JPH05142958A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device in which suspending toner is hardly stuck around an electrical conduction means when an image is formed by attracting a transfer material to the outside circumferential part of a rotary type transfer material carrying means by an electric discharge means and the electrical conduction means. CONSTITUTION:In the image forming device which forms the image by attracting the transfer material P on the rotary type transfer material carrying means 40 by the electric discharge means and the electrical conduction means 42 disposed by being faced to the inside and the outside of the carrying means 40 and which is provided with a moving means 60 which makes the electrical conduction means 42 abut on the outside surface of the carrying means 40 or separates the means 42 from it, the ground of the conduction means 42 is released when the means 42 is separated from the carrying means 40. Since the suspending toner is easily stuck on the conduction means 42 when the means 42 is grounded, the ground of the means 42 is released when the means 42 is separated from the carrying means 40 to which the material P need not be attracted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic copying machine or an electrostatic recording apparatus, and more particularly to an image forming apparatus having a rotary transfer material carrying means (transfer drum).

[0002]

2. Description of the Related Art Toner images of a plurality of color toners are sequentially formed on the outer surface of a drum-shaped or endless belt-shaped image carrier, and the toner images are transferred onto a transfer drum (rotary transfer material carrying means).
2. Description of the Related Art There is known an image forming apparatus that forms a multicolor image by sequentially transferring onto a transfer material that is positioned and held above.

In this case, the method for positioning and holding the transfer material on the transfer drum is to hold the transfer material by gripping the tip of the transfer material with a gripper, or to hold the transfer material by electrostatic attraction (Coulomb force). There is a method, but the one that uses this electrostatic attraction force can hold the transfer material at any position of the transfer drum, and when holding a plurality of small size transfer materials on the transfer drum, the interval between the transfer materials is Since the size of the gripper can be reduced to improve the efficiency of transfer, it is widely used as compared with the one using the gripper.

What utilizes this electrostatic attraction force is a corona discharger disposed inside the transfer drum and a contact state on the outer peripheral surface of the transfer drum so as to face the corona discharger. A corona discharger is provided between the conductive member and the outer peripheral surface of the transfer drum to discharge the transfer material onto the outer peripheral surface of the transfer drum by corona discharge. It is electro-adsorbed.

[0005]

However, an image forming apparatus capable of forming a multicolor image has a plurality of developing devices each having magenta, cyan, yellow, and black toners, and the toner floating in the apparatus is also included. With many
Since these developing devices are arranged in the vicinity of the conductive member, the floating toner adheres to the conductive member that is grounded and has an electric attraction force (Coulomb force), and the conductive member is soiled with the toner. There was an inconvenience.

If the conductive member is left in this state, the conductive member loses its function and the transfer material cannot be sufficiently attracted to the transfer drum. Also,
If the toner adhering to the conductive member is cleaned with a cleaning tool, the toner lumps generated at the time of cleaning are mixed into a nearby developing device, which causes a problem that a developed image is mixed.

The present invention has been made in view of the above problems. An object of the present invention is to form an image by adsorbing a transfer material to the outer peripheral portion of a rotary transfer material carrying means by a discharging means and a conductive means. Another object of the present invention is to provide an image forming apparatus in which floating toner is less likely to adhere around the conductive means.

[0008]

In order to achieve the above-mentioned object, the present invention provides a discharging member and a conducting member which are disposed inside and outside the rotary transfer material holding means so as to face each other. The developed image formed through the developing means on the image carrier is transferred onto the transfer material electrostatically adsorbed on the outer peripheral surface to form an image, and the conductive means is provided on the outer surface of the transfer material carrying body. In the image forming apparatus provided with the moving means of the conductive means for contacting or separating from the outer surface, the grounding of the conductive means is released when the conductive means is separated from the transfer material carrying means.

[0009]

[Operation] From the discharge means inside the rotary transfer material carrying means,
When the outer conductive means is discharged to electrostatically adsorb the transfer material to the transfer material carrying means, the conductive means is grounded so that the transfer material is sufficiently adsorbed to the transfer material carrying means. On the other hand, if the conductive means is grounded, the floating toner is attracted to the conductive means and the conductive means is soiled with the toner, which causes various problems.

Therefore, when the electrostatic attraction of the transfer material to the transfer material carrying means is completed and the conductive means is separated from the transfer material carrying means via the moving means in order to prevent image disturbance on the transfer material, The grounding of the conductive means was released so that the floating toner did not adhere to the conductive means as much as possible. In this case, since the time when the conductive means is in contact with the transfer material carrying means is sufficiently longer than the time when the conductive material is in contact with the transfer material carrying means, the adhesion of toner to the conductive means is significantly reduced.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 4 shows a cross section of an image forming apparatus capable of forming a multicolor image. Reference numeral 1 in the drawing denotes a photosensitive drum (electrophotographic photosensitive member) as an image bearing member which is rotated in the direction of an arrow shown in the drawing. A primary charger 2, a developing device 3, a transfer device 4, and a cleaning device 5 are arranged around the photosensitive drum 1, and two large and small paper feed cassettes 6 are provided on the paper feed side of the transfer device 4.
6 ', paper feed rollers 7 and 7', and registration rollers 8 are provided, and a transport unit 9 and a fixing device 1 are provided on the paper discharge side of the transfer device 4.
0, a paper discharge tray 11 is provided. Further, an image reading unit 12 and a scanner unit 13 that receives a signal from the image reading unit 12 and emits image light L to the photosensitive drum 1 are arranged above the photosensitive drum 1 and the transfer device 4.

