A dual-rotor axial flux generator using a hybrid unequal-thickness Halbach permanent magnet array

Abstract

The present invention relates to the technical field of permanent magnet synchronous generators, specifically a dual-rotor axial flux generator using a mixed unequal thickness Halbach permanent magnet array, comprising a rotor part, a stator part, and a casing, wherein the rotor part comprises a rotor bracket and a mixed unequal thickness Halbach permanent magnet array; the stator part comprises a stator bracket, a modular stator core, and a fractional slot concentrated winding; the casing part comprises bearings on both sides, an output casing, and a fixed casing, and the stator-rotor bracket, the fixed casing, and the output casing are all made of 3D printed POM materials; the rotor bracket is conical and hollow; the modular stator core is made of silicon steel stacked in radial positive and negative directions. Compared with the prior art, the 3D printed axial flux generator of the present invention has short axial dimensions, small volume, small mass, high power density, and low cost, and can achieve "light wind start-up and light wind power generation", and also has the advantages of high efficiency, low loss, high mechanical strength, and good stability.

Description

Technical Field

[0001] The invention relates to the technical field of permanent magnet synchronous generators, in particular to a dual-rotor axial flux generator adopting a mixed unequal thickness Halbach permanent magnet array. Background Art

[0002] The use of wind energy as an alternative energy source for power generation is increasing. With the continuous innovation of manufacturing technology, the discovery and improvement of new materials, the application of axial flux permanent magnet generators in small wind turbines is increasing. This puts higher requirements on small axial flux wind turbines, which should have the characteristics of small mass, low cost, high power density, high efficiency, high mechanical strength, good stability, easy starting and easy power generation.

[0003] Traditional axial flux generators generally use magnetic conductive metal to make the rotor back iron, and the permanent magnets are attached to the rotor back iron. The stator core is made of laminated silicon steel sheets, and the stator has a yoke. Due to the high metal density and large rotor mass, the surface-mounted magnetic steel is not stable, the starting torque is large, the generator is difficult to start, the stator core has low mechanical strength, and the loss is also large. The motor power density is not high, the efficiency is low, and the cost is high. For motors using Halbach permanent magnet arrays, the thickness of the magnetic steel in the two magnetizing directions is the same, and the permanent magnets cover the circumference of the rotor. However, rare earth permanent magnet materials are expensive and account for most of the motor cost, so the motor cost is high.

[0004] After searching, the Chinese patent publication number CN214850853U discloses a disc-type coreless generator, which includes a disc-type casing, a permanent magnet turntable and two sets of stator winding assemblies, the permanent magnet turntable is built into the disc-type casing, the permanent magnet turntable is configured on the shaft, the shaft is rotatably connected to the disc-type casing, the two sets of stator winding assemblies are symmetrically arranged at both ends of the permanent magnet turntable, the stator winding assembly is fixed to the inner wall of the disc-type casing, a number of fan blades are evenly distributed on the circumferential surface of the permanent magnet turntable, a number of air inlets are distributed on the two end faces of the disc-type casing, and a number of air outlets are distributed on the circumferential surface of the disc-type casing, which can increase the air intake in the casing and improve the cooling efficiency. However, the motor has no iron core, a large air gap length, low motor power density, low efficiency, and requires more permanent magnet materials to construct a magnetic field, which is costly.

[0005] In addition, after searching, the Chinese patent publication number CN109690926A discloses an axial flux generator, which includes two magnetic rings and a coil ring, and the magnetic ring and the coil ring have a common axis; the two magnetic rings define multiple magnetic fields around the common axis and extending across the gap between the two magnetic rings, and the coil ring has a series of coils around the common axis in the gap, so that the magnetic flux lines from the magnetic field cut multiple turns of coils, thereby generating induced current in the coil when the magnetic ring rotates relative to the coil ring; its advantage is that the coil includes a wound flat strip conductor. However, the generator is a multi-disc mechanism, the permanent magnet is attached to the metal, and a lot of permanent magnetic materials are required, the generator is heavy, difficult to start, low in efficiency, and high in cost. Summary of the invention

[0006] The object of the present invention is to provide a dual-rotor axial flux generator using a mixed unequal thickness Halbach permanent magnet array to solve the problems raised in the above background technology.

