JP3269945B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel injection control device for an internal combustion engine.

[0002]

2. Description of the Related Art In fuel injection control or air-fuel ratio control of an internal combustion engine, a PID control law is generally used, and a deviation between a target value and an operation amount (control target input) is represented by a P term (proportional term) and an I term.
The feedback correction coefficient (feedback gain) is obtained by multiplying the term (integral term) and the D term (differential term).
Recently, it has also been proposed to obtain a feedback correction coefficient using a modern control theory as in the technology described in Japanese Patent Application Laid-Open No. 1-110853. Depending on the state, the control amount may oscillate and control stability may be reduced.

[0003] For this reason, for example, Japanese Patent Laid-Open No. 4-209940
The technique disclosed in Japanese Patent Laid-Open Publication No. H11-107556 obtains a first feedback correction coefficient using modern control theory, and obtains a second feedback correction coefficient that is less responsive than the first feedback correction coefficient using a PI control law. It is proposed to determine the control amount using the second feedback correction coefficient at the time of deceleration.

[0004] For the same reason, Japanese Patent Application Laid-Open No. H05-5214.
The technique described in Japanese Patent Application Laid-Open No. 0-244400 proposes that when the air-fuel ratio sensor is in a semi-active state, the control amount is determined by using a second feedback correction coefficient having low response.

[0005]

The present applicant has also proposed a technique for determining the fuel injection amount using an adaptive controller in, for example, Japanese Patent Application No. 6-66594.

[0006] In the fuel injection control of the internal combustion engine, the fuel supply is stopped (fuel cut) in a predetermined operating state such as during cruise of the vehicle, and as shown in FIG. The air-fuel ratio is controlled by open loop (O / L).

The stoichiometric air-fuel ratio (14.7:
When the fuel supply is resumed as much as possible in 1), the fuel supply amount determined in the feedforward system according to the characteristics obtained in advance through experiments is supplied, and the true air-fuel ratio (A / F) is reduced to 14.7 from the lean side. Although it changes suddenly, it takes some time for the supplied fuel to burn and reach the air-fuel ratio sensor,
Since the air-fuel ratio sensor itself has a detection delay, the detected air-fuel ratio does not follow the true air-fuel ratio, but takes a value as shown by a broken line in FIG.

At this time, when the feedback correction coefficient (shown as KSTR in the figure) is determined by using a high response control law such as the adaptive control law proposed by the present applicant, the adaptive controller:
The feedback correction coefficient KSTR is determined to eliminate the deviation between the target value and the detected value at once. However, the difference in this case is due to a sensor detection delay or the like, and the detected value does not indicate the true air-fuel ratio. Nevertheless, since the adaptive controller tries to absorb this relatively large difference at a stroke, the KSTR oscillates greatly as shown in FIG.
The control amount also oscillates, and the stability of the control decreases.

[0009] Such inconvenience does not occur only when returning from the fuel cut. The same applies when returning from the full-open increase control to the feedback control, or when returning from the lean burn control to the stoichiometric air-fuel ratio control. Furthermore, the same applies when switching from perturbation control for intentionally oscillating the target air-fuel ratio to control for a constant target air-fuel ratio. In other words, this is a problem commonly occurring when the target air-fuel ratio fluctuates greatly. However, in the above-described conventional technology, no measure is taken in such a case.

Therefore, using a plurality of control rules such as an adaptive control law and a PID control law, a high response feedback correction coefficient and a low response feedback correction coefficient (see FIG.
(Referred to as KLAF) and it is desirable to select one according to driving conditions. However, when switching the feedback correction coefficients determined based on different control laws, since the characteristics are different from each other, a step occurs in the correction coefficients, the operation amount changes suddenly, the control amount becomes unstable, and the control amount becomes unstable. The stability may be reduced.

Accordingly, a first object of the present invention is to determine a plurality of types of feedback correction coefficients having different responsiveness by using a plurality of types of control laws, and to appropriately switch (select) according to the operating state of the engine. In order to improve the stability of the control, it is possible to smoothly perform the switching and prevent the control amount from becoming unstable due to a sudden change in the operation amount due to the occurrence of a step between a plurality of types of feedback correction coefficients. And a fuel injection control device for an internal combustion engine.

Further, the step between the above-mentioned feedback correction coefficients becomes significant when switching from a low-response feedback correction coefficient to a high-response feedback correction coefficient.

Accordingly, a second object of the present invention is to determine a plurality of types of feedback correction coefficients having different responsiveness using a plurality of types of control laws, and to appropriately switch (select) them according to the operating state of the engine. Even when switching from a low-response feedback correction coefficient to a high-response feedback correction coefficient, it is possible to prevent the control amount from becoming unstable due to a sudden change in the manipulated variable due to a step between a plurality of types of feedback correction coefficients. It is an object of the present invention to provide a fuel injection control device for an internal combustion engine which prevents the fuel injection and thereby improves the stability of control.

Further, a third object of the present invention is to provide a response using a plurality of types of control laws when returning to feedback control after open loop control is performed during fuel cut, full opening, or EGR execution. Determines multiple types of feedback correction coefficients that differ in control characteristics and smoothly switches according to operating conditions to properly determine the manipulated variable to prevent oscillation of the control variable and optimize control stability and convergence. It is an object of the present invention to provide a fuel injection control device for an internal combustion engine that is balanced.

Further, when the manipulated variables are calculated using the adaptive controller proposed by the present applicant, the fuel injection and the air-fuel ratio can be controlled with high accuracy, and the target value and the detected value can be controlled between the target value and the detected value. When there is a difference, the feedback gain is calculated to eliminate the difference at once, so that control with excellent convergence can be realized.However, the feedback correction coefficient calculated by the adaptive controller is unstable depending on the operation state. And the stability of the control is rather lowered as it is.

Therefore, a fourth object of the present invention is to determine a feedback correction coefficient by using an adaptive controller or the like, and to effectively take measures even when the feedback correction coefficient oscillates, to achieve control stability and convergence. An object of the present invention is to provide a fuel injection control device for an internal combustion engine, which is capable of continuing feedback control while optimally balancing performance.

[0017]

According to a first aspect of the present invention, there is provided a fuel injection control apparatus for an internal combustion engine, wherein at least an air-fuel ratio of exhaust gas of the internal combustion engine is detected. Means for detecting an operating state of the internal combustion engine, including a detection means, and an adaptive controller for controlling the amount of fuel supplied to the internal combustion engine based on the air-fuel ratio detected by the air-fuel ratio detection means to a target value. A first calculating means for calculating a first feedback correction coefficient for correcting the supplied fuel amount using: and a correction coefficient for correcting the supplied fuel amount similarly to the first feedback correction coefficient,
A second calculating means for calculating a second feedback correction coefficient having a lower response than the first feedback correction coefficient, and an output of the first calculating means and the second calculating means according to the detected operating state. Switching means for switching between the first and second feedback correction coefficients selected via the switching means, and a supplied fuel amount correcting means for correcting the supplied fuel amount based on the first or second feedback correction coefficient. Comprises switching means for replacing at least a part of the internal elements of the first feedback correction coefficient and the second feedback correction coefficient when switching the output of the first calculation means and the output of the second calculation means. Configured.

According to a second aspect of the present invention, the switching means switches between the outputs of the first calculating means and the second calculating means when the detected air-fuel ratio is within a predetermined range. .

According to a third aspect of the present invention, the predetermined range is configured so that the equivalent ratio is 1 or near the equivalent ratio.

Preferably, the air-fuel ratio detecting means for detecting the air-fuel ratio of the exhaust gas of the internal combustion engine and the air-fuel ratio detected by the air-fuel ratio detecting means are adjusted so as to match the target air-fuel ratio. A first calculating means for calculating a first feedback correction coefficient using a controller in the form of an equation, and an air-fuel ratio detected by the air-fuel ratio detecting means so as to match the target air-fuel ratio,
Second calculating means for calculating a second feedback correction coefficient having a lower response than the first feedback correction coefficient, switching means for switching the outputs of the first and second calculating means, and switching Means for correcting the amount of fuel supplied to the internal combustion engine based on the first or second feedback correction coefficient selected via the means. When the control is shifted from the open loop control to the feedback control, the supply fuel amount is corrected based on the output of the second calculating means for a predetermined period.

According to a fifth aspect of the present invention, the transition from the open loop control to the feedback control is a time when the fuel supply to the internal combustion engine is stopped and then the fuel supply is restarted.

According to a sixth aspect of the present invention, the first calculating means and the second calculating means calculate the first feedback correction coefficient and the second feedback correction coefficient in parallel and perform the switching. The means is configured to switch by selecting the output of the first calculation means and the output of the second calculation means in accordance with the detected operating state.

According to a seventh aspect of the present invention, the controller of the recurrence type is configured to be an adaptive controller.

According to an eighth aspect, the second calculating means calculates the second feedback correction coefficient using a PID controller including at least one of a P term, an I term, and a D term. It was configured to calculate.

According to a ninth aspect of the present invention, the second calculating means is configured to calculate the second feedback correction coefficient using a recurrence type adaptive controller.

According to a tenth aspect, the first and the second
Calculating means for calculating the first and second feedback correction coefficients using an adaptive controller, wherein the first calculating means calculates the first and second feedback correction coefficients using at least one of a variable gain and a fixed gain. The first feedback correction coefficient is calculated, and the second calculating means is configured to calculate the second feedback correction coefficient using the other one.

In the eleventh aspect, the supplied fuel amount correcting means is configured to correct the supplied fuel amount by multiplying the supplied fuel amount by the first or second feedback correction coefficient.

[0028]

According to the first aspect, the first calculating means and the second calculating means
When the output of the calculation means is switched, at least a part of the internal elements of the first feedback correction coefficient and the second feedback correction coefficient is replaced.
The value of the feedback correction coefficient after switching can be made substantially the same as the value of the feedback correction coefficient before switching, and there is no step between the feedback correction coefficients. The control amount does not become unstable due to a sudden change in the operation amount, including when the feedback correction coefficient is switched to the above-mentioned feedback correction coefficient, so that the control stability can be improved.

