JP2010116883A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine for controlling the engine according to an estimated air amount by accurately estimating the air amount sucked into the cylinder of the engine by a comparatively simple calculation. <P>SOLUTION: A valve opening time TIVO in which an intake valve is open even during a compression stroke is calculated according to the rotational speed NE of the engine, and a basic blow-back air amount GBBM is calculated by researching the GBBM map preset according to the valve opening time TIVO and an intake pressure PBA. A blow-back air amount GBB which is the air amount returned from the cylinder into an intake passage in a compression stroke is calculated by correcting the basic blow-back air amount GBBM according to an intake air temperature TA. A corrected cylinder air amount GCYLC is calculated by deducting the blow-back air amount GBB from the cylinder air amount GCYL calculated according to the intake pressure PBA and the intake air temperature TA, and a fuel injection amount FOUT is calculated according to the corrected cylinder air amount GCYLC and the blow-back air amount GBB. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to an apparatus that estimates an air amount in a cylinder immediately after engine startup and performs control based on the estimated air amount.

  The intake air amount of the internal combustion engine is generally detected by an intake air amount sensor provided in the intake passage. However, since the intake air amount sensor is not activated immediately after the engine is started, the intake air amount detected by the intake pressure sensor is detected. A method of calculating the intake air amount based on the atmospheric pressure is applied. Since the lift curve is usually set so that the intake valve is opened at the beginning of the compression stroke, a part of the air supplied into the cylinder is returned to the intake passage by so-called blowback. Therefore, in order to accurately calculate the amount of air sucked into the cylinder without using the intake air amount sensor, it is necessary to consider the amount of air returned to the intake passage by blowback (hereinafter referred to as “blowback air amount”). is there.

  Japanese Patent Application Laid-Open No. 2004-133867 discloses a method for estimating the in-cylinder pressure from the time when the intake valve opens to the time when the intake valve closes by sequential calculation, and calculating the amount of air sucked into the cylinder using the estimated in-cylinder pressure. It is shown.

International Publication WO2003 / 33897

  The technique disclosed in Patent Document 1 calculates the in-cylinder pressure and the intake air amount (in-cylinder air amount) by sequential calculation based on the control target model obtained by modeling the intake system including the combustion chamber of the engine. Therefore, although a relatively accurate intake air amount can be obtained, there is a problem that the calculation load of the calculation device increases.

  The present invention has been made paying attention to this point, and accurately estimates the amount of air sucked into the cylinder by a relatively simple calculation, and controls the engine based on the estimated in-cylinder air amount. An object of the present invention is to provide an engine control device.

  In order to achieve the above object, the invention described in claim 1 is directed to an intake pressure detecting means (8) for detecting an intake pressure of an internal combustion engine, and an intake pressure (PBA) detected by the intake pressure detecting means (8). And a cylinder air amount estimating means for estimating an air amount (GCYL) in a cylinder of the engine on the basis thereof, and detecting a valve opening time (TIVO) of an intake valve in a compression stroke of the engine A valve opening time detecting means, a blowback air amount (GBB) that is an amount of air returned from the cylinder to the intake passage (2) of the engine during the compression stroke, the valve opening time (TIVO), and the suction The storage means storing the correlation (GBBM map) of the atmospheric pressure (PBA) in advance, the detected intake pressure (PBA) and the valve opening time (TIVO), and the correlation (GBBM map) stored in the storage means Based on A correction cylinder is obtained by subtracting the blown air amount (GBB) from the blown air amount calculating means for calculating the blown air amount (GBB) and the air amount (GCYL) estimated by the in-cylinder air amount estimating means. A correction air amount calculating means for calculating an internal air amount (GCYLC), and controlling the engine using the corrected in-cylinder air amount (GCYLC).

  According to a second aspect of the present invention, in the control device for an internal combustion engine according to the first aspect, the fuel injection means (6) for injecting fuel into the intake passage (2) or the cylinder of the engine, and the correction cylinder Fuel injection amount calculation means for calculating the fuel injection amount (FIN) by the fuel injection means (6) based on the internal air amount (GCYLC), and the intake passage (2) together with the air returned to the intake passage (2) A blowback fuel amount calculation means for calculating a blowback fuel amount (FR) that is an amount of fuel returned to the fuel, and a subtraction of the blowback fuel amount (FR) from the fuel injection amount (FIN) calculated by the fuel injection amount calculation means And a corrected fuel injection amount calculating means for calculating a corrected fuel injection amount (FOUT), and the fuel injection means (6) is driven in accordance with the corrected fuel injection amount (FOUT). That.

