JP2011026969A - Fuel injection control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device of an internal combustion engine which accurately controls an air-fuel ratio of an air-fuel mixture in a combustion chamber by properly performing the fuel injection control of the internal combustion engine equipped with fuel injection valves for injecting fuel into an intake passage and into the combustion chamber. <P>SOLUTION: The fuel injection control device calculates a residual ratio Cfw indicating a ratio of fuel remaining in a combustion chamber without being blown back to an intake passage by using a port injection residual ratio Cfw0 corresponding to the case that only a port fuel injection valve for injecting fuel into an intake passage is used, a residual cylinder injection residual ratio Cfw1 corresponding to the case that only a cylinder fuel injection valve for injecting fuel into a combustion chamber is used, and a direct injection ratio RINJD showing a ratio of a fuel injection quantity by a cylinder fuel injection valve, and calculates a fuel injection quantity Tout so as to ignite fuel equivalent to a required fuel quantity by using the residual ratio Cfw. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly to a fuel injection control device for an internal combustion engine that includes a fuel injection valve that injects fuel into an intake passage and a fuel injection valve that injects fuel into a combustion chamber.

  Patent Document 1 discloses a fuel injection control device for an internal combustion engine that includes a port injector that injects fuel into an intake port and an in-cylinder injector that injects fuel into a combustion chamber. According to this device, the amount of fuel contained in the blow-back gas blown back from the combustion chamber to the intake port in the intake stroke of the previous cycle (k-1) and again taken into the combustion chamber in the intake stroke of the current cycle (k). The fuel injection amount is calculated in consideration of the (blow-back fuel amount) and the fuel in the residual gas that has not been discharged in the exhaust stroke.

Japanese Patent Laid-Open No. 2007-92088

  When the fuel is injected by the port injector and when the fuel is injected by the in-cylinder injector, the fuel mixing state in the combustion chamber is different. Therefore, even if the same amount of the air-fuel mixture is blown back to the intake passage, the fuel to be blown back The amount of can vary greatly. The tendency of the fuel in the combustion chamber to be blown back into the intake passage is particularly noticeable when the operation of closing the intake valve late is performed. When the amount of fuel blown back is estimated according to the amount of air-fuel mixture blown back, the estimated fuel amount And the actual amount of fuel blown back, the air-fuel ratio deviates from a desired value, leading to deterioration of exhaust characteristics.

  However, Patent Document 1 only describes that the amount of blown fuel is calculated using a map corresponding to the engine operating state, and does not describe details of parameters or maps indicating the engine operating state. Therefore, the apparatus disclosed in Patent Document 1 cannot solve the above problem.

  The present invention has been made paying attention to this point, and more appropriately performs fuel injection control of an internal combustion engine including a fuel injection valve that injects fuel into an intake passage and a fuel injection valve that injects fuel into a combustion chamber. It is an object of the present invention to provide a fuel injection control device for an internal combustion engine that can be accurately executed to accurately control the air-fuel ratio of the air-fuel mixture in the combustion chamber.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a first fuel injection valve (6P) for injecting fuel into an intake passage (2) of an internal combustion engine, and a second fuel injection for injecting fuel into a combustion chamber of the engine. In a fuel injection control device for an internal combustion engine comprising a fuel injection valve (6C), required fuel amount calculation means for calculating a required fuel amount (Tcylf) according to the operating state of the engine, and from the combustion chamber to the intake passage The fuel injection amount (Tout) is calculated by using the blowback fuel amount calculation means for calculating the blowback fuel amount (Fwg), which is the amount of fuel blown back, and the required fuel amount (Tcylf) and the blowback fuel amount (Fwg). Fuel injection amount calculation means for calculating, and drive control means for drivingly controlling at least one of the first fuel injection valve (6P) and the second fuel injection valve (6C) according to the fuel injection amount (Tout). , Serial backflow fuel amount calculating means, said first and second fuel injection valves (6P, 6C) according to the drive state of, and calculates the backflow fuel quantity (FWG).

  According to a second aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the first aspect, an injection amount ratio (which is a ratio of fuel injection amounts by the first and second fuel injection valves (6P, 6C)) RINJD) is calculated, and the drive control means controls at least one of the first fuel injection valve and the second fuel injection valve (6P, 6C) according to the injection amount ratio (RINJD). Drive-controlled, the blowback fuel amount calculation means includes a first blowback rate (1-Cfw0) corresponding to fuel injection by only the first fuel injection valve (6P), and the second fuel injection valve (6C). The blowback fuel amount (Fwg) is calculated using the second blowback rate (1-Cfw1) corresponding to the fuel injection only by the fuel injection and the injection amount ratio (RINJD).

  According to a third aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the second aspect, the blow-back fuel amount calculating means immediately after the change when the injection amount ratio (RINJD) is changed. When the first fuel injection is executed, the blowback rate corresponding to the injection amount ratio (RINJDM) before the change is used, and from the second and subsequent fuel injection executions after the change, the changed injection amount ratio (RINJD) is supported. It is characterized by using a blowback rate.

  According to a fourth aspect of the present invention, in the fuel injection control device for an internal combustion engine according to any one of the first to third aspects, an intake valve closing valve that changes a closing timing (CAIC) of the intake valve of the engine. It further comprises timing change means, wherein the blowback fuel amount calculation means calculates the blowback fuel amount according to a closing timing (CAIC) of the intake valve.

  According to the first aspect of the invention, the required fuel amount is calculated according to the engine operating state, the blowback fuel amount blown back from the fuel chamber to the intake passage is calculated, and the required fuel amount and the blowback fuel amount are calculated. Using this, the fuel injection amount is calculated. At least one of the first fuel injection valve and the second fuel injection valve is driven according to the fuel injection amount, and the blowback fuel amount is calculated according to the driving state of the first and second fuel injection valves. Therefore, for example, by calculating the blowback fuel amount in accordance with the ratio of the fuel amount injected from the first and second fuel injection valves, the blowback fuel amount is accurately calculated and actually burned in the combustion chamber. The amount of fuel that contributes can be accurately controlled taking into account the amount of fuel blown back. As a result, regardless of the fuel injection valve to be used, the air-fuel ratio of the air-fuel mixture in the combustion chamber can be accurately controlled and good exhaust characteristics can be maintained.

