Reciprocating piston of BOG compressor

Abstract

The invention relates to the technical field of compressors, in particular to a BOG compressor reciprocating piston which comprises a fixing ring, a piston ring, a middle rotating ring, a connecting rod and a driving assembly, the interior of the fixing ring is hollow, an annular through groove is formed in the periphery of the fixing ring, the piston ring is arranged on the periphery of the fixing ring in a sleeving mode, and the middle rotating ring is coaxially and rotationally sealed in the annular through groove. The fixing ring, the middle rotating ring, the connecting rod and the driving assembly are arranged, in the working state, BOG in the area with large pressure in the cylinder body is firstly driven by the driving assembly to flow into the area of the external thread groove along the preset path, and then the middle rotating ring is driven to rotate in the preset direction; therefore, the BOG in the external thread groove moves in the direction of the small-pressure area of the cylinder body, the pressure on the low-pressure side of the piston ring is increased, the pressure difference between the left side and the right side of the piston ring is reduced, and the probability that the piston ring is deformed due to the fact that the piston ring cannot bear the pressure of gas flowing into a compression chamber is lowered.

Description

Technical Field

[0001] The present invention relates to the technical field of compressors, and particularly to a reciprocating piston of a BOG compressor. Background Art

[0002] During the storage and transportation of liquefied gas, due to the inflow of external heat, part of the liquefied gas inevitably changes from liquid to gas, which is the so-called boil-off gas (BOG). If not processed, these boil-off gases will cause the pressure in the storage tank to rise, increasing the probability of safety hazards. A BOG compressor, that is, a boil-off gas compressor, is a device used to process the gas naturally evaporated during the storage and transportation of liquefied natural gas. During operation, the BOG compressor first inhales low-pressure evaporated gas from the storage tank or other sources, compresses the inhaled gas to the required pressure through piston movement, and finally discharges the compressed gas to the combustion supply system or the flare combustion device.

[0003] The core component of a BOG compressor is the piston system, and the quality of its sealing performance is an important indicator determining the working efficiency of the compressor. In the Chinese invention patent with the authorization announcement number CN111989511B, a piston ring and a compressor are disclosed. In its background art, it is disclosed that the sealing performance of the piston system is mostly reduced because the piston ring sleeved on the outer periphery of the piston is deformed due to the inability to withstand the pressure of the gas flowing in from the compression chamber, thus there is a problem that the sealing performance of the piston ring is damaged. Summary of the Invention

[0004] Based on this, in view of the problems existing in the current piston, it is necessary to provide a reciprocating piston of a BOG compressor to solve the problem that the piston ring is easily deformed due to the inability to withstand the gas pressure flowing into the compression chamber.

[0005] The above object is achieved by the following technical solutions: A reciprocating piston of a BOG compressor is slidably disposed inside the cylinder block of the BOG compressor, dividing the inside of the cylinder block into two non-communicating regions. The reciprocating piston includes: A fixed ring, the inside of the fixed ring is hollow, and an annular through groove is provided on its outer periphery; A piston ring, the piston ring is sleeved on the outer periphery of the fixed ring; An intermediate rotating ring, the intermediate rotating ring is rotationally sealed coaxially in the annular through groove, and an external thread groove is provided on the outer peripheral surface of the intermediate rotating ring; A connecting rod, the connecting rod is coaxially and fixedly connected with the fixed ring; A driving assembly, the driving assembly is disposed inside the fixed ring; In the working state, the driving component is used to first drive the BOG in the area with a large pressure in the cylinder body to flow along a preset path into the area of the external thread groove, and then drive the intermediate rotating ring to rotate in a preset direction, so that the BOG in the external thread groove moves in the direction of the area with a small pressure in the cylinder body.

