Axial motor underwater small shaftless propeller

Abstract

The utility model discloses an underwater propeller, in particular to an axial motor underwater small shaftless propeller, which comprises a shell, an axial motor and an impeller, the axial motor and the impeller are positioned in the shell, a water flow channel is arranged in the middle of the shell, blades of the impeller are positioned in the water flow channel, the axial motor comprises a stator and a rotor, the stator is arranged on the axial outer side of the rotor, and the axial motor is arranged on the axial outer side of the rotor. The impeller comprises a wheel frame of a hollow structure, the wheel frame is provided with an inner wall layer and an outer wall layer, blades are evenly arranged on the inner side of the inner wall layer, a supporting beam is arranged in the middle between the inner wall layer and the outer wall layer to form an upper installation groove and a lower installation groove which are symmetrical, a protruding block is arranged in the middle of the outer side of the outer wall layer, and installation openings are formed in the two sides of the protruding block. The rotor is tightly matched in the mounting groove, a water-lubricated bearing assembly is mounted on the mounting opening, and a water-permeable hole is formed in the shell and is communicated with the interior of the water-lubricated bearing assembly; water enters the shaftless propeller through the water permeable holes and is used for lubricating an internal sliding bearing, mechanical abrasion is reduced, reliability is improved, and the service life is prolonged.

Description

TECHNICAL FIELD

[0001] The utility model relates to belong to ocean engineering technical field, relate to a underwater propeller, especially an axial motor underwater small shaftless propeller. BACKGROUND

[0002] In the underwater propulsion technology field, shaftless propeller is paid close attention to with its unique advantage. Different types of shaftless propeller have significant difference in performance and application. At present, most shaftless propellers use radial motor, this design is effective in some occasions, but also has some limitations, such as low propulsion efficiency, high noise level, relatively complex maintenance and repair, etc. And axial motor underwater shaftless propeller has obvious advantages in efficiency, noise control, maintenance and maneuverability compared with radial motor underwater shaftless propeller, making it become the preferred technology for many underwater applications. The patents with publication number CN115817778A and announcement number CN219948534U both propose an axial motor underwater shaftless propeller, which has the advantages of small size and simple structure, but also has the following technical defects:

[0003] The two patents mentioned axial motor shaftless propeller rotor core is in direct contact with radial bearing and thrust bearing, which can simplify the structure of shaftless propeller, but also brings a very serious problem: the rotor core rotates during work, its outer circumference directly rubs with radial bearing, and its side surface rubs with thrust bearing. The rotor core is used to fix the rotor and drive the impeller to rotate, and is not a professional device for sliding friction, so when the shaftless propeller works for a long time, the service life of the bearing in contact with it will be reduced first; Secondly, the service life of the rotor core itself will also be reduced; Finally, because the rotor core is not a professional device for sliding friction, its friction loss will be larger, thereby reducing the efficiency of the shaftless propeller itself. UTILITY MODEL CONTENTS

[0004] The technical problem to be solved by the utility model is: in order to solve the problem that the rotor core of the existing axial shaftless propeller is in direct contact with the radial bearing and the thrust bearing, which reduces the service life of the bearing and the rotor core, and even causes the efficiency of the shaftless propeller to be reduced, an axial motor underwater small shaftless propeller is provided, the structure and installation position of the water lubricated bearing assembly are improved, the water lubrication function is realized by connecting the water lubricated bearing assembly with the water permeable hole, the mechanical wear is reduced, and the reliability and service life of the entire underwater shaftless propeller are improved.

[0005] The utility model discloses a technical scheme that solves its technical problems is: a kind of underwater small shaftless propeller of axial motor, including shell, axial motor and impeller located in shell, the shell middle has a water flow passage, the blade of the impeller is located in this water flow passage, the axial motor includes stator and rotor, the stator is arranged in the axial outer side of rotor,

[0006] The impeller includes a hollow structure of wheel frame, the wheel frame has an inner wall layer and an outer wall layer, the blades are evenly arranged on the inner side of the inner wall layer, a support beam is arranged between the inner wall layer and the outer wall layer, to form two symmetrical mounting slots, a protrusion is arranged on the middle of the outer side of the outer wall layer, and mounting ports are formed on both sides of the protrusion.

