JP2683986B2 - Fuel injection amount control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection amount control device for an internal combustion engine, and more specifically, it adaptively corrects a fuel transport delay caused by the injected fuel adhering to an intake pipe and the like. The present invention relates to a fuel injection amount control device for an internal combustion engine that always matches the actual intake fuel amount with a target value.

[0002]

2. Description of the Related Art During a transient operation of an engine, an actual in-cylinder actual intake fuel amount may not match a target value, and a lean spike or a rich spike may occur. One of the causes is a delay in fuel transportation caused by the fuel adhering to the wall surface of the intake pipe. The behavior of the fuel transportation delay changes due to engine operating conditions, initial variations, and changes over time due to deposits on the intake pipe. Therefore, as in the technique described in JP-A-2-173334 or JP-A-3-26839, an adhesion plant and a parameter adjusting mechanism are provided so that the plant output (actual intake fuel amount) is the target fuel even during transient operation. It has been proposed to adaptively control to match the inhaled amount.

[0003]

By the way, the problem of time delay is always present in the fuel injection amount control. That is,
The air-fuel ratio of the injected fuel cannot be grasped until the combustion ends and the exhaust gas reaches the air-fuel ratio sensor and is taken out as a detection value change. In addition to the detection delay, there is a delay due to the time required for calculating the fuel injection amount and the timing of sensing and output. These are also the same when trying to adaptively control the fuel injection amount. Therefore, unless the correspondence between the input and output of the adaptive controller is accurately recognized and the two are matched, the fuel behavior cannot be corrected accurately, especially in a transient operating state. The control value cannot be determined properly. However, in the above-mentioned conventional technique, only the dead time until the air-fuel ratio sensor detects it is recognized, and the time alignment between the input and output of the adaptive controller is not particularly conscious of.

Therefore, the object of the present invention is to eliminate the above-mentioned drawbacks and to prevent a time difference between the target fuel intake amount and the output (actual intake fuel amount) of the fuel adhering plant, so that the target can be achieved even during transient operation. An object of the present invention is to provide a fuel injection amount control device for an internal combustion engine, which is capable of accurately converging to an air-fuel ratio.

[0005]

In order to solve the above-mentioned problems, according to the present invention, for example, in claim 1, a fuel transport delay is based on a transport delay of fuel injected into an intake pipe of an internal combustion engine.
A fuel transportation delay correction means for performing the correction is provided, and parameters are adaptively identified so that the in- cylinder actual intake fuel amount matches the target in-cylinder intake fuel amount, and the controller parameter is determined according to the parameter. A fuel injection amount control device for an internal combustion engine, comprising: an adaptive controller for adjusting a control output, which is provided between a control input u given to a plant and a parameter identification / adjustment mechanism, or between a plant output y or its estimated value and a parameter identification / adjustment mechanism. A time delay between the generation time point of the control input u and the generation time point of the plant output y or its estimated value between the adjusting mechanism and / or at least one of the plant output y or its estimated value and the adaptive controller. Is configured to insert a time delay element corresponding to
The order of the operating state of the internal combustion engine or the fuel injection
It is configured to change depending on the state of the radiation control device .

[0006]

[Operation] Control input u and parameter identification given to the plant
.With the adjusting mechanism, or with the plant output y or
Between the estimated value of and the parameter identification / adjustment mechanism, or
The plant output y or its estimated value and the adaptive controller
During, at least one of, since to insert delay elements (dead time) time, that the time difference between the even target fuel intake amount and the plant output during transient operation (actual intake fuel amount) occurs Therefore, the target air-fuel ratio can be accurately converged. Also, the order of the time delay element
Is the operating state of the internal combustion engine or the fuel injection amount control.
Since it is configured to change depending on the state of the control device,
The target fuel intake amount and plant output (actual intake fuel
There is no time difference between the
Not affected by changes in the state of the fuel injection control device
Therefore, the target air-fuel ratio can be more accurately converged.
You.

[0007]

1 is a block diagram showing an overall control device according to the present invention. Referring to FIG.
This control device is preset from the engine speed Ne, intake pressure Pb, etc., and searches a mapped characteristic to determine a target in-cylinder intake fuel amount (Ti), a MAP block, a throttle opening θTH, an intake pressure. Gai for estimating the dynamic behavior of the actual intake air amount (Gair) from Pb, atmospheric pressure Pa, etc.
The r model block, an A / F observer block that estimates the air-fuel ratio of each cylinder from the air-fuel ratio of the exhaust system collecting portion, and a fuel injection control block that determines the fuel injection amount (Tout). In this configuration, the cylinder intake fuel amount Gfuel at each time (combustion cycle) is calculated from the estimated actual cylinder intake air amount Gair and the air-fuel ratio A / F of each cylinder.
Is estimated, and the parameter of the fuel injection block is adjusted so that it matches the target fuel amount Ti, and the injected fuel amount Tout is determined.

Each of these will be described in detail below.

First, the fuel injection control will be described.

Regarding fuel injection control, FIG. 1 is rewritten as shown in FIG. Here, the input parameters are as follows. (1) Target in-cylinder intake fuel amount Ti. . . . . A value obtained by dividing the in-cylinder actual intake air amount calculated or estimated using the inputs from various sensors by the target air-fuel ratio. The calculation of the actual cylinder intake air amount will be described later in detail. (2) In-cylinder actual intake fuel amount Gfuel. . . Similarly, a value obtained by dividing the above-mentioned in-cylinder actual intake air amount by the actual air-fuel ratio for each cylinder obtained from the wide-range air-fuel ratio sensor measurement value. The calculation of the actual air-fuel ratio for each cylinder will also be described later.

