JPH02161166A - Fuel injection nozzle - Google Patents

Abstract

PURPOSE:To reduce the dispersion of injection quantity during a term of seat throttling in a low lift range by forming the tip part of a nozzle body into a tapered shape to decrease wall thickness, and providing the tip part with plural nozzles whose diameters are established to be smaller. CONSTITUTION:A fuel injection nozzle 30 is composed of a nozzle body 2 and a needle valve 7 which is slidably accommodated in its inside. The nozzle body 2 is formed with a sack part 9 and a body seat face 10 at its outer end, and the body seat face 10 is provided with plural nozzles 32. The needle valve 7 is formed with a needle seat face 11 which is seated in the body seat face 10 to open and shut each nozzles 32 on its periphery. In this case, the nozzle body 2 is formed into a shape tapering toward a tip part 31 to decrease the wall thickness of the tip part 31. The nozzles 32 are severally composed of a pair of a main nozzle 33 and an auxiliary nozzle 34 which are established to be smaller in their diameter and located in mutually parallel at upper and lower positions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel injection nozzle for a diesel engine, and particularly to a fuel injection nozzle called a suckless type among hole-type nozzles.

[Prior Art] Conventionally, direct injection type diesel engines have been developed, for example, by Utility Model Application No. 54-112918 or No. 57-150288.
Fuel injection valves equipped with hole-type nozzles, such as those disclosed in No. 1, are mainly used. With this hole-type nozzle, various spray properties can be obtained depending on the angle, number, etc. of the nozzles. There are two types of hole-type nozzles, the so-called sack type and the sackless type.While the latter has the advantage of less leakage of fuel, it has the following problems.

These problems will be explained below based on FIGS. 9 to 13.

Figure 9 shows the conventional sackless type (or V C
O (Valve Covered 0riffice)
Figure 1 is a cross-sectional view of the fuel injection nozzle of the type (type) showing the closed state.
Figure θ is an enlarged sectional view of the main part of the tip, showing the closed state, and Figs. This figure shows the sequential opening states of the valves as they are lifted, and the penetration (see from the axial direction of the needle valve 7) is shown at the top of each figure.
This figure shows the distance traveled by the fuel injected from the nozzle 6 within the combustion chamber.

The fuel injection nozzle 1 shown in FIG. 9 has a nozzle body 2.
, a fuel passage 3 communicating with an injection pipe from a fuel injection pump (both shown as paths shown), a fuel reservoir chamber 4 and a guide hole 5 communicating with this fuel passage 3. A plurality of nozzles 6 are formed at the tip. Inside this guide hole 5 is a needle valve 7.
is slidably stored, and the pressure spring (path shown)
The needle valve 7 is urged in the direction of the nozzle 6 by the urging force, and the nozzle 6 is closed at a predetermined pressure. and.

The pressure of the high-pressure fuel pumped through the fuel passage 3 acts on the pressure stage 8 of the needle valve 7, and the needle valve 7 resists the biasing force of the pressure spring.
By lifting the fuel, fuel is injected from the nozzle 6.

As shown in FIG. 10, the nozzle body 2
A sack portion 9 consisting of an opening formed by a machined hole and a body seat surface 10 formed obliquely upward from the sack portion 9 are provided at the tip thereof. The jet nozzle 6 is provided so as to open into the body seat surface 10.

The needle seat surface 11 of the needle valve 7 is seated on the body seat surface 10 under a predetermined pressure due to the biasing force of the pressure spring, so that the nozzle 6 can be opened and closed. Further, the tip portion of the needle valve 7 from the needle seat surface 11 to the tip 12 is located at the sack portion 9 of the nozzle body 2.
In view of this, the internal volume of this sack portion 9 (so-called sack volume) is made as small as possible to prevent fuel from dripping.

Further, the tip portion 13 of the nozzle body 2 is formed into a conical shape.
Since the wall thickness of is constant, the axis center angle (
Angle formed by each nozzle 6 with respect to the axis of the needle valve 7)Al
, A2, the flow of high-pressure fuel differs between each injection port 6. Furthermore, the wall thickness of the nozzle 6 portion is also substantially different. Therefore, since the axial center angle differs between each nozzle 6, even if the left and right wall thicknesses of the inclined tip 13 are the same and the diameter of the nozzle 6 is the same, the length of the nozzle 6 relative to the diameter is The ratio L/D of the length L is different between one nozzle 6 and the other nozzle 6.

