Rotor assembly, motor and blower

Abstract

The present application relates to a rotor assembly, a motor and a hair dryer, comprising: a shell with openings at both ends; a plurality of magnetic elements fixed to the inner circumferential surface of the shell at intervals along the circumferential direction; an end cover, which is arranged on an opening at one end of the shell and fixed to one end of the magnetic element; a rotating shaft, which is passed through an inner cavity formed by the shell and the end cover, and one end of the rotating shaft is fixedly connected to the end cover; and a magnetic shield, which comprises a fixed ring and a plurality of fixed teeth extending along the axial direction of the rotating shaft; the fixed ring is fixed to the open end surface of the other end of the shell, and all the fixed teeth are arranged at the inner edge of the fixed ring along annular intervals, and a first slot is formed between two adjacent fixed teeth; one end of each magnetic element away from the end cover is embedded in the corresponding first slot. A rotor assembly, a motor and a hair dryer according to an embodiment of the present application can effectively prevent the magnetic element from falling off.

Description

Technical Field

[0001] The present application relates to the technical field of gardening equipment, and in particular to a rotor assembly, a motor and a hair dryer. Background Art

[0002] At present, traditional brushless outer rotor motors on the market are directly fixed by magnetic component glue or by injection molding the magnetic component and the housing as a whole and then magnetizing the magnetic component. However, it is difficult to ensure that the magnetic component will not fall off under high speed and high impact loads using the adhesive bonding process, and this magnetic component falling off is also a common problem and difficulty for all outer rotor brushless motors; although the problem of magnetic component falling off can be solved by the injection molding structure, the injection molding process is complicated, involving more equipment and process flows, and the magnetic component must be magnetized later, which is difficult for most brushless motor manufacturers to achieve. Summary of the invention

[0003] Based on this, it is necessary to provide a rotor assembly, a motor and a hair dryer to address the problem of magnetic components falling off.

[0004] The first aspect of an embodiment of the present application provides a rotor assembly, comprising: a shell with openings at both ends; a plurality of magnetic elements fixed to the inner circumferential surface of the shell at intervals along the circumferential direction; an end cover, which is arranged on an opening at one end of the shell and fixed to one end of the magnetic elements; a rotating shaft, which is passed through an inner cavity surrounded by the shell and the end cover, and one end of the rotating shaft is fixedly connected to the end cover; and a magnetic protection sleeve, which comprises a fixing ring and a plurality of fixing teeth extending axially along the rotating shaft; the fixing ring is fixed to the open end surface of the other end of the shell, all of the fixing teeth are arranged at annular intervals on the inner edge of the fixing ring, and a first slot is formed between two adjacent fixing teeth; one end of each of the magnetic elements away from the end cover is embedded in the corresponding first slot.

[0005] In one embodiment, the end cover includes a cover body and a plurality of latch teeth extending axially along the rotating shaft; all of the latch teeth are arranged along annular intervals on a surface of the cover body facing the shell, and a second latch groove is formed between two adjacent multiple latch teeth; the fixed teeth correspond one-to-one to the latch teeth, and the two ends of the magnetic element are respectively embedded in the first latch groove and the second latch groove.

[0006] In one embodiment, along the axial direction of the rotating shaft, the length of the fixed tooth extending from the fixed ring is S, the length of the latch tooth extending from the cover body is M, and the length of the magnetic element is N; and the following relationship is satisfied: 0.3*N≤S, 0.3*N≤M, S+M<N.

[0007] In one embodiment, an axial hole is formed in the middle of the cover body, and the rotating shaft is connected to the axial hole by interference fit.

[0008] In one of the embodiments, the magnetic element is adhesively connected to the inner circumference of the shell.

[0009] In one embodiment, the magnetic element is a magnetic strip made of sintered NdFeB material.

[0010] In one embodiment, the shell is made of carbon steel, cold-rolled steel plate or stainless steel plate; and / or the magnetic shield is made of carbon steel, cold-rolled steel plate or stainless steel plate; and / or the fixing ring is integrally formed with the fixing tooth; and / or the fixing ring is fixed to the shell by welding.

