JPH11229938A - Fuel injector for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injector capable of preventing noise due to operation sound of a solenoid valve by reducing a current value of driving current fed to the solenoid of the injector when an engine load is low, for an engine. SOLUTION: When an engine load is low, a controller reduces a current value of pulse type driving current I fed to a solenoid of a solenoid value in an injector from a high current value Ph in a high load operation time to a low current value PI. As a response speed of the solenoid valve is lowered, a valve element of the solenoid valve is operated against a return spring, so that an impact in a collision against a valve main body is reduced. Therefore, a ratio of the solenoid valve operation sound in engine noise, which is lowered in a low load operation condition, is not increased, so that the solenoid operation sound causes no acoustic disturbance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection valve formed in a nozzle by driving a solenoid valve provided in an injector to introduce a working fluid to the injector, and raising and lowering a needle valve based on the pressure action of the working fluid. The present invention relates to a fuel injection device for an engine that injects fuel from a hole.

[0002]

2. Description of the Related Art FIG. 12 shows a known fuel injection system for an engine in which an injector 1 is incorporated. In the fuel injection system, an injector 1 is provided for each cylinder of the engine. The injector 1 is provided with a common rail 51 which is a common passage for fuel supply. The fuel in the fuel tank 52 is supplied to the common rail 51 through the fuel filter 54 by driving the fuel pump 53. The common rail 51 communicates with each injector 1 and has a fuel recovery passage 55.
Through the fuel tank 52. That is, the injector 1 is disposed on the common rail 51 in which fuel at a predetermined pressure is constantly supplied to the fuel supply port 11 and the fuel discharge port 12 thereof.

The injector 1 is configured to supply a high-pressure working fluid, that is, working oil, to a pressure chamber 8 to increase the fuel pressure. The injectors 1 are connected to high-pressure oil manifolds 56, respectively. Oil from an oil reservoir 57 is supplied to the high-pressure oil manifold 56 through an oil supply path 61 by operation of an oil pump 58, and an oil cooler 59 and an oil filter 60 are provided in the oil supply path 61. The oil supply passage 61 branches into a lubrication passage 67 leading to the oil gallery 62 and a working oil passage 66 supplied to the pressure chamber 8 of the injector 1. A high-pressure oil pump 63 is provided in the working oil system passage 66, and the supply of oil from the high-pressure oil pump 63 to the high-pressure oil manifold 56 is controlled via a flow control valve 64. The controller 50 is configured to control the flow control valve 64 and control the solenoid valve 10 of the injector 1. The controller 50 includes, as the operation state of the engine, the engine speed detected by the rotation sensor 68,
The accelerator opening detected by the load sensor 69 and the crank angle detected by the position sensor 70 are input. The controller 50 includes a high-pressure oil manifold 56.
The operating oil pressure of the high-pressure oil manifold 56 detected by the pressure sensor 71 installed in the controller is input.

A conventional hydraulically operated electronically controlled fuel injection device for an engine is disclosed, for example, in Japanese Patent Publication No. Hei 6-511527. This fuel injection device variably controls the fuel flow rate characteristics of a hydraulically operated injector during a fuel injection stroke of an engine and enables quick start-up. The injector used in such a fuel injection device has, for example, a structure as shown in FIG. 13 and is also used as an example of the injector 1 shown in FIG.

[0005] As shown in FIG.
The nozzle body 2 (constituting the nozzle) having the hollow hole 46 and the injection hole 13 formed therein, the fuel supply body (plunger barrel) forming the pressure increasing chamber 7, and the space between the nozzle body 2 and the fuel supply body 5 Spacer body 81 and hollow hole 29 located at
, An injector body 4 having a pressure chamber 8 to which high-pressure hydraulic oil is supplied, and a solenoid body 3 having a drain groove 39 and a drain passage 38 as leak passages and having the solenoid valve 10 disposed therein. Each body is provided. The case 6 surrounds the nozzle main body 2, the spacer main body 81, the hollow spacer main body 21, and the fuel supply main body 5, and has a fuel chamber 2 between the case 6 and each of these main bodies.
The body is fixed to the injector body 4 in order to form a zero and integrate these bodies. The case 6 has one end locked to the contact surface 14 of the step portion of the nozzle body 2 and is sealed.
The other end is sealed by a fitting surface 80 screwed into the injector body 4. Fuel supply port 11 formed in case 6
The fuel outlet 12 is opened to the common rail 51, and fuel is constantly supplied from the common rail 51 to the fuel chamber 20.

