US20050201864A1 - Centrifugal fan - Google Patents

Centrifugal fan Download PDF

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Publication number
US20050201864A1
US20050201864A1 US10/906,895 US90689505A US2005201864A1 US 20050201864 A1 US20050201864 A1 US 20050201864A1 US 90689505 A US90689505 A US 90689505A US 2005201864 A1 US2005201864 A1 US 2005201864A1
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US
United States
Prior art keywords
sleeve
centrifugal fan
impeller
shaft
fan according
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US10/906,895
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English (en)
Inventor
Yusuke Yoshida
Yoshiaki Oguma
Hideaki Konishi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nidec Corp
Original Assignee
Nidec Corp
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Filing date
Publication date
Application filed by Nidec Corp filed Critical Nidec Corp
Assigned to NIDEC CORPORATION reassignment NIDEC CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: KONISHI, HIDEAKI, OGUMA, YOSHIAKI, YOSHIDA, YUSUKE
Publication of US20050201864A1 publication Critical patent/US20050201864A1/en
Abandoned legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/05—Shafts or bearings, or assemblies thereof, specially adapted for elastic fluid pumps
    • F04D29/056—Bearings
    • F04D29/057—Bearings hydrostatic; hydrodynamic
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D25/00—Pumping installations or systems
    • F04D25/02—Units comprising pumps and their driving means
    • F04D25/06—Units comprising pumps and their driving means the pump being electrically driven
    • F04D25/0606—Units comprising pumps and their driving means the pump being electrically driven the electric motor being specially adapted for integration in the pump
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D25/00—Pumping installations or systems
    • F04D25/02—Units comprising pumps and their driving means
    • F04D25/08—Units comprising pumps and their driving means the working fluid being air, e.g. for ventilation
    • F04D25/082—Units comprising pumps and their driving means the working fluid being air, e.g. for ventilation the unit having provision for cooling the motor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/26—Rotors specially for elastic fluids
    • F04D29/28—Rotors specially for elastic fluids for centrifugal or helico-centrifugal pumps for radial-flow or helico-centrifugal pumps
    • F04D29/281—Rotors specially for elastic fluids for centrifugal or helico-centrifugal pumps for radial-flow or helico-centrifugal pumps for fans or blowers
    • F04D29/282—Rotors specially for elastic fluids for centrifugal or helico-centrifugal pumps for radial-flow or helico-centrifugal pumps for fans or blowers the leading edge of each vane being substantially parallel to the rotation axis
    • F04D29/283—Rotors specially for elastic fluids for centrifugal or helico-centrifugal pumps for radial-flow or helico-centrifugal pumps for fans or blowers the leading edge of each vane being substantially parallel to the rotation axis rotors of the squirrel-cage type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/58—Cooling; Heating; Diminishing heat transfer
    • F04D29/5806—Cooling the drive system
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
    • F16C33/02—Parts of sliding-contact bearings
    • F16C33/04—Brasses; Bushes; Linings
    • F16C33/043—Sliding surface consisting mainly of ceramics, cermets or hard carbon, e.g. diamond like carbon [DLC]
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F1/00—Details not covered by groups G06F3/00 - G06F13/00 and G06F21/00
    • G06F1/16—Constructional details or arrangements
    • G06F1/20—Cooling means
    • G06F1/203—Cooling means for portable computers, e.g. for laptops

Definitions

  • the present invention relates to a centrifugal fan for cooling embedded in electronic equipment.
  • cooling fans embedded in electronic equipment such as a personal computer have become smaller and thinner.
  • most electronic equipment incorporates a cooling fan of an axial flow type. It is because the axial flow type cooling fan typically has a structure suitable for a thin shape or a low profile.
  • centrifugal fans have an advantage of having higher static pressure than axial fans, they also have a disadvantage of difficulty in reducing a dimension in the axial direction for a low profile compared with axial fans.
  • FIG. 6 is a cross sectional view in the axial direction showing a structure of a long thin centrifugal fan.
  • FIG. 7 is a cross sectional view in the direction perpendicular to the rotational axis of an impeller in a typical centrifugal fan.
  • the long thin centrifugal fan shown in FIG. 6 includes a housing 101 having a substantially cylindrical shape elongated in the axial direction, which houses an impeller 102 and a motor 103 for rotating the impeller 102 .
  • the impeller 102 is disposed at the top side (the right side in FIG. 6 ), in the axial direction within the housing 101
  • the motor 103 is disposed at the bottom side (the left side in FIG. 6 ) in the axial direction within the housing 101 .
  • the impeller 102 includes a blade portion 104 (at the top side) having plural blades 104 a of a shape elongated in the axial direction that are arranged at a predetermined pitch in the circumferential direction and a bottom end portion 105 having a substantially cylindrical shape for supporting the blade portion 104 .
