A rotor system of a high torque density axial flux motor

Abstract

The application relates to the technical field of new energy automobile driving motors, and discloses a rotor system of a high-torque-density axial flux motor, which comprises a first rotor disc and a second rotor disc, and the main body of the first rotor disc is integrally formed with a rotating shaft; each rotor disc further comprises a segmented iron core group, a segmented magnetic steel group and a carbon fiber support from the near to the far relative to the main body, the carbon fiber support comprises a plurality of support body ribs which are radially arranged at equal angles from the center; the end of each support body rib is reserved with a locking bolt hole; the circumferential direction of the main body is provided with an axial bolt hole, the axial bolt hole of the main body and the locking bolt hole of the carbon fiber support are fixed through a fixing piece, the segmented iron core group and the segmented magnetic steel group are clamped, and each support body rib is embedded into the gap of the segmented magnetic steel group. The rotor system of the axial flux motor breaks through the existing torque density of the axial flux motor in the market by designing a brand-new rotor system.

Description

Technical Field

[0001] This invention relates to the field of new energy vehicle drive motor technology, specifically to a rotor system of a high torque density axial flux motor. Background Technology

[0002] In recent years, with the rise of concepts such as distributed systems and wheel-end drive, axial flux motors have become a research hotspot due to their compact size, high torque density, and high power density. Because of the significant axial attraction between the stator and rotor of an axial flux motor, the new energy vehicle motor industry often employs a symmetrical stator-rotor disk topology to counteract the axial force of the entire motor, thereby increasing the stability of the shaft system and the electric drive system. At the same performance level, compared to radial motors, axial motors can more than double the torque density, shorten the axial dimension by more than 50%, and reduce the weight to less than one-third of the original. This allows for a more compact motor and assembly structure, reducing overall vehicle weight and increasing the vehicle's driving range.

[0003] Currently, the mainstream axial flux motor topologies in the new energy industry are divided into single-stator dual-rotor and single-rotor dual-stator structures. Specifically, the single-stator dual-rotor structure can achieve higher torque density, power density, and a more compact size, with a smaller stator core. Because the stator core of the single-rotor dual-stator structure is tightly attached to both end caps, and the overall shaft system structure is relatively loose, the torque density, power density, and overall integration of the single-rotor dual-stator structure are lower than the former structure at the same torque and power level.

[0004] In related technologies, the peak torque of axial flux motors with single stator and dual rotors currently on the market is generally between 600 Nm and 700 Nm, with a torque density of around 20 Nm / kg and a peak power ranging from 100 to 150 kW. Specifically, the rotor system of these single-stator, dual-rotor axial flux motors requires simultaneous consideration of tangential torque transmission and axial limiting fixation in its dual rotor disc and shaft fixing method. Therefore, the shaft often has limiting steps with bolt holes, and is axially bolted to the rotor disc for secure fixing; alternatively, keyways are simultaneously cut on both the shaft and rotor disc, and a flat key with a lock nut is used for fixing. These methods effectively achieve the functions of torque transmission and axial limiting.

[0005] However, the method of using a limiting step with bolt holes and axial bolt locking, or a flat key with a locking nut, occupies a large radial space, which will squeeze the space of electromagnetic components (iron core, winding, magnet, etc.) in the structural design, resulting in a decrease in motor output performance. With the development of technology, new energy vehicles have put forward higher performance requirements for the torque density of axial flux motors. The rotor system of the above-mentioned single stator dual rotor axial flux motor cannot further improve the torque density performance index. Summary of the Invention

[0006] This application provides a rotor system for a high torque density axial flux motor, which breaks through the existing torque density of axial flux motors on the market by designing a completely new rotor system.

[0007] This application provides a rotor system for a high torque density axial flux motor. The rotor system includes two symmetrically arranged first rotor disks and second rotor disks. The main body of the first rotor disk is integrally formed with a shaft coaxial with itself. The end of the shaft is connected to the main body of the second rotor disk via a spline.

[0008] Each rotor disk, relative to the main body, also includes a segmented iron core assembly, a segmented magnet assembly, and a carbon fiber support from near to far. The carbon fiber support includes several support main ribs arranged radially from the center at equal angles. Each support main rib has a pre-drilled locking bolt hole at its end. The main body has axial bolt holes arranged circumferentially. The axial bolt holes of the main body and the locking bolt holes of the carbon fiber support are fixed by fasteners, clamping the segmented iron core assembly and the segmented magnet assembly. Each support main rib is embedded in the gap of the segmented magnet assembly.

[0009] Based on the above technical solution, n fan-ring limiting grooves are divided on the opposite sides of the main body of the two rotor disks; the segmented iron core group includes n fan-ring iron core units, and the n iron core units are filled in the n fan-ring limiting grooves, and each iron core unit has an iron core protrusion at the center of the two inclined sides.

[0010] The segmented magnet assembly comprises n fan-shaped magnet units, each magnet unit being arranged between two adjacent iron core protrusions, with a magnet gap between two adjacent magnet units; the carbon fiber support also comprises an inner ring connecting rib, with n support main ribs arranged radially along the inner ring connecting rib, and the n support main ribs located in the n magnet gaps.

[0011] Based on the above technical solution, each of the two straight sides of the magnet unit is provided with a side boss, the side bosses of two adjacent magnet units clamp the iron core rib, and the height of the iron core rib is less than or equal to the height of the side boss; the magnet gap is used to accommodate the main support rib of the bracket by the part other than the side boss, and two adjacent side bosses are pressed together by one of the main support ribs.

[0012] Based on the above technical solution, the gaps between the fan ring limiting groove and the segmented iron core group, the gaps between the segmented iron core group and the segmented magnet group, and the gaps between the magnet gaps of the segmented iron core group and the segmented magnet group and the carbon fiber support are filled with glue to form the overall structure of the rotor disk.