[0006] The injector 1 includes a pressure increasing chamber 7 formed in a fuel supply main body 5 for increasing the pressure of the fuel supplied from the fuel chamber 20, and a spacer for supplying fuel from the pressure increasing chamber 7 to the injection hole 13. A main body 81, a hollow spacer main body 21, a fuel passage 22 formed in the nozzle main body 2, a needle valve 23 slidably held in a hollow hole 46 of the nozzle main body 2 to open the injection hole 13 by fuel pressure, A pressure-intensifying piston 9 for increasing the pressure of the fuel in the chamber 7, a pressure chamber 8 for supplying a high-pressure operating oil for applying a high pressure to an end of the pressure-increasing piston 9, and an electromagnetic valve for controlling the supply of the high-pressure operating oil to the pressure chamber 8. It has ten.

The return spring 18 is disposed in a hollow hole 29 formed in the hollow spacer main body 21, and
A spring force is applied to the needle valve 23 in a direction to close the needle valve 3. One end of the return spring 18 contacts the upper end of the needle valve 23,
The other end is in contact with the spacer body 81. The hollow spring chamber 30 formed by the large-diameter hollow hole 26 formed in the injector body 4 is formed between the end face of the large-diameter section 25 of the pressure-intensifying piston 9 and the end face of the fuel supply body 5. I have. In the spring chamber 30, a pressure-increasing piston 9 is provided.
A return spring 17 that biases to the side is disposed. A hollow hole 85 formed in the injector body 4 has
A return spring 19 for urging the valve body 16 is disposed on the side where the operating oil is cut. The spring chamber 30 in which the pressure-intensifying piston 9 is disposed is provided with a discharge passage 83 formed in the fuel supply main body 5 and a check valve 8 disposed in the discharge passage 83.
4 communicates with the fuel chamber 20. Normally, the leaked fuel enters the spring chamber 30 and is in the same state as the fuel pressure in the fuel chamber 20.
And a void is formed.

The pressure-intensifying piston 9 has a small-diameter portion 24 as a plunger that forms a part of the pressure-increasing chamber 7 at the lower end surface, a part of the pressure chamber 8 that is formed at the upper end surface, and a large-diameter hollow hole of the injector body 4. Large-diameter portion 25 reciprocating inside 26 and large-diameter portion 2
5 comprises a guide ring portion 41 which hangs down from the entire periphery of the outer periphery of the large diameter hollow hole 26 to form a sliding surface 49 which slides. The guide ring portion 41 is provided with the pressure increasing piston 9.
Has the function of stabilizing the vertical movement of The small-diameter portion 24 of the pressure-intensifying piston 9 is formed in the small-diameter hollow hole 4 formed in the fuel supply main body 5.
2 reciprocate, the large diameter portion 25 reciprocates through a large diameter hollow hole 26 formed in the injector body 4. A sealing member 44 made of a rubber O-ring is disposed in the large-diameter hollow hole 26 formed in the injector body 4, and the pressure-increasing piston 9
The gap between the pressure chamber 8 and the large-diameter hollow hole 26 is sealed by a seal member 44, and the spring chamber 30 and the pressure chamber 8 are shut off so that the high-pressure working oil in the pressure chamber 8 does not leak to the spring chamber 30. In order to return the pressure-intensifying piston 9, a return spring 17 is disposed between the fuel supply main body 5 and the pressure-increasing piston 9 in a compressed state.

The small-diameter hollow hole 4 formed in the fuel supply main body 5
A pressure-increasing chamber 7 is formed at the end of 2. The fuel is supplied to the pressure intensifying chamber 7 from the fuel chamber 20 through a fuel passage 37 formed in the hollow spacer main body 21 and a fuel passage 35 formed in the spacer main body 81. A check valve 36 is incorporated in the fuel passage 35 to prevent the high-pressure fuel in the pressure-intensifying chamber 7 from flowing back into the fuel chamber 20. The pressurized fuel in the pressurizing chamber 7 is supplied to the spacer body 8.
1, the fuel is supplied to the injection hole 13 through a fuel passage 22 formed in the hollow spacer body 21 and the nozzle body 2. A fuel passage is formed between the nozzle body 2 and the needle valve 23,
The needle valve 23 is lifted by applying high-pressure fuel pressure to the tapered surface 45 formed on the needle valve 23. Needle valve 23
Is slidably held in the hollow hole 46 of the nozzle body 2 and lifted by the fuel pressure to open the injection hole 13.

