Piston and internal combustion engine

Abstract

The invention discloses a piston and an internal combustion engine, and relates to the technical field of internal combustion engine structures.The piston is internally provided with a cavity, the top wall of the cavity protrudes downwards to form an annular boss, the annular boss surrounds the inner side wall of the cavity in the circumferential direction, and an annular oil cavity is formed in the position, close to the top, of the annular boss; a plurality of oil collecting holes communicated with the oil cavity and the cavity are formed in the bottom of the annular boss, each oil collecting hole comprises an equal-diameter section and an expansion section which are communicated with each other, the end, away from the expansion section, of the equal-diameter section is communicated with the oil cavity, the end, away from the equal-diameter section, of the expansion section is communicated with the cavity, the end, connected with the equal-diameter section, of the expansion section is a first end, and the other end is a second end; the expansion section is gradually expanded from the first end to the second end, and a porous medium is arranged on the inner wall of the equal-diameter section in the circumferential direction of the equal-diameter section. According to the piston, the utilization rate of cooling oil is increased; and the porous medium is arranged, so that rebound and splashing of the cooling oil are greatly inhibited, the loss of the cooling oil is avoided, and the working temperature of the piston is remarkably reduced.

Description

Technical Field

[0001] This invention relates to the field of internal combustion engine structure technology, and particularly to a piston and an internal combustion engine. Background Technology

[0002] As the core moving component of an internal combustion engine, the piston directly withstands the high temperature and high pressure impact generated by the combustion gas explosion during operation, making its working environment extremely harsh. High temperatures not only reduce the strength of the piston material but can also cause serious malfunctions such as cylinder scoring, piston crown burning, and oil coking, directly affecting the engine's reliability, lifespan, and emissions levels. Therefore, efficient and reliable piston cooling is crucial to ensuring the overall performance of the engine.

[0003] Currently, most high-performance engines employ oscillation cooling to cool the piston head. The principle is to periodically spray cooling oil into the annular oil chamber inside the piston via nozzles fixed to the cylinder block. After entering the oil chamber, the oil oscillates violently with the high-speed reciprocating motion of the piston, absorbing and carrying away the enormous heat from the piston top. Finally, the oil flows back to the oil pan under gravity, completing a cooling cycle.

[0004] The efficiency of this cooling system hinges on the amount of cooling oil that can be effectively "captured" and enter the oil chamber, i.e., the instantaneous oil filling ratio. However, existing piston oil collection hole structures have defects, making it difficult to improve the oil filling ratio, mainly due to the following reasons: First, because the piston moves at high speed relative to the fixed nozzle, the relative position between the two changes constantly, and the ejected oil jet is not always directly aligned with the oil collection port inlet. In existing technologies, the oil collection port is mostly a simple straight oil hole with a limited opening area. When the oil jet is slightly deviated or the angle is not good, a considerable portion of the oil jet will hit the piston skirt or the outer area of ​​the oil collection port, and will be lost before entering the oil collection port, resulting in a waste of cooling oil.

[0005] Secondly, significant splashing loss occurs after the oil enters the straight oil hole. Even if some oil jets successfully enter, they typically possess high kinetic energy. These high-speed oil jets directly impact the sidewalls of the straight oil hole, creating a violent splashing effect. A large number of oil droplets are bounced and splashed out of the straight oil hole instead of flowing into the oil chamber along the intended path. This splashing loss is particularly severe under high-speed operating conditions, greatly reducing the actual amount of oil participating in heat exchange.

[0006] Therefore, the existing piston cooling oil utilization rate is low, resulting in poor piston heat dissipation. Summary of the Invention

[0007] The main objective of this invention is to propose a piston and internal combustion engine that aims to solve the technical problem of low piston cooling oil utilization rate, resulting in poor piston heat dissipation.

