JP2004108262A - Internal egr amount estimating device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely estimate an internal EGR amount from the quantity of state in the cylinder of the engine by using a physical equation. <P>SOLUTION: When an exhaust valve is closed, based on signals from an exhaust temperature sensor 12, an intake pressure sensor 10, and exhaust pressure sensor 11, a cylinder temperature and a cylinder pressure are calculated, the gas constant of exhaust gas according to a combustion air/fuel ratio is calculated, and a cylinder gas amount is calculated. Then, based on signals from a crank angle sensor 14, a water temperature sensor 15, cam angle sensors 16 and 17, and an accelerator opening sensor 18, a blowback gas amount during overlapping in an intake valve opening period and an exhaust valve opening period is calculated. Based on the calculated values of the cylinder gas amount and the blowback gas amount, the internal EGR amount is calculated. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a device for estimating an internal EGR amount (reflux amount of exhaust gas) of an internal combustion engine.
[0002]
[Prior art]
Conventionally, a spark ignition type internal combustion engine uses a variable valve mechanism in order to reduce NOx (nitrogen oxide) by suppressing combustion temperature by increasing inert components and to reduce fuel consumption by reducing pump loss. In some cases, the amount of overlap between the exhaust valve open period and the intake valve open period is increased to increase the internal EGR amount. In this case, it is desirable to perform control for correcting ignition timing, fuel injection amount, valve opening / closing timing, and the like according to the internal EGR amount.
[0003]
Further, in Patent Document 1, a basic value of an internal EGR amount is calculated from engine operating conditions (load, rotation speed, air-fuel ratio, EGR ratio, intake negative pressure, etc.) when there is no overlap, and operation during overlap is performed. It is disclosed that the internal EGR amount is corrected according to a change amount of a condition.
[0004]
[Patent Document 1]
JP 2001-221105 A
[0005]
[Problems to be solved by the invention]
However, it is difficult to uniquely estimate the internal EGR amount from the overlap amount because the operating state changes and the combination of the load, the rotation speed, the combustion air-fuel ratio, the intake negative pressure, and the like changes.
Further, in Patent Literature 1, when the internal EGR amount is corrected from the change amount of the operating condition, the accuracy of the internal EGR amount calculated based on the change of each parameter is not sufficient.
[0006]
The present invention has been made to solve the above-described problem, and has as its object to accurately estimate an internal EGR amount according to operating conditions of an engine.
[0007]
[Means for Solving the Problems]
Therefore, in the present invention, the in-cylinder temperature when the exhaust valve is closed, the in-cylinder pressure when the exhaust valve is closed, and the gas constant of the exhaust gas composition according to the combustion air-fuel ratio are calculated, and the exhaust gas is calculated based on at least these. The in-cylinder gas amount when the valve is closed is calculated. Then, the blowback gas amount during the overlap between the exhaust valve open period and the intake valve open period is calculated. Then, the internal EGR amount is calculated based on the in-cylinder gas amount and the blowback gas amount.
[0008]
【The invention's effect】
According to the present invention, the internal EGR amount can be accurately estimated based on the state quantity (temperature, pressure, and gas constant of exhaust gas) inside the cylinder after the end of combustion, regardless of the operating conditions.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a system configuration diagram of an internal EGR amount estimating device for an internal combustion engine.
A combustion chamber 3 defined by a piston 2 of each cylinder of the engine 1 is provided with an intake valve 5 and an exhaust valve 6 so as to surround a spark plug 4. The lift characteristics (opening / closing timing) of the intake valve 5 and the exhaust valve 6 are controlled by changing the phase of the cam with respect to the cam shaft by the variable valve solenoids 22 and 23 provided on the intake side and the exhaust side. Is possible.
[0010]
An electronically controlled throttle valve 19 is provided in the intake passage 7 to control the intake fresh air amount. Fuel is supplied by an injector 20 provided in the intake passage 7 for each cylinder (or directly facing each combustion chamber 3). In the combustion chamber 3, the air-fuel mixture is ignited by an ignition plug 4 and burns, and is discharged to an exhaust passage 8.
Here, the operations of the electronic control throttle valve 19, the injector 20, the ignition plug 4 (the ignition coil 21 with a built-in power tiger), and the variable valve solenoids 22 and 23 are controlled by an engine control unit (ECU) 30.
[0011]
For these controls, signals from various sensors are input to the ECU 30.
The crank angle sensor 14 outputs a crank angle signal in synchronization with the engine rotation, and thereby can detect the engine rotation speed together with the crank angle position. The cam angle sensors 16 and 17 can detect the cam angles of the intake valve 5 and the exhaust valve 6, and thereby can detect the operating states of the variable valve solenoids 22 and 23.
[0012]
An air flow meter 9 for detecting a fresh intake air amount in the intake passage 7, an intake pressure sensor 10 for detecting intake pressure downstream of the electronic control throttle valve 19, and an exhaust pressure sensor 11 for detecting exhaust pressure in the exhaust passage 7. An exhaust temperature sensor 12 for detecting an exhaust gas temperature in the exhaust passage 8, an O2 sensor (oxygen sensor) 13 for detecting an amount of oxygen contained in the exhaust gas in the exhaust passage 8, and a water temperature sensor for detecting a temperature of a cooling water of the engine 1. 15. The output signal of the accelerator opening sensor 18 for detecting the accelerator opening is also input to the ECU 30, and these states can be detected.
