JP4527580B2 - Gas sensor evaluation method and gas sensor evaluation apparatus - Google Patents

Description

  The present invention relates to a gas sensor evaluation method and an evaluation apparatus.

  In general, a gas sensor that detects an oxygen concentration in exhaust gas is used for combustion control of an internal combustion engine. This gas sensor includes a solid electrolyte body made of a ceramic such as zirconia having oxygen ion conductivity, a measurement electrode made of platinum or the like provided on one surface of the solid electrolyte body and exposed to a gas to be measured, and a solid electrolyte. The reference electrode is provided on the other surface of the body and is made of platinum or the like in contact with the reference gas. Furthermore, in order for the gas sensor to operate from an earlier stage and feed back the oxygen concentration in the exhaust gas as soon as possible, the measurement electrode contains a base metal such as lead or zinc in order to operate stably even at low temperatures. Some are.

  The gas sensor extracts an electromotive force generated in the solid electrolyte body in accordance with the oxygen concentration in the gas to be measured from the reference electrode and the measurement electrode, and also refers to the value of the electromotive force (hereinafter referred to as “output value”). ) Is used to detect the oxygen concentration.

By the way, in order to respond to the recent tightening of exhaust gas regulations, more precise combustion control of an internal combustion engine is required. For this reason, higher measurement accuracy is also required for the gas sensor. There is also a demand for an evaluation apparatus for evaluating how accurately the gas sensor can output the gas sensor. As an evaluation apparatus for such a gas sensor, for example, as described in Patent Document 1, a gas obtained by alternately switching a reducing gas and an oxidizing gas having the same flow rate is regarded as a gas to be measured and supplied to the gas sensor. There are some which evaluate the responsiveness of the gas sensor by the output of the gas sensor.
JP 2003-185621 A

  However, the above gas sensor evaluation apparatus evaluates the responsiveness, which is the output of the gas sensor itself, and can determine whether the gas sensor is good or bad, but if the responsiveness is poor, it indicates which part of the gas sensor is defective. Could not be identified. In particular, when a base metal such as lead or zinc is applied to the measurement electrode of the gas sensor element, the amount or degree of oxidation is one factor that changes the responsiveness of the gas sensor. It was difficult to directly evaluate the condition.

  The present invention has been made to solve the above problems, and an object thereof is to provide a gas sensor evaluation method and an evaluation apparatus for evaluating the state of a base metal applied to a measurement electrode of a gas sensor element.

In order to achieve the above object, a gas sensor evaluation method according to claim 1 of the present invention is directed to a solid electrolyte body having oxygen ion conductivity, and a measurement electrode exposed to a gas to be measured and the measurement electrode. A gas sensor evaluation method for evaluating the characteristics of a gas sensor element provided with a reference electrode, using at least propane gas and oxidizing gas, fixing one of these flow rates and changing the other. When the gas sensor element is exposed to an atmosphere, the amount of base metal applied to the measurement electrode or the degree of oxidation of the base metal is evaluated based on the output value output from the gas sensor.

The gas sensor evaluation method according to claim 2 of the present invention is characterized in that, in addition to the configuration of the invention according to claim 1, the base metal contains at least one of lead or zinc.

Furthermore, in the gas sensor evaluation apparatus according to claim 3 of the present invention, the measurement electrode exposed to the gas to be measured and the reference electrode facing the measurement electrode are disposed on the solid electrolyte body having oxygen ion conductivity. A gas supply means for supplying an atmosphere composed of at least propane gas and an oxidizing gas to the gas sensor element, and a flow rate of either the propane gas or the oxidizing gas supplied by the gas supply means is fixed. A flow rate adjusting means for changing the other, an output measuring means for measuring an output value output from a gas sensor provided with the gas sensor element by exposing the gas sensor element to the atmosphere adjusted by the flow rate adjusting means, and the output measuring means to evaluate the degree of oxidation of the coating amount, or該卑metal base metal that is applied to the measuring electrode based on the measured output value by Characterized by comprising an evaluation unit.

The gas sensor evaluation apparatus according to claim 4 of the present invention is characterized in that, in addition to the configuration of the invention according to claim 3 , the base metal contains at least one of lead or zinc.

