JPH0226696B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to an air-fuel ratio learning control device in an electronically controlled fuel injection type internal combustion engine.

<Background technology> In an electronically controlled fuel injection type internal combustion engine, the injection amount
Ti is determined by the following formula.

Ti=Tp×COEF×α+Ts Here, Tp is the basic injection amount, and Tp=K×Q/N. K is a constant, Q is the intake air flow rate, and N is the engine speed. COEF is various correction coefficients. α
is an air-fuel ratio feedback correction coefficient for air-fuel ratio feedback control (λ control) to be described later. Ts is a voltage correction amount, which is used to correct changes in the injection amount of the electromagnetic fuel injector due to changes in battery voltage.

Regarding λ control, an O ₂ sensor is installed in the exhaust system to detect the actual air-fuel ratio, and the slice level determines whether the air-fuel ratio is richer or leaner than the stoichiometric air-fuel ratio, and fuel is injected to achieve the stoichiometric air-fuel ratio. For this purpose, the above-mentioned air-fuel ratio feedback correction coefficient α is determined, and by varying this α, the stoichiometric air-fuel ratio is maintained.

Here, the value of the air-fuel ratio feedback correction coefficient α is changed by proportional-integral (PI) control to ensure stable control.

In other words, the output of the _O2 sensor is compared with the slice level, and if it is higher or lower than the slice level, the air-fuel ratio is not suddenly richer or leaner, but when the air-fuel ratio is rich (lean). is controlled to make the air-fuel ratio leaner (richer) by first lowering (raising) it by P, then gradually lowering (raising) it by I minutes.

However, in the region where λ control is not performed, α=
1 and set various correction coefficients COEF to obtain the desired air-fuel ratio.

By the way, if the base air-fuel ratio when α = 1 in the λ control region could be set to the stoichiometric air-fuel ratio (λ = 1), feedback control would not be necessary. valves, pressure regulators,
control unit) variations and changes over time,
Due to factors such as the non-linearity of the pulse width-flow rate characteristic of the fuel injector, and changes in operating conditions and environment, the base air-fuel ratio λ may change.
= 1), feedback control is performed.

However, if the base air-fuel ratio deviates from λ=1, it takes time to set the step in the base air-fuel ratio to λ=1 by feedback control when the operating range changes significantly. For this purpose, the proportionality and integral constants (P/I) are increased, which causes overshoot and undershoot, resulting in poor controllability. In other words, if the base air-fuel ratio deviates from λ=1, the air-fuel ratio will be controlled within a range that deviates considerably from the stoichiometric air-fuel ratio.

As a result, the three-way catalyst is operated at a point where its conversion efficiency is poor, and not only does the cost increase due to the increase in the amount of precious metal in the catalyst, but the conversion efficiency further deteriorates as the catalyst deteriorates, forcing the catalyst to be replaced. There was a problem.

Therefore, by setting the base air-fuel ratio to λ = 1 through learning, the deviation from λ = 1 caused by the step in the base air-fuel ratio during transient times can be eliminated, and the P/I
A base air-fuel ratio learning device has been devised to improve controllability by making it possible to reduce the amount of fuel, thereby reducing the cost of the catalyst.

In other words, a map of the learning correction coefficient α ₀ corresponding to the engine speed and load operating conditions is provided in the RAM.
When calculating the injection amount Ti, use the basic injection amount as shown in the following formula.
Correct Tp by α ₀ .

Ti=Tp×COEF×α×α ₀ +Ts Then, the learning of α ₀ proceeds as follows.

(i) Detect the engine operating conditions and the control center value αc of α in a steady state.

(ii) Search for α ₀ that has been learned and stored up to now in accordance with the engine operating conditions.

(iii) Find the value of α ₀ +Δα/M from αc and α ₀ and update the memory with the result (learning value) as new α ₀ .

Note that Δα indicates the amount of deviation from the reference value α ₁ , Δα=αc−α ₁ , and the reference value α ₁ is generally 1.0. Also,
M is a constant.

By the way, in such a conventional learning method in air-fuel ratio feedback control, since the deviation amount Δα cannot be detected accurately unless it is in a steady state, learning is performed by detecting Δα only in a steady state.
In this case, learning is not performed in the operating range where the vehicle operates only temporarily during the transient operating state.

