Outer-rotor electric motor

Abstract

An outer-rotor electric motor, comprising an axially-extending electric motor shaft, an outer-rotor assembly for holding the electric motor shaft, and an inner-stator assembly located between the electric motor shaft and the outer-rotor assembly. The outer-rotor assembly comprises an outer-rotor housing for accommodating the inner-stator assembly, the outer-rotor housing comprising an annular wall sleeved on the outer periphery of the inner-stator assembly, and an end wall connected to the axial rear end of the annular wall. The outer-rotor housing further comprises an inner extension portion and an outer extension portion which extend axially from the end face of the end wall, wherein the inner extension portion and the outer extension portion are located on front and rear sides of the end wall, respectively; and an outer peripheral wall of the electric motor shaft is held on inner peripheral walls of the inner extension portion and the outer extension portion. By means of such an arrangement, the fitting area between the electric motor shaft and the outer-rotor housing is increased, thereby effectively improving the bonding force between the electric motor shaft and the outer-rotor housing, and improving the dimensional accuracy after press-fitting, improving the strength of the outer-rotor housing during rotation; and the process of integrally forming the outer-rotor housing through cold heading is simple.

Description

Outer rotor motor [Technical field]

[0001] The present invention relates to the technical field of outer rotor motors, and in particular to an outer rotor motor with an improved outer rotor casing. [Background Technology]

[0002] Motors are generally categorized as inner rotor motors and outer rotor motors based on the relative position of the rotor and stator. Outer rotor motors are gaining increasing attention due to their compact structure, easy installation, and reliable operation. Traditional outer rotor motor outer rotor casings are manufactured in two ways: One method involves press-fitting an annular aluminum component with a steel assembly to form a complete outer rotor casing. The motor shaft is then fitted into the steel assembly. Because the steel assembly is manufactured separately, the desired structure can be achieved. This approach ensures the bond between the motor shaft and the outer rotor casing, but the aluminum component and steel assembly must meet certain bonding strength and dimensional accuracy requirements, resulting in a complex and costly process.

[0003] The second is that the outer rotor casing is formed in one piece using a stamping process. This solution solves the problems of bonding strength and dimensional accuracy in Solution 1. However, due to the characteristics of the stamping parts themselves, the wall thickness of the outer rotor casing is the same, so the fitting part between the motor shaft and the outer rotor casing is restricted. The bonding force between the two is small, and the strength of the fitting part of the outer rotor casing is low. During the rotation of the outer rotor motor, the fitting part between the outer rotor casing and the motor shaft may be broken.

[0004] In view of this, it is indeed necessary to provide an improved outer rotor motor to overcome the defects of the prior art. [Summary of the invention]

[0005] In view of the deficiencies of the prior art, the object of the present invention is to provide an outer rotor motor with an outer rotor housing of higher strength, which can effectively improve the bonding force between the motor shaft and the outer rotor housing and improve the dimensional accuracy of the motor shaft and the outer rotor housing after press-fitting.

[0006] The technical solution adopted by the present invention to solve the existing technical problems is: an outer rotor motor, including a motor shaft extending in the axial direction, an outer rotor assembly that fixes the motor shaft, and an inner stator assembly located between the motor shaft and the outer rotor assembly; the outer rotor assembly includes an outer rotor casing that accommodates the inner stator assembly, the outer rotor casing includes an annular wall that is sleeved on the outer periphery of the inner stator assembly and an end wall connected to the axial rear end of the annular wall; the outer rotor casing also includes an inner extension part and an outer extension part that connect the two end surfaces of the end wall, the inner extension part is located inside the annular wall, and the outer peripheral wall of the motor shaft is fixed on the inner extension part and the outer extension part.

[0007] A further improved solution is: the axial rear end of the motor shaft includes a first coupling portion, the outer extension portion of the outer rotor housing includes a second coupling portion, and the axial rear end of the motor shaft is installed in the second coupling portion of the outer rotor housing through the first coupling portion.

[0008] A further improved solution is that the shapes of the first combining portion and the second combining portion are adapted to each other, and one of the first combining portion and the second combining portion is configured as a protrusion, and the other is configured as a depression.

[0009] A further improved solution is: the number of the first combining parts and the second combining parts is at least three, and the axial length of the first combining part is not greater than the axial length of the second combining part.

[0010] A further improvement is as follows: the outer diameter of the first coupling portion is not less than the inner diameter of the second coupling portion, and the first coupling portion and the second coupling portion are connected by an interference fit or a transition fit; the outer diameter of the motor shaft is larger than the inner diameter of the inner extension portion, and the motor shaft is interference-fitted in the inner extension portion.

[0011] A further improvement is that the wall thickness of the inner extension portion and the outer extension portion is not less than the wall thickness of the end wall, and the axial length of the inner extension portion and the outer extension portion is not less than 2 mm.

[0012] A further improvement is that the outer rotor housing is integrally formed by a cold heading process, and the annular wall, the end wall, the inner extension and the outer extension are an integral structure.

