JP2007046568A - High pressure fuel supply controller for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high pressure fuel supply controller capable of reducing unevenness in amount of fuel injection and improving exhaust emission characteristic. <P>SOLUTION: This high pressure fuel supply controller 1 is provided with a high pressure fuel supply system for pressurizing and supplying the fuel fed out from a low pressure fuel feed pump 51 into a pressure accumulation chamber 53 by a high pressure fuel feed pump 60 and supplying the fuel in the pressure accumulation chamber 53 into a fuel injection valve 30 for jetting the fuel into a combustion chamber 17 directly, pressure adjusting means 65, 90, 91, etc. for adjusting pressure by returning the fuel onto a low pressure side when pressure in the pressure accumulation chamber 53 rises above a predetermined value, a means 56 for detecting pressure in the pressure accumulation chamber 53, and a control means 100 for controlling pressure in the pressure accumulation chamber 53. A plurality of pressure accumulation chambers 53, 58 are provided, a shutoff valve 57 capable of opening and closing a section between them selectively is provided, and opening and closing control of the shutting-off valve is performed by the control means 100. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a high-pressure fuel supply control device for an engine mounted on an automobile or the like, and more particularly to pressurize and supply fuel to a pressure accumulating chamber by a high-pressure fuel pump and inject the fuel in the pressure accumulating chamber directly into a combustion chamber. The present invention relates to a high-pressure fuel supply control device for an engine provided with a high-pressure fuel supply system that supplies a fuel injection valve.

  Current automobiles are required to reduce exhaust gas substances such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx) contained in automobile exhaust gas from the viewpoint of environmental conservation. In order to reduce this, in-cylinder injection engines have been developed. An in-cylinder injection engine performs fuel injection by a fuel injection valve directly into a combustion chamber of a cylinder, promotes combustion of injected fuel by reducing the particle size of fuel injected from the fuel injection valve, and emits exhaust gas. It aims to reduce substances and improve engine output.

  In the in-cylinder injection engine, it is necessary to control to a desired fuel injection pressure in accordance with engine operating conditions.

  In response to this requirement, in the high-pressure fuel supply control device described in Patent Document 1 below, the feedforward control amount set based on the fuel injection amount from the fuel injection valve and the fuel stock detected by the fuel pressure sensor. The fuel pump discharge amount is controlled by a feedback control amount such that the fuel pressure in the pressure chamber (hereinafter referred to as a common rail) matches the target pressure, and the fuel pressure is controlled.

  Further, since the fuel pressure in the common rail pulsates, the following is intended to ensure the detection response of the actual fuel pressure while avoiding the offset of the actual fuel pressure in the steady state and the fluctuation of the actual fuel pressure in a long cycle. In Patent Document 2, the weight in the weighted average process is set for the fuel pressure in accordance with the engine rotation speed.

JP 11-324757 A Japanese Patent Laid-Open No. 9-256897

  Here, the fuel pressure pulsation generation mechanism will be described with reference to FIG. Fuel pressure pulsation occurs when fuel is injected from the fuel injection valve and the fuel pressure decreases during the non-discharge period of the pump. For this reason, as the fuel injection amount increases, the amount of decrease in fuel pressure increases and the amplitude of fuel pressure pulsation increases.

  When the amplitude of the pulsation of the actual fuel pressure is large, the fuel pressure and the fuel injection amount from the fuel injection valve cannot be controlled with high accuracy.

  The fuel pressure and the amount of fuel injected from the fuel injection valve cannot be controlled accurately, so that the particle size of the fuel injected from the fuel injection valve becomes large, the air-fuel ratio varies, etc., and stable combustion cannot be obtained. It causes deterioration of gas performance.

  In order to reduce the amplitude of the fuel pressure pulsation, it is conceivable to increase the volume of the common rail. However, if the volume is increased, the responsiveness of the fuel pressure is deteriorated.

  The present invention has been made in view of such circumstances, and the object of the present invention is to reduce the influence of the pulsation of the actual fuel pressure by increasing the common rail volume under an operating condition with a large pulsation amplitude. To provide a high-pressure fuel supply control system for engines that contributes to improving combustion pressure responsiveness by reducing the common rail volume, and improving combustion stability and exhaust gas performance (exhaust emission characteristics) by reducing the volume of the common rail under operating conditions with little impact. It is in.

