Outer rotor motor heat dissipation structure based on self-generated convection of airfoil rotor

Abstract

The invention discloses an outer rotor motor heat dissipation structure based on self-generated convection of an airfoil rotor, and relates to the technical field of motor heat management. The outer rotor and the built-in stator are arranged in the shell, the outer rotor is provided with a plurality of wing-shaped protrusions, a central hole is prefabricated in a stator core, a heat conduction cylinder is tightly assembled, a first annular air gap is reserved between the outer rotor and the shell, a second annular air gap is reserved between the built-in stator and the outer rotor, and three annular air holes are machined in the shell. The bottom plate is fixed to the bottom end of the heat conduction cylinder to form a passive convection heat exchange path, and the arc-shaped composite groove bottom surrounds the bottom of the edge of the outer rotor to connect the stator iron core with the shell and communicates with the first annular air gap and the second annular air gap to form an active convection heat exchange path. The arc-shaped composite groove bottom and the heat conduction cylinder are additionally arranged, winding heat is shunted and conducted to the inner side and the outer side in a heat transfer mode, a plurality of wing-shaped protrusions arranged on the outer rotor are combined, an active convection heat exchange path and a passive convection heat exchange path are formed inside, the structure is compact, and the heat dissipation capacity is high.

Description

Technical Field

[0001] This invention relates to the field of motor thermal management technology, specifically a heat dissipation structure for an external rotor motor based on self-generated convection of an airfoil rotor. Background Technology

[0002] Drones need to operate for long periods of time in scenarios such as inspection, logistics, and surveying. During operation, the motor is in an environment with changing working conditions and continuous load. The airflow organization in the gaps of the casing and the gaps between the rotor and stator is poor, and heat is difficult to be dissipated in time. This leads to heat accumulation in the windings and tooth tips, resulting in high temperature rise and affecting motor efficiency and stability.

[0003] Currently, there are various heat dissipation structures for motors, such as passive cooling with heat sinks or simple airflow guides, but these methods offer limited improvement and have low cooling efficiency. Another approach involves adding small cooling fans to the motor within the equipment to achieve active cooling by enhancing convection; however, this method introduces additional weight and power consumption, and the increased structural layers also complicate assembly and maintenance.

[0004] In summary, traditional heat dissipation methods that rely on simple ventilation and heat sink structures are insufficient to meet steady-state cooling requirements. Adding active components would increase quality and complexity. There is an urgent need to improve the operational stability of UAV motors by optimizing the shell openings, heat dispersion and conduction, and intake and exhaust paths, without introducing additional components such as independent cooling fans, in order to promote internal gas flow and wall heat exchange, reduce hot spots and temperature rise. Summary of the Invention

[0005] To address the shortcomings of the prior art, this invention provides a heat dissipation structure for an external rotor motor based on self-generated convection of an airfoil rotor. It adds an arc-shaped composite groove bottom and a heat-conducting cylinder to conduct heat from the windings to the inner and outer sides through heat transfer. Combined with multiple airfoil protrusions on the external rotor, two convection heat transfer paths, one active and one passive, are formed inside. The structure is compact and has strong heat dissipation capacity.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a heat dissipation structure for an external rotor motor based on self-generated convection of an airfoil rotor, comprising a shell, an external rotor, an internal stator, a heat-conducting cylinder, a base plate, and an arc-shaped composite groove bottom;

[0007] The outer rotor is fitted with the built-in stator and coaxially arranged inside the outer casing. Multiple airfoil protrusions are evenly arranged on the outer side wall of the outer rotor along the circumference and can generate a downwash airflow when rotating. The stator core of the built-in stator has a pre-made central hole. The heat-conducting cylinder is coaxially positioned and assembled in the central hole and is in close contact with the stator core to form a heat conduction structure.

[0008] The outer shell is made of a side cover and a top cover, which are respectively covered on the side and top of the outer rotor. A first annular air gap is left between the outer rotor and the inner side wall of the outer shell, and a second annular air gap is left between the inner stator and the outer rotor. Three annular air holes are coaxially arranged on the surface of the top cover, and the three annular air holes correspond one-to-one with the first annular air gap, the second annular air gap and the heat conduction cylinder.

[0009] The base plate is coaxially fixed to the bottom end of the heat-conducting cylinder and leaves a gap between it and the bottom end of the outer shell. Multiple gradually narrowing flow channels are evenly arranged around the center on the upper surface edge of the base plate, and the heat-conducting cylinder and the base plate form a passive convection heat transfer path.

