JPH0988726A - Egr device for diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely control a real EGR rate by computing a reference driving state made at the time when a desired EGR rate is acquired from engine speed, a load signal and target opening of an EGR valve and feedback-correcting the target opening of the EGR valve in accordance with a difference between the reference driving state and an actual driving state. SOLUTION: EGR valve target opening is set from each of output signals of a fuel injection quantity setting part 1, an engine speed sensor 2 and an air flow meter 3 and a target EGR rate by a target opening setting part 13. Additionally, target opening of the EGR valve after correction is set from each of the output signals of each of the means 1-3 and the EGR valve target opening in the same way at a target opening correction part 17 consisting of a reference air flow meter output computing part 18 and a target opening feedback correction part 19. Thereafter, opening of the EGR valve is controlled by a control part 8 in accordance with target opening after correction. Target opening is corrected by a difference between real air flow meter output and norm air flow meter output at the target opening feedback correction part 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EGR (exhaust gas recirculation) passage from an exhaust system to an intake system of a diesel engine.
The present invention relates to a diesel engine EGR device that includes a GR valve and controls the EGR rate according to the operating state of the engine.
In the following, the EGR rate is treated as the ratio of the recirculation exhaust gas to the fresh air drawn into the engine, but the EGR rate may be treated as the ratio of the recirculation exhaust gas to the engine intake gas (fresh air + recirculation exhaust gas).

[0002]

[Prior art]

[1] As a conventional EGR device for a diesel engine, there is, for example, a device shown in JP-A-61-215426. Hereinafter, this is referred to as first prior art. The outline is shown in FIG. 1 is a fuel injection amount setting unit, 2 is an engine speed sensor, 3 is an air flow meter, 4 is an atmospheric pressure sensor, and 5 is a cooling water temperature sensor.

Reference numeral 6 denotes a target EGR rate setting unit, which refers to a preset map from the output of the fuel injection amount setting unit 1 and the output of the engine speed sensor 2, and a target EGR rate (basic target EGR rate). To set. Reference numeral 7 denotes a target opening degree setting section, which is composed of a target EGR rate correction section 9, a cylinder intake gas flow rate calculation section 10, an actual EGR rate estimation section 11, and a target opening degree calculation section 12.

The target EGR rate correction unit 9 corrects the target EGR rate (basic target EGR rate) with the output of the atmospheric pressure sensor 4 and the output of the cooling water temperature sensor 5 to obtain the target EGR rate e.
Calculate r. The cylinder intake gas flow rate calculation unit 10 calculates the cylinder intake gas flow rate (mass flow rate) Qo from the output of the engine speed sensor 2 with reference to a preset map.

The actual EGR rate estimator 11 uses the cylinder intake gas flow rate Qo and the output (fresh air flow rate; mass flow rate) Qc of the air flow meter 3 from the following equation to calculate the actual EGR rate e.
Estimate 1. e1 = (Qo−Qc) / Qc The target opening degree calculation unit 12 calculates the target EGR rate er according to the following equation.
And the actual EGR rate el are multiplied by a predetermined function Gfb to obtain E
Calculate the target opening Aegr-v of the GR valve.

Aegr-v = (er-e1) × Gfb 8 is an EGR valve control unit, which controls the opening of the EGR valve based on the target opening Aegr-v. In this way, the EG is adjusted so that the actual EGR rate el approaches the target EGR rate er.
Controls the opening of the R valve. [2] In addition, Japanese Patent Application No. 7-20952 filed by the present applicant.
Some are proposed in No. 7. Hereinafter, this is referred to as second prior art.

The outline is shown in FIG. 1 is a fuel injection amount setting unit, 2 is an engine speed sensor, and 3 is an air flow meter. Reference numeral 6 denotes a target EGR rate setting unit, which refers to a preset map from the output of the fuel injection amount setting unit 1 and the output of the engine speed sensor 2 to determine the target EGR rate er.
Set.

Reference numeral 13 denotes a target opening setting unit, which is composed of an engine model 14 modeling the dynamics (dynamic characteristics) of the engine to be controlled, a target EGR flow rate calculation unit 15, and a target opening calculation unit 16. The fuel injection amount setting unit 1
Of the engine speed sensor 2, the output of the air flow meter 3 (fresh air flow rate) Qc, and the target EGR rate e
From r and the following procedure, the target opening Aegr-v of the EGR valve
Set.

