Abstract:
A motor ( 10 ) and a pump having the motor are provided. The motor ( 10 ) includes a stator ( 14 ) and a rotor ( 16 ) rotatable relative to the stator ( 14 ). At least one of the stator ( 14 ) and the rotor ( 16 ) has a magnetic core ( 20 ) and a winding ( 22 ) wound around the magnetic core ( 20 ). The magnetic core is mounted to a base body ( 18 ). The base body ( 18 ) has at least one recess ( 54 ) for receiving debris produced by mutual friction between the magnetic core ( 20 ) and the base body ( 18 ).

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. CN201510548299.9 filed in The People&#39;s Republic of China on Aug. 31, 2015. 
       FIELD OF THE INVENTION 
       [0002]    The present disclosure relates to electric motor. 
       BACKGROUND OF THE INVENTION 
       [0003]    In home appliances such as washing machines or dish washers, liquid pumps are used to pressurize and deliver water so as to introduce clean water into the appliances for cleaning clothes or dishes, and finally discharge the waste water out of the appliances. 
         [0004]    The existing liquid pumps usually use a single phase permanent magnet motor to drive an impeller to rotate. The motor has an stator core and a permanent magnet rotor rotatably disposed in the stator core. The stator core is wound with windings. The windings are connected to a driving circuit. Upon energization of the windings, the stator core is polarized which interacts with permanent magnet rotor to drive the rotor to rotate. The impeller is connected to the rotor for synchronous rotation with the rotor to drive the water to flow. stator core 
         [0005]    In a conventional design, a rotor housing is disposed between the rotor and the stator core. However, when the stator core is assembled to the rotor housing, the stator core may scratch the rotor housing to produce debris. If the debris is clamped between the stator core and the rotor housing, the stator core cannot be assembled in place, which makes the axes of the stator and rotor offset from each other, thereby causing unsmooth rotation of the rotor and large noise. 
       SUMMARY OF THE INVENTION 
       [0006]    According to one aspect of the present disclosure, a motor includes a stator and a rotor rotatable relative to the stator. At least one of the stator and the rotor includes a magnetic core and a winding wound around the magnetic core. The magnetic core is mounted to a base body. The base body has at least one recess for receiving debris produced by mutual friction between the magnetic core and the base body. 
         [0007]    Preferably, the base body is disposed between the stator and the rotor in a radial direction. 
         [0008]    Preferably, the base body has a step with an axial end surface for positioning the magnetic core, and the recess and the magnetic core are disposed at two sides of the axial end surface. 
         [0009]    Preferably, the base body has an axially-extending rib for guiding relative movement between the magnetic core and the base body, the rib intersects with an axial end surface of a step of the base body, and the base body has two recesses disposed at two circumferential sides of the rib respectively. 
         [0010]    Preferably, the rib extends to the step and the two recesses are defined by the rib and the step. 
         [0011]    Preferably, the base body has a sleeve receiving the rotor, the stator has a stator core which has a pair of pole shoes, and inner wall surfaces of the pair of pole shoes are recessed to form pole arc surfaces surrounding the sleeve. 
         [0012]    Preferably, the pole arc surfaces of the pole shoes lay on an outer wall surface of the sleeve, and the sleeve has an axially-extending rib which is inserted into a slot between pole tips of the pole shoes. 
         [0013]    Preferably, a step is projected from an outer wall surface of the sleeve and defines recesses at two circumferential sides of the rib. 
         [0014]    Preferably, the pole arc surfaces have a diameter greater than an outer diameter of the sleeve, the pole arc surfaces and an outer wall surface of the sleeve are radially spaced apart, and the sleeve has at least one axially-extending rib contacting the pole arc surfaces. 
         [0015]    Preferably, the sleeve has a plurality of ribs which are evenly spaced along a circumferential direction. 
         [0016]    Preferably, the pole arc surface is formed with a startup groove. 
         [0017]    Preferably, a slot is formed between pole tips of the pair of pole shoes, an air gap is formed between the outer wall surface of the rotor and the pole arc surfaces of the stator, and a ratio of a width of the slot to a width of the air gap is greater than zero and less than two. 
         [0018]    Preferably, a slot is formed between distal ends of the pair of pole shoes, an axially-extending end surface of pole tip of each pole shoe and the pole arc surface intersect to form a sharp angle. 
         [0019]    Preferably, the axially-extending end surface of the pole tip of each pole shoe and the pole arc surface perpendicularly intersect with each other. 