[0013] Based on the above technical solution, the depth of the magnetic steel gap is greater than or equal to the sum of the height of the iron core protrusion and the thickness of the main support rib of the carbon fiber support.

[0014] Based on the above technical solution, the ends of the rotating shaft include an external spline section and an external thread section from the inside out. An internal spline hole is opened in the center of the main body of the second rotor disk, and the internal spline hole is matched with the external spline section. The external thread section is pressed against the main body of the second rotor disk by an axial locking nut.

[0015] Based on the above technical solution, the main body includes a large circular boss located at the center of the plane where the rotating shaft is located, and a thin convex plate located at the periphery of the circle; n reinforcing rib structures are provided between the large circular boss and the thin convex plate, forming n fan-shaped limiting grooves; each reinforcing rib structure corresponds to the center line position of a magnet unit; the thin convex plate adjacent to the axial bolt hole has a clearance notch for the main body rib of the support to pass through.

[0016] Based on the above technical solution, a positioning hole is provided on the end face of the rotating shaft, and the axis of the positioning hole is perpendicular to the center line of one of the reinforcing rib structures; the center line of one of the spline grooves of the outer spline segment is also perpendicular to the axis of the positioning hole.

[0017] A positioning groove is provided on the back of the main body of the second rotor disk. The center line of the positioning groove is parallel to the center line of one of the reinforcing rib structures, and the center line of the positioning groove coincides with the center line of one of the spline teeth of the inner spline hole.

[0018] Based on the above technical solution, a small circular boss is provided on the side of the large circular boss; the rotor system also includes a steel bushing, a pair of bearings and a pair of bearing bushings, the steel bushing is sleeved on the rotating shaft, and the pair of bearing bushings are arranged opposite to each other and symmetrically, and both are sleeved outside the steel bushing.

[0019] The inner ring of the left bearing abuts against the small circular boss of the main body of the first rotor disk and the steel bushing on both sides; the outer ring of the left bearing is held and fixed by the bearing bushing; shims for adjusting the air gap thickness are provided between the outer ring of the left bearing and the bearing bushing, between the outer ring of the right bearing and the bearing bushing, and between the inner ring of the right bearing and the small circular boss.

[0020] Based on the above technical solution, the main body of the second rotor disk is provided with an inner recessed groove away from the reinforcing rib structure 112. The inner recessed groove is used to accommodate the axial locking nut. After the axial locking nut is engaged with the external thread section, the outer end faces of the external thread section and the axial locking nut do not exceed the outer end face of the main body of the second rotor disk.

[0021] The beneficial effects of the technical solutions provided in this application include at least the following:

[0022] 1. The rotor system of this application differs from existing dual-rotor systems that use a flat key with a locking nut or a limiting step with bolt holes and axial bolts for locking. The fixing method of the two rotor discs and the shaft is uniquely designed, featuring an integral rigid connection that eliminates the need for additional machining of radial mating features. The main body of the first rotor disc and the shaft are integrally rigidly connected, meaning the first main body and the shaft are integrally formed using a single machining process. The end of the shaft is connected to the main body of the second rotor disc via a spline. This integral machining combined with the spline fit significantly reduces the axial space occupied by the rotor back plate and the shaft mating features, making the shaft... The bearing and shaft system dimensions allow for greater design flexibility, ensuring structural strength and increasing torque density. Each rotor disc is matched with the locking bolt holes of the carbon fiber bracket and the axial bolt holes of the main body, clamping the segmented iron core assembly and segmented magnet assembly in the middle to form a single unit. This reduces the assembly difficulty with the stator and avoids interference between the inner circle of the stator housing and the rotor system during stator-rotor assembly, ensuring assembly feasibility. More importantly, the main support ribs are embedded in the gaps of the segmented magnet assembly. While forming a stable structure, the two rotor discs further greatly reduce the radial space occupied, significantly increasing torque density.

[0023] 2. In the rotor system of this application, each magnet unit has side bosses on both straight sides. With the carbon fiber bracket fixed to the main body, the main support ribs of the carbon fiber bracket are embedded in the gaps of the magnets and pressed by the side bosses. The iron core ribs are embedded between adjacent side bosses, and the iron core unit is embedded in the fan ring limiting groove. The main body, the segmented iron core group, the segmented magnet group and the carbon fiber bracket form circumferential rigid limiting between each other and rotate synchronously. The structure is ingeniously designed, compact and stable.

[0024] 3. The rotor system of this application provides mechanical support, overcoming the axial attraction between the stator and rotor, and also participates in the construction of the rotor's main magnetic circuit, acting as part of the yoke magnetic circuit. Simultaneously, the segmented iron core assembly filled between the main body and the segmented magnet assembly acts as an isolation layer, effectively reducing backplate eddy current losses. The carbon fiber bracket is locked to the main body using external axial bolts, freeing up internal design space in the rotor disk, improving the structural strength and load-bearing capacity of the entire shaft system and bearings, resulting in a more compact structure and significantly increased torque density.

[0025] 4. In the rotor system of this application, the second body and the shaft are connected by a spline connection. An internal spline hole is provided in the center of the second body, and an external spline section is provided at the end of the shaft. This connection method greatly saves radial assembly space, making the overall structure more compact. The spline fit distributes the traditional flat key or even convex key scheme, which occupies a large radial dimension, into a small toothed groove fit evenly distributed around the circumference. This achieves the same torque transmission capacity while greatly reducing the radial space occupied. This integrated machining combined with the spline fit significantly reduces the axial space occupied by the rotor back plate and shaft mating features, allowing for greater design space for bearings and shaft systems to ensure structural strength and greatly improve torque density. The second body and shaft assembly is axially locked using an axial lock nut to ensure the assembly strength of the rotor system and maintain the stability and reliability of the entire structure.

