JP4205561B2 - Fuel supply control device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel supply control device for an internal combustion engine, and more particularly to a control device for a fuel supply system of an internal combustion engine that supplies fuel pressurized to a high pressure by a high-pressure pump to the internal combustion engine.

  In recent years, so-called in-cylinder injection internal combustion engines, in which fuel is directly injected into a cylinder and burned, have been put to practical use in spark ignition internal combustion engines. In such an in-cylinder injection type internal combustion engine, in general, fuel pressurized to a high pressure by a high-pressure pump is discharged to a delivery pipe (accumulation chamber), and the fuel that has reached a desired pressure is discharged to the engine via an injector. The injection is performed during the compression stroke or the intake stroke.

As a fuel supply control device that controls the fuel pressure of the delivery pipe (that is, the pressure of the fuel supplied to the injector) by adjusting the discharge amount of the high-pressure pump, for example, Patent Document 1 can be cited. In the technology described in this publication, in a piston-type high-pressure pump provided with a plunger, check valves for preventing backflow of fuel are provided on the discharge side and the suction side, respectively, and an electromagnetic valve is provided between the check valves It is comprised so that it may provide. With this configuration, fuel can be sucked by closing the electromagnetic valve when the plunger is lowered. Then, by continuing the closing of the electromagnetic valve for a predetermined period after the plunger starts to rise, the fuel is pressurized and discharged to the delivery pipe, and when the fuel discharge is stopped, the electromagnetic valve is The fuel that is opened and pressurized is spilled (refluxed).
JP 11-324757 A

  Note that the discharge amount of the high-pressure pump is normally such that the fuel pressure in the delivery pipe is detected and the deviation between the detected actual fuel pressure in the delivery pipe and the target fuel pressure is eliminated, as described in Patent Document 1 above. Is feedback controlled.

  By the way, in the fuel supply control device having a general hardware configuration as described in Patent Document 1, the fuel supplied to the delivery pipe cannot be spilled due to the structure. For this reason, the followability of the actual fuel pressure when the target fuel pressure is decreased is not always satisfactory, leaving room for improvement.

  Accordingly, an object of the present invention is to solve the above-described problems and improve the fuel supply control device for an internal combustion engine when the target fuel pressure of the fuel supplied to the injector is reduced. Is to provide.

In order to solve the above-mentioned problem, in claim 1, a fuel tank that stores fuel supplied to an injector of an internal combustion engine, a fuel supply pipe that connects the injector and the fuel tank, and the fuel A high-pressure pump that sucks fuel stored in a tank, pressurizes the fuel to a high pressure, and discharges the fuel to the injector; and a fuel pressure control unit that controls the pressure of the fuel supplied to the injector by adjusting the discharge amount of the high-pressure pump The high-pressure pump includes a check valve disposed on the discharge side to prevent backflow of the discharged fuel, and an electromagnetic solenoid disposed on the suction side to spill the sucked fuel. The pressure control means drives the electromagnetic solenoid to adjust the fuel spill amount, and thus adjusts the discharge amount of the high-pressure pump to adjust the injection amount. In the fuel supply control device for an internal combustion engine that controls the pressure of the fuel supplied to the engine, the fuel pressure control means includes engine speed detection means for detecting the speed of the internal combustion engine, and the detected engine speed. Target fuel pressure determining means for stepwise determining the target fuel pressure based on the above, fuel pressure detecting means for detecting the pressure of the fuel supplied to the injector, and a deviation between the detected fuel pressure and the target fuel pressure. Fuel pressure deviation calculating means for calculating, and when the target fuel pressure is reduced and the calculated fuel pressure deviation exceeds a predetermined value, the electromagnetic solenoid is set so that the spill amount is maximized. while driving, when the fuel pressure deviation the calculated is determined to be satisfied end condition equal to or less than the predetermined value, the spill amount is maximum such electromagnetic Sole Together to terminate the drive of the id, the drive of the electromagnetic solenoid as the spill amount is maximum is determined to be being satisfied the termination condition when continues for a predetermined time, the electromagnetic as the spill amount is maximum The configuration was such that the drive of the solenoid was terminated .

In the fuel supply control device for an internal combustion engine according to claim 1, the injector is a high-pressure pump comprising a check valve for preventing backflow disposed on the discharge side and an electromagnetic solenoid for spill disposed on the suction side. In addition to supplying fuel to the internal combustion engine, the rotational speed of the internal combustion engine is detected, the target fuel pressure is determined stepwise based on the detected rotational speed of the engine, and the pressure of the fuel supplied to the injector is detected and detected. When the target fuel pressure is reduced and the calculated fuel pressure deviation exceeds a predetermined value , the electromagnetic solenoid is driven so that the spill amount is maximized. to contrast, when the fuel pressure deviation calculated is determined to be satisfied end condition equal to or less than a predetermined value, so that spill amount to terminate the drive of the electromagnetic solenoid such that the maximum Since form was, it is possible to improve the follow-up of the actual fuel pressure when the target fuel pressure of the fuel supplied to the injector has been reduced. In addition, when the driving of the electromagnetic solenoid that maximizes the spill amount continues for a predetermined time, it is determined that the end condition is satisfied, and the driving of the electromagnetic solenoid that maximizes the spill amount is terminated. When the fuel pressure deviation does not indicate a correct value for some reason, it is possible to prevent the fuel pressure from being maintained at a low pressure and the driving feeling from being significantly lowered.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a fuel supply control device for an internal combustion engine according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram showing the overall fuel supply control system for an internal combustion engine according to the first embodiment of the present invention.

  In the figure, reference numeral 10 denotes an OHC in-line four-cylinder internal combustion engine (hereinafter referred to as “engine”) mounted on a vehicle (not shown). The intake air introduced from the intake (intake) manifold 12 via an air filter or throttle valve (not shown) flows into each cylinder (cylinder) 14 of the engine 10 via two intake valves (not shown). FIG. 1 shows only one cylinder.

  Each of the cylinders 14 is provided with a piston 16 so as to be movable, and a recess is formed at the top thereof, and a combustion chamber 20 is formed between the top of the piston 16 and the inner wall of the cylinder head 18. An injector (fuel injection valve) 22 is provided near the center of the position facing the combustion chamber 20.

