JPH0461181B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a learning control device for an air-fuel ratio feedback control system in an internal combustion engine having an electronically controlled fuel injection device.

<Prior Art> A fuel injection valve used in an electronically controlled fuel injection device opens in response to a drive pulse signal given in synchronization with engine rotation, and injects fuel at a predetermined pressure during the valve opening period. It has become commonplace. Therefore, the fuel injection amount is controlled by the pulse width of the drive pulse signal, and if this pulse width is set as Ti and the control signal corresponds to the fuel injection amount, then in order to obtain the stoichiometric air-fuel ratio, which is the target air-fuel ratio, Ti is as follows. determined by the formula.

Ti=Tp・COEF・α+Ts However, Tp is the basic pulse width corresponding to the basic fuel injection amount and is called the basic fuel injection amount for convenience. Tp＝
K·Q/N, where K is a constant, Q is the engine intake air flow rate, and N is the engine speed. COEF is various correction coefficients such as water temperature correction. α is a 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 flow rate of the 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 whether the air-fuel ratio is richer or leaner than the stoichiometric air-fuel ratio is controlled by the slice level. A coefficient α is determined and the stoichiometric air-fuel ratio is maintained by varying this α.

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

In other words, the output voltage of the O ₂ sensor is compared with the slice level voltage, and if it is higher or lower than the slice level, the air-fuel ratio is rich (lean) without suddenly enriching or thinning the air-fuel ratio. ), the air-fuel ratio is controlled to be leaner (richer) by first lowering (raising) it by P, and then gradually lowering (raising) it by I.

However, under conditions where λ control is not performed, α
The desired air-fuel ratio is obtained by clamping and setting various correction coefficients COEF.

By the way, the base air-fuel ratio under λ control conditions, that is, the air-fuel ratio when α=1, is the stoichiometric air-fuel ratio (λ
= 1), there is no need for feedback control; however, in reality, it is difficult to control due to variations in component parts (for example, air flow meters, fuel injection valves, pressure regulators, control units), changes over time, and fuel injection. Feedback control is performed because the base air-fuel ratio deviates from λ=1 due to factors such as non-linearity in the pulse width-flow rate characteristic of the valve and changes in operating conditions and environment.

However, if the base air-fuel ratio deviates from λ=1, it takes time to stabilize the step in the base air-fuel ratio to λ=1 through 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. .

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
The applicant has developed an air-fuel ratio learning control device that improves controllability by making it possible to reduce the
It was filed as Japanese Patent Application No. 58-76221 (Japanese Unexamined Patent Publication No. 59-203828) or Japanese Patent Application No. 58-197499.

This is because if the base air-fuel ratio deviates from the stoichiometric air-fuel ratio during air-fuel ratio feedback control, the feedback correction coefficient α increases to fill the gap, so the engine operating state and α at this time are detected. , calculate the learning correction coefficient Kl based on α and store it, and when the same engine operating condition returns, the base air-fuel ratio is corrected using the stored learning correction coefficient Kl so that it is more responsive to the stoichiometric air-fuel ratio. do. Here, the learning correction coefficient Kl is stored for each region of a predetermined range obtained by dividing the RAM map into a grid according to appropriate parameters of the engine operating state such as engine speed and load.

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

Ti=Tp・COEF・Kl・α＋Ts Then, learn Kl by following the steps below.

In the steady state, the region of the engine operating state at that time is detected, and the deviation Δα (=α−α ₁ ) of α from the reference value α ₁ during that period is detected as an average value. The reference value α ₁ is generally set to 1.0 as a value corresponding to λ=1.

The Kl that has been learned up to now corresponding to the region of the engine operating state is searched.

The value of Kl + M ₁ · Δα is calculated from Kl and Δα, and the memory is updated using the result (learning value) as a new Kl _(oew) . M ₁ is a constant, 0<M ₁ <1.

