JP2010007628A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device capable of executing appropriate pilot injection timing collection irrespective of shift position of a transmission under a transient operation condition of an internal combustion engine, suppressing combustion noise, and inhibiting degradation of emission characteristics and fuel economy. <P>SOLUTION: Injection quantity collection value DQIP and injection timing collection value DCAIP are calculated according to engine operation conditions, acceleration collection coefficient KACC is calculated according to the change quantity DQ, and shift position collection coefficient KNGR is calculated according to shift position parameter NGR when change quantity DQ of fuel injection quantity QINJ exceeds judgment threshold DQTH (S15, S17-S19). Injection timing interval CAINT is calculated by adding collection quantity (DCAIP×KACC×XKNGR) to base injection timing interval CAINTB (S20). Pilot injection timing CAIP is calculated by adding injection timing interval CAINT to main injection timing CAIM (S21). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly to an apparatus that performs pilot fuel injection before main fuel injection.

  Patent Document 1 discloses a fuel that controls the fuel injection amount (pilot injection amount) in pilot injection and the execution timing (pilot injection timing) of pilot injection according to the change amount of the fuel injection amount calculated according to the engine operating state. An injection control device is shown. According to this device, the acceleration state of the engine is determined according to the fuel injection amount change amount. In the acceleration state, the pilot injection amount is increased, the pilot injection timing is advanced, and the combustion noise in the acceleration state is increased. Is suppressed.

JP 2007-332858 A

  In the above-described conventional apparatus, the same correction amount is applied even if the shift position of the transmission of the vehicle driven by the engine is different. Therefore, the correction amount is particularly large at the shift position on the high speed side (fourth speed or fifth speed). Excessive exhaust characteristics and fuel consumption may be deteriorated.

  The present invention has been made paying attention to this point, and corrects the pilot injection timing appropriately regardless of the shift position of the transmission in the transient operation state of the engine, thereby suppressing combustion noise and improving exhaust characteristics and fuel consumption. An object of the present invention is to provide a fuel injection control device for an internal combustion engine that can suppress deterioration.

  In order to achieve the above object, according to a first aspect of the present invention, fuel injection means for injecting fuel into a combustion chamber of an internal combustion engine, main injection by the fuel injection means, and pilot injection before the main injection are executed. In a fuel injection control device for an internal combustion engine comprising an injection control means, a transient operation state determination means for determining a transient operation state of the engine, and execution of the pilot injection when a transient operation state of the engine is detected And a correction means for correcting an interval (CAINT) between a timing (CAIP) and a main injection execution timing (CAIM) according to a shift position (NGR) of a transmission of a vehicle driven by the engine. And

  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, the correction means sets the correction amount of the interval (DCAIP × KACC × KNGR) as the shift position becomes higher. It is characterized by decreasing.

  According to the first aspect of the present invention, when the transient operation state of the engine is detected, the interval between the execution timing of the pilot injection and the execution timing of the main injection is the shift position of the transmission of the vehicle driven by the engine. Therefore, correction suitable for the shift position can be performed, combustion noise can be suppressed, and deterioration of exhaust characteristics and fuel consumption can be suppressed.

  According to the second aspect of the invention, the correction is performed so that the correction amount of the interval is reduced as the shift position becomes higher. Since the combustion noise tends to decrease as the shift position is on the higher speed side, it is possible to suppress deterioration of exhaust characteristics and fuel consumption by reducing the correction amount.

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 referred to as “engine”) 1 is a diesel engine that directly injects fuel into a combustion chamber, and a fuel injection valve 16 is provided in each cylinder. The fuel injection valve 16 is electrically connected to an electronic control unit (hereinafter referred to as “ECU”) 20, and the valve opening time and valve opening timing of the fuel injection valve 16 are controlled by the ECU 20.

  The engine 1 includes an intake pipe 2, an exhaust pipe 4, an exhaust gas recirculation passage 6, and a supercharger 8. The exhaust gas recirculation passage 6 is provided between the intake pipe 2 and the exhaust pipe 4, and the exhaust gas recirculation passage 6 has an exhaust gas recirculation control valve (hereinafter referred to as “EGR valve”) 7 for controlling the exhaust gas recirculation amount. Is provided. The valve opening degree of the EGR valve 7 is controlled by the ECU 20.

The supercharger 8 includes a turbine 10 that is driven by exhaust kinetic energy, and a compressor 9 that is rotationally driven by the turbine 10 and compresses intake air.
The turbine 10 includes a plurality of variable vanes (not shown), and is configured to change the turbine rotational speed (rotational speed) by changing the opening degree of the variable vanes. The vane opening degree of the turbine 10 is electromagnetically controlled by the ECU 20.

  The exhaust pipe 4 is provided with a NOx adsorption catalyst 11 for purifying NOx in the exhaust and a diesel particulate filter (hereinafter referred to as “DPF”) 12. The NOx adsorption catalyst 11 adsorbs NOx when it is in an oxidizing atmosphere where the oxygen concentration in the exhaust gas is relatively high, and desorbs and reduces the adsorbed NOx when it is in a reducing atmosphere where the concentration of reducing components in the exhaust gas is relatively high. discharge. When the exhaust gas passes through fine holes in the filter wall, the DPF 12 converts soot, which is particulate (particulate matter) mainly composed of carbon (C), into the filter wall surface and the filter wall. Collect by depositing in the pores inside.

