JPH10238412A - Egr controller for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly control the feedback of an EGR quantity depending on pressure difference generated in an EGR passage by computing a request EGR valve opening area based on a request EGR quantity and an EGR differential pressure determined in accordance with the operating state of an engine and computing a desired EGR valve opening degree considering a flow coefficient. SOLUTION: During the operation of an engine, a prescribed EGR area is decided based on engine rotating speed, fuel injection quantity, cooling water temperature, etc., in a desired EGR quantity setting means 31, a desired EGR quantity is computed based on a desired EGR rate and an inlet air quantity which are set depending on the engine rotating speed, the fuel injection quantity in the EGR area. Then, EGR differential pressure is computed depending on inlet pressure and exhaust pressure detecting signals by an EGR differential pressure detecting means 32 and a request EGR valve opening area corresponding to the desired EGR quantity is calculated 33 based on the EGR differential pressure. Then, the desired opening degree of an EGR valve is computed 38 depending on a flow coefficient and the request EGR valve opening area which are set 36 based on the rotating speed and load of the engine to control the EGR valve.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an apparatus for controlling an EGR amount (amount of exhaust gas recirculated to an intake system) according to a pressure difference generated between both ends of an EGR passage.

[0002]

2. Description of the Related Art In an automobile engine or the like, in order to suppress the generation of NOx which is a harmful component in exhaust gas,
A so-called EGR device for recirculating inert exhaust gas in the intake passage is provided.

[0003] However, if the generation of NOx is suppressed by recirculating the inactive exhaust gas into the intake passage, the combustion atmosphere becomes insufficient in oxygen, and the amount of exhaust particulates, HC, CO and the like tends to increase.

The trade-off relationship between NOx and exhaust particulates becomes remarkable when the engine is under a high load or when the EGR amount is large and the excess air ratio is low. It is necessary to precisely control the EGR amount according to the operating conditions.

[0005] As a device for controlling the EGR amount, for example, one disclosed in Japanese Patent Application Laid-Open No. 57-148048 detects the amount of air taken into the engine and the amount of fresh air, respectively.
The difference between the two is regarded as the EGR amount, and the EGR rate (= EGR amount /
The opening area of the EGR passage is adjusted via the EGR valve so that the (new air amount) matches the target EGR rate. Thus, the target EGR rate can be controlled without considering the behavior of the exhaust gas flowing through the EGR valve, and the clogging of the EGR valve can be self-corrected.

However, in this conventional apparatus, when the actually measured EGR amount deviates from the target EGR amount, it is necessary to adjust how to control the opening of the EGR valve. For control, the P and I components must be adapted. Further, as described later, the rotation speed, the load,
Depending on the operating conditions such as the opening degree of the GR valve, the change in the EGR amount with respect to the change in the opening degree of the EGR valve is not constant, so various corrections are required, and it is difficult to precisely control the EGR amount according to the operating conditions.

To cope with this, an apparatus for controlling the flow rate of exhaust gas flowing through the EGR valve is disclosed in, for example, Japanese Patent Laid-Open No. 2-118.
The device disclosed in Japanese Patent No. 58 is configured to measure the differential pressure across the EGR valve and adjust the openings of the EGR valve and the intake throttle valve that can obtain a target EGR rate. This is because the flow of the exhaust gas passing through the EGR valve is considered as a one-dimensional incompressible fluid, and the flow rate of the EG is determined according to the difference between the target value and the measured value of the EGR rate.
In order to obtain the required amount of change in the opening area of the R valve, only the control constant of the actuator itself of the EGR valve needs to be adapted.

[0008]

However, such a conventional engine EGR control device has the following problems.

First, assuming that the flow of exhaust gas passing through the EGR valve is an incompressible steady flow, the following Bernoulli equation is established between the differential pressure ΔP across the EGR valve, the EGR amount Q, and the opening area A of the EGR valve. Holds.

Q = k × A (2 × ρ × ΔP) ^1/2 (1) where k is a flow coefficient and ρ is a viscosity of the exhaust gas.