[0008] To achieve the above objectives, the present invention proposes a piston, wherein a cavity is formed inside the piston, and an annular boss is formed by the downward protrusion of the top wall of the cavity. The annular boss surrounds the inner sidewall of the cavity circumferentially. An annular oil cavity is formed near the top of the annular boss. A plurality of oil collecting holes communicating with the oil cavity and the cavity are opened at the bottom of the annular boss. Each oil collecting hole includes an equal-diameter section and an expansion section that are interconnected. The end of the equal-diameter section away from the expansion section is connected to the oil cavity, and the end of the expansion section away from the equal-diameter section is connected to the cavity. The end of the expansion section connected to the equal-diameter section is a first end, and the other end is a second end. The expansion section is gradually widened from the first end to the second end. A porous medium is provided on the inner wall of the equal-diameter section circumferentially.

[0009] In one embodiment, the wall of the equal-diameter section is smoothly transitioned to the wall of the oil cavity, and the equal-diameter section has the same diameter as the first end, and the wall of the equal-diameter section is smoothly transitioned to the wall of the expansion section.

[0010] In one embodiment, the expansion angle of the expansion section from the first end to the second end is 5° to 20°; and / or, the maximum aperture of the expansion section is 8mm to 20mm, and the length of the equal diameter section is 2mm to 8mm.

[0011] In one embodiment, the porosity of the porous medium is 50% to 85%; and / or, the size of each pore in the porous medium is 0.3 μm to 0.8 μm.

[0012] In one embodiment, the porous medium completely covers the inner wall of the equal-diameter section circumferentially, and the radial thickness of the porous medium along the equal-diameter section is 0.2 mm to 1 mm.

[0013] In one embodiment, the direction from the second end to the first end is defined as the oil inlet direction, and the porous medium includes a plurality of pore layers distributed sequentially along the oil inlet direction; Along the oil inlet direction, the pore size of the multiple pore layers increases in a gradient, and the gradient range of pore size is 0.3μm~0.8μm; And / or, along the oil inlet direction, the porosity of the plurality of pore layers increases in a gradient, and the gradient range of the porosity is 50% to 85%.

[0014] In one embodiment, the direction from the second end to the first end is defined as the oil inlet direction, and a plurality of medium regions are formed on the porous medium in sequence along the oil inlet direction, each of the medium regions including a plurality of pore layers in sequence along the oil inlet direction; Within each of the medium regions, along the oil inlet direction, the pore size of the multiple pore layers increases in a gradient, and the gradient range of the pore size is 0.3μm~0.8μm; And / or, within each of the media regions, along the oil inlet direction, the porosity of the plurality of pore layers increases in a gradient, and the gradient range of the porosity is 50% to 85%.

[0015] In one embodiment, the direction from the second end to the first end is defined as the oil inlet direction. A plurality of medium regions are formed on the porous medium and are distributed sequentially along the oil inlet direction. Each medium region includes a plurality of pore layers distributed sequentially along the oil inlet direction, and all the pores in each medium region have the same size. Along the oil inlet direction, the pore size in the multiple medium zones increases in a gradient, and the gradient range of pore size is 0.3μm~0.8μm; And / or, along the oil inlet direction, the porosity of the plurality of medium zones increases in a gradient, and the gradient range of the porosity is 50% to 85%.

[0016] In one embodiment, the portion of the porous medium other than the pores is a porous skeleton, a transition zone is formed on the porous skeleton between any two adjacent medium regions, and the other regions on the porous skeleton other than the transition zone are oleophilic regions. The contact angle of the oleophilic region is 30°~60°; and / or, along the oil inlet direction, the contact angle of the transition region gradually changes from 120° to 10°.

[0017] The present invention also proposes an internal combustion engine that uses a piston as described above.

