Piston structure for relieving knocking impact and engine

Abstract

The utility model discloses a piston structure for relieving knocking impact and an engine, a piston comprises a piston firepower bank close to a cylinder sleeve, the piston is provided with a first piston ring groove used for assembling a piston ring and a pressure relief groove formed in the piston firepower bank, and a first avoiding gap and a second avoiding gap are formed between the groove wall of the first piston ring groove and the piston ring; the pressure relief groove is located above the first piston ring groove, and high-temperature and high-pressure gas flows to the first avoiding gap and the second avoiding gap through the pressure relief groove. When an engine is knocked, high-temperature and high-pressure gas descends to the pressure relief groove along a piston firepower bank, the circulation space of airflow is enlarged, the pressure reduction effect on the gas is achieved, the gas subjected to pressure reduction through the pressure relief groove enters the first avoiding gap and the second avoiding gap, the high-temperature and high-pressure gas is prevented from impacting the bottom side of a first piston ring groove from the side of a cylinder sleeve, and the service life of the piston ring groove is prolonged. And meanwhile, the circulation space of the gas is increased through the first avoiding gap and the second avoiding gap, and pressure reduction of the high-pressure gas is further achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of engine pistons, and particularly relates to a piston structure for relieving knock impact and an engine. BACKGROUND

[0002] The piston is an important component of the combustion chamber of an engine and has an important influence on the performance of the engine; at the same time, the piston bears the combustion pressure in the cylinder and transmits the force to the connecting rod and the crankshaft to realize power output.

[0003] The piston is usually provided with three piston rings, which mainly play the roles of sealing, scraping and distributing oil, wherein the first piston ring is a gas ring and is mainly used for sealing the gas in the cylinder to prevent the gas from leaking to the oil pan. In a free state, the closed opening of the piston ring is opened by a certain distance, which is a free opening. When the piston ring is assembled, it is in a circular tight state, has a certain elastic force to the cylinder liner, and is well fitted with the cylinder liner. Under the condition that the ring structure and the material are certain, the greater the free opening, the higher the ring elastic force, and vice versa.

[0004] Clean energy such as methanol and hydrogen has a broad application prospect, and the problem accompanying the clean energy is that the first piston ring is impacted by fuel knock, which causes plastic deformation of the first piston ring, thereby reducing the free opening of the first piston ring, further causing the ring body to be out of round and not to be well fitted with the cylinder liner, increasing the gas leakage in the cylinder, and being difficult to form an oil film between the inner wall of the cylinder and the piston ring, thereby causing poor lubrication and even dry friction phenomenon, causing obvious longitudinal mechanical scratches and scratches on the inner wall of the cylinder in the movement range of the piston ring, and causing serious fusion wear, engine starting difficulty or self-extinguishing failure. Deep grooves appear on the inner wall of the cylinder due to dry friction, the piston, the piston ring and the cylinder wall lose sealing when they are rubbed, thereby reducing the compression pressure of the cylinder and losing power. CONTENT OF THE UTILITY MODEL

[0005] The application provides a piston structure for relieving knock impact and an engine. In the engine knock condition, the piston structure weakens the impact of high-temperature and high-pressure gas of knock, speeds up the balance of explosion pressure, weakens the impact of the piston ring in the first piston ring groove on the piston ring, and keeps the shape and performance of the piston ring stable.

[0006] The technical scheme adopted by the application is as follows:

[0007] A piston structure for relieving knock impact, the piston comprises a piston combustion chamber wall close to a cylinder liner, the piston is provided with a first piston ring groove for assembling a piston ring and a pressure relief groove arranged on the piston combustion chamber wall, a first relief gap and a second relief gap are arranged between the groove wall of the first piston ring groove and the piston ring, the pressure relief groove is located above the first piston ring groove, and high-temperature and high-pressure gas flows through the pressure relief groove to the first relief gap and the second relief gap.

[0008] Preferably, the piston is provided with a retracted section which is circumferentially arranged along the piston to form the pressure relief groove in the circumferential direction of the piston, and the opening of the pressure relief groove is directed towards the cylinder liner.

[0009] Preferably, a gap is provided between the piston fire deck and the cylinder liner to form an air passage which is in communication with the pressure relief groove.

[0010] Preferably, the air passage comprises a horizontal flow section, and the end of the pressure relief groove extends in the vertical direction towards the first piston ring groove to form the horizontal flow section between the piston and the cylinder liner.

