Magnetic drive shaftless submersible electric pump
By adopting a modular design and material selection for the magnetic drive shaftless submersible pump, the problems of complex disassembly and assembly and difficulty in reducing weight of shaftless submersible pumps have been solved, achieving the effects of easy maintenance and lightweight design.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- CHANGSHA DEWATER MECHANICAL TECHNOLOGY CO LTD
- Filing Date
- 2025-07-24
- Publication Date
- 2026-07-14
AI Technical Summary
Existing shaftless submersible pumps have a large number of components and mechanical connection points, making disassembly and assembly complex and making it difficult to reduce the system weight.
The modular design of the magnetically driven shaftless submersible electric pump includes a stator assembly, rotor assembly, front shroud, rear shroud, and bearing assembly. The ring motor is integrated with the pump casing, reducing the number of components and mechanical connection points. Aluminum alloy and stainless steel materials are used to reduce weight.
It facilitates disassembly and maintenance, reduces system weight, maintains structural strength, and improves motor power density and drainage efficiency.
Smart Images
Figure CN224496797U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of submersible pump technology, and in particular to a magnetically driven shaftless submersible pump. Background Technology
[0002] A submersible pump is a type of water pump in which both the pump body, impeller, and the motor driving the impeller are submerged in water. Shaftless submersible pumps employ a structure where the annular rotor and impeller are tightly integrated, forming a highly efficient pumping system.
[0003] Currently, existing shaftless submersible pumps have a large number of components and mechanical connection points, making the disassembly and assembly process complex and inconvenient for maintenance. Furthermore, there is still room for improvement in reducing system weight.
[0004] In view of the problems existing in the prior art, those skilled in the art urgently need a magnetically driven shaftless submersible electric pump. Utility Model Content
[0005] The purpose of this invention is to provide a magnetically driven shaftless submersible pump to solve the problems existing in the prior art, which is easy to disassemble and maintain, and can reduce the system weight while meeting structural strength requirements.
[0006] To achieve the above objectives, this utility model provides the following solution:
[0007] This utility model provides a magnetically driven shaftless submersible pump, including a stator assembly, a rotor assembly, a front shroud, a rear shroud, and a bearing assembly. The stator assembly includes a stator housing, a stator core, and coils. The outer wall of the stator core is connected and fixed to the inner wall of the stator housing. Multiple coils are arranged circumferentially on the inner wall of the stator core. The rotor assembly includes a rotor body, an impeller, and permanent magnets. The rotor body is coaxially disposed inside the stator housing. Multiple permanent magnets, opposite to the stator core, are embedded circumferentially on the outer wall of the rotor body. The inner wall of the rotor body is integrally connected with multiple impellers along the circumferential direction; the front shunting cover includes a first outer connecting arm and a first inner connecting arm, and the rear shunting cover includes a second outer connecting arm and a second inner connecting arm; the two ends of the stator housing are respectively sealed to the ends of the first outer connecting arm and the second outer connecting arm, and the two ends of the rotor body are respectively dynamically sealed to the ends of the first inner connecting arm and the second inner connecting arm; the bearing assemblies are respectively disposed between the inner walls of the first outer connecting arm and the second outer connecting arm and the outer wall of the rotor body.
[0008] In some embodiments, one end of the first outer connecting arm and the first inner connecting arm are integrally connected, and the first inner connecting arm is located inside the first outer connecting arm, and the axial length of the first outer connecting arm is greater than the axial length of the first inner connecting arm; one end of the second outer connecting arm and the second inner connecting arm are integrally connected, and the second inner connecting arm is located inside the second outer connecting arm, and the axial length of the second outer connecting arm is greater than the axial length of the second inner connecting arm.
[0009] In some embodiments, the inner wall of the stator core is provided with a plurality of teeth along the circumferential direction, and each of the teeth is provided with a coil, with a gap between two adjacent coils.
[0010] In some embodiments, the inner wall of the front fairing, the inner wall of the rotor body, and the inner wall of the rear fairing are smoothly connected in sequence; the inner diameter of the front fairing gradually decreases from the inlet end to the position on the inner wall of the rotor body corresponding to the position where the impeller is set, and the inner diameter gradually increases from the position on the inner wall of the rotor body corresponding to the position where the impeller is set to the outlet end of the rear fairing.
