Rotor system of high-torque-density axial flux motor

Abstract

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

Description

Technical Field

[0001] The present invention relates to the technical field of drive motors for new energy vehicles, and particularly to a rotor system of an axial flux motor with high torque density. Background Art

[0002] In recent years, with the popularity of concepts such as distributed systems and in-wheel drive, axial flux motors have become a research hotspot due to their compact space, high torque density, and high power density. Since there is a large axial suction force between a single stator and a rotor of an axial flux motor, the new energy vehicle motor industry mostly adopts a symmetric stator-rotor disk topology structure to offset the axial force of the entire motor, thereby increasing the stability of the shafting and the electric drive system. Under the same performance level, compared with radial motors, axial motors can more than double the torque density of the motor, shorten the axial dimension by more than 50%, and reduce the weight to less than 1 / 3 of the original, enabling a more compact motor structure and assembly structure, reducing the vehicle mass, and increasing the vehicle's cruising range.

[0003] Currently, the mainstream axial flux motor topologies in the new energy industry are divided into single stator double rotor and single rotor double stator. Specifically, the single stator double rotor structure can achieve higher torque density, power density, and more compact dimensions, with a smaller stator core. In the single rotor double stator structure, since the stator core is closely attached to both end covers, and the entire shafting structure is relatively loose, at the same torque and power level, the torque density, power density, and assembly integration of the single rotor double stator structure are lower than those of the previous structure.

[0004] In related technologies, currently in the market, for axial flux motors with a peak torque in the range of 600 Nm to 700 Nm of single stator double rotor axial flux motors, the torque density is generally about 20 Nm / kg, and the peak power varies from 100 to 150 kW. Specifically, for the rotor system of the single stator double rotor axial flux motor in the market, the fixing method of the double rotor disk and the rotating shaft needs to consider both tangential torque transmission and axial position limiting and fixing. Therefore, the rotating shaft is mostly provided with a limiting step with bolt holes, and is fixed to the rotor disk by axially locking with bolts; or key grooves are simultaneously opened on the rotating shaft and the rotor disk, and fixed by using a flat key and a locking nut. These methods can effectively complete the functions of torque transmission and axial position limiting.

[0005] However, the method of using a limiting step with bolt holes plus axial bolt locking, or the method of using a flat key plus a locking nut occupies a large radial space, which will squeeze the space of electromagnetic components (iron core, winding, permanent magnet, etc.) in the structural design, resulting in a decrease in the output performance of the motor. 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 double rotor axial flux motor cannot further improve the performance index of torque density. Summary of the Invention

[0006] This application provides a rotor system for a high torque density axial flux motor. By designing a brand-new rotor system, the existing torque density of axial flux motors on the market is broken through.

[0007] An embodiment of this application provides a rotor system for a high torque density axial flux motor. The rotor system includes two symmetrically arranged first rotor discs and second rotor discs. The main body of the first rotor disc is integrally formed with a rotating shaft coaxial with itself. The end of the rotating shaft is connected to the main body of the second rotor disc through a spline.

[0008] Each rotor disc further includes a segmented iron core group, a segmented magnet group, and a carbon fiber bracket from near to far relative to the main body. The carbon fiber bracket includes several bracket main ribs arranged radially at equal angles from the center. A locking bolt hole is reserved at the end of each bracket main rib. Axial bolt holes are provided in the circumferential direction of the main body. The axial bolt holes of the main body and the locking bolt holes of the carbon fiber bracket are fixed through fixing parts, clamping the segmented iron core group and the segmented magnet group, and each bracket main rib is embedded in the gap of the segmented magnet group.

[0009] Based on the above technical solution, n fan-shaped ring limiting grooves are separated on the relative sides of the main bodies of the two rotor discs. The segmented iron core group includes n fan-shaped iron core units, and the n iron core units are filled in the n fan-shaped ring limiting grooves. And each iron core unit is provided with an iron core rib at the central position of the two slant sides.

[0010] The segmented magnet group includes n fan-shaped magnet units. Each of the magnet units is arranged between two adjacent iron core ribs, and there is a magnet gap between two adjacent magnet units. The carbon fiber bracket further includes inner ring connecting ribs. The n bracket main ribs are arranged radially along the inner ring connecting ribs, and the n bracket main ribs are located in the n magnet gaps.

[0011] Based on the above technical solution, side bosses are provided on both straight sides of each magnet unit. 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 uses the part other than the side boss to accommodate the bracket main rib, and two adjacent side bosses are pressed by one bracket main rib.

[0012] Based on the above technical solution, glue injection treatment is performed between the fan-shaped ring limiting groove and the gap of the segmented iron core group, between the gap of the segmented iron core group and the segmented magnet group, and between the magnet gaps of the segmented iron core group and the segmented magnet group and the contact gap of the carbon fiber bracket to form the overall structure of the rotor disc.

[0013] On the basis of the above technical solution, the depth of the magnet steel gap is greater than or equal to the sum of the height of the iron core rib and the thickness of the rib of the support body of the carbon fiber support.

[0014] On the basis of the above technical solution, the end of the rotating shaft includes an external spline section and an external thread section from the inside to the outside. An internal spline hole is provided 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 presses the main body of the second rotor disk through an axial locking nut.

