Image forming apparatus that utilizes an adjustable alternately switching voltage

Patent metadata

Field	Value
Publication number	US-9639032-B2
Application number	US-201615041574-A
Country	US
Kind code	B2
Filing date	Feb 11, 2016
Priority date	Feb 24, 2015
Publication date	May 2, 2017
Grant date	May 2, 2017

Abstract

An image forming apparatus includes an image bearer, a transfer device, and a transfer bias power source. The transfer bias power source is configured to output an alternately switching voltage that alternates between a transfer-directional voltage having a polarity to transfer the toner image from the image bearer onto the recording medium and a return-directional voltage having an opposite polarity to the polarity of the transfer-directional voltage. The transfer bias power source is configured to reduce a target value of Vdc as an image area ratio of a toner image to be printed increases, and to increase the target value of Vdc as the image area ratio reduces, where Vdc is an average value of the alternately switching voltage during printing.

First claim

What is claimed is:

1. An image forming apparatus, comprising:
an image bearer having a surface to bear a toner image to be printed;
a transfer device that contacts the surface of the image bearer to form a transfer nip; and
a transfer bias power source that outputs a transfer bias to transfer the toner image from the image bearer onto a recording medium interposed between the transfer device and the image bearer in the transfer nip, wherein
the transfer bias power source outputs an alternately switching voltage that alternates between a transfer-directional voltage having a polarity to transfer the toner image from the image bearer onto the recording medium and a return-directional voltage having an opposite polarity to the polarity of the transfer-directional voltage, and
the transfer bias power source reduces a target value of Vdc as an image area ratio of the toner image increases, the transfer bias power source increases the target value of Vdc as the image area ratio reduces, and the transfer bias power source increases the target value of Vdc as an edge ratio of the toner image increases, where Vdc is an average value of the alternately switching voltage during printing.

2. The image forming apparatus according to claim 1 , wherein the transfer bias power source increases the target value of Vdc as an image area ratio of the toner image to an entire longitudinal area of the transfer nip reduces.

3. The image forming apparatus according to claim 1 , wherein the transfer bias power source increases the target value of Vdc as a ratio of a line-and-character image to a solid image of the toner image increases.

4. The image forming apparatus according to claim 1 , wherein a time period of application of the transfer-directional voltage is longer than a time period of application of the return-directional voltage.

5. The image forming apparatus according to claim 1 , wherein the transfer bias power source
switches between a first mode to output only a direct current voltage and a second mode to output the alternately switching voltage,
maintains the target value of Vdc constant irrespective of the image area ratio in the first mode, and
increases the target value of Vdc as the image area ratio reduces in the second mode.

6. The image forming apparatus according to claim 1 , wherein the transfer bias power source outputs a superimposed voltage in which an alternating component is superimposed on a direct component, the direct component to be under constant current control.

7. The image forming apparatus according to claim 1 , further comprising:
control circuitry that controls a superimposed voltage, in which an alternating component is superimposed on a direct component, that is output from the transfer bias power source, wherein
the control circuitry controls the transfer bias power source to reduce an amount of the direct current component as the target value of Vdc decreases, and to increase the amount of the direct current component as the target value of Vdc increases.

8. The image forming apparatus according to claim 1 , wherein the toner image is a color image.

9. The image forming apparatus according to claim 7 , wherein
the control circuitry receives a detection signal from a sensor that detects a toner adhesion amount on the image bearer, and
the control circuitry adjusts the direct current component of the superimposed voltage according to the toner adhesion amount.

10. An image forming apparatus, comprising:
an image bearer having a surface to bear a toner image to be printed;
a transfer device that contacts the surface of the image bearer to form a transfer nip; and
a transfer bias power source that outputs a transfer bias to transfer the toner image from the image bearer onto a recording medium interposed between the transfer device and the image bearer in the transfer nip, wherein
the transfer bias power source outputs an alternately switching voltage that alternates between a transfer-directional voltage having a polarity to transfer the toner image from the image bearer onto the recording medium and a return-directional voltage having an opposite polarity to the polarity of the transfer-directional voltage,
the transfer bias power source switches between a first mode to output only a direct current voltage and a second mode to output the alternately switching voltage,
the transfer bias power source reduces a target value of Vdc as an image area ratio of the toner image increases, the transfer bias power source increases the target value of Vdc as the image area ratio reduces, the transfer bias power source reduces the target value of Vdc as the image area ratio reduces in the first mode, and the transfer bias power source increases the target value of Vdc as the image area ratio reduces in the second mode, where Vdc is an average value of the alternately switching voltage during printing.

11. The image forming apparatus according to claim 10 , further comprising:
control circuitry that controls a superimposed voltage, in which an alternating component is superimposed on a direct component, that is output from the transfer bias power source, wherein
the control circuitry controls the transfer bias power source to reduce an amount of the direct current component as the target value of Vdc decreases, and to increase the amount of the direct current component as the target value of Vdc increases.

12. The image forming apparatus according to claim 11 , wherein
the control circuitry receives a detection signal from a sensor that detects a toner adhesion amount on the image bearer, and
the control circuitry adjusts the direct current component of the superimposed voltage according to the toner adhesion amount.

13. An image forming apparatus, comprising:
a transfer device that contacts a surface of an image bearer to form a transfer nip, the surface carrying a toner image to be printed; and
a transfer bias power source configured to
output a transfer bias to transfer the toner image from the image bearer onto a recording medium interposed between the transfer device and the image bearer in the transfer nip;
output an alternately switching voltage that alternates between a transfer-directional voltage having a polarity to transfer the toner image from the image bearer onto the recording medium and a return-directional voltage having an opposite polarity to the polarity of the transfer-directional voltage;
reduce a target value of Vdc as an image area ratio of the toner image increases, Vdc being an average value of the alternately switching voltage during printing of the tone image;
increase the target value of Vdc as the image area ratio reduces; and
increase the target value of Vdc as an edge ratio of the toner image increases.

14. The image forming apparatus according to claim 13 , wherein the transfer bias power source increases the target value of Vdc as an image area ratio of the toner image to an entire longitudinal area of the transfer nip reduces.

15. The image forming apparatus according to claim 13 , wherein the transfer bias power source increases the target value of Vdc as a ratio of a line-and-character image to a solid image of the toner image increases.

16. The image forming apparatus according to claim 13 , wherein a time period of application of the transfer-directional voltage is longer than a time period of application of the return-directional voltage.

17. The image forming apparatus according to claim 13 , wherein the transfer bias power source
switches between a first mode to output only a direct current volt

Assignees

• Tanaka Shinya
• Ricoh Co Ltd

Inventors

• Tanaka Shinya

Classifications

• G03G15/1675

  with means for controlling the bias applied in the transfer nip · CPC title

• G03G15/1665 Primary

  by introducing the second base in the nip formed by the recording member and at least one transfer member, e.g. in combination with bias or heat · CPC title

• G03G15/161 Primary

  with means for handling the intermediate support, e.g. heating, cleaning, coating with a transfer agent · CPC title