JP2003185621A - Apparatus and method for evaluating characteristics of gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for evaluating the characteristics of a gas sensor capable of evaluating and testing the responsivity of the gas sensor with high accuracy and satisfactory reproducibility. <P>SOLUTION: The apparatus for evaluating the characteristics of the gas sensor is provided with a gas switching device 5 for alternately switching between a reducing gas and an oxidizing gas in a predetermined cycle and supplying them for a base gas to be supplied for the gas sensor 61. The quantity of flow of the reducing gas (a mixed gas of H<SB>2</SB>gas, C<SB>3</SB>H<SB>8</SB>gas, and CO gas) and the quantity of flow of the oxidizing gas (a mixed gas of O<SB>2</SB>gas and N<SB>2</SB>gas) to be supplied for the base gas from a base gas supplying part 2 are made equal. The quantity of flow of the overall gases to be supplied for the gas sensor 61 become constant, and the flow velocity of the gases to be supplied for the gas senor does not change at the addition of the reducing gas and at the addition of the oxidizing gas. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for evaluating and testing the characteristics of a gas sensor, and more particularly to an apparatus and method for evaluating the characteristics of a gas sensor used for quality inspection of products in a gas sensor production line.

[0002]

2. Description of the Related Art When a three-way catalyst for purifying exhaust gas is used as a measure against exhaust gas from an internal combustion engine, the air-fuel ratio of the air-fuel mixture is maintained at an appropriate value in order to maximize the function of this catalyst. There is a need. But normal gasoline, LP
In carburetors and fuel injection devices for internal combustion engines such as gas,
Even if the air-fuel ratio of the air-fuel mixture is made constant, the air-fuel ratio actually changes greatly due to various factors. Therefore,
In order to keep the air-fuel ratio constant, it is necessary to detect the actual air-fuel ratio from the exhaust gas component with a gas sensor and feed back the signal to the carburetor and the fuel injection device.

This gas sensor uses an oxygen ion conductive solid electrolyte or a semiconductive transition metal oxide.
Since it is used for the above-mentioned purpose, there is a demand for a gas sensor characteristic evaluation device which has a simple structure and is labor-saving and has high accuracy for manufacturing a sensor having good output characteristics. As a conventional technology of such a gas sensor characteristic evaluation device,
There is one disclosed in JP-A-53-78886. This conventional technique supplies a base gas by alternately switching a reducing gas and an oxidizing gas in a certain cycle,
This is to evaluate and test the characteristics (responsiveness) of the gas sensor.

[0004]

However, in the above prior art, although the reducing gas and the oxidizing gas are alternately supplied to the base gas, the amount of the reducing gas supplied and the oxidizing gas are supplied. The amount may differ. When the flow rate of the reducing gas and the flow rate of the oxidizing gas supplied to the base gas are different as described above, the flow rate of the gas supplied to the gas sensor is the same as when the reducing gas is added and when the oxidizing gas is added. It changes with time, and the responsiveness of the gas sensor is affected by this change in flow velocity. Therefore, it has been difficult to evaluate and test the response of the gas sensor with high accuracy and reproducibility.

The present invention has been made in view of such conventional problems, and an object thereof is to provide a gas sensor characteristic evaluation device capable of evaluating and testing the response of the gas sensor with high accuracy and reproducibility. To do.

[0006]

[Means for Solving the Problems] Means for attaining the above-mentioned objects and their effects will be described below. The invention according to claim 1 is a gas sensor characteristic evaluation device comprising a switching means for alternately switching a first gas and a second gas, which have different components, to a base gas supplied to a gas sensor at a constant cycle. The gist is to make the flow rates of the first gas and the second gas supplied to the base gas equal.

According to this structure, the same amount of the first gas and the second gas are alternately supplied to the base gas, so that the flow rate of the entire gas supplied to the gas sensor becomes constant. As a result, the flow velocity of the gas supplied to the gas sensor is
There is no change between when the gas is added and when the second gas is added. That is, the responsiveness of the gas sensor can be measured without changing the flow velocity of the gas supplied to the gas sensor. Therefore, the response of the gas sensor can be evaluated and tested with high accuracy and reproducibility.

According to a second aspect of the present invention, in the characteristic evaluation device for a gas sensor according to the first aspect, first gas supply means for supplying the first gas and second gas supply means for supplying the second gas. And a flow rate adjusting gas supply means for supplying a flow rate adjusting gas to at least one of the first gas and the second gas in order to equalize the flow rates of the first gas and the second gas.

According to this structure, the flow rate of the flow rate adjusting gas supplied to at least one of the first gas and the second gas may be adjusted so that the flow rates of the first gas and the second gas become equal. Therefore, it is possible to easily perform the adjustment for equalizing the flow rates of the first gas and the second gas supplied to the base gas.

According to a third aspect of the present invention, in the gas sensor characteristic evaluation device according to the second aspect, the flow rate adjusting gas is supplied by switching to the one of the first gas and the second gas having the smaller flow rate. The gist is to provide a flow path switching valve.