[0006] Preferably, the driving component includes a conduit, a pipe joint, a sliding ring, a one-way air valve and a first elastic member. The axis of the conduit is parallel to the axis of the fixed ring. There are multiple conduits and they are evenly divided into two groups. One group of conduits is arranged circumferentially and equidistantly around the axis of the fixed ring, and one end of this group of conduits penetrates through one end of the fixed ring. The other group of conduits is arranged circumferentially and equidistantly around the axis of the fixed ring, and one end of this group of conduits penetrates through the other end of the fixed ring. The one-way air valve is arranged at the end of the conduit where it exits from the fixed ring, and the one-way air valve restricts the BOG in the conduit from flowing into the cylinder body. The pipe joint is slidably arranged at the end of the conduit away from the one-way air valve. The sliding ring is fixedly connected to the end of the pipe joint away from the conduit. The diameter of the sliding ring is the same as the inner diameter of the intermediate rotating ring, and the sliding ring is slidably connected to the inner peripheral wall of the intermediate rotating ring. The first elastic member is arranged between the fixed ring and the sliding ring, and the first elastic member is used to make the end of the sliding ring away from the fixed ring; Two groups of ventilation holes are formed inside the intermediate rotating ring. The two groups of ventilation holes are arranged circumferentially and equidistantly and alternately along the axis of the intermediate rotating ring. One end of one group of ventilation holes penetrates through to the middle area of the external thread groove, and the other end penetrates through to one side of the inner peripheral wall of the intermediate rotating ring. One end of the other group of ventilation holes penetrates through to the middle area of the external thread groove, and the other end penetrates through to the other side of the inner peripheral wall of the intermediate rotating ring.

[0007] Preferably, a communication hole is formed on the outer peripheral wall of the pipe joint; In the initial state, the communication hole is blocked by the inner peripheral wall of the conduit, so that the inside of the conduit and the ventilation holes are isolated from each other.

[0008] Preferably, the driving component further includes an intermediate moving ring. The intermediate moving ring is coaxially arranged between two sliding rings. The intermediate moving ring is slidably connected to the conduit, and the outer periphery of the intermediate moving ring is in spiral cooperation with the intermediate rotating ring.

[0009] Preferably, a spiral groove is formed on the outer peripheral wall of the intermediate moving ring, and a spiral strip is arranged on the inner peripheral wall of the intermediate rotating ring. The spiral strip is slidably connected in the spiral groove, so that the intermediate moving ring is in spiral cooperation with the intermediate rotating ring.

[0010] Preferably, a spiral groove is formed on the outer peripheral wall of the intermediate moving ring, and a protrusion is arranged on the inner peripheral wall of the intermediate rotating ring. The protrusion is slidably connected in the spiral groove, so that the intermediate moving ring is in spiral cooperation with the intermediate rotating ring.

[0011] Preferably, a sliding seal is provided between the inner peripheral walls of the intermediate moving ring and the fixed ring.

[0012] Preferably, the first elastic member is any one of a spring or a spiral spring strip.

[0013] Preferably, a fixed stop block is provided at one end of the connecting rod away from the output shaft of the BOG compressor.

[0014] Preferably, the connecting rod is slidably sealed with the cylinder block.

[0015] The beneficial effects of the present invention are as follows: The present invention is provided with a fixed ring, an intermediate rotating ring, a connecting rod and a driving assembly. In the working state, the driving assembly first drives the BOG in the area with high pressure in the cylinder block to flow along a preset path to the area of the external thread groove, and then drives the intermediate rotating ring to rotate in a preset direction, so that the BOG in the external thread groove moves towards the direction where the pressure in the cylinder block is low, thereby increasing the pressure on the low-pressure side of the piston ring, reducing the pressure difference between the left and right sides of the piston ring, and reducing the probability of the problem that the piston ring deforms due to the inability to withstand the gas pressure flowing into the compression chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is an overall schematic diagram of a reciprocating piston of a BOG compressor according to the present invention; Figure 2 is a cross-sectional view of a reciprocating piston of a BOG compressor according to the present invention; Figure 3 is a schematic structural diagram of a fixed ring and an intermediate rotating ring in a reciprocating piston of a BOG compressor according to the present invention; Figure 4 is Figure 3 the upper view of; Figure 5 is Figure 4 the A-A cross-sectional view in; Figure 6 is Figure 5 the enlarged schematic diagram of the structure at B in; Figure 7 is a schematic structural diagram of an intermediate moving ring in a reciprocating piston of a BOG compressor according to the present invention; Figure 8 is a schematic structural diagram of an intermediate rotating ring in a reciprocating piston of a BOG compressor according to the present invention.

[0017] Wherein: 100, cylinder block; 210, fixed ring; 220, piston ring; 230, intermediate rotating ring; 231, external thread groove; 232, vent hole; 233, spiral strip; 240, connecting rod; 250. Driving component; 251. Conduit; 252. Pipe joint; 2521. Communication hole; 253. Sliding ring; 254. One-way air valve; 255. First elastic member; 256. Intermediate moving ring; 2561. Spiral groove; 257. Fixed stop block. Detailed implementation mode

[0018] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0019] The serial numbers assigned to the components in this article itself, such as "first", "second", etc., are only used to distinguish the described objects and do not have any sequential or technical meanings. The "connection" and "coupling" mentioned in the present invention, unless otherwise clearly specified and defined, both include direct and indirect connections (couplings). In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention.

