JPH0694830B2 - Air-fuel ratio learning controller for internal combustion engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to a learning control device for an air-fuel ratio feedback control system of an internal combustion engine.

<Prior Art> A fuel injection valve used in an electronically controlled fuel injection device is opened by a drive pulse signal given in synchronization with the rotation of an engine, and a fuel of a predetermined pressure is injected during the valve opening period. Has become. Therefore, the fuel injection amount is controlled by the pulse width of the drive pulse signal, and if this pulse width is used as a control signal corresponding to the fuel injection amount, Ti is the following formula in order to obtain the theoretical air-fuel ratio that is the target air-fuel ratio. Defined by

Ti = Tp ・ COEF ・ α + Ts However, Tp is the basic pulse width corresponding to the basic injection amount and is called the basic injection amount for convenience. Tp = K · Q / N, K is a constant, Q is the engine intake air flow rate, and N is the engine speed. COEF is various correction factors such as water temperature correction, α is the air-fuel ratio feedback correction factor for the air-fuel ratio feedback control (λ control) described later, Ts is the fuel injection flow rate error correction amount, and the fluctuation of the battery voltage with respect to the basic injection amount. This is to correct the fuel injection flow rate error due to the opening and closing delay of the fuel injection valve due to.

Regarding λ control, an O ₂ sensor is provided in the exhaust system to detect the actual air-fuel ratio, and the slice level controls whether the air-fuel ratio is richer or thinner than the theoretical air-fuel ratio. The feedback correction coefficient α is defined and changed to maintain the stoichiometric air-fuel ratio. Here, the value of the air-fuel ratio feedback correction coefficient α is changed by proportional-plus-integral (P1) control for stable control.

That is, the output voltage of the O ₂ sensor is compared with the slice level voltage, and when the slice level is higher or lower than the slice level, the air-fuel ratio does not suddenly become thick or thin, but the air-fuel ratio becomes rich (thin In such a case, the air-fuel ratio is controlled to be thin (thick) by first lowering (raising) P minutes and then gradually lowering (raising) I minutes each.
However, under the condition that λ control is not performed, α is clamped and various correction factors COEF are set to obtain a desired air-fuel ratio.

By the way, if the base air-fuel ratio under the λ control condition, that is, the air-fuel ratio when α = 1 can be set to the theoretical air-fuel ratio (λ = 1), the feedback control is unnecessary, but in reality, the air flow meter, Since the deviation of the base air-fuel ratio from λ = 1 occurs due to factors such as variations in the components of the fuel injection valve, changes over time, and non-linearity of the pulse width-flow rate characteristics of the fuel injection valve, feedback control is performed. .

However, if the base air-fuel ratio deviates from λ = 1, it takes time to stabilize the step of the base air-fuel ratio to λ = 1 by feedback control when the operating region changes greatly. Therefore, since the proportional and integral constants (P / I) are increased, overshoot and undershoot occur, and the controllability to λ = 1 becomes poor. That is, when the base air-fuel ratio deviates from λ = 1, the air-fuel ratio control is performed within a range that is considerably different from the theoretical air-fuel ratio.

As a result, the operation is performed in a place where the conversion efficiency of the three-way catalyst is poor, and the cost is increased due to an increase in the amount of precious metal in the catalyst, and the catalyst is replaced due to the deterioration of the conversion efficiency due to the deterioration of the catalyst. .

Therefore, by setting the base air-fuel ratio to λ = 1 by learning, it is possible to eliminate the deviation from λ = 1 caused by the step of the base air-fuel ratio at the time of transition, and to reduce the P / I component, which makes controllability easier. An air-fuel ratio learning control device for improving the above has been disclosed by the present applicant in Japanese Patent Application Laid-Open No. 59-203828.