According to this structure, the flow rate adjusting gas can be supplied by switching to the one of the first gas and the second gas having the smaller flow rate by the flow passage switching valve. Therefore, the first
The flow rate of the flow rate adjusting gas may be adjusted so that the gas and the second gas have the same flow rate. Therefore, even when the flow rate of either the first gas or the second gas is low, adjustment can be easily performed to equalize the flow rates of the first gas and the second gas alternately supplied to the base gas. it can. Further, since the flow path switching valve is provided, only one flow rate adjusting gas supply means is required, so that the cost can be reduced.

According to a fourth aspect of the present invention, in the gas sensor characteristic evaluation apparatus according to the second aspect, the flow rate adjusting gas is put in both the first gas and the second gas, and the first gas and the second gas are mixed. The gist is to make the total flow rate of the flow rate adjusting gas equal to the total flow rate of the gas and the flow rate adjusting gas.

According to this structure, the flow rates of the flow rate adjusting gas to be introduced into both of the first gas and the second gas may be adjusted so that the flow rates of the first gas and the second gas become equal. For this reason,
It is possible to equalize the flow rates of the first gas and the second gas that are alternately supplied to the base gas without changing the flow rates of the two gases.

According to a fifth aspect of the present invention, in the gas sensor characteristic evaluation device according to any one of the first to fourth aspects, the switching means is controlled to open and close alternately at a constant cycle, with respect to the base gas. A pair of first solenoid valves that alternately supply the first gas and the second gas, and a gas discharge passage downstream of the gas sensor that communicates with a gas passage that sends the base gas to the gas sensor, The pair of first
The gist of the present invention is to include a pair of second solenoid valves that are controlled to open and close in synchronization with the solenoid valve so that either one of the first gas and the second gas is supplied.

According to this structure, the pair of first electromagnetic valves are alternately opened and closed to alternately supply the first gas and the second gas to the base gas, and at the same time, the pair of second electromagnetic valves are alternately arranged. A gas that is different from the gas supplied to the base gas is supplied to the gas exhaust passage through the gas exhaust passage. Therefore, the pulsation of the gas generated in the gas passage when the pair of solenoid valves is opened and closed is canceled by the gas supplied to the gas discharge passage, and the change in the flow rate of the gas supplied to the gas sensor is suppressed. Therefore, the responsiveness of the gas sensor can be measured more stably.

According to a sixth aspect of the present invention, in the gas sensor characteristic evaluation device according to the fifth aspect, pressure regulating valves are provided on the downstream sides of the pair of second solenoid valves, respectively, and the first pressure regulating valve is used for the first regulating valve. The gist is to equalize the pressures on the outlet side of the solenoid valve and the second solenoid valve.

The pressure on the outlet side of the first solenoid valve becomes higher than the pressure on the outlet side of the second solenoid valve due to the pressure loss in the pipes before and after the gas sensor, and the gas is less likely to flow on the first solenoid valve side than on the second solenoid valve side. On the other hand, according to this configuration, the pressures on the outlet sides of the first solenoid valve and the second solenoid valve are equalized by the pressure regulating valve, and the flow rate of gas supplied to the gas passage and the gas discharge passage are supplied. The gas flow rate can be made equal. This facilitates gas flow on the first solenoid valve side. Further, by making the flow rate of the gas supplied to the gas passage and the flow rate of the gas supplied to the gas discharge passage equal,
The pulsation of the gas generated in the gas passage is effectively canceled by the gas supplied to the gas discharge passage. Therefore,
The flow rate change of the gas supplied to the gas sensor can be further suppressed.

The invention according to claim 7 is the gas sensor characteristic evaluation device according to claim 5 or 6, wherein each of the first electromagnetic valve and the second electromagnetic valve is an injector with a small dead volume, and each injector is a gas sensor. The point is that it is directly connected to the piping on the inlet side.

According to this structure, the first solenoid valve and the second solenoid valve
Since each solenoid valve is an injector with a small dead volume and each injector is directly connected to the pipe,
When switching at least one of the gas and the second gas to a gas having a different component, the switching can be instantaneously performed.
Further, the switching between the first gas and the second gas alternately supplied to the gas passage can be switched instantaneously.

According to an eighth aspect of the present invention, in the gas sensor characteristic evaluation device according to any one of the fifth to seventh aspects, the opening / closing detection for detecting the opening / closing timing of each of the first electromagnetic valve and the second electromagnetic valve is performed. The gist of the present invention is to include a means and a correcting means for correcting the variation in the opening / closing timing of each solenoid valve based on the detection result of the detecting means.

With this configuration, it is possible to correct the variation in the opening / closing timing of each solenoid valve in consideration of the drive voltage of each solenoid valve and the response delay due to the change over time. Claim 9
In the gas sensor characteristic evaluation device according to claim 8, the invention according to claim 8 is characterized in that the opening / closing detection means detects an opening / closing timing of each solenoid valve from a change in a drive current when each solenoid valve is opened. To do.

