JPH06159197A - Fuel injection nozzle - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve fuel injection characteristics in a fuel injection nozzle that performs fuel injection in stages. [Structure] The pilot injection holes 3 and the main injection holes 9 are made to intersect each other near their respective outlets, and the diameter D _{3 of} each pilot injection hole 3 is crossed.
Is set to be smaller than the diameter D ₉ of each main injection hole 9, and the needle valve 2
At the time of the initial lift, the effective inlet opening area As defined between the seat line portion 22 and the seat surface 11 is set smaller than the sum of the opening areas A ₃ of the pilot injection holes 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a fuel injection nozzle used in a direct injection diesel engine or the like.

[0002]

2. Description of the Related Art In order to reduce ignition delay of a diesel engine and realize smooth combustion, there is a fuel injection nozzle that performs fuel injection in stages.

As a fuel injection nozzle of this type, there is a conventional one shown in FIG. 8, for example (see Japanese Patent Laid-Open No. 59-147862).

Explaining this, the nozzle body 4
1, a plurality of pilot injection holes 43 and main injection holes 49 are respectively radially opened, and only the pilot injection holes 43 having a small diameter are opened when the needle valve 42 is initially lifted. Fuel is injected into the cavity 40 of the piston 45, and as the needle valve 42 lifts, the main injection hole 49 with a large hole is opened and a large amount of fuel is injected as indicated by arrow C.

[0005]

However, in such a conventional device, the fuel spray from the pilot injection hole 43 and the fuel spray from the main injection hole 49 are generated during the main injection in which a large amount of fuel is injected. There was a problem that the smoke was deteriorated by overlapping with each other and creating a region where the fuel was excessively concentrated in the combustion chamber.

In view of the above problems, the present invention has an object to improve fuel injection characteristics in a fuel injection nozzle which carries out fuel injection in stages.

[0007]

SUMMARY OF THE INVENTION The present invention is directed to a fuel injection nozzle in which a needle valve lifts in multiple stages in response to fuel pressure fed from a fuel injection pump in synchronization with engine rotation to inject fuel. A conical recessed seating surface is formed on the nozzle body that houses the valve, while a conically projecting seat surface is formed on the needle valve, and a linear shape with respect to the seating surface is formed at the base end edge of the seat surface. A seat line portion that is in contact with the seat line portion, and a plurality of pilot injection holes that open on the seat surface immediately downstream of the seat line portion and a plurality of main injection holes that open at a position relatively distant from the seat line portion are radially formed. Then, cross the corresponding pilot injection holes and main injection holes near their respective outlets,
Set the sum of the opening areas of the pilot nozzle holes to be smaller than the sum of the opening areas of the main nozzle holes, and set the effective inlet opening area defined between the seat line and seat surface during the initial lift of the needle valve. Set smaller than the total opening area of pilot injection holes.

[0008]

When the needle valve is initially lifted, the fuel flow guided through the conical tubular flow passage defined between the seat surface portion and the seat surface is strongly throttled between the seat wire portion and the seat surface. Since the effective inlet opening area defined between the seat and the seat surface is set smaller than the total opening area of each pilot injection hole,
Most of the fuel is prevented from flowing into each pilot injection hole opened immediately downstream of the seat line portion, while being prevented from flowing into each main injection hole opened away from the seat line portion. As a result, a small amount of fuel injected during the initial lift is ejected toward the center of the combustion chamber through each pilot injection hole.

Since the sum of the opening areas of the pilot injection holes is set smaller than the sum of the opening areas of the main injection holes to correspond to a predetermined initial injection amount, the injection rate at the initial lift can be suppressed to a low level. Further, by forming the pilot injection hole to have a small diameter, atomization of the fuel spray injected into the combustion chamber through the pilot injection hole is promoted. As a result, stable and smooth combustion with less ignition delay and hence less vibration and noise is realized.

When the needle valve is lifted beyond the initial lift amount, the throttling effect by the inlet defined between the seat line portion and the seat surface becomes relatively small, and is defined between the seat surface portion and the seat surface. The fuel pressure guided through the conical cylindrical flow path becomes uniform, and a large amount of fuel is ejected through each main injection hole with a large opening area and a shallow injection angle, and the remaining fuel is passed through each pilot injection hole. Gush out.

Since the pilot injection hole and the main injection hole intersect each other in the vicinity of their respective outlets, the fuel flows passing through the injection holes collide with each other immediately before they are injected into the combustion chamber, and atomization of the spray is promoted. At the same time, the injection direction changes from the lower side to the lateral side of the combustion chamber during one injection, and the fuel spray having a strong penetration force is supplied as the fuel injection amount increases. As a result, it is possible to activate diffusion combustion and suppress smoke, and delay fuel injection timing to some extent to reduce NOx.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 2, in the fuel injection nozzle 10 provided in the direct injection type diesel engine, the needle valve 2 is 2 depending on the fuel pressure pumped from the fuel pump through the passage.
The fuel is injected in stages by lifting in stages. A dish-shaped cavity is formed on the top surface of the piston (not shown), and the fuel injection nozzle 10 is provided vertically facing the center of the combustion chamber from the cylinder head.

