JPH109021A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compensate transient change of an engine in a good condition by finding out a control parameter from a detected operating condition, inputting it to a controller of a recurrent type, and compensation transient change of an internal combustion engine or a dynamic change. SOLUTION: When a feed back control range is judged, a detecting air-fuel ratio KACT (K) and a target air-fuel ratio KCMD are inputted to a PID controller, a feed back correction coefficient KLAF is calculated, and it is corrected by multiplication of a requirement fuel rate Tcyl (k). Elements b0 , r1 , r2 , s0 of an adaptive parameter θ hat are retrieved from a map which is set beforehand by every operating ranges divided according to engine speed, an engine load, and the like, and a plant input u (k) (a feed fuel ratio) is calculated so as to equalize a target value Tcyl (k) and a detecting value Gfuel (k) to each other, following with the controller of a recurrent type by an adaptive parameter θhat which is found out. Various kinds of correction coefficient which is carried out by the additional type of atmospheric pressure correction and the like is added to a calculated value, and it is set as an output fuel rate.

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 Recently, adaptive control theory has been introduced for internal combustion engines, and a technique has been proposed for adaptively controlling the amount of fuel actually taken into a cylinder so as to match a target fuel amount. As an example, the technology described in JP-A-7-109943 can be mentioned.

[0003]

In the prior art described above, the fuel amount is determined using an optimum regulator including a feedback system. However, the dynamic characteristic of a controlled object including a dead time, such as an internal combustion engine, is reduced. Even if it fluctuated, it could not be completely canceled. For this reason, in the above-described related art, a measure is taken by accumulating the deviation between the detected value and the target value and adding the accumulated deviation to the air-fuel ratio correction coefficient.

[0004] In order to solve the problem, the present applicant has proposed a fuel injection control for an internal combustion engine using adaptive control in, for example, Japanese Patent Application Laid-Open No. 6-161511. In the proposed technology, the dynamic characteristics of the control plant are grasped (identified) from the input / output of the control plant (internal combustion engine) via an adaptive parameter adjustment mechanism, and thereby the dynamics of the control plant (such as an internal combustion engine) including dead time can be obtained. The intended fuel injection control is realized by compensating for variations in characteristics.

However, when an adaptive controller (rule) is used, the amount of calculation of the control parameter, more specifically, the control parameter performed by the adaptive parameter adjusting mechanism is higher than when another controller (rule) is used. The amount of calculation of (adaptive parameters) increases. Therefore, when such control is to be realized using an in-vehicle microcomputer, a relatively high-performance microcomputer must be used.

In addition, since the calculation time is shortened in the high speed region of the internal combustion engine, the amount of calculation is a serious problem in realizing this type of control in a real machine.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reduce the amount of calculation and compensate for fluctuations in the supply / discharge air-fuel ratio with respect to dynamic behavior in a transient state in a control plant including dead time such as an internal combustion engine. It is an object of the present invention to provide a fuel injection control device for an internal combustion engine, which is capable of realizing the control of the period.

A second object of the present invention is to reduce the amount of calculation while compensating for fluctuations in the supply / discharge air-fuel ratio with respect to the dynamic behavior in a transient state, thereby realizing the present invention using a vehicle-mounted microcomputer. It is also an object of the present invention to provide a fuel injection control device for an internal combustion engine, which can perform control effectively even at a high rotation speed in which the calculation time is short, while having a relatively low performance.

[0009]

In order to achieve the above object, according to the present invention, there is provided an air-fuel ratio detecting means for detecting an air-fuel ratio of exhaust gas of an internal combustion engine, and at least an engine speed of the internal combustion engine. Operating state detecting means for detecting an operating state including an engine load and an engine load; a supplied fuel amount calculating means for calculating an amount of fuel supplied to the internal combustion engine in accordance with the detected operating state; and a recurrence type controller Engine transient change correction for determining the control parameters from the detected operating state, inputting the control parameters to the controller, and operating to compensate for the transient change of the internal combustion engine to transiently correct the supplied fuel amount. Means, feedback correction means for performing feedback correction of the supplied fuel amount so as to reduce the deviation between the detected air-fuel ratio and the target air-fuel ratio, and the engine transient change compensation means. Means and supply fuel amount corrected by the feedback correction means is composed as and a fuel supply means for supplying to the internal combustion engine.

According to a second aspect of the present invention, the engine transient change correction means stores at least a part of control parameter elements of the recurrence type controller in accordance with an operation state of the internal combustion engine. Means, and a search means for searching the stored element from the detected operating state, wherein the control parameter is obtained using the searched element.

According to a third aspect of the present invention, the engine transient change correction means is configured to transiently correct the supplied fuel amount such that the detected air-fuel ratio matches the target air-fuel ratio.

Specifically, this is performed by calculating a correction coefficient so that the detected air-fuel ratio matches the target air-fuel ratio, and multiplying and correcting the calculated correction coefficient by the supplied fuel amount. .

According to a fourth aspect of the present invention, the engine transient change correction means is configured to adjust the supplied fuel amount such that an actual intake fuel amount obtained based on the detected air-fuel ratio matches a target supplied fuel amount. Was configured to perform transient correction.

