A semi-closed outer rotating brushless motor with self-circulating air flow heat dissipation and operation method thereof

Abstract

This invention discloses a semi-enclosed external brushless motor with self-circulating airflow cooling and its operating method. The motor includes a motor shaft, a housing, a semi-enclosed housing cover, a motor base, fixing screws, bearings, and several guide vanes. The housing, semi-enclosed housing cover, and motor base are detachably connected by fixing screws to form a semi-enclosed cavity. The motor shaft passes through the semi-enclosed cavity, with one end rotatably connected to the motor base via a bearing, and the other end fixedly connected to the semi-enclosed housing cover. Several first airflow grooves are evenly distributed on the outer side of the motor base. Several guide vanes are disposed on the inner bottom wall of the semi-enclosed housing cover, and several second airflow grooves are evenly distributed on the side wall of the semi-enclosed housing cover. This invention solves the problems of magnet demagnetization, winding aging, and efficiency reduction caused by heat accumulation, as well as rotor jamming and motor burnout caused by foreign object entry, ultimately improving the working performance, operational stability, and service life of the external brushless motor.

Description

Technical Field

[0001] This invention relates to the field of brushless motor technology, specifically to a semi-enclosed external brushless motor with self-circulating airflow for heat dissipation and its operating method. Background Technology

[0002] External brushless motors, due to their advantages such as high output torque, compact structure, and high power transmission efficiency, have become an important alternative to traditional internal brushless motors and are widely used in various power transmission equipment. However, the existing external brushless motors have inherent structural design flaws, resulting in two major problems in actual operation: poor heat dissipation and susceptibility to stalling. These issues severely restrict the performance and lifespan of the motors.

[0003] In terms of heat dissipation, traditional external brushless motors mostly adopt open or simple closed structures, lacking a dedicated airflow circulation cooling design. When the motor rotates at high speed, the Joule heat and iron loss heat generated by the core heat-generating components such as the stator windings and rotor magnets cannot be effectively dissipated. At the same time, the external low-temperature airflow is difficult to enter the motor to complete heat exchange, resulting in heat accumulation inside the motor and a continuous increase in temperature. Excessive operating temperature not only causes demagnetization of the motor magnets and aging of the stator winding insulation layer, significantly reducing the motor's power output efficiency and service life, but may also trigger the motor's overheat protection shutdown, affecting the continuous operation stability of the equipment. Some improved external brushless motors attempt to add external cooling devices such as cooling fans, which can improve the cooling effect to some extent, but additionally increases the structural complexity and energy consumption of the motor. Moreover, external cooling components are prone to failure, increasing maintenance costs.

[0004] In terms of protection, traditional external brushless motors typically have large ventilation openings to ensure airflow, but lack effective foreign object blocking structures. In complex working conditions such as mines, construction machinery, and outdoor equipment, foreign objects such as sand, gravel, debris, and dust can easily enter the core operating area of ​​the motor through the ventilation openings, causing rotor jamming, bearing wear, and ultimately motor stalling, or even direct motor burnout. If the size of the ventilation openings is simply reduced to block foreign objects, it will further exacerbate the heat dissipation problem inside the motor, creating a technical contradiction between "heat dissipation" and "protection." Existing technologies cannot effectively balance both aspects.

[0005] In summary, existing external brushless motors have not yet solved the technical problems of low heat dissipation efficiency, poor anti-stalling capability, and difficulty in balancing heat dissipation and protection in terms of structural design and operation control. There is an urgent need for a new structural design and operation method to achieve efficient self-circulating heat dissipation and reliable anti-stalling protection for external brushless motors. Summary of the Invention

[0006] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a semi-enclosed external brushless motor with self-circulating airflow cooling and its operation method. Through an innovative mechanical structure design combined with a fluid dynamics-based operation control strategy, the external brushless motor achieves efficient self-circulating active cooling. At the same time, it constructs a reliable anti-stall protection system, solving the problems of magnet demagnetization, winding aging, and efficiency reduction caused by heat accumulation in traditional motors, as well as rotor jamming and motor burnout caused by foreign object intrusion. Ultimately, it improves the working performance, operational stability, and service life of the external brushless motor.

[0007] To solve the above problems, the technical solution adopted by the present invention is as follows: A semi-enclosed external brushless motor with self-circulating airflow for heat dissipation includes a motor shaft, a housing, a semi-enclosed housing cover, a motor base, fixing screws, bearings, and several guide vanes. The housing, the semi-enclosed housing cover, and the motor base are detachably connected by fixing screws to form a semi-enclosed cavity. The motor shaft passes through the semi-enclosed cavity, and one end of the motor shaft is rotatably connected to the motor base through a bearing, while the other end is fixedly connected to the semi-enclosed housing cover. Among them, several first airflow grooves are evenly opened on the outer side of the motor base, and the first airflow grooves are connected to the semi-enclosed cavity. Several guide vanes are set on the inner bottom wall of the semi-enclosed housing cover, and several second airflow channels are evenly opened on the side wall of the semi-enclosed housing cover. The second airflow channels are connected to the semi-enclosed cavity.

[0008] Preferably, the guide vanes are integrally formed on the inner bottom wall of the semi-enclosed housing cover and are evenly distributed along the circumference of the semi-enclosed housing cover. The guide vanes are connected to the second airflow channel via the guide section to guide the heat exchange airflow to be discharged quickly from the second airflow channel; The first airflow channel is equipped with a channel guide surface.

[0009] A method for operating a semi-enclosed external brushless motor with self-circulating airflow for heat dissipation includes the following steps: After the motor is powered on, the outer rotor starts to rotate. The guide vanes on the semi-enclosed casing rotate synchronously with the outer rotor. Under the dynamic pressure of the guide vanes, the low-temperature airflow outside the motor forms a directional tendency to flow towards the motor base. The low-temperature airflow enters the semi-enclosed cavity through the first airflow channel of the motor base, and forms a heat exchange airflow after sufficient heat exchange with the inner wall of the housing, the stator winding and the rotor magnet. Driven by the pressure difference continuously generated by the guide vanes, the heat exchange airflow is discharged from the second airflow channel of the semi-enclosed casing to the outside of the motor, completing a single self-circulation heat dissipation process, and achieving circulation heat dissipation as the outer rotor continues to rotate. During the motor's operating cycle, the diameters of the first and second airflow channels restrict large-diameter foreign objects from entering the motor while allowing normal airflow.

[0010] Preferably, in the initial stage when the guide vanes rotate synchronously with the outer rotor, the outer rotor accelerates from zero speed to a set speed using a gradient acceleration strategy, causing the negative pressure value in the semi-enclosed cavity to increase in a gradient manner, thereby achieving a smooth introduction of low-temperature airflow.

[0011] Preferably, when the outer rotor accelerates from zero speed to a set speed using a gradient acceleration strategy, it includes: The acceleration process is divided into three gradient stages. The first stage is the low-speed start-up stage, where the outer rotor accelerates from zero speed to the first rotational speed value with the first angular acceleration and maintains the rotational speed for the first time period, so that a basic negative pressure is formed in the semi-enclosed cavity and the initial replacement of the residual static air in the cavity is completed. The second stage is the medium-speed acceleration stage, in which the outer rotor accelerates from the first speed value to the second speed value with the second angular acceleration, and maintains the speed for a second time period, so that the negative pressure value in the semi-enclosed cavity increases linearly, thereby achieving stable introduction of low-temperature airflow and initial heat exchange with the internal components of the motor. The third stage is the high-speed constant speed stage. The outer rotor accelerates from the second speed value to the set speed value with the third angular acceleration. After the acceleration is completed, it maintains the set speed and runs stably, so that a working negative pressure is formed in the semi-enclosed cavity, and the cooling airflow is used for self-circulation cooling.

[0012] Preferably, the above operating method further includes: when the low-temperature airflow enters the semi-enclosed cavity through the first airflow channel, it first forms a swirling flow through the channel opening guide surface of the first airflow channel; The swirling flow diffuses bidirectionally along the axial and circumferential directions of the semi-enclosed cavity, allowing the low-temperature airflow to fully exchange heat with the inner wall of the casing, the stator windings, and the rotor magnets.

[0013] Preferably, the above operating method further includes: before the heat exchange airflow is discharged, it first forms a convergence and pressurization at the guide section where the guide vane is connected to the second airflow channel, so that the heat exchange airflow is discharged from the second airflow channel at a higher flow rate, and the discharged airflow forms an air curtain outside the motor to block fine particles from approaching the second airflow channel.

