gas sensor element

Abstract

To provide a gas sensor element that can accurately detect a temperature of a specific portion.SOLUTION: A gas sensor element 1 has: a solid electrolyte body 2 that has oxygen ion conductivity; a heater 5 that heats the solid electrolyte body 2; a sensor electrode 31 and a reference gas-side electrode 32 that are provided on the solid electrolyte body 2; and a thermocouple 4 that is printed on at least one of the solid electrolyte body 2 and the sensor electrode 31 and reference gas-side electrode 32.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a gas sensor element.

Background Art

[0002] In an exhaust system of an internal combustion engine or the like, a gas sensor for detecting the concentration of a specific gas component in the gas to be measured is mounted. As a gas sensor element incorporated in such a gas sensor, there is one including a solid electrolyte having oxygen ion conductivity, a gas-side electrode to be measured and a reference gas-side electrode provided on the solid electrolyte, and a heater for heating the element.

[0003] In order to improve the detection accuracy of the concentration of a specific gas component, the gas sensor element needs to be controlled at an appropriate activation temperature. Therefore, the temperature of the gas sensor element is controlled to a predetermined temperature by controlling the heater. For example, as disclosed in Patent Document 1, the gas sensor element has a basic characteristic of a predetermined relationship between the element temperature and the impedance. Based on this basic characteristic, controlling the heater by feedback is described in Patent Document 1. Even in this case, in order to grasp the basic characteristic of the gas sensor element, it is necessary to measure in advance the temperature of a predetermined part of the gas sensor element and the impedance at that temperature. Therefore, means for measuring the temperature of a predetermined part of the gas sensor element is required.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, Patent Document 1 does not disclose any specific means for measuring the temperature of a predetermined part of a gas sensor element. Patent Document 1 describes attaching a thermocouple to measure the element temperature, but even if a normal thermocouple can be attached to the gas sensor element, it is extremely difficult to attach it accurately to the desired position. As a result, it becomes difficult to accurately detect the temperature of a specific part of the gas sensor element.

[0006] This invention has been made in view of the above problems, and aims to provide a gas sensor element that enables high-precision temperature detection of a specific part. [Means for solving the problem]

[0007] One aspect of the present invention comprises a solid electrolyte (2) having oxygen ion conductivity, A heater (5) for heating the above solid electrolyte, The above solid electrolyte is provided with electrodes on the gas side to be measured (31, 33, 34) and a reference gas side electrode (32), A thermocouple (4) printed on at least one of the above-mentioned solid electrolyte, the above-mentioned electrode on the gas to be measured, and the above-mentioned electrode on the reference gas, A gas sensor element (1) having And, The above-mentioned electrode on the gas to be measured has a sensor electrode that is active for a specific gas that is the target of measurement in the gas to be measured, and the sensor cell (3) is composed of the sensor electrode, the reference gas side electrode, and a portion in the solid electrolyte that conducts oxygen ions between the sensor electrode and the reference gas side electrode, and the thermocouple temperature measuring junction (41) is printed on the sensor cell. A gas sensor element used in a gas detection system configured to control the heater based on the relationship between the power applied to the heater and the temperature of the sensor cell. It is located there. Another aspect of the present invention is a solid electrolyte (2) having oxygen ion conductivity, A heater (5) for heating the above solid electrolyte, The above solid electrolyte is provided with electrodes on the gas side to be measured (31, 33, 34) and a reference gas side electrode (32), A thermocouple (4) printed on at least one of the above-mentioned solid electrolyte, the above-mentioned electrode on the gas to be measured, and the above-mentioned electrode on the reference gas, A gas sensor element (1) having, The above-mentioned electrode on the gas to be measured has a sensor electrode that is active for a specific gas that is the target of measurement in the gas to be measured, and the sensor cell (3) is composed of the sensor electrode, the reference gas side electrode, and a portion in the solid electrolyte that conducts oxygen ions between the sensor electrode and the reference gas side electrode, and the thermocouple temperature measuring junction (41) is printed on the sensor cell. A gas sensor element used in a gas detection system, which has a pump cell (30) that has the function of pumping oxygen in a chamber (71) facing the sensor electrode, and is configured to control the heater based on the impedance of the pump cell. . [Effects of the Invention]

[0008] The gas sensor element has a thermocouple printed on at least one of the solid electrolyte body, the measured gas side electrode, and the reference gas side electrode. Therefore, the temperature of a specific site in at least one of the solid electrolyte body, the sensor electrode, and the reference gas side electrode can be accurately detected. That is, the printed thermocouple can be accurately arranged. Thereby, the temperature of the specific site can be accurately detected.

