Developing unit and image forming apparatus which forces consumption of toner

• US 7,672,602 B2
• Filed: 08/24/2006
• Issued: 03/02/2010
• Est. Priority Date: 11/10/2005
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Fujimori, Kohta, Ariizumi, Osamu, Morimoto, Ryohta, Uchida, Fukutoshi, Kobayashi, Shinji, Ishibashi, Hitoshi, Hasegawa, Shin, Enami, Takashi, Takeuchi, Nobutaka, Tanaka, Kayoko, Hirayama, Yushi, Kobayashi, Kazumi, Kato, Shinji, Watanabe, Naoto
• Primary Examiner(s): GRAINGER, QUANA MASHELL
• Application Number:
  US11/508,823
• Publication Number:
  US 20070104499A1
• Time in Patent Office: 1,286 Days
• Field of Search: 399/27, 399/29
• US Class Current: 399/27
• CPC Class Codes: G03G 15/0849 Detection or control means for the developer concentration
• CPC Class Codes: G03G 15/0856 Detection or control means for the developer level
• CPC Class Codes: G03G 15/5062 by measuring the characteristics of an image on the copy material
• CPC Class Codes: G03G 15/556 for toner consumption, e.g. pixel counting, toner coverage detection or toner density measurement
• CPC Class Codes: G03G 2215/00755 of sheet toner density

Abstract

A developing unit supplies toner from a developing roller to an electrostatic latent image formed on an image carrier, and creates a visual image. A forced consumption unit causes, when a proportion of number of pixels used for forming the electrostatic latent image for a maximum image effective-width is equal to or less than a predetermined value, a forced consumption of toner by an amount corresponding to a difference between a toner amount corresponding to the number of pixels and a predetermined toner consumption amount. The forced consumption unit adds toner of an amount used in the forced consumption to an amount of toner to be supplied in a next imaging process.

Claims

1. A developing unit that supplies toner from a developing roller to an electrostatic latent image formed on an image carrier, and creates a visual image, the developing unit comprising:

a forced consumption unit that causes a forced consumption of a quantity of forcedly consumed toner, the forced consumption occurring when a proportion of a number of pixels used for forming a maximum effective-width of a first electrostatic latent image formed on the image carrier is equal to, or less than, a threshold value, wherein

the forced consumption unit determines a first quantity of forcedly consumed toner, the first quantity of forcedly consumed toner corresponding to a difference between a quantity of toner corresponding to a number of pixels of the first electrostatic latent image and a first predetermined quantity of toner,

the forced consumption unit causes a correction in the first quantity of forcedly consumed toner based on an average image area ratio for a plurality of images, the corrected first quantity of forcedly consumed toner corresponding to a difference between a quantity of toner corresponding to an average number of pixels for the plurality of images and a second predetermined quantity of toner, and

the forced consumption unit adds, to the developing roller, the corrected first quantity of forcedly consumed toner to a quantity of toner to be supplied in forming on the image carrier a next electrostatic latent image.

2. The developing unit according to claim 1, wherein the forced consumption unit causes the forced consumption of the toner by forming a latent image of a halftone dot-shaped pattern on a non-image portion on the image carrier and visualizing the latent image.

4. The developing unit according to claim 1, wherein the image area ratio is calculated by Image area ratio (maximum image effective-width)(%)={image area (cm²)/((length of transfer paper in sub scanning direction (cm))×

maximum image effective-width (cm))}×

100.

5. The developing unit according to claim 4 wherein when the image area ratio is used, an average value per “

n”

paper(s) is used, and the image area ratio is calculated by “

Image area ratio (progressive average)={image ratio (progressive average)×

(n−

1)+image area ratio (a newest maximum image effective-width)}/n.”

6. The developing unit according to claim 5, wherein the forced consumption unit determines whether a forced consumption is required or not based on the expressions:

Image area ratio (progressive average)≧

image area ratio (threshold value); and

Image area ratio (progressive average)<

image area ratio (threshold value).

7. The image forming apparatus according to claim 2, wherein the image area ratio is calculated by Image area ratio (maximum image effective-width)(%)={image area (cm²)/(length of transfer paper in sub scanning direction (cm))×

(maximum image effective-width (cm))}×

100.”

8. The image forming apparatus according to claim 7, wherein when the image area ratio is used, an average value per “

n”

paper(s) is used, and the image area ratio is calculated by “

Image area ratio (progressive average)={Image area ratio (progressive average)×

(n−

1)+image area ratio (a newest maximum image effective-width)}/n.”

9. The image forming apparatus according to claim 8, wherein the forced consumption unit determines whether a forced consumption is required or not based on the expressions:

Image area ratio (progressive average)≧

image area ratio (threshold value); and

Image area ratio (progressive average)<

image area ratio (threshold value).

3. An image forming apparatus comprising:

a developing unit that supplies toner from a developing roller to an electrostatic latent image formed on an image carrier, and creates a visual image thereon, wherein the developing unit includes a forced consumption unit that causes a forced consumption of a quantity of forcedly consumed toner, the forced consumption occurring when a proportion of a number of pixels used for forming a maximum effective-width of a first electrostatic latent image formed on the image carrier is equal to, or less than, a threshold value, wherein

the forced consumption unit determines a first quantity of forcedly consumed toner, the first quantity of forcedly consumed toner corresponding to a difference between a quantity of toner corresponding to a number of pixels of the first electrostatic latent image and a first predetermined quantity of toner,

the forced consumption unit causes a correction in the first quantity of forcedly consumed toner based on an average image area ratio for a plurality of images, the corrected first quantity of forcedly consumed toner corresponding to a difference between a quantity of toner corresponding to an average number of pixels for the plurality of images and a second predetermined quantity of toner, and

the forced consumption unit adds, to the developing roller, the corrected first quantity of forcedly consumed toner to a quantity of toner to be supplied in forming on the image carrier a next electrostatic latent image.

10. The image forming apparatus according to claim 3, wherein the forced consumption unit causes the forced consumption of the toner by forming a latent image of a halftone dot-shaped pattern on a non-image portion on the image carrier and visualizing the latent image.