JPH11247699A - Fuel injection device of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection device of engine which prevents an overrun operation by lowering the fuel injecting pressure when the engine operation is in overrun condition. SOLUTION: When an overrun judging means 47 judges that the engine operation is in an overrun condition, switching circuits 42a and 42b are changed over, and a signal from a setting means 48 which has set to zero the pulse width Pw of the drive pulse current, is emitted and fed to a solenoid valve driving means 43 for a solenoid valve to control the pressure action at injection of a working fluid, and thereby the fuel injecting amount is nullified substantially, and from the setting means 48, a signal in which the duty ratio of the control current to a flow control valve to control the supply pressure to the injector of the working fluid is selected to zero, is emitted and fed to a flow control valve driving means 46 so that the pressure of the working fluid is lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device for an engine capable of performing overrun control for stopping the engine when the engine is overrun.

[0002]

2. Description of the Related Art In recent years, an electronically controlled fuel injection system for a diesel engine has been required to provide a fuel injection pressure in addition to a fuel injection amount and a fuel injection timing in order to further improve engine characteristics including output and fuel efficiency and exhaust gas characteristics. A variety of controllable devices have been developed. A fuel injection system for such an engine includes a needle valve that moves up and down in a main body to control opening and closing of an injection hole, and an electromagnetic valve that is supplied with a drive current that controls a working fluid to move the needle valve up and down. The controller controls the fuel injection timing, the fuel injection amount, and the fuel injection pressure injected from the injector according to the operating state of the engine by the controller.

The above-mentioned electronically controlled fuel injection system includes, for example, an injector having working fluid as engine oil pressurized by a high-pressure oil pump and having a booster piston that operates based on the pressure action of the engine oil. A hydraulically operated system that boosts fuel in a pressurized chamber by a booster piston, raises and lowers a needle valve with the pressure of the boosted fuel, and injects fuel that has been boosted from an injection hole opened by the needle valve. A high-pressure fuel supplied by a high-pressure fuel pump and stored in a common rail, and an injector having a pressure control chamber formed in the main body, and controlling the inflow and outflow of the high-pressure fuel into and from the pressure control chamber,
There has been proposed a fuel pressure operated type system in which a needle valve is raised and lowered based on the pressure of the high-pressure fuel, and high-pressure fuel is injected from an injection hole opened by the needle valve. Regardless of the type of electronically controlled fuel injection system, the injector is equipped with a solenoid valve, and the electronic control unit as a controller controls the timing and duration of the drive current supplied to the solenoid valve. The working fluid pressurized to a high pressure is supplied to and discharged from the injector, and fuel is injected from an injection hole formed at the tip of the injector at a predetermined fuel injection timing at a predetermined injection amount.

As one of the electronically controlled fuel injection systems employing the above-mentioned hydraulically operated unit injector, there is an electronically controlled fuel injection system disclosed in Japanese Patent Publication No. 6-511526. In this electronically controlled fuel injection system, the fuel injection amount and fuel injection timing are simultaneously controlled by controlling the pressure action of the engine oil, which is the working fluid, via an electronic device such as a solenoid valve provided in the injector. can do.

FIG. 4 is a sectional view showing an example of a unitized injector used in the above-mentioned hydraulically operated fuel injection system. Injector 5
The main body 0 has a nozzle body 52 having an injection hole 64 for injecting fuel at the tip, a solenoid body 53 having a solenoid 60 as an electromagnetic actuator, an injector body 54, and a fuel supply body 55. The injector 50 is driven by the pressure increasing chamber 57 to which the fuel from the common rail 63 is supplied, the pressure chamber 58 to which the working fluid is supplied, and the working fluid supplied to the pressure chamber 58 to increase the pressure of the fuel in the pressure increasing chamber 57. A pressure booster piston 59, a return spring 71 for returning the pressure booster piston 59, and a case 56 having a fuel supply port 61 and a fuel discharge port 62 opened to a common rail 63 for forming a fuel chamber 70 are provided. . In the injector 50, the needle valve 65 moves up and down based on the pressure of the fuel from the pressure increasing chamber 57 and
Open and close 4. The pressure-intensifying piston 59 is slidably fitted in a hollow hole 66 formed in the main body and has a pressure chamber 58.
And a small diameter portion 69 slidably fitted in the hollow hole 67 and forming a part of the wall surface of the pressure increasing chamber 57.

