JPH0953519A - Exhaust recirculation controller of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control EGR quantity to its adequate value even during transient operation without being influenced by any environmental change by setting a target EGR quantity absorbed in cylinder(s) based upon the intake air quantity and the set target EGR rate of an engine. SOLUTION: An intake air flow is found out from the output value of the intake air flow shown by an air flow meter 16 by means of a conversion table. By multiplying the found cylinder intake air quantity with a target EGR rate, the target EGR quantity to the cylinder(s) is found out. Thus while the target EGR quantity is calculated so as to apply advance treatment to each delayed amount, a required flow passage area of an EGR passage is found out to know the control value of an EGR control valve 9. Next, a throttle valve 31 is closed for the purpose of improving exhaust gas and executing noise countermeasure principally during idling and/or low load operation and simultaneously the opening of the EGR control valve 9 is controlled to carry out EGR control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation (EGR) control device for an internal combustion engine.

[0002]

2. Description of the Related Art As a conventional transient control system for an EGR control system for an internal combustion engine, there is a system disclosed in Japanese Patent Laid-Open No. 58-35255. In a vehicle diesel engine, an EGR control device is generally adopted to reduce NOx. In the EGR control device, for example, a target EGR rate is set for each operating state consisting of the engine speed, the fuel injection amount, the engine load such as the accelerator opening degree, and the intake system and the exhaust system are set to the target EGR rate. There is a device in which the opening degree of an EGR control valve interposed in the EGR passage connecting the two is controlled.

[0003]

However, for example, the intake air amount changes in the lowland and the highland because the air density changes even under the same operating conditions. Therefore, even if the EGR control valve opening is controlled so as to reach the target EGR rate set for each operating state, the EGR control valve opening is constant with respect to the change in the air density in the same operating state as described above. Therefore, the amount of EGR is too large and smoke and PM (exhaust particulates) increase, and
In some cases, the amount was too small to obtain a sufficient NOx reduction effect.

Further, there is a problem in that if EGR is performed when the fuel injection amount rapidly increases, such as during rapid acceleration, the excess air ratio is greatly reduced and smoke and exhaust particulate matter (PM) increase. Conventionally, in consideration of this, the EGR is cut when the fuel injection amount is rapidly increased and a large excess air ratio is likely to be reduced, such as during rapid acceleration.

However, in such a conventional EGR control system, the EGR is cut more than necessary,
On the other hand, it is difficult to optimally control EGR during a transition because it is not cut.
The increase in NOx is caused by the shortage of R, and if it is not done, the increase in PM still occurs.
A problem was found that GR optimization was not possible. Further, in the case of an engine with a supercharger, it has also been found that the above-mentioned problems are more remarkable because variations in the operating characteristics of the supercharger occur due to oil deterioration and the like.

The present invention has been made in view of the above-mentioned conventional problems, and it is possible to control the smoke amount by controlling the EGR amount to an appropriate value during the transient operation without being affected by the environmental change during the steady operation. EG of an internal combustion engine in which PM, NOx, etc. are reduced in a well-balanced manner so that good exhaust gas purification performance can be obtained.
An object is to provide an R control device.

[0007]

The invention according to claim 1 is
As shown by a solid line in FIG. 1, an exhaust gas recirculation control device for an internal combustion engine, which recirculates a part of exhaust gas to an intake system via an EGR control valve provided in an EGR passage connecting an exhaust system and an intake system of the engine. In, an intake air flow rate detecting means for detecting a flow rate of air taken into the engine, an operating state detecting means for detecting an operating state of the engine, and a target EGR rate for setting a target EGR rate based on the detected operating state of the engine. Rate setting means, target EGR amount setting means for setting a target EGR amount to be sucked into the cylinder based on the detected intake air flow rate of the engine and the set target EGR rate, and the set target EGR
Valve opening control means for controlling the valve opening of the EGR control valve based on the amount.

In this way, even if the intake fresh air amount changes due to a change in the environment, for example, the air density changes even in the same operating condition in the lowland and the highland, the change in the intake fresh air amount is reflected in the intake air. The target EGR rate is detected as a change in the flow rate, and the target EGR rate is set for the detected value of the intake air flow rate.
It is set as an EGR rate called GR amount.

