Abstract:
An electric pump includes a rotor including a magnet portion formed of a ring shaped structure and having a polar anisotropic ring magnet, and an impeller portion pressure-supplying a fluid and formed integrally with the magnet portion, and a stator rotating the rotor.

Description:
[0001]     This application is based on and claims priority under 35 U.S.C. § 119 to Japanese Patent Application 2005-214859, filed on Jul. 25, 2005, the entire content of which is incorporated herein by reference.  
       FIELD OF THE INVENTION  
       [0002]     This invention relates to an electric pump. More particularly, the present invention pertains to an electric pump, which can improve performance and productivity thereof.  
       BACKGROUND  
       [0003]     A known electric pump is disclosed in JP2004-308562A. According to the disclosed electric pump, a stator, which is made by winding a coil around a core, is provided in a casing, a shaft is placed in a center of the stator, a rotor is rotatably located at an outer circumference of the stator around the shaft, an impeller is integrally rotatable with the rotor, fluid, which is fed into a pump chamber through an intake hole in accordance with a rotation of the impeller, is exhausted to an outside from an exhaust hole, the shaft is penetrating through the stator and is fixed to the stator, the rotor is rotatably supported by an end portion of the shaft, a base portion of the shaft is supported by a lower plate, and the stator is formed with a casing into a single member by means of resin molding. The whole rotor is made of a plastic magnet and the rotor and the impeller are formed into a single member.  
         [0004]     Further, an electric pump, which is provided with a motor portion and a pumping portion is also known. The motor portion includes a rotor, to which a yoke and a magnet are fixed, and a stator, which is provided at an outer circumference of the rotor and is wound by winding wires. The pumping portion includes an impeller connected to the rotor.  
         [0005]     However, according to the electric pump disclosed in JP2004-308562A, the rotor and the impeller are formed into a single member and the impeller is also made of the plastic magnet. Thus, the impeller portion, which basically does not require a magnet, includes a magnetic particle. Therefore, the whole weight of the electric pump may be increased. Further, because the impeller portion includes magnetic force, magnetic foreign substances in working fluid may be magnetically attracted to the impeller and pumping efficiency may occasionally be lowered.  
         [0006]     Further, with the configuration of the later described electric pump, if an attempt for reducing a material cost is made, there is a danger of lowering the magnetic force and an output of the pump. Moreover, according to the later described electric pump, the magnet, the yoke, and the impeller are assembled to the rotor. With such configuration, a cost for assembling may be increased.  
         [0007]     A need thus exists for an electric pump, which can improve performance and productivity thereof.  
       SUMMARY OF THE INVENTION  
       [0008]     According to an aspect of the present invention, An electric pump includes a rotor including a magnet portion formed of a ring shaped structure and having a polar anisotropic ring magnet, and an impeller portion pressure-supplying a fluid and formed integrally with the magnet portion, and a stator rotating the rotor.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The foregoing and additional features and characteristics of the present invention will become more apparent from the following detailed description considered with reference to the accompanying drawings, wherein:  
         [0010]      FIG. 1  is a sectional view schematically illustrating a structure of an electric pump according to an embodiment of the present invention;  
         [0011]      FIG. 2  is a sectional view schematically illustrating a structure of a rotor of the electric pump according to the embodiment of the present invention; and  
         [0012]      FIG. 3  is a schematic view for explaining magnetic field flux flow of the rotor&#39;s magnet portion of an electric pump according to the embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0013]     An embodiment of the present invention will be explained hereinbelow with reference to the attached drawings.  
         [0014]     As illustrated in  FIG. 1 , an electric pump  1 , which is electrically activated and pumps fluid, includes a shaft  10 , a rotor  11 , a stator  12 , a dividing wall  13 , winding wires  14 , a pump housing  15 , and a motor housing  16 .  
         [0015]     The shaft  10  is fitted together with a central axis of the rotor  11  by insertion. A first end of the shaft  10  is rotatably supported by the pump housing  15  and a second end of the shaft  10  is rotatably supported by the motor housing  16 .  