[0007] The rotor is tightly fitted in the mounting slot, a water-lubricated bearing assembly is mounted on the mounting port, and a water-permeable hole is formed in the shell, which is communicated with the inside of the water-lubricated bearing assembly.

[0008] By mounting the hollow structure of the wheel frame and the inner side of the blade, the compact design of the shaftless propeller of the utility model is realized. The support beam between the inner wall layer and the outer wall layer enhances the structural strength of the impeller, and at the same time forms the upper and lower symmetrical mounting slots, providing a stable mounting position for the rotor and the bearing assembly. By mounting the water-lubricated bearing assembly on the mounting port and communicating with the water-permeable hole, the water-lubricated function is realized, the mechanical wear is reduced, and the reliability and service life of the shaftless propeller of the utility model are improved.

[0009] As an embodiment of the utility model, the water-lubricated bearing assembly includes a ceramic bearing and a graphite bearing, the ceramic bearing is tightly fitted on the protrusion of the mounting port, a notch is formed on the outer edge of the ceramic bearing to form a stepped structure, and the graphite bearing is arranged on the notch and loosely fitted with the ceramic bearing.

[0010] The ceramic bearing has high hardness, wear resistance and corrosion resistance, and is suitable for underwater harsh environment; the graphite bearing has good self-lubricating performance and high temperature resistance, and the combination of the two improves the comprehensive performance of the water-lubricated bearing assembly. The notch stepped structure of the ceramic bearing and the loose fitting of the graphite bearing not only ensure the installation accuracy of the two bearings, but also allow certain thermal expansion and mechanical deformation, to enhance the installation reliability; at the same time, the risk of wear of the water-lubricated bearing assembly due to insufficient lubrication is reduced.

[0011] As an embodiment of the utility model, the graphite bearing is a circular ring structure, and the inner diameter is greater than the outer diameter of the notch position of the ceramic bearing and less than the outer diameter of the ceramic bearing.

[0012] The inner diameter of the graphite bearing ensures that it can be tightly fitted on the notch of the ceramic bearing, while avoiding excessive extrusion, ensuring stability and flexibility during operation.

[0013] As an embodiment of the present application, the shell comprises an upper shell, a lower shell and an outer shell, the upper shell and the lower shell are oppositely arranged, and the outer shell is sleeved on the outer periphery of the upper shell and the lower shell.

[0014] The split design of the upper shell, the lower shell and the outer shell makes the assembly and maintenance of the underwater shaftless thruster more convenient, the components can be independently processed and replaced, and the maintenance cost is reduced; the size and shape of the shell can be flexibly adjusted according to the requirements of different application scenarios, and the universality and adaptability of the underwater shaftless thruster are improved.

[0015] As an embodiment of the present application, a lower notch is formed in the lower edge of the upper shell, an upper notch is formed in the upper edge of the lower shell, and the graphite bearing is tightly fitted in the annular cavity formed by the upper notch and the lower notch and limited by the outer shell.

[0016] The annular cavity formed by the upper notch and the lower notch enables the graphite bearing to be stably installed in the shell, avoiding displacement caused by vibration or impact. The limiting effect of the outer shell ensures that the graphite bearing always maintains the correct position during operation, improving the overall stability of the thruster.

[0017] As an embodiment of the present application, stator grooves are formed in the upper shell and the lower shell, a sealing sleeve is tightly fitted in the stator grooves, and a sealing groove accommodating the stator is formed on the sealing sleeve.

[0018] The sealing sleeve provides a sealed environment for the stator, preventing water from entering the interior of the stator and improving the waterproof performance and reliability of the axial motor.

[0019] As an embodiment of the present application, the sealing sleeve is a hollow cylindrical structure having an inner wall and an outer wall in a cylindrical structure, one end of the inner wall and the outer wall is connected, and the other end is open to form a sealing groove, and the opening is sealed by the upper shell or the lower shell to form a sealing cavity.