[0013] A further improvement scheme is: the inner stator assembly includes an inner stator bracket sleeved on the outer circumference of the motor shaft and an inner stator core fixed to the inner stator bracket, the outer rotor motor includes a rear bearing accommodated in the axial rear end of the inner stator core, the outer circumferential surface of the rear bearing is in contact with the inner circumferential wall of the inner stator core, and the motor shaft is supported at the axial rear end of the inner stator core through the rear bearing.

[0014] A further improved solution is: the rear bearing is located at the axial front end of the inner extension portion, and the end portion of the inner extension portion abuts against the end surface of the rear bearing.

[0015] A further improved solution is: the outer rotor motor includes a fan fixed to the outer extension portion, and the fan is integrally injection-molded on the outer extension portion.

[0016] A further improvement is: a first mating portion is formed on the outer periphery of the outer extension, and a second mating portion is formed on the inner periphery of the fan, wherein the second mating portion matches the shape of the first mating portion and the two are interlocked and installed. A further improvement is: the first mating portion is configured as an annular groove, and the second mating portion is configured as an annular protrusion.

[0017] A further improvement is that the axial length of the outer extension portion is not less than 4 mm.

[0018] A further improved solution is that the axial rear end surface of the fan protrudes beyond the axial rear end surface of the outer extension portion.

[0019] A further improved solution is: a plurality of air outlets penetrating the end wall are provided on the end wall, the air outlets are located at the axial front end of the fan, and the fan is arranged adjacent to the air outlets.

[0020] A further improvement is that the fan is a centrifugal fan.

[0021] A further improvement is that the number of the air outlets is 6, which are circular in shape and arranged around the center of the end wall.

[0022] A further improved solution is that the fan is attached to the end surface of the end wall.

[0023] An outer rotor motor comprises an axially extending motor shaft, an outer rotor assembly that holds the motor shaft, and an inner stator assembly located between the motor shaft and the outer rotor assembly; the outer rotor assembly comprises an outer rotor housing that accommodates the inner stator assembly, the outer rotor housing comprising an annular wall sleeved around the outer periphery of the inner stator assembly and an end wall connected to the axial rear end of the annular wall; the outer rotor housing is characterized in that the outer rotor housing further comprises an inner extension portion and an outer extension portion connecting both end surfaces of the end wall, and the fan is integrally injection molded on the inner extension portion.

[0024] A further improvement is that the fan is an axial flow fan.

[0025] Compared to existing technologies, the present invention offers the following advantages: the outer rotor housing further includes an inner extension and an outer extension connecting the two end surfaces of the end wall. The inner extension is located within the annular wall, and the outer peripheral wall of the motor shaft is retained by the inner and outer extensions. This arrangement increases the mating surface between the motor shaft and the outer rotor housing, effectively improving the bonding strength between the motor shaft and the outer rotor housing and the dimensional accuracy after press-fitting, thereby enhancing the strength of the outer rotor housing during rotation. Furthermore, the integral cold-forging process for forming the outer rotor housing is simple. [Brief Description of the Drawings]

[0026] The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings:

[0027] FIG1 is a perspective schematic diagram of an outer rotor motor of the present invention;

[0028] FIG2 is a cross-sectional view of the outer rotor motor shown in FIG1 ;

[0029] FIG3 is an exploded view of the outer rotor motor shown in FIG2 ;

[0030] FIG4 is a perspective schematic diagram of an inner stator assembly of the outer rotor motor shown in FIG1 ;

[0031] FIG5 is a perspective schematic diagram of an inner stator bracket of the outer rotor motor shown in FIG1 ;

[0032] FIG6 is a cross-sectional view of the inner stator bracket of the outer rotor motor shown in FIG5 ;

[0033] FIG7 is a perspective schematic diagram of the outer rotor housing of the outer rotor motor shown in FIG1 ;

[0034] FIG8 is a perspective schematic diagram of the outer rotor housing of the outer rotor motor shown in FIG7 from another angle;

[0035] FIG9 is a cross-sectional view of the outer rotor housing and magnetic steel of the outer rotor motor shown in FIG8 ;

[0036] FIG10 is a perspective schematic diagram of the outer rotor housing of the outer rotor motor shown in FIG1 ;

[0037] FIG11 is a perspective schematic diagram of the outer rotor housing of the outer rotor motor shown in FIG10 from another angle;

[0038] FIG12 is a cross-sectional view of the outer rotor housing and the fan of the outer rotor motor shown in FIG1 ;

[0039] FIG13 is a perspective schematic diagram of an insulating gasket of the outer rotor motor shown in FIG1 ;

[0040] FIG14 is a perspective schematic diagram of the motor shaft of the outer rotor motor shown in FIG1 .

