High-torque-density magnetic transmission speed reducer and built-in motor of power-assisted bicycle

Abstract

The utility model discloses a high-torque-density magnetic transmission speed reducer and a built-in motor of a power-assisted bicycle, and belongs to the power-assisted technology of bicycles. A magnetic transmission speed reducer and a motor in the prior art have the defects of large torque fluctuation, low transmission efficiency, easy magnetic field mismatch, uncontrollable eddy current loss and the like, the magnetic transmission speed reducer comprises a first stator, a first rotor and a modulation ring, the modulation ring is located between the first rotor and the first stator, a first air gap is kept between the modulation ring and the first stator, and a second air gap is kept between the modulation ring and the second stator. A second air gap is kept between the modulation ring and the first rotor, the modulation ring comprises modulation teeth, the total number of the modulation teeth is p2, the number of pole pairs of the first stator magnetic ring is p3, the number of pole pairs of the first rotor magnetic ring is p1, p1 = p2-p3, a magnetic field of the first air gap is coupled with a magnetic field of the second air gap, and rotation from the first rotor is output in a speed reduction mode through the modulation ring. The motor part and the reduction gear realize transmission through magnetic force, thereby improving the motor operation efficiency and reducing the overall noise of the motor.

Description

Technical Field

[0001] This utility model relates to the assist technology of mid-drive motors for power-assisted bicycles, specifically to a high torque density magnetic transmission deceleration device and a mid-drive motor for power-assisted bicycles. Background Technology

[0002] Mid-drive motors in electric bicycles or regular bicycles typically output power after being reduced in speed by a reduction gear, such as a gear reducer, cycloidal pin reducer, or harmonic reducer. This results in a large size, low rotational efficiency, high noise levels, and a short lifespan for mid-drive motors. Patent application CN118554721A discloses a magnetic drive reduction device and a mid-drive motor for electric bicycles. It places a modulation ring between the first rotor and the first stator, transmitting power through magnetic field coupling. A first air gap exists between the modulation ring and the first stator, and a second air gap exists between the modulation ring and the first rotor. During operation, the motor drives the first rotor to rotate. The magnetic fields generated by the first rotor and the first stator are modulated by the modulation ring, producing a series of spatial harmonic magnetic fields in the first and second air gaps. These harmonic magnetic fields, coupled with magnetic coupling, generate a stable output torque on the modulation ring, achieving both speed reduction and torque amplification. Due to the frictionless nature of magnetic drive, combined with the ultra-high torque density resulting from the magnetically concentrated structure and high-permeability materials of this invention, the system efficiency is improved, and operating noise is reduced.

[0003] The technical solution involved in this patent document has the following defects:

[0004] (1) Uneven magnetic field distribution leads to large torque fluctuations and obvious noise. The ratio of stator and rotor poles lacks theoretical basis and the transmission efficiency is low.

[0005] (2) Existing modulation rings are mostly designed based on experience. In order to establish that the pole distance and size are mathematically related, magnetic field mismatch is likely to occur.

[0006] (3) Insufficient material performance: Traditional ferrite or low-performance neodymium iron boron magnets result in low magnetization efficiency (remanence Br < 1.2T) and insufficient field strength in the modulation ring region.

[0007] (4) Risk of temperature rise and demagnetization: The material has poor temperature stability under high load (remanence temperature coefficient α(Br) > -0.12% / ℃), and the magnetic field decays significantly.

[0008] (5) Uncontrollable eddy current losses: Low magnetic ring resistivity (<1×10) -6 The Ω•m) caused the eddy current loss in the casing to account for more than 20%. Utility Model Content

[0009] This invention addresses at least one of the shortcomings of existing mid-drive motors, such as large size, low rotational efficiency, high noise during operation, and short service life, by providing a magnetic drive reduction device with high torque density and low eddy current loss, as well as a mid-drive motor for electric bicycles. It aims to solve the torque limitations and losses of traditional magnetic gears through dual Halbach arrays, optimized modulation ring parameters, and quantitative design of the shielding ring. It also addresses at least one of the technical problems caused by gluing together separate magnetized rotor and stator magnetic pole components, resulting in dimensional errors, detachment of individual magnetic blocks, uneven magnetic field distribution, and large torque fluctuations.

[0010] To achieve the above objectives, the high torque density magnetic drive reduction device of this utility model includes a first stator, a first rotor, and a modulation ring, wherein:

[0011] The first stator includes an integral first stator magnetic ring, which is used to provide the first stator magnetic field. The circumference of the first stator magnetic ring is divided into 2p3 arc segments, where p3 is the number of pole pairs of the first stator magnetic ring. A Halbach array is used to magnetize each arc segment, and the magnetic fields of all arc segments together constitute the first stator magnetic field.

[0012] The first rotor includes an integral first rotor magnetic ring, which provides a first rotor magnetic field that rotates with the first rotor. The first rotor is located inside the modulation ring and is coaxial with the modulation ring. The circumference of the first rotor magnetic ring is divided into 2p1 arc segments, where p1 is the number of pole pairs of the first rotor magnetic ring. Each arc segment is magnetized using a Halbach array. The magnetic field direction difference between adjacent arc segments is 360 / (4p1)°. The magnetic fields of all arc segments together constitute the first rotor magnetic field.

[0013] A modulation ring is located between the first rotor and the first stator. The modulation ring is coaxial with the first rotor and the first stator. A first air gap is maintained between the modulation ring and the first stator. A second air gap is maintained between the modulation ring and the first rotor. The modulation ring includes modulation teeth, and the total number of modulation teeth is p2.

[0014] Where p1=|p2-p3|, the magnetic field of the first air gap is coupled with the magnetic field of the second air gap, and the rotation from the first rotor is decelerated and output by the modulation ring.

