JPH0544539A - Air-fuel ratio control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To renew a learning value with accuracy and control an air-fuel ratio with smoothness and efficiency by judging the order of rich and lean peaks and whether both the peak values exceed threshold levels or not under an acceleration condition, calculating learning values according to the judgment result, renewing the learning values based on the resultant calculation value, controlling the air-fuel ratio with the renewd value. CONSTITUTION:When an opening TH of a throttle valve 17 is a specified value or more under an accelerating condition, a fuel injection TAU is corrected considering a calculated learning value KG in order to increase the fuel injection amount compared to a normal one to an engine 11. Next, it is judged whether a peak A/F value PAFR under a rich condition and a peak A/F value PAFL under a lean condition exceed rexpectively the set threshold levels or not. When they exceeds the threshold levels, the learning values KG are calculated. The resultant learning values KG are compared to the former learning values KG01, and then renewed. The order of rich and lean conditions is judged with accuracy, and thereby the learning value KG is renewd accordint thereto.

Description

Detailed Description of the Invention

[0001]

This invention relates to an air-fuel ratio detector (A /
And an air-fuel ratio control device using an F sensor),
In particular, the present invention relates to an air-fuel ratio control device for an internal combustion engine that learns an acceleration / deceleration correction amount and controls a fuel injection amount based on the learned value.

[0002]

2. Description of the Related Art In the operation of an internal combustion engine, an air-fuel ratio control method in which transient learning is performed by using feedback control to correct acceleration increase during a transition such as acceleration / deceleration is disclosed in, for example, Japanese Patent Publication No.
No. 3-38533. This method detects a rich state and a lean state using an oxygen concentration sensor, and learns based on the length of time in the rich state or the lean state.

However, in this method, the air-fuel ratio deviation determination uses an indirect determination criterion such as rich or lean state time determination, and it is not possible to increase the learning speed due to concern about erroneous learning.

As a means for solving such a problem, an air-fuel ratio control device as disclosed in, for example, JP-A-60-32949 is considered. In this air-fuel ratio control device, the state of the air-fuel ratio of the internal combustion engine is directly detected using the A / F sensor, and the learning correction amount is determined based on the detected value. Then, the air-fuel ratio control means shown here performs learning when it is determined that the air-fuel ratio deviation is equal to or greater than the specified set value within the acceleration determination section.

Explaining the case of insufficient acceleration increase with reference to FIG. 7A, when the feedback control is in the open state, the correction amount takes a certain amount of time after the acceleration lean as shown by the broken line in the figure. It will return to the base level, and there is no particular shift to the rich side.

However, if the correction is performed by feedback as shown by the solid line, the lean time is shortened, but when the lean state of the air-fuel ratio is large, the air-fuel ratio correction coefficient becomes large and the acceleration amount increases. The sum with the air-fuel ratio correction coefficient becomes overcorrection, and an overrich state occurs due to overcorrection.

In general, in such feedback control, it is judged whether the A / F sensor output appears leaner or richer in the judgment section to judge whether it is lean or rich. There is. For this reason,
If the overrich state exceeds the determination threshold level for updating the learning value within the acceleration determination section of the transient learning, there is a risk of erroneous learning that it is substantially lean but rich. (B) of the figure shows the case where the acceleration increase is excessive.

When such learning is carried out, the lean at the beginning of acceleration becomes larger due to the decrease in the amount of acceleration increase, and problems such as poor drivability, misfire, and leaving the window of the catalyst occur. ..

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is possible to increase or decrease the learning value of the air-fuel ratio correction amount without being confused by the state of overrich or overlean due to feedback control. It is an object of the present invention to provide an air-fuel ratio control device for an internal combustion engine that can make a determination and can always calculate an appropriate fuel injection amount.

[0010]

In the air-fuel ratio control system for an internal combustion engine according to the present invention, the acceleration section is determined, and which of the rich peak state and the lean peak state occurs first in this acceleration section. Then, it is determined whether or not the rich or lean peak value exceeds the threshold level. Then, a rich or lean learning value is calculated corresponding to this determination result, the learning value is updated based on the calculated value, and the fuel injection amount control is executed based on this learning value.