  According to the second aspect of the present invention, the injection amount ratio, which is the ratio of the fuel injection amounts by the first and second fuel injection valves, is calculated, and the first fuel injection valve and the second fuel injection are determined according to the injection amount ratio. At least one of the valves is drive-controlled, a first blowback rate corresponding to fuel injection by only the first fuel injection valve, a second blowback rate corresponding to fuel injection by only the second fuel injection valve, and an injection amount ratio Are used to calculate the blowback fuel amount. Accordingly, it is possible to accurately calculate the amount of blowback fuel corresponding to the change in the injection amount ratio and accurately control the amount of fuel actually contributing to combustion in the combustion chamber in consideration of the amount of fuel blown back. it can.

  According to the third aspect of the present invention, when the injection amount ratio is changed, the blow-back rate corresponding to the injection amount ratio before the change is applied at the time of the first fuel injection immediately after the change. From the time of the second and subsequent fuel injection executions, the blowback rate corresponding to the changed injection amount ratio is applied. Immediately after the change of the injection amount ratio, the injected fuel is blown back according to the injection ratio before the change, and therefore, the blowback rate corresponding to the injection amount ratio before the change is applied at the time of the first fuel injection immediately after the change. And by applying the blowback rate corresponding to the injection amount ratio after the change from the time of the second or subsequent fuel injection execution, the blowback fuel amount can be accurately calculated.

  According to the fourth aspect of the present invention, the blow-back fuel amount is calculated according to the closing timing of the intake valve. Since the amount of fuel blown back to the intake passage changes depending on the closing timing of the intake valve, the amount of blowback fuel is accurately calculated by calculating the amount of blowback fuel according to the closing timing of the intake valve. Can be calculated.

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 figure for demonstrating operation | movement of the valve action phase variable mechanism shown in FIG. It is a figure for demonstrating a fuel transport delay model (1st Embodiment). It is a flowchart (1st Embodiment) of the process which performs fuel-injection control. It is a flowchart of the residual rate calculation process performed by the process of FIG. It is a figure which shows the table referred by the process of FIG. It is a flowchart of the fuel injection amount calculation process performed by the process of FIG. It is a figure for demonstrating a fuel transport delay model (2nd Embodiment). It is a figure which shows the relationship between the stroke of each cylinder, and the stage used for fuel injection control. It is a flowchart (2nd Embodiment) of the process which performs fuel-injection control. It is a flowchart of the fuel injection amount calculation process performed by the process of FIG. It is a flowchart of a residual rate calculation process (2nd Embodiment). It is a flowchart of a residual rate calculation process (2nd Embodiment). 13 is a flowchart of a fuel injection stage (FISTG) calculation process executed in the process of FIG. It is a figure which shows the table referred by the process of FIG. It is a time chart for demonstrating the process of FIG.12 and FIG.13. It is a figure for demonstrating the switching timing control parameter (OFFSET) of a residual rate. It is a flowchart of a residual rate calculation process (3rd Embodiment). It is a flowchart of a residual rate calculation process (4th Embodiment).

Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
FIG. 1 is a diagram showing a configuration of an internal combustion engine and its control device according to an embodiment of the present invention. In FIG. 1, for example, an internal combustion engine (hereinafter simply referred to as “engine”) 1 having four cylinders includes an intake valve and an exhaust valve, a cam for driving them, and a valve operation phase variable mechanism 40. The valve operation phase variable mechanism 40 is a cam phase variable mechanism that continuously changes the operation phase of the cam that drives the intake valve with reference to the crankshaft rotation angle. The operating phase of the cam that drives the intake valve is changed by the valve operating phase variable mechanism 40, and the operating phase of the intake valve is changed.

  A throttle valve 3 is arranged in the intake passage 2 of the engine 1. A throttle valve opening (TH) sensor 4 is connected to the throttle valve 3, and an electric signal corresponding to the opening of the throttle valve 3 is output to an electronic control unit (hereinafter referred to as “ECU”) 5. Supply. An actuator 7 that drives the throttle valve 3 is connected to the throttle valve 3, and the operation of the actuator 7 is controlled by the ECU 5. An intake air amount sensor 13 for detecting an intake air amount GAIR [g / sec] is provided on the upstream side of the throttle valve 3 in the intake passage 2, and the detection signal is supplied to the ECU 5.

  The engine 1 is provided for each cylinder slightly upstream of the intake valve of each cylinder, and a port fuel injection valve 6P that injects fuel into the intake passage 2 (intake port), and directly injects fuel into the combustion chamber of each cylinder. And an in-cylinder fuel injection valve 6C. Each injection valve 6P, 6C is connected to a fuel pump (not shown) and electrically connected to the ECU 5, and the valve opening timing (fuel injection timing) and the valve opening time (fuel injection time) are controlled by a signal from the ECU 5. Is done. The ignition plug 15 of each cylinder of the engine 1 is connected to the ECU 5, and the ECU 5 supplies an ignition signal to the ignition plug 15 to perform ignition timing control.

  An intake pressure sensor 8 for detecting the intake pressure PBA and an intake air temperature sensor 9 for detecting the intake air temperature TA are attached downstream of the throttle valve 3. An engine cooling water temperature sensor 10 that detects the engine cooling water temperature TW is attached to the main body of the engine 1. Detection signals from these sensors are supplied to the ECU 5.