The pressure-increasing piston 9 is formed on a flat surface 74 provided on an outer peripheral portion of a top surface 75 of the large-diameter portion 25 facing the pressure chamber 8. The wall surface of the injector body 4 forming the pressure chamber 8 is formed as a flat surface 47 parallel to the top surface 75 of the pressure increasing piston 9. Therefore, in the pressure chamber 8, a narrow gap 40 is formed between the flat surface 74 of the pressure-intensifying piston 9 and the flat surface 47 of the injector body 4. Further, in the pressure-intensifying piston 9, the central protruding portion of the top surface 75 is in contact with the flat surface 47 of the injector body 4 by the spring force of the return spring 17.

In the injector 1, a spring chamber 30 accommodating the return spring 17 is formed in a large-diameter hollow hole 26 formed in the injector body 4 in which the large-diameter portion 25 of the pressure-intensifying piston 9 and the guide ring portion 41 slide. Have been. Leakage of fuel from the spring chamber 30 to the pressure chamber 8 is prevented by the seal member 44. In the spring chamber 30 in which the return spring 17 for the pressure-intensifying piston 9 is disposed, the sliding around the plunger of the small-diameter portion 24, that is, between the small-diameter hollow hole 42 of the fuel supply main body 5 and the outer peripheral surface 28 of the small-diameter portion 24. Fuel leaks from the booster chamber 7 through a very small gap in the surface. In addition, the injector body 4
Very small gap 4 between the contact surfaces of the fuel supply main body 5 and
Fuel also leaks from the fuel chamber 20 through 8.
Normally, a space corresponding to the stroke of the pressure-intensifying piston 9 is formed in the spring chamber 30, and fuel enters. Then, when the fuel enters to such an extent that the empty space in the spring chamber 30 becomes equal to or less than the stroke of the pressure boosting piston 9, the fuel existing in the spring chamber 30 along with the reciprocating motion of the pressure boosting piston 9 causes the fuel chamber to pass through the discharge path 83. Discharged to 20. The backflow of the discharged fuel is stopped by the action of the check valve 84.

In the injector 1, the opening and closing operation of the injection hole 13 by the needle valve 23 is performed by controlling the solenoid valve 10. When the solenoid 15 of the solenoid valve 10 is excited by a command from the controller 50, the armature 32 is opened. Is sucked, and the valve body 16 fixed to the armature 32 lifts against the spring force of the return spring 19. Valve body 1
When the valve 6 is lifted, the passage 33 formed between the tapered surface 86 of the valve body 16 and the valve seat 87 of the injector body 4 is opened, and high-pressure operating oil is supplied from the high-pressure oil manifold 56 to the injector body 4. The pressure is supplied to the pressure chamber 8 through the passage 31 and the passage 34. When the high-pressure hydraulic oil is supplied to the pressure chamber 8, the high-pressure hydraulic oil is supplied to the gap 40 formed between the flat surface 74 of the large-diameter portion 25 of the pressure-intensifying piston 9 and the wall surface (flat surface) 47 of the injector body 4. The working oil is supplied, and the working pressure is urged to the pressure increasing piston 9.
On the other hand, the fuel of the common rail 51 is supplied to the fuel chamber 20 from the supply port 11 formed in the case 6, and then the fuel passage 37 formed in the hollow spacer body 21 and the fuel formed in the spacer body 81 from the fuel chamber 20. The pressure is supplied to the pressure increasing chamber 7 through the passage 35.

When the pressure-increasing piston 9 is lowered by the pressure of the working oil in the pressure chamber 8, the fuel passage 35 is closed by a check valve 36, and the pressure in the pressure-increasing chamber 7 is increased. Booster chamber 7
When the fuel pressure is increased, the fuel pressure is increased by the return spring 1
The needle valve 23 is lifted against the spring force of No. 8. When the urging force on the valve body 16 by the solenoid 15 is released,
The valve body 16 is lowered by the spring force of the return spring 19,
The drain groove 39 provided in the solenoid valve 10 is opened, and the high-pressure operating oil in the pressure chamber 8 is discharged through the drain groove 39 and the drain passage 38. When the high-pressure hydraulic oil in the pressure chamber 8 is discharged, the pressure-intensifying piston 9 returns to the original pressure by the spring force of the return spring 17, and the pressure in the pressure-increasing chamber 7 becomes equal to that of the fuel chamber 20, and is applied to the needle valve 23. The fuel pressure decreases, and the tapered surface 45 of the needle valve 23 is seated on the valve seat of the nozzle body 2 by the spring force of the return spring 18, and the injection hole 13 is closed.

