A high-pressure gas multi-channel rotary sealing joint

Abstract

The present invention relates to a high-pressure gas multi-channel rotary sealing joint. A dual-gas channel rotary joint is formed by arranging an inner shaft cylinder and two outer cylinders. Two sets of single-channel rotary sealing joints are combined. When gas leaks from the single-channel rotary sealing joint located in the middle, the gas does not leak into the atmosphere but enters the cavity of the outer cylinder, thereby reducing the gas leakage rate to the maximum extent. Both the inner core shaft and the outer core shaft are stationary components, which are sealed by two sealing rings. Both the inner rotary shell and the rotary shell are rotating components, which remain relatively stationary, thereby further reducing the gas leakage rate. Multiple sealing units are arranged between the core shaft and the rotary shell to form a combined seal, thereby effectively reducing the gas leakage rate.

Description

Technical Field

[0001] The invention relates to a rotary joint, in particular to a high-pressure gas multi-channel rotary sealing joint. Background Art

[0002] Wind power generation is the fastest growing green energy technology in the world. While the construction of onshore wind farms is developing rapidly, people have noticed some limitations on the use of onshore wind energy, such as large land area and noise pollution.

[0003] The rotor coil of the superconducting generator is made of superconducting materials, which can greatly improve the power generation capacity of the generator under the condition of the same external dimensions. The cold head is an indispensable and important component of the superconducting generator, which can provide a sufficiently low temperature for the superconducting coil. When the cold head is working, high-pressure helium is required as a refrigerant. The helium supply pipe and return pipe will rotate synchronously with the rotor of the superconducting generator together with the cold head. However, in the prior art, during the rotation of the supply pipe and the return pipe, there is helium leakage due to poor sealing effect, which leads to reduced refrigeration efficiency and damage to the equipment.

[0004] Therefore, it is necessary to find a rotary joint that can achieve a low gas leakage rate in the gas channel when the cold head rotates with the superconducting generator rotor. Summary of the invention

[0005] In view of all or part of the deficiencies of the prior art described above, the object of the present invention is to provide a high-pressure gas multi-channel rotary sealing joint, which effectively reduces the gas leakage rate during the rotation of the rotor by adopting dual gas channels and a combined sealing method.

[0006] To achieve the above-mentioned invention objectives, the present invention provides the following technical solutions: a high-pressure gas channel rotary sealing joint, an end connected to the generator is the first end, and an end connected to the compressor is the second end, comprising an inner shaft cylinder and a plurality of outer shaft cylinders arranged on the outer periphery thereof, the outer shaft cylinder being sealed and connected to the inner shaft cylinder; the inner shaft cylinder comprises an inner core shaft, an inner rotating shell is arranged on the outer periphery of the inner core shaft close to the first end, the inner rotating shell is sealingly and rotatably connected to the inner core shaft, and a gas channel is formed in the inner core shaft; the outer shaft cylinder comprises an outer core shaft, an outer rotating shell is arranged on the outer core shaft close to the first end, the outer rotating shell is sealingly and rotatably connected to the outer core shaft; the second end of the outer core shaft is fixedly and sealedly connected to the second end of the inner core shaft, the first end of the inner rotating shell is fixedly and sealedly connected to the first end of the outer rotating shell, and a cavity is formed between the outer core shaft and the inner rotating shell. The beneficial effect of this technical solution lies in that, by setting an inner cylinder and several outer cylinders, a cavity is formed in the inner cylinder and the outer cylinder, the inner rotating shell is sealed and connected to the outer periphery of the inner core shaft; the outer rotating shell is sealed and connected to the outer core shaft, the second end of the inner core shaft is fixedly sealed and connected to the second end of the outer core shaft, and the first end of the inner rotating shell is sealed and connected to the first end of the outer rotating shell; through the above-mentioned device, it can be achieved that when gas leakage occurs in the gas channel located in the middle position, it does not leak into the atmosphere, but enters the cavity around the inner cylinder of the shaft, that is, the outer cylinder, and continues to circulate in the gas system, so that the gas leakage rate of the rotating joint during rotation is effectively reduced.

