JPS6027782Y2 - Direct injection combustion chamber of diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a direct injection combustion chamber mainly applied to small diesel engines.

By the way, this type of direct injection combustion chamber has advantages such as a simpler structure and better startability compared to the pre-chamber type combustion chamber, but on the other hand, it has the advantage of emitting a large amount of soot and nitrogen oxides. , there are disadvantages such as poor exhaust conditions and high noise levels due to the high maximum pressure inside the cylinder, especially in small engines, the diameter of the cavity formed at the top of the piston is small, so it is injected from the nozzle. The fuel spray directly collides with the inner surface of the cavity and does not mix well with the air.In addition, if the nozzle hole is narrowed to shorten the distance the spray reaches, the hole may become clogged. This results in harmful effects such as making it easier to use.

To address these drawbacks of direct injection combustion chambers, it is effective to create a vortex in the intake air by creating a special shape for the intake port, thereby quickly forming a uniform air-fuel mixture. However, in the case of a small engine, if the nozzle must be eccentric to the cavity due to the layout of the intake and exhaust valves, the distance from each nozzle hole to the inner surface of the cavity is not constant, so the intake Even if a vortex is formed, a uniform mixture will not be formed.
Therefore, the above-mentioned drawbacks of the direct injection combustion chamber cannot be completely eliminated.

The present invention was developed in view of the above circumstances, and is a small-sized device in which the nozzle is eccentric to the cavity formed at the top of the piston with a circular planar shape, and the nozzle is installed with the nozzle orifice directed into the cavity. In a direct injection combustion chamber of a diesel engine, a constriction part is formed in the upper part of the above-mentioned cavity formation range on the upper surface of the piston, and the planar shape of the constriction part is such that the side closer to the nozzle is square, and the side closer to the nozzle is square. One side of the nozzle has a square semicircular and semiangular shape with a corner near the directional position when viewed from the plane of the nozzle nozzle hole, and an inclined groove is formed on the inner circumferential surface of the circular side of the constriction part. By forming vertical grooves on the inner circumferential surface of the square side, the vortex flow is attenuated on the square side far from the nozzle nozzle hole, extending the reach of the fuel spray, thereby forming a uniform air-fuel mixture. At the same time, the inclined grooves on the circular sides give vortices to the squish and reverse squish to promote the formation or combustion of an air-fuel mixture, thereby achieving complete combustion and improving the exhaust condition,
Furthermore, the maximum pressure can be lowered to reduce the noise level.

This will be explained below with reference to an embodiment shown in the drawings. In FIG. 1, 1 is a cylinder block, 2 is a piston, and 3 is a cylinder head, and a combustion chamber 4 is formed by these.

5 is a cavity with a circular planar shape formed by recessing the top of the piston, 6 is a fuel injection nozzle attached to the head, and the center of the cavity is an intake and exhaust valve (not shown). Due to the layout of the combustion chamber, the nozzle is eccentric from the center of the combustion chamber, and the nozzle is also eccentric from the center of the cavity. The holes are directed into the cavity.

Although the constriction part 7 is formed in the upper part of the cavity formation range on the upper surface of the piston, the planar shape of the constriction part is the side part 7a closer to the nozzle 6 as shown in FIG. is circular, and the far side 7b is square with corners 7c, 7c near the orientation position when viewed from the plane of the nozzle nozzle hole, and the overall shape is semicircular and semiangular. A plurality of inclined grooves 8a are formed on the inner peripheral surface of the side portion 7a, and a plurality of vertical grooves 8 are formed on the inner peripheral surface of the rectangular side portion 7b.
b are formed respectively.

Here, the corner 7C is preferably formed to be slightly shifted from the directional position of the nozzle injection hole in the direction of the vortex flow.

According to the above configuration, the intake vortex formed in the combustion chamber 4 due to the shape of the intake port during the intake stroke of the piston 2 is preserved without being attenuated inside the cavity 5, and the upper part of the cavity is constricted. In the section 7, since the shape of the section is semicircular and half square, the vortex flow as a whole is slower than the inside of the cavity, and especially in the square side section 7b, the corner 7C and the vertical groove 8b create resistance. As a result, the vortex flow is significantly attenuated.

