JPH06185431A - Fuel injection nozzle for diesel engine - Google Patents

Abstract

PURPOSE:To enlarge an atomizing angle, promote mixing with air, shorten an ignition delay time, reduce generation of noises and discharge of toxic gas in an initial period of fuel injection of a diesel engine, and to perform injection with a small atomizing angle and large penetrating force in addition thereto in the intermediate period and after, and then to improve output. CONSTITUTION:A needle valve 9 has a needle pin 10 which has a tapered portion 10b on its end and a sub-injection port 12 opened to the end. A bar-like center rod 21 and a coil spring 22 are arranged in a center portion of a fuel chamber 20 formed in a nozzle holder 4. The sub-injection port 12 is communicated with the fuel chamber 20 at its bottom surface through a sub-injection valve 13. With a lifting amount not less than a specified value of the needle valve 9, the sub-injection valve 13 is opened and the fuel chamber 20 is communicated with the sub-injection port 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pin type fuel injection nozzle for a diesel engine.

[0002]

2. Description of the Related Art An example of a conventional diesel engine pin type fuel injection device is shown in FIG. In the figure, the fuel in the fuel tank 1 is sucked up by the fuel injection pump 2 and pumped into the fuel injection nozzle 3, and is formed between the nozzle body 6 and the needle valve 9 via the fuel inflow passage 5 in the nozzle 3. When the pressure of the fuel in the oil sump 7 becomes equal to or higher than the valve opening pressure set by the spring 17, the needle valve 9 rises and the injection port 8 opens to inject fuel. In addition, 4 in the figure shows a nozzle holder. At this time, the excess fuel leaked into the spring chamber 18 through the gap between the needle valve 9 and the nozzle body 6 is discharged to the outside of the injection nozzle 3 through the oil leakage passage 19 and returned to the fuel tank 1. Be done.

In the conventional pin type injection nozzle described above, the spray angle α is the needle pin 10 at the tip of the needle valve 9.
It was fixed by the shape of, and was fixed regardless of the crank angle and fuel injection timing. However, as mentioned above, the spray angle α
Is fixed, for example, when α is set to a large value, the fuel after injection is well dispersed and atomized immediately and mixed with air in the vicinity of the injection nozzle, so the ignition delay period can be shortened, but the spray penetration Since the force is small, there is a small amount of fuel that reaches the opposite side of the injection nozzle in the combustion chamber, and there is a drawback that the utilization rate of the air at this position decreases. On the contrary, when α is set to be small, the penetration force of the spray becomes large, and the fuel reaches the opposite side of the injection nozzle in the combustion chamber sufficiently and mixes well with the air in the entire combustion chamber, so that the utilization rate of air improves, On the other hand, there is a drawback in that it takes time to atomize the fuel and mix it with air, and the ignition delay period is extended.

Conventionally, the above-mentioned advantages and disadvantages have been taken into consideration, and an appropriate spray angle α has been determined and adopted in between, but in reality, this spray angle α is variable, and a wide angle is set at the initial stage of injection by the injection nozzle. It is desirable to improve the mixing with air to shorten the ignition delay period, and to narrow α in the main injection in the latter half of injection to increase the penetration force of the spray.

Japanese Utility Model Laid-Open No. 59-141164 discloses an injection nozzle of a type in which the spray angle α is variable. That is, in the throttle type fuel injection nozzle,
In the pre-injection, the fuel is injected at a wider angle than the sub-injection hole consisting of the taper hole that is widened in the tip at the tip of the needle, and in the main injection after that, the main injection hole consists of the right cylindrical shape around the pin. As a result, the spray angle is narrowed and the penetrating force is large.

