JP4640279B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel injection control device for an internal combustion engine.

  As a technology for injecting and supplying fuel to an internal combustion engine such as a diesel engine, an accumulator fuel that stores high-pressure fuel using an accumulator piping such as a common rail, and supplies the high-pressure fuel to an injector and injects it into the internal combustion engine. Injectors are known. It has also been proposed to variously change the injection mode of the injector in order to improve the combustion state of the fuel in the internal combustion engine (see, for example, Patent Document 1 and Patent Document 2). Specifically, there is a technique for appropriately changing the injection rate by switching the fuel injection pattern to realize multi-injection, boot injection, rectangular injection (also referred to as trapezoidal injection), and the like.

Here, according to the rectangular injection in which the injection waveform is rectangular, the rise of the injection rate immediately after the start of injection can be made relatively steep, and atomization of the spray is promoted by the rectangular injection. Also, immediately after the start of injection by the injector, there is a concern that the spray particle size temporarily increases in the process until the needle valve for opening and closing the nozzle reaches the fully open position, but by performing rectangular injection, It becomes possible to suppress the enlargement of the spray particle size as much as possible.
Japanese Patent Laid-Open No. 5-321732 JP 2004-44493 A

  As described above, the combustion state in the cylinder can be improved by making the fuel injection rectangular. However, for example, in an internal combustion engine, the amount of fresh air introduced into the cylinder fluctuates according to the EGR rate and the like, and accordingly, the balance between the amount of fuel and the amount of fresh air introduced in the cylinder may be lost. In addition, the balance between the fuel amount and the fresh air introduction amount is lost, which may cause deterioration of the combustion state.

  The main object of the present invention is to provide a fuel injection control device for an internal combustion engine that can maintain an appropriate balance between the amount of fuel in the cylinder and the amount of fresh air, and thus achieve good in-cylinder combustion. It is.

  Hereinafter, means for solving the above-described problems and the effects thereof will be described.

In the present invention, a fuel injection valve having a valve member for opening and closing the nozzle and a solenoid as a drive unit for opening and closing the valve member is a driving target, and fuel injection by the fuel injection valve is started. The initial operating energy is supplied to the solenoid initially, and the supply of valve opening holding energy for holding the valve open state of the fuel injection valve is supplied to the solenoid following the supply of the initial operating energy. When supplying the initial operating energy, the initial peak current for starting the valve member is supplied to the solenoid and the valve opening speed is adjusted until the valve member reaches the fully open position. A valve-opening state maintaining current for maintaining the valve-opening state of the valve member when supplying the valve-opening holding energy after supplying a valve-opening speed maintaining current for maintaining the valve-opening holding energy. So that flow. In particular, according to the first aspect of the present invention, when the initial operating energy is supplied, the change rate of the injection rate immediately after the start of injection is adjusted by increasing or decreasing the valve opening speed maintaining current based on the operating state parameter of the internal combustion engine. To control.

In short, if the operating state of the internal combustion engine is different, the state of air introduction or the like in the cylinder (combustion chamber) of the internal combustion engine may change, and the combustion state may also fluctuate due to the influence. In this case, when supplying the initial operating energy, if the gradient of change in the injection rate immediately after the start of injection is constant, the amount of fuel injected and supplied into the cylinder and the amount of fresh air introduced into the cylinder (in-cylinder oxygen concentration) And the balance may be lost, and the combustion state may deteriorate. In this respect, according to the present invention, the gradient of change in the injection rate immediately after the start of injection becomes variable depending on the operating state of the internal combustion engine, so that the balance between the fuel amount in the cylinder and the fresh air amount is properly maintained, As a result, good in-cylinder combustion can be realized.
In addition, by adjusting the valve opening speed maintenance current to increase or decrease, the change rate of the injection rate immediately after the start of injection is controlled, so that the valve opening speed of the valve member becomes low or high by increasing or decreasing the valve opening speed maintenance current. Thereby, the change gradient of the injection rate immediately after the start of injection can be controlled as desired.
As a more specific configuration, a constant current circuit for supplying a valve opening speed maintaining current to the solenoid is provided in the drive circuit for the fuel injection valve, and the constant current output of the constant current circuit is variable. And it is good to increase or decrease the constant current output (valve opening speed maintenance current) from a constant current circuit according to the change gradient of the injection rate requested | required each time.
Further, as described in claim 2, in addition to the valve opening speed maintaining current, the change rate of the injection rate immediately after the start of injection may be controlled by adjusting the initial peak current to increase or decrease. In this configuration, by increasing or decreasing the initial peak current, the initial valve opening speed of the valve member becomes low or high, and the injection rate control immediately after the start of injection can be performed more precisely.
As a more specific configuration, a capacitor for supplying an initial peak current to a solenoid to a drive circuit for a fuel injection valve, and a charging circuit (charging coil, etc.) for charging the capacitor after the initial peak current is discharged And the charging current of the capacitor is variable. Then, it is preferable to increase or decrease the energization amount (initial peak current) from the capacitor to the solenoid in accordance with the required change rate of the injection rate.