<Problems to be Solved by the Invention> By the way, in such a conventional learning control device for an air-fuel ratio feedback control system, the deviation Δα
Detection accuracy cannot be obtained unless the engine is in a steady state, so if the steady state, that is, the engine operating state, is
For example, if the direction of increase/decrease of the feedback correction coefficient α is continuously in one region and in that region,
Since learning is performed by detecting Δα only after the rotation is reversed, learning is not performed in a region that is only temporarily passed during transient operation.

For this reason, there are areas where the learning progress is large (learning areas) and other areas where the learning progress is small (unlearning areas).

In this state, during transient operation in which the engine operating state is transferred between the learned region and the unlearned region or between the unlearned regions, a step is created in the air-fuel ratio, causing deterioration of exhaust emissions in the transient state. However, there was a problem that the effect of learning control was not sufficiently improved.

Specifically, as shown in Fig. 6, when the engine operating state changes from region to region, and only temporarily passes through the region, it is difficult to learn enough about the region. carried out,
As a result of obtaining almost optimal learning correction coefficients Kl() and Kl(), even if the feedback correction coefficient α in the region is controlled around the reference value α ₁ (=1.0), the region is still undeveloped. If the learning region remains and its learning correction coefficient Kl() remains almost at its initial value (1.0), and its optimal value is, for example, 1.2, then the feedback correction coefficient α is 1.2.
During the transition and return, a step occurs in the air-fuel ratio, leading to deterioration of exhaust emissions during transient conditions.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to expand the effectiveness of learning control by enabling effective learning even in regions that only pass through transiently.

<Means for Solving the Problems> In order to achieve the above object, the present invention provides an air-fuel ratio learning control device for an internal combustion engine, as shown in FIG. It is constructed by means (J) for learning in a transient state.

(A) A first detection means for detecting the engine intake air flow rate, a second detection means for detecting the engine speed, and a third detection means for detecting the engine exhaust component and thereby detecting the air-fuel ratio of the engine intake air mixture. An engine operating state detecting means (B) including at least a detecting means, which calculates a basic fuel injection amount based on the engine intake air flow rate outputted by the first detecting means and the engine rotational speed outputted by the second detecting means. Basic fuel injection amount calculation means (C) Rewritable storage means that stores learning correction coefficients for correcting the basic fuel injection amount for each region of engine operating conditions (D) Storage means that stores learning correction coefficients for correcting the basic fuel injection amount for each region of engine operating conditions. a learning correction coefficient search means (E) for searching a learning correction coefficient for a corresponding region from the means; comparing the air-fuel ratio outputted by the third detection means with the target air-fuel ratio so as to bring the actual air-fuel ratio closer to the target air-fuel ratio; (F) feedback correction coefficient setting means for increasing or decreasing a feedback correction coefficient by a predetermined amount for correcting the basic fuel injection amount; (F) the basic fuel injection amount calculated by the basic fuel injection amount calculation means; fuel injection amount calculation means (G) for calculating the fuel injection amount based on the learning correction coefficient searched by the correction coefficient search means and the feedback correction coefficient set by the feedback correction coefficient setting means; Fuel injection means (H) that injects fuel into the engine on and off in response to a drive pulse signal corresponding to the fuel injection amount When the actual engine operating condition is in one arbitrary region, the direction of increase or decrease of the feedback correction coefficient in that region Steady and transient state determination means (I) that determines a steady state when the state has been reversed a predetermined number of times or more, and determines the other states as a transient state. First learning correction coefficient correction means (J) that corrects and rewrites the learning correction coefficient corresponding to the region of the engine operating state during the period in the direction of learning and decreasing the learning correction coefficient. The increase/decrease value of the feedback correction coefficient is learned during the time period from when the engine moves to the current area until the direction of increase/decrease of the feedback correction coefficient is reversed, and based on this increase/decrease value, learning correction corresponding to the area of the engine operating state during this period is performed. Second learning correction coefficient correction means for correcting and rewriting the coefficient (Operation) The basic fuel injection amount calculation means B calculates the basic fuel injection amount corresponding to the target air-fuel ratio from the engine intake air flow rate and the engine speed. The learning correction coefficient retrieval means D searches the storage means C for a learning correction coefficient in a region corresponding to the actual engine operating state, and the feedback correction coefficient setting means E calculates the actual air-fuel ratio. and the target air-fuel ratio, and the feedback correction coefficient is set to increase or decrease by a predetermined amount based on, for example, proportional-integral control so that the actual air-fuel ratio approaches the target air-fuel ratio. Then, the fuel injection amount calculation means F calculates the fuel injection amount by correcting the basic fuel injection amount using a learning correction coefficient (the one retrieved or the one modified as described later after the search) and further correcting it with a feedback correction coefficient. . Then, the fuel injection means G is actuated by a drive pulse signal corresponding to this fuel injection amount.

