Piston for internal combustion engine

Abstract

A piston (10) for an internal combustion engine, includes shaft wall sections (18) for supporting in a cylinder or a cylinder liner, and at least one base support (20) that is connected thereto in the circumferential direction, and which has at least one contour that forms a section of a helix.

Claims

1. A piston for an internal combustion engine, comprising: a pair of shaft wall sections 18 for support in a cylinder or cylinder liner; at least one base support extending in a circumferential direction from at least one of the shaft wall sections, wherein a bottom side of the at least one base support includes a curved segment having a positive length and extending along a path of a helix in the circumferential direction, and wherein the helix has a slope (k) ranging from 1:10 to 1:1 according to the following equation: $k=\frac{h}{2?r}$ where r is radius of a cylindrical outer surface of the base support and his thread pitch.

2. The piston according to claim 1, wherein a base support is provided at least on the pressure side of the piston.

3. The piston according to claim 1, wherein a base support is provided on both sides of at least one shaft wall section.

4. The piston according to claim 1, wherein at least one base support extends as far as the region of a pin boss limit.

5. The piston according to claim 1, wherein a depth, as measured in the radial direction, of at least one base support is at least the same as a depth, as measured in the radial direction, of a lowermost annular groove.

6. The piston according to claim 5, wherein the depth of the base support is no more than twice the depth of the lower most annular groove.

7. The piston according to claim 1, wherein the at least one base support is spaced apart from a connecting wall connecting the pair of shaft wall sections.

8. The piston according to claim 1, wherein a transition between one of the pair of shaft wall sections and the at least one base support is provided with rounded section.

9. The piston according to claim 1, wherein the helix has a slope of 1:2.

10. The piston according to claim 1, wherein the slope (k) ranges from about 1:2 to 1:1.

11. The piston according to claim 1, wherein the helix is expressed as follows in Cartesian coordinates: $\stackrel{.fwdarw.}{x}\left(t\right)=\left(\begin{array}{c}r\cos \left(t\right)\\ r\sin \left(t\right)\\ \frac{h}{2?}t\end{array}\right)$ where r is radius of a cylindrical outer surface of the base support, h is thread pitch, and t is curve parameter.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following, a preferred embodiment example of the invention will be described in more detail with reference to the drawings. In the drawings:

(2) FIG. 1 shows a side view of a piston according to the invention;

(3) FIG. 2 shows a bottom view of a piston according to the invention; and

(4) FIG. 3 shows a perspective bottom view of a piston according to the invention with the helix drawn in.

DETAILED DESCRIPTION

(5) As can be seen from FIG. 1, the piston according to an embodiment comprises on its top side according to FIG. 1 a piston crown 12, an annular region 14 with a lowermost annular groove 16 and shaft wall sections 18, only one of which can be seen in its entirety in FIG. 1. The shaft wall sections 18 have a more or less constant width when 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), with a slight widening toward the bottom side, i.e. away from the piston crown 12.

(6) So-called base supports 20 connect in the circumferential direction to both sides of the pressure-side shaft wall section 18 shown, which base supports are formed so as to be mirror-symmetrical in the case shown. FIG. 1 shows the contour on the bottom side of the base support 20 as an inclined surface, but FIG. 3 reveals that this contour follows a helix.

(7) A detailed description is provided in the following in conjunction with FIG. 3. With reference to FIG. 1 it should once again be noted that the transition from the shaft wall section 18 to the respective base support 20 is configured in the form of a rounded section 22.

(8) In addition to this, FIG. 2 shows the depth T, as measured in the radial direction, of the base support 20. It also shows that each base support 20 is spaced apart from the connecting wall 24 connecting the shaft wall sections, although the connecting walls 24 diverge somewhat in the direction of the piston pin axis. As a result, the pockets 26 that are advantageous for weight-saving remain between them.

(9) FIG. 3 now shows in detail the contour of a base support 20. It should be noted that this also applies to the base support on the other side, with opposite helicity. The helicity shown in FIG. 3 can be described as positive. In other words, if the x axis is mentally flipped onto they axis, the helix moves in the direction of the z axis.

(10) It can also be seen from FIG. 3 that the base support begins in the region of the rounded section 22 towards the shaft wall section 18 (arrow B) and ends more or less in the region of the pin boss limit 28 (arrow A). In the case shown, the slope is approximately 1:2, and the depth T (cf. FIG. 2) is at approximately 6 mm roughly twice as deep as the depth of the lowermost annular groove 16.

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