JP4581221B2 - EGR control device for diesel engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an EGR control device for a diesel engine.
[0002]
[Prior art]
As a prior art, there is an EGR control device for a diesel engine described in Japanese Patent Laid-Open No. 60-122259.
This EGR control device has exhaust O₂O to detect concentration₂The actual EGR amount is calculated from the sensor output, and the EGR control valve is feedback-controlled (hereinafter referred to as F / B) according to the deviation between the actual EGR amount and the target EGR amount.
[0003]
[Problems to be solved by the invention]
However, O₂Exhaust gas detected by sensor₂The concentration of EGR gas generated by opening and closing the EGR control valve recirculates to the intake pipe and is sucked into the engine cylinder from the intake pipe and then discharged from the cylinder to the exhaust pipe through the combustion stroke. O provided₂It reaches the sensor and is detected. That is, OGR from EGR control valve₂Due to the presence of the system (physical path length) to the sensor, the exhaust O in association with the opening / closing operation of the EGR control valve₂The effect on concentration is actually O₂There is a delay time until it is detected by the sensor.
As a result, in the above prior art, the responsiveness to the F / B control of the EGR control valve is deteriorated, and it is difficult to perform highly accurate EGR control.
[0004]
Especially for turbo engines, the EGR control valve₂Since the delay time due to the system to the sensor increases, the worst case is that the operation timing of the EGR control valve and the OGR₂The output timing of the sensor is out of phase with the risk of hunting.
The present invention has been made based on the above circumstances, and its purpose is to exhaust the exhaust gas that accompanies the opening / closing operation of the EGR control valve.₂An object of the present invention is to provide an EGR control device capable of realizing a highly responsive and highly accurate EGR control by predicting a change in concentration for each engine operating region and correcting an EGR amount.
[0005]
[Means for Solving the Problems]
(Means of Claim 1) The control means for controlling the opening and closing operation of the EGR control valve is an exhaust O which changes in accordance with the opening and closing operation of the EGR control valve.₂Concentration behavior is O₂The time delay that occurs until the sensor detects itModel setting means for modeling according to the operation direction of the EGR control valve, respectively, when operating to the close side and when operating to the open side;Using the model set by the model setting means, the exhaust O generated with respect to the operation amount of the EGR control valve corresponding to the operating state of the diesel engine.₂It has a correction amount calculating means for obtaining a predicted value of concentration and calculating a correction amount of the EGR control valve from a deviation between the predicted value and the target value, and is calculated by the operation amount of the EGR control valve and the correction amount calculating means. The EGR control valve is feedback-controlled based on the correction amount. According to the present invention, the EGR control valve₂Model the time delay to the sensor and exhaust O₂Since the predicted concentration value is obtained, it is possible to improve the deterioration of the responsiveness to the F / B control of the EGR control valve, and to realize highly accurate EGR control.
  Further, the model setting means sets a model corresponding to the operation direction of the EGR control valve when the EGR control valve is operated to the close side and when the EGR control valve is operated to the open side. Since the EGR control valve has different responsiveness to the operation amount between the closed side and the open side due to the structure of the main body of the EGR control valve, when operating to the closed side and operating to the open side, respectively, By setting a corresponding model, more accurate EGR control can be realized.
[0006]
(Means of Claim 2)
In the EGR control device of the diesel engine according to claim 1,
The correction amount calculating means calculates the correction amount of the EGR control valve by state amount feedback using the model set by the model setting means.
[0007]
(Means of claim 3)
In the EGR control device of the diesel engine according to claim 1 or 2,
The model setting means is switched from the EGR control valve to O₂The time delay to the sensor is modeled as a transfer function represented by waste time and time constant (first-order delay).
Exhaust O that changes with the opening and closing operation of the EGR control valve₂Concentration behavior is O₂The delay time until it is detected by the sensor is determined by the exhaust gas from the operation of the EGR control valve.₂Waste time to reach the sensor and the exhaust gas O₂Concentration is O₂It can be approximated by the first-order delay until detection by the sensor. Therefore, from the EGR control valve, O₂The time delay to the sensor can be modeled as a transfer function represented by waste time and time constant (first order delay).
