JPH04298628A - Direct injection type diesel engine - Google Patents

Abstract

PURPOSE:To stabilize dispersion action when an engine is retarded in the injection timing, and prevent generation of an over-thick region on an impact plate caused by fuel atomization splashing in a linear injection type diesel engine for forcing injected fuel to collide with the impact plate once in a combustion chamber, and widely dispersing it in the radial direction. CONSTITUTION:A deep dish type combustion chamber 4 is formed on a piston 3, and a fuel injection valve 6 is arranged in its center. An impact plate 11 is supported by the fuel injection valve 6 through a leg portion 12, and faced to an injection hole so that injected fuel may collide thore with. The injection hole side surface of the leg portion 12 is formed into a circular arc inclined surface, so as to spread atomized fuel dispersed in the radial direction outside the impact plate 11 when the atomized fuel collides therewith.

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 direct injection diesel engine in which fuel injected from a fuel injection valve is caused to collide with a collision plate within a combustion chamber to be widely dispersed in the radial direction.

0002

[Prior Art] In a typical direct injection diesel engine, a multi-hole fuel injection valve injects fuel toward the inner wall of a combustion chamber on the top surface of a deep-dish piston. Since diffusion combustion is performed from the outer circumferential side of the combustion chamber by contacting with air of It is easy to carbonize and be emitted as black smoke.

Therefore, in recent years, fuel injected from a fuel injector is made to collide with a collision plate in the combustion chamber to be dispersed widely in the radial direction, and then to move in the axial direction of the combustion chamber by utilizing the squish caused by the upward movement of the piston. A direct injection diesel engine that performs diffuse combustion has been proposed (for example, "Internal Combustion Engine", October issue 79, published by Sankaido Co., Ltd., October 1989).
(see page).

FIG. 6 shows this conventional direct injection diesel engine, in which a fuel injection valve 3 with a single injection hole is disposed on the cylinder head 33 side, facing the center of the combustion chamber 32 on the piston 31 side.
4 is mounted vertically. Disc-shaped collision plates 35 are formed in the center of the combustion chamber 32 in a stacked manner in multiple stages so as to face the nozzle holes of the fuel injection valves 34 .

In this engine, fuel vertically injected from the fuel injection valve 34 collides with the collision plate 35, so that fuel spray is dispersed in a disk shape within the combustion chamber 32. In particular, since the collision plate 35 is always kept at a high temperature, atomization and vaporization are promoted during fuel collision. Mixing with air is promoted by the squish flow accompanying the rise of the piston 31, and diffusive combustion is performed along the axial direction. Therefore, less fuel is placed in a high-temperature atmosphere with insufficient oxygen, and the generation of black smoke is suppressed.

[0006]

However, in the case where the collision plate 35 is formed on the piston 31 as described above, depending on the position of the piston 31, the nozzle hole of the fuel injection valve 34 and the collision plate 3
The relative position with 5 changes. That is, due to changes in the fuel injection timing, the relative positions of the two are not constant, and the fuel dispersion effect by the collision plate 35 becomes unstable. Further, in the region where the fuel injection pressure is low at the start and end of fuel injection, the position of the collision plate 35 becomes far from the nozzle hole, and the fuel tends to be insufficiently dispersed. In particular, when the fuel injection timing is retarded to reduce NOx, the collision plate 35 becomes further away from the nozzle hole in the latter stage of injection, resulting in poor fuel dispersion.

On the other hand, if the collision plate 35 is positioned above the combustion chamber 32 in an attempt to bring the collision plate 35 closer to the nozzle hole, the collided fuel will be dispersed at the upper part of the combustion chamber 32, and the inside of the combustion chamber 32 will be The air utilization rate decreases, and fuel tends to scatter outside the combustion chamber 32, causing an increase in HC.

Furthermore, in the above configuration, it is not possible to test or confirm the fuel dispersion effect of the fuel injection valve 34 alone, and it is difficult to check its variations and adjust its characteristics.

In addition, Japanese Utility Model Application Publication No. 59-43631 discloses that a plurality of collision plates directed diagonally downward are formed on the lower surface of the cylinder head covering the upper part of the combustion chamber, thereby preventing the flow of air from the multi-hole fuel injection valve. A system has also been disclosed in which the injected fuel is collided with each other to atomize the particles, but in such a configuration, the space around the fuel injection valve is largely occupied by the collision plate, and the diameter of the intake and exhaust valves is reduced. It is difficult to accurately obtain the relative position of the collision plate and each nozzle hole, and the fuel diffusion effect tends to vary.Therefore, it cannot be used in practical applications.

