BACKGROUND OF THE INVENTION

The invention relates to a piston with swirl-inducing device for Diesel engines.

PRIOR ART

It is well-known in the art that the constructors lay high stress on the inducement and utilization of air turbulence in the differently constructed combustion chambers of Diesel engines, which during compression and expansion of the gases are aimed at improvement of the carburation and com¬ bustion.

In the direct injection Diesel engines the combustion chamber in the upper part of the piston is a differently shaped, e.g. spherical, dual spherical cavity (such are for example in the practice the HESSELMAN, MAN, JUNKERS, or SAURER engines) . The combustion chamber is in communica¬ tion with the main combustion chamber in the cylinder space. The inflowing air receives swirling spin already in the suc¬ tion stroke, which goes on during compression too. Such solutions are disclosed for instance in the book of Jurek titled: "Internal combustion engines" (Tankδnyvkiadό, Buda¬ pest, Hungary, 1955, p. 565- 573.).

The profession regards essentially even today these typs and their different versions as the most developed ones.

The experiences acquired in the practice indicate that efficiency, economy and exhaust gas emission of the Diesel engines having a piston provided with the known swirl-in¬ ducing device can hardly be further improved over the present level, if the traditional ways are followed, that is limited by the construction itself.

THE ESSENCE OF THE INVENTION

The present invention is aimed at elimination of above shortcomings, i.e. at the realization of an improved swirl- inducing device for the piston of Diesel engines, whereby the combustion process, the economic efficiency of opera¬ tion, and thereby the efficiency of the engine and the ex¬ haust gas emission can be considerably improved.

The invention is based on the recognition, that the above problem can be solved if the heat storage capacity is improved with special insert-like element of the piston head swirl-inducing device, and if the combustion process and efficiency are improved by extending the combustion process with a special swirl-inducement.

A piston provided with a swirl-inducing device - mentioned above - used as starting point to solve the problem, where the upper part of the piston is provided with a recess being in connection with the main combustion chamber of the Diesel engine when the piston is built in.

The development according to the invention lies in that the swirl-inducing device has a heat storage insert fixed in the nest-like recess of the piston by way of reduced heat transfer connection and with an axial spacing from the bottom plate of the recess, and the insert is pro¬ vided with series of swirl or gas turbulence-inducing ducts.

In a preferred embodiment of the invention the insert is

shaped as a plate-like circular disc provided with circular grooves along its cylinder mantle partly receiving a ring retainer. Furthermore, a part of the ring retainer radially protruding from the disc-like insert sits in a radial groove machined in the nest-like recess of the piston. This way a very simple and inexpensive construction is obtained. By this fixing connection of the insert and piston a reduced heat transfer can be obtained.

According to a further characteristic feature of the in¬ vention the manufacture of the disc-like insert can be further simplified if the swirl-inducing ducts are machined preferably as radial slots starting from the outer edge of the insert, and passing through the whole thickness of the insert, while direction of the slots is at an acute angle to the end plate of the insert.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in detail with the aid of en¬ closed drawings showing an preferred embodiment od the so¬ lution according to the invention given by way of example, in which:

Fig.l: Longitudinal section showing a detail of the piston provided with swirl-inducing device according to the invention;

Fig.2: Top view of the insert of the swirl-inducing device according to Fig.l in dismounted state;

Fig.3: Side view of the solution according to Fig.2.

DESCRIPTION OF A PREFERRED EMBODIMENT

Fig.l presents only the upper part of a Diesel engine's

piston 1 in schematic longitudinal section. A nest-like recess 3 is machined from an upper end-face 2 of the piston 1, in this case as a cylindrical blind hole.

The piston 1 is provided with a swirl-inducing device 4 according to the invention, having a heat storage insert 5. This insert 5 is fixed in the recess 3 of the piston 1 with an axial spacing 7 from a bottom plate 6 of said recess 3. Concerning the fixing method of said insert 5 in the nest¬ like recess 3, such fixing connection is recommended ac¬ cording to the invention, which entails reduced heat trans¬ fer between the heat storage insert 5 and the adjoining body of the piston 1.

In this embodiment - given by way of example -, the insert 5 made of the usual material of exhaust valves is a circular disc, its diameter is marked with *'D" and its thickness with "B" (Fig.2 and 3). The diameter "D" of the insert 5 should be multiple of its thickness "B" and it is selected to fit removeable the hole diameter of the piston's recess 3.