That is, as described above, at a certain time (k-
n) in-cylinder actual intake air amount Gair (k-
n) is obtained and divided by the target air-fuel ratio A / F (k−n) to determine the target in-cylinder intake fuel amount Ti (k−n). In addition, the cylinder actual intake air amount Gair (k-
n) is divided by the measured air-fuel ratio A / F (k−n) of the cylinder to determine the in-cylinder actual intake fuel amount Gfuel (k−n). Then, in the adaptive controller, the target in-cylinder intake fuel amount T
i (k-n) is the in-cylinder actual intake fuel amount Gfuel (k-n)
The compensator is adjusted so as to always coincide with each other, and the control value (injected fuel amount) Tout is determined. Here, in order to immediately respond to the change in the adhesion parameter, a wall adhesion correction compensator having a transfer function opposite to that is inserted in series in front of the wall adhesion plant. If the adhesion parameter of the wall adhesion correction compensator is equal to the true adhesion parameter of the actual machine, the transfer function of both is 1 from the outside, that is, the product of the transfer function of the plant and the compensator is 1, and the target Since the in-cylinder intake fuel amount = the in-cylinder actual intake fuel amount, a complete correction should be made. However, since the adhesion parameters generally change intricately depending on the engine operating state, it is difficult to completely match them. In addition, the actual machine has initial variations, and further changes with time due to deposits and the like. For these reasons, when the adhesion parameters of the two differ, the transfer function becomes a value other than 1 (or in the vicinity) and a time response occurs, so the target in-cylinder intake fuel amount and the in-cylinder actual intake fuel amount are not equal. .

Therefore, when the transfer characteristic of the virtual plant including the adhesion correction compensator is regarded as one virtual plant and the transfer characteristic of the virtual plant becomes a value other than 1 (or a value in the vicinity thereof), the transfer characteristics of the virtual plant and the adaptive controller. Is set to 1 (or a value in the vicinity thereof) as a whole, more specifically, the adaptive controller is operated so as to have the inverse transfer characteristic of the virtual plant. The target in-cylinder intake fuel amount is input as a target value to the adaptive controller, and an adaptive parameter that changes so that the in-cylinder actual intake fuel amount that is the output of the virtual plant matches the target value is used. The parameters of the adaptive controller are calculated by the adaptive parameter adjuster (identifier). Input / output values including past values to the virtual plant are used for the adaptive parameter adjuster (identifier). In the above, the adaptive controller also serves to absorb the error of the cylinder intake air amount. That is, even if there is an error in the estimation of the in-cylinder intake air amount, as a result, the in-cylinder actual intake fuel amount and the target in-cylinder intake fuel amount obtained by dividing the in-cylinder intake air amount by the measured air-fuel ratio and the target air-fuel ratio, respectively. Since the adaptive parameter is adjusted so that the amount and the amount always match, the air amount estimation error is absorbed.

The details will be described below.

As the wall adhering plant, a primary system model as shown in equation 1 is used. Here, the number of parameters is two.

[0015]

(Equation 1)

When expressed by a discrete type transfer function, it becomes as shown in Equation 2. In addition, the block diagram is as shown in FIG.

[0017]

(Equation 2)

Further, Equation 3 shows the transfer function of the wall surface adhesion correction compensator. As before, take the inverse transfer function of that of the wall-attached plant. In addition, in this specification, "hat" means an estimated value.

[0019]

(Equation 3)

Next, the adaptive controller will be described. The conditions required for wall surface adhesion correction are that it always works in the direction of reducing the transportation delay and that it can follow changes in the A and B terms, but such a plant is time-varying (temporal change). MRACS (model reference adaptive control) is well known as a method for adaptive control following the above. Therefore, when MRACS is applied to the wall surface adhesion correction, it becomes as shown in FIG. At this time, the reference model may be set near the median of the time-varying plant, or may be set so that the wall adhesion correction compensator can be easily controlled. Since MRACS is effective only for plants having dead time, the dead time is apparently inserted by delaying the input to the adhering plant by d cycles to make it a virtual plant (the word "virtual" is added to the insertion block). .

What is noticed here is that the virtual adhesion correction compensator and the virtual reference model are arranged in series. Since these have an inverse transfer function relationship with each other, they can be canceled. As a result, z immediately after the virtual reference model
The block of ^d and D (z ^-1 ) remain, but z ^d is a transfer function that outputs a future value and cannot exist as it is.
Therefore, by setting D (z ⁻¹ ) to D (z ⁻¹ ) = z ^−d , both of them are canceled. Usually, D (z ^-1 ) is
D (z ⁻¹ ) = 1 + d ₁ z ⁻¹ + ... + d _n z ⁻ⁿ , but there is no problem in stability even if D (z ⁻¹ ) = z ^−d . Therefore, when FIG. 4 is arranged, it becomes like FIG. 5 (this causes the adaptive controller to deal with the regulator problem and STR (self-tuning regulator)).
Transforms into). Here, the adaptive controller receives the coefficient vector identified by the parameter identification mechanism and forms a feedback compensator. However, this operation itself is publicly known, and for example, “Compute Roll” No. 2
7, "Digital Adaptive Control", page 28 to page 41, and detailed description thereof will be omitted.

