A low-blow-gas, low-oil-consumption piston assembly suitable for hydrogen fuel cell engines

Abstract

This utility model discloses a low-blow-gas, low-oil-consumption piston assembly suitable for hydrogen fuel cell engines, including a piston ring assembly and a piston; the piston has a first ring groove and a second ring groove arranged sequentially from top to bottom; the piston ring assembly includes a top ring and an oil scraper ring, which are respectively disposed in the first ring groove and the second ring groove; the top ring includes a ring body and a scraper, the lower end face of the ring body has a first groove that runs through the circumference, which extends from the outer edge of the ring body inward for embedding the scraper, and the scraper can extend and retract radially along the first groove; the ring body and the scraper are respectively provided with a first and a second opening that runs through the radial and axial directions, and the offset angle α of the two openings on the circumference satisfies 90°≤α≤180°; the outer circular surface of the oil scraper ring is a combination of a vertical surface and a conical surface, and the vertical surface is located below the conical surface; the height g of the vertical surface satisfies 0.1mm≤g≤0.7mm; the conical surface is inclined from the vertical surface towards the center of the oil scraper ring, and the inclination angle γ satisfies 1.5°≤γ≤2.5°; and the inner side of the oil scraper ring near the upper end face has a triangular notch.

Description

Technical Field

[0001] This utility model relates to the field of hydrogen fuel cell engine technology, and in particular to a low-blow-gas and low-oil-consumption piston assembly suitable for hydrogen fuel cell engines. Background Technology

[0002] With the rapid development of the new energy vehicle industry, hydrogen engines have become an important development direction for automotive power systems due to their significant advantages such as zero carbon emissions, high energy density, and excellent combustion efficiency. However, the special operating conditions of hydrogen engines place stringent requirements on the performance of core components: on the one hand, hydrogen fuel burns rapidly, with in-cylinder explosion pressures as high as 10-18 MPa, and frequent pressure fluctuations can easily lead to an increase in the sealing gap between the piston rings and cylinder liners, causing high-pressure gas to leak into the crankcase (i.e., blow-by); on the other hand, hydrogen combustion products contain a large amount of water vapor, which easily condenses under low-load conditions (such as idling). When mixed with residual engine oil on the cylinder wall, it forms carbon deposits, which not only hinder piston ring movement but also accelerate component wear, further deteriorating the sealing effect and increasing oil consumption, seriously affecting the engine's power performance, reliability, and service life. In addition, the hydrogen embrittlement effect exacerbates the risk of cracking at stress concentration points in metal materials, and the structural design of traditional piston ring assemblies is difficult to balance sealing reliability, resistance to hydrogen embrittlement, and carbon deposit suppression requirements.

[0003] In existing technologies, piston ring assemblies typically include a top ring (compression ring) and an oil scraper ring. The top ring is primarily responsible for gas sealing, while the oil scraper ring is mainly responsible for scraping oil from the cylinder wall. However, traditional top rings often employ a single annular structure, and the opening design results in a single sealing channel. Even with staggered openings, it is difficult to effectively block the flow path of high-pressure gas. Oil scraper rings, on the other hand, are mostly single conical or vertical structures, separating oil scraping and sealing functions. The design of the conical angle and vertical height lacks specificity, leading to either insufficient oil scraping efficiency or poor sealing performance. Furthermore, the issues of water vapor retention and carbon buildup under hydrogen combustion conditions are not considered. Simultaneously, the cooperation between the top ring and the oil scraper ring lacks synergistic optimization. The structural strength of the top ring and the wall-adhering performance of the oil scraper ring are difficult to adapt to high-pressure fluctuations and high-frequency vibrations, resulting in persistently high blow-by rates and oil consumption. In addition, existing structures are insufficiently designed to address hydrogen embrittlement effects, making components prone to cracking under high pressure and stress concentration, failing to meet the requirements for long-term stable operation of hydrogen combustion engines. Therefore, there is an urgent need for a piston ring assembly structure that can adapt to the special operating conditions of hydrogen-fired engines and take into account low blow-by, low oil consumption, resistance to hydrogen embrittlement, and resistance to carbon deposits, in order to solve the above-mentioned defects of existing technologies.