A needle valve 2 is slidably accommodated in a hollow cylindrical nozzle body 1, and a first spring 6 and a second spring 7 for biasing the needle valve 2 to close are interposed in parallel to each other. The first spring 6 operates in the stage up to the initial lift where the valve 2 comes into contact with the retainer 8. When the initial lift is exceeded, the urging force of the second spring 7 also works via the push rod 5 to allow fuel injection. The needle valve 2 is lifted stepwise with respect to the pressure, and a large amount of main injection is performed after the initial injection fuel is ignited. Here, the initial lift amount L ₁ is set to 0.06 mm, and the total lift amount L ₂ is set to 0.25 mm, for example.

As shown in FIG. 1, the nozzle body 1 is formed with a conical recessed seat surface 11, and a plurality of pairs of main injection holes 9 and pilot injection holes 3 are formed in the seat surface 11 at the nozzle center line O _1. Are formed radially from. The pilot injection hole 3 is largely inclined toward the lower cavity, whereas the main injection hole 9 is inclined slightly downward from the horizontal. The paired pilot injection hole 3 and main injection hole 9 intersect each other at their respective outlets. Centerline O ₉ centerline O ₃ and the main injection hole 9 of the pilot injection hole 3 is located on a plane including the nozzle center line O _1, respectively, the center line O ₃ of the pilot injection hole 3 and the center of the main injection hole 9 The intersection E of the line O ₉ is located on the outer surface of the nozzle body 1. A fuel injection nozzle having a tip-merging type injection hole has already been filed by the applicant as Japanese Patent Application No. 2-404075.

A conical seat surface portion 21 is provided at the tip of the needle valve 2.
Is formed, a conical surface 23 is formed on the base end side of the seat surface portion 21, and a conical surface 24 is formed on the tip end side of the seat surface portion 21. The conical angles of the conical surface 23, the seat surface portion 21, and the conical surface 24 are respectively formed. It is set gradually in the order of.
The conical angle of the seat surface portion 21 is formed larger than the conical angle of the seat surface 11 at a predetermined ratio, and when the needle valve 2 is seated (when the valve is closed).
A fuel flow passage having a conical tubular shape in which a seat line portion 22 that abuts a base end edge portion (a boundary line between the conical surface 23 and the seat surface portion 21) of the seat surface portion 21 is brought into line contact with the seat surface 11 and reaches the respective injection holes 3 and 9. Is designed to be blocked.

The inlet 3a of the pilot injection hole 3 is located immediately downstream of the seat line portion 22 and opens to the seat surface 11, while the main injection hole 9 has its inlet 9a facing the tip of the seat surface portion 21. Open to the seat surface 11. That is, the inlet 9a of the main injection hole 9 opens at a position relatively far from the seat line portion 22.

The inlets 3a of the pilot injection holes 3 are arranged at a predetermined interval on the circumferential surface orthogonal to the nozzle center line O _1, and the inlets 9a of the main injection holes 9 are different from each other and are also orthogonal to the nozzle center line O _1. They are lined up at a predetermined interval on the circumference.

As the gist of the present invention, the sum ΣA ₃ of the opening areas A ₃ (= D ₃ ² × π / 4) of each pilot injection hole ₃ is the opening area A ₉ (of each main injection hole ₉ ). = D ₉ ² × π
It is formed smaller than the sum ΣA ₉ of / 4). That is,
The diameter D ₃ of the pilot injection hole 3 is set smaller than the diameter D ₉ of the main injection hole 9 at a predetermined ratio. The diameter D ₃ of the pilot injection hole 3 is arbitrarily set so that the injection rate required at the initial lift can be obtained as described later, while the diameter D ₉ of the main injection hole 9 is the injection rate required at the main injection. Is set arbitrarily so that

The left half of FIG. 1 shows the state in which the needle valve 2 is lifted by the initial lift amount L _{1. The} effective inlet opening area As during the initial lift is shown by the needle valve 2 in this initial lift state. Assuming that the opening area of the annular flow path defined between the seat line portion 22 and the seat surface 11 of the nozzle body 1 is the sum ΣA ₃ of the opening areas A ₃ of the pilot injection holes 3, the effective inlet opening at the initial lift The area is set to be larger than the area As at a predetermined ratio, and most of the fuel is initially injected from each pilot injection hole 3.