[0009]
    (Means of Claim 4) Claims 1 to 3In any of the diesel engine EGR control apparatuses described, the model setting means sets a model corresponding to each operating region depending on the rotational speed of the diesel engine. Exhaust O that changes with the opening and closing operation of the EGR control valve₂Concentration behavior is O₂Responsiveness until detection by the sensor is affected by the amount of exhaust gas, exhaust gas pressure, and the like, and therefore varies depending on the operating range of the diesel engine. Therefore, more accurate EGR control can be realized by setting a model corresponding to each engine operating range.
[0010]
    (Means of Claim 5) Claim 4In the described EGR control device for a diesel engine, the model setting means sets the modeled delay time to be shorter in the operating region where the rotational speed is higher than in the operating region where the rotational speed of the diesel engine is low. Exhaust O that changes with the opening and closing operation of the EGR control valve₂Concentration behavior is O₂The response until detection by the sensor becomes better as the rotational speed of the diesel engine increases. Therefore, more accurate EGR control can be realized by setting the modeled delay time to be shorter in the operating range where the rotational speed is higher than in the operating range where the rotational speed of the diesel engine is low.
[0011]
(Means of Claim 6) Claims 1 to 5In any of the described diesel engine EGR control devices, when the control unit determines that the model set for each diesel engine operating region has been switched, the control unit stores the previous time in a memory corresponding to the operating region after the switching. The correction amount thus read is read out from the correction amount learning means, and the EGR control valve is feedback-controlled based on the correction amount. In this case, when the model is switched, it is possible to quickly set the correction amount by using the correction amount stored last time as it is rather than newly calculating the correction amount this time, and the correction amount due to erroneous calculation. It is also possible to prevent setting errors.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of an EGR control system, and FIG. 2 is a control block diagram of the EGR control system.
As shown in FIG. 1, the EGR control system of the present embodiment includes an EGR passage 4 (exhaust gas recirculation passage) that connects the exhaust pipe 2 and the intake pipe 3 of the diesel engine 1, and an EGR control valve provided in the EGR passage 4. 5, the compressor 6 provided in the intake pipe 3, the exhaust turbine 7 provided in the exhaust pipe 2, various sensors used for control of the system (described below), and the EGR control valve 5 based on each sensor information It is comprised from the control apparatus (henceforth ECU8) etc. which control an action | operation.
[0013]
As shown in FIG. 12A, the EGR control valve 5 includes an electric vacuum metering valve (hereinafter referred to as EVRV9), a mechanical valve (hereinafter referred to as EGRV10), and a vacuum pump 11.
The EVRV 9 adjusts the amount of vacuum received from the vacuum pump 11 by the control current IEFIN output from the ECU 8, and generates a control negative pressure corresponding to the control current IEFIN as shown in FIG.
[0014]
The EGRV 10 includes a back pressure chamber 10a into which a control negative pressure is introduced from the EVRV 9, a diaphragm 10b that is displaced according to pressure fluctuations in the back pressure chamber 10a, a valve body 10c that is linked to the diaphragm 10b, and the diaphragm 10b. As shown in FIG. 12C, the valve lift is generated according to the controlled negative pressure introduced into the back pressure chamber 10a.
Therefore, the EGR control valve 5 is configured to vary the valve lift amount of the EGRV 10 by the control current IEFIN output from the ECU 8, as shown in FIG.
[0015]
The various sensors described above detect the intake pressure sensor 12 that detects the intake pressure in the intake pipe 3, the rotation angle sensor 13 that outputs a signal in synchronization with the rotation angle of the diesel engine 1, and the cooling water temperature of the diesel engine 1. Oxygen (O) in the exhaust pipe 2 downstream of the water temperature sensor 14 and the exhaust turbine 7₂) O to detect concentration₂An accelerator opening sensor 17 for detecting the accelerator opening from the depression amount of the sensor 15 and the accelerator pedal 16 is used.
