DE2757668A1 - INSULATING MULTIPLE PISTON FOR COMBUSTION ENGINES - Google Patents

Description

2757668 Andrejewski, Honke, Gesthuysen & Masch patent attorneys

-ι-

Physicist Dr. Walter Andrejewski Graduate engineer Dr.-lng. Manfred Honke Graduate engineer Hans Dieter Gesthuysen Physicist Dr. Karl Gerhard Masch Lawyer file: 51 193 / W1 ¹ '

43 Essen 1, Theaterplatz 3, Postf. 789

December 22nd 1977

Patent application

Cummins Engine Company, Inc.

1000 Fifth Street Columbus, Indiana 47201, USA

Insulating multi-part piston for internal combustion engines

The invention relates to an insulating multi-part piston for internal combustion engines.

In the construction of internal combustion engines, in particular diesel engines, it is known to use the combustion chambers of the cylinders of to isolate the rest of the engine parts in order to increase the efficiency to increase the combustion and to reduce the emission of harmful exhaust gases. The combustion efficiency will be

8 0 9 8 2ψ / 0 8 5 0

Andrejewski, Honke, Gesthuysen & Masch, patent attorneys in Essen

-Jt-

increased because the proportion of the Heat of combustion is reduced to a minimum. In addition, the temperature of the turbine is a turbocharged one Combustion engine driving exhaust gases increased significantly.

The paths taken so far to isolate the combustion chambers can be broken down into several basically different categories classify. On the one hand, it is known to cover the surfaces of a combustion chamber with a ceramic, insulating, d. H. bad to spray thermally conductive material. Treatment includes the piston crown, cylinder head, and often the cylinder walls as well. The problem with this type of isolation of the The combustion chamber is located in the ceramic coating despite the loads occurring in the course of the combustion cycles and the associated problems of different thermal expansion, to keep hairline cracks or the like free. For another, it is known to produce one or more of the parts forming the combustion chamber from insulating material or a ceramic one Insert considerable thickness in one or more of these parts. The problems that arise here are based on that the parts made of ceramic material or provided with a ceramic insert on one side with the hot combustion gases, on the other hand with considerably cooler parts of the engine block near the combustion chamber get in touch. In this way, significant temperature differences (up to 700 K) occur between the corresponding surfaces. The resulting very high temperature gradient in the ceramic material leads to considerable thermal stresses and deformations, at least if not Material with an extremely low coefficient of expansion is used.

80982 ^ / 0850

Andrejewslci, Honke, Gesthuysen & Masch, patent attorneys in Essen

-X-

On the basis of the prior art set out above, the object of the invention is therefore to provide a piston for internal combustion engines specify, with which on the one hand an isolated combustion chamber can be realized, on the other hand the one in the the temperature gradient occurring with the material coming into contact with the hot combustion gases is as low as possible.

The insulating multi-part piston according to the invention for internal combustion engines, in which the above-mentioned object is achieved, is initially characterized in that the piston from a substantially annular piston head, a substantially annular piston body and a fastening element for fastening the piston head to the piston body and that the front end surface of the piston body and the rear surface of the piston crown forms a low heat conduction contact surface. The one provided according to the invention Contact surface with low heat conduction guarantees that only one on the rear surface of the piston crown temperature slightly below the temperature on the combustion chamber-side surface of the piston crown occurs. This guarantees that only a small temperature gradient occurs within the piston crown.

The essentially ring-shaped piston head is preferably made of temperature-resistant ceramic material. Instead of of ceramic material, however, a temperature-resistant metal can also be used for the piston crown.

Further features of the invention emerge from the following description of two exemplary embodiments of the invention insulating multi-part piston based on the drawing;

8 0 9 8 2 ^ / 0 8 5 0

Andrejewski, Honke, Gesthuysen & Masch, patent attorneys in Essen

it shows

Fig. 1 shows a first embodiment of the invention insulating multi-part piston in section and

Fig. 2 shows the detail from a second embodiment of the insulating multi-part piston according to the invention for internal combustion engines.

1 shows a piston 10 with an annular piston body 12 and a piston ring mount 14 arranged on the outer surface of the annular piston body 12. The piston ring mount 14 comprises a plurality of circumferential grooves 16 which are used to receive sealing rings 15 and oil scraper rings 17. The sealing rings 15 or oil control rings 17 run in a bore 19, the upper end of which forms a combustion chamber 21 together with the piston 10. The piston 10 is in the bore 19 arranged to be longitudinally displaceable.

The piston body 12 has piston pin bearings 18 with aligned bores 23 for receiving a piston pin serve, via which the piston body 12 is connected to a connecting rod can be. Piston pin and connecting rod are not shown. On the piston body 12 of the piston 10 can be via the piston pin a separate scraper body can be attached, but this is not to be described in detail here. Of course the separate wiper body can also be made in one piece with the piston body 12.

