Molecular sensor

Abstract

To provide a molecular sensor that can improve the accuracy of measuring a concentration of molecules in a target gas based on the temperature of an electrolyte layer measured by a thermocouple without using a compensation lead wire.SOLUTION: A molecular sensor comprises: a concentration measuring unit 3 including a concentration sensor element 31 formed of an electrolyte having ion conductivity for at least one type of molecule, and a pair of sensor electrodes, a measurement electrode 32 and a reference electrode 33, disposed across the concentration sensor element 31; a thermocouple 5 for measuring a temperature of the concentration sensor element 31; and a connector unit 6 to which the measurement electrode 32, the reference electrode 33 and the thermocouple 5 are connected, and which transmits electric signals of the measurement electrode 32, the reference electrode 33 and the thermocouple 5 to the outside. The molecular sensor comprises a reference temperature measuring unit 7 for measuring a temperature of the connector unit 6 as a reference temperature 54 of the thermocouple 5, and transmits an electric signal of the reference temperature measuring unit 7 to the outside via the connector unit 6.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to molecular sensors. [Background technology]

[0002] Molecular sensors that measure the concentration of specific molecules by utilizing a selective oxidation-reduction reaction of the specific molecule have been known. For example, the oxygen concentration measuring device described in Patent Document 1 utilizes the fact that an electromotive force corresponding to the ratio of the oxygen molecular concentrations in contact with the two electrodes is generated by an oxidation-reduction reaction between oxygen molecules and oxygen ions that occurs on electrodes processed on both sides of a zirconia element, a solid electrolyte that selectively transmits oxygen ions at high temperatures. A reference gas with a known oxygen molecular concentration is brought into contact with one electrode, and a measured gas is brought into contact with the other electrode. The electromotive force generated between the two electrodes and the temperature of the solid electrolyte when the electromotive force is generated can be used to measure the oxygen molecular concentration in the measured gas based on the Nernst equation.

[0003] As is clear from the Nernst equation, the electromotive force varies depending on the temperature of the solid electrolyte. Therefore, to accurately measure the oxygen molecule concentration, it is necessary to accurately measure the temperature of the solid electrolyte (the temperature of the reference gas surrounding the solid electrolyte). The oxygen concentration measuring device of Patent Document 1 uses a thermocouple to measure the temperature of the reference gas. The thermocouple is configured to generate a current due to an electromotive force corresponding to the temperature difference between the measurement junction and the reference junction. The invention described in Patent Document 1 addresses the issue of variation in the measured temperature caused by variations in the position of the measurement junction of the thermocouple due to individual manufacturing differences, by arranging the measurement junction of the thermocouple in a small space formed in a structural member, thereby suppressing variation in the temperature of the reference gas detected by the thermocouple. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-122834 Summary of the Invention [Problem to be solved by the invention]

[0005] When measuring the temperature of the heated solid electrolyte using a thermocouple, as in the oxygen concentration measuring device described above, the measurement junction of the thermocouple is placed at the electrode of the solid electrolyte. The reference junction (cold junction) of the thermocouple is directly connected to the thermocouple measuring instrument to enable cold junction compensation. On the other hand, in the case of a molecular sensor connected to a control device via a multi-core cable, the reference junction of the thermocouple cannot be directly connected to the thermocouple measuring instrument in the control device, so the reference junction of the thermocouple is provided inside the molecular sensor.

[0006] Furthermore, the compensating wire that improves the thermocouple's measurement accuracy is vulnerable to repeated bending, twisting, pulling, abrasion, etc., making it difficult to wire from the molecular sensor to the thermocouple measuring instrument. If a pair of cores of the multi-core cable were made up of the compensating wire of the thermocouple, the versatility of the multi-core cable would be reduced and the price would rise. Therefore, in such a molecular sensor, a current is output to the thermocouple measuring instrument due to the electromotive force of the thermocouple based on the temperature difference between the temperature of the measurement junction and the reference junction inside the molecular sensor.

[0007] Based on the assumption that the temperature of the reference junction is the same as that of the control board that calculates the temperature of the thermocouple, the temperature of the control board detected by the temperature sensor installed on the control board is used. However, in the molecular sensor in which the reference junction is located, the temperature of the reference junction becomes higher than the temperature of the control board due to the influence of the high-temperature solid electrolyte. Therefore, as the temperature of the solid electrolyte increases, the temperature difference between the temperature of the reference junction and the temperature of the control board increases, resulting in a problem of reduced measurement accuracy of the molecular sensor.

[0008] Even in molecular sensors in which the solid electrolyte is not heated, the temperature of the reference junction within the sensor may differ from the temperature of the control board due to the influence of the ambient temperature and differences in the degree of heat dissipation caused by individual differences in the structure of the molecular sensor, which can reduce the measurement accuracy of the molecular sensor.