  In consideration of the change in the injection rate following the displacement of the valve member in the fuel injection valve, “the change rate of the injection rate immediately after the start of injection” is the valve opening response of the fuel injection valve (valve member). In other words.

  For example, when the introduction of fresh air into the cylinder is small and the change rate of the injection rate immediately after the start of injection is steep with respect to the amount of fresh air introduced (that is, when the rise rate of the injection rate rises rapidly), the injection Immediately after the start, the fuel temporarily becomes excessive, resulting in deterioration of the combustion state. Conversely, when there is a large amount of fresh air introduced into the cylinder, if the gradient of change in the injection rate immediately after the start of injection is slow with respect to the amount of fresh air introduced (that is, if the rise rate of the injection rate is slow). Immediately after the start of injection, the state temporarily becomes excessively oxygen, which also causes deterioration of the combustion state.

Therefore, as described in claim 3, it is preferable to acquire a fresh air introduction parameter related to a fresh air introduction amount as the operating state parameter and perform injection rate control based on the fresh air introduction parameter. In this case, by increasing or decreasing the gradient of change in the injection rate in accordance with the amount of fresh air introduced, the balance between the amount of fuel supplied into the cylinder and the amount of fresh air introduced is maintained immediately after the start of injection, and the combustion state Improvements can be made.

As a variation factor of the fresh air introduction amount, a change in the EGR rate, a change in the supercharging pressure, or the like can be considered. Therefore, as described in claim 4 , the EGR rate by the EGR device is acquired as the fresh air introduction parameter, and the change gradient of the injection rate immediately after the start of injection is reduced as the EGR rate is increased each time (the change gradient is changed). It is better to control the injection rate in such a way as to lie down.

Alternatively, as described in claim 5 , the supercharging pressure by the supercharging device is acquired as the fresh air introduction parameter, and the smaller the supercharging pressure is, the smaller the gradient of change in the injection rate immediately after the start of injection ( The injection rate control is preferably performed in such a manner that the change gradient is laid down.

  That is, when the EGR rate is large or when the supercharging pressure is small, it is considered that the amount of fresh air introduced into the cylinder decreases. In such a case, by laying down the gradient of change in the injection rate immediately after the start of injection (that is, slowing down the change in injection rate), the fresh air in the cylinder can be utilized to the maximum, and the combustion state can be improved as described above. it can.

In an internal combustion engine, the air flow in the cylinder and the charging efficiency vary depending on the rotational speed. Therefore, as described in claim 6 , the rotational speed of the internal combustion engine is acquired as the operating state parameter, and the smaller the engine rotational speed is, the smaller the gradient of change in the injection rate immediately after the start of injection (the change gradient is reduced). It is better to control the injection rate in such a way as to lie down. Thereby, the injection rate control in consideration of the air flow in the cylinder and the change in the charging efficiency can be realized, and the combustion state can be further improved.

Further, the penetration and diffusion degree of the supply spray change according to the fuel pressure. Therefore, as described in claim 7 , the pressure of the fuel supplied to the fuel injection valve is acquired as the operating state parameter, and the change gradient of the injection rate immediately after the start of injection is reduced as the fuel pressure is reduced each time. It is preferable to perform the injection rate control in such a manner that the change gradient is laid down. Thereby, the injection rate control in consideration of the penetration of the supply spray and the change in the diffusion degree can be realized, and the combustion state can be further improved.

Further, when the fuel injection amount is different, the amount of air required for combustion in the cylinder is also different. Therefore, as described in claim 8 , the fuel injection amount by the fuel injection valve is acquired as the operation state parameter, and the smaller the fuel injection amount in each case, the smaller the change gradient of the injection rate immediately after the start of injection (change) It is preferable to control the injection rate in such a manner that the gradient is laid down. Thereby, the injection rate control commensurate with the fuel injection amount can be realized.

In addition, by temporarily pause its energy supply in the middle the supply of initial operating energy, may be controlled gradient change of the injection rate immediately after the injection start. In this case, if the supply of the initial operating energy is temporarily stopped, the change gradient of the injection rate immediately after the start of injection becomes slow. Thereby, the change gradient of the injection rate immediately after the start of injection can be controlled as desired.

Here, the fuel injection valve has a pressure control chamber for storing high-pressure fuel acting on the valve member to hold the valve member in a closed state, and a fuel discharge passage communicating with the pressure control chamber, and the drive unit In some cases, the discharge state of the high-pressure fuel through the fuel discharge passage is variable depending on the energy supply mode. In the fuel injection valve, the discharge state of high-pressure fuel (that is, the speed of pressure drop in the pressure control chamber) is made variable, so that the responsiveness of the valve member changes, and the change rate of the injection rate can be changed accordingly. It has become a thing. In the configuration using such fuel injection valve, by changing the energy supply mode for the previous SL driver, it may control the change gradient of the injection rate immediately after the injection start. Thereby, the change gradient of the injection rate immediately after the start of injection can be controlled as desired.

