JPH1122561A - Egr control device for diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve exhaust performance and facilitate engine design considering heat resistance, by judging abnormality of an EGR valve, and performing EGR control without correcting target fuel injection timing when the EGR valve is normal, and with correcting target fuel injection time only when the EGR valve is abnormal. SOLUTION: A setting means 3a is provided which sets a target EGR valve aperture from a target EGR ratio which is set by a setting means 1, and based on the target EGR valve aperture an operating means 5 controls aperture of an EGR valve. A first target fuel injection time setting means 4 for setting target fuel injection timing and a means 2 for detecting EGR ratio are provided, and a processing means 9 calculates correcting amount of the first target fuel injection timing from the target EGR rate and detected EGR rate. Furthermore, when the EGR valve is judged to be abnormal by an abnormality judging means 10a, a second target fuel injection timing correcting means 6b sets a second target fuel injection timing from the first target fuel injection timing and correction amount, and controls fuel injection timing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EGR control device for a diesel engine configured to recirculate exhaust gas led to an exhaust passage of a diesel engine to an intake passage.

[0002]

2. Description of the Related Art Conventionally, for the purpose of reducing the amount of NOx in exhaust gas discharged from a diesel engine, as a technique for recirculating a part of the exhaust gas into intake air (EGR), for example, Japanese Patent Application Laid-Open No. 8-112261 is disclosed. The techniques shown are known.

In this prior art, as shown in FIG. 7, a target EGR rate setting means 1 for setting a ratio of EGR to fresh air to be made to exist in a cylinder, that is, a target EGR rate.
EGR rate detecting means 2 for detecting an actual EGR rate;
Target EG for setting the target EGR valve opening from the target EGR rate
R valve opening setting means 3a, target fuel injection timing setting means 4 for setting target fuel injection timing, EGR valve operating means 5 for operating the EGR valve opening according to the target EGR valve opening, and correction amount calculation described later Target fuel injection timing correction means 6a for calculating a correction value of the target fuel injection timing from the correction amount calculated by the means 9 and the target fuel injection timing set by the target fuel injection timing setting means 4, and a correction value of the target fuel injection timing From the outputs of the fuel injection timing operating means 7, the diesel engine 8, the target EGR rate setting means 1 and the EGR rate detecting means 2 so that the EGR rate approaches the target EGR rate. Correction amount calculating means 9 for calculating a correction amount of the target fuel injection timing set by the setting means 4.

In the conventional example configured as described above, the target E
The target fuel injection timing is corrected based on the difference between the GR rate and the detected actual EGR rate. Therefore, by utilizing the fact that the differential pressure before and after the EGR valve changes depending on the fuel injection timing, for example, appropriate EGR control can be performed even at the time of abnormality such as when the EGR valve is stuck.

[0005]

However, in such a device, the fuel injection timing is better as close as possible to the target fuel injection timing as far as possible in terms of exhaust performance. Therefore, since the EGR control is performed by correcting the target fuel injection timing, the EGR control is performed.
When the valve is normal, there is a problem that the exhaust performance deteriorates because the fuel injection timing does not match the target fuel injection timing.

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and has as its object to provide a means for determining whether an EGR valve is abnormal. By not performing the correction, it is possible to prevent the exhaust performance from deteriorating. In addition, when the EGR valve is abnormal, the target fuel injection timing is corrected to perform the EGR control. Is the lower target EG
It is an object of the present invention to provide an EGR control device for a diesel engine that can easily perform engine design in consideration of heat resistance by realizing an R rate and preventing a large amount of high-temperature EGR from flowing into a collector. .

[0007]

In order to achieve the above-mentioned object, according to the present invention, an EGR control device for a diesel engine is provided as shown in FIG. Means 3a for setting a target EGR valve opening based on the EGR rate, means 5 for operating the EGR valve based on the target EGR valve opening, and first target fuel injection timing setting means 4 for setting a target fuel injection timing. Means 2 for detecting the EGR rate, means 9 for calculating the correction amount of the first target fuel injection timing from the target EGR rate and the detected value of the EGR rate 9
Means 10a for determining an abnormality of the EGR valve;
Means 6b for setting a second target fuel injection timing based on the output of the first target fuel injection timing and the correction amount based on the output of the means for determining an abnormality of the R valve; And means 7 for controlling the injection timing.

