In-wheel motor

Abstract

Provided is a hub motor, including a stator and a patent. The stator includes a stator core and a coil assembly. The stator core includes 27 pole teeth. The coil assembly includes a first-phase coil group, a second-phase coil group, and a third-phase coil group. The first-phase coil group includes: a first-phase first branch, including a single first wire; a first-phase second branch, including a single second wire; and a first-phase third branch, including a single third wire. The second-phase coil group includes: a second-phase first branch, including a single fourth wire; a second-phase second branch, including a single fifth wire; and a second-phase third branch, including a single sixth wire. The third-phase coil group includes: a third-phase first branch, including a single seventh wire; a third-phase second branch, including a single eighth wire; and a third-phase third branch, including a single ninth wire. The rotor includes a rotor skeleton and 30 sheet-shaped permanent magnets arranged at intervals in the circumferential direction.

Description

Technical Field

[0001] The present disclosure relates to a hub motor, in particular to a 27-slot 30-pole hub brushless motor. Background Art

[0002] In the field of electric bicycles, the 27-slot 30-pole hub brushless motor is used. Generally, the voltage of a commonly used lithium battery pack is 36V, 48V, etc. The battery pack voltage cannot be too high (such as 72V). This is because a higher voltage requires more series-connected battery cells and a stronger battery protection function module, which will increase the battery cost significantly and directly lead to an increase in the user's vehicle purchase cost. Since the battery pack voltage cannot be too high, a high-efficiency hub motor is required. Summary of the Invention

[0003] At least one embodiment of the present disclosure provides a wheel hub motor, which includes a stator and a rotor. The stator includes a stator core and a coil assembly. The stator core includes a stator body and 27 pole teeth radially extending outward from the stator body. The 27 pole teeth include first to twenty-seventh pole teeth arranged in sequence in the circumferential direction. The coil assembly includes a first-phase coil group, a second-phase coil group, and a third-phase coil group. The first-phase coil group includes: a first-phase first branch, which includes a single first wire; a first-phase second branch, which includes a single second wire; and a first-phase third branch, which includes a single third wire. The second-phase coil group includes: a second-phase first branch, which includes a single fourth wire; a second-phase second branch, which includes a single fifth wire; and a second-phase third branch, which includes a single sixth wire. The third-phase coil group includes: a third-phase first branch, including a single seventh wire; a third-phase second branch, including a single eighth wire; and a third-phase third branch, including a single ninth wire. The first wire winds from the wire head around the first pole tooth along the first winding direction in sequence, around the second pole tooth along the second winding direction opposite to the first winding direction, and around the third pole tooth along the first winding direction to the wire tail. The second wire winds from the wire head around the tenth pole tooth along the first winding direction in sequence, around the eleventh pole tooth along the second winding direction, and around the twelfth pole tooth along the first winding direction to the wire tail. The third wire winds from the wire head around the nineteenth pole tooth along the first winding direction in sequence, around the twentieth pole tooth along the second winding direction, and around the twenty-first pole tooth along the first winding direction to the wire tail. The fourth wire winds from the wire head around the fourth pole tooth along the first winding direction in sequence, around the fifth pole tooth along the second winding direction, and around the sixth pole tooth along the first winding direction to the wire tail. The fifth wire winds from the wire head around the thirteenth pole tooth along the first winding direction in sequence, around the fourteenth pole tooth along the second winding direction, and around the fifteenth pole tooth along the first winding direction to the wire tail. The sixth wire winds from the wire head around the twenty-second pole tooth along the first winding direction in sequence, around the twenty-third pole tooth along the second winding direction, and around the twenty-fourth pole tooth along the first winding direction to the wire tail. The seventh wire winds from the wire head around the seventh pole tooth along the first winding direction in sequence, around the eighth pole tooth along the second winding direction, and around the ninth pole tooth along the first winding direction to the wire tail. The eighth wire winds from the wire head around the sixteenth pole tooth along the first winding direction in sequence, around the seventeenth pole tooth along the second winding direction, and around the eighteenth pole tooth along the first winding direction to the wire tail. The ninth wire winds from the wire head around the twenty-fifth pole tooth along the first winding direction in sequence, around the twenty-sixth pole tooth along the second winding direction, and around the twenty-seventh pole tooth along the first winding direction to the wire tail. And the wire heads of the first wire to the third wire are electrically connected, the wire heads of the fourth wire to the sixth wire are electrically connected, the wire heads of the seventh wire to the ninth wire are electrically connected, and the wire tails of the first wire to the ninth wire are electrically connected to form a common end. The rotor includes a rotor skeleton and 30 sheet-shaped permanent magnets. The rotor skeleton is cylindrical and annular, and a rotor cavity is defined inside it.The 30 sheet-shaped permanent magnets are arranged in the rotor cavity at intervals in the circumferential direction.

[0004] For example, in some embodiments, the diameters of the first to ninth wires are in the range of 0.75 - 1.2 mm, the pole teeth of the iron core have a pole tooth gap at the radially outer end, the pole tooth gap is in the range of 1.8 - 2.5 mm, and the rotor has a pole arc coefficient in the range of 0.65 - 0.9. The pole arc coefficient refers to the ratio between the central angle of a single permanent magnet with respect to the longitudinal axis of the rotor and 12 degrees.

[0005] For example, in some embodiments, the height of the permanent magnet is 1 - 2 mm less than the height of the stator iron core.

[0006] For example, in some embodiments, the air gap between the outer circle of the stator and the inner circle of the rotor is in the range of 0.3 - 0.5.

[0007] For example, in some embodiments, the spacing distance between the permanent magnets is greater than 1.4 mm.

[0008] For example, in some embodiments, the stator further includes a rigid short-circuit member, which includes a short-circuit body and nine connection parts that are connected to the short-circuit body and arranged at intervals in the circumferential direction. The wire tails of the first to ninth wires are electrically and mechanically connected to the nine connection parts respectively, and the short-circuit body electrically connects the nine connection parts to form a common end of the first to ninth wires.

