JP3054997B2 - Limit current type oxygen sensor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring an oxygen concentration in an atmosphere, and performs self-diagnosis of the presence or absence of deterioration when using an oxygen sensor. The present invention relates to a limiting current type oxygen sensor device configured as described above.

[0002]

2. Description of the Related Art In recent years, environmental problems, particularly air pollution, are uncompromising problems. Deterioration of an oxygen sensor in an oxygen sensor device for measuring oxygen concentration in the atmosphere is one of the important issues.

Hereinafter, a conventional limiting current type oxygen sensor device will be described with reference to the drawings. FIG. 12 is a block diagram showing the configuration of a conventional limiting current type oxygen sensor device, in which the oxygen sensor is shown in cross section. In the figure, reference numeral 1 denotes a solid electrolyte plate having oxygen ion conductivity, on one surface of which a cathode electrode film 2a is formed and on the other surface, an anode electrode film 2b. Also, the cathode electrode film 2a
, A spiral spacer 4 having a start end and an end spaced from each other is disposed, and a seal plate 5 is disposed thereon. The spiral spacer 4 and the seal plate 5 constitute a diffusion-controlling body. The oxygen diffusion passage 6 is formed by a spiral space surrounded by opposing partition walls of the spiral spacer 4, the solid electrolyte plate 1, and the seal plate 5, and oxygen is passed through the oxygen diffusion passage 6 through the cathode electrode film. Diffuses to 2a. A heating unit 7 is provided on the outer surface of the sealing plate 5, and a power supply 1 is provided.
5, the solid electrolyte plate 1 is heated to improve oxygen ion conduction. A voltage is applied to the cathode electrode film 2a and the anode electrode film 2b by a power supply 8 via a resistor 10.

The operation of the above configuration will be described. In FIG. 12, a predetermined voltage is applied to a heating unit 7 by a power supply 15 to heat the solid electrolyte plate 1 to a predetermined temperature. on the other hand,
The power supply 8 also applies a predetermined voltage to the electrode films 2a and 2b formed on both surfaces of the solid electrolyte plate 1. In this state, oxygen in the air flows in through the oxygen diffusion passage 6, and oxygen ions flow in the solid electrolyte plate 1 from the cathode electrode film 2a toward the anode electrode film 2b. Oxygen moves in the solid electrolyte plate 1 by this oxygen pumping action, but the inflow of oxygen molecules is restricted by the oxygen diffusion passage 6, so that a saturation current (hereinafter referred to as a limiting current) corresponding to the oxygen concentration is generated. The oxygen concentration is determined by measuring the limit current value. Also, since this limit current value is constant irrespective of the voltage value applied between the cathode electrode film 2a and the anode electrode film 2b, if a constant current value is obtained even when the voltage value is changed, It can be determined that a current has been obtained.

[0005]

In such a conventional limiting current type oxygen sensor device, it is determined that the limiting current is obtained by obtaining a constant current value even when the voltage value is changed. Therefore, there is a problem that at least two measured voltage values are required to identify a deteriorated product for which a limit current cannot be obtained, and at least two types of DC power supplies having different applied voltage values are required.

The present invention solves the above-mentioned problems, and
It is an object of the present invention to provide a limiting current type oxygen sensor device that can easily perform self-diagnosis of deterioration during use by using a DC power supply of various voltage values, and issue an alarm when deterioration occurs to prevent erroneous measurement. I do.

[0007]

In order to achieve the above object, the present invention according to claim 1 is directed to an oxygen ion conductive plate-shaped solid electrolyte and a solid electrolyte sandwiched therebetween. An oxygen sensor having a configuration in which each cathode electrode film of two pairs of electrodes formed of a cathode electrode film and an anode electrode formed so as to face each other is disposed in a communication space from one oxygen diffusion passage; The comparison value between the current value when the two sets of electrode pairs are driven simultaneously by applying the DC power supply voltage and the current value when only the one set of electrode pairs are driven is within a set value area stored in advance. A self-diagnosis of the deterioration of the oxygen sensor depending on whether the current limit value is out of the set value range, and determines that the oxygen sensor is deteriorated and issues an alarm. Type oxygen sensor device According to a second aspect of the present invention, there are provided two sets of a plate-shaped solid electrolyte body having oxygen ion conductivity, and a cathode electrode film and an anode electrode formed so as to face each other with the solid electrolyte body interposed therebetween. An oxygen sensor having a configuration in which the respective cathode electrode films of the electrode pairs are arranged in a communication space from one oxygen diffusion passage, and a predetermined DC power supply voltage was applied to drive the two electrode pairs simultaneously. Whether the current value is within the initial value area stored in advance, and the current value when the two electrode pairs are driven simultaneously and the current value when only the one electrode pair is driven The self-diagnosis of the deterioration of the oxygen sensor is performed based on whether or not the comparison value is within the set value area stored in advance, and the current value when the two electrode pairs are simultaneously driven is out of the initial value area. When and before A limiting current type oxygen sensor device configured to determine that the oxygen sensor has deteriorated and to issue an alarm when the current comparison value is out of the set value region, and the present invention according to claim 6 In two electrode pairs, the area of the cathode electrode film in one electrode pair is larger than the area of the cathode electrode film in the other electrode pair at most within 7 times, and the area is larger when driving one electrode pair. This is a limiting current type oxygen sensor device using one of the electrode pairs.

