Outer rotor type motor
By adjusting the winding direction of the preload spring in an external rotor motor, the problems of noise and scratches between the preload spring and the rolling bearing and the rotor yoke were solved, achieving quieter operation and extended component life.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHINANO KENSHI CO LTD
- Filing Date
- 2025-11-27
- Publication Date
- 2026-06-05
AI Technical Summary
In external rotor type axial flow fan motors, the synchronous rotation of the preload spring between the rolling bearing and the rotor yoke causes abnormal noise and scratches. Especially when the load on the rolling bearing increases, the coiled end of the spring hooks more strongly with the sliding surface, affecting the life of the component.
A compression helical spring is used as a preload spring, which is embedded on the outer circumference of the rotor shaft and placed between the rotor yoke and the rolling bearing. The winding direction is adjusted according to the rotor rotation direction to avoid the winding end from hindering the driven rotation and to reduce the snagging of the sliding surface.
It effectively suppresses the generation of abnormal noise, extends the life of components, reduces scratches on sliding surfaces, and achieves both quiet operation and long lifespan.
Smart Images
Figure CN122159565A_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to an external rotor type electric motor used as a drive source for, for example, vehicle-mounted equipment or HVAC (Heating, Ventilation, and Air Conditioning) equipment. Background Technology
[0002] For example, in an external rotor type axial flow fan motor, external forces can easily be applied from the blower side assembled with the rotor yoke. If the rotor is displaced axially, the bearings supporting the rotor shaft and the insulators covering the stator core may be damaged. Therefore, a preload spring (coil spring) is provided between the rolling bearing (inner ring) and the bushing of the rotor yoke. The preload spring is compressed from its natural length and embedded in the outer circumference of the rotor shaft. Even if an external force is applied from the blower side, the elasticity of the preload spring will absorb the impact and prevent interference between the rotor and the stator (Patent Document 1; Japanese Patent Publication No. 6-1963).
[0003] Existing technical documents
[0004] Patent documents
[0005] Patent Document 1: Japanese Patent Publication No. 6-1963 Summary of the Invention
[0006] The technical problem that the invention aims to solve
[0007] In the structure of Patent Document 1 mentioned above, the preload spring (coil spring) is installed between the rolling bearing (inner ring) and the bushing of the rotor yoke in a manner that provides elastic reaction force. Therefore, when the fan and the rotor yoke rotate together, the preload spring also rotates synchronously. Specifically, the rotor yoke and rotor shaft rotate synchronously with the inner ring of the rolling bearing and the preload spring.
[0008] When the rolling elements of a pair of rolling bearings generate motion marks, the grease deteriorates and forms lumps, or the grease viscosity increases at low temperatures (e.g., -40°C), causing the rotating load on the rolling bearings to become heavier, the inner ring and preload spring of the rolling bearing no longer rotate synchronously with respect to the rotor. At this time, with the rotor's rotation direction opposite to the winding end of the preload spring, the winding end of the preload spring experiences increased hooking relative to the sliding surface, resulting in abnormal noise.
[0009] In addition, scratches occur on the bushing of the rotor yoke that abuts against the winding end of the helical spring and on the end face of the rolling bearing, shortening the lifespan of the components.
[0010] Technical solutions adopted to solve technical problems
[0011] This disclosure is made to solve these problems, and its purpose is to provide an external rotor type electric motor that can achieve quiet operation by suppressing the generation of abnormal noise by suppressing the hooking of the winding end of the preload spring relative to the sliding surface, even when the rotational load of the rolling bearing supporting the rotor shaft increases, and can also expect to extend the service life of the components by suppressing the generation of scratches.
[0012] To achieve the above objectives, the following embodiments include the following structure.
[0013] An external rotor type electric motor includes: a stator having stator poles; and a rotor having rotor poles formed by permanent magnets arranged opposite to the stator poles on the radially outer side of the stator, characterized in that it includes: a rotor shaft, the shaft end of which is integrally assembled with a hub of a rotor yoke formed in a cup shape; a pair of rolling bearings assembled in a bearing housing provided in the motor housing to support the rotor shaft for rotation; and a preload spring embedded in the outer periphery of the rotor shaft and between the hub of the rotor yoke and the rolling bearings arranged opposite to each other along the axial direction, compressed and installed from its natural length, the preload spring being a compression helical spring and wound relative to the rotation direction of the rotor yoke toward the winding end in a direction that does not hinder driven rotation.