In such a hydraulically operated injector, the fuel pressurized to a relatively low pressure by the fuel pump is supplied to the pressure increasing chamber 57 through the common rail 63, the fuel supply port 61 and the fuel chamber 70. Booster chamber 5
The fuel in 7 is sent out from the pressure intensifying chamber 57 by the fuel injection pressure by being pressurized by the pressure intensifying piston 59. The engine oil as the working fluid whose pressure has been increased to a high pressure by the high-pressure oil pump is stored in a high-pressure oil manifold (or an oil rail, see FIG. 6). Booster piston 5
9 to operate the oil rail and injector 50
A solenoid valve 51 is connected to a pressure chamber 58 in the inside and opens and closes a hydraulic path through which engine oil is supplied.
It is arranged in. When a drive current from the controller is applied to the solenoid 60, the valve body 72 operates to open the solenoid valve 51, and the engine oil is supplied to the pressure chamber 58 through the hydraulic path as indicated by the arrow, and the booster piston 59
To drive (stroke) the pressure increasing piston 59. The fuel in the booster chamber 57 is
The needle valve 65 moves up and down in the main body of the injector 50 based on the fuel pressure from the pressure increasing chamber 57, thereby opening and closing the injection hole 64 formed at the tip of the nozzle main body 52, and opening the injection port. Fuel is injected from the hole 64 into the combustion chamber. In the injector 50, since the pressure-intensifying piston 59 pressurizes the fuel in the pressure-intensifying chamber 57, the fuel is injected at a fuel injection pressure independent of the engine speed.

In this hydraulically operated type electronically controlled fuel injection system, the fuel injection pressure is determined by the pressure action of the working fluid on the pressure-intensifying piston 59, that is, the oil rail pressure. The fuel injection pressure can be controlled by controlling the flow control valve and changing the oil rail pressure. As the flow control valve, a solenoid valve whose opening is controlled by the duty ratio is used. The oil rail pressure is controlled by controlling the amount of oil supplied from a high-pressure oil pump to the oil manifold through the flow control valve. can do. The duty ratio, which is the control amount of the flow control valve, is the operating state of the engine, that is, the basic target rail pressure determined according to the engine speed and the target injection amount, and the deviation between the basic target rail pressure and the actual rail pressure. Is determined according to the target rail pressure corrected by the PID control based on.

As described above, the hydraulically actuated electronically controlled fuel injection system includes the controller for calculating the target injection amount, the target injection timing, and the target injection pressure (target rail pressure) according to the operating state of the engine. Then, based on the respective target values, the energizing time to the solenoid valve provided in the injector, the energizing timing, and the duty ratio of the control current output to the flow control valve provided in the high-pressure oil pump are determined.

In addition to the above-mentioned hydraulically operated electronically controlled fuel injection system, there is known a fuel pressure operated type fuel injection system having an injector which operates based on a fuel pressure pressurized to a high pressure. Such a fuel injection system is, for example, of the type disclosed in Japanese Patent Publication No. Hei 4-19381. FIG. 6 is a cross-sectional view illustrating an example of an injector used in a fuel pressure operated fuel injection system. This injector supplies high-pressure fuel to a pressure control chamber formed on the back pressure side of the needle valve, controls the lift of the needle valve by leaking the high-pressure fuel, and performs fuel injection.

In this fuel injection system in which the working fluid is fuel itself which has been pressurized to a high pressure, the high-pressure fuel is stored in a common rail (see reference numeral 78 in FIG. 5) and supplied from the common rail to each injector 80 through a fuel supply pipe 88. Is done. On the upper side of the injector 80, a fuel inlet joint 9 is provided.
The fuel supply pipe 88 is connected through the “0”. Inside the injector main body 81 constituting the injector 80,
Fuel passages 91 and 92 are formed, and a fuel supply pipe 88 is provided.
And the fuel passages 91 and 92 constitute a fuel passage.
A part of the fuel supplied from the common rail through the fuel flow path is supplied to a fuel reservoir 93 formed in the nozzle 82, and from the fuel reservoir 93 through a passage around a needle valve 84 slidable in the hollow hole 83. , Is injected into the combustion chamber from an injection hole 85 formed at the tip of the nozzle 82 and opened when the needle valve 84 is lifted. The needle valve 84 has a tapered surface 94 that receives the pressure of the high-pressure fuel supplied to the fuel reservoir 93, and receives a force in the lift direction based on the pressure of the high-pressure fuel. Excess fuel is returned to the common rail through the return pipe 89.

The injector 80 is provided with a pressure control chamber type needle valve lift mechanism for controlling the lift of the needle valve 84. That is, the high-pressure fuel pressurized by the high-pressure fuel pump is supplied to the pressure control chamber 100 formed inside the injector 80 in addition to the fuel injected from the injection hole 85. An electromagnetic valve 96 as a control valve is provided in a head portion of the injector 80, and a drive current as a control signal from a controller 95 is sent to a solenoid 98 of the electromagnetic valve 96 through a signal line 97. When the solenoid 98 is excited, the armature 99 rises and the on-off valve 102 provided at the end of the fuel passage 101 as a leak passage is opened.
When the fuel supplied to the pressure control chamber 100 is discharged, the high fuel pressure in the pressure control chamber 100 is released through the fuel passage 101.

