JPS5985951A - Apparatus for measuring oxygen concentration - Google Patents

Abstract

PURPOSE:To obtain an oxygen concentration measuring apparatus, which is characterized by definite ON-OFF characteristics of an electromotive force when the partial pressure of oxygen is changed, high measuring accuracy, long life, compact configuration, simple operation and easy manufacture, by keeping the partial pressure of reference oxygen approximately constant during the measurement of the concentration of the oxygen, thereby steadily measuring the partial pressure of the oxygen without decreasing the electromotive force with the elapse of time. CONSTITUTION:A reference electrode electron conducting layer 2 is formed on the surface of a molded body 10. The surface of the conducting layer 2 is completely coated by a porous solid state electrolyte layer 3, which can pass oxygen gas. On the surface of the solid state electrolyte layer 3, a measuring electron conducting layer 1 is provided. Both electron conducting layers 1 and 2 are connected to a voltage measuring device 6 such as a potentiometer by a conducting wire 5. The electromotive force is generated by the difference between the partial pressure PO2( I ) of the oxygen gas in a gas atmosphere to be measured and the partial pressure PO2(II) of oxygen at the interface between the reference electrode electron conducting layer 2 and the solid state electrolyte layer 3. Said electromotive force is measured. Furthermore, a DC power soure circuit 7 is connected to the voltage measuring device 6 in parallel, and a constant voltage or a constant current can be supplied across both electron conducting layers 1 and 2. Thus effects due to the change in atmosphere can be eliminated, and highly accurate measurement and control can be maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oxygen concentration measuring device for detecting oxygen concentration in a fluid.

Such oxygen concentration measuring devices have been used in recent years to control the air-fuel ratio of internal combustion engines by detecting the oxygen content in exhaust gas from internal combustion engines such as automobiles, and are generally made of zirconia, which is a good conductor of oxygen ions. 1) Baking conductive electrodes such as platinum on the inside and outside of a solid electrolyte tube or plate, such as
All of the gas to be measured with an unknown oxygen partial pressure is introduced to the outside of these electrodes, a reference gas with a known oxygen partial pressure, such as air, is introduced to the inside, and both electrodes are connected to a 1st position difference meter. The electromotive force Evf generated between the two electrodes due to the difference between the oxygen partial pressure PO2 in the reference gas and the oxygen partial pressure PO8' in the reference gas is measured, and Nernst's formula is given by R: Gas constant T: Absolute temperature F: Farate Knowing the oxygen partial pressure of the gas whose oxygen concentration should be measured by a certain number,
By keeping the total pressure of the gas to be measured constant, the oxygen partial pressure is made to indicate the oxygen concentration.

Various types of oxygen concentration measuring devices have been proposed in the past, and a typical example is a tubular ceramic device as described in JP-A-4-9-180292. A type is known in which a sintered compact is used as a solid electrolyte base and air sound is used as a reference gas. However, in this type, the quality b1 of the tubular solid electrolyte substrate is large, so the heat capacity is large, and the electric resistance is also large, so it is difficult to maintain temperature characteristics and damage or cracking due to heat of the tubular solid electrolyte substrate. V4 is the best, but it has the drawback of being expensive. In order to eliminate this drawback, it has been proposed to miniaturize the substrate, but in this case, new reference gas is always placed inside the tubular solid electrolyte substrate while measuring the oxygen concentration in the gas to be measured. The oxygen concentration involved in the electrode reaction is not necessarily the same as that of the reference gas, and the formation of a diffusion layer on the surface caused by the electrode reaction changes the oxygen partial pressure of the reference gas near the electrode. There is a drawback that it is impossible to accurately measure the oxygen concentration in the gas to be measured. Therefore, JP-A-49-
In the oxygen concentration measuring device of the type described in Publication No. 113+1292, in order to accurately measure the cumulative concentration in the gas to be measured, a method is used to keep the concentration gradient due to diffusion of the reference gas in the gas detection electrode section sufficiently small. A metabolic mechanism for the reference gas is required, and as a result there is necessarily a limit to reducing the spatial volume accommodating the reference gas, and therefore it is not possible to reduce the size of the sensing part.

