JP4244850B2 - Blowing gas passage opening area estimation device - Google Patents

Description

  The present invention relates to a technique for calculating a passage opening area of a blown gas with high accuracy in order to estimate a blown gas amount during an overlap period between an intake valve open period and an exhaust valve open period of an internal combustion engine.

Conventionally, as an apparatus for estimating an internal EGR amount (residual gas amount) of an internal combustion engine, an amount of gas remaining in a volume obtained by subtracting a stroke volume from a cylinder volume is added to an overlap period between an intake valve open period and an exhaust valve open period. There is one in which the amount of blown-out gas is added and estimated (Patent Document 1).
JP 2001-221105 A (paragraph number 0059)

The amount of blown gas is estimated from the pressure ratio between the intake pressure and the exhaust pressure during the overlap period, and the passage opening area of the blown gas determined by the intake valve opening and the exhaust valve opening.
However, since the passage opening area of the blown gas changes with time due to wear or deposit of the valve system, there is a problem that it is difficult to maintain highly accurate estimation.
The present invention has been made paying attention to such a conventional problem, and the passage opening area of the blown-out gas can be estimated satisfactorily by learning the change over time. As a result, the blown-out gas amount and the internal EGR amount can be increased. The purpose is to enable estimation with accuracy.

The present invention relates to a blowout gas blown between an exhaust side and an intake side based on valve operating characteristic values of an intake valve and an exhaust valve during an overlap period of an intake valve opening period and an exhaust valve opening period of an internal combustion engine. The amount of the blown-out gas is inhaled on the condition that the throttle valve interposed in the intake passage is substantially fully open and the engine speed is in a low speed range below a predetermined value. A first method for estimation based on the detected air flow rate and a second method for estimation based on the passage opening area of the blown gas determined based on the intake pressure, the exhaust pressure, and the valve operating characteristics during the overlap period The passage opening area of the blown gas is learned by using the area converted value of the passage opening area calculated based on the deviation between the blown gas amounts estimated by these two methods as a learning value. .

  According to the present invention, when the blow-off gas passage opening area changes due to wear or deposit of the valve system, the first method is used to estimate the change in the blow-off gas amount corresponding to the change in the blow-off gas passage opening area. A deviation corresponding to a change in the area of the passage opening of the blown gas is generated between the blown gas amount and the blown gas amount estimated using parameters other than those described above. Therefore, it is possible to learn the blowout gas passage opening area based on the deviation, and it is possible to always estimate the opening area with high accuracy by the learning.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a configuration of an engine (internal combustion engine) 1 according to an embodiment of the present invention.
An air cleaner 12 is attached to the introduction portion of the intake passage 11, and dust or the like in the intake air is removed by the air cleaner 12. In the intake passage 11, an electronically controlled throttle valve 13 is installed downstream of the air cleaner 12. A surge tank 14 is attached downstream of the throttle valve 13, and a branch 15 is attached to the surge tank 14 to constitute an intake manifold. The intake air in the surge tank 14 flows into the cylinder through the branch 15 and the intake port 16 formed in the cylinder head. A fuel supply injector 17 is installed in the intake port 16 of each cylinder.

  In the engine body, the combustion chamber 18 is formed as a space sandwiched between the cylinder head and the piston 19. The combustion chamber 18 is connected to the intake port 16 on one side with respect to the cylinder center axis, and the intake port 16 is opened and closed by the intake valve 20. The intake valve 20 is driven by an intake cam 21. In addition, the combustion chamber 18 is connected to the exhaust port 22 on one side opposite to the intake port 16, and the exhaust port 22 is opened and closed by an exhaust valve 23. The exhaust valve 23 is driven by an exhaust cam 24. An intake side variable valve device 25 is provided for the intake cam 21, and an exhaust side variable valve device 26 is provided for the exhaust cam 24, and the intake cam 21 or the exhaust cam is provided by these variable valve devices 25, 26. The operation characteristic of the intake valve 20 or the exhaust valve 23 can be changed by changing the phase with respect to the crankshaft 24. The variable valve operating devices 25 and 26 may be of any type such as a hydraulic type or a solenoid type. In this embodiment, the opening / closing timing of the intake valve 20 or the exhaust valve 23 (that is, the valve timing) is determined. By changing, an overlap period between the intake valve opening period and the exhaust valve opening period (hereinafter simply referred to as “overlap period”) is adopted. A spark plug 27 is installed in the cylinder head so as to face the substantially upper center of the combustion chamber 18.

