JP2010031816A - Control device for pressure accumulation type fuel supply system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent damage of a fuel supply system and deterioration of operation performance of an internal combustion engine when excess delivery abnormality occurs in a high pressure pump. <P>SOLUTION: Fuel is supplied to an engine 10 through a low pressure pump part 30 for pressurizing the fuel in a fuel tank 25, a high pressure pump part 40 for further pressurizing the fuel delivered from the low pressure pump part 30, and a delivery pipe 35 for accumulating the high pressure fuel delivered from the high pressure pump part 40. An ECU 60 controls a fuel pressure in the delivery pipe 35 by controlling a fuel delivery quantity of the high pressure pump part 40 by a fuel quantity adjusting valve 43. When it is detected that the high pressure fuel is excessively delivered from the high pressure pump part 40 to the delivery pipe 35, the fuel delivery quantity of the high pressure pump part 40 is controlled by the low pressure pump part 30. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device for an accumulator fuel supply system, and more particularly to a control device for an accumulator fuel supply system for an internal combustion engine including a low pressure pump section, a high pressure pump section, and an accumulator chamber.

  For example, as a fuel supply system for an in-cylinder gasoline engine, a low-pressure pump that pumps fuel from a fuel tank and pressurizes it, a high-pressure pump that further increases the pressure of fuel pumped from the low-pressure pump, and a high-pressure pump that discharges from the high-pressure pump A pressure accumulating chamber for storing fuel and injecting high pressure fuel in the accumulating chamber directly from a fuel injection valve into a cylinder of an internal combustion engine has been put into practical use. In this system, a fuel metering valve is generally provided in a high-pressure pump, and the fuel discharge amount of the high-pressure pump is controlled by opening and closing the fuel metering valve. Thereby, the fuel pressure in the pressure accumulating chamber is controlled, and further, the injection pressure of the fuel injection valve is controlled.

  In the above fuel supply system, for example, when a disconnection of the fuel metering valve or a solenoid failure occurs, it is considered that the fuel discharge amount from the high-pressure pump cannot be properly controlled. For example, when a situation occurs in which the fuel discharged from the high pressure pump does not become high pressure due to a failure of the fuel metering valve, the amount of fuel supplied to the pressure accumulating chamber becomes insufficient. Alternatively, when an excessive amount of fuel is continuously discharged from the high pressure pump (for example, a full discharge abnormality in which the maximum discharge amount of the high pressure pump is continuously discharged) occurs, the amount of fuel supplied to the pressure accumulation chamber is excessive. become. When these situations occur, the fuel pressure in the pressure accumulating chamber cannot be controlled, and as a result, the injection pressure of the fuel injection valve cannot be controlled. For this reason, combustion is not properly performed in the internal combustion engine, and there is a concern that the evacuation traveling cannot be performed in the worst case. Further, when an excessive discharge abnormality occurs, an excessive amount of fuel continues to be discharged from the high pressure pump, so that the fuel pressure increases excessively on the downstream side (high pressure side) of the high pressure pump, causing damage in the fuel supply system. There is a fear.

Therefore, various methods have been proposed for enabling the operation of the internal combustion engine when a discharge abnormality of the high-pressure pump occurs (for example, Patent Document 1). In Patent Document 1, a bypass passage for supplying fuel pumped from a low pressure pump to a pressure accumulating chamber by bypassing the high pressure pump is provided in the fuel supply system. When the high pressure pump is abnormal, fuel from the low pressure pump is supplied to the bypass passage. It is disclosed to supply the pressure accumulating chamber via
Japanese Patent No. 3827814

  However, in the system of Patent Document 1, since the pressure of the fuel supplied to the pressure accumulating chamber is about the feed pressure, it is conceivable that the injection pressure of the fuel injection valve is low and the fuel amount corresponding to the required injection amount cannot be injected. Therefore, in the conventional configuration in which fuel is supplied from the low pressure pump to the fuel injection valve by bypassing the high pressure pump, combustion is not sufficiently performed in the internal combustion engine when the discharge of the high pressure pump is abnormal, and the operability of the internal combustion engine is greatly reduced. There is a fear.

  On the other hand, when the high-pressure pump is overdischarged abnormally, the high-pressure pump can discharge fuel higher than the feed pressure, so there is room for high-pressure fuel to be supplied to the accumulator using the pressurizing function of the high-pressure pump. It is thought that there is.

  The present invention has been made to solve the above-described problems, and prevents the fuel supply system from being damaged and the operability of the internal combustion engine when an excessive discharge abnormality of the high-pressure pump occurs in the fuel supply system. The main object of the present invention is to provide a control device for an accumulator fuel supply system that can suppress the decrease in the pressure.

  The present invention employs the following means in order to solve the above problems.