[0011] Preferably, the horizontal flow section is located between the first piston ring groove and the pressure relief groove, and the horizontal flow section is in communication with the first piston ring groove.

[0012] Preferably, the pressure relief groove comprises a vertical side wall on the side away from the first piston ring groove and an inclined side wall on the side close to the first piston ring groove, the end of the vertical side wall is located on the same horizontal line as the end of the piston fire deck, and the distance between the inclined side wall and the cylinder liner is greater than the distance between the vertical side wall and the cylinder liner.

[0013] Preferably, the pressure relief groove is provided with a necked section on the side close to the center of the piston to make the pressure relief groove V-shaped, and the inclined side wall is inclined away from the first piston ring groove to form the necked section.

[0014] Preferably, the piston ring is in abutment with the groove wall of the first piston ring groove on the side away from the pressure relief groove, the first clearance is formed between the piston ring and the groove wall of the first piston ring groove on the side close to the pressure relief groove, the second clearance is formed between the piston ring and the groove bottom of the first piston ring groove, and the first clearance and the second clearance are in communication.

[0015] Preferably, the height d of the first clearance in the vertical direction is in the range of 0.2mm≤d≤0.4mm.

[0016] An engine comprises a body, a cylinder and a cylinder liner, and the cylinder is provided with a piston structure as described above.

[0017] Thanks to the above technical solutions, the application has the following beneficial effects:

[0018] The scheme sets the pressure relief groove on the fire bank of the piston, and the pressure relief groove is located above the first piston ring groove. When the engine is in knock condition, the high-temperature and high-pressure gas flows downward to the pressure relief groove along the fire bank of the piston, the flow space of the gas flow is large, the pressure relief effect is realized, the groove shape of the pressure relief groove makes the gas entering the pressure relief groove have the tendency of rolling out of the groove, so that the impact kinetic energy of the downward gas flow is further offset, the gas pressure reaching the piston ring is further relieved, and the impact force of the gas on the piston ring under the knock condition is reduced.

[0019] Meanwhile, the scheme further has the first and second avoidance gaps, the gas relieved through the pressure relief groove enters the first and second avoidance gaps, the high-temperature and high-pressure gas is prevented from impacting from the side of the cylinder sleeve to the bottom side of the first piston ring groove, so that the piston ring is further prevented from being deformed by contraction, and the flow path of the gas is further increased through the first and second avoidance gaps, so that the pressure relief effect of the high-temperature and high-pressure gas is further realized.

[0020] In addition, the pressure relief groove is set on the fire bank of the piston, which is beneficial to reducing the overall weight of the piston, so as to be beneficial to relieving the knocking and collision of the piston on the cylinder sleeve. The pressure relief groove is set, the carbon storage volume is increased through the pressure relief groove, the gradually accumulated carbon on the fire bank of the piston is prevented from causing abnormal friction with the cylinder sleeve, the problem that the clearance is increased due to excessive wear of the cylinder sleeve and the abnormal increase of the oil consumption is avoided, and the operation reliability of the engine is further improved. BRIEF DESCRIPTION OF DRAWINGS

[0021] The drawings described herein are used to provide further understanding of the present application, constitute a part of the present application, the schematic embodiments of the present application and the description thereof are used to explain the present application, and do not constitute improper limitation on the present application. In the drawings:

[0022] Figure 1 It is a result schematic view of the piston in an embodiment of the present application;

[0023] Figure 2 It is a sectional view of the piston in an embodiment of the present application;

[0024] Figure 3 It is a part gas flow direction schematic view in an embodiment of the present application.

[0025] EXPLANATION OF REFERENCE NUMERALS:

[0026] 100-piston, 101-pressure relief groove, 1011-vertical side wall, 1012-inclined side wall, 102-first piston ring groove, 1021-first avoidance gap, 1022-second avoidance gap, 103-piston ring, 104-piston fire bank, 200-gas passing passage, 201-horizontal flow section, 300-cylinder sleeve, 400-engine body. DETAILED DESCRIPTION

[0027] In order to make the overall concept of the present application more clear, the following will be described in detail with reference to the accompanying drawings.

[0028] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. The present application, however, can be practiced in a variety of ways other than those specifically described herein, and the scope of the present application is not limited to the specific embodiments described herein. It is to be noted that embodiments of the present application and each feature thereof can be combined with those of other embodiments without conflict.

