JPS6229611B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The invention provides that the recess of the piston is provided in the upper surface of the piston and has an inlet opening having a cylindrical neck and a side wall that widens conically from the neck towards the bottom of the recess. At an opening radius greater than the total depth of the recess, the side walls transition to the bottom of the recess, which is formed flat;
The present invention relates to a self-igniting internal combustion engine with a rotationally symmetrical piston recess, in which the injection nozzle injects fuel into the recess so as to wet the wall. In such internal combustion engines, the swirling movement of the incoming and compressed air is usually effected by known means. That is, by appropriate selection of the nozzle position and jet direction, fuel injection takes place in the direction of air movement.

Such an internal combustion engine is already known from German Patent Application No. 1032597 and is provided with an injection nozzle that injects a wide fan-shaped jet, with an injection cone extending in the direction of the injection nozzle axis. Upon hitting the edge of the piston recess, only a portion of the fuel jet reaches the piston recess.

Another configuration with a trapezoidal cross section in the longitudinal direction is also known (German Patent No. 864 475),
In this case, the injection nozzle is moved closer to the neck of the combustion chamber recess, and the multi-hole injection nozzle also makes it possible to carry out the injection in a fan-like manner.

Furthermore, annular, cylindrical or hyperboloid piston recesses are also known.

All these configurations of the piston recess have the disadvantage that they are unsatisfactory with regard to the generation of noxious exhaust gases and noise. The reason is that although by wetting the walls a somewhat better and relatively quiet combustion process is obtained, especially at low speeds and intermediate speeds in no-load and half-load operation,
Also, the unburned fuel reaches the relatively cold edges and bottom of the piston recess, where it mixes only insufficiently with the combustion air, especially in the center of the vortex, and is therefore only incompletely combusted. Furthermore, the jet is directed diagonally from top to bottom so as to wet the wall, and despite the fact that the side wall of the piston recess is tilted diagonally downward, the jet flow and expansion stroke begin, so that the jet flows upward. It has been found that the violent collision with the directed flow causes the fuel to move undesirably upwardly along the sloping frustoconical sidewalls and wet the end faces of the piston. Therefore, these fuel particles are also incompletely combusted. The incomplete combustion process of the fuel adhering to the bottom of the recess and the end face of the piston is additionally adversely affected by cooling due to expansion.

The object of the invention is to make it possible for the fuel injected into the recess to remain in the recess space until it is completely combusted.

To solve this problem, according to the invention, the neck of the inlet opening is formed as a radially inwardly projecting collar, the inner surface of which transitions with a maximum transition radius of 3 mm into a conical side wall, which side wall However, at a distance of about 12 to 33% of the total depth of the recess from the bottom of the recess, the annular ridge transitions into the radially inwardly projecting ridge side of the annular ridge that protrudes into the recess. The other raised side surface is rounded and moves to the bottom of the recess, and a plurality of The fuel injected in a jet is directed towards the side wall.

According to the invention, the neck of the inlet opening is formed as a radially inwardly projecting collar, the inner surface of which transitions into the conical side wall with a maximum transition radius of 3 mm, so that it The other part of the still liquid fuel film moving upwards is stopped by a projecting collar or deflected into a substantially horizontal plane. This deflection provides a flow-direction damming of the fuel particles wetting the wall, thereby providing sufficient time for the evaporating fuel particles to swirl together with the passing air-fuel mixture for throttling flow. The sharp ridge formed at the transition from the collar to the inlet opening facilitates the separation of fuel particles. Furthermore, a discontinuous transition that narrows to the inlet opening creates a vortex in the opposite direction to the overall flow.
and act against the fuel rising along the side walls of the piston recess and wetting the walls, stripping it from the side walls and into the overall flow. This results in a better mixture formation and a better combustion of this fuel fraction. Furthermore, by setting the axial distance between the surface of the annular raised side surface and the bottom of the piston recess to approximately 12 to 33% of the total depth of the piston recess, the separation of the residual fuel film can be achieved under the same flow conditions over the entire circumference. It will be held in By providing a pointed, protruding annular ridge in the transition area between the side wall and the bottom, the disadvantages associated with wetting of the bottom of the piston recess and the end faces of the piston with fuel are avoided, especially in the first stage. During injection, which is carried out with distributed air, the fuel particles can be trapped by the swirls and mixed well with the combustion air.
While most of the fuel film flows down towards the bottom of the piston recess, the swirl provides continuous mixing with the combustion air until it reaches the annular ridge where the remaining fuel film is sharpened. Because of the protrusion, the hot annular ridge evaporates, peels off and swirls perfectly, so that the fuel particles do not wet the bottom of the piston recess. In addition to good efficiency due to almost complete combustion, a high power output is ensured with maximum utilization of the air charge and, above all, the noise generation is reduced to a minimum. Combustion is further improved by the fact that the jet of fuel injected from the injection nozzle is directed against the side wall of the piston recess, and that the point of impact of the jet is approximately midway in the axial direction between the annular ridge and the upper surface of the piston.