  In order to achieve the above object, the high-pressure fuel supply control apparatus for an engine according to the present invention basically supplies a pressurized fuel to a pressure accumulating chamber by a high-pressure fuel pump and directly injects the fuel in the pressure accumulating chamber into the combustion chamber. A high pressure fuel supply system for supplying fuel to the fuel injection valve, a pressure adjusting means for adjusting the pressure by returning the fuel to a low pressure side when the pressure in the pressure accumulating chamber rises above a predetermined value, and the pressure accumulating Pressure detecting means for detecting the pressure in the room, and control means for controlling the pressure in the pressure accumulating chamber.

  A plurality of the pressure accumulating chambers are provided, and a shutoff valve for opening and closing the pressure accumulating chambers is provided.

  The shut-off valve is preferably opened and closed selectively by the control means, and the pressure adjusting means is preferably provided with the fuel injection valve of the plurality of pressure accumulating chambers. Attached to the accumulator side.

  In a preferred embodiment, each of the plurality of pressure accumulating chambers is provided with the pressure detecting means.

  Preferably, the control means sets the opening / closing timing of the shutoff valve based on at least one of an engine speed, a fuel injection amount, an intake air amount, and a pressure in the pressure accumulating chamber. .

  In another preferred aspect, the control means increases the discharge amount of the high-pressure pump until a predetermined time elapses after the shut-off valve is opened.

  In another preferred aspect, the control means obtains an increase period or an increase in the discharge amount of the high-pressure pump based on the pressure in the pressure accumulating chamber.

  The control means preferably opens the shut-off valve based on the pressure in the pressure accumulating chamber when the engine is stopped.

  In a preferred aspect, the control means closes the shut-off valve when the engine is started.

  In another preferred aspect, the control means determines whether or not the shut-off valve has failed based on a pressure change rate in the pressure accumulating chamber.

  In still another preferred aspect, the control means determines the presence or absence of a failure of the shutoff valve based on a pressure difference in the plurality of pressure accumulating chambers.

  In the high pressure fuel supply control device for an engine according to the present invention, in addition to the first pressure accumulation chamber (common rail), a second pressure accumulation chamber (common rail) and a shut-off valve are provided, and the opening and closing of the shut-off valve is controlled according to operating conditions. In addition, since the common rail volume is variable, the fuel pressure can be controlled optimally and quickly, and the fuel pressure pulsation can be reduced, thereby suppressing variations in the fuel injection amount. Therefore, it is possible to stabilize combustion and improve exhaust gas performance (exhaust emission characteristics).

  More specifically, as the fuel injection amount increases, the common rail volume is increased and the fuel pressure pulsation is reduced. By reducing the fuel pressure pulsation, it is possible to reduce the variation in the fuel injection amount. By reducing the variation in the fuel injection amount, misfire can be prevented and the air-fuel ratio can be accurately controlled, which contributes to the improvement of exhaust emission characteristics.

  Embodiments of a high-pressure fuel supply control device for an engine according to the present invention will be described below with reference to the drawings.

  FIG. 1 is an overall configuration diagram showing an embodiment of a high-pressure fuel supply control device according to the present invention together with an example of an in-vehicle in-cylinder injection engine to which the high-pressure fuel supply control device is applied.

  The illustrated in-cylinder injection engine 10 is, for example, an in-line four-cylinder engine having four cylinders # 1, # 2, # 3, and # 4, and includes a cylinder head 11, a cylinder block 12, and the inside of the cylinder block 12. And a piston 15 that is slidably inserted into the piston 15. A combustion chamber 17 is defined above the piston 15. In the combustion chamber 17, an ignition plug 35 to which a high voltage is applied from the ignition coil 34 and a fuel injection valve 30 that injects fuel directly into the combustion chamber 17 are provided. In the drawing, the ignition plug 35 and the fuel injection valve 30 are provided side by side on the left and right of the ceiling portion of the combustion chamber 17 for convenience, but their arrangement positions can be set as appropriate.

  Air to be used for fuel combustion is taken from an inlet 21a of an air cleaner 21 provided at the start end of the intake passage 20, passes through an air flow sensor 24, passes through a throttle body 26 in which an electric throttle valve 25 is accommodated. The intake 27 is opened and closed by an intake camshaft 29 arranged at the downstream end of the branch passage (intake pipe, intake port) that forms the downstream portion of the intake passage 20 from the collector 27. The gas is sucked into the combustion chambers 17 of the cylinders # 1, # 2, # 3, and # 4 through the valve 28.