FIG. 12 shows a flow path model of the EGR valve.
Assuming a pipe having a flow path area extending from A1 to A2 as shown in (1), the flow coefficient k is calculated by the following equation.

K = [1− (A2 / A1) ² ] ^−1/2 (2) However, when actually measuring the differential pressure ΔP before and after the EGR valve and the EGR amount, the demand calculated by the equation (1) As shown in FIG. 13, the opening area is 1.4 to the actual opening area.
A 4.0-fold correction is required.

It is considered that the flow coefficient k varies depending on the engine speed, the load, and the opening area of the EGR valve because the actual flow of the exhaust gas is unsteady and compressible. Further, unlike the expansion pipe, the shape of the EGR valve is considered to be changed by the surface roughness of the EGR valve and the bending of the EGR passage.

The cause of the change in the flow coefficient k depending on the engine rotation and the load is as follows. When the pressure change before and after the EGR valve is actually measured, as shown in FIG. 14, it depends on the intake stroke and the exhaust stroke of the engine. It is conceivable that exhaust gas flows back through the EGR valve depending on the engine speed and load due to intake and exhaust pulsations.

The conventional device disclosed in Japanese Patent Laid-Open No. 11858/1990 performs feedback control so that the differential pressure ΔP across the target EGR valve approaches the target value instead of the target EGR rate, and the flow rate coefficient It is designed to absorb the change in k. However, as is clear from FIG.
Since the rate of change of the EGR amount with respect to the change in the degree of opening of the EGR valve differs depending on the operating conditions, E
It is difficult to calculate the required opening area change amount of the GR valve.
For example, when the P and I components of the feedback control are adapted under the operating condition where the rate of change of the EGR amount is small relative to the lift of the EGR valve, the feedback control is performed under the operating condition where the rate of change of the EGR amount is large relative to the lift of the EGR valve. Excessive amounts can cause control hunting. In the opposite case, there is a possibility that the feedback control amount is insufficient and a control response delay occurs.

That is, engine speed, load, EGR
Since the flow coefficient k of the EGR valve greatly increases and decreases depending on operating conditions such as the valve opening degree, the control error of the EGR amount is large, and NO
There is a problem in that the amount of x or exhaust particulates increases.

Further, in order to bring the EGR amount or the EGR rate close to the target value, it is necessary to experimentally set the target value of the differential pressure across the EGR valve in accordance with the engine speed and the load. However, there is a problem that the number of experimental steps required to conform to the above is increased.

The present invention has been made in view of the above problems, and has as its object to provide an EGR control device that accurately performs feedback control of an EGR amount in accordance with a pressure difference generated in an EGR passage.

[0019]

According to a first aspect of the present invention, there is provided an EGR control system for an engine, wherein an EGR passage connecting an exhaust passage and an intake passage of the engine, and an EGR passage interposed in the EGR passage.
A GR valve, EGR differential pressure detecting means for detecting a pressure difference generated between both ends of the EGR passage as an EGR differential pressure Dlp, required EGR amount setting means for setting a required EGR amount Tqe according to operating conditions, and a required EGR amount Tqe EGR valve opening area calculating means for calculating the opening area Aevs of the EGR valve required in accordance with the EGR differential pressure Dlp, engine speed detecting means for detecting the engine speed, and engine load detecting for detecting the engine load. Means, a flow coefficient setting means for setting a flow coefficient a according to the engine speed and the engine load, and a target EGR valve for calculating a target opening degree Aev of the EGR valve according to the required EGR valve opening area Aevs and the flow coefficient a And an opening calculating means.

According to a second aspect of the present invention, there is provided an EGR control device for an engine according to the first aspect of the invention, further comprising a correction coefficient setting means for setting a correction coefficient b for the opening degree of the EGR valve; degree calculating means is assumed for calculating the target opening Aev of the EGR valve as Aev = a × Aevs ^b in response to a request EGR valve opening area Aevs and flow coefficient a.