[0009] As described above, according to the above aspect, a gas sensor element capable of highly accurately detecting the temperature of a specific site can be provided. The reference numerals in parentheses described in the claims and the means for solving the problems indicate the correspondence with the specific means described in the embodiments described later, and do not limit the technical scope of the present invention.

Brief Description of Drawings

[0010] [Figure 1] It is a cross-sectional explanatory view of a gas sensor element along the longitudinal direction in Embodiment 1, and is a cross-sectional view taken along the arrow I-I in FIG. 2. [Figure 2] A cross-sectional view taken along the arrow II-II in FIG. 1. [Figure 3] (a) A cross-sectional view taken along the arrow IIIa-IIIa in FIG. 1, (b) A cross-sectional view taken along the arrow IIIb-IIIb in FIG. 1. [Figure 4] It is a plan explanatory view of a thermocouple in Embodiment 1. [Figure 5] A cross-sectional explanatory view of a state where a general thermocouple is in contact with a site near a sensor cell in a gas sensor element. [Figure 6] It is a diagram schematically showing the relationship between the heater power and the temperature of the sensor cell in Embodiment 2. [Figure 7] It is a cross-sectional explanatory view of a gas sensor element along the longitudinal direction in Embodiment 3. [Figure 8] A cross-sectional view taken along the arrow VIII-VIII in FIG. 7. [Figure 9] It is a diagram schematically showing the relationship between the temperature of the sensor cell and the temperature of the pump cell and the impedance of the pump cell in Embodiment 3. [Figure 10] Explanatory drawing for explaining the control system of the heater power in Embodiment 3. [Figure 11] Cross-sectional explanatory drawing of the gas sensor element along the longitudinal direction in Embodiment 4. [Figure 12] Cross-sectional explanatory drawing of a state where a general thermocouple is in contact with the reference gas side electrode in the gas sensor element.

MODE FOR CARRYING OUT THE INVENTION

[0011] (Embodiment 1) An embodiment related to the gas sensor element will be described with reference to FIGS. 1 to 4. The gas sensor element 1 of this embodiment has, as shown in FIGS. 1 and 2, a solid electrolyte body 2, a heater 5, a sensor electrode 31 as a measured gas side electrode, a reference gas side electrode 32, and a thermocouple 4.

[0012] The solid electrolyte body 2 has oxygen ion conductivity. The heater 5 heats the solid electrolyte body 2. The sensor electrode 31 and the reference gas side electrode 32 are provided on the solid electrolyte body 2. The thermocouple 4 is printed on at least one of the solid electrolyte body 2, the sensor electrode 31, and the reference gas side electrode 32.

[0013] The gas sensor element 1 includes a sensor cell 3 that detects the concentration of a specific gas in the measured gas. The sensor cell 3 is constituted by the sensor electrode 31, the reference gas side electrode 32, and a site that conducts oxygen ions between the sensor electrode 31 and the reference gas side electrode 32 in the solid electrolyte body 2. The temperature measurement contact 41 of the thermocouple 4 is printed on the sensor cell 3.

[0014] In this embodiment, the temperature measurement contact 41 of the thermocouple 4 is arranged on the sensor electrode 31 or the reference gas side electrode 32. Particularly in this embodiment, the temperature measurement contact 41 is arranged on the sensor electrode 31.

[0015] The gas sensor element 1 in this embodiment is a laminated type gas sensor element in which multiple ceramic layers are stacked. The gas sensor element 1 has a sensor electrode 31 and a reference gas side electrode 32 formed on one side and the other side of a plate-shaped solid electrolyte 2, respectively. The sensor electrode 31 and the reference gas side electrode 32 are positioned opposite each other with a portion of the solid electrolyte 2 in between. The sensor electrode 31, the reference gas side electrode 32, and the portion of the solid electrolyte 2 between the sensor electrode 31 and the reference gas side electrode 32 form a sensor cell 3. The sensor electrode 31 is active for a specific gas in the gas to be measured. For example, the gas to be measured is exhaust gas from an internal combustion engine, and the specific gas is oxygen. The sensor electrode 31 that is active for oxygen contains, for example, platinum (Pt) and gold (Au).