[0029] In addition, in the description of the present application, it needs to be understood that the terms "top", "bottom", "inner", "outer", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0030] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting", "fixing" and the like should be understood in a broad sense, for example, can be fixed connection, can also be detachable connection, or integral; can be mechanical connection, can also be electrical connection, or communication; can be directly connected, or indirectly connected through an intermediate medium; can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0031] In the present application, unless otherwise explicitly specified and limited, the first feature "on" or "under" the second feature can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. In the description of the specification, the description referring to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0032] The present application provides a piston structure for mitigating knock impact, as shown in Figures 1 to 3 Figure 3 ​The arrow direction is the gas flow direction. The piston 100 includes a piston fire bank 104 close to the cylinder liner 300. The piston 100 is provided with a first piston ring groove 102 for assembling a piston ring 103, and a pressure relief groove 101 arranged on the piston fire bank 104. The first piston ring groove 102 is provided with a first clearance 1021 and a second clearance 1022 between the groove wall and the piston ring 103. The pressure relief groove 101 is located above the first piston ring groove 102. High-temperature and high-pressure gas flows through the pressure relief groove 101 to the first clearance 1021 and the second clearance 1022.

[0033] The present scheme sets the pressure relief groove 101 on the piston fire bank 104, and the pressure relief groove 101 is located above the first piston ring groove 102. When the engine is in knock condition, high-temperature and high-pressure gas flows down along the piston fire bank 104 to the pressure relief groove 101. The flow space of the gas flow is large, which reduces the pressure of the gas. The groove shape of the pressure relief groove 101 makes the gas entering the pressure relief groove 101 have a tendency to roll out of the groove, thereby further offsetting the impact kinetic energy of the downward gas flow, further reducing the gas pressure reaching the piston ring 103, and thereby reducing the impact force of the gas on the piston ring 103 in the knock condition.

[0034] Meanwhile, the present scheme is also provided with the first clearance 1021 and the second clearance 1022. The gas reduced by the pressure relief groove 101 enters the first clearance 1021 and the second clearance 1022, avoiding the impact of high-temperature and high-pressure gas from the side of the cylinder liner 300 to the bottom side of the first piston ring groove 102, thereby further avoiding the contraction and deformation of the piston ring 103. At the same time, the first clearance 1021 and the second clearance 1022 also increase the flow path and flow space of the gas, further reducing the pressure of the high-temperature and high-pressure gas.

[0035] In addition, the pressure relief groove 101 is opened on the piston fire bank 104, which is beneficial to reduce the overall weight of the piston 100, effectively reduce the reciprocating inertia force, thereby facilitating the alleviation of the knocking and collision of the piston 100 to the cylinder liner 300. The setting of the pressure relief groove 101 can increase the carbon storage volume through the pressure relief groove 101, avoid the gradual accumulation of carbon on the piston fire bank 104, and avoid abnormal friction with the cylinder liner 300, avoid excessive wear of the cylinder liner 300, and avoid the problem of increased abnormal oil consumption, thereby further improving the operation reliability of the engine.

[0036] It should be noted that due to the knock characteristics of fuels such as methanol and hydrogen, the pressure relief groove 101 will not store too much or be full of carbon, and the pressure relief groove 101 will be continuously impacted while continuously relieving and reversing the knock impact. The accumulated carbon will be knocked off and moved and shaken at the same time, and will be taken away from the pressure relief groove 101 at the exhaust time, thereby avoiding the influence of the carbon storage in the pressure relief groove 101 on the pressure reduction effect.

[0037] In one embodiment, asFigure 1 As shown, the piston 100 is provided with a retracted section, which is circumferentially arranged along the piston 100 to form the pressure relief groove 101 in the circumferential direction of the piston 100, and the opening of the pressure relief groove 101 faces the cylinder liner 300.

[0038] As can be easily understood, although the retracted section is not shown in the figure, the inner recessed part of the piston 100 in the figure is the retracted section, which forms the pressure relief groove 101 in the circumferential direction of the piston 100. The retracted section is formed by partially recessing the piston 100, and the retracted section is arranged in the circumferential direction of the piston 100 to form the pressure relief groove 101 in a full circle of the piston 100, so that the pressure relief groove 101 can achieve the pressure reduction effect on the gas at all angles and directions. The opening of the pressure relief groove 101 faces the cylinder liner 300, and when the gas flows downward through the pressure relief groove 101, the gas flow space increases, the gas flow diffuses into the pressure relief groove 101, so that the high-temperature and high-pressure gas realizes pressure reduction after passing through the pressure relief groove 101, and the gas flow entering the pressure relief groove 101 flows back from the groove bottom to the outside of the groove, which achieves impact and offset to the gas flow outside the groove, further weakening the gas flow strength, so that the impact force of the high-temperature and high-pressure gas is weakened when it reaches the piston ring 103, avoiding the deformation and failure of the piston ring 103 caused by the impact of the high-temperature and high-pressure gas, thereby ensuring the use stability of the piston ring 103.