In the present invention, the second target fuel injection timing setting means 6b includes the EGR valve abnormality determining means 1
When 0a outputs a signal for determining the abnormality of the EGR valve, the target fuel injection timing is calculated from the correction amount calculated by the correction amount calculating means 9 and the target fuel injection timing set by the first target fuel injection timing setting means 4. Is calculated. And the above E
When the GR valve abnormality determination means 10a determines that the EGR valve is normal, the second target fuel injection timing setting means 6b outputs the input target injection timing as it is.

In this case, the EGR valve abnormality determining means 10
It is preferable that a is configured to determine the operating state based on either the engine speed or the target fuel injection amount.

In the present invention, the target EGR
The valve opening is calculated from the target EGR rate and the detected value of the EGR rate.

Further, in the present invention, the means for detecting the EGR rate includes means for detecting the amount of fresh air sucked into the collector, means for detecting the pressure in the collector,
Means for detecting the temperature in the collector, means for estimating the volumetric efficiency, and suction into the cylinder based on dynamic characteristics from the amount of fresh air sucked into the collector to the gas sucked into the collector. Means for calculating the amount of fresh air to be supplied, means for calculating the amount of air-fuel mixture sucked into the cylinder from the engine speed, the temperature in the collector, the pressure in the collector, the volumetric efficiency and the stroke volume, and the cylinder Means for calculating an EGR rate from the amount of air-fuel mixture sucked into the cylinder and the amount of fresh air sucked into the cylinder.

In this case, the temperature in the collector is obtained by estimating from the detected value of the EGR rate and the target fuel injection amount.

Further, in this case, the dynamic characteristics until the gas sucked into the collector is sucked into the cylinder are as follows:
It is determined by estimating from the engine speed, the volumetric efficiency, the stroke volume and the collector volume.

The means for estimating the volume efficiency is as follows:
It is determined by estimating from the engine speed and the pressure in the collector. In this case, it is desirable that the volumetric efficiency be a predetermined constant.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the accompanying drawings.

FIGS. 2 and 3 show the configuration of an EGR control device for a diesel engine according to a first embodiment of the present invention. FIG. 3 shows a detailed configuration of the EGR rate detecting means 2b shown in FIG.

EGR for a diesel engine according to this embodiment
The control device includes a target EGR rate setting means 1, an EGR rate detecting means 2b, a target EGR valve opening calculating means 3b for setting a target EGR valve opening based on the target EGR rate, and a target fuel for setting a target fuel injection timing. Injection timing setting means 4 and target EG
The target fuel injection timing set by the target fuel injection timing setting means 4 based on the output of the EGR valve operation means 5 which operates the EGR valve based on the R valve opening degree and the EGR valve abnormality determination means 10b described later, and the correction amount Target fuel injection timing correcting means 6b for setting a second target fuel injection timing from
A correction amount calculating means 9 for calculating a correction amount of the target fuel injection timing setting means 4 from the R rate and the EGR rate detection value; a diesel engine 8; and a target fuel injection timing correcting means 6b.
A fuel injection timing operating means 7 for operating the fuel injection timing based on the target fuel injection timing corrected in the above, an EGR valve abnormality determining means 10b, an operating state determining means 11, an engine rotational speed detecting means 12, a target fuel injection It comprises an amount setting means 13, a collector suction fresh air amount detecting means 14, a collector pressure detecting means 15, and a collector temperature detecting means 16.

[0018] The EGR rate detecting unit 2b includes a collector dynamic characteristic calculation means 2b ₁ for gas to be Inhalation collector to estimate the dynamic characteristics to be sucked into the cylinder, the volumetric efficiency estimation unit 2b _2, cylinder intake Air-fuel mixture calculation means 2b ₃
When a cylinder intake fresh air amount calculation means 2b _4, the EGR rate calculating means 2b _5, and a.