[0011] The second aspect of the embodiment of the present application provides a motor, including a fixed shaft, a wire winding and the above-mentioned rotor assembly; the rotating shaft is rotatably inserted in the fixed shaft; the wire winding is wound on the outer circumference of the fixed shaft and is located in the inner cavity enclosed by the shell and the end cover.

[0012] In one embodiment, the motor includes a spring, the rotating shaft passes through the spring, one end of the spring is in conflict with the end cover, and the other end is in conflict with the top of the fixed shaft toward the end cover; both ends of the spring are ground.

[0013] A third aspect of an embodiment of the present application provides a hair dryer, comprising the above-mentioned motor.

[0014] The beneficial effects are:

[0015] A rotor assembly, a motor and a hair dryer according to an embodiment of the present application are provided with a shell, a plurality of magnetic elements, an end cover and a magnetic protection sleeve; the shell is a hollow shell structure with openings at both ends; the plurality of magnetic elements are fixed to the inner circumferential surface of the shell at intervals along the circumferential direction; the end cover is provided at one end opening of the shell and is fixed to one end of the magnetic element; the magnetic protection sleeve may include a fixing ring and a plurality of fixing teeth extending along the axial direction of the rotating shaft; the fixing ring is fixed to the open end surface of the other end of the shell, and all the fixing teeth are arranged at the inner edge of the fixing ring along annular intervals, and a first slot is formed between two adjacent fixing teeth. In this way, one end of each magnetic element is fixed to the end cover, and the other end of each magnetic element away from the end cover is embedded in the corresponding first slot, so that the two ends of each magnetic element are respectively embedded and fixed. When the motor is running at high speed, the end cover and the magnetic protection sleeve can provide stable circumferential fixation for the magnetic element, thereby avoiding relative displacement of the magnetic element and the shell along the circumferential direction. Combined with the magnetic element itself and the interval fixation on the inner circumferential surface of the shell, it is ensured that during the high-speed operation of the motor, the magnetic element is stably fixed on the inner circumferential surface of the shell without loosening in the axial and radial directions. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of the structure of a rotor assembly provided in some embodiments of the present application.

[0017] Figure 2 A schematic structural diagram of a rotor assembly from another perspective provided in some embodiments of the present application.

[0018] Figure 3 for Figure 2 An AA section view of the rotor assembly is provided.

[0019] Figure 4 An exploded view of a rotor assembly provided for some embodiments of the present application.

[0020] Figure 5 A schematic diagram of the structure of a motor provided in some embodiments of the present application.

[0021] Figure 6 for Figure 5 A BB section view of the provided rotor assembly.

[0022] Figure 7 An exploded view of a motor provided for some embodiments of the present application. DETAILED DESCRIPTION

[0023] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0025] In the description of the embodiments of the present application, if the technical terms "first", "second", etc. appear, these terms are only used for descriptive purposes to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0026] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0027] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0028] In the description of the embodiments of the present application, if the term "multiple" appears, "multiple" means at least two (including two), such as two, three, etc., unless otherwise clearly and specifically defined. Similarly, if the term "multiple groups" appears, "multiple groups" refers to more than two groups (including two groups), and if the term "multiple sheets" appears, "multiple sheets" refers to more than two sheets (including two sheets).

[0029] In the description of the embodiments of the present application, if the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. appear, the orientation or position relationship indicated by these terms is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the embodiments of the present application and simplifying the description, and does not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0030] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, if the technical terms "installed", "connected", "connected", "fixed" and the like appear, these terms should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0031] In the present application, unless otherwise clearly specified and limited, if there is a description that a first feature is "above" or "below" a second feature, etc., or similar descriptions appear, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0032] It should be noted that if an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. If an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. If any, the terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in this application are for illustrative purposes only and do not represent the only implementation method.