This is because when the base air-fuel ratio deviates from the stoichiometric air-fuel ratio during feedback control of the air-fuel ratio, the deviation of the air-fuel ratio feedback correction coefficient α becomes large in order to fill the gap. Deviation Δα from the reference value (generally set to α = 1) of
A learning correction coefficient Kl based on α is obtained and stored, and when the same engine operating state is again generated, the stored learning correction coefficient Kl is used to correct the base air-fuel ratio so that it is responsive to the theoretical air-fuel ratio. The learning correction coefficient Kl is stored here for each area in a predetermined range obtained by dividing the map of the RAM according to an appropriate parameter of the engine operating state such as the engine speed and the load.

Specifically, a map of the learning correction coefficient Kl corresponding to the engine operating conditions such as engine speed and load is provided on the RAM, and when calculating the fuel injection amount Ti, the basic injection amount Tp is learned as in the following equation. Correct with the correction coefficient Kl.

Ti ＝ Tp ・ COEF ・ α ・ Kl ＋ Ts And, the learning of Kl proceeds in the following procedure.

i) The region of the engine operating state is detected, and the average value of α during that period is detected.

ii) Search for Kl learned up to now corresponding to the region of the engine operating state.

iii) Kl is newly set and stored based on Kl and.

<Problems to be Solved by the Invention> However, in a conventional learning control device that simply sets a learning correction value for each area divided into a grid according to such an engine operating state, in each learning area having a width Since the feedback control deviation amount is repeatedly learned, an air-fuel ratio step is likely to occur near the area boundary. In order to eliminate such a difference in the air-fuel ratio, if each learning area division is set finely, the time to stay in that area will be reduced, the learning update speed will be slower and unlearned areas may occur. When the vehicle passes through the learning area, a step of the air-fuel ratio occurs, which causes problems such as torque shock and deterioration of exhaust emission characteristics.

The present invention has been made in view of the above circumstances, and is a fuel injection flow rate due to a delay in opening and closing of the common fuel injection valve in the entire operating region, which is one of the factors causing the deviation of the base air-fuel ratio from λ = 1. It is an object of the present invention to provide an air-fuel ratio control device for an internal combustion engine, which can achieve both learning accuracy and learning speed by learning-correcting the error correction amount and prevents a difference in air-fuel ratio from occurring.

<Means for Solving the Problem> Therefore, according to the present invention, as shown in FIG. 1, a basic injection amount setting means for setting a basic injection amount from a parameter related to an intake air flow rate and an engine rotation speed, and an exhaust gas. Air-fuel ratio feedback correction coefficient setting means for setting an air-fuel ratio feedback correction coefficient by comparing an actual air-fuel ratio detected based on a signal from the air-fuel ratio detection means provided in the system with a theoretical air-fuel ratio, and the basic injection Fuel injection flow rate error correction amount setting means for setting an injection flow rate error correction amount for correcting an injection flow rate error due to opening and closing delay of the fuel injection valve with respect to the amount,
First learning correction coefficient search means for searching the learning correction coefficient stored in the map on the RAM corresponding to the engine operating conditions such as engine speed and load, the air-fuel ratio feedback correction coefficient, and the learning correction Learning correction coefficient updating means for setting a new learning correction coefficient from the coefficient and updating the data of the same engine operating condition in RAM with the learning correction coefficient, basic injection amount, air-fuel ratio feedback correction coefficient, and learning correction An internal combustion engine including an injection amount calculation means for calculating an injection amount by a coefficient and a fuel injection flow rate error correction amount, and a drive pulse signal output means for outputting a drive pulse signal corresponding to the calculated injection amount to a fuel injection valve. In an air-fuel ratio learning control device for an engine, an intake air flow rate region determination means for determining whether or not the intake air flow rate is within a predetermined flow rate region, and the intake air flow rate region is a predetermined flow rate region. Second learning correction coefficient retrieval means for retrieving the learning correction coefficient stored in the map on the RAM corresponding to a plurality of engine rotation speed regions set in advance when set, and the second learning correction coefficient retrieval Setting by the fuel injection flow rate error correction amount setting means for determining whether the plurality of learning correction coefficients retrieved by the means have a tendency of monotonous increase or monotonous decrease with respect to changes in the engine speed The fuel injection flow rate error correction amount correction unit corrects a decrease when the determination of the determination unit is a monotonous increase and an increase correction when the determination is a monotonous decrease.