[0013]
Next, the estimation of the internal EGR amount and the internal EGR rate performed by the ECU 30 will be described below. 2 to 7 are control configuration diagrams, FIGS. 8 to 16 are control flowcharts, and FIGS. 17 to 22 are tables for obtaining respective values.
The calculation of the internal EGR rate MRESFR will be described with reference to the control configuration diagram of the internal EGR rate calculating means of FIG. 2 and the internal EGR rate MRESFR calculation flow of FIG.
[0014]
The intake fresh air amount calculating means shown in FIG. 2 calculates the intake fresh air amount (fresh air mass) MACYL, the target combustion equivalent ratio calculating means calculates the target combustion equivalent ratio TFBYA, and the internal EGR amount calculating means calculates the internal EGR amount MRES. Based on these calculated values, the internal EGR rate calculation means calculates the internal EGR rate MRESFR.
In step 1 of FIG. 8, the intake fresh air amount MACYL per cylinder is calculated based on the intake fresh air amount measured by the air flow meter 9.
[0015]
In step 2, the engine speed is detected based on the signal of the crank angle sensor 14, the accelerator opening detected based on the signal of the accelerator opening sensor 18, and detected based on the signal of the water temperature sensor 15. A target combustion equivalent ratio TFBYA determined according to the cooling water temperature is calculated.
When the stoichiometric air-fuel ratio is 14.7, the target combustion equivalent ratio TFBYA is expressed by the following equation from the target combustion air-fuel ratio, and becomes 1 when the target combustion air-fuel ratio is stoichiometric.
[0016]
TFBYA = 14.7 / target combustion air-fuel ratio (1)
In step 3, the internal EGR amount MRES per cylinder is calculated according to the flowchart of FIG. 9 described later.
In step 4, the internal EGR rate MRESFR (the ratio of the internal EGR amount to the total gas amount per cylinder) is calculated by the following equation, and the process ends.
[0017]
MRESFR = MRES / {MRES + MACYL × (1 + TFBYA / 14.7)} (2)
Here, the calculation of the internal EGR amount MRES in step 3 will be described with reference to the control configuration diagram of the internal EGR amount calculation means in FIG. 3 and the internal EGR amount calculation flow in FIG.
[0018]
When the exhaust valve shown in FIG. 3 is closed (shown as “EVC” in the figure), the in-cylinder gas amount calculation means uses the in-cylinder gas amount MRESCYL and overlaps the intake valve 5 and the exhaust valve 6 (“O / L)), the return gas amount calculating means calculates the return gas amount MRESOL, respectively, and the internal EGR amount calculating means calculates the internal EGR amount MRES based on these calculated values.
[0019]
In step 5 of FIG. 9, an in-cylinder exhaust valve gas amount MRESCYL, which is an amount of gas remaining in the cylinder when the exhaust valve is closed, is calculated according to a flowchart of FIG.
In step 6, in accordance with the flowchart of FIG. 11 described later, an overlap blowback gas amount MRESOL, which is a gas amount blown back from the exhaust side to the intake side during overlap, is calculated.
[0020]
In step 7, the in-cylinder gas amount MRESCYL when the exhaust valve is closed and the blow-back gas amount MRESOL during overlap are added, and the internal EGR amount MRES is calculated by the following equation.
MRES = MRESCYL + MRESOL (3)
Here, regarding the calculation of the in-cylinder gas amount MRESCYL when the exhaust valve is closed in step 5, the control configuration of the in-cylinder gas amount calculation means when the exhaust valve is closed in FIG. This will be described with reference to a gas amount MRESCYL calculation flow.
[0021]
The target combustion equivalence ratio calculation means shown in FIG. 4 calculates the target combustion equivalence ratio TFBYA of the exhaust gas, and the exhaust gas gas constant calculation means calculates the gas constant REX based on this value. The exhaust valve closing cylinder volume calculating means calculates the cylinder volume VEVC, the exhaust valve closing cylinder temperature calculating means calculates the cylinder temperature TEVC, and the exhaust valve closing pressure calculating means calculates the cylinder pressure PEVC. Then, based on these calculated values, the in-cylinder gas amount calculation means when the exhaust valve is closed calculates the in-cylinder gas amount MRESCYL.
[0022]
In step 8 in FIG. 10, the in-cylinder volume VEVC when the exhaust valve is closed is obtained from the table shown in FIG. FIG. 17 is a table for calculating the in-cylinder volume VEVC when the exhaust valve is closed, in which the horizontal axis indicates the exhaust valve opening / closing timing change amount VTCNOWE and the vertical axis indicates the in-cylinder volume VEVC when the exhaust valve is closed.
Here, in an engine having a mechanism for changing the exhaust valve closing timing, the exhaust valve shown in FIG. 17 is changed according to the exhaust valve opening / closing timing change amount VTCNOWE detected based on the signal of the exhaust cam angle sensor 17. The in-cylinder volume VEVC when the valve is closed is obtained from a table.
[0023]
In an engine having a mechanism for changing the compression ratio, the in-cylinder volume VEVC when the exhaust valve is closed according to the amount of change in the compression ratio is obtained from a table.
Further, in an engine having a mechanism for simultaneously changing the exhaust valve closing timing and the compression ratio, the exhaust valve closing cylinder volume VEVC according to the exhaust valve closing timing and the compression ratio change amount is obtained from a table. .
