STEEL PISTON WITH OPTIMAL DESIGN

Description

[0001] The invention relates to a steel piston for an internal combustion engine, comprising an upper part in which an annular field with at least one annular groove is arranged, wherein a lower part adjoins the upper part, the lower part having two opposing shaft wall sections, the two shaft wall sections being connected via two opposing box walls, each box wall having a bolt bore surrounded by a piston hub, according to the features of the preamble of claim 1, and a method for manufacturing such a steel piston.

[0002] Pistons made of a steel material with the aforementioned characteristics (so-called box design) are generally known. They are used in internal combustion engines with high performance requirements in order to withstand the parameters that must be met, such as combustion temperature and combustion pressure. However, the steel material has the disadvantage of being heavy in such pistons, which in turn has a particularly high impact on fuel consumption.

[0003] From the prior art for steel pistons, in particular forged steel pistons, it is known that the piston in the case wall and window surface (piston hub) has an approximately straight course in the direction of the piston longitudinal axis (also referred to as piston stroke axis) with small demolding angles due to manufacturing.

[0004] The invention is based on the objective of optimizing a steel piston with regard to its function and / or weight through special design features.

[0005] This problem is solved by the features of claim 1.

[0006] According to the invention, at least one opening or at least one recess is arranged in an area around the bolt bore. When viewed from the outside, the at least one recess or at least one opening is located, for example, to the right and / or left and / or above and / or below the bolt bore, but can also be located in intermediate areas. In particular, in one embodiment of the invention, at least one opening or at least one recess is provided in the cylinder wall in the area between the piston hub and the shaft wall section.The at least one opening around the piston pin bore, particularly in the at least one cylinder wall, results in a significant weight reduction in the area of ​​the steel piston where such an opening can be placed without adversely weakening the piston's strength during operation in the cylinder of the internal combustion engine. The opening can be, for example, round (preferably produced by drilling), square (preferably produced by milling), rectangular (again preferably produced by milling), oval (also preferably produced by milling), or in any other suitable geometric shape. The at least one opening can be subsequently created after the production of a piston blank (casting or, preferably, forging) of the steel piston.Alternatively (and preferably), it is conceivable to introduce at least one opening into the piston blank during its production, which is manufactured using a material-displacing process (such as, in particular, a forging process). The optimal size, i.e., the area of ​​the opening in the cylinder wall, can be determined, depending on the design, i.e., the construction of the piston, either experimentally or, more preferably, by known and established finite element methods. The same applies to the arrangement of a recess around the piston pin bore, particularly in the cylinder wall, which can be provided only on the cylinder wall facing outwards (towards a cylinder wall of the internal combustion engine), only on the cylinder wall facing inwards (towards the centrally running piston stroke axis), or on both sides of the cylinder wall.By means of such a recess, material is also removed or displaced during the forging process at those points on the steel piston that do not impair its strength, while simultaneously saving weight through material removal. However, the arrangement of at least one opening in a box wall is preferred, as this allows for significantly more material savings and weight reduction compared to a recess.

[0007] According to the invention, a through-hole is provided to the right and left of the bolt hole and a recess is provided above the bolt hole (each viewed from a top view of the bolt hole from the outside).

[0008] According to the invention, the cylinder wall is further inclined at an angle α (alpha) with respect to a piston stroke axis (vertical axis). This allows the piston blank, on the basis of which the finished stall piston is manufactured, to be produced very efficiently in a forging process with suitable tool selection and machining direction, in order to achieve a strong microstructure and consequently a structural optimization for the finished, operational, and highly stressed piston produced from this piston blank. The inclined cylinder walls also advantageously reduce friction, noise generation, oil consumption, and blow-by effects.

[0009] In a further development of the invention, a removal groove, in particular a removal groove not located on the longitudinal axis of the piston, is arranged in a bolt face of the bolt bore. A retaining ring for the piston pin can be arranged in the removal groove in a manner known per se. This removal groove also results in material removal, thereby further reducing the weight of the steel piston. Additionally, at least one recess extends from the removal groove towards at least one end of the bolt bore. This at least one recess also reduces weight at those points on the steel piston where the material removal does not weaken the piston. The removal groove can also be subsequently incorporated after the piston blank has been manufactured (again by casting, forging, or the like).Preferably, however, it is introduced using a material-displacing process (such as forging) and only subsequently brought to size by machining (such as by a machining process).

[0010] In a further development of the invention, it is provided that, starting from the at least one annular groove, at least one recess extends upwards and / or downwards in the upper part of the steel piston with respect to the piston stroke axis. Such a recess not only saves material and thus reduces the weight of the steel piston, but also allows oil to be drained from the annular groove, in which an oil ring or no oil ring may be located.

[0011] One or more of the elements described above, or a combination thereof, or all of the elements described above of the steel piston, such as the at least one recess and / or the at least one opening and / or the inclined box walls and / or the extraction groove in the bolt bore and / or the recess extending from the extraction groove towards at least one end of the bolt bore and / or the at least one recess extending upwards and / or downwards with respect to the piston stroke axis from the at least one annular groove in the upper part of the steel piston, are already realized during the production of the piston blank by means of a material-displacing process (such as a forging process) and subsequently machined, if necessary. This machining is carried out in a manner known per se by means of a machining process (such as a milling process).

[0012] A steel piston with some of the features described above, but also with all of the features described above, is summarized below: The steel piston has features on its outer shape, especially on the cylinder walls and window surfaces, that deviate from the main contour along the piston's longitudinal axis, such as recessed or inwardly or outwardly inclined features, like, for example, Box walls inclined inwards or outwards from bottom to top, recesses located in the area of ​​the oil ring groove and serving for oil drainage, recesses located on the outside of the bolt bore and serving as a removal groove for the retaining ring, recesses located in the box surface or projecting obliquely inwards from the box surface behind the ring field and serving to reduce weight, depressions in the box wall and / or openings through the box wall serving to reduce weight.

[0013] The features of the invention mentioned above improve the function of the steel piston, such as oil consumption, noise characteristics, and ease of assembly. Furthermore, the weight of the steel piston can be significantly reduced compared to known, conventional designs. In addition, the features of the invention, when used in the cylinder of an internal combustion engine, result in improved engine performance and contribute to a reduction in emissions and fuel consumption.

[0014] In the following, an embodiment of the steel piston according to the invention is described using the Figures 1 to 4 explained.

[0015] In the Figure 1A section of a steel piston 1 is shown, which has a shaft wall section 2 (and an opposing shaft wall section not shown). The two opposing shaft wall sections 2 are connected to each other via a box wall 3, wherein the two opposing box walls 3 (in Figure 1 (Only one box wall 3 is shown) are set back from the outer diameter of the steel piston 1, on which the outer surface of the shaft wall sections 2 is located. Opposite one end of the shaft wall section 2, which runs parallel to the piston stroke axis and from which the box wall 3 extends, is in Figure 1 A bolt hole 4 is indicated.

[0016] Figure 2 shows a section of the steel piston 1 in a sectional view, whereas the Figures 3 and 4 Further detailed views (again in part) of the steel piston 1 are shown.

[0017] In these Figures 2 to 4The figure shows that the box wall 3 connecting the shaft wall sections 2 is inclined at an angle α (alpha) with respect to the piston stroke axis (shown with dashed lines). Reference numeral 5 denotes an inwardly facing bolt surface of the bolt bore 4. Reference numeral 6 denotes a piston hub arranged around the bolt bore 4. The piston hub 6 can transition directly into a box wall 3 without any step, bulge, or the like. However, it is also conceivable that a stepped or bulged transition exists at the transition from the piston hub 6 towards the adjoining box wall 3. An annular field 7 in the upper part of the steel piston 1 has at least one annular groove 8. In this embodiment, the annular field 7 has a total of three superimposed annular grooves 8 in the upper part of the steel piston 1. The rings are not shown.

[0018] The steel piston 1 of the exemplary embodiment further comprises an annular cooling channel 9 and a combustion chamber recess 10 located concentrically within the cooling channel 9. These two elements can be present individually or together, although it is also possible for only the cooling channel 9 or only the combustion chamber recess 10 to be present. The reference numeral 11 designates a recess 11 located in the pin surface 5, into which a retaining ring for the piston pin (not shown) is inserted when the piston pin is inserted in the pin bore 4. In this exemplary embodiment, a single recess 12 extends outwards from the recess 11, i.e., towards the piston hub 6, although more than one recess 12 can also be provided. The at least one recess 12 can also be directed inwards.

[0019] Reference numeral 13 designates at least one further recess extending from an annular groove 8 (in Figure 4 The lower annular groove 8) in the upper part of the steel piston 1 is shown when considering the Figure 4 extending downwards. Of course, it is also conceivable to provide at least one recess 13 in the area of ​​the other ring grooves 8. Likewise, the at least one recess 13 can be considered not only from the perspective of Figure 4 not downwards, but only upwards, or both downwards and upwards.

[0020] Another feature of the invention is in Figure 1Another opening 14 in the box wall 3 is shown. This opening 14 may be the only opening in this box wall 3, although it is also conceivable to provide more than the one opening 14 shown in the box wall 3. The same applies to providing at least one opening 14 not only in the one box wall 3 shown, but also in at least one other box wall 3, preferably in all four existing box walls 3. Alternatively or additionally to the at least one opening 14 shown, at least one recess can also be provided in the box wall (on the outward-facing side and / or the inward-facing side of the box wall 3). Reference symbol list

[0021] 1. Steel piston 2. Shaft wall section 3. Cylinder wall 4. Pin bore 5. Pin surface 6. Piston hub 7. Ring field 8. Ring groove 9. Cooling channel 10. Combustion chamber recess 11. Lifting groove 12. Recess 13. Recess 14. Opening

Claims

1. Steel piston (1) for a combustion engine, comprising an upper part, in which a ring section (7) with at least one ring groove (8) is arranged, wherein the upper part is connected to a lower part, which has two opposite skirt wall sections (2), wherein the two skirt wall sections (2) are connected by two mutually opposite case walls (3), wherein a pin bore (4) surrounded by a piston boss (6) is provided in each case wall (3), wherein at least one aperture (14) or at least one recess is arranged in a region around the pin bore (4) and the case wall (3) inclined by an angle alpha with respect to a piston stroke axis, and wherein an aperture (14) is provided to the right and left of the pin bore (4) and a recess is provided above the pin bore (4).

2. Steel piston (1) according to Claim 1, characterized in that the at least one aperture (14) or the at least one recess is provided in the case wall (3) in the region between the piston boss (6) and the skirt wall section (2).

3. Steel piston (1) according to Patent Claim 1, characterized in that the aperture (14) or the recess is provided in each case wall (3).

4. Steel piston (1) according to Patent Claim 1, 2 or 3, characterized in that an excavation groove (11) is arranged in a pin surface (5) of the pin bore (4).

5. Steel piston (1) according to one of the preceding patent claims, characterized in that, starting from the excavation groove (11), a recess (12) extends in the direction of at least one end of the pin bore (4).

6. Steel piston (1) according to one of the preceding patent claims, characterized in that, starting from the at least one ring groove (8), at least one recess (13) in the upper part of the steel piston (1) extends upwards and / or downwards with respect to the piston stroke axis.

7. Method for producing a steel piston (1) according to one of the preceding patent claims, characterized in that a piston blank is produced by means of a material displacement process, and the at least one recess and / or the at least one aperture (14) and / or the case walls (3) positioned obliquely by an angle alpha with respect to a piston stroke axis and / or the excavation groove (11) in the pin bore and / or the recess (12) extending starting from the excavation groove (11) in the direction of at least one end of the pin bore and / or the at least one recess (13) extending starting from the at least one ring groove (8) upwards and / or downwards with respect to the piston stroke axis is / are realized in the upper part of the steel piston (1) already with the production of the piston blank by means of the material displacement process.

8. Method for producing a steel piston (1) according to Patent Claim 7, characterized in that the piston blank is subsequently reworked at least in regions.