JP2005256703A - Accumulator fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an accumulator fuel injection device in which the deterioratin of engine fuel conditions and deteriaoratin of a combustion noise level can be prevented by positively dropping the fuel pressure in a common rail notwithstanding eliminating the need for a pressure reducing valve and a pressure reducing valve driving circuit, the common rail pressure can be controlled with higher precision notwithstanding eliminating the need for the pressure reducing valve and the pressure reducing valve driving circuit, and a driver can be prevented from feeling intended acceleration by consuming only an increment of the engine output shaft torque, causing the injection of fuel by extra injection quantity. <P>SOLUTION: The fuel is injected into a combustion chamber of each cylinder in the engine by the increment of the fuel quantity more than the requested injection quantity so that the fuel pressure in the common rail is positively dropped. Since the released quantity of high pressure fuel per unit time is more than that in a pressure reducing control method only by a dynamic leak quantity in the pressure reducing control method, the control responsibility and following-up of the common rail pressure for the target fuel pressure are more improved than that in the pressure reducing method by the dynamic leak quantity only, providing that it is judged in a range of a gear position of a transmission and the extra injection quantity whether the engine torque-balance control is conducted or not by racing the increment of the engine output shaft torque to increase by the injection increment more than the requested injection quantity. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an accumulator fuel injection device that injects high-pressure fuel accumulated in a common rail into a combustion chamber of an engine cylinder via an injector at a predetermined injection timing, and more particularly to a common rail pressure detected by a fuel pressure sensor. Is an accumulator fuel injection with a pressure drop acceleration function that can quickly drop the common rail pressure to the target fuel pressure when it is higher than the target fuel pressure set in accordance with the engine operating state by a predetermined value or more. Related to the device.

[Conventional technology]
Conventionally, for example, a common rail fuel injection system (engine control system) has been proposed as a fuel injection system for a diesel engine. This is generally made up of a common rail, a fuel supply pump, an injector for the number of cylinders of the engine, a high-pressure pipe for connecting them as a fuel circuit, a low-pressure pipe for collecting leaked fuel in a fuel tank, and a fuel An engine control unit (ECU) for calculating the operation of the supply pump and the injector, an electromagnetic valve driving circuit for opening and driving the electromagnetic valve of the injector, a wire harness for sending an electric signal and driving power, and the like.

  The fuel pressure in the common rail is sampled at a predetermined timing by the common rail pressure sensor. If there is a pressure deviation between the common rail pressure (actual fuel pressure) and the target fuel pressure, the common rail pressure is increased or decreased by feedback control. It is controlled by. On the boost side of the common rail pressure, the amount of fuel sucked into the pressurized chamber of the fuel supply pump is adjusted by an electromagnetic suction metering valve with a variable flow path area, and the fuel injection amount and fuel leak amount from the injector The common rail pressure is controlled by pumping and supplying the fuel discharge amount suitable for

[Conventional technical problems]
However, the pressure reduction side of the common rail pressure is reduced by the amount of fuel injected from the injector, the amount of dynamic leak that leaks when the solenoid valve of the injector is driven to open, and the amount of static leak that leaks between each component. In the case where the common rail pressure is higher than the target fuel pressure and the required injection amount is very small, there is no means for positively reducing the pressure. As one method for solving this problem, a common rail fuel injection system in which a pressure reducing valve is installed at an end of the common rail has been proposed (see, for example, Patent Document 1). However, this is the amount by which the high pressure fuel in the common rail is released by opening the fuel recirculation path by the pressure reducing valve when the driver releases the accelerator pedal and makes the accelerator operation amount zero. However, there is a demerit of cost increase by adding a pressure reducing valve and a pressure reducing valve driving circuit.

  In addition, an electromagnetic valve that drives an electromagnetic valve of an injector mounted in another cylinder different from an injection cylinder that performs regular fuel injection in a time width shorter than a valve opening delay time until the nozzle needle opens. As a result, the common rail pressure is reduced by causing the high pressure fuel in the control chamber supplied from the common rail via the fuel supply path to overflow to the low pressure side of the fuel system via the fuel return path. A common rail fuel injection system has also been proposed (see, for example, Patent Document 2). This is because the current flow is shorter than normal fuel injection, which can be non-injection, in order to improve the pressure drop in the non-injection state where the driver releases his accelerator pedal and sets the accelerator operation amount to zero. A periodical pulsed injector drive current is applied to the injector solenoid valve to drive the solenoid valve idle. However, this is limited to when normal fuel injection is not performed, and is not used during normal fuel injection.

Here, with the recent tightening of exhaust gas regulations, there is a strict requirement for improving the pressure controllability for controlling the common rail pressure with higher accuracy. Also, considering the case where the common rail pressure when performing regular fuel injection is higher than the target fuel pressure set corresponding to the operating state of the engine, it is more than necessary from the injector to the combustion chamber of the engine cylinder. Since fuel with a high injection pressure is injected, there is a problem that the combustion state of the engine is deteriorated to generate more NOx and the combustion noise level is deteriorated.
JP 2000-282929 A (page 1-8, FIG. 1 to FIG. 15) JP 2000-282998 A (page 1-12, FIG. 1 to FIG. 20)

  The object of the present invention is to suppress the deterioration of the combustion state of the engine and the deterioration of the combustion noise level by actively lowering the fuel pressure in the common rail even when performing regular fuel injection. The object is to provide an accumulator fuel injection device. Another object of the present invention is to provide an accumulator fuel injection device that can control the common rail pressure with higher accuracy while eliminating the pressure reducing valve and the pressure reducing valve driving circuit. In addition, the accumulator fuel that can suppress the driver's feeling of unintentional acceleration by consuming the increased amount of engine output shaft torque caused by injecting fuel by the excess injection amount. It is in providing an injection device.

  According to the first aspect of the present invention, the fuel pressure in the common rail (actual fuel pressure) detected by the fuel pressure detecting means is the engine operating state (for example, the basic injection amount, the required injection amount, the command injection amount, and the engine speed). When the fuel pressure is higher than the target fuel pressure set corresponding to the speed), the injector valve opening period is such that fuel is injected in excess of the required injection amount set corresponding to the driver's accelerator operation amount. The fuel pressure in the common rail is lowered by an amount corresponding to the excess injection amount than during normal fuel injection. As a result, it is possible to positively lower the fuel pressure in the common rail even when the regular fuel injection is performed, and while eliminating the pressure reducing valve and the pressure reducing valve driving circuit, the engine combustion It is possible to suppress the deterioration of the state (for example, increase in the amount of NOx generated) and the deterioration of the combustion noise level, and it is possible to control the common rail pressure with higher accuracy.

  According to the second aspect of the present invention, as described above, the engine output shaft torque is caused by the fact that the fuel is injected and supplied to the cylinders of the engine, which is larger by the excess injection amount than during normal fuel injection. For example, after the time when the driver releases the accelerator pedal and sets the accelerator operation amount to 0, an extra portion of the injection amount corresponding to the injection amount during idling is to be injected. Since a larger amount is injected by the injection amount, it is possible to suppress the driver from feeling an unintended acceleration. According to the third aspect of the present invention, the slip ratio of the torque converter or the lockup clutch that transmits the engine output shaft torque to the transmission as the engine torque balance means increases the slip ratio by the increase of the engine output shaft torque. Increase means are provided. Accordingly, it is possible to consume an increase in engine output shaft torque that is increased by an extra injection amount than during normal fuel injection and caused by injecting and supplying fuel to the cylinders of the engine.

  According to the invention described in claim 4, as the engine torque balance means, the braking force is applied to the drive shaft or the drive wheel to which the engine output shaft torque is transmitted via the transmission and the differential mechanism by the increase of the engine output shaft torque. A braking force adding means is provided. Accordingly, it is possible to consume an increase in engine output shaft torque that is increased by an extra injection amount than during normal fuel injection and caused by injecting and supplying fuel to the cylinders of the engine. According to the fifth aspect of the present invention, the throttle valve is set to the fully closed side with respect to the required throttle opening set corresponding to the accelerator operation amount of the driver by the increase of the engine output shaft torque. By closing, the resistance of the intake air sucked into the engine cylinder is increased and the engine rotation speed is decreased. Accordingly, it is possible to consume an increase in engine output shaft torque that is increased by an extra injection amount than during normal fuel injection and caused by injecting and supplying fuel to the cylinders of the engine.