  The air-fuel mixture of the air sucked into the combustion chamber 17 and the fuel injected from the fuel injection valve 30 is ignited by the spark plug 35 and explosively burned. The combustion waste gas (exhaust gas) is exhausted by the exhaust camshaft 49. The exhaust gas is discharged to the exhaust passage 40 through the exhaust valve 48 that is driven to open and close, and after being purified by the catalytic converter 46 disposed in the exhaust passage 40, the exhaust gas is discharged to the outside.

  On the other hand, fuel such as gasoline injected from the fuel injection valve 30 is primarily pressurized from the fuel tank 50 by the low-pressure fuel pump 51 and regulated to a constant pressure (for example, 3 kg / cm 2) by the fuel pressure regulator 52. At the same time, in the high-pressure fuel pump 60 driven by the pump drive cam 47 provided on the exhaust camshaft 49, the secondary pressure is increased to a higher pressure (for example, 50 kg / cm 2) to the pressure accumulation chamber (first common rail) 53. The fuel is pumped and fuel is supplied from the common rail 53 to the fuel injection valve 30 provided for each of the cylinders # 1, # 2, # 3, and # 4. The fuel pressure (fuel pressure) supplied to the fuel injection valve 30 is detected by a fuel pressure sensor 56.

Further, the common rail 53 is provided with a relief valve 55, a fuel pressure sensor 56, and a cutoff valve 57 in addition to the fuel injection valve 30 in accordance with the number of cylinders (here, 4) of the engine 10. Is connected to the second common rail 58, thereby making it possible to make the volume of the common rail variable (detailed later).
In the high-pressure fuel supply control device 1 of the present embodiment, a control unit 100 incorporating a microcomputer is provided to perform various controls of the engine 10 including the high-pressure fuel pump 60.

  As shown in FIG. 2, the control unit 100 is basically composed of an MPU 101, an EP-ROM 102, a RAM 103, an I / O LSI 104 including an A / D converter, and the like, and an airflow sensor 24 as an input signal. A signal corresponding to the intake air amount detected by the fuel pressure sensor, a signal corresponding to the fuel pressure detected by the fuel pressure sensor 56, a signal corresponding to the opening of the throttle valve 25 detected by the throttle sensor 23, a cam angle sensor (phase sensor) ) A detection (angle) signal indicating the phase (rotation position) of the exhaust camshaft 49 from 36 and the rotation position of the pump drive cam 47 of the high-pressure fuel pump 60, and rotation of the crankshaft 18 from the crank angle sensor (position sensor) 37. Detection (angle) signal indicating angle / phase (rotation position), disposed in exhaust passage 40 In addition to the signal corresponding to, for example, the oxygen concentration in the exhaust gas detected by the fuel ratio sensor 44 and the signal corresponding to the engine cooling water temperature detected by the water temperature sensor 19 disposed in the cylinder block 12, FIG. A signal indicating the start of start (cranking start) from a non-ignition switch, a signal indicating the depression amount of the accelerator pedal obtained from the accelerator sensor, and the like are also supplied.

  The control unit 100 fetches each signal with a predetermined period, executes a predetermined calculation process, and uses the control signal calculated as the calculation result as each fuel injection valve 30, the ignition coil 34, the high pressure fuel pump 60, the low pressure. Supplied to the fuel pump 51, the electric throttle valve 25, the shut-off valve 57 described later, etc., and performs fuel injection (injection amount, injection timing) control, ignition timing control, fuel pressure control, throttle valve 25 opening control, etc. To do.

  The high-pressure fuel supply control device 1 according to the present embodiment is characterized by the output control of the control (drive) signal for the actuator (solenoid 90) and the shutoff valve 57 (the solenoid 57b) provided in the high-pressure fuel pump 60. This will be described in detail below.

  FIG. 3 shows an overall configuration of a fuel supply system including the high-pressure fuel pump 60 in the present embodiment, and FIG. 4 shows an enlarged vertical cross section of the high-pressure fuel pump 60.

  The high-pressure fuel pump 60 pressurizes fuel from the fuel tank 50 and pumps high-pressure fuel to the first common rail 53. The high-pressure fuel pump 60 includes a cylinder chamber 67, a pump chamber 68, and a solenoid chamber 69. The cylinder chamber 67 is disposed below the pump chamber 68, and the solenoid chamber 69 is disposed on the suction side of the pump chamber 68.

