JPH03192283A - Image forming device - Google Patents

Abstract

PURPOSE:To improve the efficiency of a charger and the durability of a transfer belt, to facilitate the manufacture of a device and to reduce a cost by disposing conductive belts which contact to the transfer belt and rotate in synchronism with the rotation of the transfer belt on the position opposite to chargers for giving a charge to the transfer belt or attracting a toner image from the upper side of the transfer belt through the transfer belt. CONSTITUTION:The conductive belts 12 and 16 which contact to the transfer belt 5 and rotate in synchronism with the rotation of the transfer belt are disposed on the position opposite to the chargers 18 and 19 for giving the charge to the transfer belt 5 or attracting the toner image from the upper side of the transfer belt 5 through the transfer belt 5. Then, the conductive belts 12 and 16 act as the counter-electrodes of the chargers 18 and 19 and also the contact area of the conductive belts 12 and 16 and the transfer belt 5 can be enlarged and also the optimum material can be selected for the transfer belt 5 and the conductive belts 12 and 16 in accordance with each function. And attrition can be reduced since the transfer belt 5 and the conductive belts 12 and 16 rotate in synchronism with each other. Thus, the efficiency of the charger and the durability of the transfer belt can be improved and the manufacture of the device can be facilitated and the cost can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image forming apparatus, and particularly to an image forming apparatus using a transfer belt.

(Prior Art) Image forming apparatuses have heretofore been known in which a toner image formed on a photoconductor is primarily transferred onto a transfer belt, and the toner image on the transfer belt is secondarily transferred onto transfer paper. ing. The transfer belt used is a dielectric type in which a thin dielectric layer with high volume resistance is formed on the surface of a conductive layer. The toner image on the photoreceptor is electrostatically attracted by applying a charge to the photoreceptor, and the secondary transfer from the transfer belt to the transfer material is performed by electrostatically adsorbing the toner image via the transfer material with a charger. In addition, since the conductive layer needs to be made of a material that has excellent adhesiveness with the dielectric layer,
A material such as polyester, which has a considerably higher volume resistance than a metal film or a chloroprene rubber layer in which carbon is dispersed, is used.

Further, an image forming apparatus is also known in which a transfer material is supported on the charged transfer belt and passed through a transfer position of a photoreceptor, thereby transferring a toner image from the photoreceptor onto the transfer material. .

Furthermore, using a transfer belt consisting of a semiconductor belt having a volume resistance between the transfer material and the path, a charger performs primary transfer from the photoreceptor to the transfer belt, and secondary transfer from this transfer belt to the transfer material. It is also possible to consider an image forming apparatus in which the charger performs the process.

(Problem to be solved by the invention!!i) By the way, in an image forming apparatus using a transfer belt as described above, there is a method for applying an electric charge to the transfer belt or for electrostatically adsorbing a toner image from the transfer belt. Although a charger is used, it is generally known that to improve the efficiency of the charger, it is sufficient to place a counter electrode. In this case, the counter electrode is placed on the back side of the transfer belt so as to face the charger. do it. However, if the counter electrode is fixedly installed, the transfer belt will move in sliding contact, resulting in severe abrasion of the transfer belt, resulting in a problem in durability. Therefore, it may be possible to arrange metal rollers, but
If the diameter is small, sufficient effect cannot be obtained, and if the diameter is large, a large space is required and the driving torque is also large, and furthermore, there are problems such as poor separation of the transfer material at the secondary transfer position from the transfer material. There is.

It is also conceivable to provide a vapor-deposited metal layer, a conductive rubber layer in which carbon is dispersed, or a conductive polymer layer on the back surface of the transfer belt using the technical means disclosed in JP-A No. 57-672. However, when a metal layer is formed, it wears out due to contact with the roller, resulting in durability problems, and carbon dispersion layers and conductive polymer layers have poor adhesion to the base of the transfer belt, making them difficult to manufacture. There were problems in that it was difficult and expensive.

In view of the above conventional problems, it is an object of the present invention to provide an image forming apparatus that can improve the efficiency of the charger in the transfer belt, does not impair the durability of the transfer belt, etc., and can be easily and inexpensively manufactured.

(Means for Solving the Problems) In order to achieve the above object, the image forming apparatus of the present invention transfers a toner image from a photoreceptor to its surface, or supports a transfer material on the surface and transfers toner thereon. In an image forming apparatus equipped with a transfer belt to which an image is transferred, a charger is provided in contact with the transfer belt at a position opposite to a charger that applies an electric charge to the transfer belt or attracts a toner image from the transfer belt through the transfer belt. It is characterized by having a conductive belt that rotates synchronously with each other.

