JPH01271622A - Device for controlling fuel injection quantity of internal combustion engine with egr device - Google Patents

Abstract

PURPOSE:To conform an air-fuel ratio with a target air-fuel ratio by estimating the new-air partial pressure and exhaust-gas partial pressure of a mixture based on a recirculating exhaust gas quantity estimated from the behavior of an EGR value, the engine speed of an internal combustion engine, a pressure inside an intake air passage, and a new air temperature. CONSTITUTION:A first estimating means M8 estimates an exhaust gas quantity recirculated into an intake air passage M2 from the behavior of the EGR value of an EGR device M3 which is estimated by a behavior estimating means M7. Then, a second estimating means M9 estimates the new-air partial pressure and an exhaust-gas partial pressure of a mixture based on the estimated recirculating exhaust gas quantity, the engine speed of an internal combustion engine M5 detected by an operating condition detecting means M6, a pressure inside the intake air passage and an intake air temperature. From these, a new air quantity taken into a cylinder at the time of an intake stroke is calculated by a calculating means M10, and a corresponding fuel quantity is calculated by a calculating means M11. Thereby, an air-fuel ratio can be conformed with a target air fuel ratio.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a fuel mixture supplied into the cylinder of an internal combustion engine equipped with an EGR device (i.e., an exhaust gas recirculation device) that recirculates exhaust gas to the intake system. The present invention relates to a fuel injection amount control device for an internal combustion engine with an EGR device, which controls the amount of fuel injection from a fuel injection valve so that the fuel-air ratio becomes a desired fuel-air ratio.

[Prior Art] In conventional internal combustion engines for vehicles, the exhaust system is usually equipped with a three-way catalyst for purifying harmful components HC, Go, and NOX in the exhaust gas. In addition, in this type of internal combustion engine, in order to maintain the exhaust purification efficiency of the three-way catalyst in a good state, the fuel-air ratio of the fuel mixture supplied to the internal combustion engine is set to the target fuel-air ratio (usually the excess air ratio). 1) A fuel injection amount control device is provided that controls the amount of fuel injection from the fuel injection valve so as to achieve the following.

In addition, as one of the fuel injection amount control devices, conventionally,
The basic fuel injection amount according to the load of the internal combustion engine is determined based on the rotational speed of the internal combustion engine and the pressure inside the intake passage downstream of the throttle valve (hereinafter referred to as intake pressure), and the basic fuel injection amount is It is known that the fuel-air ratio is corrected according to the detection result of an oxygen sensor that detects the fuel-air ratio from the oxygen concentration of the fuel-air ratio, and determines the amount of fuel injected from the fuel injection valve.

On the other hand, some internal combustion engines are equipped with an EGR device that recirculates the exhaust gas to the intake system and lowers the maximum combustion temperature of the fuel in order to reduce NOx components contained in the exhaust gas.

By the way, in an internal combustion engine equipped with an EGR device, when exhaust gas is recirculated to the intake passage by the operation of the EGR device, the basic fuel injection amount determined from the rotational speed and intake pressure of the internal combustion engine is controlled by the fuel injection amount control device. In some cases, the fuel-air ratio does not correspond to the load, and the fuel-air ratio deviates significantly from the target fuel-air ratio. In other words, in the fuel injection amount control device that calculates the basic fuel injection amount from the rotational speed of the internal combustion engine and the intake pressure as described above, when the EGR device operates and exhaust gas is recirculated to the intake passage, the intake pressure changes to the EGR device. The value corresponds to the amount of mixture of the exhaust gas recirculated by the exhaust gas and the air flowing in through the throttle valve (hereinafter referred to as fresh air), and the basic fuel injection amount calculated based on this value is based on the amount of fresh air. If the amount increases too much, the fuel-air ratio will deviate greatly from the target fuel-air ratio.

Therefore, conventionally, when the EGR device is activated, the basic fuel injection amount is corrected according to the amount of exhaust gas that is recirculated to the intake passage via the EGR device (hereinafter also referred to as EGR amount) based on the rotational speed of the internal combustion engine and the intake pressure. It has been considered to calculate the value, correct the basic fuel injection amount using this correction value, and execute fuel injection control using the corrected value as the basic fuel injection amount. In addition, when the vehicle moves from a lowland to a highland and the atmospheric pressure changes, EGRI changes accordingly, so prepare multiple maps of correction values for the basic fuel injection amount for each atmospheric pressure, and use them when calculating the correction value. It has also been considered to use a map for calculating correction values that is switched depending on the atmospheric pressure (for example, Japanese Patent Laid-Open No. 8443/1983).

[Problems to be Solved by the Invention] However, as described above, the basic fuel injection amount is determined from the rotational speed and intake pressure of the internal combustion engine, and when the EGR system is activated, the basic fuel injection amount is further calculated based on the rotational speed and intake pressure of the internal combustion engine. In a device that performs fuel injection control by correcting with a correction value obtained from
Another problem is that the control accuracy of the fuel-air ratio deteriorates significantly for a while after the EGR device starts operating or stops operating.

This is because it takes time for the exhaust gas recirculated by the EGR device to flow into the cylinder of the internal combustion engine.
This is due to the response delay of the EGR valve of the R device. In other words, the amount of fuel injected from the fuel injection valve can be set according to the amount of fresh air flowing into the cylinders of the internal combustion engine so that the fuel mixture flowing into the cylinders of the internal combustion engine has the target fuel-air ratio. However, in the past, the fuel injection amount corresponding to the mixture of exhaust gas and fresh air was simply determined based on the rotational speed of the internal combustion engine and the intake pressure, and from that value, the fuel injection amount was reduced in accordance with the EGR amount. The system is configured to calculate the amount of fuel to be injected into the internal combustion engine through the correction, taking into account the time delay until the mixture of exhaust gas and fresh air actually flows into the cylinder of the internal combustion engine, and the response delay of the EGR valve. Because the EGR system was not installed, internal combustion occurred when the EGR system was activated.