To be more specific, in the state shown in FIG. 10, the left nozzle 6 is in a more horizontal state, and its axial center angle AI is larger than the axial center angle A2 of the right nozzle 6. Comparing the ratio Ll/D at the nozzle 6 on the right side with the ratio L2/D at the right nozzle 6, the ratio Ll/D is larger. Therefore, as shown in the upper part of FIG. In the early stage of valve opening when the lift amount of the nozzle 7 is small, the penetration differs between the nozzles 6.

Furthermore, nozzle holes are formed between each nozzle port 6 and a so-called seat constriction portion 14 formed between the body seat surface 10 and the needle seat surface 11 in the above-mentioned initial valve open state as shown in FIG. Since the inclination angles B1 and B2 of 6 are different for each nozzle 6, the penetration is also different between each nozzle 6. It has been pointed out that in addition to such variations in penetration, there are also large variations in the particle size and injection amount of the injected fuel.

As mentioned above, in the conventional suckless type fuel injection nozzle l, since the face sheet of the needle valve 7 is adopted, the suck volume can be reduced.
There is a problem in that the fuel throttling effect by the seat throttle section 14 is large.

Further, as the needle valve 7 swings left and right at the beginning of the lift, the seat surfaces 1O111 may touch each other at the beginning of the fuel injection, and there is also the problem that the fuel injection state among the nozzles 6 varies greatly. Therefore, it is difficult to achieve uniform injection of fuel at the initial stage of fuel injection as described above, the usage rate of air within the combustion chamber is reduced, there is a problem of smoke generation, and the maximum penetration reaches the inner wall of the combustion chamber. There were problems such as the content of hydrocarbons in the exhaust gas due to

In order to solve these various problems, nozzle body 2
Although an improvement can be seen by making the wall thickness of the tip portion 13 uniformly thin, there is another problem that there is a limit to the mechanical strength of the nozzle body 2, and there is a risk that the nozzle body 2 may be damaged. There is.

FIG. 14 is an enlarged cross-sectional view showing the main part of the tip of a conventional sack-type fuel injection nozzle, a so-called mini-sack nozzle 20, for comparison with the sackless type fuel injection nozzle 1 described above. It is. In the figure, the same parts as in FIGS. 9 to 13 are given the same reference numerals, and the nozzle 6 is located below the body seat surface 10A corresponding to the body seat surface 10.

[Problems to be Solved by the Invention] In view of the above-mentioned problems, the present invention has been developed to solve the problems in accordance with the shape of the combustion chamber, particularly in a fuel injection nozzle of a fuel injection valve that adopts a sackless type among Hall type nozzles. This was done to solve the above-mentioned problems caused by differences in the flow of high-pressure fuel from each nozzle with a set inclination angle. To shorten the sheet squeezing period by the squeezing section. In other words, by making it possible to shift from sheet throttle injection to nozzle throttle injection early from the low lift period of the needle valve, variations in the amount of injected oil during the seat throttle period in the low lift range of the needle valve can be reduced. It is an object of the present invention to provide a fuel injection nozzle that makes it possible to eliminate non-uniformity of penetration among the nozzles or to extend the average penetration.

[Means to solve the problem] That is, the present invention includes a sack portion at the tip.

A nozzle body having a body seat surface and a plurality of nozzles opening to the body seat surface, and a nozzle body that is slidably housed within the nozzle body.

A fuel injection nozzle having a needle valve formed with a needle seat surface that seats on the body seat surface so as to be able to open and close the nozzle, the tip of the nozzle body having a tapered shape or forming a plurality of steps. This fuel injection nozzle is characterized in that the wall thickness is gradually reduced by, for example, a plurality of main and sub-nozzles arranged in upper and lower stages, each of the plurality of nozzles having a smaller diameter.

[Function] In the fuel injection nozzle according to the present invention, the tip portion of the nozzle body is tapered or stepped to gradually reduce the wall thickness of the substantial nozzle portion of the tip portion, and the plurality of Since each of the nozzles is formed from a plurality of nozzles having a smaller diameter, when the needle valve lift is opened/started, the nozzle that is closer to the sack part among the plurality of nozzles having a smaller diameter, for example, the sub nozzle, fuel injection is the mainstream. Then,
As the needle valve lifts, injection from other nozzles of the plurality of nozzles having smaller diameters, such as the main nozzle, begins in earnest, and fuel injection from these multiple nozzles having smaller diameters causes the nozzle to The influence on the penetration due to the ratio L/D of the length L to the diameter of the sheet, the sheet constriction part, or the inclination angle of each nozzle is equalized as much as possible, and variations in penetration, particle size, and injection amount between each nozzle are reduced. In addition to suppressing
It is possible to extend the average penetration.

