JP2005321346A - Oxygen gas detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oxygen gas detector making the best use of a single proton conductive layer to detect precisely an oxygen gas concentration by simple constitution. <P>SOLUTION: A direct-current voltage enough to saturate a current flowing from a positive electrode 1420 to a negative electrode 1430 is impressed between the positive electrode 1420 and the negative electrode 1430, by a variable direct-current power source 2200, and the current flowing from the positive electrode 1420 to the negative electrode 1430 is measured by a direct-current ammeter 2300 to detect the oxygen gas concentration in a measured gas. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an oxygen gas detection device.

  In recent years, various fuel cells have been actively researched as efficient and clean energy sources due to social demands for the global environment and nature conservation. Among these fuel cells, for example, due to advantages such as low-temperature operation and high output density, development of a polymer electrolyte fuel cell is expected as an energy source for home use or in-vehicle use.

  As the anode gas of such a fuel cell, the use of hydrogen gas obtained by reforming natural gas, methanol or the like is considered promising, while as the cathode gas of the fuel cell, for example, humidified air is used. Adopted. The oxygen in the cathode gas is consumed by the power generation of the fuel cell. However, in order to further improve the efficiency, it is required to develop a detection device that can directly detect the concentration of oxygen in the cathode gas.

  In order to ensure safety in consideration of leakage of hydrogen gas from the anode gas side, a detection device having a low operating temperature of, for example, 100 (° C.) is required as a detection device for this request. As such a low temperature operation type oxygen gas detection device, a current detection type oxygen gas detection device using a Nafion (registered trademark) membrane (hereinafter also referred to as a Nafion membrane) as a proton conductive membrane is disclosed in Non-Patent Document 1 below. Are disclosed.

  In this current detection type oxygen gas detection device, the upper and lower Nafion membranes are supported in parallel with each other through a porous sheet, and platinum electrodes are respectively formed on both sides of each Nafion membrane. Yes. Here, the platinum electrode located on the porous sheet side of both platinum electrodes of the upper Nafion membrane passes through the void of the porous sheet, and the platinum electrode located on the porous sheet side of both platinum electrodes of the lower Nafion membrane Opposite the electrode. A diffusion layer is formed on the upper platinum electrode of the upper Nafion film.

  Under such a two-layer structure, when a DC voltage is applied between the platinum electrodes of the lower Nafion membrane, water vapor flowing from the lower side toward the two-layer structure on the lower platinum electrode of the lower Nafion membrane To generate protons. The protons generated in this way move through the lower Nafion membrane to the upper platinum electrode, and are supplied as hydrogen gas into the voids of the porous sheet.

Accordingly, in the upper Nafion membrane, a fuel cell is configured between the oxygen gas in the gas to be measured and the hydrogen gas accumulated in the space. For this reason, when both platinum electrodes of the upper Nafion film are electrically short-circuited, a short-circuit current flows between the two platinum electrodes. Here, since the diffusion layer is formed on the upper platinum electrode of the upper Nafion film as described above, supply of oxygen gas to the upper platinum electrode is restricted. For this reason, the short-circuit current depends on the oxygen partial pressure in the gas to be measured. Therefore, if this short circuit current is measured, the concentration of oxygen gas can be detected.
"A solid-state amperometric oxygen sensor using NAFION menbrane operative at room temperature", Chemistry Letters by Norio Miura etc. pp.1197-1200,1988

  However, in the current detection type oxygen gas detection device, as described above, in order to supply the hydrogen gas necessary for constituting the fuel cell in measuring the short-circuit current, the porosity provided with a space for storing the hydrogen gas is provided. The sheet, the lower Nafion membrane, and both platinum electrodes are essential. Therefore, the porous sheet, the lower Nafion membrane, and both the platinum electrodes become extra constituent members, causing a problem that the configuration of the oxygen gas detection device is complicated.

  In view of the above, the present invention provides an oxygen gas detection apparatus that uses a single proton conduction layer to accurately detect the concentration of oxygen gas with a simple configuration in order to deal with the above-described problems. The purpose is to do.

  In solving the above-mentioned problems, an oxygen gas detection device according to the present invention comprises an oxygen gas sensor (1000) and a detection control means (2000) according to claim 1.

Oxygen gas sensor
A proton conducting layer (1410) made of a polymer electrolyte;
A positive electrode (1420) provided along one of both sides of the proton conducting layer;
A negative electrode (1430) provided along the other of both sides of the proton conducting layer;
A one-side support member (1200) provided along the negative electrode so as to face the proton conduction layer via the negative electrode;
And an other side support member (1300) provided along the positive side electrode so as to face the proton conductive layer via the positive side electrode.

  Here, the one side support member has a diffusion rate controlling portion (1280) that allows the gas to be measured from the outside to flow into the negative electrode, and the other side support member allows the gas to be measured from the outside to be the positive electrode. And an inflow port portion (1321) to be introduced into the water.

The detection control means
A DC power supply (2200) for applying a DC voltage within a predetermined voltage range between the positive electrode and the negative electrode is provided. Here, the predetermined voltage range is such that protons are generated on the positive electrode based on water vapor in the gas to be measured flowing from the inlet of the other side support member, and the generated protons are supplied to the one side support member. It is set to a DC voltage range required for pumping out to the negative electrode through the proton conduction layer so as to react with oxygen in the gas to be measured flowing from the diffusion rate controlling portion.

  In this way, the DC voltage applied between the positive electrode and the negative electrode generates protons on the positive electrode based on the water vapor in the gas to be measured flowing from the inlet of the other side support member. The generated proton is set to a voltage within the DC voltage range required for pumping to the negative electrode through the proton conduction layer so as to react with the oxygen gas in the gas to be measured flowing from the diffusion-controlling portion of the one side support member. Has been.

  Therefore, when a DC voltage set in this way is applied between the positive electrode and the negative electrode, water vapor in the gas to be measured flowing from the inlet port of the other side support member is placed on the positive electrode. Electrolyze to produce protons. The generated protons are pumped to the negative electrode under the conductive action of the proton conductive layer made of the polymer electrolyte, and are generated into hydrogen gas on the negative electrode. This hydrogen gas is consumed by reacting with the oxygen gas in the gas to be measured flowing from the diffusion-controlling portion of the one side support member to become water vapor, so that an increase in the hydrogen gas concentration on the negative electrode is suppressed. Is done.

  In such a state, when the DC voltage from the DC power supply is increased, the amount of generated protons pumped to the negative electrode increases as described above. Accordingly, the amount of hydrogen gas generated on the negative electrode as described above also increases.

  On the other hand, all of the oxygen gas flowing in from the diffusion rate controlling part is consumed by reacting with the increasing hydrogen gas as described above. Accordingly, at the time of such consumption, unreacted hydrogen gas with oxygen gas remains on the negative electrode, and the concentration of hydrogen gas on the negative electrode increases rapidly. For this reason, a difference occurs between the concentration of hydrogen gas on the positive electrode and the concentration of hydrogen gas on the negative electrode, and a voltage corresponding to this difference is generated between the positive electrode and the negative electrode.

  Here, the voltage generated between the positive electrode and the negative electrode in this way has a reverse polarity with respect to the DC voltage of the DC power supply, and acts as a counter electromotive force. For this reason, the substantially applied voltage from the DC power source to the positive side electrode and the negative side electrode is reduced to a voltage obtained by subtracting the back electromotive force from the DC voltage. Therefore, the current flowing from the positive side electrode to the negative side electrode as the generated protons are pumped out as described above becomes saturated, and the oxygen in the gas to be measured is consumed by reacting with the hydrogen gas flowing in from the diffusion rate controlling part. It is proportional to the amount of gas, in other words, the concentration of the oxygen gas.

  Therefore, as described above, a voltage sufficient to saturate the current flowing from the positive electrode to the negative electrode, that is, a DC voltage within the predetermined voltage range is applied between the positive electrode and the negative electrode. Thus, if the current flowing from the positive electrode to the negative electrode is measured, the concentration of oxygen gas in the gas to be measured can be accurately detected.

  In addition, when detecting the oxygen gas concentration with high accuracy, only one proton conductive layer may be employed, and the oxygen gas sensor can be provided with a simple configuration.

  According to a second aspect of the present invention, there is provided an oxygen gas sensor according to the second aspect of the present invention, wherein, in the first aspect of the invention, an oxygen gas sensor (1000) as follows is used instead of the oxygen gas sensor according to the present invention. It is configured to be equipped.

