WO2008153198A1

WO2008153198A1 - Egr control device using egr rate control

Info

Publication number: WO2008153198A1
Application number: PCT/JP2008/061168
Authority: WO
Inventors: Shingo Kimura; Seiji Asano
Original assignee: Hitachi, Ltd.
Priority date: 2007-06-12
Filing date: 2008-06-12
Publication date: 2008-12-18
Also published as: JPWO2008153198A1

Abstract

A control device that accurately calculates an EGR recirculation amount in EGR control of an internal combustion engine. A control device for an internal combustion engine includes EGR control having means for obtaining a recirculation amount correcting amount based on a difference between an actual EGR recirculation amount and a target EGR recirculation amount obtained from a target EGR rate that is based on an intake air amount of the engine and on conditions of the engine, and the EGR control also having means for obtaining the degree of opening of an EGR valve from the degree of opening of a standard EGR valve and from the recirculation amount correcting amount. The degree of opening of the EGR valve is feedback-controlled based on a difference between the target EGR recirculation amount and the actual EGR recirculation amount.

Description

Specification

EGR control system by EGR rate management

TECHNICAL FIELD The present invention relates to control of the EGR return amount of an internal combustion engine, and more particularly, to a control device of an internal combustion engine that controls the EGR return amount based on a target EGR ratio according to the state of the engine. Background art

As described in, for example, Patent Document 1 below, as an EGR control device for an internal combustion engine, an EGR valve is opened so that the EGR valve is adjusted to a preset value set in advance by the engine speed and the engine load. It is known that the degree is controlled by a control value such as a step value corresponding to the set value or a duty value.

Patent Document 1: Japanese Patent Application Publication No. 2000-199454 Disclosure of the Invention

However, in the above-mentioned conventional method, the EGR valve opening is managed by the map of the operating conditions, and in each operating region, the EGR valve opening-combustion state (such as engine speed fluctuation etc.) Since it is necessary to look at the correlation and the EGR rate will be confirmed later, there is a problem that the adaptation including the management of the EGR rate requires a large number of steps.

In order to solve the above-mentioned problems, a control device for an internal combustion engine having EGR control according to the present invention comprises means for obtaining a target EGR rate based on the state of the internal combustion engine, means for obtaining an intake air amount of the engine, A means for obtaining a target EGR recirculation amount from the intake air amount and the target EGR rate, a means for determining an opening degree of a basic EGR valve based on the target EGR recirculation amount, and a return at the critical pressure from the opening degree of the EGR valve. A means for obtaining a flow rate, a means for computing a differential pressure between an exhaust pressure and an air suction pressure, a means for obtaining an actual EGR recirculation amount of the differential pressure from the relationship between the valve opening degree of the EGR and the recirculation amount; A means for determining a correction amount of reflux amount based on a difference between the flow rate and the actual E GR reflux amount; Means for determining the opening degree of the EGR valve from the valve opening degree and the reflux amount correction amount, and the EGR valve opening degree is feedback-controlled based on the difference between the target EGR flow amount and the actual EGR return amount. It is characterized by

Further, in addition to the above features, the control device of an internal combustion engine having EGR control according to the present invention is characterized in that the means for obtaining the target EGR includes factors related to external EGR and internal EGR.

Further, in the control device for an internal combustion engine having EGR control according to the present invention, in addition to the above features, the means for determining the relationship between the actual EGR return amount under the differential pressure includes: a table of valve opening degree and return amount; It is characterized in that it is provided for at least one or more differential pressure. Further, in addition to the above features, the control device for an internal combustion engine having EGR control according to the present invention determines the correction amount of the amount of recirculation based on the difference between the target amount of EGR recirculation and the actual amount of EGR recirculation. The means includes means for determining a factor related to the correction sensitivity, and means for integrating the factor related to the correction sensitivity to the EGR basic opening degree, and a new real EG based on the integrated EGR basic opening degree. The apparatus is characterized in that the amount of R reflux is determined, and the integration is performed until the difference between the target EGR reflux and the actual EGR reflux becomes equal to or less than a predetermined value.

Further, in the control device for an internal combustion engine having EGR control according to the present invention, in addition to the above features, the factor relating to the correction sensitivity is that a difference between the target EGR return amount and the actual EGR return amount is 0. It is characterized in that it is a table in which a dead zone is set in the vicinity of. Further, in the control device for an internal combustion engine having EGR control according to the present invention, in addition to the above features, the factor relating to the front correction sensitivity is that the correction amount in the closing direction of the EGR valve is the correction amount in the opening direction. It is characterized in that the table is set larger.