If the engine is operated transiently and the EGR amount changes suddenly, or if the EGR
The fuel injection amount when the R device starts operating or stops operating is
The value does not correspond to the amount of fresh air actually flowing into the cylinders of the internal combustion engine, and the fuel-air ratio deviates significantly from the target fuel-air ratio.

In order to solve the above-mentioned problems, the applicant of the present application has made inventions and proposals in Japanese Patent Application No. 62-209772 that take into consideration the inflow delay of the recirculated exhaust gas. However, it is difficult to say that these inventions and proposals take into consideration the response delay of the EGR valve.

Therefore, the present invention has a method of controlling the amount of fuel injected from the fuel injection valve in accordance with the amount of fresh air that always flows into the cylinder of the internal combustion engine without being affected by the operating state of the EGR device or the operating state of the internal combustion engine. The purpose of this invention is to provide a fuel injection amount control device for an internal combustion engine equipped with an EGR device.

[Means for solving the problem] That is, the configuration of the present invention made to achieve the above object is as follows:
As illustrated in FIG. 1, it is equipped with an EGR device M3 that recirculates exhaust gas to the intake passage M2 downstream from the throttle valve M1, and combines the exhaust gas recirculated by the EGR device M3 with fresh air flowing in through the throttle valve M1. A fuel injection amount control device for an internal combustion engine M5 equipped with an EGR device in which a mixture of air and air is taken into a cylinder M4, the rotational speed ω of the internal combustion engine M5, the intake passage M
2 an operating state detecting means M6 for detecting an internal pressure P1 and a temperature 7-i of fresh air flowing in through the throttle valve M1; and an intake passage M2 of the internal combustion engine M5 detected by at least the operating state detecting means M6. Based on the internal pressure P, the above EG
The behavior of the EGR valve of the R device M3 is captured by the behavior estimation means M7, and from the behavior of the EGR valve, the above-mentioned intake passage M
a first estimating means M8 for estimating the amount me of exhaust gas recirculated to
and the internal combustion engine M detected by the operating state detection means M6.
5, the pressure P inside the intake passage M2, and the fresh air temperature Ti. 2
fresh air pressure calculation for calculating the fresh air amount mc sucked into the cylinder M4 during the intake stroke from the fresh partial pressure P estimated by the second estimation means M9 and the exhaust partial pressure Pe. The means MIO multiplies the fresh air amount mC calculated by the fresh air interval calculation means M10 by a preset target fuel-air ratio λr to determine the fuel amount me・ to be supplied into the cylinder M4 during the intake stroke. A fuel amount calculation means M11 that calculates λr, and a fuel injection valve M according to the calculated fuel i1mc·λr.
Fuel injection control means M1 that drives 12 and supplies fuel.
3, and a fuel injection amount control device for an internal combustion engine equipped with an EGR device.

Here, the behavior estimating means M7 of the first estimating means M8 performs EGR estimation based on the pressure P inside the intake passage M2 of the internal combustion engine M5.
Any device that captures (estimates) the behavior of the EGR valve of the device M3 may be used, and it may be configured to estimate the lift amount of the EGR valve in relation to the pressure P inside the intake passage M2.

Next, the second estimating means M9 calculates, from the EGR amount me estimated by the first estimating means M8, the rotational speed ω, the intake pressure P1 and the fresh air temperature Ti detected by the operating state detecting means M6. This is for estimating the fresh partial pressure Pi of the air-fuel mixture existing in the intake passage M2 and the exhaust partial pressure Pe, which are determined from the mass conservation equation for fresh air and exhaust gas and the energy conservation law for internal combustion engines, as described later. , new partial pressure P1 and exhaust partial pressure P
It can be designed based on a state equation in which e is a state variable.

Further, the fresh air amount sieving means MIO includes the second estimating means M9.
This is to calculate the amount of fresh air flowing into the cylinder M4 during the intake stroke from the fresh partial pressure Pi in the intake passage M2 and the exhaust partial pressure Pe estimated in It can be constructed using a rigid expression obtained from conservation laws.

Next, the fuel injection control means M13 drives the fuel injection valve M12 so that the amount of fuel calculated by the fuel amount calculation means M11 flows into the cylinder M4 of the internal combustion engine M5 during the intake stroke of the internal combustion engine M5. The fuel injection valve M12 may be configured to perform injection control, and to open the fuel injection valve M12 for a time corresponding to the calculated fuel amount in each intake stroke of the internal combustion engine M2.

In this case, all of the fuel injected from the fuel injection valve M12 does not directly flow into the cylinder M4 of the internal combustion engine M2;
A part of it adheres to the inside of the intake passage M2, and also
Since it remains as evaporated fuel inside, it is desirable to control the amount of fuel injected from the fuel injection valve M12 (i.e., the opening time of the fuel injection valve M12) by considering the amount of adhering fuel, the amount of evaporated fuel, etc. .

A physical model for configuring the second estimating means M9 can be obtained as follows.

First, it is assumed that the exhaust gas recirculated to the intake passage M2 via the EGR device M3 and the fresh air flowing into the intake passage M2 via the throttle valve M1 are uniformly mixed by the surge tank inside the intake passage M2. The change in the amount of fresh air inside the intake passage M2 is expressed by the following formula (1
) can be written as follows.

