JPH01271642A - Device for controlling fuel injection quantity of internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the accuracy of air-fuel ratio control by correcting a temporary estimated intake pipe pressure at the point of intake time which is calculated from an intake pipe pressure at the point of detecting time by a feedback gain, etc. based on a dynamic physical model, and calculating an estimated intake pipe pressure. CONSTITUTION:At the time of determining a fuel feeding quantity by a control means M7 based on the engine speed of an internal combustion engine M1 detected by an operating condition detecting means M2 and an estimated intake pipe pressure, a temporary estimated intake pipe pressure at the point of intake time is calculated by a temporary estimating means M4 from the intake pipe pressure at the point of detecting time based on a dynamic physical model. The temporary estimated intake pipe pressure is subjected to feedback correction by an estimating means M5 based on the deviation between an intake pipe pressure at the point of detecting time obtained from an estimated intake pressure at the point of intake time and an intake pipe pressure at the point of detecting time, and a correcting quantity calculated by a correcting means M6 from a feedback gain determined based on a dynamic physical model, to always accurately calculate the estimated intake pipe pressure. Thereby, a proper quantity of fuel can be fed even in a transient operating condition.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to the method of measuring the intake pipe pressure at the time when the fuel supplied to the internal combustion engine is taken into the combustion chamber by measuring the intake pipe pressure detected before the intake time. The present invention relates to a fuel injection amount control device for an internal combustion engine that predicts from pressure and controls the fuel injection amount based on at least the predicted intake pipe pressure.

[Prior Art] As a fuel injection amount control device for an internal combustion engine, one that employs a speed density method (so-called DJ method) is known. This method detects the intake pipe pressure and rotational speed of the internal combustion engine, calculates the amount of air taken into the cylinder during the intake stroke of the internal combustion engine based on these detection results, and determines whether the air-fuel ratio matches the target air-fuel ratio. The fuel injection amount is calculated so that the fuel injection is performed.

In general, the point in time when the intake pipe pressure used to calculate the amount of air taken into a cylinder is detected is a predetermined time from the point in time when the amount of air is actually taken into the cylinder, that is, 2 to 3 strokes in the stroke of the internal combustion engine. ,Running late. For this reason, for example,
In transient operating conditions such as sudden acceleration/deceleration, the intake pipe pressure fluctuates greatly over time, so the intake pipe pressure at the time of detection is significantly different from the intake pipe pressure at the time of intake, and the calculation accuracy of the fuel injection amount decreases, causing the air pressure to increase. The fuel ratio is greatly disturbed, causing problems with exhaust characteristics, driving performance, etc. Therefore, in order to perform accurate fuel injection control using the DJ method, the estimated intake pipe pressure, which is the intake pipe pressure at the time of intake, is estimated from the intake pipe pressure at the time of detection, and the estimated intake pipe pressure and rotational speed are It is necessary to calculate the fuel injection amount based on the following. As a countermeasure to this problem, the following techniques have been proposed in the past, for example. That is, (1) Estimated intake pipe pressure p at the time of intake (k+i)
M(k+i) is expressed as (n+1) past data (PM(
k), PM(k-1), . . . -, PM(k-n)) predicted by the linear predictor shown in the following equation (1).

pM(k+i) = final α(j)・PM(k-j)
... (1) However, the coefficient α(j) is the intake pipe pressure P
A value determined from M(k-j), rotational speed Ne(k-j), etc.

(2) The transfer characteristic from the throttle valve opening to the intake pipe pressure, which represents the behavior of the intake pipe pressure when the throttle valve moves, is expressed by the autoregressive moving average model (Autoregressive Mov) shown in the following equations (2) and (3).
ing-AverageModel).

Furthermore, according to the following equation (4), the above equation (2), (3)
``Fuel injection control method for an internal combustion engine'' which calculates the estimated value x(k+1) of the state variable x(k) and determines the change in intake pipe pressure from the reference value ΔP M(k) -20
6241), “Fuel injection control device for internal combustion engine”
(Japanese Patent Application No. 60-206242), [Fuel Injection Control Method for Internal Combustion Engine] (Japanese Patent Application No. 60-20E3243), "Fuel Injection Control Method for Internal Combustion Engine" (Japanese Patent Application No. 1982)
``Fuel injection control device for internal combustion engine'' (Japanese Patent Application No. 60-206245).

x(k+1)==A−x(k)+B◆△T H(k
)... (2) ΔPM(k) = C-x(k)
... (3) Intersection (k+1) = (A
-F-C) ・Cross(k)+B◆ΔTH(k)+F
・ΔP M(k) ... (4) However, A, E
, C is a constant matrix, ΔTH and ΔPM are changes in throttle valve opening and intake pipe pressure from preset reference values, and F is a constant matrix indicating estimated gain.

[Problems to be Solved by the Invention] However, the above-mentioned conventional technology has the following problems. That is, (1) In a configuration using a linear predictor, the estimated future intake pipe pressure PM is calculated based on the past intake pipe pressure PM(k).
(k+i) is being calculated. However, the intake pipe pressure PM
(k) is determined according to the difference between the amount of air passing through the throttle valve and the amount of air sucked into the cylinder. Therefore, it is necessary to consider the interrelationship between the intake pipe pressure and the amount of rain air. However, since it is not possible to set the coefficients of the linear predictor described above to satisfy this correlation, the estimated intake pipe pressure PM(k+i) that adapts to a wide range of operating conditions of the internal combustion engine
The problem was that it was extremely difficult to calculate. This causes a response delay and an overshoot of the control amount in the fuel injection amount control based on the estimated intake pipe pressure pM(k+i).

(2) Generally, the transmission characteristic from the throttle valve opening to the intake pipe pressure is nonlinear.