  The ECU 5 includes a crank angle position sensor 11 that detects a rotation angle of a crankshaft (not shown) of the engine 1 and a cam angle that detects a rotation angle of a camshaft to which a cam that drives an intake valve of the engine 1 is fixed. A position sensor 12 is connected, and signals corresponding to the rotation angle of the crankshaft and the rotation angle of the camshaft are supplied to the ECU 5. The crank angle position sensor 11 generates one pulse (hereinafter, referred to as “CRK pulse”) every predetermined crank angle period (for example, 30 degree period) and a pulse for specifying a predetermined angle position of the crankshaft. The cam angle position sensor 12 has a pulse (hereinafter referred to as “CYL pulse”) at a predetermined crank angle position of a specific cylinder of the engine 1 and a pulse (hereinafter referred to as “TDC”) at the start of the intake stroke of each cylinder. "TDC pulse"). These pulses are used for various timing controls such as fuel injection timing and ignition timing, and detection of engine speed (engine speed) NE. The actual operating phase CAIN of the camshaft is detected from the relative relationship between the TDC pulse output from the cam angle position sensor 12 and the CRK pulse output from the crank angle position sensor 11.

  The ECU 5 includes an accelerator sensor 31 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 a vehicle speed sensor 32 for detecting a traveling speed (vehicle speed) VP of the vehicle. , And an atmospheric pressure sensor 33 for detecting the atmospheric pressure PA is connected. Detection signals from these sensors are supplied to the ECU 5.

  The valve operation phase variable mechanism 40 includes an electromagnetic valve whose opening degree can be changed continuously in order to continuously change the operation phase of the intake valve. The opening degree of the electromagnetic valve is controlled by the ECU 5. The A specific configuration of the valve operation phase varying mechanism 40 is disclosed in, for example, Japanese Patent Application Laid-Open No. 2000-227013. FIG. 2 is a diagram showing the lift curve of the intake valve (the vertical axis is the lift amount LFT), and the intake valve is controlled by the valve operation phase variable mechanism 40, with the characteristics of the cam centered on the characteristics indicated by solid lines L3 and L4 in FIG. Driven by a phase from the most advanced angle phase indicated by broken lines L1 and L2 to the most retarded angle phase indicated by alternate long and short dash lines L5 and L6 in accordance with a change in operating phase CAIN (hereinafter referred to as “intake valve operating phase”) . In the present embodiment, the intake valve operation phase CAIN is set so that the intake valve closing timing CAIC is after the start of the compression stroke, and the mirror cycle (Atkinson cycle) operation is performed. Further, in the present embodiment, the intake valve operation phase CAIN is defined such that the most retarded angle phase is “0” and the value increases as the angle advances.

  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 unit (hereinafter referred to as “CPU”). ) In addition to a storage circuit that stores a calculation program executed by the CPU, a calculation result, and the like, the actuator 7, the fuel injection valves 6P and 6C, and an output circuit that supplies a drive signal to the electromagnetic valve of the valve operation phase variable mechanism Is done.

  The CPU of the ECU 5 controls the opening degree of the throttle valve 3, the fuel injection control (control of the fuel injection timing and the fuel injection time by the fuel injection valves 6P and 6C), and the intake valve operation phase in accordance with the detection signal of the sensor. Control.

  FIG. 3 is a diagram for explaining a fuel transport delay model applied to fuel injection control. In the present embodiment, taking into account that the intake valve is closed after the start of the compression stroke, the blowback fuel amount Fwg, which is the amount of fuel blown back from the combustion chamber to the intake port, is calculated, and the blowback fuel amount Fwg is calculated. Is used to calculate the fuel injection amount Tout. In the present embodiment, either the port fuel injection valve 6P or the in-cylinder fuel injection valve 6C is selected according to the engine operating state, and fuel injection is performed.

  The fuel injection amount Tout is the fuel injection amount by the fuel injection valve 6P or 6C (actually the fuel injection time, but the amount of fuel injected is called the fuel injection amount because it is almost proportional to the fuel injection time). “Fw” is the amount of fuel adhering to the inner wall of the intake port or the combustion chamber wall (including the piston top), and hereinafter referred to as “adhered fuel amount Fw”. “Tcyl” is the amount of fuel other than the adhering fuel existing in the combustion chamber, and is the amount of fuel before being blown back to the intake port, and is hereinafter referred to as “in-cylinder fuel amount Tcyl”. “Tcylf” is the amount of fuel used for combustion, and is hereinafter referred to as “combustion fuel amount Tcylf”. “Afw” is a parameter indicating the proportion of the injected fuel that does not adhere to the inner wall of the intake port and flows directly into the combustion chamber, or does not adhere to the combustion chamber wall and exists in the combustion chamber. Hereinafter, it is referred to as “direct rate Afw”. Therefore, (1-Afw) corresponds to the adhesion rate. “Bfw” is a parameter indicating a ratio of fuel sucked into the combustion chamber out of the fuel adhering to the inner wall of the intake port or vaporized out of fuel adhering to the wall of the combustion chamber. It is called “Leave Rate Bfw”. “Cfw” is a parameter indicating the ratio of the fuel other than the adhering fuel existing in the combustion chamber that remains without being blown back to the intake port, and is hereinafter referred to as “residual rate Cfw”. Therefore, (1-Cfw) corresponds to a blowback rate that indicates the proportion of fuel that is blown back to the intake port of the in-cylinder fuel.

  The fuel transport delay model shown in FIG. 3 can be expressed by the following formulas (1) to (4). (K) and (k-1) are parameters indicating the discretization time at which the fuel injection amount is calculated, and indicate the current value and the previous value, respectively. In the mathematical formula defining this model, the amount of fuel blown back last time (Fw (k-1)) is all sucked into the combustion chamber this time, and the amount of fuel multiplied by the residual rate Cfw remains in the combustion chamber, and combustion Is used (see equation (4)).