[0015] This invention achieves deceleration through magnetic transmission, which increases the maximum output torque under the premise of limited installation space for the mid-mounted motor, thereby improving the motor's operating efficiency and reducing the overall noise of the motor.

[0016] This invention integrates the first stator magnetic ring and the first rotor magnetic ring into a single structure, dividing their circumference into arc segments. A Halbach array is used to magnetize each arc segment, and the magnetic fields of all arc segments collectively constitute the magnetic field of the first stator magnetic ring and the first rotor magnetic ring. This dual Halbach array increases the magnetic field strength in the modulation ring region by 30% to 50%.

[0017] Preferably, the reduction gear includes a housing, with a first stator fixed to the housing. When d5-d1 < d1·sin(360 / (4p1)), a shielding ring is embedded in the inner wall of the housing to reduce magnetic leakage to the outside of the housing, where d1 is the outer diameter of the first rotor and d5 is the outer diameter of the first stator. This reduces eddy current losses by 40% to 60%. Furthermore, the housing thickness can be reduced to 60% to 70% of the original design thickness, with the shielding ring compensating for the strength.

[0018] Preferably, the thickness of the shielding ring H4 is ≥ 0.2d1·sin(360 / (4p1))+0.1(d5-d1).

[0019] Preferably, the shielding ring is made of a high-permeability alloy (such as permalloy).

[0020] Preferably, the modulation ring includes p2 modulation teeth that are circumferentially spaced. The axial projection profile of the modulation teeth is fan-shaped. The circumferential included angle D1 of a single modulation tooth is (0.5~0.6)×(360 / p2)°. The radial thickness H2 and the circumferential width W2 of a single modulation tooth satisfy H2 / W2∈[0.55, 1.3].

[0021] Preferably, the modulation ring includes a cage, which includes two end plates and a plurality of connecting rods connected between the two end plates. The connecting rods extend axially and are distributed circumferentially, and the modulation teeth are fixed in the gap between adjacent connecting rods.

[0022] Preferably, the connecting rod is cylindrical, and arc grooves are formed at the middle of both circumferential sides of the modulation teeth. The arc grooves fit against the surface of the connecting rod, allowing the connecting rod and the cylindrical shape to support each other. The mechanical strength is increased by more than 20% compared to structures without this mutual support, thus improving the structural reliability of the modulation ring.

[0023] Preferably, the radial thickness H1 of the first rotor and the circumferential width W1 of the arc segment satisfy H1 / W1∈[0.8, 1.5], and after the magnetic fields of the first rotor and the first stator are superimposed, the field strength in the modulation ring region is ≥2.0T.

[0024] Preferably, the magnetic field of the first stator is focused inward, and the magnetic field of the first rotor is focused outward.

[0025] Preferably, the first rotor is made of neodymium iron boron (N52SH), with remanence Br ≥ 1.4T and coercivity Hcj ≥ 2000kA / m.

[0026] Preferably, the modulated teeth are made of iron-cobalt alloy with a saturation magnetic induction intensity Bs≥2.3T.

[0027] Preferably, the first stator is made of neodymium iron boron (N52SH) with remanence Br ≥ 1.4T and coercivity Hcj ≥ 2000kA / m.

[0028] The mid-mounted motor of this utility model for electric bicycles includes:

[0029] chassis;

[0030] A torque assembly that runs through the housing and extends out of the housing at both ends to receive external torque;

[0031] The motor part includes a second stator and a second rotor. The second stator includes an iron core attached to the housing and a winding wound on the iron core. When the winding is energized, it generates a rotating magnetic field. The second rotor is used to provide a permanent magnet magnetic field that matches the electromagnetic field generated by the stator winding. The second rotor is located inside the second stator and is coaxial with the second stator. A third air gap is maintained between the second rotor and the second stator.

[0032] In this high torque density magnetic transmission speed reduction device, the first rotor is driven to rotate synchronously by the second rotor.

[0033] A two-way clutch, disposed between a torque assembly and a modulation ring, for selectively transmitting torque to either the torque assembly or the modulation ring, the two-way clutch having a cylindrical output shaft extending out of the housing for outputting torque, the cylindrical output shaft being sleeved radially outward at one end of the torque assembly.

[0034] This electric bicycle features a mid-mounted motor. The permanent magnet of the second rotor couples with the rotating magnetic field generated by the second stator, producing effective torque. The first rotor rotates synchronously with the second rotor, transmitting the power from the motor to the reduction gear, which outputs the torque through the modulation ring. Both the motor and the high-torque-density magnetic drive reduction gear utilize magnetic force for transmission, significantly increasing the field strength in the space occupied by the modulation ring. This greatly increases the maximum output torque (torque density) of the reduction gear under a fixed installation space, thereby improving motor operating efficiency and reducing overall motor noise.

[0035] This invention achieves speed reduction through magnetic transmission. When the mid-mounted geared motor is working, the second rotor rotates using the magnetic flux generated by the second stator, and the first rotor rotates synchronously driven by the second rotor, transmitting the power from the motor to the reduction gear, which then reduces the output speed. Both the motor and the reduction gear use magnetic transmission, which greatly increases the field strength in the space where the modulation ring is located, significantly increasing the maximum output torque of the reduction gear under a fixed installation space, thereby improving motor operating efficiency and reducing overall motor noise.

[0036] The mid-mounted geared motor of this invention utilizes magnetic transmission to achieve speed reduction, thereby reducing the size of the mid-mounted motor, improving its rotational efficiency, and reducing noise and extending its service life while ensuring the reduction ratio.