  The injector 22 is connected to a fuel tank 28 via a fuel supply pipe 24. A low pressure pump 30 is provided at the most upstream position of the fuel supply pipe 24. A high pressure pump 32 is provided in the fuel supply pipe 24 at a position downstream of the low pressure pump 30 (between the low pressure pump 30 and the injector 22). Hereinafter, a fuel supply pipe (indicated by reference numeral 24a) connecting the low pressure pump 30 and the high pressure pump 32 is referred to as a “low pressure fuel supply pipe”.

  The high-pressure pump 32 is connected to a delivery pipe (pressure accumulation chamber) 34 provided at a downstream position (between the high-pressure pump 32 and the injector 22). Hereinafter, a fuel supply pipe (indicated by reference numeral 24b) connecting the high pressure pump 32 and the delivery pipe 34 is referred to as a “high pressure fuel supply pipe”. An injector 22 provided in each cylinder 14 is connected to the delivery pipe 34. In FIG. 1, for convenience of illustration, the high-pressure pump 32 and the delivery pipe 34 are shown at positions separated from the engine 10, but actually they are both attached to the cylinder head 18 of the engine 10.

  The low pressure pump 30 is driven by an electric motor (not shown) and sucks fuel (gasoline fuel) stored in the fuel tank 28, pressurizes the sucked fuel to a low pressure (for example, 0.35 MPa), and discharges the fuel to the high pressure pump 32. (Pressing). The high-pressure pump 32 is driven by a high-pressure pump driving cam (not shown in FIG. 1) provided on the camshaft of the engine 10 and sucks the fuel discharged from the low-pressure pump 30. For example, the pressure is increased to 12 MPa at the maximum and discharged (pumped) to the delivery pipe 34.

  Although not shown in FIG. 1, the high-pressure pump 32 includes a check valve and an electromagnetic valve, and the discharge amount (discharge time) is adjustable by driving the electromagnetic valve. In addition, the low pressure fuel pipe 24a has a regulator that returns excess fuel to the fuel tank 28 when the fuel pressure inside the fuel pipe 24a rises to a predetermined value or more, and an air filter (both not shown) that removes impurities in the fuel. Provided.

  The injector 22 opens at a predetermined fuel injection timing determined according to the operating state of the engine 10 and the like, and high-pressure fuel corresponding to the fuel pressure of the delivery pipe 34 (hereinafter referred to as “fuel pressure”) enters the combustion chamber 20. Inject directly.

  A spark plug 36 is further disposed in the combustion chamber 20. The spark plug 36 is supplied with ignition energy from an ignition device (not shown) including an ignition coil, and ignites a mixture of injected fuel and intake air at a predetermined ignition timing. The ignited air-fuel mixture burns and explodes, and drives the piston 16.

  Thus, the engine 10 according to this embodiment is a spark ignition type in-cylinder injection internal combustion engine that directly injects gasoline fuel into the combustion chamber 20 of each cylinder 14 via the injector 22.

  The combustion gas is discharged to an exhaust (exhaust) manifold 40 through two exhaust valves (not shown), purified by a NOx component removal catalyst device or a three-way catalyst device (not shown), and then released to the atmosphere.

  The piston 16 is connected to the crankshaft 44 via a connecting rod 42, and a crank angle sensor 46 is disposed in the vicinity of the crankshaft 44. The crank angle sensor 46 includes a pulsar 46a attached to the crankshaft 44 and a magnetic pickup 46b disposed opposite thereto.

  The crank angle sensor 46 performs CRK signals for cylinder discrimination at every crank angle of 720 degrees, TDC signals at every BTDC predetermined crank angle of each cylinder 14, and CRK at every 30 degrees crank angle obtained by subdividing the TDC signal interval into six. Output a signal.

  The delivery pipe 34 is provided with a fuel pressure sensor 48 and outputs a signal corresponding to the fuel pressure (actual fuel pressure) PF of the delivery pipe 34. That is, the fuel pressure sensor 48 outputs a signal corresponding to the pressure of the fuel discharged from the high pressure pump 32 and supplied to the injector 22.

  In addition, a battery (power supply, not shown) for supplying voltage to the injector 22, the spark plug 36, the electromagnetic valve of the high-pressure pump 32, and the like is mounted at an appropriate position of the vehicle. A voltage sensor 50 is connected to the battery, and a signal corresponding to the battery voltage (power supply voltage) VB is output.

  Outputs of the above-described sensors and a sensor group (not shown) that detects the throttle opening, the coolant temperature, and the like are sent to an electronic control unit (hereinafter referred to as “ECU”) 52. The ECU 52 includes a microcomputer, and includes an input circuit 52a, a CPU 52b, a memory 52c, an output circuit 52d, and a counter (not shown).

  The CRK signal output from the crank angle sensor 46 is input via the input circuit 52a, then counted by a counter, and the engine speed NE is detected and stored (stored) in the memory 52c. Other sensor output values are also input via the input circuit 52a, and after being subjected to processing such as A / D conversion, they are stored (stored) in the memory 52c. The CPU 52b calculates the fuel injection amount of the injector 22, the ignition timing of the spark plug 36, the discharge amount (discharge time) of the high-pressure pump 32, etc. based on the detected engine speed NE and the input sensor output value. A corresponding energization command value is sent to the corresponding device via the output circuit 52d.

  FIG. 2 is an enlarged explanatory view of the high-pressure pump 32 described above.

  Hereinafter, the structure of the high-pressure pump 32 will be described with reference to FIG. 2. The high-pressure pump 32 includes a single plunger 64 that is reciprocally driven by a high-pressure pump driving cam 62 provided on the camshaft 60 of the engine 10. Piston type pump. The high pressure pump 32 has two openings, of which the opening indicated by reference numeral 68 is connected to the low pressure pump 30 via the low pressure fuel supply pipe 24a, and the opening indicated by reference numeral 70 is connected via the high pressure fuel supply pipe 24b. Connected to the delivery pipe 34.