  The cylinder chamber 67 is provided with a plunger 62, a lifter 63, and a plunger lowering spring 64. The plunger 62 is provided with an exhaust cam shift 49 and a lifter 63 pressed against a pump drive cam 47 that rotates integrally therewith. The volume of the pressurizing chamber 72 is changed.

  The pump chamber 68 includes a suction passage 71 for low-pressure fuel, a pressurization chamber 72, and a discharge passage 73 for high-pressure fuel. Between the suction passage 71 and the pressurization chamber 72, a suction valve serving as a fuel passage valve is provided. 65 is provided. The intake valve 65 is a check valve that restricts the direction of fuel flow, and is biased in the valve closing direction (the direction from the pump chamber 68 toward the solenoid chamber 69) by a valve closing spring 65a. A discharge valve 66 is provided between the pressurizing chamber 72 and the discharge passage 73. The discharge valve 66 is also a check valve that restricts the direction of fuel flow, and is closed by a valve closing spring 66a. Is biased in the direction. The valve closing spring 65a has a pressure on the pressure chamber 72 side equal to or higher than the pressure on the suction passage 71 side with the suction valve 65 sandwiched by the volume change in the pressure chamber 72 by the plunger 62. In this case, the suction valve 65 is urged to close.

  In the solenoid chamber 69, a solenoid 90, which is an actuator, a suction valve operating member 91, and a valve opening spring 92 are disposed. The suction valve operating member 91 is disposed at a position opposite to the suction valve 65. When the solenoid 90 is energized and energized, its tip (rod portion) is brought into contact with and separated from the suction valve 65, and is attracted to the solenoid chamber 69 side by the electromagnetic force. 65 is moved in the valve closing direction. On the other hand, in a state where the solenoid 90 is not energized, the suction valve 65 is opened via the suction valve operating member 91 by the biasing force of the valve opening spring 92 that presses against the rear end of the suction valve operating member 91. The valve is moved in the valve direction and opened.

  The fuel adjusted to a predetermined pressure from the fuel tank 50 via the fuel pump 51 and the fuel pressure regulator 52 is guided to the suction passage 71 of the pump chamber 68, and then, in the pressurizing chamber 72 in the pump chamber 68. The pressure is increased by the reciprocating motion of the plunger 62, and the pressure is fed from the discharge passage 73 of the pump chamber 68 to the first common rail 53.

  In addition to the fuel injection valves 30, 30, 30, 30, a second common rail 58 is connected to the first common rail 53 via a shutoff valve 57.

  The shut-off valve 57 includes a shut-off chamber 57d disposed between the first common rail 53 and the second common rail 58, and a shut-off valve body that shuts off (closes) -opens (opens) the shut-off chamber 57d. 57a, a shutoff valve solenoid 57b that is an actuator that drives the shutoff valve body 57a in the valve opening direction, and a valve opening spring 57c that biases the shutoff valve body 57a in the valve closing direction.

  The shut-off valve 57 is closed when the shut-off valve solenoid 57b is OFF (when no power is supplied), and the fuel does not flow to the second common rail 58. Since the fuel does not flow to the second common rail 58, the total common rail volume becomes only the volume of the first common rail 53, and the fuel pressure responsiveness can be improved.

  On the other hand, when the shut-off valve solenoid 57b is ON (when energized), the shut-off valve body 57a moves in the valve opening direction, so that the fuel also flows to the second common rail 58. The flow of fuel to the second common rail 58 also increases the common rail volume, and as a result, the pulsation amplitude width is reduced.

  Here, the control unit 100 controls the shut-off valve 57 (the solenoid 57b) based on detection signals from the crank angle sensor 37, the cam angle sensor 36, the fuel pressure sensor 56 provided on the common rail 53, and the like. A (drive) signal is output to control opening / closing of the shutoff valve 57. A relief valve 57 is arranged between the common rail 53 and the fuel tank 50 in order to prevent damage to the piping system, and the pressure in the common rail 53 has a predetermined value. If exceeded, the valve is opened.

