Centrifugal blower

Abstract

A centrifugal multi-blade fan has multiple blades about a rotational shaft and draws in air along the rotational shaft and then blows the air approximately perpendicular to the rotational shaft to reduce wind noise. A scroll casing encloses the multi-blade fan and defines a scroll-shaped airflow passage for directing the air blown from the multi-blade fan. The scroll casing has an intake opening and an outlet opening at a scroll end, in a downstream scroll casing portion. The scroll casing expands such that a flow passage cross-sectional area on the airflow downstream side is larger than that on an airflow upstream side. A ratio of a blade length to a diameter of the multi-blade fan is greater than or equal to 0.12, and an outer scroll casing radius, relative to the rotational axis, increases as a logarithmic spiral, its expansion angle being from 3.3° to 4.80°.

What is claimed is:  
     
         1 . A centrifugal blower comprising: 
 a centrifugal multi-blade fan having multiple blades about a rotational shaft, wherein said centrifugal fan takes in air along an axial direction of said rotational shaft and blows said air outward in a radial direction with respect to said rotational shaft; and    a scroll casing for storing said centrifugal multi-blade fan, said scroll casing defining a scroll-shaped airflow passage for directing said air blown out from said centrifugal multi-blade fan, said scroll casing having an intake opening at a first end of said rotational shaft and an outlet opening at a scroll end at an airflow downstream portion, wherein    a first expanded part and a second expanded part are expanded in a direction parallel with said rotational shaft and are provided in said airflow passage such that a flow passage cross-sectional area on the airflow downstream side is larger than that on an airflow upstream side,    a ratio of a blade length of said blades to a diameter of the centrifugal multi-blade fan is equal to or over 0.12, and    an outer peripheral radius of said scroll casing expands as a logarithmic spiral, and its expansion angle is from 3.3° to 4.8°.    
     
     
         2 . A centrifugal blower comprising: 
 a centrifugal multi-blade fan provided with multiple blades about a rotational shaft for drawing in air along said rotational shaft and blowing said air outward in a radial direction, perpendicular to said rotational shaft; and    a scroll casing for storing said centrifugal multi-blade fan, said scroll casing defining a scroll-shaped airflow passage for directing said air blown out from said centrifugal multi-blade fan, and said scroll casing defines an intake opening on a first end in the axial direction of said rotational shaft, and an outlet opening at an airflow downstream side of a scroll end, wherein    a plurality of expanded parts extending in a direction parallel to said rotational shaft are provided in said airflow passage such that a flow passage cross-sectional area on the airflow downstream side is larger than that on an airflow upstream side,    a ratio of a blade length (L) of said blades to a diameter of the centrifugal multi-blade fan is equal to or over 0.12,    an outer peripheral radius of said scroll casing extends as a logarithmic spiral, wherein its expansion angle is from 3.5° to 4.5°.    
     
     
         3 . The centrifugal blower according to  claim 1 , wherein a dimension of said winding-end portion in a direction parallel with said rotational shaft is from 1.1 times to 2.3 times a dimension of a nose in said scroll casing in a direction parallel with said rotational shaft.  
     
     
         4 . The centrifugal blower according to  claim 2 , wherein a dimension of said winding-end portion in a direction parallel with said rotational shaft is from 1.1 times to 2.3 times a dimension of a nose in said scroll casing in a direction parallel with said rotational shaft.  
     
     
         5 . The centrifugal blower according to  claim 1 , wherein a dimension of said winding-end portion in a direction parallel with said rotational shaft is from 1.3 times to 2.1 times of a dimension of a nose in said scroll casing in a direction parallel with said rotational shaft.  
     
     
         6 . The centrifugal blower according to  claim 2 , wherein a dimension of said winding-end portion in a direction parallel with said rotational shaft is from 1.3 times to 2.1 times of a dimension of a nose in said scroll casing in a direction parallel with said rotational shaft.  
     
     
         7 . The centrifugal blower according to  claim 1 , wherein said airflow passage has an approximately rectangular cross-section.  
     