         [0020]    Preferably, the motor is a single phase synchronous motor, and the rotor of the motor is a permanent magnet motor. 
         [0021]    According to another aspect of the present disclosure, a pump includes above described motor and an impeller couple to the rotor of the motor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  illustrates a liquid pump according to one embodiment of the present disclosure. 
           [0023]      FIG. 2  is an exploded view of  FIG. 1 . 
           [0024]      FIG. 3  illustrates the liquid pump of  FIG. 1 , viewed from another aspect. 
           [0025]      FIG. 4  is a perspective view of a magnetic core of the liquid pump of  FIG. 3 . 
           [0026]      FIG. 5  is a perspective view of a rotor housing of the liquid pump of  FIG. 3 . 
           [0027]      FIG. 6  is an assembled view of the magnetic core of  FIG. 4  and the rotor housing of  FIG. 5 . 
           [0028]      FIG. 7  is a front view of  FIG. 6 . 
           [0029]      FIG. 8  is a perspective view of the rotor housing of the liquid pump according to another embodiment of the present disclosure. 
           [0030]      FIG. 9  is an assembled view of the rotor housing of  FIG. 8  and the magnetic core. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0031]    It should be noted that the figures are not drawn to scale and that elements of similar structures or functions are generally represented by like reference numerals for illustrative purposes throughout the figures. It also should be noted that the figures are only intended to facilitate the description of the preferred embodiments. The figures do not illustrate every aspect of the described embodiments and do not limit the scope of the present disclosure. 
         [0032]    Referring to  FIG. 1  to  FIG. 3 , a pump in accordance with one embodiment of the present disclosure includes a motor  10  and an impeller  12  driven by the motor  10 . The motor  10  is preferably a single phase permanent magnet motor which includes a stator  14 , a rotor  16 , and a rotor housing (which may also be referred to as a base body)  18 . The base body has a sleeve disposed between the rotor  16  and the stator  14 . The stator  14  includes a magnetic core  20 , windings  22  wound around the magnetic core  20 , an a circuit board connected with the windings  22 . Preferably, the magnetic core  20  is a U-shaped stator core. The rotor  16  is a permanent magnet rotor. Each of the magnetic core  20  and the rotor  12  forms a pair of magnetic poles, and the poles of the magnetic core  20  and the rotor  16  interact with each other to drive the rotor  16  to rotate. The impeller  12  is coupled to a shaft  17  of the rotor  16  for synchronous rotation with the rotor  16  to drive liquid such as water to flow. 
         [0033]    Referring to  FIG. 4 , the magnetic core  20  includes an end portion  24  and two pole arms  26  vertically extending from the end portion  24 . In this embodiment, the end portion  24  and the pole arms  26  are each formed by stacking a plurality of laminations such as silicon steel sheets and are mechanically connected to each other. The end portion  24  and the pole arms  26  are connected with a dovetail joint which prevents the end portion  24  and the pole aims  26  from disconnection from each other. In this embodiment, the end portion  24  forms engagement grooves  28  at opposite sides thereof, respectively. The two pole arms  26  form corresponding engagement protrusions  30  engaged in the engagement grooves  28 , respectively. In another embodiment, the engagement grooves may alternatively be formed in the pole arms  26 , the engagement protrusions  30  are accordingly formed on the end portion  24 , and the magnetic core  20  is likewise formed by a mortise joint. In this embodiment, the end portion  24  and the pole aims  26  are separately formed and then mechanically connected, which facilitates the winding process of the windings  22 . In some embodiments, the magnetic core  20  may alternatively be a monolithic structure. 
         [0034]    The two pole arms  26  of the magnetic core  20  have substantially the same construction and are spacingly disposed in parallel with each other. Each pole arm  26  is elongated, including a connecting arm  32  and a pole shoe  34  formed at a distal end of the connecting arm  32 . The two connecting arms  32  are spacingly disposed in parallel with each other. One engagement protrusion  30  protrudes outwardly from an end surface of each connecting arm  32  that faces toward the end portion  24 , which is engaged in one corresponding engagement groove  28 . In this embodiment, the windings  22  are wound around the connecting arms  32  and are connected in series. The two pole shoes  34  are disposed away from the end portion  24  and act as a pair of magnetic poles of the magnetic core  20  of the stator  14 . Upon energization of the windings  22 , the pole shoes  34  are polarized to have opposite polarities. The two pole shoes  34  are opposed to and spaced apart from each other. Inner wall surfaces of the pole shoes  34  are recessed inwardly such that a space  38  for receiving the rotor  16  is formed between the two pole shoes  34 . The inner wall surfaces of the two pole shoes  34  form pole arc surfaces  36  surrounding the space  38 . The space  38  is cylindrical, and the pole arc surfaces  36  are substantially cylindrical surfaces, confronting the outer wall surface of the rotor  12  in a radial direction. 