Further, as the fuel injection valve, which has a plurality of said fuel discharge passage, Ru Monogaa having a plurality of solenoids for each individual opening and closing a plurality of fuel discharge passage as said drive unit. In such a configuration, it is preferable to control the change gradient of the injection rate immediately after the start of injection by changing which of the plurality of solenoids is energized. In this case, depending on which of the plurality of solenoids is energized, through which fuel discharge passage high pressure fuel is discharged (including how many fuel discharge passages high pressure fuel is discharged) is switched. Thus, the change gradient of the injection rate immediately after the start of injection can be controlled as desired.

Furthermore, as also the fuel injection valves, a plurality of fuel discharge passage, Ru Monogaa pore size each of which is composed of a plurality of different orifices. In such a configuration, when increasing the gradient of change in the injection rate immediately after the start of injection, the solenoid corresponding to the large-diameter orifice among the plurality of orifices is energized to reduce the gradient of change in the injection rate immediately after the start of injection. In this case, it is preferable to energize the solenoid corresponding to the small-diameter orifice among the plurality of orifices. In this case, the speed of the pressure drop in the pressure control chamber is switched depending on which solenoid on the large-diameter orifice side or small-diameter orifice side is energized, thereby controlling the change rate gradient of the injection rate immediately after the start of injection as desired. can do.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. In the present embodiment, an engine control system is constructed by using a multi-cylinder diesel engine for vehicles as a control target. In the control system, various control of the engine is performed with an electronic control unit (hereinafter referred to as ECU) as a center. Is done. First, the outline of the engine control system will be described with reference to FIG.

  The engine 10 employs a common rail fuel injection system. First, the fuel injection system will be described. That is, the engine body 11 is provided with an electromagnetically driven injector (fuel injection valve) 12 for each cylinder. The injector 12 is connected to a common rail (pressure accumulation pipe) 13 common to each cylinder. A high pressure pump 14 as a fuel supply pump is connected to the common rail 13, and high pressure fuel corresponding to the injection pressure is continuously accumulated in the common rail 13 as the high pressure pump 14 is driven. The high-pressure pump 14 is driven as the engine 10 rotates, and fuel is repeatedly sucked and discharged in synchronization with the engine rotation. The high-pressure pump 14 is provided with a suction metering valve (SCV) 14a at its fuel suction portion, and low-pressure fuel pumped from a fuel tank (not shown) is connected to the fuel chamber of the pump 14 via the suction metering valve 14a. Inhaled. The common rail 13 is provided with a common rail pressure sensor 13a, and the fuel pressure (actual rail pressure) in the common rail 13 is detected by the common rail pressure sensor 13a.

  An intake pipe (including a manifold part) 15 and an exhaust pipe (including a manifold part) 16 are connected to the engine body 11, and an intake pressure sensor 17 is provided in the intake pipe 15. The intake pipe 15 is provided with a throttle actuator 18 having a throttle valve 18a. The intake pipe 15 and the exhaust pipe 16 are connected by an EGR passage 20, and an EGR cooler 21 and an EGR valve 22 are provided in the EGR passage 20.

  Further, in this system, a turbocharger 24 is provided as a supercharging device. The turbocharger 24 has an intake air compressor 25 provided in the intake pipe 15 and an exhaust turbine 26 provided in the exhaust pipe 16. The exhaust turbine 26 rotates by the exhaust gas flowing through the exhaust pipe 16, and the rotation thereof. The force is transmitted to the intake compressor 25 via a shaft (not shown). Then, the intake air flowing in the intake pipe 15 is compressed by the intake compressor 25 and supercharging is performed. The air supercharged by the turbocharger 24 is cooled by the intercooler 27 and then fed to the downstream side of the intake pipe 15.

  In the intake pipe 15, an air flow meter 28 for detecting the intake air amount is provided upstream of the intake compressor 25, and an air cleaner 29 is provided at the uppermost portion thereof. In addition, a DPF (diesel particulate filter) 31 as an exhaust purification device is installed downstream of the exhaust turbine 26 in the exhaust pipe 16, and PM (particulate matter) in the exhaust is collected by the DPF 31. Is done. In addition to the DPF 31, the exhaust pipe 16 is appropriately provided with an exhaust purification device such as an oxidation catalyst or a NOx catalyst, an oxygen concentration sensor, an exhaust temperature sensor, and the like, but the description thereof is omitted here.

  The ECU 40 is mainly composed of a microcomputer (hereinafter referred to as a microcomputer) 41 composed of a CPU, a ROM, a RAM, and the like. The microcomputer 41 includes the above-described common rail pressure sensor 13a, intake pressure sensor 17, air flow meter 28, oxygen Detection signals from the sensors such as the concentration sensor 32 and the exhaust temperature sensor 33, other rotational speed sensors 45 for detecting the rotational speed of the engine, accelerator sensors 46 for detecting the accelerator operation amount (accelerator opening) by the driver, and the like. Detection signals are sequentially input from the various sensors. Then, the microcomputer 41 determines an optimal fuel injection amount and injection timing based on engine operation information such as engine speed and accelerator operation amount, and outputs an injection control signal corresponding to the fuel injection amount to the injector 12. Thereby, fuel injection by the injector 12 is controlled in each cylinder.