  According to a third aspect of the present invention, there is provided the control apparatus for an internal combustion engine according to the first or second aspect, wherein an intake air amount detecting means (7) for detecting an intake air amount (GA) of the engine, and the intake air amount An activation determination unit that determines whether or not the detection unit (7) is activated, and from when the start of the engine starts until it is determined that the intake air amount detection unit (7) is activated. Control using the corrected in-cylinder air amount (GCYLC) is performed.

  According to the first aspect of the present invention, there is a correlation between the valve opening time of the intake valve in the compression stroke, the amount of blowback air that is the amount of air returned from the cylinder to the intake passage during the compression stroke, and the intake pressure. The blow-back air amount is calculated based on the intake pressure and valve opening time that are stored in advance in the storage means and detected, and the stored correlation. Then, the corrected in-cylinder air amount is calculated by subtracting the blow-back air amount from the in-cylinder air amount estimated based on the intake pressure, and the engine is controlled using the corrected in-cylinder air amount. By using the detected valve opening time and intake pressure and the correlation stored in advance, it is possible to accurately estimate the amount of blown-back air with a relatively simple calculation. Therefore, a corrected in-cylinder air amount that accurately indicates the actual air amount in the cylinder can be obtained by subtracting the blow-back air amount from the in-cylinder air amount calculated according to the intake pressure.

  According to the second aspect of the present invention, the fuel injection amount is calculated based on the corrected in-cylinder air amount, and the blowback fuel amount that is the amount of fuel returned to the intake passage together with the air returned to the intake passage is calculated. . Then, the corrected fuel injection amount is calculated by subtracting the blowback fuel amount from the fuel injection amount calculated based on the corrected in-cylinder air amount, so that an amount of fuel suitable for the actual in-cylinder air amount is injected. be able to. As a result, it is possible to appropriately control the air-fuel ratio of the air-fuel mixture in the cylinder.

  According to the third aspect of the invention, since the control using the corrected in-cylinder air amount is performed from the start of the engine start until it is determined that the intake air amount detection means is activated, the intake air Deviation from the desired value of the air-fuel ratio during the period until the amount detection means is activated can be prevented.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of an internal combustion engine and a control device thereof according to an embodiment of the present invention. An internal combustion engine (hereinafter simply referred to as “engine”) 1 has an intake passage 2, and a throttle valve 3 is disposed in the intake passage 2. The throttle valve 3 is provided with a throttle valve opening sensor 4 for detecting the opening TH of the throttle valve 3, and a detection signal thereof is supplied to an electronic control unit (hereinafter referred to as “ECU”) 5. An actuator 12 that drives the throttle valve 3 is connected to the throttle valve 3, and the operation of the actuator 12 is controlled by the ECU 5.

  A fuel injection valve 6 is provided for each cylinder slightly upstream of an intake valve (not shown). Each injection valve is connected to a fuel pump (not shown) and electrically connected to the ECU 5 to receive a signal from the ECU 5. Thus, the valve opening time of the fuel injection valve 6 is controlled. Each cylinder of the engine 1 is provided with a spark plug 13, and an ignition signal is supplied to the spark plug 13 from the ECU 5.

  An intake air flow rate sensor 7 for detecting the intake air flow rate GA is provided on the upstream side of the throttle valve 3 in the intake passage 2. An intake pressure sensor 8 for detecting the intake pressure PBA is provided immediately downstream of the throttle valve 3, and an intake air temperature sensor 9 for detecting the intake air temperature TA is attached downstream of the intake pressure sensor 8. A cooling water temperature sensor 10 that detects the cooling water temperature TW of the engine 1 is attached to the main body of the engine 1. Detection signals from these sensors 7 to 10 are supplied to the ECU 5.

