JP5115822B2 - Fuel injection control device for in-cylinder injection engine - Google Patents

Description

  The present invention relates to a fuel injection control device for a direct injection engine, and in particular, a fuel injection control device including a fuel injection valve that directly injects fuel into a combustion chamber, a high-pressure fuel pump, and a delivery pipe that accumulates high-pressure fuel. The present invention relates to a fuel injection control device for a direct injection type engine that can reduce fuel leakage from a fuel injection valve to a combustion chamber when the engine is stopped.

  An in-cylinder direct injection engine (hereinafter referred to as “engine”) includes a fuel injection valve that directly injects fuel into a combustion chamber, a high-pressure fuel pump, and fuel sent from the high-pressure fuel pump to the fuel injection valve. A delivery pipe for supplying the fuel, and the fuel pressure is controlled by a fuel injection control device to inject the fuel directly into the combustion chamber. When the engine is stopped after the normal operation, the fuel is not injected from the fuel injection valve, so that the fuel pressure in the delivery pipe acts as a residual pressure on the fuel injection valve and the high-pressure fuel pump. Over time, the fuel in the delivery pipe leaks into the combustion chamber from the tip of the fuel injection valve (needle and seat) due to the action of this residual pressure, which causes a problem of deteriorating exhaust gas performance at the next engine start. .

In a conventional fuel injection control device for a direct injection engine, when the engine is stopped, an electromagnetic relief valve that returns the fuel in the delivery pipe to the fuel tank is opened to reduce the fuel pressure, thereby reducing the amount of fuel leaking into the combustion chamber. In some cases, when the engine is idling and stopped, the electromagnetic relief valve is closed and the fuel pressure is maintained at a high pressure to smoothly restart the engine.
JP 2006-258032 A

In addition, the conventional fuel injection control device for a direct injection engine determines whether or not the engine has just stopped, and if it is determined that the engine has just stopped, the target fuel pressure is reduced in advance, so that the fuel injection while the engine is stopped Some reduce fuel leakage from the valve.
JP 2007-46482 A

Further, in a conventional fuel injection control device for a direct injection type engine, when the engine stop condition is satisfied, the fuel supply amount is reduced and the fuel injection from the fuel injection valve is continued so that the fuel pressure in the delivery pipe is increased. There is one that stops the engine after lowering to the target fuel pressure.
JP 2004-293354 A

  However, the situation in which the engine is stopped includes not only a normal stop by a driver's operation and an idle stop by control, but also a stop by heat damage.

  For this reason, the fuel injection control device described in Patent Document 1 can reduce fuel leakage at the time of normal engine stop or engine idle stop, but cannot cope with fuel leakage at the time of engine stop due to heat damage. There's a problem. In addition, the fuel injection control device described in Patent Document 1 is provided with an electromagnetic relief valve in the middle of a return path that connects the delivery pipe and the fuel tank, so that the opening and closing control is performed. is there.

  In addition, the fuel injection control device described in Patent Document 2 needs to determine whether or not it is immediately before the engine is stopped, and in the case of erroneous determination, not only is there a concern about a decrease in fuel injection valve spray quality, but also thermal restart At times (bubbles are generated in the fuel in the delivery pipe and restarting becomes difficult), there is a problem that the effect on fuel leakage cannot be expected.

  Furthermore, the fuel injection control device described in Patent Document 3 cannot be expected to have an effect on fuel leakage at the time of thermal damage restart, and also leaks during idle stop control (because it restarts immediately and fuel pressure cannot be reduced). There is a problem that the effect on can not be expected.

  This invention sets the value of the target fuel pressure at the time of stop according to under what circumstances the engine is stopped, so that the start performance at the time of the next engine start after engine stop is not reduced. An object is to prevent fuel from leaking from the fuel supply system into the combustion chamber and to contribute to the improvement of exhaust gas purification performance at the time of starting.