[0018] The piston of this invention features an annular boss on the top wall of the cavity, with an annular oil chamber formed at the top of the boss. Multiple oil collecting holes, communicating with the oil chamber and the cavity, are formed on the annular boss. These oil collecting holes can be considered as oil inlets for the oil chamber. Each oil collecting hole includes an equal-diameter section and an expanding section that communicate with each other. When cooling oil enters the oil chamber, it passes through the expanding section and the equal-diameter section sequentially. The expanding section gradually widens from the first end to the second end, forming a trumpet-shaped structure. The second section of the expanding section effectively increases the oil-facing area, allowing more cooling oil to be introduced into the oil collecting holes, thus improving the utilization rate of the cooling oil. Furthermore, a porous medium with numerous micropores is provided on the inner wall of the equal-diameter section. When high-speed cooling oil impacts the porous medium, its kinetic energy is rapidly absorbed, and the cooling oil is captured and immersed in the pores, thereby greatly suppressing the rebound and splashing of the cooling oil and preventing its loss. This invention fundamentally improves the utilization efficiency of cooling oil, thereby effectively controlling the thermal load on the piston. Furthermore, the piston of this invention significantly increases the instantaneous oil filling ratio of the oil chamber, allowing more cooling oil to participate in the piston's oscillating heat exchange, thereby significantly reducing the piston's operating temperature. In particular, it effectively reduces the temperature of the top and ring groove regions where the piston's thermal load is highest, improving the reliability and lifespan of the internal combustion engine. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the piston structure provided in an embodiment of the present invention; Figure 2 for Figure 1 Enlarged view of point A in the middle; Figure 3 This is a schematic diagram of the structure of a porous medium provided in an embodiment of the present invention; Figure 4 This is another structural schematic diagram of a porous medium provided in an embodiment of the present invention; Figure 5 Figure 'a' represents the temperature field distribution of a piston with a straight oil hole in the background art of this invention after 10 cooling cycles. Figure 5 b is a temperature field distribution diagram of the piston after 10 cooling cycles in one embodiment of the present invention.

[0021] Explanation of icon numbers: 100. Piston; 1. Cavity; 2. Annular boss; 3. Oil cavity; 4. Oil collection hole; 41. Equal diameter section; 42. Expansion section; 5. Porous medium; 51. Pore; 52. Porous skeleton; 53. Medium zone; 54. Porous layer.

[0022] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0025] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0026] This invention proposes a piston 100.

[0027] Please see Figure 1 and Figure 2In one embodiment of the present invention, a cavity 1 is formed inside the piston 100. An annular boss 2 is formed by the downward protrusion of the top wall of the cavity 1. The annular boss 2 surrounds the inner side wall of the cavity 1 in the circumferential direction. An annular oil cavity 3 is formed near the top of the annular boss 2. A plurality of oil collecting holes 4 are provided at the bottom of the annular boss 2, which are connected to the oil cavity 3 and the cavity 1. Each oil collecting hole 4 includes an equal diameter section 41 and an expansion section 42 that are connected to each other. The end of the equal diameter section 41 away from the expansion section 42 is connected to the oil cavity 3. The end of the expansion section 42 away from the equal diameter section 41 is connected to the cavity 1. The end of the expansion section 42 connected to the equal diameter section 41 is the first end, and the other end is the second end. The expansion section 42 is gradually expanded from the first end to the second end. A porous medium 5 is provided on the inner wall of the equal diameter section 41 in the circumferential direction.

