JP4144375B2 - Accumulated fuel injection system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pressure accumulation fuel injection device that injects high pressure fuel accumulated in a common rail to an engine via an injector, and in particular, a pressure accumulation type that is excellent in step-down performance for reducing the fuel pressure in the common rail from high pressure to low pressure. The present invention relates to a fuel injection device.
[0002]
[Prior art]
Conventionally, as a fuel injection system for a diesel engine, a common rail that accumulates high-pressure fuel corresponding to the fuel injection pressure, an injector that injects high-pressure fuel in the common rail into the cylinder of the engine, and a suction chamber that is sucked into the pressurized chamber Metering type fuel supply pump (supply pump) that pressurizes and boosts the fuel to be supplied to the common rail, a fuel pressure sensor that detects the fuel pressure in the common rail, and the actual fuel detected by the fuel pressure sensor Fuel pressure in the common rail by changing the amount of fuel drawn into the pressurizing chamber based on the pressure difference between the pressure (common rail pressure) and the target fuel pressure (target common rail pressure) set according to the operating state of the engine An accumulator fuel injection system having an engine control unit (ECU) for controlling Are (e.g., see Patent Document 1).
[0003]
In this accumulator fuel injection system, a suction metering valve (SCV) with excellent boosting performance for boosting the common rail pressure from low pressure to high pressure is built into the supply pump. For example, during acceleration, the fuel tank, the pressurizing chamber, By adjusting the degree of opening of the fuel supply path that communicates with the fuel pump, the pump discharge amount (fuel discharge amount) discharged from the discharge port of the supply pump to the common rail is changed to quickly increase the common rail pressure. . In addition, a pressure reducing valve with excellent pressure reduction performance that reduces the common rail pressure from high pressure to low pressure is installed at the end of the common rail. For example, during deceleration, the fuel discharge passage that connects the common rail and the fuel tank is opened. It is configured to quickly reduce the common rail pressure.
[0004]
In addition, an injector used in an accumulator fuel injection system includes a nozzle having a nozzle needle that opens and closes an injection hole for injecting fuel into each cylinder of the engine, and a pressure formed in a nozzle holder that holds the nozzle. By controlling the fuel pressure in the control chamber, it is composed of an electromagnetic valve that drives the nozzle needle in the valve opening direction and a spring that biases the nozzle needle in the valve closing direction. Then, the high pressure fuel in the common rail overflows to the low pressure side of the fuel system by driving the solenoid valve that controls the opening and closing of the nozzle needle of the injector with a time width shorter than the time required for the nozzle needle to open. An accumulator fuel injection system is also proposed in which the common rail pressure is lowered by flowing it (see, for example, Patent Document 2). In such an injector, since there is a predetermined delay time (so-called invalid injection time) from when the solenoid valve is opened to when the nozzle needle is actually opened, the solenoid valve is operated for a time shorter than this delay time. By performing idle driving, which opens the valve, the high pressure fuel supplied into the pressure control chamber of the injector is overflowed to the low pressure side to reduce the common rail pressure.
[0005]
[Patent Document 1]
JP 2000-282929 A (page 1-13, FIG. 1 to FIG. 15)
[Patent Document 2]
JP 2000-282998 A (page 1-18, FIGS. 1-17)
[0006]
[Problems to be solved by the invention]
However, in an accumulator fuel injection system having a supply pump with a built-in intake metering valve and a common rail with a pressure reducing valve, the common rail pressure is reduced by the basic injection amount (Q) and the engine speed (NE) when decelerating. ), The fuel discharge path is opened by the pressure reducing valve installed at the end of the common rail, and the fuel in the common rail is released to the low pressure side, and the common rail pressure is changed from high pressure to low pressure. In addition to the intake metering valve and the metering valve drive circuit for driving the intake metering valve, the decompression valve and the decompression valve drive circuit for driving the decompression valve are used to perform decompression control for decompressing (decreasing). Is required, resulting in an increase in cost.
[0007]
Also, in the case of the one that gives a drive pulse that does not inject fuel to the solenoid valve of the injector (blank driving) or the one that injects a very small amount immediately after deceleration, it is very short unlike the normal method of using the injector. Since the solenoid valve of the injector is driven by the drive pulse, the operation of the injector itself is unstable, and there are injections or not. As a result, the fuel pressure in the common rail (common rail pressure) cannot be controlled well, and the fuel at an unnecessarily high pressure is injected into each cylinder of the engine from the injector until the common rail pressure drops to the target common rail pressure. Therefore, there is a problem that the combustion state of the engine deteriorates and the combustion noise increases.
[0008]
OBJECT OF THE INVENTION
The object of the present invention is to reduce the fuel pressure in the common rail from a high pressure to a low pressure during a period of transition from steady running to decelerating travel while eliminating the need for a pressure reducing valve and a pressure reducing valve drive circuit for driving the pressure reducing valve. An object of the present invention is to provide a pressure accumulation type fuel injection device that is excellent in pressure-lowering performance. Also provided is a pressure accumulation type fuel injection device capable of improving engine noise such as combustion noise until the fuel pressure in the common rail drops to the target fuel pressure during a period of transition from steady running to decelerating running. There is.
[0009]
[Means for Solving the Problems]
  According to the first aspect of the present invention, the fuel overflow flow (injector dynamic leak) that overflows the high-pressure fuel supplied into the pressure control chamber to the low-pressure side of the fuel system during the period of transition from steady running to decelerating running. The amount of fuel) until the actual fuel pressure substantially matches the target fuel pressure with respect to the above standard amount of fuel overflow when the target fuel pressure and the actual fuel pressure match. While not requiring a pressure reducing valve drive circuit for driving the pressure reducing valve, it is possible to improve the pressure reducing performance for reducing the fuel pressure in the common rail from a high pressure to a low pressure. Therefore, since the number of parts and the number of assembly steps can be reduced, the cost can be reduced.
  Further, according to the present invention, the fuel overflow rate increasing means drives the injector a plurality of times during one combustion stroke of the engine, and performs an injection rate control means for performing multi-stage injection that performs fuel injection divided into a plurality of times, And an injection number determining means for setting the number of injections of the multistage injection according to the pressure difference between the actual fuel pressure detected by the fuel pressure detecting means and the target fuel pressure after deceleration. The number of times of the multistage injection is set to be large. As a result, the fuel overflow flow from the target fuel pressure before deceleration to the target fuel pressure after deceleration causes the high pressure fuel supplied into the pressure control chamber of the injector by multistage injection of the injector to overflow to the low pressure side of the fuel system. Since (injector dynamic leak amount) can be earned more than before deceleration, it is possible to improve engine noise such as combustion noise until the fuel pressure in the common rail decreases to the target fuel pressure.