Furthermore, the piston 10 has a substantially annular shape Piston head 20, which is above the front end surface 22 of the

80982 ^ 0850

Andrejewski, Honke, Gesthuysen & Masch, patent attorneys in Essen

Piston body 12 is arranged. The piston head 20, which is preferably made of ceramic material, has a combustion chamber side Surface 24, which is drawn in in a known manner in order to achieve a particularly effective combustion chamber shape is. Of course, the surface 24 on the combustion chamber side can also be shaped in any other way. Of the Piston crown 20 can be made from a variety of ceramic materials, such as silicon nitrite, Silicon aluminum silicate, silicon dioxide and silicon carbide, sintered silicon carbide, reaction sintered silicon carbide and reaction solidified silicon nitride. All of these materials are those commonly found in combustion chambers Temperatures have increased, but often have high coefficients of thermal conduction and thermal expansion. Due to the invention Construction of the insulating multi-part piston, however, they can all be used.

The piston head 20 and the piston body 12 each have coaxial bores 26 and 28, respectively. A screw 30 with a screw head 32, which is held in a recess 34 of the piston head 20, has a shaft 36 which contains the coaxial bores 26 and 28 interspersed. The screw head 32 of the screw 30 preferably has a shape that is that of the combustion chamber-side Surface 24 of the piston head 20 is adapted. The screw 30 is made of a high-strength, temperature-resistant material, for example made of a nickel or cobalt alloy.

The shaft 36 of the screw 30 ends in a drawn-in end 38 which is inserted in a recess 40 in the interior of the piston body 12 expires. The recess 40 has a shoulder 42 on which a side surface 44 of a collar-shaped spacer 46

8 0 9 8 ίψ / 0 8 5 0

Andrejewski, Honlce, Gesthuysen & Masch, patent attorneys in Essen

comes to the plant. A nut 48 is screwed onto the end 38 of the screw 30. Between the inner wall of a recess 52 in the collar-shaped spacer 46 and the nut 48, a spring arrangement 50 engages _f by which rotation of the nut 48 is prevented. As a result, the piston head 20 and piston body 12 are held in a fixed connection with one another independently of different thermal expansions, since corresponding mutual changes in position are compensated for via the spring arrangement 50. As FIG. 1 shows, the spring arrangement 50 has a plurality of disc springs or anti-rotation rings of a known type.

An essential feature of the present invention is one Contact surface 54 with extremely low heat conduction between the piston head 20 and the piston body 12. As in FIG. 1 further shows, a plurality of disks 56 are provided on the contact surface 54, which between the rear surface 58 of the piston head 20 and the bottom of an annular Socket 60 are stacked on the front end surface 22 of the piston body 12. Each of the disks 56 has one central bore 62 through which the shaft 36 of the screw 30 is guided. The discs 56 are selected so that the heat conduction through the contact surfaces between the individual Disks 56 is as small as possible. Low heat conduction between the individual disks 56 can be achieved even when using commonly available material by using steel disks with roughened surfaces, for example a surface unevenness of 5 μm. However, surrendered even normal spacers without special surface properties have an overall satisfactorily low heat conduction.

The arrangement of layered disks 56 between piston bodies

80982> / 0850

Andrejewski, Honke, Gesthuysen & Masch, patent attorneys in Essen

per 12 and piston crown 20 leads here to a reduction in the heat transfer by over 99% compared to a piston in which the rear surface 58 of the piston head 20 is directly connected to the front end surface 22 of the piston body 12 comes into contact. Depending on how many disks 56 are used, the heat transfer can can be set in a wide range at this point.

Since the radial extension of the disks 56 does not extend to the outer edge of the piston head 20 or the piston body 12, the thickness of the discs 56 chosen so that the area of the piston head 20, which is outside the radial extent of the Disks 56 is ii in any case no contact with the front End surface 22 of the piston body 12 has. More precisely, the piston head 20 is of the disks 56 over a comparatively wide annular area supported, the inner edge of the bore 28 and the outer edge is determined by the radial extent of the disks 56. The size of the contact area guarantees a low load of the disks 56 at a predetermined pressure in the combustion chamber 21, which in addition to a low heat transfer between the disks 56 contributes. The circular contact area described above divides the piston crown 20 in the radial direction in two approximately equal sections. As can be seen from Fig. 1, the radial distance between the bore 26 and an imaginary extension of the outer wall of the bore 28 approximately equal to the radial distance between the outer edge of the disks 56 and the outer edge of the piston head 20. The on the piston head 20 in the course of the combustion strokes The bending forces exerted are thus balanced against each other.

80982 ^ / 0850

Andrejewski, Honke, Gesthuysen & Masch, patent attorneys in Essen

The disks 56 shown in FIG. 1 are only one of the possibilities to remove the piston head 20 from the piston body 12 to isolate. In Fig. 2, an alternative design of the contact surface 54 is shown in which a single disc 64 comparatively low heat conduction is used. This disk 64 can be made of porous metallic material or be made of pressed steel wool, the steel wool must be pressed strong enough to the occurring Press to hold stand. If necessary, it can be advantageous to provide a plurality of disks 64 here as well.