[0041] Meanings of the reference numerals in the figures: Outer rotor motor 100 Motor shaft 1 Front bearing 10 Gasket 101 Circlip 102 Rear bearing 11 First coupling portion 12 Outer rotor assembly 2 Outer rotor housing 20 Annular wall 201 Magnetic steel groove 2010 Accommodating groove 2011 End wall 202 Air inlet 2020 Inner extension 203 Outer extension 204 Second coupling portion 2040 First matching portion 2041 Extension 205 Inner stator assembly 3 Inner stator bracket 30 Base 301 Main body 302 Support portion 303 Step portion 304 Annular sleeve 31 Insulating gasket 32 ​​Outer ring 321 Inner ring 322 Boss 323 Inner stator core 33 Winding 34 Fan 4 Second matching portion 40 Radial width D1 of the magnetic steel groove Radial width D2 of the accommodating groove Radial depth D3 of the magnetic steel groove Radial depth D4 of the receiving groove [Specific implementation method]

[0042] The terms used in this disclosure are for the purpose of describing specific embodiments only and are not intended to limit the disclosure. For example, terms such as "upper," "lower," "front," and "rear" indicating orientation or positional relationships are based solely on the orientation or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the disclosure. They do not indicate or imply that the device or element referred to must have a specific orientation or be constructed or operated in a specific orientation. Therefore, they should not be construed as limiting the disclosure.

[0043] Figures 1 to 14 illustrate an outer rotor motor 100 according to the present invention, typically used in conjunction with a power tool. This outer rotor motor 100 features convenient operation and maintenance, simple assembly, compact structure, reliable operation, and environmental and economic advantages. This outer rotor motor 100 includes an axially extending motor shaft 1, an outer rotor assembly 2 connected to the motor shaft 1, and an inner stator assembly 3 positioned between the motor shaft 1 and the outer rotor assembly 2. The motor shaft 1 rotates relative to the inner stator assembly 3 along with the outer rotor assembly 2.

[0044] Please refer to Figures 1 to 3. The outer rotor assembly 2 shown has an outer rotor housing 20 for accommodating the inner stator assembly 3. The outer rotor housing 20 includes an annular wall 201 that is sleeved on the outer periphery of the inner stator assembly 3 and an end wall 202 located axially rearward of the annular wall 201. The annular wall 201 extends axially forward from the circumferential side of the end wall 202, and the motor shaft 1 is arranged through the end wall 202.

[0045] The outer rotor housing 20 can be cylindrical, with an outer diameter greater than that of the inner stator assembly 3. One end of the outer rotor housing 20 is open, allowing the inner stator assembly 3 to pass through. In this embodiment, the outer rotor housing 20 is made of metal; however, in alternative embodiments, the outer rotor housing 20 can be made of other materials.

[0046] 9 , the outer rotor housing 20 further includes an extension portion 205 protruding axially from the end wall 202 , wherein the extension portion 205 includes an inner extension portion 203 located at the axial front end of the end wall 202 and an outer extension portion 204 located at the axial rear end of the end wall 202 .

[0047] The annular wall 201, the end wall 202, the inner extension portion 203 and the outer extension portion 204 are integrally formed by a cold heading process. After the outer rotor housing 20 is cold headed, each part can be further processed by a finishing process, for example: the axial length, wall thickness, etc. of the inner extension portion 203 and the outer extension portion 204 can be changed by cutting.

[0048] In conventional solutions, the outer rotor housing 20 is integrally formed using a stamping process. Due to the inherent characteristics of stamped parts, the end wall 202 and the inner extension 203 have the same wall thickness. Furthermore, the stamping process cannot form the inner extension 203 and the outer extension 204 at the axial ends of the end wall 202. Typically, only the inner extension 203 at the axial front end of the end wall 202 is formed. After the motor shaft 1 is assembled with the end wall 202 and the inner extension 203, during use of the outer rotor motor 100, the junction between the motor shaft 1 and the outer rotor housing 20 may fracture, causing failure or damage to the outer rotor motor 100.

[0049] In this embodiment, when the outer rotor housing 20 is cold-forging, the inner extension portion 203 and the outer extension portion 204 are integrally formed at both axial ends of the end wall 202. After the motor shaft 1 is fitted with the inner extension portion 203, the end wall 202, and the outer extension portion 204, the bonding force at the fitting point between the motor shaft 1 and the outer rotor housing 20 and the dimensional accuracy after press-fitting can be improved, and the strength of the outer rotor housing 20 during rotation can be improved.

[0050] As shown in FIG. 3 , the outer diameter of the motor shaft 1 is larger than the inner diameter of the inner extension portion 203 , and the outer circumference of the motor shaft 1 is installed on the inner circumference of the inner extension portion 203 by interference fit.

[0051] Further, please refer to Figures 7 and 14. The inner wall of the outer extension portion 204 includes several second coupling portions 2040, and the axial rear end of the motor shaft 1 includes several first coupling portions 12. The first coupling portions 12 are the same in number and shape as the second coupling portions 2040. The outer circumferential surface of the first coupling portion 12 is fitted on the inner circumferential surface of the second coupling portion 2040. The outer diameter of the first coupling portion 12 is larger than the inner diameter of the second coupling portion 2040. The motor shaft 1 is fitted in the second coupling portion 2040 of the outer extension portion 204 by a small interference fit or overfit of the first coupling portion 12.