This oxygen gas sensor
It has a bottom wall (1110) having an inlet portion (1111) and a cylindrical peripheral wall (1120) having an inlet portion (1121), and the bottom wall is provided at the bottom end side opening of the peripheral wall. A cylinder (1100);
A one-side support member (1200) received in the cylinder and seated on the bottom wall;
A negative electrode (1430) laminated on the one side support member;
A proton conducting layer (1410) made of a polymer electrolyte laminated on the negative electrode;
A positive electrode (1420) laminated on the proton conductive layer so as to face the negative electrode through the proton conductive layer;
The other side support member (1300) laminated on the positive side electrode so as to face the proton conduction layer via the positive side electrode;
A pressing member (1500) that is fitted into the cylindrical body from its distal end opening and presses the other side support member onto the bottom wall via the positive side electrode, proton conductive layer, negative side electrode, and one side support member. It has.

  Here, the one-side support member has a diffusion-controlling portion (1280) that allows the measurement gas to flow into the negative electrode through the inlet of the bottom wall from the outside, and the other-side support member is the peripheral wall. And an inflow port portion (1321) through which the gas to be measured flowing in from the outside flows into the positive electrode.

  2. The sensor device according to claim 1, wherein the sensor element having a laminated structure of the proton conduction layer, the positive electrode, and the negative electrode is stably held by both support members by employing the oxygen gas sensor having such a configuration. The same effects as the invention can be achieved.

  According to a third aspect of the present invention, there is provided an oxygen gas detection device according to the third aspect of the present invention, wherein the detection control means (3000) is replaced with the detection control means (2000) according to the present invention. It is the composition provided with.

This detection control means
Charging voltage generating means (3060) for generating a charging voltage by being charged with a voltage generated between the positive electrode and the negative electrode;
A reference voltage generating means (3070) for generating a reference voltage within a predetermined voltage range;
Voltage applying means (3050) for applying a DC voltage between the positive electrode and the negative electrode;
Voltage control means for controlling the DC voltage applied between the positive electrode and the negative electrode based on the charging voltage so as to maintain the voltage generated between the positive electrode and the negative electrode at the reference voltage ( 3010, 3020).

  Here, the predetermined voltage range is that protons are generated on the positive electrode based on water vapor in the gas to be measured flowing from the inlet of the other side support member, and the generated protons are supplied to the one side support member. It is set to a DC voltage range required for pumping out to the negative electrode through the proton conduction layer so as to react with oxygen gas in the gas to be measured flowing from the diffusion rate controlling portion.

  By adopting the detection control means configured as described above, the DC voltage applied between the positive electrode and the negative electrode of the oxygen gas sensor from the voltage application means is the reference voltage of the charge voltage from the charge voltage generation means. It is controlled to maintain the voltage, that is, to keep the concentration of hydrogen gas on the negative electrode constant. Accordingly, an increase in current flowing from the positive electrode to the negative electrode is also suppressed. As a result, the current is saturated. The current in such a state is proportional to the amount of oxygen gas flowing in through the diffusion rate controlling hole, that is, the concentration of the oxygen gas.

  Accordingly, a voltage sufficient to saturate the current flowing from the positive electrode to the negative electrode so as to maintain the charging voltage at a reference voltage within the predetermined voltage range is not When applied between the negative electrode and the negative electrode, the current flowing from the positive electrode to the negative electrode is measured, so that the concentration of oxygen gas in the gas to be measured can be accurately detected. Other functions and effects are the same as those of the first aspect of the invention.

  According to the description of claim 4, the oxygen gas detection device according to the present invention is the oxygen according to claim 2, in place of the oxygen gas sensor according to the present invention. The gas sensor is adopted.

  Thus, both the operational effect based on the configuration of the oxygen gas sensor in the invention described in claim 2 and the operational effect based on the detection control means in the invention described in claim 3 can be achieved.

According to the fifth aspect of the present invention, in the oxygen gas detection device according to the third or fourth aspect,
The charging voltage generating means is a capacitor,
The reference voltage generating means is a variable reference power source that generates the reference voltage,
The voltage application means is a differential amplification means,
The voltage control means performs a first switching operation based on a pulse drive signal generating means (3010) for generating a pulse drive signal at a predetermined cycle and a level change in one direction of the pulse drive signal sequentially generated from the pulse drive signal generating means. Switching operation means (3020) that operates to switch to a state and operates to switch to a second switching state based on a level change in the other direction of the pulse drive signal,
The capacitor is charged with a voltage generated between the positive side electrode and the negative side electrode based on the operation of the switching operation means to the first switching state to generate the charging voltage,
The differential amplifying means generates a differential amplified voltage by amplifying the difference between the reference voltage and the charging voltage based on the operation of the switching operation means to the second switching state. The DC voltage is applied so as to generate a voltage corresponding to the differential amplification voltage between the side electrode and the negative side electrode.

  As a result, the differential amplification voltage applied between the positive electrode and the negative electrode is increased to the reference voltage by repeating the switching operation of the switching operation means as described above. It will decrease with time. Accordingly, the amount of hydrogen gas pumped from the positive electrode to the negative electrode is saturated as described above, and the concentration of each hydrogen gas on the positive electrode and the negative electrode becomes a constant value.

  In other words, the differential amplification voltage is controlled so as to maintain the charging voltage at the reference voltage, that is, to keep the concentration of hydrogen gas on the negative electrode constant. As a result, the increase in current flowing from the positive electrode to the negative electrode is suppressed and saturated as described above. The current in such a state is proportional to the amount of oxygen gas flowing in through the diffusion rate controlling portion, that is, the concentration of the oxygen gas. Therefore, by measuring the current, it is possible to more reliably achieve the same effect as the invention of the third or fourth aspect while accurately detecting the concentration of oxygen gas in the gas to be measured.

  According to a sixth aspect of the present invention, in the oxygen gas detection device according to any one of the first to fifth aspects, the predetermined voltage range is 0.7 (V) to 1.. The voltage range is 4 (V).

  Thereby, the same effect as the invention according to any one of claims 1 to 5 can be achieved more reliably.

  According to the seventh aspect of the present invention, in the oxygen gas detection device according to any one of the first to sixth aspects, the positive electrode includes a platinum group metal powder and a polymer electrolyte. It is characterized by being formed of a material obtained by mixing.

  Thereby, it can suppress that the positive side electrode receives the influence of the oxygen which generate | occur | produces by the electrolysis of the water vapor | steam in to-be-measured gas, and is oxidized. For this reason, the effect similar to the invention as described in any one of Claims 1-6 can be achieved, improving durability as an oxygen gas sensor.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

Hereinafter, each embodiment of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 shows a first embodiment of an oxygen gas detector according to the present invention. This oxygen gas detection device includes an oxygen gas sensor 1000 and a detection control circuit 2000.

  The oxygen gas sensor 1000 includes a metal cylindrical cylinder 1100, and the cylinder 1100 has an inlet portion 1111 at the center of the bottom wall 1110. The cylindrical body 1100 includes two inlet portions 1121 at the peripheral wall 1120, and these inlet portions 1121 are equiangularly spaced along the circumferential direction of the peripheral wall 1120 in the vicinity of the bottom wall 1110. Is formed. 1 and 2, reference numeral 1140 denotes an annular flange, and the flange 1140 is formed to extend outward from the distal end side opening of the peripheral wall 1120 in the radial direction.

  Further, as shown in FIG. 1, the oxygen gas sensor 1000 includes a lower support member 1200, an upper support member 1300, a sensor element 1400, and an annular seal 1450 housed in a cylindrical body 1100.

  As shown in detail in FIG. 2, the lower support member 1200 includes lower, middle, and upper substrates 1210, 1220, and 1230 that are circular, and the substrates 1210, 1220, and 1230 are both It is made of a ceramic material.

  An annular lower electrode layer 1240 is coaxially stacked on the back surface of the lower substrate 1210. Further, the intermediate substrate 1220 is coaxially stacked on the surface of the lower substrate 1210 with a disk-shaped intermediate electrode layer 1250 interposed therebetween. Here, the intermediate electrode layer 1250 is electrically connected to the lower electrode layer 1240 through a through hole 1211 formed in the lower substrate 1210 in the thickness direction. Both the substrates 1210 and 1220 have the same outer diameter. Further, the outer diameter of the intermediate electrode layer 1250 is smaller than the outer diameters of both the substrates 1210 and 1220 and larger than the inner diameter of the lower electrode layer 1240.

