JPS6142225B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses the combustion gas of HC fuel such as isobutane, which generates a component gas almost equal to the exhaust gas component of the engine, to reduce the stoichiometric ratio at the sudden change point of the output of the O ₂ sensor. The present invention relates to an O ₂ sensor evaluation device that evaluates the deviation of .

In general, in an engine equipped with an exhaust purification catalytic converter, when the air-fuel ratio is the stoichiometric air-fuel ratio, the exhaust gas is completely combusted in the exhaust purification catalytic converter for re-reaction, and almost no harmful gases are emitted. Such an engine is evaluated as having good characteristics, and these characteristics also match well when the engine is actually driven and the characteristics are recorded. For example, Figure 1 shows the relationship between the air-heat ratio and exhaust gas composition when the engine is operated at a constant load.As shown by the solid line, when gasoline is used as fuel, the air-fuel ratio is When the air-to-heat ratio is 14.6 (corresponding to excess air ratio λ = 1), harmless carbon dioxide reaches its maximum level, and the amounts of other harmful gases and oxygen are at the stoichiometric ratio, so this exhaust gas When oxidized or reduced by an exhaust purification catalytic converter, most of the harmful Co, NOx, and THC gases in the exhaust gas are converted into CO ₂ , N ₂ ,
Since it is converted to H ₂ O and no longer contained, engines with these characteristics pass the standards of the Exhaust Emission Control Act.

The air-fuel ratio detector for setting and controlling the air-fuel ratio of this exhaust gas purification system to the stoichiometric air-fuel ratio is
Generally, an O ₂ sensor is used. This O ₂ sensor uses the principle of a zirconia oxygen concentration battery, and its output electromotive force is as shown in Figure 2.
When the fuel is rich (hereinafter simply referred to as rich)
When the fuel is lean (hereinafter simply referred to as lean), an electromotive force of approximately 1v is generated, and when the fuel is lean (hereinafter simply referred to as lean), an electromotive force of approximately 0.1v is generated, and the boundary point between rich and lean at this air-fuel ratio,
In other words, it has characteristics that change rapidly at a certain air-fuel ratio close to the stoichiometric air-heat ratio. Therefore, when an engine is operated and an O ₂ sensor is inserted into its exhaust port, if the engine's fuel flow rate is adjusted to an air-fuel ratio at which the output of this O ₂ sensor changes rapidly, the engine's air-fuel ratio will become O. The air-fuel ratio, where the electromotive force of _{the two} sensors suddenly changes, can be controlled to be almost constant. In this case, if the output of the O ₂ sensor has the characteristic of suddenly changing at the stoichiometric air-fuel ratio, that is, λ = 1, then by combining a three-way catalyst, this engine can generate the output as shown by the dotted line in Figure 1. It is possible to create a pollution-free engine that hardly generates harmful gases such as CO, THC, and NOx.

However, even if these O ₂ sensors have the same structure and are manufactured under the same manufacturing conditions, they do not necessarily have exactly the same λ-electromotive force characteristics.
Even if the output of the O ₂ sensor inserted into the engine's exhaust port is controlled mainly around air-fuel ratios that suddenly change, if the output of this O ₂ sensor changes suddenly at a value other than λ = 1, the engine exhaust If the gas components deviate from the stoichiometric air/heat ratio, they will no longer be in the stoichiometric state (λ = 1), and even if the exhaust gas is oxidized or reduced with a three-way catalyst, it will not be completely processed.
As shown by the dotted line in Figure 1, the amount of NOx or Co emitted increases, and the exhaust gas contains harmful gases.

Taking this point into consideration, it has been traditionally
The method for evaluating the characteristics of an O ₂ sensor is to insert the O ₂ sensor into the exhaust port of an actual engine and plot the relationship between the engine's air-fuel ratio and the electromotive force of the O ₂ sensor. Since the air-fuel ratio and driving conditions vary greatly with small changes in the amount of fuel supplied, it is not possible to set this air _- fuel ratio to a constant constant. The drawback was that it was not possible to accurately determine how much the air-fuel ratio deviated from the stoichiometric air-fuel ratio.