[0007] A first sealing unit and a second sealing unit are provided between the inner core shaft and the inner rotating shell, the first sealing unit is provided close to the first end of the inner core shaft, and the second sealing unit is provided on the side of the first sealing unit away from the first end; the first sealing unit includes a thread groove on the outer periphery of the inner core shaft; the length of the first sealing unit along the axis direction of the inner core shaft is less than 80 mm. By providing a thread groove on the outer periphery of the inner core shaft, and the length of the area provided with the thread groove is less than 80 mm, the first sealing unit is formed, which effectively reduces the gas leakage rate for the labyrinth seal.

[0008] The second sealing unit includes a plurality of compression rings and a plurality of sealing rings arranged at intervals. By arranging compression rings and sealing rings between the inner shaft and the inner rotating shell, and arranging the plurality of compression rings and the plurality of sealing rings at intervals, a packing seal is formed, further improving the sealing performance of the rotary joint.

[0009] Preferably, the pressure ring is a copper pressure ring, and the sealing ring is a polytetrafluoroethylene sealing ring. Five copper pressure rings are provided, and four polytetrafluoroethylene sealing rings are provided. The five copper pressure rings and the four polytetrafluoroethylene sealing rings are arranged at intervals.

[0010] A third sealing unit is further provided between the inner core shaft and the inner rotating shell, the third sealing unit is provided between the front end of the inner core shaft and the first end of the inner rotating shell, and the third sealing unit includes a sealing gasket; the first end of the inner core shaft is in close contact with the sealing gasket. The third sealing unit is formed by setting the first end of the inner core shaft as a spherical surface and setting a sealing gasket between the front end spherical surface of the inner core shaft and the inner rotating shell.

[0011] A sealing auxiliary unit is also provided on the side of the second sealing unit facing away from the first sealing unit; the sealing auxiliary unit includes an elastic member and a clamping block, the elastic member is provided on the side close to the second sealing unit; the clamping block is provided on the side of the elastic member facing away from the second sealing unit, and the clamping block is threadedly connected to the inner rotating shell. By providing an auxiliary sealing unit on one side of the second sealing unit, which includes an elastic member and a clamping block, the elastic member and the clamping block interact with each other to provide a clamping force for the third-level seal between the inner core shaft and the sealing gasket, thereby enhancing the sealing effect; the clamping block is threadedly connected to the inner rotating shell, and the tension of the spring can be adjusted.

[0012] A stopper is provided between the inner rotating shell and the pressing block to limit the relative rotation between the pressing block and the inner rotating shell. The stopper is used to limit the relative rotation between the pressing block and the inner rotating shell, further ensuring the sealing of the rotary joint; when adjusting the pressing block, the stopper needs to be removed first.

[0013] There are two outer cylinders, and the outer cylinders include a first outer cylinder and a second outer cylinder; the first outer cylinder and the second outer cylinder are arranged on both sides of the shaft inner cylinder; a first gas passage is formed between the shaft inner cylinders, and the cavity in the first outer cylinder is the second gas passage; the shaft inner cylinder coincides with the rotation axis of the first outer cylinder; the sealing structure between the outer rotating shell and the outer core shaft is the same as the sealing structure between the inner core shaft and the inner rotating shell. The beneficial effect of this technical solution is that by arranging two outer cylinders on the outer periphery of the shaft inner cylinder, and one of the outer cylinders is formed with a gas passage, a double gas passage is formed in combination; the double-channel rotary sealing joint is composed of two sets of single-channel rotary sealing joints, the rotation axes of the two coincide, the inner core shaft and the outer core shaft are both stationary parts, and the two are sealed by two sealing rings, which is a static seal, and the leakage rate is lower than 1.0×10-6Pa·m³ / s. The inner rotating shell and the outer rotating shell are both rotating parts, which remain relatively still and are sealed by two O-rings. They are static seals with a leakage rate lower than 1.0×10-6Pa·m³ / s. Through the above settings, when gas leakage occurs in the gas channel located in the middle position, it does not leak into the atmosphere, but enters the surrounding cavity or gas channel, thereby minimizing the gas leakage rate.