[0014] Preferably, the above operating method further includes: when the internal temperature of the motor is detected to exceed a preset threshold, the negative pressure value generated by the guide vanes is changed by adjusting the rotational speed of the outer rotor; The internal temperature detection points of the motor are set in the heat exchange core area between the stator winding and the rotor magnet. The detection data is fed back to the motor control module in real time. The motor control module adjusts the speed of the outer rotor in a closed loop according to the temperature change, so as to realize the adaptive dynamic control of the heat dissipation airflow.

[0015] Preferably, when adjusting the external rotor speed in a closed loop based on temperature changes, the method includes: The preset temperature threshold of the heat exchange core area inside the motor is divided into three levels, including the first level warning threshold, the second level control threshold and the third level emergency threshold. The threshold intervals of each level do not overlap and are continuously connected. When the temperature reaches the first-level warning threshold, the outer rotor increases its speed by a first percentage from the original set speed, maintains this speed, and monitors temperature changes in real time. When the temperature reaches the second-level control threshold, the outer rotor increases its speed by a second percentage from the speed corresponding to the first-level warning threshold, and at the same time, the airflow swirl intensity enhancement mode of the semi-enclosed cavity is activated. When the temperature reaches the third-level emergency threshold, the outer rotor accelerates to the maximum safe speed of the motor with a fourth-angle acceleration and maintains this speed until the temperature drops below the second-level control threshold.

[0016] Preferably, the airflow swirl intensity enhancement mode is to adjust the rotational angular velocity fluctuation frequency of the outer rotor through the motor control module, so that the outer rotor generates periodic angular velocity fluctuations based on the rotational speed corresponding to the second-level control threshold, which drives the guide vanes to form a pulsating dynamic pressure airflow, causing turbulent disturbances in the swirling flow within the semi-enclosed cavity, thereby improving the heat transfer coefficient between the low-temperature airflow and the semi-enclosed cavity wall.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention relies on the rotation of the outer rotor to drive the guide vanes to generate dynamic pressure and negative pressure, which drives the external low temperature airflow to form a directional self-circulating path. There is no need to add an external cooling fan or other additional power device. While reducing the complexity of the motor structure and energy consumption, it realizes the continuous active heat dissipation of the core heat-generating components such as the stator winding and rotor magnet inside the motor, effectively avoiding heat accumulation, preventing the magnet from being demagnetized and the insulation layer of the stator winding from aging, and greatly improving the power output efficiency and working life of the motor.

[0018] (2) By combining the semi-enclosed cavity structure with the design of the first and second airflow channels with a diameter of ≤3mm, large-volume foreign objects are blocked from the structural level, and large-diameter sand and debris are physically intercepted from the channel level. At the same time, the size of the flow channel ensures the normal passage of heat dissipation airflow, which completely solves the technical contradiction of traditional motors that "heat dissipation requires large ventilation openings and protection requires small ventilation openings". In addition, the air curtain formed by the high-speed discharge of heat exchange airflow achieves secondary active blocking of fine particles, further improving the anti-blockage protection capability and adapting to complex and harsh working conditions.

[0019] (3) The first airflow channel of the motor base is provided with a channel guide surface, so that the low temperature airflow forms an axial and circumferential swirling flow and diffuses bidirectionally in the cavity, eliminating heat exchange dead angles and maximizing the contact area and contact time between the low temperature airflow and the heat-generating components; the guide part between the guide vane and the second airflow channel realizes the convergence and pressurization of heat exchange airflow, reduces the energy loss of airflow discharge, improves the overall flow efficiency of the heat dissipation path, and makes heat exchange more sufficient and airflow circulation more stable.

[0020] (4) The gradient speed-up strategy is adopted to increase the speed of the outer rotor in stages, so that the negative pressure value in the cavity increases in a gradient manner, and the low-temperature airflow is smoothly introduced, avoiding the airflow impact and turbulence problems caused by sudden negative pressure changes. At the same time, the residual air in the cavity is replaced in an orderly manner. Based on the real-time temperature detection of the core area of ​​the motor heat exchange, a closed-loop control system of three-level temperature threshold and speed gradient adjustment is constructed. It can adaptively adjust the heat dissipation airflow according to the motor heating state, and can also improve the heat transfer coefficient through the swirling intensity enhancement mode, so as to achieve precise temperature control of "more heat generation means stronger heat dissipation, less heat generation means weaker heat dissipation", taking into account both heat dissipation reliability and operating economy.

[0021] (5) The guide vanes and the semi-enclosed housing cover are integrally molded to improve the structural strength and fatigue resistance of the vanes, avoid loosening and falling off during high-speed rotation, and ensure long-term stable operation of the motor. The gradient speed-up strategy and the parameters of temperature closed-loop control can be adaptively matched according to the rated power of the motor, making the present invention applicable to different specifications of external brushless motors, with good versatility and adaptability, and reducing the application cost in different scenarios.

[0022] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0023] Figure 1 This is a structural diagram of the semi-enclosed casing cover of Embodiment 1 of the present invention; Figure 2 This is a cross-sectional view of the semi-enclosed external brushless motor of Embodiment 1 of the present invention; Figure 3 This is a half-sectional view of the semi-enclosed external rotating brushless motor of Embodiment 1 of the present invention; Figure 4 This is a front view of the semi-enclosed external brushless motor of Embodiment 1 of the present invention; Figure 5 These are the operation steps of the semi-enclosed external rotating brushless motor in Embodiment 2 of the present invention; Figure 6 This is a flowchart of the closed-loop adjustment process of the external rotor speed in Embodiment 2 of the present invention.

[0024] Explanation of reference numerals in the attached drawings: 1. Motor shaft; 2. Housing; 3. Semi-enclosed housing cover; 4. Motor base; 5. Fixing screw; 6. Bearing; 7. Guide vane; 8. Semi-enclosed cavity; 9. First airflow channel; 10. Second airflow channel; 11. Guide section; 12. Channel opening guide surface. Detailed Implementation

[0025] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0026] At the same time, it should be understood that, for ease of description, the dimensions of the various parts shown in the accompanying drawings are not drawn according to actual scale.

[0027] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the scope of this application and its application or use.

[0028] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0029] Example 1, the present invention provides as follows Figure 2-4 The semi-enclosed external brushless motor with self-circulating airflow cooling shown includes a motor shaft 1, a housing 2, a semi-enclosed housing cover 3, a motor base 4, fixing screws 5, bearings 6, and several guide vanes 7. The housing 2, the semi-enclosed housing cover 3, and the motor base 4 are detachably connected by fixing screws 5 to form a semi-enclosed cavity 8. The motor shaft 1 passes through the semi-enclosed cavity 8, and one end of the motor shaft 1 is rotatably connected to the motor base 4 through the bearing 6, while the other end is fixedly connected to the semi-enclosed housing cover 3. Among them, a number of first airflow channels 9 are evenly opened on the outer side of the motor base 4, and the first airflow channels 9 are connected to the semi-enclosed cavity 8. Several guide vanes 7 are disposed on the inner bottom wall of the semi-enclosed housing cover 3. Several second airflow channels 10 are evenly opened on the side wall of the semi-enclosed housing cover 3. The second airflow channels 10 are connected to the semi-enclosed cavity 8. When the outer rotor rotates, the guide vanes 7 rotate synchronously with the outer rotor under the drive of the motor shaft 1, generating dynamic pressure airflow and creating negative pressure inside the semi-enclosed cavity 8. This drives the external low-temperature airflow through the first airflow channel 9 of the motor base 4 into the semi-enclosed cavity 8. After sufficient heat exchange with the inner wall of the housing 2, the stator winding, and the rotor magnet, the airflow is discharged to the outside of the motor through the second airflow channel 10 of the semi-enclosed housing cover 3, forming a self-circulating heat dissipation path. At the same time, the semi-enclosed housing cover 3 prevents external sand and debris from entering the motor, avoiding motor stalling.

[0030] Specifically, this semi-enclosed external brushless motor with self-circulating airflow cooling integrates a semi-enclosed protective structure with the principle of self-circulating airflow cooling. Relying on mechanical structure design and fluid dynamics effects, it achieves the dual functions of heat dissipation and anti-stalling. Its overall working principle can be divided into three core parts: structural foundation support, airflow self-circulation cooling, and semi-enclosed anti-stalling, as detailed below: The motor is detachably connected to the housing 2, the semi-enclosed housing cover 3, and the motor base 4 by fixing screws 5, forming a relatively closed semi-enclosed cavity 8. The motor shaft 1 passes through this cavity and is rotatably connected to the motor base 4 through bearing 6, providing basic mechanical support for the motor's rotation. At the same time, the semi-enclosed cavity 8 defines a dedicated channel for the directional flow of air, avoiding irregular diffusion of airflow, ensuring heat dissipation efficiency, and also providing a structural basis for blocking external foreign objects.