In order to eliminate the drawbacks of the conventional example, the present invention uses HC fuel such as isobutane, which generates gas components equivalent to engine exhaust gas components by combustion, and supplies a constant flow of air to the fuel chamber. At the same time, the flow rate of the HC fuel such as isobutane is varied depending on the difference between the output of the O ₂ sensor under test and the reference voltage, and the flow rate of the HC fuel such as the air and isobutane is varied depending on the difference between the output of the O ₂ sensor under test and the reference voltage. The present invention provides an O ₂ sensor testing device that evaluates the characteristics of an O ₂ sensor under test from the flow rate of fuel. The configuration of this O ₂ sensor evaluation device includes a sensor chamber in which the O ₂ sensor under test is installed, a combustion chamber connected to the supply port of the sensor chamber, and a certain amount of air or a component equivalent to it injected into the combustion chamber. a gas supply device that supplies a gas having a temperature of 100%, a fuel supply device that supplies vaporized HC fuel to the combustion chamber, a recording device that records the output of the O ₂ sensor to be tested, and a recording device that records the output of the O ₂ sensor to be tested; a comparison circuit that compares the magnitude of the output and a reference voltage; a valve control device that controls a flow rate adjustment valve that varies the flow rate of the HC fuel based on the output of the comparison circuit;
It consists of a surface circuit that displays the air excess ratio λ value or the air-fuel ratio A/F from the flow rate of the air or a gas having a component equivalent thereto and the flow rate of the HC fuel, and the display circuit displays the display and the recording circuit records the record. This system is designed to evaluate the characteristics of the O ₂ sensor under test, and includes a sensor chamber in which the O ₂ sensor under test is installed, a combustion chamber connected to the supply port of the sensor chamber, and a a fuel supply device that supplies a certain amount of vaporized HC fuel; a gas supply device that supplies air or a gas of a component equivalent thereto to the combustion chamber; and a recording device that records the output of the O ₂ sensor under test. , a comparison circuit that compares the output of the O ₂ sensor under test and a reference voltage; and a valve control device that controls a flow rate adjustment valve that varies the flow rate of the air or a gas equivalent to it using the output of the comparison circuit. It consists of a display circuit that displays the air excess ratio λ value or the air-fuel ratio A/F from the flow rate of the air or a gas having a component corresponding thereto and the flow rate of the HC fuel, and the display circuit displays the display and the record circuit records the record. This is to evaluate the characteristics of the O ₂ sensor under test. Hereinafter, embodiments will be explained in detail with reference to the drawings.

Figure 3 shows the relationship between excess air ratio λ and exhaust composition when _isobutane is burned as an example of _{HC fuel} . It has almost the same components as the exhaust gas components of the engine shown in the figure. Therefore, by burning this isobutane and recording the output of the sensor under test using the combustion gas, it is possible to easily evaluate the characteristics of the _O2 sensor under test.Also, isobutane is a liquid like gasoline. Because it is a gaseous and pure fuel, it mixes well with air.
Fuel gas with desired components can be stably supplied with good reproducibility. Also, some HC fuels, such as benzene, are solid at room temperature, but they can be used by heating them to a temperature where they vaporize.
Similarly, even if other HC fuels are burned, the first
It has almost the same components as the exhaust gas components shown in the figure, and can be used in the same way as isobutane.

Next, Figure 4 shows the test sample using isobutane.
This shows an embodiment of the present invention for evaluating an O ₂ sensor, in which air from a compressed air supply device 1 is sent to a combustion chamber 4 through a pressure reducing valve 2 and a flow meter 3, and is also sent to an isobutane supply device 5. The isobutane from is sent to the combustion chamber 4 through a pressure reducing valve 6, a flow meter 7, and a flow rate adjustment valve 8, where it is mixed with air and combusted, and the combustion gas is sent to a sensor chamber 10 in which a sensor under test 9 is installed. Sent. In addition, a bypass 11 connected to a flow meter 12 is connected to the inlet and outlet of the combustion chamber 4, and a sensor chamber 10
The gas sent to is exhausted from the exhaust port 13.