[0010]
According to the second aspect of the present invention, the post-deceleration injection in which the fuel injection amount to be injected into each cylinder of the engine is set according to the operating state or operating condition of the engine during the transition from the steady running to the decelerating running. Injection annealing to mitigate deceleration surges and deceleration shocks by decreasing in steps with a predetermined step amount per unit time until reaching the amount, or continuously decreasing with a predetermined gradient amount per unit time It can be performed.
[0011]
According to the third aspect of the present invention, the period during which the vehicle shifts from the steady traveling to the deceleration traveling is reduced from the target fuel pressure before deceleration to the target fuel pressure after deceleration by a predetermined value or more, and the actual fuel pressure is decelerated. It is a period until it substantially coincides with the later target fuel pressure. Alternatively, the period of transition from steady running to decelerating running is the period of time until the fuel injection amount injected into each cylinder of the engine reaches the post-deceleration injection amount set according to the engine operating state or operating conditions. It is characterized by being.
[0012]
  Claim4 and 5According to the invention described in, BurningAs the pressure difference between the actual fuel pressure detected by the fuel pressure detecting means and the target fuel pressure after deceleration becomes smaller, the number of injections of multistage injection is decreased step by step N times. As a result, the fuel overflow flow from the target fuel pressure before deceleration to the target fuel pressure after deceleration causes the high pressure fuel supplied into the pressure control chamber of the injector by multistage injection of the injector to overflow to the low pressure side of the fuel system. Since (injector dynamic leak amount) can be earned more than before deceleration, it is possible to improve engine noise such as combustion noise until the fuel pressure in the common rail decreases to the target fuel pressure.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
[Configuration of First Embodiment]
1 to 7 show a first embodiment of the present invention. FIG. 1 is a diagram showing the entire structure of a common rail fuel injection system. FIG. 2 is a structure of an injector with a two-way solenoid valve. FIG.
[0016]
A common rail fuel injection system according to this embodiment includes a common rail 2 that accumulates high-pressure fuel corresponding to a fuel injection pressure to be injected into a combustion chamber of each cylinder of an internal combustion engine (hereinafter referred to as an engine) 1 such as a multi-cylinder diesel engine. , A suction metering type supply pump 3 that pressurizes the fuel sucked into the pressurizing chamber and pumps it to the common rail 2, a plurality (four in this example) of injectors 5, and a suction metering valve of the supply pump 3 (Actuator) 4 and an engine control unit (hereinafter referred to as ECU) 10 for electronically controlling electromagnetic valves (actuators) 7 of a plurality of injectors 5 are provided.
[0017]
The common rail 2 needs to continuously accumulate high-pressure fuel corresponding to the fuel injection pressure, and is connected to a discharge port of a supply pump 3 that discharges high-pressure fuel through a fuel pipe (high-pressure passage) 11 for that purpose. ing. The leaked fuel from the injector 5 and the supply pump 3 is returned to the fuel tank 9 through leak pipes (fuel recirculation paths) 12, 13, and 14. A pressure limiter 16 is attached to a return pipe (fuel return path) 15 from the common rail 2 to the fuel tank 9. The pressure limiter 16 is a pressure safety valve that opens when the fuel pressure in the common rail 2 exceeds the limit set pressure, and keeps the fuel pressure below the limit set pressure.
[0018]
The supply pump 3 is a known feed pump (low pressure supply pump: not shown) that pumps up fuel in the fuel tank 9 by rotating a pump drive shaft 22 as the crankshaft (crankshaft) 21 of the engine 1 rotates. And a plunger (not shown) driven by the pump drive shaft 22 and a pressurizing chamber (plunger chamber: not shown) for pressurizing fuel by the reciprocating motion of the plunger. The supply pump 3 is a high-pressure supply pump (fuel supply pump) that pressurizes the fuel sucked by the feed pump through the fuel pipe 19 and discharges the high-pressure fuel from the discharge port to the common rail 2. A common rail pressure control suction that opens and closes the fuel supply path that connects the fuel tank 9 and the pressurization chamber of the supply pump 3, particularly a fuel supply path that connects the feed pump and the pressurization chamber. A metering valve (SCV) 4 is attached.
[0019]
The intake metering valve 4 is electronically controlled by a pump drive signal from the ECU 10 via a pump drive circuit (not shown), thereby adjusting the amount of fuel sucked from the feed pump of the supply pump 3 into the pressurized chamber. A fuel injection pressure (fuel pressure) supplied from each injector 5 to the engine 1, that is, a common rail pressure is changed by a pump flow rate control valve (intake amount adjusting electromagnetic valve). Here, the intake metering valve 4 of the present embodiment adjusts the valve opening degree of the valve according to the valve (valve element) that changes the opening degree of the fuel flow path in the supply pump 3 and the pump drive signal. This is a normally open type solenoid valve (pump control valve) in which the valve opening degree is fully opened when energization to the solenoid coil is stopped.
[0020]
The injector 5 of each cylinder is mounted corresponding to each cylinder of the engine 1, and is connected to the downstream ends of a plurality of branch pipes 17 branched from the common rail 2. This injector 5 is a two-way drive that drives a nozzle 6 for injecting high-pressure fuel accumulated in the common rail 2 into the combustion chamber of each cylinder of the engine 1 and a nozzle needle 33 accommodated in the nozzle 6 in the valve opening direction. This is an electromagnetic fuel injection valve constituted by a valve type electromagnetic valve (hereinafter referred to as an electromagnetic valve) 7 and a coil spring (needle urging means: not shown) that urges the nozzle needle 33 in the valve closing direction.
[0021]
The nozzle 6 includes a nozzle body 32 having a plurality of injection holes 31 and a nozzle needle 33 that is slidably accommodated in the nozzle body 32 and opens and closes the plurality of injection holes 31. The nozzle body 32 is formed with a fuel passage 35 that communicates from the joint portion to the fuel reservoir 34. In addition, a command piston 36 that moves in the vertical direction in the figure in conjunction with the nozzle needle 33 is assembled on the upper end side in the figure in the axial direction of the nozzle needle 33.
[0022]
The nozzle holder 37 connected to the upper end of the nozzle body 32 is formed with a fuel supply passage 40 for supplying fuel from the joint portion into the pressure control chamber 39 via the inlet orifice 41. In the nozzle body 32 and the nozzle holder 37, the fuel overflowing from the sliding portion between the nozzle needle 33 and the nozzle body 32 into the internal space 54 is guided to a fuel discharge passage 51 (injector static leak). A fuel discharge path 55 is formed.