[0011] In some embodiments, a guide vane assembly is provided on the inner wall of the rear fairing near the outlet end; the guide vane assembly includes an intermediate cylinder and a plurality of guide vanes, the intermediate cylinder is coaxially arranged with the rear fairing, and a plurality of guide vanes are arranged circumferentially between the outer wall of the intermediate cylinder and the inner wall of the rear fairing, the guide vanes having a rectangular plate structure and being twisted.
[0012] In some embodiments, the system further includes a filter and a handle; the filter includes two symmetrically arranged split filters, the open ends of the two split filters are fitted onto the outer wall of the open end of the front fairing, and the opposite ends of the two split filters are connected and fixed by fasteners; the handle is respectively provided on the outer wall of the open end of the two split filters.
[0013] In some embodiments, sealing rings are provided between the two ends of the stator housing in the axial direction and the ends of the first outer connecting arm and the second outer connecting arm, respectively; floating oil seals are provided between the two ends of the rotor body in the axial direction and the ends of the first inner connecting arm and the second inner connecting arm, respectively.
[0014] In some embodiments, a connecting flange is integrally connected to the outer wall of the stator housing, and the connecting flange is provided with a through hole communicating with the interior of the stator housing; the two ends of the outer wall of the stator housing in the axial direction are respectively connected and fixed to the outer walls of the first outer connecting arm and the second outer connecting arm by fasteners.
[0015] In some embodiments, the impellers are triangular in structure and twisted, with the tips of the plurality of impellers all facing the axial direction of the rotor body; the bearing assembly is a waterproof bearing.
[0016] In some embodiments, the stator housing, the front fairing, and the rear fairing are all made of aluminum alloy, and the rotor body is made of stainless steel; and / or the surface of the rotor body is provided with a ceramic coating.
[0017] The present invention achieves the following technical advantages over the prior art:
[0018] This utility model discloses a magnetically driven shaftless submersible electric pump. The stator assembly of the ring motor is integrated with the pump housing, forming the stator housing. Both the front and rear shrouds include two connecting arms, one inner and one outer, which are respectively connected to the stator housing and the rotor body. The inner ring of the bearing assembly is connected to the outer wall of the rotor body, and the outer ring of the bearing assembly is connected to the outer connecting arm. This utility model adopts a highly modular design, using a ring motor and pump housing integrated structure, which reduces the number of components and mechanical connection points, lowers the risk of failure, and facilitates maintenance, replacement, and disassembly. Furthermore, the two-connecting-arm design of both the front and rear shrouds reduces the housing thickness, allowing for a thin-walled design that reduces system weight while maintaining strength. Attached Figure Description
[0019] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0020] Figure 1 This is a three-dimensional structural diagram of a magnetically driven shaftless submersible electric pump in some embodiments of the present invention.
[0021] Figure 2 This is a front view of a magnetically driven shaftless submersible electric pump in some embodiments of this utility model;
[0022] Figure 3 for Figure 2 Sectional view of section AA;
[0023] Figure 4 for Figure 2 Sectional view of section BB;
[0024] Figure 5 for Figure 3 A magnified view of a section at point C;
[0025] Figure 6 This is a three-dimensional structural diagram of the front fairing in some embodiments of the present invention;
[0026] Figure 7 This is a cross-sectional view of the front fairing in some embodiments of the present invention;
[0027] Figure 8 This is a three-dimensional structural diagram of the rear fairing in some embodiments of the present invention;
[0028] Figure 9 This is a cross-sectional view of the rear fairing in some embodiments of the present invention;
[0029] Figure 10 This is a schematic diagram of the stator housing structure in some embodiments of this utility model;
[0030] Figure 11 This is a cross-sectional view of the stator housing in some embodiments of the present invention;
[0031] Figure 12 This is a schematic diagram of the stator core structure in some embodiments of this utility model;
[0032] Figure 13 This is a schematic diagram showing the installation of the stator core and coil in some embodiments of this utility model;
[0033] Figure 14 This is a schematic diagram of the rotor assembly in some embodiments of the present invention;
[0034] Figure 15 This is a cross-sectional view of the rotor assembly in some embodiments of the present invention;
[0035] Figure 16 This is a schematic diagram of the structure of the floating oil seal in some embodiments of this utility model.