  • the tip of the blade portion 104 is provided with a ring-like linking portion 106 for linking and supporting tip portions of the plural blades 104 a .
  • the motor 103 includes a rotor yoke 111 and a rotor magnet 112 that corresponds a rotational member rotating with the impeller 102 , a stator armature 113 and a fixed shaft 114 on a stational side, a pair of ball bearings 115 , and a base member 116 for fixing the fixed shaft 114 to the housing 101 .
  • the bottom end portion 105 of the impeller 102 is engaged with and fixed to the outer surface of the rotor yoke 111 that is a cylindrical magnetic member.
  • a plurality of rotor magnets 112 is arranged in the circumferential direction at a predetermined pitch on the inner surface of the rotor yoke 111 at the middle portion in the axial direction, and a pair of outer ring portions of the ball bearings 115 is disposed separately in the axial direction at both sides of the rotor magnets 112 .
  • the stator armature 113 is fixed substantially at the middle portion in the axial direction of the fixed shaft 114 so as to be opposed to the rotor magnets 112 with a constant gap.
  • a pair of inner ring portions of the ball bearings 115 is fixed to the fixed shaft 114 separately in the axial direction at both sides of the stator armature 113 .
  • the bottom side of the fixed shaft 114 is engaged with and fixed to a center hole of the base member 116 so that an axis of the fixed shaft 114 agrees the rotation axis of the rotor yoke 111 .
  • the rotor magnet 112 , the rotor yoke 111 and the impeller 102 are rotated as one unit body responding to the revolving magnetic field. Then, as described above, the rotation of the impeller 102 causes air flow that is taken in through the suction opening 107 at the tip portion in the axial direction of the housing 101 and is blown out through an outlet opening formed at a part in the circumferential direction of the housing 101 .
  • the long thin centrifugal fan having the above-mentioned structure is required to have a large length of the impeller in the axial direction and to be rotated at a high rotation speed in order to compensate low capacity of air blowing due to a small diameter of the impeller.
  • the diameter of the impeller is small, noise (wind noise) due to the rotation of the impeller is not so large despite of the high rotation speed. Indeed, its noise is smaller than an ordinary centrifugal fan.
  • a centrifugal fan includes an impeller including a blade portion having plural elongated blades arranged at a predetermined pitch in the circumferential direction and a motor for rotating the impeller.
  • the impeller and the motor are arranged tandem in the axial direction.
  • a bearing portion that constitutes the motor is a slide bearing including a shaft member and a sleeve having a cylindrical shape that engages the shaft with a clearance.
  • One of the shaft member and the sleeve is made of a ceramic, and the other is made of a ceramic or a metal.
  • a slide bearing also referred to as a sleeve bearing
  • noise due to rotation can be reduced compared with the conventional ball bearing.
  • at least one of the shaft member and the sleeve that constitute the slide bearing is made of a ceramic, a good durability can be obtained. Note that it is preferable that both of them are made of a ceramic for a long life because seizing up occurs hardly between them. If one of them is made of a ceramic and the other is made of a metal, the sliding surface of the metal is preferably hardened by a surface treatment or coating so that a long life is obtained.
  • a reduced diameter portion is formed on the shaft member at a middle portion in the axial direction of the sliding portion with the sleeve, the reduced diameter portion having a diameter a little smaller than other portions.
  • an area of the sliding surface is reduced so that a bearing loss due to sliding friction can be reduced.
  • means for keeping lubricating oil that is supplied to the sliding surfaces of the shaft member and the sleeve are attached to the shaft member or the sleeve.
  • a felt member having a ring-like shape impregnated with lubricating oil can be attached to the shaft member or the sleeve as the means for keeping lubricating oil.
  • the shaft member is fixed to a rotational member, and the sleeve that retains the shaft member in a rotatable manner is fixed to the housing directly or via a base member.
  • This structure is a so-called rotational shaft (or fixed sleeve) structure, and the number of components can be reduced by fixing the sleeve to a base member (that is fixed to the housing) directly.
  • the sleeve holder is attached to the housing directly, the number of components can be reduced further.
  • a sleeve made of a ceramic is fixed to the rotational member, and a shaft member is fixed to the housing directly or via a base member.
  • This structure is a so-called rotational sleeve (or fixed shaft) structure, and the number of components can be reduced by fixing the shaft member to a base member (that is fixed to the housing) directly. In addition, the number of components can be further reduced by attaching the shaft member to the housing directly.
  • the top side of the shaft member is disposed within the inner space of the blade portion of the impeller.
  • a dimension in the axial direction of the entire centrifugal fan can be reduced.
  • the bottom side of the shaft member is a free end without a thrust bearing.