  Further, the upper substrate 1230 is coaxially laminated on the surface of the intermediate substrate 1220 via the disk-shaped intermediate electrode layer 1260, and the upper electrode layer 1270 is coaxial with the surface of the upper substrate 1230. Are stacked. Here, the intermediate electrode layer 1260 is electrically connected to the intermediate electrode layer 1250 through a through-hole 1221 formed in the intermediate substrate 1220 in the thickness direction. The upper electrode layer 1270 is electrically connected to the intermediate electrode layer 1260 through a through hole 1231 formed in the upper substrate 1230 in the thickness direction. The outer diameter of the upper substrate 1230 is smaller than the outer diameter of the intermediate substrate 1220 and is the same as the outer diameter of the upper electrode layer 1270. Further, the outer diameter of the intermediate electrode layer 1260 is smaller than the outer diameter of the intermediate electrode layer 1250.

  The upper electrode layer 1270, the upper substrate 1230, the intermediate electrode layer 1260, the intermediate substrate 1220, the intermediate electrode layer 1250, and the lower substrate 1210 stacked in this manner are diffused from the upper electrode layer 1270 to the lower substrate 1210. The rate limiting hole 1280 is formed coaxially.

  The lower support member 1200 configured as described above is accommodated in the cylindrical body 1100 so as to be seated on the inner surface of the bottom wall 1110 of the cylindrical body 1100 with the lower substrate 1210 through the lower electrode layer 1240. (See FIG. 1).

  On the other hand, as shown in detail in FIG. 2, the upper support member 1300 includes an annular lower substrate 1310, an annular intermediate substrate 1320, and circular upper substrates 1330 and 1340. Both 1340 are formed of a ceramic material so as to have the same outer diameter.

  The intermediate side substrate 1320 is coaxially stacked on the surface of the lower side substrate 1310, and four groove-shaped inlet portions 1321 are formed at the upper end side opening surface on the outer peripheral portion of the intermediate side substrate 1320. It is formed by contacting the back surface of the upper substrate 1330. These inflow ports 1321 are formed at equal angular intervals along the circumferential direction of the substrate 1320. Here, each inflow port portion 1321 communicates the hollow portion in the substrate 1320 outward from the inner peripheral surface of the substrate 1320 every 90 degrees in the circumferential direction of the substrate 1320.

  The upper substrate 1330 is coaxially laminated on the surface of the intermediate substrate 1320, and a disk-shaped lower electrode layer is formed on the back surface portion of the back surface of the upper substrate 1330 exposed in the hollow portion of the intermediate substrate 1320. 1350 is provided. The upper substrate 1340 is coaxially stacked on the surface of the upper substrate 1330 via the intermediate electrode layer 1360, and the upper electrode layer 1370 is coaxially stacked on the surface of the upper substrate 1340.

  Here, the intermediate electrode layer 1360 is electrically connected to the lower electrode layer 1350 through a through hole 1331 formed in the upper substrate 1330 in the thickness direction. The upper electrode layer 1370 is electrically connected to the intermediate electrode layer 1360 through a through hole 1341 formed in the upper substrate 1340 in the thickness direction. Note that the outer diameters of the intermediate electrode layer 1360 and the upper electrode layer 1370 are smaller than the outer diameter of the substrate 1330 and are the same as the outer diameter of the lower electrode layer 1350.

  The upper support member 1300 configured as described above is seated on the outer peripheral portion of a proton conductive layer 1410 (described later) of the sensor element 1400 with the annular lower substrate 1310.

  As shown in FIGS. 1 and 2, the sensor element 1400 is sandwiched between the support members 1200 and 1300. The sensor element 1400 includes a proton conductive layer 1410, positive and negative side electrodes 1420 and 1430, and diffusion. A member 1440 is provided.

  The proton conductive layer 1410 is formed in a disk shape with a fluorine-based resin material that functions at a relatively low temperature, for example, Nafion (registered trademark of DuPont), and the proton conductive layer 1410 is formed on the outer periphery thereof. Thus, the support members 1200 and 1300 are sandwiched between the outer peripheral portions via the annular seal 1450. Here, the annular seal 1450 is airtightly sandwiched between the outer periphery of the proton conducting layer 1410 and the outer periphery of the intermediate substrate 1220 of the lower support member 1200.

  The positive side electrode 1420 is formed in a disk shape together with the negative side electrode 1430 and the diffusion member 1440, and the positive side electrode 1420 is formed along with the diffusion member 1440 on the lower substrate 1310 and the intermediate substrate 1320 of the upper support member 1300. It is fitted in both the hollow portions and is sandwiched between the proton conductive layer 1410 and the lower electrode layer 1360 of the upper support member 1300 via the diffusion member 1440.

  Here, the positive electrode 1420 is in contact with the positive side surface (the upper side surface shown in FIG. 2) of the proton conducting layer 1410 on the back surface, and the positive electrode 1420 is on the surface with the diffusion member. 1440 is in contact with the back surface of the lower electrode layer 1360.

  In the first embodiment, the positive electrode 1440 is formed of a material obtained by mixing a powder of platinum group metal or the like and a polymer electrolyte. Specifically, the positive electrode 1440 is obtained by kneading both a platinum group metal powder and a polymer electrolyte into a paste, applying the paste to the positive side of the proton conductive layer 1410, and then drying. It is formed.

  The negative electrode 1430 is sandwiched between the upper electrode layer 1270 of the lower support member 1200 and the negative side surface of the proton conductive layer 1410. The negative electrode 1430 is a porous electrode material such as a platinum group metal. It is formed using carbon paper formed by applying a catalyst such as one side to the other side. Specifically, the negative electrode 1430 is bonded to the negative side surface of the proton conductive layer 1410 by hot pressing so that the carbon paper is in close contact with the negative side surface of the proton conductive layer 1410 with the catalyst. And formed.

  The diffusion member 1440 is sandwiched between the positive electrode 1420 and the lower electrode layer 1350 of the upper support member 1300, and the respective inlet portions 1121 and the respective inlet ports of the upper support member 1300 from the outside of the cylindrical body 1100. Water vapor flowing in through the portion 1121 is diffused and guided to the positive electrode 1420. The diffusion member 1440 is formed of, for example, a titanium mesh plated with platinum in consideration of corrosion resistance.

  The cylindrical resin member 1500 is coaxially fitted into the cylindrical body 1100 from the opening on the front end via both annular seals 1510 and 1520, and the resin member 1500 is connected to the sensor via the upper support member 1300. The element 1400 is pressed onto the lower support member 1200. The resin member 1500 is made of an electrically insulating resin material.

  The annular seal 1510 is coaxially fitted to a small diameter portion 1540 formed at the lower end portion of the resin member 1500, and is airtight between the outer peripheral portion of the upper support member 1300 and the lower end surface of the large diameter portion 1530 of the resin member 1500. Is pinched. The annular seal 1520 is coaxially fitted in a groove 1531 formed in an annular shape at an axially intermediate portion of the large diameter portion 1530 of the resin member 1500, and the peripheral wall 1120 of the cylindrical body 1100 and the bottom surface of the annular groove 1531 It is sandwiched in an airtight manner.

  The negative side connection terminal 1600 is composed of a crank-shaped terminal, and the negative side connection terminal 1600 is formed in an L shape from the upper surface to the outer peripheral surface of the resin member 1500 at the intermediate portion 1610 and the tip portion 1620 thereof. Housed in a recess 1550. Here, the negative connection terminal 1600 is in contact with the peripheral wall 1120 of the cylindrical body 1100 at the convex curved portion 1621 formed at the intermediate portion of the distal end portion 1620 and is electrically connected to the cylindrical body 1100. Yes.

  Further, the positive side connection terminal 1700 is a substantially L-shaped terminal, and the positive side connection terminal 1700 is inserted into the through hole 1560 and the recess 1570 of the resin member 1500 as shown in FIG. Is contained. Here, the positive side connection terminal 1700 is located in the recess 1570 at the leg portion 1710 and is in contact with and electrically connected to the upper electrode layer 1370 of the upper support member 1300.

  The above-described through hole 1560 is formed coaxially with the resin member 1500. The recess 1570 is formed in communication with the through hole 1560 in an L shape at the lower end of the resin member 1500. Further, in the first embodiment, in the oxygen gas sensor 1000, the constituent members other than the cylindrical body 1100 extend from the lower support member 1200 located on the lower side in the drawing to the negative connection terminal located on the upper side in the drawing in FIG. These are sequentially accommodated in the cylinder 1100.