[0014]

A controller of a recurrence type is provided, and its control parameters are determined from the detected operating state and input to the controller to operate so as to compensate for transient changes in the internal combustion engine to reduce the amount of fuel supplied. Engine transient change correction means for transient correction, feedback correction means for feedback correcting the supplied fuel amount so as to reduce the deviation between the detected air-fuel ratio and target air-fuel ratio, and the engine transient change correction means and feedback correction And a fuel supply means for supplying the supply fuel amount corrected by the means to the internal combustion engine, so that the amount of calculation can be reduced and the supply / discharge air to the dynamic behavior in the control plant including the dead time can be reduced. Desired control can be realized by compensating for fluctuations in the fuel ratio.

That is, the control parameters are obtained from the detected operating state and input to the controller. In other words, an adaptive parameter adjusting mechanism is provided so that the adaptive parameters are not calculated. The amount of calculation of parameters) can be reduced, and a relatively low-performance one is sufficient when using an in-vehicle microcomputer, and control is effectively continued even at high revolutions when the calculation time is reduced. Can be.

Further, a controller of a recurrence type is provided, and its control parameter is obtained from the detected operating state and inputted to the controller to compensate for a transient or dynamic change of the internal combustion engine. In this way, the supply fuel amount is transiently corrected, so that the transient change of the engine can be well compensated.

Furthermore, since the supplied fuel amount is feedback-corrected to reduce the deviation between the detected air-fuel ratio and the target air-fuel ratio, the steady-state deviation of the engine can be eliminated. Therefore, even in a control plant including a dead time, such as an internal combustion engine, the desired control can be realized by canceling the fluctuation of the dynamic characteristics.

[0018]

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 FIG. 1, reference numeral 10 denotes an OHC in-line four-cylinder internal combustion engine having one stroke and four strokes.
The intake air introduced from the air cleaner 14 disposed at the front end of the pump 2 passes through a surge tank 18 and an intake manifold 20 while its flow rate is adjusted by a throttle valve 16, and passes through two intake valves (not shown). The fuel flows from the first cylinder to the fourth cylinder. 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 via two exhaust valves (not shown), and is purified by a catalyst device (three-way catalyst) 28 through an exhaust pipe 26 to outside 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 has an exhaust gas recirculation mechanism 100 including an exhaust gas recirculation passage 121 for recirculating exhaust gas to the intake side.
And a connection between the intake system and the fuel tank 36, and a canister / purge mechanism 200 is provided. However, the mechanism is not directly related to the gist of the present application, and therefore the description thereof 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 distributor (not shown) of the internal combustion engine 10 includes a cylinder discrimination signal at a specific crank angle of a specific cylinder and a reference crank angle signal at a predetermined crank angle of a piston (not shown) of each cylinder. , And 15
A crank angle sensor 40 that outputs a rotation speed signal every degree is provided. Further, in the internal combustion engine 10, a throttle opening sensor 42 for detecting the opening of the throttle valve 16 is provided.
An absolute pressure sensor 44 for detecting the intake pressure Pb downstream of the throttle valve 16 as an absolute pressure is also provided.

An atmospheric pressure sensor 46 for detecting the atmospheric pressure Pa is provided at an appropriate position of the internal combustion engine 10, 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 at every predetermined crank angle (for example, 15 degrees), and is sequentially stored in a buffer in the RAM 74. Similarly, the output of an analog sensor such as the throttle opening sensor 42 is also taken into the CPU 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 a waveform shaping circuit 76, a counter 78 counts a rotation speed signal, and the count value is input into the CPU to detect an engine speed. 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 regulates 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 flow chart showing the operation of the control device according to the present invention, and FIG. 5 is a block diagram functionally showing the same operation. For the sake of understanding, FIG. The fuel injection control using the adaptive controller (rule) previously proposed by the applicant will be described.

In the control system shown in the figure, a map created in accordance with characteristics determined in advance through experiments is searched from detection parameters such as the engine speed and the engine load, and the basic fuel amount (fuel injection amount) Tim (k) is obtained. Is calculated. The calculated basic fuel amount Tim includes a target air-fuel ratio correction coefficient KCMDM (k).
(To be described later) is multiplied, and the corrected value T
cyl (k) (hereinafter referred to as “requested fuel amount”) is input to the adaptive controller (STR controller in the figure and hereinafter referred to by its name) as a target value r (k).

In this specification, k means a sampling time of a discrete time system, more specifically, a starting cycle (control cycle or control cycle) of the microcomputer. This will be described later.

The STR controller is, as its name implies, of the STR type and has an adaptive parameter adjustment mechanism. The adaptive parameter adjustment mechanism identifies the dynamic characteristics of the plant and sends it to the STR controller as an adaptive parameter (coefficient vector) θ hat (k).

The STR controller receives the parameters and receives a target value r (k) (required fuel amount Tcyl (k)) and a plant output (actual intake fuel amount Gfu obtained from the detected air-fuel ratio KACT (k)).
el (k)) is calculated so that the control input u (k) (supplied fuel amount Gfuel-STR (k)) matches. In addition, the dead time in the control system of FIG. 6 was specifically set to 3 (3 control cycles).

