Abstract:
A rotor, which includes a rotor main body and a fan. The rotor main body includes a rotor core, a rotary shaft extending through the rotor core, and a permanent magnet mounted in the rotor core. The fan includes a plurality of fixing portions embedded in the rotor main body and configured to fix the permanent magnet. The rotor has a simple structure, can be easily assembled, and has a low cost.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This non-provisional patent application claims priority under 35 U.S.C. § 119(a) from Patent Application No. 201610489989.6 filed in The People&#39;s Republic of China on Jun. 28, 2016. 
       FIELD OF THE INVENTION 
       [0002]    The present disclosure relates to motors, and in particular to a rotor of a motor, a manufacturing method of the rotor, and a motor. 
       BACKGROUND OF THE INVENTION 
       [0003]    A rotor is used to cooperate with a stator, and rotate relative to the stator under the action of electromagnetic force, thereby driving a load connected to the rotor to rotate. A direct current motor, of which a rotor generally includes a rotary shaft, a rotor core, and a permanent magnet embedded in the rotor core. In order to cool the motor, a fan is generally mounted on an end of the rotor, and is driven by the rotor to rotate to cool the motor. 
         [0004]    However, an assemble process of the motor with fan is complex. 
       SUMMARY OF THE INVENTION 
       [0005]    Accordingly, there is a desire for a rotor which can be easily assembled, and a method for manufacturing the rotor. There is also a need for a motor including the rotor. 
         [0006]    In one aspect, a rotor includes a rotor main body and a fan. The rotor main body comprises a rotor core, a rotary shaft extending through the rotor core and a permanent magnet mounted in the rotor core. The fan comprises a plurality of fixing portions embedded in the rotor main body and configured to fix the permanent magnet. 
         [0007]    Preferably, the fan further comprises a top cover and an impeller that are disposed at two ends of the fixing portions, two ends of the rotary shaft extend through the impeller and the top cover, respectively, the rotor core is disposed between the impeller and the top cover, the permanent magnet is wrapped in the fixing portions, and the fixing portions are embedded in the rotor core. 
         [0008]    Preferably, the top cover, the impeller, and the fixing portions are integrally formed through injection molding. 
         [0009]    Preferably, the fixing portions wrap the permanent magnet via an over-molding process. 
         [0010]    Preferably, the fan further comprises a connection portion, the connection portion is disposed between the impeller and the fixing portion, one end of each fixing portion extending through one of the mounting grooves is connected to the connection portion, and the other end of each fixing portion is connected to the top cover. 
         [0011]    Preferably, a plurality of positioning holes is defined in the rotor core along a direction parallel to an axis of the rotor core, a plurality of positioning pins are disposed on the top cover, and each positioning pin is inserted in and extends through one of the positioning holes and is connected to the connection portion. 
         [0012]    Preferably, a plurality of recesses are defined in two ends of the rotor core, respectively, a plurality of positioning pins are disposed on the connection portion and the top cover, and each positioning pin is inserted in one of the recesses. 
         [0013]    Preferably, the top cover abuts against an end of the rotor core, a sleeve is disposed at a side of the top cover, and an end of the rotary shaft extends sequentially through the top cover and the sleeve. 
         [0014]    Preferably, an outer circumferential surface of the rotor core is in an irregular round shape, the outer circumferential surface of the rotor core comprises a plurality of arc surfaces and a plurality of transition surfaces, and the arc surfaces and the transition surfaces are alternately arranged. 
         [0015]    Preferably, the rotary shaft tightly fits the rotor core. 
         [0016]    Preferably, a plurality of mounting grooves is defined in the rotor core, and each of the fixing portions is accommodated in one of the mounting grooves. 
         [0017]    Preferably, two air grooves are disposed at two ends of each of the mounting grooves, and each air groove is communicated with one corresponding mounting groove, a lug extends from each of two side of each fixing portion, and the lug is held in one of the air grooves. 
         [0018]    Preferably, a cross section of each air groove is a triangle in shape, and each air groove is located at one side of the corresponding mounting groove adjacent the corresponding transition surface. 