Fig.1 and 2 clearly show the heat storage insert 5 is provided with a circular groove 9 along its cylindrical mantle 8 to receive partly a conventional ring retainer 10 (e.g. Seeger- ring) . The rest part of the ring retainer 10 protruding radially from the insert 5 sits in a radial groove 11 ma¬ chined in the mantle of the recess 3/ (Fig.l). Thus, the insert 5 is conventionally fixed with said ring retainer 10 in the groove 11 of the recess 3.

According to the invention, the heat storage insert 5 is provided with series of gas turbulence-inducing ducts 12, wherein one end of the ducts 12 are in communication with a main combustion chamber 13 (in the vicinity of the piston's end-face 2), while the other end thereof with a space 14 in the recess 3 formed with spacing 7 below the insert 5.

The gas turbulence-inducing ducts 12 are radial slots in the illustrated case, evenly spaced along the circumference but with different length as shown in Fig.2. The ducts 12 as slots are made with a simple notch starting from the outer mantle 8 of the insert 5, but their directions are at an angle mainly acute angle 17 to the upper and lower end plates 15 and 16 of the insert 5. The required swirl-inducing effect is achieved with these inclined slot-like ducts 12 in the space 14 and - by way of reflux - in the space above the insert 5 too.

Mass of the ring retainer 10 relative to that of the insert 5 small, thus relatively little heat passes from the insert 5 in to the piston 1. In fact, one of the most important roles of the insert 5 is heat storage for which it has adequate heat resistance and heat storage capacity.

The piston 1 provided with swirl-inducing device 4 according to the invention exerts its beneficial effects while the engine is running, as follows:

In operation, in the course of air compression the combus¬ tion air is forced through the swirl-inducing ducts 12 of the heat storage insert 5, meanwhile inducing air swirl in the space 14. While the piston 1 moves further upwards, the further compressed combustion air receiving renewed turbulent spin from the space 15 through the ducts 12 re¬ turns to the main combustion chamber 13. Owing to the heat of the heat storage insert 5, the combustion air gets pre¬ heated faster to the running temperature. This way the combustion air brought to and kept in turbulence mixes more homogeneously and efficiently with the injected fuel, and offers a more perfect combustion process than the known solutions. We believe that the beneficial effect of the heat storage insert 5 on improvement of the combustion process requires no further explanation for a person having ordinary skill in the art.

The experiments conducted with embodiment of the solution according to the invention given by way of example demonstrated the engine's improved efficiency at rela¬ tively lower fuel consumption, furthermore the harmful components present in the exhaust gases can be considerably reduced involving environment protection signigicance as well.

According to the invention a certain part of the amount of the heat generated in the combustion process is deliberately retained and stored in the heat storage insert 5, thereby the heat load of the engine's cylinder and other structural parts is considerably reduced too.

In the course of the experiments a surprising technical effect was observed, i.e. the swirl-inducing device 4 according to the invention "softens" the run of the en¬ gine, that is it eliminates the unpleasant "knocking" run of the Diesel-engine mainly in the ranges of low speed and load. This is due to the fact, that the combustion is not sudden and explosive in the main combustion chamber, but the combustion process is somewhat extendes by flow of the mixture through the ducts 12 into the space 14 and its re¬ flux from there, resulting in softer run of the engine and improved burning of the hardly burnable components present in the fuel mixture.

Naturally, the invention is not restricted to the illustrat¬ ed embodiment and described in the foregoing, but several other versions are feasible within the protective scope of the claims. E.g.: the heat storage insert 5 is not necessarily a circular disc, this is justifiable at best by the very simple manufacture and assembly. Furthermore, the direction of the swirl-inducing ducts 12 may differ from the radial, moreover, in place of the slots other suitable swirl-inducing perforation or channels may also be used. Shapes of the recess 3 may just as be different. The fixing

method of reduced heat transfer between the heat storage insert 5 and the piston 1 may be different, e.g. locally with point-like application of the heat insulating and heat resistant fixing elements. Such version is also conceivable in the embodiment according to Fig.l, where plate-like elastic steel element seated only at certain points is placed between the mantle surface of the ring retainer 10 and the insert 5, or front wall of the groove 11, which centrelizes the insert 5 in the recess 3, and further reduces the heat transfer.

Finally it is noted, that the heat storage insert 5 is heated during run, thus it instantly gasifies the after- dripping fuel drops. Air turbulence is brought about in the compression stroke by way of the ducts 12 too, and gas turbulence of oppsite sense is induced with ducts 12 in the course of the expansion stroke.

List of reference numbers

- piston - end-face - recess - swirl-inducing device - heat storage insert - bottom plate - axial spacing - mantle - groove - ring retainer - groove - gas turbulence inducing duct - main combustion chamber - space - end plate - end plate - acute angle