[0052] The provision of the first coupling portion 12 and the second coupling portion 2040 can further increase the coupling force between the motor shaft 1 and the outer rotor housing 20, thereby preventing relative sliding between the motor shaft 1 and the outer rotor housing 20 during operation of the outer rotor motor 100. In this embodiment, the first coupling portion 12 is configured as a projection, and the second coupling portion 2040 is configured as a recess. Alternatively, the first coupling portion 12 can be configured as a recess, and the second coupling portion 2040 can be configured as a projection. The shapes of the first coupling portion 12 and the second coupling portion 2040 can be selected as required, such as a projection configured as a trapezoid, a semi-cylinder, a triangle, etc. Preferably, the number of the first coupling portion 12 and the second coupling portion 2040 is at least three. This configuration can reduce the possibility of relative sliding between the two.

[0053] Providing a chamfer at the junction of the inner extension portion 203 and the end wall 202 can further improve the strength of the outer rotor housing 20 and reduce the possibility of fracture between the inner extension portion 203 and the end wall 202 .

[0054] Because the outer rotor housing 20 is integrally formed through a cold heading process, the dimensions of the inner extension 203 and the outer extension 204 can be freely selected through fine machining. Therefore, the wall thickness of the inner extension 203 and the outer extension 204 can be made greater than the wall thickness of the end wall 202, further improving the strength of the outer rotor housing 20. Preferably, the wall thickness of the outer extension 204 is no less than 2 mm, which ensures good strength between the outer extension 204 and the end wall 202 and prevents fracture and failure of the outer extension 204.

[0055] As shown in Figures 7, 9, and 12, the outer rotor housing 20 holds a fan 4, which is integrally injection-molded onto the outer rotor housing 20. Specifically, after the outer rotor housing 20 is finely machined, the fan 4 is integrally injection-molded onto the outer extension 204. The fan 4 rotates with the outer rotor housing 20.

[0056] In the traditional solution, the fan 4 is fixed to the axial rear end of the motor shaft 1, and the two are assembled by interference fit. At the same time, in order to reduce the possibility of sliding between the fan 4 and the motor shaft 1, it is necessary to add knurling to the outer peripheral surface of the motor shaft 1 or add an insert to the center hole of the inner ring of the fan 4 when injection molding. This assembly method has many parts and a complicated process.

[0057] In this embodiment, after the outer rotor housing 20 is cold-forged, it is placed in a jig and the fan 4 is directly molded onto the outer extension 204 by injection molding. This can reduce production processes and improve production efficiency. In addition, the integral molding can improve the balance between the fan 4 and the outer extension 204. The fan 4 can be injection molded from a plastic material or other metal materials such as aluminum.

[0058] Furthermore, a first matching portion 2041 is provided on the outer periphery of the outer extension portion 204 , and a second matching portion 40 is provided on the inner periphery of the fan 4 . The second matching portion 40 is adapted to the shape of the first matching portion 2041 , and the two are fitted together.

[0059] In this embodiment, the first matching portion 2041 is configured as an annular groove, and the second matching portion 40 is configured as an annular protrusion. The two match each other so that the fan 4 will not move axially or fall off due to vibration during rotation.

[0060] Considering that the outer extension portion 204 needs to be provided with the first matching portion 2040 and the fan 4 needs to be injection molded, the axial length of the outer extension portion 204 is not less than 4 mm, and the thickness of the fan 4 can be selected according to design requirements. The axial rear end face of the fan 4 can protrude from the axial rear end face of the outer extension portion 204, or the axial rear end face of the fan 4 can be flush with the axial rear end face of the outer extension portion 204, or the axial rear end face of the fan 4 can be shorter than the axial rear end face of the outer extension portion 204.

[0061] To ensure the coupling force between the first mating portion 2041 and the second mating portion 40, the axial length of the first mating portion 2041 is not less than 2 mm, and the radial depth of the first mating portion 2041 is not less than 1 mm. If the axial length and radial depth of the first mating portion 2041 are too small, the axial positioning of the fan 4 will be poor, and the fan 4 may move axially on the outer extension portion 204 or even fall off.

[0062] As shown in FIG8 , the end wall 202 is provided with a plurality of air outlets 2020 extending therethrough. The air outlets 2020 are located at the axial front end of the fan 4, and the fan 4 is disposed adjacent to the air outlets 2020. In this embodiment, the fan 4 is a centrifugal fan, with its blades disposed toward the air outlets 2020. The fan 4 can draw in external air from the axial front end of the outer rotor motor 100 and discharge it from the axial rear end, thereby cooling the outer rotor motor 100.

[0063] The air outlet 2020 is used to discharge the cooling air entering the outer rotor motor 100. When the outer rotor motor 100 is started, the outer rotor housing 20 rotates and drives the fan 4 to rotate. Due to the characteristics of the centrifugal fan, external air enters from the axial front end of the outer rotor motor 100. After the external air flows through the inner stator assembly 3, it cools the inner stator assembly 3 and is then discharged from the air outlet 2020.

[0064] In this embodiment, the number of the air outlets 2020 is 6, which are circular in shape and arranged around the center of the end wall 202, which not only ensures the air volume of cooling air but also makes the shape beautiful; preferably, the number of the air outlets 2020 can be one or more, and the shape can be any shape or a combination of different shapes.