[0029] With further extends the improvement of controllability, since comprise a first calculating means for calculating a first feedback correction coefficient using the adaptive controller so that the amount of fuel supply is equal to the target value, the control object Automatically changes the convergence speed even when the value changes depending on the state, the control amount converges quickly to the target value, and the convergence is improved.

[0030] Also when the control amount applied disturbance is shifted to the target value of the operation amount, by adaptive controller operates as a change of the controlled object, the feedback correction coefficient such that the control amount coincides with the target value Since it is determined, the toughness against disturbance is also improved. The feedback correction coefficient may be multiplied by the operation amount or added.

According to the present invention, the output of the first calculating means and the output of the second calculating means are switched when the detected air-fuel ratio is within a predetermined range. By setting as appropriate, it is possible to switch when the outputs of the first calculation means and the second calculation means are substantially the same, and it is possible to effectively reduce the difference between the feedback correction coefficients, The switching can be performed more smoothly, and the operation amount does not suddenly change and the control amount does not become unstable, so that the control stability can be improved.

In the third aspect, the predetermined range is configured to be equal to or near 1 in the equivalence ratio. Therefore, when the control is performed toward the stoichiometric air-fuel ratio, the detected value becomes 1 in the equivalence ratio. When the values are in the vicinity, the control deviation is small, that is, when the outputs of the first calculation means and the second calculation means are 1
It can be detected more accurately that the value is close to the vicinity. Therefore, by switching at that time, the difference between the feedback correction coefficients can be reduced more effectively, and the switching can be performed more smoothly.

According to a fourth aspect of the present invention, when shifting from the open loop control to the feedback control, the fuel supply amount is corrected based on the output of the second calculating means for a predetermined period. Even when the feedback control is returned after the open-loop control is performed from the execution of the full-open increase correction, the execution of the EGR, and the like, the feedback correction coefficient can be smoothly switched, and the operation amount changes suddenly and the control amount becomes unstable. Therefore, control stability can be improved.

According to the fifth aspect of the present invention, the transition from the open loop control to the feedback control is made when the fuel supply to the internal combustion engine is stopped and then the fuel supply is restarted. When the control returns to the feedback control after the open loop control is performed, the feedback correction coefficient can be switched smoothly, and the control amount does not become unstable due to a sudden change in the operation amount, thereby improving the control stability. Can be done.

According to a sixth aspect of the present invention, the first calculating means and the second calculating means calculate the first feedback correction coefficient and the second feedback correction coefficient in parallel and detect the detected operation. The first calculating means and the second calculating means depending on the state;
The switching is performed by selecting the output of the calculating means, so that the switching can be performed at an arbitrary timing while reducing the step due to the switching, and particularly, from the low-response feedback correction coefficient to the high-response feedback correction coefficient. Since the switching can be performed at an arbitrary timing even in the switching, the switching can be performed more smoothly, and the stability of the control can be further improved.

According to the present invention, the controller of the recurrence type is configured to be an adaptive controller. In addition to the above-mentioned effects, the convergence speed can be improved even when the controlled object changes depending on the state. Is automatically adjusted, so that the control amount quickly converges to the target value to improve the convergence and the robustness to disturbance.

According to the present invention, the second feedback correction coefficient is calculated by using a PID controller including at least one of the P, I, and D terms. In addition to the operation and effect, even when the stability of the control is reduced by using the feedback correction coefficient having a high response, the stable feedback correction coefficient can be set and the stability of the control can be improved.

According to the ninth aspect, since the second feedback correction coefficient is calculated by using the adaptive controller of the recurrence type, the responsiveness is ensured to some extent.
Even if the stability of the control is reduced by using the feedback correction coefficient of high response, the stability of the control can be ensured.

According to the tenth aspect, the first feedback correction coefficient is calculated using at least one of the variable gain and the fixed gain, and the second feedback correction coefficient is calculated using the other one. With such a configuration, the configuration can be simplified in addition to the above-described functions and effects.

In the eleventh aspect, the first or the second
Since the supply fuel amount is corrected by multiplying the supplied fuel amount by the feedback correction coefficient, the convergence speed can be improved in addition to the above-described effects.

[0041]

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

FIG. 1 is an overall view showing a fuel injection control device for an internal combustion engine according to the present invention.

In the figure, reference numeral 10 denotes an OHC in-line four-cylinder internal combustion engine. The intake air introduced from an air cleaner 14 disposed at the end of an intake pipe 12 is subjected to surge while its flow rate is adjusted by a throttle valve 16. The gas flows into the first to fourth cylinders via two intake valves (not shown) via the tank 18 and the intake manifold 20. An injector 22 is provided near an intake valve (not shown) of each cylinder to inject fuel. The air-fuel mixture injected and integrated with the intake air is ignited by an ignition plug (not shown) in each cylinder and burns to drive a piston (not shown).

Exhaust gas after combustion is discharged to an exhaust manifold 24 through two exhaust valves (not shown), and is purified by a catalyst device (three-way catalyst) 28 through an exhaust pipe 26 and then out of the engine. Is discharged. As described above, the throttle valve 16 is mechanically separated from the accelerator pedal (not shown), and is controlled via the pulse motor M to an opening degree corresponding to the depression amount of the accelerator pedal and the operating state. The intake pipe 12 is provided with a bypass passage 32 near the position of the throttle valve 16 for bypassing the throttle valve 16.

The internal combustion engine 10 is provided with an exhaust gas recirculation mechanism 100 including an exhaust gas recirculation passage 80 for recirculating exhaust gas to the intake side, is also connected between the intake system and the fuel tank 36, and has a canister purge mechanism 200. However, since the mechanism does not directly relate to the gist of the present application, the description is omitted.

Further, the internal combustion engine 10 has a so-called variable valve timing mechanism 300 (shown as V / T in FIG. 1). The variable valve timing mechanism 300 is described in, for example, Japanese Patent Application Laid-Open No. 2-275043, and FIG. 2 shows the valve timing V / T of the engine according to the operating state such as the engine speed Ne and the intake pressure Pb. Switching between two timing characteristics LoV / T and HiV / T. However, since the mechanism itself is a known mechanism, further description is omitted. Note that the switching of the valve timing characteristics includes an operation of stopping one of the two intake valves.

In FIG. 1, a crank angle sensor 40 for detecting a crank angle position of a piston (not shown) is provided in a distributor (not shown) of the internal combustion engine 10 and an opening of the throttle valve 16 is detected. A throttle opening sensor 42 and an absolute pressure sensor 44 for detecting the intake pressure Pb downstream of the throttle valve 16 as an absolute pressure are also provided.

At an appropriate position in the internal combustion engine 10, an atmospheric pressure sensor 46 for detecting the atmospheric pressure Pa is provided, and an intake air temperature sensor 48 for detecting the temperature of the intake air is provided upstream of the throttle valve 16. At an appropriate position of the engine, a water temperature sensor 50 for detecting an engine cooling water temperature is provided. Further, a valve timing (V / T) sensor 52 (not shown in FIG. 1) for detecting a valve timing characteristic selected by the variable valve timing mechanism 300 via hydraulic pressure is provided.

Further, in the exhaust system, the exhaust manifold 24
An air-fuel ratio sensor 54 is provided downstream of the catalyst device 28 at the upstream of the catalyst device 28 to detect the oxygen concentration in the exhaust gas (described later). These sensor outputs are sent to the control unit 34.

FIG. 3 is a block diagram showing details of the control unit 34. The output of the air-fuel ratio sensor 54 is
And outputs a detection signal having a linear characteristic proportional to the oxygen concentration in the exhaust gas in a wide range from lean to rich (hereinafter, this wide-range air-fuel ratio sensor is referred to as “ LAF sensor).

The output of the detection circuit 62 is
6 and input via the A / D conversion circuit 68 into the CPU. CPU is CPU core 70, ROM 72, RAM 7
The output of the detection circuit 62 is A / D-converted every predetermined crank angle (for example, 15 degrees), and is sequentially stored in one of the buffers in the RAM 74. Similarly, the analog sensor output of the throttle opening sensor 42 and the like is also transmitted to the CPU 66 via the multiplexer 66 and the A / D conversion circuit 68.
And stored in the RAM 74.

After the output of the crank angle sensor 40 is shaped by the waveform shaping circuit 76, the output value is counted by the counter 78, and the count value is input into the CPU.
In the CPU, the CPU core 70 calculates a control value according to a command stored in the ROM 72 as described later, and drives the injector 22 of each cylinder via the drive circuit 82. Further, the CPU core 70 includes an electromagnetic valve (EACV) 90 that opens and closes the bypass passage 32 that adjusts the amount of secondary air via the drive circuits 84, 86, and 88; The purge control solenoid valve 202 is driven.

FIG. 4 is a flowchart showing the operation of the control device according to the present invention.
For convenience of understanding, the control device according to the present invention will be outlined with reference to FIG.

In the apparatus according to the present invention, as shown in the block diagram of FIG. 5, the exhaust air-fuel ratio (KACT shown in FIG. 5) detected using the supplied fuel amount (shown as the basic injection amount Tim) as the manipulated variable.
(k). k: a first controller (control law) of a recurrence type (STR type adaptive controller (STR) so that the time of the discrete time system matches the target air-fuel ratio (shown as KCMD (k) in the figure). Adaptive control law).
(Hereinafter referred to as “adaptive correction coefficient” or “KSTR”) is provided.

At the same time, the second controller (control law), more specifically, controls the exhaust air-fuel ratio KACT (k) detected using the supplied fuel amount as an operation amount so as to match the target value KCMD (k). The second feedback correction coefficient KLAF (k) (hereinafter referred to as “PID correction coefficient”), which is inferior to the first feedback correction coefficient in response using a PID controller (indicated by PID in the drawing) comprising a PID controller (control law) Or "KL
AF)), and switches (selects) one of the outputs of the first calculation means and the second calculation means in accordance with the detected operating state as described later. The output fuel amount Tout (k) is obtained by correcting the supply fuel amount Tim based on the calculated value.

Explaining the adaptive correction coefficient KSTR, the adaptive controller shown in FIG. 5 comprises an STR controller and an adaptive (control) parameter adjusting mechanism for adjusting its adaptive (control) parameter (vector). The STR controller calculates the target value KC of the feedback system of the fuel injection control.
MD (k) and control amount y (k) (plant output) are input, the coefficient vector identified by the adaptive parameter adjustment mechanism is received, and output KSTR (k) (plant input u (k)) is calculated.

