Gap geometry in a cohesively joined cooling-channel piston

Abstract

The invention relates to a cooling-channel piston for an internal combustion engine, having an upper part and a lower part, wherein the upper part and the lower part are connected to one another by way of a cohesive joint in the form of a weld seam, and the upper part and the lower part form an annularly encircling cooling channel which is arranged approximately behind a ring section, wherein a gap geometry is provided between a lower edge of the ring section and an upper edge of the lower part, wherein the gap geometry has at least one sliding surface which is arranged on a lower edge of the ring section of the cooling-channel piston and/or on the corresponding upper edge of the lower part of the cooling-channel piston, and to several methods for the operation of a cooling-channel piston.

Claims

1. A cooling-channel piston for an internal combustion engine, having an upper part and a lower part, wherein the upper part and the lower part are connected to one another by way of a cohesive joint in a form of a weld seam and the upper part and the lower part form an annular circumferential cooling channel that is located behind a ring belt, wherein a gap geometry is provided between a lower edge of the ring belt and an upper edge of the lower part, wherein the gap geometry has at least one sliding surface that is arranged on a lower edge of the ring belt of the cooling-channel piston and/or on the corresponding upper edge of a lower part of the cooling-channel piston.

2. The cooling-channel piston from claim 1, wherein the lower edge of the ring belt of the cooling-channel piston and/or the corresponding upper edge of the lower part of the cooling-channel piston follows a diagonal path with respect to a piston stroke axis.

3. The cooling-channel piston from claim 1, wherein the lower edge of the ring belt of the cooling-channel piston and/or the corresponding upper edge of the lower part of the cooling-channel piston follows a curvilinear path.

4. The cooling-channel piston from claim 1, wherein a projection is provided on a side of the ring belt facing the cooling channel.

5. The cooling-channel piston from claim 4, wherein the projection follows a curvilinear path.

6. The cooling-channel piston from claim 4, wherein the projection forms a contoured guide for a cooling medium.

7. The cooling-channel piston from claim 4, wherein the lower edge of the ring belt of the cooling-channel piston and/or the corresponding upper edge of the lower part of the cooling-channel piston follows a diagonal path with respect to a piston stroke axis.

8. The cooling-channel piston from claim 4, wherein the lower edge of the ring belt of the cooling-channel piston and/or the corresponding upper edge of the lower part of the cooling-channel piston follows a curvilinear path.

9. The cooling-channel piston from claim 4, having a gap within the gap geometry that separates the upper part and the lower part, wherein a separation between the upper part and the lower part is greater at an upper end of the gap than at a lower end of the gap.

10. The cooling-channel piston from claim 1, having a gap within the gap geometry that separates the upper part and the lower part, wherein a separation between the upper part and the lower part is greater at an upper end of the gap than at a lower end of the gap.

11. The cooling-channel piston from claim 10, wherein at least one section of the gap separating the upper part and the lower part is parallel to a piston stroke axis.

12. The cooling-channel piston from claim 10, wherein the lower edge of the ring belt of the cooling-channel piston and/or the corresponding upper edge of the lower part of the cooling-channel piston follows a diagonal path with respect to a piston stroke axis.

13. The cooling-channel piston from claim 10, wherein the lower edge of the ring belt of the cooling-channel piston and/or the corresponding upper edge of the lower part of the cooling-channel piston follows a curvilinear path.

14. A method for operating the cooling-channel piston for internal combustion engines in accordance with claim 1, wherein the gap geometry has a contoured guide that guides a cooling medium around the gap geometry.

15. The method from claim 14, wherein a projection is provided on a side of the ring belt facing the cooling channel.

16. The method from claim 15, wherein the projection is configured as a contoured guide for the cooling medium, wherein a defined direction of flow for the cooling medium during upward motion of the cooling-channel piston and another defined direction of flow for the cooling medium during downward motion of the cooling-channel piston is achieved.

17. A method for operating a cooling-channel piston for internal combustion engines in accordance with claim 1, wherein in the event of contact between the upper part and the lower part of the cooling-channel piston, at least one sliding surface arranged on the upper part and/or lower part enables the upper part and the lower part to slide relative to one another.

18. The method from claim 17, wherein the upper part and the lower part slide along a curvilinear sliding surface.

19. The cooling-channel piston from claim 1, wherein the lower edge of the ring belt of the cooling-channel piston and/or the corresponding upper edge of the lower part of the cooling-channel piston follows a diagonal path with respect to a piston stroke axis; wherein the lower edge of the ring belt of the cooling-channel piston and/or the corresponding upper edge of the lower part of the cooling-channel piston follows a curvilinear path; wherein a projection is provided on a side of the ring belt facing the cooling channel; and wherein a gap within the gap geometry that separates the upper part and the lower part has an upper gap dimension that is greater than a lower gap dimension.