In addition to the above configuration, a fuel injection flow rate error correction amount correction stop means for stopping the correction by the fuel injection flow rate error correction amount correction means in an engine operating state in which the intake air flow rate fluctuates greatly is provided.

<Operation> In the above configuration, the degree of influence of the deviation of the set value of the fuel injection flow rate error correction amount Ts on the fuel injection amount Ti is larger as the injection amount Ti is smaller, as is clear from the arithmetic expression of the fuel injection amount Ti. From this fact, when the intake air flow rate is constant, as the engine speed N is changed, N becomes larger, and when the setting of Ts is too large, the air-fuel ratio tends to become richer, and the setting of Ts becomes When it is too small, the air-fuel ratio tends to be leaner. Therefore, by setting a certain intake air flow rate region and examining the tendency of the learning correction coefficient according to the engine rotation speed in this region, it becomes possible to know how the setting of the injection flow rate error correction amount deviates. .

Based on this relationship, when the intake air flow rate region determining means determines whether the incoming air flow rate is within the predetermined flow rate region, and when the second learning correction coefficient searching means determines that the air flow rate region is within the predetermined flow rate region. The learning correction coefficient stored in the map on the RAM corresponding to a plurality of engine rotation speed regions set in advance is searched. Then, the determination means determines whether the plurality of learning correction coefficients retrieved by the second learning correction coefficient retrieval means tend to monotonically increase or monotonically decrease with respect to changes in the engine speed, and monotonically increases. At this time, the injection flow rate error correction amount set by the error correction amount setting means is decrementally corrected, when it is monotonically decreasing, it is increased and the latest correction value is stored as a learning value. As a result, it is possible to prevent an error in the air-fuel ratio due to a setting error in the fuel injection flow rate error correction amount or a change over time in the flow rate characteristic of the fuel injection valve (see FIG. 6).

Further, in an operating state in which the intake air flow rate varies greatly, such as in the intake pulsation region or during acceleration / deceleration, the detection accuracy of the detected intake air flow rate deteriorates, and the air-fuel ratio deviates from λ = 1. Since erroneous learning occurs, the learning of the injection flow rate error correction component Ts is stopped at this time to improve the reliability of correction of the set value for the injection flow rate error correction component.

<Example> Hereinafter, an example of the present invention is described based on a drawing.

In FIG. 2, air is sucked into the engine 1 from an air cleaner 2 through an intake duct 3, a throttle valve 4 and an intake manifold 5. A fuel injection valve 6 is provided in each branch of the intake manifold 5 for each cylinder. The fuel injection valve 6 is an electromagnetic fuel injection valve that is energized by a solenoid to open and stop energized to be closed. The fuel injection valve 6 is energized and opened by a drive pulse signal from a control unit 12 described later, and a fuel not shown is shown. Fuel that is pumped and adjusted to a predetermined pressure by a pressure regulator is injected and supplied. Although this example is a multi-point injection system, it may be a single-point injection system in which a single fuel injection valve is provided in common to all cylinders upstream of the throttle valve.

A spark plug 7 is provided in the combustion chamber of the engine 1 to spark-ignite and ignite and burn the air-fuel mixture. And
From engine 1, exhaust manifold 8, exhaust duct 9, three-way catalyst
Exhaust gas is exhausted through 10 and the muffler 11. Three-way catalyst
Reference numeral 10 is an exhaust gas purification device that oxidizes CO and HC in exhaust components and reduces NOx to convert them to other harmless substances.When the air-fuel mixture is burned at the stoichiometric air-fuel ratio, both are converted. The efficiency is the best.

The control unit 12 includes a microcomputer including a CPU, a ROM, a RAM, an A / D converter and an input / output interface, receives input signals from various sensors and a battery 17, and performs arithmetic processing as described later. Thus, the operation of the fuel injection valve 6 is controlled.

As the various sensors, a hot-wire type air flow meter 13 is provided in the intake duct 3, and the intake air flow rate Q
Output a voltage signal corresponding to.

