JPH06221243A - Electromagnetic spill valve control unit injector - Google Patents

Abstract

PURPOSE:To embody a compact electromagnetic spill valve control unit injector, which can restrict the initial injection rate without performing a two-stage injection. CONSTITUTION:The tip of a plunger 3 is provided with a small diameter part 26 for releasing the fuel inside of a pressurization chamber 6 at the initial stage of a pressurizing stroke, and an additional capacity part 28 is provided on the way of a fuel passage 15 to the pressurization chamber 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a unit injector in which a fuel injection amount and injection timing are controlled by an electromagnetic spill valve.

[0002]

2. Description of the Related Art An electromagnetic spill valve control type unit injector is provided with an electromagnetic spill valve that opens and closes a fuel passage communicating with a pressurizing chamber at the top of a plunger. By closing, the injection pressure is generated in the pressurizing chamber, and the electromagnetic spill valve is opened again to determine the end of injection. Such an electromagnetic spill valve type unit injector can freely control the injection timing and injection amount, and
Since there is no high-pressure pipe, there is an advantage that fuel is not compressed unnecessarily, high-pressure injection is possible, and the fuel runs out well.

By the way, recently, NOx of diesel engine
Is required to reduce the emission of NO
It is known that the emission amount of x can be improved by suppressing the initial injection rate into the combustion chamber and lowering the combustion temperature at the start of combustion. However, in the electromagnetic spill valve type unit injector, the injection pressure rises immediately when the spill valve is closed, and since the distance from the pressurizing chamber to the nozzle is short, the propagation of pressure waves due to the oil feeding of the plunger reaches the nozzle. Since it is transmitted directly, there is the inconvenience that the injection pressure rises linearly immediately after it begins to rise. Therefore, there is a drawback that it is difficult to improve the exhaust performance such as NOx based on the suppression of the initial injection rate as described above.

Therefore, conventionally, in such an electromagnetic spill valve control type, it has been considered to perform injection in two stages, pilot injection and main injection.

[0005]

However, in order to perform the two-stage injection as described above, a solenoid having a strong suction force is required to operate the electromagnetic spill valve, and the entire size increases and There is a drawback that it is not very effective in reducing NOx in the high output range.

An object of the present invention is to solve the above-mentioned conventional drawbacks and to realize a small electromagnetic spill valve control unit injector capable of suppressing the initial injection rate without performing two-stage injection. It is what

[0007]

In order to solve the above problems, according to the present invention, an electromagnetic spill valve is provided in the middle of a fuel supply passage communicating with a pressurizing chamber at the tip of a plunger, and an electromagnetic spill valve for opening and closing the passage is arranged. In the valve type unit injector, a small diameter portion is formed on the outer peripheral surface of the plunger top portion for communicating the pressurizing chamber with the fuel escape port at the beginning of the fuel pressure feeding process, and further, a fuel supply passage from the spill valve to the pressurizing chamber. An additional volume part whose actual volume is variable is provided midway.

[0008]

[Function] When the electromagnetic spill valve is closed to start the pressure feeding of the fuel, the compressed fuel escapes to the fuel escape port side through the small diameter portion, so that the initial injection pressure rise is suppressed, and the initial injection rate is accordingly accompanied. Is suppressed. The suppression pattern of the injection rate, that is, the increase pattern of the injection pressure can be appropriately set by changing the additional volume.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, (1) is an injector main body, and a plunger insertion hole (2) is formed from the upper end of the injector main body (1) to an intermediate portion, and the insertion hole (2) is inserted from above. The plunger (3) is slidably inserted. A tappet (5) biased upward by a plunger spring (4) is attached to an upper end of the plunger (3), and the tappet (5) is moved downward by a fuel cam (not shown) or the like to move the plunger (5). 3) is similarly slid downward to pressurize the fuel in the pressurizing chamber (6) in the insertion hole (2) on the top side thereof. Below the pressurizing chamber (6), a fuel injection nozzle (8) for supplying fuel through a fuel oil supply passage (7) is attached. The injection nozzle (8) is composed of a nozzle body (11) having an injection port (9) and a needle (10) also inserted in the nozzle body (11). Further, a needle spring (13) for urging the needle (10) downward is inserted into a recess (12) formed in the injector body (1) so as to face the nozzle body (11).

