JP2556002B2 - Air-fuel ratio control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an air-fuel ratio control device for an air-fuel mixture supplied to an internal combustion engine, and more particularly to a concentration signal input from an exhaust sensor provided in an exhaust system of the internal combustion engine. The present invention relates to an air-fuel ratio control device for controlling an air-fuel ratio to a predetermined air-fuel ratio, by which fluctuations from the predetermined air-fuel ratio due to supply of lead-containing fuel can be prevented and an increase in exhaust gas harmful components can be prevented.

[Prior Art] In recent years, in an internal combustion engine, in order to reduce the fuel consumption rate and the harmful components of exhaust gas, a feedback control type air-fuel ratio control device that converges to an air-fuel ratio that should obtain the best combustion state is proposed. Has been done. The air-fuel ratio control device controls the amount of fuel supplied and the amount of air supplied based on a rich signal and a lean signal, which are concentration signals input from an O ₂ sensor, which is an exhaust sensor provided in the exhaust system, to control the intake mixture to a predetermined amount. Control to the air-fuel ratio. In addition, there is a system in which a catalytic converter such as a three-way catalyst is provided in the exhaust system in order to reduce harmful components in exhaust gas after combustion. Further, in order to effectively act the function of reducing exhaust harmful components by these devices, it is desirable to supply fuel containing no lead or the like.

[Problems to be solved by the invention]

Incidentally, in the method of feedback control to a predetermined air-fuel ratio based on the concentration signal serving rich signal and a lean signal from the O ₂ sensor, O ₂ sensor takes time at the transition between the rich signal and the lean signal. That is, the sixth
As shown in the figure, the response time Tr → l is required for the transition from the rich signal to the lean signal, and the response time Tl → r is required for the transition from the lean signal to the rich signal.
Cost. However, in these response times Tr → l · Tl → r, the response time Tr → l as the time required for the transition from the rich signal to the lean signal is when the low concentration lead-containing fuel is supplied as the fuel. , As shown in FIG. That is, the O2 sensor generates an electromotive force according to the oxygen concentration in the exhaust gas. The output voltage of the O2 sensor due to this electromotive force is
Around the oxygen concentration in the exhaust gas near the stoichiometric air-fuel ratio, there is a sudden change between the highest value side when the oxygen concentration is high and the lowest value side when the oxygen concentration is low. The air-fuel ratio control device compares the output voltage of the O2 sensor with a reference voltage, and when the output voltage is higher than the reference voltage, the rich signal is output. When the output voltage is lower than the reference voltage, the lean signal is output. A predetermined air-fuel ratio is controlled based on the signal and the lean signal.

However, the O2 sensor has a problem that when a low-concentration lead-containing fuel is supplied, the O2 sensor gradually deteriorates due to lead over time, the electromotive force decreases, and the maximum output voltage decreases. Therefore, the maximum value of the output voltage of the O2 sensor approaches the reference voltage with the passage of time.

As described above, the O2 sensor has a response time Tr → l required when the maximum value of the output voltage as the rich signal approaches the reference voltage with the passage of time, so that the rich signal crosses the reference voltage and changes to the lean signal. Becomes shorter. On the other hand, in the O2 sensor, even if the maximum value of the output voltage decreases due to deterioration, the minimum value of the output voltage as the lean signal does not change with respect to the reference voltage, so that the transition from the lean signal to the rich signal occurs. The required response time Tl → r does not change.

Therefore, when the response time Tr → l at the initial time point A is set to control to a predetermined air-fuel ratio, the response time Tr → l becomes short and changes from the predetermined air-fuel ratio when a certain time elapses. There is an inconvenience to do. As a result, as shown in FIG. 8, there is a disadvantage that exhaust harmful components such as CO and T / HC increase.

Furthermore, when a high-concentration lead-containing fuel is supplied as the fuel, the O2 sensor is rapidly deteriorated by lead, the maximum value of the output voltage rapidly approaches the reference voltage, and the transition from the rich signal to the lean signal occurs. The required response time Tr → l is drastically shortened, and there is the inconvenience that the harmful components of the exhaust gas rapidly increase by fluctuating from the predetermined air-fuel ratio, and the exhaust gas purification performance of not only the O2 sensor but also the catalytic converter is significantly reduced. It is inconvenient and causes a problem of discharging a large amount of exhaust harmful components.

[Object of the Invention]

Therefore, an object of the present invention is to prevent fluctuations from a predetermined air-fuel ratio due to the supply of low-concentration lead-containing fuel, to prevent an increase in exhaust harmful components, and to improve high-concentration lead-containing fuel. An object of the present invention is to realize an air-fuel ratio control device capable of avoiding a decrease in exhaust purification performance of a catalytic converter due to supply and preventing an increase in exhaust harmful components.