[0009] For example, in some embodiments, the short-circuit body is a copper ring. The nine first connection parts are nine tabs extending radially outward from the copper ring. The wire tails of the first to ninth wires are respectively hung on and welded to the nine tabs to form a common end of the first to ninth wires.

[0010] For example, in some embodiments, the stator further includes a stator skeleton. The short-circuit body of the short-circuit member is a first PCB board, including first conductive traces provided thereon. The nine first connection parts include pins fixed in the stator skeleton and protruding from the stator skeleton, and the pins are inserted into and welded to the welding holes of the first PCB board to be electrically connected to the first conductive traces, thereby forming a common end of the first to ninth wires.

[0011] For example, in some embodiments, the short-circuit body is a circular ring-shaped first PCB board, including first conductive traces provided thereon. The nine first connection parts include first recessed parts recessed from the circumferential edge of the first PCB board and first conductive materials provided in the first recessed parts to be electrically connected to the first conductive traces. The wire tails are placed in the first recessed parts and welded to the first conductive materials, thereby forming a common end of the first to ninth wires.

[0012] For example, in some embodiments, the stator further includes a circuit connection member, which includes a connection body and nine second wiring portions. The connection body is a second PCB board, which includes a plurality of second conductive traces disposed thereon. The nine second wiring portions include second recesses recessed from the circumferential edge of the second PCB board and second conductive materials disposed in the second recesses for electrically connecting to the corresponding second conductive traces. The wire ends are placed in the corresponding second recesses and welded to the corresponding second conductive materials to achieve electrical connection of the first to third wires, electrical connection of the fourth to sixth wires, and electrical connection of the seventh to ninth wires.

[0013] For example, in some embodiments, the first to ninth wires are single enameled wires. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present disclosure and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0015] Figure 1 FIG.

[0016] Figure 2 is a perspective view of a stator according to an embodiment of the present disclosure; Figure 1 is an exploded perspective view of the stator in

[0017] Figure 3 FIG. Figure 1 is a top view of the stator in

[0018] Figure 4 FIG. Figure 1 is a schematic diagram of wire connection of the coil assembly of the stator in

[0019] Figure 5 FIG. Figure 1 is a plan view of the circuit connection member of the stator in

[0020] Figure 6 FIG. Figure 1 is a perspective view of the short-circuit member of the stator in

[0021] Figure 7 is an exploded perspective view of a stator according to another embodiment of the present disclosure;

[0022] Figure 8 is a top view of a stator according to still another embodiment of the present disclosure;

[0023] Figure 9 FIG.

[0024] Figure 10 is Figure 9 a plan view of the rotor in

[0025] Figure 11 is Figure 10 an enlarged view of the part within the dashed box in

[0026] Figure 12 is Figure 9 an exploded perspective view of the rotor in

[0027] Figure 13 is Figure 9 a perspective view of the magnetic isolation bridge of the rotor in

[0028] Figure 14 is Figure 9 a plan view of the magnetic isolation bridge of the rotor in

[0029] Figure 15 is a cross-sectional view of a 27-slot 30-pole hub motor according to an embodiment of the present disclosure;

[0030] Figure 16 includes the cogging torque of a conventional 27-slot 30-pole hub motor; and

[0031] Figure 17 is the cogging torque of a 27-slot 30-pole hub motor according to an embodiment of the present disclosure. Detailed Embodiments

[0032] Hereinafter, a hub motor according to an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. To make the objectives, technical solutions, and advantages of the present disclosure clearer, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present disclosure. Apparently, the described embodiments are some, but not all, of the embodiments of the present disclosure.

[0033] Therefore, the following detailed description of the embodiments of the present disclosure provided in conjunction with the accompanying drawings is not intended to limit the scope of the claimed present disclosure, but merely represents selected embodiments of the present disclosure. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present disclosure without creative efforts fall within the scope of protection of the present disclosure.

[0034] Unless otherwise defined in the context, the singular forms include the plural forms. Throughout the specification, the terms "including", "having", etc. are used herein to specify the presence of the described features, numbers, steps, operations, elements, components, or combinations thereof, but do not exclude the presence or addition of one or more other features, numbers, steps, operations, elements, components, or combinations thereof.

[0035] In addition, even though ordinal terms such as "first" and "second" are used to describe various components, these components are not limited by these terms, and these terms are only used to distinguish one element from other elements.

[0036] Overview

[0037] Embodiments of the present disclosure provide a hub motor, in which the efficiency of the stator and the rotor is respectively improved, and parameters related to each other such as the diameter of the wire in the coil assembly of the stator, the pole tooth gap, and the pole arc coefficient of the rotor are optimized, thereby maximizing the motor efficiency and reducing the manufacturing cost.

[0038] Stator

[0039] Generally, when the performance of all components remains unchanged, in order to improve the motor efficiency, the most effective way is to increase the slot fill factor of the coil assembly of the stator and reduce the copper loss. However, the stator of the existing hub brushless motor has defects such as low yield rate, poor safety, low efficiency, high electromagnetic noise, and low productivity.

[0040] The windings of each phase in the stator of the existing hub brushless motor are composed of coils connected in series (i.e., series windings). The series windings need to be made of a single thick copper wire with a large diameter. However, due to the limitation of the mechanical design size of the stator core, it is impossible to wind a single thick enameled wire with a large diameter (>1.3 mm) on the core, so instead, relatively thin multi-strand wires are combined into one strand and then used for winding.

[0041] However, in the process of winding the multi-strand thin wires, after a single thin wire is drawn out from the bobbin under the tension of the winding machine, it is combined into one strand through a combining fixture, then passes through the flying fork of the winding machine, and finally slides into the stator core slot through the winding fixture. In this process, it is very easy to cause damage to the insulation skin, resulting in short circuit breakdown of the winding and damage to the motor.

