The invention relates to a piston of an internal combustion engine.
Known pistons with a so-called “slipper” design are known and are used if it is sought to reduce the weight of the piston. Moreover, in the case of such pistons of the type in question, the connecting walls which connect the mutually opposite piston skirts (also referred to as supporting skirt wall portions) are obliquely positioned and in each case accommodate one pin bore. It has been shown in practice by this oblique position that the combustion forces acting on the piston can be transmitted very well and the deformation of the piston resulting therefrom is effectively limited. In addition, the separate production of a lower part and of an upper part, which are joined together after their production, is of advantage since certain elements of the piston are better accessible prior to the joining-together operation than would be the case after the joining-together operation.
A piston of the type in question is known from DE 10 2005 041 001.
The invention relates to a piston of an internal combustion engine, formed from an upper part which is joined together with a lower part, wherein the lower part is formed from mutually opposite, obliquely positioned connecting walls which are set back with respect to the outside diameter of the piston, wherein in each case one connecting wall has a pin bore and the respective end of each connecting wall merges into a piston skirt.
The object on which the invention is based is to provide a piston of an internal combustion engine which, by comparison with pistons of the type in question, is improved in terms of its production but in particular in which the weight is also further reduced without the stability of the piston during operation in the cylinder of the internal combustion engine being limited as a result.
According to the invention, there is provision that the lower part has at least one cutout which faces in the direction of the upper part and the upper part has at least one cutout which faces in the direction of the lower part, wherein the cutouts overlap after the joining-together operation, wherein, furthermore, a permanent connection between the lower part and the upper part is a positively locking connection and the positively locking connection is formed by at least one tongue and at least one groove which can be brought into operative connection therewith. By virtue of this at least one cutout, preferably a plurality of cutouts per lower part and per upper part, it is possible for material savings to be made locally in order to reduce the weight of the piston after it has been joined together. As a result of the overlapping of the cutouts in the upper part and in the lower part, sharp-edged transitions between the two parts are avoided in order thereby to be able to avoid crack formations, in particular when a joining operation, such as, for example, a welding operation or the like, has taken place in the transition region between upper part and lower part. The overlapping of the two parts can be realized in a positionally accurate manner by the positively locking connection, with the result that a defined position of the upper part with respect to the lower part is always already predefined either by the positively locking connection (with the result that the two parts no longer have to be moved relative to one another after being brought together) or a defined position can be established by relative movement of the two parts with respect to one another.
In a development of the invention, the at least one cutout of the lower part (and thus correspondingly also the cutout of the upper part) is arranged above and outside of the connecting wall. Consequently, the at least one local cutout formed by the joining-together of upper part and lower part is arranged below the upper part of the piston and is situated outside of the inner region of the piston, with the result that material can be saved at points in which the piston is not highly loaded.
Alternatively or in addition thereto, there is provision according to the invention that the at least one cutout of the lower part (and thus also the corresponding at least one cutout of the upper part) is arranged above and inside of the two connecting walls. By this means, too, material of the piston can be saved reduced at points which are arranged above the inner region, that is to say between the two connecting walls and the two mutually opposite supporting skirt wall portions. This applies in particular when the piston has no combustion-space recess. Valve pockets which are of flat design can, but do not have to, be present.
In a development of the invention, there is provision that a wall region of the connecting wall merges in a transition-free manner into a wall region of the at least one cutout of the lower part. If the at least one cutout in the lower part (and also in the upper part) is arranged above the connecting wall, it is of advantage that a transition from the wall region of the connecting wall into the wall region of the at least one local cutout merges in a transition-free manner, with the result that sharp-edged transitions, step-like transitions or the like, are also avoided here in order to counteract a crack formation. This transition-free transition can, but does not have to, be arranged in the region of a joining plane between upper part and lower part. Moreover, it can be realized very simply in an advantageous manner by the positively locking connection (tongue-and-groove principle).
In one particular embodiment of the invention, there is provision that one cutout of the lower part is arranged above the pin bore and in each case one cutout of the lower part is arranged above and next to the pin bore. By virtue of this symmetrical arrangement of three local cutouts, there is a substantial saving of material on the one hand, and, by virtue of the regions (webs) remaining between the local cutouts, a very good support of the upper part with respect to the combustion pressures acting on the piston is achieved on the other hand.
The invention is explained below in more detail below with reference to an exemplary embodiment, to which the invention is not limited, however, and is shown in the figures.
The remaining details of this upper part 3 which are provided in
In order to form bearing surfaces between the lower part 2 and the upper part 3, it is possible, for example, for an outer ring 8 to be present from which at least one web, here a plurality of webs 9, extend in the direction of the center of the piston. These webs 9 can start from the outer ring 8, specifically in the same plane or in a plane arranged offset thereto. In the case of the lower part 2 according to
However, it is also conceivable and evident on viewing the Figure that the outer ring 8 and the peripheral region, extending parallel thereto, at the outwardly facing end of the webs 9 (that is to say the inner ring 10) and/or the inner ring 10 and the central region 11 are arranged in one and the same plane. As a result there is also formed in this variant, between the outer ring 8 and the inner ring 10 and/or the inner ring 10 and the central region 11, one groove or two groves in the lower part 2 to form a part of the positively locking connection.
The reference number 12 designates at least one cutout in the lower part 2 which can in principle be provided at a suitable point for the purpose of saving material.
In the case of the exemplary embodiment according to
The outer ring 8 of the lower part 2 corresponds with an outer ring 13 (
As is evident on viewing the two parts 2, 3 according to
It is very clearly evident on viewing
The operationally ready piston 1 illustrated in
The design of the two parts 2, 3, as have been shown in
However, in the case of the piston 1 according to
This positively locking connection is formed, as is illustrated in
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102016108271.6 | May 2016 | DE | national |
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PCT/EP2017/060534 | 5/3/2017 | WO | 00 |
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WO2017/191189 | 11/9/2017 | WO | A |
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