[0015] On the basis of the above technical solution, the main body includes a large circular surface convex platform arranged at the center of the plane where the rotating shaft is located and a thin convex plate arranged at the circular peripheral edge; n reinforcing rib structures are arranged between the large circular surface convex platform and the thin convex plate, enclosing n fan-shaped ring limiting grooves; the center line position of each reinforcing rib structure corresponds to a magnet steel unit; an avoidance notch for the rib of the support body to pass through is provided on the thin convex plate adjacent to the axial bolt hole.

[0016] On the basis of 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 external spline section 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 internal spline hole.

[0018] On the basis of the above technical solution, a small circular surface convex platform is provided on the side surface of the large circular surface convex platform; the rotor system further includes a steel shaft sleeve, a pair of bearings and a pair of bearing bushings. The steel shaft sleeve is sleeved on the rotating shaft, and the pair of bearing bushings are arranged back to back and symmetrically, and both are sleeved outside the steel shaft sleeve;

[0019] The two sides of the inner ring of the left bearing respectively abut against the small circular surface convex platform of the main body of the first rotor disk and one side of the steel shaft sleeve; the outer ring of the left bearing is held and fixed by the bearing bushing; gaskets 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 surface convex platform.

[0020] On the basis of the above technical solution, an inner concave groove is provided on the main body of the second rotor disk facing away from the reinforcing rib structure 112, and the inner concave groove is used to accommodate the axial locking nut; after the axial locking nut is matched 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 brought by the technical solution provided by the embodiments of the present application at least include:

[0022] 1. The rotor system of the present application is different from the existing dual-rotor system. The existing dual-rotor system uses a combination of a flat key and a locking nut or a limiting step with bolt holes plus axial bolt locking. The fixing method of the two rotor discs and the rotating shaft is uniquely designed. It is integrally and rigidly connected without additional machining of radial mating features. The main body of the first rotor disc and the rotating shaft are integrally and rigidly connected, that is, the first main body and the rotating shaft are integrally formed by integral machining. The end of the rotating shaft is connected to the main body of the second rotor disc through a spline; this method of integral machining plus spline fitting greatly reduces the axial space occupied by the mating features of the rotor back plate and the rotating shaft, allowing for a larger design space for the bearing and shafting dimensions to ensure structural strength and improving the torque density; each rotor disc is matched through the locking bolt holes of the carbon fiber bracket and the axial bolt holes of the main body, and the segmented iron core group and the segmented magnet group are clamped in the middle to form a separate whole, reducing the assembly difficulty with the stator and avoiding the problem of interference between the inner circle of the stator housing and the rotor system during the stator-rotor assembly process, ensuring the feasibility of the assembly; more importantly, the main body ribs of the bracket are embedded in the gaps of the segmented magnet group. While the two rotor discs form a stable structure, it further greatly reduces the radial space occupied and significantly improves the torque density.

[0023] 2. In the rotor system of the present application, side bosses are provided on both straight edges of each magnet unit. When the carbon fiber bracket is fixed to the main body, the main body ribs of the carbon fiber bracket are embedded in the magnet gaps and pressed by the side bosses, and the iron core ridges are embedded between adjacent side bosses. The iron core units are embedded in the fan-shaped ring limiting grooves. The main body, the segmented iron core group, the segmented magnet group, and the carbon fiber bracket form circumferential rigid limits to each other and rotate synchronously. The structural design is ingenious, compact, and stable.

[0024] 3. In the rotor system of the present application, the main body provides mechanical support. While overcoming the axial suction force between the stator and the rotor, it also participates in the construction of the main magnetic circuit of the rotor and acts as a part of the yoke magnetic circuit. At the same time, the segmented iron core group filled with SMC iron core between the main body and the segmented magnet group acts as an isolation layer, effectively reducing the eddy current loss of the back plate. The carbon fiber bracket and the main body are locked by external circular axial bolts, releasing the internal design space of the rotor disc, improving the structural strength and load-bearing capacity of the entire shafting and bearing, making the structure more compact, and significantly improving the torque density.

[0025] 4. In the rotor system of the present application, the second main body and the rotating shaft are connected by a spline connection. An internal spline hole is provided in the center of the second main body, and an external spline section is provided at the end of the rotating shaft. This connection method greatly saves the radial assembly space and makes the overall structure more compact. The spline fit disperses the traditional flat key or even convex key scheme that occupies more radial dimensions into a small tooth groove fit method evenly distributed in the circumference, greatly reducing the radial space occupation while achieving the same torque transmission capacity. This method of integral machining plus spline fit greatly reduces the axial space occupation of the mating features between the rotor back plate and the rotating shaft, providing a larger design space for the bearing and shafting dimensions to ensure the structural strength and greatly improving the torque density. The assembly of the second main body and the rotating shaft will be axially locked by an axial locking nut to ensure the assembly strength of the rotor system and maintain the stable reliability of the entire structure.