For this reason, there are areas where the learning progress is large (hereinafter referred to as learning areas) and other areas where the learning progress is small (hereinafter referred to as unlearning areas). If the operating condition changes in this state, if a deviation occurs in the air-fuel ratio in the system, there will be a deviation in the correspondence between α and the air-fuel ratio λ between the learning area and the unlearning area, so the learning area A difference in the air-fuel ratio λ occurs when moving between the and unlearned region, leading to deterioration of exhaust emission characteristics and deterioration of fuel efficiency in a transient state, and there is virtually no effect of learning.

Furthermore, even during transient operation when moving between unlearned regions, the reliability of the learning correction coefficient α ₀ is poor, making it impossible to suppress overshoot or undershoot of the air-fuel ratio feedback correction coefficient α. This resulted in deterioration of characteristics and fuel consumption. On the other hand, among the factors that cause the base air-fuel ratio to deviate from λ = 1, the error in calculating the intake air flow rate Q by the air flow meter is thought to account for a fairly large proportion; for example, in the case of a hot-wire air flow meter, , the measurement error progresses significantly due to dust adhering to the heating wire and deterioration of the heating wire itself.

In this case, in the region where the intake air flow rate Q is equal, Q
It is considered that the measurement errors ΔQ of are also equal.

<Purpose of the Invention> The present invention has been made in view of the above points, and is based on the learning value learned in the driving region where the learning progress is large. It is an object of the present invention to provide an air-fuel ratio learning control device for an electronically controlled fuel injection type internal combustion engine, which improves the reliability of learned values by performing learning in the operating region, and improves the accuracy of air-fuel ratio control.

<Configuration of the Invention> For this reason, the present invention, as shown in _FIG . an air-fuel ratio feedback correction coefficient setting means for setting an air-fuel ratio feedback correction coefficient by proportional-integral control by comparing the actual air-fuel ratio detected based on the signal of the stoichiometric air-fuel ratio with the stoichiometric air-fuel ratio; a learning correction coefficient search means for searching a learning correction coefficient stored in a map on the RAM corresponding to the operating conditions; and setting a new learning correction coefficient from the air-fuel ratio feedback correction coefficient and the learning correction coefficient; And with that learning correction coefficient
a first learning correction coefficient updating means for updating data on the operating conditions of the same engine in RAM; and learning for determining the learning progress based on the number of data updates for each operating condition in the first learning correction coefficient updating means. When the progress determining means and the learning correction coefficient data are updated, the intake air flow rate is equal to the operating condition updated based on the updated data, and the learning progress determining means determines that the learning progress is small. a second learning correction coefficient updating means for setting learning correction coefficient data under other operating conditions determined as such and updating the memory map in the RAM; an injection amount calculation means that calculates the injection amount by multiplication; a drive pulse signal output means that outputs a drive pulse signal corresponding to the calculated injection amount to the fuel injection valve;
The configuration includes the following.

<Example> Examples will be described below.

Figure 2 shows the hardware configuration.

1 is CPU, 2 is P-ROM, 3 is for learning control
CMOS-RAM, 4 is an address decoder.
Note that a backup power supply circuit is used for the RAM 3 in order to retain the memory contents even after the key switch is turned off.

The hot wire air flow meter 5 is used as an analog input signal to the CPU 1 for controlling the fuel injection amount.
intake air flow rate signal from the throttle sensor 6, throttle opening signal from the throttle sensor 6, water temperature signal from the water temperature sensor 7, exhaust oxygen concentration signal from the _O2 sensor 8,
There is a battery voltage from the battery 9, which is adapted to be input via an analog input interface 10 and an A/D converter 11. 1
2 is an A/D conversion timing controller.

Digital input signals include ON/OFF signals from an idle switch 13, a start switch 14, and a neutral switch 15, and these are inputted via a digital input interface 16.

In addition, for example, from the crank angle sensor 17
A reference signal every 180 degrees and a position signal every 1 degree are inputted via a one-shot multi-circuit. Further, a vehicle speed signal from a vehicle speed sensor 19 is inputted via a waveform shaping circuit 20.

An output signal from the CPU 1 (a drive pulse signal to the fuel injection valve) is sent to the fuel injection valve 22 via a current waveform control circuit 21.

Here, the CPU 1 performs input/output operations, arithmetic processing, etc. according to a program (stored in the ROM 2) based on the flowchart (fuel injection amount calculation routine) shown in FIG. 3, and controls the fuel injection amount.

Next, the flowchart shown in FIG. 3 will be explained.

The intake air flow rate Q obtained from the signal from the air flow meter 5 at S1 and the crank angle sensor 17
The basic injection amount Tp (=K×Q/N) is calculated from the engine speed N obtained from the signal from the engine.