[0026] 5. The rotor system of this application maintains a straight pole structure by cleverly setting positioning holes and positioning slots. Specifically, since the second body and the shaft are connected by a spline, the angle of the second body relative to the first body is not continuously adjustable. The minimum adjustable angle depends on the number of teeth of the spline. Since the dual rotor system is designed with a straight pole connection, if the spline connection cannot guarantee that the magnetic poles of the first rotor disk and the second rotor disk are completely aligned, it will lead to a decrease in the performance of the axial flux motor. Therefore, positioning holes and positioning slots are designed to ensure that the magnetic poles of the first rotor disk and the second rotor disk are completely aligned. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 An exploded view of the rotor system provided in an embodiment of this application;

[0029] Figure 2 This is an assembly diagram of the rotor system provided in an embodiment of this application;

[0030] Figure 3 A structural schematic diagram of the first main body and the rotating axis from one perspective, provided in an embodiment of this application;

[0031] Figure 4 A structural schematic diagram of the first body and the rotating shaft from another perspective, provided in an embodiment of this application;

[0032] Figure 5 This is a schematic diagram of the structure and arrangement of the rotor segmented core assembly provided in the embodiments of this application;

[0033] Figure 6This is a schematic diagram of the structure of a single iron core provided in an embodiment of this application;

[0034] Figure 7 This is a schematic diagram of the structure and arrangement of the rotor segmented magnet assembly provided in an embodiment of this application;

[0035] Figure 8 This is a schematic diagram of the carbon fiber support structure provided in the embodiments of this application;

[0036] Figure 9 A schematic diagram of the structure of the second subject provided in an embodiment of this application;

[0037] Figure 10 This is a structural schematic diagram of the second subject from another perspective, provided in an embodiment of this application.

[0038] Figure 11 A schematic diagram of the rear side of the second body provided in an embodiment of this application;

[0039] In the diagram: 1. First rotor disk; 2. Second rotor disk;

[0040] 11. First main body; 12. Segmented iron core assembly; 13. Segmented magnet assembly; 14. Carbon fiber support; 15. Bearing; 16. Bearing bushing; 17. Shaft; 171. External spline section; 172. External thread section; 18. Steel bushing;

[0041] 21. Second body; 22. Axial locking nut; 23. Positioning groove;

[0042] 111. Thin convex plate; 112. Reinforcing rib structure; 113. Clearance notch; 114. Axial bolt hole; 115. Process hole; 116. Positioning hole; 117. Small round boss; 119. Large round boss;

[0043] 121. Core unit; 123. Core protrusion;

[0044] 131. Magnet unit; 132. Magnet gap; 133. Side boss;

[0045] 141. Main support reinforcement; 142. Locking bolt holes; 143. Inner ring connecting reinforcement;

[0046] 211. Internal spline hole. Detailed Implementation

[0047] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0048] This application provides a rotor system for a high torque density axial flux motor. By designing a completely new rotor system, it breaks through the existing torque density of axial flux motors on the market, and experimental verification shows that it can increase the torque density by more than 40%.

[0049] Currently, axial flux motors with single stator and dual rotors on the market typically have a peak torque in the range of 600Nm to 700Nm, a torque density of around 20Nm / kg, a peak power ranging from 100 to 150kW, a stator core outer diameter of around 270mm, and a speed generally below 10,000rpm. However, by adopting the rotor system described in this application, the peak torque density can be increased by more than 40%, the power density by more than 30%, and the axial dimension of the motor reduced by more than 60%.

[0050] like Figures 1 to 11 As shown, this application discloses an embodiment of a rotor system for a high torque density axial flux motor.

[0051] The rotor system includes two symmetrically arranged first rotor disk 1 and second rotor disk 2. The first rotor disk 1 and the second rotor disk 2 are two rotor structures of a single stator dual rotor axial flux motor.

[0052] The main body of the first rotor disk 1, namely the first main body 11, is integrally formed with the rotating shaft 17 coaxial with itself. That is, the first main body 11 and the rotating shaft 17 are integrally formed by a one-piece machining method, resulting in high structural strength. The end of the rotating shaft 17 is connected to the main body of the second rotor disk 2 via a spline. The end of the rotating shaft 17 is also matched with a fixing member, and the fixing member presses against the back of the main body of the second rotor disk 2.

[0053] The main bodies of the first rotor disk 1 and the second rotor disk 2 are opposite each other. Each rotor disk, relative to the main body, also includes a segmented iron core group 12, a segmented magnet group 13 and a carbon fiber support 14 from near to far. The carbon fiber support 14 includes a number of support main body ribs 141 arranged radially from the center at equal angles. Each support main body rib 141 has a pre-reserved locking bolt hole 142 at its end.

[0054] The main body has circumferentially arranged axial bolt holes 114, which are aligned and paired with locking bolt holes 142. The axial bolt holes 114 of the main body and the locking bolt holes 142 of the carbon fiber bracket 14 are fixed by fasteners. The main body and the carbon fiber bracket 14 clamp the segmented iron core assembly 12 and the segmented magnet assembly 13, and each main body rib 141 of the bracket is embedded in the gap of the segmented magnet assembly 13. The main body rib 141 of the bracket is accommodated in the gap of the segmented magnet assembly 13.

