Control device for internal combustion engine

Abstract

The present disclosure provides a control device for an internal combustion engine with which it is possible to reduce overshooting of a common rail fuel pressure with respect to a target pressure. This control device 100 for an internal combustion engine comprises an injection amount control unit 110 and a pressure control unit 120. The pressure control unit 120 includes a feedback control unit 121, a discharge flow rate computation unit 122, a discharge flow rate limiting unit 123, and an energization start angle computation unit 124. The feedback control unit 121 calculates a target discharge flow rate FRt for fuel discharged from a high-pressure fuel pump to a common rail on the basis of a pressure deviation ∆P between a fuel pressure Pf and a target pressure Pt. The discharge flow rate computation unit 122 calculates a balanced discharge flow rate FRb that is the result of increasing or decreasing the target discharge flow rate FRt so that the target discharge flow rate FRt and an outflow flow rate of fuel that is injected from an injector and that flows out from the common rail are balanced. The discharge flow rate limiting unit 123 outputs a limited discharge flow rate FRr that has the balanced discharge flow rate FRb as the upper limit, on the basis of the pressure deviation ∆P. The energization start angle computation unit 124 calculates an energization start angle θes, which is a phase angle of reciprocating motion of a plunger at the start of energization of a solenoid valve of the high-pressure fuel pump, on the basis of the limited discharge flow rate FRr.

Description

[Technical Field]

[0001] The present disclosure relates to a control device for an internal combustion engine. [Background technology]

[0002] There are known inventions relating to technologies for controlling the fuel system of an internal combustion engine. For example, Patent Document 1 listed below describes a control device for controlling an internal combustion engine including an engine-driven high-pressure fuel pump that supplies high-pressure fuel from a fuel tank to a fuel injection means. The high-pressure fuel pump is driven by a cam of the internal combustion engine, and a desired discharge amount of high-pressure fuel is discharged by closing an on-off valve on the inlet side of the high-pressure fuel pump at a desired timing based on the angle of a shaft that drives the cam.

[0003] The conventional control device includes means for detecting the rotation speed of the internal combustion engine, means for detecting the pressure of high-pressure fuel, and control means for feedback-controlling the high-pressure fuel pump so that the detected pressure of high-pressure fuel becomes a target pressure. The control means includes means for calculating a deviation between the detected pressure of high-pressure fuel and the target pressure, means for calculating a feedback manipulated variable based on the deviation, and means for calculating a required discharge amount of the high-pressure fuel pump based on the feedback manipulated variable.

[0004] The control means also includes means for calculating an angle of the shaft that satisfies the required discharge amount, taking into consideration the rotation speed of the internal combustion engine and the pressure of the detected high-pressure fuel, and means for controlling the on-off valve to close when the calculated shaft angle is reached.

[0005] In addition, the conventional control device further includes a determination means for determining the operating state of the internal combustion engine, a storage means for storing feedback control parameters corresponding to the operating state, and a means for changing the parameters in the feedback control to the stored parameters when it is determined that the specific operating state has been entered (Patent Document 1, paragraph 0017, and claim 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-032321 Summary of the Invention [Problem to be solved by the invention]

[0007] Fuel discharged from a high-pressure fuel pump is supplied to a common rail that supplies high-pressure fuel to multiple injectors, and is then injected from each injector. The conventional control system described above performs feedback control using the deviation between the pressure of the high-pressure fuel and a target pressure. Therefore, if the injection amount of the injectors suddenly decreases relative to the fuel discharge amount from the high-pressure fuel pump, the fuel pressure in the common rail may exceed the target pressure, causing an overshoot and possibly exceeding an allowable value.

[0008] The present disclosure provides a control device for an internal combustion engine that is capable of reducing overshoot of the common rail fuel pressure relative to a target pressure. [Means for solving the problem]

[0009] One aspect of the present disclosure is a control device for an internal combustion engine in which fuel discharged from a high-pressure fuel pump including a pressurizing chamber, a solenoid valve that opens a fuel supply path to the pressurizing chamber when energized, and a plunger that performs reciprocating motion to introduce fuel into the pressurizing chamber via the solenoid valve and pressurize the fuel is supplied to an injector via a common rail, the control device comprising: an injection amount control unit that controls a fuel injection amount of the injector to a target injection amount; and a pressure control unit that controls a discharge flow rate of the fuel discharged from the high-pressure fuel pump to control a fuel pressure of the common rail to a target pressure, and the pressure control unit controls an injection amount of the fuel discharged from the high-pressure fuel pump based on a pressure deviation between the fuel pressure and the target pressure. a discharge flow rate calculation unit that calculates a balanced discharge flow rate by increasing or decreasing the target discharge flow rate so that the target discharge flow rate to the common rail and the outflow flow rate injected from the injector and flowing out of the common rail are balanced; a discharge flow rate limiting unit that outputs a limited discharge flow rate having the balanced discharge flow rate as an upper limit based on the pressure deviation; and a current supply start angle calculation unit that calculates a phase angle of the reciprocating motion of the plunger at the start of current supply to the solenoid valve of the high-pressure fuel pump based on the limited discharge flow rate. [Effects of the Invention]