[0010] The arc-shaped composite groove bottom is arranged around the bottom edge of the outer rotor to connect the stator core and the side cover to form a heat conduction structure. At the same time, a guide channel is formed between the outer rotor and the arc-shaped composite groove bottom, connecting the bottom of the first annular air gap and the bottom of the second annular air gap to form an active convection heat transfer path.

[0011] Furthermore, the heat-conducting cylinder consists of three parts: an outer cylinder and an inner cylinder arranged coaxially, and multiple radial support arms that are evenly arranged to connect the two into one. The heat-conducting cylinder is made of aluminum nitride ceramic material. The bottom end of the inner cylinder is extended for the assembly and positioning of the base plate. The multiple radial support arms are provided with threaded holes for the outer shell and the heat-conducting cylinder to be assembled by bolts.

[0012] Furthermore, the inner wall of the central hole of the stator core is provided with a toothed groove along the circumference, and the outer wall of the outer cylinder of the heat-conducting cylinder is provided with a toothed protrusion along the circumference. The toothed protrusion and the toothed groove fit together to increase the contact area between the heat-conducting cylinder and the stator core.

[0013] Furthermore, the gap between the toothed protrusion and the toothed groove is filled with a high thermal conductivity insulating potting compound based on epoxy resin composite alumina.

[0014] Furthermore, a fan-shaped heat exchange zone is formed between every two adjacent tapered flow channels on the upper surface of the base plate. The surface of the fan-shaped heat exchange zone and the corresponding position of the bottom of the arc-shaped composite tank are coated with an inorganic black ceramic high emissivity coating for radiative heat exchange.

[0015] Furthermore, several flow-disrupting elements are fixed in an array on the inner wall of the outer cylinder of the heat-conducting cylinder, and a single flow-disrupting element is fixed at the middle position of the surface of each sector heat exchange zone of the base plate.

[0016] Furthermore, the baffle adopts a figure-eight structure. The baffle located on the heat-conducting cylinder array has its opening direction vertically upward, and the two adjacent rows of baffles are arranged alternately. The individual baffles on the bottom plate are arranged radially and their opening direction faces outward.

[0017] Furthermore, the bottom end of the outer rotor is made into an arc-shaped protrusion, and the bottom of the arc-shaped composite groove is made of aluminum nitride ceramic material.

[0018] Furthermore, the outer side wall of the side cover is uniformly machined with several arc-shaped grooves along the circumference to increase the heat dissipation area.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention sets heat-conducting cylinders and shells on the inner and outer sides of the built-in stator respectively. Through heat transfer, the heat of the winding is diverted to the inner and outer sides to form a solid heat-conducting path with low thermal resistance, which quickly conducts heat to areas that are easier to dissipate heat. Airfoil protrusions are set on the outer side wall of the outer rotor, which generate downwash airflow in the first annular air gap as the rotor rotates. After being guided by the bottom of the arc-shaped composite groove, the airflow enters the second annular air gap to purge the winding area, forming an active convection heat transfer path. The heat-conducting cylinders and the bottom plate cooperate to form a passive convection heat transfer path. With the help of the baffle, the heat transfer of the wall is enhanced, which improves the heat transfer efficiency per unit air volume. In addition, the fan-shaped heat transfer area on the surface of the bottom plate and the corresponding position of the bottom of the arc-shaped composite groove are coated with an inorganic black ceramic high emissivity coating for radiation heat transfer. There is no need to add an additional cooling fan. The structure is compact and efficient, and heat transfer, convection heat transfer and radiation heat transfer are synergistically enhanced to improve heat dissipation. This solves the problem that the heat inside the stator is not easy to dissipate and the local temperature rise is too high in the existing structure, thus improving the heat dissipation capacity and operational reliability of the UAV outer rotor motor. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall assembly of the present invention;

[0021] Figure 2 This is a schematic diagram of the outer shell structure in this invention;

[0022] Figure 3 This is an assembly diagram of the outer rotor, the built-in stator, and the heat-conducting cylinder in this invention;

[0023] Figure 4 This is a schematic diagram of the structure of the base plate in this invention;

[0024] Figure 5 This is a cross-sectional schematic diagram of the location of the guide channel in this invention.