  • a member (thrust plate, for example) for a thrust bearing can be eliminated, and generation of noise due to friction at the thrust bearing portion as well as wear of the tip portion of the shaft member on the bottom side can be avoided. Note that it is possible to support the bottom side of the shaft member by using air dumping or oil dumping.
  • a torque generating portion including an armature and a field magnet, and a bearing portion are arranged tandem in the axial direction.
  • a dimension in the radial direction of the centrifugal fan can be reduced. Namely, if the torque generating portion and the bearing portion are arranged substantially at the same position in the axial direction in a coaxial manner, an outer diameter of the motor depends on a total sum of the outer diameter of the bearing portion and a size (thickness) of the torque generating portion in the radial direction.
  • the outer diameter of the motor depends on either the outer diameter of the bearing portion or the size (outer diameter) of the torque generating portion that is larger one than the other. Therefore, it is possible to reduce the outer diameter of the motor, thereby reducing further the dimension in the radial direction of the centrifugal fan.
  • a combination of this structure and the sleeve bearing utilizing a ceramic member as described above can reduce the number of components so that the dimension in the radial direction can be further reduced.
  • the rotational member rotates integrally as one element
  • the bearing portion is disposed at a barycenter of the element or at vicinity of the barycenter.
  • This structure facilitates stabilization of rotation of the impeller. Namely, vibration of the impeller accompanying rotation thereof can be reduced, and a load to the bearing portion can be suppressed so that a life of the bearing portion can be increased.
  • This structure is useful particularly in the case where the impeller is rotated at a high rotation speed.
  • the structure that the bearing portion is disposed at a barycenter of the element or at vicinity of the barycenter means a structure that an intermediate point in the axial direction of the slide bearing (sleeve bearing) is disposed at a barycenter or at vicinity of the barycenter.
  • a centrifugal fan includes an impeller including a blade portion having plural blades arranged at a predetermined pitch in the circumferential direction and a motor for rotating the impeller.
  • the impeller is rotated at a rotation speed more than or equal to 15,000 revolutions per minute
  • a bearing portion that constitutes the motor is a slide bearing including a shaft member and a sleeve having a cylindrical shape that engages the shaft member with a clearance, one of the shaft member and the sleeve is made of a ceramic, and the other is made of a ceramic or a metal.
  • a slide bearing also referred to as a sleeve bearing
  • noise due to rotation can be reduced compared with the conventional ball bearing even at high speed rotation.
  • at least one of the shaft member and the sleeve that constitute the slide bearing is made of a ceramic, a good durability can be obtained even the high speed rotation is maintained.
  • a small centrifugal fan can be rotated silently and at high speed. Therefore, a centrifugal fan can be downsized while increasing quantity of airflow and static pressure thereof. Note that it is preferable that both of them are made of a ceramic for a long life because seizing up occurs hardly between them.
  • the sliding surface of the metal is preferably hardened by a surface treatment or coating so that a long life is obtained.
  • liquid lubricant can be eliminated, thereby a seal mechanism for the liquid lubricant can be eliminated so that the structure can be simplified.
  • the sleeve and the shaft member are both made of the same type of ceramic.
  • a ceramic is an insulator, generation of static electricity due to electrification of the surface can be prevented by using the same type of ceramic for the sliding surfaces. If static electricity is generated, the bearing may adsorb dust or micro particles, which may deteriorate performance of the bearing.
  • the present invention can be preferably used particularly in an environment where a lot of dust or the like exists.
  • a plurality of shallow grooves is formed on at least one of the inner surface of the sleeve and the outer surface of the shaft member.
  • the shallow grooves can be linear grooves extending in the vertical direction (axial direction) or grooves having a herringbone shape, a screw-like shape (a spiral shape) or a curved shape.
  • pressure varies along the axial direction so that stiffness of the bearing is enhanced at a part of high pressure when relative rotation between the sleeve and the shaft member is generated. Therefore, contact between the sleeve and the shaft member can be prevented, and stability when an external force is applied can be increased.
  • a set of grooves may be provided, or plural sets of grooves may be provided separately in the axial direction.
  • FIG. 1 is a cross sectional view showing a structure of a long thin centrifugal fan according to a first embodiment of the present invention.
  • FIGS. 2 ( a ) and 2 ( b ) show partial cross sections of the bearing portion according to variations of the embodiment shown in FIG. 1 .
  • FIGS. 3 ( a ) and 3 ( b ) show partial cross sections of the bearing portion according to other variations of the embodiment shown in FIG. 1 .
  • FIG. 4 is a cross sectional view showing a structure of a long thin centrifugal fan according to a second embodiment of the present invention.
  • FIG. 5 is a cross sectional view showing a structure of a long thin centrifugal fan according to a third embodiment of the present invention.
  • FIG. 6 is a cross sectional view showing a structure of a conventional long thin centrifugal fan.
