JP2013199916A - Fuel injection system for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly maintain an actual fuel pressure of fuel injected from a fuel injection hole independently of a lift amount of a needle part, in a fuel injection system intermediately lifting the needle part of a fuel injection valve.SOLUTION: A fuel injection system for an internal combustion engine comprises: a lift control means for controlling a lift position of a needle part inside an injection valve body to a full open position where a fuel injection hole is brought into a full open state or any intermediate position between the full open position and a fully closed position where the fuel injection hole is brought into a fully closed state, on the basis of an operation condition of the internal combustion engine; and a fuel pressure correction means for correcting a pressure of the fuel supplied to a fuel injection valve to a high pressure side when performing intermediate lift injection in which the needle part is controlled to be at the intermediate position by the lift control means as compared with a case when performing full lift injection in which the needle part is controlled to be at the full open position by the lift control means.

Description

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

  When the internal combustion engine is provided with a plurality of fuel injection valves, there is a possibility that the suitable combustion in the internal combustion engine will be affected considerably due to the variation in the injection characteristics due to the difference between the individual fuel injection valves. Therefore, in particular, in consideration of the injection delay time for each fuel injection valve, the drive current of the needle valve that constitutes the fuel injection valve is controlled, and the lift amount and the lift speed are adjusted to thereby achieve suitable fuel injection. A technique is disclosed (see, for example, Patent Document 1).

  In addition, regarding fuel injection devices for internal combustion engines, generally, pressurized fuel is supplied from a common rail or the like to a fuel injection valve. If the fuel pressure in the common rail has become high, the same as otherwise. Thus, when the fuel injection valve is opened, excessive fuel is injected, and problems such as combustion noise may occur. Therefore, a technique for suppressing excessive fuel injection by reducing the lift amount of the needle valve in the fuel injection valve in such a case is disclosed (for example, see Patent Document 2).

JP 2009-138639 A JP 2010-90804 A JP 2010-255444 A

  The fuel injection valve is configured such that a needle part that opens and closes the injection hole by contacting and separating from the seat part near the fuel injection hole is lifted inside the fuel injection valve body to inject fuel. In general, a configuration in which is executed is adopted. Here, when the lift position is controlled to an arbitrary intermediate position between the fully closed position where the needle portion fully closes the fuel injection hole and the fully open position where the needle is fully open, the needle portion is in the fully open state. The fuel injection different from the fuel injection can be realized. For example, the minimum injection amount can be improved by lifting the needle valve to an intermediate position.

  However, when the needle portion is lifted to the intermediate position (hereinafter referred to as “intermediate lift”), the distance between the needle portion and the seat portion is larger than when the needle portion is lifted to the fully open position (hereinafter referred to as “full lift”). Therefore, the pressure loss inside the fuel injection valve increases, and the pressure of the actually injected fuel (actual fuel pressure) tends to decrease. In general, the fuel injection hole provided in the fuel injection valve is designed to be preferably injected from the injection hole when the assumed pressure is applied to the fuel, and thus the actual fuel pressure of the fuel is reduced in this way. If it does so, possibility that fuel spray formation in a cylinder will not be performed suitably becomes high.

  The present invention has been made in view of the above-described problems, and in a fuel injection system that intermediate lifts the needle portion of the fuel injection valve, the actual fuel injected from the fuel injection hole regardless of the lift amount of the needle portion. It aims at maintaining a fuel pressure suitably.

In the present invention, in order to solve the above-described problems, a configuration is adopted in which when the intermediate lift is performed in the fuel injection valve, the pressure of the fuel supplied to the fuel injection valve is corrected to the high pressure side. With this configuration, it is possible to compensate for the pressure loss caused by the intermediate lift and to suppress as much as possible the decrease in the actual fuel pressure of the fuel injected from the fuel injection hole.

  Therefore, in detail, the present invention is arranged such that an injection valve main body for injecting fuel of an internal combustion engine through a fuel injection hole, and the inside of the injection valve main body can be lifted in its axial direction, A fuel injection system for an internal combustion engine by a fuel injection valve having a needle portion that opens and closes. The fuel injection system includes a lift position of the needle portion inside the injection valve main body, a fully open position where the fuel injection hole is fully open based on an operating state of the internal combustion engine, or the fuel injection hole is Lift control means for controlling to an arbitrary intermediate position between the fully closed position and the fully open position in which the valve is fully closed, and intermediate lift injection in which the needle unit is controlled to the intermediate position by the lift control means The fuel pressure correction for correcting the pressure of the fuel supplied to the fuel injection valve to the high pressure side as compared with the case where the lift control means performs the full lift injection in which the needle portion is controlled to the fully open position. And means.