The ECU 8 determines the operating state of the diesel engine 1 based on the sensor information input from each of the above sensors, and calculates the optimum opening of the EGR control valve 5 (the valve lift amount of the EGRV 10) according to the operating state. Then, a control current (see FIG. 9) for realizing the valve lift amount is output to the EVRV 9.
[0016]
Next, the control procedure of the EGR control valve 5 by the ECU 8 will be described below.
First, a description will be given based on the base routine shown in FIG.
Execution is disclosed simultaneously with power-on of the control system, and memory (RAM, ROM) used for program execution is initialized only once immediately after startup. Thereafter, the following Step 100 to Step 500 included in the base routine are processed.
[0017]
Step 100 ... The basic EGRV operation amount (basic control current) corresponding to the current operating state of the diesel engine 1 is calculated.
Step200 ... Ideal exhaust gas in the current operating condition of diesel engine 1.₂Calculate the concentration as the target value.
Step300 ... Exhaust O for the basic EGRV manipulated variable calculated in Step100₂Calculate the F / B correction amount (hereinafter referred to as F / B correction amount).
[0018]
Step400… O₂Exhaust gas O detected by sensor 15₂The F / B correction amount when the concentration is stable at the target value is stored for each operating range of the diesel engine 1 and learned.
Step 500 ... The final EGRV operation amount is calculated using the basic EGRV operation amount calculated in Step 100, the F / B correction amount calculated in Step 300, and the learning value stored in Step 400.
When a series of base routines including Step 100 to Step 500 are completed, the process returns to immediately after the initialization process and repeats the re-execution.
FIG. 2 is a block diagram schematically showing the control contents of this base routine.
[0019]
Next, the basic EGRV manipulated variable calculation procedure described in Step 100 of the base routine will be described based on the subroutine shown in FIG.
This routine is executed every 16 ms.
Step 101 ... Read the rotational speed Ne of the diesel engine 1.
Step102 ... The fuel injection amount Qf is read.
[0020]
Step 103 ... The basic EGRV manipulated variable is calculated from the IEBSE map using Ne and Qf as parameters. For example, when Ne = N1 and Qf = Q1 in the figure, α is calculated by map search. Here, the basic EGRV manipulated variable embedded in the map was tested in advance so that the emission, fuel consumption, drivability, etc. would be ideal values for each operating range of the diesel engine 1 in the initial central product of the control system. The value obtained by setting the EGR rate at.
Step 104 ... α obtained in Step 103 is stored in the memory as the basic EGRV operation amount: IEBSE, and this routine is terminated.
[0021]
Subsequently, the target exhaust O described in Step 200 of the base routine₂The density calculation procedure will be described based on the subroutine shown in FIG.
This routine is executed every 16 ms.
Step 201 ... Read the rotational speed Ne of the diesel engine 1.
Step 202 ... Read the fuel injection amount Qf.
[0022]
Step203 ... Target exhaust O from RO2TRG map with Ne and Qf as parameters₂Calculate the concentration. For example, when Ne = N2 and Qf = Q2 in the figure, β is calculated by map search. Here, the target exhaust O buried in the map₂Concentration is O discharged from diesel engine 1₂The concentration is a value obtained in advance by experiments so that good emission, fuel consumption, drivability, etc. are always obtained for each driving region.
Step204… β obtained in Step203 is the target exhaust gas O₂Concentration: Store in memory as RO2TRG, and end this routine.
[0023]
Subsequently, the exhaust O described in Step 300 of the base routine₂An outline of a method for calculating the F / B correction amount (hereinafter referred to as F / B correction amount) will be described with reference to a block diagram shown in FIG.
Block30A ... EGRV10 exhaust O₂Determine whether to execute density F / B (when F / B is enabled: XFB = 1).