[0004] The above background information is provided only to aid in understanding the concept and technical solution of this utility model. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above information was disclosed on the filing date of this patent application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Utility Model Content

[0005] The purpose of this invention is to propose a low-blow-gas and low-oil-consumption piston assembly suitable for hydrogen fuel cell engines, in order to solve the technical problems of insufficient piston ring sealing reliability, high blow-gas volume and oil consumption rate, carbon buildup and sticking, and weak resistance to hydrogen embrittlement in the prior art.

[0006] Therefore, this utility model proposes a piston assembly with low blow-by and low oil consumption suitable for hydrogen fuel cell engines.

[0007] Preferably, the present invention may also have the following technical features:

[0008] A low-blow-gas, low-oil-consumption piston assembly suitable for hydrogen fuel cell engines includes a piston ring assembly and a piston.

[0009] The piston is provided with a first annular groove and a second annular groove from top to bottom;

[0010] The piston ring assembly includes a top ring and an oil scraper ring, wherein the top ring is disposed in the first ring groove and the oil scraper ring is disposed in the second ring groove;

[0011] The top ring includes a ring body and a scraper. The lower end face of the ring body is provided with a first groove that runs through the circumference. The first groove extends from the outer edge of the ring body inward. The first groove is used to embed the scraper, and the scraper can extend and retract radially along the first groove. The ring body and the scraper are respectively provided with a first opening and a second opening that both penetrate radially and axially. The circumferential offset angle α between the first opening and the second opening satisfies 90°≤α≤180°.

[0012] The outer circular surface of the oil scraper ring is a combination structure of a vertical surface and a conical surface, and the vertical surface is located below the conical surface; the height of the vertical surface is g, and g satisfies 0.1mm≤g≤0.7mm; the conical surface is inclined from the vertical surface towards the center of the oil scraper ring, and its inclination angle is γ, which satisfies 1.5°≤γ≤2.5°; and the inner side of the oil scraper ring near the upper end face is provided with a triangular notch.

[0013] Preferably, the oil scraper ring has a transition fillet R between its conical surface and vertical surface, and the transition fillet R satisfies 0.1mm≤R≤0.3mm.

[0014] Preferably, the axial thickness of the oil scraper ring is D, the first side length e of the triangular notch satisfies 0.2D≤e≤0.4D, the second side length f satisfies 0.2D≤f≤0.4D, and e=f.

[0015] Preferably, the oil scraper ring is made of stainless steel or ductile iron, and its outer surface is provided with a nitrided layer or a DLC-type coating.

[0016] Preferably, the surface roughness Ra of the conical and vertical surfaces of the oil scraper ring is ≤0.8μm.

[0017] Preferably, the scraper blade and the first groove are in a transition fit with a clearance of 0.01~0.03mm.

[0018] The beneficial effects of this utility model compared with the prior art include:

[0019] 1. The top ring of this utility model forms a first labyrinth seal through a combination structure of "ring body + scraper" and an opening staggered design of 90°≤α≤180°, initially intercepting high-pressure gas in the cylinder of a hydrogen fuel cell engine; the oil scraper ring has a combination structure of "conical surface on top and vertical surface on the bottom". The upper conical surface uses an inclination angle of 1.5°≤γ≤2.5° to elastically fit with the inner wall of the cylinder liner, providing a secondary seal for the small amount of gas that is not blocked by the top ring. The inner triangular notch further enhances the wall-fitting effect when the oil scraper ring moves upward, eliminating sealing gaps; the lower vertical surface precisely matches the inner wall of the second ring groove to form a third rigid sealing barrier. The three work together to achieve a graded seal of "labyrinth interception - elastic fit - rigid blocking". The amount of gas leakage is reduced compared with the traditional structure, and it is better adapted to the harsh operating conditions of high-pressure fluctuations in hydrogen fuel cell engines.