The present invention relates to an in-cylinder injection engine that includes a fuel injection valve that directly injects fuel into a combustion chamber, a high-pressure fuel pump, and a delivery pipe that supplies fuel sent from the high-pressure fuel pump to the fuel injection valve. The fuel injection control apparatus of claim 1, further comprising a fuel pressure detecting means for detecting a fuel pressure in the delivery pipe, wherein the fuel pressure detected by the fuel pressure detecting means is controlled to become a target fuel pressure. As a plurality of engine stop modes set in advance for each reason the engine has stopped, a normal stop mode for stopping the engine based on the driver's will and a command from the engine operating state control means to stop the engine To stop the engine in the idle stop mode in which the fuel temperature rises and may affect the next engine restart. And a heat damage stop mode, selecting any engine stop mode, an engine stop mode judging means for judging whether the engine is stopped, depending on the determined engine stop mode in the engine stop mode determination unit An engine stop fuel pressure control means for setting a target fuel pressure value controlled by the fuel pressure control means ; in the normal stop mode, the target fuel pressure is set lower than the idle fuel pressure; In the mode, the target fuel pressure is set higher than the idling fuel pressure. In the thermal damage stop mode, the target fuel pressure is set higher than the idling fuel pressure according to the engine water temperature, and the fuel pressure, the target fuel pressure, The fuel cut and ignition cut are performed when the difference between the two is less than the predetermined value, and then the engine is stopped. And performing.

In the fuel injection control device for a direct injection type engine according to the present invention, the target fuel pressure value at the time of stopping is set according to under what circumstances the engine is stopped. It is possible to prevent the fuel from leaking from the fuel supply system to the combustion chamber without degrading the starting performance when starting the engine.
As a result, the fuel injection control device for a direct injection engine according to the present invention can contribute to the improvement of the exhaust gas purification performance at the time of starting.

A fuel injection control device for a direct injection type engine according to the present invention sets a target fuel pressure value at the time of stopping according to under what circumstances the engine is stopped, so that the fuel supply system can This prevents the fuel from leaking.
Embodiments of the present invention will be described below with reference to the drawings.

1 to 13 show an embodiment of the present invention. FIG. 1 is a system configuration diagram of a fuel injection control device for a direct injection engine, FIG. 2 is a diagram showing a relationship between fuel pressure and a leak amount, FIG. 3 is a diagram showing a relationship between time and a leak amount, and FIG. FIG. 5 is a flowchart of a stop mode determination routine, FIG. 6 is a flowchart of a normal stop mode routine, FIG. 7 is a table showing a target fuel pressure according to water temperature in the normal stop mode, and FIG. FIG. 9 is a flow chart of an idle stop mode routine, FIG. 10 is a diagram showing a target fuel pressure difference determination threshold MAP according to engine speed in the idle stop mode, FIG. 11 is a flowchart of the thermal damage stop mode routine, and FIG. It shows a table, Fig. 13 is a MAP of difference determination threshold value of the target fuel pressure according to engine speed heat damage stop mode.
In FIG. 1, 1 is a cylinder injection engine having a plurality of cylinders (hereinafter referred to as “engine”), 2 is a cylinder block, 3 is a cylinder head, 4 is a cylinder head cover, 5 is a piston, 6 is a combustion chamber, 7 is an intake port, and 8 is an exhaust port. An engine 1 mounted on a vehicle supports an intake cam shaft 9 and an exhaust cam shaft 10 on a cylinder head 3 and is driven by an intake cam 11 of the intake cam shaft 9 and an exhaust cam 12 of the exhaust cam shaft 10, respectively. An intake valve 13 and an exhaust valve 14 are provided. The intake valve 13 and the exhaust valve 14 open and close the intake port 7 and the exhaust port 8 that communicate with the combustion chamber 6 of each cylinder, respectively.
In the engine 1, as an intake device 15, an air cleaner 16, an intake pipe 17, a throttle body 18, a surge tank 19, and an intake manifold 20 are sequentially connected, and an intake passage 21 communicating with the intake port 7 is provided. A throttle valve 22 is provided in the intake passage 21 of the throttle body 18. In addition, the engine 1 is provided with an exhaust passage 27 that sequentially connects an exhaust manifold 24, a catalytic converter 25, and an exhaust pipe 26 as an exhaust device 23 and communicates with the exhaust port 8.
The engine 1 is provided with a supercharger (turbocharger) 28. The supercharger 28 is provided with a supercharger case 29 in the middle of the intake pipe 17 and between the exhaust manifold 24 and the catalytic converter 25, and a compressor 30 is provided in the intake passage 21 in the supercharger case 29. A turbine 31 for driving the compressor 30 is provided in the exhaust passage 27 in the machine case 29.
The engine 1 is provided with a bypass passage 32 that bypasses the turbine 31 and communicates with the exhaust passage 27, a waste gate valve 33 that opens and closes the bypass passage 32, and a waste gate actuator 34 that opens and closes the waste gate valve 33. A waste gate control valve 35 for controlling the operation of the waste gate actuator 34 is provided. The waste gate control valve 35 controls the operation of the waste gate actuator 34 by adjusting a part of the operating pressure introduced from the intake passage 21 downstream of the compressor 30 to the waste gate actuator 34 to the upstream side of the compressor 30 for adjustment. Then, the waste gate valve 33 is opened and closed to control the supercharging pressure to the set supercharging pressure.
Further, the engine 1 is provided with an air bypass passage 36 that communicates the intake passage 21 upstream and downstream of the compressor 30, an air bypass valve 37 that opens and closes the air bypass passage 36, and an air that opens and closes the air bypass valve 37. A bypass actuator 38 is provided, and an air bypass control valve 39 for controlling the operation of the air bypass actuator 38 is provided. The air bypass control valve 39 controls the operation of the air bypass actuator 38 by adjusting the operating pressure introduced into the air bypass actuator 38 from the intake passage 21 on the downstream side of the compressor 30, and air bypass when the throttle valve 22 is suddenly closed. The valve 37 is opened to prevent the compressor 30 from surging. In the engine 1, an intercooler 40 that cools the intake air supercharged by the supercharger 28 is provided in the intake pipe 17 between the compressor 30 and the throttle body 18.