[0016] The gas sensor element 1 has a chamber 71 in which a sensor electrode 31 is placed, and a duct 72 in which a reference gas side electrode 32 is placed. A chamber forming layer 11 and a shielding layer 12 are sequentially laminated on the side of the solid electrolyte 2 where the sensor electrode 31 is provided. In addition, a duct forming layer 13 and a heater layer 14 are sequentially laminated on the side of the solid electrolyte 2 where the reference gas side electrode 32 is provided.

[0017] In this specification, the lamination direction in which multiple ceramic layers are stacked is referred to as the Z direction. The gas sensor element 1 has a long plate-like shape in one direction perpendicular to the Z direction. The longitudinal direction of this gas sensor element 1 is referred to as the X direction. The direction perpendicular to both the X direction and the Z direction is referred to as the Y direction.

[0018] Chamber 71 is provided with a gas inlet 150 for introducing the gas to be measured (e.g., exhaust gas from an internal combustion engine) into the chamber 71, and a diffusion resistance section 15 is positioned at the gas inlet 150. Duct 72 opens at the base end of the gas sensor element 1 and is configured to introduce atmospheric air as a reference gas from the base end side.

[0019] The solid electrolyte 2 is a ceramic layer mainly composed of zirconia. The chamber forming layer 11, shielding layer 12, duct forming layer 13, and heater layer 14 are all ceramic layers mainly composed of alumina. The diffusion resistance section 15 is also mainly composed of alumina. However, the diffusion resistance section 15 is made of a porous ceramic material that allows the gas to be measured to pass through.

[0020] The heater 5 is formed in the heater layer 14. That is, a heater pattern is formed on the surface of the heater layer 14 that faces the duct forming layer 13. As shown in Figure 3(b), the heater 5 has a heater heating element 51 and a heater lead element 52. The heater lead element 52 is connected to the base end of the heater heating element 51 and extends toward the base end. The heater heating element 51 has a higher conductivity resistance than the heater lead element 52. As a result, when the heater 5 is energized, the heater heating element 51 is the main source of heat generation.

[0021] The heater 5 is formed on the heater layer 14 by printing. The sensor electrode 31 and the reference gas side electrode 32 are also formed on the surface of the solid electrolyte 2 by printing. The thermocouple 4 is also formed on the surface of the sensor electrode 31 by printing. As shown in Figures 3(a) and 4, the two metal wires constituting the thermocouple 4 can be, for example, a metal wire 4P made of a platinum-rhodium alloy and a metal wire 4N made of platinum. In this case, the former is the positive leg and the latter is the negative leg.

[0022] The thermocouple 4 can have a thickness in the Z direction of, for example, about 8 to 12 μm. Furthermore, the wire widths of the metal wires 4P and 4N constituting the thermocouple 4, i.e., the positive and negative legs, can be, for example, about 80 to 100 μm each. The distance between the positive and negative legs can be, for example, about 400 to 500 μm.

[0023] The thermocouple 4 has a portion, including the temperature sensing junction 41, positioned on the surface of the sensor electrode 31, while the other portion is positioned on the surface of the solid electrolyte 2. However, an insulating layer made of alumina or the like is formed between the thermocouple 4 and the sensor electrode 31, and between the thermocouple 4 and the solid electrolyte 2 to provide electrical insulation (not shown). As shown in Figure 4, the two metal wires 4P and 4N of the thermocouple 4 are electrically led to terminals 42 provided at the base end of the gas sensor element 1.

[0024] When manufacturing the gas sensor element 1 of this embodiment, a conductive paste that will serve as the heater 5 is printed onto a ceramic green sheet that will serve as the heater layer 14. In addition, a conductive paste that will serve as the sensor electrode 31 and a conductive paste that will serve as the reference gas side electrode 32 are screen printed onto the respective surfaces of the green sheets of the solid electrolyte 2.

[0025] Furthermore, the thermocouple 4 is also formed during the manufacturing of the gas sensor element 1 by screen printing a metal paste that will become the thermocouple 4 onto the surface of the sensor electrode 31. However, since it is necessary to ensure electrical insulation between the sensor electrode 31 and the thermocouple 4, an insulating layer made of alumina or the like is formed between the thermocouple 4 and the sensor electrode 31. That is, after covering the surface of the sensor electrode 31 with a ceramic paste that will serve as an insulating layer, the metal paste that will become the thermocouple 4 is screen printed onto the ceramic paste.

