Dynamic pressure bearing pump

Abstract

A pump a shaft portion arranged to extend in a vertical direction; a rotor portion arranged to surround an outer circumference of the shaft portion, and including a magnet; and a housing joined to the shaft portion, and arranged to contain the rotor portion. The housing includes a stator arranged opposite to the magnet; a rotor accommodating portion arranged to accommodate the rotor portion; and an inlet and an outlet each of which is arranged to pass through a portion of the rotor accommodating portion. A surface of at least one of the rotor portion, the shaft portion, and the rotor accommodating portion includes at least one first dynamic pressure groove arranged to support rotation of the rotor portion. A surface of at least one of the rotor portion and the rotor accommodating portion includes at least one second dynamic pressure groove arranged to transfer a fluid from the inlet to the outlet. The rotor portion includes a through hole arranged to pass therethrough in an axial direction.

What is claimed is: 
     
         1 . A dynamic pressure bearing pump comprising:
 a shaft portion arranged to extend in a vertical direction;   a rotor portion arranged to surround an outer circumference of the shaft portion, and including a magnet; and   a housing joined to the shaft portion, and arranged to contain the rotor portion; wherein   the housing includes:
 a stator arranged opposite to the magnet; 
 a rotor accommodating portion arranged to accommodate the rotor portion; and 
 an inlet and an outlet each of which is arranged to pass through a portion of the rotor accommodating portion; 
   a surface of at least one of the rotor portion, the shaft portion, and the rotor accommodating portion includes at least one first dynamic pressure groove arranged to support rotation of the rotor portion;   a surface of at least one of the rotor portion and the rotor accommodating portion includes at least one second dynamic pressure groove arranged to transfer a fluid from the inlet to the outlet; and   the rotor portion includes a through hole arranged to pass therethrough in an axial direction.   
     
     
         2 . The dynamic pressure bearing pump according to  claim 1 , wherein
 the rotor portion is arranged to have the shaft portion as a central axis thereof, is substantially cylindrical, and is arranged to have the shaft portion inserted therethrough in the axial direction; and   at least one of a shaft outer circumferential surface of the shaft portion and a rotor inner circumferential surface of the rotor portion includes a radial dynamic pressure groove being one of the at least one first dynamic pressure groove.   
     
     
         3 . The dynamic pressure bearing pump according to  claim 1 , wherein
 the rotor portion is arranged to have the shaft portion as a central axis thereof, and includes a rotor upper surface and a rotor lower surface each of which is perpendicular or substantially perpendicular to the shaft portion;   at least one of the rotor upper surface, the rotor lower surface, and an inner surface of the rotor accommodating portion includes a thrust dynamic pressure groove being one of the at least one first dynamic pressure groove; and   the through hole is arranged to have an opening in at least one of the rotor upper surface and the rotor lower surface.   
     
     
         4 . The dynamic pressure bearing pump according to  claim 1 , wherein the at least one second dynamic pressure groove includes a plurality of spiral grooves or a plurality of herringbone grooves. 
     
     
         5 . The dynamic pressure bearing pump according to  claim 1 , wherein
 the rotor portion is arranged to have the shaft portion as a central axis thereof, is substantially cylindrical, and is arranged to have the shaft portion inserted therethrough in the axial direction;   the rotor portion includes:
 a rotor inner circumferential surface arranged opposite to a shaft outer circumferential surface of the shaft portion; 
 a rotor outer circumferential surface arranged opposite to a housing inner circumferential surface of the rotor accommodating portion; and 
 a rotor upper surface and a rotor lower surface each of which is perpendicular or substantially perpendicular to the shaft portion; 
   the through hole is arranged to have an opening in at least one of the rotor upper surface and the rotor lower surface;   at least one of the shaft outer circumferential surface and the rotor inner circumferential surface includes at least one radial dynamic pressure groove defined therein;   at least one of an inner surface of the rotor accommodating portion, the rotor upper surface, and the rotor lower surface includes at least one thrust dynamic pressure groove defined therein; and   the at least one second dynamic pressure groove is defined in at least one of the housing inner circumferential surface and the rotor outer circumferential surface.   
     
     
         6 . The dynamic pressure bearing pump according to  claim 5 , wherein the at least one thrust dynamic pressure groove is a plurality of spiral grooves arranged to transfer the fluid in a direction of the rotor inner circumferential surface. 
     
     
         7 . The dynamic pressure bearing pump according to  claim 5 , wherein
 the at least one radial dynamic pressure groove is a plurality of herringbone grooves; and   a gap between the shaft outer circumferential surface and the rotor inner circumferential surface is arranged to have a width smaller than a width of a gap between the housing inner circumferential surface and the rotor outer circumferential surface.   
     
     
         8 . The dynamic pressure bearing pump according to  claim 5 , wherein the magnet and the at least one second dynamic pressure groove are arranged radially opposite to each other with respect to the central axis. 
     
     
         9 . The dynamic pressure bearing pump according to  claim 5 , wherein the magnet and the at least one second dynamic pressure groove are arranged one above the other in the axial direction. 
     
     
         10 . The dynamic pressure bearing pump according to  claim 5 , wherein
 the at least one second dynamic pressure groove is a plurality of spiral grooves; and   the plurality of spiral grooves are arranged in such an orientation that rotation of the rotor portion transfers the fluid from the inlet to the outlet.   
     