[0009] An object of the present invention is to provide a molecular sensor that improves the accuracy of measuring the molecular concentration in a gas to be measured based on the temperature of the electrolyte layer measured by a thermocouple without using a compensating lead wire. [Means for solving the problem]

[0010] The present inventors have studied the configuration of a molecular sensor that measures the temperature of a solid electrolyte using a thermocouple, and that accurately measures the temperature of the solid electrolyte and improves the accuracy of measuring the molecular concentration in a measurement gas. As a result of extensive research, the present inventors have come up with the following configuration.

[0011] A molecular sensor according to an embodiment of the present invention includes a concentration measurement unit including an electrolyte layer formed of a solid electrolyte having ionic conductivity for at least one type of molecule and a pair of sensor electrodes arranged to sandwich the electrolyte layer, a thermocouple for measuring the temperature of the electrolyte layer, and a connector unit to which the sensor electrode and the thermocouple are connected and for transmitting electrical signals from the sensor electrode and the thermocouple to the outside. The molecular sensor includes a reference temperature measurement unit that measures the temperature of the connector unit as a reference temperature of the thermocouple, and transmits the electrical signal of the reference temperature measurement unit to the outside via the connector unit.

[0012] The reference junction of the thermocouple that measures the temperature of the electrolyte layer is connected to the connector. The temperature of the connector is measured by a reference temperature measurement unit. The molecular sensor measures the temperature of the electrolyte layer using the temperature of the connector as the reference temperature, which is the temperature of the reference junction of the thermocouple. Therefore, when the reference junction is located in a range affected by the heat of the electrolyte layer, the molecular sensor can measure the temperature of the electrolyte layer more accurately and precisely without using a compensating conductor and without being affected by the electrolyte layer or the surrounding temperature environment. Therefore, the molecular sensor calculates the concentration of a specific gas component using the Nernst equation based on the electromotive force generated by the solid electrolyte and the temperature of the solid electrolyte measured by the thermocouple. This allows a molecular sensor using a solid electrolyte to improve the accuracy of measuring the molecular concentration of a measured gas based on the temperature of the electrolyte layer measured by a thermocouple without using a compensating conductor.

[0013] From another viewpoint, the molecular sensor of the present invention preferably includes the following configuration: The reference temperature measurement unit measures the temperature of a connector pin of the connector unit to which the reference junction is connected.

[0014] By measuring the temperature of the connector pin of the connector portion, which is assumed to be equivalent to the temperature of the reference junction of the thermocouple, the reference temperature can be measured more stably. Therefore, the molecular sensor can measure the temperature of the electrolyte layer more accurately and precisely without using a compensating conductor and without being affected by the electrolyte layer or the ambient temperature environment. Therefore, the molecular sensor calculates the concentration of a specific gas component using the Nernst equation based on the electromotive force generated by the solid electrolyte and the temperature of the solid electrolyte measured by the thermocouple. This allows a molecular sensor using a solid electrolyte to improve the accuracy of measuring the molecular concentration of a measured gas based on the temperature of the electrolyte layer measured by a thermocouple without using a compensating conductor.

[0015] From another viewpoint, the molecular sensor of the present invention preferably includes the following configuration: The reference temperature measurement unit measures the temperature of the reference junction of the thermocouple.

[0016] By measuring the temperature of the reference junction of the thermocouple, the reference temperature can be measured more accurately. Therefore, the molecular sensor can measure the temperature of the electrolyte layer more accurately and with precision without using a compensating conductor and without being affected by the electrolyte layer or the ambient temperature environment. Therefore, the molecular sensor calculates the concentration of a specific gas component using the Nernst equation based on the electromotive force generated by the solid electrolyte and the temperature of the solid electrolyte measured by the thermocouple. This allows a molecular sensor using a solid electrolyte to improve the accuracy of measuring the molecular concentration in a measured gas based on the temperature of the electrolyte layer measured by a thermocouple without using a compensating conductor.

[0017] From another viewpoint, the molecular sensor of the present invention preferably includes the following configuration: The reference temperature measurement unit is a semiconductor temperature sensor.

[0018] In this way, the linearity characteristic of semiconductor temperature sensors can be utilized to simplify the reference temperature measurement circuit mounted in the control device and to measure the reference temperature more accurately. As a result, in a molecular sensor using a solid electrolyte, the accuracy of measuring the molecular concentration in the measurement gas based on the temperature of the electrolyte layer measured by a thermocouple can be improved without using a compensating conductor.

[0019] From another viewpoint, the molecular sensor of the present invention preferably includes the following configuration: The reference temperature measurement unit is sealed with an insulator at the reference junction of the thermocouple.

[0020] Because heat transfers through the insulator that seals the pair of metal wires that make up the thermocouple, the temperature of the pair of metal wires at the reference junction becomes approximately the same as the temperature of the insulator. Furthermore, because the reference junction and the reference temperature measurement unit are covered by the insulator, they are less susceptible to the influence of the surrounding environment. In other words, the reference temperature measurement unit can stably measure the temperature of the reference junction. This allows for improved accuracy in measuring the molecular concentration in a measurement gas based on the temperature of the electrolyte layer measured by a thermocouple in a molecular sensor using a solid electrolyte, without using a compensating conductor.

