JP3369292B2 - Transfer device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a toner on an image carrier.
The present invention relates to a transfer device that transfers an image onto a transfer sheet, and more particularly to a so-called roller transfer type (contact charging type) transfer device.

[0002]

2. Description of the Related Art As a conventional transfer device, there is a transfer charger system utilizing corona discharge. Further, recently, a roller transfer system is often used to reduce the generation of ozone. For example, Japanese Patent Application Laid-Open No. 1-280782 and Japanese Patent Application Laid-Open No. 1-269967 disclose a transfer device of a roller transfer system, in which an elastic roller (transfer roller) pressed against an image carrier is disclosed. -The transfer paper is passed through the nip part (a).

In a transfer roller type transfer device, for example, a transfer paper is applied to a toner image (negative / positive image) in which a toner having a negative charge property is attached to an electrostatic latent image of a negative charge type image carrier. A positive voltage is applied to the transfer rollers facing each other by sandwiching the transfer roller, and a negative toner (toner image) is transferred onto the transfer paper.

The transfer roller is constantly pressed against the image bearing member, and the developer gradually adheres to the surface of the transfer roller to deteriorate the transfer characteristics, so that the transfer roller needs to be cleaned or replaced. There's a problem. In order to prevent this
The transfer device disclosed in Japanese Patent Application Laid-Open No. 56-126873 and Japanese Patent Application Laid-Open No. 56-126873 includes a mechanism for driving the transfer roller from the contact position to the retracted position.

[0005]

However, the cause of the adhesion is that a small amount of the developer adhered to the image carrier outside the image range (paper interval portion) adheres to the transfer roller.
The image on the image carrier may be transferred due to improper feeding of the transfer paper.
Some of them are transferred and adhered onto the sheet, and in particular, the latter has a problem that a large amount of developer adheres and the transfer performance is deteriorated, and at the same time, the back surface of the next transfer paper is stained. Even if a mechanism for driving the transfer roller from the contact position to the retracted position is provided, this problem cannot be solved.

An object of the present invention is to prevent such a problem due to toner adhesion to the transfer member.

[0007]

The present invention provides an image carrier (1
In a transfer device having a transfer member (12) facing 1) and a transfer power supply circuit (15) for applying a transfer voltage to the transfer member (12), the transfer member (12) is moved from the image carrier (11). The transfer member (12), which is movably supported in a direction approaching from a distant position, and is located at a position distant from the image carrier (11), has a transfer paper (16) that is electrically attracted to the transfer paper (16) by a transfer voltage. Supporting means (13) for allowing movement in the movement direction of (16) are provided. In addition, in order to facilitate understanding,
The symbols given to the corresponding elements in the examples described later are added for reference.

[0008]

[Operation] When the transfer operation is not performed, the transfer member (12) is located at a position away from the image carrier (11) (Figs. 1 and 2), and the transfer operation is in progress so that the transfer paper (16) is correctly fed. Only when you are asked
The electric attraction between the transfer paper (16) and the transfer member (12) causes the transfer member (1) to move as the transfer paper (16) moves to the image carrier (11).
2) is attracted to the image carrier (11) side and transferred (FIGS. 3 and 5). That is, the image carrier (1) of the transfer member (12)
The attraction to 1) is performed by the force generated by the attraction force by the electrostatic charge between the image carrier (11) / transfer paper (16) / transfer member (12).

Therefore, when the transfer paper (16) is misfed, the transfer member (12) remains in the retracted position, and the image carrier
Since it does not come into contact with (11), the conventional problem that a large amount of toner (image toner) is transferred to the transfer member (12) is improved.

[0010]

FIG. 1 shows an embodiment of the present invention. In this embodiment, the image carrier 11 is a photoconductor, is uniformly charged by a charger (not shown), and image light is projected by an exposing means (not shown) to form an electrostatic latent image corresponding to the image light. . The electrostatic latent image is developed by a toner by a developing device (not shown) to form a toner image. This toner image is a transfer member 12 which is a thin-walled cylindrical body, and is a transfer paper 16 sent from the registration rollers 19 and 20 toward the image carrier 11 (FIG. 2).
And the transfer paper is sent out through a fixing device (not shown).