  • FIG. 7 is a cross sectional view in the direction perpendicular to the axis of a housing and an impeller in a typical centrifugal fan.
  • FIG. 1 is a cross sectional view showing a structure of a long thin centrifugal fan according to a first embodiment of the present invention.
  • This long thin centrifugal fan includes a housing 11 having a substantially cylindrical shape elongated in the axial direction, which houses an impeller 12 and a motor 13 for rotating the impeller 12 .
  • the impeller 12 is disposed mainly at the top side (the right side in FIG. 1 ) in the axial direction within the housing 11
  • the motor 13 is disposed at the bottom side (the left side in FIG. 1 ) in the axial direction within the housing 11 .
  • the impeller 12 includes a blade portion 14 (at the top side) having plural blades of a shape elongated in the axial direction that are arranged at a predetermined pitch in the circumferential direction, and a bottom end portion 15 having a substantially cylindrical shape for supporting the blade portion 14 .
  • the tip of the blade portion is provided with a ring-like linking portion 16 for linking and supporting tip portions of the plural blades.
  • the impeller 12 having a shape elongated in the axial direction has a diameter less than or equal to 25 millimeters.
  • the impeller 12 is rotated at a rotation speed more than or equal to 15,000 revolutions per minute, or at a relative speed more than or equal to 0.8 meters per minute between the shaft and the bearing surface.
  • a rotation speed of the impeller 12 secures sufficient quantity of airflow even by the long thin centrifugal fan with a reduced dimension (particularly in the radial direction).
  • the motor 13 includes a stator armature 21 , a rotor magnet 22 , a rotor yoke 25 , a sleeve 31 and a sleeve holder 32 that constitute a sleeve bearing as a slide bearing, a rotational shaft 33 and other members.
  • the rotor yoke 25 that is a rotational member is provided with step portions so that its diameter decreases from the bottom side to the top side by three steps. In other words, the rotor yoke 25 has a large diameter portion 25 a , a medium diameter portion 25 b and a small diameter portion 25 c .
  • a plurality of the rotor magnets 22 is arranged on the inner surface of the large diameter portion 25 a of the rotor yoke 25 at a predetermined pitch in the circumferential direction, and each of the rotor magnets 22 is opposed to the stator armature 21 with a constant gap.
  • the bottom end portion 15 of the impeller 12 is engaged with and fixed to the outer surface of the medium diameter portion 25 b and the small diameter portion 25 c of the rotor yoke 25 .
  • the rotational shaft 33 that is a rotatable shaft portion is fit in and fixed to the small diameter portion 25 c of the rotor yoke 25 .
  • the rotational shaft 33 is retained by the cylindrical sleeve 31 in a rotatable manner, so that the rotational shaft 33 , the rotor yoke 25 and the impeller 12 are rotated as one unit body.
  • the sleeve 31 is engaged with the inner surface of the sleeve holder 32 and is fixed to the same.
  • both the rotational shaft 33 and the sleeve 31 are made of a ceramic.
  • alumina, silicon nitride, artic, zirconia or the like can be used as the ceramic material. It is possible to use a ceramic for making one of the rotational shaft 33 and the sleeve 31 and use a metal for making the other. In this case, it is preferable to use a martensitic stainless steel as the metal material for example, and to perform a surface hardening process (nitriding treatment, for example) or DLC (diamond-like carbon) coating so that hardness of the surface (sliding surface) is increased.
  • the sleeve holder 32 has a cylindrical shape with an opening at the top side, and its bottom end portion is fixed to a center through-hole of a base member 24 that is a stational member by press fitting.
  • the base member 24 is fixed to the inner wall at the bottom side of the housing 11 made of a resin (or a metal).
  • the inner surface of the sleeve holder 32 at the bottom side is provided with a thrust plate 34 made of a metal or a ceramic to which the bottom end portion of the rotational shaft 33 can abut.
  • a thrust bearing is constituted.
  • the rotational shaft 33 is made of a ceramic
  • the thrust plate 34 is also made of a ceramic or a metal having a hardened surface by the above-mentioned surface hardening process or the like.
  • air dumping or oil dumping may be used for retaining the bottom end portion of the rotational shaft 33 .
  • a seal member is provided for sealing a ring-like gap between the opening of the sleeve holder 32 at the top side and the rotational shaft 33 .
  • FIGS. 2 ( a )- 2 ( b ) and 3 ( a )- 3 ( b ) show partial cross sections of the bearing portion according to some variations of the embodiment shown in FIG. 1 .
  • the sleeve 31 and the sleeve holder 32 in the structure shown in FIG. 1 are made as one unit member (hereinafter, it is simply referred to as a sleeve 31 ).
  • the sleeve holder 32 is eliminated, and the bottom end portion of the cylindrical sleeve 31 is directly fixed to the base member 24 .
