JPS60119361A - Double step opening pressure fuel injection valve - Google Patents

Abstract

PURPOSE:To suppress fuel noise under low speed thus to reduce engine noise and to produce required horse power under high speed, by maintaining the injection rate low and high respectively under low and high speed of engine. CONSTITUTION:Under low speed of engine, a portion of pressure feed fuel will leak through the pressure leak path 41 of central plunger 34 to prevent the pressure in injection tube from reaching to such level as necessary for lifting more than initial lift interval L. While under low engine speed, lift of nozzle needle 25 will cause choking of the lower end opening of pressure leak path 41 by means of first movable spring seat 29 in the upstream of nozzle needle 25. Consequently, said fuel leak will complete through the pressure leak path 41 resulting in further increase of pressure in the injection tube.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a two-stage valve opening pressure fuel injection valve, and an object of the present invention is to obtain a fuel injection valve that has different injection rate waveforms at low speed and high speed.

In diesel engines, it is necessary to delay injection timing in order to reduce nitrogen oxide emissions. However, if the injection timing is simply delayed, the output will be insufficient and other harmful components such as hydrocarbons will be generated significantly, making it unusable.

Therefore, it is necessary to shorten the injection period by increasing the fuel injection rate to obtain the necessary output and reduce harmful exhaust components. However, on the other hand, increasing the injection rate is relatively Accompanied by shortening of injection time.

For this reason, there is a problem in that most of the fuel is injected during the ignition delay period that is always inherent in diesel engine combustion, and that it ignites all at once, leading to rapid combustion of the fuel and increased combustion noise. This was felt as a loud noise, especially during idling.

Conventionally, in order to solve this problem, a small amount of fuel is injected at the beginning of injection to create a spark, and then main injection is performed, thereby shortening the ignition delay time during main injection and allowing the main injected fuel to burn little by little. A two-stage valve-opening pressure fuel injector is provided.

As shown in FIG. 1, this fuel injection valve is configured such that fuel is fed under pressure from a fuel injection pump (not shown) from an inlet 1 to a fuel passage 2.
. 6
When the initial injection valve opening pressure that overcomes the urging force of is reached,
The nozzle needle 7 resists the biasing force of the nozzle spring 6, moves to an initial lift distance, lifts a certain amount, enters the throttle injection state, and injects fuel from the injection hole 8. After that, the pressure of fuel from the fuel injection pump continues, and the pressure inside the injection pipe further increases, causing the biasing force F (T, the biasing force after the lift of the nozzle spring 6) and the central plunger 10 of the nozzle spring 6 to increase.
The cross-sectional area Ac on the side of the injection pipe, the internal pressure P of the injection pipe, and the cross-sectional area As inside the inflow chamber 5 of the nozzle needle 7 (the cross-sectional area obtained by subtracting the cross-sectional area of the pin portion at the tip of the nozzle needle from the cross-sectional area of the nozzle needle 7). The relationship is P>F/(A s −A c
) (main injection valve opening pressure), the nozzle needle 7 resists the pressing force of the injection pipe internal pressure via the nozzle spring 6 and the central plunger 10, and the central plunger 1
0, the main injection lift interval is lifted by a, and the main injection state is entered and fuel is injected from the injection port 8.

In such a conventional two-stage valve opening pressure fuel injection valve, the pressure of the pumped fuel is applied to the nozzle needle at every step, so even at low speeds with a small pumping amount, the pressure in the injection pipe easily reaches the main injection valve opening pressure. rise above. Therefore, the injection rate waveform becomes as shown by the solid line in FIG. 3 even at low speeds, and as shown by the solid line in FIG. 4 even at high speeds. In other words, the injection rate wave A-shape was almost the same at both low and high speeds.

Therefore, at high speeds, the rapid combustion necessary to produce output is possible, but at low speeds, rapid combustion is also carried out, which is felt as a loud noise, especially during idling.

The present invention was made in view of the above circumstances, and maintains a low injection rate at low engine speeds and a high injection rate at high speeds, suppresses combustion noise at low speeds as much as possible, quiets engine noise, and improves engine speed at high speeds. The objective is to obtain a two-stage open-pressure fuel injection valve that can sometimes obtain the necessary horsepower.

For this purpose, the two-stage open pressure fuel injection valve of the present invention includes a nozzle holter having an inlet connected to a fuel injection pump, and a nozzle holder supported by the nozzle holder and communicating with the inlet at the lower end side. a nozzle body having an injection hole; a nozzle needle that is liftably mounted in the nozzle body and biased by a nozzle spring to a closed position that closes the injection hole; and a nozzle needle integrally attached to the upper end of the nozzle needle. It consists of a movable spring seat that supports the lower end of the nozzle spring and a central plunger that is installed in the nozzle holder so that it can be lifted freely in response to the pressure inside the injection pipe, and the lower end surface of the central plunger is closed. The central plunger is arranged to face the upper end surface of the movable spring seat with an initial lift distance between the movable spring seat and the upper end surface of the movable spring seat in the valve position, and the central plunger has one end opening at the lower end surface of the central plunger and the other end opening at the inflow port. A pressure leak passage communicating with the nozzle needle is provided, and the movable spring seat closes the pressure leak passage when the initial lift of the nozzle needle is completed.