[0039] Further, a gap is provided between the piston fire bank 104 and the cylinder liner 300 to form the gas passage 200, and the gas passage 200 communicates with the pressure relief groove 101.

[0040] The high-temperature and high-pressure gas directly flows through the gas passage 200 into the pressure relief groove 101, and the pressure of the gas is rapidly reduced during the downward process of the high-temperature and high-pressure gas, so that the high-temperature and high-pressure gas realizes pressure reduction before reaching the first piston ring groove 102, thereby weakening the impact of the high-temperature and high-pressure gas on the piston ring 103 in the first piston ring groove 102, and protecting the piston ring 103.

[0041] In one embodiment, as shown in Figure 3 The gas passage 200 includes a horizontal flow section 201, and the end of the pressure relief groove 101 extends in the vertical direction towards the first piston ring groove 102, so as to form the horizontal flow section 201 between the piston 100 and the cylinder liner 300.

[0042] Preferably, the horizontal flow section 201 is located between the first piston ring groove 102 and the pressure relief groove 101, and the horizontal flow section 201 communicates with the first piston ring groove 102.

[0043] In this embodiment, the high-temperature and high-pressure gas first flows through the gas passage 200 to the pressure relief groove 101, the gas flow path is expanded at the pressure relief groove 101, and the gas has a tendency to flow to an area with a smaller pressure, so that the high-temperature and high-pressure gas flows to the pressure relief groove 101, and then reverses and flows out of the groove at the bottom of the pressure relief groove 101. As the opening end of the pressure relief groove 101 extends vertically in the direction of the first piston ring groove 102, a uniform flow section 201 is formed, so that the gas at the opening of the pressure relief groove 101 first buffers along the uniform flow section 201 after passing through the pressure relief groove 101, and then flows to the first piston ring groove 102, further slowing down the flow rate and impact force of the gas flow to the ring groove, and achieving protection of the piston ring 103 at the first piston ring groove 102 from the impact of the gas.

[0044] In one embodiment, as shown in FIG. 1, the pressure relief groove 101 includes a vertical side wall 1011 away from the first piston ring groove 102 and an inclined side wall 1012 close to the first piston ring groove 102. The end of the vertical side wall 1011 is on the same horizontal line as the end of the piston fire deck 104, and the distance between the inclined side wall 1012 and the cylinder liner 300 is greater than the distance between the vertical side wall 1011 and the cylinder liner 300. Figure 2

[0045] Further, the side of the pressure relief groove 101 close to the center of the piston 100 is provided with a necked section to make the pressure relief groove 101 V-shaped, and the inclined side wall 1012 is inclined away from the first piston ring groove 102 to form the necked section.

[0046] By providing the vertical side wall 1011 at the pressure relief groove 101, the high-temperature and high-pressure gas first reaches the vertical side wall 1011 during downward flow. Compared with the inclined arrangement at the bottom of the pressure relief groove 101, the vertical side wall 1011 is beneficial to ensure that the side first contacted by the gas has better thickness and support strength, which can strengthen the resistance effect of the shock impact and avoid breakage due to insufficient strength, thereby ensuring the application reliability of the pressure relief groove 101 and the piston 100.

[0047] At the same time, the other side inner wall of the pressure relief groove 101 is provided as an inclined side wall 1012. When the gas passes through this side, the pressure relief groove 101 as a whole is V-shaped due to the inclined direction, i.e., the opening width is greater than the bottom, (when the inclined side wall 1012 of the pressure relief groove 101 is gradually necked, the entire inclined side wall 1012 forms a necked section), which has a blocking effect on the gas passing through the inclined side wall 1012, and is beneficial to further weaken the impact force of the high-pressure gas. At the same time, for the gas that reverses from the inside of the pressure relief groove 101 to the outside, the gas has a backflow tendency after passing through the expanded inclined side wall 1012, which can further weaken the impact force of the gas, and cooperate with the uniform flow section 201 to achieve better gas flow buffering and pressure reduction effect.