According to a third aspect of the present invention, there is provided an EGR control apparatus for an engine according to the first or second aspect of the invention, wherein an intake pressure detecting means for detecting a pressure Pm in an intake passage and an intake pressure for detecting a pressure Pexh in an exhaust passage. Pressure detecting means,
The EGR differential pressure detecting means converts the EGR differential pressure Dlp to Dlp =
The calculation was performed as Pexh-Pm.

According to a fourth aspect of the present invention, there is provided an EGR control device for an engine according to the first or second aspect of the invention, wherein an intake air amount detecting means for detecting an intake air amount and an intake pressure P in accordance with the intake air amount.
m, an engine load detecting means for detecting an engine load, and an exhaust pressure calculating means for calculating an exhaust pressure Pexh according to the engine load.
The GR differential pressure detecting means calculates the EGR differential pressure Dlp as Dlp = Pex
The calculation was made as h-Pm.

[0023]

In the EGR control system for an engine according to the first aspect, the required EGR valve opening area Aev
s is derived from Bernoulli's equation assuming that the flow of exhaust gas passing through the EGR valve is an incompressible steady flow. However, since the actual exhaust gas is a compressible unsteady flow, and the flow coefficient changes depending on the engine speed, the engine load, the opening of the EGR valve, and the like, the EGR amount adjusted by the required EGR valve opening area Aevs is set to the target value. It may be significantly different from the EGR amount TQe.

In response to this, the flow coefficient setting means calculates the flow coefficient a according to the engine speed and the engine load, and the target EGR valve opening area calculating means calculates the required EGR valve opening area Aevs and the flow coefficient a. To calculate.

FIG. 5 shows the required opening area (differential pressure, EG) of the EGR valve by changing the engine speed Ne and the generated torque, respectively.
The relationship between the R amount and the required opening area (determined by the geometric shape) and the required opening area (determined by Bernoulli's equation) is shown.
From this, it can be seen that there is a relationship of y = a × x ^b between the two, the coefficient a changes according to the engine speed and the load, and the slope b is constant.

Therefore, according to the present invention, the EGR amount is changed according to the engine speed and the load, and the target EGR valve opening area Aev is calculated according to the required EGR valve opening area Aevs and the flow coefficient a. Can be precisely controlled.

In the engine EGR control device according to the second aspect, the correction coefficient setting means sets the correction coefficient b according to the degree of opening of the EGR valve, and the target EGR valve opening area calculation means sets the target EGR valve opening area Aev. Aev = a × Aevs
Calculate as ^b .

FIG. 6 shows the EGR valve geometry and EGR.
The relationship between the required opening area and the required opening area of the EGR valve is shown by changing the pipe shape of the passage and the pipe shape of the intake / exhaust system of the engine. From now on, y = a ×
It can be seen that there is a relationship of ^xb , and the slope b changes according to the geometric shape of the flow path.

[0029] Accordingly, the present invention is the configuration which is varied in accordance with the opening degree of the EGR valve inclination b (geometry of the flow channel), calculates a target EGR valve opening area Aev as Aev = a × Aevs ^b , EGR amount can be precisely controlled.

In the engine EGR control device according to the third aspect, the pressure Pm in the intake passage and the pressure Pe in the exhaust passage.
xh is detected, and the EGR differential pressure Dlp is calculated as the pressure difference Pexh-Pm between the exhaust passage and the intake passage.
As a result, the EGR differential pressure Dlp becomes a differential pressure across the EGR passage, and even during operation with a small EGR amount, the EGR differential pressure Dlp
Accordingly, the required EGR valve opening area Aevs for the target EGR amount TQe can be accurately calculated.

In the engine EGR control device according to the fourth aspect, the intake pressure Pm is calculated according to the intake air amount, and the exhaust pressure Pexh is calculated according to the engine load. According to the intake pressure Pm and the exhaust pressure Pexh thus obtained, EG
The R differential pressure Dlp is calculated as Dlp = Pexh-Pm. As a result, the EGR differential pressure Dlp becomes a differential pressure across the EGR passage, and even during operation with a large EGR amount, the EGR differential pressure Dlp
The required EGR valve opening area Aevs for the target EGR amount TQe can be accurately calculated in accordance with p.

