JPS6088834A - Air-fuel ratio controller for internal-combustion engine - Google Patents

Abstract

PURPOSE:To surely prevent an engine from fluctuating in rotation or from stalling, by providing a control circuit with a control means for forcibly returning an air-fuel ratio compensation value to a prescribed value if the compensation value has reached a predetermined thickness limit. CONSTITUTION:An air-fuel ratio controller comprises an exhaust sensor 10 provided in an exhaust system, a control circuit 2, which determines a compensation value for the air-fuel ratio in a carburetor on the basis of the output signal of the exhaust sensor 10, and a control valve 6 for regulating the flow rate of fuel. The control circuit 2 includes a control means 26 for forcibly returning the air-fuel ratio compensation value to a prescribed value if the compensation value has reached a prescribed thickness limit. As a result, the air-fuel ratio is kept from becoming too high or low, to surely prevent an engine from fluctuating in rotation or from stalling.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an air-fuel ratio control device for an internal combustion engine, and in particular,
The present invention relates to an air-fuel ratio control device for an internal combustion engine that avoids engine trouble caused by erroneously inputting information on a value richer than the actual air-fuel ratio to a feedbank control method.

[Technical Background of the Invention] Recently, exhaust gas components (for example, C01) have been added to the engine exhaust system.
An exhaust sensor that detects the concentration of CQ2, HC, NOx, 02, etc.) is provided, and a control signal based on a comparison signal between the output of the exhaust sensor and a set value (for example, a proportional signal or integral signal of the comparison signal or The air-fuel ratio of the intake air-fuel mixture converges to a preset value by controlling the fuel supply amount and air supply amount of the fuel metering device (carburizer, fuel injection device, etc.) using a signal that is the sum of these two signals, etc. An air-fuel ratio control device using a feedbank control method has been proposed.

[Problems with the Background Art] However, in an internal combustion engine that uses an exhaust sensor signal as a control signal to control the air-fuel ratio of the carburetor, for example, unburned gas may solidify at some point and adhere to the area around the exhaust sensor. or a failure of one part of the control system,
Due to various causes such as an error in the air-fuel ratio due to an abnormal temperature or malfunction, information with a value that is darker than the actual air-fuel ratio may be erroneously input. When rich value information is input, the feedbank control method changes the air-fuel ratio correction value to the lean side in order to make the air-fuel ratio leaner, and as a result, the air-fuel ratio, which is not actually rich, is diluted. However, there are disadvantages in that the engine speed becomes unstable and engine troubles such as the engine sometimes stops. On the other hand, if information with a low value is input, although this is the opposite of the above, there is a problem in that the same engine trouble as described above occurs due to the excessively rich air-fuel ratio.

[Object of the Invention] Therefore, the object of the present invention is to eliminate the above-mentioned inconvenience (by forcibly returning the air-fuel ratio correction value to prevent the air-fuel ratio from becoming too rich or too lean based on the above-mentioned erroneous information. Another object of the present invention is to realize an air-fuel ratio control device for an internal combustion engine that can reliably prevent engine rotation fluctuations or engine stalls caused by variations in the air-fuel ratio.

[Configuration of the Invention] To achieve this object, the present invention includes an exhaust sensor provided in an exhaust system, a control circuit unit that determines a correction value for the air-fuel ratio of a carburetor based on an input signal from the exhaust sensor, In an air-fuel ratio control device for an internal combustion engine, which comprises a control valve that adjusts a fuel flow rate based on a control signal from the control circuit, the control circuit has a constant value when the air-fuel ratio correction value reaches a predetermined concentration limit setting value. The present invention is characterized in that it includes a control means for forcibly returning to the corrected value.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described in detail and specifically based on the drawings.

FIG. 1 shows a schematic system diagram of the present invention. Reference numeral 2 denotes a control circuit section forming the central part for forcibly controlling the air-fuel ratio correction value of the carburetor 4. The control circuit section 2 is shown in FIG. It is configured to operate according to the flowchart 1- shown in FIG.

A control valve 6 adjusts the flow rate of fuel flowing into the intake passage 8, and the control valve 6 operates based on a control signal from the control circuit section 2. Reference numeral 10 denotes an 02 sensor which is a type of exhaust sensor provided in the exhaust passage 12. The O2 sensor 10 has a function of detecting the proportion of O2 contained in the exhaust gas, and the information is sent to the control circuit section 2. sent to. Reference numeral 14 denotes a rotational speed detection sensor that detects the engine rotational state of the internal combustion engine 16, and the information detected here is transmitted to the control circuit section 2. 18 is a throttle valve; 20 is a throttle valve switch for controlling the opening degree of the throttle valve 18; the throttle valve switch 2o is controlled by a control signal from the control circuit section 2;

FIG. 2 is a block diagram of the control circuit unit 2. The control circuit unit 2 includes a comparison circuit 22 that compares the 02 sensor signal transmitted from the 02 sensor 1o with a reference value, and a comparison circuit 22 that inputs information from multiple locations. It consists of an input circuit 24, a computer 26 that judges the input input from the input circuit 24, and a drive circuit 28 that sends a control signal to the control valve 6 based on the judgment of the computer 26, as described above and shown in FIG. It is configured to operate according to the flowchart. 3o is an accelerator switch.