[0014] Compared with the prior art, the present invention has at least the following beneficial effects: by setting the inner cylinder and the outer cylinder of the shaft, a dual-gas channel rotary joint is formed, and two sets of single-channel rotary sealing joints are combined, and the rotation axes of the two coincide, when the gas of the single-channel rotary sealing joint located in the middle position leaks, it does not leak into the atmosphere, but enters the outer cylinder, thereby minimizing the gas leakage rate; the inner core shaft and the outer core shaft are both stationary parts, and the two are sealed by two sealing rings, and the inner rotating shell and the rotating shell are both rotating parts, and the two remain relatively stationary, further reducing the gas leakage rate; by setting multiple units between the core shaft and the rotating shell, a combined seal is formed, which effectively reduces the gas leakage rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0016] Figure 1 Schematic diagram of an application scenario of an embodiment of the present invention.

[0017] Figure 2 Schematic diagram of the structure of a single high-pressure gas channel according to an embodiment of the present invention.

[0018] Figure 3 Schematic diagram of the structure of the high-pressure gas dual-channel embodiment of the present invention.

[0019] Figure 4 It is a three-dimensional structural cross-sectional view of a high-pressure gas dual-channel rotary joint according to an embodiment of the invention.

[0020] Figure numerals: 1- shaft inner cylinder; 11- inner core shaft; 12- inner rotating shell; 13- sealing gasket Ⅰ; 14- copper pressure ring Ⅰ; 15- polytetrafluoroethylene sealing ring Ⅰ; 16- spring Ⅰ; 17- clamping block Ⅰ; 18- stop screw Ⅰ; 19- thread groove Ⅰ; 2- first outer cylinder; 21- outer core shaft; 22- outer rotating shell; 23- sealing gasket Ⅱ; 24- copper pressure ring Ⅱ; 55- polytetrafluoroethylene sealing ring Ⅱ; 26- spring Ⅱ; 27- clamping Block II; 28-stop screw II; 29-O-ring; 30-thread groove II; 3-second outer cylinder; 31-helium compressor; 32-low-pressure helium pipe; 33-high-pressure helium pipe; 34-dual-channel rotary sealing joint; 35-rotating frame; 36-superconducting wind turbine; 37-fixed frame; 38-air supply pipe; 39-air return pipe; 4-second sealing unit; 5-sealing auxiliary unit; 6-fourth sealing unit; 7-first sealing auxiliary unit. DETAILED DESCRIPTION

[0021] The technical solutions in the specific embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example

[0022] In this embodiment, a high-pressure gas multi-channel rotary sealing joint is provided. Figure 1 The application scenario of the present disclosure is shown, involving a helium compressor 31, a low-pressure helium tube 32, a high-pressure helium tube 33, a dual-channel rotary sealing joint 34, a rotating frame 35, a superconducting wind turbine 36, a fixed frame 37, an air supply pipe 38, and an air return pipe 39. Among them, the left side of the dual-channel rotary sealing joint 34 is connected to the low-pressure helium tube 32 and the high-pressure helium tube 33, which are stationary parts, and the right side is connected to the air supply pipe 38 and the air return pipe 39, which are rotating parts. The rotating frame 35 is used to connect the rotating parts of the superconducting wind turbine 36 and the rotating shell of the dual-channel rotary sealing joint 34, so that the two remain relatively still and rotate synchronously. The fixed frame 37 is used to fix the core shaft of the dual-channel rotary sealing joint 34 so that it is coaxial with the rotating parts of the superconducting wind turbine 36.

[0023] In this embodiment, if Figure 2 As shown, a single rotating channel (here, an inner shaft cylinder 1 composed of an inner core shaft 11 and an inner rotating shell 12) includes an inner core shaft 11, an inner rotating shell 12, and a first sealing unit, a second sealing unit 4, and a third sealing unit are arranged between the inner core shaft 11 and the inner rotating shell 12, wherein, in this embodiment, the left side is the rear end of the inner core shaft 11 and the inner rotating shell 12, and the right side is the front end of the inner core shaft 11 and the inner rotating shell 12. The third sealing unit is arranged between the front end of the inner core shaft 11 and the front end of the inner rotating shell 12, and the first sealing unit and the second sealing unit are arranged in sequence on the rear side thereof, that is, the second sealing unit 4, the first sealing unit, and the third sealing unit are arranged in sequence between the inner core shaft 11 and the inner rotating shell 12 from the rear end to the front end of the inner core shaft 11. In this embodiment, the front end of the inner core shaft 11 is designed to be a spherical surface, and a sealing gasket I13 is arranged between it and the front end 12 of the inner rotating shell. The shape of the sealing gasket I13 is consistent with the shape of the front end of the inner core shaft 11. The inner core shaft 11 is a fixed part and is in close contact with the sealing gasket I13, forming a third sealing unit as the first-level seal.

