COOLING CHANNEL WITH DAM AND FUNNEL

Description

[0001] The invention relates to a piston, consisting of an upper part and a lower part, which are joined together, with a cooling channel, preferably an annular cooling channel, wherein at least one inlet opening is provided for the supply of cooling oil and at least one outlet opening is provided for the discharge of the cooling oil, according to the features of the preamble of patent claim 1.

[0002] The aforementioned inlet or outlet opening extends from an inner area of ​​the piston toward the cooling channel and penetrates the lower wall, particularly the lower apex of the cooling channel. Consequently, the opening is located at the lowest point of the cooling channel, so that cooling oil always flows out of the cooling channel, at least when the piston is stationary, and cannot be stored there.

[0003] DE 10 2011 007 285 A1 discloses a piston for an internal combustion engine comprising a piston upper part and a piston lower part, which has an internal, preferably annular cooling channel for cooling the piston during operation of the internal combustion engine. At least one inlet opening and at least one outlet opening are provided on the piston lower part, through which coolant flows into and out of the cooling channel. Each opening is surrounded by an annular bead or a ramp-like elevation that prevents the coolant level from falling below a predefined level. The annular bead or the ramp-like elevation is formed integrally with the piston lower part.

[0004] As an alternative to forming the annular bead around the opening, DE 10 2015 206 375 A1 discloses that, after the inlet or outlet opening has been created, a tube is inserted into this opening to maintain a certain coolant level in the cooling channel. The outlet opening of the tube, which faces the cooling channel, is positioned above the lowest point of the cooling channel. This also establishes a certain coolant level in the cooling channel. This solution requires an additional part and an additional assembly step, making it unsuitable for practical use.

[0005] JP 2003 307153 A describes a piston for an internal combustion engine which is capable of effectively increasing the efficiency of piston cooling by improving the flow of a cooling oil having turbulence in a cooling channel.

[0006] DE 10 2012 216 367 A1 shows a method for producing a piston for an internal combustion engine having at least one cooling channel, which piston is produced from at least one upper part and a lower part, wherein the cooling channel of the piston is formed by means of the upper part and the lower part and the upper part and the lower part of the piston are each produced by means of a forging process.

[0007] FR 2 839 116 A1 describes a piston of an internal combustion engine having an annular cooling channel which runs coaxially to the piston axis and is provided on its lower wall with an inlet opening through which lubricating oil penetrates and an outlet opening through which the lubricating oil exits.

[0008] The invention is based on the object of providing a piston with a cooling channel which is improved in terms of its cooling effect compared to the known pistons with cooling channels.

[0009] This problem is solved by the features of patent claim 1.

[0010] According to the invention, both a dam-shaped elevation in the area of ​​the inlet and / or outlet opening is formed by a finished forged contour of the lower cooling channel area, and the inlet contour of the inlet and / or outlet opening on the inside of the piston is formed by pre-forging. This allows contours that enable a minimum level to be maintained in the cooling channel (particularly when the piston is stationary) to be created directly during the production of the lower part of the piston, which is manufactured independently of the upper part of the piston, in a forging process. Manufacturing by forging has the advantage of a high-strength structure and stress-adapted flow lines, so that a high-strength lower part is formed that already has the necessary contours to fulfill its function.

[0011] In a further development of the invention, the pre-forging is funnel-shaped at the inlet opening, whereas it is additionally or alternatively cylindrical on the outlet side (i.e. in the area of ​​the outlet opening).

[0012] In a further development of the invention, a dam is created (formed) as a dam-shaped elevation during the forging process during the production of the lower part. This dam extends across the width of the cooling channel (i.e., extends radially outward from the direction of the piston center, through which the piston stroke axis runs), so that bypassing the dam-shaped elevation (dam) in the cooling channel is largely prevented, whereas bypassing is possible in the piston according to DE 10 2011 007 285 A1. In a further development of the invention, the elevation should reach a height of 20% to 80%, preferably 30% to 70%, of the total height of the cooling channel.

[0013] According to the invention, the dam (the dam-shaped elevation) produced transversely to the cooling channel has at least one recess, preferably a plurality of recesses, at the transition between the dam and the wall of the cooling channel.

[0014] Furthermore, the invention provides that the cooling channel in the piston crown of the piston, which consists of the upper and lower sections, is also optionally manufactured by forging. A V-shaped element is forged in the area of ​​the inlet opening, which extends into the cooling channel. This element ensures that the impinging oil jet is deflected in equal or different proportions in both directions of the cooling channel. This V-shaped element thus serves as a jet splitter for the impinging oil jet injected through the inlet opening.

[0015] The measures according to the invention achieve an improved cooling effect for the thermally stressed areas of the piston through the measures on the cooling channel. The dam-shaped elevation ensures a predeterminable coolant level remains in the cooling channel while simultaneously preventing backflow of the incoming oil jet. Furthermore, the funnel-shaped design of the inlet opening increases the capture rate of the oil effectively entering the cooling channel.

