Hollow static shaft centrifugal air-cooled axial flux motor

Abstract

The application discloses a hollow static shaft centrifugal air-cooled axial flux motor, which comprises a stator assembly (100), a rotor assembly (200), a hollow static shaft (300) and a sensor integrated module (400). The hollow static shaft is a multi-layer nested structure, an outer layer chamber (340) is formed between an outer tube (310) and an inner tube (320), and a hollow chamber (350) is formed inside the inner tube. The outer layer chamber is circumferentially separated into independent air ducts and wiring channels. The stator assembly is fixedly connected with the static shaft through a connecting ring (146), the end surface of the connecting ring is provided with a retreat space, and an encoder read head chip (147) is installed on the retreat space. A gas stirring structure (222) protruding towards the shaft center is arranged on the inner wall of a rotor connecting ring (220), and air outlet holes (224) are formed on the outer wall of the rotor connecting ring (220). When the rotor rotates, external cold air enters through the air duct, flows through the stator-rotor air gap, and is discharged from the air outlet holes under the action of centrifugal force, so that self-driven cooling is formed. The sensor integrated module is arranged in the central chamber and is integrated with a main control unit, an attitude sensor and a communication interface. The application realizes high power density, high-efficiency self-heat dissipation and deep integration of sensors in an ultrathin axial space.

Description

Technical Field

[0001] This invention relates to the field of motor technology, specifically to an axial flux motor, and more particularly to a hollow stationary shaft centrifugal air-cooled axial flux motor suitable for the power system of a coaxial multi-rotor UAV. Background Technology

[0002] 2.1 Applications and Challenges of Axial Flux Motors in Coaxial Aircraft Axial flux motors (also known as disc motors) have higher torque and power densities in the same volume compared to traditional radial flux motors because their magnetic field is distributed along the axial direction. This characteristic makes them an ideal choice for the propulsion system of coaxial dual-rotor UAVs, which are extremely sensitive to space and weight. Their flattened structural shape also facilitates layout integration in compact aircraft shaft systems.

[0003] However, the widespread application of axial flux motors in coaxial dual-rotor UAVs still faces significant technical obstacles: The primary obstacle lies in heat dissipation. Its compact "sandwich" structure (i.e., the stator assembly is sandwiched between two rotor assemblies) makes it difficult to effectively dissipate the heat generated by the windings. Due to the limitations of the drone's payload and space, it is difficult to deploy a liquid cooling system. When relying on air cooling, under continuous high-power output conditions, the motor temperature rise is prone to exceed the limit, which can lead to magnet demagnetization and insulation aging, seriously threatening flight safety and system reliability. Existing air-cooling solutions mostly rely on external fans or natural convection, failing to fully utilize the centrifugal force generated by the high-speed rotation of the rotor to build an efficient, self-sustaining internal forced air-cooling cycle.

[0004] Secondly, the sensors have low integration and encroach on axial space. In traditional solutions, rotor position detection components such as encoders and Hall sensors are usually mounted on the motor shaft or externally; while the attitude sensor (IMU) required for flight control is mounted as a separate module in the fuselage. This discrete layout not only increases the overall size of the system, but also makes it difficult to meet the design requirements of ultra-thin motors with strict limitations on axial thickness (such as 30mm).

[0005] Furthermore, hollow shafts have limited functionality. Although some solutions employ hollow shaft structures, they are mostly limited to accommodating wiring harnesses or serving as coolant channels, failing to utilize them as a multifunctional integrated platform to house and shield sensitive sensors and signal processing circuits, thus failing to achieve structural and functional integration.

[0006] 2.2 System Architecture Bottlenecks from Coaxial Dual Rotors to Coaxial Multi-Rotors In existing technologies, whether it is a traditional mechanical coaxial dual-rotor system or an electric coaxial system using a tail-to-tail motor direct drive, the core feature is that the two rotors share the same axis of rotation.

[0007] When this configuration needs to be expanded to more rotor systems such as coaxial quadcopters and coaxial hexacopters, significant axial stacking and expansion bottlenecks arise. Specifically, increasing the number of rotors requires either a complex, highly difficult-to-manufacture multi-axis nested mechanical system, or, even with multiple independent "tail-to-tail" motor units, the central axis of each unit is a rotating component, making it impossible to simply connect and fix them with a single fixed central rod. This means that expanding the power system inevitably leads to a sharp increase in the overall structure, weight distribution, and control complexity, making rapid modular expansion difficult.

[0008] Therefore, the industry urgently needs a brand-new motor architecture that not only has the aforementioned high power density and efficient heat dissipation capabilities, but also axial modular expansion capabilities, so that multiple power units can be easily connected in series along the same axis, thereby constructing a flexible and variable power system skeleton. Summary of the Invention

[0009] 3.1 Purpose of the Invention To address the problems existing in the prior art, this invention provides a hollow stationary shaft centrifugal air-cooled axial flux motor suitable for coaxial multi-rotor UAV power systems. Its purpose is: 1. By integrating the position detection element, attitude sensor and signal processing circuit inside the hollow stationary shaft, the motor sensing system is deeply integrated, thereby reducing the axial dimension of the motor and improving the system's anti-electromagnetic interference capability. 2. By utilizing the rotation of the rotor assembly, an efficient self-driven centrifugal air-cooling circulation path is constructed inside the motor to achieve efficient heat dissipation; 3. A motor architecture with a fixed central shaft is provided, which facilitates the connection of multiple power units in series through the central shaft to meet the application requirements of complex configurations such as coaxial multi-rotor.