[0021] The terminology used herein is for the purpose of defining particular embodiments only and is not intended to limit the invention.

[0022] As used herein, the use of "including," "comprising," or "having" and variations thereof identify the presence of stated features, steps, operations, elements, components, and / or equivalents thereof, but may include one or more of the steps, operations, elements, components, and / or groups thereof.

[0023] As used herein, the terms "attached," "connected," "coupled," and / or their equivalents are used broadly to encompass both "direct and indirect" attachments, connections, and couplings. Furthermore, "connected" and "coupled" are not limited to physical or mechanical connections or couplings, but can also include direct or indirect electrical connections or couplings.

[0024] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. [Effects of the Invention]

[0025] According to one embodiment of the present invention, the molecular sensor can improve the accuracy of measuring the molecular concentration in the gas to be measured based on the temperature of the electrolyte layer measured by a thermocouple without using a compensation wire. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a diagram showing the overall configuration of a molecular sensor according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] FIG. 3 is a configuration diagram of the concentration measurement unit of the molecular sensor according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Figure 5] FIG. 5 is a cross-sectional view taken along line VV in FIG. [Figure 6] FIG. 6 is a block diagram showing the control of the molecular sensor in the first embodiment of the present invention. [Figure 7] FIG. 7 is a cross-sectional view of a molecular sensor according to a fourth modification of the first embodiment of the present invention. [Figure 8] FIG. 8 is a cross-sectional view taken along line XII-XII in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0027] The molecular sensor according to the present invention will be described below with reference to the drawings. In each drawing, the same parts are designated by the same reference numerals, and the description of the same parts will not be repeated. The dimensions of the components in each drawing do not faithfully represent the actual dimensions of the components and the dimensional ratios of each component.

[0028] [Embodiment 1] The molecular sensor 1 according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 5. FIG. 1 is an overall configuration diagram of the molecular sensor according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1. FIG. 3 is a configuration diagram of the concentration measurement unit of the molecular sensor according to the first embodiment of the present invention. FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. 3. FIG. 5 is a cross-sectional view taken along the line VV in FIG. 1. In the following description of the embodiment, the specific gas component to be measured is limited to oxygen, but as long as the molecular sensor uses a solid electrolyte having a similar configuration to that of this embodiment, the specific gas component is not limited to oxygen, and the molecular sensor can be applied to any molecular sensor that measures the concentration of at least one component in a gas to be measured.

[0029] The molecular sensor 1 is a device that measures the concentration of a specific gas component in a gas to be measured. The molecular sensor 1 is, for example, a gas sensor that measures the oxygen concentration in the exhaust gas of an automobile or the like. As shown in FIGS. 1 and 2, the molecular sensor 1 has a housing 2, a concentration measurement unit 3, a heating unit 4, a thermocouple 5, a connector 6, and a reference temperature measurement unit 7.

[0030] The casing 2 accommodates a concentration measuring unit 3, a heating unit 4, a thermocouple 5, and a reference temperature measuring unit 7. The casing 2 is also configured to accommodate a measurement gas and a reference gas. The casing 2 has a housing 21, a cover 22, and a sealing member 23.

[0031] The housing portion 21 has a cylindrical shape. The housing portion 21 has an internal columnar space with a space on one axial side and a space on the other axial side. The columnar space on the one axial side has a smaller inner diameter than the columnar space on the other axial side.

[0032] The sealing member 23 is a member that seals the cylindrical space on one side of the housing portion 21 in the axial direction with respect to the axis of the cylindrical space on the other side of the housing portion 21 in the axial direction. The sealing member 23 is located in the cylindrical space on the other side of the housing portion 21 in the axial direction. The sealing member 23 divides the internal space of the housing portion 21 into a cylindrical space on one side of the axial direction and a cylindrical space on the other side of the axial direction. The sealing member 23 also holds the concentration measuring unit 3, the heating unit 4, and the thermocouple 5. The sealing member 23 has a holding portion 23a that holds the concentration measuring unit 3, the heating unit 4, and the thermocouple 5.

[0033] The holding portion 23a is a through-hole that penetrates in the axial direction when the sealing member 23 is positioned in the cylindrical space on the other side in the axial direction. The sealing member 23 is attached to the housing portion 21 in a state in which it can hold the concentration measuring unit 3, the heating unit 4, and the thermocouple 5.

[0034] A cylindrical cover portion 22 is located at one axial end of the housing portion 21. The cover portion 22 is provided so as to cover the opening of a cylindrical space on one axial side of the housing portion 21. Therefore, a first storage portion 24 is formed by the cover portion 22 and the cylindrical space on the one axial side of the housing portion 21.

[0035] A heat insulating material 22a is attached to the inner peripheral surface of the cover portion 22. The cover portion 22 has a cover-side through-hole 22b that penetrates the outer wall of the cover portion 22.