[0026] 5. In the rotor system of the present application, the straight pole structure is maintained by cleverly setting positioning holes and positioning grooves. Specifically, since a spline fit is used between the second main body and the rotating shaft, the angle of the second main body relative to the first main body is not continuously adjustable, and the minimum adjustable angle depends on the number of teeth of the spline. Due to the design of the dual-rotor system as a straight pole connection, if the spline fit cannot ensure the complete correspondence of the magnetic poles of the first rotor disk and the second rotor disk, it will lead to a decline in the performance of the axial flux motor. Therefore, positioning holes and positioning grooves are designed to ensure the complete correspondence of the magnetic poles of the first rotor disk and the second rotor disk. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0028] Figure 1 It is an exploded view of the structure of the rotor system provided by the embodiment of the present application;

[0029] Figure 2 It is an assembly schematic diagram of the rotor system provided by the embodiment of the present application;

[0030] Figure 3 It is a schematic diagram of the structure of the first main body and the rotating shaft from one perspective provided by the embodiment of the present application;

[0031] Figure 4 It is a schematic diagram of the structure of the first main body and the rotating shaft from another perspective provided by the embodiment of the present application;

[0032] Figure 5 It is a schematic diagram of the structure and arrangement of the rotor segmented iron core group provided by the embodiment of the present application;

[0033] Figure 6Schematic diagram of the structure of a single-piece iron core provided by an embodiment of the present application;

[0034] Figure 7 Schematic diagram of the structure and arrangement of a segmented magnet group of a rotor provided by an embodiment of the present application;

[0035] Figure 8 Schematic diagram of the structure of a carbon fiber bracket provided by an embodiment of the present application;

[0036] Figure 9 Schematic diagram of the structure of a second main body from one perspective provided by an embodiment of the present application;

[0037] Figure 10 Schematic diagram of the structure of a second main body from another perspective provided by an embodiment of the present application;

[0038] Figure 11 Schematic diagram of the back of a second main body provided by an embodiment of the present application;

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

[0040] 11. First main body; 12. Block iron core group; 13. Segmented magnet group; 14. Carbon fiber bracket; 15. Bearing; 16. Bearing bushing; 17. Rotating shaft; 171. External spline section; 172. External thread section; 18. Steel bushing;

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

[0042] 111. Thin convex plate; 112. Reinforcing rib structure; 113. Avoidance notch; 114. Axial bolt hole; 115. Process hole; 116. Positioning hole; 117. Small circular surface convex platform; 119. Large circular surface convex platform;

[0043] 121. Iron core unit; 123. Iron core rib;

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

[0045] 141. Bracket main body rib; 142. Locking bolt hole; 143. Inner ring connecting rib;

[0046] 211. Internal spline hole. Detailed implementation manners

[0047] To enable those skilled in the art to better understand the solution of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without making creative efforts belong to the scope of protection of this application.

[0048] The embodiment of this application provides a rotor system of an axial-flux motor with high torque density. By designing a brand-new rotor system, the existing torque density of axial-flux motors on the market is broken through, and it can be verified by experiments that it can be increased by more than 40%.

[0049] Currently, for axial-flux motors with a single stator and double rotors on the market, the torque density of axial-flux motors with peak torque in the range of 600 Nm to 700 Nm is generally about 20 Nm / kg, the peak power varies from 100 to 150 kW, the outer diameter of the stator core is about 270 mm, and the rotational speed is generally within 10,000 rpm. After adopting the rotor system of this application, the peak torque density can be increased by more than 40%, the power density can be increased by more than 30%, and the axial dimension of the motor can be reduced by more than 60%.

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

[0051] The rotor system includes two symmetrically arranged first rotor disks 1 and second rotor disks 2, and the first rotor disk 1 and the second rotor disk 2 are the two rotor structures of an axial-flux motor with a single stator and double rotors.

[0052] The main body of the first rotor disk 1, i.e., 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 an integral processing method, with high structural strength. The end of the rotating shaft 17 is connected to the main body of the second rotor disk 2 through a spline. The end of the rotating shaft 17 also matches with a fixing member, and the fixing member presses the back surface of the main body of the second rotor disk 2.

[0053] On the opposite surfaces of the main bodies of the two rotor disks, the first rotor disk 1 and the second rotor disk 2, each rotor disk further includes a segmented iron core group 12, a segmented magnet group 13, and a carbon fiber bracket 14 from near to far relative to the main body. The carbon fiber bracket 14 includes a number of bracket main body ribs 141 arranged radially at equal angles from the center, and locking bolt holes 142 are reserved at the ends of each bracket main body rib 141.

[0054] Axial bolt holes 114 are circumferentially provided on the main body. The axial bolt holes 114 and the locking bolt holes 142 are aligned and paired one by one. The axial bolt holes 114 of the main body and the locking bolt holes 142 of the carbon fiber bracket 14 are fixed by fixing parts. The main body and the carbon fiber bracket 14 clamp the segmented iron core group 12 and the segmented permanent magnet group 13, and each bracket main body rib 141 is embedded in the gap of the segmented permanent magnet group 13. The bracket main body rib 141 is accommodated in the gap between the segmented permanent magnet groups 13.