Further, the crank angle sensor 14 is provided, and in the case of four cylinders, it outputs a reference signal for each crank angle of 180 ° and a unit signal for each crank angle of 1 ° or 2 °. Here, the engine speed N can be calculated by measuring the cycle of the reference signal or the number of unit signals generated within a predetermined time.

A water temperature sensor 15 for detecting the cooling water temperature Tw of the water jacket of the engine 1 is also provided.

Further, an O ₂ sensor 16 is provided at the collecting portion of the exhaust manifold 8 to detect the crank angle sensor of the air-fuel mixture sucked into the engine 1 via the O ₂ concentration in the exhaust. 17 is a battery.

Here, the CPU of the microcomputer incorporated in the control unit 12 controls the fuel injection by performing arithmetic processing according to the flowcharts of FIGS.

Next, the learning control of the present embodiment will be described based on the flowcharts of FIGS.

FIG. 3 is a learning value calculation routine of the correction amount Ts of the fuel injection flow rate error due to the opening and closing delay of the fuel injection valve based on the battery voltage fluctuation.

In step (denoted by S in the figure, the same applies hereinafter) 1,
It is determined whether the operating state is in the pulsation region of the intake air flow rate.
Here, the intake pulsation region is a high load operation region. When it is not in the intake pulsation region (NO), the routine proceeds to step 2, where it is determined whether or not the acceleration / deceleration operation is being performed, for example, the change rate ΔTVO of the throttle valve opening.
Is determined by whether ΔTVO ≠ 0. When it is in the intake pulsation region (YES) or during acceleration / deceleration (YES) in step 1 or step 2, this routine is ended.
If the routine is in a steady operation state other than during acceleration / deceleration, the routine proceeds to step 3. The steps 1 and 2 correspond to the fuel injection flow rate error correction amount correction stop means.

In step 3, the intake air flow rate Q obtained from the signal from the air flow meter 13 and the engine rotation speed N obtained from the crank angle sensor 14 are input.

In step 4, the flow rate region of the input intake air flow rate Q is determined. In this embodiment, the Q area is divided into four areas Q1 to Q4. For example, the Q1 area is 15 to 25 kg / h and the Q2 area is 35.
~ 45kg / h, 55-65kg / h in Q3 area and 75-85kg / h in Q4 area
There is. Therefore, in step 4, it is first determined whether or not it is the Q1 region. If YES is determined here, the process proceeds to step 5.

In step 5, the learning correction coefficient Kl corresponding to the area including the engine rotation speed N input in step 3 in the Q1 area is searched and stored from the learning correction coefficient map on the RAM described later. Here, the region of the engine rotation speed N is divided into a plurality of regions, for example, four regions N1 to N4, where N1 is 80
0-2000, N2 2000-3000, N3 3000-4000 and N4 4000
That is all. This portion corresponds to the second learning correction coefficient search means.

In step 6, it is determined whether or not the learning correction coefficient Kl of all the areas N1 to N4 in the area Q1 has been searched. If the learning correction coefficient Kl for all areas has been searched and stored, the process proceeds to step 7.

In step 7, it is determined whether or not the retrieved learning correction coefficient Kl monotonically increases with respect to the change in the engine rotation speed N. When it is monotonically increasing, the routine proceeds to step 8, where the current correction amount b is set to a predetermined value Δ to decrease and correct the injection flow rate error correction amount Ts.
Only b is subtracted to obtain a new correction amount b. On the other hand, when it is not monotonically increasing, the routine proceeds to step 9, where it is judged whether or not it is monotonically decreasing. In the case of a monotonic decrease, the routine proceeds to step 10, where the current correction amount b is added by a preset predetermined value Δb to increase and correct the fuel injection flow rate error correction amount Ts to obtain a new correction amount b. Here, steps 7 and 9 correspond to the determination means,
Steps 8 and 10 correspond to the fuel injection flow rate error correction amount correction means.

When the execution of step 8 or step 10 is completed, the process proceeds to step 11, and the stored learning correction coefficient Kl is cleared.

