Piston assembly, cylinder body, engine and vehicle

Abstract

The utility model relates to a piston assembly, a cylinder body, an engine and a vehicle, and the piston assembly comprises a body part, an oil ring assembly and a gas ring; an oil ring groove and an air ring groove are formed in the peripheral wall of the body part at intervals in the axial direction, the oil ring assembly is installed in the oil ring groove, and the air ring is installed in the air ring groove. The oil ring assembly comprises an upper scraping piece, a lining ring and a lower scraping piece which are sequentially arranged in a stacked mode, and the upper scraping piece is arranged towards one side of the gas ring. An opening of the gas ring, an opening of the upper scraper, an opening of the bushing ring and an opening of the lower scraper are arranged in a staggered mode at intervals in the circumferential direction of the body part. By limiting the positions of the openings of the air rings in the piston assembly and the openings of the upper scraping piece, the bushing ring and the lower scraping piece of the oil ring assembly, the sealing performance of the oil ring assembly is improved, the air leakage amount is effectively reduced, and oil consumption is reduced.

Description

Technical Field

[0001] This application relates to the field of piston technology, specifically to a piston assembly, cylinder block, engine, and vehicle. Background Technology

[0002] Piston assemblies include compression rings and oil rings. For ease of installation, compression rings and oil rings are provided with openings. If the positions of the openings of compression rings and oil rings are not restricted during installation, at least some of the openings may be close together in the circumferential direction, resulting in a short blow-by path. This leads to poor sealing performance, large leakage, and increased oil consumption in the piston assembly.

[0003] Therefore, how to improve the sealing performance of piston assemblies, reduce the leakage of piston assemblies, and thus reduce oil consumption is a technical problem that urgently needs to be solved by those skilled in the art. Utility Model Content

[0004] The purpose of this application is to provide a piston assembly, cylinder block, engine, and vehicle that improves the sealing performance of the oil ring assembly by limiting the positions of the openings of each compression ring in the piston assembly and the openings of the upper scraper, bushing, and lower scraper of the oil ring assembly, thereby effectively reducing air leakage and lowering fuel consumption.

[0005] To solve the above-mentioned technical problems, this application provides a piston assembly, including a body, an oil ring assembly, and a gas ring; the outer peripheral wall of the body is provided with an oil ring groove and a gas ring groove spaced apart along the axial direction, the oil ring assembly is installed in the oil ring groove, and the gas ring is installed in the gas ring groove; the oil ring assembly includes an upper scraper, a bushing ring, and a lower scraper stacked sequentially, the upper scraper being disposed on the side facing the gas ring; the openings of the gas ring, the upper scraper, the bushing ring, and the lower scraper are staggered along the circumferential direction of the body.

[0006] The openings of the piston ring, the upper scraper, the bushing, and the lower scraper are all staggered along the circumferential direction of the body, so that any two openings at any position are staggered in the axial direction of the body. This arrangement increases the length of the blow-by path formed by any two openings on the outer peripheral wall of the body, reduces air leakage, improves the sealing performance of the piston assembly, and thus reduces fuel consumption.

[0007] Optionally, the projection of the center plane of the opening onto the reference plane forms a projection line, and the included angle between the projection lines corresponding to two adjacent openings is not less than 45°, and the reference plane is perpendicular to the axis of the body.

[0008] Optionally, the air rings include at least two, and the included angle between the projection lines corresponding to the openings of two adjacent air rings is in the range of 150°-180°.

[0009] Optionally, the angle between the projection lines corresponding to any two openings is not less than 45°.

[0010] Optionally, the lower part of the body is provided with grooves on opposite sides in the radial direction, and the body is provided with pin holes that penetrate the bottom of the grooves.

[0011] Optionally, there are two air rings, namely a first air ring and a second air ring; the projection of the center plane of the opening of the first air ring onto the reference plane forms a first projection line, the projection of the center plane of the opening of the second air ring onto the reference plane forms a second projection line, the projection of the center plane of the opening of the upper scraper onto the reference plane forms a third projection line, the projection of the center plane of the opening of the bushing onto the reference plane forms a fourth projection line, the projection of the center plane of the opening of the lower scraper onto the reference plane forms a fifth projection line, and the projection of the axis of the pin hole onto the reference plane forms a sixth projection line; among the six projection lines, the included angle between two adjacent projection lines is 90°, 180°, 135°, 45°, and 135° respectively.