However, in the above structure, the fuel passage for the secondary injection port is bored vertically and horizontally in the thin pin portion at the tip of the needle, and a desired amount of fuel is wide-angled within a short time when the pre-injection is performed. Precise processing work is required to form a fuel passage having an appropriate flow rate characteristic for sufficient dispersion and injection. Further, in the above configuration, the wide-angle injection and the narrow-angle injection are switched at a certain time, but due to the structure, the injection time from the auxiliary injection port, that is, the injection time at the wide angle is limited. For this reason, the air in the vicinity of the injection nozzle is not fully utilized, and the improvement of the utilization rate of the entire air is not sufficient.

In view of the above circumstances, in the present invention, at the initial stage of fuel injection, the spray angle is increased to a wide angle to disperse the spray, improve the mixing with air, and improve the ignition delay. To prevent noise from occurring by shortening the timing,
In the latter stage, in addition to this, a pin type that improves the distribution of the spray and improves the utilization rate of air in the combustion chamber by performing injection that spreads well throughout the combustion chamber with a narrow spray angle and a large penetration force. An object is to provide a fuel injection nozzle.

[0008]

In order to achieve the above object, in the present invention, it is integrated with a needle pin that goes in and out of a main injection port provided at the tip of a nozzle body, and the tip of the needle pin has a tapered portion. In a fuel injection nozzle provided with a needle valve, a sub-injection port formed in a vertical hole that extends in the axial direction and opens at the tip of the needle pin is provided in the needle valve, a fuel chamber is provided in the nozzle holder, and a central portion of the fuel chamber is provided. A center rod extending axially downward from the top of the fuel chamber so that its lower end maintains a predetermined gap with the bottom of the fuel chamber; and a coil surrounding the center rod. A fuel chamber spring is provided for communicating the fuel chamber at its bottom with the auxiliary injection port of the needle valve via the auxiliary injection valve, and the auxiliary injection valve is normally closed. A fuel for a diesel engine, characterized in that the needle valve is opened by being brought into contact with and pressed by the lower end of the center rod when the needle valve is lifted by a predetermined amount or more so that the fuel chamber and the auxiliary injection port communicate with each other. Provide an injection nozzle.

[0009]

In the initial stage of fuel injection from the injection nozzle, when the needle valve rises, the main injection port opens, and the spray is dispersed along the tapered portion of the needle pin and is well mixed with air. In the latter half of fuel injection, when the needle valve further rises and reaches a predetermined lift amount of the needle valve, the sub-injection valve abuts and presses against the lower end of the center rod in the fuel chamber provided in the nozzle holder. As a result, the sub-injection valve is opened, the fuel chamber and the sub-injection port communicate with each other, and a spray having a small spray angle and a large penetrating force is linearly injected from the sub-injection hole to improve the output.
At this time, the spray of dispersed spray along the needle pin taper portion is also performed at the same time.

[0010]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of the fuel injection device according to the present invention. Figure 1
As shown in (a), the fuel in the fuel tank 1 is pumped into the pin-type injection nozzle 3 by the fuel pump 2.

The fuel injection nozzle 3 comprises a nozzle holder 4 (upper nozzle holder 4a, lower nozzle holder 4b), a nozzle body 6, and a needle valve 9, and the needle valve 9 is
The tip becomes the needle pin 10 and the needle pin 1
Reference numeral 0 is composed of a base end cylindrical portion 10a and a taper portion 10b which is continuous with the base end cylindrical portion and spreads in the distal direction.
A ring-shaped injection port 11 is formed by fitting the ring-shaped injection port 11 with a predetermined gap. Further, the needle valve 9 is provided with a sub-injection port 12 formed of a vertical hole extending in the central axis direction and opening at the tip of the needle pin 10.