  In the fuel injection system according to the present invention, the lift position of the needle portion is controlled by the lift control means. For example, when it is necessary to inject a relatively large amount of fuel injection, the lift control means performs lifting of the needle portion to the fully open position and holding the state for a time corresponding to the required injection amount. On the other hand, when it is necessary to reduce the fuel injection amount, the lift control means controls the needle portion to a predetermined intermediate position that the needle portion should reach in accordance with the required injection amount. Even when the fuel injection rate into the cylinder is reduced, lift position control of the needle portion to the intermediate lift position by the lift control means is performed. Thus, the lift control means controls the lift position of the needle portion according to the operating state of the internal combustion engine, that is, the fuel injection mode required in the cylinder. In addition, the intermediate position regarding the needle part in the present invention does not indicate a specific position between the fully closed position and the fully open position, and realizes the form of fuel injection required depending on the operating state of the internal combustion engine. Therefore, the position may be appropriately changed according to the fuel injection mode.

  Thus, by controlling the lift position of the needle portion by the lift control means, the fuel injection system according to the present invention can realize an appropriate fuel injection mode according to the operating state of the internal combustion engine. Become. However, when the position of the needle portion is controlled to the intermediate position by the lift control means (during the intermediate lift), the space between the tip of the needle portion and the vicinity of the fuel injection hole (seat portion) is located at the fully open position. Narrower than when controlled (during full lift). Therefore, at the time of intermediate lift, the pressure loss inside the fuel injection valve increases, the actual fuel pressure of the fuel injected from the fuel injection hole decreases, and there is a high possibility that desired fuel injection will be difficult.

  Therefore, in the fuel injection system according to the present invention, when intermediate lift injection is performed, the fuel pressure is corrected by the fuel pressure correction means to the high pressure side compared to when full lift injection is performed. In a general internal combustion engine, the fuel injection valve is configured so that pressurized fuel stored in a stock pressure chamber such as a delivery pipe or a common rail is sequentially supplied. The pressure may be corrected to the high pressure side. Further, when the full lift injection is performed again after the intermediate lift injection is performed, the fuel pressure correcting means may correct the fuel pressure to the low pressure side in order to adapt to the full lift injection.

  In this way, according to the lift amount of the needle portion, in other words, by correcting the pressure of the fuel supplied to the fuel injection valve in the case where the intermediate lift is performed and the case where the full lift is performed, the final is achieved. Thus, the actual fuel pressure of the fuel injected from the fuel injection hole can be maintained in a suitable state. Thereby, a suitable fuel spray can be formed in the cylinder even during intermediate lift injection.

  Here, in the fuel injection system for an internal combustion engine, the fuel pressure correction means may be configured to reduce the fuel pressure when the lift amount of the needle portion is smaller than a predetermined lift amount when the intermediate lift injection is performed by the lift control means. May be corrected to the high pressure side as compared with the case where the full lift injection is performed.

  When an intermediate lift is performed in the fuel injection valve, particularly when the lift amount of the needle portion is smaller than a predetermined lift amount, the pressure loss there may be significant. Therefore, when the lift amount related to the intermediate lift is smaller than the predetermined lift amount, the fuel pressure is corrected by the fuel pressure correcting means, so that the effective actual fuel pressure can be maintained efficiently.

  In the fuel injection system of the internal combustion engine, the fuel pressure correction means may continuously increase the fuel pressure as the lift amount of the needle portion decreases when the intermediate lift injection is performed by the lift control means. You may make it correct | amend so that it may become. By continuously correcting the fuel pressure in this way, it is easy to avoid a sudden change in the actual fuel pressure in the fuel injection valve. Note that the rate of change of the fuel pressure with respect to the lift amount is not necessarily constant for the continuous correction. The lift amount of the needle part and the change of the internal pressure loss are not necessarily in a linear relationship due to the structure inside the fuel injection valve, so the continuous change of the fuel pressure with respect to the lift amount depends on the relationship between them. What is necessary is just to set a rate suitably.

  According to the present invention, in the fuel injection system that intermediately lifts the needle portion of the fuel injection valve, the actual fuel pressure of the fuel injected from the fuel injection hole can be suitably maintained regardless of the lift amount of the needle portion.

