion-adjusting section 11 is provided between an upper surface of a first bridging section 5a of the spacer layer 5 and the lower surface of the second solid electrolyte layer 6. The diffusion-adjusting section 11b is provided between a lower surface of the first bridging section 5a and the upper surface of the first solid electrolyte layer 4. As shown in the Fig. As shown in Figure 3, the first bridging section 5a is a section that provides a bridge to the left and right and is located in a front face of the buffer chamber 12, which is a section of the spacer layer 5 that has been punched out. The buffer chamber 12 is a space provided for guiding the sample gas, which is introduced from the first diffusion control section 11, to the second diffusion control section 13. The second diffusion control section 13 is a section that exerts a predetermined diffusion resistance on the sample gas, which is introduced from the buffer chamber 12 into the first inner cavity 20. As shown in Figure 3, the first bridging section 5a is located in a space that provides a bridge to the left and right. Fig. 1 and Fig. As shown in Figure 2, the second diffusion adjustment section 13 is provided between an upper surface of a second bridging section 5b of the spacer layer 5 and the lower surface of the second solid electrolyte layer 6, and between a lower surface of the second bridging section 5b and the upper surface of the first solid electrolyte layer 4. As shown in the Fig. As shown in Figure 3, the second bridging section 5b is a section that provides a bridge to the left and right and is located between the buffer chamber 12 and the first inner cavity 20. The sections of the spacer layer 5 are punched out. When the sample gas is introduced from the outside of the sensor element 101 into the first inner cavity 20, the sample gas, which is forced into the outside space due to pressure fluctuations of the sample gas (due to a pulsation of the exhaust pressure, if the sample gas is the exhaust gas of a motor vehicle, etc.), is held in place by the buffer chamber.The gas from the automotive component (which is rapidly drawn into the sensor element 101 through the gas inlet opening 10) is not introduced directly into the first inner cavity 20. Instead, the gas is introduced into the first inner cavity 20 after pressure fluctuations in the gas have been corrected by the first diffusion control section 11, the buffer chamber 12, and the second diffusion control section 13. This design renders pressure fluctuations of the gas introduced into the first inner cavity 20 almost negligible. The first inner cavity 20 serves to set the oxygen partial pressure in the gas introduced through the second diffusion control section 13. This oxygen partial pressure is set by the operation of a main pump cell 21.

[0030] The main pump cell 21 is an electrochemical pump cell comprising an inner pump electrode 22, which includes an upper electrode section 22a arranged on the lower surface of the second solid electrolyte layer 6 over substantially the entirety of a region directed towards the first inner cavity 20; an outer pump electrode 23, which is arranged on the upper surface of the second solid electrolyte layer 6 over a region corresponding to the upper electrode section 22a such that it is exposed to the outside of the sensor element 101; and the second solid electrolyte layer 6, the spacer layer 5 and the first solid electrolyte layer 4, which form a current path between the electrodes 22 and 23.

[0031] The inner pump electrode 22 is formed above the upper and lower solid electrolyte layers (the second solid electrolyte layer 6 and the first solid electrolyte layer 4), which define the first inner cavity 20, and the spacer layer 5, which provides a side wall.In particular, the upper electrode section 22a is formed on the lower surface of the second solid electrolyte layer 6, which provides an upper surface of the first inner cavity 20; a lower electrode section 22b is formed on the upper surface of the first solid electrolyte layer 4, which provides a lower surface; a side electrode section (not shown) is formed on the side wall surface (inner surface) of the spacer layer 5, whereby both side wall sections form the first inner cavity 20, so that the upper electrode section 22a and the lower electrode section 22b are connected; and the inner pump electrode 22 is arranged with a structure in a tunnel shape at a section where the side electrode section is arranged.

[0032] The inner pump electrode 22 and the outer pump electrode 23 are each designed as a porous cermet electrode (for example, a cermet electrode made of Pt and ZrO2 with an Au content of 1 percent). The inner pump electrode 22, which comes into contact with a gas used in the measurement, is made of a material whose reducing capacity for NOx components in the gas used in the measurement is reduced.

[0033] By conducting a pump current Ip0 in a positive direction or a negative direction between the inner pump electrode 22 and the outer pump electrode 23 by applying a desired voltage Vp0 between the inner pump electrode 22 and the outer pump electrode 23, the main pump cell 21 can pump oxygen in the first inner cavity 20 out to the outer space or pump oxygen in the outer space into the first inner cavity 20.

[0034] To detect an oxygen concentration (an oxygen partial pressure) in an atmosphere in the first inner cavity 20, an electrochemical sensor cell, i.e., an oxygen partial pressure detection sensor cell for main pump control 80, is formed from the inner pump electrode 22, the second solid electrolyte layer 6, the spacer layer 5, the first solid electrolyte layer 4, the third substrate layer 3 and the reference electrode 42.

[0035] The oxygen concentration (oxygen partial pressure) in the first inner cavity 20 is determined by measuring an electromotive force (voltage V0) in the oxygen partial pressure sensing sensor cell for the main pump control 80. Furthermore, the pump current Ip0 is controlled by regulating the voltage Vp0 of a variable current source 24 such that the voltage V0 reaches a target value. With this setup, the oxygen concentration in the first inner cavity 20 can be maintained at a predetermined constant value.

[0036] The third diffusion control section 30 is a section that exerts a predetermined diffusion resistance on a gas sample, the oxygen concentration (oxygen partial pressure) of which is controlled or set by the operation of the main pump cell 21 in the first inner cavity 20 for directing the gas sample to the second inner cavity 40. As described in the Fig. As shown in Figure 1, the third diffusion adjustment section 30 is provided between an upper surface of a third bridging section 5c of the spacer layer 5 and the lower surface of the second solid electrolyte layer 6, and between a lower surface of the third bridging section 5c and the upper surface of the first solid electrolyte layer 4. As shown in the Fig. As shown in Figure 3, the third bridging section 5c is a section that provides a bridging to the left and right and is located between the first inner cavity 20 and the second inner cavity 40, which are sections of the spacer layer 5 that has been punched out.

[0037] The second inner cavity 40 is provided as a space for further adjusting the oxygen partial pressure using an auxiliary pump cell 50 for the gas being measured. The oxygen concentration (oxygen partial pressure) of this gas is preset in the first inner cavity 20 and is then introduced through the third diffusion adjustment section 30. With this setup, the oxygen concentration in the second inner cavity 40 can be maintained at a constant value with high accuracy, allowing the NOx concentration to be measured with high accuracy using the gas sensor 100.

[0038] The auxiliary pump cell 50 is an electrochemical auxiliary pump cell comprising an auxiliary pump electrode 51 with an upper electrode section 51a, which is provided substantially on the entire lower surface of the second solid electrolyte layer 6, which is directed towards the second inner cavity 40, the outer pump electrode 23 (not limited to the outer pump electrode 23 and a suitable electrode outside the sensor element 101 may be used), the second solid electrolyte layer 6, the spacer layer 5 and the first solid electrolyte layer 4.

[0039] The auxiliary pump electrode 51 is arranged in the second inner cavity 40 with a structure in a corresponding tunnel shape like that of the inner pump electrode 22, which is provided in the first inner cavity 20 described above.In other words, the auxiliary pump electrode 51 has a tunnel-like structure such that an upper electrode section 51a is formed on the lower surface of the second solid electrolyte layer 6, which provides the upper surface of the second inner cavity 40; a lower electrode section 51b is formed on the upper surface of the first solid electrolyte layer 4, which provides the lower surface of the second inner cavity 40; and a side electrode section (not shown), connecting the upper electrode section 51a and the lower electrode section 51b, is formed on each of the two wall surfaces of the spacer layer 5, thus providing a side wall of the second inner cavity 40. The auxiliary pump electrode 51 and the inner pump electrode 22 are formed using a material whose reducing capacity for NOx components in the gas being measured is reduced.

[0040] By applying a desired voltage Vp1 between the auxiliary pump electrode 51 and the outer pump electrode 23, the auxiliary pump cell 50 can pump oxygen in an atmosphere in the second inner cavity 40 out to the outer space or pump oxygen from the outer space into the second inner cavity 40.

[0041] To set an oxygen partial pressure in an atmosphere in the second inner cavity 40, an electrochemical sensor cell, i.e., an oxygen partial pressure detection sensor cell for auxiliary pump control 81, is formed from the auxiliary pump electrode 51, the reference electrode 42, the second solid electrolyte layer 6, the spacer layer 5, the first solid electrolyte layer 4 and the third substrate layer 3.

[0042] The auxiliary pump cell 50 performs pumping with a variable current source 52, the voltage of which is controlled according to an electromotive force (voltage V1) detected by the oxygen partial pressure sensing sensor cell for auxiliary pump control 81. With this setup, the oxygen partial pressure in an atmosphere in the second inner cavity 40 is set to a low partial pressure that does not substantially affect the NOx measurement.

[0043] Simultaneously, its pump current Ip1 is used to control the electromotive force of the oxygen partial pressure sensing sensor cell for the main pump control 80. Specifically, the pump current Ip1 is fed into the oxygen partial pressure sensing sensor cell for the main pump control 80 as a control signal, and the gradient of the oxygen partial pressure in the gas sample, which is to be introduced from the third diffusion control section 30 into the second inner cavity 40, is controlled or adjusted by adjusting the target voltage V0 described above so that it remains constant. When used as an NOx sensor, the oxygen concentration in the second inner cavity 40 is maintained at a constant value of approximately 0.001 ppm by the functions of the main pump cell 21 and the auxiliary pump cell 50.