In such an injector 1, 1
The control amount that determines the amount of fuel injected into the combustion chamber in each injection is the injection pressure and the energization time to the solenoid valve that determines the fuel injection period. The operating oil pressure can be controlled in multiple stages between an operation state at low speed and low load such as idle operation and an operation state at high speed and high load. In order to reliably close the solenoid valve 10 even when the working fluid pressure is high,
The return spring 19 has a large spring force. The solenoid valve 10 against such a large spring force
Needs to be opened in a short time, the current value of the drive current supplied to the solenoid 15 as the electromagnetic actuator of the solenoid valve 10 is set to a large value. Since the drive current is set as described above, the impact when the shoulder 76 of the valve body 16 collides with the end 77 of the solenoid body 3 when the solenoid valve 10 is opened is large, and the engine noise is relatively low. In an operating state at a low speed and a low load, the operation sound of the solenoid valve 10 occupies a large part of the engine noise and becomes annoying.

[0015]

Therefore, the driving current supplied to the solenoid valve of the injector is not always kept constant, but is controlled by controlling the driving current in accordance with the operating state of the engine. Therefore, there is a problem to be solved in reducing the collision sound of the electromagnetic valve which causes annoying noise.

[0016]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems, and an engine fuel injection device capable of reducing collision noise of an electromagnetic valve which causes annoying noise according to the operating state of the engine. It is to provide. Also,
At low speeds and low loads, even if the collision noise of the solenoid valve is reduced, the lift speed of the needle valve is reduced due to the setting of the working fluid pressure, and the injection rate is reduced and the injection rate is reduced. An object of the present invention is to provide a fuel injection device for an engine that can prevent a situation in which a delay in starting occurs, and as a result, a target injection amount and a target injection timing cannot be achieved.

According to the present invention, there is provided a nozzle having an injection hole for injecting fuel, and a needle valve for opening and closing the injection hole by moving up and down in the nozzle in response to the pressure action of the working fluid introduced into the main body. An injector provided with an electromagnetic valve that is opened and closed by a solenoid to which a drive current is supplied to control the pressure action of the working fluid, detection means for detecting an operation state including an engine load, and a fuel injection amount. A controller for controlling an energization period and an energization start time of the drive current supplied to the solenoid according to an operation state of the engine detected by the detection means for controlling a fuel injection timing; Changes the current value of the drive current supplied to the solenoid according to the operating state of the engine. To.

Since the present invention is configured as described above, the controller changes the current value of the drive current according to the operating state of the engine detected by the detecting means. The operating speed of the valve is changed, and the operating noise of the solenoid valve can be suppressed in accordance with the operating state of the engine. In particular, if the current value of the drive current is small at least when the load on the engine is small compared to when the load is large, the response speed of the solenoid valve becomes
The response speed is slower than when such control is not performed, the impact of the solenoid valve body colliding with the valve body is suppressed, and the operating noise of the solenoid valve accounts for the proportion of engine noise. The increase is suppressed.

Further, in the fuel injection device for an engine according to the present invention, the controller performs a control to advance an energization start timing of the driving current when the current value of the driving current is small as compared with when the current value is large. Do.

Further, in the fuel injection device for an engine according to the present invention, the controller makes the energizing period of the drive current longer when the current value of the drive current is small as compared with when the current value is large. Further, the controller increases the pressure of the working fluid when the current value of the drive current is small as compared with when the current value is large.

If the current value of the drive current to the solenoid valve is reduced in response to the decrease in the operating load of the engine, the response speed of the solenoid valve is reduced, so that the impact sound of the solenoid valve is reduced. However, the flow rate of the working fluid into the injector decreases, and as a result, the pressure action of the working fluid is delayed and the needle valve opens, that is, the fuel injection timing is delayed and the fuel injection end timing is reduced. If not changed, the fuel injection amount may decrease, and the switching speed may suddenly decrease when switching the current value of the drive current. Similarly, when the drive current to the solenoid valve is increased again, there is a problem that the fuel injection amount increases and the engine speed rapidly increases. As described above, when the current value of the drive current is changed, the fuel injection amount changes abruptly, the engine speed rapidly increases and decreases, and the engine speed becomes unstable. Therefore, in response to the change of the drive current value, the energization period of the drive current and the pressure of the working fluid are changed so that the fuel injection amount does not greatly change from before the change of the drive current, and the engine speed is changed. It is preferable to prevent a sudden change in the number.