Block 30B: An area determination for selecting an F / B control model (described later) corresponding to the operating range of the diesel engine 1 is performed.
[0024]
Block30C: Detects when the learning area or control model is switched, and operates the control initialization permission SW (when initialization is permitted: INT.SW = 1).
Block30D ... F / B permission flag: XFB, initialization permission SW: INT.SW, speed Ne, actual exhaust O₂Concentration: RO2, target exhaust O₂Concentration: From each input of RO2TRG, calculate the F / B correction amount: IEO2FB of EGRV10 that matches the operating conditions of the diesel engine 1.
Block30E ... Calculated F / B correction amount: IEO2FB is subjected to upper and lower guard processing, and final F / B correction amount: IEO2FBF is calculated.
[0025]
Next, the details of the outline shown in FIG. 6 will be described based on the flowcharts of FIGS. 7 and 8. This routine is executed every 16 ms.
Step 301 ... Basic EGRV manipulated variable: IEBSE is read.
Step 302 ... Judge whether the read IEBSE is smaller than the judgment value: 250 mA (IEBSE <250 mA). As shown in FIG. 9, the determination value: 250 mA is the fully closed point of EGRV10. If the above relationship (IEBSE <250 mA) is satisfied, it is determined that EGRV10 is in the fully closed position and the process proceeds to Step 303. . On the other hand, when the above relationship is not established, the process proceeds to Step 304.
[0026]
Step 303 ... Since it is instructed to fully close the EGRV 10, it is determined that the EGR control is prohibited and the exhaust O₂To prohibit the density F / B, set the F / B permission flag: XFB = 0.
Step304… Exhaust O₂To permit the density F / B, set the F / B permission flag: XFB = 1.
Step305 ... Number of revolutions of diesel engine 1 Ne, O₂Actual exhaust O detected by sensor 15₂Concentration: RO2 and target exhaust O₂Concentration: Read RO2TRG.
Step 306 ... Judges whether or not the relationship RO2 = RO2TRG is established.
When the above relationship is established, that is, exhaust O₂When the measured value of the concentration has converged to the target value, the process proceeds to Step 307, and when not established, the process proceeds to Step 308.
[0027]
Step 307 ... Control model selection No: Set NMDL = 0, and go to Step 311.
Step 308 ... Judge whether or not the relationship of RO2 <RO2TRG is established.
When the above relationship is established, that is, exhaust O₂When the measured value of the concentration is lower than the target value, the process proceeds to Step 309.₂When the actual measured value of concentration is equal to or higher than the target value, the process proceeds to Step 310.
Step 309 ... The control model selection No: NMDL corresponding to the closed side of the EGRV 10 is set (see FIG. 10).
Step 310 ... The control model selection No: NMDL corresponding to the open side of the EGRV 10 is set (see FIG. 11).
[0028]
Here, the concept of the above-described control model will be described.
The control model is the OGR provided in the exhaust pipe 2 when the EGRV 10 is caused to make a step response with an arbitrary operation amount.₂Exhaust gas O measured by sensor 15₂Concentration response is a transfer function.
Referring to FIG. 1, for example, when the EGRV 10 moves to the open side, the EGR gas recirculated to the intake pipe 3 rapidly increases simultaneously with the opening operation of the EGRV 10, and the amount of air sucked from the air cleaner side is increased by the increase in EGR gas. Suppressed and sucked into the cylinder of the diesel engine 1. At this time, if the amount of fuel before and after the EGR gas increases is equal, the amount of fresh air intake decreases, and the A / F (air-fuel ratio) becomes deeper, and the exhaust O₂The concentration decreases. That is, the EGR rate of the diesel engine 1 and the exhaust O₂The relationship with the density is inversely proportional as shown in FIG.