  The ECU 40 is provided with an injector drive circuit 42 for driving the injector 12, details of which will be described later. The injector drive circuit 42 is provided integrally with the microcomputer 41 (control unit) in the ECU 40, or may be provided separately from the microcomputer 41 (control unit).

  Further, the microcomputer 41 calculates a target value of the common rail pressure (injection pressure) based on the engine speed and the fuel injection amount at each time, and the fuel discharge amount of the high-pressure pump 14 so that the actual rail pressure becomes the target rail pressure. Feedback control. Actually, the target discharge amount of the high-pressure pump 14 is determined based on the deviation between the actual rail pressure and the target rail pressure, and the opening degree of the intake metering valve 14a is controlled accordingly. At this time, the amount of fuel discharged by the high-pressure pump 14 is adjusted by increasing or decreasing the opening of the intake metering valve 14a. In addition, the microcomputer 41 appropriately controls the throttle actuator 18, the EGR valve 22, and the like based on the respective engine operating conditions.

  Here, the configuration of the injector 12 will be described with reference to FIG. As shown in FIG. 2, the injector 12 includes an injector main body 51 and an electromagnetic driving unit 52 including a two-way electromagnetic valve. In the injector main body 51, a needle 54 and a command piston 55 as a valve member are slidably accommodated in the body 53, and a fuel reservoir chamber 56 provided on the tip end side of the needle 54, and a command High pressure fuel is introduced from the common rail 13 to the pressure control chamber 57 provided on the back side of the piston 55 (upper end portion in the figure). In this configuration, the needle 54 and the command piston 55 attach the pressure in the pressure control chamber 57 (downward force in the figure), the pressure in the fuel reservoir chamber 56 (upward force in the figure), and the needle 54 downward. It operates according to the balance with the biasing force of the spring 58 that biases.

  The pressure control chamber 57 is connected to the low pressure fuel chamber 62 through the orifice 61. In addition, leaked fuel leaking from the fuel reservoir chamber 56 and the pressure control chamber 57 is introduced into the low pressure fuel chamber 62 through the leak passage 63. The low pressure fuel chamber 62 is provided with a valve body 65 for opening and closing the opening of the orifice 61. The valve body 65 is normally biased by a spring 66 in a direction to close the orifice opening, and the orifice opening is closed by the valve body 65 in the electromagnetic drive unit 52 when the solenoid 67 is not energized. On the other hand, when the solenoid 67 is energized by the energization signal from the ECU 40, the valve body 65 moves upward in the figure to open the orifice opening, and the pressure control chamber 57 and the low pressure fuel chamber 62 are communicated accordingly. . The fuel in the low pressure fuel chamber 62 is returned to the fuel tank (not shown) through the return fuel passage 68 and the like.

  In the above configuration, when the solenoid 67 is not energized, the valve body 65 is in the valve closing position, so that the pressure control chamber 57 is held at a high pressure, and the nozzle 69 is closed by the tip of the needle 54 as shown. It is done. In this state, fuel injection is not performed. On the other hand, when the solenoid 67 is energized, the valve body 65 moves to the valve open position, and the high pressure fuel in the pressure control chamber 57 flows into the low pressure fuel chamber 62 through the orifice 61. At this time, since the pressure in the pressure control chamber 57 is reduced at once, the needle 54 is moved upward in the drawing. Thereby, the injection hole 69 opens and fuel injection is performed.

  Next, a schematic configuration of the injector drive circuit 42 will be described with reference to FIG. In FIG. 3, only the injector solenoid (solenoid 67) for one cylinder is shown for convenience of explanation.

  In FIG. 3, one end of a charging coil 72 is connected to a power supply unit 71 made of a battery or the like, and a transistor 73 as a charging switching element is connected to the other end of the charging coil 72. The base terminal of the transistor 73 is connected to the microcomputer 41. Further, a capacitor circuit 75 is connected between the charging coil 72 and the transistor 73 via a backflow preventing diode 74. The capacitor circuit 75 includes a first capacitor 76 and a second capacitor 77 provided in parallel, and a transistor 78 provided on the + terminal side of the first capacitor 76, and the base terminal of the transistor 78 is the microcomputer 41. It is connected to the. In the above configuration, when the transistor 73 is intermittently turned on / off by the microcomputer 41, the capacitors 76 and 77 in the capacitor circuit 75 are charged by the charging coil 72.

  Here, in the capacitor circuit 75, the two capacitors 76 and 77 are basically charged simultaneously. In discharging, if the transistor 78 is ON, discharging is simultaneously performed from the two capacitors 76 and 77, and if the transistor 78 is OFF, discharging is performed only by one capacitor 77.

  In addition, one end of a solenoid 67 is connected to the capacitor circuit 75 via a diode 81, and a transistor 82 as an injection control switching element is connected to the other end of the solenoid 67. The base terminal of the transistor 82 is connected to the microcomputer 41, and the transistor 82 is turned on or off in accordance with the injector drive signal output from the microcomputer 41.