[0044] The fourth diffusion control section 60 is a section that exerts a predetermined diffusion resistance on the gas being measured, the oxygen concentration (oxygen partial pressure) of which is set by the operation of the auxiliary pump cell 50 in the second inner cavity 40 to guide the gas being measured to the third inner cavity 61. The fourth diffusion control section 60 plays a role in limiting the amount of NOx flowing into the third inner cavity 61. As described in the Fig. As shown in Figure 1, the fourth diffusion adjustment section 60 is provided between an upper surface of a fourth bridging section 5d of the spacer layer 5 and the lower surface of the second solid electrolyte layer 6, as well as between a lower surface of the fourth bridging section 5d and the upper surface of the first solid electrolyte layer 4. As shown in the Fig. As shown in Figure 3, the fourth bridging section 5d is a section that provides a bridging to the left and right and is located between the second inner cavity 40 and the third inner cavity 61, which are sections of the spacer layer 5 that has been punched out.

[0045] The third inner cavity 61 is provided as a space for carrying out a process related to measuring the nitrogen oxide (NOx) concentration in a sample gas. The sample gas's oxygen concentration (oxygen partial pressure) is preset in the second inner cavity 40 and is then introduced through the fourth diffusion control section 60. The NOx concentration measurement is primarily performed by operating a measuring pump cell 41 in the third inner cavity 61.

[0046] The measuring pump cell 41 measures the NOx concentration in the sample gas within the third inner cavity 61. The measuring pump cell 41 is an electrochemical pump cell consisting of a measuring electrode 44, located on the upper surface of the first solid electrolyte layer 4, which faces the third inner cavity 61, the outer pump electrode 23, the second solid electrolyte layer 6, the spacer layer 5, and the first solid electrolyte layer 4. The measuring electrode 44 is a porous cermet electrode made of a material whose reducing capacity for NOx components in the sample gas is increased compared to the inner pump electrode 22. The measuring electrode 44 also acts as an NOx reduction catalyst, reducing NOx present in the atmosphere within the third inner cavity 61.

[0047] The measuring pump cell 41 can pump out oxygen, which is produced as a result of the decomposition of nitrogen oxides in an atmosphere around the measuring electrode 44, and record the amount of oxygen produced as pump current Ip2.

[0048] To detect an oxygen partial pressure around the measuring electrode 44, an electrochemical sensor cell, i.e., an oxygen partial pressure detection sensor cell for measuring pump control 82, is formed from the first solid electrolyte layer 4, the third substrate layer 3, the measuring electrode 44, and the reference electrode 42. A variable current source 46 is controlled according to an electromotive force (voltage V2) detected by the oxygen partial pressure detection sensor cell for measuring pump control 82.

[0049] A sample gas, introduced into the second inner cavity 40, reaches the measuring electrode 44 in the third inner cavity 61 through the fourth diffusion control section 60 under a set oxygen partial pressure. Nitrogen oxides in the sample gas around the measuring electrode 44 are reduced (2 NO → N2 + O2), thus generating oxygen. The generated oxygen is pumped through the measuring pump cell 41. The voltage Vp2 of the variable current source 46 is controlled such that the voltage V2, detected by the oxygen partial pressure sensor cell for pump control 82, remains constant (target value). The amount of oxygen generated around the measuring electrode 44 is proportional to the concentration of nitrogen oxides in the sample gas, so the nitrogen oxide concentration in the sample gas is calculated using the pump current Ip2 in the measuring pump cell 41.

[0050] When an oxygen partial pressure detection device is formed as an electrochemical sensor cell by combining the measuring electrode 44, the first solid electrolyte layer 4, the third substrate layer 3 and the reference electrode 42, an electromotive force can be detected which is the difference between the amount of oxygen produced by the reduction of the NOx component in the atmosphere around the measuring electrode 44 and the amount of oxygen contained in the reference gas, and accordingly the concentration of the NOx component in the gas being measured can be determined.

[0051] Furthermore, an electrochemical sensor cell 83 is formed from 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, and an oxygen partial pressure in a sample gas outside the sensor can be detected using an electromotive force (voltage Vref) obtained by the sensor cell 83.

[0052] In the gas sensor 100 with such a configuration, a sample gas, whose oxygen partial pressure is maintained at a constant, unchanged, low value (a value that does not substantially affect the NOx measurement), is supplied to the measuring pump cell 41 by operating the main pump cell 21 and the auxiliary pump cell 50. Therefore, a NOx concentration in the sample gas can be determined according to a pump flow Ip2, which flows through the measuring pump cell 41 as a result of the pumping out of oxygen generated by the reduction of NOx, essentially proportional to the NOx concentration in the sample gas.

[0053] The sensor element 101 comprises the heating element section 70, which plays a role in temperature control for maintaining the temperature of the sensor element 101 by heating it to increase the oxygen ion conductivity of the solid electrolyte. The heating element section 70 comprises a heating element connector electrode 71, a heating element 72, a through-hole 73, a heating element insulating layer 74, and a pressure relief hole 75.

[0054] The heating device connector electrode 71 is an electrode configured to be in contact with the lower surface of the first substrate layer 1. The connection of the heating device connector electrode 71 to a heating device power source 76 (see the Fig. 2) enables the supply of electric current from the heating device power source 76 to the heating device section 70.

[0055] The heating element 72 is an electrical resistor configured such that it is surrounded on its lower and upper sides by the second substrate layer 2 and the third substrate layer 3. The heating element 72 is connected to the heating element connector electrode 71 via the through-hole 73 and is supplied with electric current from a heating element power source 76, thus generating heat to raise and maintain the temperature of the solid electrolyte that forms the sensor element 101.

[0056] The heating device 72 is embedded in the entire area from the first inner cavity 20 to the third inner cavity 61 and can set the entire sensor element 101 to a temperature at which the solid electrolyte is activated.

[0057] The heating element insulating layer 74 is an electrically insulating layer formed from an insulating material, such as aluminum oxide, on the upper and lower surfaces of the heating element 72. The heating element insulating layer 74 is designed to provide electrical insulation between the second substrate layer 2 and the heating element 72, and between the third substrate layer 3 and the heating element 72.

[0058] The pressure relief hole 75 is a section provided such that it extends through the third substrate layer 3 and the reference gas inlet layer 48 and communicates with the reference gas inlet chamber 43. The pressure relief hole 75 is provided to mitigate an increase in internal pressure resulting from an increase in temperature in the heating device insulation layer 74.

[0059] As it is in the Fig. As shown in Figure 4, the control device 95 comprises the variable current sources 24, 46 and 52 described above, the heating device current source 76 described above, and a control unit 96. The control unit 96 is a microprocessor comprising a CPU 97, a memory unit 98, etc. The memory unit 98 is a non-volatile memory that can be overwritten with information and can, for example, store various programs and various data.The control device 96 is designed to receive the voltage V0 of the oxygen partial pressure sensing sensor cell for the main pump control 80, the voltage V1 of the oxygen partial pressure sensing sensor cell for the auxiliary pump control 81, the voltage V2 of the oxygen partial pressure sensing sensor cell for the measuring pump control 82, the voltage Vref of the sensor cell 83, the pump current Ip0 flowing through the main pump cell 21, the pump current Ip1 flowing through the auxiliary pump cell 50, and the pump current Ip2 flowing through the measuring pump cell 41. The control device 96 is designed to output control signals to the variable current sources 24, 46 and 52 and consequently to control the voltages Vp0, Vp1 and Vp2, which are to be output by the variable current sources 24, 46, and 52, thereby controlling the main pumping cell 21, the measuring pumping cell 41 and the auxiliary pumping cell 50.The control unit 96 is configured to output a control signal to the heating device power source 76, thereby controlling the electrical current supplied from the heating device power source 76 to the heating device 72. The memory unit 98 further stores target values ​​V0*, V1*, V2*, and the like, which are described below. The CPU 97 of the control unit 96 is configured to refer to the target values ​​V0*, V1, and V2* and consequently controls the pump cells 21, 41, and 50.

[0060] The control unit 96 performs an auxiliary pump control process by controlling the auxiliary pump cell 50 such that the oxygen concentration in the second inner cavity 40 reaches a target concentration. Specifically, the control unit 96 controls the auxiliary pump cell 50 by regulating the voltage Vp1 of the variable current source 52 such that the voltage V1 reaches a constant value (referred to as the target value V1*). The target value V1* is defined as the value that causes the oxygen concentration in the second inner cavity 40 to reach a predetermined low oxygen concentration, which does not substantially affect the NOx measurement.

[0061] The control unit 96 performs a main pump control operation of the main pump cell 21 such that the pump current Ip1, which flows when the oxygen concentration in the second inner cavity 40 is set by the auxiliary pump cell 50 in the auxiliary pump control operation, reaches a target current (referred to as target value Ip1*). In particular, the control unit 96 sets (regulates) a target value (referred to as target value V0*) of the voltage V0 based on the pump current Ip1 such that the pump current Ip1, whose flow is caused by the voltage Vp1, reaches the constant target current Ip1*. The control unit 96 then regulates the voltage Vp0 of the variable current source 24 such that the voltage V0 reaches the target value V0* (in other words, the oxygen concentration in the first inner cavity 20 reaches the target concentration).The gradient of the oxygen partial pressure in the sample gas, which is to be introduced from the third diffusion control section 30 into the second inner cavity 40, is kept constant by the main pump control process. The target value V0* is set to a value that causes the oxygen concentration in the first inner cavity 20 to be higher than 0%, thus achieving a low oxygen concentration. The pump current Ip0, which flows during the main pump control process, varies according to the oxygen concentration in the sample gas (i.e., the sample gas in the vicinity of the sensor element 101) that flows through the gas inlet opening 10 into the sample gas flow section. Consequently, the control device 96 can also detect the oxygen concentration in the sample gas based on the pump current Ip0.