A control piston 1 is provided in a central hollow hole 103 formed in the central body of the injector 80.
04 is provided so as to be able to move up and down. Due to the force based on the pressure in the pressure control chamber 100 reduced when the solenoid valve 96 is actuated and the spring force of the return spring 105, the fuel pool 93 is smaller than the pressing force acting on the control piston 104.
The control piston 104 rises because the force for pushing up the control piston 104 is superior based on the taper surface 94 facing the front end and the fuel pressure acting on the tip of the needle valve 84. As a result, the needle valve 84 is lifted, and fuel is injected from the injection hole 85. The fuel injection amount is determined by the fuel pressure in the fuel flow path and the lift of the needle valve 84 (lift amount, lift period). The drive current sent to the solenoid 98 to control the opening and closing of the on-off valve 102 is a pulse current.

In this fuel pressure operated electronically controlled fuel injection system, since the fuel injection pressure is determined by the fuel pressure of the high pressure fuel supplied to the injector 80, the flow control valve provided in the high pressure fuel pump is provided. The fuel injection pressure can be controlled by controlling the pressure and changing the common rail pressure. As the flow control valve, a solenoid valve controlled by a duty ratio is used as in the above-mentioned hydraulically operated system, and by controlling the duty ratio of the control current supplied to the flow control valve, the fuel pressure of the common rail is controlled. Is changed to control the fuel injection pressure.

As described above, also in the fuel pressure operated electronically controlled fuel injection system, similarly to the hydraulically operated system, the controller determines the target injection amount, the target injection timing, and the target injection timing in accordance with the operating state of the engine. Calculates the target injection pressure (target rail pressure), and based on each target value, the energization time to the solenoid valve provided in the injector, the energization timing, and the control output to the flow control valve installed in the high-pressure fuel pump The duty ratio of the current is determined.

[0015]

In general, when the engine enters an overrun state for some reason, that is, a state where the engine is operated at a speed exceeding a predetermined maximum rotation speed,
Since inconvenience such as breakage of engine parts occurs, control is performed to stop fuel injection when an overrun state is detected. An example of such a control is disclosed in Japanese Utility Model Publication No. 5-36997. This publication states that when the engine is not connected to the drive shaft and the accelerator pedal depression amount is smaller than the reference value,
When the engine speed rises above the reference speed, the engine is stopped by closing the throttle valve arranged in the intake manifold.

In an engine equipped with the above-mentioned hydraulically operated or fuel pressure operated electronically controlled fuel injection system,
When the overrun state occurs, it is conceivable to cut off the power supply to the solenoid valves 51 and 96 of the injector, which is an electronic device that directly controls the fuel injection, as in the above-mentioned publication. However, in such a method, for example, when the power supply circuit to the solenoids 60, 98 of the solenoid valves 51, 96 is short-circuited, the controller issues a command to cut off the power supply to the solenoid valves 51, 96. Output from the battery, the solenoid 6
Since the flow continues to 0, 98, the solenoid valves 51, 96 continue to be driven, and the fuel injection is not stopped. In such a state, there is a problem that the rotation speed of the engine does not decrease and overrun cannot be avoided.

In any of the above types of electronically controlled fuel injection systems, fuel injection is performed when a high-pressure oil or a working fluid, which is high-pressure fuel, exerts a high-pressure action. In other words, in the hydraulically actuated electronically controlled fuel injection system, fuel injection is performed when the rail pressure of the working oil supplied from the high pressure oil pump to the oil rail exerts a pressure action on the booster piston. In the pressure-actuated electronically controlled fuel injection system, the fuel pressure of the high-pressure fuel itself lifts the needle valve to inject fuel when the pressure in the pressure control chamber is released. Especially,
In the fuel pressure operated electronically controlled fuel injection system, the solenoid valve 9
If the operation of No. 6 is kept on, there is a problem that the needle valve 84 is lifted by the high-pressure fuel pressure and the injection of fuel from the injection hole 85 which is kept open does not stop. Therefore, there is a problem to be solved in that fuel injection from the injector is stopped when the solenoid valve fails.

[0018]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problem. When an overrun condition of an engine occurs, for example, the inflow and discharge of a working fluid provided in the injector and into the injector are performed. Even if it is impossible to control the solenoid valve that controls the engine, it is possible to reduce the fuel injection amount or set it to substantially zero to reduce the rotational speed and prevent overrun. It is to provide a fuel injection device.

According to the present invention, there is provided a working fluid supply source for delivering a high-pressure working fluid, an injector for injecting fuel into a combustion chamber of an engine at a fuel injection pressure corresponding to a pressure of the working fluid supplied from the working fluid supply source. Working fluid pressure changing means for changing the pressure of the working fluid supplied to the injector, fuel injection amount changing means for changing a fuel injection amount injected from the injector, and detecting an operating state including a rotation speed of the engine. Detecting means and a controller for controlling the working fluid pressure changing means and the fuel injection amount changing means for injecting fuel with the fuel injection pressure and the fuel injection amount obtained according to the operating state of the engine. Wherein the controller detects that the engine is over based on the operating state of the engine detected by the detection means. When it is determined that the fuel injection amount is in the operating state, the fuel injection amount changing means is controlled so that the fuel injection amount becomes substantially zero, and the working fluid pressure is changed so that the fuel injection pressure decreases. Controlling the means for controlling the fuel injection of the engine.