[0042] In addition, the stator winding process includes drawing out multi-strand thin wires from the bobbin and then combining them into a wire harness and leading it to the flying fork position of the flying fork winding machine. Then, through the flying fork jig, the combined wire harness is slid into the stator winding position for winding. Since the multi-strand thin wires are combined together and must pass through the flying fork jig and slide into the stator slot, when the multi-strand thin wires are wound simultaneously, due to the different radii of the inner and outer circles, the passing speeds of different strands of thin wires between the jigs are different. The tension in the wire wound on the outer circle is greater than the tension in the wire wound on the inner circle. Furthermore, due to the large tension, the wire on the outer circle is wound tightly, while the wire on the inner circle is wound loosely, causing part of the inner circle to be locally extruded from between the outer circles, and the winding of the entire coil is messy and disorderly. This results in a low slot fill factor, low motor efficiency, and greatly affects the inductance and drive efficiency after power-on, and is also the source of electromagnetic noise.

[0043] Furthermore, when multiple thin wires are wound together, there will definitely be mutual friction and extrusion forces. Therefore, the winding machine can only wind the wires at a very slow speed (one revolution every 2 - 4 seconds), which seriously affects the production efficiency. However, if the winding speed is increased, wire damage and insulation problems will occur, and serious safety hazards will arise when the motor is under high load.

[0044] Therefore, in order to improve the motor efficiency, as well as the noise, safety, yield rate, and production efficiency of the motor, it is necessary to improve the stator, which is an important part of the in - wheel motor.

[0045] Figure 1 A perspective view of a stator according to an embodiment of the present disclosure. Figure 2 is Figure 1 an exploded perspective view of the stator in Figure 3 is Figure 1 a top view of the stator in

[0046] As Figures 1 - 3 shown, the stator includes a shaft 110, a stator skeleton 120, a stator core 130, a coil assembly 140, a circuit connection member 150, and a short - circuit member 160.

[0047] The stator core 130 includes a stator body 133 and 27 pole teeth 131 radially extending outward from the stator body 133. These 27 pole teeth 131 respectively include first to twenty - seventh pole teeth 131 arranged in sequence in the circumferential direction. Figure 3 The serial numbers of the pole teeth 131 are shown beside the corresponding pole teeth 131 in . The stator skeleton 120 is used to electrically insulate the pole teeth 131 of the stator core 130. Alternatively, the pole teeth 131 of the stator core 130 can also be electrically insulated by coating an insulating material.

[0048] The coil assembly 140 includes a first - phase coil group for flowing a first - phase current, a second - phase coil group for flowing a second - phase current, and a third - phase coil group for flowing a third - phase current. The first - phase coil group includes a first - phase first branch, a first - phase second branch, and a first - phase third branch, which are respectively formed by winding a single first wire 141, a single second wire 142, and a single third wire 143. The second - phase coil group includes a second - phase first branch, a second - phase second branch, and a second - phase third branch, which are respectively formed by winding a single fourth wire 144, a single fifth wire 145, and a single sixth wire 146. The third - phase coil group includes a third - phase first branch, a third - phase second branch, and a third - phase third branch, which are respectively formed by winding a single seventh wire 147, a single eighth wire 148, and a single ninth wire 149.

[0049] Specifically, as Figure 3As shown, the first to ninth wires 141 to 149 are wound in the following manner: The first wire 141 is wound from the wire head around the first pole tooth 131 in the first winding direction in sequence, around the second pole tooth 131 in the second winding direction, and around the third pole tooth 131 in the first winding direction to the wire tail. The second wire 142 is wound from the wire head around the tenth pole tooth 131 in the first winding direction in sequence, around the eleventh pole tooth 131 in the second winding direction, and around the twelfth pole tooth 131 in the first winding direction to the wire tail. The third wire 143 is wound from the wire head around the nineteenth pole tooth 131 in the first winding direction in sequence, around the twentieth pole tooth 131 in the second winding direction, and around the twenty-first pole tooth 131 in the first winding direction to the wire tail. The fourth wire 144 is wound from the wire head around the fourth pole tooth 131 in the first winding direction in sequence, around the fifth pole tooth 131 in the second winding direction, and around the sixth pole tooth 131 in the first winding direction to the wire tail. The fifth wire 145 is wound from the wire head around the thirteenth pole tooth 131 in the first winding direction in sequence, around the fourteenth pole tooth 131 in the second winding direction, and around the fifteenth pole tooth 131 in the first winding direction to the wire tail. The sixth wire 146 is wound from the wire head around the twenty-second pole tooth 131 in the first winding direction in sequence, around the twenty-third pole tooth 131 in the second winding direction, and around the twenty-fourth pole tooth 131 in the first winding direction to the wire tail. The seventh wire 147 is wound from the wire head around the seventh pole tooth 131 in the first winding direction in sequence, around the eighth pole tooth 131 in the second winding direction, and around the ninth pole tooth 131 in the first winding direction to the wire tail. The eighth wire 148 is wound from the wire head around the sixteenth pole tooth 131 in the first winding direction in sequence, around the seventeenth pole tooth 131 in the second winding direction, and around the eighteenth pole tooth 131 in the first winding direction to the wire tail. The ninth wire 149 is wound from the wire head around the twenty-fifth pole tooth 131 in the first winding direction in sequence, around the twenty-sixth pole tooth 131 in the second winding direction, and around the twenty-seventh pole tooth 131 in the first winding direction to the wire tail. The first winding direction can be one of clockwise and counterclockwise, and the second winding direction is opposite to the first winding direction. Therefore, each phase coil group is separated by 6 pole teeth 131, and the winding directions of the wires on two adjacent pole teeth 131 in each branch are opposite. The adjacent branches of the same phase coil group are spaced 120° apart.

[0050] The wire heads of the first to third wires 141 to 143 are electrically connected to serve as the first-phase connection end of the first-phase coil group, the wire heads of the fourth to sixth wires 144 to 146 are electrically connected to serve as the second-phase connection end of the second-phase coil group, and the wire heads of the seventh to ninth wires 147 to 149 are electrically connected to serve as the third-phase connection end of the third-phase coil group. The wire tails of the first to ninth wires 141 to 149 are electrically connected to form a common end.