     
         8 . The centrifugal blower according to  claim 1 , wherein said airflow passage has an approximately rectangular cross-section with rounded interior passage corners.  
     
     
         9 . The centrifugal blower according to  claim 1 , wherein a protrusion protruding toward said centrifugal multi-blade fan is provided on an inner wall on an outer peripheral side of said scroll casing, and has an approximately triangular shape protruding toward said centrifugal multi-blade fan when viewed from a primary flow direction of the air flowing through said airflow passage.  
     
     
         10 . A centrifugal blower comprising: 
 a centrifugal multi-blade fan provided with multiple blades about a rotational shaft for taking in air in an axial direction of said rotational shaft, and blowing the air outward in a radial direction; and    a scroll casing for storing said centrifugal multi-blade fan, constituting a scroll-shaped airflow passage for directing the air blown out from said centrifugal multi-blade fan, and having an intake opening proximate to a first end of said rotational shaft along the axial direction of said rotational shaft, and an outlet opening at an airflow downstream side of a scroll end of said scroll casing, wherein    a ratio of a blade length of said blades to a diameter of said centrifugal multi-blade fan is 0.12 and over,    a fan inlet opening angle of said centrifugal multi-blade fan ranges from 55° to 85°,    a fan outlet opening angle of said centrifugal multi-blade fan ranges from 15° to 45°, and    a fan advancing angle, which is an angle between a line connecting an inlet opening side end of said blade with a rotational center of said multi-blade fan, and a line connecting an outlet opening side end of said blade with the rotational center of said multi-blade fan, from 4° to 10°.    
     
     
         11 . The centrifugal blower according to  claim 10 , wherein a curvature radius of said blade on an inlet opening side is equal to or less than a curvature radius of said blade on the outlet opening side.  
     
     
         12 . The centrifugal blower according to  claim 11 , wherein said blades have a shape for smoothly blending curved surfaces having two or more curvature radii.  
     
     
         13 . The centrifugal blower according to  claim 10 , wherein an outer peripheral side radius of said scroll casing extends as a logarithmic spiral, and its expansion angle is from 3.3° to 4.8°.  
     
     
         14 . The centrifugal blower according to  claim 10 , wherein an outer peripheral side radius of said scroll casing extends as a logarithmic spiral, and its expansion angle is from 3.5° to 4.5°.  
     
     
         15 . The centrifugal blower according to  claim 10 , wherein expanded parts expanded in a direction parallel with said rotational shaft are provided in said airflow passage such that a flow passage cross-sectional area on an airflow downstream side is larger than that on an airflow upstream side.  
     
     
         16 . A centrifugal multi-blade fan for an automobile air blower comprising: 
 a rotational shaft to which a plurality of air-forcing blades are equidistantly attached in a radial arrangement;    a scroll casing for encompassing said rotational shaft and said plurality of blades, wherein said scroll casing is constructed as a scroll-shaped airflow passage for directing air blown out from said air-forcing blades, said scroll casing further defining an intake opening around a first end of said rotational shaft along the axial direction of said rotational shaft and an outlet opening at a scroll end portion of said scroll casing; and    a fan advancing angle, which is an angle between a first line tangent to a first end of said blade on a forward facing side of said blade and a second line tangent to a second end of said blade on a forward facing side of said blade, both of said lines passing through a rotational center of said rotational shaft, wherein said fan advancing angle is from 4° to 10°.    
     
     
         17 . A centrifugal multi-blade fan for an automobile air blower according to  claim 16 , wherein a ratio of a blade length of said plurality of blades to a diameter of said centrifugal multi-blade fan is equal to or greater than 0.12.  
     
     
         18 . A centrifugal multi-blade fan for an automobile air blower according to  claim 17 , wherein a fan inlet opening angle of said centrifugal multi-blade fan ranges from 55° to 85°.  
     
     
         19 . A centrifugal multi-blade fan for an automobile air blower according to  claim 18 , wherein a fan outlet opening angle of said centrifugal multi-blade fan ranges from 15° to 45°.