The transfer member 12 is formed of a resin or rubber sheet having a resistance value of 10 ⁵ to 10 ¹² Ωcm in order to pass an appropriate amount of transfer current. As will be described later, it is preferable that the weight is light so that it can be moved by the adhesive force due to the electrostatic charge. The transfer member 12 is
It is supported by a support shaft 13 penetrating its inner space. Although the support shaft 13 is fixed, the support shaft 13 is provided so that the transfer member 12 can move freely in the vertical and horizontal directions with respect to the support shaft 13.
The outer diameter of the transfer member 12 is considerably smaller than the inner diameter of the transfer member 12.

The transfer paper 16 is fed in as shown in FIGS. 2 and 5 and moves right to left just below the image carrier 11, but the support shaft 13 moves from the center of rotation of the image carrier 11 to the transfer paper 16 of the transfer paper 16. It is separated from the upstream side by b in the moving direction. Further, they are separated from each other in the vertical direction by a (accurately, a + thickness of the thin-walled cylindrical body).

Reference numeral a is a gap for preventing the image carrier 11 and the transfer member 12 from adsorbing when the transfer paper 16 is not present, and b is a deviation amount provided for the transfer paper 16 and the transfer member 12 to be first adsorbed. Is.

Reference numeral 14 in the drawing is a conductive brush for applying a transfer voltage to the transfer member 12. Reference numeral 15 denotes a transfer power supply circuit, which applies a transfer voltage to the transfer member 12 at the timing (or at a predetermined timing before and after the contact) of the front end of the transfer paper 16 with the image carrier 11. Reference numerals 17 and 18 in the figure are guide members for the transfer paper.

FIG. 1 shows a standby state of the transfer device. In the standby state, the transfer member 12 is lowered downward by its own weight, and its surface is farthest from the surface of the image carrier 1.

As shown in FIG. 2, in this standby state, the transfer paper 16 is sent out by the registration rollers 19 and 20, and the leading end of the transfer paper 16 faces the image carrier 11. The leading end of the transfer paper 16 contacts the transfer member 12 or passes very close to the transfer member 12 toward the image carrier 11. As shown in FIG. 3, at a predetermined timing when the front end of the transfer paper 16 contacts the image carrier 11, the switch of the transfer power supply circuit 15 is closed and transfer electricity is applied to the transfer member 12. Then, the transfer paper 16
Is electrically attracted to the transfer member 12 and the transfer paper 16 is conveyed in the direction of the arrow, so that the transfer member 12 moves together with the transfer paper 16 and approaches the image carrier 11.

As shown in FIG. 4, when the transfer voltage is applied, the transfer member 12 becomes + potential, the inside of the transfer paper 16 is polarized, and the charge is distributed as shown in FIG. 4, and the transfer paper 16 and the transfer member 12 are distributed. The suction force is generated between the image carrier 11 and the inner wall cylindrical body 12.

After that, as shown in FIG.
Is strongly sucked by the image carrier 11 and the transfer paper 16
Driven to the left by the movement of the image carrier 11 and the transfer paper 1
6 / transfer member 12 is in a state of being in close contact (transfer state). The transfer member 12 is rotationally driven in a counterclockwise direction while being rotated around the image carrier 11 by a suction force to perform a transfer operation.

As shown in FIG. 6, in the transfer state, in the image carrier 11, the non-exposed portion is negatively charged, the exposed portion has no electric charge, and the toner is attached to the portion with no electric charge. At the transfer portion, the −charged toner is attracted by the + charge of the inner wall cylindrical body 12 and is transferred onto the transfer paper 16. After the transfer is completed, the switch of the transfer power supply circuit 15 is opened, so that the suction force is lost, and the transfer member 12 falls by its own weight and returns to the state of FIG.