In the fuel injection device for an engine, the working fluid pressure control means is a flow control valve for controlling a flow rate of the working fluid supplied from the working fluid supply source to the injector. Is controlled by the opening of the flow control valve. That is, by controlling the opening of the flow control valve, the flow rate of the working fluid supplied from the working fluid supply source to the injector via the flow control valve is changed, and the pressure of the working fluid is controlled. Further, the flow control valve is a solenoid valve operated by a control current output from the controller, and an opening of the flow control valve is determined by a duty ratio of the control current.

In the fuel injection device for an engine, the fuel injection amount changing means is an electromagnetic valve provided in a path of the working fluid and opening and closing the path by receiving a drive current output from the controller. , The fuel injection amount is controlled by an energizing period of the drive current.

In the fuel injection device for an engine, the working fluid is engine oil pressurized by a high-pressure oil pump, and the fuel injection pressure is a fuel pressure increased by a pressure action of the engine oil. .
Alternatively, the working fluid is a fuel pressurized by a high-pressure fuel pump, and the fuel injection pressure is a fuel pressure pressurized by the high-pressure fuel pump.

Further, in the fuel injection device for an engine, the operating state of the engine detected by the detecting means includes a rotational speed of the engine, and the rotational speed of the engine is a predetermined maximum rotational speed. Is continuously exceeded for a predetermined time, it is determined that the engine is in the overrun operation state.

According to the present invention, as described above, when the rotational speed of the engine detected by the detecting means exceeds a predetermined maximum rotational speed, the controller causes the fuel injection amount to be substantially reduced. The fuel injection amount changing means is controlled so as to be zero, and the working fluid pressure changing means is controlled so as to reduce the fuel injection pressure. Therefore, when the fuel injection amount changing means is functioning normally, the fuel injection Even if the amount becomes substantially zero and the engine goes into the overrun state, the engine speed thereafter drops from the overrun state to a rotation speed equal to or lower than the maximum rotation speed. Further, even if the fuel injection amount changing means is out of order and a large amount of fuel is to be injected, the working fluid pressure changing means is controlled to reduce the fuel injection pressure. Since the fuel injection is not accompanied by the fuel injection pressure, the amount of fuel actually injected is reduced, and the overrun state of the engine does not last long.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an engine fuel injection device according to the present invention will be described below with reference to the accompanying drawings.
FIG. 3 is a schematic diagram showing an example of an entire system including a hydraulically operated electronically controlled fuel injection system 10 to which the engine fuel injection device according to the present invention is applied. Engine 1
Is a multi-cylinder 4-cycle direct-injection diesel engine having a plurality of cylinders such as four cylinders in order to obtain a high output, although FIG. 3 shows only one injector 11. The engine 1 has a cylinder block 2 and a cylinder head 3. The reciprocating motion of a piston 4 slidable in a cylinder liner formed in the cylinder block 2 and the rotating motion of a crankshaft 6 connect the two. It is converted via the connecting rod 5.

The hydraulically operated electronically controlled fuel injection system 10 of the engine 1 employs an injector 11 similar to the hydraulically operated unitized injector 50 as shown in FIG. The injector 11 is disposed in the cylinder head 3 and operates with engine oil as a working fluid. The injector 11 increases the pressure of the fuel so as to have a predetermined fuel injection pressure and directly transfers the fuel into the combustion chamber 7. Inject. The fuel whose pressure has been raised to a relatively low pressure by the fuel pump 12 is supplied through a fuel supply pipe 13 to a pressure increasing chamber (see reference numeral 57 in FIG. 4) formed inside the injector 11. The engine oil is pressurized to a high pressure by a high-pressure oil pump 14, accumulated in a high-pressure oil manifold (oil rail) 15, and is supplied from the high-pressure oil manifold 15 to a pressure chamber in each injector 11 (see reference numeral 58 in FIG. 4).
Supplied to

The fuel injection pressure is controlled by the high pressure oil manifold 15.
, Ie, oil rail pressure. The flow control valve 16 provided in the high-pressure oil pump 14
It is a normally open or normally closed control valve.
Opening degree (or average valve opening time, that is, duty ratio of pulse current) according to a control signal from (described later)
Is controlled to control the amount of oil supplied to the high-pressure oil manifold 15 through the flow control valve 16, whereby the oil rail pressure in the high-pressure oil manifold 15 is controlled. As for the structure of the injector 11 and the fuel injection system itself having the injector, for example, the one disclosed in Japanese Patent Application Laid-Open No. 6-511526 can be used.

