JPH07127545A - Fuel injector - Google Patents

Abstract

(57) [Abstract] [Purpose] To reliably perform pilot injection and main injection to reduce nitrogen oxides emitted from the engine and operating noise. A fuel return passage 3 for connecting a pump chamber 22a of a unit injector 2 and a return port of a fuel distributor.
Main solenoid valves 4 arranged in series in the middle of 6
1 and the sub solenoid valve 42, and closes and opens the main solenoid valve at the start and end of the main injection, and closes and opens the sub solenoid valve at the start and end of the pilot injection. .

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 equipped with a unit injector for a diesel engine, and more particularly to a fuel injection device capable of reliably performing pilot injection and main injection.

[0002]

2. Description of the Related Art A unit injector integrally includes a fuel pressurizing mechanism and an injection nozzle, and is mounted on a cylinder head of each cylinder of an engine. A typical unit injector is a plunger that is reciprocally driven by a rocker arm that is connected to the other end of a push rod whose one end is in contact with the peripheral surface of a cam that is rotationally driven by an engine output shaft and that swings in synchronization with engine rotation. Is equipped with. In addition, the unit injector is equipped with a solenoid valve arranged in the middle of a fuel return passage that connects the pump chamber of the plunger and the return port of the fuel supply device, and the fuel return passage is closed by operating this solenoid valve. so,
The plunger is pushed down by the rocker arm to pressurize the fuel in the pump chamber and send it from the pump chamber to the needle chamber of the unit injector. When the needle chamber pressure (injection pressure) reaches the nozzle opening pressure, the fuel is burned by the engine from the nozzle. It is designed to spray inside the chamber.

It is also known that pilot injection is performed prior to main injection in an attempt to reduce nitrogen oxides (NOx) emitted from the engine and engine operating noise.

[0004]

When performing pilot injection and main injection by a conventional unit injector, the solenoid valve is closed and opened at the start and end of pilot injection, and closed at the start and end of main injection. And it is necessary to perform the opening operation. That is, from the pilot injection start time to the main injection end time,
The solenoid valve must be closed and opened twice each. Therefore, for example, the solenoid of the solenoid valve is excited at the start of pilot injection, demagnetized at the end of pilot injection, re-energized at the start of main injection, and de-energized again at the end of main injection. On the other hand, the opening / closing operation of the valve body with respect to the excitation and demagnetization of the solenoid is delayed, and residual magnetism is generated in the solenoid immediately after the solenoid is demagnetized.

Therefore, according to the conventional device, when the main injection is to be started immediately after the end of the pilot injection, the fuel injection may continue between the pilot injection and the main injection. That is, even if the pilot injection is attempted prior to the main injection, the main injection with a long injection time is performed. In such a case, the engine operation cannot be controlled.

Therefore, an object of the present invention is to provide a fuel injection device which can reliably perform pilot injection and main injection, and can reduce nitrogen oxides emitted from the engine and operating noise.

[0007]

SUMMARY OF THE INVENTION The present invention is a fuel injector having a unit injector including a plunger that reciprocates in synchronization with the rotation of an engine output shaft, and a pump chamber and a fuel supply device defined by the plunger. Of the first valve means while driving the plunger in a pressure increasing direction from the start of pilot injection to the end of main injection. The opening operation and the closing operation, and the opening operation and the closing operation of the second valve means are performed once in a predetermined order to perform the pilot injection and the main injection.

[0008]

The fuel is supplied from the fuel supply device to the pump chamber while the plunger reciprocates in synchronization with the rotation of the engine output shaft. Then, from the start of pilot injection to the end of main injection, the plunger moves in the pressure increasing direction,
The opening operation and the closing operation of the first valve means and the opening operation and the closing operation of the second valve means are performed once only in the predetermined order.

