IMAGE FORMING APPARATUS

• US 20120328314A1
• Filed: 06/18/2012
• Published: 12/27/2012
• Est. Priority Date: 06/22/2011
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: SUGIMOTO, Naomi, Tanaka, Shinya
• Granted Patent: US 8,983,322 B2
• Time in Patent Office: Days
• US Class Current: 399/66
• CPC Class Codes: G03G 15/1605 using at least one intermediate support G03G15/1625 takes precedence
• CPC Class Codes: G03G 15/1675 with means for controlling the bias applied in the transfer nip
• CPC Class Codes: G03G 15/234 by inverting and refeeding the image receiving material with an image on one face to the recording member to transfer a second image on its second face, e.g. by using a duplex tray; Details of duplex trays or inverters

Abstract

An image forming apparatus including an image forming device, a transfer device, a fixing device, an inverting device, and a processor. The transfer device includes an intermediate transfer member, a nip forming member, and an electric potential difference generator to generate an electric potential difference between the intermediate transfer member and the nip forming member. The processor causes the electric potential difference generator to generate a first electric potential difference containing only a DC component when a toner image is transferred onto a first side of a recording sheet, and to generate a second electric potential difference containing a DC component and a superimposed AC component when the toner image is transferred onto a second side of the recording sheet. The second electric potential difference has an averaged absolute value per unit of time smaller than an absolute value of the first electric potential difference.

Claims

1. An image forming apparatus, comprising:

an image forming device to form a toner image;

a transfer device comprising;

an intermediate transfer member having a surface to bear the toner image formed in the image forming device;

a nip forming member to press against the intermediate transfer member to form a transfer nip between the intermediate transfer member and the nip forming member; and

an electric potential difference generator to generate an electric potential difference between the intermediate transfer member and the nip forming member,

the transfer device transferring the toner image on the surface of the intermediate transfer member onto a recording sheet clamped in the transfer nip in a state in which the electric potential difference generator generates the electric potential difference between the intermediate transfer member and the nip forming member;

a fixing device to fix the toner image on the recording sheet after the recording sheet is passed through the transfer nip;

an inverting device to invert the recording sheet after the toner image is transferred and fixed onto a first side of the recording sheet upon passing through the transfer nip and the fixing device and to then transport the recording sheet to the transfer nip again; and

a processor to cause the electric potential difference generator to generate a first electric potential difference containing only a direct current (DC) component when the toner image is transferred onto the first side of the recording sheet, and to generate a second electric potential difference containing a DC component and a superimposed alternating current (AC) component when the toner image is transferred onto a second side of the recording sheet,

wherein the second electric potential difference has an averaged absolute value per unit of time smaller than an absolute value of the first electric potential difference.

2. The image forming apparatus according to claim 1, wherein, with a frequency of the AC component in the second electric potential difference represented by f [Hz], a nip width corresponding to a length in a direction in which the recording sheet is moved in the transfer nip represented by d [mm], and a surface movement velocity of the intermediate transfer member represented by V [mm/s], the following relation obtains:

f>

(4/d)×

V

3. The image forming apparatus according to claim 1, wherein the electric potential difference generator generates the second electric potential difference having the AC component whose duty ratio in a toner returning direction in which the toner is moved from the recording sheet to the intermediate transfer member is lower than 50%.

4. The image forming apparatus according to claim 3, wherein the electric potential difference generator generates the second electric potential difference having the AC component whose duty ratio in the toner returning direction is equal to or higher than 8%.

5. The image forming apparatus according to claim 1, wherein the transfer device further comprises a facing member to contact an inner face of the intermediate transfer member to face the nip forming member via the intermediate transfer member,

wherein the electric potential difference generator outputs a transfer bias to at least one of the facing member and the nip forming member to generate the electric potential difference between the intermediate transfer member and the nip forming member.

6. The image forming apparatus according to claim 5, wherein the electric potential difference generator outputs the transfer bias to the facing member.

7. An image forming apparatus, comprising:

an image forming device to form a toner image;

a transfer device comprising;

an intermediate transfer member having a surface to bear the toner image formed in the image forming device;

a nip forming member to press against the intermediate transfer member to form a transfer nip between the intermediate transfer member and the nip forming member; and

an electric potential difference generator to generate an electric potential difference between the intermediate transfer member and the nip forming member,

the transfer device transferring the toner image on the surface of the intermediate transfer member to the recording sheet clamped in the transfer nip in a state in which the electric potential difference generator generates the electric potential difference between the intermediate transfer member and the nip forming member;

a fixing device to fix the toner image on the recording sheet after the recording sheet is passed through the transfer nip;

an inverting device to invert the recording sheet after the toner image is transferred and fixed onto a first side of the recording sheet upon passing through the transfer nip and the fixing device and to then transport the recording sheet to the transfer nip again; and

a processor to cause the electric potential difference generator to generate a first electric potential difference containing only a direct current (DC) component when the toner image is transferred onto the first side of the recording sheet, and a second electric potential difference containing either a DC component alone or a superimposed component in which an AC component is superimposed on a DC component when the toner image is transferred onto a second side of the recording sheet,

the processor selectively switching the electric potential difference generator between a second DC electric potential difference containing the DC component alone and a second superimposed electric potential difference containing the superimposed component in which the AC component is superimposed on the DC component, as the second electric potential difference,

wherein the second superimposed electric potential difference has an averaged absolute value per unit of time smaller than an absolute value of the first electric potential difference.