The electronically controlled fuel injection system 10 includes a controller 20 as an electronic control unit (ECM). The controller 20 receives detection signals from various detecting means for detecting the operating state of the engine 1, The controller 20 controls the solenoid valve 17 of the injector 11 (the injector 5 shown in FIG. 4) based on these detection signals.
0), the oil pump 14, the flow control valve 16, and the like.

Specifically, the detection means for detecting the operating state of the engine 1 inputted to the controller 20 includes the following. Rotation speed Ne of engine 1
Is rotated by being fixed to the crankshaft 6 and missing teeth (for three teeth) in a part of the periphery.
It comprises an electromagnetic pickup for detecting a gear 8 (having 57 teeth at equal intervals) having a portion 9. Missing part 9
The rotational speed of the crankshaft 6 is determined from the number of times of detecting the rotation speed and the time required for the detection. The accelerator pedal depression amount sensor 22 for detecting the accelerator pedal depression amount (or accelerator opening degree) Ac includes a potentiometer for detecting the depression stroke of the accelerator pedal. Further, the high-pressure oil manifold 15 is provided with a pressure sensor 24 and an oil temperature sensor 25 in order to detect the rail pressure in the high-pressure oil manifold 15 and the oil temperature To as a representative value of the engine friction and the viscosity of the working fluid. . As a representative value of the engine friction, a water temperature sensor 23 provided in the cylinder head 3 and detecting a cooling water temperature may be used.

The crank angle detected by the crank angle sensor 21 is used together with the detection signal of each sensor for detecting that the piston has reached the compression top dead center of the reference cylinder or each cylinder or a predetermined position before the compression top dead center. It is used to control the current application start time and current application period. An intake pipe 26 of the engine 1 is provided with an intake pressure sensor 27 for detecting intake pressure of the intake pipe 26 and an intake temperature sensor 28 for detecting intake temperature. The opening of the intake throttle valve 29 provided in the intake pipe 26 is controlled by the controller 20.
The throttle valve position is detected by a position sensor 30. In order to reduce NOx, the exhaust pipe 31 and the intake pipe 26 of the engine 1 are
An EGR (exhaust gas recirculation) pipe 32 for recirculating a part of the exhaust gas to the intake pipe 26 is connected between them. E
The valve lift position of the EGR valve 33 provided in the middle of the GR pipe 32 utilizes the negative pressure of a vacuum pump 34 as a vacuum source whose introduction is controlled by a pressure regulating valve (EVRV) 35 controlled by the controller 20. The EGR pressure sensor 36 detects the valve lift position as a valve lift negative pressure. Further, the controller 20 includes a shift position sensor 37 of the automatic transmission, a warm-up switch 38 operated to promote warm-up of the engine 1, and an air-conditioner switch operated to operate an air conditioner as an auxiliary machine. The signal from 39 is also input.

The intake pressure sensor 27 is located on the downstream side of the compressor of the turbocharger 19 provided in the intake pipe 26.
Further, it is provided upstream of an outlet of an EGR pipe 32 connecting the intake pipe 26 and the exhaust pipe 31. The atmospheric pressure sensor may be provided separately, but in this example, it is also used as the EGR pressure sensor 36. The EGR pressure sensor 36 detects the operating pressure of the EGR valve 33 at the time of EGR operation.
When not operating, it functions as an atmospheric pressure sensor. EGR
Since the atmospheric pressure detected during non-operation is stored in the memory at regular intervals, even when the intake pressure sensor 27 is determined to be abnormal or malfunction, the latest atmospheric pressure stored in the memory is maintained even during EGR operation. It can be substituted as the intake pressure.

The injector 11 is provided with a solenoid valve 17, which is arranged to open and close an oil path from the high pressure oil manifold 15 to a pressure chamber in the injector 11. By controlling the operation of the solenoid valve 17 by the timing and duration of application of the control current from the controller 20, the timing and duration of supply of high-pressure hydraulic oil to the pressure chamber in the injector 11 are controlled.
The fuel injection timing and the fuel injection amount from the injector 11 are controlled. That is, the controller 20 determines the energization period (pulse width) to the solenoid valve based on the target fuel injection amount determined by the calculation of the target fuel injection amount, and energizes the solenoid valve 17 with this pulse width to perform fuel injection. Controlling the amount. The controller 20 calculates a target fuel injection amount, a target fuel injection timing, and a target fuel injection pressure according to the operating state of the engine, and based on the respective target values, the energizing timing and energizing period of the solenoid valve 17 and the flow control valve. A duty ratio of 16 is determined.