Fw (k) = (1-Afw) × Tout (k)
+ (1-Bfw) × Fw (k-1) (1)
Fwg (k) = (1-Cfw) × Tcyl (k)
+ (1-Cfw) × Fwg (k-1) (2)
Tcyl (k) = Afw × Tout (k) + Bfw × Fw (k−1) (3)
Tcylf (k) = Cfw × (Tcyl (k) + Fwg (k−1)) (4)

By applying the formula (3) to the formulas (2) and (4), the following formulas (5) and (6) are obtained.
Fwg (k) = (1-Cfw) × (Afw × Tout (k) + Bfw × Fw (k−1))
+ (1-Cfw) × Fwg (k-1) (5)
Tcylf (k) = Cfw ×
(Afw × Tout (k) + Bfw × Fw (k−1) + Fwg (k−1)) (6)

The following equation (7) is obtained by modifying the equation (6), and the fuel injection amount Tout (k) in consideration of the transport delay due to the adhesion and blowback of the fuel can be calculated from the equation (7). The initial values of the adhered fuel amount Fw and the blowback fuel amount Fwg are “0”.

FIG. 4 is a flowchart of the fuel injection control process, and this process is executed by the CPU of the ECU 5 in synchronization with the generation of the TDC pulse.
In step S11, an Afw map (not shown) is searched according to the engine speed NE and the intake pressure PBA, and the direct rate Afw is calculated. In step S12, a Bfw map (not shown) is searched according to the engine speed NE and the intake pressure PBA, and a carry-off rate Bfw is calculated.

  In step S13, a residual rate calculation process shown in FIG. 5 is executed to calculate a residual rate Cfw. In step S14, the fuel injection amount calculation process shown in FIG. 6 is executed, and the fuel injection amount Tout is calculated using the direct rate Afw, the carry-off rate Bfw, and the residual rate Cfw calculated in steps S11 to S13.

  The fuel injection is executed by opening the port fuel injection valve 6P or the in-cylinder fuel injection valve 6C according to the calculated fuel injection amount Tout.

FIG. 5 is a flowchart of the residual rate calculation process executed in step S13 of FIG.
In step S21, it is determined whether or not the direct injection, that is, the in-cylinder fuel injection valve 6C is selected. If the answer is affirmative (YES), the direct injection flag FINJ is set to "1" (step S22). On the other hand, when the port fuel injection valve 6P is selected, the direct injection flag FINJ is set to “0” (step S23).

  In step S24, it is determined whether or not the direct injection flag FINJ is “1”. If the answer to step S24 is negative (NO), that is, if the port fuel injection valve 6P is selected, it is determined according to the intake valve operating phase CAIN. Then, the Cfw0 table indicated by the solid line in FIG. 6 is searched to calculate the port injection residual rate Cfw0 (step S27). The Cfw0 table is set so that the port injection residual rate Cfw0 increases as the intake valve operation phase CAIN increases (advance). In step S28, the residual rate Cfw is set to the port injection residual rate Cfw0.

  If the answer to step S24 is affirmative (YES), that is, if the in-cylinder fuel injection valve 6C is selected, the Cfw1 table indicated by the broken line in FIG. Cfw1 is calculated (step S25). The Cfw1 table is set so that the in-cylinder injection residual ratio Cfw1 increases as the intake valve operation phase CAIN increases (advance). In step S26, the residual rate Cfw is set to the in-cylinder injection residual rate Cfw1.

  In the Cfw0 table and the Cfw1 table shown in FIG. 6, Cfw1> Cfw0 is established at the same intake valve operating phase, but this relationship may be reversed depending on the engine operating state.

FIG. 7 is a flowchart of the fuel injection amount calculation process executed in step S14 of FIG.
In step S31, the previous value Fwg (k-1) of the blowback fuel amount is calculated by the following equation (5a). Formula (5a) is obtained by replacing “k” in Formula (5) with “k−1”.
Fwg (k-1) = (1-Cfw)
× (Afw × Tout (k-1) + Bfw × Fw (k-2))
+ (1-Cfw) × Fwg (k-2) (5a)

In step S32, the previous value Fw (k-1) of the attached fuel amount is calculated by the following equation (1a). Formula (1a) is obtained by replacing “k” in Formula (1) with “k−1”.
Fw (k-1) = (1-Afw) × Tout (k-1)
+ (1-Bfw) × Fw (k-2) (1a)

  In step S33, combustion is performed so that the air-fuel ratio of the air-fuel mixture in the combustion chamber becomes the target air-fuel ratio (usually the stoichiometric air-fuel ratio) according to the engine speed NE, the intake pressure PBA, the engine cooling water temperature TW, the intake air temperature TA, and the like. A fuel amount (required fuel amount) Tcylf is calculated. More specifically, the basic fuel amount TI is calculated according to the engine speed NE and the intake pressure PBA, and the correction coefficient KCR is calculated according to the engine coolant temperature TW, the intake air temperature TA, etc., and the basic fuel amount TI is calculated. By correcting with the correction coefficient KCR, the combustion fuel amount Tcylf is calculated.

  In step S34, the previous value Fwg (k-1) of the blowback fuel amount, the previous value Fw (k-1) of the attached fuel amount, and the combustion fuel amount Tcylf (k) calculated in steps S31 to S33 are expressed by the above formula ( 7), the fuel injection amount Tout (k) is calculated.

  As described above, in the present embodiment, the combustion fuel amount Tcylf corresponding to the required fuel amount is calculated according to the engine operating state, the blowback fuel amount Fwg blown back from the fuel chamber to the intake port is calculated, and the combustion fuel amount The fuel injection amount Tout is calculated using Tcylf and the blowback fuel amount Fwg. Then, by driving the port fuel injection valve 6P or the in-cylinder fuel injection valve 6C according to the fuel injection amount Tout, fuel injection is performed, and a residual rate Cfw corresponding to the fuel injection valve being used is calculated. A blowback fuel amount Fwg is calculated using the residual rate Cfw. Therefore, the blowback fuel amount Fwg can be accurately calculated, and the combustion fuel amount Tcylf that actually contributes to combustion in the combustion chamber can be accurately controlled in consideration of the blowback fuel amount Fwg. As a result, regardless of the fuel injection valve used, the air-fuel ratio of the air-fuel mixture in the combustion chamber can be accurately controlled and good exhaust characteristics can be maintained.