  According to the sixth aspect of the present invention, the injector is mounted corresponding to each cylinder of the engine, and is controlled from the control chamber and the common rail that perform back pressure control of the command piston that operates integrally with the nozzle needle. A fuel supply path for supplying high pressure fuel into the room, a fuel return path for overflowing high pressure fuel from the control room to the low pressure side of the fuel system, and an electromagnetic valve for opening and closing the fuel return path are provided. According to the seventh aspect of the present invention, as the pressure drop accelerating means, the solenoid valve of the injector is driven to open, so that the high pressure fuel in the control chamber overflows to the low pressure side of the fuel system, and the nozzle An electromagnetic valve drive circuit for injecting fuel from the injector by opening the needle is provided. In this case, by driving the solenoid valve to open, high pressure fuel overflows from the control chamber to the low pressure side of the fuel system, and the fuel pressure in the control chamber decreases. As a result, the nozzle needle is opened and the high-pressure fuel in the common rail is injected into the cylinder of the engine, so that the engine rotates.

  According to the eighth aspect of the present invention, the fuel pressure in the common rail (actual fuel pressure) detected by the fuel pressure detecting means is the engine operating state (for example, the basic injection amount, the required injection amount, the command injection amount, and the engine speed). If the target fuel pressure is higher than the target fuel pressure set in response to the speed, the injector solenoid valve of a cylinder different from the cylinder that performs normal injection is connected to the nozzle before the normal injection (including immediately before normal injection). By performing idle driving of the solenoid valve, which is driven to open within a time width shorter than the valve opening delay time until the needle opens, high pressure fuel in the control chamber overflows to the low pressure side of the fuel system. As a result, fuel injection from the injector of the cylinder for normal injection to the cylinder of the engine can be performed at a fuel pressure closer to the target fuel pressure, so that the engine combustion state deteriorates (for example, the amount of NOx generated increases) and combustion noise It becomes possible to suppress the deterioration of the level.

  According to the ninth aspect of the present invention, the fuel pressure in the common rail (actual fuel pressure) detected by the fuel pressure detecting means is the engine operating state (for example, the basic injection amount, the required injection amount, the command injection amount, and the engine speed). If the target fuel pressure is higher than the target fuel pressure, the nozzle needle is opened before the normal injection (including immediately before the normal injection). By performing idle driving of the solenoid valve, which is driven to open in a time width shorter than the valve opening delay time until valve opening, the high pressure fuel in the control chamber overflows to the low pressure side of the fuel system. As a result, fuel injection from the injector of the cylinder for normal injection to the cylinder of the engine can be performed at a fuel pressure closer to the target fuel pressure, so that the engine combustion state deteriorates (for example, the amount of NOx generated increases) and combustion noise It becomes possible to suppress the deterioration of the level.

  According to the tenth aspect of the present invention, the number of idle driving of the solenoid valve in a cylinder different from the cylinder for normal injection or in the cylinder for normal injection is determined according to the deviation between the actual fuel pressure and the target fuel pressure. Set. For example, the greater the deviation between the actual fuel pressure and the target fuel pressure, the greater the number of idle driving of the solenoid valve, the closer the fuel pressure is to the target fuel pressure, the normal injection from the injector of the cylinder to the engine cylinder Fuel injection can be performed.

  According to the eleventh aspect of the invention, as the pressure drop accelerating means, energy higher than the power supply voltage is stored in the capacitor, and the stored energy is released from the capacitor, so that the solenoid valve is driven to be blown out. A drive circuit is provided. If the number of idle driving of the solenoid valve in the cylinder different from the cylinder for normal injection or the cylinder for normal injection is two or more times, the standby interval between the idle driving of the solenoid valve is set as the charge amount of the capacitor. By setting the time interval to correspond to, do not perform the idle driving of the solenoid valve by the next non-injection pulse until the standby interval elapses after the idle drive of the solenoid valve by the first non-injection pulse is performed. can do.

  In this way, after waiting for recovery of the charged amount of the capacitor that has released the stored energy, the idle driving of the solenoid valve with the next non-injection pulse is performed, so that the number of idle driving of the solenoid valve is two times or more. However, since all of the solenoid valves can be driven satisfactorily, the fuel pressure in the common rail can be reduced (decompressed) efficiently, and the cylinder injectors that perform regular injection at a fuel pressure closer to the target fuel pressure. Therefore, the deterioration of the combustion state of the engine (for example, increase in the amount of NOx generated) and the deterioration of the combustion noise level can be suppressed.

  The best mode for carrying out the present invention is to positively control the fuel pressure in the common rail even when regular fuel injection is performed, with the aim of suppressing deterioration of the combustion state and combustion noise level of the engine. Realized by stepping down the pressure. In addition, the purpose of controlling the common rail pressure with higher accuracy while eliminating the need for the pressure reducing valve and the pressure reducing valve driving circuit has been realized by actively reducing the fuel pressure in the common rail. Furthermore, the object of suppressing the driver from feeling unintentional acceleration is realized by consuming an increase in engine output shaft torque caused by injecting fuel by an excess injection amount.

[Configuration of Example 1]
FIGS. 1 to 7 show the first embodiment of the present invention, FIG. 1 is a diagram showing the overall configuration of a common rail fuel injection system, and FIG. 2 is a diagram showing an injector structure and an injector drive circuit. is there.

  A fuel injection device for an internal combustion engine according to the present embodiment is a common rail fuel injection system (accumulated pressure) known as a fuel injection system for an internal combustion engine (hereinafter referred to as an engine) such as a multi-cylinder diesel engine mounted on a vehicle such as an automobile. A plurality of electromagnetic fuel injection valves (hereinafter referred to as injectors) mounted on the common rail 1 corresponding to each cylinder of the engine 2. ) Through the combustion chamber of each cylinder of the engine 2.

  Here, an output shaft of the engine 2 (for example, a crankshaft: hereinafter referred to as a crankshaft 3) is a drive shaft (drive shaft) that transmits rotational power of the engine 2 via a torque converter and a lock-up clutch as an automatic clutch mechanism (not shown). And it is connected with the input shaft of the automatic transmission as a power transmission device for transmitting to a driving wheel (drive wheel). In this embodiment, an automatic transmission that shifts the rotational speed of the engine 2 to a predetermined gear ratio (hereinafter referred to as transmission 4) is mounted as an automatic transmission. Yes. A manual transmission may be used as the power transmission device.

  The common rail fuel injection system of the present embodiment pressurizes the fuel sucked into the pressurizing chamber through the common rail 1 for accumulating high-pressure fuel corresponding to the fuel injection pressure and the intake metering valve (SCV) described later. A fuel supply pump (supply pump) 5 of an intake fuel metering system for increasing the pressure, and a plurality (four in this example) of injectors 6 for supplying fuel into a combustion chamber of each cylinder of the engine 2 at a predetermined injection timing. And an engine control unit (hereinafter referred to as “ECU”) 10 that electronically controls a suction metering valve of the supply pump 5 and a solenoid valve (described later) of the injector 6. The common rail 1 is connected to a discharge port of a supply pump 5 that discharges high-pressure fuel through a fuel supply pipe 11 serving as a high-pressure pipe. A pressure limiter 14 is attached to a relief pipe (fuel return pipe) 13 from the common rail 1 to the fuel tank 12. The pressure limiter 14 opens when the fuel pressure in the common rail 1 exceeds the limit set pressure, and keeps the fuel pressure in the common rail 1 below the limit set pressure.

  The supply pump 5 is provided with two or more pumping systems (pump elements) that pressurize the sucked low-pressure fuel to increase the pressure and supply the pressure into the common rail 1 and supply fuel into all the pumping systems with one suction metering valve 7. This is a high-pressure supply pump of the type that controls the amount by metering the amount of intake fuel. This supply pump 5 is a known feed pump (low pressure supply pump) that pumps low pressure fuel from a fuel tank 12 by rotating a pump drive shaft (drive shaft or camshaft) 8 as the crankshaft 3 of the engine 2 rotates. : A cam (not shown) that is rotationally driven by the pump drive shaft 8, and a plurality of plungers that are driven by this cam to reciprocate between the top dead center and the bottom dead center (see FIG. And a plurality of pressurizing chambers (plunger chambers: not shown) that pressurize the fuel by reciprocating movement of these plungers to increase the pressure.

  The supply pump 5 pressurizes and raises the pressure of the low-pressure fuel sucked into the plurality of pressurizing chambers from the fuel tank 12 through the fuel supply piping 15 by reciprocatingly sliding the plunger in the pump cylinder. A fuel filter (not shown) is installed in the middle of the fuel supply pipe 15. The supply pump 5 is provided with a leak port so that the internal fuel temperature does not become high, and the leaked fuel from the supply pump 5 is returned to the fuel tank 12 via the fuel recirculation pipe 16. Here, in the middle of the fuel suction path (not shown) formed in the supply pump 5 from the feed pump to the pressurizing chamber, the degree of opening of the fuel suction path (the lift amount of the valve element or the valve hole) An intake metering valve 7 for adjusting the opening area is attached. The intake metering valve 7 is electronically controlled by a pump drive current (pump drive signal) applied from the ECU 10 via a pump drive circuit (not shown), so that the fuel suction sucked into the pressurizing chamber of the supply pump 5 is performed. The amount of fuel discharged from the pressurizing chamber of the supply pump 5 into the common rail 1 is controlled by adjusting the amount.