In such adaptive control, I.I. D. There is a parameter adjustment rule proposed by Landau et al. This method converts the adaptive control system into an equivalent feedback system consisting of a linear block and a non-linear block, and adjusts the non-linear block so that Popov's integral inequality for input and output is satisfied and the linear block is strongly positive. By deciding the rule,
This is a method to guarantee the stability of the adaptive control system.

That is, in the parameter adjustment rule proposed by Landau et al., The adjustment rule (adaptive rule) expressed in a recurrence formula uses at least one of the above-mentioned Popov's hyperstable theory or Lyapunov's direct method. This guarantees its stability.

This method is described in, for example, “Computer Roll” (Corona) No. 27, 28-41, or "Automatic Control Handbook" (Ohm), pages 703-707, "A Survey of Model Reference Adaptive
Techniques-Theory and Ap-plications "ID LANDA
U "Automatica" Vol. 10, pp. 353-379, 1974, "Uni-f
ication of Discrete Time Explicit Model Reference
Adaptive ControlDesigns "IDLANDAU and others" Automat
ica "Vol. 17, No. 4, pp. 593-611, 1981, and" Co
mbining Model Reference Adaptive Controllers and S
tochasticSelf-tuning Regulators "ID LANDAU" Aut
omatica ", Vol. 18, No. 1, pp. 77-84, 1982.

The adaptive control technique of the illustrated example also uses the adjustment law of Landau et al. To explain below, Landau et al.'S adjustment rule states that the transfer function B (Z ^-1 ) / A
When the polynomial of the denominator and numerator of (Z ^-1 ) is represented by Equations 1 and 2, the adaptive parameter θ hat (k) identified by the parameter adjustment mechanism is represented by a vector (transposed vector) as shown by Equation 3. . Input to parameter adjustment mechanism
(k) is defined as in Equation 4. Here, m = 1,
A case where n = 1 and d = 3, that is, a plant having a dead time of three control cycles in the primary system is taken as an example.

[0039]

(Equation 1)

[0040]

(Equation 2)

[0041]

(Equation 3)

[0042]

(Equation 4)

Here, the adaptive parameter θ shown in equation (3)
The hat is a scalar quantity b0 that determines the gain hat- ¹ (k)
, The control element BR hat (Z ⁻¹ ,
k) and elements of a control element S hat (Z ⁻¹ , k) expressed using a control amount, and are expressed as Equations 5 to 7, respectively.

[0044]

(Equation 5)

[0045]

(Equation 6)

[0046]

(Equation 7)

The parameter adjusting mechanism identifies and estimates the scalar amount and the respective coefficients of the control element, and sends them to the STR controller as the adaptive parameter θ hat shown in the above equation (3). In other words, the parameter adjustment mechanism uses the plant input u
(I) and control amount y (j) (i and j include past values)
Is used to calculate the adaptive parameter θ hat so that the deviation between the target value and the control amount becomes zero. The adaptive parameter θ hat is specifically calculated as shown in Expression 8.

In Equation 8, Γ (k) is the identification of the adaptive parameter.
A gain matrix (m + n + d order) and e asterisk (k) for determining the estimation speed are signals indicating identification / estimation errors, and are represented by recurrence formulas such as Expressions 9 and 10. In Equation 10, D (z ^-1 ) is a desired asymptotically stable polynomial given by the designer, and is set to 1 in this example.

[0049]

(Equation 8)

[0050]

(Equation 9)

[0051]

(Equation 10)

Various specific algorithms are given depending on how to select λ1 (k) and λ2 (k) in equation (9). For example, assuming that λ1 (k) = 1, 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) =
If λ2 (0 <λ2 <λ), a variable gain algorithm (weighted least squares method when λ2 = 1), λ1 (k)
When / λ2 (k) = σ and λ3 is expressed as in Equation 11, setting λ1 (k) = λ3 (k) results in a fixed trace algorithm.

When λ1 (k) = 1 and λ2 (k) = 0, the fixed gain algorithm is used. In this case, as is apparent from Equation 9, Γ (k) = Γ (k−1), and thus Γ (k) =
It becomes the fixed value of Γ. For time-varying plants such as fuel injection or air-fuel ratios, any of the progressive gain algorithm, the variable gain algorithm, the fixed gain algorithm, and the fixed trace algorithm are suitable. In Equation 11, tr１１ (0) is a trace of the initial value of Γ.

[0054]

[Equation 11]

As described above, the STR controller shown in FIG. 6 operates upon input of the adaptive parameter θ hat. Conversely, since the STR controller is a controller, the STR controller should operate even if an adaptive parameter is obtained and input by, for example, a map search without providing a parameter adjustment mechanism. The present invention has been made in view of this fact.

Hereinafter, referring to FIG. 7, even if the STR controller is used alone without providing a parameter adjusting mechanism,
A description will be given of the fact that the transmission characteristics of the plant (internal combustion engine) can be canceled by appropriately determining the elements bo hat, r1, r2, r3, so that determine the gain.

When following the method proposed by Landau et al., The transfer function of the control target (plant) is expressed by the following general formula:
2, when the plant has a transfer characteristic of a dead time d of order m / n, when a control input u (k) expressed by a recurrence formula shown in Expression 13 is given to the plant, The dynamic characteristics of the plant can be canceled.

