JP3344134B2 - Fuel injection device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device for an internal combustion engine, and more particularly, to a fuel pump for storing fuel injected into all cylinders of the engine required for one combustion cycle of the internal combustion engine (hereinafter simply referred to as engine). The present invention relates to a fuel injection device for an internal combustion engine that supplies a single pressure feed to a chamber.

[0002]

2. Description of the Related Art High-pressure fuel discharged from a fuel pump is supplied to a fuel storage chamber via a fuel supply pipe, and high-pressure fuel in the fuel storage chamber is supplied to a fuel injection valve via an injection pipe. An engine is known which detects the fuel pressure of the fuel pump and controls the discharge amount of a fuel pump so that the fuel pressure becomes a target fuel pressure which changes according to the operating state of the engine. Japanese Patent Laying-Open No. 4-31670 discloses such a fuel injection device.

[0003]

SUMMARY OF THE INVENTION
Each time fuel is injected from a fuel injection valve, it is necessary to pump the fuel required for injection into the fuel accumulator by a fuel pump. Therefore, the pumping of the fuel pump, that is, the reciprocating motion of the piston in the cylinder of the fuel pump is frequently performed, and the friction generated between the cylinder and the piston deteriorates the durability of the fuel pump.

Therefore, the present invention solves the above-mentioned problems, that is, the number of piston reciprocating motions in the cylinder of the fuel pump is reduced, the friction caused by the piston reciprocating motion is reduced, the life of the fuel pump is extended, and the piston reciprocating motion is reduced. It is intended to reduce the generated operating noise.

[0005]

FIG. 1 is a basic block diagram of the present invention. A fuel injection device for an internal combustion engine according to the present invention that achieves the above object supplies high-pressure fuel discharged from a fuel pump to a fuel accumulator through a fuel supply pipe, and supplies high-pressure fuel in the fuel accumulator through the injection pipe. The fuel pressure is supplied to a plurality of fuel injection valves, the fuel pressure in the fuel storage chamber is detected, and the discharge amount of the fuel pump is controlled so that the fuel pressure becomes a target fuel pressure that changes according to the operating state of the engine. A fuel pressure detecting means for detecting the fuel pressure that changes each time the high-pressure fuel is injected from each of the fuel injection valves into a corresponding cylinder of the engine; and A discharge fuel pressure calculating means for calculating a discharge fuel pressure by the fuel pump based on the fuel pressure detected by the fuel pressure detecting means each time the fuel injection to all the cylinders is completed; and A pumping quantity control means for controlling the fuel pump to pump the fuel amount, characterized by comprising a.

[0006]

According to the fuel injection device for an internal combustion engine of the present invention, the amount of fuel injected in one combustion cycle of the engine from the fuel injection valves corresponding to a plurality of cylinders of the engine is accumulated by one reciprocating movement of the piston by the fuel pump. Feeding into the chamber reduces the number of piston reciprocations, thereby reducing the friction created.

[0007]

FIG. 1 is a basic block diagram of the present invention. The fuel injection system for an internal combustion engine according to the present invention to achieve the object, the piston 1 combustion cycle
Supplying high-pressure fuel discharged from one reciprocating fuel pump to a plurality of fuel accumulators via a fuel supply tube, and supplying high-pressure fuel in the fuel accumulator to a plurality of fuel injection valves via an injection tube; the fuel injection system for an internal combustion engine which is adapted fuel pressure by detecting the fuel pressure in the fuel accumulation chamber to control the discharge amount of the fuel pump so that the target fuel pressure that varies in accordance with the operating condition of the engine And fuel pressure detecting means for detecting the fuel pressure that changes each time the high-pressure fuel is injected from each of the fuel injection valves to each of the cylinders of the engine, and completes the injection to all the cylinders of the engine. A discharge fuel pressure calculation means for calculating a discharge fuel pressure by the fuel pump based on the fuel pressure detected by the fuel pressure detection means every time; and Characterized in that and a pumping quantity control means for controlling the charge pump.