[0014] According to the above structure, when the rotor rotates, the preload spring (compression coil spring), which is embedded between the hub of the rotor yoke and the rolling bearings arranged axially opposite each other with elastic reaction force, also rotates synchronously. At this time, the preload spring does not obstruct the direction of the driven rotation accompanying the rotation of the rotor yoke when it is wound toward the winding end. Therefore, even if the rotational load on the pair of rolling bearings increases, it can suppress the abnormal noise caused by the increased hooking between the winding end of the preload spring with elastic reaction force and the sliding surface of the rotor yoke or rolling bearing, thereby achieving noise reduction. In addition, even if the sliding between the winding end of the preload spring and the bushing portion of the rotor yoke or the end face of the rolling bearing that it abuts increases, scratches can be reduced and the service life of the components can be extended.
[0015] Specifically, preferably, when the rotor is viewed from one axial end, the preload spring is wound in a left-handed manner when the rotor yoke is rotating clockwise, and in a right-handed manner when the rotor yoke is rotating counterclockwise. Thus, even if the rotational load on the pair of rolling bearings increases, the wound end of the preload spring does not hinder the driven rotation accompanying the rotor yoke. Therefore, it is possible to suppress abnormal noise caused by increased hooking with the hub of the rotor yoke or the sliding surface of the rolling bearings, thereby achieving noise reduction and also reducing scratches and extending the life of the components.
[0016] Furthermore, when observing the helical spring from one end, winding it counterclockwise from the starting point (the end of the helical spring) is described as "left-handed," and winding it clockwise is described as "right-handed."
[0017] Alternatively, the preload spring can be embedded in the outer circumference of the rotor shaft and between the hub of the rotor yoke and the inner ring of the rolling bearing, which is axially opposed to each other. This allows the outer diameter of the preload spring to be minimized, and enables the preload spring to be assembled without any wobble between the rotor yoke and the rolling bearing.
[0018] Invention Effects
[0019] It is possible to provide an external rotor type motor that can achieve noise reduction by suppressing the hooking of the preload spring's winding end relative to the sliding surface, even when the rotational load of the rolling bearing supporting the rotor shaft increases, and can also expect to extend the service life of the components by suppressing the occurrence of scratches. Attached Figure Description
[0020] Figure 1 This is a 3D diagram of a centrifugal blower.
[0021] Figure 2 yes Figure 1 A 3D view of the centrifugal blower with its top casing removed.
[0022] Figure 3 yes Figure 1 A vertical sectional view of the main parts of a centrifugal blower.
[0023] Figure 4 yes Figure 3 An enlarged sectional view of the motor section.
[0024] Figure 5 This is an explanatory diagram showing an example of the rotor's rotation direction and the winding direction of the preload spring.
[0025] Figure 6 This is an illustrative diagram showing another example of the rotor's rotation direction and the winding direction of the preload spring.
[0026] Figure 7 The graph shows the relationship between the intensity of each frequency (Hz) and the noise level (dB) after performing a fast Fourier transform on the measured noise data when the rotor 3 rotates to the right (clockwise) and the preload spring is wound in the right-hand (Figure A) and left-hand (Figure B) directions.
[0027] Figure 8 It is shown that... Figure 7 The image shows the sliding part of the preloaded spring corresponding to line A in the graph.
[0028] Figure 9 It is shown that... Figure 7 The image shows a photograph of the sliding portion of the rotor yoke corresponding to line A in the graph.
[0029] Figure 10 It is shown that... Figure 7 The image shows the sliding part of the preloaded spring corresponding to line B in the graph.
[0030] Figure 11 It is shown that... Figure 7 The photograph of the sliding part of the rotor yoke corresponding to line B in the graph. Detailed Implementation
[0031] Hereinafter, an embodiment of the external rotor type electric motor of the present invention will be described with reference to the accompanying drawings. First, referring to... Figures 1 to 6 The schematic structure of an external rotor type motor will be explained. The external rotor type motor M is illustrated using a brushless DC motor used in vehicle-mounted equipment as an example. The following explanation will use a centrifugal blower 1 driven by the external rotor type motor M as an example.
[0032] Figure 1 In the centrifugal blower 1, the centrifugal fan 2 and rotor 3 are assembled as one unit, and the external rotor type motor M that drives them to rotate is housed within the blower casing 4. Figure 2 In this design, the blower housing 4 is formed by combining a top housing 4a and a bottom housing 4b. The top housing 4a is assembled to cover the centrifugal fan 2, and the bottom housing 4b supports the shaft of the external rotor type motor M (rotor 3 and stator 5) so that it can rotate. An air intake opening 4c is provided in the center of the top housing 4a, through which air is drawn in, and through an exhaust port 4d provided circumferentially, air pressurized from the radial outward is discharged.
[0033] exist Figure 2 In the centrifugal fan 2, a hub 2a is integrally assembled with a rotor yoke 3a at its radial center. The centrifugal fan 2 and the rotor yoke 3a are formed as inserts, and the top surface of the rotor yoke 3a is integral with the hub 2a. A main plate 2b, continuous with the hub 2a, extends radially outward in a stepped manner, and multiple impellers 2c are formed on the main plate 2b, curving from radially inward to radially outward.
