DE7421863U - PISTONS FOR COMBUSTION ENGINES - Google Patents

Description

I I

KARL SCHMIDT GMBH "5 _Ffnu ^ 25.6.1974

7107 Neckarsulm DrQ / GKp /;

Christian-Schmidt-Strasse 8/12 ΙΛ-

Prov. No. 7413 KS

Pistons for internal combustion engines

The invention relates to a piston for internal combustion engines, preferably made of aluminum or its alloys, in which the freely hanging
Pin bosses are connected to the piston head as well as to the piston skirt via ribs and openings are arranged in the piston skirt opposite the pin bosses.

In all those gasoline and diesel engines in those from
Single-metal pistons, preferably made of aluminum or its alloys, with regard to low noise, oil consumption, seizure resistance, groove wear and general adaptability to strongly changing
Operating conditions, in particular with regard to the degree of the piston, where extraordinary is required, so-called control pistons are used.

In the broader sense, a control piston is understood to be a single-metal piston. in which it is effected by special constructive measures that the radial heat expansion preferably only in the direction of the bolt axis in appearance occurs, or in which the supporting shaft parts are designed so that they the radial thermal expansion Able to compensate by elastic aftertaste.

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In the narrower sense, these are pistons, the elongation-resistant control elements that are usually cast into the skirt at a suitable point made of steel, with which the help of the light metal, especially in the direction perpendicular to the Bolt axis prevented undesirably high expansion under operating temperature and "deflected" in the direction of the bolt axis and the piston clearance in the pressure and counter-pressure direction under all operating conditions and the cylinder diameter is adjusted. The nominal piston play measured in the running direction can be used in this way in the entire operating range be kept almost constant, although the cylinder also has a larger diameter under temperature accepts. The control characteristic, to be equated with the expansion coefficient of the piston, is due to the Determined temperature gradient between piston head and skirt. This gradient is different for each engine and is influenced by constructive measures.

The interaction of piston play, control action and skirt deformation is decisive for straight line guidance of the piston. It should always be noted that a compromise between the requirement for sufficient Rigidity, structural strength and control function must be closed. Only then can the claims are met in terms of smoothness and seizure security.

At operating temperature, an average expansion coefficient is established which, depending on the wall thickness ratios, lies between the expansion coefficients of the light metal and steel. This mean expansion coefficient causes an even greater difference in deformation in the existing temperature gradient between the piston head and the skirt. It is therefore higher and stronger in relation to the temperature difference

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accordingly again the oval deformation of the skirt by the piston crown. With the almost constant This results in an increase in diameter in the direction of the bolt and a decrease in diameter in the Pressure and GeÄrtruckriclrhi.jrig achieved.

Since the expansion of the light metal is not completely prevented, a larger shaft ovality than normal is necessary. Almost all control pistons have a more or less pronounced separation between the piston crown and skirt. The ability to regulate is significantly enhanced, for example, by separating slots, which are preferably located in the oil ring groove. Single-metal pistons without regulating inserts, but with this separating slot, for example, already show an approach to regulating effect. Pistons with steel inserts, but without a noticeable separation of the base and skirt, have only a low resel effect ₌

The known control piston types (DT-PS 909 163, DT-AS 1 078 387, DT-PS 1 245 657), their control values the upper edge of the shaft at 15 to 20.10 "mm / mm ° C and on the lower edge of the skirt are between 18 and 22.10 mm / mm ° G, are limited to certain areas of application depending on the liter capacity and piston diameter.

In a certain sense, so-called slit-jacket pistons are also counted among the control pistons »This type (without cast steel control links) came especially in the 1940s and is still used occasionally today. The essential is there in that the shaft is separated from the hot piston head by two slots in or under the lowermost groove and one or more longitudinal slots are arranged at suitable locations on the shaft.

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The transverse slots have a certain regulating effect, the longitudinal slots great elasticity of the shaft. The one in operation Any increase in diameter of the light metal is absorbed by the elastic deformation of the shaft. Schlit2üiantel-Kolbsii are because of the possibility of evasion and communication of the shaft largely insensitive to chewing. A major disadvantage, however, is that the creep rupture strength of the light metal at higher temperatures and higher load changes that are common today as a result of higher The speed of the motors is too low and after a long period of operation with permanent deformation and thus louder noise, possibly seizure, cracking and breaking of the shaft must be expected.

The present invention has the task of proceeding from the piston mentioned at the beginning, in which the free-hanging bolt hubs each over a rib running parallel to the pressure-counterpressure plane with the Piston crown and each over two ribs with the Piston shaft connected to a control piston develop, which is suitable for all areas of application if there is no cast-in control elements made of steel is and with normal shaft ovality one of all needs and has a control effect that meets requirements in engine operation.

The solution of this problem is the fact that the piston head from the piston shaft at circumferential length is wholly or partially separated by a transverse slot and the pin bosses with the piston shaft connecting ribs at an angle of 0 to 45 °, preferably 0 to less than 45 °, to the Bolt level are arranged.

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It has proven to be particularly advantageous - with regard to an optimal control effect - if the ribs that the Connect the pin hubs to the piston skirt at an angle of 0 to 30 to the · stud hinge p v *? Rlau.fsn.

According to an advantageous embodiment of the invention, the piston head extends from the piston skirt to a circumferential length separated from 70 to 110 ° on pressure and counter pressure side.

Through the transverse slot that extends the entire piston skirt or partially separates the circumferential length from the piston crown, an obstruction to the flow of heat is effected. For the piston skirt In general, this means a significant temperature decrease, that is, one that has been additionally achieved smaller expansion. The piston skirt is therefore only through the ribs over the pin bosses with the Piston crown in connection. The high temperature level of the floor compared to the upper end of the shaft causes there here there are no obstructing steel inserts - a relatively large expansion that can only be reached via the webs to the bolt, eyes on the shaft - in the direction of the bolt axis - is transferred. The upper part of the piston skirt is accordingly stretched in the direction of the bolt axis and - since the shank circumference remains practically the same - perpendicular to it scaled down. This type of regulation corresponds exactly to the need to make the warmer upper part of the shaft stronger to regulate than the colder shaft lower part. The regulation can be made possible by the greater possibility of variation of the factors that are decisive for the control behavior, such as the length of the Cross slot, direction of shaft support and choice the heat flow cross-section, floor support, shaft support, better matched to the cylinder diameter.

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By this regulating effect is achieved at normal ovality and crown, that the actual dimension of the Kclbenschafts in all operating ranges of the motor is approximately the same size as that of the cylinder, regardless of whether it is made of cast iron or Al umi nium. Through this coordination, all positive and negative control effects can be achieved, so that its area of application is not determined by the dependency existing in conventional control pistons between Litt, engine power and piston diameter.

With the measures according to the invention are also a smooth running of the control piston, lower oil consumption and an optimal contact pattern achieved. With a given running game Compared to conventional control pistons, the piston skirt does not need to be so oval. When the piston is at operating temperature, it achieves a comparatively lower preload, so that a Reduction of the frictional power takes place.

With the control piston according to the invention, a weight saving of up to 25 % can be achieved compared to conventional control pistons.

The control piston according to the invention is shown by way of example in the drawing and is explained in more detail below explained:

Fig. 1 illustrates a longitudinal section through a control piston along the bolt plane.

FIG. 2 shows a cross section through the control piston along the section line I - I in FIG. 1.

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To achieve the control effect within the scope of the invention, the pin bosses 3 hanging freely on the piston head 1 via the ribs 2 are connected to the piston skirt 5 with the ribs 4 running at an angle of 30 °. In the pressure and counterpressure area, the piston has a transverse slot 6 between the piston head 1 and the piston shaft 5, which extends over a circumferential length of 110 °. Compared to the piston pin bosses 7 there are openings 8 in the piston rod 5. This control spool has in the region of the shank top edge of an area of 14.10 "-zzzjr and at the shaft bottom edge of an area of 17 * 10" in gjjjjo ^.

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Claims (3)

t ι · t I · B I I ι ·> I CLAIMS 1) Pistons for internal combustion engine * !, preferably made of Alumi.nium or its alloys, in which the freely hanging pin bosses are connected to both the piston crown and the piston skirt via ribs and perforations in the piston skirt are arranged opposite the pin bosses, characterized that the piston head (1) is completely or partially separated from the piston skirt (p) on the circumferential length by a transverse slot (6) and the ribs (4) connecting the piston bosses (3) to the piston skirt at an angle of 0 to 45 ° to Bolt level are arranged. 2) Piston according to claim 1, characterized in that the ribs (4) connecting the piston bosses (3) to the piston skirt (5) are arranged at an angle of 0 to less than 45 °, preferably 0 to 30 °. 3) Piston according to claims 1 and 2, characterized geken n is characterized in that the piston head (1) from the piston skirt (5) on pressure and counter pressure is te on a circumferential length of 70 to 110 is separated. 7421863 3Q.1176