The output of the sensor under test 9 is amplified by an amplifier 14 and input to a comparison circuit 15 . This comparison circuit 15
Since the standard sensor's standard sensor's fuel rich output voltage and fuel lean output voltage are set at approximately the center voltage as the reference voltage, the oxygen concentration in the combustion gas flowing through the sensor chamber 10 is at a stoichiometric ratio. If the oxygen concentration in the combustion gas is higher than the reference voltage, the output of the sensor under test 9 will be lower than the reference voltage, and if the oxygen concentration in the combustion gas is at a stoichiometric ratio, the output of the sensor under test 9 will be lower than the reference voltage. Becomes higher. In this manner, the comparison circuit 15 outputs a constant positive voltage when the output electromotive force of the sensor under test 9 is higher than the reference, and outputs a constant negative voltage when the output electromotive force of the sensor under test 9 is lower. The output of this comparison circuit is input to the flow rate adjustment valve drive circuit 16, and when the output of the comparison circuit 15 is positive, the oxygen concentration in the combustion gas is lower than the oxygen concentration at the stoichiometric ratio, so the flow rate adjustment valve is When the output of the comparator circuit 15 is negative, the oxygen concentration in the combustion gas is higher than the stoichiometric oxygen concentration, so the flow rate is adjusted. The ratio of the opening time of the valve 8 is increased to increase the amount of isobutane supplied and lower the oxygen concentration sent to the sensor chamber 10. The outputs of the flowmeters 3 and 7 are input to a λ value calculation device 17, where a λ value is calculated from the ratio of isobutane to air, smoothed by a filter 18, and displayed by a voltmeter 19.

Next, the operation of this embodiment will be explained. First, the pressure of air from the compressed air supply device 1 is adjusted by the pressure reducing valve 2, and the amount is set to be a constant amount, and then sent to the combustion chamber 4. The pressure of isobutane from the isobutane supply device 5 is regulated by a pressure reducing valve 6, and then sent to the combustion chamber 4 through a flow meter 7 and a flow rate regulating valve 8, where a mixed gas of air and isobutane is combusted, and the mixture of air and isobutane is combusted. The temperature is set at 900°C, which corresponds to the temperature at the exhaust port of the sensor chamber 10. Also, a part of the mixed gas of isobutane and air is sent to the sensor chamber 10 through a bypass 11 and a flow meter 12, but this is so that the combustion gas passing through the sensor chamber 10 is close to the exhaust gas components of the automobile. be. In other words, this is to supplement the THC component. In addition, the air flow rate is 9/
min, the flow rate of isobutane is about 277 c.c./min, and the flow rate flowing into the bypass 11 is 150 c.c./min.

When the output of the sensor under test 9 is input to the comparison circuit 15 while combustion gas is flowing in the sensor chamber 10 in this way, this output is compared with the reference voltage.
If it is higher than this reference voltage, the oxygen concentration in the gas passing through the sensor chamber 10 is low, so the flow rate adjustment valve 8 is operated to reduce the flow rate of isobutane gas to reduce the amount of oxygen consumed in the combustion chamber 4, and the sensor chamber 10 When the oxygen concentration in the gas sent to the sensor chamber 10 increases, the flow rate adjustment valve 8
Increase the amount of isobutane that passes through.

In this way, the flow rate passing through the flow rate regulating valve 8 is adjusted depending on the output of the sensor under test 9, and when the output is recorded by the recording device 20, as shown in FIG. A waveform in which the bottom peak appears for a large proportion of the time is recorded, but due to automatic balancing, the proportion of the time that the top and bottom peaks appear becomes the same. At this time, the λ value is calculated based on the outputs of the flowmeters 3 and 7, but since the flow rate of isobutane is pulsating due to the flow rate adjustment valve 8, the flowmeter 7
A flow rate pulsation absorbing device 21 is connected between the flow rate regulating valve 8 and the flow rate regulating valve 8 to absorb this pulsation. However, since the output of the λ value calculation device 17 still pulsates, the filter 18
The voltage is smoothed through the voltmeter 19, and the value is recorded.