[0034] like Figure 3 As shown, the external rotor type motor M includes a rotor 3 and a stator 5. The rotor 3 has a rotor shaft 3b mounted on a hub of a cup-shaped rotor yoke 3a. An annular rotor magnet 3c is provided on the inner circumferential surface of the rotor yoke 3a. The rotor magnet 3c has rotor poles formed by permanent magnets that are alternately magnetized with N and S poles in the circumferential direction. The rotor 3 is assembled on the radially outer side of the stator 5 in such a way that the rotor poles formed by the rotor magnet 3c are opposite to the stator poles.
[0035] exist Figure 3In this embodiment, the stator 5 has a plurality of pole teeth 5c around which the motor coil 5d is wound and forms stator poles, with the pole teeth 5c protruding radially outward from the back side 5b of the annular stator core 5a. In this embodiment, a single-phase coil is wound, but it can also be a three-phase coil, etc. In addition, the insulator 7 has coil pins 5e (not shown) at two locations that are connected to the motor coil 5d. The coil leads pulled from the motor coil 5d are connected to the coil pins respectively.
[0036] exist Figure 3 In the blower housing 4, a cylindrical metal bearing housing 8a is inserted into the bottom housing 4b and assembled integrally with the housing housing part 4e. The upper end 4f of the housing housing part 4e defines the assembly position of the stator core 5a (core back 5b). Inside the cylindrical hole of the bearing housing 8a, a pair of rolling bearings (bearings 8b) are respectively inserted on both sides of the bearing housing 8a in the longitudinal direction. The rotor shaft 3b is inserted into the bearing housing 8a and supported by the pair of bearings 8b to enable rotation. Furthermore, a locking washer 8c is embedded on the shaft end side of the rotor shaft 3b, and axial movement is restricted by the bearing 8b on the lower axial end side.
[0037] exist Figure 3 In this design, the motor base plate 6 is fixed to the blower housing 4 (bottom housing 4b). Additionally, a coil pin (not shown) connected to the motor coil 5d wound on the pole teeth 5c of the stator core 5a is inserted into the base plate terminal hole and soldered. The motor base plate 6 is equipped with a magnetic pole detection element (not shown), such as a Hall effect IC, for detecting the magnetic pole position of the rotor 3. The magnetic pole detection element detects the magnetic pole position of the rotor 3 and switches the direction of the current flowing through the motor coil 5d to apply force to the rotor 3 to make it rotate. Alternatively, in a sensorless motor, the magnetic pole detection element can be omitted.
[0038] like Figure 3 As shown, the stator core 5a and the insulator 7 are assembled by integral molding. The insulator 7 is formed, for example, by insert molding of the stator core 5a with PBT (polybutylene terephthalate) resin. Alternatively, the insulator 7 may be molded only and assembled around the pole teeth 5c of the stator core 5a without insert molding.
[0039] The insulator 7 has cylindrical portions 7a protruding radially inward and axially to both sides of the stator core 5a. A motor base plate 6 is assembled on one of the cylindrical portions 7a as described later (see reference). Figure 4 The stator 5 and the motor base plate 6 (stator assembly) are assembled on the bottom housing 4b in such a way that the cylindrical portion 7a is concentrically embedded into the outer periphery of the housing portion 4e that houses the cylindrical metal bearing housing 8a. (Refer to...) Figure 2 ).
[0040] In addition, such as Figure 4As shown, a preload spring 8d is embedded around the rotor shaft 3b in a compressed state (compressed beyond its natural length) between the hub 3a1 of the rotor yoke 3a and the bearing 8b (inner ring) positioned axially opposite to it on the upper side, thereby improving the rotational stability of the rotor 3. This preload spring 8d is a compression helical spring, wound in a direction relative to the rotational direction of the rotor yoke 3a toward the winding end 8d1 without hindering the driven rotation. Furthermore, the preload spring 8d can be placed only between the hub 3a1 and the bearing 8b, and therefore can also be placed between the outer ring of the bearing 8b and the hub 3a1. However, if the preload spring 8d is placed between the bearing 8b (inner ring) and the hub 3a1, the outer diameter of the preload spring 8d can be minimized, and the preload spring 8d can be assembled between the rotor yoke 3a and the bearing 8b without any wobble, thus proving effective.
[0041] Specifically, such as Figure 5 As shown, when the rotor 3 is viewed from one axial end (top) and the rotor yoke 3a is rotating to the left, the preload spring 8d is preferably wound in a right-hand rotation. Additionally, as... Figure 6 As shown, when the rotor yoke 3a rotates to the right, the preload spring 8d is preferably wound to the left.
