Fluid pump apparatus

Abstract

In an air supply pump, having an electric motor and a blower driven by the electric motor, the blower has an impeller having multiple blades for compressing and pumping out the air. A value (F) obtained by a formula (F=N×S) is made to be higher than the audible frequency band to the human beings, wherein “N” means number of blades of the impeller, and “S” means a number of rotation of the impeller for each second at a normal rotational speed. (“×” is a symbol for a mathematical multiplication.) The frequency (F=N×S) of fan noises at a primary peak appears at higher frequencies out of the audible frequency band, so that the noises audible to the human beings can be reduced.

1 . A fluid pump apparatus comprising: 
 an electric motor;    a blower operatively connected to and driven by the electric motor, wherein the blower has a fluid flow chamber and an impeller rotatably supported in the fluid flow chamber, and the impeller has multiple blades,    wherein a value “F” obtained by a formula of “F=N×S” is made to be a higher value than an audible frequency band,    wherein    “N” is a number of blades, and    “S” is a rotational number of the electric motor for each second at its normal rotational speed.    (“×” is a symbol of a mathematical multiplication.)    
   
   
       2 . A fluid pump apparatus according to  claim 1 , wherein 
 fin pitch angles of the respective blades are made to be equal to each other.    
   
   
       3 . A fluid pump apparatus according to  claim 1 , wherein 
 the number of the blades is made to be a prime number.    
   
   
       4 . A fluid pump apparatus according to  claim 1 , wherein 
 the blower has a blower housing forming the fluid flow chamber therein,    a partitioning portion is formed in the fluid flow chamber between a starting portion and an ending portion of the fluid flow, and    a volume decreasing means is formed in the partitioning portion adjacent to the ending portion of the fluid flow chamber, so that across sectional area of the fluid flow chamber is gradually decreased at the ending portion in a rotational direction of the impeller.