[0031] The motor's heat dissipation is achieved through a self-circulating airflow path driven by dynamic negative pressure, entirely driven by the mechanical motion of the rotating external rotor, requiring no additional cooling power device. Negative pressure generation: When the outer rotor rotates, it drives the guide vanes 7, which are fixed to the bottom wall of the semi-enclosed housing cover 3, to rotate synchronously. The rotation of the guide vanes 7 generates dynamic pressure airflow, which creates a negative pressure environment in the semi-enclosed cavity 8, forming a pressure difference that allows the external low-temperature airflow to flow into the cavity. Airflow entry: Driven by negative pressure, the low-temperature airflow outside the motor enters the semi-enclosed cavity 8 inside the motor through several first airflow channels 9 evenly opened on the outside of the motor base 4. Heat exchange: The low-temperature airflow in the semi-enclosed cavity 8 comes into full contact with the inner wall of the casing 2, the stator winding and the rotor magnet, which generate a lot of heat during the operation of the motor, to complete the heat exchange, absorb the Joule heat and iron loss heat generated by the motor, and form a heat exchange airflow itself. Airflow discharge: Driven by the pressure difference generated by the continuous rotation of the guide vanes 7, the heat exchange airflow flows towards the semi-enclosed housing cover 3, and is finally discharged to the outside of the motor through several second airflow channels 10 opened on its side wall, completing a complete airflow cycle; the outer rotor continues to rotate, and the above process is repeated continuously, forming a continuous self-circulating heat dissipation path to achieve active heat dissipation of the motor.

[0032] The semi-enclosed cavity structure of the motor, combined with the size design of the airflow channel, effectively blocks external foreign objects and prevents the motor from stalling. The semi-enclosed housing cover 3 structurally prevents large-volume sand and debris from directly entering the core operating area inside the motor; at the same time, the first and second airflow channels are designed to ensure airflow through the channels, and their size can limit the entry of sand and debris with excessive particle size into the cavity through the channels, further blocking foreign objects from the channel level. This double protection avoids foreign objects from entering the motor and causing rotor jamming or motor stalling.

[0033] In one possible embodiment, see [reference] Figure 1 The semi-enclosed housing cover structure diagram shows that the guide vanes 7 are integrally formed on the inner bottom wall of the semi-enclosed housing cover 3 and are evenly distributed along the circumference of the semi-enclosed housing cover 3. The guide vane 7 is connected to the second airflow channel 10 through the guide part 11 to guide the heat exchange airflow to be discharged quickly from the second airflow channel 10.

[0034] Specifically, this embodiment optimizes the motor's self-circulating cooling system from three dimensions: structural stability, airflow drive uniformity, and heat exchange airflow guidance, through the molding method, distribution form, and connection design of the guide vanes 7 and the airflow discharge groove. This allows the generation, flow, and discharge of airflow to form a more efficient directional path. The design principle and working logic are as follows: The guide vane 7 and the inner bottom wall of the semi-enclosed casing cover 3 are integrally molded, eliminating the connection gaps and assembly clearances between the vane and the casing cover. This makes the vane an integral part of the casing cover structure, significantly improving the structural strength and fatigue resistance of the vane. This prevents the vane from loosening, falling off, or vibrating abnormally due to airflow impact and centrifugal force when the outer rotor rotates at high speed, ensuring the reliability of the vane's synchronous rotation with the outer rotor and providing a structural foundation for the continuous and stable generation of dynamic pressure airflow.

[0035] The blades are evenly distributed around the semi-enclosed housing cover 3. When the outer rotor drives the housing cover to rotate, each blade can synchronously and evenly push the surrounding air in all circumferential directions, creating a uniform negative pressure field within the semi-enclosed cavity 8, rather than a localized concentration of negative pressure. This allows the external low-temperature airflow to enter the motor evenly through the first airflow channel 9 around the motor base 4, avoiding dead airflow zones within the cavity and maximizing the contact area between the low-temperature airflow and the inner wall of the housing 2, stator windings, and other heat-generating components, thereby improving overall heat exchange efficiency.

[0036] The guide section 11 is a transitional structure between the guide vane 7 and the second airflow channel 10. Its core function is to plan the flow path of the heat exchange airflow and eliminate the resistance and turbulence of the airflow discharge. Driven by the pressure difference generated by the continuous rotation of the guide vane 7, the hot airflow that has completed heat exchange in the cavity will naturally flow towards the vane side. The airflow that was originally unguided is prone to backflow and turbulence at the slot opening, resulting in a decrease in discharge efficiency. The guide section 11, which is integrated with the vane, provides a directional flow channel for the hot airflow, gathers the dispersed heat exchange airflow and guides it to the slot opening of the second airflow channel 10, allowing the airflow to enter the channel body and be discharged outside the motor without obstruction along the contour of the guide section 11.

[0037] This design allows the heat exchange airflow to form a continuous directional path of "flow-convergence-discharge", reducing energy loss of airflow in the discharge stage, improving the overall flow efficiency of the self-circulating airflow, and avoiding local airflow accumulation caused by turbulence, further ensuring the stability of the negative pressure field in the cavity.

[0038] The structural design of this embodiment is a refined optimization of the motor's self-circulating heat dissipation. The integrated structure ensures operational reliability, the circumferential uniform distribution ensures the uniformity of airflow drive and entry, and the directional design of the guide part 11 ensures the high efficiency of airflow discharge. The three work together to make the airflow in the self-circulating heat dissipation path smoother, the heat exchange more sufficient, and the operation more stable.

[0039] In one possible embodiment, the diameters of the first airflow channel 9 and the second airflow channel 10 are both less than or equal to 3 mm, which is used to prevent sand and debris with a particle size greater than 3 mm from entering the motor.

[0040] Specifically, in this embodiment, the diameter of the two airflow channels is uniformly limited to ≤3mm. The difference between the channel diameter and the size of the foreign object particles forms a physical interception: when sand, gravel and debris move into the motor, foreign objects with a diameter greater than 3mm cannot pass through the channel diameter space and will be directly blocked outside the motor and cannot enter the semi-enclosed cavity 8. From the "channel entrance" level of foreign objects, the path of motor stall caused by large-diameter foreign objects is completely cut off.

[0041] The ≤3mm slot diameter limit is not simply a protective setting, but a balanced design between heat dissipation airflow and foreign object protection: air, as a fluid, has a molecular particle size much smaller than 3mm. This slot diameter size can provide sufficient flow space for low-temperature airflow and heat exchange airflow, and will not cause a sudden increase in airflow resistance due to excessively small slot diameter. This ensures that the external low-temperature airflow can smoothly enter the motor through the first airflow channel 9, and the hot airflow after heat exchange can also smoothly exit through the second airflow channel 10. This ensures that the airflow velocity and flow rate of the motor's self-circulating heat dissipation path meet the heat dissipation requirements, so that the core function of normal airflow is not affected by the protective design.

[0042] In one possible embodiment, see [reference] Figure 3 A semi-sectional view of a semi-enclosed external rotating brushless motor, wherein the first airflow channel 9 is provided with a channel guide surface 12.

[0043] Specifically, the slot guide surface 12 of the first airflow channel 9 is a fluid dynamics guiding structure designed for the low-temperature airflow to enter the semi-enclosed cavity 8 of the motor. The core principle is to change the inflow direction and flow pattern of the low-temperature airflow by processing the slot opening into a streamlined curved surface, thereby optimizing the diffusion and heat exchange effect of the airflow in the cavity and reducing the flow resistance of the airflow. The specific principle can be divided into three aspects: The slotted guide surface 12 provides directional guidance for the airflow, causing the low-temperature airflow, which originally entered the cavity vertically in a straight line, to change its trajectory under the constraint of the guide surface, forming a swirling flow pattern along the cavity's axial and circumferential directions. This swirling flow will undergo bidirectional diffusion within the semi-enclosed cavity 8, rather than localized direct blowing, allowing the low-temperature airflow to more evenly contact all heat-generating core components such as the inner wall of the casing 2, the stator windings, and the rotor magnets. This eliminates dead zones in the airflow heat exchange within the cavity, maximizes the contact area and contact time between the low-temperature airflow and the heat-generating components, and significantly improves the adequacy of heat exchange.