The engine model 14 includes a fuel injection amount setting unit 1
Output, the output of the engine speed sensor 2, the output Qc of the air flow meter 3, and the EG calculated as described below.
From the target opening Aegr-v of the R valve, the cylinder intake gas flow rate Qo, the EGR valve front-back differential pressure ΔP, and the collector delay coefficient Gc are estimated. Here, the engine model 14 may mathematically model the intake / exhaust system of the engine or may be experimentally obtained.

The target EGR flow rate calculation unit 15 calculates the target cylinder EGR flow rate Qegrc from the target EGR rate er and the cylinder intake gas flow rate Qo by the following equation. Qegrc = [er / (1 + er)] × Qo The target opening calculation unit 16 calculates the target cylinder EGR flow rate Qegrc.
And the EGR valve front-rear differential pressure ΔP and the collector delay coefficient Gc from the following equation, the EGR valve target opening Aegr-v
Is calculated.

Aegr-v = Gc × Qegrc × (ΔP) ^−1/2 8 is an EGR valve controller, which controls the opening of the EGR valve based on the target opening Aegr-v. In this way, the opening of the EGR valve is controlled using the engine model so as to obtain the target EGR rate er.

[0012]

[Problems of First Prior Art]

1) Since the actual cylinder intake gas flow rate Qo depends on the engine speed and the intake pressure (collector internal pressure), the cylinder intake gas flow rate Qo obtained only from the engine speed is not accurate particularly in the transient region.

2) Actually, since there is accumulation of gas inside the collector (change in gas density inside the collector), EGR
The flow rate passing through the valve does not become the difference between the cylinder intake gas flow rate Qo and the air flow meter output (fresh air flow rate) Qc. 3) Since there is a capacity such as a collector and an intake pipe between the air flow meter and the cylinder, the fresh air flow rate Qc, which is the output of the air flow meter, does not match the fresh air flow rate component in the cylinder intake gas flow rate Qo.

Due to the above factors, the first prior art has a problem that it is impossible to control the true EGR rate, especially in the transient region, and the control deteriorates in some cases. FIG. 14 shows a comparison between the true EGR rate by simulation and the EGR rate predicted value in the first prior art. [Problem of Second Prior Art] By calculating the target opening degree of the EGR valve using an engine model that describes the dynamics of the engine, the true E
The GR rate control can be performed accurately.

However, the engine model is used only as a feedforward (F / F) compensator, and a feedback (F / B) loop is not formed. Therefore, if there is a characteristic change or variation in the engine, it cannot be corrected. For example, when foreign matter adheres to the EGR valve, the true EGR rate actually decreases due to a decrease in the EGR flow rate, but it cannot be detected to correct the opening degree of the EGR valve.

In the second prior art, when the opening degree of the EGR valve becomes half of the normal state (when foreign matter is attached).
FIG. 15 shows the result of simulation of the EGR rate of. The present invention aims to solve the problems of the first and second prior arts.

[0017]

Therefore, in the invention according to claim 1, in the EGR passage from the exhaust system to the intake system, the EGR passage is provided.
A target EGR rate setting section for setting a target EGR rate, a target opening setting section for setting a target opening of the EGR valve such that the EGR rate matches the target EGR rate, and the target opening EGR that controls the opening of the EGR valve based on
In a diesel engine EGR device including a valve control unit, an operating state detection unit that detects an operating state of at least one engine other than an engine speed and a load signal, an engine speed, a load signal, and a target opening of an EGR valve. Degree, the normative operating state calculator that calculates the normative operating state that is the norm of the operating state, the actual operating state detected by the operating state detector, and the normative operating state calculated by the normative operating state calculator. A feedback target opening degree correction unit that corrects the target opening degree of the EGR valve according to the difference from the state;
Is provided.

That is, when the operating state of at least one engine other than the engine speed and the load signal is detected, a desired EGR rate is obtained from the engine speed, the load signal and the target opening degree of the EGR valve. Calculate the normative operating conditions that will occur in. Then, the target opening degree of the EGR valve is feedback-corrected by the difference between the actual operating state and the reference operating state, and the EG is adjusted by the corrected target opening degree.
Control the R valve. This can solve the problem of the second prior art.

According to a second aspect of the present invention, the target opening degree setting section calculates the target opening degree of the EGR valve by using the first engine model which describes the dynamic characteristics of the engine. And That is, similarly to the second prior art, the problem of the first prior art can be solved by calculating the basic target opening degree of the EGR valve by using the engine model.