The engine 1 is provided with an electromagnetic low-pressure fuel pump 43 that pumps fuel to the engine 1 side in a fuel tank 42 as a fuel supply device 41 that can supply fuel directly into the combustion chamber 6. One end side of the low-pressure fuel supply passage 46 is connected to the discharge side of this through a filter 44 and a pressure regulator 45. The pressure regulator 45 adjusts the discharge amount by returning a part of the fuel discharged from the low-pressure fuel pump 43 to the fuel tank 42, and maintains the fuel pressure in the low-pressure fuel supply passage 46 at a low pressure set value. The other end of the low pressure fuel supply passage 46 is connected to the suction side of a mechanical high pressure fuel pump 47. The high-pressure fuel pump 47 is attached to the cylinder head 3 and is mechanically driven by the rotation of the intake camshaft 9 to increase the pressure of the low-pressure fuel supplied from the low-pressure fuel supply passage 46 to the engine 1 side.
The high-pressure fuel pump 47 has one end side of the high-pressure fuel supply passage 48 connected to the discharge side. The other end side of the high pressure fuel supply passage 48 is connected to a delivery pipe 49. In the middle of the high-pressure fuel supply passage 48, a check valve 50 that restricts the backflow of fuel from the delivery pipe 49 to the high-pressure fuel pump 47 is provided. A fuel injection valve 51 for each cylinder attached to the cylinder head 3 is connected to the delivery pipe 49. The delivery pipe 49 distributes the high-pressure fuel supplied from the high-pressure fuel supply passage 48 to each fuel injection valve 51. The fuel injection valve 51 is attached to the cylinder head 3 so as to face the combustion chamber 6 and directly injects fuel into the combustion chamber 6.
The high-pressure fuel pump 47 has one end side of the fuel return passage 52 connected to the discharge side so as to communicate with the high-pressure fuel supply passage 48 closer to the high-pressure fuel pump than the check valve 50. The other end of the fuel return passage 52 opens into the fuel tank 42. The high pressure fuel pump 47 includes a spill valve 53 that opens and closes the fuel return passage 52 with respect to the high pressure fuel supply passage 48. The spill valve 53 is feedback-controlled by a fuel pressure control means 85 provided in the control means 78 described later, and a part of the fuel discharged from the high-pressure fuel pump 47 is returned to the fuel tank 42 by the fuel return passage 52 to reduce the discharge amount. The fuel pressure in the high pressure fuel supply passage 48 is adjusted and maintained at a high pressure set value (target fuel pressure).
One end of an evaporation passage 55 is connected to the fuel tank 42 via a two-way check valve 54. The evaporation passage 55 is connected to the canister 56 at the other end. One end of a purge passage 57 is connected to the canister 56. The other end of the purge passage 57 communicates with the intake passage 21 on the downstream side of the throttle valve 22. A purge control valve 58 is provided in the middle of the purge passage 57. The purge control valve 58 controls the introduction amount (purge amount) of the fuel evaporative gas adsorbed by the canister 56 into the engine 1.