[0032]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, in a distribution type fuel injection pump provided in a diesel engine, fuel is sucked by a feed pump 53 driven by a drive shaft 52, and supplied to a pump chamber 55 from the feed pump 53. Is sent to a high-pressure plunger pump 57 through a suction port 56.

Plunger 58 of plunger pump 57
Is rotationally driven at a speed of エ ン ジ ン of the engine speed in synchronism with the engine speed by the drive shaft 52 via the joint 79.

The cam disk 59 fixed to the plunger 58 has the same number of face cams as the number of cylinders of the engine. Each time the cam disk 59 rotates and passes over the roller 62 provided on the roller ring 61, it opposes the spring 69. The plunger 58 is reciprocated by a predetermined cam lift. By the reciprocating movement of the plunger 58, the fuel sucked into the plunger high-pressure chamber 54 from the suction port 56 through the suction slit formed in the plunger 58, passes from the distribution port 63 through the delivery valve 64, and the injection nozzle (not shown) of each cylinder. 77.

The plunger 58 moves to the right side in the drawing and moves from the plunger high pressure chamber 54 through the distribution slit to the distribution port 6.
When the opening of the cut-off port exceeds the right end of the control sleeve 66 in the drawing in the process of pumping the fuel to the fuel tank 3, the fuel that has been pumped is released to the low-pressure pump chamber 5.

The fuel injection amount is controlled by a control sleeve 6 for opening and closing a cutoff port formed in the plunger 58.
It is determined by the position of 6. That is, when the control sleeve 66 is displaced to the right in the drawing, the fuel injection timing is delayed and the fuel injection amount is increased, and when the control sleeve 66 is displaced to the left in the drawing, the fuel injection timing is advanced and the fuel injection amount is reduced.

A rotary solenoid 71 is provided as an electronically controlled governor for automatically adjusting the position of the control sleeve 66. The rotary solenoid 71 is connected to the rotor 7
2 is rotated, and the control sleeve 66 is linearly moved via a ball provided eccentrically at the tip.

The fuel injection timing is determined by setting the face cam to the roller 6 by the timer piston 75 via the roller ring 61.
It is adjusted by rotating relative to 2. By adjusting the hydraulic pressure difference acting on both ends of the timer histone 75 through the duty solenoid valve 76, the timer piston 75 is moved to
1 is rotated to change the timing at which the face cam rides on the roller 62.

A control unit 70 provided as control means for the rotary solenoid 71 and the duty solenoid valve 76 sets the control voltage of the rotary solenoid 71 as map information in advance, and sets the starter switch 8
0, the accelerator opening Acc detected by the accelerator opening sensor 81, the engine speed Ne detected by the pump speed sensor 82, the engine water temperature Tw detected by the water temperature sensor 83, and the detection by the nozzle lift sensor 84. And the like to calculate the appropriate fuel injection amount and fuel injection timing in accordance with the detected operating conditions. The calculated fuel injection amount is used as the control voltage of the rotary solenoid 71. The output is converted and output, and the calculated fuel injection timing is output as a duty signal of the duty solenoid valve 76.
In the figure, reference numeral 65 denotes a fuel temperature sensor.

FIG. 2 is a diagram showing an E provided in a diesel engine.
1 shows an outline of a GR device. An EGR passage 3 that connects the exhaust passage 2 of the engine and the intake manifold 8 of the intake passage 1 is provided, and an EGR valve 4 is interposed in the EGR passage 3. As the opening of the EGR valve 4 increases, the EG
The amount of EGR recirculated to the intake passage 1 via the R passage 3 increases. The EGR valve 4 is driven by a step motor 5. The number of steps of the step motor 5 is controlled by the control unit 30 according to the engine operating conditions, so that the opening of the EGR valve 4 is adjusted.