Therefore, even if the target EGR rate is the same, if the intake fresh air amount changes due to changes in the air density, etc.
The R amount changes, and the EGR control valve opening also changes. That is, even if the environment changes, the target EGR amount changes but the target EGR amount changes.
The rate does not change and can be controlled to the optimum EGR rate. The invention according to claim 2 is, as shown by a dotted line in FIG.
The valve opening control means performs a predetermined advance process on the target EGR amount set by the target EGR amount setting means to set a command EGR amount, and the command EGR amount setting means. Valve opening degree control amount setting means for setting the valve opening degree control amount of the EGR control valve based on the command EGR amount set by the means.

With this configuration, the EGR is performed during the transient operation.
EGR amount passing through control valve and EGR sucking into cylinder
There is a response delay with respect to the target EGR amount, but by advancing the target EGR amount and setting the command EGR amount,
The effect of response delay can be suppressed and good EG can be achieved even during transient operation.
The R rate can be controlled. In the invention according to claim 3, in the predetermined advance processing in the command EGR amount setting means, a time constant of the advance processing is determined according to an intake system capacity from the EGR control valve to the cylinder inlet and a cylinder capacity. It is characterized by being done.

With this configuration, the delay of the cylinder intake EGR amount with respect to the EGR amount passing through the EGR control valve during the transient operation can be effectively suppressed by performing the advance process based on the dynamic characteristic. . Further, the invention according to claim 4 is characterized in that the command EGR amount setting means sets the command EGR amount by performing the advance processing by the following equation.

Tqec = GKQE × Tqeco + (GKQE-1) × Rqec _n-1 Rqec = Rqec _n-1 × (1-Kv) + Tqeco × Kv Kv = NV × VC / VM / CYL Tqec: command EGR amount GKQE: advance Gain (constant) Tqeco: Target EGR amount NV: Volume efficiency equivalent value VC: Cylinder volume VM: Intake system volume CYL: Number of cylinders In this way, advance processing based on the dynamic characteristics can be performed with high accuracy.

Further, in the invention according to claim 5, as indicated by a chain line in FIG. 1, the command EGR amount setting means is configured so that the command EGR amount and the EGR amount actually sucked into the cylinder are desired to be sucked into the cylinder. And a response characteristic setting unit configured to set response characteristic between the EGR gas and the EGR control valve, and a dynamic characteristic estimation unit configured to estimate a dynamic characteristic until the EGR gas is sucked into the cylinder from the EGR control valve. A command EG which is desired to pass the EGR control valve by advancing the target EGR amount based on the estimated dynamic characteristic so that
It is characterized in that the R amount is set.

By doing so, the advance processing can be performed so that the response characteristic is set in consideration of the dynamic characteristic. In the invention according to claim 6, the dynamic characteristic estimating means estimates the time constant of the dynamic characteristic according to the engine speed, the volumetric efficiency, the intake system capacity from the EGR control valve to the cylinder inlet, and the cylinder capacity. The response characteristic setting means sets the time constant of the response characteristic to a positive number smaller than the time constant of the dynamic characteristic.

With this configuration, the response delay can be reduced as much as possible without causing hunting due to overshoot or undershoot. Also,
The invention according to claim 7 is, as shown by a two-dot chain line in FIG.
An intake pressure detection unit that detects an intake pressure and an exhaust pressure detection unit that detects an exhaust pressure are provided, and the valve opening control amount setting unit includes the set command EGR amount and the detected intake pressure and exhaust pressure. The EGR required flow passage area is calculated based on the atmospheric pressure, a target valve opening corresponding to the EGR required flow passage area is set, and a predetermined advance process is performed on the target valve opening to obtain a valve opening control amount. It is characterized by setting.

With this configuration, the EGR required flow passage area can be accurately calculated according to the command EGR amount and the differential pressure between the intake pressure and the exhaust pressure, and the operation delay of the EGR control valve or the like can be dealt with. The valve opening control amount can be set with high accuracy by the predetermined advance processing.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. Referring to FIG. 2 showing the overall configuration of one embodiment, a supercharger 1 uses an air compressor 2 to remove air from an air filter 2 and suck air into an intake passage 3.
A is supercharged by compression and fed to the intake manifold 4 on the downstream side.