According to this structure, since the opening / closing detecting means detects the opening / closing timing of each electromagnetic valve from the change in the drive current when opening / closing each electromagnetic valve, the variation in the opening / closing timing of each electromagnetic valve can be accurately corrected. it can.

According to a tenth aspect of the present invention, there is provided a gas sensor characteristic evaluation method, wherein the first gas and the second gas having different components are alternately switched to a base gas supplied to the gas sensor at a constant cycle. The gist is to make the flow rates of the first gas and the second gas alternately supplied to the base gas equal.

According to this structure, the same amount of the first gas and the second gas are alternately supplied to the base gas, so that the flow rate of the entire gas supplied to the gas sensor is constant. As a result, the flow velocity of the gas supplied to the gas sensor is
There is no change between when the gas is added and when the second gas is added. Therefore, the response of the gas sensor can be evaluated and tested with high accuracy and reproducibility.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In the description of each embodiment, the same parts are designated by the same reference numerals, and duplicate description will be omitted.

First Embodiment FIG. 1 schematically shows the system configuration of the entire gas sensor characteristic evaluation apparatus according to the first embodiment. This gas sensor characteristic evaluation device is
A reducing gas supply unit 1, a base gas supply unit 2, an oxidizing gas supply unit 3, a flow rate adjusting gas supply unit 4, a gas switching device 5, and a measuring device 6 are provided.

The reducing gas supply unit 1 uses H2 gas and C3H.
The reducing gas as the first gas, in which the 8 gas and the CO gas are mixed at a predetermined ratio, is individually supplied at a predetermined flow rate.
The reducing gas supply unit 1 includes three gas cylinders (not shown) filled with H2 gas, C3H8 gas, and CO gas, and three gas cylinders for appropriately adjusting the mass flow rate of each gas supplied from each gas cylinder. A mass flow controller 11 is provided. The reducing gas supply unit 1 is connected to the pipe 9, and the reducing gas is supplied from the supply unit 1 to the pipe 9.

The base gas supply unit 2 individually supplies a base gas containing N 2 gas as a main component at a predetermined flow rate. The base gas supply unit 2 is provided with a gas cylinder (not shown) filled with N2 gas and a mass flow controller 21 that appropriately adjusts the mass flow rate of N2 gas.
The base gas supply unit 2 is connected to the pipe 7, and the base gas is supplied from the supply unit 2 to the pipe 7.

The oxidizing gas supply unit 3 individually supplies the oxidizing gas (O 2 gas) as the second gas at a predetermined flow rate. The oxidizing gas supply unit 3 is provided with a gas cylinder (not shown) filled with O 2 gas and a mass flow controller 31 that appropriately adjusts the mass flow rate of the gas.

The flow rate adjusting gas supply unit 4 supplies N 2 gas as a flow rate adjusting gas added to the oxidizing gas supplied from the oxidizing gas supply unit 3. The flow rate adjusting gas supply unit 4 has a gas cylinder (not shown) filled with N2 gas.
And a mass flow controller 41. The downstream side of the controller 41 is connected to the downstream side of the mass flow controller 31 via a pipe.
The mass flow rates of the oxidizing gas and the N2 gas are adjusted so that the oxidizing gas and the N2 gas are mixed at a predetermined ratio and the total flow rate of these two gases (flow rate of the oxidizing gas) becomes equal to the reducing gas flow rate. It is adapted to be properly adjusted by the mass flow controllers 31 and 41. The oxidizing gas obtained by adding N2 gas to the oxidizing gas (O2 gas) is pipe 1
Supplied to zero.

The measuring device 6 is provided with a gas sensor 61 having a gas detecting section in the pipe 7 to which the base gas is supplied from the base gas supplying section 2, and a measuring section 62 for measuring the output of the gas sensor 61. There is. The base gas supplied from the base gas supply unit 2 is supplied to the gas detection unit of the gas sensor 61 through the inside of the pipe 7 (gas passage), and is further connected to the exhaust pipe (gas connected to the downstream side of the gas sensor 61). It is designed to be discharged through the inside of the discharge passage) 8.

The gas sensor 61 has a gas detecting portion mainly composed of a fixed electrolyte having an oxygen ion conductivity such as zirconia (ZrO2) or a semi-conductive metal oxide such as titania (TiO2). The gas sensor 61 senses the oxygen concentration in the gas, and the output suddenly changes at, for example, the stoichiometric air-fuel ratio. For example, the gas sensor 61 uses 800 to 10 when a zirconia tube is used for the gas detection unit when the oxygen concentration in the gas is lower than the stoichiometric air-fuel ratio, that is, when the atmosphere of the supplied gas is reducing.
An electromotive force of 00 mv (0.8 to 1 V) is generated. Also,
The gas sensor 61 generates an electromotive force of 200 to 0 mv (0.2 to 0 V) when the oxygen concentration in the gas is higher than the stoichiometric air-fuel ratio, that is, when the atmosphere of the supplied gas is oxidizing.

Although not shown in the drawing, the gas sensor characteristic evaluation apparatus according to the present embodiment has a gas sensor 61.
An electric heating furnace for heating the gas detection unit is provided. Then, the energization of the electric heating furnace is controlled so that the temperature of the gas sensor 61 is kept substantially constant.