[0029]
The gas discharged from the cylinder is discharged through a long system due to the intake pipe 3, the exhaust pipe 2, the volume in the cylinder, the time delay from the intake valve opening to the intake valve closing of the diesel engine 1, etc.₂Reaching sensor 15, O₂Exhaust O with sensor 15₂A change in concentration is detected.
Next, with reference to FIG. 14, the OGR corresponding to the step change of the EGRV manipulated variable is explained.₂The output of the sensor 15 can be approximated by a function (time constant T) of waste time L and first order lag. Therefore, EGRV10 to O₂The time delay due to the system up to the sensor 15 can be modeled as a transfer function represented by a waste time L and a time constant T.
[0030]
It should be noted that the exhaust gas O with the operation of the EGRV 10₂Concentration is O₂Responsiveness until it is detected by the sensor 15 is affected by the amount of exhaust gas, exhaust gas pressure, etc., and therefore varies depending on the operating range of the diesel engine 1. Even in the same operating range, because of the function of the EGRV 10, the valve lift response to the EGRV manipulated variable is different between the open side and the closed side.₂Concentration responsiveness changes as shown in FIG.
[0031]
Here, the description returns to the flowcharts of FIGS. 7 and 8.
In Steps 309 and 310, the control model for the EGRV 10 closed side operation and the open side operation is set.₂Since the responsiveness of the concentration changes (see FIG. 15), as shown in FIGS. 10 and 11, a control model selection No: NMDL corresponding to each operation region is set (NMDL = 0 to 5). Then go to Step311.
Step311… Learning area selection No ： NLEARN is read.
Step 312 ... It is determined whether or not the previous and current NMDLs are different, that is, whether or not the control model has been switched. When the control model is not switched, the process proceeds to Step 313. When the control model is switched, the process proceeds to Step 314.
[0032]
Step 313: It is determined whether or not the learning area has been switched. When it is switched, the process proceeds to Step 314. When it is not switched, the process proceeds to Step 315.
Step 314... Initial SW: INT.SW is set when the control model or learning area is switched (INT.SW = 1).
Step 315: Since the control model and the learning area are not switched, INT.SW is cleared (INT.SW = 0), and the process proceeds to Step 316.
Step316… Exhaust O₂Concentration F / B permission flag: Judges whether or not F / B is permitted from the state of XFB. If not permitted, the process proceeds to Step 317, and if permitted, the process proceeds to Step 318.
[0033]
Step317… F / B correction amount: Clear IEO2FB (IEO2FB = 0) and disable correction.
Step 318 ... Initial SW: It is determined whether there is a control initialization request from the state of INT.SW. When there is a request (INT.SW = 1), the process proceeds to Step 319. When there is no request (INT.SW = 0), the process proceeds to Step 320.
Step 319 ... Hold the previous correction amount without calculating the current correction amount.
This is to prevent a mistake in setting the correction amount due to an erroneous calculation when switching the control model or switching the learning area.
[0034]
Step 320 to 333 ... If F / B is permitted in Step 316 and control initialization is not requested in Step 318, normal F / B conditions are established. Therefore, a control model selected by the control model selection No: NMDL and a correction gain corresponding to a control model in which responsiveness and convergence are matched in advance through experiments are selected.
Step334… Next exhaust O by the control model selected in Step320 ~ 333₂EGRV10 state correction amount: IEO2FBB for predicting the concentration and causing it to converge to the target value is calculated. The method is exhaust O from the past.₂Each of a plurality of past data is weighted with a correction gain from the density and EGRV manipulated variable data, and is calculated from the state quantity correction control formula shown below (see FIG. 16).
[0035]
IEO2FBB = K1 · RO2 + K2 · IEO2FB (i-1) + K3 · IEO2FB (i-2) + ... + KL · IEO2FB (i-L)
K1, K2, K3... KL: correction gain, this correction gain is set for waste time / 16 ms.
Step335 ... Calculate the integral correction amount of the control equation: ZI from the following equation.