[0020] The hollow cylindrical structure of the sealing sleeve provides physical protection for the stator, reduces the influence of external impact on the stator, and prolongs the service life of the axial motor. By sealing the opening with the upper shell or the lower shell, a sealing cavity is formed, further enhancing the sealing performance of the stator and ensuring the safety of the motor during underwater operation.

[0021] As an embodiment of the present application, the stator is a plastic-sealed stator.

[0022] The plastic sealing stator has good waterproof and moisture-proof performance, can effectively prevent water and moisture from corroding the stator winding, and improves the reliability and service life of the axial motor; meanwhile, the stator structure is more compact, and the volume and weight are reduced.

[0023] As an embodiment of the utility model, the end surface of the upper shell and the lower shell is provided with a lead-out hole, and the water permeable hole is provided on the shell.

[0024] The lead-out hole provides convenience for the electrical connection of the axial motor, and ensures the normal operation of the axial motor.

[0025] As an embodiment of the utility model, the upper shell and the lower shell are both provided with a mounting flange, the mounting flange is provided with a screw hole, and the two ends of the shell are also provided with screw holes.

[0026] The mounting flange and the screw hole enable the upper shell, the lower shell and the shell to be tightly connected, and improve the overall structural stability of the underwater shaftless thruster.

[0027] The utility model has the advantages of:

[0028] (1) The impeller adopts a hollow structure, is provided with an inner wall layer and an outer wall layer and a support beam, and forms an installation groove for tightly fitting the rotor, thereby ensuring the strength of the impeller and reducing the weight, and facilitating installation and maintenance;

[0029] (2) The water-lubricated bearing assembly (including a ceramic bearing and a graphite bearing) reduces friction and wear, and improves the durability and reliability of the thruster; the hardness and wear resistance of the ceramic bearing and the self-lubricating property of the graphite bearing ensure long-term stable operation of the bearing assembly in the underwater environment;

[0030] (3) The combination of the ceramic bearing and the graphite bearing ensures the stiffness of the bearing and reduces the friction resistance, thereby improving the propulsion efficiency;

[0031] (4) The design of the sealing sleeve and the sealing groove effectively protects the stator from the underwater environment, and improves the service life of the motor;

[0032] (5) The combination of the upper shell, the lower shell and the shell, and the tight fit of the graphite bearing in the annular cavity formed by the upper notch and the lower notch, enhances the sealing performance of the thruster and prevents water from entering the axial motor;

[0033] (6) The connecting mode of the upper shell, the lower shell and the outer shell makes the assembly and maintenance more convenient, and reduces the maintenance cost;

[0034] (7) The water permeable hole is designed to allow water to enter the inside of the water lubricating bearing assembly, thereby ensuring the lubrication and cooling of the bearing, and improving the safety and reliability of the propeller;

[0035] (8) The use of the plastic package stator improves the moisture-proof performance and insulation performance of the motor, and further enhances the safety of the propeller.

[0036] (9) The axial motor underwater small shaftless propeller realizes multiple advantages such as efficient propulsion, durability and reliability, convenient maintenance and safety upgrade, and is suitable for the propulsion system of various underwater vehicles or underwater robots. BRIEF DESCRIPTION OF DRAWINGS

[0037] The utility model will be further described below in combination with the drawings and examples.

[0038] Figure 1 is the external structure schematic diagram of the axial motor underwater small shaftless propeller embodiment one of the utility model.

[0039] Figure 2 is the sectional view of the axial motor underwater small shaftless propeller embodiment one of the utility model.

[0040] Figure 3 is the explosion view of the axial motor underwater small shaftless propeller embodiment one of the utility model.

[0041] Figure 4 is the sectional view of Figure 3 .

[0042] Figure 5 is the plan view of Figure 1 .

[0043] Figure 6 is the structure schematic diagram of the sealing sleeve in the axial motor underwater small shaftless propeller embodiment one of the utility model.

[0044] Figure 7 is the assembly drawing of the stator, the sealing sleeve and the upper shell in the axial motor underwater small shaftless propeller embodiment one of the utility model.