  FIG. 5 shows an operation time chart of the high-pressure fuel pump 60. Note that the actual stroke (actual position) of the plunger 62 driven by the pump drive cam 47 is a curve as shown in the lower part of FIG. 6, but in order to make the positions of the top dead center and the bottom dead center easy to understand. In the figure (FIG. 13 etc.) in which the stroke of the plunger 62 other than FIG. 6 is shown, the stroke of the plunger 62 is drawn linearly.

  When the plunger 62 moves from the top dead center side to the bottom dead center side according to the biasing force of the plunger lowering spring 64 by the rotation of the pump drive cam 47, the suction stroke of the pump chamber 68 is performed. In this intake stroke, the intake valve operating member 91 moves the intake valve 65 in the valve opening direction in accordance with the biasing force of the valve opening spring 92. Thereby, the pressure in the pressurizing chamber 72 decreases.

  Next, when the plunger 62 moves from the bottom dead center side to the top dead center side against the biasing force of the plunger lowering spring 64 by the rotation of the cam 47, the compression stroke of the pump chamber 68 is performed. In this compression stroke, when the drive signal of the solenoid 90 as an actuator is output from the control unit 100 and the solenoid 90 is energized and excited (ON state), the suction valve operating member 91 is biased by the valve opening spring 92. The suction valve 65 is moved in the direction to close the valve, the tip of the suction valve 65 moves away from the suction valve 65, and the suction valve 65 moves in the valve closing direction according to the urging force of the valve closing spring 65a. . Thereby, the pressure in the pressurizing chamber 72 rises.

  When the suction valve operating member 91 is most attracted to the solenoid 90 side and the suction valve 65 synchronized with the reciprocation of the plunger 62 is closed to increase the pressure in the pressurizing chamber 72, the pressure in the pressurizing chamber 72 is increased. The fuel presses the discharge valve 66, and the discharge valve 66 is automatically opened against the urging force of the valve closing spring 66a, and the high pressure fuel corresponding to the volume reduction of the pressurizing chamber 72 is discharged to the common rail 53 side. Is done. The energization of the solenoid 90 (output of the drive signal) is stopped (OFF) when the suction valve 65 is moved to the solenoid 90 side and closed, but as described above, the pressurizing chamber 72 is turned off. Since the internal pressure is high, the intake valve 65 is maintained in a closed state, and fuel is discharged to the common rail 53 side.

  When the plunger 62 moves from the top dead center side to the bottom dead center side according to the biasing force of the plunger lowering spring 64 by the rotation of the cam 47, the suction stroke of the pump chamber 68 is performed, and the pressurizing chamber As the pressure in 72 is reduced, the suction valve operating member 91 is moved in the direction to open the suction valve 65 in accordance with the urging force of the valve opening spring 92, and the suction valve 65 is reciprocated by the plunger 62. The valve is automatically opened in synchronism, and the open state of the intake valve 65 is maintained. The discharge valve 66 is not opened due to the pressure drop in the pressurizing chamber 72. Thereafter, the above operation is repeated.

  Therefore, when the solenoid 90 is turned on (energized excitation state) in the middle of the compression stroke before the plunger reaches the top dead center, the fuel pumping to the common rail 53 is performed and the fuel pumping is started once. For example, since the pressure in the pressurizing chamber 72 has risen, even if the solenoid 90 is turned off thereafter, the suction valve 65 remains closed, but automatically in synchronism with the start of the suction stroke. The valve can be opened. Therefore, the fuel discharge amount to the common rail 53 side can be adjusted by the output start timing of the drive signal of the solenoid 90. Further, by setting an appropriate output start timing based on the signal from the fuel pressure sensor 56 and controlling the solenoid 90, the pressure of the common rail 53 can be feedback controlled to the target value.

  FIG. 7 is a flowchart showing an example of a control routine for the shutoff valve 57 executed by the control unit 100 in the present embodiment.

  First, in step 701, the interrupt process of this routine starts. The interrupt process is time synchronized, for example, every 10 ms. In steps 702 to 704, the engine speed, fuel injection amount, and intake air amount are read. The purpose of this reading is to determine whether or not the fuel pressure pulsation that increases as the rotational speed and the fuel injection amount increase is in an unacceptable region.

  In the following step 705, it is determined whether or not the fuel pressure responsiveness is required. If it is determined that the fuel pressure responsiveness is required (necessary region determination flag: # FPRESNES = 1), the cutoff valve solenoid control signal ON flag: # FSHTSOL = 0, and the process proceeds to step 708 to control the cutoff valve solenoid 57b. Is set to OFF. In step 706, it is determined whether or not the pulsation must be reduced. If it is determined that the pulsation is reduced, the cutoff valve solenoid control signal ON flag: # FSHTSOL = 1 is set, and the process proceeds to step 707. The control signal of the shut-off valve solenoid 57b is turned ON.

