阅读说明：本技术 用于内燃机的活塞 (Piston for an internal combustion engine ) 是由 朱利安·齐尔克 迈克尔·谢勒 奥尔加·塞勒 斯文·翁格曼 拉尔夫·马斯克 于 2020-06-25 设计创作，主要内容包括：本发明涉及一种用于内燃机的活塞(10),该活塞包括轴壁部分(18)以及至少一个基部支承件(20),该轴壁部分用于支承在汽缸或汽缸衬套中,该至少一个基部支承件在圆周方向上与轴壁部分连接,该基部支承件具有形成螺旋线的部分的至少一个轮廓。(The invention relates to a piston (10) for an internal combustion engine, comprising a shaft wall section (18) for mounting in a cylinder or a cylinder liner, and at least one base support (20) which is connected to the shaft wall section in the circumferential direction and has at least one contour which forms part of a spiral.)

1. A piston (10) for an internal combustion engine, comprising a shaft wall portion (18) for bearing in a cylinder or cylinder liner, and at least one base support (20) connected to the shaft wall portion in a circumferential direction, the base support having at least one profile forming part of a helix.

2. The piston (10) of claim 1,

the base support (20) is arranged at least on the pressure side of the piston (10).

3. The piston (10) of claim 1 or 2,

the base support (20) is arranged on both sides of at least one shaft wall portion (18).

4. The piston (10) of any one of the preceding claims,

the at least one base support extends up to the area of the pin boss limit (28).

5. The piston (10) of any one of the preceding claims,

the helix has a slope of 1:10 to 1:1, in particular 1: 2.

6. The piston (10) of any one of the preceding claims,

the depth (T) of the at least one base support (20) measured in the radial direction is at least the same as the depth of the lowest annular groove (16) measured in the radial direction and/or the depth of the at least one base support is at most twice the depth of the lowest annular groove.

7. The piston (10) of any one of the preceding claims,

the at least one base support (20) is spaced apart from a connecting wall (24) connecting the shaft wall portion (18).

8. The piston (10) of any one of the preceding claims,

the transition between the shaft wall portion (18) and the at least one base support (20) is provided with a rounded portion (22).

Technical Field

The present invention relates to a piston for an internal combustion engine.

Pistons for internal combustion engines are subject to extremely high loads, in particular in the case of gasoline engines with a high specific power (specific power), which may be of the order of 100 kW/l. This is due on the one hand to the high ignition pressure (which may be around 120 bar) and on the other hand to the extremely high temperatures prevailing in the combustion chamber. Due to the kinematics of the crank drive (crank drive) on the pressure side of the piston, and in this case in particular in the lowest annular groove of the piston, particularly high loads occur. In particular in the case of loads which can be described as "maximum lateral forces", high tensile stresses occur in the lowest annular groove of the piston on the pressure side, since the piston skirt (piston skirt) reacts to the lateral forces in a more elastic manner than the piston crown (piston crown) which comprises the annular region. Furthermore, in order to keep the loads to which piston pin bosses (piston boss) and other engine components are subjected due to inertial forces low, it is desirable to reduce the weight as much as possible. This is achieved, for example, by forming so-called pockets (pockets) radially on the outside of the piston pin in the axial direction of the piston pin. In other words, the connecting wall connecting the support shaft wall portions is retracted radially inward.

Background

Many pistons in the prior art are designed in this manner. A rounded portion is typically formed between the shaft wall portion and the pocket.

Disclosure of Invention

Against this background, the object of the invention is to ensure the fatigue strength, in particular in the lowest groove of the piston, without significantly increasing the weight of the piston, in particular by reducing the maximum stresses occurring there.

This object is achieved by a piston as claimed in claim 1.

According to this purpose, the piston comprises a shaft wall portion for bearing in a cylinder or cylinder liner (cylinder liner), a so-called base support being connected to the shaft wall portion in the circumferential direction towards the piston crown, said base support having at least one profile forming part of a spiral (helix). In other words, the distance between the bottom edge (i.e. the end of the base support facing away from the piston crown) and the lowermost annular groove follows the slope of the rolling around the cylinder. Such a bottom edge may be the same over substantially the entire radial depth of the base support. In other words, looking radially at the base support, this is shown as a line. However, the described profile may only appear radially on the outside or inside of the base support, and the bottom periphery of the base support may descend or ascend from this edge. In a rectangular coordinate system (Cartesian coordinates), the spiral can be expressed as follows:

where r is the radius of the cylinder, h is the pitch, and t is the curve parameter. The slope k is:

as the initial simulations show, this can significantly reduce the stress in the lowest piston ring groove. The maximum principal stress can be reduced by about 30MPa compared to currently used designs. This results in an improvement of fatigue strength of about 25%. Furthermore, it has been shown that in the case of a typical piston, the weight increase is only about 2 g. The object of configuring the piston both relatively light and at the same time robust can thus be achieved in an advantageous manner by means of the invention. The base support thus ensures an advantageous support of the piston crown.

Advantageous refinements of the piston according to the invention are described in the other claims.

Although the described design can be provided on both sides of the piston, it is preferred in view of the above-mentioned load situation that the contour according to the invention is provided at least on the pressure side of the piston.

It is also preferred that the profiles according to the invention are provided on both sides of the shaft wall section, so that the advantages according to the invention can be utilized in combination.

This also applies to the preferred measure according to which at least one base support extends from the shaft wall portion up to the region of the pin boss limit (pin boss limit).

Initial simulations show that the slope of the helix according to the invention should be at least 1:10 and at most 1: 1. currently, about 1: a value of 2.

The base support designed according to the invention has a depth measured in the radial direction, which is preferably more or less the same as the depth of the lowest annular groove of the piston measured in the same direction. This allows a particularly reliable implementation of low-stress bearing of the region weakened by the annular groove of the piston. The depth described may be up to twice the depth of the piston ring groove and in the case of a normal gasoline engine piston the depth described may be about 6 mm.

The connecting wall connecting the shaft wall portions is located radially inside the described base support and, in view of weight saving, it is preferable to provide a space here, or in other words, at least one base support is spaced from the connecting wall in the radial direction. Thus, what remains here is a "pocket" which contributes to weight savings.

In order to avoid the notch effect, a rounded portion is preferably provided at the transition between the shaft wall portion and the at least one base cover.

Drawings

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings. In the drawings:

FIG. 1 shows a side view of a piston according to the present invention;

FIG. 2 shows a bottom view of a piston according to the present invention; and

fig. 3 shows a perspective bottom view of a piston according to the invention with a spiral drawn.

Detailed Description

As can be seen from fig. 1, the piston according to the invention comprises a piston crown 12 on the top side of the piston according to fig. 1, an annular region 14 with the lowest annular groove 16, and shaft wall portions 18, only one of which can be completely shown in fig. 1. The shaft wall portion 18 has a more or less constant width as measured in the circumferential direction. In the embodiment example shown, the width is more or less constant along the piston stroke axis (vertical in fig. 1), widening slightly towards the bottom side (i.e. away from the piston crown 12).

According to the invention, so-called base supports 20 are connected to both sides of the shown pressure-side shaft wall section 18 in the circumferential direction, which base supports are formed mirror-symmetrically in the shown case. Fig. 1 shows the profile on the bottom side of the base support 20 as an inclined surface, but fig. 3 reveals that the profile follows a spiral. A detailed description is provided below in conjunction with fig. 3. Referring to fig. 1, it should again be noted that the transition from the shaft wall portion 18 to the respective base support 20 is configured in the form of a rounded portion 22.

In addition to this, fig. 2 shows the depth T of the base support 20 measured in the radial direction. Fig. 2 also shows that each base support 20 is spaced from the connecting wall 24 connecting the shaft wall portions, although the connecting wall 24 is slightly offset in the direction of the piston pin axis. As a result, pockets 26 that facilitate weight reduction remain between the base support and the connecting wall.

Fig. 3 now shows the outline of the base support 20 in detail. It should be noted that this also applies to the base support on the other side, which has the opposite helicity. The helicity shown in fig. 3 may be described as positive. In other words, if the x-axis is psychologically flipped onto the y-axis, the helix will move in the direction of the z-axis.

It can also be seen from fig. 3 that the base support begins in the region of the rounded portion 22 towards the shaft wall portion 18 (arrow B) and ends more or less in the region of the pin boss limit 28 (arrow a). 2 and a depth T (see fig. 2) of about 6mm, about twice as deep as the lowest annular groove 16.

It should also be mentioned that the radially outer side of the at least one base support may be on the same cylinder outer surface as the shaft wall portion. However, since the base support is not required for radial support on the cylinder (liner) wall, the base support can be retracted in a radial direction relative to the shaft wall portion.