| CPC G03G 21/20 (2013.01) [G03G 15/0865 (2013.01); G03G 15/0891 (2013.01); G03G 15/0893 (2013.01); G03G 15/0896 (2013.01); G03G 21/1814 (2013.01); G03G 21/206 (2013.01); G03G 2221/1645 (2013.01); G03G 2221/1648 (2013.01)] | 10 Claims |

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1. A developing device to develop a latent image formed on a surface of an image bearer, the developing device comprising:
a plurality of conveyance passages in which developer stored in the developing device is circulated and is conveyed in a longitudinal direction of the developing device;
an opening portion disposed in one conveyance passage of the plurality of conveyance passages, the opening portion communicating with an outside of the developing device; and
a filter fitted in the opening portion, the filter having both a collecting ability to collect the developer and a ventilation ability to ventilate the one conveyance passage to the outside of the developing device,
wherein the collecting ability of the filter is higher in a high-bulk portion in which bulk of the developer increases in the one conveyance passage than in a low-bulk portion in which the bulk of the developer decreases in the one conveyance passage, and
wherein the ventilation ability of the filter is lower in the high-bulk portion than in the low-bulk portion.
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