JP2750715B2 - Fuel injection nozzle - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel injection nozzle of a diesel engine, and more particularly to a fuel injection nozzle called a suckless type among hole type nozzles.

2. Description of the Related Art Conventionally, a direct injection type diesel engine mainly includes a fuel injection valve equipped with a hole type nozzle as disclosed in Japanese Utility Model Laid-Open No. 54-112918 and Japanese Utility Model Laid-Open No. 57-150268. Used. In this hole type nozzle, various spray properties can be obtained according to the angle and number of the nozzles. The hole type nozzle includes a sock type and a suckless type. The latter has an advantage in that fuel leakage is small, but has the following problems.

These problems will be described below with reference to FIGS. 9 to 13.

Fig. 9 shows the conventional suckless type (or VCO
(Valve Covered Oriffice type) fuel injection nozzle is shown in a cross-sectional view, showing a closed state. FIG. 10 is an enlarged cross-sectional view of the main part of the distal end showing the valve closed state, and FIGS. 11 to 13 are sectional views of the main part of the distal end showing the needle valve 7 from the closed state (FIG. 11). The state of the penetration (the reach distance of the fuel injected from the injection port 6 in the combustion chamber) viewed from the axial direction of the needle valve 7 is shown in the upper part of each figure. Is shown.

A fuel injection nozzle 1 shown in FIG. 9 has a nozzle body 2, a fuel passage 3 communicating with an injection pipe (both not shown) from a fuel injection pump, a fuel reservoir 4 communicating with the fuel passage 3, and a guide. Hole 5, multiple nozzles 6 at the tip
Is formed. A needle valve 7 is slidably housed in the guide rail 5, and the needle valve 7 is urged in the direction of the nozzle 6 by the urging force of a pressure spring (not shown), and the nozzle 6 is closed at a predetermined pressure. It is. Then, the pressure of the high-pressure fuel that has been pressure-fed through the fuel passage 3 acts on the pressure stage 8 of the needle valve 7 to lift the needle valve 7 against the urging force of the pressure spring. 6 to inject fuel.

Then, as shown in FIG.
At the front end thereof, there is provided a sack portion 9 composed of an opening formed by a machined hole, and a body seat surface 10 formed diagonally upward from the sack portion 9. The nozzle 6 is provided so as to open to the body sheet surface 10.

The needle seat surface 11 of the needle valve 7 is seated on the body seat surface 10 at a predetermined pressure by the urging force of the pressure spring, so that the injection port 6 can be opened and closed. Further, the tip portion of the needle valve 7 from the needle seat surface 11 to the point 12 faces the sack portion 9 of the nozzle body 2, and the internal volume (so-called sack volume) of the sack portion 9 is made as small as possible to allow the fuel to drain. Is to be prevented.

Further, a conical tip portion 13 of the nozzle body 2 is formed.
Since the wall thickness is constant, the axial center angle at each nozzle 6 (the angle formed by each nozzle 6 with respect to the axis of the needle valve 7) A
The flow of the high-pressure fuel due to the difference between A1 and A2 is different between the nozzles 6. In addition, the wall thickness of the nozzle 6 is also substantially different. Therefore, since the axial center angle is different between the nozzles 6, the left and right wall thicknesses of the inclined tip portion 13 are the same, and
Even if the diameter D is the same, the ratio L / D of the length L to the diameter D of the injection port 6 is different between the one injection port 6 and the other injection port 6.

More specifically, in the state shown in FIG. 10, the left orifice 6 is in a more horizontal state, and its axial center angle is
Since A1 is larger than the axial center angle A2 of the right orifice 6, the ratio L1 / D at the left orifice 6 and the ratio L2 at the right orifice 6
When compared with / D, the ratio L1 / D will be larger,
Therefore, as shown in the upper part of FIG. 12, especially in the early stage of the valve opening when the lift amount of the needle valve 7 is small,
The penetration differs between the nozzles 6.

Further, nozzles formed between the so-called seat throttle portions 14 formed between the body seat surface 10 and the needle seat surface 11 and the respective nozzles 6 in the initial valve opening state as shown in FIG. Since the inclination angles B1 and B2 of the nozzles 6 are different in each of the nozzles 6, the penetration
Vary between. It is pointed out that, together with such a variation in the penetration, the particle size and the injection amount of the injected fuel also vary greatly.

