JPH0115814B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultra-precise air-fuel ratio meter that measures the air-fuel ratio of exhaust gas from an automobile engine or other combustion device very accurately, for example, on a test stand.

In today's society, there is a need to reduce as much as possible harmful components contained in exhaust from various combustion devices including automobile engines. Various adjustments are being made to meet this demand, including ignition timing and EGR, but among these adjustments, air-fuel ratio adjustment can be said to be the most fundamental. Therefore, there are many opportunities to measure the air-fuel ratio at maintenance shops, research departments, and the like. In general, in combustion devices such as engines, combustion near the stoichiometric air-fuel ratio provides high output, and in many cases, there are few harmful components in the exhaust gas. Therefore, in many cases they are designed to burn at a stoichiometric air-fuel ratio.

However, in reality, deviations in the air-fuel ratio occur due to various causes, so it becomes necessary to measure and adjust the air-fuel ratio.

Engine control has become more sophisticated in recent years, especially those using catalysts, which require extremely high precision control because the characteristics of the catalyst are extremely sensitive to the air-fuel ratio.
Therefore, there is a need for highly accurate air-fuel ratio measurements.

However, there was a problem that conventional products could not achieve the required high precision.

In order to measure the air-fuel ratio of exhaust gas as described above, until now, air-fuel ratio meters based on non-dispersive infrared absorption (NDIR) analyzers have often been used.

For example, there is a method in which the concentrations of the three components CO ₂ , CO, and HC are measured using infrared analyzers, and the air-fuel ratio is determined using a calculation formula. However, if the calculations are done manually, immediacy is lost and it is difficult to keep up with continuous air-fuel ratio measurements. It is designed to display the air-fuel ratio output. In addition, a certain ratio of air is mixed into the sampled gas, and CO, HC, _H2 , etc. are oxidized and converted to _CO2 ( _H2O ), creating a nearly linear relationship between _CO2 concentration and air-fuel ratio. This method measures the CO ₂ concentration with an infrared analyzer, converts it into an air-fuel ratio, and displays it.

A method similar to the above is to mix a certain ratio of air into the sampled gas, oxidize CO, HC, H ₂ , etc. and convert it to CO ₂ (H ₂ O), reducing the excess O ₂ concentration and air-fuel ratio to approximately There is also a method that derives a linear relationship, measures the O ₂ concentration, and converts it into an air-fuel ratio and displays it. Further, most O ₂ concentration measurements are usually performed using a magnetic method, but some use an oxygen concentration battery method using an ionic conductor such as zirconia.

In addition, attempts are also known to utilize the fact that the resistance of an oxide semiconductor changes depending on the air-fuel ratio, and measure the resistance to determine the air-fuel ratio. Although this type of product has been reported in the literature, it does not appear to be commercially available yet.

As mentioned above, various types of air-fuel ratio meters have been known in the past, but the accuracy of these air-fuel ratio meters is 3.
It is about 5%.

When the air-fuel ratio measurement range is wide and the air-fuel ratio change range is wide, when minute changes in the air-fuel ratio do not cause noticeable changes in engine characteristics, or when the air-fuel ratio control itself cannot be very precise. In many cases, the above accuracy is sufficient.

However, in response to recent demands for reducing harmful components in exhaust gas, systems that use catalysts to purify harmful components are somewhat different from conventional systems. This is due to the following reasons.

(1) The purification rate of the catalyst changes sensitively even if the air-fuel ratio changes within 1%.

(2) High-precision air-fuel ratio control methods have been developed and put into practice in order to make the catalyst work in a high purification rate range (for example, EFI + three-way catalyst + O ₂ sensor control).

The accuracy of conventional air-fuel ratio meters is insufficient to handle minute changes in air-fuel ratio in these systems. Therefore, even if there is a case where the emissions of harmful components differ significantly due to a slight difference in the air-fuel ratio, the difference is so small that it is less than the accuracy of the air-fuel ratio meter, and the difference in air-fuel ratio In some cases, it has been impossible to effectively detect this phenomenon, which has been a significant hindrance to measurement experiments and analyses.