[0025] In the diagram: 1. Outer shell; 2. Outer rotor; 3. Internal stator; 4. Heat-conducting cylinder; 5. Base plate; 6. Side cover; 7. Arc-shaped groove; 8. Top cover; 9. Annular vent; 10. Airfoil protrusion; 11. Stator core; 12. Flow guide channel; 13. Arc-shaped protrusion; 14. Arc-shaped composite groove bottom; 15. Toothed groove; 16. Toothed protrusion; 17. Turbulence-inducing component; 18. Gradually narrowing flow channel; 19. Fan-shaped heat exchange zone. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] like Figures 1-5 As shown, a heat dissipation structure for an external rotor motor based on self-generated convection of an airfoil rotor includes a housing 1, an external rotor 2, an internal stator 3, a heat-conducting cylinder 4, a base plate 5, a side cover 6, an arc-shaped groove 7, a top cover 8, an annular vent 9, an airfoil protrusion 10, a stator core 11, a flow guide channel 12, an arc-shaped protrusion 13, an arc-shaped composite groove bottom 14, a toothed groove 15, a toothed protrusion 16, a flow-disrupting element 17, a gradually narrowing flow channel 18, and a fan-shaped heat exchange zone 19.

[0028] Combination Figure 1 As shown, the outer rotor 2 and the built-in stator 3 form a motor unit and are coaxially arranged inside the housing 1. Furthermore, the stator core 11 of the built-in stator 3 has a pre-drilled central hole, and the heat-conducting cylinder 4 is coaxially positioned and assembled at the center of the built-in stator 3. A first annular air gap is left between the outer rotor 2 and the inner wall of the housing 1, and a second annular air gap is left between the built-in stator 3 and the outer rotor 2 (corresponding to the motor winding area). The heat-conducting cylinder 4 and the built-in stator 3 are in close contact to form a heat conduction structure.

[0029] Combination Figure 2 As shown, the outer shell 1 is made of a side cover 6 and a top cover 8 as one piece and covers the side and top of the motor unit. The side cover 6 is an annular shell and its outer side wall is uniformly machined with several arc-shaped grooves 7 along the circumference to increase the heat dissipation area. The top cover 8 is a frustum-shaped shell and is coaxially set on the top of the side cover 6. Three annular air holes 9 are coaxially arranged on the surface of the top cover 8. Each annular air hole 9 is composed of multiple heat dissipation ports arranged in the circumference. The positions of the three annular air holes 9 correspond one-to-one with the first annular air gap, the second annular air gap and the inner area of ​​the heat-conducting cylinder 4, respectively, so as to realize the function of introducing external air and dissipating internal heat, reducing the stagnant area and improving the overall heat exchange efficiency.

[0030] Combination Figure 3As shown, the inner wall of the central hole of the stator core 11 has a toothed groove 15 formed circumferentially. The heat-conducting cylinder 4 consists of three parts: an outer cylinder and an inner cylinder arranged coaxially, and multiple radial support arms evenly arranged to connect the two. The whole is made of non-magnetic, insulating aluminum nitride ceramic material. The bottom end of the inner cylinder is extended for the assembly and positioning of the base plate 5, and the hollow structure of the inner cylinder is conducive to further heat dissipation of the heat-conducting cylinder 4. The multiple radial support arms have threaded holes for the outer shell 1 and the heat-conducting cylinder 4 to be assembled by bolts. The outer wall of the outer cylinder has a toothed protrusion 16 formed circumferentially. The toothed protrusion 16 and the toothed groove 15 fit together to increase the contact area between the heat-conducting cylinder 4 and the stator core 11, forming a solid-solid heat conduction path with surface contact. The gap between the toothed protrusion 16 and the toothed groove 15 is filled with epoxy resin-based composite alumina high thermal conductivity insulating potting compound, which has both electrical insulation and non-magnetic properties, and at the same time reduces the interface thermal resistance to improve the heat conduction efficiency. In addition, multiple airfoil protrusions 10 are uniformly arranged on the outer side wall of the outer rotor 2 along the circumference. The airfoil protrusions 10 are airfoil shapes with an angle of attack, have a certain length along the circumference and have downward curved trailing edges. When the multiple airfoil protrusions 10 rotate with the outer rotor 2, they can generate downward forced airflow in the first annular air gap, thereby forming self-generated convection to enhance the circumferential convection heat transfer of the outer rotor 2.

[0031] Combination Figures 4-5 As shown, the arc-shaped composite groove bottom 14 is arranged around the bottom edge of the outer rotor 2, connecting the bottom end of the stator core 11 to the inner side wall of the side cover 6 of the outer casing 1. The arc-shaped composite groove bottom 14 uses aluminum nitride ceramic material to transfer the heat generated by the stator core 11 to the outer casing 1. At the same time, the bottom end of the outer rotor 2 is made into an arc-shaped protrusion 13. The arc-shaped protrusion 13 and the arc-shaped composite groove bottom 14 form a guide channel 12. The guide channel 12 connects the bottom of the first annular air gap and the second annular air gap, so that the downwash airflow generated by the multiple airfoil protrusions 10 of the outer rotor 2 in the first annular air gap is introduced into the second annular air gap through the guide channel 12 to form a bottom-up heat dissipation airflow. The heat dissipation airflow sweeps over the windings of the outer rotor 2 and the inner stator 3, carrying away the generated heat and dissipating it upward, realizing the effective flow of gas inside the outer casing 1.