  A discharge check valve 74 is provided on the discharge side of the pressurizing chamber 72 of the high-pressure pump 32 (between the pressurizing chamber 72 and the delivery pipe 34). The discharge check valve 74 is opened when the fuel pressure in the pressurizing chamber 72 (that is, the discharge pressure of the high-pressure pump 32) exceeds the fuel pressure PF of the delivery pipe 34, and is closed when it is not necessary. The fuel is prevented from flowing backward from the delivery pipe 34 to the high pressure pump 32.

  An electromagnetic valve (electromagnetic solenoid) 80 is provided on the suction side of the pressurizing chamber 72 (between the pressurizing chamber 72 and the low pressure pump 30). The electromagnetic valve 80 is closed when energized (excited) and opened when not energized.

  The operation of the high-pressure pump 32 will be briefly described. When the plunger 64 descends, the electromagnetic valve 80 is opened without being energized, so that the fuel discharged from the low-pressure pump 30 is sucked into the pressurizing chamber 72.

  Thereafter, when the plunger 64 turns upward, the fuel pressure in the pressurizing chamber 72 increases by energizing the electromagnetic valve 80 to close it. When the fuel pressure (discharge pressure) in the pressurizing chamber 72 exceeds the pressure downstream of the discharge check valve 74 (that is, the fuel pressure PF of the delivery pipe 34), the discharge check valve 74 is opened and fuel is supplied to the delivery pipe 34. Discharged.

  On the other hand, if energization to the electromagnetic valve 80 is not started even when the plunger 64 starts to rise, the fuel sucked into the pressurizing chamber 72 is not allowed to flow through the electromagnetic valve 80 unless the pressure exceeds the fuel pressure PF of the delivery pipe 34. To the low-pressure fuel supply pipe 24a. Hereinafter, the fuel recirculation performed on the low-pressure fuel supply pipe 24a is referred to as "spill". The spilled fuel is returned to the fuel tank 28 through the regulator.

  As described above, the high-pressure pump 32 according to this embodiment drives the electromagnetic valve 80 to adjust the spill amount, thereby discharging the discharge amount (discharge time. In other words, the amount of fuel supplied to the delivery pipe 34). Therefore, the fuel pressure PF of the delivery pipe 34 (that is, the pressure of the fuel supplied to the injector 22) can be controlled.

  Next, the operation of the fuel supply control device for the internal combustion engine according to this embodiment, more specifically, the energization control of the electromagnetic valve 80 will be described in detail.

  FIG. 3 is a main routine flowchart showing the operation. The illustrated program is executed by the ECU 52 every time a TDC signal is output from the crank angle sensor 46.

  In the following, first, in S10, a determination process is performed as to whether or not the operation of the high-pressure pump 32 (specifically, the fuel pressurizing operation) should be executed.

  FIG. 4 is a subroutine flowchart showing the high-pressure pump operation execution determination process. The high pressure pump operation execution determination process will be described with reference to FIG. It is determined whether the CYLINI bit is set to 1. Flag F. The bit of CYLINI is set to 1 at a predetermined crank angle (for example, TDC) at which the operation of the high-pressure pump 32 is to be executed in a program (not shown).

  When the result in S100 is negative and it is determined that it is not the time to execute the operation of the high-pressure pump 32, the process proceeds to S102 and the high-pressure pump operation execution flag F.S. Reset the HPUMPACT bit to 0. The high-pressure pump operation execution flag F.I. HPUMPACT indicates that the operation of the high pressure pump 32 is performed when the bit is set to 1, and indicates that the operation of the high pressure pump 32 is not performed when the bit is reset to 0.

  On the other hand, when the result of S100 is affirmative and it is determined that it is time to execute the operation of the high-pressure pump 32, the process proceeds to S104, where the fail-safe flag F.S. It is determined whether or not the FSHPUMP bit is set to 1. Fail safe flag FSPHPUMP has its bit set to 1 by a program (not shown) when an abnormality such as a failure occurs in the high-pressure pump 32.

  When the result in S104 is affirmative, the program proceeds to S102, in which the high pressure pump operation execution flag F.S If the HPUMPACT bit is reset to 0 and the result in S104 is negative, the program proceeds to S106, in which the high-pressure pump operation execution flag F.S. The HPUMPACT bit is set to 1 to indicate that the operation of the high-pressure pump 32 is to be executed.

  Returning to the description of the flowchart of FIG. 3, the process then proceeds to S12, in which it is determined whether a request for full spill (maximizing the spill amount) or full discharge (maximizing the discharge amount) is made.

  FIG. 5 is a subroutine flowchart showing the full spill / full discharge request determination processing. The full spill / full discharge request determination process will be described with reference to the same drawing. First, in S200, a fuel pressure deviation calculation process is performed.

  FIG. 6 is a subroutine flowchart showing the fuel pressure deviation calculation processing. First, in step S300, the status ST. PFOJ (described later) is changed to the previous status ST. Set to PFOJZ, the previous status ST. Update PFOJZ.

  Next, the process proceeds to S302, in which the high pressure pump operation execution flag F.S. It is determined whether the HPUMPACT bit is set to 1, that is, whether execution of the operation of the high-pressure pump 32 is instructed.

  When the result in S302 is affirmative, the program proceeds to S304, in which it is determined whether the engine speed NE is equal to or lower than a first predetermined speed # NPFOJ1. The first predetermined rotation speed # NPFOJ1 is set to a low rotation speed of about 1000 rpm, for example.

  When the result in S304 is affirmative and it is determined that the engine speed NE is in the low speed range of 1000 rpm or less, the process proceeds to S306, and the first predetermined target fuel pressure # PFOBJ0 (for example, 8 MPa) is set to the target fuel pressure PFOBJ of the delivery pipe 34. In step S308, the first status 00h is set to the status ST. Set to PFOJ.

  On the other hand, when the result in S304 is negative, the program proceeds to S310, in which it is determined whether the engine speed NE is equal to or lower than a second predetermined speed # NPFOJ2. The second predetermined rotation speed # NPFOJ2 is set to a high rotation speed of about 5000 rpm, for example.

