IMAGE FORMING APPARATUS

• US 20120237271A1
• Filed: 03/12/2012
• Published: 09/20/2012
• Est. Priority Date: 03/18/2011
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: SENGOKU, Kenji, Ogiyama, Hiromi, Takeuchi, Tomokazu, Haga, Hiroyoshi, Shimizu, Yasunobu
• Granted Patent: US 8,682,231 B2
• Time in Patent Office: Days
• US Class Current: 399/296
• CPC Class Codes: G03G 15/0131 for transferring a pattern to a second base
• CPC Class Codes: G03G 15/161 with means for handling the intermediate support, e.g. heating, cleaning, coating with a transfer agent
• CPC Class Codes: G03G 15/1675 with means for controlling the bias applied in the transfer nip
• CPC Class Codes: G03G 15/5058 using a test patch
• CPC Class Codes: G03G 21/0023 with electric bias
• CPC Class Codes: G03G 2215/0129 horizontal medium transport path at the secondary transfer
• CPC Class Codes: G03G 2215/1661 of transfer belt

Abstract

An image forming apparatus includes an image bearing member, an image forming unit for forming a toner image and a toner pattern comprising toner not to be transferred onto a recording medium for adjustment of a density of toner on a surface of the image bearing member, a nip forming member contacting the surface of the image bearing member to form a transfer nip therebetween, a transfer bias applicator for applying a transfer bias in which an alternating current component and a direct current component are superimposed to transfer the toner image onto the recording medium in the transfer nip, a first cleaning device to mechanically remove toner remaining on the image bearing member after passing through the transfer nip. The transfer bias applicator applies a charge eliminating bias to remove charge from toner in the toner pattern when the toner pattern passes through the transfer nip.

Claims

1. An image forming apparatus, comprising:

an image bearing member to bear a toner image and a toner pattern comprising toner not to be transferred onto a recording medium for adjustment of a density of toner on an image bearing surface of the image bearing member;

an image forming unit disposed opposite the image bearing member, to form the toner image and the toner pattern on the image bearing surface of the image bearing member, the toner pattern being formed on the image bearing member at predetermined timing;

a nip forming member to contact the image bearing surface of the image bearing member to form a transfer nip therebetween;

a transfer bias applicator to apply a transfer bias in which an alternating current component and a direct current component are superimposed to transfer the toner image onto the recording medium in the transfer nip, the transfer bias applicator applying a charge eliminating bias to remove charge from toner in the toner pattern when the toner pattern passes through the transfer nip; and

a first cleaning device to mechanically remove toner remaining on the image bearing member after the image bearing member passes through the transfer nip.

2. The image forming apparatus according to claim 1, wherein the charge eliminating bias is composed only of an alternating current component.

3. The image forming apparatus according to claim 1, further comprising:

a second cleaning device disposed opposite the nip forming member to remove toner adhered to the nip forming member,

wherein the charge eliminating bias is a superimposed bias in which an alternating current component and a direct current component are superimposed, and the direct current component thereof is smaller than the direct current component of the transfer bias.

4. The image forming apparatus according to claim 2, wherein a peak-to-peak voltage of the alternating current component of the charge eliminating bias is greater than a peak-to-peak voltage of the alternating current component of the transfer bias.

5. The image forming apparatus according to claim 1, wherein the peak-to-peak voltage of the alternating current component of the transfer bias applied by the transfer bias applicator is four times greater than an absolute value of the voltage of the direct current component.

6. The image forming apparatus according to claim 1, wherein the transfer bias applicator comprises a direct current power source to output a direct current voltage and an alternating current power source to output an alternating current voltage.

7. The image forming apparatus according to claim 1, wherein the first cleaning device includes a blade-type cleaning member.

8. The image forming apparatus according to claim 1, wherein the nip forming member is a roller, the surface of which is coated with a conductive rubber layer.

9. The image forming apparatus according to claim 3, wherein the second cleaning device includes a blade-type cleaning member.