This application claims priority to German Patent Application No. 10 2013 004 577.0, filed Mar. 18, 2013, German Patent Application No. 10 2013 014 344.6, filed Aug. 28, 2013, and International Patent Application No. PCT/DE2014/000139, filed Mar. 18, 2014, all of which are hereby incorporated by reference in their entirety.
The present invention relates to a method for producing a piston for an internal combustion engine, having a piston main body and a piston ring part, wherein the piston main body has a combustion depression with a dome and has piston bosses equipped with boss bores, which piston bosses are connected to one another by way of running surfaces, wherein the piston ring section has a piston crown, an encircling fire land and an encircling ring section, and wherein the piston main body and the piston ring section form an encircling cooling duct. The present invention also relates to a piston that can be produced by way of said method.
A method for producing a piston is known from the German patent applications 10 2011 013 141 A1 and DE 10 2011 013 067 A1, in which method the blank of the piston main body is finished by forging in the entire region of the combustion depression. The contour of the combustion depression is thus not involved in the secondary machining process. Said production method can however be used only for pistons in which the piston upper part comprises the piston head and the piston lower part comprises the piston skirt. Other piston structures cannot be realized.
It is the object of the present invention to further develop a generic method such that different piston structures can be realized.
The solution consists in that, in step a), during the production of the blank of the piston main body, the contour of the combustion depression is fully produced.
The present invention also relates to a piston producible by way of the method according to the invention.
The method according to the invention is characterized in that pistons can be produced in which the ring section can be composed of a different material thann structures. It is for example possible to realize pistons with a reinforced ring section.
Advantageous refinements will emerge from the subclaims.
It is expediently provided that, in step c), cooling duct regions are formed into the blanks and/or are finish-machined, because the cooling duct regions are no longer accessible after the welding of the blanks.
It is furthermore advantageous if, in step c), in the blank of the piston main body, the interior space is finish-machined and inlet and outlet openings for cooling oil are formed into the cooling duct region. The piston main body is easier to handle for this purpose than the welded piston body.
Furthermore, based on the same considerations, it is recommended that, in step c), on the blank of the piston main body and/or of the piston ring part, the outer diameter be pre-machined, and/or, on the blank of the piston main body, the piston bosses be pre-machined.
A preferred refinement provides that, in step e), the boss bores are formed into the piston bosses after the piston crown has been finish-machined. Since the compression high of a piston is defined by the distance between the piston crown and central axis of the boss bore, the predetermined compression height of the finished piston can be obtained in a particularly simple manner.
Various deformation methods may be selected for the production of the blank of the piston main body. The blank may be forged by hot working at 1200° C. to 1300° C. and subsequently subjected to cold calibration. The blank may also be forged by hot working at 1200° C. to 1300° C. and subsequently subjected to cold working at a temperature of at most 150° C. The blank may furthermore be forged by warm working at 600° C. to 900° C. Furthermore, the blank may, after the warm working, be subjected to cold working at a temperature of at most 150° C. Finally, the blank may be forged by cold working at at most 150° C.
An exemplary embodiment of the present invention will be discussed in more detail below on the basis of the appended drawings in which, in each case in a schematic illustration which is not to scale:
The piston 10 furthermore has a piston ring part 17 with a piston crown 18, with an encircling fire land 19 and with an encircling ring section 21 with annular grooves for receiving piston rings (not illustrated). An encircling cooling duct 22 with inlet and outlet openings for cooling oil (not illustrated) is provided at the level of the ring section 21.
In the present exemplary embodiment, the piston main body 11 and the piston ring part 17 are connected to one another by way of a welding process, for example electron beam welding or laser welding.
The piston main body 11 is produced from a material which can be subjected to a deformation process. This is typically a tempering steel, for example 42CrMo4 or an AFP steel such as 38MnVS6.
According to the invention, it is the intention to be able to produce even a combustion depression of complex geometry. It is the intention, furthermore, to be able to produce, by means of the method according to the invention, combustion depressions which are radially offset with respect to the piston central axis or which are in an inclined arrangement. Stated alternatively, the piston 10 may have a combustion depression 12 which is asymmetrical and/or radially offset with respect to the piston central axis and/or inclined.
For this purpose, as illustrated in
In the exemplary embodiment, the geometry of the combustion depression 12 is finished by forging. This means that, for the production of the finished piston 10, no secondary machining of the combustion depression 12 is necessary.
A blank 17′ of the piston ring part 17 may be produced from any suitable material, for example by deformation or casting.
As illustrated in
On the blank 11′ for the piston main body 11, it is also possible for the boss region to be pre-machined. Finally, the interior space 24 can be finish-machined. Furthermore, a cooling duct region 22a, which in the finished piston 10 forms a part of the cooling duct 22, is formed into the blank 11′. The cooling duct region 22a may also be formed in during the forging process, and in this case is finish-machined after the forging process. The inlet and outlet openings for cooling oil are formed into the cooling duct region 22a.
On the blank 17′ for the piston ring part 17, it is for example the case that a cooling duct region 22b, which in the finished piston 10 forms a part of the cooling duct 22, is formed into the blank 17′.
Finally, after the forging process, in both blanks 11′, 17′, the welding surfaces 26, 27 and 28, 29, respectively, by way of which the blanks 11′, 17′ are to be connected to one another, are finish-machined.
Then, the blanks 11″, 17″ are, by way of their welding surfaces 26 and 28, and 27 and 29, respectively, connected to one another in a manner known per se by way of a suitable welding process to form a piston body 30, such as is illustrated in
To complete the method according to the invention, the piston body 30 is finish-machined by virtue, for example, of the final fine contour being produced, the piston crown 18 being finish-machined and the annular grooves being formed into the ring section 21 and the boss bores 15 being formed into the piston bosses 14. The boss bores 15 are formed in such that the predetermined compression height of the finished piston is determined by the central axis of said boss bores in relation to the piston crown 18. A piston as per
Number | Date | Country | Kind |
---|---|---|---|
10 2013 004 577 | Mar 2013 | DE | national |
10 2013 014 344 | Aug 2013 | DE | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/DE2014/000139 | 3/18/2014 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2014/146637 | 9/25/2014 | WO | A |
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