The gas sensor evaluation method according to claim 1 of the present invention is a gas sensor in which a measurement electrode exposed to a gas to be measured and a reference electrode facing the measurement electrode are provided on a solid electrolyte body having oxygen ion conductivity. Since the element is exposed to an atmosphere created by using at least propane gas and oxidizing gas, with the flow rate of one of these being fixed and changing the other , measurement is performed based on the output value output from the gas sensor to this atmosphere. The amount of base metal applied to the constant electrode or the degree of oxidation of the base metal can be evaluated. Therefore, the amount of base metal applied to the measurement electrode or the degree of oxidation of the base metal can be directly evaluated without being influenced by other factors, only by evaluation from the static characteristics of the gas sensor. Further, the amount of base metal applied to the measurement electrode or the degree of oxidation of the base metal can be evaluated without destructive inspection of the gas sensor, which is also effective when the gas sensor to be evaluated is to be reused.

When evaluating the application amount of the noble metal is as follows. Specifically, propane gas reacts with oxygen in the oxidizing gas by the action of a catalyst such as platinum that forms the measurement electrode. As a result, in the gas sensor, the difference between the output value of the electromotive force in the reducing atmosphere and the output value of the electromotive force in the oxidizing atmosphere is greatly different. Here, when the base electrode is applied to the measurement electrode, the catalytic activity of the measurement electrode is further reduced, so the reaction between propane gas and oxygen does not proceed, and the electromotive force from the gas sensor is reduced even in a reducing atmosphere (rich). The output value is kept low. Therefore, as the amount of base metal applied increases, the catalytic activity of the measurement electrode decreases and the amount of reacting oxygen decreases, so the output value of the electromotive force in the reducing atmosphere decreases, and the output value of the electromotive force in the oxidizing atmosphere The difference of becomes smaller. In this way, since the value of the electromotive force changes according to the change in the amount of base metal applied to the measurement electrode, if the response on the rich side of the gas sensor is poor, is there a cause in the base metal applied? You can specify whether. Furthermore, it is possible to evaluate up to the amount of base metal applied.

When evaluating the degree of oxidation of the noble metal is as follows. Even if the base metal is applied to the measurement electrode, if the base metal has already been oxidized, the catalytic activity is not reduced, and therefore the output is the same as that of the measurement electrode not applied with the base metal. If such a gas sensor element is exposed to a reducing atmosphere and then the gas sensor evaluation method of the present invention is performed again, the base metal that has been oxidized returns to its original state when the base metal is applied. As a result, the catalytic activity of the measurement electrode is reduced, and the amount of reacting oxygen is reduced, so that the value of the electromotive force in the reducing atmosphere is lowered. Thus, the oxidation degree of a base metal can also be evaluated by combining with exposure to a reducing atmosphere.

Further, in the gas sensor evaluation method according to claim 2 of the present invention, in addition to the effects of the invention according to claim 1, the base metal contains at least one of lead or zinc. Lead or zinc is often used as a base metal contained in the measurement electrode of the gas sensor, and the evaluation method of the present invention can effectively evaluate the state of the base metal applied to the measurement electrode such as the coating amount and the degree of oxidation. .

Furthermore, in the gas sensor evaluation apparatus according to claim 3 of the present invention, the measurement electrode exposed to the gas to be measured and the reference electrode facing the measurement electrode are disposed on the solid electrolyte body having oxygen ion conductivity. Since the gas sensor element is exposed to an atmosphere created by using at least propane gas and oxidizing gas and fixing one of these flow rates and changing the other, depending on the output value output by the gas sensor to this atmosphere , it is possible to evaluate the degree of oxidation of the coating amount or該卑metal, base metal, which is applied to the measurement electrodes. Therefore, the amount of base metal applied to the measurement electrode or the degree of oxidation of the base metal can be directly evaluated without being influenced by other factors, only by evaluation from the static characteristics of the gas sensor. Further, the amount of base metal applied to the measurement electrode or the degree of oxidation of the base metal can be evaluated without destructive inspection of the gas sensor, which is also effective when the gas sensor to be evaluated is to be reused.