ZI = ZI (i-1) + Ka (RO2TRG-RO2)
Ka: Correction gain (Similar to K1 to KL, calculated according to the control model)
[0036]
Step336 ... State correction amount: IEO2FBB is added to integral correction amount: ZI to calculate final F / B correction amount: IEO2FB.
IEO2FB = IEO2FBB + ZI
Step337 ... Final F / B correction amount calculated in Step336: IEO2FB upper / lower limit guard is performed, and this routine is finished.
IEMIN <IEO2FB <IEMAX
IEMIN: Lower guard value, IEMAX: Upper guard value
[0037]
Next, the F / B correction amount learning method described in Step 400 of the base routine will be described based on the subroutine shown in FIG. 17 and the time chart shown in FIG.
This routine is executed every 16 ms.
Step401… O₂Actual exhaust O from sensor 15₂Concentration: RO2 is read and the target exhaust gas O calculated by the subroutine of FIG.₂Concentration: Read RO2TRG.
Step 402 ... It is determined whether or not the following relationship is established between RO2 and RO2TRG.
RO2 <RO2TRG-γ
When this relationship is not established, the process proceeds to Step 403, and when established, the process proceeds to Step 404.
[0038]
Step403 ... It is determined whether or not the following relationship is established between RO2 and RO2TRG.
RO2> RO2TRG + γ
When this relationship is not established, the process proceeds to Step 405, and when established, the process proceeds to Step 404.
The processing in Step 402 and Step 403 above is to determine whether RO2 has converged to the target value: RO2TRG. If the determination result in Step 402 or Step 403 is YES, RO2 has converged to the target value: RO2TRG. It can be judged that there is no.
[0039]
On the other hand, when the determination results of Step 402 and Step 403 are both NO, the following relationship is established, so it can be determined that RO2 has converged to the target value: RO2TRG (see FIG. 19).
(RO2TRG −γ) ≦ RO2 ≦ (RO2TRG + γ)
“Γ” is a value for determining the convergence of RO2 to the target value, and is, for example, a value of 0.3% of the target value: RO2TRG.
Step 404 ... Clear the learning condition counter: CLEARN (CLEARN = 0).
[0040]
Step 405: Increment CLEARN (CLEARN = CLEARN + 1).
Step 406: It is determined whether or not CLEARN is smaller than the determination value.
When CLEARN is smaller than the judgment value, the process proceeds to Step 407, and when larger, the process proceeds to Step 408.
The processing of Step 406 is to determine whether or not an arbitrary time (1000 ms in this embodiment) has elapsed since RO2 converged to the target value: RO2TRG. Therefore, since this routine is repeatedly executed every 16 ms in order to count 1000 ms, the determination value is set to “63” (1000 ms ÷ 16 ms≈63).
[0041]
Step 407… Learning permission SW: Clear LEARN.SW (LEARN.SW = 0).
Step 408... The learning condition counter CLEARN is set to “63”.
Step409 ... LEARN.SW = 1 and learning is permitted.
Step 410 ... Read the rotational speed Ne and the fuel injection amount Qf.
Step 411... Learning area No: NLEARN is searched from the learning area map shown in FIG. 18 using Ne and Qf as parameters. For example, Ne = 1200rpm, Qf = 9mm^ThreeIf / st, NLEARN = 6.
[0042]
Step412… Judge whether the F / B permission flag XFB is enabled or not.
When it is in the permission state (XFB = 1), the process proceeds to Step 413. When it is in the permission prohibition state (XFB = 0), the process proceeds to Step 415.
Step 413… Learning permission SW: It is determined whether or not LEARN.SW is permitted.
When the permission state (LEARN.SW = 1), the process proceeds to Step 414. When the permission prohibition state (LEARN.SW = 0), the process proceeds to Step 415.
Step414… F / B correction amount: Learn IEO2FB.
In this learning of IEO2FB, the value of F / B correction amount: IEO2FB at that time is stored in the memory: IELEARN (X) corresponding to the learning area No: NLEARN. For example, if NLEARN = 6, the value of IEO2FB is stored in memory: IELEARN (6).