[0055] Specifically, the first rotor disk 1 includes a first body 11, a segmented iron core assembly 12, a segmented magnet assembly 13, and a carbon fiber support 14; the first body 11 is integrally formed with the rotating shaft 17. The second rotor disk 2 includes a second body 21, a segmented iron core assembly 12, a segmented magnet assembly 13, and a carbon fiber support 14. The carbon fiber support 14 of the first rotor disk 1 presses the segmented iron core assembly 12 and the segmented magnet assembly 13 to the first body 11 through axial bolt holes 114 and locking bolt holes 142. The carbon fiber support 14 of the second rotor disk 1 presses the segmented iron core assembly 12 and the segmented magnet assembly 13 to the second body 21 through axial bolt holes 114 and locking bolt holes 142.

[0056] Both the first main body 11 and the second main body 21 are disc-shaped.

[0057] Preferably, the rotor system adopts a 10-pole, 12-slot pole-slot configuration structure. Therefore, each rotor disk is equipped with a segmented magnet group 13 consisting of 10 magnet units 131 and a segmented iron core group 12 consisting of 10 iron core units 121. However, this topology can also be extended to other pole-slot configurations, such as 8-pole, 9-slot, 4-pole, 12-slot, etc.

[0058] The rotor system of this application differs from existing dual-rotor systems that use a flat key with a locking nut or a limiting step with bolt holes and axial bolt locking. The fixing method between the two rotor discs and the shaft is uniquely designed, featuring an integral rigid connection that eliminates the need for additional machining of radial fit features. The main body of the first rotor disc 1 and the shaft 17 are integrally rigidly connected; that is, the first main body 11 and the shaft 17 are integrally formed using a single machining method. The end of the shaft 17 is connected to the main body of the second rotor disc 2 via a spline. This integral machining combined with the spline fit significantly reduces the axial space occupied by the rotor back plate and shaft fit features, allowing for better bearing and... The shaft system dimensions allow for greater design flexibility, ensuring structural strength and increasing torque density. Each rotor disc is matched with the locking bolt holes 142 of the carbon fiber bracket 14 and the axial bolt holes 114 of the main body, clamping the segmented iron core assembly 12 and the segmented magnet assembly 13 in the middle to form a single unit. This reduces the difficulty of assembly with the stator and avoids interference between the inner circle of the stator housing and the rotor system during stator-rotor assembly, ensuring assembly feasibility. More importantly, the main body rib 141 of the bracket is embedded in the gaps of the segmented magnet assembly 13. While forming a stable structure, the two rotor discs further reduce the radial space occupation, greatly increasing torque density.

[0059] In one embodiment, such as Figure 4 As shown, the two rotor discs are divided into n sector ring limiting grooves on opposite sides of their main bodies.

[0060] The segmented core assembly 12 comprises n fan-shaped core units 121, which are filled and disposed within n fan-shaped ring limiting grooves. Each core unit 121 is accommodated within one fan-shaped ring limiting groove, and adjacent core units 121 are spaced apart from each other. Each core unit 121 has a core protrusion 123 at the center position of its two inclined sides. Here, n is a positive integer.

[0061] Specifically, when n equals 10, the overall arrangement of the segmented iron core group 12 is shown in the diagram below. Figure 5 As shown, the structural diagram of the core unit 121 is as follows: Figure 6 As shown, 10 iron core units 121 are evenly distributed around the circumference. The outer surface of the iron core unit 121 is in close contact with the outer surface of the fan ring limiting groove, and the inner surface of the iron core unit 121 is in close contact with the inner surface of the fan ring limiting groove. The gap between adjacent iron core units 121 coincides with the center line of each magnet unit 131. Since the main magnetic circuit reaches the adjacent magnetic pole from one magnetic pole through the yoke composed of the main body and the segmented iron core group 12, there is no large amount of magnetic flux flow at the center line position of the magnet. Therefore, the gap does not cause an isolation effect on the main magnetic circuit. The iron core unit 121 matches the fan ring limiting groove, ensuring that the iron core unit 121 will not undergo tangential displacement within the fan ring limiting groove. Two adjacent iron core protrusions 123 form tangential limiting for the magnet unit 131, forming a stable structure.

[0062] Preferably, such as Figure 6 As shown in the enlarged view, the edge of the iron core unit 121 adopts a flat-edge boss plus a beveled chamfer instead of a single chamfer, which reduces the difficulty of iron core pressing and demolding while ensuring that it does not interfere with other components.

[0063] The segmented magnet assembly 13 comprises n fan-shaped annular magnet units 131, which are arranged between n iron core protrusions 123. Adjacent magnet units 131 are spaced apart from each other, and one magnet unit 131 is placed between every two adjacent iron core protrusions 123. There is a magnet gap 132 between two adjacent magnet units 131.

[0064] Similarly, when n equals 10, the overall arrangement of the segmented magnet group 13 is shown in the diagram below. Figure 7 As shown, 10 magnet units 131 are evenly distributed around the circumference. The outer surface of each magnet unit 131 is in close contact with the outer surface of the fan ring limiting groove, and the inner surface of each magnet unit 131 is in close contact with the inner surface of the fan ring limiting groove. The gap between two adjacent magnet units 131 is fitted with an iron core protrusion 123. The width of the gap 132 between two adjacent magnet units 131 matches the width of the iron core protrusion 123, ensuring that the magnet units 131 do not undergo tangential displacement.

[0065] like Figure 8 As shown, the carbon fiber support 14 also includes an inner ring connecting rib 143, n support main ribs 141 are radially arranged along the inner ring connecting rib 143, the n support main ribs 141 are located in n magnet slots 132, the n support main ribs 141 are arranged at equal angles along the inner ring connecting rib 143, and the support main ribs 141 are accommodated in the magnet slots 132 to press the magnet unit 131 and the iron core unit 121 to the main body.