[0062] The main pump control process and the auxiliary pump control process described above are collectively referred to as the adjustment pump control process. The first inner cavity 20 and the second inner cavity 40 are collectively referred to as the oxygen concentration adjustment chamber. The main pump cell 21 and the auxiliary pump cell 50 are collectively referred to as the adjustment pump cell. The control device 96 performs the adjustment pump control process, such that the adjustment pump cell adjusts the oxygen concentration in the oxygen concentration adjustment chamber.

[0063] Furthermore, the control unit 96 performs a measuring pump control process of controlling the measuring pump cell 41 such that the voltage V2 reaches a constant value (referred to as the target value V2*) (in other words, so that the oxygen concentration in the third inner cavity 61 reaches a predetermined low concentration). Specifically, the control unit 96 controls the measuring pump cell 41 by regulating the voltage Vp2 of the variable current source 46 such that the voltage V2 reaches the target value V2*. Oxygen is pumped out of the third inner cavity 61 by the measuring pump control process.

[0064] The execution of the measuring pump control process causes oxygen to be pumped out of the third inner cavity 61, so that the oxygen produced in the third inner cavity 61 due to the reduction of NOx in the gas of the sample becomes essentially zero. The control device 96 receives a pump flow rate Ip2 as a detected value, which corresponds to the oxygen produced in the third inner cavity 61 from the specific gas (in this case NOx), and calculates the NOx concentration in the gas of the sample based on the pump flow rate Ip2.

[0065] The storage unit 98 stores a relational expression (for example, an expression of a linear or quadratic function) or a characteristic map as a correspondence between the pump current Ip2 and the NOx concentration. Such a relational expression or characteristic map can be determined in advance through an experiment.

[0066] The control unit 96 performs a heating device control process of controlling the heating device 72 by outputting a control signal to the heating device power source 76 such that the temperature of the heating device 72 reaches a target temperature (for example, 800°C). The temperature of the heating device 72 can be expressed as a linear function of its resistance value. Consequently, in the heating device control process, the control unit 96 calculates the resistance value of the heating device 72 as a value (a value that can be converted into temperature) which is considered the temperature of the heating device 72, and controls the heating device power source 76 such that the calculated resistance value reaches a target resistance value (a resistance value that corresponds to the target temperature).The control unit 96 receives, for example, the voltage and current flowing through the heating device 72 and can calculate the resistance of the heating device 72 based on these values. The control unit 96 can calculate the resistance of the heating device 72, for example, using a 3-terminal or a 4-terminal method. When an electric current is passed through the heating device 72, the heating device power source 76 adjusts the electric current supplied to the heating device 72 by changing the voltage applied to the heating device 72, for example, based on a control signal from the control unit 96.

[0067] The control device 95, including the variable current sources 24, 46 and 52, the heating device current source 76, etc., which are located in the Fig. As shown in Figure 4, in practice each electrode within the sensor element 101 is connected via connecting wires not shown, which are formed within the sensor element 101, and the connecting electrodes not shown (only the heating device connecting electrode 71 is shown in the Fig. 1 shown), which are formed on the rear end side of the sensor element 101, connected.

[0068] The first diffusion control section 11 is described in detail below. The first diffusion control section 11 is provided on the upstream side of the first inner cavity 20, the second inner cavity 40, and the third inner cavity 61 of the sample gas flow section. As described above, the first diffusion control section 11 comprises diffusion control section 11a and diffusion control section 11b. As described in the Fig. As shown in Figure 2, the diffusion control section 11a has the first spatial section or free space section 85a and a first porous body 87a, and the diffusion control section 11b has a second spatial section or free space section 85b and a second porous body 87b. In the Fig. In Figure 1, the first porous body 87a and the second porous body 87b are omitted from the drawing. The first and second spatial sections 85a and 85b, as well as the first and second porous bodies 87a and 87b, allow the gas of the measured object to flow in the front-to-back direction (first direction). Since, in the present embodiment, the diffusion control section 11b (the second spatial section 85b and the second porous body 87b) has the same structure as the diffusion control section 11a (the first spatial section 85a and the first porous body 87a), a detailed description of the diffusion control section 11b is omitted, and the diffusion control section 11a is described.

[0069] The first porous body 87a is positioned such that it occupies a portion of the cross-section of the diffusion control section 11a perpendicular to the front-to-back direction. The first porous body 87a allows the gas of the sample to pass through it. The first spatial section 85a is a portion of the cross-section perpendicular to the front-to-back direction of the diffusion control section 11a that is not occupied by the first porous body 87a. The first porous body 87a is positioned such that it occupies the lower half of the diffusion control section 11a, and the first spatial section 85a is the upper half of the diffusion control section 11a. The diffusion control section 11a, the first spatial section 85a, and the first porous body 87a each have a cross-section perpendicular to the front-to-back direction that is approximately rectangular. The term "rectangle" refers to a quadrilateral in which all four angles are equal, and includes a square.In the present embodiment, the diffusion-adjusting section 11a, the first space section 85a, and the first porous body 87a each have a cross-sectional shape perpendicular to the front-back direction, with a length in the left-right direction that is greater than its length in the top-bottom direction. The first porous body 87a can be provided in the diffusion-adjusting section 11a such that it occupies 30% to 70% of the cross-section perpendicular to the front-back direction of the diffusion-adjusting section 11a. In the present embodiment, as shown in the... Fig. As shown in Figure 5, the first porous body 87a occupies 50% of the cross-section of the diffusion control section 11a. In the present embodiment, the first porous body 87a extends from the front end to the rear end of the diffusion control section 11a. Furthermore, the first space section 85a and the first porous body 87a each have the shape shown in Figure 5. Fig. 5 is shown in the cross-section perpendicular to the front-back direction at each section of the diffusion adjustment section 11a in the front-back direction.

[0070] The first porous body 87a is formed from a porous ceramic body, such as a porous aluminum oxide body, a porous zirconium oxide body, a porous spinel body, a porous cordierite body, a porous titanium oxide body, and a porous magnesium oxide body. In the present embodiment, it is assumed that the first porous body 87a is formed from a porous aluminum oxide body.

[0071] In this way, since the diffusion control section 11a comprises the first spatial section 85a and the first porous body 87a, the flow velocity of the gas of the sample passing through the first porous body 87a can be set differently from the flow velocity of the gas of the sample passing through the first spatial section 85a in the cross-section of the diffusion control section 11a perpendicular to the front-to-back direction. In particular, the gas of the sample passing through the first porous body 87a has a lower flow velocity than the gas of the sample passing through the first spatial section 85a. This can cause turbulence in the gas of the sample after it has passed through the first spatial section 85a and the first porous body 87a.In the present embodiment, since the gas of the sample that has passed through the first chamber section 85a and the gas of the sample that has passed through the first porous body 87a merge in the buffer chamber 12 downstream of the diffusion control section 11a, turbulence can occur in the gas of the sample in the buffer chamber 12. It is possible to increase the pressure drop of the gas of the sample due to this turbulence. Similarly, the pressure drop of the gas of the sample through the diffusion control section 11b, which comprises the second chamber section 85b and the second porous body 87b, can be increased. These features reduce the effect of the dynamic pressure of the gas of the sample on the main pump cell 21, which includes the inner pump electrode 22 located downstream of the diffusion control section 11.For example, even if the composition of the gas being measured is identical, the operation of the main pump cell 21 (e.g., the value of the pump current Ip0 flowing through the main pump cell 21, etc.) can differ if the dynamic pressure of the gas being measured differs. As a result, the dynamic pressure of the gas being measured can impair the accuracy of measuring the concentration of a specific gas. In contrast, in the first diffusion control section 11 of the present embodiment, the pressure drop of the gas being measured through the first and second chamber sections 85a and 85b and the first and second porous bodies 87a and 87b is increased, thereby reducing the effect of the dynamic pressure of the gas being measured on the main pump cell 21.Furthermore, since not only the main pump cell 21, but also the auxiliary pump cell 50 and the measuring pump cell 41 have auxiliary pump electrodes 51 and measuring electrodes 44 located downstream of the first diffusion control section 11, the effects of the dynamic pressure of the gas of the object being measured on the auxiliary pump cell 50 and the measuring pump cell 41 can also be reduced.

[0072] It is sufficient if the first porous body 87a allows the gas of the sample to pass through it; however, the porosity of the first porous body 87a can be, for example, 10% or more. The porosity of the first porous body 87a can be 15% or less. If the porosity of the first porous body 87a is 15% or less, the flow velocity of the gas of the sample passing through the first porous body 87a can be made more different from the flow velocity of the gas of the sample passing through the first space section 85a, and the pressure drop of the gas of the sample after passing through can be further increased. The same applies to the porosity of the second porous body 87b.

[0073] The first space section 85a, the second space section 85b, the first porous body 87a and the second porous body 87b of the first diffusion control section 11 are located in the same cross-section perpendicular to the front-to-back direction and form flow paths that are parallel to each other. Furthermore, the gas of the sample that has passed through the diffusion control section 11a and the gas of the sample that has passed through the diffusion control section 11b merge in the buffer space 12 downstream of the first diffusion control section 11.

