IMAGE FORMING APPARATUS

• US 20130078014A1
• Filed: 07/24/2012
• Published: 03/28/2013
• Est. Priority Date: 09/28/2011
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Hiromi Ogiyama
• Inventors: OGIYAMA, Hiromi
• Granted Patent: US 8,755,723 B2
• Time in Patent Office: Days
• US Class Current: 399/315
• CPC Class Codes: G03G 15/0189 primary transfer to an intermediate transfer belt G03G15/0184 takes precedence
• CPC Class Codes: G03G 15/1675 with means for controlling the bias applied in the transfer nip
• CPC Class Codes: G03G 2215/0129 horizontal medium transport path at the secondary transfer

Abstract

An image forming apparatus that includes a carrier that carries a toner image, a transfer member electrically-grounded and located on outer surface of the carrier, a facing transfer member that faces an inner surface of the carrier, and a charge eliminator located downstream from the transfer member in a direction of recording medium movement and that eliminates electric charge from the recording medium. The facing transfer member has a transfer bias applied thereto that is an alternating voltage including a superimposed voltage of a direct current that has a same polarity as a toner image. The charge eliminator has one of a first alternating current voltage and a second alternating current voltage.

Claims

1. An image forming apparatus, comprising:

a carrier that carries a toner image;

a transfer member electrically-grounded and located on an outer surface of the carrier;

a facing transfer member that faces an inner surface of the carrier, wherein the facing transfer member has a transfer bias applied thereto that is an alternating current (AC) voltage including a superimposed voltage of a direct current that has a same polarity as the toner image; and

a charge eliminator located downstream from the transfer member in a direction of recording medium movement and that eliminates electric charge from the recording medium,

wherein the charge eliminator has one of a first AC voltage and a second AC voltage, the second AC voltage includes a superimposed voltage of a direct current applied thereto, and

wherein the frequency of the AC voltage applied to the facing transfer member and the AC voltage applied to the charge eliminator is set to be the same, and a phase difference between the transfer bias applied to the facing transfer member and the AC voltage applied to the charger eliminator is set to be equal to or less than ¼

cycle.

2. The image forming apparatus as claimed in claim 1, wherein a distance between a discharge point on the charge eliminator and the carrier is longer than a distance between the discharge point on the charge eliminator and the transfer member.

3. The image forming apparatus as claimed in claim 1, wherein the first or second alternating voltage applied to the facing transfer member is a constant voltage.

4. The image forming apparatus as claimed in claim 1, wherein the facing transfer member includes a roller that has a layer structure with a resistance layer around a metal core having the transfer bias applied thereto.

5. The image forming apparatus as claimed in claim 4, wherein a resistance between the metal core and a metal plate, on which the facing transfer member, is equal to or more than 10⁷Ω

.

6. The image forming apparatus as claimed in claim 4, wherein an inner surface of the carrier has a surface resistivity of 10^9.5 to 10^11.5 Ω

/□ and

volume resistivity of 10⁸ to 10¹⁰ Ω

cm.

7. An image forming method, comprising:

forming a toner image on a carrier;

transferring the toner image to a recording medium using a member to which is applied a transfer bias that is an alternating current (AC) voltage including a superimposed voltage of a direct current that has a same polarity as the toner image, and

eliminating a charge on the recording medium by applying an AC voltage to the recording medium that has a same frequency as the transfer bias and a phase difference equal to or less than ¼

cycle.

8. The image forming method as claimed in claim 7, wherein the member to which is applied the transfer bias is a facing transfer member that faces an inner surface of the carrier.

9. The image forming method as claimed in claim 7, wherein the eliminating further comprises eliminating a charge on the recording medium by using an eliminator.

10. The image forming method as claimed in claim 8, wherein the facing transfer member includes a roller that has a layer structure with a resistance layer around a metal core having the transfer bias applied thereto.

11. An image forming apparatus, comprising:

a toner image carrying means for carrying a toner image;

a transfer means for transferring the toner image to a recording medium using a member to which is applied a transfer bias that is an alternating current (AC) voltage including a superimposed voltage of a direct current that has a same polarity as the toner image;

a charge eliminating means for eliminating a charge on the recording medium by using an eliminator applying an AC voltage that has a same frequency as the transfer bias and a phase difference equal to or less than ¼

cycle.