  As shown in FIG. 1, the detection control circuit 2000 includes an operation switch 2100 and a variable DC power source 2200, and the variable DC power source 2200 generates a DC voltage. This DC voltage is changed by adjusting the voltage of the variable DC power supply 2200. Here, the variable DC power supply 2200 is connected to the positive electrode 1700 through the lead wire 1720 via the DC ammeter 2300 at the positive terminal thereof, and the negative terminal of the variable DC power supply 2200 is The lead wire 1630 is connected to the negative electrode 1600 via the operation switch 2100.

  In the first embodiment configured as described above, an example of oxygen gas detection by the oxygen gas detection device will be described. When the oxygen gas sensor 1000 is disposed in the atmosphere to be measured, the gas to be measured in the atmosphere to be measured flows into the cylindrical body 1100 from each inlet portion 1121 and the inlet portion 1111.

  Thus, when the gas to be measured flows into the cylindrical body 1100 from each inflow port 1121 as described above, the gas to be measured is diffused by the diffusion member 1440 and flows into the positive electrode 1420. On the other hand, when the gas to be measured flows into the cylindrical body 1100 from the inlet portion 1111 as described above, the gas to be measured flows into the negative electrode 1430 through the diffusion limiting hole portion 1280 of the lower support member 1200.

  In this state, when the operation switch 2100 is turned on, the variable DC power supply 2200 applies a DC voltage between the positive connection terminal 1700 and the negative connection terminal 1600 of the oxygen gas sensor 1000 via the DC ammeter 2300. . This means that a DC voltage from the variable DC power source 2200 is applied between the positive electrode 1420 and the negative electrode 1430 of the sensor element 1400.

  Then, as described above, the water vapor in the gas to be measured flowing into the positive electrode 1420 is generated on the positive electrode 1420 based on the DC voltage applied between the positive electrode 1420 and the negative electrode 1430 described above. Electrolyzed to produce protons. Accordingly, the proton is pumped out to the negative electrode 1430 under the conduction action of the proton conduction layer 1410 and is generated as hydrogen gas.

  At this time, the direct current generated by pumping out protons as described above is the positive electrode 1420 of the sensor element 1400, the proton conductive layer 1410 and the negative electrode 1430, the upper electrode layer 1270 of the lower support member 1200, and the upper substrate 1230. Through hole 1231, intermediate electrode layer 1260, through hole 1221 in intermediate substrate 1220, intermediate electrode layer 1250, through hole 1211 and lower electrode layer 1240 in lower substrate 1210, cylinder 1100, negative connection terminal 1600 , Operation switch 2100, variable DC power supply 2200, DC ammeter 2300, positive side connection terminal 1600, upper electrode layer 1370 of upper support member 1300, through hole 1341 of upper substrate 1340, intermediate electrode layer 1360, through hole 1331 and lower Side electrode layer 1350 and diffusion member 1440 As flows to the positive electrode 1420.

  At this stage, if oxygen gas is contained in the gas to be measured flowing into the negative electrode 1430 as described above, the oxygen gas is generated on the negative electrode 1430 with the hydrogen gas generated as described above. It reacts and is consumed to become water vapor. For this reason, an increase in the concentration of hydrogen gas due to the generation on the negative electrode 1430 is suppressed.

  Here, as described above, when the DC voltage applied between the positive electrode 1420 and the negative electrode 1430 (hereinafter also referred to as applied voltage) is increased by adjusting the voltage of the variable DC power supply 2200, As described above, the amount of protons generated on the positive electrode 1420 and pumped to the negative electrode 1430 increases. Accordingly, the amount of hydrogen gas generated on the negative electrode 1430 increases as described above.

  Then, as described above, the oxygen gas in the measurement gas flowing into the negative electrode 1430 through the diffusion rate controlling hole 1280 reacts with the generated hydrogen gas increasing on the negative electrode 1430 as described above and is consumed. The Then, when consumed in this way, hydrogen gas that has not reacted with oxygen gas remains on the negative electrode 1430. As a result, the concentration of hydrogen gas on the negative electrode 1430 increases rapidly.

  Accordingly, a difference occurs between the concentration of hydrogen gas on the positive electrode 1420 and the concentration of hydrogen gas on the negative electrode 1430, and this difference in hydrogen gas concentration is the difference between the positive electrode 1420 and the negative electrode 1430. A voltage is generated between

  Here, the voltage thus generated has a reverse polarity with respect to the applied voltage. This means that the voltage generated between the positive electrode 1420 and the negative electrode 1430 as described above acts as a counter electromotive force on the DC voltage from the variable DC power supply 2200. For this reason, the voltage substantially applied between the positive electrode 1420 and the negative electrode 1430 is reduced to a voltage obtained by subtracting the counter electromotive force from the DC voltage from the variable DC power supply 2200.

  Accordingly, an increase in current flowing from the positive electrode 1420 to the negative electrode 1430 is also suppressed. As a result, the current is saturated. The current in such a state is proportional to the amount of oxygen gas flowing through the diffusion rate limiting hole 1280, that is, the concentration of the oxygen gas.

  Therefore, if a DC voltage sufficient to saturate the current flowing from the positive electrode 1420 to the negative electrode 1430 is applied between the positive electrode 1420 and the negative electrode 1430 with the variable DC power supply 2200, By measuring the current flowing from the side electrode 1420 to the negative side electrode 1430 with the DC ammeter 2300, the concentration of oxygen gas in the gas to be measured can be accurately detected.

  Here, as described above, the sensor element 1400 only needs to have a single proton conductive layer 1410 as a proton conductive layer, and the oxygen gas sensor 1000 can be simply configured. May be provided in configuration. In addition, the sensor element 1400 can detect the oxygen gas concentration with high accuracy as described above without relying on the reference electrode, and with a simpler electrode configuration of the two-electrode configuration of the positive electrode 1420 and the negative electrode 1430. it can.

  Further, as described above, since the proton conductive layer has only a single proton conductive layer 1410, it is not necessary to employ the configuration for measuring the short-circuit current as described at the beginning of this specification, and oxygen High detection accuracy of gas concentration can be maintained.

  Further, as can be seen from the configuration of the oxygen gas sensor 1000 described above, the lower support member 1200, the sensor element 1400, and the upper support member 1300 are sequentially placed on the bottom wall 1110 of the cylindrical body 1100 in the respective plate thickness directions. Are stacked. The upper support member 1300 is pressed by the resin member 1500 onto the bottom wall 1110 via the sensor element 1400 and the lower support member 1200.

  Therefore, the sensor element 1400 is firmly sandwiched between the support members 1200 and 1300 in the thickness direction. As a result, even if vibration or impact is applied to the oxygen gas sensor 1000, the sensor element 1400 can be stably supported between the support members 1200 and 1300 without being displaced in the cylindrical body 1100. As a result, it is excellent in earthquake resistance and impact resistance as an oxygen gas sensor.

  In addition, as described above, the positive electrode 1420 is formed of a material obtained by mixing a white metal powder and a polymer electrolyte, so that the positive electrode 1420 is an electric current of water vapor in the gas to be measured. Oxidation due to the influence of oxygen generated by decomposition can be suppressed. For this reason, durability as the oxygen gas sensor 1000 can be improved.

  Incidentally, when the oxygen gas concentration in the measurement gas (hereinafter also referred to as oxygen gas concentration) was detected using the oxygen gas detection device of the first embodiment, as shown in the graph of FIG. A detection result was obtained. In this detection, the detection conditions are as follows.

The gas composition of the measured gas is 1 (%), 5 (%), 10 (%), 15 (%) or 20 (%) oxygen (O ₂ ), 20 (%) water (H ₂ O). ) And nitrogen (N ₂ ). The temperature and flow rate of the gas to be measured are 80 (° C.) and 10 (liter / min). However, the DC voltage applied between the positive electrode 1420 and the negative electrode 1430 is 1 (V).

  The graph of FIG. 3 shows the relationship between the oxygen gas concentration and the DC current (pump current flowing from the positive electrode to the negative electrode) measured by the DC ammeter 2300. According to this, it can be seen that the concentration of oxygen gas has a substantially direct relationship with the direct current.