[0028] The piston 100 of the present invention has an annular boss 2 provided on the top wall of the cavity 1. An annular oil cavity 3 is formed on the top of the annular boss 2. A plurality of oil collecting holes 4 are provided on the annular boss 2, which communicate with the oil cavity 3 and the cavity 1. The oil collecting holes 4 can be regarded as oil inlets of the oil cavity 3. The oil collecting holes 4 include an equal diameter section 41 and an expansion section 42 that are interconnected. When the cooling oil enters the oil cavity 3, it passes through the expansion section 42 and the equal diameter section 41 in sequence. The expansion section 42 is gradually expanded from the first end to the second end, that is, it expands... The expansion section 42 has a trumpet-shaped structure. The second section of the expansion section 42 effectively increases the oil-facing area, allowing more cooling oil to be introduced into the oil collecting hole 4, thus improving the utilization rate of the cooling oil. In addition, by providing a porous medium 5 on the inner wall of the equal-diameter section 41, the porous medium 5 has a large number of micropores. When high-speed cooling oil impacts the porous medium 5, its kinetic energy is rapidly absorbed by the porous medium 5, and the cooling oil is captured and immersed in the pores 51, thereby greatly suppressing the rebound and splashing of the cooling oil and preventing the loss of cooling oil. This fundamentally improves the utilization efficiency of the cooling oil, thereby effectively controlling the heat load of the piston 100. Moreover, the piston 100 of this invention significantly increases the instantaneous oil filling ratio of the oil chamber 3, allowing more cooling oil to participate in the oscillating heat exchange of the piston 100, thereby significantly reducing the operating temperature of the piston 100, especially effectively reducing the temperature of the top and annular groove areas where the piston 100 has the highest heat load, thus improving the reliability and life of the internal combustion engine.

[0029] In one embodiment, the wall of the equal-diameter section 41 smoothly transitions with the wall of the oil cavity 3, and the equal-diameter section 41 has the same diameter as the first end, and the wall of the equal-diameter section 41 smoothly transitions with the wall of the expansion section 42. Understandably, by smoothly transitioning the wall of the equal-diameter section 41 with the wall of the oil cavity 3, cooling oil can smoothly enter the oil cavity 3, ensuring stable oil flow; furthermore, the smooth transition between the wall of the equal-diameter section 41 and the wall of the expansion section 42 further prevents cooling oil splashing.

[0030] In one embodiment, the expansion angle of the expansion section 42 from the first end to the second end is 5° to 20°. Understandably, when the expansion angle is less than 5°, the improvement in cooling oil guidance is not significant, while an expansion angle greater than 20° would excessively reduce the material of the piston 100 around the oil collecting hole 4, resulting in insufficient strength of the piston 100 and potentially causing turbulence. Therefore, an expansion angle of 5° to 20° not only facilitates the guidance of cooling oil but also ensures the strength of the piston 100. It should be noted that the expansion angle is preferably 10°.

[0031] In one embodiment, the maximum aperture of the expansion section 42 is 8mm to 20mm, and the length of the constant-diameter section 41 is 2mm to 8mm. Understandably, the expansion section 42 with this maximum aperture helps maintain the strength of the piston 100, and the length of the constant-diameter section 41 facilitates the placement of a porous medium 5 of a suitable size, improving the anti-splashing effect of the cooling oil. It should be noted that the maximum aperture of the expansion section 42 is preferably 12mm, as this size achieves a good balance between increasing the capture area and ensuring structural strength. The length of the constant-diameter section 41 is preferably 5mm, so that the porous medium 5 placed on it best ensures the stability of the oil flow direction.

[0032] In one embodiment, the porosity 51 of the porous medium 5 is 50% to 85%; and / or, the size of each pore 51 in the porous medium 5 is 0.3 μm to 0.8 μm. Understandably, the porosity 51 ratio and pore size together determine the permeability and capillary properties of the porous medium 5. This range of porosity 51 ratio ensures sufficiently high capillary suction while also providing low flow resistance, which is beneficial for the rapid intake and subsequent transport of cooling oil.

[0033] It should be noted that, in this embodiment, the size of each pore 51 in the entire porous medium 5 may be different, and each pore 51 may be randomly and irregularly distributed. Furthermore, since the pores 51 may be irregular pores, the size of the pores 51 can generally be understood as the diameter of an equivalent circle, that is, all pores 51 are regarded as circular pores, and the size of the pores 51 is also the diameter of the pores 51.

