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

Abstract

The invention 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 reduction device and a motor in the prior art have the defects of large torque fluctuation, low transmission efficiency, easiness in causing magnetic field mismatch, uncontrollable eddy current loss and the like, speed reduction is realized through magnetic transmission, when a middle speed reduction motor works, a second rotor rotates by virtue of magnetic flux generated by a second stator, and a first rotor is driven by the second rotor to synchronously rotate, so that the speed reduction efficiency is improved. And the power of the motor part is transmitted to the speed reducer and is output after being decelerated by the speed reducer. The motor part and the speed reducer realize transmission through magnetic force, the field intensity of the space where the modulation ring part is located is greatly improved, the maximum output torque of the speed reducer under the condition that the size of the installation space is fixed is greatly improved, the operation efficiency of the motor is further improved, and the overall noise of the motor is reduced.

Description

Technical Field

[0001] The invention belongs to the power-assisting technology of a mid-mounted motor of a power-assisting bicycle, and specifically relates to a high-torque density magnetic transmission speed reducer and a mid-mounted motor of a power-assisting bicycle. Background Art

[0002] The central motor of a power-assisted bicycle or bicycle is usually outputted after the motor is decelerated by a reduction device, wherein the reduction device is a gear reduction device, a cycloidal needle reduction device or a harmonic reduction device, which makes the central motor larger in size, low in rotation efficiency, loud in noise during operation, and short in service life. The patent document with application publication number CN118554721A discloses a magnetic transmission reduction device and a central motor of a power-assisted bicycle, which places a modulation ring between the first rotor and the first stator, and transmits power by magnetic field coupling. There is a first air gap between the modulation ring and the first stator, and a second air gap between the modulation ring and the first rotor. When the motor is running, the first rotor is driven to rotate, and the magnetic fields generated by the first rotor and the first stator are modulated by the modulation ring to generate a series of spatial harmonic magnetic fields in the first air gap and the second air gap, and a stable output torque is generated on the modulation ring through magnetic field coupling, so as to achieve the effect of deceleration and torque amplification. Due to the frictionless characteristics of magnetic transmission, coupled with the ultra-high torque density brought by the magnetic field structure and high magnetic permeability materials of the present invention, the system efficiency is improved and the operating noise is reduced.

[0003] The technical solution involved in this patent document has the following defects: (1) The uneven magnetic field distribution leads to large torque fluctuations and obvious noise. The stator and rotor pole ratio lacks a theoretical basis and the transmission efficiency is low.

[0004] (2) Existing modulation rings are mostly designed based on experience to establish a mathematical relationship between pole pitch and size, which can easily lead to magnetic field mismatch.

[0005] (3) Insufficient material performance: Traditional ferrite or low-performance NdFeB magnets result in low magnetic concentration efficiency (remanent magnetism Br < 1.2T) and insufficient field strength in the modulation ring area.

[0006] (4) Temperature rise and demagnetization risk: The material has poor temperature stability under high load (remanent magnetization temperature coefficient α(Br)>-0.12% / ℃), and the magnetic field attenuates significantly.

[0007] (5) Eddy current loss is uncontrollable: the magnetic ring resistivity is low (<1×10⁻ 6 Ω•m) causes the eddy current loss of the casing to account for more than 20%. Summary of the invention

[0008] The present invention firstly aims at at least one of the defects of the existing mid-mounted motor, such as large volume, low rotation efficiency, loud noise during operation, and short service life, and provides a magnetic transmission speed reducer with high torque density and low eddy current loss and a mid-mounted motor for power-assisted bicycles. The invention aims to solve the torque limitation and loss problems of traditional magnetic gears through double Halbach array, modulation ring parameter optimization and shielding ring quantitative design, and solve at least one of the technical problems such as dimensional error and single-piece magnetic block shedding caused by the existing rotor magnetic pole assembly and stator magnetic pole assembly being magnetized in blocks and glued together, uneven magnetic field distribution, and large torque fluctuation.

[0009] To achieve the above object, the high torque density magnetic transmission reduction device of the present invention comprises a first stator, a first rotor and a modulation ring, wherein: A first stator, comprising a first stator magnetic ring of an integrated structure, the first stator magnetic ring is used to provide a first stator magnetic field, the circumference of the first stator magnetic ring is divided into 2p3 arc segments, 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; A first rotor, comprising a first rotor magnetic ring of an integral structure, the first rotor magnetic ring being used to provide a first rotor magnetic field rotating with the first rotor, the first rotor being located inside a modulation ring and being coaxial with the modulation ring, the circumference of the first rotor magnetic ring being divided into 2p1 arc segments, p1 being the number of pole pairs of the first rotor magnetic ring, a Halbach array being used to magnetize each arc segment, the magnetic field direction difference between adjacent arc segments being 360 / (4p1)°, and the magnetic fields of all arc segments together constituting the first rotor magnetic field; 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 the modulation teeth is p2. Among them, p1=|p2-p3|, so that 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.