  Next, when the optimum range of the DC voltage (applied voltage) applied between the positive electrode 1420 and the negative electrode 1430 was examined, the measurement results shown in the graph of FIG. 4 were obtained. The graph of FIG. 4 shows the change range of the applied voltage in relation to the pump current. In this measurement, the measurement conditions are as follows.

The gas composition of the measurement gas is 20 (%) oxygen (O ₂ ), 20 (%) water (H ₂ O), and nitrogen (N ₂ ). The temperature and flow rate of the gas to be measured are set to 80 (° C.) and 10 (liter / minute) in the same manner as described above. The change range of the applied voltage is set within a range of 0.5 (V) to 1.6 (V).

  According to the graph of FIG. 4, it can be seen that when the applied voltage is less than 0.7 (V), the applied voltage increases with the pump current. This is due to the following reason. That is, when the applied voltage is less than 0.7 (V), the concentration of hydrogen gas generated on the negative electrode 1430 is lower than the concentration of oxygen gas flowing in through the diffusion rate controlling hole 1280. For this reason, unreacted oxygen gas with hydrogen gas remains on the negative electrode 1430. Therefore, the pump current in such a state is hardly reflected in the concentration of oxygen gas, and as a result, the applied voltage increases with the pump current as described above.

  It can also be seen that when the applied voltage increases above 1.4 (V), the applied voltage increases with the pump current. This is due to the following reason. That is, when the applied voltage is higher than the voltage generated due to the difference in hydrogen gas concentration between the positive electrode 1420 and the negative electrode 1430, the pump current increases with the applied voltage. In such a state, since the amount of hydrogen gas on the negative electrode 1430 is larger than the amount of oxygen gas flowing in through the diffusion rate controlling hole portion 1280, the pump current is difficult to reflect on the concentration of oxygen gas. It is.

  Moreover, when the said applied voltage exists in the range of 0.7 (V)-1.4 (V), it turns out that a pump electric current hardly changes and is saturated. This is due to the following reason. That is, the concentration of hydrogen gas on the negative electrode 1430 increases, and the voltage generated due to the difference in hydrogen gas concentration between the positive electrode 1420 and the negative electrode 1430 acts on the applied voltage as a back electromotive force. To do. For this reason, the substantially applied voltage applied between the positive electrode 1420 and the negative electrode 1430 does not increase. In other words, the oxygen gas flowing from the diffusion-controlling hole 1280 reacts with the hydrogen gas on the negative electrode 1430 and is all consumed.

  From the above, if the applied voltage is adjusted to a voltage within the range of 0.7 (V) to 1.4 (V), such a voltage causes a current flowing from the positive electrode 1420 to the negative electrode 1430 described above. It can be seen that this corresponds to a DC voltage sufficient to saturate.

Therefore, by applying a voltage within the range of 0.7 (V) to 1.4 (V) between the positive side electrode 1420 and the negative side electrode 1430 as the applied voltage, the positive side electrode 1420 and the negative side electrode 1420 are applied. When the pump current flowing between the electrodes 1430 is measured by the DC ammeter 2300, the concentration of oxygen gas in the gas to be measured can be detected with high accuracy.
(Second Embodiment)
Next, a second embodiment of the oxygen gas detection device according to the present invention will be described with reference to FIGS. In the second embodiment, as shown in FIG. 5, the oxygen gas detection device described in the first embodiment employs a detection control circuit 3000 instead of the detection control circuit 2000.

  The detection control circuit 3000 includes a drive circuit 3010 and a semiconductor switch circuit 3020 driven by the drive circuit 3010. The drive circuit 3010 includes a pulse generation circuit. The drive circuit 3010 generates a drive pulse signal at a predetermined cycle and outputs the drive pulse signal to the semiconductor switch circuit 3020.

  The semiconductor switch circuit 3020 is configured to electronically connect the fixed terminal 3021 to both of the switching terminals 3022 and 3023 in accordance with the switching operation. Therefore, the semiconductor switch circuit 3020 performs switching operation based on the pulse drive signals sequentially output from the drive circuit 3010.

  Specifically, when the pulse drive signal becomes a low level L (see FIG. 6), the semiconductor switch circuit 3020 connects the fixed terminal 3021 to the switching terminal 3022. In other words, the semiconductor switch circuit 3020 is connected to the differential amplifier 3050 via the DC ammeter 3040 at the switching terminal 3022, and the differential amplification voltage output from the differential amplifier 3050 is transferred to the fixed terminal 3021 and The voltage is applied between the positive connection terminal 1700 and the negative connection terminal 1600 of the oxygen gas sensor 1000 through the operation switch 3030.

  When the pulse drive signal becomes high level H (see FIG. 6), the semiconductor switch circuit 3020 connects the fixed terminal 3021 to the switching terminal 3023. In other words, the semiconductor switch circuit 3020 inputs a DC voltage from the positive connection terminal 1700 of the oxygen gas sensor 1000 through the operation switch 3030 and applies it to the capacitor 3060. In the second embodiment, each time corresponding to the high level width and the low level width of the pulse drive signal is, for example, 0.1 (msec) and 2 (msec) (see FIG. 6).

  Here, the semiconductor switch circuit 3020 is connected to the positive connection terminal 1700 of the oxygen gas sensor 1000 through the lead wire 1720 via the operation switch 3030 at the fixed terminal 3021. The semiconductor switch circuit 3020 is connected to the output terminal of the differential amplifier 3050 via the DC ammeter 3040 at the switching terminal 3022. The switching terminal 3023 of the semiconductor switch circuit 3020 is connected via the capacitor 3060. Grounded.

  The differential amplifier 3050 includes a reference voltage Vref (refer to reference numeral 3071 in FIG. 6) from the variable reference power supply 3070 and a terminal voltage Vc of the capacitor 3060 (hereinafter also referred to as capacitor voltage Vc; refer to reference numeral 3061 in FIG. 6). The difference is differentially amplified and output to the switching terminal 3022 of the semiconductor switch circuit 3020 via the DC ammeter 3040 as a differential amplified voltage Vdif (see reference numeral 3051 in FIG. 6).

  The variable reference power supply 3070 outputs a DC voltage corresponding to the voltage adjustment as the reference voltage Vref. The capacitor 3060 is charged by applying the DC voltage from the oxygen gas sensor 1000 from the switching terminal 3023 of the semiconductor switch circuit 3020. The capacitor 3060 discharges through the differential amplifier 3050 when the fixed terminal 3021 and the switching terminal 3022 of the semiconductor switch circuit 3020 are connected, that is, when the switching terminal 3023 is disconnected from the fixed terminal 3021.

  In the second embodiment, the capacitance of the capacitor 3060 and the semiconductor switch circuit 3020 are formed between the capacitor 3060, the semiconductor switch circuit 3020, and the oxygen gas sensor 1000 in a state where the fixed terminal 3021 is connected to the switching terminal 3023. The charging time constant is small. Further, the discharge time constant formed by the capacitor 3060 and the differential amplifier 3050 in a state where the semiconductor switch circuit 3020 blocks the fixed terminal 3021 from the switching terminal 3023 is considerably larger than the charge time constant. Other configurations are the same as those of the second embodiment.

  In the second embodiment configured as described above, the oxygen gas sensor 1000 is disposed in the measured atmosphere in the same manner as in the first embodiment. Along with this, the gas to be measured in the atmosphere to be measured flows from the respective inlet portions 1121 into the cylindrical body 1100, is diffused by the diffusion member 1440, and flows into the positive electrode 1420. On the other hand, the gas to be measured flows into the cylindrical body 1100 from the inlet portion 1111, and then flows into the negative electrode 1430 through the diffusion limiting hole 1280 of the lower support member 1200.

  In such a state, if the operation switch 3030 is in an off state and the capacitor 3060 is in a discharge completed state with the drive circuit 3010 stopped, the reference voltage Vref from the variable reference power supply 3070 is the terminal voltage of the capacitor 3060. It is higher than the capacitor voltage Vc, and the difference between the reference voltage Vref and the capacitor voltage Vc is the maximum (see FIG. 6).

  Therefore, the difference between the reference voltage Vref and the capacitor voltage Vc is differentially amplified by the differential amplifier 3050 and output to the semiconductor switch circuit 3020 through the DC ammeter 3040 as a differentially amplified voltage.