The steady and transient state determination means H determines that the actual engine operating state exists continuously and stably in one arbitrary region, that is, that the feedback correction coefficient has been inverted a predetermined number of times or more after entering a certain region. We know that the state is in a steady state, and we know that the other state is in a transient state.

In a steady state, the first learning correction coefficient correction means I learns the average value of the deviation of the feedback correction coefficient from the reference value during that period, and responds to the region of the engine operating state during that period in a direction to reduce this. The learning correction coefficient is corrected and the data in the storage means C is rewritten.

In the transient state, the second learning correction coefficient correction means J adjusts the feedback correction coefficient during the time until the direction of increase/decrease of the feedback correction coefficient is reversed after moving from another area different from the current area to the current area. Based on the increase/decrease value, the learning correction coefficient corresponding to the region of the engine operating state during this period is corrected, and the data in the storage means C is rewritten.

That is, in a region where the feedback correction coefficient passes only in a transient manner, the increase/decrease value of the feedback correction coefficient during the time when the feedback correction coefficient is deflected is learned.
In this way, an optimal learning correction coefficient is obtained, and learning accuracy and learning speed are improved.

<Example> An embodiment of the present invention will be described below.

In FIG. 2, air is taken into the engine 1 through an air cleaner 2, an intake duct 3, a throttle chamber 4, and an intake manifold 5. As shown in FIG.

The intake duct 3 is provided with an air flow meter 6 as means for detecting the intake air flow rate Q, and outputs a voltage signal corresponding to the intake air flow rate Q signal. The throttle chamber 4 is provided with a primary throttle valve 7 and a secondary throttle valve 8 which are operated in conjunction with an accelerator pedal (not shown) to control the intake air flow rate Q. Further, an auxiliary air passage 9 is provided that bypasses these throttle valves 7 and 8, and an idle control valve 10 is interposed in this auxiliary air passage 9. The intake manifold 5 or the intake port of the engine 1 is provided with a fuel injection valve 11 as a fuel injection means. The fuel injection valve 11 is an electromagnetic fuel injection valve that opens when the solenoid is energized and closes when the energization is stopped, and opens when the solenoid is energized by a drive pulse signal.
The engine 1 is injected with fuel that is pressure-fed from a fuel pump (not shown) and controlled to a predetermined pressure by a pressure regulator.

Exhaust gas is exhausted from the engine 1 via an exhaust manifold 12, an exhaust duct 13, a three-way catalyst 14, and a muffler 15.

The exhaust manifold 12 is provided with an O ₂ sensor 16 . This O ₂ sensor 16 outputs a voltage signal according to the ratio of the oxygen concentration in the atmosphere (constant) and the oxygen concentration in the exhaust gas, and is known to cause a sudden change in electromotive force when the air-fuel mixture is combusted at the stoichiometric air-fuel ratio. It is a sensor of Therefore, the O ₂ sensor 16 is a means for detecting the air-fuel ratio (rich/lean) of the air-fuel mixture. Three-way catalyst 14
is a catalyst device that efficiently oxidizes or reduces CO, HC, and NOx in exhaust gas near the stoichiometric air-fuel ratio of the air-fuel mixture and converts them into other harmless substances.