The diesel engine E thus constructed
The operation of the GR control device will be described assuming, for example, a four-cylinder supercharged diesel engine. In addition, the calculation performed thereafter is
It shall be performed in time synchronization. Further, Z in the formula is an operator of Z conversion, and Z ^-1 represents one operation delay.

[0020] In the collector dynamic characteristic calculating means 2b _1,
Output and the engine speed is the engine speed detecting means 12, by using the volumetric efficiency which is the output of the volumetric efficiency estimation unit 2b _2, performs calculations, such as the number 1.

Τa = (30 × Vcol) / (Ne × Vcyl × ηv) (Equation 1)

In the equation, τa (s): time constant of dynamic characteristics generated by the collector Ne (rpm): engine speed Vcol (m ³ ): collector volume Vcyl (m ³ ): stroke volume ηv: volume efficiency

The volume efficiency estimating means ₂ b ₂ is prepared in advance by using the engine rotational speed output from the engine rotational speed detecting means 12 and the pressure in the collector output from the collector internal pressure detecting means 15. Output the volumetric efficiency from the map. FIG. 5 shows an example of a volume efficiency setting map. in this case,
The volume efficiency may be a predetermined constant.

In the cylinder intake air-fuel mixture calculating means 2b ₃ , the volume efficiency which is the output of the volume efficiency estimating means 2b ₂
Using the engine rotation speed output from the engine rotation speed detection means 12, the temperature inside the collector output from the collector temperature detection means 16, and the pressure inside the collector output from the collector pressure detection means 15, For example, a calculation as shown in Equation 2 is performed.

Qo = ηv × (To / Tcol) × (Pcol / Po) × ρcol × Vcyl × (30 / Ne) (Equation 2)

In the equation, Qo (kg / s): the amount of air-fuel mixture sucked into the cylinder ηv: volumetric efficiency Tcol (K): temperature in the collector Pcol (Pa): pressure in the collector Ne (rpm): Engine rotation speed To (K): Absolute temperature indicating the standard state Po (Pa): Absolute pressure indicating the standard state ρcol (kg / m ³ ): Density of gas present in the collector in the standard state Vcyl (m ³ ): Stroke Here, To, Po, and Vcyl are given as constants. ρco
l may be sensed or a standard value may be given.

The cylinder intake fresh air amount calculating means 2b ₄
In using the amount of fresh air sucked into the collector is the output of the collector intake fresh air amount detecting means 14, the time constant of the dynamic characteristics caused by the collector is the output of the collector dynamic characteristic estimating unit 2b _1, for example, several A calculation like 3 is performed. still,
Equation 3 expresses the relationship of the first-order lag using a discrete-time equation.

[0028] Qcw = exp (- Δt / τa ) × (Z -1 Qcw) + {1-exp (- Δt / τa)} × (Z -1 Qw) ... ( Equation 3)

In the above equation, Qcw (kg / s): a fresh air amount sucked into the cylinder Qw (kg / s): a new air amount sucked into the collector τa (s): a dynamic characteristic generated by the collector Constant Δt (s): sampling time Here, Δt is given as a constant.

[0030] Next, in the EGR rate calculating means 2b _5,
Using output and mixed air amount sucked into the cylinder is a cylinder intake air-fuel mixture amount calculation means 2b _3, the amount of fresh air sucked into the cylinder, which is the output of the cylinder intake fresh air amount calculation means 2b _4, for example, A calculation as shown in Equation 4 is performed.

Yegr = 100 × (Qo−Qcw) / Qcw (Equation 4)

In the equation, Yegr (%): EGR rate Qo (kg / s): air-fuel mixture intake to cylinder Qcw (kg / s): fresh air intake to cylinder

The EGR valve operating means 5 operates the EGR valve so that the actual EGR valve opening approaches the target EGR valve opening which is the output of the target EGR valve opening calculating means 3b.

In the target fuel injection timing correction means 6b, EG
When the R valve abnormality determination unit 10b outputs a signal indicating an abnormality of the EGR valve, the correction amount of the target fuel injection timing, which is the output of the correction amount calculation unit 9, and the output of the target fuel injection timing setting unit 4 Using a certain target fuel injection timing, for example, a calculation as shown in Expression 5 is performed. When the EGR valve abnormality determining means 10b does not output a signal indicating the abnormality of the EGR valve, the EGR valve abnormality determining means 10b outputs a value equal to the target fuel injection timing as the corrected fuel injection timing.