[0011]

In the air-fuel ratio control device configured as described above, when performing feedback control, for example, if a rich peak state occurs first during the acceleration determination period,
Even if an over-lean state occurs thereafter, the learning value is updated by prioritizing the richer situation first. Therefore, the learning value increase / decrease is determined without being confused by overrich or over lean, and the air-fuel ratio control during acceleration / deceleration is smoothly performed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an engine 11 and its peripheral devices in which air-fuel ratio control is performed. An electronic control circuit (ECU) controls the ignition timing Ig of the engine 11 and the fuel injection amount TAU.
Done at 12.

The engine 11 is of a spark ignition type with four cylinders and four cycles, for example, and intake air is taken in through an air cleaner 13, an intake pipe 14, a surge tank 15, and an intake branch pipe 16. In this case, the intake air amount is controlled by the throttle valve 17 which is driven by an accelerator pedal (not shown) set in the intake pipe section 14.

The fuel injection valves 181 to 184 which are set in the intake branch pipe 16 of the engine 11 in correspondence with the respective cylinders,
Fuel pumped from a fuel tank (not shown) is supplied,
Fuel is injected into each cylinder of the engine 11 in an amount corresponding to the valve opening time of the fuel injection valves 181-184 controlled to open by a command from the electronic control circuit 12.

Spark plugs 191 to 194 are provided for the respective cylinders of the engine 11, and the spark plugs 191 to 194 are provided.
A high-voltage ignition signal from an ignition circuit 21 is distributed and supplied to each of 191 to 194 via a distributor 20.

The distributor 20 includes a gear wheel made of, for example, a magnetic material, which is rotated by the engine 11, and a rotation sensor set near the outer circumference of the gear wheel.
The rotation speed Ne of the engine 11 is detected by 22. From this rotation sensor 22, 24 pulse signals are generated at two rotations of the engine 11, that is, at 720 ° CA.

The detection signal Ne from the rotation sensor 22 is
Which is supplied to the input port 121 of the electronic control circuit 12,
The input port 121 further includes a throttle sensor 23 for detecting the opening TH of the throttle valve 17, an intake pressure sensor 24 for detecting the intake pressure PM on the downstream side of the throttle valve 17, and an intake temperature sensor for detecting the intake temperature Tam. Each of the detection signals from 25 is supplied. From the throttle sensor 23,
Further, an on / off signal is output from an idle switch (not shown) that detects that the throttle valve 14 is almost fully closed.

In the exhaust pipe 26 of the engine 11, harmful components (CO, HC, NO) in the exhaust gas discharged from the engine 11 are connected.
A three-way catalyst 27 that reduces x) is set. An air-fuel ratio sensor 28, which is an oxygen concentration sensor that outputs a linear detection signal according to the air-fuel ratio λ of the air-fuel mixture supplied to the engine 11, is provided on the upstream side of the three-way catalyst 27, and further downstream side. Is provided with an O ₂ sensor 29 that outputs a signal corresponding to whether the air-fuel ratio λ of the air-fuel mixture supplied to the engine 11 is rich or lean with respect to the stoichiometric air-fuel ratio λ o. The detection signals from these sensors 28 and 29 are sent to the electronic control circuit.
Twelve input boats 121 are input.

As is generally known, the electronic control circuit 12 is configured as an arithmetic and logic operation circuit centering on a CPU 122, a ROM 123, a RAM 124, a backup RAM 125, etc., and is operated on the basis of information input to an input port 121. The result is output from the output port 126.

In this electronic control circuit 12, the input port 121
The optimum fuel injection amount TAU and the ignition timing Ig are calculated based on the intake pressure PM, the intake temperature Tam, the throttle opening TH, the cooling water temperature Thw, the air-fuel ratio λ, and the rotational speed Ne which are input via the Fuel injection valves 181 to 18 based on the injection amount TAU
The valve opening time of 4 is controlled, and the ignition circuit 21 is controlled by the calculated ignition timing Ig.