It is a figure showing a schematic structure of a fuel injection system of an internal-combustion engine concerning an example of the present invention. It is a figure which shows the structure of the fuel injection valve used with the fuel-injection system shown in FIG. It is a figure which shows roughly the structure relevant to the fuel supply to the fuel injection valve shown in FIG. It is the figure which compared the lift amount of the needle valve when the needle valve fully lifts and the intermediate lift in the fuel injection valve. 2 is a first flowchart of fuel injection control executed in the fuel injection system shown in FIG. 1. FIG. 6 is a first diagram showing a correlation between an actual fuel pressure, a control fuel pressure, a pressure loss inside the fuel injection valve, and a lift amount of the needle valve when the fuel injection control shown in FIG. 5 is performed. FIG. 6 is a second diagram showing the correlation between the actual fuel pressure, the control fuel pressure, the pressure loss inside the fuel injection valve, and the lift amount of the needle valve when the fuel injection control shown in FIG. 5 is performed. FIG. 3 is a second flowchart of fuel injection control executed in the fuel injection system shown in FIG. 1. FIG. 6 is a third flowchart of fuel injection control executed in the fuel injection system shown in FIG. 1.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the present embodiment are not intended to limit the technical scope of the invention to those unless otherwise specified.

  An embodiment of a fuel injection system for an internal combustion engine according to the present invention will be described with reference to the drawings attached to the present specification. FIG. 1 is a schematic configuration of a fuel injection system 1 according to the present embodiment, and is a diagram illustrating a schematic configuration of a vertical cross section focusing particularly on the vicinity of a fuel injection valve 7. The internal combustion engine on which the fuel injection system 1 is mounted is a cylinder ignition type spark ignition internal combustion engine for driving a vehicle. In the internal combustion engine, an intake port 2 and an exhaust port 3 are connected to the cylinder 8. The intake port 2 sends intake air into the cylinder 8 through opening and closing of the intake valve 3, and the exhaust port 3 sends combustion gas and the like as exhaust to the exhaust system of the internal combustion engine through opening and closing of the exhaust valve 5. A piston 9 is disposed in the cylinder 8, and a spark plug 6 is disposed on the top of the cylinder 8 facing the piston 9 so that the air-fuel mixture in the cylinder can be ignited. In the internal combustion engine, the fuel injection valve 7 is provided on the lower side of the intake port 2 (that is, on the side closer to the cylinder block side in the cylinder head provided with the intake port 2). The injection direction of the fuel injection valve 7 is generally set obliquely downward within the cylinder 8.

  Here, the detailed structure of the fuel injection valve 7 is demonstrated based on FIG. FIG. 2 is a schematic sectional view of the fuel injection valve 7. The fuel injection valve 7 is a solenoid-driven fuel injection valve. A passage 71 through which fuel flows is formed in a body 78. The passage 71 is connected to the delivery pipe 10 shown in FIG. Fuel is supplied, and the supplied fuel is injected from the fuel injection hole 76 in accordance with the operation of a needle valve 73 described later. The introduction port 77 is provided with a filter for removing minute foreign matters contained in the fuel.

  In the fuel injection valve 7, a plunger 72 is slidably provided inside the passage 71. A needle valve 73 is formed at the tip of the plunger 72, and the needle valve 73 is normally biased by a coil spring 74 in a direction to close the fuel injection hole 76 (downward bias in FIG. 2). . An annular solenoid coil 75 is provided in the body 78 so as to surround the plunger 72, and when this solenoid coil 75 is excited, a suction force acts on the plunger 72, and the biasing force of the coil spring 74 is increased. It becomes possible to raise the plunger 72 against it. Therefore, in the fuel injection valve 7, the suction force acting on the plunger 72 is controlled by adjusting the amount of current supplied to the solenoid coil 75, and the needle valve is controlled by the balance between the suction force and the biasing force by the coil spring 74. The opening and closing of the fuel injection hole 76 by 73 is controlled. The lift position control of the needle valve 73 will be described later.

