JP2006170848A - Gas sensor evaluation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas sensor evaluation device that supplies sample gas at a gas flow velocity equivalent to a real operating environment of a gas sensor, and speedily changes the gas component contained in the sample gas. <P>SOLUTION: In the gas sensor evaluation device 1, the sectional area at a forming position of an evaluated gas sensor installation section 49 is set smaller than that at a forming position of a first gas introducing section 45 of a gas flow channel of a reaction section gas pipe 41. Therefore, the flow velocity of the sample gas at the forming position of the evaluated gas sensor installation section 49 is increased, and is made to approach the flow velocity in the real operating environment. An additional gas supply section 61 injects additional gas with an injector 67 for gas, hence can supply gas supply amount per unit time required for establishing a condition equivalent to the real operating environment, and can change the air-fuel ratio of the sample gas at an operation response speed required for establishing a condition equivalent to the operating environment. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a gas sensor evaluation apparatus that evaluates a gas sensor that detects a specific component contained in exhaust gas of an internal combustion engine.

  Conventionally, in evaluating a gas sensor for detecting a specific component contained in the exhaust gas of an internal combustion engine, a sample gas containing at least the specific component is brought into contact with the gas sensor, and based on the sensor output of the gas sensor at the time of contact with the sample gas, Gas sensor evaluation apparatuses for evaluating gas sensors have been proposed (Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4).

  That is, such a gas sensor evaluation apparatus detects a sensor output of a gas sensor by bringing a sample gas containing a gas component substantially similar to the measurement target gas of the gas sensor into contact with the gas sensor and detecting the sensor output of the gas sensor under conditions close to the actual use environment. The gas sensor is evaluated based on the sensor output.

For example, a gas sensor evaluation apparatus that evaluates a gas sensor for detecting a specific component in exhaust gas of an internal combustion engine brings a sample gas containing a component similar to the exhaust gas of the internal combustion engine into contact with the gas sensor as the sample gas, Is configured to evaluate.
Japanese Patent No. 2624531 (FIG. 1) Japanese Patent Laid-Open No. 2001-141685 (FIG. 1) JP-A-60-95341 (FIG. 1) JP 2003-185621 A

  However, since the conventional gas sensor evaluation apparatus described above has a low flow rate of sample gas and a low flow rate, it is difficult to achieve a flow rate equivalent to the exhaust gas flow rate in an actual internal combustion engine. There is a problem that it is difficult to evaluate the gas sensor.

  On the other hand, in the conventional gas sensor evaluation apparatus, in order to realize a flow rate equivalent to the actual environment, the supply amount of the sample gas is increased and the sample gas corresponding to the actual exhaust gas is supplied. There is a need to.

The conventional gas sensor evaluation apparatus uses a solenoid valve or a liquid injector to control the supply amount of the sample gas.
However, the solenoid valve has a large amount of sample gas that can be supplied per unit time, but its operation response speed is slow, so it is difficult to quickly switch the air / fuel ratio of the sample gas, and the gas sensor for applications in which the air / fuel ratio changes suddenly is difficult. It is difficult to evaluate the responsiveness to air-fuel ratio changes. In addition, although the liquid injector has a high operation response speed, the amount of sample gas that can be supplied per unit time is small, so that it is difficult to supply an amount of sample gas corresponding to the actual exhaust gas.

  In other words, the electromagnetic valve and the liquid injector have a problem in that it is impossible to achieve both the gas supply amount per unit time and the rapid air-fuel ratio switching of the sample gas when realizing the same conditions as the actual use environment.

  Therefore, the present invention has been made in view of these problems, and while supplying sample gas at a gas flow rate equivalent to the actual use environment of the gas sensor, the gas component contained in the sample gas is quickly changed to evaluate the gas sensor. An object of the present invention is to provide a gas sensor evaluation apparatus.