Therefore, the linear autoregressive moving average model (ARMA) cannot accurately express the transfer characteristic from the throttle valve opening to the intake pipe pressure. Therefore, a plurality of linear mathematical models have been used that are valid only between changes in the vicinity of a predetermined reference value by linear approximation in the vicinity of a predetermined reference value. Therefore, it is necessary to switch the reference value according to changes in the operating state of the internal combustion engine. However, it is impossible to have as many linear mathematical models as possible to cover all operating conditions over a wide range of internal combustion engines and to store their coefficients and the like.

Furthermore, PM(k) and ΔT are calculated based on the changes in intake pipe pressure PM(k) and throttle valve opening TH(k) from the reference values.
A logical hand IllI(
Algorithm) is easily affected by parameter fluctuations due to disturbances and sensor noise. As a result, both the disturbance characteristic specification (sensitivity specification) and the robust stability specification (sensor noise characteristic specification) deteriorated, and the stability of the estimated value could not be sufficiently guaranteed.

(3) In this way, 'estimated intake pipe pressure pM(k+i)
Because the accuracy of calculation was insufficient, the accuracy of fuel injection IiJ amount control also decreased, causing disturbances in the air-fuel ratio.

As a result, exhaust characteristics, fuel consumption efficiency, and operating performance were particularly deteriorated during transient operating conditions.

(4) Furthermore, it is necessary to memorize multiple parameters corresponding to multiple linear mathematical models and to execute various complex operations, which requires large storage capacity and advanced computing power. Valve opening T H
(k) and the accelerator operation amount with high precision and output them as analog signals, a dedicated sensor is required, resulting in a complicated device configuration.

The present invention enables a simple device configuration to calculate the amount calculated based on the intake pipe pressure detected at the time of detection, even when the intake pipe pressure fluctuates rapidly, such as during transient operating conditions. An object of the present invention is to provide a fuel injection amount side 'a device for an internal combustion engine that accurately estimates the intake pipe pressure at the time of suction when compressed air containing fuel is drawn into a cylinder, and calculates the fuel injection amount.

[Means for Solving the Problems] The present invention, which has been made to achieve the above object, as illustrated in FIG. 1, includes at least the intake pipe pressure and rotational speed of the internal combustion engine M1. An operating state detection means M2 for detecting an operating state; and a fuel supply means M3 for supplying an amount of fuel commanded from the outside to the internal combustion engine M1, and according to the detection result of the operating state detection means M2. In the fuel injection amount control device for an internal combustion engine that supplies a predetermined amount of fuel from the fuel supply means M3, the operating state is further controlled based on a dynamic physical model constructed according to the law of conservation of mass regarding the intake air amount of the internal combustion engine M1. Based on the intake pipe pressure and rotational speed detected at the time of detection by the detection means M2, an amount of fuel determined according to the intake pipe pressure detected at the time of detection is taken into the cylinder in the intake stroke of the internal combustion engine M1. a provisional estimation means M4 that calculates a provisional estimated intake pipe pressure corresponding to the predicted intake pipe pressure of the internal combustion engine M1 at the time of intake;
an estimating means M5 that performs feedback correction based on a correction amount instructed from the outside and calculates an estimated intake pipe pressure corresponding to the intake pipe pressure at the time of intake of the internal combustion engine M1; and an estimated intake pipe calculated by the estimating means M5. From the feedback gain determined based on the deviation between the intake pipe pressure of the internal combustion engine M1 at the time of detection determined from the pressure and the intake pipe pressure detected at the time of detection by the operating state detection means M2 and the dynamic physical model, a correction means M6 that calculates a correction amount and instructs the estimation means M5; and supply of fuel in an amount determined based on the rotational speed detected by the operating state detection means M2 and the estimated intake pipe pressure calculated by the estimation means M5. The gist of the present invention is a fuel injection amount control device for an internal combustion engine, characterized by comprising: a control means M7 for instructing the fuel supply means M3 to perform the following steps.

The operating state detection means M2 detects the operating state of the internal combustion engine M1, including at least intake pipe pressure and rotational speed. For example, it can be realized by an intake pipe pressure sensor made of a semiconductor pressure sensor or the like, an electromagnetic pickup type rotation speed sensor, or the like.

The fuel supply means M3 supplies an amount of fuel commanded from the outside to the internal combustion engine M1. For example, electromagnetic
Alternatively, it can be realized by a fuel injection valve using a piezoelectric element.

The provisional estimating means M4 is based on a dynamic physical model constructed according to the law of conservation of mass regarding the intake air amount of the internal combustion engine M1, and calculates the detection time from the intake pipe pressure and rotational speed detected at the detection time by the operating state detection means M2. Calculate a provisional estimated intake pipe pressure corresponding to the predicted intake pipe pressure of the internal combustion engine M1 at the time of intake when an amount of fuel determined according to the intake pipe pressure detected in the intake stroke of the internal combustion engine M1 is taken into the cylinder in the intake stroke of the internal combustion engine M1. It is something. Here, the dynamic physical model is
For example, based on the law of conservation of mass, the equation expressing the time change in the amount of intake air of the internal combustion engine M1 as the difference between the amount of intake air passing through the throttle valve and the amount of intake air taken into the cylinder in the intake stroke is expressed as: It can be constructed by transforming it using the equation of state of gas, the equation of state change in adiabatic change, etc. Therefore, for example, the predicted intake pipe pressure of the internal combustion engine M1 at the time of intake can be determined by parameters that depend on the intake pipe pressure of the internal combustion engine M1 at the time of detection, the amount of change in intake pipe pressure over time, the intake air amount in the air height, and the rotation speed. It can be configured by the arithmetic expressions, etc. to be written.

The estimating means M5 feedback-corrects the provisionally estimated intake pipe pressure calculated by the provisional estimating means M4 based on a correction amount instructed from the outside, and calculates an estimated intake pipe pressure corresponding to the intake pipe pressure at the time of intake of the internal combustion engine M1. It calculates pressure. Here, the correction amount is the difference between the estimated intake pipe pressure at the detection time obtained by inversely converting the estimated intake pipe pressure from the intake time to the detection time and the intake pipe pressure actually detected at the detection time. is the amount of feedback correction.

