Abstract: A developing apparatus has: a developer container including a developer transportation unit that transports, while mixing, a developer containing a toner and a carrier along an axis of rotation by a rotatable mixing transportation member; and a cover member provided in part of the developer transportation unit so as to cover an upper portion of the mixing transportation member. A preset case disposed on top of the developer transportation unit has: a developer feed port provided on that bottom surface of the preset case which lies on a side of the developer container; and a sealing member that seals a developer feed port, the sealing member being mounted so as to be removable, when putting the preset case to use, longitudinally of the mixing transportation member. The developer feed port is provided except for a position that lies opposite to the cover member.

Abstract: A pressing wall is provided in a part of the entire area of the first carrying chamber in which a first screw member is housed. The area is opposed to a bottom wall of the first carrying chamber on the lower side in the gravity direction of the first screw member and opposed to the side walls of the first carrying chamber on both lateral sides orthogonal to a rotation axis direction of the first screw member. In the area, a toner concentration of a K developer being carried is detected by a K toner concentration sensor. The pressing wall comes into contact with, from above in the gravity direction, the K developer, which moves from a lower side to an upper side in the gravity direction according to the rotation of the first screw member, and presses the K developer downward in the gravity direction.

Abstract: An image forming apparatus capable of reducing the number of toner concentration detection errors caused by variation in the volume of a toner includes a reverse vane for transferring developer in an opposite direction and protruding from the rotary shaft member in a region where a lower side faces a bottom wall of a first transfer chamber and two lateral sides that are orthogonal to the rotary axis direction face respective side walls of the first transfer chamber, and a toner concentration detection sensor is disposed to detect the toner concentration of the developer as the developer is transferred between the reverse transfer vane and a location of the screw vane adjacent to the reverse transfer vane.

Abstract: A black developer is conveyed in a first conveyance chamber in a rotation axis direction while agitating with rotation of a first screw member. A black-toner-concentration detecting sensor detects a toner concentration of the black developer by having contact with the black developer conveyed inside the first conveyance chamber. An average of peak amounts of a pressing force on the black developer, which is conveyed inside the first conveyance chamber by the first screw member, with respect to the black toner-concentration detecting sensor is set within a range of 9.8 15 [N/m2] to 9.8 100 [N/m2].

Abstract: A black developer is conveyed in a first conveyance chamber in a rotation axis direction while agitating with rotation of a first screw member. A black-toner-concentration detecting sensor detects a toner concentration of the black developer by having contact with the black developer conveyed inside the first conveyance chamber. An average of peak amounts of a pressing force on the black developer, which is conveyed inside the first conveyance chamber by the first screw member, with respect to the black toner-concentration detecting sensor is set within a range of 9.8 15 [N/m2] to 9.8 100 [N/m2].

Abstract: A developing apparatus has: a developer container including a developer transportation unit that transports, while mixing, a developer containing a toner and a carrier along an axis of rotation by a rotatable mixing transportation member; and a cover member provided in part of the developer transportation unit so as to cover an upper portion of the mixing transportation member. A preset case disposed on top of the developer transportation unit has: a developer feed port provided on that bottom surface of the preset case which lies on a side of the developer container; and a sealing member that seals a developer feed port, the sealing member being mounted so as to be removable, when putting the preset case to use, longitudinally of the mixing transportation member. The developer feed port is provided except for a position that lies opposite to the cover member.

Abstract: A pressing wall is provided in a part of the entire area of the first carrying chamber in which a first screw member is housed. The area is opposed to a bottom wall of the first carrying chamber on the lower side in the gravity direction of the first screw member and opposed to the side walls of the first carrying chamber on both lateral sides orthogonal to a rotation axis direction of the first screw member. In the area, a toner concentration of a K developer being carried is detected by a K toner concentration sensor. The pressing wall comes into contact with, from above in the gravity direction, the K developer, which moves from a lower side to an upper side in the gravity direction according to the rotation of the first screw member, and presses the K developer downward in the gravity direction.

Abstract: In an image forming apparatus capable of reducing the number of toner concentration detection errors caused by variation in the volume of a toner below that of the related art, a reverse vane for transferring K developer in an opposite direction to a screw vane as a rotary shaft member rotates protrudes from the rotary shaft member in a region of an entire rotary axis direction region of a first screw member where a gravitational direction lower side faces a bottom wall of a first transfer chamber and two lateral sides that are orthogonal to the rotary axis direction face respective side walls of the first transfer chamber, and a K toner concentration detection sensor is disposed to detect the toner concentration of the K developer as the K developer is transferred between the reverse transfer vane and a location of the screw vane adjacent to the reverse transfer vane.