JPH06294361A - Fuel injection device - Google Patents

Abstract

PURPOSE:To provide a fuel injection device which can obtain stable and small injection amount prior to main injection, and obtain the stable and small injection amount irrespective of rotation of an engine. CONSTITUTION:A solenoid valve 20 is arranged on the way of a fuel supply passage 34 leading to a compression chamber 15 of a fuel injection pump 1. In a fuel injection device, a fuel injection amount is adjusted by opening and closing the solenoid valve 20. A valve body 23 is moved until it seats a valve seat 24 during pre-injection process prior to main injection. This fuel injection device has a leak port 42 for leaking fuel inside the compression chamber 15. The timing for leaking the fuel inside the compression chamber 15 is matched with the timing for throttling a fuel supply passage 34 with the valve body 23 seating the valve seat 34 through the leak port 42. Motion of the valve body 23 is stabilized while proper and small pre-projection amount is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention adjusts the amount of fuel injected to an internal combustion engine by controlling the opening / closing of a solenoid valve provided midway in a fuel supply passage leading to a compression chamber of a fuel injection pump. The present invention relates to an injection device.

[0002]

2. Description of the Related Art As a conventional fuel injection pump of this type,
For example, Japanese Unexamined Patent Application Publication No. 1-151751 discloses that pilot injection is performed prior to main injection.

This will be described with reference to the characteristic diagram of FIG. 7. The drive pulse supplied to the solenoid valve is composed of a main pulse having a long section and a sub pulse having a short section, which is necessary to guide the ignition of fuel. It is designed to realize such minute injection by supplying sub-pulses. Generally, the pilot injection amount is required to be as small as ^{3 to} 5 mm ³ / st per unit stroke of the plunger, but in the throttle process of the fuel supply passage by the sub-pulse, the required amount is reached before the solenoid valve is fully lifted. . Therefore, it is considered that the supply period of the sub-pulse is shortened so that the solenoid valve returns before being fully lifted.

[0004]

However, since the solenoid valve receives the valve closing instruction and returns before the solenoid valve is fully lifted, the lift amount is not stable. For this reason, there is an inconvenience such that the injection quantity fluctuates even though a good injection is to be obtained by the pilot injection. Further, when the pilot injection is simply adjusted by the instantaneous lift of the solenoid as in the conventional art, when the engine speed increases and the main injection amount increases, the pilot injection also increases accordingly. There was also. In the first place, if the pilot injection itself is too large, there is an adverse effect such as an increase in smoke, so it is desirable that the amount be small regardless of the rotation of the engine.

Therefore, an object of the present invention is to provide a fuel injection device capable of obtaining a stable small amount injection prior to the main injection. Another object of the present invention is to obtain an almost constant small amount injection regardless of the rotation of the engine.

[0006]

SUMMARY OF THE INVENTION Therefore, the gist of the present invention is to provide a compression chamber formed in a cylinder into which a plunger is slidably inserted, a high pressure passage for guiding fuel in the compression chamber to a nozzle, And a fuel injection pump having at least a fuel supply passage for supplying the fuel introduced from the fuel inlet to the compression chamber, and a fuel injection pump provided in the middle of the fuel supply passage of the fuel injection pump and connected to the compression chamber side of the fuel supply passage. A solenoid valve that has a valve body that adjusts the communication state with the inlet side and that controls the movement of this valve body by a control signal from the outside that is supplied to a solenoid; and a lift of the plunger that is formed on the side surface of the cylinder. In response to a leak port that allows the compression chamber and the fuel supply passage to communicate with each other, and a control signal from the outside that is supplied to the solenoid. It is composed of a pulse and a sub-pulse that forms a small amount of injection prior to the main pulse, and the sub-pulse is made longer than the time until the valve body is seated on the valve seat, and the compression chamber and the fuel supply passage are provided with the main injection. The point is that we made it possible to communicate in the earlier period.

[0007]

[Function] Therefore, the fuel introduced from the fuel inlet is
Although it is guided to the compression chamber via the solenoid valve, fuel is not injected from the nozzle even during the pressure feeding process of the plunger unless the fuel supply passage is throttled by the solenoid valve. When a sub-pulse is issued in the cam lift range where a small injection is required, the valve body of the solenoid valve lifts and narrows the fuel supply passage, so that the fuel in the compression chamber is pressurized and injected from the nozzle. After that, when the sub-pulse ends and the fuel supply passage is returned to the initial state, this preliminary injection disappears, and when the main pulse is issued and the fuel supply passage is throttled again, main injection is started.