In such adaptive control, one of the adjustment rules is I. D. There is a parameter adjustment rule proposed by Landau et al. This method converts the adaptive system into an equivalent feedback system consisting of a linear block and a non-linear block. For nonlinear blocks, Popov's integral inequality for input and output is established, and the linear block is adjusted so that it is strongly positive. Is a method that guarantees the stability of the adaptive system. This method is described in, for example, “Computer Roll” (Corona) No. It is a known technique as described on pages 27, 28 to 41 or "Automatic Control Handbook" (Ohm), pages 703 to 707.

In the illustrated adaptive controller, the adjustment law of Landau et al. Is used. To explain below, according to Landau's adjustment rule, the transfer function A (Z ^-1 ) /
When the polynomial of the denominator and numerator of B (Z ^-1 ) is expressed by Expression 1, the adaptive parameter θ hat (k) and the input 適 応 (k) to the adaptive parameter adjustment mechanism are defined by Expression 1. . In Equation 1, when m = 1, n = 1, d = 3,
That is, a plant having a dead time of three control cycles in the primary system is taken as an example. Here, k indicates a time, more specifically, a control cycle.

[0059]

(Equation 1)

The scalar quantity bo hat ^-1 (k) for determining the gain, the control element BR hat (Z ^-1 , k) using the manipulated variable, and the control element S hat using the control quantity shown here.
(Z ⁻¹ , k) is expressed as in Equations 2 to 4, respectively.

[0061]

(Equation 2)

[0062]

(Equation 3)

[0063]

(Equation 4)

The adaptive parameter adjusting mechanism identifies the scalar amount and each coefficient of the control element and supplies them to the STR controller. When these coefficients are put together into an adaptive parameter (vector) θ hat (k) as described above,
It is expressed as in Equation 5.

[0065]

(Equation 5)

Γ (k) and e asterisk in Equation 5
(k) is a gain matrix and an identification error signal, respectively, and is represented by a recurrence formula as shown in Expressions 6 and 7.

[0067]

(Equation 6)

[0068]

(Equation 7)

Various specific algorithms are given depending on how to select λ1 (k) and λ2 (k) in equation (6). λ
When 1 (k) = 1 and λ2 (k) = λ (0 <λ <2), a gradually decreasing gain algorithm (least square method when λ = 1),
λ1 (k) = λ1 (0 <λ1 <1), λ2 (k) = λ2 (0
<Λ2 <λ, the variable gain algorithm (λ2 =
1, weighted least squares method), λ1 (k) / λ2
(k) = σ, and when λ3 is expressed as shown in Expression 8, λ
If 1 (k) = λ3, a fixed trace algorithm is obtained. When λ1 (k) = 1 and λ2 (k) = 0, the fixed gain algorithm is used. In this case, as is apparent from Equation 6, Γ (k) = Γ (k−1), and thus Γ (k) = Γ is a fixed value.

[0070]

(Equation 8)

Here, in FIG. 5, the aforementioned STR
The controller (adaptive controller) and the adaptive parameter adjustment mechanism are located outside the fuel injection amount calculation system, and the detected air-fuel ratio KACT
(k) is the target air-fuel ratio KCMD (k-d ') (where d' is KCMD
The feedback correction coefficient KSTR (k) is calculated by operating so as to adaptively match with the dead time before being reflected on the CT. That is, the STR controller calculates the coefficient vector θ hat adaptively identified by the adaptive parameter adjustment mechanism.
(k) is received and a feedback compensator is formed so as to match the target air-fuel ratio KCMD (k-d ').

Calculated feedback correction coefficient KSTR
(k) is multiplied by the basic injection amount Tim together with various correction terms (described later), and the corrected fuel injection amount is output fuel injection amount Tout (k).
As a control plant (internal combustion engine).

The adaptive correction coefficient KSTR obtained as described above
(k) (indicated by u (k) in the figure) and the detected air-fuel ratio KA
CT (k) is input to the adaptive parameter adjustment mechanism, where the adaptive parameter θ hat (k) is calculated and input to the STR controller. The target air-fuel ratio KCMD (k) is given to the STR controller as an input so that the detected air-fuel ratio KACT (k) matches the target air-fuel ratio KCMD (k) (more precisely, KCMD (k-d ')). Feedback correction coefficient KSTR using recurrence formula
Calculate (k).

The feedback correction coefficient KSTR (k) is specifically obtained as shown in Expression 9.

[0075]

(Equation 9)

As shown, the detected air-fuel ratio KACT (k) and the target air-fuel ratio KCMD (k) are determined by a controller (PID) based on the PID control law.
And the PID based on the PID control law in order to eliminate the deviation between the detected air-fuel ratio of the exhaust system collecting portion and the target air-fuel ratio.
The correction coefficient KLAF (k) is calculated. Adaptive correction coefficient KSTR by adaptive control law and PID correction coefficient KLAF by PID control law
Is used for multiplication correction of the fuel injection amount via the switching mechanism 400.

Next, the calculation of the PID correction coefficient KLAF will be described. First, the target air-fuel ratio KCMD and the detected air-fuel ratio
The control deviation DKAF of KACT is obtained as DKAF (k) = KCMD (k-d ')-KACT (k). In the above, KCMD (k-d '): target air-fuel ratio (where d' indicates a dead time until KCMD is reflected in KACT as described above, and thus means a target air-fuel ratio before a dead time control cycle). , KACT (k): Indicates the detected air-fuel ratio (of the current control cycle).

In this specification, the air-fuel ratio is actually the equivalence ratio, ie, M, for both the target value KCMD and the detected value KACT for convenience of calculation.
st / M = 1 / λ (Mst: stoichiometric air-fuel ratio, M =
A / F (A: air consumption, F: fuel consumption), λ: excess air ratio).

Next, the P term (proportional term) KLAFP (k), the I term (integral term) KLAFI (k), and the D term (differential term) KLAFD (k) are multiplied by a predetermined coefficient to obtain a P term: KLAFP (k) = DKAF (k) × KP I: KLAFI (k) = KLAFI (k-1) + DKAF (k) × KI D: KLAFD (k) = (DKAF (k) −DKAF (k-1) ) × KD.

As described above, the P term is obtained by multiplying the deviation by the proportional gain KP, and the I term is obtained by adding the value obtained by multiplying the deviation by the integral gain KI to the previous value KLAFI (k-1). Is the current value of the deviation
It is obtained by multiplying the difference between DKAF (k) and the previous value DKAF (k-1) by the derivative gain KD. The gains KP, KI, and KD are determined according to the engine speed and the engine load, and more specifically, are set so that they can be searched from the engine speed Ne and the intake pressure Pb using a map. .

Finally, the value thus obtained is added to KLAF (k) = KLAFP (k) + KLAFI (k) + KLAFD (k) to obtain the present value KLAF (k) of the PID correction coefficient.
When the PID correction coefficient KLAF is selected, the STR controller sets the feedback correction coefficient KSTR to 1.0.
The adaptive parameter is held so as to stop at (initial state) or around 1.0.

In this case, in order to obtain a feedback correction coefficient in a multiplication form, the offset 1.0 is an I term.
KLAFI (k) (ie, Section I KLAFI
(The initial value of (k) is 1.0).

Either the obtained adaptive correction coefficient KSTR or PID correction coefficient KLAF is the feedback correction coefficient KFB.
It is multiplied by the basic injection amount Tim as a generic term for both. Specifically, the basic injection amount Tim is multiplied by various correction terms KCMDM and KTOTAL and a feedback correction coefficient KFB, and another correction term TTOTAL is added to determine the output injection amount Tout (operating amount), which is input to the control plant. Is done. That is, the output injection amount Tout is determined by Tout = Tim × KCMDM × KFB × KTOTAL + TTOTAL.

Here, KCMDM is a target air-fuel ratio correction coefficient, and is a value obtained by correcting the target air-fuel ratio (equivalent ratio) KCMD to compensate for a difference in intake air charging efficiency due to heat of vaporization. KTOT
AL indicates the total value of various correction coefficients performed in a multiplication term such as water temperature correction. Further, TTOTAL indicates the total value of various correction coefficients performed in an addition term such as atmospheric pressure correction (however, the invalid time of the injector is not included because it is separately added when the output injection amount Tout is output).

Another characteristic of FIG. 5 is that, first, the STR controller is placed outside the fuel injection amount calculation system, and the target value is not the fuel injection amount but the air-fuel ratio (more precisely, the equivalent ratio) for the sake of calculation convenience. It was that. That is, the manipulated variable is indicated by the fuel injection amount, and the parameter adjustment mechanism operates so that the exhaust air-fuel ratio generated in the exhaust system matches the target air-fuel ratio, determines the feedback correction coefficient KFB, and provides robustness against disturbance. Is to improve the performance. However, since this point is described in an application proposed by the present applicant (Japanese Patent Application No. 6-66,594), a detailed description is omitted.

Further, the operation amount is corrected by multiplying the operation amount by the feedback correction coefficient. Thereby, the convergence of the control is remarkably improved. On the other hand, the configuration has a disadvantage that the control amount is likely to oscillate if the operation amount is not appropriate.

Based on the above, the operation of the control device according to the present invention will be described with reference to the flowchart of FIG.
The program in FIG. 4 is started at a predetermined crank angle.

First, the engine speed N detected in S10
e, the intake pressure Pb, etc. are read out, and the program proceeds to S12, in which it is determined whether or not cranking is performed. The fuel cut is performed in a predetermined operation state, for example, when the throttle opening is in a fully closed position and the engine speed is equal to or higher than a predetermined value.The fuel supply is stopped, and the fuel injection and the air-fuel ratio are also opened. Controlled by the loop.

If it is determined in S14 that the fuel cut is not performed, the process proceeds to S16, where a map (corresponding to the value calculated in the feedforward system described above) is searched from the detected engine speed Ne and intake pressure Pb. The aforementioned basic fuel injection amount Tim is calculated.