[0010] According to the above aspect of the present disclosure, it is possible to provide a control device for an internal combustion engine that can reduce overshoot of the fuel pressure in the common rail relative to a target pressure. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a block diagram showing an embodiment of a control device for an internal combustion engine according to the present disclosure; [Figure 2] FIG. 2 is a functional block diagram of the control device for the internal combustion engine of FIG. 1. [Figure 3] 3 is a time chart showing the calculation timing of the control device for the internal combustion engine of FIG. 2; [Figure 4] FIG. 3 is a block diagram showing an example of the configuration of a discharge flow rate calculation unit in FIG. 2. [Figure 5]FIG. 3 is a block diagram showing another example of the configuration of the discharge flow rate calculation unit in FIG. 2. [Figure 6] 3 is a graph illustrating an example of the output of the discharge flow rate restricting unit in FIG. 2. [Figure 7] FIG. 10 is a block diagram showing a modified example of the control device for an internal combustion engine according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] 1 is a block diagram showing one embodiment of a control device for an internal combustion engine according to the present disclosure. The control device for an internal combustion engine of this embodiment is configured by an electronic control unit (ECU) 10 that is part of an engine system 1 mounted on, for example, a vehicle. The engine system 1 includes, for example, an engine 2 that is an internal combustion engine, a fuel tank 3, a low-pressure fuel pump 4, a high-pressure fuel pump 5, a fuel injector 6, an accelerator position sensor 7, and the ECU 10.

[0013] The engine 2 includes, for example, an intake pipe, a throttle body, a throttle valve, an intake manifold, an intake port, a cylinder, a spark plug, a piston, a crankshaft, a camshaft, an exhaust port, and an exhaust pipe, all of which are not shown. The engine 2 takes in intake air into the intake pipe based on the movement of the piston, for example. The flow rate of the intake air taken into the intake pipe is controlled by a throttle valve provided in the throttle body as it passes through the throttle body.

[0014] Intake air that passes through the throttle body passes through the intake manifold and is mixed with fuel injected from an injector 62 installed in the intake port, and the resulting air-fuel mixture is introduced into the combustion chamber of the cylinder. The spark plug ignites the air-fuel mixture in the combustion chamber explosively, generating mechanical energy that rotates the crankshaft and camshaft connected to the piston. The gas generated by the combustion is discharged from the combustion chamber of the cylinder through the exhaust port into the exhaust pipe, and is then emitted from the exhaust pipe to the outside of the vehicle.

[0015] The fuel tank 3 stores liquid fuel such as gasoline, diesel, or ethanol. The low-pressure fuel pump 4 is provided, for example, midway through a fuel supply line 8 that connects the fuel tank 3 and the high-pressure fuel pump 5, and pumps fuel from the fuel tank 3 to the high-pressure fuel pump 5 through the fuel supply line 8. The high-pressure fuel pump 5 pressurizes the fuel supplied via the fuel supply line 8 and discharges it into a common rail 61 of the fuel injection device 6, for example.

[0016] The fuel discharge pressure of the low-pressure fuel pump 4 is lower than the fuel discharge pressure of the high-pressure fuel pump 5, and the fuel discharge pressure of the high-pressure fuel pump 5 is higher than the fuel discharge pressure of the low-pressure fuel pump 4. In other words, the "low pressure" and "high pressure" of the low-pressure fuel pump 4 and the high-pressure fuel pump 5 represent the relative relationship between the discharge pressures of the respective fuel pumps, and do not define specific pressure ranges.

[0017] High-pressure fuel pump 5 includes, for example, an intake port 51, a solenoid valve 52, a pressurizing chamber 53, a plunger 54, a discharge valve 55, and a discharge port 56. Intake port 51 is connected, for example, to a fuel supply passage 8, and receives fuel pumped by low-pressure fuel pump 4. Solenoid valve 52 is provided, for example, midway along a fuel supply passage 57 that supplies fuel from intake port 51 to pressurizing chamber 53, and is controlled to open and close by ECU 10 to open and close fuel supply passage 57 that supplies fuel to pressurizing chamber 53.

[0018] Fuel is introduced into pressurization chamber 53 from fuel tank 3 via low-pressure fuel pump 4. More specifically, the fuel introduced into suction port 51 from fuel tank 3 via low-pressure fuel pump 4 passes through a fuel supply passage 57 from suction port 51 to pressurization chamber 53 and solenoid valve 52, which opens fuel supply passage 57 when energized, by the reciprocating motion of plunger 54, and is then introduced into pressurization chamber 53. High-pressure fuel pump 5 may include, for example, a pulsation reduction unit 58 that reduces pressure pulsations of the fuel drawn in through suction port 51 and discharged from discharge port 56.

[0019] The plunger 54 reciprocates to introduce fuel into the pressurization chamber 53 via the solenoid valve 52 and pressurize the fuel. The plunger 54 is housed in, for example, a cylinder 59, and together with the cylinder 59, defines the pressurization chamber 53. The plunger 54 is provided so as to be capable of reciprocating in the axial direction by a drive mechanism (not shown). The drive mechanism reciprocates the plunger 54 in the axial direction, for example, by rotation of a cam attached to a camshaft of the engine 2.

[0020] The phase angle θp of the reciprocating motion of the plunger 54 is detected, for example, by a cam angle sensor that detects the rotation angle of the camshaft, and is input to the ECU 10. In other words, the phase angle θp of the reciprocating motion of the plunger 54 can be calculated based on the rotation angle of the camshaft, and the cam angle sensor functions as an angle sensor that detects the phase angle θp of the plunger 54 of the high-pressure fuel pump 5.