The present invention includes a low pressure pump unit that pressurizes fuel in a fuel tank, a high pressure pump unit that further pressurizes fuel discharged from the low pressure pump unit, and a pressure accumulation chamber that stores high pressure fuel discharged from the high pressure pump unit. Applied to an accumulator fuel supply system of an internal combustion engine,
The present invention relates to a control device for an accumulator fuel supply system that controls a fuel pressure in the accumulator chamber by controlling a fuel discharge amount of the high-pressure pump section. The invention according to claim 1 is a discharge abnormality detection unit that detects that high pressure fuel is excessively discharged from the high pressure pump unit to the pressure accumulation chamber, and the discharge abnormality detection unit detects the high pressure. And a metering control means for controlling the fuel discharge amount of the high-pressure pump portion by the low-pressure pump portion when an excessive discharge state of the pump portion is detected.

  In short, when an excessive discharge abnormality occurs in the high-pressure pump unit, there is a concern that the fuel pressure will rise excessively on the downstream side (high-pressure side) from the high-pressure pump unit, and the high-pressure fuel supply system such as the accumulator chamber may be damaged. . The present invention is a case in which when the excessive discharge abnormality of the high-pressure pump unit is detected, the fuel discharge amount of the high-pressure pump unit is controlled by the low-pressure pump unit. In addition, the fuel pressure in the pressure accumulating chamber can be controlled. Thereby, it is possible to prevent the high-pressure fuel supply system such as the pressure accumulating chamber from being damaged when an excessive discharge abnormality of the high-pressure pump occurs. Further, since the fuel discharged into the pressure accumulating chamber passes through a high pressure pump in an excessive discharge state (for example, full discharge state), the fuel pressure in the pressure accumulating chamber is relatively fed (for example, the discharge side pressure of the low pressure pump unit). The pressure of the fuel injection valve connected to the pressure accumulating chamber can be kept higher than the feed pressure. Therefore, it is possible to suppress a decrease in the drivability of the internal combustion engine when the high-pressure pump part is excessively discharged abnormally.

  In an accumulator fuel supply system equipped with a pressure release valve that opens and closes according to the fuel pressure in the accumulator chamber, if an abnormality such as clogging of the opening of the pressure release valve or the inability to open the valve occurs, the decompression of the accumulator chamber is properly controlled. There is concern about not being implemented. In this state, if an excessive discharge abnormality occurs in the high-pressure pump unit, the fuel pressure in the pressure accumulator chamber exceeds the valve opening pressure of the pressure release valve, resulting in damage to the high-pressure fuel supply system such as the pressure accumulator chamber. Can be considered. In view of this point, the invention described in claim 2 is a pressure release valve that opens when the fuel pressure in the pressure accumulating chamber reaches a predetermined valve opening pressure and depressurizes the pressure accumulating chamber; A pressure reduction abnormality detecting means for detecting a function abnormality, wherein the metering control means detects the pressure reduction function abnormality of the pressure release valve by the pressure reduction abnormality detection means, and Controls the amount of fuel discharged from the high-pressure pump unit. According to this configuration, when an abnormality in the pressure reducing function of the pressure release valve is detected such that the fuel pressure in the pressure accumulation chamber exceeds the valve opening pressure of the pressure release valve, the fuel discharge of the high pressure pump unit is performed by the low pressure pump unit. Since the amount is controlled, it is possible to suitably obtain an effect of preventing the fuel supply system from being damaged when an excessive discharge abnormality occurs in the high-pressure pump unit.

  In order to enable various operation controls in the internal combustion engine, it is preferable to make the fuel pressure in the pressure accumulating chamber variable. In order to sufficiently perform combustion while reducing the drive loss of the low-pressure pump unit, the injection pressure of the fuel injection valve, that is, the fuel pressure in the pressure accumulating chamber is variably controlled according to, for example, the operating state of the internal combustion engine. More specifically, it is desirable to increase the fuel pressure in the pressure accumulating chamber as the engine speed increases and the load on the internal combustion engine increases. In view of this, the invention according to claim 3 further includes target fuel pressure setting means for variably setting a target value of the fuel pressure in the pressure accumulating chamber when an excessive discharge abnormality of the high pressure pump unit occurs. The metering control unit controls the fuel discharge amount of the high-pressure pump unit by the low-pressure pump unit based on the target value set by the target fuel pressure setting unit. According to this configuration, the target fuel pressure in the pressure accumulating chamber is variably set when the discharge of the high-pressure pump is abnormal, and the low-pressure pump is driven based on the target value. However, fuel injection can be performed at an injection pressure corresponding to the operating state of the internal combustion engine. Thereby, even when the discharge of the high-pressure pump unit is abnormal, various operation controls can be performed in the internal combustion engine, and combustion can be preferably performed while reducing the drive loss of the low-pressure pump unit.

  According to a fourth aspect of the present invention, the target fuel pressure setting means sets the target value to a value smaller than that when the high-pressure pump unit is normal when the high-pressure pump unit is abnormally discharged excessively. According to this configuration, when the excessive discharge of the high pressure pump unit is abnormal, the fuel pressure in the pressure accumulating chamber is set to a smaller value than normal, so the load on the low pressure pump unit and the high pressure pump unit can be reduced. It is possible to suppress the occurrence of a secondary failure in the part or the like.