         [0019]    In another aspect, a manufacturing method of a rotor includes the following steps:
       providing a rotor core, a rotary shaft and a plurality of permanent magnets, a plurality of mounting grooves being formed in the rotary core, and an air groove being formed at each of two sides of each mounting groove and communicated with the each mounting groove;   extending the rotary shaft through the rotor core along an axis of the rotor core and fixing the rotary shaft to the rotor core, each permanent magnet being accommodated in one of the mounting grooves;   placing the rotor core, the rotary shaft and the permanent magnets that have been assembled into a mold, with each permanent magnet located in a middle of the one of the mounting grooves;   injecting high pressure melting plastic into the mold, thereby forming a fan through injection molding; and   removing the rotor composed of the rotor main body and the fan from the mold through a demolding mechanism.       
 
         [0025]    Preferably, the melting plastic is filled in the mounting groove and the air grooves to form a fixing portion at an outside of the permanent magnet to wrap the permanent magnet, and form lugs mating with the air grooves at two sides of each fixing portion, and the melting plastic is filled in positioning holes to form positioning pins. 
         [0026]    In another aspect, a motor includes a stator and an endcap disposed at an end of the stator. The motor further comprises the rotor described above, and the rotor is supported by the endcap and is rotatably received in the stator. 
         [0027]    In still another aspect, a power tool includes the motor described above. 
         [0028]    The rotor of the present disclosure includes the rotor main body and the fan which are embedded with each other, and the fan is integrally formed on the rotor main body via injection molding, thereby solving the problems in the conventional rotor assembly process that there are an unduly large amount of assembly parts and the assembly process is complex. Further, by forming the fixing portion at the outside of the permanent magnet via injection molding, the permanent magnet is sealed, and it can be ensured that a position of the permanent magnet will not changed as well. The lugs extending along two sides of each fixing portion, used in combination with the air grooves, further enhance the effect of magnetic isolation, and also make the connection between the fan and the rotor main body even tighter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]      FIG. 1  is a perspective view of a motor according to an embodiment of the present disclosure. 
           [0030]      FIG. 2  is an exploded view of the motor shown in  FIG. 1 . 
           [0031]      FIG. 3  is an exploded view of the motor shown in  FIG. 1 , viewed from another direction. 
           [0032]      FIG. 4  is an exploded view of a rotor shown in  FIG. 2 . 
           [0033]      FIG. 5  is a sectional view of the rotor shown in  FIG. 2  take alone line V-V thereof. 
           [0034]      FIG. 6  is a sectional view of the rotor shown in  FIG. 2  take alone line VI-VI thereof 
           [0035]      FIG. 7  is a perspective view of a power tool according to an embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0036]    Below, embodiments of the present disclosure will be described in greater detail with reference to the drawings. Elements of similar structures or functions are generally represented by like reference numerals for illustrative purposes throughout the figures. It should be noted that the figures are illustrative rather than limiting. The figures are not drawn to scale, do not illustrate every aspect of the described embodiments, and do not limit the scope of the present disclosure. Unless otherwise specified, all technical and scientific terms used in this disclosure have the ordinary meaning as commonly understood by people skilled in the art. 
         [0037]    It should be noted that, when a component is described to be “fixed” to another component, it can be directly fixed to the another component or there may be an intermediate component. When a component is described to be “connected” to another component, it can be directly connected to the another component or there may be an intermediate component. When a component is described to be “disposed” on another component, it can be directly disposed on the another component or there may be an intermediate component. 
         [0038]    Referring to  FIG. 1 , a rotor  50  of one embodiment of the present disclosure is a permanent magnet rotor, which is applied in a motor  100 . The motor  100  may be, but not limited to, a single-phase motor, or a multi-phase motor. In this embodiment, the motor  100  is a single-phase permanent magnet motor. The motor  100  further includes a housing  10 , an endcap  20  disposed at an end of the housing  10  and a stator  30 . The stator  30  is mounted in the housing  10 . The rotor  50  is rotatably received in the stator  30 , and rotates relative to the stator  30  under an electromagnetic force. Two ends of the rotor  50  are supported by bearings disposed at the endcap  20  and the housing  10 . 