[0021] The discharge valve 55 is provided between the pressurizing chamber 53 and the discharge port 56. When there is no pressure difference between the fuel inside the pressurizing chamber 53 and the fuel downstream of the discharge valve 55, the valve element contacts the seating surface of the seat member due to the biasing force of a spring, and the discharge valve 55 is in a closed state. When the pressure of the fuel inside the pressurizing chamber 53 becomes greater than the pressure of the fuel downstream of the discharge valve 55 and the pressure difference exceeds the biasing force of the spring, the valve element separates from the seating surface of the seat member, and the valve is in an open state. The discharge port 56 is connected to, for example, a common rail 61 of the fuel injection device 6, and high-pressure fuel pressurized in the pressurizing chamber 53 is discharged from the discharge port 56 to the common rail 61.

[0022] The fuel injection device 6 includes, for example, a common rail 61, injectors 62, and a pressure sensor 63. The common rail 61 stores high-pressure fuel discharged from the high-pressure fuel pump 5 and supplies the high-pressure fuel to the multiple injectors 62. Each injector 62 injects the high-pressure fuel supplied via the common rail 61 into a cylinder of the engine 2. The pressure sensor 63 detects the pressure of the high-pressure fuel discharged from the high-pressure fuel pump 5 to the common rail 61, and outputs the detected fuel pressure Pf of the common rail 61 to the ECU 10 via a signal line.

[0023] Accelerator opening sensor 7 is connected to ECU 10, for example, via a signal line, detects the amount of depression of the accelerator pedal by the vehicle driver as accelerator opening, and outputs the detected accelerator opening to ECU 10. ECU 10 is configured by, for example, one or more microcontrollers, and is connected to low-pressure fuel pump 4, high-pressure fuel pump 5, and fuel injection device 6 via signal lines, and controls these low-pressure fuel pump 4, high-pressure fuel pump 5, and fuel injection device 6.

[0024] Fig. 2 is a functional block diagram of an internal combustion engine control device 100 configured by the ECU 10 of Fig. 1. The internal combustion engine control device 100 of this embodiment includes an injection amount control unit 110 and a pressure control unit 120. The internal combustion engine control device 100 also includes, for example, a high-pressure fuel pump control unit 130. Each unit of the internal combustion engine control device 100 shown in Fig. 2 represents each function of the internal combustion engine control device 100 that is realized by, for example, a central processing unit (CPU) of the ECU 10 executing a program stored in a memory such as a ROM or RAM.

[0025] The injection amount control unit 110 controls the fuel injection amount of each injector 62 to a target injection amount Qi based on, for example, the operating state of the internal combustion engine 2. More specifically, the control device 100 for the internal combustion engine receives, for example, the rotation speed ES of the engine 2 based on the detection result of a rotation sensor that detects the rotation of the crankshaft, the intake air amount IA based on the detection result of an air flow sensor provided in an intake passage of the engine 2, and the fuel pressure Pf in the common rail 61 detected by the pressure sensor 63.

[0026] The injection amount control unit 110 calculates a target injection amount Qi of fuel to be injected from the injector 62 based on the operating conditions of the internal combustion engine, including, for example, the input rotation speed ES, intake air amount IA, and fuel pressure Pf. The injection amount control unit 110 also outputs a drive voltage DVi that causes the injector 62 to inject fuel in the target injection amount Qi. The drive voltage DVi is, for example, a pulse-like voltage signal that controls the power supply time of the injector 62.

[0027] The pressure control unit 120 controls the discharge flow rate FR of the fuel discharged from the high-pressure fuel pump 5, and controls the fuel pressure Pf in the common rail 61 to the target pressure Pt. More specifically, the pressure control unit 120 includes a feedback control unit 121, a discharge flow rate calculation unit 122, a discharge flow rate restriction unit 123, and a current distribution start angle calculation unit 124.

[0028] The feedback control unit 121 receives, for example, a fuel pressure Pf in the common rail 61 detected by a pressure sensor 63 provided in the common rail 61 and a target pressure Pt of the fuel in the common rail 61. The feedback control unit 121 calculates, for example, a pressure deviation ΔP between the input fuel pressure Pf and the target pressure Pt.

[0029] Furthermore, the feedback control unit 121 outputs the calculated pressure deviation ΔP to the discharge flow rate limiting unit 123. Furthermore, the feedback control unit 121 calculates a target discharge flow rate FRt of fuel discharged from the high-pressure fuel pump 5 to the common rail 61 based on the pressure deviation ΔP. The feedback control unit 121 outputs the calculated target discharge flow rate FRt to the discharge flow rate calculation unit 122.

[0030] The target discharge flow rate FRt of the high-pressure fuel pump 5 output from the feedback control unit 121 is input to the discharge flow rate calculation unit 122. In addition, the discharge flow rate calculation unit 122 acquires the target injection amount Qi of the injector 62 from the injection amount control unit 110, for example, and calculates the outflow rate of fuel flowing out from the common rail 61 based on the target injection amount Qi.