The gas switching device 5 includes two first solenoid valves 5
1, 52, two second solenoid valves 54, 55, and a control circuit 53 for controlling the opening and closing of these solenoid valves.
These solenoid valves 51, 52, 54, 55 and the control circuit 53
And constitute a switching means.

The inlet side of the solenoid valve 51 is connected to the pipe 9 to which the reducing gas from the reducing gas supply unit 1 is supplied, and the outlet side thereof is connected to the pipe 7 via the pipe 9a and upstream of the gas sensor 61. Connected by the side. The inlet side of the solenoid valve 52 is connected to the pipe 10 to which the oxidizing gas from the oxidizing gas supply unit 3 is supplied, and the outlet side thereof is connected to the pipe 7 via the pipe 10a on the upstream side of the gas sensor 61. Has been done. The inlet side of the solenoid valve 54 is connected to the pipe 9,
The outlet side is connected to the discharge pipe 8 through the pipe 9b. The inlet side of the solenoid valve 55 is connected to the pipe 10, and the outlet side thereof is connected to the discharge pipe 8 via the pipe 10b.

These solenoid valves 51, 52, 54, 55 have the same construction, and the construction of each solenoid valve is the same as the first solenoid valve 5
1 will be described on the basis of FIG. First solenoid valve 51
Is a normally closed solenoid valve, and a drive signal (control circuit output shown in FIG. 4) of a predetermined voltage from the control circuit 53 is applied to the solenoid 5
When it is applied to 1a, the valve element 51b is displaced from the fully closed position to the fully open position against the biasing force of the spring 51c, so that the upstream side flow path and the downstream side flow path communicate with each other. . The first solenoid valve 51 is configured such that the valve body 51b is held at the fully open position while the drive signal is applied to the solenoid 51a.

The control circuit 53 uses the four solenoid valves 5
Opening / closing control of 1, 52, 54, 55 is performed in the pattern shown in FIG. That is, the control circuit 53 opens and closes the solenoid valves 51 and 55 at the same time, and the solenoid valve 5
2, 54 can be opened and closed at the same time. By opening the solenoid valve 55 in synchronization with the opening of the solenoid valve 51, the reducing gas is supplied to the pipe 7 through the pipes 9 and 9a and starts to be added to the base gas, and at the same time, the oxidizing gas is oxidized. The characteristic gas starts to be supplied to the discharge pipe 8 through the pipes 10 and 10b. On the other hand, the solenoid valve 5 is synchronized with the opening of the solenoid valve 52.
When the valve 4 is opened, the oxidizing gas is transferred to the pipe 10 and the pipe 10.
At the same time as being supplied to the pipe 7 through the inside of a and being added to the base gas, the reducing gas starts to be supplied to the discharge pipe 8 through the pipe 9 and the pipe 9b.

In the gas sensor characteristic evaluation apparatus according to the present embodiment, as described above, the reducing gas supply unit 1 to the pipe 9 is reduced by mixing H2 gas, C3H8 gas and CO gas at a predetermined ratio. The characteristic gas is supplied at a predetermined flow rate (total flow rate of individual gases). On the other hand, the oxidizing gas (O 2 supplied from the oxidizing gas supply unit 3 is supplied to the pipe 10.
2 gas) and N2 supplied from the flow rate adjusting gas supply unit 4.
The oxidizing gas is mixed with the gas at a predetermined ratio and adjusted so that the total flow rate of these gases is equal to the flow rate of the reducing gas.

Further, the control circuit 53 controls the first solenoid valve 5
1, 55 and the second solenoid valves 52, 54 are alternately opened and closed at a constant cycle, so that the gas sensor 61 passes through the inside of the pipe 7.
The reducing gas and the oxidizing gas (mixed gas of O 2 gas and N 2 gas) having the same flow rate are alternately supplied to the base gas supplied to the gas detection unit. The "constant cycle" mentioned here is a cycle corresponding to a frequency of about 0.1 to 10 Hz, for example, a cycle of 5 seconds in this example.

When the solenoid valves 51, 55 are opened and the reducing gas is supplied to the base gas in this way, the gas of the reducing atmosphere is supplied to the gas detecting portion of the gas sensor 61, so that the gas sensor 61 operates at 800 to 1000 mv. Generates electromotive force. On the other hand, when the solenoid valves 52 and 54 are opened and the oxidizing gas is supplied to the base gas, the gas of the oxidizing atmosphere is supplied to the gas detecting portion of the gas sensor 61. Generates electromotive force.