[0074] The following is an example of the process for manufacturing the sensor element 101, which is incorporated into the gas sensor 100. First, six uncalcined ceramic green layers, each containing an oxygen-ion-conducting solid electrolyte, are produced as a ceramic component. In each of these green layers, a plurality of layer holes for use in positioning during printing or stacking, as well as necessary through-holes and the like, are provided beforehand. Furthermore, the green layer that is to become the spacer layer 5 is pre-treated by a punching operation or the like, in which a space is provided that is to become the gas flow section of the measured object.In particular, by punching out the green layer, which is to become the spacer layer 5, such that the parts intended to become the first to fourth bridging sections 5a to 5d are left intact, spaces are formed that are to become the buffer space 12, the first inner cavity 20, the second inner cavity 40, and the third inner cavity 61. Similarly, the green layer, which is to become the first solid electrolyte layer 4, is subjected to a process to provide a space that is to become the reference gas introduction space 43. Then, a structural printing process and a drying process are carried out to form various structures in the ceramic green layers corresponding to the first substrate layer 1, the second substrate layer 2, the third substrate layer 3, the first solid electrolyte layer 4, the spacer layer 5, and the second solid electrolyte layer 6.Specific structures to be formed include, for example, structures that serve as electrodes, such as the measuring electrode 44 described above, the connecting wires attached to the electrodes, the connecting electrodes, such as the heating device connecting electrode 71, the reference gas introduction layer 48, and the heating device section 70. The structure printing process, in which a structure-forming paste, prepared according to the properties required for an object to be formed, is applied to a green layer using a known screen printing technique, is carried out. The drying process is carried out using a known drying technique.Once the structure formation and drying processes are complete, a printing and drying process is performed in which a bonding paste is printed and dried to stack and bond the green layers corresponding to the respective layers. A stacking process is then carried out in which the green layers coated with the bonding paste are stacked in a predetermined sequence while positioned at the layer holes. Next, a pressure bonding process is performed in which the stacked green layers are subjected to predetermined temperature and pressure conditions, causing them to press-bond into a single layer body. The resulting layer body contains a plurality of sensor elements 101. The layer body is then cut into pieces, each the size of a sensor element 101.Then a calcination process is carried out in which the layered body is calcined at a predetermined calcination temperature, resulting in a sensor element 101.

[0075] The following describes a method for manufacturing the first diffusion control section 11 of the sensor element 101. Fig. Figure 6 is a partial cross-sectional view showing a process for manufacturing the diffusion control section 11a. Since the diffusion control section 11b can be manufactured using the same process as the diffusion control section 11a, a detailed description of a process for manufacturing the diffusion control section 11b is omitted, and a process for manufacturing the diffusion control section 11a is described. First, as shown in the Fig. As shown in Figure 6A, in the structure printing process described above, a porous material layer 187a, which is to become the first porous body 87a, is printed and formed on the upper surface of a bridging section 105a (corresponding to the first bridging section 5a) of a green layer 105, which is to become the spacer layer 5. The porous material layer 187a is formed, for example, using a paste containing the material of the first porous body 87a described above (aluminum oxide in the present embodiment), a pore-forming material, a solvent, a binder, etc. The porosity of the first porous body 87a can be adjusted by changing the proportion of the pore-forming material contained in the porous material layer 187a. Next, a vanishing or volatile material layer 185a is printed and formed on the upper surface of the porous material layer 187a.The vanishing material layer 185a is a layer for forming the first spatial section 85a and is formed using a paste containing a material that burns in the calcination process described above (e.g., theobromine, etc.). After printing in this manner, the stacking process described above is carried out, whereby a green layer 106, which is to become the second solid electrolyte layer 6, is stacked on the vanishing material layer 185a, as shown in the figure. Fig. 6A is shown.

[0076] The layered body is formed by carrying out the pressure bonding process described above, starting from the one in the Fig. The state shown in 6A is produced, leading to the state shown in the Fig. 6B is shown. In the layered body, as shown in the Fig. As shown in Figure 6B, since the green layers 105 and 106 are softer than the porous material layer 187a and the vanishing material layer 185a, the upper surface of the green layer 105 and the lower surface of the green layer 106 are recessed, and the green layers 105 and 106 surround these layers from above, below, left, and right. The viscosity (hardness) of the green layers 105 and 106 can be adjusted, for example, by the type or proportion of a binder and a plasticizer contained in them. The viscosity (hardness) of the porous material layer 187a and the vanishing material layer 185a can be adjusted, for example, by the solids content or the proportion of binder in the paste used for printing these layers. By adjusting their viscosity (hardness), the green layers 105 and 106 can be deepened, as described in the Fig. 6B is shown.

[0077] The layered body is then cut into pieces, each the size of the sensor element 101, and the calcination process described above is carried out on the cut layered body, causing the disappearing material layer 185a to burn away and become the first space section 85a, as described in the Fig. Figure 6C shows that the porous material layer 187a is calcined and becomes the first porous body 87a. The green layer 105, which includes the bridging section 105a, and the green layer 106 are calcined and become the spacer layer 5, which includes the first bridging section 5a and the second solid electrolyte layer 6. In this way, the diffusion-adjusting section 11a is formed with the first space section 85a and the first porous body 87a.

[0078] The relationships between the components in the present embodiment and the components in the present invention are explained below. Layers 1 to 6 according to the present embodiment each correspond to the solid electrolyte layer according to the present invention. The element body 102 corresponds to the element body. The first inner cavity 20, the second inner cavity 40, and the third inner cavity 61 each correspond to the inner cavity. The inner pump electrode 22, the auxiliary pump electrode 51, and the measuring electrode 44 each correspond to the inner electrode. The outer pump electrode 23 corresponds to the outer electrode. The main pump cell 21, the auxiliary pump cell 50, and the measuring pump cell 41 each correspond to the pump cell. The first diffusion control section 11 (diffusion control section 11a and diffusion control section 11b) corresponds to the diffusion control section.The first and second porous bodies 87a and 87b each correspond to the porous body. The first and second spatial sections 85a and 85b each correspond to the spatial section.

[0079] In the sensor element 101, which is incorporated into the gas sensor 100 according to the present embodiment described in detail above, the first diffusion control section 11 comprises the first and second porous bodies 87a and 87b and the first and second spatial sections 85a and 85b, which are provided in at least a portion of the first diffusion control section 11 in the front-to-back direction (first direction). The first and second porous bodies 87a and 87b are positioned such that they occupy portions of the cross-section of the first diffusion control section 11 perpendicular to the front-to-back direction and allow the gas of the object being measured to pass through them. The first and second space sections 85a and 85b comprise the parts of the cross-section that are not occupied by the first and second porous bodies 87a or 87b, and allow the gas of the object to pass through them.As a result, it is possible to differentiate the flow velocities of the sample gas passing through the first and second porous bodies 87a and 87b from the flow velocities of the sample gas passing through the first and second spatial sections 85a and 85b in the cross-section of the first diffusion control section 11 perpendicular to the front-to-back direction. Therefore, turbulence can be induced in the sample gas after passing through, and the pressure drop of the sample gas can be increased. Consequently, the effects of the dynamic pressure of the sample gas on the main pump cell 21, the auxiliary pump cell 50, and the measuring pump cell 41, located downstream of the first diffusion control section 11, can be reduced.

[0080] Furthermore, since the porosity of the first porous body 87a is 15% or less, the flow velocity of the gas passing through the first porous body 87a can be made more distinct from the flow velocities of the gas passing through the first and second sections 85a and 85b, and the pressure drop of the gas after passing through can be increased. The same advantageous effect can be obtained if the porosity of the second porous body 87b is 15% or less.

[0081] It should be noted that the present invention is by no means limited to the embodiment described above and can of course be implemented in various modes within the technical scope of the present invention.

[0082] For example, in the embodiment described above, the diffusion control section 11a has a first spatial section 85a and a first porous body 87a, but at least one of the spatial section and the porous body can be provided in a plurality. For example, as shown in the Fig. As shown in Figure 7, the diffusion control section 11a comprises spatial sections 85a1 and 85a2 and porous bodies 87a1 and 87a2, which are arranged alternately in the left-right direction. A majority of the spatial sections 85a1 and 85a2 are located in the same cross-section perpendicular to the front-back direction and form flow paths that are parallel to each other. A majority of the porous bodies 87a1 and 87a2 are located in the same cross-section perpendicular to the front-back direction and form flow paths that are parallel to each other.

[0083] In the foregoing embodiment, the first spatial section 85a and the first porous body 87a each have a cross-section perpendicular to the front-back direction, which is approximately rectangular; however, the present invention is not limited thereto. For example, an embodiment can be used which in the Fig. 8 is shown. In the Fig. In Figure 8, the first spatial section 85a and the first porous body 87a each have a cross-section perpendicular to the front-back direction, which has the shape of a rectangle with curved long sides. In particular, the first spatial section 85a has, in a cross-section perpendicular to the front-back direction, the first to fourth sections 86a to 86d as an outer perimeter of the cross-section. The first section 86a, the second section 86b, the third section 86c, and the fourth section 86d correspond to the top, bottom, left, and right sides of the outer perimeter of the cross-section of the first spatial section 85a. The first section 86a and the second section 86b are oriented towards each other in the top-bottom direction (the layering direction) and each extend along the left-right direction (the second direction).The third section 86c and the fourth section 86d are oriented towards each other in the left-right direction and each extend along the top-bottom direction. The first section 86a and the second section 86b each have a curved shape. The first section 86a and the second section 86b are each curved such that they form a convex shape on the same side in the top-bottom direction (in this case, the bottom side). The third section 86c and the fourth section 86d each have a straight shape along the top-bottom direction. The cross-section of the first spatial section 85a has a length in the left-right direction that is greater than a length in the top-bottom direction. The first porous body 87a is also shaped according to the first spatial section 85a.Furthermore, the entirety of the diffusion adjustment section 11a also has a cross-section perpendicular to the front-back direction, which has the shape of a rectangle with curved long sides corresponding to the first space section 85a and the first porous body 87a.

