JPS59183067A - Fuel injection nozzle for diesel engine - Google Patents

Abstract

PURPOSE:To reduce the amount and pressure of injection in the initial period of lift and obtain comparatively quick lift characteristics in the latter period of the lift. CONSTITUTION:A part of high pressure fuel is introduced into the oil pressure chamber 29 at the back side of a free piston 27 from a high pressure fuel path 21 through a communicating path. When the amount of lift of a needle valve 14 becomes larger than DELTAl1+DELTAl2, the outer peripheral surface of the free piston 27 blocks a side hole 30a, therefore, the communicating path 30 is interrupted. According to this method, the high pressure fuel is not supplied to the oil pressure chamber 29 thereafter and the fuel is only flowed out of the oil pressure chamber 29 after being choked by an oil pressure regulating hole 34. Accordingly, the free piston 27 and the needle valve 14 are lifted comparatively quickly and arrive at the maximum lift (l). According to this method, the amount and pressure of injection may be increased in the latter period of injection.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a fuel injection nozzle for a diesel engine.

<Prior art> As a conventional fuel injection nozzle, for example,
It is known whether it was described in Publication No. 2918).

To explain this, referring to FIG. 1, the tip of the nozzle body 1 has a hollow, substantially conical shape, and a nozzle seat portion 2 is formed on the inner wall surface. Also, nozzle body 1
A plurality of nozzle holes 3 are formed at the tip of the nozzle seat portion 2 . Nozzle: A needle valve 4 is housed in the D 1, and at the tip of the needle valve 4 there is a substantially Ifl that seats on the nozzle seat 2 and closes the nozzle hole 3.
A conical needle face portion 5 is formed. Also,
A pressure stage 6 is formed in the needle valve 4, and the pressure in the oil reservoir 7 acts on the pressure stage 6.

Here, the pressure of the fuel supplied to the oil sump 7.

As the force increases, the pressure of the fuel acts on the pressure stage 6 and pushes the needle/<lube 4 upwards in the figure. Then, a gap is created between the nozzle seat part 2 and the needle face part 5, and fuel flows into the nozzle body 1 through this gap.
It flows toward the tip and is injected from the injection hole 3 into the combustion chamber.

However, in such conventional fuel injection nozzles, the lift of the needle valve changes rapidly, and the area of the flow path formed in the gap between the nozzle seat and the needle face increases rapidly. The initial injection rate is high and a large amount of fuel is injected during the ignition delay period. Therefore, a large amount of fuel burns rapidly at the same time as ignition.
Increase in Noxfi degree in exhaust gas due to rapid temperature rise,
There was a problem in that the rapid pressure rise caused an increase in combustion noise.

Therefore, as disclosed in SAE paper 810479, a free piston is slidably provided in the nozzle holder, a hydraulic chamber is formed on the back side of the free piston, and high-pressure fuel for injection is supplied to the hydraulic chamber. A part of the free piston is guided, and an adjusting rod that moves integrally with the free piston is provided on the tip side of the free piston, and this adjusting rod is opposed to the back side of the needle valve with a predetermined gap maintained. There is.

According to this, when the needle valve starts to lift,
Since it comes into contact with the adjusting rod and thereafter lifts while pushing up the free piston, the change in lift becomes gradual.

However, although this method can reduce the injection amount at the initial stage of rift 1, it is only limited to lift regulation, so the injection pressure cannot be reduced, and there is still room for improvement. In addition, since the ref i and speed are regulated even in the later stages of lift, there is a problem that the injection period becomes longer and smoke worsens in the high rotation/high load range.

<Object of the Invention> In view of the above-mentioned actual situation, the present invention provides a fuel injection nozzle that can reduce both the injection amount and the injection pressure in the early stage of lift, and can obtain relatively quick lift characteristics in the latter stage of lift. The purpose is to

<Structure of the Invention> For this reason, the present invention forms a hydraulic chamber behind the needle valve, and communicates this hydraulic chamber with a hydraulic source having a lower pressure than the high-pressure fuel passage for injection and the high-pressure fuel hydraulic pressure for injection. Further, a valve device is provided that shuts off a communication path between the high pressure fuel passage and the hydraulic chamber when the lift amount of the needle valve exceeds a predetermined value.

<Example> Examples will be described below.