[0033] A first aspect of an embodiment of the present application provides a rotor assembly 100 ; the rotor assembly 100 is used in a motor to drive an external mechanism to rotate.

[0034] See also Figures 1 to 7 As shown, the rotor assembly 100 includes a housing 10 , a plurality of magnetic elements 20 , an end cover 30 , a magnetic shield 40 and a rotating shaft 50 .

[0035] Among them, the shell 10 is a hollow shell structure with openings at both ends, and its cross-section can usually be circular; the shell 10 can be made of carbon steel, cold-rolled steel plate or stainless steel plate, specifically, it can be 10# carbon steel or 20# carbon steel and other materials obtained by stamping and stretching to obtain the required shape.

[0036] Multiple magnetic elements 20 are fixed to the inner circumference of the housing 10 at intervals along the circumferential direction. Each magnetic element 20 can be made of a permanent magnet material, such as ferrite or neodymium iron boron. The magnetic element 20 can be made into a tile-like structure by sintering, that is, the magnetic element 20 has two opposite arc-shaped surfaces, which is convenient for fitting and fixing with the inner circumference of the housing 10.

[0037] The end cover 30 is disposed at one end opening of the housing 10 and fixed to one end of the magnetic element 20 ; the magnetic shielding sleeve 40 is disposed at the other end opening of the housing 10 and is used to fix the other end of the magnetic element 20 .

[0038] Specifically, the magnetic shield 40 may include a fixing ring 42 and a plurality of fixing teeth 41 extending along the axial direction of the rotating shaft 50; the fixing ring 42 is fixed to the open end surface of the other end of the housing 10, and all the fixing teeth 41 are arranged at the inner edge of the fixing ring 42 along the annular interval, and a first clamping groove 23 is formed between two adjacent fixing teeth 41. In this way, one end of each magnetic element 20 is fixed to the end cover 30, and the other end of each magnetic element 20 away from the end cover 30 is embedded in the corresponding first clamping groove 23, so that the two ends of each magnetic element 20 are respectively embedded and fixed. During the high-speed operation of the motor, the end cover 20 and the magnetic shield 40 can provide stable circumferential fixation for the magnetic element 20, thereby preventing the magnetic element 20 from relative displacement with the housing 10 along the circumferential direction. Combined with the magnetic element 20 itself and the interval fixed to the inner circumferential surface of the housing 10, it is ensured that during the high-speed operation of the motor, the magnetic element 20 is stably fixed to the inner circumferential surface of the housing 10 without being loosened in the axial direction and radial direction.

[0039] The rotating shaft 50 can generally be a thin metal rod, such as a stainless steel rod, which has good processability and structural strength. The rotating shaft 50 is arranged in the inner cavity surrounded by the shell 10 and the end cover 30, and one end of the rotating shaft 50 is fixedly connected to the end cover 30; the other end of the rotating shaft 50 extends through the other end opening of the shell 10 away from the end cover 30. The rotor assembly 100 as a whole can rotate around the axial direction of the rotating shaft 50 (that is, the axial direction, the same below), and then the end cover 30 drives the rotating shaft 50 to rotate, thereby driving the external structure to rotate, and completing the corresponding driving function.

[0040] Optionally, the magnetic element 20 and the inner circumferential surface of the housing 10 can be connected by gluing. In this way, the magnetic element 20 is fixed by gluing on the one hand, and the magnetic element 20 can be stably fixed in the circumferential direction by combining the end cover 20 and the magnetic shield 40 on the other hand, thereby preventing the relative displacement of the magnetic element 20 and the housing 10 along the circumferential direction, ensuring that the magnetic element 20 is stably fixed on the inner circumferential surface of the housing 10 during high-speed operation of the motor without loosening in the axial and radial directions.

[0041] Optionally, the fixing ring 42 and the housing 10 can be made of the same material, such as carbon steel, cold-rolled steel plate or stainless steel plate. The fixing ring 42 and the housing 10 are fixed by welding, which has a simple process and good connection strength and can adapt to high-speed operation of the motor.