[0012] Optionally, the gas ring groove is further provided with a positioning part corresponding to the opening of the gas ring;

[0013] And / or, the oil ring groove is provided with positioning parts corresponding to the openings of the upper scraper, the liner ring, and the lower scraper, respectively.

[0014] Optionally, the outer peripheral wall of the main body is further provided with an oil guide groove along the circumferential direction. The oil guide groove is located below the oil ring groove, and the depth of the oil guide groove is less than the depth of the oil ring groove. The side wall of the oil ring groove facing the oil guide groove is provided with a plurality of oil return grooves at intervals along the circumferential direction. The oil return grooves are connected between the oil guide groove and the oil ring groove.

[0015] Optionally, the top end face of the body is further provided with a clearance groove for avoiding the valve.

[0016] This application also provides a cylinder block including the piston assembly described above.

[0017] This application also provides an engine, including the cylinder block as described above.

[0018] This application also provides a vehicle including the engine described above.

[0019] The technical effects of the cylinder block with the above-mentioned piston assembly, the engine with the above-mentioned cylinder block, and the vehicle with the above-mentioned engine are similar to those of the above-mentioned piston assembly, and will not be described in detail here for the sake of brevity. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of a piston assembly provided in an embodiment of this application;

[0021] Figure 2 yes Figure 1 Front view of the main body section;

[0022] Figure 3 yes Figure 2 Top view;

[0023] Figure 4 yes Figure 1 Exploded view of the gas ring and oil ring assembly.

[0024] Appendix Figures 1-4 The reference numerals in the attached figures are explained as follows:

[0025] 1 Body section, 11 First air ring groove, 12 Second air ring groove, 13 Oil ring groove, 14 Oil guide groove, 15 Oil return groove, 16 Groove section, 17 Pin hole, 18 Groove, 19 Clearance groove.

[0026] 2. First air ring;

[0027] 3. Second air ring;

[0028] 4. Oil ring assembly, 41. Upper scraper, 42. Bushing, 43. Lower scraper;

[0029] a. First projection line, b. Second projection line, c. Third projection line, d. Fourth projection line, e. Fifth projection line, f. Sixth projection line;

[0030] S-datum plane. Detailed Implementation

[0031] To enable those skilled in the art to better understand the technical solutions of this application, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] This application provides a piston assembly, a cylinder block, an engine, and a vehicle. The vehicle includes the aforementioned engine, which provides power to the vehicle. The engine includes a cylinder block, and the cylinder block includes a piston assembly. The piston assembly is a core component within the engine. Figure 1 As shown, the piston assembly includes a body 1, an oil ring assembly 4, and a compression ring. The compression ring is positioned above the oil ring assembly 4 and primarily functions as a seal to prevent cylinder leakage. It also conducts heat from the top of the piston assembly to the engine cylinder liner, where it is then carried away by the coolant. The oil ring assembly 4 itself can store some engine oil for lubricating the cylinder liner and can also scrape off excess oil from the cylinder liner.

[0033] The upper part of the main body 1 is a cylindrical structure. The outer peripheral wall of the upper part of the main body 1 is provided with multiple oil ring grooves 13 and gas ring grooves at intervals along the axial direction. Both the oil ring grooves 13 and the gas ring grooves are arranged circumferentially along the cylindrical section, and the gas ring grooves are all located on the upper side of the oil ring grooves 13. Among them, the oil ring assembly 4 is installed in the oil ring groove 13, and the gas ring is located in the gas ring groove.

[0034] The oil ring assembly 4 includes an upper scraper 41, a bushing 42, and a lower scraper 43 arranged in sequence. The upper scraper 41 is positioned facing the gas ring, while the lower scraper 43 is located on the side away from the gas ring. The upper scraper 41, bushing 42, and lower scraper 43 each have an opening in the circumferential direction to facilitate fitting into the oil ring groove 13.