A cylindrical fuel chamber 20 is provided in the central portion of the upper nozzle holder 4a in the axial direction, and a center rod (also called a push rod) extending axially downward from the ceiling portion 20a is provided in the central portion of the upper nozzle holder 4a. 21) and a coil-shaped fuel chamber spring 22 surrounding the center rod 21. The center rod 21 is formed so that its lower end portion 21b holds a predetermined gap with the fuel chamber bottom portion 20b. The bottom of the fuel chamber 20 has a sub-injection valve 1
3 through the auxiliary injection port 12 in the needle valve 9. Further, the valve holder 14 is fitted on the upper center of the needle valve 9 coaxially with the needle valve 9, and is integrated with the needle valve 9. The sub-injection valve 13 is located inside the valve holder 14, is supported upward by the valve hold spring 16 in the valve holder chamber 15, and is normally closed. Further, when the auxiliary injection valve 13 and the needle valve 9 are in the closed state, that is, when the injection nozzle 3 does not operate before the engine is started as shown in FIG. 1, the top portion 13a of the auxiliary injection valve 13 and the center. Lower end 2 of rod 21
The gap with 1b is set to maintain a predetermined gap L ₁ .

An oil reservoir (fuel reservoir) 7 communicating with the fuel inflow passage 5 is provided between the needle valve 9 and the nozzle body 6. Further, the nozzle body 6, the needle valve 9, the valve holder 14, and the bottom portion 20 of the fuel chamber 20.
Fuel chamber bottom plate 2 which is one of the elements forming b
There is a vacant chamber 25 formed between the chambers surrounded by 3, which communicates with the oil leakage passage 19 formed in the upper nozzle holder 4a. The fuel chamber bottom plate 23 is a plate held between the upper nozzle holder 4a and the nozzle body 6 and forms a part of the bottom portion 20b of the fuel chamber 20, and the central portion of the plate is circularly opened. Is
The circular opening is fluid-tightly fitted to the outer peripheral wall of the valve holder 14 in a slidable manner.

Next, the operation of the injection nozzle 3 having the above structure will be described. The fuel pressurized by the fuel pump 2 is supplied from the fuel inflow passage 5 in the nozzle 3 to the fuel chamber 20 and the oil sump 7.
Get in The fuel chamber 20 is filled with high-pressure fuel, and at this time, the upper surfaces of the valve holder 14 and the sub-injection valve 13 exposed on the fuel chamber 20 side receive this hydraulic pressure (fuel pressure). The circular area M projected from the BB portion of FIG. 1A as shown in FIG. 1B by the biasing force of the fuel chamber spring 22 (this is the circular opening of the fuel chamber lower plate 23). (Equal to the area) exerts a downward force F _M. On the other hand, the high pressure fuel in the oil sump 7 is shown in FIG.
As shown in (c), an upward force F _N by hydraulic pressure acts on an annular area N projecting the portion C-D in FIG. 1 (a).

FIG. 2 shows a diagram for explaining the operation of the needle valve 9.
FIG. 2A shows the same state as in FIG. 1A in which the engine is stopped and there is no injection. There is no hydraulic pressure in the fuel chamber 20 and the oil sump 7, and therefore the urging force of the fuel chamber spring 22 is set. The valve holder 14 is pushed downward by the valve holder 14 and the needle valve 9 integrated with the valve holder 14 also receives a downward force, whereby the needle valve 9 comes into close contact with the valve seat of the nozzle body 6 and the main injection port 8 Is closed by a needle valve 9.

Next, fuel injection from the injection nozzle is started.
Fuel in the injection nozzle 3 at the beginning of the injection,
When the hydraulic pressure in the cylinder increases, the area N shown in FIG.
Since the area M of FIG.
Downward force F even if the forces are combined _MForce F above_Nof
It becomes bigger. (F_M<F_N). To this end, FIG.
As shown in (b), the needle valve 9 and the valve holder 14
Rise together, which causes the spring 22 to
The power of the spring 22 and the inside of the fuel chamber 20
Downward force F summed with hydraulic pressure_MIs the upward force F_NAnd fishing
Matching state (F_M= F_N), The needle valve 9 rises
To do. At this time, the top 13a of the auxiliary injection valve 13 and the center
The gap between the lower end 21b of the rod 21 and the initial L₁
Is L₂However, the two have not touched each other yet. This
2 (b), the main injection port 8 is
The fuel is injected from the nozzle 11 which is opened by the valve 9 and has an annular shape.
At this time, the spray flow is at the taper part of the needle pin 10.
It is dispersed in a wide angle by 10b. Above at the beginning of injection
In this state, the spray angle is large and the mixture with air is good.
The injection is continued in the state.