[0066] Specifically, the main body of each support main rib 141 is accommodated in the magnet gap 132 between two adjacent magnet units 131, and the main body of the support main rib 141 presses against the magnet unit 131 and the iron core unit 121. The locking bolt hole 142 at the end of the support main rib 141 is fixed to the circumferential axial bolt hole 114 of the main body.

[0067] When n equals 10, the carbon fiber support is as follows: Figure 8 As shown, in order to avoid the inner bearing bushing and bearing space, no axial locking structure is designed in the inner ring of the main body. The locking bolt hole 142 reserved at the end of the main body rib 141 of the carbon fiber bracket 14 is locked and fixed with the axial bolt hole 114 set in the circumferential direction of the outer circle of the main body. The main body rib 141 of the bracket will be pressed into the gap 132 between two adjacent magnets to axially limit the magnet unit and the iron core unit.

[0068] Furthermore, in the two rotor disk structures, the first main body 11 connected to the shaft is made of the same magnetically conductive structural steel as the shaft, and together with the segmented iron core group 12, it forms the main magnetic circuit of the rotor's yoke. The outer circular surface of the rotor back plate is provided with 10 arc-shaped protrusions, corresponding to the inter-pole position of each pole. The protrusions have axial bolt holes 114 inside, which are used to make axial connections with the locking bolt holes 142 at the end of the support main rib 141 of the carbon fiber support 14, so that the main structure of the first rotor disk 1 and the main structure of the second rotor disk 2 each form a stable connected whole, which counteracts the huge centrifugal force generated by the magnets and segmented iron cores when the rotor rotates at high speed.

[0069] The rotor system of this application, since its main body does not have a traditional segmented or laminated structure, would generate significant eddy current losses inside the back plate if it directly contacted the segmented magnet assembly 13. While a monolithic main body design improves mechanical strength, it also necessitates design considerations to reduce eddy current losses. Therefore, a segmented iron core assembly 12 is added between the main body and the segmented magnet assembly 13. This serves to both increase buffering and reduce eddy current losses, and also to fix the segmented magnet assembly 13. The segmented iron core assembly 12 is made of soft magnetic composite material SMC. The thickness of the segmented iron core assembly 12 and the rotor back plate thickness have been optimized to ensure the main body provides structural support for the entire rotor while effectively reducing eddy current losses in the back plate. Since the manufacturing process of soft magnetic composite material SMC is powder pressing, a large SMC iron core would pose significant difficulties for the pressing process and mold processing. Therefore, this design uses a segmented iron core structure to reduce the difficulty of the manufacturing process. The segmented iron core assembly 12 is arranged in the fan ring limiting groove. The gap width between the iron core units is matched with the width of the reinforcing rib. Furthermore, the iron core unit is also designed with an iron core protrusion 123 on the side facing the magnet unit, which plays a circumferential limiting role for the magnet unit.

[0070] Axial limiting of each iron core unit 121 and magnet unit 131 is achieved by a carbon fiber bracket. The carbon fiber bracket 14 includes 10 main bracket ribs 141, which are located between the 10 magnet units 131. The outermost part of the main bracket rib 141 has a locking bolt hole 141. The carbon fiber bracket 14 is fixed to the back plate by the arc-shaped protruding axial bolt hole 114 on the outer side of the main body. At the same time, the carbon fiber bracket 14 axially presses the segmented magnet group 13 and the segmented iron core group 12 to prevent the magnets and iron cores from detaching from the main body axially when rotating at high speed, thus forming a stable structure.

[0071] The rotor system of this application provides mechanical support to overcome the axial attraction between the stator and rotor, while also participating in the construction of the rotor's main magnetic circuit, acting as part of the yoke magnetic circuit. Simultaneously, the segmented iron core assembly 12, filled between the main body and the segmented magnet assembly 13, acts as an isolation layer, effectively reducing backplate eddy current losses. The carbon fiber bracket 14 is locked to the main body using external axial bolts, freeing up internal design space in the rotor disk, improving the structural strength and load-bearing capacity of the entire shaft system and bearings, resulting in a more compact structure and significantly increased torque density.

[0072] In one embodiment, each magnet unit 131 has a side boss 133 on both straight sides. The side bosses 133 of two adjacent magnet units 131 clamp the core protrusion 123, and the height of the core protrusion 123 is less than or equal to the height of the side boss 133. The magnet gap 132 uses the portion other than the side bosses 133 to accommodate the support body rib 141, and two adjacent side bosses 133 are pressed together by a support body rib 141.

[0073] In the rotor system of this application, each magnet unit 131 has a side boss 133 on both straight sides. With the carbon fiber bracket 14 fixed to the main body, the main support rib 141 of the carbon fiber bracket 14 is embedded in the magnet gap 132 and pressed by the side boss 133. The iron core rib 123 is embedded between adjacent side bosses 133, and the iron core unit is embedded in the fan ring limiting groove. The main body, the segmented iron core group 12, the segmented magnet group 13 and the carbon fiber bracket 14 form circumferential rigid limiting between each other and rotate synchronously. The structure is ingeniously designed, compact and stable.

[0074] Specifically, both the iron core unit 121 and the magnet unit 131 are fan-shaped rings, and two side bosses 133 extend from the straight sides of the magnet unit 131. The height of the side bosses 133 is the same as the height of the iron core ridge 123. The inner and outer sides of the magnet unit 131 are both arc-shaped. The outer circular surface of the magnet unit 131 is in close contact with the outer circular boss of the rotor back plate to prevent the magnet from detaching radially due to centrifugal force during high-speed rotation. The inner circular arc of the magnet is in close contact with the inner circle of the carbon fiber support. C-corners are used at the two vertices of the inner circle of the magnet unit 131 instead of rounded corners to reduce the processing difficulty. Due to the high peak speed of the motor, each pole magnet is radially divided into 20 segments to reduce eddy current losses. To prevent each segment of the magnet from having extremely short sides, the magnet is segmented into 20 equal segments on each side.