However, when the piston 2 moves to the compression stroke in this state,
The so-called squish in which air is forced into the cavity 5 from the combustion chamber 4 is swirled by the inclined groove 8a formed on the inner circumferential surface of the circular side part 7a of the constriction part 7, so that the vortex flow in the cavity is further promoted. At the same time, when the fuel is injected from the nozzle 6 at the end of the stroke,
When the fuel spray passes through the constriction part 7, as shown in FIG. 2, the vortex is relatively strong in the circular side 7a near the nozzle. While it flows in the circumferential direction and reaches a longer distance,
Since the vortex flow is attenuated as described above in the rectangular side part 7b, it reaches a long distance, so that the state of the fuel spray on both sides becomes approximately equal and a uniform air-fuel mixture is formed. Furthermore, since a strong vortex is formed inside the cavity as described above, the air-fuel mixture formed in the constriction section 7 quickly mixes with the air inside the cavity, thereby promoting the formation of the air-fuel mixture. Moreover, after ignition, the so-called reverse squish blown out from the cavity 5 into the combustion chamber 4 is swirled by the inclined groove 8a, and the combustion gas is stirred, so that combustion is completed in a short time. As a result, fuel is completely combusted, soot and nitrogen oxide emissions are significantly reduced, and at the same time, output is improved.

Note that FIG. 3 shows an embodiment in which the bottom surface of the cavity 15 formed at the top of the piston 12 is flat and has no protrusion in the center, unlike the cavity 5 in the embodiments of FIGS. 1 and 2. Also in the embodiment, the constriction portion 17 and the slope 11
118a, vertical radius 18b, etc., the same effect as in the embodiment shown in FIGS. 1 and 2 is achieved.

As described above, in the present invention, the nozzle is eccentric to the cavity formed in the top of the piston with a circular planar shape,
In a direct injection combustion chamber of a small diesel engine in which the nozzle hole is installed with the nozzle hole directed into the cavity, a constriction part is formed in the upper part within the cavity forming range,
The planar shape of the constriction part is a semicircle and a half square in which the side of the force near the nozzle is circular and the corner is square near the pointing position when viewed from the plane of the nozzle nozzle hole on the far side, and By forming an inclined groove on the inner peripheral surface of the circular side part and a vertical groove on the inner peripheral surface of the rectangular side part, the nozzle is eccentric to the cavity. First, the reach distance of the fuel spray is substantially adjusted between the side close to the nozzle and the side far from the nozzle, so that a mixture is uniformly formed, and the squish and reverse squish are caused to swirl by the inclined groove. As a result, the air-fuel mixture is formed or burned quickly, which improves combustion conditions.
The emissions of soot and nitrogen oxides are reduced, resulting in better exhaust conditions, and the required output performance can be obtained even if the maximum pressure is lowered, reducing noise, which is a drawback of direct injection combustion chambers. This has the effect of making it possible to

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of the vicinity of the combustion chamber in an embodiment of the present invention, FIG. 2 is a plan view of the piston in the embodiment, and FIG.
The figure is a longitudinal sectional view of a piston showing another embodiment of the cavity. 2 is a piston, 5 is a cavity, 6 is a nozzle, 7 is a constriction part, 7a is a side close to the nozzle (circular side), 7b is a side far from the nozzle (square side), 8a is an inclined groove ,8b
is a vertical groove.

Claims (1)

[Scope of utility model registration request] In a configuration in which the nozzle is installed eccentrically with respect to the center of a cavity formed with a circular planar shape at the top of the piston, and the nozzle hole is directed into the cavity, the nozzle is constricted to the upper part within the area where the cavity is formed. At the same time, the planar shape of the constricted part is such that the side part near the nozzle is circular;
The far side has a rectangular semicircular and semiangular shape with even parts near the orientation position when viewed from the plane of the nozzle nozzle hole, and an inclined groove is formed on the circumferential surface of the circular side in the constriction part. A direct injection combustion chamber for a diesel engine, characterized in that vertical grooves are formed on the circumferential surface of each side of the combustion chamber.