[0008]

According to the first aspect of the present invention, there is provided an oxygen sensor in which two cathode electrode films are arranged in a communication space from one oxygen diffusion hole, and a flow rate of oxygen is regulated by the oxygen diffusion hole. When the oxygen sensor is in a normal state, the current values of any pair of electrode pairs are created so as to indicate a saturation current value, that is, a limit current value from an applied voltage equal to or lower than a predetermined DC power supply voltage. Therefore, at a predetermined DC power supply voltage, the current value when two electrode pairs are driven simultaneously and the current value when only one electrode pair is driven show almost the same limit current value. However, in the deteriorated state, the oxygen ion current decreases, and the current value when the two pairs of electrodes are driven at the same time shows a limit current value due to the large electrode area, but only one pair of the electrodes is driven. In this case, the limit current value is not reached. Therefore, the current comparison value between the current value when two electrode pairs are driven simultaneously and the current value when only one electrode pair is driven is different from the value in the normal state. Therefore,
By comparing the current comparison value with a value set in advance corresponding to a normal state, deterioration is self-diagnosed and determined. This self-diagnosis operation is possible with a single DC power supply voltage.

Further, in the present invention according to claim 2,
Along with the self-diagnosis operation according to claim 1, a change in the current value when the two electrode pairs are simultaneously driven corresponds to either a change in the shape of the oxygen flow passage in the oxygen sensor or an abnormality in the oxygen concentration. By comparing with the initial value stored in advance, the self-diagnosis operation of the deterioration of the oxygen sensor and the abnormality detection of the oxygen concentration can be performed. This operation is also possible with a single DC power supply voltage.

According to a sixth aspect of the present invention, the ratio of the areas of the cathode electrode films of the two electrode pairs is set to be within 7 times each other, so that the change in the current comparison value can be reduced. And make accurate judgments by sufficiently reflecting the deterioration of

In the limiting current type oxygen sensor device of the present invention, the sensor configuration in which an oxygen diffusion path is formed in a spiral space surrounded by a solid electrolyte and a partition wall of a spiral spacer and a sealing body opposed to each other is a thick film. It is possible to form an oxygen diffusion path using printing and to easily form two sets of electrode films.

[0012]

【Example】

(Embodiment 1) Hereinafter, a first embodiment of a limiting current type oxygen sensor device of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the present embodiment, and the oxygen sensor shows a cross section. In the figure, 1
Is a plate-shaped solid electrolyte member having oxygen ion conductivity, and is composed of an electrode pair 2a-2b including two cathode electrode films 2a and an anode electrode film 2b, and a cathode electrode film 3a and an anode electrode film 3b. The electrode pairs 3a-3b are formed so as to face both surfaces of the solid electrolyte body 1, respectively. A single spiral spacer 4 surrounding the cathode electrode film 2a and the cathode electrode film 3a and having a start end and an end spaced from each other is disposed on the upper side of one side of the solid electrolyte plate 1. Seal plate 5 above spacer 4
Are arranged to form a diffusion-controlling body with the spiral spacer 4 and the seal plate 5, and the oxygen diffusion passage 6 is surrounded by the partition wall, the solid electrolyte body 1, and the seal plate 5 of the spiral spacer 4 opposed to each other. Is formed in the space. Therefore, the cathode electrode film 2a and the cathode electrode film 3a are arranged in one space communicating with the oxygen diffusion passage 6, and
Oxygen is passed through the oxygen diffusion passage 6 to the cathode-side electrode film 2a.
And 3a. Note that a heating unit 7 is disposed above the seal plate 5 and is heated by the power supply 15.

A cathode electrode film 2a and an anode electrode film 2b
A DC power supply 8 for applying a DC voltage to the electrode pair 2a-2b, and the electrode pair 3a-3b formed by the cathode electrode pair 3a and the anode electrode film 3b. A closed circuit is formed through the membrane 2a, the solid electrolyte member 1, and the electrode film 2b, and a closed circuit is formed through the DC power supply 8, the electrode film 3a, the solid electrolyte member 1, and the electrode film 3b. . The switch means 9 is a switch for applying a DC voltage only to the electrode pairs 3a-3b. Further, in the closed circuit, a current detecting means 10 for detecting a current value is provided, and a current storing means 11 is connected to the current detecting means 10, and an electrode pair 2a-2b and an electrode pair 3a-3b are provided. Are driven simultaneously, and
The current value when only the electrode pairs 3a-3b are driven is read and stored. Current detection means 10 and current storage means 1
1 is connected to a current comparison value calculation means 12, and the current comparison value calculation means 12 includes an electrode pair 2a-2b and an electrode pair 3a.
-3b and a comparison value between the current value during simultaneous driving and the current value during driving only the electrode pairs 2a-2b. The current comparison value calculation means 12 is connected to a judgment means 13 for judging whether the calculated current comparison value is inside or outside a set value area stored in advance. An alarm generating means 14 is connected to the judging means 13 and issues an alarm when the calculated current comparison value is out of the set value range.

The outline of the self-diagnosis operation of the oxygen sensor in the above configuration will be described. Electrode pairs 2a-2b;
A current value obtained when the electrode pairs 3a-3b were driven simultaneously and a current value obtained when only the electrode pairs 3a-3b were driven were compared to calculate a comparison value, and this comparison value was stored in advance. If both are different from the set value, an alarm is issued. The current values are compared with the current values obtained when the electrode pairs 2a-2b and 3a-3b are simultaneously driven and the current values obtained when only the electrode pairs 2a-2b are driven. May be compared. Further, the current value used for comparison is a current value after a lapse of a predetermined time at a normal operating voltage.