[0023]
The solenoid valve 7 is attracted upward in the figure by a solenoid coil 45 electrically connected via a normally open switch 44 built in an in-vehicle power source 43 and an injector drive circuit (EDU), and a magnetomotive force of the solenoid coil 45. And a return spring 47 that urges the valve body 46 in the valve closing direction. The fuel injection from the injector 5 into the combustion chamber of each cylinder of the engine 1 is electronically controlled by an electromagnetic valve control signal (INJ control command value) from the ECU 10 to the injector driving circuit (EDU) that drives the electromagnetic valve 7. .
[0024]
An injector driving current is applied from the injector driving circuit (EDU) to the solenoid coil 45 of the electromagnetic valve 7, and the valve body 46 of the electromagnetic valve 7 is connected to the pressure control chamber 39 via the outlet orifice 42. When the valve is opened, the fuel supplied into the pressure control chamber 39 passes through the outlet orifice 42, the fuel discharge passages 51 and 52, and the fuel discharge port 53, and the fuel return passages 13 and 14 on the low pressure side of the fuel system and the fuel. The tank 9 overflows (injector dynamic leak). As a result, when the fuel pressure in the pressure control chamber 39 decreases and the fuel pressure in the fuel reservoir 34 acting in the direction of raising the nozzle needle 33 upward in the figure overcomes the biasing force of the coil spring, the nozzle needle 33 The valve seat is lifted (separated) upward in the figure, and the injection hole 31 and the fuel reservoir 34 communicate with each other. At this time, the high-pressure fuel accumulated in the common rail 2 is injected and supplied into the combustion chamber of each cylinder of the engine 1.
[0025]
The ECU 10 has functions such as a CPU for performing control processing and arithmetic processing, memories (ROM, RAM) for storing various programs and data, an input circuit, an output circuit, a power supply circuit, an injector drive circuit (EDU), a pump drive circuit, and the like. A microcomputer having a well-known structure is provided. Further, when the ignition switch is turned on (IG / ON), the ECU 10 is supplied with ECU power, and based on a control program stored in the memory, for example, the intake metering valve 4 of the supply pump 3 and the injector 5 The electromagnetic valve 7 is configured to be electronically controlled. Further, the ECU 10 is configured to forcibly terminate the above-described control based on the control program stored in the memory when the ignition switch is turned off (IG / OFF) and the supply of ECU power is cut off. ing.
[0026]
Here, sensor signals from various sensors are A / D converted by an A / D converter and then input to a microcomputer built in the ECU 10. The microcomputer has a rotation speed sensor 61 for detecting an engine rotation speed (also referred to as engine rotation speed: NE) as an operation condition detection means for detecting an operation state or operation condition of the engine 1, an accelerator opening degree. Accelerator opening sensor 62 for detecting (ACCP), cooling water temperature sensor 63 for detecting engine cooling water temperature (THW), and fuel temperature (THF) on the pump suction side sucked into supply pump 3 A fuel temperature sensor 64 for detecting the outside air temperature (TAM) which is the outside air temperature outside the passenger compartment, and a common rail pressure sensor for detecting the fuel pressure (common rail pressure: Pc) in the common rail 2 (of the present invention). 66 etc. (corresponding to a fuel pressure sensor) is connected.
[0027]
The ECU 10 determines the basic injection amount (Q), the command based on the engine operation information such as the engine rotation speed (NE) detected by the rotation speed sensor 61 and the accelerator opening (ACCP) detected by the accelerator opening sensor 62. The injection timing (T) is calculated, and the electromagnetic of the injector 5 calculated from the engine operation information such as the engine speed (NE) or the like, or the actual common rail pressure (Pc) detected by the common rail pressure sensor 66 and the basic injection amount (Q). Depending on the energizing time of the valve 7 (injection pulse length, injection pulse width, injection pulse time, command injection period: Tq), the electromagnetic valve 7 of the injector 5 of each cylinder is pulsed via an injector drive circuit (EDU). Injector drive current (INJ drive current value, injector injection pulse) is applied.As a result, the engine 1 is operated.
[0028]
Further, the ECU 10 calculates the optimum common rail pressure according to the operating conditions of the engine 1 and drives the suction metering valve (SCV) 4 of the supply pump 3 through the pump drive circuit, thereby discharging from the supply pump 3. The fuel pressure control means for controlling the fuel pressure in the common rail 2 (common rail pressure) by changing the amount of fuel discharged is provided.
That is, the ECU 10 calculates a target common rail pressure (PF) from engine operation information such as the engine rotation speed (NE) detected by the rotation speed sensor 61, and supplies the supply pump to achieve the target common rail pressure (PF). 3 adjusts the pump drive signal (SCV control amount, SCV control command value, drive current value) to the intake metering valve 4 to control the pumping amount of fuel discharged from the supply pump 3 (pump discharge amount). It is configured as follows.
[0029]
More preferably, the common rail pressure sensor 66 is attached to the common rail 2, and the actual common rail pressure (Pc) detected by the common rail pressure sensor 66 substantially matches the target common rail pressure (PF) determined by the engine operation information. Thus, it is desirable to feedback-control the pump drive signal (SCV control amount, SCV control command value, drive current value) to the suction metering valve 4 of the supply pump 3.
[0030]
The control of the drive current value to the intake metering valve 4 is desirably performed by duty (DUTY) control. For example, according to the pressure deviation (ΔP) between the actual common rail pressure (Pc) and the target common rail pressure (PF), the pump drive signal ON / OFF ratio (energization time ratio / duty ratio) per unit time is adjusted. By using duty control that changes the valve opening degree of the intake metering valve 4, high-precision digital control is possible.
[0031]
Here, in the common rail fuel injection system of the present embodiment, in the injector 5 of the specific cylinder of the engine 1, during one cycle of the engine 1 (1 stroke: intake stroke-compression stroke-expansion stroke (explosion stroke) -exhaust stroke). That is, while the crankshaft of the engine 1 makes two revolutions (720 ° CA), multi-stage injection is performed in which fuel is injected in a plurality of times, particularly during one combustion stroke of each cylinder of the engine 1 (injection rate control means). It is possible. For example, by driving the electromagnetic valve 7 of the injector 5 a plurality of times during the compression stroke and the expansion stroke of the engine 1, a multi-injection that performs a plurality of pilot injections and pre-injections before the main injection, or a main injection It is possible to perform multi-injection in which after-injection is performed a plurality of times later, or multi-injection in which at least one after-injection is performed after main injection and at least one after-injection is performed after main injection.
