Blower and image forming apparatus

1. A blower comprising:

a fan that blows air; and

an air duct having a passage formed therein, the air duct guiding the air blown by the fan to a corona discharger and blowing the air onto the corona discharger, the corona discharger including a discharge wire stretched therein, the air duct including

an increasing-width portion in which a passage width gradually increases downstream in an air flow direction, the passage width being a dimension of the passage along a direction in which the discharge wire is stretched,

a decreasing-height portion in which a passage height gradually decreases downstream in the air flow direction, the passage height being a distance between a top and a bottom of the passage, the decreasing height portion being included in a region of the increasing-width portion or included in a region including the increasing-width portion,

an extension portion extending from a downstream end of the decreasing-height portion to a position near the corona discharger, the passage height of the passage throughout the extension portion being the same as the passage height at the downstream end of the decreasing height portion,

a bent portion that is bent from a downstream end of the extension portion toward the corona discharger so as to be connected to the corona discharger,

an opening formed at a downstream end of the bent portion in the air flow direction, the opening having a width at least corresponding to an effective length of the discharge wire, and

a plate-shaped member disposed in the passage at a position on an inner wall of any of the decreasing-height portion and the extension portion, the inner wall being on the corona discharger side, the plate-shaped member extending over the entire passage width.

2. The blower according to claim 1 ,

wherein the plate-shaped member is disposed in a middle portion of the extension portion with respect to the air flow direction.

3. The blower according to claim 1 ,

wherein the plate-shaped member has a shape such that a height from the inner wall is not constant along the passage width.

4. The blower according to claim 1 ,

wherein the plate-shaped member has low portions at both ends thereof along the passage width, the low portions each having a height above the inner wall lower than a height of a portion of the plate-shape member corresponding to a center of the passage width.

5. The blower according to claim 1 ,

wherein the plate-shaped member includes a portion in which a distance from an opening in the bent portion in the air flow direction varies.

6. The blower according to claim 1 ,

wherein the corona discharger includes a plurality of the discharge wires that are stretched parallel to each other with a distance therebetween, and

wherein an opening in the bent portion of the air duct is located at a position such that the air is blown onto the parallel discharge wires of the corona discharger.

7. An image forming apparatus comprising:

a corona discharger including a discharge wire that is stretched; and

a blower that blows air onto the corona discharger,

wherein the blower is the blower according to claim 1 .

8. The image forming apparatus according to claim 7 ,

wherein the corona discharger includes a plurality of the discharge wires that are stretched parallel to each other with a distance therebetween, and

wherein an opening in the bent portion of the air duct of the blower is located at a position such that air is blown onto the parallel discharge wires of the corona discharger.