JPS63189669A - Fuel injector for diesel engine - Google Patents

Abstract

PURPOSE:To suppress NOx content in the high revolution region and reduce noise by forming at least a part of a fuel feeding passage leading to an injection nozzle from a fuel injection pump into two parallel passages having different length and diameter. CONSTITUTION:A fuel injection pump 1 and a fuel injection nozzle 2 are connected through a fuel feeding passage 3 consisting of two passages 4 and 5 in parallel. The length of one passage 4 is made longer than that of the other passage 5, and the diameter is made larger. Therefore, each of the pressure wave and injection rate of the supplied fuel in the fuel injection nozzle in the high revolution region is an engine represents the injection characteristic in two stages, and the nitrogen oxide in exhaust gas and noise can be reduced.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a fuel injection device for a diesel engine that improves the injection characteristics of a fuel injection nozzle to reduce nitrogen oxides in exhaust gas and noise. It is.

(Prior Art) As a conventional technology of this kind, as the fuel supply pressure in the fly fuel injection nozzle increases, the fuel flows through the nozzle opening formed between the needle pulp and the nozzle seat and is discharged from the needle. In a diesel engine fuel injection method that changes with the lift amount of pulp, the fuel is increased in an initial state as the needle pulp lift (13) increases, then is decreased, and then increased to reach an increased discharge amount. There is something. (Japanese Unexamined Patent Publication No. 59-190470) In other words, the nozzle hole area is changed depending on the lift amount of the needle pulp to provide two-stage injection characteristics.
When the engine rotates at high speeds, the lift amount of the needle pulp changes very quickly, so the nozzle opening area becomes almost uniform, making it impossible to obtain the two-stage injection characteristics described above, which is expected to reduce nitrogen oxides. It is also possible to improve the injection characteristics of the fuel injection nozzle by supplying fuel out of phase with two fuel injection pumps, but this would require multiple fuel injection pumps. Therefore, there was a problem of increased costs.

(Objective of the Invention) The present invention provides a fuel injection device for a diesel engine that can be expected to reduce nitrogen oxides by obtaining two-stage injection characteristics of the fuel injection nozzle even in the high rotational range of the engine, and that is simple in structure and inexpensive. The purpose is to provide the following.

(Structure of the Invention) To achieve the above object, the present invention provides that, in a fuel supply passage leading from a fuel injection pump to a fuel injection nozzle of a combustion chamber, at least a part of the fuel supply passage is connected to a first passage having a large diameter. and a second passage with a small diameter, and the first passage is made longer than the second passage by a predetermined length (Example) The present invention will be described in detail below based on the drawings. .

(1) is a fuel injection pump, (2) is a fuel injection nozzle in the combustion chamber, and (3) is a fuel supply passage arranged from the fuel injection pump (1) to the fuel injection nozzle (2).

The fuel supply passage (3) has at least a portion of the first passage having a large diameter.
A parallel passage consisting of a passage (4) and a second passage (5) with a small diameter is formed, and the first passage (4) has a U-shaped bend part (4a) and the second passage (5) has a U-shaped bend portion (4a). ) than the predetermined length C
1) is longer.

This predetermined length C1> is such that the injected fuel is in each of the passages (4),
(5) It can be determined by the desired crank angle (α) of the difference between the leading pressure wave and the lagging pressure wave at the velocity (V) at which the pressure wave propagates in the engine and the desired engine speed (n).

For example, when the fuel is light oil, the propagation velocity v-=1400
m/s, the desired engine speed n = 250 Qrpm, and the desired crank angle α = 2°. Also, the ratio of the fuel supply amount to the total injection of the first passage (4), which is the main injection, is determined by the diameter of the passage. Depending on the size, it can be trimmed 8 times.

Next, looking at the movement of pressure waves at each part of the fuel supply passage (3), the pressure waves at each point A, B, and C shown in FIG. Third. This is represented by the graph shown in FIG.

That is, since the pressure wave at point A of the fuel supply passage (3) is before the passage branches, it shows one large waveform as shown in Fig. 2, and at point B, the passage branches as shown in Fig. 3. After that, the waveform immediately before entering the fuel injection nozzle (2) is shown, and the pressure wave in the second passage (5) with a short passage length (5) and the long first passage (4) are shown. (
The pressure waves in 4) are shown superimposed on each other, and the latter is shown to be faster at time (1).
I can see that you are late. Here, this time (1)
It is desirable to match the time required from fuel injection from the nozzle to ignition.

At the 0 point inside the nozzle, two pressure waves overlap as shown in Figure 4, showing a so-called two-stage injection characteristic with a small waveform at first and a large waveform later. The graph of the accompanying injection rate also has a so-called trailing waveform that is substantially similar to the pressure wave shown in FIG.

As a result, ignition is performed by a small amount of fuel supplied from the second passage (5), and combustion is gradually started by a large amount of fuel supplied from the first passage (4) with a delay of time (1) after the ignited fuel. proceed.

Therefore, explosive combustion does not occur, so the amount of NOX (nitrogen oxides) that is generated in large quantities at high temperatures and high pressures is suppressed, and the noise associated with explosions within the combustion chamber is also reduced.

In addition, in the case shown in Fig. 1, a parallel passage is formed over almost the entire area of the fuel supply passage (3), but even if the part just before the U-shaped bend part (4a) is made into a single passage, the fuel The first and second passages (4) and (5) before entering the injection nozzle (2).
It is good to have them merge.

(Effects of the Invention) According to the present invention, at least a part of the fuel supply passage from the fuel injection pump to the fuel injection nozzle is formed into a parallel passage consisting of two passages having different lengths and thicknesses. The pressure waves and injection rate of the supplied fuel within the fuel injection nozzle in the high rotation range of the engine exhibit a two-stage injection characteristic, which can be expected to reduce nitrogen oxides in exhaust gas and noise. In addition, unlike conventional methods, there is no need to modify the fuel injection pump or nozzle, so the desired purpose can be achieved at low cost.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing one embodiment of the fuel injection device for a diesel engine according to the present invention, and FIGS. 2 to 4 are diagrams showing graphs of pressure waves of supplied fuel at different parts of the fuel supply passage. It is. (1) Fuel injection pump (2) Fuel injection nozzle (3) Fuel supply passage (4) First passage
(5)...Second Passage Patent Applicant: Takashi Mihara, Patent Attorney, Mazda Motor Corporation (1 other person) Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] In the fuel supply passage leading from the fuel injection pump to the fuel injection nozzle of the combustion chamber, at least a part of the fuel supply passage is a parallel passage consisting of a first passage with a large diameter and a second passage with a small diameter, and A fuel injection device for a diesel engine, characterized in that a passage is longer than a second passage by a predetermined length.