[0010] 3.2 Technical Solution To achieve the above objectives, the present invention provides the following technical solution: An axial flux motor includes a stator assembly, a rotor assembly, a hollow stationary shaft, and a sensor integration module.

[0011] 3.2.1 Overall Architecture and Electromagnetic Scheme The motor adopts a single stator and dual rotor structure, with the stator assembly disposed between the dual rotors to form an axial magnetic field air gap.

[0012] Preferably, the stator assembly adopts a yokeless segmented armature (YASA) structure, consisting of multiple independent stator tooth units distributed along the circumference. The dual rotor assembly is axially opposed to the stator assembly and is respectively fixed to a rotor connecting ring to form a whole.

[0013] Preferably, the stator tooth unit is made of amorphous alloy material or ultra-thin silicon steel sheet laminated together to reduce high-frequency iron loss.

[0014] Preferably, the stator tooth unit is installed in the pole shoe, which is made of aluminum alloy or engineering plastic. The pole shoe is annular groove shaped, with a hollow internal area for accommodating the stator tooth unit and an outer annular groove area serving as a winding skeleton. The winding wire is wound in the outer annular groove of the pole shoe, and its axial height is limited between the two side plates of the annular groove.

[0015] Preferably, the phase wire of the winding is a single flat copper wire or a multi-strand twisted Litz wire, wound on the pole shoe in a flat and upright manner, and its axial thickness is limited between the upper and lower wheel plates of the pole shoe to prevent the winding from exceeding the limit and interfering with the rotor assembly.

[0016] The hollow stationary shaft passes through the stator assembly and the rotor assembly along the central axis of the motor.

[0017] 3.2.2 Integrated mounting structure of stator assembly The hollow stationary shaft is fixedly connected to the stator assembly via at least one connecting ring.

[0018] A recessed space is formed axially between the connecting ring and the end face of the stator assembly. A read head circuit board is disposed within the recessed space, and a read head chip with a position detection element is mounted on the read head circuit board.

[0019] The recessed space is provided with a wire-passing hole near the outer wall of the hollow stationary shaft, and the signal line of the read head chip enters the wiring channel inside the hollow stationary shaft through the wire-passing hole.

[0020] 3.2.3 Rotor assembly and centrifugal air-cooled structure The rotor assembly is characterized in that it includes a first rotor and a second rotor located on opposite axial sides of the stator assembly, and a rotor connecting ring. The first rotor and the second rotor are respectively fixed to the axial ends of the rotor connecting ring.

[0021] The inner wall of the rotor connecting ring is provided with an air-guiding structure protruding towards the axis; the outer wall of the rotor connecting ring is provided with multiple air outlet holes.

[0022] Preferably, the axis of the air outlet is inclined at an acute angle of 30° to 45° to the rotation direction of the rotor connecting ring, and the inclination direction is opposite to the rotation direction; the opening of the air outlet on the inner wall of the rotor connecting ring faces the rotation direction to form a scoop-shaped air inlet for drawing in hot air from inside the motor.

[0023] When the rotor assembly rotates, the air-dispersing structure agitates the air inside the motor to form an airflow. External cooling air enters from the air duct of the hollow stationary shaft and flows through the radial air gap between the stator assembly and the rotor assembly. Under the action of centrifugal force, the air carrying heat is finally thrown out from the air outlet on the rotor connecting ring, forming a self-driven cooling cycle.

[0024] 3.2.4 Multifunctional Layered Structure of Hollow Stationary Shaft Its characteristic is that the hollow static shaft has a multi-layer nested structure, including at least one outer tube and one inner tube.

[0025] An outer cavity is formed between the outer tube and the inner tube; a hollow cavity is formed inside the inner tube.

[0026] The outer chamber is divided into multiple independent channels along the circumference, including air ducts for circulating cooling gas and wiring channels for laying wire harnesses.

[0027] The hollow cavity is used to house the sensor integration module.

[0028] The outer tube has ventilation holes on its wall that connect the air duct to the inside of the stator assembly, allowing cooling gas to flow into the motor from the air duct.

[0029] 3.2.5 Sensor Integration Module (Capsule) Its characteristic is that the sensor integration module is disposed in the hollow cavity of the hollow static shaft.

[0030] The sensor integration module includes a core circuit board assembly, on which the following are integrated: The main control unit (MCU) is used to process signals; An attitude sensor (IMU) is used to detect the attitude of a motor. Communication interfaces (such as CAN FD transceivers) are used to communicate with external controllers.

[0031] The sensor integration module is connected to the read head chip of the position detection element via a signal line to obtain the motor rotor position information and to interact with external devices through the communication interface.