More specifically, the first and second pilot injection start and end times and the main injection start and end time, respectively,
A corresponding one of the opening and closing operations of the valve means and the opening and closing operations of the second valve means is performed. In other words, the opening / closing operation of each valve means is performed only once within the period from the start of pilot injection to the end of main injection, and therefore, the influence of residual magnetism occurs after a considerable time has elapsed from the previous opening / closing operation. It will be done after reaching the end. As a result, each valve means is reliably opened and closed, thus ensuring the intended pilot injection and main injection, which reduces nitrogen oxide emissions and operating noise.

The fuel passage connecting the pump chamber and the fuel supply device is closed at the start of pilot injection. The fuel in the pump chamber is pressurized by the movement of the plunger in the pressure increasing direction and is pumped to the needle chamber. Then, when the needle chamber pressure (injection pressure) reaches the nozzle valve opening pressure, fuel is injected from the nozzle into the engine combustion chamber, and pilot injection is started. Then, when the pilot injection is completed, the fuel passage is opened, the fuel in the pump chamber escapes to the fuel supply device side through the fuel passage, and the pilot injection is completed. next,
The fuel passage is closed again at the start of main injection, and the fuel passage is opened again at the end of main injection, whereby main injection is performed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A fuel injection device according to a first embodiment of the present invention mounted on a multi-cylinder diesel engine will be described below with reference to FIGS. The fuel injection device has the same number of unit injectors 2 as the number of cylinders of the diesel engine 1.
And a fuel tank (not shown) driven by the engine 1.
A fuel feed pump 3 for pumping low-pressure fuel from the fuel tank 1 and a fuel distribution device 4 for distributing the pressurized fuel from the pump 3 to the respective unit injectors 2. Each of the unit injectors 2 is mounted on the cylinder head of the corresponding cylinder.

As shown in FIG. 2, the unit injector 2 includes an injector body 21 and a stepped shaft hole 21a.
A plunger 22 slidably inserted into the inside, and a follower 23 coupled to the plunger 22 and inserted into the shaft hole 21a.
And a spring 24 is provided between the injector body 21 and the follower 23. Plunger 22
The follower 23 and the follower 23 are constantly urged outward by the spring 24. Therefore, the outer end surface of the follower 23 is always in contact with one end of the rocker arm 1b.

As shown in FIG. 1, the rocker arm 1b is
The cam shaft 1f is supported by the rocker arm shaft 1c and is connected to one end of the push rod 1d at the end opposite to the follower side end, and the other end of the push rod 1d rotates in synchronization with the rotation of the engine output shaft 1e. It is in contact with the peripheral surface of the cam 1g mounted on the. Therefore, the plunger 22 and the follower 23 reciprocate in the injector body shaft hole 21a when the rocker arm 1b swings as the engine output shaft 1e rotates.

Referring again to FIG. 2, the injector 2
Is a nozzle holder 2 connected to the injector body 21.
5 and a nozzle body 26 coupled thereto, a spring chamber 25a and a needle chamber 26a are formed in the nozzle holder 25 and the nozzle body 26. A nozzle needle 27 is slidably arranged in the needle chamber 26a, and the needle 27 is always urged in the nozzle closing direction by a spring 28 arranged in the spring chamber 25a. Then, as described below, the needle chamber 26
When fuel is supplied to a and the fuel pressure (injection pressure) in the needle chamber 26a reaches a predetermined nozzle opening pressure, the needle 27 lifts against the spring force of the spring 28 and the nozzle opens. It is like this.

Both ends of the plunger 22 are the plunger 2
A fuel passage 31 is formed on each of the inner end surface and the peripheral surface of the fuel passage 2, and the injector main body 21 is formed with a fuel passage 32, one end of which is communicated with the fuel passage 31.
The other end of the fuel passage 32 is connected to the fuel distribution device 4 via the fuel feed pipe 2a. Therefore, when the plunger 22 reaches a predetermined sliding position within the injector body shaft hole 21a, the fuel passage 31 communicates with the fuel passage 32,
The fuel from the fuel distributor 4 is fed to the fuel feed pipe 2a.
It is designed to be supplied into the pump chamber 22a defined by the shaft hole forming surface of the injector main body 21 and the inner end surface of the plunger 22 via (FIG. 1) and the fuel passages 32 and 31.