V/Ci 2- d Pi/d t='hnt-'?
nc-(1) (However, ■: Internal volume of the intake passage from the throttle valve to the cylinder, C1: Speed of sound in fresh air, Pi: Fresh partial pressure, TS: Flow rate of fresh air from the throttle valve to the intake passage, ' tnc: Fresh air flow rate from the intake passage to the cylinder) Similarly, the exhaust amount inside the intake passage M2 (i.e. EGR amount)
The change in can be described as shown in the following equation (2) using the exhaust mass conservation equation.

V/ Ce 2- d pe/d t-'rne-Tr
+ce-(2) (Ce: Sound velocity during exhaust, Pe: Exhaust partial pressure, 'hle: Exhaust flow rate from the EGR device to the intake passage, ')nce: Exhaust flow rate from the intake passage to the cylinder)
On the other hand, the amount of fresh air flowing into cylinder M4 during the intake stroke is mc, the displacement is mCe, and the throttle valve M
The temperature of fresh air flowing into the intake passage M2 through Ti
,E The energy stored in the cylinder M12 while moving from top dead center to bottom dead center (i.e. the difference between the energy when the piston moves to bottom dead center and the energy when the piston is at top dead center) is:
Since it is equal to the sum of the energy of the air-fuel mixture (that is, fresh air and exhaust gas) flowing into cylinder M4 during the intake stroke and the amount of heat received from the cylinder wall surface minus the loss due to piston movement, the following equation (3) is obtained. It can be written as follows.

(1/Kc-1) φP-Vc-(1/Kr-1) +
1Pr -Vt= (Ki/K1-1)・Ri'・T
i −mc+ (Kr/K 1-1) φRe −T
e −mce+qW −f:j P −dV
...(3) (However, P: Pressure in the intake passage (i.e. intake pressure), Pr residual gas pressure in the cylinder, ■=Intake passage volume, vt: Cylinder volume at the piston top dead center, ■
C: Cylinder volume at piston bottom dead center, R1: Gas constant of fresh air (i.e., atmosphere), Re: Gas constant of exhaust gas, KC: Specific heat ratio of air-fuel mixture, Kr: Specific heat ratio of residual gas (=exhaust gas), K
i: specific heat ratio of fresh air) In the above equation (3), when the intake pressure P is the same, the fresh air temperature Ti is the reference temperature TiO, and the exhaust gas is not recirculated by the EGR device M3 (i.e. mCe-Q) Fresh air flows into the cylinder! When mc @mCO, the above equation (3) becomes the following equation (4).

(1/KC'-1)-P-VC-(1/K 1-1) ・Pr' ・V t= (Ki
/K1-1)・Ri-Tio-mc.

+QW -f,','P-dV...(
4) Here, in the above formula (4), KC'=KCSPr'
=pr and subtracting both sides from both sides of equation (3), the following equation (5) is obtained.

(Ki /K1-1> ・Ri ・Ti −mc+
(Kr /Kr-1) ・Re −Te −mce=
(Ki /K1-1) ・Ri-Tio-mc
o-(5) On the other hand, if the volume of 1 mc of fresh air in the intake passage M2 is Vi, the volume of the displacement me is also Vi, so the energy of the fresh air and exhaust gas flowing into the cylinder M4 is:
Each can be described as shown in the following equations (6) and (7).

pi-Vi=mc-Ri-T...16) Pe
・■i=mCe-Re-T...(7) Therefore, the above formula (
6) and (7), the exhaust gas 5 flowing into the cylinder M4
1mce can be written as in the following equation (8).

mce-mc (Ri-Pe /Re ΦPi
)...(8) By substituting this equation (8) into the above equation (5), the following equation (9) is obtained.

mc ((Kr /Kr-1> ・Ri −Ti +(
Kr /Kr-1) Re * Te ・(Ri /R
e)(Pe/Pi))=(Ki/K1-1)
・Ri −Ti0− mco− (9) Then, rearranging this equation (9), the following equation (1
0) is obtained.

mc =mco/ ((Ti /Tio> +Kr
(Ki-1)Te −Pe/Ki (Kr-1>Ti
o-Pi) ...The fresh air amount calculation means M10 can be configured using this equation (10).

Next, let the rotational speed of the internal combustion engine M5 be ω, and one intake stroke is 1
If it is 80deg, the intake stroke time is ΔT=30/ω (11). In addition, in the above formula (1), Pi (k+1 >= Pi (to t+8)...
(12) Pi (k) = Pi (t)
...(13), then equation (1) can be written as the following equation (14).

Pi (k+1) = Pi (k)+ (Ci 2/
V) f, "'Box・dt (Ci 2/V) ft"
'tr+c -d t- (14) Also, in the above equation (14), f:4'Ltnc -dt =mc (k)
−(15) is t−dt=30sum t(k)/ω(k)
...(16). Therefore, these (15) and (16)
), equation (14) (i.e., equation (1) becomes the following equation (17)
It can be written as follows.

Pi (k+1) -pi (k)+3Q-Ci
2-')nt(k)/V”(i) (k)-Ci 2
-mC(k)/V- (17) On the other hand, in the above equation (2), Pe (k+1)=Pe (t+Δt) -
(1B>Pe (k)=Pe (t)
-(19), equation 2) can be written as the following equation (20).

Pe (k+1)−Pe (k)+ (Ce 2 /V
) e""h>e-dt - (Ci 2/V) f,"
ce-dt ・(20) Also, in the above equation (20), f:”rne-dt =me (k) −(
21), /””'1nce −d t =mce
−(22). Therefore this (
From equations (21) and (22), equation (20) (ie, equation (2)) can be written as shown in equation (23) below.