Regarding these problems, it is not possible to point out the problems with each specific configuration of the conventional air-fuel ratio meter, but the short answer is that the accuracy is insufficient.

As mentioned above, it is considered that it is completely impossible to meet the high demands for accuracy, which is several tens of times higher than that of conventional air-fuel ratio meters, by improving conventional methods.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to realize an air-fuel ratio meter with a high degree of accuracy that could never be achieved with conventional air-fuel ratio meters.

This invention is not based on an improvement on the prior art, but is based on an original idea, and the basic idea is as follows. That is, if the air-fuel ratio of the sampled gas to be measured deviates from the stoichiometric air-fuel ratio, it can be considered that either fuel or oxygen (air) is insufficient.
Therefore, if it is possible to know which gas is deficient and at what rate, it is possible to make the gas at the stoichiometric air-fuel ratio by replenishing the deficient gas. The basic idea of the present invention is to calculate and display the air-fuel ratio of the gas to be measured from the type and mixing rate of the replenished gas.

FIG. 1 is a block diagram for explaining the outline of the configuration of the present invention.

As shown in the figure, the main elements of the invention are:
There are a constant flow rate supply section 1, a reactor 2, an O ₂ sensor 3, a calculation section 4, a supplementary gas control section 5, and an air-fuel ratio display section 6. The constant flow rate supply section 1 takes in a constant flow rate from the gas system to be measured and supplies the gas to the reactor and subsequent parts. The reactor 2 is used to thoroughly mix the gas to be measured and the replenishment gas and promote the reaction to bring the gas to a state close to chemical equilibrium. _O2
Sensor 3 detects whether the gas to be measured and the supplementary gas are either fuel rich (hereinafter simply referred to as rich) or fuel lean (hereinafter simply referred to as lean).
This is a detector for detecting whether

Here, we will add some explanation about the O ₂ sensor. It is known that the resistance of oxide semiconductors and the electromotive force of oxygen concentration batteries suddenly change with the theoretical air twist ratio.
FIG. 2 shows the resistance characteristics of the N-type oxide semiconductor with respect to the air-fuel ratio. Similarly, FIG. 3 shows the characteristics of a P-type oxide semiconductor, and FIG. 4 shows the characteristics of an oxygen concentration battery. In these sensors, the resistance and electromotive force change in proportion to the logarithm of the oxygen partial pressure (log ₁₀ Po ₂ ), and gas that has sufficiently reacted (reached chemical equilibrium) has a stoichiometric air-fuel ratio of log ₁₀ Po ₂ Due to the combination of phenomena in which the resistance and electromotive force suddenly change, the resistance and electromotive force suddenly change at the stoichiometric air-fuel ratio as shown in FIGS. 2 to 4. These sensors whose characteristics change suddenly at the stoichiometric air-fuel ratio are called O ₂ sensors.

The calculation unit 4 has three functions: determining whether the gas is rich or lean based on the O ₂ sensor signal, determining the type and flow rate of the gas to be replenished, and calculating the air-fuel ratio of the gas to be measured. The supplementary gas control section 5 supplies insufficient gas according to the output of the calculation section 4. The air-fuel ratio display section 6 is a section that displays the air-fuel ratio calculated by the calculation section 4.

Now, the outline of the operation shown in FIG. 1 is as follows.
A constant flow rate supply section 1 sucks a constant flow rate of gas from the gas to be measured. If this flow rate fluctuates, it may be given as a variable instead of being given as a constant in the later air-fuel ratio calculating section. Then, a combination of the gas to be measured and the replenishment gas from the replenishment gas control section 5 is introduced into the reactor 2, where they are thoroughly mixed and the reaction is sufficiently promoted. The gas is guided to the O ₂ sensor 3. In the calculation unit 4, the intermediate value between the output on the rich side and the output on the lean side of the O ₂ sensor 3 is set as a reference value, and the O ₂ sensor 3
It is determined whether the output is rich or lean depending on whether the output is larger or smaller than the reference value. In response to the determination result, the replenishment gas control unit 5 gradually increases the amount of oxygen (or air) until it reaches the stoichiometric air-fuel ratio if it is determined that the gas is rich. If it is determined that the fuel is lean, the amount of fuel is gradually increased until the stoichiometric air-fuel ratio is reached. In this way, when the gas in the O ₂ sensor 3 reaches a state close to the stoichiometric air-fuel ratio due to an increase or decrease in oxygen or fuel, the calculation unit 4 calculates the air-fuel ratio and provides it to the air-fuel ratio display unit 6 to display the air-fuel ratio. The fuel ratio display section 6 displays it.