[0032] Preferably, the core circuit board assembly adopts a cross-shaped vertical structure, that is, two circuit boards are vertically spliced ​​together in a cross shape to enhance the structural rigidity of the module and improve space utilization.

[0033] 3.3 Beneficial Effects Compared with existing technologies, the present invention has the following significant advantages: 3.3.1 Extreme thinness: By installing the read head chip in the recessed space between the stator and the stationary shaft, and integrating the main control, IMU and other core circuits into the central cavity of the stationary shaft, the thickness of the motor is greatly reduced and the power density is significantly improved.

[0034] 3.3.2 High-efficiency self-driven heat dissipation: Utilizing the combined effect of the air-guiding structure on the rotor connecting ring and the inclined air outlet, a forced air-cooling cycle can be constructed solely by the centrifugal force generated by the rotation of the motor itself, without the need for an additional power source. This effectively reduces the temperature rise of the motor and ensures the ability to continuously output high power.

[0035] 3.3.3 Excellent anti-interference capability and reliability: The sensitive sensors and signal processing circuits are placed in the hollow cavity of the metal stationary shaft, using the stationary shaft itself as an electromagnetic shield to effectively isolate external electromagnetic interference. At the same time, the cross-shaped vertical circuit board structure enhances the rigidity of the module itself and improves its vibration resistance.

[0036] 3.3.4 Excellent system scalability: Due to the use of a hollow static shaft as a fixed support, multiple motor units of this invention can be connected in series through a central rod, providing a modular expansion solution for building complex power systems such as coaxial multi-rotor rotors.

[0037] 3.3.5 Excellent versatility: The motor has an axially symmetrical structure with consistent upper and lower surface structures; when the motor is installed in the forward direction, the output rotates in the forward direction, and when the motor is installed in the reverse direction (upside down), the output rotates in the reverse direction. No modifications are required to the motor body, which enhances the motor's universal adaptability to different rotor rotation requirements. Attached Figure Description

[0038] The embodiments of the present invention will now be described with reference to the accompanying drawings. It should be noted that the accompanying drawings are for illustrative purposes only, and the proportional relationships between the components are not limited to actual manufacturing. Due to the complex internal structure of the motor, with numerous nested and overlapping parts, some parts are drawn in color to clearly distinguish each layer of structure and its boundaries.

[0039] Figure 1 This is a three-dimensional schematic diagram of the decomposed state of each part of the stator assembly described in this invention.

[0040] Figure 2 for Figure 1 The diagram shows a three-dimensional representation of the stator assembly in its fully assembled state.

[0041] Figure 3 for Figure 2 Top view of the stator assembly shown.

[0042] Figure 4 for Figure 3 The sectional view along direction 1-1 is shown.

[0043] Figure 5 This is a three-dimensional schematic diagram of the exploded state of each component of the rotor assembly described in this invention.

[0044] Figure 6 for Figure 5 The diagram shows a three-dimensional view of the rotor assembly process before the upper rotor disk is lowered (sealed).

[0045] Figure 7 for Figure 6 A top view of the rotor disk in the indicated state (excluding the upper rotor disk).

[0046] Figure 8 This is a three-dimensional schematic diagram of the hollow static shaft described in this invention.

[0047] Figure 9 for Figure 8 The cross-sectional view of the hollow stationary axis along the ventilation hole is shown.

[0048] Figure 10 for Figure 8 The diagram shows a longitudinal section exploded three-dimensional schematic of the hollow stationary shaft.

[0049] Figure 11 This is a three-dimensional schematic diagram of the disassembled state of each component of the sensor integration module described in this invention.

[0050] Figure 12 for Figure 11 The diagram shows a three-dimensional representation of the sensor integration module after assembly.

[0051] Figure 13 for Figure 12 The sensor integration module shown is a cross-sectional view along the wire hole.

[0052] Figure 14 This is a three-dimensional schematic diagram showing the disassembled state of each component of the axial flux motor assembly described in this invention.

[0053] Figure 15 for Figure 14 A three-dimensional schematic diagram of the state of the upper rotor disk before it is lowered (sealed) during the assembly process.

[0054] Figure 16 for Figure 14 The diagram shows a three-dimensional representation of the final assembly status.

[0055] Figure 17 for Figure 16 The side view shows the final assembly state.

[0056] Figure 18 for Figure 16 The motor shown is a cross-sectional view along the exhaust port.

[0057] Figure 19 To be according to Figure 18 The sectional view along the cutting direction shown in Figure 1-1.

[0058] Figure 20 To be according to Figure 18 The sectional view along the cutting direction shown in Figure 2-2.

[0059] Figure 21 To be according to Figure 18 The sectional view along the cutting direction shown in Figure 3-3.

[0060] Figure 22 for Figure 16 The diagram shows a longitudinal section exploded three-dimensional schematic diagram of the motor.

[0061] Figure 23 This is an exploded three-dimensional schematic diagram of the assembly process of the motor and sensor integrated module and the end fixing component described in this invention.

[0062] Figure 24 for Figure 23 The diagram shows a three-dimensional representation of the assembled state.