Further, in the control device for an internal combustion engine having EGR control according to the present invention, in addition to the above features, feedback control of the EGR valve opening degree is performed based on the difference between the target EGR recirculation amount and the actual EGR recirculation amount. It is characterized in that one multiplied by the gain is added once. Further, in addition to the above features, in the control device for an internal combustion engine having EGR control according to the present invention, the feedback control of the EGR valve opening is performed when the EGR valve reaches the maximum opening. It is characterized by stopping.

The present invention controls ignition by the EGR rate by managing the EGR amount with the EGR rate. Correction of angle map and calculation of actual EGR rate with intake pipe pressure enable EGR rate feedback etc. Also, even after the pressure difference before and after the EGR valve reaches the critical pressure, feedback control is performed so that the actual EGR return amount approaches the target EGR return amount by correction according to the pressure difference between the intake pipe pressure and the exhaust pressure. , Enables precise control of the EGR valve opening. Brief description of the drawings

FIG. 1 is a block diagram of an example of an internal combustion engine provided with EGR control means according to the invention.

FIG. 2 is a block diagram showing an outline of the EGR control means according to the present invention.

FIG. 3 is a main part related to control of an engine equipped with a control device for an internal combustion engine provided with the EGR control means according to the present invention.

FIG. 4 is an example of an internal configuration of a control device for an internal combustion engine provided with the E G R control means according to the present invention.

FIG. 5 is an example showing details of blocks 20 1 to 2 10 of FIG. FIG. 6 is an example showing the blocks 2 1 1 to 2 1 3 of FIG. 2 in detail. FIG. 7 is an example showing the blocks 2 1 4 of FIG. 2 in detail.

FIG. 8 is an example showing the setting of block 702 in FIG.

Fig. 9 is an example showing the setting of block 7 in Fig. 7.

FIG. 10 is an example showing the setting of block 702 in FIG.

FIG. 11 is an example showing the block of block 214 in FIG. 2 in detail.

FIG. 12 is an example showing the block 215 of FIG. 2 in detail.

FIG. 13 is an example showing each variable behavior at the time of the control of the control device for an internal combustion engine provided with the EGR control means according to the present invention.

FIG. 14 is an example of a detailed flow chart of the fuel calculation relationship of the control block diagram of FIG. 1 of the present invention.

FIG. 15 is an example of a detailed flow chart of the ignition timing calculation relationship of the control block diagram of FIG. 1 of the present invention.

Figure 16 is a detailed flow chart of blocks 20 1 to 2 1 0 of Figure 2 of the present invention. It is an example.

FIG. 17 is an example of a detailed flowchart of blocks 21-11 of FIG. 2 of the present invention.

FIG. 18 is an example of a detailed flow chart of the block of FIG. 7 of the present invention. FIG. 19 is an example of a detailed flow chart of the block of FIG. 11 of the present invention. Explanation of sign

1 0 9 E G R control means

2 0 5 Target E G Reflux Amount Base Value Operation Unit

2 0 6 Exhaust gas residual amount calculator

2 1 0 Basic E G R opening calculation unit

2 1 3 Real E G R reflux calculation unit

2 1 4 Critical pressure extra-reflux amount correction operation unit

2 1 5 £ 0 1 Opening degree 0? ; Command value calculator

3 0 5 Intake pipe pressure sensor

3 0 6 injector

3 1 0 oxygen concentration sensor

3 1 2 Engine control unit

3 1 3 E G R valve BEST MODE FOR CARRYING OUT THE INVENTION

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

FIG. 1 is a block diagram showing an example of a control device of an internal combustion engine provided with an EGR control means according to the present invention. A block 101 is an engine rotational speed calculating means, and the number of pulses per unit time of the pulse signal which is an electric signal from the crank angle sensor set at a predetermined crank angle position of the engine. The number of revolutions per unit time of the engine is calculated by calculation processing.

Block 1 02 calculates the basic fuel required by the engine from the engine speed and engine load calculated in block 1 0 1. As the engine load, the output of the intake pipe pressure sensor installed in the intake pipe is calculated and converted to the intake pipe pressure. Or, let's use a representative of the amount of intake air of the engine measured with a thermal air flow meter etc.