[0065] The fan 4 does not need to be assembled by press-fitting, so the length of the fan 4 from the end wall 202 can be selected according to design requirements. Preferably, the fan 4 is attached to the end surface of the end wall 202, which can increase the amount of cooling air entering the outer rotor motor 100, achieve better heat dissipation effect, and also reduce the axial size, making the outer rotor motor 100 compact.

[0066] In another embodiment, the fan 4 is integrally injection molded with the inner extension portion 203, and the first mating portion 2041 is provided on the inner extension portion 203 to prevent the fan 4 from axially moving on the inner extension portion 203. In this case, in order to cool the outer rotor motor 100, the fan 4 needs to be an axial flow fan.

[0067] Please refer to Figures 4 and 5. The inner stator assembly 3 includes an inner stator bracket 30 that is sleeved on the outer periphery of the motor shaft 1, an inner stator core 33 fixed to the inner stator bracket 30, and a plurality of windings 34 wound on the inner stator core 33. The inner stator core 33 is cylindrical and has a hollow structure with both ends through. It is stamped from multiple sheet-like steel sheets. An inner stator overmolding component (not shown) is provided between the tooth slots (not shown) of the inner stator core 33. The inner stator overmolding component can separate different teeth and act as an insulator. The windings 34 are wound around the teeth of the inner stator core 33 through the inner stator overmolding component. The windings 34 are arranged corresponding to the teeth. The windings 34 can be multiple groups. The windings 34 can generate electromagnetic induction when powered.

[0068] When winding the winding 34, a winding machine can be used to independently wind each stator core 33 using a flying fork method. After the winding is completed, the wire ends are welded. This operation is not only simple in process and easy to operate, but also can achieve a higher slot fill rate.

[0069] Furthermore, the motor shaft 1 may be cylindrical, and its length may be greater than that of the inner stator assembly 3. One end of the motor shaft 1 passes through the inner stator bracket 30 and is rotatably connected to the inner stator bracket 30, and the other end of the motor shaft 1 passes through the outer extension portion 204 and is rotatably connected to the outer rotor housing 20.

[0070] The inner stator bracket 30 includes a base 301 located at the axial front end of the inner stator core 33, a main body 302 extending axially backward from the base 301, and a support portion 303 extending axially backward from the main body 302. The outer diameter of the main body 302 is different from the outer diameter of the support portion 303. The inner stator bracket 30 is integrally injection molded by aluminum metal.

[0071] An annular sleeve 31 is provided around the outer periphery of the support portion 303, and the inner peripheral wall of the inner stator core 33 is fitted onto the outer peripheral surface of the annular sleeve 31. The annular sleeve 31 is made of the same material as the inner stator core 33. Specifically, the annular sleeve 31 is made of steel, and its hardness is greater than that of the support portion 303.

[0072] In this embodiment, after the inner stator bracket 30 is roughly machined, the annular sleeve 31 is press-fitted to the outer periphery of the support portion 303. The outer diameter of the support portion 303 is larger than the inner diameter of the annular sleeve 31. Due to the difference in materials of the two, the annular sleeve 31 will cut the support portion 303 and generate aluminum chips during the press-fitting process. The aluminum chips can be removed after the press-fitting is completed. At the same time, the inner stator bracket 30 after the annular sleeve 31 is press-fitted is fine-machined to obtain the required design dimensions and meet the accuracy requirements to the greatest extent.

[0073] In conventional assembly schemes, the inner circumferential wall of the inner stator core 33 is directly mated with the outer circumferential surface of the support portion 303. The inner diameter of the inner stator core 33 is smaller than the outer diameter of the support portion 303. During installation, the steel inner stator core 33 cuts the outer circumferential surface of the aluminum support portion 303, generating aluminum chips that fall into the interior of the outer rotor motor 100. The aluminum chips can affect the outer rotor motor 100 and other components therein, and can even cause failure. An existing improvement is to provide a chip storage groove on the outer circumferential surface of the support portion 303. The aluminum chips generated by cutting can accumulate in the chip storage groove. However, excessive aluminum chips can cause the steel sheets of the stator core 33 to be squeezed and deformed, and the aluminum chips can fall out of the press-fit stop surface of the inner stator bracket 30 into the interior of the outer rotor motor 100, resulting in poor insulation withstand voltage, increased noise, and even failure. Another improvement solution is to refrigerate the inner stator bracket 30 before press-fitting, which can avoid the generation of cutting aluminum chips. However, the refrigeration process currently on the market uses liquid helium rapid cooling, which has certain safety risks and is too costly.

[0074] In this embodiment, after the annular sleeve 303 is sleeved around the outer periphery of the support portion 303, the inner stator core 33 is press-fitted onto the annular sleeve 31. The inner diameter of the inner stator core 33 is smaller than the outer diameter of the annular sleeve 31. The inner stator core 33 is installed on the annular sleeve 31 via an interference fit, ensuring a high degree of bonding between the inner stator core 33 and the inner stator core 33. Because the annular sleeve 31 and the inner stator core 33 are made of the same material, their material properties are similar, such as being manufactured from steel. Therefore, no cutting waste is generated during press-fitting. Furthermore, the stable bonding between the inner stator core 33 and the inner stator core 33 greatly reduces or even eliminates the possibility of relative slippage, thereby ensuring the safety of the outer rotor motor 100 during operation.