  A constant current circuit 85 is connected to the power supply unit 71, and a solenoid 67 is connected to the constant current circuit 85 via a diode 86. The constant current circuit 85 receives power supplied from the power supply unit 71 and generates and outputs a constant current. The constant current level can be appropriately switched by a control signal from the microcomputer 41.

  Next, the operation of the injector drive circuit 42 will be described with reference to FIG. FIG. 4 shows an energization current waveform for the injector solenoid and the transition of the injection rate associated with the energization of the solenoid. In FIG. 4, the transistor 82 is turned on during the fuel injection period from timing ta to tc, and fuel injection is performed accordingly.

  In FIG. 4, at a timing ta that is a fuel injection start timing, the transistor 82 is turned on, whereby a large current flows from the capacitor circuit 75 to the solenoid 67 at once. At the same time, a constant current starts to flow from the constant current circuit 85 to the solenoid 67. At this time, in the first energization period T1, a valve opening initial current (initial peak current) required to initially drive (start) the needle 54 in the valve opening direction flows, and in the subsequent second energization period T2, the needle 54 A high level constant current (valve opening speed maintaining current) required for maintaining the valve opening speed flows. As a result, the injector 12 is fully opened as soon as fuel injection is started.

  Thereafter, at timing tb, the constant current output from the constant current circuit 85 is switched from the high level constant current to the lower level constant current (valve open state holding current) lower than that. At this time, in the third energization period T3, a low-level constant current required for maintaining the needle 54 in an open state flows. Thereby, the fully open state of the injector 12 is maintained.

  As described above, in the present embodiment, the energization current to the injector solenoid is controlled in three stages (periods T1, T2, T3). At that time, energization control is performed so that the injection rate is substantially rectangular. The energization current supplied in the periods T1 and T2 corresponds to “initial operating energy”, and the energization current supplied in the period T3 corresponds to “valve opening holding energy”.

  By the way, in the engine 10, if the operating state is different, the balance between the amount of fuel injected into the cylinder (combustion chamber) and the amount of fresh air introduced into the cylinder (corresponding to the amount of air passing through the throttle) is lost. This may cause the combustion state to deteriorate. Specifically, if the EGR rate and supercharging pressure differ depending on the engine operating conditions, etc., the amount of fresh air increases or decreases according to the EGR rate and supercharging pressure, and the combustion state is affected by the effect. Changes. For example, when the EGR rate is large, or when the supercharging pressure is small, the amount of fresh air decreases. Therefore, the gradient of the injection rate immediately after the start of injection with respect to the amount of fresh air (change at the rise of the injection rate) When the ratio is steep, the fuel temporarily becomes excessive, and the combustion state deteriorates due to this. Conversely, when the EGR rate is small or when the supercharging pressure is large, the amount of fresh air increases. Therefore, the gradient of change in the injection rate immediately after the start of injection with respect to the amount of fresh air (when the injection rate rises). If the rate of change) is slow, the state temporarily becomes excessively oxygen, and the combustion state also deteriorates.

  Therefore, in the present embodiment, the change rate of the injection rate immediately after the start of injection (change rate at the time of rising of the injection rate) is made variable in accordance with the engine operating state every time. As a result, the balance between the amount of fuel injected into the cylinder and the amount of fresh air introduced is properly maintained, and as a result, the improvement of in-cylinder combustion is intended.

  FIG. 5 is a flowchart showing a main process related to injector driving. This process is repeatedly executed by the microcomputer 41 in the ECU 40 at a predetermined time period.

  In FIG. 5, in step S101, various parameters representing the engine operating state are read. Specifically, the engine rotational speed, accelerator opening, fuel pressure (actual rail pressure), and the like calculated from detection signals from various sensors and the like are read.

  Next, in steps S102 to S104, calculation of the fuel injection amount, calculation of the EGR rate, and calculation of the supercharging pressure are performed. Specifically, in step S102, the required torque is calculated using the accelerator opening or the like as a parameter, and the fuel injection amount is calculated using map data or the like using the required torque and engine speed as parameters. In step S103, the EGR rate is calculated using map data or the like using the fuel injection amount and the engine speed as parameters. In step S104, the boost pressure is calculated using map data and the like using the fuel injection amount and the engine rotation speed as parameters. In calculating the fuel injection amount, the EGR rate, and the supercharging pressure, it is also possible to appropriately perform a micro injection amount correction for correcting variations in the micro injection region of the injector, other fuel temperature corrections, and the like. Regarding the acquisition of the supercharging pressure information, a method of estimating from the detection value of the intake pressure sensor 17, a method of obtaining a supercharging pressure sensor on the downstream side (upstream side of the throttle) of the intake compressor 25 and obtaining from the detection value of the sensor, etc. Is applicable.

  Thereafter, in step S105, a target change gradient of the injection rate immediately after the start of fuel injection (target change gradient) is set. The details will be described with reference to the subroutine of FIG. In FIG. 6, in step S201, various correction amounts H1 to H5 are added to a base value of a predetermined change gradient to calculate a target change gradient (target change gradient = base value + correction amounts H1 to H5).