[0007] The technical solution of the present invention is: a dual-rotor axial flux generator using a mixed unequal thickness Halbach permanent magnet array, comprising a rotor part, a stator part and a casing part, wherein the rotor part comprises a rotor bracket and a at both sides, wherein two parts of the mixed Halbach permanent magnet array and a with unequal thickness are respectively placed in the hollow inner sides of the rotor bracket and a, and the rotor bracket and the remaining part on the back side are potted with potting glue;

[0008] The stator part includes a stator support, a modular stator core and a fractional slot concentrated winding between the two rotor parts, and the stator core is fixed on the stator support after the coil is wound;

[0009] The casing part includes an outermost output casing, a fixed casing and bearings on the two casings.

[0010] Preferably, the two parts of the mixed Halbach permanent magnet array of unequal thickness are connected to two rotor brackets and are free of rotor yokes, and the two rotor brackets and are both made of 3D printed POM material.

[0011] Preferably, the two parts of the unequal thickness mixed Halbach permanent magnet array both use 7 pairs of poles, and the axially magnetized magnetic steels facing each other in the permanent magnet arrays on both sides are NS poles facing each other; the axially magnetized magnetic steels are trapezoidal and made of NdFeB N35 material, and the circumferentially magnetized magnetic steels are square and made of NdFeB N25 material; the thickness of the axially magnetized magnetic steels is greater than the thickness of the circumferentially magnetized magnetic steels.

[0012] Preferably, the two parts of the rotor bracket and are conical hollow structures, and the thickness of the two parts of the rotor bracket and are greater than the thickness of the permanent magnet; the inner and outer diameters of the side of the hollow cone facing the stator are smaller than the inner diameter of the permanent magnet, and the inner and outer diameters of the other side are greater than the outer diameter of the permanent magnet, and the potting glue pots the two parts of the rotor bracket and the side facing away from the stator; the inner diameter of the two parts of the rotor bracket and is the inner diameter of the bearing, and the rotor part is fixed on the shaft.

[0013] Preferably, there are 12 modular stator cores, which are made of silicon steel material stacked in radial direction, and the motor has no stator yoke.

[0014] Preferably, the fractional-slot concentrated winding has 12 coils with a pitch of 1, and the 12 coils are respectively wound on each modular stator core.

[0015] Preferably, the stator bracket is made of 3D printed POM material, 12 supporting prisms divide the stator bracket into 12 empty bayonet holes, the modular stator core is fixed to the stator bracket by the bayonet holes after the coil is wound, and the remaining part of the bayonet hole is sealed with a hot melt glue stick with a softening point of 65°C; the inner diameter of the stator bracket is larger than the inner diameter of the bearing, the outer diameter of the stator bracket is the same as the outer diameter of the ear of the output casing, 8 bolt holes are opened on the outer diameter side of the stator bracket, and the stator bracket is fixed to the casing.

[0016] Preferably, the output housing and the fixed housing are both made of 3D printed POM material, and are each equipped with a bearing at the inner diameter.

[0017] Preferably, the output housing is provided with four fan-shaped ventilation holes.

[0018] Preferably, the two ears of the casing facing each other have the same outer diameter as the stator bracket, the positions and sizes of the bolt holes of the three are the same, the outer diameter of the ear of the fixed casing facing away from the stator is larger than the outer diameter of the inner ear, and four bolt holes are provided on the ear of the fixed casing facing away from the stator.

[0019] The present invention provides a dual-rotor axial flux generator using a mixed unequal thickness Halbach permanent magnet array through improvement, which has the following improvements and advantages compared with the prior art:

[0020] First, the rotor bracket, stator bracket and casing of the present invention are all made of 3D printed POM materials, which makes the motor more precise, lighter and less expensive, so that the generator can achieve "light wind start and light wind power generation";

[0021] Second, the generator structure of the present invention is a double outer rotor single stator, the magnetic tension is balanced, the stator has no magnetic yoke, the rotor part adopts Halbach permanent magnet array, there is no rotor magnetic yoke, the stator loss is small, there is no eddy current loss of the rotor back iron, and the motor has higher power density and efficiency;