[0058]

(Equation 12)

[0059]

(Equation 13)

That is, target value r (k) = plant output y (k)
It can be.

In the following, m = 1, n = 1, d
= 2, ie, the first-order delay and the dead time are 2 (control cycle)
A plant as shown in FIG. 7 will be described as an example.

The transfer function of the plant shown in FIG. 7 is represented by the following equation (14).

[0063]

[Equation 14]

[0064]

(Equation 15)

The control input u (k) can be expressed as shown in Expression 16, and becomes the Expression 17 after z-transform.

[0066]

(Equation 16)

[0067]

[Equation 17]

By substituting equation 17 for equation 15, equation 18 is obtained, which is transformed to equation 19.

[0069]

(Equation 18)

[0070]

[Equation 19]

Therefore, the transfer function y (z ^-1 ) / r (z ^-1 ) from r (k) to y (k) is as shown in Expression 20.

[0072]

(Equation 20)

Here, assuming that the transfer characteristic from r (k) to y (k) is canceled and becomes 1, only the dead time is obtained.

[0074]

(Equation 21)

In order for Equations 20 and 21 to be an identity,
Bo hat, r1, such that equations 22 to 25 hold
It is sufficient to provide r2, so to the adaptive controller (the element r3 does not exist because it is quadratic). This corresponds to a state where identification has been completed in ordinary adaptive control.

[0076]

(Equation 22)

[0077]

(Equation 23)

[0078]

(Equation 24)

[0079]

(Equation 25)

From Equations 22 and 23, r1 is as shown in Equation 26.

[0081]

(Equation 26)

Equations 27 and 28 are derived from Equations 24 and 26.

[0083]

[Equation 27]

[0084]

[Equation 28]

Expression 29 is derived from Expression 25 and Expression 28, so
Is shown as Equation 30.

[0086]

(Equation 29)

[0087]

[Equation 30]

From Equations 28 and 30, r2 is as shown in Equation 31.

[0089]

(Equation 31)

Therefore, if the bo hat and r1, r2, so can be given as shown in Equations 22, 26, 31, and 30, respectively, the transmission characteristics of the illustrated plant can be canceled. Although the description has been given by taking the example of the plant having the primary system with the dead time of 2 as an example, the above description is also applicable to the plant of the secondary system and the dead time of 3 or more.

Further, when the present invention is applied to the control of the internal combustion engine, since the transfer characteristic of the internal combustion engine changes depending on the operation state, bo hat, r1, r2, and so are defined as the operation state of the internal combustion engine,
For example, it may be changed depending on the engine speed, engine load (intake pressure), engine cooling water temperature, and the like. If the dead time is 3 or more, it is necessary to determine r3 or more. In that sense, in the following description, r3 is added in parentheses.

With this configuration, when the target fuel amount is equal to the fuel amount required by the cylinder, in other words, when the calculation of the basic fuel amount obtained from the map data is accurate, dynamic fluctuations such as fuel transport delay of the internal combustion engine can be realized with this configuration. Characteristics can be neglected. From the above, the control device according to this embodiment is the same as that of FIG.
It was configured as follows.

However, since the configuration shown in FIG. 5 does not have a parameter adjusting mechanism, it is not a true STR controller. However, it is a recurrence type controller (rule), and as described above, it compensates for a transient change of the internal combustion engine as a recurrence type controller (rule) using the control parameters for identifying and estimating the dynamic characteristics of the plant. It is a configuration that can be performed. Hereinafter, the controller (rule) in the recurrence type is referred to as a simplified STR.

Further, as described above, since there is no parameter adjustment mechanism, the feedback system is not configured as a feedback system capable of absorbing a steady-state error, but a term s corresponding to a feedback term for feeding back the plant output to the input side.
o, the control deviation can be absorbed to some extent even if the calculation of the basic fuel amount is slightly inaccurate.

By the way, when the canister purging is performed via the canister purging mechanism 200 described above, the disturbance becomes large and remains as a steady-state error, so that the target fuel amount cannot be accurately calculated. Therefore, a feedback system is provided in addition to the configuration of FIG.
It is shown in FIG. A PID controller (control law) is used as a feedback system.

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 shown in FIG. 4 is executed at a predetermined crank angle, for example, TD.
It is started in synchronization with C. In this case, the operation cycle is TDC
Therefore, the starting cycle k of the microcomputer
Is the TDC cycle.

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. If the result is negative, the program proceeds to S14 in which it is determined whether or not fuel cut is performed. The fuel cut is performed in a predetermined operating 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. Controlled by the loop.

When it is determined in S14 that the fuel cut is not performed, the process proceeds to S16, in which a map is searched from the detected engine speed Ne and the intake pressure Pb, and the basic fuel amount Tim (k) (= r (k )) Is calculated.

Next, the routine proceeds to S18, where the basic fuel amount Tim (k)
Is multiplied by various correction terms, that is, KCMDM (k), KTOTAL, to calculate a required fuel amount Tcyl (k). Here, KCMDM (k) is the target air-fuel ratio correction coefficient as described above, and indicates a value obtained by correcting the target air-fuel ratio KCMD (k) to compensate for the difference in intake air charging efficiency due to heat of vaporization. KTOTAL indicates the total value of various correction coefficients performed in a multiplication format such as water temperature correction.