  The ECU 5 is connected to a crank angle position sensor 11 that detects a rotation angle of a crankshaft (not shown) of the engine 1, and a signal corresponding to the rotation angle of the crankshaft is supplied to the ECU 5. The crank angle position sensor 11 is a cylinder discrimination sensor that outputs a pulse (hereinafter referred to as “CYL pulse”) at a predetermined crank angle position of a specific cylinder of the engine 1, and relates to a top dead center (TDC) at the start of the intake stroke of each cylinder. It consists of a TDC sensor that outputs a TDC pulse at a crank angle position before a predetermined crank angle, and a CRK sensor that generates a CRK pulse at a constant crank angle cycle shorter than the TDC pulse (for example, a cycle of 6 degrees), and includes a CYL pulse, a TDC pulse and a CRK pulse. Is supplied to the ECU 5. These signal pulses are used for various timing controls such as fuel injection timing and ignition timing, and detection of engine speed (engine speed) NE.

  The ECU 5 is connected to an accelerator sensor 14 for detecting an accelerator pedal depression amount (hereinafter referred to as “accelerator pedal operation amount”) AP of a vehicle driven by the engine 1 and an atmospheric pressure sensor 15 for detecting an atmospheric pressure PA. The detection signals of these sensors are supplied to the ECU 5.

  The ECU 5 shapes input signal waveforms from various sensors, corrects the voltage level to a predetermined level, converts an analog signal value into a digital signal value, etc., and a central processing circuit (hereinafter referred to as “CPU”). A storage circuit that stores various calculation programs executed by the CPU, calculation results, and the like, an output circuit that supplies a drive signal to the fuel injection valve 6, and the like. The ECU 5 controls the valve opening time of the fuel injection valve 6 and the ignition timing of the spark plug 13 based on the detection signal of the above-described sensor, and at the same time opens the throttle valve 3 according to the accelerator pedal operation amount AP. The degree THCMD is calculated, and drive control of the actuator 12 is performed so that the detected throttle valve opening TH matches the target opening THCMD.

  In the present embodiment, since the intake air flow rate sensor 7 is not activated immediately after the start of the engine 1, the in-cylinder air amount is calculated based on the intake pressure PBA, and the fuel injection amount according to the in-cylinder air amount. Is calculated. FIG. 2 is a block diagram showing the configuration of a module for calculating the fuel injection amount FOUT immediately after the start of the engine. The functions of the blocks shown in FIG. 2 are actually realized by arithmetic processing by the CPU of the ECU 5.

  The module shown in FIG. 2 includes a valve opening time calculation unit 21, a basic blow-back air amount calculation unit 22, a correction unit 23, an in-cylinder air amount calculation unit 24, a subtraction unit 25, and a fuel injection amount calculation unit 26.

  The valve opening time calculation unit 21 calculates the valve opening time TIVO of the intake valve in the compression stroke according to the engine speed NE. From the lift curve of the intake valve (curve indicating the relationship between the crank angle and the lift amount), the valve opening angle period CAIVO of the intake valve in the compression stroke is known, and from the reciprocal number of the engine speed NE and the valve opening angle period CAIVO, the valve is opened. A valve time TIVO is calculated. The valve opening time TIVO may be calculated using the CRK pulse generation time interval CRME (a parameter proportional to the reciprocal of the engine speed NE) instead of the engine speed NE.

  The basic blow back air amount calculation unit 22 searches the GBBM map shown in FIG. 3 according to the valve opening time TIVO and the intake pressure PBA, and calculates the basic blow back air amount GBBM. The basic blow-back air amount GBBM is a basic value of the amount of air returned from the cylinder to the intake passage 2 in the compression stroke. In FIG. 3, PBA1, PBA2, PBA3, and PBA4 are predetermined intake pressures set to 26.7 kPa, 53.3 kPa, 80, 0 kPa, and 101.3 kPa, for example. The GBBM map is set such that the basic blowback air amount GBBM increases as the valve opening time TIVO increases, and the basic blowback air amount GBBM increases as the intake pressure PBA increases. The GBBM map is set by changing the valve opening time TIVO and the intake pressure PBA and experimentally measuring the amount of blown air, or by calculating the amount of blown air by theoretical calculation as described later. Data corresponding to lattice points determined by the values of the valve opening time TIVO and the intake pressure PBA are stored in the storage circuit of the ECU 5.

The correction unit 23 performs the intake air temperature correction by applying the basic blow-back air amount GBBM and the intake air temperature TA to the following equation (1), and calculates the blow-back air amount GBB. The derivation of Equation (1) will be described later. TA0 in equation (1) is a reference intake air temperature applied when the GBBM map is set, and is set to 25 ° C., for example.