[0032] The base plate 5 is a circular plate, and its center is coaxially fixed with the bottom end of the inner cylinder of the heat-conducting cylinder 4. A gap is left between the upper surface of the base plate 5 and the bottom end of the outer shell 1. In addition, multiple tapering channels 18 are evenly arranged around the center of the upper surface of the base plate 5. The width of the tapering channels 18 gradually narrows from the inside to the outside in the radial direction, and a fan-shaped heat exchange zone 19 is formed between each two adjacent tapering channels 18. During the flight of the UAV, the ambient cold air will pass through the outer shell 1 and enter the interior of the heat-conducting cylinder 4, then impact the upper surface of the base plate 5, and be discharged from the side under the restriction of the multiple tapering channels 18. The tapering channels 18 can increase the airflow velocity before discharge and reduce the stagnation in the inner cavity. The surface of the fan-shaped heat exchange zone 19 and the corresponding position of the arc-shaped composite tank bottom 14 are coated with an inorganic black ceramic high emissivity coating (ε≥0.9) for radiative heat exchange, which enhances the heat dissipation capacity of the arc-shaped composite tank bottom 14.

[0033] Furthermore, several flow-disrupting elements 17 are fixed in an array on the inner wall of the outer cylinder of the heat-conducting cylinder 4. The flow-disrupting elements 17 adopt an eight-shaped structure, with all the openings of the flow-disrupting elements 17 pointing vertically upwards. The two adjacent rows of flow-disrupting elements 17 are arranged alternately. After the heat from the stator core 11 is transferred to the heat-conducting cylinder 4, the convective heat transfer capacity inside the heat-conducting cylinder 4 is improved, allowing the heat to be better transferred and discharged with the airflow. Alternatively, a single flow-disrupting element 17 can be fixed at the middle position of the surface of each fan-shaped heat exchange zone 19 on the bottom plate 5. Here, the flow-disrupting elements 17 are arranged radially along the bottom plate 5 and the opening direction is facing outwards. During the flight of the UAV, the convective heat transfer between the fan-shaped heat exchange zone 19 and the ambient cold air is enhanced, and the heat dissipation capacity of the arc-shaped composite groove bottom 14 is further enhanced by the synergistic radiative heat transfer.

[0034] In summary, this invention provides a heat dissipation structure for the external rotor motor commonly used in UAVs. It achieves heat dissipation through the coordinated action of heat transfer, convection heat transfer, and radiation heat transfer, with the area where the motor generates the most heat mainly concentrated in the winding position. By setting the arc-shaped composite groove bottom 14 and the heat-conducting cylinder 4, the heat of the stator core 11 is conducted to the outer shell 1 and the inner heat-conducting cylinder 4 respectively. The outer shell 1 is directly exposed to the ambient cold air, while the hollow structure of the heat-conducting cylinder 4 is also conducive to the passage of ambient cold air. Heat transfer and heat dissipation at the winding position are achieved through the solid-solid heat conduction path of the inner and outer parts. Multiple airfoil protrusions 10 set on the outer rotor 2 can actively generate downwash airflow, which acts on the winding position through the first annular air gap, the guide channel 12 and the second annular air gap, forming an active convection heat transfer path. The heat-conducting cylinder 4 and the bottom plate 5 are used for the passive inflow and outflow of ambient cold air, forming a passive convection heat transfer path. Convection heat transfer and heat dissipation at the winding position are achieved through the two paths. The fan-shaped heat transfer area 19 on the surface of the bottom plate 5 and the arc-shaped composite groove bottom 14 are coated with an inorganic black ceramic high emissivity coating, and radiation heat transfer and heat dissipation of the arc-shaped composite groove bottom 14 are achieved during heat transfer.

