High-efficiency heat dissipation outer rotor motor

Abstract

The application discloses a high-efficiency heat-dissipation outer rotor motor, and aims at solving the problem of poor heat dissipation of a stator when a small air gap is kept in the prior art. The motor comprises a stator part, a rotor part covered outside the stator part, and a heat-dissipation part located in an air gap of 1-2 mm between the stator part and the rotor part. The heat-dissipation part comprises spiral flow guide ridges A arranged on the outer surface of the stator, spiral flow guide ridges B arranged on the inner surface of the rotor, and turbulence protrusions A and B distributed on the air inlet side of the stator and the air outlet side of the rotor. The cooperation of the flow guide ridges A and B forms a "screw pump" effect, drives the air in the air gap to generate directional axial flow, the gradually changing height and S-shaped extension design of the ridges accelerate the airflow and induce vortex flow, and the turbulence protrusions further destroy the thermal boundary layer. The application significantly improves the convective heat exchange efficiency in the air gap without increasing the air gap and external fan, and realizes the high-efficiency heat dissipation of the motor.

Description

TECHNICAL FIELD

[0001] The present application relates to an outer rotor motor, in particular, an outer rotor motor with high heat dissipation efficiency. BACKGROUND

[0002] As a kind of motor with advanced design concept, the outer rotor motor has been applied and verified in more and more fields. It is generally believed that the outer rotor motor has excellent heat dissipation performance. However, it should be pointed out that the "excellent heat dissipation performance" of the outer rotor motor usually refers to the heat dissipation of the rotor part, and the stator is just the "bottleneck" of the heat dissipation path. The stator part of the existing outer rotor motor has the following problems in heat dissipation:

[0003] 1. The heat is generated in the internal stator, but the heat dissipation must be realized through the external rotating rotor. This leads to a long and inefficient heat dissipation path.

[0004] Long heat conduction path:

[0005] Heat source (stator winding and iron core) → stator yoke → air gap between stator and rotor → rotor yoke → rotor shell → external environment.

[0006] This path is long, and each link has thermal resistance. In particular, the air gap between the stator and the rotor, although it is a very small physical gap, is air with very poor thermal conductivity, which constitutes the main thermal resistance.

[0007] 2. Dependence on air convection in air gap:

[0008] Because of the existence of the above-mentioned objective factors of the long heat conduction path, the heat dissipation of the stator mainly depends on the weak air convection in the air gap, and the smoothness of the air flow in the air gap and the heat exchange efficiency with the stator and the rotor will directly affect the heat dissipation efficiency of the motor.

[0009] 3. The air gap is too small, which leads to low air flow in the air gap

[0010] It should be known that when the air gap is close to the value range of 1-2mm, a thermal boundary layer almost only existing in advection will be generated between the inner surface of the rotating rotor and the outer surface of the stator. The existence of this thermal boundary layer leads to the fact that the heat between the stator and the rotor cannot be quickly exchanged, and the heat generated on the stator (main heat source) cannot be quickly dissipated outward.

[0011] The existing means to improve the heat dissipation efficiency of the outer rotor motor are usually the following two kinds:

[0012] 1. In the end of the motor, a heat dissipation fan blade is installed to blow axial heat dissipation air into the motor to achieve forced heat dissipation. However, although this heat dissipation method is very efficient, the axial space occupied by the auxiliary fan is large, and for small external rotor fans in the volute, it is obviously not possible to install an auxiliary fan.

[0013] 2. By expanding the air gap, the smoothness of the axial flow in the cavity is improved, and the preferred way is to set a fan blade on the inner surface of the rotor to improve the flow of air. However, it should be noted that the air gap of a small external rotor motor is usually between 1-2mm, which ensures the performance of the motor. If the air gap is expanded to 3mm or even larger, although the air flow is enhanced, the problem that follows is that as the air gap increases, the magnetic resistance in the magnetic circuit also increases. According to the Ohm's law of magnetic circuit, the magnetic flux is inversely proportional to the magnetic resistance. The larger the air gap, the greater the loss of electromagnetic performance of the motor, and the performance will be greatly affected. Therefore, simply increasing the air gap or even adding a fan blade is not advisable

[0014] Therefore, it is obviously necessary to design an external rotor motor that can destroy the thermal boundary layer in the motor air gap under the condition of a small air gap (1-2mm), achieve smooth flow and heat exchange of air inside and outside the motor air gap, and obtain good heat dissipation effect. SUMMARY

[0015] The purpose of the present application is to provide an external rotor motor with high heat dissipation efficiency, which can improve the air flow in the air gap and break the thermal boundary layer in the narrow space without increasing the air gap, thereby improving the heat dissipation efficiency.