On the other hand, to the fuel injection nozzle 6 mounted in the combustion chamber of the engine 5, the fuel is pressure-fed and supplied from the injection pump 7 to each cylinder, and the fuel is supplied from the fuel injection nozzle 6 toward the combustion chamber. The injected fuel is ignited and burned at the end of the compression stroke. Further, an EGR passage 10 having an EGR control valve 9 interposed between the exhaust manifold 8 and the intake manifold 4 is connected, and the intake air is throttled to the upstream side of the intake compressor 1A of the intake passage 3 during EGR control to be discharged. A throttle valve 31 for increasing the differential pressure between the atmospheric pressure and the intake pressure to facilitate the EGR is provided, and the throttle valve 31 is throttled at the same time as the throttle valve 31 is throttled for improving exhaust and noise measures mainly during idling and low load. The EGR control is performed by controlling the opening degree of the control valve 9. Specifically, the negative pressure from the vacuum pump 11 is guided to the diaphragm device 33 via the solenoid valve 32 to throttle the throttle valve 31, and at the same time, the negative pressure is diluted with the atmosphere by the solenoid valve 12 whose duty is controlled. By controlling the ratio, the pressure introduced into the pressure chamber of the EGR control valve 9 is controlled, and by controlling the opening, the EGR rate is controlled. The EGR rate and the fuel injection control are performed by the control unit 13.

The EGR control valve 9 is provided with a lift sensor 34 for detecting the lift amount of the valve body. The exhaust gas after combustion is contained in the exhaust gas after the exhaust turbine 1B of the supercharger 1 is rotationally driven by the exhaust manifold 8.
M and the like are collected by the filter 14, silenced by the muffler 15, and then released into the atmosphere.

An air flow meter 16 for detecting the intake air flow rate is provided in the intake passage 3 upstream of the intake compressor 1A of the supercharger 1, a rotation speed sensor 17 for detecting an engine rotation speed Ne, and the fuel injection. A lever opening sensor 18, which detects the control lever opening of the pump 7,
A water temperature sensor 19 for detecting the water temperature is provided, and the maximum allowable fuel injection amount commensurate with the cylinder intake air amount is set as described later while detecting the intake system pressure and the exhaust system pressure based on these detected values. To be done.

Various calculations by the control unit 13 will be described below. First, a routine for calculating the intake system pressure (hereinafter referred to as intake pressure) Pm will be described with reference to the flowchart of FIG. This routine corresponds to the intake pressure detecting means. In step (denoted as S in the figure. The same applies to the following), at 1, the intake air amount Qac per cylinder, the intake EGR amount Qec per cylinder, the intake air temperature Ta, the EGR temperature Te, which are respectively calculated by another routine described later,
Input the value Kin equivalent to the volumetric efficiency.

In step 2, the intake pressure Pm is calculated by the following equation based on each value input in step 1 and the volume ratio (volume per cylinder / collector volume of the intake system) Kvol known in advance. . Pm = R / Kvol / Kin × (Qac × Ta + Qec
XTe) Next, a routine for calculating the exhaust system pressure (EGR outlet pressure, hereinafter referred to as exhaust pressure) Pexh will be described with reference to the flowchart of FIG. This routine corresponds to the exhaust pressure detecting means.

At step 11, the exhaust amount Qe exhausted from one cylinder calculated by another routine described later, respectively.
Input xh, intake EGR amount Qec per cylinder, exhaust temperature Texh, and engine speed Ne. Step 12
Then, each value entered in step 11 and the constant Kpexh,
Opexh and the exhaust pressure Pexh by the following equation based on
Is calculated.

Pexh = (Qexh-Qe) × Texh
× Ne × Kpexh + Opexh FIG. 5 shows a flowchart for calculating the intake air amount per cylinder (hereinafter referred to as cylinder intake air amount) Qac. In step 21, the output value (voltage) Q ₀ of the intake air flow rate from the air flow meter 16 is read.

In step 22, the intake air flow rate Qasm is obtained from the output value Q _{0 using a} conversion table. The air flow meter 16 and the function of step 22 constitute intake air flow rate detecting means. In step 23, a weighted average process is performed on the intake air flow rate Qasm to obtain Qa.
Find s0.

In step 24, the engine rotation speed Ne detected by the rotation speed sensor 17 is read. Step 25
Then, the cylinder intake air amount Qac0 with respect to the intake air flow rate detected by the air flow meter 16 is calculated from the weighted average value Qas0 of the intake air flow rate, the engine rotation speed Ne, and the constant Kc by the following equation.

Qac0 = Qas0 / Ne × Kc In step 26, the intake air amount Qac per cylinder is
The delay processing is performed for 0 times n times, and the intake air amount Qacn at the intake collector inlet is calculated. Specifically, the Qac0 from the latest to the past n times before is stored, and the Qac0 value n times before is taken out as Qacn.

