JPH0728343A - Image forming device - Google Patents

Abstract

(57) [Abstract] [Purpose] In an image forming apparatus equipped with a transfer device for performing multiple transfer, which has a charge eliminating roller and a suction roller, a transfer material is prevented from becoming dirty and image unevenness is prevented from occurring, and a high quality image is obtained. obtain. [Structure] A relationship of L ₂ ≧ L ₁ is set between a width L _{2 in} the longitudinal direction of the charge eliminating roller 9 and a width L _{1 in} the longitudinal direction of the suction roller 8. As a result, all the electric charges applied to the transfer drum 2 by the suction roller 8 are removed by the charge removing roller 9, and the transfer material is prevented from becoming dirty and image unevenness is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic type or electrostatic recording type image forming apparatus such as a laser printer or a copying machine, and more particularly to winding a transfer material around a transfer material supporting means for multiple transfer. With this, it can be suitably embodied in a multicolor image forming apparatus provided with a means for forming a color image on a transfer material.

[0002]

2. Description of the Related Art Conventionally, as a multicolor image forming apparatus, a multicolor image forming apparatus using an electrophotographic system for performing multiple transfer as shown in FIG. 3 is well known. In the figure, the electrophotographic photosensitive drum 3, which is an electrostatic latent image bearing member, rotates in the direction of the arrow and is uniformly charged by the charging means 10, and thereafter, a light image is irradiated by the laser exposure device 11 or the like onto the photosensitive drum 3. An electrostatic latent image is formed on. This latent image is, for example, yellow (Y), magenta (M), cyan (C), black (B
developing device (1) containing a color developer such as
a, 1b, 1c, 1d) makes a visible image, that is, a toner image.

On the other hand, the transfer material 7 is sandwiched by the gripper 5 on the surface of the transfer drum 2 which is, for example, a drum-shaped transfer material supporting means, and is guided to the facing portion of the photosensitive drum 3.
The toner image on the photosensitive drum 3 is transferred onto the transfer material 7 wound around the transfer drum 2 by an electric field applied between the photosensitive drum 3 and the transfer drum 2. At this time, the transfer material 7
Are simultaneously electrostatically attracted to the transfer drum 2.

To explain further, first, the electrostatic latent image formed on the photosensitive drum 3 by exposure based on the image signal of the first color is developed, for example, a developing device 1a containing a yellow (Y) developer.
Then, it is transferred onto the transfer material 7 held on the transfer drum 2. Then, after cleaning the residual developer on the photosensitive drum 3 with the cleaner 12, an electrostatic latent image of the second color is formed on the photosensitive drum 3 by exposure based on the image signal of the second color. ) After being visualized by the developing device 1b having a developer, it is transferred onto the transfer material 7 on the transfer drum 2 onto which the first color yellow visible image has been transferred. Next, by repeating the same steps as described above, for example, a toner image of cyan (C) as the third color and a toner image of black (Bk) as the fourth color are superimposed and transferred onto the transfer material 7 on the transfer drum 2. After that, the transfer material 7 is separated by the separating device 6.
Is separated from the transfer drum 2 and is fixed by the fixing device 4 to obtain a permanent image.

After the transfer material 7 is separated from the transfer drum 2, the developer attached to the surface of the transfer drum 2 is removed by the transfer body cleaner 13, and the charge is removed by the charge removing roller 9 to be electrically initialized. The charge eliminating roller 9 is also used to eliminate the electric charge charged when the transfer drum 2 transfers from the photosensitive drum 3.

[0006]

In the above-described multicolor image forming apparatus, as shown in FIG. 3, the attraction roller 8 is disposed substantially in the middle between the charge eliminating roller 9 and the photosensitive drum 3 and with respect to the transfer drum 2. It is provided so that it can be connected and disconnected. The adsorption roller 8 charges the transfer drum 2 before the visible image on the photosensitive drum 3 is transferred to the transfer material 7, and thus the transfer material 7 is charged.
The initial adsorptivity of was increased, and it was very effective in this respect.

However, by attaching the suction roller 8 to the transfer drum 2 in this manner, the transfer material 7 becomes dirty, and image unevenness occurs on both sides of the transfer material 7 in the conveying direction. Upon investigating the causes of these problems, the following facts were found. That is, as shown in FIG. 4, the width L ₁ of the attraction roller 8 in the longitudinal direction is larger than the width L _{2 of} the static elimination roller 9 in the longitudinal direction, that is, the width L of the both.
_Since L ₁ and L ₂ are in the relationship of L ₁ > L ₂ , among the charges given to the transfer drum 2 by the attraction roller 8 when the transfer material 7 is attracted, the charges which cannot be removed by the charge eliminating roller 9 are on the transfer drum 2. Remained in. As a result, the developer adheres to the area of the transfer drum 2 where the charge remains, and the transfer material becomes dirty. Also, when continuous paper feeding is performed,
The electric charges remaining without being discharged by the discharging roller 9 are accumulated, so that image unevenness occurs on both sides in the conveyance direction of the transfer material, which are areas where the charges remain.