[0051] Since the stator uses a single wire to form the coil assembly 140, the stator winding process is greatly simplified, which is conducive to automated and large-scale production. Additionally, since a single wire is used to form the coil assembly 140, during the winding process, the frictional and extrusion forces between wires are reduced, the reliability of the wire is increased, and damage to the wire insulation skin that may occur when the coil assembly 140 is composed of multiple strands of wire is avoided. Furthermore, since a single wire is used to form the coil assembly 140, the wire is wound more neatly, avoiding the chaos and disorder of the coil assembly 140 caused by the tension difference between multiple strands of wire when the coil assembly 140 is composed of multiple strands of wire. Consequently, the slot fill factor of the coil assembly 140 is increased (e.g., about 35%), the inductance and drive efficiency are improved, and the electromagnetic noise is reduced. Moreover, since a single wire is used to form the coil assembly 140, the winding speed is higher compared to the case where the coil assembly 140 is composed of multiple strands of wire, improving the production efficiency. Finally, the floor area of the equipment for single-wire winding is reduced, which is conducive to the efficient layout of the production line.

[0052] To cooperate with the use of a single wire to maximize the motor efficiency, a specific winding method as described above is adopted for the 27-slot stator. Figure 4 For Figure 1 Schematic diagram of the wire connection of the coil assembly 140 of the stator in the figure, where the numbers in the squares correspond to the serial numbers of the pole teeth 131. Figure 4 The figure shows the first-phase coil group 1401 including the first branch 1410 of the first phase, the second branch 1420 of the first phase, and the third branch 1430 of the first phase; the second-phase coil group 1402 including the first branch 1440 of the second phase, the second branch 1450 of the second phase, and the third branch 1460 of the second phase; and the third-phase coil group 1403 including the first branch 1470 of the third phase, the second branch 1480 of the third phase, and the third branch 1490 of the third phase. Figure 4 The figure also shows the first-phase connection end 140a, the second-phase connection end 140b, the third-phase connection end 140d, and the common end 140d.

[0053] As Figure 4 As shown, since there are 3 wires connected in parallel to each other, with such a winding method, even when using a single wire to wind the coil assembly 140, the current-carrying capacity requirements of the stator can be met. Moreover, not only that, the above-mentioned specific winding method, including the winding direction of the coil and the arrangement of the pole teeth 131 in each branch of each phase, cooperates with the single wire to maximize the efficiency of the motor to which the stator is installed. Through such a winding method, it is not necessary to use a single wire with a very large diameter to meet the efficiency requirements of the 27-slot stator for an electric bicycle.

[0054] Under the same specifications and dimensions, compared with a conventional stator, a motor using the stator of the embodiments of the present disclosure has higher power and the motor efficiency is improved.

[0055] In this example, the first to ninth wires 141 to 149 are single enameled wires. Different from a wire harness composed of multiple wires, the outside of a single wire is coated with a single insulating sleeve. In a wire harness composed of multiple wires, the multiple wires are respectively coated with insulating sleeves and combined into a wire harness during winding. For example, the enameled wire can be of a high-temperature type.

[0056] In addition, the diameters of the first to ninth wires 141 to 149, the gap between the pole teeth 131 of the iron core 130, etc. are also optimized to further improve the efficiency of the stator.

[0057] For example, the diameters of the first to ninth wires 141 to 149 can be in the range of 0.75 - 1.2 mm. By setting the diameters of the single first to ninth wires 141 to 149 in the range of 0.75 - 1.2 mm, the maximization of the stator efficiency is achieved. On the one hand, during the winding process of the coil assembly 140, the flying fork jig is placed in the gap between the pole teeth 131, and the wire is wound by sliding the wire along the flying fork jig into this gap. Therefore, the gap between the pole teeth 131, especially the gap between the pole teeth 131 at the radially outer end (pole tooth gap 132), limits the diameter of the wire. And if the pole tooth gap 132 is too large, magnetic flux leakage will occur, which will in turn lead to a reduction in the stator efficiency. Therefore, the diameter of the wire cannot be too large. On the other hand, although the efficiency of the stator composed of single wires has been improved by optimizing the winding method, it is still necessary to increase the diameter of the wire as much as possible to improve the efficiency. Therefore, the diameter of the wire cannot be too small. By weighing the influence of the diameter of the single wire on the stator efficiency, the diameters of the single first to ninth wires 141 to 149 are set in the range of 0.75 - 1.2 mm, thereby achieving the maximization of the stator efficiency.

[0058] For example, the pole teeth 131 of the iron core 130 have a pole tooth gap 132 at the radially outer end, and this pole tooth gap 132 is in the range of 1.8 - 2.5 mm. By setting the pole tooth gap 132 of the pole teeth 131 of the iron core 130 at the radially outer end in the range of 1.8 - 2.5 mm, the optimization of the trade-off between the stator efficiency and the production efficiency is achieved. When the pole tooth gap 132 at the radially outer end is less than 1.8 mm, the winding difficulty increases, which may cause a reduction in the production efficiency and mechanical damage to the single wire, such as scratches. When the pole tooth gap 132 at the radially outer end is greater than 2.5 mm, the magnetic flux leakage between the two pole teeth 131 increases, resulting in a reduction in the stator efficiency.

[0059] In addition, in order to improve the automation level and production efficiency of manufacturing the stator, the connection methods of the wire heads and wire tails of the first to ninth wires 141 to 149 are improved.