The engine fuel injection device according to the present invention is not limited to the above-mentioned hydraulically operated fuel injection system. For example, the fuel pressure operated electronically controlled fuel injection system shown in FIG. Of course, it can be applied to the system. FIG. 5 schematically shows an example of such a fuel pressure operated electronically controlled fuel injection system. That is,
The fuel supply to the plurality of injectors 80 is supplied from a common rail 78 through a fuel supply pipe 79. From the fuel tank 73 through the filter 74a, the feed pump 74
The fuel sucked up by b and pressurized to a predetermined suction pressure is sent to a high-pressure fuel pump 75 through a fuel pipe 74. The high-pressure fuel pump 75 is a so-called plunger-type supply fuel supply pump driven by, for example, an engine, pressurizes fuel to a high pressure determined based on an operation state and supplies the fuel to the common rail 78 through a fuel pipe 77a. . The supplied fuel is stored in the common rail 78 in a state where the fuel is pressurized to a predetermined pressure, and supplied to each injector 80 from the common rail 78. Injector 80
Are usually provided in plural numbers according to the type of the engine (the number of cylinders). Under the control of the controller 95, the fuel supplied from the common rail 78 is adapted to the optimal injection timing with the optimal fuel injection amount. Inject into the combustion chamber.
Since the injection pressure of the fuel injected from the injector 80 is substantially equal to the pressure of the fuel stored in the common rail 78, the injection pressure is controlled by controlling the flow control valve 76 to supply the high-pressure fuel to the common rail 78. By controlling the amount, the fuel pressure of the common rail 78 is controlled.

The fuel relieved from the high-pressure fuel pump 75 is returned to the fuel tank 73 through the return pipe 77c. Further, of the fuel supplied to the injector 80 from the fuel supply pipe 79, the fuel not consumed for injection into the combustion chamber is returned to the fuel tank 73 through the return pipe 77b. The controller 95 includes various sensors shown in FIG. 3, that is, a crank angle sensor for detecting the engine speed Ne, an accelerator opening sensor for detecting the accelerator operation amount Acc, and a coolant temperature detection. Signals from various sensors for detecting the operating state of the engine, such as a water temperature sensor of the above and an intake pipe pressure sensor for detecting the intake pipe pressure, are input. Controller 9
The control unit 5 controls the fuel injection characteristics of the injector 80, that is, the fuel injection timing and the injection amount, based on these signals, so that the engine output becomes the optimum output according to the operating state. The common rail 78 is provided with a pressure sensor 78a, and a detection signal of the fuel pressure in the common rail 78 detected by the pressure sensor 78a is sent to the controller 95. Even if the fuel in the common rail 78 is consumed by the fuel being injected from the injector 80, the controller 95 controls the discharge pressure of the high-pressure fuel pump 75 so that the fuel pressure in the common rail 78 becomes constant.

FIG. 1 is a conceptual diagram of control of an injector and a high-pressure oil pump in a fuel injection device for an engine according to the present invention. Here, a case will be described in which the fuel injection device for an engine according to the present invention is applied to the hydraulically operated electronically controlled fuel injection system shown in FIG. 3 including the injector 11 shown in FIG. The target injection amount calculation means 40 calculates the engine rotation speed Ne obtained from the signal detected by the crank angle sensor 21 and the accelerator depression amount Ac detected by the accelerator depression amount sensor 22.
Based on the above, the basic injection amount obtained by referring to data such as a map is corrected according to the water temperature, the intake pressure and the like to calculate the target injection amount Qd. The pulse width calculation means 41 converts data such as a map based on the target injection amount Qd calculated by the target injection amount calculation means 40 and the actual rail pressure Pr detected by the pressure sensor 24 disposed in the high-pressure oil manifold 15. By reference, the target pulse width P that can realize the injection of the fuel of the final target injection amount Qd from the injector 11
Calculate w. The target pulse width Pw calculated by the pulse width calculation means 41 is normally output to the solenoid valve driving means 43 through a switching circuit (switch) 42a for selecting the target pulse width Pw. The solenoid valve driving means 43 outputs a drive pulse current having a target pulse width Pw to the solenoid valve 17 provided in the injector 11 at an appropriate energizing time, and
7 during an energizing period corresponding to the target pulse width Pw,
Injector 1 for realizing fuel injection of target injection amount Qd
Inject fuel from 1.

The target injection pressure calculation means 44 converts data such as a map based on the engine rotation speed Ne obtained from the signal detected by the crank angle sensor 21 and the target injection quantity Qd calculated by the target injection quantity calculation means 40. The basic injection pressure (basic rail pressure) is determined by reference, and the basic injection pressure determined in this way is corrected by feedback control of the actual rail pressure Pr detected by the pressure sensor 24 disposed in the high-pressure oil manifold 15. Finally, the target injection pressure Prd is calculated. The duty ratio calculation unit 45 calculates a target duty ratio Dpr that can realize the target injection pressure Prd calculated by the target injection pressure calculation unit 44 by referring to data such as a map. Target duty ratio Dpr
Is normally output to the flow rate control valve driving means 46 through a switching circuit (switching device) 42b for selecting the target duty ratio Dpr. The flow control valve driving means 46 outputs a control current having a duty ratio equal to the target duty ratio Dpr to the flow control valve 16. The opening of the flow control valve 16 becomes an opening corresponding to the target duty ratio Dpr,
The amount of oil discharged from the high-pressure oil pump 14 to the high-pressure oil manifold 15 is controlled so that the fuel injection pressure, that is, the oil rail pressure Pr in the high-pressure oil manifold 15 is controlled to the target injection pressure Prd. .