0010

[Means for Solving the Problems] A direct injection diesel engine according to the present invention includes a combustion chamber recessed in the top surface of the piston, and a combustion chamber mounted on the cylinder head side facing approximately the center of the combustion chamber. A fuel injection valve with a single injection hole, which is disposed facing the injection hole of the fuel injection valve and substantially parallel to the top surface of the piston, and is supported by the fuel injection valve via a leg part, and is arranged on the piston. and a collision plate located in the combustion chamber at the dead center position, and is characterized in that the surface of the leg on the nozzle hole side is formed into a convex arcuate surface or an inclined surface.

[0011]

[Operation] In the above structure, the fuel injected from the injection hole of the fuel injection valve collides with the collision plate supported by the fuel injection valve,
Distribute widely around the area. Since the collision plate is supported by the fuel injection valve, its relative position with respect to the nozzle hole does not change, and a stable dispersion effect can be obtained. In addition, some of the fuel dispersed by the collision plate collides with the legs that support the collision plate, but in this case, the surface of the legs on the nozzle hole side is a convex arcuate surface or an inclined surface. Therefore, it does not bounce above the collision plate, but scatters outward from the collision plate. .

0012

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing a first embodiment of a direct injection diesel engine according to the present invention, in which a cylinder 2 is formed in a cylinder block 1, and a piston 3 is installed in the cylinder block 1.
are slidably fitted.

A combustion chamber 4 in the shape of, for example, a deep dish is recessed approximately in the center of the top surface of the piston 3.

The lower surface of the cylinder head 5 covering the upper end of the cylinder 2 is flat, and a fuel injection valve 6 is attached to the cylinder head 5 side. For more information,
An injection valve mounting hole 7 is vertically formed above the center of the combustion chamber 4, into which a cylindrical fuel injection valve 6 is inserted together with a seal member 9, and a nozzle tip 10 with a small diameter is inserted into the cylinder head. 5 through the lower deck 5a,
It protrudes slightly toward the combustion chamber 4 side. The fuel injection valve 6 has a single injection hole having an injection direction along its central axis, that is, it injects fuel perpendicularly to the top surface of the piston 3.

A disc-shaped collision plate 11 is supported at the tip of the fuel injection valve 6. The collision plate 11 is
It faces the nozzle hole with an appropriate gap maintained between it and the tip of the fuel injection valve 6, and is arranged parallel to the top surface of the piston 3. In other words, it is perpendicular to the injection axis. Further, as shown in FIG. 2, the collision plate 11 is supported via four parallel legs 12 fitted to the outer peripheral surface of the nozzle tip 10, and is supported by a cylindrical portion on the base end side of the legs 12. The continuous annular flange portion 13 forms a housing tip portion 14 of the fuel injection valve 6.
and the seal member 9. That is, the collision plate 11 is supported at a position protruding from the lower surface of the cylinder head 5, and is in a state of being inserted into the combustion chamber 4 at the top dead center position of the piston 3, as shown in FIG.

Here, the four legs 12 are connected to the outer circumference of the circular collision plate 11 at positions 90° apart, as shown in FIG. Each of the side surfaces 12a is a convex arcuate surface, more specifically, an arcuate surface close to a semicircle. Note that this leg portion 12 is formed as thin as possible within a range that does not cause any problems in terms of strength and durability.

In the configuration of the above embodiment, the piston 3
Fuel injected from the fuel injection valve 6 near the top dead center position collides with the collision plate 11 and widely disperses in the radial direction over the entire circumference. At this time, the relative position between the nozzle hole and the collision plate 11 remains unchanged regardless of the position of the piston 3, etc., and a good dispersion effect can always be stably obtained. Further, even at the start and end of injection when the fuel injection pressure is relatively low, or in the low speed and low load range, the distance between the two is kept optimal, so a sufficient dispersion effect can be obtained.

During the fuel injection period, the piston 3 moves up and down, thereby causing the combustion chamber 4 and the collision plate 11 to move relative to each other. Therefore, the fuel spray heading in the radial direction from the collision plate 11 is more widely diffused along the vertical direction of the combustion chamber 4, and the fuel distribution within the combustion chamber 4 is equalized, and the fuel spray is mixed with the air. becomes good. This makes it possible to achieve combustion with less smoke and less NOx.