The correction means M6 refers to the difference between the intake pipe pressure of the internal combustion engine M1 at the time of detection obtained from the estimated intake pipe pressure calculated by the estimation means M5 and the intake pipe pressure detected at the time of detection by the operating state detection means M2. A correction amount is calculated from the feedback gain determined based on the dynamic physical model and is instructed to the estimation means M5. Here, the feedback gain refers to the amount of intake air passing through the throttle valve, which is human power, when the behavior of the amount of intake air in the internal combustion engine M1 is modeled, and the amount of intake air passing through the throttle valve, which is a human input, is expressed in a dynamic physical model constructed in accordance with the law of conservation of mass. This is a feedback gain when the deviation between the estimated intake pipe pressure, which is the output when manually applied, and the detected intake pipe pressure of the internal combustion engine M1 is fed back to the dynamic physical model. This feedback gain can be determined, for example, using the same method as in the case where the intake air system of the internal combustion engine M1 is controlled and a state observation device based on the above-mentioned dynamic physical model, that is, a so-called observer is configured.

The control means M7 instructs the fuel supply means M3 to supply fuel in an amount determined based on the rotational speed detected by the operating state detection means M2 and the estimated intake pipe pressure calculated by the estimation means M5. For example, it can be realized by a map or an arithmetic expression that defines the correlation between the rotational speed, estimated intake pipe pressure, and fuel supply amount. For example, the fuel supply amount calculated as described above may be further corrected to increase or decrease depending on the operating state of the internal combustion engine M1, such as the cooling water temperature, intake air temperature, exhaust oxygen level, etc. good.

The provisional estimating means M4, the estimating means M5, the correcting means M6,
The control means M7 includes, for example, a well-known CPU, R
A logic operation circuit consisting of OM, RAM, and other peripheral circuit elements can be realized by a configuration that executes a predetermined processing procedure.

[Operation] In the fuel injection amount control device for an internal combustion engine of the present invention, as illustrated in FIG. 1, the operating state detection means M2 detects the intake pipe pressure and rotational speed of the internal combustion engine M1 at the time of detection. Then, based on a dynamic physical model constructed according to the law of conservation of mass regarding the amount of intake air of the internal combustion engine M1, the provisional estimating means M4 determines that an amount of fuel determined according to the intake pipe pressure detected at the time of the detection is applied to the internal combustion engine M1. A provisional estimated intake pipe pressure corresponding to the predicted intake pipe pressure of internal combustion engine M1 at the time of intake into the cylinder in the intake stroke of M1 is calculated. Further, the estimating means M5 performs feedback correction on the provisionally estimated intake pipe pressure based on a correction amount instructed from the outside,
An estimated intake pipe pressure corresponding to the intake pipe pressure at the time of intake of the internal combustion engine M1 is calculated. On the other hand, the correction means M6 corrects the deviation between the intake pipe pressure of the internal combustion engine M1 at the time of detection obtained from the estimated intake pipe pressure and the intake pipe pressure detected at the time of detection by the operation state detection means M2, and The correction amount is calculated from the feed punch gain determined based on the physical model and is instructed to the estimation means M5. The control means M7 operates to instruct the fuel supply means M3 to supply fuel in an amount determined based on the rotational speed detected by the operating state detection means M2 and the estimated intake pipe pressure calculated by the estimation means M5.

That is, when determining the amount of fuel to be supplied based on the rotational speed and estimated intake pipe pressure of the internal combustion engine M1, detection The provisional estimated intake pipe pressure at the time of intake calculated from the intake pipe pressure detected at the time,
Feedback correction is performed using the correction amount calculated from the feedback gain determined based on the deviation between the intake pipe pressure at the time of detection obtained from the estimated intake pipe pressure at the time of intake and the intake pipe pressure detected at the time of detection, and the above dynamic physical model. It calculates the estimated intake pipe pressure.

Therefore, the fuel injection amount control device for an internal combustion engine according to the present invention always accurately calculates the estimated intake pipe pressure and works to supply an appropriate amount of fuel even under transient operating conditions.

The technical problems of the present invention are solved by each component of the present invention acting as described above.

[Example] Next, a preferred example of the present invention will be described in detail based on the drawings. FIG. 2 shows a system configuration of a fuel injection amount control device for an engine, which is an embodiment of the present invention.

As shown in the figure, an engine fuel injection amount control device 1 includes an engine 2 and an electronic control unit (hereinafter simply referred to as ECU) 3 that controls the engine 2.

The engine 2 includes a cylinder 4, a piston 5, and a cylinder head 6 to form a combustion chamber 7, and a spark plug 8 is disposed in the combustion chamber 7.

The intake system of the engine 2 includes the combustion chamber 7 and the intake valve 9.
An intake pipe 10 that communicates with the intake pipe 10, an electromagnetic fuel injection valve 11 that is installed in the intake pipe 10 and injects fuel, a surge tank 12 that absorbs the pulsation of intake air, and an intake air amount that is linked to the accelerator pedal. It is composed of a throttle valve 13 and an air cleaner 14 to be adjusted.

The exhaust system of the engine 2 includes an exhaust manifold 16 communicating with the combustion chamber 7 via an exhaust valve 15, a catalytic converter 17 filled with a three-way catalyst, and an exhaust pipe.

The ignition system of the engine 2 includes an igniter 19 equipped with an ignition coil that outputs a high voltage necessary for ignition, and an igniter 19 that is connected to a crankshaft (not shown).
It consists of a distributor 20 that distributes and supplies the high voltage generated by the spark plug to the spark plug.