Hereinafter, one embodiment of the present invention will be described with reference to FIG.

In FIG. 2, a nozzle body 22 is supported at the lower end of the nozzle holder 20 via a distance piece 21 from a retaining lever 23.

A nozzle needle 25 is fitted into the internal fitting hole 24 of the nozzle body 22 so as to be vertically movable. An injection hole 26 is formed at the lower end of the nozzle body 22, and an inflow chamber 27 is formed between the injection hole 26 and the lower end of the fitting hole 24. The nozzle needle 25 lifts according to the pressure inside the injection pipe (the fuel pressure inside the inflow chamber 27), and closes the injection hole 26 when it is located at the lowest end. A movable spring seat 29 is attached to the head pin 28 at the upper end of the nozzle needle 25.
is attached, and the movable spring seat 29 is attached to the head pin 28.
The distance piece 21 is also located within a central through hole 30 formed in the distance piece 21. The lower end of the nozzle spring 31 is indicated on the movable spring seat 29, and the nozzle spring 3
1 is located in a spring fitting chamber 32 provided from a substantially middle part in the axial direction to a lower end of the nozzle holder 20, and its upper end is supported by a fixed spring seat 33 provided at the upper end of the spring fitting chamber 32. ing.

The spring fitting chamber 32 is open to atmospheric pressure via a fuel discharge passage (not shown). The nozzle needle 25 is urged by a nozzle spring 31 in a direction to close the injection hole. A central plunger 34 is fitted inside the nozzle holder 20 so as to be able to move up and down, and the central plunger 34 has a larger diameter on the upper end side than the lower end side from the approximately middle part, and has a large diameter part 34a and a small diameter part. A flange-shaped stopper 35 is provided at the boundary with the portion 34b, and a flange-shaped second movable spring seat 36 is provided at the lower end side of the small diameter portion 34b.

The central plunge splint 34 has its large diameter portion 34a inserted into the fitting hole 37 of the nozzle holder 20, its collar-shaped stopper 35 placed inside the second fitting hole 38 of the nozzle holder 20, and its small diameter portion 34b inserted into the fixing hole 37 of the nozzle holder 20. They are respectively located in the spring fitting chamber 32 of the nozzle holder 20 through a through hole 39 in the center of the spring seat 33 .

The central plunger 34 is located inside the nozzle spring 31, and its lower end is connected to the second movable spring seat 36.
It is returned to the rest position by a return spring 40 whose upper end is supported by the fixed spring seat 33. The lower end surface of the central plunger 34 and the upper end surface of the first movable washer 29 at the upper end of the nozzle needle 25 are opposed to each other with an initial lift distance I. Further, the upper end surface of the nozzle needle 25 and the lower end surface of the distance piece 21 are opposed to each other with a main injection lift distance 2 and a.

The central plunger 34 has a top-'/
- A pressure leak passage 41 whose lower end is open is bored, and an orifice 42 is formed on the inner surface of the upper end side of the pressure leak passage 41.
is formed. The pressure leak passage 41 communicates with an inlet 43 provided at the upper end of the nozzle holder 20, and the inlet 43 is connected to a fuel injection pump (not shown 11i) to receive pressure inside the injection pipe. There is. The opening at the lower end of the pressure leak passage 41 is closed by the first movable spring seat 29 at the upper end of the nozzle needle 25 when the nozzle needle 25 is lifted by the initial lift distance. Note that the inlet 43 and the nozzle needle 2
A passage 44 provided in the nozzle holder 20 and a passage 4 provided in the distance piece 21 are connected to the inflow chamber 27 of No. 5.
5 and the nozzle body 22 through a passage 46 provided therein.

Next, the operation of the two-stage valve opening pressure fuel injection valve configured as described above will be explained.

When fuel is pumped from a fuel injection pump (not shown),
The pumped fuel flows from the inlet 43 through passages 44, 45 and 46 into the inlet chamber 27.

8- As the pressurized fuel flows into the inflow chamber 27, the pressure within the injection pipe increases, and this pressure acts on the pressure stage 25b of the nozzle needle 25. Then, the inflow chamber 2
When the pressure inside 7 increases to overcome the biasing force of the nozzle spring 31 (initial injection valve opening pressure), the nozzle needle 2
5 rises against the urging force of the nozzle spring 31, the seat surface of the nozzle needle 25 separates from the seat surface 22a of the nozzle body 22, and fuel is injected from the injection hole 26. At this time, while the nozzle needle 25 is lifted to the initial lift distance, a portion of the pressurized fuel leaks from the pressure leak passage 41 of the central plunger 34, so when the engine is operating at low speed (low load), Similarly, when the fuel pumping speed is slow, the pressure within the injection tube does not reach the pressure required to lift the fuel over the initial lift interval.