[0060] As Figure 1 shown, in this embodiment, the circuit connection member 150 is used to connect the wire heads of the first to ninth wires 141 to 149, and it includes a connection body and nine second wiring parts. Figure 5 For Figure 1 the plan view of the circuit connection member 150 of the stator in Figure 5 shown, the connection body 151 is in the form of a second PCB (printed circuit board). A plurality of second conductive traces (not shown) are provided on the second PCB. The wire heads of the first to ninth wires 141 to 149 are electrically connected to the plurality of second conductive traces to achieve the electrical connection of the wire heads of the first to third wires 141 to 143, the electrical connection of the wire heads of the fourth to sixth wires 144 to 146, and the electrical connection of the wire heads of the seventh to ninth wires 147 to 149. The circuit connection member 150 further includes nine second wiring parts 152. The nine second wiring parts 152 include nine second recessed parts recessed from the circumferential edge of the second PCB and second conductive materials provided at the nine second recessed parts to be electrically connected to the second conductive traces. The nine second recessed parts are arranged at intervals in the circumferential direction to correspond to the positions where the wire heads of the first to ninth wires are located. The wire heads of the first to ninth wires 141 to 149 can be placed in the nine second recessed parts automatically or manually, and these wire heads are respectively welded to the corresponding second recessed parts to achieve the electrical connection as described above through the second conductive traces. In this example, the second recessed parts are recessed from the outer peripheral edge of the second PCB. In other examples, the second recessed parts can also be recessed from the inner peripheral edge of the second PCB. The circuit connection member 150 is fixed to the stator frame 120 by a fastener such as a screw.

[0061] For the electrical connection of the common terminal 140d, in the embodiments of the present disclosure, a dedicated short-circuit member 160 can be used to connect the wire tails of the first to ninth wires 141 to 149 to form the common terminal 140d. The short-circuit member 160 is rigid. That is to say, the short-circuit member 160 does not have flexibility and will not be deformed due to accidental touch. In addition, the short-circuit member 160 further includes a short-circuit body and nine first wiring parts connected to the short-circuit body and arranged at intervals in the circumferential direction. The wire tails of the first to ninth wires 141 to 149 are respectively electrically connected and mechanically connected to the nine first wiring parts, and the short-circuit body electrically connects the nine first wiring parts to form the common terminal 140d of the first to ninth wires 141 to 149.

[0062] In a traditional stator, the common terminal 140d is usually formed by stripping the enameled wires at the ends of 9 wires, tinning the 9 wire ends and then twisting them together, and then covering the 9 wire ends with a high-temperature insulating sleeve. Such a method for forming the common terminal 140d is not conducive to automated production. In some embodiments of the present disclosure, a rigid short-circuit member 160 is used to connect the 9 wire ends to form the common terminal 140d. Since the short-circuit member 160 is rigid, it is conducive to connecting the wire ends of the wires 141-149 to the short-circuit member 160 through automated equipment to form the common terminal 140d. In addition, since the 9 first wiring portions are arranged at intervals in the circumferential direction and are electrically connected by the short-circuit body, the 9 first wiring portions can be arranged near the pole teeth 131 where the corresponding wires are finally wound, so as to reduce the length of the wire ends, thereby reducing the stator harmonic components and improving the reliability of the stator.

[0063] Figure 6 For Figure 1 the perspective view of the short-circuit member 160 of the stator in Figure 6 As shown, the short-circuit body of the short-circuit member 160 is an annular body 161, and the 9 first wiring portions are 9 tabs 162 extending radially outward from the annular body 161. For example, the short-circuit member 160 can be an integral part made of a conductive material such as copper or copper alloy. The wire ends of the first to ninth wires 141-149 are respectively hung on and welded to the 9 tabs 162 to form the common terminal 140d. The wire ends of the first to ninth wires 141-149 can be automatically hung on the corresponding tabs 162 by using automated equipment, and then the wire ends are automatically welded to the tabs 162, such as by resistance welding. During welding, the enameled wire will melt, omitting the step of stripping the enameled wire. Therefore, it is conducive to simplifying and automating the manufacturing process of the stator. For example, the tab 162 can extend outward from the outer peripheral wall of the annular body 161 and form an angle within the range of 20-45 degrees with the longitudinal axis of the annular body 161. Such an angle formed by the tab 162 and the longitudinal axis of the annular body 161 helps to conveniently hang the wire end on the tab 162 and reduces the possibility of the wire end falling off. The reliability of the stator is improved and the automation difficulty is reduced. The annular body 161 can be arranged inside the 27 pole teeth 131 in the radial direction and at one end of the 27 pole teeth 131 in the axial direction. The tab 162 can be arranged between adjacent pole teeth 131 and extend outward along the longitudinal axis. The annular body 161 can be fixed to the stator skeleton 120 by interference fit or injection molded into the stator skeleton 120. In this example, the short-circuit member 160 can be installed on the stator skeleton 120 before forming the coil assembly 140.

[0064] Figure 7 is an exploded perspective view of a stator according to another embodiment of the present disclosure. Figure 7 The stator shown inFigures 1 - 6 The difference between the stators shown lies in the structure of the short - circuit member. As Figure 7 shown, the short - circuit body of the short - circuit member 160' is a circular - ring - shaped first PCB board 161', including first conductive traces (not shown) provided thereon. Nine first connection portions 162' are in the form of pins, which are fixed in the stator frame 120 and protrude from the stator frame 120. These nine first connection portions 162' are welded to the first PCB board 161' to be electrically connected to the first conductive traces, so as to form a common end 140d of the first to ninth electric wires 141 - 149 through the first conductive traces. The nine first connection portions can be injection - molded together with the stator frame 120 or inserted into corresponding mounting holes of the stator frame 120 by interference fit. The wire tails can be automatically welded to the first connection portions 162' by using automated equipment, and then the first PCB board 161' is welded and fixed to the first connection portions 162' to electrically connect the first connection portions 162' and the first conductive traces, thereby forming the common end 140d. As Figure 7 shown, the first PCB board 161' can be fixed to the stator frame 120 by using screws 163'. In this example, the first connection portions 162' are in the form of pins, which are inserted and welded into the welding holes 1611' of the first PCB board 161'. Therefore, using the short - circuit member 160' composed of the first PCB board 161' and the first connection portions 162' fixed in the stator frame 120 and protruding from the stator frame 120 helps to simplify and automate the manufacturing process of the stator. In this example, the first connection portions 162' can be installed in the stator frame 120 before forming the coil assembly 140, and the first PCB board 161' can be installed in the stator frame 120 after forming the coil assembly 140.