[0010] The present invention achieves deceleration through magnetic transmission, and under the premise that the installation space of the central motor is limited, the maximum output torque is increased, thereby improving the motor operation efficiency and reducing the overall noise of the motor.

[0011] The present invention makes the first stator magnetic ring and the first rotor magnetic ring into an integrated structure and divides the circumference into arc segments, uses a Halbach array to magnetize each arc segment, and the magnetic fields of all arc segments together constitute the magnetic fields of the first stator magnetic ring and the first rotor magnetic ring. This double Halbach array increases the magnetic field strength of the modulation ring area by 30% to 50%.

[0012] Preferably, the reduction gear comprises a housing, and the first stator is 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, wherein d1 is the outer diameter of the first rotor, and d5 is the outer diameter of the first stator. Accordingly, eddy current loss can be reduced, and the eddy current loss of the housing can be reduced by 40% to 60%. In addition, the thickness of the housing can be reduced, and the thickness of the housing body is 60% to 70% of the original design, and the strength is compensated by the shielding ring.

[0013] Preferably, the shielding ring thickness H4 ≥ 0.2d1·sin(360 / (4p1))+0.1(d5-d1).

[0014] Preferably, the shielding ring is made of a high magnetic permeability alloy (such as Permalloy).

[0015] Preferably, the modulation ring includes p2 modulation teeth distributed at circumferential intervals, the axial projection profile of the modulation teeth is fan-shaped, the circumferential angle D1 of a single modulation tooth is D1 = (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].

[0016] Preferably, the modulation ring comprises a cage, the cage comprises two end plates and a plurality of connecting rods connected between the two end plates, the connecting rods extend axially and are distributed along the circumference, and the modulation teeth are fixed in the gaps between adjacent connecting rods.

[0017] Preferably, the connecting rod is cylindrical, and arc grooves are provided in the middle of the two circumferential sides of the modulation teeth, and the arc grooves are fitted to the surface of the connecting rod so that the connecting rod and the cylindrical shape support each other. The mechanical strength is increased by more than 20% compared with the structure without the mutual support, thereby improving the structural reliability of the modulation ring.

[0018] 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.

[0019] Preferably, the magnetic field of the first stator focuses inwards, and the magnetic field of the first rotor focuses outwards.

[0020] Preferably, the first rotor is made of neodymium iron boron N52SH, with a remanence Br≥1.4T and a coercive force Hcj≥2000kA / m.

[0021] Preferably, the material of the modulation teeth is an iron-cobalt alloy, and the saturation magnetic induction intensity Bs≥2.3T.

[0022] Preferably, the material of the first stator is neodymium iron boron N52SH, with a remanence Br≥1.4T and a coercive force Hcj≥2000kA / m.

[0023] The mid-mounted motor of the power-assisted bicycle of the present invention comprises: chassis; A torque assembly, which penetrates the casing and has two ends extending out of the casing to receive external torque; The motor part includes a second stator and a second rotor, wherein the second stator includes an iron core attached to the housing and a winding wound on the iron core, the winding generates a rotating magnetic field when energized, and the second rotor is used to provide a permanent magnetic field matching the electromagnetic field generated by the stator winding, the second rotor is located inside the second stator and coaxial with the second stator, and a third air gap is maintained between the second rotor and the second stator; The high torque density magnetic transmission reduction device according to any one of claims 1 to 12, wherein the first rotor is rotated synchronously with the second rotor; A two-way clutch is arranged between the torque assembly and the modulation ring for selectively transmitting torque to it by the torque assembly or by the modulation ring. The two-way clutch has a cylindrical output shaft extending out of the housing for outputting torque, and the cylindrical output shaft is sleeved on the radial outer side of one end of the torque assembly.

[0024] The power-assisted bicycle has a central motor, and the permanent magnetic field of the second rotor is coupled with the rotating magnetic field generated by the second stator to generate effective torque. The first rotor is driven by the second rotor to rotate synchronously, and the power of the motor part is transmitted to the reduction device, which is output by the modulation ring. The motor part and the high-torque density magnetic transmission reduction device both use magnetic force to achieve transmission, which greatly improves the field strength of the space where the modulation ring part is located, and greatly improves the maximum output torque (i.e. torque density) of the reduction device when the installation space size is fixed, thereby improving the motor operation efficiency and reducing the overall noise of the motor.

[0025] The present invention realizes deceleration through magnetic transmission. When the central reduction motor is working, the second rotor rotates by means of the magnetic flux generated by the second stator, and the first rotor is driven by the second rotor to rotate synchronously, and the power of the motor part is transmitted to the reduction device, which is decelerated and output by the reduction device. Both the motor part and the reduction device use magnetic force to realize transmission, which greatly improves the field strength of the space where the modulation ring part is located, and greatly improves the maximum output torque of the reduction device when the installation space size is fixed, thereby improving the motor operation efficiency and reducing the overall noise of the motor.

[0026] The center-mounted reduction motor of the present invention realizes reduction in speed by means of magnetic transmission, so that the volume of the center-mounted motor can be reduced, the rotation efficiency can be improved, and the noise during operation can be reduced and the service life can be extended while ensuring the reduction ratio.