As a modification of the oxygen concentration measuring device of the above-mentioned type, instead of sending the reference gas inside, the reference gas is sealed and held in a sealed space, and a catalyst electrode provided inside the space between the reference gas seal 9 and the object to be measured on the outside are used. JP-A-5A-71298 discloses an oxygen concentration measuring device configured to measure the oxygen concentration in a gas to be measured using a catalyst plate and a pole provided in the gas. With this oxygen concentration measuring device, the reference oxygen gas in the sealed space is consumed by electrolysis during measurement, and the oxygen partial pressure of the reference gas changes.
Then, use another reference gas such as air with a known oxygen concentration and energize until the electromotive force of the measuring device reaches a constant value again (7. It is necessary to replenish the oxygen gas inside the completely enclosed space, For this reason, there is a drawback that oxygen cannot be detected continuously for a long period of time.In order to eliminate this drawback and enable continuous measurement for a long period of time, the oxygen of the reference gas in the closed space during measurement is It is necessary to seal and hold a reference gas whose partial pressure hardly changes, which has the disadvantage of increasing the size of this fruiting device.Furthermore, with this type of measuring device, the reference gas flows in at full speed during measurement. Since the convection of the reference gas is even smaller than in the case of the type 19, the layer where the flow is stagnant becomes extremely large, making it impossible to accurately measure the oxygen partial pressure in the gas to be measured. .

Otaku, this type of book is structurally rough like the previous type, and the solid electrolyte is in the form of a thick tube or plate, making it easy to break. There is.

As mentioned above, if a gas with a constant rie partial pressure such as air is used as a reference gas, the above-mentioned lag cannot be avoided, so metals and metal oxides that have a kind of buffering effect using thermodynamic equilibrium are used. U.S. Pat. No. 8,578,578 discloses a type in which an equilibrium pixel gas of a mixed porous material with a mixed porous material is used as a reference gas, and the reference gas space is isolated from the outside.
It is known as described in JP-A-52-186689 and the like. This type of solid electrolyte is made of a thick film, and generally consists of an electrode, an oxygen interface region, a solid IT electrolyte thin film layer, and a porous electrode formed sequentially on a substrate. It compensates for the shortcomings of the standard, and has succeeded in being extremely compact.

However, when the FC oxygen concentration measuring device uses a metal-metal oxide as the reference oxygen generating substance mentioned above and measures the oxygen partial pressure in an atmosphere with high oxygen partial pressure at high temperature, the metal in contact with the solid electrolyte oxidized or mixed with the outside atmosphere: Therefore, it no longer generates the standard equilibrium oxygen partial pressure, and the measured electromotive force decreases over time.
It is impossible to measure the oxygen partial pressure on a regular basis, and the service life is extremely short. In addition, gold, 1"4 and metal oxides are deposited in a vacuum by vapor deposition, VL deposition, heat treatment, and sputtering. Because it is formed by adhering the metal and metal oxide in a molar ratio of about 1:1, it is difficult to form a product with the most stable and robust standard oxygen partial pressure. There are 11 while the cost is high.

The object of the present invention is to eliminate and improve the drawbacks of the various types of oxygen concentration measuring devices previously known as described above.

It is possible to constantly measure the oxygen partial pressure without the force decreasing over time, and the on-off control of the electromotive force is clear when the elemental partial pressure changes.
The object of the present invention is to provide a novel oxygen concentration measuring device that has high measurement accuracy, long life, and is extremely compact and simple in structure and easy to manufacture.