Then, the program proceeds to S18, in which it is determined whether the activation of the LAF sensor 54 has been completed. This is, for example, LA
This is performed by comparing the difference between the output voltage of the F sensor 54 and the center voltage thereof with a predetermined value (for example, 0.4 V), and determining that activation has been completed when the difference is smaller than the predetermined value.

If it is determined in step S18 that the activation has been completed, the flow advances to step S20 to determine whether or not the current state is in the feedback control area. This is performed in a separate routine that is not disclosed. For example, when the engine is fully increased, when the engine speed is high, or when the operating state is suddenly changed due to the influence of EGR or the like, open loop control is performed.

When the result in S20 is affirmative, the program proceeds to S22, in which the detected exhaust air-fuel ratio (A / F) is read.
Proceeding to 4, the detected equivalent ratio KACT (k) is calculated from the detected exhaust air-fuel ratio.
Then, the process proceeds to S26, where a feedback correction coefficient KFB is obtained.

FIG. 6 is a subroutine flowchart showing the operation.

Referring to FIG. 10, in S100, it is determined whether or not the open loop control was performed last time (previous control or calculation cycle, that is, last program start time). If it was the last time in open loop control such as fuel cut, the result is affirmative and the routine proceeds to S102, where the counter value C is reset to 0, and the routine proceeds to S104 where the flag FKST
The bit of R is reset to 0, and the flow advances to S106 to calculate the feedback correction coefficient KFB.

In S104, the bit of the flag FKSTR is set to 0.
Resetting to means that the fuel injection amount is in the PID operating region and the fuel injection amount correction should be performed using the PID correction coefficient KLAF. Also, when the bit of the flag FKSTR is set to 1, it means that the fuel injection amount is in the STR (controller) operation region and the fuel injection amount should be corrected by the adaptive correction coefficient KSTR.

FIG. 7 is a subroutine flowchart showing a specific operation of the feedback correction coefficient KFB calculation. In the following, it is determined in S200 whether the bit of the flag FKSTR is set to 1, that is, whether or not the flag is in the STR (controller) operation area. Since this flag has been reset to 0 in S104 of the flow chart of FIG. 6, the determination in this step is denied, and S2
Proceeding to 02, it is determined whether the bit of the previous flag FKSTR has been set to 1, that is, whether or not it was in the STR (controller) operation area last time.

If open loop control such as fuel cut was previously performed, the determination here is naturally denied, and the routine proceeds to S204, where the PID correction coefficient KLAF (k) is calculated using the above-described method (PID controller calculates The selected feedback correction coefficient KLAF (k)). Subsequently, FIG.
Returning to the flow chart, the process proceeds to S108, where KLAF (k) is set.
KFB.

In the flow chart of FIG. 6, when it is determined in S100 that the control is not the previous open loop control, that is, the control is returned from the open loop control to the feedback control, the process proceeds to S110 and the previous value KCMD of the target air-fuel ratio is obtained.
The difference DKCMD between (k-1) and the current value KCMD (k) is calculated, and the reference value DKCM
Compare with Dref. When it is determined that the difference DKCMD exceeds the reference value DKCMDref, S102, S104, S10
6, S200, S202 (S216), S204, S1
In step 08, the PID correction coefficient is calculated.

This is because when the change in the target air-fuel ratio is large, the detected value does not always indicate a true value due to the detection delay of the air-fuel ratio sensor, as in the case of the return of the fuel cut. This is because the control amount may become unstable. Examples of the case where the change in the target equivalence ratio is large include, for example, when returning from the full-open increase, when returning from lean burn control (for example, air-fuel ratio = 20: 1 or leaner) to stoichiometric air-fuel ratio control, When returning from the perturbation control in which the target air-fuel ratio is oscillated to the stoichiometric air-fuel ratio control in which the target air-fuel ratio is kept constant, and the like are mentioned.

On the other hand, in step S110, the difference DKCMD is equal to the reference value DKCMDr.
If it is determined to be less than or equal to ef, the process proceeds to S112, where the counter value C is incremented. The process proceeds to S114 to determine whether the engine is idling. If the result is affirmative, the process proceeds to S104 and thereafter to calculate a PID correction coefficient.

This is because the operation state is almost stable at the time of idling and does not require a high gain such as the STR control law. In addition, since the intake air amount is controlled by using the EACV 90 so as to keep the engine speed constant at the time of idling, the intake air amount control and the air-fuel ratio feedback control may interfere with each other. Was used to make the gain relatively low.

On the other hand, if it is determined in S114 that the vehicle is not idling, the flow advances to S116 to set the counter value C to a predetermined value.
For example, compare with 5. As long as the counter value C is determined to be equal to or less than the predetermined value, the process proceeds to S104 and thereafter, and the PID correction coefficient is selected in the same manner as described above.

That is, in FIG. 16, a period from time T1 (counter value C = 1 mentioned in FIG. 6) at which fuel cut ends and returns from open loop control to feedback control to time T2 (counter value C = 5). In (corresponding to the "predetermined period" described in the claims), the feedback correction coefficient is a value KLAF according to a PID control law determined by the PID controller.

That is, the feedback correction coefficient KLAF based on the PID control law is different from the adaptive correction coefficient KSTR based on the STR controller, and the control deviation DKAF between the target value and the detected value is different.
It does not attempt to absorb the gas at once, but has the characteristic of absorbing it relatively slowly.

Therefore, the PID correction coefficient does not oscillate like the adaptive correction coefficient due to the delay until the combustion of the fuel whose supply has been resumed as shown in FIG. 16 and the detection delay of the air-fuel ratio sensor. And therefore the controlled variable (plant output)
Does not become unstable. Here, the predetermined value is set to 5, in other words, 5 control cycles, because it is considered that the combustion delay and the detection delay described above can be absorbed in this period.

This period (predetermined value) may be determined from the engine speed, the engine load, etc., which are the exhaust gas transport delay parameters. For example, the exhaust gas transport delay parameter may be determined according to the engine speed and the intake pressure. The predetermined value may be set small when the value is small, and may be set large when the exhaust gas transport delay parameter is large.

Returning to the description of the flow chart of FIG.
If it is determined in step 116 that the counter value C exceeds the predetermined value, that is, if it is determined that the value is 6 or more, the process proceeds to step S118, where the flag FKSTR is set.
Is set to 1, and the flow advances to S120 to calculate the feedback correction coefficient KFB again according to the flow chart of FIG. In this case, S in the flow chart of FIG.
The determination at 200 is affirmed and the process proceeds to S206, where the previous flag
It is determined whether the bit of FKSTR has been reset to 0, that is, whether or not it was in the PID operation area last time.

When the counter value exceeds the predetermined value for the first time, this determination is affirmed, and the routine proceeds to S208, where the detected air-fuel ratio (equivalent ratio) KACT (k) is compared with a lower limit value a, for example, 0.95. If it is determined that the detected value is equal to or larger than the lower limit, S21
The process proceeds to 0, the detected value is compared with an upper limit value b, for example, 1.05, and when it is determined to be smaller than the upper limit value b, the process proceeds to S214 via S212 (described later), and the adaptive correction coefficient KSTR (k) is calculated using the STR controller. Calculation (selection of the adaptive correction coefficient KSTR (k) calculated by the STR controller). That is, when the detected air-fuel ratio (equivalent ratio) is between the upper and lower limit values b and a, it is determined that the detected air-fuel ratio is near 1.0, and the adaptive correction coefficient KSTR is calculated.

That is, when the control is performed toward the stoichiometric air-fuel ratio, the fact that the detected air-fuel ratio (equivalent ratio) is close to 1 means that the control deviation is small. In such a case, PI
The correction coefficient calculated using the D control law or the adaptive control law is substantially a value close to 1, and the operation amount does not suddenly change even when the PID correction coefficient KLAF is switched to the adaptive correction coefficient KSTR. Absent.

Therefore, switching from PID control to STR (adaptive) control is performed in the operating range of the STR controller.
In addition, the detection is performed when the detection equivalent ratio KACT becomes a value near 1. Thereby, the STR (adaptive) is changed from the PID control.
Switching to control can be performed smoothly, and oscillation of the control amount can be prevented.

When the detected equivalence ratio KACT (k) is determined to be equal to or less than the upper limit value b in S210, the process proceeds to S212, where the scalar amount b ₀ for determining the gain in the STR controller is fed back by PID control as shown in the figure. It is the value obtained by dividing by the previous value KLAF (k-1) of the correction coefficient.

To explain this, the adaptive correction coefficient KS
TR (k) is originally obtained as shown in Equation 9 as described above. However, when the result is affirmed in S206 and the process proceeds to S208 and thereafter, the feedback correction coefficient is determined based on the PID control law in the previous control cycle. I have. Then, in FIG.
When the feedback correction coefficient is determined by the ID control, the STR controller is configured to stop the feedback correction coefficient KSTR at 1.0 (initial value) as described above. Therefore, when the adaptive correction coefficient KSTR is determined again by the STR controller, if the calculated value greatly deviates from 1.0, the control amount becomes unstable.

Therefore, the scalar quantity b ₀ for determining the gain among the adaptive parameters held so that the adaptive correction coefficient KSTR becomes 1.0 or near 1.0 is determined by the PID.
By dividing by the previous value KLAF (k-1) of the correction coefficient KLAF, since the combination of the adaptive parameters is KSTR = 1.0, the first term becomes 1 as shown in Expression 10, and The value of the second term KLAF (k-1) becomes the current correction coefficient KSTR (k).
Thereby, in addition to switching at the detection value KACT of 1 or near in S208 and S210,
Switching from PID control to STR control can be performed more smoothly.

[0114]

(Equation 10)

Incidentally, in the flowchart of FIG.
If the answer is 2 in the affirmative, that is, if it is determined that the current time is in the STR (controller) operation region, the process proceeds to S216 and the adaptive correction coefficient KSTR
Is set as the previous value KLAFI (k-1) of the I term of the PID correction coefficient KLAF. As a result, in S204, P
When calculating the ID correction coefficient KLAF (k), its I term KLAFI
Is KLAFI (k) = KSTR (k-1) + DKAF (k) .times.KI. The I term thus found is then added to the P and D terms to determine the PID correction coefficient KLAF (k).