Note that, in practice, the air-fuel ratio is equivalent to the equivalence ratio, ie, the target air-fuel ratio KCMD and the detected air-fuel ratio KACT, for convenience of calculation.
Mst / M = 1 / λ (Mst: stoichiometric air-fuel ratio, M
= A / F (A: air consumption, F: fuel consumption), λ: excess air ratio).

Then, the process proceeds to S20, where it is determined whether the activation of the LAF sensor 54 is 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 S20 that the activation has been completed, the flow advances to step S22 to determine whether or not the activation is in the feedback control region. This is performed in a separate routine (not shown). For example, open-loop control is performed when the engine is fully opened, when the engine speed is high, or when the operating state changes suddenly due to the influence of EGR or the like.

When the result in S22 is affirmative, the program proceeds to S24 in which the detected air-fuel ratio (exhaust air-fuel ratio) is calculated from the LAF sensor output.
KACT (k) is obtained, and the program proceeds to S26, where the feedback correction coefficient KLAF is calculated by the PID controller (control law).
Find (k). That is, as shown in FIG. 5, the detected air-fuel ratio KACT
(k) and the target air-fuel ratio KCMD are input to the PID controller, where the feedback correction coefficient KLAF is calculated. Hereinafter, the calculation will be described.

First, as described below, the target air-fuel ratio KCMD (k-d '
) And the control deviation DKAF of the detected air-fuel ratio KACT, DKAF, DKAF (k) = KCMD (k-d ')-KACT (k). In the above, d 'indicates a dead time until KCMD is reflected in KACT as described above. In this embodiment, d 'is 2 in a general sense based on the combustion cycle of the internal combustion engine 10. However, specifically, since the internal combustion engine 10 has four cylinders, d '= 2 based on the starting cycle (control cycle) k of the microcomputer described above.
× 4 = 8.

Then, 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) +1.0 to obtain the current value KLAF (k) of the feedback correction coefficient. As shown in FIG. 5, the obtained value is multiplied by the required fuel amount Tcyl (k) to correct it. In the above, the addition value 1.0 is an offset for obtaining a feedback correction coefficient in a multiplication format.

As described above, the transient change of the engine is compensated for by the recurrence type controller (simplified STR), and the steady-state deviation is compensated for by the PID controller. It is desirable to set the integral gain KI to a relatively large value, which is relatively small.

In the flow chart of FIG.
Proceeding to 28, the required fuel amount Tcyl (k) is corrected by multiplying it by the feedback correction coefficient KLAF (k) just obtained. Thereby, the required fuel amount Tcyl (k) in which the steady-state deviation has been corrected can be obtained.

Then, the program proceeds to S30, in which, as described above, an adaptation is made from a map which is set in advance using the detected engine speed Ne, engine load (intake pressure Pb) and the like and whose characteristics are shown in FIG. B which is an element of the parameter θ hat
Search for o, r1, r2 (r3), so. Next, the value is obtained by multiplying the retrieved value by a correction coefficient determined according to the engine cooling water temperature Tw.

More specifically, the elements bo, r1, r2 (r3), and so of the adaptive parameters are originally values identified through the parameter adjustment mechanism in each operating state, and they are mutually Therefore, these elements are collectively obtained as a set as an adaptive parameter θ hat and stored in advance for each operation region classified according to the engine speed or the like, as shown in FIG.

Although not shown, different values are prepared for the map data depending on whether idle operation, EGR execution, canister purge execution, and the like are performed. Further, when a variable valve timing mechanism is provided, different values are prepared when the high-speed valve timing characteristic is selected and when the low-speed valve timing characteristic is selected. This is because the dynamic characteristics of the internal combustion engine 10 differ in each case.

Subsequently, the flow advances to S32, where the plant output y (k) is output.
That is, the actual intake fuel amount Gfuel (k) is calculated. The actual intake fuel amount, that is, the estimated fuel amount actually sucked into the cylinder can be obtained by detecting the air amount and dividing the detected air-fuel ratio by the detected air-fuel ratio. Since no amount detecting means (air flow meter) is provided, the required fuel amount Tcyl (k) is multiplied by the detected air-fuel ratio KACT. Thereby, a value equivalent to that obtained from the air amount can be obtained.

More specifically, when the dead time is 8 in the start cycle (control cycle) of the microcomputer (as described above, the dead time is 2 in the combustion cycle), the following calculation is made. Actual intake fuel amount Gfuel (k) = (required fuel amount Tcyl (k-8) × detected air-fuel ratio KACT (k)) More specifically, actual intake fuel amount Gfuel (k) = (required fuel amount Tcyl (k) -8) x detected air-fuel ratio KACT (k)) / target air-fuel ratio KCMD (k-8).

That is, in FIG. 5, the target value of the simplified STR is the input r (k), but Tcyl (k) = r (k) × KCMDM (k). To operate so that (k-8) = Gfuel (k), Tcyl (k-8) is multiplied by its original value r (k-8) by KCMDM (k-8). Have been.