  The intake metering valve 7 includes a valve body (not shown) that changes the opening degree of the fuel intake path in accordance with the lift amount, a solenoid coil that drives the valve body in the valve closing direction (or valve opening direction), and the like. And a valve body urging means (not shown) such as a spring for urging the valve body in the valve opening direction (or valve closing direction). doing. The intake metering valve 7 adjusts the amount of fuel discharged from the pressurizing chamber of the supply pump 5 into the common rail 1 in proportion to the magnitude of the pump drive current applied to the solenoid coil. The fuel pressure in the common rail 1 (hereinafter referred to as common rail pressure) corresponding to the injection pressure of the fuel supplied from the injector 6 into the combustion chamber of each cylinder of the engine 2 is changed.

  A plurality of injectors 6 mounted corresponding to each cylinder of the engine 2 are connected to downstream ends of a plurality of fuel supply pipes (branch pipes) 17 branched from the common rail 1, and combustion of each cylinder of the engine 2 is performed. A fuel injection nozzle 21 for injecting fuel into the room, a two-way valve type electromagnetic valve (hereinafter abbreviated as electromagnetic valve) 23 as an actuator for driving a nozzle needle 22 accommodated in the fuel injection nozzle 21 in the valve opening direction; And an electromagnetic fuel injection valve composed of a spring 24 or the like as a needle biasing means for biasing the nozzle needle 22 in the valve closing direction. The fuel injection nozzle 21 includes a nozzle body having a plurality of injection holes 25 and a nozzle needle 22 that is slidably accommodated in the nozzle body and opens and closes the plurality of injection holes 25.

  Note that a command piston 27 that moves in the vertical direction in the figure in conjunction with the nozzle needle 22 is accommodated in a nozzle body (housing) 26 including a nozzle body and a nozzle holder connected to the nozzle body. Further, a back pressure control chamber 30 that performs back pressure control of the command piston 27 that operates integrally with the nozzle needle 22 is provided in the housing 26. Further, a fuel supply path 31 for introducing high-pressure fuel supplied from the common rail 1 through the fuel supply pipe 17 into the fuel reservoir 29 and the back pressure control chamber 30 is formed in the housing 26. Further, the fuel overflowing from the fuel reservoir 29 via the sliding gap between the nozzle needle 22 and the housing 26 and the fuel overflowing from the back pressure control chamber 30 via the sliding gap between the command piston 27 and the housing 26 are: It is configured to flow into a fuel return path 34 on the electromagnetic valve 23 side through a spring chamber 32 that houses the spring 24 and a fuel return path 33. Reference numerals 35 and 36 denote inlet-side and outlet-side orifices (fixed restrictors) for adjusting the flow rate of the passing fuel. The outlet side orifice 36 is formed in an orifice plate 37 fixed in the housing 26.

  Here, the electromagnetic valve 23 of the injector 6 includes a solenoid coil 42 electrically connected to an in-vehicle power source (battery) 41 via an injector drive circuit (electromagnetic valve drive circuit: EDU) 9, and a magnetomotive force of the solenoid coil 42. And a return spring 44 as a valve urging means for urging the valve 43 in the valve closing direction (downward in the figure). Has been. The solenoid valve 23 is provided with fuel discharged from each sliding portion in the injector 6 through the fuel return path 33 to the fuel return path 34 on the solenoid valve 23 side, and an outlet side orifice 36 from the back pressure control chamber 30. A leak port 45 for overflowing the fuel discharged to the fuel return path 34 on the electromagnetic valve 23 side to the fuel tank 12 on the low pressure side of the fuel system is provided, and each sliding portion in the injector 6 is provided. The leaked fuel from the back pressure control chamber 30 flows out of the fuel recirculation path 34 and is returned to the fuel tank 12 through the fuel recirculation pipe 19.

  As shown in FIG. 2, when the injector drive circuit 9 receives an injector drive signal from the ECU 10, the injector drive circuit 9 individually applies pulse-shaped injectors to the solenoid coils 42 of the solenoid valves 23 of the injectors 6 mounted for each cylinder of the engine 2. This is a solenoid valve drive circuit that opens the solenoid valve 23 by applying a drive current. This injector drive circuit 9 is composed of a constant current circuit 51 that controls the injector drive current flowing through the solenoid coil 42 of the solenoid valve 23 of the injector 6 to a predetermined value or less, for example, a DC-DC converter that is controlled by switching, and the like. A booster circuit 52 that boosts the power supply voltage from the power supply 41, a capacitor 53 that accumulates energy higher than the power supply voltage, a charge amount detection circuit 54 that detects the charge amount of the capacitor 53, and a switching operation that is controlled by a control circuit (not shown). An element (for example, a semiconductor switching element such as a MOSFET, an IGBT, or a power transistor) 55 is formed.

  The injector drive circuit 9 accumulates energy higher than the power supply voltage boosted by the booster circuit 52 in the capacitor 53, and at a predetermined timing (when a pulsed injector drive signal from the ECU 10 is applied). 55 is operated to apply a pulsed injector driving current to the solenoid coil 42 of the electromagnetic valve 23 of the injector 6 by releasing (discharging) the stored energy, thereby driving the valve 43 of the electromagnetic valve 23 to open. As a result, the fuel overflows from the back pressure control chamber 30 of the injector 6 to the low pressure side of the fuel system via the fuel recirculation path 34, thereby pushing down the fuel pressure in the back pressure control chamber 30 (the nozzle needle 22 downward in the figure). When the fuel pressure in the fuel reservoir 29 (the pressure acting on the side pushing up the nozzle needle 22 upward) overcomes the urging force of the spring 24, the nozzle needle 22 moves upward in the figure. Start the lift to. That is, after a predetermined valve opening delay time has elapsed since the energization of the solenoid coil 42 of the electromagnetic valve 23 of the injector 6 has started, the nozzle needle 22 is separated from the valve seat of the nozzle body and opens. While the nozzle needle 22 is open, the high-pressure fuel accumulated in the common rail 1, the fuel supply pipe (branch pipe) 17, the fuel reservoir 29 of the injector 6 and the fuel supply path 31 is supplied to each cylinder of the engine 2. Injected into the combustion chamber. As a result, the engine 2 is operated.

  Then, energization to the solenoid coil 42 of the solenoid valve 23 of the injector 6 is stopped, and the high pressure fuel supplied from the common rail 1 through the fuel supply path 31 into the back pressure control chamber 30 is filled in the back pressure control chamber 30. Then, the fuel pressure in the back pressure control chamber 30 (pressure that acts to push the nozzle needle 22 downward in the figure) and the urging force of the spring 24 push up the fuel pressure in the fuel reservoir 29 (the nozzle needle 22 upward in the figure). The nozzle needle 22 starts to move downward in the figure at a stage where the pressure acting on the side is overcome. That is, after a predetermined valve closing delay time has elapsed since the energization of the solenoid coil 23 of the solenoid valve 23 of the injector 6 has been stopped, the nozzle needle 22 is seated on the valve seat of the nozzle body and closes.

  The ECU 10 of this embodiment includes a CPU for performing control processing and arithmetic processing, various programs, a storage device for storing control logic and control data (ROM or memory such as RAM and standby RAM), an input circuit, an output circuit, A microcomputer and a pump drive circuit having a known structure configured to include functions such as a power supply circuit are incorporated. The pump drive circuit is pump drive means for applying a pump drive current to the solenoid coil of the suction metering valve 7 of the supply pump 5.

  Then, 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 fuel injection amount or the common rail pressure is set to the control target value. It is comprised so that it may become electronically controlled. Further, when the ignition switch is turned off (IG / OFF) and the supply of ECU power is cut off, the ECU 10 forcibly terminates the above control based on the control program and control logic stored in the memory. It is configured. The ECU 10 outputs an output value (common rail pressure signal) output from the fuel pressure sensor 65 installed on the common rail 1, sensor signals from various other sensors, and switch signals from some switches installed in the vehicle. Are input to a microcomputer built in the ECU 10 after being A / D converted by an A / D converter.

  An input circuit of the microcomputer includes an accelerator operation amount (hereinafter referred to as an accelerator opening amount) which is a depression amount of a driver's accelerator pedal (not shown) as an operation state detecting means for detecting an operation state and an operation condition of the engine 2. Accelerator opening sensor (accelerator operation amount detecting means) 61 for detecting ACCP), crank angle sensor 62 for detecting the rotation angle of the crankshaft 3 of the engine 2, and engine coolant temperature (THW) are detected. A cooling water temperature sensor 63 for performing the operation, a fuel temperature sensor 64 for detecting a fuel temperature (THF) on the suction side of the pump sucked into the supply pump 5, and the like are connected. Among the above sensors, the accelerator opening sensor 61 outputs an accelerator opening signal corresponding to the accelerator opening (ACCP).