  Returning to FIG. 1, the fuel injection system 1 is equipped with an ECU 30 that is an electronic control unit, and various controls are executed in the fuel injection system 1 and an internal combustion engine in which the ECU 30 is mounted. Further, the accelerator opening sensor 31 is electrically connected to the ECU 30 in the internal combustion engine, and the ECU 30 receives a signal corresponding to the accelerator opening, and calculates an engine load required for the internal combustion engine 1 from the signal. To do. Further, the crank position sensor 32 is electrically connected to the ECU 30, and the ECU 30 receives a signal corresponding to the rotation angle of the output shaft of the internal combustion engine 1 and calculates the engine rotational speed and the like of the internal combustion engine 1.

Further, the ECU 30 is also electrically connected to a fuel pressure sensor 33 provided on the delivery pipe 10. Here, based on FIG. 3, the structure relevant to the fuel supply to the fuel injection valve 7 including the delivery pipe 10 will be described. In the delivery pipe 10, the fuel stored in the fuel tank 13 is pumped by the low pressure fuel pump 11 and the high pressure fuel pump 12. The low-pressure fuel pump 11 is an electric fuel pump (turbine pump), and is a pump for pumping up fuel stored in the fuel tank 13. The fuel discharged from the low-pressure fuel pump 11 is guided to the suction port of the high-pressure fuel pump 12 by the low-pressure fuel passage 14.

  The high-pressure fuel pump 12 is a pump for boosting (pressurizing) the fuel discharged from the low-pressure fuel pump 11. The high-pressure fuel pump 12 is a reciprocating pump (plunger pump) driven by the power of the internal combustion engine (for example, the rotational force of the camshaft). A suction valve 12 a for switching between conduction and blockage of the suction port is provided at the suction port of the high-pressure fuel pump 12. The intake valve 12a is an electromagnetically driven valve mechanism, and changes the discharge amount of the high-pressure fuel pump 12 by changing the opening / closing timing with respect to the position of the plunger. The base end of the high-pressure fuel passage 15 is connected to the discharge port of the high-pressure fuel pump 12. The end of the high pressure fuel passage 15 is connected to the delivery pipe 10.

  Here, four fuel injection valves 7 are connected to the delivery pipe 10 shown in FIG. 3, and high-pressure fuel pumped from the high-pressure fuel pump 12 to the delivery pipe 10 is distributed to each fuel injection valve 7. The fuel injection valve 7 directly injects fuel into the cylinder 8 of the internal combustion engine. Therefore, FIG. 1 schematically shows the fuel injection system 1 centering on one of the fuel injection valves 7. Note that the number of fuel injection valves 7 connected to the delivery pipe 10 is appropriately changed depending on the configuration of a specific internal combustion engine.

  A base end of the branch passage 16 is connected to the low pressure fuel passage 14 in the middle. The end of the branch passage 16 is connected to the fuel tank 13. A pressure regulator 17 is provided in the middle of the branch passage 16. The pressure regulator 17 opens when the pressure (fuel pressure) in the low-pressure fuel passage 14 exceeds a predetermined value, so that excess fuel in the low-pressure fuel passage 14 passes to the fuel tank 13 via the branch passage 16. Configured to return. Further, a check valve 18 is disposed in the middle of the high-pressure fuel passage 15 described above. The check valve 18 is a one-way valve that allows the flow from the discharge port of the high-pressure fuel pump 12 toward the delivery pipe 10 and restricts the backflow from the delivery pipe 10 to the discharge port of the high-pressure fuel pump 12.

  The delivery pipe 10 is connected to a return passage 19 for returning surplus fuel in the delivery pipe 10 to the fuel tank 13. In the middle of the return passage 19, a relief valve 20 that switches between return and passage of the return passage 19 is arranged. The relief valve 20 is an electric or electromagnetically driven valve mechanism, and is opened when the fuel pressure in the delivery pipe 10 exceeds a target value. In the middle of the return passage 19, the end of the communication passage 21 is connected, and the base end of the communication passage 21 is connected to the high-pressure fuel pump 12. The communication passage 21 is a passage for guiding surplus fuel discharged from the high-pressure fuel pump 12 to the return passage 19.

  In the fuel supply system to the fuel injection valve 7 configured as described above, the ECU 30 changes the discharge amount of the high-pressure fuel pump 12 by changing the opening / closing timing of the intake valve 12a, and finally the inside of the delivery pipe 10 It is possible to adjust the fuel pressure. The ECU 30 can detect the fuel pressure (control fuel pressure) in the delivery pipe 10 by being electrically connected to the fuel pressure sensor 33, and the opening / closing timing of the intake valve 12a is controlled based on the detection result. Is done. The ECU 30 is also electrically connected to various sensors provided in the internal combustion engine other than the above, and controls the fuel injection amount and fuel injection timing from the fuel injection valve 7, and other ECUs 30. It is used for various controls.