[0037] This invention integrates the first stator magnetic ring and the first rotor magnetic ring into a single structure, dividing their circumference into arc segments. A Halbach array is used to magnetize each arc segment, and the magnetic fields of all arc segments collectively constitute the magnetic fields of the first stator and first rotor magnetic rings. This invention increases torque density; the dual Halbach array increases the magnetic field strength in the modulation ring region by 30%–50%. It also reduces eddy current losses, thereby reducing eddy current losses in the housing by 40%–60%. Furthermore, it allows for a reduction in housing thickness, with the housing body thickness reduced to 60%–70% of the original design, compensated for by the shielding ring. The connecting rod of this invention is cylindrical, with arc grooves at the midpoint of both circumferential sides of the modulation teeth. These arc grooves fit against the surface of the connecting rod, providing mutual support between the connecting rod and the cylindrical shape. This increases mechanical strength by more than 20% compared to structures without this mutual support, improving the structural reliability of the modulation ring.

[0038] This invention utilizes a high torque density magnetic ring based on a dual Halbach array. Through the coordinated material design of the rotor (NdFeB N52SH) and stator (NdFeB N50M / amorphous alloy), optimization of the modulated ring iron-cobalt alloy, and a permalloy shielding ring on the housing, it achieves a magnetic field strength ≥2.0T, a 116% increase in torque density, and a 61% reduction in eddy current losses. The inner rotor magnetization angle difference is 360 / (4p1)°, and the shielding ring thickness dynamically adapts to the gap conditions, making it suitable for high-reliability transmission scenarios. This invention achieves high torque density and low vibration and noise through the pole pair matching and size optimization of the integrated Halbach magnetic ring. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the orthographic projection of the mid-mounted motor of the electric bicycle according to Embodiment 1 of this utility model from one perspective;

[0040] Figure 2 for Figure 1 Sectional view along axis AA;

[0041] Figure 3 for Figure 1 BB-direction sectional view;

[0042] Figure 4 for Figure 1 CC-direction sectional view;

[0043] Figure 5 for Figure 1The diagram shows an exploded view of the mid-mounted motor.

[0044] Figure 6 for Figure 1-4 A schematic cross-sectional view of the reduction gear of the mid-mounted motor shown in the diagram;

[0045] Figure 7 for Figure 6 A partially enlarged schematic diagram of the unipolar magnetic circuit orientation of the first rotor magnetic ring in the process;

[0046] Figure 8 for Figure 6 A partially enlarged schematic diagram of the modulation loop;

[0047] Figure 9 for Figure 6 A partially enlarged schematic diagram of the unipolar magnetic circuit orientation of the first stator magnetic ring;

[0048] Figure 10 for Figure 6 A partially enlarged schematic diagram of the middle shielding ring;

[0049] Figure 11 for Figure 5 An exploded view of the structure of the first housing and the first stator shown in the figure;

[0050] Figure 12 for Figure 5 The diagram shown is an exploded view of the structure in which the first and second rotors are configured together on the same cylindrical rotor shaft.

[0051] Figure 13 for Figure 5 The diagram shows a schematic orthographic projection of the first and second rotors arranged together on the same cylindrical rotor shaft from one viewpoint.

[0052] Figure 14 for Figure 13 DD section view;

[0053] Figure 15 for Figure 14 EE-directed sectional view;

[0054] Figure 16 This is a schematic diagram of the magnetic circuit of the second rotor magnetic ring;

[0055] Figure 17 for Figure 14 FF section view;

[0056] Figure 18 for Figure 5 The diagram shows an exploded view of the modulation ring structure.

[0057] Figure 19 for Figure 5 A schematic diagram of an orthographic projection of one axis of the modulation loop shown;

[0058] Figure 20 for Figure 19 GG-direction sectional view;

[0059] Figure 21 for Figure 20 HH-direction sectional view;

[0060] Figure 22 This is a schematic diagram of a bidirectional clutch according to the present invention;

[0061] Figure 23 for Figure 22 A schematic diagram of the structure shown from one perspective of orthographic projection;

[0062] Figure 24 for Figure 23 A partially enlarged view of the JJ-direction cross-section;

[0063] Figure 25 for Figure 24 KK-direction sectional view;

[0064] Figure 26 This is a schematic diagram showing the position of the centrally mounted motor of the electric bicycle according to this utility model on the bicycle.

[0065] Figure 27 This is an exploded view of the assembly structure of the centrally mounted motor of the electric bicycle and the bicycle frame according to this utility model.

[0066] Figure 28 This is a schematic diagram of the overall magnetic circuit of the first rotor magnetic ring of this utility model;

[0067] Figure 29 This is a schematic diagram of the overall magnetic circuit of the first stator magnetic ring of this utility model;

[0068] Figure 30 This is a schematic diagram of the overall magnetic circuit of the second rotor magnetic ring of this utility model;

[0069] Figure 31 for Figure 2 A partial schematic diagram of the second stator core;

[0070] Figure 32 This is a schematic diagram of another structure of the second stator core of this utility model;

[0071] Figure 33 This is a schematic diagram comparing the surface magnetism of the first rotor integrated magnetic ring and the spliced ​​magnetic ring of this utility model;

[0072] Figure 34 This is a schematic diagram comparing the surface magnetism of the first stator integrated magnetic ring and the spliced ​​magnetic ring of this utility model;

[0073] Explanation of the labels in the diagram:

[0074] 100 Housing, 101 First Housing, 102 Second Housing, 103 First End Cap, 104 Second End Cap, 105 Shielding Ring, 106 Inner Housing, 107 First Bearing, 108 Second Bearing, 109 Third Bearing, 110 Fourth Bearing, 111 Fifth Bearing; Shielding Ring Thickness H4, Shielding Ring Inner Diameter d5.

[0075] 200 torque assembly, 201 motor shaft, 202 torque sleeve;

[0076] 300 motor part,

[0077] 310 Second stator, 311 Second stator core, 312 Winding, 313 Stator teeth, 314 Winding slots, 315 Stator slot openings, 316 Stator shoe.