  At this time, the correction amounts H1 to H5 are correction terms calculated using the engine speed, fuel pressure, fuel injection amount, EGR rate, and supercharging pressure as parameters, for example, FIGS. It is calculated based on the relationship. Each parameter used for calculating each of the correction amounts H1 to H5 corresponds to an “operating state parameter”.

  FIG. 7A shows the relationship between the engine rotation speed and the correction amount H1 calculated using the rotation speed as a parameter. According to the relationship shown in the figure, the correction amount H1 is calculated as a larger value as the engine speed increases.

  FIG. 7B shows the relationship between the fuel pressure and the correction amount H2 calculated using the fuel pressure as a parameter. According to the relationship shown in the figure, the correction amount H2 is calculated as a larger value as the fuel pressure increases.

  FIG. 7C shows the relationship between the fuel injection amount and the correction amount H3 calculated using the fuel injection amount as a parameter. According to the relationship shown in the figure, the correction amount H3 is calculated as a larger value as the fuel injection amount is larger.

  FIG. 7D shows the relationship between the EGR rate and the correction amount H4 calculated using the EGR rate as a parameter. According to the relationship shown in the drawing, the correction amount H4 is calculated as a smaller value as the EGR rate is larger.

  FIG. 7E shows the relationship between the supercharging pressure and the correction amount H5 calculated using the supercharging pressure as a parameter. According to the relationship shown in the figure, the correction amount H5 is calculated as a larger value as the boost pressure is larger.

  Thereafter, in step S202, it is determined whether or not the calculated target change gradient is equal to or greater than a predetermined lower limit guard value. If the target change gradient ≧ the lower limit guard value, the process is terminated as it is. If the target change gradient <the lower limit guard value, the process proceeds to step S203, where the lower limit guard is applied to the change gradient using the lower limit guard value, and then the present process is terminated.

  Returning to FIG. 5, in step S106, energization conditions for energizing the injector solenoid are determined. In this case, based on the target change gradient calculated in step S105, the energization amount during the first energization period T1 during the energization of the solenoid (first energization amount: equivalent to the initial peak current) and the energization amount during the second energization period T2 ( 2nd energization amount: It corresponds to valve-opening speed maintenance current). In the present embodiment, the first and second energization amounts are determined based on the relationship shown in FIG. 8, and according to the relationship of FIG. 8, the first and second energization amounts are large and small according to the target change gradient. It is variably set in two stages. At this time, if the target change gradient is less than the predetermined value A, a relatively small value is obtained as the first and second energization amounts. If the target change gradient is equal to or greater than the predetermined value A, the first and second energization amounts are obtained. As a relatively large value.

  In the injector drive circuit 42, solenoid energization is performed by discharging from the capacitor circuit 75 in the first energization period T1, and 2 according to the determined solenoid energization condition (first energization amount). Switching between simultaneous discharge from one of the capacitors 76 and 77 or only discharge from one of the capacitors 77 is switched. Further, in the second energization period T2, solenoid energization is performed by a constant current output from the constant current circuit 85, and a constant current output is generated according to the determined solenoid energization condition (second energization amount). Switching between large and small constant current levels.

  Finally, in step S107, an injection command signal is generated based on the determined solenoid energization condition, other energization start timing, command injection amount, and the like, and the command signal is output to the injector drive circuit 42. It should be noted that the energization start timing of the injector solenoid can be variably set according to the engine speed, the required torque, and the like.

  FIG. 9 is a time chart showing a difference in solenoid energization mode when the target change gradients are different. 9A shows a case where the target change gradient is relatively large, and FIG. 9B shows a case where the target change gradient is relatively small.

  9A and 9B, the first energization amount and the second energization amount are different from each other, and each energization amount of (a) having a larger target change gradient is a large current. Thereby, the change gradient of the injection rate immediately after the start of injection satisfies (a)> (b). That is, in (a), the rising change of the injection rate is steeper.

  According to the embodiment described in detail above, the following excellent effects can be obtained.

  Since the change rate of the injection rate immediately after the start of injection is variably controlled according to the engine operating state each time, the balance between the amount of fuel in the cylinder and the amount of fresh air can be properly maintained, which in turn is good. In-cylinder combustion can be realized.

  Specifically, the engine speed, the fuel pressure, the fuel injection amount, the EGR rate, and the supercharging pressure are used as parameters to control the change rate of the injection rate. In this case, by using the engine rotation speed as a parameter, it is possible to realize injection rate control that takes into account changes in the air flow and filling efficiency in the cylinder. By using the fuel pressure as a parameter, it is possible to realize injection rate control that takes into account changes in the penetration and diffusion degree of the supply spray. By using the fuel injection amount as a parameter, it is possible to realize injection rate control commensurate with each fuel injection amount. Further, by using the EGR rate and the supercharging pressure as parameters, it is possible to realize injection rate control that takes into account the change in the amount of fresh air introduced into the cylinder.