A butterfly-type intake throttle valve 9 is interposed in the intake passage 1 upstream of the junction of the EGR passage 3. The intake throttle valve 9 opens and closes via a diaphragm actuator 6. In the intake passage 1 downstream of the intake throttle valve 9, an intake negative pressure is generated as the opening degree of the intake throttle valve 9 decreases, and the EGR amount is returned to the intake passage 1 via the EGR passage 3. Increase.

The diaphragm type actuator 6 operates according to a negative pressure guided from a vacuum pump (not shown) via a solenoid valve 21 and a negative pressure guided via a solenoid valve 22 and an orifice 23. The opening of the intake throttle valve 9 is adjusted by controlling the opening of the solenoid valves 21 and 22 by the control unit 30 according to the engine operating conditions.

A hot-wire type air flow meter 12 is provided upstream of the throttle valve 9 in the intake passage 1. Since the resistance of the hot wire (heating resistor) heated by energization changes according to the intake air amount, it outputs a signal corresponding to the intake new air amount Qac.

An intake pressure sensor 13 is interposed in the intake manifold 8 downstream of the throttle valve 9 in the intake passage 1.
The intake pressure sensor 13 outputs a signal corresponding to the intake pressure Pm of the intake manifold 8.

An exhaust pressure sensor 14 is interposed in the exhaust passage 2. The exhaust pressure sensor 14 detects the exhaust pressure Pexh of the exhaust passage 2.
And outputs a signal corresponding to.

As shown in FIG. 3, the control unit 30 includes a target EGR amount setting means 31 for setting a target EGR amount according to engine operating conditions. The target EGR amount setting means 31 inputs, as signals representing the engine operating conditions, signals representing, for example, the engine speed Ne, the fuel injection amount Qf, the fuel injection timing, the engine cooling water temperature, the engine oil temperature, and the like. A predetermined EGR region is determined based on the EGR region. In this EGR region, the engine speed N
e, a target EGR preset according to the fuel injection amount Qf
The target EGR amount T according to the rate Megr and the intake fresh air amount Qac
Calculate Qe.

The EGR differential pressure detecting means 32 detects the intake pressure Pm detected by the intake pressure sensor 13 and the exhaust pressure Pexh detected by the exhaust pressure sensor 14,
The EGR differential pressure Dlp is calculated as Dlp = Pexh-Pm. Since the EGR differential pressure Dlp is a differential pressure across the EGR passage 3, the target EGR amount TQe is determined according to the EGR differential pressure Dlp.
, The required EGR valve opening area Aevs can be calculated accurately.

As shown in FIG. 7, the intake pressure and the exhaust pressure are actually pulsating, but the EGR differential pressure Dlp is calculated as a pressure difference obtained by averaging the two. As a result, the load on the control unit 30 can be reduced, and control stability can be ensured.

The required EGR valve opening area calculating means 33 calculates the required EGR amount in accordance with the required EGR amount TQe and the EGR differential pressure Dlp.
The GR valve opening area Aevs is calculated as Aevs = TQe / (2 × R
OU # × Dlp) ^−Calculate as ^−1/2 . However, ROU #
Is the viscosity of the exhaust gas.

The required EGR valve opening area Aevs is E
The flow of the exhaust gas passing through the GR valve 4 is derived from Bernoulli's equation as an incompressible steady flow. However, since the actual exhaust gas is a compressible unsteady flow, and the flow coefficient changes depending on the engine speed Ne, the engine load, the opening of the EGR valve 4, and the like, the EGR amount adjusted by the required EGR valve opening area Aevs May greatly differ from the target EGR amount TQe.

In response to this, the flow coefficient setting means 36
Inputs the engine speed Ne detected by a pump speed sensor 82 provided as the engine speed detecting means 34, and the fuel injection amount Qf as a load signal from the engine load detecting means 35, and To calculate the flow coefficient a.

The correction coefficient setting means 37 sets the correction coefficient b according to the opening of the EGR valve 4.