A first catalytic converter 29 is interposed in the exhaust passage 28 immediately after the exhaust manifold, and a second catalytic converter 30 is interposed downstream thereof. The exhaust gas flowing out to the exhaust port 22 passes through the catalytic converters 29 and 30 and the muffler 31 and is released into the atmosphere.
The operations of the injector 17, the spark plug 27 and the variable valve gears 25 and 26 are controlled by an electronic control unit (hereinafter referred to as “ECU”) 41 as an engine control unit. The ECU 41 includes an intake air amount detection signal from the air flow meter 51, an intake pressure detection signal from the pressure sensor 52, a coolant temperature detection signal from the temperature sensor 53, and a crank angle detection signal from the crank angle sensor 54 (the ECU 41 Based on this, the engine speed NE is calculated.), The exhaust pressure detection signal from the pressure sensor 55, the exhaust temperature detection signal from the temperature sensor 56, the air-fuel ratio detection signal from the oxygen sensor 57, and the accelerator sensor 58 Accelerator pedal operation amount detection signal, throttle valve opening detection signal from the throttle sensor 59, and cam angle detection signals from the cam angle sensors 60 and 61 (based on this, the phase difference between the camshaft and the crankshaft is calculated. Is detected). In the present embodiment, as the air flow meter 51, a hot wire type or semiconductor type air flow meter capable of detecting the flow rate during reverse flow is employed. The ECU 41 sets the control amount of each device described above based on each input signal.

In the present embodiment, the ECU 41 has a function as a blown gas passage opening area estimation device in the engine 1. The estimation of the blown gas passage opening area by the ECU 41 will be described.
FIG. 2 shows the relationship between the crank angle CA, the valve operating characteristic value CAMPF, and the valve lift amount VLIFT. The valve operation characteristic value CAMPF is a displacement of the valve given by the cam profile itself, and the valve lift amount VLIFT is an actual valve displacement obtained by subtracting the valve clearance VCLR from the valve operation specific value CAMPF. The valve operating characteristic value CAMPF and the valve lift amount VLIFT are both based on the valve closing time (= 0).

  In the present embodiment, the overlap period at the time of the maximum overlap is divided for each predetermined crank angle DCA (here, 1 °), and the ECU 41 controls the valves of the intake valve 20 and the exhaust valve 23 in each divided section. The operating characteristic values CAMPFIn and CAMPFEn (n = 1 to N) are stored. These valve operating characteristic values CAMPFIn and CAMPFEn are unique to the cam, and are adapted each time the cam profile is changed. When the engine 1 is in operation, the valve clearances VCLRIn and VCLREN related to the intake valve 20 or the exhaust valve 23 are subtracted from the stored valve operation characteristic values CAMPFIn and CAMPFEn, and the section opening area VAREAI formed by the intake valve 20 and the exhaust valve A section opening area VAREAE formed by 23 is calculated. The calculated section opening areas VAREAI and VAREAE are stored as an array corresponding to each section (FIG. 3). In the calculation of the effective opening area ASUMOL, with reference to the stored arrangement, the smaller one of the intake side and exhaust side section opening areas VAREAI and VAREAE is selected as the selected section opening area VAREAn and selected. After the interval opening area VAREAn is integrated over the overlap period and converted into a time integrated value, the area learning value is added to calculate the effective opening area ASUMOL.

FIG. 4 is a flowchart of an opening area array creation routine.
In S101, 1 is added to the column number display value n. The column number display value n is set to 0 each time the creation of the array by this routine is completed.
In S102, the valve operating characteristic values CAMPFIn and CAMPFEn of the intake valve 20 and the exhaust valve 23 specified by the column number display value n are read.

  In S103, the valve clearances VCLRIn and VCLREn are subtracted from the read valve operating characteristic values CAMPFIn and CAMPFEn, and the valve lift amounts VLIFTIn and VLIFTEn of the intake valve 20 and the exhaust valve 23 are calculated. Note that the valve clearances VCLRIn and VCLREN can be estimated based on the coolant temperature Tw, the exhaust temperature Tex, and the like.