In the inventions according to claims 3 to 7, the operating condition detecting section respectively determines, as the operating conditions, the fresh air flow rate, the intake pressure, the EGR valve front-rear differential pressure, the upstream pressure inside the intake throttle valve, and the EGR passage. The internal pressure of the pipe (EGR internal pressure) is detected. In the invention according to claim 8, the normative operating state calculation unit describes the dynamic characteristics of the engine, and calculates the normative operating state using a second engine model to which the engine speed and the load signal are input. It is characterized by being a thing.

In the invention according to claim 9, the second engine model is set on the basis of a mathematical model of the intake and exhaust systems of the engine and a chemical model of the combustion system, and the normative operating condition is determined from the engine speed and the load signal. It is characterized in that it is composed of a gain matrix describing the transfer characteristics up to and an integrator (or an arithmetic unit equivalent to the integrator).

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. [1] FIG. 1 shows a first embodiment of the present invention. 1
Is a fuel injection amount setting unit, 2 is an engine speed sensor, and 3 is an air flow meter.

Reference numeral 6 denotes a target EGR rate setting unit, which refers to a preset map from the output of the fuel injection amount setting unit 1 and the output of the engine speed sensor 2 to determine the target EGR rate er.
Set. Reference numeral 13 denotes a target opening setting unit, a first engine model 14 that models the dynamics (dynamic characteristics) of the engine to be controlled, a target EGR flow rate calculation unit 15,
The target opening degree calculation unit 16 is provided, and the output of the fuel injection amount setting unit 1, the output of the engine speed sensor 2, and the output of the air flow meter 3 (fresh air flow rate; mass flow rate) Qc
And the target EGR rate er, the target opening (basic target opening) Aegr-v of the EGR valve is set in the following procedure.

The first engine model 14 includes the output of the fuel injection amount setting unit 1, the output of the engine speed sensor 2, the output Qc of the air flow meter 3, and the target opening of the EGR valve calculated as described later. From the degree Aegr-v, the cylinder intake gas flow rate (mass flow rate) Qo, the EGR valve front-rear differential pressure ΔP,
The delay coefficient Gc due to the collector is estimated. Here, the first engine model 14 may mathematically model the intake / exhaust system of the engine or may be obtained by experiment.

The target EGR flow rate calculation unit 15 calculates the target cylinder EGR flow rate Qegrc from the target EGR rate er and the cylinder intake gas flow rate Qo by the following equation. Qegrc = [er / (1 + er)] × Qo (1) The target opening calculation unit 16 calculates the target cylinder EGR flow rate Qegrc.
Then, the target opening degree (basic target opening degree) Aegr-v of the EGR valve is calculated by the following equation from the EGR valve front-back differential pressure ΔP and the collector delay coefficient Gc.

Aegr-v = Gc × Qegrc × (ΔP) ^−1/2 (2) Up to this point, the process is the same as the second prior art. Reference numeral 17 denotes a target opening correction unit, which is a reference airflow meter output calculation unit (reference fresh air flow rate calculation unit) as a reference operation state calculation unit 18
And an F / B controller 19 as a target opening feedback correction unit, and the fuel injection amount setting unit 1
Output, the output of the engine speed sensor 2, and the output of the air flow meter 3 as the operating state detection unit (fresh air flow rate)
From Qc and the target opening Aegr-v of the EGR valve, the corrected target opening Aegr0 of the EGR valve is set in the following procedure. E
The GR valve control unit 8 controls the opening of the EGR valve based on the corrected target opening Aegr0.

The reference air flow meter output calculation unit 18 uses the second engine model to output the fuel injection amount setting unit 1, the output of the engine speed sensor 2, and the target opening Aegr-v of the EGR valve. From this, the normative value of the airflow meter output and the normative airflow meter output (normative fresh air flow rate) Qc0 that will occur when the desired EGR rate is obtained are calculated.

Here, the reference air flow meter output calculation unit
18 may mathematically model the intake / exhaust system of the engine or may be experimentally determined. When mathematically modeling, it should be composed of a gain matrix that describes the transfer characteristics from the output of the fuel injection amount setting unit 1 and the output of the engine speed sensor 2 to the reference air flow meter output, and an integrator. You can also

The F / B controller 19 uses the following equation:
The target opening Aegr-v of the EGR valve is corrected by the difference between the actual air flow meter output Qc and the reference air flow meter output Qc0 to calculate the corrected target opening Aegr0 of the EGR valve. _{Aegr0 = Aegr-v + G 1} × (Qc-Qc0) ··· (3) wherein, G ₁ is the desired function, an example of formula (3) into equation (3 '). G ₁ is set in advance by an experiment or a simulation, but it may be changed depending on the operating state of the engine.