The present invention has achieved the above-mentioned object by providing a source of reference oxygen partial pressure with a new configuration based on a principle different from the conventional one described above. A conductive layer and an oxygen ion conductive solid 1: a solute material layer, a reference electrode electron conductive layer, and a diaphragm layer are sequentially laminated, and the reference electrode electron conductive layer is the oxygen ion conductive solid electrolyte material layer. "I!TAKE" The membrane layer and the oxygen ion conductive solid electrolyte material layer are brought into contact with the atmosphere to be measured through the porous openings in both layers, and the measurement electrode is placed between the measurement electrode electron conduction layer and the reference electrode electron conduction layer. A measuring means for taking out an electromotive force is connected to a controlling means for applying a control current 'ff' to control the reference oxygen partial pressure in the reference electrode electron conductive layer. By configuring this to be carried out, the reference oxygen partial pressure tube is kept constant during the oxygen concentration measurement, and in this way, during the 81++ measurement, the oxygen ion conductive solid electrolyte material layer is constantly energized, and both the oxygen ion conductive solid electrolyte material layer is By adopting a configuration in which the entire electromotive force generated between the N1 conductive layers is measured, it has been possible to significantly stabilize the output of the electromotive force concentration measuring device.

The invention will now be explained with reference to the drawings.

The tK1 diagram shows the basic structure of the floor concentration measuring device according to the present invention, and as shown in the drawing, the measurement electron conduction layer l, r! 9
It is constructed as a laminate in which an elementary ion conductive solid electrolyte material layer 8, a reference electrode electron conductive layer 2, and a diaphragm layer 4 are sequentially laminated. Although not specifically shown in Figure 1, the diaphragm/e 4
is constructed as a structural base, and this structural base supports the entire laminate 1, 2, 13.4 in the atmosphere of the gas to be measured 7'. Both layers, the conductive solid electrolyte material layer B or diaphragm layer Φ and the oxygen ion conductive solid electrolyte layer IA, are composed of porous materials, and the reference electrode electron conductive layer 2 is not directly exposed to the atmosphere to be measured. Ion conductive solid @solate negative layer B or diaphragm Jti 4 can be used as the entire coating material, or other suitable coating material can be used to cover the entire outer periphery of the reference electrode electron conductive layer 2. The electrode electron conductive layer 2 is brought into contact with the atmosphere to be measured through the bending through the porous openings in the oxygen ion conductive isoconductive layer 8 or the diaphragm layer 4 or both of these shoulders, and the measurement electrode electron conductive layer 1 and The reference electrode 11 is connected to a voltage measuring device 6 such as a potentiometric needle as a measuring means for extracting the entire electromotive force for measurement by a conductive wire 5 between the conductive skin 2 and the partial pressure of the gas aζ in the gas atmosphere to be measured PO, (I) and the ultimate partial pressure PO2 (It) at the interface between the reference electrode electron conductive layer 2 and the solid electrolyte material layer 8.
A DC power supply circuit 7 is connected in parallel with the voltage measuring device 6 so that a voltage "i!" or a current can be supplied between both electron conductive layers 1.2.

The operation of the oxygen concentration measuring device having the above-mentioned configuration will be explained next.@Before explaining the mechanism for maintaining the reference oxygen partial pressure almost constant according to the present invention, first, without applying a full voltage between both electron-conducting layers, When considering the case of measuring electromotive force using a potentiometer, the oxygen partial pressure PO(I) in the gas to be measured, the oxygen partial pressure PO9(n) at the interface between the solid electrolyte layer 8 and the reference electrode electron conductive layer 2, and If there is a difference between them, the re elementary ions move within the solid electrolyte layer 8 in the same direction, and when po (1)>PO, (II), the electron conduction layer l and O, +419-) at the interface with solid electrolyte layer 8
A reaction of 20- occurs, and 0- moves toward the electron conductive layer 2 through the solid electrolyte layer 8, and as a result, 20----→0. +4
The reaction of e occurs, po, (If) 751 gradually increasing final K U PO, (Il j PO, (11
), an equilibrium state is reached, and the electromotive force E becomes zero.