Then, the target EGR valve opening area calculation means 3
8 is the target EGR valve opening area Aev = Aev = a × Ae
Compute as vs ^b .

Subsequently, the EGR valve area lift amount conversion means 3
9 is an EGR valve 4 according to the target EGR valve opening area Aev.
Of the lift amount Tlift is calculated.

Subsequently, the EGR valve driving means 40 calculates the number of steps to be output to the step motor 5 according to the lift amount Tlift.

FIG. 5 shows the required opening area of the EGR valve 4 (differential pressure, E
It shows the relationship between the GR amount and the required opening area (determined by the geometric shape) from the Bernoulli equation. From now on, there is a relationship of y = a × x ^b ,
The coefficient a changes according to the engine speed and the load, and the slope b
Is constant.

FIG. 6 shows the geometric shape of the EGR valve 4 and the EG.
The relationship between the required opening area and the required opening area of the EGR valve 4 is shown by changing the pipe shape of the R passage 3 and the pipe shape of the intake / exhaust system of the engine. From now on, y
= A × x ^b , indicating that the slope b changes.

Therefore, according to the present invention, the coefficient a is changed according to the engine speed and the load, and the slope b is changed according to the opening degree of the EGR valve 4 (the geometrical shape of the flow path).
The arrangement for calculating the GR valve opening area Aev as Aev = a × Aevs ^b, as shown in FIG. 8, it is possible to precisely control the EGR quantity.

FIG. 4 is a flowchart showing a routine for controlling the lift amount of the EGR valve 4, which is executed by the control unit 30 at regular intervals.

More specifically, the intake pressure Pm detected by the intake pressure sensor 13 in Step 1 is read.

Subsequently, the program proceeds to Step 2 where the exhaust pressure Pexh detected by the exhaust pressure sensor 14 is read.

Then, the process proceeds to Step 3, where the EGR differential pressure D
lp is calculated as Dlp = Pexh-Pm.

On the other hand, in Step 4, as a signal representative of the engine operating conditions, a target EGR rate Megr preset according to the engine speed Ne, the fuel injection amount Qf, etc.
Search for.

Subsequently, the program proceeds to Step 5, where the new intake air amount Qac detected by the air flow meter 12 is read.

Subsequently, the process proceeds to Step 6, where the target EGR amount TQe is calculated as TQe = Megr × Qac according to the target EGR rate Megr and the intake fresh air amount Qac.

Then, the process proceeds to Step 7, wherein the required EGR valve opening area Aevs is changed to the required EGR amount TQe and the EGR differential pressure D.
Aevs = TQe / (2 × ROU # × D, depending on lp
lp) ^-1/2 . Here, ROU # is the viscosity of the exhaust gas.

On the other hand, in Step 8, the flow coefficient a is searched according to the engine speed Ne and the fuel injection amount Qf.

[0069] Then the process proceeds to Step9, calculates a target EGR valve opening area Aev as Aev = a × Aevs ^b in accordance with the flow rate coefficient a and the required EGR valve opening area Aevs. However, the coefficient b is a value set in advance according to the opening degree of the EGR valve 4.

Subsequently, the routine proceeds to Step 10, where the target EGR
Lift amount Tli of EGR valve 4 with respect to valve opening area Aev
Search for ft.

Then, the process proceeds to Step 11, where the lift amount T
The number of steps according to the lift is output to the step motor 5.

Next, the embodiment shown in FIG. 9 will be described. The parts corresponding to those in FIG. 2 are denoted by the same reference numerals.

In the above embodiment, since the pressure detection accuracy of the exhaust pressure sensor 14 and the intake pressure sensor 13 has an error of about ± 10 mmHg, the EGR amount increases, and the pressure difference Pexh-Pm between the exhaust passage 3 and the intake passage 1 decreases. E
It is difficult to accurately detect the GR differential pressure Dlp.

The exhaust pressure sensor 14 and the intake pressure sensor 13
Since it is exposed to the exhaust gas or the EGR gas, there is a possibility that the detection accuracy may be deteriorated due to thermal deterioration or clogging of the detection unit.