[0032]
[Control Method of First Embodiment]
Next, a method for controlling the intake metering valve 4 of the supply pump 3 and the electromagnetic valve 7 of the injector 5 according to the present embodiment will be briefly described with reference to FIGS. Here, FIGS. 3 and 4 are flowcharts showing an injector injection amount control method and a common rail pressure control method.
[0033]
3 and 4 are repeated at predetermined timings after an ignition switch (not shown) is turned on. For example, the injection amount control of the k-cylinder injector 5 may be started immediately after the end of the injection of the k-cylinder injector 5 in the previous cycle, or the immediately preceding injection cylinder (k cylinder is # 1 in the current cycle). # 2 cylinder for cylinder, # 1 cylinder for k cylinder # 3, # 3 cylinder for k cylinder # 4, # 4 cylinder for k cylinder # 2) You may start immediately.
[0034]
First, when the flowcharts of FIGS. 3 and 4 are started, engine parameters (engine operating information), such as engine speed (NE), accelerator opening (ACCP), engine coolant temperature (THW), pump suction side fuel temperature ( (THF) and the like, and the outside air temperature (TAM) and the actual common rail pressure (Pc) are taken in (step S1). Next, an accelerator opening difference (ΔACCP) between the accelerator opening (ACCPi−1) acquired last time and the accelerator opening (ACCPi) acquired this time is calculated (step S2).
[0035]
Next, a normal injection command value is calculated (step S3). Specifically, the basic injection amount (Q) is calculated based on the engine rotation speed (NE), the accelerator opening (ACCP), and a characteristic map or an arithmetic expression that has been previously measured through experiments or the like (basic injection amount determining means). ). Here, the target pressure difference (ΔPF) between the previous basic injection amount (Qi−1) and the current basic injection amount (Qi) may be calculated.
[0036]
Subsequently, the target common rail pressure (PF) is calculated based on the engine rotation speed (NE), the basic injection amount (Q), and a characteristic map or calculation formula that has been previously measured through experiments or the like (fuel pressure determining means). Here, the injection amount difference (ΔQ) between the previous target common rail pressure (PFi−1) and the current target common rail pressure (PFi) may be calculated.
[0037]
Subsequently, the command injection timing (normal main injection timing: T) is calculated from the engine rotation speed (NE), the basic injection amount (Q), and a characteristic map or calculation formula that has been previously prepared by experiments and the like (injection at normal time: T). Time determination means).
[0038]
Next, it is determined whether or not the accelerator opening difference (ΔACCP) obtained in step S2 is equal to or less than a predetermined value (−α). Alternatively, it is determined whether or not the target pressure difference (ΔPF) or the injection amount difference (ΔQ) has decreased by a predetermined value or more (step S4). If the determination result is NO, it is determined whether or not the accelerator opening difference (ΔACCP) obtained in step S2 is equal to or greater than a predetermined value (+ β). Alternatively, it is determined whether or not the target pressure difference (ΔPF) or the injection amount difference (ΔQ) has increased by a predetermined value or more (step S5). If the determination result is YES, it is determined that the vehicle is accelerating (accelerated traveling or acceleration state), the deceleration flag (fg) is defeated, fg = 0 is set, and stored in the memory (step S6).
[0039]
Next, the normal injection pattern is calculated and stored in the memory (step S7). Thereafter, the process proceeds to the determination process in step S13. Specifically, the number of multi-stage injections (the number of multi-injections, the number of INJ injections) is calculated based on the engine speed (NE), the basic injection amount (Q), and a characteristic map that has been previously measured through experiments or the like.
[0040]
For example, the number of INJ injections is set to three times (pilot injection 1, pre-injection and main injection) as shown in FIG. 5A, or three times (pilot injection 2 as shown in FIG. 5A). , Pilot injection 1 and main injection) or twice (pilot injection 1 and main injection) as shown in FIG. FIG. 5B shows a display method of the injection form (injection pattern) of FIG. That is, each bit is made to correspond to each injection of the multistage injection, and if “1”, it is determined that the injection is performed, and if “0”, it is determined that the injection is not performed, and the injection pattern is determined.
[0041]
If the determination result in step S4 is YES, it is determined that the vehicle is decelerating (during deceleration or in a decelerating state), and the deceleration flag (fg) is set to fg = 1 and stored in the memory (step S8). ). Thereafter, the processing proceeds to step S9.
[0042]
If the determination result in step S4 is NO and the determination result in step S5 is NO, it is determined that the vehicle is in a steady state (steady running or steady state), and the deceleration injection amount is set (step S9). . Specifically, the current basic injection amount (Qi) set in step S3 is set as the current deceleration injection amount (Qgi), and the smoothed injection amount (dQ) is calculated from the current deceleration injection amount (Qgi). The next deceleration injection amount (Qg = Qgi−dQ) is calculated by subtracting. As a result, as shown in the timing chart of FIG. 6, the smoothed injection amount gradually decreases the injection amount from the previous injection amount before starting deceleration (normal injection amount) to the current post-deceleration injection amount. Fuel injection is performed.
[0043]
Next, it is determined whether or not the difference (Qg−Q) between the aforementioned deceleration injection amount (Qg) and the basic injection amount (post-deceleration injection amount: Q) is equal to or less than a predetermined value (γ) (step S10). ). If this determination is YES, the process proceeds to step S6, and the deceleration flag (fg) is reset.
[0044]
If the determination result in step S10 is NO, a deceleration injection command value is calculated (step S11). Specifically, the target common rail pressure (PFg) during deceleration is calculated based on the engine speed (NE), the basic injection amount (Q), and a characteristic map or calculation formula that has been previously measured through experiments or the like (determination of fuel pressure) means). Subsequently, the deceleration injection timing (deceleration main injection timing: Tg) is calculated from the engine rotation speed (NE), the basic injection amount (Q), and a characteristic map or calculation formula created by measurement in advance through experiments or the like ( Injection timing determining means).
[0045]
Next, the deceleration injection pattern is calculated (step S12). Specifically, an injection pattern (INJ injection count) during deceleration is calculated according to the pressure difference (Pcr-PFg) between the actual common rail pressure (Pcr) and the target common rail pressure during deceleration (PFg), and a predetermined injection It is determined how many times the amount is to be injected (see the timing chart in FIG. 6).