Pe (k+1)=l)e (k)+Ce 2-m
e (k)/V-Ce 2-mce (k)/V
-(23) Therefore, from the above equations (17), (23), and (8), a state equation with fresh partial pressure Pi and exhaust partial pressure pe as state variables for configuring the second estimating means M9 can be obtained. It is obtained as shown in the following equation (24).

Also, P (k)=Pi (k)+Pe (k)・
The state equation (25) is established.

[Operation] In the fuel injection amount control device of the present invention configured as described above, the first estimating means M8 uses at least the intake pressure P to capture the behavior of the EGR pulp of the EGR device M3 using the behavior estimating means M7. , From the behavior of this EGR valve, the EGR
Exhaust gas m (i.e. E
The second estimating means M9 estimates the estimated EGR amount, the rotational speed ω of the internal combustion engine M5, the intake pressure P, and the fresh air temperature detected by the operating state detecting means M6. A new partial pressure Pi inside the intake system and an exhaust partial pressure Pe are estimated from Ti. Then, the fresh air space calculating means M'IO calculates the estimation result of the second estimating means M9, that is, the fresh air amount mc flowing into the cylinder M4 of the internal combustion engine M5 during the intake stroke, and the fuel amount calculating means M11 calculates the fresh air amount mc flowing into the cylinder M4 of the internal combustion engine M5 during the intake stroke. The calculated amount of fresh air mc is multiplied by a preset target fuel-air ratio λr to calculate the amount of fuel to be supplied into the cylinder M4 during the intake stroke. Then, the fuel injection control means M13 drives the fuel injection valve 12 according to the calculated fuel amount to execute fuel injection control.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

First, FIG. 2 is a schematic configuration diagram showing the configuration of an internal combustion engine 2 with an EGR device and its peripheral devices to which the present invention is applied.

In the figure, numeral 4 represents an intake pipe that sucks air through an air cleaner 6, and this intake pipe 4 has a throttle valve 8 for reducing the amount of fresh air flowing into the intake passage 4a by υtml.
, a surge tank 10 for suppressing intake pulsation, an intake pressure sensor 12 for detecting the internal pressure (intake pressure) P,
A fresh air amount sensor 14 that detects the temperature Ti of fresh air flowing into the intake passage 4a through the throttle valve 8, and a throttle opening sensor 1 that detects the opening of the throttle valve 8.
6 is provided.

On the other hand, 18 is an exhaust pipe, and from the oxygen concentration in the exhaust gas, the internal combustion engine 2
An oxygen sensor 20 for detecting the fuel-air ratio λ of the fuel mixture that has flowed into the cylinder 2a, and a three-way catalytic converter 22 for purifying exhaust gas are provided. Further, the exhaust pipe 18 is provided with an EGR device 24 that recirculates exhaust gas to the surge tank 10 under predetermined operating conditions after warming up the internal combustion engine.

The EGR device 24 includes an EGR valve 26 that opens and closes an exhaust passage connecting the exhaust pipe 18 and the surge tank 10;
A pressure regulating valve 28 adjusts the negative pressure applied to the valve 26 to control the EGR amount, and the pressure regulating valve 28 opens and closes a passage for the collapsed negative pressure to prohibit or permit the recirculation of exhaust gas by the EGR pulp 26. It consists of an EGR permission valve 30.

That is, the constant pressure chamber 26a of the EGR valve 26 and the exhaust pipe 18, and the valve chamber 26b and the surge tank 10 are communicated with each other, and the diaphragm chamber 26d, which is connected to the valve chamber 26i) via the diaphragm 26C, is connected to the EGR permission valve 3.
0 to the upper chamber 28a of the pressure regulating valve 28, the valve body 26e connected to the diaphragm 26C is connected to the upper chamber 28a of the pressure regulating valve 28.
It is moved up and down in the figure in response to the negative pressure transmitted from the pressure regulating valve 28 via the EGR permission valve 30, thereby opening and closing the exhaust passage between the exhaust pipe 18 and the surge tank 14.

In addition, the pressure regulating valve 28
An upper chamber 28a communicates with the diaphragm chamber 26d of the R valve 26 and the surge tank 10.

Constant pressure chamber 2 communicating with constant pressure chamber 26a of EGR pulp 26
The installation of the throttle valve 8b1 and the throttle valve 8 consists of a diaphragm chamber 28C1 that communicates with the EGR boat 4b formed in the intake pipe 4 slightly upstream from the position, and the opening degree of the throttle valve 8 is adjusted to the position of the EGR port 4b. When it is smaller, the pressure in the diaphragm chamber 28C becomes as high as atmospheric pressure, and the upper chamber 28a and the diaphragm chamber 28C
and conversely, the opening of the throttle valve 8 is EGR.
When it becomes larger than the position of the boat 4b, the pressure in the diaphragm chamber 28C decreases due to the negative pressure in the surge tank 10, and the upper chamber 28a and the diaphragm chamber 28C are cut off.

Therefore, the EGR permission valve 30 is driven, and the pressure regulating valve 2
When the upper chamber 28a of the EGR valve 8 and the diaphragm chamber 26b of the EGR pulp 26 are communicated with each other (that is, permission to execute EGR control is given), and when the throttle valve 10 reaches a predetermined opening degree or more, the diaphragm chamber 26b of the EGR valve 26 26C
The negative pressure in the surge tank 10 is transmitted to the valve body 26e, and the valve body 26e operates accordingly, thereby controlling the amount of exhaust gas recirculation, that is, the amount of EGR.