FIG. 6 shows the response result of the simulation for the illustrated configuration. From this figure, MRACS
It can be seen that the parameter identification mechanism of 1 operates normally in the above configuration. However, the behavior of the air-fuel ratio remains rampant. In order to see this microscopically, when the target intake fuel amount as shown in FIG. 7A is input, the plant output and the air-fuel ratio are as shown in FIGS. 7B and 7C. From this, it can be seen that the plant output is delayed by one cycle. Since the dead time is inserted in the plant as a virtual plant, the delay causes the time difference between the target fuel amount and the plant for one cycle at the time of transient operation, so that it is understood that the air-fuel ratio has a spike. Therefore, it is necessary to make a time match between the plant, the parameter identification mechanism, and the controller.

Here, when the virtual plant is viewed from the outside, it is equivalent ^whether the dead time z ^-d is inserted before or after the plant. Therefore, it is first attached after the plant. Then, the output y ′ (k) of the plant is taken out immediately after the plant, and is inserted after that, the dead time z ^−d.
After that, the virtual plant output y (k) required by the parameter identification mechanism will be extracted. This way input r
There is no dead time in the path from (k) to the plant output y ′ (k), and the parameter identification mechanism can use the virtual plant output y (k) with dead time. The structure is shown in FIG. Further, FIG. 9 shows a simulation result of the configuration of FIG. After the convergence, as shown in FIG. 9C, the actual intake fuel amount becomes almost the target fuel amount, and the air-fuel ratio at that time is also 1
It has been flat near 4.7. Also, when the microscopic response after completion of identification is viewed on the same scale as before, it is shown in FIG.
It becomes 0 (the broken line is the response before countermeasures against dead time for comparison). Even if this is seen, the response after the dead time countermeasure has a very flat air-fuel ratio when the identification is completed. Therefore, it can be seen that it is very important to make time alignment including dead time when introducing adaptive control.

By the way, as described above, in the fuel injection amount control, the detection delay of the air-fuel ratio sensor and the sensor output A
There are various delays such as the delay due to the D / D conversion timing, the delay due to the calculation of the fuel injection amount, the delay due to the timing at which the calculated value is output, and moreover, depending on the operating state of the internal combustion engine or the state of the fuel injection amount control device. Although it may change, one of the features of the present invention is to utilize the dead time so that the above-mentioned plant, the parameter identification mechanism, and the controller can be time-matched while coping with the change. There is something I did.

Specifically, the configuration shown in FIG. 8 is modified as shown in FIG. 11, and a dead time element is inserted between the plant and the parameter identification mechanism or the adaptive controller as needed, and the configuration is used. To adapt to changes. This will be described below.

In the configuration of FIG. 11, the parameter identification rule will be described. The adaptive parameter θ hat (k) is
It can be expressed as in Equation 4 using a technique such as Landau. The identification error signal e star (k) and the gain matrix Γ (k) in Expression 4 can be expressed by Expressions 5 and 6, respectively.

[0027]

(Equation 4)

[0028]

(Equation 5)

[0029]

(Equation 6)

Here, the degree of the vector of θ hat (k) and the degree of the matrix of Γ (k) are uniquely determined by the degree of the virtual plant and the degree of the dead time (time delay element) of the virtual plant. Therefore, when the dead time changes depending on the operating state of the internal combustion engine, the orders of the vector and matrix used in the parameter identification mechanism must be changed. That is, the algorithm itself must be changed. This is not practical for implementing this device.

Therefore, as one method for solving the problem, the order of the vector and the matrix used for the calculation in the parameter identification mechanism is adjusted to the case where the dead time is the longest, and the actual dead time becomes shorter than that. Has
As shown by an imaginary line in FIG. 11, dead time is inserted so as to cope with various time delays existing between the input and output of the plant. For example, in the high rotation range, various delays are larger than the calculation cycle of the fuel injection control device,
It is assumed that the order of the dead time may reach d = 4 at the maximum. At that time, the configurations of the parameter identification mechanism and the adaptive controller are adjusted to d = 4. And in the low rotation range, the calculation cycle becomes long, so the dead time becomes relatively short,
If d = 2, in that case, by setting h, i, j in FIG. 11 as h = 2, i = 0, j = 2, the dead time of the plant output is calculated from the parameter identification mechanism and the adaptive controller. Apparently, d = 4 can be apparently set.

As another solution, the parameter identification mechanism and the adaptive controller are set to have a configuration shorter than the case where the dead time is the longest, and as shown by an imaginary line in FIG. The dead time may be inserted so as to cope with various time delays. For example, when the order of dead time is d = 4 and the parameter identifying mechanism is configured to correspond to the case where the order of dead time of the plant is 2, h = 0, i = 2, j = If 0, u
Since y (k) includes the dead time order d = 4 with respect to (k−2), the difference in the dead time between the two is 2, and the parameter identification mechanism configured by combining the dead time orders to the second order ,
It can operate stably.

In cases other than the above, it is effective to appropriately insert a dead time in the plant input and output in order to cope with various time delays existing between the input and output of the plant or changes thereof. In the control in this application, it is one of the features as described above.

