A centrifugal fan includes an upstream side impeller, a downstream side impeller, a motor, and a housing arranged to accommodate the upstream side impeller, the downstream side impeller, and the motor. The housing includes a first intake port through which a gas is drawn from an outside, an exhaust
A centrifugal fan includes an upstream side impeller, a downstream side impeller, a motor, and a housing arranged to accommodate the upstream side impeller, the downstream side impeller, and the motor. The housing includes a first intake port through which a gas is drawn from an outside, an exhaust port through which the gas is discharged to the outside, and a flow path defined within the housing to bring the first intake port and the exhaust port into communication with each other. The flow path includes a first wind tunnel portion positioned below the upstream side impeller to extend in a circumferential direction and arranged to receive a gas stream from the upstream side impeller and a second wind tunnel portion positioned above the downstream side impeller to extend in the circumferential direction and arranged to receive a gas stream from the downstream side impeller.
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1. A centrifugal fan, comprising: an upstream side impeller arranged to rotate about a center axis extending in an axial direction;a downstream side impeller positioned below the upstream side impeller and arranged to rotate about the center axis;a motor arranged to rotate the upstream side impeller
1. A centrifugal fan, comprising: an upstream side impeller arranged to rotate about a center axis extending in an axial direction;a downstream side impeller positioned below the upstream side impeller and arranged to rotate about the center axis;a motor arranged to rotate the upstream side impeller and the downstream side impeller; anda housing arranged to accommodate the upstream side impeller, the downstream side impeller, and the motor; whereinthe housing includes: a first intake port through which a gas is drawn from outside;an exhaust port through which the gas is discharged to the outside; anda flow path defined within the housing to bring the first intake port and the exhaust port into communication with each other;the flow path includes a first wind tunnel portion positioned below the upstream side impeller to extend in a circumferential direction and arranged to receive a gas stream from the upstream side impeller and a second wind tunnel portion positioned above the downstream side impeller to extend in the circumferential direction and arranged to receive a gas stream from the downstream side impeller;the flow path includes: a first impeller chamber arranged to accommodate the upstream side impeller;a second impeller chamber arranged to accommodate the downstream side impeller; anda connecting flow path arranged to interconnect the first impeller chamber and the second impeller chamber;the first intake port is positioned above the upstream side impeller;the housing further includes a second intake port arranged between the connecting flow path and the second impeller chamber;the second intake port is positioned below the downstream side impeller;the connecting flow path includes an intermediate arc-shaped portion positioned below the first impeller chamber and above the second impeller chamber, the intermediate arc-shaped portion extends in the circumferential direction; andthe intermediate arc-shaped portion includes an outermost diameter smaller than an outermost diameter of each of the first impeller chamber and the second impeller chamber. 2. The centrifugal fan of claim 1, wherein the intermediate arc-shaped portion is defined around the motor over an extent of more than one half of a perimeter of the motor and less than the perimeter of the motor. 3. The centrifugal fan of claim 1, wherein the motor is arranged below the upstream side impeller and above the downstream side impeller, the motor including an outer circumferential surface at least partially exposed to the intermediate arc-shaped portion. 4. The centrifugal fan of claim 3, wherein the motor includes a metal motor holding member exposed to the intermediate arc-shaped portion. 5. The centrifugal fan of claim 4, wherein the motor holding member includes an outer circumferential surface and a heat sink attached to the outer circumferential surface, the heat sink including fins protruding radially outward. 6. The centrifugal fan of claim 5, wherein the heat sink includes circumferentially-extending gaps defined between the fins. 7. The centrifugal fan of claim 1, wherein the intermediate arc-shaped portion is arranged to open toward an outer circumferential surface of the motor, the intermediate arc-shaped portion including an inner peripheral portion and a radial middle portion, the inner peripheral portion including an axial dimension equal to or greater than an axial dimension of the radial middle portion. 8. The centrifugal fan of claim 1, wherein the intermediate arc-shaped portion includes a cross section orthogonal or substantially orthogonal to the circumferential direction, each of the first wind tunnel portion and the second wind tunnel portion including a cross section orthogonal or substantially orthogonal to the circumferential direction, the cross section of the intermediate arc-shaped portion being smaller in area than the cross section of each of the first wind tunnel portion and the second wind tunnel portion. 9. The centrifugal fan of claim 1, wherein the intermediate arc-shaped portion includes an upstream portion arranged to communicate with the first wind tunnel portion and a downstream portion arranged to communicate with the second intake port through a passageway arranged radially outward of the second impeller chamber. 10. The centrifugal fan of claim 1, wherein each of the first impeller chamber, the second impeller chamber, and the intermediate arc-shaped portion is defined between two members arranged one above the other. 11. The centrifugal fan of claim 10, wherein a sealing material is interposed between the two members. 12. The centrifugal fan of claim 1, wherein the housing includes: a first connecting member including an upper surface defining a lower interface of the first impeller chamber and a lower surface defining an upper interface of the intermediate arc-shaped portion; anda second connecting member including an upper surface defining a lower interface of the intermediate arc-shaped portion and a lower surface defining an upper interface of the second impeller chamber. 13. The centrifugal fan of claim 1, wherein the upstream side impeller and the downstream side impeller have a mirror symmetry shape or a substantial mirror symmetry shape with respect to each other and are arranged in a vertically inverted posture with respect to each other. 14. The centrifugal fan of claim 1, wherein the exhaust port is arranged higher than the downstream side impeller. 15. The centrifugal fan of claim 1, wherein the upstream side impeller includes an upper surface and a first annular protrusion protruding upward from the upper surface;the downstream side impeller includes a lower surface and a second annular protrusion protruding downward from the lower surface;the housing includes a first annular groove corresponding to the first annular protrusion and a second annular groove corresponding to the second annular protrusion; andlabyrinth portions having a reduced clearance are defined between the first annular protrusion and the first annular groove and between the second annular protrusion and the second annular groove. 16. The centrifugal fan of claim 15, wherein a recess portion is arranged near the first annular protrusion or the second annular protrusion, a balancing member being attached to the recess portion. 17. The centrifugal fan of claim 1, wherein the motor is an inner-rotor-type motor.
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Graham Mark A. ; Neely Michael J. ; Savage John R., Blower assembly having integral air flow cooling duct.
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