  In the present embodiment, the port fuel injection valve 6P and the in-cylinder fuel injection valve 6C correspond to a first fuel injection valve and a second fuel injection valve, respectively, and the ECU 5 includes a required fuel amount calculation means, a blowback fuel amount calculation means, And a fuel injection amount calculating means. Specifically, step S33 in FIG. 7 corresponds to the required fuel amount calculating means, step S31 corresponds to the blowback fuel amount calculating means, and step S34 corresponds to the fuel injection amount calculating means.

[Second Embodiment]
In the present embodiment, the blow-back fuel amount Fwg is calculated by using an injector-dependent residual rate Cfwa that takes a different value depending on the fuel injector used and an injector-independent residual rate Cfwb that does not depend on the fuel injector used. It is what you do. The air-fuel mixture containing the fuel blown back to the intake port has elapsed since the air and fuel were mixed, and the mixture of air and fuel has become uniform due to the flow of the air-fuel mixture This is because the residual rate when the blown back fuel flows into the combustion chamber again is considered not to depend on the used fuel injection valve.
The present embodiment is the same as the first embodiment except for the points described below.

  FIG. 8 is a diagram for explaining a fuel transportation delay model in the present embodiment. Compared with the model shown in FIG. 3, the residual rate applied to the in-cylinder fuel amount Tcyl is changed to the injector-dependent residual rate Cfwa, and the residual rate applied to the blowback fuel amount Fwg is changed to the injector-independent residual rate Cfwb. Has been.

The fuel transport delay model shown in FIG. 8 can be expressed by the following formulas (11) to (14). Expressions (11) and (13) are the same as Expressions (1) and (3) in the first embodiment.
Fw (k) = (1-Afw) × Tout (k)
+ (1-Bfw) × Fw (k-1) (11)
Fwg (k) = (1-Cfwa) × Tcyl (k)
+ (1-Cfwb) × Fwg (k-1) (12)
Tcyl (k) = Afw × Tout (k) + Bfw × Fw (k−1) (13)
Tcylf (k) = Cfwa × Tcyl (k)
+ Cfwb × Fwg (k-1) (14)

By applying the formula (13) to the formulas (12) and (14), the following formulas (15) and (16) are obtained.
Fwg (k) = (1-Cfwa)
× (Afw × Tout (k) + Bfw × Fw (k-1))
+ (1-Cfwb) × Fwg (k-1) (15)
Tcylf (k) = Cfwa × (Afw × Tout (k) + Bfw × Fw (k−1))
+ Cfwb × Fwg (k-1)) (16)

The following equation (17) is obtained by modifying the equation (16). In the present embodiment, the fuel injection amount Tout (k) is calculated by the equation (17).

  FIG. 9 is a diagram showing the relationship between the strokes of cylinder # 1 to cylinder # 4 and the stage set for every 30 degrees of crank angle. In this embodiment, the fuel injection timing of each cylinder is set by the fuel injection stages FISTG (# 1) to FISTG (# 4), and fuel injection is performed in the set fuel injection stages FISTG (# 1) to FISTG (# 4). Is executed. The fuel injection stages FISTG (# 1) to FISTG (# 4) take values from “0” to “23” corresponding to one combustion cycle. In addition, a cyclic stage STG is defined and used in arithmetic processing described later. The cyclic stage STG takes a value corresponding to the fuel injection stage FISTG of the cylinder in the compression stroke, that is, takes a value from “0” to “5” with a crank angle of 180 degrees. Each stage is set in synchronization with the generation time of the CRK pulse, and the start time of stage “0” is defined to be slightly behind the time when the piston is located at the top dead center.

  FIG. 10 is a flowchart of the fuel injection control process in this embodiment. This process is executed by the CPU of the ECU 5 in synchronization with the generation of the TDC pulse. In this process, step S13 of the process shown in FIG. 4 is deleted, and step S14 is changed to step S14a.

  In step S14a, the fuel injection amount calculation process shown in FIG. 11 is executed, and the fuel injection amount Tout (k) is calculated using the injector-dependent residual rate Cfwa and the injector-independent residual rate Cfwb as described above.

The process shown in FIG. 11 is obtained by replacing steps S31 and S34 in FIG. 7 with steps S31a and S34a, respectively.
In step S31a, the previous value Fwg (k-1) of the blowback fuel amount is calculated by the following equation (15a). Formula (15a) is obtained by replacing “k” in Formula (15) with “k−1”.
Fwg (k-1) = (1-Cfwa)
× (Afw × Tout (k-1) + Bfw × Fw (k-2))
+ (1-Cfwb) × Fwg (k-2) (15a)

  In step S34a, the fuel injection amount Tout (k) is calculated by the above equation (17).

12 and 13 are flowcharts of the residual rate calculation process. This process is executed by the CPU of the ECU 5 in synchronization with the generation of the CRK pulse.
In step S41, it is determined whether or not the direct injection, that is, the in-cylinder fuel injection valve 6C is selected. If the answer is affirmative (YES), the direct injection flag FINJ is set to “1” (step S42). On the other hand, when the port fuel injection valve 6P is selected, the direct injection flag FINJ is set to “0” (step S43).

