JP2004340043A - Fuel injection device comprising fuel pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection pump less affected by fluctuation of pressure of fuel supplied by the plunger type fuel pump. <P>SOLUTION: After a specified time after a time when a crank angle obtained based on crank pulse signals reaches a reference crank angle, the driving of the fuel injection pump is started, and when the crank angle reaches a specified fuel injection start crank angle after the reference crank angle, the driving of an injector is started. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel injection device for an internal combustion engine including a plunger type fuel pump.
[0002]
[Prior art]
As a fuel pump that sucks fuel from a fuel tank of an internal combustion engine and pumps the fuel to an injector or a carburetor, there is, for example, a plunger type fuel pump (for example, see Japanese Patent Application Laid-Open No. 8-114179).
The plunger type fuel pump has a cylindrical plunger having a magnetic piston, a spring for urging the piston of the plunger in the fuel discharge direction, and a coil for moving the piston in the fuel suction direction when excited. An oscillation circuit for intermittently exciting the coil. When the power supply voltage is supplied to the oscillation circuit, the excitation of the coil is intermittently performed by the oscillation circuit, and the movement of the plunger piston in the fuel suction direction and the movement of the plunger piston in the fuel discharge direction due to the bias of the spring are performed. The fuel is discharged alternately by the reciprocating motion acting as a pump.
[0003]
[Problems to be solved by the invention]
In a fuel injection device for an internal combustion engine using such a plunger-type fuel pump, when an ignition switch is turned on, the fuel pump is periodically driven at a predetermined frequency. Since the pressure of the fuel fed to the injector fluctuates due to the reciprocating motion of the plunger piston, the fuel injection amount fluctuates due to the pressure fluctuation even when the injector opening time is kept constant, and the combustion state becomes unstable. There was a problem.
[0004]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a fuel injection device that is less affected by a change in fuel supply pressure by a plunger fuel pump.
[0005]
[Means for Solving the Problems]
A fuel injection device including a fuel pump according to the present invention includes an injector that injects fuel into an internal combustion engine, a plunger-type fuel pump that supplies the fuel to the injector, and an injector drive that injects the injector according to a fuel injection command. Means for driving the fuel pump in accordance with a pump driving command, and a control means for supplying the fuel driving command and the pump driving command to the injector driving means and the pump driving means. The control means, when detecting that the crank angle position for each engine cycle of the internal combustion engine has reached a predetermined reference timing position, a detection means for issuing a timekeeping command, and a predetermined delay time according to the timekeeping command When a timer is started and the timer for the predetermined time is finished, a pump for issuing the pump drive command is issued. A drive command means, the crank angular position and wherein the fuel injection instruction means for issuing the fuel injection command and that reaches the fuel injection timing position detecting every engine cycle of the internal combustion engine, in that it consists of.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows an engine control system of a vehicle-mounted four-stroke internal combustion engine including a fuel injection device using a plunger-type fuel pump according to the present invention.
A throttle valve 2 is provided in an intake pipe 1 of the internal combustion engine, and an amount of intake air corresponding to an opening degree of the throttle valve 2 is supplied to an intake port of an engine body 3 through the intake pipe 1. I have. An injector 4 for fuel injection is provided in an intake pipe 1 near an intake port of the engine body 3. A fuel supply pipe 7 from a fuel tank 6 is connected to the injector 4. A plunger type fuel pump 8 is provided in the middle of the fuel supply pipe 7. The fuel pump 8 has a configuration disclosed in, for example, Japanese Patent Application Laid-Open No. H08-114179, and operates in response to a drive command from an ECU (electronic control unit) 10 to be described later. Is sucked in through the fuel supply pipe 7 on the suction side, and is fed to the injector 4 via the fuel supply pipe 7 on the discharge side. The injector 4 injects fuel into the intake pipe when driven by the ECU 10.
[0007]
An ignition plug 11 is fixed to the engine body 3, and the ignition plug 11 is connected to an ignition device 12. The ignition device 12 applies a high voltage to the ignition plug 11 in response to an ignition command from the ECU 10 to cause a spark discharge in the cylinder.
