A waste toner collecting device includes an intermediate collection box, a conveying path, a conveying screw, an exhaust path and a floating toner collection chamber. The conveying path is provided in the intermediate collection box. The conveying screw is rotatable in the conveying path. Through the exhaust path, air containing a floating toner is sucked and passed. The floating toner collection chamber is provided on a part of the exhaust path in the intermediate collection box. The floating toner collection chamber has a discharge opening opened to an inside of the intermediate collection box and a discharge door. Rotation of the conveying screw in a normal direction turns the discharge door into a storage position where the discharge opening is closed. Rotation of the conveying screw in a reverse direction turns the discharge door into a discharge position where the discharge opening is opened.

An image forming apparatus includes: an image bearing member; a developing unit; a discharge portion which is provided in the developing unit and configured to discharge a developer in the developing unit to the outside of the developing unit; a collection portion which collects the developer discharged from the discharge portion; a conveying pipe which is separable from the developing unit, includes a conveying screw therein, and conveys the developer discharged from the discharge portion to the collection portion; and a toner density sensor which detects toner density in the conveying pipe and of which a detection surface is positioned below a rotational axis of the conveying screw in a vertical direction, wherein the developing unit is removed from the image forming apparatus in a state in which the conveying pipe and the toner density sensor remain in the image forming apparatus.

A developing device has a developer container, a first stirring/transporting member, a second stirring/transporting member, a developer carrying member, a developer supply port, a developer discharge port, a regulating portion, and a height adjustment opening. The developer container has a partition partitioning between first and second transport chambers, and communication portions through which the first and second transport chambers mutually communicate. The first and second stirring/transporting members stir and transport developer in the first and second transport chambers in opposite directions respectively. The regulating portion regulates movement of the developer toward a developer discharge port. The height adjustment opening is formed in the partition, and when the height of the developer in the second transport chamber is equal to or higher than a predetermined height, part of the developer passes through the height adjustment opening and moves to the first transport chamber.

A developing device includes a developer holder that holds a developer containing toner and carrier and being supplied to an image holder forming an electrostatic latent image; and a conveyance section that agitates and conveys the developer flowing in from an inlet using a rotation member to cause the developer to flow out toward the developer holder at an outlet, that includes, as a part constituting a portion of the rotation member, a first blade part for conveyance to the outlet and a second blade part for conveyance in a direction opposite to the outlet, and in which a greater amount of the developer flows in from the inlet than the developer flows out from the outlet.

A developing device includes a developer carrying member, a first chamber for feeding developer to the developer carrying member, a second chamber for collecting developer from the developer carrying member, and a feeding member provided rotatably in the first chamber for feeding the developer. The feeding member includes a rotation shaft and a spiral blade wound helically in a developer feeding direction. The feeding member includes a first region corresponding to a developer coating region of the developer carrying member, a second region provided downstream of the first region with respect to a feeding direction of the feeding member, and a third region provided upstream of the first region. An average feeding power per unit driving time of the feeding member is set at a smaller value in the first region than in the second region and in the third region.

A developing device includes a development container, a first conveyance member, a second conveyance member, and a developer carrier. The second conveyance member includes a regulation blade that is formed downstream of a second conveyance blade with respect to a second direction which is a conveyance direction of the developer, and that conveys the developer in a direction opposite to the second conveyance blade. A developer replenishment port is formed in an upper surface of the development container, and at least part of an opening length thereof in the second direction is included in a regulation area which is an area inside a second conveyance chamber where the regulation blade is disposed. At least part of the developer replenished through the developer replenishment port falls into both a first conveyance chamber and the regulation area.

A development device includes a development container having a first conveyance chamber and a second conveyance chamber above it, first and second stirring conveyance members that stir developer in the first and second conveyance chambers and convey it in the opposite directions, a developer carrying member that carries on its surface the developer in the second conveyance chamber, and a regulation blade. Feeding of the developer to the developer carrying member and collection of the developer from the developer carrying member are performed in the second conveyance chamber. A horizontal straight line L1 through the center of the rotation shaft of the second stirring conveyance member is above a horizontal straight line L2 through the center of the rotation shaft of the developer carrying member and the straight line L2 is above a horizontal straight line L3 through the center of the rotation shaft of the first stirring conveyance member.

A development device includes a developer container having a first conveyance chamber and a second conveyance chamber above it, a first stirring-conveyance member, a second stirring-conveyance member, a developer carrying member, and a regulation blade. The developer carrying member includes a magnetic member having a regulation pole, a main pole, a release pole, and an attracting pole. A release start position at which the magnetic force of the release pole becomes 5 [mT] or less is below a straight line L1 horizontally passing through the center of a rotation shaft of the second stirring-conveyance member and when the central angle of a developer releasing region where the magnetic force between the release pole and the attracting pole is 5 [mT] or less is represented by X [] and the peak magnetic force of the attracting pole is represented by Y [mT], Y2.1X32.7 is satisfied.

A developing device includes a developer container, a developer carrier, and a stirring/conveying member. The developer container includes: a lower housing having a first accommodating portion and a first edge portion formed in a top end portion of it; and an upper housing having a second accommodating portion and a second edge portion formed in a bottom end portion of it. The first edge portion has a depression extending along the first edge portion, a first contact face formed inward of the depression, and a first opposite face formed outward of the depression. The second edge portion has an elevation inserted in the depression, a second contact face making contact with the first contact face, and a second opposite face facing the first opposite face. When the first and second contact faces are in contact, the first and second opposite faces face each other across a predetermined interval.