  In order to achieve the above object, according to the first aspect of the present invention, a gas sensor for detecting a specific component contained in exhaust gas of an internal combustion engine evaluates the gas sensor based on a sensor output characteristic for at least a sample gas containing the specific component. A gas sensor evaluation apparatus comprising a gas flow path forming section having a gas flow path for a sample gas and having a sensor mounting portion to which the gas sensor is mounted in a state where the detection section of the gas sensor is disposed in the gas flow path. Base gas supply means for supplying the sample gas to the gas flow path forming unit, and the base gas flowing in the gas flow path forming unit is supplied with a constant amount of the rich additive gas in the reducing atmosphere and the lean additive gas in the oxidizing atmosphere. Additional gas supply means for alternately supplying in a cycle, and the gas flow path forming portion is located at the base gas supply position in the gas flow path. The cross-sectional area at the position where the sensor mounting portion is formed is smaller than the cross-sectional area to be formed, and the additive gas supply means includes a gas injector, and is rich at a rate of 0.5 [L / min] or more by the gas injector. The gas sensor evaluation apparatus is characterized by supplying an additive gas or a lean additive gas.

In general, the gas flow rate of the sample gas flowing through the gas flow path forming portion is faster at the location where the cross-sectional area of the gas flow path is smaller than at the location where the cross-sectional area of the gas flow path is large.
And the gas flow path formation part is formed so that the cross-sectional area in the formation position of the sensor attachment part is smaller than the cross-sectional area in the supply position of the base gas in the gas flow path. For this reason, the flow rate of the sample gas at the position where the sensor mounting portion is formed in the gas flow path is faster than the flow rate of the sample gas at the base gas supply position.

Thereby, the flow rate of the sample gas contacting the gas sensor can be made close to the flow rate in the actual use environment, and the sensor output of the gas sensor can be detected under conditions close to the actual use environment.
The additive gas supply means supplies the rich additive gas or the lean additive gas by the gas injector. The gas injector, like the liquid injector, has a fast operation response speed, so that it is possible to quickly switch the air-fuel ratio necessary for realizing the same conditions as the actual use environment. In addition, the gas injector, like the solenoid valve, has a large amount of gas supply per unit time, so it supplies the gas supply amount per unit time necessary to achieve the same conditions as the actual usage environment. The additive gas (rich additive gas or lean additive gas) is supplied at a rate of at least 0.5 [L / min] or more (more preferably, 1.0 [L / min] or more).

  That is, the additive gas supply means can supply the gas supply amount per unit time and the gas supply amount per unit time required to realize the same conditions as the actual use environment with respect to the gas supply amount and the air-fuel ratio switching speed. It is possible to switch the air-fuel ratio of the sample gas at the operation response speed required to realize the same conditions as the environment.

  Therefore, according to the present invention, the sample gas can be brought into contact with the gas sensor at a gas flow rate under conditions equivalent to the actual sensor usage environment, and the gas sensor can be evaluated under conditions equivalent to the actual usage environment. it can.

  In the gas sensor evaluation apparatus described above, for example, as described in claim 2, the gas flow path forming portion has a circular shape in which the cross section of the sensor mounting portion of the gas flow path has an inner diameter of 3.0 [cm] or less. It is good to be formed.

  Thus, by defining the cross-sectional shape of the gas flow path at the position where the sensor mounting portion is formed, the flow rate of the sample gas that contacts the gas sensor can be reliably brought close to the flow rate in the actual use environment.

Therefore, according to the present invention, it is possible to realize a gas flow velocity under the same conditions as the actual sensor usage environment, and it is possible to evaluate the gas sensor under the same conditions as the actual usage environment.
In addition, the flow rate of the sample gas contacting the gas sensor can be further increased by forming the cross section of the sensor mounting portion in the gas flow path in a circular shape having an inner diameter of 2.5 [cm] or less.

  By the way, when the temperature of the sample gas in contact with the gas sensor is lowered, the temperature of the gas sensor is lowered due to the influence of the sample gas, and the activated state of the gas sensor may be defective. If the activation state becomes defective as described above, the gas sensor does not generate a sensor output even when a specific component is present, or the sensor output is lowered, so that the gas sensor may not be properly evaluated.

Therefore, as described in claim 3, the gas sensor evaluation apparatus described above may include an additive gas heating means for heating the rich additive gas or the lean additive gas.
Thus, by providing the additive gas heating means, it is possible to prevent the temperature of the sample gas from decreasing due to the influence of the additive gas. As a result, it is possible to prevent the temperature of the gas sensor from greatly decreasing due to the low temperature of the sample gas contacting the gas sensor.

  Therefore, according to the present invention, it is possible to prevent the activation state of the gas sensor from being deteriorated due to the temperature decrease of the sample gas due to the influence of the additive gas, and it is possible to appropriately evaluate the gas sensor.