  In an in-cylinder injection type internal combustion engine, it is necessary to atomize the injected fuel in order to suitably perform combustion, and in order to atomize the fuel, it is necessary to keep the fuel injected into the cylinder at a high pressure. On the other hand, at the fuel pressure (feed pressure) that is pressurized by the low-pressure pump unit, the injection pressure of the fuel injection valve is low, so that the atomization of the injected fuel is not sufficient and the combustion may deteriorate. In view of this point, in the invention according to claim 5, the invention is a pressure accumulation fuel supply system for a cylinder injection type internal combustion engine including a fuel injection valve that directly injects high pressure fuel in the pressure accumulation chamber into the cylinder. Applied. According to this configuration, fuel having a pressure higher than the feed pressure is supplied to the pressure accumulating chamber, so that the injection pressure of the fuel injection valve can be maintained at or above the feed pressure. Therefore, for example, compared with the case where the fuel is directly supplied from the low pressure pump unit to the high pressure pump unit by bypassing the high pressure pump unit, the atomization of the injected fuel can be preferably performed. It is possible to suppress the deterioration of the combustion of the internal combustion engine.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the drawings. In the present embodiment, an engine control system is constructed for an in-cylinder injection type on-vehicle multi-cylinder gasoline engine that is an internal combustion engine. In this control system, an electronic control unit (hereinafter referred to as ECU) is used as a center to control the fuel injection amount, control the ignition timing, and the like. FIG. 1 shows an overall schematic configuration diagram of the engine control system.

  In FIG. 1, the engine 10 is disposed at the front portion of the vehicle. In the engine 10, an air flow meter 12 for detecting the amount of intake air is provided upstream of the intake pipe 11. A throttle valve 14 whose opening degree is adjusted by a throttle actuator 13 such as a DC motor is provided on the downstream side of the air flow meter 12. The opening of the throttle valve 14 (throttle opening) is detected by a throttle opening sensor built in the throttle actuator 13. A surge tank 16 is provided downstream of the throttle valve 14, and an intake pipe pressure sensor 17 for detecting the intake pipe pressure is provided in the surge tank 16. The surge tank 16 is connected to an intake manifold 18 that introduces air into each cylinder of the engine 10. In the intake manifold 18, an airflow control that generates a swirl flow or a tumble flow near the intake port of each cylinder. A valve 19 is provided.

  An intake valve 21 and an exhaust valve 22 are provided at an intake port and an exhaust port of the engine 10, respectively. The air in the surge tank 16 is introduced into the combustion chamber 23 by the opening operation of the intake valve 21, and the exhaust gas after combustion is discharged to the exhaust pipe 28 by the opening operation of the exhaust valve 22.

  A fuel injection valve 24 that directly supplies fuel into the combustion chamber 23 is attached to the cylinder block of the engine 10. A fuel tank 25 disposed at the rear of the vehicle (for example, slightly in front of the rear wheels) is connected to the fuel injection valve 24 via a high-pressure fuel pipe 27 and a low-pressure fuel pipe 26. The fuel in the fuel tank 25 passes through the low pressure fuel pipe 26 and the high pressure fuel pipe 27 and is supplied to the fuel injection valve 24.

  In the fuel supply path from the fuel tank 25 to the fuel injection valve 24, a low-pressure pump unit 30 is disposed at the most upstream part (that is, the rear part of the vehicle), and is downstream of the low-pressure pump part 30 and the front part of the vehicle ( For example, in the engine room), it is connected to the high pressure pump section 40 via the low pressure fuel pipe 26. A delivery pipe 35 serving as a pressure accumulation chamber is provided on the downstream side of the high-pressure pump unit 40, and is connected to the fuel injection valve 24 via the high-pressure fuel pipe 27 on the downstream side. Note that the low-pressure fuel pipe 26 and the high-pressure fuel pipe 27 are longer than the high-pressure fuel pipe 27 because the low-pressure fuel pipe 26 extends from the rear of the vehicle to the front of the vehicle.

  The low-pressure pump unit 30 is provided with an electromagnetically driven low-pressure pump 31 that is driven by power supply from a battery (not shown), and is disposed in the fuel tank 25. The low pressure pump 31 pumps up the fuel stored in the fuel tank 25, pressurizes it to a feed pressure (for example, 0.3 MPa), and pumps the fuel to the high pressure pump unit 40 via the fuel pipe 26. Further, for example, a mechanical regulator 32 is connected between the low-pressure pump 31 and the high-pressure pump unit 40, and the discharge pressure of the low-pressure pump 31 is adjusted to a constant pressure (feed pressure) by the regulator 32, and surplus fuel is supplied. Is returned to the fuel tank 25 by the fuel return pipe 33.

  The high-pressure pump unit 40 is provided with an engine-driven high-pressure pump 41. The high-pressure pump 41 discharges the fuel at a predetermined pressure (feed pressure) pumped from the low-pressure pump 31 to a further higher pressure (for example, 4 to 20 MPa) downstream. The fuel discharged from the high-pressure pump 41 is sent to the delivery pipe 35 via the check valve 42 and then distributed from the delivery pipe 35 to the fuel injection valve 24 of each cylinder.