[0045] Figure 8 is the structure schematic diagram of the impeller in the axial motor underwater small shaftless propeller embodiment one of the utility model.

[0046] Figure 9 is the assembly drawing of the water lubricating bearing assembly in the axial motor underwater small shaftless propeller embodiment one of the utility model.

[0047] Figure 10It is the assembly view of the impeller, the rotor and the water lubricating bearing assembly in the axial motor underwater small shaftless propeller embodiment one of the utility model.

[0048] Figure 11 It is the assembly view of the upper shell, the impeller, the rotor and the water lubricating bearing assembly and the lower shell in the axial motor underwater small shaftless propeller embodiment one of the utility model.

[0049] In the drawing: 1, impeller;10, blade;11, wheel frame;111, inner wall layer;112, outer wall layer;113, support beam;12, mounting groove;14, lug;2, stator;3, rotor;4, upper shell;41, water outlet;42, lower notch;51, water inlet;52, upper notch;5, lower shell;6, outer shell;61, water permeation hole;7, fastening screw;8, sealing sleeve;81, sealing groove;82, inner wall;83, outer wall;15, ceramic bearing;16, graphite shaft;40, lead-out wire hole;50, stator slot. DETAILED DESCRIPTION

[0050] The utility model will be further explained in detail in combination with the drawings. These drawings are all simplified schematic views, and only schematically show the basic structure of the utility model, so they only show the structure related to the utility model.

[0051] Embodiment one

[0052] As Figures 1-5 shown, the axial motor underwater small shaftless propeller of the embodiment includes a shell, an axial motor and an impeller 1 located in the shell, the shell has a water flow channel in the middle, the blade 10 of the impeller 1 is located in the water flow channel, the axial motor includes a stator 2 and a rotor 3, and the stator 2 is arranged on the axial outer side of the rotor 3. Specifically, the shell includes an upper shell 4, a lower shell 5 and an outer shell 6, the upper shell 4 and the lower shell 5 are oppositely arranged, and the outer shell 6 is sleeved on the outer periphery of the upper shell 4 and the lower shell 5. The upper shell 4 and the lower shell 5 are both provided with mounting flanges, screw holes are formed in the mounting flanges, screw holes are also formed in the two ends of the outer shell 6, and the upper shell 4 and the lower shell 5 are connected with the outer shell 6 through fastening screws 7. The upper shell 4 and the lower shell 5 are both provided with circular channels in the center, which are respectively a water outlet 41 and a water inlet 51 of the water flow channel. Lead-out wire holes 40 are formed in the end faces of the upper shell 4 and the lower shell 5, which are used for leading out the connecting wires connected with the stator 2 in the axial motor. The shell is provided with water permeation holes 61, and when working underwater, water enters the interior of the shaftless propeller through the water permeation holes 61 to lubricate the sliding bearings in the interior.

[0053] As Figure 3 , Figure 4 and Figure 6As shown, the upper shell 4 and the lower shell 5 are provided with stator grooves 50, and a sealing sleeve 8 is tightly fitted in the stator grooves 50, and the sealing sleeve 8 is provided with a sealing groove 81 for accommodating the stator 2. Specifically, the sealing sleeve 8 is a hollow cylindrical structure, which has an inner wall 82 and an outer wall 83, and the inner wall 82 and the outer wall 83 are connected at one end and open at the other end to form the sealing groove 81, and the opening is sealed by the upper shell 4 or the lower shell 5 to form a sealing cavity.

[0054] In the embodiment, the stator 2 is a plastic-sealed stator, which has good waterproof and moisture-proof performance, can effectively prevent water and moisture from eroding the stator winding, and improves the reliability and service life of the axial motor.

[0055] As shown in the figure, Figure 7 When assembled, the plastic-sealed stator 2 is placed in the sealing groove 81 of the sealing sleeve 8, and then the combined structure is pressed into the stator groove 50 of the upper shell 4 (or the lower shell 5) to ensure that it is pressed to the bottom of the stator groove 50. At this time, the stator groove 50 just completely accommodates the combined structure, and this matching mode also plays a sealing and waterproof role.