[0022] Thirdly, the present invention adopts unequal thickness hybrid Halbach permanent magnet arrays for the two parts of the rotor, and the axial magnetized magnetic steels of the permanent magnet arrays on both sides are opposite to each other with NS poles; the axial magnetized magnetic steels are made of NdFeB N35 material, and the circumferential magnetized magnetic steels are made of NdFeB N25 material; the axial magnetized magnetic steels are thicker than the circumferential magnetized magnetic steels, thus enhancing the air gap magnetic flux density, improving the sinusoidality of the air gap magnetic flux density waveform, reducing the cost, and reducing the mass of the rotor part;

[0023] Fourthly, the present invention sets both rotor brackets to be conical hollow structures, the thickness of which is larger than that of the permanent magnet; the inner and outer diameters of the side of the hollow cone facing the stator are smaller than the inner and outer diameters of the permanent magnet, and the inner and outer diameters of the other side are larger than the inner and outer diameters of the permanent magnet. After the permanent magnet is placed, the side of the rotor bracket facing away from the stator is potted with potting glue; thus, the mechanical stability of the motor during operation is increased;

[0024] Fifth, the modular stator core of the present invention is made of silicon steel material laminated in radial direction, which has greater mechanical strength than traditional silicon steel sheet lamination. The generator pole slot combination is 14 poles and 12 slots, which is a fractional slot unit motor, weakening tooth harmonics and reducing tooth slot torque. The coil pitch is 1, which shortens the coil circumference and the extension length of the winding end, reduces the amount of copper used, reduces copper loss, and improves motor efficiency. The ends of the coils do not overlap, and there is no need to set phase-to-phase insulation, which reduces economic costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be further explained below in conjunction with the accompanying drawings and embodiments:

[0026] Figure 1 It is a structural exploded diagram of the present invention;

[0027] Figure 2 It is a partial magnetic circuit schematic diagram of the present invention;

[0028] Figure 3 It is a schematic diagram of the permanent magnet structure of the present invention;

[0029] Figure 4 is a schematic diagram of the top view of the rotor support on the output casing side of the present invention;

[0030] Figure 5 It is a schematic diagram of the top view structure of the stator bracket of the present invention;

[0031] Figure 6 is a schematic diagram of winding connection of the present invention;

[0032] Figure 7 It is a schematic diagram of the top view of the output housing of the present invention;

[0033] Figure 8 It is a schematic diagram of the top view structure of the fixed casing of the present invention.

[0034] Description of reference numerals:

[0035] Rotor part 1, rotor bracket 1-1 on the output casing side, rotor bracket 1-2 on the fixed casing side, unequal thickness mixed Halbach permanent magnet array 1-3 on the output casing side, unequal thickness mixed Halbach permanent magnet array 1-4 on the fixed casing side, conical hollow part 1-1-1 of the rotor bracket on the output casing side, two adjacent axial magnetized permanent magnets 1-3-1 and 1-3-1' on the output casing side, circumferential magnetized permanent magnet 1-3-2 in the middle, two axial magnetized permanent magnets 1-4-1 and 1-4-1' opposite to each other on the fixed casing side, circumferential magnetized permanent magnet 1-4-2 in the middle, stator part 2, stator bracket 2-1, stator fractional slot concentrated winding 2-2, mold Block stator core 2-3, stator bracket prism 2-1-1, fixing bolts 2-1-2 on stator bracket, two adjacent modular stator cores 2-3-1 and 2-3-1', casing part 3, output casing 3-1, fixed casing 3-2, output casing side bearing 3-3, fixed casing side bearing 3-4, output casing side ear 3-1-1, fixing bolts 3-1-2 on output casing side ear, output casing side ventilation hole 3-1-3, fixed casing side ear 3-2-1 for fixing motor, fixed casing side ear 3-2-2 for fixing stator bracket, fixed casing side bolt 3-2-3 for fixing motor, fixed casing side bolt 3-2-4 for fixing stator bracket. DETAILED DESCRIPTION

[0036] The present invention is described in detail below, and the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] The present invention provides a dual-rotor axial flux generator using a mixed unequal thickness Halbach permanent magnet array through improvement. The technical solution of the present invention is:

[0038] like Figure 1-Figure 8 As shown, a dual-rotor axial flux generator using a mixed unequal thickness Halbach permanent magnet array includes a rotor part 1, a stator part 2, and a casing part 3.