[0016] In addition, the funnel-shaped inlet opening serves to capture the oil volume flows of at least two parallel or mutually inclined oil jets (emitted by one or more spray nozzles) over large areas of the piston stroke and to direct the oil into the cooling channel. The funnel-shaped forging can take on any surface shape. The oil supplied by the oil spray nozzle can exit from one or more nozzle openings, although not all nozzle openings need to be open simultaneously.

[0017] Because both contours (dam and funnel) are created directly through the forging process, the piston is manufactured much more effectively and there is no need to insert a separate catching element.

[0018] Finally, the design of the opposing contours of the dam and funnel makes it possible to achieve a wall thickness that is as uniform as possible, which has a positive effect on the manufacturing process and the weight of the piston. The effectiveness of piston manufacturing can be further increased by also producing the top side of the cooling channel through a forging process in the piston top, thus largely or completely eliminating the need for machining or post-machining.

[0019] Overall, the invention offers improved cooling efficiency through contours integrally formed on the piston without the need for additional elements. This results in more efficient piston manufacturing and simplifies processes. Furthermore, such a piston can be subjected to higher thermal loads while simultaneously reducing cooling oil requirements.

[0020] An embodiment of a piston according to the invention is shown in various views in the figures and described in more detail below.

[0021] In Figure 1 A piston 1 is shown in section, consisting of a lower part 2 and an upper part 3. The two parts 2, 3 are manufactured separately and joined together in a suitable manner.

[0022] The piston 1 has, in a manner known per se, an outer circumferential ring field 4 and may, but need not, contain a combustion chamber bowl.

[0023] The lower part 3 forms a piston skirt 5 and a pin bore 6.

[0024] Further elements of a functional piston 1 are present, but are not described in detail or provided with reference numbers.

[0025] The two parts 2, 3 are permanently and permanently joined together by means of a suitable joining process, thus forming a one-piece, functionally ready piston 1. The joining process takes place in at least one joining plane 7. In the exemplary embodiment, the joining process is a friction welding process.

[0026] Furthermore, the piston 1 has a cooling channel 8. In this exemplary embodiment, the cooling channel 8 is formed by partial recesses in both the upper part 2 and the lower part 3. This has the advantage that their partial recesses are accessible before the two parts 2, 3 are joined together, and therefore these partial recesses can be optimally manufactured or reworked, since they are no longer accessible after the two parts 2, 3 are joined together.

[0027] Also in a manner known per se, the piston 1 has at least one inlet opening 9, into which a free oil jet, emitted by an injection nozzle, is injected toward the cooling channel 8. This inlet opening 9, if it is the only opening, can also serve as an outlet opening for the cooling oil circulating in the cooling channel 8. Alternatively, in addition to the at least one or exactly one inlet opening 9, at least one further outlet opening, in particular exactly one outlet opening, is also present (this will be described later).

[0028] According to the invention, a dam-shaped elevation 10 is provided next to the drain opening 9, starting from the lower bottom of the cooling channel 8.

[0029] This dam-shaped elevation 10 is formed during the production of the lower part 3. The lower part 3 can thus be produced, for example, in a casting process, and the dam-shaped elevation can be formed in the process. Alternatively, the lower part 3 can be produced in a casting process, and the dam-shaped elevation 10 can then be formed by a forming process (such as a forging process). Particularly preferably, both the lower part 3 with its geometries and the dam-shaped elevation 10 are produced in a forming process (such as a forging process).

[0030] During the production of the lower part 3, this lower part is given an internal geometry 11 with a particularly funnel-shaped inlet contour 12 of the inlet opening 9. The inlet contour 12 can also have a shape other than a funnel. It is important to form the inlet contour 12, preferably using a forging process, and to give it a shape that directs the oil jet injected into the inlet opening 9 in a targeted manner toward the cooling channel 8. It is also important that the dam-shaped elevation 10 next to the inlet opening 9 does not impede the entry of the injected oil jet, so that the injected oil is guided circumferentially into the cooling channel 8.

[0031] Figure 2shows a plan view of the upper side of the lower part 3, pointing in the direction of the upper part 2. Here, it can be seen that, in addition to an inlet opening 9, there is also an outlet opening 13. In this exemplary embodiment, there is exactly one inlet opening 9 and exactly one inlet opening 13, from which a circumferential cooling channel 8 extends. However, it is also conceivable that the cooling channel 8 is not completely circumferential, but is divided into, for example, at least two sub-segments. In this case, for example, each sub-segment has its own inlet opening and its own outlet opening.

[0032] As shown in Figure 2can be removed, a dam-shaped elevation 10 is provided on the lower part 3 on each side in the direction of the cooling channel 8 next to the inlet opening 9 and the outlet opening 13 and is formed integrally therefrom. However, it is also conceivable to provide only a dam-shaped elevation 10 at one of the openings 9, 13 or even no dam-shaped elevation 10 at all, particularly in the area of ​​the outlet opening 13.