[0055] Specifically, the first rotor disk 1 includes a first main body 11, a segmented iron core group 12, a segmented permanent magnet group 13, and a carbon fiber bracket 14; the first main body 11 is integrally formed with the rotating shaft 17. The second rotor disk 2 includes a second main body 21, a segmented iron core group 12, a segmented permanent magnet group 13, and a carbon fiber bracket 14. The carbon fiber bracket 14 of the first rotor disk 1 presses and fixes the segmented iron core group 12 and the segmented permanent magnet group 13 to the first main body 11 through the axial bolt holes 114 and the locking bolt holes 142. The carbon fiber bracket 14 of the second rotor disk 1 presses and fixes the segmented iron core group 12 and the segmented permanent magnet group 13 to the second main body 21 through the axial bolt holes 114 and the 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 pole-slot combination structure of 10 poles and 12 slots. Therefore, each rotor disk is equipped with a segmented permanent magnet group 13 composed of 10 magnet units 131 and a segmented iron core group 12 composed of 10 iron core units 121. However, this topological structure can also be extended to other pole-slot combinations, such as 8 poles and 9 slots, 4 poles and 12 slots, etc.

[0058] The rotor system of the present application is different from the existing double-rotor system. The existing double-rotor system adopts a structural form of a flat key plus a locking nut or a limiting step with bolt holes plus an axial bolt for locking. The fixing method of the two rotor discs and the rotating shaft is uniquely designed. The integral rigid connection does not require additional machining of radial mating features. The main body of the first rotor disc 1 and the rotating shaft 17 are integrally rigidly connected, that is, the first main body 11 and the rotating shaft 17 are integrally formed by integral machining. The end of the rotating shaft 17 is connected to the main body of the second rotor disc 2 through a spline; this way of integral machining plus spline fitting greatly reduces the axial space occupied by the mating features of the rotor back plate and the rotating shaft, enabling a larger design space for the bearing and shafting dimensions to ensure the structural strength and improving the torque density; each rotor disc is matched through the locking bolt holes 142 of the carbon fiber bracket 14 and the axial bolt holes 114 of the main body, and the segmented iron core group 12 and the segmented magnet group 13 are clamped in the middle to form a separate whole, reducing the assembly difficulty with the stator and avoiding the problem of interference between the inner circle of the stator housing and the rotor system during the stator-rotor assembly process, ensuring the feasibility of the assembly; more importantly, the main body ribs 141 of the bracket are embedded in the gaps of the segmented magnet group 13. While the two rotor discs form a stable structure, the radial space occupied is further greatly reduced, and the torque density is greatly improved.

[0059] In one embodiment, as Figure 4 shown, n sector ring limiting grooves are defined on the relative sides of the main bodies of the two rotor discs.

[0060] The segmented iron core group 12 includes n sector ring-shaped iron core units 121. The n iron core units 121 are filled and arranged in the n sector ring limiting grooves. Each iron core unit 121 is accommodated in a sector ring limiting groove. Adjacent two iron core units 121 are spaced apart from each other, and each iron core unit 121 is provided with an iron core rib 123 at the central position of the two hypotenuses on both sides. Herein, n is a positive integer.

[0061] Specifically, when n is equal to 10, the overall layout effect diagram of the segmented iron core group 12 is as Figure 5 shown, and the structural diagram of the iron core unit 121 is as Figure 6 shown. The 10 iron core units 121 are evenly distributed in a circle. The outer circular surface of the iron core unit 121 is in close contact with the outer circular surface of the sector ring limiting groove, and the inner circular surface of the iron core unit 121 is in close contact with the inner circular surface of the sector ring limiting groove. The gaps between adjacent iron core units 121 coincide with the center lines of the respective magnet units 131. Since the main magnetic circuit passes from one magnetic pole through the yoke composed of the main body and the segmented iron core group 12 to the adjacent magnetic pole, there is no large amount of magnetic flux flowing at the center line position of the magnet, so the gaps do not cause a blocking effect on the main magnetic circuit. The iron core unit 121 matches the sector ring limiting groove to ensure that the iron core unit 121 will not undergo tangential displacement in the sector ring limiting groove. The adjacent two iron core ribs 123 form tangential limits on the magnet units 131, forming a stable structure.

[0062] Preferably, as Figure 6 shown in the enlarged partial view in

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

[0064] Similarly, when n is equal to 10, the overall layout effect diagram of the segmented magnet group 13 is as Figure 7 shown. The 10 magnet units 131 are evenly distributed on the circumference. The outer circular surfaces of each magnet unit 131 are in close contact with the outer circular surface of the fan-shaped limiting groove, and the inner circular surfaces of each magnet unit 131 are in close contact with the inner circular surface of the fan-shaped limiting groove. The gaps between adjacent two magnet units 131 will embed the iron core ridges 123. The width of the magnet gap 132 between adjacent two magnet units 131 matches the width of the iron core ridge 123 to ensure that each magnet unit 131 will not have tangential displacement.

[0065] As Figure 8 shown, the carbon fiber bracket 14 further includes an inner ring connecting rib 143. The n bracket main body ribs 141 are arranged radially along the inner ring connecting rib 143. The n bracket main body ribs 141 are located in the n magnet gaps 132. The n bracket main body ribs 141 are arranged at equal angular intervals along the inner ring connecting rib 143. The bracket main body ribs 141 are accommodated in the magnet gaps 132 to press the magnet units 131 and the iron core units 121 and are fixed to the main body.