[0027] The present invention makes the first stator magnetic ring and the first rotor magnetic ring into an integral structure and divides the circumference into arc segments, adopts Halbach array to magnetize each arc segment, and the magnetic fields of all arc segments together constitute the magnetic fields of the first stator magnetic ring and the first rotor magnetic ring. The present invention improves the torque density, and the double Halbach array increases the magnetic field strength of the modulation ring area by 30% to 50%. The present invention reduces the eddy current loss, thereby reducing the eddy current loss and reducing the eddy current loss of the casing by 40% to 60%. The thickness of the casing can also be reduced, and the thickness of the casing body is 60% to 70% of the original design, and the strength is compensated by the shielding ring. The connecting rod of the present invention is cylindrical, and arc grooves are opened in the middle of the two circumferential sides of the modulation teeth. The arc grooves are attached to the surface of the connecting rod so that the connecting rod and the cylindrical shape support each other. The mechanical strength is increased by more than 20% compared with the structure that does not support each other, which improves the structural reliability of the modulation ring.

[0028] The present invention is based on a high torque density magnetic ring with a double Halbach array. Through the coordinated design of the rotor (NdFeB N52SH) and stator (NdFeB N50M / amorphous alloy) materials, the optimization of the modulation ring iron-cobalt alloy and the casing Permalloy shielding ring, the magnetic field strength ≥ 2.0T, the torque density is increased by 116%, and the eddy current loss is reduced by 61%. The inner rotor magnetization angle difference is 360 / (4p1)°, and the thickness of the shielding ring dynamically adapts to the gap conditions, which is suitable for high-reliability transmission scenarios. The present invention achieves high torque density and low vibration noise through the Halbach integrated magnetic ring pole pair matching and size optimization. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of an orthographic projection of a mid-mounted motor of an electric power-assisted bicycle according to Embodiment 1 of the present invention from one viewing angle; Figure 2 for Figure 1 AA section view; Figure 3 for Figure 1 BB section view; Figure 4 for Figure 1 CC section view; Figure 5 for Figure 1 The schematic diagram of the structure of the mid-mounted motor is shown; Figure 6 for Figure 1-4 A schematic cross-sectional view of the reduction gear of the mid-mounted motor shown in FIG. Figure 7 for Figure 6 A partial enlarged schematic diagram of the orientation of the unipolar magnetic circuit of the first rotor magnetic ring; Figure 8 for Figure 6A partial enlarged schematic diagram of the modulation ring in the middle; Fig. 9 for Figure 6 A partial enlarged schematic diagram of the single-pole magnetic circuit orientation of the first stator magnetic ring; Fig.10 for Figure 6 A partial enlarged schematic diagram of the middle shielding ring; Fig.11 for Figure 5 A schematic diagram of the structural decomposition of the first housing and the first stator shown in ; Fig.12 for Figure 5 A schematic diagram of the structure in which the first rotor and the second rotor are co-arranged on the same cylindrical rotor shaft; Fig.13 for Figure 5 , a schematic diagram of an orthographic projection of a first rotor and a second rotor being co-arranged on the same cylindrical rotor shaft from one viewing angle; Fig.14 for Fig.13 DD section view; Fig.15 for Fig.14 EE section view; Fig.16 is a schematic diagram of the magnetic circuit of the second rotor magnetic ring; Fig.17 for Fig.14 FF section view; Fig.18 for Figure 5 Schematic diagram of the structural decomposition of the modulation ring shown in; Fig.19 for Figure 5 An axial orthographic projection diagram of the modulation ring shown in ; Fig. 20 for Fig.19 GG section view; Fig.21 for Fig. 20 HH sectional view; Fig. 22 A schematic diagram of a two-way clutch of the present invention; Fig.23 for Fig. 22 a schematic orthographic projection of one view of the structure shown; Fig.24 for Fig.23 A partial enlarged view of the JJ section; Fig.25 for Fig.24 KK section view; Fig.26 This is a schematic diagram of the position of the mid-mounted motor of the power-assisted bicycle of the present invention on the bicycle; Fig. 27 It is an exploded schematic diagram of the assembly structure of the mid-mounted motor of the power-assisted bicycle and the frame of the bicycle of the present invention; Fig.28 It is a schematic diagram of the overall magnetic circuit of the first rotor magnetic ring of the present invention; Fig.29 It is a schematic diagram of the overall magnetic circuit of the first stator magnetic ring of the present invention; Fig.30 It is a schematic diagram of the overall magnetic circuit of the second rotor magnetic ring of the present invention; Fig.31 for Figure 2 A partial schematic diagram of the second stator core; Fig.32 Another structural schematic diagram of the second stator core of the present invention; Fig.33 It is a schematic diagram comparing the surface magnetic properties of the first rotor integrated magnetic ring and the spliced ​​magnetic ring of the present invention; Fig.34 It is a schematic diagram showing the comparison of the surface magnetic properties of the first stator integrated magnetic ring and the spliced ​​magnetic ring of the present invention; Description of the numbers in the figure: 100 housing, 101 first housing, 102 second housing, 103 first end cover, 104 second end cover, 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; 200 torque assembly, 201 motor shaft, 202 torque sleeve; 300 motor part, 310 second stator, 311 second stator core, 312 winding, 313 stator tooth, 314 winding slot, 315 stator notch, 316 stator boot, 320 second rotor, 321 second rotor magnetic ring, 330 third air gap; 400 high torque density magnetic transmission reduction device; 410 a first stator, 411 a first stator magnetic ring, The radial thickness of the first stator magnetic ring is H3, the circumferential average width of the first stator monopole magnetic circuit orientation is W3, and the angle between the two radial sides of the first stator monopole magnetic circuit orientation is D2. 420 a first rotor, 421 a first rotor magnetic ring, The radial thickness of the first rotor permanent magnet is H1, the circumferential average width of the first rotor permanent magnet is W1, and the outer diameter of the first rotor is d1. 430 modulation ring, 431 squirrel cage, 432 end plate, 433 connecting rod, 434 arc groove, 435 modulation tooth, The 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. 440 first air gap, 450 second air gap; 500 bidirectional clutch, 501 cylindrical output shaft, 502 inner sleeve, 503 outer sleeve, 504 first clutch member, 505 second clutch member; 601 sensor, 602 controller; 700 cylindrical rotor shaft; 800 power-assisted bicycle, 801 frame, 802 crank, 803 pedal, 804 driving sprocket, 805 driving sprocket locking nut, 806 chain, 807 driving wheel, 808 driven sprocket; 900 power-assisted bicycle with mid-mounted motor. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all 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.

