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 4.8°.

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;    an outer peripheral radius of said scroll casing expands as a logarithmic spiral, and its expansion angle is from 3.3° to 4.8°;    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.    
   
   
       2 . 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.  
   
   
       3 . 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°; and    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 3 , 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.  
   
   
       5 . 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;    an outer peripheral radius of said scroll casing expands as a logarithmic spiral, and its expansion angle is from 3.3° to 4.8°;    said airflow passage has an approximately rectangular cross-section with rounded interior passage corners.    
   
   
       6 . 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;    an outer peripheral radius of said scroll casing expands as a logarithmic spiral, and its expansion angle is from 3.3° to 4.8°;    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.