In the engine 1, an ignition coil 60 for each cylinder is attached to the cylinder head cover 4 as an ignition device 59. The ignition coil 60 supplies a high voltage to a spark plug that faces the combustion chamber 6 of each cylinder to cause a spark.
Further, the engine 1 communicates with one end side of the tank side blow-by gas passage 62 through the PCV valve 61 in the cylinder head cover 4. The tank side blow-by gas passage 62 communicates the other end side with the intake passage 21 of the surge tank 19. In the engine 1, one end side of the cleaner side blow-by gas passage 63 is communicated with the cylinder head cover 4. The cleaner side blow-by gas passage 63 communicates the other end side with the air cleaner 16.
The engine 1 also includes an idle air passage 64 that bypasses the throttle valve 22 and communicates with the intake passage 21. In the middle of the idle air passage 64, an idle air amount control valve 65 for adjusting the amount of idle air passing through the idle air passage 64 while bypassing the intake passage 21 is provided.
Further, the engine 1 is provided with an EGR passage 66 having one end connected to the exhaust passage 27 of the exhaust manifold 24 and the other end connected to the intake passage 21 of the surge tank 19. In the middle of the EGR passage 66, an EGR control valve 67 for adjusting the amount of exhaust gas (EGR amount) recirculated to the intake passage 21 is provided.

The engine 1 is provided with a throttle opening sensor 68 that detects the throttle opening of the throttle valve 22, and an intake pressure sensor 69 that detects an intake pipe pressure downstream of the throttle valve 22, and an intake air temperature that detects an intake air temperature. A sensor 70 is provided, a crank angle sensor 71 for detecting the engine rotation speed of the engine 1 and a crank angle for determining the crank position is provided, the cylinder of the engine 1 is determined, and the cam position of the intake camshaft 9 is determined. A cam angle sensor 72 for detecting a cam angle for determination, a fuel pressure sensor 73 as a fuel pressure detecting means for detecting a fuel pressure in the delivery pipe 49, a knocking sensor 74 for detecting knocking, and a cooling are provided. A water temperature sensor 75 for detecting the water temperature is provided, and an O2 sensor 76 for detecting the oxygen concentration in the exhaust gas is provided.
The wastegate control valve 35, the air bypass control valve 39, the low pressure fuel pump 43, the fuel injection valve 51, the spill valve 53, the purge control valve 58, the ignition coil 60, the idle air amount control valve 65, the EGR control valve 67, and the throttle opening. The degree sensor 68, the intake pressure sensor 69, the intake temperature sensor 70, the crank angle sensor 71, the cam angle sensor 72, the fuel pressure sensor 73, the knocking sensor 74, the water temperature sensor 75, and the O 2 sensor 76 are a fuel injection control device for the engine 1. 77 is connected to control means 78 constituting 77. A battery 81 is connected to the control means 78 via a main switch 79 and a fuse 80. The fuel injection valve 51 is connected to the control means 78 via a fuel injection valve drive unit 82 that increases the drive voltage.
The fuel injection control device 77 of the engine 1 supplies a fuel injection valve 51 that directly injects fuel into the combustion chamber 6, a high-pressure fuel pump 47, and the fuel sent from the high-pressure fuel pump 47 to the fuel injection valve 51. It has a delivery pipe 49 and has a fuel injection control function for controlling the amount of fuel injected by the fuel injection valve 51 by a control means 78 that inputs detection signals from various sensors 68 to 76. The fuel injection control function is executed by the fuel injection control means 83 of the control means 78. The fuel injection control means 83 controls the fuel injection valve 51 so as to supply the required fuel into the combustion chamber 6 according to various states including the internal state of the engine 1.
The fuel injection control device 77 of the engine 1 has an engine operation state control function for controlling automatic stop / automatic start of the engine 1 by a control means 78 that inputs detection signals from various sensors 68 to 76. . The engine operation state control function is executed by the engine operation state control unit 84 of the control unit 78. The engine operation state control means 84 outputs a command to stop / start the engine 1 according to the automatic stop condition / automatic start condition, and the fuel injection valve 51 and the ignition so as to automatically stop (idle stop) / start the engine 1. The coil 60 is controlled.

