JPS5823967Y2 - Air-fuel ratio correction control device for internal combustion engines - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an air-fuel ratio correction control device that includes an air-fuel ratio feedback control device that detects the oxygen concentration in exhaust gas of an internal combustion engine and corrects and controls the air-fuel ratio.

When supplying a mixture to the combustion system of an internal combustion engine, for example, E, F, I (Electronic Fuel
Electronic control means such as njection) are widely used.

This electronic control means operates in an open loop to bring the air-fuel ratio close to the theoretical value by inputting various information such as engine speed, intake air flow rate, and water temperature.

However, it is difficult to bring the air-fuel ratio close to the theoretical value with high precision using this open-loop method alone, so in recent years, methods have been developed to directly detect the oxygen concentration in the exhaust gas and successively feed it back to the intake system in order to achieve the stoichiometric air-fuel ratio. We are trying to

The means for directly detecting the oxygen concentration in the exhaust gas is called an 02 sensor, and the circuit that corrects and controls the air-fuel ratio based on the output of the 02 sensor is called an air-fuel ratio feedback control device.

With the introduction of this air-fuel ratio feedback control device, the air-fuel ratio can now be brought close to the theoretical value with high precision.

However, depending on the operating conditions of the internal combustion engine, it may be advantageous to stop the air-fuel ratio feedback control and supply a mixture having another specific air-fuel ratio.

Then, if the air-fuel mixture having the specific air-fuel ratio is not being supplied under the corresponding specific operating conditions, it is better to issue a warning or to correct the air-fuel ratio by the open loop.

Therefore, the purpose of the present invention is to detect that the internal combustion engine is under a specific operating condition and stop the air-fuel ratio feedback control device, and check whether the air-fuel mixture is at a corresponding specific air-fuel ratio under the specific operating condition. It is an object of the present invention to propose an air-fuel ratio correction control device for an internal combustion engine, which is equipped with a monitoring circuit that can determine whether the open-loop air-fuel ratio control device is open-loop, and can apply a warning or a predetermined correction to the open-loop air-fuel ratio control device based on the determination result.

In accordance with the above object, the present invention has a gate circuit which inputs the output of a sensor that detects a specific operating condition and the output of the 02 sensor, and adds a monitoring circuit consisting of the gate circuit to the air-fuel ratio correction control device. It is characterized by:

The present invention will be explained below according to the drawings.

FIG. 1 is a block diagram showing a general air-fuel ratio correction control device to which the present invention is applied.

In the figure, reference numeral 11 denotes a combustion system within the internal combustion engine, and by injecting an appropriate amount of fuel from a fuel injection valve 12, an air-fuel mixture close to the stoichiometric air-fuel ratio (λ=1) is supplied to the combustion system 11.

Control to inject an appropriate amount of fuel from the fuel injection valve 12 is basically performed by a basic air-fuel ratio calculation circuit 13, which receives control information from various sensors 14, such as engine speed, water temperature, intake air flow rate, etc. A predetermined calculation is performed on the input.

However, since it is difficult to sufficiently pursue the stoichiometric air-fuel ratio with this alone, the oxygen concentration contained in the exhaust gas from the combustion system 11 is directly monitored by the 02 sensor 15, and the monitoring results are sent to the air-fuel ratio feedback circuit 16. The signal is fed back to a correction means such as the adder 17 via the .

On the other hand, in a catalyst device using a so-called three-way catalyst whose purpose is to purify exhaust gas, the exhaust gas purification rate changes variously with respect to the air-fuel ratio.

Moreover, the manner of change is different for each of the three different gas components.

This situation is shown in FIG. 2, in which the horizontal axis represents the excess air ratio λ and the vertical axis represents the purification rate.

λ21 indicates that there is an amount of air necessary to completely burn a certain amount of fuel; when λ>1, there is an excess of air, and when λ<1, there is an excess of fuel.

The higher the purification rate, the better the purification.

In the figure, the solid line shows the characteristics of nitrogen oxides NOx, the dotted line shows the characteristics of hydrocarbon HC, and the dashed line shows the characteristics of carbon monoxide CO. Regarding HC and CO, the higher the amount of oxygen, the better.

(λ〉1) The purification rate is high.On the other hand, regarding NOx, purification is a reduction effect, so the lower the amount of oxygen, the lower the amount of oxygen (λ〈1)
The purification rate will be higher.

Therefore, in order to purify these most efficiently, approximately λ=1
It must be set within ±(1φ), and a value of λ within the range of two dashed double-dashed lines in the figure is appropriate.