[0020] 2. The conical surface of the oil scraper ring of this utility model is located at the top, which perfectly matches the oil scraping movement direction when the piston moves upward. When the piston moves upward, the edge of the conical surface can efficiently scrape off the oil adhering to the cylinder wall, preventing the oil from entering the combustion chamber with the gas. The inward tilt angle design of the conical surface guides the scraped oil to slide down the conical surface to the lower vertical surface, and then quickly flow back to the oil pan through the gap between the vertical surface and the ring groove, solving the pain point of "oil retention" in traditional oil scraper rings.

[0021] 3. The large amount of water vapor produced by the combustion of hydrogen fuel cells easily condenses in the annular groove, mixing with the engine oil to form carbon deposits. The structure of the scraper ring of this invention, with the conical surface on top and the vertical surface on the bottom, allows the condensed water and scraped engine oil to flow back quickly along the continuous path of the conical surface and the vertical surface, avoiding long-term stagnation in the annular groove. The inner triangular notch not only provides an additional channel for fluid return, but the size range of 0.2D≤e / f≤0.4D also provides a return channel for the engine oil in the second annular groove where the scraper ring is located. The reasonable size range avoids the notch being too small, which would cause engine oil to accumulate in the second annular groove. The groove is designed to prevent poor flow and oil buildup, while ensuring rapid oil return to the crankcase. Combined with the scraping action of the vertical surface of the oil scraper ring and the sealing action of the conical surface, an independent closed loop of "oil scraping-sealing-flow guidance" is formed in the second ring groove, without relying on the structural assistance of the first ring groove where the top ring is located. This size range is strictly matched to the axial thickness D of the oil scraper ring, so that the inner structural strength of the oil scraper ring is not weakened by the gap being too large (avoiding its breakage due to stress concentration during high-frequency reciprocating motion), and the dead corner for carbon accumulation is not formed by the gap being too deep, thus reducing the risk of carbon accumulation from a structural perspective.

[0022] 4. The elastically fitted structure of the top ring, consisting of a ring body and a scraper, can absorb the impact of high-pressure fluctuations through the radial expansion and slight axial movement of the scraper, avoiding local stress concentration in the ring body. The combined structure of the oil scraper ring, consisting of a conical surface and a vertical surface, allows the high-pressure gas force to be evenly distributed throughout the ring body along the conical surface (1.5°≤γ≤2.5°), resulting in better force balance and reduced stress peaks compared to a single structure. The layout of the inner triangular notch optimizes the stress distribution inside the ring body, preventing stress concentration in the notch area due to abrupt changes in rigidity. Simultaneously, the staggered angle of 90°≤α≤180° between the first and second openings of the top ring reduces the local force of gas impact on the opening edges, further reducing the risk of stress concentration. Through a balanced force design, the overall structure effectively resists the hydrogen embrittlement effect of hydrogen-fueled engines, reduces the probability of cracking, reduces component wear, extends the service life of piston assemblies, and meets the long-term high-frequency operation requirements of hydrogen-fueled engines. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the piston assembly according to a specific embodiment of the present invention.

[0024] Figure 2 This is a top view of the top ring according to a specific embodiment of this utility model.

[0025] Figure 3 This is a cross-sectional view of the top ring according to a specific embodiment of this utility model.

[0026] Figure 4 This is a specific embodiment of the present utility model. Figure 3 Enlarged diagram of point A in the middle.

[0027] Figure 5 This is a top view of the oil scraping ring according to a specific embodiment of this utility model.

[0028] Figure 6 This is a specific embodiment of the present utility model. Figure 5 Enlarged diagram of point B in the middle.

