DE102021128787A1 - Pistons for an internal combustion engine - Google Patents

Abstract

The invention relates to a piston (100) for an internal combustion engine, comprising a cooling system for cooling the piston (100), the cooling system comprising an inflow, an outflow, an annular channel (101), a central area (103) and cooling spokes (102), wherein the ring channel (101) forms an outer closure of the cooling system, wherein the ring channel (101) is arranged in a ring around the central area (103) and the cooling spokes (102) each connect the ring channel (101) with the central area (103) in a radial direction connect fluidically, wherein the cooling system is designed so that a fluid (300) flows into the cooling system via the inflow, through the annular channel (101), the cooling spokes (102) and the central area (103) and flows out of the cooling system via the outflow exits, wherein the annular channel (101) comprises an upper volume (500), wherein the annular channel (101) comprises a lower volume (501), wherein the cooling system is designed such that when the piston (100) moves downwards, at least a part of the fluid flowing through the cooling system is pushed into the upper volume (500) and that when the piston (100) moves upwards, at least part of the fluid (300) flowing through the cooling system is pushed into the lower volume (501), the lower Volume (501) is greater than or equal to the upper volume (500).

Description

The present invention relates to a piston for an internal combustion engine according to the preamble of claim 1.

Pistons are used in internal combustion engines to compress fuel and convert the energy generated during combustion into kinetic energy. During operation, the piston is heated. Out of DE 38 32 022 C1 a piston is known in which the heat is dissipated by means of an oil. For this purpose there is an outer, ring-shaped cooling chamber and an inner cooling chamber connected to it via transfer bores.

In contrast, the object of the present application is to improve the cooling capacity.

This object is achieved by a piston according to claim 1, a motor vehicle according to claim 7 and a method according to claim 8. Embodiments of the invention are given in the dependent claims.

The piston includes a cooling system for cooling the piston. The cooling system includes an inflow, an outflow, an annular channel, a central area and cooling spokes. The ring channel forms an outer closure of the cooling system. In the context of this description, this means in particular that the ring channel surrounds the other components of the cooling system. It is possible, for example, that the annular channel is arranged on a geometric circle and that no component of the cooling system is arranged outside of this geometric circle. The ring channel is arranged in a ring around the central area. The cooling spokes each fluidly connect the ring channel to the central area in a radial direction. In the context of this description, a fluidic connection is understood in particular to mean that a fluid can flow between the two connected components. It can be a pipe or tube, for example.

The cooling system is designed so that a fluid, which can be oil, for example, flows into the cooling system via the inflow, flows through the annular channel, the cooling spokes and the central area and exits the cooling system via the outflow. The fluid can flow through the ring channel, the cooling spokes and the central area in exactly the order mentioned or in a different order. As the fluid flows through the cooling system, it absorbs heat. After exiting the cooling system, it can give up the heat - for example in a heat exchanger - and flow through the cooling system again.

The annular channel comprises an upper volume which is delimited at the top and at the sides by a first wall. In addition, the annular channel comprises a lower volume which is delimited at the bottom and at the sides by a second wall. The terms “top” and “bottom” in this description are understood to mean the position when the piston is used as intended in the internal combustion engine. When used as intended, the upper volume and the lower volume can each be delimited by a horizontal geometric plane. A geometric plane is understood to be a plane that only serves to define the volumes and does not have to be present as a component. In this case, the plane that delimits the upper volume can be arranged at an upper end of the transition between the cooling spokes and the ring channel. The plane delimiting the lower volume may be located at a lower end of this transition.

The cooling system is designed such that at least part of the fluid flowing through the cooling system is pressed into the upper volume when the piston moves downwards. This can occur due to the inertia of the fluid due to the movement of the piston. In particular, it is possible for the entire upper volume to be filled with the fluid. With an upward movement of the piston, at least part of the fluid is pushed into the lower volume. Again, this is due to the inertia of the fluid due to the movement of the piston. In particular, it is possible for the entire lower volume to be filled with the fluid. It is also possible that all of the fluid flowing through the cooling system is pushed into the lower volume.