The developing device has four developing units 31 (specifically, magenta, cyan, yellow, and black developing units 31M and 31) each having magenta toner, cyan toner, yellow toner, and black toner on the moving table 30.
C, 31Y, 31B) are positioned and supported. By moving the moving table 30 below the photosensitive drum 1 and the transfer device 4, the developing device 31 having a desired color toner is positioned directly below the photosensitive drum 1. After that, the developing device 31 is brought close to the photosensitive drum 1 to perform the developing work.

The transfer device 4 allows the toner image on the photosensitive drum 1 to be transferred onto the transfer material P in a superimposed manner, and includes a transfer drum 40 which is a rotary transfer material carrying means, a suction corona charger 41, and The transfer drum 4 includes a conductive roller 42.
0, the electrostatic attraction means for positioning and holding the transfer material P by electrostatic attraction on the outer peripheral surface, the transfer charger 43 disposed at the position facing the photosensitive drum 1 inside the transfer drum 40, and the transfer drum 40. Of a pair of static eliminator chargers 44, 44 disposed inside and outside of the static eliminator for facilitating separation of the transfer material P from the transfer drum 40, and at the time of static erasing by the static eliminator chargers 44, 44. The charging device 45 includes a charging device 45 that prevents the image from being disturbed due to the peeling discharge that occurs, a separation claw 46 that separates the transfer material P from the transfer drum 40 after the charge removal, and the like.

Here, the attraction charger 41 of the electrostatic attraction means.
Is arranged inside the transfer drum 40, and the conductive roller 42 is arranged outside the transfer drum 40 facing the attraction charger 41. The conductive roller 42 is grounded and the opposite electrode of the attraction charger 41. The action of injecting electric charge into the transfer material P and electrostatically adsorbing the transfer material P onto the outer peripheral surface of the transfer drum 40 (made of a dielectric sheet) in accordance with corona discharge by the adsorption charger 41. have. When the transfer material P is adsorbed to the transfer drum 40, the conductive roller 42 contacts the outer surface of the transfer drum 40 and is driven to rotate as the transfer drum 40 rotates. And the image on the transfer material P is not disturbed.

That is, when the image light L of magenta image information is exposed through the scanner unit 13 onto the photosensitive drum 1 uniformly charged by the primary charger 2, an electrostatic latent image is formed on the photosensitive drum 1. An image is formed. The electrostatic latent image is directed toward the developing device 3 as the photosensitive drum 1 rotates, and is visualized as a toner image by the desired magenta developing device 31M. The toner image is transferred to the transfer drum 4 of the transfer device 4.
It is directed to the 0 side and transferred onto the transfer material P on the transfer drum 40. Then, after the residual toner is cleaned by the cleaning device 5 on the photosensitive drum 1 after the transfer is completed, the scanner unit 13 is mounted on the photosensitive drum 1 again.
The image light L of cyan image information is exposed via the light to form an electrostatic latent image. Then, the electrostatic latent image is visualized as a toner image by the cyan developing device 31C of the developing device 3, and the toner image is transferred onto the transfer material P on the transfer drum 40 in an overlapping manner. Similarly, toner images of yellow and black toners based on yellow and black image information are formed on the photosensitive drum 1, and these toner images are transferred onto the transfer material P in an overlapping manner.

On the other hand, for example, the transfer material P in the paper feed cassette 6
After being taken out one by one through the paper feed roller 7, they are sent to the registration roller 8 and are supplied to the electrostatic attraction means of the transfer device 4 at the same timing by the registration roller 8. The transfer material P is the conductive roller 4 of this electrostatic attraction means.
While being fed between the outer peripheral surface of the transfer drum 40 and the outer peripheral surface of the transfer drum 40, it is electrostatically adsorbed while being positioned on the outer peripheral surface of the transfer drum 40 by discharge from the adsorption charger 41. Then, as the transfer drum 40 rotates, four color toner images are transferred onto the transfer material P in an overlapping manner. In this case, the conductive roller 4
2 is separated from the transfer drum 40.

When the transfer is completed, the transfer material P on the transfer drum 40 is discharged by the discharging chargers 44, 44, and peeling discharge is prevented by the charger 45, and separated from the transfer drum 40 by the separating claw 46. Then, it is sent to the fixing device 10 via the carrying section 9. Then, the transfer material P on which the toner images are fused and mixed by the fixing device 10 and fixed as a full-color image is stacked on the discharge tray 11.
The image forming work ends.

