JPH10196492A - Diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress an amount of unburned HC at the time of low load operation and reduce an amount of smoke generated at the time of high load operation by forming a main injection hole and an auxiliary injection hole in a nozzle body of a fuel injection nozzle and forming a groove which is apart from the auxiliary injection hole in the peripheral direction and is extended from below a seat part to a main injection hole side. SOLUTION: A fuel injection nozzle 10 is provided in such a manner that a tip of a nozzle part 11 faces a combustion chamber, and the nozzle part 11 is such that a needle valve 14 is stored in a nozzle body 13. A seat part 22 is formed in the nozzle body 13, and fuel injection is stopped when a valve seat 23 of the needle valve 14 is seated on the seat part 22. Moreover, a main injection hole 17 is formed below a hole part 25 of the nozzle body 13 along the nozzle center C, and a plurality of auxiliary injection holes 27 are formed on and pass through a tapered surface 24 radially centered on the nozzle center C. Furthermore, a fanlike groove 28 having a predetermined depth is provided on the tapered surface 26 between the auxiliary injection holes 27, and each groove 28 is provided in such a manner that it is communicated with the main injection hole 17 through the hole part 25.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct injection type diesel engine having a so-called OSKA type combustion chamber.

[0002]

2. Description of the Related Art In a direct injection type diesel engine, a plurality of injection holes are radially provided in a fuel injection nozzle in order to atomize the spray and promote mixing of the spray and the air. It is becoming mainstream to arrange it facing the center.

On the other hand, in the layout described above, especially when the injection pressure is increased to promote atomization, the penetration force of the spray is increased and the flight distance is increased, and the spray adheres to the side wall of the combustion chamber. It becomes easy to be discharged as unburned HC. This problem of unburned HC is often observed during low engine load operation in which the injection amount is small and the temperature in the cylinder is relatively low, and is particularly noticeable in a small engine in which the diameter of the combustion chamber cannot be made large.

[0004] A technique for atomizing the spray by causing the injected fuel to collide with the fuel collision surface in the combustion chamber and disperse (diffuse) the fuel (a so-called OSKA combustion chamber) is disclosed in, for example, Japanese Patent Laid-Open Publication No. Sho.
It is disclosed in JP-A-62-63121.

In the OSKA type combustion chamber, the injected fuel is diffused by the collision and the penetration force is weakened, so that even in a small engine (small diameter combustion chamber), the spray can be prevented from adhering to the side wall of the combustion chamber, and the low fuel consumption can be achieved. Unburned HC emissions during load can be suppressed.

[0006]

However, in the OSKA type combustion chamber where the penetration force of the spray is weak, unburned HC emission at a low load can be suppressed. However, at the time of a high load where the injection amount is large, a large amount only in the combustion chamber. The fuel burns, resulting in rich combustion and a lot of smoke.

That is, in a conventional combustion chamber using a multi-hole nozzle, the flame after ignition flows out of the combustion chamber by the penetration force of the spray itself, and the lower surface of the cylinder head and the upper surface of the piston formed as the piston descends. On the other hand, in the OSKA type combustion chamber, almost no flame flows out of the combustion chamber, and poor combustion occurs due to insufficient air.

On the other hand, JP-A-5-141243 discloses that the OS
The fuel injection nozzle provided to the KA type combustion chamber is provided with a plurality of radial injection holes, and the distance between the collision surface at the center bottom of the combustion chamber and the injection hole pointing to this collision surface is determined by the distance between the combustion chamber side wall and the radiation direction. The spray that collides and diffuses at the collision surface is ignited prior to the spray injected in the radial direction by forming it smaller than the distance to the injection hole, and the pilot combustion induces the ignition of the spray in the radial direction A technique for performing this is disclosed.

According to this technique, since the penetration force of the spray injected in the radial direction is added to the combustion by the collision diffusion spray, the combustion gas easily flows out of the combustion chamber. It is thought that poor combustion due to lack of air at high load in the room is also improved.

However, according to this technique, the fuel is always equally distributed between the injection hole directed to the collision surface and the injection hole in the radial direction, and the injection is also performed at the same time. The amount of injection from the injection hole directed toward the collision surface decreases, the collision force and the diffusivity weaken, and pilot combustion as expected is not obtained, and the fuel injected in the radial direction adheres to the side wall of the combustion chamber and becomes unburned HC is generated. Therefore, this technology can reduce smoke emission at high load,
It is not possible to reduce the amount of unburned HC emission at low load.