20. The cooling channel piston from claim 1 wherein the at least one sliding surface allows at least one of the upper part or the lower part to slide along the at least one sliding surface towards a piston stroke axis or opposite to the piston stroke axis.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a piston with a gap geometry,

(2) FIGS. 2A and 2B show a detail identified by II in FIG. 1,

(3) FIG. 3 shows a further embodiment of a piston with a gap geometry and

(4) FIG. 4 shows a detail identified by IV in FIG. 3.

(5) In the following description of the Figures, terms such as up, down, above, below, left, right, front, back refer solely to the representation chosen as an example and the position of the device in the respective Figures. These terms are not to be understood as restrictive, that is to say these references can change as the result of different positions and/or mirror-image layout or similar.

(6) Identical parts are given identical reference numerals in all the Figures.

DETAILED DESCRIPTION

(7) FIG. 1 shows a cooling-channel piston 1 and FIG. 3 shows a cooling-channel piston 100. Cooling-channel piston 1 has an upper part 2 and lower part 3. Cooling-channel piston 100 has an upper part 102 and a lower part 103. Both cooling-channel piston 1, 100 have a ring belt 4 to receive piston rings (not shown). Adjacent the ring belt 4 in the direction of a central piston stroke axis 5 there is a cooling channel to receive a cooling medium, preferably to receive oil. The piston upper part 2, 102 and the piston lower part 3, 103 are connected to each other by means of a friction-weld joint.

(8) After these two parts 2, 3; 102, 103 have been joined, they form the circumferential, annular cooling channel 6 which is located approximately behind the ring belt. Cooling pockets 8 adjoin the cooling channel 6 in the direction of a combustion bowl 7. These cooling pockets 8 are optional and may be, but do not have to be, present. These cooling pockets 8 are wetted by the cooling medium during the upward and downward motion of the cooling-channel piston 1, 100. A cooling chamber 9, connected to the cooling channel 6, is located centrally below the combustion bowl 7. Transfer passages 10 provide the connection between the cooling channel 6 and the cooling chamber 9. These transfer passages 10 may be, but do not have to be, present. It is conceivable to design the cooling channel 6 without transfer passages 10 and/or cooling pockets 8. Even the cooling chamber 9 is optional and may therefore be present, but does not have to be present. A weld seam 11 joins the upper parts 2, 102 to the lower parts 3, 103 of the cooling-channel piston 1, 100. Piston pin bores 12 are located below the cooling chamber 9 to receive piston pins (not shown).

(9) A gap geometry 13 is located below the ring belt 4 in the area where the upper part 2 and the lower part 3 of the cooling-channel piston 1 make contact. A gap geometry is provided between the upper part 102 and the lower part 103 of the cooling-channel piston 100 below the ring belt 4. A skirt and boss area 14 adjoins the gap geometries 3, 113. The gap geometries 13, 113 have at least one sliding surface 19 which is located at a lower edge 16 of the ring belt 4 of the cooling-channel piston 1, 100 and/or at the corresponding upper edge 17 of a lower part 3, 103 of the cooling-channel piston 1, 100. The lower edge 16 of the ring belt 4 of the cooling-channel piston 1, 100 and/or the corresponding upper edge 17 of a lower part 3, 103 of the cooling-channel piston 1, 100 can trace a diagonal path with respect to the piston stroke axis 5, or a curvilinear path.

(10) All geometric forms which allow the lower edge 16 of the ring belt 4 of the cooling-channel piston 1, 100 and/or the corresponding upper edge 17 of a lower part 3, 103 of the cooling-channel piston 1, 100 to slide on each other are similarly conceivable.

(11) The embodiments of the gap geometries 13, 113 in accordance with the invention are described in greater detail in what follows. FIGS. 2A and 2B show the gap geometry 13 as a detail identified in FIG. 1 by II. FIG. 4 shows the gap geometry 113 as a detail identified in FIG. 3 by IV.

(12) In order to avoid the disadvantages described at the beginning, or to achieve the corresponding benefits, a first gap geometry 13 is shown in FIGS. 1, 2A and 2B, and a further gap geometry 113 is shown in FIGS. 3 and 4. Common to these gap geometries, that are located below the ring belt 4 of the upper part 2, 102 and above the skirt and boss area 14 of the lower part 3, 103, is the fact that they form a defined gap geometry X.sub.1, X.sub.2, X.sub.3, X.sub.4 (e.g. FIGS. 2A and 4) during each operating state of the cooling-channel piston 1, 100 (e.g. during a cold start, under heavy load, and during normal operation). An upper gap dimension X.sub.1, X.sub.3 is, for example, designed to be larger in each case than a lower gap dimension X.sub.2, X.sub.4. The geometry 3, 113 of the gap area and the clearance, i.e. the gap opening, is selected such that the cooling medium is prevented from penetrating the gap area due to the upward and downward motion of the cooling-channel piston 1, 100, or the gap area is so small that either no volume of cooling medium or only the smallest possible, only just acceptable volume of cooling medium can escape.