At step 27, the constant Kvol (= Vc /
Vm, Vc: 1 cylinder volume, Vm: intake system volume),
The intake air amount Qac per cylinder is calculated by the following equation using the volumetric efficiency equivalent value Kin obtained as described later. Qac = Qac _n-1 x (1-Kvol x Kin) + Qa
cn × Kvol × Kin This is a first-order lag equation, and Kvol × Kin is Qac.
The percentage of n (fresh air entering the intake air collector) enters the cylinder, so the latter term represents the amount of fresh air that entered the cylinder this time, and the previous term entered the cylinder by the previous time. Since it represents the fresh air amount, by adding these, the current cylinder intake air Qac is obtained.

In this way, the intake air amount Qac per cylinder can be accurately obtained. Next, a routine for calculating the intake EGR amount per cylinder during EGR control will be described with reference to the flowchart of FIG. In step 31, the EGR flow rate Qe to the intake system calculated by the routine described below is input.

In step 32, the engine speed Ne is read. In step 33, the EGR amount Qecn per cylinder volume sucked into the intake collector portion is calculated from the EGR amount Qe, the engine rotation speed Ne, and the constant KCON # by the following equation. Qecn = Qe / Ne × KCON # At step 34, the constant Kvol and the volumetric efficiency equivalent value K
The cylinder EGR amount Qec sucked into the cylinder is calculated by the following equation using in and.

Qec = Qec _n-1 × (1-Kvol × K
in) + Qecn × Kvol × Kin FIG. 7 is a flowchart of a routine for calculating the temperature Ta of intake air (fresh air not containing EGR gas). still,
This process is unnecessary when the sensor has a sensor that directly detects the intake air temperature.

In step 41, the intake pressure Pm _n-1 obtained last time is input. In step 42, the intake air temperature Ta is calculated from the relationship of adiabatic change according to the following equation. Ta = TA # × (Pmn _-1 / PA #) ^{(K-1) / K} + TOF
F # Here, TA # and PA # are the temperature and pressure in the standard state, K is the specific heat ratio of air, and TOFF # is the temperature increase due to the intake pressure increase from the atmosphere to the intake collector. , These values may be corrected by multiplying by the correction coefficients K _{t A} and K _tOFF which increase proportionally with the rise of the water temperature.

FIG. 8 is a flowchart of a routine for calculating the temperature Te at the inlet of the EGR gas to the intake collector. In step 51, the exhaust gas temperature Texh obtained in the routine described later is input. In step 52,
The EGR temperature Te is calculated by the following equation.

Te = Texh × KTLOS # KTLOS # is a temperature reduction coefficient of the EGR due to the EGR passage. FIG. 9 is a flowchart of a routine for calculating the volumetric efficiency equivalent value Kin. . In step 61, the intake pressure Pmn _-1 obtained last time is input. In step 62, the pressure correction coefficient Kinp is calculated from the intake pressure Pmn _-1 using a table as shown in FIG.

In step 63, from the engine speed Ne,
The rotation correction coefficient Kin is calculated using the table shown in FIG.
Calculate n. In step 64, the pressure correction coefficient Ki
Using np and the rotation correction coefficient Kinn, the volumetric efficiency Ki
n is calculated by the following equation. Kin = Kinp × Kinn In addition, swirl control valve (SC
V), the volumetric efficiency K is further multiplied by the SCV correction coefficient Kins set proportionally to the SCV opening.
It suffices to calculate in.

FIG. 12 is a flowchart of a routine for calculating the exhaust gas temperature Texh at the EGR outlet. In addition, this process, if you have a sensor that directly detects the exhaust temperature,
It is unnecessary. In step 71, the fuel injection amount Qfo injected retrospectively by the cycle delay from the fuel injection in the intake stroke to the exhaust stroke is input.

At step 72, the intake air temperature Tno calculated retroactively by the same cycle delay as described above is input. In step 73, the exhaust pressure Pexh _n-1 calculated in FIG.
Enter In step 74, the basic exhaust gas temperature Texhb is retrieved from the table as shown in FIG. 13 from the cycle delay fuel injection amount Qfo.

In step 75, the intake temperature correction coefficient Ktehxh1 is calculated from the intake temperature Tno by the following equation. Ktexh1 = (Tno / TA #) ^{KN The} intake air temperature correction coefficient Ktehxh1 is obtained as the KN-th power of the ratio of the intake air temperature Tno to the standard temperature TA # as described above. It is shown.