Further, the injector main body 21 is formed with a fuel passage 33 whose one end opens to the pump chamber 22a, and the other end of the fuel passage 33 is formed in the nozzle holder 25 and the nozzle body 26, respectively. And to communicate with the needle chamber 26a. Therefore, the pump chamber 22
The fuel supplied to a is supplied to the needle chamber 26a via the fuel passages 33 to 35 as the plunger 22 moves in the pump chamber pressure increasing direction.

The fuel distributor 4 has a return port 4a,
The return port 4a is connected via the drain pipe 2b (FIG. 1), the fuel return passage 36 formed in the injector body 21 so as to communicate with the drain pipe 2b, and the corresponding one of the fuel passages 33 to 35 described above. It communicates with each of the pump chamber 22a and the needle chamber 26a. In the middle of the fuel return passage 36, a normally open main solenoid valve 41 as a first valve means for closing the passage 36 and the main solenoid valve 4 are provided.
Regarding No. 1, the normally open sub electromagnetic valve 42 as the second valve means for closing the fuel return passage 36 on the side opposite to the pump chamber 22a is provided in series with each other. The main solenoid valve 41 includes, for example, a valve body 41a, a spring (not shown) for urging the valve body in the fuel return passage opening direction,
A solenoid (not shown) is provided, and the valve body 41a is driven in the fuel return passage closing direction when the solenoid is excited. The sub solenoid valve 42 is also similarly configured.

The fuel return passage 36 has two valve chambers 36a, in which the valve elements 41a, 42a of the solenoid valves 41, 42 are arranged, respectively.
36b, both valve chambers communicate with each other through a passage portion 36c, and also communicate with the pump chamber 22 and the drain pipe 2b (FIG. 1) through passage portions 36d and 36e. The fuel injection device includes a control unit 5 for controlling the operation of a main solenoid valve 41 and a sub solenoid valve 42 (both solenoid valves are collectively indicated by reference numeral 40 in FIG. 1).
0 (FIG. 1) is further provided. Control unit 5
Reference numeral 0 includes a microprocessor, a memory, an input / output circuit, etc., and an input side detects an intake pressure sensor, a water temperature sensor, an intake pressure sensor, a water temperature sensor, etc. It is connected to various sensors (collectively indicated by reference numeral 60 in FIG. 1) such as an accelerator sensor and a crank angle sensor, and its output side is connected to solenoid valves 41 and 42. The controller 50 controls the injection start timing and the injection end timing of the fuel to each cylinder by controlling the opening / closing timing of the solenoid valves 41, 42 according to the engine operating state represented by the detected engine operating parameter. Has become.

That is, when both the solenoid valves 41 and 42 are in the non-operating state (FIG. 2) under the control of the controller 50 and the pump chamber 22a communicates with the drain pipe 2b through the fuel return passage 36, When the plunger 22 moves in the pump chamber pressure increasing direction, the pressurized fuel from the pump chamber 22a escapes to the return port of the fuel distribution device 4 so that the needle chamber pressure does not reach the nozzle opening pressure.
Further, one of the solenoid valves 41 and 42 is activated to operate the fuel return passage 3
When 6 is closed, the needle 27 is lifted and the nozzle is opened when the pump chamber pressure and thus the needle chamber pressure reaches the nozzle opening pressure.

The operation of the fuel injection device having the above structure will be described below.
One cylinder 1a of the engine 1 will be mainly described. During operation of the engine 1, the rocker arm 1b associated with the cylinder 1a swings around the rocker arm shaft 1c in synchronization with the rotation of the engine output shaft 1e, and the follower 23 and the plunger 22 reciprocate accordingly. During this time, when the open end of the fuel passage 31 of the plunger 22 on the plunger peripheral surface side reaches the plunger moving position where it communicates with the fuel passage 32 of the injector body 21, the fuel from the fuel distributor 4 flows into the pump chamber 22a. On the other hand, when the plunger 22 reaches the plunger moving position where the communication between the fuel passages 31 and 32 is blocked, the fuel inflow is blocked.