[0031] The terms "including" and "having" and any variations thereof in the specification and claims of the present invention are intended to cover non-exclusive inclusions. For example, a method or product comprising a series of technical features is not necessarily limited to those technical features clearly listed, but may also include other technical features that are not clearly listed and can be included in the method or product.

[0032] In the description of the present invention, it is necessary to understand that the technical features defined by the terms "first", "second", "third" and the like with sequential concepts are only for the purpose of clearly describing the defined technical features so that the defined technical features can be clearly distinguished from other technical features, but do not represent such naming in actual implementation, and therefore cannot be understood as a limitation of the present invention.

[0033] The present invention is described in detail below in conjunction with specific embodiments and accompanying drawings.

[0034] Power-assisted bicycles are well known, and they drive the bicycle forward by transmitting torque to the wheels through the rider's pedals. Equipping a bicycle with a mid-mounted motor can provide external power without affecting pedaling, which can save the rider more effort. Compared with a hub motor, the hub motor will generate resistance to the vehicle when the vehicle slides forward because the hub motor is coaxial with the wheel and transmits power directly to the wheel. The mid-mounted motor is installed in the middle of the frame and transmits power to the wheel through a transmission mechanism, so that the bicycle is basically not subject to resistance from the mid-mounted motor when sliding forward, allowing the bicycle to slide a longer distance.

[0035] Various embodiments of the present invention provide such a mid-mounted motor for an assisted bicycle.

[0036] like Figure 1-5 The figure shows a mid-mounted motor for a power-assisted bicycle according to an embodiment, which includes: a housing 100 , a torque assembly 200 , a motor part 300 , a high torque density magnetic transmission reduction device 400 , a two-way clutch 500 , a sensor 601 and a controller 602 .

[0037] The housing 100 is used as a base for assembling the torque assembly, the motor part, the high torque density magnetic transmission speed reducer, and the two-way clutch, and is also used to assemble the mid-mounted speed reducer motor on the bicycle. Figure 5 The housing 100 shown includes a first shell 101, a second shell 102 and a first end cover 103 assembled together by fasteners.

[0038] The torque assembly 200 passes through the housing 100 and its two ends extend out of the housing to receive external torque, such as the torque generated by pedaling when riding. In this embodiment, the torque assembly 200 includes a motor shaft 201 and a torque sleeve 202. The torque sleeve 202 is sleeved on the motor shaft and assembled with the motor shaft by splines so that the torque sleeve rotates with the motor shaft. A fixed inner shell 106 is configured on the outer side of the torque assembly, and one end of the inner shell 106 is fixed to the second end cover 104, so that the torque assembly can rotate relative to the inner shell.

[0039] The motor part 300 is Figure 4 The motor part 300 is enclosed by a double-dot chain line, and 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 integrated annular 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 that the axial size of the product is compact.

[0040] 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. Fig.31 , Fig.32 As shown, uniformly distributed and equal-width stator teeth 313 are formed on the second stator core 311, winding slots 314 are formed between adjacent stator teeth, and the winding slots 314 have stator slots 315 facing the third air gap. The number of pole pairs generated by the winding is P1, the number of stator teeth is P2, the number of second rotor pole pairs is P3, and P1+P3=P2. A stator shoe 316 extending toward the stator slot is provided near the third air gap on the stator tooth 313.

[0041] Applying an alternating signal to the winding 312 can generate a changing magnetic field for driving the second rotor to rotate.

