Piston for a combustion engine

Abstract

The invention relates to a piston (10) for an internal combustion engine. The piston (10) has an internal piston cooling channel (20) for cooling the piston (10). The piston (10) has an inlet channel (16) that opens into an inlet (28) of the piston cooling channel (20), wherein a flow cross-section of the inlet channel (16) tapers at least partially, in particular in a funnel shape, in one direction towards the inlet (28) of the internal piston cooling channel (20), and the inlet channel (16) is additionally designed to convey a flow of cooling fluid to the inlet (28) of the internal piston cooling channel (20). The invention makes it possible to ensure sufficient cooling of the piston (10) even at high piston speeds.

Description

[0001] The invention relates to a piston for an internal combustion engine.

[0002] To cool a piston in an internal combustion engine, the piston can have an internal piston cooling channel. This cooling channel may have an inlet on the underside of the piston. Cooling fluid, for example, oil, injected by a cooling fluid injector in the direction of the inlet, can enter the cooling channel through this inlet. The cooling fluid can then exit the cooling channel through an outlet on the underside of the piston.

[0003] From DE 197 36 135 C1, a liquid-cooled piston for internal combustion engines is known, which has a cooling channel that is at least partially ring-segment shaped. The cooling channel is formed in a piston crown below the piston crown. The cooling channel has openings for the inlet and outlet of the coolant. The openings are formed with a collecting funnel.

[0004] From EP 2 348 207 A2, a piston is also known in which an inlet channel for a piston cooling channel is arranged completely in a piston skirt. The inlet channel has a funnel-shaped inlet area.

[0005] For further information on the state of the art regarding cooling fluid injected by a cooling fluid injection nozzle in one direction towards an intake port of a piston, reference is made to KR 2014 0023602 A, EP 1 925 805 A1, JP 2007 315244 A, DE 20 2006 020280 U1, DE 10 2011 106379 A1, DE 10 2017 113014 A1, KR 2015 0099102 A, DE 10 2012 211060 A, WO 2016 / 171004 A1 and CN 203 835 518 U.

[0006] Especially at high piston speeds, the capture efficiency of the cooling fluid channel inlet can decrease significantly. This means that the relative proportion of cooling fluid entering the piston's inner cooling fluid channel is reduced.

[0007] The invention is based on the objective of improving the supply of cooling fluid to a piston cooling channel. In particular, sufficient cooling fluid should be supplied to the piston cooling channel of the piston even at high piston speeds.

[0008] The problem is solved by the features according to the independent claim. Advantageous further developments are specified in the dependent claims and the description.

[0009] The piston is suitable for an internal combustion engine (e.g., a reciprocating internal combustion engine). The piston has an internal piston cooling channel for cooling the piston. The piston has an inlet channel that opens into the piston cooling channel. The flow cross-section of the inlet channel narrows in one direction towards the inlet of the internal piston cooling channel, at least partially, in a funnel shape. The inlet channel is also designed to convey (e.g., improve, increase) a flow of cooling fluid (e.g., reduce cooling fluid friction losses) to the inlet of the internal piston cooling channel.

[0010] In particular, the cooling fluid can be oil.

[0011] For example, in addition to the at least partial narrowing, the inlet channel may have means (e.g. surface treatment, coating and / or flow control element(s)) to promote a cooling fluid flow to the piston cooling channel.

[0012] This ensures sufficient piston cooling, even at high piston speeds. The tapered intake port directs a greater quantity of injected coolant to the inlet of the piston cooling channel. This increases the flow of coolant into the cooling channel, allowing it to dissipate heat more effectively and thus reduce piston temperature. Furthermore, the specific design of the intake port, for example by reducing coolant friction losses, can promote coolant flow through the intake port into the inlet of the cooling channel.

[0013] In particular, the intake port can be located below the underside of the piston. For example, the intake port can be located directly below an inlet of the piston cooling channel.

[0014] It is possible that the piston cooling channel inlet opens on the underside of the piston.