Therefore, as shown by the dotted line in Figure 3, the injection rate waveform at low speed is low and the injection time is long, so the fuel injection state is the same as throttle injection in the conventional two-stage open pressure fuel injection valve. become. Therefore, combustion becomes slow, and the generation of combustion noise can be suppressed, especially when noise is a concern, such as during idling operation.

Also, when the fuel pumping speed is high, such as when the engine is operating at high speed (high load), the pumping amount becomes extremely large compared to the leakage amount, so the pressure inside the injection pipe should be lifted by the initial lift interval. can reach the necessary and sufficient pressure. Therefore, the opening at the lower end of the pressure leak passage 41, which corresponds to the lift of the nozzle needle 25, is closed by the first movable spring seat 29 at the upper end of the nozzle needle 25.

Therefore, the leak of fuel through the pressure leak passage 41 ends, and the pressure inside the injection pipe can further increase. This state is similar to the conventional two-stage valve opening pressure fuel injection valve, and when the injection pipe internal pressure P rises to P>F/(As-A, c) (main injection valve opening pressure), the nozzle needle 25 resists the sum of the pressing force due to the pressure inside the injection pipe via the nozzle spring 31 and the central plunger 34, and lifts with the central plunger 34 by the main injection lift interval La to enter the main injection state and open the injection hole. Fuel is injected from 26.

Therefore, the injection rate waveform at high speed is the same as the conventional waveform with throttle injection timing and main injection timing, as shown by the dotted line in FIG. 4, making it possible to obtain the output required at high speed.

In the above embodiment, the nozzle type is a throttle nozzle, but the nozzle type is not limited to this, and it goes without saying that a hole nozzle may also be used.
Various changes may be made without departing from the spirit of the invention.

As described above, according to one aspect of the present invention, the injection rate waveform can be changed between low speed and high speed, thereby making it possible to reduce noise at low speed and secure the output at high speed. Furthermore, according to the present invention, when the nozzle needle 25 descends at the end of fuel pumping, the nozzle needle 25 descends together with the central plunger 34 during the main injection lift interval La, and the nozzle needle 25 descends together with the central plunger 34 during the main injection lift interval La. Interval 1. Between the pressure leak passage 4
Since the lower end opening of No. 1 is opened and only the nozzle needle 25 is lowered, the internal pressure of the injection pipe decreases rapidly via the pressure leak passage 41. Therefore, the nozzle needle 25 can be rapidly closed by the force of the nozzle spring alone. This improves the sharpness of the injection and completely prevents the generation of harmful components in the exhaust gas. This is because the conventional two-stage open-pressure fuel injection valve has an injection rate waveform that is nearly symmetrical as shown by the solid line in Figures 3 and 4, and the a and mouth portions of that waveform occur, resulting in the injection rate. It also has the effect of resolving the disadvantages of not being able to completely prevent the generation of harmful components in exhaust gas due to poor cutting quality.

[Brief explanation of drawings]

Figure 1 is a longitudinal sectional view of a conventional two-stage open pressure fuel injection valve;
FIG. 3 is a longitudinal sectional view showing an embodiment of the present invention, FIG. 3 is an injection rate waveform diagram of the present invention and the conventional technique at low speed, and FIG. 4 is an injection rate waveform diagram of the present invention and the conventional technique at high speed. 20... Nozzle holder, 22... Nozzle body. 25... Nozzle needle, 26... Injection hole, 29...
...Movable spring seat, 31...Nozzle spring, 34...Central plunger, 41...Pressure leak passage, 43
...Inflow Lt- Oral agent Patent attorney Toshihiko Watanabe? 8 Kaisho GO-119361 (5) Figure 3 Figure 4

Claims (1)

[Claims] 1. A nozzle holder having an inlet connected to a fuel injection pump, a nozzle body supported by the nozzle holder and having an injection hole communicating with the inlet on the lower end side, and a liftable part inside the nozzle body. A nozzle needle is attached and biased by a nozzle spring to a closed position that closes the injection hole, and a movable needle is attached to the upper end of the nozzle needle so as to be able to lift together with the nozzle needle and supports the lower end of the nozzle spring. It consists of a spring seat and a central plunger that is installed in the nozzle holder so that it can be lifted freely in response to the pressure inside the injection pipe, and the lower end surface of the central plunger is connected to the upper end surface of the movable spring seat in the valve closing position during the initial lift. The central plunger is provided with a pressure leak passage whose one end opens at the lower end surface of the central plunger and whose other end communicates with the inflow port, and the central plunger is provided with a pressure leak passage which opens at the lower end surface of the central plunger and communicates with the inflow port, A two-stage open pressure fuel injection valve, characterized in that the movable spring seat is configured to close the pressure leak passage when completed.