  In step S44, the FISTG calculation process shown in FIG. 14 is executed. In step S71 of FIG. 14, it is determined whether or not the direct injection flag FINJ is “1”. If the answer is negative (NO), the FISTGPI map (in accordance with the engine coolant temperature TW and the intake pressure PBA) The port fuel injection stage FISTGPI is calculated (step S74). In step S75, the fuel injection stage FISTG is set to the port fuel injection stage FISTGPI, and the process proceeds to step S76.

  If the answer to step S71 is affirmative (YES), a FISTGDI map (not shown) is searched according to the engine coolant temperature TW and the intake pressure PBA, and an in-cylinder fuel injection stage FISTGDI is calculated (step S72). In step S73, the fuel injection stage FISTG is set to the in-cylinder fuel injection stage FISTGDI, and the process proceeds to step S76.

In step S76, the TDC fuel injection stage FISTGtdc is calculated by the following equation (18). The right side of Expression (18) is an expression for calculating a remainder obtained by dividing the fuel injection stage FISTG by “6”. For example, when FISTG is “22”, the TDC fuel injection stage FISTGtdc is “4”.
FISTGtdc = mod (FISTG, 6) (18)

Returning to FIG. 12, in step S45, the injector switching flag FISW is calculated by the following equation (19). “FINJZ” in Expression (19) is the previous value of the direct injection flag FINJ (see Step S64).
FISW = | FINJ−FINJZ | (19)

  In step S46, it is determined whether or not the injector switching flag FISW is “1”. If the answer is affirmative (YES), that is, immediately after the fuel injector to be used is switched, the counting parameter COUNT is set to “0”. To "" (step S47). In step S48, it is determined whether or not the current cyclic stage STG is smaller than the TDC fuel injection stage FISTGtdc, that is, whether or not the fuel injection valve has been switched immediately before fuel injection.

If the answer to step S48 is affirmative (YES), the switching timing control parameter OFFSET is set to the current cyclic stage STG (step S49). On the other hand, when the answer to step S48 is negative (NO), that is, when the fuel injection valve is switched at or immediately after the fuel injection stage, the switching timing control parameter OFFSET is calculated by the following equation (20). To do.
OFFSET =-(6-STG) (20)

After execution of step S49 or S50, the process proceeds to step S52.
If the answer to step S46 is negative (NO), that is, not immediately after switching of the fuel injection valve, the count parameter COUNT is incremented by “1” (step S51), and the process proceeds to step S52.

  In step S52, it is determined whether or not the value of the counting parameter COUNT is greater than (24−OFFSET). While this answer is negative (NO), steps S53 to S57 are executed, and the residual rate corresponding to the fuel injector before switching is calculated as the injector-dependent residual rate Cfwa. On the other hand, if the answer to step S52 is affirmative (YES), steps S58 to S62 are executed, and the residual rate corresponding to the fuel injection valve after switching is calculated as the injector-dependent residual rate Cfwa.

  In step S53, it is determined whether or not the direct injection flag FINJ is "1". If the answer is affirmative (YES), the Cfw0 table corresponding to the port fuel injection valve 6P before switching is operated as an intake valve. The search is performed according to the phase CAIN, and the port injection residual ratio Cfw0 is calculated (step S54). In step S55, the injector-dependent residual rate Cfwa is set to the port injection residual rate Cfw0 calculated in step S54.

  If the answer to step S53 is negative (NO), the Cfw1 table corresponding to the in-cylinder fuel injection valve 6C before switching is searched according to the intake valve operating phase CAIN to calculate the in-cylinder injection residual ratio Cfw1 ( Step S56). In step S57, the injector-dependent residual rate Cfwa is set to the in-cylinder injection residual rate Cfw1 calculated in step S56.

  In step S58, the same determination as in step S53 is performed. If the answer to step S58 is affirmative (YES), the Cfw1 table corresponding to the in-cylinder fuel injection valve 6C is searched according to the intake valve operating phase CAIN, and the cylinder is searched. The internal injection residual rate Cfw1 is calculated (step S59). In step S60, the injector dependent residual rate Cfwa is set to the in-cylinder injection residual rate Cfw1 calculated in step S59.

  If the answer to step S58 is negative (NO), the Cfw0 table corresponding to the port fuel injection valve 6P is searched according to the intake valve operating phase CAIN to calculate the port injection residual rate Cfw0 (step S61). In step S62, the injector dependent residual rate Cfwa is set to the port injection residual rate Cfw0 calculated in step S61.

In step S63, the Cfwb table shown in FIG. 15 is searched according to the intake valve operating phase CAIN, and the injector independent residual rate Cfwb is calculated. The Cfwb table is set according to the engine specifications such as the shape of the intake port, intake port, intake valve, and maximum lift amount of the intake valve, and as the intake valve operation phase CAIN increases, the injector-independent residual rate increases. Cfwb is set to increase.
In step S64, the previous value FINJZ of the direct injection flag is set to the current value.

  FIG. 16 is a time chart for explaining the above-described residual rate calculation processing. When the direct injection flag FINJ switches from “0” to “1” at time t11, the injector switching flag FISW becomes “1”, and the value of the counting parameter COUNT is reset to “0”. At this time, the switching timing control parameter OFFSET is calculated in steps S48 to S50. CNTTH shown in FIG. 16C is compared with the value of the counting parameter COUNT in step S52 (24-OFFSET), and is hereinafter referred to as “switching threshold value”. When the switching timing control parameter OFFSET is calculated, the switching threshold value CNTTH is determined. Until the time t12 when the value of the counting parameter COUNT reaches the switching threshold value CNTTH, the port injection residual rate Cfw0 corresponding to the port fuel injection valve 6P is applied as the injector dependent residual rate Cfwa, and after the time t12, the in-cylinder fuel injection valve The in-cylinder injection residual rate Cfw1 corresponding to 6C is applied.