[0044] Without the slotted guide surface 12, when airflow enters the narrow flow channel from the normal pressure environment outside the motor, the right-angled structure of the slot will cause airflow impact, turbulence, and backflow, increasing the local resistance to airflow entry, resulting in a decrease in airflow velocity and flow rate, and affecting the overall efficiency of self-circulating heat dissipation. The streamlined slotted guide surface 12 provides a smooth transition channel for airflow, allowing airflow to slide smoothly along the curved surface of the guide surface into the flow channel and into the cavity, reducing energy loss and flow disturbance at the slot opening, ensuring that the low-temperature airflow enters the cavity at a stable and efficient flow rate, and ensuring that the airflow of the self-circulating heat dissipation path meets the motor's heat dissipation requirements.

[0045] The slot guide surface 12 changes the direction of airflow, preventing low-temperature airflow from directly impacting precision components such as the stator windings and rotor magnets inside the cavity in a vertical, high-pressure manner. On the one hand, it prevents high-speed airflow from causing wear on the winding insulation layer and peeling off the coating on the magnet surface, protecting the structural integrity of the core components; on the other hand, it avoids the accumulation of small suspended particles from the outside on the surface of the components due to the direct impact of airflow, reducing potential problems such as decreased heat exchange efficiency and component jamming caused by particle adhesion.

[0046] The slot guide surface 12 is a structural design that optimizes the inflow process of low-temperature airflow from three dimensions: airflow pattern, flow efficiency, and component protection. This makes the airflow introduction process of self-circulating heat dissipation more efficient and stable, while also taking into account the operation protection of the core components inside the motor.

[0047] Example 2, see Figure 5The invention provides a flowchart illustrating the operation steps of a semi-enclosed external rotating brushless motor. Figure 5 The operating method of a semi-enclosed external brushless motor with self-circulating airflow cooling, as shown, includes the following steps: Step S1: After the motor is powered on, the outer rotor starts to rotate. The guide vanes 7 of the semi-enclosed housing cover 3 rotate synchronously with the outer rotor. Under the dynamic pressure of the guide vanes 7, the low-temperature airflow outside the motor forms a directional tendency to flow towards the motor base 4. Step S2: The low-temperature airflow enters the semi-enclosed cavity 8 through the first airflow channel 9 of the motor base 4, and fully exchanges heat with the inner wall of the housing 2, the stator winding and the rotor magnet. After absorbing the Joule heat and iron loss heat generated by the motor operation, it forms a heat exchange airflow. Step S3: Driven by the pressure difference continuously generated by the guide vanes 7, the heat exchange airflow is discharged from the second airflow channel 10 of the semi-enclosed casing cover 3 to the outside of the motor, completing a single self-circulation heat dissipation process, and achieving circulating heat dissipation as the outer rotor continues to rotate. Step S4: During the motor's operating cycle, the diameters of the first airflow channel 9 and the second airflow channel 10 restrict large-diameter foreign objects from entering the motor while allowing normal airflow, thus balancing heat dissipation performance and anti-blockage protection.

[0048] Specifically, the operating method of this semi-enclosed external brushless motor with self-circulating airflow cooling is based on the conversion of the mechanical kinetic energy of the rotating external rotor into airflow pressure / negative pressure potential energy, constructing a self-circulating airflow cooling path inside the motor. Simultaneously, the semi-enclosed structure and slot diameter limitations achieve coordinated operation of heat dissipation and anti-stallization. The overall operating principle forms a closed loop around four core links: directional airflow drive, heat exchange, airflow discharge, and foreign object obstruction. The principles and collaborative logic of each step are as follows: Step S1 is the power source and airflow guidance basis for self-circulating heat dissipation. The core utilizes the hydrodynamic pressure effect to achieve directional airflow. After the motor is powered on, the outer rotor rotates, and the semi-enclosed housing cover 3, which is linked to the outer rotor, rotates synchronously. Its circumferential guide vanes 7 rotate together, and the vanes exert a pushing effect on the surrounding air during rotation, forming a hydrodynamic pressure airflow. The hydrodynamic pressure airflow will create a negative pressure environment inside the semi-enclosed cavity 8 of the motor relative to the outside. Under the pressure difference between the normal pressure outside the cavity and the negative pressure inside the cavity, the low-temperature natural airflow outside the motor is driven to form a directional flow trend towards the motor base 4, laying the power and direction foundation for the subsequent airflow to enter the cavity to complete heat dissipation.

[0049] Step S2 is the core heat exchange stage of self-circulating heat dissipation, relying on the principle of convection heat transfer to absorb the heat generated during motor operation. Driven by the pressure difference formed in step S1, the directional flow of low-temperature airflow passes through the first airflow channel 9 opened on the motor base 4 and smoothly enters the semi-enclosed cavity 8 of the motor. After entering the cavity, the low-temperature airflow comes into full contact with the inner wall of the casing 2, the stator windings, and the rotor magnets (the core heat-generating components of the motor, whose heat originates from Joule heating, iron loss, etc.) that continuously generate heat during motor operation. Through convection heat transfer, the heat on the components is transferred to the low-temperature airflow. After absorbing heat, the temperature of the low-temperature airflow rises, forming a heat exchange airflow, thereby realizing the transfer and collection of heat inside the motor.

[0050] Step S3 is the closed-loop airflow circulation stage of self-circulating heat dissipation, relying on continuous pressure difference to drive the discharge of heat exchange airflow and heat dissipation circulation. The guide vane 7 rotates continuously with the outer rotor, providing a continuous and stable negative pressure difference for the semi-enclosed cavity 8. Under the continuous drive of this pressure difference, the heat exchange airflow that has absorbed heat in the cavity will flow directionally to the guide vane 7 and finally be discharged to the outside of the motor through the second airflow channel 10 on the side wall of the semi-enclosed housing cover 3, completing a single self-circulating heat dissipation process. Since the outer rotor rotates continuously during motor operation, the above process of "low-temperature air flowing into the cavity - heat exchange - hot airflow discharge" will be repeated continuously, forming a continuous self-circulating heat dissipation path, realizing continuous active heat dissipation of the motor, and always keeping the internal temperature of the motor within a reasonable range.

[0051] Step S4 is the core implementation step of the motor protection function. Relying on the principle of physical barrier, foreign object blocking is achieved without affecting the flow of heat dissipation airflow. Throughout the entire motor operation cycle, the second airflow channel 10 of the semi-enclosed housing cover 3 adopts a limited channel diameter design. This channel diameter is much larger than the particle size of air molecules, which can ensure the normal passage of heat dissipation airflow (low temperature airflow, heat exchange airflow) without reducing heat dissipation efficiency due to channel restriction. At the same time, the channel diameter is smaller than the particle size of large-diameter foreign objects such as sand and debris, preventing such foreign objects from entering the semi-enclosed cavity 8 of the motor through the channel. This cuts off the path for foreign objects to enter the core operating area of ​​the motor from the channel level, avoiding rotor jamming and motor stalling caused by foreign objects, and achieving a balance between heat dissipation performance and anti-stall protection capability.

[0052] The core logic of this operating method is self-circulating heat dissipation without additional power, which fully converts the rotational kinetic energy of the outer rotor into the power driven by airflow, and completes the continuous discharge of heat inside the motor through the hydrodynamic effect; at the same time, the heat dissipation structure and the protection structure are integrated into the design, so that the airflow channel also becomes a defense line to block foreign objects, realizing the coordinated operation of the two major functions of heat dissipation and anti-stalling, and solving the core problems of poor heat dissipation and easy stalling of traditional external brushless motors.

[0053] In one possible embodiment, in step S1 above, during the initial stage of the guide vane 7 rotating synchronously with the outer rotor, the outer rotor is accelerated from zero speed to a set speed using a gradient acceleration strategy, so that the negative pressure value in the semi-enclosed cavity 8 increases in a gradient manner, thereby achieving the smooth introduction of low-temperature airflow.