Aegr0 = Aegr-v + K × ∫ (Qc−Qc0) dt (3 ′) In the formula (3 ′), the integrator and the gain K are G ₁ and K
Is set in advance by experiment or simulation.
Further, K may be a constant or a variable that changes depending on the operating state of the engine. The simulation results when the actual opening of the EGR valve has become 1/2 are shown in FIGS.

FIG. 2 shows an EGR rate simulation result when foreign matter adheres to the EGR valve in the present invention, and FIG. 3 shows EGR valve opening simulation when foreign matter adheres to the EGR valve in the present invention. The results are shown in FIG. 4, which shows an air flow meter output simulation result when foreign matter adheres to the EGR valve in the present invention. The solid line shows the response when the present invention is compensated, the broken line shows the response when no compensation operation is performed, and the dashed line shows the response when there is no disturbance.

Further, in FIG. 5, in the first embodiment,
The simulation result when the output error of the air flow meter is 10% is shown. Thus, even if the air flow meter has an error, the control result does not become unstable. Particularly according to this first embodiment, the only sensor used is an air flow meter. Therefore, the hardware configuration is the same as that of the first prior art, and the cost increase is small. Further, since the first engine model and the second engine model can be almost the same operation block, the operation to be added to the second prior art is F /
It is only the B controller part. Therefore, it is not necessary to use an expensive microcomputer to improve the calculation speed. [2] FIG. 6 shows a second embodiment of the present invention.

Reference numeral 1 is a fuel injection amount setting unit, 2 is an engine speed sensor, and 3 is an air flow meter. 6 is the target EG
This is an R rate setting section, and sets a target EGR rate er from the output of the fuel injection amount setting section 1 and the output of the engine speed sensor 2 with reference to a preset map.

Reference numeral 13 denotes a target opening degree setting section, which includes a first engine model 14 modeling the dynamics (dynamic characteristics) of the engine to be controlled, a target EGR flow rate calculation section 15,
The target opening calculation unit 16 is provided, and the output of the fuel injection amount setting unit 1, the output of the engine speed sensor 2, the output of the air flow meter 3 (fresh air flow rate) Qc, and the target EG
The target opening Aegr-v of the EGR valve is set from the R rate er.

The process up to this point is the same as in the first embodiment (second prior art). Reference numeral 20 denotes a target opening correction unit, which includes a reference intake pressure calculation unit 21 as a reference operation state calculation unit and an F / B controller 22 as a target opening feedback correction unit, and a fuel injection amount setting unit. 1 output, the output of the engine speed sensor 2, the output (intake pressure) Pint of the intake pressure sensor 23 as the operating state detection unit, and the target opening Aegr-v of the EGR valve from the following procedure. The corrected target opening Aegr0 of the EGR valve is calculated. The EGR valve control unit 8 controls the opening of the EGR valve based on the corrected target opening Aegr0.

The reference intake pressure calculation unit 21 uses the second engine model to output the fuel injection amount setting unit 1, the output of the engine speed sensor 2, and the target opening Aegr-v of the EGR valve.
From the above, the reference value of the intake pressure that will occur when the desired EGR rate is obtained, and the reference intake pressure Pint0 are calculated. Here, the reference intake pressure calculation unit 21 may mathematically model the intake / exhaust system of the engine or may be obtained by experiment.
When mathematically modeling, a gain matrix that describes the transfer characteristics from the output of the fuel injection amount setting unit 1 and the output of the engine speed sensor 2 to the reference intake pressure, and an integrator may be used. it can.

The F / B controller 22 uses the following equation:
The target opening Aegr-v of the EGR valve is corrected by the difference between the actual intake pressure Pint and the reference intake pressure Pint0 to calculate the corrected target opening Aegr0 of the EGR valve. _{Aegr0 = Aegr-v + G 2} × (Pint -Pint0) ··· (4) wherein, G ₂ is the desired function, an example of formula (4) into equation (4 '). G ₂ is set in advance by an experiment or a simulation, but may be changed according to the operating state of the engine.