Further, in the fuel injection device for an engine according to the present invention, the injector is slidable in a pressure increasing chamber formed in a main body to which fuel is supplied from a common rail, and in a hollow hole formed in the main body. A large diameter portion that is fitted and forms a part of the wall surface of the pressure chamber, and a small diameter portion that is slidably fitted in the hollow hole and forms a part of the wall surface of the pressure boosting chamber; A booster piston driven by the working fluid supplied to the pressure chamber formed in the main body to boost the fuel in the booster chamber, a return spring for returning the booster piston, and a fuel chamber are formed. A fuel supply port and a fuel discharge port which are arranged on the outer periphery of the main body and open to the common rail, and the needle valve is provided with a fuel supply port based on the pressure of fuel from the pressure intensifying chamber. By lifting the nozzle to open and close the injection hole, said solenoid valve controls the supply to the pressure chamber of the working fluid.

[0023]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the embodiment of the present invention, the specific structure of the fuel injection system of the engine and the injector used in the system can employ the fuel injection system and the injector shown in FIGS. 12 and 13, respectively. In the following description,
Since the same reference numerals are used for the corresponding components and parts, the detailed description of these components and parts will not be repeated.

Hereinafter, a description will be given of a case where the procedure of the fuel injection according to the present invention performed by the controller 50 is applied to a 4-cycle, 4-cylinder diesel engine similar to that shown in FIG. The ignition order of the cylinders arranged in a line sequentially from the first cylinder to the fourth cylinder with respect to the crankshaft is the order of the first cylinder, the third cylinder, the fourth cylinder, and the second cylinder. The controller 50 executes fuel injection according to the routines shown in the following flowcharts based on the cylinder discrimination signal and the top dead center signal of each cylinder. FIG. 1 is a diagram showing a main routine of the engine fuel injection device of the present invention, and FIGS.
FIG. 5 is a flowchart showing the control contents of each routine in FIG.

With the start of the execution of the cylinder control routine, the clock in the controller 12 starts clocking (T _n ), and the following fuel injections are repeatedly performed for each cylinder in the injection order. (1) The pulse width of the drive current supplied to the solenoid 15 of the injector 1 is determined based on the setting of the target injection amount to be injected by one fuel injection from the injector 1 for each cylinder (S1). The setting of the target injection amount is performed according to a preset map or the like based on the operating state of the engine detected by each sensor. (2) The timing to start energizing the drive current having the pulse width determined in S1 is determined (S2). (3) The counting is performed in accordance with the rotation of the crank angle, and the energization of the drive current is started when the energization start time comes (S3). (4) In accordance with the operating state of the engine, a correction flag necessary for determining whether or not to obtain the correction amount of the drive current pulse width in S1 and the correction amount of the drive current start time in S2 (S4).

FIG. 2 is a flowchart showing the details of the routine (S1 in FIG. 1) for determining the pulse width of the drive current to be supplied to the solenoid valve based on the setting of the target injection amount. (1) The engine speed Ne detected by each sensor, the accelerator pedal depression amount Ac, the rail pressure Pr of the high-pressure oil manifold 56, and the temperature To of the working oil are periodically read into the controller (S11). (2) On the basis of the engine speed Ne and the accelerator pedal depression amount Ac read in S11, for example, a predetermined map as shown in FIG. 9 (the engine rotation speed Ne and the target using the accelerator depression amount Ac as parameters). A map showing the relationship with the injection amount Qb)
Is calculated (S12). (3) The basic drive current pulse width Pwb is calculated in accordance with the target injection amount Qb calculated in S12 and the rail pressure Pr read in S11 (S13). The basic drive current pulse width Pwb is calculated based on a predetermined map as shown in FIG. 10 (a graph showing a relationship between the basic drive current pulse width Pwb using the rail pressure Pr as a parameter and the target injection amount Qb). Is done. A map as shown in FIG. 10 is prepared for each of several oil temperatures To, and the basic drive current pulse width Pwb is obtained from the corresponding map based on the detected oil temperature To. (4) It is determined whether the correction flag Fc is 1 (S14). That is, it is determined whether or not the current value of the drive current is set to be small. Details of the correction flag Fc will be described later. (5) If the correction flag Fc is determined to be 1 in S14, this corresponds to setting the current value of the drive current to be small, and the target injection amount Qb and the rail pressure P
The drive current pulse width correction amount ΔPw is calculated based on r (S15). The drive current pulse width correction amount ΔPw is stored in advance in a map (rail pressure Pr) as shown in FIG.
Is a parameter indicating the relationship between the target injection amount Qb and the drive current pulse width correction amount ΔPw). In general, the lower the rail pressure Pr, the larger the drive current pulse width correction amount ΔPw is, and the more the injection amount is secured. (6) If it is determined in S14 that the correction flag Fc is not 1, the drive current pulse width correction amount ΔPw is set to 0 (S16). (7) The final drive current pulse width Pwf is obtained by adding the drive current pulse width correction amount ΔPw to the target drive current pulse width Pwb.
Is calculated (S7).