The preferred embodiments of the present invention will be described below.
In addition, this invention is not limited to the following embodiment at all, and it cannot be overemphasized that various forms may be taken as long as it belongs to the technical scope of this invention.

FIG. 1 is a configuration diagram showing a schematic configuration of a gas sensor evaluation apparatus 1 of the present invention.
The gas sensor evaluation apparatus 1 includes a sample gas supply unit 11, a sensor reaction unit 13, an apparatus control unit 15, a sample gas analysis unit 17, and an additive gas supply unit 61.

The sample gas supply unit 11 stores a first gas (N ₂ , CO ₂ , O ₂ ) and a second gas (CO, H ₂ , C ₃ H ₈ , NO, NO ₂ , HC). And a flow rate adjusting unit 23 (mass flow controller (MFC)) for adjusting the supply amount of each gas, and a water adding unit 19 for adding water to the sample gas. The sample gas supply unit 11 supplies the first gas to the sensor reaction unit 13 via the first gas supply path 31 and the second gas to the second gas supply path in response to a command from the apparatus control unit 15. It is supplied to the sensor reaction unit 13 via 33. The supply amount of each gas is set based on a command from the apparatus control unit 15.

The water addition unit 19 is water (H ₂ O ) And a water flow rate adjusting unit 37 that adjusts the supply amount of moisture, and commands from the device control unit 15 to the first gas flowing through the first gas supply path 31. The moisture content of the sample gas is adjusted by supplying an amount of moisture corresponding to.

The additive gas supply unit 61 includes a lean exhaust gas component contained in the lean air-fuel ratio exhaust gas, that is, an oxidizing atmosphere gas (N ₂ , O ₂ , NO, NO ₂ ) and a rich air-fuel ratio exhaust gas. An additive gas storage unit 63 for storing exhaust gas components, that is, reducing atmosphere gases (CO, H ₂ , HC, N ₂ ), and an additive amount adjusting unit 65 (mass flow controller (MFC)) for adjusting the supply amount of each gas ) And a plurality of gas injectors 67 for injecting each gas. As the gas injector 67, for example, a known injector for injecting natural gas can be used, and detailed description thereof is omitted.

  Then, the additive gas supply unit 61 supplies the lean additive gas in the oxidizing atmosphere to the sensor reaction unit 13 via the lean additive gas supply path 69 in accordance with a command from the apparatus control unit 15, or the reducing atmosphere. The rich additive gas is supplied to the sensor reaction unit 13 via the rich additive gas supply path 71. The supply amount of each gas is set based on a command from the apparatus control unit 15.

  The sensor reaction unit 13 includes a reaction unit gas pipe 41 in which the gas sensor 51 to be evaluated is installed, and a gas heating unit 43 that heats the sample gas in the reaction unit gas pipe 41. .

The reaction section gas pipe 41 includes a first gas introduction section 45, a second gas introduction section 47, an additive gas introduction section 48, and an evaluation target gas sensor installation section 49 from upstream to downstream.
Further, the gas flow path of the reaction part gas pipe 41 has a smaller cross-sectional area at the formation position of the evaluation target gas sensor installation part 49 than the cross-sectional area at the formation position of the first gas introduction part 45. Specifically, the cross-sectional shape of the gas flow path at the position where the first gas introduction part 45 is formed is a circular shape having a diameter of 6.0 [cm], and the cross-sectional shape of the gas flow path in the evaluation target gas sensor installation part 49 is the diameter. It has a circular shape of 2.0 [cm].

  And the reaction part gas piping 41 is provided with the lean addition component introduction part 73 and the rich addition component introduction part 75 as the addition gas introduction part 48, and is added gas (rich addition gas or lean addition gas) with respect to base gas. Is configured to be added.

Moreover, the diameter dimension L1 of the gas flow path in the evaluation object gas sensor installation part 49 of the reaction part gas piping 41 is 2.0 [cm].
The gas heating unit 43 is disposed so as to surround a portion between the first gas introduction unit 45 and the second gas introduction unit 47 in the reaction unit gas pipe 41, and by heating the reaction unit gas pipe 41, The first gas temperature is adjusted. The gas heating unit 43 controls the gas temperature to the target temperature by detecting the internal temperature of the reaction unit gas pipe 41 using a temperature sensor (not shown) and performing feedback control. At this time, the gas heating unit 43 heats the sample gas (base gas) so that the temperature of the sample gas in the evaluation target gas sensor installation unit 49 becomes the sensor activation temperature (in this embodiment, 450 [° C.]). .