In the pre-injection process performed prior to the main injection, the sub-pulse is set longer than the time until the valve body is seated on the valve seat, so that the valve body is once seated on the valve seat. Since the valve body is moved, and the valve body is not returned before sitting, the movement of the valve body can be uniformly determined. In this case, although there is a concern that the preliminary injection becomes large, in combination with the movement of the valve element, the compression chamber and the fuel supply passage communicate with each other through the leak port at a stage before the main injection. The increase in the injection amount of the preliminary injection can be suppressed, so that the above-mentioned problems can be achieved.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, the fuel injection device has a unit injector type injection pump 1 for injecting fuel into each cylinder of a diesel engine, for example, and this injection pump 1 has a cylinder 3 at the base of a plunger barrel 2. Is formed, and the plunger 4 is slidably inserted into the cylinder 3. A spring receiver is formed on the plunger barrel 2, and a spring 6 is interposed between the spring receiver of the plunger barrel 2 and a tappet 5 connected to the plunger 4, and the spring 6 moves the plunger 4 from the plunger barrel 2 to the plunger barrel 2. It always urges in the direction of moving away (the direction of the arrow indicated by A in the figure). A cam formed on a drive shaft (not shown) is in contact with the tappet 5, and the drive shaft is connected to an engine to rotate and cooperates with the spring 6 to reciprocate the plunger 4 in the cylinder 3. It has become. The reciprocating motion of the plunger 4 compresses the fuel in the compression chamber 15 formed by being surrounded by the plunger 4 and the plunger barrel 2 and sucks the fuel into the compression chamber 15.

A holder portion 7 is attached to the tip of the plunger barrel 2 by assembling a holder nut 8 for locking the holder portion 7 around the tip of the plunger barrel 2.
A nozzle 10 is assembled to the holder portion 7 via a spacer 9, and the spacer 9 and the nozzle 10 screw a retaining nut 11 that locks on their peripheral surfaces around the tip of the holder portion 7. It is fixed. A spring accommodating chamber 12 is formed in the holder portion 7, and the nozzle spring 1 accommodated in the spring accommodating chamber 12 is formed.
3, the needle valve of the nozzle (not shown) is pressed in the tip direction of the nozzle (the direction of the arrow indicated by B in the figure). The structure of the nozzle is known per se, and when high-pressure fuel is supplied through the high-pressure passage 14 described below, the needle valve is opened and the fuel is injected from the injection hole formed at the tip of the nozzle. ing.

The high-pressure passage 14 is formed in the plunger barrel 2 and has one end open to the compression chamber 15, a passage 17 formed in the holder portion 7 communicating with the passage 16 and a spacer 9 communicating with the passage 17. And a passage (not shown) formed in the nozzle 10 and communicating with the passage 18.

A valve housing 21 provided with a solenoid valve 20 to be described later is integrally extended to the side of the plunger barrel 2, and the plunger barrel 2 and the valve housing 2 are provided.
1, a fuel supply passage 34 for supplying fuel to the compression chamber 15 is provided. This fuel supply passage 34
Is a fuel inlet 3 formed on the side of the plunger barrel 2.
5, a first supply passage 34a to which fuel is supplied, and an annular recess 34 formed in a portion of the cylinder 3 which is connected to the first supply passage 34a and in which the plunger 4 is constantly sliding.
b, a second supply passage 34c that is connected to the annular recess 34b and communicates with a valve body storage chamber 27 of the solenoid valve 20 described below, and around the rod 22 so as to communicate with the valve body storage chamber 27 via the valve body. The third fuel supply passage 34d has one end connected to the formed annular groove 39 and the other end connected to the compression chamber 15.

The supply of fuel to the compression chamber 15 is regulated by a solenoid valve 20.
The rod 22 is slidably inserted into a sliding hole 38 formed in the valve housing 21. Valve housing 21
Is provided with a valve seat 24 that abuts a poppet type valve body 23 formed at the tip of a rod 22, and a header 25 is screwed to the valve housing 21 so as to cover the valve body 23. A valve body housing chamber 27 surrounded by the header 25 and the valve housing 21 is formed on the joint surface between the header 25 and the valve housing 21.
Is provided with a valve body stopper 26 fixed to the header 25 side and facing the valve body 23.

Further, the rod 22 has a holder 28, which is screwed on the opposite side of the header 25 of the valve housing 21, inserted therethrough, and an armature 31 is fixed to the tip thereof. A solenoid storage barrel 30 is assembled to the holder 28 via a spacer 40 by a holder nut 29. The armature 31 is stored in an armature chamber 41 formed between the holder 28 and the spacer 40, and the spacer It faces the solenoid 32 housed in the solenoid housing barrel 30 via the mounting hole 40. The holder 28 accommodates and holds a spring 33 for urging the valve body 23 in a direction in which the valve body 23 is always separated from the valve seat 24. Normally, the valve body 23 is separated from the valve seat 24, and a solenoid is used. When the armature 31 is attracted to the solenoid 32 by energizing 32, the valve body 2
3 is driven in a direction in which it abuts on the valve seat 24.

