Centrifugal fan

Abstract

A centrifugal fan includes an impeller that rotates inside the elongated cylindrical housing and a motor for driving the impeller. The impeller and the motor are arranged tandem in the axial direction. The impeller includes a blade portion having plural blades elongated in the axial direction, and the blades are arranged at a predetermined pitch in the circumferential direction. When the impeller rotates, air is taken in through a suction opening provided to the tip portion in the axial direction of the housing and is blown out through an outlet opening that is provided to a part in the circumferential direction of the housing. A bearing portion that constitutes the motor is a sleeve 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 fixed to a rotational member, while the other is fixed to a base member. One of the shaft member and the sleeve is made of a ceramic, while the other is made of a ceramic or a metal.

1 . A centrifugal fan comprising: 
 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, wherein the impeller and the motor are arranged tandem in the axial direction,    a shaft having a cylindrical outer peripheral surface,    a sleeve having a cylindrical inner peripheral surface opposed to the outer peripheral surface of the shaft in the radial direction with a minute gap,    a bearing portion that constitutes the motor including said shaft and said sleeve,    wherein one of the shaft and the sleeve is made of a ceramic, and the other is made of a ceramic or a metal.    
   
   
       2 . The centrifugal fan according to  claim 1 , wherein the impeller is rotated at a rotation speed more than or equal to 15,000 revolutions per minute.  
   
   
       3 . The centrifugal fan according to  claim 1 , wherein the sleeve and the shaft are both made of the same type of ceramic.  
   
   
       4 . The centrifugal fan according to  claim 2 , wherein the sleeve and the shaft are both made of the same type of ceramic.  
   
   
       5 . The centrifugal fan according to  claim 1 , wherein 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.  
   
   
       6 . The centrifugal fan according to  claim 2 , wherein 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.  
   
   
       7 . The centrifugal fan according to  claim 3 , wherein 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.  
   
   
       8 . The centrifugal fan according to  claim 4 , wherein 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.  
   
   
       9 . The centrifugal fan according to  claim 1 , wherein among elements that constitute the motor, a torque generating portion including an armature and a field magnet, and a bearing portion are arranged tandem in the axial direction.  
   
   
       10 . The centrifugal fan according to  claim 1 , wherein 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.  
   
   
       11 . The centrifugal fan according to  claim 9 , wherein 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.  
   
   
       12 . The centrifugal fan according to  claim 1 , wherein a sleeve made of a ceramic is fixed to a rotational member, and a shaft member is fixed to the housing directly or via a base member.  
   
   
       13 . The centrifugal fan according to  claim 9 , wherein a sleeve made of a ceramic is fixed to a rotational member, and a shaft member is fixed to the housing directly or via a base member.  
   
   
       14 . The centrifugal fan according to  claim 13 , wherein the top side of the shaft member is disposed within the inner space of the blade portion of the impeller.  
   
   
       15 . The centrifugal fan according  claim 10 , wherein the bottom side of the shaft member is a free end without a thrust bearing.  
   
   
       16 . The centrifugal fan according to  claim 1 , wherein when plural members rotating as one unit body including the impeller and the rotational member are regarded as one element, the bearing portion is disposed at a barycenter of the element or at vicinity of the barycenter.  
   
   
       17 . The centrifugal fan according to  claim 2 , wherein when plural members rotating as one unit body including the impeller and the rotational member are regarded as one element, the bearing portion is disposed at a barycenter of the element or at vicinity of the barycenter.  
   
   
       18 . The centrifugal fan according to  claim 9 , wherein when plural members rotating as one unit body including the impeller and the rotational member are regarded as one element, the bearing portion is disposed at a barycenter of the element or at vicinity of the barycenter.  
   
   
       19 . The centrifugal fan according to  claim 1 , wherein 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.