(13) In addition, the gap geometry 13, 113 and the clearance are selected such that the areas facing each other (lower edge 16 of the ring belt 4 and/or upper edge 17 of the lower part 3, 103) can deflect if they contact each other to prevent the upper part 2, 102 from bearing unduly on the lower part 3, 103. This circumstance is shown in FIG. 2B. There the lower edge 16 of the ring belt 4 is coming to bear on the upper edge 17 of the lower part 3. Consequently, the gap dimension X.sub.1 no longer exists and is therefore not drawn in. The gap dimension X.sub.2 shrinks from the dimension shown in FIG. 2A to the dimension shown in FIG. 2B. Y indicates the direction of motion of the lower edge 16 of the ring belt 4 and the direction of motion of the upper edge 17 of the lower part 3 under an unduly high load. In order to obviate resulting damage to the cooling-channel piston 1 and a subsequent failure of the internal combustion engine, the lower edge 16 of the ring belt 4 is of a curvilinear shape. As a result of this curvilinear shape, the lower edge of the ring belt 4 slides off on the upper edge 17 of the lower part 3. This controlled deformation in the area of the ring belt 4 prevents failure of the internal combustion engine in which a correspondingly shaped cooling-channel piston 1 is used. Normal operating conditions for an internal combustion engine, however, do not result in the aforementioned deformation in the area of the lower edge 16 of the ring belt 4 of a cooling-channel piston 1. This safety precaution, however, guarantees that even abnormal operating conditions of an internal combustion engine with a cooling-channel piston 1 do not lead to a failure of this internal combustion engine.

(14) The projection 18 formed in the area of the lower edge 16 of the ring belt 4 of the gap geometry 113 shown in FIG. 4 also follows a curvilinear path. Under an appropriate load, which, however, is not foreseen in normal operation of an internal combustion engine with a cooling-channel piston 100, the projection 18 slides off on the chamfered area of the upper edge 17 of the lower part 103. This also effectively prevents a failure of the internal combustion engine that is operated with a cooling-channel piston 100. The upper part 102 is precluded from bearing unduly on the lower part 103.

(15) Finally, the geometry 3, 113 in FIGS. 2A and 4 is selected for normal operating conditions such that upper part 2, 102 and lower part 3, 103 are stopped from being able to bear on each other in the area of the gap geometry 13, 113. FIGS. 2A and 4 thus show the gap geometries 13, 113 in their normal state.

(16) At the same time, the gap geometry 13, 113 is selected such that under the prevailing operating conditions of the cooling-channel piston a gap 15, even if only a minimal gap, is maintained, but at the same time the cooling medium is prevented from being able to penetrate into the gap area and on towards the piston skirt. This is achieved by a specific geometry and, as a result, precise regulation of the cooling medium during the upward and downward motion of the cooling-channel piston 100 in the internal combustion engine.

(17) Z represents the direction of motion of the cooling medium during the upward and downward motion of the cooling-channel piston 100. The cooling medium flow is steered by a projection 18 that is located at the ring belt on the cooling channel side in such a way that it cannot pass through the gap 15, or the gap geometry 113. Z.sub.1 identifies the direction in which the cooling medium flows during the upward motion of the cooling-channel piston 100. Z.sub.2 identifies the direction in which the cooling medium flows during the downward motion of the cooling-channel piston 100. The projection 18 thus forms a contoured guide at the gap geometry 113 for the cooling medium during operation of the internal combustion engine.

(18) A list of reference numbers used in the figures follows: 1 Cooling-channel piston 100 Cooling-channel piston 2 Upper part 102 Upper part 3 Lower part 103 Lower part 4 Ring belt 5 Piston stroke axis 6 Cooling channel 7 Combustion bowl 8 Cooling pocket 9 Cooling space 10 Transfer passage 11 Weld seam 12 Piston pin bore 13 Gap geometry 113 Gap geometry 14 Skirt and boss area 15 Gap 16 Lower edge 17 Upper edge 18 Projection 19 Sliding surface X.sub.1 Upper gap dimension X.sub.2 Lower gap dimension X.sub.3 Upper gap dimension X.sub.4 Lower gap dimension Y Direction of motion Z.sub.1 Direction of flow of cooling medium during upward motion of the cooling-channel piston Z.sub.2 Direction of flow of cooling medium during downward motion of the cooling-channel piston