[0016] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0017] An external rotor motor with high heat dissipation efficiency, comprising

[0018] A stator portion comprising a stator body, the center of the stator body is provided with an axial through channel, both ends of the channel are provided with bearing chambers, and bearings are coaxially arranged in the bearing chambers;

[0019] A rotor portion comprising a rotor body, the rotor body is covered outside the stator body, a rotating shaft is coaxially connected to the rotor body, the rotating shaft can be rotatably inserted into the bearings, a magnetically conductive ring and a spoke-shaped permanent magnet arranged inside the magnetically conductive ring are embedded in the inner side of the rotor body, and the arc-shaped inner surface of the permanent magnet and the arc-shaped outer surface of the stator body form an air gap of 1-2mm;

[0020] The heat dissipation part comprises a plurality of flow guide ridges A and flow guide ridges B, the flow guide ridges A are arranged in a spiral ring on the arc-shaped outer surface of the stator part, and the sum of the radial heights of the flow guide ridges A and the flow guide ridges B is 0.6-0.7 mm.

[0021] Preferably, the maximum radial height of the flow guide ridges A is 0.2 mm, and the maximum radial height of the flow guide ridges B is 0.5 mm.

[0022] Preferably, the spiral included angle of the flow guide ridges A and the flow guide ridges B is 60-75°.

[0023] Preferably, the flow guide ridges A extend in an S shape while maintaining the spiral shape on the arc-shaped surface of the rotor body.

[0024] Preferably, the radial height of the flow guide ridges B gradually decreases from the air inlet side to the air outlet side, and the radial height of the flow guide ridges A gradually increases from the air inlet side to the air outlet side.

[0025] Preferably, the inclination of the ridges A and the ridges B is 1:200-1:300.

[0026] Preferably, the arc-shaped surface of the stator part is uniformly provided with a plurality of turbulence ridges A, and the turbulence ridges A are located on the air inlet side of the stator body; the arc-shaped inner surface of the permanent magnet of the rotor part is uniformly provided with turbulence ridges B, and the turbulence ridges B are located on the air outlet side of the rotor body.

[0027] Preferably, the turbulence ridges A and the turbulence ridges B are triangular ridges with a larger inclination on the air inlet side than on the air outlet side.

[0028] Preferably, the turbulence ridges A and the turbulence ridges B are uniformly distributed in a staggered manner.

[0029] Compared with the prior art, the application has the following beneficial effects:

[0030] 1. The scheme constructs directional flow in a "parasitic pumping" manner instead of relying on increasing space. Traditional heat dissipation ideas often improve ventilation by increasing air gap, but this directly leads to an increase in magnetic resistance of the magnetic circuit and deterioration of electromagnetic performance. The scheme discards this path and innovatively utilizes the self kinetic energy of the rotor rotation to form an internal "viscous pump" with no additional energy consumption through the spiral flow guide ridges (A ridges and B ridges) on the surfaces of the stator and the rotor. The circumferential viscous shear force of the air gap air by the rotor is efficiently converted into strong axial thrust through the spiral angle, driving the air to flow unidirectionally and at high speed. This ensures that strong cooling airflow can be generated even in a compact air gap of 1-2 mm, fundamentally avoiding the sacrifice of torque density and power factor for heat dissipation.

[0031] 2. The scheme accelerates airflow and enhances disturbance by "flow channel form regulation", rather than simply relying on high flow rate. In the design process, the scheme goes beyond the simple "acceleration" flow concept, and through the gradual height design of the guide rib, it changes the shear position of the air flow in the air gap, thereby increasing the disturbance of the thermal boundary layer at different positions by guide rib A and guide rib B. At the same time, by designing guide rib A as an S-shaped mechanism, guide rib B is nonlinearly extended in the air flow channel during the rotation of the rotor part, and this nonlinear extension design makes the air flow in the air flow channel repeatedly compressed and expanded, thereby further increasing the disturbance of the air flow in the air gap.