[0066] Specifically, the main body part of each bracket main body rib 141 is accommodated in the magnet gap 132 between adjacent two magnet units 131, and the main body part of the bracket main body rib 141 presses the magnet unit 131 and the iron core unit 121. The locking bolt holes 142 at the ends of the bracket main body ribs 141 are fixed to the circumferentially arranged axial bolt holes 114 on the main body.

[0067] When n is equal to 10, the carbon fiber bracket is as Figure 8 shown. To avoid the inner side bearing bush and bearing space, no axial locking related structure is designed on the inner ring of the main body. The locking bolt holes 142 reserved at the ends of the bracket main body ribs 141 of the carbon fiber bracket 14 are locked and fixed with the circumferentially arranged axial bolt holes 114 on the outer circle of the main body, and the bracket main body ribs 141 will be pressed into the gaps between adjacent two magnet gaps 132 to axially limit the magnet units and the iron core units.

[0068] Furthermore, in the two rotor disc structures, the first main body 11 connected to the rotating shaft is made of the same permeable structural steel material as the rotating shaft, and together with the segmented iron core group 12, it constitutes the main magnetic path of the yoke of the rotor. Ten arc-shaped protrusions are arranged on the outer circumference of the rotor back plate, corresponding to the inter-pole positions of each pole. Axial bolt holes 114 are opened inside the protrusions to make axial connections with the locking bolt holes 142 at the ends of the support body ribs 141 of the carbon fiber support 14, so that the main body structures of the first rotor disc 1 and the second rotor disc 2 respectively form a stable and connected whole, offsetting the huge centrifugal force generated by the permanent magnets and the segmented iron cores during the high-speed rotation of the rotor.

[0069] In the rotor system of this application, since the main body is not of the traditional segmented or laminated structure, if it directly contacts the segmented permanent magnet group 13, relatively large eddy current losses will be generated inside the back plate. Although the design of the integral main body structure improves the mechanical strength, relevant designs for reducing eddy current losses are thus required. Therefore, a segmented iron core group 12 is added between the main body and the segmented permanent magnet group 13, which not only increases the buffer to reduce eddy current losses but also plays a role in fixing the segmented permanent magnet group 13. The segmented iron core group 12 is made of soft magnetic composite material SMC. The thickness of the segmented iron core group 12 and the thickness of the rotor back plate are reasonably optimized to not only ensure the strength support of the main body for the entire rotor but also effectively reduce the eddy current losses of the back plate. Since the manufacturing process of the soft magnetic composite material SMC is powder pressing, the relatively large SMC iron core will cause great difficulties in the pressing process and die processing. Therefore, this design adopts a segmented iron core structure to reduce the process difficulty. The segmented iron core group 12 is arranged in the fan-shaped ring limiting groove. The gap width between the iron core units matches the width of the reinforcing ribs. And iron core ribs 123 are also designed on the side of the iron core unit facing the permanent magnet unit to play a circumferential limiting role for the permanent magnet unit.

[0070] The axial limitation of each iron core unit 121 and permanent magnet unit 131 is achieved through the carbon fiber support. The carbon fiber support 14 includes ten support body ribs 141, which are respectively located between the ten permanent magnet units 131. Locking bolt holes 141 are opened on the outermost sides of the support body ribs 141. The carbon fiber support 14 is fixed to the back plate through the axial bolt holes 114 of the arc-shaped protrusions on the outside of the main body. At the same time, the carbon fiber support 14 axially presses the segmented permanent magnet group 13 and the segmented iron core group 12 to prevent the permanent magnets and the iron cores from axially detaching from the main body during high-speed rotation, forming a stable structure.

[0071] The rotor system of the present application, the main body provides mechanical support. While overcoming the axial suction force between the stator and the rotor, it also participates in the construction of the main magnetic circuit of the rotor, acting as a part of the yoke magnetic circuit. At the same time, a segmented iron core group 12 filled with SMC iron core is filled between the main body and the segmented magnet group 13, acting as an isolation layer, effectively reducing the eddy current loss of the back plate. The carbon fiber bracket 14 and the main body adopt an outer circle axial bolt locking method, releasing the internal design space of the rotor disc, improving the structural strength and load-bearing capacity of the entire shafting and bearings, making the structure more compact, and greatly improving the torque density.

[0072] In one embodiment, side bosses 133 are provided on both straight sides of each magnet unit 131. The side bosses 133 of adjacent two 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 bosses 133; the magnet gap 132 uses the part other than the side bosses 133 to accommodate the bracket main body rib 141, and adjacent two side bosses 133 are pressed by one bracket main body rib 141.