  FIG. 8 is a flowchart showing details of step 705. Here, as an area where it is necessary to improve the fuel pressure response, the start time will be described as an example.

  At start-up, high-pressure fuel is required to promote fuel atomization. Therefore, interrupt processing is started in step 801, and in steps 802 and 803, a starter drive signal and fuel pressure are read. In step 804, it is determined whether the starter is being driven. If it is determined that the starter is being driven, the routine proceeds to step 807, where it is determined that the fuel pressure responsiveness required region is required, and a necessary region determination flag: # FPRESNES = 1 is set. In step 805, it is determined whether or not the fuel pressure is within a predetermined time after starting and not more than a predetermined fuel pressure. As the predetermined time after the start, a time sufficient to reach the target fuel pressure at the start is set, and the target fuel pressure is set as the predetermined fuel pressure. If it is determined that the above condition is satisfied, the process proceeds to step 807, and the necessary area determination flag: # FPRESNES = 1 is set as the fuel pressure responsiveness required area.

  Next, the pulsation reduction region determination method (step 706 in FIG. 7) will be described with reference to FIG. Since the fuel pressure pulsation increases as the engine speed and the fuel injection amount increase, the region above the curve E in FIG. 9 is a region where pulsation is desired to be reduced. For example, the pulsation reduction region is determined by a map of the fuel injection amount axis and the rotation speed axis.

  FIG. 10 is a flowchart showing an example of a control routine for the high-pressure fuel pump 60 corresponding to the cutoff valve solenoid control signal ON flag: #FSHTSOL executed by the control unit 100 in the present embodiment. The purpose of this control routine is to prevent a deviation between the target fuel pressure and the actual fuel pressure at the moment when the shutoff valve 57 is opened from the closed state.

  First, interrupt processing is started in step 1001, and fuel pressure is read in step 1002. In the subsequent step 1003, the open / close state of the shutoff valve 57 is determined by the shutoff valve solenoid control signal ON flag: #FSHTSOL. If # FSHTSOL = 1, that is, if the shut-off valve 57 is open, the process proceeds to step 1004. In step 1004, the target fuel pressure is compared with the actual fuel pressure. If the target fuel pressure is larger, the process proceeds to step 1005, and the discharge amount of the high-pressure fuel pump 60 is increased. In this example, full discharge is performed, but a method of increasing the amount proportional to the difference between the target fuel pressure and the actual fuel pressure may be used. If it is determined in step 1004 that the target fuel pressure is equal to the actual fuel pressure, the pump increase is terminated.

  Next, the operation and effect obtained by adding the second common rail 58 and performing the control will be described with reference to the time chart of FIG.

  The second common rail 58 has a smaller number of connected valves than the common rail 53 (only the shut-off valve 57 is connected to the second common rail 58), so that the remaining pressure in the common rail is maintained. Is long. Therefore, after a certain period of time has elapsed after the engine is stopped, the fuel pressure in the second common rail 58 becomes higher than the fuel pressure in the first common rail 53 (see FIG. 11).

  In FIG. 12, when the control unit 100 is turned on, the shutoff valve solenoid control signal ON flag: # FSHTSOL = 1. As a result, the fuel pressure in the first common rail 53 is increased by the fuel pressure in the second common rail 58. By increasing the fuel pressure in the first common rail 53 before starting the starter, atomization of fuel injection at the time of start-up is promoted, and exhaust gas purification performance (exhaust emission characteristics) is improved. #FSHTSOL is cleared when the starter drive signal is turned on because the shut-off valve 57 should be closed at the start as described above.

  Here, the purpose of this control is to assist the fuel pressure in the first common rail 53 with the fuel pressure in the second common rail 58, and the control can also be used immediately before the restart after the idle stop.

  FIG. 14 is a flowchart showing an example of a shut-off valve closing failure determination routine executed by the control unit 100 in the present embodiment. First, in step 1401, interrupt processing is started, and in step 1402, the fuel pressure is read. In Step 1403, it is determined whether or not the shutoff valve solenoid control signal ON flag: # FSHTSOL = 1. If # FSHTSOL = 1, that is, if a command to open the shutoff valve 57 is issued, the process proceeds to step 1404. In step 1404, it is determined whether the pressure change rate in the first common rail 53 is equal to or greater than a predetermined value.