  When the solenoid is energized by the injector drive circuit 42, the previous two energization amounts (the first energization amount and the second energization amount) are variably set among the energization amounts of the three stages before and after. The injection amount control can be easily realized. In this case, there is also an advantage that the injector 12 that is generally used can be used as it is in performing the injection rate control.

  The present invention is not limited to the description of the above embodiment, and may be implemented as follows, for example.

  In the above embodiment, the solenoid energization condition (first and second energization amounts) is variably set to two large and small current levels according to the target change gradient (see FIG. 8), but this is changed. For example, the solenoid energization conditions (first and second energization amounts) are variably set to three or more current levels according to the target change gradient, and the solenoid energization conditions (first and second) are similarly set according to the target change gradient. It is also possible to apply a configuration in which the energization amount) is set linearly.

  In the above embodiment, when the solenoid is energized by the injector drive circuit 42, the first energization amount (initial peak current) and the second energization amount (valve opening speed maintaining current) among the energization amounts of the three stages before and after are variably set. The rate change gradient is controlled, but this is changed. For example, only the second energization amount (valve opening speed maintaining current) is variably set to control the change gradient of the injection rate. In this case, the first energization amount (initial peak current) is fixed. Even in this configuration, as described above, the change gradient of the injection rate immediately after the start of injection can be controlled as desired.

  When the solenoid is energized by the injector drive circuit 42, it is possible to control the change gradient of the injection rate immediately after the start of injection by temporarily stopping the energy supply during the supply of the initial operating energy. That is, as shown in FIG. 10, the energization of the solenoid is temporarily stopped after energization (capacitor discharge) by the initial peak current in the first energization period. More specifically, the energization by the constant current circuit 85 does not start at the timing t11 when the capacitor discharge is started, but starts at the timing t12 after the end of the capacitor discharge. In this case, due to the temporary stop of the energy supply, the change rate of the injection rate is temporarily slowed (as a whole becomes slow), and as a result, the change rate of the injection rate immediately after the start of injection can be controlled as desired. .

  An injector having a variable injection rate structure may be used as the injector to be driven. The configuration will be described with reference to FIG. In addition, the injector 90 shown in FIG. 11 is obtained by changing a part of the configuration of the injector 12 (see FIG. 2) described above, and the same components are denoted by the same member numbers and the description thereof is omitted. In the injector 90, the configuration of the electromagnetic drive unit 91 is different from that of the injector 12 (see FIG. 2) described above.

  The electromagnetic drive unit 91 of the injector 90 is provided with two systems of solenoids 92a and 92b, and valve bodies 93a and 93b corresponding to the solenoids 92a and 92b. When the solenoids 92a and 92b are individually energized by the ECU 40, the valve bodies 93a and 93b are displaced against the urging force of the springs 94a and 94b with the energization. The low pressure fuel chamber 96 and the pressure control chamber 57 are communicated with each other via two orifices 95a and 95b as fuel discharge passages. The two orifices 95a and 95b have different hole diameters. The orifice 95a is a large-diameter orifice and the orifice 95b is a small-diameter orifice.

  In this case, when the solenoids 92a and 92b are not energized, the orifices 95a and 95b are closed by the valve bodies 93a and 93b, respectively, and when the solenoids 92a and 92b are energized, the orifices 95a and 93b are opened by the valve bodies 93a and 93b.

  In the system using the injector 90 having the above-described configuration, when increasing the change gradient of the injection rate immediately after the start of injection, the ECU 40 energizes the solenoid 92a on the large-diameter orifice 95a side and passes through the large-diameter orifice 95a in the pressure control chamber 57. The high pressure fuel is discharged to the low pressure fuel chamber 96 side. In order to reduce the change rate gradient of the injection rate immediately after the start of injection, the ECU 40 energizes the solenoid 92b on the small diameter orifice 95b side, and discharges the high pressure fuel in the pressure control chamber 57 to the low pressure fuel chamber 96 side through the small diameter orifice 95b. To do. In such a case, the speed of pressure drop in the pressure control chamber 57 is different between when the fuel is discharged from the large-diameter orifice 95a and when the fuel is discharged from the small-diameter orifice 95b, and the former has a change gradient of the injection rate immediately after the start of injection. growing. Also in this configuration, the change gradient of the injection rate immediately after the start of injection can be controlled as desired.

  In the above-described configuration, in addition to energizing the solenoids 92a and 92b alternatively, it is also possible to energize both solenoids 92a and 92b at the same time. When the injector 90 shown in FIG. 11 is employed, it is not necessary to vary the initial operating energy (initial peak current, valve opening speed maintaining current), and the conventional circuit configuration can be applied to the injector drive circuit 42.

  The two orifices 95a and 95b may have the same hole diameter. In this case, the rate of pressure drop in the pressure control chamber 57 differs depending on whether one or two of the two orifices 95a and 95b are energized, and the change gradient of the injection rate immediately after the start of injection. Can be variably controlled.