  At this stage, when the operation switch 3030 is turned on and the drive circuit 3010 is operated, the operation switch 3030 connects the fixed terminal 3021 of the semiconductor switch circuit 3020 to the positive connection terminal 1700 of the oxygen gas sensor 1000 and its lead wire 1720. And the drive circuit 3010 sequentially outputs pulse drive signals to the semiconductor switch circuit 3020.

  Thus, when the drive circuit 3010 sequentially outputs the pulse drive signal to the semiconductor switch circuit 3020 in this way, the semiconductor switch circuit 3020 is based on the change of the pulse drive signal sequentially output from the drive circuit 3010 to the low level L. The fixed terminal 3021 is connected to the switching terminal 3022. Further, the semiconductor switch circuit 3020 connects the fixed terminal 3021 to the switching terminal 3023 based on the change of the pulse drive signal sequentially output from the drive circuit 3010 to the high level H.

  In other words, the semiconductor switch circuit 3020 connects the output terminal of the differential amplifier 3050 to the positive connection terminal of the oxygen gas sensor 1000 via the DC ammeter 3040 and the operation switch 3030 every time the pulse drive signal changes to a low level L. 1700 and the positive terminal of the capacitor 3060 are disconnected from the operation switch 3030. The semiconductor switch circuit 3020 connects the positive terminal of the capacitor 3060 to the positive connection terminal 1700 via the operation switch 3030 and outputs the differential amplifier 3050 each time the pulse drive signal changes to the high level H. Is disconnected from the operation switch 3030.

  Therefore, every time the pulse drive signal sequentially output from the drive circuit 3010 becomes the low level L, the differential amplification voltage output from the differential amplifier 3050 as described above is the DC ammeter 3040 and the semiconductor switch circuit 3020. The voltage is applied between the positive side connection terminal 1700 and the negative side connection terminal 1600 of the oxygen gas sensor 1000 through the switching terminal 3022, the fixed terminal 3021 and the operation switch 3030. This is because each time the pulse drive signal sequentially output from the drive circuit 3010 becomes a low level L, the differential amplification voltage output from the differential amplifier 3050 is the positive side electrode 1420 and the negative side electrode 1430 of the sensor element 1400. It is applied between.

  Therefore, whenever the differential amplification voltage from the differential amplifier 3050 is applied between the positive electrode 1420 and the negative electrode 1430 of the sensor element 1400 as described above, it flows into the positive electrode 1420 as described above. The water vapor in the gas to be measured is electrolyzed on the positive electrode 1420 to generate protons. Accordingly, the proton is pumped out to the negative electrode 1430 under the conduction action of the proton conduction layer 1410 and is generated as hydrogen gas.

  At this time, a direct current generated by pumping out protons as described above flows through the positive electrode 1420, the proton conductive layer 1410 and the negative electrode 1430, the lower support member 1200, and the cylinder 1100 of the sensor element 1400.

  At the present stage, as described above, since the difference between the reference voltage Vref and the capacitor voltage Vc is the maximum, the proton generated on the positive electrode 1420 and pumped to the negative electrode 1430 as described above. There is a lot of. Accordingly, the amount of hydrogen gas generated on the negative electrode 1430 is also large as described above.

  In such a state, a large amount of oxygen gas in the measurement gas flowing into the negative electrode 1430 through the diffusion rate controlling hole 1280 is generated on the negative electrode 1430 as described above, as in the first embodiment. It reacts with hydrogen gas and is consumed. Then, when consumed in this way, hydrogen gas that has not reacted with oxygen gas remains on the negative electrode 1430. As a result, the concentration of hydrogen gas on the negative electrode 1430 increases rapidly.

  Accordingly, a difference occurs between the concentration of hydrogen gas on the positive electrode 1420 and the concentration of hydrogen gas on the negative electrode 1430, and this difference in hydrogen gas concentration is the difference between the positive electrode 1420 and the negative electrode 1430. A voltage is generated between Here, the voltage generated in this way has a reverse polarity with respect to the differential amplification voltage. This means that the voltage generated between the positive side electrode 1420 and the negative side electrode 1430 as described above acts as a counter electromotive force on the differential amplification voltage from the differential amplifier 3050. Therefore, the voltage substantially applied between the positive electrode 1420 and the negative electrode 1430 is reduced to a voltage obtained by subtracting the counter electromotive force from the differential amplification voltage of the differential amplifier 3050.

  Further, as described above, the voltage generated between the positive electrode 1420 and the negative electrode 1430 is applied to the capacitor 3060 every time the pulse drive signal from the drive circuit 3010 changes to the high level H as described above. The capacitor 3060 is charged. Therefore, the capacitor 3060 generates the capacitor voltage Vc corresponding to the voltage corresponding to the difference in hydrogen gas concentration generated between the positive electrode 1420 and the negative electrode 1430 as described above. Note that the capacitor voltage Vc of the capacitor 3060 increases abruptly before the time corresponding to the high level H elapses every time the pulse drive signal becomes the high level H as described above (see FIG. 6).

  By repeating the above operation, the capacitor voltage Vc increases so as to approach the reference voltage Vref of the variable reference power supply 3070 while increasing stepwise as shown in FIG. As a result, the differential amplification voltage Vdif output from the differential amplifier 3050 decreases stepwise as shown in FIG. Accordingly, the amount of hydrogen gas pumped from the positive electrode 1420 to the negative electrode 1430 is saturated stepwise, and the difference in concentration of the hydrogen gas on both electrodes 1420 and 1430 becomes constant.

  In other words, the differential amplification voltage from the differential amplifier 3050 to the oxygen gas sensor 1000 maintains the capacitor voltage Vc at the reference voltage Vref, that is, makes the concentration of hydrogen gas on the positive electrode 1420 constant. Controlled. Accordingly, an increase in current flowing from the positive electrode 1420 to the negative electrode 1430 is also suppressed. As a result, the current is saturated. The current in such a state is proportional to the amount of oxygen gas flowing through the diffusion rate limiting hole 1280, that is, the concentration of the oxygen gas.

  Therefore, if a differential amplification voltage sufficient to saturate the current flowing from the positive electrode 1420 to the negative electrode 1430 is applied between the positive electrode 1420 and the negative electrode 1430 with the differential amplifier 3050. By measuring the current flowing from the positive electrode 1420 to the negative electrode 1430 with the DC ammeter 3040, the concentration of oxygen gas in the gas to be measured can be detected with high accuracy.

  As understood from the above description, under the charge control of the capacitor 3060, the voltage generated between the positive electrode 1420 and the negative electrode 1430 is maintained at a constant voltage (reference voltage Vref). A differential amplification voltage of the differential amplifier 3050 is increased or decreased in accordance with an increase or decrease in the concentration of oxygen gas in the gas to be measured, and is applied as a control voltage between the positive electrode 1420 and the negative electrode 1430. As a result, the concentration of hydrogen gas on the negative electrode 1430 is maintained constant. For this reason, in such a state, when the current flowing from the positive side electrode 1420 to the negative side electrode 1430 is measured by the DC ammeter 3040 as a pump current, the concentration of oxygen gas in the gas to be measured can be accurately detected. Other functions and effects are the same as those of the first embodiment.

  Incidentally, in the second embodiment, when the optimum range of the reference voltage Vref of the variable reference power supply 3070 was examined, the result shown in the graph of FIG. 7 was obtained. This graph shows the change range of the reference voltage in relation to the pump current. In this measurement, the measurement conditions are as follows.

In the second embodiment, as in the first embodiment, the gas composition of the gas to be measured is 20 (%) oxygen (O ₂ ), 20 (%) water (H ₂ O), and nitrogen ( N ₂ ), and the temperature and flow rate of the gas to be measured are 80 (° C.) and 10 (liter / min). However, the change range of the reference voltage Vref is set within the range of 0.5 (V) to 1.5 (V).

  Here, according to the graph of FIG. 7, when the reference voltage is less than 0.7 (V), it can be seen that the reference voltage increases with the pump current. This is due to the following reason. That is, when the reference voltage is less than 0.7 (V), the concentration of the hydrogen gas generated on the negative electrode 1430 is lower than the concentration of the oxygen gas flowing through the diffusion rate limiting hole 1280. Gas and unreacted oxygen gas are left on the negative electrode 1430. Therefore, since the pump current at this time does not reflect the oxygen gas concentration, the reference voltage increases with the pump current.