Set various correction coefficients COEF in S2.

In S3, the output voltage of the O ₂ sensor 8 and the slice level voltage are compared and the air-fuel ratio feedback correction coefficient α is set by proportional-integral control. However, in the region where λ control is not performed, α is clamped to 1. Further, the data α ₀ already learned from the learning MAP on the RAM 3 is referred to in correspondence with (N, Tp) at that time.

In S4, a voltage correction amount Ts is set based on the battery voltage from the battery 9.

In S5, parameters indicating the engine operating state include engine speed N and basic injection amount (load).
The driving area according to Tp is divided into multiple areas, and the current (N, Tp) is calculated from a map (stored in RAM3) stored in the learning correction coefficient α ₀ described later for each area.
The area where the area exists is searched and data indicating the area is set in a predetermined location A of the RAM 3.

In S6, the current (N,
The data in the area where Tp) exists is also stored in RAM3.
Last searched (N,
Tp) is compared with the data of the area where it exists to determine whether they are the same. If the answer is YES, that is, if it is determined that the operating conditions are substantially the same, the process advances to S7.

In S7, the output voltage of O ₂ sensor 8 is determined by S6.
Determine whether it has been reversed n times after becoming YES,
If YES, proceed to S8.

In other words, S6 and S7 are provided to determine whether the operating state is in a steady state.
If the determination is YES, it is determined that the state is in a steady state. Although such a steady state determination method can be performed easily and with high accuracy, there is also a method of determining whether a predetermined time has elapsed with the vehicle speed constant, the gear position non-neutral, and the throttle opening constant. etc. may be adopted. If the determination in either S6 or S7 is NO, it is determined that the state is unsteady, and in this case, the process proceeds to S16 without going through the processes from S8 to S15, which will be described later.

In S8, the control center value αc of the air-fuel ratio feedback correction coefficient α in the steady operating state is calculated.
This is, for example, the air-fuel ratio feedback correction coefficient α
It is also possible to find the average value from the time when the value of increases or decreases until the time of reversal, or to find the average value of only the value of the air-fuel ratio feedback correction coefficient α at the time of reversal.In this way, the steady state The control value αc can be determined more accurately.

In S9, from engine speed N and basic injection amount Tp
The learning correction coefficient α ₀ corresponding to (N, Tp) stored in the area of the RAM 3 where (N, Tp) exists is searched. Note that α ₀ stored in the map
The values of are all α ₀ = at the time when learning has not started.
1.

In S10, the learning correction coefficient α ₀ found in S9
and the control center value αc calculated in S8 according to the following formula, set the value as a new learning correction coefficient α ₀ , update the value in the corresponding area of the α ₀ map, and The count value of the learning counter provided for each area is updated.

α ₀ ← α ₀ + Δα/M In addition, in Δα, αc indicates the amount of deviation from the reference value, Δα=αc−α ₁ , and the reference value α ₁ is generally 1.0. Also M
is a constant.

The value of M, which determines the rate at which the learning deviation amount Δα of the learning correction coefficient α ₀ is added, may be constant, but if it is set to a value proportional to the engine speed, the PI control coefficient of α can be adjusted according to the increase in the injection cycle. Since the injection amount can be decreased, more accurate injection amount control can be performed.

In S11, the data of the previous area (N, Tp) set at address LA of RAM 3 is updated by transferring the data of the current area (N, Tp) set at address A. .

In S12, from the α ₀ map of RAM3, the intake air flow rate Q (=Tp・
Search for an area with operating conditions that have Q equal to N).

In S13, the count value C of the learning counter in each area searched in S12 is searched, and then in S14
, the count value of each area is a predetermined value.
The degree of learning progress is determined by determining whether C is ₁ or less.

Then, if the determination in S14 is YES,
In other words, if it is determined that the learning progress is in a small area,
Proceed to S15 and set the learning correction coefficient α ₀ in the area
is updated by replacing the data with the data of learning correction coefficient α ₀ learned in the current area.

If the determination in S14 is NO, that is, in areas where the degree of learning progress is determined to be high, the data is not updated and is maintained at the current state.

In S16, the injection amount Ti is calculated according to the following formula.

Ti=Tp×COEF×α×α ₀ +Ts Here, in a steady state, the learning correction coefficient α ₀ updated in S10 is used, and in a transient state, the one updated in S10 is used. Used.

The injection amount Ti is calculated above, and this injection amount is calculated in S17.
A drive pulse signal corresponding to Ti is given to the fuel injection valve 22 at a predetermined timing via the current waveform control circuit 21.