Hit = MIt + ΔIt (Equation 5)

In the equation, Hit (° BTDC): corrected fuel injection timing Mit (° BTDC): target fuel injection timing ΔIt (° BTDC): correction amount

In the correction amount calculating means 9, the target EGR
And the target EGR rate, which is the output rate setting means 1, which is the output of the EGR rate calculating means 2b ₅ in EGR rate detecting means 2b E
Equations such as Equations 6 and 7 are performed using the GR rate.

ΔIt = Kpl × (Megr−Yegr) + R (Equation 6)

In the equation, ΔIt (° BTDC): correction amount Yegr (%): EGR rate Megr (%): target EGR rate Kpl: proportional gain Here, Kpl is set in advance by experiment or simulation. , May vary depending on the operating state of the engine.

R = Z ⁻¹ R + Δt × Kil × Z ⁻¹ (Megr−Yegr) (Equation 7)

In the equation, Y egr (%): EGR rate Megr (%): target EGR rate Kil: integral gain Δt (sec): sampling time Here, Kil is set in advance by experiment or simulation. It may change depending on the operating state of the engine. Δt is given as a constant.

Further, in the EGR valve abnormality determining means 10b, the target EGR rate which is the output of the target EGR rate setting means 1 and the EGR rate calculating means 2b ₅ in the EGR rate detecting means 2b.
For example, the following is performed based on the EGR rate, which is the output of (i), and the output of the operating state determination means 11. When Expression 8 is satisfied and the operating state determination means 11 outputs a signal indicating a steady state as the current operating state, it outputs a signal indicating an abnormality of the EGR valve.

ΔEGR <| Yegr−Megr | (Expression 8)

In the equation, Yegr (%): EGR rate Megr (%): target EGR rate ΔEGR (%): abnormality determination set value Here, ΔEGR (%) is a setting used to determine the abnormality of the EGR valve. Value, given as a constant. The use of a signal representing the steady state is generally due to the fact that the steady state has a higher E than the transient state.
This is because the error of the GR rate with respect to the target EGR rate is small, and when determining an abnormality of the EGR valve, it is expected to improve the determination accuracy by limiting to a steady state.

Next, in the operating state determining means 11, the target fuel injection amount, which is the output of the target fuel injection amount setting means 13, is calculated.
From the engine rotation speed output from the engine rotation speed detection means 12, for example, the following is performed.

A map is set for each area centered on the target fuel injection amount and the engine speed, and a point having coordinates of the above two inputs is within a specific area for a predetermined period or more. , A signal representing a steady state is output. It is assumed that the target fuel injection amount substantially matches the actual fuel injection amount.

The engine rotational speed detecting means 12 detects the engine rotational speed, and the target fuel injection amount setting means 13 sets the target fuel injection amount. The collector suction fresh air amount detecting means 14 detects a fresh air amount sucked into the collector. Further, the collector pressure detecting means 15 detects the pressure inside the collector. In-collector temperature detecting means 16 detects the temperature in the collector.

On the other hand, in the target EGR rate setting means 1,
The target EGR rate is set, and the target fuel injection timing setting means 4 sets the target fuel injection timing. Further, the fuel injection timing operating means 7 operates the fuel injection timing so that the actual fuel injection timing approaches the corrected fuel injection timing output from the target fuel injection timing correcting means 6b.

The target EGR valve opening degree setting means 3
b, the target EG which is the output of the target EGR rate setting means 1
EGR rate calculating means 2b in R rate and EGR rate detecting means 2b
_From the EGR rate which is the output of ₅ , for example,
Is calculated.

MAegr = Kp2 × (Megr−Yegr) + Y (Equation 9)

In the equation, MAegr (%): target EGR valve opening degree Megr (%): target EGR rate Yegr (%): EGR rate Kp2: proportional gain Here, Kp2 is set in advance by experiment or simulation. In addition, it may be changed according to the operating state of the engine.