         [0039]    In this embodiment, a plurality of hollow portions  12  is defined in the housing  10 . The hollow portions  12  are used to reduce a weight of the motor  100 , and facilitate heat dissipation of the motor  100 . A bearing seat  13  is disposed at an end of the housing  10 , and a bearing seat  23  is disposed at the endcap  20 . The two bearing seats  13 ,  23  are used to mount the bearings for supporting the rotor  50 . 
         [0040]    Referring to  FIG. 2  and  FIG. 3 , the rotor  50  can include a rotor main body  52  and a fan  53 . In this embodiment, the rotor main body  52  and the fan  53  are embedded with each other to form a unitary body. The rotor main body  52  can include a rotor core  521 , a rotary shaft  523  and a plurality of permanent magnets  525 . The rotary shaft  523  extends through the rotor core  521  along an axis of the rotor core  521 . The rotary shaft  523  is fixed in the rotor core  521  and intimately fits with the rotor core  521 . Two ends of the rotary shaft  523  are supported at the housing  10  and the endcap  20  of the motor  100  through bearings  526 , respectively. Referring also to  FIG. 4 , a shaft hole  5211  is defined in the rotor core  521  along the axis of the rotor core  521  for mounting the rotary shaft  523 . A plurality of mounting grooves  5212  and a plurality of positioning holes  5214  are defined in the rotor core  521 . Each of the mounting grooves  5212  and the positioning holes  5214  extends through the rotor core  521  along a direction parallel to the axis of the rotor core  521 . The mounting grooves  5212  are used to accommodate the permanent magnet  525  and partially accommodate the fan  53 . The mounting grooves  5212  are evenly disposed in the rotor core  521  and centered around the axis of the rotor core  521 . The positioning holes  5214  are used to hold the fan  53 . The positioning holes  5214  are evenly disposed in the rotor core  521  and centered around the axis of the rotor core  521 . A plurality of mating holes  5215  are defined in the rotor core  521 . The mating holes  5215  are defined in a circumferential surface of the shaft hole  5211  of the rotor core  521 , and are communicated with the shaft hole  5211 . The mating holes  5215  are used to hold the fan  53 . 
         [0041]    It should be understood that, in other embodiments of the present disclosure, the positioning holes  5214  may also be recesses  5216  disposed at two ends of the rotor core  521 , and the recesses  5216  are used to hold the fan  53 . 
         [0042]    An outer circumferential surface of the rotor core  521  is in an irregular round shape. The outer circumferential surface of the rotor core  521  includes a plurality of arc surfaces  5217  and a plurality of transition surfaces  5218 , and the arc surfaces  5217  and the transition surfaces  5218  are alternately arranged. The presence of the arc surfaces  5217  and the transition surfaces  5218  results in an uneven air gap being formed between the rotor core  521  and the stator  30 , so that the motor  100  can avoid a startup dead point. In this embodiment, a plurality of air grooves  5213  is disposed in the rotor core  521 . Two of the air grooves  5213  are disposed at two ends of each mounting groove  5212  at one side thereof adjacent a transition surface  5218 , and each air groove  5213  is communicated with the corresponding mounting groove  5212 . In this embodiment, a cross section of the air groove  5213  perpendicular to an axis of the rotor main body  52  is a triangle in shape. A length of a bottom of the air groove  5213  is less than a length of the mounting groove  5212 , and a distance between the transition surface  5218  and a lateral side of the air groove is as small as possible so as to reduce magnetic circuit loss. The air grooves  5213  are further used to prevent short circuit of magnetic flux of two adjacent permanent magnets  525 . It should be understood that the rotor core  521  is formed by stacking sequentially a plurality of magnetic conductive laminations. The magnetic conductive laminations are made of soft magnetic material having magnetic permeability, such as silicon steel sheet, permalloy, or ferrite. 
         [0043]    In this embodiment, there are four permanent magnets  525 . Each permanent magnet  525  is accommodated in one mounting groove  5212  to form one rotor pole. The rotor  50  further includes a magnetic ring  524 . The magnetic ring  524  is disposed around one end of the rotary shaft  523 . The magnetic ring  524  abuts against the fan  53  adjacent one end of the housing  10  where the bearing seat  13  is disposed, and rotates along with the rotary shaft  523 . The magnetic ring  524  is used to limit displacement of the rotor core  521  and the fan  53  along an axial direction of the rotary shaft  523 . 