  Here, FIG. 18 shows the rate of pressure increase when the discharge amount of the high-pressure fuel pump 60 is constant. The rate of pressure increase increases as the common rail volume decreases. When the predetermined value is a pressure change rate corresponding to the volume obtained by adding the second common rail 58 to the first common rail 53, the shutoff valve 57 is closed when the pressure change rate exceeds the predetermined value. it is conceivable that. Therefore, if it is determined in step 1404 that the pressure change rate in the common rail 53 is equal to or greater than a predetermined value, it is determined in step 1405 that the shut-off valve 57 is closed.

  FIG. 15 is a flowchart showing an example of a shut-off valve open failure determination routine executed by the control unit 100 in the present embodiment. First, interrupt processing is started in step 1501, and fuel pressure is read in step 1502. In step 1503, it is determined whether or not the shutoff valve solenoid control signal ON flag: # FSHTSOL = 0. If # FSHTSOL = 0, that is, if a command to close the shutoff valve 57 is issued, the process proceeds to step 1504. In step 1504, it is determined whether or not the pressure change rate in the first common rail 53 is equal to or less than a predetermined value. When the predetermined value is a rate of change in pressure corresponding to the volume of the common rail 53, it is considered that the shutoff valve 57 is open when the pressure change rate is equal to or less than the predetermined value. Therefore, when it is determined in step 1504 that the pressure change rate in the common rail 53 is equal to or less than the predetermined value, it is determined in step 1505 that the shut-off valve 57 is open.

  FIG. 16 shows another example of the overall configuration of the fuel supply system including the high-pressure fuel pump 60. In this example, a fuel pressure sensor 59 is added to the second common rail 58 with respect to the configuration example shown in FIG. Other configurations are basically the same as those in the above embodiment.

  An example of a shut-off valve closing failure determination routine executed by the control unit 100 in the configuration example shown in FIG. 16 is shown in a flowchart in FIG. First, interrupt processing is started in step 1701, and in step 1702, the fuel pressure in the common rail 53 (referred to as fuel pressure A) is read. In step 1703, the fuel pressure in the second common rail 58 (referred to as fuel pressure B) is read. In step 1704, it is determined whether or not the shutoff valve solenoid control signal ON flag: # FSHTSOL = 1. If # FSHTSOL = 1, that is, if a command to open the shutoff valve 57 is issued, the process proceeds to step 1705. In step 1705, it is determined whether or not the state in which the absolute value of fuel pressure A-fuel pressure B is equal to or greater than a predetermined value is equal to or greater than a predetermined time.

  When the state where the absolute value of fuel pressure A-fuel pressure B is equal to or greater than a predetermined value has elapsed for a predetermined time or more, it is considered that the shutoff valve 57 is closed. Therefore, when it is determined in step 1705 that the state where the absolute value of fuel pressure A-fuel pressure B is equal to or greater than the predetermined value is equal to or longer than the predetermined time, it is determined in step 1405 that the shutoff valve 57 is closed. .

  In the high pressure fuel supply control device of the present embodiment configured as described above, the following operational effects can be obtained.

  That is, in addition to the first common rail 53, a second common rail 58 and a shutoff valve 57 are provided, and the opening and closing of the shutoff valve 57 is controlled according to the operating conditions, and the common rail volume is made variable. It is possible to control quickly and reduce fuel pressure pulsation, thereby suppressing variations in the injection amount. Therefore, it is possible to stabilize combustion and improve exhaust gas performance (exhaust emission characteristics).

  More specifically, as shown in the time chart of FIG. 19, as the fuel injection amount increases, the common rail volume is increased and the fuel pressure pulsation is reduced. By reducing the fuel pressure pulsation, it is possible to reduce the variation in the fuel injection amount. By reducing the variation in the injection amount, misfire can be prevented and the air-fuel ratio can be accurately controlled, which contributes to the improvement of exhaust emission characteristics.