This will be described with reference to FIG. t0
At this point, when the output of the control circuit 53 indicated by the arrow A is changed to open the solenoid valves 51, 55, the reducing gas causes the pipe 9,
The gas in the reducing atmosphere is supplied to the base gas in the pipe 7 through the inside of 9a, and the gas in the reducing atmosphere is supplied to the gas detection unit of the gas sensor 61. As a result, the output of the gas sensor 61 shown by the arrow B sharply increases from the time point t1. The time from time t0 to time t1 is a gas transportation delay time from when the solenoid valves 51 and 55 are opened until the reducing gas is supplied to the gas detection unit of the gas sensor 61. Further, the response time of the gas sensor 61 when the oxidizing gas is switched to the reducing gas is 63 when the output is 1000 mv from the time t1 when the output starts rising.
It is the time until the time t2 when 630 mv, which is%, is reached. This response time is approximately 200-250 ms.

At time t3, the output of the control circuit 53 is changed to close the solenoid valves 51, 55 and close the solenoid valves 52, 54.
When opened, oxidative gas (O2 gas, N2 gas) is added to piping 1
The gas is supplied to the base gas in the pipe 7 through 0, 10b, and the output of the gas sensor 61 sharply drops from the time point t4.
The time from the time point t3 to the time point t4 is the solenoid valves 52, 54.
Is the gas transportation delay time from the opening of the gas sensor until the oxidizing gas is supplied to the gas detection section of the gas sensor 61. Further, the gas sensor 6 when switching from reducing gas to oxidizing gas
The response time of 1 is the time from time t4 when the output starts to decrease to time t5 when the output reaches 370 mv, which is 37% of 1000 mv. This response time is approximately 200 to 2
It is 50 ms.

The response time (response time) of the gas sensor 61 is measured by measuring the response time (time from time t1 to time t2 and time from time t4 to time t5) of the gas sensor 61, respectively. The quality can be determined and evaluated.

According to the first embodiment constructed as described above, the following operational effects can be obtained. (A) Since the reducing gas and the oxidizing gas, which are alternately supplied to the base gas in a constant cycle, have the same flow rate, the total flow rate of the gas supplied to the gas sensor 61 is constant. As a result, the flow velocity of the gas supplied to the gas detection unit of the gas sensor 61 does not change when the reducing gas is added and when the oxidizing gas is added. That is, the responsiveness of the gas sensor 61 can be measured without changing the flow rate of the gas supplied to the gas sensor 61. Therefore, the responsiveness of the gas sensor can be measured without being affected by the change in the gas flow velocity as in the above-mentioned conventional technique, and the responsiveness of the gas sensor can be accurately measured
Moreover, it is possible to evaluate and test with good reproducibility.

(B) The flow rate of the reducing gas supplied from the reducing gas supply section 1 is kept constant, and the mass flow rate of the N2 gas added to the O2 gas supplied from the oxidizing gas supply section 3 is adjusted to the flow rate adjusting gas. Mass flow controller 4 of supply unit 4
Adjust with 1. Alternatively, the mass flow rates of the O2 gas and the N2 gas are set to the mass flow rate so that the total flow rate of the O2 gas and the N2 gas (flow rate of the oxidizing gas) becomes equal to the flow rate of the reducing gas.
Adjustment is performed by the controllers 31 and 41.

In this way, the flow rate of the reducing gas is constant,
The total flow rate of O2 gas and N2 gas (flow rate of oxidizing gas) may be adjusted to be equal to the flow rate of reducing gas.
By providing the flow rate adjusting gas supply unit 4 in this manner, adjustment for equalizing the flow rates of the reducing gas and the oxidizing gas supplied to the base gas can be easily performed.

(C) When the solenoid valves 51 and 55 are simultaneously opened, the reducing gas starts to be supplied to the base gas in the pipe 7 through the pipes 9 and 9a, and at the same time, the oxidizing gas is changed to the pipes 10 and 10b. It also starts to be supplied to the discharge pipe 8 through the inside.
As a result, the pulsation of the gas generated in the pipe 7 when the solenoid valve 51 is opened is canceled by the reducing gas supplied to the discharge pipe 8, and the change in the flow rate of the gas supplied to the gas sensor 61 is suppressed. The responsiveness of can be measured more stably. Similarly, when the solenoid valves 52 and 54 are simultaneously opened, the oxidizing gas starts to be supplied to the base gas in the pipe 7 through the pipes 10 and 10a, and at the same time, the reducing gas passes through the pipes 9 and 9b. Then, it is also supplied to the discharge pipe 8. As a result, the pulsation of the gas generated in the pipe 7 when the solenoid valve 52 is opened is canceled by the reducing gas supplied to the discharge pipe 8, and the change in the flow rate of the gas supplied to the gas sensor 61 is suppressed. The responsiveness of can be measured more stably.

Second Embodiment FIG. 5 schematically shows the system configuration of the entire gas sensor characteristic evaluation apparatus according to the second embodiment. In this embodiment, the first embodiment shown in FIG.
In the embodiment, the flow rate adjusting gas is put in both the reducing gas and the oxidizing gas, and the total flow rate of the reducing gas and the flow rate adjusting gas is equal to the total flow rate of the oxidizing gas and the flow rate adjusting gas. It is configured to do. Therefore, a flow rate adjusting gas supply unit 4 ′ similar to the flow rate adjusting gas supply unit 4 is also provided in the reducing gas supply unit 1. Other configurations are the same as those in the first embodiment.