Therefore, an object of the present invention is to provide an image forming apparatus capable of obtaining a good image while preventing the transfer material from becoming dirty and causing image unevenness while ensuring the initial suction force of the transfer material. It is to be.

[0009]

The above object can be achieved by an image forming apparatus according to the present invention. In summary, the present invention is
The toner image formed on the image carrier is transferred onto the transfer material which is electrostatically attracted to the transfer material supporting means by the attraction roller and wound around the transfer material, and the transfer material supporting means after the transfer material is separated is removed from the charge eliminating roller. In an image forming apparatus that performs static elimination and electrical initialization by means of the suction roller, the width L in the longitudinal direction of the suction roller is
_The image forming apparatus is characterized in that the longitudinal width L ₂ of ₁ and the static elimination roller has a relationship of L ₂ ≧ L ₁ .

It is preferable that the electric field V _DC applied to the attraction roller and the alternating electric field V _pp applied to the static elimination roller have a relationship of V _pp ≧ | V _DC |.

[0011]

Embodiments of the image forming apparatus according to the present invention will be described below in more detail with reference to the drawings. In the embodiment described below, the image forming apparatus of the present invention is embodied in the multicolor image forming apparatus shown in FIG. Therefore, detailed description of the overall configuration and functions of the multicolor image forming apparatus will be omitted. Further, the same members are designated by the same reference numerals.

First Embodiment A first embodiment of the image forming apparatus according to the present invention will be described with reference to FIGS. As shown in FIG. 2, the transfer device of the present image forming apparatus includes a photosensitive drum 3, which is an image carrier that carries a toner image developed by a color developer, around a transfer drum 2, which is a transfer material supporting unit. A separating device 6 for separating the transfer material 7 after the transfer is completed from the transfer drum 2, a fixing device 4 for fixing the transfer material 7 separated from the transfer drum 2, and a transfer drum 2 after the transfer material 7 is separated are electrically neutralized. Static elimination roller 9 that initializes the transfer drum 2, an attraction roller 8 that applies an initial attraction force to the transfer drum 2, and a transfer body cleaner 13 that removes residual developer on the surface of the transfer drum after the transfer is completed.
Is provided. Further, a gripper 5 for sandwiching the transferred transfer material 7 is attached on the surface of the transfer drum 2.

The transfer drum 2 includes an aluminum cored bar 21 on which an elastic body 22 having a thickness of 5.5 mm and a volume resistance of 10 ⁴ Ω · cm or less is fitted, and further having a thickness of 75 μm and a volume resistance of 1 μm.
The dielectric sheet 23 of 0 ¹⁴ to 10 ¹⁶ Ω · cm is covered.

The attracting roller 8 and the discharging roller 9 are
As shown in FIG. 1, they are arranged in parallel with the center line CL of rotation of the transfer drum 2 and in the direction of the arrow with respect to the circumferential surface of the transfer drum 2.

Further, the width L _{2 in} the longitudinal direction of the discharging roller 9
Is set to be equal to or larger than the longitudinal width L ₁ of the suction roller 8. In other words, the static elimination roller 9
The relationship between the width L ₂ and the width L ₁ of the suction roller 8 is L ₂ ≧ L ₁ . In this embodiment, the width L _{1 of the} suction roller is
= 224 mm and the width L _{2 of the charge} eliminating roller was 226 mm.

In the transfer device constructed as described above, the transfer material 7 is conveyed along the transfer drum 2.
The front end of the sheet is clamped by the gripper 5 and is conveyed to the photosensitive drum 3 as the transfer drum 2 rotates. At this time, the attracting roller 8 is brought into contact with the transfer drum 2 by an appropriate means and an electric charge is applied thereto, so that the transfer material 7 is electrostatically attracted and wound around the transfer drum 2. The transfer material 7 onto which the toner images on the photosensitive drum 3 have been transferred is separated by the separating device 6
Then, it is separated from the transfer drum 6 and sent to the fixing device 4. Fixing is performed by the fixing device 4, and a permanent image is obtained on the transfer material 7.

On the other hand, in the transfer drum 2, after the transfer material 7 is separated, the developer attached to the surface of the transfer drum 2 is removed by the transfer body cleaner 13. Further, the charge eliminating roller 9 is brought into contact with the transfer drum 2 by an appropriate means, the charge on the transfer drum 2 is eliminated, and the charge is electrically initialized.