Next, the operation in the middle and second half of injection will be described.
Then, the oil pressure of the fuel further rises, and F _M<F_NAnd the figure
2 (c), the needle valve 9 is further raised and
The top 13a of the sub-injection valve 13 is below the center rod 21.
Abutting on the end 21b, the gap L between them₃= 0. More oil
When the pressure rises, the auxiliary injection valve 13 is pushed onto the center rod 21.
The sub-injection valve opens and the fuel in the fuel chamber 20
Enter the holder chamber 15 and then open the needle pin 10.
It is jetted from the auxiliary jet port 12 thus formed. This secondary nozzle 12 is
-Because it extends straight in the axial direction of the dollar valve 9,
The angle is close to 0, the dispersion of the spray is small, but the penetration force is large.
In addition, the spray reaches a long distance.
During the period, fuel spread well throughout the combustion chamber
Therefore, the combustion is performed well.

When the auxiliary injection port 12 is opened, the needle valve 9 further rises as the hydraulic pressure rises.
As shown in (c), the gap between the main injection port 8 and the valve seat of the needle valve 9 is further widened, and the injection amount from here also increases as the hydraulic pressure increases, and this fuel is tapered at the tip of the needle pin 10. 10b, the particles are dispersed and jetted with a large spray angle, and mixing with air is also performed well. Therefore, the spray is sufficiently dispersed even in the middle and latter stages of the injection, and it is possible to simultaneously satisfy both contradictory performances of the spray dispersion and the penetration.

As the needle valve 9 rises as the fuel oil pressure increases, the volume of the vacant chamber (oil leakage chamber) 25 decreases as can be seen from the progress from FIG. 2 (a) to (c). . Along with this, the oil leak accumulated in the empty chamber 25 is discharged to the outside of the injection nozzle 3 through the oil leak passage 19.
It is returned to the fuel tank 1.

According to the above construction, the fuel chamber spring 22
And strength of valve hold spring 16 and auxiliary injection valve 1
By changing the shape of 3 variously and devising a combination thereof, it is possible to provide a spray state suitable for the operating state and performance of the engine. For example, the auxiliary injection valve 13 may have various shapes as shown in FIGS. 3 (a), 3 (b) and 3 (c). Regarding the respective shapes, FIG. (A), FIG. (B), and FIG. (C), the flow rate of the fuel passing through the auxiliary injection valve 13 when the auxiliary injection valve 13 is opened (this is the auxiliary injection valve 13 Is proportional to the flow passage area of the opening), that is, the auxiliary injection fuel flow rate Q is plotted on the ordinate, and the lift amount of the needle valve 9 at that time is plotted on the abscissa. Point P on the abscissa indicates the position where the needle valve 9 rises from the state where the lift amount H of the needle valve 9 is 0 and the auxiliary injection valve top 13a abuts the center rod lower end 21b. From this point, the needle valve 9 As the lift amount H of the sub injection valve 13 increases, the injection amount Q from the sub injection port 12 increases. The state of the increase is different depending on the shape of each sub-injection valve 13 and, as shown in FIG.
It is shown in (d).

As can be seen from the above example, the amount Q of fuel passing through the auxiliary injection port 12 can be changed in various ways. If the strength and weakness states of the fuel chamber spring 22 and the valve hold spring 16 are combined with this, the selection range that can be further changed becomes wider. Therefore, according to the means of the present embodiment, the degree of freedom in design for obtaining the fuel injection state that matches the operating state of the engine is high, and the applicable range of the present device is very wide.