[0035] The openings of the compression ring, the upper scraper 41, the bushing 42, and the lower scraper 43 are staggered along the circumferential direction of the body part 1. In other words, any two openings at any position are staggered in the axial direction of the body part 1. This arrangement increases the length of the blow-by path formed by any two openings on the outer peripheral wall of the body part 1, reduces air leakage, improves the sealing performance of the piston assembly, and thus reduces fuel consumption.

[0036] In this embodiment, the number of air rings is not limited, but preferably there are at least two air rings. Each air ring is located above the oil ring assembly. The number of air ring grooves is the same as the number of air rings and is set accordingly. The openings of each air ring, as well as the openings of the upper scraper 41, the liner ring 42, and the lower scraper 43, are arranged at intervals along the circumferential direction of the body part 1.

[0037] like Figure 1 The piston assembly shown includes two compression rings: a first compression ring 2 and a second compression ring 3. The body 1 has two compression ring grooves: a first compression ring groove 11 and a second compression ring groove 12. The first compression ring 2 is installed in the first compression ring groove 11, and the second compression ring 3 is installed in the second compression ring groove 12. The number of compression rings can be three, four, or more. The number of compression ring grooves in the body 1 corresponds to the number of compression rings, with each compression ring corresponding to its respective groove. Each compression ring has an opening in its circumferential direction to facilitate fitting into the corresponding compression ring groove.

[0038] The use of two compression rings simplifies the overall structure while ensuring sealing, and also reduces the resistance of the piston assembly during movement within the cylinder liner. For ease of explanation, the following description will use an example where there are two compression rings, namely the first compression ring 2 and the second compression ring 3, and the body part 1 has two compression ring grooves, the first compression ring groove 11 and the second compression ring groove 12.

[0039] The angle between the projections of the center planes of two adjacent openings onto the reference plane S is not less than 45°. The opening is formed between two side walls, and the center plane of the opening is equidistant from the two side walls. The reference plane S is a plane perpendicular to the axis of the main body 1. The center plane of the opening passes through the axis of the main body 1 and is perpendicular to the reference plane S. Therefore, the projection of the center plane of the opening onto the reference plane S can form a projection line.

[0040] The projection line corresponding to the opening of the first air ring 2 is defined as the first projection line a, the projection line corresponding to the opening of the second air ring 3 is defined as the second projection line b, the projection line corresponding to the opening of the upper scraper 41 is defined as the third projection line c, the projection line corresponding to the opening of the liner ring 42 is defined as the fourth projection line d, and the projection line corresponding to the opening of the lower scraper 43 is defined as the fifth projection line e.

[0041] Taking the openings of the first gas ring 2 and the second gas ring 3, which are arranged adjacently, as an example, the angle between the projection lines formed by the projection of the center planes of the two gas ring openings onto the reference plane S is not less than 45°, that is, the angle between the first projection line a and the second projection line b is not less than 45°. Specifically, it can be 45°, 90°, 120°, 135°, 150°, 180°, etc. After the gas passes through the opening of the first gas ring 2, it needs to flow circumferentially along the outer peripheral wall of the body part 1 to the location of the opening of the second gas ring 3. The larger the angle, the longer the gas leakage path. When the angle between the projection lines corresponding to the two adjacent openings is set to not exceed 45°, the length of the gas leakage path can be extended, the difficulty of the gas passing through each opening can be increased, and thus the sealing performance of the piston assembly can be improved.

[0042] If the angle between the first projection line a and the second projection line b is less than 45°, such as 30° or 15°, the gas leakage path formed between the opening of the first gas ring 2 and the opening of the second gas ring 3 along the outer peripheral wall of the body part 1 is relatively short, and the sealing performance of the piston assembly is relatively poor.

[0043] Therefore, the piston assembly provided in this embodiment, by limiting the position of each opening, can extend the blow-by path, improve the sealing performance of the sealing assembly, reduce the amount of leakage, and thus reduce engine fuel consumption and improve engine performance.

[0044] Furthermore, the angle between the projections of the center planes of any two openings onto the reference plane S is not less than 45°. The "any two openings" mentioned here include two openings spaced apart along the axial direction of the body part 1, such as the opening of the first air ring 2 and the opening of the upper scraper 41, the opening of the first air ring 2 and the opening of the liner ring 42, the opening of the first air ring 2 and the opening of the lower scraper 43, etc., which will not be listed one by one here.