When evaluating the application amount of the noble metal is as follows. Specifically, propane gas reacts with oxygen in the oxidizing gas by the action of a catalyst such as platinum that forms the measurement electrode. As a result, the difference between the output value of the electromotive force in the reducing atmosphere and the output value of the electromotive force in the oxidizing atmosphere is greatly different. Here, when the base electrode is applied to the measurement electrode, the catalytic activity of the measurement electrode is further reduced, so the reaction between propane gas and oxygen does not proceed, and the electromotive force from the gas sensor is reduced even in a reducing atmosphere (rich). The output value is kept low. Therefore, as the amount of base metal applied increases, the catalytic activity of the measurement electrode decreases and the amount of reacting oxygen decreases, so the output value of the electromotive force in the reducing atmosphere decreases, and the output value of the electromotive force in the oxidizing atmosphere The difference of becomes smaller. In this way, since the value of the electromotive force changes according to the change in the amount of base metal applied to the measurement electrode, if the response on the rich side of the gas sensor is poor, is there a cause in the base metal applied? You can specify whether. Furthermore, it is possible to evaluate up to the amount of base metal applied.

When evaluating the degree of oxidation of the noble metal is as follows. Even if the base metal is applied to the measurement electrode, if the base metal has already been oxidized, the catalytic activity is not reduced, and therefore the output is the same as that of the measurement electrode not applied with the base metal. If such a gas sensor element is exposed to a reducing atmosphere and then the gas sensor evaluation method of the present invention is performed again, the base metal that has been oxidized returns to its original state when the base metal is applied. As a result, the catalytic activity of the measurement electrode is reduced, and the amount of reacting oxygen is reduced, so that the value of the electromotive force in the reducing atmosphere is lowered. Thus, the oxidation degree of a base metal can also be evaluated by combining with exposure to a reducing atmosphere.

Further, in the gas sensor evaluation apparatus according to claim 4 of the present invention, in addition to the effects of the invention according to claim 3 , the base metal contains at least one of lead or zinc. Lead or zinc is often used as a base metal contained in the measurement electrode of the gas sensor, and the evaluation method of the present invention can effectively evaluate the state of the base metal applied to the measurement electrode such as the coating amount and the degree of oxidation. .

  Next, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a block diagram schematically showing the overall system configuration of the gas sensor evaluation apparatus 100. FIG. 2 is a cross-sectional view showing the overall configuration of the gas sensor 1. As shown in FIG. 1, the evaluation apparatus 100 includes a gas supply unit 110 that supplies gas and a reaction furnace unit 120 in which the gas sensor 1 to be evaluated is installed.

  The gas supply unit 110 includes three gas cylinders: a propane gas cylinder 102 filled with propane gas, an oxygen gas cylinder 103 filled with oxygen gas, and a nitrogen gas cylinder 104 filled with nitrogen gas. Connected to the propane gas cylinder 102 is a mass flow controller (MFC) 112 for adjusting the flow rate of the propane gas supplied therefrom. The oxygen gas cylinder 103 is connected to a mass flow controller 113 for adjusting the flow rate of oxygen gas supplied therefrom. Further, a mass flow controller 114 for adjusting the flow rate of nitrogen gas supplied from the nitrogen gas cylinder 104 is connected to the nitrogen gas cylinder 104. Note that the oxygen gas supplied from the oxygen gas cylinder 103 is the oxidizing gas of the present invention, but in addition to the oxygen gas, NO gas or NO 2 gas can also be used as the oxidizing gas.

  The gas supply unit 110 is connected to a pipe 115, and a mixed gas composed of propane gas, oxygen gas, and nitrogen gas whose flow rate is adjusted by each mass flow controller 112, 113, 114 is supplied to the pipe 115 as a gas to be measured. Is done. In the present embodiment, the flow rate of the propane gas supplied from the propane gas cylinder 102 is made constant, the flow rate of the oxygen gas supplied from the oxygen gas cylinder 103 is increased and decreased, and the amount of nitrogen gas supplied from the nitrogen gas cylinder 104 is changed to the oxygen gas flow rate. The flow rate is adjusted by the mass flow controller 114 so as to increase or decrease according to the amount, and the entire flow rate of the mixed gas supplied from the gas supply unit 110 to the pipe 115 is made constant. The gas whose flow rate is constant may be oxygen gas, the flow rate of propane gas may be increased or decreased, and the flow rate of nitrogen gas may be adjusted according to the flow rate.