[0042] In some possible embodiments, see Figures 1 to 7 As shown, the end cover 30 includes a cover body 31 and a plurality of latch teeth 32 extending axially along the rotating shaft 50; all the latch teeth 32 are arranged along annular intervals on the side of the cover body 31 facing the shell 10, and a second latch groove 33 is formed between two adjacent multiple latch teeth 32; the fixed teeth 41 correspond to the latch teeth 32 one by one, and the two ends of the magnetic element 20 are respectively embedded in the first latch groove 23 and the second latch groove 33.

[0043] In this way, one end of each magnetic element 20 is embedded and fixed in the second slot 33 on the end cover 30, and the other end is embedded in the corresponding first slot 23, so that the two ends of each magnetic element 20 are respectively embedded and fixed. When the motor is running at high speed, the end cover 20 and the magnetic shield 40 can provide stable circumferential fixation for the magnetic element 20, thereby avoiding the relative displacement of the magnetic element 20 and the shell 10 along the circumferential direction. Combined with the magnetic element 20 itself and the inner circumferential surface fixed to the shell 10 at intervals, it is ensured that during the high-speed operation of the motor, the magnetic element 20 is stably fixed on the inner circumferential surface of the shell 10 without loosening in the axial and radial directions.

[0044] In some possible embodiments, see Figures 1 to 4 The structure shown, combined with Figure 4 In the shown orientation, along the axial direction of the rotating shaft 50 , the fixed teeth 41 extend upward from the fixed ring 42 , and the length of the fixed teeth 41 is S.

[0045] Along the axial direction of the rotating shaft 50 , the latching teeth 32 extend downward from the cover body 31 , and the length of the latching teeth 32 is M.

[0046] The length of the magnetic element 20 along the axial direction of the rotating shaft 50 is N.

[0047] The above numbers should satisfy the following relationship: 0.3*N≤S, 0.3*N≤M, S+M<N. That is to say, the length of the fixed tooth 41 should not be less than 0.3 times the length of the magnetic element 20, so as to ensure that the fixed tooth 41 limits the circumferential position of one end of the magnetic element 20. Similarly, the length of the latch tooth 32 should not be less than 0.3 times the length of the magnetic element 20, so as to ensure that the latch tooth 32 limits the circumferential position of the other end of the magnetic element 20. Then, the latch tooth 32 cooperates with the fixed tooth 41 to realize the circumferential position limitation of the entire magnetic element 20, so as to ensure that the magnetic element 20 is stably fixed on the inner circumferential surface of the housing 10 without being loosened in the axial and radial directions.

[0048] At the same time, the length control should ensure that the sum of the length of the fixed tooth 41 and the length of the latch tooth 32 is less than the length of the magnetic element 20. In this way, when the end cover 20 and the magnetic shield 40 are assembled from both ends of the shell 10, there can be a gap between the fixed tooth 41 and the latch tooth 32 to avoid interference with each other.

[0049] In some possible embodiments, see Figures 1 to 7As shown, the end cap 30 may include ten latch teeth 32, the arc length of each latch tooth 32 along the circumferential direction is L, the interval width of two adjacent latch teeth 32 is K, and the width of the second latch groove 33 satisfies: 1mm≤L≤3mm, 2mm≤K≤5mm. In this way, it is ensured that the latch teeth 32 have sufficient strength to provide circumferential limitation for the magnetic element 20.

[0050] Similarly, the magnetic shield 40 includes ten fixed teeth 41, and the arc length of each fixed tooth 41 along the circumferential direction is J. The interval width between two adjacent fixed teeth 41 is H, and the width of the first slot 23 satisfies: 1mm≤J≤3mm, 2mm≤H≤5mm. In this way, it is ensured that the fixed teeth 41 have sufficient strength to provide circumferential limitation for the magnetic element 20. The slot width of the first slot 23 should generally be consistent with the slot width of the second slot 33, and the slot width should be slightly larger than or equal to the width of the magnetic element 20 to avoid circumferential shaking of the magnetic element 20 in the slot.