[0045] During movement, the outer edge of the second gas ring 3 can adhere tightly to the inner wall of the cylinder liner to ensure sealing. If the outer edge of the second gas ring 3 has a defect due to machining errors or other reasons, the sealing performance between the defect location and the cylinder liner will be relatively weak. In this case, if the angle between the first projection line a and the third projection line c is less than 45°, such as 30° or 15°, and at least part of the defect location is in the circumferential direction of the body part 1, located between the opening of the first gas ring 2 and the opening of the upper scraper 41, the blow-by path formed by the opening of the first gas ring 2, the defect location, and the opening of the upper scraper 41 will be shorter.

[0046] The angle between the first projection line a and the third projection line c is not less than 45°, such as 45°, 90°, 135°, 150°, or 180°. The distance between the opening of the first gas ring 2 and the opening of the upper scraper 41 is relatively large, which makes the gas leakage path formed by the opening of the first gas ring 2, the defect location, and the opening of the upper scraper 41 relatively long, further improving the sealing performance of the piston assembly.

[0047] The angle between the projection lines corresponding to the openings of two adjacent air rings is in the range of 150°-180°. For example, the angle between the first projection line a and the second projection line b can be 150°, 160°, 170°, or 180°. The air rings mainly serve a sealing function. The larger the angle between the projection lines corresponding to the openings of two adjacent air rings, the longer the gas leakage path formed by passing through the openings of these two air rings. Figure 3 and Figure 4 As shown, the angle between the first projection line a and the second projection line b is 180°. Compared with schemes where the angle between the first projection line a and the second projection line b is set to 100° or less than 150°, this setting can further extend the gas leakage path formed between the opening of the first gas ring 2 and the opening of the second gas ring 3, thereby improving the sealing performance of the piston assembly.

[0048] like Figure 1 and Figure 2 As shown, the upper part of the main body 1 is provided with a gas ring groove, an oil ring groove 13 and an oil guide groove 14. The radially opposite side walls of the lower part of the main body 1 are respectively provided with grooves 16, and the groove openings of the two grooves 16 are opposite in direction. A pin hole 17 is provided through the lower part of the main body 1. The pin hole 17 passes through the bottom of the two grooves 16, and the axis of the pin hole 17 is perpendicular to the axis of the main body 1. A pin can be inserted into the pin hole 17. The pin is rotatably disposed in the pin hole 17. The pin is used to connect with the small end of the connecting rod. During the movement of the piston assembly, it can act on the connecting rod through the pin and convert the reciprocating motion of the piston assembly into the rotational motion of the crankshaft. At the same time, the force acting on the piston is converted into the output torque on the crankshaft to drive the vehicle.

[0049] The arrangement of the groove 16 is not limited. The groove 16 penetrates the lower end face of the main body 1, that is, the downward-facing side of the groove 16 is an open structure without a groove wall. Specifically, the groove 16 is only open on the downward-facing side without a groove wall, while the other sides are provided with groove walls. Alternatively, it can be as follows: Figure 1 As shown, the groove 16 has a groove wall only on the upward-facing side, while the other sides are open structures without groove walls. The groove 16 effectively reduces the overall weight of the main body 1.

[0050] like Figure 4 The exploded view shown is of the first gas ring 2, the second gas ring 3, and the oil ring assembly 4. The positions of the openings in the view are consistent with the positions of the openings in the installed state. Figure 3 The diagram shows the arrangement of each opening relative to the circumferential position of the main body 1.

[0051] Define the projection line corresponding to the axis of pin hole 17 as the sixth projection line f. Among the six projection lines, the sixth projection line f, the first projection line a, the second projection line b, the third projection line c, the fourth projection line d, and the fifth projection line e, the included angles between any two adjacent projection lines are 90°, 180°, 135°, 45°, and 135°, respectively. That is, the included angle between the sixth projection line f and the first projection line a is 90°, the included angle between the first projection line a and the second projection line b is 180°, the included angle between the second projection line b and the third projection line c is 135°, the included angle between the third projection line c and the fourth projection line d is 45°, and the included angle between the fourth projection line d and the fifth projection line e is 135°.