  The in-cylinder air amount calculation unit 24 calculates the in-cylinder air amount GCYL, which is the amount of air sucked into the cylinder in the intake stroke, using a state equation indicating the relationship between the mass, temperature, volume, and pressure of the gas. . The subtraction unit 25 calculates the corrected in-cylinder air amount GCYLC by subtracting the blown back air amount GBB from the in-cylinder air amount GCYL.

  The fuel injection amount calculation unit 26 calculates the fuel injection amount FOUT so that the air-fuel mixture in the cylinder becomes a desired air-fuel ratio according to the corrected in-cylinder air amount GCYLC and the blow back air amount GBB.

  Next, the calculation method in the cylinder air amount calculation unit 24 will be described in detail. In this embodiment, the cylinder volume when the piston in the cylinder is located at the top dead center is defined as the minimum volume VMIN, and the cylinder volume when the piston is located at the bottom dead center is defined as the maximum volume VMAX. A difference (VMAX−VMIN) between the maximum volume VMAX and the minimum volume VMIN is defined as a stroke volume VSTR. Immediately after starting the engine, the minimum volume VMIN is filled with air, but after fuel injection is once performed, it is filled with residual gas after combustion or unburned gas. Therefore, in the present embodiment, the cylinder air amount GCYL immediately after the start of the start is calculated as an air amount that satisfies the minimum volume VMIN and the stroke volume VSTR (hereinafter, the air amount that satisfies the minimum volume VMIN is referred to as “minimum volume air amount GCYLM”). After the fuel injection is performed once, it is calculated as an air amount satisfying the stroke volume VSTR (hereinafter referred to as “stroke volume air amount GCYLS”).

FIG. 4 is a flowchart of a process for calculating the in-cylinder air amount GCYL. This process is executed by the CPU of the ECU 5 in synchronization with the TDC pulse.
In step S11, the intake pressure PBA, the initial cooling water temperature TWini at the start of engine start, the intake air temperature TA (where TWini and TA are converted into absolute temperatures), and the stroke volume VSTR are applied to the following equation (2), and the #N cylinder A stroke volume air amount GCYLS (N) of (N = 1 to 4) is calculated.

  “R” in Equation (2) is a gas constant, and KTGCYLS is a first weighting factor. The first weighting coefficient KTGCYLS is determined when the immediately preceding engine stop period TSTP is in a predetermined range (a range of a stop period in which the engine temperature is higher than the outside air temperature and the intake air temperature TA can be increased by the influence of engine heat). The initial value is set to an initial value greater than “0” and less than or equal to “1” at the start of startup, and is set to decrease as the number of elapsed strokes from the start of startup increases (the minimum value is “0”). In addition, when the engine stop period TSTP is outside the predetermined range, the first weighting coefficient KTGCYLS is set to “0” from the beginning. By correcting the intake air temperature TA immediately after the start of the start using the initial cooling water temperature TWini and the first weighting coefficient KTGCYLS, taking into account the case where the air in the intake passage 2 receives the heat of the engine, the stroke volume air amount GCYLS Can be calculated accurately.

  In step S12, it is determined whether or not the initial fuel injection execution flag FINI (N) of the #N cylinder is “1”. The initial fuel injection execution flag FINI (N) is set to “1” when the first fuel injection is performed after starting in the #N cylinder.

Since the answer to step S12 is negative (NO) immediately after the start of the start, the process proceeds to step S13, and the atmospheric pressure PA, the initial cooling water temperature TWini, the intake air temperature TA (however, TWini and TA are absolute temperature converted values). ), The minimum volumetric volume VMIN is applied, and the minimum volumetric air amount GCYLM (N) of the #N cylinder is calculated.

  KTGCYLM in equation (3) is a second weighting coefficient set to a value between “0” and “1” in accordance with the engine stop period TSTP. Specifically, when the engine stop period TSTP is shorter than a predetermined time TSTP0 (for example, 30 seconds), the second weighting coefficient KTGCYLM is set to a smaller value (minimum value “0”) as the stop time TSTP becomes shorter. When the stop time TSTP becomes longer than the predetermined time TSTP0, it is set to “1”. By correcting the intake air temperature TA immediately after the start of startup using the initial cooling water temperature TWini and the second weighting coefficient KTGCYLM, the influence of the heat that the air in the combustion chamber receives from the engine while the engine is stopped is taken into consideration, and the minimum volume air amount GCYLM Can be calculated accurately.