On the other hand, the internal combustion engine 2 includes the above-mentioned intake pressure sensor 12, fresh air amount sensor 14, throttle opening sensor 16, and oxygen sensor 2 as sensors for detecting its operating state.
0, internal combustion engine 2 from the rotation of the distributor 32
a rotational speed sensor 34 for detecting the rotational speed ω of the distributor 32; a crank angle sensor 36 for detecting the fuel injection timing to the internal combustion engine 2 from the rotation of the distributor 32;
and attached to the water jacket of the internal combustion engine 2,
A water temperature sensor 38 for detecting cooling water temperature T is provided. The distributor 32 is for applying the high voltage from the igniter 40 to the spark plug 42 at a predetermined ignition timing.

Detection signals from each of the above sensors are output to an electronic control circuit 50 configured as a logic operation circuit centered on a microcomputer.

The electronic control circuit 50 controls the fuel injection valve 52 so that the fuel-air ratio λ of the fuel mixture flowing into the cylinder 2a of the internal combustion engine 2 becomes a target fuel-air ratio λr set according to the operating state of the internal combustion engine 2. fuel injection amount control that performs feedback control on the fuel injection amount q, and determines whether the operating state of the internal combustion engine 2 satisfies predetermined EGR execution conditions at predetermined time intervals;
An EG that drives the EGR permission valve 30 to permit EGR control by the EGR device 24 when EGR control conditions are satisfied.
This is for executing the R permission control, and as is conventionally known, the CPU 60. C.P.L.J.
A ROM 62 in which the control programs and initial data necessary to execute arithmetic processing in the 60 are pre-recorded, the same <CPU
A RAM 64 into which data used to execute arithmetic processing is temporarily read and written, an input port 6 for inputting detection signals from each of the above-mentioned sensors, and a CPU 6.
an output port 8 for outputting a drive signal to the fuel injection valve 52 and the EGR permission valve 30 according to the calculation result at 0;
It is composed of etc.

Next, a control system for fuel injection amount control executed by the electronic control circuit 50 will be explained using block diaphragms shown in FIGS. 3 and 4. Note that Figures 3 and 4 are diagrams showing the control system, and do not show the hardware configuration.Actually, by executing a series of programs shown in the flowchart in Figure 5, it is possible to control the system as a discrete system. Realized.

As shown in FIG. 3, in the fuel injection amount control system of this embodiment, first, the first calculation unit P1 calculates the throttle opening degree θ, fresh air temperature Ti, intake pressure P, and rotation speed detected by the above-mentioned sensors. The amount of fresh air mc flowing into the cylinder 2a during the intake stroke of the internal combustion engine 2 is calculated based on the speed ω. This first calculation unit P1 corresponds to the above-mentioned first estimating means M8, second estimating means M9, and fresh air interval calculating means MIO, and more specifically, as shown in FIG. be done.

The fresh air amount mc calculated by the first calculation section P1 is output to the first multiplication section P2 as the fuel amount calculation means M10 described above, and the target fuel-air ratio is set according to the operating state of the internal combustion engine 2. In other words, by multiplying the amount of fresh air flowing into the cylinder 2a by the target fuel-air ratio λr, the amount of fuel to be supplied into the cylinder 2a during the intake stroke of the internal combustion engine 2, i.e. The target fuel supply amount mcλr@ is calculated.

The fresh air amount mc calculated by the first calculation section P1 is also output to the second multiplication section P3. The second multiplier P3 has a fresh air amount m
c is multiplied by the fuel-air ratio λ of the fuel mixture that has flowed into the cylinder 2a detected by the oxygen sensor 20 to calculate the amount of fuel that actually flowed into the cylinder 2a during the previous intake stroke (actual fuel supply mC).・Calculate λ.

Next, the target fuel supply amount mc calculated by the first multiplier P2
・λr and the actual fuel supply amount mc calculated by the second multiplication section P3. ・λ are both output to the lit difference calculation section P4,
A deviation mc (λ-λr) between the target value and the actual measurement value is calculated. Then, the calculation results are sequentially added in a sequential addition section P5, and the calculation results are multiplied by a preset coefficient f3 in a coefficient f3 multiplication section P6. The target fuel supply amount mc·λr calculated by the first multiplier P1 is also output to the coefficient f4 multiplier P7, and multiplied by a preset coefficient f4.

On the other hand, the cooling water temperature T detected by the water temperature sensor 38, the intake pressure P detected by the intake pressure sensor 12, and the rotation speed sensor 3
The rotation speed ω of the internal combustion engine 2 detected by 4, the actual fuel supply amount mc·λ calculated by the second multiplier P3, and the previous fuel injection Wkq from the fuel injection valve 52 are sent to the second calculation unit P8. is input.

This second calculation section P8 calculates the saturated vapor pressure PS in the intake passage 4a from the input cooling water temperature T, and calculates the evaporation of the fuel attached to the wall of the intake passage 4a from that value and the intake pressure P. Calculate lVf @. Further, the calculated fuel evaporation amount Vf is divided by the rotational speed ω of the internal combustion engine 2. The division result Vf/ω is the coefficient f5 multiplier P9
is input and multiplied by a preset coefficient f5.

Next, using an arithmetic expression set based on a physical model representing fuel behavior in an internal combustion engine, the actual fuel amount mcλ, the division result Vf/ω, and the fuel injection q coefficient are multiplied by 1 at a unit P10.
The coefficients f1 and f2 are multiplied by the coefficients f1 and f2 in the squaring unit P11.