[0036] The heat insulating material 22a prevents heat from escaping to the outside from the storage space surrounded by the cover portion 22 and one axial side of the housing portion 21. The heat insulating material 22a is cylindrical in shape. The heat insulating material 22a is a porous material that is permeable to gas.

[0037] In the casing 2, a first storage section 24 surrounded by the housing section 21 and the cover section 22 is a space that stores the measurement gas that flows in from the cover-side through-hole 22b of the cover section 22. The measurement gas is, for example, exhaust gas from an automobile or the like.

[0038] A connector portion 6 is attached to the other axial end of the housing portion 21. The connector portion 6 has a plurality of connector pins 61 that connect the concentration measuring portion 3, the heating portion 4, and the thermocouple 5. The connector portion 6 is provided so as to cover the opening on the other axial side of the housing portion 21. Therefore, the cylindrical space on the other axial side of the housing portion 21 and the connector portion 6 form a second storage portion 25. The housing portion 21 has a housing-side through-hole 21a that connects the second storage portion 25 to the outside.

[0039] In the casing 2, a second accommodating section 25 surrounded by the housing section 21 and the connector section 6 is a space that accommodates a reference gas that flows in from the housing-side through-hole 21a of the housing section 21. The reference gas is the atmosphere.

[0040] 3 and 4, the concentration measurement unit 3 is, for example, an oxygen concentration meter that calculates the oxygen partial pressure ratio between a reference gas and a measurement gas. The concentration measurement unit 3 has a concentration sensor element 31 and a pair of sensor electrodes: a measurement electrode 32 and a reference electrode 33.

[0041] The concentration sensor element 31 is configured with a solid electrolyte layer made of an electrolyte having ion conductivity. The concentration sensor element 31 is configured with, for example, a solid electrolyte layer (zirconia ceramic) whose main component is zirconia. The concentration sensor element 31 is cylindrical. An opening on one axial side of the concentration sensor element 31 is covered with a covering member 31a.

[0042] The covering member 31a is made of, for example, glass. The covering member 31a prevents gas that flows in from the opening on the other axial side of the concentration sensor element 31 from flowing out from the opening on one axial side. The covering member 31a also prevents gas from flowing in from the opening on one axial side of the concentration sensor element 31.

[0043] One of the sensor electrodes, the measurement electrode 32, is attached to the outer peripheral surface of one axial side of the concentration sensor element 31. The measurement electrode 32 comes into contact with the gas to be measured. The measurement electrode 32 is, for example, a platinum paste. A measurement electrode lead wire 32a is connected to the measurement electrode 32. The measurement electrode lead wire 32a is, for example, a platinum wire.

[0044] The other sensor electrode, the reference electrode 33, covers the inner circumferential surface of the concentration sensor element 31 from one axial end to the other axial end. Furthermore, the reference electrode 33 covers the inner circumferential surface of the concentration sensor element 31 from the other axial end to the other axial end of the concentration sensor element 31 and the other axial end of the outer circumferential surface. The reference electrode 33 comes into contact with the reference gas. The reference electrode 33 is, for example, platinum paste. A reference electrode lead wire 33a is connected to the reference electrode 33. The reference electrode lead wire 33a is, for example, a platinum wire.

[0045] The concentration measurement unit 3 is held by a holding portion 23a between the measurement electrode 32 and the reference electrode 33. A part of the concentration sensor element 31 and the measurement electrode 32 are located inside the cover portion 22 of the first storage portion 24. A part of the concentration sensor element 31 and the reference electrode 33 are located inside the second storage portion 25.

[0046] 5, the measurement electrode lead wire 32a extends from the measurement electrode 32 toward the other axial side of the concentration sensor element 31. The measurement electrode lead wire 32a passes through the first housing portion 24, the sealing member 23, and the second housing portion 25 and is connected to the connector portion 6. The reference electrode lead wire 33a extends from the reference electrode 33 toward the other axial side of the concentration sensor element 31. The reference electrode lead wire 33a passes through the second housing portion 25 and is connected to the connector portion 6.

[0047] As shown in FIG. 2, the heating unit 4 heats the concentration sensor element 31. The heating unit 4 is, for example, a heater. The heating unit 4 extends from one side to the other side in the axial direction of the concentration sensor element 31 and is attached to the concentration sensor element 31. As shown in FIG. 5, the heating unit 4 has a heating unit first wiring 41 and a heating unit second wiring 42. The heating unit 4 is electrically connected to the connector unit 6 by the heating unit first wiring 41 and the heating unit second wiring 42. The heating unit 4 is held by the sealing member 23.

[0048] The thermocouple 5 measures the temperature of the concentration sensor element 31. More specifically, the thermocouple 5 measures the temperature near the measurement electrode 32 of the concentration sensor element 31. The thermocouple 5 is composed of two metal wires made of different materials, a first metal wire 51 and a second metal wire 52. The thermocouple 5 has a measurement junction 53 where one end of the first metal wire 51 and one end of the second metal wire 52 are joined to each other. The measurement junction 53 is attached to the outer circumferential surface of the concentration sensor element 31 near the measurement electrode 32.