[0032] 3. The scheme overcomes the uneven heat dissipation of the motor inlet and outlet sides caused by small air volume and fast air kinetic energy transmission loss in a small air gap, by gradually increasing the height of guide rib A from the air inlet side to the air outlet side, and gradually reducing the height of guide rib B from the air inlet side to the air outlet side.

[0033] 4. The "vortex generator" is used to implement precise strikes and completely disintegrate the thermal boundary layer. The scheme sets asymmetric triangular turbulence convex particles and S-shaped extended guide ribs A / B at key positions (inlet / outlet sides). This design constitutes a micro "converging-diverging" flow channel. The airflow accelerates at the narrowest part of the flow channel, and according to Bernoulli's principle, its static pressure decreases, and the convective heat transfer coefficient significantly increases; the airflow is decelerated and expanded at the outlet expansion section to restore static pressure and ensure stable discharge. This controlled acceleration-deceleration process can more efficiently destroy the thermal boundary layer than uniform high-speed flow, with less energy loss. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a structural schematic diagram of the present application;

[0035] Figure 2 is a sectional view of the present application;

[0036] Figure 3 is an exploded view of the present application;

[0037] Figure 4 is a local enlarged view of guide rib A and turbulence convex particle A on the stator part in the present application;

[0038] Figure 5 is a local enlarged view of guide rib B and turbulence convex particle B on the rotor part in the present application;

[0039] Figure 6 is a front view of guide rib A;

[0040] Figure 7 is a front view of guide rib B;

[0041] Figure 8 Fig. 1 is a structural schematic diagram of the stator part of the motor.

[0042] Fig. 1 is a structural schematic diagram of the stator part of the motor. Fig. 2 is a structural schematic diagram of the rotor part of the motor. Fig. 3 is a structural schematic diagram of the heat dissipation part of the motor. DETAILED DESCRIPTION

[0043] The technical solutions of the present application will be described clearly and completely below in conjunction with the drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0044] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0045] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral connection; it can be mechanical connection, or electrical connection; it can be direct connection, or indirect connection through intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0046] This solution targets external rotor motors with a speed range of 500-10000 rpm, specifically medium-to-high speed motors. It's important to note that when the motor speed is below 500 rpm, the shearing force generated by the rotor rotation in the air gap is significantly reduced, and the axial pumping effect of the low-speed motor is correspondingly weakened. At this point, even minor structural optimizations are insufficient to effectively disturb the air within the air gap. However, when the motor rotor speed exceeds 10000 rpm, the shearing force generated by the high-speed rotor rotating the air adhering to its surface is sufficient to create significant disturbance and break the thermal boundary layer; therefore, structural optimization is unnecessary.

[0047] like Figures 1-3 The illustrated high-efficiency heat-dissipating external rotor motor includes a stator section 1 and a rotor section 2. The stator section 1 includes a stator body 11, which is formed by stacking silicon steel sheets and on which windings are wound. An axially penetrating channel 12 is provided at the center of the stator, and bearing chambers 13 are provided at both ends of the channel 12 for mounting bearings 14. It should be noted that in this design, the stator section 1 is manufactured using the BCM molding principle, achieving high-precision one-piece molding of the entire structure.

[0048] like Figure 2 As shown, the rotor part 2 includes a cup-shaped rotor body 21, which also adopts the BCM molding principle for integral molding support to achieve high precision requirements. Specifically, the rotor body 21 covers the outside of the stator body 11, and a rotating shaft 22 is coaxially fixedly connected to the rotor body 21. The rotating shaft 22 is rotatably inserted into the bearing 14 to achieve a rotatable connection with the stator. At the same time, during the molding process of the rotor body 21, a magnetic ring 23 and a permanent magnet 24 are also embedded on its inner surface. Specifically, the magnetic ring 23 is coaxially placed in the rotor body 21, while the permanent magnet 24 is placed inside the magnetic ring and evenly distributed in a spoke-like pattern. It should be noted that through this integral molding process, an air gap of 1~2mm can be effectively ensured between the inner surface of the permanent magnet 24 and the outer surface of the stator part 1 (the arc-shaped protrusion of the silicon steel sheet).