[0039] The rotor part 1 includes rotor brackets 1-1 and 1-2 on both sides. The conical hollows of the rotor brackets 1-1 and 1-2 respectively place two parts of mixed Halbach permanent magnet arrays 1-3 and 1-4 of unequal thickness. The remaining parts on the back of the rotor brackets 1-1 and 1-2 are potted with potting glue.

[0040] The stator part 2 includes a stator support 2-1, a modular stator core 2-3, and a fractional slot concentrated winding 2-2 between the two rotors. The stator core is fixed on the stator support 2-1 after the coil is wound.

[0041] The housing portion 3 includes an outermost output housing 3-1, a fixed housing 3-2, and bearings 3-3 and 3-4 on the two housings.

[0042] The two rotor brackets 1-1 and 1-2, the stator bracket 2-1, and the two housings 3-1 and 3-2 are all made of 3D printed POM material.

[0043] The rotor part 1 has no yoke, and the two rotor brackets 1-1 and 1-2 are conical hollow structures with a thickness larger than that of the permanent magnet; the inner and outer diameters of the side of the hollow cone facing the stator are smaller than the inner and outer diameters of the permanent magnet, and the inner and outer diameters of the other side are larger than the inner and outer diameters of the permanent magnet. After placing the permanent magnet, the side of the rotor brackets 1-1 and 1-2 facing away from the stator is potted with potting glue; the inner diameter of the two-part rotor brackets 1-1 and 1-2 is the inner diameter of the bearing, and the rotor part 1 is fixed on the shaft and rotates with the shaft; the two parts of the unequal thickness hybrid Halbach permanent magnet arrays 1-3 and 1-4 both use 7 pairs of poles, and the axially magnetized magnetic steels facing the permanent magnet arrays on both sides have opposite polarities; the axially magnetized magnetic steel is trapezoidal and uses NdFeB N35 material, and the circumferentially magnetized magnetic steel is square and uses NdFeB N25 material; the axially magnetized magnetic steel is thicker than the circumferentially magnetized magnetic steel.

[0044] The stator part 2 has no yoke, and there are 12 modular stator cores 2-3, which are made of silicon steel material and stacked in reverse along the radial direction. The fractional slot concentrated winding 2-2 has 12 coils with a pitch of 1, which are wound on each modular stator core 2-3 respectively; the stator bracket 2-1 has 12 supporting prisms 2-1-1 to divide it into 12 empty bayonet holes. After the modular stator core 2-3 is wound with coils, it is fixed on the stator bracket 2-1 by the bayonet holes, and the remaining part of the bayonet is melted and sealed with a hot melt glue stick with a softening point of 65°C; the inner diameter of the stator bracket 2-1 is slightly larger than the inner diameter of the bearing, and the outer diameter is the same as the outer diameter of the ear 3-1-1 of the output casing 3-1, and 8 bolt holes 2-1-2 are opened on the outer diameter side, and the stator bracket 2-1 is fixed to the casing.

[0045] The output housing 3-1 is provided with four fan-shaped ventilation holes 3-1-3. The ears 3-1-1 and 3-2-2 facing each other on the two housings have the same outer diameter as the stator bracket 2-1. The bolt holes of the three are in the same position and size for fixing. The ear 3-2-1 for fixing the motor on the side of the fixed housing facing away from the stator has a larger outer diameter and is provided with four bolt holes 3-2-3, which are slightly larger than the bolt holes of the inner ear for fixing the motor.

[0046] Working principle:

[0047] like Figure 1 The figure shows the exploded view of the overall structure of the motor. The generator is a double outer rotor single stator structure with 14 poles and 12 slots, which is a fractional slot unit motor. The rotor part combines the Halbach array with the rotor without yoke, and the stator part adopts a yoke-free modular stator core. Each stator core is made of silicon steel material stacked in radial positive and negative directions to increase the mechanical strength. The rotor bracket, stator bracket, and casing are 3D printed POM materials to reduce losses, reduce motor quality and economic costs. The generator has high power density and high efficiency, and can "start with light wind and generate electricity with breeze".