[0043]
Step 415 Initialize SW: Judges whether INT.SW is in the permitted state.
When it is in the permission state (INT.SW = 1), the process proceeds to Step 416. When it is in the permission prohibition state (INT.SW = 0), this routine is terminated.
Step 416... Learning area No: Memory corresponding to NLEARN: The learning value is read from IELEARN (X), and the learning value is set to IELEARN.
Here, the condition of INT.SW = 1 is to initialize the control when the control model or the learning area is switched to the previous time (16 ms before) as shown in Steps 311 to 319 described above.
[0044]
Next, the procedure for calculating the final EGRV manipulated variable described in Step 500 of the base routine will be described based on the subroutine shown in FIG.
This routine is executed every 16 ms.
Step501… F / B correction amount: Read IEO2FB.
Step502… Learning value: IELEARN is read.
Step503 ... Basic EGRV operation amount: IEBSE is read.
Step 504... The total sum of the values read in Steps 501 to 503 is calculated, and the final EGRV manipulated variable is IEFIN.
IEFIN = IEBSE + IEO2FB + IELEARN
After calculating the final EGRV manipulated variable: IEFIN, this routine is terminated.
[0045]
Next, the operation and effect of the present embodiment will be described with reference to the time chart shown in FIG.
During acceleration, when the accelerator is depressed, the accelerator opening changes as shown in FIG. In conjunction with this, generally, the fuel injection amount Qf increases from the parameters of the accelerator opening and the rotational speed Ne (c).
At this time, the rotational speed Ne cannot be increased rapidly due to traveling resistance, the capacity of the diesel engine 1, and the like, but starts to increase gradually (b).
[0046]
In order to prevent the A / F over-concentration against the rapid increase in the fuel injection amount Qf (the A / F over-concentration causes an increase in smoke due to incomplete combustion), the EGRV 10 is closed and the EGR amount I want to increase the amount of fresh air intake by the amount of drastically decreasing the₂For F / B control, O₂Exhaust gas O detected by sensor 15₂Since the EGR amount is corrected after waiting for the change in concentration, the fresh air intake amount is delayed (f) and smoke is generated (g) compared to the rise of the fuel. In the steady state, the target exhaust O₂Although there is a merit that it can converge to the concentration, there is a large delay at the time of transition, and smoke generation becomes large.
[0047]
On the other hand, in the present EGR control system, the exhaust gas O accompanying the operation of the EGRV 10 is₂Since the change in the concentration is accurately predicted for each operating region and the EGR amount is corrected (e), the rise of the fresh air intake amount is accelerated not only in the steady state but also in the transient state (f).₂The density can be quickly converged to a predetermined target value (d). As a result, high-response and high-precision EGR control can be realized, and the generation of smoke can be greatly reduced as compared with conventional control (g).
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an EGR control system.
FIG. 2 is a control block diagram of an EGR control system.
FIG. 3 is a flowchart of a base routine in a control program.
FIG. 4 is a flowchart showing a procedure for calculating a basic EGRV manipulated variable.
FIG. 5: Target exhaust O₂It is a flowchart which shows the calculation procedure of a density | concentration.
FIG. 6 Exhaust O₂FIG. 6 is a block diagram schematically illustrating a calculation procedure of F / B correction amount.
FIG. 7 Exhaust O₂It is a flowchart which shows the calculation procedure of F / B correction amount.
FIG. 8 Exhaust O₂It is a flowchart which shows the calculation procedure of F / B correction amount.
FIG. 9 is a characteristic diagram of EGRV.
FIG. 10 is a control model setting table on the closed side of EGRV.
FIG. 11 is a control model setting table on the open side of EGRV.
FIG. 12 is a configuration diagram (a) and characteristic diagrams (b) and (c) of a negative pressure control type EGR control valve.
FIG. 13: EGR rate and exhaust O₂It is a relationship figure with a density | concentration.