In addition, in the above explanation, we have explained the case where both oxygen and fuel are made variable as the supplementary gas, but there is also a method in which one of the supplementary gases is always flowed at a constant flow rate and only the other gas is made variable. You can also do it. In this case, only one system of flow rate controllers is required, and accordingly, calculations for one system of computing devices are required, which is advantageous in terms of simplifying the device and reducing costs.

Next, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 5 shows the configuration of the embodiment. This device uses a constant flow rate (2
~6 [/min]) gas is sucked. For this purpose, a pump 7, a constant flow control valve 8 and a flow meter 9 are used. Note that a filter 10 is also provided for removing soot.

H ₂ and O ₂ are used as supplementary gases. A method is adopted in which the H ₂ flow rate is a constant value (20 to 60 [cm ³ /min]) and the O ₂ flow rate is varied. A gas cylinder 11, a pressure reducing valve 12, a constant flow control valve 13, and a flow meter 14 are provided to flow H ₂ at a constant flow rate.

In order to vary the O ₂ flow rate, a gas cylinder 15, a pressure reducing valve 16, and a flow rate detection controller 17 (for example, Okura Electric's mass flow controller MFC-1) are provided.

A gas mixture of the gas to be measured and supplementary gas (H ₂ , O ₂ ) is introduced into the precatalyst 18 and reacted. The size of the container for the precatalyst 18 is approximately 10 [cm ² ], and the precatalyst 18 is heated at a temperature suitable for reaction promotion (400 to 900°C).
Heat to [℃]). For this purpose, the temperature detection section 1
9 (for example, a thermocouple), a temperature regulator 20, and a heater 21.

Although combusted exhaust gas is generally supplied as the gas to be measured, in some cases, there is a possibility that unignited air-fuel mixture may be supplied due to an ignition error or the like. In that case, a large amount of heat is generated in the precatalyst 18, so it is necessary to give sufficient consideration to the heat resistance and heat dissipation of the catalyst and the container. Precatalyst 1
The gas that has undergone the reaction in step 8 is supplied to the O ₂ sensor 22. A TiO ₂ sensor is used as the O ₂ sensor 22. Temperature suitable for operation of TiO ₂ sensor: 400 [℃] ~
In order to heat to 900 [℃], temperature detection section 23 (thermocouple), temperature controller 24 (Okura Electric EC-76A04),
A heater 25 is provided.

As shown in FIG _{. 2, the resistance of TiO 2} has a characteristic that the resistance changes suddenly at the stoichiometric air-fuel ratio. Since the resistance change range is extremely wide, about 10 ^3.5 to 10 ^4.5 , a logarithmic conversion type resistance meter 26 (filed as Utility Application No. 1983-69848) was developed and used for this purpose. Reference resistance setting section 27
The reference resistance value is set to a value midway between the resistance on the rich side and the resistance on the lean side. The rich lean determination unit 28 determines that the resistance value of the TiO ₂ sensor 22 is lean when it is higher than the reference resistance value, and determines that it is rich when it is lower.
Then, when it is determined to be rich, the O ₂ flow rate is increased, and conversely, when it is determined to be lean, the O 2 flow rate is increased.
The integrator 29 is operated with a polarity that reduces the O ₂ flow rate. The output of the integrator 29 corresponds to the oxygen flow value fo ₂ . The portion consisting of the logarithmic conversion type resistance meter 26, reference resistance setting section 27, rich lean determining section 28, and integrator 29 is collectively referred to as a first calculation section. Then, the O ₂ flow rate is adjusted via the flow rate detection controller 17 using the output of the first calculation section, that is, the output of the integrator 29. In this case, it is necessary to appropriately select the integral gain. If the integral gain is too high, the flow rate control state becomes oscillatory and the amplitude of the air-fuel ratio increases, causing poor agreement between the average value of the air-fuel ratio and the stoichiometric air-fuel ratio, causing an increase in error. On the other hand, if the gain is made too small, the responsiveness will deteriorate, so the gain should be set so as to provide high accuracy and quick response as much as possible.