[0036] In the diagram: 1-Stator assembly; 2-Rotor assembly; 3-Front fairing; 4-Rear fairing; 5-Bearing assembly; 6-Filter screen; 7-Handle; 8-Sealing ring; 9-Floating oil seal;
[0037] 11-Stator housing; 12-Stator core; 13-Coil; 14-First sealing part;
[0038] 21-Rotor body; 22-Impeller; 23-Permanent magnet; 24-Second sealing part; 25-First bearing mounting part;
[0039] 31-First outer connecting arm; 32-First inner connecting arm; 33-Third sealing part; 34-Fourth sealing part; 35-Second bearing mounting part;
[0040] 41-Second outer connecting arm; 42-Second inner connecting arm; 43-Intermediate cylinder; 44-Guide plate; 45-Fifth sealing part; 46-Sixth sealing part; 47-Third bearing mounting part;
[0041] 111-Connecting flange. Detailed Implementation
[0042] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.
[0043] The purpose of this invention is to provide a magnetically driven shaftless submersible pump to solve the problems existing in the prior art, which is easy to disassemble and maintain, and can reduce the system weight while meeting structural strength requirements.
[0044] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, the utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0045] This utility model provides a magnetically driven shaftless submersible electric pump, such as... Figures 1 to 16 As shown, it includes a stator assembly 1, a rotor assembly 2, a front fairing 3, a rear fairing 4, and a bearing assembly 5; wherein, as... Figure 3 , Figures 10-13 As shown, the stator assembly 1 includes a stator housing 11, a stator core 12, and coils 13. The outer wall of the stator core 12 is connected and fixed to the inner wall of the stator housing 11 to form an integral structure. The inner wall of the stator core 12 is provided with multiple teeth along the circumference, and each tooth is provided with a coil 13. There is a gap between two adjacent coils 13. This utility model adopts a modular single-tooth winding design and manufacturing process. Each tooth coil 13 is independent, the winding end is short, the thermal resistance is small, and there is a natural ventilation gap between the blocks, which is conducive to heat dissipation, reduces temperature rise, and increases the power density of the motor.
[0046] like Figure 3 , Figure 14 and Figure 15 As shown, the rotor assembly 2 includes a rotor body 21, impellers 22, and permanent magnets 23. The rotor body 21 is coaxially disposed inside the stator housing 11. Multiple permanent magnets 23 are embedded in the outer wall of the rotor body 21 along the circumferential direction and are disposed opposite to the stator core 12. Multiple impellers 22 are integrally connected to the inner wall of the rotor body 21 along the circumferential direction. There is a gap between the permanent magnets 23 and the stator core 12.
[0047] like Figure 3 , Figures 6-9 As shown, the front fairing 3 includes a first outer connecting arm 31 and a first inner connecting arm 32, and the rear fairing 4 includes a second outer connecting arm 41 and a second inner connecting arm 42; the two ends of the stator housing 11 are respectively sealed to the ends of the first outer connecting arm 31 and the second outer connecting arm 41, and the two ends of the rotor body 21 are respectively dynamically sealed to the ends of the first inner connecting arm 32 and the second inner connecting arm 42.
[0048] Bearing assemblies 5 are respectively provided between the inner walls of the first outer connecting arm 31 and the outer wall of the rotor body 21.
[0049] It should be noted that the first outer connecting arm 31, the first inner connecting arm 32, the stator housing 11, the rotor body 21, the second outer connecting arm 41, and the second inner connecting arm together form a sealed cavity structure. The two bearing assemblies 5, multiple coils 13, and multiple permanent magnets 23 are all located inside the cavity structure.
[0050] In some embodiments, see further reference. Figure 6 and Figure 7 As shown, one end of the first outer connecting arm 31 and the first inner connecting arm 32 are integrally connected, and the first inner connecting arm 32 is located inside the first outer connecting arm 31. The axial length of the first outer connecting arm 31 is greater than the axial length of the first inner connecting arm 32.