  The intake pipe 2 is provided with an intake air flow rate sensor 21 that detects a flow rate of fresh air (hereinafter referred to as “intake air flow rate”) MAIR sucked into the engine 1. An oxygen concentration sensor 22 that detects the oxygen concentration O2C in the exhaust gas is provided on the exhaust pipe 4 upstream of the NOx adsorption catalyst 11. Further, a crank angle position sensor 24 for detecting the rotation angle of the crankshaft of the engine 1 and an accelerator sensor 25 for detecting an operation amount (hereinafter referred to as “accelerator pedal operation amount”) AP of a vehicle driven by the engine 1. Is provided. Detection signals from these sensors are supplied to the ECU 20. The rotational speed NE of the engine 1 is calculated from the output of the crank angle position sensor 24. Further, the required torque TRQ of the engine is calculated according to the accelerator pedal operation amount AP, and is set to increase as the accelerator pedal operation amount AP increases.

  The ECU 20 is connected to a shift position sensor 26 for detecting the shift position of the transmission of the vehicle driven by the engine 1, and a shift position parameter NGR indicating the shift position (for example, “ Is set to an integer value between “1” and “5”).

  The ECU 20 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, a central processing unit (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 control signal to the fuel injection valve 16 and the EGR valve 7.

  The ECU 20 calculates the fuel injection amount by the fuel injection valve 16 according to the operating state of the engine 1 (engine speed NE and required torque TRQ), and performs the actual fuel injection by the pilot injection preceding the main injection and the main injection. Execute. That is, the ECU 20 performs the fuel injection amount (hereinafter referred to as “main injection amount”) QIM in the main injection, the fuel injection amount (hereinafter referred to as “pilot injection amount”) QIP in the pilot injection, and the main injection by the processing shown in FIG. An execution timing (hereinafter referred to as “main injection timing”) CAIM and a pilot injection execution timing (hereinafter referred to as “pilot injection timing”) CAIP are calculated, and main injection is performed in accordance with the calculated fuel injection parameters QIM, QIP, CAIM, CAIP. And pilot injection. The pilot injection timing CAIP is calculated by adding an injection timing interval CAINT defined as an advance amount to the main injection timing CAIM.

FIG. 2 is a flowchart of processing for controlling combustion injection by the fuel injection valve 16. This process is executed by the CPU of the ECU 20 every predetermined time.
In step S11, the fuel injection amount QINJ is calculated according to the engine speed NE and the accelerator pedal operation amount AP. The fuel injection amount QINJ is set so as to be substantially proportional to the accelerator pedal operation amount AP.

In step S12, the change amount DQ of the fuel injection amount QINJ is calculated by the following equation (1). Here, k is a control time discretized in the execution cycle of this process.
DQ = QINJ (k) -QINJ (k-1) (1)
In step S13, a CAIM map (not shown) is searched according to the engine speed NE and the fuel injection amount QINJ to calculate the main injection timing CAIM. In step S14, the QIPB map shown in FIG. 3A and the CAINTB map shown in FIG. 3B are retrieved according to the engine speed NE and the fuel injection amount QINJ, and the basic pilot injection amount QIPB and the basic injection timing interval CAINTB are searched. Is calculated. The QIPB map is set so that the basic pilot injection amount QIPB increases as the engine speed NE increases, and the basic pilot injection amount QIPB increases as the fuel injection amount QINJ increases. The CAINTB map is set so that the basic injection timing interval CAINTB increases as the engine speed NE increases, and the basic injection timing interval CAINTB increases as the fuel injection amount QINJ increases.

  In step S15, it is determined whether or not the change amount DQ is larger than the determination threshold value DQTH. If the answer is negative (NO), the pilot injection amount QIP is set to the basic pilot injection amount QIPB and the injection timing interval is determined. CAINT is set to the basic injection timing interval CAINTB (step S16). Thereafter, the process proceeds to step S21.

  In step S15, when DQ> DQTH and the engine 1 is in a predetermined acceleration state, the basic pilot injection amount QIPB and the basic injection timing interval CAINTB are corrected by steps S17 to S20, and the pilot injection amount QIP and injection timing are corrected. The interval CAINT is calculated.

  In step S17, the DQIP map shown in FIG. 3C is searched according to the engine speed NE and the fuel injection amount QINJ, and the pilot injection amount correction value DQIP is calculated. The DCAIP map shown in FIG. A search is made to calculate a pilot injection timing correction value DCAIP. In the DQIP map, a correction value DQIP (for example, a value corresponding to about 30 to 40% of the basic pilot injection amount QIPB) is set corresponding to the operation region indicated by hatching in FIG. “0” is set in the operation region without hatching. In the DCAIP map, the correction value DCAIP is set corresponding to the operation region indicated by hatching in FIG. 3D, and “0” is set in the operation region not indicated by hatching. The correction value DCAIP is set to a negative value when correcting in the direction of decreasing the injection timing interval CAINT. The map value of the correction value DCAIP is set to an optimal value experimentally.

