Internal-combustion engines – Particular piston and enclosing cylinder construction – Piston
Reexamination Certificate
1999-08-27
2001-05-01
McMahon, Marguerite (Department: 3747)
Internal-combustion engines
Particular piston and enclosing cylinder construction
Piston
Reexamination Certificate
active
06223711
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a piston, especially for an internal combustion engine, with double crank drive.
An internal combustion engine with double crank drive is, for example, known from German patent application 32 38 030 A1. For such a double crank drive each piston is connected with at least one connecting rod to one of the two crank shafts which rotate at the same rpm in opposite directions and are connected to one another by a toothing. An advantage of such a double crank drive is that the piston runs without lateral forces in the cylinder and that the force of the piston is transmitted by at least two connecting rods onto the crankshafts so that the weight of the connecting rods can be reduced and a higher rpm stability can be achieved. Furthermore, with a proper selection of the slanted position of the connecting rod at the top dead center and bottom dead center of the piston the movement kinematics of the piston relative to the rotation of the crankshaft can be designed different from a sine-shaped movement so that the thermodynamic conditions and thus the output development and the torque can be favorably affected.
In general, high requirements are placed on pistons which have a bottom conventionally delimiting the combustion chamber or, in the case of pumps, the working chamber, wherein the bottom has a transition into a mantle at its outer circumference which mantle extends parallel to the cylinder wall. The pistons must be sufficiently resistant to the effects of heat in order to withstand the peak pressures during combustion and the high acceleration and deceleration forces. Furthermore, the pistons should be lightweight so that high masses are not moved unnecessarily in a reciprocating manner.
It is therefore an object of the present invention to provide a piston which has a sufficient stability especially in connection with minimal weight and a simple manufacturing process.
SUMMARY OF THE INVENTION
A first solution of this inventive object is realized in that the piston is comprised of at least two shaped sheet metal parts having integral flaps that are bent out of the plane of the sheet metal parts and support at least one connecting rod. This provides an inexpensive very lightweight piston which can be adapted in multiple ways to the respective requirements. Expediently, two of the flaps, which are provided at different shaped sheet metal parts, are combined to serve as a common bearing means or attachment location for the connecting rod. In a preferred embodiment, two shaped sheet metal parts are provided which extend over the entire surface area of the piston bottom. At least one bendable flap is stamped out of each of the shaped sheet metal parts, whereby the flaps are arranged such that the flap of one of the sheet metal parts penetrates through the opening resulting from bending the flap out of the plane of the other sheet metal part. The two flaps are then connected to one another.
In another embodiment, multiple flaps are arranged at the bottom of the piston for supporting a plurality of connecting rods in order to provide a uniform loading of the piston.
Preferably, at least one shaped sheet metal part is bent at its outer circumference in order to form a groove for receiving a piston ring.
Another object of the invention is solved by providing a conically shaped tapered projection of a shaped sheet metal part which forms at least a portion of the bottom of the piston and ends in an area for connecting the piston rod.
In this design of a multi-component piston the connecting rod or piston rod is not connected to one or more flaps bent out of the plane of the shaped sheet metal parts but is provided in the form of a conical tapered projection of a shaped sheet metal part that forms at least one portion of the bottom of the piston.
Expediently, the piston is manufactured without a skirt. Such a skirtless piston, which is advantageously useful for pumps or internal combustion engine in which the piston is linearly guided, is extremely lightweight and therefore suitable for high rpm.
In yet another embodiment of the invention, the piston at its circumference is provided with an annular disk that in a direction toward the combustion chamber is curved and is embodied of an elastic material. Upon pressure loading from the combustion chamber it flattens out under enlargement of its outer diameter. This piston is not provided with an individual piston ring for sealing between cylinder wall and outer circumference of the piston. This function is provided by the annular disk facing the combustion chamber which is flattened by the pressure within the combustion chamber so that its diameter will increase and will seal the piston and cylinder walls relative to one another.
Preferably, the piston at the end face facing the combustion chamber is provided with a thermal insulation coating.
REFERENCES:
patent: 3848518 (1974-11-01), Martin
patent: 5014599 (1991-05-01), Kocsis et al.
patent: 5029562 (1991-07-01), Kamo
patent: 5317958 (1994-06-01), Martins Leites et al.
patent: 5778846 (1998-07-01), Mielke
patent: 5947065 (1999-09-01), Bing et al.
patent: 32 38 030 A1 (1983-04-01), None
McMahon Marguerite
Robert W. Becker & Associates
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