  The crank angle sensor 62 faces the outer periphery of an NE timing rotor (not shown) attached to the crankshaft 3 of the engine 2 or the pump drive shaft (drive shaft or camshaft) 8 of the supply pump 5. The electromagnetic pickup coil is provided. On the outer peripheral surface of the NE timing rotor, a plurality of convex teeth are arranged for each predetermined rotation angle. Then, the crank angle sensor 62 repeats the approach and separation of the convex teeth of the NE timing rotor with respect to the crank angle sensor 62, thereby causing a pulsed rotational position signal (NE signal pulse), particularly the engine 2, by electromagnetic induction. NE signal pulses synchronized with the rotational speed of the crankshaft 3 (engine rotational speed) and the rotational speed of the supply pump 5 (pump rotational speed) are output. The ECU 10 functions as a rotational speed detecting means for detecting the engine rotational speed (also referred to as engine rotational speed: NE) by measuring the interval time of NE signal pulses output from the crank angle sensor 62.

  Further, the ECU 10 is configured to perform CAN communication (for example, current gear position, engine output shaft torque increase / decrease request, idle up request, etc.) between the transmission control unit (TCM: not shown) and the air conditioner system. Has been. Here, the TCM is connected to the accelerator opening sensor 61 and a vehicle speed sensor (not shown) for detecting the travel speed of the vehicle (hereinafter referred to as vehicle speed). The vehicle speed sensor is, for example, a reed switch type vehicle speed sensor or a magnetoresistive element type vehicle speed sensor, and measures the rotational speed of the output shaft of the transmission 4 and outputs a vehicle speed signal corresponding to the traveling speed (vehicle speed) of the vehicle. Vehicle speed detection means. A wheel speed sensor that detects the wheel speed of the vehicle may be used as the vehicle speed detecting means.

  The TCM is an accelerator position signal corresponding to the accelerator position (ACCP) from the accelerator position sensor 61 and a vehicle speed corresponding to the vehicle speed (SPD) from the vehicle speed sensor when the select lever is in the D range or the 2 range. Depending on the signal, the hydraulic circuit is switched by a combination of ON and OFF of an actuator such as a solenoid valve for shifting, and a plurality of gear positions (first speed to fourth speed in the case of four forward speeds or five speeds in the forward direction) 1st speed to 5th speed are selected (gear position detecting means) to control the shift state of the transmission 4. As a result, a shift is performed.

  Then, after the ignition switch is turned on (IG / ON), the ECU 10 calculates the optimum common rail pressure corresponding to the operating state or operating condition of the engine 2 at every predetermined timing, and supplies it via the pump drive circuit. Fuel pressure control means (common rail pressure control means) for driving the solenoid coil of the suction metering valve 7 of the pump 5 is provided. This has fuel pressure determining means for calculating a target common rail pressure (target fuel pressure: PFIN) based on the engine speed (NE) and the required injection amount (QFIN), in order to achieve this target fuel pressure (PFIN). And applied to the solenoid coil of the intake metering valve 7 based on the pressure deviation (ΔP) between the common rail pressure (hereinafter referred to as actual fuel pressure: Pc) detected by the fuel pressure sensor 65 and the target fuel pressure (PFIN). The pump drive current is adjusted, and the fuel discharge amount of the supply pump 5 is feedback-controlled.

  Then, the ECU 10 calculates the optimum fuel injection amount and injection timing corresponding to the operating state or operating conditions of the engine 2, and sets the solenoid coil of the solenoid valve 23 of the injector 6 of each cylinder via the injector drive circuit (EDU). It has the injection quantity control means to drive. Further, the ECU 10 determines an injection amount larger than the required injection amount (QFIN) when the actual fuel pressure (Pc) detected by the fuel pressure sensor 65 is higher than the target fuel pressure (PFIN) by a first predetermined value (α) or more. The common rail pressure is reduced by the control, that is, the first pressure drop accelerating means for actively reducing the common rail pressure is provided. Further, the ECU 10 controls the common rail pressure to be reduced by the non-injection pulse in the injector 6 that performs normal injection when the actual fuel pressure (Pc) is higher than the target fuel pressure (PFIN) by a second predetermined value (β) or more. Second pressure drop promoting means for actively lowering the pressure is provided. Further, the ECU 10 controls the common rail pressure to be reduced by the non-injection pulse other than the injector 6 that performs normal injection when the actual fuel pressure (Pc) is higher than the target fuel pressure (PFIN) by a third predetermined value (γ) or more. Third pressure drop promoting means for actively lowering the common rail pressure is provided. Here, α> β> γ and γ ≠ 0. Further, the ECU 10 has an engine torque balance means for consuming an increase in engine output shaft torque caused by injecting fuel by an injection amount that is more than the required injection amount (QFIN). .

[Control Method of Example 1]
Next, a control method of the common rail fuel injection system according to this embodiment will be briefly described with reference to FIGS. Here, FIGS. 3 and 4 are flowcharts showing a method of controlling the injector injection amount and the common rail pressure. The main routines of FIGS. 3 and 4 are executed at predetermined timings after the ignition switch is turned on (IG · ON). The fuel injection amount (basic injection amount, required injection amount, etc.) injected and supplied into the combustion chamber of each cylinder of the engine 2 may be calculated individually for each cylinder of the engine 2.

  First, sensor signals from various sensors are captured (step S1). Specifically, the accelerator opening (ACCP) is calculated based on the accelerator opening signal acquired from the accelerator opening sensor 61 (accelerator operation amount detecting means). Further, the engine rotational speed (NE) is calculated by measuring the interval time of NE signal pulses taken in from the crank angle sensor 62 (engine rotational speed detecting means). Further, the actual fuel pressure (Pc) is calculated based on the common rail pressure signal taken from the fuel pressure sensor 65 (fuel pressure detecting means).

  Next, the basic injection amount (Q) is calculated from the accelerator opening (ACCP) and the engine speed (NE) (step S2). Next, the injection amount correction amount (ΔQ) for the basic injection amount (Q) is calculated from the engine coolant temperature (THW), the fuel temperature (THF), and the like (correction amount calculation means: step S3). Here, the injection amount correction amount (ΔQ) may be calculated using known proportional integral (PI) control or proportional integral derivative (PID) control. In this case, the injection amount correction amount (ΔQ) is based on the vehicle speed deviation between the actual vehicle travel speed (vehicle speed) detected by the vehicle speed sensor and the target travel speed calculated corresponding to the accelerator opening (ACCP). The feedback is calculated. Next, the required injection amount (also called command injection amount: QFIN) is calculated by adding the injection amount correction amount (ΔQ) calculated in step S3 to the basic injection amount (Q) calculated in step S2 (step S4). ).

  Next, a command injection timing (T) is calculated from the engine speed (NE) and the required injection amount (QFIN) (injection timing determination means: step S5). Next, the valve opening drive time (energization time, injection pulse length, command injection period: TQ) of the electromagnetic valve 23 of the injector 6 is calculated from the actual fuel pressure (Pc) and the required injection amount (QFIN) (injection period). Determination means: Step S6). Next, a target fuel pressure (PFIN) is calculated from the required injection amount (QFIN) and the engine speed (NE) (step S7). When the actual fuel pressure (Pc) detected by the fuel pressure sensor 65 is equal to or lower than the target fuel pressure (PFIN), the solenoid of the solenoid valve 23 of the injector 6 of each cylinder is passed through the injector drive circuit (EDU) 9. A pulsed injector drive current is applied to the coil 42 until the command injection period (TQ) elapses from the command injection timing (T) (injector drive means: step S14). Thereafter, the main routine of FIGS. 3 and 4 is exited.

  Also, when the actual fuel pressure (Pc) is equal to or lower than the target fuel pressure (PFIN), PI is set so that the actual fuel pressure (Pc) detected by the fuel pressure sensor 65 substantially matches the target fuel pressure (PFIN). Using the (proportional integral) control or PID (proportional integral derivative) control, the supply pump 5 performs feedback control of the fuel discharge amount of the supply pump 5 and the common rail pressure boosting control is executed. Specifically, there is a correlation with the fuel discharge amount of the supply pump 5 based on the pressure deviation (ΔP) between the actual fuel pressure (Pc) and the target fuel pressure (PFIN) (the solenoid coil of the intake metering valve 7). Feedback control of the pump drive current. This corresponds to the ON / OFF ratio (energization) of the control pulse signal (pulsed pump drive signal) per unit time corresponding to the pressure deviation (ΔP) between the actual fuel pressure (Pc) and the target fuel pressure (PFIN). High-precision digital control is possible by adjusting the time ratio and duty ratio) and using duty control that changes the lift amount of the valve body of the intake metering valve 7 and the opening area of the fuel intake path of the supply pump 5 become. As a result, the control response and followability of the common rail pressure with respect to the target fuel pressure (PFIN) can be improved.