Aegr0 = Aegr-v + K × ∫ (Pint−Pint0) dt (4 ′) In the equation (4 ′), the integrator and the gain K are G ₂ , and K
Is set in advance by experiment or simulation.
Further, K may be a constant or a variable that changes depending on the operating state of the engine. In FIG. 7, in the second embodiment, E
The EGR rate simulation result when foreign matter adheres to the GR valve is shown.

The response when the solid line is compensated by the present invention,
The one-dot chain line shows the response when no compensation operation was performed, and the broken line shows the response when there was no disturbance. Particularly, according to the second embodiment, since the intake pressure sensor is included, the calculation of the first engine model can be simplified. Therefore, even if the second engine model is added, it is not necessary to use an expensive microcomputer in order to improve the calculation speed. Further, by comparing the intake pressure calculated by the first engine model with the measured intake pressure, it is possible to easily realize the fail-safe logic that detects an abnormality in the air flow meter or the intake pressure sensor. [3] FIG. 8 shows a third embodiment of the present invention.

Reference numeral 1 is a fuel injection amount setting unit, 2 is an engine speed sensor, and 3 is an air flow meter. 6 is the target EG
This is an R rate setting section, and sets a target EGR rate er from the output of the fuel injection amount setting section 1 and the output of the engine speed sensor 2 with reference to a preset map.

Reference numeral 13 denotes a target opening degree setting section, which is a first engine model 14 modeling the dynamics of the engine to be controlled, a target EGR flow rate calculation section 15,
The target opening calculation unit 16 is provided, and the output of the fuel injection amount setting unit 1, the output of the engine speed sensor 2, the output of the air flow meter 3 (fresh air flow rate) Qc, and the target EG
The target opening Aegr-v of the EGR valve is set from the R rate er.

The process up to this point is the same as that of the first embodiment (second prior art). Reference numeral 24 denotes a target opening correction unit, which is a reference EGR valve front-back differential pressure calculation unit 25 as a reference operating state calculation unit.
And an F / B controller 26 as a target opening feedback correction unit, and the fuel injection amount setting unit 1
Of the engine speed sensor 2 and the output of the EGR valve front-back differential pressure sensor 27 (EG
From the R valve front-back differential pressure) ΔP and the EGR valve target opening Aegr-v, the corrected EGR valve target opening Aegr0
Is calculated. The EGR valve control unit 8 controls the opening of the EGR valve based on the corrected target opening Aegr0.

The reference EGR valve front-back differential pressure calculation unit 25 uses the second engine model to output the fuel injection amount setting unit 1, the output of the engine speed sensor 2, and the target opening Aegr- of the EGR valve. v, the reference value of the EGR valve differential pressure across the EGR valve that will occur when the desired EGR rate is obtained, and the reference EGR
Calculate the differential pressure ΔP0 across the valve. Here, the reference EGR valve front-rear differential pressure calculation unit 25 may mathematically model the intake / exhaust system of the engine or may be experimentally obtained. When mathematically modeling, a gain matrix that describes the transfer characteristics from the output of the fuel injection amount setting unit 1 and the output of the engine speed sensor 2 to the reference differential pressure across the EGR valve and an integrator are used. You can also do it.

The F / B controller 26 uses the following equation:
The target opening Aegr-v of the EGR valve is corrected by the difference between the actual EGR valve front-rear differential pressure ΔP and the reference EGR valve front-rear differential pressure ΔP0 to calculate the corrected target opening Aegr0 of the EGR valve. _{Aegr0 = Aegr-v + G 3} × (ΔP-ΔP0) ··· (5) where, G ₃ is the desired function, an example of formula (5) into equation (5 '). G ₃ is set in advance by an experiment or a simulation, but may be changed according to the operating state of the engine.

Aegr0 = Aegr-v + K × ∫ (ΔP−ΔP0) dt (5 ′) In the equation (5 ′), the integrator and the gain K are G ₃ and K
Is set in advance by experiment or simulation.
Further, K may be a constant or a variable that changes depending on the operating state of the engine. In FIG. 9, in the third embodiment, E
The EGR rate simulation result when foreign matter adheres to the GR valve is shown.

The response when the solid line is compensated according to the invention,
The one-dot chain line shows the response when no compensation operation was performed, and the broken line shows the response when there was no disturbance. Particularly, according to the third embodiment, since the EGR valve front-back differential pressure sensor is provided, the calculation of the first engine model can be simplified. Therefore, even if the second engine model is added, it is not necessary to use an expensive microcomputer in order to improve the calculation speed.
Further, by comparing the EGR valve front-rear differential pressure calculated by the first engine model with the measured EGR valve front-rear differential pressure,
A fail-safe logic that detects an abnormality in the air flow meter or the EGR valve differential pressure sensor can be easily realized. [4] FIG. 10 shows a fourth embodiment of the present invention.
It should be noted that this embodiment is premised on having an intake throttle valve for performing intake throttle.