By the way, although the parameter identification rules are shown in the equations 4 to 6, the specific parameter identification rule is determined by the selection of λ1 (k) and λ2 (k) in the equation 6. MRACS
The typical identification rules of (1) are roughly classified into four types: a fixed gain method, a gradually decreasing gain method (including a least square method), a variable gain method (including a weighted least square method), and a fixed trace method. Simulations were performed for them under the following conditions based on the configuration shown in FIG. Here, since there is a high possibility that the time-varying plant will be the target in the application to the actual machine, the time-varying plant was used. The simulation results are shown in FIGS. As you can see from the simulation results,
In the fixed gain method (FIG. 12), the plant output value causes severe hunting around the target value. This is particularly remarkable when the target value is changing (transient operation). During transient operation, the difference between the reference model output and its target value, the plant output value, becomes large.
The parameter identification mechanism of tries to change the parameters drastically at once. Therefore, when the plant changes too fast, overshoot occurs and hunting occurs. On the other hand, in the gradually decreasing gain method (FIG. 13), the variable gain method (FIG. 14), and the fixed tracing method (FIG. 15), the plant output properly follows the reference model that is the target value. Although some vibration is seen, it can be seen that it converges to the target value. This level of vibration can be suppressed by adjusting the parameters for convergence, for example, by changing the value of the gain matrix or D (z ⁻¹ ) without sacrificing the convergence speed. Therefore, these three identification rules show that the convergence speed is faster than that of the fixed gain method, and that it can follow even if the plant is time-varying.

Next, the estimation of the in-cylinder actual intake air amount Gair will be described.

As described above, the in-cylinder actual intake fuel amount Gfu
In order to obtain el accurately, it is necessary to accurately obtain the intake air amount. Conventionally, a mass flow method that directly measures the intake air amount and a speed density method that indirectly estimates the intake air pressure have been proposed.However, these conventional methods are basically the same as the cylinder intake air amount. Mapping (mapping) is performed using parameters with high correlation, and it is searched for and obtained,
It was completely helpless against changes in parameters that were not taken into consideration during mapping, and was not tough against deterioration, variations, and secular changes. In addition, since mapping can basically be performed only in a steady state and does not represent a transient operating state, the cylinder intake air amount during a transition had to rely on the setting. Therefore, in the present invention, a fluid dynamic model that can reflect changes in the intake air amount under various conditions is applied to the intake system, and even if the measurement itself is indirect as usual, mapping and setting are eliminated. I tried to obtain it accurately. That is, the throttle is regarded as an orifice, a fluid dynamics model around the throttle is constructed, the amount of air passing through the throttle is estimated, and the actual amount of intake air is dynamically estimated in consideration of the chamber filling delay. This will be described below.

First, as shown in the intake system model of FIG.
When the throttle is regarded as an orifice, the compressive fluid used in the throttle type flow meter shown in the formula 10 is obtained from the Bernoulli's formula shown in the formula 7, the continuous formula shown in the formula 8, and the relational expression of the adiabatic change shown in the formula 9. Can be derived, and the throttle passing air amount Gth per unit time can be obtained.

[0038]

(Equation 7)

[0039]

(Equation 8)

[0040]

(Equation 9)

[0041]

(Equation 10)

Next, the amount Gb of air in the chamber is obtained from the equation shown in equation 11 based on the gas state equation. Here, the “chamber” means not only a so-called surge tank-corresponding portion but also all portions from the downstream side of the throttle valve to the intake port.

[0043]

[Equation 11]

Therefore, the change Δ in the amount of air filled this time
Gb can be obtained from the equation of Expression 12 from the pressure change.

[0045]

(Equation 12)

That is, in the steady operation state, Gth = Ga
It becomes ir. On the other hand, in transient conditions, the suction pressure is high when the throttle valve is suddenly opened, for example, because the air is filling the chamber. Conversely speaking, if the amount of air filling the chamber and the amount of air passing through the throttle valve are known, the amount of air flowing into the cylinder can be known.
That is, assuming that the amount of air filled in the chamber is not sucked into the cylinder as a matter of course, the in-cylinder actual intake air amount Gair per unit time ΔT can be expressed by Equation 13, and the actual intake air amount Behavior can be estimated. FIG. 17 shows the simulation result by this calculation method.

[0047]

(Equation 13)

Experimental results for the above are shown. FIG. 18 shows an outline of the test apparatus.

In the experiment, the throttle opening was kept constant, the air amount was changed, and the pressures on the upstream and downstream of the throttle at that time were measured, and at the same time, the air flow rate was also measured. The test was conducted for ten throttle openings on the upstream side of the throttle. The result for the throttle opening of 31.6 degrees is shown in FIG. The following was found from the experimental results including those shown in the figure. (1) The pressure downstream of the throttle is 1D ~
2D (D: diameter of throttle valve) drops once, 3D ~
It recovers in 4D, and the pressure gradually decreases toward the downstream side again (the downward flow is caused by the throttle valve causing contraction, swirling, and separation of the flow). (2) When the dropped pressure is measured, the differential pressure across the throttle becomes larger than it actually is, so it is necessary to use the recovered pressure value to calculate the amount of air passing through the throttle.

Further, it has been found that the pressure decreases in front of the throttle upstream of the throttle.