The multiplication results from these multipliers P10 and Pll are added together with the multiplication results from other multipliers P6, P7, and P9 in adders P12 to P15, thereby increasing the fuel injection amount q from the fuel injection valve 32. It is determined.

The control system of this embodiment as described above controls the amount of fuel lfw attached to the inner wall surface of the intake passage 4a and the amount of evaporated fuel fv within the intake passage 4a.
It is designed in accordance with a physical model that expresses the fuel behavior in the internal combustion engine 2 using the state variable as the state variable. Note that a description of the physical model for designing this control system and its design method will be omitted. An example of a design method for this type of control system is "Digital Control of Actual Systems" by Katsuhisa Furuta.
System and Control, Vol, 2B, ω0.12 (1984
2000) Familiar with the Society of Instrument and Control Engineers, etc.

Here, the amount of fresh air mc flowing into the cylinder 2a is EG
If there is no recirculation of exhaust gas by the R device 24, it can be easily calculated from the intake pressure P and the rotational speed ω of the internal combustion engine 2. However, in this embodiment, since the exhaust gas is recirculated into the intake passage 4a by the operation of the EGR device 24, the amount of fresh air flowing into the cylinder 2a mC based on the intake pressure P and the rotational speed ω.
@Cannot be calculated. Therefore, in this embodiment, based on the above-mentioned equations (10) and (24), the cylinder 2a
A first calculation unit P for calculating the amount of fresh air flowing into the
1, and based on this design, the amount of fresh air mc flowing into the cylinder 2a can be accurately calculated regardless of the operating state of the EGR device 24.

Hereinafter, the configuration of this first calculation section P1 will be explained based on FIG. 4.

As shown in the figure, the first calculation unit P1 uses a map or calculation formula using the intake pressure P and the rotational speed ω as parameters to determine whether the EGR device 24 stops operating when the fresh air temperature Ti is the reference temperature Tto. Fresh air reference value calculation unit P2 that calculates fresh air @ (hereinafter referred to as fresh air amount reference value) mco flowing into the cylinder 2a when it is assumed that
1, an EGR amount estimation unit P22 that estimates the amount of exhaust gas recirculated into the intake passage 4a via the EGR device 24 based on the rotational speed ω and the intake pressure P of the internal combustion engine 2 (i.e., EGRI>me); EGR1me1 estimated in section P22 Exhaust partial pressure Pe in the intake passage 4a is calculated based on the exhaust partial pressure Pe in the intake passage 4a previously estimated in this first calculating part P1, the new partial pressure P1, and the fresh air amount mc. Estimating exhaust partial pressure estimating part P
23, a new partial pressure calculating unit P24 that calculates a new partial pressure Pi in the intake passage 4a from the exhaust gas partial pressure Pe and the intake pressure P estimated by the exhaust partial pressure estimating unit P23, a fresh air temperature T1, and During the intake stroke, the cylinder 2a is
Fresh air amount reference value P25 for calculating the amount of fresh air flowing into the interior mc
It is composed of and.

The EGR amount estimating section P22 corresponds to the first estimating means M8 described above, and is configured as follows.

As mentioned above, the valve body 26e of the EGR pulp 26 operates according to the negative pressure (intake pressure P) in the surge tank 10.
behavior), but its behavior is assumed to be a first-order response delay with respect to the intake pressure P. Therefore, if the cross-sectional area of the diaphragm 26c is S and the spring constant of the diaphragm 26c is 1, then the lift amount 1 of the valve body 26e is 1=P-3・<1-6″>/1...(30 ) Here, α represents a time constant specific to the system.

As a result, the EGR amount me via the EGR valve 26
can be determined (estimated) as shown in the following equation (31).

Hatake e = 2-P-s-<1-e> -Ishi Takumi lower...(
31) In the above equation (31), K2 indicates the identified number of threads unique to the system including 1 in the spring constant, and PB indicates the exhaust pressure determined from the map of rotational speed ω and intake pressure P.

Next, the exhaust partial pressure estimating section P23 and the new partial pressure calculating section P24 correspond to the above-mentioned second estimating means M9, and the above-mentioned (24)
It is constructed based on the formula and formula (25).

That is, the above equations (24) and (25) are transformed into the following equations (32) and
Using formula (33), Xc(k+1)= +C-XC(k)+fc-
uc(k)-(32)ycth)=ec-XC(k
) −(33), but [+c
ec] is not observable. However, since equation 24) is usually stable, if the initial state PeO is known, then Pe
(k) can be known. Further, the EGR device is not operated after the internal combustion engine 2 is started until the EGR control conditions are satisfied, and the initial value peo of the exhaust partial pressure pe is zero.

Therefore, in this embodiment, the exhaust partial pressure estimator P23 first calculates the exhaust partial pressure Pe using the following equation (34), and calculates Pe = Pe
+Ce 2-me/V -Ce2・R1-mC/■・Re-Pi=pe +3 to −me −4 ◆ pe −mc/Pi・
...(34) (However, 4 is a constant in K3.) After that, the new partial pressure calculation unit P24 is configured to calculate the new partial pressure Pi using the following equation (35).

Pi = P-Pe - (35) Also, the fresh air amount calculating section P25 corresponds to the above-mentioned fresh air amount calculating means MIO, and is configured based on the above-mentioned equation (10).

That is, in equation (10), Tio is the reference temperature of fresh air,
Fresh air specific heat ratio Kr, exhaust specific heat ratio Ki, and exhaust temperature T
Since e is approximately constant, the fresh air amount calculating section P25 is configured to calculate the fresh air amount mC using the following equation (10)'.

mc = mco/ (K5- Ti 10 to 6 ・Pe
/Pi)・−(10)' (However, K5 and 6 are constants.) Next, the fuel injection control executed by the electronic control circuit 30 is
This will be explained based on the flowchart shown in the figure. In the following explanation, the amount handled in the current process is expressed as the subscript (k
).