[0020] In the present invention, unless otherwise clearly specified and defined, the first feature being "above" or "below" the second feature may 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. Moreover, the first feature being "above", "over" and "on" the second feature may be that the first feature is directly above or obliquely above the second feature, or simply means that the first feature has a higher horizontal height than the second feature. The first feature being "below", "under" and "beneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or simply means that the first feature has a lower horizontal height than the second feature.

[0021] Such as Figures 1 to 8As shown in the figure, a reciprocating piston of a BOG compressor is slidably disposed inside a cylinder block 100 of the BOG compressor, dividing the interior of the cylinder block 100 into two non-communicating regions. The reciprocating piston includes a fixed ring 210, a piston ring 220, an intermediate rotating ring 230, a connecting rod 240, and a driving assembly 250. The interior of the fixed ring 210 is hollow, and an annular through groove is formed on its outer periphery. The piston ring 220 is sleeved on the outer periphery of the fixed ring 210. The intermediate rotating ring 230 is rotationally sealed coaxially in the annular through groove. An external thread groove 231 is formed on the outer peripheral surface of the intermediate rotating ring 230. The connecting rod 240 is coaxially and fixedly connected to the two fixed rings 210. The driving assembly 250 is disposed inside the fixed ring 210. In the working state, the driving assembly 250 is used to first drive the BOG in the region with a large pressure inside the cylinder block 100 to flow along a preset path into the region of the external thread groove 231, and then drive the intermediate rotating ring 230 to rotate in a preset direction, so that the BOG in the external thread groove 231 moves in the direction of the region with a small pressure in the cylinder block 100.

[0022] In the working state, the power end of the compressor drives the connecting rod 240 to reciprocate along the axis of the cylinder block 100, and the connecting rod 240 drives the fixed ring 210 to reciprocate synchronously inside the cylinder block 100, so as to Figure 2As shown, when the fixed ring 210 moves from right to left, the volume of the left region of the cylinder block 100 decreases, causing the BOG in the left region of the cylinder block 100 to be compressed. As a result, the pressure of the BOG in the left region of the cylinder block 100 increases after compression. At the same time, the volume of the right region of the cylinder block 100 increases, and the air pressure in the right region of the cylinder block 100 decreases accordingly. The piston ring 220 is sleeved on the outer periphery of the fixed ring 210, and the fixed ring 210 is located between the left and right regions of the cylinder block 100. Therefore, the gas pressure received by the left side of the piston ring 220 is greater than the gas pressure received by the right side of the piston ring 220. During the process of the fixed ring 210 moving from right to left, the driving assembly 250 first drives the BOG in the left region of the cylinder block 100 to flow along a preset path to the middle region of the external thread groove 231, and then drives the intermediate rotating ring 230 to rotate in a preset direction, so that the BOG in the external thread groove 231 moves in the direction of the low-pressure region in the cylinder block 100 under the driving action of the external thread groove 231, that is, drives the BOG in the external thread groove 231 to move towards the right side of the cylinder block 100, in order to increase the pressure received by the right side of the piston ring 220, achieve the purpose of reducing the pressure difference between the left and right sides of the piston ring 220, and thus reduce the probability of the problem that the piston ring 220 deforms due to being unable to withstand the gas pressure flowing into the compression chamber. Conversely, when the reciprocating piston moves from left to right, similarly to the above process, the BOG in the external thread groove 231 moves in the direction of the low-pressure region in the cylinder block 100 under the driving action of the external thread groove 231, that is, drives the BOG in the external thread groove 231 to move towards the left side of the cylinder block 100, in order to increase the pressure received by the left side of the piston ring 220, achieve the purpose of reducing the pressure difference between the left and right sides of the piston ring 220. The specific process will not be elaborated here.