Here, in the fuel injection system 1 for the internal combustion engine shown in FIG. 1, the fuel injection from the fuel injection valve 7 is controlled in accordance with the operation state (engine load, engine speed, etc.) of the internal combustion engine in accordance with a command from the ECU 30. The Here, the needle valve 73 directly controls the opening and closing of the fuel injection hole 76 in the fuel injection valve 7. The needle valve 73 is lifted upward so as to open the fuel injection hole 76, descends again and closes the fuel injection hole 76, whereby one fuel injection by the fuel injection valve 7 is realized. If the lift amount of the needle valve 73 is constant, the minimum fuel injection amount per one time by the fuel injection valve 7 is that the fuel injection hole 76 starts from the fully closed position where the needle valve 73 closes the fuel injection hole 76. This is the injection amount when the fully open position (that is, the highest lift position) that is fully open is reciprocated once without stopping at the fully open position. Therefore, if the lift amount of the needle valve 73 becomes constant in this way, it becomes substantially difficult to inject less fuel than the minimum fuel injection amount. Therefore, in the fuel injection system 1 according to the present invention, control for making the lift amount of the needle valve 73 variable, that is, at the time of fuel injection so as to realize an amount of fuel injection appropriately corresponding to the engine load of the internal combustion engine. Control is performed so that the lift position of the needle valve 73 (the position reached after reaching the fully closed position) can be any intermediate position between the fully closed position and the fully open position. In this specification, a case where the needle valve 73 is lifted from the fully closed position to the fully open position is referred to as “full lift”, and a case where the needle valve 73 is lifted from the fully closed position to the intermediate position is referred to as “intermediate lift”. The injection is referred to as “full lift injection” and “intermediate lift injection”, respectively.

  The intermediate lift of the needle valve 73 is executed by adjusting the drive current supplied to the solenoid coil 75. For example, when the intermediate lift is executed, the pressing force necessary for the needle valve 73 to compress the coil spring 74 and the frictional force acting on the plunger 72 in the passage 71 are taken into consideration, and the solenoid coil 75 is applied to the solenoid coil 75 during full lift. The supply current may be adjusted and supplied to the solenoid coil 75.

  As described above, in the fuel injection valve 7, by performing the intermediate lift of the needle valve 73, an appropriate amount of fuel injection according to the operating state of the internal combustion engine can be realized. However, as shown in FIG. 4, since the lift amount L1 of the needle valve 73 during the intermediate lift is smaller than the lift amount Lf during the full lift, the separation distance between the tip portion of the needle valve 73 and the seat portion 73a is also large. The intermediate lift is smaller. Therefore, in the fuel flow immediately upstream of the fuel injection hole 76, the resistance (pressure loss) to the fuel flow is greater during the intermediate lift than during the full lift. As a result, the fuel is injected from the fuel injection hole 76. The actual pressure of fuel (actual fuel pressure) will be reduced. In general, the shape and arrangement of the fuel injection holes 76 are designed so that fuel with an assumed actual fuel pressure is efficiently injected. Therefore, if the actual fuel pressure decreases during intermediate lift, There is a high possibility that fuel injection from the nozzle hole 76 is not performed as expected.

  Thus, if it becomes difficult to perform fuel injection as expected during the intermediate lift, it is difficult to form a suitable fuel spray in the cylinder 8, and this may cause a reduction in combustion efficiency and a deterioration in emissions. Accordingly, fuel injection control that can suitably perform fuel injection during the intermediate lift in the fuel injection system 1 having the fuel injection valve 7 capable of fuel injection by the intermediate lift will be described with reference to FIG. The fuel injection control is executed by the ECU 30.

  First, in S101, conditions relating to fuel injection from the fuel injection valve 7 are determined according to the operating state of the internal combustion engine (engine speed, engine load, engine temperature, etc.). For example, the ECU 30 has a control map in which the fuel injection amount is associated with the operating state of the internal combustion engine, and the fuel injection amount is determined by accessing the map. As an example of determination of the fuel injection amount, the fuel injection amount is set to increase as the engine load and the engine speed increase, and when the engine temperature is low such as at the time of engine start, warm-up is promptly performed. Since it is necessary to do this, the fuel injection amount is set to be larger than when the engine temperature is high. Then, the valve opening time required for injecting the determined amount of fuel from the fuel injection valve 7 is calculated based on the control fuel pressure acquired from the fuel pressure sensor 33. When the process of S101 ends, the process proceeds to S102.