  In the above embodiment, an electromagnetically driven injector having a solenoid as a driving unit is a driving target, but other injectors can be a driving target. For example, a piezo drive type injector having a piezo stack as a drive unit may be used as a drive target, and the fuel injection control device of the present invention may be realized using the injector.

The block diagram which shows the outline of the engine control system in embodiment of invention. Sectional drawing which shows schematic structure of an injector. The circuit diagram which shows schematic structure of an injector drive circuit. The time chart which shows the transition of the injection rate accompanying the energization current waveform with respect to an injector solenoid, and the solenoid energization. The flowchart which shows the main process regarding an injector drive. The flowchart which shows the subroutine for the change gradient setting of an injection rate. FIG. 6 is a relationship diagram for calculating various correction amounts. The related figure for demonstrating the setting content of solenoid energization conditions. The time chart which shows the transition of the injection rate accompanying the energization current waveform with respect to an injector solenoid, and the solenoid energization. The time chart which shows the transition of the injection rate accompanying the energization current waveform with respect to an injector solenoid, and the solenoid energization. Sectional drawing which shows schematic structure of the injector in another embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine, 12 ... Injector, 13 ... Common rail, 14 ... High pressure pump, 22 ... EGR valve, 24 ... Turbocharger, 40 ... ECU, 41 ... Microcomputer, 42 ... Injector drive circuit, 51 ... Injector main part, 52 ... Electromagnetic Drive unit, 54 ... needle, 55 ... command piston, 57 ... pressure control chamber, 61 ... orifice, 67 ... solenoid, 69 ... jet, 72 ... charge coil, 75 ... capacitor circuit, 76,77 ... capacitor, 85 ... constant Current circuit, 90 ... injector, 91 ... electromagnetic drive unit, 92a, 92b ... solenoid, 95a, 95b ... orifice.

Claims (8)

A fuel injection valve provided in an internal combustion engine and having a valve member for opening and closing the nozzle hole and a solenoid as a drive unit for driving the valve member to open and close is a driving target.
An initial operating energy is supplied to the solenoid at the beginning of fuel injection by the fuel injection valve, and following the supply of the initial operating energy, an opening that holds the open state of the fuel injection valve to the solenoid is maintained. Fuel injection control is performed by supplying valve holding energy ,
When supplying the initial operating energy, an initial peak current for starting the valve member is supplied to the solenoid and the valve opening speed is maintained to maintain the valve opening speed until the valve member reaches the fully open position. In the fuel injection control device for an internal combustion engine in which a valve opening state holding current for holding the valve opening state of the valve member is supplied when supplying the valve opening holding energy thereafter .
Parameter acquisition means for acquiring an operation state parameter representing an operation state of the internal combustion engine;
An injection rate control means for controlling the change gradient of the injection rate immediately after the start of injection based on the operating state parameter acquired by the parameter acquisition means when supplying the initial operating energy;
With
The fuel injection control device for an internal combustion engine, wherein the injection rate control means controls a change gradient of the injection rate immediately after the start of injection by adjusting the valve opening speed maintaining current to increase or decrease . The injection rate control means controls the change gradient of the injection rate immediately after the start of injection by adjusting the initial peak current to increase or decrease in addition to the valve opening speed maintaining current . A fuel injection control device for an internal combustion engine. The parameter acquisition means acquires a fresh air introduction parameter related to a fresh air introduction amount as the operation state parameter,
The fuel injection control device for an internal combustion engine according to claim 1 or 2 , wherein the injection rate control means performs injection rate control based on the fresh air introduction parameter . It is applied to a system equipped with an EGR device that circulates part of the exhaust to the intake system,
The parameter acquisition means acquires an EGR rate by the EGR device as the fresh air introduction parameter,
4. The internal combustion engine according to claim 3 , wherein the injection rate control unit performs the injection rate control such that a change gradient of the injection rate immediately after the start of injection is reduced as the EGR rate is increased each time . Fuel injection control device. Applied to systems with supercharging devices that supercharge intake air,
The parameter acquisition means acquires a supercharging pressure by the supercharging device as the fresh air introduction parameter,
The said injection rate control means performs injection rate control by making the change gradient of the injection rate immediately after the said injection start small, so that each supercharging pressure is small . A fuel injection control device for an internal combustion engine. The parameter acquisition means acquires the rotational speed of the internal combustion engine as the operating state parameter,
The injection rate control means performs the injection rate control such that the gradient of change in the injection rate immediately after the start of the injection becomes smaller as the engine speed at each time decreases . A fuel injection control device for an internal combustion engine according to claim 1. The parameter acquisition means acquires the pressure of the fuel supplied to the fuel injection valve as the operating state parameter,
The said injection rate control means performs injection rate control by making the change rate gradient of the injection rate immediately after the said injection start small, so that fuel pressure in each case is small. A fuel injection control device for an internal combustion engine as described. The parameter acquisition means acquires a fuel injection amount by the fuel injection valve as the operation state parameter,
The injection rate control means performs the injection rate control so that the change rate of the injection rate immediately after the start of injection becomes smaller as the fuel injection amount for each time is smaller . A fuel injection control device for an internal combustion engine according to claim 1.

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