In the transfer apparatus as described above, the width L _{2 in} the longitudinal direction of the charge eliminating roller 9 is set to be equal to or larger than the width L _{1 in} the longitudinal direction of the suction roller 8, so that the transfer material 7 is kept stationary. The charges applied to the transfer drum 2 by the attraction roller 9 when the electricity is attracted by the electrostatic attraction roller 8
It is possible to eliminate all static electricity when it is neutralized by.
Therefore, it is possible to prevent the transfer material from becoming dirty and to prevent image unevenness, and to obtain a good image while securing the initial suction force of the transfer material.

Second Embodiment Next, a second embodiment of the image forming apparatus according to the present invention will be described with reference to FIGS. The structure of the transfer device in the image forming apparatus of this embodiment is the same as that of the first embodiment, and therefore the description of the structure is omitted.

When an electric field is applied to the attraction roller 9 and the static elimination roller 8, discharge is generated at their ends, but experiments have shown that the width of the discharge at the ends of both rollers is proportional to the magnitude of the applied electric field. found. Therefore, in order to surely remove the electric charge discharged at the end of the attraction roller 8, it is necessary to make the alternating electric field V _pp applied to the electricity removal roller 8 larger than the electric field | V _DC | applied to the attraction roller 8. .

[0021] Therefore, in this embodiment, the width L ₁ of the suction roller 8, the width L _2, and the adsorption roller 8 of discharging roller 9
The following relationship was applied to the electric field V _DC applied to and the alternating electric field V _pp applied to the static elimination roller 9. _{L 2 ≧ L 1 V pp ≧} | V DC | Specifically, the width L ₁ = 224 mm of the suction roller, the width L ₂ = 225 mm of the discharging roller, an electric field V _DC = -1000 V applied to the attraction roller, the discharging roller Alternating electric field V to be applied
_pp = 3200V.

As a result, all the electric charges applied to the transfer drum by the suction roller can be eliminated, and a high quality image can always be obtained.

Third Embodiment Next, a third embodiment of the image forming apparatus according to the present invention will be described. The structure of the transfer device in the image forming apparatus of this embodiment is the same as that of the first embodiment, and therefore the description of the structure is omitted.

In this embodiment, the width L _{1 of the} suction roller is
And the width L _{2 of the charge} eliminating roller is made equal. That is, L
₁ = 224 mm and L ₂ = 224 mm.

The electric field V _DC applied to the suction roller and the alternating electric field V _pp applied to the charge eliminating roller are set as follows. In other words, the V _pp = 4400V, and V _DC = -1000V.

As a result, all the electric charges applied to the transfer drum by the suction roller can be eliminated, and a high quality image can always be obtained. Furthermore, the suction roller and the static elimination roller can be made to have exactly the same structure, and the manufacturing cost can be reduced.

[0027]

As is apparent from the above description, in the image forming apparatus according to the present invention, the longitudinal width L ₁ of the suction roller is
And the width L _{2 in} the longitudinal direction of the static elimination roller have a relationship of L ₂ ≧ L _1, so that when the transfer material is electrostatically attracted to the transfer material support means, it is applied to the transfer material support means by the attraction roller. It is possible to remove all the electric charges that have been removed by the charge removing roller. Therefore, it is possible to prevent the transfer material from becoming dirty and to prevent image unevenness, and to obtain a good image while securing the initial suction force of the transfer material.

[Brief description of drawings]

FIG. 1 is an explanatory view of a main part of a transfer device of an image forming apparatus according to the present invention.

FIG. 2 is a configuration diagram showing a transfer device of the image forming apparatus according to the present invention.

FIG. 3 is an overall configuration diagram showing a conventional multicolor image forming apparatus.

FIG. 4 is an explanatory view of a main part of a conventional transfer device.

[Explanation of symbols]

 2 transfer drum (transfer material support means) 3 photosensitive drum (image carrier) 7 transfer material 8 adsorption roller 9 charge eliminating roller

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiaki Miyashiro 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Toshihiko Ochiai 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation

Claims (2)

[Claims] 1. A toner image formed on an image carrier,
An image forming apparatus that electrostatically attracts a transfer material to a transfer material by a suction roller and transfers the wound transfer material onto the wound transfer material, and the transfer material support means after the transfer material is separated is neutralized by a static elimination roller to perform electrical initialization. In the image forming apparatus, the width L ₁ of the suction roller in the longitudinal direction and the width L ₂ of the static elimination roller in the longitudinal direction have a relationship of L ₂ ≧ L ₁ . 2. The image forming apparatus according to claim 1, wherein the electric field V _DC applied to the attraction roller and the alternating electric field V _pp applied to the static elimination roller have a relationship of V _pp ≧ | V _DC | .