As described above, in the conventional suckless fuel injection nozzle 1, the face sheet of the needle valve 7 is employed, so that the suck volume can be reduced. There is a problem that is large. Further, when the needle valve 7 swings right and left in the initial stage of the lift, the seat surfaces 10 and 11 may come into contact with each other in the early stage of the fuel injection, and there is a problem that there is a large variation in the fuel injection state between the respective nozzle holes 6. Therefore, it is difficult to achieve uniform fuel injection in the early stage of the fuel injection as described above, the air usage rate in the combustion chamber is reduced, the problem of generation of smoke, and the maximum penetration reaches the inner wall of the combustion chamber. There was a problem of the content of hydrocarbons in the exhaust gas.

In order to solve these various problems, an improvement tendency can be seen by forming the tip portion 13 of the nozzle body 2 to have a uniform thickness, but there is a limit in the mechanical strength of the nozzle body 2. There is another problem that the nozzle body 2 may be damaged.

FIG. 14 is an enlarged sectional view showing a main part of a tip of a conventional sack type combustion injection nozzle, that is, a so-called mini sack nozzle 20, for comparison with the sackless type fuel injection nozzle 1 described above. . In the drawings, the same parts as those in FIGS. 9 to 13 are denoted by the same reference numerals, and
The injection port 6 is located below the body sheet surface 10A corresponding to the opening 10.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-described problems, and in particular, in a fuel injection nozzle of a fuel injection valve that employs a suckless type among hole-type nozzles, the shape of a combustion chamber depends on the shape thereof. The purpose of the present invention is to solve the above-mentioned problems caused by the difference in the flow of the high-pressure fuel from each injection port with the set inclination angle, and particularly to the above-described sheet throttle in the range from the idling rotation range to the low-speed rotation range of the engine. The sheet throttle period in the low lift region of the needle valve is reduced by shortening the sheet throttle period by the section, that is, by enabling the transition from the sheet throttle injection to the injection port throttle injection earlier from the low lift timing of the needle valve. The unevenness of the injection oil volume at the same time, and eliminate the non-uniformity between each injection port of the penetration SUMMARY OF THE INVENTION It is an object of the present invention to provide a fuel injection nozzle capable of extending the average penetration.

[Means for Solving the Problems] That is, according to the present invention, there is provided a nozzle body having a sack portion, a body sheet surface, and a plurality of injection ports opened to the body sheet surface at a front end portion. A needle valve having a needle seat surface that is slidably housed and that opens and closes the injection port on the body seat surface, the tip end of the nozzle body having a tapered shape. Or, while gradually reducing the wall thickness by forming a plurality of steps, etc., each of the plurality of nozzles, so as to obtain the same amount of injection required by the conventional single nozzle, A fuel injection nozzle characterized by being formed from a plurality of upper and lower main injection ports and sub injection ports, for example, having a smaller diameter than the single injection port.

[Operation] In the fuel injection nozzle according to the present invention, the tip of the nozzle body has a tapered shape or a stepped shape, whereby the thickness of the substantial injection port at the tip is gradually reduced, and the plurality of nozzles are formed. Each of the orifices was formed from a plurality of orifices having a smaller diameter than the single orifice so as to obtain the required injection amount to be injected by the conventional single orifice, so that the needle valve lift At the start, the injection of fuel from the injection port closer to the sack portion among the plurality of injection ports having a smaller diameter, for example, the fuel injection from the auxiliary injection port occupies the mainstream. Then, along with the lift of the needle valve, the injection from other nozzles of the plurality of nozzles having a smaller diameter, for example, the main nozzle, is in full swing,
Fuel injection from these multiple nozzles with smaller diameters results in a ratio L / L of the length L to the diameter D of the nozzle.
D, it is possible to equalize the influence of the sheet squeezed portion or the inclination angle of each injection port on the penetration as much as possible, suppress variations in the penetration, particle diameter, injection amount between each injection port, and extend the average penetration. It is.

