DE2615213A1 - LIGHT ALLOY PISTON - Google Patents

Description

KARL SCHMIDT GMBH 04/05/19 76

Christian-Schmidt-Strasse 8/12 -DrQ / GKp-

7107 Neckarsulm

Prov. No. 7875 KS

Light alloy pistons

The invention relates to a single-metal full-skirt control piston for piston engines, preferably cast from light metal for highly loaded internal combustion engines, in which the freely hanging pin bosses each with the piston crown via support ribs attached transversely to the pin direction and with the piston skirt via two each on the circumference of the piston pin bosses connected at an angle of 0 to 4-5 °, preferably 30 to 4-5 °, to the bolt plane arranged support walls are.

The piston, made of light metal as a transfer element for thermal to mechanical energy, is in Modern internal combustion engines are indispensable. At Such pistons are nowadays subject to a large number of requirements in all operating conditions.

To avoid dead spaces and harmful pinch gaps in the combustion chamber of reciprocating engines are partially Complicated piston shapes were created, the thermal load of which can be very high.

Since the introduction of the light metal piston, a large number of developments have been made to improve it been. It was always the goal to use the light alloy piston despite the very different coefficient of thermal expansion

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to achieve a good straight line guidance compared to cylinders which are preferably made of gray cast iron.

All such piston designs are based on the idea, with the help of stretch-inhibiting, in the upper Area of the piston skirt arranged in the form of a ring or plate Steel inserts to prevent the undesired thermal enlargement of the piston diameter. It will tries to deflect the piston expansion preferably in the direction of the pin axis and to reduce the piston clearance in pressure and .The direction of the back pressure should be adapted to the cylinder diameter under all operating conditions as far as possible. This The process is referred to as the control effect.

The cylinder of the internal combustion engine is deformed under the thermal load and the acting pressures in the radial and longitudinal direction and hardly retains its cylindrical shape. The piston must follow these deformations and through play and elasticity one Enable customization. This adjustment is made easier by regulating pistons and thus their necessity underlined.

For a perfect function of the control piston are already in the design of the internal combustion engine .As well as fulfilling certain basic conditions in the design and configuration of the piston. Above all is knowledge the load values of an engine type are very important in order to meet the requirements when designing the piston in terms of control effect and material.

The control characteristic, to be equated with the expansion coefficient of the piston, is through that

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Determined temperature gradient between piston head and skirt. This gradient is different for every internal combustion engine and is influenced by design measures.

The interaction of piston play, control effect and Deformation of the piston skirt is crucial 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 in terms of smoothness and seizure security are met.

The requirements for the piston in the internal combustion engine are particularly due to increased driving comfort with higher engine power and good acceleration behavior of vehicles increased. The compulsion to use the vehicles economically makes it necessary that Design the drive unit as compact as possible. That means the demand for a small displacement and nevertheless high liter output also with regard to the future emissions legislation.

In addition to the main tasks of the piston, power transmission, Straight guidance, sealing and heat dissipation are today the previously secondary functions came more and more to the fore. The requirements for smoothness must be coordinated with the requirements for structural strength, minimal wear and tear and seizure resistance will. Simply through suitable constructions, dimensionally accurate processing and a functional surface quality can seal against oil and

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Combustion gases in the ring field flawlessly over long periods of time being held. Furthermore, the piston weight gains due to the tendon frequency of the internal combustion engines is becoming more and more important and takes up a lot of space in the design. Based on these Strict requirement, pistons in lightweight construction are used predominantly today. The exact knowledge of the Stress, control effect and behavior of the piston material is one of the prerequisites for the correct one Design of a control piston.

In all control pistons, the stiff and hot piston head looks for the bridge over the ring field and pin hub To deform the piston skirt oval in the direction of the bolt.

Such control pistons have a more or less pronounced separation between the piston crown and the supporting surfaces of the shaft. The ability to be regulated is e.g. through transverse slots in the area of the lower Ring field can be favored. Pistons of this type have become used in internal combustion engines Well proven under lower thermal load (Bensinger, W.-D. and A. Meier: Pistons, connecting rods and Crankshaft with tendons accumulating internal combustion engines, Springer-Verlag 1961, pages 15 to 19).

In the case of internal combustion engines subject to high thermal loads however, an unslotted control piston is advantageous because the heat transfer from the hot piston head to the relatively thin-walled piston skirt is not inhibited. Of the Piston is given additional stability, which reduces the deformability in the direction of the tilting plane.

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It is therefore in Aluminum 4 ^ 5, 1969, page 545, a Unslotted light metal piston provided with control elements, in which the previously considered necessary Cross slots between the shaft and the ring zone have been omitted taking into account certain design guidelines became. Despite the slotless design, a good control of the thermal expansion is achieved, which by the temperature dependence of the stress distribution is steered in the direction of the bolt axis.

Furthermore, according to DT-OS 24 · 30 829 is a single metal piston Made of light metal without standard inserts with complete or partial separation of the piston crown from the load-bearing Shank is provided in which the pin bosses are arranged hanging on the piston crown via support ribs via two support walls with the piston skirt attached at an angle of 0 to 4-5 ° to the bolt plane are connected.

Due to the transverse slot, this control piston has very good control behavior and thus one correspondingly good straight line guidance in the cylinder. Sufficient for pistons for highly loaded internal combustion engines because of the heat flow hindered by the transverse slits and with regard to the strength of this But piston design is not enough.

It is therefore proposed according to the invention that at a control piston of the embodiment described above, the piston crown and ring field comprehensive rigid Head part and the cylindrical thin-walled shaft part connected to one another in one piece over the entire circumference with the height of the attached at the height of the pin hubs

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Retaining walls each M-5 to 65%, preferably 50 to 60%, the shaft length is. This means that the amounts of heat transferred from the piston crown preferably have two paths to disposal. The main flow of heat takes place via those attached to the inner shape of the piston crown Bolt hubs and support walls to the shaft. A small proportion of the amount of heat is transferred to the ring field Derived piston skirt. In addition, the warmth, due to the very large interior of the Piston, by splashing lubricating oil of the internal combustion engine released to this medium.

This is high compared to the closed shaft part The temperature level of the piston crown and the pin bosses cause a sufficiently large expansion, which over the Support walls to the shaft - is transferred in the direction of the bolt axis. The piston skirt is thus in the direction Bolt axis stretched and, since the shaft circumference remains practically the same, one in the pressure and counter-pressure direction Diameter reduction causes.

With the appropriate ovality and crowning, this regulating effect ensures that the actual expansion of the deformation-resistant cylindrical piston skirt in almost all operating ranges of the internal combustion engine is the same size as that of the cylinder, regardless of »whether it is made of gray cast iron or aluminum.

Many positive control effects can be achieved by this coordination, so that the scope of this unslotted control piston does not differ from that of conventional control pistons between liter capacity and piston diameter existing dependency is determined.

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With these measures, piston noises are the cause the change of system in the cylinder is much easier to control thanks to optimal shaft guidance.

Due to the construction of this stable control piston, the wall thicknesses can be made relatively thin, which is associated with a considerable weight reduction compared to known control pistons with steel inserts.

In the context of the special embodiment of the invention, the free-hanging piston pin bosses are on the Support ribs with an asymmetrical shaped base that is adapted to the shape of the combustion chamber and at different heights tied together.

The piston designed according to the invention is in the The drawing is shown as an example and is explained in more detail below:

Fig. 1 illustrates the cross section through the unslotted j control piston designed with a mold bottom in the piston pin plane. The piston with a proportionate thick-walled piston head part consisting of the mold bottom 1 and the ring field 2 shows the connection to the thin-walled piston skirt adjoining the ring zone 2

FIG. 2 shows the control piston in the sectional plane I - I of FIG. 1.

To achieve the control effect within the scope of the invention, the ones on the asymmetrical piston crown part 1 are above Support ribs 4 freely hanging pin hubs 5 with the

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running at an angle of 45 in their height 60% of the piston skirt length having supporting walls 6 connected to the cylinder-shaped piston skirt 3. In the direction of the piston pin longitudinal axis 7, In alignment with the pin bosses 5, there are openings 8 in the piston skirt 3.

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Claims (3)

PATENT CLAIMS Γl. ^ One-metal full-shaft control piston, cast from light metal, for piston engines, preferably for highly stressed internal combustion engines, in which the freely suspended pin bosses with the piston crown
Via supporting ribs attached transversely to the pin direction and connected to the piston skirt via two support walls arranged on the circumference of the piston pin bosses at an angle of 0 to 4-5 °, preferably 30 to 15 °, to the pin plane, characterized in that the piston crown (1) and ring field (2) comprehensive rigid head part with the cylindrical thin-walled
Piston skirt (3) in one piece over the entire circumference
connected, with the amount of at the amount of
Support walls (6) attached to the bolt hubs (5) are each 45 to 65% of the shaft length. 2. Light metal piston according to claim 1, characterized in that the height of the support walls (6) in each case
50 to 60% of the shaft length. 3. Light metal piston according to claims 1 and 2,
characterized in that the freely hanging piston pin bosses (5) are connected via the support ribs (4) to an asymmetrical mold base (1) adapted to the shape of the combustion chamber and at different heights. 709843/0121 ORIGINAL INSPECTED