[Means for solving problems]

In order to achieve this object, the present invention, the input time of the rich signal and the lean signal input from the O ₂ sensor provided in the exhaust system of the internal combustion engine is respectively a filter constant for the rich signal or more and a filter constant for the lean signal or more. In an air-fuel ratio control device that controls the rich signal and the lean signal to be valid at a predetermined air-fuel ratio only when there is a response time required for the transition from the rich signal to the lean signal and the transition from the lean signal to the rich signal. Measure the required response time and compare it with the response time that should be the predetermined air-fuel ratio, and adjust the filter constant for the rich signal and the filter constant for the lean signal according to the difference to prevent fluctuation from the predetermined air-fuel ratio Control and the response time required for the transition from the rich signal to the lean signal. The response time required for the transition from the rich signal to the lean signal is smaller than the response time required for the transition from the rich signal to the lean signal as compared with the response time required for the transition from the lean signal to the rich signal. In this case, a control circuit section is provided for detecting that the high concentration lead-containing fuel is supplied and controlling the warning circuit to operate.

[Action]

According to the present invention, which is configured as described above,
The control circuit measures the response time required for the transition from the rich signal to the lean signal and the response time required for the transition from the lean signal to the rich signal, compares the response time with the response time at which the predetermined air-fuel ratio should be obtained, and responds to the difference. The filter constant for the rich signal and the filter constant for the lean signal are adjusted so as to prevent fluctuation from a predetermined air-fuel ratio. Further, according to the present invention, the control circuit unit measures the response time required for the transition from the rich signal to the lean signal and compares it with the response time required for the transition from the lean signal to the rich signal, and then the rich signal to the lean signal. When the response time required for the transition to is smaller than the response time required for the transition from the lean signal to the rich signal, the warning circuit is activated by detecting that the high concentration lead-containing fuel is supplied. To control.

As a result, when a low-concentration lead-containing fuel is supplied, the O2 sensor deteriorates over time and the response time required for the transition from the rich signal to the lean signal and the response time required for the transition from the lean signal to the rich signal. Even when the air-fuel ratio changes, it is possible to prevent the air-fuel ratio from fluctuating from the predetermined air-fuel ratio, and when a high concentration lead-containing fuel is supplied,
The exhaust gas purification performance of the catalytic converter deteriorates by detecting this by issuing a warning by the rapid reduction in the response time required for the transition from the rich signal to the lean signal due to the rapid deterioration of the O2 sensor, and by taking measures. To prevent the increase of harmful components in exhaust gas.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

The present invention relates to an air-fuel ratio control device that controls a predetermined air-fuel ratio based on a concentration signal input from an exhaust sensor provided in an exhaust system of an internal combustion engine, and more specifically, an exhaust sensor provided in an exhaust system of an internal combustion engine. According to an air-fuel ratio control device that controls the concentration signal to a predetermined air-fuel ratio by validating the concentration signal only when the input time of the concentration signal input from the filter is equal to or more than a set value, a filter for adjusting the set value according to the operating state. A constant is set. In such an air-fuel ratio control device, when a fuel containing lead is supplied, fluctuations from the predetermined air-fuel ratio are prevented to prevent an increase in exhaust harmful components.

1 to 5 show an embodiment of the present invention.
In FIG. 2, 2 is a control circuit unit, 4 is an internal combustion engine, and 6 is a carburetor. The control circuit portion 2 forms a central portion for feedback-controlling the air-fuel ratio of the carburetor 6 provided in the intake passage 10 downstream of the air cleaner 8. The control circuit unit 2 takes in the rich signal and the lean signal, which are the concentration signals input from the O ₂ sensor 14, which is an exhaust sensor for detecting the oxygen concentration in the exhaust gas provided in the exhaust passage 12, with the filter constants as described above, The control valve 16 is operated to adjust the air-fuel ratio in the passage 10 to a predetermined air-fuel ratio. The control valve 16 controls opening / closing of the fuel passage or the air passage of the carburetor 6 to adjust the air-fuel ratio. Further, in the middle of the exhaust passage 12, a catalytic converter 18 including a three-way catalyst for performing a post-treatment of exhaust gas is provided.

As shown in FIG. 1, the control circuit unit 2 includes the O ₂ sensor 14
A comparison circuit 20 for comparing the rich signal and the lean signal which are concentration signals input from the reference voltage with the reference voltage, an input circuit 22 for receiving various signals as inputs, and a CPU 24 for judging and processing by the signals input from the input circuit 22. And this CPU
And an output circuit 26 for outputting a control signal for air-fuel ratio correction to the control valve 16 based on the judgment of 24. The control circuit unit 2 sets the filter constants of the rich signal and the lean signal input from the O ₂ sensor 14 to adjust the air-fuel ratio to a predetermined air-fuel ratio. Further, a rotation speed sensor 28 and a throttle switch 30 are provided as means for detecting the operating state of the internal combustion engine 4,
A signal is input to the input circuit 22. Reference numeral 32 is an ignition switch, and 34 is a battery.