When the switching control valve 17 blocks the communication between the atmosphere passage 18 and the pressure control chamber 13, the fuel pressure accumulating chamber 22
The high-pressure fuel inside is supplied into the fuel passage 20 on the one hand,
On the other hand, the fuel is supplied into the back pressure chamber 12 via the fuel supply port 19, the inside of the switching control valve 17, the pressure control chamber 13 and the check valve 14. At this time, the needle 11 closes the nozzle port 10 by the fuel pressure acting on the top surface of the needle 11. Next, the solenoid 16 is energized to switch the switching control valve 17.
Rises, the communication between the fuel supply port 19 and the pressure control chamber 13 is cut off, and the pressure control chamber 13 is connected to the atmosphere passage 18. At this time, the fuel in the back pressure chamber 12 gradually flows out into the atmosphere passage 18 via the throttle 15 and the pressure control chamber 13. As a result, since the fuel pressure in the back pressure chamber 12 gradually decreases, the needle 11 gradually rises and fuel injection is started.
When the solenoid 16 is deenergized, the communication between the pressure control chamber 13 and the atmosphere passage 18 is cut off by the switching control valve 17, and fuel is supplied into the back pressure chamber 12 via the check valve 14, and fuel injection is performed. Stopped.

On the other hand, the fuel pump 2 comprises a plunger 30 and
A pressure chamber 31 defined by the top of the plunger 30. A cam 32 driven by an engine is provided below the plunger 30, and a roller 33 that rolls on the cam 32 is rotatably attached to a lower end of the plunger 30. Therefore, it can be seen that when the cam 32 rotates, the plunger 30 is moved up and down accordingly. Pressurizing chamber 31
A fuel supply port 34 is opened below the fuel cell, and an upper part of the pressurizing chamber 31 is connected to the fuel pressure accumulating chamber 22 via a check valve 36 and a fuel supply pipe 37. A control valve 39 driven by a solenoid 38 is provided at the top of the pressurizing chamber 31, and the pressurizing chamber 31 is connected to the fuel release passage 40 via the control valve 39.

[0010] The cam 32 is 1/1 of the crankshaft of the engine.
2 and the plunger 30 is rotated at a crank angle 72
One reciprocation is performed every 0 ° CA. When the plunger 30 is at the lower position, the fuel supply port 34 opens into the pressurizing chamber 31, and at this time, fuel is supplied from the fuel supply port 34 into the pressurizing chamber 31. Next, the plunger 30 is raised. At this time, since the control valve 39 is opened, the fuel in the pressurizing chamber 31 is discharged into the fuel release passage 40 without being pressurized. Next, the solenoid 38 is energized and the control valve 3
When the valve 9 is closed, the fuel in the pressurizing chamber 31 is pressurized as the plunger 30 moves upward, and the pressurized fuel is supplied through the check valve 36 and the fuel supply pipe 37 to the fuel accumulating chamber 22.
Supplied within.

As shown in FIG. 2, a pressure sensor 3 for detecting the fuel pressure in the fuel accumulator 22 is attached to the fuel accumulator 22, and the pressure sensor 3 is used to detect the engine speed. A sensor 4 and a load sensor 5 for detecting an amount of depression of an accelerator pedal are connected to a control device 6. The solenoid 16 of the fuel injection valve 1 is controlled based on an output signal of the control device 6 so that the fuel injection time needle 11 determined by a crank angle interruption process before fuel injection described later opens the nozzle port 10. The fuel injection amount from the injection valve 1 is controlled based on the fuel pressure in the fuel accumulator 22. The target fuel pressure of the fuel accumulator 22 is calculated in advance as a function of the engine load and the engine speed and stored in the ROM. The fuel pressure in the fuel accumulator 22 detected by the pressure sensor 3 is equal to the target fuel pressure. So that the fuel pump 2
The solenoid 38 is controlled based on an output signal of the control device 6 described later. Generally speaking, the target fuel pressure of the fuel accumulator 22 increases as the engine load increases. The control device 6 is composed of a digital computer, and although not shown, a CPU and a RO connected to each other by a bidirectional bus.
M, RAM, input circuit and output circuit. The processing of the flowchart described later is executed.