[0078] 320 Second rotor, 321 Second rotor magnetic ring,

[0079] 330 third air gap;

[0080] 400 high torque density magnetic drive reduction device;

[0081] 410 First stator, 411 First stator magnetic ring,

[0082] The radial thickness of the first stator magnetic ring is H3, the average circumferential width of the first stator unipolar magnetic circuit orientation is W3, and the included angle between the two radial sides of the first stator unipolar magnetic circuit orientation is D2.

[0083] 420 First rotor, 421 First rotor magnetic ring,

[0084] The radial thickness of the first rotor permanent magnet is H1, the average circumferential width of the first rotor permanent magnet is W1, and the outer diameter of the first rotor is d1.

[0085] 430 Modulation ring, 431 Squirrel cage, 432 End plate, 433 Connecting rod, 434 Arc groove, 435 Modulation tooth

[0086] The included angle between the two radial sides of the modulation tooth is D1, the radial thickness of the modulation tooth is H2, and the average circumferential width of the modulation tooth is W2.

[0087] 440 First air gap,

[0088] 450 second air gap;

[0089] 500 Two-way clutch, 501 Cylindrical output shaft, 502 Inner sleeve, 503 Outer sleeve, 504 First clutch component, 505 Second clutch component;

[0090] 601 Sensor, 602 Controller;

[0091] 700 cylindrical rotor shaft;

[0092] 800 Assisted Bicycle, 801 Frame, 802 Crank, 803 Pedals, 804 Drive Sprocket, 805 Drive Sprocket Lock Nut, 806 Chain, 807 Drive Wheel, 808 Drive Sprocket;

[0093] 900 electric bicycle with a mid-mounted motor. Detailed Implementation

[0094] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0095] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this utility model are intended to cover non-exclusive inclusion, such as a method or product that includes a series of technical features, not limited to those technical features explicitly listed, but also including other technical features that may be included in the method or product but not explicitly listed.

[0096] In the description of this utility model, it should be understood that the technical features defined by terms such as "first," "second," and "third," which have a sequential concept, are only used to clearly describe the defined technical features and to clearly distinguish the defined technical features from other technical features, and do not represent that they are named in this way in actual implementation. Therefore, they should not be construed as limitations on this utility model.

[0097] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings.

[0098] E-bikes are well-known; they propel the bicycle forward by transmitting torque to the wheels through the rider's pedals. Equipping a bicycle with a mid-drive motor provides external power without affecting pedaling, making it easier for the rider. Compared to hub motors, which transmit power directly to the wheel via a coaxial design, creating resistance during forward motion, a mid-drive motor, mounted in the middle of the frame and transmitting power to the wheels through a transmission mechanism, results in minimal resistance during forward motion, allowing the bicycle to travel greater distances.

[0099] The various embodiments of this utility model provide such a mid-mounted motor for electric bicycles.

[0100] like Figure 1-5 The image shows a mid-mounted motor for a power-assisted bicycle according to one embodiment, which includes: a housing 100, a torque assembly 200, a motor section 300, a high torque density magnetic transmission reduction device 400, a two-way clutch 500, a sensor 601, and a controller 602.

[0101] The housing 100 serves as the assembly base for the torque assembly, motor section, high torque density magnetic transmission reduction device, and two-way clutch; it also serves to assemble the mid-mounted geared motor onto the bicycle. In this embodiment, for ease of assembly, such as... Figure 5 The housing 100 shown includes a first housing 101, a second housing 102, and a first end cap 103 assembled together by fasteners.

[0102] The torque assembly 200 passes through the housing 100 and extends out of the housing at both ends to receive external torque, such as the torque generated by pedaling during cycling. In this embodiment, the torque assembly 200 includes a motor shaft 201 and a torque sleeve 202. The torque sleeve 202 is fitted onto the motor shaft and assembled with the motor shaft using splines, allowing the torque sleeve to rotate with the motor shaft. A fixed inner shell 106 is disposed on the outside of the torque assembly. One end of the inner shell 106 is fixed to the second end cap 104, thereby allowing the torque assembly to rotate relative to the inner shell.

[0103] Motor part 300 Figure 4 Enclosed in double-dotted circles, the motor section 300 includes a second stator 310 and a second rotor 320. The second rotor 320 is located inside the second stator 310 and is coaxial with the second stator. A third air gap 330 is maintained between the second rotor 320 and the second stator 310. In particular, the magnetic ring of the second rotor is an integral ring structure, and the axial height of the second rotor magnetic ring is consistent with the axial thickness of the second stator core, which can ensure the compact axial dimensions of the product.

[0104] The second stator 310 includes a second stator core 211 attached to the second housing 102 of the casing and a winding 312 wound around the second stator core. For example... Figure 31 , Figure 32 As shown, the second stator core 311 has evenly distributed and equally wide stator teeth 313, and winding slots 314 are formed between adjacent stator teeth. The winding slots 314 have stator slot openings 315 facing the third air gap. The number of magnetic field pole pairs generated by the winding is P1, the number of stator teeth is P2, the number of pole pairs of the second rotor is P3, and P1+P3=P2. The stator teeth 313 have stator shoe portions 316 extending towards the stator slot openings near the third air gap.

[0105] Applying an alternating signal to winding 312 can generate a changing magnetic field, which can be used to drive the second rotor to rotate.

[0106] like Figure 5 , Figure 13 , Figure 15 As shown, the second rotor 320 includes an annular second rotor magnetic ring 321, which is used to provide a second rotor magnetic field that rotates with the second rotor. Figure 16 The arc-shaped arrow in the image indicates the unipolar magnetic circuit orientation of the second rotor magnetic ring. Figure 30 The arc-shaped arrow in the image indicates the unipolar magnetic circuit orientation of the second rotor magnetic ring.

[0107] like Figure 6 As shown, the high torque density magnetic drive reduction device 400 includes a first stator 410, a first rotor 420, a modulation ring 430, and a housing.