In FIG. 2, a nozzle seat portion 12 and a nozzle hole 13 are formed in a nozzle body 11. Nozzle body 11
A needle valve 14 is slidably housed inside, and the needle valve 14 is formed with a needle face portion 15 and a pressure stage 16.

The pressure in the oil reservoir 17 between the nozzle body 11 and the needle valve 14 acts on the blemish intermediate stage 16.

The nozzle body 11 is joined to the tip of the nozzle holder 1 through a distance piece 19, and the nozzle nand 20
The maximum lift (β) of the needle valve 14 is regulated by the distance piece 19. A high pressure fuel passage 2 is connected to the nozzle holder 18, distance piece 19 and nozzle body 11.
1 is formed, and a fuel injection pump 22 shown in FIG.
The high-pressure fuel supplied from the high-pressure fuel vibrator 23 is guided to the oil sump 17.

A bushing rod 24 is fixed to the back of the needle valve 14, and a valve spring 26 is interposed between the bushing rod 24 and a spring retainer 25 locked to the nozzle holder 18 side.

A free piston 27 is slidably inserted into the nozzle holder 18, and an adjusting rod 28 is provided on the distal end side of the free piston 27 to abut thereon and move integrally therewith. The adjusting rod 28 is guided by the spring retainer 25, and the adjusting rod 28 is guided by the spring retainer 25.
A locking portion 28a formed at an intermediate portion of the adjusting rod 28 is locked to the spring retainer 25, so that the most F movement position of the adjusting rod 28 is regulated.

In this state, the tip of the adjusting rod 2B faces the Puno Schrodt 24 of the 14 needle valves through a predetermined gap Δβ1 (<β).

A hydraulic chamber 29 is formed on the back side of the free piston 27. The hydraulic chamber 29 has a side hole 30a formed in its inner peripheral surface.
It communicates with the high-pressure fuel passage 21 through a communication passage 30 that includes. Here, the lift amount of the free piston 27 is Δ7!2
(<(1-ΔlI) or more, the side hole 30a is closed by the outer peripheral surface of the free piston 27. Therefore, the side hole 30a and the free piston 27
A valve device is constructed. Further, the side hole 30a is formed to have a small diameter and also functions as a diaphragm.

Further, the hydraulic chamber 29 has another communication port 31.

A check valve 33 biased by a spring 32 is provided in the communication port 31, and a hydraulic pressure adjustment hole 34 is bored in the check valve 33. A fuel pipe 35 (not shown in FIG. 3) that guides the fuel inside the pump housing of the fuel injection pump 22 is connected to this communication port 31.

The space between the needle valve 14 and the spring retainer 25 and the space between the spring retainer 25 and the free piston 27 communicate with a fuel tank (not shown) through a spill passage 36.

Next, the action will be explained.

High pressure fuel is supplied to the high pressure fuel passage 21 by the fuel injection pump 22.
When the fuel pressure in the oil reservoir 17 reaches the valve opening pressure, the needle valve 14 starts the rift 1-, and Δll
When it is lifted by I, it comes into contact with the adjusting nose 28.

As a result, from now on, adjusting 11sol" 2B
The free piston 27 is lifted while being pushed up through the .

Here, a part of the high-pressure fuel is guided from the high-pressure fuel passage 21 to the hydraulic chamber 29 on the back side of the free piston 27 via the communication passage 30, and the high-pressure fuel guided to the hydraulic chamber 29 is adjusted to adjust the hydraulic pressure. Since the oil flows out through the hole 34 into the pump housing of the fuel injection pump 22, approximately a predetermined oil pressure is generated in the oil pressure chamber 29. Therefore, the free piston 27 rises against the hydraulic pressure in the hydraulic chamber 29, and as a result, the lift of the needle valve 14 is suppressed, thereby reducing the initial injection amount. Furthermore, since a portion of the high-pressure fuel for injection flows out, the initial injection pressure is also reduced.

Then, the lift it of the needle valve 14 is Δ11+Δ
When the lift amount of the free piston 27 is ΔI!2 or more, the outer circumferential surface of the free piston 27 is in the side hole 30.
The communication path 3o is cut off due to the cold temperature.

