Piston ring for an engine having a three-ring structure and an engine system

Abstract

The application provides a piston ring with a three-ring structure for an engine and an engine system, the piston ring comprising: a first ring body installed between a piston and an inner wall of a cylinder body, the first ring body being symmetrically formed with arc-shaped protrusions extending in a circumferential direction on upper and lower sides of the first ring body, and a cross-sectional area of the arc-shaped protrusions being configured as a trapezoid gradually decreasing towards the first ring body; and two second ring bodies installed on the upper and lower sides of the first ring body and facing each other, each of the second ring bodies being formed with a matching arc-shaped protrusion matched with the arc-shaped protrusion to limit movement of the two second ring bodies relative to the first ring body in an axial direction.

Description

Technical Field

[0001] At least one embodiment of the present invention relates to the field of internal combustion engine component technology, and particularly to a piston ring for an engine having a three-ring structure and an engine system. Background Technology

[0002] Piston rings are a key component of internal combustion engines, consisting of elastic metal rings located within grooves in the piston. Firstly, they seal the combustion chamber to prevent gases from entering the crankcase through gaps in the piston walls. Secondly, since some energy generated during combustion can be transferred to the piston boundaries, they also transfer heat from the piston to the engine cooling system. Thirdly, piston rings control oil flow between the piston and cylinder wall, scraping away excess oil to limit its intrusion into the combustion chamber and reduce harmful gas emissions. Furthermore, piston rings also provide structural support.

[0003] Existing piston rings typically employ a monolithic design, which is widely used in engines due to its simple manufacturing process and convenient installation. However, monolithic piston rings are prone to uneven heating and thermal expansion on both the upper and lower surfaces, leading to ring deformation and ultimately seal failure.

[0004] To address the aforementioned issues, the prior art provides a composite piston ring with a two-ring stacked design. By stacking the two rings, the flexibility of the piston ring is enhanced, allowing it to fit more tightly against the inner wall of the cylinder.

[0005] However, when the cylinder is operating at high temperature and high pressure, relative movement will occur between the two piston rings, causing them to separate in the axial direction, which will cause the lubricating oil in the piston rings to flow to the outside of the piston rings. Summary of the Invention

[0006] In view of this, the present invention provides a piston ring for an engine with a three-ring structure to prevent the first ring body from separating from the two second ring bodies in the axial direction and to prevent the lubricating oil in the piston ring from flowing to the outside of the piston ring.

[0007] According to an embodiment of the present invention, a piston ring for an engine with a three-ring structure is provided, comprising: a first ring body, installed between a piston and the inner wall of a cylinder, wherein the first ring body has symmetrically formed arcuate protrusions extending in a circumferential direction on its upper and lower sides, and the cross-sectional area of ​​the arcuate protrusions is configured as a trapezoid that gradually decreases toward the first ring body; and two second ring bodies, installed facing each other on the upper and lower sides of the first ring body, each second ring body having a mating arcuate protrusion adapted to the arcuate protrusions to restrict the two second ring bodies from moving in the axial direction relative to the first ring body.

[0008] According to an embodiment of the present invention, the first ring body has a first notch in the circumferential direction, and each of the second ring bodies has a second notch in the circumferential direction. The two arc-shaped protrusions are configured such that their ends are aligned with the ends of the first ring body in the axial direction. The mating arc-shaped protrusions are configured such that their ends are aligned with the ends of the second ring bodies in the axial direction. The mating arc-shaped protrusions of the two second ring bodies are respectively combined with two arc-shaped protrusions located on both sides of the first ring body, so that the first ring body and the two second ring bodies respectively form a complete circumferential surface in the circumferential direction.

[0009] According to an embodiment of the present invention, the annular outer wall surface of the first ring body and the annular outer wall surface of the second ring body are both configured to bulge radially outward in the middle portion. The maximum outer diameter of the first ring body and the second ring body are the same, and at the position where the annular outer wall surface of the first ring body and the annular outer wall surface of the second ring body abut against each other, the outer diameter of the first ring body and the second ring body are the same, such that the stacked first ring body, the two second ring bodies and the inner wall of the cylinder form a cavity for storing lubricating oil.

[0010] According to an embodiment of the present invention, the width of the end of each of the arcuate protrusions that engages with the first ring body in the radial direction is 1 / 2 of the maximum width of the first ring body in the radial direction; the width of the end of the mating arcuate protrusion that engages with the first ring body in the axial direction in the radial direction is 1 / 2 of the maximum width of the second ring body in the radial direction.