This optimum gain is affected by the amount, temperature, and properties of the precatalyst, the gas flow rate, and the responsiveness of the flow rate detection controller, so it is somewhat difficult to specify it using a simple formula.

Now, if the air-fuel ratio of the gas reaching the stoichiometric air-fuel ratio detection sensor 22 such as TiO ₂ is made to match the stoichiometric air-fuel ratio by adjusting the gas amount, the relationship between the flow rate and the gas to be measured at that time is calculated and displayed. There is a need to. Air-fuel ratio calculation unit 30 (second calculation unit) that calculates for this purpose
and an air-fuel ratio display section 31 that displays the results.

Next, the relationship between flow rate and air-fuel ratio will be explained.

The air-fuel ratio A/F of the gas to be measured is calculated from the stoichiometric air-fuel ratio (A/F).
F) Define excess air ratio λ by normalizing with _stpich .

λ=A/F/(A/F) _stpich ......(1) The excess oxygen concentration O _2ex at this time is O _2ex = 0.21 (1-1/λ)......(2) However, in the above equation, 0.21 indicates the oxygen concentration in the air.

If the sampling gas amount is F _s , the surplus oxygen flow rate is
fo _2ex is fo _2ex = F _s・O _2ex …………(3) On the other hand, let f _H2 be the flow rate of the mixed hydrogen gas, and fo ₂ be the flow rate of the mixed oxygen gas.

From the condition that the air-fuel ratio is at the stoichiometric air-fuel ratio, fo _2ex + fo ₂ = f _H2 / ν _H2 ………(4) ν _i = (f _i / fo ₂ ) _stpich ………(5) However, f _i : arbitrary component Fuel flow rate ν _i : Ratio of fuel flow rate that achieves stoichiometric ratio to O ₂ flow rate From formula (4) fo _2ex = f _H2 /ν _H2 −fo ₂ ......(6) From formula (3) O _2ex ＝fo _2ex ／F _s ……(7) ＝f _H2 ／υ _H2 −fo ₂ ／F _s ……(8) From formula (2), O _2ex ／0.21=1−1/λ ……(9 ) 1/λ=1−O _{2 ex} /0.21 ………(10) λ=1/1−O ₂ ex/0.21 ………(11) Substituting formula (8) into formula (11), λ=1 /1−(f _H2 /υ _H2 −fo ₂ )/0.21F _S ………
(12) From equation (1), A/F=λ・(A/F) _stpich ......(13) Substituting equation (12) into equation (13), A/F=(A/F) _stpich / 1−f _H2 /υ _H2 −fo ₂ /
0.21F _S (14) When H ₂ is used as fuel, ν _H2 =2. Similarly, when CO is used, ν _CO =2.

In a system that controls mainly the stoichiometric air-fuel ratio, the deviation from the stoichiometric air-fuel ratio is often within about ±2%. According to this assumption, the second term in the denominator of equation (14) only needs to be variable within the range of ±0.02. Therefore
The variation range of fo ₂ /0.21F _s may be about 0.04. Assuming that the accuracy of fo ₂ flow rate measurement is 2.5%,
The accuracy of A/F is 0.04×2.5 [%] = 0.1 [%], which means that extremely high precision measurement can be performed. This is a good value that fully satisfies the recent demands for high precision measurement.

In addition, in equations (4) to (14), the equations are shown for the case where H ₂ is used as the replenishing fuel and 100 [%] O ₂ is used as the oxidizing agent, but fuel of arbitrary composition and arbitrary concentration When using O ₂ of , just convert as shown in the following equation.