FIG. 2 is a flowchart showing the self-diagnosis operation of this embodiment. When the start button is pressed, the RAM of the computer is cleared in step 1 so that new data can be input. Next, the process proceeds to step 2, in which the switch means 9 is turned on and the electrode pair 2a-
The two electrode pairs 2b and 3a-3b are simultaneously driven, and a current I2 flows. The value of the current I2 at the time of simultaneous driving of the two sets of electrode films is detected and read by the current detection means 10, and is temporarily stored in the current storage means 11 in step 3.
Next, in step 4, the switch means 9 is operated, and the circuit of the electrode pair 2a-2b is opened, so that one electrode pair 3a-
Only 3b is driven, and the current I1 at that time is detected and read by the current detecting means 10. Then step 5
In step (2), the stored value of the current I2 is called from the storage means 11, and the process proceeds to step 6, where the electrode pair 2a-2b
I2 and electrode pair 3 during simultaneous driving of electrode pair 3a-3b
The current comparison value C is calculated by the current comparison value calculation means 12 with the current I1 when only a-3b is driven. Next, in step 7, a preset set value E is called,
The process proceeds to step 8, and the judging means 13 sets the judgment current comparison value C
Is compared with the set value E, and it is determined in step 9 whether or not the area is within the area. If the area is within the area, it is determined that the sensor is normal. Then, the flow goes to 11 to cause the alarm generation means 14 to generate an alarm.

FIG. 3 is a partially cutaway perspective view showing the detailed configuration of the limiting current type oxygen sensor of this embodiment. In the figure,
Reference numeral 1 denotes a plate-shaped oxygen ion conductive solid electrolyte plate,
Reference numerals a and 3a denote cathode electrode films, respectively. One spiral spacer 4 surrounding the cathode-cathode electrode film 2a and the cathode electrode film 3a and having a start end and an end spaced from each other is arranged, and a seal plate 5 is arranged above the spiral spacer 4. The spiral spacer 4 and the seal plate 5 constitute a diffusion-controlling body, and the oxygen diffusion passage 6 is formed in a spiral space. Oxygen diffuses into the cathode electrode film 2a and the cathode electrode film 3a via the oxygen diffusion passage 6. Note that a heating unit 7 is provided above the seal plate 5.

The anode electrode film 2b and the anode electrode film 3b (both not shown) may be integrally formed.
The total area of the two anode electrode films is at least substantially equal to or greater than the total area of the two cathode electrode films. Further, one of the cathode electrode films 2a and 3a has a larger area than the other, and the smaller one is the electrode film 2a, and the larger one is the electrode film 3a. Further, there is no particular need to consider the positional relationship between the positions of the two cathode electrode films as being upstream or downstream of the oxygen diffusion passage 6.

As described above, according to the limiting current type oxygen sensor device of this embodiment, two cathode electrode films of two pairs of electrodes are provided in the communication space where the flow rate is restricted by the oxygen diffusion passage. In the oxygen sensor having the above configuration, the comparison between the current value obtained when the two electrode pairs are driven simultaneously and the current value obtained when only one electrode pair is driven is within the previously stored set value area. By making the judgment, the deterioration of the oxygen sensor can be self-diagnosed in the operation at the predetermined DC power supply pressure, and when it is judged that the oxygen sensor has been deteriorated, the alarm can be issued so that the user can easily know the deterioration.

(Embodiment 2) FIG. 4 is a block diagram showing a limiting current type oxygen sensor device according to a second embodiment of the present invention.
The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted. This embodiment is different from the first embodiment in that an initial current judging means 16 and an initial current alarm are provided in order to issue an alarm when the current value during simultaneous driving of the two electrode pairs is different from the initial value stored in advance. Means 17 are provided. In the figure, an initial current judging means 16 is connected to a current detecting means 10 and a current value at the time of simultaneous driving of two pairs of electrodes is within or outside an area of an initial value corresponding to a previously stored oxygen concentration of 20%. Determine which one. Further, the initial current judging means 16 is connected to the initial current alarm means 17, and generates an alarm when the current value at the time of simultaneous driving of two pairs of electrodes is outside the previously stored initial value area.

FIG. 5 is a flowchart showing the self-diagnosis operation of the limiting current type oxygen sensor device of the present embodiment. The operation is basically the same as that of the first embodiment, but the operation of issuing an alarm is different when the current during simultaneous driving of two pairs of electrodes is different from the initial value stored in advance.

First, when the start button is pressed, the RAM of the computer is cleared in step 1 so that new data can be input. Next, in step 2, the two electrode pairs are simultaneously driven, and the current value of the current I2 is read. Next, in step 3, the previously stored initial current value A is called, and the process proceeds to step 4 where the initial current determining means 16 compares the current value I2 with the initial current value A.
Is within the region of the initial current value A. If it is out of the range, the process proceeds to step 16 and the initial current alarm means 17
Generates an alarm. If the current I2 is within the range of the initial current value A, the process proceeds to step 6 to determine that the current is normal, and proceeds to step 7 to store the current value I2 in the current storage unit 11.
Is stored once. Subsequent operations are the same as in the embodiment,
Description is omitted.

As described above, according to the limiting current type oxygen sensor device of the present embodiment, the deterioration of the oxygen sensor can be self-diagnosed as in the case of the first embodiment, and when the two electrode pairs are simultaneously driven. By judging whether or not the current value is within the initial value area stored in advance, the deterioration of the oxygen sensor due to the change of the diffusion passage can be self-diagnosed, and the abnormality of the oxygen concentration can be detected together.