On the contrary, in the case of PO(I)<PO,(I), 0° present at the interface between the electron-conducting N9 and the solid %I electrolyte material layer flows into the gas to be measured and similarly PO (I) =
It becomes PO□(II). Thus both oxygen partial pressures po, (I
) and PO, (II), no electromotive force is generated.

According to the present invention, the reference electrode is measured by constantly supplying current between both electron conduction layers 2 and 2, and the interface between the electron conduction layer 2 and the electrolyte material layer 8 and the material.

A reference oxygen gas is electrolytically generated within the pores of the sensor, thereby maintaining the reference oxygen partial pressure almost constant.The principle of operation will be explained below.

First, when connecting the measuring electrode electron conductive layer 1f to the negative side of the DC power supply circuit 7 and connecting the reference electrode electron conductive layer 2 to the positive side, the negatively charged oxygen ions in the solid electrolyte #B are connected to the reference electrode. It moves toward the electron conduction layer 2, and as a result, the oxygen partial pressure at the interface between the solid electrolyte layer 8 and the reference electrode electron conduction layer 2 becomes quotient.

The reactions that occur in this case are listed below.

(1) At the interface between the measurement electrode electron conductive layer 1, the solid m″, and the solute layer 8, 02 (in the gas to be measured) +4e−→2O
--(Solid Electrolyte Layer) (2) Within the solid electrolyte layer 8, 20- moves from the measurement electrode electron conduction layer 1 to the reference electrode electron conduction layer 2.

(B) At the interface between the reference & electron conductive layer 2 and the solid electrolyte R4B, 20 (in the solid electrolyte) → Q, + 48 OfA generated here is at the interface between the solid electrolyte layer 8 and the reference electrode electron conductive layer 2. % multiplied. Therefore, PO(II) becomes high.

Apart from the reactions of lx), (9) and (8) mentioned above, the reference electrode electron conduction (meaning both the solute layer B and the diaphragm layer 4), it accumulates and some of the 7"C acid (means both the solute layer B and the diaphragm layer 4)
That is, a reaction that flows out into the gas to be measured also occurs. - Therefore, after a certain period of time has passed after the start of side redundancy, the oxygen partial pressure at the interface between the solid electrolyte layer 8 and the reference electrode electron conductive layer 2 becomes approximately constant. In this way, the reference oxygen partial pressure of the oxygen concentration measuring device can be maintained at approximately the same level.

Contrary to the above-mentioned π, when the measurement electrode electron-conducting layer l is connected to the positive side of the DC power supply circuit 7 and the reference & electron-conducting layer 2 is connected to the negative side, the above-mentioned (1), (2) ) and (8), the opposite reaction occurs. That is, (1)' At the interface between the solid electrolyte No. 8 and the reference electrode electron conductive layer 2, 0, ++e → 2o−- (solid electrolyte) (2y In the solid electrolyte layer 8, 20− is the reference electrode electron conductive layer 2, the measurement electrode moves toward the electron-conducting layer l.

(8)' At the interface between the measurement electrode electron conductive layer 1 and the solid electrolyte layer 8, 20-(solid πiJ mass → O, (in the gas to be measured) +4・
e Although such a reaction lowers the oxygen partial pressure at the interface between the reference electrode electronic conductive layer and the solid electrolyte layer, the oxygen gas in the external measured gas As time passes, the oxygen partial pressure PO2 (II) becomes approximately constant as described above. Therefore, in this J1 case as well, the reference oxygen partial pressure of the value of Habo-W can be maintained.