FIG. 14 is a model diagram showing a delay in sensor output with respect to an EGRV manipulated variable by a transfer function.
FIG. 15 is an engine characteristic diagram of waste time and time constant representing a transfer function.
FIG. 16 is a supplementary diagram for explaining state quantity correction;
FIG. 17 is a flowchart showing a learning control routine.
FIG. 18 is a learning area setting map;
FIG. 19 is a time chart of a learning method.
FIG. 20 is a flowchart showing a procedure for calculating a final EGRV manipulated variable.
FIG. 21 is a control time chart of the present system.
[Explanation of symbols]
1 Diesel engine
2 Exhaust pipe (exhaust passage)
3 Intake pipe (intake passage)
4 EGR passage (exhaust gas recirculation passage)
5 EGR control valve
8 ECU (control means)
(Step 309, 310 ... model setting means)
(Steps 334 to 337 ... correction amount calculation means)
(Step 402 to 408 ... convergence determination means)
(Step 414… correction amount learning means)
(Step 415 ... model determination means)
15 O₂Sensor

Claims (6)

An exhaust gas recirculation passage communicating the intake passage and the exhaust passage of the diesel engine;
An EGR control valve capable of adjusting the amount of EGR gas flowing through the exhaust gas recirculation passage;
An O ₂ sensor for detecting an exhaust O ₂ concentration in the exhaust passage;
A diesel engine EGR control device comprising control means for feedback controlling the EGR control valve so that the exhaust O ₂ concentration detected by the O ₂ sensor converges to a target value,
The control means includes
When operating the time delay that occurs until the O ₂ sensor detects the behavior of the exhaust gas O ₂ concentration that changes with the opening / closing operation of the EGR control valve, when operating to the close side, and when operating to the open side, Model setting means for modeling in accordance with the operation direction of the EGR control valve,
Using the model set by the model setting means, a predicted value of the exhaust O ₂ concentration generated for the operation amount of the EGR control valve corresponding to the operating state of the diesel engine is obtained, and the predicted value and the target Correction amount calculation means for calculating a correction amount of the EGR control valve from a deviation from the value,
An EGR control device for a diesel engine, wherein the EGR control valve is feedback-controlled based on an operation amount of the EGR control valve and a correction amount calculated by the correction amount calculation means. In the EGR control device of the diesel engine according to claim 1,
The EGR control device for a diesel engine, wherein the correction amount calculation means calculates a correction amount of the EGR control valve by state quantity feedback using the model set by the model setting means. In the EGR control device of the diesel engine according to claim 1 or 2,
The EGR control apparatus for a diesel engine, wherein the model setting means models the time delay as a transfer function represented by a waste time and a time constant.   In the EGR control apparatus of any diesel engine as described in Claims 1-3,
  The EGR control device for a diesel engine, wherein the model setting means sets a model corresponding to each operating region based on the rotational speed of the diesel engine.   In the EGR control device of the diesel engine according to claim 4,
  The model setting means is characterized in that the modeled delay time is set shorter in the operating range where the rotational speed is higher than in the operating range where the rotational speed of the diesel engine is low. .   In the EGR control device for any diesel engine according to claim 1,
  The control means includes
  Exhaust O for each operating range of the diesel engine ₂ Convergence determining means for determining that the concentration has converged to the target value;
  From the information of the convergence determination means, the exhaust O ₂ Correction amount learning means for storing the correction amount of the EGR control valve calculated based on the operation state at that time when it is determined that the concentration has converged to the target value in a memory corresponding to the operation region at that time;
  Model determination means for determining whether or not the model set for each operating range of the diesel engine has been switched,
  When it is determined that the model has been switched from the information of the model determination means, the correction amount stored in the memory corresponding to the driving range after the switching is read from the correction amount learning means, and the EGR is based on the correction amount. An EGR control device for a diesel engine, wherein the control valve is feedback-controlled.

Images