  If the result in S310 is affirmative and it is determined that the engine speed NE is in the medium speed range between 1000 rpm and 5000 rpm, then the process proceeds to S312 where the value is higher than the first predetermined target fuel pressure # PFOBJ0 (for example, 10 MPa). After setting the second predetermined target fuel pressure # PFOBJ1 set to the target fuel pressure PFOBJ, the process proceeds to S314, and the second status 01h is set to the status ST. Set to PFOJ.

  On the other hand, when the result in S310 is negative and it is determined that the engine rotational speed NE is in a high speed range exceeding 5000 rpm, the process proceeds to S316, where the value is higher than the second predetermined target fuel pressure # PFOBJ1 (for example, 11 MPa). The set third predetermined target fuel pressure # PFOBJ2 is set to the target fuel pressure PFOBJ, and the process proceeds to S318, and the third status 02h is set to the status ST. Set to PFOJ.

  On the other hand, if the result in S302 is negative, the program proceeds to S320, where the value is lower than the first predetermined target fuel pressure # PFOBJ0 (for example, 0.35 MPa, more specifically, the discharge pressure of the low-pressure pump 30). The set fourth predetermined target fuel pressure #PFFED is set to the target fuel pressure PFOBJ, and the process proceeds to S322 to set the fourth status 03h to the status ST. Set to PFOJ. Thus, status ST. PFOJ represents which of first to fourth predetermined target fuel pressures # PFOBJ0, # PFOBJ1, # PFOBJ2, and #PFFED is selected as the target fuel pressure PFBOJ.

  As described above, in this embodiment, the target fuel pressure PFOBJ is determined stepwise (in three steps) based on the engine speed NE. The reason why the target fuel pressure PFOBJ is set to a larger value as the engine speed NE becomes higher is that the higher the engine speed NE, the shorter the period during which fuel injection is possible and the higher fuel pressure is required. It is.

  6 is continued, the target fuel pressure PFOBJ and the status ST. After PFOJ is set, the process further proceeds to S324, and the previous fuel pressure deviation DPFOBJZ is updated by setting the value of the fuel pressure deviation DPFOBJ calculated at the previous program execution to the previous fuel pressure deviation DPFOBJZ. In S326, the target fuel pressure PFOBJ is subtracted from the detected fuel pressure (actual fuel pressure) PF to calculate (set) the current value of the fuel pressure deviation DPFOBJ.

  Next, the process proceeds to S328, where the primary difference value DDPFOBJ calculated at the time of the previous program execution is set to the previous primary difference value DDPFOBJZ to update the previous primary difference value DDPFOBJZ, and the process proceeds to S330 to change from the fuel pressure deviation DPFOBJ to the previous time. The fuel pressure deviation DPFOBJZ is subtracted (that is, the difference between the current value and the previous value of the fuel pressure deviation DPFOBJ is obtained), and the current value of the primary difference value DDPFOBJ is calculated (set). Then, the process further proceeds to S332, where the previous primary difference value DDPFOBJZ is subtracted from the primary difference value DDPFOBJ (the difference between the current value and the previous value of the primary difference value DDPFOBJ is obtained), and the secondary difference value DDDPFOBJ is calculated (set). The primary difference value DDPFOBJ and the secondary difference value DDDPFOBJ are both values for the D term used in the feedback control (PID control) of the fuel pressure PF.

  Returning to the description of the flowchart of FIG. It is determined whether the HPUMPACT bit is set to 1. When the result in S202 is negative, the program proceeds to S204 where the full discharge request flag F.S. The bit of HPSTGFL is reset to 0, and then the process proceeds to S206 and the full spill request flag F.F. The HPNFLSP bit is also reset to zero.

  The full discharge request flag F.I. HPSTGFL indicates that when the bit is set to 1, all the fuel sucked into the high-pressure pump 32 is discharged to the delivery pipe 34, that is, the fuel discharge amount (discharge time) is maximized. The case where it is not necessary to be reset is shown. The full spill request flag F.I. HPNFLSP indicates that when the bit is reset to 0, the high-pressure pump 32 spills all the fuel sucked (maximizes the spill amount), that is, the fuel discharge amount is zero. When it is set to, it indicates a case where it is not necessary.

  Accordingly, when the result of S202 is negative and execution of the operation of the high pressure pump 32 is not instructed, the full discharge request flag F. The HPSTGFL bit is reset to 0 and the full spill request flag F.F. The HPNFLSP bit is also reset to 0 so that fuel is not discharged from the high-pressure pump 32.

  On the other hand, when the result in S202 is affirmative, the program proceeds to S208, in which the fuel cut flag F.I. It is determined whether the FC bit is set to 1. Fuel cut flag F.R. The bit of FC is set to 1 when a fuel cut is to be performed in a program (not shown) such as when the vehicle is decelerated.

  If the result of S208 is affirmative and it is determined that fuel cut should be performed, it is not necessary to supply fuel, so that the process proceeds to S204 and S206 described above to reset each flag so that fuel is not discharged from the high-pressure pump 32.

  On the other hand, when the result in S208 is negative, the program proceeds to S210, in which processing when the target fuel pressure PFOBJ is decreased is performed.

  FIG. 7 is a subroutine flowchart showing the target fuel pressure reduction process. Hereinafter, the target fuel pressure decrease process will be described with reference to FIG. It is determined whether the bit of STMOD is set to 1. Start flag F. When the bit is set to 1, STMOD indicates that the current program loop is a program loop executed for the first time after the engine 10 is started. The starting flag F. The bit of STMOD is generated based on a determination as to whether the engine speed NE has reached the complete explosion speed in a program (not shown).

  When the result is affirmative in S400 and it is determined that the engine is started, the process proceeds to S402, a predetermined time #TMASPFDN is set in the timer TASPFDN (down counter) after the start, and the process proceeds to S404 and the predetermined time is set in the full spill execution timer TPFDN (down counter). Set #TMPFDN. Then, in S406, the target fuel pressure decrease full spill request flag F.S. Reset to bit 0 of RQPFDN.