The fuel injection control device 77 of the engine 1 includes a fuel pressure sensor 73 as fuel pressure detection means for detecting the fuel pressure in the delivery pipe 49, and the fuel pressure detected by the fuel pressure sensor 73 is a target fuel pressure. The control means 78 is provided with a fuel pressure control means 85 for controlling the engine 1 so that the engine stop mode is selected from a plurality of engine stop modes set in advance for each reason that the engine 1 is stopped. The engine stop mode determination means 86 for determining whether the engine has been stopped is provided in the control means 78, and the target controlled by the fuel pressure control means 85 in accordance with the engine stop mode determined by the engine stop mode determination means 86. The control means 78 includes an engine stop time fuel pressure control means 87 for setting a fuel pressure value.
The engine stop mode determined by the engine stop mode determination unit 86 includes a normal stop mode in which the engine 1 is stopped based on the driver's will, and an idle stop in which the engine 1 is stopped by a command from the engine operation state control unit 84. And a thermal damage stop mode in which the engine 1 is stopped in a state where the fuel temperature rises and may affect the next engine restart.
The engine stop fuel pressure control means 87 sets the target fuel pressure lower than the idling fuel pressure in the normal stop mode, and sets the target fuel pressure higher than the idling fuel pressure in the idling stop mode. In the thermal damage stop mode, the target fuel pressure is set higher than the idling fuel pressure in accordance with the engine water temperature.

That is, the in-cylinder direct injection type engine 1 that directly injects fuel into the combustion chamber 6 accumulates high-pressure fuel produced by the high-pressure fuel pump 47 attached to the rear end of the intake camshaft 9 in the delivery pipe 49, The fuel injection valve 51 is operated by being injected into the combustion chamber 6.
In the high-pressure fuel pump 47, the low-pressure fuel from the low-pressure fuel pump 43 (feed pump) attached in the fuel tank 42 is converted into the vertical movement of the piston in the pump by converting the rotational movement of the intake camshaft 9. By using it, it is compressed to a high pressure and is pumped to the delivery pipe 49 through the high-pressure fuel supply passage 48. At this time, the control means 78 of the fuel injection control device 77 monitors the pressure in the delivery pipe 49 by the fuel pressure sensor 73 attached to the delivery pipe 49, and the high-pressure fuel pump 47 adjusts the target fuel pressure. A command is sent to the spill valve 53, and a part of the compressed high pressure fuel is returned to the fuel tank 42 on the low pressure side to adjust the discharge amount, and feedback control is performed to achieve the target fuel pressure.
In the conventional system configuration of the fuel injection control device 77, the fuel accumulated in the delivery pipe 49 acts on the high-pressure fuel pump 47 and the fuel injection valve 51 as a residual pressure when the engine 1 is stopped from operation. However, on the high pressure fuel pump 47 side, the fuel injection valve 51 has a structure in which the fuel is difficult to flow back from the delivery pipe 49 to the high pressure fuel pump 47 by the check valve 50 provided in the middle of the high pressure fuel supply passage 48. The fuel leaked into the combustion chamber 6 from the seat and needle side, which are internal parts of the engine.
In general, the amount of fuel leakage varies depending on the structure of the fuel injection valve 51. However, in the case of the same fuel injection valve 51, as shown in FIGS. 2 and 3, the amount of fuel leakage varies depending on the fuel pressure acting on the seat and needle. . 2 and 3 show the relationship between the fuel pressure and the leakage amount, and the relationship between the elapsed time and the leakage amount, respectively. As can be seen from the figure, the amount of leakage is low when the fuel pressure is high and low (FIG. 2), and the needle adapts to the seat due to the residual pressure, so the amount of leakage decreases with time. (Fig. 3).

Therefore, the fuel injection control device 77 of the engine 1 sets a plurality of engine stop modes for each reason that the engine 1 is stopped in advance, and depending on which engine stop mode of the plurality of engine stop modes is stopped. The fuel control for changing the residual pressure in the delivery pipe 49 is performed. The fuel injection control device 77 sets a normal stop mode, an idle stop mode, and a heat damage stop mode as the engine stop mode.
In the normal stop mode in which the engine 1 is stopped based on the driver's will, the spill valve 53 of the high-pressure fuel pump 47 is controlled to be in a low fuel pressure state in the shutdown mode (control at the time of stop). That is, the residual pressure (fuel pressure) in the delivery pipe 49 is lowered, and the amount of leakage from the fuel injection valve 51 is reduced.
Further, an idle stop mode in which the engine 1 is stopped by a command from the engine operating state control means 84, or a thermal damage stop in which the engine 1 is stopped in a state where the fuel temperature rises and may affect the next engine restart. In the case where restart is possible, such as in the mode, the spill valve 53 of the high-pressure fuel pump 47 is controlled to be in a high fuel pressure state, contrary to the normal stop mode, and the residual pressure (fuel) in the delivery pipe 49 is controlled. (Pressure) is increased to reduce the amount of leakage from the fuel injection valve 51.
As described above, the fuel injection control device 46 of the engine 1 controls the fuel pressure in the delivery pipe 49 after the stop determination of the engine 1, and divides the engine stop determination into three modes (idle stop mode, (Heat damage stop mode, normal stop mode), set the target fuel pressure in each mode (set the target fuel pressure high in the idle stop mode and the heat damage stop mode, set the target fuel pressure low in the normal stop mode) ing.