From the above, the pressure Pthdown downstream of the throttle
(P _{2 in} the equations such as Equation 7) is the position where the pressure is recovered, that is, about 3D from the throttle valve (ideally 3D to 4D).
At a distant position, the pressure Pthup upstream of the throttle (P _{1 in} the equations such as Equation 7) is a position where the influence of the throttle valve is not exerted, and a position as close as possible to the throttle valve, that is, about 1D (or more) from the throttle valve. ) It has been found desirable to make measurements at remote locations. The pressure downstream of the throttle can be regarded as equivalent to the pressure in the chamber (surge tank) in that sense. Therefore, as will be described later, a pressure sensor is provided in the surge tank, and the detected pressure in the surge tank is used as the throttle downstream pressure Pthdo.
It may be wn.

In the equation shown in the equation 10, only the flow coefficient α is set as an unknown number, and the flow coefficient is identified by the above-mentioned test. Here, the identification is performed by using the measured pressures before and after the throttle, and from the formula 10
Calculate h (initial value is set appropriately), then compare the calculated value with the measured value, change the value of the flow coefficient so that they match, and repeat the above to minimize the error. Was adopted as the flow coefficient. FIG. 20 shows the value of the flow coefficient with respect to the throttle opening identified by the method. Further, FIG. 21 shows a comparison between the value estimated using the identified flow coefficient and the actually measured value (only shown for the throttle opening of 31.6 degrees).

In FIG. 22, the flow coefficient obtained by the above method is used, 4D downstream from the throttle valve and 1D upstream.
The values calculated by simulation using the values measured at distant positions and the values actually measured are shown in comparison. still,
Shown in the figure are data when the throttle opening is changed to 7 to 20 degrees. Further, Pb indicates an actual measurement value of the intake pressure sensor, and Gth indicates an actual measurement value by the air flow meter. From this figure, it can be seen that this calculation method is effective.

In addition, in the equation 10, the measured value is Pthup.
Since (P ₁ ), Pthdown (P ₂ ), and θTH, they are mapped (mapping) to reduce the square root calculation time in particular. It is shown in Equation 14. still,
In the equation, M indicates map data.

[0055]

[Equation 14]

Next, the relationship with the resolution of the sensor will be described. FIG. 23 shows the measurement data with the vertical axis representing the control error for a certain measurement error and the horizontal axis representing the throttle opening.
From the figure, it can be seen that for a constant measurement error, the control error increases as the opening degree decreases. Therefore, it is desirable that the sensor has a smaller measurement error on the lower opening side, that is, has a higher resolution on the lower opening side. Further, FIG. 24 shows the measurement data in which the vertical axis similarly shows the control error and the horizontal axis shows the pressure ratio before and after the throttle valve. From this, similarly, it is understood that it is desirable to use an intake pressure sensor having high resolution on the high load side (atmospheric pressure side, indicated by 1 in the figure). Therefore, it is desirable to use both the throttle opening sensor and the intake pressure sensor, or at least one of them, having such a resolution when applied in an actual machine.

Incidentally, to add some remarks on the above-mentioned measurement of the air amount, when the pressure ratio before and after the throttle is a predetermined value or less, the flow velocity is sonic velocity, and therefore, it is set to a predetermined value (for example, 0.528). Fix it. Further, the intake air temperature sensor is provided near the upstream side of the throttle valve in order to improve the calculation accuracy. Further, it is desirable to provide a humidity sensor to correct the specific weight of air in the formula (10).

Next, the detection of the air-fuel ratio for each cylinder will be described. In a multi-cylinder internal combustion engine, generally only one air-fuel ratio sensor is arranged in the collecting portion of the exhaust system due to cost or durability problems. Therefore, it is necessary to specify the air-fuel ratio of each cylinder from the air-fuel ratio of the collecting portion. Therefore, by modeling the behavior of the air-fuel ratio of the collecting portion, conversely, the air-fuel ratio of each cylinder is estimated by numerical calculation from the air-fuel ratio of the collecting portion.

First, the response delay of the wide-range air-fuel ratio sensor is modeled as a first-order delay, its state equation is calculated, and it is discretized with the period ΔT, as shown in Formula 15. Where L
AF: wide-range air-fuel ratio sensor output, A / F: input air-fuel ratio.

[0060]

(Equation 15)

If Expression 15 is expressed by a transfer function using Z conversion, Expression 16 is obtained. That is, as shown in FIG. 25, the air-fuel ratio at the previous time (time k−1) can be obtained by multiplying the inverse transfer function of Expression 16 by the sensor output LAF at this time (time k).

[0062]

(Equation 16)

Next, a method of separating and extracting the air-fuel ratio of each cylinder from the air-fuel ratio obtained by delay correction as described above will be explained. First, as shown in FIG. 26, the exhaust system of the internal combustion engine is modeled (this is modeled). In FIG. 1, "EXMN PLAN
"T"). In this model (plant), F
The fuel-air ratio F / A is used to control (fuel amount).

Here, according to the knowledge of the inventors, the air-fuel ratio of the collecting portion can be expressed as a weighted average considering the temporal contribution of the air-fuel ratio of each cylinder. Like

[0065]

[Equation 17]

When the air-fuel ratio of each cylinder is expressed in the form of a recurrence formula, the formula 18 is obtained.