         [0016]     As illustrated in  FIG. 2 , the rotor  11  includes a magnet portion  11   a , an impeller portion  11   b , and a connecting portion  11   c . The connecting portion  11   c  is formed into a substantial tubular shape which includes a hollow portion  11   d . The shaft  10  is inserted through the hollow portion  11   d  of the connecting portion  11   c  and the rotor  11  is fixed to the shaft  10 . The magnet portion  11   a  is formed at a first end of the connecting portion  11   c  in an axial direction and the impeller portion  11   b  is formed at a second end of the connecting portion  11   c  in the axial direction. The magnet portion  11   a  is formed in the vicinity of an inner circumference of the stator  12  and is rotatably housed in the motor housing  16 . The magnet portion  11   a  is formed into a substantial annular shape (cylinder) and is made of a polar anisotropic ring magnet (i.e., a Multi-Pole Ring). For example, a polar anisotropic rare-earth bonded magnet is applicable for the magnet portion  11   a . The rare-earth bonded magnet is made of high heat-resistant and low water absorption synthetic resin (binder) such as Polyphenylene Sulfide (PPS), unsaturated polyester, or the like, which includes, therein, a rare-earth magnet (magnetic particle) such as Neodymium Magnet (Nd—Fe—B), or the like. Alternatively, or in addition, any material, magnetic field flux of which is oriented as shown in  FIG. 3  (polar anisotropic material), is applicable for the magnet portion  11   a . The rotor  11  is integrally rotated with the shaft  10  and includes the impeller portion  11   b , which propels the fluid. The impeller portion  11   b  is rotatably housed inside of the pump housing  15 . Parts of the rotor  11  except for the magnet portion  11   a , in other words, the impeller portion  11   b  and the connecting portion  11   c , do not include the magnetic particle, and the high heat-resistant and low water absorption synthetic resin used for the resin (binder) of the magnet portion  11   a  such as the Polyphenylene Sulfide (PPS), the unsaturated polyester, or the like, is applicable for the impeller portion  11   b  and the connecting portion  11   c . The rotor  11  can be formed by means of two-color injection molding. More particularly, the magnet portion  11   a  of the rotor  11  is formed by means of injection molding in a permanent magnet embedded die so as to form a polar anisotropic magnetic field, and then, the impeller portion  11   b  and the connecting portion  11   c  are formed by means of the injection molding. According to the embodiment of the present invention, the impeller portion  11   b  and the connecting portion  11   c  are made of resin identical to the resin used as the binder of the magnet portion  11   a . Therefore, compatibility of the magnet portion  11   a  and the impeller portion  11   b  and the connecting portion  11   c  can be well remained, and fixation thereof can be improved by means of the two-color injection molding.  
         [0017]     The stator  12  is provided at an outer circumference of the rotor  11  and includes protruded portions in a radiating direction. Further, the stator  12  is made of corrosion-resistant material and rotationally activates the rotor  11  by means of a rotational magnetic field generated at the stator  12 . The stator  12  is formed by laminated substantial star shaped hollow thin plates, which are made by connected substantial T-shaped members in a circle. Stainless steel plate such as SUS430-CP, or the like, is applicable for material of the stator  12 .  
         [0018]     The dividing wall  13  is arranged along an outer circumference of the stator  12  and houses the stator  12  therein. The dividing wall  13  includes nonmagnetic material made of resin, or the like. An outer circumference of the dividing wall  13  is wound by the winding wires  14  in such a manner that the winding wires  14  wind around the protruded portions of the stator  12 .  
         [0019]     The winding wires  14  wind around an external side of the dividing wall  13 .  
         [0020]     A manufacturing method for the electric pump according to the embodiment of the present invention will be explained hereinafter.  
         [0021]     First, the dividing wall  13  is arranged around the stator  12  and is integrally formed with the stator  12  by means of resin molding. Then, the dividing wall  13  is wound by the winding wires  14  from the external side thereof. Thereafter, the stator  12 , the dividing wall  13 , and the winding wires  14  are formed into a single member by means of the resin molding so as to form the motor housing  16 .  
         [0022]     After the rotor  11  is inserted into the motor housing  16 , the motor housing  16  is fixed to the pump housing  15 .  