From equation (12), λ=1/1−fi/υi−C _X・f _OX /0.21F _S ………(15
) However, C _x : Oxygen concentration in the replenishing oxidizing gas fo _x : Flow rate of the replenishing oxidizing gas From equation (14), A/F=(A/F) _stpich /1-fi/υi-C _X・f
_OX /0.21F _S Next, FIG. 7 shows a part of the embodiment shown in FIG. 5 in detail.

The TiO ₂ sensor 22 is connected to a logarithmic conversion resistance meter 26 . As mentioned above, the resistance of the TiO ₂ sensor changes at a large rate of 10 ^3.5 to 10 ^4.5 times as the air-fuel ratio changes, so a logarithmic conversion type sensor is used to measure the resistance continuously and accurately without changing the range. A resistance meter 26 is used. Figure 6 shows the resistance to be measured by the logarithmic conversion type resistance meter 26 (resistance of the TiO ₂ sensor).
This shows the relationship between the output voltage and the output voltage, and shows the characteristics when the standard resistance is set to 10 ⁵ [Ω] and the gain is set to 1 [V/decode]. Note that since the TiO ₂ sensor 22 is non-polar, the connection direction is irrelevant. The output of the logarithmic conversion type resistance meter 26 is the positive (+) of the comparator C.
The negative (-) input of the comparator C receives the output of the inverting potentiometer _P1 . +10V for its reversing potentiometer P ₁
is input, and the coefficient a is set so that the output of _P1 becomes an intermediate value between the output voltage of the logarithmic conversion resistance meter 26 when the TiO ₂ sensor atmosphere is rich and the output voltage when it is lean. It is assumed that the above intermediate value is a negative value, but if it is a positive value, P ₁
It is necessary to change the +10V input to -10V.

By connecting in this manner, comparator C28 is turned ON and relay R is turned ON when the voltage of the positive input is higher with respect to the negative input, that is, when the atmosphere around the TiO ₂ sensor is lean. vice versa,
When rich, comparator C turns OFF,
Turn off relay R.

Also, -10 [V] is a potentiometer with an inverting amplifier.
_P2 is connected to the input of P2, and its output is connected to the normally open (NO) terminal of the relay and the -1 times input of adder A. The output of adder A is the normally closed relay (NC).
Connect to the terminal. Potentiometer with inverting amplifier
The set value b of P ₂ determines the integral gain and is a very important value as mentioned above, so it must be adjusted so that the balance between stability, precision, and responsiveness is just right. The role of the adder A is to also increase the output of the integrator I when the fuel is rich, thereby increasing the O ₂ flow rate via the flow rate detection controller 17.
The reason for using -1 as the gain is to equalize the rate when decreasing and increasing the rate, but if it is necessary to control at different rates, adder A can be replaced with a potentiometer with an inverting amplifier. You can do this by replacing it with P.

The common terminal (COM) of the relay is also -1 of the integrator I.
Connect to input. The output of the integrator I is connected to a flow rate detection controller 17. This flow rate detection controller 17 is adapted to operate with a positive voltage input.

The output of the integrator I corresponds to the oxygen flow rate value fo ₂ and is input to the air-fuel ratio calculation unit 30. Air fuel ratio A/F
is calculated using equation (14). All values except fo ₂ are given as constants.

If f _H2 or F fluctuates, do not give them as constants, but use them as variables together with fo ₂ in calculation unit 3.
Must be entered as 0. The calculated value of the air-fuel ratio A/F is led to the air-fuel ratio display section 31 and displayed.

In the example, a variable resistance oxide was used as the O ₂ sensor 22, and a TiO ₂ sensor was given as an example, but other N-type oxide semiconductors such as Nb ₂ Os and CeO ₂ sensors can also be used in the same way as TiO ₂ . .

In addition, in the case of P-type oxide semiconductors such as NiO and CoO, the characteristics are opposite to those of N-type oxide semiconductors as shown in Figure 3, so the resistance is between the resistance on the rich side and the resistance on the lean side. is set as a reference resistance, and when it is lower than the reference resistance, it is judged as lean, and when it is higher, it is judged as rich.

