Patent ID: 6971846
Filing Date: 2005-12-06
Classification: F04D

Abstract:
1. A centrifugal blower comprising: a centrifugal fan including a boss portion, a plurality of blades arranged on a periphery of the boss portion in parallel to an axial direction, and a shroud connecting to ends of the blades, wherein the shroud defines a fan inlet port through which air is sucked in the centrifugal fan and the blades define discharging ports through which air is discharged in a radial direction; a motor connected to the boss portion for driving the centrifugal fan; and a scroll casing including a first casing wall defining a casing suction port, a second casing wall opposing the first casing wall and holding the motor, and a scroll duct connecting an outer periphery of the first casing wall and an outer periphery of the second casing wall; wherein the scroll casing houses the centrifugal fan such that the fan inlet port is adjacent to the casing suction port; the scroll duct includes a first wall portion that extends from the outer periphery of the first casing wall and includes a curve, a second wall portion that extends from the outer periphery of the second casing wall and includes a curve, and a third wall portion connecting the first wall portion and the second wall portion; the first wall portion extends from the outer periphery of the first casing wall in the axial direction and the second wall portion extends from the outer periphery of the second casing wall in the radial direction; the curve of the first wall portion has a radius of curvature smaller than that of the second wall portion; and the third wall portion smoothly connecting the first wall portion and the second wall portion so that the scroll duct has a radius of curvature that gradually reduces from the second wall portion to the first wall portion.