In step 76, the exhaust pressure Pexh is set.
_The temperature rise correction coefficient Ktexh2, which is the rate of rise in exhaust gas temperature due to the rise in exhaust gas pressure, is calculated from _{n-1 based} on the adiabatic change. Ktexh2 = (Pnehx _n-1 / PA #) ^{(Ke-1) / Ke In} step 77, the basic exhaust gas temperature Texhb, the intake air temperature correction coefficient Ktexh1, and the temperature increase correction coefficient Ktehx.
From h2, the exhaust temperature Texh is calculated by the following equation.

Texh = Texhb × Ktexh1 × Ktexh2 FIG. 14 is a flowchart of a routine for calculating the EGR flow rate Qe. . In step 81, the intake pressure Pm, the exhaust pressure Pexh, and the actual lift amount Lifts of the EGR control valve are input. In step 82, the opening area AVe of the EGR passage is retrieved from the actual lift amount Lifts from a table as shown in FIG. 15, for example.

At step 83, the EGR flow rate Q is calculated by the following equation.
Calculate e. Qe = Ave × (Pexh−Pm) ^1/2 × KR # where KR # is a constant and the flow velocity q at the front-rear differential pressure ΔP.
Equation q = (ΔP · 2ρ) ^1/2 to a value approximately equal to (2ρ) ^1/2 (where ρ is the density of the exhaust gas). FIG. 16 shows a flowchart of a cycle processing routine for the cylinder intake air amount, the fuel injection amount, and the cylinder intake temperature.

In step 91, the cylinder intake air amount Qa
c, fuel injection amount Qsol, and cylinder intake air temperature Tn are input. The cylinder intake air temperature Tn can be calculated, for example, by the following equation. (Qac × Ta + Qec × Te) / (Qac + Qec) In step 92, the Qac, Qsol, and Tn are cycled. In order to match the phase with the exhaust stroke, delay processing is performed by Qac and Tn in the intake stroke by the number of cylinders minus one, and by Qsol in the compression stroke by the number of cylinders minus two.
The processing ends with xh, Tno, and Qfo.

FIG. 17, FIG. 19 and FIG. 20 show flowcharts of actual EGR control. FIG. 17 is a flowchart of a routine for calculating the command lift amount Liftt of the EGR control valve. In step 101, the intake pressure Pm,
The exhaust pressure Pexh and the required EGR flow rate Tqe are input.

In step 102, the required flow passage area Tav of the EGR control valve is calculated by the following equation. Here, KR # is the one used in step 83 of FIG. Step 10
At 3, the target lift amount Mlift is calculated from the Tav from a table showing the relationship between the flow path area and the lift amount as shown in FIG. 18, for example. In step 104, the target lift amount Mlift is advanced by the valve operation delay, and the value is output as the command lift amount Liftt.

FIG. 19 is a flow chart for calculating the required EGR flow rate Tqe. In step 111, the engine speed Ne, the target EGR rate Megr, the cylinder intake air amount Q
Enter ac. In step 112, the target EGR amount Tqec0 for the cylinder is obtained by multiplying the cylinder intake air amount Qac by the target EGR rate Megr. The function of this step 112 constitutes a target EGR amount setting means.

In step 113, the intake EGR amount Tq
A process for advancing the intake system volume is advanced to ec0 (see FIG. 25 described later) to obtain a command EGR amount Tqec. The function of this step 113 constitutes the command EGR amount setting means. In step 114, the required EGR flow rate T is calculated from the commanded EGR amount Tqec, the engine rotation speed Ne and the constant KCON #.
Find qe.

FIG. 20 is a flow chart of a routine for calculating the target EGR rate Megr. This routine constitutes a target EGR rate setting means. In step 121, the engine speed Ne and the fuel injection amount Qsol are input. In step 122, based on the engine speed Ne and the fuel injection amount Qsol which is a representative value of the load, for example, as shown in FIG.
The target EGR rate Megr is searched from the table as shown in FIG.

FIG. 22 is a flow chart of a routine for calculating the fuel injection amount Qsol. In step 131, the engine speed Ne and the control lever opening CL are read. In step 132, the basic fuel injection amount Mqdrv is calculated from the engine speed Ne and the control lever opening CL.
Is searched from a table as shown in FIG. 23, for example.

