DE1898220U - LIGHT ALLOY PISTON FOR COMBUSTION MACHINERY. - Google Patents

Description

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Mahle Komm.-Ges., 7000 Stuttgart-Eäd "Gannstatt, Pragstrasse 26/46

Light metal pistons for internal combustion engines

The innovation relates to light metal pistons for internal combustion engines with one arranged on the piston rim above the piston rings and made of a more heat-resistant material existing reinforcement ring, which by means of a one-piece connected to it, Y / and Durchbreehungen having flange is anchored joint-free by casting in the piston body.

There are known such pistons of a type in which the reinforcing ring made of a material with is formed with a much smaller thermal expansion value than that of the piston material, and at which flange connected to the reinforcement ring restricts the flow of heat to the piston rings should effect and accordingly only a few wall openings with a relatively small overall cross-section having. Reinforcement rings designed in this way are only found in pistons that are subject to moderate thermal stress useful. If the incidence of heat on the piston crown becomes greater, it causes the throttling of the heat outflow Flange a strong heating of the already dangerous

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th edge zone of the piston head; it then also makes the different thermal expansion of the Materials very noticeable and soon leads to a loosening of the reinforcement ring in its anchorage.

It is also known to manufacture parts to be connected to a light metal piston from a material whose coefficient of thermal expansion is matched to that of the piston material. Such materials are z. B, cast iron with?, 2-2.8 $ C, 1.6-2.2 $ Si, 1-1.6 $ Mn, 12-16 <fo Ni, 5-6 $> Gu or with 2.7 -3.4 1 ° C, 2.5-4.5 f Si, 9-12? 6 Mn and 4-6 # 'Ni. Depending on their composition, these materials have thermal expansion

"values between 17 and 20 χ 10 - cm / cm C. The known However, light metal piston alloys have coefficients of thermal expansion that are up to 25 x 10 cm / cm ° C reachable. Therefore a complete approach

'' equation only possible if you click on the use of light metal alloys with a coefficient of thermal expansion en over 20 χ 10 - cm / cm Q waived. Just un-

> _Ti ter this, there are those who exclusively by particularly good hot strength and thermal conductivity

, draw and on which one therefore in cases of high thermal Load would like to fall back.

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This is made possible by the fact that the reinforcement ring is designed in such a way that it is able to follow the possibly greater thermal expansion of the piston material even with differences in the thermal expansion coefficients of up to 20 $>, as can occur when using the materials listed above, without its anchoring being endangered. The measures required for this are as follows: First, the flange used to anchor the reinforcement ring, which is rigid in known designs,

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ί 'through a multitude of different

divided and close to the inner edge of the reinforcement ring reaching, vand breakthroughs divided into narrow 3tegp, so that it can follow any tangential pull. Second, the webs are given such a shape that they widen inward and are consequently secured against radial displacement. Instead of this measure, the inner ends of the webs can also be connected to one another by a full-walled ring part, which also ensures good anchoring. Third; may the radial wall thickness of the reinforcement ring, and if one is available, d ^e s the webs connecting the inner ring not exceed 3 $ dep piston diameter, so that dieae vo ^ lwandigen .Ringteile are sufficiently flexible.

The innovation consists in the simultaneous application of these individual measures in connection with a material selection in such a way that the coefficient of thermal expansion of the reinforcement ring material is no more than 20 % less than that of the piston material, the latter measure avoiding the occurrence of excessive stresses.

Two execution examples are shown in the drawing 1 and 3 each show a part of a radial section through a piston head, while the Pig. 2 and 4 partial plan views of the cast into the pistons according to FIGS. 1 and 3 Represent reinforcement rings.

In FIGS. 1 and 2, the piston body is denoted by 1 and the reinforcement ring as a whole is denoted by 2. The reinforcement ring consists of a sleeve-like part 21 and serving to reinforce the piston edge

an inwardly protruding flange, which through openings 22 in a series of webs 23 and one Inner ring 24 is divided. The radial wall thicknesses S of the ring parts 21 and 24 are preferred equal and must not exceed 3 $ of the piston diameter.

In Figures 3 and 4, in which corresponding parts are denoted by the same numbers, the webs 23 are completely separated from each other, widen but inward, so that a dovetail-like anchorage is formed.

Claims (1)

RA.4ooe59-5.6.64 Claim to protection Light metal pistons for internal combustion engines with a reinforcement ring made of a more heat-resistant material, which is arranged on the piston rim above the piston rings and which is anchored in the piston body without joints by means of a wall perforations connected to it in one piece, characterized in that the wall openings (22) close to the inner Reach the edge of the reinforcement part (21) and are distributed over the entire circumference so close to one another that only narrow webs (23) remain between them, which widen towards the inner flange edge and / or inside ^; ; ¹ , are connected to one another by a full-walled Hingtexl (24), the radial wall thickness of which, like that of the reinforcement ring, is less than 3 $ of the "piston diameter, and that the coefficient of thermal expansion of the reinforcement ring material is not more than 20 $> less than that of the piston material.