[0031] Fig. 3 is a time chart showing the calculation timing of the feedback control of the internal combustion engine control device 100 shown in Fig. 2. The top graph in Fig. 3 shows the lift amount PL of the plunger 54 of the high-pressure fuel pump 5. The plunger 54 reciprocates between top dead center TDC and bottom dead center BCD, and discharges fuel, for example, in the hatched area DA from just before top dead center TDC to top dead center TDC.

[0032] 3 shows the timing at which a detection value θd of a sensor that detects the angle of an exhaust cam of the engine 2 is input. The timing at which the detection value θd of the exhaust cam angle is input corresponds to, for example, the control reference position CRP of the high-pressure fuel pump 5. In other words, the interval at which the sensor detection value of the exhaust cam angle is input is the control reference position interval CRPD of the high-pressure fuel pump 5.

[0033] 3 shows the drive pulse IDP of the injector 62. The drive pulse IDP of the injector 62 rises after a predetermined time has elapsed from the current supply start angle θes, which is the phase angle of the plunger 54 at which current starts to be supplied to the solenoid valve 52 of the high-pressure fuel pump 5. As a result, fuel is injected from the injector 62 at the same time that fuel is discharged from the high-pressure fuel pump 5.

[0034] 3 shows the calculation timings of the feedback (FDBK) control by the internal combustion engine control device 100. For example, based on the operating state of the internal combustion engine at each calculation timing, the injection amount control unit 110 predicts the target injection amount Qi of the injector 62 at the timing of fuel discharge by the high-pressure fuel pump 5 that is later than that calculation timing.

[0035] 2, the operating conditions of the internal combustion engine used by the injection amount control unit 110 to calculate the target injection amount Qi include, for example, the rotation speed ES of the engine 2, the intake air amount IA, and the fuel pressure Pf of the common rail 61. The discharge flow rate calculation unit 122 calculates the outflow flow rate of fuel from the common rail 61 based on the target injection amount Qi of the injector 62 calculated based on the operating conditions of the internal combustion engine.

[0036] Note that the discharge flow rate calculation unit 122 may, for example, obtain the drive voltage DVi from the injection amount control unit 110 and calculate, based on the drive voltage DVi, the outflow rate of the fuel injected from each injector 62 and flowing out of the common rail 61. More specifically, the discharge flow rate calculation unit 122 calculates the fuel injection amount of each injector 62 using, for example, the valve opening time based on the drive voltage DVi of the injector 62 and the fuel pressure Pf.

[0037] Furthermore, the discharge flow rate calculation unit 122 uses the calculated fuel injection amount to calculate the outflow rate of fuel from the common rail 61. Thereafter, the discharge flow rate calculation unit 122 calculates a balanced discharge flow rate FRb by increasing or decreasing the target discharge flow rate FRt so that the outflow rate of fuel from the common rail 61 and the target discharge flow rate FRt of fuel from the high-pressure fuel pump 5 to the common rail 61 input from the feedback control unit 121 are balanced.

[0038] Fig. 4 is a block diagram showing an example of the discharge flow rate calculation unit 122. In the example shown in Fig. 4, the discharge flow rate calculation unit 122 has, for example, an inlet / outlet flow rate difference calculation unit 122a. For example, the inlet / outlet flow rate difference calculation unit 122a calculates the outflow rate of fuel flowing out of the common rail 61 based on the input target injection amount Qi of the injector 62, and calculates the inlet / outlet flow rate difference ΔFR by subtracting the target discharge flow rate FRt from the outflow rate. Furthermore, the discharge flow rate calculation unit 122 adds the calculated inlet / outlet flow rate difference ΔFR to the target discharge flow rate FRt to calculate the balanced discharge flow rate FRb.

[0039] In this case, if the flow rate of fuel flowing out from the common rail 61 due to injection by the injector 62 is less than the target discharge flow rate FRt of fuel from the high-pressure fuel pump 5 to the common rail 61, the inlet / outlet flow rate difference ΔFR becomes negative. As a result, the negative inlet / outlet flow rate difference ΔFR is added to the target discharge flow rate FRt, and the balanced discharge flow rate FRb becomes less than the target discharge flow rate FRt. On the other hand, if the flow rate of fuel flowing out from the common rail 61 is greater than the target discharge flow rate FRt of fuel flowing into the common rail 61, the inlet / outlet flow rate difference ΔFR becomes positive. As a result, the positive inlet / outlet flow rate difference ΔFR is added to the target discharge flow rate FRt, and the balanced discharge flow rate FRb becomes greater than the target discharge flow rate FRt.

[0040] Fig. 5 is a block diagram showing another example of the discharge flow rate calculation unit 122. In the example shown in Fig. 5, the discharge flow rate calculation unit 122 has a ratio calculation unit 122b and a table 122c, and calculates a balanced discharge flow rate FRb based on the ratio Roi between the flow rate of fuel outflowing from the common rail 61 and the target discharge flow rate FRt of fuel flowing into the common rail 61.

[0041] More specifically, the ratio calculation unit 122b calculates the outflow flow rate of fuel flowing out from the common rail 61 based on the target injection amount Qi acquired from the injection amount control unit 110. Furthermore, the ratio calculation unit 122b divides the calculated outflow flow rate by the target discharge flow rate FRt input from the feedback control unit 121 to calculate the ratio Roi of the outflow flow rate to the target discharge flow rate FRt.