The diameter of the rod 22 is slightly smaller in the front portion than the valve body 23, and the sliding hole 38 has an annular groove 39 having a larger diameter than this portion so as to face the small diameter portion.
And the third supply passage 34 is formed in the annular groove 39.
d communicates. The second fuel supply passage 34c communicates with the valve body storage chamber 27 as described above, and the passage 3
The fuel is constantly supplied through 4c and is full. Therefore, the valve body 23 separates from the valve seat 24, and during the intake stroke of the plunger 4, the fuel filled in the valve body storage chamber 27 passes through the gap between the rod 22 and the sliding hole 38 and enters the annular groove 39. From this annular groove 39 to the third fuel supply passage 3
It is supplied to the compression chamber 15 via 4d. The fuel pressure at that time is about 5 kg / cm ² .

When the solenoid 32 is energized, that is, the valve body 23
When the valve seat 24 is seated on the valve seat 24, the fuel supply passage 34 is cut off by the solenoid valve 20, so that the fuel already supplied to the compression chamber 15 is discharged from the plunger 4
And is supplied to the nozzle 10 through the high pressure passage 14. In this pressure-feeding of fuel, the solenoid 32 is de-energized, the valve body 23 separates from the valve seat 24, and a portion of the high-pressure fuel on the high-pressure side (high-pressure passage 14, compression chamber 15, third fuel supply passage 34d) Is returned to the valve body accommodating chamber 27, and the fuel pressure in the compression chamber decreases, and the process ends.

By the way, the annular recess 3 of the plunger 4 is provided.
As shown in FIGS. 2A to 2C, an annular groove 41 communicating with the compression chamber 15 via a communication hole 40 formed in the plunger 4 is provided on a side portion closer to the compression chamber than 4b.
And a leak port 42 communicating with the first supply passage 34a is formed on a side portion of the cylinder 3, and the relationship between the leak port 42 and the annular groove 41 is as follows. There is.

FIG. 2A shows the bottom dead center where the plunger 4 moves upward in FIG. 1, and the leak port 42 has already faced the annular groove 41 at this point. From this state, the plunger 4 moves downward in the drawing (see FIG.
Moving in the direction of arrow), the annular groove 41 of the leak port 42 and the desired position move relatively upward in the initial stage of movement, and when the plunger reaches the position shown in FIG. 2B, the annular groove 41 moves. It is disengaged from the leak port 42 and communication with the leak port 42 is cut off. The time from the bottom dead center until the communication between the leak port 42 and the annular groove 41 is cut off is tcut. After tcut, the plunger 4 is further lifted and the volume of the compression chamber 15 is reduced without the leak port 42 and the annular groove 41 communicating with each other (FIG. 2C).

Such a leak port 42 and an annular groove 41
With respect to the movement of the plunger 4 having a relationship with, the energization of the solenoid 32 is controlled by the control unit 42 shown in FIG. The control unit 42 is composed of an A / D converter, a multiplexer, a microcomputer, a drive circuit, etc., which are not shown, and detects an accelerator opening degree detecting section for detecting a depression amount (accelerator opening degree) of an accelerator pedal and an engine rotation state. Each signal of a rotation detecting unit for detecting, a reference pulse generating unit attached to the drive shaft and generating a pulse each time the drive shaft reaches the reference angular position, etc. is input, and the drive pulse shown in FIG. 3 is output.

This drive pulse is supplied to the solenoid 32 of the solenoid valve 20, and the plunger 4 lifts from the bottom dead center (t = 0) to perform the main injection t3.
~ T4 before the main pulse of t4
It has a sub-pulse that performs small injection (or pilot injection) over two short intervals. The pulse width (t2-t1) of this sub-pulse is longer than the time required for the fully opened valve body 23 to move against the spring 33 and to be seated on the valve seat 24. The time between the pulse and the pulse is longer than the time from the seated state of the valve body 23 to the initial open state. The tcut is set after the sub pulse is emitted and the valve is opened again, and before t3 when the main pulse is emitted.