In an advantageous embodiment of the invention, the apex of the annular raised cross-section is formed by two raised flanks approaching each other approximately at right angles, and furthermore, the cross-section of the annular raised flank closer to the inlet opening is approximately parallel to the upper surface of the piston. and can have a transition to the side wall with a radius of 2 to 5 mm. As a result, a good flow down to the annular ridge edges is achieved while wetting the walls, and a reliable separation of the fuel film at the hot ridges of the annular ridges is achieved.

Furthermore, the annular edge of the annular protuberance can extend in a plane parallel to the upper surface of the piston.

To ensure that the residual release film can be removed by turbulence at the annular ridge ridge, the diameter of the annular ridge ridge is approximately 0.9 to 1.1 times the diameter of the inlet opening, which is approximately 0.38 to 0.4 times the piston diameter. can be made so that

Furthermore, the injection nozzle can be arranged eccentrically with respect to the piston recess in its inlet opening.

In another embodiment of the invention, the cone angle of the side walls can be between about 7 and 15 degrees. A large cone angle thereby results in less swirl, which is disadvantageous for good mixing of air and fuel.

Finally, the total depth of the piston recess can be approximately 0.6 to 0.8 times the diameter of the inlet opening.

The invention will be further explained with reference to the embodiments shown in the drawings.

The piston 1 shown in FIGS. 1 and 2 has a rotationally symmetrical piston recess 3 in its upper surface 2, which piston recess 3 is formed by a cylindrical neck 4 and a conical side wall 5 adjoining it. 5 and the bottom 6 is provided with a protruding annular ridge 7 with a pointed cross section.

The annular ridge 7 is formed by two annular ridge flanks 8, 9 approaching each other at approximately right angles. Entrance opening 1
The cross-section of the annular raised side surface 9, which is closer to 0, is approximately parallel to the piston upper surface 2 and transitions into the side wall 5 with a radius 9' of approximately 2 to 5 mm. The annular ring 11 of the annular bulge 7 extends in a plane parallel to the bottom 6 of the piston recess 3 in this case. The axial spacing 12 between the surface of the annular raised flank 9 and the bottom 6 is approximately 12 to 33% of the total depth 18 of the piston recess 3. It has been found advantageous that the diameter of the annular raised ridge 11 is adjusted to approximately 0.9 to 1.1 times the diameter of the inlet opening 10, and that the diameter of the inlet opening 10 is approximately 0.38 to 0.4 times the piston diameter 19.

The bottom 6 of the piston recess 3 can transition into an annular raised side surface 8 at a radius of about 20 to 35% of the total depth 18.

A jet nozzle 13 is attached to the piston recess 3, and the jets 14, 15, 16 are all directed to the piston recess 3.
The piston is directed toward the side wall 5 of the piston, and abuts approximately midway between the annular raised ridge 11 and the piston upper surface 2 in the axial direction. The injection nozzle 13 can be arranged eccentrically with respect to the piston recess 3 in its inlet opening 10 .
It has been found to be advantageous to maintain the cone angle 17 of the side wall 5 in the range from 7 to 15 DEG in order to perform the swivel.
〓〓〓〓
However, in this case the total depth 18 should not be greater than 0.6 to 0.8 times the diameter of the inlet opening 10.