In block 103, the engine rotational speed calculated in block 101 and the engine load described above are used to map the correction factor in each operating region of the engine to the basic fuel calculated in block 102. calculate. In block 104, the optimum basic ignition timing in each region of the engine is obtained and calculated based on the engine speed and the engine load.

A block 105 is a valve set in the intake pipe, and detects the degree of opening of a throttle throttle valve that adjusts the amount of intake air of the engine, and determines the state of the engine desired by the driver. The state to be determined is whether it is idle or not, and whether it is acceleration or deceleration. Block 106 corrects the optimal basic ignition timing retrieved in block 104 according to the state of the engine determined in block 100.

A block 107 determines the optimum target air-fuel ratio in each region of the engine by map search or the like based on the engine speed and the engine load. In block 108, the feedback control coefficient (air-fuel ratio feedback coefficient) by PID control is calculated by the output of the oxygen concentration sensor set in the exhaust pipe so that the target air-fuel ratio determined in block 107 is obtained. Do.

The block 109 calculates the optimum E G R opening based on the above-mentioned engine speed, the above-mentioned engine load, throttle throttle valve opening, intake air temperature, engine coolant temperature at startup, and the like. Block 1 10 0 corrects the basic fuel calculated in block 1 0 2 according to the basic fuel correction coefficient, the engine coolant temperature, and the air-fuel ratio feedback coefficient.

Blocks 11 1 to 1 14 are fuel injection means for supplying the amount of fuel corrected in block 1 10 to the engine. Blocks 115-15 are ignition means for igniting the fuel mixture that has flowed into the cylinder in accordance with the required ignition timing of the engine corrected by the block 106 described above.

FIG. 2 is a block diagram showing an outline of the EGR control means of the internal combustion engine according to the present invention. Block 201 retrieves the target EGR rate from the map based on the detected engine speed and engine load (throttle opening). In block 2 0 2, detect The internal EGR rate is retrieved from the map based on the selected engine speed and engine load. Block 203 calculates the air flow rate drawn into the engine from the detected intake pipe pressure and engine speed. From the intake air amount, an actual EGR recirculation amount, which will be described later, is subtracted by an adder 204 to calculate the actual intake air amount. When measuring the amount of intake air with a thermal air flow meter, block 203 and adder 204 are not required.

In block 205, a target EGR return flow rate base value is calculated from the target EGR rate and the actual intake air amount. In block 206, the exhaust gas residual amount is calculated from the internal EGR rate and the actual intake air amount. In block 207 and block 208, the target EGR reflux base value and the exhaust gas residual amount are respectively subjected to weighted averaging, and the adder 209 calculates a difference to calculate the target EGR reflux. In block 210, the basic EGR opening is calculated from the target EGR recirculation amount described above. In block 215, an EGR opening degree CPU command value is calculated from the basic EGR opening degree described above and the critical pressure extra-reflux amount correction value described later.

The block 21 searches the exhaust pressure by the map based on the engine speed and the engine load. The intake pipe pressure is subtracted from the exhaust pressure by the adder 212 to calculate the differential pressure between the exhaust pressure and the intake pipe pressure. In block 2113, the actual EGR recirculation amount is calculated from the EGR opening degree CPU instruction value in accordance with the differential pressure. block

In 214, according to the target EGR rate, the target EGR recirculation amount and the actual E

From the GR reflux amount, the above-mentioned critical pressure extra-reflux correction value is calculated.

FIG. 3 shows a main part related to control of an engine equipped with a control device for an internal combustion engine provided with the EGR control means according to the present invention.

In FIG. 3, the thermal air flowmeter 30 la, which measures the amount of air intake by the engine, is connected to the intake pipe 304 by bypassing the throttle throttle valve 302 outside the engine body 301 and measuring the amount of air intake by the engine. Idle speed control valve 303 which controls the engine rotation speed by controlling the flow passage area of the flow passage, intake pipe pressure sensor 305 which detects the pressure in the intake pipe 304, fuel required by the engine The fuel injection valve 306 for supplying fuel, the crank angle sensor 307 set at a predetermined crank angle position of the engine, the spark plug for igniting the mixture of fuel supplied into the engine cylinder from the engine control device 3 1 2 Ignition energy based on the ignition signal of The ignition module 308 that supplies the engine torque, the water temperature sensor 309 that detects the engine coolant temperature, is set to the cylinder cylinder of the engine, and the oxygen concentration sensor that detects the oxygen concentration in the exhaust gas. The main engine switch for engine operation and shutdown is a key switch 31 1 1. A part of exhaust gas is returned to the intake pipe 304 EGR valve 3 1 3. Engine accessories are controlled. The gin controller 3 1 2 is shown. The intake pipe pressure sensor 305 is integrated with an intake air temperature sensor that measures the temperature of the intake air.