By the way, when the internal combustion engine is under a specific operating condition, for example, when idling, there is no need to set the air-fuel ratio of the air-fuel mixture to a state near λ=1 in FIG. 2.

This is because during idle time, the internal combustion engine does not emit NOx, so only the purification of HC and CO needs to be considered.

Therefore, when idling, the air-fuel ratio feedback control is stopped and λ
>1 side, that is, lean and smooth.

When the broken internal combustion engine is under other specific operating conditions, such as high load and high rotation, there is no need to set the air-fuel ratio of the air-fuel mixture to a state near λ=1 in FIG. 2.

Rather, in order to prevent the reaction heat in the catalyst from increasing, it is necessary to make the catalyst λ<1, that is, rich, to prevent NOx emissions and prevent the catalyst from overheating.

In this case as well, air-fuel ratio feedback control must be stopped.

The monitoring circuit according to the present invention sets the air-fuel ratio for each specific operating condition mentioned above and stops the air-fuel ratio feedback control necessary for this purpose.

FIG. 3 is a block diagram showing an air-fuel ratio correction control device based on the present invention, which is equipped with this monitoring circuit.

In the figure, 31 is a monitoring circuit, and 32 is a sensor that detects specific operating conditions of the internal combustion engine.

The sensors 32 include first sensors 32-1 and 3, which respectively indicate that the internal combustion engine is in high-load operation and high-speed operation.
2-1', and the second indicating that it is idle link time.
It has a sensor 32-2.

When there is an output from the first sensors 32-1 and 32-1', the load and rotation are high, so as already mentioned,
It is desirable that the mixture is rich.

Therefore, the control of the air-fuel ratio feedback circuit 16 is stopped by the feedback stop circuit 33, and the output of the 02 sensor 15 is checked to determine whether or not it is rich.

If this is rich, an abnormal lean signal sL is sent out.

Conversely, when there is an output from the second sensor 32-2, 74197
Since it was 7 o'clock, it was desirable that the air-fuel mixture was at 1, as already stated.

Therefore, the control of the air-fuel ratio feedback circuit 16 is stopped by the feedback stop circuit 33, and the output of the 02 sensor 15 is checked to determine whether or not the engine is lean.

If this is the case, an abnormal rich signal sR is sent out.

Here, the reason for stopping the control by the air-fuel ratio feedback circuit 16 is that if this operates up to 1, even if you try to set a specific air-fuel ratio, feedback will be added to offset this, which is the purpose. This is because it cannot be achieved.

At this time, as the feedback circuit 16 becomes unnecessary, 0
The two sensors 15 are also unnecessary.

However, as described above, the monitoring circuit 31 does not make the 02 sensor 15 unnecessary, but rather uses it effectively.

Incidentally, when the abnormal lean signal SL and abnormal rich signal SR described above are sent out, they may be utilized to drive a warning device, or may be added to correction means, such as the adder 17, for correction control.

At this time, the polarities of SL and SR are set to be opposite to each other by an inverter or the like.

Generally, this warning device can also warn when there is a failure in the basic air-fuel ratio calculation circuit 13.

FIG. 4 is a block diagram showing a specific example of the monitoring circuit 31 of FIG. 3 and its associated circuits.

In this figure, the same reference numbers as in FIG. 3 indicate the same components.

When the first sensor 32-1, for example, a power switch, is turned on, its output is applied to the first OR means 41 and the second OR means 42.

When the first comparator 43 detects that the output of another first sensor 32-1', for example, an engine tachometer, has reached a high rotation rate higher than a specified value, the detected output is determined by the first and second logical sums. applied to means 41 and 42.

Further, when the second sensor 32-2, for example, a known idle switch, is turned on, its output is applied to the first OR means 41 and the first AND means 44.

Thus, when a signal from the sensor is input to any of the inputs of the first OR means 41, its output drives the feedback stop circuit 33, and first the feedback control is turned off.

On the other hand, the output from the 02 sensor 15 is applied to the second comparator 45, and if the mixture is positive, the second comparator 45
If it is rich, it outputs a "1'" signal, and if it is rich, it outputs a "0" signal.

Furthermore, it is applied to the second AND means 46 and the first AND means 44 via the inverter 47 .

Now, when either of the sensors 32-1 and 32-1' is turned on and a "1" signal is applied to the second OR means 42, the OR means 42 sends a 1" signal to the second AND means 46. Send out.

At this time, as already mentioned, the air-fuel mixture needs to be rich.

On the other hand, assuming that the O2 sensor 15 is currently detecting a rich state, the comparator 45 outputs a "0" signal as described above, and the AND means 46 outputs a "0" signal.