As described above, the output waveform of the sensor under test recorded by the recording device 20 and the λ value indicated by the voltmeter 19 are compared with the recorded waveform and λ value of the standard sensor, and the characteristics of the sensor under test are evaluated. . The recorded waveform and λ value of this standard sensor may be obtained by installing the standard sensor in the sensor chamber 10, taking the recorded waveform with the recording device 20, and indicating the λ value with the voltmeter 19. Standard waveforms can also be obtained.

FIG. 6 shows another embodiment of the present invention, in which the same reference numerals as in FIG. A master sensor chamber 24 equipped with a master sensor 23 is provided through the master sensor chamber 24 , and the combustion gas passing through the master sensor chamber 24 is discharged from an exhaust port 25 . Further, the output terminal of the master sensor 23 and the output terminal of the sensor under test 9 are switched by a switch 26 and connected to the amplifier 14.

Next, the operation of this embodiment will be explained. First, the switch 26 is connected to the output terminal of the master sensor 23, and the recording circuit 20 records the standard recording waveforms as shown in FIG.
Also, adjust the indication using the voltmeter 19 to the reference λ value.

Next, the switch 26 is connected to the output terminal of the sensor under test 9, the waveform shown in FIG. 5 is recorded as in the previous embodiment, and the indicated value of the voltmeter 19 is measured.
Then, the recorded waveform of the master sensor 23 and the recorded waveform of the sensor under test are compared, and the λ values are compared to evaluate the characteristics of the sensor under test.

Note that it is not necessary to use a standard O ₂ sensor as the master sensor 23, and the sensor under test 9 can be used as the master sensor. By passing it through a catalyst, any gas composition is brought into chemical equilibrium, and in this chemical equilibrium, all gas components (O ₂ , H ₂ , CO, etc.) are in stoichiometric ratios (rich and lean). boundary). Therefore,
This is because the voltage of any sensor changes suddenly, and there is no sensor whose voltage rise point deviates from the stoichiometric ratio. Further, in this embodiment, the catalyst 22 and the master sensor chamber 24 are provided at the exhaust port of the sensor chamber 10, but the catalyst 22 is directly connected to the exhaust port of the combustion chamber 4,
Next, a master sensor chamber 24 is provided, and the sensor chamber 1
It goes without saying that the sensor chamber 0 and the master sensor chamber 24 may be provided in parallel.

In this embodiment configured as described above, the characteristics of the sensor under test can be easily evaluated by comparing the output of the master sensor provided in the master sensor chamber with the sensor under test.

In the above two embodiments, the air supply amount is constant and the isobutane supply amount is variable. However, the same problem will occur even if the isobutane supply amount is constant and the air supply amount is variable. The characteristics of the test sensor can be evaluated.

As explained above, according to the present invention, component gas equivalent to automobile exhaust gas is produced using HC fuel, and this is sent to the sensor chamber equipped with the sensor under test, and the output of the sensor under test is by
The characteristics of the sensor under test can be evaluated from the output of the sensor under test by varying the amount of HC fuel supplied.
A simple and highly accurate O ₂ sensor evaluation device can be provided.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the engine air-fuel ratio and exhaust composition, FIG. 2 is a diagram showing the relationship between the air-fuel ratio and electromotive force of the O ₂ sensor, and FIG.
FIG. 4 is a diagram showing the relationship between excess air ratio and combustion gas composition when isobutane is combusted, FIG. 4 is a block diagram of an embodiment of the present invention, and FIG. 5 is a diagram showing the output of the sensor under test. FIG. 6 is a block diagram of another embodiment of the present invention, and FIG. 7 is a waveform diagram.
It is an output waveform diagram of a master sensor. 1... Compressed air supply device, 2... Pressure reducing valve, 3...
...flow meter, 4 ... combustion chamber, 5 ... isobutane supply device, 6 ... pressure reducing valve, 7 ... flow meter, 8 ... solenoid valve, 9 ... sensor under test, 10 ... sensor chamber, 1
1...Bypass, 12...Flowmeter, 13...Exhaust port, 14...Amplifier, 15...Comparison circuit, 16...
...Flow rate adjustment valve control device, 17...λ value calculation device,
18... Filter, 19... Voltmeter, 20... Recording device, 21... Flow rate pulsation absorber, 22... Catalyst, 23... Master sensor, 24... Master sensor chamber, 25... Exhaust port, 26 ...Switch.