  • the base member 24 and the sleeve 31 are made as one unit member, which is directly fixed to the housing 11 . It is preferable to use a ceramic as a material of these unit members.
  • the seal that is necessary in the structure shown in FIG. 1 is not necessary in the structure shown in FIG. 2 ( a ).
  • the thrust plate 34 is also eliminated in the structure shown in FIG. 2 ( a ).
  • the number of components is reduced in the structure shown in FIG. 2 ( a ), and the man-hour for assembling is also reduced.
  • a dimension in the radial direction of the long thin centrifugal fan can be reduced compared with the structure shown in FIG. 1 .
  • FIG. 2 ( b ) is an enlarged cross section of the sleeve 31 and the rotational shaft 33 in the structure shown in FIG. 2 ( a ).
  • the rotational shaft 33 has a reduced diameter portion 33 a at a middle portion in the axial direction of the part sliding with the sleeve 31 , and the reduced diameter portion 33 a has its diameter that is slightly smaller than other portion.
  • an area of the sliding surface is reduced. Namely, there is no sliding action at the reduced diameter portion 33 a between the rotational shaft 33 and the sleeve 31 , and the sliding action occurs only at the parts at both sides of the reduced diameter portion 33 a (i.e., a bottom side part 33 b and a top side part 33 c ). As a result, a bearing loss due to the sliding friction is reduced.
  • the method of forming the reduced diameter portion 33 a on the rotational shaft 33 at the part sliding with the sleeve 31 so as to reduce an area of the sliding surface for reducing a bearing loss can be applied to the structure of the first embodiment shown in FIG. 1 .
  • the method can also be applied to a structure with rotational sleeve (fixed shaft) that will be described later, namely a structure in which the shaft member is not the rotational shaft but a fixed shaft.
  • the sleeve 31 is divided into two members in the axial direction, and between them there is a felt tube 36 that is means for keeping lubricating oil and is attached to the rotational shaft 33 .
  • the felt tube 36 is impregnated with a lubricating oil such as an ester lubricating oil having a coefficient of viscosity less than 0.02 Pa-s.
  • a lubricating oil such as an ester lubricating oil having a coefficient of viscosity less than 0.02 Pa-s.
  • the step level (cut portion) of the reduced diameter portion 33 a that is formed on the rotational shaft 33 in the structure shown in FIG. 2 ( b ) is a little larger, and the felt tube 36 that is means for keeping lubricating oil is attached to that portion.
  • the lubricating oil that is impregnated in the felt tube 36 is supplied to and kept on the sliding surfaces of the rotational shaft 33 and the sleeve 31 so that a bearing loss due to friction between the sliding surfaces can be reduced similarly to the structure shown in FIG. 3 ( a ).
  • the means for keeping lubricating oil is not limited to the felt tube 36 as shown in FIGS. 3 ( a ) and 3 ( b ).
  • FIG. 4 is a cross sectional view showing a structure of a long thin centrifugal fan according to a second embodiment of the present invention.
  • This long thin centrifugal fan includes a housing 11 having a substantially cylindrical shape elongated in the axial direction, which houses an impeller 12 and a motor 13 for rotating the impeller 12 .
  • the impeller 12 is disposed mainly at the top side (the right side in FIG. 4 ) in the axial direction within the housing 11
  • the motor 13 is disposed mainly at the bottom side (the left side in FIG. 4 ) in the axial direction within the housing 11 .
  • the impeller 12 includes a blade portion 14 (at the top side) having plural blades of a shape elongated in the axial direction that are arranged at a predetermined pitch in the circumferential direction, and a bottom end portion 15 having a substantially cylindrical shape for supporting the blade portion 14 .
  • the tip of the blade portion is provided with a ring-like linking portion 16 for linking and supporting tip portions of the plural blades.
  • the motor 13 has a structure in which a torque generating portion 13 a including a stator armature 21 and a rotor magnet 22 , and a bearing portion 13 b that retains a rotational member in a rotatable manner are arranged tandem in the axial direction.
  • the bearing portion 13 b is disposed between the impeller 12 and the torque generating portion 13 a . According to this structure, it is possible to reduce a dimension in the radial direction can be reduced compared with the structure of the first embodiment shown in FIG. 1 .
  • an outer diameter of the motor 13 depends on a total sum of the outer diameter of the bearing portion 13 b and a size (thickness) of the torque generating portion 13 a in the radial direction in the structure shown in FIG. 1
  • the outer diameter of the motor 13 depends on either the outer diameter of the bearing portion 13 b or the size (outer diameter) of the torque generating portion 13 a that is larger one than the other (the outer diameter of the torque generating portion 13 a in the embodiment shown in FIG. 4 ) in the structure shown in FIG. 4 .
  • a dimension in the radial direction of the long thin centrifugal fan can be reduced.