[0075] Because the peak speed of the axial flux motor is high, in order to avoid excessive eddy current loss at high speed, each magnet unit 131 adopts a segmented bonding method, and there are many segments. Adhesive is used as an insulating boundary between segments. In order to avoid interference with the carbon fiber support and reduce the processing difficulty, the two vertices of the inner circle of the magnet unit 131 adopt a large C-angle machining method. The C-angle covers both the magnet body and the side boss structure.

[0076] In one embodiment, glue is applied to the gaps between the fan ring limiting groove and the segmented iron core assembly 12, the gaps between the segmented iron core assembly 12 and the segmented magnet assembly 13, and the gaps at the contact points between the magnet gaps 132 of the segmented iron core assembly 12 and the segmented magnet assembly 13 and the carbon fiber support 14 to form the main structure of the rotor disk. This glue application method allows the segmented iron core assembly 12, the segmented magnet assembly 13, and the carbon fiber support 14 to form a stable whole, and avoids the design of an axial fixing structure in the middle of the rotor disk. It strengthens the structural strength of the inner circle side, and prevents the inner circle side of the segmented iron core assembly 12 and the segmented magnet assembly 13 from peeling off from the main body and causing rubbing during high-speed operation, resulting in a more compact overall structure and improved torque density.

[0077] Specifically, the main body refers to the first main body 11 and the second main body 21. The first main body 11 and the second main body 21 are connected in the same way as their respective segmented iron core group 12, segmented magnet group 13 and carbon fiber bracket 14, and all of them are treated with glue.

[0078] Preferably, the adhesive used is a high-temperature resistant adhesive to prevent excessive rotor temperature rise at high speeds, which could cause the adhesive to fail.

[0079] In one embodiment, the depth of the magnet gap 132 is greater than or equal to the sum of the height of the iron core protrusion 123 and the thickness of the support main rib 141 of the carbon fiber support 14. The magnet gap 132 is fully utilized to connect and form two independent rotor main structures. While ensuring structural stability, it occupies as little space as possible in other areas, thereby maximizing space utilization and improving torque density.

[0080] In one embodiment, the ends of the shaft 17 include an external spline section 171 and an external thread section 172 from the inside out (see...). Figure 4 The second rotor disk 2 has an internal spline hole 211 in the center of its main body (i.e., the second main body 21), and the internal spline hole 211 cooperates with the external spline section 171 to form a synchronously rotating main body structure. The external thread section 172 is pressed against the main body of the second rotor disk 2 (i.e., the second main body 21) by an axial locking nut 25.

[0081] In the rotor system of this application, the second body 21 and the shaft 17 are connected by a spline. The second body 21 has an internal spline hole 211 in the center, and the shaft 17 has an external spline section 171 at its end. This connection method greatly saves radial assembly space, making the overall structure more compact. The spline fit distributes the traditional flat key or even convex key scheme, which occupies a large radial dimension, into a small toothed groove fit that is evenly distributed around the circumference. This achieves the same torque transmission capacity while greatly reducing the radial space occupation. This one-piece machining combined with the spline fit greatly reduces the axial space occupation of the rotor back plate and shaft mating features, allowing for greater design space for bearings and shaft system dimensions to ensure structural strength and greatly improve torque density. The assembly of the second body 21 and the shaft 17 is axially locked by an axial locking nut 25 to ensure the assembly strength of the rotor system and maintain the stability and reliability of the entire structure.

[0082] like Figure 3 and Figure 4 As shown, in one embodiment, the main body includes a large circular boss 119 disposed at the center of the plane where the rotating shaft 17 is located, and a thin convex plate 111 disposed at the periphery of the circle; n reinforcing rib structures 112 are disposed between the large circular boss 119 and the thin convex plate 111, forming n fan-shaped limiting grooves. The thin convex plate 111 adjacent to the axial bolt hole 114 has a clearance notch 113 for the support body rib 141 to pass through.

[0083] The clearance notch 113 is a notch designed to avoid the support body rib 141 of the carbon fiber support 14. The carbon fiber support 14 reaches the outer side of the outer circle and is locked and fixed with the axial bolt hole 114 on the body through this notch.

[0084] A thin convex plate 111 is designed on the outer circle of the main body facing the magnet, which serves to form a fan-ring limiting groove and protect each magnet unit 131 and the iron core unit 121, and counteract the huge centrifugal force generated by the magnet unit 131 and the iron core unit 121 when the rotor rotates at high speed; each reinforcing rib structure 112 corresponds to the center line position of each pole magnet, and the reinforcing rib structure 112, together with the large circular boss 119 and the thin convex plate 111, constitute circumferential and radial limiting.

[0085] like Figure 3 , Figure 4 and Figure 11 As shown, in one embodiment, a positioning hole 116 is provided on the side end face of the rotating shaft 17, and the axis of the positioning hole 116 is perpendicular to the center line of one of the reinforcing rib structures 112; the center line of one of the spline grooves of the outer spline segment 171 is also perpendicular to the axis of the positioning hole 116.

[0086] by Figure 3 In the projection direction, the centerline of the reinforcing rib structure 112 coincides with the centerline of one of the spline grooves of the outer spline segment 171, and at the same time passes through the center of the positioning hole 116.

[0087] The back of the main body of the second rotor disk 2 is provided with a positioning groove 23. The center line of the positioning groove 23 is parallel to the center line of one of the reinforcing rib structures 112, and the center line of the positioning groove 23 coincides with the center line of one of the spline teeth of the inner spline hole 211.

