US 7,257,338 B2Granted

Image forming apparatus

AssigneeBrother Kogyo Kabushiki Kaisha

InventorYukimasa Yoshida

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Abstract

An image forming apparatus that forms an image having proper density regardless of changes in a charged amount of developer per unit mass is provided. When image data is received in a laser printer, a main motor is driven to rotate a photosensitive drum, etc., and charging bias is applied to a charger to charge the photosensitive drum. Then, paper is fed. Predetermined current detection developing bias is applied to a developing roller for a predetermined period of time. A current value of a developing current during the application is detected. Developing bias applied to the developing roller is calculated so as to keep constant density in the printed image. Particularly, a charged amount of toner per unit mass (Q/M) is calculated from the detected current value. Based on the Q/M, the developing bias is calculated. A print process is performed by applying the developing bias to the developing roller.

Claims18

Dependent claims

An image forming apparatus comprising:

a rotary driven photoreceptor;
a charging device that charges a surface of the photoreceptor;
an exposing device that exposes the photoreceptor charged by the charging device to form an electrostatic latent image;
and
a developing device that develops, using developer, the electrostatic latent image formed on the photoreceptor by the exposing device to form a developer image,
wherein the image forming apparatus transfers the developer image on a recording material to form an image on the recording material,
the image forming apparatus further comprising:
a charged amount detection device that detects a charged amount per unit mass of the developer used by the developing device, based on a current value of the electric current flowing between a part of the photoreceptor charged by the charging device but not exposed by the exposing device and the developing device, so that the charged amount per unit mass of the developer is detected in an indirect manner;
and
a developing bias adjustment device that adjusts a developing bias to regulate a ratio of the charged amount per unit mass detected by the charged amount detection device to an electric current which flows between the developing device and the photoreceptor at the time of developing the electrostatic latent image representing a reference image.

7 more elements

An image forming apparatus comprising:

a rotary driven photoreceptor;
a charging device that charges a surface of the photoreceptor;
an exposing device that exposes the photoreceptor charged by the charging device to form an electrostatic latent image;
and
a developing device that develops, using developer, the electrostatic latent image formed on the photoreceptor by the exposing device to form a developer image,
wherein the image forming apparatus transfers the developer image on a recording material to form an image on the recording material,
the image forming apparatus further comprising:
a charged amount detection device that detects a charged amount per unit mass of the developer used by the developing device, based on a current value of the electric current flowing between a part of the photoreceptor charged by the charging device but not exposed by the exposing device and the developing device, so that the charged amount per unit mass of the developer is detected in an indirect manner;
and
a developing bias adjustment device that adjusts a developing bias, based on the charged amount per unit mass detected by the charged amount detection device.

7 more elements

Dependencies are inferred from the claim text.