  • the bearing portion 13 b i.e., the intermediate point thereof in the axial direction
  • the bearing portion 13 b is disposed at a barycenter of the element or at vicinity of the barycenter.
  • the bearing portion 13 b includes the rotational shaft 33 and the sleeve 31 having a cylindrical shape that engages the outer surface of the rotational shaft 33 with a clearance, and both the rotational shaft 33 and the sleeve 31 are made of a ceramic.
  • one of the rotational shaft 33 and the sleeve 31 is made of a metal, on which a surface hardening process or coating of the sliding surface is performed so as to increase its hardness as mentioned in the first embodiment.
  • the rotational shaft 33 is fixed to the rotor yoke 25 that is the rotational member, and the sleeve 31 is engaged with and fixed to the inner surface of the sleeve holder 32 .
  • the rotor yoke 25 having a substantially cylindrical shape is elongated in the axial direction and extends from the torque generating portion 13 a to the bearing portion 13 b .
  • the rotor yoke 25 is provided with step portions so that its diameter decreases from the bottom side to the top side by three steps.
  • the rotor yoke 25 has a large diameter portion 25 a , a medium diameter portion 25 b and a small diameter portion 25 c .
  • a plurality of the rotor magnets 22 is arranged on the inner surface of the large diameter portion 25 a of the rotor yoke 25 at a predetermined pitch in the circumferential direction.
  • Each of the rotor magnets 22 is opposed to the stator armature 21 with a constant gap.
  • the bottom end portion 15 of the impeller 12 is engaged with and fixed to the outer surface of the medium diameter portion 25 b and the small diameter portion 25 c of the rotor yoke 25 .
  • the rotational shaft 33 is fixed to the small diameter portion 25 c of the rotor yoke 25 by press fitting. Therefore, the rotational shaft 33 , the rotor yoke 25 and the impeller 12 rotate as one unit body.
  • the top end portion 33 d of the rotational shaft 33 is disposed within the inner space of the blade portion 14 of the impeller 12 . Namely, the rotational shaft 33 extends from the inside of the bottom end portion 15 of the impeller 12 to the inside of the blade portion 14 in the axial direction.
  • the small diameter portion 25 c of the rotor yoke 25 also extends from the inside of the bottom end portion 15 of the impeller 12 to the inside of the blade portion 14 .
  • sufficient length in the axial direction for secure fixing and aligning between the rotational shaft 33 and the rotor yoke 25 is ensured, while a dimension in the axial direction of the long thin centrifugal fan can be reduced.
  • the sleeve holder 32 that is made of a metal includes a cylindrical portion 32 a for engaging with the outer surface of the sleeve 31 so as to retain the same and a shaft portion 32 b that extends from the center of the bottom end surface of the cylindrical portion 32 a toward the bottom side.
  • the axis of the cylindrical portion 32 a agrees the axis of the shaft portion 32 b .
  • the shaft portion 32 b fits in the stator armature 21 , and further the bottom end portion thereof fits in the center through-hole of the base member 24 made of a resin (or a metal) and fixed to the same.
  • the base member 24 is fixed to the inner wall of the bottom side of the housing 11 made of a resin (or a metal).
  • the sleeve holder 32 is fixed so that the axis of the sleeve holder 32 agrees the center axis of the substantially cylindrical housing 11 .
  • the inner surface at the bottom side is provided with a thrust plate 34 made of a metal to which the bottom end portion of the rotational shaft 33 can abut.
  • a thrust bearing is constituted.
  • the rotational shaft 33 is made of a ceramic
  • the thrust plate 34 is made of a ceramic too or a metal having enhanced surface hardness by the surface hardening process or the like as described above.
  • air dumping or oil dumping may be used for retaining the bottom end portion of the rotational shaft 33 .
  • a seal member is provided for sealing a ring-like gap between the opening of the sleeve holder 32 at the top side and the rotational shaft 33 , so as to prevent dust from entering the inside of the cylindrical portion 32 a of the sleeve holder 32 .
  • the structure of the bearing portion that is described as a variation of the first embodiment can be applied to this second embodiment, too.
  • the sleeve 31 and the sleeve holder 32 can be made as one unit member, and/or the reduced diameter portion 33 a can be formed on a part of the rotational shaft 33 so that an area of the sliding surface (i.e., the bearing loss) can be reduced, and/or means for keeping lubricating oil that is supplied to the sliding surface can be provided.
  • FIG. 5 is a cross sectional view showing a structure of a long thin centrifugal fan according to a third embodiment of the present invention.
  • This long thin centrifugal fan includes a housing 11 having a substantially cylindrical shape elongated in the axial direction, which houses an impeller 12 and a motor 13 for rotating the impeller 12 .
  • a structure of the impeller 12 is the same as the embodiments described above, so overlapping description is omitted here.