[0034] In one embodiment, the porous medium 5 completely covers the inner wall of the constant diameter section 41 circumferentially, and the radial thickness of the porous medium 5 along the constant diameter section 41 is 0.2 mm to 1 mm. The porous medium 5 in this range has good strength and anti-splash performance.

[0035] It should be noted that the materials of porous media 5 include, but are not limited to, aluminum, copper, stainless steel, and titanium.

[0036] In a preferred embodiment, the porous medium 55 is made of 316L stainless steel, giving it good wear resistance, corrosion resistance, and good thermal expansion compatibility with the aluminum alloy substrate piston 100. The porous medium 5 can also be a porous copper sintered layer or a porous alumina ceramic layer prepared by micro-arc oxidation. The thickness of the porous medium 5 is preferably 0.5 mm. If it is too thin, the energy absorption and splash prevention effect will be insufficient; if it is too thick, the risk of detachment due to thermal stress or vibration may increase, and it will reduce the flow area of ​​the cooling oil.

[0037] Please see Figure 3 In another embodiment, the direction from the second end to the first end is defined as the oil inlet direction, and the porous medium 5 includes a plurality of pore layers 54 distributed sequentially along the oil inlet direction; along the oil inlet direction, the pore size 51 of the plurality of pore layers 54 increases in a gradient, and the gradient range of the pore size 51 is 0.3μm~0.8μm; and / or, along the oil inlet direction, the porosity 51 of the plurality of pore layers 54 increases in a gradient, and the gradient range of the porosity 51 is 50%~85%.

[0038] It should be noted that, as Figure 3 As shown, with Figure 3 The area shown within the two adjacent dashed lines is a porous layer.

[0039] The multi-layered porous layers 54 can be sequentially divided into a first porous layer 54, a second porous layer 54, a third porous layer 54, ..., an (N-1)th porous layer 54, and an Nth porous layer 54 along the oil inlet direction, where the specific value of N is not limited. The pore size 51 of the multiple porous layers 54 increases in a gradient along the oil inlet direction. It can be considered that the pore size 51 in the second porous layer 54 is larger than the pore size 51 in the first porous layer 54, the pore size 51 in the third porous layer 54 is larger than the pore size 51 in the second porous layer 54, and the pore size 51 in the Nth porous layer 54 is larger than the pore size 51 in the (N-1)th porous layer 54. Furthermore, the pore size gradient range is 0.3 μm to 0.8 μm. This can be interpreted as the pore size of the first pore layer 54 being 0.3 μm, the pore size of the Nth pore layer 54 being 0.8 μm, and the pore size gradually increasing from 0.3 μm to 0.8 μm. The porosity of the multiple pore layers 54 also exhibits a gradient increase. This can be interpreted as the porosity of the first pore layer 54 being 50%, the porosity of the Nth pore layer 54 being 85%, and the porosity gradually increasing from 50% to 85%.

[0040] Understandably, since the pore size 51 of the porous medium 5 gradually increases along the oil inlet direction, the gradient distribution of pores 51 generates a Laplace pressure difference when the cooling oil is immersed, driving the oil droplets to spontaneously move from small pores 51 to large pores 51. Furthermore, the gradient porosity 51 further reduces the resistance to the flow of cooling oil into the oil cavity 3. This, combined with the gradient pore structure, enhances the self-driving ability of the oil droplets, allowing the captured cooling oil to flow autonomously from the bottom of the constant diameter section 41 into the oil cavity 3. This prevents cooling oil accumulation, ensures continuous cooling oil capture capability, and promotes the filling of the oil cavity 3 with cooling oil.

[0041] It should be noted that, since the pores 51 may be irregular pores, the size of all pores 51 in any pore layer 54 is approximately equal.