A fuel passage (15) communicating with the pressurizing chamber (6) is formed in the injector body (1), and a spill that opens and closes the fuel passage (15) is formed in the fuel passage (15). Valve (16) is inserted and its spill valve (16)
An armature (17) attached to the upper end of the injector body projects upward from the upper end surface of the injector body (1) and is covered by a solenoid case (18) attached to the upper end surface of the injector body (11). A solenoid core (20) having a solenoid coil (19) is mounted in the solenoid case (18) toward the armature (17) side. That is, the controller (2
The solenoid drive current generator (22) driven by the control signal of (1) energizes the solenoid coil (19) to attract the armature (17) upward, which causes the spill valve (16) to move to the fuel When the passage (15) is closed and the power is turned off, the spill valve (1
The passage (15) is opened by the force of the spring (23) that pushes 6) downward. And spill valve (16)
When the fuel passage (15) is opened downwards and the fuel passage (15) is opened, the pressurizing chamber (6) is opened, so that the fuel is not pumped to the injection nozzle (8) side. When it is closed to, the fuel passage (15) is shut off, so that the interior of the pressurizing chamber (6) is pressurized by the plunger (3) and the fuel is pressure-fed and fuel injection is performed.

In the above-mentioned structure, the plunger (3) is in the raised position.
A fuel escape port (25) for opening the plunger insertion hole (2) to the outside is formed at the top of the plunger (3), and the plunger (3) is made to correspond to the fuel escape port (25). ), A small diameter portion (26) is formed on the outer peripheral surface of the lower end apex through a low step portion, and the small diameter portion (26) allows the pressurizing chamber until the plunger descends from the top dead center position to a certain position. (6) is made to communicate with the fuel escape port (25) side. This small diameter part (26) is provided with a plunger (3).
The diameter is slightly smaller than the diameter of 0.1 mm, and the length is about 1 mm. Further, an additional volume (28) is formed in the fuel passage (15) between the pressurizing chamber (6) and the spill valve (16) so as to communicate with the fuel passage (15). ing. The adjusting piece (29) is screwed so as to close the mouth end of the additional volume (28) on the outer surface side of the injector body (1), and the main body (at the tip of the adjusting piece (29) ( 30)
Protrudes into the additional volume section (28) to determine the actual volume of this additional volume section (28). That is, the actual volume of the additional volume section (28) can be arbitrarily adjusted by changing it to an adjustment piece (29) having a different size of the piece main body section (30).

Therefore, when the plunger (3) descends,
Operate the spill valve (16) as described above to activate the fuel passage (1
When 5) is closed, the fuel in the pressurizing chamber (6) is pressurized and oil feeding is started. At the beginning of this oil feeding, the compressed fuel in the pressurizing chamber (6) is The fuel leaks to the fuel escape port (25) side through a small gap between the small diameter portion (26) and the pressurizing chamber (6), and in addition to the fuel in the fuel passage (15), the fuel in the additional volume portion (28) Since it is also necessary to compress, the rise of the initial injection pressure can be suppressed low. Further, when the plunger (3) is lowered and the fuel escape port (25) is closed by the outer peripheral portion of the plunger (3), the fuel pressure in the pressurizing chamber (6) rapidly rises, The injection pressure also rises. FIG. 2 shows changes in the injection pressure and the injection rate in this case in comparison with the conventional example. In the conventional example shown by the dashed line in the figure, the injection pressure rises substantially linearly from the initial stage of injection and the injection rate The injection pressure and the injection rate are suppressed in the case where the small diameter portion (26) is provided, and more in the case where the additional volume portion (28) shown by the solid line is provided. It can be seen that the initial injection rate can be greatly suppressed.
The small-diameter portion (26) does not need to be formed on the entire surface of the periphery of the plunger (3), and may be a partially formed groove or grooves.