[0084] In the embodiment described in the Fig. As shown in Figure 8, the element body 102 has a structural section 88 that forms at least part of the outer circumference of the diffusion control section 11a (an outer wall of the diffusion control section 11a). The structural section 88 has a first structural section 88a, a second structural section 88b, and a third structural section 88c. The first structural section 88a is provided on the lower surface of the second solid electrolyte layer 6. The first structural section 88a is thin at both its left and right ends in the cross-section perpendicular to the front-back direction and becomes thicker towards the center in the left-right direction. As a result of this construction, a lower surface of the first structural section 88a is curved in such a way that the lower surface has a convex shape in the downward direction, thereby forming a top surface of the diffusion setting section 11a, i.e., the first section 86a of the first spatial section 85a.The second structural section 88b and the third structural section 88c are provided on the upper surface of the spacer layer 5. The second structural section 88b is thick at its left end in the cross-section perpendicular to the front-back direction and becomes thinner towards the center of the first spatial section 85a in the left-right direction. The third structural section 88c is thick at its right end in the cross-section perpendicular to the front-back direction and becomes thinner towards the center of the first spatial section 85a in the left-right direction. Due to these configurations, the upper surfaces of the second structural section 88b and the third structural section 88c are curved as a whole, so that the upper surfaces have a convex shape in the downward direction, thus forming the shape of a lower side of the diffusion-adjusting section 11a, i.e., a shape of a lower side of the first porous body 87a.The left and right sides of the diffusion control section 11a (including the third section 86c and the fourth section 86d of the first spatial section 85a), which has a straight shape, are not formed by the structural section 88, but by the spacer layer 5 and the second solid electrolyte layer 6, respectively. The structural section 88 is made of a high-density material that prevents the gas of the measured object from flowing through it and, in the present embodiment, is made of an aluminum oxide ceramic. The first spatial section 85a, the first porous body 87a, and the structural section 88 each have the same shape (the shape shown in the figure). Fig. 8 is shown) in the cross-section perpendicular to the front-back direction at every section in the front-back direction.

[0085] In the Fig. 8 The cross-section of the first spatial section 85a has a predetermined shape perpendicular to the front-back direction, the outer perimeter of which is longer than that of a reference rectangle. The reference rectangle is defined by means of the Fig. 9 described. First, it is assumed that a circumscribed rectangle R of the cross-section of the first space section 85a is formed from two sides parallel to the top-bottom direction and two sides parallel to the left-right direction (upper part of Fig. 9) Next, the circumscribed rectangle R is modified by shortening the short sides while maintaining the length of the long sides, so that the area is identical to that of the cross-section of the first space section 85a, and the resulting rectangle is designated as the reference rectangle S1 (lower part of Fig. 9) If the circumscribed rectangle R is a square, it is sufficient to shorten either any two sides parallel to the top-bottom direction or the two sides parallel to the left-right direction within the circumscribed rectangle R. The reference rectangle S1 has a shape corresponding to the conventional cross-sectional shape (rectangle) of the space of the diffusion adjustment section 11a and is a rectangle with the same cross-sectional area as the first space section 85a, so that it can be compared with the first space section 85a. The cross-sectional area of ​​the first space section 85a is identical to that of the reference rectangle S1, and unlike the reference rectangle S1, the first section 86a and the second section 86b each have a curved shape, so that the length of the outer perimeter of the first space section 85a is greater than that of the reference rectangle S1.Furthermore, the length of the outer perimeter of the first spatial section 85a can be made larger the greater the degree of curvature of the first section 86a and the second section 86b. Since the cross-sectional shape of the first spatial section 85a is the specified shape with a longer outer perimeter than that of a reference rectangle, the hydraulic diameter of the first spatial section 85a is smaller than the hydraulic diameter of the reference rectangle S1. The hydraulic diameter is expressed as four times the value obtained by dividing the cross-sectional area by the wetted perimeter (i.e., the length of the outer perimeter of the cross-section) (hydraulic diameter = cross-sectional area / wetted perimeter x 4).Since the cross-sectional area of ​​the first space section 85a is identical to that of the reference rectangle S1, if the length of the outer circumference of the first space section 85a (the sum of the lengths of the first to fourth sections 86a to 86d) is greater than the length of the outer circumference of the reference rectangle S1, the hydraulic diameter of the first space section 85a will be smaller than that of the reference rectangle S1. Furthermore, the small hydraulic diameter increases the pressure drop of the gas used in the measurement as it passes through the first space section 85a. Therefore, in the diffusion control section 11a of . Fig. 8 The diffusion control section 11a not only comprises a first space section 85a and a first porous body 87a, but also has the cross-sectional shape perpendicular to the front-back direction of the first space section 85a, which is the predetermined shape, so that the effect of the dynamic pressure of the gas used in the measurement on the main pump cell 21, the auxiliary pump cell 50, and the measuring pump cell 41, which is located downstream of the diffusion control section 11a, can be reduced. In the embodiment in the Fig. 8 The first porous body 87a and the entirety of the diffusion adjustment section 11a each also have a cross-section perpendicular to the front-back direction, which has the specified shape according to the first space section 85a.

[0086] Furthermore, the pressure drop can also be increased by reducing the cross-sectional area of ​​the first chamber section 85a. For example, even if the shape of the cross-section of the first chamber 85a is made smaller than its cross-sectional area, while maintaining the same rectangular shape as the reference rectangle S1, the pressure drop will be higher than that of the reference rectangle S1. However, if the cross-sectional area is reduced, the flow velocity of the gas passing through the first chamber section 85a will decrease, and, for example, the pump currents Ip0, Ip1, and Ip2 flowing through the main pump cell 21, the auxiliary pump cell 50, and the measuring pump cell 41 downstream of the first diffusion control section 11 will always be in the range of small values, and the detection accuracy of the concentration of a specific gas by the gas sensor 100 may decrease.In contrast, the diffusion control section 11a, which is located in the . Fig. As shown in Figure 8, the cross-sectional area of ​​the first chamber section 85a has a predetermined shape, so that the pressure drop can be increased without reducing the cross-sectional area of ​​the first chamber section 85a compared to conventional shapes, such as the reference rectangle S1. Therefore, the effects exerted on the main pump cell 21, etc., by the dynamic pressure of the gas in the sample can be reduced, while maintaining the flow velocity of the gas in the sample passing through the diffusion control section 11a.

[0087] Furthermore, a definition that differs from that of the reference rectangle S1, which is in the Fig. As shown in 9, the definition of the reference rectangle is different from that used. For example, as shown in the Fig. As shown in 10, the reference rectangle S2 (lower part of Fig. 10) be a rectangle obtained by deforming the circumscribed rectangle R so that it is identical to the cross-sectional area of ​​the first space section 85a (upper part of Fig. 10) Alternatively, the circumscribed rectangle R can be a reference rectangle S3 (not shown in the figure) in which the length of each side has been modified so that the area is identical to that of the cross-sectional area of ​​the first space section 85a and the overlap area with the cross-sectional area of ​​the first space section 85a is maximized. It should be noted that the reference rectangle S3 may ultimately have the same shape as the reference rectangle S1 or the reference rectangle S2.If the cross-sectional shape perpendicular to the front-back direction of the first space section 85a is a predetermined shape with a longer outer circumference than at least one of the reference rectangles S1 to S3 defined in this way, the hydraulic diameter of the first space section 85a will be smaller than that of the reference rectangle, and it can be assumed that the first space section 85a has a shape that causes a higher pressure drop for the gas of the sample passing through it. In the first space section 85a, which is in the . Fig. As shown in Figure 8, the degree of curvature of the first section 86a and the second section 86b is determined such that the cross-sectional shape of the first spatial section 85a has a predetermined shape with a longer outer perimeter than any of the reference rectangles S1 to S3.

[0088] The following describes a method for manufacturing the diffusion control section 11a in the Fig. 8 with reference to the Fig. 11 described. First, as described in the Fig. As shown in Figure 11A, in the structure printing process described above, a second structural material layer 188b and a third structural material layer 188c, which are to become the second structural section 88b and the third structural section 88c respectively, are printed and formed on the upper surface of a bridging section 105a (corresponding to the first bridging section 5a) of a green layer 105, which is to become the spacer layer 5. The second structural material layer 188b and the third structural material layer 188c are formed using a paste that contains, for example, aluminum oxide as a ceramic component. The second structural material layer 188b and the third structural material layer 188c can also be a paste made of the same material as the porous material layer 187a, except that the paste does not contain any pore-forming material.The second structural material layer 188b and the third structural material layer 188c are designed such that they tend to become thinner towards the center in the left-right direction, so that their upper surfaces will have a shape corresponding to the curved shape of the lower side of the first porous body 87a and the second section 86b of the first spatial section 85a after the pressure bonding process. Fig. 11A, the second structural material layer 188b and the third structural material layer 188c are formed at the positions corresponding to the left and right ends, respectively, of the diffusion-adjusting section 11a on the upper surface of the first bridging section 5a, and no structural material layer is formed in the area around the center of the diffusion-adjusting section 11a in the left-right direction. Next, a porous material layer 187a is printed and formed on the upper surface of the green layer 105 in an area from a left edge of the second structural material layer 188b to a right edge of the third structural material layer 188c, and a vanishing material layer 185a is formed on the upper surface of the porous material layer 187a. Then, a first structural material layer 188a, which is to become the first structural section 88a, is printed and formed on an upper surface of the vanishing material layer 185a.The first structural material layer 188a is formed using a paste containing aluminum oxide as a ceramic component, in the same manner as the second structural material layer 188b and the third structural material layer 188c. The first structural material layer 188a is designed such that it tends to become thicker towards the center in the left-right direction, so that a lower surface of the first structural material layer 188a will have a shape corresponding to the curved shape of the first section 86a of the first spatial section 85a after the pressure joining process. Fig. 11A, the width of the first structural material layer 188a in the left-right direction is made smaller than the width of the vanishing material layer 185a in the left-right direction, and the first structural material layer 188a is not formed in positions corresponding to the left and right ends of the first spatial section 85a. After printing in this manner, the stacking process described above is carried out, whereby a green layer 106, which is to become the second solid electrolyte layer 6, is stacked on the first structural material layer 188a, as described in the Fig. 11A is shown.