(Embodiment 3) Hereinafter, a third embodiment of the limiting current type oxygen sensor device of the present invention will be described based on specific experimental examples. In the limiting current type oxygen sensor device shown in FIG. 3, ZrO ₂ .Y ₂ O _{3 is used} as the solid electrolyte plate 1.
(8 mol% addition of Y ₂ O ₃ ), platinum as the electrode films 2 a, 2 b and 3 a, 3 b, glass as the helical spacer 4 (coefficient of thermal expansion is substantially the same as that of ZrO ₂ .Y ₂ O ₃ ,
Forsterite was used as the seal plate 5 and a platinum heater was used as the heating unit 7.

First, a method for manufacturing the oxygen sensor will be described. First, the electrode films 2a, 2b and 3a, 3b were formed on the surface of the solid electrolyte plate 1, and the helical spacers 4 were formed on the surface of the solid electrolyte plate 1 using a thick film printing technique and a firing technique. Further, the heating unit 7 was formed on the upper surface of the seal plate 5 by using a thick film printing technique and a baking technique. Next, the helical spacer 4 and the seal plate 5 were laminated and melted by heating to form an oxygen diffusion passage 6. Next, a lead wire (not shown) was attached to each electrode film. The oxygen sensor was wrapped with a heat-resistant material, and the heat insulating material was wrapped with a stainless steel mesh to form a package.

Hereinafter, the results of testing the sensor characteristics and effects of the mounted body will be described. As a current generated by the oxygen sensor, a current after a lapse of a predetermined time at a predetermined operating voltage (a stable current after about 5 minutes) was used.

(Experiment 1-1) A sensor having a size of 10 × 10 × 0.9 mm was experimentally manufactured. The area of the cathode electrode film 2a is 8
mm ² , and the area of the cathode electrode film 3a is 27 mm ² . The area of the anode electrode film 2b is 10 mm ² , and the area of the anode electrode film 3b is 30 mm ² . These two total area 40 mm ² of the anode electrode film is somewhat larger configuration than the total area 35 mm ² of the two cathode films.

In the atmosphere of the oxygen sensor (oxygen 20
%) Is shown in FIG. In this case, only the electrode pair 2a-2b by the electrode films 2a and 2b is driven, and the electrode pair 3a-3 by the electrode films 3a and 3b.
The voltage-current characteristics were measured for three cases, ie, when only b was driven, and when two pairs of electrode pairs 2a-2b and 3a-3b were simultaneously driven. In addition,
The sensor operating temperature is 500 ° C.

When only the electrode pairs 3a-3b were driven, the limiting current characteristics were obtained from the applied voltage of 0.8V. On the other hand, when the electrode pairs 2a-2b and the electrode pairs 3a-3b were simultaneously driven, a limiting current characteristic was obtained from an applied voltage of 0.5V. Further, when only the electrode pairs 2a-2b are driven, no limit current is obtained because the electrode area is small.

FIG. 7 shows the result of calculating the current comparison value during each drive. This current comparison value is the current value obtained when only the electrode pair 3a-3b is driven in the current value obtained in FIG. 6, and the current value obtained when the electrode pair 2a-2b and the electrode pair 3a-3b are simultaneously driven. It is the value divided by the current value. As shown in the figure, the current comparison value differs for each applied voltage, but a constant value of 0.95 or more is applied when the applied voltage is 0.8 V or more.
showed that. Therefore, assuming that the operating voltage is 0.8 V, the current comparison value of the oxygen sensor in the initial stage of use is 0.95 V.
The current comparison value may be a method of calculating the difference between the currents. When the limiting current characteristic can be obtained, the electrode pair 2
The current value when only a-2b is driven may be used.

(Experiment 1-2) FIG. 8 shows the voltage-current characteristics in the atmosphere when the operating temperature was lowered to 450 ° C. in the prototype oxygen sensor. This corresponds to the characteristics of a deteriorated product in which the temperature of the heating unit has decreased. The operation method of the sensor in the figure is the same as that in (Experiment 1-1), in which only the electrode pair 2a-2b is driven and the electrode pair 3a-3b
Only the electrode pair 2a-2b and the electrode pair 3
a-3b are simultaneously driven in two cases.

When only the electrode pairs 3a-3b are driven, a limit current characteristic is obtained from the applied voltage of 1.0 V. When the electrode pairs 2a-2b and the electrode pairs 3a-3b are driven simultaneously, And a limiting current characteristic was obtained from an applied voltage of 0.8 V. However, when only the electrode pairs 2a-2b are driven, the limiting current characteristic is not obtained as shown in FIG. This is because the electrode area is small and the operating temperature is lowered, so that the current value is further lowered.

FIG. 9 shows the current comparison value in this state. The current comparison value differs for each applied voltage.
Above V, a constant value of 0.95 was shown. Therefore, if the operating voltage is 0.8 V, the current comparison value is 0.80
It is. It can be seen that the current comparison value 0.80 of the oxygen sensor whose operating temperature has decreased is lower than the current comparison value 0.95 of the normal sensor in the initial stage of use.

(Experiment 1-3) FIG. 10 shows the voltage-current characteristics in the atmosphere when the electrodes of the prototype oxygen sensor deteriorated due to long-term use. The operation method of the oxygen sensor is the same as in (Experiment 1-1). The operating temperature is a predetermined 500 ° C.

When only the electrode pairs 3a and 3b are driven, the limiting current characteristic is obtained from the applied voltage of 1.2 V.
When a-2b and the electrode pairs 3a-3b were simultaneously driven, a limiting current characteristic was obtained from an applied voltage of 0.8V. When only the electrode pairs 2a-2b are driven, no limit current is obtained. This is because the electrode area is small, and the electrode deteriorates due to long-term use, and the current further decreases.