If it is determined in step 4 that the area is not the Q1 area, the process proceeds to step 12 and it is determined whether or not the area is the Q2 area. Judgment is NO
If, then go to step 13 to determine whether it is in the Q3 region,
If NO, proceed to step 14 to determine whether or not it is in the Q4 region, and NO
At this time, the routine is terminated without correcting the fuel injection flow rate error correction amount. On the other hand, when the determination is YES in any of steps 12 to 14, in steps 5 to 11 in the correction routine 15 to 17 for the corresponding fuel injection flow rate error correction amount Ts.
Similarly, the learning correction coefficient Kl corresponding to each engine rotation speed N region in the intake air flow rate region is retrieved to correct the correction amount b of the fuel injection flow rate error correction amount Ts. Step
The portions 4, 12 to 14 correspond to the intake air flow rate region determination means.

FIG. 4 shows a normal learning routine of the learning correction coefficient Kl for each area.

In step 21, it is determined whether or not a predetermined air-fuel ratio feedback control condition is satisfied. Here, the predetermined air-fuel ratio feedback control condition is that the engine speed N is equal to or lower than a predetermined value and the basic injection amount Tp representing the load is equal to or lower than a predetermined value. If this condition is not satisfied, this routine ends. When the air-fuel ratio feedback condition is satisfied, the routine proceeds to step 22.

In step 22, it is determined whether the engine speed N and the basic injection amount Tp are in the same area as the previous time, and if the area is changed, this routine is ended. On the other hand, if the areas are the same, the process proceeds to step 23, where the output of the O ₂ sensor 16 is reversed,
That is, it is determined whether or not the increasing / decreasing direction of the feedback correction coefficient α has been inverted a predetermined number of times, and if YES, the process proceeds to step 24.

In step 24, the average value of the present and past values of the air-fuel ratio feedback correction coefficient α during steady operation is calculated.

In step 25, from the engine speed N and the basic injection amount Tp,
The learning correction coefficient Kl corresponding to the current area on the RAM is searched. This step 25 corresponds to the first learning correction coefficient search means.

In step 26, an operation is performed according to the following equation from the retrieved Kl and the average value of the air-fuel ratio feedback correction coefficient, and the value is set as a new learning correction coefficient Kl
Update the value in the applicable area above. This step 26 corresponds to learning correction coefficient updating means.

Kl ← Kl + Δα / M where Δα is the deviation between the average value and the reference value α ₁ and Δα
= −α ₁ , and the reference value α ₁ is generally 1.0.
Further, M is a constant.

FIG. 5 shows a fuel injection amount calculation routine.

In step 31, the intake air flow rate Q obtained by the signal from the air flow meter 13, the engine rotation speed N obtained by the crank angle sensor 14, and the cooling water temperature Tw obtained by the water temperature sensor 15 are input.

In step 32, the intake air flow rate Q and the engine speed N
The basic injection amount Tp is calculated by and. This step 32 corresponds to the basic injection amount setting means.

In step 33, the cooling water temperature Tw and other engine operating conditions
Set COEF.

In step 34, the air-fuel ratio feedback correction coefficient α is set based on the signal from the O ₂ sensor 16. This Step 34
Corresponds to the air-fuel ratio feedback correction coefficient setting means.

In step 35, the latest learning correction coefficient Kl is read.

In step 36, the fuel injection flow rate error correction amount Ts is set based on the battery voltage. This portion corresponds to the fuel injection flow rate error correction amount setting means.

In step 37, the correction amount b set in the correction routine of the fuel injection flow rate error correction amount Ts of FIG. 3 is read.

In step 38, the fuel injection amount Ti is calculated according to the following equation. This step 38 corresponds to the injection amount calculation means.

Ti = Tp · COEF · α · Kl + Ts + b In step 39, a drive pulse signal having the calculated Ti pulse width is output to the fuel injection valve 6. This step 39 corresponds to drive pulse signal output means.