[0051] Continue reading Figure 8 and Figure 9 As shown, one end of the second outer connecting arm 41 and the second inner connecting arm 42 are integrally connected, and the second inner connecting arm 42 is located inside the second outer connecting arm 41. The axial length of the second outer connecting arm 41 is greater than the axial length of the second inner connecting arm 42.
[0052] In some embodiments, such as Figure 3 As shown, the inner wall of the front fairing 3, the inner wall of the rotor body 21, and the inner wall of the rear fairing 4 are smoothly connected in sequence; and the inner diameter of the front fairing 3 gradually decreases from the inlet end to the position on the inner wall of the rotor body 21 corresponding to the position where the impeller 22 is set, and the inner diameter of the rear fairing 4 gradually increases from the position on the inner wall of the rotor body 21 corresponding to the position where the impeller 22 is set to the outlet end.
[0053] It should be noted that, driven by the permanent magnet rotor drive device, the impeller 22 of this invention propels the surrounding liquid to rotate at high speed. Under the action of centrifugal force, the liquid is thrown from the center of the impeller 22 to the outer edge, thereby gaining kinetic and pressure energy. The thrown liquid enters the wide flow channel of the pump casing. As the flow channel gradually expands, the liquid velocity decreases, and some of the kinetic energy is converted into pressure energy. Finally, the liquid is discharged from the pump outlet. At the same time, a low-pressure zone is formed at the center of the impeller 22, and external liquid continuously flows into the center of the impeller 22 under the action of atmospheric pressure, realizing a continuous liquid transportation process.
[0054] In some embodiments, such as Figure 8 and Figure 9 As shown, a guide vane assembly is provided on the inner wall of the rear fairing 4 near the outlet end. The guide vane assembly includes an intermediate cylinder 43 and multiple guide vanes 44. The intermediate cylinder 43 is coaxially arranged with the rear fairing 4, and multiple guide vanes 44 are arranged circumferentially between the outer wall of the intermediate cylinder 43 and the inner wall of the rear fairing 4. The guide vanes 44 have a rectangular plate structure and are twisted at a preset angle.
[0055] This utility model, by setting multiple guide plates 44, can guide the water flow to be discharged along the torsion direction of the guide plates 44, thereby improving the drainage effect.
[0056] In some embodiments, such as Figure 1 and Figure 2 As shown, it also includes a filter screen 6 and a handle 7. The filter screen 6 includes two symmetrically arranged split filters. The open ends of the two split filters are fitted onto the outer wall of the open end of the front fairing 3, and the opposite ends of the two split filters are connected and fixed by fasteners.
[0057] Each of the two separate filter screens has a handle 7 on the outer wall of its open end.
[0058] This invention uses a filter screen to filter out larger impurities in the water, preventing clogging of the submersible pump. The handle 7 makes it easy to pick up the submersible pump.
[0059] In some embodiments, such as Figure 5 and Figure 16 As shown, sealing rings 8 are provided between the two ends of the stator housing 11 in the axial direction and the ends of the first outer connecting arm 31 and the second outer connecting arm 41, respectively; the sealing rings 8 can be O-rings.
[0060] A floating oil seal 9 is provided between the two ends of the rotor body 21 in the axial direction and the ends of the first inner connecting arm 32 and the second inner connecting arm 42, respectively. The floating oil seal 9 can be a heavy-duty DF floating oil seal.
[0061] In some embodiments, a connecting flange 111 is integrally connected to the outer wall of the stator housing 11, and the connecting flange 111 is provided with a through hole communicating with the interior of the stator housing 11. The connecting flange 111 can be connected to a float ring to facilitate operation in water.
[0062] One axial end of the outer wall of the stator housing 11 is connected and fixed to the outer wall of the first outer connecting arm 31 by fasteners, and the other axial end of the outer wall of the stator housing 11 is connected and fixed to the outer wall of the second outer connecting arm 41 by fasteners.
[0063] In some embodiments, the impeller 22 has a triangular structure and is twisted, with the tips of multiple impellers 22 all facing the axial direction of the rotor body 21; the bearing assembly 5 is a waterproof bearing.