That is, the desired air-fuel ratio is maintained. Conversely, if it is assumed that the 02 sensor 15 detects lean, the comparator 45 outputs a "1 pass signal, and the AND means 46 outputs n 19
Outputs 1 signal.

That is, an abnormal lean signal sL is output to warn that the air-fuel ratio is not the desired one.

Section 32-2 For example, if a signal "1" indicating an idle time is applied to the AND means 44 from a known idle switch, the air-fuel mixture must be at one level, as described above.

On the other hand, if it is assumed that the 02 sensor 15 is detecting lean in the composite, the comparator 45 outputs a "1" signal, and the "Otl signal is applied to the AND means 44 through the inverter 47, and its output is"0''.

In other words, the desired air-fuel ratio is maintained.

Conversely, if the O2 sensor 15 detects a rich state, the comparator 45 outputs an ON signal, a "1" signal is applied to the AND means 44, and its output becomes 1".

That is, the abnormal rich signal SR is output to warn that the air-fuel ratio is not the desired one.

Incidentally, when the 02 sensor is not turned on when the internal combustion engine is started, the sensor is inactive and its output is always 0 rich, resulting in an erroneous determination.

In order to prevent this, a flip-flop circuit 48 is provided, and when starting the engine, the starter switch 49
Reset this by

Therefore, the Q output of the flip-flop circuit 48 is an "O" signal, and the AND means 44 and 46 are closed.

Therefore, neither the abnormal lean signal SL nor the abnormal rich signal sR is sent out.

However, if the 02 sensor 15 is in the starting position 1, it becomes active and an accurate determination is given.

Therefore, the flip-flop circuit 48 is set with a 1" signal when the 02 sensor 15 detects lean for the first time, and its Q output is set to 1".
and 46 are opened.

In FIG. 4, two ways of using the signals sL and sR are described. On the one hand, these signals are added to the adder 17 via signal lines LL and LR to perform correction control, and on the other hand, LED (
The light emitting diode) 50 is made to emit light to give a warning to the driver.

As explained above, according to the present invention, it is possible not only to pursue the stoichiometric air-fuel ratio during normal driving, but also to pursue the optimum air-fuel ratio under specific driving conditions, thereby improving the exhaust gas purification function.

Further, since the feedback circuit 16 is turned off under specific operating conditions, a failure in the basic air-fuel ratio calculation system can also be detected.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a general air-fuel ratio correction control device to which the present invention is applied, Fig. 2 is a graph showing the relationship between air-fuel ratio λ and purification rate in a three-way catalyst, and Fig. 3 is a monitoring circuit. FIG. 4 is a block diagram showing a specific example of the monitoring circuit of FIG. 3 and its associated circuits. In the figure, 13 is the basic air-fuel ratio control circuit, 15 is the 02 sensor, 17 is the adder, 31 is the monitoring circuit, and 32-1.32
-1', 32-2 are sensors, and 50 is a light emitting diode serving as a warning device.

Claims (1)

[Claims for Utility Model Registration] 1. A basic air-fuel ratio calculation circuit and an 02 sensor for detecting oxygen concentration in exhaust gas are arranged, and the output of the 02 sensor is used as input to provide feedback control to the basic air-fuel ratio calculation circuit. In the air-fuel ratio correction control device for an internal combustion engine, the internal combustion engine is provided with at least two types of specific operating conditions, namely, a first specific operating condition corresponding to high-load/high-speed operation; The second equivalent to idling
at least two sensors individually detecting specific operating conditions, the first sensor detecting the first specific operating condition or the second sensor detecting the first specific operating condition; a feedback stop circuit that disconnects the feedback control when a certain operating condition is detected; and a first AND means that combines the output of the 02 sensor with a first human power and outputs the first sensor with a second human power. and a second logical product means which uses an output obtained by inverting the output of the 02 sensor as a first human power and an output of the second sensor as a second human power, and an empty output from the first logical product means. An air-fuel ratio correction control device for an internal combustion engine, characterized in that a monitoring circuit is added that functions to send a signal indicating an abnormally lean fuel ratio and send a signal indicating an abnormally rich air-fuel ratio from the second logical product means. . 2. Utility model registration claim 1, which is equipped with a warning device that issues a warning of abnormally lean residue or abnormally rich residue based on the logical sum of the output of the first logical product means and the output of the second logical product means. Air-fuel ratio correction control device for internal combustion engines. 3. Air-fuel ratio correction for an internal combustion engine as set forth in claim 1 of the utility model registration claim, comprising a correction means for adding the output of the first AND means and the output of the second AND means to the output of the basic air-fuel ratio calculation circuit. Control device.