[0052] Figure 3 and Figure 4 The embodiment shown is a preferred embodiment. In fact, there are no specific restrictions on the arrangement of each opening. As long as each opening is staggered along the circumference of the body part 1, and the included angle between the projection lines corresponding to two adjacent openings is not less than 45°, it is preferable that the included angle between the projection lines corresponding to any two openings is not less than 45°, and the included angle between the projection lines corresponding to the openings of two adjacent air rings is within the range of 150°-180°.

[0053] In this embodiment, the gas ring groove may also be provided with positioning parts corresponding to the openings of the gas ring, and the oil ring groove 13 may also be provided with positioning parts corresponding to the openings of the upper scraper 41, the liner ring 42, and the lower scraper 43, respectively. During installation, the positioning parts can be used to position each opening, ensuring that each opening is installed in the preset position, thus ensuring the overall sealing performance of the piston assembly.

[0054] The positioning part can locate the opening, reducing the number of adjustments and time during installation, making installation convenient and quick and improving assembly efficiency. There are no restrictions on the specific structure of the positioning part, such as it can be a positioning protrusion or an indicator component.

[0055] If the positioning part is a positioning protrusion, in the installed state, the positioning protrusion is located in the corresponding opening. During use, the positioning protrusion can limit the position of the opening, preventing the first air ring 2, the second air ring 3, the upper scraper 41, the liner ring 42, and the lower scraper 43 from rotating relative to the main body 1, ensuring the stability of the arrangement of each opening. At the same time, the positioning protrusion can also at least partially block the opening, reducing gas passage and improving sealing. If the positioning part is an indicator component, it can be a notch, scribing, etc., which can simplify the overall structure and reduce the manufacturing process.

[0056] like Figure 2 As shown, an oil guide groove 14 is also provided circumferentially on the outer peripheral wall of the main body 1. The oil guide groove 14 is located below the oil ring groove 13 and is connected to the oil ring groove 13. The depth of the oil guide groove 14 is less than the depth of the oil ring groove 13. That is, the oil guide groove 14 is provided on the side of the bottom wall of the oil ring groove 13 facing the groove opening. The groove opening of the oil guide groove 14 is radially outward along the main body 1. An oil return groove 15 is also provided on the side wall of the oil ring groove 13 facing the oil guide groove 14. The oil return groove 15 is connected between the oil guide groove 14 and the oil ring groove 13. The oil in the oil guide groove 14 can enter the oil ring groove 13 from the oil return groove 15 along the depth direction.

[0057] The oil ring assembly 4 serves to distribute and scrape oil. When the piston assembly moves upward along the cylinder liner, the lower scraper 43 can evenly distribute a layer of oil film on the cylinder liner. When the piston assembly moves downward along the cylinder liner, the lower scraper 43 can scrape off excess oil from the cylinder liner. This not only reduces the wear and frictional resistance between the piston assembly and the cylinder liner, but also reduces the amount of oil entering the combustion chamber to participate in combustion, thus playing an auxiliary sealing role.

[0058] As the piston moves down along the cylinder liner, the oil scraped off by the lower scraper 43 enters the oil guide groove 14 and then enters the oil ring groove 13 through the return oil groove 15. This ensures that the oil volume in the oil ring groove 13 is stable, so that the cylinder liner can form an oil film as the piston assembly moves along the cylinder liner, thereby ensuring that the piston assembly can slide smoothly and reducing wear and frictional resistance.

[0059] Specifically, there is no limit to the number of oil return grooves 15, which can be set according to the specific situation. Each oil ring groove 13 is arranged at intervals along the circumference of the main body 1. The arrangement of multiple oil return grooves 15 facilitates the smooth and rapid entry of the oil in the oil guide groove 14 into the oil ring groove 13. Preferably, each oil return groove 15 is evenly spaced along the circumference of the main body 1 to further ensure the uniformity of the amount of oil at each position in the circumference of the oil ring groove 13, thereby ensuring the uniformity of the oil film.

[0060] like Figure 1 As shown, the top end face of the main body 1 is also provided with a groove 18. The top of the piston assembly and the engine cylinder head enclose to form a combustion chamber. The groove 18 can increase the volume of the combustion chamber, and the inner wall of the groove 18 is a spherical structure, which can also guide airflow and reduce tumble resistance.