         [0023]     According to the embodiment of the present invention, when the winding wires  14  are applied with electricity, the magnetic field is generated from the substantial T-shaped member of the stator  12  through the rotor  11 . The rotor  11  is rotated by switching current of each winding wire corresponding to each substantial T-shaped member of the stator  12 .  
         [0024]     According to the embodiment of the present invention, the polar anisotropic ring magnet is used for the magnet portion  11   a  of the rotor  11 . Therefore, fixation of a yoke with the magnet is not required and productivity thereof can thereby be improved. Further, because the rotor  11  can be formed by means of the two-color injection (integral) molding, in other words, the magnet portion  11   a  of the rotor  11  and the other parts of the rotor  11 , except for the magnet portion  11   a , can be formed by means of the two-color injection (integral) molding, productivity thereof can be improved. According to the embodiment of the present invention, because the polar anisotropic ring magnet is used for the magnet portion  11   a  of the rotor  11 , a magnetic pass in the magnet becomes longer therefore leading to a higher coercive force. Therefore, the electric pump according to the embodiment of the present invention is applicable for a long-term use. According to the embodiment of the present invention, the rare-earth magnet, which is superior in magnetic force, is used for the magnet portion  11   a  of the rotor  11 . Therefore, reduction in size and weight of the electric pump and promotion of pumping efficiency can be achieved. Further, because the impeller portion  11   b  of the rotor  11  does not include magnetic particle, waste of magnetic particle material can be prevented and magnetic attraction of foreign substances can be prevented.  
         [0025]     According to the embodiment of the present invention, the electric pump includes the rotor, which includes the magnet portion and the impeller portion, and the stator, which rotary activates the rotor. The magnet portion is made of the polar anisotropic ring magnet, and is formed into the substantial annular shape. The impeller portion pumps the fluid. The magnet portion and the impeller portion are formed into a single member so as to form the rotor.  
         [0026]     The present invention is applicable when the magnet portion of the rotor is made of the resin which includes the magnetic particle therein, and the other parts of the rotor, except for the magnet portion, is made of the resin identical to the resin used for the magnet portion.  
         [0027]     The present invention is applicable when the resin includes the Polyphenylene Sulfide and the magnetic particle includes the rare-earth magnet.  
         [0028]     The present invention is applicable when the rotor is formed by means of the two-color injection molding. More particularly, the magnet portion of the rotor is formed by means of the injection molding in the permanent magnet embedded die so as to form the polar anisotropic magnetic field, and then, the other parts of the rotor except for the magnet portion is formed by means of the injection molding.  
         [0029]     According to the embodiment of the present invention, the polar anisotropic ring magnet is used for the magnet portion of the rotor. Therefore, the fixation of the yoke and the magnet is not required and productivity thereof can thereby be improved. Further, because the rotor is formed by means of the two-color injection (integral) molding, in other words, the magnet portion of the rotor and the other parts of the rotor, except for the magnet portion, is formed by means of the two-color (integral) molding, productivity thereof can be improved. According to the embodiment of the present invention, because the polar anisotropic ring magnet is used for the magnet portion of the rotor, the magnetic pass in the magnet becomes longer and coercive force becomes higher. Therefore, the electric pump according to the embodiment of the present invention is applicable for a long-term use, especially under a high-temperature environment. According to the embodiment of the present invention, the rare-earth magnet, which is superior in magnetic force, is used for the magnet portion of the rotor. Therefore, reduction in size and weight of the electric pump and promotion of pumping efficiency can be achieved. Further, because the impeller portion of the rotor does not include the magnetic particle, waste of magnetic particle material can be prevented and magnetic attraction of the foreign substance can be prevented. Moreover, because the magnet portion of the rotor is made of mixed material of the resin and the magnetic particle and the other parts of the rotor, except for the magnet portion, is made of the resin identical to the resin used for the magnet portion, compatibility of the magnet portion of the rotor and the other parts of the rotor except for the magnet portion can be well remained and fixation thereof can be improved.  
         [0030]     The principles, preferred embodiments and mode of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents which fall within the spirit and scope of the present invention as defined in the claims, be embraced thereby.