[0048] ​In addition, the extension length of the inclined side wall 1012 of the pressure relief groove 101 is affected by the radial thickness of the piston ring 103, that is, the cross-sectional width, and the end of the inclined side wall 1012 of the pressure relief groove 101 is aligned with the piston ring 103, and the exposed part of the piston ring 103 is required to be not more than one-third (as shown in Figure 2 、 Figure 3 For example, the piston ring 103 is provided with a radial thickness of 3 mm, and therefore the inclined side wall 1012 of the pressure relief groove 101 exposes the piston ring 103 by a maximum length of 1 mm. The radial thickness of 3 mm is only an example, and the specific setting is determined according to actual working requirements, which can be understood by those skilled in the art.

[0049] In this way, the distance between the inclined side wall 1012 and the cylinder sleeve 300 is greater than the distance between the vertical side wall 1011 and the cylinder sleeve 300, which can make the gas flow out of the pressure relief groove 101 more quickly enter the first piston ring groove 102, that is, enter the first avoidance gap 1021, and then enter the second avoidance gap 1022 through the first avoidance gap 1021, that is, enter the bottom of the first piston ring groove 102, thereby facilitating the reduction of high-pressure gas flow to the cylinder sleeve 300, weakening the impact of high-pressure gas on the piston ring 103 from one side of the cylinder sleeve 300, and avoiding the collapse of the piston ring 103 to the bottom of the first piston ring groove 102. If the extension length of the inclined side wall 1012 is too short, on the one hand, the exposed area of the piston ring 103 is too large, which can cause the gas flow space of the first avoidance gap 1021 to be too small, which is not conducive to pressure reduction, and the protection and limiting effect of the piston ring 103 is weakened, which is not conducive to the stability of the piston ring 103 in the first piston ring groove 102; on the other hand, it can cause the space of the pressure relief groove 101 to be reduced, and the gas can be more quickly rolled out of the groove, which can weaken the pressure reduction effect of the high-temperature and high-pressure gas, and the impact of the gas on the piston ring 103 is enhanced. Therefore, as a preferred embodiment of the present scheme, the exposed part of the piston ring 103 is not more than one-third, which can achieve the pressure reduction effect of the high-temperature gas and the limiting and protection effect of the piston ring 103.

[0050] In addition, the inclined side wall 1012 can also be partially parallel to the vertical side wall 1011 and partially inclined inward toward the bottom of the groove to form a necked section, which can also achieve the buffering and pressure reduction effect of the gas.

[0051] In one embodiment, as shown in Figure 2 、 Figure 3 The piston ring 103 abuts against the groove wall on the side of the first piston ring groove 102 away from the pressure relief groove 101, a first avoidance gap 1021 is formed between the piston ring 103 and the groove wall on the side of the first piston ring groove 102 close to the pressure relief groove 101, a second avoidance gap 1022 is formed between the piston ring 103 and the bottom of the first piston ring groove 102, and the first avoidance gap 1021 and the second avoidance gap 1022 are communicated.

[0052] The normal state of the piston ring 103 in the first piston ring groove 102 is that its side surface is in abutment with the lower side wall of the first piston ring groove 102 under the action of gravity, and due to the elastic property of the piston ring 103, its outer circumferential surface will expand outward so that the piston ring 103 abuts against the cylinder liner 300. During the operation of the engine, due to the influence of knocking and the like, the piston ring 103 will collapse inward to be deformed, and the piston ring 103 will be impacted into the first piston ring groove 102. According to the scheme, when the high-pressure gas passes through the pressure relief groove 101 to reach the first piston ring groove 102, the high-pressure gas can enter the first piston ring groove 102 along the first avoiding gap 1021 close to the pressure relief groove 101, and then flow along the first avoiding gap 1021 to the second avoiding gap 1022 at the bottom of the groove, so that the piston ring 103 in the first piston ring groove 102 is pressed against the cylinder liner 300, thereby avoiding the piston ring 103 from being impacted and deformed to collapse into the first piston ring groove 102, and at the same time, the piston ring 103 will not vibrate due to the impact, so that the piston ring 103 is tightly attached to the cylinder liner 300. At the same time, the first avoiding gap 1021 and the second avoiding gap 1022 are beneficial to increase the gas flow space and further strengthen the effect of buffering and depressurizing the gas.