  It should be noted that the full spill request flag F. RQPFDN indicates that when the bit is set to 1, a full spill is required to prevent a decrease in the followability of the actual fuel pressure caused by the target fuel pressure PFOBJ being decreased. The case where it is not necessary when it is reset is shown. Therefore, if the result in S400 is affirmative, the target fuel pressure PFOBJ is not decreased because the engine 10 is being started, and therefore the full spill request flag F. The bit of RQPFDN is reset to 0.

  When the result in S400 is negative, the program proceeds to S408, in which it is determined whether the value of the timer TASPFDN after starting has reached zero. When the result in S408 is negative, the fuel pressure PF should be increased for a predetermined time after the engine is started, so the process proceeds to S404 and S406. When the result in S408 is affirmative, the process proceeds to S410, and a full spill request when the target fuel pressure is reduced Flag F. It is determined whether or not the bit of RQPFDN is set to 1.

  When the value of the after-start timer TASPFDN reaches zero for the first time after the engine 10 is started, the result in S410 is negative, and the process proceeds to S412. In S412, the status ST. It is determined whether or not PFOJ is set to the first status 00h. If the result is affirmative, the process proceeds to S414 and the previous status ST. It is determined whether PFOJZ is set to the second status 01h.

  Here, the status ST. The target fuel pressure PFOBJ when PFOJ is set to the first status 00h is 8 MPa as described above. On the other hand, status ST. The target fuel pressure PFOBJ when PFOJ is set to the second status 01h is 10 MPa. Therefore, if both S412 and S414 are affirmed, it means that the target fuel pressure PFOBJ has been changed in a decreasing direction, and if it is affirmed in S412 and then denied in S414, the target fuel pressure PFOBJ is increased. Means that it was changed or not changed.

  When the result in S412 or S414 is negative, the program proceeds to S416 and the status ST. It is determined whether or not PFOJ is set to the second status 01h. If the result is affirmative, the process proceeds to S418, and the previous status ST. It is determined whether PFOJZ is set to the third status 02h. That is, when both S416 and S418 are affirmed, it means that the target fuel pressure PFOBJ has been changed in a decreasing direction, and when it is affirmed in S416 and then negative in S418, the target fuel pressure PFOBJ is increased. Means that it was changed or not changed.

  If it is determined in S416 or S418 that the target fuel pressure PFOBJ has been changed in the increasing direction or has not been changed, the process proceeds to S404 and S406 described above. On the other hand, when it is affirmed in S414 or S418 and it is determined that the target fuel pressure PFOBJ is decreased, the process proceeds to S420, and it is determined whether or not the fuel pressure deviation DPFOBJ is equal to or less than a predetermined value #DPFFBDN. When the result in S420 is negative, the program proceeds to S422, in which it is determined whether or not the value of the full spill execution timer TPFDN has reached zero. When the result in S422 is negative, the program further proceeds to S424, in which the target fuel pressure reduction full spill request flag F.S. Set the RQPFDN bit to 1 to perform a full spill of fuel.

  F. Full spill request flag when target fuel pressure decreases When the bit of RQPFDN is set to 1, the next program execution is affirmed in S410 and proceeds from S420 to S424, and full fuel spill is continued unless affirmed in S420 or S422.

  Thus, in this embodiment, when the target fuel pressure PFOBJ is decreased and the fuel pressure deviation DPFOBJ exceeds the predetermined value #DPFFBDN, the fuel is fully spilled (the fuel sucked into the high pressure pump 32). All fuel was spilled) so that no new fuel was supplied to the delivery pipe 34, and the fuel pressure PF of the delivery pipe 34 was quickly reduced. Thereby, the followability of the actual fuel pressure (fuel pressure PF) when the target fuel pressure PFOBJ is decreased can be improved, and thus desired fuel injection can be executed.

  When the fuel pressure deviation DPFOBJ becomes equal to or smaller than the predetermined value #DPFFBDN (when affirmative in S420), it is determined that the actual fuel pressure has followed the target fuel pressure PFOBJ, and the process proceeds to S404 and S406 to complete the fuel full spill. . Further, when the value of the full spill execution timer TPFDN reaches zero (when affirmed in S422), in other words, it is determined that the state where the fuel pressure deviation DPFOBJ exceeds the predetermined value #DPFFBDN has continued for a predetermined time. Sometimes, the process proceeds to S404 and S406 to complete the fuel full spill. This is to prevent the operation feeling from being significantly lowered due to the fuel pressure PF being maintained at a low pressure when the fuel pressure deviation DPFOBJ does not show a correct value for some reason.

  Returning to the description of the flowchart in FIG. 5, the process proceeds to S <b> 212, and a process of calculating the high-pressure pump control fuel injection amount TOUTHPMX used for controlling the high-pressure pump 32 is performed.

  FIG. 8 is a subroutine flowchart showing the high-pressure pump control fuel injection amount calculation process. In the following description, first, the number i of cylinders is reset to 0 in S500, then the maximum value toutnmax of the required fuel amount for each cylinder is reset to 0 in S502, and the process proceeds to S504 where the number i of cylinders is incremented by one.

Next, the routine proceeds to S506, where the required fuel amount toutnttmp for each cylinder is calculated based on various parameters such as the actual fuel injection amount TNET [i] for each cylinder and the fuel adhesion amount. Of the value toutnmax and the cylinder-specific required fuel amount toutntmp calculated in S506, a larger value is set as the new maximum value toutnmax of the cylinder-specific required fuel amount.

  Next, in S510, it is determined whether the number of cylinders i has reached the number of cylinders NOFCYL (that is, 4) provided in the engine 10. When the result in S510 is NO, the processing from S504 to S508 is executed again. When the result in S510 is YES, the process proceeds to S512, and the maximum value toutnmax of the required fuel amount for each cylinder is set to the fuel injection amount TOUTHPMX for high-pressure pump control. To do.

  Returning to the description of the flowchart of FIG. It is determined whether or not the bit of RQPFDN is set to 1. When the result in S214 is affirmative, the process proceeds to the above-described S204 and S206. When the result in S214 is negative, the process proceeds to S216, in which it is determined whether or not the fuel pressure PF (actual fuel pressure) exceeds the first predetermined fuel pressure #PFFLL. . The first predetermined fuel pressure #PFFLL is set to a low value of about 0.4 MPa, for example.