  In S102, based on the fuel injection condition determined in S101 and the control fuel pressure acquired from the fuel pressure sensor 33, it is determined whether or not the fuel injection performed by the fuel injection valve 7 is intermediate lift injection. It is possible to determine whether or not the needle valve 73 is lifted to the fully open position from the relationship between the control fuel pressure and the valve opening time of the fuel injection valve 7. Therefore, if a positive determination is made in S102, the process proceeds to S103, and if a negative determination is made, the process proceeds to S105.

  In S103, it is determined whether or not the lift amount L1 of the needle valve 73 is smaller than the predetermined lift amount L0 in the fuel injection valve 7 in which the intermediate lift injection is performed. The predetermined lift amount L0 is a threshold value set in consideration that the pressure loss inside the fuel injection valve 7 becomes remarkable when the lift amount of the needle valve 73 becomes small to some extent. That is, as shown in the third stage of FIG. 6A, in the fuel injection valve 7, even when intermediate lift injection is performed, if the lift amount is relatively large, a pressure loss is generated, but the magnitude is high. Although the height is very small, the pressure loss suddenly increases when the lift amount falls below L0. Therefore, when this L0 is set to a predetermined lift amount and the lift amount falls below the predetermined lift amount L0 and the pressure loss in the fuel injection valve 7 becomes significant, the control fuel pressure, which will be described later, is corrected. In addition, the determination process of S103 is performed.

  Then, when an affirmative determination is made in S103 and the process proceeds to S104, processing for correcting the control fuel pressure in the delivery pipe 10 to the high pressure side is performed. Specifically, the amount of fuel supplied to the high-pressure fuel pump 12 via the intake valve 12a is increased in accordance with an instruction from the ECU 30, thereby boosting the pressure in the delivery pipe 10. This pressure increase is performed so that the control fuel pressure in the delivery pipe 10 reaches a pressure that compensates for the pressure loss inside the fuel injection valve 7 via the fuel pressure sensor 33. By the processing of S104, the control fuel pressure in the delivery pipe 10 is increased as shown in the second stage of FIG. 6A. As a result, the lift amount of the needle valve is lower than L0 as shown by the solid line in the first stage of FIG. 6A. Even if it is small, it is avoided that the actual fuel pressure of the fuel injected from the fuel injection hole 76 of the fuel injection valve 7 decreases. In addition, what is shown with a dashed-dotted line in the 1st step | level of FIG. When the process of S104 ends, this control is repeated again from the beginning.

  On the other hand, if a negative determination is made in S103 or a negative determination is made in S102 and the process proceeds to S105, the control fuel pressure in the delivery pipe 10 is not increased as in the process of S104, and the control fuel pressure is the normal fuel pressure. Set to The normal fuel pressure is a pressure to be applied to the fuel so that the fuel supplied from the delivery pipe 10 is suitably injected from the fuel injection hole 76 when full lift injection is performed in the fuel injection valve 7. Therefore, it can be said that the normal fuel pressure is a pressure that is a base of the correction process to the high pressure side in S104. When the process of S105 ends, this control is repeated again from the beginning.

  As described above, according to the present fuel injection control, when the pressure loss becomes significant inside the fuel injection valve 7 due to the intermediate lift injection, the control fuel pressure in the delivery pipe 10 is corrected to the high pressure side. Thereby, even when the lift amount of the needle valve 73 becomes relatively small, it is possible to avoid a decrease in the actual fuel pressure from the fuel injection hole 76.

<Modification>
Here, a modified example of the fuel injection control shown in FIG. 5, in particular, a modified example of the correction form to the high pressure side of the control fuel pressure related to the process of S <b> 104 will be described based on FIG. 6B. As shown in FIG. 6A, in the fuel injection control shown in FIG. 5, when the lift amount of the needle valve 73 is smaller than the predetermined lift amount L0, the process of S104, that is, the process of correcting the control fuel pressure to the high pressure side is performed. Is called. In the modified example, instead of this, as shown in the second stage of FIG. 6B, when the intermediate lift injection is performed, the control fuel pressure is continuously increased to the high pressure side according to the lift amount of the needle valve 73. Correction processing may be performed.

