Patent ID: 8167550
Filing Date: 2012-05-01
Classification: F04D

Abstract:
1. A blower unit comprising: a rotation shaft; a centrifugal multi-blade fan supported by the rotation shaft, the centrifugal multi-blade fan including a plurality of blades arranged in a circumferential direction defining a center on the rotation shaft; and a blower casing that houses the centrifugal multi-blade fan therein, wherein the blower casing has a wall part on a first axial side with respect to an axial direction along the axis of the rotation shaft, the wall part extending in a radial direction of the centrifugal multi-blade fan and having an opening portion defining an opening, the centrifugal multi-blade fan has a ring part having a ring shape defining a center on the rotation shaft and supporting the blades adjacent to the first axial side of the blower casing with respect to the axial direction, the centrifugal multi-blade fan has a base wall separate from the ring part with respect to the axial direction, the base wall extends in a radially outward direction and toward a second axial side of the blower casing, over a circumference of the rotation shaft, and supports the blades adjacent to the second axial side of the blower casing, the blades are configured to rotate with rotation of the rotation shaft and to blow air from a radially inside of the centrifugal multi-blade fan toward a radially outside of the centrifugal multi-blade fan in accordance with the rotation, the ring part includes an arcuate wall having an arcuate cross-section, the arcuate wall is disposed inside of the opening portion with respect to the radial direction of the centrifugal multi-blade fan, the arcuate wall is disposed such that a maximum diameter portion thereof is located adjacent to the first axial side of the blower casing and a minimum diameter portion thereof is located closer to the second axial side of the blower casing than the maximum diameter portion with respect to the axial direction, the arcuate wall has a curved shape between the maximum diameter portion and the minimum diameter portion, the curved shape protruding toward a flow of air suctioned into the centrifugal multi-blade fan through a radially inner space of the arcuate wall, the casing has an air outlet to discharge air blown out from the centrifugal multi-blade fan, the ring part is disposed so that a clearance is defined between a radially outer portion of the ring part and the opening portion, the blower unit further comprising: a first part having a ring shape defining a center on the rotation shaft, the first part being disposed on a radially outer side of the blades and extending from the ring part toward the second axial side of the blower casing; a second part having a ring shape defining a center on the rotation shaft, the second part extending from the wall part of the blower casing toward the second axial side of the blower casing with respect to the axial direction; a third part having a ring shape defining a center on the rotation shaft, the third part projecting toward the second part from one of the first part and the ring part; and a fourth part having a ring shape defining a center on the rotation shaft, the fourth part projecting toward the first part from one of the second part and the wall part of the blower casing and being displaced from the third part with respect to the axial direction, wherein the first part, the second part, the third part and the fourth part form a labyrinthine structure that reduces a flow of air that flows out from a radially inner side of the blades to an outside of the casing through the clearance while bypassing the air outlet.