[0054] Specifically, the core principle of this gradient acceleration strategy for smoothly introducing low-temperature airflow is to controllably increase the rotational speed of the outer rotor in a stepwise manner. This allows the dynamic pressure effect generated by the rotation of the guide vanes 7 to change in a gradient, resulting in a stable and gradual increase in the negative pressure value within the semi-enclosed cavity 8. This avoids problems such as airflow impact and turbulence caused by sudden changes in negative pressure, achieving a smooth transition of the low-temperature airflow from stillness to directional and stable inflow into the cavity. At the same time, it completes the orderly replacement of residual air within the cavity, laying the foundation for subsequent stable self-circulating heat dissipation. The specific principle is as follows: The rotational speed of the outer rotor directly determines the rotational angular velocity of the guide vanes 7. The dynamic pressure airflow generated by the vane rotation is the sole driving force for the formation of negative pressure within the cavity, and the two are positively correlated: the lower the vane speed, the weaker the dynamic pressure effect and the smaller the negative pressure value in the cavity; the higher the vane speed, the stronger the dynamic pressure effect and the larger the negative pressure value in the cavity. Gradient acceleration achieves precise control over the rate of increase of negative pressure value from the root by controlling the stepwise increase of the rotational speed.

[0055] If the outer rotor suddenly increases from zero speed to the set speed, the guide vane 7 will instantly generate a strong dynamic pressure effect, causing the negative pressure value in the cavity to increase abruptly. The external low-temperature airflow will rush into the cavity rapidly and disorderly under a large pressure difference, which can easily cause the airflow to impact the precision components inside the cavity, forming local turbulence and backflow. This will not only affect the heat exchange efficiency between the airflow and the heat-generating components, but may also damage the stator winding insulation layer and the rotor magnet coating due to the impact of the airflow.

[0056] The gradient acceleration allows the rotational speed to increase in stages and at a fixed angular acceleration, thereby gradually enhancing the dynamic pressure effect of the guide vane 7. The negative pressure value inside the cavity increases slowly and predictably in a gradient manner, and the pressure difference experienced by the external low-temperature airflow also increases steadily. As the negative pressure gradually increases, the airflow will gradually transition from slow inflow to stable inflow, maintaining a directional and orderly flow state throughout the process. This fundamentally avoids the airflow impact and turbulence problems caused by sudden changes in negative pressure, and achieves smooth airflow introduction.

[0057] Before the motor starts, there is still room temperature air in the semi-enclosed cavity 8. If it starts at high speed directly, the still air in the cavity will be squeezed by the suddenly rushed low temperature airflow, forming a local airflow accumulation, which will affect the normal circulation of heat dissipation airflow.

[0058] The low-speed phase of the gradient acceleration first establishes a basic negative pressure, driving a small amount of low-temperature airflow slowly into the cavity to gradually replace the residual stagnant air inside the cavity, completing the initial renewal of the airflow inside the cavity. The subsequent medium-speed and high-speed acceleration further increases the negative pressure based on the initial replacement, allowing the low-temperature airflow to flow in steadily and exchange heat with the internal components. Finally, a stable working negative pressure is formed at the set speed, matching the airflow inflow rate with the heat exchange and exhaust rates, ensuring the continuous and stable operation of the self-circulating heat dissipation path.

[0059] In this strategy, the angular acceleration and pressure holding time at each stage can be adaptively adjusted according to the rated power of the motor. The larger the rated power of the motor, the larger the cavity volume and the greater the heat generation power. The longer the pressure holding time in the low-speed start-up stage, the more fully the residual air in the large-volume cavity can be replaced, avoiding insufficient basic negative pressure. The smaller the angular acceleration in the medium-speed acceleration stage, the more smoothly the negative pressure value can be increased, adapting to the greater airflow requirements of high-power motors, further improving the accuracy of negative pressure control for motors of different specifications, and ensuring that all types of motors can achieve stable introduction of low-temperature airflow.

[0060] The core of this principle is to transform "speed control" into "negative pressure control". By changing the speed gradient, the negative pressure gradient increases, matching the airflow introduction process with the negative pressure formation and air replacement process of the cavity, ultimately achieving the goal of stable and orderly entry of low-temperature airflow into the semi-enclosed cavity 8.

[0061] In one possible embodiment, accelerating the outer rotor from zero speed to a set speed using a gradient acceleration strategy includes: The acceleration process is divided into three gradient stages. The first stage is the low-speed start-up stage, where the outer rotor accelerates at a speed of 0.5~1 rad / s. 2 The angular acceleration increases from zero speed to 30% of the set speed, and this speed is maintained for 5~10s to create a basic negative pressure in the semi-enclosed cavity 8 and complete the initial replacement of the residual static air in the cavity. The second stage is the medium-speed acceleration stage, with the external rotor accelerating at 1~2 rad / s. 2 The angular acceleration increases from 30% to 70% of the set speed and is maintained at that speed for 3-5 seconds, so that the negative pressure value in the semi-enclosed cavity 8 increases linearly, thereby achieving stable introduction of low-temperature airflow and initial heat exchange with the internal components of the motor. The third stage is the high-speed constant-speed stage, with the outer rotor operating at 0.3~0.8 rad / s. 2 The angular acceleration increases from 70% of the set speed to the set speed value. After the acceleration is completed, the set speed is maintained and the operation is stable, so that a working negative pressure is formed in the semi-enclosed cavity 8, and the heat dissipation airflow is used for self-circulation heat dissipation. The angular acceleration and holding time of each stage can be adaptively matched according to the rated power of the motor. The larger the rated power of the motor, the longer the holding time of the low-speed start-up stage and the smaller the angular acceleration of the medium-speed acceleration stage.

[0062] Specifically, this three-stage gradient acceleration strategy is based on the positive correlation between the external rotor speed and the dynamic pressure effect of the guide vanes 7 and the negative pressure value inside the cavity. By precisely controlling the angular acceleration and pressure holding time during the acceleration process in stages, the negative pressure inside the semi-enclosed cavity 8 is gradually built from zero to high. At the same time, the orderly connection of cavity air replacement, stable airflow introduction and heat exchange is completed, ultimately forming a stable negative pressure field and a self-circulating heat dissipation path adapted to the operation of the motor. The core principles of each stage and the overall synergistic logic are as follows: The first stage uses a low angular acceleration (0.5~1 rad / s²). 2 The speed increase causes the guide vane 7 to rotate slowly, generating a weak dynamic pressure effect, which gradually forms a basic negative pressure (far lower than the working negative pressure) in the semi-enclosed cavity 8, creating only a small internal and external pressure difference, driving the external low-temperature airflow to flow slowly into the cavity, thus preventing the airflow from impacting the precision components such as the stator winding and rotor magnet inside the motor from the source. The 5-10s pressure holding time provides sufficient time for the initial replacement of the residual still air in the cavity. The low-temperature airflow flowing in at low speed will gradually squeeze and replace the room temperature still air in the cavity, completing the initial renewal of the airflow inside the cavity. This avoids the still air being squeezed by the suddenly rushing airflow during the subsequent high-speed acceleration, forming accumulation and turbulence, thus clearing obstacles for the subsequent negative pressure increase and stable airflow.

[0063] The second stage uses a moderate angular acceleration (1~2 rad / s²). 2 The rotational angular velocity of the guide vane 7 is linearly increased, the dynamic pressure effect is continuously enhanced, the negative pressure value inside the cavity increases linearly, the pressure difference between the inside and outside gradually expands, and the inflow rate of the external low-temperature airflow is also steadily increased, realizing the transition from "slow inflow" to "stable quantitative inflow", so that the airflow inflow rate matches the cavity's capacity and heat exchange capacity. The pressure holding time of 3 to 5 seconds allows the stable inflow of low-temperature airflow to conduct preliminary convective heat exchange with the inner wall of the casing 2, the stator winding, the rotor magnet and other motor heating components. This not only completes the transfer of the small amount of heat generated during the initial operation of the motor, but also allows the cavity to form a preliminary airflow path, establishing a flow foundation for efficient self-circulating heat dissipation in the subsequent high-speed stage, and avoiding airflow turbulence caused by directly entering a strong heat exchange state in the high-speed stage.

[0064] The third stage uses a lower angular acceleration (0.3~0.5 rad / s²) than the first two stages. 2This is to ensure that the rotational angular velocity of the guide vane 7 reaches the set value smoothly, so as to avoid the sudden increase in speed in the final stage, which would cause the negative pressure value in the cavity to suddenly rise, and prevent problems such as untimely discharge of heat exchange air and pressure fluctuation in the cavity caused by the sudden increase in airflow inflow rate, thus ensuring the stability of the negative pressure field. Stable operation at the set speed allows the guide vanes 7 to generate a continuous and constant dynamic pressure effect, creating a stable working negative pressure inside the cavity. At this time, the inflow of external low-temperature airflow, the efficient heat exchange with the heating components, and the discharge of the heat exchange airflow form a closed-loop self-circulation path with a matching rate. The motor enters a continuous and efficient active heat dissipation state, keeping the internal temperature within a safe operating range.