The lower volume is greater than or equal to the upper volume. As a result, more fluid is pushed into the lower volume during the upward movement of the piston than can be pushed into the upper volume during the downward movement. During the downward movement, part of the fluid thus flows through the cooling spokes in the direction of the central area. This part of the fluid is pressed against an upper wall of the cooling spokes and thus continues to absorb heat. The cooling effect is thus improved. Due to the usually relatively fast speed of the piston, the part of the fluid that cannot be pushed into the upper volume flows from the annular channel into the cooling spokes at a relatively high flow rate. This further improves the cooling effect.

According to an embodiment of the invention, the central area can be delimited by the cooling spokes, a top wall and a bottom wall. The lower wall can have a lead-through via which the central area is connected to the drain. The top wall and/or the bottom wall can be free of projections, extensions and/or undercuts. This improves the flow of fluid in the central area. This distinguishes this embodiment in particular from that in DE 38 32 022 C1 depicted item. In DE 38 32 022 C1 an extension protrudes downwards from the upper wall.

According to one embodiment of the invention, the inflow can open into the ring channel. In particular, the inflow can open into the lower volume.

According to one embodiment of the invention, the central area and the ring channel can be arranged concentrically.

According to one embodiment of the invention, the first wall and the second wall can each merge into walls of the cooling spokes. The transition can in particular be formed directly, that is to say without a section arranged in between or a component arranged in between.

The internal combustion engine according to claim 6 comprises a piston according to an embodiment of the invention and a cylinder. The piston is arranged in the cylinder.

The motor vehicle according to claim 7 comprises an internal combustion engine according to an embodiment of the invention.

In the method according to claim 8, according to one embodiment of the invention, the piston is moved up and down in the cylinder. The fluid flows into the cooling system via the inflow, through the ring channel, the cooling spokes and the central area. The fluid exits the cooling system via the drain. As the piston moves downward, at least a portion of the fluid flowing through the cooling system is forced into the upper volume. As the piston moves up, some of the fluid flowing through the cooling system is pushed into the lower volume. It is possible for the method to include features that are described earlier in this specification with reference to the piston.

According to one embodiment of the invention, the fluid can flow into the cooling system via the inflow during the downward movement. It should be noted that in certain time ranges, due to inertia, the fluid also flows in via the inflow during the upward movement when an oil jet is faster than the piston. Thus, there is a dependence of the flow in relation to the flow rate of the oil jet and the piston speed.

According to one embodiment of the invention, the fluid can exit the cooling system via the drain during the upward movement.

From a physical point of view, there are of course phases during the upward movement in which oil is pushed upwards. The movement of the oil is created by inertial forces created by the piston movement. The course of the piston acceleration therefore determines the position of the oil.

• 1 eine schematische Schnittansicht durch einen Kolben;
• 2 eine schematische perspektivische Ansicht eines teilweise durchsichtig dargestellten Kolbens nach einer Ausführungsform der Erfindung;
• 3 eine schematische Schnittansicht durch ein Kühlsystem eines Kolbens während einer Abwärtsbewegung des Kolbens;
• 4 eine schematische Schnittansicht durch das Kühlsystem aus 3 während einer Aufwärtsbewegung des Kolbens; und
• 5 eine schematische Schnittansicht durch einen Ringkanal eines Kolbens nach einer Ausführungsform der Erfindung.

Further features and advantages of the present invention become clear from the following description of preferred exemplary embodiments with reference to the attached figures. The same reference symbols are used for the same or similar features and for features with the same or similar functions. It shows:

• 1 a schematic sectional view through a piston;
• 2 a schematic perspective view of a piston shown partially in phantom according to an embodiment of the invention;
• 3 a schematic sectional view through a cooling system of a piston during a downward movement of the piston;
• 4 a schematic sectional view through the cooling system 3 during an upward movement of the piston; and
• 5 a schematic sectional view through an annular channel of a piston according to an embodiment of the invention.

The piston 100 includes a cooling system with an annular channel 101, cooling spokes 102 and a central area 103. The annular channel 101 represents an outer boundary of the cooling system. The cooling spokes 102 extend, starting from the annular channel 101, radially inward to the central area 103 and connect the central area 103 fluidly with the ring channel 101.