1 is an overall configuration diagram showing an embodiment of a high-pressure fuel supply control device according to the present invention together with an engine to which it is applied. The block diagram with which it uses for description of the control unit which comprises the principal part of the high pressure fuel supply control apparatus shown by FIG. The figure which shows an example of the whole structure of the fuel supply system provided with the high pressure fuel pump in embodiment shown by FIG. FIG. 2 is an enlarged longitudinal sectional view of the high pressure fuel pump shown in FIG. 1. The time chart used for operation | movement description of a high pressure fuel pump. Supplementary explanatory drawing of the time chart of FIG. The flowchart which shows an example of the control routine of a cutoff valve. The flowchart which shows the detail of step 705 (fuel pressure responsiveness required area | region determination) of FIG. FIG. 7 is a diagram used for explaining step 706 (pulsation reduction region determination) in FIG. 7. The flowchart which shows an example of the control routine of a high pressure fuel pump. Diagram used to explain the residual pressure in the common rail after the engine stops The time chart used for description of the effect by extending the 2nd common rail and performing opening-and-closing control of a cutoff valve. Diagram for explaining fuel pressure pulsation generation mechanism The flowchart which shows an example of a shut-off valve closing fault determination routine. The flowchart which shows an example of a shut-off valve open failure determination routine. The figure which shows the other example of the whole structure of the fuel supply system provided with the high pressure fuel pump. The flowchart which shows an example of the shut-off valve closing fault determination routine in the structural example shown by FIG. The figure used for description of the relationship between the common rail volume and the pressure increase rate. The figure used for description of the effect of embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 High pressure fuel supply control apparatus 10 In-cylinder injection type engine 30 Fuel injection valve 36 Cam angle sensor 37 Crank angle sensor 47 Pump drive cam 49 Exhaust cam shaft 53 1st common rail 55 Relief valve 56, 59 Fuel pressure sensor 57 Shut-off valve 57b Shut off Valve solenoid 58 Second common rail 60 High-pressure fuel pump 65 Suction valve 90 Solenoid (actuator)
100 control unit

Claims (11)

A high-pressure fuel pump pressurizes and supplies fuel to the pressure accumulating chamber, and supplies the fuel in the pressure accumulating chamber to a fuel injection valve for directly injecting the fuel into the combustion chamber; and the pressure in the pressure accumulating chamber exceeds a predetermined value A pressure adjusting means for adjusting the pressure by returning the fuel to the low pressure side, a pressure detecting means for detecting the pressure in the pressure accumulating chamber, and a control means for controlling the pressure in the pressure accumulating chamber. A high pressure fuel supply control device for an engine,
A high-pressure fuel supply control device for an engine, wherein a plurality of the pressure accumulating chambers are provided and a shutoff valve for opening and closing the pressure accumulating chambers is provided.   2. The high pressure fuel supply control device for an engine according to claim 1, wherein the shutoff valve is selectively opened and closed by the control means.   3. The high-pressure fuel for an engine according to claim 1, wherein the pressure adjusting unit is attached to a pressure accumulating chamber side where the fuel injection valve is provided among the plurality of pressure accumulating chambers. Supply control device.   The high-pressure fuel supply control device for an engine according to any one of claims 1 to 3, wherein the pressure detecting means is provided in each of the plurality of pressure accumulating chambers.   The control means sets the opening / closing timing of the shut-off valve based on at least one of an engine speed, a fuel injection amount, an intake air amount, and a pressure in the pressure accumulating chamber. The high-pressure fuel supply control device for an engine according to any one of 2 to 4.   The high-pressure fuel supply control device according to claim 5, wherein the control means increases the discharge amount of the high-pressure pump until a predetermined time elapses after the shut-off valve is opened.   7. The high pressure fuel supply control device for an engine according to claim 6, wherein the control means obtains an increase period or an increase in the discharge amount of the high pressure pump based on the pressure in the pressure accumulating chamber. .   The engine high-pressure fuel supply control device according to any one of claims 2 to 7, wherein the control means opens the shut-off valve based on a pressure in the pressure accumulating chamber when the engine is stopped. .   The engine high-pressure fuel supply control device according to any one of claims 2 to 8, wherein the control means closes the shut-off valve when the engine is started.   9. The high-pressure fuel supply control for an engine according to claim 1, wherein the control unit determines whether or not the shut-off valve has failed based on a pressure change rate in the pressure accumulating chamber. apparatus.   5. The high-pressure fuel supply control device for an engine according to claim 4, wherein the control unit determines whether or not the shut-off valve has failed based on pressure differences in the plurality of pressure accumulating chambers.

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