[0065] This three-stage gradient acceleration strategy essentially transforms "motor speed control" into "precise construction and dynamic regulation of the negative pressure field within the cavity." Through staged angular acceleration and pressure holding time design, the formation of negative pressure, the introduction of airflow, the replacement of air, and the heat exchange proceed sequentially and orderly, avoiding problems such as airflow impact, turbulence, and pressure fluctuations caused by sudden parameter changes at any stage. At the same time, through adaptive matching based on rated power, this strategy has versatility, ultimately achieving the smooth introduction of low-temperature airflow during the startup phase of various external brushless motors, as well as the stable and efficient operation of the self-circulating heat dissipation path during the working phase.

[0066] In one possible embodiment, in step S2 above, when the low-temperature airflow enters the semi-enclosed cavity 8 through the first airflow channel 9, it first forms a swirling flow through the channel opening guide surface 12 of the first airflow channel 9. The swirling flow diffuses bidirectionally along the axial and circumferential directions of the semi-enclosed cavity 8, allowing the low-temperature airflow to fully exchange heat with the inner wall of the casing 2, the stator windings, and the rotor magnets.

[0067] Specifically, the guide surface 12 of the first airflow channel 9 is a streamlined curved surface structure, replacing the traditional right-angle channel design. When the low-temperature airflow moves towards the channel under the negative pressure of the cavity, it does not rush in vertically in a straight line, but changes its trajectory under the constraint of the curved surface of the guide surface. The airflow is given a composite motion velocity in the axial direction (extension direction of motor shaft 1) + circumferential direction (circumferential direction of motor cavity), changing from the original straight flow to a spiral swirling shape.

[0068] This design utilizes the fluid's adhesion effect to allow airflow to smoothly enter the cavity along the guide surface. This avoids airflow impact and turbulence at the right-angle slot and enables controllable transformation of airflow motion through directional guidance, laying the flow foundation for subsequent efficient heat exchange.

[0069] After the swirling flow enters the semi-enclosed cavity 8, under the combined action of its own spiral motion inertia and the negative pressure field inside the cavity, it will extend and diffuse along the axial direction of the motor cavity (from the motor base 4 to the semi-enclosed housing cover 3), and at the same time, it will diffuse in a circular direction (around the motor axis 360°), forming a bidirectional flow coverage throughout the entire cavity.

[0070] Compared to the localized direct flow of airflow without a guide surface, the bidirectional diffusion swirling flow fills the entire internal space of the semi-enclosed cavity 8, achieving coverage of all areas of the cavity.

[0071] The inner wall of the motor housing 2, the stator windings, and the rotor magnets are the core heat-generating components that produce Joule heat and iron loss heat during operation, distributed in various axial and circumferential positions within the semi-enclosed cavity 8. The enhanced heat transfer effect of the bidirectional diffusion swirling flow on these heat-generating components is reflected in two key dimensions: The 360° circumferential diffusion of the swirling flow allows the low-temperature airflow to contact the entire circumferential surface of the stator winding and rotor magnets, while the axial diffusion covers the entire axial area of ​​the inner wall of the casing 2, eliminating the "heat exchange dead zone" caused by local direct blowing and allowing the low-temperature airflow to make full contact with the heat-generating components. The spiral swirling motion significantly increases the flow path of the airflow within the cavity. Compared to the rapid passage of a straight flow, the swirling motion within the cavity extends the contact time between the low-temperature airflow and the heating components, allowing for a more thorough convective heat transfer process and more efficient absorption of the heat generated by the motor.

[0072] The slot guide surface 12 transforms the straight airflow into a swirling flow through shape guidance. The swirling flow then achieves full space coverage of the cavity through bidirectional diffusion. Finally, by maximizing the contact area and extending the contact time, the low-temperature airflow and the core heat-generating components of the motor can complete sufficient convective heat exchange, thereby achieving efficient absorption and transfer of heat from the motor.

[0073] In one possible embodiment, in step S3 above, before the heat exchange airflow is discharged, it first forms a convergence and pressurization at the guide part 11 connected to the guide vane 7 and the second airflow channel 10, so that the heat exchange airflow is discharged from the second airflow channel 10 at a higher flow rate. The discharged airflow forms an air curtain outside the motor, blocking fine particles from approaching the second airflow channel 10.

[0074] Specifically, the guide section 11 between the guide vane 7 and the second airflow channel 10 is a streamlined directional guide structure, which is a dedicated transition channel for the heat exchange airflow to flow from the cavity to the discharge channel.

[0075] Driven by the pressure difference continuously generated by the guide vanes 7, the heat exchange airflow will diffuse towards the second airflow channel 10 on the side of the semi-enclosed casing cover 3. If it directly enters the discharge channel, the airflow will form turbulence due to the path dispersion, resulting in backflow and mutual collision, causing airflow energy loss and a significant reduction in flow velocity.

[0076] The guide section 11 uses its curved profile to plan a unified directional flow path for the dispersed heat exchange airflow, which gathers the heat exchange airflow in each region of the cavity into each guide section 11, so that the originally dispersed airflow can be superimposed to achieve the effect of convergence and pressurization.

[0077] The heat exchange airflow after confluence and pressurization is discharged from the second airflow channel 10 at a higher velocity. The key is to reduce the energy loss in the airflow discharge stage, so as to form a closed loop improvement in the airflow efficiency of the self-circulating heat dissipation path. The negative pressure generated by the rotation of the guide vanes 7 provides the initial power for the airflow, while the converging and pressurizing of the guide section 11 allows this power to be converted into the exhaust kinetic energy of the airflow more efficiently, avoiding the power waste caused by turbulence. The high-speed exhaust heat exchange airflow can quickly release the heat absorbed inside the motor to the outside, while keeping the negative pressure field inside the semi-enclosed cavity 8 stable, ensuring that the external low-temperature airflow can continuously and smoothly enter the cavity, making the self-circulating heat dissipation process of "low-temperature airflow into the cavity - heat exchange - hot airflow exhaust" more efficient, forming a closed loop with flow rate matching.

[0078] The heat exchange airflow discharged at high speed from the second airflow channel 10 forms a high-pressure air curtain that diffuses outward along the outlet of the channel outside the motor. This air curtain relies on the dynamic pressure barrier effect of the airflow to block fine particles, which is a secondary active protection after the semi-enclosed structure + physical interception of the channel diameter: Fine particles (less than 3 mm in diameter) in the motor's working environment move towards the inlet of the second airflow channel 10 with the ambient airflow, attempting to enter the motor through the channel. The high-speed airflow discharged from the channel outlet creates a high-pressure airflow area around the outlet. When suspended fine particles in the environment approach this area, they are pushed away by the dynamic pressure of the high-pressure air curtain and cannot overcome the pressure of the air curtain to move towards the channel inlet, thus being blocked outside the motor.

[0079] The guide section 11 allows the heat exchange airflow to be discharged at high speed through directional confluence, which not only improves the overall efficiency of self-circulating heat dissipation, but also uses the kinetic energy of high-speed exhaust to form a dynamic pressure air curtain outside the motor, realizing further synergy between heat dissipation function and foreign object prevention function, making the protection and heat dissipation performance of the semi-enclosed external rotating brushless motor better.

[0080] In one possible embodiment, when the internal temperature of the motor is detected to exceed a preset threshold, the flow rate of the cooling airflow is adjusted by changing the negative pressure value generated by the guide vanes 7 through adjusting the rotational speed of the outer rotor. The internal temperature detection points of the motor are set in the heat exchange core area between the stator winding and the rotor magnet. The detection data is fed back to the motor control module in real time. The motor control module adjusts the speed of the outer rotor in a closed loop according to the temperature change, so as to realize the adaptive dynamic control of the heat dissipation airflow.

[0081] Specifically, the temperature detection points are precisely set in the core heat exchange area between the stator winding and the rotor magnet. This area is the main area where Joule heat and iron loss heat are generated during motor operation. It is also the part with the highest internal temperature and the most core heat exchange in the motor. Its temperature data can accurately and directly reflect the actual heating state of the motor, avoiding the problems of temperature data distortion and control lag caused by the detection points deviating from the core area.

[0082] The detection module collects the temperature of the core area in real time, and the collected temperature data is fed back to the motor control module in the form of electrical signals in real time, forming a real-time transmission link for temperature data. This provides accurate and timely signal input for subsequent speed adjustment and airflow control, and is the foundation of the entire adaptive control system.