During this time, the controller 50 determines, based on the detection signals from the various sensors 60, whether or not the pilot injection start timing related to the engine cylinder 1a has been reached. When it is determined that the pilot injection start timing has not been reached, the controller 50 causes the solenoid valves 41, 4 to
For example, a low-level control output is sent to 2. As a result, both solenoid valves 41 and 42 are deactivated (deenergized) and maintained in the open state, and therefore, the pump chamber 22a is moved to the fuel distribution device 4 via the fuel return passage 36 and the drain pipe 2b.
To the return port 4a. In this case, the plunger 2
Pump chamber 22a pressurized by the movement of 2 in the pressure increasing direction
The fuel inside escapes to the return port and the nozzle remains closed.

After that, when it is judged that the pilot injection start time (TPS time in FIG. 3) has been reached, the controller 50
Sends a high-level control output to the sub solenoid valve 42, for example. As a result, the fuel return passage 36 is connected to the sub solenoid valve 4
The second valve body 42a closes the valve chamber, and thus the communication between the valve chamber 36b and the pump chamber 22a is cut off. When the plunger 22 is driven in the pressure increasing direction in such a state, the pump chamber pressure, and hence the pump chamber side of the fuel return passage 36 and the needle chamber 26a, both increase, and the needle chamber pressure (injection pressure) increases. When the valve opening pressure is reached, the nozzle opens and pilot injection is started.

Next, when it is determined that the pilot injection end time (time TPE in FIG. 3) has been reached while the plunger 22 continues to be driven in the pressure increasing direction, the controller 50
Sends a low-level control output to the sub solenoid valve 42. As a result, the closing of the fuel return passage 36 by the sub electromagnetic valve 42 is released, and the pressurized fuel in the pump chamber 22a escapes to the return port 4a of the fuel distribution device 4, so that the pilot injection ends.

Thereafter, the main injection is started (time TMS in FIG. 3) while the plunger 22 continues to move in the pressure increasing direction.
When it is determined that the fuel return passage 36 is reached, the controller 50 sends a high-level control output to the main solenoid valve 41.
Therefore, the valve chamber 36a and the pump chamber 2 are closed.
The communication with 2a is cut off. As a result, the plunger 22
Pressure inside the needle (injection pressure) as the pressure increases
When the nozzle opening pressure reaches the nozzle opening pressure, the nozzle opens and main injection is started.

Next, the main injection end time (time TME in FIG. 3) while the plunger 22 continues to be driven in the pressure increasing direction.
When the controller 50 determines that the temperature has reached, the controller 50 sends a low-level control output to the main solenoid valve 41. As a result, the fuel return passage 36 is unblocked and the pressurized fuel escapes to the return port 4a, so that the main injection ends. As described above, the closing operation and the opening operation of the sub electromagnetic valve 42 and the closing operation and the opening operation of the main electromagnetic valve 41 are performed at the start and the end of the pilot injection and the start and the end of the main injection, respectively. In other words, the opening / closing operation of each of the solenoid valves 41, 42 is performed only once within the period from the start of pilot injection to the end of main injection. It will be done after the influence of the. As a result, the solenoid valves 41 and 42 are surely opened / closed at the required operation timing, and therefore the intended pilot injection and main injection are reliably performed, whereby the emission of nitrogen oxides and the operating noise are reduced.

The injectors associated with the other cylinders are also
Under the control of the controller 50, it operates similarly to the injector 2 of the cylinder 1a. Hereinafter, a fuel injection device according to a second embodiment of the present invention will be described with reference to FIG. Compared with the device of the first embodiment in which two solenoid valves are provided in series in the middle of the fuel return passage, the device of the present embodiment is different in that two solenoid valves are provided in parallel, while other The structure and operation of the part are substantially the same as those of the first embodiment, and the description of the structure and operation will be partially omitted.