Reference numeral 1 is a fuel injection amount setting unit, 2 is an engine speed sensor, and 3 is an air flow meter. 6 is the target EG
This is an R rate setting section, and sets a target EGR rate er from the output of the fuel injection amount setting section 1 and the output of the engine speed sensor 2 with reference to a preset map.

Reference numeral 13 denotes a target opening degree setting section, which is a first engine model 14 modeling the dynamics (dynamic characteristics) of the engine to be controlled, a target EGR flow rate calculation section 15,
The target opening calculation unit 16 is provided, and the output of the fuel injection amount setting unit 1, the output of the engine speed sensor 2, the output of the air flow meter 3 (fresh air flow rate) Qc, and the target EG
The target opening Aegr-v of the EGR valve is set from the R rate er.

Up to this point, the procedure is the same as in the first embodiment (second prior art). Reference numeral 28 denotes a target opening correction unit, which is a reference operation state calculation unit, which is a reference intake air pressure upstream upstream pressure calculation unit.
29, and an F / B controller 30 as a target opening degree feedback correction unit, which outputs the fuel injection amount setting unit 1, the output of the engine speed sensor 2, and the intake throttle as an operating state detection unit. The corrected target opening degree Aegr0 of the EGR valve is calculated from the output of the valve upstream-side internal pressure sensor 31 (intake upstream of the intake throttle valve) Pcom and the target opening degree Aegr-v of the EGR valve in the following procedure. The EGR valve control unit 8 controls the opening of the EGR valve based on the corrected target opening Aegr0.

Using the second engine model, the reference intake air throttle upstream direct internal pressure calculation unit 29 outputs the fuel injection amount setting unit 1, the output of the engine speed sensor 2, and the target opening Aegr of the EGR valve. From -v, the reference value of the intake throttle valve upstream direct internal pressure, which will occur when the desired EGR rate is obtained, and the reference intake throttle valve upstream upstream internal pressure Pcom0 are calculated. Here, the reference intake air throttle valve just upstream internal pressure calculation unit 29 may mathematically model the intake / exhaust system of the engine or may be obtained by experiment. When mathematically modeling, a gain matrix that describes the transfer characteristics from the output of the fuel injection amount setting unit 1 and the output of the engine speed sensor 2 to the internal pressure directly upstream of the reference intake throttle valve and the integrator are used. It can also be configured.

The F / B controller 30 has the following equation:
The target opening Aegr-v of the EGR valve is corrected by the difference between the actual upstream intake pressure Pcom of the intake throttle valve and the upstream upstream internal pressure Pcom0 of the reference intake throttle valve to calculate the corrected target opening Aegr0 of the EGR valve. _{Aegr0 = Aegr-v + G 4} × (Pcom -Pcom0) ··· (6) where, G ₄ is the desired function, an example of formula (6) into equation (6 '). G ₄ is set in advance by an experiment or a simulation, but may be changed according to the operating state of the engine.

Aegr0 = Aegr-v + K × ∫ (Pcom−Pcom0) dt (6 ′) In the equation (6 ′), the integrator and the gain K are G ₄ , and K
Is set in advance by experiment or simulation.
Further, K may be a constant or a variable that changes depending on the operating state of the engine. Since the fourth embodiment basically only changes the sensor position in the third embodiment,
An effect equivalent to that of the third embodiment can be obtained. [5] FIG. 11 shows a fifth embodiment of the present invention.

Reference numeral 1 is a fuel injection amount setting unit, 2 is an engine speed sensor, and 3 is an air flow meter. 6 is the target EG
This is an R rate setting section, and sets a target EGR rate er from the output of the fuel injection amount setting section 1 and the output of the engine speed sensor 2 with reference to a preset map.

Reference numeral 13 denotes a target opening setting section, which is a first engine model 14 modeling the dynamics (dynamic characteristics) of the engine to be controlled, a target EGR flow rate calculation section 15,
The target opening calculation unit 16 is provided, and the output of the fuel injection amount setting unit 1, the output of the engine speed sensor 2, the output of the air flow meter 3 (fresh air flow rate) Qc, and the target EG
The target opening Aegr-v of the EGR valve is set from the R rate er.