[0049] The first metal wire 51 and the second metal wire 52 are formed of, for example, a platinum-based metal wire. The first metal wire 51 and the second metal wire 52 also extend from near the measurement electrode 32 of the concentration sensor element 31 toward the other axial direction of the concentration sensor element 31. The first metal wire 51 and the second metal wire 52 are connected to the connector 6 through the first housing 24, the sealing member 23, and the second housing 25. The thermocouple 5 has a reference junction 54 formed at the end of the first metal wire 51 and the second metal wire 52 connected to the connector 6. In other words, the reference junction 54 is located within the second housing 25 of the housing 2. The thermocouple 5 generates an electromotive force Et based on the temperature difference between the measurement junction 53 and the reference junction 54.

[0050] Thermocouple 5 measures the surface temperature of concentration sensor element 31, which is a zirconia tube. In other words, measurement junction 53 measures the part of concentration sensor element 31 whose temperature changes when it comes into contact with gas. Therefore, thermocouple 5 directly measures the temperature of concentration sensor element 31, which is necessary for calculating the gas concentration. This improves the accuracy of concentration measurement by concentration measurement unit 3.

[0051] As shown in FIG. 1 , the connector portion 6 electrically connects the multiple wirings and metal wires of the molecular sensor 1 to the multiple wirings from a control device and a power source (not shown). The connector portion 6 has multiple connector pins 61 and a connector main body portion 62. The connector portion 6 is detachably provided on the other axial side of the housing portion 21. One axial end of the connector portion 6 is located within the second accommodating portion 25. The other axial end of the connector portion 6 is located outside the housing portion 2.

[0052] The connector pin 61 is a terminal made of a conductor such as iron. The measurement electrode lead wire 32a and reference electrode lead wire 33a of the concentration measurement unit 3, the heating unit first wiring 41 and heating unit second wiring 42 of the heating unit 4, and the first metal wire 51 and second metal wire 52 of the thermocouple 5 are electrically connected to the connector pin 61. The reference temperature measurement unit first conducting wire 71, reference temperature measurement unit second conducting wire 72, and reference temperature measurement unit third conducting wire 73 of the reference temperature measurement unit 7, which will be described later, are also electrically connected to the connector pin 61. Each of the wiring and metal wires is connected to a different connector pin 61.

[0053] The connector main body 62 is a housing that holds the connector pins 61. The connector main body 62 is made of resin or the like. The connector main body 62 is a cylindrical member. The connector main body 62 is detachably provided on the other axial side of the housing 21. The connector pins 61 are arranged in the connector main body 62 so as to extend in the axial direction of the connector main body 62. When the connector main body 62 is located on the other axial side of the housing 21, one axial end of the connector pin 61 is located within the second accommodating portion 25, and the other axial end of the connector pin 61 is located outside the housing 2. The other axial end of the connector pin 61 is configured to be electrically connectable to wiring or metal wire.

[0054] The reference temperature measurement unit 7 is located inside the second housing portion 25. The reference temperature measurement unit 7 measures the temperature inside the second housing portion 25. The reference temperature measurement unit 7 is, for example, a contact sensor that measures the temperature of a measurement target location by contacting the measurement target location. The reference temperature measurement unit 7 is, for example, a semiconductor temperature sensor that utilizes the temperature characteristics of an electronic component. In this embodiment, the reference temperature measurement unit 7 measures the temperature of the connector portion 6. The reference temperature measurement unit 7 is electrically connected to the connector portion 6 by a reference temperature measurement unit first conductor 71, a reference temperature measurement unit second conductor 72, and a reference temperature measurement unit third conductor 73.

[0055] The reference temperature measurement unit 7 measures the temperature around a portion of the connector 6 where the first metal wire 51 and the second metal wire 52 of the thermocouple 5 are connected. The reference temperature measurement unit 7 is disposed around a connector pin 61 to which the first metal wire 51 and the second metal wire 52 are connected. The reference temperature measurement unit 7 is disposed, for example, in contact with the connector main body 62 between the connector pin 61 to which the first metal wire 51 is electrically connected and the connector pin 61 to which the second metal wire 52 is connected. The reference temperature measurement unit 7 measures the temperature of a portion of the connector main body 62 located near the reference junction 54 of the thermocouple 5. In this way, the reference temperature measurement unit 7 measures the temperature of a portion, such as the connector main body 62, that is approximately equal to the temperature of the reference junction 54 of the thermocouple 5.

[0056] Next, a control method for the molecular sensor 1 in the first embodiment of the present invention will be described with reference to Fig. 2 and Fig. 6. Fig. 6 is a block diagram showing the control of the molecular sensor 1 in the first embodiment of the present invention. As shown in Fig. 6, the molecular sensor 1 is electrically connected to the control device 100 via a cable (not shown) connected to the connector part 6.