[0023] In this embodiment, as Figures 2 to 7As shown in the figure, the driving component 250 includes a conduit 251, a pipe joint 252, a sliding ring 253, a one-way air valve 254 and a first elastic member 255. The axis of the conduit 251 is parallel to the axis of the fixed ring 210. There are multiple conduits 251 and they are evenly divided into two groups. One group of conduits 251 is arranged circumferentially and equidistantly around the axis of the fixed ring 210, and one end of this group of conduits 251 penetrates through one end of the fixed ring 210. The other group of conduits 251 is arranged circumferentially and equidistantly around the axis of the fixed ring 210, and one end of this group of conduits 251 penetrates through the other end of the fixed ring 210. The one-way air valve 254 is arranged at the end of the conduit 251 that penetrates out of the fixed ring 210. The one-way air valve 254 restricts the BOG in the conduit 251 from flowing into the cylinder body 100. The pipe joint 252 is slidably arranged at the end of the conduit 251 away from the one-way air valve 254. The sliding ring 253 is fixedly connected to the end of the pipe joint 252 away from the conduit 251. The diameter of the sliding ring 253 is the same as the inner diameter of the middle rotating ring 230, and the sliding ring 253 is slidably connected to the inner peripheral wall of the middle rotating ring 230. The first elastic member 255 is arranged between the fixed ring 210 and the sliding ring 253. The first elastic member 255 is used to make the end of the sliding ring 253 away from the fixed ring 210. Two groups of ventilation holes 232 are provided inside the middle rotating ring 230. The two groups of ventilation holes 232 are arranged circumferentially and equidistantly and alternately along the axis of the middle rotating ring 230. One end of one group of ventilation holes 232 penetrates to the middle area of the external thread groove 231, and the other end penetrates to one side of the inner peripheral wall of the middle rotating ring 230. One end of the other group of ventilation holes 232 penetrates to the middle area of the external thread groove 231, and the other end penetrates to the other side of the inner peripheral wall of the middle rotating ring 230.

[0024] It should also be added that the one-way air valve 254 is a one-way pressure valve. When the pressure received by the one-way air valve 254 is greater than or equal to the threshold value, the one-way air valve 254 will be pushed open, and the BOG inside the cylinder body 100 can enter the inside of the conduit 251 through the one-way air valve 254.

[0025] In the initial state, the ends of the conduits 251 away from the one-way air valve 254 are all slidably sealed with the pipe joint 252. Therefore, the interiors of the two groups of conduits 251 are isolated from the corresponding ventilation holes 232.

[0026] During the working state (the principle is described in the process of the fixed ring 210 moving from right to left), as the fixed ring 210 moves from right to left, the gas pressure in the left region of the cylinder block 100 gradually increases. When the gas pressure in the left region of the cylinder block 100 is greater than or equal to the threshold value, the one-way gas valve 254 is pushed open, and the BOG in the left region of the cylinder block 100 enters the corresponding conduit 251 through the one-way gas valve 254. When the pressure of the BOG in the conduit 251 on the sliding ring 253 connected thereto is greater than the acting force of the first elastic member 255 on the sliding ring 253, the sliding ring 253 and the corresponding pipe joint 252 move synchronously away from the corresponding conduit 251, so that the end of the conduit 251 away from the one-way gas valve 254 is no longer sealed by the pipe joint 252. At this time, the BOG in the conduit 251 flows into the region formed by the two sliding rings 253 and the intermediate rotating ring 230. The vent hole 232 is opened on the inner peripheral wall of the intermediate rotating ring 230 and is located between the two sliding rings 253 at this time. Therefore, the inside of the conduit 251 is communicated with the vent hole 232, and the BOG in the conduit 251 enters the vent hole 232. Then, the BOG enters the region where the external thread groove 231 is located through the vent hole 232, realizing the flow of the BOG in the region with a large pressure in the cylinder block 100 along the preset path to the region of the external thread groove 231. The process of the fixed ring 210 moving from left to right is the same and will not be elaborated.

[0027] It should be added that the reason for making the vent hole 232 communicate with the middle region of the external thread groove 231 is to enable the BOG to flow left and right along the external thread groove 231 after entering the external thread groove 231, so as to facilitate the pressurization of the left side and the right side of the intermediate rotating ring 230 to the intermediate rotating ring 230.

[0028] In this embodiment, as Figure 6 shown, a communication hole 2521 is opened on the outer peripheral wall of the pipe joint 252. In the initial state, the communication hole 2521 is blocked by the inner peripheral wall of the conduit 251.