[0020]

【The invention's effect】

1. The transfer member comes into close contact during the transfer operation and only when the transfer paper is correctly conveyed, so that the developer adhered to the transfer member outside the image area of the image carrier (the portion between the paper passing). It can prevent adhesion. Further, even when there is no transfer paper in the image area due to conveyance failure (jam) of the transfer paper, the transfer member is separated from the image carrier, so that a large amount of developer can be reliably prevented from adhering to the transfer member. (In the case of the conventional transfer roller system, when the transfer paper is not conveyed properly, all the phenomenon agents that form an image adhere to the transfer roller.) By making the transfer member cylindrical, an operation of first adsorbing the transfer paper and the transfer member and then closely adhering to the image carrier can be obtained. Further, since it can be rotated around, a good transferred image can be obtained.

3. By shifting the support shaft from the transfer position to the upstream side in the transfer paper moving direction and in the direction of retracting from the image carrier, the transfer member is normally separated from the image carrier, and the transfer paper is properly transferred. Only then is the transfer member automatically moved to the image carrier side in accordance therewith, so that it is not necessary to add a retracting drive mechanism.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a main part of an embodiment of the present invention, showing a standby state.

FIG. 2 is a cross-sectional view of the main part of one embodiment of the present invention, showing a state in which the leading edge of the transfer paper is fed until it touches the image carrier 11. The transfer device is in a standby state.

FIG. 3 is a cross-sectional view of a main part of one embodiment of the present invention, showing a state immediately after the transfer voltage is applied to the transfer member 14 after the front end of the transfer paper touches the image carrier 11.

FIG. 4 is an enlarged cross-sectional view showing a part of FIG. 3 in an enlarged manner.

FIG. 5 is a cross-sectional view of a main part of one embodiment of the present invention, showing a state in which a toner image is transferred onto a transfer paper.

FIG. 6 is an enlarged cross-sectional view showing a part of FIG. 5 in an enlarged manner.

[Explanation of symbols]

11: image carrier 12: transfer member 13: support shaft 14: conductive brush body 15: transfer power supply circuit 16: transfer paper 17, 18: guide member for transfer paper 19, 20: registration roller

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sou Kai 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Inventor Satoshi Muramatsu 1-3-3 Nakamagome, Ota-ku, Tokyo No. 6 Inside the Ricoh Company (72) Inventor Yoshiko Ishii 1-3-3 Nakamagome, Ota-ku, Tokyo No. 6 Inside the Ricoh Company (72) Nobuto Yokogawa 1-chome Nakamagome, Ota-ku, Tokyo No. 3-6 Inside Ricoh Co. Ltd. (72) Inventor Masako Suzuki No. 3-6 Nakamagome, Oma-ku, Tokyo Inside Ricoh Co. Ltd. (56) Reference JP-A-2-178686 (JP, A) ) JP-A-61-186971 (JP, A) JP-A-6-266202 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 15/16

Claims (3)

(57) [Claims] 1. A transfer device having a transfer member facing an image carrier and a transfer power supply circuit for applying a transfer voltage to the transfer member, wherein the transfer member is movable in a direction approaching from a position away from the image carrier. And a supporting member that allows the transfer member located at a position distant from the image carrier to move in the moving direction of the transfer paper by an electric attraction force with the transfer paper due to the transfer voltage. Transfer device. 2. The transfer member according to claim 1, wherein the transfer member is a thin-walled cylindrical body, and the supporting means is a support shaft having an outer diameter smaller than the inner diameter of the thin-walled cylindrical body for supporting the inner wall surface of the thin-walled cylindrical body. apparatus. 3. The transfer device according to claim 2 , wherein the center of the support shaft is located upstream of the transfer contact portion of the image carrier in the transfer paper conveyance direction.