[0042] like Figure 4 As shown, in another embodiment, the direction from the second end to the first end is defined as the oil inlet direction. A plurality of medium regions 53 are formed on the porous medium 5, which are sequentially distributed along the oil inlet direction. Each medium region 53 includes a plurality of pore layers 54 sequentially distributed along the oil inlet direction. Within each medium region 53, along the oil inlet direction, the pore size 51 of the plurality of pore layers 54 increases in a gradient, and the gradient range of the pore size 51 is 0.3μm to 0.8μm. And / or, within each medium region 53, along the oil inlet direction, the porosity 51 of the plurality of pore layers 54 increases in a gradient, and the gradient range of the porosity 51 is 50% to 85%.

[0043] It should be noted that, as Figure 4 As shown, with Figure 4 The area within the two adjacent dashed lines is a medium region.

[0044] For ease of understanding, the multiple porous layers 54 of each medium region 53 can be sequentially divided into a first porous layer 54, a second porous layer 54, a third porous layer 54, ... a (N-1)th porous layer 54, and an Nth porous layer 54 along the oil inlet direction. In this embodiment, the pore size 51 of the multiple porous layers 54 in each medium region 53 increases in a gradient along the oil inlet direction. This can be understood as follows: within any medium region 53, the pore size 51 in the second porous layer 54 is larger than that in the first porous layer 54, the pore size 51 in the third porous layer 54 is larger than that in the second porous layer 54, and the pore size 51 in the Nth porous layer 54 is larger than that in the (N-1)th porous layer 54. Furthermore, the pore size gradient range is 0.3 μm to 0.8 μm. This can be interpreted as the pore size of the first pore layer 54 being 0.3 μm, the pore size of the Nth pore layer 54 being 0.8 μm, and the pore size gradually increasing from 0.3 μm to 0.8 μm. The porosity of the multiple pore layers 54 also exhibits a gradient increase. This can be interpreted as the porosity of the first pore layer 54 being 50%, the porosity of the Nth pore layer 54 being 85%, and the porosity gradually increasing from 50% to 85%.

[0045] This embodiment also enables the cooling oil to be self-driven, allowing the captured cooling oil to flow autonomously from the bottom of the equal diameter section 41 into the oil cavity 3, avoiding the accumulation of cooling oil, ensuring continuous cooling oil capture capability, and promoting the filling of the oil cavity 3 with cooling oil.

[0046] Preferably, the number of medium regions 53 in this embodiment is three.

[0047] In another embodiment, the direction from the second end to the first end is defined as the oil inlet direction. A plurality of medium regions 53 are formed on the porous medium 5, which are sequentially distributed along the oil inlet direction. Each medium region 53 includes a plurality of pore layers 54 sequentially distributed along the oil inlet direction. All pores 51 in each medium region 53 have the same size. Along the oil inlet direction, the size of pores 51 in the plurality of medium regions 53 increases in a gradient, and the gradient range of pore size 51 is 0.3μm to 0.8μm. And / or, along the oil inlet direction, the porosity 51 of the plurality of medium regions 53 increases in a gradient, and the gradient range of porosity 51 is 50% to 85%.

[0048] For ease of understanding, the multiple medium zones 53 can be divided along the oil inlet direction into a first medium zone 53, a second medium zone 53, ... a (N-1)th medium zone 53, and an Nth medium zone 53. The multiple pore layers 54 of each medium zone 53 can be sequentially divided into a first pore layer 54, a second pore layer 54, a third pore layer 54, ... a (N-1)th pore layer 54, and an Nth pore layer 54. Understandably, in this embodiment, all pores 51 in any medium region 53 have the same size, and the porosity 51 of each medium region 53 is fixed. For example, the size of all pores 51 in the first medium region 53 is 0.3 μm, and the overall porosity 51 of the first medium region 53 is 50%; the size of all pores 51 in the Nth medium region 53 is 0.8 μm, and the overall porosity 51 of the Nth medium region 53 is 85%; the porosity 51 of the first medium region 53 gradually increases from 50% to 85% to the overall porosity 51 of the Nth medium region 53, and the size of the pores 51 in the first medium region 53 gradually increases from 0.3 μm to 0.8 μm to the overall porosity 51 of the Nth medium region 53.