Next, the operation of this embodiment will be described.
As shown in FIG. 4, the fuel injection control device 77 of the engine 1 determines that the engine 1 is stopped by an engine stop routine. In the engine stop routine (100), it is determined whether the ignition switch is turned off (Ig. SW: OFF) (101).
If this determination (101) is NO, the process returns to the start of the engine stop routine (100) (102). If this determination (101) is YES, the routine proceeds to a stop mode determination routine (103).

As shown in FIG. 5, in the stop mode determination routine (200), engine operating conditions such as engine speed, intake air temperature, and water temperature are read from the detection signals of the various sensors 68 to 76 (201), and the idle stop mode determination is performed. It is determined whether the condition is satisfied (202).
If this determination (202) is established, the routine proceeds to an idle stop mode routine (203). If this determination (202) is not satisfied, it is determined whether a thermal damage stop mode determination condition is satisfied (204).
If this determination (204) is established, the routine proceeds to a thermal damage stop mode routine (205). If this determination (204) is not established, the routine proceeds to a normal stop mode routine (206).
Thus, in the stop mode determination routine (200), it is determined whether the stop mode is determined based on the engine operating conditions, that is, whether the stop mode is the idle stop mode, the thermal damage stop mode, or the normal stop mode by the user operation.

As shown in FIG. 6, in the normal stop mode routine (300), the target fuel pressure is set according to the water temperature table (the target fuel pressure table according to the water temperature shown in FIG. 7) (301). By setting the target fuel pressure in the normal stop mode to be lower than the normal idling target fuel pressure, the amount of leakage from the fuel injection valve 51 is reduced.
Subsequently, the spill valve 53 of the high pressure fuel pump 47 is controlled by the fuel pressure control means 85 (302), the fuel pressure Pf in the delivery pipe 49 detected by the fuel pressure sensor 73 is read (303), and the fuel pressure Pf and the target are read. The difference with the fuel pressure is calculated (304), and it is determined whether the condition is less than the difference MAP threshold value (MAP of the difference determination threshold value of the target fuel pressure based on the engine speed shown in FIG. 8) (305). .
The control (302) of the spill valve 53 is different from the normal feedback control of the spill valve 53. When the fuel pressure Pf is lower than the target fuel pressure, the spill valve 53 is closed and when it is higher, the spill valve 53 is controlled. 53 is controlled to immediately change the fuel pressure Pf to the target fuel pressure. (Normally, since the target fuel pressure becomes low, the spill valve 53 is in a fully open state (fully open) and there is no feedback control.)
If the determination (305) is not established, the control returns to the control (302) of the spill valve 53. If the determination (305) is satisfied, that is, if the difference is less than the difference MAP threshold, the control of the spill valve 53 is stopped, fuel cut and ignition cut are performed (306), and the engine 1 is stopped. (307) and the program is stopped (308).