According to the second embodiment, the following operational effects are obtained. (D) For adjusting the flow rate of the reducing gas and the oxidizing gas so that the total flow rate of the reducing gas and the adjusting gas is equal to the total flow rate of the oxidizing gas and the adjusting gas. The gas flow rates may be adjusted respectively. For this reason,
It is possible to equalize the flow rates of the reducing gas and the oxidizing gas, which are alternately supplied to the base gas, without changing the flow rates of the reducing gas and the oxidizing gas.

[Third Embodiment] FIG. 6 schematically shows the system configuration of the entire gas sensor characteristic evaluation apparatus according to the third embodiment. This embodiment is different from the first embodiment shown in FIG. 1 in that the flow rate adjusting gas is provided with one flow path switching valve 56 which is switched to supply one of a reducing gas and an oxidizing gas having a smaller flow rate. Is. This flow path switching valve 5
6 is a first position for supplying the flow rate adjusting gas supplied from the flow rate adjusting gas supply unit 4 to the pipe 10 via the pipe 14,
The flow rate adjusting gas can be switched between a second position in which the gas is supplied to the pipe 9 through the pipe 13. Other configurations are the same as those in the first embodiment.

According to the third embodiment, the following operational effects are exhibited. (E) The flow rate adjusting gas can be switched by the flow path switching valve 56 and supplied to the reducing gas or the oxidizing gas having the smaller flow rate. Therefore, even when the flow rate of both the reducing gas and the oxidizing gas is low, it is possible to easily perform the adjustment for equalizing the flow rates of the reducing gas and the oxidizing gas alternately supplied to the base gas. it can.

Fourth Embodiment FIG. 7 schematically shows the system configuration of the entire gas sensor characteristic evaluation apparatus according to the fourth embodiment. This embodiment is different from the third embodiment shown in FIG. 6 in that pressure adjusting valves 57 and 58 are provided on the downstream side of the second electromagnetic valves 54 and 55, respectively, and the first electromagnetic valves 51 and 52 and the first electromagnetic valves 51 and 52 are provided by the pressure adjusting valves. The pressures on the outlet sides of the two solenoid valves 54, 55 are made equal. Other configurations are similar to those of the third embodiment.

According to the fourth embodiment, the following operational effects are exhibited. (F) Without the pressure adjusting valves 57 and 58, the gas sensor 61
The pressure on the outlet side of the 1st solenoid valve is 2
The pressure becomes higher than the outlet side pressure of the solenoid valve, and it becomes more difficult for gas to flow on the first solenoid valve side than on the second solenoid valve side. In order to eliminate such a problem, pressure adjusting valves 57 and 58 are provided on the downstream side of the second electromagnetic valves 54 and 55, respectively. Therefore, the first solenoid valves 51, 52 and the second solenoid valves 54, 55
The pressures on the outlet side of are equalized, and the flow rate of the gas supplied to the pipe 7 (gas passage) and the flow rate of the gas supplied to the discharge pipe 8 (gas discharge passage) can be made equal. This facilitates gas flow on the first solenoid valve 51, 52 side.

Since the flow rate of the gas supplied to the pipe 7 and the flow rate of the gas supplied to the discharge pipe 8 become equal,
The pulsation of the gas generated in the pipe 7 is effectively canceled by the gas supplied to the discharge pipe 8. Therefore, the change in the flow rate of the gas supplied to the gas sensor 61 can be further suppressed.

[Fifth Embodiment] FIG. 8 schematically shows the system configuration of the entire gas sensor characteristic evaluation apparatus according to the fifth embodiment. In this embodiment, in the fourth embodiment shown in FIG. 7, instead of the solenoid valves 51, 52, 54, 55, the first injector 7 having a small dead volume is used.
1, 72 and the second injectors 74, 75 are used. Further, the first injectors 71 and 72 are directly connected to the pipe 7 on the inlet side of the gas sensor 61. Other configurations are similar to those of the fourth embodiment.

These injectors 71, 72, 74,
75 has the same configuration, and the configuration of each injector will be described based on FIG. 9 on behalf of the first injector 71. The first injector 71 has a solenoid valve, and when a drive pulse (drive signal) is applied to the solenoid of this solenoid valve from the control circuit 53, the internal working piston rises and the needle valve 7
1a is lifted, the injection hole at the tip of the nozzle is opened, and gas (reducing gas in this injector) is injected into the pipe 7.

According to the fifth embodiment, the following operational effects are obtained. (G) Instead of the solenoid valves 51, 52, 54, 55, the first injectors 71, 72, 7 having a small dead volume
Injectors 71 and 72 are directly connected to the pipe 7 on the gas sensor inlet side by using Nos. 4 and 75. Thus, when switching at least one of the reducing gas and the oxidizing gas to the gas having different components, the switching can be instantaneously performed.
Further, switching between the reducing gas and the oxidizing gas, which are alternately supplied to the pipe 7 (gas passage), can be switched instantaneously.