The engine fuel injection amount control device 1 includes, as detectors, an intake air temperature sensor 21 that is installed downstream of the air cleaner 14 and measures the intake air temperature, and a throttle position sensor 22 that detects the throttle valve opening degree in conjunction with the throttle valve 13. , an idle switch 23 that detects the fully open state of the throttle valve 13, an intake pipe pressure sensor 24 that communicates with the surge tank 12 and detects the intake pipe pressure, and an intake pipe pressure sensor 24 that is installed in the cooling system of the cylinder block 4a and detects the cooling water temperature. A water temperature sensor 25, an oxygen concentration sensor 26 installed in the exhaust manifold 16 to detect the residual oxygen concentration in the exhaust gas, and a distributor 200. A reference signal is output every 1 revolution of the camshaft, that is, every 2 revolutions of the crankshaft (not shown). A rotation angle sensor 28 that also serves as a rotation speed sensor that outputs a rotation angle signal every 1/24 revolution of the camshaft of the distributor 20, that is, every integer multiple of the crank angle from 0° to 30°. We are prepared.

Detection signals from the sensors and switches described above are input manually to the ECU 3, and the ECU 3 controls the engine 2. The ECU 3 is configured as a logic operation circuit mainly including a CPU 3a, a ROM 3b, a RAM 3c, and a backup RAM 3d, and is connected to a human output section 3f via a common bus 3e to perform human output with the outside. The CPU 3a manually outputs the detection signals of the above-mentioned sensors and switches via the human output section 3f.

On the other hand, the CPU 3a drives and controls the fuel injection valve 11 and the igniter 19 via the human output section 3f.

Next, the control system of the first embodiment will be explained based on the control system diagram shown in FIG. Note that FIG. 3 is a diagram showing the control system, and does not show the hardware configuration. The control system shown in FIG. 3 is actually realized as a discrete system by executing the fuel injection amount calculation process shown in the flowchart of FIG. 5 and the fuel injection control process shown in FIG.

As shown in the figure, the intake pipe pressure change amount calculation unit P1 calculates the intake pipe pressure from the amount obtained by applying a time delay operator z −1 to the intake pipe pressure PM(k) at the detection time point k of the engine 2, which is the controlled object. This is to calculate the amount of change in pipe pressure ΔPM(k).

The cylinder intake air amount calculation unit P2 at the time corresponding to the detection time calculates the cylinder intake air amount Ga(k) at the detection time from the intake pipe pressure PM(k) and rotational speed Ne(k) at the detection time k. It is something to do.

The first provisional estimated intake pipe pressure calculation unit P3 calculates the intake pipe pressure P M (k) at the detection time point k multiplied by a coefficient of 1, and calculates the amount of change in intake pipe pressure by multiplying PM (k) by a coefficient of 2. From the amount, a first provisional estimated intake pipe pressure (k+i) of +i is calculated at a time point corresponding to the intake time point.

The cylinder intake air amount calculation unit P4 of +i at the time corresponding to the intake time calculates the first provisional estimated intake pipe pressure pM(1'(k+i)) of +1 at the time corresponding to the intake time, and the rotational speed Ne( at the detection time) k), the cylinder intake air amount "Qa(k+i)" of +i at time point is calculated.

The second provisional estimated intake pipe pressure calculation unit P5 calculates +i at the time of intake.
The first provisional estimated intake pipe pressure pM” (k+i) is given a coefficient of 3.
The cylinder intake air amount Ga(k
) multiplied by a coefficient of 4, and the cylinder intake air amount Qa(k+i) of +i at the time of intake multiplied by a coefficient of 5.
This is to calculate the provisional estimated intake pipe pressure p M + 21 (k+).

The estimated intake pipe pressure calculation unit P6 calculates an amount obtained by multiplying the second provisional estimated intake pipe pressure pM'' (k+i) by a coefficient of 6, + at the time of intake.
Time delay operator 2 is applied to the estimated intake pipe pressure PM(k+i) of i.
−· is applied and the intake pipe pressure PM at the time of detection (k
) is calculated by multiplying the coefficient by 7 to calculate the estimated intake pipe pressure PM(k+i).

The fuel injection amount calculation unit P7 calculates the estimated intake pipe pressure PM(k+i
) and the rotational speed N e (k), the fuel injection time TAU
(k+i) is calculated.

Then, fuel is supplied to the engine 2 over the fuel injection time TAU(k+i).

The hardware configuration of the engine fuel injection amount control device 1 and the configuration of the control system realized by executing each process described later have been described above. Therefore, next, we will construct a dynamic physical model of the intake system of engine 2 and each coefficient Kl,
K2. K3. K4. K5゜K6. The calculation of 7 will be explained below.

First, a dynamic physical model of the intake system of the engine 2 is constructed. The mass conservation law for the amount of intake air flowing through the intake system of the engine 2 can be described as shown in the following equation (5).

dM/dt = mt - ga... (
5) However, d/d t: time differential operator M: mass of air in the surge tank 12, mt: amount of inflowing air that passes through the throttle valve 13 and flows into the surge tank 12 within a unit time, ga: within a unit time The amount of intake air drawn from the surge tank 12 into the cylinder that has reached the intake stroke.

On the other hand, the equation of state for an ideal gas can be described as the following equation (6), the defining equation for the speed of sound can be described as the following equation (7), and the equation for adiabatic change in state can be described as the following equation (8).

PM◆ρ−1=R◆T... (6)c2
== to ◆R◆T... (7) PMφ
ρ- = Const - (8) Also, the following equation (9)
The relationship holds true.

ρ = M/V ... (9) However, PM: intake pipe pressure, ρ: intake air density, R: intake air gas constant, T: intake air temperature, C: sound velocity, NI: specific heat ratio, V: surge Tank volume.

Therefore, when the above equation (5) is transformed using the above equations (6) to (9), it can be written as the following equation (10), and furthermore, the following equation (11) is obtained.

dM/dt = (V/c2) ・(dPM/dt
)... (10) dPM/d t = (c”/V) φ (mt-
ga)... (11) The above equation (11) is integrated over the intake stroke time of the engine cycle as shown in the following equation (12).