[0024]
In step 9 in FIG. 10, the gas constant REX of the exhaust gas corresponding to the target combustion equivalent ratio TFBYA is obtained from the table shown in FIG. FIG. 18 is an exhaust gas constant REX calculation table. The horizontal axis indicates the target combustion equivalent ratio TFBYA, and the vertical axis indicates the gas constant REX of the exhaust gas. The dotted line in FIG. 18 indicates stoichiometry.
In step 10, the in-cylinder temperature TEVC when the exhaust valve is closed is estimated based on the exhaust gas temperature detected based on the signal of the exhaust gas temperature sensor 12. Since the in-cylinder temperature TEVC at the time of closing the exhaust valve changes depending on the amount of heat corresponding to the fuel injection amount of the injector 20, it may be obtained from a table utilizing such characteristics.
[0025]
In step 11, the in-cylinder pressure PEVC when the exhaust valve is closed is estimated based on the exhaust pressure detected based on the signal of the exhaust pressure sensor 11. The in-cylinder pressure PEVC when the exhaust valve is closed is determined by the air-fuel mixture volume and the pipe resistance of the exhaust system, and may be obtained from a table corresponding to the air-fuel mixture volume flow rate.
In step 12, calculated values of the exhaust valve closing cylinder volume VEVC, the exhaust gas gas constant REX, the exhaust valve closing cylinder temperature TEVC, and the exhaust valve closing cylinder pressure PEVC calculated in steps 8 to 11 are calculated. From this, the in-cylinder gas amount MRESCYL when the exhaust valve is closed remaining inside the cylinder when the exhaust valve is closed is calculated by the following equation.
[0026]
MRESCYL = (PEVC × VEVC) / (REX × TEVC) (4)
Here, regarding the calculation of the gas amount MRESOL that is blown back from the exhaust side to the intake side during the overlap in step 6 of FIG. 9, the control configuration diagram of the calculation of the gas flow back during overlap in FIG. 5 and the blow back during overlap in FIG. This will be described with reference to a gas amount MRESOL calculation flow.
[0027]
The opening / closing timing change amount calculation means for the exhaust valve and the intake valve shown in FIG. 5 calculates the overlap change amount VTCOL from the opening / closing timing change amounts VTCNOW and VTCNOWE between the intake valve and the exhaust valve, and calculates the over-lapping change amount VTCOL based on the calculated value. The in-lap integrated effective area calculation means calculates an integrated effective area ASUMOL. The target combustion equivalence ratio calculation means calculates the equivalence ratio TFBYA, and based on the calculated value, the exhaust gas gas constant calculation means calculates the gas constant REX. Then, the calculated values are compared with the engine speed calculating means, the exhaust gas specific heat ratio calculating means, the in-cylinder temperature calculating means when the exhaust valve is closed, the in-cylinder pressure calculating means when the exhaust valve is closed, the intake pressure calculating means, and the choke excess. On the basis of the values calculated by the supply determination calculating means, the blowback gas amount calculating means during the overlap calculates the blowback gas amount MRESOL.
[0028]
In step 13 of FIG. 11, the intake valve opening / closing timing change amount VTCNOW detected based on the signal of the cam angle sensor 16 detecting the phase of the intake cam, and the signal of the cam angle sensor 17 detecting the phase of the exhaust cam. From the exhaust valve opening / closing timing change amount VTCNOWE detected based on the above equation, the overlap change amount VTCOL is calculated by the following equation.
[0029]
VTCOL = VTCNOW + VTCNOWE (5)
In step 14, the integrated effective area ASUMOL during the overlap is obtained from the table shown in FIG. 19 according to the overlap change amount VTCOL calculated by the equation (5). FIG. 19 is a table for calculating the integrated effective area during the overlap. The horizontal axis indicates the overlap change amount VTCOL, and the vertical axis indicates the integrated effective area ASAMOL during the overlap. As the overlap change amount VTCOL increases, the integrated effective area ASUMOL increases.
[0030]
Here, FIG. 20 is an explanatory diagram of the integrated effective area ASUMOL during the overlap, the horizontal axis shows the crank angle, and the vertical axis shows the opening area of each of the intake valve 5 and the exhaust valve 6. The effective opening area at a certain point during the overlap is the smaller of the exhaust valve opening area and the intake valve opening area. That is, the integrated effective area ASAMOL for the entire period during the overlap is shown as an integrated value (the hatched portion in the figure) during the period when the intake valve 5 and the exhaust valve 6 are open.
[0031]
By calculating the integrated effective area ASAMOL during the overlap in this manner, the amount of overlap between the intake valve 5 and the exhaust valve 6 can be simulated as one orifice (outflow hole), and the state of the exhaust system and the state of the intake system From this, the flow rate passing through this orifice is simply calculated.
In step 15 of FIG. 11, the engine speed NRPM is calculated based on the signal of the crank angle sensor 14.
[0032]
In step 16, the exhaust gas specific heat ratio SHEATR is calculated from the map shown in FIG. This control configuration is shown in FIG.
The target combustion equivalence ratio calculation means shown in FIG. 6 calculates the target combustion equivalence ratio TFBYA, and the in-cylinder temperature at exhaust valve closing calculation means calculates the in-cylinder temperature TEVC, respectively, and based on these calculated values, the exhaust gas specific heat ratio calculation means. Calculates the exhaust gas specific heat ratio SHEATR.