[Embodiment] Next, an embodiment of the fuel injection nozzle according to the present invention will be described with reference to FIGS. However, the same portions as those in FIGS. 9 to 14 are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 is an enlarged sectional view showing a tip portion of the fuel injection nozzle 30 according to the embodiment, and FIGS. 2 to 4 show the valve closed state (FIG. (Fig. 2)
FIGS. 3A and 3B are cross-sectional views of a main part of the tip showing sequential states of opening of the needle valve 7 as the needle valve 7 is lifted, showing the state of penetration as viewed from the axial direction of the needle valve 7 at the top of each figure.

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 tapered from near the base end portion of the conventional tip portion 13 to the tip further. By doing so, the thickness of the tip portion 31 is gradually reduced. The degree of taper of the tip 31 can be arbitrarily set. Further, as the nozzle 32 corresponding to the conventional nozzle 6 formed at the tip 31, it is necessary to spray with a single nozzle 6. A plurality of injection ports having a smaller diameter than the single injection port 6 are formed in a plurality of stages in the axial direction of the nozzle body so as to obtain the same amount as the injection amount. For example, a pair of mutually parallel main injection ports 33 and sub injection ports 34 are formed in two stages, upper and lower. In other words, when the diameter of the main injection port 33 is D1 and the diameter of the sub injection port 34 is D2,
D1 and D2 of the respective diameters so that the injection amount from the main injection hole 33 and the sub injection hole 34 becomes the same as the injection amount from the single injection hole 6.
Shall be determined.

The magnitude relationship between the diameters D1 and D2 can be determined according to the injection characteristics to be set and other conditions.
For example, D1> D2. In addition, the number of the orifices of the conventional orifice 6 is divided into,
These can be arbitrarily determined with respect to the formation position.

In the fuel injection nozzle 30 having such a configuration, the thickness of the distal end portion 31 of the sub-injection port 34 at the more distal end is smaller than the thickness of the main injection port 33 of the base end portion. Of the orifice length to the orifice diameter of L12 / D2 and L22 / D2
In the initial lift state of the needle valve 7, as shown in FIG. 3, the sub-injection port 34 performs the same function as that of the sack portion 9, so that the injection from the sub-injection port 34 is advanced. (See the dotted line in the figure) and the needle valve 7
Is lifted, the injection from the main injection port 33 occupies the main part (see FIG. 4). Similarly, the ratios L11 / D1 and L21 / D1 of the injection port length to the injection port diameter of the main injection port 33 can also be reduced as compared with the conventional tip 13, so from this point also the distance between each injection 32 It is possible to minimize variations in penetration.

That is, even if the seat throttle portion 14 is formed during the initial lift of the needle valve 7, the influence of the seat throttle portion 14 can be relatively reduced, and the seat throttle period can be shortened. 34 and main nozzle 33
In this case, the fuel injection is shifted to the injection port throttle.

Therefore, as shown in FIG.
With reference to the relationship of the penetration with respect to the pressure or time on the side, in the conventional standard fuel injection nozzle 1, the range between the maximum penetration and the minimum penetration is large, that is, the dispersion of the 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 them is narrowed down (dotted line in the figure).

Further, as shown in FIG. 6, referring to the relationship of the average penetration with respect to the pressure or time on the side of the fuel injection nozzle 30, when the lift amount of the needle valve 7 is small in the conventional standard fuel injection nozzle 1, That is, the lower the pressure on the nozzle side, the lower the penetration, and the longer the pressure, the longer the penetration.

Further, in the so-called conventional sack type mini-sack nozzle 20 (FIG. 14), as shown by the phantom line in the figure, the ratio L / D of the nozzle length to the nozzle diameter and the influence of the sheet throttle portion are small. In addition, the change in penetration with respect to the change in pressure on the nozzle side is small.

On the other hand, in the fuel injection nozzle 30 according to the present invention, it is possible to obtain a high value of the average penetration of each of the conventional nozzles 1 and 20. Can be reduced (see the dotted line in the figure).

Further, referring to the relationship between the lift amount of the needle valve 7 and the hydraulic flow rate, as shown in FIG. 7, the present invention also shows that the hydraulic flow rate has less variation than the conventional standard fuel injection nozzle 1. You can see that it is.

Next, in the present invention, instead of forming the distal end portion 31 into a tapered shape, a first step portion 41 and a second step portion 42 are formed at the distal end portion 40 of the nozzle body 2 as shown in FIG. The intended purpose can also be achieved by forming the main injection port 33 and the sub injection port 34 in the first step portion 41 and the second step portion 42, respectively.