FIG. 3 is a time chart showing changes in fuel pressure in the fuel storage chamber of the embodiment according to the present invention. This figure shows an example in which the fuel injection amount of all cylinders is supplied to the fuel pressure accumulating chamber by one pumping of the fuel pump in the four-cylinder engine, and the fuel supplied to the fuel accumulating chamber 22 by the pressure pumping of the fuel pump 2 is shown. Accumulator chamber 22 is injected into four cylinders (not shown) from four fuel injection valves 1 connected to fuel accumulator chamber 22.
3 shows a change in fuel pressure in the inside. The upper stage is the crank angle CA of the engine, the upper stage is the timing at which the four fuel injection valves 1 are opened, the middle stage is the timing at which fuel is pumped into the fuel accumulator 22 by the fuel pump 2, and the lower stage is the fuel pressure in the fuel accumulator 22. , Respectively, showing the time change. Fuel is supplied into the fuel accumulator 22 for a certain period immediately before the position of the piston in the fuel pump 2 reaches the top dead center (TDC) of the piston. During that time, the fuel pressure rises linearly and becomes constant after the completion of fuel supply. In the present embodiment, one revolution of the fuel pump 2 corresponds to one combustion cycle of the engine, that is, a crank angle of the engine of 720 ° C.
A. Also, the top dead center of the piston in the fuel pump 2 and the top dead center of the first in-cylinder piston of the engine match. After the fuel is pumped by the fuel pump 2, when the fuel is injected from the # 1 fuel injection valve 1 to the first cylinder of the engine, the fuel pressure decreases as shown in the figure. Next, as the fuel is sequentially injected from the # 3, # 4, and # 2 fuel injection valves 1 into the corresponding third, fourth, and second cylinders, the fuel pressure gradually decreases as illustrated. After the fuel injection from the four fuel injection valves 1 to the four cylinders of the corresponding engine is completed, as described above, the fuel storage chamber 2 of the fuel pump 2 for the fuel required for the next combustion cycle
2 and the fuel injection from the four fuel injection valves 1 to the four cylinders are repeated.

In this embodiment, the pumping by the fuel pump 2 is performed immediately before the fuel injection from the # 1 fuel injection valve 1 to the first cylinder. However, the pumping timing is # 2, # 3 or # 4.
May be immediately before fuel injection from any one of the fuel injection valves 1 to the corresponding cylinder. Next, how to calculate and supply the amount of fuel required to inject fuel from the four fuel injection valves 1 in one pressure feed by the fuel pump 2 will be described with reference to a flowchart below.

FIG. 4 is a flowchart of a crank angle interrupting process immediately before fuel pressure feeding. This process is performed at 720 ° C of the engine.
Executed for each A. In the flowcharts after this figure, the numbers following S indicate step numbers. In step S1, the engine speed NE obtained experimentally in advance and stored in the ROM is set.
And accelerator pedal angle PA (pedal depression amount)
Is obtained from NE and PA at that time on the basis of the two-dimensional map of the fuel injection amount Q with respect to. The fuel injection amount Q is the amount of fuel injected from each fuel injection valve into each cylinder of the corresponding engine in each combustion cycle of the engine. Four times the fuel amount is the amount of fuel required for one combustion cycle of the engine. is there. In step S2, the average value p of the fuel pressure before and after each fuel injection calculated in a crank angle interrupting process after fuel injection described later.
calculating an average fuel pressure pf of the fuel accumulation chamber in the previous combustion cycle from the following equation using the data of f _{x (x} = 1~4). pf = (pf ₁ + pf ₂ + pf ₃ + pf ₄ ) / 4