[0024] A first sealing unit is arranged between the inner core shaft 11 and the inner rotating shell 12 at the rear side of the third sealing unit. In this embodiment, the first sealing unit is arranged on the outer periphery of the inner core shaft 11, and includes a plurality of thread grooves Ⅰ19, and the length of the overall thread groove Ⅰ19 is less than 80 mm. In this interval, Teflon is sprayed on the outer periphery of the inner core shaft 11 and designed into a threaded groove Ⅰ19, which forms a labyrinth seal with the inner rotating shell 12, which belongs to the second-level seal and further improves the sealing effect. A second sealing unit 4 is also arranged between the inner core shaft 11 and the inner rotating shell 12 at the rear side of the first sealing unit. The second sealing unit 4 includes a plurality of pressure rings and a plurality of sealing rings, and the pressure rings and the sealing rings are arranged at intervals. In this embodiment, the pressure ring is a copper pressure ring Ⅰ14, and the sealing ring is a polytetrafluoroethylene sealing ring Ⅰ15. Of course, in other embodiments, pressure rings made of other metal materials or sealing rings made of other polymers can also be used, as long as the purpose of the present disclosure is achieved, and no limitation is made here. In a preferred example of this embodiment, the number of copper pressure rings Ⅰ14 is five, the number of polytetrafluoroethylene sealing rings Ⅰ15 is four, and the five copper pressure rings Ⅰ14 and the four polytetrafluoroethylene sealing rings Ⅰ15 are arranged at intervals to form a packing seal, which belongs to the third-level seal and further improves the sealing performance. Specifically, from the front end to the rear end, the first copper pressure ring Ⅰ14 is arranged on the side close to the first sealing unit, and the fifth copper pressure ring Ⅰ14 is arranged on the side close to the auxiliary sealing unit 5. Of course, in other embodiments, the number of copper pressure rings Ⅰ14 and polytetrafluoroethylene sealing rings Ⅰ15 can be set as needed, and is not limited here.

[0025] In this embodiment, an auxiliary sealing unit 5 is further provided between the inner core shaft 11 and the inner rotating shell 12 on one side of the second sealing unit 4, i.e., near the rear end of the inner core shaft, and the inner rotating shell 12. The elastic member and the pressing block Ⅰ17 are used to enhance the sealing effect. The elastic member is provided on one side near the second sealing unit 4; the pressing block Ⅰ17 is provided on the other side of the elastic member, and the pressing block Ⅰ17 is threadedly connected to the inner rotating shell 12. Specifically, the elastic member is in close contact with the copper pressure ring Ⅰ14 at the end of the second sealing unit 4. In this embodiment, the elastic member is a spring Ⅰ16, which acts on the second sealing unit 4 to compress the polytetrafluoroethylene sealing ring Ⅰ15 therein, and also provides a pressing force for the first-level seal between the inner core shaft 11 and the sealing pad Ⅰ13. Of course, in other embodiments, the elastic member can also be other elements that can achieve the purpose of the present invention, such as elastic rubber, which is not limited here.

[0026] The pressing block I17 is connected to the inner rotating housing 12 by a threaded connection, which is used to adjust the pressing force of the spring I16. A stopper is provided between the inner rotating housing 12 and the pressing block I17. In this embodiment, the stopper is a stop screw I18, which is used to limit the relative rotation between the pressing block I17 and the inner rotating housing 12. When adjusting the pressing block I17, the stop screw I18 needs to be removed first. Of course, in other embodiments, the stopper may also be other elements that can achieve the purpose of the present invention, such as a stopper block.