[0042] Furthermore, the table 122c outputs, for example, a coefficient F according to the ratio Roi input from the inlet / outlet flow rate difference calculation unit 122a. The discharge flow rate calculation unit 122 multiplies the target discharge flow rate FRt input from the feedback control unit 121 by the coefficient F output from the table 122c to calculate the balanced discharge flow rate FRb.

[0043] As a result, if the flow rate of fuel outflowing from the common rail 61 is less than the target discharge flow rate FRt of fuel flowing into the common rail 61, the ratio Roi and coefficient F become less than 1, and the balanced discharge flow rate FRb becomes less than the target discharge flow rate FRt. On the other hand, if the flow rate of fuel outflowing from the common rail 61 is more than the target discharge flow rate FRt of fuel flowing into the common rail 61, the ratio Roi and coefficient F become greater than 1, and the balanced discharge flow rate FRb becomes greater than the target discharge flow rate FRt.

[0044] Fig. 6 is a graph illustrating an example of the restricted discharge flow rate FRr output by the discharge flow rate restricting unit 123. The upper and lower graphs on the left side of Fig. 6 show the time change in fuel pressure Pf in the common rail 61 and the time change in the discharge flow rate FR of the high-pressure fuel pump 5 under the control of a comparative internal combustion engine control device that is different from the internal combustion engine control device according to the present disclosure. The upper and lower graphs on the right side of Fig. 6 show the time change in fuel pressure Pf in the common rail 61 and the time change in the restricted discharge flow rate FRr and the discharge flow rate FR of the high-pressure fuel pump 5 under the control of the internal combustion engine control device 100 of the present embodiment.

[0045] 2, the discharge flow rate limiting unit 123 receives the pressure deviation ΔP output from the feedback control unit 121 and the balanced discharge flow rate FRb output from the discharge flow rate calculation unit 122. The discharge flow rate limiting unit 123 outputs a limited discharge flow rate FRr, with the balanced discharge flow rate FRb as its upper limit, based on the pressure deviation ΔP. The discharge flow rate limiting unit 123 calculates, for example, the amount of change in the pressure deviation ΔP between the target pressure Pt of the fuel inside the common rail 61 and the fuel pressure Pf in the common rail 61 detected by the pressure sensor 63.

[0046] The discharge flow rate limiting unit 123 predicts the occurrence of an overshoot, in which the fuel pressure Pf exceeds the target pressure Pt, based on the amount of change in the pressure deviation ΔP. More specifically, the discharge flow rate limiting unit 123 predicts the occurrence of an overshoot if the amount of change in the pressure deviation ΔP exceeds a threshold value when the fuel pressure Pf reaches 63.2% of the target pressure Pt, as shown in the graph in the upper right of Fig. 6. If the amount of change in the pressure deviation ΔP is equal to or less than the threshold value and the occurrence of an overshoot is not predicted, the discharge flow rate limiting unit 123 outputs a restricted discharge flow rate FRr that is equal to the balanced discharge flow rate FRb input from the discharge flow rate calculation unit 122.

[0047] On the other hand, when the discharge flow rate limiting unit 123 predicts the occurrence of an overshoot, it outputs a restricted discharge flow rate FRr that is less than the balanced discharge flow rate FRb input from the discharge flow rate limiting unit 123 and that can suppress the overshoot, as indicated by arrow A1 in the graph at the bottom right of Fig. 6. Furthermore, the discharge flow rate limiting unit 123 brings the restricted discharge flow rate FRr closer to the balanced discharge flow rate FRb in response to a decrease in the pressure deviation ΔP between the fuel pressure Pf in the common rail 61 and the target pressure Pt, as indicated by arrow A2 in the graph at the bottom right of Fig. 6.

[0048] 2, the limited discharge flow rate FRr output from the discharge flow rate restricting unit 123 is input to a power distribution start angle calculation unit 124. In addition, for example, the rotation speed ES and the battery voltage BV are also input to the power distribution start angle calculation unit 124. For example, the power distribution start angle calculation unit 124 calculates a power distribution start angle θes, which is the phase angle of the reciprocating motion of the plunger 54 at the start of power distribution to the solenoid valve 52 of the high-pressure fuel pump 5, based on the limited discharge flow rate FRr, the rotation speed ES, and the battery voltage BV. The power distribution start angle calculation unit 124 outputs the calculated power distribution start angle θes to the high-pressure fuel pump control unit 130.

[0049] The high-pressure fuel pump control unit 130 receives, for example, the current distribution start angle θes output from the current distribution start angle calculation unit 124 and the phase angle θp of the plunger 54 output from a cam angle sensor that detects the rotation angle of the camshaft that reciprocates the plunger 54. The high-pressure fuel pump control unit 130 outputs a drive pulse VEP that drives the solenoid valve 52 of the high-pressure fuel pump 5 based on the current distribution start angle θes and the phase angle θp of the plunger 54.

[0050] The operation of the control device 100 for an internal combustion engine according to this embodiment will be described below in comparison with a control device for an internal combustion engine of a comparative example.

[0051] 1, for example, in a gasoline direct injection engine system 1, fuel pressurized by a high-pressure fuel pump 5 is discharged into a common rail 61, and the fuel is injected from an injector 62 into a combustion chamber of an engine 2. For example, the ECU 10 controls a discharge flow rate FR, which is the flow rate of fuel discharged by the high-pressure fuel pump 5 into the common rail 61, and performs feedback control of the fuel pressure Pf so that the fuel pressure Pf inside the common rail 61 becomes a target pressure Pt.

