Piston

Abstract

A piston for an internal combustion engine may include two pin bosses configured to receive a gudgeon pin. The two pin bosses may respectively include a nadir pocket of at least two nadir pockets at =180 and extending outward from a piston axis. The at least two nadir pockets may have a respective length that is smaller than a length of a respective pin boss of the at least two pin bosses. The piston may also include a pin boss axis that is axially offset from the piston axis by 0.1-1.0 mm.

Claims

1. A piston for an internal combustion engine, comprising two pin bosses configured to receive a gudgeon pin, the two pin bosses respectively including a nadir pocket of at least two nadir pockets at =180, the at least two nadir pockets each extending outward from a piston axis and having a respective length along a pin boss axis that is smaller than a length of a respective pin boss of the at least two pin bosses, wherein: the pin boss axis is axially offset from the piston axis by 0.1-1.0 mm; a depth of the at least two nadir pockets decreases along the respective length of the at least two nadir pockets from the piston axis toward a respective boss outer side of the two pin bosses; the depth of the at least two nadir pockets is from 0.1 to 1.0 mm; and the at least two nadir pockets extend over a circumferential angle of 30 to 130.

2. The piston as claimed in claim 1, wherein the respective length of the at least two nadir pockets is 10-75% of the length of the respective pin boss.

3. The piston as claimed in claim 1, wherein the depth of the at least two nadir pockets decreases from a respective inner side of the at least two nadir pockets proximal to the piston axis to a respective outer side of the at least two nadir pockets remote from the piston axis.

4. The piston as claimed in claim 1, wherein the two pin bosses are configured as one of symmetrically shaped pin bores and asymmetrically shaped pin bores.

5. The piston as claimed in claim 1, wherein the two pin bosses have at least one of a superimposed transverse ovality and a vertical ovality.

6. The piston as claimed in claim 1, wherein the two pin bosses include oil pockets.

7. The piston as claimed in claim 1, wherein the two pin bosses respectively include a circumferential lubricating groove.

8. The piston as claimed in claim 6, wherein the oil pockets are at least one of i) slots, ii) straight oil pockets, and iii) oblique oil pockets.

9. A piston for an internal combustion engine, comprising two pin bosses configured to receive a gudgeon pin; the two pin bosses respectively including a nadir pocket of at least two nadir pockets at =180; the at least two nadir pockets each extending outward from a central piston axis and having a respective length that is smaller than a length of a respective pin boss of the at least two pin bosses; the at least two nadir pockets having a depth from 0.1 to 1.0 mm, the depth of the at least two nadir pockets continuously decreasing along a pin boss axis in a direction extending away from the central piston axis; wherein the pin boss axis is axially offset from the central piston axis by 0.1 to 1.0 mm; and wherein, in a cross section perpendicular to the pin boss axis, the two pin bosses respectively define a circular shape along the entire respective length at a zenith disposed proximal to a piston crown relative to the at least two nadir pockets.

10. A piston for an internal combustion engine, comprising two pin bosses configured to receive a gudgeon pin; the two pin bosses having at least one of a superimposed transverse ovality and a superimposed vertical ovality and respectively having a circumferential boss face in which a nadir pocket of at least two nadir pockets is disposed at =180; the at least two nadir pockets each extending outward from a piston axis and over a circumferential angle of 30 to 130; the at least two nadir pockets each having a respective length along a pin boss axis that is smaller than a length of a respective pin boss of the at least two pin bosses; the at least two nadir pockets respectively having a depth of 0.1 to 1.0 mm from the circumferential boss face, the depth of the at least two nadir pockets continuously decreasing along the respective length in a direction extending away from the piston axis; and wherein the pin boss axis is axially offset from the piston axis by 0.1 to 1.0 mm and defines an axis of the circumferential angle.

11. The piston as claimed in claim 10, wherein the nadir pocket extends across 10% to 75% of the length of the respective pin boss from a proximal edge to a distal edge.

12. The piston as claimed in claim 7, wherein the circumferential lubricating groove is disposed spaced apart from the nadir pocket in a circumferential direction of the respective pin boss.

13. The piston as claimed in claim 1, wherein the =180 is disposed at a nadir of the two pin bosses, and wherein the nadir is disposed opposite to a zenith of the two pin bosses that is arranged proximal to a piston crown with respect to the nadir.

14. The piston as claimed in claim 13, wherein the two pin bosses have a superimposed transverse ovality where the two pin bosses each have a circular cross-sectional shape at the zenith along the entire respective length and an oval shape at an equator of the two pin bosses, the equator disposed at 90 and 270 with respect to the zenith.

15. The piston as claimed in claim 1, wherein the two pin bosses respectively have a circumferential boss face in which the nadir pocket is disposed, and wherein a transition between the boss face and the nadir pocket is defined by a parabolic edge.

16. The piston as claimed in claim 3, wherein the depth of the at least two nadir pockets is from 0.1 to 1.0 mm at a respective nadir and the depth decreases along each circumferential direction of the respective pin boss from the respective nadir.

17. The piston as claimed in claim 15, wherein the parabolic edge defines an obtuse angle.

18. The piston as claimed in claim 1, wherein the pin boss axis defines an axis of the circumferential angle.

19. The piston as claimed in claim 9, wherein the at least two nadir pockets are defined by a depression disposed in a circumferential boss face of each of the two pin bosses, and wherein a transition between the boss face and the nadir pocket is defined by a parabolic edge.