[0049] It should be noted that, under this air gap specification, the air flow within the air gap is generally considered to be very low, even essentially stationary. Since air is a poor conductor of heat, this stationary state severely hinders the transfer of heat generated by the stator to the rotor, which often leads to the stator section 1 being prone to burnout due to high temperatures.

[0050] To address the above problems, existing methods include the following:

[0051] 1. Increase an axial fan blade, when the outer rotor motor rotates, the axial fan blade rotates to the air gap and forcibly blows in the axial cooling air. However, the installation of the axial fan blade needs to reserve an axial arrangement space, and for the outer rotor motor used in a narrow and high integration environment, it is obviously not practical.

[0052] 2. The technical means of expanding the air gap to improve the air flow, which will cause the magnetic circuit to increase, the magnetic resistance will also increase, and the motor performance will be affected, which is not a desirable means.

[0053] Therefore, the present scheme optimizes the motor structure to improve the turbulence and flow of air in the air gap, and finally achieves the purpose of improving the heat dissipation efficiency of the motor.

[0054] From the foregoing, it can be seen that the stator part 1 and the rotor part 2 in the present scheme are formed by BCM plastic sealing and basic forming, so as to ensure the manufacturing precision, that is, the motor air gap is 1-2mm, and the air gap is preferably controlled at 1.5-2mm. Within the air gap gap value, the present scheme also provides a heat dissipation part 3 in the air gap. Specifically, as shown in the figure, Figure 3 The heat dissipation part 3 includes a plurality of flow guide ribs A31 and flow guide ribs B32. The flow guide ribs A31 are arranged on the arc-shaped outer surface of the stator part 1, and the flow guide ribs B32 are uniformly arranged on the arc-shaped inner surface of the rotor part 2.

[0055] In the above scheme, the combined radial height between the flow guide ribs A31 and the flow guide ribs B32, that is, the sum of the radial height of the flow guide ribs A31 and the radial height of the flow guide ribs B32 is between 0.6-0.7mm, so as to leave enough gap for the flow guide ribs A31 and the flow guide ribs B32 to avoid the occurrence of scanning boring. At the same time, the flow guide ribs A31 and the flow guide ribs B32 in the present scheme are spirally arranged on the corresponding stator part 1 and rotor part 2.

[0056] When the rotor part 2 of the outer rotor motor rotates rapidly (500-10000rpm), the flow guide ribs B32 rotate synchronously with the rotor part 2, and when the rotor rotates, the flow guide ribs B32 fixed on the rotor part 2 cooperate with the flow guide ribs A31 fixed on the stator, like a "viscous screw pump", generating a directional axial airflow in the narrow air gap from the air inlet side to the air outlet side of the motor, guiding the static air in the air gap to flow, and improving the heat exchange efficiency. In addition, it should be noted that the flow guide ribs B32 are higher than the inner surface of the rotor part 2 (permanent magnet 24), and the linear speed of the protruding part of the rapid rotation is obviously higher than that of the air in the air gap. Therefore, the flow guide ribs B32 can also play a rotating disturbance role, that is, similar to the protruding object (flow guide ribs B32) moving to disturb the static air.

[0057] In summary, the static air in the air gap realizes axial flow and disturbance matching in the flow process under the joint action of the guide convex ridge A31 and the guide convex ridge B32, thereby fundamentally greatly destroying the possibility of the existence of the thermal boundary layer, greatly improving the efficiency of the rotor to the stator to deliver heat, and the air flowing out of the air gap in part can also provide part of the heat dissipation efficiency.

[0058] Need to be explained, the difference between this scheme and some embodiments by increasing the air gap and increasing the fin in the air gap is that this scheme does not need to expand the air gap, increase the magnetic resistance, and sacrifice the motor performance to improve the air disturbance rate in the air gap, break the thermal boundary layer in the motor air gap, and thereby realize the purpose of efficient heat conduction. This scheme mainly improves the heat exchange efficiency of the air in the air gap to improve the conduction efficiency of the stator heat to the rotor heat.