Milk (dPM/d t) d t = S”, '* ((C2/V) ・ (mt-ga) ) dt - (12) where,
The amount of incoming air mt that passes through the throttle valve 13 and flows into the surge tank 12 is a constant value m t (
k), the following equation (13) holds true.

S','m t d t = m t (k) ◆(
tl-tO) = mt(k)・(1/2) (Ne/60) = mt(k)◆(30/Ne) ... (13) Also, the cylinder that has reached the intake stroke from the surge tank 12 The following equation (14) holds true for the intake air amount ga taken into the engine.

, V:gadt = Ga(k) −(
14) Therefore, the above formula (12) is changed to the above formula (13).

By transforming according to (14), the following equation (15) is obtained.

PM (k÷1) = PM (k) + (c”/V) ◆mt(k)・ (30/Ne
) - (C2/V) φGa(k) - (15) However, PM (tl) = PM (k+1), PM (
tO) = PM(k).

Here, assuming that the amount of increase in intake pipe pressure does not change, the following relationship (16) holds true.

PM(k+1)-PM(k) = PM(k+j)-PM(k+j-1)...
(16) (j = 1. 2..., i) Therefore, by changing the notation as in the following equations (17) and (1B), the following equation 19 is obtained.

A(i)=iX(c”/V)−(1
7) B(i)=-i X (c"/V)...
・(1B) PM(k÷1)= PM(k) + A (j) ・mt(k)・(30/Ne)+
B (i) building Ga(k)...
(19) Therefore, the dynamic physical model of the intake system of the engine 2 can be described by the discrete state equation of the following equation (20) and the output equation of the following equation (21) obtained from the above equation (19).

PM(k+1) = Φ◆PM(k) + [” ・Ga(k)+E
◆mt(k) ... (20) PM(k)=
CφPM(k) ... (21) However, the coefficient φ is the value 1, the coefficient F is the value B (i), and the coefficient E is the value A
(i)◆(30/Ne), the coefficient C has a value of 1.

Note that it is also possible to use the above equation (15) as the basic identification equation, measure human power and output through experiments, and determine the coefficient c''/V of each term using a system identification method such as the method of least squares. can.

Next, calculation of various quantities for calculating the estimated intake pipe pressure P M (k + i) will be explained.

From the above equation (15), the intake pipe pressure change amount ΔPM(k) can be written as shown in the following equation (22).

ΔPM(k)=PM(k+1)−PM(k)=A
(1) ・mt(k)・ (30/Ne)+ B (
1) ◆Ga(k) =-(22) Above formula (19),
From (22), the first provisional estimated intake pipe pressure [)M"'(
k+i) can be calculated as shown in the following equation (23).

“1=5”M mouth’(k+i) = PM(k)+j・△PM(k) ・・・ (23
) Therefore, the above-mentioned first provisional estimated intake pipe pressure calculation section P3
A coefficient of 1 has a value of 1, and a coefficient of 2 has a value of i.

Here, since the cylinder intake air amount Ga(k) is a function of the intake pipe pressure PM(k) and the rotational speed Ne(k),
After correction, the second provisional estimated intake pipe pressure pM(2)(k
+i) can be expressed as in the following equation (24).

pMC2'(k+i) = PM(k)+i φ△PM(k) −B (i) ・G a (k) +B (i) ・tea(k+i) = pM”(k+1) −B (i)・Ga (k) +B (i) ・Ga (k+i) +++ (24
) Therefore, the above-mentioned second provisional estimated intake pipe pressure calculation section P5
3 is the value 1 for the coefficient, 4 is the value -B (i), and 5 is the coefficient
becomes the value B(i).

Note that the cylinder intake air amount a(k+i) is the first provisional estimated intake pipe pressure pM(1)(k+i) and the rotation speed N.
It can be calculated from e (k).

Second provisional estimated intake pipe pressure p calculated by the above formula (24)
When M''(k+i) is corrected by the correction amount obtained by multiplying the deviation from the intake pipe pressure by the feedback gain, the estimated intake pipe pressure pM(k+i) is calculated as shown in the following equation (25).
is obtained.

P M (k + i) = pM""' (k + i) + Cf-E r r (k)
(25) However, the deviation E r r (k) can be written as in the following equation (26).

E r r(k) = PM(k) − PM(
k) (2B) Note that the coefficient 6 of the estimated intake pipe pressure calculation unit P6 described above is the value 1, and the coefficient 7 is the feedback gain Cf.

Next, the feedback gain C, which is a value of 7, is added to the above coefficient.
The calculation of f will be explained based on FIG. 4. As shown in the figure, the estimated value PM(k) of the state variable P M(k) of the controlled object described by the above equations (20) and (21)
If a state observer (observer) that calculates .function.

PM(k+1) = φ・pM(k) 10r'-Ga(k)+E-mt(
k)-(27) As shown in the figure, the configuration is such that feedback correction is performed using a correction amount obtained by multiplying the deviation between the output P M (k) of the controlled object and the estimated output pM (1<) of the observer by a feedback gain Cf. Then, the following equation (28) is obtained.

PM(k+1) = Φ −pM(k) + r' conflict G a(k)
- in Cf (PM(k)-C-PM(k)) = (φ
-Cf◆C) ◆pM(k) + r' ◆Ga(k)+Cf -PM(k)・
(2B) Therefore, the feedback gain Cf may be determined so that the closed-loop matrix [φ-Cf-C] is a stable matrix and all the eigenvalues are on the left half plane. Here, the coefficient Φ has a value of 1,
The coefficient C also has a value of 1. Therefore, in the first embodiment, the value of the feedback gain Cf is set to a value in the range of -1 minus Cf(1).