Y = Z ⁻¹ Y + Δt × Ki2 × Z ⁻¹ (Megr−Yegr) (Equation 10)

In the equation, Megr (%): target EGR rate Yegr (%): EGR rate Ki2: integral gain Δt (sec): sampling time Here, Ki2 is set in advance by experiment or simulation. It may change depending on the operating state of the engine. Δt is given as a constant.

FIG. 4 shows a second embodiment of the present invention. An EGR control device for a diesel engine according to this embodiment includes a target EGR rate setting means 1 and an EGR rate detecting means 2b.
When a collector dynamic characteristic calculating means 2b _1, the body bonds efficiency estimator 2b _2, the cylinder intake mixture amount calculation means 2b _3,
Cylinder intake fresh air amount calculating means 2b ₄ , EGR rate calculating means 2b ₅ , target EGR valve opening calculating means 3b, target fuel injection timing setting means 4, EGR valve operating means 5, target fuel injection timing correction Means 6b and fuel injection timing operating means 7
, Diesel engine 8, correction amount calculating means 9, EGR
Valve abnormality determining means 10b, operating state determining means 11, engine rotational speed detecting means 12, target fuel injection amount setting means 1
3, a collector suction fresh air amount detecting means 14, a collector pressure detecting means 15, and a collector temperature estimating means 16b.
And is composed of Note that, in the present embodiment, the configuration different from the first embodiment is that
6b, and the other configuration is the same as that of the first embodiment. Therefore, the same reference numerals as in the first embodiment denote the drawings, and a detailed description thereof will be omitted here.

That is, in the collector temperature estimating means 16b in this embodiment, first, in order to avoid an algebraic loop, an equation 11 is used from the EGR rate output from the EGR rate calculating means 2b ₅ in the EGR rate detecting means 2b. The value of one operation delay of the EGR rate (Yegr (-1)) is obtained.

Yegr (-1) = Z ^-1 Yegr (Equation 11)

In the equation, Yegr (%): EGR rate Yegr (-1) (%): value of one calculation delay of EGR rate

Next, the one operation delay value Yegr (-1) is calculated as follows:
Using the target fuel injection amount output from the target fuel injection amount setting means 13, the temperature in the collector is output from a map prepared in advance. FIG. 6 shows an example of the collector temperature setting map. It is assumed that the target fuel injection amount substantially matches the actual fuel injection amount.

[0059]

As described above, according to the first aspect of the present invention, there is provided means for judging abnormality of the EGR valve, and the target fuel injection timing is not corrected when the EGR valve is normal. By doing so, exhaust performance can be improved. Further, when the EGR valve is abnormal, even if the EGR valve is stuck open at a high load, a low target EGR rate at a high load can be realized, and a large amount of high-temperature EGR can be prevented from flowing into the collector. In addition, the effect that the engine design considering heat resistance is facilitated is obtained.

According to the second aspect of the present invention, it is possible to specify the EGR valve abnormality determining method according to the first aspect of the present invention. Furthermore, according to the invention described in claim 3, it is possible to specify the determination method of the driving state determination means in the invention described in claim 2.

Next, according to the fourth aspect of the present invention, the target EGR valve opening degree in the present invention is
It can be derived by calculation from the detected values of the rate and the EGR rate.

According to the invention described in claim 5, the method of detecting the EGR rate in the present invention can be specified.

Further, according to the invention described in claim 6, by estimating the temperature in the collector according to the present invention, compared with the case of detecting using the measuring means of claim 5, the measuring means can be used. The effect that it becomes unnecessary is obtained.

According to the seventh aspect of the present invention, it is possible to specify a method for estimating the dynamic characteristic until the gas drawn into the collector is drawn into the cylinder.

According to the eighth aspect of the present invention, a method for estimating the volumetric efficiency according to the fifth aspect can be specified.

Further, according to the ninth aspect of the invention, an effect is obtained that the estimating means is not required as compared with the case of estimating the volumetric efficiency of the fifth aspect.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of a diesel engine EGR control device according to the present invention.

FIG. 2 is a block diagram showing a configuration of an EGR control device for a diesel engine according to a first embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of an EGR rate detecting means of the EGR control device for the diesel engine.