The contact / separation mechanism of the conductive roller 42 of the electrostatic attraction means with respect to the transfer drum 40 will be described with reference to FIG. 1. The conductive roller 42 has the other end of the guide plate 60 whose one end is pivotally supported by the fixed shaft 61. Since the guide plate 60 is pivotally supported by the section and is biased toward the photosensitive drum 1 side through the coil spring 62, the conductive roller 42 is pressed toward the photosensitive drum 1 side. Further, eccentric cams 63, 63 fixed to the cam shaft 64 are engaged with the guide plate 60, and the rotation of the cam shaft 64 causes the guide plate 60 to swing by the action of the eccentric cams 63, 63 and the coil spring 62. Therefore, the conductive roller 42 comes into contact with or separates from the transfer drum 40. Incidentally, the conductive roller 42 is the transfer drum 40.
When it comes into contact with the transfer roller 40, the conductive roller 42 is mainly pressed by the end portions of the transfer drum 40 via the rollers 42a, 42a at the end of the shaft and is driven to rotate. It doesn't take too much force.

Now, in such an image forming apparatus capable of forming a multicolor image, the developing device 3 having four developing devices 31 is provided, and the toner scattered and floating outside the developing device 3 at the time of development is also compared. And a developing device 31 of the developing device 3
Is moved to the vicinity of the electrostatic attraction means of the transfer device 4, and the conductive roller 42 of the electrostatic attraction means is moved to the attraction charger 41.
Since the transfer material P is grounded so that the transfer material P is attracted to the transfer drum 40 by the discharge of, a large amount of toner adheres to the outer surface of the conductive roller 42. If the floating toner is left on the conductive roller 42, the conductive roller 42 loses its function and the transfer material P cannot be sufficiently adsorbed to the transfer drum 40 by static heat. If you clean it with a cleaning tool and scatter the toner in the device,
The toner lumps generated at this time are mixed in the developing device 31 to cause an image defect.

Therefore, in the present invention, in order to reduce the adhesion of toner to the conductive roller 42 of the electrostatic attraction means as much as possible, the grounding of the conductive roller 42 is limited to the necessary minimum. That is, as shown in FIG. 1, a ground leaf spring 47 for grounding the conductive roller 42 is provided on the transfer drum 40 side of the main body of the image forming apparatus, and the conductive roller 42 contacts the transfer drum 40 as shown in FIG. Only when the transfer material P is electrostatically attracted to the transfer drum 40 by contacting the earth plate spring 47 with the grounding shaft 42b of the conductive roller 42, the conductive roller 42 is removed from the transfer drum 40 as shown in FIG. When it is not necessary to separate the transfer material P to be attracted to the transfer drum 40 by separating the transfer material P from the ground shaft 42b of the conductive roller 42 to the ground leaf spring 4.
7 are separated from each other, and the conductive roller 42 is not grounded.

Thus, while the conductive roller 42 is grounded, that is, while the conductive roller 42 is in contact with the transfer drum 40 and the transfer material P is electrostatically adsorbed to the transfer drum 40,
While the conductive roller 42 is not grounded, that is, much shorter than the time when the conductive roller 42 is separated from the transfer drum 40, grounding of the conductive roller 42 is limited to the necessary minimum, so that the conductive toner of the floating toner is not transferred. Adhesion to 42 will be greatly reduced.

[0023]

As is apparent from the above description, according to the present invention, the grounding of the conductive means is canceled while the conductive means is separated from the transfer material carrier by the moving means. Adhesion of airborne toner to the means is greatly reduced. Therefore, the defective adhesion of the transfer material to the transfer material carrying means due to the adhesion of the toner to the conductive means is reduced, and scattered toner lumps generated when the conductive means is cleaned are mixed in the developing means to cause an image defect. Not even.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a contact / separation mechanism of a conductive roller with respect to a transfer drum.

FIG. 2 is an operation explanatory diagram when a conductive roller is in contact with a transfer drum.

FIG. 3 is an operation explanatory diagram when a conductive roller is separated from a transfer drum.

FIG. 4 is a side sectional view of the image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum (image carrier) 40 Transfer drum (transfer material carrying means) 41 Charging device (discharging means) 42 Conductive roller (conductive means) 60 Guide member (moving means) P Transfer material

Claims (1)

[Claims] 1. An image is formed on a transfer material electrostatically adsorbed on the outer peripheral surface of the transfer material holding means by a discharging means and a conductive means which are arranged inside and outside the rotary transfer material holding means so as to face each other. A moving means of the conductive means is provided for transferring the developed image formed through the developing means on the carrier to form an image and for bringing the conductive means into contact with or away from the outer surface of the transfer material carrier. In the image forming apparatus, the conductive means is grounded when the conductive means is separated from the transfer material carrying means.