[0026] As described above, the thermocouple 4 can be formed from, for example, a platinum-rhodium alloy and platinum. In this case, a paste of the platinum-rhodium alloy and a platinum paste are printed in a predetermined pattern (for example, a wiring pattern as shown in Figure 4) at predetermined positions. In the thermocouple 4, the joint between the wiring portion formed of the platinum-rhodium alloy and the wiring portion formed of platinum becomes the temperature sensing junction 41.

[0027] Each printed paste is fired together with the laminated ceramic green sheet, etc. This forms the thermocouple 4, along with the sensor electrode 31, the reference gas side electrode 32, the heater 5, etc., as part of the gas sensor element 1.

[0028] Next, we will explain the effects and benefits of this embodiment. The gas sensor element 1 has thermocouples 4 printed on the sensor electrode 31, etc. Therefore, it can accurately detect the temperature of a specific location. In other words, the printed thermocouples 4 can be precisely positioned. This allows for accurate detection of the temperature of a specific location.

[0029] Specifically, the temperature sensing junction 41 of the thermocouple 4 is printed on the sensor cell 3. This allows for accurate detection of the temperature of the sensor cell 3. In other words, because the thermocouple 4 is formed by printing, its formation position can be determined with high precision. Furthermore, since the printed thermocouple 4 does not deviate from its formed position on the printed surface, the temperature at a predetermined location can be accurately detected when measuring the temperature of the sensor cell 3.

[0030] Furthermore, the printed thermocouple 4 can be made thinner. Therefore, it can be placed in a narrow space within the gas sensor element 1. Consequently, the thermocouple 4 can be placed in a predetermined position without particularly changing the structure of the gas sensor element 1. In other words, there is no need to specifically change the structure of the gas sensor element 1 solely to accommodate the thermocouple 4.

[0031] Furthermore, in this embodiment of the gas sensor element 1, the temperature measuring junction 41 of the thermocouple 4 is positioned on the sensor electrode 31. This allows for accurate detection of the temperature at a location important for the detection accuracy of a specific gas concentration by the gas sensor element 1.

[0032] On the other hand, the chamber 71 facing the sensor electrode 31 tends to be an extremely small space, with a thickness in the Z direction of, for example, about 30 μm. Inserting a typical thermocouple into such a narrow space is difficult, and for example, as shown in Figure 5, the thermocouple 94 is fixed near the sensor cell 3. As a result, it becomes impossible to directly measure the temperature of the sensor cell 3, including the sensor electrode 31, and it can only be measured indirectly. Therefore, it is not possible to accurately detect the temperature at a desired location. Furthermore, in this case, methods such as embedding the thermocouple 94 in a part of the shielding layer 12 can be considered, but this requires extra work, such as cutting away a part of the shielding layer 12 to embed the thermocouple 94. Moreover, it is difficult to achieve high accuracy in the placement of the thermocouple 94.

[0033] In contrast, in the gas sensor element 1 of this embodiment, the thermocouple 4 is positioned by printing, so it can be easily and accurately positioned on the surface of the sensor electrode 31 facing the chamber 71. Therefore, the thermocouple 4 can detect the temperature of a specific part of the gas sensor element 1 with high accuracy.

[0034] As described above, this embodiment provides a gas sensor element that enables high-precision temperature detection of a specific part.

[0035] (Embodiment 2) This embodiment, as shown in Figure 6, is used in a gas detection system configured to control the heater 5 based on the relationship between the power applied to the heater 5 (hereinafter also referred to as "heater power") and the temperature of the sensor cell 3.

[0036] As described above, the gas sensor element 1 can perform highly accurate gas detection when the temperature of the sensor cell 3 is maintained at an appropriate activation temperature. Therefore, the gas sensor element 1 has an advantage in that the temperature of the sensor cell 3 can be accurately measured by the thermocouple 4 printed on the sensor cell 3.

[0037] On the other hand, constantly monitoring the sensor cell 3 with the thermocouple 4 and feeding back the detected temperature when detecting gas concentration with the gas sensor element 1 becomes a system-wide complexity. Therefore, for example, it is conceivable to measure the relationship between the power applied to the heater 5 and the temperature of the sensor cell 3 before shipping the gas sensor element 1, and store the measured relationship map in the gas sensor's control device. The control device is composed of a well-known microcomputer consisting of a CPU, ROM, RAM, etc., and its peripheral circuits.