[0083] The core logic of this control method is to indirectly change the flow rate of the cooling airflow by adjusting the rotational speed of the external rotor. Its underlying principle relies on the linear positive correlation of three key parameters: The rotational speed of the outer rotor directly determines the rotational angular velocity of the guide vane 7. The higher the rotational speed of the outer rotor, the faster the guide vane 7 rotates, and the stronger the dynamic pressure airflow effect generated. The strength of the dynamic pressure effect of the guide vane 7 directly determines the magnitude of the negative pressure value inside the semi-enclosed cavity 8. The stronger the dynamic pressure effect, the greater the pressure difference between the cavity and the outside. The negative pressure difference inside the cavity is the core driving force for the external low-temperature airflow to enter the motor. The greater the pressure difference, the greater the flow rate of the low-temperature airflow entering the cavity through the first airflow channel 9 per unit time, and the faster the overall circulation rate of the heat dissipation airflow.

[0084] As the core of the entire control system, the motor control module continuously compares and analyzes the real-time collected core area temperature data with the preset temperature threshold, and adjusts the outer rotor speed in real time based on the comparison results. This ultimately forms a closed-loop control chain of "temperature detection → data feedback → speed adjustment → airflow change → temperature change → re-detection." The specific execution logic is as follows: When the motor is running under low load and the core area temperature is within the normal operating range, the outer rotor maintains the set base speed, the guide vanes 7 generate a stable base negative pressure, and the cooling airflow maintains the base flow rate to meet the cooling needs of the motor under low heat generation and avoid energy waste caused by excessive heat dissipation. When the motor load increases and the core area temperature rises and gradually approaches the preset threshold, the control module increases the speed of the outer rotor step by step according to the temperature rise rate and a preset rule. Through the above parameter correlation, the negative pressure value and heat dissipation airflow in the cavity are increased simultaneously to enhance the motor's heat dissipation capacity and quickly remove the excess heat generated by the motor. When the motor load decreases and the core area temperature gradually drops back to the normal range as heat dissipation increases, the control module then gradually reduces the speed of the outer rotor and adjusts the airflow of the cooling system back to the basic level, so that the heat dissipation capacity is rematched with the actual heat demand of the motor.

[0085] The entire control process is completed automatically and in real time by the control module without manual intervention. It achieves dynamic adaptive matching between the heat dissipation airflow and the motor's heating state: when the motor heats up, the heat dissipation is strong, and when the motor heats up less, the heat dissipation is weak. This ensures that the motor will never burn out or the magnets will demagnetize due to excessive temperature, while also avoiding the loss of motor kinetic energy caused by continuous high-speed heat dissipation, thus balancing heat dissipation reliability and operating economy.

[0086] In one possible embodiment, see [reference] Figure 6 The flowchart of closed-loop adjustment of external rotor speed shows that when adjusting the external rotor speed in a closed loop according to temperature changes, it includes two consecutively executed steps: temperature threshold grading and speed gradient adjustment. Among them, the temperature threshold classification is as follows: the preset temperature threshold of the heat exchange core area inside the motor is divided into three levels. The first level warning threshold is 70%~80% of the rated operating temperature of the motor, the second level regulation threshold is 81%~95% of the rated operating temperature of the motor, and the third level emergency threshold is 96%~105% of the rated operating temperature of the motor. The threshold ranges of each level do not overlap and are continuously connected. Speed ​​gradient adjustment: When the temperature reaches the first-level warning threshold, the outer rotor increases its speed by 5%~10% based on the original set speed, maintains this speed, and monitors temperature changes in real time; when the temperature reaches the second-level control threshold, the outer rotor increases its speed by another 10%~15% based on the speed corresponding to the first-level warning threshold, and simultaneously activates the airflow swirl intensity enhancement mode of the semi-enclosed cavity 8; when the temperature reaches the third-level emergency threshold, the outer rotor operates at a speed of 0.2~0.5 rad / s 2 The angular acceleration is increased to the maximum safe speed of the motor and maintained at that speed until the temperature drops below the second-level control threshold.

[0087] Specifically, the first-level warning threshold (70%~80% of rated operating temperature): This is a mild overheating risk range. The temperature of the core area of ​​the motor has exceeded the normal temperature under low load, but has not reached the rated operating temperature. There is no direct risk of failure. Only a slight increase in heat dissipation capacity is needed. It is an early warning node to prevent the temperature from continuing to rise and causing higher risks. Second-level control threshold (81%~95% of rated operating temperature): This is the medium-heat risk range. The temperature of the core area of ​​the motor is close to the rated operating temperature. If the temperature continues to rise, there will be risks such as demagnetization of the magnet and aging of the winding insulation layer. It is necessary to significantly enhance the heat dissipation capacity and cooperate with auxiliary heat dissipation methods. This is the core node of active temperature control. Level 3 emergency threshold (96%~105% of rated operating temperature): This is the high-risk range for severe overheating. The temperature of the core area of ​​the motor reaches or exceeds the rated operating temperature, and it has entered a critical state of failure. Serious problems such as motor burnout and stalling may occur at any time. It is necessary to maximize the heat dissipation capacity for emergency cooling, which is the last point to ensure the safety of the motor.

[0088] Speed ​​gradient adjustment is a step-by-step response action that corresponds one-to-one with temperature threshold levels. The core principle is "the higher the risk, the greater the heat dissipation control force". By gradually increasing the speed of the external rotor, the negative pressure value in the cavity is amplified, thereby continuously increasing the heat dissipation airflow. At the same time, in the medium and high risk range, the swirling intensity enhancement mode and the maximum safe speed are fully matched to achieve a step-by-step improvement in heat dissipation capacity. Real-time temperature monitoring is maintained after each adjustment to ensure the control effect and provide a basis for subsequent actions.

[0089] Swirl Enhancement Mode: The motor control module adjusts the rotational angular velocity of the outer rotor to generate periodic fluctuations of ±2% to ±5% based on the current speed. This drives the guide vanes 7 to form a pulsating dynamic pressure airflow, causing turbulent disturbances in the heat dissipation swirling flow within the cavity. This disturbance significantly improves the heat transfer coefficient between the low-temperature airflow and the cavity walls, stator windings, and rotor magnets, allowing for more thorough heat exchange with the same flow rate of low-temperature airflow. This achieves dual heat dissipation enhancement from two dimensions: "increasing airflow" and "improving heat exchange efficiency," matching the high heat dissipation requirements of the motor with moderate heat generation.

[0090] In one possible embodiment, the airflow swirl intensity enhancement mode is to adjust the rotational angular velocity fluctuation frequency of the outer rotor through the motor control module, so that the outer rotor generates a periodic angular velocity fluctuation of ±2%~±5% based on the rotational speed corresponding to the second-level control threshold, which drives the guide vanes 7 to form a pulsating dynamic pressure airflow, causing turbulent disturbance in the swirl within the semi-enclosed cavity 8, thereby increasing the heat transfer coefficient between the low-temperature airflow and the wall of the semi-enclosed cavity 8.

[0091] Specifically, the airflow swirl intensity enhancement mode is a heat exchange efficiency enhancement method designed for the second-stage temperature control threshold of a semi-enclosed external rotor brushless motor. The core is to generate turbulent disturbances in the heat dissipation swirl within the cavity by precisely and dynamically controlling the rotational angular velocity of the motor's external rotor, breaking the laminar boundary layer between the airflow and the heat exchange wall, thereby improving the heat transfer coefficient between the low-temperature airflow and the heat-generating components such as the semi-enclosed cavity wall, stator windings, and rotor magnets. Without simply increasing the airflow, it achieves a significant improvement in heat dissipation efficiency, adapting to the enhanced heat dissipation requirements when the motor is moderately heated.

[0092] The motor control module uses the external rotor speed corresponding to the second-level control threshold as the reference speed and performs dynamic frequency control on its rotational angular velocity, so that the angular velocity generates a periodic fluctuation of ±2% to ±5% around the reference value. This fluctuation is a controllable and regular dynamic adjustment, rather than an irregular change in speed.

[0093] The outer rotor is rigidly linked to the guide vanes 7 inside the semi-enclosed housing cover 3. The periodic fluctuation of the outer rotor's angular velocity will directly drive the guide vanes 7 to rotate synchronously in a periodic manner of "micro-acceleration-micro-deceleration". This will transform the dynamic pressure airflow generated by the guide vanes 7 from the original stable continuous dynamic pressure into a pulsating dynamic pressure airflow whose intensity fluctuates with the angular velocity, providing a power basis for the morphological changes of the swirling flow inside the cavity.