FIG. 3 is a flowchart showing the details of the routine (S2 in FIG. 1) for determining the start time of the drive current having the final drive current pulse width Pwf obtained as described above. (1) Similar to S11, the engine speed Ne, the accelerator pedal depression amount Ac, the rail pressure Pr, and the oil temperature To
Is read into the controller (S21). (2) Based on the engine speed Ne and the target injection amount Qb read in S21, the target injection start timing Tib is calculated by a predetermined map or the like (S22). (3) The target injection start timing Tib calculated in S22 and the rail pressure Pr and oil temperature T read in S21.
Based on o, the basic energization start time Tcb of the drive current is calculated (S23). (4) It is determined whether or not the correction flag Fc is 1, that is, whether or not the current value of the drive current is set small (S24). (5) If it is determined in S24 that the correction flag Fc is 1, that is, if the current value of the drive current is set to a small value Pl, the rail pressure Pr and the oil temperature T
On the basis of o, an energization start timing correction amount ΔTc (a negative value when the energization start timing is determined by the crank angle calculated from the cylinder discrimination signal REF) is calculated (S2).
5). (6) If it is determined in S24 that the correction flag Fc is not 1, the power supply start timing correction amount ΔTc is set to 0 (S26). (7) The power supply start timing correction amount Δ is added to the basic power supply start timing Tcb.
By adding Tc, the final energization start timing Tcf is calculated (S27).

FIG. 4 is a flowchart showing the details of the routine for counting the crank angle (S3 in FIG. 1). (1) It is determined whether or not the cylinder determination sensor detects a specific crank angle (for example, top dead center) of a cylinder serving as a reference of a multi-cylinder engine and outputs a cylinder determination signal (REF) (S31). (2) In S31, when the cylinder discrimination sensor outputs the cylinder discrimination signal, the count value Cnt of the crank angle becomes 0.
Is set (S32). As the count value, for example, a count value of 1 corresponds to a crank angle of 1 °. (3) If the cylinder discrimination sensor does not detect the top dead center of the reference cylinder in S31, the count value Cnt of the crank angle is updated by incrementing by 1 (S33). (4) It is determined whether or not the count value Cnt of the crank angle is the final energization start time Tcf (S34). (5) If it is determined in step S34 that the count value Cnt of the crank angle is the final energization start timing Tcf, energization of the injector 1 with the drive current having the pulse width Pwf obtained in S17 is started. (S3
5). (6) If it is determined in step S34 that the count value Cnt of the crank angle is not the final energization start time Tcf, the process returns to the main routine (S36).

FIG. 5 shows a correction flag setting routine (FIG. 1).
4 is a flowchart showing details of S4). (1) The engine speed Ne, the accelerator pedal depression amount Ac, the rail pressure Pr, and the oil temperature To detected by each sensor are periodically read into the controller (S4).
1). (2) Based on the latest data read periodically, the engine speed Ne is less than a predetermined low threshold value Nei (for example, about 800 rpm corresponding to an idle speed),
And the accelerator pedal depression amount Ac is equal to a predetermined depression amount Ac.
i (for example, 3% of the total depression amount corresponding to idling operation)
Is determined (S42). (3) If the determination in S42 is YES, a small value Pl is set to the peak current value Pci of the drive current, and the correction flag Fc is set to 1 (S43). (4) If the determination in S42 is NO, a large value Ph is set to the peak current value Pci of the drive current, and the correction flag Fc is set to 0 (S44).

As described above, when the correction flag Fc is 1, the current value of the drive current is set to a small value, and the target drive current pulse is calculated by adding the drive current pulse width correction amount ΔPw. The solenoid valve 10 of the injector 1 is driven with the final drive current pulse width Pwf larger than the width Pwb. As a result, a rapid decrease in the fuel injection amount is avoided, and a rapid decrease in the engine speed is prevented.