[0015] For example, the cooling fluid channel can be annular and / or have multiple sub-channels. It is possible that the cooling fluid channel is located below a piston crown in a piston crown.

[0016] The piston cooling channel can advantageously have an outlet. For example, the outlet can be positioned opposite the inlet of the cooling fluid channel with respect to the central axis of the piston.

[0017] In a particularly preferred embodiment, the inlet channel is surface-treated, at least in sections, to promote the flow of cooling fluid, particularly to reduce surface roughness. Preferably, the inlet channel can be polished. This reduces cooling fluid friction losses in the inlet channel and thus increases the cooling fluid flow rate.

[0018] In particular, a circumferential surface of the inlet channel can be surface-treated, at least in sections, especially to reduce surface roughness. For example, the circumferential surface can be polished, at least in sections.

[0019] In a further particularly preferred embodiment, the inlet channel for conveying the flow of cooling fluid is coated with a coating that reduces flow resistance and / or surface roughness. In particular, the coating can be applied by thermal spraying. This also reduces cooling fluid friction losses in the inlet channel and thus increases the cooling fluid flow into the cooling fluid channel.

[0020] In particular, a circumferential surface of the inlet channel can be coated, at least in sections.

[0021] According to the invention, the inlet channel for conveying the coolant flow has at least one flow guide element for directing the coolant in one direction towards the inlet of the inner piston cooling channel. This guide allows the coolant to be directed precisely to the inlet of the inner piston cooling channel. The coolant can flow more quickly into the cooling channel, thus increasing the coolant flow rate into the cooling channel.

[0022] In a further development, the at least one flow-guiding element is designed as a groove in a circumferential surface of the inlet channel. Alternatively or additionally, the at least one flow-guiding element is designed as a projection, in particular as a guide fin, on a circumferential surface of the inlet channel.

[0023] The groove and / or projection can be advantageously rounded (e.g., with a radius between 0.1 mm and 5 mm) or angular (e.g., rectangular, trapezoidal, etc.). For example, the groove and / or projection can have a width between 0.1 mm and 5 mm. In particular, a side face of an angular groove and / or projection can form an angle in a range between 0° and 90° with a normal to the circumferential surface.

[0024] Advantageously, at least one flow guiding element can have a height or depth in a range between 0.1 mm and 5 mm.

[0025] In one embodiment, the at least one flow-guiding element extends in one direction towards the inlet of the inner piston cooling channel. It is also possible for the at least one flow-guiding element to extend at least partially in a straight line and / or at least partially in a helical shape. Thus, the cooling fluid can be supplied to the inlet of the inner cooling fluid channel in a straight line or a helical shape.

[0026] In a further embodiment, the at least one flow guidance element has a plurality of flow guidance elements arranged, in particular symmetrically, around a circumference of the inlet channel.

[0027] In particular, at least one flow guidance element can be pressed, cut or incorporated into a circumferential surface of the inlet channel.

[0028] In one embodiment, the inlet channel is at least partially formed by a funnel-shaped catch that is connected to the underside of the piston.

[0029] In a further development, the funnel is integrally formed in one piece with the underside of the piston or formed separately and connected to the underside, in particular detachably.

[0030] In another design variant, the collection funnel and the underside of the piston are made of the same material or of different materials. This allows, for example, the use of cost-effective materials and / or easily formable or machinable materials for the collection funnel.

[0031] For example, the collection funnel may have a height greater than 0 mm and / or less than 60 mm, particularly in a range between 5 mm and 40 mm.

[0032] In one embodiment, the collecting funnel is at least partially formed by a piston shaft. For example, the piston shaft can form a wall segment of the collecting funnel, which is connected to another wall segment of the collecting funnel formed separately from the piston shaft.

[0033] In a further embodiment, the inlet channel tapers at least section by section at an angle greater than 0° and / or less than 45°, in particular between 5° and 30°, to a longitudinal axis of the inlet channel. Alternatively or additionally, the inlet channel opens into the inlet of the piston cooling channel in a rounded manner, in particular with a radius greater than 0 mm and / or less than 30 mm, preferably between 5 mm and 20 mm.