[0073] In the rotor system of the present application, side bosses 133 are provided on both straight sides of each magnet unit 131. When the carbon fiber bracket 14 is fixed to the main body, the bracket main body rib 141 of the carbon fiber bracket 14 is embedded in the magnet gap 132 and pressed by the side bosses 133, and the iron core rib 123 is embedded between adjacent side bosses 133. The iron core unit is embedded in the fan-shaped ring limit groove. The main body, the segmented iron core group 12, the segmented magnet group 13 and the carbon fiber bracket 14 form a circumferential rigid limit with each other and rotate synchronously. The structural design is ingenious, 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 both straight sides of the magnet unit 131. The height of the side bosses 133 is the same as the height of the iron core rib 123. Both the inner and outer sides of the magnet unit 131 are processed in an arc shape. The outer circular surface of the magnet unit 131 is closely attached to the outer circular boss of the rotor back plate to prevent the magnet from radially coming off due to the centrifugal force during high-speed rotation. The inner circular arc of the magnet is closely attached to the inner circle of the carbon fiber bracket. C corners are designed at the two vertexes of the inner circle of the magnet unit 131 instead of rounded corners to reduce the processing difficulty. Since the peak speed of the motor is relatively high, each pole magnet is radially divided into 20 segments to reduce the eddy current loss. To prevent the situation of extremely short side edges for each segment of the magnet, the magnet segmentation method is to evenly divide the magnet side into 20 segments.

[0075] Due to the relatively high peak speed of the axial flux motor, to avoid too large eddy current loss under high-speed operation, each magnet unit 131 adopts a segmented bonding method, and the number of segments is relatively large. The bonding adhesive is used as the insulation boundary between segments. To avoid interference with the carbon fiber bracket and at the same time reduce the processing difficulty, a larger C angle processing method is adopted at the two vertexes of the inner circle of the magnet unit 131, and the C angle covers both the magnet main body and the side boss structure at the same time.

[0076] In one embodiment, glue filling treatment is carried out between the clearance of the sector-ring limiting groove and the segmented iron core group 12, between the clearance of the segmented iron core group 12 and the segmented permanent magnet group 13, and between the clearance of the permanent magnet clearance 132 of the segmented iron core group 12 and the segmented permanent magnet group 13 and the contact part of the carbon fiber bracket 14, so as to form the main structure of the rotor disc. Such a glue filling form can make the segmented iron core group 12, the segmented permanent magnet group 13 and the carbon fiber bracket 14 form a stable whole, and avoid designing an axial fixing structure in the middle of the rotor disc, strengthen the structural strength of the inner circle side, avoid the inner circle side of the segmented iron core group 12 and the segmented permanent magnet group 13 peeling and yawing from the main body during high-speed operation, thus causing rubbing, making the overall structure more compact and improving the torque density.

[0077] Specifically, the main body refers to the first main body 11 and the second main body 21. The connection forms of the first main body 11 and the second main body 21 with their respective segmented iron core groups 12, segmented permanent magnet groups 13, and carbon fiber brackets 14 are the same, and glue filling treatment is carried out on all of them.

[0078] Preferably, a high-temperature resistant glue will be selected as the bonding glue to avoid the glue failure caused by excessive temperature rise of the rotor at high speed.

[0079] In one embodiment, the depth of the permanent magnet clearance 132 is greater than or equal to the sum of the height of the iron core rib 123 and the thickness of the bracket main rib 141 of the carbon fiber bracket 14, making full use of the permanent magnet clearance 132 to connect and form two independent rotor main body structures. While ensuring the structural stability, it occupies as little space in other places as possible, maximizing the space utilization rate and improving the torque density.

[0080] In one embodiment, the end of the rotating shaft 17 includes an external spline section 171 and an external thread section 172 from the inside to the outside (see Figure 4 ), an internal spline hole 211 is opened in the center of the main body (i.e., the second main body 21) of the second rotor disc 2, and the internal spline hole 211 is matched with the external spline section 171 to form a main body structure form of synchronous rotation. The external thread section 172 presses the main body (i.e., the second main body 21) of the second rotor disc 2 through an axial locking nut 25.

[0081] In the rotor system of the present application, the second body 21 and the rotating shaft 17 are connected by a spline connection. An internal spline hole 211 is provided in the center of the second body 21, and an external spline section 171 is provided at the end of the rotating shaft 17. This connection method greatly saves the radial assembly space and makes the overall structure more compact. The spline fit disperses the traditional flat key or even convex key scheme that occupies more radial dimensions into a small tooth groove fit method evenly distributed in a circle, greatly reducing the radial space occupation while achieving the same torque transmission capacity. This method of integral machining plus spline fit greatly reduces the axial space occupation of the mating features between the rotor back plate and the rotating shaft, allowing for a larger design space for the bearing and shafting dimensions to ensure structural strength, and greatly improving the torque density. The assembly of the second body 21 and the rotating shaft 17 will be 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] As Figure 3 and Figure 4 shown, in one embodiment, the main body includes a large circular surface boss 119 provided at the center of the plane where the rotating shaft 17 is located, and a thin convex plate 111 provided at the circular periphery; n reinforcing rib structures 112 are provided between the large circular surface boss 119 and the thin convex plate 111, enclosing n sector ring limiting grooves. An avoidance notch 113 for the bracket main body rib 141 of the carbon fiber bracket 14 to pass through is provided on the thin convex plate 111 adjacent to the axial bolt hole 114.

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

[0084] On the side of the outer circular surface of the main body facing the magnetic steel, there is a thin convex plate 111, which plays a role in forming the sector ring limiting groove, protecting each magnetic steel unit 131 and the iron core unit 121, and offsetting the huge centrifugal force generated by the magnetic steel unit 131 and the iron core unit 121 during the high-speed rotation of the rotor; each reinforcing rib structure 112 corresponds to the center line position of each pole of the magnetic steel, and the reinforcing rib structure 112, the large circular surface boss 119, and the thin convex plate 111 together constitute circumferential and radial limits.