FIG. 3 shows an example of the change in the air-fuel ratio with respect to the filter constant, in which the filter constant Fr for the rich signal of the O ₂ sensor 14 is made constant and the filter constant Fl for the lean signal is changed. For example, if the filter constant Fl for validating the lean signal of the O ₂ sensor 14 is set large, that is, if the valid input time t is set to be long, the lean signal is valid only if it has a long input time as shown in FIG. ,
There are more valid rich signals. By inputting these valid lean signal and rich signal, the control circuit section 2 tilts the signal for correcting the air-fuel ratio to the lean side,
The output circuit 26 operates the control valve 16 to make the air-fuel ratio lean.

On the contrary, when the filter constant Fl that makes the lean signal valid is set small, the lean signal becomes valid even for an input signal of a short time, and thus becomes larger than the rich signal. Therefore, the control circuit unit 2 tilts the signal for correcting the air-fuel ratio to the rich side and operates the control valve 16 to make the air-fuel ratio rich.

On the other hand, although not shown, contrary to FIG. 3, when the filter constant Fl for the lean signal of the O ₂ sensor 14 is fixed and the filter constant Fr for the rich signal is changed, the filter constant Fl
When Fr is set to a large value, the number of effective lean signals increases, and the control circuit unit 2 enriches the air-fuel ratio. On the contrary, when the filter constant Fr is set small, the number of effective rich signals becomes large, and the air-fuel ratio becomes lean.

In this way, the air-fuel ratio fluctuates to the rich side or the lean side by changing the filter constants Fr · Fl of the rich signal and the lean signal input from the O ₂ sensor 14 to the control circuit unit 2. Therefore, various air-fuel ratios corresponding to the operating state can be adjusted by setting various filter constants Fr · Fl of the rich signal and the lean signal in combination.

Therefore, by changing the filter constant, for example, by changing the filter constant to adjust to a predetermined air-fuel ratio during steady state and to the corresponding rich-side or lean-side air-fuel ratio during non-steady state, it is possible to adjust to the operating state. The air-fuel ratio can be adjusted to improve the drivability and stabilize the exhaust gas components for cleaning, and automatically according to the operating conditions such as high temperature and high altitude conditions.
Alternatively, the filter constant can be changed manually.

In order to change the filter constant and adjust the air-fuel ratio depending on the operating condition, a rotational speed sensor 28 and a throttle switch 30 are provided as operating condition detecting means as shown in FIG. Based on signals from the rotation speed sensor 28 and the throttle switch 30 that detect the operating state of the internal combustion engine 4, the control circuit unit 2 inputs a rich signal from the O ₂ sensor 14 to adjust the air-fuel ratio according to the operating state. And change the filter constant of the lean signal. As a result, as described above, the air-fuel ratio is adjusted to correspond to the operating state, and the operability is improved and the exhaust gas components are stabilized for cleaning.

In such an air-fuel ratio control device, the present invention prevents a change from a predetermined air-fuel ratio and prevents an increase in harmful components of exhaust gas when a fuel containing lead is supplied.

Therefore, the control circuit unit 2, as shown in FIG.
2 The rich signal and the lean signal from the sensor 14 are taken in by the filter constants Fr and Fl (101), and the response time Tr → l as the time required for the transition from the rich signal to the lean signal shown in FIG. 6 is measured. Also measures the response time Tl → r as the time required for the transition from the lean signal to the rich signal (102).

The response time Tr → is compared with a response time that should be a predetermined air-fuel ratio, which is a reference value, and the filter constant Fr is adjusted according to the difference, and the response time Tl → r is also a reference value. The difference is adjusted (103) by comparing with a response time at which a certain predetermined air-fuel ratio should be obtained, and fluctuation from the predetermined air-fuel ratio is prevented.

That is, the coefficient for the rich signal is Ar, the coefficient for the lean signal is Al, and when the response time Tr → l · Tl → r changes, the filter constant Fr · Fl is Fr = Ar × Tr → l Fl = Al × Tl → Calculate by the formula of r and adjust to prevent fluctuation of air-fuel ratio.

For example, it is possible to prevent the disadvantage that the response time Tr → l from the rich signal to the lean signal becomes short and the air-fuel ratio fluctuates as shown in FIG. 7 by adjusting the filter constant Fr for the rich signal. Of course, the filter constant
By adjusting Fr and Fl respectively, it is possible to prevent fluctuations in the air-fuel ratio.