Further, the effective entrance opening area As during the initial lift is set to be smaller than the total sum ΣAc of the entrance curtain areas Ac of the pilot injection holes 3. However, the entrance curtain area Ac is the opening edge of the pilot injection hole 3 (entrance circumference)
And the opening area of the annular flow path defined between the seat surface portion 21 of the needle valve 2.

A pilot hole 12 is formed at the tip of the seat surface 11. The prepared hole 12 serves as a relief for processing the seat surface 11 and has a predetermined volume so as to make the fuel pressure introduced into each main injection hole 9 during main injection uniform.

Next, the operation will be described.

The fuel sent from the fuel injection pump to the fuel injection nozzle 10 in synchronism with the rotation of the engine compresses only the first spring 6 as the pressure rises, and the needle valve 2 is initially lifted to generate a small amount of fuel. After the initial injection, when the pressure rises above a predetermined value, the second spring 7 is now fully compressed while the second spring 7 is being compressed, and a large amount of fuel is mainly injected.

When the needle valve 2 is initially lifted, the effective inlet opening area As defined between the seat line portion 22 and the seat surface 11 is smaller than the sum ΣA ₃ of the opening areas A ₃ of the pilot injection holes 3, and the pilot Sum of entrance curtain area Ac of injection hole 3 ΣA
Since it is set smaller than c, the seat surface portion 21 and the seat surface 1
The pressure of the fuel guided through the conical tubular flow path defined between the two is strongly narrowed between the seat line portion 22 and the seat surface 11, and is more downstream than near the seat line portion 22. Therefore, most of the fuel is injected from each pilot injection hole 3 that is opened immediately downstream of the seat line portion 22 and flows into each main injection hole 9 that is opened downstream from the seat line portion 22. Is suppressed. As a result, the initial injected fuel is mainly ejected through the pilot injection holes 3 toward the center of the combustion chamber.

By appropriately setting the hole diameter D ₃ of the pilot injection hole 3 so as to obtain a predetermined initial injection amount, the injection rate at the initial lift can be suppressed low, and at the same time, the pilot injection hole 3 of small diameter is passed. Since the fuel is injected, atomization of the fuel spray is promoted. As a result, stable and smooth combustion with less ignition delay and hence less vibration and noise is realized.

When the needle valve 2 lifts beyond the initial lift amount as the fuel pressure increases, the seat wire portion 22 and the seat surface 11
Since the effective inlet opening area As defined between the _two is larger than the total sum ΣA ₃ of the opening areas A ₃ of the pilot injection holes 3 and larger than the total sum ΣAc of the entrance curtain areas Ac of the pilot injection holes 3, the seat surface portion 21 The fuel pressure in the conical tubular flow path defined between the seat and the seat surface 11 becomes almost the same in the upstream and the downstream, and a large amount of fuel is ejected through each main injection hole 9 having a large opening area, and the remaining Fuel is ejected through each pilot injection hole 3.

Therefore, the main flow of fuel is injected from the main injection holes 9 into the combustion chamber with a strong penetrating force, and the pilot injection holes 3 and the main injection holes 9 intersect each other at their outlets, so that the injection holes The fuel flows passing through 3 and 9 collide with each other immediately before jetting into the combustion chamber, and atomization of the fuel spray is achieved. As a result, after the ignition by the initial injection, the diffusion combustion of the main injection fuel can be activated to suppress the smoke, and the ignition is stable even if the fuel injection timing is delayed to some extent, so that NOx can be reduced. Becomes

When the fuel injection is stopped, the seat wire portion 22 of the needle valve 2 is attached to the seat surface 11 of the nozzle body 1 as the fuel pressure decreases.
The fuel is prevented from flowing into the conical tubular flow path by linearly joining to the conical tubular flow path.

Next, another embodiment shown in FIG.
1, the opening portion 3a of the pilot injection hole 3 for 1 is curved in an arcuate cross section. The chamfering of the opening 3a is performed by electrolytic processing, for example.

As a result, the circumferential length L ₃ of the opening edge portion of the pilot injection hole 3 is increased, and the inlet curtain area Ac defined between the pilot injection hole 3 and the needle valve 2 at the time of the initial lift is increased. Since the sum ΣAc of the entrance curtain areas Ac of the pilot injection holes 3 becomes larger than the entrance effective opening area As defined between the portion 22 and the seat surface 11, the fuel flowing into the pilot injection holes 3 during the initial lift is increased. Can be made smoother and the atomization of fuel spray can be promoted.

Next, another embodiment shown in FIG.
An annular groove 31 is formed on the inner circumference of the pilot groove 1, and each pilot injection hole 3 is opened in this annular groove 31. The groove cross section of the annular groove 31 is curved in an arc shape.