FIG. 4 is a block diagram showing a configuration of an EGR control device for a diesel engine according to a second embodiment of the present invention.

FIG. 5 is an explanatory diagram showing an example of a volume efficiency setting map according to the present invention.

FIG. 6 is an explanatory view showing an example of a collector internal temperature setting map according to the present invention.

FIG. 7 is a block diagram illustrating a configuration of a conventional diesel engine EGR control device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Target EGR rate setting means _2, 2b EGR rate detecting means 2b ₁ Collector dynamic characteristic calculating means 2b ₂ Volume efficiency estimating means 2b ₃ Cylinder suction air-fuel mixture calculating means 2b ₄ Cylinder suction fresh air amount calculating means 2b ₅ EGR rate calculating means 3a Target EGR valve opening setting means 3b Target EGR valve opening calculating means 4 Target fuel injection timing setting means 5 EGR valve operating means 6a, 6b Target fuel injection timing correcting means 7 Fuel injection timing operating means 8 Diesel engine 9 Correction amount calculation Means 10a, 10b EGR valve abnormality judging means 11 Operating state judging means 12 Engine rotational speed detecting means 13 Target fuel injection amount setting means 14 Collector suction fresh air amount detecting means 15 Collector pressure detecting means 16 Collector temperature detecting means 16b In collector Temperature estimation means

Claims (9)

[Claims] 1. Means for setting a target EGR rate, means for setting a target EGR valve opening based on the target EGR rate, means for operating an EGR valve based on the target EGR valve opening, and target fuel injection timing A first target fuel injection timing setting means for setting the EGR rate; a means for detecting an EGR rate; a means for calculating a correction amount of the first target fuel injection timing from the target EGR rate and the EGR rate detection value; Based on the output of the means for determining the abnormality of the EGR valve and the output of the means for determining the abnormality of the EGR valve, the second target fuel injection timing and the correction amount are used to determine
Means for setting a target fuel injection timing, and means for operating the fuel injection timing based on the second target fuel injection timing,
An EGR control device for a diesel engine, comprising: 2. The means for judging an abnormality of the EGR valve,
When the operating state is in the steady state, the target E is determined based on the output of the operating state determination means that outputs a signal indicating the steady state.
The EGR control device for a diesel engine according to claim 1, wherein the determination is performed based on a GR rate and a detected value of the EGR rate. 3. The EGR control device for a diesel engine according to claim 2, wherein the operating state determining means determines the operating state based on one of an engine rotation speed and a target fuel injection amount. 4. The target EGR valve opening is determined by the target EG
The EGR control device for a diesel engine according to any one of claims 1 to 3, wherein the EGR control device is calculated from an R ratio and a detection value of the EGR ratio. 5. The means for detecting the EGR rate includes: means for detecting an amount of fresh air sucked into a collector; means for detecting a pressure in the collector; means for detecting a temperature in the collector; Means for estimating volumetric efficiency; means for calculating the amount of fresh air drawn into the cylinder based on the dynamic characteristics from the amount of fresh air drawn into the collector until the gas drawn into the collector is drawn into the cylinder; Means for calculating the amount of air-fuel mixture sucked into the cylinder from the engine rotational speed, the temperature in the collector, the pressure in the collector, the volumetric efficiency, and the stroke volume; 2. A means for calculating an EGR rate from the amount of fresh air to be sucked.
An EG for a diesel engine according to any one of claims 1 to 4.
R control device. 6. The EGR control device for a diesel engine according to claim 5, wherein the temperature in the collector is estimated from the detected value of the EGR rate and the target fuel injection amount. 7. The dynamic characteristic until the gas sucked into the collector is sucked into the cylinder is estimated from the engine speed, the volumetric efficiency, the stroke volume, and the collector volume. 7. An EGR control device for a diesel engine according to claim 6. 8. The EGR control for a diesel engine according to claim 5, wherein the means for estimating the volumetric efficiency estimates from the engine rotational speed and the pressure in the collector. apparatus. 9. The EGR control device for a diesel engine according to claim 5, wherein the volume efficiency is a predetermined constant.