In addition, a crank angle sensor 17 is provided. The crank angle sensor 17 is connected to the crank pulley 1
8 is provided with a signal disk plate 19,
For example, the teeth provided on the outer circumference of the plate 19
It outputs a reference signal every 120 degrees and a position signal every 1 degree. Here, the engine rotation speed N can be calculated by measuring the period of the reference signal. Therefore, the crank angle sensor 17 is a means for detecting not only the crank angle but also the engine speed N.

The air flow meter 6 and the crank angle sensor 1
7 and the O ₂ sensor 16 are both input to a control unit 30. Furthermore, the voltage of a battery 20 is directly applied to the control unit 30 via an engine key switch 21 as its operating power source and for detecting the power supply voltage. Furthermore, control unit 3
0 includes, as necessary, a water temperature sensor 22 that detects the engine cooling water temperature, a throttle sensor 23 including an idle switch that detects the throttle opening of the primary throttle valve 7, and a continuous speed sensor 2 that detects the vehicle speed.
4. A signal from a neutral switch 25 or the like that detects the neutral position of the transmission is input. The control unit 30 performs arithmetic processing based on various input signals and outputs a drive pulse signal with an optimal pulse width to the fuel injection valve 11 to obtain the fuel injection amount for obtaining the optimal air-fuel ratio.

As shown in FIG. 3, the control unit 30 includes a CPU 31, a P-ROM 32, a CMOS-
It has a RAM 33 and an address decoder 34. Here, the RAM 33 is a rewritable storage means for learning control, and as an operating power source for the RAM 33, a battery 20 is used as the operating power source without using the engine key switch 21 in order to retain the memory contents even after the engine key switch 21 is turned off. Connect via a stabilized power supply.

Among the input signals to the CPU 31, each voltage signal from the air flow meter 6, O ₂ sensor 16, battery 20, water temperature sensor 22, and throttle sensor 23 is an analog signal. The signal is input via a converter 36. The A/D converter 36 is controlled by the CPU 31 via an address decoder 34 and an A/D conversion timing controller 37. The reference signal and position signal from the crank angle sensor 17 are inputted via a one-shot multi-circuit 38. The signal from the idle switch built into the throttle sensor 23 and the signal from the neutral switch 25 are inputted via the digital input interface 39, and the signal from the vehicle speed sensor 24 is inputted via the waveform shaping circuit 40. It's getting old.

An output signal from the CPU 31 (a driving pulse signal for the fuel injection valve 11 ) is sent to the fuel injection valve 11 via a current waveform control circuit 41 .

Here, the CPU 31 performs input/output operations, arithmetic processing, etc. according to a program (stored in the ROM 32) based on the flowchart (fuel injection amount calculation routine and learning subroutine) shown in FIGS. 4 and 5. Controls fuel injection amount.

Furthermore, basic fuel injection amount calculation means, learning correction coefficient retrieval means, feedback correction coefficient setting means, fuel injection amount calculation means, steady and transient state determination means, first learning correction coefficient correction means, and second learning correction coefficient correction means The function as a means is achieved by the program.

Next, the operation will be explained with reference to the flowcharts of FIGS. 4 and 5.

In FIG. 4, in step 1 (S1 in the figure), basic fuel injection is performed based on the intake air flow rate Q obtained from the signal from the air flow meter 6 and the engine speed N obtained from the signal from the crank angle sensor 17. Calculate the quantity Tp (=K·Q/N). This part corresponds to the basic fuel injection amount calculation means.

In step 2, various correction coefficients COEF are applied as necessary.
Set.

In step 3, a corresponding learning correction coefficient Kl is searched from the engine speed N representing the engine operating state and the basic fuel injection amount (load) Tp. This part corresponds to the learning correction coefficient search means.