[0067]

(Equation 18)

Since the input U (k) is unknown, if the recurrence formula is constructed assuming that the air-fuel ratio is reproduced for every 4TDC with four cylinders, the formula 19 is obtained, and thus the problem of the ordinary state equation as the formula 20 is obtained. Return to.

[0069]

[Equation 19]

[0070]

(Equation 20)

Therefore, if the temporal contribution C is known, X (k) at each time can be estimated from Y (k) by designing a Kalman filter and constructing an observer as shown in FIG. It will be possible. That is, an X-hat (k) of the formula as shown in the equation (21) is considered by taking an appropriate gain matrix for the above equation of state.

[0072]

(Equation 21)

If (A-KC) is a stable matrix, X hat (k) becomes X (k), and X (k) (air-fuel ratio of each cylinder) is set to Y (k) (collection part It can be estimated from the air-fuel ratio). The details are described in the technique previously proposed by the applicant (Japanese Patent Application No. 3-359340, December 1991).
(Filed 27th of the month), so further explanation is omitted.

An embodiment will be described for the case where the above is applied to an actual machine.

[0075]

28. FIG. 28 is a schematic view showing it as a whole.
In the figure, reference numeral 10 indicates a four-cylinder internal combustion engine, and the intake air introduced from an air cleaner 14 arranged at the tip of an intake passage 12 has its flow rate adjusted by a throttle valve 16 and a surge tank (chamber) 18 And through the intake manifold 20 into the first to fourth cylinders. An injector 22 is provided near the intake valve (not shown) of each cylinder.
Is provided to inject fuel. The air-fuel mixture that has been injected and integrated with the intake air is ignited by a spark plug (not shown) in each cylinder, burns, and drives a piston (not shown). The exhaust gas after combustion is discharged to the exhaust manifold 24 via an exhaust valve (not shown), is purified by the three-way catalytic converter 28 via the exhaust pipe 26, and is discharged to the outside of the engine.

A crank angle sensor 34 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 a throttle for detecting an opening θTH of a throttle valve 16 is provided. Intake pressure P downstream of the opening sensor 36 and the throttle valve 16
An intake pressure sensor 38 for detecting b in absolute pressure is also provided. Further, on the upstream side of the throttle valve 16, an atmospheric pressure sensor 40 for detecting the atmospheric pressure Pa, an intake air temperature sensor 42 for detecting the temperature of intake air, and a humidity sensor 44 for detecting the humidity of intake air are provided. Further, in the exhaust system, a wide-range air-fuel ratio sensor 46 including an oxygen concentration detecting element is provided on the downstream side of the exhaust manifold 24 and on the upstream side of the three-way catalytic converter 28 to detect the air-fuel ratio of the exhaust gas. The outputs of these sensors 34 and the like are sent to the control unit 50. In the above description, the atmospheric pressure sensor 40 for detecting the pressure on the upstream side of the throttle is arranged at a position 1D (D: the diameter of the intake passage 12) or more away from the position where the throttle valve 16 is arranged, and the pressure on the downstream side of the throttle is arranged. The intake pressure sensor 38 for detecting the above is arranged in the surge tank 18 3D or more away from the position where the throttle valve 16 is arranged. The intake air temperature sensor 42 and the humidity sensor 44 are arranged as close to the throttle valve 16 as possible. The throttle opening sensor 3
6 and the intake pressure sensor 38 have a resolution of 0.01
And 0.1 mmHg or more.

FIG. 29 is a block diagram showing the details of the control unit 50. The output of the wide-range air-fuel ratio sensor 46 is input to the detection circuit 52, where appropriate linearization processing is performed, and the air-fuel ratio (A having a linear characteristic proportional to the oxygen concentration in the exhaust gas in a wide range from lean to rich is provided (A
/ F) is detected. The details are described in the application previously proposed by the present applicant (Japanese Patent Application No. 3-169456, filed on June 14, 1991), and therefore further description will be omitted. The output of the detection circuit 52 is taken into the microcomputer including the CPU 56, the ROM 58, and the RAM 60 via the A / D conversion circuit 54, and stored in the RAM 60. Similarly, the analog output of the throttle opening sensor 36 and the like is subjected to waveform shaping through the level conversion circuit 62, the multiplexer 64 and the second A / D conversion circuit 66, and the output of the crank angle sensor 34 is subjected to waveform shaping by the waveform shaping circuit 68. rear,
The output value is counted by the counter 70, and the count value is input into the microcomputer. In the microcomputer, the CPU 56 calculates the control value based on the adaptive control method as described above according to the instruction stored in the ROM 58, and drives the injector 22 of each cylinder via the drive circuit 72.

Next, the operation of the control device shown in FIG. 29 will be described with reference to FIG.
This will be described with reference to the flow chart.

First, in S10, the crank angle sensor 34
Is read by the engine speed Ne, the atmospheric pressure Pa (same as the above-mentioned throttle upstream pressure Pthup), the intake pressure Pb (same as the above-mentioned throttle downstream pressure Pthdown) detected by the atmospheric pressure sensor 40 in S12, the throttle opening Degree θT
Read H, air-fuel ratio A / F, etc.

Next, in S14, it is determined whether or not cranking has been performed. If the determination is negative, then the control proceeds to S16 and it is determined whether or not a fuel cut has occurred. If the result is negative, the program proceeds to S18, the map is searched from the engine speed Ne and the intake pressure Pb (shown in FIG. 1), the target in-cylinder intake fuel amount Ti is calculated, and the program proceeds to S20 to proceed to the basic mode. The fuel injection amount Tout is calculated by the formula. Here, the basic mode means a method that does not rely on the above-mentioned adaptive control and that is based on a conventionally known method.