  On the other hand, when the actual fuel pressure (Pc) is higher than the target fuel pressure (PFIN), first, whether or not the actual fuel pressure (Pc) is higher than the target fuel pressure (PFIN) by a first predetermined value (α) or more. Is determined (step S8). If the determination result is NO, it is determined whether or not the actual fuel pressure (Pc) is higher than the target fuel pressure (PFIN) by a second predetermined value (β) or more (step S9). When the determination result is NO, it is determined whether or not the actual fuel pressure (Pc) is higher than the target fuel pressure (PFIN) by a third predetermined value (γ) or more. That is, it is determined whether the actual fuel pressure (Pc) is higher than the target fuel pressure (PFIN) (step S10). When this determination result is NO, the boost control by the supply pump 5 described above is executed.

  If the decision result in the step S10 is YES, as shown in FIG. 5, the solenoid coil 42 of the solenoid valve 23 of the injector 6 of a cylinder other than the next cylinder to be normally injected (a cylinder different from the cylinder to be normally injected). In addition, a non-injection pulse for non-injection is energized (pressure drop promotion means: step S11). Thereafter, the process proceeds to step S14. Note that the decompression control method using the non-injection pulse in the injectors of the cylinders other than the normal cylinder that performs normal injection shown in FIG. 5 is performed immediately before the injector 6 of the cylinder that performs normal injection performs fuel injection, except for the next cylinder that performs normal injection. The example in which the injector 6 of this cylinder performs dynamic leak by a non-injection pulse is shown.

  Specifically, when the next cylinder to be normally injected is the # 1 cylinder, the normal injection is performed two times after the # 1 cylinder (after 360 ° CA) before the fuel injection of the # 1 cylinder # 4. A non-injection pulse is applied to the solenoid coil 42 of the solenoid valve 23 of the cylinder injector 6. In addition, when the next cylinder to be normally injected is the # 2 cylinder, the injector for # 3 cylinder that performs the normal injection two times after the # 2 cylinder (after 360 ° CA) before the fuel injection of the # 2 cylinder. The non-injection pulse is energized to the solenoid coil 42 of the sixth solenoid valve 23. In addition, when the next cylinder to be normally injected is the # 3 cylinder, the injector for the # 2 cylinder that performs the normal injection two times after the # 3 cylinder (after 360 ° CA) before the fuel injection of the # 3 cylinder. The non-injection pulse is energized to the solenoid coil 42 of the sixth solenoid valve 23. Also, when the next cylinder to be normally injected is the # 4 cylinder, the injector for the # 1 cylinder that performs the normal injection before the fuel injection of the # 4 cylinder and after the cylinder # 2 (after 360 ° CA) The non-injection pulse is energized to the solenoid coil 42 of the sixth solenoid valve 23.

  Here, the normal injection pulse shown in FIG. 5 means that the electromagnetic valve 23 of the injector 6 is opened with a time width longer than the valve opening delay time until the nozzle needle 22 opens to perform normal injection. A pulse-like injector driving current that can be valve-driven, and the pulse width of this injector driving current is set corresponding to the command injection period (TQ) calculated in step S6. In FIG. 5, the opening of the electromagnetic valve 23 of the injector 6 is performed a plurality of times during the engine compression stroke, and the injection rate is small before main injection with a large injection rate that can be, for example, engine output shaft torque. The injection rate waveform at the time of implementing pilot injection is shown.

  Further, the non-injection pulse shown in FIG. 5 means that the electromagnetic valve 23 of the injector 6 of the cylinder other than the next cylinder to be normally injected is opened with a time width shorter than the valve opening delay time until the nozzle needle 22 is opened. A pulse-like injector drive current that can be valve-driven (performs idling drive of the solenoid valve 23), depending on the pressure deviation (ΔP) between the actual fuel pressure (Pc) and the target fuel pressure (PFIN), The number of idle driving times of the electromagnetic valve 23 is calculated. For example, the larger the pressure deviation (ΔP) between the actual fuel pressure (Pc) and the target fuel pressure (PFIN), the greater the number of idle driving of the solenoid valve 23 for the purpose of improving the pressure reduction performance of the common rail pressure. Is done.

  Then, when a non-injection pulse is applied to the solenoid coil 42 of the solenoid valve 23 of the injector 6 of the cylinder 6 other than the next cylinder to be normally injected, the valve 43 of the solenoid valve 23 is opened and the cylinders other than the next cylinder to be normally injected are opened. The fuel overflows from the fuel supply path 31 of the injector 6 and the back pressure control chamber 30 through the fuel recirculation path 34 into the fuel tank 12 on the low pressure side of the fuel system. That is, immediately before the fuel injection in the next cylinder for normal injection is performed, the fuel pressure in the back pressure control chamber 30, that is, the common rail pressure, is reduced by dynamic leak from the injectors 6 in the cylinders other than the next cylinder for normal injection. Therefore, the conventional technology for reducing the pressure only by the amount of static leak that overflows to the low pressure side of the fuel system from the sliding portions of the injectors 6 and the like of all cylinders of the engine 2 and the gaps between the components. As compared with the above, the common rail pressure can be made closer to the target fuel pressure (PFIN) in the cylinders other than the next cylinder that performs normal injection. As a result, at a common rail pressure closer to the target fuel pressure (PFIN), a plurality of injection holes 25 formed at the tip of the nozzle body of the injector 6 of the next cylinder that performs normal injection enter the combustion chamber of the cylinder of the engine 2. Fuel injection can be performed. Therefore, it is possible to suppress deterioration of the combustion state of the engine (for example, increase in the amount of NOx generated) and deterioration of the combustion noise level.

  If the decision result in the step S9 is YES, as shown in FIG. 6, a non-injection pulse for non-injection is energized to the solenoid coil 42 of the solenoid valve 23 of the injector 6 of the next cylinder that performs normal injection. (Pressure drop promoting means: step S12). Thereafter, the process proceeds to step S14. Note that the decompression control method using the non-injection pulse in the injector of the next cylinder that performs normal injection shown in FIG. 6 is performed immediately before the injector 6 of the cylinder that performs normal injection performs fuel injection. The example which performs a dynamic leak with a non-injection pulse is shown.

  Specifically, when the next cylinder to be normally injected is the # 1 cylinder, the non-injection pulse is energized to the solenoid coil 42 of the solenoid valve 23 of the injector 6 of the # 1 cylinder before the fuel injection of the # 1 cylinder. To do. When the next cylinder to be normally injected is the # 2 cylinder, a non-injection pulse is energized to the solenoid coil 42 of the solenoid valve 23 of the injector 6 of the # 2 cylinder before the fuel injection of the # 2 cylinder. Further, when the next cylinder to be normally injected is the # 3 cylinder, the non-injection pulse is supplied to the solenoid coil 42 of the solenoid valve 23 of the injector 6 of the # 3 cylinder before the fuel injection of the # 3 cylinder. When the next cylinder to be normally injected is the # 4 cylinder, the non-injection pulse is supplied to the solenoid coil 42 of the solenoid valve 23 of the injector 6 of the # 4 cylinder before the fuel injection of the # 4 cylinder.

  Here, the normal injection pulse shown in FIG. 6 is set corresponding to the command injection period (TQ) calculated in step S6 as in FIG. In FIG. 6, as in FIG. 5, the solenoid valve 23 of the injector 6 is driven open several times during the engine compression stroke, for example, before main injection with a large injection rate that can be the engine output shaft torque. The injection rate waveform at the time of implementing pilot injection with a small injection rate is shown. Further, the non-injection pulse shown in FIG. 6 drives the electromagnetic valve 23 of the injector 6 of the next cylinder to perform normal injection with a time width shorter than the valve opening delay time until the nozzle needle 22 opens. The electromagnetic valve 23 is a pulse-like injector drive current capable of performing idling driving of the solenoid valve 23 according to the pressure deviation (ΔP) between the actual fuel pressure (Pc) and the target fuel pressure (PFIN). Is calculated. For example, the larger the pressure deviation (ΔP) between the actual fuel pressure (Pc) and the target fuel pressure (PFIN), the greater the number of idle driving of the solenoid valve 23 for the purpose of improving the pressure reduction performance of the common rail pressure. Is done.