  The additive gas heating unit 77 is disposed so as to surround a part of the lean additive gas supply path 69 and a part of the rich additive gas supply path 71, and heats the lean additive gas supply path 69 and the rich additive gas supply path 71. Thus, the temperatures of the lean additive gas and the rich additive gas are adjusted to the additive gas target temperature (120 [° C.] in the present embodiment). The additive gas heating unit 77 controls the additive gas temperature to the target temperature by detecting the internal temperature of the reaction part gas pipe 41 using a temperature sensor (not shown) and performing feedback control.

  The apparatus control unit 15 (CPU 15) installs the evaluation target gas sensor 51 in the exhaust system of the internal combustion engine based on the sensor output output from the evaluation target gas sensor 51 when the sample gas is supplied, and extracts a specific component contained in the exhaust gas. Sensor evaluation processing is performed to determine whether or not the gas sensor (exhaust gas sensor) is suitable for detection.

  In the sensor evaluation process, a command signal is output to the sample gas supply unit 11 and the additive gas supply unit 61, and the supply amount of each gas component contained in the sample gas is controlled to correspond to an arbitrary air-fuel ratio λ. A process of supplying the sample gas to the evaluation target gas sensor 51 and a process of detecting the sensor output of the evaluation target gas sensor when the sample gas is supplied are performed. Details of the evaluation determination process executed by the device control unit 15 will be described later.

  The sample gas analysis unit 17 analyzes the components contained in the sample gas in the vicinity of the evaluation target gas sensor installation unit 49 in the sensor reaction unit 13 and analyzes the sample gas components actually supplied to the evaluation target gas sensor 51. Is output to the apparatus control unit 15. The apparatus control unit 15 determines how many values of the air-fuel ratio λ of the sample gas supplied to the evaluation target gas sensor 51 correspond to the analysis result from the sample gas analysis unit 17.

  Next, as an example of the evaluation target gas sensor 51, a gas sensor 101 (oxygen sensor 101) that is mounted on an exhaust pipe of an internal combustion engine and detects oxygen in the exhaust gas will be described with reference to FIG. FIG. 2 is a cross-sectional view showing the overall configuration of the gas sensor 101. Further, in the gas sensor 101 shown in FIG. 2, the lower side in the drawing is described as “the front end side of the gas sensor”, and the upper side in the drawing is described as “the rear end side of the gas sensor”.

As shown in FIG. 2, the gas sensor 101 includes a detection element 102 formed in a hollow shaft shape having a closed end with an oxygen ion conductive solid electrolyte mainly composed of zirconia (ZrO ₂ ), and the inside of the detection element 102. A shaft-shaped ceramic heater 103 disposed in the casing, a casing 104 for housing the detection element 102, and the like.

  The detection element 102 includes a detection unit 125 for detecting the measurement target gas at the distal end (lower end in the drawing) and outputs a gas detection signal corresponding to the measurement target gas detected by the detection unit 125. A pair of signal output electrodes (outer signal output electrode 126 and inner signal output electrode 127). The outer signal output electrode 126 and the inner signal output electrode 127 are configured as porous electrodes made of, for example, Pt or a Pt alloy.

  The ceramic heater 103 is formed in a rod-like shape and includes a heat generating portion 142 having a resistance heat generating wire (not shown) inside. The heat generating portion 142 is energized through the heater lead wires 119 and 122. Generates heat and heats the tip (detection part 125) of the detection element 102.

  The casing 104 holds the detection element 102 and causes the detection part 125 to protrude into the exhaust pipe or the like, and a cylindrical inner cylinder member 114 connected to the opening on the rear end side of the metal shell 105. And a cylindrical outer cylinder member 116 connected to the opening on the rear end side of the inner cylinder member 114. When the metal shell 105, the inner cylinder member 114, and the outer cylinder member 116 are connected to form the casing 104, a reference gas (atmosphere) used for gas detection (in this embodiment, oxygen detection) is introduced into the casing 104. A reference gas space 158 (internal space) for accumulation is formed.