[0108] The first stator 410 includes an integrally formed first stator magnetic ring 411, which provides the first stator magnetic field. The circumference of the first stator magnetic ring is divided into 2p3 arc segments, where p3 is the number of pole pairs of the first stator magnetic ring. A Halbach array is used to magnetize each arc segment, and the magnetic field directions of adjacent arc segments differ by (360 / 4p3)°. The magnetic fields of all arc segments together constitute the first stator magnetic field. Figure 9 , Figure 29 The curved arrow in the image indicates the unipolar magnetic circuit orientation of the first stator magnetic ring. See also... Figure 11 The first stator 410 is fixed to the first housing 101 of the housing 100. The magnetic field of the first stator 410 is inwardly focused. The first stator 410 is made of neodymium iron boron (N52SH), with a remanence Br ≥ 1.4T and coercivity Hcj ≥ 2000 kA / m.

[0109] The first rotor 420 includes an integrally formed first rotor magnetic ring 421, which provides a first rotor magnetic field that rotates with the first rotor. The first rotor 420 is located inside the modulation ring 430 and is coaxial with the modulation ring. The circumference of the first rotor magnetic ring is divided into 2p1 arc segments, where p1 is the number of pole pairs of the first rotor magnetic ring. A Halbach array is used to magnetize each arc segment, and the magnetic field directions of adjacent arc segments differ by 360 / (4p1)°. The magnetic fields of all arc segments together constitute the first rotor magnetic field. Figure 7 , Figure 28 The arc-shaped arrow in the diagram indicates the unipolar magnetic circuit orientation of the first rotor magnetic ring. The radial thickness H1 of the first rotor and the circumferential width W1 of the arc segment satisfy H1 / W1∈[0.8, 1.5]. After the magnetic fields of the first rotor and the first stator are superimposed, the field strength in the modulation ring region is ≥2.0T. The magnetic field of the first rotor 420 is focused outward. The material of the first rotor is neodymium iron boron N52SH, with remanence Br≥1.4T and coercivity Hcj≥2000kA / m.

[0110] The modulation ring 430 is located between the first rotor and the first stator. The modulation ring is coaxial with the first rotor and the first stator. A first air gap 440 is maintained between the modulation ring and the first stator, and a second air gap 450 is maintained between the modulation ring and the first rotor.

[0111] like Figure 8 As shown, the modulation ring 430 includes p2 modulation teeth 435 distributed circumferentially, each modulation tooth having the same size and an axial projection profile of a fan shape. The modulation teeth 435 are made of iron-cobalt alloy with a saturation magnetic induction intensity Bs≥2.3T. The circumferential angle D1 of a single modulation tooth is (0.5~0.6)×(360 / p2)°, and the radial thickness H2 and circumferential width W2 of a single modulation tooth satisfy H2 / W2∈[0.55, 1.3].

[0112] like Figure 18-20 As shown, the modulation ring 430 includes a cage 431, which includes two end plates 432 and a plurality of connecting rods 433 connected between the two end plates. The connecting rods extend axially and are distributed circumferentially, and the modulation teeth 435 are fixed in the gap between adjacent connecting rods 433.

[0113] In other embodiments, such as Figure 21 As shown, the connecting rod 433 is cylindrical, and the modulation teeth 435 have arc grooves at the middle positions on both sides of the circumference. The arc grooves fit against the surface of the connecting rod, allowing the connecting rod and the cylindrical shape to support each other. The circumferential width of the modulation teeth is the chord width determined by the annulus containing the geometric center of the axial projection profile of the modulation teeth.

[0114] In other embodiments, the gap between the modulation teeth 435 and the adjacent connecting rods 433 can be embedded in the gap between the adjacent connecting rods 433, or the modulation ring can be completed by injection molding. The cage is made of composite material, and the cage end plate and the modulation teeth are integrally injection molded into the mold, thereby ensuring the size and strength requirements of the modulation teeth, the cage and the cage end plate.

[0115] Where p1 = |p2 - p3|, the magnetic field of the first air gap is coupled with the magnetic field of the second air gap, and the rotation from the first rotor is decelerated and output by the modulation ring. The first stator and the first rotor are configured with different numbers of pole pairs. The modulation ring modulates the magnetomotive force of the first rotor, coupling the magnetic field of the first air gap with the magnetic field of the second air gap. The rotation from the first rotor is decelerated by the modulation ring and output coaxially with the first rotor to increase torque.

[0116] When d5-d1<d1·sin(360 / (4p1)), the inner wall of the casing is embedded. Figure 10The shielding ring 105 shown is used to reduce magnetic leakage to the outside of the housing, where d1 is the outer diameter of the first rotor and d5 is the outer diameter of the first stator. The thickness of the shielding ring H4 ≥ 0.2d1·sin(360 / (4p1)) + 0.1(d5-d1). The shielding ring is made of a high-permeability alloy, such as permalloy.

[0117] like Figure 12-15 , Figure 17 As shown, the first rotor 420 (first rotor magnetic ring 421) and the second rotor 320 (second rotor magnetic ring 321) are jointly configured on the same cylindrical rotor shaft 700, and the first rotor is driven to rotate synchronously by the second rotor.