[0065] Figure 8 is a perspective view of a stator according to another embodiment of the present disclosure. Figure 8 The stator shown and Figures 1 - 6 the stator shown are different in the structure of the short - circuit member 160. As Figure 8As shown, the short-circuit member 160 comprises a first PCB 161″ in the shape of a circular disk, including first conductive traces disposed thereon. Nine first wiring portions 162″ comprise a first recessed portion recessed from the outer peripheral edge of the first PCB and a second conductive material disposed in the first recessed portion for electrical connection to the conductive traces, thereby forming a common end 140d for the first through ninth wires 141-149. Wire tails can be placed manually or automatically using automated equipment into the first recessed portion and then soldered to the first conductive material in the first recessed portion, thereby forming the common end 140d. Therefore, the use of the short-circuit member 160, comprised of the first PCB 161″, the first recessed portion, and the first conductive material in the first recessed portion, helps simplify and automate the stator manufacturing process. In this example, the first PCB 161″ and the nine first wiring portions 162″ can be mounted to the stator frame 120 after the coil assembly 140 is formed. The first PCB 161″ is secured to the stator frame 120 via screws 163″.

[0066] Rotor

[0067] In order to improve the efficiency of the motor, the rotor, which is an important part of the hub motor, also needs to be improved.

[0068] The rotor includes multiple permanent magnets arranged in a circumferential direction. The rotor rotates relative to the stator through the interaction between these multiple permanent magnets and the stator's pole teeth, which are wound with coils. In conventional rotors, the permanent magnets are arranged closely together, with almost no gaps between them. The self-attraction of the south and north poles of two adjacent permanent magnets forms a self-circuit. This part of the magnetic field cannot be used in the effective magnetic circuit of the motor and is considered an unused magnetic circuit, resulting in waste. In addition, there are magnetic saturation regions on the surfaces of adjacent permanent magnets that face each other, which will generate additional harmonics and vibrations, degrading the performance of the motor.

[0069] The rotor according to the embodiments of the present disclosure features appropriate spacing between permanent magnets, effectively preventing magnetic saturation. This effectively avoids harmonics and vibrations caused by magnetic saturation, reducing motor noise. Furthermore, the reduced size of the permanent magnets reduces material usage and costs, indirectly conserving rare earth resources.

[0070] Figure 9 is a perspective view of a rotor according to an embodiment of the present disclosure, Figure 10 for Figure 9 The plan view of the rotor in Figure 11 for Figure 10 The enlarged view of the dotted box portion, and Figure 12 for Figure 9 The exploded perspective view of the rotor in Figures 9 - 12As shown, the rotor includes a hub body 210, a magnetic conductive ring 220 disposed inside the cylindrical wall of the hub body 210, a first bearing 250 installed at the central hole of the hub body 210, a plurality of permanent magnets 230, and a magnetic isolation bridge 240. To clearly show the structure inside the rotor, Figures 9 - 12 a hub cover that closes the opening of the hub body 210 and a second bearing installed at the central hole of the hub cover are not shown. The hub body 210 and the hub cover together form a hub housing to define the internal space of the rotor, i.e., the rotor cavity. The hub body 210 and the hub cover can be made of aluminum alloy material. The magnetic conductive ring 220 can be an iron ring for guiding the magnetic path of the permanent magnets 230. The plurality of permanent magnets 230 are arranged circumferentially inside the magnetic conductive ring 220 and adhered to the magnetic conductive ring 220.

[0071] Figure 13 For Figure 9 the three-dimensional view of the magnetic isolation bridge 240 of the rotor in Figure 14 For Figure 9 the plan view of the magnetic isolation bridge 240 of the rotor in Figure 13 and Figure 14 As shown, the magnetic isolation bridge 240 includes an annular body 241 and magnetic isolation arms 242 extending axially from the annular body 241. Return Figures 9 - 12 , the plurality of permanent magnets 230 are arranged at intervals from each other, and the magnetic isolation arms 242 of the magnetic isolation bridge 240 are inserted between adjacent permanent magnets 230 to keep the permanent magnets 230 arranged at intervals from each other. Or rather, the permanent magnets 230 are inserted into the notches formed by the magnetic isolation arms 242 of the magnetic isolation bridge 240 being spaced apart from each other, so as to be arranged at intervals from each other. In this embodiment, the rotor is used for a 27-slot 30-pole hub motor. The rotor includes 30 permanent magnets 230.

[0072] The permanent magnets 230 are made of, for example, sintered neodymium iron boron material, are in sheet shape, and are preferably in arc sheet shape to conform to the shape of the circular magnetic conductive ring 220. For example, the two surfaces of the permanent magnet 230 facing the circumferential direction are parallel to each other. In this example, the central angle of the permanent magnet 230 with respect to the longitudinal axis of the rotor remains unchanged in the axial direction. In other examples, the two surfaces of the permanent magnet 230 facing the circumferential direction are not parallel to each other. For example, the permanent magnet 230 is a trapezoidal sheet piece. In this example, the central angle of the permanent magnet 230 with respect to the longitudinal axis of the rotor changes in the axial direction. The central angle of the permanent magnet with respect to the longitudinal axis of the rotor is defined as the measured maximum central angle.

[0073] The motor power is divided into two parts, one part is the useful work and the other part is the useless work. The efficiency of the motor refers to the ratio of the useful work to the total power. The more the proportion of the useful work of the motor, the higher the efficiency of the motor. The power consumed in the magnetic saturation region at the surfaces of adjacent permanent magnets 230 facing each other (i.e., the surfaces facing the circumferential direction) belongs to the useless work. Therefore, it is necessary to minimize the magnetic saturation intensity, and the distance between the N-pole magnet and the S-pole magnet of adjacent permanent magnets 230 is positively correlated with the magnetic saturation intensity. For example, in this example, there are 30 permanent magnets 230, so there are 15 pairs of NS-pole saturation regions, and these saturation regions are evenly distributed in the circumferential direction in the rotor magnetic field. When the motor is running normally, the magnetic fields in these magnetic saturation regions all hinder the magnetic field circulation of the useful work part. Therefore, it is necessary to select an appropriate gap between the permanent magnets 230 to optimize the magnetic circuit arrangement between the permanent magnets 230, thereby maximizing the motor efficiency.