  It can also be seen that when the reference voltage increases from 1.4 (V), the reference voltage increases rapidly with the pump current. This is due to the following reason. That is, a voltage higher than the voltage generated due to the difference in hydrogen gas concentration between the positive side electrode 1420 and the negative side electrode 1430 is supplied from the differential amplifier 3050 as a differential amplification voltage. Since the voltage is applied to 1430, the pump current increases rapidly with the reference voltage. In other words, in such a state, the amount of hydrogen gas flowing in from each inlet portion 1321 of the upper support member 1300 is larger than the oxygen gas flowing in through the diffusion rate controlling hole portion 1280, and the pump current is This is because the reference voltage increases rapidly with the pump current because it is not reflected in the concentration.

  Further, it can be seen that when the reference voltage is within the range of 0.7 (V) to 1.4 (V), the pump current tends to be saturated with respect to the reference voltage. The reason is as follows. In other words, the differential amplification voltage substantially applied between the positive electrode 1420 and the negative electrode 1430 causes the positive electrode 1420 and the negative electrode 1430 to increase as the concentration of hydrogen gas on the negative electrode 1430 increases. This is because the pump current saturates with respect to the reference voltage because it does not increase due to the reverse polarity effect of the voltage caused by the difference in hydrogen gas concentration between the pump current and the reference voltage. In other words, since all of the oxygen gas flowing in from the diffusion rate controlling hole portion 1280 reacts with the hydrogen gas on the negative electrode 1430 and is consumed, the pump current is saturated with respect to the reference voltage. Therefore, the pump current at this time is reflected in the concentration of oxygen gas.

From the above, if the reference voltage Vref is a voltage within the range of 0.7 (V) to 1.4 (V), the voltage generated between the positive electrode 1420 and the negative electrode 1430 is the reference voltage. By controlling the differential amplification voltage of the differential amplifier 3050 so as to be maintained at Vref, the concentration of oxygen gas can be accurately detected.
(Third embodiment)
FIG. 8 shows a main part of a third embodiment of the oxygen gas detection device according to the present invention. In the third embodiment, the oxygen gas detection device is the same as the oxygen gas detection device described in any one of the first and second embodiments, except that the oxygen gas sensor 1000 (see FIGS. 1, 2, and 5) is used. Instead, an oxygen gas sensor having the configuration shown in FIG. 8 is adopted.

  The oxygen gas sensor according to the third embodiment uses the oxygen gas sensor 1000 described in any of the first and second embodiments as a sensor body, and a casing 4100, a filter 4200, an annular seal 1150, and a sensor body. The heater 4300 is added.

  The casing 4100 includes a cylindrical casing body 4110 and a U-shaped lid body 4120. The casing 4100 is configured by fitting the lid body 4120 into an opening of the casing body 4110. Yes.

  Further, as shown in FIG. 8, the sensor body, the filter 4200, the annular seal 1150, and the heater 4300 are housed in the casing body 4110 as follows. The sensor body is seated on the inner surface of the bottom wall 4111 of the casing body 4110 via the filter 4200 at the bottom wall 1110 of the cylindrical body 1100. Here, the annular seal 1150 is airtightly sandwiched between the flange 1140 of the cylindrical body 1100 and the annular step portion 4112 formed at the axially intermediate portion of the inner wall of the casing body 4110.

  The filter 4200 is formed of a filter material that has both water repellency and permeability for the gas to be measured, and this filter 4200 flows in from the outside through the inlet 4113 formed in the bottom wall 4111 of the casing body 4110. Water droplets attached to the gas are excluded and only a gas such as oxygen gas is allowed to permeate toward the inlet portion 1111 of the cylindrical body 1100.

  The heater 4300 is accommodated on the sensor main body in the casing main body 4110, and the heater 4300 includes a cylindrical bobbin 4310 and a coil 4320 wound around the bobbin 4310 coaxially. . Here, the positive side connection terminal 1700 and the negative side connection terminal 1600 of the sensor body are formed in the center of the upper wall 4121 of the lid body 4120 through both insertion holes 4311 formed in the axial direction in the center part of the bobbin 4310. Projecting to the outside from both openings 4122. Further, both terminals 4321 of the coil 4320 pass through a portion between both insertion holes 4311 of the bobbin 4310 and extend from the center of the upper wall 4121 of the lid 4120 to the outside.

  The gas to be measured flowing into the positive electrode 1420 flows from the inlet 4113 of the casing 4100 through the annular gap between the filter 4200 and the peripheral wall 1120 of the cylindrical body 1100 and the peripheral wall of the casing body 4110. It flows in from the inlet 1121. Moreover, in FIG. 8, each code | symbol 4322 shows a crimp terminal. Other configurations are the same as those in the first or second embodiment.

  In the third embodiment configured as described above, the oxygen gas sensor of the third embodiment is fastened in the female screw hole portion of the gas pipe (not shown) by the male screw portion 4114 of the casing body 4110. Along with this, the casing body 4110 is seated at the flange 4115 in the vicinity of the mounting hole portion of the peripheral wall of the gas pipe.

  In such a state, when the heater 4300 is connected to a heating power source (not shown) at both terminals 4321 of the coil 4320, the casing 4100 and the sensor body are heated by the heater 4300. For this reason, even if the inside of the measured atmosphere is an atmosphere of high humidity, condensation does not occur in the casing 4100. As a result, clogging of the diffusion-controlling hole 1280 of the lower support member 1200 of the sensor body can be prevented.

  In such a state, the gas to be measured passes through the inlet 4113 of the casing 4100, the filter 4200, and the inlet 1111 of the cylindrical body 1100, and smoothly passes through the diffusion-controlling hole 1280. Therefore, there is no shortage of oxygen gas flowing into the sensor element 1400. Therefore, by detecting such a concentration of oxygen gas by the detection circuit 2000 (see FIG. 1) or the detection control circuit 3000, the accuracy can be improved more accurately than in the case of either the first or second embodiment. The concentration of oxygen gas can be detected. Other functions and effects are the same as those of the first or second embodiment.

In carrying out the present invention, the following various modifications are possible without being limited to the above embodiment.
(1) The diffusion-controlling hole portion 1280 formed in the support member 1200 may be a plurality of through-hole portions instead of a single through-hole portion. Further, a columnar portion made of a porous material such as alumina may be employed in place of the diffusion rate controlling hole portion 1280. In addition, you may grasp | ascertain the said columnar part and the diffusion control hole part 1280 as a diffusion control part.
(2) The substrates of the support members 1200 and 1300 may be formed of an electrically insulating synthetic resin instead of the ceramic material.
(3) Instead of the variable reference power supply 3070, a fixed reference voltage power supply in which the reference voltage Vref is set to a voltage within the range of 0.7 (V) to 1.4 (V) described above may be employed. .
(4) The oxygen gas sensor is not limited to the configuration described in the above embodiments, and may have the following configuration. That is, instead of the configuration in which the sensor element 1400 is sandwiched between the support members 1200 and 1300, a configuration in which the sensor element 1400 is sandwiched between the two conductive support members is adopted, and the metal insulating body 1100 is replaced with the electrical insulating property. A cylindrical body may be employed, and the positive and negative connection terminals 1700 and 1600 may be eliminated.

In this case, the DC voltage of the variable DC power source 2200 is applied between the positive electrode 1420 and the negative electrode 1430 of the sensor element 1400, or the semiconductor switch circuit is connected between the positive electrode 1420 and the negative electrode 1430. A charging voltage from the capacitor 3060 through 3020 is applied.
(5) The resin member 1500 is not limited to one made of an electrically insulating synthetic resin, and may be a pressing member made of an appropriate material. Accordingly, the support members 1200 and 1300 are formed of an electrically insulating material as a whole, and the cylindrical body 1100 is not limited to being made of metal, and may be formed of, for example, an electrically insulating synthetic resin.

It is a figure which shows the cross section of the oxygen gas sensor in 1st Embodiment of the oxygen gas detection apparatus which concerns on this invention with a detection control circuit. It is an expanded sectional view of the oxygen gas sensor of FIG. It is a graph which shows the density | concentration of oxygen gas in the said 1st Embodiment in relation to a pump current. It is a graph which shows the applied voltage (DC voltage) between the positive side electrode and negative side electrode in the said 1st Embodiment by the relationship with pump current. It is a figure which shows the cross section of the oxygen gas sensor in 2nd Embodiment of the oxygen gas detection apparatus which concerns on this invention with a detection control circuit. It is a timing chart which shows each output of the drive circuit in the said 2nd Embodiment, a capacitor | condenser, and a differential amplifier in relation to passage of time. It is a graph which shows the reference voltage of the variable reference power supply in the said 2nd Embodiment by the relationship with pump current. It is sectional drawing of the oxygen gas sensor in 3rd Embodiment of the oxygen gas detection apparatus which concerns on this invention.