[0057] The control device 100 includes a storage unit 101 and a calculation unit 102 .

[0058] The memory unit 101 stores a reference oxygen concentration Pr, which is data relating to the oxygen concentration of a reference gas measured in advance, relational equation data Dn relating to the Nernst equation, and relational equation data Dt relating to the electromotive force Et of the thermocouple 5 relative to the temperature difference between the measurement junction 53 and the reference junction 54 of the thermocouple 5.

[0059] The calculation unit 102 is electrically connected to the concentration measurement unit 3 of the molecular sensor 1. The control device 100 can acquire information related to the electromotive force En of the concentration measurement unit 3 from the concentration measurement unit 3.

[0060] The calculation unit 102 is electrically connected to the reference temperature measurement unit 7 of the molecular sensor 1. The control device 100 can acquire information related to the temperature T1 from the concentration measurement unit 3.

[0061] The calculation unit 102 is electrically connected to the thermocouple 5 of the molecular sensor 1. The control device 100 can acquire information relating to the electromotive force Et of the thermocouple 5 from the thermocouple 5.

[0062] The calculation unit 102 is electrically connected to the heating unit 4 of the molecular sensor 1. The control device 100 can transmit a control signal W to the heating unit 4 to supply the power required to heat the concentration measurement unit 3 from a power supply device 200 (not shown).

[0063] The calculation unit 102 can calculate the temperature T2 of the measurement junction 53 attached to the concentration sensor element 31 based on the relational expression data Dt pre-stored in the memory unit 101, the electromotive force Et of the thermocouple 5, and the temperature T1 measured by the reference temperature measurement unit 7. The calculation unit 102 can calculate the measured oxygen concentration Pm of the measurement gas based on the relational expression data Dn and the reference oxygen concentration Pr pre-stored in the memory unit 101, the electromotive force En of the concentration measurement unit 3, and the temperature T2.

[0064] (Control of heating section) First, the temperature control of the heating unit 4 by the control device 100 will be described.

[0065] The reference temperature measurement unit 7 measures the temperature T1 of the portion of the connector unit 6 where the reference junction 54 of the thermocouple 5 is connected. Therefore, the temperature T1 measured by the reference temperature measurement unit 7, which is disposed near the reference junction 54, can be regarded as the reference temperature of the reference junction 54 of the thermocouple 5. The calculation unit 102 calculates the temperature T2 of the measurement junction 53 of the thermocouple 5 based on the temperature T1 measured by the reference temperature measurement unit 7. As a result, the control device 100 can control the power supplied from the power supply device 200 to the heating unit 4 based on the calculated T2 so that the temperature T2 becomes a predetermined value.

[0066] (concentration measurement) Next, the concentration measurement control by the control device 100 will be described.

[0067] The calculation unit 102 acquires the electromotive force Et of the thermocouple 5 and the temperature T1 of the reference junction 54 measured by the reference temperature measurement unit 7. Based on the relational expression data Dt stored in advance in the storage unit 101, the calculation unit 102 uses the acquired electromotive force Et and temperature T1 to calculate the temperature T2 of the measurement junction 53 attached to the concentration sensor element 31.

[0068] The concentration sensor element 31 generates an electromotive force En according to the ratio of the reference oxygen concentration Pr of the reference gas in contact with the reference electrode 33 on the inner circumferential surface to the measured oxygen concentration Pm of the measurement gas in contact with the measurement electrode 32 on the outer circumferential surface, for example, at a high temperature of 700° C. or higher. The calculation unit 102 acquires the electromotive force En generated by the concentration sensor element 31.

[0069] The calculation unit 102 calculates the measured oxygen concentration Pm of the measurement gas based on the relational equation data Dn pre-stored in the memory unit 101, using the acquired electromotive force En, the calculated temperature T2, and the reference oxygen concentration Pr pre-stored in the memory unit 101.

[0070] The molecular sensor 1 configured as described above uses the reference temperature measurement unit 7 to measure the temperature of the portion of the connector unit 6 where the reference junction 54 of the thermocouple 5 is connected. The reference junction 54 and the connector unit 6 to which the reference junction 54 is connected are located within the second housing unit 25. The thermocouple 5 measures the temperature T2 of the measurement junction 53 based on the temperature of the reference junction 54 heated by the heating unit 4. Even if the reference junction 54 is located within an area affected by the heating unit 4, the thermocouple 5 can accurately measure the temperature of the measurement junction 53 while taking into account the influence of the heating unit 4. Therefore, the molecular sensor 1 calculates the concentration of a specific gas component based on the electromotive force En generated by the solid electrolyte and the temperature T2 of the solid electrolyte measured by the thermocouple 5. This improves the accuracy of concentration measurement by the concentration measurement unit 3 based on the temperature of the concentration sensor element 31 measured by the thermocouple 5 without using a compensating lead wire.