[0059] It also needs to be explained that on the basis of the above scheme, the maximum radial height of the guide convex ridge A31 in this scheme is 0.2mm (see Figure 6 ), and the radial height of the guide convex ridge B32 is 0.5mm (see Figure 7 ). It needs to be explained that in this scheme, the guide convex ridge B32 acts as the active part, which undertakes most of the disturbance of the air in the air gap and drives the air movement. For this reason, the radial height of the guide convex ridge B32 is designed to be 0.5mm.

[0060] In some embodiments, the helix included angle between the guide convex ridge A31 and the guide convex ridge B32 is also set to 60-70°. It needs to be known that the size of the helix included angle and the smoothness of the guide channel formed by the guide convex ridge A31 and the guide convex ridge B32 and the disturbance effect are significantly related. When the helix included angle is larger, the axial extension length of the guide convex ridge A31 and the guide convex ridge B32 is larger in the same angle, and the disturbance effect on the air is more obvious. On the contrary, the larger the helix included angle, the smoother the air passing through the guide channel (the guiding function of the guide convex ridge A31 and the guide convex ridge B32 is reduced), so it is necessary to select an optimal balance value between them. As known from the foregoing, the heat dissipation mode of this scheme is mainly to improve the heat exchange efficiency, so that the heat of the stator part 1 can be quickly conducted to the rotor part 2. Therefore, this scheme should pay more attention to increasing the disturbance ability of the guide convex ridge A31 and the guide convex ridge B32 to the air in the air gap. The helix included angle of the guide convex ridge A31 and the guide convex ridge B32 is obviously the optimal value of 60-70°.

[0061] On the basis of the above scheme, this scheme further proposes a technical scheme for further increasing the air disturbance in the air gap. See Figure 4As shown, the guide protrusion A31 extends in S shape on the basis of keeping helical shape and adhering to the stator body 11. It is to be noted that during the rotation of the guide protrusion B32 following the rotor, the helical structure of the guide protrusion B32 pumps part of the air into the guide channel, and after the air enters, the distance between the guide protrusion B32 and the guide protrusion A31 changes continuously, that is, the air in the guide channel formed by the guide protrusion A31 and the guide protrusion B32 is continuously compressed and expanded, so that disturbance occurs. At the same time, due to the introduction of the S-shaped mechanism, the distance between the guide protrusion A31 and the guide protrusion B32 also becomes a nonlinear structure, and when the air flows through, a series of alternating vortexes are generated behind the S-shaped structure, achieving a technical effect similar to the Karman vortex street. These micro-vortices are very strong heat exchange promoters. At the same time, this enhanced vortex phenomenon can further destroy the thermal boundary layer in the air gap and improve the heat exchange strength between the stator part 1 and the rotor part 2.

[0062] In some embodiments, it is found that the temperature distribution of the axial temperature change of the motor shows that the temperature of the air inlet side of the motor is usually different from the temperature of the air outlet side of the motor by 5-7℃ or even higher. Through analysis, it is found that after the air enters the air gap, due to the small air gap space, the overall kinetic energy of the air is insufficient, and during the flow from the air inlet side to the air outlet side, the kinetic energy of the air is continuously attenuated due to the influence of disturbance and air viscous resistance. In this process, the thermal boundary layer on the surface of the stator part on the air outlet side also thickens. At this time, if the technical scheme of extending the guide protrusion A31 and the guide protrusion B32 at the same height is continued, the radial height of the guide protrusion B31 is greater than the radial height of the guide protrusion A32. The stator part as the main heat source, the heat exchange efficiency of the air outlet side will be greatly reduced due to the decrease of the heat boundary layer destruction ability caused by the attenuation of the kinetic energy of the air. However, the air gap width of the motor cannot be changed. In order to ensure the stable operation of the motor, especially the uniformity of the axial heat dissipation of the motor, the following technical scheme is proposed.

[0063] Specifically, in some embodiments, as shown in Figure 7 , Figure 8 The radial height of the guide protrusion B32 gradually decreases from the air inlet side to the air outlet side, and the radial height of the guide protrusion A31 gradually increases from the air inlet side to the air outlet side, and both extend in the same slope and parallel to the axis. The preferred slope is 1:200-1:300.