That is, when the feedback control coefficient is calculated by switching from the adaptive control to the PID control, the integral term may change abruptly. In this way, the PID correction is performed using the value of the adaptive correction coefficient KSTR. By determining the initial value of the I term of the coefficient, the previous value KSTR of the adaptive correction coefficient KSTR
The difference between (k-1) and the current value KLAF (k) of the PID correction coefficient can be kept small. As a result, even when switching from the high-response STR control to the low-response PID control, the gain difference of the feedback correction coefficients can be made small and can be smoothly continued, and a sudden change in the control amount can be prevented.

In the flow chart of FIG. 7, S2
If the answer is affirmative in 00, that is, if it is determined that the STR (controller) operation area is not satisfied, and if it is also determined in S206 that the current time is not the PID operation area, the process proceeds to S214, and the adaptive correction coefficient KSTR
(k) is calculated, which is calculated as shown in Equation 9 as described above.

Returning to the flow chart of FIG.
Proceeding to 122, it is confirmed whether or not the correction coefficient obtained in the flowchart of FIG. 7 is the adaptive correction coefficient KSTR.
24, the difference between the adaptive correction coefficient and 1.0 (1-KSTR
(k)), and calculate the absolute value to the specified threshold value.
Compare with KSTRref.

This is partially related to what has been described above in relation to the fourth object of the present invention. However, when the adaptive correction coefficient KSTR fluctuates greatly, the control amount also changes suddenly, and the control becomes stable. Is reduced. Therefore, the absolute value of the difference between the obtained feedback correction coefficient and 1.0 is compared with the threshold value.
The feedback correction coefficient is determined again based on the ID control.

Thus, stable control can be realized without a sudden change in the control amount. in this case,
When the absolute value of the difference between the adaptive correction coefficient KSTR and 1.0 was compared, the threshold value KSTRref was, as shown in FIG.
The values may be separately set on the large and small sides with the feedback correction coefficient of 1.0 as a boundary.

The adaptive correction coefficient KSTR obtained in S124
If the absolute value of the difference between (k) and 1.0 does not exceed the threshold value, the process proceeds to S126, where the adaptive correction coefficient KSTR is set as the feedback correction coefficient KFB. If the result in S122 is NO, the program proceeds to S128, where the bit of the flag FKSTR is reset to 0, and the program proceeds to S130, where the PID correction coefficient is set.
Let KLAF be the feedback correction coefficient KFB.

Returning to the flow chart of FIG.
In step 28, the fuel injection amount Tim is multiplied by the feedback correction coefficient KFB and the like, and the addition term TTOTAL is added to determine the output fuel injection amount Tout as described above. Next, the routine proceeds to S30, where the output fuel injection amount Tout is output to the drive circuit 82 of the injector 22 as an operation amount.

If it is determined in step S12 that cranking has occurred, the routine proceeds to step S34, in which the fuel injection amount Ticr at the time of starting is searched from the engine cooling water temperature, and the routine proceeds to step S36. Calculate Tout. If it is determined in S14 that the fuel is cut, S
Proceeding to 38, the output fuel injection amount Tout is set to zero.

If the result in S18 or S20 is negative, the air-fuel ratio is under open-loop control, so the program proceeds to S32, in which the value of the feedback correction coefficient KFB is set to 1.0, and
Proceeding to 28, the output fuel injection amount Tout is determined. S12,
When the result in S14 is affirmative, open-loop control is also performed.
The output fuel injection amount Tout becomes a predetermined value.

In the embodiment of the present invention, when the feedback control is resumed after the open loop control of the fuel injection and the air-fuel ratio is completed, such as when returning from the fuel cut, the feedback is performed based on the PID control law for a predetermined period. The correction coefficient KLAF is determined. As a result, it takes time for the supplied fuel to burn,
Since the sensor itself has a detection delay, the adaptive correction coefficient KSTR is not used when there is a relatively large difference between the detected air-fuel ratio and the true air-fuel ratio. Therefore, the control amount (air-fuel ratio) does not become unstable, so that the control stability can be improved.

On the other hand, since the period is set to a predetermined value, when the detected value is stabilized, an operation is performed to absorb the control deviation between the target air-fuel ratio and the detected air-fuel ratio at once using the feedback correction coefficient based on the adaptive control law. As a result, the convergence of the control can be improved. Particularly, in the embodiment of the present invention, since the operation amount is corrected by multiplying the operation amount by the feedback correction coefficient, the convergence of the control can be improved, and the stability and the convergence of the control can be more preferably improved. Can be balanced.

Further, when the fluctuation of the target value is large, the feedback correction coefficient is determined based on the PID control law even after the lapse of a predetermined period. Even when returning from control, the stability and convergence of control can be optimally balanced. Further, when the adaptive correction coefficient becomes unstable, correction is performed using the PID correction coefficient, so that control stability and convergence can be more optimally balanced.

Further, at the time of shifting from the adaptive control to the PID control, at least a part of the elements (internal variables) of the PID correction coefficient KLAF, that is, the I term is calculated from the adaptive correction coefficient KSTR. When returning from the PID control to the adaptive control, when the detected value KACT is at or near 1, the calculated value of the adaptive correction coefficient KSTR is changed to the PID correction coefficient KLAF.
Started from almost the same value as. From them,
The switching between the PID control and the adaptive control becomes smoother, and the feedback correction coefficient does not have a step, so that the operation amount does not suddenly change and the control amount does not become unstable.
Therefore, control stability can be improved.

Further, at the time of idling, the feedback correction coefficient is determined based on the PID control law. Therefore, at the time of idling, high response air-fuel ratio feedback control such as intake air amount control and adaptive control interferes. Nothing.

In the embodiment of the present invention, S110, S114 and S124 are inserted in the flow chart of FIG. 6, but all or some of them may be omitted.
Similarly, in the flowchart of FIG. 7, S208 (S2
10), part of S212 and S216 may be omitted.

FIG. 9 is a timing chart showing a second embodiment of the present invention, which is similar to FIG. 8 of the first embodiment. In the case of the second embodiment, a second threshold value KSTRref2 is set in addition to the first threshold value KSTRref1 corresponding to the threshold value KSTRref used in the first embodiment.

Then, the absolute values of the adaptive correction coefficient KSTR (k) are converted into first and second threshold values KSTRref1 and KSTRref2.
If the absolute value exceeds the second threshold value KSTRref2 for a predetermined time, the adaptive correction coefficient KS
TR is reset to an initial value, that is, reset to 1.

When the absolute value exceeds the first threshold value KSTRref1 for a predetermined time, it is determined that oscillation has occurred, and a feedback correction coefficient is obtained from the adaptive control law instead of the PID control law. The reset to the initial value or the determination of the feedback correction coefficient according to the PID control law is stopped when the fuel cut is started or the feedback control mode is exited.

Also in the second embodiment, with the above configuration, the feedback correction coefficient can be determined more optimally, and the control stability can be further improved.

FIGS. 10 and 11 are flow charts showing a third embodiment of the present invention.

FIG. 10 is a main flow chart corresponding to FIG. 4 of the first embodiment, but in the case of the third embodiment, FIG.
The step of judging whether or not it is in the feedback control area in S20 of the flow chart is a subroutine of FIG.
Move to the chart, and if affirmative in S18, immediately proceed to S2.
The process proceeds to step 2 and thereafter to calculate the feedback correction coefficient KFB.

FIG. 11 is a subroutine flowchart showing the operation.

In the following, it is determined in S300 whether or not the vehicle is in the feedback control region. This is performed in the same manner as in the first embodiment. If the result in S300 is affirmative, S30
Proceeding to 2, the PID correction coefficient KLAF is calculated, and the processing advances to S304 to calculate the adaptive correction coefficient KSTR.

Here, a supplementary explanation of the parallel calculation of the feedback correction coefficient by the adaptive control law and the PID control law is as follows. The adaptive parameter adjustment mechanism shown in Expressions 5 to 7 includes an intermediate variable 中間 (kd), ie, u (k) (KSTR (k)) and y (k) (KACT (k)) Input a vector that summarizes the current value and the past value, and calculate the adaptive parameter θ hat (k) from the causal relationship. I have.

U (k) used here is a feedback correction coefficient that is actually used for calculating the fuel injection amount. In the state where PID control is performed without performing adaptive control in the next control cycle, the PID correction coefficient KL is added to this feedback correction coefficient.
Use AF.

Here, when the PID control is performed,
Even if u (k) input to the adaptive parameter adjustment mechanism is replaced with the PID correction coefficient KLAF (k) from the adaptive correction coefficient KSTR and input to the adaptive parameter adjustment mechanism, the u (k) according to the feedback correction coefficient used for the fuel injection control can be obtained. The control output, that is, KACT (k
+ d ′) is output, so that a causal relationship between input and output is established, and the adaptive parameter adjustment mechanism can perform calculations without diverging the adaptive parameter θ hat (k).

At this time, if this θ hat (k) is input to Equation 9, KSTR (k) can be calculated. This KSTR
The calculation of (k) may be KSTR (k) calculated by replacing KSTR (ki) = KLAF (ki) (i = 1, 2, 3).

As described above, even when the PID controller is operating, the adaptive correction coefficient KSTR can be calculated, and the PID correction coefficient KLAF and the adaptive correction coefficient KSTR at that time substantially match. As a result, when switching from the PID correction coefficient KLAF to the adaptive correction coefficient KSTR, the PID correction coefficient KLAF and the adaptive correction coefficient KSTR have approximate values, and the switching is smooth.

In the flow chart of FIG. 11, the flow then advances to S306, where the adaptive correction coefficient KSTR and the PID correction coefficient KL
It is determined which of the AFs is used to execute the feedback control.

FIG. 12 is a subroutine flow chart showing the area determination work.

More specifically, first, in S400, it is determined whether or not the control was performed in the open loop last time, that is, at the time of the previous start (last control cycle) in the flow chart of FIG. Here, when affirmed, the process proceeds to S402, and P
An ID correction coefficient KLAF, that is, a region in which feedback control is to be performed using a low response correction coefficient (hereinafter, referred to as a “low response feedback region”).

This is because it is better not to perform a high-response feedback control during the entry from the open-loop control for the above-described reason. Note that a low-response feedback control, for example, 5TDC, may be performed for a predetermined period at the time of entry from the open loop control.
After that, if it is in that period, it is sufficient to provide a determination step for continuously proceeding to S402.

