JPH11190964A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make not only residual toner but also another attachment removable from an image carrier surface and to make a stable image quality always obtainable by constituting so that the nap of a developer carrier of a developing method comes into contact with a whole peripheral surface of the image carrier independently of development size on the image carrier. SOLUTION: In the image forming device of which developable size of one peripheral surface of a photosensitive drum 2 is 304.8 mm×457.7 mm maximally when a diameter of the photosensitive drum 2 is increased, the device is constituted and controlled so that naps of developing sleeves 25 of developing devices 4Y, 4M, 4C, 4Bk come into contact with at least the whole peripheral surface of the photosensitive drum 2 independently of developable side on the photosensitive drum 2. In this device, the photosensitive drum 2 is charged uniformly by a primary charging device. And light image color-dissolved by an exposure means using a laser beam exposing device and the like or light image corresponding to the above image are projected, and electrostatic latent image is formed at peripheral surface of the photosensitive drum 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus using an electrostatic transfer process, such as an electrostatic copying machine and a printer.

[0002]

2. Description of the Related Art A known image forming apparatus which repeats a process of supplying toner to an electrostatic latent image electrostatically formed on the surface of an image carrier to form a toner image and transferring the toner image to a transfer material such as paper. It is difficult to transfer all the toner from the image carrier to the transfer material at the time of transfer, and it is inevitable that some toner remains on the image carrier. Thorough cleaning is required. Various cleaning means have been proposed in the past, but a sharp edge formed on a cleaning blade made of an elastic material such as urethane rubber has a sharper edge than a transfer portion when viewed in the running direction of the image carrier. On the downstream side, a structure in which the residual toner is scraped by pressing against the surface of the image carrier has advantages such as a simple structure, small size, and cost advantages. Is well known.

In the case of using the above-mentioned cleaning blade, the edge of one edge of the blade is usually pressed in a direction facing the running direction of the image carrier. It is inevitable that the friction with the pressing edge is increased, and therefore, at the beginning of use of the image forming apparatus, a suitable powder such as toner is previously attached to a contact portion between the blade edge and the image carrier. At the start of use, frictional reversal of the blade edge, so-called blade turning, is prevented. After each use, every time a copy is made, a part of the residual toner that reaches the cleaning area remains on the edge of the blade and acts as a lubricant, which prevents the blade from turning up and small vibrations from occurring. Cleaning function can be maintained.

Such a cleaning blade not only collects the toner remaining on the image carrier, but also retains the waste toner near the cleaning blade, and utilizes the polishing effect of the toner to remove the toner from the surface of the image carrier. There is also an effect of polishing the top. Further, since the cleaning blade itself is pressed against with a certain pressure, there is an effect of polishing the surface of the image carrier. Further, the spikes on the developer carrier of the developing device have an effect of removing such deposits. That is, the spikes on the developer carrier of the developing device come into contact with the surface of the image carrier,
In addition, when rubbing, it wipes off the deposits on the surface of the image carrier.

However, when forming an electrostatic latent image on the image bearing member surface, the use of charging means such as a primary charger, where the corona product (ozone, NO _x, etc.) is generated. The corona product (ozone and NO _X, etc.) is present in the atmosphere in the image forming apparatus that owns them, which is deposited on the image bearing member, it is also possible to increase the friction between the cleaning blade and the image bearing member . In addition, impurities such as paper dust and talc are also generated, and these may damage the image carrier or adhere to the image carrier by being rubbed. When such deposits adhere to the surface, there is an effect that the residual toner on the image carrier is easily adhered to the image carrier.

Further, if the diameter of the photosensitive drum as an image carrier is increased, for example, if the developable size for one round on the photosensitive drum is 304.8 mm × 457.2 mm at the maximum, the image range (that is, the developing device is There is a possibility that the area on which the developer is developed is not the entire area on the drum (when the paper size is smaller than the above size). Then
Outside the image range, the spikes on the developer carrier do not come into contact with the surface of the photosensitive drum, and the polishing effect on the drum is reduced as compared with writing a full size image.

If such impurities or scratches are generated on the surface of the photosensitive drum, it may affect the image. Therefore, it is necessary to keep the surface of the photosensitive drum as initial as possible.