As shown in FIG. 9, in the idle stop mode routine (400), the target fuel pressure constant value is read and the target fuel pressure is set based on the target fuel pressure constant value (401). The target fuel pressure in the idle stop mode is set higher than the normal idling target fuel pressure, thereby reducing the amount of leakage from the fuel injection valve 51. Further, at the time of idle stop control in which the engine 1 is stopped by a command from the engine operating state control means 84, the engine 1 can be restarted. Therefore, the fuel pressure in the delivery pipe 49 is kept high so that the engine 1 can be restarted. It is possible to improve the spray quality at the time.
Subsequently, the spill valve 53 of the high pressure fuel pump 47 is controlled by the fuel pressure control means 85 (402), the fuel pressure Pf in the delivery pipe 49 detected by the fuel pressure sensor 73 is read (403), the fuel pressure Pf and the target The difference with the fuel pressure is calculated (404), and it is determined whether the difference is less than the difference MAP threshold value (MAP of the difference determination threshold value of the target fuel pressure based on the engine speed shown in FIG. 10) (405). .
The control (402) of the spill valve 53 is different from the normal feedback control of the spill valve 53. When the fuel pressure Pf is lower than the target fuel pressure, the spill valve 53 is closed and when it is higher, the spill valve 53 is controlled. 53 is controlled to immediately change the fuel pressure Pf to the target fuel pressure. (Normally, since the target fuel pressure becomes high, the spill valve 53 is in a fully closed state (fully closed) and there is no feedback control.)
If the determination (405) is not established, the process returns to the control (402) of the spill valve 53. Further, when the determination (405) is established, that is, when the difference is less than the difference MAP threshold, the fuel cut and the ignition cut are performed while the control of the spill valve 53 is continued (406). The stop is determined (407), and the program is stopped (408). Since the engine 1 rotates by inertia even after the fuel cut is executed, the fuel pressure can be continuously generated by continuously controlling the spill valve 53 of the high-pressure fuel pump 47. Since an increase in fuel pressure due to the inertia of the engine 1 can be expected, the engine 1 can be quickly stopped.

As shown in FIG. 11, in the thermal damage stop mode routine (500), the target fuel pressure is set according to the water temperature table (the target fuel pressure table based on the water temperature shown in FIG. 12) (501). The target fuel pressure in the thermal damage stop mode is set to be higher than the normal idling target fuel pressure, thereby reducing the amount of leakage from the fuel injection valve 51. Further, when the engine 1 is stopped under the heat damage condition, the fuel in the delivery pipe 49 is warmed, and the restartability is deteriorated due to gasoline percolation. In the present invention, the deterioration of the heat damage restartability can be suppressed by setting the fuel pressure higher according to the water temperature under the condition of the heat damage stop mode.
Subsequently, the spill valve 53 of the high pressure fuel pump 47 is controlled by the fuel pressure control means 85 (502), the fuel pressure Pf in the delivery pipe 49 detected by the fuel pressure sensor 73 is read (503), and the fuel pressure Pf and target The difference with the fuel pressure is calculated (504), and it is determined whether the condition is satisfied whether the difference is less than the difference MAP threshold value (MAP of the difference determination threshold value of the target fuel pressure based on the engine speed shown in FIG. 13). (505).
The control (402) of the spill valve 53 is different from the normal feedback control of the spill valve 53. When the fuel pressure Pf is lower than the target fuel pressure, the spill valve 53 is closed and when it is higher, the spill valve 53 is controlled. 53 is controlled to immediately change the fuel pressure Pf to the target fuel pressure. (Normally, since the target fuel pressure becomes high, the spill valve 53 is in a fully closed state (fully closed) and there is no feedback control.)
If the determination (505) is not established, the control returns to the control (502) of the spill valve 53. If the determination (505) is satisfied, that is, if the difference is less than the difference MAP threshold, the fuel cut and the ignition cut are performed while continuing the control of the spill valve 53 (506). Stop is determined (507), and the program is stopped (508). Since the engine 1 rotates by inertia even after the fuel cut is executed, the fuel pressure can be continuously generated by continuously controlling the spill valve 53 of the high-pressure fuel pump 47. Since an increase in fuel pressure due to the inertia of the engine 1 can be expected, the engine 1 can be quickly stopped.

As described above, the fuel injection control device 77 of the in-cylinder injection type engine 1 determines under what circumstances the engine 1 is stopped (which engine stop mode is stopped among a plurality of engine stop modes). Accordingly, the value of the target fuel pressure at the time of stopping is set, so that the fuel is supplied from the fuel injection valve 51 of the fuel supply system to the combustion chamber 6 without degrading the starting performance at the next engine starting after the engine is stopped. Can be prevented from leaking.
Thereby, the fuel injection control device 76 of the engine 1 can contribute to the improvement of the exhaust gas purification performance at the time of starting.
Further, the fuel injection control device 77 of the in-cylinder injection type engine 1 corresponds to a plurality of engine stop modes (normal stop mode, idle stop mode, thermal damage stop mode) set for each reason why the engine 1 is stopped. Since the target fuel pressure can be set, highly accurate fuel pressure control when the engine is stopped can be performed.
Further, the fuel injection control device 76 of the in-cylinder injection type engine 1 leaks from the fuel injection valve 51 into the combustion chamber 6 by setting the target fuel pressure lower than the idling fuel pressure in the normal stop mode. The amount of fuel can be reduced, and in the idle stop mode, the target fuel pressure can be set higher than the idling fuel pressure so that the restart after the idle stop can be carried out satisfactorily. Sometimes, by setting the target fuel pressure higher than the idling fuel pressure according to the engine water temperature, the target fuel pressure can be set according to the engine water temperature, so that the restart performance can be improved.
In the above-described embodiment, the target fuel pressure is set depending on which engine stop mode is stopped in the plurality of engine stop modes. However, the target fuel pressure at the start is set as follows. To do.
-In the normal stop mode by the driver's operation, the target fuel pressure is set in the target fuel pressure table corresponding to the engine operating conditions (intake air temperature, water temperature, oil temperature, etc.).
Even in the idling stop mode when the idling stop condition is satisfied, the target fuel pressure is set in the idling stop target fuel pressure table according to the engine operating conditions (intake air temperature, water temperature, oil temperature, etc.).