[0049] Preferably, in this embodiment, there are three medium regions 53. The pore size 51 of the first medium region 53 is 0.3 μm and the porosity 51 is 50%; the pore size 51 of the second medium region 53 is 0.5 μm and the porosity 51 is 70%; and the pore size 51 of the third medium region 53 is 0.7 μm and the porosity 51 is 85%.

[0050] Understandably, the gradient changes in the pore size and porosity of the multiple medium zones 53 mentioned above can also achieve self-driving of the cooling oil, so that the captured cooling oil can flow autonomously from the bottom of the equal diameter section 41 into the oil cavity 3, avoiding the accumulation of cooling oil, ensuring continuous cooling oil capture capability, and promoting the filling of the oil cavity 3 with cooling oil.

[0051] In one embodiment, the portion of the porous medium 5 other than the pores 51 is a porous framework 52, and a transition zone is formed on the porous framework 52 at the position between any two adjacent medium regions 53. The other regions on the porous framework 52 other than the transition zone are oleophilic regions. The contact angle of the oleophilic region is 30°~60°. And / or, along the oil inlet direction, the contact angle of the transition zone gradually changes from 120° to 10°.

[0052] Understandably, by setting a transition zone, and the contact angle of the transition zone gradually changes from 120° to 10° along the oil inlet direction, the wettability of the transition zone gradually changes from oleophobic to oleophilic along the oil inlet direction. The Young-Laplace force generated by this gradient wettability and the Laplace pressure difference generated by the gradient pore size 51 work together to strongly guide the oil droplets to the cooling oil cavity 3.

[0053] Furthermore, the porous framework 52, excluding the transition zone, is provided with oleophilic zones having a contact angle of 30° to 60° to facilitate the entry of impacted cooling oil droplets into the porous medium 5, promoting rapid adsorption and penetration of the oil droplets. In addition, this moderate oleophilicity ensures that the oil droplets can quickly spread and wet the porous medium 5 after impact, while avoiding the problem of excessive affinity causing the cooling oil to adhere and obstruct subsequent oil flow.

[0054] Specifically, the height of each medium region 53 is equal, and the height of the transition region is 0.15 to 0.25 times the height of the medium region 53.

[0055] It should be noted that the above implementation method can be achieved in the following way: First, a low surface energy perfluorosilane oleophobic coating is formed on the surface of the dielectric skeleton in the dielectric region 53 by vapor deposition. Then, microtexturing is performed at the transition region using femtosecond laser processing or micro / nano imprinting technology, and the fluorinated coating in this region is removed in a gradient manner along the oil inlet direction using laser ablation or masking technology. The exposed metal surface exhibits oleophilicity, thereby forming a transition region where the contact angle gradually changes from 120° to 10°. For the region outside the transition region, after the above process, an ultrathin polymer oleophilic coating (such as polyvinylpyrrolidone PVP) is coated by immersion to stabilize its contact angle within the preferred range of 30° to 60°.

[0056] like Figure 5 As shown, Figure 5 In the diagram, 'a' represents the temperature field distribution of a piston with a straight oil hole in the background technology after 10 cooling cycles. Figure 5 In Figure 'b', the temperature field distribution of the piston 100 in this embodiment after 10 cooling cycles is shown. It can be seen that the piston 100 in this embodiment has a maximum temperature 16.86 °C lower than the piston in the prior art, and a minimum temperature difference of 20.72 °C.

[0057] The present invention also proposes an internal combustion engine that uses the piston 100 as described above. The specific structure of the piston 100 is as described in the above embodiments. Since the internal combustion engine adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be described in detail here.