  The reaction furnace unit 120 includes a gas sensor 1, an air-fuel ratio sensor 125, and a heater 124 in a pipe 121 connected to a pipe 115 to which each gas is supplied from the gas supply unit 110. The output from the gas sensor 1 is measured by a measuring unit 123 that is a computer provided outside the reaction furnace unit 120. The electric heater 124 is for heating the mixed gas supplied to the pipe 115, and the temperature of the gas supplied to the gas sensor 1 is kept substantially constant by controlling the energization of the heater 124. It is like that. The pipe 121 is provided with a monitoring air-fuel ratio sensor 125, and the output of the air-fuel ratio sensor 125 is measured by an air-fuel ratio (A / F) meter 126 and input to the measuring unit 123. In addition, the ratio of the mixed gas supplied to the piping 121 is analyzed by the gas analyzer 127, and an appropriate ratio is ensured.

  Here, the gas sensor 1 to be evaluated in the evaluation apparatus 100 will be described with reference to FIG. As shown in FIG. 2, the gas sensor 1 includes a sensor element 2 having a bottomed cylindrical shape with a closed end, a ceramic heater 3 inserted into the bottomed hole 25 of the sensor element 2, and the sensor element 2 on its inner side. The metal shell 5 is held. In the present embodiment, of the directions along the axis of the sensor element 2 shown in FIG. 2, the side facing the tip exposed to the measurement target gas (exhaust gas) (the closed side, the lower side in the figure). Will be described as “front end side”, and the side in the opposite direction (upper side in the drawing) as “rear end side”.

  The sensor element 2 includes a solid electrolyte body 28 having oxygen ion conductivity mainly composed of partially stabilized zirconia in which yttria is dissolved as a stabilizer, and an inner surface of a bottomed hole 25 of the solid electrolyte body 28. The internal electrode layer 27 (corresponding to the reference electrode of the present invention) formed to be porous with Pt or a Pt alloy so as to cover almost the entire surface, and the internal electrode layer 27 on the outer surface of the solid electrolyte body 28 Has an external electrode layer 26 (corresponding to the measurement electrode of the present invention) formed in a porous shape. The external electrode layer 26 is coated with lead, which is a base metal. In the present embodiment, lead is applied as a base metal, but zinc, tin, and the like can be given as other base metals.

  The sensor element 2 is further provided with a porous electrode protection layer 99 that covers the external electrode layer 26. This protective layer is made of a heat-resistant ceramic such as alumina magnesia spinel and carries catalytic metal particles. Further, an engagement flange portion 92 that protrudes radially outward is provided at a substantially intermediate position in the axial direction of the sensor element 2. The ceramic heater 3 is formed in a rod shape and includes a heat generating portion 42 having a heat generating resistor therein. When the ceramic heater 3 is energized through heater lead wires 19 and 22, which will be described later, the heat generating portion 42 generates heat, and has a function of heating the sensor element 2 to activate the sensor element 2. Fulfill.

  The metal shell 5 has a screw part 66 for attaching the gas sensor 1 to the attachment part of the exhaust pipe, and a hexagonal part 93 to which an attachment tool is applied when the gas sensor 1 is attached to the attachment part of the exhaust pipe. The metal shell 5 includes an alumina support member 51 that supports the sensor element 2 from the front end side, a filling member 52 made of talc powder that fills the rear end side of the support member 51, and the filling member 52 at the rear end. An alumina sleeve 53 that presses from the side toward the tip side is configured to be housed inside.

  The metal shell 5 is provided with a metal-side stepped portion 54 projecting radially inward on the inner periphery of the front end side, and the support member 51 is locked to the metal-side stepped portion 54 via a packing 55. Yes. The sensor element 2 is supported by the metal shell 5 when the engagement flange portion 92 is supported on the support member 51. A filling member 52 is disposed between the inner surface of the metal shell 5 on the rear end side of the support member 51 and the outer surface of the sensor element 2, and a sleeve 53 and an annular ring 15 are provided on the rear end side of the filling member 52. It arrange | positions in the state inserted sequentially coaxially.