Accordingly, by setting Gfuel (k) = (Tcyl (k-8) × KACT (k)) / KCMD (k-8), the target value Tcyl (k-8) and the detected value Gfuel (k-8)
The plant input u (k) (supplied fuel amount Gfuel-STR (k)) can be determined so that (k) becomes equal. Gfuel (k) = (u (k-8) × KACT (k)) / KCMD (k-8).

Subsequently, the flow advances to S34, where the plant input u (k) (supplied fuel amount) Gfu is set so that the target value and the detected value are equal using the obtained adaptive parameter θ hat as described above.
Calculate el-STR (k). Specifically, this is performed in accordance with the above-described equation 16 or the like, that is, a controller (control law) of a recurrence type. The control cycle of Equation 16 is based on the combustion cycle of the internal combustion engine. However, if this is rewritten in accordance with the control cycle of each TDC, Equation 32 is obtained. Actually, Gfuel-STR (k) is calculated using the equation shown in Equation 32.

[0118]

(Equation 32)

Subsequently, the flow advances to S36, where an added term is added to the calculated value.
TTOTAL is added to output fuel amount Tout (k). here,
TTOTAL indicates the total value of various correction coefficients performed in an addition format such as atmospheric pressure correction. However, the invalid time of the injector, etc. shall be separately added when the output fuel amount Tout (k) is output,
Not included in this.

The output fuel amount Tout (k) is specifically determined by the valve opening time of the injector 22. Next, the routine proceeds to S38, where the output fuel amount Tout (k) is set as an operation amount and the injector 22
Is output to the drive circuit 82.

If the result in S20 or S22 is NO, the air-fuel ratio is set to open-loop control, so the routine proceeds to S40, where the required fuel amount Tcyl (k) is set as the output fuel amount Tout (k), and the required fuel amount Tcyl (k) is reduced in S12. S42 when it is determined to be a ranking
In step S44, the fuel amount Ticr at the start is retrieved from the engine coolant temperature, and in step S44, the output fuel amount Tout (k) is calculated from the retrieved value according to the equation of the start mode. If it is determined in S14 that the fuel is cut, the process proceeds to S46, in which the output fuel amount Tout (k) is set to zero.

In this embodiment, the adaptive parameter adjusting mechanism is removed from the STR controller to simplify the S type.
TR was set, and a parameter corresponding to the adaptation parameter was set in advance as map data according to the operation state. Then, the map is searched and found from the detected driving state.

That is, without providing an adaptive parameter adjusting mechanism,
Therefore, since there is no need to calculate the adaptive parameters, this control can be realized using a relatively low-level microcomputer mounted on the vehicle. Further, control can be continued even in a high rotation range where the calculation time is shortened, and controllability can be improved.

The simplified STR corrects or determines the supplied fuel amount Gfuel-STR (k) so that the detected value Gfuel (k) coincides with the target value (required fuel amount Tcyl (k-8)). Since the corrected supply fuel amount Gfuel-STR (k) is input to the plant (the internal combustion engine 10), it is possible to compensate for a change in the supply / discharge air-fuel ratio with respect to the dynamic behavior of the internal combustion engine 10 in a transient state. Can be.

Further, among the control parameters, s ₀ is a term corresponding to the feedback term, so that the difference between the target value and the detected value can be absorbed to some extent, and for example, the transport caused by the fuel adhering to the intake pipe. Transient or dynamic changes such as delays can be absorbed to a large extent.

Further, apart from the simplified type STR, P is used to correct the required fuel amount to reduce the deviation between the detected value and the target value.
Because it was configured to provide an ID controller, EGR,
Even when a canister purge or the like is executed and a disturbance becomes large and a steady-state error occurs, the steady-state error can be eliminated to achieve desired control.

As described above, in the apparatus according to this embodiment, the amount of calculation is relatively small, and the dynamic characteristics of a control target including a dead time, such as an internal combustion engine, are completely canceled. be able to.

FIG. 9 is a flowchart similar to FIG. 4, showing the operation of the apparatus according to the second embodiment of the present invention, and FIG. 10 is a functional block diagram similar to FIG. FIG. Note that the start cycle of the program shown in FIG.
This is the same as in FIG.

As is apparent from FIG. 10, in the second embodiment, a correction coefficient is calculated instead of directly determining the supplied fuel amount by the simplified STR, and the correction coefficient is multiplied by the required fuel amount. It was corrected. That is, the target value of the simplified STR is defined as the air-fuel ratio, and the detected air-fuel ratio KACT (k) is determined by the target air-fuel ratio.
The correction coefficient KSTR (k) (= u (k)) (hereinafter referred to as “KCMD (k-8)) (the dead time 8 = 2 (dead time in the meaning of the combustion cycle) × 4 cylinders) according to the algorithm described above so as to match KCMD (k-8). (Referred to as "transient correction coefficient"), and the obtained transient correction coefficient KSTR is multiplied by the required fuel amount Tcyl (k) to correct it.

As in the first embodiment, the target air-fuel ratio KCMD (k-8) and the detected air-fuel ratio KACT (k) are controlled by the PID controller.
The feedback correction coefficient KLAF (k) is calculated based on the PID control law in order to eliminate the deviation.