[0011] According to an embodiment of the present invention, two first protrusions extending in the axial direction are formed on the upper and lower sides of the first ring body, and the two first protrusions extend into the second notches of the two second ring bodies respectively, so as to restrict the rotation of each second ring body relative to the first ring body.

[0012] According to an embodiment of the present invention, the two first protrusions are symmetrically arranged about the radial extension line of the first ring body where the first notch is located.

[0013] According to an embodiment of the present invention, each of the second ring bodies has a second protrusion extending in the axial direction on the side facing the first ring body, and the two second protrusions extend into the first notch from the upper and lower sides of the first ring body respectively.

[0014] According to an embodiment of the present invention, a groove extending in the circumferential direction is formed on the outer side of the second ring body located on the upper side away from the upper surface of the first ring body, so that when the second ring body located on the upper side moves inside the cylinder, under the action of the piston, the second ring body located on the upper side generates torque to adhere to the inner wall of the cylinder body, thereby increasing the contact force between the second ring body located on the upper side and the inner wall of the cylinder body.

[0015] According to an embodiment of the present invention, the coefficient of thermal expansion of the second ring located on the upper side, a2, is greater than the coefficient of thermal expansion of the first ring, a1, and the coefficient of thermal expansion of the second ring located on the lower side, a3.

[0016] According to an embodiment of the present invention, an engine system is provided, comprising: a cylinder block; a piston mounted inside the cylinder block; and piston rings for an engine having a three-ring structure as described in the above embodiment, mounted between the piston and the cylinder block.

[0017] According to the above embodiments of the present invention, a piston ring for an engine with a three-ring structure has symmetrically formed arcuate protrusions extending in the circumferential direction on the upper and lower sides of a first ring body. The cross-sectional area of ​​the arcuate protrusions is configured as a trapezoid that gradually decreases towards the first ring body. Two second ring bodies are mounted facing each other on the upper and lower sides of the first ring body. Each second ring body has a matching arcuate protrusion adapted to the arcuate protrusions to restrict the movement of the two second ring bodies relative to the first ring body in the axial direction, thereby preventing the first ring body from separating from the two second ring bodies in the axial direction and avoiding the lubricating oil in the piston ring from flowing to the outside of the piston ring. Attached Figure Description

[0018] Figure 1 This is a cross-sectional view of a piston ring with a three-ring structure for an engine, which is combined with the piston and cylinder block according to an embodiment of the present invention.

[0019] Figure 2 yes Figure 1 A magnified view of part M in the middle;

[0020] Figure 3 The piston rings for engines with a three-ring structure according to an embodiment of the present invention are... Figure 1 A magnified view of part M in the middle;

[0021] Figure 4 This is a three-dimensional schematic diagram of a piston ring for an engine with a three-ring structure according to an embodiment of the present invention;

[0022] Figure 5 This is a three-dimensional schematic diagram of the upper second ring of a piston ring for an engine with a three-ring structure according to an embodiment of the present invention.

[0023] Figure 6 This is a front view of the second notch of the upper second ring body of a piston ring for an engine with a three-ring structure according to an embodiment of the present invention;

[0024] Figure 7 yes Figure 6 A magnified view of part A in the middle;

[0025] Figure 8This is a three-dimensional schematic diagram of the first ring of a piston ring for an engine with a three-ring structure according to an embodiment of the present invention;

[0026] Figure 9 This is a front view of the first notch of the first ring body of a piston ring for an engine with a three-ring structure according to an embodiment of the present invention;

[0027] Figure 10 yes Figure 9 A magnified view of part B in the middle section;

[0028] Figure 11 This is a perspective view of the second ring body located on the lower side of the piston ring for an engine with a three-ring structure according to an embodiment of the present invention;

[0029] Figure 12 This is a front view of the second notch of the second ring body located on the lower side of the piston ring for an engine with a three-ring structure according to an embodiment of the present invention;

[0030] Figure 13 yes Figure 12 A magnified view of part C in the middle;

[0031] Figure 14 This is a perspective view of a piston ring for an engine with a three-ring structure, wherein two first protrusions of the first ring body extend into the second notches of two second ring bodies, respectively, according to an embodiment of the present invention; and

[0032] Figure 15 This is a perspective view of a piston ring for an engine with a three-ring structure according to an embodiment of the present invention, showing that the second protrusions of the two second ring bodies extend into the first notch of the first ring body.