(Function) According to the above structure of the present invention, the conductive belt acts as a counter electrode of the charger, and the contact area between the conductive belt and the transfer belt can be widened, and the transfer belt and the conductive belt can be used for their respective functions. Since the most suitable material can be selected, the efficiency of the charger can be improved, and since the transfer belt and conductive belt rotate synchronously, there is less wear and tear and durability, and the conductive belt can be arranged in any shape. Space can be used effectively, and the conductive belt and the transfer belt can be bent with a small radius of curvature without any problem, so the separation of the transfer material can also be improved.

(Example) An example of the present invention will be described below with reference to FIGS. 1 to 3.

In FIG. 1, reference numeral 1 denotes a photosensitive drum, around which a charger 2, an exposure section 3 using an optical system (not shown), a developing section 4, a transfer belt 5, a drum cleaner 6, and an eraser 7 are arranged in the rotational direction. has been done. The developing section 4 includes:
A yellow developer 4Y, a magenta developer 4M, a cyan developer 4c, and a black developer 4B are installed. Further, each developing device is equipped with a developing sleeve, a grain cutting shutter, a toner concentration detector, a toner replenishing device, and the like.

As shown in FIG. 2, the transfer belt 5 has good environmental resistance and flexibility, and has a volume resistivity of 1×10 4 to 1×, for example.
350am made of polyester of about 10'Ω・cm
A 50 μm thick dielectric layer 5b made of polyethylene and having a volume resistance of 1×10 ISΩ·cm or more is formed on the surface of a thick conductive layer 5a.

On the inner periphery of the transfer belt 5, there is a 1 which transfers the toner image from the photoreceptor drum 1 to the transfer belt 5 along the moving direction of the transfer belt 5.
a pair of pressure rollers 8a arranged on both sides of the next transfer position;
8b, a drive roller 9, a tensile roller 10, and a pair of rollers 11a and llb arranged on both sides of the secondary transfer position where the toner image is transferred from the transfer belt 5 to the transfer material and at least one of which is grounded. As shown, a conductive belt 12 wound between these rollers, a backup roller 14 that supports the transfer belt 5 at a cleaning position to scrape off toner remaining on the surface of the transfer belt 5, and a charging roller that applies an electric charge to the transfer belt 5. A pair of rollers 15a and 15b are disposed on both sides of the position, at least one of which is grounded, and a conductive belt 16 is wound between these rollers as shown in FIG. A secondary transfer charger 17 and a separation charger 18 are disposed on the outer periphery of the transfer belt 5, facing the conductive belt 12 at the secondary transfer position,
A belt cleaner 13 is disposed opposite the backup roller 14 at the cleaning position, and a belt charger 19 is disposed opposite the conductive belt 16 at the charging position.

The conductive belt 12.16 is made of carbon-dispersed chloroprene rubber having a thickness of 500 μm, for example, and the rollers lla, llb, 15a, and 15b are made of aluminum.

Reference numeral 20 denotes a paper feed cassette, 21 and 22 a paper feed roller and a separating plate that take out the transfer paper S one by one from the paper feed cassette 20 and supply it to the secondary transfer position between the transfer belt 5 and the secondary transfer charger 17; 23 is a registration roller that sends out the transfer paper S to the secondary transfer position in a timely manner, 24 is a transfer paper conveyance belt that conveys the transfer paper S after the secondary transfer toward the fixing section 25, and 25a has a built-in heater. The fixing roller 25b is a pressure roller that presses the transfer paper S against the fixing roller.

Next, the operation will be explained.

First, an overview of the process of forming a monochrome image will be explained. The photosensitive drum 1 is charged by a charging charger 2 and exposed by an exposure section 3 using an optical system (not shown) to form an electrostatic latent image. This latent image is developed with toner in the developing section 4. The developing devices used at this time are yellow developing device 4Y,
Any one of the magenta developer 4M, the cyan developer 4C, and the black developer 4B is selected. The toner image on the photosensitive drum 1 is transferred at a primary transfer position onto the transfer belt 5, which is charged with a polarity opposite to that of the toner by a belt charger 19. Thereafter, the photosensitive drum 1 is cleaned by a drum cleaner 6, residual potential is removed by an eraser 7, and the same process is repeated again.

The toner image transferred to the transfer belt 5 is transferred to the transfer paper S which is sent in synchronization with the toner image by the secondary transfer charger 17.
The image is transferred to the fixing unit 25, fixed by the fixing unit 25, and then discharged. The transfer belt 5 after the secondary transfer is cleaned by the belt cleaner 13, and the same process is repeated again.

Next, an overview of the process of forming a full-color image will be explained. Through the same process as for monochrome images,
A yellow toner image is formed on the photosensitive drum 1 and transferred onto the transfer belt 5.