  When the result in S216 is NO, the program proceeds to S218, where the full spill request flag F.S. It is determined whether or not the bit of HPNFLSP is set to 1 (whether full spill is not required), and when the result is negative (when full spill is required), the process proceeds to S220, and high pressure pump control is performed. It is determined whether the fuel injection amount TOUTHPMX for fuel (specifically, the maximum value of the required fuel amount toutnttmp for each cylinder) exceeds the maximum discharge amount #TOUTHPON of the high-pressure pump 32.

  If the determination in S220 is affirmative, even if the discharge amount of the high-pressure pump 32 is maximized, all of the fuel amount required for the engine 10 cannot be supplied, so the process proceeds to S204 and S206, and the fuel sucked into the high-pressure pump 32 Make a full spill. At this time, if the fuel pressure PF of the delivery pipe 34 is lower than the discharge pressure (0.35 MPa) of the low pressure pump 30, the fuel is discharged to the delivery pipe 34 by the discharge pressure of the low pressure pump 30.

  On the other hand, when the result in S220 is negative, the program proceeds to S222, where the full discharge request flag F. The bit of HPSTGFL is reset to 0, and the process further proceeds to S224, where the full spill request flag F.S. The HPNFLSP bit is set to 1 and the routine shifts to normal feedback control for operating the high-pressure pump 32.

  Thus, in this embodiment, it is determined whether or not the high-pressure pump control fuel injection amount TOUTHPMX (the maximum value of the cylinder-specific required fuel amount toutntmp) exceeds the maximum discharge amount #TOUTHPON of the high-pressure pump 32. When the fuel injection amount TOUTHPMX for high-pressure pump control exceeds the maximum discharge amount #TOUTHPON, the pressurization of fuel by the high-pressure pump 32 is stopped and the fuel is supplied to the injector 22 (delivery pipe 34) with the discharge pressure of the low-pressure pump 30. Thus, when the high pressure pump 32 cannot supply all of the required amount of fuel, such as during a cold start, the fuel can be supplied by the low pressure pump 30 and the startability of the engine 10 is improved. be able to. Further, when the high-pressure pump 32 can supply the fuel, the high-pressure pump 32 can be operated immediately, so that the fuel pressure PF can be quickly raised to atomize the injected fuel and improve the emission. it can.

  If the description of the flowchart of FIG. 5 is continued, when the result in S216 is affirmative, the process proceeds to S226, in which it is determined whether or not the fuel pressure PF (actual fuel pressure) exceeds the second predetermined fuel pressure #PFFLH. The second predetermined fuel pressure #PFFLH is set to a value higher than the first predetermined fuel pressure #PFFLL, for example, about 5 MPa.

  When the result in S226 is affirmative, that is, when it is determined that a sufficiently high fuel pressure exceeding 5 MPa has been secured, the routine proceeds to S222 and S224 and shifts to normal feedback control. On the other hand, when the result in S226 is negative and it is determined that the fuel pressure PF is a relatively low value of 0.4 MPa to 5 MPa, the routine proceeds to S228, where the full discharge request flag F.I. The HPSTGFL bit is set to 1 and fuel is fully discharged. That is, the fuel pressure PF is quickly raised by maximizing the discharge amount (discharge time) of the high-pressure pump 32.

  Thus, in this embodiment, when the fuel pressure PF of the delivery pipe 34 is detected and the detected fuel pressure PF is lower than the second predetermined fuel pressure #PFFLH (5 MPa), the discharge amount of the high-pressure pump 32 is detected. Therefore, the followability of the actual fuel pressure (fuel pressure PF) with respect to the target fuel pressure PFOBJ immediately after the engine is started can be improved, so that desired fuel injection can be executed. Specifically, the fuel pressure PF immediately after the engine is started can be quickly increased, so that misfire of the engine 10 can be prevented.

  Returning to the description of the flowchart in FIG. 3, the process proceeds to S <b> 14, and a calculation process of the feedback coefficient KHPFPID of the fuel pressure PF is performed.

  FIG. 9 is a subroutine flowchart showing the feedback coefficient calculation processing. In the following, the figure will be described. First, in S600, it is determined whether or not the value of the calculation completion counter CKHPFPID (down counter) has reached zero. When the result in S600 is negative, the program proceeds to S602, where the value of the feedback control delay counter CHPFBDLY (down counter) is reset to zero. Next, in S604, the feedback control execution flag F.S. The bits of HPFPFB are reset to 0, and the feedback coefficient KHPFPID is set to the initial value #KHPFPIDINI in S606. The feedback control execution flag F.I. HPFPFB indicates that the feedback control of the fuel pressure PF is executed when the bit is set to 1, and indicates that it is not necessary when the bit is reset to 0.

  On the other hand, when the result in S600 is affirmative, the program proceeds to S608, where the full spill request flag F. It is determined whether the HPNFLSP bit is set to 1. If the result in S608 is negative, that is, if execution of a full spill is requested, the process proceeds to S610, where the predetermined value #CTHPFBDLY is set in the feedback control delay counter CHPFBDLY. Next, in S612, the feedback control execution flag F.S. The bit of HPFPFB is reset to 0, and the process further proceeds to S614 to set the feedback coefficient KHPFPID to 1.0.

  When the result in S608 is affirmative, the program proceeds to S616, in which the full discharge request flag F.I. It is determined whether the HPSTGFL bit is set to 1. If it is affirmed in S616 and it is determined that execution of full discharge is requested, the process proceeds from S610 to S614. If the result in S616 is negative, the process proceeds to S618, and the value of the feedback control delay counter CHPFBDLY is zero. Judge whether or not.

  When the result in S618 is negative, the program proceeds to S612 and S614. When the result in S618 is positive, the program proceeds to S620, in which the feedback control execution flag F.S. Set the HPFPFB bit to 1.