[0063] Figure 25 for Figure 24 according to Figure 18 The sectional view shown in section 3-3 illustrates the installation state of the capsule in the hollow chamber of the stationary axis, as well as the correspondence between the capsule's threading hole and the pre-reserved threading hole in the hollow chamber.

[0064] Figure 26 This is a cross-sectional view of a hollow stationary shaft with a cross-sectional cavity classification of C5 at the location of the exhaust port.

[0065] Figure 27 This is a cross-sectional schematic diagram of various separation methods between the hollow static shaft outer layer chamber and the hollow chamber described in this invention (including the C5 type classification).

[0066] The meanings of the labels in the attached diagram are as follows: 1000-Hollow stationary shaft centrifugal air-cooled axial flux motor; 100-Stator assembly; 110 - Stator core assembly; 120-Extreme Boot Assembly; 130 - Winding assembly; 140 - Stator support assembly; 141 - Stator support body; 142 - Winding pit; 143 - Phase wire connection ring groove; 144 - Wiring hole between the connection groove and the stationary shaft routing channel; 145 - Notch between the root of the winding pit and the connection groove; 146 - Stator inner hole and stationary shaft connection fixing ring (recessed); 147 - Encoder reader head; 148 - Phase wire in the connection groove; 200-Rotor assembly; 210 - Rotor disc (including upper and lower rotor discs); 211 - Rotor disc body; 212 - Rotor disc center hole; 213 - Permanent magnet inlay pit; 214 - Encoder magnetic ring groove; 215 - Bearing mounting step; 216 - Rotor disc tie bolt hole; 217 - Rotor mounting screw hole; 220 - Rotor connecting ring; 221 - Rotor connecting ring body; 222 - Air deflector rib; 223 - Rotor connecting ring tie bolt hole; 224 - Rotor connecting ring exhaust hole; 225 - Guide groove; 230 - Magnetic pole (permanent magnet); 231 - N-pole facing stator; 232 - S-pole facing stator; 240 - Encoder magnetic ring; 300 - Hollow stationary shaft; 300c5 - Hollow stationary shaft with a cross-sectional cavity classification of c5; 310 - Static axis outer tube; 311 - Outer tube pre-drilled hole (ventilation / wiring); 320 - Static shaft inner tube; 320c5 - Static shaft inner tube with a cross-sectional cavity classification of c5; 321 - Inner tube with reserved thread hole; 322 - Internal thread on the end of the inner tube; 330 - Outer chamber partition rib; 340 - Outer chamber; 340c5 - Outer chamber with cross-sectional area classified as c5; 350 - Hollow cavity; 350c5 - Hollow cavity with a cross-sectional cavity classification of c5; 400-Sensor Integrated Module; 410 - Capsule body; 411 - Capsule body outer shell; 412 - Capsule top cover; 413 - Pre-drilled wire hole in the capsule body; 414 - Vertical rib of the fixing groove; 420 - Cross-shaped PCB board; 421 - Cross-shaped PCB substrate; 422 - Electronic components; 430 - Vibration damping rubber sleeve; 500-Bearing; 600-Stationary shaft external circlip; 700 - Internal retaining ring in the cavity; 800-Stationary shaft end fixing assembly; 2000 - Hollow static shaft centrifugal air-cooled axial flux motor equipped with sensor integration module and end fixing component; JQ - Air Inlet; PQ - Exhaust port. Detailed Implementation

[0067] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples. The following description is exemplary and not restrictive; modifications and variations can be made by those skilled in the art within the spirit of the present invention.

[0068] 5.1 Example 1 A hollow static shaft centrifugal air-cooled axial flux motor (1000).

[0069] In this embodiment, the axial flux motor (1000) has an outer diameter of 130mm and a total axial thickness of 33.4mm. It adopts a single stator and dual rotor configuration and has a continuous output power greater than 8.2kW. The motor adopts a hollow stationary shaft structure. External cooling air enters the motor through the stationary shaft air duct, flows through two radial air gaps, and is thrown out from the air outlet of the rotor connecting ring under the action of rotor centrifugal force, forming a self-driven air-cooling cycle.

[0070] 5.1.1 Overall Electromagnetic Architecture The overall electromagnetic architecture of this embodiment is as follows: The motor adopts a single stator and dual rotor configuration, with the rotor enveloping the stator. It features a yokeless axial flux structure to maximize torque density. It has 10 pole pairs (20 poles), suitable for speeds up to 10,000 RPM, at which point the electrical frequency is approximately 1667 Hz, which can be covered by conventional FOC electronic speed controllers. It has 18 slots, forming a fractional-slot concentrated winding with the 20 poles. The winding factor is 0.945, resulting in extremely low torque ripple.

[0071] The stator support (140) has an outer diameter of 119 mm and a radial clearance of 5.5 mm for the rotor housing and gap. The stator inner hole has a diameter of 33 mm (for the hollow stationary shaft to pass through); the stationary shaft (300) has an outer diameter of 26 mm. Two connecting and fixing rings (146) are provided between the stator inner hole and the stationary shaft. The rings are 3.5 mm wide and 4 mm thick, and are 3 mm away from the upper and lower end faces of the stator disk, respectively, forming a recessed space for installing the encoder read head chip (147) and a wiring channel (340) for the phase line and signal line to pass through to the stationary shaft.