As shown in FIG. 4, the fuel return passage 36 is
Valve bodies 41a of the main solenoid valve 41 and the sub solenoid valve 42,
42a is provided with two valve chambers 36a and 36b, respectively. The valve chamber 36a communicates with the pump chamber 22a and the drain pipe 2b (FIG. 1) via the passage portions 36d and 36e, and the valve chamber 36b is the passage portion. It communicates with the pump chamber 22a and the drain pipe 2b via 36d 'and 36e'. That is, the main solenoid valve 41 and the sub solenoid valve 42
Are provided in parallel with each other in the fuel return passage 36. The main solenoid valve 41 is a normally open solenoid valve,
The sub solenoid valve 42 is a normally closed solenoid valve. The other elements of this embodiment are the same as those of the first embodiment, and the description thereof is omitted.

The operation of the fuel injection device having the above structure will be described below. During operation of the engine 1, fuel is supplied to the pump chamber 22a in the same manner as in the first embodiment. Until the pilot injection start timing (time TPS in FIG. 5) is reached, the solenoid valves 41, 42 are deactivated under the control of the controller 50. Therefore, the passage portion 36d of the fuel return passage 36, the valve chamber 36a, and The pump chamber 22a communicates with the return port 4a of the fuel distributor 4 via the passage portion 36e and the drain pipe 2b, and the fuel in the pump chamber 22a pressurized by the movement of the plunger 22 in the pressure increasing direction is It escapes to the return port and the nozzle remains closed. Incidentally, the passage portions 36d ′, 36 of the fuel return passage 36
The e's are shut off from each other by the valve body 42a of the normally closed sub electromagnetic valve 42.

Thereafter, when it is determined that the pilot injection start time has been reached, the controller 50 causes the main solenoid valve 41 to
Send high level control output to. As a result, the passage portions 36d and 36e of the fuel return passage 36 are closed by the valve body 41a of the solenoid valve 41, and thus the communication between the valve chamber 36b and the pump chamber 22a is cut off. In this state, when the needle chamber pressure (injection pressure) reaches the nozzle opening pressure by driving the plunger 22 in the pressure increasing direction, the nozzle opens and pilot injection is started. Next, when it is determined that the pilot injection end time point (time point TPE in FIG. 5) has been reached, the controller 50 sends a high-level control output to the sub electromagnetic valve 42, which causes the sub electromagnetic valve 42 to close the fuel return passage 36. Is released and the pressurized fuel in the pump chamber 22a escapes to the return port 4a of the fuel distribution device 4, so that the pilot injection ends.

After that, when it is determined that the main injection start time (time TMS in FIG. 5) has been reached, the controller 50 sends a low level control output to the sub solenoid valve 42, which causes the fuel return passage 36 to move to the solenoid valve. When the needle chamber pressure reaches the nozzle opening pressure with the movement of the plunger 22 in the pressure increasing direction, the nozzle is opened and the main injection is started. Next, at the end of the main injection (see FIG.
When the controller 50 determines that the
Sends a low level control output to the main solenoid valve 41,
As a result, the fuel return passage 36 is unblocked and the main injection ends.

Also in the case of this embodiment, the solenoid valves 41 and 42 are surely opened / closed at the required operation timing for the reason described in the above embodiments, so that the intended pilot injection and main injection are surely performed. Hereinafter, with reference to FIG.
A fuel injection device according to a modification of the second embodiment will be described.

Compared with the second embodiment in which two solenoid valves provided in parallel with each other in the middle of the fuel return passage are housed in separate valve chambers, in this modification, the two solenoid valves are common to both solenoid valves. They are different in that they are accommodated in a chamber to reduce the number of fuel passages to which high pressure is applied and to make the device compact. As shown in FIG. 6, the fuel return passage 36 includes the normally open main solenoid valve 4
1 and a valve chamber 36a in which both the valve bodies 41a, 42a of the normally-closed sub-electromagnetic valve 42 are arranged, and the valve chamber 36a is opened and closed by the valve bodies 41a, 42a of the solenoid valves 41, 42, respectively. First and second ports 36f and 36g, which communicate with the pump chamber 22a via 36d and 36d ', respectively, and a third port 36h, which communicates with the drain pipe 2b via the passage portion 36e, are formed.