[0085] As Figure 3 、 Figure 4 and Figure 11 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 external spline section 171 is also perpendicular to the axis of the positioning hole 116.

[0086] Taking Figure 3 the projection direction where it is located, the center line of the reinforcing rib structure 112 coincides with the center line of one of the spline grooves of the external spline section 171 and passes through the center of the positioning hole 116 at the same time.

[0087] On the back surface of the main body of the second rotor disk 2, a positioning groove 23 is provided. 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 internal spline hole 211.

[0088] In Figure 11 the projection direction where it is located, the center lines of the positioning groove 23, one of the spline teeth of the internal spline hole 211, and the center line of the positioning groove 23 coincide with each other.

[0089] For the rotor system of the present application, by cleverly arranging the positioning holes 116 and the positioning grooves 23, the straight pole structure is maintained. Specifically, since spline fitting is adopted between the second main body 21 and the rotating shaft 17, the angle of the second main body 21 relative to the first main body 11 is not continuously adjustable, and the minimum adjustable angle depends on the number of teeth of the spline. Since the dual-rotor system is designed for straight pole connection, if the spline fitting cannot ensure that the magnetic poles of the first rotor disk 1 and the second rotor disk 2 completely correspond, it will lead to a decline in the performance of the axial flux motor. Therefore, the positioning holes 116 and the positioning grooves 23 are designed to ensure that the magnetic poles of the first rotor disk 1 and the second rotor disk 2 completely correspond.

[0090] Specifically, in Figure 3 the projection direction where it is located, the center line of the reinforcing rib structure 112 coincides with the center line of one of the spline grooves of the external spline section 171, and at the same time passes through the center of the positioning hole 116. In Figure 11 the projection direction where it is located, the center lines of the positioning groove 23, one of the spline teeth of the internal spline hole 211, and the center line of the positioning groove 23 coincide with each other. In this way, when the second rotor disk is spline-engaged with the rotating shaft, it can be ensured that each pole of the left and right disks can completely correspond, ensuring that the two rotor disks maintain a straight pole structure.

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

[0092] The rotor system further 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 back to back and symmetrically, and are both sleeved outside the steel bushing 18.

[0093] The two sides of the inner ring of the left bearing 15 respectively abut against the small circular surface convex platform 117 of the first main body 11 and one side of the steel bushing 18; the outer ring of the left bearing 15 is abutted and fixed by the bearing bushing 16.

[0094] Gaskets 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 circular surface convex platform 117.

[0095] The first body 11 is integrally machined with the rotating shaft 17. In the whole assembly process, the left bearing is first pressed onto the rotating shaft 17 by interference fit. One side of the inner ring of the left bearing abuts against the pressing small circular surface boss 117. Then, the steel bushing 10 is nested on the shaft and abuts against the other side of the inner ring of the left bearing axially. Subsequently, the first body 11 and the left bearing are pressed into the left bearing bushing as a whole. A first set of gaskets 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 passes through the inner circular through-hole of the stator. Then, the right bearing is pressed into the right bearing bushing from the right side simultaneously. An interference fit is maintained between the right bearing and the shaft, and a clearance fit is maintained between the right bearing and the right bearing bushing. The inner ring of the right bearing abuts against the steel bushing 10 from the right side. At the same time, a second set of gaskets is designed between the outer ring of the right bearing and the end face of the right bearing bushing to neutralize the cumulative dimension chain deviation. After that, the assembled second rotor disk 2 enters the shaft from the spline side at the right end. The inner spline hole 211 cooperates with the outer spline section 171. A third set of gaskets is designed between the small circular surface boss 117 of the second body 12 and the inner ring of the right bearing. The thickness adjustment of the second set of gaskets and the third set of gaskets jointly ensure 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 the present application, a set of gaskets is provided 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 surface boss 117 of the second body 12. These three sets of gaskets are designed to adjust the axial relative positions between the two rotor disks and the stator, so as to offset the problem of uneven air gap thickness caused by the superposition of the axial dimension chains of the entire stator-rotor system, and avoid generating a large axial eccentric force, which causes a large axial load on the entire shafting and leads to the failure of the shafting structure. At the same time, a steel bushing is arranged between the left and right bearings to provide a rigid connection between the two bearings, complete the dimension chain transfer between the two rotor disks, and avoid the relative slip of the inner ring of the right bearing towards the left bearing during the operation of the motor, resulting in the failure of the stability of the entire shafting.

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

[0098] In one embodiment, a concave groove is provided on the main body of the second rotor disc 2 facing away from the reinforcing rib structure 112. The concave 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 are both lower than the end face of the main body of the second rotor disc 2, which can minimize the occupied space as much as possible, ensure that the axial locking nut 22 contacts the main body surface, and avoid too small pressing force.

[0099] In the description of the present application, it should be noted that the orientation or positional relationship indicated by terms such as "upper" and "lower" is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of the present application. Unless otherwise clearly specified and limited, the terms "mounted", "connected" and "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0100] It should be noted that in the present application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including the element.