[0088] by Figure 11 The centerline of the positioning groove 23, the centerline of one of the spline teeth of the inner spline hole 211, and the centerline of the positioning groove 23 coincide in the projection direction.

[0089] The rotor system of this application maintains a straight pole structure by cleverly setting positioning holes 116 and positioning grooves 23. Specifically, since the second body 21 and the rotating shaft 17 are connected by a spline, the angle of the second body 21 relative to the first body 11 is not continuously adjustable. The minimum adjustable angle depends on the number of teeth of the spline. Since the dual rotor system is designed with a straight pole connection, if the spline connection cannot guarantee that the magnetic poles of the first rotor disk 1 and the second rotor disk 2 are completely aligned, it will lead to a decrease in the performance of the axial flux motor. Therefore, positioning holes 116 and positioning grooves 23 are designed to ensure that the magnetic poles of the first rotor disk 1 and the second rotor disk 2 are completely aligned.

[0090] Specifically, with Figure 3 In the projection direction, the centerline of the reinforcing rib structure 112 coincides with the centerline of one of the spline grooves of the outer spline segment 171, and both pass through the center of the positioning hole 116. Figure 11 The centerline of the positioning groove 23, the centerline of one of the spline teeth of the inner spline hole 211, and the centerline of the positioning groove 23 coincide in the projection direction. In this way, when the second rotor disk meshes with the shaft spline, it can be ensured that each pole of the left and right disks can be completely corresponding, ensuring that the two rotor disks maintain a straight pole structure.

[0091] like Figure 2 As shown, a small circular boss 117 is provided on the side of the large circular boss 119.

[0092] The rotor system also includes a steel bushing 18, a pair of bearings 15 and a pair of bearing bushings 16. The steel bushing 18 is fitted onto the rotating shaft 17, and the pair of bearing bushings 16 are arranged opposite to each other and symmetrically, and are both fitted onto the outside of the steel bushing 18.

[0093] The inner ring of the left bearing 15 is supported on both sides by the small round protrusion 117 of the first main body 11 and the steel bushing 18; the outer ring of the left bearing 15 is supported and fixed by the bearing bushing 16.

[0094] Shims for adjusting the air gap thickness are provided between the outer ring of the left bearing 15 and the bearing bush 16, between the outer ring of the right bearing 15 and the bearing bush 16, and between the inner ring of the right bearing 15 and the small round boss 117.

[0095] The first main body 11 and the rotating shaft 17 are integrally machined. In the assembly process, the left bearing is first pressed onto the rotating shaft 17 with an interference fit. One side of the inner ring of the left bearing abuts against the small circular protrusion 117. Then, the steel bushing 10 is nested into the shaft and pushes against the other side of the inner ring of the left bearing axially. Then, the first main body 11 and the left bearing are pressed into the left bearing bushing as a whole. A first set of shims is designed between the outer ring of the left bearing and the left bearing bushing to adjust the air gap thickness between the first rotor disk 1 and the stator. During this process, the rotating shaft 17 will pass through the inner circular through hole of the stator. Then, the right bearing will be pressed into the right bearing bushing from the right side at the same time. The right bearing and the shaft maintain an interference fit, and the right bearing and the right bearing bushing maintain a clearance fit. The inner ring of the right bearing will push against the steel bushing 10 from the right side. At the same time, a second set of shims is designed between the outer ring of the right bearing and the end face of the right bearing bushing to neutralize the cumulative dimensional chain deviation. After that, the assembled second rotor disk 2 enters the shaft from the right spline side. The inner spline hole 211 mates with the outer spline section 171. A third set of shims is designed between the small round boss 117 of the second body 12 and the inner ring of the right bearing. The thickness adjustment of the second set of shims and the third set of shims together ensures the air gap thickness between the right rotor disk and the stator. At the same time, the rotation positioning of the inner and outer splines ensures that the N pole of the first rotor disk is opposite to the S pole of the second rotor disk.

[0096] In the rotor system of this application, a set of shims is installed between the left bearing and the left bearing bushing, between the right bearing bushing and the right bearing, and between the right bearing and the small circular boss 117 of the second main body 12. These three sets of shims are designed to adjust the axial relative position between the two rotor discs and the stator, thereby offsetting the uneven thickness of the two air gaps caused by the superposition of the axial dimensional chains of the entire stator and rotor system. This prevents the generation of large axial eccentric forces, which would cause large axial loads on the entire shaft system and lead to shaft system failure. Simultaneously, a steel bushing is placed between the left and right bearings to provide a rigid connection between the two bearings, completing the dimensional chain transmission between the two rotor discs and preventing the inner ring of the right bearing from slipping relative to the left bearing during motor operation, thus preventing the entire shaft system from failing in stability.

[0097] like Figure 3 As shown, in one embodiment, a process hole 115 is also provided between two adjacent axial bolt holes 114. The process hole 115 is used to lock the rotor surface to the assembly flange during stator and rotor assembly. The axis of each process hole 115 is perpendicular to the centerline of a reinforcing rib structure 112. The process hole 115 can improve assembly efficiency.

[0098] In one embodiment, the main body of the second rotor disk 2 is provided with an inner recessed groove away from the reinforcing rib structure 112. The inner recessed groove is used to accommodate the axial locking nut 22. After the axial locking nut 22 is engaged with the external thread section 172, the outward end faces of the external thread section 172 and the axial locking nut 22 are both lower than the end face of the main body of the second rotor disk 2. This can minimize the space occupied, ensure that the axial locking nut 22 is in contact with the main body surface, and avoid insufficient clamping force.