The structure and operation of the other parts of this modification are the same as in the case of the second embodiment, and a description thereof will be omitted. Hereinafter, a fuel injection device according to a third embodiment of the present invention will be described with reference to FIG. In the present embodiment, the valve bodies of two electromagnetic valves having different valve body driving forces are integrally coupled to each other, and both valve bodies are housed in a common valve chamber for both, so that the number of fuel passages is further reduced. In addition to that, it is characterized by making the device more compact. The structure and operation of the other parts are first
The structure and operation are almost the same as in the case of the second embodiment, and some description thereof is omitted.

As shown in FIG. 7, the fuel return passage 36 is
Valve body 4 of normally open main solenoid valve 41 and sub solenoid valve 42
1a and 42a are provided in the valve chamber 36a, and the valve chamber 36a includes a first port 36f that is opened and closed by the valve body 41a of the main solenoid valve and communicates with the pump chamber 22a via the passage portion 36d, and a passage. A second port 36h that communicates with the drain pipe 2b via the portion 36e is formed. The sub solenoid valve 42 is driven by a drive current larger than that of the main solenoid valve 41. Therefore, the main solenoid valve 41 in the closed operation state cuts off the communication between the valve chamber 36a and the pump chamber 22a. When the sub solenoid valve 42 is driven in the opening direction while the sub solenoid valve 42 is open, the sub solenoid valve 42 resists the closing direction operation of the main solenoid valve 41 and forcibly cancels the communication cutoff state between the valve chamber 36a and the pump chamber 22a. It is supposed to do. The other elements of this embodiment are the same as those of the first and second embodiments, and their explanations are omitted.

The operation of the fuel injection device having the above structure will be described below. During operation of the engine 1, fuel is supplied to the pump chamber 22a in the same manner as in the first and second embodiments. Until the pilot injection start timing is reached, the solenoid valves 41, 42 are deactivated under the control of the controller 50. Therefore, the passage portion 36d of the fuel return passage 36, the valve chamber 36a and the passage portion 36e, and the drain pipe 2b.
The pump chamber 22a communicates with the return port 4a of the fuel distribution device 4 via the, the fuel in the pump chamber 22a pressurized by the movement of the plunger 22 in the pressure increasing direction escapes to the return port, and the nozzle is It is kept closed.

Thereafter, when it is determined that the pilot injection start time point (TPS time point in FIG. 8) has been reached, the controller 50
Sends a high level control output to the main solenoid valve 41. As a result, the valve chamber 36a of the fuel return passage 36 and the passage portion 36d are closed by the valve body 41a of the electromagnetic valve 41, and thus the communication between the valve chamber 36a and the like and the pump chamber 22a is cut off. In this state, when the needle chamber pressure (injection pressure) reaches the nozzle opening pressure by driving the plunger 22 in the pressure increasing direction, the nozzle opens and pilot injection is started.

Next, when it is determined that the pilot injection end time (time TPE in FIG. 8) has been reached, the controller 50
Sends a high level control output to the sub solenoid valve 42.
As a result, the closing of the fuel return passage 36 by the main solenoid valve 41 in the closed state is forcibly released by the sub solenoid valve 42, and the pressurized fuel in the pump chamber 22a is returned to the return port 4 of the fuel distributor 4. Since it escapes, the pilot injection ends.

After that, when it is determined that the main injection start time (time TMS in FIG. 8) has been reached, the controller 50 sends a low level control output to the sub solenoid valve 42. As a result, the action of the sub solenoid valve 42 forcibly releasing the closed operation state of the main solenoid valve 41 disappears. On the other hand,
The closing operation of the main solenoid valve 41 continues, and therefore the fuel return passage 36 is closed by the solenoid valve 41. After that, when the needle chamber pressure reaches the nozzle opening pressure as the plunger 22 moves in the pressure increasing direction, the nozzle opens and main injection is started.