[0052] However, the following problem may occur in a comparative example of an internal combustion engine control device that does not have the characteristic features of the internal combustion engine control device according to the present disclosure: For example, if the fuel injection amount of the injector 62 suddenly decreases relative to the discharge flow rate FR of the fuel flowing into the common rail 61, the fuel pressure Pf in the common rail 61 may exceed the target pressure Pt, causing an overshoot, as shown in the graph of the comparative example in the upper left of Figure 6.

[0053] In contrast, the control device 100 for an internal combustion engine of this embodiment is characterized by the following configuration. As shown in Fig. 1, the control device 100 for an internal combustion engine of this embodiment is configured by an ECU 10 that controls an engine 2 as an internal combustion engine in which fuel discharged from a high-pressure fuel pump 5 is supplied to injectors 62 via a common rail 61. The high-pressure fuel pump 5 includes a pressurizing chamber 53, an electromagnetic valve 52 that opens a fuel supply path 57 to the pressurizing chamber 53 when energized, and a plunger 54 that performs reciprocating motion to introduce and pressurize fuel into the pressurizing chamber 53 via the electromagnetic valve 52. As shown in Fig. 2, the control device 100 for an internal combustion engine of this embodiment includes an injection amount control unit 110 that controls the fuel injection amount of the injector 62 to a target injection amount Qi, and a pressure control unit 120 that controls the discharge flow rate FR of the fuel discharged from the high-pressure fuel pump 5 to control the fuel pressure Pf in the common rail 61 to a target pressure Pt. The pressure control unit 120 includes a feedback control unit 121, a discharge flow rate calculation unit 122, a discharge flow rate restriction unit 123, and a power distribution start angle calculation unit 124. The feedback control unit 121 calculates a target discharge flow rate FRt of fuel discharged from the high-pressure fuel pump 5 to the common rail 61 based on a pressure deviation ΔP between the fuel pressure Pf and the target pressure Pt. The discharge flow rate calculation unit 122 calculates a balanced discharge flow rate FRb by increasing or decreasing the target discharge flow rate FRt so as to balance the target discharge flow rate FRt to the common rail 61 and the outflow rate of fuel injected from the injectors 62 and flowing out of the common rail 61. The discharge flow rate restriction unit 123 outputs a limited discharge flow rate FRr, with the balanced discharge flow rate FRb as its upper limit, based on the pressure deviation ΔP input from the feedback control unit 121. The power distribution start angle calculation unit 124 calculates a power distribution start angle θes, which is the phase angle of the reciprocating motion of the plunger 54 at the start of power distribution to the solenoid valve 52 of the high-pressure fuel pump 5, based on the limited discharge flow rate FRr.

[0054] With this configuration, the control device 100 for an internal combustion engine of this embodiment can suppress overshoot of the fuel pressure Pf relative to the target pressure Pt, as shown in the graph in the upper right of FIG. 6 , even if the fuel injection amount of the injector 62 suddenly decreases relative to the discharge flow rate FR of the fuel flowing into the common rail 61. More specifically, when the fuel injection amount of the injector 62 suddenly decreases, the outflow rate of fuel from the common rail 61 calculated by the discharge flow rate calculation unit 122 suddenly decreases. As a result, the discharge flow rate calculation unit 122 outputs a balanced discharge flow rate FRb obtained by reducing the target discharge flow rate FRt so as to balance the suddenly decreased outflow rate with the target discharge flow rate FRt to the common rail 61. Furthermore, the discharge flow rate limiting unit 123 outputs a limited discharge flow rate FRr obtained by limiting the balanced discharge flow rate FRb based on the pressure deviation ΔP between the fuel pressure Pf in the common rail 61 and the target pressure Pt, with the balanced discharge flow rate FRb as an upper limit. Then, the power distribution start angle calculation unit 124 outputs the power distribution start angle θes based on the limited discharge flow rate FRr, and the high-pressure fuel pump 5 is controlled based on the power distribution start angle θes. As a result, the limited discharge flow rate FRr, which is less than the target discharge flow rate FRt, is discharged from the high-pressure fuel pump 5 to the common rail 61, as indicated by arrow A1 in the graph at the lower right of Fig. 6, and an overshoot of the fuel pressure Pf exceeding the target pressure Pt is suppressed, as indicated by the graph at the upper right of Fig. 6. Therefore, according to the control device 100 for an internal combustion engine of this embodiment, it is possible to suppress an overshoot of the fuel pressure Pf in the common rail 61 relative to the target pressure Pt, thereby improving the exhaust performance and fuel economy of the engine 2.

[0055] 4, the discharge flow rate calculation unit 122 calculates an inlet / outlet flow rate difference ΔFR by subtracting a target discharge flow rate FRt from the outflow rate of fuel in the common rail 61 based on the target injection amount Qi of the injector 62. Furthermore, the discharge flow rate calculation unit 122 adds the calculated inlet / outlet flow rate difference ΔFR to the target discharge flow rate FRt to calculate a balanced discharge flow rate FRb.