As a result, high-pressure fuel is no longer supplied to the hydraulic chamber 29 from now on, and the fuel only flows out from the hydraulic chamber 29 while being throttled by the hydraulic pressure adjustment hole 34. Therefore, the free piston 2 is closed and the needle valve 14 is released relatively quickly. to reach the maximum lift l. Therefore, both the injection amount and the injection pressure can be increased in the latter stage of injection.

In this embodiment, the internal pressure of the pump housing of the fuel injection pump 22 is guided to the communication port 31 of the hydraulic chamber 29, but the communication port 31 may be connected to the spill passage 36, in other words, the high pressure fuel It is sufficient to communicate with a hydraulic pressure source with a pressure lower than that of hydraulic pressure.

In addition, the check valve 33 is not necessary when the oil pressure supplied to the communication passage 31 can be secured to a certain extent or when the oil pressure adjustment hole 34 can be formed to a certain extent large.
As shown in FIG. 4, it is sufficient to simply provide a hydraulic pressure adjustment hole 34. However, if necessary, a return spring 37 is provided for the free piston 27.

In addition to the configuration of the embodiment shown in FIG. 2, the embodiment shown in FIG. The cross-sectional area of the fuel flow path formed between the tapered fuel flow control section 38 and the needle valve 14 is made variable in accordance with the lift amount of the valve 14. According to this, the initial injection rate can be suppressed more actively.

In the embodiment shown in FIG. 6, the locking part 28a of the embodiment shown in FIG. Therefore, in this case, when the needle valve 14 lifts, the hydraulic pressure in the hydraulic chamber 29 immediately comes into play via the free piston 27, and the lift speed of the needle valve 14 is limited.

Even in this case, almost the same effect can be obtained.

In this embodiment, the needle valve 14, the needle valve 24, the adjusting rod 28, and the free piston 27 may be formed integrally. Further, the hydraulic chamber 29 may be formed directly on the back side of the needle valve 14 without providing the free screw 1-27 or the like.

In the following, an example of a ball nozzle has been shown, but it goes without saying that the present invention is also applicable to a throttle nozzle and a pin I-nozzle used in a pre-chamber type diesel engine.

<Advantageous Effects of the Invention> As explained above, according to the present invention, it is possible to reduce the initial injection amount by suppressing the rapid lift change at the initial stage of the lift of the needle valve, and also to release a part of the high-pressure fuel for injection. can reduce the initial injection pressure, which reduces the NO.
x and engine noise can be reduced. Also,
In the latter half of the lift, the lift speed is relatively accelerated to shorten the injection period and increase the injection pressure, which prevents smoke from worsening at high speeds and high loads, and is also advantageous in terms of output.

Therefore, it is particularly effective in improving the combustion of small, high-speed diesel engines.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the tip of the fuel injection nozzle showing a conventional example;
FIG. 2 is a sectional view of a fuel injection nozzle showing one embodiment of the present invention, FIG. 3 is a piping system diagram of the fuel injection nozzle and fuel injection pump of the same L, and FIGS. 4, 5, and 6. Each figure is a sectional view of a fuel injection nozzle without showing other embodiments. 11... Nozzle boulder 13... Nozzle hole 14.
・・2、-Tor valve １８・・・Nozzle boulder
21... High pressure fuel passage 22... Fuel injection pump 26... Halve spring 27... Free piston 28... Adjusting rod 29.
...Hydraulic chamber 30...Communication path 30a...Side hole
31...1 communication 34...Hydraulic pressure adjustment hole 36...
・Spill passage patent applicant Nissan Motor Co., Ltd. agent Patent attorney Fujio Sasashima Figure 3 35 Figure 4 Mori 1 / 5th 1 1

Claims (1)

[Claims] Fuel injection for a diesel engine comprising a nozzle body with a nozzle hole formed at its tip, and a needle valve that is slidably housed within the nozzle body and is lifted by high-pressure fuel oil pressure for injection to inject fuel from the nozzle hole. In the nozzle, a hydraulic chamber is formed behind the needle valve, and this hydraulic chamber is communicated with a high-pressure fuel passage for injection and a hydraulic pressure source lower than the high-pressure fuel oil pressure for injection, and the lift amount of the needle valve is A fuel injection nozzle for a diesel engine, comprising a valve device that shuts off a communication path between the high pressure fuel passage and the hydraulic chamber when the pressure exceeds a predetermined value.