  When a non-injection pulse is applied to the solenoid coil 42 of the solenoid valve 23 of the injector 6 of the next cylinder for normal injection, the valve 43 of the solenoid valve 23 opens and the fuel supply path of the injector 6 of the next cylinder for normal injection The fuel overflows from the fuel tank 12 on the low pressure side of the fuel system through the fuel recirculation path 34 from the back pressure control chamber 30 and the back pressure control chamber 30. That is, immediately before the fuel injection in the next cylinder for normal injection is performed, the fuel pressure in the back pressure control chamber 30, that is, the common rail pressure, can be lowered by dynamic leak from the injector 6 of the next cylinder for normal injection. Therefore, as compared with the conventional technique in which the pressure is reduced only by the static leak amount overflowing from the sliding portions of the injectors 6 and the like of all cylinders of the engine 2 and the gaps between the components to the low pressure side of the fuel system. Further, fine adjustment can be made so that the common rail pressure in the next cylinder for normal injection is more actively brought closer to the target fuel pressure (PFIN). Thus, fuel can be injected into the combustion chamber of the next cylinder of the engine 2 from the injector 6 of the next cylinder that performs normal injection at a common rail pressure closer to the target fuel pressure (PFIN). Therefore, it is possible to suppress deterioration of the combustion state of the engine (for example, increase in the amount of NOx generated) and deterioration of the combustion noise level.

  Further, if the determination result in step S8 is YES, that is, if the actual fuel pressure (Pc) is very high with respect to the target fuel pressure (PFIN), the cylinders other than the next cylinder that performs normal injection shown in FIG. Since the pressure reduction control method by the non-injection pulse in the injector of FIG. 6 and the pressure reduction control method by the non-injection pulse in the injector of the next cylinder for normal injection shown in FIG. 6 are not in time, the above steps are performed as shown in FIG. The valve opening drive time (command injection period: TQ) of the injector 6 of the next cylinder to be normally injected is an amount corresponding to the excess injection amount (ΔQ) so that the fuel is injected in excess of the required injection amount (QFIN) calculated in S4. Set only longer. Then, a normal injection pulse for normal injection is applied to the solenoid coil 42 of the solenoid valve 23 of the injector 6 of the next cylinder for normal injection (pressure drop promoting means: step S13). Note that the pressure reduction control method with the injection amount larger than the required injection amount shown in FIG. 7 is that the fuel injection of the injector 6 of the cylinder for normal injection and the dynamic leakage of the injector 6 of the next cylinder for normal injection due to the normal injection pulse. An example is shown.

  Specifically, an injection amount (required injection amount: QFIN + increase in injection amount: ΔQ) larger than the required injection amount (QFIN) is a regular injection timing (command injection timing: T), and # 1 cylinder → # 3 cylinder → # 4 cylinder → # 2 cylinder In this order, the fuel is recirculated from the fuel supply path 31 and the back pressure control chamber 30 of the injector 6 of the next cylinder for normal injection by injecting into the combustion chamber of each cylinder of the engine 2 a plurality of times. The fuel is overflowed into the fuel tank 12 on the low pressure side of the fuel system via the fuel system 34, and at the same time, the fuel is injected into the combustion chamber of each cylinder of the engine 2 a plurality of times. In particular, the actual fuel injection amount injected and supplied into the combustion chamber of the cylinder of the engine 2 becomes an injection amount (example) larger than the injection amount (conventional example) by an increase in the injection amount. The common rail pressure (= actual fuel pressure (example)) closer to the target fuel pressure (PFIN) than the pressure (conventional example)), from the injector 6 of the cylinder for normal injection into the combustion chamber of the cylinder of the engine 2 The fuel injection can be carried out. Therefore, it is possible to further suppress deterioration in the combustion state of the engine (for example, increase in the amount of NOx generated) and deterioration in the combustion noise level.

  Here, when the decompression control method shown in FIG. 7 is performed, in an area where the excess engine output shaft torque is felt as if the driver did not intend to accelerate, the transmission 4 is idled during that period and the excess engine output shaft torque is consumed. (Engine torque balance means) As this engine torque balance means, a slip ratio increasing means for increasing the slip ratio of the torque converter or lockup clutch that transmits the engine output shaft torque to the transmission 4 by the increase of the engine output shaft torque may be provided. As a result, as described above, an increase in the engine output shaft torque caused by injecting fuel into the combustion chamber of each cylinder of the engine 2 is increased by an extra injection amount than during normal normal injection. By consuming, for example, a small injection amount corresponding to the injection amount during idling is injected after the driver releases the accelerator pedal and sets the accelerator operation amount to 0 (accelerator opening: ACCP = 0%). Since the power should be ejected by the excessive injection amount, it is possible to suppress the driver from feeling unintended acceleration.

[Effect of Example 1]
In the conventional common rail fuel injection system, when the actual fuel pressure (Pc) is higher than the target fuel pressure (PFIN) and the required injection amount (QFIN) set by the driver's accelerator operation amount is very small. Although a pressure reducing valve is installed as a pressure reducing means that can positively reduce the common rail pressure, there is a demerit of cost increase by adding a pressure reducing valve and a pressure reducing valve drive circuit. Therefore, in the common rail fuel injection system according to the present embodiment, the control program or the control logic is changed using the existing configuration to actively control the reduction of the common rail pressure. Such common rail pressure depressurization control methods can be roughly divided into three depressurization control methods, but it is desirable to use them properly depending on the pressure deviation (ΔP) between the actual fuel pressure (Pc) and the target fuel pressure (PFIN).

  First, when the actual fuel pressure (Pc) is higher than the target fuel pressure (PFIN) by a third predetermined value (γ) or more, as shown in FIG. An injector driving pulse (non-injection pulse) having a pulse width that causes no injection even when the valve 43 of the electromagnetic valve 23 is opened is energized to the solenoid coil 42 of the electromagnetic valve 23 of the injector 6 of a cylinder other than the next cylinder to be injected. Thus, idle driving of the electromagnetic valve 23 of the injector 6 of the cylinder other than the next cylinder to be normally injected is performed. As a result, the fuel overflows from the back pressure control chamber 30 of the injector 6 of the cylinder other than the next cylinder that performs normal injection to the low pressure side of the fuel system via the fuel return path 34. That is, the common rail pressure is positively reduced by the amount of dynamic leak from the injector 6 of the cylinder other than the normal cylinder for normal injection by the dynamic leak from the injector 6 of the cylinder other than the normal cylinder for normal injection. The common rail pressure is corrected so that the normal injection is performed at the target fuel pressure (PFIN).

  At this time, the number of non-injection pulses is calculated according to the pressure deviation (ΔP) between the actual fuel pressure (Pc) and the target fuel pressure (PFIN), and the number of idle driving of the solenoid valve 23 is made variable. In the decompression control method shown in FIG. 5, the dynamic leak from the injector 6 of the cylinder other than the next cylinder to be normally injected is used. If the number of pulses is increased, a relatively large common rail pressure can be reduced.

  Next, when the actual fuel pressure (Pc) is higher than the target fuel pressure (PFIN) by a second predetermined value (β) or more, as shown in FIG. 6, immediately before the fuel injection of the next cylinder for normal injection, An injector driving pulse (non-injection pulse) having a pulse width that causes no injection even when the valve 43 of the electromagnetic valve 23 is opened is energized to the solenoid coil 42 of the electromagnetic valve 23 of the injector 6 of the next cylinder that performs regular injection, The solenoid valve 23 of the injector 6 of the next cylinder for normal injection is driven idle. As a result, the fuel overflows from the back pressure control chamber 30 of the injector 6 of the next cylinder for normal injection to the low pressure side of the fuel system via the fuel return path 34. That is, the common rail pressure is positively reduced by the amount of dynamic leak from the injector 6 of the cylinder other than the normal cylinder for normal injection by the dynamic leak from the injector 6 of the cylinder other than the normal cylinder for normal injection. The common rail pressure is corrected so that the normal injection is performed at the target fuel pressure (PFIN).

  In the depressurization control method shown in FIG. 6, the common cylinder pressure that is positively depressurized by the supply pump 5 or the depressurization control method shown in FIG. There is a possibility that the target fuel pressure (PFIN) may be changed or the target fuel pressure (PFIN) may be deviated again due to the change of the target fuel pressure (PFIN) immediately before the fuel injection, and if the common rail pressure needs to be reduced, Used as a fine adjustment just before fuel injection. Since the depressurization control is performed immediately before fuel injection of the next cylinder for normal injection, the number of idle driving of the solenoid valve 23 is limited, but the actual fuel pressure (Pc) and the target fuel are the same as in the depressurization control method shown in FIG. The number of non-injection pulses is calculated in accordance with the pressure deviation (ΔP) from the pressure (PFIN), and the number of idle driving times of the solenoid valve 23 is variable.

  Here, as described above, the decompression control method shown in FIG. 5 applies a non-injection pulse to the solenoid coil 42 of the solenoid valve 23 of the injector 6 of a cylinder other than the next cylinder that performs normal injection, and causes a common rail due to dynamic leakage. In this method, the pressure is positively reduced. However, since the pressure range in which the common rail pressure can be reduced by the amount of dynamic leak is small, the actual fuel pressure (Pc) is less than the target fuel pressure (PFIN) by a first predetermined value (α ) When the pressure deviation (ΔP) between the actual fuel pressure (Pc) and the target fuel pressure (PFIN) is very large as in the case where it is higher than the above, the control response and tracking of the common rail pressure with respect to the target fuel pressure (PFIN) I cannot expect much sex.