The above describes the construction of the dynamic physical model of the intake system of engine 2, the calculation procedure for the estimated intake pipe pressure, and the feedback gain C.
The calculation of f has been explained. These parameters are calculated in advance, and only the results are used inside the ECU 3 to calculate the fuel injection amount.

Next, the fuel injection amount calculation process executed by the ECU 3 will be explained based on the flowcharts shown in FIG. 5, and the fuel injection control process executed by the ECU 3 will be explained based on the respective flowcharts shown in FIG.

First, the fuel injection amount calculation process will be explained based on the flowchart shown in FIG. This fuel injection amount calculation process is performed by EC
After starting U3, it is executed at every predetermined crank angle (for example, 180 ['CA] in a 4-cylinder engine). In addition, in the following explanation, the amount handled in the current process is expressed as the subscript (k
). First, in step 100, a process is performed to read the intake pipe pressure PM(k) and rotational speed Ne(k) based on the detection signals of each sensor described above. In the subsequent step 110, a process is performed to calculate the intake pipe pressure change amount ΔPM(k) as shown in the following equation (29). □Δ
PM(k)=PM(k)-PM(k-1)...
(29) The process in step 110 functions as the intake pipe pressure change amount calculation unit P1 shown in FIG.

Next, the process proceeds to step 120, where the cylinder intake air amount Ga(k) at time k is calculated according to the map shown in FIG.
k) and the rotational speed Ne(k). The process of step 120 functions as the cylinder intake air amount calculation unit P2 at the time shown in FIG.

In the following step 130, a process is performed to calculate the first provisional estimated intake pipe pressure PM"'(k+i) at time +i as shown in the following equation (30). Note that the process in step 130 is It functions as the first provisional estimated intake pipe pressure calculation unit P3 in FIG.

pM”(k+i) = PM(k)+1φ△PM(k) ・・・ (30
) Next, the process proceeds to step 140, where the cylinder intake air amount Qa(k+i) at time +i is calculated as the first provisional estimated intake pipe pressure pM(1) according to the map shown in FIG. 6, which is stored in the ROM 3b in advance. (k+i) and rotational speed Ne(k). The process of step 140 functions as +i cylinder intake air amount calculating section P4 at the time shown in FIG.

In the following step 150, the second provisional estimated intake pipe pressure pM
(2) A process is performed to calculate (k+i) as shown in the following equation (31). The process in step 150 functions as the second provisional estimated intake pipe pressure calculation unit P5 in FIG.

PMC2)(k+i) = pM"'(k+1) -B (i)・Ga(k) +B(i)・Ga(k+i)...(31) Next, proceed to step 160 and calculate the deviation E r r ( k) by the feedback gain Cf to calculate the correction amount using the following equation (32
) is calculated as follows.

CfφErr(k) = Cf ・(PM(k) −PM(k+i)・z−”r・
(32) In the following step 170, the estimated intake pipe pressure PM(k+i) at time +i is calculated as shown in the following equation (33). Above step 160, this step 1
70 functions as the estimated intake pipe pressure calculation section P6 in FIG.

PM(k+i) = pM""(k+i) + Cf-E r r(k)
(33) Next, proceed to step 180, and calculate the estimated intake pipe pressure PM(k+i) calculated in step 170 above.
A process of storing the data in the RAM 3c is performed. Next step 1
At step 90, the value 1 is added to the subscript k indicating the number of sampling and calculations, and then the process returns to step 100. Thereafter, this fuel injection amount calculation process repeats steps 100 to 190 at every predetermined crank angle.

Next, the fuel injection control process will be explained based on the flowchart shown in FIG. This fuel injection control process is performed by the ECU3
After starting, every predetermined crank angle (for example, 360['
CAI'). First, in step 200, the rotational speed Ne(k) is calculated as described above and stored in the RAM.
Estimated intake pipe pressure PM of engine 2 stored in 3c
(k+i), a process is performed to read each data including the air-fuel ratio feedback correction coefficient FAF calculated and stored in a process not shown. In the following step 210,
According to the map shown in FIG. 8, which is stored in the ROM 3b in advance, the basic fuel injection time TP (k+
A process of calculating i) is performed. Next, Ste-Nbu 220
Then, various correction coefficients KA and KB, such as a warm-up increase coefficient, an acceleration increase coefficient, and a battery correction coefficient, are calculated by interpolation according to a map (not shown) stored in advance in the ROM 3b, depending on the operating state of the engine 2. The calculation process is performed by. Next, the process proceeds to step 230, where the actual fuel injection time T
A process of calculating AU(k+i) as shown in the following equation (34) is performed.

TAU (k+1) = TP (k+i) ◆ FAF -KA+KB
(34) In the following step 240, the actual fuel injection time TAU (k
After the control signal for opening the fuel injection valve 11 is output to the fuel injection valve 11 over +i), the present fuel injection control process ends at -i. Thereafter, this fuel injection control process repeats steps 200 to 240 at every predetermined crank angle. Steps 200 to 230 of this fuel injection control process function as the fuel injection amount calculation section P7 in FIG.

Note that in the first embodiment, the engine 2 is an internal combustion engine M1.
, the intake pipe pressure sensor 24 and the rotation angle sensor 28 serve as the operating state detection means M2, and the fuel injection valve 11 serves as the fuel supply means M2.
3 applies to each of them. In addition, the ECU3 and the ECU3
Among the processes executed, steps (100-150) are used as provisional estimation means M4, step (170) is used as estimation means M5, step (160) is used as correction means M6, and steps (200-230) are used as control means. Each functions as M7.

As explained above, according to this embodiment, the dynamic characteristics of calculating the estimated intake pipe pressure PM(k+i) are dramatically improved.

Therefore, in transient conditions such as sudden start, sudden acceleration/deceleration, etc., the intake pipe pressure P
Fuel injection amount T that can optimally maintain the air-fuel ratio even when shifting to an operating state in which M(k) fluctuations exhibit significant nonlinear characteristics.
Since AU(k+i) can be calculated, the control accuracy of fuel injection amount control can be maintained at a high level at all times.