FIG. 11 shows the current comparison value at each drive.
Shown in Although the current comparison value differs for each applied voltage, a constant value of 0.95 is obtained at an applied voltage of 1.2 V or more. Therefore, when the operating voltage is 0.8 V, the voltage comparison value is 0.80. It can be seen that the current comparison value 0.80 of the oxygen sensor whose electrode has deteriorated is lower than the current comparison value 0.95 of the oxygen sensor in the initial stage of use.

(Experiment 2) A new oxygen sensor was experimentally manufactured. The area of the cathode electrode film 2a is 27 mm ² , and the area of the cathode electrode film 3a is 8 mm ² . In addition, one anode electrode film 2b was commonly used, and its area was 40 mm ² . The current value of this oxygen sensor in the atmosphere is shown in the column of Experiment 2 in Table 1. In addition, the current at the time of driving one set uses the electrode pairs 2a-2b having a large area.

The initial product of the prototype is used at an applied voltage of 0.
At the time of simultaneous driving of two pairs of electrodes at 8V, the current value I2 is 1
It is 35 μA, and it has been confirmed that a voltage-current characteristic in which a limit current is obtained at an applied voltage of 0.5 V or more is obtained.
At an operating voltage of 0.8 V, a sufficient limit current is obtained. When the initial current A stored in advance is set to 131 to 139 μA in consideration of accuracy, 135 μA of the current value I 2 at the time of simultaneous driving of two pairs of electrodes is in the area of the initial current value A, and is determined to be normal. . On the other hand, the current I1 at the time of driving one set of electrode pairs at an applied voltage of 0.8 V is 130 μA, and it has been confirmed that a limiting current can be obtained at an applied voltage of 0.6 V or more. Current I when two pairs of electrodes are driven simultaneously
When the current comparison value C of the current I1 at the time of driving the two pairs of electrodes is calculated, it is 0.83. Since the set value E stored in advance is 0.90 to 1.05, the current comparison value C is out of the range of the set value E, and an alarm is issued. From this alarm, it can be determined that the sensor has deteriorated.

In the deteriorated product, since the electrode was deteriorated, 2
The current value I2 at the time of simultaneous driving of the pair of electrodes is 138 μA, and the voltage-current characteristics are such that a limiting current can be obtained only at an operating voltage of 0.8 V. Since the initial current value A stored in advance is 131 to 139 μA, the current value 138 μA when two sets of electrodes are simultaneously driven is within the area of the initial current value A, and is determined to be normal. However, the current value I1 at the time of driving one set of electrodes was 115 μA, and no limit current was obtained. Next, the current I at the time of simultaneous driving of two electrode pairs
Current comparison value C based on current value I1 at the time of driving two and one set of electrode pairs
Is 0.83, and the preset value E stored in advance is 0.
90 to 1.05, it is outside the range of the set value E,
It is determined that there is an abnormality due to the deterioration and an alarm is issued. It is possible to know that the battery has deteriorated by this alarm.

(Experiment 3) Another oxygen sensor was newly manufactured. The area of the cathode electrode film 2a is 20 mm ² , and the area of the cathode electrode film 3a is 15 mm ² . The area of the anode electrode film 2b is 20 mm ² , and the area of the anode electrode film 3b is 20 mm ² . The current characteristics of this oxygen sensor in the atmosphere are shown in Table 3 in Experiment 3. At the time of driving one set of electrode pairs, electrode pairs 2a-2b having a large area are used.

An initial product of this oxygen sensor has a current value I2 when two pairs of electrodes are simultaneously driven at an applied voltage of 0.8V.
Is 186 μA, and it has been confirmed that a limiting current can be obtained at an operating voltage of 0.5 V or more. In consideration of accuracy, the initial current value A stored in advance is set to 181 to 191 μm.
Assuming that A is 18 of the current I2 at the time of simultaneous driving of two pairs of electrodes.
5 μA is in the area of the initial current value A, and it is determined that the initial current is normal. On the other hand, the current I1 at the time of driving one set of electrode pairs at an applied voltage of 0.8 V is 180 μA, and a voltage-current characteristic in which a limit current can be obtained from an operating voltage of 0.8 V has been confirmed. Current I2 and 1 when two sets of electrode pairs are driven simultaneously
When the current comparison value C is calculated based on the current I1 at the time of driving the pair of electrodes, the value is 0.97. Therefore, if the set value E stored in advance is set to 0.90 to 1.05 in consideration of accuracy, the current comparison value C is within the range of the set value E and is determined to be normal.

In the deteriorated product, the current I2 at the time of simultaneous driving of two pairs of electrodes was 185 μA because the electrodes were deteriorated, and the voltage-current characteristics at which the limiting current was finally obtained at an operating voltage of 0.8 V were confirmed. Since the initial current value A stored in advance is 181 to 191 μA, 182 μA of the current I 2 at the time of simultaneous driving of two pairs of electrodes is within the area of the initial current value A, and the initial current is determined to be normal. on the other hand,
The current I1 at the time of driving one set of electrode pairs was 130 μA, and no limiting current was obtained at an operating voltage of 0.8 V.
When the current comparison value C is calculated from the current I2 when the two pairs of electrodes are simultaneously driven and the current I1 when the single pair of electrodes are driven, the current comparison value C is 0.71, and the preset value E stored in advance is.
Since it is 75 to 0.85, the current comparison value C is out of the range of the set value E, and an alarm is issued. This alarm allows the user to know that the sensor has deteriorated.

