Image forming apparatus
An image forming apparatus includes a developer bearing member that transports developer to an electrostatic latent image formed on an image bearing member; a supply roller, including a foam elastic member, that supplies the developer to the developer bearing member; a power source device that applies a developing voltage to the developer bearing member and applies a supply voltage to the supply roller; a power source control unit that controls supply of the developer from the supply roller to the developer bearing member by controlling the developing voltage and the supply voltage; and an image control unit that controls formation of the electrostatic latent image based on image information. The image control unit controls, based on a predetermined value, a change amount of the supply voltage in a period during which image formation is performed.
1 . An image forming apparatus, comprising:
an image bearing member;
a developer bearing member configured to transport developer to an electrostatic latent image formed on the image bearing member based on image data;
a supply roller including a foam elastic member configured to come into contact with the developer bearing member to supply, to a surface of the developer bearing member, the developer charged to a normal charging polarity;
a power source device configured to apply a developing voltage to the developer bearing member and apply a supply voltage to the supply roller;
an acquisition unit configured to acquire, for each of a plurality of regions on the image bearing member in a rotation direction of the image bearing member, information regarding a print-pixel area obtained from the image data; and
a control unit configured to control supply of the developer from the supply roller to the developer bearing member by controlling the developing voltage and the supply voltage,
wherein the control unit is configured to control an image forming operation in which an image formed of the developer on the surface of the image bearing member is produced and then printed on a recording material, and
when executing the image forming operation for one sheet of the recording material, in a case in which, among the plurality of regions on the image bearing member, a second region having a second print-pixel area that is smaller than a first print-pixel area is formed after a first region having the first print-pixel area, the control unit controls the supply voltage so that the supply voltage is continuously increased toward the normal charging polarity from the first region to the second region, and an increase amount per unit length in the rotation direction of the image bearing member of the supply voltage within the first region is greater than an increase amount per unit length in the rotation direction of the image bearing member of the supply voltage within the second region.
2 . The image forming apparatus according to claim 1 ,
wherein the acquisition unit acquires an amount of the developer used for forming an image based on the image data when acquiring the information.
3 . The image forming apparatus according to claim 1 ,
wherein the control unit controls a change amount of the supply voltage per distance in a direction orthogonal to a rotation axis of the developer bearing member.
4 . The image forming apparatus according to claim 1 ,
wherein the control unit performs control such that the supply voltage is changed by a predetermined change amount in a high-print-percentage section in which the print percentage is equal to or greater than a threshold determined through analysis of the image data, and the supply voltage is constant in a low-print-percentage section in which the print percentage is less than the threshold.
5 . The image forming apparatus according to claim 1 ,
wherein the control unit performs control such that the higher a print percentage in an image to be formed based on the image data is, the greater the change amount of the supply voltage is.