Here, the learning correction coefficient Kl is determined by partitioning the map with the engine speed N on the horizontal axis and the basic fuel injection amount Tp on the vertical axis using a grid of about 8 x 8, dividing the area, and storing each area on the RAM 33. A learning correction coefficient Kl is stored for each time. Note that at the time when learning has not started, all learning correction coefficients Kl are set to an initial value of 1.0.

In step 4, a voltage correction amount Ts is set based on the voltage value of the battery 20.

In step 5, it is determined whether the λ control condition is met.

Here, if the condition is not the λ control condition, for example, in a high rotation, high load region, etc., the feedback correction coefficient α is clamped to the previous value (or reference value α ₁ ), and the process proceeds from step 5 to step 10, which will be described later.

For λ control conditions, steps 6 to 8
The output voltage of the O ₂ sensor 16 is compared with the slice level voltage to determine whether the air-fuel ratio is rich or lean, and the feedback correction coefficient α is set by integral control or proportional-integral control. This portion corresponds to the feedback correction coefficient setting means. Specifically, in the case of integral control, the air-fuel ratio =
When it is determined that the air-fuel ratio is rich, the feedback correction coefficient α is decreased by a predetermined integral ( is increased by a predetermined integral (). In the case of proportional-integral control, in addition to this, when reversing rich←→lean, an increase or decrease is performed by a predetermined proportional amount (P) larger than the integral () in the same direction as the integral ().

In the next step 9, the learning subroutine shown in FIG. 5 is executed. This will be discussed later.

Thereafter, in step 10, the fuel injection amount Ti is calculated according to the following equation. This part corresponds to the fuel injection amount calculation means.

Ti=Tp・COEF・Kl・α+Ts When the fuel injection amount Ti is calculated, a drive pulse signal with a pulse width of that Ti is output at a predetermined timing in synchronization with the engine rotation, and is output via the current waveform control circuit 41. is applied to the fuel injection valve 11, and fuel injection is performed.

Next, the learning subroutine shown in FIG. 5 will be explained.

In step 11, it is determined whether the engine rotational speed N, which represents the engine operating state, and the basic fuel injection amount Tp are in the same range as the previous time. Only in the case of the same area as the previous time, the process proceeds to step 12, and it is determined whether or not the feedback correction coefficient α is in a steady state. Specifically, when the direction of increase or decrease of the feedback correction coefficient α is reversed twice or more in the same area,
In other words, when the output of the O ₂ sensor 16 is reversed twice or more, it is regarded as a steady state and the process proceeds to step 13, whereas before that it is regarded as a transient state and the process proceeds to step 1.
Proceed to step 6. This part corresponds to the steady state and transient state determining means.

In a steady state, each time the output of the O ₂ sensor 16 (and thus the direction of increase or decrease of the feedback correction coefficient α) is reversed in step ₁₃ , the deviation Δα (=
α−α ₁ ) is taken as the average value. Specifically, referring to FIG. 6 and looking at the region, between the third and fourth reversals in that region, the deviation at the third reversal Δα ₁ and the deviation at the fourth reversal Δα ₂ As the average value of Δα=(Δα ₁ +Δα ₂ )/2
It is sufficient to obtain the average value of the deviation Δα between the fourth reversal and the fifth reversal.

Next, in step 14, the reference value α ₁ of the feedback correction coefficient α is set to the current learning correction coefficient Kl as shown in the following equation.
A new learning correction coefficient Kl _(oew) is set by adding a predetermined proportion of the average deviation Δα from . This portion corresponds to the first learning correction coefficient correction means.

Kl _(oew) ←Kl+M ₁・Δα (M ₁ is a constant, 0<M ₁ <1) In a transient state, in step 16, the output of the O ₂ sensor 16 (and therefore the direction of increase or decrease of the feedback correction coefficient α) is Every time there is a reversal, the reversal time tx and the increase/decrease value X of the feedback correction coefficient α
(See Figure 6).