[0033]
FIG. 21 is an exhaust gas specific heat ratio calculation map, in which the horizontal axis indicates the target combustion equivalent ratio TFBYA, and the vertical axis indicates the exhaust gas specific heat ratio SHEATR. The dotted line in the figure indicates the position of stoichiometry. When the target combustion equivalent ratio TFBYA is near stoichiometry, the exhaust gas specific heat ratio SHEATR decreases, and when the target combustion equivalent ratio TFBYA becomes rich or lean, the specific heat ratio SHEATR increases. Then, the case where the in-cylinder temperature TEVC at the time of closing the exhaust valve changes is indicated by a thick arrow. Here, the exhaust gas specific heat ratio SHEATR is determined according to the target combustion equivalence ratio TFBYA calculated in step 2 of FIG. 8 and the in-cylinder temperature TEVC when the exhaust valve is closed calculated in step 10 of FIG.
[0034]
In step 17, the supercharge determination TBCRG and the choke determination CHOKE are performed according to the control configuration diagram of the supercharge / choke determination means of FIG. 7 described later and the supercharge determination TBCRG / choke determination CHOKE flow of FIG.
In step 18, it is determined whether or not the supercharging determination flag TBCRG in step 17 is 0, that is, the supercharging state is determined. When the supercharging determination flag TBCRG is 0, the routine proceeds to step 19, and when the supercharging determination flag TBCRG is not 0, the routine proceeds to step 22.
[0035]
In step 19, it is determined whether or not the choke determination flag CHOKE in step 17 is 0, that is, the choke state is determined.
If the choke determination flag CHOKE is 0, the process proceeds to step 20, and an average blowback gas flow rate MRESOLtmp during overlap without supercharging and without choke is calculated from the flow of FIG. 13 described later.
[0036]
On the other hand, if it is determined in step 19 that the choke determination flag CHOKE in step 17 is not 0, the process proceeds to step 21, and from the flow of FIG. 14 described below, the blowback gas flow rate MRESOLtmp during the overlap when there is no supercharging and there is choke. Is calculated.
In step 18, if the supercharging determination flag TBCRG in step 17 is 1, that is, it is in the supercharging state, and if the choke determination flag CHOKE is 0 in step 22, the process proceeds to step 23, and the flow of FIG. The average blowback gas flow rate MRESOLtmp during the overlap with the supercharge and without the choke is calculated.
[0037]
On the other hand, if the choke determination flag CHOKE in step 17 is 1 in step 22, the process proceeds to step 24, and the blowback gas flow rate MRESOLtmp when there is supercharging and choke is calculated from the flow of FIG.
After calculating the blowback gas flow rate MRESOLtmp in steps 20, 21, 23, and 24, the process proceeds to step 25.
[0038]
In step 25, the blowback gas amount MRESOL during the overlap is calculated by integrating the blowback gas flow rate MRESOLtmp and the integrated effective area ASAMOL during the overlap period in accordance with the state of the presence or absence of the supercharging and the presence or absence of the choke. It is calculated by the formula.
MRESOL = (MRESOLtmp × ASUMOL × 60) / (NRPM × 360) (7)
Here, the supercharging / choke determination in step 17 will be described with reference to the control configuration diagram of the supercharging / choke determining means in FIG. 7 and the supercharging determination TBCRG / choke determination CHOKE flow in FIG.
[0039]
As shown in FIG. 7, based on the calculated values of the exhaust gas specific heat ratio calculating means, the in-cylinder pressure calculating means for closing the exhaust valve, and the intake pressure calculating means, the supercharging / choke determining means performs the supercharging determination TBCRG and the choke determination CHOKE. And do.
In step 26 of FIG. 12, the ratio between the intake pressure PIN detected based on the signal of the intake pressure sensor 10 and the in-cylinder pressure PEVC when the exhaust valve is closed calculated in step 11 of FIG. 10, that is, the intake exhaust pressure The ratio PINBYEX is calculated by the following equation.
[0040]
PINBYEX = PIN / PEVC (8)
In step 27, it is determined whether the intake / exhaust pressure ratio PINBYEX is equal to or less than 1, that is, a supercharging state.
If the intake / exhaust pressure ratio PINBYEX is 1 or less, that is, if there is no supercharging, the routine proceeds to step 28, where the supercharging determination flag TBCRG = 0 is set to 0, and the routine proceeds to step 31.
[0041]
On the other hand, if the intake / exhaust pressure ratio PINBYEX is larger than 1, that is, if there is supercharging, the routine proceeds to step 29, where the supercharging determination flag TBCRG is set to 1, the routine proceeds to step 30, and the calculation is performed in step 16 of FIG. The exhaust gas specific heat ratio SHEATR is defined as a mixed air specific heat ratio MIXAIRSHR of air and fuel obtained from the table shown in FIG.
[0042]
FIG. 22 is a mixture specific heat ratio MIXAIRSHR calculation table. The horizontal axis represents the target combustion equivalent ratio TFBYA, and the vertical axis represents the mixture specific heat ratio MIXAIRSHR. Note that the dotted line in the figure indicates stoichiometry, and the specific heat ratio MIXAIRSHR is large on the lean side and small on the rich side. Then, the mixture specific heat ratio MIXAIRSHR corresponding to the target combustion equivalent ratio TFBYA calculated in step 2 of FIG. 2 is obtained from the table.