[0046]
When the calculation process in step S7 or the calculation process in step S12 in FIG. 3 is completed, the process proceeds to the flowchart in FIG. 4 to determine whether there is a request for main injection (step S13). When the determination result is NO, the main injection amount (Qmain) is set to 0 and no injection is performed (step S14). Thereafter, the process proceeds to step S21.
[0047]
Moreover, when the determination result of step S13 is YES, a main injection command value is calculated (step S15). Specifically, the main injection amount (Qmain) is calculated from the engine speed (NE), the basic injection amount (Q), and a characteristic map (not shown) or an arithmetic expression created by measurement in advance through experiments or the like ( Main injection amount determining means).
[0048]
Subsequently, the main injection timing (Tmain) is calculated from the basic injection amount (Q), the engine rotational speed (NE), and a characteristic map (not shown) or an arithmetic expression created by measurement in advance or the like (main injection). Time determination means). The main injection amount (Qmain) may be calculated by subtracting the pre-injection amount (Qpre), the pilot injection amount (Qpilot), and the after injection amount (Qaft) from the total injection amount (totalQ).
[0049]
Next, it is determined whether there is a request for injection other than main injection (step S16). When the determination result is NO, the setting of the injection other than the main injection is not performed, the injection amount of the injection other than the main injection is set to 0, and the fuel is not injected except for the main injection (step S17). Thereafter, the process proceeds to step S21.
[0050]
If the determination result in step S16 is YES, a pre-injection command value is calculated (step S18). Specifically, the pre-injection amount (Qpre) is calculated from the engine speed (NE), the basic injection amount (Q), and a characteristic map (not shown) or an arithmetic expression created by measurement in advance through experiments or the like ( Pre-injection amount determining means).
[0051]
Subsequently, the pre-injection timing (Tpre) is calculated from the basic injection amount (Q), the engine rotation speed (NE), and a characteristic map (not shown) or an arithmetic expression prepared in advance by experiments or the like (pre-injection). Time determination means). Alternatively, the interval between the pre-injection and the main injection in the multi-stage injection from the engine rotation speed (NE), the basic injection amount (Q), and a characteristic map (not shown) or an arithmetic expression that is created in advance through experiments or the like. Is calculated (non-injection interval determining means). In addition, when not performing pre-injection, the process of step S18 does not need to be implemented.
[0052]
Next, a pilot injection command value is calculated (step S19). Specifically, the pilot injection amount (Qpilot) is calculated from the engine rotation speed (NE), the basic injection amount (Q), and a characteristic map (not shown) or an arithmetic expression prepared by measurement in advance through experiments or the like ( Pilot injection amount determining means).
[0053]
Subsequently, the pilot injection timing (Tpilot) is calculated from the basic injection amount (Q), the engine rotation speed (NE), and a characteristic map (not shown) or an arithmetic expression prepared in advance by experiments or the like (pilot injection). Time determination means). Alternatively, the pilot injection and the main injection or the pre-injection in the multi-stage injection can be determined from the engine rotation speed (NE), the basic injection amount (Q), and a characteristic map (not shown) or an arithmetic expression prepared in advance through experiments or the like. The interval between them is calculated (non-injection interval determining means). In addition, when not performing pilot injection, it is not necessary to perform the process of step S19.
[0054]
Next, an after injection command value is calculated (step S20). Specifically, the after injection amount (Qaft) is calculated from the engine rotation speed (NE), the basic injection amount (Q), and a characteristic map (not shown) or an arithmetic expression created by measurement in advance through experiments or the like ( After injection amount determining means).
[0055]
Subsequently, the after injection timing (Taft) is calculated from the basic injection amount (Q), the engine rotation speed (NE), and a characteristic map (not shown) or an arithmetic expression that is created in advance through experiments or the like (after injection). Time determination means). Alternatively, the interval between the main injection and the after injection in the multi-stage injection from the engine rotation speed (NE), the basic injection amount (Q), and a characteristic map (not shown) or an arithmetic expression that is created in advance through experiments or the like. Is calculated (non-injection interval determining means). In addition, when not performing after injection, the process of step S20 does not need to be implemented.
[0056]
Next, the INJ control amount that is the INJ control command value is converted into an injection pulse width (step S21). Specifically, the energization time (injection pulse length, injection pulse length, Qcr), the actual common rail pressure (Pcr), and the characteristic map or calculation formula created by measurement in advance through experiments or the like. An injection pulse width, an injection pulse time, and a command injection period: Tq) are calculated (injection period determining means).
[0057]
Next, a pump control amount that is an SCV control command value is calculated (step S22). Specifically, the SCV correction amount (Di) is calculated according to the pressure deviation (Pcr−PFg, orPcr−PF) between the actual common rail pressure (Pcr) and the target common rail pressure (PF). Subsequently, the SCV correction amount (Di) is added to the previous SCV control amount (Dscv) to calculate the current pump control amount (SCV control command value: Dscv).
[0058]
Next, the INJ control amount (INJ control command value: Tq) and the command injection timing (T) are set in the output stage of the ECU 10. Further, the pump control amount (SCV control command value: Dscv) is set in the output stage of the ECU 10 (step S23). Thereafter, the process returns to step S1, and the above-described control is repeated.
[0059]
[Operation of First Embodiment]
Next, the operation of the common rail fuel injection system of this embodiment will be briefly described with reference to FIGS.
[0060]
In the present embodiment, the driver greatly depresses the accelerator pedal, and the difference (ΔACCP) between the previous accelerator opening (ACCPi−1) and the current accelerator opening (ACCPi) becomes greater than or equal to a predetermined value (+ β). During acceleration in which the current target common rail pressure (PF) or the current basic injection amount (Q) increases by a predetermined value or more compared to the previous time, that is, during the period of transition from steady running to accelerated running, the injection of the injector 5 The form (INJ injection frequency) is set to 1 or 2 and the actual common rail pressure (Pc) detected by the common rail pressure sensor 66 substantially matches the target common rail pressure (PF). The SCV control command value to the intake metering valve 4 is feedback controlled. As a result, the degree of opening of the fuel supply path that connects the fuel tank 9 and the pressurizing chamber of the supply pump 3 is adjusted, so that the pump discharge amount discharged from the discharge port of the supply pump 3 to the common rail 2 is changed quickly. The fuel pressure in the common rail 2 (common rail pressure) is increased.