On the other hand, in the region where λ control is not performed, the air-fuel ratio feedback correction coefficient α is 1.
Although the steps S5 to S14 are omitted, the learning result set on the equal intake air flow rate line is referred to as α ₀ in S3. Therefore, the injection amount is given by the following equation.

Ti=Tp×COEF×α ₀ +Ts However, Tp=K×Q/ _N In this way, even in areas where the learning progress is small, the learning correction coefficient Since it is updated based on the learning correction coefficient, it is possible to eliminate the difference in the air-fuel ratio λ when moving between the learning area and the unlearning area, and even during transient operation when moving between the unlearning area. By increasing the learning progress, overshoot and undershoot of the air-fuel ratio feedback correction coefficient α can be suppressed, and the settling to λ=1 is accelerated, resulting in a significant improvement in controllability.

In this embodiment, the data in the unlearned area is updated using the learned data, but considering the influence of the measurement error of the intake air flow rate Q on the deviation from λ=1, A predetermined percentage of data in the unlearned area may be updated. In addition, the learned data and the old data in the unlearned area may be updated with a value obtained by averaging them using a weighted average or the like.

Also, the judgment based on the learned count value of the unlearned area can be done by comparing it with the learning count value in the learned area and determining the area below this as an unlearned area, or by calculating the count for each area for all areas. A method of determining based on the ratio of values may also be used. In this way, it is possible to update the learning correction coefficient in the unlearned area from the beginning of learning, that is, to perform actual learning, and even after the overall learning has progressed, it is possible to update the learning correction coefficient in the unlearned area (the actual learning frequency is small and the learning This has the advantage of being able to update the learning correction coefficients (areas with poor reliability), allowing good learning to be performed permanently.

Furthermore, although omitted in this example, in areas where the learning progress is large, the air-fuel ratio feedback correction coefficient α
It is also possible to suppress overshoot and undershoot by reducing the P and I components.

<Effects of the Invention> As explained above, according to the present invention, based on the data of the latest learning correction coefficient α ₀ , the data of the learned operating area and the operating area where the intake air flow rate Q is equal and the learning progress is small are calculated. Since it is configured to update, it is possible to eliminate the difference in air-fuel ratio when moving between the learning area and the unlearning area, and also during transient operation when moving between the learning areas as well as between the unlearning areas. Overshoot and undershoot of the air-fuel ratio feedback correction coefficient can be suppressed, and the settling to λ=1 can be accelerated. As a result, the accuracy of air-fuel ratio feedback control can be greatly improved, which in turn improves exhaust emission characteristics, leading to improved fuel efficiency, and other excellent features.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the configuration of the present invention, FIG. 2 is a hardware configuration diagram showing one embodiment of the present invention, and FIG. 3 is a flowchart showing the control process of the same embodiment. 1...CPU, 3...CMOS for learning control
RAM, 5...Air flow meter, 8... _O2 sensor, 17...Crank angle sensor, 22...Fuel injection valve.

Claims (1)

[Claims] 1 Basic injection amount calculation means that calculates the basic injection amount from the intake air flow rate and engine speed, and the actual air-fuel ratio and theoretical air-fuel ratio detected based on the signal from the O ₂ sensor installed in the exhaust system. An air-fuel ratio feedback correction coefficient setting means that compares and sets an air-fuel ratio feedback correction coefficient by proportional-integral control, and learning that corresponds to engine operating conditions such as engine speed and load and is stored in a map on the RAM. A learning correction coefficient search means for searching a correction coefficient, setting a new learning correction coefficient from the air-fuel ratio feedback correction coefficient and the learning correction coefficient, and updating data for the same engine operating condition in the RAM with the learning correction coefficient. a first learning correction coefficient updating means;
learning progress determining means for determining the degree of learning progress based on the number of times data is updated for each type of driving condition in the learning correction coefficient updating means; Setting learning correction coefficient data under other operating conditions in which the intake air flow rate is equal to the operating condition and the learning progress is determined to be small by the learning progress determining means, and updating the memory map in the RAM. 2, learning correction coefficient updating means, and injection amount calculation means for calculating the injection amount by multiplying the basic injection amount by the air-fuel ratio feedback correction coefficient and the learning correction coefficient;
A learning control device for an air-fuel ratio in an electronically controlled fuel injection type internal combustion engine, comprising a drive pulse signal output means for outputting a drive pulse signal corresponding to the calculated injection amount to the fuel injection valve. .