During operation, when the piston 100 moves downwards, an oil is pressed into the annular channel 101 via an inflow. From there, the oil flows through the cooling spokes 102 to the central area 103. During the upward movement of the piston 100 the oil is pushed down in the central area 103 where the drain is located, so that the oil comes out of the drain.

As the oil flows through the cooling system, it absorbs heat from the piston. After exiting the drain, it can reject the heat, for example in a heat exchanger, and be used again to remove heat from the bulb 100 .

In 3 shows how the fluid 300 is pushed upwards when the piston 100 moves downwards. In the process, a large part of the fluid 300 is pressed into an upper volume of the ring channel 101 . In 4 shows how the fluid 300 is pushed down when the piston 100 moves up. In the process, a large part of the fluid is pressed into a lower volume of the ring channel 101 .

In 5 it is shown that the lower volume 501 is larger than the upper volume 500 . This is achieved by the vertical distance b between a lower end of the annular channel 101 and a lower end of the cooling spokes 102 being greater than the vertical distance a between an upper end of the annular channel 101 and an upper end of the cooling spokes 102.

Since more fluid 300 can be accommodated in the lower volume 501 than in the upper volume 500, part of the fluid 300 cannot be accommodated in the upper volume 500 when the piston 100 moves downwards. This part flows along the top of the cooling spokes 102 and continues to absorb heat, thereby improving the cooling effect of the cooling system. In addition, this part of the fluid 300 flows relatively quickly over the edge between the upper volume 500 and the cooling spokes 102. This also results in a cooling effect.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 3832022 C1 [0002, 0010]

Claims (10)

Piston (100) for an internal combustion engine, comprising a cooling system for cooling the piston (100), the cooling system comprising an inflow, an outflow, an annular channel (101), a central area (103) and cooling spokes (102), the annular channel ( 101) forms an outer closure of the cooling system, the ring channel (101) being arranged in a ring around the central area (103) and the cooling spokes (102) each fluidically connecting the ring channel (101) to the central area (103) in a radial direction, wherein the cooling system is designed so that a fluid (300) flows into the cooling system via the inflow, through the annular channel (101), the cooling spokes (102) and the central area (103) and exits the cooling system via the outflow, with the Annular channel (101) into an upper volume (500) which is bounded at the top and to the sides by a first wall, the annular channel (101) comprising a lower volume (501) which is bounded at the bottom and to the sides by a second wall, wherein the cooling system is designed such that when the piston (100) moves down, at least part of the fluid flowing through the cooling system is pressed into the upper volume (500) and that when the piston (100) moves up, at least a portion of the fluid (300) flowing through the cooling system is forced into the lower volume (501), characterized in that the lower volume (501) is greater than or equal to the upper volume (500). Piston (100) after claim 1 , characterized in that the central area (103) is delimited by the cooling spokes (102), an upper wall and a lower wall, the lower wall having a passage via which the central area (103) is fluidically connected to the drain, and wherein the top wall and/or the bottom wall is free of projections, appendages and/or undercuts. Piston (100) according to one of the preceding claims, characterized in that the inflow opens into the annular channel (101). Piston (100) according to one of the preceding claims, characterized in that the central area (103) and the annular channel (101) are arranged concentrically. Piston (100) according to one of the preceding claims, characterized in that the first wall and the second wall each merge into walls of the cooling spokes (102). Internal combustion engine for a motor vehicle, comprising a piston (100) according to any one of the preceding claims and a cylinder, the piston (100) being arranged in the cylinder. Motor vehicle comprising an internal combustion engine according to the preceding claim. Method for operating an internal combustion engine according to claim 6 , characterized in that the piston (100) is moved up and down in the cylinder, with the fluid (300) flowing into the cooling system via the inflow, through the ring channel (101), the cooling spokes (102) and the central area (103) flows and exits the cooling system via the drain, with a downward movement of the piston (100) at least part of the fluid (300) flowing through the cooling system being pressed into the upper volume (500), and with an upward movement of the piston (100 ) at least part of the fluid (300) flowing through the cooling system is pushed into the lower volume (501). Method according to the preceding claim, characterized in that the fluid (300) flows into the cooling system during the downward movement essentially via the inflow. Method according to one of the two preceding claims, characterized in that during the upward movement the fluid (300) exits the cooling system via the drain.

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