  • a motor 13 of the long thin centrifugal fan in this embodiment is similar to that of the second embodiment.
  • the motor 13 has a structure in which a torque generating portion 13 a including a stator armature 21 and a rotor magnet 22 , and a bearing portion 13 b that retains a rotational member in a rotatable manner are arranged tandem in the axial direction, and a bearing portion 13 b is disposed between the impeller 12 and the torque generating portion 13 a .
  • An effect of this structure is also the same as described in the second embodiment.
  • the bearing portion 13 b i.e., the intermediate point thereof
  • the bearing portion 13 b is disposed at a barycenter of the element or at vicinity of the barycenter. This structure and its effect are also the same as described in the second embodiment.
  • the long thin centrifugal fan of this embodiment has a bearing portion 13 b of the motor 13 whose structure is substantially different from the embodiments described above. Namely, unlike the embodiments described above in which the bearing portion 13 b has a rotational shaft (fixed sleeve) structure, the bearing portion 13 b in the third embodiment has a rotating sleeve (fixed shaft) structure.
  • the bearing portion 13 b in this embodiment is also a sleeve bearing including a shaft member and a sleeve having a cylindrical shape that engages the outer surface of the shaft with a clearance
  • the shaft member is a fixed shaft 33 that is fixed to a base 24
  • a sleeve 31 is fixed to a rotor yoke 25 that is a rotational member via a sleeve holder 32 .
  • the fixed shaft that is the shaft member is denoted by the reference numeral 33 that is the same as the rotational shaft in the embodiments described above.
  • Other members including the sleeve 31 and the sleeve holder 32 are also denoted by the same reference numerals as the embodiments described above.
  • the rotor yoke 25 having a substantially cylindrical shape extends from the torque generating portion 13 a to the bearing portion 13 b in the axial direction.
  • the rotor yoke 25 has step portions so that its diameter decreases from the bottom side to the top side by three steps. Namely, the rotor yoke 25 has a large diameter portion 25 a , a medium diameter portion 25 b and a small diameter portion 25 c .
  • a plurality of the rotor magnets 22 is arranged on the inner surface of the large diameter portion 25 a of the rotor yoke 25 at a predetermined pitch in the circumferential direction. Each of the rotor magnets 22 is opposed to the stator armature 21 with a constant gap.
  • the bottom end portion 15 of the impeller 12 is engaged with and fixed to the outer surface of the medium diameter portion 25 b and the small diameter portion 25 c of the rotor yoke 25 .
  • the small diameter portion 25 c of the rotor yoke 25 has a closed end surface at the top side, which seals the opening of the impeller 12 at the boundary between the blade portion 14 and the bottom end portion 15 .
  • a cylindrical sleeve holder 32 having a closed end surface at the top side is engaged with and fixed to the inner surface of the medium diameter portion 25 b and the inner end surface of the small diameter portion 25 c of the rotor yoke 25 , while a cylindrical sleeve 31 is fixed to the inner surface of the sleeve holder 32 .
  • the top side of the fixed shaft 33 that is the shaft member is engaged with the inner surface of the sleeve 31 with a clearance, and the bottom side of the fixed shaft 33 fits in the stator armature 21 and further fits in and fixed to the center through-hole of the base member 24 made of a resin (or a metal).
  • the base member 24 is fixed to the inner wall of at the bottom side of the housing 11 made of a resin (or a metal).
  • the inner surface of the sleeve holder 32 at the top side is provided with a thrust plate 34 made of a metal to which the top end portion of the fixed shaft 33 can abut.
  • a thrust bearing is constituted.
  • the fixed shaft 33 is made of a ceramic
  • the thrust plate 34 is made of a ceramic too or a metal having enhanced surface hardness by the surface hardening process or the like as described above.
  • air dumping or oil dumping may be used for retaining the bottom end portion of the rotational shaft 33 .
  • a seal member is provided for sealing a ring-like gap between the opening of the sleeve holder 32 at the bottom side and the fixed shaft 33 , so as to prevent dust from entering the inside of the sleeve holder 32 .
  • the rotating sleeve (fixed shaft) bearing structure of this embodiment can be realized easily by structure in which the torque generating portion 13 a and the bearing portion 13 b for retaining the rotational member in a rotatable manner are arranged tandem in the axial direction, and the bearing portion 13 b is disposed between the impeller 12 and the torque generating portion 13 a .
  • use of the sleeve made of a ceramic also contributes largely to realizing the structure.
  • the sleeve 31 and the sleeve holder 32 can be made as one unit member, and/or the reduced diameter portion 33 a can be formed on a part of the rotational shaft 33 so that an area of the sliding surface (i.e., the bearing loss) can be reduced, and/or means for keeping lubricating oil that is supplied to the sliding surface can be provided.