[0033] In the picture:

[0034] 1-First ring body; 11-Arch-shaped protrusion; 12-First notch; 13-First protrusion;

[0035] 2-Second ring body; 21-Matching arc-shaped protrusion; 22-Second notch; 23-Second protrusion; 24-Groove;

[0036] 3-Piston; 31-First annular groove; 32-Second annular groove; 33-Third annular groove; 34-Fourth annular groove;

[0037] 4-Cylinder block;

[0038] 5-Cavity. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0040] According to one aspect of the invention, a piston ring for an engine with a three-ring structure is provided, comprising: a first ring body, installed between a piston and the inner wall of a cylinder, wherein the first ring body has symmetrically formed arcuate protrusions extending in a circumferential direction on its upper and lower sides, and the cross-sectional area of ​​the arcuate protrusions is configured as a trapezoid that gradually decreases toward the first ring body; and two second ring bodies, installed facing each other on the upper and lower sides of the first ring body, each second ring body having a matching arcuate protrusion adapted to the arcuate protrusions to restrict the two second ring bodies from moving relative to the first ring body in the axial direction.

[0041] Figure 1 This is a cross-sectional view of a piston ring with a three-ring structure for an engine, which is combined with the piston and cylinder block according to an embodiment of the present invention. Figure 2 yes Figure 1 A magnified view of part M in the middle; Figure 3 The piston rings for engines with a three-ring structure according to an embodiment of the present invention are... Figure 1 A magnified view of part M in the middle; Figure 4 This is a three-dimensional schematic diagram of a piston ring for an engine with a three-ring structure according to an embodiment of the present invention.

[0042] According to an exemplary embodiment of the present invention, please refer to Figures 1-4 A piston ring for an engine with a three-ring structure is provided, comprising a first ring body 1 and two second ring bodies 2. The first ring body 1 is mounted between the piston 3 and the inner wall of the cylinder 4. Symmetrical arc-shaped protrusions 11 extending circumferentially are formed on the upper and lower sides of the first ring body 1. The cross-sectional area of ​​the arc-shaped protrusions 11 is configured as a trapezoid that gradually decreases towards the first ring body 1. The two second ring bodies 2 are mounted facing each other on the upper and lower sides of the first ring body 1. Each second ring body 2 has a mating arc-shaped protrusion 21 adapted to the arc-shaped protrusions 11. The mating arc-shaped protrusion 21 of each second ring body 2 engages with the two arc-shaped protrusions 11 of the first ring body 1 respectively, thereby restricting the axial movement of the two second ring bodies 2 relative to the first ring body 1.

[0043] In this embodiment, symmetrical arc-shaped protrusions 11 extending in the circumferential direction are formed on the upper and lower sides of the first ring body 1. The cross-sectional area of ​​the arc-shaped protrusions 11 is constructed as a trapezoid that gradually decreases towards the first ring body 1. Two second ring bodies 2 are installed facing each other on the upper and lower sides of the first ring body 1. Each second ring body 2 has a matching arc-shaped protrusion 21 that is adapted to the arc-shaped protrusions 11 to restrict the movement of the two second ring bodies 2 relative to the first ring body 1 in the axial direction, thereby preventing the first ring body 1 from separating from the two second ring bodies 2 in the axial direction and preventing the lubricating oil in the piston ring from flowing to the outside of the piston ring.

[0044] Furthermore, through the above-mentioned arrangement, the positive torsional force and elastic force formed between the two second rings 2 and the first ring 1 enhance the axial connection between the two second rings 2 and the first ring 1, resulting in better sealing and stability.

[0045] Figure 5 This is a three-dimensional schematic diagram of the upper second ring of a piston ring for an engine with a three-ring structure according to an embodiment of the present invention. Figure 6 This is a front view of the second notch of the upper second ring body of a piston ring for an engine with a three-ring structure according to an embodiment of the present invention; Figure 7 yes Figure 6 A magnified view of part A in the middle; Figure 8 This is a three-dimensional schematic diagram of the first ring of a piston ring for an engine with a three-ring structure according to an embodiment of the present invention; Figure 9 This is a front view of the first notch of the first ring body of a piston ring for an engine with a three-ring structure according to an embodiment of the present invention; Figure 10 yes Figure 9 A magnified view of part B in the middle section; Figure 11 This is a perspective view of the second ring body located on the lower side of the piston ring for an engine with a three-ring structure according to an embodiment of the present invention; Figure 12 This is a front view of the second notch of the second ring body located on the lower side of the piston ring for an engine with a three-ring structure according to an embodiment of the present invention; Figure 13 yes Figure 12 A magnified view of part C in the middle.