  Next, in S622, the P-term map DKHPFP is searched based on the above-described primary difference value DDPFOBJ, and the P-term DKHPFPX for feedback control is determined. Similarly, in S624 and S626, the I-term map DKHPFI is searched based on the fuel pressure deviation DPFOBJ to determine the I-term DKHPFIX for feedback control, and the D-term map DKHPFD is searched based on the secondary difference value DDDPFOBJ. Thus, the D term DKHPFDX for feedback control is determined. In S628, the P term DKHPFPX, the I term DKHPFIX, and the D term DKHPFDX are added to calculate an addition / subtraction term DKHPFPID for feedback control.

  Next, the process proceeds to S630, the value obtained by adding the above-mentioned addition / subtraction term DKHPFPID to the feedback coefficient KHPFPID calculated at the previous program execution is set to the provisional feedback coefficient khpfpidtmp, and the process further proceeds to S632 to limit the provisional feedback coefficient khpfpidtmp. The value obtained in this manner is set as the final feedback coefficient KHPFPID. The upper limit value #KHPFPIDH of the limit process is set to 1.5, the lower limit value #KHPFPIDL is set to 0.5, and the feedback coefficient KHPFPID is calculated as a value between them.

  Returning to the description of the flowchart in FIG. 3, the process proceeds to S <b> 16, and the discharge time THPCAL of the high-pressure pump 32 is calculated.

  FIG. 10 is a subroutine flowchart showing the discharge time calculation processing. In the following, the full spill request flag F. It is determined whether the HPNFLSP bit is set to 1.

  If the result in S700 is negative and it is determined that full spill execution is required, then the process proceeds to S702, where the discharge time THPCAL is set to zero.

  On the other hand, when the result in S700 is affirmative, the program proceeds to S704, in which the full discharge request flag F.I. It is determined whether the HPSTGFL bit is set to 1. If the result of S704 is affirmative and it is determined that execution of full discharge is requested, then the process proceeds to S706, where the full discharge map THPMFL based on the engine speed NE (that is, the target fuel pressure PFOBJ is 5 MPa or less (from Specifically, the map) between 0.4 MPa and 5 MPa) is searched to determine the basic discharge time THPMX.

  When the result in S704 is negative, the program proceeds to S708 and the status ST. It is determined whether or not the first status 00h is set in the PFOJ. When the result in S708 is affirmative, the program proceeds to S710, where the first status map THPM0 (map when the target fuel pressure PFOBJ is 8 MPa) is searched based on the engine speed NE and the high-pressure pump control fuel injection amount TOUTHPMX, and the basic The discharge time THPMX is determined.

  On the other hand, when the result in S708 is negative, the program proceeds to S712, where the status ST. It is determined whether the second status 01h is set in the PFOJ. When the result in S712 is affirmative, the program proceeds to S714, where a second status map THPM1 (map when the target fuel pressure PFOBJ is 10 MPa) is searched based on the engine speed NE and the high-pressure pump control fuel injection amount TOUTHPMX. When the basic discharge time THPMX is determined and the result in S712 is negative, the program proceeds to S716, and the third status map THPM2 (target fuel pressure PFOBJ is 11 MPa based on the engine speed NE and the high-pressure pump control fuel injection amount TOUTHPMX). Time map) is searched to determine the basic discharge time THPMX.

  Here, the map for full discharge and the first to third status maps are selected when the target fuel pressure PFOBJ is large when compared with the same engine speed NE and the same high-pressure pump control fuel injection amount TOUTHPMX. The basic discharge time THPMX is set longer for the map to be displayed. This is because the fuel amount injected in the same time increases as the fuel pressure PF increases.

  When the basic discharge time THPMX is determined, the process proceeds to S718, where the map THPVB is searched based on the battery voltage VB, and the energization invalid time (delay invalid time) THPVBX is determined.

  Next, the routine proceeds to S720, where the value obtained by multiplying the basic discharge time THPMX by the feedback coefficient KHPFPID is set to the provisional basic discharge time thtptmp with feedback correction, and further to S722, the map THPFBH is set based on the engine speed NE. The maximum discharge time THPFBHX is determined by searching.

  In S724, the temporary basic discharge time thtptmp with feedback correction that has been subjected to the limit processing with the maximum discharge time THPFBHX as the upper limit value is set to the basic discharge time THPFB with feedback correction, and the process further proceeds to S726 to energize the basic discharge time THPFB with feedback correction A value obtained by adding the invalid time THPVBX is set as the final discharge time THPCAL.

  The electromagnetic valve 80 is supplied with power over the discharge time THPCAL set as described above, and the fuel sucked by the high-pressure pump 32 is supplied to the delivery pipe 34.

  Thus, in this embodiment, the target fuel pressure PFOBJ is determined stepwise (in three steps) based on the engine speed NE, the target fuel pressure PFOBJ is decreased, and the fuel pressure deviation DPFOBJ is a predetermined value. Since the fuel has been fully spilled (when the amount of spill is maximized) so that no new fuel is supplied to the delivery pipe 34 when #DPFFBDN is exceeded, the fuel pressure PF of the delivery pipe 34 is quickly reduced. The followability of the actual fuel pressure (fuel pressure PF) when the target fuel pressure PFOBJ is decreased can be improved, and thus desired fuel injection can be executed.

  Further, when the high-pressure pump control fuel injection amount TOUTHPMX (the maximum value of the cylinder-specific required fuel amount toutntmp) exceeds the maximum discharge amount #TOUTHPON of the high-pressure pump 32, the pressurization of fuel by the high-pressure pump 32 is stopped. Since the fuel is supplied to the injector 22 (delivery pipe 34) with the discharge pressure of the low-pressure pump 30, the low-pressure pump is used when the high-pressure pump 32 cannot supply all of the required fuel amount, such as during cold start. The fuel can be supplied at 30 and the startability of the engine 10 can be improved. Further, when the high-pressure pump 32 can supply the fuel, the high-pressure pump 32 can be operated immediately, so that the fuel pressure PF can be quickly raised to atomize the injected fuel and improve the emission. it can.