[0056] As shown in the figure, Figure 8 The impeller 1 includes a hollow structure of a wheel frame 11, the wheel frame 11 has an inner wall layer 111 and an outer wall layer 112, the blades 10 are uniformly arranged on the inner side of the inner wall layer 111, a support beam 113 is arranged at the middle part between the inner wall layer 111 and the outer wall layer 112 to form two symmetrical mounting grooves 12, a protrusion 14 is arranged at the middle part of the outer side of the outer wall layer 112, and mounting ports are formed at both sides of the protrusion 14; the rotor 3 is tightly fitted in the mounting grooves 12, and a water-lubricated bearing assembly is mounted on the mounting ports. The blades 10 and the impeller 1 are formed in an integrated structure in a manner of tight fitting, gluing, screwing or one-piece forming.

[0057] As shown in the figure, Figure 9 The water-lubricated bearing assembly includes a ceramic bearing 15 and a graphite bearing 16, the ceramic bearing 15 is tightly fitted on the protrusion 14 of the mounting port, a notch is formed on the outer edge of the ceramic bearing 15 to form a stepped structure, and the graphite bearing 16 is arranged on the notch and loosely fitted with the ceramic bearing 15. Specifically, the graphite bearing 16 is a circular ring structure, and the inner diameter of the graphite bearing 16 is greater than the outer diameter of the notch position of the ceramic bearing 15 and less than the outer diameter of the ceramic bearing 15.

[0058] As shown in the figure, Figure 10As shown, the support beam 113 of the impeller 1 is symmetrical, and the upper and lower sides are provided with the rotor 3. The rotor 3 is installed in the installation groove 12, and the rotor 3 and the installation groove 12 form an integrated structure through tight fitting, so that the rotor 3 drives the impeller 1 to rotate when the rotor 3 rotates. When the ceramic bearing 15 is installed, the inner peripheral wall of the ceramic bearing 15 is tightly attached to the outer wall layer 112 of the impeller 1, and is tightly fitted with the impeller 1, and rotates with the impeller 1. The protrusion 14 also plays a limiting role. When the graphite bearing 16 is installed, the inner wall of the graphite bearing 16 is sleeved on the gap of the ceramic bearing 15, and the ceramic bearing 15 also has a limiting function similar to the protrusion 14. The graphite bearing 16 and the ceramic bearing 15 are loosely fitted.

[0059] As shown in Figure 11 The lower edge of the upper shell 4 is provided with a lower gap 42, and the upper edge of the lower shell 5 is provided with an upper gap 52, that is, the outer diameter of the end portion of the upper shell 4 and the lower shell 5 is smaller than that of other portions. The graphite bearing 16 is tightly fitted in the annular cavity formed by the upper gap 52 and the lower gap 42 and is limited by the outer shell 6. When the axial motor works, the graphite bearing 16 is tightly fitted with the upper shell 4 or the lower shell 5 and is fixed, the ceramic bearing 15 is tightly fitted with the rotor 3 and rotates integrally, and the ceramic bearing 15 and the graphite bearing 16 are loosely fitted in a non-contact manner. Thus, the ceramic bearing 15 and the graphite bearing 16 will slide relative to each other. This is the sliding friction between the two bearings, and water is used as lubrication to avoid dry grinding and improve the service life of the axial motor. This double-bearing structure avoids the direct friction between the rotor core and the bearing in the background art.

[0060] The installation process of the underwater small shaftless propeller of the axial motor of the embodiment is as follows:

[0061] Firstly, the rotor 3 is placed in the installation groove 12 of the impeller 1, and the rotor 3 is connected with the installation groove 12 through tight fitting or gluing. The ceramic bearing 15 is sleeved on the outer periphery of the protrusion 14 of the impeller 1 and is attached to the outer wall layer 112. The ceramic bearing 15 and the outer wall layer 112 are also connected through tight fitting, gluing or screwing. At the same time, the protrusion 14 plays an axial limiting role, and the ceramic bearing 15 is pressed to the position of the protrusion 14, which means that the installation is in place.