[0042] like Figure 5 , Fig.13 , Fig.15 As shown, the second rotor 320 includes an annular second rotor magnetic ring 321 , and the second rotor magnetic ring 321 is used to provide a second rotor magnetic field that rotates with the second rotor. Fig.16 The arc arrow in the figure indicates the single-pole magnetic circuit orientation of the second rotor magnetic ring. Fig.30 The arc arrow in represents the unipolar magnetic circuit orientation of the second rotor magnetic ring.

[0043] like Figure 6 As shown, the high torque density magnetic transmission reduction gear 400 includes a first stator 410, a first rotor 420, a modulation ring 430 and a housing.

[0044] The first stator 410 includes a first stator magnetic ring 411 of an integrated structure. The first stator magnetic ring is used to provide a 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. 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. Fig. 9 , Fig.29 The curved arrow in the figure indicates the single-pole magnetic path orientation of the first stator magnetic ring. Fig.11 The first stator 410 is fixed to the first shell 101 of the housing 100. The magnetic field of the first stator 410 is concentrated inward. The material of the first stator 410 is neodymium iron boron N52SH, with a remanence Br≥1.4T and a coercive force Hcj≥2000kA / m.

[0045] The first rotor 420 includes a first rotor magnetic ring 421 of an integrated structure. 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. A Halbach array is used to magnetize each arc segment. 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 , Fig.28 The arc arrow in represents 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 focuses magnetism outward. The material of the first rotor is neodymium iron boron N52SH, the remanence Br≥1.4T, and the coercive force Hcj≥2000kA / m.

[0046] 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.

[0047] like Figure 8 As shown, the modulation ring 430 includes p2 modulation teeth 435 distributed at intervals in the circumferential direction, each modulation tooth has the same size, and the axial projection profile of the modulation tooth is fan-shaped. The material of the modulation tooth 435 is an iron-cobalt alloy, and the 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].

[0048] 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 along the circumference. The modulation teeth 435 are fixed in the gaps between adjacent connecting rods 433 .

[0049] In other embodiments, Fig.21 As shown, the connecting rod 433 is cylindrical, and arc grooves are opened in the middle of the two circumferential sides of the modulation tooth 435, and the arc grooves fit the surface of the connecting rod so that the connecting rod and the cylindrical shape support each other. Among them, the circumferential width of the modulation tooth is the chord length width confirmed by the circle where the geometric center of the axial projection profile of the modulation tooth is located.

[0050] In other embodiments, the modulation tooth 435 is fixed in the gap between adjacent connecting rods 433 and can be embedded in the gap between adjacent connecting rods 433, or the modulation ring can be completed by injection molding, and its cage is a composite material. The cage end plate and the modulation tooth are placed in a mold for integral injection molding, thereby ensuring the size requirements and strength requirements of the modulation tooth, the cage and the cage end plate.

[0051] Among them, p1=|p2-p3|, so that 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. Among them, the first stator and the first rotor are configured with different pole pairs, and the modulation ring modulates the magnetic field of the magnetomotive force of the first rotor, so that 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 through the modulation ring and output coaxially with the first rotor to increase the torque.

[0052] When d5-d1<d1·sin(360 / (4p1)), the inner wall of the casing is embedded Fig.10 The shielding ring 105 is used to reduce magnetic leakage to the outside of the housing, wherein d1 is the first rotor outer diameter, d5 is the first stator outer diameter. The shielding ring thickness H4 is ≥ 0.2d1·sin(360 / (4p1))+0.1(d5-d1). The shielding ring is made of a high magnetic permeability alloy, such as Permalloy.

[0053] like Figure 12-15 , Fig.17 As shown, the first rotor 420 (first rotor magnetic ring 421 ) and the second rotor 320 (second rotor magnetic ring 321 ) are co-arranged on the same cylindrical rotor shaft 700 , and the first rotor is driven by the second rotor to rotate synchronously.

[0054] like Figure 4-5 , Figure 22-25As shown, the bidirectional clutch 500 is arranged between the torque assembly 200 and the modulation ring 430. It is used to transmit torque to it by the torque assembly or by the modulation ring, and the bidirectional 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 members 504 and a plurality of second clutch members 505. The inner sleeve 502 is configured on the torque assembly 200 through spline matching and rotates with the torque assembly. The outer sleeve 503 is fixedly configured on the modulation ring by die-casting with one end face of the modulation ring and rotates with the modulation ring. The cylindrical output shaft 501 is sleeved on the radial outer side of the inner sleeve 502, and the outer sleeve 503 is sleeved on the radial outer side of the cylindrical output shaft 501. The plurality of first clutch members 504 are distributed between the cylindrical output shaft 501 and the inner sleeve 502, and the plurality of second clutch members 505 are distributed between the cylindrical output shaft 501 and the outer sleeve 503. The first clutch member 504 and the second clutch member 505 are arranged in opposite directions. In order to make the first clutch and the second clutch evenly distributed on the circumference to make the two-way clutch sensitive, adjacent first clutches are separated by rollers in the circumferential direction and fill the circumferential gap between the cylindrical output shaft and the inner sleeve together with the rollers, and adjacent second clutches are separated by rollers in the circumferential direction and fill the circumferential gap between the cylindrical output shaft and the outer sleeve together with the rollers. In the illustrated structure, the first clutch and the second clutch have the same cross-sectional structure, and the first clutch and the second clutch are arranged in reverse, which means that their installation directions are opposite.