In step S3, R is obtained in advance by calculation.
BDUTY is obtained from a one-dimensional map of the solenoid valve base duty ratio BDUTY with respect to the fuel injection amount Q stored in the OM. This BDUTY determines the opening / closing timing for opening and closing the solenoid valve of the fuel pump 2, that is, the control valve 39, in order to pump the fuel amount required for one combustion cycle, which is four times the fuel injection amount Q, from the fuel pump to the fuel accumulator. Duty ratio. In step S4, a target fuel pressure pfT corresponding to the operating state of the engine is determined from a two-dimensional map of the engine speed NE and the target fuel pressure pfT with respect to the accelerator pedal angle PA previously stored in the ROM, and this target fuel pressure pfT and step S4 are determined.
2. Compare the average fuel pressure pf obtained in 2. If the comparison result is pf = pfT, the process proceeds to step S7 without updating the KDUTY, and if pf> pfT, 1 is subtracted from the KDUTY to update the KDUTY (step S5), and pf <pfT
In this case, 1 is added to KDUTY to update KDUTY (step S6), and the process proceeds to step S7. Here KDUTY
Is a correction value of the base duty ratio for calculating the actual duty ratio RDUTY as can be understood from the following equation. The control valve 39 of the fuel pump 2 is controlled to open and close at this actual duty ratio. RDUTY = BDUTY + KDUTY

In step S7, the fuel pressure pf _4b in the fuel accumulator after fuel injection for one combustion cycle of the engine is read.
In step S8, a predicted pressure increase fuel pressure pf _1c immediately after the fuel necessary for the next combustion cycle of the engine is pumped into the fuel storage chamber by the fuel pump is calculated from the following equation. In _{pf 1c = pf 4b + (Q} P × pf) / (Vd × cf) where, Q _P is the fuel pumping quantity, pf is the average fuel pressure, Vd is the fuel accumulation chamber volume, cf denotes a fuel compression ratio, respectively.

In step S9, the pressure obtained by calculation
Fuel pressure pf immediately after sending_1cAnd maximum fuel pressure pf _maxAnd p
f_1c≧ pf_maxIn step S10, pf_1c<P
f_{ma x}If this is the case, this interrupt processing is terminated. Step S1
At 0, the fuel pressure pf immediately after pumping_1cIs the maximum fuel pressure pf_maxGar in
And pf_1c= Pf_maxAnd its fuel pressure
pf_maxOf the fuel pump 2 for pumping the fuel equivalent to the pressure
The duty ratio of the valve 39 is calculated, and the process ends. Therefore,
Add KDUTY updated in step S4 to BDUTY and find
RDUTY or the solenoid valve 39 determined in step S10.
The fuel is pumped to the fuel accumulator based on the duty ratio.
Thus, the opening and closing of the solenoid valve 39 of the fuel pump is controlled.

FIG. 5 is a flowchart of the crank angle interrupt processing before fuel injection. This flowchart calculates the fuel injection time of each fuel injection valve according to the fuel pressure in the fuel accumulating chamber that drops each time fuel is injected from each fuel injection valve, and opens each fuel injection valve during that time to perform each fuel injection. This is for controlling the fuel injection amount of the valve to be constant. This processing is performed by the agency's 180
° Executed for each CA. In step S11, the fuel pressure pf _xa in the fuel storage chamber before fuel injection in each cylinder is read. In step S12, the fuel pressure drop due to the fuel injection is predicted, and the average pressure pf _for TAU in the fuel storage chamber during the fuel injection is estimated.
Is calculated from the following equation. _{pf for TAU = (2 × pf} x - (Q × pf) / (Vd × cf)) / 2 where, pf _x is pf ₁ ~pf _4, Q is the injection fuel quantity, p
f indicates the average fuel pressure, Vd indicates the fuel pressure accumulation chamber volume, and cf indicates the fuel compression ratio.

In step S13, the injection rate K _for the pf _for TAU, which is previously calculated and stored in the ROM, is 2
The injection rate K is obtained from the dimensional map. Since the injection ratio K there is a difference between the actual fuel pressure and the target fuel pressure is for correcting the difference, since the fuel pressure the greater pf _for TAU is high to shorten the fuel injection time TAU, the pf _for TAU Since the smaller the value, the lower the fuel pressure, the coefficient is a correction for increasing the fuel injection time TAU. In step S14, the fuel injection time TAU is calculated from Q obtained in step S1 and K obtained in step S13. From step S15 to step S19, control is performed such that each of the fuel injection valves 1 is injected in the order of # 1, # 3, # 4, and # 2. Each fuel injection valve 1 is opened for a fuel injection time TAU determined in step S14 from a predetermined crank angle at which fuel injection is started.