  The element lead wires 120 and 121 and the heater lead wires 119 and 122 are provided in the casing 104 from the outside through the seal member lead wire insertion hole 117 of the seal member 111 and the separator lead wire insertion hole 171 of the separator 107. It is arranged toward the gas space 158. The element lead wire 120 is electrically connected to the outer signal output electrode 126 of the detection element 102 via the element outer surface fixing bracket 143. The other element lead 121 is electrically connected to the inner signal output electrode 127 of the detection element 102 via the element inner surface fixing bracket 144.

  The gas sensor 101 configured in this manner outputs a gas detection signal (sensor output signal) corresponding to the oxygen concentration in the measurement target gas when the tip portion is exposed to the measurement target gas, whereby the measurement target gas in the measurement target gas is output. It is configured to detect the oxygen concentration.

  Therefore, when the gas sensor 101 is evaluated by the gas sensor evaluation apparatus 1, the gas sensor 101 is used as the evaluation target gas sensor 51 in a state where the front end side of the gas sensor 101 is disposed from the evaluation target gas sensor installation unit 49 to the inside of the reaction unit gas pipe 41. The gas sensor 101 is evaluated by being attached to the sensor reaction unit 13 and supplying the sample gas.

In addition, the front end side of the gas sensor 101 corresponds to the detection unit described in the claims.
Next, a flowchart showing the processing contents of the evaluation determination process executed by the apparatus control unit 15 is shown in FIG. 3, and the processing contents of the evaluation determination process will be described.

  When the evaluation determination process is started, first, in S110 (S represents a step. The same applies hereinafter), a gas supply start command signal is output to the sample gas supply unit 11 and the additive gas supply unit 61. Thereby, the sample gas supply unit 11 starts supplying the base gas (first gas, second gas, moisture) to the sensor reaction unit 13, and the additive gas supply unit 61 supplies the sensor reaction unit 13 to the sensor reaction unit 13. Supply of additional gas (reducing gas component or oxidizing gas component) is started.

In the present embodiment, the gas supply amount of the sample gas to the evaluation target gas sensor 51 is set to 60 [L / min].
In the next S120, the component control of the sample gas is performed in accordance with the change of the air-fuel ratio, the sensor output of the evaluation target gas sensor 51 is detected, and the sensor output result for the air-fuel ratio of the sample gas is stored in the storage unit (memory) of the apparatus control unit 15 Etc.), a process for detecting the sensor output characteristics of the gas sensor 51 to be evaluated with respect to the air-fuel ratio change is performed.

  In S120, the additive gas supply unit 61 is controlled so as to alternately supply the reducing gas component and the oxidizing gas component at a constant period, thereby the exhaust gas having a lean air-fuel ratio (λ = 1.05). The lean additive gas corresponding to the above and the rich additive gas corresponding to the exhaust gas having the rich air-fuel ratio (λ = 0.95) are alternately supplied to the base gas.

  In the next S130, a gas supply stop command signal is output to the sample gas supply unit 11 and the additive gas supply unit 61. Thereby, the sample gas supply unit 11 stops the supply of the base gas (first gas, second gas, moisture) to the sensor reaction unit 13, and the additive gas supply unit 61 adds the additive gas (reduction gas) to the sensor reaction unit 13. Supply of the reactive gas component or oxidizing gas component).

  In subsequent S140, based on the sensor output result stored in S120, a process of calculating a response delay time of the sensor output of the evaluation target gas sensor 51 with respect to a change in the component of the sample gas (a change in the air-fuel ratio) is performed. Note that the response delay time is the time until the sensor output of the gas sensor changes starting from the air-fuel ratio switching timing of the sample gas.

  In S140, as the response delay time, a rich change response delay time when the sample gas component changes from lean to rich and a lean change response delay time with respect to the change of the sample gas component from rich to lean are: Perform processing to calculate each.

  In the next S150, it is determined whether or not the response delay time, which is the calculation result in S140, is included in the normal determination reference range, and when the response delay time is included in the normal determination reference range (when an affirmative determination is made). When the response delay time is not included in the normal determination reference range (when negative determination is made), the process proceeds to S170.

  At this time, it is determined whether each of the rich change response delay time and the lean change response delay time is included in the normal determination reference range, and an affirmative determination is made when both response delay times are included in the normal determination reference range. On the other hand, if the response delay time is not included in the normal determination reference range, a negative determination is made.

  The normal determination reference range includes a rich change normal determination reference range when the sample gas component changes from lean to rich, and a lean change normal determination reference range when the sample gas component changes from rich to lean. Are preset. In other words, the normal determination reference range is obtained by collecting measured data of sensor output characteristics using a gas sensor that can be used in an actual usage environment in advance, and measuring data corresponding to the rich change response delay time and the lean change response delay time described above. Is set based on the actual measurement data.

  When an affirmative determination is made in S150 and the process proceeds to S160, it is determined in S160 that the evaluation target gas sensor 51 is suitable for the exhaust gas sensor, and the determination result is output to the outside. If a negative determination is made in S150 and the process proceeds to S170, it is determined in S170 that the evaluation target gas sensor 51 is not suitable for the exhaust gas sensor, and the determination result is output to the outside.

  As an output form of the determination result to the outside, an output form for displaying the determination result on a display device such as an LED or a liquid crystal display or a determination result on a print medium (recording paper or the like) by a printing device such as a printer. It is possible to adopt an output form for printing, an output form for outputting the determination result as a sound by a sound output device such as a speaker, and the like.

When the process in S160 or S170 ends, the evaluation determination process ends.
As described above, the gas sensor evaluation apparatus 1 according to the present embodiment forms the evaluation target gas sensor installation unit 49 rather than the cross-sectional area at the formation position of the first gas introduction unit 45 in the gas flow path of the reaction unit gas pipe 41. The cross-sectional area at the position is small. Accordingly, the flow rate of the sample gas at the formation position of the evaluation target gas sensor installation portion 49 in the gas flow path is faster than the flow velocity of the sample gas in the first gas introduction portion 45 that is the supply position of the base gas.

  Thereby, the flow velocity of the sample gas contacting the evaluation target gas sensor 51 can be made close to the flow velocity in the actual use environment, and the sensor output of the gas sensor can be detected under conditions close to the actual use environment.

  In addition, the additive gas supply unit 61 injects an additive gas (rich additive gas or lean additive gas) by the gas injector 67, and then reacts through the lean additive gas supply path 69 or the rich additive gas supply path 71. An additive gas is supplied to the pipe 41.

  Since the gas injector 67 has a fast operation response speed like the liquid injector, it is possible to perform rapid air-fuel ratio switching necessary to realize the same conditions as the actual use environment. In addition, the gas injector 67 supplies a gas supply amount per unit time which is necessary for realizing the same conditions as the actual use environment because the gas supply amount per unit time is large like the solenoid valve. The additive gas (rich additive gas or lean additive gas) is supplied at a rate of at least 0.5 [L / min] or more.

  That is, the additive gas supply unit 61 can supply the gas supply amount per unit time necessary for realizing the same conditions as the actual use environment for the gas supply amount per unit time and the air-fuel ratio switching speed, It is possible to switch the air-fuel ratio of the sample gas at the operation response speed required to realize the same conditions as the usage environment.

  Therefore, according to the gas sensor evaluation apparatus 1, since the gas flow rate is larger than the conventional one, the sample gas can be brought into contact with the evaluation target gas sensor 51 at the gas flow rate under the same conditions as the actual sensor usage environment. The evaluation target gas sensor 51 can be evaluated under conditions equivalent to the usage environment.

  Here, FIG. 4 shows the measurement results obtained by measuring the sensor output of the gas sensor with respect to the air-fuel ratio switching of the sample gas when the gas flow rate is set to two patterns (gas flow rate: small, gas flow rate: large). In FIG. 4, a command signal for setting the air-fuel ratio of the sample gas is represented as an injector signal.

  According to the measurement results, it can be seen that the response delay time from the switching timing of the injector signal to the response of the sensor output is smaller when the gas flow velocity is larger than when the gas flow velocity is small. In addition, by setting the gas flow rate large, the time interval from the air-fuel ratio switching timing to the next air-fuel ratio switching timing can be shortened.

  In other words, since the response delay time can be shortened by setting the gas flow rate large, the sample gas after the air-fuel ratio switching can be brought into rapid contact with the gas sensor to be evaluated, and the time interval between the air-fuel ratio switching timings By shortening, it is possible to realize an environment where the air-fuel ratio changes suddenly.

  Therefore, the gas sensor evaluation apparatus 1 can shorten the response delay time and shorten the time interval between the air-fuel ratio switching timings as compared with the conventional case. Therefore, the gas sensor for applications in which the air-fuel ratio changes suddenly is responsive to changes in the air-fuel ratio. Can be evaluated.

In addition, the gas sensor evaluation apparatus 1 includes an additive gas heating unit 77 that heats the rich additive gas or the lean additive gas.
Thus, by providing the additive gas heating unit 77, the temperature of the additive gas (rich additive gas or lean additive gas) can be prevented from becoming significantly lower than the activation temperature of the evaluation target gas sensor 51. The temperature drop of the sample gas due to the influence can be prevented. As a result, it is possible to prevent the temperature of the evaluation target gas sensor 51 from greatly decreasing due to the low temperature of the sample gas that contacts the evaluation target gas sensor 51.

  Therefore, according to the gas sensor evaluation apparatus 1, it is possible to prevent the activation state of the evaluation target gas sensor 51 from becoming defective as the temperature of the sample gas decreases, and the evaluation target gas sensor 51 can be appropriately evaluated.

  Further, the additive gas introduction part 48 of the reaction part gas pipe 41 is formed at a position close to the evaluation target gas sensor installation part 49. For this reason, when the air / fuel ratio (rich, lean) of the sample gas is switched by switching the additive gas (rich additive gas or lean additive gas), the sample gas to which the additive gas after switching has been added reaches the gas sensor to be evaluated. The time until it can be shortened.

  As a result, the air-fuel ratio switching (rich / lean switching) of the sample gas brought into contact with the gas sensor to be evaluated can be executed very quickly, so that the gas sensor for applications in which the air-fuel ratio changes suddenly is evaluated for the response to the air-fuel ratio change. Is possible.

  In the gas sensor evaluation apparatus 1 of the present embodiment, the reaction part gas pipe 41 corresponds to the gas flow path forming part described in the claims, the evaluation target gas sensor installation part 49 corresponds to the sensor attachment part, and the sample The gas supply unit 11 corresponds to a base gas supply unit, the additive gas supply unit 61 corresponds to an additive gas supply unit, and the additive gas heating unit 77 corresponds to an additive gas heating unit.

  Here, in the gas sensor evaluation apparatus 1 of the above embodiment, the reaction part gas pipe 41 is replaced, and the cross-sectional area at the position where the evaluation target gas sensor installation part 49 is formed in the gas flow path is changed. A measurement result obtained by measuring a change in the gas flow rate of the sample gas at the formation position of the evaluation target gas sensor installation portion 49 will be described.

FIG. 5 shows a measurement result obtained by measuring the change in the gas flow rate of the sample gas with respect to the change in the inner diameter dimension (diameter in the gas pipe) at the formation position of the evaluation target gas sensor installation portion 49 in the gas flow path.
In the measurement, the temperature of the sample gas in contact with the evaluation target gas sensor 51 is constant (450 [° C.]), and the sample gas supply amount per unit time is 3 patterns (40 [L / min], 50 [L / min]. , 60 [L / min]) and detecting each gas flow rate.

  According to the measurement result, when the gas supply amount is 60 [L / min] and the gas pipe diameter is 30 [mm] or less, the gas flow rate is 2.5 [m / sec] or more. . Moreover, since the gas supply amount is 60 [L / min] and the gas pipe inner diameter is 20 [mm], the gas sensor evaluation apparatus 1 of the above embodiment has a gas flow rate of about 7.5 [m / sec]. Become.

  As an actual use environment, for example, when the rotational speed of the internal combustion engine is 1000 [rpm], the gas flow rate of the exhaust gas is about 8.0 [m / sec], and the gas sensor evaluation apparatus of the above embodiment is used. 1 can realize a gas flow rate equivalent to the exhaust gas of the internal combustion engine when the rotational speed is 1000 [rpm].

  Further, in the conventional gas sensor evaluation apparatus, the gas pipe inner diameter is generally set to 40 [mm] or more and the gas supply amount is 40 [L / min] at the maximum, so that the gas flow rate is 1.2 [ m / sec].

  As a result, the gas sensor evaluation apparatus 1 of the present embodiment detects the sensor output of the gas sensor under conditions close to the actual use environment, because the gas flow rate is significantly increased compared to the conventional gas sensor evaluation apparatus. It can be seen that the gas sensor can be evaluated based on the sensor output.

As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, It can take a various aspect.
For example, the cross-sectional shape at the formation position of the evaluation target gas sensor installation unit 49 in the gas flow path of the reaction unit gas pipe 41 is not limited to a circular shape, and may be an elliptical shape or a polygonal shape. Moreover, when the cross-sectional shape of a gas flow path is circular, the diameter dimension is not restricted to the circular shape of 2.0 [cm], What is necessary is just a diameter of 3.0 [cm] or less.

  Further, the gas supply amount of the sample gas to the gas sensor to be evaluated is not limited to 60 [L / min], and the gas supply amount per unit time required to realize the same conditions as the actual use environment If it is. For example, the gas supply amount of the sample gas to the evaluation target gas sensor is set to 40 [L / min] by setting the cross-sectional area at the formation position of the evaluation target gas sensor installation portion 49 in the gas flow path of the reaction part gas pipe 41 to be small. Even if it is set to, it is possible to realize the same conditions as the actual use environment.

  The supply amount of the additive gas is set to at least 0.5 [L / min] or more (more preferably, 1.0 [L / min] or more), so that the air-fuel ratio of the sample gas is appropriately switched. can do.

Further, the gas sensor to be evaluated is not limited to the above-described gas sensor 101. For example, a plate having at least an element portion in which a detection electrode and a reference electrode are provided on the front and back surfaces of a solid electrolyte layer having oxygen ion conductivity. It may be a gas sensor provided with a gas-like detection element, or a gas sensor provided with a detection element having a gas detection part made of a semiconductive metal oxide such as titania (TiO ₂ ).

It is a block diagram which shows schematic structure of a gas sensor evaluation apparatus. It is sectional drawing which shows the whole structure of a gas sensor. It is a flowchart showing the processing content of an evaluation determination process. It is the measurement result which measured the sensor output of the gas sensor with respect to the air-fuel ratio switching of sample gas about each when the gas flow rate is set to 2 patterns (gas flow rate: small, gas flow rate: large). It is the measurement result which measured the change of the gas flow rate of sample gas with respect to the change of the internal-diameter dimension (diameter in a gas pipe) in the formation position of the evaluation object gas sensor installation part among gas flow paths.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Gas sensor evaluation apparatus, 11 ... Sample gas supply part, 13 ... Sensor reaction part, 15 ... Apparatus control part, 17 ... Sample gas analysis part, 23 ... Flow volume adjustment part, 41 ... Reaction part gas piping, 48 ... Addition gas introduction 49: Evaluation object gas sensor installation part, 51 ... Evaluation object gas sensor, 61 ... Additive gas supply part, 67 ... Injector for gas, 73 ... Lean additive component introduction part, 75 ... Rich additive component introduction part, 77 ... Additive gas heating Department.

Claims (3)

A gas sensor evaluation apparatus for evaluating a gas sensor for detecting a specific component contained in exhaust gas of an internal combustion engine based on a sensor output characteristic for a sample gas containing at least the specific component,
A gas flow path forming part having a gas flow path for the sample gas and having a sensor mounting part to which the gas sensor is mounted in a state where the detection part of the gas sensor is disposed in the gas flow path;
Base gas supply means for supplying a base gas as the sample gas to the gas flow path forming unit;
An additive gas supply means for alternately supplying a rich additive gas in a reducing atmosphere and a lean additive gas in an oxidizing atmosphere with a constant period with respect to the base gas flowing in the gas flow path forming unit;
With
The gas flow path forming portion is formed so that a cross-sectional area at a position where the sensor mounting portion is formed is smaller than a cross-sectional area at the supply position of the base gas in the gas flow path,
The additive gas supply means includes a gas injector, and the rich additive gas or the lean additive gas is supplied by the gas injector at a rate of 0.5 [L / min] or more,
A gas sensor evaluation apparatus characterized by the above. The gas flow path forming portion is formed such that a cross section of the sensor mounting portion in the gas flow path is formed in a circular shape having an inner diameter of 3.0 [cm] or less.
The gas sensor evaluation apparatus according to claim 1. Comprising an additive gas heating means for heating the rich additive gas or the lean additive gas;
The gas sensor evaluation apparatus according to claim 1 or 2, wherein

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