In step S14, the in-cylinder air amount GCYL (N) is calculated as the sum of the minimum volume air amount GCYLM (N) and the stroke volume air amount GCYLS (N) by the following equation (4).
GCYL (N) = GCYLM (N) + GCYLS (N) (4)

  After the first fuel injection is performed, the answer to step S12 is affirmative (YES), and the cylinder air amount GCYL (N) is set to the stroke volume air amount GCYLS (N).

  FIG. 5 is a diagram for explaining the processing of FIG. 4. In the period TST from the fuel injection start time to time tB, the cylinder air amount GCYL (N) is calculated in step S14, and the period TNR after time tB. In step S15, the cylinder air amount GCYL (N) is calculated.

  Therefore, an in-cylinder air amount GCYL that appropriately reflects the amount of air that satisfies the minimum volume VMIN immediately after the start of startup is obtained, and the air-fuel ratio immediately after the start of startup can be prevented from deviating from a desired value.

  Next, a method of calculating the fuel injection amount FOUT in the fuel injection amount calculation unit 26 of FIG. 2 will be described in detail with reference to FIG.

  FIG. 6 illustrates a method for calculating the fuel injection amount FOUT [n] corresponding to one cylinder (“n” is a discretization time discretized in a period of two rotations of the crankshaft (one combustion cycle)). FIG. In this figure, FIN is the basic fuel injection amount calculated in accordance with the corrected in-cylinder air amount GCYLC and the target air-fuel ratio AFCMD, and FR is the blowback fuel amount returned to the intake passage together with the air returned to the intake passage. .

The initial (n = 1) fuel injection amount FOUT [1] is set to the basic fuel injection amount FIN [1] as shown by the following equation (11). At this time, the blowback fuel amount FR [1] is calculated by the following equation (12) using the blowback air amount GBB and the corrected in-cylinder air amount GCYLC.
FOUT [1] = FIN [1] (11)
FR [1] = FIN [1] × GBB [1] / GCYLC [1] (12)

The second (n = 2) fuel injection amount FOUT [2] is given by the following equation (13) because the first blow back fuel amount FR [1] is sucked into the cylinder.
FOUT [2] = FIN [2] −FR [1] (13)

The blowback fuel amount FR [2] is given by the following formula (14).
FR [2] = FIN [2] × GBB [2] / GCYLC [2] (14)
From the above, the fuel injection amount FOUT [n] and the blowback fuel amount FR [n] for the second and subsequent times are generally given by the following equations (15) and (16).
FOUT [n] = FIN [n] −FR [n−1] (15)

The blowback fuel amount FR [n-1] is given by the following equation (14).
FR [n-1] = FIN [n-1] × GBB [n-1] / GCYLC [n-1] (16)
Thus, by taking into account the blowback air amount GBB and the blowback fuel amount FR, the actual air-fuel ratio of the air-fuel mixture in the cylinder can be accurately controlled to the target air-fuel ratio.

  In addition, when fuel is injected into the intake passage, it is necessary to perform known adhesion correction in consideration of the amount of fuel adhering to the inner wall of the intake passage. The fuel injection amount is calculated.

  FIG. 7 is a flowchart of a switching process between the fuel injection control immediately after the start of the above-described operation and the fuel injection control based on the intake air flow rate GA detected by the intake air flow rate sensor 7.

  In step S21, it is determined whether or not the number of elapsed strokes (number of strokes after starting) TACR from the start of engine start is greater than a predetermined stroke number TASX (for example, 50 strokes), and while the answer is negative (NO). Then, it is determined that the intake air flow rate sensor 7 is not activated, and fuel injection control based on the corrected in-cylinder air amount GCYLC is executed (step S22). When the number of post-start strokes TACR exceeds the predetermined number of strokes TASX, it is determined that the intake air flow rate sensor 7 is activated, and fuel injection control based on the detected intake air flow rate GA is executed (step S23). The predetermined number of strokes TASX is set to the number of strokes in which the activation of the intake air flow rate sensor 7 is surely completed.