FIG. 7 is a graph showing a change in the drive current I to the solenoid valve 10 and a change in the lift amount L of the needle valve 23 in accordance with the progress of the crank angle. FIG. 8 is a graph showing the drive current to the solenoid valve. I
7 is a graph showing how the engine speed Ne changes when the power supply period and the pressure of the working fluid are corrected and not changed when the current value level is switched. In FIG. 7, Tib, T relating to the start of fuel injection and drive current
For example, cb, Tcf, and the like are set based on a cylinder determination signal (REF) for detecting a reference cylinder.

As shown by the solid line in FIG. 7, when the peak value Pci of the driving current I as the pulse current is set to a large value Ph, the lift L of the needle valve 23 is changed as shown by the solid line. When the needle valve 23 rises relatively steeply and lifts beyond the predetermined threshold value La, fuel injection is started.
When the peak value Pci of the drive current I is set to a small value Pl, the lift L of the needle valve 23 rises relatively slowly as shown by a broken line, and the needle valve 23 reaches a predetermined threshold La.
, Fuel injection is started. Therefore, the fuel injection start timing is delayed, and the fuel injection amount also decreases.
As a result, as shown in the middle graph B of FIG. 8, the engine speed Ne fluctuates greatly when the drive current is switched. When the peak value Pci of the drive current I is set to a small value Pl, the energization start timing of the drive current I is advanced by ΔTc as shown by the dashed line in FIG. 7, and the delay of the fuel injection start timing is prevented. In addition, since the correction is performed so that the energization period represented by the final drive current pulse width Pwf becomes longer, a decrease in the fuel injection amount can be avoided.
At this time, as shown by the graph A in the upper part of FIG. 8, no rapid change occurs in the engine speed Ne.

To prevent a sudden change in the injection amount from occurring, it is one measure to lengthen the period during which the drive current is applied. However, since the fuel injection period with respect to the top dead center of the piston becomes longer, the best combustion is achieved. It becomes difficult to get the status.
Since the fuel injection amount is determined by the fuel injection pressure in addition to the fuel injection period, increasing the fuel injection pressure when the current value of the drive current is reduced is also an effective countermeasure for improving the combustion state. Becomes Figure 6 shows the high pressure manifold 6
9 is a flowchart illustrating a control routine of a third rail pressure Pr. (1) The engine speed Ne, the accelerator pedal depression amount Ac, the rail pressure Pr, and the oil temperature To detected by each sensor are read into the controller 50 (S5).
1). (2) Based on the engine speed Ne, the target injection amount Qb, and the oil temperature To read in S51, the target rail pressure Prt is calculated by a predetermined map or the like (S52). (3) It is determined whether the correction flag Fc is 1 (S53). (4) If the correction flag Fc is 1 in the determination in S53, the rail pressure correction amount ΔPrt (normal, positive value) is calculated based on the engine speed Ne, the target injection amount Qb, and the oil temperature To at that time. (S54). (5) If the correction flag Fc is not 1, there is no need to correct the rail pressure, so the rail pressure correction amount ΔPr
t is set to 0 (S55). (6) The final rail pressure Prt is the target rail pressure Prt
And the rail pressure correction amount ΔPrt is calculated by the following equation (S56). Prf ← Prt + ΔPrt (7) A deviation ΔPr between the final rail pressure Prf and the actual rail pressure Pr is obtained (S57). ΔPf ← Prf−Pr (8) A flow control provided for supplying rail pressure from the high-pressure oil pump 63 to the working oil system passage 66 by a predetermined map or the like based on the deviation ΔPr obtained in S57. A duty ratio Dpr that determines a valve opening period of the valve 64 is obtained (S58). (9) Based on the duty ratio Dpr obtained in S58,
The duty ratio control of the flow control valve 64 is executed (S5).
9).

[0034]

Since the fuel injection device for an engine according to the present invention is configured as described above, the controller controls the drive current supplied to the solenoid of the solenoid valve in accordance with the operating state of the engine detected by the detection means. Is changed, it is possible to prevent a situation in which the operation sound of the solenoid valve becomes noticeable with respect to the operating state of the engine. In particular, at least when the engine load is small, the current value of the drive current supplied to the solenoid of the solenoid valve is controlled to a small value. Can be prevented from being harsh. In addition, in response to the fact that the current value of the drive current supplied to the solenoid of the solenoid valve is set to a small value, the correction of the drive current supply start timing and the correction of the drive current supply period or the working fluid pressure are performed. By doing so, the delay of the injection start timing can be recovered, and a predetermined injection rate can be secured to prevent the engine speed from becoming unstable.