Further, in the present invention, the ratio L / D of the nozzle length to the nozzle diameter of each nozzle at each stage can be made substantially the same by eccentrically aligning the needle valve and the nozzle body.

[Effects of the Invention] As described above, according to the present invention, the tip of the nozzle body, which is the portion forming the nozzle, is tapered or stepped, and a plurality of nozzles having a diameter smaller than the tip are formed. In particular, it is possible to minimize the effect of the ratio of the nozzle diameter to the nozzle length or the impact on the penetration due to the sheet throttle section, etc., especially at the intended lift of the needle valve, and the variation in hydraulic flow rate during the sheet throttle period. It is possible to realize the reduction, the variation in the penetration between the injection ports, the extension of the average penetration, and the like.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a main part showing a valve closing state of an injection port portion of a fuel injection nozzle 30 according to an embodiment of the present invention. FIGS. 2 to 4 show the valve closing state (FIG. 2). FIG. 5 is a sectional view of a main part of a tip showing a state of a penetration as viewed from an axial direction of the needle valve 7 in an upper part of each drawing, showing a sequential valve opening state accompanying a lift of the needle valve 7; FIG. 6 is a graph showing the relationship between the pressure or time on the injection nozzle 30 side and the penetration, and FIG. 6 is a graph showing the relationship between the pressure or time on the fuel injection nozzle 30 side and the average penetration, and FIG. 7 is the hydraulic pressure with respect to the lift amount of the needle valve 7. 8 is a graph showing the relationship between the flow rates, FIG. 8 is an enlarged sectional view of a main part of another embodiment of the present invention, FIG. 9 is a longitudinal sectional view of a conventional fuel injection nozzle 1, and FIG. The valve closed state FIGS. 11 to 13 show an enlarged sectional view of the essential part, showing the sequential valve opening state following the lift of the needle valve 7 from the valve closed state (FIG. 11). FIG. 14 is a cross-sectional view of a main part of the distal end showing a state of penetration when viewed from the axial direction of the needle valve 7, and FIG. 14 is an enlarged cross-sectional view of a main part of a conventional mini-sack nozzle 40. DESCRIPTION OF SYMBOLS 1 ... Fuel injection nozzle 2 ... Nozzle body 3 ... Fuel passage 4 ... Fuel storage chamber 5 ... Guide hole 6 ... Injection port 7 ... Needle valve 8 ... Pressure stage 9 ... Sack part 10, 10A ... … Body seat surface 11… Needle seat surface 12… Pointed end 13… Tip of nozzle body 2 14… Sheet squeezing part 20… Mini-sack nozzle 30… Fuel injection nozzle 31… Tip 32… 33 Main jet 34 Sub-jet 40 Tip 41 First stage 42 Second stage A1 Axial center angle of left outlet 6 A2 Axial center of right outlet 6 Angle B1 ... Inclination angle of left outlet 6 B2 ... Inclination angle of right outlet 6 D ... Diameter of outlet 6 D1 ... Diameter of main outlet 33 D2 ... Diameter of auxiliary outlet 34 L ... Outlet 6 Length L1 ... Length of left outlet 6 L2 ... Length of right outlet 6 L11 ... Length of left main outlet 33 L12 ... Left side outlet 3 4 Length L21… Length of right main outlet 33 L22… Length of right auxiliary outlet 34

Claims (1)

(57) [Claims] 1. A sack portion at a front end portion, a body seat surface,
A nozzle body having a plurality of nozzles formed on the body sheet surface and opening to the upstream side of the sack portion; and a body body slidably housed in the nozzle body and capable of opening and closing the nozzles all at once. A single needle valve that forms a needle seat surface capable of closing each injection port by directly seating on a surface of the fuel injection nozzle, wherein the thickness of the tip portion of the nozzle body is gradually reduced; The plurality of nozzles having a smaller diameter than the single nozzle are formed in a plurality of stages in the axial direction of the nozzle body so as to obtain an amount equivalent to a required injection amount injected at the nozzle. A fuel injection nozzle characterized in that, at an early stage of a lift, injection is mainly performed from an injection port of a stage closer to the sack portion of the nozzle body.