[0048] like Figure 2 As shown, it is a schematic diagram of part of the magnetic circuit of the motor. The magnetic flux starts from the axially magnetized magnetic steel 1-4-1 on the fixed casing side, passes through the air gap on the fixed casing side, the modular stator core 2-3-1, the air gap on the output casing 3-1 side, the axially magnetized magnetic steel 1-3-1 on the output casing 3-1 side, the circumferentially magnetized magnetic steel 1-3-2 on the output casing 3-1 side, and the adjacent axially magnetized magnetic steel 1-3-1' on the output casing 3-1 side, and then passes through the air gap on the output casing 3-1 side, the modular stator core 2-3-1', the air gap on the fixed casing side, the axially magnetized magnetic steel 1-4-1' on the fixed casing side, and the circumferentially magnetized magnetic steel 1-4-2 on the fixed casing side, and returns to the axially magnetized magnetic steel 1-4-1 on the fixed casing side, thereby forming a closed loop.

[0049] like Figure 3 and Figure 4 As shown, it is a schematic diagram of the permanent magnet structure of the motor and a schematic diagram of the top view of the rotor bracket structure on the side of the output casing 3-1. The axially magnetized permanent magnet 1-3-1 is trapezoidal, and its thickness is larger than that of the square circumferentially magnetized permanent magnet 1-3-2; the rotor bracket 1-1 on the side of the output casing 3-1 has a conical hollow structure 1-1-1, and the inner and outer diameters of the hollow cone on the side facing the stator are smaller than the inner and outer diameters of the permanent magnet, and the inner and outer diameters on the other side are larger than the inner and outer diameters of the permanent magnet. After placing the permanent magnets, the side of the rotor bracket facing away from the stator is potted with potting glue, and the rotor on the fixed casing side has the same structure, which increases the mechanical stability of the motor during operation.

[0050] like Figure 5As shown, it is a schematic diagram of the top view of the stator bracket 2-1 of the motor. The stator bracket 2-1 has 12 supporting prisms 2-1-1 which divide it into 12 empty bayonet holes. The modular stator core is made of silicon steel material stacked in positive and negative directions along the radial direction to increase the mechanical strength of the stator core. Each modular stator core is fixed to the stator bracket by the bayonet after the coil is wound. The remaining part of the bayonet is melted and sealed with a hot melt glue stick with a softening point of 65°C; the inner diameter of the stator bracket is slightly larger than the inner diameter of the bearing, and the outer diameter is the same as the outer diameter of the ear 3-1-1 of the output housing 3-1. There are 8 bolt holes 2-1-2 on the outer diameter side, and the stator bracket is fixed to the housing.

[0051] like Figure 6 The figure shows the winding connection diagram of the motor. The motor is a 14-pole 12-slot fractional slot unit motor, the number of phases is 3, the number of parallel branches is 1, that is, each phase winding is composed of 4 stator coils connected in series.

[0052] like Figure 7 and Figure 8 As shown, it is a schematic diagram of the top view of the output housing 3-1 of the motor and a schematic diagram of the top view of the fixed housing 3-2. The output housing 3-1 has four fan-shaped ventilation holes 3-1-3. The ears 3-1-1 and 3-2-2 facing each other have the same outer diameter as the stator bracket 2-1. The positions and sizes of the bolt holes of the three are the same for fixing. The ear 3-2-1 of the fixed housing 3-2 that fixes the motor on the side facing away from the stator has a larger outer diameter and has four bolt holes 3-2-3 on it, which are slightly larger than the bolt holes of the inner ear, for fixing the motor.

[0053] The above description enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be 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 the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A dual-rotor axial flux generator using a mixed unequal thickness Halbach permanent magnet array, comprising a rotor part (1), a stator part (2) and a casing part (3), characterized in that: The rotor part (1) comprises rotor supports (1-1) and (1-2) on both sides, two parts of mixed Halbach permanent magnet arrays (1-3) and (1-4) of unequal thickness are respectively placed inside the hollow of the rotor supports (1-1) and (1-2), and the remaining parts of the back sides of the rotor supports (1-1) and (1-2) are potted with potting glue; The two parts of the unequal thickness hybrid Halbach permanent magnet arrays (1-3) and (1-4) both use 7 pairs of poles, and the axial magnetized magnetic steels of the permanent magnet arrays on both sides are NS poles opposite to each other; the axial magnetized magnetic steels are trapezoidal and made of NdFeB N35 material, and the circumferential magnetized magnetic steels are square and made of NdFeB N25 material; the thickness of the axial magnetized magnetic steels is greater than the thickness of the circumferential magnetized magnetic steels; The stator part (2) comprises a stator support (2-1) between the two rotor parts (1), a modular stator core (2-3) and a fractional slot concentrated winding (2-2), wherein the stator core is fixed on the stator support (2-1) after the coil is wound; The housing part (3) comprises an outermost output housing (3-1) (3-1), a fixed housing (3-2) and bearings (3-3) and (3-4) on the two housings.