[0051] In some possible embodiments, see Figures 1 to 7 As shown, a shaft hole 34 is formed in the middle of the cover body 31, and the rotating shaft 50 is connected with the shaft hole 34 by interference fit. In this way, the structure is simple and the connection strength between the two is good.

[0052] In some possible embodiments, see Figures 1 to 7 As shown, the cover body 31 is also provided with a plurality of hollow slots (not marked), which are evenly distributed along the circumference, so as to reduce the weight of the cover body 31, and further reduce the mass of the rotor assembly 100, thereby realizing a lightweight design of the motor.

[0053] Optionally, the magnetic element 20 is a magnetic strip made of sintered NdFeB material, which has better magnetic strength and is suitable for high-speed operation of the motor.

[0054] Optionally, the housing 10 is made of carbon steel, cold-rolled steel plate or stainless steel plate, which has good structural strength and low cost. The magnetic shielding sleeve 40 is made of carbon steel, cold-rolled steel plate or stainless steel plate, which has good structural strength and low cost.

[0055] Optionally, the fixing ring 42 and the fixing teeth 41 are integrally formed; for example, the fixing ring 42 and the fixing teeth 41 are stamped from carbon steel, cold-rolled steel plate or stainless steel plate, which have good processability and high strength and can adapt to high-speed operation of the motor.

[0056] A second aspect of an embodiment of the present application provides a motor that can be used for a garden hair dryer or other electrical appliances.

[0057] See also Figures 1 to 7As shown, the motor includes a fixed shaft 200, a winding 300 and the above-mentioned rotor assembly 100; wherein the rotating shaft 50 is rotatably inserted in the fixed shaft 200; the winding 300 is wound on the outer periphery of the fixed shaft 200 and is located in the inner cavity surrounded by the housing 10 and the end cover 30. Current passes through the winding 300 to generate an excitation signal, and the excitation signal interacts with the magnetic element 20 on the housing 10, driving the magnetic element 20 to drive the rotor assembly 100 to rotate as a whole.

[0058] Optionally, the fixed shaft 200 includes two bearings 220; one of the rotating shafts 220 is fixedly disposed at the top end of the fixed shaft 200 close to the end cover 20, and the other rotating shaft 220 is fixedly disposed at the bottom end of the fixed shaft 200 away from the end cover 20, and the rotating shaft 50 passes through the two bearings 220 in sequence and is connected to the fixed inner ring of the rotating shaft 50.

[0059] In some possible embodiments, see Figures 1 to 7 As shown, the motor includes a spring 210, and the rotating shaft 50 is passed through the spring 210. One end of the spring 210 conflicts with the end cover 30, and the other end conflicts with the top of the fixed shaft 200 facing the end cover 30; both ends of the spring 210 are ground flat. The spring 210 can be used to adjust the clearance between the bearings. Therefore, when the motor drives the fan blades of the hair dryer to rotate at high speed, the anti-axial tension generated by the fan blades can be overcome by the spring 210, avoiding excessive wear on the rotating structure of the fixed shaft 200 and the rotor assembly 100, effectively extending the service life of the equipment. In addition, since the spring 210 can elastically transmit vibration, it can also improve the vibration and abnormal sound of the hair dryer, thereby improving the noise, vibration and acoustic harshness characteristics (NVH characteristics) of the motor.

[0060] A third aspect of an embodiment of the present application provides a hair dryer, comprising the above-mentioned motor.

[0061] The motor on the hair dryer of the embodiment of the present application is designed so that the magnetic element 20 can be connected to the inner circumference of the shell 10 by gluing, and the first card slot 23 on the end cover 20 and the second card slot 33 on the magnetic shield 40 provide stable circumferential fixation for both ends of the magnetic element 20, respectively, to prevent the magnetic element 20 from being loosened axially and radially under high impact when stopped or started. Furthermore, since the magnetic element 20 can remain relatively fixed with the inner circumference of the shell 10, the motor output power can reach 2500 watts to 3500 watts, and it can ensure that the motor can work for a long time at a speed of 21,000 rpm, thereby ensuring that the wind force of the hair dryer can reach a flow rate of 1000 CFM, far exceeding the mainstream products currently on the market.