In the present embodiment, the oxygen concentration sensor 310 outputs a signal proportional to the exhaust air-fuel ratio. However, the exhaust gas on the ratchet side Z lean side with respect to the theoretical air-fuel ratio is used. It may be one that outputs a signal. Although the intake pipe pressure is detected and used as the fuel control parameter of the internal combustion engine in the present embodiment, the intake air amount may be detected and used by a thermal air flow meter.

FIG. 4 shows an example of the internal configuration of a control device for an internal combustion engine provided with EGR control means according to the present invention. Inside the CPU 401, an I / O unit 402 is set which functions as an interface for converting the electric signals of the sensors installed in the engine into signals for digital arithmetic processing. Signals from a water temperature sensor 404, a crank angle sensor 405, an oxygen concentration sensor 406, an intake pipe pressure sensor 407, a throttle opening sensor 408, and an information switch SW409 are input to the / O unit 402. In a system that measures the amount of intake air with a thermal air flow meter or the like, a hot-wire air flow meter 403 is provided.

The output signal from the CPU 40 1 is via the dry flow 4 1 0 to the fuel injection valve 4 1 1 to 4 14, the ignition coil 4 1 5 to 4 1 8, to the idle speed control (ISC) valve. It is sent to the I 2 C opening command value 4 1 9, E GR opening command value 420 to E GR valve.

FIG. 5 is a detailed representation of the blocks 20 1 to 2 10 of FIG. A block 501 retrieves a target EGR rate EGRR from the engine speed and the engine load, or from the engine speed and the throttle opening degree, according to a previously set target EGR rate map. In block 502, the intake air pressure QAR is multiplied by a constant to calculate the intake air amount QAR. When the EGR valve opens and the EGR recirculation starts, the intake pipe pressure also rises, so the actual EGR recirculation amount EGRGER described later is subtracted from the calculated intake air amount QAR to be described later to calculate the actual intake air amount QER Do. In the present embodiment, the intake air amount QAR is calculated from the intake pipe pressure. However, in a system that measures the intake air amount with a thermal air flow meter etc., the blocks 502 and 503 are unnecessary, and the measured intake The amount of air QAR is directly used as the actual amount of intake air QER, but the intake pipe pressure as an engine load used by other blocks is an engine obtained by dividing the amount of intake air QAR by the engine speed N e The load T p will be used.

In the present embodiment, the actual intake air amount QER is switched by the block 506 switch block by setting “1” or “0” to the D jetrono L jetro determination software SW of the block 505. The target EGR return amount base value calculation unit of block 507 calculates a target EGR return amount base value EGRGE B from the target EGR rate EGRR and the actual intake air amount QER.

The number 1 represents the basic equation of the EGR rate.

[Number 1]

EGRR = ~ ^-Qa + Ge

Ge EGR recirculation amount

Assuming that QA intake air flow number 1 is converted to the EGR recirculation amount Ge equation, Ge is the target EGR rate EGRR, and the intake air amount Qa is the actual intake air amount QER, it is shown in block 507 of FIG. The following equation is obtained, and this equation calculates the target EGR recirculation amount base value.

A block 508 retrieves an internal EGR rate EG R I NR from the engine speed and the engine load, or from the engine speed and the throttle opening degree, according to a preset internal EGR rate map.