[0043]
Then, in step 30, by replacing the exhaust gas specific heat ratio SHEATR with the mixture specific heat ratio MIXAIRSHR, the gas flow during the overlap at the time of supercharging such as turbocharging or inertia supercharging goes from the intake system to the exhaust system ( Even at the time of blow-through, by changing the specific heat ratio of the gas passing through the orifice from the specific heat ratio of the exhaust gas to the specific heat ratio of the intake air-fuel mixture, the amount of gas flowing through is accurately estimated, and the internal EGR amount is accurately calculated. .
[0044]
In step 31, based on the exhaust gas specific heat ratio SHEATR calculated in step 16 or 30, the minimum and maximum choke determination thresholds SLCHOKEL and SLCHOKEH are calculated by the following equations.
SLCHOKEL = {2 / (SHEATR + 1)} SHEATR / (SHEATR-1)} (9a)
SLCHOKEH = {2 / (SHEATR + 1)}-SHEATR / (SHEATR-1)} (9b)
The choke determination threshold values SLCHOKEEL and SLCHOKEH are calculated as choke limit values.
[0045]
If it is difficult in step 31 to calculate the exponentiation due to the control configuration, the calculation results of equations (9a) and (9b) are preliminarily converted into the minimum choke determination threshold value SLCHOKEL table and the maximum choke determination threshold value SLCHOKEH. It may be stored as a table, and determined in accordance with the exhaust gas specific heat ratio SEATR.
In step 32, it is determined whether or not the intake / exhaust pressure ratio PINBYEX calculated in step 26 is in the range of not less than the minimum choke determination threshold SLCHOKEEL and not more than the maximum choke determination threshold SLCHOKEH, that is, the choke state is determined.
[0046]
When the intake / exhaust pressure ratio PINBYEX is within the range, that is, when it is determined that there is no choke, the process proceeds to step 33, and the choke determination flag CHOKE is set to 0.
On the other hand, when the intake / exhaust pressure ratio PINBYEX is not within the range, that is, when it is determined that there is a choke, the process proceeds to step 34, and the choke determination flag CHOKE is set to 1.
[0047]
Further, the calculation of the blowback gas flow rate MRESOLtmp in step 20 in FIG. 11 will be described using the flow chart for calculating the blowback gas flow rate during overlap without supercharging and without choke in FIG.
In step 35, the gas flow rate calculation equation density term MRSOLD is calculated based on the gas constant REX of the exhaust gas calculated in step 9 in FIG. 10 and the in-cylinder temperature TEVC when the exhaust valve is closed calculated in step 10. It is calculated by the formula.
[0048]
MRSOLD = SQRT {1 / (REX × TEVC)} (10)
Here, SQRT is a coefficient relating to temperature and gas constant. If it is difficult to calculate the density term MRSOLD in the gas flow rate calculation equation due to the control configuration, the calculation result of the equation (10) is stored in advance as a map, and the calculation result is calculated according to the exhaust gas gas constant REX and the in-cylinder temperature TEVC. You may ask for it.
[0049]
In step 36, based on the exhaust gas specific heat ratio SHEATR calculated in step 16 in FIG. 11 and the intake / exhaust gas pressure ratio PINBYEX calculated in step 26 in FIG. 12, the gas flow rate calculation equation pressure difference term MRSOLP is calculated by the following equation. calculate.
MRSOLP = SQRT [SHEATR / (SHEATR-1) × {PINBYEX} (2 / SHEATR) -PINBYEX} ((SHEATR + 1) / SHEATR)} (11)
In step 37, the in-cylinder pressure PEVC at the time of closing the exhaust valve calculated in step 11 in FIG. 10, the gas flow rate calculation equation density term MRSOLD and the gas flow rate calculation pressure calculated in steps 35 and 36 in FIG. Based on the difference term MRSOLP, a blowback flow rate MRESOLtmp during overlap without supercharging and no choke is calculated by the following equation.
[0050]
MRESOLtmp = 1.4 × PEVC × MRSOLD × MRSOLP (12)
The blow-back gas flow rate MRESOLtmp in step 21 will be described with reference to the flow chart of FIG. 14 for calculating the blow-back gas flow rate when there is no supercharging and there is a choke.
[0051]
In step 38, similarly to step 35 in FIG. 13, the gas flow rate calculation equation density term MRSOLD is calculated from the above equation (10).
In step 39, a gas flow rate calculation equation choke pressure difference term MRSOLPC is obtained by the following equation based on the exhaust gas specific heat ratio SHEATR calculated in step 16 in FIG.
[0052]
MRSOLPC = SQRT [SHEATR × {2 / (SHEATR + 1)} (SHEATR + 1) / (SHEATR-1)}] (13)
If the power calculation is difficult due to the control configuration, the calculation result of Expression (13) is stored in advance as a gas flow rate calculation equation choke-time pressure difference term MRSOLPC map, and is calculated according to the exhaust gas specific heat ratio SHEATR. You may ask.
[0053]
In step 40, the in-cylinder pressure PEVC at the time of closing the exhaust valve calculated in step 11 of FIG. 10, the gas flow rate calculation formula density term MRSOLD calculated in step 38 of FIG. 14, and the choke time calculated in step 39. Based on the pressure difference term MRSOLPC, the overlap return flow rate MRESOLtmp when there is no supercharging and there is a choke is calculated by the following equation.
[0054]
MRESOLtmp = PEVC × MRSOLD × MRSOLPC (14)
Further, the calculation of the average blowback gas flow rate MRESOLtmp during the overlap in step 23 will be described with reference to the flow chart of FIG.