The air-fuel ratio control executed in the electronic control circuit 12 will be described. First, the fuel injection amount TAU
The process of setting is performed according to the flow shown in FIG.
This process is executed in synchronization with the rotation of the engine 11 (for example, every 360 ° CA in a simultaneous injection type engine),
First, at step 101, the basic fuel injection amount Tp is calculated according to the intake pressure PM, the rotation speed Ne, and the like. Then, in the next step 102, the air-fuel ratio correction coefficient FAF is set so that the air-fuel ratio λ becomes the target air-fuel ratio λ _TG .

In step 103, it is determined whether or not the vehicle is currently in a predetermined acceleration state. If it is determined that the vehicle is in a predetermined acceleration state, the process proceeds to step 104. If not, the process proceeds to step 105. Whether or not the vehicle is in the acceleration state is determined based on whether or not the opening TH of the throttle valve 17 is equal to or larger than a predetermined opening.

In step 104, the fuel injection amount TAU is calculated in consideration of the learning value KG calculated by the method described later in order to correct the fuel injection amount to the normal engine 11 so that the fuel injection amount is larger than the normal fuel injection amount. to correct. For details, set based on the following formula. TAU = FAF * Tp * FALL * KG where FAF is the air-fuel ratio correction coefficient calculated in step 102 and FALL is another correction coefficient determined by the intake air temperature Tam and the like.

Further, in step 105, the fuel injection amount TAU is corrected based on the following equation. TAU = FAF * Tp * FALL Then, the operation signal obtained in accordance with the fuel injection amount TAU thus obtained is supplied to the fuel injection valves 181 to 184.

Here, the fuel injection amount in step 104
When calculating TAU, the learning correction amount subroutine 200
The fuel injection amount TAU is corrected in accordance with the transient operating condition of the engine 11, for example.

3 to 5 show this learning correction subroutine. First, in step 201 shown in FIG. 3, it is judged whether or not the learning flag is set, and it is confirmed that the learning flag is set. If so, the routine (A) shown in FIG. 4 is immediately entered. If it is confirmed that they are not set, the routine proceeds to step 202, where it is judged if the intake air pressure change amount DLPM exceeds the set pressure difference 20 mmHg. If the set pressure difference is exceeded, the learning flag is set in step 203 and the acceleration counter CDPC1 is set.

In the routine (A) shown in FIG. 4, in the first step 301, it is judged whether or not it is the acceleration detection section based on the value of the acceleration counter CDPC1. And
If it is confirmed that it is in the acceleration judgment section, step
At 302, it is determined whether the air-fuel ratio value AF is larger than the target air-fuel ratio value AFTG (λ = 1). If it is determined that AF is large, the routine proceeds to step 303, where this air-fuel ratio value AF is on the lean side A. / F
It is determined whether it is larger than the peak value PAFL. When it is determined in step 302 that the air-fuel ratio value AF is smaller than the target air-fuel ratio value, the routine proceeds to step 304, where it is determined whether this AF is larger than the rich side A / F peak value.

In step 303, the air-fuel ratio AF is the peak value PAFL
If it is determined that it is larger than the above, the routine proceeds to step 305, where the peak value PAFL is set as the air-fuel ratio value AF at this time, and the peak counter CPAFL is set to the acceleration counter CDPC1 value. Further, when it is determined in step 304 that the air-fuel ratio value AF is larger than the peak value PAFR, the routine proceeds to step 306, where this peak value PAFR is set as the air-fuel ratio value AF at this time, and the peak counter
Set CPAFR to the acceleration counter CDPC1 value. That is,
In steps 302 to 306, the peak value and the acceleration counter value CDPC1 at that time are detected.

In step 307, the value of the acceleration counter CDPC1 is compared with the set value "26" to determine whether the acceleration period has ended. If it is determined that the acceleration section has not ended yet, the process proceeds to step 308 and the acceleration counter
Add "1" to CDPC and return.