[0089] The layered body is formed by carrying out the pressure bonding process described above, starting from the one in the Fig. The state shown in 11A is produced, leading to the state shown in the Fig. 11B is shown. In the layered body, as shown in the Fig. As shown in Figure 11B, the green layer 105 and the green layer 106 are softer than the vanishing material layer 185a, the porous material layer 187a and the first to third structural material layers 188a to 188c, the upper surface of the green layer 105 and the lower surface of the green layer 106 are recessed, and the green layer 105 and the green layer 106 surround these layers from above, below, left and right. Furthermore, the vanishing material layer 185a, the porous material layer 187a and the first to third structural material layers 188a to 188c are deformed by being pushed from above and below through the green layers 105 and 106, whereby the vanishing material layer 185a assumes the shape of the first space section 85a, the porous material layer 187a assumes the shape of the first porous body 87a and the first to third structural material layers 188a to 188c assume the shapes of the first to third structural section 88a to 88c.Furthermore, the viscosity of the first to third structural material layer 188a to 188c can be adjusted using the same procedure as for the porous material layer 187a and the vanishing material layer 185a.

[0090] The layered body is then cut into pieces, each the size of the sensor element 101, and the calcination process described above is carried out on the cut layered body, causing the disappearing material layer 185a to burn away and become the first spatial section 85a, as described in the Fig. Figure 11C is shown. Furthermore, the green layer 105, which includes the bridging section 105a, and the green layer 106 are calcined and become the spacer layer 5, which includes the first bridging section 5a, and the second solid electrolyte layer 6. The porous material layer 187a is calcined and becomes the first porous body 87a. The first to third structural material layers 188a to 188c are calcined and become the first to third structural sections 88a to 88c. In this way, the diffusion-adjusting section 11a with the first spatial section 85a and the first porous body 87a is produced. A diffusion-adjusting section 11a with a first spatial section 85a and a first porous body 87a with a cross-section perpendicular to the front-back direction, having the specified shape, is formed.

[0091] In the Fig. In the embodiment described above, the first section 86a and the second section 86b of the first space section 85a each have the curved shape, but if the cross-sectional shape of the first space section 85a is the predetermined shape described above (the shape with a longer outer circumference than at least one of the reference rectangles S1 to S3), the cross-sectional shape of the first space 85a can have different embodiments.

[0092] For example, one of the first section 86a and the second section 86b may have a curved shape, and the other may have a straight shape. In a diffusion adjustment section 11a according to a modification described in the Fig. As shown in Figure 12, the first part 86a has a curved shape and the second part 86b has a straight shape. In the Fig. 12. A first porous body 87a has a straight upper side and a curved lower side. The diffusion control section 11a in the Fig. 12 can be achieved, for example, by forming the vanishing material layer 185a such that its thickness tends to decrease towards the center in the left-right direction, and by forming the porous material layer 187a such that its thickness tends to increase towards the center in the left-right direction, in the Fig. 11A can be formed. For example, by forming the vanishing material layer 185a by printing it several times and by forming the central section of the vanishing material layer 185a in the left-right direction with shorter printing times than the other sections, the thickness of the vanishing material layer 185a can be made partially different, so that the thickness at the central section in the left-right direction is less.

[0093] In the Fig. 8. The overall shape of the first section 86a of the first spatial section 85a in the embodiment described above is the curved shape; however, at least a part of the first section 86a may have a curved shape, such as a combination of straight and curved shapes. The same applies to the second section 86b. Although the first section 86a and the second section 86b in the Fig. 8 each are curved such that they each have a convex shape in the downward direction, at least one of them can be curved such that it has a convex shape in the upward direction. Although the first section 86a and the second section 86b in the Fig. 8 each have a convex shape on the same side in the top-bottom direction, the present invention is not limited to this embodiment, and, for example, as described in the Fig. As shown in Figure 13, the first section 86a and the second section 86b each have a convex shape on one side, approaching each other in the top-bottom direction. As shown in the Fig. As shown in Figure 14, the first section 86a and the second section 86b can each have a convex shape on one side where they are separated from each other in the top-bottom direction. At least a part of the first section 86a and / or at least a part of the second section 86b can each have a polygonal line shape instead of a curved shape. For example, as shown in the Fig. As shown in Figure 15, the first section 86a can be configured as a polygonal linear shape with two curved sections, and the second section 86b can be configured as a straight shape. Even in these embodiments, since the cross-section perpendicular to the front-back direction of the first spatial section 85a has the predetermined shape described above (the shape with a longer outer circumference than at least one of the reference rectangles S1 to S3), the effect of the dynamic pressure of the gas in the measuring object on the main pumping cell 21, etc., which is located downstream of the diffusion control section 11a, can be further reduced. Fig. 15 the shape of the cross-section perpendicular to the front-back direction of the first spatial section 85a is formed into a polygonal shape (here a hexagonal shape) with five or more sides.

[0094] The embodiment, which is in the Fig. As shown in 16, it can be used. In the embodiment of Fig. 16 The sensor element 101 comprises a structural section 88 corresponding to that of Fig. 12, and the diffusion control section 11a comprises space sections 85a1 and 85a2 arranged alternately in the left-right direction, and porous bodies 87a1 and 87a2 as shown in the Fig. 7. In the diffusion control section 11a of Fig. 16 Each of the spatial sections 85a1 and 85a2 has a curved shape such that an upper side (first section) and a lower side (second section) thereof each have a convex shape in the downward direction, and has a cross-section perpendicular to the front-back direction, which has the predetermined shape described above. In addition, in the embodiment described in the Fig. As shown in Figure 16, the porous body 87a1 and 87a2 and the entirety of the diffusion adjustment section 11a also have a cross-section perpendicular to the front-back direction, which has the specified shape corresponding to the space sections 85a1 and 85a2.

[0095] The first spatial section 85a described above can be divided into a plurality of spatial sections by the first porous body 87a. For example, as shown in Fig. 17 and Fig. As shown in Figure 18, the first space section 85a is divided into two space sections by the first porous body 87a, i.e., an upper space section 85a1 and a lower space section 85a2. In the Fig. 17. The spatial section 85a1 has a curved shape such that its upper side (first section) has a convex shape in the downward direction, as is the case in the first spatial section 85a in the Fig. 12, and has a cross-section perpendicular to the front-back direction, which has the predetermined shape described above. The upper side of the spatial section 85a1 is formed by the lower surface of the first structural section 88a. The lower side (second part) and the left and right sides of the spatial section 85a1 each have a straight shape. The lower side of the spatial section 85a1 is formed by the upper surface of the first porous body 87a. The spatial section 85a2 has a curved shape such that its lower side (second section) has a convex shape in the upward direction and has a cross-section perpendicular to the front-back direction, which has the predetermined shape described above. The lower side of the spatial section 85a2 is formed by the upper surface of the second structural section 88b.The upper side (first section) and the left and right sides of space section 85a2 each have a straight section. In the . Fig. 18. The spatial section 85a1 has a curved shape such that its upper side (first section) has a convex shape in the upward direction and has a cross-section perpendicular to the front-back direction, which has the predefined shape described above. The upper side of the spatial section 85a1 is formed by the lower surfaces of the first structural section 88a and the fourth structural section 88d. The spatial section 85a2 has a curved shape such that its lower side (second section) has a convex shape in the downward direction and has a cross-section perpendicular to the front-back direction, which has the predefined shape described above. The lower side of the spatial section 85a2 is formed by the upper surfaces of the second structural section 88b and the third structural section 88c. The diffusion control section 11a in the Fig. 18 has the same structure as the diffusion control section 11a in the Fig. 17, with the exception of the points mentioned above. The embodiments of Fig. 7 and Fig. The 16 described above can also be considered as examples of the embodiment in which the first space section 85a is divided into a plurality of space sections by the first porous body 87a.

[0096] In the Fig. In Figure 8, the third section 86c and the fourth section 86d of the first spatial section 85a each have a straight shape along the top-bottom direction in the cross-section perpendicular to the front-back direction; however, the present invention is not limited to this embodiment. For example, a third section 86c and a fourth section 86d can each have a curved shape, as shown in Figure 8. Fig. 19 is shown. In the Fig. 19 The third section 86c and the fourth section 86d each have a convex shape on one side, separating them in the left-right direction. For example, by adjusting the viscosity of the green layers 105 and 106, the vanishing material layer 185a, the porous material layer 187a, and the first to third structural material layers 188a to 188c, which are in the Fig. As shown in Figure 11A, the disappearing material layer 185a, the porous material layer 187a, and the first to third structural layers 188a to 188c are deformed in such a way that they bulge to the left and right during the pressure joining process, and the first spatial section 85a with the shapes of the third section 86c and the fourth section 86d, which are shown in the Fig. The 19 shown can be formed.

[0097] If the cross-sectional shape of the first spatial section 85a is the predetermined shape described above (the shape with a longer outer perimeter than at least one of the reference rectangles S1 to S3), then in the modifications described above, the first spatial section 85a has the first to fourth sections 86a to 86d; however, the present invention is not limited to this embodiment. For example, in the Fig. 14 the first space section 85a does not include the third section 86c and the fourth section 86d and the shape of the outer perimeter of the cross-section of the first space section 85a can be a shape in which the first section 86a and the second section 86b are directly connected at the left and right ends.