20. The piston as claimed in claim 10, wherein: the at least two nadir pockets are defined by a depression disposed in the circumferential boss face of each of the two pin bosses; the at least one of a superimposed transverse ovality and a superimposed vertical ovality includes the superimposed transverse ovality; the circumferential boss face of each of the two pin bosses has the superimposed transverse ovality such that the two pin bosses each have an oval cross-sectional shape at an equator of the two pin bosses and a circular cross-sectional shape at a zenith, the oval cross-sectional shape and the circular cross-sectional shape extending along the entire respective length of the two pin bosses; and the zenith is arranged proximal to a piston crown with respect to the two nadir pockets, and the equator is disposed at 90 and 270 with respect to the zenith.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Preferred exemplary embodiments of the invention are shown in the drawings and will be described in greater detail in the following description, identical designations relating to identical or similar or functionally identical components.

(2) In the drawings, in each case diagrammatically:

(3) FIG. 1 shows a sectioned view of a piston according to the invention,

(4) FIG. 2 shows a detailed illustration from FIG. 1 in the region of a nadir pocket,

(5) FIG. 3 shows a further sectional illustration through the piston according to the invention in the region of a pin boss, with a plan view of the nadir pocket according to the invention,

(6) FIG. 4 shows a further sectional illustration through the piston according to the invention,

(7) FIG. 5 likewise shows a sectional illustration through the piston according to the invention.

DETAILED DESCRIPTION

(8) In accordance with FIGS. 1-5, a piston 1 according to the invention for an internal combustion engine (otherwise not shown) has two pin bosses 2, of which merely one is shown in FIGS. 1-3 and 5, a gudgeon pin for fastening a connecting rod to the piston 1 being received in the pin bosses 2 in the case of an assembled internal combustion engine. According to the invention, the pin bosses 2 then have a nadir pocket 3 in each case at =180 (nadir), which nadir pocket 3 extends to the outside 9 from a piston axis 4 (cf. FIGS. 4 and 5) and runs merely over a part, namely over a length L1, of the entire axial length L of the pin boss 2 at the nadir.

(9) If, for example, FIGS. 1-4 are considered, it can be seen that the nadir pockets 3 extend over a length L1 of approximately 60% of the length L of the pin boss 3. Here, a depth T of the nadir pockets 3 is between 0 and 1.0 mm, the depth T being measured at the nadir, that is to say at =180. The depth T decreases toward a surrounding boss face 5, and likewise toward the outside 9 from the piston axis 4. Here, a transition between the nadir pocket 3 and the boss face 5 which surrounds it is described by a parabolic edge 6 (cf. FIGS. 1-4). The lower the depth T of the nadir pocket 3 at the nadir itself, the more obtuse is the transition angle at the edge 6.

(10) If FIG. 5 is considered, it can be seen that a pin boss axis 7 differs in the horizontal direction from the piston axis 4, to be precise preferably by between 0.1 and 1 mm. This affords the great advantage that the contact behavior of the piston in the cylinder is defined clearly, as a result of which the acoustics can be influenced positively. An offset of the pin boss axis 7 with respect to the piston axis 4 (axial offset) brings about a modified contact behavior of the piston 1 during the changeover, and influences the lateral forces and impact impulses decisively. The position and magnitude of the offset with respect to the piston axis 4 can be optimized by way of a calculation of the piston movement, and the piston running noise and the risk of cavitation on the cylinder liner can thus be reduced considerably.

(11) In a further advantageous embodiment of the solution according to the invention, the nadir pockets 3 extend over a circumferential angle (cf. FIG. 5) of between 30 and 130. The force introduction point of a pin into the boss face 5 can be influenced indirectly by way of the magnitude of the circumferential angle W, since, for example, the greater the circumferential angle W and the deeper the depth T of the nadir pocket 3, the further a force introduction point is moved in the direction of a snap ring. In the case of floating pin mounting, the gudgeon pin is held in the pin boss merely axially by way of snap rings, whereas, in the case of a shrink fit, the gudgeon pin is shrink-fitted on the connecting rod, that is to say fixedly, and can move only in the pin boss. In the case of a shrink fit, no snap rings are accordingly required.

(12) In a further advantageous embodiment of the solution according to the invention, the pin bosses 2 are of symmetrical or asymmetrical configuration and have, for example, a superimposed transverse ovality and/or a superimposed vertical ovality. In the case of the vertical ovality, the introduction of force takes place on the left and on the right outside the zenith, which results in a stress reduction on the crown.

(13) The pin bosses 2 expediently have oil pockets, in particular narrow straight oil pockets (slots), large straight oil pockets or oblique large oil pockets (side reliefs). An oil retaining volume can be provided by way of oil pockets of this type, as a result of which the lubrication between the pin boss 2 and the gudgeon pin can be improved and therefore the service life of the piston 1 can be increased. For improved lubrication, a circumferential lubricating groove 8 (cf. FIG. 4) can additionally be provided in the pin boss 2.

(14) By way of the piston 1 according to the invention and, in particular, the nadir pockets 3 which are provided according to the invention in the nadir region, a force introduction point can be shifted, in particular, at the top dead center (TDC) of the piston 1, at which a high inertia force acts on the pin boss 2, and a harmonization of the stresses can be achieved as a result, which harmonization leads to a considerable stress reduction. A considerable stress reduction of this type in turn brings about a considerable increase in the service life of the piston 1 according to the invention.

(15) The nadir pocket 3 according to the invention is usually provided only on the inner side, that is to say toward the piston interior; it goes without saying that it is also possible to also provide it on the outside, in particular also as an outer shaped bore.

(16) In general, the following further advantages can be achieved by way of the nadir pockets 3 according to the invention:

(17) an improved oil supply,

(18) an optimization of the friction performance as a result of a small contact area, and improved oil supply,

(19) a reduction in costs and a lower weight, since the wall thicknesses can be of thinner configuration as a result of the improved introduction of force.