  Therefore, when the actual fuel pressure (Pc) is higher than the target fuel pressure (PFIN) by a second predetermined value (β) or more, for example, the driver suddenly removes his / her foot from the accelerator pedal (accelerator opening: ACCP). When the pressure deviation (ΔP) between the actual fuel pressure (Pc) and the target fuel pressure (PFIN) becomes very large, as shown in FIG. A pressure reduction control method is used in which the injection amount larger than the corresponding required injection amount (QFIN) is injected several times, the pressure width per unit time in which the common rail pressure can be reduced is increased, and the common rail pressure is greatly reduced.

  Since the decompression control method shown in FIG. 7 has a larger release amount of high-pressure fuel per unit time than the decompression control method shown in FIGS. 5 and 6 using only the dynamic leak amount, the target fuel pressure (PFIN) The control response and follow-up performance of the common rail pressure with respect to is further improved. However, in the decompression control method shown in FIG. 7, for example, after the driver suddenly removes his / her foot from the accelerator pedal and the accelerator operation amount (accelerator opening: ACCP) suddenly becomes 0%, a small injection amount is reduced. Because there is a lot of fuel to be injected, there is a possibility that the driver may feel unintentional acceleration. In order to suppress this driver's feeling, an increase in engine output shaft torque that is caused by injecting fuel into the combustion chamber of each cylinder of the engine 2 that is larger than the required injection amount (QFIN). Whether or not to perform engine torque balance means (for example, slip ratio increasing means for increasing the slip ratio of the torque converter or lockup clutch of the transmission 4 by the increase of the engine output shaft torque) and the gear position of the transmission 4 Judgment is made in the region of the excess injection amount.

  In the decompression control method of this embodiment, as shown in the flowcharts of FIGS. 3 and 4, when the actual fuel pressure (Pc) is higher than the target fuel pressure (PFIN) by a second predetermined value (β) or more. 6 is executed, and when the actual fuel pressure (Pc) is higher than the target fuel pressure (PFIN) by a third predetermined value (γ) or more, the pressure reduction control method shown in FIG. However, when the actual fuel pressure (Pc) is higher than the target fuel pressure (PFIN) by a second predetermined value (β) or more, the decompression control method shown in FIG. The pressure reduction control method shown in FIG. 6 may be executed when the pressure (Pc) is higher than the target fuel pressure (PFIN) by a third predetermined value (γ) or more.

  In the decompression control method of the present embodiment, as shown in the flowcharts of FIGS. 3 and 4, when the actual fuel pressure (Pc) is higher than the target fuel pressure (PFIN) by a first predetermined value (α) or more. 7 is executed, and when the actual fuel pressure (Pc) is higher than the target fuel pressure (PFIN) by a second predetermined value (β) or more, the pressure reduction control method shown in FIG. And when the actual fuel pressure (Pc) is higher than the target fuel pressure (PFIN) by a third predetermined value (γ) or more, the depressurization control method shown in FIG. When the pressure (Pc) is higher than the target fuel pressure (PFIN) by a first predetermined value (α) or more, the pressure reduction control method shown in FIG. 7 is executed, and the actual fuel pressure (Pc) is set to the target fuel pressure (Pc). When the second predetermined value (β) is higher than PFIN), the decompression control shown in FIG. Only the control method or the decompression control method shown in FIG. 6 may be executed. However, α> β and β ≠ 0.

  FIG. 8 shows a second embodiment of the present invention, and is a flowchart showing a pressure reduction control method using non-injection pulses. The subroutine shown in FIG. 8 is executed at predetermined timings after the ignition switch is turned on (IG / ON).

  In this embodiment, as shown in FIG. 2, the capacitor 53 is charged with energy (high voltage) boosted by the booster circuit 52 and higher than the battery voltage as the power supply voltage, and the stored energy is discharged from the capacitor 53. Then, an injector drive circuit that applies a non-injection pulse to the solenoid coil 42 of the solenoid valve 23 of the injector 6 of the cylinder 6 that is different from the cylinder that performs normal injection or the cylinder that performs normal injection, and actively reduces the common rail pressure by dynamic leakage. (Electromagnetic valve drive circuit) 9 is provided. The injector drive circuit 9 is a switching unit that electrically connects the charge amount detection circuit 54 that detects the charge amount of the capacitor 53, the constant current circuit 51, and the capacitor 53 and the solenoid coil 42 of the solenoid valve 23 of the injector 6. An element (for example, a semiconductor switching element such as a MOSFET, an IGBT, or a power transistor) 55 is incorporated.

  Note that the booster circuit 52 is a voltage conversion circuit configured by, for example, a DC-DC converter that is controlled by switching, and when the DC-DC converter starts operating, boosts the battery voltage, which is a power supply voltage, to a high voltage. (For example, DC high voltage of about 200V). The charge amount detection circuit 54 is a charge amount monitoring circuit that monitors the charge state of the capacitor 53, and outputs a charge completion signal to the ECU 10 or the like when the charge amount of the capacitor 53 reaches a predetermined charge amount. The ECU 10 outputs a pulsed injector drive signal to the injector drive circuit 9 at a predetermined timing after inputting the charge completion signal. The charging circuit that charges the capacitor 53 with a high voltage starts charging when the DC-DC converter starts operating after a predetermined time has elapsed since the end of the previous discharge.

  In this injector drive circuit 9, the battery voltage as the power supply voltage is boosted by the booster circuit 52 to be a high voltage (for example, a DC high voltage of about 200 V), the high voltage is charged in the capacitor 53, and the pulse voltage from the ECU 10 When the injector drive signal rises, the switching element 55 is operated to discharge the high voltage charged in the capacitor 53, and a large current (peak current) due to the discharge is different from the cylinder for normal injection, or Supplying to the solenoid coil 42 of the solenoid valve 23 of the injector 6 of the cylinder 6 for regular injection, the valve 43 of the solenoid valve 23 is driven to the valve opening side at high speed. Further, after the valve 43 of the solenoid valve 23 is opened, the solenoid of the solenoid valve 23 of the injector 6 of a cylinder different from the cylinder that performs normal injection or the cylinder 6 that performs normal injection in order to keep the valve 43 open. A constant current for holding is supplied to the coil 42, and the supply of the constant current is stopped in accordance with the fall of the pulse-like injector drive signal from the ECU 10, so that the valve 43 of the electromagnetic valve 23 is moved to the valve closing side. I try to drive it.

  Here, when the flowchart of FIG. 8 is started, as described in the first embodiment, the number of non-injection pulses is determined according to the pressure deviation (ΔP) between the actual fuel pressure (Pc) and the target fuel pressure (PFIN). It is done. The number of idle driving of the solenoid valve 23 of the injector 6 (the number of non-injection pulses applied to the solenoid coil 42) in the cylinders other than the next cylinder to be normally injected or the next cylinder to be normally injected is 2 or 3. It is determined whether or not the number of times is over (step S21). If this determination result is NO, the flowchart of FIG. 8 is exited.

  If the determination result in step S21 is YES, that is, if the number of non-injection pulses is two or three or more, the charge amount of the capacitor 53 measured by the charge amount detection circuit 54 is detected (step S22). . Next, the charge amount detection circuit 54 measures a standby interval (no-injection pulse interval) between idle driving of the solenoid valve 23 of the injector 6 in a cylinder other than the next cylinder that performs normal injection or the next cylinder that performs normal injection. The time interval corresponding to the charged amount of the capacitor 53 is set (or updated) at any time (step S23). Next, a non-injection pulse is applied to the solenoid coil 42 of the solenoid valve 23 of the injector 6 of the cylinder other than the next cylinder that performs normal injection or the next cylinder that performs normal injection. The idle driving of the solenoid valve 23 of the injector 6 in the next cylinder to be injected is performed (step S24). Thereafter, the flowchart of FIG. 8 is exited.

  Accordingly, it is possible to prevent the idle driving of the electromagnetic valve 23 by the next non-injection pulse from being performed until the standby interval elapses after the idle driving of the electromagnetic valve 23 by the first non-injection pulse is performed. Therefore, after waiting for recovery of the charge amount of the capacitor 53 that has released the stored energy, the idle driving of the solenoid valve 23 by the next non-injection pulse is performed, whereby the solenoid valve 23 as shown in FIGS. Since the idle driving of the solenoid valve 23 by all the non-injection pulses can be satisfactorily performed even when the number of idle driving times (the number of non-injection pulses) is two or three or more, the common rail pressure can be reduced efficiently ( The fuel can be injected into the combustion chamber of the cylinder of the engine 2 from the injector 6 of the next cylinder for normal injection at a common rail pressure closer to the target fuel pressure (PFIN). It is possible to suppress the deterioration of the fuel consumption (for example, the increase in the amount of NOx generated) and the deterioration of the combustion noise level.