FIG. 3 shows an enlarged cross-sectional view of the essential parts of the carburetor for adjusting the fuel flow rate, and the control valve 6 is composed of a driving section 32, a valve body 34, a valve hole 36, and the like. In addition, with codes other than the above,
38 is an air bleed passage for slow system air-fuel ratio adjustment; 4o is an air bleed passage for main system air-fuel ratio adjustment; 42 is a slow air bleed passage; 44 is a main air bleed passage;
6 is a choke valve, 48 is a float chamber, 5o is a slow fuel passage, 52 is a main fuel passage, 54 is an idle, 56 is a bypass, and 58 is a main nozzle.

Since the present invention is configured as described above, when information having a higher value than the actual air-fuel ratio is input, it operates as follows.

Despite the fact that the air-fuel ratio is not rich, due to the various causes mentioned above, the 02 sensor signal indicating that the air-fuel ratio is rich is input to the control circuit section 2, and the input state is changed to the fifth sensor signal.
(A) in the diagram or (B) with a voice that leans toward the rich side,
At the time of (C), in the feedbank control method, the air-fuel ratio correction signal changes to the lean side by an operation based on an integral constant in order to reduce the air-fuel ratio that is erroneously detected as rich.

At this time, in the conventional feed bank control method, when the 02 sensor input is in the states shown in Fig. 5 (b) and (c), the air-fuel ratio correction signal that has changed to the lean side will stick to the lean side as shown in Fig. 6. It will remain.

If this continues for a long period of time, the air-fuel ratio in the intake passage of the carburetor, which is not actually rich, will remain diluted due to the air-fuel ratio correction signal that remains biased toward the lean side.

As a result, the engine speed fluctuated and the engine stopped due to the leaner air-fuel ratio.

On the other hand, according to the present invention, when the air-fuel ratio correction signal reaches the upper limit set value on the lean side, the closed-loop control becomes open-loop control, and as shown in FIGS. The correction value is returned to the target value. For this reason, the air-fuel ratio temporarily becomes richer, and dilution is avoided. When the correction value is returned to the above-mentioned correction value, the closed-loop feedback control is returned to, and the above-described feedback control is performed using the 02 sensor signal. Then, the above-described operation is repeated (see the flowchart in FIG. 4). Incidentally, if the upper limit set value of the air-fuel ratio correction value is changed by receiving a signal from the idle switch and the rotation speed sensing sensor 14, better stability can be obtained.

Next, when information with a value thinner than the actual air-fuel ratio is input, the air-fuel ratio correction signal changes to the rich side, but the effect of forcing this back to the corrected value is similar to the effect described above. .

[Effects of the Invention] As is clear from the above detailed description, according to the configuration of the present invention, information on values that are more concentrated than the actual air-fuel ratio is input, and the air-fuel ratio correction value tends to lean toward the lean side or rich side. When this occurs, the air-fuel ratio correction value is temporarily changed from closed-loop control to open-loop control and the air-fuel ratio correction value is forcibly returned to the correction value at an arbitrary speed, so the air-fuel ratio of the air-fuel mixture in the carburetor temporarily becomes richer or leaner. Become. This can prevent the air-fuel ratio from becoming too dark or too dark based on the above-mentioned incorrect information.
It is possible to reliably prevent engine troubles such as engine rotational fluctuations or engine stalls caused by the air-fuel ratio becoming too concentrated. After that, feedback control is performed again using the exhaust sensor signal, and when the air-fuel ratio reaches the lean side or the rich side again, the above operation can be repeated, which is an extremely beneficial effect.

[Brief explanation of drawings]

1 to 5 show an embodiment of the air-fuel ratio control device for an internal combustion engine according to the present invention, and FIG. 1 is a schematic system diagram, and FIG.
3 is an enlarged sectional view of the main part of the carburetor, FIG. 4 is a flowchart, and FIGS. 5(A) to 5(C) are relationship diagrams between the 02 sensor input and the air-fuel ratio correction signal. FIG. 6 is a diagram showing the relationship between the 02 sensor input and the air-fuel ratio correction signal in the conventional device. In the figure, 2 is a control circuit section, 4 is a carburetor, 6 is a control valve, and 10
is the 02 sensor, and 12 is the exhaust passage. Figure 1 jli2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1. An exhaust sensor provided in the exhaust system, a control circuit unit that determines a correction value for the air-fuel ratio of the carburetor based on an input signal from the exhaust sensor, and a control signal from the control circuit unit. In an air-fuel ratio control device for an internal combustion engine, the air-fuel ratio control device comprises a control valve that adjusts the fuel flow rate based on the control circuit, and the air-fuel ratio correction value is controlled to be forcibly returned to a certain correction value when it reaches a predetermined concentration limit setting value. 1. An air-fuel ratio control device for an internal combustion engine, comprising: means. 2. The air-fuel ratio control device for an internal combustion engine according to claim 1, wherein the predetermined concentration limit setting value is a limit setting value set based on an idling state and an engine rotation speed.