[0055] exist Figure 4 In the embodiment, the first clutch 504 and the second clutch 505 are located at different positions in the axial direction, and the first clutch 504 and the second clutch 505 are misaligned in the axial direction. In other structures, the first clutch 504 and the second clutch 505 are located at the same position in the axial direction and correspond to each other in the radial direction. Any structure can be selected according to the requirements.

[0056] As described above, a first bearing 107 is assembled between the pivot 201 and the second end cover 104 of the second shell, a second bearing 108 is assembled between the pivot 201 and the cylindrical output shaft 501 of the two-way clutch, a third bearing 109 is assembled between the cylindrical rotor shaft 700 and the second end cover 104 of the second shell, a fourth bearing 110 is assembled between the cylindrical rotor shaft 700 and the cylindrical output shaft 501 of the two-way clutch, and a fifth bearing 111 is assembled between the cylindrical rotor shaft 700 and the first end cover 103, so that the torque assembly 200, the first rotor 420 and the second rotor 320 can all rotate relative to the casing 100, and the cylindrical output shaft 501 of the two-way clutch can rotate relative to the torque assembly and the modulation ring.

[0057] like Figure 26-27 The figure shows a schematic diagram of configuring a mid-mounted motor on a bicycle.

[0058] Reference Fig.24 As shown, when the inner sleeve 502 is rotated clockwise by pedaling, the first clutch 504 is subjected to friction and has a tendency to rotate counterclockwise, and the long diameter direction of the first clutch is squeezed 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 by the first clutch in the same direction, causing the cylindrical output shaft 501 to rotate clockwise. Further, when the cylindrical output shaft 501 rotates clockwise, the second clutch 505 is subjected to friction and has a tendency to rotate counterclockwise, and the short diameter direction of the second clutch corresponds to the cylindrical output shaft 501 and the outer sleeve 503. The second clutch 505 will 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 will not be transmitted to the outer sleeve and the modulation ring. This situation is suitable for driving the bicycle forward by pedaling.

[0059] Reference Fig.24 As shown, the mid-mounted motor is started by supplying power to the mid-mounted motor, and the second rotor rotates by means of the magnetic flux generated by the second stator. The first rotor is driven by the second rotor to rotate synchronously, and the power of the motor part is transmitted to the modulation ring of the reduction device. Its outer sleeve is connected to the modulation ring. When its outer sleeve 503 rotates clockwise, the second clutch 505 has a tendency to rotate clockwise due to friction. The long diameter direction 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 has a tendency to rotate clockwise due to friction, and the short diameter direction of the first clutch 504 corresponds to the cylindrical output shaft 501 and the inner sleeve 502, and 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 situation is suitable for driving the bicycle forward by the mid-mounted motor.

[0060] When riding a bicycle, when the bicycle slides forward, according to the one-way clutch mechanism of the transmission mechanism between the mid-mounted motor and the driving wheel, such as the ratchet pawl mechanism configured in the driving wheel and the driven sprocket, the power transmission between the driving sprocket and the driven sprocket of the mid-mounted motor is cut off, and there is no need to provide pedal power or motor power to the bicycle.

[0061] During riding, when the bicycle is turned around and moves backward, the bicycle driving wheel establishes transmission with the cylindrical output shaft through the transmission mechanism. According to the above-mentioned rotation of the cylindrical output shaft in the clockwise direction when the bicycle moves forward, the backward movement of the bicycle driving wheel causes the cylindrical output shaft 501 to rotate counterclockwise. The counterclockwise rotation of the cylindrical output shaft causes the inner sleeve 502 and the torque assembly 200 to rotate counterclockwise through the first clutch 504, and causes the outer sleeve and the modulation ring to rotate counterclockwise through the second clutch 505. At this time, the mid-mounted motor is not powered and is in a non-working state.

[0062] During riding, the bicycle may be driven forward by pedaling and by the mid-mounted motor alternately. To this end, the mid-mounted reduction motor includes a sensor 601 and a controller 602. The controller receives a signal of the pedal driving torque provided by the sensor to instruct the motor part to work. Accordingly, when the mid-mounted reduction motor is installed on the bicycle, the pedal action instructs the motor part to work to drive the power-assisted bicycle forward. Figure 5 As shown, the sensor 601 is arranged on the inner shell 106 to detect the torque component receiving the pedal drive torque. The pedal drive torque can be a pressure signal or the rotation of the torque component. The controller 602 can be arranged on the mid-mounted motor or the vehicle. When the rider wants to ride the bicycle forward, the rider pedals the pedal, and the pedal drive torque generated by the pedaling action is transmitted to the torque component through the crank. The sensor detects the rotation trend of the torque component or the pressure signal or rotation signal generated by the rotation and provides the signal to the controller.