  In step S18, the KACC table shown in FIG. 3E is searched according to the change amount DQ, and the acceleration correction coefficient KACC is calculated. The KACC table is set so that the acceleration correction coefficient KACC increases as the change amount DQ increases in the range between the first value DQ1 and the second value DQ2 where the change amount DQ corresponds to the determination threshold value DQTH. ing. Further, the acceleration correction coefficient KACC is set to “0” when the change amount DQ is smaller than the first value DQ1, and the correction coefficient KACC is set to “1.0” when the change amount DQ is larger than the second value DQ2. Is set.

  In step S19, a KNGR table shown in FIG. 4 is searched according to the shift position parameter NGR, and a shift position correction coefficient KNGR is calculated. The KNGR table is set so that the shift position correction coefficient KNGR decreases as the shift position parameter NGR increases.

In step S20, the basic pilot injection amount QIPB, the pilot injection amount correction value DQIP, and the acceleration correction coefficient KACC are applied to the following equation (2) to calculate the pilot injection amount QIP, and the basic injection timing interval CAINTB, pilot injection timing Apply the correction value DCAIP, the acceleration correction coefficient KACC, and the shift position correction coefficient KNGR to the following equation (3) to calculate the injection timing interval CAINT: QIP = QIPB + DQIP × KACC (2)
CAINT = CAINTB + DCAIP × KACC × KNGR (3)

In step S21, the fuel injection amount QINJ and the pilot injection amount QIP are applied to the following equation (4) to calculate the main injection amount QIM, and the main injection timing CAIM and the injection timing interval CAINT are applied to the following equation (5). To calculate the pilot injection timing CAIP. .
QIM = QINJ-QIP (4)
CAIP = CAIM + CAINT (5)

  The ECU 20 supplies the fuel injection valve 16 with a drive signal corresponding to the calculated pilot injection amount QIP, pilot injection timing CAIP, main injection amount QIM, and main injection timing CAIM, and executes fuel injection.

  As shown in FIG. 4B, in the present embodiment, when the accelerator pedal is depressed, the fuel injection amount QINJ increases substantially in proportion to the accelerator pedal operation amount AP. Since the change amount DQ exceeds the first value DQ1 (determination threshold DQTH), steps S17 to S20 in FIG. 2 are executed, and the increase correction of the pilot injection amount QIP and the correction of the pilot injection timing CAIP are performed. More specifically, the acceleration correction coefficient KACC is set to a larger value as the change amount DQ increases, and control is performed so that the amount of increase in the pilot injection amount and the correction amount (absolute value) of the pilot injection timing increase. Thereby, the combustion noise at the time of acceleration can be reduced about 20%.

  Further, since the injection timing interval CAINT is corrected according to the shift position parameter NGR, correction suitable for the shift position of the transmission is performed, and combustion noise can be suppressed and deterioration of exhaust characteristics and fuel consumption can be suppressed. . The combustion noise tends to decrease as the shift position parameter NGR increases, that is, as the shift position is on the high speed side. Therefore, by reducing the correction amount (absolute value), the shift position on the high speed side (for example, the 4th speed) 5th gear) can suppress deterioration of exhaust characteristics and fuel consumption.

  In the present embodiment, the ECU 20 constitutes an injection control unit, a transient operation state determination unit, and a correction unit. Specifically, steps S11, S12, and S13 in FIG. 2 correspond to transient operation state determination means, and steps S19 and S20 correspond to correction 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, when the change amount DQ of the fuel injection amount QINJ exceeds the determination threshold value DQTH, both the increase correction of the pilot injection amount and the correction of the pilot injection timing are executed. Only the correction of the injection timing may be executed. Even in this case, combustion noise during acceleration can be reduced by about 10%.

  In the above-described embodiment, the correction value DQIP is a constant value within the hatched area in FIG. 3C. However, as the engine speed NE increases within this area, the fuel injection amount QINJ is also increased. As the value increases, the correction value DQIP may be set to a larger value.

  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 flowchart of the process which performs fuel-injection control. It is a figure which shows the map and table which are referred by 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.

Explanation of symbols

1 Internal combustion engine 16 Fuel injection valve (fuel injection means)
20 Electronic control unit (injection control means, transient operation state determination means, correction means)

Claims (2)

In a fuel injection control apparatus for an internal combustion engine, comprising: fuel injection means for injecting fuel into a combustion chamber of the internal combustion engine; main injection by the fuel injection means; and injection control means for executing pilot injection before the main injection ,
A transient operating state determining means for determining a transient operating state of the engine;
Correction means for correcting an interval between the execution timing of the pilot injection and the execution timing of the main injection according to a shift position of a transmission of a vehicle driven by the engine when a transient operation state of the engine is detected And a fuel injection control device for an internal combustion engine.   2. The fuel injection control device for an internal combustion engine according to claim 1, wherein the correction unit decreases the correction amount of the interval as the shift position becomes higher.

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