This means that in Figure 6, the area is the learning area,
This is because, assuming that the region is an unlearned region, the increase/decrease value X approximately represents the deviation of the optimal learning correction coefficient of the region from the learning correction coefficient Kl( ) of the learning region. However, strictly speaking, it is the time from when fuel injection is performed until its influence appears on the O ₂ sensor 16.
It is desirable to use the increase/decrease value X ₀ between (tx - td) minus td. This time td can be estimated based on the engine speed N and the basic fuel injection amount (load) Tp. Therefore, in this embodiment, Xo is determined from X.

Therefore, in the next step 17, the time td is searched from a predetermined map based on the engine speed N and the basic fuel injection amount Tp, and in the next step 18, the time (tx-
Increase/decrease value of feedback correction coefficient α in td)
Find Xo using the following formula.

X ₀ = X・(tx−td)/tx This increase/decrease value X ₀ is the current learning correction coefficient Kl
Since the optimum learning correction coefficient can be obtained by adding to the current learning correction coefficient Kl, in step 19, the increase _/ decrease value _(oew) is set, and in step 20, the learning correction coefficient data for the same area is corrected and rewritten. This part corresponds to the second learning correction coefficient correction means.

Kl _{( oew)} ←Kl＋ _{M 2 ·} Even in a region that only passes through in a transient state, learning is performed to obtain the optimal learning correction coefficient from the increase/decrease value of the feedback correction coefficient during the time during which the feedback correction coefficient is deflected in the transient state, which improves learning accuracy. The learning speed is improved, the effect of learning control is expanded, and controllability during transient operation is also improved.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram showing the configuration of the present invention.
FIG. 2 is a block diagram showing one embodiment of the present invention, FIG. 3 is a block circuit diagram of the control unit in FIG. 1, FIGS. 4 and 5 are flowcharts showing control contents, and FIG. It is a control characteristic diagram. DESCRIPTION OF SYMBOLS 1... Engine, 6... Air flow meter, 10... Idle control valve, 11... Fuel injection valve, 16... _O2 sensor, 17... Crank angle sensor, 30... Control unit.

Claims (1)

[Scope of Claims] 1. A first detection means for detecting the engine intake air flow rate, a second detection means for detecting the engine rotation speed, and detecting engine exhaust components, thereby detecting the air-fuel ratio of the engine intake air mixture. a basic fuel injection amount based on the engine intake air flow rate output from the first detection means and the engine rotational speed output from the second detection means; basic fuel injection amount calculation means for calculating the basic fuel injection amount; rewritable storage means for storing learning correction coefficients for correcting the basic fuel injection amount for each region of the engine operating state; learning correction coefficient retrieval means for retrieving a learning correction coefficient for a corresponding region from the storage means; and comparing the air-fuel ratio outputted by the third detection means with the target air-fuel ratio so as to bring the actual air-fuel ratio closer to the target air-fuel ratio. a feedback correction coefficient setting means for increasing or decreasing a feedback correction coefficient by a predetermined amount to correct the basic fuel injection amount; and searching for the basic fuel injection amount calculated by the basic fuel injection amount calculation means and the learning correction coefficient. a fuel injection amount calculation means for calculating a fuel injection amount based on a learning correction coefficient retrieved by the means and a feedback correction coefficient set by the feedback correction coefficient setting means; a fuel injection means for injecting fuel into an engine on and off in response to a corresponding drive pulse signal; and a fuel injection means for injecting fuel into an engine on and off in response to a corresponding drive pulse signal; a steady state/transient state determination means for determining a steady state based on the current state and a transient state for any other state; a first learning correction coefficient correcting means for correcting and rewriting a learning correction coefficient corresponding to an area of the engine operating state between in the direction; Learns the increase/decrease value of the feedback correction coefficient during the time until the direction of increase/decrease of the feedback correction coefficient is reversed, and based on this increase/decrease, corrects and rewrites the learning correction coefficient corresponding to the range of engine operating conditions during this period. A learning control device for an air-fuel ratio of an internal combustion engine, comprising: a second learning correction coefficient correcting means;