  The fuel injection control device for a direct injection engine according to the present invention can prevent the fuel from leaking from the fuel supply system to the combustion chamber without degrading the starting performance at the next engine starting after the engine is stopped. The present invention can be applied to an engine including a fuel injection valve that directly injects fuel into a combustion chamber.

1 is a system configuration diagram of a fuel injection control device for a direct injection type engine showing an embodiment. FIG. It is a figure which shows the relationship between a fuel pressure and the amount of leaks. It is a figure which shows the relationship between time and the amount of leaks. It is a flowchart of an engine stop routine. It is a flowchart of a stop mode determination routine. It is a flowchart of a normal stop mode routine. It is a figure which shows the table of the target fuel pressure by the water temperature of a normal stop mode. It is a figure which shows MAP of the difference determination threshold value of the target fuel pressure by the engine speed of a normal stop mode. It is a flowchart of an idle stop mode routine. It is a figure which shows MAP of the difference determination threshold value of the target fuel pressure by the engine speed of idle stop mode. It is a flowchart of a heat damage stop mode routine. It is a figure which shows the table of the target fuel pressure by the water temperature of thermal damage stop mode. It is a figure which shows MAP of the difference determination threshold value of the target fuel pressure by the engine speed of a thermal damage stop mode.

Explanation of symbols

1 engine (in-cylinder injection engine)
6 Combustion chamber 21 Intake passage 27 Exhaust passage 42 Fuel tank 47 High-pressure fuel pump 48 High-pressure fuel supply passage 49 Delivery pipe 50 Check valve 51 Fuel injection valve 52 Fuel return passage 53 Spill valve 68 Throttle opening sensor 70 Intake temperature sensor 71 Crank Angle sensor 73 Fuel pressure sensor 75 Water temperature sensor 77 Fuel injection control device 78 Control means 83 Fuel injection control means 84 Engine operating state control means 85 Fuel pressure control means 86 Engine stop mode determination means 87 Fuel pressure control means at engine stop

Claims (1)

Fuel injection control for a cylinder injection engine comprising a fuel injection valve that directly injects fuel into a combustion chamber, a high-pressure fuel pump, and a delivery pipe that supplies fuel sent from the high-pressure fuel pump to the fuel injection valve In the device
A fuel pressure detecting means for detecting the fuel pressure in the delivery pipe;
Fuel pressure control means for controlling the fuel pressure detected by the fuel pressure detection means to be a target fuel pressure;
As a plurality of engine stop modes set for each reason why the engine has been stopped in advance, a normal stop mode for stopping the engine based on the driver's will and an idle stop for stopping the engine by a command from the engine operating state control means And a thermal damage stop mode that stops the engine in a state where the fuel temperature rises and may affect the next engine restart,
An engine stop mode determining means for determining which engine stop mode is selected and determining whether the engine is stopped;
Engine stop fuel pressure control means for setting a target fuel pressure value controlled by the fuel pressure control means according to the engine stop mode determined by the engine stop mode determination means ;
In the normal stop mode, the target fuel pressure is set lower than the idle fuel pressure, in the idle stop mode, the target fuel pressure is set higher than the idle fuel pressure, and in the thermal damage stop mode, the target fuel pressure is set. Is set higher than the idling fuel pressure according to the engine water temperature, fuel cut and ignition cut are performed when the difference between the fuel pressure and the target fuel pressure is less than the predetermined value, and then the engine stop is judged A fuel injection control device for an in-cylinder injection engine.

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