To cope with this, in the present embodiment, the intake pressure is calculated from the new intake air amount and the fresh air temperature, and the exhaust pressure is calculated from the new intake air amount, the fuel injection amount, and the engine speed. The EGR differential pressure Dlp is calculated from the value to precisely control the EGR amount.

FIG. 10 is a flowchart showing a routine for calculating the intake pressure Pm.
At 0, it is executed at regular intervals.

To explain this, the output voltage of the air flow meter 12 is read in Step 1 and converted into the intake air weight Qas0 per unit time.

Subsequently, the routine proceeds to Step 2, where the intake air weight Qa
An intake air amount Qacb per unit cycle is calculated according to s0 and the engine speed Ne.

Subsequently, the program proceeds to Step 3, in which the intake air amount Qacb is converted into a new intake air amount Qac corrected in accordance with the engine speed Ne in order to correct the output of the air flow meter 12 with respect to the flow path shape of the intake passage 1. I do.

On the other hand, at Step 4, the engine speed N
A correction coefficient KinHQ is retrieved according to e and the new intake air amount Qsol.

At Step 5, the engine speed N
eH and the correction coefficient KinH2 according to the intake air amount Qac (load).
Search for.

Then, the process proceeds to Step 6, in which the volume efficiency equivalent value Kin is calculated as Kin = KinHQ × KinH2.

On the other hand, in Step 7, the intake air temperature sensor 1
8 is converted to the intake air temperature Ta0.

Subsequently, the program proceeds to Step 8, in which the temperature rise with respect to the intake pressure is corrected and output as the intake fresh air temperature Tint.

Subsequently, the routine proceeds to Step 9, where the intake pressure index C
pm is calculated as Cpm = Qac × Tint ÷ Kin.

Subsequently, the routine proceeds to Step 10, where the intake pressure Pm
Is calculated as Pm = Kpm # × Cpm + Opm #.

The flowchart of FIG. 11 shows the exhaust pressure Pexh
Is calculated, and is executed in the control unit 30 at regular intervals.

To explain this, a basic exhaust temperature corresponding to the fuel injection amount Qf is searched in Step 1.

Subsequently, the program proceeds to Step 2, in which the basic exhaust gas temperature is corrected in accordance with the swirl control valve opening and converted to a corrected basic exhaust gas temperature Texhi. A swirl control valve (not shown) is interposed in the intake passage, and changes the flow velocity of the intake air flowing into the cylinder according to the operating conditions to generate swirl in the cylinder.

At Step 3, the intake air temperature correction coefficient Ktm
Pe is searched according to the intake air temperature Tne / TA #.

At Step 4, the exhaust pressure correction coefficient Ktm
pp is searched according to the exhaust pressure Pexh / PA #.

At Step 5, the injection timing correction coefficient Ktm
pit according to the injection timing ITTDC # etc. Ktmpit = (ITTD
C-Itistd) / ITTDC # × GIT-Texhi # + 1

Then, the process proceeds to Step 6, where the exhaust temperature-equivalent value Tmpeh is calculated as Tmpeh = Ktexhi × Ktmpe.
It is calculated as × Ktmpp × Ktmpit.

On the other hand, in Step 7, the cycle processing is performed by the difference between the intake stroke and the exhaust stroke according to the intake air amount Qac.
It is output as the working exhaust gas amount Qexh.

Subsequently, the routine proceeds to Step 8, where the exhaust pressure index Cpexh is calculated, and the routine proceeds to Step 9, where the exhaust pressure Pe is calculated.
xh is Pexh = Kpexh # × Cpexh + Opex
Calculate as h #.

The intake pressure Pm and the exhaust pressure P thus determined
exp, the EGR differential pressure Dlp is calculated as Dlp = Pexh
Calculate as -Pm. Thereby, the EGR differential pressure Dlp
Is the differential pressure across the EGR passage, and the required EGR valve opening area Aevs for the target EGR amount TQe can be accurately calculated according to the EGR differential pressure Dlp even during operation with a large EGR amount.