In step 133, the basic fuel injection amount M
Qs is corrected by correcting qdrv with various correction factors such as water temperature.
ask ol. In step 134, the maximum fuel injection amount is limited and output as Qsol. FIG. 25 is a flowchart of a routine for setting the command lift amount Liftt by advancing the target lift amount Mlift in step 104 of FIG.

In step 145, the target lift amount Mift
Read t. In step 146, the read target lift amount Mlift is compared with the previous value Mlift1. If the current value Mlift is greater than or equal to the previous value Mlift1, the routine proceeds to step 147, where the time constant TCL1 # during the operation from the small lift amount to the large lift amount is set as the time constant TCL1.
If the current value Mlift is smaller, the routine proceeds to step 148, where the time constant TCL2 # during the operation from the large lift amount to the small lift amount is set as the time constant TCl.

In step 149, advance processing is performed by the following equation to calculate the command lift amount Liftt. Liftt = GKL♯ × Mlift- (GKL♯- 1) × Rlift n-1 _{However, Rlift n = Rlift n-1} × (1-Tcl) + Mlift × Tcl Figure 24, at step 113 of FIG. 19, the command EGR amount T
9 is a flowchart of a routine for setting qec by advancing the target EGR amount Tqe0.

In step 151, the target EGR amount Tqeo
Read. In step 152, advance processing is performed by the following equation to calculate the command EGR amount Tqec. Tqec = GKQE # × Tqe0 + (GKQE # -1) × Rqe _n-1 Rqe = Rqe _n-1 × (1-Kv) + Tqe0 × Kv Kv = Kin × Vc / Vm / CYLN # Thus detected by the air flow meter The target EGR amount is calculated by using the intake air flow rate thus determined, and the advance processing for each delay is performed, while the required flow passage area of the EGR passage is obtained from the intake pressure and the exhaust pressure, and the EGR control valve By determining the control value, it is possible to optimally control the EGR regardless of the way of driving and various variations, so that it is possible to absorb the environmental variations during steady operation and optimize during transient operation. Exhaust gas purification performance can be favorably maintained over the entire operating range.

Next, an embodiment of the invention according to claim 5 will be described. The outline of the first embodiment will be described. When the target EGR amount to be sucked into the cylinder is set, and when the engine rotation speed Ne and the estimated volumetric efficiency and the dynamic characteristics of the EGR gas from the EGR control valve to the cylinder are determined, A constant is estimated, and a target EGR amount desired to pass through the EGR control valve is calculated by performing advance processing from the target EGR amount and the time constant,
Target EGR control valve lift amount corresponding to the target EGR amount
(Opening degree) is calculated and controlled so that the lift amount is obtained.

When the time constant of the dynamic characteristic at this time is τa, the second target EGR amount to be passed through the EGR control valve is a Laplace conversion calculation formula (hereinafter, s represents a Laplace operator).
It will be as follows. M ₂ Qe = {(1 + G ・ τa ・ s) / (1 + τa ・ s)} ・ MQce ・ ・ (1) However, the dynamic characteristic from the EGR control valve to the cylinder: τa (sce) Target to pass the EGR control valve EGR amount: M ₂ Qe (kg / st) Advance gain: G Target EGR amount desired to be sucked into the cylinder: MQce (kg / st) As a result, EGR amount Qce actually sucked into the cylinder
Is approximately expressed using the following equation. At this time, EGR
The target EGR amount that is desired to pass through the control valve is equal to the EGR amount that actually passes through the EGR control valve.

Qce = {(1 + G · τa) / (1 + τa) ² } · MQce (2) In this method, the EGR amount Qce actually sucked into the cylinder depends on how the advance gain G is selected. In some cases, the target EGR amount desired to be inhaled may be overshot, and if the overshoot is reduced, there is a problem that the responsiveness deteriorates.

When the target EGR amount to be sucked into the cylinder is used as a step input, the EGR amount sucked into the cylinder when the process according to the formula (1) is performed, and when the process according to the formula (1) is not performed FIG. 26 shows the simulation result of the EGR amount sucked into the cylinder. From FIG. 26, it is understood that by performing the processing according to the equation (1), overshoot occurs when G> 1 and the responsiveness deteriorates when G <1.

The present embodiment takes measures against the above points. The system configuration of this embodiment is shown in the block diagram of FIG. The cylinder target EGR amount setting unit 31 sets the first target EGR amount to be sucked into the cylinder. τs setting section
32 is the first target EGR amount and the EG actually inhaled
Set the response characteristic (time constant) between R amount.

