JPH0151735B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio controller, and particularly to an air-fuel ratio controller suitable for use in combustors and internal combustion engines.

Conventionally, as an air-fuel ratio controller for controlling the air-fuel mixture to an excess oxygen state, a controller using an oxygen pump type oxygen concentration detector disclosed in JP-A-53-116896 etc. has been disclosed. The detection lag is large;
It has the disadvantage of reduced controllability.

The purpose of the present invention is to control the air-fuel ratio of the combustor,
An air-fuel ratio that eliminates the above drawbacks by setting the current flowing to the oxygen concentration detector according to the operating state and controlling the amount of air or fuel so that the voltage representing the oxygen concentration becomes the set voltage determined by the previously set current. It is in providing the controller.

In the present invention, when the operating state shifts to a different air-fuel ratio range, a set current corresponding to each air-fuel ratio range is passed through the oxygen concentration detector, and the output voltage representing the oxygen concentration becomes the set voltage determined by the previous set current. This improves responsiveness by controlling the amount of air or fuel.

In FIG. 1, a combustor 1 is an internal combustion engine. It may also be a boiler, stove, etc. Air amount in combustor 1,
Controllers 2, 3 are provided for controlling the amount of fuel.

The controller 2 is, for example, a throttle valve, and the controller 3 is a fuel injection valve. A concentration detector 5 is provided in the exhaust pipe 4 of the combustor 1 . The detector 5 is composed of an orifice 7 which is a diffusion resistor, a chamber 6, and an electrolyte 8. The orifice 7 may be porous. The electrolyte 8 is an oxygen ion conductive substance, for example ZrO ₂ -Y ₂ O ₃
It is a mixture of Electrodes on both sides of the electrolyte 8 are connected to a controller 9. Controller 9 causes an arbitrary current I to flow through electrolyte 8 .
The structure is such that oxygen in the chamber 6 is pumped out by this current I. controller 9
A signal from the detector 10 indicating the aperture opening degree θ is inputted to the . This may be any other signal such as an accelerator pedal as long as it corresponds to the load. In addition, combustor 1
A signal from a sensor 11 indicating the state of the engine, for example, temperature, rotation speed, etc., is input. Furthermore, current detection means 12 and voltage detection means 13 are provided at the positions shown in the figure.

The operation of the above configuration is as follows. The air/fuel ratio A/F of the combustor 1 is set as shown in FIG. 2 with respect to the load, for example, with respect to the throttle valve opening θ. This depends on the characteristics of the combustor 1. In FIG. 2, in a region where A/F is smaller than curve D, there is a state of oxygen deficiency, and the θ signal of the controller 9 is input to set I=0. In the oxygen-deficient region where A/F is larger than the D curve, the second
A current of Ic shown in the figure is applied. Here, Ic and the oxygen concentration in the exhaust gas (this is a function of A/F) are as shown in Figure 3. If you want to set the _O2 in the exhaust to %, then to Ic ₁ ,
When O ₂ is set to 4%, the current is controlled to be Ic ₂ . When Ic is set to ₁ , O ₂ in the exhaust is 2
%, _O2 in chamber 4 increases and V drops to _V1 . Also, O ₂ in the exhaust gas is 2
%, the O ₂ in the chamber 6 decreases and V increases to V ₂ . Therefore, V−V ₀
>0, the air-fuel ratio is controlled to the set air-fuel ratio by controlling the combustors 2 and 3 to increase the air-fuel ratio, and when V-V ₀ <0, to decrease the air-fuel ratio. Can be adjusted. In the case of an internal combustion engine, if the fuel amount is adjusted by the combustor 3, the shaft torque will vary depending on the fuel amount, so the air amount by the combustor 2
It is desirable to adjust the