[0029] Explanation of reference numerals in the attached drawings: 1-Top ring; 11-Ring body; 111-First groove; 112-First opening; 12-Scraper; 121-Second opening; 2-Oil scraper ring; 21-Vertical surface; 22-Conical surface; 23-Triangular notch; 3-Piston; 31-First ring groove; 32-Second ring groove. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to specific embodiments and the accompanying drawings. It should be emphasized that the following description is merely exemplary and is not intended to limit the scope and application of the present invention.

[0031] Non-limiting and non-exclusive embodiments will be described with reference to the following figures, wherein the same reference numerals denote the same parts unless otherwise specifically stated.

[0032] This embodiment provides a low-blow-gas, low-oil-consumption piston assembly suitable for hydrogen fuel cell engines. The following is in conjunction with the attached... Figures 1-6 This application provides a further detailed description of its technical solution. This application and the "Piston Assembly with Combined Piston Ring and Unloading Groove Structure" submitted by the applicant on the same day are complementary technical solutions. The former's core innovation is based on the "piston ring land unloading groove + combined top ring," which uses the unloading groove to relieve the upward thrust of high-pressure gas on the top ring and the combined top ring to enhance sealing and fit. These two technologies work together to solve the problems of high-pressure floating of the top ring and increased sealing gap. This application focuses on the collaborative sealing and oil-scraping design of "combined top ring 1 + oil scraper ring 2," solving the technical problems of secondary sealing and efficient oil scraping. Both applications address different pain points in hydrogen fuel cell engines under different operating conditions, and their technical paths are completely independent. The specific structure of the piston assembly in this application is as follows:

[0033] The piston assembly includes a piston ring assembly and a piston 3. The piston 3 has a first annular groove 31 and a second annular groove 32 arranged sequentially from top to bottom. The piston ring assembly includes a top ring 1 and a scraper ring 2. The top ring 1 is disposed within the first annular groove 31, and the scraper ring 3 is disposed within the second annular groove 32. The top ring 1 includes a ring body 11 and a scraper 12. The lower end face of the ring body 11 has a first groove 111 extending circumferentially. The first groove 111 extends inward from the outer edge of the ring body 11 and is used to embed the scraper 12, using a transition fit with a clearance of 0.01~0.03mm. The scraper 12 can extend and retract radially along the first groove 111. This elastic embedding structure is achieved through the opening of the scraper 12 itself... The elasticity of the opening eliminates the need for additional elastic components, simplifying the structure while improving reliability. The ring body 11 and the scraper 12 are respectively provided with a first opening 112 and a second opening 121 that penetrate both radially and axially. The circumferential offset angle α between the first opening 112 and the second opening 121 satisfies 90°≤α≤180°. The outer circular surface of the scraper ring 2 is a combination of a vertical surface 21 and a conical surface 22, with the vertical surface 21 located below the conical surface 22. The height of the vertical surface 21 is g, satisfying 0.1mm≤g≤0.7mm. The conical surface 22 is inclined from the vertical surface 21 towards the center of the scraper ring 2, with an inclination angle γ satisfying 1.5°≤γ≤2.5°. A triangular notch 23 is provided on the inner side of the scraper ring 2 near its upper end face.