[0035] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0036] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An external rotor motor heat dissipation structure based on self-induced convection of airfoiled rotors, characterized by: It comprises a shell (1), an outer rotor (2), an embedded stator (3), a heat-conducting cylinder (4), a bottom plate (5) and an arc-shaped composite groove bottom (14). The outer rotor (2) is coaxially arranged inside the shell (1) in cooperation with the embedded stator (3), the outer sidewall of the outer rotor (2) is uniformly provided with a plurality of airfoil-shaped protrusions (10) along the circumference and can generate a downward washing airflow when rotating, the stator core (11) of the embedded stator (3) is provided with a preformed central hole, the heat-conducting cylinder (4) is coaxially positioned and assembled in the central hole and tightly contacts with the stator core (11) to form a heat-conducting structure. The shell (1) is integrally made of a side cover (6) and a top cover (8) and is respectively covered on the side and top of the outer rotor (2), a first annular air gap is left between the outer rotor (2) and the inner sidewall of the shell (1), a second annular air gap is left between the embedded stator (3) and the outer rotor (2), three annular air holes (9) are coaxially arranged on the surface of the top cover (8), and the three annular air holes (9) correspond to the first annular air gap, the second annular air gap and the heat-conducting cylinder (4) one by one. The bottom plate (5) is coaxially fixed at the bottom end of the heat-conducting cylinder (4) and leaves a gap between the bottom plate (5) and the bottom end of the shell (1), a plurality of tapered flow channels (18) are uniformly arranged around the center on the upper surface edge of the bottom plate (5), and the heat-conducting cylinder (4) and the bottom plate (5) form a passive convection heat exchange path. The arc-shaped composite groove bottom (14) is arranged around the edge bottom of the outer rotor (2) to connect the stator core (11) and the side cover (6) to form a heat-conducting structure, and a flow guide channel (12) is formed between the outer rotor (2) and the arc-shaped composite groove bottom (14) to connect the first annular air gap and the second annular air gap to form an active convection heat exchange path.

2. An external rotor motor heat sink structure based on self-induced convection of airfoiled rotor blades according to claim 1, characterized in that: The heat-conducting cylinder (4) is composed of an outer cylinder and an inner cylinder coaxially arranged and a plurality of radial arms uniformly arranged to connect the two into one, the whole heat-conducting cylinder (4) is made of aluminum nitride ceramic material, the bottom end of the inner cylinder is lengthened and extended for assembly and positioning of the bottom plate (5), and the plurality of radial arms are provided with threaded holes for bolt connection assembly of the shell (1) and the heat-conducting cylinder (4).

3. An external rotor motor heat sink structure based on self-induced convection of airfoiled rotor according to claim 2, characterized in that: The inner wall of the central hole of the stator core (11) is provided with a tooth-shaped groove (15) along the circumference, the outer sidewall of the outer cylinder of the heat-conducting cylinder (4) is provided with a tooth-shaped protrusion (16) along the circumference, and the tooth-shaped protrusion (16) and the tooth-shaped groove (15) are embedded with each other to increase the contact area of the heat-conducting cylinder (4) and the stator core (11).

4. An external rotor motor heat sink structure based on self-induced convection of airfoiled rotors as recited in claim 3, characterized by: The gap between the tooth-shaped protrusion (16) and the tooth-shaped groove (15) is filled with epoxy resin-based composite alumina high-thermal-conductivity insulation potting glue.

5. An external rotor motor heat sink structure based on self-induced convection of airfoiled rotor according to claim 2, characterized in that: Each adjacent two tapered flow channels (18) on the upper surface of the bottom plate (5) form a fan-shaped heat exchange area (19), and the surface of the fan-shaped heat exchange area (19) is coated with an inorganic black ceramic high-emissivity coating at the corresponding position of the arc-shaped composite groove bottom (14) for radiation heat exchange.

6. An external rotor motor heat sink structure based on self-induced convection of airfoiled rotor blades according to claim 5, characterized in that: The inner sidewall of the outer cylinder of the heat-conducting cylinder (4) is arrayed with a plurality of flow disturbing members (17), and the surface of each fan-shaped heat exchange area (19) of the bottom plate (5) is fixed with a single flow disturbing member (17) at the middle position.

7. An external rotor motor heat sink structure based on self-induced convection of airfoiled rotors as recited in claim 6, characterized by: The spoiler (17) adopts a splayed structure, is located vertically upward in the opening direction of the fixed spoiler (17) of the array of heat conducting cylinders (4), and the two adjacent rows of spoilers (17) are staggered, and the single spoiler (17) of the bottom plate (5) is arranged in the radial direction and the opening direction is outward.

8. An external rotor motor heat sink structure based on self-induced convection of airfoiled rotor according to claim 1, characterized in that: The bottom end of the outer rotor (2) is made into an arc-shaped convex (13), and the arc-shaped composite groove bottom (14) is made of aluminum nitride ceramic material.

9. An external rotor motor heat sink structure based on self-induced convection of airfoiled rotor blades according to claim 1, characterized in that: The outer side wall of the side cover (6) is uniformly processed with a plurality of arc-shaped grooves (7) in the circumferential direction to increase the heat dissipation area.

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