[0071] [Modification 1 of Embodiment 1] Next, the configuration of the molecular sensor 1 in Modification 4 of Embodiment 1 of the present invention will be described with reference to Figures 7 and 8. Figure 7 is a cross-sectional view of the molecular sensor 1 in Modification 4 of Embodiment 1 of the present invention. Figure 8 is a cross-sectional view taken along XII-XII in Figure 7. The molecular sensor 1 in Modification 4 of Embodiment 1 of the present invention differs from the molecular sensor 1 of Embodiment 1 in the position of the reference temperature measurement unit 7 and in the presence of a sealing member 8.

[0072] As shown in FIG. 7 , the molecular sensor 1 has a sealing member 8 that seals the portions of the first metal wire 51 and the second metal wire 52 of the thermocouple 5 that are connected to the connector pin 61, the connector pin 61, and the reference temperature measurement unit 7. The sealing member 8 is made of an insulator. The sealing member 8 is made of, for example, a thermoplastic resin. The sealing member 8 seals the ends of the first metal wire 51 and the second metal wire 52 and the reference temperature measurement unit 7 so as to cover the reference junction 54 of the thermocouple 5 and the reference temperature measurement unit 7.

[0073] The reference temperature measurement unit 7 is connected to the first metal wire 51 and the second metal wire 52 via a sealing member 8. The reference temperature measurement unit 7 is disposed at a position where it can measure the temperature of the reference junction 54 of the thermocouple 5 by the sealing member 8. The reference temperature measurement unit 7 measures the temperature around the reference junction 54 including the first metal wire 51 and the second metal wire 52 of the thermocouple 5 that is connected to the connector pin 61, for example.

[0074] The sealing member 8 is, for example, an insulator with high thermal conductivity. The thermal conductivity of the sealing member 8 is higher than that of air. The thermal conductivity of the sealing member 8 is also higher than that of the connector pins 61. The sealing member 8 is, for example, aluminum oxide. The sealing member 8 connects the first metal wires 51 and the connector pins 61 to which the first metal wires 51 are connected and the connector pins 61 to which the second metal wires 52 and the second metal wires 52 are connected. In other words, the sealing member 8 is in contact with the connector pins 61 to which the first metal wires 51 and the first metal wires 51 are connected and the connector pins 61 to which the second metal wires 52 and the second metal wires 52 are connected. Therefore, when there is a thermal gradient between the connector pins 61 to which the first metal wires 51 and the first metal wires 51 are connected and the connector pins 61 to which the second metal wires 52 and the second metal wires 52 are connected, the sealing member 8 conducts heat from the connector pins 61 with a higher temperature to the connector pins 61 with a lower temperature. This makes the temperature of the connector pin 61 to which the first metal wire 51 is connected and the temperature of the connector pin 61 to which the second metal wire 52 is connected uniform.

[0075] In the molecular sensor 1 configured as described above, the sealing member 8, which has a higher thermal conductivity than the connector pin 61, transfers heat so as to reduce the temperature difference between the connector pin 61 to which the first metal wire 51 is connected and the connector pin 61 to which the second metal wire 52 is connected. This allows the reference temperature measurement unit 7 to further reduce measurement errors in the reference temperature due to the influence of the reference gas. Furthermore, because the reference junction 54 and the reference temperature measurement unit 7 are covered by the sealing member 8, they are less susceptible to influence from the surrounding environment. In other words, the reference temperature measurement unit 7 can stably measure the temperature of the reference junction 54. This improves the accuracy of concentration measurement by the concentration measurement unit 3 without using a compensating lead wire.

[0076] [Other embodiments] Although the embodiments of the present invention have been described above, the above-described embodiments are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiments, and it is possible to appropriately modify the above-described embodiments within the scope of the spirit of the present invention.

[0077] In the above-described first embodiment, the concentration sensor element 31 is made of a solid electrolyte containing zirconia as a main component. However, the concentration sensor element may be made of a solid electrolyte containing a component other than zirconia as a main component.

[0078] In the first embodiment described above, the concentration sensor element 31 is cylindrical. However, the concentration sensor element may have a tubular shape other than a cylindrical shape. That is, the concentration sensor element may have a rectangular tubular shape such as a triangular tubular shape or a square tubular shape, or an elliptical tubular shape.

[0079] In the first embodiment described above, the measurement electrode 32 and the reference electrode 33 are platinum paste. However, the measurement electrode and the reference electrode do not have to be made of platinum or be in a paste form. The measurement electrode and the reference electrode only need to be conductive.

[0080] In the above-described first embodiment, the measurement electrode lead wire 32a and the reference electrode lead wire 33a are platinum wires. However, the measurement electrode lead wire and the reference electrode lead wire may be conductive wires other than platinum wires.

[0081] In the above-described first embodiment, the first metal wire 51 and the second metal wire 52 are made of a platinum-based metal wire. However, the first metal wire and the second metal wire may be made of a metal wire based on a material other than platinum.

[0082] In the first embodiment described above, the connector portion 6 is made of stainless steel. However, the connector portion may be made of resin. The connector portion may also be made of a metal other than stainless steel.