[0064] In the above scheme, the height of the air inlet side of the guide protrusion B32 is high, and the height of the air inlet side of the guide protrusion A31 is low. This structure provides a wide channel for air inflow and reduces air intake resistance. According to the foregoing embodiment, the height of the air inlet side of the guide protrusion B32 is set to 0.5 mm, and then decreases to 0.2 mm towards the air outlet side. At the same time, the height of the air inlet side of the guide protrusion A31 is set to 0.2 mm, and then increases to 0.5 mm towards the air outlet side.

[0065] Through the above structure optimization, the rotor protrusion B with high height on the air inlet side acts as a "powerful starter" to strongly disturb the air with the maximum linear speed, overcome the air intake resistance, and inject sufficient and kinetic energy-rich cooling air into the system. At this time, the small stator protrusion A has little interference, ensuring smooth initialization of the flow field.

[0066] When the air kinetic energy naturally decays, the rotor protrusion B weakens gently; and the gradually increasing stator protrusion A becomes a flow field converter, forcing the air with kinetic energy decay to flow close to the stator surface, and making a choice between preferentially destroying the rotor side thermal boundary layer or preferentially destroying the stator side thermal boundary layer, so as to ensure that the air has sufficient kinetic energy to destroy the stator side thermal boundary layer, so that the heat of the thermal boundary layer can be preferentially conducted out. The specific effect can be seen from Table 2 and Table 3 in Experiment 2.

[0067] In addition, it should be noted that the gradual change mechanism of the guide protrusion A31 and the guide protrusion B32 in this scheme can also effectively break the problem of laminar solidification caused by the equal-height protrusion structure, further improving the disturbance of the air and the exchange of air on the rotor side and the stator side.

[0068] In some embodiments, as shown in Figure 4 , Figure 5 As shown in Figs. 1 and 2, a plurality of disturbance protrusions A33 are uniformly distributed on the arc surface of the stator part 1, and the disturbance protrusions A33 are located on the air inlet side of the stator body 11. A plurality of disturbance protrusions B34 are uniformly distributed on the arc inner surface of the permanent magnet 24 of the rotor part 2, and the disturbance protrusions B34 are located on the air outlet side of the rotor body 21.

[0069] The disturbance protrusions A33 on the air inlet side of the stator are used to "scatter" the airflow into turbulent flow at the initial stage of airflow; the disturbance protrusions B34 on the air outlet side of the rotor are used for the last strong heat exchange before the heat is finally taken out.

[0070] On the basis of the above embodiment, the disturbance protrusions A33 and the disturbance protrusions B34 in this scheme are triangular particles. The disturbance protrusions A33 and the disturbance protrusions B34 are designed to have a larger inlet side inclination than an outlet side inclination. This further improves the ability of the disturbance particles A and the disturbance particles B to form turbulent flow, and achieves the purpose of further destroying the thermal boundary layer.

[0071] On the basis of the above-mentioned embodiments, the turbulence convex particles A33 and the turbulence convex particles B34 in the present scheme are uniformly and staggered arranged.

[0072] It should be noted that the flow guide convex rib A31, the flow guide convex rib B32, the turbulence convex particle A33 and the turbulence convex particle B34 in the present scheme are integrally formed when the BCM is molded.

[0073] Working principle: the working principle of the present application is based on the following three core mechanisms, which work together to destroy the thermal boundary layer in the air gap and greatly enhance heat dissipation.

[0074] 1. Parasitic screw pump effect, build directional axial airflow

[0075] The helical flow guide convex rib A31 is arranged on the outer surface of the stator, and the helical flow guide convex rib B32 is arranged on the inner surface of the rotor (permanent magnet 24). When the rotor rotates at high speed, the convex rib B cooperates with the convex rib A, like a passive "viscous screw pump", which efficiently converts the circumferential shear force of the rotor to the air into a powerful axial thrust. Through the above structure, the present scheme forcibly generates a directional cooling airflow from the air inlet side to the air outlet side in a very small air gap of 1-2mm, which fundamentally changes the nearly stationary state of the air in the air gap.