  Specifically, as shown in FIG. 2, the high-pressure pump 41 is a piston pump that sucks / discharges fuel by reciprocating a plunger 45 within a pump chamber 44 disposed in the middle of the fuel passage 48. The plunger 45 is driven by a cam 46 that is driven to rotate as the cam shaft 29 of the engine 10 rotates. On the fuel suction side of the high-pressure pump 41, a normally-open fuel metering valve 43 that closes when energized is provided. By controlling the valve closing time of the fuel metering valve 43, the high-pressure pump unit 40. The fuel discharge amount is adjusted.

  That is, when the plunger 45 descends, fuel is sucked into the pump chamber 44 and a predetermined amount of fuel sucked is stored in the pump chamber 44. Thereafter, when the fuel metering valve 43 is not energized when the plunger 45 starts to rise, the fuel metering valve 43 remains open to return the fuel in the pump chamber 44 to the upstream side. . On the other hand, when the fuel metering valve 43 is closed as the fuel metering valve 43 is energized, the fuel pressure in the pump chamber 44 increases, and the high-pressure fuel is discharged to the delivery pipe 35 side. That is, in the high-pressure pump unit 40, the fuel discharge amount increases by increasing the energization time to the fuel metering valve 43, and the fuel discharge amount decreases by shortening the energization time to the fuel metering valve 43. .

  The fuel metering valve 43 may be a normally closed type instead of the normally open type. In this case, the fuel discharge amount of the high-pressure pump unit 40 is controlled by controlling the valve opening time of the fuel metering valve 43.

  In addition, a relief valve 47 serving as a pressure release valve for limiting the fuel discharge pressure is provided on the downstream side of the check valve 42 in the high pressure pump unit 40. The relief valve 47 is opened when the fuel discharge pressure of the high-pressure pump unit 40 is equal to or higher than a predetermined relief pressure (for example, 25 MPa), and the fuel discharged from the high-pressure pump 41 is supplied via the fuel return pipe 49 when the valve is opened. Return to tank 25. As a result, the fuel pressure in the delivery pipe 35 does not exceed the relief pressure. Note that the relief valve 47 may be provided in the delivery pipe 35 instead of being provided in the high-pressure pump unit 40.

  Returning to the description of FIG. 1, a spark plug 15 is attached to the cylinder head of the engine 10 for each cylinder. A high voltage is applied to the spark plug 15 at a desired ignition timing through an ignition device (not shown) including an ignition coil. By applying this high voltage, a spark discharge is generated between the counter electrodes of each spark plug 15, and the air-fuel mixture in the combustion chamber 23 is ignited and used for combustion.

  The exhaust pipe 28 is provided with a catalyst 51 such as a three-way catalyst for purifying CO, HC, NOx and the like in the exhaust gas. Further, on the upstream side of the catalyst 51, an O2 sensor 52 for detecting the air-fuel ratio (oxygen concentration) of the air-fuel mixture with exhaust gas as a detection target is provided.

  The exhaust pipe 28 is connected to the surge tank 16 via an EGR pipe 53, and an electromagnetically driven EGR valve 54 is provided in the middle of the EGR pipe 53. Note that the exhaust side connection portion of the EGR pipe 53 may be downstream of the three-way catalyst 51. In the EGR valve 54, the amount of exhaust gas (EGR gas amount) recirculated from the exhaust pipe 28 to the intake passage side is controlled by adjusting the opening degree (EGR opening degree).

  Further, the engine 10 is provided with a coolant temperature sensor 55 that detects the coolant temperature, and a crank angle sensor 56 that outputs a rectangular crank angle signal at every predetermined crank angle of the engine (for example, at a cycle of 30 ° CA). Yes. In addition, this system is provided with a fuel pressure sensor 57 that detects the fuel pressure in the delivery pipe 35 and an accelerator sensor 58 that detects the amount of accelerator operation by the driver, for example, provided in front of the driver's seat and lights when an abnormality is detected. An abnormality warning lamp 59 is provided.

  The ECU 60 is composed mainly of a microcomputer (hereinafter referred to as a microcomputer) 61 composed of a CPU, a ROM, a RAM, and the like as is well known, and executes various control programs stored in the ROM, so that the engine operation state can be changed each time. In response, various controls of the engine 10 are performed. That is, the microcomputer 61 of the ECU 60 inputs detection signals from the various sensors described above, calculates the fuel injection amount, ignition timing, and the like based on the various detection signals, and the fuel injection valve 24 and other fuel supply systems. The control of each part (low pressure pump 31 and fuel metering valve 43) and ignition device is controlled, or throttle control and EGR control are performed.

  Regarding fuel injection control, the microcomputer 61 calculates the fuel injection amount from the intake air amount of the engine 10 and the engine speed, and converts the fuel injection amount into the injection time from the fuel pressure (injection pressure) in the delivery pipe 35 and the like. Then, the fuel injection valve 24 is opened for the calculated injection time. As for the fuel pressure of the delivery pipe 35, the target fuel pressure is set within a predetermined range (for example, 4 to 20 MPa) according to the accelerator operation amount and the engine speed, and the fuel metering valve 43 is closed so as to reach the target fuel pressure. The fuel discharge amount of the high-pressure pump unit 40 is adjusted by controlling the valve time.

