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 first expanded part expands the flow passage cross-sectional area on the side of the inlet opening and is formed proximate the scroll end toward the outlet opening; and   the second expanded part expands the flow passage cross-sectional area on the opposite side of the inlet opening and is formed from a range of a part up to about 60° from a neighborhood of the nose in the rotational direction of the fan toward the outlet opening.   
   
   
       2 . The centrifugal blower according to  claim 1 , wherein a dimension of said scroll 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. 
   
   
       3 . The centrifugal blower according to  claim 1 , wherein a dimension of said scroll 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. 
   
   
       4 . The centrifugal blower according to  claim 1 , wherein said airflow passage has an approximately rectangular cross-section. 
   
   
       5 . The centrifugal blower according to  claim 1 , wherein said airflow passage has an approximately rectangular cross-section with rounded interior passage corners. 
   
   
       6 . 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. 
   
   
       7 . 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°; and   an expanded dimension (Hup) on the side of the inlet opening is less than 0.4 times an expanded dimension (HLR) on the opposite side of the inlet opening in the first and second expanded parts.   
   
   
       8 . The centrifugal blower according to  claim 7 , wherein a dimension of said scroll 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. 
   
   
       9 . The centrifugal blower according to  claim 7 , wherein a dimension of said scroll 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. 
   
   
       10 . The centrifugal blower according to  claim 7 , wherein said airflow passage has an approximately rectangular cross-section. 
   
   
       11 . The centrifugal blower according to  claim 7 , wherein said airflow passage has an approximately rectangular cross-section with rounded interior passage corners. 
   
   
       12 . The centrifugal blower according to  claim 7 , 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.