Claims (1)

[Scope of Claims] 1. A sensor chamber equipped with an O ₂ sensor to be tested, a combustion chamber connected to a supply port of the sensor chamber, and a certain amount of air or a gas having a component equivalent thereto supplied to the combustion chamber. a gas supply device for supplying gas, a fuel supply device for supplying vaporized HC fuel to the combustion chamber, a recording device for recording the output of the O ₂ sensor to be tested, and an output and a reference for the O ₂ sensor to be tested. a comparison circuit that compares the magnitude of voltage; a valve control device that controls a flow rate regulating valve that varies the flow rate of the HC fuel based on the output of the comparison circuit; and a valve control device that detects the flow rate of the air or a gas having a component equivalent thereto. a flowmeter that detects the flow rate of the HC fuel; a calculation device that calculates the excess air ratio λ value or the air-fuel ratio A/F from the outputs of these flowmeters; and displays the output of the calculation device. 1. An O ₂ sensor evaluation device comprising a display circuit that evaluates characteristics of the O ₂ sensor under test from the display of the display circuit and the recording of the recording device. 2. A master sensor chamber equipped with a master sensor is connected to the exhaust port of the sensor chamber via a catalyst, the output of the master sensor is compared with the reference voltage of the comparison circuit, and the output of the comparison circuit is used to control the HC system fuel. Claim 1, wherein the recording device and the display circuit are calibrated by controlling the flow rate of the recording device and the display circuit.
_O2 sensor evaluation device. 3. A master sensor chamber equipped with a master sensor is connected to the combustion chamber in parallel with the sensor chamber via a catalyst, the output of the master sensor is compared with the reference voltage of the comparison circuit, and the output of the comparison circuit is used to
2. The O ₂ sensor evaluation device according to claim 1, wherein the recording device and the display circuit are calibrated by controlling the flow rate of the HC fuel. 4. A sensor chamber in which the O ₂ sensor to be tested is installed, a combustion chamber connected to the supply port of the sensor chamber, a fuel supply device that supplies a certain amount of vaporized HC fuel to the combustion chamber, and the combustion chamber. A gas supply device that supplies air or a gas with a component equivalent to it into the room; a recording device that records the output of the O ₂ sensor under test; and a comparison that compares the output of the O ₂ sensor under test with a reference voltage. a valve control device that controls a flow rate adjustment valve that varies the flow rate of the air or a gas having a component equivalent thereto based on the output of the comparison circuit; and a flow rate controller that detects the flow rate of the air or a gas having a component equivalent thereto. a flowmeter that detects the flow rate of the HC fuel; a calculation device that calculates an excess air ratio λ value or an air-fuel ratio A/F from the output of the flowmeter; and a display circuit that displays the output of the calculation device. An O ₂ sensor evaluation device comprising: a characteristic of the O ₂ sensor under test is evaluated from the display of the display circuit and the recording of the recording device. 5 Connect a master sensor chamber equipped with a master sensor to the exhaust port of the sensor chamber via a catalyst, compare the output of the master sensor with the reference voltage of the comparison circuit, and use the output of the comparison circuit to determine whether the air or 5. The O ₂ sensor evaluation device according to claim 4, wherein the recording device and display circuit are calibrated by controlling the flow rate of the corresponding fuel gas. 6. Connect a master sensor chamber equipped with a master sensor to the combustion chamber in parallel with the sensor chamber via a catalyst, compare the output of the master sensor with the reference voltage of the comparison circuit, and use the output of the comparison circuit to 5. The O ₂ sensor evaluation device according to claim 4, wherein the recording device and the display circuit are calibrated by controlling the flow rate of air or a gas having a component equivalent thereto.