[0061]
Further, when the driver removes his / her foot from the accelerator pedal, the difference (ΔACCP) between the previous accelerator opening (ACCPi−1) and the current accelerator opening (ACCPi) becomes greater than or equal to a predetermined value (α). During deceleration when the target common rail pressure (PF) or the current basic injection amount (Q) is reduced by a predetermined value or more compared to the previous time, that is, during the transition from steady running to slow running, injection smoothing is performed first Thus, the deceleration injection amount (Qg) is set. This is from the previous basic injection amount (Q) set before the start of deceleration to the current post-deceleration injection amount (Qg), that is, in the steady state when the accelerator opening (ACCP) does not change after the start of deceleration. As shown in the timing chart of FIG. 6, during the predetermined time, the injection is actually supplied into the combustion chamber of each cylinder of the engine 1 from the previous basic injection amount (Q) to the post-deceleration injection amount (Qg). The fuel injection is performed by the smoothed injection amount that gradually decreases the fuel injection amount. In the present embodiment, the injection smoothing for continuously decreasing the actual fuel injection amount at a predetermined gradient amount (Qgi−dQ) per unit time is performed, but a predetermined step amount (Qgi per unit time) is implemented. -DQ) may be executed to reduce the actual fuel injection amount step by step.
[0062]
Here, fuel injection from the injector 5 mounted in each cylinder of the engine 1 into the combustion chamber of each cylinder of the engine 1 is performed as follows. When the command injection timing (T) of the injector 5 or each injection timing of multistage injection, that is, the pilot injection timing (Tpilot), the pre-injection timing (Tpre), the main injection timing (Tmain), and the after injection timing (Taft), each injector is reached. The normally open switch 44 built in the drive circuit (EDU) is closed, and a pulsed injector drive current (INJ injection pulse) is applied to the solenoid coil 45 of the solenoid valve 7 of the injector 5. Then, the valve body 46 of the electromagnetic valve 7 of the injector 5 is opened.
[0063]
While the valve body 46 of the electromagnetic valve 7 of the injector 5 is open, the high-pressure fuel supplied from the branch pipe 17 of the common rail 2 to the pressure control chamber 39 via the fuel supply path 40 and the inlet orifice 41 is communicated. Overflow (injector dynamic leak) from the fuel discharge port 53 to the leak pipes 13 and 14 through the hole 49, the outlet orifice 42, and the fuel discharge passages 51 and 52. Accordingly, the nozzle needle 33 is lifted (separated) from the valve seat of the nozzle body 32 by overcoming the biasing force of the needle biasing means such as a spring. Thereby, since the injection hole 31 and the fuel reservoir 34 communicate with each other, the high-pressure fuel accumulated in the common rail 2 is injected and supplied into the combustion chamber of each cylinder of the engine 1.
[0064]
Thereafter, the injection pulse width (Tq) or each injection period of the multistage injection from the injector injection pulse start timing for starting the output of the injector (INJ) injection pulse, that is, the pilot injection period, the pre-injection period, the main injection period, the after-injection period When the injector injection pulse end timing at which the output of the injector (INJ) injection pulse ends is reached, the normally open switch 44 of the injector drive circuit is opened. Then, the valve body 46 of the electromagnetic valve 7 of the injector 5 is closed.
[0065]
While the electromagnetic valve 7 of the injector 5 is closed, high-pressure fuel is supplied from the branch pipe 17 of the common rail 2 through the fuel supply path 40 and the inlet orifice 41 into the pressure control chamber 39, so that the inside of the pressure control chamber 39 Since the high pressure fuel is filled, the nozzle needle 33 is seated on the valve seat of the nozzle body 32 by the biasing force of the needle biasing means such as a spring. As a result, the communication state between the injection hole 31 and the fuel reservoir 34 is cut off, so that fuel injection into the combustion chamber of each cylinder of the engine 1 is completed.
[0066]
Here, FIG. 7 is a graph showing an experimental result of measuring the injector dynamic leak amount by changing the number of times of multistage injection (INJ injection number) from 0 to 5. From the result of FIG. 7, if the number of INJ injections is set to an optimal number during the period when the above-described injection smoothing is performed, that is, during deceleration where the target common rail pressure (PF) is greatly decreased by a predetermined value or more, FIG. As shown in the timing chart of Fig. 5, the actual common rail pressure (Pc) is stepped down from the steady-state target common rail pressure (PF) to the deceleration target common rail pressure (PFg). It can be seen that is improved.
[0067]
Therefore, in this embodiment, as shown in the timing chart of FIG. 6, when the normal injection pattern and the post-deceleration injection pattern are two times (one pilot injection and one main injection), the pressure difference ( 5 times (4 pilot injections and 1 main injection) when Pcr−PFg is the largest, and 3 times (2 pilot injections when the pressure difference (Pcr−PFg) is the smallest). When the pressure difference (Pcr-PFg) is in the meantime, it is set to 3 times (3 times for pilot injection and 1 time for main injection). Note that after injection or pre-injection may be performed instead of pilot injection.
[0068]
[Effect of the first embodiment]
As described above, in the common rail fuel injection system of the present embodiment, predetermined conditions from the start of deceleration at which the accelerator opening (ACCP), the target common rail pressure (PF), and the basic injection amount (Q) decrease by a predetermined value or more. 6, that is, as shown in the timing chart of FIG. 6, the injection that softens the deceleration surge and deceleration shock until the post-deceleration injection amount reaches the post-deceleration injection amount from the pre-deceleration injection amount (steady-state injection amount). At the same time that the annealing is performed, the injector 5 during one combustion stroke of the engine until the actual common rail pressure (Pc) follows the target common rail pressure (PFg) after deceleration from the target common rail pressure (PF) before deceleration. The multi-stage injection is performed by driving the solenoid valve 7 a plurality of times to inject the high pressure fuel into the combustion chamber of each cylinder of the engine 1 in a plurality of times. To have.
[0069]
In the period during which the above-mentioned injection annealing is performed, that is, the period until the actual common rail pressure (Pc) follows the target common rail pressure (PFg) after deceleration from the target common rail pressure (PF) before deceleration. If the number of INJ injections is set to be greater than outside the period, the amount of injector dynamic leak increases, and the actual common rail pressure (Pc) changes from the target common rail pressure (PF) before deceleration to the target common rail pressure (PFg) after deceleration. The step-down performance or the follow-up performance can be improved.
[0070]
Accordingly, since the fuel pressure in the common rail 2 (common rail pressure) can be controlled so as to quickly decrease, the actual common rail pressure (Pc) from the target common rail pressure (PF) before deceleration to the target common rail pressure (PFg) after deceleration. It is possible to shorten the period until it decreases. As a result, the period during which fuel with an unnecessarily high pressure is injected and supplied from the injector 5 into the combustion chamber of each cylinder of the engine 1 can be shortened, so that the combustion state of the engine 1 becomes slow and engine noise such as combustion noise is improved. can do.