The τa estimating unit 33 estimates the engine rotational speed Ne detected by the rotational speed sensor 17 and the volumetric efficiency estimating unit 34.
Based on the volumetric efficiency estimated by the EGR gas and the dynamic characteristics until the EGR gas is sucked into the cylinder from the EGR control valve.
Estimate (time constant). The advance processing calculation unit 35 performs advance processing based on the estimated EGR dynamic characteristic so that the set cylinder intake EGR amount response characteristic is obtained, and passes the EGR control valve from the first target EGR amount. A desired second target EGR amount is calculated.

The target EGR control valve opening area calculator 36 calculates the target EGR control valve opening area from the second target EGR amount.
Calculate the lift amount. The volume efficiency estimation unit 34 estimates the cylinder volume efficiency using the engine rotation speed Ne and the collector internal pressure. You may search by the map as shown in FIG. Next, the operation will be described assuming a 4-cylinder diesel engine.

In the τs setting section 32, the first target EG
The time constant τs of the response characteristic between the R amount and the actually inhaled EGR amount is set. At that time, as shown in the equation (3),
It is set to be a positive number smaller than the time constant τa of the dynamic characteristic from the EGR control valve 9 to the cylinder estimated by the τa estimation unit 33. 0 <τs <τa (3) Further, the advance processing in the advance processing calculation unit 35 is performed by the time constant τs of the response characteristic, the time constant τa of the dynamic characteristic, and the first target E.
Using the GR amount, an arithmetic expression such as the expression (4) is used.

MQe = {(1 + τa · s) / (1 + τs · s)} · MQce ·· (4) At this time, the EGR amount actually sucked into the cylinder is approximately expressed by using the equation (5). It However, the second target EGR amount that is desired to pass through the EGR control valve and the EGR amount that actually passes through the EGR control valve are equal. Qce = {1 / (1 + τs · s)} · MQce (5) When the first target EGR amount to be sucked into the cylinder is used as the step input, the processing according to the above equation (4) is performed. The EGR amount sucked into the cylinder and the EGR amount sucked into the Linda when the process is not performed (this is sucked into the cylinder when the process of the formula (1) is not performed in the first embodiment. 29 shows the simulation result of (equal to EGR amount) (τs was set to 0.05 sec and τa was set to 0.13 sec).

From FIG. 29, it can be seen that the responsiveness is improved by performing the processing according to the equation (4). Also, τ
The response is improved as s is decreased, but the second target EGR amount (= actually E
The amplitude of the EGR amount passing through the GR control valve) becomes large,
The opening width required for the EGR control valve may become too large and exceed the limit.
It is sufficient to set s as small as possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration and functions of the present invention.

FIG. 2 is a diagram showing a system configuration of the first embodiment of the present invention.

FIG. 3 is a flowchart of a routine for calculating an intake system pressure according to the above embodiment.

FIG. 4 is a flowchart of a routine for similarly calculating an exhaust system pressure.

FIG. 5 is a flowchart of a routine for similarly calculating a cylinder intake air amount.

FIG. 6 is a flowchart of a routine for similarly calculating a cylinder intake EGR amount.

FIG. 7 is a flowchart of a routine for similarly calculating an intake air temperature.

FIG. 8 is a flowchart of a routine for similarly calculating the EGR temperature.

FIG. 9 is a flowchart of a routine for similarly calculating a volumetric efficiency equivalent value.

FIG. 10 is a pressure correction table used to calculate the volumetric efficiency equivalent value.

[FIG. 11] Similarly, a rotation correction table.

FIG. 12 is a flowchart of a routine that similarly calculates the exhaust temperature.

FIG. 13 is a table of basic exhaust temperature used for calculating the exhaust temperature.

FIG. 14 is a flowchart of a routine that similarly calculates an EGR flow rate.

FIG. 15 is a valve lift passage area characteristic table used for the EGR flow rate calculation.

FIG. 16 is a flowchart showing a cycle processing routine for each value.

FIG. 17 is a flowchart of a routine that similarly calculates a command EGR valve lift amount.

FIG. 18 is a flow passage area lift characteristic table used for calculating the commanded EGR valve lift amount.

FIG. 19 is a flowchart of a routine for similarly calculating a required EGR amount.

FIG. 20 is a flowchart of a routine that similarly calculates a target EGR rate.

FIG. 21 is a target EGR used to calculate the target EGR rate.
Rate map table.