         [0044]    The fan  53  and the rotor main body  52  are embedded with each other, and the fan  53  rotates along with the rotor main body  52  for cooling the motor  100 . In this embodiment, the fan  53  is formed on the rotor main body  52  through injection molding. 
         [0045]    Referring to  FIG. 5  and  FIG. 6 , the fan  53  can include an impeller  531 , a connection portion  532 , a plurality of fixing portions  534 , a top cover  535  and a sleeve  536 . The connection portion  532  is substantially of a cylindrical or truncated cone structure. The impeller  531  is disposed at an end of the connection portion  532 , and the fixing portions  534  are disposed at the other end of the connection portion  532 . 
         [0046]    In this embodiment, a plurality of holding portions  5323  are disposed at an end surface of one end of the connection portion  532  adjacent the fixing portion  534 . Each holding portion  5323  is inserted into one of the mating holes  5215 , and abuts against the rotary shaft  523  accommodated in the shaft hole  5211 . The fixing portions  534  are evenly arranged at one end of the connection portion  532  and are centered around the axis of the connection portion  532 . The other ends of the fixing portions  534  are connected to the top cover  535 . 
         [0047]    In this embodiment, each fixing portion  534  is a hollow structure, which accommodates one permanent magnet  525  therein. Preferably, after two ends of the fixing portion  534  are connected to the connection portion  532  and the top cover  535 , respectively, a hollow portion of the fixing portion  534  becomes a sealed space. A lug  5343  is disposed at and extends from each of two sides of each fixing portion  534 , and matches with the air groove  5213  in shape. Each lug  5343  is accommodated in one corresponding air groove  5213 . In this embodiment, the cross section of the air groove  5213  perpendicular to the axis of the rotor main body  52  is a triangle in shape, and the air groove  5213  is located at one side of the mounting groove  5212  adjacent an edge of the rotor main body  52 . In manufacutring the rotor  50 , the fixing portion  534  with the permanent magnet  525  accommodated therein extends through and is held in one corresponding mounting groove  5212 . A number of the fixing portions  534  is equal to a number of the permanent magnets  525 . In this embodiment, there are four fixing portions  534  which cooperatively define an accommodating space  5341 . The rotor main body  52  is partially embedded in the accommodating space  5341 . 
         [0048]    In this embodiment, the top cover  535  is disc-shaped, which abuts against one end of the rotor core  521  for fixing the rotor main body  52 . A plurality of positioning pins  5351  extends from one side of the top cover  535  facing towards the fixing portion  534 . Specifically, in one embodiment where a plurality of positioning holes  5214  is defined through the rotor core  521  along a direction parallel to the axis of the rotor core  521 , each positioning pin  5351  is inserted into and extends though one of the positioning holes  5214 , and is connected to the connection portion  532 . In another embodiment where a plurality of recesses  5216  is defined in two ends of the rotor core  521 , respectively, a plurality of positioning pins  5321  is disposed at an end surface of one end of the connection portion  532  adjacent the fixing portion  534 , and each positioning pin  5321  is inserted into one of the recesses  5216  adjacent the top cover  535 . The sleeve  536  is disposed at one side of the top cover  535  away from the fixing portion  534 . One end of the rotary shaft  523  extending out of the rotor core  521  extends sequentially through the connection portion  532  and the impeller  531 , and the other end thereof extends sequentially through the top cover  535  and the sleeve  536 . The sleeve  536  is used to make a tighter connection between the rotary shaft  523  and the fan  53 . 
         [0049]    Referring to  FIG. 7 ,  FIG. 7  is a perspective view of the motor  100  utilized in a power tool  200 . In this embodiment, the power tool  200  is an electric drill. In other embodiments, the power tool  200  may also be an electric saw, an electric hammer, and the like. The motor  100  drives a drill (not labelled) mounted at an end of the electric drill through a transmission mechanism (not shown). 
         [0050]    The present disclosure provides a method for manufacturing a rotor of a motor, which includes the following steps. 