[0072] Stator core (110): The material is 0.1mm thick amorphous alloy strip (Metglas 2605SA1) or ultra-thin silicon steel, with low iron loss at high frequency. At 1.6kHz, the iron loss is about 1 / 5 of that of ordinary 0.35mm silicon steel. Magnets (230) are N52H sector-shaped sintered NdFeB, 20 pieces per rotor, embedded installation, H-class temperature resistance 120℃, residual magnetic flux density 1.35T.

[0073] Winding (130): 18 single coils, fractional slot concentrated winding; using a single flat copper wire (2mm wide, 0.5mm thick), with the wide side facing up (parallel to the axial direction) and the narrow side close to the iron core, wound on the pole shoe.

[0074] Pole shoe (120): The stator core is connected inside the pole shoe and placed in the shoe hole to prevent silicon steel sheets from falling out; the winding is connected to the outside, which is equivalent to a wire wheel. The copper wire of the winding is wound on it. The thickness of the wheel plate at both ends is 0.5mm. The net height of the winding area is 19mm, which limits the winding coil within this 19mm range to prevent it from going out of bounds and contacting the rotor.

[0075] 5.1.2 Stator Manufacturing Process The stator manufacturing process of this embodiment is as follows: The stator adopts a yokeless structure - without back iron ring, consisting only of 18 independent teeth and coils (including pole shoes) wound on them, and is installed in the pits (142) on the stator bracket (140) corresponding to the 18 winding assemblies; the stator bracket is made of 7075 aluminum alloy by integral carving or 3D printing, and the gaps are sealed and fixed with high-strength epoxy resin after assembly.

[0076] The tooth material is 0.1mm amorphous ribbon, laser-cut into seed-shaped tooth pieces (12.8mm widest tooth body, slightly wider tip, 35mm long), with each tooth stacked 20mm thick (approximately 200 pieces). All tooth pieces are stamped in the same mold to ensure dimensional consistency.

[0077] The winding uses a single flat copper wire (2mm wide and 0.5mm thick). After 18 teeth are assembled, a complete disc shape is formed, and the thickness is controlled at 19.0±0.05mm. This is the basis for ensuring magnetic circuit symmetry and air gaps for dual rotors.

[0078] The pole shoe (120) is annular groove-shaped, and its hollow interior area is used to accommodate the stator core (i.e., the shoe hole) to prevent the silicon steel sheets from falling out; its outer annular groove is used as a winding skeleton (winding wheel), and the winding copper wire is wound in the annular groove.

[0079] The stator support (140) has an outer diameter of 119 mm and 18 pits (142) are evenly distributed around the circumference. Each pit has a notch (145) at its root (near the stationary shaft) for winding wiring. Near the stationary shaft, there is a phase wire connection ring groove (143) with a width of 2 mm and a depth of 2.5 mm for connecting the 18 winding phase wires.

[0080] Two connecting and fixing rings (146) with a width of 3.5 mm and a thickness of 4 mm are provided between the inner diameter of the stator (100) (33 mm) and the outer diameter of the stationary shaft (26 mm); the upper and lower connecting rings form a 3 mm high step with the upper and lower end faces of the stator.

[0081] 5.1.3 Rotor and Magnet The rotor and magnet structure of this embodiment are as follows: the two rotors are completely identical, one of each. The overall structure adopts a "5.5mm inlaid" structure, and the rotor disk body (211) is made of 7075 aluminum alloy.

[0082] The lower rotor assembly is 5.5mm thick: the back aluminum blank is 5.5mm thick, the magnet slot is 2.5mm deep, the effective base plate is 3.0mm thick, and the magnet is 2.5mm thick. The 2.5mm thick magnet is embedded into the slot and is completely flush with the back aluminum surface, forming a solid 5.5mm thick unit.

[0083] Lower radial air gap (mechanical clearance): 1.2mm thick. The stator winding end protrusion is reduced to within 0.5mm of the pulley plate, with no additional protrusion, ensuring a pure air gap of 1.2mm.

[0084] Stator assembly thickness 20.0mm: core stack thickness 20.0mm, winding height 19mm, gaps are completely sealed and fixed with epoxy resin.

[0085] The upper radial air gap has a thickness of 1.2 mm and is completely symmetrical with the lower side.

[0086] Upper rotor assembly: 5.5mm thick, completely symmetrical with the lower rotor.

[0087] Total thickness of the motor body: 5.5 + 1.2 + 20.0 + 1.2 + 5.5 = 33.4mm.

[0088] Rotor connecting ring (220) (material 7075-T6): Two rotors are connected as one unit by a 7075-T6 aluminum alloy connecting ring, forming a double rotor cage. The connecting ring has an outer diameter of 130mm, an inner diameter of 123mm, and a wall thickness of 3.5mm. A 2mm gap is formed between the inner wall of the connecting ring and the outer wall of the stator. M2 threaded holes with a distribution circle diameter of 125mm are directly machined on the outer surface of the connecting ring for mounting the rotor blades.