Next, a method for theoretically obtaining the basic blow back air amount GBBM will be described.
FIG. 8 is a diagram schematically showing the intake passage 2, the intake valve 1 b, and the cylinder (combustion chamber) 1 a of the engine 1. Assuming that the air passing through the intake valve 1b is a compressible fluid and the flow thereof is an adiabatic flow and the influence of the viscosity of the air is negligible, the flow velocity u of the air passing through the intake valve 1b is expressed by the following equation (21 ). In equation (21), PCYL is the in-cylinder pressure, ρB is the density of air in the cylinder, and κ is the specific heat ratio (1.4).

Assuming that the entropy does not change, the following equation (22) (KCONST is a constant) is established, so the density ρA of the air in the intake passage is given by the following equation (23).

Further, the intake valve passage mass flow rate GAIRVLV is given by the following equation (24) from the continuous equation, and the following equation (25) is obtained by applying the equations (21) and (23) thereto. “Cd” in the equations (24) and (25) is a flow coefficient of the intake valve 1b, and “A” is an opening area of the intake valve 1b.

With respect to the pressure PCYL, the volume VCYL, and the mass GCYL of the air in the cylinder, when the temperature TA (absolute temperature conversion value) and the gas constant R are used, the relationship expressed by the following equation (26) is established. The air density ρB (= GCYL / VCYL) is given by the following equation (27).

By applying the equation (27) to the equation (25), the following equation (28) is obtained. RP in the equation (28) is a pressure ratio represented by the following equation (29), and ψ (RP) is a flow rate function given by the following equation (30).

However, the flow rate function ψ (RP) is a constant given by the following equation (32) when the pressure ratio RP is equal to or less than the critical pressure ratio RPC given by the following equation (31). FIG. 9A illustrates the flow function Ψ (RP).

Since it is difficult to theoretically calculate the flow coefficient Cd in the equation (28), the valve opening coefficient KVLV is defined by the following expression (33), and the valve opening coefficient KVLV is experimentally obtained by a steady flow test. And the relationship shown in FIG. 9B is obtained. The horizontal axis of FIG.9 (b) is the lift amount LFT of the intake valve 1b.
KVLV = Cd · A (33)

Next, a method for calculating the basic blowback air amount GBBM based on the intake valve passage mass flow rate GAIRVLV will be described.
Assuming that the initial position is when the piston of the cylinder to be calculated is at the bottom dead center at the start of the intake stroke, the intake valve (intake Since the exchange of air through the mouth is stabilized, the following formula (41) is established. It is assumed that the blowback amount GVLV [1] in this initial state is “0”.
PCYL [1] = PBA [1] (41)

The in-cylinder air amount GCYL [1] is given by the following formula (42). VCYL in the formula (42) is a cylinder volume.

The increase in the in-cylinder pressure during the compression stroke and the phenomenon in which the air in the cylinder is blown back to the intake passage through the intake valve actually occur almost at the same time. Then, it can be approximated that the flow of air to the intake passage occurs due to the increased pressure. Here, the in-cylinder pressure (cylinder pressure not considering the blow-back air amount) PCYL ′ [1] after the minute time dt has elapsed is assumed to be the following formula (43), assuming that the air in the cylinder is adiabatically compressed. Given. [1] and [2] in the equation (43) indicate the discretization time discretized by the minute time dt.

Therefore, the blowback amount GVLV [2] within the minute time dt is given by the following formula (44). The in-cylinder air amount GCYL [2] and the in-cylinder pressure PCYL [2] after the minute time dt has elapsed are given by the following equations (45) and (46).

By sequentially using the equations (43) to (46), the blowback amount GVLV [i] at the discretization time i = 1, 2, 3,... Is calculated, and the sum during the time when the intake valve 1b is opened is calculated. Is calculated by the following equation (47), the basic blow-back air amount GBBM can be calculated.
GBBM = ΣGVLV [i] (47)

  The PBA [i] applied to the equation (44) always uses the initial value PBA [1] regardless of the value of the discretization time i. Strictly speaking, PBA [i] changes, but the air amount GIN in the intake passage is generally much larger than the blown back air amount GBBM, and the amount of change is small.

  As described above, the basic blow-back air amount GBBM can be calculated. The above calculation is performed by setting the intake air temperature TA to the reference intake air temperature TA0.