The fuel jets 14, 15, 16 impinging on the side wall 5 are each decomposed into two components 14a, 14b, etc., of which the larger component 14a is directed downwards towards the bottom 6 and the smaller component 14b is directed upwards into the inlet opening 10. directed towards. Fuel that wets the walls and moves undesirably upwards is caused by an upwardly directed flow 21
The upward movement is further encouraged and stopped at the collar 20. The upwardly moving fuel is separated from the side wall 5 by the vortex 22 formed at the discontinuous transition that narrows to the neck 4 of the inlet opening 10 and acts counter to the rising fuel, causing the upwardly moving fuel to be separated from the side wall 5 and to reduce the overall flow. I can be placed in 21. The larger downwardly directed component 14a is deflected by the annular ridge 7 and peels off at the annular ridge ridge 11, so that a film of liquid fuel fine particles adhering to the wall is formed on both the bottom 6 and the piston top surface 2. never be done. The collar 20 transitions into the side wall 5 at the inner contour 20' in the form of a blade or with a maximum radius of 3 mm.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a part of the upper surface of the piston together with the injection valve in the cylinder head, FIG. 2 is a plan view of the piston and injection nozzle, and FIG. 3 is an enlarged view of a part of FIG. 1. DESCRIPTION OF SYMBOLS 1... Piston, 2... Piston top surface, 3... Piston recess, 4... Neck, 5... Conical side wall, 6... Recess bottom, 7... Annular ridge, 8, 9... Raised side surface, 10... Inlet opening, 11... Annular raised ridge, 13... injection nozzle,
14, 15, 16...Jet flow, 18...Total depth, 20
…Color. 〓〓〓〓

Claims (1)

[Scope of Claims] 1. The recess of the piston has an inlet opening provided on the upper surface of the piston and having a cylindrical neck, and a side wall that widens conically from the neck toward the bottom of the recess. At the neck of the inlet opening 10, the side wall transitions to the bottom of the recess, which is flat and the fuel injection into the recess is carried out in such a way that the injection nozzle wets the wall. 4 is formed as a radially inwardly projecting collar 20, the inner surface of which transitions with a maximum transition radius of 3 mm into a conical side wall 5, which extends approximately the total depth 18 of the recess 3. At a distance of 12 to 33% from the recess bottom 6, there is a transition to a radially inwardly projecting raised side surface 9 of the annular ridge 7 which sharply projects into the recess, and another raised side surface 8 of the annular ridge 7. is rounded and moves to the recess bottom 6, and the impact point of the fuel jets 14, 15, 16 injected from the injection nozzle 13 is approximately midway between the annular raised ridge 11 and the piston top surface 2 in the axial direction. A self-igniting internal combustion engine with a rotationally symmetrical piston recess, characterized in that the fuel injected in multiple jets is directed towards the side wall 5. 2 An annular raised side surface 9 closer to the inlet opening 10
2. An internal combustion engine according to claim 1, wherein the piston is substantially parallel to the upper surface of the piston. 3 Annular raised side surface 9 closer to inlet opening 10
3. An internal combustion engine according to claim 1, wherein the internal combustion engine transitions into the side wall 5 with a transition radius 9' of 2 to 5 mm. 4. The internal combustion engine according to claim 1 or 2, wherein the raised edge 11 of the annular raised part 7 extends in a plane parallel to the piston upper surface 2. 5. Inlet opening 10 in which the diameter of the raised ridge 11 of the annular ridge is about 0.38 to 0.4 times the piston diameter 19.
Internal combustion engine according to claim 4, characterized in that the diameter of the internal combustion engine is approximately 0.9 to 1.1 times the diameter of the internal combustion engine. 6 The annular raised side surface 8 near the bottom 6 of the piston recess 3 extends approximately 22 or more of the total depth 18 of the recess 3.
Internal combustion engine according to claim 1, characterized in that there is a transition to the bottom part 6 with a transition radius of 35%. 〓〓〓〓
7. Internal combustion engine according to claim 1, characterized in that the injection nozzle 13 is provided in the inlet opening 10 eccentrically with respect to the piston recess 3. 8. Internal combustion engine according to claim 1, characterized in that the cone angle of the side wall 5 is approximately 7 to 15°. 9 The total depth 18 of the piston recess 3 is the inlet opening 10
Internal combustion engine according to claim 1, characterized in that the diameter of the internal combustion engine is approximately 0.6 to 0.8 times the diameter of the internal combustion engine.