(Experiment 4) Another sensor was newly manufactured.
The area of the cathode electrode film 2a is 5 mm ² , and the area of the cathode electrode film 3a is 31 mm ² . The area of the anode electrode film 2b is 6 mm ² , and the area of the anode electrode film 3b is 34 mm ² . The current characteristics of this oxygen sensor in the atmosphere are shown in the column of Experiment 4 in Table 1. At the time of driving one set of electrodes, an electrode pair 2a-2b having a large area is used.

An initial product of this oxygen sensor has a voltage-current characteristic in which a current I2 at the time of simultaneous driving of two pairs of electrodes at an applied voltage of 0.8 V is 120 μA and a limiting current is obtained at an applied voltage of 0.4 V or more. I have confirmed. The initial current value A stored in advance is set to 116 to 1 in consideration of accuracy.
Assuming 24 μA, the current I2 at the time of simultaneous driving of two electrode pairs
120 μA is in the region of the initial current value A, and it is determined that the initial current is normal. On the other hand, the current I1 at the time of driving one set of electrode pairs at an applied voltage of 0.8 was 180 μA, and it was confirmed that a limit current was obtained from an operating voltage of 0.5V. Current values I2 and 1 when two sets of electrode pairs are driven simultaneously
When the current comparison value C is calculated from the current value I1 at the time of driving the set of electrode pairs, the current comparison value C is 1.00. If the previously stored set value E is 0.90 to 1.05 in consideration of the accuracy, the current comparison value C Is within the range of the set value E and is determined to be normal.

The deteriorated product has a current I 2 of 140 μA when two pairs of electrodes are simultaneously driven due to deterioration of the electrodes, and shows a value larger than the initial use value of 120 μA. If these current values are interpreted as they are, the oxygen concentration is 23%, which is inconsistent with the measured atmospheric oxygen concentration of 20%. The reason for this is that in this deteriorated product, the oxygen diffusion resistance is reduced because the oxygen diffusion path is larger than the initial use value, and the current value is increased. Here, since the initial current value A stored in advance is 116 to 124 μA, 140 μA of the current I 2 at the time of simultaneous driving of two pairs of electrodes is outside the range of the initial current value A, and an initial current alarm is generated. . From this alarm, it can be determined that the sensor has deteriorated. For reference, a current comparison value C obtained by calculating the current value I2 when two pairs of electrodes are driven simultaneously and the current I1 when driving one pair of electrodes is 0.99. The set value E stored in advance is 0.90-1.
Since it is 05, the current comparison value C is within the range of the set value. This state is because when the deteriorated product has an operating voltage of 0.8 V, a sufficient limit current is obtained in both operating methods.

[0046]

[Table 1]

(Experiment 5) Another trial oxygen sensor was newly manufactured, and the areas of the cathode electrode film 2a and the cathode electrode film 3a were examined. As a result, it was found that when the area of one cathode electrode film was larger than the area of the other cathode electrode film at most within 7 times, deterioration was easily determined.

Considering the reason, if the area of one of the cathode electrode films is eight times or more larger than the other, the area of the other cathode electrode film is too small, so that the voltage and the current when the two pairs of electrodes are simultaneously driven are used. This is because the characteristics and the voltage-current characteristics at the time of driving one set of electrodes are almost the same, and the deterioration cannot be identified in a region where accuracy is considered. That is, even if the oxygen sensor is deteriorated, the current comparison value C is equal to the set value E.
Is sometimes determined to be within the region of the above, and an erroneous determination occurs. On the other hand, when a cathode electrode film having a relatively large area is used, the limit current can be obtained from the applied voltage side lower than the actual operating voltage. . This is also correlated with the fact that the area of one cathode electrode film is larger than the area of the other cathode electrode film by at most seven times.

On the other hand, even with a configuration in which one anode electrode film is used as a common electrode film, a current I2 when two pairs of electrodes are driven simultaneously and a current I1 when one pair of electrodes are driven are obtained with high accuracy. Was done. The reason for this is that the current during each drive is dominated by the cathode electrode film side.

Based on the above experimental results, deterioration of the limiting current type oxygen sensor will be summarized. The deterioration phenomena of the limiting current type oxygen sensor can be roughly classified into two types. One is deterioration of the oxygen diffusion passage, which is a symptom in which the current value increases / decreases even though the limit current is obtained. Other deteriorations are deterioration of the electrodes and lowering of the operating temperature. When a significant deterioration occurs, a limit current cannot be obtained, and this is a symptom that the current value decreases.

When the current value increases or decreases due to the deterioration of the oxygen diffusion passage, the oxygen sensor displays a concentration different from the true oxygen concentration. When the current value shows a value different from the initial value (current corresponding to 20% in the normal atmosphere) stored in advance, it means that the oxygen sensor is deteriorated or the oxygen concentration is abnormal. Since both of these occurrences are abnormal conditions, issuing an alarm further enhances safety. In the present invention, this determination is made first by using the current at the time of simultaneous driving of two pairs of electrodes, and it is possible to determine whether the oxygen sensor has significantly deteriorated or the oxygen concentration is abnormal. However, in this determination, even if the sensor is determined to be normal and the oxygen concentration is also determined to be normal, it is not possible to determine the slight electrode deterioration of the oxygen sensor, the decrease in operating temperature, and the extent to which the progress is occurring.