[0058] The above description is merely an exemplary embodiment of the present invention and does not limit the scope of protection of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A piston, characterized in that, A cavity is formed inside the piston. The top wall of the cavity protrudes to form an annular boss. The annular boss surrounds the inner wall of the cavity circumferentially. An annular oil cavity is formed near the top of the annular boss. Multiple oil collecting holes communicating with the oil cavity and the cavity are opened at the bottom of the annular boss. Each oil collecting hole includes an equal-diameter section and an expanding section that communicate with each other. The end of the equal-diameter section away from the expanding section communicates with the oil cavity. The end of the expanding section away from the equal-diameter section communicates with the cavity. The end of the expanding section connected to the equal-diameter section is the first end, and the other end is the second end. The expanding section is gradually widened from the first end to the second end. A porous medium is provided on the inner wall of the equal-diameter section circumferentially.

2. The piston as claimed in claim 1, characterized in that, The wall of the equal-diameter section is smoothly transitioned to the wall of the oil cavity, and the equal-diameter section has the same diameter as the first end, and the wall of the equal-diameter section is smoothly transitioned to the wall of the expansion section.

3. The piston as claimed in claim 1, characterized in that, The expansion angle of the expansion section from the first end to the second end is 5° to 20°; and / or, the maximum aperture of the expansion section is 8mm to 20mm, and the length of the equal diameter section is 2mm to 8mm.

4. The piston as claimed in claim 1, characterized in that, The porosity of the porous medium is 50% to 85%; and / or, the size of each pore in the porous medium is 0.3 μm to 0.8 μm.

5. The piston as claimed in claim 1, characterized in that, The porous medium completely covers the inner wall of the equal-diameter section circumferentially, and the radial thickness of the porous medium along the equal-diameter section is 0.2mm~1mm.

6. The piston as claimed in claim 1, characterized in that, The direction from the second end to the first end is defined as the oil inlet direction, and the porous medium includes multiple pore layers distributed sequentially along the oil inlet direction; Along the oil inlet direction, the pore size of the multiple pore layers increases in a gradient, and the gradient range of pore size is 0.3μm~0.8μm; And / or, along the oil inlet direction, the porosity of the plurality of pore layers increases in a gradient, and the gradient range of the porosity is 50% to 85%.

7. The piston as claimed in claim 1, characterized in that, The direction from the second end to the first end is defined as the oil inlet direction. Multiple medium regions are formed on the porous medium and are distributed sequentially along the oil inlet direction. Each medium region includes multiple pore layers distributed sequentially along the oil inlet direction. Within each of the medium regions, along the oil inlet direction, the pore size of the multiple pore layers increases in a gradient, and the gradient range of the pore size is 0.3μm~0.8μm; And / or, within each of the media regions, along the oil inlet direction, the porosity of the plurality of pore layers increases in a gradient, and the gradient range of the porosity is 50% to 85%.

8. The piston as claimed in claim 1, characterized in that, The direction from the second end to the first end is defined as the oil inlet direction. Multiple medium regions are formed on the porous medium and are distributed sequentially along the oil inlet direction. Each medium region includes multiple pore layers distributed sequentially along the oil inlet direction. All the pores in each medium region have the same size. Along the oil inlet direction, the pore size in the multiple medium zones increases in a gradient, and the gradient range of pore size is 0.3μm~0.8μm; And / or, along the oil inlet direction, the porosity of the plurality of medium zones increases in a gradient, and the gradient range of the porosity is 50% to 85%.

9. The piston as claimed in claim 7 or 8, characterized in that, The portion of the porous medium other than the pores is a porous skeleton, and a transition zone is formed on the porous skeleton between any two adjacent medium regions. Other regions on the porous skeleton other than the transition zone are oleophilic regions. The contact angle of the oleophilic region is 30°~60°; and / or, along the oil inlet direction, the contact angle of the transition region gradually changes from 120° to 10°.

10. An internal combustion engine, characterized in that, The internal combustion engine uses a piston as described in any one of claims 1 to 9.

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