[0062] Secondly, the graphite bearing 16 is sleeved on the gap position of the ceramic bearing 15. The lower half of the ceramic bearing 15 has a limiting effect similar to the protrusion 14 of the impeller 1, which limits the fitting of the graphite bearing 16. The gap portion of the graphite bearing 16 and the ceramic bearing 15 is loosely fitted. When the propeller works, the rotor 3 drives the impeller 1 and the ceramic bearing 15 to rotate, and the graphite bearing 16 is fixed. There is relative movement between the ceramic bearing 15 and the graphite bearing 16, and the graphite powder and water generated by the friction between the two bearings play a lubricating role.

[0063] Then, the stator 2 is assembled into the seal sleeve 8, and the two are tightly fitted, one is to fix the plastic encapsulated stator, and the other is to separate the plastic encapsulated stator from water. When the small underwater shaftless thruster is working, water flows into the water inlet 51, passes through the channel formed by the inner wall 82, and flows through the seal sleeve 8. The inner wall 82 separates the water and the stator 2, which separates the water and the stator 2, that is, protects the stator winding, and at the same time, the water takes away the heat generated by the winding, achieving the effect of liquid cooling.

[0064] Then, the assembled structure is assembled into the shell, ensuring that the stator slot 50 of the upper shell 4 and the lower shell 5 is aligned with the plastic encapsulated stator 2, and the assembled structure is pressed to the bottom of the stator slot 50. At this time, the stator slot 50 just completely contains the assembled structure, and such cooperation also plays a sealing and waterproof role.

[0065] Finally, the upper shell 4 and the lower shell 5 are assembled on the shell 6 through the fastening screw 7. After installation, the fastening screw 7 provides axial force for the entire device, fixing each component along the axial direction. The shell 6 provides radial force for the entire device, ensuring that each component is fixed along the radial direction.

[0066] Therefore, the underwater small shaftless thruster of the axial motor of the embodiment adopts the combination of the ceramic bearing 15 and the graphite bearing 16. The ceramic bearing 15 is tightly fitted with the rotor 3 and rotates with the impeller 1, and the graphite bearing 16 is fixed. The two form a loose water-lubricated sliding friction, avoiding dry grinding of the two bearings, reducing wear and tear, and significantly improving the service life of the bearings. By introducing external water flow through the water hole 61 to lubricate the bearings, not only the friction and heat are reduced, but also the pollution and failure of traditional lubricating oil in underwater environment are avoided. The ceramic bearing 15 and the graphite bearing 16 have excellent corrosion resistance and are suitable for long-term use in seawater environment. The plastic encapsulated stator 2 has good waterproof and moisture-proof performance, which can effectively prevent water and moisture from eroding the stator winding, prolonging the service life of the motor. The tight fitting design of the seal sleeve 8 and the stator slot 50 forms a reliable sealed cavity, further preventing water from entering the motor, and ensuring the stable operation of the motor in high-pressure underwater environment. The double-bearing structure, water-lubricated structure and sealing structure not only improve the performance and service life of the entire thruster, but also reduce the operating cost and maintenance difficulty.

[0067] Example Two

[0068] The difference from example one is that the water-lubricated bearing assembly adopts a silicon carbide bearing and a graphite bearing 16. The silicon carbide bearing is tightly fitted on the protrusion 14 of the mounting port, and the outer edge of the silicon carbide bearing is provided with a notch to form a stepped structure. The graphite bearing 16 is arranged on the notch and loosely fitted with the silicon carbide bearing. The loose fitting design of the silicon carbide bearing and the graphite bearing 16 can be further optimized to reduce friction and wear.

[0069] Example Three

[0070] The difference from the second embodiment is that the inner ring wall of the graphite bearing 16 is provided with lubricating grooves or micro-hole structures to improve the lubricating effect.

[0071] Fourth embodiment

[0072] The difference from the first embodiment is that an anti-bioadhesion coating is coated on the surface of the shell to prevent marine organisms from adhering, thereby reducing the maintenance frequency and the running resistance.

[0073] With the above ideal embodiments according to the present application as the inspiration, through the above description, relevant personnel can certainly make various changes and modifications without deviating from the technical idea of the present application. The technical scope of the present application is not limited to the content in the specification, and the technical scope must be determined according to the scope of claims.