Then, while being supported on the transfer belt 5, it goes around once again and returns to the primary transfer position. At this time, paper is not fed and 2
The next transfer charger 17 and the separation charger 18 do not operate, the belt cleaner 13 retreats from the transfer belt 5, and the belt charger 19 also does not operate.

A magenta toner image is formed on the photosensitive drum 1 in synchronization with the yellow toner image on the transfer belt 5, and is transferred onto the transfer belt 5 in an overlapping manner.

Similarly, a cyan toner image and a black toner image are transferred onto the transfer belt 5 in an overlapping manner, and a full-color toner image is formed on the transfer belt 5, which is transferred onto the transfer paper S by the secondary transfer charger 17 and fixed. and discharged. Further, residual toner that has not been transferred to the transfer paper S is cleaned by a belt cleaner 13.

In the case of two colors or three colors, an image is formed by the same operation.

In the image forming process as described above, when the belt charging charger 19 applies electric charge to the transfer belt 5 and when the secondary transfer charger 17 transfers the toner image on the transfer belt 5 to the transfer paper S, these belt charging chargers 19 and the secondary transfer charger 17 with the transfer belt 5 in between.
16 are arranged, so these conductive bells) 12.
16 acts as a counter electrode, and the area of the portion that contacts the transfer belt 5 and functions as a counter electrode can be sufficiently large, so that the efficiency of the belt charging charger 19 and the secondary transfer charger 17 is high, resulting in high charging and transfer efficiency. is ensured.

Furthermore, if the transfer paper S is separated from the transfer belt 5 at the roller 11b on the lower side in the movement direction of the transfer belt 5 at the secondary transfer position, the separation can be ensured because the diameter of the roller llb is small, and the separation of the transfer paper S will be avoided. does not occur. Moreover, even if the diameters of the rollers lla and llb are small, they do not affect the transfer efficiency, nor do they significantly affect the durability of the transfer belt 5 or the conductive belt 12.

Incidentally, the conductive belts 12, 16 can be appropriately selected from any material with low volume resistance, but if conductive rubber is used, assembly is easy and the meandering prevention mechanism is simple.

Further, in the above embodiment, the conductive belt 12.16 was brought into contact with the transfer belt 5 and rotated synchronously, but teeth are formed on the inner peripheral surface of the conductive belt 12.16 to drive it. Alternatively, the driving of the transfer belt 5 may be assisted.

Further, in the above embodiment, an example was shown in which a dielectric type belt was used as the transfer belt 5, but a semiconductor type belt having a volume resistance such as between the transfer paper S and the path may also be used as the transfer belt 5. For example, the volume resistance is 1×1O10~
A 10 to 30 μm thick surface coating layer is formed by coating the surface of a polyurethane rubber belt of approximately 1×10′3 Ω-cm with a fluorine-based paint of approximately 1×10” to 1×101!Ω-cm, and the thickness is approximately 600 μm. When using this semiconductor belt, pressing rollers 8a and 3 can be used instead of the belt charger 19.
A primary transfer charger is disposed between b.

Further, in the above embodiment, an example of an image forming apparatus is shown in which the toner image is primarily transferred onto the transfer belt 5 and the toner image is secondarily transferred onto the transfer paper S.
It can also be applied to an image forming apparatus in which a transfer paper is adsorbed or supported on top of the transfer paper and a toner image is transferred onto the transfer paper.

(Effects of the Invention) According to the image forming apparatus of the present invention, as is clear from the above description, the area of the portion where the conductive belt acts as the counter electrode of the charger and also contacts the transfer belt and functions as the counter electrode. It is possible to increase the efficiency of the charger by selecting the most suitable material for the transfer belt and conductive belt according to their respective functions, and since the transfer belt and conductive belt rotate synchronously, there is less wear and tear and durability. Moreover, since the conductive belt does not require difficult adhesion, it can be constructed at low cost.Furthermore, the conductive belt can be arranged in any shape, making effective use of space, and can be configured to be advantageous for paper passing. Since there is no problem even if the transfer belt is bent with a small radius of curvature, great effects such as preventing poor separation of the transfer material can be achieved.

[Brief explanation of drawings]

1 to 3 show an embodiment of the image forming apparatus of the present invention, in which FIG. 1 is a schematic diagram of the overall configuration with the optical system omitted, FIG. 2 is a sectional view of the transfer belt, and FIG. 3 is a conductive FIG. 2 is a perspective view of a sex belt.

Claims (1)

[Claims] (1) In an image forming apparatus equipped with a transfer belt on which a toner image is transferred from a photoreceptor to its surface, or a transfer material is supported on the surface and a toner image is transferred thereon, an electric charge is applied to the transfer belt. Alternatively, an image forming apparatus characterized in that a conductive belt that contacts the transfer belt and rotates synchronously is disposed at a position opposite to a charger that attracts a toner image from the transfer belt with the transfer belt interposed therebetween.