JP3050011B2 - Limit current type oxygen sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a limiting current type oxygen sensor for detecting oxygen concentration.

[0002]

2. Description of the Related Art As shown in FIGS. 4 and 5, a conventional limiting current type oxygen sensor has a cathode electrode 15 and an anode electrode 1 on both sides of an oxygen ion conductive solid electrolyte plate 14. As shown in FIG.
6 and the cathode electrode 1 on the solid electrolyte plate 14
On the fifth surface side, spiral glass spiral spacers 17 are arranged so as to be spaced from the cathode electrode 15 and to be spaced from the start end to the end. A seal plate 18 is provided at a position opposite to the solid electrolyte plate 14 with the glass spiral spacer 17 interposed therebetween.
On the opposite surface of the glass spiral spacer 17, a pair of lead wire film heaters 19 are provided. In this manner, an oxygen diffusion passage 20 and an electrode space 21 which are formed by laminating the solid electrolyte plate 14, the glass spiral spacer 17, and the seal plate 18 are formed.

In the above configuration, a voltage 22 is applied between the cathode electrode 15 and the anode electrode 16 on both surfaces of the solid electrolyte plate 14.
Is applied, and an electric current flows, an electrochemical reaction of injecting and releasing oxygen generated at the cathode electrode 15 and the anode electrode 16 occurs. By limiting the supply of oxygen during the process of injecting and releasing oxygen, a saturation current characteristic appears in the voltage-current characteristic as shown in FIG. 6, and its magnitude is almost proportional to the oxygen concentration in the atmosphere. The limiting current type oxygen sensor utilizes this characteristic to supply oxygen to the electrode space 21 through the oxygen diffusion passage 21.
By limiting the diffusion rate at this stage, a limit current proportional to the supplied oxygen concentration is obtained.

Although this limiting current type oxygen sensor is excellent in stability, it has a drawback that it must be operated by heating to a high temperature because of its large internal resistance. For this reason, this type of oxygen sensor has a heater 19 mounted in the vicinity of the oxygen sensor portion, applies a predetermined voltage 23, and self-heats before use.

In addition, the limiting current type oxygen sensor obtains a limiting current proportional to the supplied oxygen concentration by controlling the oxygen diffusion rate by itself, so that the size of the sensor is very precise and small. In addition, the heater 19 is also arranged in close contact with it, so that it is heated with a very small area.

[0006]

However, in the conventional limiting current type oxygen sensor, the cathode electrode 15 and the anode electrode 16 are separately printed on both surfaces of the solid electrolyte plate 14 and fired, and then the solid electrolyte plate is further cooled. 14 is formed by printing and firing a glass spiral spacer 17 on a seal plate 18 printed and fired by a heater 19 and then firing again. That is, the cathode electrode 15 is printed and baked on the solid electrolyte plate 14, the anode electrode 16 is printed and baked, the glass spiral spacer 17 is printed, the heater 19 is printed and baked on the seal plate 18, and the partially assembled solid electrolyte plate 14 and seal plate Since the respective steps of bonding and baking 18 are separately configured, the positions of the respective components are easily shifted, and therefore, when the cathode electrode 15 is brought very close to the glass spiral spacer 17, they partially polymerize. The area changes and the output varies. In order to prevent the effective area from changing, there is a problem that the area of the cathode electrode 15 cannot be increased if the space between the glass spiral spacer 17 and the cathode electrode 15 is made sufficiently large so that the cathode electrode 15 does not cover the glass spiral spacer 17 even if printing misalignment occurs.

Therefore, in proportion to the amount of oxygen injected and released,
That is, there is a problem that the accuracy of variation of the limit current of the oxygen sensor, which is proportional to the area of the cathode electrode 15 and the activation temperature of the solid electrolyte plate 14, is poor. If the temperature of the heater 19 is set higher to reduce the variation, there is a problem that the service life is shortened due to the high temperature.

The present invention solves the above-mentioned problems, and absorbs variations such as printing misregistration at the time of manufacturing, thereby achieving high accuracy.
Another object is to provide an oxygen sensor having a long life.