[0071]
Further, the pressure reducing performance for reducing the fuel pressure in the common rail 2 from high pressure to low pressure can be improved while eliminating the pressure reducing valve and the pressure reducing valve driving circuit for driving the pressure reducing valve. Therefore, since the number of parts and the number of assembly steps can be reduced, the cost can be reduced.
[0072]
  [Reference example]
  FIG. 8 shows the present invention.Reference exampleFIG. 5 is a timing chart showing the behavior of the deceleration accelerator opening, the injection amount, and the common rail pressure when shifting from steady traveling to decelerating traveling.
[0073]
Here, when the engine 1 is operating in a high-load operation state, when the engine 1 is decelerated (accelerator pedal is OFF, fuel injection is stopped) and then is changed to the acceleration state (accelerator pedal is ON) again, the common rail When the fuel pressure in 2 (actual common rail pressure: Pc) is higher than a target common rail pressure (PF) by a specified value (for example, 15 MPa) or more, there are problems of deterioration in combustion noise and increase in NOx emission. Therefore, in the conventional technology, the injection amount and the injection timing at the time of reacceleration are increased / decreased and advanced / retarded. .
[0074]
  So bookReference exampleThen, at the time of deceleration when the accelerator opening (ACCP) is decreased by a predetermined value or more, that is, when the fuel pressure in the common rail 2 (actual common rail pressure: Pc) is higher than the target common rail pressure (PF) by a predetermined value (for example, 15 MPa). In order to improve the step-down performance, multiple-cycle injection is performed to such an extent that deceleration and drivability do not deteriorate during deceleration. That is, a period during which the vehicle travels from a steady state to a decelerating state (accelerator opening is 0%), that is, the target common rail pressure (PF) before deceleration decreases from the target common rail pressure after deceleration to a target common rail pressure after deceleration by more than a specified value (for example, 15 MPa) In the period until the actual common rail pressure (Pc) substantially matches the target common rail pressure after deceleration, the solenoid valve 7 of the injector 5 decreases as the pressure difference between the actual common rail pressure (Pc) and the target common rail pressure after deceleration decreases. The energization time (injection pulse width, command injection period: Tq) is decreased stepwise by a predetermined step amount (predetermined attenuation amount from the previous cycle: eqpcd) per unit time.
[0075]
Thereby, the injection amount (eqpcdn) at the time of step-down injected from the injector 5 to the engine 1 between the target common rail pressure (PF) before deceleration and the target common rail pressure after deceleration is reduced from the previous cycle (eqpcd). Since the actual common rail pressure (Pc) decreases to the target common rail pressure after deceleration, that is, during the period of transition from steady traveling to decelerating traveling (deceleration). The step-down performance can be improved (see the behavior of the actual common rail pressure (Pc) when there is a multi-cycle injection at the time of step-down (example) with respect to when there is no multi-cycle injection at the time of step-down (conventional example) in FIG. In addition, since the period during which fuel with an unnecessarily high pressure is injected and supplied from the injector 5 into the combustion chamber of each cylinder of the engine 1 can be shortened, the combustion state of the engine 1 becomes slow and engine noise such as combustion noise is improved. be able to. In addition, drivability at the time of re-acceleration (acceleration with respect to changes in accelerator opening) can be improved.
[0076]
The injection amount during deceleration (eqpcdn) between the target common rail pressure (PF) before deceleration and the target common rail pressure after deceleration is the injection amount after deceleration from the injection amount before deceleration when the accelerator opening changes. It may be calculated from the number of injections (ecqpcdn) until reaching the basic injection amount Q when the engine speed is a predetermined value and the accelerator opening is 0%. Thereby, said effect can be exhibited on the driving | running conditions of all the engines 1, and a contradiction can be suppressed. Note that the above-described injection amount at the time of step-down (eqpcdn) is determined based on the operating conditions of the engine 1 during deceleration (for example, engine load (accelerator opening: ACCP), engine speed (NE), basic injection amount (Q), command injection amount). (QFIN), actual common rail pressure (PC), target common rail pressure (PF), engine temperature, engine cooling water temperature (THW), intake air temperature, atmospheric pressure, etc.).
[0077]
[Other Embodiments]
In the present embodiment, the common rail pressure sensor 66 is directly attached to the common rail 2 to detect the fuel pressure accumulated in the common rail 2 (actual common rail pressure), but the fuel pressure sensor is used as the plunger chamber of the supply pump 3. It is attached to a fuel pipe or the like from the (pressurization chamber) to the fuel passage in the injector 5 and is injected and supplied to the fuel pressure discharged from the pressurization chamber of the supply pump 3 or the combustion chamber of each cylinder of the engine 1. The fuel injection pressure may be detected.
[0078]
In this embodiment, an example in which the injector 5 with a two-way valve type solenoid valve is used as an example of an injector that injects and supplies fuel into the combustion chamber of each cylinder of the engine 1 has been described. Other injectors or other types of injectors may be used. In the present embodiment, an example using the injector 5 made of an electromagnetic fuel injection valve has been described. However, an injector made of a piezoelectric fuel injection valve may be used.
[0079]
Here, in the present embodiment, the basic injection amount (Q), the command injection timing (T), the target common rail using the rotational speed sensor 61 and the accelerator opening sensor 62 as the operating condition detecting means for detecting the operating condition of the engine 1. Although the pressure (PF) is calculated, the cooling water temperature sensor 63 and the fuel temperature sensor 64 as operating condition detection means, and other sensors (for example, an intake air temperature sensor, an intake air pressure sensor, a cylinder discrimination sensor, an injection timing sensor) The basic injection amount (Q), the command injection timing (T), and the target common rail pressure (PF) may be corrected in consideration of a detection signal (engine operation information) from the above.
[0080]
The command injection amount (QFIN) is calculated by adding the injection amount correction amount considering the engine coolant temperature (THW), the pump intake side fuel temperature (THF), etc. to the basic injection amount (Q) (command injection) Amount determining means), the command injection amount (QFIN), the actual common rail pressure (Pc), and a characteristic map or an arithmetic expression that has been measured in advance through experiments or the like, and the energization time (injection pulse width, injection pulse width, The command injection period (Tq) may be calculated.
[Brief description of the drawings]
FIG. 1 is a schematic view showing the overall structure of a common rail fuel injection system (first embodiment).