[0027] In this embodiment, two outer cylinders are arranged on the outer periphery of the shaft inner cylinder 1, one of the outer cylinders is formed with a gas channel, which is combined with the gas channel in the shaft inner cylinder 1 to form a double gas channel. In this embodiment, a gas channel is formed in the first outer cylinder 2. Figure 3 and Figure 4 It can be seen that the outer cylinder rotating with dual gas channels includes an outer core shaft 21 and an outer rotating shell 22, wherein the sealing structure between the outer core shaft 21 and the outer rotating shell 22 is the same as the sealing structure between the inner core shaft 11 and the inner rotating shell 12. Specifically, the fourth sealing unit 6, the fifth sealing unit and the sixth sealing unit are sequentially arranged between the outer core shaft 21 and the outer rotating shell 22 from the rear end to the front end of the outer core shaft 21, which correspond to the second sealing unit 4, the first sealing unit and the third sealing unit between the inner core shaft 11 and the inner rotating shell 12, respectively.

[0028] Specifically, the sixth sealing unit includes a sealing gasket II 23, and the side of the front end of the outer core shaft 21 close to the outer rotating shell 22 is designed as a spherical surface, which is in close contact with the sealing gasket II 23. The fifth sealing unit includes a plurality of thread grooves II 30, and the length of the overall thread groove II 30 is less than 80 mm. In this interval, Teflon is sprayed on the outer periphery of the inner and outer core shafts 21 and designed as a threaded groove II 30, forming a labyrinth seal with the outer rotating shell 22; the fourth sealing unit 6 includes a plurality of pressure rings and a plurality of sealing rings, and the pressure rings and the sealing rings are arranged at intervals. In this embodiment, the pressure ring is a copper pressure ring II 24 and a sealing ring polytetrafluoroethylene sealing ring II 25, wherein the number and arrangement of the copper pressure ring II 24 and the sealing ring polytetrafluoroethylene sealing ring II 25 are consistent with those in the second sealing unit. Of course, in other embodiments, the number and arrangement of the copper pressure ring II 24 and the sealing ring polytetrafluoroethylene sealing ring II 25 in the fourth sealing unit 6 may be different from those in the second sealing unit 4, as long as the purpose of the present disclosure can be achieved, and no limitation is made here. Of course, a first sealing auxiliary unit 7 is also provided on one side of the fourth sealing unit 6, which includes a spring II 26 and a clamping block II 27, and the arrangement of the above two is consistent with the sealing auxiliary unit 5 in the shaft inner tube 1. A stop screw II 28 is also provided between the outer rotating housing 22 and the clamping block 27, and its function and installation method are consistent with the stop screw I 18.

[0029] The dual-channel rotary seal joint is composed of two sets of single-channel (i.e., the shaft inner tube 1 and the first outer tube 2) rotary seal joints, and the rotation axes of the two coincide. The inner core shaft 11 and the outer core shaft 21 are both stationary parts, and the two are sealed by two O-rings 29, which are static seals, and the leakage rate between the two is less than 1.0x10-6Pa·m³ / s. The inner rotating shell 12 and the outer rotating shell 22 are both rotating parts, and the two remain relatively stationary, and are sealed by two O-rings 29, which are static seals, and the leakage rate between the two is less than 1.0×10-6Pa·m³ / s. Through the above arrangement, when the single-channel rotary seal joint located in the middle position leaks gas, the leaked gas does not leak into the atmosphere, but enters the gas channel rotary seal joint formed by the first outer tube 2 outside the shaft inner tube 1, and continues to circulate in the gas system or enters the cavity of the second outer tube 3 outside the shaft inner tube. Therefore, although two sets of single-channel rotary sealing joints are used in the dual-channel rotary sealing joint, the actual helium leakage rate is not twice that of the single-channel rotary sealing joint, and is even lower than the leakage rate of the single-channel rotary sealing joint. The present invention adopts a combined sealing method (labyrinth seal + packing seal), and the leakage rate can reach 5×10-6Pa·m³ / s, and the maximum rotation speed is ≤120RPM.

[0030] The structure disclosed by the present invention can contain helium and other gases for cooling the high-pressure rotary joint in its gas channel.