By the way, a part of the fuel dispersed in the radial direction by the collision plate 11 collides with the leg portion 12 that supports the collision plate 11. At this time, the fuel spray that collided with the leg part 12 hits the collision plate 1.
1 center side, that is, above the collision plate 11, the space surrounded by the legs 12 becomes a partially concentrated area, causing an increase in smoke and HC. Since it forms an arcuate surface, arrows F1 and F2 are shown in Fig. 2.
As shown, the fuel spray that collides with the leg portion 12 is always guided to the outside of the collision plate 11. Therefore, the upper portion of the collision plate 11 does not become a partially concentrated region.

Furthermore, with the above configuration, the fuel dispersion effect can be tested and confirmed with the collision plate 11 attached to the fuel injection valve 6, and it becomes easy to check for variations. Further, the state of scattering of fuel spray on the leg portions 12 can also be easily confirmed.

Next, FIG. 3 shows the main part of a second embodiment of the present invention. In this embodiment, the leg portion 12 has a substantially triangular cross-sectional shape. In other words, the surface 12a on the nozzle hole side is V
It has a slanted surface in the shape of a letter. Therefore, also in this embodiment, the fuel spray that collides with the leg portion 12 is always guided to the outside of the collision plate 11. Incidentally, if such a substantially triangular shape is used, the processing becomes easier than in the above-mentioned embodiments.

Further, FIGS. 4 and 5 show essential parts of a third embodiment of the present invention. In this embodiment, the nozzle hole side surface 12a of the leg portion 12 is formed into an arcuate surface similarly to the first embodiment, and the lower portion of the leg portion 12 and the collision plate 11 are arranged at an arcuate corner portion 15. connected smoothly. This corner portion 15 gradually tapers as it approaches the collision plate 11.

Therefore, in this embodiment, the leg portion 12
The fuel spray heading toward the bottom does not change direction suddenly, and its scattering direction changes very smoothly. Therefore, the fuel is even better dispersed in each part.

In each of the above embodiments, the fuel injection valve 6 is arranged perpendicularly to the center of the combustion chamber 4, but in the present invention, the fuel injection valve 6 is arranged at a position slightly offset from the center of the combustion chamber 4. The same applies to cases where the device is installed in a tilted position or in a tilted position.

[0026]

[Effects of the Invention] As is clear from the above explanation, according to the direct injection diesel engine according to the present invention, since the collision plate for colliding the injected fuel is supported by the fuel injection valve, the collision plate is formed on the piston side. Unlike in the case where the fuel injection pressure is relatively low, the positional relationship between the nozzle hole and the collision plate can be maintained constant, and a good fuel dispersion effect can be maintained even in a region where the fuel injection pressure is relatively low. Then, it becomes possible to retard the injection timing for reducing NOx.

Furthermore, since the surface of the nozzle hole side of the leg that supports the collision plate is an arcuate surface or an inclined surface, even if the fuel spray dispersed in the radial direction from the collision plate collides, it will spread outward. Therefore, no local over-concentration area is generated above the collision plate. Therefore, combustion with less smoke and NOx can be achieved by effectively utilizing the dispersion effect of the collision plate.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a first embodiment of a direct injection diesel engine according to the present invention.

FIG. 2 is an enlarged sectional view taken along line A-A in FIG. 1.

FIG. 3 is an enlarged sectional view of essential parts showing a second embodiment of the invention.

FIG. 4 is an enlarged sectional view of main parts showing a third embodiment of the invention.

FIG. 5 is a sectional view taken along line BB in FIG. 4;

FIG. 6 is a sectional view showing an example of a conventional direct injection diesel engine.

[Explanation of symbols]

3...Piston 4... Combustion chamber 5...Cylinder head 6...Fuel injection valve 11...Collision plate 12... Legs

Claims (1)

[Claims] [Claim 1] A combustion chamber recessed in the top surface of the piston;
a single injection hole fuel injection valve mounted on the cylinder head side facing substantially the center of the combustion chamber; and a single injection hole disposed substantially parallel to the top surface of the piston opposite the injection hole of the fuel injection valve;
and a collision plate supported by the fuel injector via a plurality of legs and located inside the combustion chamber at the top dead center position of the piston, the surface of the leg on the nozzle hole side being convex. A direct injection diesel engine characterized by having a shaped circular arc surface or inclined surface.