[0075] Optionally, the annular sleeve 31 can be made of a variety of materials. The outer circumferential wall of the annular sleeve 31 that contacts the inner circumferential wall of the inner stator core 33 is made of steel; the inner circumferential wall of the annular sleeve 31 that contacts the outer circumferential wall of the support portion 303 is made of other materials, such as plastic, metal, etc.

[0076] The axial length of the annular sleeve 31 is not greater than the axial length of the inner stator core 33 , and the combined portion of the two needs to maintain a certain fitting length to meet the fitting force requirements of the two.

[0077] A step portion 304 is provided at the connection between the main body portion 302 and the support portion 303 . The end of the annular sleeve 31 abuts against the step portion 304 . The step portion 304 can provide axial positioning when the annular sleeve 31 is press-fitted onto the support portion 303 .

[0078] After the inner stator core 33 is press-fitted into the inner stator bracket 30, when the winding slot fill rate of the inner stator core 33 is high, the lead wires and bridge wires on the winding 34 will be close to or even in contact with the inner stator bracket 30 in the axial direction. Although the outer layer of the enameled wire of the winding 34 has a layer of insulating varnish, the insulating varnish may be scratched. At this time, when the damaged enameled wire contacts the metal inner stator bracket 30, the outer rotor motor 100 may suffer from poor insulation withstand voltage or even fail.

[0079] As shown in Figures 4, 6, and 13, the inner stator assembly 3 includes an insulating gasket 32 ​​sleeved around the outer periphery of the main body 302. The insulating gasket 32 ​​is located between the inner stator core 33 and the base 301. Preferably, the insulating gasket 32 ​​is positioned adjacent to the base 301 and can be attached to an end surface of the base 301. The insulating gasket 32 ​​is made of an insulating material and axially separates the enameled wires of the winding 34 from the inner stator support 30, preventing electrical contact between the enameled wires and the inner stator support 30.

[0080] Furthermore, the insulating gasket 32 ​​is annular and includes an outer ring 321 located on the outside, an inner ring 322 located on the inside, and several bosses 323 located on the inner ring 322. The bosses 323 can be semicircular, semi-trapezoidal, or other shapes. The diameter of the inner ring 322 is larger than the outer diameter of the main body 302, while the inner diameter of the bosses 323 is smaller than the outer diameter of the main body 302. The insulating gasket 32 ​​is held against the outer circumference of the main body 302 by the bosses 323, and the inner ring 322 does not contact the main body 302.

[0081] The insulating gasket 32 ​​is made of soft material and has a certain resilience. Therefore, when the insulating gasket 32 ​​is clamped on the main body 302 by the boss 323, a certain bonding force can be ensured between the two and the insulating gasket 32 ​​will not produce excessive deformation.

[0082] The thickness of the insulating gasket 32 ​​can be selected based on design requirements, such as selecting an appropriate size based on the distance between the inner stator core 33 and the inner stator bracket 30 after the inner stator core 33 is installed. Optionally, the thickness of the insulating gasket 32 ​​is 0.1 mm to 2 mm. In addition, when the outer rotor motor 100 is a high-voltage motor, the thickness of the insulating gasket 32 ​​needs to be increased accordingly. After the inner stator core 33 is assembled, the distance between its axial front end and the insulating gasket 32 ​​is approximately 5 mm to 20 mm. The enameled wire of the winding 34 may approach or touch the insulating gasket 32. In this case, the insulating gasket 32 ​​made of insulating material can achieve axial insulation between the winding 34 and the inner stator bracket 30, improving the insulation performance of the outer rotor motor 100 and making it safer and more reliable to use.

[0083] Referring to Figures 9 to 11 , the outer rotor assembly 2 includes several magnets 21 attached to the inner wall of the outer rotor housing 20. These magnets 21 surround the inner stator core 33. The outer rotor housing 20 also includes several magnet slots 2010 recessed within the inner wall of the annular wall 201, with each magnet 21 housed within a magnet slot 2010. The magnets 21 cooperate with the inner stator assembly 3 through electromagnetic induction, converting electrical energy into mechanical energy. This rotation drives the outer rotor housing 20, further driving the motor shaft 1.

[0084] Furthermore, the magnetic steel 21 is one of Alnico magnetic steel, ferrite magnetic steel and NdFeB magnetic steel. Of course, the types of the magnetic steel 21 are not limited to the three types mentioned above, and those skilled in the art can also select other types of the magnetic steel 21 according to actual conditions and needs.