[0009]

In order to achieve the above object, the present invention provides an oxygen ion conductive solid electrolyte plate having anode and cathode electrode films formed on both sides, and a cathode of the electrode film on the solid electrolyte plate. A glass spiral type spacer which is positioned on the surface side and surrounds the cathode and is spirally disposed so as to keep an interval from a start end to an end, and disposed at opposing positions of a solid electrolyte plate with the glass spiral type spacer interposed therebetween. A sealing plate, a heater in which a pair of lead wire films are formed on the surface opposite to the glass helical spacer of the seal plate, and an oxygen diffusion path surrounded by stacking and surrounding the solid electrolyte plate, the glass helical spacer and the sealing plate. An electrode film space on the cathode electrode film at the center thereof, wherein the outer peripheral edge of the film of the cathode electrode is located substantially at the center of the width of the glass spiral spacer, and the entire periphery thereof is a glass spiral space. It is arranged to polymerize service.

[0010]

According to the present invention, the cathode and anode electrodes printed on the solid electrolyte body due to printing misregistration during the manufacturing process, etc., because the entire periphery of the electrode film is polymerized on the inner edge of the glass spiral spacer by the above configuration. Even if the position of the spiral spacer is shifted up to half the width of the glass spiral spacer, the effective electrode area is not changed just by changing the overlapping area. Since the effective area of the inside is reduced to form an oxygen diffusion passage, the amount of injected and released oxygen is almost cancelled, the limiting current can be obtained stably, and the accuracy is improved.

In addition, the effective area of the cathode and anode electrodes can be made to be a portion not hidden by the glass spiral spacer, that is, the entire electrode film space, so that a higher limit current can be obtained and the accuracy can be further improved and the temperature can be improved. It is not necessary to set a higher value, so that the life is improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 and 2, reference numeral 1 denotes an oxygen ion conductive solid electrolyte plate having a size of 10 mm square and having an anode electrode 2 and a cathode electrode 3 formed of a platinum material on both surfaces, and ZrO ₂ · Y ₂ O ₃ (Addition of 8 mol% of Y ₂ O ₃ ). Reference numeral 4 denotes a glass spiral type spacer which is located on the surface of the cathode electrode 3 on the solid electrolyte plate 1 and surrounds the cathode and is spirally arranged from the start end to the end so as to be spaced apart from each other. Polymerization is performed so that the outer periphery of the cathode electrode 3 is located substantially at the center of the spacer width of 0.5 mm. Numeral 5 is a forsterite 10 mm square sealing plate disposed at opposing positions of the solid electrolyte plate 1 with the glass spiral spacer 4 interposed therebetween. A pair of leads is provided on the sealing plate 5 opposite to the glass spiral spacer. A platinum film heating heater 6 is formed. Reference numeral 7 denotes an oxygen diffusion passage formed by the solid electrolyte plate 1, the glass spiral spacer 4, and the seal plate 5, and an electrode space 8 is formed on the central cathode electrode 3.

FIG. 3 shows a control block for controlling the oxygen sensor. Reference numeral 9 denotes a sensor control unit which applies a voltage between the cathode electrode 3 and the anode electrode 2 on both surfaces and outputs a signal corresponding to a current flowing therebetween. is there. 10
Is a heater control unit which can set the temperature of the heater 6 arbitrarily. 11 is the sensor control unit 9
And a control output unit that sends a signal to the heater control unit 10. The control output unit converts the signal from the sensor control unit 9 into an oxygen concentration value, and outputs the oxygen concentration value to the sensor display control unit 12. The sensor display control unit 12 displays the output value on the sensor display. It is configured to be displayed by the unit 13.