The overrun judging means 47 judges whether or not the engine is in an overrun state by monitoring the engine rotational speed Ne obtained based on the signal detected by the crank angle sensor 21. When an overrun condition is detected in the engine, the pulse width calculating means 4
A switching circuit (switching device) 42a disposed between the electromagnetic valve driving means 43 and the electromagnetic valve driving means 43;
A control signal is output to a switching circuit (switch) 42b disposed between the control circuit 5 and the flow control valve driving means 46.
The switching circuits 42a and 42b are switched. The setting means 48 in which 0 is substituted for the pulse width Pw is output to the solenoid valve driving means 43, and the flow rate control valve driving means 4
Since the setting means 49 in which 0 is substituted for the duty ratio Dpr is output to 6, both the pulse width Pw and the duty ratio are forcibly set to 0.

At this time, since the pulse width Pw of the driving pulse current to the solenoid valve 17 provided in the injector 11 is 0, the solenoid valve 17 is not driven at all, and the supply of the working oil to the pressure chamber in the injector 11 is not performed. No, booster piston 5
9 (see FIG. 4) is not affected by the pressure action of the working oil. At the same time, the target duty ratio Dpr of the control current to the flow control valve 16 provided in the high-pressure oil pump 14 also becomes 0, so that the supply of high-pressure oil to the high-pressure oil manifold 15 through the flow control valve 16 is eliminated. Therefore, even if the solenoid energizing circuit of the solenoid valve 17 fails and current continues to flow, the injector 11
, The fuel injection is reliably stopped.

The fuel injection device for an engine according to the present invention shown in the control block diagram of FIG. 1 is also applicable to a fuel pressure operated electronically controlled fuel injection system (see FIG. 5) having an injector 80 shown in FIG. Applicable. When the present invention is applied to a fuel pressure operated electronically controlled fuel injection system, the solenoid valve driving unit 43 controls the solenoid valve 96 provided in the injector 80, and the flow control valve driving unit 46 controls the flow control valve 76. Thus, the supply amount of the high-pressure fuel sent to the common rail 78 is adjusted, and the common rail pressure in the common rail 78 is controlled.

FIG. 2 is a diagram showing a flowchart for determining whether or not the engine is in an overrun state in the fuel injection device for an engine according to the present invention. This flowchart includes the following steps (S1 to S7). (1) The engine speed Ne is read (S1).
That is, the engine rotation speed Ne obtained based on the signal from the crank angle sensor 21 is read into the controller. (2) It is determined whether or not the engine rotation speed Ne read in S1 exceeds a predetermined normal allowable maximum rotation speed Nemax (S2). (3) If it is determined in S2 that the engine rotation speed Ne exceeds the maximum rotation speed Nemax, the count value Cnt (initial value = 0) of the timer that measures the duration of the overrun state is set to 1 Is counted up (S3). (4) The count value Cnt is a predetermined reference value Cnt
It is determined whether Lv has been exceeded (S4). That is, it is determined whether or not the state where the engine rotation speed Ne has exceeded the maximum rotation speed Nemax has continued for a certain period corresponding to the reference value CntLv.

(5) In the determination of S4, the count value C
When nt exceeds a predetermined reference value CntLv,
The engine is determined to be in the overrun state, and 1 is substituted into the overrun flag FlagOR.
(S5). (6) If it is determined in S2 that the engine rotation speed Ne does not exceed the maximum rotation speed Nemax,
The count value Cnt of the timer is cleared to 0 (S6).
Therefore, the engine rotation speed Ne becomes the maximum rotation speed Ne.
Even if the count value Cnt continues to be counted up after exceeding the maximum value, once the engine rotation speed Ne drops below the maximum rotation speed Nemax before reaching the reference value CntLv, the count value Cnt of the timer is cleared to 0. You. (7) After the count value Cnt of the timer is cleared to 0 and when the count value Cnt does not exceed the predetermined reference value CntLv in the determination of S4,
It is determined that the engine is not in the overrun state, and 0 is substituted for the overrun flag FlagOR (S7).