[0038] The relationship map can be obtained, for example, as shown in Figure 6, as the relationship between the power applied to the heater 5 and the temperature of the sensor cell 3. That is, the greater the applied power, the higher the temperature of the sensor cell 3. This relationship map means that if a predetermined power is continuously applied, the temperature of the sensor cell 3 will stabilize at a predetermined temperature.

[0039] When the gas sensor incorporating the gas sensor element 1 is used to detect the concentration of a specific gas in the gas to be measured in an exhaust system or the like, power is applied to the heater 5 based on the relationship map. This allows the temperature of the sensor cell 3 to be maintained at the desired temperature while the gas sensor is in use.

[0040] To obtain the relationship map necessary for this type of control, a highly accurate relationship map can be obtained by measuring the temperature of the sensor cell 3 using the thermocouple 4 printed on the sensor cell 3. As a result, the temperature of the sensor cell 3 can be controlled with high precision, and consequently, highly accurate detection of specific gas concentrations becomes possible.

[0041] Otherwise, it is the same as in Embodiment 1 and has the same effects and advantages. In addition, among the reference numerals used in Embodiment 2 and later, those that are the same as those used in the previously described embodiments represent the same components, etc., as those in the previously described embodiments, unless otherwise specified.

[0042] (Embodiment 3) In this embodiment, as shown in Figures 7 and 8, the gas sensor element 1 is replaced with a NOx sensor element.

[0043] In other words, the gas sensor element 1 of this embodiment has a pump cell 30 that has the function of pumping oxygen in the chamber 71. The pump cell 30 has a pump electrode 33. The pump electrode 33 is provided on the surface of the solid electrolyte 2 that faces the chamber 71. When viewed from the Z direction, the pump electrode 33 is positioned to overlap with a part of the reference gas side electrode 32 which is provided facing the duct 72. The pump cell 30 is composed of this reference gas side electrode 32, the pump electrode 33, and the portion of the solid electrolyte 2 between the reference gas side electrode 32 and the pump electrode 33.

[0044] In this embodiment, the sensor electrode 31 is positioned on the base end side of the pump electrode 33. Furthermore, as shown in Figure 8, a monitor electrode 34 is formed at a position adjacent to the pump electrode 33 in the Y direction. The monitor electrode 34 is also positioned so as to overlap with a portion of the reference gas side electrode 32, which is located facing the duct 72, when viewed from the Z direction. The monitor cell 3M is composed of this reference gas side electrode 32, the monitor electrode 34, and the portion of the solid electrolyte 2 between the reference gas side electrode 32 and the monitor electrode 34. The monitor cell 3M can detect the oxygen concentration in the chamber 71. In this embodiment, the pump electrode 33, sensor electrode 31, and monitor electrode 34 are the electrodes for the gas being measured. In this embodiment, the sensor electrode 31 is made of NOx (nitrogen oxides), which is the specific gas to be measured, and a material active to oxygen. The sensor electrode 31 includes, for example, platinum (Pt) and rhodium (Rh). Furthermore, the pump electrode 33 and the monitor electrode 34 contain, for example, platinum and gold, and are active against oxygen.

[0045] In this embodiment, the gas sensor element 1, which is a NOx sensor, can pump oxygen from the chamber 71 to the duct 72 side using the pump cell 30. This reduces the oxygen concentration in the chamber 71 to a predetermined concentration. Then, the sensor cell 3 detects the NOx concentration in the chamber 71. Since some oxygen may remain in the chamber 71, its concentration is detected by the monitor cell 3M. Because the output of the sensor cell 3 is superimposed with the amount due to residual oxygen, it is possible to measure the NOx concentration with high accuracy by subtracting the output of the monitor cell 3M from the output of the sensor cell 3.

[0046] Both the pump electrode 33 and the monitor electrode 34 are formed on the solid electrolyte 2 by printing. These electrodes can also be formed by screen printing, similar to the sensor electrode 31 shown in Embodiment 1.

[0047] Furthermore, as shown in Figure 9, the gas sensor element 1 in this embodiment is configured to control the heater 5 based on the impedance of the pump cell 30.

