Image forming apparatus comprising image density detector and toner concentration detector

Patent metadata

Field	Value
Publication number	US-9696654-B2
Application number	US-201615089275-A
Country	US
Kind code	B2
Filing date	Apr 1, 2016
Priority date	Apr 3, 2015
Publication date	Jul 4, 2017
Grant date	Jul 4, 2017

Abstract

An image forming apparatus includes an image bearer, an image forming device, a toner concentration detector, a toner supply device, an image density detector, and a controller including a memory device. At a predetermined timing before image formation is started, the controller adjusts a developing potential to adjust an image density of a detection toner image on the image bearer and drives the toner supply device or the developing device to adjust a toner concentration in the developing device. After the image formation is started, the controller drives the toner supply device to adjust the toner concentration, and, in a predetermined sheet interval, adjusts the target concentration based on the image density of the detection toner image formed in a non-image area of the image bearer. When the toner concentration is higher than the target concentration plus a threshold, the controller suspends image formation and readjusts the developing potential.

First claim

What is claimed is:

1. An image forming apparatus comprising:
an image bearer;
an image forming device including a developing device to develop, with a developer including a toner and a carrier, a latent image on a surface of the image bearer into a detection toner image, the developing device including a developer bearer disposed facing the image bearer, the developer bearer to bear the developer;
a toner concentration detector to detect a toner concentration of the developer in the developing device;
a toner supply device to supply the toner to the developing device;
an image density detector disposed facing the surface of the image bearer to detect an image density of the detection toner image on the surface of the image bearer; and
a controller including a memory device to store a target concentration for the toner concentration and a target density for the image density of the detection toner image,
wherein, at a predetermined adjustment timing before image formation is started, the controller causes the image forming device to form the detection toner image on the surface of the image bearer, adjusts a developing potential, which is a difference between a developing bias applied to the developer bearer and a latent image potential on the image bearer, to keep the image density of the detection toner image detected by the image density detector at the target density, and drives at least one of the toner supply device and the developing device to keep the toner concentration detected by the toner concentration detector at the target concentration,
wherein, after the image formation is started, the controller drives the toner supply device to keep the detected toner concentration at the target concentration,
wherein, at a predetermined sheet interval timing after the image formation is started, the controller causes the image forming device to form the detection toner image in a non-image area on the surface of the image bearer, adjusts the target concentration based on the detected image density of the detection toner image, and controls the toner concentration based on the adjusted target concentration, and
wherein, when the detected toner concentration is higher than the target concentration plus a threshold, the controller suspends the image formation, causes the image forming device to form the detection toner image on the surface of the image bearer, and readjusts the developing potential to keep the detected image density of the detection toner image at the target density.

2. The developing device according to claim 1 , further comprising:
a timer to count an image formation interval during which image formation is not executed; and
a humidity sensor to detect an ambient humidity,
wherein the controller readjusts the developing potential before image formation is started in a case where the counted image formation interval is longer than a predetermined period and the ambient humidity detected by the humidity sensor during the counted image formation interval exceeds a predetermined humidity.

3. The developing device according to claim 1 , further comprising a humidity sensor to detect an ambient humidity during an image formation interval during which image formation is not executed,
wherein the controller sets the threshold to a reduced value as the ambient humidity in the image formation interval increases.

4. The developing device according to claim 1 , further comprising a timer to count an image formation interval during which image formation is not executed,
wherein the controller sets the threshold to a reduced value as the image formation interval counted by the timer increases.

5. The developing device according to claim 1 ,
wherein, in readjusting the developing potential, the controller sets the threshold to an increased value as an accumulative pixel number of toner images formed after the image formation is started increases.

6. The developing device according to claim 1 ,
wherein the image bearer includes:
a latent image bearer; and
an intermediate transfer member,

wherein the image forming device further includes:
a writing device to form a latent image on the latent image bearer according to image data; and
a transfer device to transfer a toner image from the latent image bearer onto the intermediate transfer member, and

wherein the image density detector is disposed facing a surface of the intermediate transfer member to detect the image density of the detection toner image on the intermediate transfer member.

7. An image forming apparatus comprising:
an image bearer;
an image forming device including a developing device to develop, with a developer including a toner and a carrier, a latent image on a surface of the image bearer into a detection toner image, the developing device including a developer bearer disposed facing the image bearer, the developer bearer to bear the developer;
a toner concentration detector to detect a toner concentration of the developer in the developing device;
a toner supply device to supply the toner to the developing device;
an image density detector disposed facing the surface of the image bearer to detect an image density of the detection toner image on the surface of the image bearer; and
a controller including a memory device to store a target concentration for the toner concentration, a target density for the image density of the detection toner image, and a minimum value of the detected toner concentration after image formation is started,
wherein, at a predetermined adjustment timing before image formation is started, the controller causes the image forming device to form the detection toner image on the surface of the image bearer, adjusts a developing potential, which is a difference between a developing bias applied to the developer bearer and a latent image potential on the image bearer, to keep the image density of the detection toner image detected by the image density detector at the target density, and drives at least one of the toner supply device and the developing device to keep the detected toner concentration at the target concentration,
wherein, after the image formation is started, the controller drives the toner supply device to keep the detected toner concentration at the target concentration,
wherein, at a predetermined sheet interval timing after the image formation is started, the controller causes the image forming device to form the detection toner image in a non-image area on the surface of the image bearer, adjusts the target concentration based on the detected image density of the detection toner image, and controls the toner concentration based on the adjusted target concentration, and
wherein, when the detected toner concentration is higher than the minimum value of the toner concentration plus a threshold, the controller suspends the image formation, causes the image forming device to form the detection toner image on the surface of the image bearer, and readjusts the developing potential to keep the detected image density of the detection toner image at the target density.

8. An image forming apparatus comprising:
an image bearer;
an image forming device including a developing device to develop, with a developer including a toner and a carrier, a latent image on the image bearer into a detection toner image, the developing device including a developer bearer disposed facing the image bearer, the developer bearer to bear the developer;
a toner concentration detector to detect a toner concentration of the developer in the developing device;
a toner supply device to supply the toner to the developing device;
an image density detector disposed facing a surface of the image bearer to detect an image density of the detecti

Assignees

• Nakayama Masayoshi
• Higa Takuma
• Kunii Hiroyuki
• Sukesako Masaki
• Kamihara Kazuaki
• Aizawa Yuichi
• Katoh Masahiro
• Matsumoto Kohei
• Ricoh Co Ltd

Inventors

• Nakayama Masayoshi
• Higa Takuma
• Kunii Hiroyuki
• Sukesako Masaki
• Kamihara Kazuaki
• Aizawa Yuichi
• Katoh Masahiro
• Matsumoto Kohei

Classifications

• G03G15/556

  for toner consumption, e.g. pixel counting, toner coverage detection or toner density measurement · CPC title

• G03G15/0877

  Arrangements for metering and dispensing developer from a developer cartridge into the development unit · CPC title

• G03G15/5058

  using a test patch · CPC title

• G03G15/0849 Primary

  Detection or control means for the developer concentration · CPC title