[Brief description of the drawings]

FIG. 1 is a diagram showing a main routine of fuel injection of an engine according to the present invention.

FIG. 2 is a flowchart showing details of a routine for determining a pulse width of a drive current to be supplied to the solenoid valve shown in FIG.

FIG. 3 is a flowchart showing details of a routine for determining a drive current energization start timing shown in FIG. 1;

FIG. 4 is a flowchart showing details of a routine for counting the crank angle shown in FIG. 1;

FIG. 5 is a flowchart showing details of a correction flag setting routine shown in FIG. 1;

FIG. 6 is a flowchart illustrating a control routine of a rail pressure of a high-pressure manifold.

FIG. 7 is a graph showing a change with time in a drive current to a solenoid valve and a lift amount of a needle valve.

FIG. 8 is a graph showing how the fuel injection amount changes when the drive current level is switched and when it is not corrected.

FIG. 9 is a graph showing a relationship between an engine speed and a target injection amount with the accelerator depression amount Ac as a parameter.

FIG. 10 is a graph showing a relationship between a basic drive current pulse width using a rail pressure as a parameter and a target injection amount.

FIG. 11 is a graph showing a relationship between a target injection amount using a rail pressure as a parameter and a drive current pulse width correction amount.

FIG. 12 is a diagram showing an outline of a fuel injection system.

FIG. 13 is a sectional view showing an example of an injector applied to FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 injector 2 nozzle body 3 solenoid body 4 injector body 5 fuel supply body 6 case 7 booster chamber 8 pressure chamber 9 booster piston 10 solenoid valve 11 fuel supply port 12 fuel outlet 13 injection hole 15 solenoid 16 valve body 17 return spring Reference Signs List 20 fuel chamber 23 needle valve 24 small-diameter portion 25 large-diameter portion 26 large-diameter hollow hole 42 small-diameter hollow hole 50 controller 51 common rail 68 rotation sensor 69 accelerator depression amount sensor 70 crank angle sensor 71 pressure sensor Pr rail pressure Pwf final driving current pulse Width Tcf Final energization start timing

Claims (6)

[Claims] A nozzle having an injection hole for injecting fuel, a needle valve for raising and lowering the inside of the nozzle in response to a pressure action of a working fluid introduced into a main body to open and close the injection hole, An injector having an electromagnetic valve that is opened and closed by a solenoid to which a drive current is supplied to control the pressure action of the working fluid, detection means for detecting an operation state including an engine load, and fuel injection amount and fuel injection And a controller for controlling a start time and an energization period of the drive current supplied to the solenoid according to an operation state of the engine detected by the detection means for controlling a timing. A fuel injection device for an engine, comprising changing a current value of the drive current supplied to the solenoid according to an operation state of the engine. 2. The engine fuel injection device according to claim 1, wherein the controller reduces the value of the drive current at least when the load of the engine is small as compared with when the load is large. . 3. The engine fuel according to claim 2, wherein the controller has a function to advance the timing of starting the drive current when the current value of the drive current is small compared to when the current value of the drive current is large. Injection device. 4. The engine according to claim 2, wherein the controller makes the energizing period of the drive current longer when the current value of the drive current is small than when the current value of the drive current is large. Fuel injector. 5. The controller according to claim 2, wherein the controller increases the pressure of the working fluid when the current value of the drive current is small compared to when the current value of the drive current is large. 2. The fuel injection device for an engine according to claim 1. 6. The injector is slidably fitted in a pressure-increasing chamber formed in a main body to which fuel from a common rail is supplied and a hollow hole formed in the main body, and is provided on a wall of the pressure chamber. A large-diameter portion forming a part thereof and a small-diameter portion slidably fitted in the hollow hole and forming a part of a wall surface of the pressure intensifying chamber, for increasing the pressure of the fuel in the pressure intensifying chamber. A pressure booster piston driven by the working fluid supplied to the pressure chamber formed in the main body, a return spring for returning the pressure booster piston, and a pressure chamber disposed on an outer periphery of the main body to form a fuel chamber; A needle formed with a fuel supply port and a fuel discharge port opened to a common rail, wherein the needle valve moves up and down in the nozzle based on the pressure of fuel from the pressure intensifying chamber to open and close the injection hole. , The solenoid valve is front The fuel injection device for an engine according to any one of claims 1 to 5, wherein the supply of the working fluid to the pressure chamber is controlled.