VLIFTIn = CAMPFIn−VCLRIn (1)
VLIFTEN = CAMPFEn−VCLREN (2)
In S104, the calculated valve lift amounts VLIFTIn and VLIFTen are multiplied by coefficients KCVI # and KCVE # corresponding to the flow rate sensitivity coefficient Cv and the valve element projection areas VAREAI0 # and VAREAE0 # of the intake valve 20 or the exhaust valve 23, respectively. Then, intake side and exhaust side section opening areas VAREAI, VAREAE are calculated. The flow rate sensitivity coefficient Cv is expressed as a ratio of the flow rate theoretically given to the valve lift amount VLIFT and the flow rate actually given. In the low lift range where both the intake valve 20 and the exhaust valve 23 are opened, It is approximately proportional to the lift amount VLIFT. The coefficients KCVI # and KCVE # are calculated as the slope of the approximate straight line drawn by the flow rate sensitivity coefficient Cv and are stored in the ECU 41 as fixed values. Further, the number of intake valves 20 or exhaust valves 23 provided per cylinder is a and b (for example, a and b = 2), and the seat contact portion diameters of the intake valves 20 and exhaust valves 23 are VDI and VDE. To do.

VAREAI = VLIFTIn × KCVI # × VAREAI0 # × a (3)
VAREAE = VLIFTEN × KCVE # × VAREAE0 # × b (4)
VAREAI0 # = π × (VDI / 2) ² (5)
VAREAE0 # = π × (VDE / 2) ² (6)
In S105, the calculated section opening areas VAREAI and VAREAE are stored in association with the column number display value n.

VAREAIn = VAREAI (7)
VAREAen = VAREAE (8)
In S106, it is determined whether or not the column number display value n has reached the final column number N. If reached, the process proceeds to S107. If not reached, the process returns to S101, and the intake side and exhaust side section opening areas VAREAI, VAREAE are calculated and stored for the next column.

In S107, the column number display value n is set to 0.
FIG. 5 is a flowchart of an effective opening area calculation routine.
In S201, the intake cam twist angle ANGI and the exhaust cam twist angle ANGE are read.
In S202, based on the read cam twist angles ANGI and ANGE, a relative change amount SIFTEVC of the exhaust valve closing timing with respect to the intake valve opening timing from the maximum overlap time is calculated, and the intake side section opening area VAREAI is calculated. Then, the arrangement of the exhaust side section opening area VAREAE is advanced by the number of columns corresponding to the calculated relative change amount SIFTEVC (see FIG. 2). For example, when the change amount of the intake valve opening timing and the exhaust valve closing timing from the maximum overlap is 30 ° and 10 ° in the crank angle, the relative change amount SIFTEVC is 40 °, which is excessive when creating the array. Since the lap period is divided every 1 °, the arrangement of the exhaust side section opening area VAREAE is advanced by the number of columns (= 40) corresponding to 40 °.

In S203, 1 is added to the column number display value n.
In S204, the section opening areas VAREAIn and VAREAEn of the column corresponding to the column number display value n are read from the arrangement of the intake side section opening area VAREAI and the advanced exhaust side section opening area VAREAE.
In S205, it is determined whether or not the read intake side section opening area VAREAIn is larger than the exhaust side section opening area VAREAEn. When it is larger than VAREAEn, the process proceeds to S206, and when it is equal to or smaller than VAREAEn, the process proceeds to S207.

In S206, the exhaust side section opening area VAREAn is set as a substantial section opening area VAREAn for the section.
In S207, the intake side section opening area VAREAIn is set as a substantial section opening area VAREAn for the section.
In S208, the section opening area VAREAn calculated for each section is integrated over the overlap period.

SIGMA = SIGMA + VAREAn × DCA (9)
In S209, it is determined whether or not the column number display value n has reached the final column number N. When it has reached, the process proceeds to S210, and when it has not reached, the process returns to S203, and the section opening area VAREAn is calculated and integrated for the next column.
In S210, an effective opening area ASUMOL is obtained by adding the area learning value GA to the calculated integrated value SIGMA. As the area learning value GA, a value calculated and updated by a blowout gas passage opening area learning calculation routine according to the present invention described later is used.