[0118] like Figure 4-5 , Figure 22-25 As shown, a two-way clutch 500 is disposed between the torque assembly 200 and the modulation ring 430. For selectively transmitting torque to it via either the torque assembly or the modulation ring, the two-way clutch has a cylindrical output shaft 501 extending out of the housing for outputting torque. The bidirectional clutch 500 includes an inner sleeve 502, an outer sleeve 503, a plurality of first clutch elements 504, and a plurality of second clutch elements 505. The inner sleeve 502 is splined and configured on the torque assembly 200 and rotates with the torque assembly. The outer sleeve 503 is fixedly configured on the modulation ring by die-casting it to one end face of the modulation ring and rotates with the modulation ring. A cylindrical output shaft 501 is fitted radially outward of the inner sleeve 502, and the outer sleeve 503 is fitted radially outward of the cylindrical output shaft 501. The plurality of first clutch elements 504 are distributed between the cylindrical output shaft 501 and the inner sleeve 502, and the plurality of second clutch elements 505 are distributed between the cylindrical output shaft 501 and the outer sleeve 503. The first clutch elements 504 and the second clutch elements 505 are arranged in opposite directions. To ensure the first and second clutch components are evenly distributed circumferentially, facilitating sensitive bidirectional clutch operation, adjacent first clutch components are separated circumferentially by rollers and, together with the rollers, fill the circumferential gap between the cylindrical output shaft and the inner sleeve. Similarly, adjacent second clutch components are separated circumferentially by rollers and, together with the rollers, fill the circumferential gap between the cylindrical output shaft and the outer sleeve. In the illustrated structure, the first and second clutch components have the same cross-sectional structure, and their reverse configuration is reflected in their opposite installation directions.

[0119] exist Figure 4 In one configuration, the first clutch element 504 and the second clutch element 505 are located at different positions axially, and are misaligned axially. In other configurations, the first clutch element 504 and the second clutch element 505 are located at the same position axially and correspond radially. Either configuration can be selected based on requirements.

[0120] As described above, a first bearing 107 is assembled between the pivot 201 and the second end cover 104 of the second housing; a second bearing 108 is assembled between the pivot 201 and the cylindrical output shaft 501 of the bidirectional clutch; a third bearing 109 is assembled between the cylindrical rotor shaft 700 and the second end cover 104 of the second housing; a fourth bearing 110 is assembled between the cylindrical rotor shaft 700 and the cylindrical output shaft 501 of the bidirectional clutch; and a fifth bearing 111 is assembled between the cylindrical rotor shaft 700 and the first end cover 103. This allows the torque assembly 200, the first rotor 420, and the second rotor 320 to rotate relative to the housing 100, and the cylindrical output shaft 501 of the bidirectional clutch to rotate relative to the torque assembly and the modulation ring.

[0121] like Figure 26-27 The diagram shows a mid-mounted motor mounted on a bicycle.

[0122] Reference Figure 24 As shown, when the inner sleeve 502 is rotated clockwise by pedaling, the first clutch 504 experiences friction and tends to rotate counterclockwise. The long axis of the first clutch is pressed between the cylindrical output shaft 501 and the inner sleeve 502. The clockwise rotation of the inner sleeve 502 is transmitted to the cylindrical output shaft 501 in the same direction by the first clutch, causing the cylindrical output shaft 501 to rotate clockwise. Furthermore, when the cylindrical output shaft 501 rotates clockwise, the second clutch 505 experiences friction and tends to rotate counterclockwise. The short axis of the second clutch corresponds to the cylindrical output shaft 501 and the outer sleeve 503. The second clutch 505 does not transmit the clockwise rotation of the cylindrical output shaft to the outer sleeve 503 in the same direction. At this time, the torque of the torque assembly is not transmitted to the outer sleeve and the modulation ring. This situation is suitable for pedaling a bicycle.

[0123] Reference Figure 24As shown, the mid-drive motor is started by supplying power to it. The second rotor rotates by the magnetic flux generated by the second stator, and the first rotor rotates synchronously with the second rotor, transmitting the power of the motor to the modulation ring of the reduction gear. Its outer sleeve is connected to the modulation ring. When the outer sleeve 503 rotates clockwise, the second clutch 505 is subjected to friction and tends to rotate clockwise. The long axis of the second clutch 505 is squeezed between the cylindrical output shaft 501 and the outer sleeve 503. The clockwise rotation of the outer sleeve 503 is transmitted to the cylindrical output shaft 501 in the same direction by the second clutch 505, causing the cylindrical output shaft 501 to rotate clockwise. Furthermore, when the cylindrical output shaft 501 rotates clockwise, the first clutch 504, subjected to friction, tends to rotate clockwise. Since the minor diameter of the first clutch 504 corresponds to the cylindrical output shaft 501 and the inner sleeve 502, the first clutch 504 will not transmit the clockwise rotation of the cylindrical output shaft to the inner sleeve 502 in the same direction. At this time, the torque of the modulation ring will not be transmitted to the torque assembly. This configuration is suitable for driving a bicycle forward using a mid-mounted motor.

[0124] During bicycle riding, when the bicycle glides forward, the power transmission between the driving sprocket and the driven sprocket of the mid-mounted motor is cut off due to the one-way clutch mechanism of the transmission mechanism between the mid-mounted motor and the drive wheel, such as the ratchet and pawl mechanism configured in the drive wheel and the driven sprocket. Therefore, it is not necessary to provide pedal power or motor power to the bicycle.

[0125] During bicycle riding, when actions such as turning around cause the bicycle to move backward, the bicycle drive wheel establishes a transmission with the cylindrical output shaft via the transmission mechanism. As mentioned earlier, when the bicycle moves forward, the cylindrical output shaft rotates clockwise. The backward movement of the bicycle drive wheel causes the cylindrical output shaft 501 to rotate counterclockwise. This counterclockwise rotation of the cylindrical output shaft, via the first clutch 504, causes the inner sleeve 502 and torque assembly 200 to rotate counterclockwise, and via the second clutch 505, causes the outer sleeve and modulation ring to rotate counterclockwise. At this time, no power is supplied to the mid-drive motor, and the mid-drive motor is in a non-operating state.