         [0035]    In this embodiment, each pole shoe  34  is substantially C-shaped, two circumferential ends of which extend laterally from the connecting arm  32  to form two pole tips  40 . The pole tips  40  are substantially parallel to the end portion  24 . An internal angle α of a distal end of each pole tip  40 , i.e. an angle formed between an axially-extending end surface of the pole tip  40  and the pole arc surface  36 , is a sharp angle which is preferably 90 degrees. Preferably, the extending length of the pole tip  40  is slightly less than a half of a width of the interval between the two connecting aims  32 . After the connecting arms are joined, a small slot  42  is formed between distal ends of the pole tips  40  at opposing sides of the two pole shoes  34 . The slot  42  has a width d 1  far less than the width of the interval between the connecting arms  32 , which significantly reduces the cogging torque while avoiding the magnetic leakage, thereby resulting in more smooth rotation of the rotor  16  and reduced noise. 
         [0036]    Preferably, a startup groove  44  is formed in the pole arc surface  36 . The startup groove  44  is offset from a central axis X (see  FIG. 7 ) of the pole shoe  34  by an angle. In this embodiment, there are two startup grooves  44  disposed in the two pole shoes  34 , respectively. One startup groove  44  is disposed adjacent an inner one of the pole tips  40  of its corresponding pole shoe  34 , the other startup groove  44  is disposed adjacent an outer one of the pole tips  40  of its corresponding pole shoe  34 , and the two startup grooves  44  are spaced 180 degrees in the circumferential direction. The startup grooves  44  are offset from the central axis of the pole shoe  34 , such that when the motor is powered off to stop, a pole axis of the rotor  16  is offset from the central axis X of the pole shoe  34  by an angle, i.e. the dead point is avoided, which ensures that the motor  10  can be successfully started when energized again. 
         [0037]    Referring to  FIG. 5 , the rotor housing  18  has a cylindrical structure with an open end and a closed end, and the rotor  16  is rotatably received in the rotor housing  18 . The rotor  16  and the stator  12  are isolated from each other by the base body  18 . An outer wall surface of the rotor  16  and the pole arc surfaces of the stator are spaced in the radial direction to define a main air gap therebetween. The main air gap has a width d 2 . The air gap between the rotor  16  and the stator  12  increases in width at the area of the startup groove  44 . Preferably, a ratio of the width d 1  of the slot  42  to the width d 2  of the main air gap is greater than zero but less than two, i.e. 0&lt;d 1 /d 2  &lt;2, which reduces the cogging torque and hence results in a smooth rotation of the motor and reduced noise. The shaft  17  of the rotor  16  extends out through the open end of the rotor housing  18  to drive the impeller  12  to rotate. In this embodiment, the rotor housing  18  integrally connects to an outer housing  13  of the impeller  12  at the open end of the rotor housing  18 . Alternatively, the rotor housing  18  and the outer housing  13  may form a monolithic structure by injection molding. 
         [0038]    Referring also to  FIG. 6  and  FIG. 7 , an outer diameter of the sleeve  18  is substantially equal to a diameter of the pole arc surfaces  36  of the pole shoes  34 , i.e. a diameter of the space  38  between the pole shoes  34 . After assembly of the magnetic core  20  and the rotor housing  18 , substantially no gap exists between the pole arc surfaces  36  of the pole shoes  34  and the outer wall surface  46  of the sleeve  18  except for the areas of the startup grooves  44 . A step  48  projects radially outwardly from the outer wall surface  46  of the sleeve  18  at the opening end thereof, i.e. one end of the sleeve  18  adjacent the impeller  12 . The step  48  has an outer diameter greater than the remaining part of the outer wall surface  46  of the sleeve  18 , i.e. greater than the diameter of the pole arc surfaces  36 . In assembly, the closed end of the sleeve  18  is inserted into the space  38  between the two pole shoes  34  of the magnetic core  20  and is moved axially relative to the magnetic core  20  until an axial end surface  50  of the step  48  of the sleeve  18  contacts the magnetic core  20  to be axially positioned. 