  As described above, the pressure loss inside the fuel injection valve 7 becomes significant when the lift amount becomes relatively small (see the third stage in FIG. 6B). However, when an intermediate lift is performed, the pressure loss occurs although the magnitude varies depending on the lift amount. Therefore, continuous control is performed so as to correspond to the generated pressure loss. By correcting the fuel pressure to the high pressure side, the actual fuel pressure of the fuel from the fuel injection hole 76 can be maintained substantially constant (see the first stage in FIG. 6B).

  Next, FIG. 7 shows a second embodiment of the fuel injection control related to the fuel injection valve 7. This embodiment is based on the fact that the engine temperature of the internal combustion engine is relatively low and oil dilution due to adhesion of the injected fuel to the inner wall surface of the cylinder 8 is likely to occur, so that fuel injection control for avoiding the oil dilution is performed. It is about. In this embodiment, in order to avoid oil dilution, the intermediate lift control is performed, and at the same time, the control fuel pressure in the delivery pipe 10 is corrected to the high pressure side. The details will be described below.

  In S201, it is determined whether or not the engine temperature of the internal combustion engine is equal to or lower than a predetermined temperature. This predetermined temperature is a threshold value for determining whether oil dilution by the injected fuel occurs due to a low engine temperature. Therefore, if an affirmative determination is made in S201, it means that the internal combustion engine is in a state where oil dilution is likely to occur, and the processing from S202 onward is performed. On the other hand, if a negative determination is made in S201, it means that oil dilution is not likely to occur in the internal combustion engine, and the process of S205 is performed. The engine temperature of the internal combustion engine is determined based on a detection value of a water temperature sensor that detects a coolant temperature of the internal combustion engine (not shown).

  Next, in S202, the fuel injection from the fuel injection valve 7 is set to the oil dilution compatible mode. In this mode, in order to make it difficult for oil dilution to occur due to the fuel injected from the fuel injection valve 7, the fuel injection mode is set to a specific mode. Specifically, the fuel injection valve 7 performs intermediate lift injection and performs fuel injection a plurality of times in one combustion cycle, thereby reducing the injection amount per one time. Furthermore, in order to compensate for the decrease in the actual fuel pressure during the intermediate lift, the control fuel pressure of the delivery pipe 10 is corrected to the high pressure side as will be described later. When the process of S202 ends, the process proceeds to S203.

  In S203, the fuel injection condition of the fuel injection valve 7 is determined according to the oil dilution mode. As described above, in this mode, on the assumption that the intermediate lift injection is performed, the fuel injection amount per one intermediate lift injection and the intermediate lift injection in one combustion cycle are performed based on the fact that multiple fuel injections are performed. The number of times is determined from the operating state of the internal combustion engine (engine load, engine speed, etc.). When the process of S203 ends, the process proceeds to S204.

  In S204, as in S104, a process for correcting the control fuel pressure in the delivery pipe 10 to the high pressure side is performed. However, in this embodiment, the control fuel pressure is increased as much as possible in the fuel injection system 1. By increasing the pressure in this way, a decrease in the actual fuel pressure of the injected fuel from the fuel injection hole 76 is avoided, and by increasing the actual fuel pressure, the vaporization of the injected fuel is promoted and adhesion to the inner wall surface of the cylinder 8 is prevented. This is because it is easier to avoid as much as possible. When the process of S204 ends, this control is repeated again from the beginning.

  Further, when a negative determination is made in S201, the process proceeds to S205, where the control fuel pressure in the delivery pipe 10 is set to a normal fuel pressure, as in S105.

Thus, according to the present fuel injection control, by using the intermediate lift injection, it is possible to reduce the amount of one fuel injection, and by correcting the control fuel pressure to the high pressure side, it is possible to avoid the decrease in the actual fuel pressure and The vaporization of the injected fuel can be promoted. As a result, it is possible to effectively avoid oil dilution.

  Next, FIG. 8 shows a third embodiment of the fuel injection control related to the fuel injection valve 7. This embodiment relates to fuel injection control for starting the internal combustion engine at a low temperature. In this embodiment, in order to start the engine quickly, the intermediate lift control is performed, and at the same time, the control fuel pressure in the delivery pipe 10 is corrected to the high pressure side. The details will be described below. In addition, about the process which is common in the fuel-injection control which concerns on a present Example, and the fuel-injection control which concerns on the said 2nd Example, detailed description of the said process is omitted by attaching | subjecting the same reference number.