Claims

1. An underwater small shaftless propeller of an axial motor, comprising a shell, an axial motor and an impeller (1) in the shell, the shell having a water flow channel in the middle, the blades (10) of the impeller (1) being in the water flow channel, the axial motor comprising a stator (2) and a rotor (3), the stator (2) being arranged on the axial outer side of the rotor (3), characterized in that: the impeller (1) comprises a hollow structure of a wheel frame (11), the wheel frame (11) having an inner wall layer (111) and an outer wall layer (112), the blades (10) being uniformly arranged on the inner side of the inner wall layer (111), a support beam (113) being arranged in the middle between the inner wall layer (111) and the outer wall layer (112) to form two symmetrical mounting grooves (12) above and below, a protrusion (14) being arranged on the middle of the outer side of the outer wall layer (112), the two sides of the protrusion (14) forming mounting ports; the rotor (3) is tightly fitted in the mounting groove (12), a water lubrication bearing assembly is mounted on the mounting port, and a water permeable hole (61) is formed on the shell and communicates with the inside of the water lubrication bearing assembly. the water lubrication bearing assembly comprises a ceramic bearing (15) and a graphite bearing (16), the ceramic bearing (15) is tightly fitted on the protrusion (14) of the mounting port, a notch is formed on the outer edge of the ceramic bearing (15) to form a stepped structure, and the graphite bearing (16) is arranged on the notch and loosely fitted with the ceramic bearing (15).

2. The underwater small shaftless propeller of an axial motor according to claim 1, characterized in that: the graphite bearing (16) is a circular ring structure, the inner diameter of which is greater than the outer diameter of the notch position of the ceramic bearing (15) and less than the outer diameter of the ceramic bearing (15).

3. The underwater small shaftless propeller of axial electric machine according to claim 2, characterized in that: the shell comprises an upper shell (4), a lower shell (5) and an outer shell (6), the upper shell (4) and the lower shell (5) are arranged oppositely, and the outer shell (6) is sleeved on the outer periphery of the upper shell (4) and the lower shell (5).

4. The underwater small shaftless propeller of axial electric machine according to claim 2, characterized in that: a lower notch (42) is formed on the lower edge of the upper shell (4), an upper notch (52) is formed on the upper edge of the lower shell (5), and the graphite bearing (16) is tightly fitted in the annular cavity formed by the upper notch (52) and the lower notch (42) and is limited by the outer shell (6).

5. The underwater small shaftless propeller of axial electric machine according to claim 4, characterized in that: a stator groove (50) is formed on the upper shell (4) and the lower shell (5), a sealing sleeve (8) is tightly fitted in the stator groove (50), and a sealing groove (81) for accommodating the stator (2) is arranged on the sealing sleeve (8).

6. The underwater small shaftless propeller of axial electric machine according to claim 4, characterized in that: the sealing sleeve (8) is a hollow cylindrical structure, which has an inner wall (82) and an outer wall (83) in a cylindrical structure, one end of the inner wall (82) and the outer wall (83) is connected, and the other end is open to form a sealing groove (81), the opening is sealed by the upper shell (4) or the lower shell (5) to form a sealing cavity.

7. The underwater small shaftless propeller of axial electric machine according to claim 6, characterized in that: the stator (2) is a plastic encapsulated stator.

8. The underwater small shaftless propeller of axial electric machine according to claim 1 or 6, characterized in that: lead hole (40) is formed on the end face of the upper shell (4) and the lower shell (5), and the water permeable hole (61) is formed on the outer shell (6).

9. The underwater small shaftless propeller of axial electric machine according to claim 6, characterized in that: ​ 10. The underwater small shaftless propeller of axial electric machine according to claim 6, characterized in that: The upper shell (4) and the lower shell (5) are provided with mounting flanges, screw holes are formed in the mounting flanges, and screw holes are also formed in both ends of the outer shell (6); the upper shell (4) and the lower shell (5) are connected with the outer shell (6) through fastening screws (7).

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