Image forming apparatus

1. An image forming apparatus to which a developer supplying container having a developer stored in the developer supplying container is detachably attached, the image forming apparatus comprising:

an image bearing member;

a developer bearing member;

a stirring member that is movable;

a frame that supports the developer bearing member and constitutes a developer housing chamber that contains a developer to be supplied to the developer bearing member, wherein the developer housing chamber has an attachment port to which the developer supplying container is detachably attached and, by using the developer supplied from the developer housing chamber, the developer bearing member develops an electrostatic latent image formed on the image bearing member; and

a cover movable between a first position and a second position,

wherein, the first position is a position at which the cover covers the attachment port, and the second position is a position at which the cover opens the attachment port to allow the developer supplying container to be attached to the attachment port,

wherein, when the cover is at the second position and the developer supplying container is attached to the attachment port so as to allow an interior of the developer supplying container and the developer housing chamber to communicate with each other, the developer stored in the developer supplying container is moved to the developer housing chamber due to own weight of the stored developer, and

wherein, in a state in which the developer supplying container is attached to the attachment port, an upper portion of the developer supplying container is located over the first position so that the cover is not movable from the second position to the first position in the image forming apparatus and, in a state in which the developer supplying container is detached from the attachment port, the cover is movable from the second position to the first position.

2. The image forming apparatus according to claim 1 , further comprising:

an output device configured to provide an output urging developer replenishment,

wherein the stirring member is rotatable, and configured to move developer within a rotation radius and feed the moved developer toward the developer bearing member,

wherein, within a space on an inner side of the frame, the stirring member serves as a rotating and moving member that is disposed at a position closest to the attachment port, and

wherein, when the developer is supplied from the developer supplying container after the developer replenishment is urged, a level of the developer in the developer housing chamber after the developer replenishment is positioned above a rotation center of the stirring member in a direction of gravitational force.

3. The image forming apparatus according to claim 1 ,

wherein the stirring member has a shape that extends in a direction intersecting a rotational direction of the stirring member and feeds developer toward the developer bearing member, and

wherein, the stirring member is only one that is disposed in a space, with respect to a moving direction of the developer by the gravitational force, upstream from the image bearing member and downstream from a supply port of the developer supplying container when the developer supplying container is attached to the attachment port.

4. The image forming apparatus according to claim 1 , wherein the stirring member is configured to be rotated by force provided from external driving force supply device.

5. The image forming apparatus according to claim 1 , further comprising a controller configured to detect that the cover is open or that the developer supplying container is attached to the attachment port,

wherein, in response to a detection by the controller, the controller keeps operation of the image forming apparatus stopped.

6. The image forming apparatus according to claim 1 , wherein an initial amount of the developer contained in the developer supplying container is smaller than a maximum amount of the developer that can be contained in the developer housing chamber.

7. The image forming apparatus according to claim 1 , wherein an initial amount of the developer contained in the developer supplying container is smaller than an amount obtained by subtracting (i) an amount of the developer contained in the developer housing chamber at the time when a notification urging developer replenishment is provided (ii) from a maximum amount of the developer that can be contained in the developer housing chamber.

8. The image forming apparatus according to claim 1 ,

wherein an initial amount of the developer contained in the developer supplying container is larger than an amount obtained by subtracting (i) an amount of the developer contained in the developer housing chamber at the time when a notification urging developer replenishment is provided (ii) from an amount of the developer that can be contained in a lower portion of the developer housing chamber, and

wherein the lower portion is a portion that lies below a plane that passes through a highest point of the developer bearing member when the developer housing chamber assumes a position for image formation.

9. The image forming apparatus according to claim 1 , wherein a charge amount of developer at the time when a notification urging developer replenishment is provided is less than 55% of a charge amount of the developer contained in the developer housing chamber at an initial stage.

10. The image forming apparatus according to claim 9 , further comprising a current detecting unit configured to detect an electric current generated along with movement of the developer,

wherein a detection result of the current detecting unit is used to determine that the charge amount is less than 55% of the charge amount of the developer contained in the developer housing chamber at the initial stage.

11. The image forming apparatus according to claim 1 , wherein the developer in the developer supplying container and the developer housing chamber is a toner having toner particles containing a binder resin and a coloring agent, and the toner has a Martens hardness of 200 MPa or more and 1100 MPa or less as measured at a maximum load of 2.0×10 −4 N.

12. The image forming apparatus according to claim 11 , wherein the toner particles each include a surface layer containing an organic silicon polymer and a toner core particle covered by the surface layer, and an average number of carbon atoms directly bonded to silicon atoms in the organic silicon polymer is 1 or more and 3 or less per silicon atom.

13. The image forming apparatus according to claim 12 , wherein an adhering ratio of the organic silicon polymer relative to the toner particles is 90% or more.

14. The image forming apparatus according to claim 1 , wherein, when the cover is at the first position, an upper surface of the cover is a part of a top surface of the image forming apparatus.

15. An image forming apparatus to which a developer supplying container having a developer stored in the developer supplying container is detachably attached, the image forming apparatus comprising:

an image bearing member;

a developer bearing member;

a frame that supports the developer bearing member and constitutes a developer housing chamber that contains a developer to be supplied to the developer bearing member, wherein the developer housing chamber has an attachment port to which the developer supplying container is detachably attached and, by using the developer supplied from the developer housing chamber, the developer bearing member develops an electrostatic latent image formed on the image bearing member; and

a cover movable between a first position and a second position,

wherein, the first position is a position at which the cover covers the attachment port, and the second position is a position at which the cover opens the attachment port to allow the developer supplying container to be attached to the attachment port,

wherein, when the developer supplying container is attached to the attachment port and an interior of the developer supplying container and the developer housing chamber are allowed to communicate with each other, the developer stored in the developer supplying container is moved to the developer housing chamber due to own weight of the stored developer, and

wherein the developer in the developer supplying container and the developer housing chamber is a toner that has toner particles containing a binder resin and a coloring agent, and is a toner that has a Martens hardness of 200 MPa or more and 1100 MPa or less as measured at a maximum load of 2.0×10 −4 N.