The O ₂ sensor may be of the variable resistance type or of the oxygen concentration battery type (for example, zirconia, etc.).
Its air-fuel ratio versus electromotive force characteristics are as shown in FIG. When measuring the electromotive force, a DC amplifier such as a measurement amplifier is used instead of the logarithmic conversion type resistance meter 26. Also, in the case of this type of sensor, there is no reference resistance, so the value between the electromotive force on the lean side and the electromotive force on the rich side is set as the reference voltage, and if the electromotive force is lower than the reference voltage, it is lean. If it is high, it is judged as rich.

Although the oxidizing gas side is selected as the gas whose flow rate is to be controlled, the oxidizing gas flow rate may be kept constant by making the fuel flow rate variable. In this case, it is natural that the flow rate must be controlled to increase when determining lean and to decrease when determining rich.

In addition, in the embodiment, the precatalyst 18 and the TiO ₂ sensor 2
In addition to this, it is also effective to incorporate the precatalyst 18 into the housing of the TiO ₂ sensor. For example, chlorides of noble metals such as platinum (Pt), rhodium (Rh), palladium (Pd), etc. are supported on alumina as a carrier, singly or in combination, and then fired.
-3 [g] This is a method in which the catalyst is placed around the sensor to serve as a pre-catalyst. This method reduces the delay time of gas in the precatalyst section, and also reduces the amount of gas that reacts even when unignited air-fuel mixture is inhaled, thereby reducing the absolute amount of heat generated. It is recognized that there are merits such as improved safety and improved safety.

In the example, an example was shown in which a precatalyst was used to promote the reaction of the mixed gas, but if the response speed is important even at the cost of some accuracy, TiO ₂
It is also effective to increase the reaction capacity by increasing the amount of catalyst supported on the sensor itself or added by other methods, and omitting the pre-catalyst.

Further, as another method for controlling the flow rate, it is possible to control both the oxidizing gas and the fuel gas, setting the excess gas to zero, and allowing only the insufficient gas to flow. This method has the advantage of minimizing the amount of supplementary gas consumed.

When it is necessary to precisely control the temperature of the TiO ₂ sensor O, a thermocouple-embedded TiO ₂ sensor may be used, but in that case, avoid interference between the resistance measurement system and the temperature measurement system. Therefore, the thermocouple can be insulated by passing through an automatic cold junction compensator, a measurement amplifier, or another isolation amplifier, and then led to the temperature controller.

In addition, in order to further reduce the cost compared to this example, instead of converting the resistance value into voltage using a logarithmic conversion type resistance measuring device, the TiO ₂ sensor could be connected to a constant voltage source via a series resistor. There is also a method of connecting it between ground and converting it to a voltage using a voltage division method, or a method of connecting it to a constant current source and converting it to a voltage proportional to the resistance. With these methods, it is sufficient to appropriately select the series resistance, constant voltage source value, and constant current value so that the determination can be made at a resistance intermediate between the resistance on the rich side and the resistance on the lean side.

Also, although it was generally explained as an air-fuel ratio meter, it may also be used as an excess air ratio meter, and instead of using formula (14), (12)
or just use equation (15) instead of equation (16).

Next, actual measurement results of the air-fuel ratio meter of the present invention will be explained with reference to FIGS. 8 to 11.

FIG. 8 is a block diagram schematically showing a combustion device (hereinafter referred to as the combustion device) used for evaluating the air-fuel ratio meter of the present invention (referred to as the present device in the figure).
C ₄ H ₁₀ and air were mixed and led to the λ measurement system of the combustion device through a flow rate ratio calculation device, and on the other hand, to the present device through an O ₂ sensor to measure λ.

When the λ of the combustion device was changed stepwise by 0.002 every 3 minutes, this device displayed the change in λ almost faithfully, as shown in FIG.

In addition, by changing λ as shown in Fig. 10, the delay time {the average value of the delay time from when the O ₂ sensor touches the fuel to the air mixture until the air-fuel ratio is detected, on the rich side and the lean side. (In the O ₂ sensor, the delay time on the rich side and the lean side is asymmetric, and the stoichiometric air-fuel ratio cannot be obtained with the average value. Therefore, it is necessary to add some correction)} of λ The results of comparing the changes are shown in Figure 11a. In the same figure, the circles have been changed from the rich side to the lean side (TR-
In the case L), the square mark indicates a change from the lean side to the rich side (TL-R), and the star mark indicates the case in between.