[0089] At the points where the 10 tie bolts pass through, a 1.5mm thick protective wall is provided, resembling a half-column (1.5mm radius) protruding into a 2mm wide gap, with a 0.5mm gap remaining at this point. That is, the inner wall of the connecting ring forms a "half-column" protruding structure at the 10 bolt points, and this protruding structure constitutes the air-dispersing rib (222), used to agitate the flow of hot air.

[0090] The outer surface of the connecting ring is provided with five rows of horizontal annular guide grooves (225), each 0.5 mm deep, with air outlets (224) evenly distributed along the circumference within the grooves. The axis of the air outlets is inclined at 45° in the opposite direction of rotation; the air inlet openings on the inner surface of the connecting ring face the direction of rotation and are shaped like a sieve to facilitate the entrainment of heat-absorbing gas. The air-guiding ribs and the inclined air outlets work together to throw the hot gas out of the air outlets under centrifugal force.

[0091] Encoder magnetic ring slot (214): Located on the inner edge of the rotor disk near the stationary shaft, the slot has an outer diameter of 38.5 mm, an inner diameter of 32.5 mm, and a depth of 1.5 mm. An axially magnetized multi-pole magnetic ring (16 poles) is embedded in the slot, with a thickness of 1.5 mm and a radial width of 3 mm.

[0092] 5.1.4 Hollow stationary shaft (300) The static shaft has an outer diameter of 26mm and adopts a two-layer nested circular tube structure: the outer tube (310) has a wall thickness of 1.5mm, and the inner tube (320) has an outer diameter of 15mm, an inner diameter of 13mm, and a wall thickness of 1mm. The material is titanium alloy.

[0093] The hollow chamber (350) has a net diameter of 13 mm and is used to accommodate the sensor integration module (capsule) (400).

[0094] The outer chamber (340) has a ring thickness of 4mm and is divided into 8 equal independent channels along the circumference, which are used as air ducts and wiring channels respectively. High-voltage wires such as phase wires and low-voltage wires such as signal wires are routed in different channels.

[0095] The outer tube wall has a 2mm diameter pre-drilled hole (311) in the radial air gap (1.2mm thick) between the upper and lower layers inside the corresponding motor, initially one per chamber, for a total of 8 holes. The inner tube wall has a 1mm diameter pre-drilled wire hole (321) for connecting the signal line between the hollow chamber and the sensor capsule. All holes are sealed after wiring is completed to prevent hot air backflow.

[0096] 5.1.5 Integrated ESC and Overall Thickness Implementation The electronic speed controller is located outside the motor and does not occupy the axial thickness of the motor body.

[0097] 5.1.6 Wiring The coils on each iron core are connected in strict accordance with the 18-slot, 20-pole fractional-slot winding pattern (A, -A, A, B, -B, B, C, -C, C...), and finally three phase lines are led out, passing through the hollow stationary shaft and connecting to the external electronic speed controller.

[0098] Signal routing path: Encoder read head chip → along the stator and stationary shaft connection ring step → enter the stationary shaft ring routing area → together with the IMU harness, pass through the low voltage channel and exit the stationary shaft to connect to the flight controller; the motor phase wires pass through the high voltage channel and exit the stationary shaft.

[0099] 5.1.7 Bearing (500) and Rotor Support The hollow stationary shaft is fitted with a pair of ultra-thin angular contact ball bearings (500), with an inner diameter of 26mm, an outer diameter of 33mm, and a thickness of 3.5mm. The outer ring of the bearing is installed in the bearing housing reserved in the rotor disc, and the inner ring of the bearing is fitted onto the hollow stationary shaft and axially limited by a snap ring (600). The bearing assembly is completely recessed into the rotor, without increasing the axial thickness of the motor.

[0100] 5.1.8 Sensor Integration Module In this embodiment, the sensor integration module adopts a three-layer distributed architecture, which decouples the magnetic ring, the read head chip and the signal conditioning unit from the mechanical structure and installs them in the optimal positions.

[0101] First layer: Rotor end magnetic ring The encoder magnetic ring (240) is installed in an annular groove (214) near the central shaft hole on the inner side of the upper and lower rotor discs (210). The groove has a radial width of 3.0 mm and a depth of 1.5 mm. The magnetic ring has a thickness of 1.5 mm and a radial width of 3.0 mm, and is flush with the surface of the rotor disc after being embedded. The magnetic ring is axially magnetized, with 16 pairs of N / S poles alternately distributed on the end face. The groove is machined and clamped with the bearing mounting seat in one go to ensure concentricity and total runout not exceeding 0.02 mm.

[0102] Second layer: Stator end reader chip The encoder readhead chip (147) is installed in the recessed space formed by the connecting fixing ring (146) between the stator assembly and the hollow stationary shaft. The recessed space has an axial height of 3 mm and a radial width of 3 mm. The readhead chip is mounted on a miniature PCB and fixed in this recessed space. The readhead chip is a giant magnetoresistive (GMR) or Hall effect magnetic encoder chip, with its sensing surface facing the rotor end magnetic ring. The two miniature PCBs are connected by ultra-fine pin headers and FPC flexible flat cables. The flexible flat cables run along the stator disk surface and enter the wiring channel of the hollow stationary shaft through the wiring holes in the recessed space.