[0099] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0100] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0101] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A rotor system for a high torque density axial flux motor, characterized in that: The rotor system includes two symmetrically arranged first rotor disks (1) and second rotor disks (2). The main body of the first rotor disk (1) is integrally formed with a rotating shaft (17) coaxial with itself. The end of the rotating shaft (17) is connected to the main body of the second rotor disk (2) by a spline. Each rotor disk, relative to the main body, also includes a segmented iron core group (12), a segmented magnet group (13), and a carbon fiber support (14) from near to far. The carbon fiber support (14) includes a number of support main ribs (141) arranged radially from the center at equal angles. Each of the support main ribs (141) has a pre-drilled locking bolt hole (142) at its end. The main body is provided with axial bolt holes (114) in the circumferential direction. The axial bolt holes (114) of the main body and the locking bolt holes (142) of the carbon fiber bracket (14) are fixed by fasteners, and the segmented iron core group (12) and the segmented magnet group (13) are clamped together. Each bracket main body rib (141) is embedded in the gap of the segmented magnet group (13). The main bodies of the two rotor disks are divided into n fan-ring limiting grooves on opposite sides; the segmented iron core group (12) includes n fan-ring iron core units (121), the n iron core units (121) are filled in the n fan-ring limiting grooves, and each iron core unit (121) has an iron core protrusion (123) at the center of the two inclined sides; the segmented magnet group (13) includes n fan-ring magnet units (131), each magnet unit (131) is arranged between two adjacent iron core protrusions (123), and there is a magnet gap (132) between two adjacent magnet units (131); the carbon fiber support (14) also includes an inner ring connecting rib (143), the n support main ribs (141) are arranged radially along the inner ring connecting rib (143), and the n support main ribs (141) are located in the n magnet gaps (132). Each of the two straight sides of the magnet unit (131) is provided with a side boss (133). The side bosses (133) of two adjacent magnet units (131) clamp the iron core rib (123), and the height of the iron core rib (123) is less than or equal to the height of the side boss (133). The magnet gap (132) uses the part other than the side boss (133) to accommodate the main support rib (141), and two adjacent side bosses (133) are pressed together by one of the main support ribs (141).

2. The rotor system of a high torque density axial flux motor as described in claim 1, characterized in that: The gaps between the fan ring limiting groove and the segmented iron core group (12), the gaps between the segmented iron core group (12) and the segmented magnet group (13), and the gaps at the contact points between the magnet gaps (132) of the segmented iron core group (12) and the segmented magnet group (13) and the carbon fiber support (14) are filled with glue to form the overall structure of the rotor disk.

3. The rotor system of a high torque density axial flux motor as described in claim 1, characterized in that: The depth of the magnetic steel gap (132) is greater than or equal to the sum of the height of the iron core protrusion (123) and the thickness of the main support rib (141) of the carbon fiber support (14).

4. The rotor system of a high torque density axial flux motor as described in claim 1, characterized in that: The end of the rotating shaft (17) includes an external spline section (171) and an external thread section (172) from the inside out. An internal spline hole (211) is opened in the center of the body of the second rotor disk (2), and the internal spline hole (211) is engaged with the external spline section (171). The external thread section (172) is pressed against the body of the second rotor disk (2) by an axial locking nut (22).

5. The rotor system of a high torque density axial flux motor as described in claim 4, characterized in that: The main body includes a large circular boss (119) located at the center of the plane where the rotating shaft (17) is located, and a thin convex plate (111) located at the periphery of the circle; n reinforcing rib structures (112) are provided between the large circular boss (119) and the thin convex plate (111) to form n fan-shaped limiting grooves; each reinforcing rib structure (112) corresponds to the center line position of a magnet unit (131); the thin convex plate (111) adjacent to the axial bolt hole (114) has a clearance notch (113) for the main body rib (141) of the support to pass through.

6. The rotor system of a high torque density axial flux motor as described in claim 5, characterized in that: The end face of the rotating shaft (17) is provided with a positioning hole (116), and the axis of the positioning hole (116) is perpendicular to the center line of one of the reinforcing rib structures (112); the center line of one of the spline grooves of the outer spline segment (171) is also perpendicular to the axis of the positioning hole (116). The back of the main body of the second rotor disk (2) is provided with a positioning groove (23). The center line of the positioning groove (23) is parallel to the center line of one of the reinforcing rib structures (112), and the center line of the positioning groove (23) coincides with the center line of one of the spline teeth of the inner spline hole (211).

7. The rotor system of a high torque density axial flux motor as described in claim 5, characterized in that: The large circular boss (119) has a small circular boss (117) on its side; the rotor system also includes a steel bushing (18), a pair of bearings (15) and a pair of bearing bushings (16). The steel bushing (18) is sleeved on the rotating shaft (17), and the pair of bearing bushings (16) are arranged opposite to each other and symmetrically, and are both sleeved outside the steel bushing (18). The inner ring of the left bearing (15) abuts against the small round boss (117) of the main body of the first rotor disk (1) and the side of the steel bushing (18) respectively; the outer ring of the left bearing (15) is held and fixed by the bearing bushing (16); shims for adjusting the air gap thickness are provided between the outer ring of the left bearing (15) and the bearing bushing (16), between the outer ring of the right bearing (15) and the bearing bushing (16), and between the inner ring of the right bearing (15) and the small round boss (117).

8. The rotor system of a high torque density axial flux motor as described in claim 5, characterized in that: The main body of the second rotor disk (2) is provided with an inner recessed groove away from the reinforcing rib structure 112. The inner recessed groove is used to accommodate the axial locking nut (22). After the axial locking nut (22) is engaged with the external thread section (172), the outer end faces of the external thread section (172) and the axial locking nut (22) do not exceed the outer end face of the main body of the second rotor disk (2).

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