[0029] In the initial state, the communication hole 2521 is blocked by the inner peripheral wall of the conduit 251. Therefore, the interiors of the two groups of conduits 251 and the corresponding vent holes 232 are isolated from each other.

[0030] In the working state, when the slip ring 253 and the corresponding pipe joint 252 move synchronously away from the corresponding conduit 251 until the communication hole 2521 is exposed, the BOG inside the conduit 251 can then enter the area between the two slip rings 253 through the communication hole 2521 and enter the area where the external thread groove 231 is located through the ventilation hole 232 opened on the inner peripheral wall of the intermediate rotating ring 230. In this way, it can be ensured that in the working state, the pipe joint 252 and the conduit 251 maintain a sliding fit, thereby preventing the pipe joint 252 and the conduit 251 from being unable to be precisely fitted again after being separated from each other.

[0031] In this embodiment, as Figure 5 shown, the driving assembly 250 further includes an intermediate moving ring 256. The intermediate moving ring 256 is coaxially arranged between the two slip rings 253. The intermediate moving ring 256 is slidably connected to the conduit 251, and the intermediate moving ring 256 is in a spiral fit with the intermediate rotating ring 230.

[0032] In the working state (taking the fixed ring 210 moving from right to left as an example), when the BOG gas enters the area between the left slip ring 253 and the intermediate moving ring 256 through the communication hole 2521, the pressure in this area increases. The gas pressure pushes the intermediate moving ring 256 to move to the right. At this time, through the spiral fit between the intermediate moving ring 256 and the intermediate rotating ring 230, the intermediate rotating ring 230 is driven to rotate circumferentially in the preset rotation direction, and then the BOG is driven to move to the right through the external thread groove 231 opened on the outer periphery of the intermediate rotating ring 230, so that the pressure on the right side of the piston ring 220 increases, thereby reducing the pressure difference between the left and right sides of the piston ring 220.

[0033] To achieve the spiral fit between the intermediate moving ring 256 and the intermediate rotating ring 230, specifically, a spiral groove 2561 is opened on the outer peripheral wall of the intermediate moving ring 256, and a protrusion is provided on the inner peripheral wall of the intermediate rotating ring 230. The protrusion is slidably connected in the spiral groove 2561, so that the intermediate moving ring 256 is in a spiral fit with the intermediate rotating ring 230. In other embodiments, to ensure good sealing between the intermediate moving ring 256 and the intermediate rotating ring 230, specifically, a spiral groove 2561 is opened on the outer peripheral wall of the intermediate moving ring 256, and a spiral strip 233 is provided on the inner peripheral wall of the intermediate rotating ring 230. The spiral strip 233 is slidably connected in the spiral groove 2561, so that the intermediate moving ring 256 is in a spiral fit with the intermediate rotating ring 230. In this way, it can be ensured that the spiral strip 233 and the spiral groove 2561 are closely fitted, preventing the BOG in the area with high pressure formed by the slip ring 253 and the intermediate moving ring 256 from entering the area with low pressure formed by the other slip ring 253 and the intermediate moving ring 256 through the gap between the spiral strip 233 and the spiral groove 2561.

[0034] In this embodiment, a seal is provided between the inner peripheral wall of the intermediate moving ring 256 and the fixed ring 210.

[0035] Specifically, this is set to prevent BOG from leaking at the connection between the inner peripheral wall of the fixed ring 210 and the intermediate moving ring 256.

[0036] In this embodiment, the first elastic member 255 is either a spring or a helical spring strip.

[0037] It can be understood that the reason for choosing a spring or a helical spring strip for the first elastic member 255 is that both a spring and a helical spring strip can be stretched and compressed.

[0038] In this embodiment, a fixed stop 257 is provided at one end of the connecting rod 240 away from the output shaft of the BOG compressor.

[0039] It can be understood that setting the fixed stop 257 can prevent the reciprocating piston from directly contacting the bottom of the cylinder block 100, thereby reducing the probability of damage to the reciprocating piston.

[0040] In this embodiment, the connecting rod 240 is in sliding seal with the cylinder block 100.

[0041] It can be understood that this is set to ensure that the BOG inside the cylinder block 100 does not leak outwards.