  Next, when the direct injection flag FINJ switches from “1” to “0” at time t13, the injector switching flag FISW becomes “1”, the value of the counting parameter COUNT is reset to “0”, and switching timing control is performed. The parameter OFFSET is calculated, and the switching threshold value CNTTH is determined. Until the time t14 when the value of the counting parameter COUNT reaches the switching threshold value CNTTH, the in-cylinder injection residual rate Cfw1 corresponding to the in-cylinder fuel injection valve 6C is applied as the injector-dependent residual rate Cfwa, and after the time t14, the port fuel injection The port injection residual rate Cfw0 corresponding to the valve 6P is applied.

  FIG. 17 is a diagram for explaining a method for setting the switching timing control parameter OFFSET. When the TDC fuel injection stage FISTGtdc is “3”, the switching timing of the fuel injection valve is the cyclic stage STG = 2. That is, when the answer to step S48 of FIG. 12 is affirmative (YES) (FIG. 17B), OFFSET = 2 and the switching threshold value CNTTH is “22”. On the other hand, as shown in FIG. 17C, when the switching timing of the fuel injection valve is the cyclic stage STG = 5, that is, when the answer to step S48 of FIG. 12 is negative (NO), OFFSET = -1. The switching threshold value CNTTH is “25”.

  As described above, in the present embodiment, when the first fuel injection is performed immediately after the fuel injection valve is switched, the residual ratio corresponding to the fuel injection valve before the switching is applied, and when the fuel injection is performed for the second and subsequent times after the switching. In, the residual rate corresponding to the fuel injection valve after switching is applied. Immediately after the switching of the fuel injection valve, the fuel injected by the fuel injection valve before the switching is blown back, so when performing the first fuel injection immediately after the switching, the residual rate corresponding to the fuel injection valve before the switching is applied, By applying the residual rate corresponding to the fuel injection valve after switching from the time of the second and subsequent fuel injection executions, the blow-back fuel amount can be accurately calculated.

  In this embodiment, the injector-dependent residual rate Cfwa and the injector-independent residual rate Cfwb are separately calculated to calculate the blowback fuel amount Fwg, so that the blowback fuel amount Fwg is calculated more accurately. can do.

  In the present embodiment, step S33 in FIG. 11 corresponds to the required fuel amount calculation means, step S31a corresponds to the blowback fuel amount calculation means, and step S34a corresponds to the fuel injection amount calculation means.

[Third Embodiment]
This embodiment uses the port fuel injection valve 6P and the in-cylinder fuel injection valve 6C at the same time instead of switching the port fuel injection valve 6P and the in-cylinder fuel injection valve 6C in the first embodiment. The fuel injection is performed by changing the ratio of the respective fuel injection amounts by the two fuel injection valves. The present embodiment is the same as the first embodiment except for the points described below.

In the present embodiment, the direct injection ratio RINJD, which is the ratio of the fuel injection amount by the in-cylinder fuel injection valve 6C, is set to a value from “0” to “1” according to the engine operating state, and the calculated fuel injection amount Using Tout and the direct injection ratio RINJD, the port injection fuel amount Toutp and the in-cylinder injection fuel amount Toutc are calculated by the following equations (31) and (32). Then, fuel injection control of the port fuel injection valve 6P is performed according to the port injection fuel amount Toutp, and fuel injection control of the cylinder fuel injection valve 6C is performed according to the cylinder injection fuel amount Toutc.
Toutp = (1-RINJD) × Tout (31)
Toutc = RINJD × Tout (32)

Further, the residual rate Cfw is calculated by the process shown in FIG.
Steps S81 and S82 are the same processes as steps S27 and S25 of FIG. 5, respectively, and the port injection residual rate Cfw0 and the in-cylinder injection residual rate Cfw1 are calculated according to the intake valve operating phase CAIN.

In step S83, the port injection residual rate Cfw0, the in-cylinder injection residual rate Cfw1, and the direct injection ratio RINJD are applied to the following equation (33) to calculate the residual rate Cfw.
Cfw = (1-RINJD) × Cfw0 + RINJD × Cfw1 (33)

  By calculating the fuel injection amount Tout using the residual rate Cfw calculated by the equation (33), the blowback fuel amount Fwg is accurately calculated according to the usage ratio (direct injection ratio RINJD) of the two fuel injection valves. can do.

Note that the first embodiment corresponds to a configuration in which the direct injection ratio RINJD in this embodiment is switched between “1” and “0”.
In the present embodiment, the ECU 5 constitutes an injection amount ratio calculating means, and the processing of FIG. 18 constitutes a part of the blowback fuel amount calculating means.

[Fourth Embodiment]
This embodiment uses the port fuel injection valve 6P and the in-cylinder fuel injection valve 6C at the same time instead of switching the port fuel injection valve 6P and the in-cylinder fuel injection valve 6C in the second embodiment. The fuel injection is performed by changing the ratio of the respective fuel injection amounts by the two fuel injection valves. This embodiment is the same as the second embodiment except for the points described below.

The port injected fuel amount Toutp and the in-cylinder injected fuel amount Toutc are calculated by the equations (31) and (32) as in the third embodiment.
Further, the residual rates Cfwa and Cfwb are calculated by the process shown in FIG. Step S91 is the same process as step S44 of FIG. 12, and the TDC fuel injection stage FISTGtdc is calculated.

In step S92, the direct injection ratio change amount DRINJD is calculated by the following equation (41). RINJDZ in the equation (41) is the previous value of the direct injection ratio (see step S106).
DRINJD = | RINJD-RINJDZ | (41)

  In step S93, it is determined whether or not the direct injection ratio change amount DRINJD is greater than “0”, and when the answer is affirmative (YES), that is, when the direct injection ratio RINJD is changed, the direct injection ratio is stored. The value RINJDM is set to the previous value RINJDZ (step S94), and steps S95 to S98 are executed.

  If the answer to step S93 is negative (NO), step S99 is executed. Steps S95 to S99 are the same processes as steps S47 to S51 in FIG.