Explanation of symbols

1000 ... oxygen gas sensor, 1100 ... cylinder, 1110 ... bottom wall,
1111, 1121, 1321 ... Inlet part, 1120 ... Perimeter wall,
1200, 1300 ... support member, 1280 ... diffusion-controlling hole,
1410 ... Proton conducting layer, 1420 ... Positive electrode, 1430 ... Negative electrode,
1500 ... resin member, 2000, 3000 ... detection control circuit, 2200 ... variable DC power supply,
3010: Drive circuit, 3020 ... Semiconductor switch circuit, 3060 ... Capacitor,
3050: Differential amplifier, 3070: Variable reference voltage power supply.

Claims (7)

An oxygen gas sensor and detection control means;
The oxygen gas sensor is
A proton conducting layer made of a polymer electrolyte;
A positive electrode provided along one of both sides of the proton conducting layer;
A negative electrode provided along the other of the two surfaces of the proton conducting layer;
A one-side support member provided along the negative electrode so as to face the proton conducting layer via the negative electrode;
The other side support member provided along the positive side electrode so as to face the proton conductive layer via the positive side electrode,
The one-side support member has a diffusion rate-limiting part that allows a gas to be measured from the outside to flow into the negative electrode,
The other side support member has an inlet portion for allowing a gas to be measured from the outside to flow into the positive electrode,
The detection control means includes
A DC power source for applying a DC voltage within a predetermined voltage range between the positive electrode and the negative electrode;
In the predetermined voltage range, protons are generated on the positive electrode based on water vapor in the gas to be measured flowing from the inlet portion of the other side support member, and the generated protons are supplied to the one side support member. An oxygen gas detection device set in a DC voltage range required for pumping out to the negative electrode through the proton conduction layer so as to react with oxygen gas in the gas to be measured flowing from the diffusion rate controlling portion. An oxygen gas sensor and detection control means;
The oxygen gas sensor is
A cylinder having a bottom wall having an inlet portion and a cylindrical peripheral wall having an inlet portion, wherein the bottom wall is provided at the bottom end side opening of the peripheral wall;
A one-side support member housed in the cylinder and seated on the bottom wall;
A negative electrode laminated on the one side support member;
A proton conducting layer made of a polymer electrolyte laminated on the negative electrode;
A positive electrode laminated on the proton conductive layer so as to face the negative electrode through the proton conductive layer;
The other side support member laminated on the positive side electrode so as to face the proton conduction layer via the positive side electrode;
A press which is fitted into the cylindrical body from its front end side opening and presses the other side support member onto the bottom wall via the positive side electrode, the proton conductive layer, the negative side electrode and the one side support member Comprising a member,
The one-side support member has a diffusion-controlling part that allows the gas to be measured to flow into the negative electrode through the inlet of the bottom wall from the outside,
The other side support member has an inlet portion for allowing the gas to be measured flowing from the outside through the inlet portion of the peripheral wall to flow into the positive electrode,
The detection control means includes
Comprising a DC power supply for applying a DC voltage within a predetermined voltage range between the positive electrode and the negative electrode;
In the predetermined voltage range, protons are generated on the positive electrode based on water vapor in the gas to be measured flowing from the inlet portion of the other side support member, and the generated protons are supplied to the one side support member. An oxygen gas detection device set in a DC voltage range required for pumping out to the negative electrode through the proton conduction layer so as to react with oxygen gas in the gas to be measured flowing from the diffusion rate controlling portion. An oxygen gas sensor and detection control means;
The oxygen gas sensor is
A proton conducting layer made of a polymer electrolyte;
A positive electrode provided along one of both sides of the proton conducting layer;
A negative electrode provided along the other of the two surfaces of the proton conducting layer;
A one-side support member provided along the negative electrode so as to face the proton conduction layer via the negative electrode;
Comprising the other side support member provided along the positive side electrode so as to face the proton conductive layer via the positive side electrode,
The one-side support member has a diffusion rate-limiting portion that allows a gas to be measured from the outside to flow into the negative electrode,
The other side support member has an inlet portion for allowing a gas to be measured from the outside to flow into the positive electrode,
The detection control means includes
Charging voltage generating means for generating a charging voltage by being charged with a voltage generated between the positive electrode and the negative electrode;
A reference voltage generating means for generating a reference voltage within a predetermined voltage range;
Voltage application means for applying a DC voltage between the positive electrode and the negative electrode;
The DC voltage applied between the positive side electrode and the negative side electrode is controlled based on the charging voltage so as to maintain the voltage generated between the positive side electrode and the negative side electrode at the reference voltage. Voltage control means,
In the predetermined voltage range, protons are generated on the positive electrode based on water vapor in the gas to be measured flowing from the inlet portion of the other side support member, and the generated protons are supplied to the one side support member. An oxygen gas detection device set in a DC voltage range required for pumping out to the negative electrode through the proton conduction layer so as to react with oxygen gas in the gas to be measured flowing from the diffusion rate controlling portion. An oxygen gas sensor and detection control means;
The oxygen gas sensor is
A cylinder having a bottom wall having an inlet portion and a cylindrical peripheral wall having an inlet portion, wherein the bottom wall is provided at the bottom end side opening of the peripheral wall;
A one-side support member housed in the cylinder and seated on the bottom wall;
A negative electrode laminated on the one side support member;
A proton conducting layer made of a polymer electrolyte laminated on the negative electrode;
A positive electrode laminated on the proton conductive layer so as to face the negative electrode through the proton conductive layer;
The other side support member laminated on the positive side electrode so as to face the proton conduction layer via the positive side electrode;
A press which is fitted into the cylindrical body from its front end side opening and presses the other side support member onto the bottom wall via the positive side electrode, the proton conductive layer, the negative side electrode and the one side support member Comprising a member,
The one side support member has a diffusion rate controlling portion for introducing a gas to be measured from the outside through the inlet portion of the bottom wall to the negative electrode,
The other side support member has an inlet portion for allowing a gas to be measured flowing from outside through the inlet portion of the peripheral wall to flow into the positive electrode,
The detection control means includes
Charging voltage generating means for generating a charging voltage by being charged with a voltage generated between the positive electrode and the negative electrode;
A reference voltage generating means for generating a reference voltage within a predetermined voltage range;
Voltage application means for applying a DC voltage between the positive electrode and the negative electrode;
The DC voltage applied between the positive side electrode and the negative side electrode is controlled based on the charging voltage so as to maintain the voltage generated between the positive side electrode and the negative side electrode at the reference voltage. Voltage control means,
In the predetermined voltage range, protons are generated on the positive electrode based on water vapor in the gas to be measured flowing from the inlet portion of the other side support member, and the generated protons are supplied to the one side support member. An oxygen gas detection device set in a DC voltage range required for pumping out to the negative electrode through the proton conduction layer so as to react with oxygen gas in the gas to be measured flowing from the diffusion rate controlling portion. The charging voltage generating means is a capacitor,
The reference voltage generating means is a variable reference power source that generates the reference voltage,
The voltage application means is a differential amplification means,
The voltage control means switches to a first switching state based on a pulse drive signal generating means for generating a pulse drive signal at a predetermined cycle and a level change in one direction of the pulse drive signals sequentially generated from the pulse drive signal generating means. Switching operation means that operates to switch and operates to switch to the second switching state based on a level change in the other direction of the pulse drive signal,
The capacitor is charged with a voltage generated between the positive side electrode and the negative side electrode based on the operation of the switching operation unit to the first switching state to generate the charging voltage, and the differential amplification The means amplifies the difference between the reference voltage and the charging voltage based on the operation of the switching operation means to the second switching state, and generates a differential amplification voltage. 5. The oxygen gas detection device according to claim 3, wherein the direct current voltage is applied between the electrode and the negative electrode so as to generate a voltage corresponding to the differential amplification voltage. .   The oxygen gas detection device according to claim 1, wherein the predetermined voltage range is a voltage range of 0.7 (V) to 1.4 (V).   The oxygen gas detection device according to any one of claims 1 to 6, wherein the positive electrode is formed of a material obtained by mixing a platinum group metal powder and a polymer electrolyte. .

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