[Example] Next, a first example of a fuel injection nozzle according to the present invention will be described.
This will be explained based on FIGS. 7 to 7.

However, the same parts as in FIGS. 9 to 14 are given the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 is an enlarged cross-sectional view showing the tip portion of the fuel injection nozzle 30 according to the above embodiment, and FIGS. 2 to 4 are similar to FIGS. 2
This figure shows the successive closing states of the needle valve 7 as the needle valve 7 is lifted.
FIG. 3 is a cross-sectional view of the main part of the tip showing the state of penetration when viewed from the axial direction.

As shown in FIG. 1, the fuel injection nozzle 30 has a tip portion 31 corresponding to the conventional tip portion 13 of the nozzle body 2.
The thickness of the distal end portion 31 is gradually reduced by tapering the conventional distal end portion 13 from near the proximal end toward the distal end. Note that the degree of taper of this tip 31 can be set arbitrarily, and the nozzle 32 corresponding to the conventional nozzle 6 formed in this tip 31 has a diameter approximately equivalent to the diameter of each nozzle 6. A pair of mutually parallel main nozzle ports 33 and sub-nozzle ports 34 are formed in upper and lower two stages so as to have a total diameter of . In other words, the diameter of the main nozzle 33 is Dl, and the diameter of the sub nozzle 34 is D? Then, the diameters D1 and D2 are determined so that the relationship D=DI+D2 holds.

The size relationship between the diameters DI and D2 can be determined depending on the injection characteristics and other conditions to be set.
For example, assume that DI>D2. Furthermore, the number of nozzles into which the conventional nozzle 6 is divided, or the formation positions of the main nozzle 33 and the auxiliary nozzle 34 can be arbitrarily determined.

In the fuel injection nozzle 30 having such a configuration, the wall thickness of the tip portion 31 at the sub-nozzle 34 portion at the more distal end is thinner than the wall thickness at the main nozzle 33 portion at the proximal end. The ratio of the nozzle length to the nozzle diameter of L12/D
2 and L22/D2 are relatively small, and in the initial lift state of the needle valve 7, as shown in FIG.
Since the sub-nozzle 34 performs the same function as the sack part 9, the injection from the sub-nozzle 34 precedes (see the dotted line in the figure). Furthermore, when the needle valve 7 is lifted, the injection from the main nozzle 33 starts from the main part. (See Figure 4)
Similarly, the ratios Lll/DI and L21/Di of the nozzle length to the nozzle diameter of the main nozzle 33 portion are also the same as those of the conventional tip 1.
3. Therefore, from this point of view as well, it is possible to minimize the variation in penetration between the respective nozzles 32 (7).

That is, even if the seat throttle part 14 is formed during the initial lift of the needle valve 7, the influence of the seat throttle part 14 can be relatively reduced, the seat throttle period can be shortened, and the sub-nozzle can be quickly closed. 34 and the main injection port 33, that is, the injection port is throttled.

Therefore, as shown in FIG.
Referring to the relationship of penetration to side pressure or time, it can be seen that in the conventional standard fuel injection nozzle 1, the range between maximum and minimum penetration is large and the variation in penetration is large (solid line in the figure). , it can be seen that in the fuel injection nozzle 30 according to the present invention, the range between these is kept narrow (dotted line in the figure).

Further, as shown in FIG. 6, referring to the relationship of average penetration to pressure or time on the fuel injection nozzle 30 side, in the conventional standard fuel injection nozzle l, when the lift amount of the needle valve 7 is small, In other words, the lower the pressure on the nozzle side, the smaller the penetration, and the higher the pressure, the longer the penetration.

In addition, in the so-called conventional sack type mini-sack nozzle 20 (Fig. 14), as shown by the imaginary line in the figure, the ratio L/D of the nozzle length to the nozzle diameter and the influence of the sheet throttle part are small. Second, the penetration changes little with respect to fluctuations in pressure on the nozzle side.

In contrast, with the fuel injection nozzle 30 according to the present invention, it is possible to obtain higher values than the average penetration of the conventional nozzle of 1.20, and the penetration changes the most with respect to pressure fluctuations on the nozzle side. The ratio can be reduced (see dotted line in the figure).