Furthermore, with the improvement of air-fuel ratio control accuracy in transient operating conditions, it is possible to reduce the amount of harmful components emitted in the exhaust, improve fuel consumption efficiency, and improve drivability.

Furthermore, in a steady state of operation such as when the engine is running normally on a ground, the amount of change in intake pipe pressure ΔPM(k) becomes a value close to zero, and its fluctuation period also becomes long. Therefore, the intake pipe pressure P M (k) and the estimated intake pipe pressure p M (k + i
) Estimated intake pipe pressure pM(k) before time 1 calculated from
The deviation E r r (k) from the above decreases, and the estimated intake pipe pressure PM (k+i) maintains high stability due to correction according to the correction amount calculated by the feedback gain Cf, so that the fuel suitable for the driving condition is maintained. Injection amount control can be achieved.

In addition, a dynamic physical model is constructed according to the mass conservation law for the intake air amount Q of the engine 2, and the feedback gain Cf is determined, and the estimated intake pipe pressure pM(k+i) is calculated from the intake pipe pressure PM(k). do. Therefore, one dynamic physical model can accurately describe the strongly nonlinear behavior of the intake air of the engine 2, and the equation of state that describes the behavior can be
It is sufficient to set only one type of coefficients φ, , C of the output equation and feedback gain Cf for calculating the correction amount.

Therefore, it is possible to simplify the device configuration, such as reducing the memory capacity of the ECU 3 and speeding up calculation speed, and also improves the accuracy of calculating the estimated intake pipe pressure PM(k+i).

Furthermore, the intake pipe pressure sensor 24 and fuel injection valve 11 can have the same configuration as existing devices, and there is no need to provide dedicated sensors such as throttle position sensors that require analog high-precision signal output performance. Versatility expands.

Next, a second embodiment of the present invention will be described in detail based on the drawings. The difference between this second embodiment and the first embodiment described above is that the procedure for calculating the second provisional estimated intake pipe pressure PM '21 (k+1) used to calculate the estimated intake pipe pressure PM (k+1) is different. be. Since the other configurations are the same,
Identical parts will be denoted by the same reference numerals and explanations will be omitted.

The control system of the second embodiment will be explained based on FIG. 9. As shown in the figure, the second provisional estimated intake pipe pressure calculation unit PIO, which is a feature of the second embodiment, calculates the first provisional estimated intake pipe pressure P M '' (k
+i), the second provisional estimated intake pipe pressure PM'' (k+i) is calculated from the rotational speed Ne(k) at the time of detection, and the cylinder intake air amount Ga(k) at the time of detection.

Here, the cylinder intake air amount Ga(k) is the rotational speed N
When e(k) is constant, it can be calculated as shown in the following equation (35).

Ga(k) = a ・pM(2)(k)+β−(3
5) However, the coefficients α and β are determined according to the rotational speed Ne(k).

On the other hand, the second provisional estimated intake pipe pressure PM'' (k+i) can be expressed as the following equation (36) as described above.

p M + 23(k+i) = PM(k)+i◆ΔPM(k) −B (i)・Ga (k) +B(i) φtea(k+i) (36) Therefore, the above formula ( 35) and (36), the second provisional estimated intake pipe pressure PM(2)(k+i) is calculated by the following equation (37)
) can be calculated as follows.

1) M””(k+i) = PM(k)+i・△PM(k) −B (i)・G a (k) +B (i) ・(α・PM(2)(k+i)+β)= (pM”(
k+1) −B (i) ・Ga(k)+B (i) ・β)/
(1+B (i) ◆α) ... (37) Next, the fuel injection amount calculation process executed in the second embodiment is
This will be explained based on the flowchart shown in FIG. This fuel injection amount calculation process is performed at every predetermined crank angle (for example, 180 [' CA
] ) is executed.

First, the intake pipe pressure PM(k) and rotational speed Ne(k) are read (step 300), and the intake pipe pressure change amount ΔPM(
In step 310) (intake pipe pressure change calculation unit PI in FIG. 9), the cylinder intake air amount Ga(k) at time k is calculated using the map shown in FIG. 6, which is stored in the ROM 3b in advance. Accordingly, the engine valve 32 should be calculated according to the intake pipe pressure PM (k) and the rotational speed Ne (k).
0) (cylinder intake air amount calculation unit P2 at the time shown in FIG. 9), the first provisional estimated intake pipe pressure P at +i at the time
Calculate M"'(k+i) (step 330) (9th
First provisional estimated intake pipe pressure calculation section P3) in the figure. Next, the process proceeds to step 345, where the above-mentioned constants α and β are stored in advance in the ROM3.
In accordance with the map shown in FIG. 6, which is stored in .b, calculation processing is performed according to the rotational speed Ne(k). In the following step 355, the second provisional estimated intake pipe pressure PM"
"(k+i)" is calculated as shown in the following equation (3 days).The process in step 355 functions as the second provisional estimated intake pipe pressure calculation unit PIO in FIG.

pM””(k+i) = (pM”’(k+1) −B (i) ・Ga(k)+B (i) ・β)/(
1+B(i) ・α) ... (38) Next, calculate the correction amount by multiplying the deviation Err(k) by the feedback gain Cf (step 360), and calculate the estimated intake pipe pressure P M (k + Step 370) (estimated intake pipe pressure calculation section P6 in FIG. 9)
), the estimated intake pipe pressure 'P M (k + i) is RA
Store it in M3c (step 380), and add the value 1 to the subscript k indicating the number of sampling operations (step 390).
), the process returns to step 300 above. Thereafter, this fuel injection amount calculation process is performed at each predetermined crank angle in step 30.
Repeat steps 0 to 390.