         [0051]    At Step S 1 , a rotor core  521 , a rotary shaft  523  and a plurality of permanent magnets  525  are provided. A plurality of mounting grooves  5212  is disposed in the rotary core  521 , and an air groove  5213  is disposed at each of two sides of each mounting groove  5212  and communicated with the mounting groove  5212 . The rotary shaft  523  extends through the rotor core  521  along an axis of the rotor core  521  and is fixed to the rotor core  521 . Each permanent magnet  525  is accommodated in one of the mounting grooves  5212 , thereby forming a rotor main body  52  with a preliminarily fixed shape. 
         [0052]    At Step S 2 , the rotor core  521 , the rotary shaft  523  and the permanent magnets  525  that have been preliminarily assembled are placed into a mold, with each permanent magnet  525  located in a middle of the mounting groove  5212 . 
         [0053]    It should be understood that the permanent magnet  525  may be mounted in the middle of the mounting groove  5212  by forming a plurality of positioning portions of foaming agent styrene on the permanent magnet  525 . 
         [0054]    It should be understood that the permanent magnet  525  may be mounted in the middle of the mounting groove  5212  by disposing the positioning portions on an inner surface of mounting groove  5212 . 
         [0055]    At Step S 3 , high pressure melting plastic is injected into the mold through an injection molding machine so that the melting plastic flows in the mold along runners to form the structure of a fan  53 . The melting plastic is filled in the mounting groove  5212  and the air grooves  5213  to form a fixing portion  534  located at an outside of the permanent magnet  525  to wrap the permanent magnet  525 , and form lugs  5343  mating with the air grooves  5213  at two sides of each fixing portion  534 . The plastic filled in the positioning holes  5214  or recesses  5216  forms positioning pins  5321 ,  5351 . The fixing portions  534  are formed via an over-molding process. 
         [0056]    The fixing portion  534  wraps the permanent magnet  525 , thereby preventing the permanent magnet  525  from being exposed to an external environment and thus avoiding corrosion. Further, the fixing portion  534  fixes the permanent magnet  525  in the mounting groove  5212 . The lugs  5343  and the positioning pins  5321  ( 5351 ) make the connection between the rotor main body  52  and the fan  53  even tighter, thereby preventing the fan  53  from sliding relative to the rotor main body  52 . 
         [0057]    At Step S 4 , pressure is continuously applied to the mold to ensure that the fan  53  is formed at high pressure, so that the fan  53  has a greater density as well as a more stable and solid structure. 
         [0058]    At Step S 5 , the mold is cooled after the pressure is kept for a preset period of time, so that the melting plastic cools to form a solid fan  53 . 
         [0059]    At Step S 6 , the rotor  50  composed of the rotor main body  52  and the fan  53  is removed from the mold through a demolding mechanism, thereby accomplishing the final product. 
         [0060]    The rotor  50  of the present disclosure includes the rotor main body  52  and the fan  53  which are embedded with each other, and the fan  53  is integrally formed on the rotor main body  52  via injection molding, thereby solving the problems in the conventional rotor manufacturing process that there are an unduly large amount of assembly parts and the assembly process is complex. In addition, by forming the fixing portion  534  at the outside of the permanent magnet  525  via injection molding, the permanent magnet  525  is sealed, and it can be ensured that a position of the permanent magnet  525  will not be changed as well. Since the permanent magnet is sealed via injection molding, corrosion of the permanent magnet is prevented, and the process of applying glue before inserting the permanent magnet in the rotor can be omitted to simplify the process of assembling the rotor. The lugs  5343  extending along two sides of each fixing portion  534 , used in combination with the air grooves  5213 , enhance the effect of magnetic isolation, and also make the connection between the fan  53  and the rotor main body  52  even tighter. 
         [0061]    Therefore, the technical solutions of embodiments of the present disclosure have been clearly and completely described above. Apparently, the described embodiments are merely part of, rather than all of, the embodiments of the present disclosure. A person skilled in the art may make various combinations of technical features in the various embodiments to meet practical needs. Based on the described embodiments of the present disclosure, any other embodiment obtained by a person skilled in the art without paying creative efforts shall also fall within the scope of the present disclosure.