[0076] 2. Flow channel morphology and vortex generation, implement global disturbance

[0077] The flow guide convex rib A31 extends in an S shape, so that the cross section of the flow channel changes nonlinearly. This not only produces alternating shedding vortexes (Kármán vortex street effect), but also makes the airflow experience repeated compression and expansion, further enhancing the turbulence and heat exchange strength.

[0078] 3. Micro vortex generator, precise attack on thermal boundary layer

[0079] At the key positions of the stator air inlet side and the rotor air outlet side, asymmetric triangular (large slope on the air inlet side) turbulence convex particles A33 and turbulence convex particles B34 are arranged respectively. These convex particles act as efficient vortex generators, which can strongly "scatter" the airflow at the beginning and before the final discharge, and completely "tear" the most stubborn thermal boundary layer. The staggered distribution ensures that there is no blind area on the heat dissipation surface. The present scheme gets superposition through the above three means, greatly improves the heat exchange rate of heat in the air gap, and finally achieves the purpose of improving the overall heat dissipation efficiency of the motor.

[0080] In order to verify the technical effects in the present scheme, the present scheme also designs the following verification experiment for testing.

[0081] Experiment 1: Overall heat dissipation performance comparison between the application and conventional motor under rated operating conditions

[0082] Test conditions:

[0083] Test samples: multiple external rotor motor samples with the same power, size, and air gap (1.5 mm) were selected.

[0084] Test environment: under room temperature environment (35℃), continuously operate under rated operating conditions (such as rated power, rated speed) until thermal equilibrium is reached (winding temperature rise changes within 1℃ / 10 minutes).

[0085] Measurement points: measure temperature at the center of the motor stator.

[0086] Core test indicators: stator winding temperature rise (ΔT, ℃), time to reach thermal equilibrium (minutes), average axial flow velocity in air gap (m / s).

[0087] Experiment group design

[0088] Control group: conventional external rotor motor, smooth surface between stator and rotor air gap.

[0089] Experiment group 1: with basic heat dissipation structure (only containing spiral flow guide protrusions A31 and flow guide protrusions B32).

[0090] Experiment group 2: with optimized heat dissipation structure (on the basis of experiment group 1, increase the S-shaped extension of flow guide protrusions A31).

[0091] Experiment group 3: with complete heat dissipation structure (on the basis of experiment group 2, increase turbulence protrusions A33 and turbulence protrusions B34, which is the complete scheme of the application).

[0092] Table 1: Basic heat dissipation performance comparison (steady-state temperature rise test)

[0093]

[0094] 1. Overall improvement: compared with the control group (average temperature rise 105.7℃), the average temperature rise of experiment groups 1, 2, and 3 is reduced by 18.9℃, 24.6℃, and 29.8℃ respectively. This clearly proves the significant and stable effect of the application's technical solutions at each stage in improving heat dissipation performance.

[0095] 2. Technical feature contribution:

[0096] Experiment group 1 verifies the strong basic heat dissipation ability of the basic spiral flow guide protrusion structure.

[0097] The average temperature rise of experiment group 2 is reduced by 5.7℃ compared with experiment group 1, which proves that the S-shaped extension design produces stronger vortex and brings additional heat dissipation gain.

[0098] The average temperature rise of the experimental group 3 is further reduced by 5.2°C compared with the experimental group 2, which proves the effective role of the turbulence convex particles in destroying the boundary layer, and finally makes the complete scheme achieve the best heat dissipation effect.

[0099] Experiment 2: Correlation verification of axial heat dissipation uniformity and flow guide convex rib A and flow guide convex rib B structure

[0100] Test conditions:

[0101] Test sample: experimental group A (gradually changing height convex rib) vs. control group B (equal height convex rib), and the experimental group A in this scheme is referred to the experimental group 1 in experiment 1.

[0102] Test environment: the ambient temperature is stabilized at 35°C.

[0103] Test condition: the motor is operated at rated power and rated speed until thermal equilibrium is reached.

[0104] Measurement points: 5 temperature measurement intervals (P1-P5) are uniformly selected on the stator surface along the axial direction, wherein P1 is the air inlet side and P5 is the air outlet side, 3 temperature measurement points are arranged in the ring direction on each interval, and the included angle of each temperature measurement point is 120°.

