Developing device and image forming apparatus

Patent metadata

Field	Value
Publication number	US-9733592-B2
Application number	US-201514820997-A
Country	US
Kind code	B2
Filing date	Aug 7, 2015
Priority date	Sep 4, 2014
Publication date	Aug 15, 2017
Grant date	Aug 15, 2017

Abstract

A developing device has a first circulation tank and a second circulation tank. A developer is conveyed from the first circulation tank to the second circulation tank through a first opening, while the developer is partly discharged through an outlet. The developer conveyed to the second circulation tank is conveyed back in the first circulation tank via a second opening. A first screw provided in the first circulation tank has a first vane, which exerts a force in a conveying direction of the first circulation path, in a first portion upstream from the first opening with respect to the conveying direction. The first screw has no vanes in a second portion near the first opening. The first screw has a second vane, which exerts a force in a direction opposite to the conveying direction, in a third portion adjacently downstream from the second portion. The outlet is located at a point of the first circulation tank, downstream from the second vane. A portion of the first circulation tank downstream from the second vane is not connected to the second circulation tank in a direction perpendicular to the conveying direction.

First claim

What is claimed is:

1. A developing device configured to develop an electrostatic latent image formed on an image supporting member with a developer containing toner and carrier, to be resupplied with a developer in proportion to toner consumption and to discharge a used developer, the developing device comprising:
a first circulation tank configured to discharge a part of the developer through an outlet while conveying the developer;
a second circulation tank divided from the first circulation tank by a partition wall, the second circulation tank configured to convey the developer conveyed thereto from the first circulation tank through a first opening in the partition wall and the developer resupplied thereto through a resupply port to the first circulation tank through a second opening in the partition wall such that the first circulation tank and the second circulation tank form a circulation pathway;
a first screw provided in the first circulation tank so as to convey the developer; and
a second screw provided in the second circulation tank so as to convey the developer, wherein:
the first screw has a first vane in a first portion upstream from the first opening with respect to a conveying direction of the first screw, the first vane exerting a force in the conveying direction on the developer;
the first screw has no vanes in a second portion near the first opening;
the first screw has a second vane in a third portion adjacently downstream from the second portion with respect to the conveying direction, the second vane exerting a force in a direction opposite to the conveying direction on the developer;
the outlet is located at a point of the first circulation tank, downstream from the second vane with respect to the conveying direction;
a portion of the first circulation tank downstream from the second vane with respect to the conveying direction is not connected to the second circulation tank in a direction perpendicular to the conveying direction;
the first opening extends from a point overlapping with a downstream end of the first vane with respect to the conveying direction to a downstream end of the second vane with respect to the conveying direction, such that all of the second vane overlaps with the first opening; and
the first screw receives the developer which is returned from the second circulation tank to the first circulation tank through the second portion, and conveys the received developer toward the outlet.

2. The developing device according to claim 1 , wherein the second portion of the first screw has a size in the conveying direction smaller than a pitch of the first vane.

3. The developing device according to claim 1 , wherein the second portion, which is provided with no vanes, of the first screw has a size in the conveying direction greater than a half of a pitch of the second vane.

4. The developing device according to claim 1 , wherein a screw diameter of the first portion, which is provided with the first vane, of the first screw is equal to a screw diameter of the third portion, which is provided with the second vane, of the first screw.

5. The developing device according to claim 1 , wherein a downstream end of the first portion, which is provided with the first vane, of the first screw is located at a point upstream from a middle point of the first opening with respect to the conveying direction.

6. The developing device according to claim 1 , wherein a pitch of the first vane of the first screw is greater than a pitch of the second vane of the first screw.

7. An image forming apparatus comprising:
the developing device according to claim 1 .

Assignees

• Konica Minolta Inc

Inventors

• Okazaki Futoshi

Classifications

• G03G15/0893

  in a closed loop within the sump of the developing device · CPC title

• G03G15/0891 Primary

  for conveying or circulating developer, e.g. augers · CPC title