DE579345C - Piston with light metal head and iron shaft - Google Patents

Description

GERMAN EMPIRE

ISSUED AIH JUNE 24, 4933

REICH PATENT OFFICE

PATENT LETTERING

. JVi 579345 ' CLASS 47 f GROUP 19oi

E 39245 Xlllwf

Date of publication of the patent grant: June 8th

Elektronmetall G. mb H. in Stuttgart-Cannstatt *) Pistons with light metal head and iron shaft

Patented in the German Empire on May 15, 1929

The low weight and the extremely good thermal conductivity of the light metals led to their use as piston building material. These great advantages stood the less good running properties as well as the high expansion coefficient of light metals as a disadvantage.

The best running properties as well as extraordinary, minor and the right one, dem The cylinder-adapted thermal expansion still shows the well-known gray cast iron piston on. Previous efforts, the two materials light metal and gray cast iron to unite favorably failed. Although it is already a piston version with Light metal head and iron shaft known, in which the iron shaft only through thin, narrow lobes with the piston head cast into the piston pin bosses

ao is connected. Pistons of this type, however, have no entry into the technology of internal combustion engines found, because with this connection of head and shaft a loosening of the connection in the course of time

»5 formation points occurs, caused by the different degrees of thermal expansion of the both materials under the influence of the operating temperature. It also does no difference whether the anchoring is attempted according to other proposals by casting shell parts in projections that start from the piston head and extend over the length of the shell, or by screwing in connection with potting.

The invention now relates to the innovation in the connection of 'piston head and -shaft, which essentially consists in reducing the connection points over the shortest possible distances restrict. The innovation is based on the knowledge that the cause of the previous Failures in the dependence of thermal expansion on spatial size of the piece, d. H. large dimensions of the body in question require large dimensions stretching. Added to this is the level of the temperature itself, which also has a direct influence on the final size of the body which it has under the occurring temperature accepts. All two-metal pistons known so far have been based on this knowledge placed little value. The joints made by casting or screwing of the two united parts are so that the expansion is very large becomes and with it the difference in the expansion paths of the two bodies.

In the operating state, this results in a piston at the considerable temperatures assumes different size both

*) The patent seeker stated as the originator:

Dr.-Ing. Erich Wilhelm Heinrich Koch in Stuttgart.

Parts that shrink back to their original size when they get cold, so when the engine is at a standstill. A constant work against each other, which ultimately leads to 5 · Loosening is the necessary one Episode.

The invention, which is explained by the drawing, avoids these inconveniences in that I. the connection points of the two parts in their mutual connection length to a minimum. limited and elastic, 2. the connection points themselves are relocated to an area where a) spatially very short casting paths of only a few millimeters are possible, and further b) there are no high temperatures and therefore no large temperature differences. The piston itself does not have a uniform a ° temperature in the operating state, instead there is a heat flow and thus a temperature gradient, according to investigations carried out so that about 80 ° / _{0 of} the heat at the end of the ring belt can be considered to have already been dissipated. The purely schematic piston representation according to Fig. 1 shows that the highest temperatures are at the piston crown, the main heat flow takes place in the part of the ring zone, while only relatively low temperatures exist on the skirt and in the zone of the piston pin boss.

The connection point is now placed in this zone around the piston pin eye, in which the relatively low operating temperature of around 130 to 150 ° prevails. According to the invention, the openings e for the piston pin boss bearings are relocated to the flat sides / of the iron piston skirt, the two curved sides k of which form the bearing surfaces of the piston (Fig. 4, cross section of the piston skirt). The distance between the flat sides is chosen with the proviso that the piston pin eye bearings are given a sufficiently large size to support the pin without touching the cylinder wall on their outer sides. Here i. In the flat surface / the iron shaft, in the zone around the bolt eye, through slots or cutouts in the shaft, narrow flaps i are formed (see Fig. 3 and 6), and 2. there are bulges m on the flat surfaces of the iron shaft (Fig. 2) attached, which is drawn in over the full width of each surface; An outwardly bent uppermost raised edge / of the shaft can also run parallel to these beads. If the piston crown and the piston pin eye bearings extending from it are cast from light metal in a manner known per se with the aid of a mold, an anchoring of the light metal with the EL shaft between the lobes, including the beads, is brought about, which experience shows that the effects of the occurring Resists temperature fluctuations, although the expansion coefficient of the light metal is almost twice that of iron. Such a favorable result would not be expected if the connection were made in the ring zone instead of in the area of the piston pin eye.

Various embodiments are shown in the drawing of the invention, in which, according to Figs. 2 to 4, the iron shaft is made in one piece from gray cast iron is, while in Fig. 5 the modification is provided that in the flat surface of the Gray cast iron shank the lobed zone around the piston pin bosses made of a different material with lower thermal expansion ,, z. B. Invar steel, which in turn through Riveting or welding is connected to the shaft. Instead of gray cast iron but also punched or welded iron sheets or hardened sheets as a building material or nitrided steel sheets to achieve maximum wear resistance.

In this way, all the advantages of these different ones, some of which have only recently become known, become available Materials fully utilized. The following advantages result:

1. Low weight of the entire piston. Tests have shown that the weight is equal to or lower than that of the light metal pistons known today.

2. By using a light metal with good thermal conductivity properties the upper part results in all the well-known good properties of light metal pistons (cold piston - large filling, high performance - low fuel and oil consumption) .

3. By using gray cast iron

byw. Steel is used for the actual shaft the same good running properties and service life achieved as before with normal cast iron pistons.

4. By using Invar steel for the cast-in flaps it is achieved, «o that the piston clearance is as small as with the so-called Nelson-Bohnalite piston, i.e. smaller than with the gray cast iron piston, and the The piston nevertheless expands evenly with the cylinder, so its little play always maintained evenly across all operating states.

5. By using e.g. B. nitrided Steel for the running surfaces of the shaft is the wear resistance, ie the life tao duration compared to the cast iron piston, increased even further.

Claims (3)

Patent claims:
ι. Piston with light metal head and iron shaft, in which the iron shaft is only connected to the piston head by thin, narrow lugs cast into the piston pin bosses, characterized in that the iron shaft consists of a body with two curved bearing surfaces (Jk) and two intermediate flat surfaces, the Piston pin bearing receiving side surfaces (f) , the side surfaces (/) form the narrow lugs (i) to be cast around with the light metal for the piston pin bosses (h) through radial slots around the openings (e) for the piston pin and the side surfaces (f) also wear beads (m) above and below the bolt openings. 2..Kolben according to claim i, characterized in that the connection serving flaps (i ') each side form a part for themselves, which is in the wall of the flat side surfaces (/) of the shaft especially used and with it Riveting, welding or the like. Connected 3. Piston according to claim 2, characterized in that the bearing the tabs Part (* ') in a known manner made of a material other than that of the Iron shaft, in particular made of a material of low thermal expansion. 1 sheet of drawings