  A front end side of the inner cylinder member 14 made of SUS304L is inserted inside the rear end side of the metal shell 5. The inner cylinder member 14 has the metal-side rear end 60 of the metal shell 5 in the direction of the inner tip, with the opening end (tip opening end 59) having an enlarged diameter on the tip side in contact with the annular ring 15. The metal shell 5 is fixed by caulking. The gas sensor 1 has a structure in which the filling member 52 is compressed and filled through the sleeve 53 by crimping the metal-side rear end portion 60 of the metal shell 5, whereby the sensor element 2 has a cylindrical shape. The metallic shell 5 is held in an airtight manner.

  The inner cylinder member 14 is formed with an inner cylinder stepped portion 83 at a substantially intermediate position in the axial direction, the tip side of the inner cylinder stepped portion 83 is formed as an inner cylinder tip side body portion 61, and the inner cylinder stepped portion is formed. The rear end side of the portion 83 is formed as the inner cylinder rear end side body portion 62. The inner cylinder rear end side body part 62 is formed to have both an inner diameter and an outer diameter smaller than the inner cylinder front end side body part 61, and the inner diameter is slightly larger than the outer diameter of a separator body 85 of the separator 7 described later. ing. In addition, a plurality of air introduction holes 67 are formed in the inner cylinder rear end side body portion 62 at predetermined intervals along the circumferential direction.

  The outer cylinder member 16 is formed into a cylindrical shape by deep drawing a plate material of SUS304L, and includes an outer cylinder rear end side portion 63 including an opening communicating from the outside to the rear end side, and an inner cylinder member on the front end side. 14, an outer cylinder front end side portion 64 that is coaxially connected from the rear end side, and an outer cylinder step portion 35 that connects the outer cylinder rear end side portion 63 and the outer cylinder front end side portion 64 are formed. The outer cylinder rear end side portion 63 is formed with a caulking portion 88 for fixing the elastic seal member 11 in an airtight manner.

  Further, a metal double protector 81, 82 having a plurality of gas intake holes is welded to the outer periphery of the front end of the main metal shell 5 so as to cover the front end portion protruding from the front end of the main metal shell 5 of the sensor element 2. It is attached.

  Further, a cylindrical filter 68 for preventing water from entering through the air introduction hole 67 is disposed outside the inner cylinder rear end side body portion 62 of the inner cylinder member 14. The filter 68 is, for example, a porous fiber structure of polytetrafluoroethylene (trade name: Gore-Tex (Japan Gore-Tex Co., Ltd.), while preventing the permeation of liquid mainly composed of water, etc. This is configured as a water repellent filter that allows permeation of gas.

  The outer cylinder front end side portion 64 of the outer cylinder member 16 is formed in a shape that covers the inner cylinder member 14 (specifically, the inner cylinder rear end side body portion 62) where the filter 68 is disposed from the outside, and the outer cylinder front end portion. A plurality of air introduction holes 84 are formed at predetermined intervals along the circumferential direction at positions corresponding to the filter 68 in the side portion 64.

  The outer cylinder member 16 and the inner cylinder member 14 are configured such that at least a part of the outer cylinder front end side portion 64 of the outer cylinder member 16 on the rear end side of the atmosphere introduction hole 84 is radially passed through the filter 68. First caulking portion 56 formed by caulking inward, and second caulking formed by caulking at least a part on the tip side from air introduction hole 84 inward in the radial direction, also through filter 68 It is fixed by the part 57. At this time, the filter 68 is held in an airtight manner between the outer cylinder member 16 and the inner cylinder member 14. Moreover, the outer cylinder front end side portion 64 of the outer cylinder member 16 is disposed so as to overlap from the outer side with respect to the inner cylinder front end side body portion 61, and at least a part of the overlapping portion faces the inner side in the circumferential direction. The connection crimping part 75 is formed by crimping.

  Thereby, the atmosphere as the reference gas is introduced into the atmosphere introduction hole 84, the filter 68, the atmosphere introduction hole 67, and the inner cylinder member 14, and is introduced into the bottomed hole 25 of the sensor element 2. On the other hand, since water droplets cannot pass through the filter 68, entry into the inner cylinder member 14 is prevented.

  The elastic seal member 11 disposed inside the rear end of the outer cylinder member 16 (outer cylinder rear end side portion 63) includes two element lead wires 20 and 21 electrically connected to the sensor element 2, and ceramic. Four lead wire insertion holes 17 for inserting two heater lead wires 19 and 22 electrically connected to the heater 3 are formed so as to penetrate from the front end side to the rear end side.