In the above structure, it is assumed that the plunger 4 is now at the bottom dead center position. From this point, the plunger 4 starts to lift, but when the sub-pulse is supplied to the solenoid 32 at t1, the armature 31 is attracted to the solenoid 32 by the electromagnetic force, and the valve body 23 starts moving toward the valve seat 24. Then, the valve body 23 is seated on the valve seat 24 after a while from t1. This seated state continues until t2, and since the electromagnetic force disappears after t2, the spring 33
The valve element 23 separates from the valve seat 24 at a speed determined by the spring force of.

In this process, the fuel in the compression chamber 15 is compressed and injected by the plunger 4 before the valve body 23 is completely closed because the fuel supply passage 14 is throttled by the solenoid valve 20. This preflow is
Since it is for guiding the ignition of the main injection, it may be minute, and if the valve body 23 is lifted until it is seated, the injection amount may become unnecessarily large. However, in this preflow section, the leak port 42 and the annular groove 41 communicate with each other, and a part of the fuel in the compression chamber passes through the communication hole 40 and from the annular groove 41 via the leak port 42 to the fuel supply passage 14. Therefore, the fuel injected from the nozzle does not increase, and the injection rate becomes small as seen in FIG. The diameter of the leak port 42 is predetermined so as to obtain such a small amount of optimum preflow. Moreover, since the valve element 23 is seated on the valve seat 24 at one end, the movement of the valve element 23 can be uniformly determined, and the variation of the injection rate is eliminated. Further, since the pulse width of the drive pulse is set longer than the valve body 23 can be seated, the injection is performed in a longer section than before, but the presence of the leak port 42 gently swells as a whole. The injection rate characteristic can be used, and the ignition of the main injection can be smoothly induced.

When the preflow is completed and tcut is reached, the communication between the leak port 42 and the annular groove 41 is cut off, so that the fuel leak action is lost thereafter and the same main injection as in the conventional case can be obtained. That is, when the drive pulse is issued after t3, the valve body 23 is again moved to the valve seat 2
4, the fuel in the compression chamber is compressed by the plunger 4 and injected from the nozzle without leaking. For this reason,
The injection rate increases, and this state is maintained until t4 when the valve body 23 separates from the valve seat 24.

In the above structure, the leak port 4
Since 2 always faces the side surface of the plunger 4, the annular groove 41 is formed in the plunger 4. However, as shown in FIG. 4, the position where the leak port 42 is formed is compressed in the initial stage of the plunger lift. Similar effects can be obtained even if the leak port 42 is closed by the tip of the plunger 4 at tcut (FIG. 4A) and the leak port 42 is closed at tcut (FIG. 4B).

FIG. 5 shows another embodiment of the present invention. Although the basic structure is the same, the description thereof is omitted, but the relationship between the leak port 42 and the annular groove 41 is as follows.

When the plunger 4 is located at the bottom dead center, the leak port 42 is located in the annular groove 41 of the plunger 4.
The leak port 42 faces the side wall closer to the tip.
Does not communicate with the annular groove 41 (FIG. 5A). When the plunger 4 moves downward (in the direction of the arrow) in this figure from this state, the leak port 42 moves relatively upward with respect to the annular groove 41 in the initial stage of movement, and the plunger 4 moves to the position shown in FIG. 5B. When it reaches, the annular groove 41 communicates with the leak port 42. Then, when the plunger 4 further reaches the position of FIG. 5C, the annular groove 41 is disengaged from the leak port 42 and the communication with the leak port 42 is blocked. From this bottom dead center, the leak port 42 and the annular groove 4
The time until the communication between 1 and 1 is defined as topen, and the time until the communication between the leak port 42 and the annular groove 41 is cut off is defined as topen.
Use cut. After tcut, the leak port 42
And the annular groove 41 do not communicate with each other, the plunger 4 is further lifted and the volume of the compression chamber 15 is reduced.

Such a leak port 42 and an annular groove 41
The solenoid 32 is energized in response to the movement of the plunger 4 having the relationship as shown in FIG.

That is, the drive pulse applied to the solenoid 32 is preceded by the main pulse from t3 to t4 at which the plunger 4 lifts from the bottom dead center (t = 0) to perform the main injection.
It has a sub-pulse for performing small injection (or pilot injection) over a short section from t1 to t2 in the initial stage of lift. The pulse width of this sub-pulse is 23
Is moved against the spring 33 and is longer than the time it takes to sit on the valve seat 24. Also, during the period between the sub-pulse and the main pulse, the seated state of the valve body 23 returns to the initial open state. It is longer than the time to. The topen is set after the sub-pulse is emitted and the valve body is seated on the valve seat in this embodiment, but is actually set at an appropriate time to prevent the preflow from rising excessively. However, it is not always necessary to match the end timing of the sub-pulse and the seating timing of the valve element, and it is determined in advance by experiments in consideration of the leak state of fuel and the like. Further, tcut is set to be a time point before t3 when the main valve is emitted.