[0053] Preferably, as shown in the first avoiding gap 1021, the height d in the vertical direction is in the range of 0.2mm≤d≤0.4mm. Figure 3

[0054] In the prior art, when the first avoiding gap 1021 is set, it is usually 0.1-0.2mm, and in the preferred scheme, the distance of the first avoiding gap 1021 is set to 0.2-0.4mm. On the one hand, the increased flow space can effectively guide the external gas to flow to the first avoiding gap 1021, so that the high-pressure gas reaches the bottom side of the first piston ring groove 102, i.e. reaches the second avoiding gap 1022, and the piston ring 103 is pressed tightly against the cylinder liner 300, thereby avoiding the high-temperature and high-pressure gas from impacting from the side of the cylinder liner 300 to the bottom side of the first piston ring groove 102, and avoiding the piston ring 103 from being deformed. On the other hand, the increased first avoiding gap 1021 also plays a role in depressurization.

[0055] The scheme also includes an engine, which comprises a body 400, a cylinder and a cylinder liner 300, and the cylinder is provided with the piston 100 structure as described in the above embodiments. The piston 100 structure can weaken the impact force of the high-temperature and high-pressure gas caused by knocking, thereby protecting the piston ring 103 from being deformed due to the impact, and being beneficial to maintaining the shape and stable function of the piston ring 103.

[0056] The places not mentioned in the present application can be realized by using or referring to the existing technology.​

[0057] The various embodiments in the specification are described in progressive manner, and the same or similar parts between the various embodiments can be mutually referred to, and each embodiment focuses on the difference from other embodiments.

[0058] The above only describes the embodiments of the present application and is not intended to limit the present application. The present application can have various changes and modifications for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the scope of claims of the present application.

Claims

1. A piston structure for mitigating knock shock, the piston (100) comprising a piston fire shore (104) near the cylinder liner (300), characterized in that, The piston (100) is provided with a first piston ring groove (102) for assembling piston rings (103) and a pressure relief groove (101) provided on the piston fire shore (104). A first clearance gap (1021) and a second clearance gap (1022) are provided between the groove wall of the first piston ring groove (102) and the piston ring (103). The pressure relief groove (101) is located above the first piston ring groove (102). High temperature and high pressure gas flows through the pressure relief groove (101) to the first clearance gap (1021) and the second clearance gap (1022).

2. The piston structure according to claim 1, characterized in that, The piston (100) is provided with an inwardly recessed section that surrounds the piston (100) circumferentially to form the pressure relief groove (101) circumferentially on the piston (100), and the opening of the pressure relief groove (101) faces the cylinder liner (300).

3. The piston structure according to claim 2, characterized in that, A gap is provided between the piston fire seat (104) and the cylinder liner (300) to form an air passage (200), which is connected to the pressure relief groove (101).

4. The piston structure according to claim 3, characterized in that, The air passage (200) includes a horizontal flow section (201), and the end of the pressure relief groove (101) extends vertically toward the first piston ring groove (102) so that the horizontal flow section (201) is formed between the piston (100) and the cylinder liner (300).

5. The piston structure according to claim 4, characterized in that, The advection section (201) is located between the first piston ring groove (102) and the pressure relief groove (101), and the advection section (201) is connected to the first piston ring groove (102).

6. The piston structure according to claim 2, characterized in that, The pressure relief groove (101) includes a vertical sidewall (1011) away from the first piston ring groove (102) and an inclined sidewall (1012) close to the first piston ring groove (102). The end of the vertical sidewall (1011) and the end of the piston fire shore (104) are located on the same horizontal line. The distance between the inclined sidewall (1012) and the cylinder liner (300) is greater than the distance between the vertical sidewall (1011) and the cylinder liner (300).

7. The piston structure according to claim 6, characterized in that, The pressure relief groove (101) has a necked section on the side near the center of the piston (100) to make the pressure relief groove (101) V-shaped, and the inclined sidewall (1012) is inclined away from the first piston ring groove (102) to form the necked section.

8. The piston structure according to claim 1, characterized in that, The piston ring (103) abuts against the groove wall of the first piston ring groove (102) on the side away from the pressure relief groove (101). A first clearance gap (1021) is formed between the piston ring (103) and the groove wall of the first piston ring groove (102) on the side close to the pressure relief groove (101). A second clearance gap (1022) is formed between the piston ring (103) and the bottom of the first piston ring groove (102). The first clearance gap (1021) and the second clearance gap (1022) are in communication.

9. The piston structure according to claim 8, characterized in that, The vertical height d of the first clearance (1021) is in the range of 0.2mm≤d≤0.4mm.

10. An engine comprising a block (400), a cylinder, and a cylinder liner (300), characterized in that, The cylinder is provided with a piston structure as described in any one of claims 1-9.

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