When the result in S400 is NO, the program proceeds to S404, in which it is determined whether or not the detected engine coolant temperature Tw is lower than a predetermined value TWSTRON. Here, the predetermined value TWSTRON is set to a relatively low water temperature, and the detected engine cooling water temperature Tw becomes the predetermined value TWSTRON.
When it is determined that it is less than N, the process proceeds to S402, and the low response feedback region is set. This is a stable detection value due to the danger of misfiring at low water temperature due to unstable combustion.
This is because KACT cannot be obtained. Although illustration is omitted,
When the water temperature is abnormally high, the low response feedback region is set for the same reason.

When it is determined that the engine cooling water temperature Tw detected in S404 is not less than the predetermined value TWSTRON, the flow proceeds to S406.
To determine whether the detected engine speed Ne is equal to or greater than a predetermined value NESTRLMT. Here, the predetermined value NESTRLMT is a relatively high speed, and when it is determined that the engine speed Ne detected in S406 is equal to or more than the predetermined value NESTRLMT, the process proceeds to S402 to set a low response feedback region. This is because the calculation time tends to be insufficient at a high rotation speed, and the combustion is not stable.

When it is determined that the engine speed Ne detected in S406 is not equal to or greater than the predetermined value NESTRLMT, the flow proceeds to S408 to determine whether or not the engine is idling. And
This is because the operation state is almost stable at the time of idling and does not require a high gain such as an adaptive correction coefficient.

If it is determined in step S408 that the engine is not idling, the process proceeds to step S410 to determine whether the engine is under a low load. If the result is affirmative, the process proceeds to step S402 to set a low response feedback area. This is because combustion is not stable in a low load range.

If it is determined in step S410 that the load is not low, the flow advances to step S412 to determine whether or not Hi V / T (high-speed valve timing) is selected in the variable valve timing mechanism. Proceeding to S402, a low response feedback region is set.

This is because when the valve timing on the high-speed side is selected, the amount of overlap between the valve timings is large, and there is a possibility that intake air escapes through the exhaust valve, that is, a phenomenon called so-called intake air blow-by. This is because a stable detection value KACT cannot be expected. Further, at the time of high rotation, the detection delay of the LAF sensor becomes difficult to ignore. still,
Here, the determination of whether or not the high-speed valve timing is selected not only determines whether or not the high-speed valve timing is actually selected, but also determines whether or not the high-speed valve timing is selected by the control unit of the variable valve timing mechanism (not shown). Whether or not a switching command from the side to the high-speed side has been issued is performed by referring to an appropriate flag.

That is, the change of the valve timing is not always performed simultaneously for all the cylinders, and the valve timing may temporarily differ depending on the cylinder in a transient state or the like. In other words, at the time of switching the valve timing to the high-speed side, it is determined that the feedback control has been performed using the PID correction coefficient after being determined to be in the low response feedback region, and then the control unit of the variable valve timing mechanism is controlled. Then, switching to the high-speed side is performed.

When the result in S412 is NO, S41 is reached.
4 and thereafter, it is determined whether or not the detected air-fuel ratio KACT is less than the lower limit a. If the result is affirmative, the process proceeds to S402. If the result is negative, the process proceeds to S416, and the detected air-fuel ratio is determined.
It is determined whether or not KACT is larger than the upper limit value b. If affirmed, the process proceeds to S402, and if denied, S4 is performed.
Proceeding to 18, the adaptive correction coefficient KSTR, that is, an area in which feedback control is to be performed using the high response correction coefficient (hereinafter, referred to as “high response feedback area”).

That is, when the air-fuel ratio is lean or rich, it is better not to perform high response control such as adaptive control. Therefore, the lower limit value a and the upper limit value b are appropriately set as in the first embodiment. To make that determination. In this operation, the target air-fuel ratio may be compared instead of the detected air-fuel ratio.

Returning to the flow chart of FIG. 11, the program proceeds to S308, where it is determined whether or not it is in the high-response feedback area.
TR is set as the feedback correction coefficient KFB, and the process proceeds to S312, where the feedback correction coefficient KFB is set as the I term KLAFI. The reason has been described in the above embodiment. Next, the routine proceeds to S314, where the bit of the flag FKSTR is set to 1 since the injection amount is corrected by the adaptive correction coefficient KSTR.

On the other hand, if it is determined in S308 that the region is not the high response region, the flow advances to S316 to set the PID correction coefficient KLAF as the feedback correction coefficient KFB, and advances to S318 to set the feedback correction coefficient KFB as the plant input u (k).
Input to STR controller (shown in FIG. 5). This is because the STR controller continues the calculation even when it is not in the STR area, and as described above, the PID correction coefficient KLAF
Is used in the calculation. Then, the process proceeds to S320, where the bit of the flag FKSTR is reset to 0.

If it is determined in step S300 that the current time is not in the feedback range, the flow advances to step S322 to determine whether or not a predetermined period has elapsed since the current time has stopped in the feedback time range. Value KL
AFI (k-1) is set to the current value KLAFI, that is, the I term is held, and the process advances to S326 to similarly set the internal variable (intermediate variable) of the adaptive controller to the previous value, that is, the last value during adaptive control. Hold.

Note that the plant input u is, as shown in FIG.
In this case, not only the current value u (k) but also its past value u (k-1) are used. Therefore, S
I of u (ki) in 326 is used to mean its current value and past value collectively, and in S326, u (k), u (k-1), u
(k-2), u (k-3), more precisely, u (k-1), u (k-2),
u (k-3) and u (k-4) are to be held.

Here, the adaptive parameter θ hat and the gain matrix Γ simply hold the previous values. When the adaptive parameter θ hat and the gain matrix Γ are stored as map values in a memory or the like, the map values may be used instead of the hold values. Although not shown, KSTR and KACT also hold the last value during adaptive control. In addition, KACT and input u (ki) are grouped together ひ と
May be held.

Next, the flow proceeds to S328, where the value of the feedback correction coefficient KFB is set to 1.0. That is, the feedback control is not performed, and the process proceeds to S330, where the flag FK is set.
Reset the bit of STR to 0.

On the other hand, if it is determined in S322 that the predetermined period has elapsed since the time has disappeared from the feedback area, the flow advances to S332 to set the value of the I term KLAFI to 1.0 (initial value). , The values of the adaptive parameter θ hat and the gain matrix Γ are set to predetermined values, for example, initial values. Here, the initial value of the plant input u is more specifically, u (k) = u (k-1) = u (k-2) = u (k-3)
= 1.

[0164] To explain this, once the accelerator pedal is returned and decelerated, the fuel is cut off and the operation shifts to the open loop control, and then the accelerator pedal is depressed again and accelerated soon, that is, the operation returns to the feedback control. Is often experienced. This is because when returning to the feedback control again in such a short time, the state of the internal combustion engine before and after the non-operating region of the STR controller hardly changes, and the causal relationship with the past combustion history is naturally established. .

Therefore, in the case of such a transient area change, the continuity of the adaptive control is maintained by holding the internal variables of the adaptive controller, and the adaptive control is performed without returning to the initial state or the like. The control is executed, and the control stability is improved.
In that sense, the predetermined period described in S322 is set to a period within a range in which a causal relationship with the past combustion history is established.
Here, the term “period” is used because control is possible not only by measuring time but also by the number of control cycles (the number of combustion cycles), the number of TDCs, and the like.

On the other hand, if the predetermined time or more has elapsed, it is expected that the state of the internal combustion engine before and after the adaptive control non-operating region has significantly changed. Returned to value. The initial value of the hat (k-1) and u (k) (= KSTR (k)) are stored in a memory for each operating region of the internal combustion engine, and the values of the hat (k-1) ) And ζ (kd). By doing so, controllability at the time of restarting adaptive control can be further improved. Furthermore, the θ hat
(k) may be learned for each operation area.

Returning to the flow chart of FIG. 10, the program then proceeds to S28 to determine the output fuel injection amount Tout, and then proceeds to S30 to output the output fuel injection amount Tout as a manipulated variable to the drive circuit 82 of the injector 22. , And these are not different from the first embodiment.

In the third embodiment, similarly to the first embodiment, immediately after the feedback control is restarted after the open-loop control of the air-fuel ratio is completed, such as when returning from fuel cut, and when the combustion becomes stable. Since the feedback correction coefficient is determined based on the PID control law when the vehicle is in an operating state where the control is not performed, the control amount does not become unstable and the control stability does not decrease.

On the other hand, after the combustion is stabilized, the operation is performed to absorb the control deviation between the target value and the detected value at once using the feedback correction coefficient based on the adaptive control law of high response. The convergence of the control can be improved in the same manner as described above.

Further, the STR controller and the PID controller are operated in parallel while replacing their internal elements with each other, and the adaptive correction coefficient KSTR and the PID correction coefficient KLAF
Is calculated in parallel, so the adaptive correction coefficient KS
The switching from TR to the PID correction coefficient KLAF or vice versa can be performed more smoothly.

Further, the switching can be performed at an arbitrary timing, so that the switching can be performed more appropriately. In addition, the spike of the air-fuel ratio at the time of the switching does not occur, and the controllability of the fuel injection or the air-fuel ratio can be improved. Can be improved.

FIG. 13 is a subroutine flow chart of a feedback correction coefficient KFB calculation similar to FIG. 11, showing a fourth embodiment of the present invention.

In the fourth embodiment, the STR controller and the PID controller are temporarily operated in parallel only during the transition from the low-response feedback region to the high-response feedback region to reduce the operation load.

To explain this, in the third embodiment, both the PID controller and the STR controller are always operated to perform the calculation. However, when the PID controller is operating, the STR controller is stopped. Even if the calculation of the adaptive correction coefficient KSTR is not performed, the same effect can be obtained, and a further effect can be obtained in terms of reducing the calculation load.

That is, as is apparent from Equations 5 to 7,
Computation of the adaptive parameter θ hat (k) requires the past value of the intermediate variable. Conversely, if there is a past value of this intermediate variable, the adaptive parameter θ hat (k) can be computed. Becomes The past values of the intermediate variables include θ hat (k-1), ζ (kd), and Γ (k-1), where ζ (kd) is the PID correction coefficient KLAF as in the third embodiment. And the adaptive correction coefficient KSTR.