In this case, since the flow passage area of the inlet portion of the pilot injection hole 3 is enlarged, the fuel smoothly flows into the pilot injection hole 3 during the initial lift, and atomization of the fuel spray can be promoted.

Next, another embodiment shown in FIG. 5 is the needle valve 2
An annular groove 32 facing the pilot injection hole 3 is formed on the outer periphery of the seat surface portion 21 of FIG. The cross section of the annular groove 32 is curved in an arc shape.

Also in this case, since the flow passage area at the inlet of the pilot injection hole 3 is enlarged, the flow of the fuel flowing into the pilot injection hole 3 at the time of the initial lift can be made smooth, and atomization of the fuel spray can be promoted. Further, since the annular groove 32 is formed on the outer surface of the needle valve 2, the processing is relatively easy.

Next, another embodiment shown in FIG. 6 and FIG.
Four pilot injection holes 3 and eight main injection holes 35 are radially formed on the seat surface 11, and two adjacent main injection holes 3 are formed.
5 are communicated with each other in the middle thereof, and one pilot nozzle hole 3 is communicated with the vicinity of the outlet of the combined main nozzle hole 35.

The opening area A ₃ (= D _{3 of} each pilot injection hole ₃
The total sum ΣA ₃ of ² × π / 4) is smaller than the total sum ΣA ₃₅ of the opening areas A ₃₅ of the main injection holes 35. The diameter D ₃₅ of the main injection hole 35 is set to be equal to or larger than the diameter D ₃ of the pilot injection hole 3.

In this case, the opening area A of each main injection hole 35
_{By making} the sum ΣA ₃₅ of ₃₅ relatively large, the pressure near the outlet of the injection hole can be increased during main injection, shortening the injection period, activating diffusion combustion to suppress smoke, and delaying the fuel injection timing to some extent. As a result, NOx can be reduced.

[0039]

As described above, according to the present invention, in the fuel injection nozzle which performs the fuel injection stepwise, the pilot injection hole and the main injection hole are intersected in the vicinity of their respective outlets, and the opening area of each pilot injection hole is reduced. Set the total sum smaller than the total opening area of each main injection hole, and set the effective inlet opening area defined between the seat line and seat surface during the initial lift of the needle valve from the total opening area of each pilot injection hole. Since it is set small, atomization of the fuel is promoted while reducing the initial injection rate, and the spray direction of the fuel is changed with the transition to the main injection to promote diffusion combustion, thereby smoothing the combustion. Reduce the noise of diesel engine,
Both smoke and NOx can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a tip portion of a fuel injection nozzle showing an embodiment of the present invention.

FIG. 2 is likewise an overall cross-sectional view of a fuel injection nozzle.

FIG. 3 is a sectional view showing another embodiment.

FIG. 4 is a sectional view showing still another embodiment.

FIG. 5 is a sectional view showing still another embodiment.

FIG. 6 is a sectional view showing still another embodiment.

FIG. 7 is a plan view of the nozzle body.

FIG. 8 is a sectional view of a fuel injection nozzle showing a conventional example.

FIG. 9 is a sectional view of a fuel injection nozzle and a piston.

[Explanation of symbols]

1 Nozzle body 2 Needle valve 3 Pilot injection hole 9 Main injection hole 11 Seating surface 21 Seat surface part 22 Seat line part A ₃ Pilot injection hole opening area Ac Initial curtain area at initial lift As Effective entrance area at initial lift D ₃ Pilot nozzle diameter D ₉ Main nozzle diameter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takushi Oishi 3-1326, Yasumi-cho, Higashimatsuyama, Saitama Prefecture XXEL Higashi-Matsuyama Factory (72) Inventor Fumitsugu 3-13, Yasumi-cho, Higashimatsuyama, Saitama No.26 Stock company Zexel Higashi Matsuyama Factory

Claims (1)

[Claims] 1. A fuel injection nozzle in which a needle valve lifts in multiple stages according to fuel pressure fed from a fuel injection pump in synchronism with engine rotation to inject fuel into a nozzle body housing the needle valve. While forming a conical recessed seating surface, a conical protruding seat surface part is formed on the needle valve, and a seat line part that linearly contacts the seat surface is formed at the base end edge of the seat surface part. On the seat surface, a plurality of pilot injection holes that are opened immediately downstream of the seat line portion and a plurality of main injection holes that are opened relatively far from the seat line portion are radially formed, and the corresponding pilot injection holes are respectively formed. And the main injection hole intersect near the respective outlets, the total opening area of each pilot injection hole is set smaller than the total opening area of each main injection hole, and the seat line and seat surface are set when the needle valve is initially lifted. There is an entrance defined between A fuel injection nozzle characterized in that the effective opening area is set smaller than the sum of the opening areas of the pilot injection holes.