"As is clear from the double series, the DC power supply circuit 7
The oxygen partial pressure in the reference electrode can also be maintained constant when the positive and negative sides of the electrode are connected to the electron conductive layer 2, but in the former case described above, a1 is electrolytically sent from the measurement electrode electron conduction layer l to the reference electrode electron conduction layer i12 to form the porous material layer 8 or 8 and 4.
This is because it replenishes the amount of oxygen gas that dissipates through
It is suitable when it is desired to increase the reference oxygen gas partial pressure, and in the latter case, the oxygen gas flowing in from the outside through the porous material layer 8 or B and 4 is eliminated and the oxygen gas is kept constant. Since the entire reference electrode electron conductive layer 2 is sent to the measurement electrode electron conductive layer by electrolysis, it is suitable when it is desired to maintain the reference oxygen partial pressure at a constant low value.

In the oxygen concentration measuring device according to the present invention, the voltage measuring device @
The voltage V measured at step 6 is the oxygen partial pressure PO(I
) and the reference oxygen partial pressure PO, (Ill), which has a certain relationship with the electromotive force E generated by the difference, and can be expressed by the following equation.

In the above equation, e: t of dispersion in a room temperature circuit
l(, pressure I (□ = resistance of the circuit R8, impedance of the pressure side tail mount T: internal resistance of the oxygen sensor or reference oxygen partial pressure PO, (II) is the current flowing through the sensor and the porous layer 8 or Since it is determined by the gas diffusion ability in 8 and 4, it is a constant value, and therefore, the oxygen concentration of the gas to be measured can be determined from the Nernst equation (1) described above.

Furthermore, as is clear from the above, the electromotive force E changes due to a change in the oxygen partial pressure of the gas to be measured, and the measurement voltage V also changes in proportion to this. Various controls are possible based on the oxygen concentration.

FIG. 2 shows an example in which a diaphragm layer is configured as a structural base, and a molded body 10 of an electrically insulating material or an electronically conductive material is used for this, and a reference electrode electron conductive layer 2 is formed on the surface of the molded body 10, The surface of the reference electron conduction layer 2 is completely covered with a porous solid electrolyte layer 8 through which oxygen gas can pass, and the measurement electron conduction layer 1vi is provided on the surface of the solid electrolyte layer 8.

Both electron conductive layers 1 and 9 are connected to a voltage measuring device 6 such as a potentiometric needle through conductive wires 5 to measure the oxygen gas partial pressure PO, (I) in the gas atmosphere to be measured, the reference electrode electron conductive layer 2, and the solid electrolyte. Vi, oxygen partial pressure PO2 at the interface between layers 8 (
Furthermore, by connecting a DC power supply circuit 7 in parallel with the voltage measuring device 6, a constant voltage between both electron conductors I@1°2 or a constant voltage V 1 [f1 flow can be supplied.

FIG. 8 shows a modification of the example shown in FIG. 2, in which the surface of the measurement electrode electron conductive layer l is covered with a protective layer 9. If necessary, the entire surface of the laminate can be covered with the protective layer. can.

The material of the solid electrolyte layer 8 in the present invention is QaO
, Y, O, SrO, MgO, WO, Ta90- stabilized with zro or Nb OSrO* WOs, 'I
'aO,'J: Dodean 2 86° stabilized 7t Bi, 08 or TrOQ-Y, O, 0a
Known materials such as O-Y and 08 can be used.

In the examples shown in FIGS. 2 and 8, the solid electrolyte layer can be provided by sputtering, vapor deposition, or other electrochemical methods using the above materials, or by applying and baking a paste.

The materials of the measurement electrode electron conductive layer 1 and the reference electrode electron conductive layer 2 include Au, Ag, and SiO, which do not have catalytic activity, and Ru, Pa, Rh, Os, and Ir, which have catalytic activity.
It is also possible to use a single platinum group element such as Pt, an alloy thereof, or an alloy of a platinum group element and a base metal element. can be provided.

In addition, as in the examples shown in FIGS. 2 and 8, the diaphragm layer 'f
In the case of constructing it as a structured substrate, the material of the molded body 10 may be a dense or slightly porous material such as alumina, norite, spinel, silica, forsterite, or a gas-insulating material such as stainless steel or nickel. Electronically conductive materials such as base J thermal alloys or mixtures of ceramics and metals such as cermets can be used.