As shown in FIG. 2, the ECU 10 includes an input interface circuit 20, a rotation speed counter 21, a CPU (Central Processing Unit) 22, a memory 23, an injector driving unit 24, and a fuel pump driving unit 25. ing. The injector driving unit 24 includes a fuel injection command unit, and is connected to the injector 4. Similarly, the fuel pump driving unit 25 includes a pump driving command unit, and is connected to the fuel pump 8. The fuel injection command means of the injector drive means 24 generates an injector drive signal Si corresponding to the injector drive time Tout in response to a command from the CPU 22, whereby fuel is injected from the injector 4 for a time width of Tout. Similarly, the pump drive command means of the fuel pump drive means 25 generates a fuel pump drive signal Sp corresponding to the fuel pump drive time Tpump in response to a command from the CPU 22, so that the fuel pump 8 operates for the time width of Tpump. Driven.
[0008]
The input interface circuit 20 includes a water temperature sensor 26 for detecting an engine cooling water temperature, an intake pressure sensor 27 for detecting a negative pressure in the intake pipe 1, and an oxygen concentration sensor provided in the exhaust pipe 13 for detecting an oxygen concentration in exhaust gas. 28 and other engine parameter detecting means are connected.
A crank angle sensor 29 is connected to the rotation speed counter 21. The crank angle sensor 29 generates a crank pulse every time the crankshaft 3a of the engine body 3 rotates by a predetermined angle (for example, 15 degrees). These crank pulses include, for example, a reference position pulse for rotation of the crank, a predetermined reference timing pulse Pst corresponding to a reference timing (crank angle θst) for driving the fuel pump, and an injection start timing (crank angle θsp) for driving the injector. A corresponding fuel injection start timing pulse Psp is included. Further, a cam angle sensor 30 is provided in the vicinity of the rotating body 3b synchronized with the rotation of the crank, and for example, the piston of a representative cylinder (a reference cylinder in the case of a multi-cylinder, itself in the case of a single cylinder). A TDC signal indicating the compression top dead center is issued, and a reference position signal is issued each time the crankshaft 3a rotates 720 degrees, and these are supplied to the CPU 22.
[0009]
The rotation number counter 21 counts clock pulses output from a clock generator (not shown) reset by a crank angle reference position pulse output from the crank angle sensor 29, and counts the number of generated clock pulses. Generates a signal indicating the engine speed Ne.
The CPU 22 is supplied with detection information of the cooling water temperature, the intake pipe negative pressure, and the oxygen concentration by the sensors 26 to 28 from the input interface circuit 20, and is supplied with the information of the engine speed from the speed counter 21 and the crank angle sensor 29. Supplies a TDC signal and a reference position signal. The memory 23 stores a program for controlling the operation of the CPU 22 and various data processed by the program.
[0010]
FIG. 3 is a flowchart showing a fuel injection timing control routine executed by the CPU 22 in synchronization with a predetermined clock. In the fuel injection timing control routine, when the reference position of the crank is detected by the crank pulse from the crank angle sensor 29, first, the engine speed Ne is read based on the count value of the speed counter 21 (step S1). Next, a fuel injection time Tout and a fuel pump drive start delay time Tp for each engine cycle are set according to the engine speed Ne (step S2). For example, the fuel injection time Tout is set using the following formula.
[0011]
Tout = Ti × K ₀₂
Here, Ti is a basic fuel injection time representing an air-fuel ratio reference control value determined by a data map search from a data table recorded in advance in the memory 23 in accordance with the engine speed and the intake pipe negative pressure. , _K02 are air-fuel ratio correction coefficients calculated in the air-fuel ratio feedback control based on the output signal of the oxygen concentration sensor 28. Note that the fuel injection time Tout can be determined by adding various corrections such as acceleration correction and deceleration correction. Further, the fuel pump drive start delay time Tp is set by searching a data map from a data table recorded in advance in the memory 23 based on the engine speed Ne at the time of fuel injection in the immediately preceding engine cycle.
[0012]
Next, the fuel pump drive time Tpump is set by searching a data map from the memory 23 according to the fuel injection time Tout set in step S2 (step S3). Subsequently, the current crank angle value θ is detected based on the crank pulse from the crank angle sensor 29 (step S4), and it is determined whether or not the current crank angle value θ is the predetermined reference crank angle θst (step S5). . When it is determined that the current value of the crank angle is θst after the arrival of the crank pulse Pst, the timer is reset (step S6), and time measurement is started (step S7). Subsequently, it is determined whether or not the elapsed time of the timer has elapsed by the fuel pump drive start delay time Tp set in step S2 (step S8). If the timer elapsed time has not reached Tp, the process returns to step S7 to continue the time measurement. If the timer elapsed time has reached Tp, a pump drive command is output from the pump drive command means of the fuel pump drive means 25 (step S9), and the routine ends.