As a result, even if the O2 sensor 14 deteriorates due to the passage of time and the response time Tr → l · Tl → r changes, as shown in FIG.
It is possible to prevent the inconvenience that exhaust harmful components such as CO and T / HC increase.

Further, the control circuit unit 2 changes the response time Tr → l from the rich signal to the lean signal to the response time Tl from the lean signal to the rich signal whose specific value does not change, as shown in FIGS. → Compare with r (104). Due to the rapid deterioration of the O2 sensor 14, the response time Tr → l from the rich signal to the lean signal becomes longer than the response time Tl from the lean signal to the rich signal.
When it becomes smaller than → r (Tr → l <Tl → r: YES), it is detected that the fuel containing a high concentration of lead is supplied.

When the control circuit unit 2 detects that the high-concentration lead-containing fuel is supplied, the control circuit unit 2 activates the warning circuit 36 provided outside by the output circuit 26 as shown by the chain double-dashed line in FIGS. Give a warning (105). As a result, measures such as refueling can be taken, the exhaust purification performance of the catalytic converter 18 can be prevented from deteriorating, and an increase in exhaust harmful components can be prevented.

Note that the response time Tr → l is a specific value and the response time Tl → r is
If it is larger than (Tr → l <Tl → r: NO), the filter constant is adjusted according to the response time Tr → l · Tl → r to prevent the air-fuel ratio from varying. Of course, the specific value can be set arbitrarily.

〔The invention's effect〕

As described above, according to the present invention, the control circuit unit measures the response time required for the transition from the rich signal to the lean signal and the response time required for the transition from the lean signal to the rich signal to obtain a predetermined air-fuel ratio. The response time is compared with the power response time, and the filter constant for the rich signal and the filter constant for the lean signal are adjusted according to the difference, and control is performed so as to prevent fluctuation from a predetermined air-fuel ratio. As a result, when a low-concentration lead-containing fuel is supplied, even if the O2 sensor deteriorates over time and the response time required for transition changes, it is possible to prevent fluctuation from the predetermined air-fuel ratio. ,
It is possible to prevent the inconvenience that the harmful components of exhaust gas such as CO and T / HC increase. Further, according to the present invention, the control circuit unit measures the response time required for the transition from the rich signal to the lean signal and compares the response time with the response time required for the transition from the lean signal to the rich signal to determine the abruptness of the O2 sensor. By rapidly reducing the response time required for the transition from the rich signal to the lean signal due to deterioration, it is possible to detect that a high concentration of lead-containing fuel has been supplied and issue a warning, and to be able to take measures. It is possible to prevent a decrease in exhaust gas purification performance of the converter and prevent an increase in exhaust gas harmful components.

[Brief description of drawings]

1 to 5 show an embodiment of the present invention, FIG. 1 is a block diagram of a control circuit unit, FIG. 2 is a schematic diagram of an internal combustion engine, and FIG. 3 is a diagram showing a relationship between a filter constant and an air-fuel ratio. 4 (a) and 4 (b) are explanatory diagrams of the rich signal / lean signal incorporation by the filter constant, and FIG. 5 is a control flowchart. FIGS. 6 to 8 show the relationship of increase in harmful components of exhaust gas due to change in response signal, FIG. 6 shows rich signal and lean signal of O ₂ sensor, FIG. 7 shows response time, FIG. 8 FIG. 4 is a diagram showing an increase relationship of exhaust gas harmful components. In the figure, 2 is a control circuit unit, 4 is an internal combustion engine, 6 is a carburetor, 14 is an O ₂ sensor, 16 is a control valve, 18 is a catalytic converter,
Reference numeral 20 is a reference voltage comparison circuit, 22 is an input circuit, 24 is a CPU, 26 is an output circuit, and 36 is a warning circuit.

Claims (1)

(57) [Claims] 1. The rich signal only when the input times of a rich signal and a lean signal input from an O ₂ sensor provided in an exhaust system of an internal combustion engine are equal to or more than a filter constant for the rich signal and equal to or more than a filter constant for the lean signal, respectively. In an air-fuel ratio control device that controls the lean signal to be valid and to a predetermined air-fuel ratio, the response time required for the transition from the rich signal to the lean signal and the response time required for the transition from the lean signal to the rich signal are measured. While controlling to prevent fluctuation from the predetermined air-fuel ratio by adjusting the filter constant for the rich signal and the filter constant for the lean signal according to the difference compared with the response time to be a predetermined air-fuel ratio, Measure the response time required for the transition from the rich signal to the lean signal, and measure the response time from the lean signal. High lead concentration when the response time required for the transition from the rich signal to the lean signal is smaller than the response time required for the transition from the lean signal to the rich signal as compared with the response time required for the transition to the H signal. An air-fuel ratio control device comprising a control circuit section for detecting that the contained fuel is supplied and controlling the warning circuit to operate.