[0034] In this embodiment, as Figure 1 and 2As shown, the offset angle α between the first opening 112 and the second opening 121 satisfies 90°≤α≤180°. It should be noted that after the top ring 1 is assembled, the scraper 12 and the first groove 111 of the ring body 11 form an embedded fit. This structural design allows the scraper 12 to extend and retract only in the radial direction of the first groove 111 to adapt to the cylinder wall clearance. The circumferential fit between the scraper 12 and the first groove 111 has no relative displacement space. Therefore, the offset angle α between the first opening 112 of the ring body 11 and the second opening 121 of the scraper 12 on the circumference almost remains at the assembly setting value and will not change with the reciprocating motion of the piston 2. Specifically, the appropriate model can be selected based on the vehicle's operating conditions to suit the usage needs of different hydrogen-powered vehicles. For example, for low-load vehicles primarily used for low-speed, short-distance travel (such as hydrogen-powered small urban commuter vehicles and short-distance delivery minivans), a top ring 1 with α=100°~110° can be selected. At this angle, the engine gas pressure is relatively low. This angle can both block direct gas leakage by staggering the openings and ensure the radial extension and retraction flexibility of the scraper 12, reducing structural rigidity redundancy and frictional power consumption. For medium-load vehicles that balance urban commuting and high-speed driving (such as hydrogen-powered compact family cars), the appropriate model can be selected. For SUVs, mid-size sedans, and intercity logistics light trucks, a top ring of α=120°~130° can be selected, balancing sealing performance and structural adaptability, stably withstanding medium gas pressure, and suitable for most common usage scenarios. For high-load vehicles with long-term heavy loads and high power output (such as hydrogen-powered heavy-duty freight trucks, engineering vehicles, and high-power commercial vehicles), a top ring of α=150°~160° can be selected. This extends the gas leakage path through a larger circumferential offset distance, improving sealing redundancy and effectively resisting the risk of gas leakage under high gas pressure. All angle selections are based on the structural characteristic that α remains constant after top ring assembly, and the angle range avoids interference at the opening edge, ensuring the proper functioning of the scraper extension and retraction function, and achieving precise matching of sealing performance for different vehicle types under different operating conditions.

[0035] In this embodiment, as Figure 1 , 5 As shown in Figure 6, the oil scraper ring 2 is located in the second ring groove 32 of the piston 3. Its outer circular surface adopts a combination structure of vertical surface 21 and conical surface 22, and the vertical surface 21 is located below the conical surface 22, forming a coordinated functional layout of upper oil scraping and lower sealing, which is suitable for the high water vapor and high blow-by risk of hydrogen fuel cell engines.

[0036] like Figure 1 , 5As shown in Figure 6, the oil scraper ring 2 is integrally forged and then precision ground. The conical surface 22 of the outer circular surface is located at the upper end, and the vertical surface 21 is located at the lower end. A transition fillet R is provided at the junction of the two, which satisfies 0.1mm≤R≤0.3mm, preferably R=0.2mm. This fillet can make the stress transmission between the conical surface 22 and the vertical surface 21 more uniform. Through finite element analysis, the stress concentration is reduced by 60% compared with the design without fillet, significantly improving the resistance to hydrogen embrittlement. The height of the vertical surface 21 is g, which satisfies 0.1mm≤g≤0.7mm, preferably g=0.4mm. This height ensures that the vertical surface 21 fits tightly with the lower wall of the second ring groove 32, forming a rigid sealing barrier to block the path of gas flowing downward into the crankcase, and also avoids the increase in the movement resistance of the oil scraper ring 2 caused by the vertical surface 21 being too high. Preferably, the inward tilt angle of the conical surface 22 is γ=2°, which is perfectly matched with the upward direction of the piston 3, and the oil scraping efficiency is improved by 35% compared with γ=1°.

[0037] The conical surface 22 and vertical surface 21 of the oil scraper ring 2 are made by ultra-precision grinding, and the surface roughness meets Ra≤0.8μm, preferably Ra=0.6μm. The low roughness can reduce the adsorption and residue of engine oil on the surface. Combined with the tilt angle of the conical surface 22, the speed at which the scraped engine oil slides down the surface is increased by 25%, avoiding mixing with the water vapor generated by hydrogen combustion to form carbon deposits.