  Further, when the fuel pressure PF of the delivery pipe 34 is lower than the second predetermined fuel pressure #PFFLH (5 MPa), the discharge amount of the high-pressure pump 32 is maximized (the discharge time is the longest). The followability of the actual fuel pressure (fuel pressure PF) with respect to the target fuel pressure PFOBJ immediately after start-up can be improved, and thus desired fuel injection can be executed. Specifically, the fuel pressure PF immediately after the engine is started can be quickly increased, so that misfire of the engine 10 can be prevented.

As described above, in the first embodiment of the present invention, the fuel tank (28) for storing the fuel supplied to the injector (22) of the internal combustion engine (engine 10), the injector and the fuel tank are provided. A fuel supply pipe (24) to be connected, a high pressure pump (32) for sucking fuel stored in the fuel tank, pressurizing the fuel to a high pressure and discharging it to the injector, and adjusting a discharge amount of the high pressure pump And a fuel pressure control means (ECU 52) for controlling the pressure of the fuel supplied to the injector (fuel pressure PF), and the high-pressure pump is arranged on the discharge side to prevent a back flow of the discharged fuel ( A discharge check valve 74) and an electromagnetic solenoid (electromagnetic valve 80) disposed on the suction side for spilling the sucked fuel; Is a fuel supply control device for an internal combustion engine that controls the pressure of fuel supplied to the injector by adjusting the amount of fuel spilled by driving the electromagnetic solenoid, and thus adjusting the discharge amount of the high-pressure pump. The fuel pressure control means includes an engine speed detecting means (crank angle sensor 46) for detecting the speed of the internal combustion engine (engine speed NE), and a target fuel pressure (target speed) based on the detected engine speed. Target fuel pressure determining means (ECU 52, S304 to S318 in the flowchart of FIG. 6) , fuel pressure detecting means (fuel pressure sensor 48) for detecting the pressure of the fuel supplied to the injector, and stepwise determining the fuel pressure PFOBJ) Fuel pressure deviation calculating means (ECU) for calculating a deviation (fuel pressure deviation DPFOBJ) between the detected fuel pressure and the target fuel pressure 2, includes a S324) and FIG. 6 flowchart, when the target fuel pressure is reduced, and the fuel pressure deviation the calculated exceeds the predetermined value (#DPFFBDN), so that the spill amount is maximum The electromagnetic solenoid is driven (S412 to S418, S424 in the flowchart of FIG. 7) , and when it is determined that the calculated fuel pressure deviation is less than a predetermined value (#DPFFBDN) and the termination condition is satisfied, the spill The driving of the electromagnetic solenoid that maximizes the amount is terminated (S420 , S404, and S406 in the flowchart of FIG. 7) , and the electromagnetic solenoid driving that maximizes the spill amount continues for a predetermined time. It is determined that the termination condition is satisfied, and the electromagnetic solenoid is driven such that the spill amount is maximized. To terminate (in FIG. 7 flowchart S422, S404, S406) the fuel supply control apparatus for an internal combustion engine, characterized in that.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing an overall internal combustion engine fuel supply control apparatus according to a first embodiment of the present invention; FIG. 2 is an enlarged explanatory view of the high pressure pump shown in FIG. 1. 1 is a main routine flowchart showing the operation of the apparatus. It is a subroutine flowchart which shows a high pressure pump operation execution judgment process among the processes of FIG. FIG. 4 is a subroutine flowchart showing a full spill / full discharge request determination process in the process of FIG. 3. It is a subroutine flowchart which shows a fuel pressure deviation calculation process among the processes of the flowchart of FIG. It is a subroutine flowchart which shows the process at the time of target fuel pressure reduction among the processes of the flowchart of FIG. It is a subroutine flowchart which shows the fuel injection amount calculation process for high pressure pump control among the processes of the flowchart of FIG. It is a subroutine flowchart which shows a feedback coefficient calculation process among the processes of FIG. It is a subroutine flowchart which shows a discharge time calculation process among the processes of the flowchart of FIG.

Explanation of symbols

10 Engine (Internal combustion engine)
22 Injector 24 Fuel Supply Pipe 28 Fuel Tank 30 Low Pressure Pump 32 High Pressure Pump 34 Delivery Pipe 46 Crank Angle Sensor (Engine Speed Detection Means)
48 Fuel pressure sensor (Fuel pressure detection means)
52 ECU (fuel pressure control means, target fuel pressure determination means, fuel pressure deviation calculation means)
74 Discharge check valve (check valve)
80 Solenoid valve (solenoid solenoid)

Claims (1)

A fuel tank for storing fuel to be supplied to an injector of an internal combustion engine; a fuel supply pipe connecting the injector and the fuel tank; and the fuel stored in the fuel tank is sucked and pressurized to a high pressure. And a fuel pressure control means for controlling the pressure of the fuel supplied to the injector by adjusting the discharge amount of the high pressure pump, and the high pressure pump is disposed on the discharge side, and A check valve for preventing backflow of discharged fuel; and an electromagnetic solenoid disposed on the suction side for spilling the sucked fuel; and the fuel pressure control means drives the electromagnetic solenoid to spill the fuel. Therefore, the fuel of the internal combustion engine that controls the pressure of the fuel supplied to the injector by adjusting the discharge amount of the high-pressure pump In the fuel supply control device, the fuel pressure control means includes an engine speed detecting means for detecting the speed of the internal combustion engine, and a target fuel pressure for stepwise determining a target fuel pressure based on the detected engine speed. Determination means , fuel pressure detection means for detecting the pressure of the fuel supplied to the injector, and fuel pressure deviation calculation means for calculating a deviation between the detected fuel pressure and the target fuel pressure , the target fuel When the pressure is reduced and the calculated fuel pressure deviation exceeds a predetermined value, the electromagnetic solenoid is driven so as to maximize the spill amount, while the calculated fuel pressure deviation is a predetermined value. when it is determined that the termination condition is satisfied becomes less, the with spill amount to terminate the drive of the electromagnetic solenoid such that the maximum, the spill amount is most Internal combustion engine, characterized in that also determines that the termination condition is satisfied, the spill amount to terminate the drive of the electromagnetic solenoid such that the maximum when the driving of the electromagnetic solenoid such that continues a predetermined time Fuel supply control device.

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