  In addition, the separator 7 in which the front end side of the inner cylinder member 14 is inserted and arranged in the inner cylinder rear end side body portion 62 is for inserting the element lead wires 20 and 21 and the heater lead wires 19 and 22. The separator lead wire insertion hole 71 is formed so as to penetrate from the front end side to the rear end side. Further, the separator 7 is formed with a bottomed holding hole 95 opened in the front end surface in the axial direction. The rear end portion of the ceramic heater 3 is inserted into the holding hole 95, and the ceramic heater 3 is positioned in the axial direction with respect to the separator 7 by abutting the rear end surface of the ceramic heater 3 against the bottom surface of the holding hole 95. .

  The separator 7 includes a separator main body 85 that is inserted inside the rear end of the inner cylinder member 14, and a separator flange 86 that extends from the rear end of the separator main body 85 to the outer side in the circumferential direction. Yes. That is, in the separator 7, the separator body 85 is inserted into the inner cylinder member 14, and the separator flange 86 is supported on the rear end surface of the inner cylinder member 14 via the annular seal member 40 made of fluoro rubber. The inner cylinder member 16 is disposed inside.

  The element lead wires 20 and 21 and the heater lead wires 19 and 22 are passed through the separator lead wire insertion hole 71 of the separator 7 and the lead wire insertion hole 17 of the elastic seal member 11, and the inner cylinder member 14 and the outer cylinder member 16. It is drawn from the inside to the outside. These four lead wires 19, 20, 21, and 22 are externally connected to a connector (not shown). The external signals such as the ECU and the lead wires 19, 20, 21, and 22 are input / output via the connector.

  Further, although not shown in detail, each lead wire 19, 20, 21, 22 has a structure in which the conducting wire is covered with an insulating film made of resin, and the rear end side of the conducting wire is a connector terminal provided in the connector. Connected. And the front end side of the conducting wire of the element lead wire 20 is crimped with the rear end portion of the terminal fitting 43 fitted on the outer surface of the sensor element 2, and the leading end side of the conducting wire of the element lead wire 21 is It is crimped to the rear end portion of the terminal fitting 44 that is press-fitted into the inner surface of the sensor element 2. Thereby, the element lead wire 20 is electrically connected to the external electrode layer 26 of the sensor element 2, and the element lead wire 21 is electrically connected to the internal electrode layer 27. On the other hand, the leading ends of the lead wires 19 and 22 for the heater are respectively connected to a pair of heater terminal fittings joined to the heating resistor of the ceramic heater 3.

  An elastic seal member 11 made of fluorine rubber or the like having excellent heat resistance is fixed to the outer cylinder member 16 at the rear end side of the separator 7 by caulking the outer cylinder member 16 and forming a caulking portion 88. Has been. The elastic seal member 11 includes a main body 31 and a seal member collar 32 extending from the side peripheral surface on the distal end side of the main body 31 toward the radially outer side. Then, four lead wire insertion holes 17 are formed so as to penetrate the main body portion 31 in the axial direction.

  Next, a method for evaluating the state of the base metal applied to the external electrode layer 26 of the sensor element 2 by the evaluation apparatus 100 will be described with reference to the following examples.

[Example]
For the gas sensor 1, three types of different amounts in which lead was applied as the base metal to the external electrode layer 26 of the sensor element 2 were prepared, and the output value of the gas sensor 1 was measured. The amount of lead applied was 0 μg / cm ² , 3 μg / cm ² , and 50 μg / cm ² . The temperature of the sensor element 2 was adjusted to 600 ° C. The temperature of the sensor element 2 is preferably adjusted between 280 ° C. and 900 ° C. Furthermore, the entire flow rate of the gas to be measured supplied from the gas supply unit 110 was set to 40 L / min, and the temperature of the gas to be measured was set to 450 degrees. Among the measured gases, the concentration of the propane gas supplied from the propane gas cylinder 102 is fixed at 1000 ppm, the flow rate of the oxygen gas supplied from the oxygen gas cylinder 103 is changed from a small amount to a large amount, and the remaining amount is supplied from the nitrogen gas cylinder 104. The total flow rate was always kept constant by adjusting the nitrogen gas. In this embodiment, the concentration of propane gas is fixed at 1000 ppm. However, even a concentration of 1000 ppm or less can be measured sufficiently. Under the above conditions, the electromotive force generated by the gas sensor 1 was measured. The measurement results are shown in FIG. FIG. 3 is a graph showing the relationship between the amount of lead applied and the output value of the gas sensor.