[0055]
In step 41, based on the exhaust gas specific heat ratio SHEATR calculated in step 30 of FIG. 12 and the intake / exhaust pressure ratio PINBYEX calculated in step 26, a gas flow rate calculation supercharging pressure difference term MRSOLPT is calculated by the following equation. Ask.
MRSOLPT = SQRT [SHEATR / (SHEATR-1) × {PINBYEX} (− 2 / SHEATR) −PINBYEX} (− (SHEATR + 1) / SHEATR)} (15)
If the power calculation is difficult due to the configuration of the control, the calculation result of the equation (15) is stored in advance as a gas flow rate calculation type supercharging pressure difference term MRSOLPT map, and the exhaust gas specific heat ratio SHEATR and the intake air It may be determined according to the exhaust pressure ratio PINBYEX.
[0056]
In step 42, based on the intake pressure PIN detected based on the signal of the intake pressure sensor 10 and the pressure difference term MRSOLPT during supercharging calculated in step 41, blow back during the overlap with supercharge and without choke The gas flow rate MRESOLtmp is calculated by the following equation.
MRESOLtmp = −0.152 × PIN × MRSOLPT (16)
Here, when the blowback gas flow rate MRESOLtmp indicates a negative value, the flow rate of gas flowing through the intake system to the exhaust system during the overlap can be represented, and the internal EGR amount is reduced based on this.
[0057]
The calculation of the blowback gas flow rate MRESOLtmp in step 24 will be described with reference to the flow chart of FIG.
In step 43, similarly to step 39 in FIG. 14, the choke pressure difference term MRSOLPC is obtained from the gas flow rate calculation equation (13) or the map.
[0058]
In step S44, based on the intake pressure PIN and the gas flow rate calculation type choke pressure difference term MRSOLPC, the overlapped blow-back gas flow rate MRESOLtmp when there is supercharging and choke is calculated by the following equation.
MRESOLtmp = −0.108 × PIN × MRSOLPC (17)
Here, when the blowback gas flow rate MRESOLtmp indicates a negative value, the flow rate of the gas flowing from the intake side to the exhaust side during the overlap can be represented, and the internal EGR amount is reduced.
[0059]
Here, in steps 20, 21, 23, and 24, the blowback gas flow rate MRESOLtmp is calculated according to the state of the presence or absence of the supercharging and the presence or absence of the choke. Then, after calculating the amount MRESOL of the blown-back gas during the overlap in step 25 described above, the process proceeds from step 6 in FIG. 9 to step 7, in which the internal EGR amount MRES is calculated in step 7 described above. Then, the process proceeds from step 3 to step 4 in FIG. 8 to calculate the above-mentioned internal EGR rate MRESFR, and ends the processing.
[0060]
According to the present embodiment, means for calculating the in-cylinder temperature TEVC when the exhaust valve is closed (step 10), means for calculating the in-cylinder pressure PEVC when the exhaust valve is closed (step 11), and a combustion air-fuel ratio Means (step 9) for calculating a gas constant REX of an exhaust gas composition according to the following formulas: and a cylinder gas when the exhaust valve is closed based on at least the cylinder temperature TEVC, the cylinder pressure PEVC, and the gas constant REX. Means for calculating the amount MRESCYL (step 12) and means for calculating the blowback gas amount MRESOL during the overlap between the exhaust valve open period and the intake valve open period (step 25). The internal EGR amount MRES is calculated based on the blowback gas amount MRESOL (step 7). Therefore, the internal EGR amount MRES can be calculated from the physical equation based on the state quantity (temperature TEVC / pressure PEVC / gas constant REX) inside the cylinder after the end of combustion. Further, it is possible to cope with a density change due to a temperature / pressure change and a density change due to a change in a gas constant due to a change in combustion air-fuel ratio, and it is possible to accurately estimate the internal EGR amount MRES regardless of operating conditions. In particular, in the transient operation state, since the state quantity inside the cylinder changes every moment, the internal EGR amount MRES can be calculated based on the changing state quantity, so that the estimation accuracy of the internal EGR amount MRES during the transient operation is obtained. Can be improved. By accurately estimating the internal EGR amount MRES, it is possible to appropriately control the ignition timing, the fuel injection amount, the valve opening / closing timing (overlap amount), and the like. Furthermore, even in the control construction including multidimensional parameters, the internal EGR amount MRES is calculated based on the physical equation (3 equations) according to each parameter, and each control value is determined based on this value MRES. , Easy to build.
[0061]
Further, according to the present embodiment, the system further includes means (step 8) for calculating the in-cylinder volume VEVC when the exhaust valve is closed. Based on these calculated values, the exhaust valve is calculated by a physical equation (4). The in-cylinder gas amount MRESCYL when the valve is closed is calculated. Therefore, taking into account the in-cylinder volume VEVC when the exhaust valve is closed, the physical equation (Equation 3) is obtained based on the state quantity (volume VEVC / temperature TEVC / pressure PEVC / gas constant REX) inside the cylinder after the end of combustion. Can be used to calculate the internal EGR amount MRES. Also in this case, it is possible to cope with a density change due to a change in temperature and pressure or a density change due to a change in gas constant due to a change in the combustion air-fuel ratio, and it is possible to accurately estimate the internal EGR amount MRES regardless of operating conditions. Further, even in the control construction including the multi-dimensional parameters, the internal EGR amount MRES is calculated based on the physical equation (3 equations) according to each parameter, so that it can be easily constructed and adapted.