In the above arrangement, it is assumed that the plunger 4 is now at the bottom dead center position. From this point, the plunger 4 starts to lift, but when the sub-pulse is supplied to the solenoid 32 at t1, the armature 31 is attracted to the stator by the electromagnetic force, and the valve body 23 starts moving toward the valve seat 24. , Valve seat 24 after a while from t1
The valve body 23 is seated on. This sitting state continues until t2,
Since the electromagnetic force disappears after t2, the valve body 23 separates from the valve seat 24 at a speed determined by the spring force of the spring 33.

In this process, the fuel in the compression chamber is compressed by the plunger 4 and injected before the valve body 23 is completely closed because the fuel supply passage 14 is throttled by the solenoid valve 20. However, in this preflow section, before the preflow becomes too large, the leak port 42 communicates with the annular groove 41, and a part of the fuel in the compression chamber 15 passes through the communication hole 40 and leaks from the annular groove 41 to the leak port 42. Since the fuel is returned to the fuel supply passage 14 via the, the amount of fuel injected from the nozzle does not increase, and a small injection rate can be obtained as seen in FIG. 6 regardless of the engine speed.

Moreover, also in this embodiment, the valve body 23
Is moved until it is seated on the valve seat 24, the movement of the valve body can be uniformly determined, and the variation of the injection rate is eliminated.

When the preflow is completed and tcut is reached, the communication between the leak port 42 and the annular groove 41 is cut off, so that there is no fuel leak action thereafter and the same main injection as in the conventional case can be obtained. That is, when the drive pulse is issued after t3, the valve body 23 is seated on the valve seat 24 again,
The fuel in the compression chamber 15 does not leak and the plunger 4
It is compressed by and jetted from the nozzle. Therefore, the injection rate increases, and this state is maintained until t4 when the valve body 23 separates from the valve seat 24.

[0034]

As described above, according to the present invention,
By combining the timing of leaking the fuel in the compression chamber through the leak port and the timing of moving the valve element until it is seated on the valve seat and narrowing the fuel supply passage, it is possible to pressurize and leak the fuel in the compression chamber at the same time or Since it is performed before the main injection with a predetermined phase difference, it is possible to make the preflow (preliminary injection) the optimum small amount while stabilizing the movement of the valve body.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a schematic configuration diagram of a fuel injection device according to the present invention.

2 (a) to 2 (c) are enlarged cross-sectional views of a main part in FIG.

3 is a diagram showing characteristics of a plunger lift, a drive pulse, a valve lift, and an injection rate of the fuel injection device in FIG.

FIG. 4A and FIG. 4B are enlarged cross-sectional views showing the configuration of the main part in another embodiment.

5 (a) to 5 (c) are enlarged cross-sectional views showing a configuration of a main part in still another embodiment.

6 is a diagram showing characteristics of a plunger lift, a drive pulse, a valve lift, and an injection rate of the fuel injection device in the embodiment of FIG.

FIG. 7 is a diagram showing characteristics of a plunger lift, a drive pulse, a valve lift, and an injection rate of a conventional fuel injection device.

[Explanation of symbols]

 1 Fuel Injection Pump 3 Cylinder 4 Plunger 14 High Pressure Passage 15 Compression Chamber 20 Solenoid Valve 23 Valve Disc 32 Solenoid 34 Fuel Supply Passage 35 Fuel Inlet 42 Leak Port

Claims (1)

[Claims] 1. A compression chamber formed in a cylinder into which a plunger is slidably inserted, a high pressure passage for guiding fuel in the compression chamber to a nozzle, and fuel supplied from the fuel inlet to the compression chamber. A fuel injection pump having at least a supply passage, and provided in the middle of the fuel supply passage of the fuel injection pump,
A solenoid valve having a valve body for adjusting the communication state between the compression chamber side and the fuel inlet side of the fuel supply passage, and controlling the movement of the valve body by a control signal from the outside supplied to a solenoid; A leak port that is formed on the side surface of the solenoid valve and that allows the compression chamber and the fuel supply passage to communicate with each other according to the lift of the plunger; and a control signal from the outside that is supplied to the solenoid, and a main pulse that forms the main injection. Prior to this main pulse, a sub-pulse that forms a small amount of injection is formed, and the pulse width of the sub-pulse is made longer than the time until the valve body sits on the valve seat, and the compression chamber and the fuel supply passage are connected to the main pulse. A fuel injection device characterized in that they are communicated with each other at a time before injection.