In the present invention, by using a comparison value between the current value at the time of driving two pairs of electrodes simultaneously and the current value at the time of driving one pair of electrodes,
It is determined whether or not the electrode of the sensor has slightly deteriorated or the operating temperature has decreased. In addition, it is possible to identify how much electrode deterioration and operating temperature decrease are occurring by this determination, and there is an advantage that all the deterioration can be identified by using this determination in combination. The determination using the comparison value of the current value during the simultaneous driving of two pairs of electrodes and the current value during the driving of one pair of electrodes may be performed first. Even in this case, it is possible to determine whether or not the electrode of the oxygen sensor is slightly deteriorated or the operating temperature is lowered, and to what extent the deterioration is occurring, and whether the deterioration is more significant.

As a reference, it is possible to judge only the deterioration of the oxygen diffusion passage and the significant electrode deterioration by the conventional judgment using only the current when the two pairs of electrodes are simultaneously driven. It is not possible to judge the temperature drop, slight electrode deterioration, or the extent to which it is occurring.

Further, in the present invention, the judgment using the comparison value between the current value at the time of simultaneous driving of two pairs of electrodes and the current value at the time of driving one pair of electrodes can also simplify the sensor characteristic inspection in the sensor manufacturing process. Available. In the inspection of sensor characteristics, it is determined that the limit current is obtained by obtaining a constant current value even if the voltage value is changed. However, two measured voltage values were required. In this regard, the present invention provides a comparison value (when both the current value obtained when the two pairs of electrodes are driven simultaneously and the operating voltage obtained when the current value obtained when the one pair of electrodes are driven are within the limit current region, For example, a value obtained by dividing current values by each other is around 1.0 (0.90 to 1.05 in an experiment in consideration of accuracy). Conversely, if the current value obtained when the two pairs of electrodes are driven simultaneously and the operating voltage obtained when the current value obtained when driving one pair of electrodes are not in the limit current region, values other than around 1.0 (in the experiment, For example, 0.8 or less). From this, for example, by setting the current comparison value to 0.90 to 1.05 for a non-defective product and 0.8 or less for a defective product, 1
Non-defective products and defective products can be identified by the types of measured voltage values.

[0055]

As is apparent from the above description, the present invention provides a plate-like solid electrolyte body having oxygen ion conductivity, a cathode electrode film and an anode electrode formed so as to face each other with the solid electrolyte body interposed therebetween. An oxygen sensor having a configuration in which respective cathode electrode films of two sets of electrode pairs are arranged in a communication space from one oxygen diffusion passage, and applying a predetermined DC power supply voltage to the two sets of electrodes. The deterioration of the oxygen sensor is determined by whether or not the comparison value between the current value when the pair is driven simultaneously and the current value when only the one electrode pair is driven is within the set value region stored in advance. Self-diagnosis,
When the current comparison value is out of the set value range, the oxygen sensor is determined to be degraded and a warning is issued, so that the oxygen sensor is self-diagnosed for deterioration by driving with a DC power supply voltage. If the battery is deteriorated, an alarm can be issued to notify the user. Also, the present invention provides a plate-shaped solid electrolyte body having oxygen ion conductivity and a cathode electrode formed so as to face the solid electrolyte body. An oxygen sensor having a configuration in which each cathode electrode film of two pairs of electrodes consisting of a membrane and an anode electrode is disposed in a communication space from one oxygen diffusion passage, and applying a predetermined DC power supply voltage to Whether the current value when the two electrode pairs are simultaneously driven is within the initial value area stored in advance, and whether the current value when the two electrode pairs are simultaneously driven and the 1
The comparison value with the current value when driving only one set of electrode pairs is
Self-diagnosis of the deterioration of the oxygen sensor depending on whether it is within a set value area stored in advance, and when the current value when the two electrode pairs are driven simultaneously is outside the initial value area, and When the current comparison value is out of the set value range, the oxygen sensor is determined to be degraded and an alarm is issued, so that the oxygen sensor can be self-diagnosed for deterioration by driving with a DC power supply voltage, Safety can be improved by detecting an abnormal oxygen concentration.
The result of the self-diagnosis reflects the slight deterioration of the electrodes of the sensor, the decrease in the operating temperature, and the extent to which it is occurring. In addition, the sensor can easily self-diagnose whether or not the sensor has deteriorated while using the sensor by using one type of DC power supply.

Further, the present invention provides two electrode pairs,
The area of the cathode electrode film in one electrode pair is larger than the area of the cathode electrode film in the other electrode pair at most within 7 times, and when driving one set of electrode pairs, the electrode pair having the larger area is used. By doing so, the reliability of deterioration detection can be improved.

Further, the limiting current type oxygen sensor of the present invention has a sensor configuration in which the oxygen diffusion path is formed in a helical space surrounded by the solid electrolyte, the opposing partition walls of the helical spacer, and the seal. The oxygen diffusion path can be formed using thick film printing, and the electrode film can also be formed using thick film printing. Therefore, two sets of electrode films can be easily formed, the mass productivity is excellent, and the sensor can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of a limiting current type oxygen sensor device of the present invention.

FIG. 2 is a flowchart showing the operation of the apparatus.

FIG. 3 is a partially cutaway perspective view showing a configuration of an oxygen sensor in the limiting current type oxygen sensor device of the present invention.

FIG. 4 is a block diagram showing a configuration of a second embodiment of the limiting current type oxygen sensor device of the present invention.

FIG. 5 is a flowchart showing the operation of the apparatus.

FIG. 6 is a voltage-current characteristic diagram showing characteristics of an oxygen sensor in the limiting current type oxygen sensor device of the present invention.

FIG. 7 is a characteristic diagram showing a current comparison value in an initial use product of the oxygen sensor in the limiting current type oxygen sensor device of the present invention.