[Brief description of the drawings]

FIG. 1 is a sectional view of a fuel injection pump according to an embodiment of the present invention.

FIG. 2 is a system diagram of the EGR device.

FIG. 3 is a configuration diagram of a control system.

FIG. 4 is a flowchart showing control contents.

FIG. 5 is a characteristic diagram showing a relationship between a required opening area and a required opening area of the EGR valve.

FIG. 6 is a characteristic diagram showing a relationship between a required opening area and a required opening area of the EGR valve.

FIG. 7 is a characteristic diagram showing a relationship between an intake pressure, an exhaust pressure, and the like.

FIG. 8 is a characteristic diagram showing EGR control accuracy.

FIG. 9 is a flowchart showing control contents according to another embodiment.

FIG. 10 is a flowchart showing control contents.

FIG. 11 is a flowchart showing control contents.

FIG. 12 is a model diagram of an EGR valve showing a conventional example.

FIG. 13 is a characteristic diagram showing a relationship between an EGR valve correction coefficient, a required opening area, and a required opening area.

FIG. 14 is a characteristic diagram showing a relationship between an intake pressure, an exhaust pressure, and the like.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 intake passage 2 exhaust passage 3 EGR passage 4 EGR valve 5 step motor 6 actuator 9 intake throttle valve 12 air flow meter 13 intake pressure sensor 14 exhaust pressure sensor 18 intake temperature sensor 30 control unit 31 required EGR amount setting means 32 EGR differential pressure detection Means 33 Required EGR valve opening area calculating means 34 Engine speed detecting means 35 Engine load detecting means 36 Flow coefficient setting means 37 Correction coefficient setting means for EGR valve opening degree 38 Target EGR valve opening area calculating means 39 EGR valve area lift amount conversion Means 40 EGR valve driving means

Claims (4)

[Claims] An EG connecting an exhaust passage and an intake passage of an engine.
An RGR passage, an EGR valve interposed in the middle of the EGR passage, EGR differential pressure detecting means for detecting a pressure difference generated at both ends of the EGR passage as an EGR differential pressure Dlp, and a required EGR amount Tqe according to operating conditions. Request E to set
GR amount setting means, and a required EGR for calculating an opening area Aevs of the EGR valve required according to the required EGR amount Tqe and the EGR differential pressure Dlp.
Valve opening area calculating means, engine speed detecting means for detecting engine speed, engine load detecting means for detecting engine load, flow coefficient setting means for setting flow coefficient a according to engine speed and engine load And E according to the required EGR valve opening area Aevs and the flow coefficient a.
An EGR control device for an engine, comprising: a target EGR valve opening calculating means for calculating a target opening Aev of the GR valve. And a correction coefficient setting means for setting a correction coefficient for the opening degree of the EGR valve, wherein the target EGR valve opening calculating means sets the EGR valve opening area Aevs and the flow coefficient a in accordance with the required EGR valve opening area Aevs. Target opening Ae
v EGR control device for an engine according to claim 1, characterized in that calculating a Aev = a × Aevs ^b a. 3. An intake pressure detecting means for detecting an intake passage pressure Pm, and an intake pressure detecting means for detecting an exhaust passage pressure Pexh, wherein the EGR differential pressure detecting means detects the EGR differential pressure Dlp as Dlp =
The EGR control device for an engine according to claim 1 or 2, wherein the calculation is performed as Pexh-Pm. 4. An intake air amount detecting means for detecting an intake air amount, an intake pressure calculating means for calculating an intake pressure Pm according to an intake air amount, an engine load detecting means for detecting an engine load, and an exhaust gas amount according to an engine load. Exhaust pressure calculating means for calculating the atmospheric pressure Pexh, wherein the EGR differential pressure detecting means sets the EGR differential pressure Dlp to Dlp =
The EGR control device for an engine according to claim 1 or 2, wherein the calculation is performed as Pexh-Pm.