[0101] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will 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 comprises 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 the first rotor disk; the end of the rotating shaft (17) is connected to the main body of the second rotor disk (2) via a spline; Each rotor disk further comprises a segmented iron core group (12), a segmented magnetic steel group (13) and a carbon fiber bracket (14) from near to far relative to the main body, wherein the carbon fiber bracket (14) comprises a plurality of bracket main body ribs (141) radially arranged at equal angles from the center; a locking bolt hole (142) is reserved at the end of each bracket main body rib (141); Axial bolt holes (114) are arranged around the body, and the axial bolt holes (114) of the body are fixed to the locking bolt holes (142) of the carbon fiber bracket (14) through fixing parts, and the segmented iron core group (12) and the segmented magnetic steel group (13) are clamped, and each bracket body rib (141) is embedded in the gap of the segmented magnetic steel group (13).

2. The rotor system of a high torque density axial flux motor according to claim 1, characterized in that: n sector ring limiting grooves are evenly divided on opposite sides of the main bodies of the two rotor disks; The segmented iron core group (12) comprises n sector ring-shaped iron core units (121), the n iron core units (121) are filled and arranged in n sector ring limiting grooves, and each iron core unit (121) is provided with an iron core convex strip (123) at the central position of the oblique edges on both sides; The segmented magnetic steel group (13) comprises n sector-shaped magnetic steel units (131), each of the magnetic steel units (131) is arranged between two adjacent iron core convex strips (123), and a magnetic steel gap (132) is provided between two adjacent magnetic steel units (131); The carbon fiber bracket (14) further comprises an inner ring connecting rib (143), n bracket main body ribs (141) are radially arranged along the inner ring connecting rib (143), and the n bracket main body ribs (141) are located in n magnetic steel gaps (132).

3. The rotor system of a high torque density axial flux motor according to claim 2, characterized in that: The two straight sides of each magnetic steel unit (131) are provided with side bosses (133); the side bosses (133) of two adjacent magnetic steel 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 bosses (133); the magnetic steel gap (132) uses the portion other than the side bosses (133) to accommodate the bracket main body rib (141), and two adjacent side bosses (133) are pressed by one of the bracket main body ribs (141).

4. The rotor system of a high torque density axial flux motor according to claim 2, characterized in that: Glue filling is performed between the sector ring limit groove and the gap of the segmented iron core group (12), between the gap of the segmented iron core group (12) and the segmented magnetic steel group (13), and between the gap at the contact point between the magnetic steel gap (132) of the segmented iron core group (12) and the segmented magnetic steel group (13) and the carbon fiber bracket (14) to form an integral structure of the rotor disk.

5. The rotor system of a high torque density axial flux motor according to claim 2, 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 support body rib (141) of the carbon fiber support (14).

6. The rotor system of a high torque density axial flux motor according to claim 1, characterized in that: The ends of the rotating shaft (17) respectively include an external spline section (171) and an external thread section (172) from the inside to the outside; an internal spline hole (211) is provided at the center of the main body of the second rotor disk (2), and the internal spline hole (211) is matched with the external spline section (171); the external thread section (172) is pressed against the main body of the second rotor disk (2) through an axial locking nut (22).

7. The rotor system of a high torque density axial flux motor according to claim 2, characterized in that: The main body comprises a large circular boss (119) arranged at the center of the surface where the rotating shaft (17) is located, and a thin convex plate (111) arranged at the edge of the circular periphery; n reinforcing rib structures (112) are arranged between the large circular boss (119) and the thin convex plate (111) to enclose and form n sector ring limiting grooves; each reinforcing rib structure (112) corresponds to the center line position of a magnetic steel unit (131); and an avoidance notch (113) for the support main body rib (141) to pass through is provided on the thin convex plate (111) adjacent to the axial bolt hole (114).

8. The rotor system of a high torque density axial flux motor according to claim 7, characterized in that: A positioning hole (116) is provided on the end surface 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 external spline segment (171) is also perpendicular to the axis of the positioning hole (116); A positioning groove (23) is provided on the back side of the main body of the second rotor disk (2), 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).

9. The rotor system of a high torque density axial flux motor according to claim 7, characterized in that: A small circular boss (117) is arranged on the side of the large circular boss (119); the rotor system further comprises a steel shaft sleeve (18), a pair of bearings (15) and a pair of bearing bushings (16); the steel shaft sleeve (18) is sleeved on the rotating shaft (17); the pair of bearing bushings (16) are arranged back to back and symmetrically, and are both sleeved outside the steel shaft sleeve (18); The inner ring of the left bearing (15) is respectively abutted against the small circular boss (117) of the main body of the first rotor disk (1) and one side of the steel sleeve (18); the outer ring of the left bearing (15) is abutted and fixed by the bearing bushing (16); gaskets for adjusting the air gap thickness are arranged 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 circular boss (117).

10. The rotor system of a high torque density axial flux motor according to claim 7, 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, and the inner recessed groove is used to accommodate the axial locking nut (22); after the axial locking nut (22) is matched with the external thread section (172), the outer end surfaces of the external thread section (172) and the axial locking nut (22) do not extend beyond the outer end surface of the main body of the second rotor disk (2).

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