  • both the sleeve and the shaft are made of a ceramic, it is preferable to use the same ceramic material for making them.
  • a ceramic is an insulator, generation of static electricity due to electrification of the surface can be prevented by using the same type of ceramic for the sliding surfaces.
  • the bearing may adsorb dust or micro particles, which may deteriorate performance of the bearing.
  • the present invention the ill effect of dust or micro particles to the bearing can be prevented, so that a long life of the centrifugal fan can be secured.
  • the present invention is useful especially in an environment with much dust.
  • a plurality of shallow grooves may be formed on at least one of the inner surface of the sleeve and the outer surface of the shaft member that are sliding surfaces of the bearing.
  • the shallow groove is preferably a linear groove extending in the vertical direction (axial direction) or a groove having a herringbone shape, a screw-like shape (a spiral shape) or a curved shape.
  • pressure varies along the axial direction so that stiffness of the bearing is enhanced at a part of high pressure when relative rotation between the sleeve and the shaft member is generated. Therefore, contact between the sleeve and the shaft member can be prevented, and stability when an external force is applied can be increased.
  • a set of grooves may be provided, or plural sets of grooves may be provided separately in the axial direction.
  • the grooves can be formed by coining, pressing, electrochemical machining, cutting or other processes.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Human Computer Interaction (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Ceramic Engineering (AREA)
  • Fluid Mechanics (AREA)
  • Thermal Sciences (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)
  • Sliding-Contact Bearings (AREA)
US10/906,895 2004-03-11 2005-03-11 Centrifugal fan Abandoned US20050201864A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2004068712A JP2005256706A (ja) 2004-03-11 2004-03-11 細長遠心ファン
JP2004-068712 2004-03-11

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US (1) US20050201864A1 (ja)
JP (1) JP2005256706A (ja)
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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20070253652A1 (en) * 2006-01-25 2007-11-01 Sony Corporation Bearing unit and motor using the same
US20110064532A1 (en) * 2008-04-18 2011-03-17 Atlas Copco Tools Ab Portable power drill with drilling implement rotating and feeding means
US20140017075A1 (en) * 2012-07-10 2014-01-16 Asia Vital Components Co., Ltd. Fan structure
US8790095B2 (en) 2008-10-14 2014-07-29 Jtekt Corporation Electric pump unit
EP4286699A1 (en) * 2022-05-31 2023-12-06 Trane International Inc. Compressor with wear sleeve and method of retrofitting a compressor

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100441877C (zh) * 2006-01-16 2008-12-10 台达电子工业股份有限公司 离心式风扇及其扇框
US8767400B2 (en) * 2011-06-27 2014-07-01 The Bergquist Torrington Company Cooling module with parallel blowers
JP2013127219A (ja) * 2011-12-19 2013-06-27 Nippon Densan Corp ファン
JP6399806B2 (ja) * 2014-05-23 2018-10-03 株式会社不二工機 ステータ組立体並びに当該ステータ組立体を備えたマグネットロータ式モータ及びポンプ

Citations (3)

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Publication number Priority date Publication date Assignee Title
US3322931A (en) * 1956-12-31 1967-05-30 Laing Nikolaus Fans
US20040202540A1 (en) * 2003-04-14 2004-10-14 Nidec Corporation Fan impeller and fan motor
US6893230B2 (en) * 2002-02-14 2005-05-17 Kuan Kuan Sung Rotation support of heat-dissipation fan

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3322931A (en) * 1956-12-31 1967-05-30 Laing Nikolaus Fans
US6893230B2 (en) * 2002-02-14 2005-05-17 Kuan Kuan Sung Rotation support of heat-dissipation fan
US20040202540A1 (en) * 2003-04-14 2004-10-14 Nidec Corporation Fan impeller and fan motor

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20070253652A1 (en) * 2006-01-25 2007-11-01 Sony Corporation Bearing unit and motor using the same
US7614791B2 (en) * 2006-01-25 2009-11-10 Sony Corporation Bearing unit and motor using the same
US20110064532A1 (en) * 2008-04-18 2011-03-17 Atlas Copco Tools Ab Portable power drill with drilling implement rotating and feeding means
US8790095B2 (en) 2008-10-14 2014-07-29 Jtekt Corporation Electric pump unit
US20140017075A1 (en) * 2012-07-10 2014-01-16 Asia Vital Components Co., Ltd. Fan structure
US9435348B2 (en) * 2012-07-10 2016-09-06 Asia Vital Components Co., Ltd. Fan structure
EP4286699A1 (en) * 2022-05-31 2023-12-06 Trane International Inc. Compressor with wear sleeve and method of retrofitting a compressor

Also Published As

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JP2005256706A (ja) 2005-09-22
CN1667277A (zh) 2005-09-14

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