     
         11 . The dynamic pressure bearing pump according to  claim 10 , wherein
 the outlet and the inlet are arranged to open toward the rotor upper surface and the rotor lower surface, respectively; and   the through hole is arranged to have openings on a side of openings of the outlet and the inlet, respectively, closer to the central axis.   
     
     
         12 . The dynamic pressure bearing pump according to  claim 5 , wherein
 the at least one second dynamic pressure groove is a plurality of herringbone grooves arranged in a circumferential direction; and   each herringbone groove includes two spiral grooves arranged to obliquely extend in different directions, and a bend portion arranged between the two spiral grooves.   
     
     
         13 . The dynamic pressure bearing pump according to  claim 12 , wherein each of the outlet and the inlet is arranged to open toward the rotor outer circumferential surface. 
     
     
         14 . The dynamic pressure bearing pump according to  claim 13 , wherein
 the at least one second dynamic pressure groove includes only one array of herringbone grooves arranged in the circumferential direction; and   an axial position of the bend portion of each herringbone groove is arranged to overlap with an axial position of an opening of one of the outlet and the inlet.   
     
     
         15 . The dynamic pressure bearing pump according to  claim 13 , wherein
 the at least one second dynamic pressure groove includes two arrays of herringbone grooves arranged in the circumferential direction;   an axial position of the bend portion of each herringbone groove of one of the arrays is arranged to overlap with an axial position of an opening of the outlet;   an axial position of the bend portion of each herringbone groove of another one of the arrays is arranged to overlap with an axial position of an opening of the inlet; and   the bend portion of each herringbone groove of the one array and the bend portion of each herringbone groove of the other array are oriented in opposite directions along a rotation direction of the rotor portion.   
     
     
         16 . The dynamic pressure bearing pump according to  claim 1 , wherein
 the rotor portion is arranged to have the shaft portion as a central axis thereof, is substantially cylindrical, and is arranged to have the shaft portion inserted therethrough in the axial direction;   the rotor portion includes:
 a rotor inner circumferential surface arranged opposite to a shaft outer circumferential surface of the shaft portion; 
 a rotor outer circumferential surface arranged opposite to a housing inner circumferential surface of the rotor accommodating portion; and 
 a rotor upper surface and a rotor lower surface each of which is perpendicular or substantially perpendicular to the shaft portion; 
   each of the shaft outer circumferential surface and the rotor inner circumferential surface includes an inclined surface arranged to increase in diameter with decreasing distance from the rotor upper surface or the rotor lower surface;   the at least one first dynamic pressure groove is defined in at least one of the inclined surface of the shaft outer circumferential surface and the inclined surface of the rotor inner circumferential surface;   the at least one second dynamic pressure groove is defined in at least one of the housing inner circumferential surface and the rotor outer circumferential surface; and   the through hole is arranged to have an opening in at least one of the rotor upper surface and the rotor lower surface.   
     
     
         17 . The dynamic pressure bearing pump according to  claim 16 , wherein
 the at least one second dynamic pressure groove is a plurality of spiral grooves; and   the plurality of spiral grooves are arranged in such an orientation that rotation of the rotor portion transfers the fluid from the inlet to the outlet.   
     
     
         18 . The dynamic pressure bearing pump according to  claim 17 , wherein
 the outlet and the inlet are arranged to open toward the rotor upper surface and the rotor lower surface, respectively; and   the through hole is arranged to have openings on a side of openings of the outlet and the inlet, respectively, closer to the central axis.   
     
     
         19 . The dynamic pressure bearing pump according to  claim 16 , wherein
 the at least one second dynamic pressure groove is a plurality of herringbone grooves arranged in a circumferential direction; and   each herringbone groove includes two spiral grooves arranged to obliquely extend in different directions, and a bend portion arranged between the two spiral grooves.   
     
     
         20 . The dynamic pressure bearing pump according to  claim 19 , wherein each of the outlet and the inlet is arranged to open toward the rotor outer circumferential surface. 
     
     
         21 . The dynamic pressure bearing pump according to  claim 20 , wherein
 the at least one second dynamic pressure groove includes only one array of herringbone grooves arranged in the circumferential direction; and   an axial position of the bend portion of each herringbone groove is arranged to overlap with an axial position of an opening of one of the outlet and the inlet.   
     
     
         22 . The dynamic pressure bearing pump according to  claim 20 , wherein
 the at least one second dynamic pressure groove includes two arrays of herringbone grooves arranged in the circumferential direction;   an axial position of the bend portion of each herringbone groove of one of the arrays is arranged to overlap with an axial position of an opening of the outlet;   an axial position of the bend portion of each herringbone groove of another one of the arrays is arranged to overlap with an axial position of an opening of the inlet; and   the bend portion of each herringbone groove of the one array and the bend portion of each herringbone groove of the other array are oriented in opposite directions along a rotation direction of the rotor portion.   
     
     
         23 . The dynamic pressure bearing pump according to  claim 1 , wherein an in-pipe pressure on the fluid flowing in the outlet is smaller than a maximum transfer pressure on the fluid generated by the at least one second dynamic pressure groove. 
     
     
         24 . The dynamic pressure bearing pump according to  claim 23 , wherein
 each of the at least one first dynamic pressure groove is arranged to have a groove depth equivalent to or smaller than a groove depth of each of the at least one second dynamic pressure groove; and   the at least one first dynamic pressure groove is arranged to have a hill width equivalent to or smaller than a hill width of the at least one second dynamic pressure groove.