[0022]

According to the present invention, by making good use of the balance of the hydraulic pressure of the fuel in the fuel injection nozzle, both spray dispersion and penetration, which cannot be obtained by the conventional method, can be effectively spread simultaneously. It can be widely used and has the following effects. (1) In the initial stage of injection of the fuel injection nozzle, the spray is well dispersed, mixes well with air, the ignition delay time is shortened, and noise is reduced. (2) In the middle and second half of the injection, in addition to this, a large amount of linear injection with a small spray angle and a large penetrating force is performed, and the fuel spreads to every corner of the combustion chamber and the utilization rate of air is increased. High output can be obtained. (3) A simple structure is also advantageous in terms of cost.

[Brief description of drawings]

1A and 1B show a pin-type fuel injection nozzle according to an embodiment of the present invention, FIG.
The figure which shows the vertical projection area of the BB section shown to (a), FIG.
(C) is a figure which shows the vertical projection area of the CD section of Fig.1 (a).

2 shows each operation of the injection nozzle of the embodiment shown in FIG. 1, FIG. 2 (a) shows a state where the engine is stopped and injection is not performed, and FIG. 2 (b) shows an initial state of the engine and the injection nozzle. The injection state, FIG. 2C is an operation explanatory view of the main parts of the injection nozzles in the middle and late injection states of the injection nozzle.

3 shows an example of the shape of the auxiliary injection valve of the injection nozzle of the embodiment shown in FIG. 1 and an example of respective injection flow rate characteristic diagrams. FIG. 3 (a) is a mold and a mold, and FIG. (B) is a mold,
FIG. 3 (c) shows examples of the shapes of various check valves shown as molds, and FIG. 3 (d) shows the characteristics of the injection flow rate of the auxiliary nozzle of the injection nozzle when the auxiliary injection valves having the above respective shapes are used. FIG.

FIG. 4 is a cross-sectional view of a main part of an example of a pin-type fuel injection nozzle according to the related art.

[Explanation of symbols]

 3 ... Fuel injection nozzle 4 ... Nozzle holder 5 ... Fuel inflow passage 6 ... Nozzle body 7 ... Oil (fuel) reservoir 8 ... Main injection port 9 ... Needle valve 10 ... Needle pin 11 ... Annular injection port 12 ... Sub injection port 13 ... Sub injection valve 14 ... Valve holder 15 ... Valve holder chamber 16 ... Valve hold spring 19 ... Fuel escape passage 20 ... Fuel chamber 20a ... Fuel chamber ceiling 20b ... Fuel chamber bottom 21 ... Center rod (push rod) 21b ... Center rod lower end 22 ... Fuel chamber Spring 23 ... Fuel chamber bottom plate 25 ... Vacancy

Claims (1)

[Claims] 1. A needle having a taper portion (10b) at the tip of the needle pin (10), which is integrated with a needle pin (10) which goes in and out of a main injection port (8) provided at the tip of a nozzle body (6). In a fuel injection nozzle (3) equipped with a valve (9), a sub injection port (1) formed of a vertical hole extending in the axial direction and opening at the tip of the needle pin (10).
2) is provided in the needle valve (9), the fuel chamber (20) is provided in the nozzle holder (4), and the central portion of the fuel chamber (20) is closer to the ceiling portion (20a) of the fuel chamber (20). A center rod (21) extending downward in the axial direction in a rod shape so that its lower end (21b) maintains a predetermined gap with the bottom portion (20b) of the fuel chamber (20), and the center rod (21). ) Surrounding the bottom of the fuel chamber (20).
0b), the auxiliary injection valve (13) communicates with the auxiliary injection port (12) of the needle valve (9), the auxiliary injection valve (13) is normally closed, and the needle valve (9) has a predetermined position. In the above lift amount, the lower end (21b) of the center rod (21) is brought into contact with and pressed to open the fuel chamber (20) and the auxiliary injection port (12). A characteristic diesel engine fuel injection nozzle.