The fuel injection control is activated when the internal combustion engine 2 starts operating, and is constantly repeatedly executed while the internal combustion engine 2 is operating.

When the process starts, first, in step 100, the value of the actual fuel injection amount q is initialized, and in step 110, the actual fuel amount mC is set.
・Integral value of deviation between λ and target fuel amount mc ・λ" Smλ
Set to O. In the subsequent step 120, the pressure inside the intake passage 4a (that is, the intake pressure) P(k) is measured using the intake pressure sensor 12, and in the next step 130, the exhaust partial pressure P(k) is measured.
Set the value of eo to O.

When various initialization processes are executed in steps 100 to 130 in this way, the following step 1
40 is executed, and based on the output signals from the various sensors described above, the fuel-air ratio λ(k), intake pressure P(k), and fresh air temperature Ti are determined.
(k), rotational speed ω(k) of the internal combustion engine 2, cooling water temperature T(
k) and throttle opening θ(k), and step 15
Transition to 0.

In step 150, the above-mentioned (31) is calculated from the intake pressure P(k) and rotational speed ω(k) obtained in step 140.
The EGR amount me is calculated using the formula. In the subsequent step 160, the exhaust gas partial pressure peo in the intake passage 4a obtained in step 130 or the previous execution of this process is determined.
From the intake pressure P(k) obtained in step 140 above,
A new partial pressure Pi is calculated using the above-mentioned equation (35).

In the next step 170, a fresh air amount reference value mco(k) is calculated based on the intake pressure P(k) and the rotational speed ω(k) of the internal combustion engine 2 obtained in the above step 140. Processing as the output section P21 is executed. In the subsequent step 180, the fresh air amount reference value mco(k) obtained in step 170, the exhaust partial pressure peo in the intake passage 4a obtained in step 130 or the previous time this process was executed,
Based on the fresh air temperature Ti (k) obtained in step 140 and the new partial pressure Pi (k) obtained in step 160, the amount of fresh air flowing into the cylinder during the intake stroke using the above-mentioned formula (10) Processing as a fresh air amount reference value P25 for calculating mc (k) is executed, and the process moves to step 190.

Then, in step 190, a target fuel-air ratio λr corresponding to the load of the internal combustion engine 2 is calculated based on the intake pressure P(k) obtained in step 140 and the rotational speed ω(k) of the internal combustion engine 2a.

In step 190, the target fuel-air ratio λr is normally set so that the excess air ratio of the fuel mixture is 1 (that is, the stoichiometric air-fuel ratio), and when the internal combustion engine 2 is operating under high load, the amount of fuel is increased more than usual. In order to increase the output of the internal combustion engine, the target fuel-air ratio λ
r is set to the rich side, and when the internal combustion engine 2 is operated under a light load, the target fuel-air ratio λr is set to the lean side in order to reduce fuel consumption compared to normal and improve fuel efficiency.

Once the target fuel-air ratio λr(k) is set in step 190, the process moves to step 200, where the saturated vapor pressure PS( k), and calculate its value and intake pressure P(k)
The amount of evaporation Vf of fuel adhering to the inner wall surface of the intake passage 4a
By calculating (k) and further dividing the calculation result by the rotational speed ω(k) of the internal combustion engine 2, it is possible to calculate the amount of fuel that evaporates from the wall surface of the intake passage 4a between the previous intake stroke and the next intake stroke. Processing as the second numbing section P8 is executed to calculate the quantity fw(k) (ie, Vf(k)/ω(k)). In the subsequent step 210, the fuel-air ratio λ(k) obtained in step 140 is multiplied by the fresh air amount mc(k) obtained in step 180, and the actual fuel that flowed into the cylinder 2a during the previous intake stroke is calculated. A second multiplier P3 that calculates the quantity mcλ(k)
Then, the process moves to step 220.

Step 220 calculates the actual fuel amount mc λ(k) obtained in step 210, the previous fuel injection amount q, and the amount of fuel evaporation from the inner wall surface of the intake passage 4a obtained in step 200 fw(k). A process of estimating the amount of adhering fuel fw(k) and the amount of evaporative fuel fv(k) is executed based on the amount of adhering fuel fwo and the amount of evaporated fuel fvo determined last time.

Once the adhering fuel 1fw and the evaporated fuel amount fv are estimated in step 220 in this way, the process moves to the following step 230, and the fresh air amount me calculated in step 180 is
(k) and the target fuel-air ratio λr(k) obtained in step 190
The target fuel amount m flowing into the cylinder 2a is obtained by multiplying by
Calculate c·λr(k). After executing the processing as the first multiplier P2, the process moves to step 240.

In step 240, the actual fuel amount mc・λ(k) obtained when this process was executed last time and the target fuel amount mC・λr(
k), the amount of adhered fuel fw(k) and the amount of evaporated fuel fv(
k) and the target fuel amount mc・λ found in step 230
r(k) and the fuel evaporation amount vfw found in step 200
(k), the fuel injection amount q(k) is calculated, and the process moves to step 250.

Then, in step 250, at the fuel injection timing determined based on the detection signal from the crank angle sensor 36,
Fuel injection control is executed in which the fuel injection valve 52 is opened for a time corresponding to the fuel injection amount Q(k) calculated in step 240 to actually perform fuel injection.

