DEVELOPING DEVICE

• US 20180335722A1
• Filed: 05/17/2018
• Published: 11/22/2018
• Est. Priority Date: 05/22/2017
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Ariizumi, Osamu, Tsuda, Shunsuke, Arakawa, Mitsuyoshi, Ootsuka, Masahiro, Saito, Fumiyoshi
• Granted Patent: US 10,642,192 B2
• Time in Patent Office: Days
• CPC Class Codes: G03G 15/0808 characterised by the developer supplying means, e.g. structure of developer supply roller
• CPC Class Codes: G03G 15/0812 characterised by the developer regulating means, e.g. structure of doctor blade
• CPC Class Codes: G03G 15/0865 Arrangements for supplying new developer
• CPC Class Codes: G03G 15/0877 Arrangements for metering and dispensing developer from a developer cartridge into the development unit
• CPC Class Codes: G03G 15/0891 for conveying or circulating developer, e.g. augers
• CPC Class Codes: G03G 15/0893 in a closed loop within the sump of the developing device
• CPC Class Codes: G03G 2215/083 with two opposed pitches on one shaft
• CPC Class Codes: G03G 2215/0833 with varying pitch on one shaft

Abstract

A developing device includes a developer carrying member, a first chamber, a second chamber, a first communicating portion, a second communicating portion, and a feeding screw, provided in the second chamber, including a feeding portion having a first helical blade and including a returning portion having a second helical blade in the form of a plurality of threads, the feeding portion and the returning portion being provided so that a boundary portion therebetween opposes the second communicating portion. The first helical blade and the second helical blade satisfy the following relationship: P2≥P1, where P1 is a pitch of the first helical blade and P2 is a pitch of the second helical blade.

Claims

1. A developing device comprising:

a developer carrying member configured to carry a developer;

a first chamber configured to accommodate the developer for supplying the developer to said developer carrying member;

a second chamber configured to form a circulating path of the developer;

a first communicating portion configured to deliver the developer from said first chamber to said second chamber;

a second communicating portion configured to deliver the developer from said second chamber to said first chamber; and

a feeding screw, provided in said second chamber, including a feeding portion having a first helical blade configured to feed the developer in a first direction from said first communicating portion toward said second communicating portion and including a returning portion having a second helical blade in the form of a plurality of threads configured to feed the developer fed to said feeding portion in a second direction opposite to the first direction, said feeding portion and said returning portion being provided as parts of said feeding screw so that a boundary portion between said feeding portion and said returning portion opposes said second communicating portion,

wherein said first helical blade and said second helical blade satisfy the following relationship;

P2≥

P1,

where P1 is a pitch of said first helical blade and P2 is a pitch of said second helical blade.

2. A developing device according to claim 1, wherein said second helical blade satisfies the following relationship:

n×

L>

P2,

where n is a number of threads of said second helical blade and L is a length of said second helical blade with respect to the first direction.

3. A developing device according to claim 1, wherein each of a part of said feeding portion and said returning portion opposes said second communicating portion.

4. A developing device according to claim 1, wherein said feeding screw includes said first helical blade and said second helical blade which are formed on the same rotation shaft so that said first helical blade is normally wound and said second helical blade is reversely wound to said first helical blade.

5. A developing device according to claim 1, wherein said feeding screw satisfies the following relationship:

L≤

P2,

where L is a length of said second helical blade with respect to the first direction.

6. A developing device according to claim 1, wherein with respect to the first direction, a downstream end of a carrying region where said developer carrying member carries the developer is positioned downstream of an upstream end of said second communicating portion and upstream of an upstream end of said second helical blade.

7. A developing device according to claim 1, wherein said feeding screw is formed so that a downstream end of said first helical blade and an upstream end of said second helical blade are spaced from each other with respect to the first direction, and

wherein with respect to the first direction, a downstream end of a carrying region where said developer carrying member carries the developer is positioned downstream of an upstream end of said second communicating portion and upstream of an intermediary position between the downstream end of said first helical blade and the upstream end of said second helical blade.

8. A developing device according to claim 1, wherein said feeding screw includes a plate-like member projecting from a rotation shaft thereof in a radial direction and extending in the first direction, said plate-like member being formed in a gap between a downstream end of said first helical blade and an upstream end of said second helical blade with respect to the first direction.

9. A developing device according to claim 1, wherein when said feeding screw is a first feeding screw including a first feeding portion having said first helical blade configured to feed the developer in the first direction and including a first returning portion having said second helical blade in the form of the plurality of threads configured to feed the developer in the second direction, said developing device includes a second feeding screw, provided in said first chamber, including a second feeding portion having a third helical blade configured to feed the developer in the second direction and including a second returning portion having a fourth helical blade in the form of a plurality of threads configured to feed the developer fed to said second feeding portion in the first direction, and

wherein said second feeding screw is provided so that an upstream end of said fourth helical blade is positioned between an upstream end and a downstream end of said first communicating portion with respect to the second direction, and is formed so as to satisfy the following relationships:

P4≥

P3 and nA×

LA>

P4,

where P3 is a pitch of said third helical blade, P4 is a pitch of said fourth helical blade, nA is a number of threads of said fourth helical blade, and LA is a length of said fourth helical blade with respect to the second direction.

10. A developing device according to claim 1, further comprising a driving means configured to rotate said feeding screw with a first number of rotations and a second number of rotations larger than the first number of rotations.