Next, in S22, the wide area air-fuel ratio sensor 4
It is determined whether or not the activation of 6 is completed, and when the determination is affirmative, the routine proceeds to S24, the cylinder-by-cylinder air-fuel ratio is estimated by the above-described method, the routine proceeds to S26, and the actual intake air amount Gair is estimated.
Then, the routine proceeds to S28 to estimate the in-cylinder actual intake fuel amount Gfuel, proceeds to S30 to determine the final fuel injection amount Tout by adaptive control, and proceeds to S32 to output to the injector 22 of the cylinder via the drive circuit 72. Incidentally, S14
If it is determined to be cranking, the process proceeds to S34 and S36 to calculate the control value for the starting mode, and if it is determined to be fuel cut in S16, the process proceeds to S38 and Tou.
Let t be zero. If it is determined in S22 that the sensor is not activated, the process immediately jumps to S32, and the injector is driven with the control value in the basic mode.

In the above configuration, the air-fuel ratio is estimated for each cylinder to accurately determine the in-cylinder actual intake fuel amount, and the parameters of the controller are adaptively controlled so that the in-cylinder actual intake fuel amount matches the target value. It is possible to realize highly accurate adaptive control.

Further, since the dead time (time delay element) of the system is inserted between the deposition plant and the parameter identification / adjustment mechanism or the adaptive controller, the target fuel intake amount and the deposition plant are also maintained during the transient operation. There is no time difference with the output (actual intake fuel amount) and the target air-fuel ratio can be accurately converged. Furthermore, since the order of the dead time is changed according to the operating state of the internal combustion engine and the state of the fuel injection amount control device, the target air-fuel ratio can be more accurately converged.

Further, a compensator having an inverse transfer function of the transfer function of the adhering plant is connected in series to the adhering plant, the compensator is included and regarded as one virtual plant, and the transfer function of the virtual plant is 1 (or The value is set to a value other than (around that value), the adaptive controller is operated so as to have the inverse transfer function, so the characteristics set in advance may differ from the actual characteristics due to aging, etc. It can be adaptively controlled so as to reach the target value by following the change.

It should be noted that the present invention having the above-described structure is shown in FIG.
However, the present invention is not limited to this, and as shown in FIG. 31, the Gir model block for estimating the dynamic behavior of the actual intake air amount is not provided, and the map value is set to “14.7”. This is also applicable to the configuration in which the actual intake air amount Gair is estimated by multiplying, and the behavior of the intake system is also absorbed by performing the adaptive control, that is, as described above, there is an error in the estimation of the actual intake air amount. Can even absorb it. Further, according to the present invention, as shown in FIG. 32, the target value Ti is not mapped and the target value Ti is determined by multiplying the actual intake air amount Gair estimated by the Gair model block by "1 / 14.7". It is also applicable to the configuration.

Further, in the above-mentioned configuration, an example in which one air-fuel ratio sensor is used to estimate the air-fuel ratio of each cylinder and control is performed to the target value has been shown. A fuel ratio sensor may be provided to directly detect the air-fuel ratio of each cylinder.

Further, in order to perform the above-mentioned control, the model of the intake system was set up and the actual intake air amount was calculated, but this method is not limited to the disclosed control, and a general fuel injection amount control is performed. It can also be used for ignition timing control.

[0088]

According to the first aspect of the present invention, the fuel transportation delay is corrected based on the transportation delay of the fuel injected into the intake pipe of the internal combustion engine.
An adaptive controller is provided, which is provided with a fuel transportation delay correction means , adaptively identifies parameters so that the actual in- cylinder intake fuel amount matches the target in-cylinder intake fuel amount, and adjusts the parameter of the controller in accordance with the parameter. A fuel injection amount control device for an internal combustion engine, comprising a control input u applied to a plant and a parameter identification / adjustment mechanism, or a plant output y.
Alternatively, at least one of the estimated value and the parameter identification / adjustment mechanism, or between the plant output y or the estimated value and the adaptive controller is input.
Insert a time delay element corresponding to the time delay between the occurrence of u and the occurrence of the plant output y or its estimated value
And the order of the time delay element is
The operating state of the internal combustion engine or the fuel injection amount control device
The target fuel intake amount and plant output (actual intake fuel amount) are configured even during transient operation because the configuration is changed according to the state of
Since there is no time difference between the target air-fuel ratio and the target air-fuel ratio, the target air-fuel ratio can be accurately converged.

[0089] The apparatus of claim 1 wherein, the order of the time delay element, the so constructed as to vary the state of the internal combustion engine operating state or the fuel injection amount control apparatus, the target fuel even during transient operation There is no time difference between the intake amount and the plant output (actual intake fuel amount),
Furthermore, since it does not depend on changes in the operating state and the state of the fuel injection amount control device, the target air-fuel ratio can be more accurately converged.

[0090] The apparatus of claim 2 wherein the said parameter identification and adjustment mechanism, decreasing gain method, since it is configured to use any of the variable gain method and a fixed tracing method, the target value even during transient operation The plant output can be tracked well.