With any of the above-described materials on the contact surface 54, the piston crown 20 becomes effective from the usual Piston body 12 made of highly thermally conductive aluminum is insulated. This insulation gives the essential advantage of reducing the temperature gradient between the combustion chamber side and the rear surface 24 and 58, respectively, of the piston crown to a minimum value. Be that way internal temperature-related stresses in the piston head 20 largely avoided. This in turn makes it possible to select a large number of materials for the KoI-oenboden 20, since these now only have to meet the requirement to withstand the combustion temperatures that occur. The essential one In the piston according to the invention, the temperature gradient occurs exclusively at the contact surface 54. Because of the large number of panes 56 stacked one on top of the other, the temperature gradient that occurs is distributed over a large number of contact surfaces, so that the temperature gradient occurring in each case in the panes 56 is comparatively small.

All changes in position between piston body 12, contact surface

80982 ^ / 0850

Andrejewski, Honke, Gesthuysen & Masch, patent attorneys in Essen

1%

54 and piston crown 20, which occur due to different thermal expansion of the individual parts, are caused by the spring arrangement 50 collected, through which an even load is exerted on the individual parts. The collar-shaped spacer 46 results in a very secure fit for receiving the spring arrangement 50 and passing on the loads that occur to the Piston body 12, since the shoulder 42 on which the spacer comes to rest has a significantly larger diameter than the corresponding system on the piston body 12 itself.

8 0 9 8 2ty 0 8 5 0

Claims (15)

Andrejewslci, Honke, Gesthuysen & Mosch, patent attorneys in Essen Patent claims: Insulating multi-part piston for internal combustion engines, characterized in that the piston (10) from an essentially annular piston body (12), an essentially annular piston head (20) and from a fastening element (30) for fastening the piston head (20) to the piston body (12) and that the front end surface (22) of the piston body (12) and the rear surface (58) of the piston head (20) form a contact surface (54) with low heat conduction. 2. Piston according to claim 1, characterized in that the piston head (20) is made of ceramic material. 3. Piston according to claim 1, characterized in that the piston head (20) is made of a temperature-resistant metal. 4. Piston according to one of claims 1 to 3, characterized in that that in the piston head (20) and the piston body (12) coaxially arranged, central bores (26 and 28) are arranged that in the piston body (12) an inner recess (40) is provided that a screw (30) with a the combustion chamber-side surface (24) of the piston head (20) resting head (32) and one through the coaxial bores (26 or 28) through shaft (36) is provided that at the end (38) of the screw (30) in the recess (40) a nut (48) is placed on the screw (30) and that a spring arrangement between the nut (48) and the piston body (12) 80982 * 70850 ORWINAL! NSPHCTED Andrejewski, Honke, Gesthuysen & Masch, patent attorneys in Essen - X- (50) is provided. 5. Piston according to claim 4, characterized in that the screw (30) consists of a high-strength, temperature-resistant Alloy. 6. Piston according to claim 4 or 5, characterized in that the spring arrangement (50) consists of a plurality of disc springs and / or anti-rotation rings. 7. Piston according to one of claims 4 to 6, characterized in that that the diameter of the bore (28) in the piston body (12) is greater than the diameter of the bore (26) in the Piston head (20) that a collar-shaped spacer (46) is arranged in the bore (28) or in the recess (40) and that the spring arrangement (50) is arranged between the collar-shaped spacer (46) and the nut (48). 8. Piston according to one of claims 1 to 7, characterized in that that between the front end surface (22) of the piston body (12) and the rear surface (58) of the piston head (20) a plurality of disks (56) of low heat conduction are arranged. 9. Piston according to claim 8, characterized in that the discs (56) each have a central bore and that the fastening element (30) is guided through the central bores in the disks (56), so that the disks (56) against one another are aligned. 10. Piston according to claim 8 or 9, characterized in that 80982 ^ 0850 Andrejewski, Honlce, Gesthuysen & Masch, patent attorneys in Essen the radial extension of the disks (56) is smaller than the radial extension of the piston head (20) or the piston body (12) and that the thickness of the discs (56) is chosen so that the piston head (20) and piston body (12) do not come into contact with each other come together. 11. Piston according to one of claims 8 to 10, characterized in that that the piston body (12) has an annular socket (60) and that the discs (56) within the annular Socket (60) are arranged so that the pressing forces exerted on the piston head (20) over a circular ring-shaped Surface are transferred to the piston body (12). 12. Piston according to claim 11, characterized in that the radial extension of the annular socket (60) is selected is that the bending forces exerted on the piston head (20) are balanced. 13. Piston according to one of claims 8 to 12, characterized in that that the discs (56) are made of steel with roughened surfaces. 14. Piston according to one of claims 8 to 12, characterized in that that the disks (56) are designed as a single disk (64) made of porous metallic material. 15. Piston according to one of claims 8 to 12, characterized in that that the discs (56) are designed as a single disc (64) made of pressed steel wool. 8 0 9 8 2 * 7 0 8 5 0