[0126] During cycling, the forward motion of the bicycle may alternate between being propelled by pedals and being propelled by a mid-mounted motor. Therefore, the mid-mounted geared motor includes a sensor 601 and a controller 602. The controller receives a signal from the sensor indicating the pedal drive torque and instructs the motor to operate. Accordingly, when the mid-mounted geared motor is installed on the bicycle, pedaling actions instruct the motor to operate and propel the bicycle forward. For example, Figure 5The sensor 601 is housed in the inner housing 106 to detect the pedal drive torque received by the torque assembly. The pedal drive torque can be a pressure signal or the rotation of the torque assembly. The controller 602 can be located in the mid-drive motor or on the vehicle. When riding a bicycle, the rider pedals, and the pedal drive torque generated by the pedaling action is transmitted to the torque assembly via the crank. The sensor detects the rotational tendency of the torque assembly or the pressure signal or rotational signal generated by the rotation and provides this signal to the controller.

[0127] In this embodiment, the permanent magnets constituting the magnetic pole assemblies of the first stator, the first rotor, and the second rotor are all distributed circumferentially on the axial projection plane.

[0128] In this embodiment, the motor section 300 and the high torque density magnetic drive reduction device 400 are coaxially connected in series, which is in Figure 4 It is shown in the text.

[0129] This embodiment integrates the first stator magnetic ring and the first rotor magnetic ring into a single structure, dividing their circumference into arc segments. A Halbach array is used to magnetize each arc segment, and the magnetic fields of all arc segments collectively constitute the magnetic fields of the first stator and first rotor magnetic rings. The first stator and first rotor magnetic rings work together to concentrate magnetism, demonstrating the technical advantages of this invention. The performance requirements of the components and their materials are as follows: A better configuration can achieve the desired effect.

[0130] I. Material Performance Requirements

[0131]

[0132] II. Material Selection and Compatibility

[0133] (1) Material of the first rotor magnetic ring

[0134] Preferred material: Neodymium iron boron (NdFeB) grade N52SH.

[0135] Performance parameters: Remanence Br = 1.48T, Coercivity Hcj = 2200kA / m, Temperature coefficient of remanence α(Br) = -0.09% / ℃, Resistivity = 1.5×10 -6 Ω·m.

[0136] Advantages: High remanence and coercivity match, suitable for strong outward magnetization; nickel plating (Ni-Cu-Ni) coating enhances corrosion resistance.

[0137] Alternative: Iron-Co-V alloy.

[0138] Applicable scenarios: Ultra-high temperature environment (>150℃), sacrificing some remanence (Br=1.3T) in exchange for temperature stability (remanence temperature coefficient α(Br)=-0.05% / ℃).

[0139] (2) Material of the first stator magnetic ring

[0140] Preferred material: Neodymium iron boron (NdFeB) N50M grade.

[0141] Performance parameters: Remanence Br = 1.42T, Coercivity Hcj = 1900kA / m, Temperature coefficient of remanence α(Br) = -0.11% / ℃, Resistivity = 1.4×10 -6 Ω·m.

[0142] Advantages: Lower cost than N52SH, meets the requirement of inward magnetization, and is compatible with the casing shielding structure.

[0143] Alternative: Amorphous alloy (Fe-Si-B)

[0144] Applicable scenarios: High-frequency operating conditions (>500Hz), resistivity up to 1.8×10⁻⁶ -6 Ω·m, significantly reducing high-frequency eddy currents.

[0145] (3) Adaptability of one-piece molding process

[0146] Sintered NdFeB: Multi-pole orientation sintering technology is adopted, and the magnetic field direction is preset in the mold to ensure that the magnetization angle difference between adjacent magnetic poles is 360 / (4p1)° (first rotor) or 360 / (4p3)° (first stator).

[0147] Process challenges: It is necessary to control the grain boundary diffusion (GBD) process to reduce the magnetic property inhomogeneity caused by grain boundary phases.

[0148] Bonded magnets: suitable for complex Halbach structures (such as thin-walled first stators), with carbon fiber (5%-10% by mass) added to the resin matrix (epoxy or nylon) to improve mechanical strength.

[0149] III. Dual Halbach Synergistic Effect and Material Interaction

[0150] (1) Enhancement of magnetic field superposition

[0151] The inner rotor focuses the magnetization outward: high Br neodymium iron boron (N52SH) generates a radial main magnetic field (Br) in the modulation ring region.

[0152] Outer stator inward magnetic focusing: N50M neodymium iron boron magnets generate a reverse tangential magnetic field (Bθ), which, after passing through the modulation ring, superimposes to form a spiral enhanced magnetic field (Bnet). Calculation formula: .

[0153] Measured data: In the prototype with p1=4 and p3=7, the field strength in the modulation ring region increased from 1.6T (single Halbach) to 2.1T (double Halbach).

[0154] (2) Eddy co-suppression

[0155] First rotor high resistivity design: N52SH resistivity (1.5×10⁻⁶) -6 (Ω·m) to reduce eddy current losses on the rotor surface.

[0156] The first stator can be made of an amorphous alloy of Fe-Si-B with a resistivity of 1.8 × 10⁻⁶. -6 (Ω·m) further blocks the path of high-frequency harmonic eddy currents.

[0157] (3) Thermal stability matching

[0158] First rotor: Through α(Br)=-0.09% / ℃ and the heat dissipation design of the casing, the temperature rise ΔT<40℃ is limited.

[0159] First stator: α(Br) = -0.11% / ℃. The magnetic field attenuation is offset by a temperature compensation algorithm (such as PID temperature control).

[0160] IV. Material Failure Avoidance Strategies

[0161] (1) Risk of demagnetization of magnetic ring

[0162] First rotor: Hcj≥2000kA / m, capable of withstanding short-time overload current (3 times rated current) and reverse magnetic field.

[0163] First stator: adopts segmented Halbach design (each pole is divided into 3-4 magnets) to avoid local demagnetization diffusion.

[0164] (2) Mechanical stress cracking

[0165] Inner rotor: The magnet and stainless steel sheath are fitted with an interference fit (interference amount 0.05-0.1mm), and the preload force counteracts the centrifugal stress.