Next, the main injection end time (time TME in FIG. 5)
When the controller 50 determines that the main solenoid valve 41 has been reached, the controller 50 sends a low-level control output to the main solenoid valve 41, thereby releasing the blockage of the fuel return passage 36 by the main solenoid valve 41 and ending the main injection. Also in the case of the present embodiment, the solenoid valves 41 and 42 are surely opened / closed at the required operation timing for the reason described in the above embodiments, so that the intended pilot injection and main injection are surely performed.

The present invention is not limited to the above embodiment, but can be variously modified. For example, the fuel return passage 36 can be used as a passage for both fuel supply and fuel return. In this case, the fuel passage 31 shown in FIG. 2 becomes unnecessary, and if the fuel passage 32 is communicated with the fuel passage 33 or 36. good.
In the first embodiment, the first and second valve means are provided in series with each other in the middle of the fuel passage, in the second embodiment both valve means are provided in parallel with each other in the middle of the fuel passage, and in the third embodiment, Although the valve bodies of both valve means are connected to each other, the first and second valve means of the present invention can be variously arranged in a form suitable for the conditions such as the installation space of the fuel injection device. The intended pilot injection and main injection can be reliably performed by opening / closing the second valve means in the order according to the arrangement of both valve means.

[0041]

As described above, in the fuel injection device having the unit injector including the plunger that reciprocates in synchronization with the rotation of the engine output shaft, the present invention provides a pump chamber defined by the plunger and a fuel supply device. The first valve means is provided in the middle of the fuel passage that connects the first valve means and the second valve means, respectively, while driving the plunger in the pressure increasing direction from the start of pilot injection to the end of main injection. Therefore, the pilot injection and the main injection are performed by performing the opening operation and the closing operation of the second valve means and the opening operation and the closing operation of the second valve means only once in the predetermined order, respectively.
The opening / closing operation of the valve means is performed after a considerable amount of time has passed from the previous opening / closing operation and the influence of the residual magnetism has stopped. As a result, the first and second valve means are surely opened / closed at the required operation timing, so that the intended pilot injection and main injection are reliably performed, thereby reducing the emission of nitrogen oxides and the operating noise. .

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a fuel injection device according to a first embodiment of the present invention together with peripheral elements.

FIG. 2 is a cross-sectional view showing the fuel injection device shown in FIG.

FIG. 3 is a graph showing the operation timing of the solenoid valve of the fuel injection device shown in FIGS. 1 and 2 and showing the change in fuel injection amount over time.

FIG. 4 is a partial sectional view showing a main part of a fuel injection device according to a second embodiment of the present invention.

5 is a graph showing an operation timing of an electromagnetic valve of the fuel injection device shown in FIG. 4 together with a change in fuel injection amount.

FIG. 6 is a partial schematic diagram showing a main part of a fuel injection device according to a modification of the second embodiment of the present invention.

FIG. 7 is a partial schematic view showing a main part of a fuel injection device according to a third embodiment of the present invention.

8 is a graph showing the operation timings of the main solenoid valve and the sub solenoid valve of the fuel injection device of FIG. 7, together with the change over time of the valve body positions of both solenoid valves and the change in fuel injection amount.

[Explanation of symbols]

 2 unit injector 2a fuel feed pipe 2b drain pipe 3 fuel feed pump 4 fuel distribution device 22 plunger 22a pump chamber 26a needle chamber 27 nozzle needle 31, 32, 33, 34, 35 fuel passage 36 fuel return passage 41 main solenoid valve 42 sub Solenoid valve 50 controller

Claims (1)

[Claims] 1. A fuel injection device having a unit injector including a plunger that reciprocates in synchronization with rotation of an engine output shaft, in the middle of a fuel passage connecting a pump chamber defined by the plunger and a fuel supply device. The first and second valve means, respectively, and the opening and closing operations of the first valve means while driving the plunger in the pressure increasing direction from the start of pilot injection to the end of main injection. Further, the fuel injection device is characterized in that the opening operation and the closing operation of the second valve means are performed once in a predetermined order to perform pilot injection and main injection.