[Modification] The present invention can be modified and embodied as follows. In each of the above embodiments, the flow rate adjusting gas supply unit 4 is the oxidizing gas (O 2 gas) supplied from the oxidizing gas supply unit 3.
It is configured to supply N2 gas as a flow rate adjusting gas, but the present invention is not limited to this configuration. That is, the flow rate adjusting gas supply unit 4 is the reducing gas supply unit 1
You may comprise so that N2 gas may be supplied to the reducing gas supplied from. In this case, the flow rate adjusting gas supply unit 4 is
A mass flow controller so that the reducing gas supplied from the reducing gas supply unit 1 and the N2 gas are mixed at a predetermined ratio and the total flow rate of the reducing gas and the N2 gas matches the flow rate of the oxidizing gas. The mass flow rate is properly adjusted by 11, 41.

In each of the above embodiments, the base gas supply unit 2 is configured to supply the base gas containing N2 gas as a main component. As the same gas, a mixed gas of air and N2 gas, or air is used. You may use the mixed gas of O2 gas, or other mixed gas. In addition, the reducing gas (mixed gas of H2 gas, C3H8 gas and CO gas) or oxidizing gas (O2
A mixed gas of gas and N2 gas) may be used as the base gas.

In the first embodiment, a pressure adjusting valve is provided on the upstream side of the first solenoid valves 51 and 52 to keep the back pressure of the line (pressure in the pipe 7 downstream of the adjusting valve) constant. It may be configured as follows. With this configuration, the gas sensor 6
The responsiveness of 1 can be measured more stably. Similarly, in the second embodiment as well, pressure adjusting valves may be provided on the upstream sides of the solenoid valves 51 and 52 and on the upstream sides of the solenoid valves 54 and 55 so as to make the back pressure of the line constant. Good. Also in this case, the responsiveness of the gas sensor 61 can be measured more stably.

The opening / closing timing of each solenoid valve 51, 52, 54, 55 in the first to fourth embodiments is preferably set in consideration of the response delay of each solenoid valve. In this case, the opening / closing timing of each solenoid valve is corrected in consideration of the drive voltage of each solenoid valve, the response delay due to the change over time, the change in the back pressure of the line due to the change over time, and the like.

As a concrete example of this correction method, for example,
The drive voltage of each solenoid valve and the elapsed time are monitored, and the response to the drive voltage (delay of the valve opening time according to the decrease of the drive voltage) and the response to the elapsed time (open valve according to the passage of time) Data such as (time delay) is mapped and stored. By referring to this map and correcting the opening / closing timing of each solenoid valve, the gas sensor 61 can always be stably operated.
Can be measured. As the drive voltage,
It is preferable to select a voltage that reduces the amount of change in the response delay of each solenoid valve even if the voltage changes.

As another example of the above correction method, the drive current and drive voltage of each solenoid valve are monitored, and the open / close timing of each solenoid valve is feedback-controlled, so that the responsiveness of the gas sensor 61 is always stable. Can be measured.

For example, at the moment when the valve body 51b (see FIG. 2) of each solenoid valve is fully lifted to the fully open position, the magnetic flux density of the magnetic circuit suddenly changes, so that the drive current waveform drops. Therefore, the valve opening timing of each solenoid valve can be detected by monitoring the drive current and detecting the time when the current drops. Based on this detection result, it is possible to correct the variation in the opening / closing timing of each solenoid valve.

Here, the opening / closing detection means for detecting the opening / closing timing of each solenoid valve from the change of the drive current when each solenoid valve is opened, and the variation of the opening / closing timing of each solenoid valve is corrected based on the detection result of the detection means. The correction means to be configured is constituted by the control circuit 53.

By monitoring the drive current and drive voltage of each solenoid valve in this way, the individual difference of each solenoid valve can be absorbed and the responsiveness of the gas sensor 61 can be measured more stably. The feedback control may be performed by monitoring only the above. A gap sensor may be used instead of the above method to detect the opening timing of each solenoid valve. Alternatively, the back pressure of the line may be monitored and the feedback control may be performed based on the back pressure.

If the opening / closing timing of each solenoid valve is monitored as described above, it is possible to monitor the change over time of the line (for example, the pipe 7), and it is possible to judge the deterioration of the line. Information that is advantageous for performing maintenance can be obtained. When a corrosive gas such as NO2, NH3, SO2 is used as the gas, the line changes rapidly with time. Therefore, it is advisable to control the line to be purged with N2 gas before and after the experiment.
This makes it possible to suppress changes over time in the lines, solenoid valves, mass flow controllers, etc. In each of the above embodiments, the flow rates of the reducing gas and the oxidizing gas supplied to the base gas are made equal, but the present invention is not limited to this. For example, when evaluating the responsiveness of the gas sensor in the lean region, two types of oxidizing gases having different O2 concentrations are used instead of the reducing gas and the oxidizing gas, and the flow rates of both oxidizing gases are made equal. You may do it. Alternatively, when evaluating the response of the gas sensor 61 in the rich region, instead of the reducing gas and the oxidizing gas, for example, two types of reducing gases having different mixing ratios of H2 gas, C3H8 gas and CO gas are used. Alternatively, the flow rates of both reducing gases may be equalized.