  First, in S301, it is determined whether or not the internal combustion engine is about to start the engine at a low temperature. Specifically, when the engine temperature of the internal combustion engine when starting the engine is equal to or lower than a threshold temperature, the determination in S301 is affirmative. If an affirmative determination is made in S301, the process proceeds to S302, and if a negative determination is made, the process proceeds to S205.

  Next, in S302, the fuel injection from the fuel injection valve 7 is set to the low temperature engine start corresponding mode. In this mode, the fuel injection mode is set to a specific mode so that the engine can be quickly started even at low temperatures by the fuel injected from the fuel injection valve 7. Specifically, the fuel injection valve 7 performs intermediate lift injection and performs fuel injection a plurality of times in one combustion cycle, thereby reducing the injection amount per one time. Furthermore, in order to compensate for the decrease in the actual fuel pressure during the intermediate lift, the control fuel pressure of the delivery pipe 10 is corrected to the high pressure side. When the process of S302 ends, the process proceeds to S303.

  In S303, the fuel injection condition of the fuel injection valve 7 is determined according to the low temperature engine start support mode. As described above, in this mode, on the assumption that the intermediate lift injection is performed, the fuel injection amount per one intermediate lift injection and the intermediate lift injection in one combustion cycle are performed based on the fact that multiple fuel injections are performed. The number of times is determined from the operating state of the internal combustion engine (engine load, engine speed, etc.). In particular, in order to quickly start the engine, the lower the engine temperature, the more the number of injections in one combustion cycle, and the smaller the fuel injection amount per one. Therefore, in this mode, the pressure loss inside the fuel injection valve 7 in one intermediate lift injection becomes relatively large. When the process of S203 ends, the process proceeds to S204, and correction processing is performed so that the control fuel pressure in the delivery pipe 10 becomes the maximum pressure, as shown in the second embodiment. Further, if a negative determination is made in S301, the process proceeds to S205, where the control fuel pressure in the delivery pipe 10 is set to a normal fuel pressure, as shown in the second embodiment.

  Thus, according to the present fuel injection control, by using the intermediate lift injection, it is possible to reduce the amount of one fuel injection, and by correcting the control fuel pressure to the high pressure side, it is possible to avoid the decrease in the actual fuel pressure and The vaporization of the injected fuel can be promoted. As a result, prompt engine start can be expected even at low temperatures.

DESCRIPTION OF SYMBOLS 1 ... Fuel injection system 2 ... Intake port 3 ... Exhaust port 4 ... Intake valve 5 ... Exhaust valve 6 ... Spark plug 7 ... Fuel injection Valve 8 ... cylinder 9 ... piston 10 ... delivery pipe 12 ... high pressure fuel pump 12a ... intake valve 30 ... ECU
31 ... Accelerator opening sensor 32 ... Crank position sensor 33 ... Fuel pressure sensor 73 ... Needle valve 73a ... Seat 76 ... Fuel injection hole

Claims (3)

A fuel having an injection valve body that injects fuel of an internal combustion engine through a fuel injection hole, and a needle part that is arranged so as to be able to lift the inside of the injection valve body in the axial direction and opens and closes the fuel injection hole An internal combustion engine fuel injection system using an injection valve,
The lift position of the needle portion inside the injection valve main body is a fully open position where the fuel injection hole is fully open based on the operating state of the internal combustion engine, or a fully closed position where the fuel injection hole is fully closed And lift control means for controlling to be an arbitrary intermediate position between the position and the fully open position;
When intermediate lift injection is performed in which the needle portion is controlled to the intermediate position by the lift control means, the pressure of the fuel supplied to the fuel injection valve is set to the fully open position by the lift control means. Fuel pressure correction means for correcting to a high pressure side compared to the case where controlled full lift injection is performed,
A fuel injection system for an internal combustion engine. When the lift amount of the needle portion is smaller than a predetermined lift amount when the intermediate lift injection is performed by the lift control unit, the fuel pressure correction unit compares the fuel pressure with that when the full lift injection is performed. Correct to the high pressure side,
The fuel injection system for an internal combustion engine according to claim 1. The fuel pressure correction means corrects the fuel pressure so as to increase continuously as the lift amount of the needle portion decreases when the intermediate lift injection is performed by the lift control means.
The fuel injection system for an internal combustion engine according to claim 1.

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