[0034] The invention also relates to a cooling fluid injection device designed to inject the cooling fluid with a swirl (e.g., helical flow and / or rotation around an axis of the cooling fluid jet). The swirl can stabilize the cooling fluid jet injected in one direction towards the underside of a piston. The cooling fluid jet thus stabilized is less affected by splashing and churning fluid in the crankcase. This allows the quantity of cooling fluid supplied to a cooling fluid channel of the piston to be increased.

[0035] According to the invention, the cooling fluid injection device is comprised of a device having a piston as disclosed herein. The cooling fluid injection device can be directed towards an inlet opening of the inlet channel.

[0036] In particular, the coolant injection device can be mounted, especially rigidly, on the crankcase of the internal combustion engine. It is possible that the coolant injection device is fluidically connected to a coolant pump that supplies coolant to the coolant injection device.

[0037] In a further development, the cooling fluid injection device has an injection nozzle with at least one swirl element, in particular a helical groove and / or a helical projection, which is designed to impart a swirl to the cooling fluid. In particular, the at least one swirl element can be pressed, cut, or machined into a channel of the injection nozzle.

[0038] The invention is also directed to a motor vehicle, in particular a commercial vehicle, with a piston as disclosed herein or a device as disclosed herein.

[0039] It is also possible, for example, to use the piston and / or the device as disclosed herein for passenger cars, large engines, off-road vehicles, stationary engines, marine engines, etc.

[0040] The preferred embodiments and features of the invention described above can be combined in any way desired. Further details and advantages of the invention are described below with reference to the accompanying drawings. These show: Figure 1: A schematic view of the underside of a piston according to one embodiment; Figure 2: A sectional view through the exemplary piston and a coolant injection device; Figure 3: A sectional view through a piston according to another embodiment and a coolant injection device; Figure 4: A schematic view of the underside of a piston according to another embodiment; Figure 5: A sectional view through the exemplary piston ofFigure 4 and a cooling fluid injection device; Figure 6 a schematic view of the underside of a piston according to another embodiment; Figure 7 a sectional view through the exemplary piston of Figure 6 and a cooling fluid injection device; Figure 8 a section of a sectional view through an exemplary collection funnel; Figure 9 a section of a sectional view through another exemplary collection funnel; Figure 10 a section of a sectional view through another exemplary collection funnel; and Figure 11 a section of a sectional view through another exemplary collection funnel.

[0041] The embodiments shown in the figures are at least partially identical, so that similar or identical parts are provided with the same reference numerals and, to avoid repetition, reference is also made to the description of the other embodiments or figures for their explanation.

[0042] The Figure 1 Figure 1 schematically shows the underside of a piston 10. The piston 10 can be located in an internal combustion engine, for example in a motor vehicle, particularly a commercial vehicle. The commercial vehicle can preferably be a truck or a bus.

[0043] The piston 10 has two piston pin bores 12, 14. The piston pin bores 12, 14 serve to receive a piston pin (not shown). The piston pin connects the piston 10 to a connecting rod (not shown) in a pivotal manner, in particular by means of a pivot.

[0044] The piston 10 also has an inlet port 16. The inlet port 16 opens into an inlet 28 of an inner piston cooling channel 20 (see Figure 2The inlet channel 16 and an outlet 18 of the piston cooling channel 20 can be arranged opposite each other with respect to a central longitudinal axis of the piston 10. The inlet channel 16 is designed to supply a cooling fluid, for example, oil, to an inlet 28 of the inner piston cooling channel 20. The piston cooling channel 20 extends inside the piston 10. Cooling fluid in the piston cooling channel 20 cools the piston 10 from the inside during operation. To ensure sufficient cooling of the piston 10 at different piston speeds, enough cooling fluid must be supplied to the piston cooling channel 20 via the inlet channel 16. The outlet 18 serves to drain the cooling fluid from the piston cooling channel 20, for example, into a crankcase of the internal combustion engine.