That is, the basic fuel amount Tim (k) is obtained in the same manner as in the first embodiment, and the required fuel amount Tcyl (k) is obtained by multiplying the basic fuel amount Tim (k) by the above-mentioned various correction terms. Correction coefficient KSTR (k) and feedback correction coefficient KL
The fuel amount multiplied by AF (k) and thus corrected is supplied to the control plant (internal combustion engine) as the output fuel amount Tout (k).

The device according to the second embodiment differs from the first embodiment in the following points. Target value r (k) First embodiment. . . Fuel amount (required fuel amount Tcyl) Second embodiment. . . Air-fuel ratio (target air-fuel ratio KCMD) Plant output y (k) First embodiment. . . Actual intake fuel amount Gfuel Second embodiment. . . Actual air-fuel ratio KACT Plant input u (k) First embodiment. . . Supply fuel amount Gfuel-STR Second embodiment. . . Transient correction coefficient KSTR

However, in the first embodiment shown in FIG. 5, since the fuel amount is determined by multiplying the calculated value by the air-fuel ratio (correction coefficient), the fuel amount is also determined in the second embodiment shown in FIG. The transfer characteristics of the system from the input r (k) (target air-fuel ratio KCMD (k)) to the plant output y (k) (detected air-fuel ratio KACT (k)) are basically the same as those of the first embodiment. Are the same,
Therefore, the description given in the first embodiment is also applicable to the second embodiment.

The operation of the apparatus according to the second embodiment will be described with reference to the flowchart of FIG.

In S100, the operation state detection parameters of the internal combustion engine 10 are read out in the same manner as in the first embodiment.
After the same processing from S102 to S114 as in the first embodiment, the process proceeds to S116, and the elements bo, r1, r2 (r3) of the control parameters (corresponding to the adaptive parameters) as in the first embodiment. , so is searched by map, and the water temperature is corrected and found. Then, the process proceeds to S118, where the plant input u (k),
That is, the above-mentioned transient correction coefficient KSTR (k) is calculated. The transient correction coefficient KSTR (k) is generally expressed as shown in Expression 33, but more specifically, when the dead time is rewritten according to the control cycle of TDC, Expression 34 is obtained.

[0136]

[Equation 33]

[0137]

(Equation 34)

Subsequently, the routine proceeds to S120, where the basic fuel amount Tim
(k) is multiplied by an air-fuel ratio correction coefficient KCMDM (k) and a correction term KTOTAL to calculate a required fuel amount Tcyl (k), and the process proceeds to S122 to add a transient correction coefficient KSTR (k) to the calculated required fuel amount Tcyl (k). ) And the feedback correction coefficient KLAF (k).
The output fuel amount Tout (k) is determined by adding AL, and the process proceeds to S124 to output. The remaining steps are not different from those of the first embodiment.

Since the second embodiment is as described above,
It has the same effect as the first embodiment.

Further, the transient correction coefficient KSTR is calculated by the simplified STR so that the detected air-fuel ratio KACT matches the target air-fuel ratio KCMD, and the required fuel amount Tcyl is corrected by the calculated transient correction coefficient. In other words, since the target value is set to the air-fuel ratio, even if disturbance occurs, the target value rarely includes an error, and the control output is a detected value, not an estimated value (actual intake fuel amount). Changes in target values are also small (
Since the stoichiometric air-fuel ratio is targeted), in addition to the above-described actions and effects, the robustness against disturbance is improved.

As described above, in the first and second embodiments, the air-fuel ratio detecting means (LAF sensor 54) for detecting the air-fuel ratio KACT of the exhaust gas of the internal combustion engine 10, and at least the engine speed of the internal combustion engine Operating state detecting means (e.g., a crank angle sensor 40 and an absolute pressure sensor 44) for detecting an operating state including a number and an engine load; and a fuel amount (basic fuel amount) supplied to the internal combustion engine according to the detected operating state. Tim) (S16, S16)
106), and a controller (simplified STR) of a recurrence type, and obtains a control parameter (θ hat) from the detected operating state and inputs the obtained control parameter (θ hat) to the controller, thereby obtaining a transient change of the internal combustion engine. The engine transient change correction means (S3) which operates so as to compensate for the
0, S34, S36, S116, S118, S122)
Feedback correction means (PID controller; S2) for performing feedback correction of the supplied fuel amount in order to reduce the deviation between the detected air-fuel ratio and the target air-fuel ratio.
6, S36, S114, S122), and fuel supply means (S38, S124) for supplying the supplied fuel amount corrected by the engine transient change correction means and feedback correction means to the internal combustion engine. .

In addition, the engine transient change correcting means is configured to control the elements bo, r1, r2 (r3), so of the control parameter θ hat of the controller of the recurrence type in accordance with the operating state of the internal combustion engine.
Storage means for storing at least a part of the control parameters, and search means (S30, S116) for searching for the stored element from the detected operating state, and using the searched element for the control parameter. It was configured to seek.

The engine transient change correcting means is configured to transiently correct the supplied fuel amount so that the detected air-fuel ratio matches the target air-fuel ratio (S122).