Next, the intake air temperature correction in the correction unit 23 of FIG. 2 will be described.
As described above, since the blowback amount GVLV is given by the equation (44), the blowback amount GVLV0 when the intake air temperature TA is the reference intake air temperature TA0 and the blowback amount GVLV1 when the intake air temperature TA is the temperature TA1. The relationship is shown by the following formula (48). Therefore, by applying the basic blowback air amount GBBM calculated by searching the GBBM map to the equation (1) (repost), the blowback air amount GBB at the intake air temperature TA can be obtained.

  As described above in detail, in the present embodiment, the valve opening time TIVO of the intake valve 1b in the compression stroke is calculated according to the engine speed NE, and preset and stored according to the valve opening time TIVO and the intake pressure PBA. The basic blown air amount GBBM is calculated by searching the GBBM map. Then, the corrected in-cylinder air amount GCYLC is calculated by subtracting the blow-back air amount GBB from the in-cylinder air amount GCYL estimated based on the intake pressure PBA, and the corrected in-cylinder air amount GCYLC is used immediately after the start of the start. Control of the fuel injection amount at is performed. By using the detected (calculated) valve opening time TIVO and the intake pressure PBA, and the GBBM map stored in advance, the blow-back air amount GBB can be accurately estimated by a relatively simple calculation. Therefore, the corrected in-cylinder air amount GCYLC that accurately indicates the actual air amount in the cylinder can be obtained by subtracting the blow back air amount GBB from the in-cylinder air amount GCYL calculated according to the intake pressure PBA.

  Further, a basic fuel injection amount FIN is calculated based on the corrected in-cylinder air amount GCYLC, and a blowback fuel amount FR that is an amount of fuel returned to the intake passage 2 is calculated. Then, the fuel injection amount FOUT is calculated by subtracting the blowback fuel amount FR from the basic fuel injection amount FIN calculated based on the corrected in-cylinder air amount GCYLC. Therefore, an amount of fuel suitable for the actual in-cylinder air amount can be injected, and the air-fuel ratio of the air-fuel mixture in the cylinder can be accurately controlled.

  Further, since the control using the corrected in-cylinder air amount GCYLC is performed from when the engine start is started until the time (TASX) required for activation of the intake air flow rate sensor 7 elapses, the intake air flow rate sensor 7 is Deviation from the desired value of the air-fuel ratio in the period until activation can be prevented.

  For cylinders that have been determined that fuel injection has been performed after the start of engine startup, the cylinder air amount GCYL is estimated based on the stroke volume VSTR of the cylinder, and for cylinders that have been determined that fuel injection has not been performed, An in-cylinder air amount GCYL is estimated on the basis of a volume (VSTR + VMIN) obtained by adding the minimum volume VMIN that is the cylinder volume when the piston of the cylinder is located at the top dead center to the stroke volume VSTR of the cylinder. Before fuel injection, the cylinder volume when the piston is at top dead center is filled with air (fresh air), not residual gas or unburned gas after combustion. By estimating the in-cylinder air amount GCYL, more accurate estimation can be performed.

  In the present embodiment, the intake pressure sensor 8 and the intake air flow rate sensor 7 correspond to intake pressure detection means and intake air amount detection means, respectively, and the fuel injection valve 6 corresponds to fuel injection means. The crank angle position sensor 11 constitutes a part of the valve opening time detection means, and the ECU 5 calculates the in-cylinder air amount estimation means, a part of the valve opening time detection means, the storage means, the blow back air amount calculation means, and the correction air amount calculation. Means, fuel injection amount calculating means, blowback fuel amount calculating means, corrected fuel injection amount calculating means, and activity determining means.

  The present invention is not limited to the embodiment described above, and various modifications can be made. For example, in the above-described embodiment, the valve opening time calculation unit 21 calculates the valve opening time TIVO according to the engine speed NE as shown in FIG. Although the basic blowback air amount GBBM is calculated according to the intake pressure PBA, the basic blowback air amount GBBM may be calculated directly from the engine speed NE and the intake pressure PBA. The map in FIG. 10A is a GBBM map used for calculating the basic blow-back air amount GBBM according to the engine speed NE and the intake pressure PBA. The predetermined rotational speeds NE1, NE2, NE3 in this figure are set to, for example, 200 rpm, 400 rpm, and 1000 rpm, respectively.