ASUMOL = SIGMA + GA (10)
In S211, the column number display value n and the integrated value SIGMA are set to zero.
Next, the blown gas passage opening area learning according to the present invention will be described. The learning of the blowout gas passage opening area is performed by calculating the first blowout gas amount and the second blowout gas amount in two ways, and further, the deviation between the first blowout gas amount and the second blowout gas amount. And the area learning value GA is calculated and updated based on the deviation.

  The first blown gas amount is determined based on the blown gas detection by the air flow meter 51, the throttle valve opening TVO is greater than or equal to a predetermined opening TVORES # (for example, 80 °) close to full opening, and the engine speed NE. Is executed under the condition that it is in a predetermined high-load low-rotation region that is equal to or lower than a predetermined rotational speed NEQRES # (for example, 2000 rpm). This is because the air flow meter 51 is arranged upstream of the throttle valve 13, so that the blow-off gas flow passing through the throttle valve 13 cannot be detected well by the air flow meter 51 unless the throttle valve 13 is sufficiently open. This is because the influence of pressure waves from other cylinders cannot be sufficiently suppressed unless the engine speed is low.

As described above, since the air flow meter 51 can satisfactorily detect the blown gas amount only in a region where the throttle valve opening is sufficiently large and the rotational speed is not more than a predetermined value, the first blown gas amount is calculated.
FIG. 6 is a flowchart of a first blown gas amount calculation routine.
In S301, an intake air amount Q is calculated. In the present embodiment, the output of the air flow meter 51 is sampled every 2 ms. The calculation of the intake air amount Q is performed by averaging the current sample value QA and the previous sample value QAz, and subtracting the offset amount QAOFST from the calculated average value QAA.

QAA = (QA + QAz) / 2 (12)
Q = QAA-QAOFST (13)
In S302, it is determined whether or not the calculated intake air amount Q is smaller than zero.
When the intake air amount Q is smaller than 0, that is, when the blown-out gas can be detected as a backflow, the process proceeds to S303, and the absolute value of the intake air amount Q (<0) is set as the instantaneous blown-out gas amount QRSAFM.

Further, when the intake air amount Q is equal to or greater than 0, it is in a state where no blowout gas is generated, so the process proceeds to S304, and the instantaneous blowout gas amount QRSAFM is set to zero.
In S305, the instantaneous blown gas amounts QRSAFM from 8 ms to the current time are integrated to calculate the blown gas amount QRSAFMCYL per cylinder in one cycle (FIG. 7).
QRSAMFCYL = ΣQRSAFM (14)
In S306, a primary advance compensation process is performed on the calculated blown gas amount QRSAFMCYL according to the following equation. The previous blown gas amount is QRSAFMCYLz, and the time constant is TRES #. The time constant TRES # is determined according to the pipe length from the engine main body to the air flow meter 51, the capacity of the surge tank 14, and the like, and in this embodiment, an experimentally obtained value is adopted.

In S307, the compensated blown gas amount QRSAFMCYL is set as the first blown gas amount MRESOL1.
As described above, the first blown gas amount can be estimated only in a limited region of high load and low rotation, but is estimated based on the actual measurement value by the air flow meter 51. It can be estimated as a value reflecting the effect of deposit.

On the other hand, the second blown-out gas amount is calculated based on the effective opening area calculated as described above, and can be calculated in the entire operation region. However, unless learning is performed, the intake valve 20 The effects of wear and deposits are not reflected.
FIG. 8 is a flowchart of a second blown gas amount calculation routine.
In S401, various operation states such as the intake pressure Pin, the exhaust pressure Pex, the exhaust temperature Tex, the throttle valve opening TVO, and the engine speed NE are read.

  In S402, the specific heat ratio κex of the exhaust is calculated. The specific heat ratio κex is calculated by searching a map in which each specific heat ratio is assigned according to the target fuel-air ratio TFBYA and the exhaust gas temperature Tex. The specific heat ratio κex is the smallest when the exhaust gas temperature Tex is constant, and is calculated as a larger value as the target fuel-air ratio TFBYA becomes smaller or larger than this. Further, when the target fuel-air ratio TFBYA is constant, the smaller the exhaust temperature Tex is, the smaller the value is calculated in both the lean side and rich side regions.