[0103] Third layer: Static axis internal signal conditioning capsule The sensor integration module (capsule) (400) is installed in the hollow chamber (350) of the hollow stationary shaft (300), which has a diameter of 13 mm. The capsule is cylindrical with a diameter of less than 13 mm and a length of about 40 mm.

[0104] The capsule employs a cross-shaped vertical PCB structure, consisting of two PCBs vertically joined at a cross intersection. Board A is the digital / bus board, integrating the main control MCU (using an STM32G431 or equivalent chip) and a CAN FD transceiver (using a TCAN4550 or equivalent chip). Board B is the analog / sensor board, integrating the attitude sensor IMU (using an ICM-42688-P or equivalent chip) and a 3.3V low-dropout linear regulator (LDO), with vibration damping grooves in the IMU chip area. Board A has power and CAN bus interface pads for connection to an external flight controller at the top, and connects to Board B at the bottom via an SPI bus. Board B has two encoder SPI signal input pads at the bottom, connected to the reader chip at the stator end.

[0105] The MCU reads two encoder signals and IMU data via the SPI bus, merges them, and outputs them in a package via a CAN FD transceiver. The flight controller only needs one pair of twisted-pair cables (CAN_H, CAN_L) and one pair of power lines to communicate with the capsule. The capsule's cross-shaped structure enhances module rigidity, and its first-order resonant frequency is higher than the motor's operating frequency.

[0106] The capsule's signal and power lines are routed through pre-drilled holes on the stationary shaft wall to the outer chamber's wiring channel, connecting to the external flight control system.

[0107] 5.1.9 Performance Prediction Under the conditions of being powered by a 14S lithium polymer battery (nominal voltage 51.8V) and running at 9000 RPM: Continuous output power: greater than 8.2 kW Torque density: approximately 8.7 N·m.

[0108] 5.2 Example 2 This embodiment provides a variation of the hollow static axis cross-section layout, the core of which lies in maximizing the hollow cavity through an irregularly shaped inner tube structure. In this embodiment, a hollow static axis (300c5) with a cross-sectional cavity classification of c5 is used, and a double-layer structure of nested outer tube (310) and inner tube (320c5) is also adopted. The difference is that the inner tube is an irregularly shaped tubular structure.

[0109] Unlike Embodiment 1, which divides the outer chamber into eight equal parts along the circumference, in this embodiment, the space between the outer tube and the inner tube is divided into two groups of four outer chambers (340c5) each, for a total of eight outer chambers. The outer chamber spaces on the left and right sides are merged into the hollow chamber (350c5), maximizing the longitudinal cross-sectional area of ​​the hollow chamber, which can accommodate a larger area of ​​PCB board to meet different usage requirements.

[0110] The upper group's four chambers and the lower group's four chambers are independently used for different functional channels: the first, second, and fourth chambers are air ducts for circulating cooling gas; the third chamber is a wiring channel for routing wire harnesses. The wiring channel is further divided into high-voltage and low-voltage wiring channels, with high-voltage wire harnesses (such as phase wires) and low-voltage wire harnesses (such as signal wires) routed in separate chambers to avoid interference. Specifically, the upper third chamber is used for high-voltage wiring, and the lower third chamber is used for low-voltage wiring.

[0111] On the wall of the outer tube (310), ventilation holes (311) are respectively provided for each outer chamber (340c5) and hollow chamber (350c5). The ventilation holes on the outer tube wall of the air duct chamber are used to connect the air duct and the radial air gap inside the motor, so that external cooling air can enter the motor. The ventilation holes on the outer tube wall of the wiring channel chamber are used to allow the wire harness to pass through and enter the wiring channel.

[0112] The inner tube (320c5) forms a hollow cavity (350c5) to accommodate the sensor integration module (400), wherein the core circuit board assembly may adopt a flat PCB structure.

[0113] The remaining structures in this embodiment (including the stator assembly, rotor assembly, centrifugal air-cooling structure, the three-layer distributed architecture of the sensor integration module, the bearing support method, etc.) are the same as in Embodiment 1, and will not be described again here.

[0114] 5.3 Other variations of the implementation method Those skilled in the art will understand that the above embodiments are merely illustrative. In actual implementation, the number of divisions of the outer chamber (340) is not limited to eight or four equal parts, and can be divided into six, eight, ten, twelve or more independent chambers as needed.

[0115] Meanwhile, the cross-sectional shape of the hollow cavity (350) can be selected as circular, polygonal or irregular as needed, or the hollow cavity can be omitted as needed (i.e. no hollow cavity).

[0116] The above-described variations and embodiments do not depart from the core concept of the present invention and should be considered as being included within the scope of protection of the present invention.