FIG. 8 is a voltage-current characteristic diagram showing characteristics of a deteriorated product of a decrease in operating temperature of the oxygen sensor in the limiting current type oxygen sensor device of the present invention.

FIG. 9 is a characteristic diagram showing a current comparison value of a deteriorated product having a lowered operating temperature of the oxygen sensor in the limiting current type oxygen sensor device of the present invention.

FIG. 10 is a voltage-current characteristic diagram showing characteristics of an electrode-deteriorated product of the oxygen sensor in the limiting current type oxygen sensor device of the present invention.

FIG. 11 is a characteristic diagram showing a current comparison value of a deteriorated electrode of the oxygen sensor in the limiting current type oxygen sensor device of the present invention.

FIG. 12 is an explanatory diagram showing a configuration of a conventional limiting current type oxygen sensor device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Oxygen ion conductive plate-shaped solid electrolyte body 2a Cathode electrode film 2b Anode electrode film 3a Cathode electrode film 3b Anode electrode film 4 Spiral spacer 5 Seal plate 6 Oxygen diffusion passage 8 DC power supply 9 Switch means 10 Current detection means 11 Current storage means 12 Current comparison value calculation means 13 Judgment means 14 Alarm generation means 15 Power supply for heating unit

Claims (8)

(57) [Claims] 1. A cathode electrode of each of two pairs of electrodes comprising an oxygen ion conductive plate-shaped solid electrolyte body, and a cathode electrode film and an anode electrode formed to face each other with the solid electrolyte body interposed therebetween. An oxygen sensor having a configuration in which a membrane is disposed in a communication space from one oxygen diffusion passage, and a current value obtained when a predetermined DC power supply voltage is applied to simultaneously drive the two electrode pairs and the one set The self-diagnosis of the deterioration of the oxygen sensor is performed based on whether or not the comparison value with the current value when only the electrode pair is driven is within the set value area stored in advance. A limiting current type oxygen sensor device which determines that the oxygen sensor has deteriorated and issues an alarm when it goes outside. 2. The cathode electrode of each of two pairs of electrodes comprising an oxygen ion conductive plate-shaped solid electrolyte body, and a cathode electrode film and an anode electrode formed to face each other with the solid electrolyte body interposed therebetween. An oxygen sensor having a configuration in which a membrane is disposed in a communication space from one oxygen diffusion passage is provided, and a current value when a predetermined DC power supply voltage is applied to simultaneously drive the two electrode pairs is stored in advance. Whether or not the current value is within the initial value region, and a comparison value between a current value when the two electrode pairs are driven simultaneously and a current value when only the one electrode pair is driven are stored in advance. Self-diagnosis of the deterioration of the oxygen sensor depending on whether it is within the set value range, and when the current value when the two pairs of electrodes are driven simultaneously is outside the initial value range, and when the current comparison is performed. Value is the set value A limiting current type oxygen sensor device which determines that the oxygen sensor has deteriorated when it is out of the range and issues an alarm. 3. A two-electrode pair comprising an oxygen ion conductive plate-shaped solid electrolyte body, a cathode electrode film and an anode electrode film formed so as to face each other with the solid electrolyte body interposed therebetween, and A helical spacer provided on one side surface of the electrolyte body so as to surround the two cathode electrode films of the two pairs of electrodes so that a start end and an end are spaced from each other; and disposed on the helical spacer. And an oxygen sensor having a configuration in which one oxygen diffusion passage is formed by a spiral space surrounded by the partition wall of the solid electrolyte member and the spiral spacer opposed to each other and the seal member. Claim 1
3. A limiting current type oxygen sensor device according to claim 2. 4. A single DC power supply for driving two pairs of electrodes, and a DC power supply is disposed in a closed circuit between the two pairs of electrodes and the DC power supply, and simultaneously drives the two pairs of electrodes. Or a switch means for switching to driving only one of the pair of electrodes, and a current when the two pairs of electrodes are simultaneously driven by applying a predetermined DC power supply voltage and arranged in the closed circuit. Current detecting means for detecting a value and a current value when only one electrode pair is driven; a current value when simultaneously driving the two electrode pairs or a current value when only one electrode pair is driven Current storage means for reading and storing at least any one of the following: a current for calculating a comparison value between a current value obtained when the two electrode pairs are simultaneously driven and a current value obtained when the one electrode pair is driven. The comparison value calculation means, and the current comparison value is 4. A system according to claim 1, further comprising: a determination unit configured to determine whether the current comparison value is within the stored set value region, and an alarm unit configured to generate an alarm when the current comparison value is out of the set value region. The limiting current type oxygen sensor device according to any one of the above. 5. An initial current judging means for judging whether or not a current value when simultaneously driving two electrode pairs is within an initial value region corresponding to a previously stored oxygen concentration of 20%, The limiting current type oxygen sensor device according to any one of claims 2 to 4, further comprising an initial current alarm unit that issues an alarm when a current value is out of the initial value range. 6. In two electrode pairs, the area of the cathode electrode film in one electrode pair is larger than the area of the cathode electrode film in the other electrode pair by at most 7 times or less.
5. The limiting current type oxygen sensor device according to claim 1, wherein when driving a pair of electrode pairs, an electrode pair having a larger area is used. 7. The limiting current type oxygen sensor according to claim 1, wherein the anode electrode films of the two electrode pairs are formed as a single body and configured as one common anode electrode film. apparatus. 8. The limiting current type oxygen sensor device according to claim 1, wherein the determination is made using a current value after a lapse of a predetermined time in a normal operating voltage value.