Further, the ratio of the blown air amount (blowback ratio) RGBBM to the in-cylinder charged air amount GCYLCS at the compression stroke start time (time when the piston is located at the bottom dead center) is used with the table shown in FIG. The basic blow back air amount GBBM may be calculated by calculating according to the rotational speed NE and multiplying the charged air amount GCYLCS calculated according to the intake pressure PBA. In that case, instead of the table shown in FIG. 10B, the blowback ratio RGBBM may be calculated using the following equation (51) that approximates the setting of the table. In formula (51), k1 and k2 are a predetermined coefficient and a predetermined added value, respectively, and Ln represents a natural logarithm.
RGBBM = −k1 × Ln (NE) + k2 (51)

  In the above-described embodiment, the example of the control device for the internal combustion engine in which the fuel injection valve is provided in the intake passage 2 is shown. However, the present invention is an internal combustion engine provided with a fuel injection valve that directly injects fuel into the cylinder. It can also be applied to a control device.

  The present invention can also be applied to control of a marine vessel propulsion engine such as an outboard motor having a crankshaft as a vertical direction.

It is a figure which shows the structure of the internal combustion engine and its control apparatus concerning one Embodiment of this invention. It is a block diagram which shows the structure of the module which calculates fuel injection amount (FOUT) immediately after the start of an engine start. It is a figure which shows the map for calculating a basic blow-back air amount (GBBM). It is a flowchart of the process which calculates the air quantity (GCYL) in a cylinder. It is a figure for demonstrating the process of FIG. It is a figure for demonstrating the calculation method of fuel injection amount. It is a flowchart for demonstrating switching of fuel injection amount control. It is a figure which shows typically the intake passage of an engine, an intake valve, and a cylinder (combustion chamber). It is a figure which shows the table for calculating the flow function and valve opening coefficient (KVLV) used in order to calculate the amount of blow-back air. It is a figure which shows the map and table which are used in the modification of embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 1a Cylinder 1b Intake valve 2 Intake passage 5 Electronic control unit (In-cylinder air amount estimation means, valve opening time detection means, storage means, blow-back air amount calculation means, correction air amount calculation means, fuel injection amount calculation means, Blow-back fuel amount calculation means, corrected fuel injection amount calculation means, activity determination means)
6 Fuel injection valve (fuel injection means)
7 Intake air flow rate sensor (intake air amount detection means)
8 Intake pressure sensor (Intake pressure detection means)
9 Intake air temperature sensor 11 Crank angle position sensor (valve opening time detection means)

Claims (3)

An internal combustion engine comprising intake pressure detecting means for detecting an intake pressure of the internal combustion engine and in-cylinder air amount estimating means for estimating an air amount in the cylinder of the engine based on the intake pressure detected by the intake pressure detecting means. In the engine control device,
A valve opening time detecting means for detecting a valve opening time of the intake valve in the compression stroke of the engine;
Storage means for storing in advance a correlation between the amount of air blown back that is the amount of air returned from the cylinder to the intake passage of the engine during the compression stroke, the valve opening time, and the intake pressure;
Blow-back air amount calculation means for calculating the blow-back air amount based on the detected intake pressure and valve opening time and the correlation stored in the storage means;
Correction air amount calculating means for calculating a corrected in-cylinder air amount by subtracting the blow-back air amount from the air amount estimated by the in-cylinder air amount estimating means,
A control device for an internal combustion engine, wherein the engine is controlled using the corrected in-cylinder air amount. Fuel injection means for injecting fuel into the intake passage or cylinder of the engine, fuel injection amount calculating means for calculating the fuel injection amount by the fuel injection means based on the corrected in-cylinder air amount, and the intake passage A blowback fuel amount calculation means for calculating a blowback fuel amount that is the amount of fuel returned to the intake passage together with the returned air, and subtracting the blowback fuel amount from the fuel injection amount calculated by the fuel injection amount calculation means. And a corrected fuel injection amount calculating means for calculating a corrected fuel injection amount,
2. The control device for an internal combustion engine according to claim 1, wherein the fuel injection means is driven in accordance with the corrected fuel injection amount. Intake air amount detection means for detecting the intake air amount of the engine, and activation determination means for determining whether or not the intake air amount detection means is activated,
The control using the corrected in-cylinder air amount is performed from the start of the engine start until it is determined that the intake air amount detecting means is activated. Control device for internal combustion engine.

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