[0042] Therefore, even if the rotational load on a pair of bearings 8b increases, the winding end 8d1 of the preload spring 8d will not hinder the driven rotation that accompanies the rotation of the rotor yoke 3a. Thus, it is possible to suppress the increased hooking of the sliding surfaces of the rotor yoke 3a hub 3a1 or bearing 8b (inner ring) that would otherwise generate abnormal noise, thereby achieving noise reduction and also reducing scratches and extending the life of the components.
[0043] Figure 7 The graph shows the relationship between the intensity of each frequency (Hz) and the noise level (dB) after performing a fast Fourier transform on the measured noise data when the rotor 3 rotates to the right (clockwise) and the preload spring 8d is wound in the right-hand (Figure A) and left-hand (Figure B) directions.
[0044] exist Figure 7 As can be seen from graph A, when the winding direction of the preload spring 8d is right-handed, the winding end 8d1 is easily hooked with the sliding surface of the hub 3a1 of the rotor yoke 3a and / or the bearing 8b (inner ring). Therefore, the rotational component of the sound of the preload spring 8d hooking is generated at multiple locations.
[0045] Figure 8 and Figure 9 It is shown that... Figure 7 The image shows a photograph of the preload spring 8d and the sliding part (hub 3a1) of the rotor yoke 3a corresponding to line A. It can be seen that the scratches on the sliding surface of the rotor yoke 3a (hub 3a1) are deeper, and the winding end 8d1, which is pressed against and slides with it, also has relatively deep scratches (see reference). Figure 8 , Figure 9 (The dashed enclosing line).
[0046] In contrast, Figure 7 As shown in graph B, when the winding direction of the preload spring 8d is left-handed, the winding end 8d1 is not easily hooked with the sliding surface of the hub 3a1 of the rotor yoke 3a and / or the bearing 8b (inner ring). Therefore, even if the rotational speed changes, there will be no peak sound (abnormal noise).
[0047] Figure 10 and Figure 11 The photograph shows the preload spring 8d and the sliding part (hub 3a1) of the rotor yoke 3a. It can be seen that although the sliding surface of the rotor yoke 3a (hub 3a1) has abrasions, they are minimal, and the winding end 8d1 that is pressed and slides against it also has abrasions, but they are minimal.
[0048] As described above, when the rotor 3 rotates, the preload spring 8d, embedded between the hub 3a1 of the rotor yoke 3a and the bearing 8b arranged axially opposite to it, also rotates synchronously. At this time, the preload spring 8d is wound towards its winding end 8d1 without obstructing the driven rotation accompanying the rotor yoke 3a. Therefore, even if the rotational load on the pair of bearings 8b increases, it can suppress the increased hooking between the winding end 8d1 of the preload spring 8d, which has elastic reaction force, and the sliding surface of the rotor yoke 3a or bearing 8b, thus suppressing noise and achieving quiet operation. Furthermore, even if the sliding between the winding end 8d1 of the preload spring 8d and the end faces of the abutting rotor yoke 3a1 and the bearing 8b (inner ring) increases, scratches can be reduced, extending the life of the components.
[0049] In the above embodiments, the motor substrate 6 is provided with a magnetic pole detection element 6a such as a Hall IC, but it can also be a sensorless DC brushless motor that omits the magnetic pole detection element 6a.
[0050] In addition, the insulator 7 does not need to be integrally formed with the stator core 5a, or it can be formed separately and then assembled.
Claims
1. An external rotor type electric motor, comprising: A stator having stator poles; and a rotor having rotor poles formed of permanent magnets arranged opposite to the stator poles on the radially outer side of the stator, characterized in that... have: The rotor shaft, the end of which is integrally assembled with the hub of the rotor yoke, which is formed in the shape of a cup; A pair of rolling bearings, assembled in a bearing housing located within the motor housing, support the rotor shaft so that it can rotate; as well as A preload spring, which is embedded in the outer circumference of the rotor shaft and between the hub of the rotor yoke and the rolling bearings arranged axially opposite each other, is compressed and installed from its natural length. The preload spring is a compression helical spring, and it is wound in a direction relative to the rotation direction of the rotor yoke toward the winding end in a direction that does not hinder the driven rotation.
2. The external rotor type electric motor according to claim 1, characterized in that, Viewed from one end of the axial direction, when the rotor yoke is turned right, the preload spring is wound in a left-handed manner; when the rotor yoke is turned left, the preload spring is wound in a right-handed manner.
3. The external rotor type electric motor according to claim 1 or 2, characterized in that, The preload spring is embedded in the outer circumference of the rotor shaft and between the hub of the rotor yoke and the inner ring of the rolling bearing, which is arranged axially opposite to each other.