Fuel injection control is executed in step 250, and the internal combustion engine 2
Once the fuel supply to is finished, the process moves to step 260, where the EGR amount me(k) obtained in step 150,
Based on the fresh air partial pressure p+rk) obtained in step 160, the fresh air amount mc(k) obtained in step 180, and the exhaust partial pressure Peo obtained during the previous process execution, the above-mentioned (34)
The exhaust partial pressure Pel is calculated using the formula, and the process moves to step 270.

Then, in the following step 270, the calculation result pet of the above step 260 is used for the next processing execution.
0, and the process moves to step 280.

Further, in step 280, the deviation between the actual fuel amount 1mc λ (k) obtained in step 210 and the target fuel amount mc ・λr (k) obtained in step 230 is added to the previously obtained integral value smλ, and the integral is calculated. The process as the sequential addition unit P5 is executed to obtain the value 3mλ, and the process moves to step 290.

Then, in step 290, the adhering fuel fi will be removed in the next process.
The adhering fuel amount fw(k) and the evaporative fuel amount fv(k) set in step 220 are used as the reference values fvo, fvo for the adhering fuel amount and evaporative fuel amount used to estimate f* and the evaporative fuel amount fv. settings, and then proceed to step 140 again.

According to this embodiment described in detail above, fuel injection
EGRIme for calculating is calculated based on the behavior of the valve body 26e of the EGR valve 26. As a result, the EGR amount me can be accurately calculated regardless of the response delay of the valve body 26e and the inflow delay of the recirculated exhaust gas.
This has the excellent effect of making the air-fuel ratio match the target air-fuel ratio, making it possible to further improve exhaust emissions, fuel efficiency, and drivability.

In addition, since the EGR amount me can be calculated using the rotational speed ω of the internal combustion engine and the intake pressure P as parameters according to the above-mentioned equation (31), the EGR amount me is Another effect is that the capacity can be kept small.

Furthermore, even if the vehicles are different, the coefficient is 1. It is only necessary to identify 2 or the constants α, S, etc., and it has an excellent effect of being extremely versatile.

Next, a second embodiment of the present invention will be described.

The second embodiment is configured to use the following equation (4o) as the state equation (34) for determining the exhaust partial pressure pe.

Pe = Pe + to 3-me+ to 5 “Ga” KEG
-...where K5 is the system-specific identified coefficient, KEG
is E obtained from the map of rotational speed ω and intake pressure P
The GR rate and Ga each indicate the previous amount of fresh air taken into the cylinder 2a, which is determined from a map using the rotational speed ω of the internal combustion engine 2 and the intake pressure P as parameters.

In the second embodiment, since the previous fresh air amount (3a) is calculated from the map, it not only has the same effect as the first embodiment, but also has the advantage that the structure of the layer can be simplified.

The fuel injection amount control device for an internal combustion engine with an EGR device of the present invention accurately calculates the amount of recirculated exhaust gas regardless of the response delay of the EGR valve and the inflow delay of the recirculated exhaust gas. This has the excellent effect of making the air-fuel ratio match the target air-fuel ratio.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a schematic configuration diagram showing an internal combustion engine and its peripheral devices, and FIG. 3 is a block diagram showing the configuration of the present invention.
The figure is a block diagram showing the fuel injection control system in the electronic control circuit, FIG. 4 is a block diagram showing the first calculation section P1 in FIG. 3, and FIG. 5 is a block diagram showing the fuel injection control executed by the electronic control circuit. It is a flowchart. Ml, 8... Throttle valve M2.4a... Intake passage M3, M24... EGR device M4.2a... Cylinder M5.2... Internal combustion engine M
6... Operating state detection means 12... Intake pressure sensor 1
4... Fresh air amount sensor 34... Rotation speed sensor M7
...Behavior estimation means M8...First estimation means M9...Second estimation means M10...Fresh air amount calculation means Mll...Fuel amount calculation means Ml2...Fuel injection valve Ml3. ...Fuel injection control means 50...Electronic control circuit agent Patent attorney Tsutomu Sadate (and 2 others) M5 Figure

Claims (1)

[Scope of Claims] An EGR device is provided that recirculates exhaust gas to an intake passage downstream of a throttle valve, and a mixture of the exhaust gas recirculated by the EGR device and fresh air flowing in through the throttle valve enters the cylinder. An intake fuel injection amount control device for an internal combustion engine with an EGR device, the operating state detecting the rotational speed of the internal combustion engine, the pressure inside the intake passage, and the temperature of fresh air flowing in through the throttle valve. The behavior of the EGR valve of the EGR device is captured by the behavior estimation means based on the pressure inside the intake passage of the internal combustion engine detected by the detection means and at least the operating state detection means, and the flow is returned to the intake passage based on the behavior of the EGR valve. a first estimating means for estimating the amount of exhaust gas to be emitted; the displacement estimated by the first estimating means; the rotational speed of the internal combustion engine detected by the operating state detecting means; and the pressure inside the intake passage; and the fresh air temperature to estimate the fresh partial pressure of the air-fuel mixture existing in the intake passage and the exhaust partial pressure.
and fresh air amount calculation means for calculating the amount of fresh air sucked into the cylinder during the intake stroke from the fresh partial pressure and the exhaust partial pressure estimated by the second estimating means; a fuel amount calculation means for calculating the amount of fuel to be supplied into the cylinder during the intake stroke by multiplying the fresh air amount calculated by the calculation means and a preset target fuel-air ratio; and the calculated fuel 1. A fuel injection amount control device for an internal combustion engine with an EGR device, comprising: fuel injection control means for supplying fuel by driving a fuel injection valve according to the amount of fuel injection.