[0045] The Figure 2Figure 1 shows an eccentric section through the piston 10 in the area of ​​the intake port 16. As shown, the intake port 16 is partially formed within a catch funnel 22. The catch funnel 22 is integrally formed on a bottom surface 24 of the piston 10. It is also possible to manufacture the catch funnel 22 as a separate component and, for example, detachably connect it to a bottom surface 24 of the piston 10. The catch funnel 22 can be made of the same material as the piston 10 or of a different material. The catch funnel 22 can be formed section by section of a piston skirt 26.

[0046] The collecting funnel 22 can, for example, have an axial extent parallel to the piston's central axis or a height H of less than 60 mm, particularly in a range between 5 mm and 40 mm. The height H can be measured from the underside 24 of the piston 10.

[0047] An inlet opening of the inlet channel 16 has a larger flow cross-section than an outlet opening of the inlet channel 16. The inlet channel 16 opens into an inlet 28 of the piston cooling channel 20 via its outlet opening. The inlet channel 16 tapers in the funnel 22 in one direction towards the piston cooling channel 20. In particular, the inlet channel 16 is funnel-shaped, as shown. In particular, a circumferential surface 30 can form an acute angle (taper angle) α with a central longitudinal axis of the inlet channel 16. The taper angle α can be greater than 0° and less than 45°, and in particular between 5° and 30°.

[0048] The enlarged inlet opening of the inlet channel 16 allows for a greater capture rate of cooling fluid, which is injected by a cooling fluid injection device 32 in one direction towards the collection funnel 22. Additionally, the collection funnel 22 protects the cooling fluid within the inlet channel 16 from splashing and churning fluid, such as oil, which might be flung from the crankshaft towards the piston 10. This minimizes the impact on the cooling fluid within the inlet channel 16.

[0049] The Figure 3 Figure 1 shows an alternative embodiment in which the collecting funnel 22' is designed such that the inlet channel 16 opens into the inlet 28 of the piston cooling channel 20 along its entire circumference with a radius R. The radius R can, for example, be less than 30 mm, in particular between 5 mm and 20 mm. The collecting funnel 22' of the embodiment according to Figure 3can have a height that corresponds to the height H of the trap 22 of the embodiment according to Figure 2 corresponds. Alternatively or additionally, the trap hopper 22' of the embodiment can be used according to Figure 3 have a taper angle that corresponds to the taper angle α of the embodiment according to Figure 2 corresponds.

[0050] The present application is specifically aimed at promoting a flow of cooling fluid within the inlet channel 16 in one direction towards the piston cooling channel 20. To achieve this, the inlet channel 16 and / or the cooling fluid injection device 32 can be specially designed, as described below by way of example.

[0051] To reduce cooling fluid friction within the inlet channel 16, for example, the surface of the circumferential surface 30 of the inlet channel 16 can be treated. The treatment can, in particular, reduce the surface roughness of the circumferential surface 30. This smooths the surface of the circumferential surface 30 and thus reduces cooling fluid friction as it flows along the circumferential surface 30 in one direction towards the piston cooling channel 20. For example, the circumferential surface 30 can be polished, at least in sections.

[0052] For example, it is also possible that the circumferential surface 30 of the inlet channel 16 is at least partially coated to reduce cooling fluid friction within the inlet channel 16. For instance, the circumferential surface 30 can be coated with a coating that reduces the flow resistance of the cooling fluid and / or the surface roughness of the circumferential surface 30. The coating could be, for example, a paint. It is also possible that the coating is applied, for example, by thermal spraying.

[0053] The Figures 4 and 5Figure 1 shows another embodiment for conveying the flow of cooling fluid in the inlet channel 16. Here, the inlet channel 16 has several flow-guiding elements 34. The flow-guiding elements 34 are arranged symmetrically around the circumference of the inlet channel 16, for example. The flow-guiding elements 34 are straight. The flow-guiding elements 34 can extend completely or partially between an inlet opening of the inlet channel 16 and an outlet opening of the inlet channel 16 that leads into the inlet 28. The flow-guiding elements 34 can help to guide the cooling fluid injected into the inlet channel 16 in one direction towards the inlet 28. It is also possible to provide more or fewer flow-guiding elements 34 than shown.