Further, the distance between the collision surface and the injection hole is defined as
It is often difficult to make the distance smaller than the distance between the injection holes due to design restrictions of the combustion chamber. That is, since the collision surface position is set above the combustion chamber, the volume of the combustion chamber is reduced, so that the diameter of the combustion chamber must be increased in order to maintain the compression ratio, and is particularly applied to a small engine having a small bore diameter. Difficult to do. Further, when the collision surface is too close to the lower surface of the cylinder head, a new problem that collision diffusion spray or flame adheres to the lower surface of the cylinder head and is rapidly cooled, leading to generation of unburned HC and smoke, also causes a new problem. .

[0012]

A diesel engine according to the present invention is provided with a combustion chamber formed by recessing a piston top surface and having a fuel collision surface in the center, and facing the combustion chamber. A fuel injection nozzle, the nozzle body of which has a main injection hole directed to the fuel collision surface, a sub injection hole directed to a side wall of the combustion chamber, and a seat for seating a needle valve; A fuel injection nozzle is provided on the inner surface, the fuel injection nozzle having a groove that is circumferentially separated from the sub injection hole and extends from below the seat portion toward the main injection hole.

According to this, when the total injection amount is small, most of the fuel that has passed between the needle valve and the seat in the nozzle body is directed to the main injection hole along the groove, so that when the load is low, In the large injection amount from the main injection hole,
The injection amount from the sub-injection hole can be reduced, thereby preventing the fuel from adhering to the combustion chamber side wall and suppressing the emission of unburned HC. When the load is high and the total injection amount is large, the fuel is equally distributed and injected into the main injection holes and the sub injection holes as in the conventional case, thereby making it possible to reduce smoke.

Here, a first notch portion and a second notch portion extending in the circumferential direction below the seat portion and above the main injection hole are provided on the inner surface of the nozzle body, respectively. Has a first projection and a second projection respectively fitted to the first notch and the second notch, and the groove is provided between the first notch and the second notch. Preferably.

[0015]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 5 shows a diesel engine according to the present invention. As shown in the drawing, in a diesel engine 1, a combustion chamber 3 is formed by recessing a top surface of a piston 2. The combustion chamber 3 is circularly depressed in a plan view, and its center coincides with the center of the piston and the center C of the nozzle, and the side wall 4 along the circumferential direction is formed of a ring-shaped plane parallel to the center C of the nozzle. ing. A shelf 6 protruding radially inward is formed integrally with the upper end of the side wall 4. The bottom portion 5 of the combustion chamber 3 has an outer peripheral portion formed in a planar shape, and a fuel collision table 7 is integrally formed at the center portion thereof so as to protrude. The fuel collision table 7 is formed in a conical column shape having a predetermined height centered on the center C of the nozzle, and the upper surface thereof forms a planar fuel collision surface 8 here. As described above, the combustion chamber 3 has an OSKA type combustion chamber.

On the other hand, a fuel injection nozzle 10 is attached to the cylinder head 9 via a nozzle sleeve 10a. In the fuel injection nozzle 10, the tip of the nozzle portion 11 projects downward from the lower surface 12 of the cylinder head and faces the combustion chamber 3. As described above, the diesel engine 1 has a direct injection type configuration, in which the displacement per cylinder, the bore diameter, and the diameter of the combustion chamber 3 (cavity diameter) are used.
Both are relatively small.

As shown in detail in FIGS. 1 and 2, the nozzle section 11 is configured such that a needle valve 14 is housed in a nozzle body 13 so as to be able to move up and down. A fuel passage 15 and an oil reservoir (not shown) are formed in the nozzle body 13.
When high-pressure fuel is introduced into the oil reservoir, the needle valve 14 is lifted (raised) by the pressure. A seat portion 22 is formed integrally with the nozzle body 13, and when the valve seat 23 of the needle valve 14 is seated on the seat portion 22 in a surface contact state, the flow of fuel downward from the fuel passage 15 is regulated, The injection nozzle 10 is in a closed state. Conversely, when the needle valve 14 is lifted, a gap is formed between the seat portion 22 and the valve seat 23, and fuel penetrates downward from this gap, and fuel injection is performed.

The nozzle body 13 further has a tapered surface 24 formed below the seat portion 22 forming the inner surface thereof, and a tip below the tapered surface 24 is continuous with the hole portion 25, and is further formed below the hole portion 25. Is formed with a main injection hole 17 therethrough. The main injection hole 17 is formed along the center C of the nozzle, so that the main injection hole 17 is directed to the fuel collision surface 8. On the other hand, a valve taper surface 26 is formed continuously below the valve seat 23 in the needle valve 14.
6 is fitted to the tapered surface 24.

A plurality of sub injection holes 27 are opened in the tapered surface 24. The sub injection hole 27 extends radially around the nozzle center C, and penetrates the nozzle body 13 slightly obliquely downward. As a result, the sub injection hole 27 is directed toward the side wall 4 of the combustion chamber 3. Here, four sub injection holes 27 are provided at 90 ° intervals in the circumferential direction.