  Here, as an abnormality in the fuel supply path from the fuel tank 25 to the fuel injection valve 24, for example, due to disconnection of the fuel metering valve 43 or solenoid failure, the maximum discharge amount of fuel from the high-pressure pump unit 40 continues. When the full discharge abnormality supplied from the unit 40 to the delivery pipe 35 occurs, the fuel pressure (injection pressure) in the delivery pipe 35 cannot be controlled to the target fuel pressure, and the fuel injection control cannot be performed properly. Conceivable.

  In particular, when the relief valve 47 fails and the pressure relief cannot be sufficiently performed by the relief valve 47, an excessive amount of fuel continues to be discharged from the high-pressure pump unit 40. As a result, the fuel pressure in the delivery pipe 35 is increased. There is a risk that the delivery pipe 35 and the high-pressure fuel pipe 27 may be damaged.

  Therefore, in the present embodiment, when a full discharge abnormality of the high-pressure pump unit 40 occurs and the maximum amount of fuel is continuously supplied from the high-pressure pump unit 40 to the delivery pipe 35, the fuel supplied to the delivery pipe 35 The amount is adjusted by the low-pressure pump unit 30. At this time, the fuel pressure in the delivery pipe 35 is made higher than the feed pressure by supplying fuel from the low-pressure pump section 30 to the delivery pipe 35 via the high-pressure pump section 40. As this process, the microcomputer 61 of the ECU 60 executes the following process.

  First, a process (abnormality detection process) when a full discharge abnormality of the high-pressure pump unit 40 is detected will be described. FIG. 3 is a flowchart illustrating an example of a processing procedure of abnormality detection processing in the present embodiment. This process is executed at predetermined intervals by the microcomputer 61 of the ECU 60.

  In FIG. 3, first, in step S11, it is determined whether or not a full discharge abnormality of the high-pressure pump unit 40 has occurred. In the present embodiment, the estimated discharge amount of the high-pressure pump unit 40 is calculated from, for example, the amount of change in fuel pressure. It is determined that the full discharge abnormality of the unit 40 has occurred. The method for detecting the full discharge abnormality of the high-pressure pump unit 40 is not limited to the above. For example, the estimated discharge amount of the high-pressure pump unit 40 is calculated from the required injection amount of the fuel injection valve 24 and the like. A state where the amount exceeds the required discharge amount continues for a predetermined time, or a state where the fuel pressure detection value detected by the fuel pressure sensor 57 is higher than the target fuel pressure continues for a predetermined time, alone or in combination with the above method. May be diagnosed.

  When the full discharge abnormality of the high-pressure pump unit 40 is detected, the process proceeds to step S12, and the abnormality warning lamp 59 is turned on. In addition, since the high-pressure pump unit 40 cannot adjust the discharge amount of the high-pressure fuel, a process for adjusting the fuel pressure in the delivery pipe 35 by the low-pressure pump 31 instead of the high-pressure pump unit 40 (low-pressure side metering process) is started. To do. Further, in step S13, an upper limit guard is set for the throttle opening, for example, in order to limit the operation.

  Next, the low-pressure side metering process will be described with reference to FIG. FIG. 4 is a flowchart illustrating an example of a processing procedure of low-pressure side metering processing. This process is executed at predetermined intervals by the microcomputer 61 of the ECU 60.

  In FIG. 4, first, in step S20, it is determined whether or not a permission condition (low pressure side metering permission condition) for adjusting the discharge amount of the high pressure fuel by the low pressure pump 31 is satisfied. In this embodiment, the low-pressure side metering permission condition is that the low-pressure pump unit 30 is not abnormal and the voltage of the battery that supplies power to the low-pressure pump 31 is equal to or higher than a predetermined value. If the low pressure side metering permission condition is not satisfied, the process proceeds to step S21 and the engine 10 is stopped.

  On the other hand, if the low-pressure metering permission condition is satisfied, the process proceeds to step S22, and the target fuel pressure (target fuel pressure Pfstr at the time of abnormality) of the delivery pipe 35 when adjusting the discharge amount of the high-pressure fuel by the low-pressure pump 31 is calculated. To do. In the present embodiment, the abnormal target fuel pressure Pfstr is variable according to the operating state of the engine 10, and for example, the relationship between the engine speed, the engine load, and the abnormal target fuel pressure Pfs is stored in advance as a map or the like. An abnormal target fuel pressure Pfstr is calculated from this relationship, the current target rotational speed, and the engine load.

  FIG. 5 is a diagram showing the relationship between the engine speed, the engine load, and the abnormal target fuel pressure Pfstr. According to FIG. 5, the abnormal target fuel pressure Pfstr is set to a larger value as the engine speed is higher and the engine load is larger. The abnormal target fuel pressure Pfstr (Pfstr1 to Pfstr5) is set to a value smaller than the target fuel pressure (normal target fuel pressure) set based on the engine speed and the engine load when the high-pressure pump unit 40 is normal. For example, the maximum value Pfstr5 is set to a fuel pressure (for example, 12 MPa) lower than the upper limit value (for example, 20 MPa) of the normal target fuel pressure. Further, the minimum value Pfstr1 of the target fuel pressure Pfstr is set to a value larger than the feed pressure (the lower limit value of the fuel pressure at which injection in the compression stroke is possible, for example, 1 MPa or 2 MPa).