[0094] The heat dissipation airflow inside the semi-enclosed cavity 8 originally flows in a regular spiral swirling pattern under the drive of stable dynamic pressure. The airflow is prone to form a laminar boundary layer (a static airflow layer with extremely low flow velocity and poor heat exchange efficiency) between the cavity wall and the surface of the heat-generating component, which becomes an obstacle to heat transfer.

[0095] When the guide vanes 7 generate pulsating dynamic pressure airflow, this pulsating pressure continuously acts on the swirling flow within the cavity, disrupting its originally stable flow state and causing turbulent disturbances within the swirling flow: the flow direction and velocity of the airflow will exhibit controllable minor disturbances, and the spiral motion trajectory of the swirling flow will no longer be regular, forming a composite flow pattern of "main swirling flow + local micro-turbulence". This turbulent disturbance will directly impact and tear apart the laminar boundary layer, eliminating the heat transfer barrier between the airflow and the heat exchange wall.

[0096] The core factors affecting the heat transfer coefficient are the sufficiency of contact between the airflow and the heat transfer wall and the heat transfer rate. The presence of a laminar boundary layer significantly reduces the efficiency of heat transfer from the wall to the airflow, while turbulent disturbances improve the heat transfer coefficient through two dimensions: After tearing the laminar boundary layer, the low-temperature airflow can directly and fully contact the cavity wall and the surface of the motor heating components, eliminating the heat insulation effect of the "static airflow layer" and improving the contact efficiency of convective heat transfer. The local microturbulence of the swirling flow increases the relative motion intensity between the airflow and the heat exchange wall, accelerating the heat transfer rate from the wall to the airflow, allowing the same volume and flow rate of the low-temperature airflow to absorb more heat.

[0097] Ultimately, without significantly increasing the airflow rate, the heat transfer coefficient is improved, thereby enhancing the heat transfer capacity of the airflow per unit volume, enabling faster heat transfer within the motor, and achieving the goal of efficient heat dissipation under moderate heating conditions.

[0098] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A semi-enclosed outer-rotor brushless motor with self-circulating airflow cooling, characterized in that, It includes a motor shaft, a housing, a semi-enclosed housing cover, a motor base, fixing screws, bearings, and several guide vanes; the housing, the semi-enclosed housing cover, and the motor base are detachably connected by fixing screws to form a semi-enclosed cavity, the motor shaft passes through the semi-enclosed cavity, and one end of the motor shaft is rotatably connected to the motor base through a bearing, while the other end is fixedly connected to the semi-enclosed housing cover. Among them, several first airflow grooves are evenly opened on the outer side of the motor base, and the first airflow grooves are connected to the semi-enclosed cavity. Several guide vanes are set on the inner bottom wall of the semi-enclosed housing cover, and several second airflow channels are evenly opened on the side wall of the semi-enclosed housing cover. The second airflow channels are connected to the semi-enclosed cavity.

2. The semi-enclosed external-rotor brushless motor according to claim 1, characterized in that, The guide vanes are integrally formed on the inner bottom wall of the semi-enclosed housing cover and are evenly distributed along the circumference of the semi-enclosed housing cover. The guide vanes are connected to the second airflow channel via the guide section to guide the heat exchange airflow to be discharged quickly from the second airflow channel; The first airflow channel is equipped with a channel guide surface.

3. A method of operating a semi-enclosed external-rotor brushless electric machine with self-circulating airflow cooling according to claim 1 or 2, characterized in that, Includes the following steps: After the motor is powered on, the outer rotor starts to rotate. The guide vanes on the semi-enclosed casing rotate synchronously with the outer rotor. Under the dynamic pressure of the guide vanes, the low-temperature airflow outside the motor forms a directional tendency to flow towards the motor base. The low-temperature airflow enters the semi-enclosed cavity through the first airflow channel of the motor base, and forms a heat exchange airflow after sufficient heat exchange with the inner wall of the housing, the stator winding and the rotor magnet. Driven by the pressure difference continuously generated by the guide vanes, the heat exchange airflow is discharged from the second airflow channel of the semi-enclosed casing to the outside of the motor, completing a single self-circulation heat dissipation process, and achieving circulation heat dissipation as the outer rotor continues to rotate. During the motor's operating cycle, the diameters of the first and second airflow channels restrict large-diameter foreign objects from entering the motor while allowing normal airflow.

4. The method of operating of claim 3, wherein, In the initial stage, when the guide vanes rotate synchronously with the outer rotor, the outer rotor accelerates from zero speed to the set speed using a gradient acceleration strategy, causing the negative pressure value in the semi-enclosed cavity to increase in a gradient manner, thus achieving the smooth introduction of low-temperature airflow.

5. The operating method according to claim 4, characterized in that, When the outer rotor accelerates from zero speed to a set speed using a gradient acceleration strategy, it includes: The acceleration process is divided into three gradient stages. The first stage is the low-speed start-up stage, where the outer rotor accelerates from zero speed to the first rotational speed value with the first angular acceleration and maintains the rotational speed for the first time period, so that a basic negative pressure is formed in the semi-enclosed cavity and the initial replacement of the residual static air in the cavity is completed. The second stage is the medium-speed acceleration stage, in which the outer rotor accelerates from the first speed value to the second speed value with the second angular acceleration, and maintains the speed for a second time period, so that the negative pressure value in the semi-enclosed cavity increases linearly, thereby achieving stable introduction of low-temperature airflow and initial heat exchange with the internal components of the motor. The third stage is the high-speed constant speed stage. The outer rotor accelerates from the second speed value to the set speed value with the third angular acceleration. After the acceleration is completed, it maintains the set speed and runs stably, so that a working negative pressure is formed in the semi-enclosed cavity, and the cooling airflow is used for self-circulation cooling.

6. The operating method according to claim 3, characterized in that, Also includes: When the low-temperature airflow enters the semi-enclosed cavity through the first airflow channel, it first forms a swirling flow through the guide surface at the opening of the first airflow channel; The swirling flow diffuses bidirectionally along the axial and circumferential directions of the semi-enclosed cavity, allowing the low-temperature airflow to fully exchange heat with the inner wall of the casing, the stator windings, and the rotor magnets.

7. The operating method according to claim 3, characterized in that, Also includes: Before the heat exchange airflow is discharged, it first forms a convergence and pressurization at the guide section where the guide vanes connect with the second airflow channel, so that the heat exchange airflow is discharged from the second airflow channel at a higher flow rate. The discharged airflow forms an air curtain outside the motor, blocking fine particles from approaching the second airflow channel.

8. The operating method according to claim 6, characterized in that, Also includes: When the internal temperature of the motor is detected to exceed the preset threshold, the negative pressure value generated by the guide vanes is changed by adjusting the rotation speed of the outer rotor. The internal temperature detection points of the motor are set in the heat exchange core area between the stator winding and the rotor magnet. The detection data is fed back to the motor control module in real time. The motor control module adjusts the speed of the outer rotor in a closed loop according to the temperature change, so as to realize the adaptive dynamic control of the heat dissipation airflow.

9. The operating method according to claim 8, characterized in that, When adjusting the external rotor speed in a closed-loop manner based on temperature changes, the following is included: The preset temperature threshold of the heat exchange core area inside the motor is divided into three levels, including the first level warning threshold, the second level control threshold and the third level emergency threshold. The threshold intervals of each level do not overlap and are continuously connected. When the temperature reaches the first-level warning threshold, the outer rotor increases its speed by a first percentage from the original set speed, maintains this speed, and monitors temperature changes in real time. When the temperature reaches the second-level control threshold, the outer rotor increases its speed by a second percentage from the speed corresponding to the first-level warning threshold, and at the same time, the airflow swirl intensity enhancement mode of the semi-enclosed cavity is activated. When the temperature reaches the third-level emergency threshold, the outer rotor accelerates to the maximum safe speed of the motor with a fourth-angle acceleration and maintains this speed until the temperature drops below the second-level control threshold.

10. The operating method according to claim 9, characterized in that, The enhanced airflow swirl intensity mode adjusts the rotational angular velocity fluctuation frequency of the outer rotor through the motor control module, so that the outer rotor generates periodic angular velocity fluctuations based on the rotational speed corresponding to the second-level control threshold, which drives the guide vanes to form a pulsating dynamic pressure airflow, causing turbulent disturbances in the swirling flow within the semi-enclosed cavity, thereby improving the heat transfer coefficient between the low-temperature airflow and the semi-enclosed cavity wall.

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