[0008]

In order to remove the deposits from the surface of the photosensitive drum only by the effect of the cleaning blade, the cleaning blade is pressed against the image carrier with a considerably large pressure. Not only may the body surface be scratched, but also the friction between the photosensitive drum and the cleaning blade may increase, causing the cleaning blade to turn upside down.

Accordingly, a main object of the present invention is to provide an image forming apparatus which removes not only residual toner from the surface of an image bearing member but also other attached substances and provides stable image quality at all times. is there.

Another object of the present invention is to provide an image forming apparatus capable of favorably cleaning the surface of an image carrier while preventing the blade turning of a cleaning means.

[0011]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
An image carrier, charging means for charging the image carrier, exposure means for exposing the charged image carrier, and developing the electrostatic latent image formed on the image carrier by the exposure A transfer unit for transferring the developed image to a recording material, and a cleaning unit for removing a developer remaining on the image carrier without being transferred by the transfer unit. In an image forming apparatus in which a region where a developing operation is not performed may be formed on the image carrier, the developer of the developing unit covers the entire circumference of the image carrier regardless of the development size of the image carrier. An image forming apparatus, wherein ears of a carrier contact.

When the spikes of the developer carrier come into contact with the surface of the image carrier other than the development size on the image carrier, toner is not positively attached to the surface of the image carrier. It is preferable to perform a proper developing operation. The ears of the developer carrier are preferably a two-component developer containing a non-magnetic toner and a magnetic carrier.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

FIG. 1 shows a full-color copying machine as an image forming apparatus according to an embodiment of the present invention. In FIG. 1, a photosensitive drum 2 serving as an image carrier is rotatably supported in a direction indicated by an arrow in the main body of the full-color copying machine 1, and image forming means disposed therearound as follows. An image is formed.

The photosensitive drum 2 is uniformly charged by a primary charger 3 and is irradiated with a light image or a light image corresponding thereto which is color-separated by exposure means (not shown) using, for example, a laser beam exposure device. An electrostatic latent image is formed on the peripheral surface of the drum 2. The electrostatic latent image is stored in each color developing device 4.
As a result, a developer (toner) is applied to form a visible image, that is, a toner image.

The developing device 4 includes four developing devices 4Y, 4M, 4C, and 4Bk that respectively store toners of four colors of yellow, magenta, cyan, and black. The developing device 4 develops an electrostatic latent image formed on the photosensitive drum 2 by bringing a desired developing device into and out of contact with the outer peripheral surface of the photosensitive drum 2. The toner image formed on the photosensitive drum 2 is transferred to a transfer material P, which is a recording material carried on a drum-shaped transfer device (hereinafter referred to as “transfer drum”) 5 and conveyed in the direction of the arrow.

The toner remaining on the photosensitive drum 2 after the image transfer is collected by a cleaning device 7 having a cleaning blade 7a disposed downstream in the drum rotation direction.

The transfer drum 5 has a transfer sheet 8 adhered to the outer peripheral surface thereof, and has a transfer material suction means for holding the transfer material P on the transfer sheet 8 by suction. The transfer material adsorbing means includes an adsorbing charger 9 for applying a charge having a polarity opposite to that of the toner image on the photosensitive drum 2 to the opposite side of the transfer sheet 8, and a conductive roller 10 provided outside the transfer drum 5.
Having. The conductive roller 10 is grounded, serves as an opposite electrode of the attraction charger 9, injects electric charge into the transfer material P, and functions to electrostatically attract the transfer material P to the transfer sheet 8.

In the transfer drum 5, a transfer charger 11 for applying a charge having a polarity opposite to that of the toner to the transfer sheet 8 is provided at a position corresponding to a pressure contact position with the photosensitive drum 2. Further, inside and outside the transfer drum 5, a pair of AC corona dischargers 1 opposed to each other with the transfer sheet 8 interposed therebetween in order to weaken the attraction force of the transfer material P after the image transfer to the transfer sheet 8.
2 and 13 are provided. AC corona discharger 1
A separation claw 14 is provided downstream of the transfer drum 5 in the rotation direction of the transfer drums 2 and 13. Further outer AC corona discharger 1
3, an AC corona discharger 15 is provided,
The AC corona discharger 15 performs an AC corona discharge in order to prevent image disturbance due to peeling discharge generated when the transfer material P and the transfer sheet 8 are separated.