  Returning to the description of FIG. 4, after step S <b> 23, the fuel discharge amount of the high-pressure pump unit 40 is adjusted by controlling the fuel discharge amount of the low-pressure pump 31. Here, in the present embodiment, since the low-pressure pump unit 30 and the high-pressure pump unit 40 are disposed apart from the rear part and the front part of the vehicle, respectively, the fuel discharged from the low-pressure pump part 30 is the high-pressure pump. There is a time delay before the portion 40 discharges to the delivery pipe 35. Therefore, in the present embodiment, as the drive control of the low-pressure pump unit 30, the low-pressure pump 31 is switched between the on state and the off state in anticipation of fuel transportation delay from the low-pressure pump unit 30 to the delivery pipe 35. Specifically, when the fuel pressure detection value Pd detected by the fuel pressure sensor 57 is lower than a value (on determination value Pfson) larger than the target fuel pressure Pfstr at the time of abnormality by the α, the low pressure pump 31 is switched from off to on. Further, the low pressure pump 31 is switched from on to off when the fuel pressure detection value Pd exceeds a value (off determination value Pfsoff) that is smaller than the abnormal target fuel pressure Pfstr by α.

  That is, in step S23 of FIG. 4, it is determined whether or not the detected fuel pressure value Pd is decreasing and the detected fuel pressure value Pd is smaller than the ON determination value Pfson. If the detected fuel pressure value Pd is decreasing and the detected fuel pressure value Pd is smaller than the on-determination value Pfson, the process proceeds to step S24, and the low-pressure pump 31 is driven with the energization of the low-pressure pump 31 turned off.

  In step S25, it is determined whether or not the fuel pressure detection value Pd is increasing and the fuel pressure detection value Pd is greater than the off determination value Pfsoff. If the detected fuel pressure value Pd is increasing and the detected fuel pressure value Pd is larger than the OFF determination value Pfsoff, the process proceeds to step S26, and the low pressure pump 31 is turned off to turn on the low pressure pump 31. To stop. On the other hand, if a negative determination is made in steps S23 and S25, the process proceeds to step S27, and the on-state or off-state of the low-pressure pump 31 is maintained as it is. That is, when the fuel pressure detection value Pd is decreasing and the fuel pressure detection value Pd is equal to or higher than the on determination value Pfson, the low pressure pump 31 is kept off. Further, when the fuel pressure detection value Pd is increasing and the fuel pressure detection value Pd is equal to or less than the off determination value Pfson, the low pressure pump 31 is kept on.

  In subsequent step S28, it is determined whether or not the engine 10 has stopped or the high-pressure pump unit 40 has returned to normal. If engine stop or normal return of the high-pressure pump unit 40 has been detected, the process proceeds to step S29. Then, the control of the fuel discharge amount of the high-pressure pump unit 40 by the low-pressure pump 31 is stopped.

  FIG. 6 is a time chart showing the transition of the fuel pressure when adjusting the fuel discharge amount of the high-pressure pump unit 40 by the low-pressure pump 31. 6A shows the diagnosis result of the full discharge abnormality of the high-pressure pump unit 40, FIG. 6B shows the change in the fuel pressure detection value Pd, and FIG. 6C shows the change in the ON / OFF state of the low-pressure pump 31. (D) shows the transition of the fuel discharge amount of the high-pressure pump unit 40. In FIG. 6, it is assumed that the engine operating state is a steady state and the abnormal target fuel pressure Pfstr is a constant value.

  In FIG. 6, when a full discharge abnormality of the high-pressure pump unit 40 is detected by the failure diagnosis, adjustment of the fuel discharge amount from the high-pressure pump unit 40 to the delivery pipe 35 is performed by the low-pressure pump 31. That is, when a full discharge abnormality of the high-pressure pump unit 40 is detected, the fuel pressure (fuel pressure detection value Pd) of the delivery pipe 35 is higher than the normal target fuel pressure. The drive of the pump 31 is stopped. Thereby, the fuel discharge amount of the high-pressure pump unit 40 becomes zero, and the fuel pressure of the delivery pipe 35 gradually decreases.

  Thereafter, when the fuel pressure detection value Pd falls below the ON determination value Pfson, the low pressure pump 31 is driven, and the fuel discharge amount of the high pressure pump unit 40 becomes the maximum discharge amount Qmax when the time delay Δt has elapsed. As a result, the fuel pressure in the delivery pipe 35 increases. Further, when the fuel pressure detection value Pd exceeds the off determination value Pfsoff, the driving of the low pressure pump 31 is stopped, and the fuel discharge amount of the high pressure pump section 40 becomes zero when the time delay Δt has elapsed. Thereby, the fuel pressure of the delivery pipe 35 falls. As described above, the fuel pressure of the delivery pipe 35 is set to the abnormal target fuel pressure Pfstr by the on / off control of the low-pressure pump 31.

