JPH0758407B2 - Transfer type image forming device - Google Patents

Description

The present invention relates to a transfer type image forming apparatus in a full color copying machine or the like.

[Conventional technology]

In a full-color copying machine, usually, toner images of three primary colors of yellow, magenta, and cyan are individually formed on a photoconductor belt, and then these are temporarily transferred onto the intermediate transfer belt in a superimposed state, and then the intermediate transfer belt is further transferred. The toner image superposed on the sheet is transferred onto a sheet.

The transfer from the intermediate transfer belt to the paper is performed by, for example, supporting the intermediate transfer belt from the back side by a backup roller covered with a dielectric film such as polyethylene terephthalate,
While feeding the paper along the intermediate transfer belt, the transfer roller made of a conductive member such as metal is pressed against the intermediate transfer belt via the paper at a position corresponding to the backup roller, and in this state, the transfer roller and the backup roller are separated from each other. It is performed by applying a transfer voltage to.

[Problems to be Solved by the Invention] However, in the above-mentioned transfer type image forming apparatus, when the backup roller is covered with a dielectric film, when a transfer voltage is applied, charges are applied to the surface of the dielectric film. They are accumulated and a potential difference is generated on the surface of the dielectric film. As a result, the strength of the electric field necessary for transferring the toner image changes, and the toner image once transferred to the paper is again transferred to the intermediate transfer belt, which causes a problem such as deterioration of image characteristics. It was

[Means for Solving the Problems]

In order to solve the above problems, a transfer type image forming apparatus according to the present invention includes an intermediate transfer belt, a backup roller coated with a dielectric film and supporting the intermediate transfer belt on the back side, and a backup roller. A transfer type image forming apparatus having a transfer roller made of a conductive member capable of contacting the intermediate transfer belt at a corresponding position, and applying a transfer voltage between the transfer roller and the backup roller. It is characterized in that a charge removing means for contacting the dielectric film of the roller is provided.

[Work]

According to the above configuration, when the transfer voltage is applied between the transfer roller and the backup roller, the electric charge generated on the surface of the dielectric film of the backup roller is removed by the charge removing unit, so that the dielectric film is formed. The potential difference that changes the strength of the electric field for transfer does not occur on the surface of the.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

As shown in FIG. 1, an intermediate transfer belt 1 in a full-color copying machine is supported by a driving roller 2, a driven roller 3 and a backup roller 4, and these rollers 2 to 4 are respectively supported.
It is possible to move in both directions along.

The drive roller 2 is made of conductive rubber and has a diameter of, for example, 50 mm.
It is considered as a degree. The driven roller 3 is made of aluminum and has a diameter of 42 mm, for example. Further, the backup roller 4 is constructed by coating the surface of an aluminum roller 4a having a diameter of, for example, about 25 mm with a dielectric film 4b.
The dielectric film 4b is made of, for example, polyethylene terephthalate having a thickness of about 100 μm.

As shown in FIG. 2, a static elimination brush 5 as a charge removing means is arranged so as to contact the dielectric film 4b of the backup roller 4, and the static elimination brush 5 is grounded.
In addition, the distance 1 from the vicinity of the backup roller 4 between the backup roller 4 and the driven roller 3, more specifically, from the point A where the backup roller 4 contacts the transfer roller 7 via the paper 12 described later, is 5 to 5. On the back side of the intermediate transfer belt 1 at a position of about 25 mm, a back electrode 6 (see FIG. 3) made of, for example, stainless steel is provided.
The back electrode 6 is arranged so as to come into contact with the back electrode 6 and is grounded.

A transfer roller 7 is disposed outside the intermediate transfer belt 1 at a position corresponding to the backup roller 4 so as to be movable in the B and reverse B directions and rotatable in the C direction, and the transfer roller 7 is in the B direction. Transfer belt 1
It is possible to press against. The applied voltage 8 is applied to the transfer roller 7.
The transfer voltage is applied from the.

A paper guide 9 and a paper feed roller 10 are arranged outside the intermediate transfer belt 1 at a position corresponding to the back electrode 6, and the paper feed roller 10 connects the backup roller 4 and the transfer roller 7 via the paper guide 9. The paper 12 is supplied to the space between them.

In the above-described configuration, when full-color copying is performed, toner images of three primary colors of yellow, magenta, and cyan are formed in different areas on a photoreceptor belt (not shown) by a known method, and these toner images are intermediate. The images are transferred on the transfer belt 1 by being superposed on each other.