[0056] With this configuration, the discharge flow rate calculation unit 122 can output the balanced discharge flow rate FRb obtained by increasing or decreasing the target discharge flow rate FRt of the high-pressure fuel pump 5 in accordance with an increase or decrease in the flow rate of fuel outflowing from the common rail 61 due to an increase or decrease in the target injection amount Qi of the injector 62. Therefore, according to the control device 100 for an internal combustion engine of this embodiment, it is possible to suppress overshoot of the fuel pressure Pf in the common rail 61 relative to the target pressure Pt, thereby improving the exhaust performance and fuel economy of the engine 2.

[0057] 5, the discharge flow rate calculation unit 122 calculates the ratio Roi between the outflow rate of fuel in the common rail 61 based on the target injection amount Qi of the injector 62 and the target discharge flow rate FRt. Furthermore, the discharge flow rate calculation unit 122 calculates the balanced discharge flow rate FRb based on the ratio Roi between the outflow rate and the target discharge flow rate FRt.

[0058] With this configuration, the discharge flow rate calculation unit 122 can output the balanced discharge flow rate FRb obtained by increasing or decreasing the target discharge flow rate FRt of the high-pressure fuel pump 5 in accordance with an increase or decrease in the flow rate of fuel outflowing from the common rail 61 due to an increase or decrease in the target injection amount Qi of the injector 62. Therefore, according to the control device 100 for an internal combustion engine of this embodiment, it is possible to suppress overshoot of the fuel pressure Pf in the common rail 61 relative to the target pressure Pt, thereby improving the exhaust performance and fuel economy of the engine 2.

[0059] In the control device 100 for an internal combustion engine of this embodiment, the discharge flow rate calculation unit 122 may calculate the fuel injection amount of the injector 62 using, for example, a valve opening time based on the drive voltage DVi of the injector 62 and the fuel pressure Pf shown in Fig. 2. In this case, the discharge flow rate calculation unit 122 calculates the outflow flow rate of fuel from the common rail 61 using the calculated fuel injection amount.

[0060] With this configuration, the discharge flow rate calculation unit 122 can output the balanced discharge flow rate FRb obtained by increasing or decreasing the target discharge flow rate FRt of the high-pressure fuel pump 5 in accordance with an increase or decrease in the flow rate of fuel outflowing from the common rail 61. Therefore, according to the control device 100 for an internal combustion engine of this embodiment, it is possible to suppress overshoot of the fuel pressure Pf in the common rail 61 relative to the target pressure Pt, thereby improving the exhaust performance and fuel economy of the engine 2.

[0061] Furthermore, in the control device 100 for an internal combustion engine of this embodiment, the discharge flow rate restricting unit 123 predicts the occurrence of an overshoot, in which the fuel pressure Pf in the common rail 61 exceeds the target pressure Pt, based on the amount of change in the pressure deviation ΔP, as shown in the graph in the upper right of Fig. 6. Then, when the discharge flow rate restricting unit 123 predicts the occurrence of an overshoot, it outputs a restricted discharge flow rate FRr that is less than the target discharge flow rate FRt and that can suppress the overshoot, as shown by arrow A1 in the graph in the lower right of Fig. 6. Furthermore, the discharge flow rate restricting unit 123 brings the restricted discharge flow rate FRr closer to the target discharge flow rate FRt in accordance with the decrease in the pressure deviation ΔP, as shown by arrow A2 in the graph in the lower right of Fig. 6.

[0062] With this configuration, the discharge flow rate restricting unit 123 can restrict the restricted discharge flow rate FRr to equal to or less than the balanced discharge flow rate FRb based on the pressure deviation ΔP between the fuel pressure Pf and the target pressure Pt in the common rail 61. Therefore, according to the control device 100 for an internal combustion engine of this embodiment, it is possible to simultaneously achieve improved stability and responsiveness in the transient response of the fuel pressure Pf.

[0063] In addition, in the control device 100 for the internal combustion engine of this embodiment, the discharge flow rate calculation unit 122 calculates the outflow flow rate of fuel from the common rail 61 based on the target injection amount Qi of the injector 62, which is calculated based on the operating state of the engine 2, which is an internal combustion engine.

[0064] With this configuration, the discharge flow rate calculation unit 122 can predict an increase or decrease in the flow rate of fuel outflowing from the common rail 61 that occurs after the calculation timing of the target injection amount Qi. Therefore, the control device 100 for an internal combustion engine of this embodiment can suppress overshoot of the fuel pressure Pf in the common rail 61 relative to the target pressure Pt, thereby improving the exhaust performance and fuel economy of the engine 2.

[0065] As described above, according to this embodiment, it is possible to provide the control device 100 for an internal combustion engine that is capable of suppressing overshoot of the fuel pressure Pf in the common rail 61 relative to the target pressure Pt and improving the exhaust performance and fuel economy of the engine 2. Note that the control device for an internal combustion engine according to the present disclosure is not limited to the control device 100 for an internal combustion engine of the above-described embodiment.

[0066] 7 is a block diagram of an engine system 1 showing a modified example of the internal combustion engine control device 100 of this embodiment. In the modified example shown in Fig. 7, the engine system 1 includes a pressure regulator 9 that is opened under the control of the ECU 10 to release fuel from the common rail 61 to the fuel tank 3 when the fuel pressure Pf in the common rail 61 exceeds a predetermined threshold value.