[0062]
Further, according to the present embodiment, the in-cylinder volume calculation means (step 8) when the exhaust valve is closed determines the in-cylinder volume value VEVC that is geometrically determined from the piston position when the exhaust valve is closed. Therefore, it is possible to appropriately calculate the in-cylinder volume VEVC when the exhaust valve is closed, and to obtain a more accurate internal EGR amount MRES.
Further, according to the present embodiment, the exhaust valve closing cylinder volume calculation means (step 8) is provided in an engine having a mechanism for relatively changing the exhaust valve closing timing and the cylinder volume at the timing. The in-cylinder volume value VEVC when the exhaust valve is closed is determined according to the change amount. Therefore, even in an engine having a mechanism (variable valve opening / closing timing, variable compression ratio) in which the in-cylinder volume VEVC changes when the exhaust valve is closed, the in-cylinder volume VEVC can be easily obtained, and a more accurate internal EGR amount can be obtained. MRES can be calculated. Then, since each value is determined geometrically, it can be easily calculated, and it is not necessary to adapt it by actual operation, and development can be performed efficiently.
[0063]
Further, according to the present embodiment, the gas constant calculation means (step 9) obtains the gas constant REX corresponding to the change in the exhaust gas composition according to the target combustion equivalent ratio TFBYA (FIG. 18). For this reason, when there is a density change due to a change in the exhaust gas composition in accordance with the target combustion equivalent ratio TFBYA, that is, when the target combustion equivalent ratio TFBYA increases or decreases after switching to the full-open operation region after the lean operation and start-up. Also, the internal EGR amount MRES can be accurately estimated. The gas constant REX can be calculated from a chemical reaction formula based on the fuel composition and the air composition, and it is not necessary to adapt the gas operation in actual operation, and development can be performed efficiently.
[0064]
Further, according to the present embodiment, the means for calculating the amount of gas to be blown back during the overlap (Step 25) includes means for calculating the in-cylinder temperature TEVC when the exhaust valve is closed (Step 10) and the in-cylinder temperature when the exhaust valve is closed. Means for calculating the pressure PEVC (step 11), means for calculating the gas constant REX corresponding to the change in the exhaust gas composition according to the combustion air-fuel ratio (step 9), and means for calculating the intake pressure PIN (step 10). Means for calculating a specific heat ratio SHEATR corresponding to a change in exhaust gas composition (step 14); means for calculating an integrated effective area ASUMOLL during an overlap between an exhaust valve open period and an intake valve open period (step 14); Means for calculating the engine speed NRPM (step 15) and means for determining the presence or absence of supercharging and choke (steps 27 and 32). In constructed, based on these calculated values to calculate the blow-back gas amount MRESOL during overlap. For this reason, the blowback gas amount MRESOL can be accurately calculated by the physical equation (Equation 7) based on the state quantities during overlap (temperature TEVC, pressure PEVC, gas constant REX, area ASUMOL). Then, it is possible to cope with a change in density or a change in volume flow rate through the orifice due to a change in the state quantity, and it is possible to accurately calculate the amount MRESOL of the blown-back gas during the overlap in any operating state. Further, in the control construction including the multidimensional parameters, the internal EGR amount MRES is calculated based on the physical equation (3 equations) according to each parameter, so that it can be easily constructed and adapted.
[0065]
Further, according to the present embodiment, the supercharging and choke determining means (steps 27 and 32) calculates the intake / exhaust pressure ratio PINBYEX based on the intake pressure PIN and the in-cylinder pressure PEVC when the exhaust valve is closed. (Step 26), and the specific heat ratio SHEATR corresponding to the change in the exhaust gas composition is set when the supercharging determination means (Step 27) determines that there is supercharging. For this reason, even at the time of inertia supercharging in the full-open operation or at the time of supercharging by the supercharger, the blowback gas amount MRESOL during the overlap can be calculated with high accuracy. Then, even when choking occurs during idling operation or the like, the blowback gas amount MRESOL can be calculated with high accuracy.
[0066]
Further, according to the present embodiment, the means for calculating the cumulative effective area during overlap (Step 14) includes a means for calculating the intake valve opening / closing timing (FIG. 20), a means for calculating the exhaust valve opening / closing timing (FIG. 20), , The overlap amount is calculated, and the integrated effective area ASAMOL is obtained according to the overlap amount. Therefore, the integrated effective area ASUMOL can be calculated based on the overlap amount, and the calculation using the physical equation (Equation 6) can be simplified.
[0067]
Further, according to the present embodiment, the integrated effective area during overlap calculating means (Step 14) integrates one of the minimum values of the opening area during the intake valve lift and the opening area during the exhaust valve lift, and calculates the integrated value. Calculate the effective area ASUMOL. For this reason, the integrated effective area ASUMOLL of the overlap period can be simulated as one orifice, and the flow rate passing through the orifice can be simply calculated from the state of the exhaust system and the state of the intake system.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram of an internal EGR amount estimating apparatus.
FIG. 2 is a control configuration diagram of an internal EGR rate calculation unit.
FIG. 3 is a control configuration diagram of an internal EGR amount calculation unit;
FIG. 4 is a control configuration diagram of an in-cylinder gas flow rate calculation means when the exhaust valve is closed.
FIG. 5 is a control block diagram of a returning gas amount calculating means during overlap.
FIG. 6 is a control configuration diagram of an exhaust gas specific heat ratio calculation unit.
FIG. 7 is a control configuration diagram of a supercharging / choke determining unit.