8. The image forming apparatus according to claim 7, wherein the processor selectively switches the electric potential difference generator between the second DC electric potential difference containing the DC component alone and the second superimposed electric potential difference containing the superimposed component in which the AC component is superimposed on the DC component when the toner image is transferred on the second side of the recording sheet, based on command from user.

9. The image forming apparatus according to claim 7, further comprising:

an ambient condition detector to detect ambient conditions in the image forming apparatus,

wherein the processor selectively switches the electric potential difference generator between the second DC electric potential difference containing the DC component alone and the second superimposed electric potential difference containing the superimposed component in which the AC component is superimposed on the DC component, based on the detection result of the ambient condition detector.

10. The image forming apparatus according to claim 9, wherein the ambient condition detector detects at least one of temperature and humidity inside the image forming apparatus.

11. The image forming apparatus according to claim 7, further comprising:

a resistance detector to detect electrical resistance of the recording sheet,

wherein the processor selectively switches the electric potential difference generator between the second DC electric potential difference containing the DC component alone and the second superimposed electric potential difference containing the superimposed component in which the AC component is superimposed on the DC component when the toner image is transferred on the second side of the recording sheet, based on the detection result of the resistance detector.

12. The image forming apparatus according to claim 7, wherein, with a frequency of the AC component in the second superimposed electric potential difference represented by f [Hz], a nip width corresponding to a length in a direction in which the recording sheet is moved in the transfer nip represented by d [mm], and a surface movement velocity of the intermediate transfer member represented by V [mm/s], the following relation obtains:

f>

(4/d)×

V

13. The image forming apparatus according to claim 7, wherein the electric potential difference generator generates the second superimposed electric potential difference having the AC component whose duty ratio in a toner returning direction in which the toner is moved from the recording sheet to the intermediate transfer member is lower than 50%.

14. The image forming apparatus according to claim 13, wherein the electric potential difference generator generates the second superimposed electric potential difference having the AC component whose duty ratio in the toner returning direction is equal to or higher than 8%.

15. The image forming apparatus according to claim 7, wherein the transfer device further comprises a facing member to contact an inner face of the intermediate transfer member to face the nip forming member via the intermediate transfer member,

wherein the electric potential difference generator outputs a transfer bias to at least one of the facing member and the nip forming member to generate the electric potential difference between the intermediate transfer member and the nip forming member.

16. The image forming apparatus according to claim 15, wherein the electric potential difference generator outputs the transfer bias to the facing member.

17. An image forming apparatus, comprising:

an image forming carrier having a surface to form and bear a toner image;

an electric potential difference generator generate an electric potential difference;

a transfer member to press against the image forming carrier to form a transfer nip between the image forming carrier and the transfer member and transfer the toner image on the surface of the image forming carrier to a recording sheet clamped in the transfer nip in a state in which the electric potential difference generator generates the electric potential difference between the image forming carrier and the transfer member;

a fixing device to fix the toner image on the recording sheet after the recording sheet is passed through the transfer nip;

an inverting device to invert the recording sheet after the toner image is transferred and fixed onto a first side of the recording sheet upon passing through the transfer nip and the fixing device and to then transport the recording sheet to the transfer nip again; and

a processor to cause the electric potential difference generator to generate a first electric potential difference containing only a direct current (DC) component when the toner image is transferred onto the first side of the recording sheet, and to generate a second electric potential difference containing a DC component and a superimposed alternating current (AC) component when the toner image is transferred onto a second side of the recording sheet,

wherein the second electric potential difference has an averaged absolute value per unit of time smaller than an absolute value of the first electric potential difference.

18. The image forming apparatus according to claim 17, wherein, with a frequency of the AC component in the second electric potential difference represented by f [Hz], a nip width corresponding to a length in a direction in which the recording sheet is moved in the transfer nip represented by d [mm], and a surface movement velocity of the image forming carrier represented by V [mm/s], the following relation obtains:

f>

(4/d)'"'"'V

19. The image forming apparatus according to claim 17, wherein the electric potential difference generator generates the second electric potential difference having the AC component whose duty ratio in a toner returning direction in which the toner is moved from the recording sheet to the image forming carrier is lower than 50%.

20. The image forming apparatus according to claim 19, wherein the electric potential difference generator generates the second electric potential difference having the AC component whose duty ratio in the toner returning direction is equal to or higher than 8%.