Fan

Abstract

A centrifugal fan includes an impeller including a main plate rotating about a center axis and a plurality of vanes fixed to the main plate in a circumferentially spaced-apart relationship, and a bell mouth arranged at an air intake side of the impeller to define an air inlet including a portion whose inner diameter is decreased toward the impeller. Each of the vanes preferably includes a protrusion protruding toward the bell mouth and extending into the air inlet.

What is claimed is: 
     
         1 . A centrifugal fan, comprising:
 an impeller including a main plate rotating about a center axis and a plurality of vanes fixed to the main plate in a circumferentially spaced-apart relationship; and   a bell mouth arranged at an air intake side of the impeller to define an air inlet including a portion whose inner diameter decreases toward the impeller, each of the vanes including a protrusion protruding toward the bell mouth and extending into the air inlet.   
     
     
         2 . The fan of  claim 1 , wherein, when seen in a center axis direction, each of the vanes is curved in a direction opposed to a rotating direction of the main plate as each of the vanes extends from a radial inner end thereof toward a radial outer end thereof. 
     
     
         3 . The fan of  claim 1 , wherein the impeller is an open impeller that does not include a shroud that is arranged to be opposed to the main plate with the vanes interposed therebetween. 
     
     
         4 . The fan of  claim 1 , wherein the protrusion includes a tip end surface located substantially at the same position in a center axis direction as a diameter reduction start position where the inner diameter of the air inlet begins to decrease toward the impeller. 
     
     
         5 . The fan of  claim 1 , wherein the protrusion includes a tip end surface including a serration arranged to suppress the generation of an air vortex on the tip end surface. 
     
     
         6 . An axial flow fan, comprising:
 a hub rotating about a center axis;   a plurality of propeller blades fixed to an outer circumferential surface of the hub in a circumferentially spaced-apart relationship to rotate about the center axis together with the hub to thereby draw air from an air intake side as one center axis direction side and discharge the air toward an air discharge side as the other center axis direction side, the propeller blades including outer peripheral portions interconnected by a ring member; and   a bell mouth provided at the air intake side with respect to the propeller blades, the bell mouth including a portion whose inner diameter decreases toward the air discharge side to guide the air drawn by the propeller blades toward the propeller blades.   
     
     
         7 . The fan of  claim 6 , wherein the bell mouth has a minimum inner diameter equal to or smaller than an inner diameter of an air intake side end of the ring member. 
     
     
         8 . The fan of  claim 6 , wherein the ring member is provided at outer peripheral ends of the propeller blades. 
     
     
         9 . The fan of  claim 6 , wherein the ring member includes a portion arranged at the air intake side to have a diameter increasing toward the air intake side. 
     
     
         10 . The fan of  claim 6 , further comprising:
 a flow straightening member provided inside the bell mouth to straighten a flow of the air drawn by the propeller blades.   
     
     
         11 . The fan of  claim 6 , further comprising:
 a base member provided at the air discharge side with respect to the hub to rotatably support the hub; wherein   the base member and the bell mouth are interconnected by a plurality of connecting members arranged at a radial outer side of the propeller blades in a circumferentially spaced-apart relationship with one another, only the connecting members being provided at the radial outer side of the propeller blades.   
     
     
         12 . The fan of  claim 6 , wherein the ring member includes an air intake side end that is substantially flush with air intake side ends of the propeller blades in a center axis direction and an air discharge side end spaced apart in the center axis direction from the air intake side ends of the propeller blades by about 50% through about 80% of a center axis direction length of the propeller blades. 
     
     
         13 . The fan of  claim 6 , further comprising:
 a guide portion provided at the air discharge side with respect to the propeller blades to guide the air discharged toward the air discharge side by the propeller blades so that the air flows radially outwards.