In this embodiment, although the internal EGR is considered, if only the external EGR is desired to be managed, it can be coped with by setting the data of the block 508 map to zero. Transform the above number 1 into the equation of EGR recirculation amount Ge, and let GE be the EGR ratio EGR IN Assuming that R is the amount of intake air Q a is the amount of actual intake air QER, the equations shown in blocks 5.0, 9, and 9 of FIG. 5 are obtained, and the exhaust gas residual amount EGR I NM is calculated by this equation. In the adder 510, the weighted average weight is applied to the above-mentioned exhaust gas residual amount EGR I NM from the value obtained by applying the weighted average to the target EGR reflux amount base value EGRGEB described above using the weighted average weight KE GRGE. Calculate the target EGR reflux amount EGRGE by subtracting the weighted average value using KEGR IN. A block 513 is a basic EGR opening degree operation unit. Here, the basic EGR opening degree EGRSTDB is retrieved from the above-mentioned target EGR return amount EG RGE by a table. Note that the table is previously determined on the assumption that a differential pressure DP 1 PM between an exhaust pressure and an intake pipe pressure described later is in a critical pressure state. FIG. 6 shows the blocks 2 1 1 to 2 14 of FIG. 2 in detail. The block 601 searches the exhaust pressure PME XT from the engine rotational speed and the engine load or the engine rotational speed and the throttle opening according to the preset exhaust pressure map. The intake pipe pressure is subtracted from the retrieved exhaust pressure PMEXT by the adder 602, and the differential pressure DP 1 PM of the exhaust pressure and the intake pressure is calculated. A block 603 is a real EGR return amount calculation unit, in which at least two or more flow rate characteristic tables of the EGR valve opening degree and the return amount are provided according to the above-mentioned differential pressure DP 1 PM. Based on the command value EGR S TD, search the table for the actual EGR recirculation amount EGRGER.

The number 2 represents the basic equation of the EGR recirculation amount. [Number 2]

= f {EGR _A) x Kx (1-Pm) (2)

(At the time of critical pressure

Ge = g {EGR_A) (3)

EGR_A: EGR opening area

PI exhaust pressure

Pm Intake pressure

The above equation (1) is a relationship between the pressure difference between the exhaust pressure and the intake pipe pressure and the EGR recirculation amount. The equation (2) is a equation which calculates the EGR recirculation amount by modifying the equation (1).

The above equation (2) represents that the EGR recirculation amount can be obtained from the difference between the EGR opening area, the coefficient, and the exhaust pressure and the pressure difference between the exhaust pressure and the intake pipe pressure. The equation (3) above incorporates the nonlinear characteristics. This is realized by the plurality of flow rate characteristic tables of the actual EGR reflux amount calculation unit 603.

In this embodiment, although the above-mentioned actual EGR return amount calculation unit 603 is configured to include a plurality of flow rate characteristic tables according to the differential pressure DP 1 PM, the plurality of tapes are replaced by maps. You can also configure it to replace it with an approximate expression from experimental values.

The above equation (3) represents the calculation of the EGR reflux amount when the difference (differential pressure) between the exhaust pressure and the intake pipe pressure is smaller than the critical pressure. When the pressure in the intake pipe is reduced relative to the exhaust pressure, the flow velocity of the EGR reflux in the EGR pipe connecting the exhaust pipe and the intake pipe reaches the speed of sound, and the pressure at this time is called the critical pressure. Since the flow velocity does not exceed the speed of sound, the flow velocity of the EGR recirculation amount does not change even if the intake pipe pressure is further lowered. In this case, the EGR recirculation amount is determined by the EGR opening area.

FIG. 7 shows in detail an example of the critical pressure extra-reflux amount correction operation unit of block 214 in FIG. The adder 701 subtracts the above-mentioned actual EGR recirculation amount EGRGER from the above-mentioned target EGR recirculation amount EGRGE, to calculate the critical pressure flow difference def g e r. In block 702, cr i i is retrieved from the EGR critical pressure correction table with the above-mentioned critical pressure flow difference de f g e r. The adder 703 adds the previous value of the critical pressure extra-recirculation correction amount EGRCR I and the cr i i to calculate the critical pressure extra-reflow correction amount EGRCR I. However, if the target EGR rate EGRR is zero, the critical pressure flow difference difference defger is set to zero at switch 705, and the critical pressure extra-recirculation amount correction amount EGRCR I is set to zero at switch 704 and critical immediately. The overpressure correction is set to 0 (disabled).

8 to 10 are setting examples of the EGR critical pressure outside correction table of FIG. The vertical axis is the crii, and the horizontal axis is the critical pressure flow difference defger, and the right half of the figure is the area where the defger is positive and represents the open side of the EGR valve. The half is the area where the defger is negative, and represents the closing side of the EGR valve. Also, in a region where .defger is small (a region where the difference between the target EGR recirculation amount and the actual EGR recirculation amount is small), set dead zones with crii equal to 0 and prevent chattering near the target.