[0083] In the first embodiment described above, the reference temperature measurement unit 7 is a contact sensor that measures the temperature of a measurement target location by contacting the measurement target location. The reference temperature measurement unit 7 is an IC temperature sensor that utilizes the temperature characteristics of an electronic component. However, the reference temperature measurement unit 7 may also be a non-contact sensor that measures the temperature of the measurement target location without contacting the measurement target location.

[0084] In the above-described first embodiment, the reference temperature measurement unit 7 measures the temperature of the connector unit 6. However, the reference temperature measurement unit may measure the ambient temperature inside the second housing unit. In other words, the reference temperature measurement unit may measure the air temperature around the reference junction.

[0085] In the above-described first embodiment, the reference temperature measurement unit 7 measures the temperature of the connector unit 6. However, the reference temperature measurement unit may measure the temperature of the reference junction of the thermocouple.

[0086] The reference temperature measurement unit is disposed, for example, at a position where it can directly measure the temperature of the reference junction of the first metal wire or the second metal wire of the thermocouple. The molecular sensor may also be configured to measure the temperatures of the first metal wire and the second metal wire of the thermocouple individually using two reference temperature measurement units.

[0087] The molecular sensor configured as described above measures the temperature of the reference junction of the thermocouple using the reference temperature measurement unit. The temperature of the reference junction is the reference temperature of the thermocouple. Therefore, by calculating the temperature of the measurement junction based on the reference temperature measured by the reference temperature measurement unit, measurement errors of the thermocouple caused by the temperature of the reference junction are suppressed. This allows for improved concentration measurement accuracy by the concentration measurement unit without using a compensating lead wire.

[0088] The reference temperature measurement unit is connected to, for example, a connector pin to which an end of a first metal wire of a thermocouple is connected. That is, the reference temperature measurement unit is disposed at a position where it can measure the temperature of the connector pin to which the end of the first metal wire is connected. The molecular sensor may use the reference temperature measurement unit to measure the temperature of the connector pin to which the second metal wire of the thermocouple is connected. The molecular sensor may also use the two reference temperature measurement units to individually measure the temperatures of the connector pins to which the first metal wire and the second metal wire are connected.

[0089] The molecular sensor configured as described above uses the reference temperature measurement unit to measure the temperature of the connector pin to which the first metal wire is connected. The temperature of the connector pin to which the reference junction of the first metal wire is connected is approximately the same as the reference temperature of the thermocouple. Therefore, by calculating the temperature of the measurement junction using the temperature measured by the reference temperature measurement unit as the reference temperature, measurement errors of the thermocouple caused by the temperature of the reference junction are suppressed. This improves the accuracy of concentration measurement by the concentration measurement unit without using a compensating lead wire. [Explanation of symbols]

[0090] Single-molecule sensor 2 Housing 21 Housing section 21a Housing side through hole 22 Cover 22a Insulation 22b Cover side through hole 23 Sealing member 23a Holding part 3 Concentration measuring section 31 Concentration sensor element 31a Covering member 32 Measuring electrode 32a Measurement electrode lead wire 33 Reference electrode 33a Reference electrode lead wire 4 Heating section 41 Heating section 1st wiring 42 Heating section 2nd wiring 5 Thermocouples 51 First metal wire 52 Second metal wire 53 Measurement junction 6 Connector part 61 connector pins 62 Connector body 7 Reference temperature measuring section 71 Temperature measurement part 1st conductor 72 Temperature measurement section 2nd conductor 73 Temperature measurement part 3rd conductor 8 Sealing member 100 control device 101 Storage section 102 Arithmetic section 200 Power supply W control signal En, Et Electromotive force T1, T2 temperature Pr Reference oxygen concentration Pm measurement oxygen concentration Dn, Dt relational data

Claims

1. a concentration measuring unit including an electrolyte layer made of an electrolyte having ion conductivity for at least one type of molecule and a pair of sensor electrodes arranged to sandwich the electrolyte layer; a thermocouple for measuring the temperature of the electrolyte layer; a connector portion to which the sensor electrode and the thermocouple are connected and which transmits electrical signals of the sensor electrode and the thermocouple to an outside, a reference temperature measurement unit that measures the temperature of the connector portion as a reference temperature of the thermocouple, and transmits an electrical signal from the reference temperature measurement unit to the outside via the connector portion; Molecular sensors.

2. The molecular sensor according to claim 1 , The reference temperature measurement unit is measuring the temperature of the connector pin of the connector portion to which the thermocouple is connected; Molecular sensors.

3. The molecular sensor according to claim 1 , The reference temperature measurement unit is measuring the temperature of the reference junction of the thermocouple; Molecular sensors.

4. The molecular sensor according to claim 1 , The reference temperature measurement unit is a semiconductor temperature sensor. Molecular sensors.

5. The molecular sensor according to claim 1 , The reference temperature measurement unit is a reference junction of the thermocouple sealed with an insulator; Molecular sensors.

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