In S403, the effective opening area ASUMOL is calculated according to the flowcharts of FIGS.
In S404, the second blown gas amount MRESOL2 is calculated by the following equation. In the following expression, the intake pressure Pin and the exhaust pressure Pex are values estimated as values considering pressure waves due to pulsation. The outline of the intake pressure Pin will be described in consideration of the fact that the synchronization state between the frequency of the pulsation pressure and the central timing of the overlap period is also affected by the engine speed, and the tuning order (basic frequency based on the intake pipe shape). The phase of the pulsating pressure is determined using the ratio of the engine speed to the engine speed, and since the pressure wave of the pulsating pressure is a traveling wave, the pressure wave with the reference pressure wave obtained in advance by simulation with the traveling wave In the comparison, the traveling wave of the tuning order is corrected, and the fundamental frequency change due to the intake air temperature change (sound speed change) is corrected to determine the engine rotational speed and the pulsation pressure fluctuation for each load. It is obtained by adding to the obtained smooth intake pressure. As for the exhaust pressure Pex, the phase shift due to the exhaust temperature change is small and can be ignored, and the pulsation is generated with the ratio of the pressure in the cylinder just before the exhaust valve is closed and the smoothed exhaust pressure (substantially atmospheric pressure) as the excitation force. The pulsation pressure fluctuation determined by the pressure ratio and the phase determined by the engine speed is added to the smooth exhaust pressure.

FIG. 9 is a flowchart of the area learning value calculation routine.
In S501, various operation states such as the engine speed NE, the throttle valve opening TVO, the coolant temperature Tw, and the exhaust temperature Tex are read.
In S502, it is determined whether or not the read throttle valve opening TVO is equal to or greater than a predetermined opening TVORES #. If it is equal to or greater than TVORES #, the process proceeds to S503. If it is equal to or less than TVORES #, this routine is terminated.

In S503, it is determined whether or not the read engine speed NE is equal to or lower than a predetermined engine speed NEQRES #. When it is equal to or lower than NEQRES #, the process proceeds to S504, and when it is larger than NEQRES #, this routine is terminated.
In S504, a change amount DTiv per unit time of the valve body temperature Tiv of the intake valve 20 is calculated, and whether the calculated change amount DTiv is equal to or less than a predetermined change amount DTIV #, that is, the intake valve 20 is in thermal equilibrium. It is determined whether or not it is in a state. If it is equal to or less than DTIV #, the process proceeds to S505. If it is greater than DTIV #, this routine is terminated. The valve body temperature Tiv can be calculated by averaging the head temperature Tdi of the intake valve 20 and the shaft temperature Tax. The head temperature Tdi is calculated as the sum of the cooling water temperature Tw and an increase corresponding to the exhaust gas temperature Tex. On the other hand, the shaft temperature Tax is the head temperature Tdi as the temperature at the center of the shaft. In addition, it is calculated in consideration of heat conduction according to the material of the shaft portion.

Tiv = (Tdi + Tax) / 2 (18)
When all of the conditions of S502 to S504 are satisfied, that is, when the first blown gas amount MRESOL1 and the second blown gas amount MRESOL2 can be calculated at the same time and the intake valve 20 is in a thermal equilibrium state, Since the conditions for performing high learning are satisfied, the process proceeds to S504 and subsequent steps to execute learning.

In S505, the first blown gas amount MRESOL1 is calculated according to the flowchart of FIG.
In S506, the second blown-out gas amount MRESOL2 is calculated according to the flowchart of FIG.
In S507, the difference between the first blown gas amount MRESOL1 and the second MRESOL2 is calculated as the blown gas amount deviation DMRESOL.

DMRESOL = MRESOL2-MRESOL1 (19)
In S508, the area converted value ADSUMOL of the blown gas amount deviation is calculated by the following equation based on the calculated blown gas amount deviation DMRESOL.

In S509, the calculated area conversion value ADSUMOL is multiplied by a predetermined coefficient KGA # to calculate an area learning value GA. The coefficient KGA # is set to 0.01, for example, in consideration of the wear of the intake valve 20 (shaving of the valve head) and the speed of deposit (combustion product) deposition.
GA = ADSUMOL × KGA # (21)
In S510, the latest calculated value of the area learning value GA is stored in the nonvolatile memory when the ignition key is OFF. Thereby, the area learning value GA memorize | stored at the time of the last driving | operation is used as an initial value at the time of the next driving | operation (when the ignition key is turned ON).