Fig. 8 shows an example in which the EGR critical pressure outside correction table is set such that crii is point symmetric on the positive side and negative side of the defer with respect to the critical pressure flow difference defger. As the amount of EGR recirculation increases, there is a risk of misfiring during deceleration.

Fig. 9 shows an example where the table is set by making the inclination of crii steeper on the minus side of defer as compared with Fig. 8. By doing this, the crii on the closing side of the EGR valve is enlarged. Misfires are prevented by accelerating the closing operation of the EGR valve outside the critical pressure.

Fig. 10 shows an example in which the EGR critical pressure correction table is set so that cr i i changes stepwise. Thus, the dead zone can be set stepwise. FIG. 11 shows in detail another example of the critical pressure extra-reflux amount correction operation unit of the block 214 of FIG. In the adder 1101, the above-mentioned actual EGR recirculation amount EGRGER is subtracted from the above-mentioned target EGR recirculation amount EGRGE to calculate the critical pressure flow difference def ge r. Block 1 120 searches a table of gain reference value GA I N S TD from the critical pressure flow difference de f g e r described above. Switch 1 1 03 is the open side gain OPGA I N of block 1 1 04 and the close side gain C L G A 1 of block 1 1 05

Switch N by the positive or negative of the above critical pressure flow difference de f g e r, gain correction G A

I Output NHOS. The gain on the open side and the gain on the close side are set by the ROM constant etc., and the close side gain is set large to prevent misfires.

A multiplier 1106 multiplies the gain reference value GA I NSTD by the gain correction GAI NHOS, and further multiplies the critical pressure flow difference defger in the multiplier 1 1 0 7 to correct the critical pressure extra-recirculation amount. Calculate the quantity EGR CRI.

However, when the target EGR rate EGRR is 0, the correction is made invalid by setting the critical pressure extra-recirculation amount correction amount EGRCR I to 0 in switch 1108.

Fig.12 shows in detail an example of the EGR opening CPU command value calculation unit 215 of Fig.2. It is a thing. The adder 1201 adds the basic EGR opening degree EGRSTD.B and the above-mentioned critical pressure extra-recirculation amount correction amount EGRCR I. Block 1 202 limits the upper and lower limits defined by a constant or the like to the above added value, and outputs the EGR opening degree CPU command value E GRS TD.

FIG. 13 is an example showing each variable behavior at the time of operation of a control device for an internal combustion engine provided with the EGR control means according to the present invention. Ch 1 130 1 is throttle opening, Ch 1 302 is engine speed, Ch 1 305 is intake air amount, Ch 1 306 is intake pipe pressure, Ch 1 308 is EG R The opening command value and chart 1 3 1 1 show the behavior of the EGR valve opening.

Section 1 303 is a transient section of the throttle opening, and chart 1 308 shows the EGR opening command value corrected by the method of the present invention. 1 307 is a point at which the intake pipe pressure reaches a critical pressure, and as shown in chart 1 308 at this boundary, the EGR opening degree is larger than that in the absence of the control of the present invention. Since the command value can be increased, as indicated by the chart 1 3 1 1, when the control of the present invention is present, the degree of opening of the EGR valve can be increased as compared with the case without the control.

FIG. 14 shows an example of a flowchart of fuel calculation in a control device for an internal combustion engine provided with the EGR control means according to the present invention shown in FIG.