[0054] As in the Figure 8As shown, the flow-guiding elements 34 can be designed as, in particular, rounded recesses / grooves in the circumferential surface 30. As shown in the Figure 9 As shown, the flow-guiding elements 34 can alternatively or additionally be designed as projections, in particular rounded ones, on the circumferential surface 30. The radius K of the flow-guiding elements 34 can, for example, be between 0.1 mm and 5 mm.

[0055] It is also possible that the flow-guiding elements 34 are angular, in particular rectangular or trapezoidal, recesses in the circumferential surface 30 (see Figure 10 ) and / or as angular, in particular rectangular or trapezoidal, projections on the circumferential surface 30 (see Figure 11 are trained.

[0056] The flow-guiding elements 34, designed as recesses and / or projections, can, for example, have a width B between 0.1 mm and 5 mm, as shown in the following examples: Figures 10 and 11is shown.

[0057] The side walls of the angularly shaped flow guidance elements 34 (see Figures 10 and 11 ) can enclose an angle β with a normal of the circumferential surface 30, which is, for example, greater than or equal to 0° and / or less than or equal to 90°.

[0058] As in the Figures 8 to 11 As shown, the flow guidance elements 34, 36 can have a height or depth V, which is, for example, in a range between 0.1 mm and 5 mm.

[0059] The Figures 6 and 7Figure 1 shows another embodiment for conveying the cooling fluid flow through the inlet channel 16. The inlet channel 16 has several flow-guiding elements 36. The flow-guiding elements 36 are arranged, for example, symmetrically around the circumference of the inlet channel 16. The flow-guiding elements 36 are helically shaped around a central longitudinal axis of the inlet channel 16. The flow-guiding elements 36 can extend completely or partially between an inlet opening of the inlet channel 16 and an outlet opening of the inlet channel 16, which leads into the inlet 28. Similar to the flow-guiding elements 34 according to the embodiment shown in Figure 1. Figures 4 and 5 The flow guide elements 36 can help to direct the cooling fluid injected into the inlet channel 16 in one direction towards the inlet 28. It is also possible that more or fewer flow guide elements 36 than shown are provided.

[0060] The flow-guiding elements 36 can be designed as, in particular, rounded or angular recesses in the circumferential surface 30 (see Figures 8 and 10 ) and / or as, in particular rounded or angular, elevations or projections on the circumferential surface 30 (see Figures 9 and 11 ) be trained.

[0061] In the Figures 5 and 7 The flow guidance elements 34 and 36, respectively, in combination with the catch funnel 22', which refers to the Figure 3 It is of course also possible to place the flow guidance elements 34 and 36, for example, in the catch funnel 22, which is described with reference to the Figure 2 as described, to integrate.

[0062] It is also possible to promote the cooling fluid flow in the inlet channel 16 by combining a surface treatment, a coating, at least one flow guidance element 34 and / or at least one flow guidance element 36.

[0063] In addition to promoting the flow of cooling fluid in the inlet channel 16, the cooling fluid injection device 32 can also be specially designed, as shown in the Figures 2, 3, 5 and 7 The coolant injection device 32 can have an injection nozzle 38. The injection nozzle 38 can be designed such that a swirl is imparted to the coolant during injection. This stabilizes the injection jet and makes it less susceptible to deflection by splashing and mixing fluid. In particular, the injection nozzle 38 can be provided with at least one helically shaped swirl element 40 to impart a swirl to the coolant during injection. The swirl elements 40 can, for example, be designed as recesses and / or projections in the injection nozzle 38. Reference symbol list