[0085] The number of the magnetic steels 21 is consistent with that of the magnetic steel slots 2010 and their shapes are adapted to each other. In the present embodiment, the shape of the magnetic steels 21 is a square. The square-shaped magnetic steels 21 can make the outer rotor motor 100 more smoothly controlled, and the square shape is more conducive to processing. Optionally, the magnetic steels 21 can be in any shape such as a tile shape or an arc shape. The number of the magnetic steels 21 is selected according to the design requirements of the outer rotor motor 100, for example, it can be 6, 8, 12, or even less or more.

[0086] In a traditional assembly solution, a plastic bracket is placed inside the outer rotor housing 20. Specifically, the plastic bracket is attached to the inner wall of the annular wall 201 and has two spaced-apart grooves. After the plastic bracket is placed at the bottom of the outer rotor housing 20, the magnets 21 are inserted into the plastic bracket's grooves. Glue is then applied to the back of the magnets 21 to ensure that the magnets 21 are more firmly attached to the inner wall of the annular wall 201. However, in this solution, the plastic bracket does not reliably position the magnets 21. Furthermore, the need to first place the plastic bracket in the outer rotor housing 20 complicates the installation process and reduces efficiency.

[0087] In this embodiment, after the outer rotor housing 20 is cold-forged, the magnetic steel slots 2010 are formed into the inner wall of the annular wall 201 through a finishing process. No additional plastic brackets are required, and the magnetic steel 21 can be directly placed into the magnetic steel slots 2010. Because the shape of the magnetic steel slots 2010 matches that of the magnetic steel 21, after the magnetic steel 21 is placed into the magnetic steel slots 2010, at least a portion of the inner wall of the magnetic steel slots 2010 abuts against the outer wall of the magnetic steel 21. This provides better positioning for the magnetic steel 21, and after installation, it is more firmly fixed to the inner wall of the magnetic steel slots 2010. This solution can simplify the process flow, improve assembly efficiency, reduce production costs, and ensure that the magnetic steel 21 is more securely fixed within the outer rotor housing 20.

[0088] Furthermore, to enhance the fixing effect of the magnetic steel 21, it is necessary to use a glue-like substance to bond and fix the magnetic steel 21. The glue-like substance can be glue, etc. The glue can more firmly adhere the magnetic steel 21 to the magnetic steel slot 2010. When the magnetic steel 21 is coated with glue and placed in the magnetic steel slot 2010, some glue will leak from the outer peripheral wall of the magnetic steel slot 2010, and the magnetic steel 21 will partially protrude from the magnetic steel slot 2010 in the radial direction, which will affect the operation of the outer rotor motor 100.

[0089] To this end, each annular wall 201 is provided with a receiving groove 2011 radially recessed from the bottom of the magnetic steel groove 2010. The receiving groove 2011 is located radially outward of the magnetic steel groove 2010. After the outer rotor housing 20 is cold-forged, the magnetic steel groove 2010 and the receiving groove 2011 are machined and formed on the inner wall of the annular wall 201. After the magnetic steel 21 is coated with glue on one side and placed in the magnetic steel groove 2010, some glue flows into the receiving groove 2011, preventing the glue from flowing out from the periphery of the magnetic steel groove 2010, thereby preventing the operation of the outer rotor motor 100.

[0090] Specifically, the axial length of the receiving groove 2011 is no greater than the axial length of the magnetic steel groove 2010, the radial width D2 of the receiving groove 2011 is no less than 60% of the radial width D1 of the magnetic steel groove 2010, the wall thickness of the annular wall 201 is at least 1.5 mm greater than the radial depth D3 of the magnetic steel groove 2010, and the radial depth D4 of the receiving groove is between 0.1 mm and 0.5 mm. The shape and size of the magnetic steel groove 2010 are compatible with the magnetic steel 21, thereby better securing the magnetic steel 21 to the annular wall 201. The receiving groove 2011 can accommodate glue on the magnetic steel 21, preventing the glue from overflowing from the sides of the magnetic steel groove 2010. The dimensions of the magnetic steel groove 2010 and the receiving groove 2011 are designed to ensure sufficient strength for the annular wall 201.

[0091] 3 and 4 , the outer rotor motor 100 is provided with a front bearing 10 and a rear bearing 11 located at both axial ends of the motor shaft 1. The front bearing 10 is received in the axial front end of the inner stator support 30, and the motor shaft 1 is supported within the inner stator support 30 via the front bearing 10. The rear bearing 11 is located at the axial rear end of the inner stator core 33. Furthermore, the rear bearing 11 is located within a through hole of the inner stator core 33, thereby supporting the motor shaft 1 within the inner stator core 33 via the rear bearing 11.

[0092] The radial dimension of the front bearing 10 can be larger than that of the rear bearing 11, and the outer diameter of the rear bearing 11 can be adapted to the inner diameter of the inner stator core 33. Placing the rear bearing 11 within the inner stator core 33 eliminates the cost of mold-making for the bearing housing for mounting the rear bearing 11, thereby simplifying the process and reducing production costs.

[0093] Furthermore, the outer rotor motor 100 includes a retaining spring 102 disposed at the axial front end of the motor shaft 1. The retaining spring 102 is configured to retain the motor shaft 1 and is located at the portion of the motor shaft 1 where it passes through the inner stator bracket 30. Specifically, the retaining spring 102 is positioned near the front bearing 10 to prevent it from falling out. A gasket 101 is also disposed between the front bearing 10 and the retaining spring 102 to prevent wear caused by friction between the front bearing 10 and the retaining spring 102.