[0048] There is a predetermined relationship between the temperature of the pump cell 30 and the impedance of the pump cell 30, as shown by the solid curve TpZp in Figure 9. That is, the higher the temperature of the pump cell 30, the higher the impedance of the pump cell 30. Therefore, by measuring the relationship between the temperature of the pump cell 30 and the impedance of the pump cell 30 in advance and storing it in the control device of the gas sensor system, and then monitoring the impedance of the pump cell 30 while the gas sensor is in use, it is possible to determine the temperature of the pump cell 30.

[0049] Therefore, by monitoring the impedance of the pump cell 30 and controlling the power applied to the heater 5 (i.e., heater power), it is possible to maintain the pump cell 30 at a predetermined temperature. In other words, by controlling the heater power so that the impedance of the pump cell 30 becomes a predetermined value, it is possible to maintain the temperature of the pump cell 30 at a predetermined temperature.

[0050] However, in order to improve the accuracy of NOx detection, it is necessary to accurately understand the temperature of sensor cell 3 and control its temperature with high precision. Here, the temperature of sensor cell 3 is not exactly the same as the temperature of pump cell 30, but there is a slight difference. Therefore, if heater power is controlled based on the relationship map between the temperature of pump cell 30 and the impedance of pump cell 30 (see the solid curve TpZp in Figure 9), it may be difficult to control the temperature of sensor cell 3 to the desired temperature.

[0051] Therefore, in this embodiment, heater power is controlled based on a relationship map between the temperature of the sensor cell 3 and the impedance of the pump cell 30 (see the dashed curve TsZp in Figure 9). In other words, although there may be a difference between the temperature of the sensor cell 3 and the temperature of the pump cell 30, there is a predetermined relationship. Through this relationship, there is also a predetermined relationship between the temperature of the sensor cell 3 and the impedance of the pump cell 30. Although there may be variations between individual gas sensor elements 1, this relationship is predetermined for each gas sensor element 1.

[0052] Therefore, it is conceivable to determine the relationship between the temperature of the sensor cell 3 and the impedance of the pump cell 30 in the gas sensor element 1 beforehand, for example, before shipment (see the solid arrow in Figure 9). Using this relationship, the heater 5 is controlled so that the impedance of the pump cell 30 becomes such that the temperature of the sensor cell 3 reaches a predetermined temperature. By controlling the heater while monitoring the impedance of the pump cell 30, the temperature of the sensor cell 3 can be controlled to a predetermined temperature with high precision.

[0053] As shown in Figure 10, a voltage application unit Vp and a current detection unit Ip are provided between the reference gas side electrode 32 and the pump electrode 33 of the pump cell 30. The control device 101 is configured to control the applied voltage from the voltage application unit Vp. For example, when the control device 101 applies a changing voltage from the voltage application unit Vp to the pump cell 30, the changing current is detected in the current detection unit Ip. From these relationships, the impedance of the pump cell 30 can be detected. The control device 101 also stores a relationship map between the temperature of the sensor cell 3 and the impedance of the pump cell 30. The control device 101 can calculate the temperature of the sensor cell 3 from this relationship map and the impedance of the pump cell 30. According to the calculated temperature of the sensor cell 3, the control device 101 controls the power supply to the heater 5. The control device is composed of a well-known microcomputer consisting of a CPU, ROM, RAM, etc., and its peripheral circuits.

[0054] As described above, in order to understand the relationship between the temperature of the sensor cell 3 and the impedance of the pump cell 30 in advance (see the solid arrow in Figure 9), it is necessary to directly measure the temperature of the sensor cell 3. In this embodiment, the gas sensor element 1 has a thermocouple 4 printed on the sensor cell 3.

[0055] This allows for highly accurate measurement of the sensor cell 3's temperature. Therefore, the relationship between the sensor cell 3's temperature and the pump cell 30's impedance can be accurately determined. Based on this, the heater power can be controlled to maintain the pump cell 30's impedance at a predetermined level, thereby maintaining the sensor cell 3's temperature at a predetermined level. As a result, the accuracy of NOx detection can be improved. Otherwise, it has the same configuration and effects as Embodiment 1.

[0056] Note that the relationship curve shown in Figure 9 is just one example, and depending on the structure of the gas sensor element 1, the temperature of the sensor cell 3 may be higher than the temperature of the pump cell 30.