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

  When the full discharge abnormality of the high-pressure pump unit 40 is detected, the fuel discharge amount of the high-pressure pump unit 40 is adjusted by the low-pressure pump 31. For example, the high-pressure pump unit due to disconnection of the fuel metering valve 43 or solenoid failure Even when the fuel discharge amount cannot be adjusted at 40, the fuel pressure in the delivery pipe 35 can be controlled. Thereby, it is possible to prevent the delivery pipe 35 and the high-pressure fuel pipe 27 from being damaged when an excessive discharge abnormality of the high-pressure pump unit 40 occurs. Further, since the fuel discharged to the delivery pipe 35 passes through the high-pressure pump in a full discharge state, the fuel pressure in the delivery pipe 35 can be made higher than the feed pressure. The injection pressure can be kept above the feed pressure. Therefore, it is possible to prevent the drivability of the engine 10 from being lowered when the high-pressure pump unit 40 is in full discharge, and as a result, the retreat travel can be performed reliably.

  Further, in the in-cylinder injection type engine 10, homogeneous combustion for igniting the air-fuel mixture generated by fuel injection in the intake stroke and ignition for the air-fuel mixture generated by fuel injection in the compression stroke are performed. The stratified combustion to be performed can be performed even at the time of full discharge abnormality of the high-pressure pump unit 40. That is, when the injection pressure of the fuel injection valve 24 is a pressure (feed pressure) equivalent to the fuel discharged from the low-pressure pump 31, the fuel injection rate is low and the combustion is limited to homogeneous combustion. In this embodiment, the low-pressure pump 31 is used. Since fuel having a pressure higher than that discharged from the fuel is pumped to the delivery pipe 35, it is preferable in that homogeneous combustion and stratified combustion can be realized.

  Since the abnormality target fuel pressure Pfstr of the delivery pipe 35 is variably set and the fuel discharge amount of the high pressure pump unit 40 is controlled by the low pressure pump 31 based on the set target fuel pressure Pfstr, the discharge abnormality of the high pressure pump unit 40 is performed. Even at times, fuel injection can be performed at various injection pressures. Thereby, even when the discharge of the high-pressure pump unit 40 is abnormal, various operation controls can be performed in the engine 10. In particular, in the present embodiment, since the abnormal target fuel pressure Pfstr is variably set according to the engine operating state (specifically, the engine speed and the engine load), the drive loss of the low-pressure pump unit 30 is reduced. Combustion can be suitably carried out.

  Since the abnormal target fuel pressure Pfstr is set to a value smaller than the normal target fuel pressure, the load on the low pressure pump 31 and the high pressure pump unit 40 can be reduced, and a secondary failure occurs in the low pressure pump 31 and the like. Can be suppressed.

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

  In the above embodiment, the abnormal target fuel pressure Pfstr is variably set in accordance with the operating state of the engine 10 (engine speed and engine load), and the low pressure is set so that the detected fuel pressure of the fuel pressure sensor 57 becomes the abnormal target fuel pressure Pfstr. Although the pump 31 is turned on / off, the abnormality target fuel pressure Pfstr may be fixed and the low pressure pump 31 may be turned on / off. The abnormal target fuel pressure Pfstr at this time is not particularly limited, but may be a value (for example, 4 MPa + α) set based on the target fuel pressure Pidl at the time of normal idle rotation control.

  In the above embodiment, when adjusting the fuel discharge amount of the high-pressure pump unit 40 in the low-pressure pump unit 30, the high-pressure pump unit 40 is controlled by energizing the low-pressure pump 31 to adjust the fuel discharge amount of the low-pressure pump 31. However, when the regulator 32 of the low-pressure pump unit 30 is an electric type, the regulator 32 is energized to adjust the return amount of the discharged fuel from the low-pressure pump 31. The fuel discharge amount of the pump unit 40 may be adjusted.

  In the above embodiment, the fuel discharge amount of the high-pressure pump unit 40 is adjusted by changing the fuel discharge amount of the low-pressure pump 31 by the on / off control of the low-pressure pump 31. When the discharge amount can be variably controlled, the fuel discharge amount of the high-pressure pump unit 40 may be adjusted by changing the fuel discharge amount of the low-pressure pump 31 by the duty control. In this case, it is desirable to calculate the fuel discharge amount of the low-pressure pump 31 based on the required injection amount of the fuel injection valve 24 and to control the operation duty of the low-pressure pump 31 based on the calculated fuel discharge amount.

  In the above-described embodiment, fuel adjustment by the low-pressure pump 31 is performed so that the fuel pressure (fuel pressure detection value) in the delivery pipe 35 detected by the fuel pressure sensor 57 becomes the target fuel pressure Pfstr at the time of abnormality. Although it is configured by feedback control that adjusts the amount, it may be configured by open control that adjusts the fuel discharge amount of the low-pressure pump 31 regardless of the detected fuel pressure value.