[0074] Here, the pole arc coefficient is defined, which is the ratio of the central angle θ (see Figure 14 ) of a single permanent magnet 230 with respect to the longitudinal axis of the rotor to the angle of the magnetic pole of the rotor, and the angle of the magnetic pole of the rotor is 360 degrees divided by the number of permanent magnets 230. In this example, the angle of the magnetic pole of the rotor is 12°. The embodiments of the present disclosure set the pole arc coefficient in the range of 0.65 - 0.9, achieving the optimization of the motor efficiency. When the pole arc coefficient is greater than 0.9, the magnetic saturation effect cannot be effectively avoided, resulting in material waste, and it is difficult to accurately maintain a small gap between the permanent magnets 230. When the pole arc coefficient is less than 0.65, the magnetic density is too small to meet the requirements of the motor for current and power.

[0075] In addition, considering the influence of the overall size of the rotor on the magnetic circuit arrangement, the spacing distance between the permanent magnets 230 is greater than 1.4 mm.

[0076] In - wheel motor

[0077] At least one embodiment of the present disclosure provides a hub motor, which includes a stator and a rotor. The stator can be the stator as described above, and the rotor can be the rotor as described above.

[0078] As described above, the diameter of the wire, the pole tooth gap, and the pole arc coefficient are interrelated with each other and jointly affect the motor efficiency. Specifically, the cooperation between the pole arc coefficient of the rotor and the pole tooth gap of the stator affects the cogging effect of the motor. And the diameter of the motor and the pole tooth gap affect and restrict each other. The hub motor according to the embodiments of the present disclosure reduces the cogging torque and the noise caused by the magnetic saturation region of the motor by reasonably setting the pole arc coefficient of the rotor and the diameter and pole tooth gap of the wire in the stator, thereby reducing the harmonic components of the motor and improving the efficiency of the motor.

[0079] Figure 15 A cross-sectional view of a 27-slot 30-pole hub motor according to an embodiment of the present disclosure. As Figure 15 shown, the motor includes a rotor and a stator. As described above, the stator includes a shaft 110, a stator core 130 fixed to the shaft 110 and including 27 pole teeth, and a coil assembly 140 wound around the pole teeth. As described above, the rotor includes a hub housing having a hub body 210 and a hub cover 260, a magnetic conducting ring 220, 30 permanent magnets 230, a first bearing 250 fixed to the hub body 210, and a second bearing 270 fixed to the hub cover. The shaft 110 of the stator is supported on the first bearing 250 and the second bearing 270, enabling the rotor to rotate relative to the stator.

[0080] The coil assembly 140 of the stator can be formed by winding around the 27 pole teeth 131 of the stator core 130 in a specific manner as described above through the first to ninth wires 141-149. The 30 permanent magnets 230 of the rotor can be arranged with spaces therebetween via magnetic isolation bridges 240 as described above. The diameters of the first to ninth wires 141-149 are in the range of 0.75-1.2 mm, the pole teeth 131 of the core 130 have a pole tooth gap 132 in the range of 1.8-2.5 mm at the radially outer end, and the rotor has a pole arc coefficient in the range of 0.65-0.9. Such configurations of the wire diameter, pole tooth gap, and pole arc coefficient allow for maximizing the motor efficiency.

[0081] In addition, in this hub motor, the air gap 300 ( Figure 15 shown as a thick black line in ) between the outer circle of the stator (i.e., the outer circle of the core 130) and the inner circle of the rotor (i.e., the inner circle of the permanent magnets) is in the range of 0.3-0.5 mm, which, in combination with the above parameters of the wire diameter, pole tooth gap, and pole arc coefficient, further optimizes the motor efficiency.

[0082] In this example, the height of the permanent magnet 230 is the same as the height of the stator core 130. In other examples, the permanent magnet 230 is 1-2 mm lower than the height of the stator core 130. In this example, even if the height is less than that of the stator core 130, the permanent magnet 230 can still generate a sufficient magnetic field at its end to cooperate with the stator core 130. The reduced volume of the permanent magnet 230 reduces the material usage and cost of the permanent magnet and protects rare earth resources.

[0083] Considering the influence of the overall size of the motor on the magnetic circuit arrangement, the spacing distance between the permanent magnets 230 is greater than 1.4 mm.

[0084] Figure 16 is the cogging torque of a conventional 27-slot 30-pole hub motor, and Figure 17 is the cogging torque of a 27-slot 30-pole hub motor according to an embodiment of the present disclosure. AsFigure 16 and Figure 17 As shown, compared with the motor including a conventional rotor, the cogging torque of the motor according to an embodiment of the present disclosure is reduced from about 0.16 N·m to about 0.06 N·m. This cogging torque can reflect the magnitude of the useless work of the motor in the magnetic saturation region. It can be seen that the motor according to the embodiment of the present disclosure achieves improved motor efficiency and reduced noise.

[0085] The above embodiments merely represent several implementation manners of the present disclosure. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the patent scope of the present disclosure. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present disclosure, several modifications and improvements can still be made, and these all belong to the protection scope of the present disclosure. Therefore, the protection scope of the patent of the present disclosure shall be subject to the appended claims.