[0064] 10 Piston 12 Piston pin eye 14 Piston pin eye 16 Inlet port 18 Outlet 20 Piston cooling channel 22 Catch funnel 24 Underside 26 Piston stem 28 Inlet 30 Circumferential surface 32 Cooling fluid injection device 34 Flow guide element 36 Flow guide element 38 Injection nozzle 40 Swirl element αTap angle βFlow element angle BWidth HHHeight KRadius RRadius VHeight / Depth

Claims

1. A piston (10) for an internal combustion engine, having: an inner piston cooling channel (20) for the cooling of the piston (10); and an inlet channel (16) which opens into an inlet (28) of the piston cooling channel (20), wherein a flow cross section of the inlet channel (16) narrows at least in sections, in particular in a funnel shape, in a direction towards the inlet (28) of the inner piston cooling channel (20), and the inlet channel (16) is additionally designed to convey a cooling fluid flow to the inlet (28) of the inner piston cooling channel (20), wherein: the inlet channel (16) is surface-treated, preferably polished, at least in certain sections for the purposes of reducing a surface roughness and / or the inlet channel (16) is coated, in particular by thermal spraying, with a coating which lowers a flow resistance and / or reduces a surface roughness; and the inlet channel (16) has at least one flow-guiding element (34; 36) for conducting the cooling fluid in a direction towards the inlet (18) of the piston cooling channel (20).

2. The piston (10) according to Claim 1, wherein: the at least one flow-guiding element (34; 36) is formed as a groove in a circumferential surface (30) of the inlet channel (16); and / or the at least one flow-guiding element (34; 36) is configured as a projection, in particular as a guide fin, on a circumferential surface (30) of the inlet channel (16).

3. The piston (10) according to Claim 1 or Claim 2, wherein: the at least one flow-guiding element (34; 36) extends in a direction towards the inlet (28) of the inner piston cooling channel (20); and / or the at least one flow-guiding element (34; 36) extends rectilinearly at least in certain sections and / or extends helically at least in certain sections.

4. The piston (10) according to any one of Claims 1 to 3, wherein: the at least one flow-guiding element (34; 36) has a multiplicity of flow-guiding elements (34; 36) which are arranged, in particular symmetrically, around a circumference of the inlet channel (16).

5. The piston (10) according to any one of the preceding claims, wherein: the inlet channel (16) is formed at least partially by a catching funnel (22) that is connected to an underside (24) of the piston (10).

6. The piston (10) according to Claim 5, wherein: the catching funnel (22) is formed integrally and as a single piece with the underside (24) of the piston (10) or is formed separately and connected, in particular detachably, to the underside (24).

7. The piston (10) according to Claim 5 or Claim 6, wherein: the catching funnel (22) and the underside (24) of the piston (10) are produced from the same material or from different materials; and / or the catching funnel (22) has a height (H) greater than 0 mm and / or less than 60 mm, in particular in a range between 5 mm and 40 mm.

8. The piston (10) according to any one of Claims 5 to 7, wherein: the catching funnel (22) is formed at least partially by a piston skirt (26).

9. The piston (10) according to any one of the preceding claims, wherein: the inlet channel (16) narrows at least in sections at an angle (α) greater than 0° and / or less than 45°, in particular between 5° and 30°, with respect to a longitudinal axis of the inlet channel (16); and / or the inlet channel (16) opens in rounded fashion into the inlet (28) of the piston cooling channel (20), in particular with a radius (R) greater than 0 mm and / or less than 30 mm, preferably between 5 mm and 20 mm.

10. A device, having a piston (10) according to any one of the preceding claims; and a cooling fluid injection device (32) which is directed towards an inlet opening of the inlet channel (16) and which is configured to impart swirl to the cooling fluid.

11. The device according to Claim 10, wherein: the cooling fluid injection device (32) has an injection nozzle (38) with at least one swirl element (40), in particular a helical groove and / or a helical projection, which is configured to impart swirl to the cooling fluid.

12. A motor vehicle, in particular utility vehicle, having a piston (10) according to any one of Claims 1 to 9 or a device according to Claim 10 or 11.

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