Further, as shown in FIG. 7, the relationship between the lift amount of the needle valve 7 and the hydraulic flow rate is referred to.

It can also be seen that in the present invention, the fluctuation in the hydraulic flow rate is smaller than in the conventional standard fuel injection nozzle l.

Next, in the present invention, instead of tapering the tip 31, a first step 41 and a second step 42 are formed at the tip 40 of the nozzle body 2, as shown in FIG. By forming the main nozzle 33 and the sub nozzle 34 in the first stage part 41 and the second stage part 42, respectively,
It is possible to achieve the intended purpose.

Furthermore, in the present invention, the ratio L/D of the nozzle length to the nozzle diameter for each nozzle at each stage can be made substantially the same by making the needle valve and the nozzle body eccentric with respect to each other.

[Effects of the Invention] As explained above, according to the present invention, the tip of the nozzle body, which is the part where the nozzle is formed, is tapered or stepped, and a plurality of nozzles having smaller diameters are formed at the tip. This makes it possible to suppress as much as possible the influence of the ratio of the nozzle diameter to the nozzle length or the penetration by the seat throttle section, etc., especially at the beginning of the lift of the needle valve, reducing the variation in hydraulic flow rate during the seat throttle period. , it is possible to reduce the variation in penetration between nozzles and extend the average penetration.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of a main part showing a closed state of the injection port of a fuel injection nozzle 30 according to an embodiment of the present invention. Figures 2 to 4 show successive valve opening states as the needle valve 7 is lifted from its closed state (Fig. 2). A cross-sectional view of the main part of the tip showing the state of penetration as seen. Figure 5 is a graph showing the relationship between penetration and pressure on the fuel injection nozzle 30 side or time. Figure 6 is a graph showing the relationship between pressure or time on the fuel injection nozzle 30 side. A graph showing the relationship between average penetration, FIG. 7 a graph showing the relationship between the lift amount of the needle valve 7 and the hydraulic flow rate, FIG. 8 an enlarged sectional view of the main part of another embodiment of the present invention, and FIG. 9 a conventional example. FIG. 1O is an enlarged sectional view of the main part showing the nozzle 6 in the closed state, and FIGS. 11 to 13 are the same and the closed state (FIG. 11). ) to the needle valve 7 as it is lifted, and at the top of each figure is a cross-sectional view of the main part of the tip showing the state of penetration as seen from the axial direction of the needle valve 7. The figure shows a conventional mini sack nozzle 40
FIG. 1. Fuel injection nozzle 2. Nozzle body 3. 1. Fuel passage 4, Fuel reservoir chamber 5, Guide hole 6, Nozzle a, Needle valve 8, Pressure stage 9, Sack portion 10, IOA, Body Seat surface 11, Needle seat surface 12, Point 13, Tip 14 of nozzle body 2, Seat constriction section 20, Mini sack nozzle 30, Fuel injection Nozzle 31, . . . Tip 32, . . . Nozzle 33, . . . Main nozzle 34, . , , tip portion 41 , , first step portion 42 , , second step portion A1 . ,,, the axial center angle A2 of the left nozzle 6. ．． ．． ．． Axial center angle B1 of the right nozzle 6. ．． ．． ．． Inclination angle B2 of the left nozzle 6. , , Inclination angle of the right nozzle 6 , , Diameter Dl of the nozzle 6 , , Diameter D2 of the main nozzle 33 . , , Diameter of the sub-nozzle 34 , Length of the nozzle 6 Ll , Length of the left nozzle 6 L2 . , Length of the right nozzle 6 Lll, , Length of the left main nozzle 33 L12. ,, Length L21 of the left sub-nozzle 34. , Length L22 of the main nozzle 33 on the right side L22 , Length of the sub nozzle 34 on the right side Patent applicant: Diesel Kiru Co., Ltd.

Claims (1)

[Scope of Claims] A nozzle body having a sack portion formed at its tip, a body seat surface, and a plurality of nozzles opening to the body seat surface; A fuel injection nozzle having a needle valve formed with a needle seat surface that seats on the body seat surface so as to be able to open and close the nozzle, wherein the thickness of the tip of the nozzle body is gradually reduced, and each of the plurality of nozzles is A fuel injection nozzle characterized in that the fuel injection nozzle is formed from a plurality of nozzles each having a smaller diameter.