FiCaO-2rO2 (calcium zirconate), alumina, spinel, etc. are soaked, fired, and
Plasma sprayed material is used.

In the oxygen concentration measuring device using "Unexploded Tsu", in order to maintain the reference oxygen partial pressure at a constant level, a known suitable constant voltage DC power supply circuit or constant current is used as the DC power supply connected between both electron conductive layers. A DC power supply circuit can be used. T
It is simplest to use a DC power supply circuit consisting of a battery and a resistor as the RR current power supply, and it is possible to construct it at low cost. However, such a constant voltage DC power supply circuit depends on the temperature of the gas being measured and other atmosphere When used in measurement fields such as measuring the oxygen concentration in automobile exhaust gas, which changes significantly, the influence of changes in the electrical resistance of solid electrolytes due to these changes in the atmosphere I.
II, it becomes impossible to maintain the reference oxygen partial pressure accurately and constant regardless of temperature changes in the exhaust gas. Therefore, for applications in the measurement field that are affected by such temperature changes, it is necessary to use a constant current DC power supply circuit as a DC power supply. Therefore, it is possible to maintain constant current control, and it also takes into account the effects of changes in the pore size of the solid electrolyte due to changes in depth and changes in the flow rate of oxygen gas inflow and outflow. By using a power supply circuit, it is possible to completely eliminate the effects of temperature changes and thereby improve the overall measurement accuracy.

Example 1 Thickness of 1 inch square Q , Q ? a? Cut a commercially available alumina substrate made by Narumi Seitai of yl into large pieces of 910 x 12 mm.
Platinum paste (manufactured by Auditory Kagaku Co., Ltd./% 8109) was printed, dried, and then heated and fired in the atmosphere at 1800° C. for 1 hour to fabricate the entire oxygen concentration measuring device shown in FIG. 2. Obtained 71.
The thickness of the platinum film was determined to be 1-2μ. Figure 6a shows a/l/
Reference numeral 11 indicates the Mina substrate, reference numeral 12 indicates the platinum paste serving as the reference electrode electron conduction layer, and reference numeral 18 indicates the platinum paste serving as the lead portion of the measurement electrode electron conduction layer. Next, a solid 1t1□ dissolving paste (a mixture of 8% by weight Y2O8-ZRO2 powder manufactured by Zilker and lacquer at a weight ratio of 1:1) was printed as shown by the hatched area 14 in FIG. 6b, and dried. Fired. The firing conditions were 1880° C. for 8 hours in the air. The film thickness of the obtained solid electrolyte was 80 to 85 μm. Next, the same platinum paste 15 as above was printed on the solid electrolyte membrane 14 as shown by the hatched area in FIG. 6C, and fired by heating at 1000° C. for 1 hour. A durability test was conducted on this oxygen concentration measuring device. 80,000 km in actual car
Until now, almost no change was observed in the performance of the oxygen concentration measuring device according to the present invention.

For comparison, all the same tests were carried out on conventional type oxygen sensors provided as Ni-N:ioNk reference oxygen partial pressure generation sources, but 8 out of 10 were tested for 80,000 km of durability. It later became a defective product.

The oxygen concentration measuring device d manufactured according to the procedure of this example is set to a battery voltage rrO of 8V, and the resistance of the circuit and the impedance of the voltage measuring device are both 1) tQ tL,
Connect the reference electrode') TL conductor to the positive electrode of the battery,
The electromotive force was measured by continuously changing the temperature of exhaust gas with an air twist ratio of approximately 18 (a state in which the oxygen partial pressure in the exhaust gas is low) and approximately 1? (a state in which the oxygen partial pressure in the exhaust gas is crystalline).・The results of this measurement are shown in Figure 7.

This shows that, in this example, a considerable electromotive force is output even if the discharged sludge source intensity is low.