[0031] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A high-pressure gas multi-channel rotary sealing joint, wherein the end connected to the generator is the first end, and the end connected to the compressor is the second end, characterized in that: The invention comprises an inner shaft cylinder (1) and a plurality of outer shaft cylinders arranged on the outer circumference thereof, wherein the outer shaft cylinder is sealedly connected to the inner shaft cylinder (1); the inner shaft cylinder (1) comprises an inner core shaft (11), an inner rotating shell (12) is arranged on the outer circumference of the inner core shaft (11) close to the first end, the inner rotating shell (12) is sealedly rotatably connected to the inner core shaft (11), and a gas passage is formed in the inner core shaft (11); the outer shaft cylinder comprises an outer core shaft (21), an outer rotating shell (22) is arranged on the outer circumference of the outer core shaft (21) close to the first end, and the outer rotating shell (22) is sealedly rotatably connected to the outer core shaft (21); The second end of the outer core shaft (21) is fixedly sealedly connected to the second end of the inner core shaft (11), the first end of the inner rotating shell is fixedly sealedly connected to the first end of the outer rotating shell, and a cavity is formed between the outer core shaft (21) and the inner rotating shell (12).

2. The high-pressure gas multi-channel rotary sealing joint according to claim 1, characterized in that: A first sealing unit and a second sealing unit (4) are arranged between the inner core shaft (11) and the inner rotating shell (12), the first sealing unit being arranged close to the first end of the inner core shaft (11), and the second sealing unit (4) being arranged on a side of the first sealing unit away from the first end.

3. The high-pressure gas multi-channel rotary sealing joint according to claim 2, characterized in that: The first sealing unit comprises a threaded groove located on the outer circumference of the inner core shaft (11).

4. The high-pressure gas multi-channel rotary sealing joint according to claim 3, characterized in that: The length of the first sealing unit along the axial direction of the inner core shaft (11) is less than 80 mm.

5. The high-pressure gas multi-channel rotary sealing joint according to claim 2, characterized in that: The second sealing unit (4) comprises a plurality of pressure rings and a plurality of sealing rings which are arranged at intervals.

6. The high-pressure gas multi-channel rotary sealing joint according to claim 1, characterized in that: A third sealing unit is also provided between the inner core shaft (11) and the inner rotating shell (12); the third sealing unit is provided between the first end of the inner core shaft (11) and the first end of the inner rotating shell (12); the third sealing unit comprises a sealing gasket; the first end of the inner core shaft (11) is in close contact with the sealing gasket.

7. The high-pressure gas multi-channel rotary sealing joint according to claim 2, characterized in that: A sealing auxiliary unit (5) is also provided on the side of the second sealing unit (4) facing away from the first sealing unit.

8. The high-pressure gas multi-channel rotary sealing joint according to claim 7, characterized in that: The sealing auxiliary unit (5) comprises an elastic member and a pressing block, wherein the elastic member is arranged on a side close to the second sealing unit (4); the pressing block is arranged on a side of the elastic member away from the second sealing unit (4), and the pressing block is threadedly connected to the inner rotating shell (12).

9. The high-pressure gas multi-channel rotary sealing joint according to claim 8, characterized in that: A stopper is provided between the inner rotating shell (12) and the pressing block, and is used to limit relative rotation between the pressing block and the inner rotating shell (12).

10. The high-pressure gas multi-channel rotary sealing joint according to claim 1, characterized in that: The outer cylinder is provided with two, including a first outer cylinder (2) and a second outer cylinder (3); the first outer cylinder (2) and the second outer cylinder (3) are arranged on both sides of the shaft inner cylinder (1).

11. The high-pressure gas multi-channel rotary sealing joint according to claim 10, characterized in that: The shaft inner cylinder (1) is formed with a first gas passage, and the cavity of the first outer cylinder (2) is a second gas passage; the rotation axis of the shaft inner cylinder (1) coincides with the rotation axis of the first outer cylinder (2).

12. The high-pressure gas multi-channel rotary sealing joint according to any one of claims 2 to 9, characterized in that: The sealing structure between the outer core shaft (21) and the outer rotating shell (22) is the same as the sealing structure between the inner core shaft (11) and the inner rotating shell (12).

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