The transfer material P accommodated in the cassette 16 is fed one by one from the uppermost one by the pickup roller 17, and is transferred by the registration roller pair 18 to the photosensitive drum 2.
The sheet is conveyed in synchronization with the toner image formed thereon. The transfer material P conveyed to the transfer drum 5 is applied to the conductive roller 10
When the transfer drum 5 passes between the attraction charger 9 and the transfer drum 8, the transfer sheet 8 is adhered and held by the transfer sheet 8 attached to the outer peripheral surface of the transfer drum 5. The toner image is transferred to the transfer material P by the device 11. The transfer material P after the image transfer is conveyed while being carried on the transfer drum 5, the adsorbing force is weakened when passing through the AC corona dischargers 12, 13, and the transfer claw 14 is separated from the transfer sheet 8 by the separation claw 14. Separated.

The separated transfer material P is transported downstream by the transport belt 19, and the toner image is heated and fixed when passing between the fixing roller 20 and the pressure roller 21. Then, at the time of single-sided image formation, the transfer material P after image fixing is discharged to a discharge tray 23 outside the apparatus by a discharge roller pair 22.

When forming a double-sided image, the transfer material P after image fixing is conveyed by a conveying roller group 24 and is temporarily stored in a double-sided cassette 24 in the apparatus. The transfer material P temporarily stored in the double-sided cassette 24 is again fed one by one from the uppermost one by the cassette pickup roller, and the image forming operation is repeated, and an image is formed on the back surface.

FIG. 2 is a cross-sectional view showing the structure of the developing units 4Y, 4C, 4M, and 4Bk arranged in the image forming apparatus. The developing device 4Y will be described. Developing unit 4Y
Has an opening on the side facing the photosensitive drum 2, and a magnet roller 34 is disposed at this portion. This magnet roller 34
, A developing sleeve 25, which is a developer carrier made of a nonmagnetic material such as aluminum, stainless steel, or titanium steel, is arranged at a predetermined distance d _SD from the photosensitive drum 2, and rotates in the direction of arrow a. .

The developing device 4Y contains a two-component developer 26 composed of a non-magnetic toner 27 and magnetic particles 30 as a carrier. The two-component developer 26 is agitated and charged by a supply roller 29 and the like. , And is attracted and conveyed to the developing sleeve 25 by the action of the magnet roller 34 to sequentially reach the developing site E facing the photosensitive drum 2.

The amount of the developer 26 conveyed by the developing sleeve 25 is regulated by a developer thickness regulating blade 33 formed of a non-magnetic material and forming a gap t _SB with the developing sleeve 25, and the photosensitive material is exposed to light. A toner image is formed by attaching to the electrostatic latent image formed on the surface of the drum 2.

A developer concentration detecting member 31 is provided in the developing device 4Y, detects the concentration of the developer on the developing sleeve 25, and, if necessary, transfers the toner 2 from the toner reservoir 34.
7 is supplied. The magnetic pole N1 of the magnet roller 34 is a regulating magnetic pole, N2 is a developing magnetic pole, S1 is a conveying magnetic pole,
2, S3 is a stripping magnetic pole.

As the photosensitive layer on the surface of the photosensitive drum, α-S
Various known materials such as e, CdS, ZnO2, OPC and α-Si can be used, but OP having relatively low mechanical strength can be used.
This is particularly effective when the present invention is applied to a C photoconductor.

Therefore, in the present embodiment, when the diameter of the photosensitive drum is increased, for example, in an image forming apparatus in which the developable size for one round on the photosensitive drum is 304.8 mm × 457.7 mm at the maximum, the developing size on the photosensitive drum is reduced. Regardless of
The developing device is configured and controlled such that the ears of the developing sleeve of the developing device contact at least the entire circumference of the photosensitive drum surface.