[Brief description of the drawings]

FIG. 1 is a block diagram generally showing a control device according to the present invention.

FIG. 2 is a block diagram operationally showing fuel injection control in FIG.

FIG. 3 is a block diagram of the wall adhering plant in FIG.

FIG. 4 is a block diagram showing a state in which MRACS (model reference adaptive control) is applied to the wall adhesion correction of FIG.

5 is a block diagram showing a state after organizing the block diagram shown in FIG. 4. FIG.

FIG. 6 is a data diagram showing a simulation result of the configuration of FIG.

FIG. 7 is a data diagram showing a simulation result of microscopically verifying the data of FIG.

8 is a block diagram showing a state in which measures against dead time are applied to the configuration of FIG.

9 is a data diagram showing a simulation result of the configuration of FIG.

FIG. 10 is a data diagram showing a simulation result of microscopically verifying the data of FIG.

11 is a block diagram showing a state in which another measure against dead time is applied to the configuration of FIG.

FIG. 12 is a data diagram showing a simulation performed for the fixed gain method in the configuration of FIG.

FIG. 13 is a data diagram showing a simulation performed for the gradually decreasing gain method in the configuration of FIG.

FIG. 14 is a data diagram showing a simulation performed for the variable gain method in the configuration of FIG.

FIG. 15 is a data diagram showing a simulation performed for the fixed trace method in the configuration of FIG.

16 is an explanatory diagram showing a model of an intake system used to calculate an actual cylinder intake air amount of the Gair model block shown in FIG. 1. FIG.

FIG. 17 is a data diagram showing a simulation result of calculating the in-cylinder actual intake air amount of the model of FIG. 16.

FIG. 18 is an explanatory diagram showing a test device for a method of calculating an actual intake air amount in a cylinder of the model of FIG. 16;

FIG. 19 is a data diagram showing a test result of the test apparatus of FIG.

FIG. 20 is a data diagram showing the identification result of the flow rate coefficient of the throttle with respect to the throttle opening degree performed by using the test device in FIG. 18;

FIG. 21 is a data diagram showing the estimated value and the actually measured value, which are obtained by using the identification result of FIG. 20, for comparison.

22 is a data diagram comparatively showing a value obtained by simulation based on the model shown in FIG. 16 and an actually measured value.

FIG. 23 is a data diagram showing the relationship between control error and throttle opening.

FIG. 24 is a data diagram showing the relationship between the control error and the pressure ratio before and after the throttle valve.

FIG. 25 is a block diagram of an estimator that models the detection delay of the air-fuel ratio sensor and estimates the true air-fuel ratio.

FIG. 26 is a block diagram showing the EXMN PLANT of FIG. 1.

27 is a block diagram showing a configuration in which an observer is incorporated in the configuration of FIG.

28 is a schematic diagram showing an overall state of a fuel injection amount control device for an internal combustion engine, showing a state in which the configuration of FIG. 1 is applied to an actual machine.

FIG. 29 is a block diagram showing the configuration of the control unit shown in FIG. 28.

30 is a flowchart showing the operation of the control unit of FIG.
It is a chart.

FIG. 31 is a block diagram similar to FIG. 1, showing another configuration example of the present invention.

FIG. 32 is a block diagram similar to FIG. 1, showing still another configuration example of the present invention.

[Explanation of symbols]

 10 Internal Combustion Engine 12 Intake Line 16 Throttle Valve 18 Surge Tank 20 Intake Manifold 22 Injector 24 Exhaust Manifold 26 Exhaust Pipe 36 Throttle Opening Sensor 38 Intake Pressure Sensor 40 Atmospheric Pressure Sensor 42 Intake Temperature Sensor 44 Humidity Sensor 46 Wide Area Air-Fuel Ratio Sensor 50 Control unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Isao Komoritani 4-1-1 Chuo, Wako-shi, Saitama Honda R & D Co., Ltd. (72) Inventor Toshiaki Hirota 4-1-1 Chuo, Wako, Saitama (56) References JP-A-4-187844 (JP, A) JP-A-60-36748 (JP, A) JP-A-3-42703 (JP, A) JP-A-1-211648 ( JP, A) JP 4-187843 (JP, A) JP 4-128523 (JP, A)

Claims (2)

(57) [Claims] 1. Transportation of fuel injected into an intake pipe of an internal combustion engine
Fuel transportation delay compensation that corrects fuel transportation delay based on delay
With a positive means to identify and adaptively parameters so that the amount of cylinder Naijitsu intake fuel is equal to the target cylinder intake fuel amount, comprising an adaptive controller for adjusting the parameters of the controller in accordance with the parameters internal combustion A fuel injection amount control device for an engine, which is provided between a control input u given to a plant and a parameter identification / adjustment mechanism, or between a plant output y or its estimated value and a parameter identification / adjustment mechanism, or A time delay element corresponding to the time delay between the generation time point of the control input u and the generation time point of the plant output y or its estimated value is provided in at least one of the plant output y or its estimated value and the adaptive controller. configured to insert
Along with the order of the time delay element,
Depending on the rotation state or the state of the fuel injection amount control device
A fuel injection amount control device for an internal combustion engine, which is changed . 2. The parameter identification / adjustment mechanism is gradually reduced.
Of gain method, variable gain method and fixed trace method
The method according to claim 1, wherein any one of them is used.
Fuel injection amount control device for fuel engine.