Thus, the area learning value GA is calculated and updated only in a specific operation region and condition, but the updated area learning value GA calculates the effective opening area according to the flowchart of FIG. 5 in all operation regions. At this time (S210).
As described above, while learning the passage opening area (effective opening area) of the blown gas, the blown gas amount in consideration of the influence of the intake valve wear and deposits can be calculated with high accuracy in the entire operation region. The internal EGR amount is obtained by adding the residual gas amount MRESCYL, which is the amount of exhaust gas remaining in the cylinder even after the exhaust valve closing timing calculated separately, to the blowout gas amount MRESOL calculated in this way. Can be calculated.

  In addition, although the intake valve wear and deposit vary greatly between cylinders, as described above, the influence of pressure waves from other cylinders is sufficiently suppressed as a learning condition (first blowout gas amount calculation condition). Since it is set in a low rotation range that can be detected, it is possible to know in advance the cylinder that has generated the detected blowout gas flow, so learning for each cylinder is performed by distinguishing and storing the area learning value GA for each cylinder As a result, the blowout gas amount can be calculated with high accuracy for each cylinder.

The figure which shows the structure of the engine which concerns on one Embodiment of this invention. The figure which shows the concept of the arrangement | sequence set with respect to the operating characteristic of an intake valve and an exhaust valve, and actual valve timing Diagram showing the concept of an array created at maximum overlap Open area array creation routine flowchart Flow chart of effective opening area calculation routine Flowchart of first blown gas amount calculation routine Diagram showing the output waveform of the air flow meter Flowchart of second blowout gas amount calculation routine Flow chart of area learning value calculation routine

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 11 ... Intake passage, 12 ... Air cleaner, 13 ... Throttle valve, 14 ... Surge tank, 16 ... Intake port, 17 ... Injector, 18 ... Combustion chamber, 19 ... Piston, 20 ... Intake valve, 21 ... Intake cam , 22 ... exhaust port, 23 ... exhaust valve, 24 ... exhaust cam, 25 ... intake side variable valve operating device, 26 ... exhaust side variable valve operating device, 27 ... spark plug, 28 ... exhaust passage, 41 ... engine control unit, DESCRIPTION OF SYMBOLS 51 ... Air flow meter, 52 ... Intake pressure sensor, 53 ... Coolant temperature sensor, 54 ... Crank angle sensor, 55 ... Exhaust pressure sensor, 56 ... Exhaust temperature sensor, 57 ... Oxygen sensor, 58 ... Accelerator sensor, 59 ... Throttle sensor 60, 61 ... Cam angle sensor.

Claims (5)

The passage opening area of the blown-out gas blown between the exhaust side and the intake side based on the valve operating characteristic values of the intake valve and the exhaust valve during the overlap period between the intake valve open period and the exhaust valve open period of the internal combustion engine A device for estimating
The amount of the blown-out gas is estimated based on the intake air flow rate detection value on the condition that the throttle valve interposed in the intake passage is in a substantially fully open state and the engine rotational speed is in a low speed range below a predetermined value. Estimated by a method and a second method for estimating the passage opening area of the blow-out gas determined based on the intake pressure, the exhaust pressure, and the valve operating characteristic during the overlap period,
The passage opening area of the blown gas is learned by using the area converted value of the passage opening area calculated based on the deviation between the blown gas amounts estimated by these two methods as a learning value. Area estimation device. 2. The blown gas according to claim 1, wherein the passage opening area of the blown gas is estimated as an integrated value of instantaneous effective opening areas determined by the opening degrees of the intake valve and the exhaust valve during the overlap period. Passage area estimation device. The blowout gas passage opening area estimation device according to claim 1 or 2, wherein learning of the blowout gas passage opening area is prohibited when the intake valve temperature is in a non-equilibrium state. 4. The blowout gas passage opening area estimation device according to claim 1, wherein the learning result of the blowout gas passage opening area in the predetermined operation region is reflected in the entire operation region. 5. . The apparatus for estimating the passage opening area of the blown gas according to any one of claims 1 to 4, wherein learning of the passage opening area of the blown gas is performed for each cylinder.

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