[0064] In some embodiments, the stator housing 11, the front fairing 3 and the rear fairing 4 are all made of aluminum alloy, and the rotor body 21 is made of stainless steel; and / or the surface of the rotor body 21 is provided with a ceramic coating.
[0065] This invention reduces weight and enhances durability by using high-strength, lightweight materials such as aluminum alloys or composite materials; the rotor enhances corrosion resistance and wear resistance by using ceramic coatings or stainless steel.
[0066] In some embodiments, such as Figure 11 The stator housing 11 has a first sealing part 14 at each of its two axial ends; as described above. Figure 15 As shown, the rotor body 21 has a second sealing part 24 at both ends in the axial direction, and a first bearing mounting part 25 is provided on the outer wall of the rotor body 21.
[0067] like Figure 7 As shown, the end of the first outer connecting arm 31 of the front fairing 3 is provided with a third sealing part 33 and the inner wall is provided with a second bearing mounting part 35, and the end of the first inner connecting arm 32 is provided with a fourth sealing part 34; wherein, a sealing ring 8 is provided between the third sealing part 33 and the corresponding first sealing part 14, and a floating oil seal 9 is provided between the fourth sealing part 34 and the corresponding second sealing part 24; and a bearing assembly 5 is provided between the second bearing mounting part 35 and the corresponding first bearing mounting part 25.
[0068] like Figure 9As shown, the end of the second outer connecting arm 41 of the rear fairing 4 is provided with a fifth sealing part 45 and the inner wall is provided with a third bearing mounting part 47, and the end of the second inner connecting arm 42 is provided with a sixth sealing part 46; wherein, a sealing ring 8 is provided between the fifth sealing part 45 and the corresponding first sealing part 14, and a floating oil seal 9 is provided between the sixth sealing part 46 and the corresponding second sealing part 24; and a bearing assembly 5 is provided between the third bearing mounting part 47 and the corresponding first bearing mounting part 25.
[0069] The magnetic drive shaftless submersible electric pump of this utility model adopts a modular and integrated design. The annular electrode stator and the pump housing are designed as an integral structure, which reduces the number of components and mechanical connection points. The stator housing 11 is connected to the outer connecting arms of the front shroud 3 and the rear shroud 4 by fasteners to form an integral structure.
[0070] Both the front fairing 3 and the rear fairing 4 adopt the structure of external connecting arms and internal connecting arms to be sealed and connected to the stator housing 11 and the rotor body 21. The thin-wall design technology is adopted to reduce the thickness of the pump housing and motor housing, thereby reducing weight while meeting the strength requirements.
[0071] The stator winding of this invention adopts a sealed protection design to prevent liquid penetration and insulation failure; the rotor uses a ceramic coating or stainless steel to enhance corrosion resistance and wear resistance, and adopts a modular design for easy maintenance and replacement. Furthermore, finite element analysis is used to optimize the structural strength of key components to ensure stability under high pressure and high-speed rotation conditions.
[0072] This invention reduces the number of segmented connecting parts, thus lowering the weight of bolts, flanges, etc. The integrated design of the motor and pump system further reduces weight. This magnetically driven shaftless submersible pump utilizes a large-diameter permanent magnet direct-drive impeller. The design considers the electrical seal between the rotor and stator, employing an end-face sealing structure with high linear velocity and low friction loss to ensure design reliability.
[0073] This invention relates to a magnetically driven shaftless submersible electric pump for drainage operations and can be used for relay-type boosting operations, such as for emergency flood drainage or water supply and intake operations.
[0074] This utility model uses specific examples to illustrate its principles and implementation methods. The above description of the embodiments is only for the purpose of helping to understand the method and core idea of this utility model. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the idea of this utility model. In summary, the content of this specification should not be construed as a limitation of this utility model.