2. A dual-rotor axial flux generator using a mixed unequal thickness Halbach permanent magnet array according to claim 1, characterized in that: The two parts of the mixed Halbach permanent magnet arrays (1-3) and (1-4) of unequal thickness are connected to the two rotor brackets (1-1) and (1-2), without a rotor yoke, and the two rotor brackets (1-1) and (1-2) are both made of 3D printed POM material.

3. The dual-rotor axial flux generator using a mixed unequal thickness Halbach permanent magnet array according to claim 1, characterized in that: The two rotor brackets (1-1) and (1-2) are conical hollow structures, and the thickness of the two rotor brackets (1-1) and (1-2) is greater than the thickness of the permanent magnet; the inner and outer diameters of one side of the hollow cone facing the stator are smaller than the inner diameter of the permanent magnet, and the inner and outer diameters of the other side are greater than the outer diameter of the permanent magnet; the potting glue pots the side of the two rotor brackets (1-1) and (1-2) facing away from the stator; the inner diameter of the two rotor brackets (1-1) and (1-2) is the inner diameter of the bearing, and the rotor part (1) is fixed on the shaft.

4. The dual-rotor axial flux generator using a mixed unequal thickness Halbach permanent magnet array according to claim 1, characterized in that: There are 12 modular stator cores (2-3) which are made of silicon steel material laminated in radial direction in both positive and negative directions, and the motor has no stator yoke.

5. The dual-rotor axial flux generator using a mixed unequal thickness Halbach permanent magnet array according to claim 1, characterized in that: The fractional slot concentrated winding (2-2) has 12 coils with a pitch of 1, and the 12 coils are respectively wound on each modular stator core (2-3).

6. The dual-rotor axial flux generator using a mixed unequal thickness Halbach permanent magnet array according to claim 1, characterized in that: The stator bracket (2-1) is made of 3D printed POM material, 12 supporting prisms (2-1-1) divide the stator bracket (2-1) into 12 empty bayonet holes, the modular stator core (2-3) is fixed on the stator bracket (2-1) by the bayonet holes after the coil is wound, and the remaining part of the bayonet is sealed with a hot melt glue stick with a softening point of 65°C; the inner diameter of the stator bracket (2-1) is larger than the inner diameter of the bearing, the outer diameter of the stator bracket (2-1) is the same as the outer diameter of the ear (3-1-1) of the output housing (3-1) (3-1), and 8 bolt holes (2-1-2) are opened on the outer diameter side of the stator bracket (2-1), and the stator bracket (2-1) is fixed on the housing.

7. The dual-rotor axial flux generator using a mixed unequal thickness Halbach permanent magnet array according to claim 1, characterized in that: The output housing (3-1) (3-1) and the fixed housing (3-2) are both made of 3D printed POM material, and are each equipped with a bearing (3-3) and (3-4) at the inner diameter.

8. The dual-rotor axial flux generator using a mixed unequal thickness Halbach permanent magnet array according to claim 1, characterized in that: The output housing (3-1) (3-1) is provided with four fan-shaped ventilation holes (3-1-3).

9. The dual-rotor axial flux generator using a mixed unequal thickness Halbach permanent magnet array according to claim 1, characterized in that: The ears (3-1-1) and (3-2-2) facing each other on the two casings have the same outer diameter as the stator bracket (2-1), and the bolt holes of the three are of the same position and size. The outer diameter of the ear (3-2-1) on the side of the fixed casing (3-2) facing away from the stator is larger than the outer diameter of the inner ear, and four bolt holes (3-2-3) are formed on the ear (3-2-1) on the side of the fixed casing (3-2) facing away from the stator.

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