A groove 28 having a predetermined depth is provided in the tapered surface 24 between the sub injection holes 27. Groove 28
Are formed in a fan shape when viewed in a plan view, four are provided between all the sub-injection holes 27, and are separated from the sub-injection holes 27 and are in a non-communication state. And the groove 28 is 8
In order to divide equally, each has a width of 45 ° in the circumferential direction and a width center interval of 90 °. The groove 28 is provided in the seat 2
2 and extends downward from just below and continues to the hole 25. That is, the groove 28 is formed in the main injection hole 17 through the hole 25.
Is in communication with

To explain the operation of the above configuration, when the needle valve 14 is lifted by the fuel pressure, the fuel in the pressurized state accumulated in the fuel passage 15 firstly receives the seat portion 22 and the valve seat 23.
, And enters the gap between the tapered surface 24 or the inner surface of the groove 28 and the valve tapered surface 26. Here, the passage in the groove 28 has a larger passage area and a smaller passage resistance, that the amount of fuel is relatively small when the engine is in a low load operation state, that the fuel is energized downward, and the like. For this reason, most of the fuel first reaches the hole portion 25 through the groove 28 and is injected from the main injection hole 17. Then, the supply of fuel is continued beyond the allowable injection amount based on the diameter of the main injection hole 17 or the like, and the tapered surface 24 or the groove 28
When the fuel has accumulated in the gap between the inner surface and the valve taper surface 26, the fuel in the gap is subsequently injected from the sub injection hole 27 (see FIG. 6A). However, if the total injection amount is such that only the main injection hole 17 can cover, the injection from the sub injection hole 27 is not substantially performed.

As described above, when the total injection amount is small and the injection pressure is relatively low, for example, during low engine load operation (for example, during idling operation), the injection amount from the main injection hole 17 is reduced to the sub injection hole 27.
, The injection amount ratio can be biased toward the main injection hole 17 side and the sub injection hole 27 side can be reduced,
Thereby, it is possible to prevent the fuel from adhering to the combustion chamber side wall 4 due to the injection of the sub injection hole 27, and it is possible to largely suppress the discharge of the unburned HC. In addition, the injection of the sub injection hole 27 is
7, the fuel is delayed from the injection by the main injection hole 17 (pilot combustion).
The fuel can be prevented from sticking to the side wall 4 in an unburned state, and the effect of suppressing unburned HC emissions can be greatly enhanced.

On the other hand, when the total injection amount and the injection pressure are both large, such as during high engine load operation, the lift amount of the needle valve 14 also increases, and fuel is injected into the main injection hole 17 and the sub injection hole 27.
From the same time. As a result, as shown in FIG. 6B, the spray or combustion gas having a strong penetration force from the sub injection hole 27 can be added to the combustion of the impinging diffusion spray by the main injection hole 17, and the sub injection Hole 27
From the combustion chamber 3 to effectively use the air between the top surface of the piston 2 and the lower surface 12 of the cylinder head,
Combustion can be performed in a relatively large area. As a result, smoke during high-load operation can be reduced. Thus, in such a configuration, as the injection amount or the injection pressure increases, the injection ratio of the sub injection hole 27 increases, and the delay time of the injection start timing is shortened.

Here, since the injection start timing of the main injection hole 17 and the sub injection hole 27 depends on the injection pressure (that is, the engine rotation speed), when the moving speed of the piston 2 is low and the engine rotation is low (low injection pressure). The outflow of the combustion gas from the combustion chamber 3 to the outside is delayed, so that the combustion gas does not flow out while the space between the piston 2 top surface and the cylinder head lower surface 12 is narrow. Smoke and unburned HC caused by rapid cooling of combustion gas
Can be prevented. On the other hand, at the time of high engine rotation (high injection pressure) in which the moving speed of the piston 2 is high, the outflow of the combustion gas is also performed quickly, so that combustion in the space between the top surface of the piston 2 and the lower surface 12 of the cylinder head is effectively performed. It can be converted to work (torque).

When combined with a fuel injection device (such as a common rail type) that can set the injection pressure independently of the engine speed, the injection amount ratio and the injection time difference between the main injection hole 17 and the sub injection hole 27 can be optimized. Can be controlled freely.

Next, another embodiment will be described.

As shown in FIGS. 3 and 4, in this embodiment, the configuration of the nozzle portion 11 of the fuel injection nozzle 10 is different. That is, on the tapered surface 24 inside the nozzle body 13, the first cutout portion 30 is provided at a position slightly below the seat portion 22, and the second cutout portion 31 is provided at a position slightly above the hole portion 25. These notches 30, 3
1 is formed in a triangular cross section, and is located in the nozzle center direction (vertical direction)
And a bottom wall perpendicular thereto, and is formed in a groove shape over the entire circumference. The first notch 30 and the second notch 30 are also provided on the valve taper surface 26 of the needle valve 14.
The first projection 32 and the second projection 32 respectively fitted into the notch 31
A projection 33 is provided. These first and second projections 32 and 33 are formed in a short column shape that fits into the first and second cutouts 30 and 31.

Further, a sub-injection hole 27 and a groove 28 are provided on the tapered surface 24 at a position between the first and second notches 30 and 31. Here, three sub injection holes 27 are radially provided at 120 ° intervals in the circumferential direction, and the groove 28 is provided at a position between these sub injection holes 27 and spaced apart from the sub injection holes 27 in the circumferential direction. Each groove 28 has a width of 60 ° in the circumferential direction and a width center interval of 120 ° so as to divide the entire circumference into six equal parts. The depth of the groove 28 is set such that the first cutout portion 30 and the second cutout portion 31 communicate with each other, and the bottom surface connects the lower end outer peripheral edges of the first and second cutout portions 30 and 31.

By doing so, the length of the groove 28 in the direction of the nozzle center can be reduced as compared with the above embodiment, and the volume itself of the groove 28 can be reduced. That is, in the above-described embodiment, since the volume of the groove 28 is relatively large, the sharpness of the fuel is deteriorated at the end of the fuel injection, and there is a possibility that a problem such as rearward dripping may occur. Can be solved.

Here, the groove 28 is stopped at the position of the second notch 31 and is not in communication with the main injection hole 17, but the fuel passing through these gaps when the needle valve 14 is lifted has a downward directivity. , The main injection hole 1 similar to the above is provided.
7 enables the execution of the initial injection.

Japanese Patent Application Laid-Open No. 4-17770 discloses a fuel injection nozzle provided with a similar groove. However, since the groove is provided in the needle valve, it is necessary to align the fuel injection nozzle with the sub injection hole. Therefore, a means for stopping the rotation of the needle valve is required, resulting in a complicated structure and high cost. Further, the present invention is advantageous in these respects because it is not considered in combination with the combustion chamber and the directing direction of each injection hole is not considered at all.

While the preferred embodiment of the present invention has been described above, the present invention can adopt various other embodiments. For example, the fuel impingement table may be formed as a separate component and attached to the bottom of the combustion chamber, or may be attached by hanging down from the lower surface of the cylinder head. The shape of the groove may be a straight line or the like instead of the fan shape as described above, and the length along the nozzle center direction and the width along the circumferential direction can be appropriately changed. Furthermore, the present invention is not only compact,
It is widely applicable to large diesel engines.

[0034]

The present invention has an excellent effect that it is possible to simultaneously suppress unburned HC during low load operation and reduce smoke during high load operation.

[Brief description of the drawings]

1 is a vertical sectional front view of a fuel injection nozzle of a diesel engine according to the present invention, and is a cross-sectional view taken along line BB of FIG. 2;

FIG. 2 shows a cross section of the nozzle body, and is a cross-sectional view taken along line AA of FIG.

FIG. 3 is a vertical sectional front view of a fuel injection nozzle according to another embodiment, and is a cross-sectional view taken along line DD of FIG. 4;

4 shows a cross section of the nozzle body, and is a cross-sectional view taken along line CC of FIG. 3;

FIG. 5 is a longitudinal sectional front view showing a main part of the diesel engine according to the present invention.

FIG. 6 is a view showing a state of fuel injection of the diesel engine according to the present invention.

DESCRIPTION OF SYMBOLS 1 Diesel engine 2 Piston 3 Combustion chamber 4 Side wall 8 Fuel collision surface 10 Fuel injection nozzle 13 Nozzle body 14 Needle valve 17 Main injection hole 22 Seat portion 27 Sub injection hole 28 Groove 30 First cutout 31 Second Notch 32 First protrusion 33 Second protrusion

Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02M 61/14 310 F02M 61/14 310D

Claims (2)

[Claims] 1. A combustion chamber formed by recessing a piston top surface and having a fuel collision surface at a center portion, and a fuel injection nozzle disposed to face the combustion chamber, the nozzle body comprising: A main injection hole directed to the fuel collision surface, a sub-injection hole directed to the side wall of the combustion chamber, and a seat for seating a needle valve; and an inner surface of the nozzle body which is circumferentially spaced from the sub-injection hole. A fuel injection nozzle having a groove extending from below the seat portion toward the main injection hole. 2. A first notch portion and a second notch portion extending in a circumferential direction below the seat portion and above the main injection hole, respectively, are provided on an inner surface of the nozzle body, and the needle valve is provided. Having a first projection and a second projection fitted into the first notch and the second notch, respectively;
The diesel engine according to claim 1, wherein the groove is provided between the first notch and the second notch.