In an image forming apparatus using such a large-diameter drum, even if the paper size is small, that is, even if the image area does not cover the entire area on the photosensitive drum irrespective of the development size on the photosensitive drum, the developing unit can be used for developing. In addition to the region where the operation is performed, the ears of the developing sleeve of the developing device are in contact with the entire surface of the photosensitive drum for at least one rotation of the photosensitive drum. And for the photosensitive drum surface outside the image area,
The developing sleeve of the developing device is configured so that the spikes of the developing sleeve do not actively adhere the toner to the surface of the photosensitive drum, and the developer on the developing sleeve is swept over the photosensitive drum by running the developing device in contact with the photosensitive drum.

An experimental example will be described. An SUS having a diameter of 24.5 mm is used for the developing sleeve 25 of the developing device, and a SUS non-magnetic blade is also used for the regulating blade 33. Are arranged so as to have a gap t _SB, and the distance d _SD between the developing sleeve 25 and the photosensitive drum 2 is about 400 μm
It is about 500 μm. Then, the potential on the surface of the photosensitive drum is charged to −800 V, and in the developing device, V _DC = −400 V as a developing bias and a frequency of 2 as an AC component.
A DC bias of AC superposition of about 6 kHz is applied in advance.

Using this device, the surface of the photosensitive drum other than the developing area is also exposed to a potential of about -550 V, and a developing operation is performed so that the developing device is brought into contact with the photosensitive drum to prevent toner from being positively attached to the surface of the photosensitive drum. Do. In this way, the application of the AC bias causes the reciprocating motion of the developer in the gap between the surface of the photosensitive drum and the surface of the developer sleeve. Power increases. This operation is performed on the surface of the photosensitive drum other than the developing range for forming a normal image, and the developer ears on the developing sleeve surface of each color developing unit abut at least on the entire surface of the photosensitive drum for one rotation. To work.

With this arrangement, when the diameter of the photosensitive drum is increased, for example, even in an image forming apparatus having a large developable size for one round on the photosensitive drum, that is, an area where a developing operation is not performed on the photosensitive drum. Even if the image area does not cover the entire area of the photosensitive drum regardless of the development size on the photosensitive drum, the carrier can strike the entire surface of the photosensitive drum, and has an effect of removing the deposits and the like attached to the photosensitive drum surface. An image forming apparatus capable of performing sufficient cleaning even when a cleaning blade is pressed against a photosensitive drum with a light pressure instead of a large pressure and capable of always obtaining stable image quality for a long period of time. it can.

[0033]

As is apparent from the above description, according to the present invention, regardless of the development size on the image carrier, the ears of the developer carrier of the developing means cover the entire circumference of the image carrier surface. The contact makes it possible to remove not only the residual toner from the surface of the image bearing member but also the attached matter of the image bearing member, so that a stable image quality can be always obtained. Further, it is possible to perform satisfactory cleaning of the surface of the image bearing member while preventing the blade turning of the cleaning unit.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a configuration diagram illustrating a developing device of the image forming apparatus of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Copier (image forming apparatus) 2 Photosensitive drum (image carrier) 3 Primary charger (charging means) 4 Developing device (developing means) 5 Transfer device (transfer means) 7 Cleaning means 25 Developing sleeve (developer carrier) 26 Two-component developer

Claims (3)

[Claims] An image carrier, a charging unit for charging the image carrier, an exposure unit for exposing the charged image carrier, and a static electricity formed on the image carrier by the exposure. Developing means for developing the electrostatic latent image, transferring means for transferring the developed image by the developing means to a recording material, and removing the developer remaining on the image carrier without being transferred by the transferring means An image forming apparatus having an area where no developing operation is performed on the image carrier, regardless of the development size on the image carrier. An image forming apparatus, wherein a spike of a developer carrying member of the developing unit contacts the whole. 2. The image forming apparatus according to claim 1, wherein the developing unit contacts an area other than the developing size on the image carrier, and when the spike of the developer carrier comes into contact, toner is positively applied to the surface of the image carrier. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus performs a developing operation so as not to adhere. 3. The image forming apparatus according to claim 2, wherein the ear of the developer carrier is a two-component developer containing a non-magnetic toner and a magnetic carrier.