If the end of the acceleration section is confirmed in step 307, the process proceeds to step 309 to clear the acceleration counter CDPC1 and the learning flag, and in the next step 310, the peak counter values CPAFL and CPAFR are set. By comparison, it is determined which of the lean peak and the rich peak occurs first.

The process proceeds to step 311 or step 312 shown in FIG. 5 according to the determination result of step 310.
In steps 311 and 312, the peak A / F value PAFR during rich and the peak A / F value PAFL during lean
, It is determined whether or not each exceeds the set threshold level. Then, when it is determined that the respective threshold levels are exceeded, step 31
At 3 and 314, the learning value KG is calculated. here,
ΔA / F is the difference between PAFL, PAFR and target A / F, or PA
It is the difference between FR and the target A / F (AFTG).

In steps 315 and 316, the learning value KG obtained respectively is compared with the previous learning value KGO1,
The learning value is updated in steps 317 to 320 corresponding to the comparison result. When the update of the learning value is completed, the peak value and the peak counter are cleared in step 321, and this process is completed.

By executing the processing as described above, it is possible to surely judge whether rich appears first or lean appears first, and the learning value KG corresponding to this can be determined.
Can be updated. Therefore, although the fuel is substantially lean, when the fuel is increased by the air-fuel ratio correction coefficient FAF and then the A / F sensor output largely shifts to the rich side, it is erroneously determined to be rich and the learning value KG Can be prevented from being updated in a decreasing direction.

FIG. 6 shows the state of learning using this A / F sensor in order to further clarify the effect of the apparatus of the embodiment. In the current learning shown in FIG. Even when the state becomes large, the learning value is set because the lean occurs first, and therefore erroneous learning does not occur. Therefore, even when the next acceleration shown in FIG.

[0035]

As described above, according to the air-fuel ratio control system for an internal combustion engine according to the present invention, it is determined whether rich is ahead or lean is ahead in the acceleration determination section, so that overrich or feedback control by feedback control is performed. You can judge the increase or decrease of learning value without being confused by Ovaleen. Therefore, the learned value used for the calculation of the fuel injection amount is updated without error, and smooth and efficient air-fuel ratio control is guaranteed.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration for explaining an air-fuel ratio control device according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a fuel injection amount calculation process.

FIG. 3 is a flowchart illustrating a subroutine for obtaining a learning correction amount used for calculating a fuel injection amount.

FIG. 4 is a flowchart illustrating a flow following FIG.

FIG. 5 is a flowchart illustrating the flow of processing that continues from FIG.

FIG. 6 is a diagram illustrating a state of learning by A / F.

7 (A) and 7 (B) are views for explaining a conventional learning state in an insufficient acceleration amount increase state and an excessive acceleration amount state, respectively.

[Explanation of symbols]

11 ... Engine, 12 ... Electronic control circuit, 13 ... Air cleaner,
14 ... Intake pipe, 17 ... Throttle valve, 181-184 ... Fuel injection valve, 191-194 ... Spark plug, 20 ... Distributor, 21 ... Ignition circuit, 22 ... Rotation sensor, 23 ... Throttle sensor, 24 ... Intake pressure sensor, 25 ... intake air temperature sensor, 27 ... three way catalyst, 28 ... air-fuel ratio sensor, 29 ... oxygen concentration sensor.

Claims (1)

[Claims] 1. An oxygen concentration sensor that outputs an analog signal according to the oxygen concentration contained in the exhaust gas of an internal combustion engine, and a predetermined determination section that is determined based on a transient state of the internal combustion engine, Detecting a rich peak state and a lean peak state of the oxygen concentration sensor, peak generation determination means for determining which one of the rich peak state and the lean peak state occurs first, and the output of the oxygen concentration sensor is a predetermined value. When it is determined that the threshold level is exceeded, learning value updating means for updating a learning value based on the determination result of the peak occurrence determining means, and fuel for the internal combustion engine based on the updating result of the learning value updating means An air-fuel ratio control device for an internal combustion engine, comprising: a fuel injection amount setting means for setting an injection amount.