FIG. 22 is a flowchart of a routine for similarly calculating a fuel injection amount.

FIG. 23 is a fuel injection amount map table used to calculate the fuel injection amount.

FIG. 24 is a flowchart of a routine for calculating a command lift amount.

FIG. 25 is a flowchart of a routine for calculating a command EGR amount.

FIG. 26 is a diagram showing a simulation result of the first embodiment.

FIG. 27 is a block diagram showing the system configuration of the second embodiment.

FIG. 28 is a volume efficiency setting map.

FIG. 29 is a diagram showing a simulation result of the second embodiment.

[Explanation of symbols]

 5 Diesel engine 6 Fuel injection nozzle 7 Fuel injection pump 9 EGR control valve 13 Control unit 16 Air flow meter 17 Rotation speed sensor 18 Lever opening sensor 19 Water temperature sensor 31 Throttle valve 34 Lift sensor

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location F02D 45/00 366 F02D 45/00 366F

Claims (7)

[Claims] 1. An EGR connecting an exhaust system and an intake system of an engine.
In an exhaust gas recirculation control device for an internal combustion engine, which recirculates a part of exhaust gas to an intake system via an EGR control valve provided in a passage, an intake air flow rate detection means for detecting a flow rate of air taken into the engine, and An operating state detecting means for detecting an operating state, a target EGR rate setting means for setting a target EGR rate based on the detected engine operating state, and a detected intake air flow rate of the engine and a set target EGR.
Target EGR amount setting means for setting a target EGR amount to be sucked into the cylinder based on the ratio, and valve opening control means for controlling the valve opening of the EGR control valve based on the set target EGR amount. An exhaust gas recirculation control device for an internal combustion engine, comprising: 2. The valve opening control means is a target EGR set by the target EGR amount setting means.
Command EGR amount setting means for setting a command EGR amount by performing a predetermined advance process on the amount, and command EG set by the command EGR amount setting means
The exhaust gas recirculation control device for an internal combustion engine according to claim 1, further comprising valve opening degree control amount setting means for setting a valve opening degree control amount of the EGR control valve based on the R amount. 3. The predetermined advance processing in the command EGR amount setting means is characterized in that the time constant of the advance processing is determined according to the intake system capacity from the EGR control valve to the cylinder inlet and the cylinder capacity. The exhaust gas recirculation control device for an internal combustion engine according to claim 2. 4. The exhaust gas recirculation control device for an internal combustion engine according to claim 3, wherein the command EGR amount setting means sets the command EGR amount by performing the advance processing by the following equation. Tqec = GKQE * Tqeco + (GKQE-1) * Rqecn _-1 Rqec = Rqecn _-1 * (1-Kv) + Tqeco * Kv Kv = NV * VC / VM / CYL Tqec: command EGR amount GKQE: advance gain (constant) ) Tqeco: Target EGR amount NV: Volume efficiency equivalent value VC: Cylinder volume VM: Intake system volume CYL: Number of cylinders 5. The command EGR amount setting means, a response characteristic setting means for setting a response characteristic between a target EGR amount to be sucked into the cylinder and an EGR amount actually sucked into the cylinder, and EGR gas Dynamic characteristic estimating means for estimating a dynamic characteristic from the EGR control valve until being sucked into the cylinder, and a target EGR amount based on the estimated dynamic characteristic so as to obtain the set response characteristic. The exhaust gas recirculation control device for an internal combustion engine according to claim 2, wherein a command EGR amount that is desired to pass through the EGR control valve is set by performing a forward process. 6. The dynamic characteristic estimating means estimates a time constant of the dynamic characteristic according to the engine speed, the volumetric efficiency, the intake system capacity from the EGR control valve to the cylinder inlet, and the cylinder capacity,
The exhaust gas recirculation control device for an internal combustion engine according to claim 5, wherein the response characteristic setting means sets the time constant of the response characteristic to a positive number smaller than the time constant of the dynamic characteristic. 7. An intake pressure detecting means for detecting an intake pressure, and an exhaust pressure detecting means for detecting an exhaust pressure, wherein the valve opening degree control amount setting means includes the set command EG.
EGR based on the R amount and the detected intake pressure and exhaust pressure
The required flow passage area is calculated, a target valve opening corresponding to the EGR required flow passage area is set, and a predetermined advance process is performed on the target valve opening to set a valve opening control amount. The exhaust gas recirculation control device for an internal combustion engine according to any one of claims 2 to 6.