Claims
1. A magnetically driven shaftless submersible electric pump, characterized in that, This includes the stator assembly, rotor assembly, front fairing, rear fairing, and bearing assembly; The stator assembly includes a stator housing, a stator core, and coils. The outer wall of the stator core is connected and fixed to the inner wall of the stator housing, and a plurality of coils are arranged circumferentially on the inner wall of the stator core. The rotor assembly includes a rotor body, impellers, and permanent magnets. The rotor body is coaxially disposed inside the stator housing. A plurality of permanent magnets are embedded in the outer wall of the rotor body along the circumferential direction and are disposed opposite to the stator core. A plurality of impellers are integrally connected to the inner wall of the rotor body along the circumferential direction. The front fairing includes a first outer connecting arm and a first inner connecting arm, and the rear fairing includes a second outer connecting arm and a second inner connecting arm; the two ends of the stator housing are respectively sealed to the ends of the first outer connecting arm and the second outer connecting arm, and the two ends of the rotor body are respectively dynamically sealed to the ends of the first inner connecting arm and the second inner connecting arm; the bearing assemblies are respectively disposed between the inner walls of the first outer connecting arm and the second outer connecting arm and the outer wall of the rotor body.
2. The magnetically driven shaftless submersible electric pump according to claim 1, characterized in that, One end of the first outer connecting arm and the first inner connecting arm are integrally connected, and the first inner connecting arm is located inside the first outer connecting arm. The axial length of the first outer connecting arm is greater than the axial length of the first inner connecting arm. The second outer connecting arm and the second inner connecting arm are integrally connected at one end, and the second inner connecting arm is located inside the second outer connecting arm. The axial length of the second outer connecting arm is greater than the axial length of the second inner connecting arm.
3. The magnetically driven shaftless submersible electric pump according to claim 1, characterized in that, The inner wall of the stator core is provided with a plurality of teeth along the circumference, and each tooth is provided with a coil, with a gap between two adjacent coils.
4. The magnetically driven shaftless submersible electric pump according to claim 1, characterized in that, The inner wall of the front fairing, the inner wall of the rotor body, and the inner wall of the rear fairing are smoothly connected in sequence. The inner diameter of the rotor body gradually decreases from the inlet end of the front fairing to the position on the inner wall corresponding to the impeller, and gradually increases from the position on the inner wall of the rotor body corresponding to the impeller to the outlet end of the rear fairing.
5. The magnetically driven shaftless submersible electric pump according to claim 4, characterized in that, The inner wall of the rear fairing is provided with a guide vane assembly near the outlet end; The guide vane assembly includes an intermediate cylinder and multiple guide vanes. The intermediate cylinder is coaxially arranged with the rear fairing, and multiple guide vanes are arranged circumferentially between the outer wall of the intermediate cylinder and the inner wall of the rear fairing. The guide vanes have a rectangular plate structure and are twisted.
6. The magnetically driven shaftless submersible electric pump according to claim 1, characterized in that, It also includes a filter and a handle; The filter screen includes two symmetrically arranged split filters. The open ends of the two split filters are sleeved on the outer wall of the open end of the front fairing, and the opposite ends of the two split filters are connected and fixed by fasteners. The handles are respectively provided on the outer walls of the open ends of the two separate filter screens.
7. The magnetically driven shaftless submersible electric pump according to claim 1, characterized in that, Sealing rings are provided between the two ends of the stator housing in the axial direction and the ends of the first outer connecting arm and the second outer connecting arm, respectively. Floating oil seals are provided at both ends of the rotor body along the axial direction between the rotor body and the ends of the first inner connecting arm and the second inner connecting arm, respectively.
8. The magnetically driven shaftless submersible electric pump according to claim 1, characterized in that, A connecting flange is integrally connected to the outer wall of the stator housing, and the connecting flange is provided with a through hole communicating with the interior of the stator housing; The two ends of the outer wall of the stator housing in the axial direction are respectively connected and fixed to the outer walls of the first outer connecting arm and the second outer connecting arm by fasteners.
9. The magnetically driven shaftless submersible electric pump according to claim 1, characterized in that, The impeller has a triangular structure and is twisted, with the tips of the multiple impellers all facing the axial direction of the rotor body; The bearing assembly is a waterproof bearing.
10. The magnetically driven shaftless submersible electric pump according to claim 1, characterized in that, The stator housing, the front fairing, and the rear fairing are all made of aluminum alloy, and the rotor body is made of stainless steel; and / or The surface of the rotor body is coated with a ceramic coating.