When changing the load on the combustor 1, for example, when changing suddenly from state A to state B in FIG. Since the fuel ratio fluctuates, combustor 2,
3 is controlled by the controller 9 so that the air amount G _A and the fuel amount G _F become G _A = (A/F) G _F ... (1) G _F = f (θ) ... (2) Program controlled. In this way, approximately
A/F is controlled to the set value. However, sufficient control accuracy cannot be obtained due to changes in the combustors 2 and 3 over time. At this time, when the current is changed from Ic ₁ to Ic ₂ as shown in FIG. 4, O ₂ in the exhaust gas is
remains at 2%, so the elapsed time t
On the other hand, V temporarily increases rapidly. Thereafter, through the program control described above, _O2 approaches 4% and V approaches _V0 . At this time, when the controller 2 is adjusted based on the signal of V, since V>V ₀ , the air-fuel ratio is over-adjusted to become large. In addition to the program control G _A , a correction amount ΔG _A based on the deviation of V is added, so _the A/
F becomes larger than the set value. Conversely, when moving from point C to point A, I decreases from Ic ₂ to Ic ₁ , so O ₂ in the chamber 6 increases and V decreases.
The correction amount -ΔG _A based on this deviation of V is used so that the A/F becomes smaller than the set value. In order to avoid these problems, in Fig. 3, V ₀ is
Varies depending on IC. FIG. 5 shows the above-mentioned flowchart. This is implemented by a microprocessor in the controller 9, and the signal a operates the controller 3, and the signal b operates the controller 2. In block 102 of FIG. 5, Ic is calculated according to θ. This relationship is shown at the bottom of Figure 2. This relationship has been input into the storage device of the controller 9 in advance. If Ic=0 in block 103, for example, when the combustor 1 is operated with insufficient oxygen during startup, warm-up, output range, etc., in block 104 G _A is determined by the program. The program has been input into the storage device in advance. Block 105 determines V ₀ for Ic. this is,
For example, V ₀ with respect to Ic can be determined by inputting the relationship shown in FIG. 6 into the storage device in advance. Block 10
In step 6, ΔG _A is determined according to the value of V, and G _A is corrected. G _A modified in block 107 is transferred to controller 2.
Output to. Here, as shown in Figure 3,
Since the change in V with respect to the change in O ₂ is step-like, it is important to determine ΔG _A by an integral operation to prevent hunting. It is also possible to store ΔG _A in a predetermined location in block 108, create a table of ΔG _A versus θ, as shown in FIG. 7, and use this table to correct G _A. The relationship between Ic and _V0 shown in FIG. 6 may need to be changed depending on the temperature. As shown in Figure 3,
When the state of Ic ₁ is O ₂ or excess, V has a lower limit value V ₁ and an upper limit value V ₂ . From this V ₁ and V ₂ , V ₀ = (V ₁ +
V ₀ can be set as follows: V ₂ )/2.
Also, find the resistance r=V ₁ /Ic ₁ of the electrolyte 8, and find V ₀ =
_V0 can also be set as rI+(0.01-0.6)V. In this way, if Ic increases,
Since the set voltage V ₀ is changed according to Ic so that V ₀ increases, it is possible to prevent fluctuations in the air-fuel ratio when Ic changes and prevent a decrease in controllability.

According to the present invention, it is possible to prevent the air-fuel ratio from fluctuating when the air-fuel ratio setting value is changed, so that it is possible to prevent the controllability of the air-fuel ratio controller from deteriorating.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIGS. 2 to 7 are schematic diagrams for explaining the principle of operation. DESCRIPTION OF SYMBOLS 1...Combustor, 2...Controller, 3...Controller, 5...Concentration detector, 9...Controller.

Claims (1)

[Claims] 1. An oxygen concentration detector that transports oxygen in the chamber through an oxygen ion conductive solid electrolyte using an electric current, and a set current that changes depending on the state of the combustor is passed through the oxygen concentration detector to measure the oxygen concentration. An air-fuel ratio controller having a controller that adjusts an air or fuel amount controller so that the voltage expressed becomes a set voltage, the air-fuel ratio control being characterized in that the set voltage is changed in accordance with the set current. vessel.