Claims

1. A hub motor, comprising: A stator, the stator comprising: A stator core, which includes a stator body and 27 pole teeth radially extending outward from the stator body, and the 27 pole teeth include first to twenty-seventh pole teeth arranged in sequence in the circumferential direction; A coil assembly, including: A first-phase coil group, including: A first branch of the first phase, including a single first wire; A second branch of the first phase, including a single second wire; and A third branch of the first phase, including a single third wire; A second-phase coil group, including: A first branch of the second phase, including a single fourth wire; A second branch of the second phase, including a single fifth wire; and A third branch of the second phase, including a single sixth wire; A third-phase coil group, including: A first branch of the third phase, including a single seventh wire; A second branch of the third phase, including a single eighth wire; and A third branch of the third phase, including a single ninth wire, wherein, The first wire winds from the wire head around the first pole tooth along the first winding direction in sequence, around the second pole tooth along the second winding direction opposite to the first winding direction, and around the third pole tooth along the first winding direction to the wire tail; The second wire winds from the wire head around the tenth pole tooth along the first winding direction in sequence, around the eleventh pole tooth along the second winding direction, and around the twelfth pole tooth along the first winding direction to the wire tail; The third wire winds from the wire head around the nineteenth pole tooth along the first winding direction in sequence, around the twentieth pole tooth along the second winding direction, and around the twenty-first pole tooth along the first winding direction to the wire tail; The fourth wire winds from the wire head around the fourth pole tooth along the first winding direction in sequence, around the fifth pole tooth along the second winding direction, and around the sixth pole tooth along the first winding direction to the wire tail; The fifth wire winds from the wire head around the thirteenth pole tooth along the first winding direction in sequence, around the fourteenth pole tooth along the second winding direction, and around the fifteenth pole tooth along the first winding direction to the wire tail; The sixth wire winds from the wire head around the twenty-second pole tooth along the first winding direction in sequence, around the twenty-third pole tooth along the second winding direction, and around the twenty-fourth pole tooth along the first winding direction to the wire tail; The seventh wire winds from the wire head around the seventh pole tooth along the first winding direction in sequence, around the eighth pole tooth along the second winding direction, and around the ninth pole tooth along the first winding direction to the wire tail; The eighth wire winds from the wire head around the sixteenth pole tooth along the first winding direction in sequence, around the seventeenth pole tooth along the second winding direction, and around the eighteenth pole tooth along the first winding direction to the wire tail; The ninth wire winds from the wire head around the twenty-fifth pole tooth along the first winding direction in sequence, around the twenty-sixth pole tooth along the second winding direction, and around the twenty-seventh pole tooth along the first winding direction to the wire tail, and The wire heads of the first wire to the third wire are electrically connected, the wire heads of the fourth wire to the sixth wire are electrically connected, the wire heads of the seventh wire to the ninth wire are electrically connected, and the wire tails of the first wire to the ninth wire are electrically connected to form a common end; and A rotor, the rotor comprising: A rotor skeleton, which is cylindrical and annular, and defines a rotor cavity inside it; 30 sheet-shaped permanent magnets are arranged in the rotor cavity at intervals in the circumferential direction.

2. The in-wheel motor according to claim 1, wherein the diameters of the first to ninth wires are in the range of 0.75 - 1.2 mm, the pole teeth of the iron core have pole tooth gaps at the radially outer ends, the pole tooth gaps are in the range of 1.8 - 2.5 mm, and the rotor has a pole arc coefficient in the range of 0.65 - 0.9, and the pole arc coefficient refers to the ratio between the central angle of a single permanent magnet with respect to the longitudinal axis of the rotor and 12 degrees.

3. The in-wheel motor according to claim 1 or 2, wherein the height of the permanent magnet is 1 - 2 mm smaller than the height of the stator iron core.

4. The in-wheel motor according to claim 1 or 2, wherein the air gap between the outer circle of the stator and the inner circle of the rotor is in the range of 0.3 - 0.

5.

5. The in-wheel motor according to claim 1 or 2, wherein the spacing distance between the permanent magnets is greater than 1.4 mm.

6. The in-wheel motor according to claim 1 or 2, wherein The stator further includes: a rigid short-circuit member, which includes a short-circuit body and nine wiring parts connected to the short-circuit body and arranged at intervals in the circumferential direction. The wire tails of the first to ninth wires are electrically and mechanically connected to the nine wiring parts respectively, and the short-circuit body electrically connects the nine wiring parts to form a common end of the first to ninth wires.

7. The in-wheel motor according to claim 6, wherein the short-circuit body is a copper ring, the nine first wiring parts are nine tabs extending radially outward from the copper ring, the wire tails of the first to ninth wires are respectively hung on and welded to the nine tabs to form a common end of the first to ninth wires.

8. The in-wheel motor according to claim 6, wherein the stator further includes a stator skeleton, wherein the short-circuit body of the short-circuit member is a first PCB board, including first conductive traces provided thereon, the nine first wiring parts include pins fixed in the stator skeleton and protruding from the stator skeleton. The pins are inserted into and welded to the welding holes of the first PCB board to be electrically connected to the first conductive traces, thereby forming a common end of the first to ninth wires.

9. The in-wheel motor according to claim 6, wherein the short-circuit body is a circular ring-shaped first PCB board, including first conductive traces provided thereon, the nine first wiring parts include first recessed parts recessed from the circumferential edge of the first PCB board and first conductive materials provided in the first recessed parts to be electrically connected to the first conductive traces. The wire tails are placed in the first recessed parts and welded to the first conductive materials, thereby forming a common end of the first to ninth wires.

10. The in-wheel motor according to claim 1 or 2, wherein the stator further includes a circuit connection member, which includes a connection body and nine second wiring parts, the connection body is a second PCB board, which includes a plurality of second conductive traces provided thereon, The nine second wiring portions include second recessed portions recessed from the circumferential edge of the second PCB board and second conductive materials disposed in the second recessed portions for electrically connecting to corresponding second conductive traces, and the wire ends are placed in corresponding second recessed portions and welded to the corresponding second conductive materials to achieve electrical connection of the first to third wires, electrical connection of the fourth to sixth wires, and electrical connection of the seventh to ninth wires.

11. The in-wheel motor according to claim 1 or 2, wherein the first to ninth wires are single enameled wires.

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