FIG. 8 is a flowchart for calculating an internal EGR rate.
FIG. 9 is a flowchart for calculating an internal EGR amount;
FIG. 10 is a flowchart for calculating the in-cylinder gas amount when the exhaust valve is closed.
FIG. 11 is a flowchart for calculating the amount of gas to be blown back during the overlap.
FIG. 12 is a flowchart of a supercharging determination / choke determination.
FIG. 13 is a flowchart for calculating the flow rate of the gas to be blown back during the overlap when there is no supercharging and no choke.
FIG. 14 is a flow chart for calculating the flow rate of blow-back gas during overlap when there is no supercharging and there is a choke.
FIG. 15 is a flow chart for calculating the flow rate of blow-back gas during overlap when there is supercharging and no choke.
FIG. 16 is a flow chart for calculating the flow rate of gas to be blown back during overlap when there is supercharging or choke.
FIG. 17 is an in-cylinder volume calculation table when the exhaust valve is closed.
FIG. 18 is an exhaust gas constant calculation table
FIG. 19 is a table for calculating an accumulated effective area during overlap.
FIG. 20 is an explanatory diagram of an accumulated effective area during overlap.
FIG. 21: Exhaust gas specific heat ratio calculation table
FIG. 22 is a mixture heat ratio calculation table.
[Explanation of symbols]
1 engine
5 Intake valve
6 Exhaust valve
10 Intake pressure sensor
11 Exhaust pressure sensor
12 Exhaust gas temperature sensor
13 O2 sensor
14 Crank angle sensor
15 Water temperature sensor
16 Intake side cam angle sensor
17 Exhaust cam angle sensor
18 Accelerator opening sensor
30 ECU

Claims (9)

Means for calculating the in-cylinder temperature when the exhaust valve is closed,
Means for calculating the in-cylinder pressure when the exhaust valve is closed,
Means for calculating a gas constant of the exhaust gas composition according to the combustion air-fuel ratio,
Means for calculating an in-cylinder gas amount when the exhaust valve is closed, based on at least the in-cylinder temperature, the in-cylinder pressure, and the gas constant;
Means for calculating a blowback gas amount during an overlap between the exhaust valve open period and the intake valve open period,
An internal EGR amount estimating device for an internal combustion engine, wherein an internal EGR amount is calculated based on the in-cylinder gas amount and the blowback gas amount. The in-cylinder gas amount calculating means at the time of closing the exhaust valve,
Means for calculating the cylinder volume when the exhaust valve is closed,
Means for calculating the in-cylinder temperature when the exhaust valve is closed,
Means for calculating the in-cylinder pressure when the exhaust valve is closed,
Means for calculating a gas constant of the exhaust gas composition according to the combustion air-fuel ratio,
2. The internal EGR amount estimating device for an internal combustion engine according to claim 1, wherein the in-cylinder gas amount when the exhaust valve is closed is calculated by a physical equation based on the calculated values. 3. The internal EGR amount estimation of an internal combustion engine according to claim 2, wherein said exhaust valve closing cylinder volume calculation means calculates a cylinder volume value which is geometrically determined from a piston position when the exhaust valve is closed. apparatus. In an engine having a mechanism for relatively changing the exhaust valve closing timing and the cylinder volume at the timing, the exhaust valve closing cylinder volume calculating means may determine whether the exhaust valve is closed in accordance with the amount of the change. 3. The internal EGR amount estimating device for an internal combustion engine according to claim 2, wherein the in-cylinder volume value at the time of valve opening is obtained. The internal combustion engine according to any one of claims 1 to 4, wherein the gas constant calculation unit obtains a gas constant corresponding to a change in exhaust gas composition according to a target combustion equivalent ratio. EGR amount estimation device. The overlapped blow-back gas amount calculating means,
Means for calculating the in-cylinder temperature when the exhaust valve is closed,
Means for calculating the in-cylinder pressure when the exhaust valve is closed,
Means for calculating a gas constant corresponding to a change in exhaust gas composition according to the combustion air-fuel ratio,
Means for calculating the intake pressure;
Means for calculating a specific heat ratio corresponding to the exhaust gas composition change,
Means for calculating an integrated effective area during the overlap between the exhaust valve open period and the intake valve open period,
Means for calculating the engine speed;
Means for determining the presence or absence of supercharging and chalk;
The internal EGR amount of the internal combustion engine according to any one of claims 1 to 5, wherein the amount of the blown-back gas during the overlap is calculated based on the calculated values. Estimation device. The supercharging and chalk determining means,
Means for calculating an intake / exhaust pressure ratio based on the intake pressure and the in-cylinder pressure when the exhaust valve is closed,
7. The internal EGR amount estimating device for an internal combustion engine according to claim 6, wherein the specific heat ratio corresponding to the change in the exhaust gas composition is set when the supercharging determination unit determines that there is supercharging. The overlapping effective area calculating means during the overlap,
Means for calculating the intake valve opening / closing timing;
Means for calculating the exhaust valve opening / closing timing;
Calculate the overlap amount from
8. The internal EGR amount estimating device for an internal combustion engine according to claim 6, wherein an integrated value of the effective area is obtained according to the overlap amount. The overlapping effective area calculating means during the overlap,
The internal combustion engine according to claim 6 or 7, wherein a minimum value of one of an opening area during an intake valve lift and an opening area during an exhaust valve lift is integrated to calculate an integrated effective area. Internal EGR amount estimating device.

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