[0038] like Figure 1 , 5 As shown in Figure 6, the axial thickness of the oil scraper ring 2 is D. The first side length e of the triangular notch 23 satisfies 0.2D≤e≤0.4D, the second side length f satisfies 0.2D≤f≤0.4D, and e=f. The triangular notch 23 provides a dedicated return channel for the oil in the second annular groove 32 where the oil scraper ring 2 is located. The reasonable size range avoids the oil from being too small, which would cause poor flow and accumulation in the second annular groove 32, while ensuring that the oil can quickly return to the crankcase. Combined with the oil scraping action of the vertical surface 21 of the oil scraper ring 2 and the sealing action of the conical surface 22, an independent closed loop of "oil scraping-sealing-flow guiding" is formed in the second annular groove 32, without relying on the structural assistance of the top ring 1 in the first annular groove 31. This size range strictly matches the axial thickness D of the oil scraper ring 2, so that the strength of the inner structure of the oil scraper ring 2 is not weakened by the notch being too large (avoiding its fracture due to stress concentration during high-frequency reciprocating motion), and the dead angle for carbon accumulation is not formed by the notch being too deep, thus reducing the risk of carbon accumulation from a structural perspective. The oil scraper ring 2 is made of stainless steel or ductile iron, and its outer circular surface (including the conical surface 22 and the vertical surface 21) is provided with a nitrided layer or a DLC-type coating.

[0039] Those skilled in the art will recognize that numerous variations are possible with respect to the above description, and the embodiments and figures are merely for describing one or more specific implementations.

[0040] Although exemplary embodiments of the present invention have been described and illustrated, those skilled in the art will understand that various changes and substitutions can be made thereto without departing from the spirit of the present invention. Furthermore, many modifications can be made to adapt specific situations to the doctrine of the present invention without departing from the central concept of the present invention described herein. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but may include all embodiments and equivalents that fall within the scope of the present invention.

Claims

1. A low-blow-gas, low-oil-consumption piston assembly suitable for hydrogen-fired engines, characterized in that: Includes piston ring assembly and piston; The piston is provided with a first annular groove and a second annular groove from top to bottom; The piston ring assembly includes a top ring and an oil scraper ring, wherein the top ring is disposed in the first ring groove and the oil scraper ring is disposed in the second ring groove; The top ring includes a ring body and a scraper. The lower end face of the ring body is provided with a first groove that runs through the circumference. The first groove extends from the outer edge of the ring body inward. The first groove is used to embed the scraper, and the scraper can extend and retract radially along the first groove. The ring body and the scraper are respectively provided with a first opening and a second opening that both penetrate radially and axially. The circumferential offset angle α between the first opening and the second opening satisfies 90°≤α≤180°. The outer circular surface of the oil scraper ring is a combination structure of a vertical surface and a conical surface, and the vertical surface is located below the conical surface; the height of the vertical surface is g, and g satisfies 0.1mm≤g≤0.7mm; the conical surface is inclined from the vertical surface towards the center of the oil scraper ring, and its inclination angle γ satisfies 1.5°≤γ≤2.5°; and the inner side of the oil scraper ring near the upper end face is provided with a triangular notch.

2. The low-blow-gas, low-oil-consumption piston assembly for hydrogen-fired engines according to claim 1, characterized in that: The oil scraper ring has a transition fillet R between its conical surface and vertical surface, and the transition fillet R satisfies 0.1mm≤R≤0.3mm.

3. The low-blow-gas, low-oil-consumption piston assembly for hydrogen-fired engines according to claim 1, characterized in that: The axial thickness of the oil scraper ring is D. The first side length e of the triangular notch satisfies 0.2D≤e≤0.4D, the second side length f satisfies 0.2D≤f≤0.4D, and e=f.

4. The low-blow-gas, low-oil-consumption piston assembly for hydrogen-fired engines according to claim 1, characterized in that: The oil scraper ring is made of stainless steel or ductile iron, and its outer surface is provided with a nitrided layer or a DLC-type coating.

5. The low-blow-gas, low-oil-consumption piston assembly for hydrogen-fired engines according to claim 1, characterized in that: The surface roughness Ra of the conical and vertical surfaces of the oil scraper ring is ≤0.8μm.

6. The low-blow-gas, low-oil-consumption piston assembly for hydrogen-fired engines according to claim 1, characterized in that: The scraper blade and the first groove are fitted with a transition fit, with a fit clearance of 0.01~0.03mm.

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