Developer container, developing device and image forming device

1. A developer container, comprising:

an outer case;

an ejection opening that is rectangular and formed on the outer case and extends longitudinally along an axial direction of the outer case, and from which a developer is ejected by a weight of the developer, wherein

a toner ejection index that is calculated from S/μdM is equal to or more than 0.79, where μ is a degree of agglomeration of the developer, d is a compact density, M is a fill amount of the developer and S is the area of the ejection opening.

2. The developer container of claim 1 , wherein

the outer case includes a curvature region, and the ejection opening is formed in the curvature region.

3. The developer container of claim 1 , wherein

the curvature region is an arc surface that is formed about an axial center.

4. The developer container of claim 3 , wherein

in a cross-section of the outer case in a direction perpendicular to the axial center,

a setting angle θ formed by two lines connecting the axial center and respective end points of a side of the ejection opening in a lateral direction is equal to or more than 26.5° and equal to or less than 72.0°.

5. The developer container of claim 3 , further comprising:

a shutter member that opens and closes the ejection opening.

6. The developer container of claim 5 , wherein

the shutter member has a cylindrical shape and includes a rotational center on the axial center.

7. The developer container of claim 5 , wherein

the shutter member includes a shutter opening.

8. The developer container of claim 7 , wherein

the shutter member is rotatably supported inside the outer case, such that

when the shutter is rotated to a point where the shutter opening is aligned over the ejection opening, the ejection opening is open.

9. The developer container of claim 1 , wherein

the developer container contains toner therein.

10. A developing device, comprising:

the developer container of claim 1 ; and

a developing device main body to which the developer is supplied from the developer container.

11. The developing device of claim 10 , wherein

the developer container is attached to an upper part of the developing device main body.

12. The developing device of claim 10 , wherein

the developing device main body includes a developer container installation part, and

the developer container is detachable from the developer container installation part.

13. An image forming device, comprising:

the developing device of claim 10 .

14. An agitation member-free developer container, comprising:

a rectangular parallelepiped body with a semicircular arc part;

an outer case provided on the semicircular arc part;

a rectangular ejection opening provided on the semicircular arc part and the outer case, the ejection opening having an area S; and

a rotatable shutter member including a shutter opening, the shutter opening having a size larger than the area S, wherein

the outer case and the shutter member are provided concentrically with semicircular arc part and each other, and

the developer container is capable of ejecting developer through the shutter member and ejection opening without an agitation member when a condition S/μdM≧0.79 is satisfied, where μ is a degree of agglomeration of the developer, d is a compact density, and M is a fill amount of the developer.

15. The agitation member-free developer device of claim 14 , wherein

the shutter member is rotatably supported inside the outer case, and the shutter member is rotated to open and close the ejection opening.

16. The agitation member-free developer device of claim 15 , wherein

the ejection opening is open when at least a portion of the shutter opening is aligned over the ejection opening.