Step 1401 calculates the engine speed based on the signal from the crank angle sensor. Step 1 402 reads the engine load. In the present embodiment, the engine load is obtained by dividing the suction negative pressure or the amount of intake air by the engine speed. Step 1403 calculates the basic fuel amount. In step 1404, a correction coefficient of a basic fuel amount is searched based on the engine speed and the engine load. Step 1 405 retrieves the required target air-fuel ratio. Step 1406 reads the output of the oxygen concentration sensor, and step 1407 performs air-fuel ratio feedback based on the output of the oxygen concentration sensor so that the air-fuel ratio becomes the target air-fuel ratio, and calculates an air-fuel ratio feedback coefficient. . Step 1408 calculates an EGR opening degree command value from the engine speed and the engine load. In step 1409, the air-fuel ratio feedback coefficient is applied to the basic fuel amount. In step 1410, the basic fuel amount corrected as described above is set to the fuel injection means. FIG. 15 is an example of a detailed flowchart of the ignition timing calculation relationship of the control block diagram of FIG. Read the engine speed and the engine load in step 1501. In step 1502, a basic ignition timing is retrieved based on the engine speed and the engine load. Step 1 503 reads the throttle opening, and step 1 504 determines the engine state for acceleration / deceleration and idle judgment. In step 1505, the ignition correction amount is calculated based on the condition determined above, and is reflected to the basic ignition timing, and set in the ignition means in step 1506. Although the fuel calculation and the ignition timing calculation are performed at different interrupt cycles in FIGS. 14 and 15, they may be performed at the same timing. Also, although it has been interrupted for a fixed time, it may be carried out at a timing synchronized with the rotation angle of the engine.

FIG. 16 is an example of a detailed flow chart of blocks 201 to 210 of FIG. Step 1 Read the engine speed, throttle opening and intake pipe pressure in step 60 1. At step 1602, the intake air amount is calculated from the engine speed and the intake pipe pressure. Also, the amount of intake air measured by a thermal air flow meter may be used as it is. In step 1603, calculate the engine load by dividing the intake air amount by the engine speed. Step 1604 searches for the target EGR rate by engine speed and engine load or engine speed and throttle opening. Step 1 Search internal EGR rate by engine speed and engine load at 605. In step 1606, the actual amount of EGR recirculation is read, and in step 1607, the amount of intake air is subtracted from the amount of actual EGR recirculation to calculate the actual amount of intake air. As described above, in the system that measures the amount of intake air with a thermal air flow meter or the like, steps 1602 and 1606 to 1607 are not necessary. In step 1 608, the target EGR return amount base value is calculated using the target EGR ratio and the actual intake air amount. Step 1 609 calculates the residual amount of exhaust gas from the internal EGR rate and the actual intake air amount. Step 16: Subtract the value obtained by applying the weighted average to the residual amount of exhaust gas from the value obtained by applying the weighted average to the target EGR recirculation amount base value in step 610, and obtain the target EG

Calculate the amount of R reflux. Step 1 6 1 1 Basic based on the target EGR recirculation amount

Calculate the EGR opening degree.

FIG. 17 is an example of a detailed flowchart of blocks 2 1 1 to 2 1 3 of FIG. Step 1 Read the engine speed, engine load and intake pipe pressure at 70 1. In step 1702, search exhaust pressure by engine speed and engine load. In step 1703, the pressure difference is calculated by subtracting the intake pipe pressure from the exhaust pressure described above. In step 1704, the actual EGR recirculation amount is calculated from the differential pressure and the EGR opening degree CPU command value.

FIG. 18 is an example of a detailed flowchart of the critical pressure extra-reflux amount correction operation unit of FIG. Step 1 In 801, it is judged whether or not the target EGR rate ≠ 0. If the target EGR rate is not 0, in Step 1 802, the critical pressure outside flow rate difference is output as ◦. If the target EGR rate ≠ 0, the aforementioned target EGR return amount is read in step 1803, and the aforementioned actual EGR return amount is read in step 1804, and the aforementioned target EGR return amount is read in step 1805. The actual EGR recirculation amount is subtracted to calculate the critical pressure outside flow difference. In step 1806, a table outside the critical pressure correction amount is retrieved based on the above critical pressure external flow rate difference. In step 1807, it is judged again whether or not the target EGR rate 、 0. If the target EGR rate ≠ 0, in step 1 808, the critical pressure outside correction amount is output as 0. If the target EGR rate ≠ 0, in step 1 809, calculation is performed by feeding back the critical pressure correction amount using the previous critical pressure correction amount and the aforementioned gain. FIG. 19 is an example of a detailed flowchart of the critical pressure extra-reflux amount correction operation unit of FIG. Step 1 90 1 Read the above-mentioned target EGR reflux, read step 1 90 2 Read the above-mentioned actual EGR reflux, Subtract the actual EGR reflux from the above-mentioned target EGR reflux at step 1 903 Calculate the outflow difference. In step 1904, a gain reference value is retrieved based on the above-mentioned critical pressure outside flow rate difference. In step 1 905, it is judged whether the critical pressure outside flow rate difference is 0 or more, and if it is not 0 or more, the gain correction value selects the close side gain in step 1 906, and if it is 0 or more, step 1 907 Select the open side gain. Note that both the closing gain and the opening gain are set by the ROM constant etc., and the closing gain is set large to prevent a misfire. In step 1 908, it is determined whether the target EGR rate ≠ 0. If the target EGR rate ≠ 0, in step 1 909, the critical pressure outside correction amount is set to 0. If the target EGR rate ≠ 0, the critical pressure outside flow rate difference, the gain reference value, and the gain correction value are respectively multiplied in step 1 9 10 to calculate the critical pressure outside correction amount.