[0098] In the embodiment described above, the diffusion control section 11a has the same shape (the shape shown in the Fig. 5) in the cross-section perpendicular to the front-back direction at any section in the front-back direction, however, the diffusion-adjusting section 11a is not limited to this embodiment, and it is sufficient that a first spatial section 85a and a first porous body 87a are present in a cross-section in at least a part of the diffusion-adjusting section 11a in the front-back direction. For example, only a front end section (upstream end) of the diffusion-adjusting section 11a can have the cross-sectional shape shown in the Fig. 5 is shown, and the other sections can have a cross-section perpendicular to the front-back direction without the first porous body 87a, and the entirety of the cross-section can be a spatial section. Similarly, if the cross-section of the first spatial section 85a and the spatial sections 85a1 and 85a2 of the diffusion-adjusting section 11a is formed according to the predetermined shape described above, as shown in Fig. 8 and Fig. As shown in Figures 12 to 19, it is sufficient that the cross-section is formed in at least part of the front-to-back direction according to the specified shape.

[0099] Furthermore, the diffusion control section 11a can be designed such that the cross-sectional area of ​​the cross-section perpendicular to the front-back direction is smaller in at least part of a downstream side of the upstream end than in the upstream end. For example, a structure can be used which in the Fig. 20 is shown. Fig. Figure 20 shows a cross-section of the diffusion control section 11a parallel to the front-back direction. In the Fig. 20 The upper and lower outlines 86e and 86f of the cross-section of the diffusion control section 11a each have a curved shape parallel to the front-back direction, and both outlines 86e and 86f extend in such a way that they are curved with respect to the front-back direction. Furthermore, outlines 86e and 86f each have a convex shape on one side where they approach each other in the top-bottom direction. As a result, the cross-sectional area of ​​the cross-section of the diffusion control section 11a is smallest at its center in the front-back direction, perpendicular to the front-back direction. In this way, the pressure loss of the gas of the object being measured increases as it passes through a section of the diffusion control section 11a with a smaller cross-sectional area than the upstream end (for example, a middle section in the front-back direction).Therefore, this shape of diffusion control section 11a can also reduce the effect of the dynamic pressure of the gas in the measuring object on the main pump cell 21, the auxiliary pump cell 50, and the measuring pump cell 41, which are located downstream of the first diffusion control section 11. The shapes of the outlines 86e and 86f of the diffusion control section 11a in the . Fig. 20 can be set by the forms of the first to third structural sections 88a to 88c according to the forms of the first section 86a and the second section 86b. In the Fig. 20 is not only the entirety of the diffusion adjustment section 11a, but also each of the first space section 85a and the first porous body 87a such that a cross-sectional area of ​​the cross-section perpendicular to the front-back direction is smaller in at least one part of a downstream side of the upstream end than in the upstream end.

[0100] Instead of the embodiment in the Fig. 20 the embodiments in Fig. 21 or Fig. 22 will be deployed. In the Fig. 21 has an outline 86e that has a curved shape, which is formed by joining two outlines 86e of Fig. 20 is formed from front to back, and an outline 86f has a curved shape, which is formed by joining two outlines 86f of Fig. 20 is formed from front to back. Therefore, the outlines 86e and 86f in the Fig. 21 each two sets of convex shapes to one side, where they approach each other in the top-bottom direction. As a result, in the Fig. 21 Two positions where the cross-sectional area of ​​the diffusion adjustment section 11a is smallest perpendicular to the front-back direction, and these two positions are located in the middle of the front-back direction (at positions different from the front end and the back end), and the pressure drop of the gas of the object passing through these two positions increases. In the Fig. 22 The upper and lower outlines 86e and 86f of the cross-section of the diffusion control section 11a each have a curved shape parallel to the front-back direction, and the outlines 86e and 86f both extend such that they are curved with respect to the front-back direction. In addition, the outlines 86e and 86f each have a convex shape on the same side (lower side) in the top-down direction. Furthermore, the outlines 86e and 86f are shaped such that the distance between them in the top-down direction decreases as they approach the rear end relative to the front end. As a result, the diffusion control section 11a has in the Fig. 22 a cross-sectional area of ​​the cross-section perpendicular to the front-back direction, which is smallest at the rear end. In this way, according to the Fig. 22 the pressure loss of the gas of the object being measured, which passes through the rear end of the diffusion control section 11a. In Fig. 21 and Fig. 22 is not only the entirety of the diffusion adjustment section 11a, but also each of the first space section 85a and the first porous body 87a such that a cross-sectional area of ​​the cross-section perpendicular to the front-back direction is smaller in at least a part of a downstream side of the upstream end than in the upstream end.

[0101] The diffusion control section 11a, which is in Fig. Figures 20 to 22 show a first space section 85a and a first porous body 87a in a cross-section perpendicular to the front-back direction in any part of the front-back direction, but there may be a part in which the first porous body 87a is not present in a part of the front-back direction (a part in which only the first space section 85a is present).

[0102] In the embodiment described above, the first diffusion control section comprises diffusion control section 11a, which is provided between the spacer layer 5 and the second solid electrolyte layer 6, and diffusion control section 11b, which is provided between the spacer layer 5 and the second solid electrolyte layer 6. However, the first diffusion control section 11 is not limited to this embodiment, and the first diffusion control section 11 can comprise only one of the diffusion control sections 11a and 11b. Diffusion control section 11a is provided between the spacer layer 5 and the second solid electrolyte layer 6, which are adjacent to each other. However, diffusion control section 11a is not limited to this embodiment.For example, the diffusion control section 11a can be a space formed by punching out any of the layers that make up the element body 102. For example, the sensor element 101 can have a first diffusion control section 211 that is in . Fig. shown in 23 to 25, instead of including the first diffusion adjustment section 11. As shown in Fig. As shown in Figures 23 to 25, the first diffusion adjustment section 211 is formed by punching out the spacer layer 5 in the top-bottom direction. Since the first diffusion adjustment section 211 has a greater length in the top-bottom direction than the diffusion adjustment section 11a of the first diffusion adjustment section 11, its length in the left-right direction is made shorter than that of diffusion adjustment section 11a, so that the cross-sectional area of ​​the first diffusion adjustment section 211 perpendicular to the front-back direction is approximately identical to that of diffusion adjustment section 11. Furthermore, the left-right length of the first diffusion adjustment section 211 is shorter than the left-right length of the buffer space 12 (see Figures 23 to 25). Fig. 24).

[0103] The first diffusion control section 211 has a space section 285 and a porous body 287. As shown in the Fig. As shown in Figure 25, the spatial section 285 and the porous body 287 each have a cross-section perpendicular to the front-back direction, which has the shape of a rectangle with a curved upper side and a curved lower side. In particular, in the cross-section perpendicular to the front-back direction, the spatial section 285 has a first to fourth section 286a to 286d as an outer perimeter of the cross-section. The first section 286a, the second section 286b, the third section 286c, and the fourth section 286d correspond to the upper, lower, left, and right sides of the outer perimeter of the cross-section of the spatial section 285. The first section 286a and the second section 286b are oriented towards each other in the top-bottom direction (the layering direction) and each extend along the left-right direction (the second direction).The third section 286c and the fourth section 286d are directed towards each other in the left-right direction and each extends along the top-bottom direction. The first part 286a and the second part 286b are aligned in the same direction as the first part 86a and the second part 86b. Fig. 8. In particular, the first part 286a and the second part 286b each have a curved shape and are each curved such that they form a convex shape on the same side in the top-bottom direction (in this case, the bottom side). The third section 286c and the fourth section 286d each have a straight shape along the top-bottom direction corresponding to the shapes of the third section 86c and the fourth section 86d in the Fig. 8. The porous body 287 also has the same shape as the space section 285. Furthermore, the entire first diffusion-adjusting section 211 also has a cross-section perpendicular to the front-back direction, which has the shape of a rectangle with a curved top side and a curved bottom side corresponding to the space section 285 and the porous body 287. The shape of the top and bottom sides of the first diffusion-adjusting section 211, i.e., the shape of the first section 286a of the space section 285 and the bottom side of the porous body 287, can be determined by the shapes of a first to third structural section 288a to 288c, which comprises a structural section 288, accordingly. Fig. 8. In particular, the first structural section 288a is provided on the lower surface of the second solid electrolyte layer 6. The first structural section 288a is thin at both its left and right ends in the cross-section perpendicular to the front-back direction and becomes thicker towards the center in the left-right direction. Consequently, the lower surface of the first structural section 288a is curved, so that the lower surface has a convex shape in the downward direction, thus forming the first section 286a of the spatial section 285. The second structural section 288b and the third structural section 288c are provided on the upper surface of the first solid electrolyte layer 4. The second structural section 288b is thick at its left end in the cross-section perpendicular to the front-back direction and becomes thinner towards the center of the spatial section 285 in the left-right direction.The third structural section 88c is thick at its right end in the cross-section perpendicular to the front-back direction and becomes thinner towards the middle of the spatial section 285 in the left-right direction. Due to this type of structure, the upper surface of the second structural section 288b and the upper surface of the third structural section 288c are curved as a whole, so that the upper surfaces have a convex shape in the downward direction, thus forming the shape of the bottom side of the porous body 287. In the . Fig. In Figure 23, structural section 288 is omitted from the illustration. The left and right sides of the first diffusion adjustment section 211 (including the third section 286c and the fourth section 286d of the spatial section 285), each of which has a straight shape, are not formed by structural section 288, but are formed as inner circumferential surfaces (side surfaces) of punched holes formed in the spacer layer 5 (holes that penetrate the spacer layer 5 in the top-bottom direction).This first diffusion control section 211 comprises the space section 285 and the porous body 287 corresponding to the diffusion control section 11a in the embodiment described above, so that the flow velocity of the gas of the object passing through the porous body 287 can be made different from the flow velocity of the gas of the object passing through the space section 285, thereby causing turbulence in the gas of the object after passing through the first diffusion control section 211 and increasing the pressure drop of the gas of the object due to the turbulence of the gas of the object. As in the first diffusion control section 11a in the embodiment described above. Fig. In section 285 of this first diffusion control section 211, the first section 286a and the second section 286b of the cross-section, perpendicular to the front-to-back direction, each exhibit a curved shape. Due to this configuration, the shape of this cross-section is the predetermined shape described above (the shape with a longer outer circumference than at least one of the reference rectangles S1 to S3). As a result, the hydraulic diameter of section 285 becomes smaller than the hydraulic diameter of at least one of the reference rectangles S1 to S3, and consequently, the pressure drop of the gas passing through section 285 is higher. Therefore, the same effect as that of the first section 85a described above can occur. Fig. 8 are obtained. The shapes of the space section 285 and the porous body 287 can assume any of the different embodiments of the first space section 85a and the porous body 87a that have been described above.