[0057] (Embodiment 4) This embodiment is a modified form of Embodiment 1, in which the thermocouple 4 is arranged on the reference gas side electrode 32, as shown in Figure 11. In other words, in this embodiment, the thermocouple 4 is printed on the surface of the reference gas-side electrode 32 via an insulating layer (not shown). This places the thermocouple 4 in the sensor cell 3. The temperature-measuring junction 41 of the thermocouple 4 is positioned on the reference gas-side electrode 32. At least a portion of the thermocouple 4, including the temperature-measuring junction 41, is placed inside the duct 72. Other aspects are the same as in Embodiment 1.

[0058] In this configuration as well, the temperature of the sensor cell 3 can be measured with high accuracy. In contrast to this configuration, it is also possible to insert a general thermocouple 94 into the duct 72 and bring it into contact with the reference gas side electrode 32, as shown in Figure 12. However, in this case, it is difficult to achieve high precision in the placement of the thermocouple 94, and therefore it is difficult to accurately detect the temperature of the sensor cell 3.

[0059] In contrast, the gas sensor element 1 of this embodiment allows the thermocouple 4 to be easily and accurately positioned in a predetermined location by printing the thermocouple 4 onto the surface of the reference gas-side electrode 32. As a result, the temperature of the sensor cell 3 can be detected with high accuracy. Furthermore, it has the same effects and advantages as Embodiment 1.

[0060] In the above embodiment, the thermocouple's temperature-measuring junction is shown to be placed on the sensor electrode or the reference gas side electrode. However, the thermocouple's temperature-measuring junction can also be provided in other locations. For example, the thermocouple's temperature-measuring junction can be printed on the surface of the solid electrolyte near the sensor electrode or the reference gas side electrode.

[0061] The present invention is not limited to the embodiments described above, and can be applied to various embodiments without departing from its spirit. [Explanation of symbols]

[0062] 1. Gas sensor element 2 Solid electrolyte body 3 Sensor Cells 31 Sensor electrodes 32 Reference gas side electrode 4 Thermocouples 5 Heater

Claims

1. A solid electrolyte (2) having oxygen ion conductivity, A heater (5) for heating the above solid electrolyte, The above solid electrolyte is provided with electrodes on the gas side to be measured (31, 33, 34) and a reference gas side electrode (32), The above solid electrolyte, the above-mentioned gas-side electrode and the above-mentioned reference gas-side electrode, and a thermocouple (4) printed on at least one of them, A gas sensor element (1) having, The above-mentioned electrode on the gas to be measured has a sensor electrode that is active for a specific gas that is the target of measurement in the gas to be measured, and the sensor cell (3) is composed of the sensor electrode, the reference gas side electrode, and a portion in the solid electrolyte that conducts oxygen ions between the sensor electrode and the reference gas side electrode, and the thermocouple temperature measuring junction (41) is printed on the sensor cell. A gas sensor element used in a gas detection system configured to control the heater based on the relationship between the power applied to the heater and the temperature of the sensor cell.

2. A solid electrolyte (2) having oxygen ion conductivity, A heater (5) for heating the above solid electrolyte, The above solid electrolyte is provided with electrodes on the gas side to be measured (31, 33, 34) and a reference gas side electrode (32), The above solid electrolyte, the above-mentioned gas-side electrode and the above-mentioned reference gas-side electrode, and a thermocouple (4) printed on at least one of them, A gas sensor element (1) having, The above-mentioned electrode on the gas to be measured has a sensor electrode that is active for a specific gas that is the target of measurement in the gas to be measured, and the sensor cell (3) is composed of the sensor electrode, the reference gas side electrode, and a portion in the solid electrolyte that conducts oxygen ions between the sensor electrode and the reference gas side electrode, and the thermocouple temperature measuring junction (41) is printed on the sensor cell. A gas sensor element used in a gas detection system, which has a pump cell (30) that has a function of pumping oxygen in a chamber (71) facing the sensor electrode, and is configured to control the heater based on the impedance of the pump cell.

3. The gas sensor element according to claim 1 or 2, wherein the temperature measuring junction of the thermocouple is arranged on the sensor electrode or the reference gas side electrode.

4. The gas sensor element according to claim 1 or 2, which is a stacked type gas sensor element comprising a plurality of ceramic layers including the above-mentioned solid electrolyte.

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