[0046] In some exemplary embodiments, reference is made to Figures 4-13 The first ring body 1 has a first notch 12 in the circumferential direction, and each second ring body 2 has a second notch 22 in the circumferential direction. Two arc-shaped protrusions 11 are configured such that their ends are aligned with the ends of the first ring body 1 in the axial direction. The matching arc-shaped protrusions 21 are configured such that their ends are aligned with the ends of the second ring body 2 in the axial direction. The matching arc-shaped protrusions 21 of the two second ring bodies 2 are respectively combined with the two arc-shaped protrusions 11 located on both sides of the first ring body 1, so that the first ring body 1 and the two second ring bodies 2 respectively form a complete circumferential surface in the circumferential direction.

[0047] With the above configuration, the two arc-shaped protrusions 21 of the two second ring bodies 2 are respectively engaged with the two arc-shaped protrusions 11 of the first ring body 1, so that the outer wall surface of the piston ring after the two second ring bodies 2 are engaged with the first ring body 1 has the same axial dimension at every point along the circumferential direction, and forms a complete circumferential surface, preventing lubricating oil from flowing to the outside of the piston ring and improving the sealing effect of the piston ring on the internal lubricating oil.

[0048] In some exemplary embodiments, reference is made to Figures 2-3The annular outer wall of the first ring body 1 and the annular outer wall of the second ring body 2 are both constructed to bulge radially outward in the middle part. The maximum outer diameter of the first ring body 1 and the second ring body 2 are the same. At the position where the annular outer wall of the first ring body 1 and the annular outer wall of the second ring body 2 abut against each other, the outer diameter of the first ring body 1 and the second ring body 2 are the same, so that the stacked first ring body 1, the two second ring bodies 2 and the inner wall of the cylinder body 4 form a cavity 5 for storing lubricating oil.

[0049] With the above arrangement, the first ring 1 and two second rings 2 are stacked and installed between the piston 3 and the cylinder 4, forming cavities 5 for storing lubricating oil between the first ring 1 and the inner wall of the cylinder 4. The formation of these cavities 5 effectively improves lubrication of the piston rings at top dead center and prevents lubricating oil from rising upwards, thereby mitigating carbon buildup from particulate matter entering the crankcase. This increases the lifespan of the lubricating oil and prevents wear on the cylinder 4 caused by carbon buildup.

[0050] It should be noted that, in this embodiment, the annular outer wall surfaces of the first ring body 1 and the second ring body 2 radially contract inward towards both ends in the axial direction, and their conical angle is 20°-70°. Preferably, it is 45°.

[0051] In some exemplary embodiments, reference is made to Figures 2-3 The width of the end of each arc-shaped protrusion 11 that engages with the first ring body 1 in the radial direction is half the maximum width of the first ring body 1 in the radial direction. The width of the end of the matching arc-shaped protrusion 21 that engages with the first ring body 1 in the axial direction in the radial direction is half the maximum width of the second ring body 2 in the radial direction.

[0052] By adopting the above configuration, the contact area between the two second ring bodies 2 and the two arc-shaped protrusions 21 of the first ring body 1 is increased, thereby improving the axial strength of the two second ring bodies 2 and the first ring body 1, and further preventing the two second ring bodies 2 from moving relative to the first ring body 1 in the axial direction.

[0053] Figure 14 This is a perspective view of a piston ring for an engine with a three-ring structure according to an embodiment of the present invention, showing that two first protrusions of the first ring body extend into the second notches of two second ring bodies respectively.

[0054] In some exemplary embodiments, reference is made to Figure 4 , Figure 5 , Figure 8 , Figure 11 as well as Figure 14The first ring body 1 has two first protrusions 13 extending in the axial direction on its upper and lower sides respectively. The two first protrusions 13 extend into the second notches 22 of the two second ring bodies 2 respectively, so as to restrict the rotation of each second ring body 2 relative to the first ring body 1 and prevent the first notches 12 and the two second notches 22 from being aligned in the axial direction. The lubricating oil flows to the outside of the piston ring through the first notches 12 and the two second notches 22.

[0055] In this embodiment, two first protrusions 13 extending in the axial direction are formed on the upper and lower sides of the first ring body 1, and the two first protrusions 13 extend into the second notches 22 of the two second ring bodies 2, respectively, to restrict the rotation of each second ring body 2 relative to the first ring body 1 and prevent the two second notches 22 from aligning with the first notches 12 in the axial direction. The lubricating oil flows to the outside of the piston ring through the first notches 12 and the two second notches 22.