Since Γ (k-1) is a gain matrix for determining the adaptive speed, a predetermined value such as an initial value may be used. θ hat (k-1), as described above, the adaptive correction coefficient KSTR
For a combination where = 1.0, a value obtained by dividing bo by KLAF (k-1) may be used.

Assuming the above, the following will be described. First, it is determined in S500 whether or not it is in the feedback control area, and if affirmative, the flow proceeds to S502 to determine the feedback area. This is determined by the same procedure as that described in the flowchart of FIG. 12 in the third embodiment. And S
At 504, it is determined whether or not it is in the high response feedback area. If the determination is affirmative, the routine proceeds to S506, where it is determined whether the bit of the flag FSTRC is set to 1.

Now, for example, immediately after returning from the low response feedback region to the high response feedback region, S
The determination at 506 is denied, and the process proceeds to S508 to set an internal variable of the STR (controller). This is described earlier in FIG.
The same operation as described in S334 of the flow chart is performed. (If the past value of the input u (k) used for ζ (kd) is set in S522 and S546 described later, Is used). Next, the processing proceeds to S510, where the adaptive correction coefficient KSTR is calculated by the same processing as described in the first embodiment, and then the processing proceeds to S512, where the PID correction coefficient KLAF is calculated.
Is calculated by the same processing as described in the first embodiment.

Then, the flow advances to S514 to increment the value of the counter C, and to S516, it is determined whether or not the calculated adaptive correction coefficient KSTR and the PID correction coefficient KLAF are completely or substantially the same. To determine whether the counter value C has exceeded a predetermined value Cref. S
If the result in S518 is negative, the program proceeds to S520, in which the PID correction coefficient KLAF is set as the feedback correction coefficient KFB, and S52 is executed.
Proceeding to 2, the feedback correction coefficient KFB is set as the plant input u (k), the flow proceeds to S524 to reset the bit of the flag FKSTR to 0, and the flow proceeds to S526 to set the bit of the flag FSTRC to 1.

Therefore, at the time of the next program loop (control cycle), the determination at S506 is affirmed, and the process proceeds to S528.
Unless affirmative at 16 or S518, the above processing is repeated. In other words, during that time, S510 and S512
, The adaptive correction coefficient KSTR and the PID correction coefficient KLAF are calculated in parallel.

If the result in S516 or S518 is YES in some program loops, the program proceeds to S53.
Proceed to step 2 to apply the adaptive correction coefficient KSTR to the feedback correction coefficient.
The process proceeds to step S534, and the feedback correction coefficient KFB is set.
Is replaced with the term I KLAFI for the reason described above, and S536
And sets the bit of the flag FKSTR to 1;
Proceeding to 8, set the bit of the flag FSTRC to 1 and
Proceeding to 40, the value of the counter C is reset to zero.

Therefore, the next time the program is started, S50
6 is affirmed and proceeds to S528, and the determination of S528 is also affirmed and proceeds to S530, where the adaptive correction coefficient KSTR is set to the first value.
The calculation is performed in the same procedure as in the embodiment.

On the other hand, if it is determined in step S504 that the area is not the high response feedback area, the flow advances to step S542 to set the PID
The correction coefficient KLAF is calculated in the same procedure as in the previous embodiment, and the flow advances to S544 to set the PID correction coefficient KLAF as the feedback correction coefficient KFB. The flow advances to S546 to set the feedback correction coefficient KFB as the plant input u (k). To reset the bit of the flag FKSTR to 0, and
Proceeding to 0, the flag FSTRC bit is set to 0.

Therefore, when returning from the open loop control to the feedback control, the low response feedback region is first set, and only when returning from the low response feedback region to the high response feedback region, the adaptive correction coefficient KSTR and the PID correction coefficient are set. The calculation of KLAF is temporarily performed in parallel, and only when the two values become almost the same or a predetermined control cycle (Cref) elapses, only the adaptive correction coefficient KSTR is calculated.

If it is determined in S500 that the current value is not in the feedback control area, the flow advances to S552 to set the value of the feedback correction coefficient KFB to 1.0, and advances to S554 to set the value of the I term KLAFI to 1.0. Go to flag
The bit of FKSTR is reset to 0, and the process proceeds to S558, where the bit of flag FSTRC is similarly reset to 0.

In the fourth embodiment, the adaptive correction coefficient KSTR and the PID correction coefficient KLAF are temporarily calculated in parallel only when returning from the low response feedback area to the high response feedback area. Since the adaptive correction coefficient KSTR is calculated only when they become the same or when a predetermined control period elapses, the switching can be performed smoothly and the calculation load can be reduced.

In the above, after the command for switching from the PID correction coefficient KLAF to the adaptive correction coefficient KSTR is issued,
The adaptive correction coefficient KSTR may be simply calculated by the predetermined number of times of control using the above ζ (kd), Γ (k-1), and θ hat (k-1). That is, the PID correction coefficient KL is determined a predetermined number of times.
After the injection amount is continuously corrected by AF, the adaptive correction coefficient KSTR may be completely switched.

Also, not after the above-mentioned predetermined number of controls, but after KLAF (k) −α ≦ KSTR (k) ≦ KLAF (k) + β, that is, after KSTR (k) ≒ KLAF (k), The feedback correction coefficient used for the amount correction is calculated from KLAF (k).
KSTR (k) may be switched (α, β: minute predetermined value).

[0189] When the determination in S516 or S518 is affirmative, the feedback correction coefficient used for the injection amount correction is switched from KLAF (k) to KSTR (k). However, even if one of S516 or S518 is omitted. good.

FIGS. 14 and 15 are a block diagram showing a fifth embodiment of the present invention and a subroutine flow chart showing still another example of calculation of feedback correction coefficient KFB.

In the case of the fifth embodiment, as shown in FIG. 14, the PID controller is removed, and a second STR controller is provided in addition to the STR controller of the first embodiment (the first embodiment). The STR controller of the embodiment is referred to as “STR controller 1”, and the second STR controller
The controller is referred to as “STR controller 2”).

A feedback correction coefficient determined by the STR controller 1 (referred to as "first adaptive correction coefficient" or "KSTR") and a feedback correction coefficient determined by the STR controller 2 ("second adaptive correction coefficient").
Or "KSTRL"), the magnitude of the responsiveness was KSTR> KSTRL. That is, the second adaptive correction coefficient KSTRL determined by the STR controller 2 is set so that the gain is relatively small, and thus the control response is low.

Here, the level of the gain of the STR controllers 1 and 2 is determined by differentiating the algorithm used between the variable gain algorithm and the fixed gain algorithm.
In other words, the convergence is increased on the high gain side as a variable gain algorithm, and the gain matrix Γ is set to a low gain on the low gain side as a fixed gain algorithm to enhance stability.

Further, more simply, both may have different gain matrices as fixed gain algorithms. In that case, the gain matrix of the STR controller 1 Γ> the gain matrix of the STR controller 2 良 い.

FIG. 15 is a flowchart showing the operation of the fifth embodiment. Note that FIG. 15 is similar to FIG. 11 of the third embodiment, and if the same step, unless otherwise noted, the same processing as in FIG. 11 is performed.

In the following, it is determined in S600 whether or not the vehicle is in the feedback control area.
04, proceeding to S606, the second adaptive correction coefficient KSTRL and the first
Is calculated in the same procedure as described in the previous embodiment, the flow proceeds to S608 to determine the feedback region, and proceeds to S610 to determine whether or not the region is the high response feedback region. Proceeds to S612, and sets the first adaptive correction coefficient KSTR to the feedback correction coefficient KFB.
In step S614, the bit of the flag FKSTR is set to 1.

If it is determined in S610 that the second adaptive correction coefficient KSTRL is not in the high response feedback area, the flow advances to S616 to set the second adaptive correction coefficient KSTRL as the feedback correction coefficient KFB.
Proceeding to 618, the bit of the flag FKSTR is reset to 0.

On the other hand, if it is determined in step S600 that the vehicle is not in the feedback control range, the flow advances to step S620 to determine whether a predetermined period has elapsed as in the case of the third embodiment.
If not, the flow advances to S622 to hold the previous value of the internal variable as in the case of the third embodiment. At this time, the internal variables are used for both the first adaptive correction coefficient KSTR and the second adaptive correction coefficient KSTRL.

Next, the flow proceeds to S624, where the value of the feedback correction coefficient KFB is set to 1.0, and the flow proceeds to S626, where the flag is set.
Reset the FKSTR bit to 0. When the result in S620 is affirmative, the program proceeds to S628, in which the internal variable is set to a predetermined value (initial value). Here, among the internal variables, the predetermined values of the plant input u (ki), the adaptive parameter θ hat (k-1), and the gain matrix Γ (k-1) are the first and second adaptive correction coefficients KSTR, It is assumed that they are different for KSTRL (however, the same value may be used except for the gain matrix Γ (k-1)).

In the fifth embodiment, as described above, a feedback correction coefficient is calculated in parallel using two kinds of control rules which are also adaptive control rules but differ in response.
Since either one is selected according to the operating state, the same effect as in the third embodiment can be obtained.

In the calculation of KSTRL and KSTR in S604 and S606, as shown in S612, S616, and 624, the KSTR,
By using the correction coefficient KFB actually used for feedback control for the calculation of KSTRL, KSTR, KSTR
L is always a correlated value, and the step caused by switching can be reduced.

In the fifth embodiment, two STR controllers are prepared. However, only one STR controller is used, and a fixed gain algorithm is used.
The level of the gain may be changed by changing the set value of Γ.

In the previous embodiment, the fifth embodiment
When the two STR controllers are provided as in the above embodiment, and the absolute value of the adaptive correction coefficient KSTR (k) exceeds the first threshold value KSTRref1, the low-gain correction coefficient output from the second controller is It may be used.

Further, in the previous embodiment, the absolute value of the difference between the adaptive correction coefficient KSTR and 1.0 is obtained and compared with the threshold value. The comparison may be made separately for each of the large and small sides, or the difference between the large and small may be obtained and compared. Further, the threshold values may be different on the large and small sides.