Further, FIG. 11b shows the λ value displayed by the present device with respect to λ of the fuel system when the skip amount shown in FIG. 10 is changed.

As is clear from Figures 11a and b, the measured values are very close to the diagonal line (dashed line) in both figures, so
It can be seen that the measured and displayed values of this device are extremely accurate.

Incidentally, a device with such high precision has not been provided in the past.

According to the present invention described in detail above, the air-fuel ratio of exhaust gas from an automobile engine or other combustion device can be measured with precision that cannot be obtained with a conventional air-fuel ratio meter.

[Brief explanation of drawings]

FIG. 1 is a block diagram for explaining the outline of the present invention, FIG. 2 is a diagram showing the characteristics of an N-type oxide semiconductor, FIG. 3 is a diagram showing the characteristics of a P-type oxide semiconductor,
FIG. 4 is a diagram showing the characteristics of an oxygen concentration battery, FIG. 5 is a diagram for explaining an embodiment of the present invention, FIG. 6 is a diagram showing the characteristics of a logarithmic conversion type resistance meter, and FIG. Figure 8 is a block diagram of the combustion device used for evaluation of the air-fuel ratio meter of the present invention; Figure 9 is a diagram showing a part of the figure in detail;
The figure shows the followability of the air-fuel ratio meter of the present invention when λ is changed stepwise. Figure 10 shows the changing waveform of λ during measurement. Figures 11a and b show changes in delay time and skip amount, respectively. FIG. 3 is a diagram showing the state of the λ display of the air-fuel ratio meter of the present invention when 1... Constant flow rate supply section, 2... Reactor, 3...
O ₂ sensor, 4... Calculation unit, 5... Replenishment gas control unit, 6... Air-fuel ratio display unit, 7... Pump, 8, 1
3... constant flow control valve, 9, 14... flow meter, 10
...Filter, 11, 15...Gas cylinder, 1
2, 16... pressure reducing valve, 17... flow rate detection controller,
18... Pre-catalyst, 19, 23... Temperature detection section,
20, 24... Temperature controller, 21, 25... Heater, 22... O ₂ sensor, 26... Logarithmic conversion type resistance meter, 27... Reference resistance setting section, 28... Rich Lean judgment section, 29... Integrator, 30...Air-fuel ratio calculation unit, 31...Air-fuel ratio display unit, _P1 , _P2 ...Potentiometer with inverting amplifier, C...Comparator, A...Adder, I...Integrator, R...Relay.

Claims (1)

[Claims] 1. An O ₂ sensor for detecting in which direction the air-fuel ratio of a mixed gas obtained by adding supplementary gas to the gas to be measured deviates from the stoichiometric air-fuel ratio, and an O 2 sensor based on the output from the O ₂ sensor. a first calculation unit that calculates the flow rate of gas to be replenished in order to bring the air-fuel ratio of the mixed gas to the stoichiometric air-fuel ratio; a control unit that controls the flow rate of gas to be replenished based on the calculation result; An ultra-precision air-fuel ratio meter comprising: a second calculation section that calculates the air-fuel ratio of a gas to be measured or an output corresponding thereto based on the above information; and a display section that displays the output of the second calculation section. 2 An O ₂ sensor is used to detect which way the air-fuel ratio of the mixed gas, which is the gas to be measured and supplementary gas is added, deviates from the stoichiometric air _- fuel ratio. a first calculation unit that calculates the flow rate of gas to be replenished in order to make the air-fuel ratio the stoichiometric air-fuel ratio; a control unit that controls the flow rate of gas to be replenished based on the calculation result; In an ultra-precision air-fuel ratio meter that is equipped with a second calculation section that calculates the air-fuel ratio of the gas to be measured or an output corresponding thereto, and a display section that displays the output of the second calculation section, supplementary gas is added to the gas to be measured. This ultra-precision air-fuel ratio meter is characterized by being equipped with a pre-catalyst to promote the reaction of the mixed gas.