         [0039]    For facilitating the assembly of the magnetic core  20  and the rotor housing  18 , the outer wall surface  46  of the sleeve  18  is formed with a rib  52 . The rib  52  is positioned in correspondence with the slot  42  between the pole shoes  34  of the magnetic core  20 . The rib  52  has a width substantially equal to or slightly less than the width of the slot  42 . In assembly, the rib  52  is aligned with the slot  42  of the magnetic core  20  in the axial direction and inserted into the slot  42  to guide the axial movement of the rotor housing  18  relative to the magnetic core  20 . As such, the rotor housing  18  and the stator  14  can be quickly assembled, and the coaxiality of the stator  14  and the rotor  16  can be ensured. Preferably, the rib  52  extends axially from the closed end of the sleeve  18  and reaches at least the axial end surface  50  of the step  48 . In this embodiment, the rib  52  extends to reach the open end of the sleeve  18 , with the rib  52  crossing the step  48 . The step  48  forms recesses  54  at two circumferential sides of the rib  52  for receiving debris formed during assembly of the rotor housing  18  and the magnetic core  20 . In this configuration, the axial end surface  50  of the step  48  breaks apart in the circumferential direction. 
         [0040]    Preferably, a radial depth of the recess  54  into the step  48  is not less than the radial thickness of the step  48  projecting outwardly. That is, a radial bottom of the recess  54  at least not projects relative to the outer wall surface  46  of the sleeve  18 . In this embodiment, the bottom of the recess  54  is coplanar with the outer wall surface  46  of the sleeve  18 . The slot  42  of the pole tips  40  of the pole shoes  34  is narrow, and the internal angle of the distal end of the pole tip  40  is a sharp corner. Therefore, in assembly of the magnetic core  20  and the rotor housing  18 , scratching can easily occur, which fowls debris. In this embodiment, even if the magnetic core  20  scratches the outer wall surface  46  of the sleeve  18 , because the axial end surface  50  breaks apart at opposite sides of the rib  52 , the debris can slide into the recesses  54  of the step  48  formed at the opposite sides of the rib  52 , without being clamped between the step  48  and the pole shoes  34  of the magnetic core  20 . As such, this ensures the symmetry of the magnetic core  20 , which makes the magnetic core  20  keep coaxial with the rotor  16  and achieves smooth operation of the rotor  16 , thus reducing noise as much as possible. 
         [0041]      FIG. 8  illustrates the rotor housing  18  of the motor  10  of the pump according to another embodiment. This embodiment differs from the above embodiment in that, in this embodiment, the outer diameter of the outer wall surface  46  of the sleeve  18  is slightly less than the diameter of the pole arc surfaces  36  of the pole shoes  34 . Multiple ribs  52  are formed on the outer wall surface  46  of the sleeve  18 , for guiding the rotor housing  18  in assembly with the magnetic core  20 . The ribs  52  are evenly spaced along the circumferential direction. Each rib  52  extends axially to the end surface  50  of the step  48 . Referring to  FIG. 9 , in assembly, the sleeve  18  is inserted into the space  38  between the pole shoes  34  and is moved axially. Because the outer diameter of the sleeve  18  is slightly smaller, a small radial gap is formed between the pole arc surfaces  36  of the pole shoes  34  and the outer wall surface  46  of the sleeve  18 , and the outer wall surface  46  of the sleeve  18  does not contact the pole shoes  34 . The ribs  52  on the outer wall surface  46  of the sleeve  18  contact the pole arc surfaces  36  of the pole shoes  34 . However, when compared against the outer wall surface of the sleeve  18 , the contact area between the ribs  52  and the pole arc surfaces  36  is almost negligible and, therefore, the scratches caused by the ribs  52  are so limited that nearly no debris is produced. In addition, the gap is formed between the pole arc surfaces  36  of the pole shoes and the outer wall surface  46  of the sleeve  18 , which can receive the debris. Likewise, this prevents the debris from being clamped between the step  48  and the pole shoes  34  and hence ensures the symmetry of the magnetic core  20 , which makes the magnetic core  20  keep coaxial with the rotor  16  after assembled, achieves smooth operation of the rotor  16 , and reduces noise. 
         [0042]    Although the present disclosure is described with reference to one or more preferred embodiments, it should be appreciated by those skilled in the art that various modifications are possible. Therefore, the scope of the present disclosure is to be determined by reference to the claims that follow.