Note that in the second embodiment, the engine 2 is an internal combustion engine M.
1, the intake pipe pressure sensor 24 and the rotation angle sensor 28 correspond to the operating state detection means M2, and the fuel injection valve 11 corresponds to the fuel supply means M3. In addition, ECU3 and the ECU
3, steps (300 to 355) serve as provisional estimating means M4, step (370) serves as estimating means M5, step (360) serves as correcting means M6, and steps (200 to 230) serve as control means M7. Each functions as a.

As explained above, according to the second embodiment, the constant α determined based on the rotational speed N e (k) of the engine 2,
Using β, the first provisional estimated intake pipe pressure 100M” (k+i
) and the cylinder intake air amount Ga(k), the second provisional estimated intake pipe pressure PM'' (k+1) is calculated, so the estimation accuracy of the estimated intake pipe pressure PM(k+i) can be further improved.

Although several embodiments of the present invention have been described above, the present invention is not limited to these embodiments.
It goes without saying that the invention can be implemented in various ways without departing from the spirit of the invention.

Effects of the Invention As described in detail above, the fuel injection amount control device for an internal combustion engine of the present invention determines the amount of fuel to be supplied based on the rotational speed of the internal combustion engine and the estimated intake pipe pressure. Based on a dynamic physical model constructed according to the law of conservation of mass, the provisional estimated intake pipe pressure at the time of intake is calculated from the intake pipe pressure detected at the time of detection, and the intake pipe pressure at the time of detection is calculated from the estimated intake pipe pressure at the time of intake. and the intake pipe pressure detected at the time of detection and a correction amount calculated from the feedback gain determined based on the dynamic physical model described above to calculate the estimated intake pipe pressure by performing feedback correction. For this reason, it is possible to improve the dynamic characteristics of calculating the estimated intake pipe pressure, and the optimum amount of fuel can be supplied even in operating conditions where intake pipe pressure fluctuations exhibit significant nonlinear characteristics, such as transient operating conditions, thereby improving the control accuracy of air-fuel ratio control. It has an excellent effect of dramatically improving performance.

Along with the above effects, the exhaust characteristics, fuel consumption efficiency, and driving performance during transient operating conditions are also improved.

Further, in a steady state of operation, the intake pipe pressure fluctuations are minute and slow. Therefore, the deviation between the intake pipe pressure at the time of detection and the intake pipe pressure at the time of intake calculated from the estimated intake pipe pressure is reduced, and the estimated intake pipe pressure calculated by feedback correction shows high stability, resulting in high accuracy. It is possible to realize fuel injection amount control.

Furthermore, we constructed a dynamic physical model based on the law of conservation of mass for the amount of intake air in an internal combustion engine, determined the feedback gain, and based on these, estimated intake pipe pressure at the time of intake from the intake pipe pressure at the time of detection. Calculate. For this reason,
One model can describe the behavior of the intake air of an internal combustion engine,
It is sufficient to set only one type of various parameters describing the behavior and feedback gain for calculating the correction amount. Therefore, it is possible to both simplify the device configuration such as storage capacity and computing power, and improve the accuracy and speed of calculating the estimated intake pipe pressure.

Further, the operating state detection means and fuel supply means can be configured in the same way as the existing device, and there is no need to provide a dedicated detection means, so the versatility of the device is expanded.

[Brief explanation of the drawing]

FIG. 1 is a basic configuration diagram conceptually illustrating the contents of the present invention, FIG. 2 is a system configuration diagram of an embodiment of the present invention, FIG. 3 is a control system diagram showing the configuration of the control system, and FIG. FIG. 4 is a block diagram showing the configuration of the observer, FIG. 5 is a flow chart showing its control, FIG. 6 is a graph showing its map, FIG. 7 is a flow chart showing its control, and FIG. 9 is a control system diagram showing the control system of another embodiment, and FIG. 10 is a flowchart showing the control of another embodiment. Ml... Internal combustion engine M2... Operating state detection means M3... Fuel supply means M4... Temporary estimating means M5... Estimating means M6... Correction means Ml... Control means 1... Engine fuel injection control iH device 2...
・ Engine 3 ... Electronic control unit (ECU) 3a ... CPU 11 ... Fuel injection valve 24 ... Intake pipe pressure sensor 2 ... Rotation angle sensor

Claims (1)

[Scope of Claims] 1. Operating state detection means for detecting the operating state of an internal combustion engine, including at least intake pipe pressure and rotational speed; and fuel supply means for supplying an externally commanded amount of fuel to the internal combustion engine. , A fuel injection amount control device for an internal combustion engine that supplies an amount of fuel determined according to a detection result of the operating state detection means from the fuel supply means, further comprising: mass conservation regarding the intake air amount of the internal combustion engine. Based on the dynamic physical model constructed according to the above-mentioned rules, the amount of fuel determined according to the intake pipe pressure detected at the detection time is determined from the intake pipe pressure and rotational speed detected by the operating state detection means at the detection time. Temporary estimation means for calculating a provisional estimated intake pipe pressure corresponding to the predicted intake pipe pressure of the internal combustion engine at the time of intake into a cylinder in the intake stroke of the internal combustion engine; and provisional estimated intake pipe pressure calculated by the provisional estimation means. an estimating means for feedback-correcting the pressure based on a correction amount instructed from the outside and calculating an estimated intake pipe pressure corresponding to the intake pipe pressure at the time of intake of the internal combustion engine; and an estimated intake pipe pressure calculated by the estimating means. The correction amount is calculated from the feedback gain determined based on the deviation between the intake pipe pressure of the internal combustion engine at the time of detection determined from the pressure and the intake pipe pressure detected at the time of detection by the operating state detection means and the dynamic physical model. correction means for calculating and instructing the estimating means; and supplying fuel in an amount determined based on the rotational speed detected by the operating state detecting means and the estimated intake pipe pressure calculated by the estimating means to the fuel supply means. A fuel injection amount control device for an internal combustion engine, comprising: a control means for issuing a command;