[0042] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0043] The above-described embodiments only represent several implementation manners of the present invention. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims

1. A reciprocating piston of a BOG compressor, which is slidably disposed inside the cylinder block of the BOG compressor and divides the interior of the cylinder block into two non-communicating regions, is characterized in that, The reciprocating piston includes: A fixed ring, which is hollow inside and has an annular through groove on its outer periphery; A piston ring, which is sleeved on the outer periphery of the fixed ring; An intermediate rotating ring, which is rotationally sealed coaxially in the annular through groove, and has an external thread groove on its outer peripheral surface; A connecting rod, which is fixedly connected coaxially with the fixed ring; A driving assembly, which is arranged inside the fixed ring; In the working state, the driving assembly is used to first drive the BOG in the area with a large pressure in the cylinder to flow along a preset path to the area of the external thread groove, and then drive the intermediate rotating ring to rotate in a preset direction, so that the BOG in the external thread groove moves towards the direction where the pressure in the cylinder is small.

2. The reciprocating piston of a BOG compressor according to claim 1, characterized in that, The driving assembly includes a conduit, a pipe joint, a sliding ring, a one-way air valve and a first elastic member. The axis of the conduit is parallel to the axis of the fixed ring. There are multiple conduits and they are evenly divided into two groups. One group of conduits is arranged circumferentially and equidistantly around the axis of the fixed ring, and one end of this group of conduits penetrates through one end of the fixed ring. The other group of conduits is arranged circumferentially and equidistantly around the axis of the fixed ring, and one end of this group of conduits penetrates through the other end of the fixed ring. The one-way air valve is arranged at the end of the conduit where it penetrates out of the fixed ring, and the one-way air valve restricts the BOG in the conduit from flowing into the cylinder. The pipe joint is slidably arranged at the end of the conduit away from the one-way air valve. The sliding ring is fixedly connected to the end of the pipe joint away from the conduit. The diameter of the sliding ring is the same as the inner diameter of the intermediate rotating ring, and the sliding ring is slidably connected to the inner peripheral wall of the intermediate rotating ring. The first elastic member is arranged between the fixed ring and the sliding ring, and the first elastic member is used to make the end of the sliding ring away from the fixed ring; Two groups of ventilation holes are arranged inside the intermediate rotating ring. The two groups of ventilation holes are arranged circumferentially and equidistantly and alternately along the axis of the intermediate rotating ring. One end of one group of ventilation holes penetrates to the middle area of the external thread groove, and the other end penetrates to one side of the inner peripheral wall of the intermediate rotating ring. One end of the other group of ventilation holes penetrates to the middle area of the external thread groove, and the other end penetrates to the other side of the inner peripheral wall of the intermediate rotating ring.

3. A reciprocating piston of a BOG compressor according to claim 2, characterized in that, A communication hole is arranged on the outer peripheral wall of the pipe joint; In the initial state, the communication hole is blocked by the inner peripheral wall of the conduit, so that the inside of the conduit and the ventilation holes are isolated from each other.

4. A reciprocating piston of a BOG compressor according to claim 2, characterized in that, The driving assembly further includes an intermediate moving ring, which is arranged coaxially between the two sliding rings. The intermediate moving ring is slidably connected to the conduit, and the outer periphery of the intermediate moving ring is in spiral cooperation with the intermediate rotating ring.

5. A reciprocating piston of a BOG compressor according to claim 4, characterized in that, A spiral groove is arranged on the outer peripheral wall of the intermediate moving ring, and a spiral strip is arranged on the inner peripheral wall of the intermediate rotating ring. The spiral strip is slidably connected in the spiral groove, so that the intermediate moving ring is in spiral cooperation with the intermediate rotating ring.

6. The reciprocating piston of a BOG compressor according to claim 4, characterized in that, A spiral groove is arranged on the outer peripheral wall of the intermediate moving ring, and a protrusion is arranged on the inner peripheral wall of the intermediate rotating ring. The protrusion is slidably connected in the spiral groove, so that the intermediate moving ring is in spiral cooperation with the intermediate rotating ring.

7. A reciprocating piston of a BOG compressor according to claim 4, characterized in that, A sliding seal is provided between the inner peripheral wall of the intermediate moving ring and the fixed ring.

8. A reciprocating piston of a BOG compressor according to claim 2, wherein, The first elastic member is any one of a spring or a spiral spring strip.

9. A reciprocating piston of a BOG compressor according to claim 1, characterized in that, A fixed stop block is arranged at one end of the connecting rod away from the output shaft of the BOG compressor.

10. A reciprocating piston of a BOG compressor according to claim 1, characterized in that, The connecting rod is slidably sealed with the cylinder.

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