[0056] In some exemplary embodiments, reference is made to Figure 8 The two first protrusions 13 are symmetrically arranged about the radial extension line of the first ring body 1 where the first notch 12 is located.

[0057] With the above configuration, when the two first protrusions 13 of the first ring body 1 are respectively inserted into the two second notches 22 of the two second ring bodies 2, the torque formed by the limiting resistance provided by the two first protrusions 13 to the two second ring bodies 2 in the circumferential direction is balanced.

[0058] Figure 15 This is a perspective view of a piston ring for an engine with a three-ring structure according to an embodiment of the present invention, showing that the second protrusions of the two second ring bodies extend into the first notch of the first ring body.

[0059] In some exemplary embodiments, reference is made to Figure 4 , Figure 5 , Figure 8 , Figure 11 as well as Figure 15 Each second ring body 2 has a second protrusion 23 extending in the axial direction on the side facing the first ring body 1. The two second protrusions 23 extend into the first notch 12 from the upper and lower sides of the first ring body 1 respectively, so as to restrict the rotation of the two second ring bodies 2 relative to the first ring body 1.

[0060] In this embodiment, each second ring body 2 has a second protrusion 23 extending in the axial direction on the side facing the first ring body 1. The two second protrusions 23 extend into the first notch 12 from the upper and lower sides of the first ring body 1, respectively, to further restrict the rotation of each second ring body 2 relative to the first ring body 1.

[0061] It should be noted that in this embodiment, the first notch 12 and the two second notches 22 are distributed circumferentially. Furthermore, due to the three-layer design, the piston ring has increased thickness, making it easier to meet the requirements of efficient engine operation under high load conditions, and improving high sealing, high oil control, and low friction capabilities. In addition, the piston ring of this embodiment overcomes the ring deformation problem caused by uneven heating and unbalanced thermal expansion on the upper and lower surfaces of a single-piece piston ring, better dispersing heat and improving the sealing effect. It also features a simple structure and convenient installation.

[0062] In some exemplary embodiments, reference is made to Figures 2-3 The outer side of the upper surface of the second ring body 2 located away from the first ring body 1 has a groove 24 extending in the circumferential direction. This causes the second ring body 2 located on the upper side to generate torque under the action of the piston 3 during the movement inside the cylinder body 4, so as to stick tightly to the inner wall of the cylinder body 4 and increase the contact force between the second ring body 2 located on the upper side and the inner wall of the cylinder body 4.

[0063] In this embodiment, a groove 24 extending in the circumferential direction is formed on the outer side of the upper surface of the second ring 2 located on the upper side of the first ring 1 away from the first ring 1. As the second ring 2 moves inside the cylinder 4, the torque generated between the two sides of the second ring 2 facing each other under the action of the piston 3 is not equal. As a result, the second ring 2 generates torque, which makes the second ring 2 stick tightly to the inner wall of the cylinder 4, increasing the contact force between the second ring 2 and the inner wall of the cylinder 4.

[0064] In some exemplary embodiments, the coefficient of thermal expansion of the second ring 2 located on the upper side, a2, is greater than the coefficient of thermal expansion of the first ring 1, a1, and the coefficient of thermal expansion of the second ring 2 located on the lower side, a3.

[0065] In this embodiment, the upper second ring 2 is located near the combustion chamber, has a large surface heat, and is typically in a high-temperature environment. The first ring 1 further seals the gas and controls oil, and acts as a buffer between the two second rings 2 located on the upper and lower sides. The lower second ring 2 mainly functions to control oil and further seal the gas. Based on the installation positions and functions of the first ring 1 and the two second rings 2, the thermal expansion coefficient a2 of the upper second ring 2 is greater than that of the first ring 1 (a1), which is greater than that of the lower second ring 2 (a3), to meet the operating requirements of the first ring 1 and the two second rings 2.

[0066] According to an exemplary embodiment of the present invention, please refer to Figure 1An engine system is provided, including a cylinder block 4, a piston 3, and piston rings with a three-ring structure as described in the above embodiments. The piston 3 is mounted inside the cylinder block 4. The piston rings with a three-ring structure as described in the above embodiments are mounted between the piston 3 and the cylinder block 4.

[0067] In this embodiment, the piston ring with a three-ring structure for the engine described in the above embodiment is installed between the piston 3 and the cylinder 4 to prevent the lubricating oil inside the piston ring from flowing to the outside of the piston ring.