3 and 4 are enlarged views of the solenoid case (18), and an air vent bolt (32) is screwed into the solenoid case (18) from the upper end thereof. The air vent bolt (32) is formed with an air vent hole (33) penetrating from its tip toward the side surface of the upper end exposed portion beyond the solenoid case (18), and the air vent hole (33) is formed in the solenoid case (18). It communicates with the periphery of the lower armature (17). That is, the fuel in the fuel passage (15) is circulated around the armature peripheral portion (34), but the air mixed in the fuel is
The air vent bolt (32) is designed to be discharged from the air vent hole (33).

An air vent passage (35) is formed on the bottom surface of the solenoid case (18) so as to surround the entire circumference of the solenoid core (20) so as to communicate with the air vent hole (33). The ceiling surface (36) of the air vent passage (35) is an inclined surface that rises toward the air vent hole (33) side. This is because the injector main body (1) is not always mounted in a completely vertical state as shown in FIG. 1, and when it is mounted in a tilted state, a portion higher than the air vent hole (33) is If there is, there is a possibility that air will not be removed from that portion, but in this example, the mixed air is discharged by guiding the air to the air vent hole (33) side by means of the inclined surface (36) as described above. It promotes. This is for the following reason. When the spill valve (16) closes the fuel passage (15), the spill valve (16) and the spill valve seat portion (37) shown in FIG. 1 come into contact with each other at high speed, but the impact causes the spill valve (16) and the armature (17) to be integrated. Try to bounce. However, if the surroundings of the armature (17) are filled with fuel oil, an action of suppressing bounce due to fluid resistance can be obtained. However, if air is mixed around the armature (17), the fluid resistance disappears and the armature (17) bounces, the operation of the spill valve (16) becomes unstable, and the injection pressure becomes unstable. become. Therefore, it is intended to prevent such an unstable operation by properly performing the air bleeding.

[0015]

As described above, according to the present invention, since the plunger has a small diameter portion for leaking the fuel in the pressurizing chamber at the initial stage of injection, the electromagnetic spill valve control type unit is provided. In the injector, it is possible to reduce the NOx by suppressing the injection rate at the initial stage of injection, and a large solenoid etc. such as those that perform two-stage injection are unnecessary,
The effect is that it can be made compact. Moreover, since the additional volume portion is provided in the middle of the fuel passage to the pressurizing chamber, the injection rate can be suppressed more effectively, and the injection volume is adjusted by adjusting the inner volume of the additional volume portion. The effect is that the rate suppression rate can be set appropriately.

[Brief description of drawings]

FIG. 1 is a sectional view of an entire unit injector showing an embodiment of the present invention.

FIG. 2 is a graph showing changes in injection pressure and injection rate of the present invention in comparison with a conventional example.

FIG. 3 is an enlarged vertical sectional view of a main part of a solenoid case.

FIG. 4 is a bottom view showing a solenoid case portion in an enlarged manner.

[Explanation of symbols]

 (3) Plunger (6) Pressurization chamber (15) Fuel passage (16) Spill valve (25) Fuel escape port (26) Small diameter part (28) Additional volume part

Claims (1)

[Claims] 1. An electromagnetic spill valve type unit injector having an electromagnetic spill valve for opening and closing a fuel supply passage communicating with a pressurizing chamber at the tip of a plunger. A small diameter portion that communicates the pressurizing chamber with the fuel escape port was formed in the initial stage of the above, and an additional volume part with a variable actual volume was provided in the middle of the fuel supply passage from the spill valve to the pressurizing chamber. Injector for electromagnetic spill valve control unit.