In the above configuration, when a signal for starting the oxygen concentration measurement is output from the control output unit 11 to the sensor control unit 9 and the heater control unit 10, the sensor control unit 9 and the heater control unit 10 output the anode 2 and the cathode 2. A rated voltage is applied between the electrodes 3 and to the heater 6. The heater 6 self-heats and maintains the solid electrolyte plate 1 at a high temperature to activate the solid electrolyte plate 1.
When a voltage is applied between the cathode electrode 3 and the anode electrode 2 on both sides of the substrate, an electrochemical reaction occurs in which oxygen generated and discharged from the cathode electrode 3 and the anode electrode 2 is generated. In the process of injecting and releasing oxygen, the supply of oxygen to the electrode space 8 is restricted by the oxygen diffusion path 7 formed by the glass spiral spacer 4, so that the saturation current characteristic appears in the voltage-current characteristic, The degree is proportional to the oxygen concentration in the atmosphere.

The sensor control unit 9 sends a signal corresponding to the obtained limit current to the control output unit 11, and the control output unit 11
Is converted into an oxygen concentration value, output to the sensor display control unit 12, and displayed on the sensor display unit 13.

Here, as in the conventional case, this oxygen sensor is also printed and baked on the solid electrolyte plate 1 on the cathode electrode 3, printed on the anode electrode 2, printed on the glass spiral spacer 4, printed on the sealing plate 5 and printed on the heater 6. The assembled solid electrolyte plate 1 and the seal plate 5 are bonded and fired so that the respective steps of baking are separately formed, and the positions of the respective components are easily shifted. However, the cathode electrode 3 has a ring width of 0 inside the glass spiral spacer 4. .5 mm, the positions of the cathode electrode 3 and the anode electrode 2 printed on the solid electrolyte plate 1 and the glass spiral spacer 4 are slightly shifted due to printing misalignment during manufacturing. Also, the effective electrode area of the electrode does not change just by changing the polymerization area,
In addition, even if the distance is further shifted, the range of the glass spiral spacer 4 is set to 0.
If it is within 5 mm, the amount of reduced effective area in the electrode film space can be used as an oxygen diffusion path, so that the amount of injected and released oxygen is almost offset, and the limiting current can be obtained stably.

Further, the effective area of the cathode electrode 3 and the anode electrode 2 can be a portion that is not hidden by the glass spiral spacer 4, that is, the entire electrode space 8, so that the cathode electrode 2 does not cover the glass spiral spacer 4. In this embodiment, the area of the cathode electrode 4 can be increased by about 1.5 times as compared with the conventional case, so that a higher limit current can be obtained, which is advantageous for accuracy, variation and life. .

[0018]

As described above, the oxygen sensor of the present invention can stabilize the limit current and have high accuracy by absorbing the unevenness such as printing deviation at the time of manufacturing. Since the heater temperature does not need to be set higher, the life can be improved.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view of an oxygen sensor according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of the oxygen sensor.

FIG. 3 is a block diagram of a control unit that controls the oxygen sensor.

FIG. 4 is a partially cutaway perspective view showing an example of a conventional oxygen sensor.

FIG. 5 is a diagram showing the operation principle of the oxygen sensor.

FIG. 6 is a representative characteristic diagram of the sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Solid electrolyte plate 2 Anode electrode 3 Cathode electrode 4 Glass spiral spacer 5 Seal plate 6 Heater 7 Oxygen diffusion passage 8 Electrode space

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-265158 (JP, A) JP-A-63-154958 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 27/41

Claims (1)

(57) [Claims] 1. An oxygen ion conductive solid electrolyte plate having an anode electrode and a cathode electrode formed on both sides thereof, and a space between the start and end which surrounds the cathode electrode and is located on the cathode electrode surface side of the solid electrolyte plate. A glass spiral spacer arranged in a spiral so as to maintain, a seal plate disposed at a position opposite to the solid electrolyte plate with the glass spiral spacer interposed therebetween, and a pair on a surface of the seal plate opposite to the glass spiral spacer. A heater formed with a lead wire film, an oxygen diffusion path surrounded by stacking the solid electrolyte plate, the glass spiral spacer, and the seal plate, and an electrode space above the central cathode electrode, The limiting current type oxygen sensor in which the outer peripheral edge of the film is positioned substantially at the center of the width of the glass spiral spacer so that the entire periphery thereof overlaps with the glass spiral spacer.