With this configuration, it is possible to prevent the air-fuel ratio from deviating due to the setting error of the fuel injection flow rate correction amount Ts. In addition, the deviation of the air-fuel ratio due to Ts is corrected when it comes to the driving area where learning has not progressed sufficiently, so the deviation of the air-fuel ratio can be minimized and the learning progress of that area can be promoted. Can be promoted. Therefore, the learning speed can be improved and the air-fuel ratio control accuracy can be improved.

Further, since the update of the correction amount of Ts is stopped during the pulsation operation region of intake air or during acceleration / deceleration, the reliability can be improved.

Although the intake air flow rate region is divided into four in this embodiment, the present invention is not limited to this. The same applies to the classification of engine rotation speed.

<Effects of the Invention> As described above, according to the present invention, it is possible to appropriately correct the fuel injection flow rate error correction amount based on the opening and closing delays of the fuel injection valve, so that learning does not proceed. Even in the area, the deviation of the air-fuel ratio can be reduced, the step difference in each area can be eliminated, the air-fuel ratio control accuracy can be improved, and harmful exhaust components can be reduced. Further, by stopping the update of the correction for the fuel injection flow rate error correction during the operation in which the intake air flow rate varies greatly, highly reliable correction can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining the configuration of the present invention, FIG. 2 is a configuration diagram showing an embodiment of the present invention, FIGS. 3 to 5 are flowcharts showing the control contents of the same embodiment, and FIG. FIG. 6 is a diagram showing changes in the flow rate characteristics of the fuel injection valve. 1 ... Engine, 6 ... Fuel injection valve, 12 ... Control unit, 13 ... Air flow meter, 14 ... Crank angle sensor, 16 ... O ₂ sensor, 17 ... Battery

Claims (2)

[Claims] 1. Actual detection based on a signal from a basic injection amount setting means for setting a basic injection amount from a parameter related to an intake air flow rate and an engine rotation speed, and a signal from an air-fuel ratio detecting means provided in an exhaust system. Air-fuel ratio feedback correction coefficient setting means for comparing the air-fuel ratio and the theoretical air-fuel ratio, and an injection flow rate error due to the opening and closing valve delay of the fuel injection valve with respect to the basic injection amount is corrected. Fuel injection flow rate error correction amount setting means for setting the injection flow rate error correction amount and the learning correction coefficient stored in the map on the RAM corresponding to this from the engine operating conditions such as engine speed and load And a new learning correction coefficient is set from the first learning correction coefficient searching means, the air-fuel ratio feedback correction coefficient, and the learning correction coefficient, and
The learning correction coefficient updating means for updating the data of the same engine operating condition in the RAM with the learning correction coefficient, and the injection amount calculated by the basic injection amount, the air-fuel ratio feedback correction coefficient, the learning correction coefficient, and the fuel injection flow rate error correction amount In the air-fuel ratio learning control device for an internal combustion engine, the intake air flow rate is set to a predetermined value, and an injection amount calculation means for controlling the injection amount and a drive pulse signal output means for outputting a drive pulse signal corresponding to the calculated injection amount to the fuel injection valve. Intake air flow rate region determining means for determining whether the flow rate region is a predetermined flow rate region, and when the intake air flow rate region is determined to be a predetermined flow rate region, it is stored in a map on the RAM corresponding to a plurality of engine rotation speed regions set in advance. Second learning correction coefficient searching means for searching for the learning correction coefficient that is present, and the plurality of learning correction coefficients searched by the second learning correction coefficient searching means correspond to changes in the engine speed. Determination means for determining whether there is a tendency of monotonous increase or monotonic decrease, and the fuel injection flow rate error correction amount set by the fuel injection flow rate error correction amount setting means is determined by the determination means to monotonically increase. And a fuel injection flow rate error correction amount correction unit that corrects the increase when it is monotonically decreasing, and an air-fuel ratio learning control device for an internal combustion engine. 2. The air-fuel ratio learning control system for an internal combustion engine according to claim 1, wherein the fuel injection flow rate for stopping the correction by the fuel injection flow rate error correction amount correction means in an engine operating state in which the intake air flow rate fluctuates greatly. An air-fuel ratio learning control device for an internal combustion engine, comprising: a correction stopping means for correcting an error.