[0063] 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 along the circumference on the axial projection surface.

[0064] In this embodiment, the motor part 300 is axially connected in series with the high torque density magnetic transmission reduction device 400. Figure 4 It is shown in .

[0065] This embodiment makes the first stator magnetic ring and the first rotor magnetic ring into an integrated structure and divides the circumference into arc segments, uses a Halbach array to magnetize each arc segment, and the magnetic fields of all arc segments together constitute the magnetic fields of the first stator magnetic ring and the first rotor magnetic ring, and the first stator magnetic ring and the first rotor magnetic ring cooperate to gather magnetic field, which reflects the technical advantages of the present invention. The performance requirements of the components and their materials involved are as follows, and the configuration can achieve better results.

[0066] 1. Material performance requirements

[0067] 2. Material selection and adaptability (1) First rotor magnetic ring material Preferred material: Neodymium Iron Boron (NdFeB) N52SH grade.

[0068] Performance parameters: remanence Br = 1.48T, coercivity Hcj = 2200kA / m, remanence temperature coefficient α(Br) = -0.09% / ℃, resistivity = 1.5×10⁻ 6 Ω·m.

[0069] Advantages: High remanence and coercive force match, suitable for strong outward magnetic concentration; nickel-plated (Ni-Cu-Ni) coating enhances corrosion resistance.

[0070] Alternative: Iron-Cobalt alloy (Fe-Co-V).

[0071] Applicable scenarios: Ultra-high temperature environment (>150℃), sacrificing part of the residual magnetism (Br=1.3T) in exchange for temperature stability (remanent magnetism temperature coefficient α(Br)=-0.05% / ℃).

[0072] (2) First stator magnetic ring material Preferred material: Neodymium Iron Boron (NdFeB) N50M grade.

[0073] Performance parameters: remanence Br = 1.42T, coercivity Hcj = 1900kA / m, remanence temperature coefficient α(Br) = -0.11% / ℃, resistivity = 1.4×10⁻ 6 Ω·m.

[0074] Advantages: The cost is lower than N52SH, it meets the demand for inward magnetic concentration, and is compatible with the casing shielding structure.

[0075] Alternative: Amorphous alloy (Fe-Si-B) Applicable scenarios: high frequency conditions (>500Hz), resistivity up to 1.8×10⁻ 6 Ω·m, significantly reducing high-frequency eddy currents.

[0076] (3) Adaptability of one-piece molding process Sintered NdFeB: Using multi-pole orientation sintering technology, the mold presets the magnetic field direction to ensure that the magnetization angle difference between adjacent magnetic poles is 360 / (4p1)° (first rotor) or 360 / (4p3)° (first stator).

[0077] Process difficulties: The grain boundary diffusion (GBD) process needs to be controlled to reduce the magnetic property inhomogeneity caused by the grain boundary phase.

[0078] Bonded magnets: Suitable for complex Halbach structures (such as thin-walled first stators), the resin matrix (epoxy or nylon) is added with carbon fibers (5%-10% by mass) to improve mechanical strength.

[0079] 3. Double Halbach synergy and material interaction (1) Magnetic field superposition enhancement The inner rotor focuses magnetic field outward: high Br neodymium iron boron (N52SH) generates a radial main magnetic field (Br) in the modulation ring area.

[0080] The external stator gathers magnetic field inward: N50M NdFeB generates a reverse tangential magnetic field (Bθ). After passing through the modulation ring, the two are superimposed to form a spiral enhanced magnetic field (Bnet). The calculation formula is: .

[0081] Measured data: In the prototype with p1=4 and p3=7, the field strength in the modulation ring area increased from 1.6T (single Halbach) to 2.1T (double Halbach).

[0082] (2) Eddy current collaborative suppression The first rotor high resistivity design: The resistivity of N52SH (1.5×10⁻ 6 Ω·m) to reduce the eddy current loss on the rotor surface.

[0083] The first stator amorphous alloy can be selected: Fe-Si-B amorphous alloy resistivity (1.8×10⁻ 6 Ω·m) to further block the high-frequency harmonic eddy current path.

[0084] (3) Thermal stability matching First rotor: through α(Br)=-0.09% / ℃ and casing heat dissipation design, the temperature rise ΔT is limited to 40℃.

[0085] First stator: α(Br)=-0.11% / ℃. The magnetic field attenuation is offset by temperature compensation algorithm (such as PID temperature control).

[0086] 4. Material Failure Avoidance Strategies (1) Risk of magnetic ring demagnetization First rotor: Hcj≥2000kA / m, can withstand reverse magnetic field of short-time overload current (3 times rated current).

[0087] First stator: adopts segmented Halbach design (each pole is divided into 3-4 magnetic steels) to avoid local demagnetization spread.

[0088] (2) Mechanical stress cracking Inner rotor: The magnet and the stainless steel sheath adopt interference fit (interference 0.05-0.1mm), and the pre-tightening force offsets the centrifugal stress.

[0089] External stator: The amorphous alloy external stator is equipped with a carbon fiber reinforcement ring, and the bending strength is increased to 180MPa.