[0033] Furthermore, the Figure 2It can be seen that the lower part 3 has an outer circumferential joining surface 14 and an inner circumferential joining surface 15, which are formed by corresponding webs of the lower part 3. These joining surfaces 14, 15 face corresponding joining surfaces of the upper part 2, which also forms webs, at the end of which the joining surfaces are formed. By means of these mutually facing and corresponding joining surfaces, the two parts 2, 3 are permanently and permanently joined together, preferably by means of a friction welding process. Other geometric configurations of the two parts 2, 3 and other joining processes that ensure a permanent and permanent connection of the two parts 2, 3 to one another are also conceivable.

[0034] Figure 3shows a sectional three-dimensional view of the piston 1, in which the two parts 2, 3 have been permanently and permanently joined together. Furthermore, the position of both the inlet opening 9 with at least one associated dam-shaped elevation 10 and the position of the outlet opening 13 (in this case also with an associated dam-shaped elevation 10) are visible.

[0035] Figure 4 shows analogous to the representation in Figure 2 in a three-dimensional view the top view of the upper part 3, where, as in Figure 2 recognizable, a portion of the cooling channel 8 is formed by the upper part 3.

[0036] Figure 5shows a three-dimensional view of the underside of the upper part 2, which points in the direction of the lower part 3. In addition to the corresponding joining surfaces 14, 15, it can be seen that in the partial area of ​​the cooling channel 8 of the upper part 2, a dam-shaped elevation 10 (in the area of ​​the inlet opening 9) is also formed by the upper part 2. In this case, the at least one dam-shaped elevation 10 is not arranged next to the opening, but is located in the extension of the cross-section of the opening (inlet opening 9 and / or outlet opening 13), so that this dam-shaped elevation 10 serves as a jet splitter in the partial area of ​​the cooling channel 8 of the upper part 2. By means of this jet splitter, the oil jet injected in particular through the at least one inlet opening 9 is split and can be divided into equal or different parts in both directions of the cooling channel 8.

[0037] In Figure 5It is also shown that the dam-shaped elevation 10 created transversely to the cooling channel 8 has at least one recess 16, preferably several recesses, at the transition between the elevation 10 and the wall of the cooling channel 8, particularly in the apex region of the cooling channel 8. This makes it possible for a portion of the cooling oil circulating in the cooling channel 8 to always circulate there without being obstructed by the dam-shaped elevation 10.

[0038] Figure 6Finally, the internal geometry 11 of the piston 1 is shown, in which the previously described parts 2, 3 have been joined together. In this case, it can be seen that in the area of ​​the outlet opening 9 on the upper part 2, a dam-shaped elevation 10 serving as a jet splitter is provided, pointing downwards in the area of ​​the cross-section of the outlet opening 9 as viewed from the side. Not visible, but present in the partial area of ​​the lower part 3, next to the inlet opening 9 (and possibly also next to the outlet opening 13), there is at least one dam-shaped elevation 10.

[0039] The orientation of the dam-shaped elevation 10 shown in either the lower part 3 and / or the upper part 2 is exemplary and preferably extends radially from the piston stroke axis. Other radial orientations deviating from this are of course also conceivable. List of reference symbols:

[0040] 1.Piston 2.Upper part 3.Lower part 4.Ring field 5.Piston skirt 6.Pin bore 7.Joining plane 8.Cooling channel 9.Inlet opening 10.Dam-shaped elevation 11.Internal geometry (inside) 12.Inlet contour 13.Outlet opening 14.Outer joining surface 15.Inner joining surface 16.Recess

Claims

1. Piston (1) of an internal combustion engine, consisting of an upper part (2) and a lower part (3) which are joined together, wherein a cooling channel (8) is provided which comprises at least one inlet opening (9) and / or at least one outlet opening (13) for a coolant, wherein both a dam-shaped elevation (10) in the region of the inlet opening (9) and / or the outlet opening (13) is formed by a finished forged contour of a lower cooling channel region and an inlet contour (12) of the inlet opening (9) and / or the outlet opening (13) is formed on an inner side (11) of the piston (1) by pre-forging, wherein a V-shaped element, which projects into the cooling channel (8), is forged onto an upper cooling channel region in the region of the inlet opening (9) as a further dam-shaped elevation (10), and wherein the dam-shaped elevation (10) produced transversely to the cooling channel (8) in the form of the V-shaped element comprises at least one recess (16) at a transition between the dam-shaped elevation (10) in the form of the V-shaped element and a wall of the cooling channel (8).

2. Piston (1) according to claim 1, characterized in that the pre-forging at the inlet opening (9) is funnel-shaped.

3. Piston (1) according to claim 1 or 2, characterized in that the pre-forging is cylindrical at the outlet opening (13).

4. Piston (1) according to claim 1, 2 or 3, characterized in that after the production of the lower part (3) during forging, a dam is formed as a dam-shaped elevation (10) which extends over the width of the cooling channel (8).

5. Piston (1) according to claim 4, characterized in that the dam-shaped elevation (10) reaches a height of 20% to 80%, preferably 30% to 70%, of the total height of the cooling channel (8).