As described above, the fuel injection time of the fuel injected from each fuel injection valve is calculated based on the fuel pressure in the fuel storage chamber, so that the amount of fuel injected from each fuel injection valve during one combustion cycle of the engine is calculated. Can be made uniform despite changes in fuel pressure.

FIG. 6 is a flowchart of a crank angle interrupting process after fuel injection. This flowchart is based on the aforementioned p
f _x is obtained. This process is performed at 180 ° C
Executed for each A. In step S21, the fuel pressure pf _xb in the fuel accumulator after fuel injection in each cylinder is read. At step S22 calculates the average pressure pf _x of the fuel injected from the following equation. pf _x = (pf _xa + pf _xb ) / 2 As can be seen from the above equation, the average fuel pressure pf _x (p
f ₁ ~pf ₄₎ before the fuel injection fuel pressure pf _xa (pf _1a ~pf
_4a ) and the fuel pressure after fuel injection pf _xb (pf _{1b to} pf _4b ).

[0022]

As described above, according to the fuel injection device for an internal combustion engine of the present invention, the number of reciprocating motions of the piston of the fuel pump is reduced, so that the friction generated by the reciprocating motion of the piston is reduced and the life of the fuel pump is reduced. Can be extended. Further, the number of times of opening and closing of the solenoid valve for adjusting the amount of fuel supplied by one pressure feed by the fuel pump can be reduced, and the life of the solenoid valve can be extended. Further, it is possible to reduce the operation noise generated when the piston reciprocates.

[Brief description of the drawings]

FIG. 1 is a basic block configuration diagram of the present invention.

FIG. 2 is a schematic configuration diagram of a fuel injection valve and a fuel pump.

FIG. 3 is a time chart showing a change in fuel pressure in a fuel pressure accumulating chamber according to the embodiment.

FIG. 4 is a flowchart of a crank angle interrupting process immediately before fuel pressure feeding.

FIG. 5 is a flowchart of a crank angle interruption process before fuel injection.

FIG. 6 is a flowchart of a crank angle interrupting process after fuel injection.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Fuel injection valve 2 ... Fuel pump 3 ... Fuel injection valve 4 ... Rotation speed sensor 5 ... Load sensor 6 ... Control device 17 ... Switching valve (fuel injection valve) 21 ... Injection pipe 22 ... Fuel accumulation chamber 37 ... Fuel supply pipe 39 ... Control valve (solenoid valve of fuel pump)

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Soichi Matsushita 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (58) Field surveyed (Int. Cl. ⁷ , DB name) F02D 41/38 F02M 37/08 F02M 47/00 F02M 55/02 350

Claims (1)

(57) [Claims] 1. One reciprocation of a piston in one combustion cycle
Supplying high-pressure fuel discharged from a fuel pump to a fuel accumulator through a fuel supply tube; supplying high-pressure fuel in the fuel accumulator to a plurality of fuel injection valves via an injection tube; the fuel injection system of an internal combustion engine as fuel pressure by detecting the fuel pressure is controlled the discharge amount of the fuel pump so that the target fuel pressure that varies in accordance with the operating state of the engine, the fuel injection Fuel pressure detecting means for detecting the fuel pressure that changes each time the high-pressure fuel is injected from each of the valves to each of the cylinders of the engine; and detecting the fuel pressure each time the injection to all the cylinders of the engine is completed. Means for calculating a fuel pressure discharged by the fuel pump based on the fuel pressure detected by the means; and controlling the fuel pump so as to pressure-feed the amount of fuel having the discharged fuel pressure to the fuel storage chamber. A fuel injection device for an internal combustion engine, comprising: