JP2000291513A - diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a direct injection type diesel engine fuel injection for a diesel engine which injects a fuel having a relatively low penetration force at a low load and injects a relatively strong fuel at a high load. Provide a valve. SOLUTION: In a diesel engine including a combustion chamber and a fuel injection valve for directly injecting fuel into the combustion chamber, the fuel injection valve has a turning force applying means, and the turning force applying means when the engine is under a low load. The fuel is injected in a hollow conical shape by applying a swirling force to the fuel, and the fuel is injected in a columnar shape without applying the swirling force to the fuel when the engine is under a high load.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a diesel engine.

[0002]

2. Description of the Related Art As a method of supplying fuel to a combustion chamber in a diesel engine, a direct injection type in which fuel is directly injected into a combustion chamber formed on a piston top surface is known. In the direct injection type fuel injection, when the load is relatively small and the load is low, the temperature of the wall of the combustion chamber is relatively low.If the fuel adheres to the wall, the fuel does not vaporize sufficiently. Since the fuel is incompletely burned, it is necessary to inject the fuel having a weak penetration force so that the fuel does not adhere to the wall surface. Also, at the time of high load where the required fuel amount is relatively large, it is necessary to use a relatively large amount of air in the combustion chamber, so that the fuel has a strong penetration force,
It is preferred that the fuel be positively collided with the wall of the combustion chamber to be atomized and dispersed. At this time, even if the fuel adheres, the fuel is vaporized because the temperature of the wall surface of the combustion chamber is relatively high, so that there is no problem such as when the load is low. Therefore, as a fuel injection valve capable of switching the strength of the penetration force of the injected fuel, a fuel injection valve described in Japanese Patent Application Laid-Open No. 7-224739 is known. This fuel injection valve has a first injection hole with a small injection hole diameter and a second injection hole with a large injection hole diameter, and at low load, a relatively weak penetration force by injecting fuel only from the first injection hole. By injecting the fuel from the second injection hole in addition to the first injection hole at the time of a high load, it is possible to inject the fuel having a relatively strong penetration force.

[0003]

However, when the load is low, even if the fuel is injected from an injection hole having a small injection hole diameter, the fuel is injected in a columnar shape, so that the penetration force of the fuel becomes relatively strong. To the wall surface, and good combustion cannot be obtained.

Accordingly, an object of the present invention is to provide a direct injection type diesel engine in which fuel is directly injected from a fuel injection valve into a concave combustion chamber formed on a piston top surface, regardless of the engine load. It is to realize.

[0005]

In order to solve the above problems, a diesel engine according to the first aspect of the present invention comprises a combustion chamber and a fuel injection valve for directly injecting fuel into the combustion chamber. In a diesel engine, the fuel injection valve has a slewing force applying means, applies a slewing force to the fuel by the slewing force applying means at a low engine load, injects the fuel into a hollow conical shape, and at a high engine load. It is characterized in that the fuel is injected in a columnar shape without imparting a turning force to the fuel.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the accompanying drawings. The diesel engine shown in FIG. 1 has a fuel injection valve 1 and a piston 3, and a concave combustion chamber 4 is formed on a top surface of the piston 3. The fuel injection valve 1 is disposed substantially vertically above the center of the combustion chamber 4. The fuel injection valve 1 mainly includes a valve body 5 and a valve body 6. The fuel injection valve 1 is an internal valve that injects fuel when the valve body 5 is lifted in the axial direction of the fuel injection valve 1.

The shape of the valve body 6 will be described with reference to FIGS. The valve body 6 includes a cylindrical portion held by the cylinder head 2 and a forked portion located below the cylindrical portion. A substantially cylindrical valve body 5 is disposed at the center inside the cylindrical portion of the valve body 6, and a cylindrical fuel passage 12 is formed between the inner surface of the valve body 6 and the outer surface of the valve body 5. I have. Valve body 6 located downstream of fuel passage 12
A conical valve body inclined portion 13 is formed on the inner surface of the circular cap-shaped portion, and a fuel reservoir 15 composed of a cylindrical portion and a hemispherical portion is formed downstream of the valve body inclined portion 13. A valve body seat portion 14 is formed at a position on the valve body inclined portion 13 where the valve body 5 sits. The first fuel injection passage 1 is located downstream of the valve body seat portion 14 in the valve body inclined portion 13.
Six inlets are formed. An inlet of the second fuel injection passage 17 is formed in the fuel reservoir 15. The first fuel injection passage 16 and the second fuel injection passage 17 communicate with each other at an injection port 18 formed on the surface of the valve body 6. The first fuel injection passage 16, the second fuel injection passage 17, and the injection port 18 are radially located at substantially equal intervals with respect to the central axis of the fuel injection valve 1.

The shape of the valve body 5 will be described with reference to FIGS. The valve element 5 includes a cylindrical valve element body section 7, a conical valve element inclined section 8 formed below the valve element body section 7, and a cylindrical guide formed below the valve element inclined section. It comprises a portion 9 and a valve needle 10 formed below the valve guide.
Since the valve body 7 is connected to a mechanism (not shown) for controlling the vertical movement of the valve 5, the valve 5 can move up and down. The valve body inclined portion 8 is formed in a conical shape so as to fit with the valve body inclined portion 13 of the valve body 6. Valve body inclined part 8
The first fuel injection passage 16 and the second fuel injection passage 17 can be shut off from the fuel passage 12 by being seated on the valve body seat portion 14 in the valve body 6.
The guide section 9 has a cross-sectional shape that matches the cross-sectional shape of the cylindrical portion of the fuel reservoir 15 of the valve body 6, and allows the second fuel injection passage 17 to pass through the fuel passage even when the valve body 5 is lifted relatively small. 12 and at this time allows the valve body 5 to be guided in the cylindrical part of the fuel reservoir 15 of the valve body 6. On the downstream side of the position where the valve element 5 is seated on the valve body 6, an elliptical groove 11 is formed in the valve element inclined section 8 so as to face the first fuel injection passage 16 with respect to the ridge line of the valve element inclined section 8. It is formed diagonally. Each groove 11
When the lift amount of the valve element 5 is relatively small, it is disposed so as to face only the periphery of the entrance with respect to the entrance of the corresponding first fuel injection passage 16. The groove 11 may be parallel to the ridge line of the valve body inclined portion 8. The cross-sectional shape of the groove 11 is not limited to a circle, but may be a rectangle.

Next, the operation of the fuel injection will be described.
When the lift amount of the valve body 5 is relatively small, a thin conical gap 19 is formed between the valve body inclined portion 8 and the valve body inclined portion 13. When the fuel stored at a high pressure passes through the gap 19, the groove 11 is deeper than the thickness of the gap 19,
Part of the fuel is sucked into the depressurized groove 11 and the groove 1
Flows along 1. Thus, the fuel provided with the velocity component in the longitudinal direction of the groove flows into the peripheral portion of the first fuel injection passage 16 formed in the valve body inclined portion 13 in the tangential direction of the peripheral portion of the inlet. Is done. As a result, the fuel advances while turning in the first fuel injection passage 16, and has a hollow conical shape immediately after the injection. Thus, the groove 1
Reference numeral 1 designates a turning force applying means for applying a turning force in the first fuel injection passage 16 to the fuel when the lift amount is relatively small. On the other hand, at this time, the second fuel injection passage 17
The fuel is not injected because it is shut off by the guide portion 9.

When the lift amount of the valve body 5 is relatively large, the valve body inclined portion 8 and the valve body inclined portion 13 are largely separated from each other so that a thick conical body is formed between the valve body inclined portion 8 and the valve body inclined portion 13. A gap 19 is formed. Further, the guide portion 9 of the valve element 5 is separated from the fuel reservoir 15. When the fuel stored at a high pressure passes through the gap 19, the fuel flows in the ridge line direction of the gap 19 because the groove 11 has a shape that can be ignored compared to the thickness of the gap 19. The fuel near the inlet of the first fuel injection passage 16 is:
The fuel is sucked into the first fuel injection passage 16 and goes straight to be injected. On the other hand, the fuel that has not been sucked into the first fuel injection passage 16 in the gap portion 19 flows to the downstream fuel reservoir 15, is sucked at the inlet of the second fuel injection passage 17, and is straightly injected. First fuel injection passage 16 and second fuel injection passage 17
The fuel coming out of both of them joins at the injection port 18 to form one fuel flow.

The fuel injection port 18 joins the fuel by guiding the fuel flow having two different directional components flowing from the first fuel injection passage 16 or the second fuel injection passage 17 on the wall surface. It plays the role of trimming in the direction of the wall. The greater the depth from the surface of the nozzle 18, the smaller the spray angle of the combined fuel flows. The combined fuel flow is
Cross-sectional area of first fuel injection passage 16 and second fuel injection passage 1
Equivalent to having a total orifice area of 7 cross-sectional areas. That is, the merged fuel flow can have a large penetration force. By combining the two fuel flows at a high engine load, the combined fuel flows realize atomization of fuel which is good for combustion due to the small injection hole area of each fuel injection passage. Fuel injection passage 16, 1
7 can have a greater penetration force than the fuel penetration force.

By selecting the amount of lift of the valve body 5 at the time of injection, the fuel injection mode can be changed. For example, when spraying with a large valve body lift during hollow cone spraying, a hollow cone-shaped spray with a small spray angle is formed, and when spraying with a small valve body lift, a hollow cone-shaped spray with a large spray angle is formed. The fuel injection mode can also be changed by changing the length of the guide portion 9 of the valve element 5. For example, when the guide portion 9 is shortened, the fuel passage 12 communicates simultaneously with both the first fuel injection passage 16 and the second fuel injection passage 17 with a small valve body lift, and the hollow conical spray is discharged from the first fuel injection passage 16. When the fuel is injected, the columnar spray can also be simultaneously injected from the second fuel injection passage 17. Preferably, when the lift amount of the valve body 5 is a lift amount of 30 to 50% of the total lift amount, fuel is injected in a hollow conical shape only from the first fuel injection passage 16 and the lift amount of 100% of the total lift amount is The length of the guide portion of the valve element 5 is selected so that the fuel is sometimes injected in a column shape from the first fuel injection passage 16 and the second fuel injection passage 17. Further, the fuel injection timing is controlled by adjusting the lift timing of the valve element 5, and the fuel injection amount is controlled by adjusting the injection time, that is, the lift time of the valve element 5.

Next, the fuel injection through each engine load will be described. In the case of a low engine load, as shown in FIG. 3, during the compression stroke, the valve element 5 is lifted by a predetermined amount for a predetermined time while the guide portion 9 of the valve element 5 is held in the fuel reservoir 15 of the valve body 5. Thereby, the fuel is injected from the first fuel injection passage 16 in a hollow conical shape. By injecting the fuel in a hollow conical shape, the fuel having a low penetration force is injected, and the fuel can be mixed with air without adhering to the wall surface.

In the case of the engine middle load, as shown in FIG. 3, at the beginning of the compression stroke, the fuel is injected in a hollow conical form only from the first fuel injection passage 16, and at the end of the compression stroke, as shown in FIG. By lifting the valve body 5 for a predetermined time by a larger predetermined amount in a state where the guide portion 9 is separated from the fuel reservoir 15, not only the first fuel injection passage 16 but also the second fuel injection passage 17 Fuel is injected. These two fuel streams merge at the nozzle 18 to form one columnar spray. The advantage that the fuel can be prevented from adhering to the wall surface as much as possible, because the amount of injection in one shot can be reduced by injecting the hollow conical spray and the columnar spray, respectively. Is injected, so that there is an advantage that a wide range of air in the combustion chamber can be used.

In the case of a high engine load, as shown in FIG. 5, in the compression stroke, the valve element 5 is lifted for a predetermined time by a predetermined amount larger than the valve element lift amount at the time of columnar spraying at a medium engine load. Accordingly, a relatively large amount of fuel is injected in a column shape from the outlets of the first fuel injection passage 16 and the second fuel injection passage 17. In this way, the fuel having a strong penetration force is injected and collides with the combustion chamber wall surface, and the fuel is well dispersed. As described above, good combustion can be obtained regardless of the engine load. The fuel injection timing is not limited to the timing described above,
The present invention can be implemented.

Another embodiment of the turning force applying means will be described. The valve body seat portion 1 in the valve body inclined portion 13
4, a groove is formed in the periphery of the inlet of the first fuel injection passage 16 so as to communicate tangentially to the periphery of the inlet. When the valve body 5 is lifted by a small amount, the groove portion is swirled in the first fuel injection passage 16 to inject the fuel into a hollow conical shape,
It constitutes a turning force applying means.

In the above description, the first fuel injection passage 1
6 and the second fuel injection passage 17 merge at the injection port 18, but the first fuel injection passage 16 and the second fuel injection passage 17
Another embodiment is also conceivable in which injection holes are separately arranged without merging. In this embodiment, the fuel flow from each fuel injection passage is not merged at the time of columnar spraying at the time of medium load of the engine, so that it has a low penetration force, and a wider range of air in the combustion chamber can be used. Is preferred.

In the above description, the fuel injection valve, valve body,
The shapes of the valve body, combustion chamber, etc. are described as preferred embodiments, but are not required to limit the invention.

[0019]

According to the present invention, in a diesel engine having a combustion chamber and a fuel injection valve for directly injecting fuel into the combustion chamber, the fuel injection valve has a turning force applying means, In order to inject the fuel in a hollow conical shape by applying a turning force to the fuel by the turning force applying means at the time of load, and to inject the fuel in a columnar shape without applying the turning force to the fuel at the time of high engine load, the engine low At the time of load, the fuel is injected in a hollow conical shape so that the fuel can be distributed without adhering to the combustion chamber wall surface. Can be atomized and dispersed, and good combustion can be realized regardless of the engine load.

[Brief description of the drawings]

FIG. 1 is a sectional view of a fuel injection valve of the present invention.

FIG. 2 is an enlarged sectional view of the fuel injection valve of the present invention.

FIG. 3 is a diagram showing a fuel injection timing at a low engine load according to the present invention.

FIG. 4 is a diagram showing a fuel injection timing at the time of an engine middle load according to the present invention.

FIG. 5 is a diagram showing a fuel injection timing when the engine is under a high load according to the present invention.

[Explanation of symbols]

 1. Fuel injection valve 4. Combustion chamber

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Ichiro Sakata 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Mikio Nakamura 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Kiyoshi Fujiwara 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Susumu 1 Toyota Town Toyota City, Aichi Prefecture Toyota Motor Corporation F-term (reference) 3G066 AA07 AB02 AD12 BA03 BA04 CC14 CC18 CC23 CC26 CC30 CC42 CC48 DA09 DB06 DB08 DB09

Claims (1)

[Claims] 1. A diesel engine comprising a combustion chamber and a fuel injection valve for directly injecting fuel into the combustion chamber, wherein the fuel injection valve has a turning force applying means, and when the engine is under a low load, A diesel engine characterized in that a swirling force is applied to fuel by a swirling force applying means and the fuel is injected in a hollow conical shape, and the fuel is injected in a columnar shape without applying a swirling force to the fuel when the engine is under a high load.