[0068] It should be noted that, in this embodiment, the piston 3 has a first annular groove 31, a second annular groove 32, a third annular groove 33, and a fourth annular groove 34 formed on it, suitable for mounting the piston ring. For example, in this embodiment of the invention, the piston ring is mounted inside the first annular groove 31.

[0069] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A piston ring for an engine with a three-ring structure, comprising: A first ring body (1) is installed between the piston (3) and the inner wall of the cylinder (4). The first ring body (1) has symmetrically formed arc-shaped protrusions (11) extending circumferentially on its upper and lower sides. The cross-sectional area of ​​the arc-shaped protrusions (11) is configured as a trapezoid that gradually decreases towards the first ring body (1). Two second ring bodies (2) are mounted facing each other on the upper and lower sides of the first ring body (1). Each second ring body (2) has a matching arc-shaped protrusion (21) adapted to the arc-shaped protrusion (11) to restrict the two second ring bodies (2) from moving in the axial direction relative to the first ring body (1). The first ring body (1) has a first notch (12) in the circumferential direction, and each second ring body (2) has a second notch (22) in the circumferential direction. The two arc-shaped protrusions (11) are configured such that their ends are aligned with the ends of the first ring body (1) in the axial direction. The matching arc-shaped protrusions (21) are configured such that their ends are aligned with the ends of the second ring body (2) in the axial direction. The matching arc-shaped protrusions (21) of the two second ring bodies (2) are respectively combined with the two arc-shaped protrusions (11) located on both sides of the first ring body (1), so that the first ring body (1) and the two second ring bodies (2) respectively form a complete circumferential surface in the circumferential direction. The first ring body (1) has two first protrusions (13) extending in the axial direction on its upper and lower sides respectively. The two first protrusions (13) extend into the second notches (22) of the two second ring bodies (2) respectively, so as to restrict each second ring body (2) from rotating relative to the first ring body (1).

2. The piston ring for an engine with a three-ring structure according to claim 1, wherein, The annular outer wall of the first ring body (1) and the annular outer wall of the second ring body (2) are both constructed to bulge radially outward in the middle part. The maximum outer diameter of the first ring body (1) and the second ring body (2) are the same. At the position where the annular outer wall of the first ring body (1) and the annular outer wall of the second ring body (2) abut against each other, the outer diameter of the first ring body (1) and the second ring body (2) are the same, so that the first ring body (1) and the two second ring bodies (2) stacked together form a cavity (5) for storing lubricating oil with the inner wall of the cylinder body (4).

3. The piston ring for an engine with a three-ring structure according to claim 2, wherein, The width of the end of each of the arcuate protrusions (11) that is joined to the first ring body (1) in the radial direction is 1 / 2 of the maximum width of the first ring body (1) in the radial direction; The width of the end of the mating arc-shaped protrusion (21) that is axially connected to the first ring body (1) is 1 / 2 of the maximum width of the second ring body (2) in the radial direction.

4. The piston ring for an engine with a three-ring structure according to claim 1, wherein, The two first protrusions (13) are symmetrically arranged about the radial extension line of the first ring body (1) where the first notch (12) is located.

5. The piston ring for an engine with a three-ring structure according to claim 4, wherein, Each of the second ring bodies (2) has a second protrusion (23) extending in the axial direction on the side facing the first ring body (1), and the two second protrusions (23) extend into the first notch (12) from the upper and lower sides of the first ring body (1) respectively.

6. A piston ring for an engine having a three-ring structure according to any one of claims 1-5, wherein, The outer side of the upper surface of the second ring (2) located on the upper side away from the first ring (1) is formed with a groove (24) extending in the circumferential direction, so that when the second ring (2) located on the upper side moves inside the cylinder (4), under the action of the piston (3), the second ring (2) located on the upper side generates torque to stick to the inner wall of the cylinder (4) and increase the contact force between the second ring (2) located on the upper side and the inner wall of the cylinder (4).

7. The piston ring for an engine with a three-ring structure according to claim 1, wherein, The coefficient of thermal expansion of the second ring (2) located on the upper side is a2 > the coefficient of thermal expansion of the first ring (1) is a1 > the coefficient of thermal expansion of the second ring (2) located on the lower side is a3.

8. An engine system comprising: Cylinder block (4); Piston (3) is installed inside the cylinder (4); as well as The piston ring for an engine with a three-ring structure as described in any one of claims 1-7 is installed between the piston (3) and the cylinder (4).

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