  Steps S100 and S101 are the same processes as steps S54 and S56 in FIG. 13, and the same determination as in step S52 in FIG. 13 is performed in step S102.

While the answer to step S102 is negative (NO), the process proceeds to step S103, and the port injection residual rate Cfw0, the in-cylinder injection residual rate Cfw1, and the direct injection ratio memory value RINJDM are applied to the following equation (42), and the injector The dependent residual rate Cfwa is calculated.
Cfwa = (1-RINJDM) × Cfw0
+ RINJDM × Cfw1 (42)

If the answer to step S102 is affirmative (YES), the process proceeds to step S104, and the port injection residual ratio Cfw0, the in-cylinder injection residual ratio Cfw1, and the direct injection ratio RINJD are applied to the following equation (43), and the injector dependent residual ratio Cfwa Is calculated.
Cfwa = (1-RINJD) × Cfw0
+ RINJD × Cfw1 (43)

  In step S105, the injector independent residual rate Cfwb is calculated in the same manner as in step S63 in FIG. In step S106, the previous value RINJDZ of the direct injection ratio is set to the current value RINJD.

  Thus, in the present embodiment, at the time of the first fuel injection immediately after the change of the direct injection ratio RINJD, the injector-dependent residual ratio Cfwa is calculated using the direct injection ratio (RINJDM) before the change, and 2 after the change. At the time of execution of fuel injection after the first time, the injector-dependent residual rate Cfwa is calculated using the changed direct injection ratio RINJD. Immediately after the change of the direct injection ratio RINJD, fuel blowback occurs in accordance with the direct injection ratio RINJDM before the change. Therefore, when the first fuel injection immediately after the change is executed, the direct injection ratio RINJDM before the change is used to depend on the injector. By calculating the residual ratio Cfwa and calculating the injector-dependent residual ratio Cfwa using the changed direct injection ratio RINJD from the time of the second and subsequent fuel injection executions, the blow-back fuel amount can be accurately calculated.

The second embodiment corresponds to a configuration in which the direct injection ratio RINJD in the present embodiment is switched between “1” and “0”.
In the present embodiment, the ECU 5 constitutes an injection amount ratio calculating means, and the processing of FIG. 19 constitutes a part of the blowback fuel amount calculating means.

  The present invention is not limited to the embodiment described above, and various modifications can be made. For example, in the embodiment described above, the residual ratios Cfw0, Cfw1, and Cfwb are calculated according to the intake valve operation phase CAIN. However, the intake valve operation phase CAIN has a fixed relationship with the intake valve closing timing CAIC. Therefore, it is substantially the same as calculating according to the intake valve closing timing CAIC.

  In the above-described embodiment, the example in which the engine is always operated in the mirror cycle is shown. However, when the intake valve closing timing CAIC is varied within a predetermined angle range including the compression stroke start timing of the cylinder, the engine is closed. When the valve timing CAIC is set after the compression stroke start timing of the cylinder, the fuel injection control considering the blow-back fuel amount Fwg is executed, and the valve closing timing CAIC is started of the compression stroke of the cylinder. When it is set before the timing, it is desirable to execute the fuel injection control with the blowback fuel amount Fwg set to “0” (residual rate Cfw set to “1”).

  Further, in the above-described embodiment, the present invention is applied to the fuel injection control of the engine in which the intake valve operation phase can be changed, but the present invention is set so that the closing timing of the intake valve is after the start of the compression stroke, It is also applicable to engine fuel injection control that is fixed to the operating phase.

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

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Intake passage 5 Electronic control unit (Required fuel amount calculation means, Blowback fuel amount calculation means, Fuel injection amount calculation means, Injection amount ratio calculation means)
6P port fuel injection valve (first fuel injection valve)
6C In-cylinder fuel injection valve (second fuel injection valve)

Claims (4)

In a fuel injection control device for an internal combustion engine, comprising: a first fuel injection valve that injects fuel into an intake passage of the internal combustion engine; and a second fuel injection valve that injects fuel into a combustion chamber of the engine.
A required fuel amount calculating means for calculating a required fuel amount according to the operating state of the engine;
Blowback fuel amount calculating means for calculating a blowback fuel amount that is a fuel amount blown back from the combustion chamber to the intake passage;
Fuel injection amount calculation means for calculating a fuel injection amount using the required fuel amount and the blowback fuel amount;
Drive control means for drivingly controlling at least one of the first fuel injection valve and the second fuel injection valve in accordance with the fuel injection amount;
The fuel injection control device for an internal combustion engine, wherein the blowback fuel amount calculation means calculates the blowback fuel amount in accordance with driving states of the first and second fuel injection valves. An injection amount ratio calculating means for calculating an injection amount ratio that is a ratio of fuel injection amounts by the first and second fuel injection valves;
The drive control means drives and controls at least one of the first fuel injection valve and the second fuel injection valve according to the injection amount ratio,
The blowback fuel amount calculating means includes a first blowback rate corresponding to fuel injection by only the first fuel injection valve, a second blowback rate corresponding to fuel injection by only the second fuel injection valve, The fuel injection control device for an internal combustion engine according to claim 1, wherein the blow-back fuel amount is calculated using an injection amount ratio.   When the injection amount ratio is changed, the blow-back fuel amount calculation means uses the blow-back rate corresponding to the injection amount ratio before the change at the time of the first fuel injection immediately after the change, and changes the 2 after the change. 3. The fuel injection control device for an internal combustion engine according to claim 2, wherein a blowback rate corresponding to the changed injection amount ratio is used from the time of execution of fuel injection after the first time. An intake valve closing timing changing means for changing the closing timing of the intake valve of the engine,
The fuel injection of the internal combustion engine according to any one of claims 1 to 3, wherein the blowback fuel amount calculation means calculates the blowback fuel amount according to a closing timing of the intake valve. Control device.

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