Patent ID: 7540722

Claim:
A blower comprising: a casing provided with a partition dividing an internal space of the casing into a fan housing and a motor housing, the partition having a first partition surface defining the motor housing and a second partition surface defining the fan housing, the casing being formed with an inlet allowing fluid communication between the fan housing and an exterior for sucking a fluid into the fan housing therethrough, and an outlet allowing fluid communication between the fan housing and the exterior for discharging fluid from the fan housing to the exterior therethrough, the casing being also formed with an introduction hole allowing fluid communication between the motor housing and the exterior; an electric motor disposed in the motor housing; and a centrifugal fan disposed in the fan housing and rotatable by the electric motor, the centrifugal fan defining a rotation axis and comprising: a generally circular base plate having a first base plate surface directly facing the second partition surface and a second base plate surface, the base plate defining a circumferential direction and being formed with a plurality of base plate through-holes arrayed in an imaginary circle whose center is coincident with the rotation axis for allowing fluid to pass therethrough; and a plurality of vanes protruding from the second base plate surface; the partition being formed with a plurality of partition through-holes arrayed in the imaginary circle and in selective alignment with the base plate through-holes in accordance with the rotation of the centrifugal fan, each partition through-hole including at least a width increasing region where a width of the partition through-holes in the circumferential direction is gradually increased toward the second partition surface; wherein a geometrical relationship of h>(e/2)/tan(β/2) is provided; in which h represents a distance between the first base plate surface of and the second partition surface; e represents a distance in the circumferential direction between a first intersection of the second linear flat plane of the first through-hole with the second partition surface and a second intersection of the first linear flat plane of the second through-hole with the second partition surface, the first linear flat plane of the second through-hole and the second linear flat plane of the first through-hole being positioned side by side in the circumferential direction; and β represents an angle between the first linear flat plane of the second through-hole and the second linear flat plane of the first through-hole, an angle of the first linear flat plane of the second through-hole relative to the rotation axis being equal to an angle of the second linear flat plane of the first through-hole relative to the rotation axis.