[0013]
When it is determined in step S5 that the current crank angle value θ is not the predetermined reference crank angle θst, it is determined whether or not the current crank angle value θ is the fuel injection crank angle θsp (step S10). When the crank pulse Psp arrives and it is determined that the current value θ of the crank angle is θsp, a fuel injection command is output from the fuel injection command means of the injector drive circuit 24 (step S11), and the routine ends. If it is determined in step S10 that the current value θ of the crank angle is not the fuel injection crank angle θsp, the routine ends.
[0014]
FIG. 4 shows a temporal relationship among the crank angle sensor signal, the fuel pump drive timing, the fuel pressure, and the fuel injection timing by executing the routine shown in FIG. At time t1, a predetermined reference timing pulse Pst of the crank angle arrives. Therefore, time t1 is a predetermined reference timing corresponding to the crank angle θst. Time t2 is the drive start timing of the fuel pump 8, which is later than time t1 by the fuel pump drive start delay time Tp set in the fuel injection timing control routine. Therefore, the fuel pump 8 is driven at, for example, a predetermined frequency from time t2 to time t5 after the time Tpump. Time t3 is the injection start timing of the injector 4, which is the time when the crank pulse Psp is generated after the time when the predetermined reference timing pulse Pst is generated, and corresponds to the crank angle θsp. Therefore, the injector 4 is driven to open from time t3 to time t4 after the time Tout.
[0015]
By executing the fuel injection timing control routine shown in FIG. 3, the fuel pump 8 starts driving at a crank angle θp delayed from the predetermined reference timing angle θst of the crank by a fuel pump driving start delay time Tp. The time (t3−t2) that elapses between the crank angles θp and θsp corresponds to the fuel pressure feeding lug, and Tp is set so that the fuel pressure is sufficiently increased within this time.
[0016]
As described above, by driving the plunger type fuel pump in advance by an appropriate time before the fuel injection start time of the injector, fuel injection with less influence of the fuel pressure fluctuation can be performed.
Further, since the fuel pump is driven for the optimum fuel pump driving time Tpump synchronized with the injection of the injector, it is possible to reduce the power consumption for driving the pump.
[0017]
In the above-described embodiment, the injector 4 is provided in the intake pipe 1 and injects the fuel into the intake pipe 1. However, the injector 4 may directly inject the fuel into the cylinder of the engine body 3. Further, in an internal combustion engine having a plurality of cylinders, there are a system in which fuel is injected by an injector provided for each cylinder and a system in which fuel is injected into all cylinders by a single injector. The present invention can be applied.
[0018]
【The invention's effect】
As described above, according to the fuel injection device including the plunger type fuel pump of the present invention, stable combustion in the engine cylinder can be performed even if the pressure of the fuel pressure-fed to the injector fluctuates.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing an engine control system to which the present invention is applied.
FIG. 2 is a block diagram showing a configuration of an ECU in the system shown in FIG.
FIG. 3 is a flowchart showing a fuel injection timing control routine.
FIG. 4 is a diagram showing a temporal relationship among a crank angle sensor signal, a fuel pump driving timing, a fuel pressure, and a fuel injection timing.
[Explanation of symbols]
1 intake pipe 2 throttle valve 3 engine body 4 injector 6 fuel tank 7 fuel supply pipe 8 fuel pump 10 ECU

Claims (2)

An injector for injecting fuel into the internal combustion engine, a plunger type fuel pump for supplying the fuel to the injector, an injector driving means for injecting and driving the injector in response to a fuel injection command, and the fuel pump in response to a pump drive command A fuel injection device including a pump driving unit that drives the fuel injection command and the pump driving command to the injector driving unit and the pump driving unit.
The control means,
Detecting means for issuing a timing command when detecting that the crank angle position of each engine cycle of the internal combustion engine has reached a predetermined reference timing position,
Pump driving command means for issuing the pump driving command when starting timing of the predetermined delay time in response to the timing command and ending the timing of the predetermined delay time,
Fuel injection command means for issuing the fuel injection command when detecting that the crank angle position has reached a fuel injection start timing position for each engine cycle of the internal combustion engine;
A fuel injection device comprising: The predetermined delay time is set based on an engine speed of the internal combustion engine at the time of issuing the fuel injection command in an engine cycle immediately before one engine cycle to which the timing command is issued. The fuel injection device according to claim 1, wherein

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