[0166] Outer stator: The amorphous alloy outer stator is equipped with carbon fiber reinforcing rings, which increases the bending strength to 180MPa.

[0167] V. Experimental Verification and Performance Comparison

[0168]

[0169] exist Figure 33 , Figure 34 In the comparison of the magnetic curve L1 (waveform curve represented by dashed line) of the first rotor integrated magnetic ring and the magnetic curve L2 (waveform curve represented by solid line) of the first rotor spliced ​​magnetic ring, and the magnetic curve L3 (waveform curve represented by dashed line) of the first stator integrated magnetic ring and the magnetic curve L4 (waveform curve represented by solid line) of the first stator spliced ​​magnetic ring, it can be seen from the figure that the magnetic amplitude (vertical axis) of the integrated magnetic ring is larger, showing better performance.

Claims

1. A high torque density magnetic drive reduction device, characterized by: It includes a first stator (410), a first rotor (420), and a modulation ring (430), wherein: The first stator (410) includes an integral first stator magnetic ring (411). The first stator magnetic ring is used to provide the first stator magnetic field. The circumference of the first stator magnetic ring is divided into 2p3 arc segments, where p3 is the number of pole pairs of the first stator magnetic ring. Each arc segment is magnetized using a Halbach array. The magnetic field directions of adjacent arc segments differ by (360 / 4p3)°. The magnetic fields of all arc segments together constitute the first stator magnetic field. The first rotor (420) includes an integral first rotor magnetic ring (421). The first rotor magnetic ring is used to provide a first rotor magnetic field that rotates with the first rotor. The first rotor (420) is located inside the modulation ring (430) and is coaxial with the modulation ring. The circumference of the first rotor magnetic ring is divided into 2p1 arc segments, where p1 is the number of pole pairs of the first rotor magnetic ring. Each arc segment is magnetized using a Halbach array. The magnetic field directions of adjacent arc segments differ by 360 / (4p1)°. The magnetic fields of all arc segments together constitute the first rotor magnetic field. A modulation ring (430) is located between the first rotor and the first stator. The modulation ring is coaxial with the first rotor and the first stator. A first air gap (440) is maintained between the modulation ring and the first stator. A second air gap (450) is maintained between the modulation ring and the first rotor. The modulation ring (430) includes modulation teeth (435). The total number of modulation teeth is p2. Where p1=|p2-p3|, the magnetic field of the first air gap is coupled with the magnetic field of the second air gap, and the rotation from the first rotor is decelerated and output by the modulation ring.

2. The high torque density magnetic drive reduction device according to claim 1, characterized in that: The speed reduction device includes a housing, and a first stator (410) is fixed to the housing (100); when d5-d1<d1·sin(360 / (4p1)), a shielding ring (105) is embedded in the inner wall of the housing to reduce magnetic leakage to the outside of the housing, wherein d1 is the outer diameter of the first rotor and d5 is the outer diameter of the first stator.

3. The high torque density magnetic drive reduction device according to claim 2, characterized in that: The thickness of the shielding ring H4 is ≥ 0.2d1·sin(360 / (4p1))+0.1(d5-d1).

4. The high torque density magnetic drive reduction device according to claim 1, characterized in that: The modulation ring includes p2 modulation teeth that are circumferentially spaced. The axial projection profile of the modulation teeth is fan-shaped. The circumferential included angle of a single modulation tooth is D1 = (0.5~0.6)×(360 / p2)°. The radial thickness H2 and the circumferential width W2 of a single modulation tooth satisfy H2 / W2∈[0.55, 1.3].

5. The high torque density magnetic drive reduction device according to claim 4, characterized in that: The modulation ring (430) includes a cage (431), which includes two end plates (432) and a number of connecting rods (433) connected between the two end plates. The connecting rods extend axially and are distributed circumferentially. Modulation teeth (435) are fixed in the gap between adjacent connecting rods (433).

6. The high torque density magnetic drive reduction device according to claim 5, characterized in that: The connecting rod (433) is cylindrical, and the middle of the two sides of the modulation tooth (435) has an arc groove. The arc groove fits into the surface of the connecting rod so that the connecting rod and the cylindrical shape support each other.

7. The high torque density magnetic drive reduction device according to claim 1, characterized in that: The radial thickness H1 of the first rotor and the circumferential width W1 of the arc segment satisfy H1 / W1∈[0.8, 1.5]. After the magnetic fields of the first rotor and the first stator are superimposed, the field strength in the modulation ring region is ≥2.0T.

8. The high torque density magnetic drive reduction device according to claim 1, characterized in that: The magnetic field of the first stator (410) is focused inward, while the magnetic field of the first rotor (420) is focused outward.

9. A mid-mounted motor in a power-assisted bicycle, characterized by: include: Casing (100); A torque assembly (200) extends through the housing and extends out of the housing at both ends to receive external torque; The motor section (300) includes a second stator (310) and a second rotor (320). The second stator includes an iron core (311) attached to the housing and a winding (312) wound around the iron core. When the winding is energized, it generates a rotating magnetic field. The second rotor (320) is used to provide a permanent magnet magnetic field that matches the electromagnetic field generated by the stator winding. The second rotor (320) is located inside the second stator (310) and is coaxial with the second stator. A third air gap (330) is maintained between the second rotor and the second stator. The high torque density magnetic drive reduction device (400) according to any one of claims 1-8, wherein the first rotor (420) is synchronously rotated by the second rotor (320); A two-way clutch (500) is disposed between a torque assembly (200) and a modulation ring (430) for selectively transmitting torque to it by the torque assembly or by the modulation ring. The two-way clutch has a cylindrical output shaft (501) extending out of the housing for outputting torque, the cylindrical output shaft being sleeved on the radially outer side of one end of the torque assembly (200).

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