As shown in FIG. 3, in the gas sensor 1 having a lead application amount of 0 μg / cm ² , the electromotive force is about 800 mV on the rich side, and the output value is about 100 mV on the lean side. On the other hand, in the gas sensor 1 having a lead application amount of 3 μg / cm ² , the output value gradually decreases from about 600 mV in the rich atmosphere to about 100 mV, which is the output value on the lean side. . Further, in the gas sensor 1 having a lead coating amount of 50 μg / cm ² , even if the atmosphere changes from rich to lean, a constant output value of about 100 mV is obtained. Thus, as the amount of lead applied increases, the output value of the electromotive force in the rich atmosphere decreases, and the difference from the output value of the electromotive force in the lean atmosphere decreases. Therefore, by using the evaluation apparatus 100 of the present embodiment, the propane gas concentration is fixed, the sensor element 2 of the gas sensor 1 is exposed to the gas to be measured that changes the oxygen gas concentration, and the output value of the gas sensor 1 is measured. The amount of base metal (lead) applied to the external electrode layer 26 of the sensor element 2 of the gas sensor 1 can be evaluated.

  As described above, according to the evaluation apparatus 100 of the present embodiment, the state of the base metal applied to the measurement electrode of the gas sensor 1 such as the amount of the base metal applied to the measurement electrode can be directly evaluated. Since it is not necessary to perform a destructive inspection and there is no influence on the evaluation result due to other factors, it is possible to effectively evaluate only the state of the base metal applied to the measurement electrode.

1 is a block diagram schematically showing a system configuration of an entire gas sensor evaluation apparatus 100. FIG. 1 is a cross-sectional view showing an overall configuration of a gas sensor 1. FIG. It is a graph which shows the relationship between the application quantity of lead, and the output value of a gas sensor.

DESCRIPTION OF SYMBOLS 1 Gas sensor 2 Sensor element 26 External electrode layer 27 Internal electrode layer 28 Solid electrolyte body 100 Evaluation apparatus 102 Propane gas cylinder 103 Oxygen gas cylinder 104 Nitrogen gas cylinder 110 Gas supply part 112 Mass flow controller 113 Mass flow controller 114 Mass flow controller 123 Measurement part

Claims (4)

A gas sensor evaluation method for evaluating the characteristics of a gas sensor element in which a measurement electrode exposed to a gas to be measured and a reference electrode facing the measurement electrode are disposed on a solid electrolyte body having oxygen ion conductivity,
When the gas sensor element is exposed to an atmosphere created by using at least propane gas and oxidizing gas, fixing the flow rate of one of these and changing the other, the output value output from the gas sensor is applied to the measurement electrode. An evaluation method for a gas sensor, characterized by evaluating the amount of base metal applied or the degree of oxidation of the base metal .   The said base metal contains at least one of lead or zinc, The evaluation method of the gas sensor of Claim 1 characterized by the above-mentioned. An atmosphere composed of at least propane gas and an oxidizing gas in a gas sensor element in which a measurement electrode exposed to a gas to be measured and a reference electrode facing the measurement electrode are disposed on a solid electrolyte body having oxygen ion conductivity Gas supply means for supplying
A flow rate adjusting means for fixing the flow rate of either the propane gas or the oxidizing gas supplied by the gas supply means and changing the other;
Output measuring means for measuring an output value output from a gas sensor including the gas sensor element by exposing the gas sensor element to the atmosphere adjusted by the flow rate adjusting means;
An evaluation device for a gas sensor, comprising: an evaluation unit that evaluates a coating amount of a base metal applied to the measurement electrode or a degree of oxidation of the base metal based on an output value measured by the output measurement unit . The said base metal contains at least one of lead or zinc, The evaluation apparatus of the gas sensor of Claim 3 characterized by the above-mentioned.

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