In the previous embodiment, an example of PID control is shown. However, by appropriately setting the gains KP, KI, and KD, it is possible to use either PI control or control using only the I term. It is. That is, the PID control mentioned here is established if it has a part of the gain term. In that sense, it is expressed as a PID controller in the claims.

Although the target value is the air-fuel ratio (more precisely, the equivalence ratio) in the previous embodiment, the target value may be the fuel injection amount.

In the previous embodiment, the feedback correction coefficients KSTR, KLAF, and KSTRL are obtained in a multiplication form, but may be in an addition form.

Although the throttle valve is operated by the pulse motor in the previous embodiment, it may be operated in response to the depression of the accelerator pedal by mechanically linking the throttle valve with the accelerator pedal.

In the previous embodiment, an example of an internal combustion engine provided with an exhaust gas recirculation mechanism, a canister / purge mechanism and the like is shown, but these are not essential.

In the above description, STR is used as the adaptive controller.
However, MRACS (Model Reference Adaptive Control) may be used.

In the above description, the output of a single air-fuel ratio sensor provided in the exhaust system collecting section is used. However, the present invention is not limited to this. An air-fuel ratio sensor is provided for each cylinder and the air-fuel ratio detected for each cylinder is used. May be used.

[0212]

According to the first aspect of the present invention, the value of the feedback correction coefficient after switching can be made substantially the same as the value of the feedback correction coefficient before switching, and a step occurs between the feedback correction coefficients. Since there is no
Even when switching from the low-response feedback correction coefficient to the high-response feedback correction coefficient, the control amount does not become unstable due to a sudden change in the manipulated variable, and thus control stability can be improved.

According to the second aspect, by appropriately setting the predetermined range, it is possible to switch when the outputs of the first calculating means and the second calculating means are substantially the same,
The difference between the feedback correction coefficients can be effectively reduced, the switching can be performed more smoothly, and the manipulated variable does not suddenly change and the control amount does not become unstable. Can be improved.

According to a third aspect of the present invention, when control is performed toward the stoichiometric air-fuel ratio, the fact that the detected value is close to 1 in the equivalence ratio means that the control deviation is small, that is, the first calculation means. It can be more accurately detected that the output of the second calculating means is substantially the same as that of the second calculating means. Therefore, by switching at that time, the difference between the feedback correction coefficients can be reduced more effectively, and the switching can be performed more smoothly.

According to the present invention, the feedback correction coefficient can be switched smoothly even when the control returns to the feedback control after the open loop control is performed from the execution of the fuel cut, the full-open increase correction, the execution of the EGR, and the like. In addition, the control amount does not become unstable due to the sudden change in the operation amount, so that the control stability can be improved.

According to the present invention, the feedback correction coefficient can be smoothly switched when the operation returns to the feedback control after the open loop control is performed particularly at the time of the fuel cut, and the control amount is changed suddenly. Does not become unstable, so that control stability can be improved.

According to the present invention, the switching can be performed at an arbitrary timing while reducing the level difference caused by the switching. In particular, the switching from the low-response feedback correction coefficient to the high-response feedback correction coefficient is performed. Can be switched at any time,
Switching can be performed more smoothly, and control stability can be further improved.

According to the present invention, in addition to the above-mentioned effects, the convergence speed is automatically adjusted even when the controlled object changes depending on the state, so that the control amount quickly converges to the target value. As a result, convergence is improved, and robustness against disturbance is also improved.

According to the present invention, in addition to the above-mentioned effects, even if the control stability is reduced when a high-response feedback correction coefficient is used, a stable feedback correction coefficient can be set. Thus, control stability can be improved.

According to the ninth aspect, it is possible to ensure the stability of the control while securing the response to some extent, even when the stability of the control is reduced by using the feedback correction coefficient of high response. it can.

According to the tenth aspect, in addition to the above-described functions and effects, the configuration can be simplified.

According to the eleventh aspect, in addition to the above-mentioned effects, the convergence speed can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram generally showing a fuel injection control device for an internal combustion engine according to the present invention.

FIG. 2 is a characteristic diagram showing valve timing characteristics of a variable valve timing mechanism provided in the internal combustion engine of FIG.

FIG. 3 is a block diagram showing a configuration of a control unit of the apparatus shown in FIG. 1 in detail.

FIG. 4 is a flowchart showing the operation of the apparatus shown in FIG. 1;

FIG. 5 is a block diagram functionally showing the operation of the apparatus shown in FIG. 1;

FIG. 6 is a subroutine flowchart showing the operation of calculating the feedback correction coefficient KFB in the flowchart of FIG. 4;

FIG. 7 is a subroutine flow chart of the flow chart of FIG. 6, showing a specific calculation operation of two kinds of feedback correction coefficients different in response.
It is a chart.

8 is a timing chart showing a reference value to be compared with the absolute value of the difference between the feedback correction coefficient and 1.0 in the flow chart of FIG. 6;

FIG. 9 is a timing chart similar to FIG. 8, showing a second embodiment of the present invention.

FIG. 10 is a main flow chart similar to FIG. 4, showing a third embodiment of the present invention.

FIG. 11 is a subroutine flowchart showing the operation of calculating a feedback correction coefficient KFB in the third embodiment.

FIG. 12 is a subroutine flowchart showing a feedback area determination operation according to the third embodiment.

FIG. 13 shows a fourth embodiment of the present invention.
12 is a subroutine flowchart showing the same operation for calculating the feedback correction coefficient KFB as in FIG.

FIG. 14 is a block diagram showing an operation of the device according to the fifth embodiment of the present invention.

FIG. 15 shows a fifth embodiment of the present invention,
7 is a subroutine flow chart showing the same operation for calculating a feedback correction coefficient KFB as in FIG.

FIG. 16 is a timing chart showing a delay in detection of an air-fuel ratio when fuel supply is restarted from fuel cut.

[Explanation of symbols]

 Reference Signs List 10 internal combustion engine 22 injector 34 control unit 54 air-fuel ratio sensor (LAF sensor)

Continuation of the front page (56) References JP-A-5-52140 (JP, A) JP-A-4-47135 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 41 / 14 330 F02D 41/02 325 F02D 45/00 324

Claims (11)

(57) [Claims] 1. A method according to claim 1, Means for detecting the operating state of the internal combustion engine, including means for detecting at least the air-fuel ratio of the exhaust gas of the internal combustion engine; b. A first feedback correction coefficient for correcting the supplied fuel amount using an adaptive controller so that the supplied fuel amount supplied to the internal combustion engine matches a target value based on the air-fuel ratio detected by the air-fuel ratio detecting means. First calculating means for calculating c. A second calculating means for calculating a second feedback correction coefficient that is lower in response than the first feedback correction coefficient and is a correction coefficient for correcting the supplied fuel amount similarly to the first feedback correction coefficient; , D. Switching means for switching the outputs of the first calculation means and the second calculation means in accordance with the detected operating state; and e. Supply fuel amount correction means for correcting the supply fuel amount based on the first or second feedback correction coefficient selected via the switching means, and the switching means comprises: f. When switching between the outputs of the first calculation means and the second calculation means, there is provided a replacement means for replacing at least a part of internal elements of the first feedback correction coefficient and the second feedback correction coefficient. A fuel injection control device for an internal combustion engine. 2. The method according to claim 1, wherein the switching unit is configured to switch the first calculating unit and the second calculating unit when the detected air-fuel ratio is within a predetermined range.
2. The fuel injection control device for an internal combustion engine according to claim 1, wherein the output of said calculation means is switched. 3. The fuel injection control apparatus for an internal combustion engine according to claim 2, wherein the predetermined range is equal to or near 1 in an equivalent ratio. 4. A method according to claim 1, Air-fuel ratio detection means for detecting the air-fuel ratio of the exhaust gas of the internal combustion engine; b. First calculating means for calculating a first feedback correction coefficient using a recurrence type controller so that the air-fuel ratio detected by the air-fuel ratio detecting means matches the target air-fuel ratio; c. Second calculating means for calculating a second feedback correction coefficient having a lower response than the first feedback correction coefficient so that the air-fuel ratio detected by the air-fuel ratio detecting means matches the target air-fuel ratio; d. . Switching means for switching the outputs of the first calculation means and the second calculation means; e. Supply fuel amount correction means for correcting the supply fuel amount supplied to the internal combustion engine based on the first or second feedback correction coefficient selected via the switching means, and the supply fuel amount correction When shifting from open loop control to feedback control,
A fuel injection control device for an internal combustion engine, wherein the supplied fuel amount is corrected based on an output of the second calculating means for a predetermined period. 5. The internal combustion engine according to claim 4, wherein the transition from the open loop control to the feedback control is a time when the fuel supply to the internal combustion engine is stopped and then the fuel supply is restarted. Fuel injection control device. 6. The first calculation means and the second calculation means calculate the first feedback correction coefficient and the second feedback correction coefficient in parallel, and the switching means performs the detected operation. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 5, wherein the switching is performed by selecting an output of the first calculation means and an output of the second calculation means according to a state. 7. The fuel injection control device for an internal combustion engine according to claim 4, wherein the controller of the recurrence type is an adaptive controller. 8. The method according to claim 1, wherein the second calculating means includes a P term, an I term, a D term,
The fuel injection control device for an internal combustion engine according to any one of claims 1 to 7, wherein the second feedback correction coefficient is calculated using a PID controller including at least one of the above items. . 9. The method according to claim 1, wherein said second calculating means calculates said second feedback correction coefficient using an adaptive controller of a recurrence type. A fuel injection control device for an internal combustion engine according to any one of the preceding claims. 10. The first and second calculating means calculate the first and second feedback correction coefficients using an adaptive controller, wherein the first calculating means comprises a variable gain and a fixed gain. Calculating the first feedback correction coefficient using at least one of the gains;
The fuel injection control device for an internal combustion engine according to any one of claims 1 to 6, wherein the second calculating means calculates the second feedback correction coefficient using the other one. 11. The fuel supply amount correcting means according to claim 1, wherein
11. The fuel injection control device for an internal combustion engine according to claim 1, wherein the supplied fuel amount is corrected by multiplying the supplied fuel amount by a second feedback correction coefficient.