[Brief description of drawings]

FIG. 1 is a block diagram schematically showing a system configuration of an entire gas sensor characteristic evaluation apparatus according to a first embodiment.

FIG. 2 is a schematic configuration diagram showing a solenoid valve used in the same embodiment.

FIG. 3 is a waveform diagram showing the opening / closing timing of the solenoid valve.

FIG. 4 is a graph showing the output of the control circuit and the output of the gas sensor in the same embodiment.

FIG. 5 is a block diagram schematically showing the system configuration of a second embodiment.

FIG. 6 is a block diagram schematically showing the system configuration of a third embodiment.

FIG. 7 is a block diagram schematically showing a system configuration of a fourth embodiment.

FIG. 8 is a block diagram schematically showing the system configuration of a fifth embodiment.

FIG. 9 is a schematic configuration diagram showing an injector used in the fifth embodiment.

[Explanation of symbols]

1 ... Reducing gas supply unit as first gas supply means, 2 ...
Base gas supply part, 3 ... Oxidizing gas supply part as second gas supply means, 4, 4 '... Flow rate adjusting gas supply part as flow rate adjusting gas supply means, 5 ... Gas switching device as switching means, 6 ... Measuring device, 7 ... Pipe as gas passage, 8 ...
Exhaust pipes as gas exhaust passages, 51, 52, 54, 55
... solenoid valve, 56 ... flow path switching valve, 57, 58 ... pressure adjusting valve, 61 ... gas sensor, 71, 72, 74, 75 ... injector.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Moriyasu Michiyasu             14 Iwatani Shimohakaku-cho, Nishio-shi, Aichi Stock Association             Company Japan Auto Parts Research Institute (72) Inventor Yoshiyuki Hayashi             14 Iwatani Shimohakaku-cho, Nishio-shi, Aichi Stock Association             Company Japan Auto Parts Research Institute (72) Inventor Rentaro Mori             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. F term (reference) 2G004 BM04 BM09

Claims (10)

[Claims] 1. A base gas supplied to a gas sensor,
A characteristic evaluation device for a gas sensor, comprising a switching means for alternately switching and supplying a first gas and a second gas having different components at a constant cycle, wherein the first gas and the second gas are supplied to the base gas.
A characteristic evaluation device for a gas sensor, wherein the gas flow rates are made equal. 2. A first gas supply means for supplying the first gas, a second gas supply means for supplying the second gas, and both of them for equalizing the flow rates of the first gas and the second gas. The gas sensor characteristic evaluation device according to claim 1, further comprising a flow rate adjusting gas supply unit that supplies a flow rate adjusting gas to at least one of the gases. 3. The gas sensor according to claim 2, further comprising a flow path switching valve for switching and supplying the flow rate adjusting gas to one of the first gas and the second gas having a smaller flow rate. Characteristic evaluation device. 4. The flow rate adjusting gas is put into both the first gas and the second gas, and the total flow rate of the first gas and the flow rate adjusting gas, and the gas and the flow rate adjusting gas. The gas sensor characteristic evaluation device according to claim 2, wherein the total flow rate of the gas sensor is equal to the total flow rate of the gas sensor. 5. The switching means is controlled to open and close alternately at a constant cycle, and the first gas and the second gas are controlled with respect to the base gas.
A pair of first solenoid valves for supplying gas alternately, and a pair of the first solenoid valves in a gas discharge passage downstream of the gas sensor for communicating the base gas to the gas sensor downstream of the gas sensor. A pair of second solenoid valves that are controlled to be opened and closed in synchronization and are supplied with either one of the first gas and the second gas.
4. The gas sensor characteristic evaluation device according to claim 4. 6. A pressure adjusting valve is provided on the downstream side of each of the pair of second electromagnetic valves, and the pressures on the outlet sides of the first electromagnetic valve and the second electromagnetic valve are equalized by the pressure adjusting valves. The gas sensor characteristic evaluation device according to claim 5. 7. The gas sensor according to claim 5, wherein each of the first electromagnetic valve and the second electromagnetic valve is an injector with a small dead volume, and each injector is directly connected to a pipe on the gas sensor inlet side. Characteristic evaluation device. 8. An opening / closing detection means for detecting opening / closing timing of each of the first electromagnetic valve and the second electromagnetic valve, and a correction means for correcting variation in opening / closing timing of each electromagnetic valve based on a detection result of the detecting means. The gas sensor characteristic evaluation device according to claim 5, further comprising: 9. The gas sensor characteristic evaluation device according to claim 8, wherein the opening / closing detection means detects the opening / closing timing of each solenoid valve from the change in the drive current when each solenoid valve is opened. 10. A characteristic evaluation method of a gas sensor, wherein a first gas and a second gas having different components are alternately switched to a base gas supplied to a gas sensor at a constant cycle, and the base gas is alternately supplied to the base gas. A method for evaluating characteristics of a gas sensor, characterized in that the flow rates of the first gas and the second gas supplied to the gas sensor are made equal.