[0094] As shown in Figure 2 , the rear bearing 11 is located at the axial front end of the inner extension 203. The end of the inner extension 203 abuts the end surface of the rear bearing 11, providing axial positioning for the rear bearing 11. The inner extension 203 can be machined to the required positioning dimensions based on the installation position of the rear bearing 11. This arrangement avoids the need for a stepped design for the motor shaft 1. The stepped portion of the motor shaft 1 serves to position the rear bearing 11, simplifying the machining process for the motor shaft 1 and reducing manufacturing costs.

[0095] In this embodiment, the outer rotor housing 20 further includes an inner extension 203 and an outer extension 204 connecting the two end surfaces of the end wall 202. The inner extension 203 is located within the annular wall 201, and the outer circumferential wall of the motor shaft 1 is retained by the inner extension 203 and the outer extension 204. This arrangement increases the mating surface between the motor shaft 1 and the outer rotor housing 20, effectively improving the bonding strength between the motor shaft 1 and the outer rotor housing 20 and the dimensional accuracy after press-fitting, thereby enhancing the strength of the outer rotor housing 20 during rotation. Furthermore, the integral cold-heading process for forming the outer rotor housing 20 is simple.

[0096] The present invention is not limited to the specific embodiments described above. Those skilled in the art will readily appreciate that many alternatives to the outer rotor motor of the present invention exist without departing from the principles and scope of the present invention. The scope of protection of the present invention shall be determined by the claims.

Claims

1. An outer rotor motor, comprising an axially extending motor shaft, an outer rotor assembly securing the motor shaft, and an inner stator assembly located between the motor shaft and the outer rotor assembly; the outer rotor assembly comprising an outer rotor housing for accommodating the inner stator assembly, the outer rotor housing comprising an annular wall sleeved around the outer periphery of the inner stator assembly and an end wall connected to an axial rear end of the annular wall; characterized in that: The outer rotor housing further includes an inner extension portion and an outer extension portion connecting both end surfaces of the end wall. The inner extension portion is located inside the annular wall, and the outer peripheral wall of the motor shaft is fixed on the inner extension portion and the outer extension portion.

2. The outer rotor motor according to claim 1, characterized in that: The axial rear end of the motor shaft includes a first coupling portion, the outer extension portion of the outer rotor housing includes a second coupling portion, and the axial rear end of the motor shaft is installed in the second coupling portion of the outer rotor housing through the first coupling portion.

3. The outer rotor motor according to claim 2, characterized in that: The shapes of the first combining portion and the second combining portion are adapted to each other, and one of the first combining portion and the second combining portion is configured as a convex portion, and the other is configured as a concave portion.

4. The outer rotor motor according to claim 3, characterized in that: The number of the first combining portions and the number of the second combining portions are at least three, and the axial length of the first combining portion is not greater than the axial length of the second combining portion.

5. The outer rotor motor according to claim 4, characterized in that: The outer diameter of the first coupling portion is not less than the inner diameter of the second coupling portion, and the first coupling portion and the second coupling portion are connected by an interference fit or a transition fit; the outer diameter of the motor shaft is larger than the inner diameter of the inner extension portion, and the motor shaft is interference fitted in the inner extension portion.

6. The outer rotor motor according to claim 1, characterized in that: The wall thickness of the inner extension portion and the outer extension portion is not less than the wall thickness of the end wall, and the axial length of the inner extension portion and the outer extension portion is not less than 2 mm.

7. The outer rotor motor according to claim 1, characterized in that: The outer rotor housing is integrally formed by a cold heading process, and the annular wall, the end wall, the inner extension portion, and the outer extension portion are an integral structure.

8. The outer rotor motor according to claim 1, characterized in that: The inner stator assembly includes an inner stator bracket sleeved on the outer circumference of the motor shaft and an inner stator core fixed to the inner stator bracket. The outer rotor motor includes a rear bearing accommodated in the axial rear end of the inner stator core. The outer circumferential surface of the rear bearing is in contact with the inner circumferential wall of the inner stator core. The motor shaft is supported at the axial rear end of the inner stator core through the rear bearing.

9. The outer rotor motor according to claim 8, characterized in that: The rear bearing is located at the axial front end of the inner extension portion, and the end portion of the inner extension portion abuts against the end surface of the rear bearing.

10. An outer rotor motor, comprising an axially extending motor shaft, an outer rotor assembly retaining the motor shaft, and an inner stator assembly located between the motor shaft and the outer rotor assembly; the outer rotor assembly comprising an outer rotor housing for accommodating the inner stator assembly, the outer rotor housing comprising an annular wall sleeved around the outer periphery of the inner stator assembly and an end wall connected to the axial rear end of the annular wall; characterized in that: The outer rotor housing further includes an inner extension portion and an outer extension portion connected to both end surfaces of the end wall, and the fan is integrally injection-molded on the inner extension portion.

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