Sharp Kabushiki Kaisha Corporation

Eiji Tenjiku

Yasuyuki Ishiguro

Hisashi Kunihiro

Hitoshi Nagahama

Katsuru Matsumoto

Takahiro Bito

Tatsuo Imafuku

Toshihiko Murakami

Takeshi Ohkawa

Sayaka Fujita

Takeshi Satoh

Akiko Tsujimoto

A developing device includes: a developing roller that rotates in a given rotation direction; and a regulating portion that regulates the amount of feed of developer. The developing roller includes a circumferential surface on which a regulating pole having single polarity is formed. At the regulating pole, a magnetic flux density in a direction normal to the circumferential surface of the developing roller takes a maximum in a first position on the circumferential surface in the rotation direction and takes a value half of the maximum in a second position and a third position on the circumferential surface in the rotation direction. The first position is shifted downstream from a intermediate position between the second and third positions. A tip portion of the regulating portion faces a position between the first position and the intermediate position or faces the first position.

Developing device

An image forming apparatus to which a plurality of process cartridges has a safety switch for detecting opening and closing of a front cover, stroke switches for detecting positions of the process cartridges, a display portion and a speaker for notifying a state of the process cartridge, and a control portion. The control portion has a cartridge information notifying function for, when closing of the front cover is detected by the safety switch and the process cartridge is not detected by the stroke switch, notifying information of the process cartridge. Further, the control portion has a cartridge information notifying function for notifying first notification information for replacing the process cartridge, a cartridge moving function for moving the process cartridge by a moving portion, and a cartridge information notification cancelling function for cancelling notification of the first notification information.

Image forming apparatus including cartridge position detector

When a two-component developer stored in a developer tank has been replaced, an image forming apparatus performs (a) a first formation step of forming a reference toner image on a photoreceptor, (b) a detection step of detecting an amount of toner of the reference toner image, and (c) a supply step of supplying a predetermined amount of toner to the developer tank when the amount of toner detected in the detection step is less than a threshold. Moreover, the image forming apparatus repeats the first formation step, the detection step, and the supply step until the amount of toner detected in the detection step becomes not less than the threshold. This makes it possible to provide an image forming apparatus that is stable in image quality even immediately after replacement of developers.

Image forming apparatus and density correction method

A toner for electrostatic image development, which contains toner particles in which not more than 13 percent by number of the toner particles have a particle diameter of smaller than 4 &#x3bc;m, not less than 20 percent by number of the toner particles have a particle diameter of 4 &#x3bc;m to 6 &#x3bc;m, and not more than 2.0 percent by volume of the toner particles have a particle diameter of 16 &#x3bc;m or greater. The toner particles have a volume average diameter of 4 &#x3bc;m to 9 &#x3bc;m, and at least an external additive is added to the toner particles.

Toner for electrostatic image development and image forming method using the same

The master comprises a polyester resin as a binder resin and a carbon black as a colorant having a primary particle size of 10 nm to 100 nm, is blended with 30 to 60 parts by weight of the carbon black, has a lightness L* of 20 or more; and the reflectance A at 400 nm thereof and the reflectance B at 700 nm thereof fall within the range satisfying the relation given by the following formula [1]:0.5&#x3c;&#x3c;5[1] The carbon black in the toner can be made to be present stably in the conditions such that the carbon black has a small primary particle size and is homogeneously dispersed.

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Osaka, Japan

Eiji Tenjiku