Transfer unit, transfer method, and image forming apparatus

A transfer unit, comprising:

• an intermediate transfer member that (i) holds a toner image that has been transferred, at a primary transfer part, from a toner image holding member and (ii) rotates to move a toner image holding surface holding the toner image;
• a secondary transfer member that comes into contact, at a secondary transfer part, with the intermediate transfer member;
• and
• an intermediate transfer member cleaning unit that mechanically removes and collects toner by using a cleaning member coming into contact with the toner image holding surface of the intermediate transfer member,
• the transfer unit transferring the toner image from the intermediate transfer member to a sheet conveyed to the secondary transfer part formed between the intermediate transfer member and the secondary transfer member,
• wherein
• the transfer unit further comprises,
• a secondary transfer member cleaning unit (i) having a power source for generating (a) a first voltage for generating an electric field that transfers normally-charged toner from the secondary transfer member to the intermediate transfer member and (b) a second voltage for generating an electric field that transfers oppositely-charged toner from the secondary transfer member to the intermediate transfer member, and (ii) sequentially applying the first voltage and the second voltage to the secondary transfer member by using the power source, and
• an intermediate transfer member displacing unit for bringing the intermediate transfer member into contact with the toner image holding member or separating the intermediate transfer member from the toner image holding member,
• wherein the intermediate transfer member displacing unit separates the intermediate transfer member from the toner image holding member while the secondary transfer member cleaning unit is applying one of the first voltage and the second voltage to the secondary transfer member.

A transfer method, comprising:

• transferring a toner image from an intermediate transfer member to a sheet conveyed to the secondary transfer part formed between the intermediate transfer member and the secondary transfer member, the intermediate transfer member being provided to (a) hold a toner image that has been transferred, at a primary transfer part, from a toner image holding member and (b) rotate to move the surface holding the toner image, and the secondary transfer member being provided to comes into contact, at a secondary transfer part, with the intermediate transfer member;
• removing and collecting the toner from the toner holding surface of the intermediate transfer member;
• and
• sequentially applying (i) a first electric field for transferring normally-charged toner from the secondary transfer member to the intermediate transfer member and (ii) a second electric field for transferring oppositely-charged toner from the secondary transfer member to the intermediate transfer member;
• and
• separating the intermediate transfer member from the toner image holding member during the sequentially applying step, the separating step separating the intermediate transfer member from the toner image holding member while applying one of the first electric field and the second electric field to the intermediate transfer member.

An image forming apparatus, comprising:

• a transfer unit (i) including,
• an intermediate transfer member that (a) holds a toner image that has been transferred, at a primary transfer part, from a toner image holding member and (b) rotates to move a toner image holding surface holding the toner image,
• a secondary transfer member that comes into contact, at a secondary transfer part, with the intermediate transfer member, and
• intermediate transfer member cleaning means for removing and collecting toner from the toner image holding surface of the intermediate transfer member, and (ii) transferring the toner image from the intermediate transfer member to a sheet conveyed to the secondary transfer part formed between the intermediate transfer member and the secondary transfer memberl and,
• secondary transfer member cleaning means for sequentially applying, to the secondary transfer member, (i) a first voltage for generating an electric field that transfers normally-charged toner from the secondary transfer member to the intermediate transfer member and (ii) a second voltage for generating an electric field that transfers oppositely-charged toner from the secondary transfer member to the intermediate transfer member;
• and
• an intermediate transfer member displacing unit for bringing the intermediate transfer member into contact with the toner image holding member or separating the intermediate transfer member from the toner image holding member,
• wherein the intermediate transfer member displacing means separates the intermediate transfer member from the toner image holding member while the secondary transfer member cleaning means is applying one of the first voltage and the second voltage to the secondary transfer member.