Up to this point, the procedure is the same as that of the first embodiment (second prior art). Reference numeral 32 denotes a target opening correction unit, which includes a reference EGR pipe pressure calculation unit 33 as a reference operation state calculation unit and an F / B controller 34 as a target opening feedback correction unit, and sets the fuel injection amount. Output of part 1, output of engine speed sensor 2, output of EGR pipe internal pressure sensor 35 (EGR pipe internal pressure) serving as an operating state detection part
From Pegr and the target opening Aegr-v of the EGR valve, the corrected target opening Aegr0 of the EGR valve is calculated by the following procedure.
The EGR valve control unit 8 controls the opening of the EGR valve based on the corrected target opening Aegr0.

Using the second engine model, the reference EGR pipe internal pressure calculation unit 33 outputs the output of the fuel injection amount setting unit 1, the output of the engine speed sensor 2, and the target opening A of the EGR valve.
egr-v and the normative value of the EGR pipe pressure that will occur when the desired EGR rate is obtained, the normative EGR pipe pressure Peg
Calculate r0. Here, the standard EGR pipe pressure calculation unit 33
The intake and exhaust system of the engine may be mathematically modeled,
It may be obtained by experiment. In mathematical modeling, a gain matrix describing the transfer characteristics from the output of the fuel injection amount setting unit 1 and the output of the engine speed sensor 2 to the EGR pipe pressure may be used, and an integrator may be used. it can.

The F / B controller 34 uses the following equation:
The target opening Aegr-v of the EGR valve is set to the actual EGR pipe pressure P.
Correct by the difference between egr and the standard EGR pipe pressure Pegr0,
The corrected target opening Aegr0 of the EGR valve is calculated. _{Aegr0 = Aegr-v + G 5} × (Pegr -Pegr0) ··· (7) where, G ₅ is desired (high-gain characteristics in a certain frequency range)
Is a function of, and an example of equation (7) is shown in equation (7 ′). G ₅
Is set in advance by experiment or simulation, but may be changed according to the operating state of the engine.

Aegr0 = Aegr-v + K × ∫ (Pegr−Pegr0) dt (7 ′) In the formula (7 ′), the integrator and the gain K are G ₅ , and K
Is set in advance by experiment or simulation.
Further, K may be a constant or a variable that changes depending on the operating state of the engine. In the fifth embodiment, the sensor position is basically changed in the third embodiment.
An effect equivalent to that of the third embodiment can be obtained.

In the first to fifth embodiments, when the intake throttle valve is used, the first engine model 14 is used to calculate the fresh air flow amount sucked by the cylinder and the differential pressure across the EGR valve. As the information to be used, information from the intake throttle valve upstream upstream internal pressure sensor 31 and the EGR pipe internal pressure sensor 35 may be used in addition to the air flow meter 3.

[0060]

As described above, according to the first aspect of the present invention, the operating state of at least one engine other than the engine speed and the load signal is detected, while the engine speed, the load signal and the EGR valve are detected. The target opening of the EGR valve is calculated based on the difference between the actual operating state and the standard operating state. Since it is corrected, the actual E
The effect that the GR rate can be controlled with high precision is obtained.

According to the second aspect of the present invention, the first engine model is used to calculate the basic target opening degree of the EGR valve.
The effect that the R rate can be controlled with high precision is obtained. According to the third aspect of the invention, by using the fresh air flow rate, the sensor to be used is only the air flow meter, and the effect that the cost increase is small can be obtained.

According to the invention of claim 4, since the intake pressure sensor is provided by using the intake pressure, it is possible to obtain the effect that the calculation of the first engine model can be simplified. According to the invention of claim 5, since the EGR valve front-rear differential pressure sensor is provided by using the EGR valve front-rear differential pressure, it is possible to obtain an effect that the calculation of the first engine model can be simplified.

According to the invention of claim 6, since the internal pressure of the upstream side of the intake throttle valve is used, only the sensor position of the invention of claim 5 is changed, and an effect equivalent to that is obtained. According to the invention of claim 7, by using the pipe internal pressure of the EGR passage, only the sensor position of the invention of claim 5 is changed, and an effect equivalent to that is obtained.

According to the invention of claim 8, by calculating the reference operating state using the second engine model, there is an effect that an accurate calculation becomes possible. According to the invention of claim 9, it is possible to obtain the effect that the second engine model can be easily configured with the gain matrix and the integrator.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

FIG. 2 is a diagram showing a simulation result of the first embodiment.