[0104] In the embodiment described above, the first diffusion control section 11 comprises the first and second porous bodies 87a and 87b and the first and second spatial sections 85a and 85b, however, the present invention is not limited thereto, and one or more of the first diffusion control section 11, the second diffusion control section 13, the third diffusion control section 30 and the fourth diffusion control section 60 may comprise a porous body and a spatial section.

[0105] In the embodiment described above, each of the front ends of the first diffusion control section 11 is a gas inlet 10, but the present invention is not limited thereto. For example, the first bridging section 5a and the first diffusion control section 11 can be arranged downstream of the gas inlet 10 in the sample gas flow section.

[0106] In the embodiment described above and the Fig. The first diffusion control sections 11 and 211 allow the gas in the sample to flow in a front-to-back direction, but the present invention is not limited to this. For example, the gas inlet 10 can be open on the left or right surface of the element body 102, and the first diffusion control section 11 can allow the gas in the sample to flow in a left-to-right direction. In this case, the left-to-right direction corresponds to the first direction, and the front-to-back direction corresponds to the second direction.

[0107] In the embodiment described above, the outer pump electrode 23 plays a role as the electrode (also referred to as the outer main pump electrode) to be paired with the inner pump electrode 22 in the main pump cell 21, plays a role as the electrode (also referred to as the outer auxiliary pump electrode) to be paired with the auxiliary pump electrode 51 in the auxiliary pump cell 50, and plays a role as the electrode (also referred to as the outer measuring electrode) to be paired with the measuring electrode 44 in the measuring pump cell 41; however, the present invention is not limited thereto. One or more of the outer main pump electrode, the outer auxiliary pump electrode, and the outer measuring electrode can be provided separately from the outer pump electrode 23 on the outer surface of the element body 102 such that they are in contact with the gas being measured.

[0108] In the embodiment described above, the outer pump electrode 23 is exposed outside the sensor element 101; however, the present invention is not limited to this embodiment, and it is sufficient if the outer pump electrode 23 is provided on the outer surface of the element body 102 in such a way that it is in contact with the gas of the object being measured. For example, the sensor element 101 can comprise a porous protective layer that covers the element body 102 and allows the gas of the object being measured to pass through it, and the outer pump electrode 23 can also be covered by the porous protective layer.

[0109] While the sensor element 101, according to the preceding embodiment, is configured to detect the concentration of NOx in the gas being measured, such an embodiment is not limited as long as the sensor element is configured to detect the concentration of any specific gas in the gas being measured. For example, the concentration of any oxide other than NOx can be defined as the concentration of a specific gas. If the specific gas is an oxide, oxygen is produced when the specific gas itself is reduced in the third inner cavity 61, as is the case in the preceding embodiment. Therefore, the measuring pump cell 41 can detect the concentration of a specific gas by detecting a value (for example, the pump current Ip2) corresponding to the oxygen. Alternatively, the specific gas can be a non-oxide, such as ammonia.If the specific gas is a non-oxide, it is converted into an oxide (e.g., NO in the case of ammonia), so that oxygen is produced when the converted gas is reduced in the third inner cavity 61. Consequently, the measuring pump cell 41 can detect a value (e.g., the pump current Ip2) corresponding to this oxygen and thus determine the concentration of a specific gas. For example, since the inner pump electrode 22 acts as a catalyst in the first inner cavity 20, the ammonia in the first inner cavity 20 is converted into NO.

[0110] In the embodiment described above, the element body 102 of the sensor element 101 is a layered body with a plurality of solid electrolyte layers (layers 1 to 6), but is not limited to this. The element body 102 of the sensor element 101 can comprise at least one oxygen ion-conducting solid electrolyte layer. For example, in the Fig. 1. Layers 1 to 5, which are different from the second solid electrolyte layer 6, can be layers (e.g., layers composed of aluminum oxide) made of a material other than a solid electrolyte. In this case, the electrodes of the sensor element 101 can be arranged in the second solid electrolyte layer 6. For example, the measuring electrode 44 can be located in the Fig.1 on the lower surface of the second solid electrolyte layer 6. Furthermore, the reference gas inlet chamber 43 can be provided in the spacer layer 5 instead of the first solid electrolyte layer 4, the reference gas inlet layer 48 can be arranged between the second solid electrolyte layer 6 and the spacer layer 5 instead of between the first solid electrolyte layer 4 and the third substrate layer 3, and the reference electrode 42 can be provided back from the third inner cavity 61 and on the lower surface of the second solid electrolyte layer 6.

[0111] The present application claims priority over Japanese patent application No. 2024-095787, which was filed on June 13, 2024, and the entire contents of which are incorporated herein by reference. Commercial applicability

[0112] The present invention is applicable to a gas sensor that detects the concentration of a specific gas, such as NOx, in a measuring gas, such as the exhaust gas of a motor vehicle or automobile. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2017-181499 A

[0003] JP 2024-095787

[0111]

Claims

[1] Sensor element for detecting the concentration of a specific gas in a gas of the object being measured, wherein the sensor element comprises: an element body having an oxygen ion-conducting solid electrolyte layer and an internal measuring object gas flow section that introduces the measuring object gas from a gas inlet and causes the measuring object gas to flow in a first direction; a pump cell comprising an inner electrode provided in an inner cavity of the sample gas flow section and an outer electrode provided on an outer surface of the element body, and a diffusion control section located upstream of the inner cavity in the sample gas flow section, which exerts a diffusion resistance on the sample gas introduced from the gas inlet, wherein the diffusion control section comprises a porous body and a space section which are provided in at least a part of the diffusion control section in the first direction, wherein the porous body is provided such that it occupies a part of a cross-section of the diffusion control section perpendicular to the first direction and allows the gas of the sample to pass through it, and the space section comprises a part of the cross-section which is not occupied by the porous body and allows the gas of the sample to pass through it. [2] Sensor element according to claim 1, wherein the porous body is provided in the diffusion control section such that it occupies 30% to 70% of the cross-section. [3] Sensor element according to claim 1 or 2, wherein the porosity of the porous body is 15% or less. [4] Sensor element according to one of claims 1 to 3, wherein the porous body is provided in a plurality such that it forms parallel flow paths in the cross-section. [5] Sensor element according to any one of claims 1 to 4, wherein the element body has a longitudinal direction and is a layered body composed of several layers stacked in a layering direction perpendicular to the longitudinal direction, a cross-sectional shape of the space segment is a predetermined shape with a longer outer perimeter than a reference rectangle, and the reference rectangle is a rectangle having the same area as the cross-section of the space section, and the reference rectangle is a rectangle formed by deforming the circumscribed rectangle of the cross-section, which is constructed from two sides parallel to the layering direction and two sides parallel to a second direction perpendicular to the layering direction, such that short sides become shorter while maintaining the length of long sides, or a rectangle formed by deforming the circumscribed rectangle while maintaining a ratio of each side, or a rectangle formed by changing the length of each side of the circumscribed rectangle such that the area of ​​overlap with the cross-section is maximized. [6] Sensor element according to claim 5, wherein the outer circumference of the given shape comprises a first section and a second section, each directed towards each other in the layering direction and extending along the second direction, and at least part of the first section and / or at least part of the second section each have a curved shape. [7] Sensor element according to claim 5 or 6, wherein the outer circumference of the given shape comprises a first section and a second section, each directed towards each other in the layering direction and extending along the second direction, and at least part of the first section and / or at least part of the second section each have a polygonal line shape. [8] Sensor element according to claim 6 or 7, wherein the first section and the second section each have a convex shape on the same side in the layering direction. [9] Sensor element according to claim 6 or 7, wherein the first section and the second section each have a convex shape on a side where they approach each other or on a side where they are separated from each other in the layering direction. [10] Sensor element according to any one of claims 5 to 9, where the diffusion adjustment section has a plurality of the spatial sections and Each of the majority of the spatial sections has a cross-sectional shape that is the specified shape. [11] Sensor element according to one of claims 1 to 10, wherein the diffusion adjustment section is configured such that a cross-sectional area of ​​a cross-section perpendicular to the first direction is smaller in at least a part of a downstream side of an upstream end than in the upstream end. [12] Sensor element according to claim 11, wherein the diffusion adjustment section has an outline of the cross-section parallel to the first direction and the outline extends such that it is curved with respect to the first direction. [13] Gas sensor comprising the sensor element according to any one of claims 1 to 12.

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