In the above embodiment, when the target duty ratio of the flow control valve 16 provided in the high-pressure oil pump is set to 0, the supply amount of the high-pressure oil supplied to the high-pressure oil manifold 15 through the flow control valve 16 Is set to 0, but the flow control valve 16 in which such a duty ratio is set is
It is a normally closed control valve. The flow control valve 16 may be a normally open type. In this case, the duty ratio is set to 100% in order to reduce the supply amount of the high-pressure oil to zero. In addition, since the flow control valve 16 leaks an amount other than the amount of high-pressure oil supplied to the high-pressure oil manifold 15 to the oil reservoir, the duty ratio may be controlled so as to determine the amount of leakage. Furthermore, the above embodiment is an example of a hydraulically operated electronically controlled fuel injection system. However, even in a fuel pressure type electronically controlled fuel injection system using a working fluid as fuel, high pressure fuel from a high pressure fuel pump is injected by an injector. Control of the flow control valve to be supplied to the injector and the solenoid valve of the injector to stop supplying high-pressure fuel to the injector when the engine is overrun, and to stop the operation of the solenoid valve of the injector Obviously, it may be done.

[0043]

Since the fuel injection device for an engine according to the present invention is configured as described above, even if the controller issues a command to cut off the energization of the solenoid valve, the current from the battery is supplied to the solenoid. Even when the flow continues, the control of the solenoid valve becomes impossible and the engine overruns, the control to reduce the fuel injection pressure to substantially zero and reduce the fuel injection pressure As a result, the rotation speed can be reduced to prevent overrun.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an outline of control of a solenoid valve and a flow control valve in a fuel injection device for an engine according to the present invention.

FIG. 2 is a flowchart for determining an overrun state of the engine in the fuel injection device for an engine according to the present invention.

FIG. 3 is a diagram showing an example of a hydraulically operated electronically controlled fuel injection system.

FIG. 4 is a cross-sectional view of an example of an injector used in a hydraulically operated electronically controlled fuel injection system.

FIG. 5 is a diagram showing an example of a fuel pressure operated electronically controlled fuel injection system.

FIG. 6 is a cross-sectional view of an example of an injector used in a fuel pressure operated electronically controlled fuel injection system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 11 Injector 14 High pressure oil pump 15 High pressure oil manifold 16 Flow control valve 17 Solenoid valve 20 Controller 21 Crank angle sensor 43 Electromagnetic valve drive means 46 Flow control valve drive means 47 Overrun determination means 48 Setting means 49 Setting means 75 High pressure fuel Pump 76 Flow control valve 80 Injector 95 Controller 96 Solenoid valve Ne Engine speed Ac Accelerator depression amount Cnt Timer count value Dpr Target duty ratio

Claims (7)

[Claims] An injector for injecting fuel into a combustion chamber of an engine at a fuel injection pressure corresponding to a pressure of the working fluid supplied from the working fluid supply source, the injector supplying a high-pressure working fluid, and the injector. Working fluid pressure changing means for changing the pressure of the working fluid supplied to the engine, fuel injection amount changing means for changing a fuel injection amount injected from the injector, detecting means for detecting an operating state of the engine, and the engine A controller for controlling the working fluid pressure changing means and the fuel injection amount changing means for injecting fuel with the fuel injection pressure and the fuel injection amount obtained according to the operating state of the controller; Is determined that the engine is in the overrun operation state based on the operation state of the engine detected by the detection means. Control the fuel injection amount changing means so that the fuel injection amount becomes substantially zero, and control the working fluid pressure changing means so that the fuel injection pressure decreases. Engine fuel injection device. 2. The working fluid pressure control means is a flow control valve for controlling a flow rate of the working fluid supplied from the working fluid supply source to the injector, and the fuel injection pressure is an opening degree of the flow control valve. 2. The fuel injection device for an engine according to claim 1, wherein the fuel injection device is controlled by: 3. The flow control valve is a solenoid valve operated by a control current output by the controller.
3. The fuel injection device for an engine according to claim 2, wherein an opening degree of the flow control valve is determined by a duty ratio of the control current. 4. The fuel injection amount changing means is a solenoid valve provided in a path of the working fluid and opening and closing the path by a drive current output by the controller. The fuel injection device for an engine according to any one of claims 1 to 3, which is controlled by: 5. The system according to claim 1, wherein said working fluid is engine oil pressurized by a high-pressure oil pump, and said fuel injection pressure is a fuel pressure increased by a pressure action of said engine oil. The fuel injection device for an engine according to any one of the preceding claims. 6. The fuel pump according to claim 1, wherein the working fluid is a fuel pressurized by a high-pressure fuel pump, and the fuel injection pressure is a fuel pressure pressurized by the high-pressure fuel pump. 2. The fuel injection device for an engine according to claim 1. 7. The operating state of the engine detected by the detecting means includes a rotational speed of the engine,
7. The engine according to claim 1, wherein the engine is determined to be in the overrun operation state when the rotation speed of the engine continuously exceeds a predetermined maximum rotation speed for a predetermined time. A fuel injection device for an engine according to any one of the preceding claims.