In the experimental example above, instead of a 0.8v battery
．． When a constant current power source of δμA was used, the reference pixel partial pressure became more stable, and the reproducibility of the results shown in FIG. 7 was further improved.

Example 2 As shown in FIG. 81, a test similar to Example 1 was conducted using an oxygen concentration measuring device in which a platinum wire was embedded as a metal heating element 16 in an alumina substrate 11 (other configurations were the same as in Example 1). I did it. The resistance of the heater was 1Ω, and a power of 8W was used. As a result of this comparative test, it was confirmed that the operating temperature range of the oxygen concentration measuring device was expanded by heating, as shown by the broken line 18 in Figure 7, and that sufficient electromotive force was output even at extremely low exhaust gas temperatures. . As the metal heating element, molybdenum, tungsten, etc. can be used in addition to platinum.

[Brief explanation of the drawing]

FIG. 1 is a route map showing the basic configuration of the oxygen concentration measuring device according to the present invention, FIG. 2 and FIG. 8 are route maps showing various embodiments of the oxygen concentration measuring device according to the present invention, and FIG. 4 is a route map showing different embodiments of the oxygen concentration measuring device according to the present invention. Figure 6 is an explanatory diagram showing the manufacturing procedure of the oxygen concentration Htn determining device according to the present invention, Figure 7 is a graph showing the results of measuring the electromotive force by alternately flowing two types of model gases with different air-fuel ratios, FIG. 8 is a diagrammatic perspective view showing another embodiment of the oxygen concentration measuring device according to the present invention. DESCRIPTION OF SYMBOLS 1...Measurement release single-layer conductive layer 2...Reference electrode electron conductive layer 8...Solid electrolyte layer 4...Porous material layer 5
...Conducting wire 6...Frost vL measuring device?・
...Battery 810. Resistance 9...protective layer
10... Structural base molded body 11... Alumina substrate 12.18... Platinum base) membrane 14... Solid electrolyte base) 15... Platinum paste 16...
heater. Figure 1 Figure 2 Figure 3 132' Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1. A measurement electrode electron conductive layer, an oxygen ion conductive solid electrolyte material layer, a reference electrode electron conductive layer, and a diaphragm layer are sequentially laminated, and the reference electrode electron conductive layer is the oxygen ion conductive layer. contact with the atmosphere to be measured through porous openings in both shoulders of the electroconductive solid electrolyte material layer or the diaphragm layer and the oxygen ion conductive solid electrolyte material layer, and between the measurement electrode electron conductive layer and the reference electrode electron conductive layer. 1. An oxygen concentration measuring device comprising: a measuring means for taking out a measuring electromotive force; and a controlling means for controlling a control current for controlling a reference oxygen partial pressure in the reference electrode electron conductive layer. 2. The oxygen concentration measuring device according to claim 1, wherein the positive side of the DC power source of the control means is connected to the reference electrode electron conductive layer. & The negative side of the DC power supply of the control means is connected to the reference electron conductive layer.
The oxygen concentration measuring device described in section. Claim 1, characterized in that both the ion conductive solid electrolyte material layer or the diaphragm layer and the ion conductive solid electrolyte material layer are porous materials that permeate oxygen. The oxygen concentration measuring device according to any one of items 1 to 8. Claim 1, characterized in that the shaped sintered body of the oxygen ion conductive solid electrolyte serves as the entire structural base.
- The oxygen concentration measuring device according to any one of item 4 or item 1. (a) The oxygen concentration measuring device according to any one of claims 1 to 8, wherein the diaphragm layer is a molded body of an electrical insulator, which serves as a structural base. t Comprised of a molded body of electrically insulating material such as alumina'
7. The oxygen concentration measuring device according to claim 6, characterized in that four heating elements are embedded in gold inside the fi-structure. 8. The oxygen concentration measuring device according to any one of claims 1 to 7, characterized in that at least the measurement electrode electron conductive layer is covered with a porous protective layer.