Claims

1. An axial flux motor, comprising a stator assembly (100), a rotor assembly (200), a hollow stationary shaft (300), and a sensor integration module (400), characterized in that: The hollow stationary shaft (300) passes through the stator assembly (100) and the rotor assembly (200) along the central axis of the motor. The hollow stationary shaft (300) has a multi-layer nested structure, including at least an outer tube (310) and an inner tube (320). An outer chamber (340) is formed between the outer tube (310) and the inner tube (320). A hollow chamber (350) is formed inside the inner tube (320). The outer chamber (340) is divided into multiple independent channels in the circumferential direction. The multiple independent channels include air ducts for circulating cooling gas and wiring channels for laying wire harnesses. The hollow chamber (350) is used to accommodate the sensor integrated module (400). The stator assembly (100) and the hollow stationary shaft (300) are fixedly connected by at least one connecting ring (146). A recessed space is formed axially between the connecting ring (146) and the end face of the stator assembly (100). A read head chip (147) is disposed in the recessed space. A wire hole is provided near the outer wall of the hollow stationary shaft (300) in the recessed space. The signal line of the read head chip (147) enters the wiring channel inside the hollow stationary shaft (300) through the wire hole. The rotor assembly (200) includes a first rotor and a second rotor located on the axial sides of the stator assembly (100) and a rotor connecting ring (220). The first rotor and the second rotor are fixed to the axial ends of the rotor connecting ring (220). The inner wall of the rotor connecting ring (220) is provided with an air-guiding structure (222) protruding towards the axial direction. The outer wall of the rotor connecting ring (220) is provided with a plurality of air outlet holes (224). When the rotor assembly (200) rotates, external cooling air enters from the air duct of the hollow stationary shaft (300), flows through the air gap between the stator assembly (100) and the rotor assembly (200), and is discharged from the air outlet holes (224) under the action of centrifugal force.

2. The axial flux motor according to claim 1, characterized in that: The axis of the air outlet (224) is inclined at an acute angle of 30° to 45° to the rotation direction of the rotor connecting ring (220), and the inclination direction is opposite to the rotation direction; the opening of the air outlet (224) on the inner wall of the rotor connecting ring (220) faces the rotation direction and is shaped like a winnowing basket.

3. The axial flux motor according to claim 1, characterized in that: The stator assembly (100) adopts a yokeless segmented armature structure, which is composed of multiple independent stator tooth units distributed along the circumference. The stator tooth units are installed in pole shoes (120). The pole shoes (120) are in the shape of annular grooves, with a hollow area inside to accommodate the stator tooth units and an outer annular groove serving as a winding skeleton.

4. The axial flux motor according to claim 3, characterized in that: The stator tooth unit is made of amorphous alloy material or ultra-thin silicon steel sheets stacked together.

5. The axial flux motor according to claim 1, characterized in that: The outer chamber (340) is divided circumferentially into four, six, eight, ten, twelve or more independent channels by partition ribs (330).

6. The axial flux motor according to claim 1, characterized in that: The sensor integration module (400) includes a core circuit board assembly, on which a main control unit, an attitude sensor and a communication interface are integrated. The sensor integration module (400) is connected to the read head chip (147) via a signal line to obtain rotor position information and to interact with external devices through the communication interface.

7. The axial flux motor according to claim 7, characterized in that: The core circuit board assembly adopts a cross-shaped vertical structure, consisting of two circuit boards that are vertically spliced ​​together in a cross shape.

8. A hollow stationary shaft for use in an axial flux motor, characterized in that: The hollow static shaft (300) has a multi-layer nested structure, including at least an outer tube (310) and an inner tube (320). An outer chamber (340) is formed between the outer tube (310) and the inner tube (320), and a hollow chamber (350) is formed inside the inner tube (320). The outer chamber (340) is divided into multiple independent channels in the circumferential direction, the multiple independent channels including air ducts for circulating cooling gas and wiring channels for laying wire harnesses; The outer tube (310) has a vent hole (311) on its wall that connects to the air duct, so that cooling gas can flow into the motor from the air duct. The hollow chamber (350) is used to accommodate the sensor integration module (400). The cross-sectional shape of the hollow cavity (350) can be selected as circular, polygonal or irregular as needed, or it can be without a hollow cavity.

9. A sensor integrated module for an axial flux motor, characterized in that: The sensor integration module (400) is disposed in the hollow cavity (350) of the hollow static shaft (300); The sensor integration module (400) includes a core circuit board assembly and a capsule body (410). The core circuit board assembly is disposed inside the capsule body (410). The core circuit board assembly integrates a main control unit, an attitude sensor and a communication interface. The core circuit board assembly adopts a cross-shaped vertical structure, consisting of two circuit boards vertically spliced ​​together in a cross shape. The sensor integration module (400) is connected to the read head chip (147) located at the end of the stator assembly (100) via a signal line to obtain rotor position information and to interact with external devices through the communication interface.

10. The sensor integration module according to claim 10, characterized in that: The main control unit is an MCU chip, the attitude sensor is an IMU chip, and the communication interface is a CAN FD transceiver; the outer wall of the capsule body (410) is provided with a wire hole (413), and a vibration damping rubber sleeve (430) is provided between the capsule body (410) and the inner wall of the hollow chamber (350).

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