FIG. 3 is a diagram showing a simulation result of the first embodiment.

FIG. 4 is a diagram showing a simulation result of the first embodiment.

FIG. 5 is a diagram showing a simulation result of the first embodiment.

FIG. 6 is a configuration diagram of a second embodiment of the present invention.

FIG. 7 is a diagram showing a simulation result of the second embodiment.

FIG. 8 is a configuration diagram of a third embodiment of the present invention.

FIG. 9 is a diagram showing a simulation result of the third embodiment.

FIG. 10 is a configuration diagram of a fourth embodiment of the present invention.

FIG. 11 is a configuration diagram of a fifth embodiment of the present invention.

FIG. 12 is a block diagram of the first prior art.

FIG. 13 is a configuration diagram of a second prior art.

FIG. 14 is a diagram showing a simulation result of the first prior art.

FIG. 15 is a diagram showing a simulation result of the second prior art.

[Explanation of symbols]

1 Fuel injection amount setting unit 2 Engine speed sensor 3 Air flow meter 6 Target EGR rate setting unit 8 EGR valve control unit 13 Target opening setting unit 14 First engine model 15 Target EGR flow rate calculation unit 16 Target opening calculation unit 17 Target Opening correction unit 18 Reference air flow meter output calculation unit (second engine model) 19 F / B controller (Target opening feedback correction unit) 20 Target opening correction unit 21 Reference intake pressure calculation unit (Second engine model) 22 F / B controller (target opening feedback correction unit) 23 Intake pressure sensor 24 Target opening correction unit 25 Reference EGR valve front-back differential pressure calculation unit (second engine model) 26 F / B controller (target opening feedback correction unit) 27 EGR valve front-back differential pressure sensor 28 Target opening correction unit 29 Reference intake throttle valve upstream upstream internal pressure calculation unit (2nd engine model) 30 F / B controller Opening position feedback correction unit) 31 Inlet upstream throttle internal pressure sensor 32 Target opening correction unit 33 Reference EGR pipe internal pressure calculation unit (second engine model) 34 F / B controller (Target opening feedback correction unit) 35 EGR pipe pressure Sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location F02D 41/02 351 F02D 41/02 351

Claims (9)

[Claims] 1. An EGR is provided in an EGR passage from an exhaust system to an intake system.
A target EGR rate setting unit that sets a target EGR rate, a target opening setting unit that sets a target opening of the EGR valve such that the EGR rate matches the target EGR rate, and the target opening EG for controlling the opening of the EGR valve based on
In an EGR device for a diesel engine including an R valve control unit, an operating state detection unit that detects an operating state of at least one engine other than an engine speed and a load signal, an engine speed, a load signal, and an EGR valve target. A normative operating state calculator that calculates a normative operating state that is the norm of the operating state from the opening, an actual operating state detected by the operating state detector, and a norm calculated by the normative operating state calculator. A target opening feedback correction unit that corrects the target opening of the EGR valve according to the difference with the operating state, and EGR for diesel engine characterized by the following:
apparatus. 2. The target opening degree setting unit calculates a target opening degree of an EGR valve by using a first engine model describing a dynamic characteristic of an engine. EGR device for diesel engine. 3. The EGR device for a diesel engine according to claim 1 or 2, wherein the operating state detection unit detects a fresh air flow rate. 4. The EGR device for a diesel engine according to claim 1 or 2, wherein an intake pressure is detected by the operating state detection unit. 5. The EGR is detected by the operating state detector.
The EGR device for a diesel engine according to claim 1 or 2, which is a differential pressure across the valve. 6. The EGR device for a diesel engine according to claim 1, wherein the operating state detecting portion detects the internal pressure immediately upstream of the intake throttle valve. 7. The EGR is detected by the operating state detector.
The EGR device for a diesel engine according to claim 1 or 2, wherein the pipe internal pressure of the passage is provided. 8. The normative operating condition calculation section describes the dynamic characteristics of the engine and calculates the normative operating condition by using a second engine model to which an engine speed and a load signal are input. The EGR device for a diesel engine according to any one of claims 1 to 7, characterized in that. 9. The second engine model is set on the basis of a mathematical model of an intake / exhaust system of an engine and a chemical model of a combustion system, and describes transfer characteristics from an engine speed and load signal to a standard operating condition. 9. The EGR device for a diesel engine according to claim 8, wherein the EGR device includes a gain matrix and an integrator.