[0090] 5. Experimental Verification and Performance Comparison

[0091] exist Fig.33 , Fig.34 In the figure, the surface magnetic curve L1 of the first rotor integrated magnetic ring (the waveform curve represented by the dotted line) is compared with the surface magnetic curve L2 of the first rotor spliced ​​magnetic ring (the waveform curve represented by the solid line), and the surface magnetic curve L3 of the first stator integrated magnetic ring (the waveform curve represented by the dotted line) is compared with the surface magnetic curve L4 of the first stator spliced ​​magnetic ring (the waveform curve represented by the solid line). It can be seen from the figure that the surface magnetic amplitude (vertical axis) of the integrated magnetic ring is larger, showing better superiority.

Claims

1. High torque density magnetic transmission speed reducer, characterized by The invention comprises a first stator (410), a first rotor (420) and a modulation ring (430), wherein: A first stator (410) comprises a first stator magnetic ring (411) of an integral structure, the first stator magnetic ring being used to provide a first stator magnetic field, the circumference of the first stator magnetic ring being divided into 2p3 arc segments, p3 being the number of pole pairs of the first stator magnetic ring, a Halbach array being used to magnetize each arc segment, the magnetic field directions of adjacent arc segments differ by (360 / 4p3)°, and the magnetic fields of all arc segments together constitute the first stator magnetic field; A first rotor (420), comprising a first rotor magnetic ring (421) of an integral structure, the first rotor magnetic ring being used to provide a first rotor magnetic field that rotates with the first rotor, the first rotor (420) being located inside a modulation ring (430) and being coaxial with the modulation ring, the circumference of the first rotor magnetic ring being divided into 2p1 arc segments, p1 being the number of pole pairs of the first rotor magnetic ring, a Halbach array being used to magnetize each arc segment, the magnetic field directions of adjacent arc segments differ by 360 / (4p1)°, and 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. Among them, p1=|p2-p3|, so that 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 transmission reduction device according to claim 1 is characterized in that: The reduction gear comprises a casing, and a first stator (410) is fixed to the casing (100); when d5-d1<d1·sin(360 / (4p1)), a shielding ring (105) is embedded in the inner wall of the casing to reduce magnetic leakage to the outside of the casing, 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 transmission reduction device according to claim 2 is characterized in that: The shielding ring thickness H4≥0.2d1·sin(360 / (4p1))+0.1(d5-d1).

4. The high torque density magnetic transmission reduction device according to claim 2 is characterized in that: The shielding ring is made of high magnetic permeability alloy.

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

6. The high torque density magnetic transmission reduction device according to claim 5 is characterized in that: The modulation ring (430) comprises a cage (431), which comprises two end plates (432) and a plurality of connecting rods (433) connected between the two end plates, wherein the connecting rods extend axially and are distributed along the circumference, and the modulation teeth (435) are fixed in the gaps between adjacent connecting rods (433).

7. The high torque density magnetic transmission reduction device according to claim 6 is characterized in that: The connecting rod (433) is cylindrical, and arc grooves are provided at the middle positions of the two circumferential sides of the modulation teeth (435). The arc grooves are fitted to the surface of the connecting rod so that the connecting rod and the cylindrical shape support each other.

8. The high torque density magnetic transmission reduction device according to claim 1 is 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.

9. The high torque density magnetic transmission reduction device according to claim 1 is characterized in that: The magnetic field of the first stator (410) focuses inward, and the magnetic field of the first rotor (420) focuses outward.

10. The high torque density magnetic transmission reduction device according to any one of claims 1 to 9, characterized in that: The material of the first rotor is neodymium iron boron N52SH, the remanence Br is ≥ 1.4T, and the coercive force Hcj is ≥ 2000kA / m.

11. The high torque density magnetic transmission reduction device according to any one of claims 1 to 9, characterized in that: The material of the modulation tooth (435) is an iron-cobalt alloy, and the saturation magnetic induction intensity Bs is ≥2.3T.

12. The high torque density magnetic transmission reduction device according to any one of claims 1 to 9, characterized in that: The material of the first stator (410) is neodymium iron boron N52SH, with a remanence Br≥1.4T and a coercive force Hcj≥2000kA / m.

13. A mid-mounted motor for a power-assisted bicycle, characterized in that include: Housing (100); A torque assembly (200) which penetrates the housing and has two ends extending out of the housing to receive external torque; The motor part (300) comprises a second stator (310) and a second rotor (320), wherein the second stator comprises an iron core (311) attached to a housing and a winding (312) wound around the iron core, the winding generates a rotating magnetic field when energized, and the second rotor (320) is used to provide a permanent magnetic field matching 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, and a third air gap (330) is maintained between the second rotor and the second stator; The high torque density magnetic transmission reduction device (400) according to any one of claims 1 to 12, wherein the first rotor (420) is driven by the second rotor (320) to rotate synchronously; A two-way clutch (500) is arranged 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 a housing for outputting torque, and the cylindrical output shaft is sleeved on the radial outer side of one end of the torque assembly (200).

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