[0061] The top end face of the main body 1 is also provided with a clearance groove 19. The clearance groove 19 is provided to provide clearance space for the intake valve and exhaust valve, so as to avoid interference with the top surface of the piston assembly when the intake valve and exhaust valve open axially. Specifically, there are no restrictions on the shape, structure and size of the clearance groove 19, and it can be set according to the structure of the intake valve and exhaust valve.

[0062] In the description of this application, it should be understood that the terms "upper", "lower", "top", "bottom", "axial", "radial", "circumferential", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0063] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0064] The above are merely preferred embodiments of this application. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A piston assembly characterized by, The body part (1), an oil ring assembly (4) and an air ring; The outer peripheral wall of the body part (1) is provided with an oil ring groove (13) and an air ring groove in the axial direction, the oil ring assembly (4) is installed in the oil ring groove (13), and the air ring is installed in the air ring groove. The oil ring assembly (4) comprises an upper scraping blade (41), a backing ring (42) and a lower scraping blade (43) which are sequentially stacked, and the upper scraping blade (41) is arranged towards one side of the air ring. The openings of the air ring, the upper scraping blade (41), the backing ring (42) and the lower scraping blade (43) are arranged in the circumferential direction of the body part (1).

2. The piston assembly of claim 1, wherein, The center of the opening is projected on the reference surface (S) to form a projection line, and the included angle between the projection lines corresponding to two adjacent openings is not less than 45°, and the reference surface (S) is perpendicular to the axis of the body part (1).

3. The piston assembly of claim 2, wherein, The air ring comprises at least two, and the included angle between the projection lines corresponding to the openings of two adjacent air rings is in the range of 150°-180°.

4. The piston assembly of claim 2, wherein, The included angle between the projection lines corresponding to any two openings is not less than 45°.

5. The piston assembly of any one of claims 1-4, wherein, The lower part of the body part (1) is provided with a groove (16) on the opposite sides in the radial direction, and the body part (1) is provided with a pin hole (17) which penetrates the groove bottom of the groove (16).

6. The piston assembly of claim 5, wherein, The number of the air ring is two, and the two air rings are a first air ring (2) and a second air ring (3). The center of the opening of the first air ring (2) is projected on the reference surface (S) to form a first projection line (a), the center of the opening of the second air ring (3) is projected on the reference surface (S) to form a second projection line (b), the center of the opening of the upper scraping blade (41) is projected on the reference surface (S) to form a third projection line (c), the center of the opening of the backing ring (42) is projected on the reference surface (S) to form a fourth projection line (d), the center of the opening of the lower scraping blade (43) is projected on the reference surface (S) to form a fifth projection line (e), and the axis of the pin hole (17) is projected on the reference surface (S) to form a sixth projection line (f), and the reference surface (S) is perpendicular to the axis of the body part (1). Among the six projection lines of the sixth projection line (f), the first projection line (a), the second projection line (b), the third projection line (c), the fourth projection line (d) and the fifth projection line (e), the included angle between two adjacent projection lines is 90°, 180°, 135°, 45° and 135° in turn.

7. The piston assembly of any one of claims 1-4, wherein, The air ring groove is further provided with a positioning part corresponding to the opening of the air ring. And / or, the oil ring groove (13) is provided with a positioning part corresponding to the opening of the upper scraping blade (41), the opening of the backing ring (42) and the opening of the lower scraping blade (43) respectively.

8. The piston assembly of any one of claims 1-4, wherein, The outer peripheral wall of the body part (1) is further provided with an oil guide groove (14) in the circumferential direction, the oil guide groove (14) is located below the oil ring groove (13), the depth of the oil guide groove (14) is less than the depth of the oil ring groove (13), a plurality of oil return grooves (15) are arranged in the circumferential direction at the side groove wall of the oil ring groove (13) towards the oil guide groove (14), the oil return grooves (15) are communicated between the oil guide groove (14) and the oil ring groove (13).

9. The piston assembly of any one of claims 1-4, wherein, The top end surface of the body part (1) is further provided with a clearance groove (19) for avoiding the valve.

10. A cylinder, characterized by The piston assembly as claimed in any one of claims 1-9.

11. An engine characterized by, The cylinder as claimed in claim 10.

12. A vehicle characterized by comprising: The engine as claimed in claim 11.

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