[0067] The control device 100 for an internal combustion engine of this modified example differs from the control device 100 for an internal combustion engine of the above-described embodiment in the operation of the discharge flow rate calculation unit 122. As described above, the pressure regulator 9 discharges fuel from the common rail 61 when the fuel pressure Pf exceeds a predetermined pressure. The discharge flow rate calculation unit 122 of this modified example calculates the balanced discharge flow rate FRb so that the outflow flow rate of fuel due to fuel injection from the injector 62, the target discharge flow rate FRt of the high-pressure fuel pump 5, and the discharge flow rate of fuel via the pressure regulator 9 are balanced.

[0068] With this configuration, the discharge flow rate calculation unit 122 of this modified example can calculate the balanced discharge flow rate FRb taking into consideration the flow rate of fuel released from the common rail 61 via the pressure regulator 9. Therefore, according to the internal combustion engine control device 100 of this modified example, even when the engine system 1 includes the pressure regulator 9, it is possible to suppress overshoot of the fuel pressure Pf in the common rail 61 relative to the target pressure Pt, thereby improving the exhaust performance and fuel economy of the engine 2.

[0069] The above describes a preferred embodiment of the control device for an internal combustion engine according to the present disclosure, but the present disclosure is not limited to the above-described embodiment and its variations, and additions, omissions, substitutions, and other modifications to the configuration are possible within the scope that does not deviate from the spirit of the present disclosure. [Explanation of symbols]

[0070] 5 High-pressure fuel pump 52 Solenoid valve 53 Pressure Chamber 54 Plunger 57 Fuel supply path 61 Common Rail 62 injector 9 Pressure Regulator 100 Internal combustion engine control device 110 Injection amount control unit 120 Pressure control section 121 Feedback control section 122 Discharge flow rate calculation section 123 Discharge flow rate restriction section 124 Energization start angle calculation section DVi Drive Voltage ES RPM (internal combustion engine operating status) FR discharge flow rate FRb Balanced discharge flow rate FRr Restricted discharge flow rate FRt Target discharge flow rate IA Intake air volume (internal combustion engine operating condition) Pf Fuel pressure (internal combustion engine operating condition) Pt Target pressure Qi target injection volume Roi ratio ΔFR (Difference between inflow and outflow rates) ΔP pressure deviation θes: Phase angle (start angle of energization)

Claims

1. A control device for an internal combustion engine, in which fuel discharged from a high-pressure fuel pump including a pressurizing chamber, an electromagnetic valve that opens a fuel supply path to the pressurizing chamber when energized, and a plunger that performs reciprocating motion to introduce fuel into the pressurizing chamber via the electromagnetic valve and pressurize the fuel, is supplied to an injector via a common rail, an injection amount control unit that controls the fuel injection amount of the injector to a target injection amount; a pressure control unit that controls the fuel pressure in the common rail to a target pressure by controlling the discharge flow rate of the fuel discharged from the high-pressure fuel pump, The pressure control unit is a feedback control unit that calculates a target delivery flow rate of the fuel delivered from the high-pressure fuel pump to the common rail based on a pressure deviation between the fuel pressure and the target pressure; a discharge flow rate calculation unit that calculates a balanced discharge flow rate by increasing or decreasing the target discharge flow rate so that the target discharge flow rate to the common rail and the outflow flow rate of fuel injected from the injector and flowing out of the common rail are balanced; a discharge flow rate limiting unit that outputs a limited discharge flow rate with the balanced discharge flow rate as an upper limit based on the pressure deviation; and a current supply start angle calculation unit that calculates a phase angle of the reciprocating motion of the plunger at a time when current supply to the solenoid valve of the high-pressure fuel pump starts based on the limited discharge flow rate.

2. 2. The control device for an internal combustion engine according to claim 1, wherein the discharge flow rate calculation unit calculates the balanced discharge flow rate by adding an inlet / outlet flow rate difference obtained by subtracting the target discharge flow rate from the outlet flow rate to the target discharge flow rate.

3. 2. The control device for an internal combustion engine according to claim 1, wherein the discharge flow rate calculation unit calculates the balanced discharge flow rate based on a ratio between the outflow flow rate and the target discharge flow rate.

4. 2. The control device for an internal combustion engine according to claim 1, wherein the discharge flow rate calculation unit calculates a fuel injection amount of the injector using a valve opening time based on a drive voltage of the injector and the fuel pressure, and calculates the outflow flow rate using the fuel injection amount.

5. 2. The control device for an internal combustion engine according to claim 1, wherein, when predicting the occurrence of an overshoot in which the fuel pressure exceeds the target pressure based on an amount of change in the pressure deviation, the discharge flow rate restricting unit outputs the restricted discharge flow rate that is smaller than the target discharge flow rate and that can suppress the overshoot, and brings the restricted discharge flow rate closer to the target discharge flow rate in accordance with a decrease in the pressure deviation.

6. 2. The control device for an internal combustion engine according to claim 1, wherein the discharge flow rate calculation unit calculates the outflow flow rate based on a target injection amount of the injector that is calculated based on an operating state of the internal combustion engine.

7. 2. The control device for an internal combustion engine according to claim 1, wherein the discharge flow rate calculation unit calculates the balanced discharge flow rate so that the target discharge flow rate, the outflow flow rate, and the discharge flow rate of the fuel via a pressure regulator that discharges the fuel from the common rail when the fuel pressure exceeds a predetermined pressure are balanced.

Images