[0105] Table 2: Temperature data record (°C)

[0106]

[0107] Table 3

[0108]

[0109] Experimental conclusion: through the structure optimization of the flow guide convex rib A and the flow guide convex rib B, the heat dissipation capacity is successfully and accurately put into the area that needs it most, so that the axial heat dissipation uniformity of the outer rotor motor is improved in quality without changing the basic air gap width and sacrificing the electromagnetic performance. It should be noted that improving the axial temperature uniformity of the motor can effectively prolong the service life of the motor and avoid the situation of burning wire (especially on the air outlet side). Moreover, while maintaining the axial uniformity of the motor temperature, the thermal expansion amount of the stator part in the axial direction is also maximized to maintain consistency, avoiding the situation of sweep boring due to high temperature on the air outlet side.

[0110] Although the embodiments of the present application have been shown and described, it can be understood by those skilled in the art that various changes, modifications, replacements and variations can be made to these embodiments without departing from the principles and spirits of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A high-efficiency heat dissipation external rotor motor, characterized in that: include The stator part (1) includes a stator body (11), the center of which is provided with an axially penetrating channel (12), and the two ends of the channel (12) are provided with bearing chambers (13), and bearings (14) are coaxially arranged in the bearing chambers (13). The arc-shaped surface of the stator part (1) is evenly distributed with several turbulent flow protrusions A (33), and the turbulent flow protrusions A (33) are located on the air inlet side of the stator body (11). The permanent magnet (24) of the rotor part (2) is evenly distributed with turbulent flow protrusions B (34), and the turbulent flow protrusions B (34) are located on the air outlet side of the rotor body (21). The rotor part (2) includes a rotor body (21), which is covered outside the stator body (11). A rotating shaft (22) is coaxially connected to the rotor body (21). The rotating shaft (22) is rotatably inserted into the bearing (14). A magnetic ring (23) and a spoke-shaped permanent magnet (24) are embedded in the inner side of the rotor body (21). The arc-shaped inner surface of the permanent magnet (24) and the arc-shaped outer surface of the stator body (11) form an air gap of 1~2mm. The heat dissipation part (3) is disposed in the air gap. The heat dissipation part (3) includes several guide ridges A (31) and guide ridges B (32). The guide ridges A (31) are spirally arranged on the arc-shaped outer surface of the stator part (1). The guide ridges B (32) are evenly arranged on the arc-shaped inner surface of the rotor part (2). The sum of the radial heights of the guide ridges A (31) and B (32) is 0.6~0.7mm.

2. The high-efficiency heat dissipation external rotor motor as described in claim 1, characterized in that: The maximum radial height of the guide ridge A (31) is 0.2 mm, and the maximum radial height of the guide ridge B (32) is 0.5 mm.

3. The high-efficiency heat dissipation external rotor motor as described in claim 1, characterized in that: The spiral angle between the guide ridge A (31) and the guide ridge B (32) is 60~75°.

4. The high-efficiency heat dissipation external rotor motor as described in claim 1, characterized in that: The guide ridge A (31) extends in an S-shape while maintaining a spiral shape attached to the arc surface of the stator body (11).

5. A high-efficiency heat dissipation external rotor motor as described in any one of claims 1 to 4, characterized in that: The radial height of the guide ridge B (32) gradually decreases from high to low from the air inlet side to the air outlet side, while the radial height of the guide ridge A (31) gradually increases from low to high from the air inlet side to the air outlet side.

6. The high-efficiency heat dissipation external rotor motor as described in claim 5, characterized in that: The inclination of the flow guiding ridge A (31) and flow guiding ridge B (32) is 1:200~1:

300.

7. The high-efficiency heat dissipation external rotor motor as described in claim 6, characterized in that: The aforementioned turbulence protrusions A (33) and B (34) are triangular protrusions with an inlet slope greater than the outlet slope.

8. The high-efficiency heat dissipation external rotor motor as described in claim 7, characterized in that: The turbulence protrusions A (33) and B (34) are both uniformly distributed in a staggered pattern.

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