[0062] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0063] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A rotor assembly, characterized in that: include: A shell (10) with openings at both ends; A plurality of magnetic elements (20) are fixed to the inner circumferential surface of the housing (10) at intervals along the circumferential direction; An end cover (30) is provided to cover an opening at one end of the housing (10) and is fixed to one end of the magnetic element (20); A rotating shaft (50) is inserted into an inner cavity formed by the housing (10) and the end cover (30), and one end of the rotating shaft (50) is fixedly connected to the end cover (30); and a magnetic shielding sleeve (40), the magnetic shielding sleeve (40) comprising a fixing ring (42) and a plurality of fixing teeth (41) extending axially along the rotating shaft (50); the fixing ring (42) is fixed to the open end surface of the other end of the housing (10); all the fixing teeth (41) are arranged at annular intervals on the inner edge of the fixing ring (42); a first slot (23) is formed between two adjacent fixing teeth (41); and one end of each magnetic element (20) away from the end cover (30) is embedded in the corresponding first slot (23).

2. The rotor assembly according to claim 1, characterized in that: The end cover (30) comprises a cover body (31) and a plurality of latching teeth (32) extending axially along the rotating shaft (50); all of the latching teeth (32) are arranged at annular intervals on a surface of the cover body (31) facing the housing (10), and a second latching groove (33) is formed between two adjacent plurality of latching teeth (32); the fixed teeth (41) correspond one-to-one to the latching teeth (32), and the two ends of the magnetic element (20) are respectively embedded in the first latching groove (23) and the second latching groove (33).

3. The rotor assembly according to claim 2, characterized in that: Along the axial direction of the rotating shaft (50), the length of the fixed tooth (41) extending from the fixed ring (42) is S, the length of the latch tooth (32) extending from the cover body (31) is M, and the length of the magnetic element (20) is N; and the following relationship is satisfied: 0.3*N≤S, 0.3*N≤M, S+M<N.

4. The rotor assembly according to claim 2, characterized in that: An axial hole (34) is formed in the middle of the cover body (31), and the rotating shaft (50) is connected to the axial hole (34) by interference fit.

5. The rotor assembly according to any one of claims 1 to 4, characterized in that: The magnetic element (20) is adhesively connected to the inner circumferential surface of the shell (10).

6. The rotor assembly according to any one of claims 1 to 4, characterized in that: The magnetic element (20) is a magnetic strip made of sintered neodymium iron boron material.

7. The rotor assembly according to any one of claims 1 to 4, characterized in that: The housing (10) is made of carbon steel, cold-rolled steel plate or stainless steel plate; and / or, The magnetic shielding sleeve (40) is made of carbon steel, cold-rolled steel plate or stainless steel plate; and / or, The fixing ring (42) and the fixing teeth (41) are integrally formed; and / or, The fixing ring (42) is fixed to the housing (10) by welding.

8. A motor, characterized in that: The invention comprises a fixed shaft (200), a wire winding (300), and a rotor assembly according to any one of claims 1 to 7; the rotating shaft (50) is rotatably inserted in the fixed shaft (200); the wire winding (300) is wound on the outer circumference of the fixed shaft (200) and is located in an inner cavity enclosed by the housing (10) and the end cover (30).

9. The motor according to claim 8, characterized in that The motor comprises a spring (210), the rotating shaft (50) is passed through the spring (210), one end of the spring (210) is in contact with the end cover (30), and the other end of the spring (210) is in contact with the top end of the fixed shaft (200) facing the end cover (30); Both ends of the spring (210) are ground flat.

10. A hair dryer, characterized in that: Comprising a motor as claimed in claim 8 or 9.

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