[Modification]
In this embodiment, in the case where the solenoid valve 23 of the injector 6 is idle driven in a cylinder other than the next cylinder for normal injection or the next cylinder for normal injection, the number of non-injection pulses is set to 2 in the same cylinder. Although it is more than once, it may be once. Further, in the case of performing idle driving of the solenoid valve 23 of the injector 6 in cylinders other than the next cylinder that performs normal injection, the number of non-injection pulses is set to two or more in the same cylinder, but in different cylinders The number of non-injection pulses may be two or more. Further, as an engine torque balance means, a braking force is applied to the drive shaft (drive shaft) or drive wheel (drive wheel) to which the engine output shaft torque is transmitted via the transmission 4 and the differential mechanism, by an increase in the engine output shaft torque. You may provide the braking force addition means to apply.

  In addition, as the engine torque balance means, the throttle valve is closed to the fully closed side with respect to the required throttle opening set by the driver corresponding to the accelerator operation amount by the increase of the engine output shaft torque. The resistance of the intake air taken into the combustion chamber of each cylinder is increased to slow down the engine speed. As a result, it is possible to consume an increase in the engine output shaft torque that is caused by injecting fuel into the combustion chamber of each cylinder of the engine 2 by an extra injection amount than during normal fuel injection. It becomes.

  Further, in the present embodiment, the solenoid valve driven injector 6 driven by the solenoid valve 23 is shown as an example, but the present invention is not limited to this example. In other words, the injection amount command value that is just before the nozzle needle opens is given to the drive body that replaces the solenoid valve, and the drive body is driven, and this drive causes the high-pressure fuel to overflow to the low-pressure side of the fuel system. The same effect as that of the electromagnetic valve driven injector 6 can be obtained if the injector generates a dynamic leak. As a drive body that replaces the above-described electromagnetic valve, for example, there are a piezo stack, a drive body that uses expansion and contraction (displacement) of a magnetostrictive element, and the like.

FIG. 1 is a schematic diagram showing the overall configuration of a common rail fuel injection system (Example 1). It is the block diagram which showed the structure of the injector, and the injector drive circuit (Example 1). It is the flowchart which showed the control method of the injector injection amount and the common rail pressure (Example 1). It is the flowchart which showed the control method of the injector injection amount and the common rail pressure (Example 1). (Example 1) which is the explanatory drawing which showed the pressure reduction control method by the non-injection pulse in the injector of cylinders other than the following cylinder which carries out regular injection. (Example 1) which is the explanatory drawing which showed the pressure reduction control method by the non-injection pulse in the injector of the next cylinder which carries out regular injection. It is explanatory drawing which showed the pressure-reduction control method by the injection amount larger than the request | requirement injection amount (Example 1). It is the flowchart which showed the pressure-reduction control method by a non-injection pulse (Example 2).

Explanation of symbols

1 common rail 2 engine (internal combustion engine)
3 Crankshaft 4 Transmission (automatic transmission)
5 Supply pump (fuel supply pump)
6 Injector (Electromagnetic fuel injection valve)
9 Injector drive circuit (solenoid valve drive circuit)
10 ECU (Engine Control Unit)
22 Nozzle needle 23 Injector solenoid valve 27 Command piston 30 Back pressure control chamber 31 Fuel supply path 33 Fuel return path 34 Fuel return path 42 Solenoid coil of solenoid valve 52 Booster circuit 53 Capacitor 54 Charge amount detection circuit

Claims (11)

(A) a common rail for accumulating high-pressure fuel pumped from a fuel supply pump;
(B) an injector for injecting high-pressure fuel accumulated in the common rail into an engine cylinder;
(C) fuel pressure detection means for detecting fuel pressure in the common rail;
(D) When the actual fuel pressure detected by the fuel pressure detecting means is higher than the target fuel pressure, the fuel is injected more than the required injection amount set corresponding to the accelerator operation amount of the driver. A pressure accumulation type fuel injection device comprising pressure drop promoting means for extending a valve opening period of the injector by an extra injection amount. The pressure accumulation type fuel injection device according to claim 1,
An accumulator fuel injection device comprising engine torque balance means for consuming an increase in engine output shaft torque caused by injecting fuel by the excess injection amount. The pressure accumulation type fuel injection device according to claim 2,
The engine torque balance means is
2. A pressure accumulation type fuel injection device, comprising: a slip ratio increasing means for increasing a slip ratio of a torque converter or a lock-up clutch for transmitting the engine output shaft torque to a transmission by an increase of the engine output shaft torque. In the pressure accumulation type fuel injection device according to claim 2 or 3,
The engine torque balance means is
A pressure accumulating fuel that is a braking force adding means that applies a braking force to the drive shaft or the drive wheels to which the engine output shaft torque is transmitted through a transmission and a differential mechanism by an increase in the engine output shaft torque. Injection device. The accumulator fuel injection device according to any one of claims 2 to 4, wherein a required throttle opening degree corresponding to an accelerator operation amount of the driver is provided in an engine intake pipe communicating with a cylinder of the engine. It has an electronically controlled throttle valve that is controlled to be
The engine torque balance means is
An accumulator fuel injection device, wherein the throttle valve is closed to a fully closed side with respect to the required throttle opening by an increase of the engine output shaft torque. The pressure accumulation type fuel injection device according to any one of claims 1 to 5, wherein the injector is mounted corresponding to each cylinder of the engine,
A control chamber for back pressure control of a command piston that operates integrally with the nozzle needle,
A fuel supply path for supplying high-pressure fuel from the common rail into the control chamber;
A fuel return path for overflowing high-pressure fuel from the control chamber to the low-pressure side of the fuel system;
And a pressure accumulating fuel injection device having an electromagnetic valve for opening and closing the fuel recirculation path. The pressure-accumulation fuel injection device according to claim 6,
The pressure drop promoting means is
By opening the solenoid valve of the injector, the high pressure fuel in the control chamber overflows to the low pressure side of the fuel system, and the nozzle needle is opened so that the fuel is injected from the injector. An accumulator fuel injection device characterized by being a valve drive circuit. In the pressure accumulation type fuel injection device according to claim 6 or 7,
The pressure drop promoting means includes
When the actual fuel pressure is higher than the target fuel pressure, the solenoid valve of the injector in a cylinder different from the cylinder that performs normal injection is set to be longer than the valve opening delay time until the nozzle needle is opened before the normal injection. An accumulator fuel injection apparatus characterized in that the high-pressure fuel in the control chamber overflows to the low-pressure side of the fuel system by performing idle driving of the solenoid valve that is driven to open in a short time width. The pressure accumulation type fuel injection device according to any one of claims 6 to 8, wherein the pressure drop promoting means is
When the actual fuel pressure is higher than the target fuel pressure, the electromagnetic valve of the injector of the cylinder for normal injection is shorter than the valve opening delay time until the nozzle needle opens before the normal injection. An accumulator fuel injection device characterized by causing the high pressure fuel in the control chamber to overflow to the low pressure side of the fuel system by performing idle driving of the electromagnetic valve that is driven to open at a width. The pressure-accumulation fuel injection device according to claim 8 or 9,
The pressure drop promoting means includes
The number of idle driving of the solenoid valve in a cylinder different from the cylinder for normal injection or in the cylinder for normal injection is set according to a deviation between the actual fuel pressure and the target fuel pressure. An accumulator fuel injection device. (A) a common rail for accumulating high-pressure fuel pumped from a fuel supply pump;
(B) a control chamber that performs back pressure control of a command piston that operates integrally with the nozzle needle, a fuel supply path for supplying high-pressure fuel from the common rail into the control chamber,
A fuel return path for overflowing high-pressure fuel from the control chamber to the low-pressure side of the fuel system;
And an injector having a solenoid valve for opening and closing the fuel recirculation path;
(C) fuel pressure detecting means for detecting a fuel pressure corresponding to the fuel injection pressure;
(D) When the actual fuel pressure detected by the fuel pressure detecting means is higher than the target fuel pressure, the solenoid valve of the injector of the cylinder different from the cylinder for normal injection or the cylinder for normal injection is set before the normal injection. In addition, by performing idle driving of the solenoid valve, which opens the valve in a time width shorter than the valve opening delay time until the nozzle needle is opened, the high pressure fuel in the control chamber is reduced to the low pressure of the fuel system. Pressure drop facilitating means to overflow to the side,
The pressure drop promoting means is
A solenoid valve drive circuit that performs idle driving of the solenoid valve by storing energy higher than a power supply voltage in a capacitor and discharging the stored energy from the capacitor,
The solenoid valve drive circuit is
When the number of idle driving of the solenoid valve in the cylinder different from the cylinder for normal injection or the cylinder for regular injection is two or more times, the standby interval between the idle driving of the solenoid valve is set to An accumulator fuel injection device, characterized in that the time interval corresponding to the amount of charge is set.

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