Subsequently, the transfer from the intermediate transfer belt 1 to the paper 12 is performed by supplying the paper 12 from the paper feed roller 10 to the space between the backup roller 4 and the transfer roller 7 via the paper guide 9 while the intermediate transfer belt 1 is being transferred. Is moved in the D direction, and when the leading edge of the paper 12 reaches the point A, the transfer roller 7 rotating in the C direction is moved in the B direction to a suitable pressure, for example, 2
It is pressed against the paper 12 with a pressure of about 3 kg. Then, in this state, a predetermined transfer voltage is applied to the transfer roller 7 from the applied power source 8 to transfer the toner image on the intermediate transfer belt 1 to the paper 12. The above transfer voltage depends on the environment around the transfer image forming apparatus and the type of the paper 12, for example, 1.
Adjusted in the range of 5 to 3.5kV.

By the way, in this embodiment, the back electrode 6 is provided on the back side of the intermediate transfer belt 1, but this brings about the following advantages.

That is, since the surface of the backup roller 4 is covered with the dielectric film 4b, in order to obtain the electric field strength necessary for transferring the toner image from the intermediate transfer belt 1 to the paper 12 when the back electrode 6 is not provided. Was required to have a high applied voltage of about 7 to 9 kV.

On the other hand, if the back electrode 6 is provided as in this embodiment,
Back electrode 6 from transfer roller 7 via intermediate transfer belt 1
Since a path for the current flowing to the back electrode 6 is formed by the current flowing through the intermediate transfer belt 1 to the back electrode 6, a part of the electric field strength necessary for the transfer can be secured. It becomes possible to set the value of the transfer voltage to be low, for example, about 1.5 to 3.5 kV as described above.

The optimum value of the transfer voltage applied to the transfer roller 7 changes depending on the environment around the transfer type image forming apparatus and the type of the paper 12, but when the back electrode 6 is not provided, the transfer voltage is applied to the transfer roller 7. Since the total current of the application power source 8 for applying the transfer voltage, that is, the total current flowing during the application of the transfer voltage is extremely small, it is difficult to finely adjust the transfer voltage, and the transfer voltage is likely to deviate from the desired optimum value. Had a problem.

On the other hand, when the back electrode 6 is installed, the total current of the applied power source 8 is increased by the current flowing from the transfer roller 7 to the back electrode 6 via the intermediate transfer belt 1, so that the transfer voltage can be adjusted more delicately. As a result, the optimum transfer voltage can be set according to the change in the environment around the transfer image forming apparatus, the type of the paper 12, and the like.

Although polyethylene terephthalate is used as the dielectric film 4b in the above embodiment, a dielectric film made of silicon rubber, polycarbonate or the like is used instead of the polyethylene terephthalate, and the static elimination brush 5 is contacted with the dielectric film. It may be allowed to.

〔The invention's effect〕

As described above, the transfer type image forming apparatus according to the present invention includes the intermediate transfer belt, the backup roller that is covered with the dielectric film and supports the intermediate transfer belt on the back side,
A transfer type image forming apparatus having a transfer roller composed of an electrodynamic member capable of contacting the intermediate transfer belt at a position corresponding to the backup roller, and applying a transfer voltage between the transfer roller and the backup roller. In the above configuration, charge removing means that comes into contact with the dielectric film of the backup roller is provided.

As a result, the charges generated on the surface of the dielectric film in the backup roller are removed by the charge removing means, so that the potential difference that changes the strength of the electric field for transferring the toner image does not occur on the surface of the dielectric film. As a result, the image characteristics are improved.

[Brief description of drawings]

1 to 3 show an embodiment of the present invention. FIG. 1 is a schematic plan view of a transfer type image forming apparatus according to the present invention, FIG. 2 is a perspective view showing a charge eliminating brush, and FIG. FIG. 3 is a perspective view showing the back electrode. 1 is an intermediate transfer belt, 4 is a backup roller, 4b is a dielectric film, 5 is a destaticizing brush, 6 is a back electrode, and 7 is a transfer roller.

Claims (1)

[Claims] 1. An intermediate transfer belt, a backup roller that is covered with a dielectric film and supports the intermediate transfer belt on the back side, and a conductive member that can contact the intermediate transfer belt at a position corresponding to the backup roller. In a transfer type image forming apparatus having a transfer roller made of a member, and a transfer voltage is applied between the transfer roller and the backup roller, charge removing means for contacting a dielectric film of the backup roller is provided. A transfer-type image forming apparatus characterized in that