  In the above embodiment, when the full discharge abnormality of the high pressure pump unit 40 is detected, the low pressure pump unit 30 controls the fuel discharge amount of the high pressure pump unit 40. In addition, it is further determined whether or not the pressure reducing function of the relief valve 47 is abnormal, and when the full discharge abnormality of the high pressure pump unit 40 and the pressure reducing function abnormality of the relief valve 47 are detected, the low pressure pump unit 30 performs the high pressure pump unit. For example, the fuel discharge amount of 40 may be controlled. That is, if the pressure reduction in the delivery pipe 35 by the relief valve 47 is restricted due to clogging of the opening of the relief valve 47 or the inability to operate the relief valve 47, the fuel pressure in the delivery pipe 35 excessively increases, There is a concern that the delivery pipe 35, the high-pressure fuel pipe 27, and the like may be damaged. Therefore, in addition to the full discharge abnormality of the high pressure pump unit 40, when the pressure reducing function abnormality of the relief valve 47 is detected, the low pressure pump unit 30 controls the fuel discharge amount of the high pressure pump unit 40, thereby When a full discharge abnormality occurs, it is possible to suitably obtain an effect of preventing the delivery pipe 35 and the high-pressure fuel pipe 27 from being damaged. Here, regarding the pressure reduction function abnormality of the relief valve 47, for example, it is determined whether or not the detected fuel pressure value detected by the fuel pressure sensor 57 exceeds the relief pressure, and when the detected fuel pressure value exceeds the relief pressure, the relief valve 47 is decompressed. It may be determined that a functional abnormality has occurred.

  In the above embodiment, the engine-driven high-pressure pump unit 40 has been described. However, the present invention may be applied to an electromagnetic-driven high-pressure pump unit. By performing fuel metering with the low-pressure pump 31 when full discharge abnormality occurs in the electromagnetically driven high-pressure pump unit, the same effect as described above can be obtained. Further, although the low pressure pump unit 30 is an electromagnetic drive type, it may be an engine drive type.

  In the above embodiment, a case where a full discharge abnormality occurs as an excessive discharge abnormality of the high-pressure pump unit 40 has been described. However, the fuel discharge amount of the high-pressure pump unit 40 is greater than the target value, not only when the full discharge abnormality occurs. Applicable to.

  In the above embodiment, the gasoline engine is used as the internal combustion engine, but a diesel engine may be used. That is, the present invention may be embodied by a control device for a common rail fuel supply system of a diesel engine.

1 is an overall schematic configuration diagram of an engine control system. The schematic block diagram of a high pressure pump part. The flowchart which shows an example of the process sequence of the process at the time of abnormality detection. The flowchart which shows an example of the process sequence of a low voltage | pressure side metering process. The figure which shows the relationship between an engine speed, an engine load, and the target fuel pressure at the time of abnormality. The time chart which shows transition of the fuel pressure when implementing fuel metering with a low pressure pump.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine, 24 ... Fuel injection valve, 25 ... Fuel tank, 26 ... Fuel piping, 30 ... Low pressure pump part, 31 ... Low pressure pump, 32 ... Regulator, 40 ... High pressure pump part, 41 ... High pressure pump, 42 ... Check Valve 43, Fuel metering valve, 47 Relief valve, 56 Crank angle sensor, 57 Fuel pressure sensor, 59 Abnormal warning lamp, 60 ECU, 61 Microcomputer.

Claims (5)

An internal combustion engine comprising: a low pressure pump portion that pressurizes fuel in a fuel tank; a high pressure pump portion that further pressurizes fuel discharged from the low pressure pump portion; and a pressure accumulating chamber that stores high pressure fuel discharged from the high pressure pump portion Applied to the accumulator fuel supply system
A control device for an accumulator fuel supply system that controls a fuel pressure in the accumulator chamber by controlling a fuel discharge amount of the high-pressure pump unit,
Discharge abnormality detection means for detecting that high pressure fuel is excessively discharged from the high pressure pump unit to the pressure accumulation chamber;
A metering control means for controlling the fuel discharge amount of the high-pressure pump section by the low-pressure pump section when the excessive discharge state of the high-pressure pump section is detected by the discharge abnormality detection means;
An accumulator fuel supply system control device comprising: A pressure release valve that opens when the fuel pressure in the pressure accumulation chamber reaches a predetermined valve opening pressure and depressurizes the pressure accumulation chamber;
A pressure reduction abnormality detecting means for detecting abnormality of the pressure reduction function of the pressure release valve;
The said metering control means controls the fuel discharge amount of the said high pressure pump part by the said low pressure pump part, when the abnormality of the pressure reduction function of the said pressure release valve is detected by the said pressure reduction abnormality detection means. Control device for accumulator fuel supply system. A target fuel pressure setting means for variably setting a target value of the fuel pressure in the pressure accumulating chamber when an excessive discharge abnormality of the high-pressure pump unit occurs;
3. The pressure accumulation type according to claim 1, wherein the metering control unit controls a fuel discharge amount of the high-pressure pump unit by the low-pressure pump unit based on the target value set by the target fuel pressure setting unit. Control device for fuel supply system.   4. The control device for an accumulator fuel supply system according to claim 3, wherein the target fuel pressure setting means sets the target value to a smaller value than when the high pressure pump part is normal when the high pressure pump part is abnormally discharged excessively.   The pressure accumulation type according to any one of claims 1 to 4, wherein the pressure accumulation type is applied to a pressure accumulation type fuel supply system of a cylinder injection type internal combustion engine including a fuel injection valve that directly injects high pressure fuel in the pressure accumulation chamber into the cylinder. Control device for fuel supply system.

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