FIG. 2 is a schematic view showing the structure of an injector with a two-way solenoid valve (first embodiment).
FIG. 3 is a flowchart showing an injector injection amount control method and a common rail pressure control method (first embodiment).
FIG. 4 is a flowchart showing an injector injection amount control method and a common rail pressure control method (first embodiment).
5A is a view showing an injection form of an injector, and FIG. 5B is a view showing a display method of the injection form (first embodiment).
FIG. 6 is a timing chart showing behaviors of a deceleration accelerator opening, a common rail pressure, an injection amount, and combustion noise when shifting from steady traveling to decelerating traveling (first embodiment).
FIG. 7 is a graph showing an injector dynamic leak amount with respect to the number of INJ injections (first embodiment).
FIG. 8 is a timing chart showing the behavior of the deceleration accelerator opening, the injection amount, and the common rail pressure when shifting from steady running to reduced running (Reference example).
[Explanation of symbols]
1 engine
2 Common rail
3 Supply pump (fuel supply pump)
4 Suction metering valve (actuator)
5 Injector
7 Solenoid valve (needle drive means, actuator)
10 ECU (fuel pressure determination means, fuel pressure control means, fuel overflow flow increase means, injection amount gradual change means, injection rate control means, injection number determination means, injection period determination means, injection period gradual change means)
31 injection hole
33 Nozzle needle
39 Pressure control room
66 Common rail pressure sensor (fuel pressure sensor)

Claims (5)

(A) a common rail for accumulating high-pressure fuel corresponding to the fuel injection pressure;
(B) a fuel supply pump that pressurizes the sucked fuel and pumps it into the common rail;
(C) A nozzle needle for opening and closing an injection hole for injecting fuel into the cylinder of the engine, a pressure control chamber for controlling the operation of the nozzle needle, and high-pressure fuel supplied to the pressure control chamber overflowing to the low-pressure side of the fuel system An injector having needle driving means for driving the nozzle needle in a valve opening direction by flowing it, and needle urging means for urging the nozzle needle in a valve closing direction;
(D) fuel pressure detecting means for detecting an actual fuel pressure corresponding to the fuel injection pressure;
(E) fuel pressure determining means for determining a target fuel pressure according to the operating state or operating conditions of the engine;
(F) changing the fuel discharge amount of the fuel supply pump according to the pressure difference between the actual fuel pressure detected by the fuel pressure detecting means and the target fuel pressure set by the fuel pressure determining means, and Fuel pressure control means for controlling the fuel pressure inside,
(G) The fuel pressure detecting means detects the fuel overflow flow rate that causes the high-pressure fuel supplied into the pressure control chamber to overflow to the low-pressure side of the fuel system during a period of transition from steady running to decelerating running. Until the fuel pressure substantially matches the target fuel pressure set by the fuel pressure determining means, the fuel overflow is increased with respect to the standard amount of the fuel overflow flow rate when the target fuel pressure and the actual fuel pressure match. An accumulator fuel injection device comprising a flow rate increasing means ,
The fuel overflow rate increasing means includes an injection rate control means for driving the injector a plurality of times during a single combustion stroke of the engine to perform multistage injection in which fuel injection is divided into a plurality of times, and the fuel pressure detection Means for determining the number of injections of the multi-stage injection according to the pressure difference between the actual fuel pressure detected by the means and the target fuel pressure after deceleration,
The pressure accumulation type fuel injection device , wherein the number of injections of the multistage injection is set to be larger as the pressure difference is larger . The pressure accumulation type fuel injection device according to claim 1,
The unit of time until the fuel injection amount injected into each cylinder of the engine reaches the post-deceleration injection amount set by the operating state or operating condition of the engine during the transition from the steady traveling to the decelerating traveling A pressure-accumulation fuel injection apparatus comprising: an injection amount gradual change means that decreases stepwise by a predetermined step amount per hit or continuously decreases by a predetermined gradient amount per unit time. In the pressure accumulation type fuel injection device according to claim 1 or 2,
The period of transition from the steady running to the decelerated running is a reduction of the target fuel pressure before deceleration from the target fuel pressure before deceleration by a predetermined value or more, and the actual fuel pressure detected by the fuel pressure detecting means is reduced. This is a period until the target fuel pressure substantially coincides with the subsequent target fuel pressure, or a period during which the vehicle shifts from the steady traveling to the decelerating traveling is the fuel injection amount to be injected into each cylinder of the engine. Or it is a period until it reaches the post-deceleration injection amount set according to the operating conditions. In the pressure accumulation type fuel injection device according to any one of claims 1 to 3 ,
The injection number determining means decreases the number of injections of the multistage injection step by step N times as the pressure difference between the actual fuel pressure detected by the fuel pressure detecting means and the target fuel pressure after deceleration decreases. accumulator fuel injection apparatus characterized by letting. (A) a common rail for accumulating high-pressure fuel corresponding to the fuel injection pressure;
(B) a fuel supply pump that pressurizes the sucked fuel and pumps it into the common rail;
(C) a nozzle needle for opening and closing an injection hole for injecting fuel into the cylinders of the engine, spilled pressure control chamber for controlling the operation of the nozzle Runidoru, a high-pressure fuel supplied to the pressure control chamber to the low pressure side of the fuel system An injector having needle driving means for driving the nozzle needle in a valve opening direction by flowing it, and needle urging means for urging the nozzle needle in a valve closing direction;
(D) fuel pressure detecting means for detecting an actual fuel pressure corresponding to the fuel injection pressure;
(E) fuel pressure determining means for determining a target fuel pressure according to the operating state or operating conditions of the engine;
(F) changing the fuel discharge amount of the fuel supply pump according to the pressure difference between the actual fuel pressure detected by the fuel pressure detecting means and the target fuel pressure set by the fuel pressure determining means, and Fuel pressure control means for controlling the fuel pressure inside,
(G) an injection rate control means for driving the injector a plurality of times during a single combustion stroke of the engine to perform multi-stage injection in which fuel injection is divided into a plurality of times;
(H) The target fuel pressure before deceleration is decreased from the target fuel pressure after deceleration by a predetermined value or more until the actual fuel pressure detected by the fuel pressure detecting means substantially matches the target fuel pressure after deceleration. Determination of the number of injections to reduce the number of injections of the multistage injection step by step N times as the pressure difference between the actual fuel pressure detected by the fuel pressure detection means and the target fuel pressure after deceleration decreases during the period Means and
Accumulator fuel injection apparatus characterized by comprising a.

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