Further, the engine transient change correction means transiently corrects the supplied fuel amount such that the actual intake fuel amount obtained based on the detected air-fuel ratio matches the target supplied fuel amount (S34). It was configured as follows.

In the first and second embodiments, the control parameter (adaptive parameter) is determined by the map search without providing the parameter adjusting mechanism.
A parameter adjusting mechanism may be provided to identify the adaptive parameter and to learn according to the operating state.

In the above-described first and second embodiments, the fuel amount may be corrected for the output fuel amount Tout obtained in consideration of the adhesion of the intake fuel to the intake pipe. This adhesion correction method is disclosed in Japanese Patent Application No. Hei.
What was proposed in -354046 may be used.
In this case, the controllability is further improved in the simplified STR because it is not necessary to correct the fuel amount due to the intake pipe attachment.

[0147] Moreover, stores as all map value in accordance with such adaptive parameter θ hat element serving b ₀ of the operating conditions, it is configured to map the it as a set or collection of each operating condition, one of which Department. This makes the elements r1, r2, r3 constant, for example,
This is because the effect of the present invention can be obtained even if only bo and so are mapped. In that sense, the claims refer to “at least a part of the control parameter elements”.
It was described.

In the PID controller, by setting the gains KP, KI, and KD as appropriate, either the PI control or the control using only the I term can be freely performed.
That is, the PID control mentioned here is established if it has a part of the gain term.

Further, the PID controller has been exemplified,
A feedback system based on an adaptive controller (rule) may be used.

In the previous embodiment, the feedback correction coefficients KSTR and KLAF 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, the throttle valve may be mechanically linked to the accelerator pedal and operated in response to the depression of 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 has been described, 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.

[0155]

According to the present invention, desired control can be realized by compensating for fluctuations in dynamic characteristics even in a control plant including dead time while reducing the amount of calculation.

That is, the control parameters are obtained from the detected operating state and input to the controller. In other words, the adaptive parameter adjusting mechanism is provided so that the adaptive parameters are not calculated. The amount of calculation of parameters) can be reduced, and a relatively low-performance one is sufficient when using an in-vehicle microcomputer, and control is effectively continued even at high revolutions when the calculation time is reduced. Can be.

Further, a controller of a recurrence type is provided, and its control parameters are obtained from the detected operating state and input to the controller, and the controller is operated so as to compensate for the transient change of the internal combustion engine to supply fuel. Since the quantity is transiently corrected, the supply / supply for the dynamic behavior of the transient state of the internal combustion engine is
Fluctuations in the exhaust air-fuel ratio can be well compensated.

Further, since the supplied fuel amount is feedback-corrected to reduce the deviation between the detected air-fuel ratio and the target air-fuel ratio, the steady-state deviation of the engine can be eliminated. Therefore, even in a control plant including a dead time, such as an internal combustion engine, the desired control can be realized by canceling the fluctuation of the dynamic characteristics.

[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 block diagram showing a fuel injection control device for an internal combustion engine using an adaptive controller (rule) previously proposed by the present applicant.

FIG. 7 is a block diagram showing a basic configuration of the present invention.

8 is an explanatory diagram showing characteristics of map data of elements of adaptive parameters (control parameters) used in the flowchart of FIG. 4;

FIG. 9 is a flowchart similar to FIG. 4, showing a second embodiment of the present invention.

FIG. 10 is a block diagram functionally showing the operation of the device according to the second embodiment.

[Explanation of symbols]

 Reference Signs List 10 internal combustion engine 22 injector 34 control unit 40 crank angle sensor 44 absolute pressure sensor 54 air-fuel ratio sensor (LAF sensor)

Claims (4)

[Claims] 1. 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. Operating state detecting means for detecting an operating state of the internal combustion engine including at least an engine speed and an engine load; c. Supply fuel amount calculation means for calculating a supply fuel amount to the internal combustion engine according to the detected operating state; d. A controller having a recurrence type is provided, and the control parameters are obtained from the detected operating state and input to the controller, and the controller is operated so as to compensate for the transient change of the internal combustion engine, thereby controlling the fuel supply amount. Engine transient change correction means for transient correction; e. Feedback correction means for performing feedback correction on the supplied fuel amount so as to reduce the deviation between the detected air-fuel ratio and the target air-fuel ratio; and f. A fuel injection control device for an internal combustion engine, comprising: a fuel supply unit that supplies a supply fuel amount corrected by the engine transient change correction unit and the feedback correction unit to the internal combustion engine. 2. The engine transient change correction means comprises: g. Storage means for storing at least some of the elements of the control parameters of the recursive controller according to the operating state of the internal combustion engine; and h. 2. The fuel for an internal combustion engine according to claim 1, further comprising: searching means for searching the stored element from the detected operating state, wherein the control parameter is obtained by using the searched element. 3. Injection control device. 3. The engine transient change correction means transiently corrects the supplied fuel amount such that the detected air-fuel ratio matches the target air-fuel ratio. A fuel injection control device for an internal combustion engine. 4. The engine transient change correction means transiently corrects the supplied fuel amount such that an actual intake fuel amount obtained based on the detected air-fuel ratio matches a target supplied fuel amount. 3. The fuel injection control device for an internal combustion engine according to claim 1, wherein: