阅读说明：本技术 用于内燃发动机的活塞 (Piston for internal combustion engine ) 是由 迈克尔·谢勒 克里斯托弗·施莫尔 基安·罗克 于 2019-03-04 设计创作，主要内容包括：一种用于内燃发动机的活塞,其具有箱壁(18),所述箱壁各自形成在裙壁(12)与轴头销凸台(10)之间,并且所述活塞的特征在于,至少下边缘上和至少内侧上的推力侧上的至少一个箱壁(18),在第一部分(20)中从所述轴头销凸台(10)开始大体笔直且向外倾斜地延伸、然后向内弯曲地延伸,且然后在第二部分(16)中大体笔直且向内倾斜地延伸到所述裙壁(12)。(A piston for an internal combustion engine having tank walls (18) each formed between a skirt wall (12) and a gudgeon pin boss (10) and characterized in that at least one tank wall (18) on at least a lower edge and on at least a thrust side on an inner side extends generally straight and obliquely outwardly from the gudgeon pin boss (10) in a first portion (20), then curves inwardly, and then extends generally straight and obliquely inwardly to the skirt wall (12) in a second portion (16).)

1. A piston for an internal combustion engine having tank walls (18) each formed between a skirt wall (12) and a gudgeon pin boss (10), characterized in that at least one tank wall (18) on at least a lower edge and on at least a thrust side on an inner side extends substantially straight and obliquely outwards from the gudgeon pin boss (10) in a first portion (20), then extends curvedly inwards, and then extends substantially straight and obliquely inwards to the skirt wall (12) in a second portion (16).

2. A piston according to claim 1, characterized in that the inclination of said first portion (20) with respect to a plane perpendicular to the gudgeon pin axis is smaller than the inclination of said second portion (16) with respect to a plane perpendicular to the gudgeon pin axis.

3. Piston according to claim 1 or 2, characterized in that the inclination of said first portion (20) with respect to a plane perpendicular to the gudgeon pin axis is less than 15 °, preferably less than 13 °.

4. Piston according to any of the preceding claims, characterized in that the inclination of said second portion (18) with respect to a plane perpendicular to the gudgeon pin axis is 10 ° to 25 °, preferably 15 ° to 20 °.

5. Piston according to any of the preceding claims, wherein the second portion (16) is longer than the first portion (20), in particular 2.0 to 3.0 times longer, and particularly preferably 2.3 to 2.7 times longer.

6. Piston according to any of the preceding claims, wherein the curved portion is shorter than the first portion (20), in particular the curved portion has an arc length which is less than 75% of the length of the first portion (20), preferably less than 65% of the length of the first portion (20).

7. Piston according to any one of the preceding claims, characterized in that the outer side of at least one tank wall extends to the inner side, optionally with the exception of a widened portion (22) in the region of the connection to the skirt wall (12), respectively.

8. Piston according to any of the preceding claims, characterized in that it has cooling ducts.

9. The piston of any one of the preceding claims wherein said piston is a piston for a spark ignition engine.

10. A combination of a piston according to any one of the preceding claims and a cooling oil nozzle (14), the cooling oil nozzle (14) preferably being arranged in the region of the second portion (16), in particular in an intermediate region in the course of the second portion (16).

Technical Field

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

Pistons of internal combustion engines have first of all diametrically opposed skirt walls (skirt walls) which are part of cylinder liner surfaces (cylinder liner surfaces) which slide along a cylinder bore (cylinder liner) or a cylinder liner (cylinder liner) inserted therein during operation. In the inner region, viewed in the direction of the piston stroke axis, there are also provided gudgeon pin bosses (gudgeon pin bosses) for receiving gudgeon pins by which the piston is connected to the connecting rod. The connection between the skirt wall and the gudgeon pin boss is called skirt connection, connecting wall or tank wall (box wall). Typically, four such tank walls are provided, two for connecting the skirt wall on the thrust side (thrust side) and two for connecting the skirt wall on the counter-thrust side (counter-thrust side).

In particular, the thrust-side wall is subjected to high mechanical loads, since during the working stroke, horizontal lateral forces act which press the thrust-side wall against the cylinder wall due to the gas pressure on the piston crown and the inclined position of the connecting rod. This lateral force is transmitted from the gudgeon pin bosses through the tank wall to the skirt wall. This results in high compressive stresses on the inner side, i.e. on the side of the tank wall facing the piston stroke axis.

Furthermore, it is necessary to consider a so-called change in contact surface, that is, if the lateral force changes from the counter-thrust side to the thrust side at the top dead center (upper dead center). In this regard, the contact between the cylinder bore and the skirt wall of the piston also varies from the thrust side to the thrust side. Also during this change of the contact surface, high compressive stresses occur on the inside of the skirt wall, in particular on the lower edge, the so-called open skirt end. Insufficient strength may result in cracking at the open skirt end, which is one of the most common types of damage in pistons for spark-ignition engines.

Background

To overcome this, it is known, for example from DE 102009032379 a1, to form the skirt links in a substantially straight manner, in particular on the inside, and to angle these inward from the gudgeon pin bosses, when viewed from below. In other words, the distance of the tank wall from an imaginary plane perpendicular to the axis of the gudgeon pin decreases from the gudgeon pin boss. A similar construction is known from DE 102012203570 a 1.

However, in constructing the skirt connection, further constraints must be observed, in particular the length of the gudgeon pins and the position of the oil nozzles for spraying cooling oil into the cooling ducts or on the underside of the piston. In particular, the above-mentioned inwardly inclined, straight course (course) of the tank wall will result in the gudgeon pin bosses being relatively far from the outside, which increases the gudgeon weight and requires an adaptation of the gudgeon pins. This conflict is solved, for example, by an integrally curved skirt connection according to DE 102013214738 a1, DE 4109160 a1, US 6,279,456B 1 and JP 56-40706B 2. This does create space for the cooling oil spray nozzle without the need for outward shifting (shift) gudgeon pin bosses, but this configuration is disadvantageous for strength.

Finally, DE 102009045437 a1 discloses a piston having connecting walls, not described in greater detail, which have cutouts for cooling oil nozzles.

Disclosure of Invention

Against this background, the object of the invention is to create a piston which is optimized with regard to the combination of design strength and flexibility with regard to the location of the cooling oil nozzles and/or the location of the gudgeon pin bosses.

The solution to this object is provided by the piston described in the claims.

Thus, the piston has, on at least the lower edge and on at least the thrust side on the inner side, at least one wall which, in a first portion, extends substantially straight and obliquely outwards from the gudgeon pin boss, then extends curved inwards, and then, in a second portion, extends substantially straight and obliquely inwards to the skirt wall. In other words, the distance from the inside of the tank wall to an imaginary plane perpendicular to the gudgeon pin boss, which initially contains the piston stroke axis, increases from the gudgeon pin boss when viewed from below along the piston stroke axis. This is combined by a relatively short curved portion connecting said first portion to the second portion extending obliquely inwards in a tangentially constant manner, so that the distance to the above-mentioned plane is reduced. In the last-mentioned region, it is thus possible to adopt a construction which is ideal from the strength point of view, which results in a very uniformly (uniform) and homogeneous (homogeneous) compressive stress, so that the risk of cracking is greatly reduced. Only a slight local stress concentration occurs in the area of the curved portion. Furthermore, the straight first portion, which is inclined outwardly from the gudgeon pin boss, provides the space necessary for cooling the oil nozzle without the need to move the gudgeon pin boss outwardly in a disadvantageous manner.

With regard to strength, it was determined that with the skirt connection of the present application the same distance to the oil nozzle could be obtained, with a strength of about 16% greater with the construction according to the invention, compared to a straight, non-inclined skirt connection. Further improved strength is obtained compared to the construction of an integrally curved skirt connector. At the same time, existing manufacturing methods can be employed, and piston weight, as well as skirt flexibility in determining frictional losses and noise, are not adversely affected.

Preferred developments (developments) of the piston according to the invention are described in the other claims.

In the first simulation, it has been found that the above-mentioned requirements can be met particularly well if the inclination (inclination) of the first portion with respect to the plane perpendicular to the piston axis is smaller than the inclination of the second portion with respect to the plane perpendicular to the piston axis.

In particular, for the outward inclination of the first portion, it is presently preferred that the angle to an imaginary plane perpendicular to the axis of the gudgeon pins is less than 15 °, in particular less than 13 °, and particularly preferably about 9 °.

In particular, with regard to strength, a tilt angle of the second portion with respect to a plane perpendicular to the axis of the gudgeon pins in the range 10 ° to 25 °, in particular in the range 15 ° to 20 °, and particularly preferably about 18 °, is expected to have good results.

The requirements are further particularly well met if the second section is formed longer than the first section, in particular 2.0 to 3.0 times longer, and particularly preferably 2.3 to 2.7 times longer, and in particular about 2.5 times longer. In this case, the edge line of the inner face of the gudgeon pin bore on the side of the tank wall under consideration, projected onto a plane perpendicular to the piston axis, is considered to be the beginning of the first portion. The end of the first portion is formed by the beginning of the bend. The second portion extends from the end of the curved portion up to the outer surface of the skirt wall.

In order to keep the unavoidable stress peaks particularly low, it is preferred that the bend between the first part and the second part is much shorter than the first part. In particular, good results are expected for configurations in which the arc length of the curved portion is less than 75% of the length of the first portion, in particular less than 65% of the length of the first portion, and particularly preferably about 64% of the length of the first portion.

Although this has little influence on the achievement of the advantages according to the invention, it is preferred that the outer side of at least one tank wall, optionally except for the widened portion in the region of the connection to the skirt wall, is constructed to correspond to the inner side, in other words with a substantially constant thickness, and/or likewise with two of the abovementioned substantially straight portions with a relatively short curved portion therebetween. As mentioned, said configurations on the inner side and the outer side apply at least to the lower edge of at least one, preferably both skirt walls on the thrust side. The skirt wall can be correspondingly configured in its further course in the direction of the piston stroke axis and in particular extend at least partially substantially parallel to the piston stroke axis.

It has been clear from the above that the piston according to the invention shows particular advantages in combination with a cooling oil nozzle arranged in the piston housing of the engine, so that it is preferred that the piston has at least one cooling duct, although it is equally conceivable that the cooling oil nozzle does not supply cooling oil to the cooling duct, but only to the underside of the piston.

Furthermore, the piston according to the present invention is preferably used as a piston for a spark ignition engine.

Drawings

The invention will be discussed in more detail below with reference to the embodiments shown in the figures.

The figure shows a partial bottom view of a piston according to the invention with a cooling oil nozzle.

Detailed Description

In the figures, about a "quarter" of a piston according to the invention is shown in a bottom view, the piston having gudgeon pin bosses 10 and a thrust side skirt wall 12. Furthermore, a cooling oil nozzle 14 is shown. 16 mark a line which is optimal for the connection between the gudgeon pin boss 10 and the skirt wall 12 or for a uniform stress distribution in the tank wall 18. However, as can be appreciated in particular by the imaginary extension of the line 16 of the drawing to the left up to the gudgeon pin boss 10, when sufficient space is created for the cooling oil nozzle 14, this will move the gudgeon pin boss relatively far outwards, i.e. downwards in the drawing, which will be disadvantageous for the necessary gudgeon pin length and piston weight.

According to the invention, it is contemplated that the tank wall according to the line 20 extends in a substantially straight manner in the first portion and is at least slightly inclined outwardly. This means that the tank wall does not extend perpendicular to the gudgeon pin axis (extending from top to bottom in the figure), but rather the distance of the tank wall to a plane perpendicular to the gudgeon pin axis increases, which distance can be considered to extend from left to right in the figure, with the line 20 moving further away from the gudgeon pin boss 10 and closer to the skirt wall 12. In this case, as mentioned above, for the preferred dimensional ratio of line 20 to line 16, line 20 begins at the projection of the inner face of the gudgeon pin boss 10, marked as line 22.

In combination with the relatively short curved and tangentially constant transition which can be seen in the figures, in particular on the inner side of the tank wall 18, the tank wall extends obliquely inwards in correspondence with the "ideal" line 16, so that the distance of the tank wall to a plane perpendicular to the piston axis decreases with the course of the tank wall in the direction of the skirt wall 12. Thus, the area of line 16 between the end of the curved portion and the skirt wall 12 forms the second portion described above, and the marked line 20 forms the first portion.

Furthermore, the above-mentioned measure (measure) can be seen in the figure, according to which the inclination of the first portion 20 is smaller than the inclination of the second portion 16, and the arc length of the curved portion is considerably shorter than the first portion 20, and the first portion 20 is considerably shorter than the second portion 16. It should be mentioned that the shape of the connecting wall with two of said substantially straight portions and a curved portion therebetween may also be referred to as a "boomerang". Furthermore, it can be seen in the figures that the outer side of the connection or tank wall 18 (at the bottom in the figures) substantially coincides with the course on the inner side, the widened portion 22 being provided in the region of the connection to the skirt wall 12.