The present invention manages the EGR amount by the EGR rate, corrects the ignition advance map by the EGR rate, calculates the actual EGR rate by the intake pipe pressure, and outputs the EGR rate feedback. Can be expected to be possible. Also, even after the pressure difference before and after the EGR valve reaches the critical pressure, feedback control is performed so that the actual EGR return amount approaches the target EGR return flow rate by correction according to the pressure difference between the intake pipe pressure and the exhaust pressure. It becomes possible to control the opening degree of the EGR valve with high accuracy. Further, when the EGR valve is changed, it is possible to cope with only the change of the valve characteristic data, and there is no need to change the control logic, so it can be said that the control logic of the present invention has high versatility.

As mentioned above, although one embodiment of the present invention was explained in full detail, the present invention is not limited to the above-mentioned embodiment. Further, each component is not limited to the above configuration as long as the characteristic functions of the present invention are not impaired.

Claims

The scope of the claims

1. a means for determining a target EGR rate based on the state of the internal combustion engine;

Means for obtaining the intake air amount of the engine;

A means for obtaining a target EGR reflux amount from the intake air amount and the target EGR rate, a means for obtaining an opening degree of a basic EGR valve based on the target EGR return amount, and a critical pressure from the opening degree of the EGR valve A means for determining the amount of reflux,

A means for calculating a differential pressure between the exhaust pressure and the intake pipe pressure;

A means for determining an actual EGR recirculation amount under the differential pressure from the relationship between the valve opening degree of the EGR and the recirculation amount;

A means for determining a correction for the amount of reflux based on the difference between the target amount of E G reflux and the actual E G reflux amount;

Means for determining the opening degree of the EGR valve from the opening degree of the basic EG valve and the reflux amount correction amount,

A control device of an internal combustion engine having an EGR control characterized by performing a return control of an EGR valve opening degree by a difference between the target EGR return amount and the actual EGR return amount.

2. The control device according to claim 1, wherein the means for obtaining the target EGR includes factors related to external EGR and internal EGR.

3. The control device according to claim 1, wherein the means for determining the relationship between the valve opening degree of the EGR and the reflux amount with respect to the differential pressure includes at least one or more tables of the valve opening degree and the reflux amount. A control device for an internal combustion engine, comprising a differential pressure of

4. The control device according to claim 1, wherein the means for determining the amount of correction of the amount of recirculation based on the difference between the target amount of EGR recirculation and the actual EGR amount of recirculation comprises: means for determining a factor related to the correction sensitivity; A means for integrating the factor relating to the correction sensitivity to the EGR basic opening degree, further obtaining a new actual EGR return quantity based on the integrated EGR basic opening degree, and the target EGR return quantity The control device for an internal combustion engine, wherein the integration is performed until the difference between the actual EGR return amount becomes equal to or less than a predetermined value.

5. In the control device according to claim 2, a factor responsible for the correction sensitivity is that a dead zone is set when the difference between the target EGR reflux amount and the real EGR reflux amount is near 0. It is a table, The control device of the internal-combustion engine provided with EGR control characterized by the above-mentioned.

6. The control device according to claim 2, wherein the factor related to the front correction sensitivity is a table in which the correction amount in the closing direction of the EGR valve is set larger than the correction amount in the opening direction. A control device for an internal combustion engine having an EGR control.

7. In the control device according to claim 1, the feedback control of the EGR valve opening degree is performed by adding one time a product of the difference between the target EGR return amount and the real EGR return amount multiplied by a gain. A control device for an internal combustion engine having EGR control characterized by:

8. The control device according to claim 1, wherein the feedback control of the EGR valve opening degree stops the feedback when the EGR valve reaches the maximum opening degree. Engine control device.